bluuebunny/crossref_metadata_2025 huggingface dataset:
Inverse Solutions of the Theis Equation Determined with Programmable Calculators
Authors: Grimestad Garry
Published: July 2006

This is the second of two articles on calculator programs for inverse solutions of the Theis equation.

Newton's method is used to develop an iteration formula for the determination of transmissivity and storage coefficient values from a combined Theissian expression that incorporates the information contained in two independent aquifer test data point sets.

The algorithm is used in a polynomial‐based program for Hewlett Packard HP 67/97 calculators that is designed to process data corresponding to the full practical range of Theis well function arguments and to accept measurements from one or two observation wells, or from entirely different tests of a given aquifer. Program modifications providing for series‐based well function calculations are appended, and example calculations are shown.
Geologic and Hydrologic Factors Controlling Radon‐222 in Ground Water in Maine
Authors: Brutsaert Willem F. , Norton Stephen A. , Hess Charles T. , Williams John S.
Published: July 2006

High Radon‐222 (222Rn) concentrations exist in ground water from most granitic rocks in Maine. Some values exceed the suggested limit of 500 pCi/1 (E.P.A., 1976) by more than 100 times. Although high values (x̄= 22,100 pCi/1) are conclusively linked with the granites, high values are also present in ground water in metasedimentary rocks from sillimanite‐ (x̄= 13,630 pCi/1) and sillimanite‐orthoclase zone metamorphic terrains. Metamorphic (anatectic) pegmatites with hydrothermally introduced uranium are thought to be the source of radon in high grade terrain. At lower grade (chlorite to staurolite), no relationship exists between 222Rn content and metamorphic grade, although each rock formation has a somewhat characteristic 222Rn range from ground water, ranges which overlap. Considerable local 222Rn variations exist within the same rock body, reflecting local geologic and hydrologic conditions. Data on well depth, type of well, well yield, overburden type and thickness, and water chemistry show that 222Rn may increase slightly with well depth up to 50 to 75 m and is essentially constant thereafter. Low yield wells, generally associated with areas of thin overburden, tend to have higher 222Rn values than high yield wells, normally associated with thick sand and gravel overburdens. 222Rn concentrations decrease with increasing sodium concentrations, suggesting that low 222Rn wells are closely linked with surface waters. No other chemical parameter (Na, K, Ca, Mg, Fe, Mn, Zn, and Cu) correlates with 222Rn content within a single rock unit.
Hydrodynamic Response of Nakhon Luang Aquifer, Bangkok, Thailand
Authors: Das Gupta A. , Siddique M.
Published: July 2006

The development of ground‐water resources in the Bangkok Metropolis over the last decades in an unplanned manner has resulted in a continual decline of the piezometric head in three aquifers underlying the city. One of these three aquifers identified as Nakhon Luang Aquifer provides the major portion of the ground‐water supply and has been considered for analyzing the hydrodynamic behavior under different operating schemes.

It is predicted that continuation of the present rate of water withdrawal will result in a severe decline of the piezometric head, and by the year 2000 most of the public supply wells will no longer be in operation due to water level decline below the maximum depth provided for pump installation. Governmental authorities are actively considering the possibilities of increasing supply from surface‐water sources so that the ground‐water use can be phased out. A need to adopt policies to control the private and industrial usage of ground water in order to maintain its future availability is indicated.
Aquifer Decontamination for Volatile Organics: A Case History
Authors: Althoff William F. , Cleary Robert W. , Roux Paul H.
Published: July 2006

Organic solvents, including 1,1,1‐trichloroethane at concentrations up to 40,000 ppb, were detected in the Old Bridge aquifer under an industrial plant in South Brunswick Township, New Jersey. A hydrogeologic investigation defined the ground‐water flow system and a plume of contamination which extended, at a concentration of at least 100 ppb, for a distance of about 1000 feet down‐gradient of the plant. A contamination abatement system was designed and installed to prevent this plume from reaching a municipal well located about 2500 feet from the site. The system includes seven extraction wells and a water treatment facility. The locations of the extraction wells and their combined pumping rate were determined in part by a computer simulation of the aquifer, which was subsequently checked by a 20‐day pumping test of the system. The on‐site treatment facility uses two cooling towers in series to air‐strip the volatile organics, and two infiltration ponds to return the treated water to the aquifer. The abatement system has been operating for about 10 months. Ground‐water monitoring results show that the plume is now significantly smaller and less concentrated than before the abatement system was installed. It is projected that in several years the aquifer will be largely decontaminated.
Estimating Aquifer Parameters for Large‐Diameter Wells
Authors: Rushton K. R. , Holt Sarah M.
Published: July 2006

Two alternative methods of analyzing the response of large‐diameter wells are considered—the curve matching technique based on analytical solutions and the use of a numerical model. For ideal situations the methods give the same results but for unconfined aquifers where the decrease in saturated depth is significant, the curve matching technique is unreliable. Two particular examples are considered in detail. In a confined aquifer, where the diameter of the dug portion of the well is much larger than the diameter of the hole bored through the confined stratum, the response is found to be particularly sensitive to the ratio of these diameters. In an unconfined aquifer test, the important feature is the reduction in abstraction rate as the well is emptied. For each example, the recovery data is of critical importance in analyzing the tests.
The Use of Geologic, Hydrologic, and Geochemical Mapping Techniques in Environmental Assessmenta
Authors: Coe Curtis J.
Published: July 2006

A method of researching data at a mine to determine the environmental and economic impact to the operator has been developed. This method consists of developing geologic, hydrologic, and geochemical maps that can be used to provide a three‐dimensional view of the subsurface environment before, during, and after mining.

The following maps were developed: a standard topographic base map, structure contour maps, static water level maps, and several iso‐concentration maps for pH, iron, manganese, sulfate, and specific conductance. Where possible geologic‐hydrologic cross sections were drawn to aid in the environmental interpretations. It is possible to use the data to develop the best possible mining plan for a geologic region which considers geographic, technical, economic, and environmental parameters. The iso‐concentration maps for a proposed surface mine site can be used to define the extent of concentration fields, point source locations, and concentration gradients.

To demonstrate the use and interpretations of the data provided by this method, the results of two mine site case studies are presented that will discuss: (1) Dewatering problems; (2) Mining recharge areas; (3) Mining coal overlain by an acid overburden; and (4) The impact of prior surface mining.
Management of Ground Water Contaminated by Aromatic Hydrocarbons in the Aquifer Supplying Ames, Iowa
Authors: Yazicigil Hasan , Sendlein Lyle V. A.
Published: July 2006

A digital model of a buried channel aquifer contaminated by hydrocarbons is used to evaluate development alternatives. The response to ground‐water pumping is critical because the hydrocarbons cause taste and odor problems. The source of contamination is an abandoned pit used to dispose of coal tar residues from an old coal‐gas plant. The hydrocarbon residues overflowed the pit, migrated a short distance and seeped into flood plain soils. The downward movement of the hydrocarbons stopped at the water table but some dissolved into the ground water. Three general approaches taken to evaluate management alternatives include: (1) regulation of pumping of the city wells and of drawdown, and recovery periods are considered and the model stressed with various pumping rates and times; (2) construction of a pumping trough barrier is considered and a hypothetical control well is simulated; (3) new well field developments in various locations are considered. Results suggest that there is no way to prevent movement of contaminants to the well field. The only feasible solution is the removal of coal tar residues from the source area and construction of a pumping trough barrier.
Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in the cavalier King Charles spaniel
Authors: Barnett K. C.
Published: July 2006

Objectives: To record a previously unreported congenital and hereditary condition affecting the eyes and skin in the cavalier King Charles spaniel.

Methods: Nineteen cases (13 litters) were investigated, with particular reference to eye and skin clinical signs. In addition, five generation pedigrees were obtained and studied from all cases with the exception of one.

Results: The eye signs were due to keratoconjunctivitis sicca, a common ocular disease in the dog, but rarely of congenital origin. The skin signs were of an ichthyosiform dermatosis; ichthyosis being a rare skin disease in the dog. In human beings, ichthyosis is a similar disease, mainly inherited and with a neonatal onset, and sometimes accompanied by other developmental defects. In the cavalier King Charles spaniel, the coat abnormality was noted at birth by the breeders as a ‘curly coat’, with deterioration of the skin signs as the animal became adult.

Clinical Significance: These two conditions occurring together in this breed is well recognised by some breeders but rarely by the veterinary profession. Successful treatment is not possible, although some improvement, particularly of the keratoconjunctivitis sicca, can be obtained. The probable hereditary nature of the condition is an important factor for control.
Vagal afferent control of opioidergic effects in rat brainstem circuits
Authors: Browning Kirsteen N. , Zheng Zhongling , Gettys Thomas W. , Travagli R. Alberto
Published: July 2006

We demonstrated recently that increasing the levels of cAMP allows opioids to modulate GABAergic synaptic transmission between the nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV). Using a combination of electrophysiological, immunohistochemical and biochemical approaches, we provide evidence that vagal afferent fibres dampen cAMP levels within the vagal brainstem circuits via tonic activation of group II metabotropic glutamate receptors (mGluRs). Whole‐cell patch‐clamp recordings were made from identified neurons of the rat DMV. Following chronic vagal deafferentation, the opioid agonist methionine‐enkephalin (ME) inhibited the amplitude of evoked IPSC (eIPSC) in 32 of 33 neurons, without exogenous enhancement of cAMP levels. The ME‐induced inhibition was prevented by the group II mGluR‐selective agonist APDC. Following perfusion with the group II mGluR‐selective antagonist EGLU, ME inhibited eIPSC amplitude in brainstem slices of control rats. Immunohistochemical experiments revealed that, following vagal deafferentation, μ‐opioid receptors were colocalized on GABAergic profiles apposing DMV neurons; the number of colocalized profiles was significantly decreased by pretreatment with APDC. Radioimmunoassay and Western blot analysis showed that cAMP and phosphorylated cyclic AMP response element binding protein (pCREB) levels in the dorsal vagal complex were increased following vagal deafferentation. Our data show that by tonically dampening the levels of cAMP within the GABAergic synaptic contacts, activated group II mGluRs prevent the modulation of this synapse by endogenous opioids. These data suggest that the plasticity, hence the response, of central circuits controlling the vagal motor outflow to visceral organs is modulated and finely tuned by vagal afferent fibres.
Prenatal exposure to interleukin‐6 results in hypertension and alterations in the renin–angiotensin system of the rat
Authors: Samuelsson Anne‐Maj , Alexanderson Camilla , Mölne Johan , Haraldsson Börje , Hansell Peter , Holmäng Agneta
Published: July 2006

Cytokines are emerging as important in developmental processes. They may induce alterations in normal gene expression patterns, activate angiotensinogen transcription, or alter expression of the renin–angiotensin system (RAS). To determine whether prenatal exposure to interleukin‐6 (IL‐6) influences gene expression of the intrarenal RAS and contributes to renal dysfunction and hypertension in adulthood, we exposed female rats to IL‐6 early (EIL‐6 females) and late (LIL‐6 females) in pregnancy and analysed blood pressure in the offspring at 5–20 weeks of age. Renal fluid and electrolyte excretion was assessed in clearance experiments, mRNA expression by real‐time PCR, and protein levels by Western blot. Systolic pressure was increased at 5 weeks in IL‐6 females and at 11 weeks in males. Circulatory RAS levels were increased in all IL‐6 females, but angiotensin‐1‐converting enzyme (ACE) activity was increased only in LIL‐6 females. LIL‐6 males and IL‐6 females showed decreased urinary flow rate and urinary sodium and potassium excretion. Dopamine excretion was decreased IL‐6 females. In adult renal cortex, renin expression was increased in all IL‐6 females, but angiotensinogen mRNA was increased only in LIL‐6 females; AT1 receptor (AT1‐R) mRNA and protein levels were increased in LIL‐6 females, whereas AT2 receptor (AT2‐R) levels were decreased in LIL‐6 females and EIL‐6 males. In adult renal medulla, AT1‐R protein levels were increased in LIL‐6 females, and AT2‐R mRNA and protein levels were decreased in EIL‐6 males and LIL‐6 females. Prenatal IL‐6 exposure may cause hypertension by altering the renal and circulatory RAS and renal fluid and electrolyte excretion, especially in females.
Changes in protein expression in the rat medial vestibular nuclei during vestibular compensation
Authors: Paterson Janet M. , Short Duncan , Flatman Peter W. , Seckl Jonathan R. , Aitken Alastair , Dutia Mayank B.
Published: July 2006

The molecular mechanisms of neural and synaptic plasticity in the vestibular nuclei during ‘vestibular compensation’, the behavioural recovery that follows deafferentation of one inner ear, are largely unknown. In this study we have used differential proteomics techniques to determine changes in protein expression in ipsi‐lesional and contra‐lesional medial vestibular nuclei (MVN) of rats, 1 week after either sham surgery or unilateral labyrinthectomy (UL). A systematic comparison of 634 protein spots in two‐dimensional electrophoresis gels across five experimental conditions revealed 54 spots, containing 26 proteins whose level was significantly altered 1 week post‐UL. The axon‐guidance‐associated proteins neuropilin‐2 and dehydropyriminidase‐related protein‐2 were upregulated in the MVN after UL. Changes in levels of further specific proteins indicate a coordinated upregulation of mitochondrial function, ATP biosynthesis and phosphate metabolism in the vestibular nuclei 1 week post‐UL. These may reflect the metabolic energy demands of processes such as gliosis, neuronal outgrowth and synaptic remodelling that occur after UL. Our findings suggest novel roles for axon elaboration and guidance molecules, as well as mitochondrial and metabolic regulatory proteins, in the post‐lesional physiology of the MVN during vestibular system plasticity.
Analysing the developing brain transcriptome with the GenePaint platform
Authors: Alvarez‐Bolado Gonzalo , Eichele Gregor
Published: July 2006

We discuss technical means by which the complexity of gene and protein signalling cascades can be projected onto the complex structure of the mammalian brain. We argue that this requires both robotics and novel computational tools to register images of gene expression, annotate expression patterns and quantify gene expression. When sufficiently enriched and detailed, such gene expression/neuroanatomical atlases are hypothesis‐generating tools and contain in themselves much of the information needed to investigate function in normal and genetically or otherwise modified brains. To be successful and useful, data‐rich and comprehensive gene expression/neuroanatomical atlases have to be web accessible and structured in a way that allows the application of data exploration and mining tools.
Transcriptional regulation of neuronal phenotype in mammals
Authors: Ma Qiufu
Published: July 2006

Transcription factors (TFs) play pivotal roles in directing the formation of neurons and glia. Here I will review the recent genome‐scale analysis of the expression of TFs in the developing mouse nervous system and discuss the logic by which TFs control the establishment of neuronal phenotype. Accumulating evidence suggests that while combinatorial action of TFs is able to define the basic framework of the nervous system, other control mechanisms, such as stochastic and epigenetic regulation of gene expression, also contribute to the generation of nerve cell diversity.
Glucose reduces endothelin inhibition of voltage‐gated potassium channels in rat arterial smooth muscle cells
Authors: Rainbow R. D. , Hardy M. E. L. , Standen N. B. , Davies N. W.
Published: July 2006

Prolonged hyperglycaemia impairs vascular reactivity and inhibits voltage‐activated K+ (Kv) channels. We examined acute effects of altering glucose concentration on the activity and inhibition by endothelin‐1 (ET‐1) of Kv currents of freshly isolated rat arterial myocytes. Peak Kv currents recorded in glucose‐free solution were reversibly reduced within 200 s by increasing extracellular glucose to 4 mm. This inhibitory effect of glucose was abolished by protein kinase C inhibitor peptide (PKC‐IP), and Kv currents were further reduced in 10 mm glucose. In current‐clamped cells, membrane potentials were more negative in 4 than in 10 mm glucose. In 4 mm d‐glucose, 10 nm ET‐1 decreased peak Kv current amplitude at +60 mV from 23.5 ± 3.3 to 12.1 ± 3.1 pA pF−1 (n= 6, P < 0.001) and increased the rate of inactivation, decreasing the time constant around fourfold. Inhibition by ET‐1 was prevented by PKC‐IP. When d‐glucose was increased to 10 mm, ET‐1 no longer inhibited Kv current (n= 6). Glucose metabolism was required for prevention of ET‐1 inhibition of Kv currents, since fructose mimicked the effects of d‐glucose, while l‐glucose, sucrose or mannitol were without effect. Endothelin receptors were still functional in 10 mm d‐glucose, since pinacidil‐activated ATP‐dependent K+ (KATP) currents were reduced by 10 nm ET‐1. This inhibition was nearly abolished by PKC‐IP, indicating that endothelin receptors could still activate PKC in 10 mm d‐glucose. These results indicate that changes in extracellular glucose concentration within the physiological range can reduce Kv current amplitude and can have major effects on Kv channel modulation by vasoconstrictors.
Effects of Differential Scheme and Mesh Density on EHL Film Thickness in Point Contacts
Authors: Liu Yuchuan , Wang Q. Jane , Wang Wenzhong , Hu Yuanzhong , Zhu Dong
Published: July 2006

This paper investigates the effects of differential scheme and mesh density on elastohydrodynamic lubrication (EHL) film thickness based on a full numerical solution with a semi-system approach. The solution variation with different schemes and mesh sizes is revealed based on a set of numerical cases in a wide range of central film thickness from several hundred nanometers down to a few nanometers. It is observed that when the film is thick, the effects of differential schemes and mesh density are not significant. However, if the film becomes ultra-thin, e.g., below 10–20 nanometers, the influence of mesh density and differential schemes becomes more significant, and a proper dense mesh and differential scheme may be highly desirable. The present study also indicates that the solutions from the 1st-order backward scheme give the largest film thickness among all the solutions from different schemes at the same mesh size.
Hybrid Flexure Pivot-Tilting Pad Gas Bearings: Analysis and Experimental Validation
Authors: San Andrés Luis
Published: July 2006

Gas film bearings offer unique advantages enabling successful deployment of high-speed microturbomachinery. Current applications encompass micro power generators, air cycle machines, and turbo expanders. Mechanically complex gas foil bearings are in use; however, their excessive cost and lack of calibrated predictive tools deter their application to mass-produced oil-free turbochargers, for example. The present investigation advances the analysis and experimental validation of hybrid gas bearings with static and dynamic force characteristics desirable in high-speed turbomachinery. These characteristics are adequate load support, good stiffness and damping coefficients, low friction and wear during rotor startup and shutdown, and most importantly, enhanced rotordynamic stability at the operating speed. Hybrid (hydrostatic/hydrodynamic) flexure pivot-tilting pad bearings demonstrate superior static and dynamic forced performance than other geometries as evidenced in a high-speed rotor-bearing test rig. A computational model including the effects of external pressurization predicts the rotordynamic coefficients of the test bearings and shows good correlation with measured force coefficients, thus lending credence to the predictive model. In general, direct stiffnesses increase with operating speed and external pressurization, whereas damping coefficients show an opposite behavior. Predicted mass flow rates validate the inherent restrictor-type orifice flow model for external pressurization. Measured coast-down rotor speeds demonstrate very low-friction operation with large system time constants. Estimated drag torques from the gas bearings indirectly validate the recorded system time constant.
Occurrence of a Noncentral Dimple in Squeezing EHL Contacts
Authors: Guo F. , Kaneta M. , Wang J. , Nishikawa H. , Yang P.
Published: July 2006

Previous studies about pure squeeze elastohydrodynamic lubrication (EHL) have disclosed a film profile with a central dimple. Two problems about pure squeeze EHL are numerically solved in this paper. One is for a very small initial impact gap, and the other is the response of a squeezed EHL conjunction under stepwise loads. None of them result in the familiar film with a central dimple, which can be attributed to the local squeeze effect generated in the periphery region. In the first problem, it has been found that when there is adequate oil present on the plate, with a decrease in the initial impact gap, a shallow circumferential dimple occurs at the periphery of the conjunction instead of the primary central dimple presented in previous studies. Correspondingly the minimum film thickness occurs at the central region. The effect of the initial impact velocity on the periphery dimple is also investigated. In the second problem, the response of a conjunction subjected to a prescribed stepwise load is studied. When the first step load is applied, a central dimple film is produced. When the applied load is increased with a second step load, a periphery dimple appears, similar to that in the first problem. The local squeeze effect for the present numerical periphery dimple has been observed in previous experiments under similar conditions.
The Effect of Inertia on Radial Flows—Application to Hydrostatic Seals
Authors: Brunetière Noël , Tournerie Bernard
Published: July 2006

A theoretical study of thin fluid film flows between rotating and stationary disks is presented. Inertia terms are included using an averaged method. It is assumed that inertia effects do not influence the shape of velocity profiles. It is shown that this assumption applies in many cases encountered in fluid film lubrication. The model is validated by comparison with experimental data and previous theoretical studies. A thermoelastohydrodynamic analysis of a hydrostatic seal is performed. The substantial influence of inertia terms on leakage rate prediction is demonstrated.
Improvement of Punch Profiles for Elastic Circular Contacts
Authors: Glovnea Marilena , Diaconescu Emanuel
Published: July 2006

Machine design and electrical contacts involve frequently elastic circular contacts subjected to normal loads. Depending on geometry, these may be Hertzian or surface contacts. Both possess highly nonuniform pressure distributions which diminish contact load carrying capacity. The achievement of a uniform pressure distribution would be ideal to improve the situation, but this violates stress continuity. Instead, the generation of a uniform pressure over most of contact area can be sought. Generally, equivalent punch profile which generates this pressure is found by numerical evaluation of double integrals. This paper simplifies the derivation of punch profile by using an existing correspondence between a polynomial punch surface and elastically generated pressure. First, an improved pressure profile is proposed seeking to avoid high Huber-Mises-Hencky stresses near contact surface. Then, this is approximated by the product between typical Hertz square root and an even polynomial, which yields directly the punch profile. Formulas for normal approach and central pressure are derived.
Squeeze Effects in a Flat Liquid Bridge Between Parallel Solid Surfaces
Authors: Meurisse Marie-Hélène , Querry Michel
Published: July 2006

When a liquid lubricant film fractionates into disjointed liquid bridges, or a unique liquid bridge forms between solid surfaces, capillary forces strongly influence the action of the fluid on the solid surfaces. This paper presents a theoretical analytical model to calculate the normal forces on the solid surfaces when squeezing a flat liquid bridge. The model takes into account hydrodynamic and capillary effects and the evolution of the geometry of the liquid bridge with time. It is shown that the global normal force reverses during the squeezing motion except in the case of perfect nonwetting; it is attractive at the beginning of the squeezing motion, and becomes repulsive at small gaps. When the external load is constant, capillary suction tends to accelerate the decrease in gap dramatically.
Characterization and Erosion Behavior of Plasma Sprayed NiCrAlY and Ni-20Cr Coatings on an Fe-based Superalloy
Authors: Mishra S. B. , Chandra K. , Prakash S.
Published: July 2006

Degradation of materials due to solid particle erosion is encountered in a variety of engineering industries, either at room temperature or elevated temperatures. Nickel-based coatings are commonly used in applications where wear resistance, combined with oxidation or hot corrosion resistance, is required. In the present work, NiCrAlY and Ni-20Cr metallic coatings were deposited on an iron-based superalloy by a shrouded plasma spray process. The coatings were characterized by scanning electron microscopy, optical microscopy, microhardness testing, and x-ray diffractometry. Erosion studies were conducted using an air-jet erosion test rig at a velocity of 40ms−1 and impingement angles of 30 and 90deg. Scanning electron microscopy was used to analyze the eroded surfaces. 3D surface roughness profiles of the eroded samples were taken using a Veeco Optical Profilometer. NiCrAlY coatings had slightly lower average porosity and lower microhardness as compared to Ni-20Cr coatings. The observed erosion rate of the NiCrAlY coatings, however was lower than that of the Ni-20Cr coatings at both 30 and 90deg impingement angles. Ni-20Cr coating had shown higher erosion rate at 90deg impingement angle than that at 30deg, whereas the effect of impingement angle on the erosion rate is negligible for plasma sprayed NiCrAlY coating. The higher bond strength of NiCrAlY coating might be one of the major contributing factors for lower erosion rate of NiCrAlY coating as compared to Ni-20Cr coating under the tested conditions. Erosion mechanisms of plasma sprayed coatings are discussed.
Approximate Analytical Model for Hertzian Elliptical Contact
Problems
Authors: Antoine J-F. , Visa C. , Sauvey C. , Abba G.
Published: July 2006

In rolling bearing analysis Hertzian contact theory is used to compute local contact stiffness. This theory does not have a closed form analytical solution and requires numerical calculations to obtain results. Using approximations of elliptical functions and with a mathematical study of Hertzian results, an empirical explicit formulation is proposed in this paper and allows us to obtain the dimensions, the displacement, and the contact stress with at least 0.003% precision and it can be applied to a large range of ellipticity of the contact surface.
Study of the Anti-Wear Properties of Coconut Oil Using Quantum Chemical Calculations and Tribological Tests
Authors: Jayadas N. H. , Nair K. Prabhakaran
Published: July 2006

In this paper Spartan 02, a molecular dynamics software, is used to analyze and predict the tribological properties of coconut oil in a qualitative manner on the basis of carbon chain length of the constituent fatty acids, their polarity (net electrostatic charge, Qr), the energies of the molecular orbitals E_HOMO (energy of the highest occupied molecular orbital), and E_LUMO (energy of the lowest unoccupied molecular orbital), and the heats of formations (H-Form) of the iron soaps of respective fatty acids. Tribological properties of the constituent fatty acids of coconut oil were evaluated using a four-ball tester as per ASTM D4172 method. The experimental results showed good correlation to the selected quantum chemical descriptors. The influence of an anti-wear additive on the tribological performance of coconut oil and the optimum additive concentration were also evaluated experimentally.
Platform for Modeling the Boundary Lubrication of Nominally Flat Metallic Contacts
Authors: Chang L.
Published: July 2006

This short paper describes a theoretical platform for modeling the boundary lubrication of nominally flat metallic contacts. The platform is of a general structure with four interrelated modules, each governing one of the four key processes of the problem. It is envisioned to be open ended allowing individual modules to be updated and/or replaced. The product and the outcome may provide an infrastructure for fundamental research in boundary lubrication among theoreticians and experimentalists and across several science/engineering disciplines.
Forced Resonant Migration of Pluto's Outer Satellites by Charon
Authors: Ward William R. , Canup Robin M.
Published: July 2006

Two small moons of Pluto have been discovered in low-eccentricity orbits exterior to Pluto's large satellite, Charon. All three satellite orbits are nearly coplanar, implying a common origin. It has been argued that Charon formed as a result of a giant impact with primordial Pluto. The orbital periods of the two new moons are nearly integer multiples of Charon's period, suggesting that they were driven outward by resonant interactions with Charon during its tidal orbital expansion. This could have been accomplished if Charon's orbit was eccentric during most of this orbital evolution, with the small moons originating as debris from the collision that produced Charon.
Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity
Authors: Westerling A. L. , Hidalgo H. G. , Cayan D. R. , Swetnam T. W.
Published: July 2006

Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.
Enhancement of In Vitro Growth of Pathogenic Bacteria by Norepinephrine: Importance of Inoculum Density and Role of Transferrin
Authors: O'Donnell Phyllis M. , Aviles Hernan , Lyte Mark , Sonnenfeld Gerald
Published: July 2006

Norepinephrine is a stress hormone that enhances bacterial growth. We examined the effects of a small inoculum on the norepinephrine-induced growth of species previously reported to be unaffected by norepinephrine. The results indicated that a reduced inoculum density is essential for observing norepinephrine-induced effects. Additional studies using serum-free media suggested that transferrin plays a role in norepinephrine-induced growth.
Method for Assessment of Viability and Morphological Changes of Bacteria in the Early Stage of Colony Formation on a Simulated Natural Environment
Authors: Shimomura Yumi , Ohno Ryuzo , Kawai Fusako , Kimbara Kazuhide
Published: July 2006

A quantitative analysis of changes in the physiological status of bacterial cells is a fundamental type of study in microbiological research. We devised a method for measuring the viability of bacteria in the early stage of colony formation on a simulated natural environment. In this method, a solid medium containing soil extract was used, and the formation of bacterial microcolonies on a membrane filter was determined by use of a laser scanning cytometer combined with live-dead fluorescent dyes. A polychlorinated biphenyl degrader,
Comamonas testosteroni
TK102, was used in this study. Surprisingly, approximately 20% of the microcolonies had their growth stopped and eventually died. In the presence of biphenyl, the growth arrest was increased to 50%, and filamentous cells were observed in the colonies. Predicted intermediate metabolites of biphenyl were added to the medium to determine the relationship between the change of viability and the production of metabolites, and the addition of 2,3-dihydroxybiphenyl showed low viability. The arrest was not observed to occur on nutrient-rich medium, suggesting that the change in viability might occur in a nutrient-poor natural condition. The results of this study demonstrated that toxic metabolites of xenobiotics might change cell viability in the natural environment.
Cladophora
(Chlorophyta) spp. Harbor Human Bacterial Pathogens in Nearshore Water of Lake Michigan
Authors: Ishii Satoshi , Yan Tao , Shively Dawn A. , Byappanahalli Muruleedhara N. , Whitman Richard L. , Sadowsky Michael J.
Published: July 2006

Cladophora glomerata
, a macrophytic green alga, is commonly found in the Great Lakes, and significant accumulations occur along shorelines during the summer months. Recently,
Cladophora
has been shown to harbor high densities of the fecal indicator bacteria
Escherichia coli
and enterococci.
Cladophora
may also harbor human pathogens; however, until now, no studies to address this question have been performed. In the present study, we determined whether attached
Cladophora
, obtained from the Lake Michigan and Burns Ditch (Little Calumet River, Indiana) sides of a breakwater during the summers of 2004 and 2005, harbored the bacterial pathogens Shiga toxin-producing
Escherichia coli
(STEC),
Salmonella
,
Shigella
, and
Campylobacter
. The presence of potential pathogens and numbers of organisms were determined by using cultural methods and by using conventional PCR, most-probable-number PCR (MPN-PCR), and quantitative PCR (QPCR) performed with genus- and toxin-specific primers and probes. While
Shigella
and STEC were detected in 100% and 25%, respectively, of the algal samples obtained near Burns Ditch in 2004, the same pathogens were not detected in samples collected in 2005. MPN-PCR and QPCR allowed enumeration of
Salmonella
in 40 to 80% of the ditch- and lakeside samples, respectively, and the densities were up to 1.6 × 10
3
cells per g
Cladophora
. Similarly, these PCR methods allowed enumeration of up to 5.4 × 10
2
Campylobacter
cells/g
Cladophora
in 60 to 100% of lake- and ditchside samples. The
Campylobacter
densities were significantly higher (P < 0.05) in the lakeside
Cladophora
samples than in the ditchside
Cladophora
samples. DNA fingerprint analyses indicated that genotypically identical
Salmonella
isolates were associated with geographically and temporally distinct
Cladophora
samples. However,
Campylobacter
isolates were genetically diverse. Since animal hosts are thought to be the primary habitat for
Campylobacter
and
Salmonella
species, our results suggest that
Cladophora
is a likely secondary habitat for pathogenic bacteria in Lake Michigan and that the association of these bacteria with
Cladophora
warrants additional studies to assess the potential health impact on beach users.
Diversity ofPlanctomycetesin Soil in Relation to Soil History and Environmental Heterogeneity
Authors: Buckley Daniel H. , Huangyutitham Varisa , Nelson Tyrrell A. , Rumberger Angelika , Thies Janice E.
Published: July 2006

Members of thePlanctomycetes, which were once thought to occur primarily in aquatic environments, have been discovered in soils on five continents, revealing that theseBacteriaare a widespread and numerically abundant component of microbial communities in soil. We examined the diversity ofPlanctomycetesin soil samples obtained from experimental plots at an agricultural site in order to assess the extent ofPlanctomycetesdiversity in soil, to determine whether management effects such as past land cover and compost addition affected the composition of thePlanctomycetescommunity, and to determine whether the observations made could provide insight into the ecological distribution of these organisms. Analysis ofPlanctomycetes16S rRNA gene sequences revealed a total of 312 ± 35 unique phylotypes in the soil at the site examined. The majority of thesePlanctomycetessequences were unique, and the sequences had phylogenetic affiliations that included all major lineages in thePlanctomycetaceae, as well as several novel groups of deeply divergentPlanctomycetes. Both soil management history and compost amendment had significant effects on thePlanctomycetesdiversity, and variations in soil organic matter, Ca2+content, and pH were associated with variations in thePlanctomycetescommunity composition. In addition,Planctomycetesrichness increased in proportion to the area sampled and was correlated with the spatial heterogeneity of nitrate, which was associated with the soil management history at the orchard site examined. This report provides the first systematic assessment of the diversity ofPlanctomycetesin soil and also provides evidence that the diversity of this group increases with area as defined by the general power law description of the taxon-area relationship.
Characterization of Emetic
Bacillus weihenstephanensis
, a New Cereulide-Producing Bacterium
Authors: Thorsen Line , Hansen Bjarne Munk , Nielsen Kristian Fog , Hendriksen Niels Bohse , Phipps Richard Kerry , Budde Birgitte Bjørn
Published: July 2006

Cereulide production has until now been restricted to the species
Bacillus cereus.
Here we report on two psychrotolerant
Bacillus weihenstephanensis
strains, MC67 and MC118, that produce cereulide. The strains are atypical with regard to pheno- and genotypic characteristics normally used for identification of emetic
B. cereus
strains. MC67 and MC118 produced cereulide at temperatures of as low as 8°C.
Further Comparison of Temperature Effects on Growth and Survival of
Clostridium perfringens
Type A Isolates Carrying a Chromosomal or Plasmid-Borne Enterotoxin Gene
Authors: Li Jihong , McClane Bruce A.
Published: July 2006

Clostridium perfringens
type A isolates can carry the enterotoxin gene (
cpe
) on either their chromosome or a plasmid, but food poisoning isolates usually have a chromosomal
cpe
gene. This linkage between chromosomal
cpe
isolates and food poisoning has previously been attributed, at least in part, to better high-temperature survival of chromosomal
cpe
isolates than of plasmid
cpe
isolates. In the current study we assessed whether vegetative cells and spores of chromosomal
cpe
isolates also survive better than vegetative cells and spores of plasmid
cpe
isolates survive when the vegetative cells and spores are subjected to low temperatures. Vegetative cells of chromosomal
cpe
isolates exhibited about eightfold-higher decimal reduction values (D values) at 4°C and threefold-higher D values at −20°C than vegetative cells of plasmid
cpe
isolates exhibited. After 6 months of incubation at 4°C and −20°C, the average log reductions in viability for spores of plasmid
cpe
isolates were about fourfold and about threefold greater, respectively, than the average log reductions in viability for spores from chromosomal
cpe
isolates.
C. perfringens
type A isolates carrying a chromosomal
cpe
gene also grew significantly faster than plasmid
cpe
isolates grew at 25°C, 37°C, or 43°C. In addition, chromosomal
cpe
isolates grew at higher maximum and lower minimum temperatures than plasmid
cpe
isolates grew. Collectively, these results suggest that chromosomal
cpe
isolates are commonly involved in food poisoning because of their greater resistance to low (as well as high) temperatures for both survival and growth. They also indicate the importance of proper low-temperature storage conditions, as well as heating, for prevention of
C. perfringens
type A food poisoning.
Phase-Variable Surface Structures Are Required for Infection of
Campylobacter jejuni
by Bacteriophages
Authors: Coward Chris , Grant Andrew J. , Swift Craig , Philp Jennifer , Towler Rebecca , Heydarian Mohammad , Frost Jennifer A. , Maskell Duncan J.
Published: July 2006

This study characterizes the interaction between
Campylobacter jejuni
and the 16 phages used in the United Kingdom typing scheme by screening spontaneous mutants of the phage-type strains and transposon mutants of the sequenced strain NCTC 11168. We show that the 16 typing phages fall into four groups based on their patterns of activity against spontaneous mutants. Screens of transposon and defined mutants indicate that the phage-bacterium interaction for one of these groups appears to involve the capsular polysaccharide (CPS), while two of the other three groups consist of flagellatropic phages. The expression of CPS and flagella is potentially phase variable in
C. jejuni
, and the implications of these findings for typing and intervention strategies are discussed.
Anaerobic Respiration on Tellurate and Other Metalloids in Bacteria from Hydrothermal Vent Fields in the Eastern Pacific Ocean
Authors: Csotonyi Julius T. , Stackebrandt Erko , Yurkov Vladimir
Published: July 2006

This paper reports the discovery of anaerobic respiration on tellurate by bacteria isolated from deep ocean (1,543 to 1,791 m) hydrothermal vent worms. The first evidence for selenite- and vanadate-respiring bacteria from deep ocean hydrothermal vents is also presented. Enumeration of the anaerobic metal(loid)-resistant microbial community associated with hydrothermal vent animals indicates that a greater proportion of the bacterial community associated with certain vent fauna resists and reduces metal(loid)s anaerobically than aerobically, suggesting that anaerobic metal(loid) respiration might be an important process in bacteria that are symbiotic with vent fauna. Isolates from Axial Volcano and Explorer Ridge were tested for their ability to reduce tellurate, selenite, metavanadate, or orthovanadate in the absence of alternate electron acceptors. In the presence of metal(loid)s, strains showed an ability to grow and produce ATP, whereas in the absence of metal(loid)s, no growth or ATP production was observed. The protonophore carbonyl cyanide
m
-chlorophenylhydrazone depressed metal(loid) reduction. Anaerobic tellurate respiration will be a significant component in describing biogeochemical cycling of Te at hydrothermal vents.
Estimation of
Staphylococcus aureus
Growth Parameters from Turbidity Data: Characterization of Strain Variation and Comparison of Methods
Authors: Lindqvist R.
Published: July 2006

Turbidity methods offer possibilities for generating data required for addressing microorganism variability in risk modeling given that the results of these methods correspond to those of viable count methods. The objectives of this study were to identify the best approach for determining growth parameters based on turbidity data and use of a Bioscreen instrument and to characterize variability in growth parameters of 34
Staphylococcus aureus
strains of different biotypes isolated from broiler carcasses. Growth parameters were estimated by fitting primary growth models to turbidity growth curves or to detection times of serially diluted cultures either directly or by using an analysis of variance (ANOVA) approach. The maximum specific growth rates in chicken broth at 17°C estimated by time to detection methods were in good agreement with viable count estimates, whereas growth models (exponential and Richards) underestimated growth rates. Time to detection methods were selected for strain characterization. The variation of growth parameters among strains was best described by either the logistic or lognormal distribution, but definitive conclusions require a larger data set. The distribution of the physiological state parameter ranged from 0.01 to 0.92 and was not significantly different from a normal distribution. Strain variability was important, and the coefficient of variation of growth parameters was up to six times larger among strains than within strains. It is suggested to apply a time to detection (ANOVA) approach using turbidity measurements for convenient and accurate estimation of growth parameters. The results emphasize the need to consider implications of strain variability for predictive modeling and risk assessment.
Simulating the Contribution of Coaggregation to Interspecies Hydrogen Fluxes in Syntrophic Methanogenic Consortia
Authors: Ishii Shun'ichi , Kosaka Tomoyuki , Hotta Yasuaki , Watanabe Kazuya
Published: July 2006

A simple model (termed the syntrophy model) for simulating the contribution of coaggregation to interspecies hydrogen fluxes between syntrophic bacteria and methanogenic archaea is described. We applied it to analyzing partially aggregated syntrophic cocultures with various substrates, revealing that large fractions of hydrogen molecules were fluxed in aggregates.