bluuebunny/crossref_metadata_2025 huggingface dataset:
The Thermal Conductivity of Nitrogen and Argon
Authors: Keyes F. G. , Vines R. G.
Published: February 2012

Recent measured values of the thermal conductivity of nitrogen are represented (140–348 C) over a range of pressure (400 atm) and also for argon for the same temperature range and a pressure of 140 atm. The conductivities have been reduced for “zero” pressure and the effect of pressure evaluated as (λp – λ0) or Δλ. The pressure effects are represented by the form Δλ = a1(p/T) + an(p/T)n. An exhaustive comparison of earlier data has not been carried out since the main objective at this time was to report our recent observations. However, most of the recent λ0 data have been formulated and compared in Table 1 (N2) and Table 5 (A). The equations for (N2) and (A) which are believed most satisfactory are the “ensemble” equations for λ0 following: (N2)λ0·103=2.433T1/21+208.8τ/1012τ(Watts/MC)(A)λ0·103=1.557T1/21+170.5τ/108τ(Watts/MC) The Δλ equations suggested are the following: (N2)Δλ=(λp−λ0)=13.56(p/T)+1.39(p/T)2P.Johannin(700C:1200atm)(N2)Δλ=(λp−λ0)=13.19(p/T)+3.35(p/T)3KeyesandVines(347C:400atm)(A)Δλ=(λp−λ0)=10.13(p/T)+5.99(p/T)2KeyesandVines(347C:140atm)
On the Mechanics of Vapor Bubble Collapse
Authors: Florschuetz L. W. , Chao B. T.
Published: February 2012

The mechanics of vapor bubble collapse under spherically symmetrical conditions is examined to ascertain the relative importance of the effects of liquid inertia and heat transfer on the collapse rate. A dimensionless parameter, Beff, is identified to characterize the mode of collapse. Discriminating values of this parameter are suggested for the simple case where the collapse is initiated by a step change in pressure or temperature. For heat transfer controlled collapse, a model is also proposed to account for the influence of a permanent gas present in the bubble. Experimental results for bubbles with initial radii ranging from 0.3 cm to 0.9 cm collapsing in water and ethyl alcohol at atmospheric pressure levels and under free fall conditions are presented. The pressure difference ranges from 12 cm Hg to 63 cm Hg and the corresponding degrees of subcooling are 5 deg C to 45 deg C. Data are also given for water vapor bubbles containing significant amounts of nitrogen, helium, and xenon. When compared with theory, reasonable agreements are obtained. For slowly collapsing bubbles, the significance of small translational velocities is brought to attention. Photographic evidences are also given for bubble instability under suitable conditions.
Laminar Pipe Flow With Mass Transfer Cooling
Authors: Peng Y. , Yuan S. W.
Published: February 2012

The effect of foreign coolant injection at the wall on the temperature distribution of a laminar flow of a fluid with variable transport and thermodynamic properties in a porous-wall pipe has been investigated. The velocity components, mass concentration, and temperature distribution were obtained by the solution of the Navier-Stokes equations, the diffusion equation, and the energy equation. A perturbation method was used to solve the first equations for small flows through the porous wall, and the eigenvalues in the latter two equations were calculated with the aid of the CDC 1604 computer. The results from this investigation depict the significant differences in both velocity distribution and temperature distribution between the present case of hydrogen coolant and the case of air coolant [1]. The results also show that the heat transfer coefficient at the wall in the present case is considerably smaller than the case of air-coolant injection.
Radiant Interchange Among Curved Specularly Reflecting Surfaces—Application to Cylindrical and Conical Cavities
Authors: Lin S. H. , Sparrow E. M.
Published: February 2012

A method of analysis is formulated for determining the radiant interchange among specularly reflecting surfaces, some or all of which may be nonplanar. The emitted radiant energy is diffusely distributed. The formulation makes use of the exchange factor, which has many of the properties of the diffuse-angle factor. Indeed, the exchange factor is constructed as a series, each term of which is a diffuse-angle factor multiplied by a power of the surface reflectance. A general formalism is developed for deriving the exchange factor. Application of the method of analysis is made to the cylindrical cavity of finite depth and to the conical cavity. Numerical results are then obtained both for the local and overall heat transfer for a wide range of the geometrical and radiative parameters. In general, it is found that specularly reflecting cavities are more efficient emitters and absorbers of radiant energy than are diffusely reflecting cavities.
Numerical Techniques for Boiling Flow Stability Analyses
Authors: Meyer J. E. , Reinhard E. A.
Published: February 2012

Approximations to mass, momentum, and energy equations are required for finite difference analyses of transient two-phase flow through a heated channel. The truncation error for mass and energy approximations can be reduced by use of the numerical techniques presented in this brief. These improvements are especially important in the study of boiling flow oscillation phenomena.
Film-Cooling Effectiveness With Injection Through a Porous Section
Authors: Goldstein R. J. , Shavit G. , Chen T. S.
Published: February 2012

An experimental study of the effectiveness of film cooling following secondary air injection through a porous section into a turbulent free stream is presented. Boundary-layer velocity and temperature profiles are described. The adiabatic wall temperatures are presented in terms of the film-cooling effectiveness. The effects of varying the secondary air temperature, the blowing rate, and the free-stream velocity are studied. It is found that the protection given to a surface downstream of a porous section through which air is injected compares favorably to earlier studies where the secondary air was injected nearly tangential to the surface.
The Effect of Anisotropic Scattering on Radiant Transport
Authors: Evans L. B. , Chu C. M. , Churchill S. W.
Published: February 2012

Numerical values are presented for the reflection and transmission of radiation falling obliquely on finite slabs of absorbing and anisotropically scattering material. The angular distribution for single scattering was represented by a finite series of Legendre polynomials. The method of Chandrasekhar was used to reduce the representation of radiant transport from an integrodifferential equation to a set of integral equations. This set of equations was solved reiteratively on a digital computer. Previous solutions have been limited to isotropic and Rayleigh scattering or infinite media. The results for different phase functions for single scattering can be interpreted reasonably well in terms of only the forward-scattered fraction.
A Dual-Element Transducer for Measuring High Gas-Stream Temperatures
Authors: Giedt W. H. , Chambers J. T.
Published: February 2012

An experimental evaluation of a dual-element transducer for measuring gas stream temperatures is described. Temperatures are inferred from simultaneous temperature-time measurements of two elements of identical geometry but unequal thermal capacity. The major effort was devoted to measurements in medium-temperature streams to prove the feasibility of the method. The accuracy of the results was within ±6 percent for measurements from 1950 to 2250 deg F, which was the best experimental accuracy predicted by an earlier analysis of the concept. A limited number of measurements were made in an oxyacetylene flame. The indicated flame temperatures were 4700 and 4789 deg F which agree within 5 percent with measurements made by sodium-line-reversal techniques for equivalent combustion conditions. A gas-stream temperature profile measurement is also presented.
Heat Transfer Across a Linearly Accelerated or Decelerated Laminar Boundary Layer
Authors: Bu¨yu¨ktu¨r A. R. , Kestin J.
Published: February 2012

The paper presents solutions to the boundary-layer equations for heat-transfer rates into an accelerated and decelerated boundary layer in the presence of a linearly varying free-stream velocity. The equations are solved for the case of constant coefficients with frictional heat neglected, but over a range of Prandtl numbers.
Film Cooling of an Adiabatic Flat Plate in Zero Pressure Gradient in the Presence of a Hot Mainstream and Cold Tangential Secondary Injection
Authors: Samuel A. E. , Joubert P. N.
Published: February 2012

Experimental investigations were conducted in order to clarify some of the problems of film cooling of an adiabatic flat plate in zero pressure gradient downstream of a tangential injection slot. The experimental conditions were a hot mainstream and cold secondary injection. Results are presented for wall temperature distributions at varying injected-to-mainstream mass flow ratios. Results are also presented of boundary layer temperature and velocity profiles in film cooling, for an injected-to-mainstream mass flow ratio of 0.88. The existing literature available in film cooling is reviewed.
Free Convection Heat Transfer Coefficients From Rectangular Vertical Fins
Authors: Welling John R. , Wooldridge C. B.
Published: February 2012

Vertical, rectangular, finned surfaces are used to effect heat transfer on much equipment. Lack of data showing the effect of various fin geometries on free-convection heat transfer prompted this experimentation. The results provide preliminary design data. For a given temperature, an optimum value of the ratio of fin height to the distance between fins is indicated. The way this ratio varies with fin temperature is also given.
Heat Transfer to Supercritical Water in Smooth-Bore Tubes
Authors: Swenson H. S. , Carver J. R. , Kakarala C. R.
Published: February 2012

Local forced convection heat-transfer coefficients for supercritical water flowing inside smooth-bore tubes were obtained experimentally over a range of pressures (3300 to 6000 psia) and bulk temperatures (167 to 1068 F). Because the thermophysical properties of supercritical fluids change rapidly with temperature in the pseudocritical range, conventional forced convection correlations were unable to fit the data. However, a satisfactory correlation for fully developed turbulent flow was obtained by properly modifying the conventional nondimensional model to account for the physical property variation across the boundary layer. Out of 2951 data points, 95 percent lie within ±15 percent of the correlation. It was also found that the same equation correlated supercritical pressure heat-transfer data of carbon dioxide over a wide range of conditions with good accuracy.
Heat Transfer From a Shrouded Rotating Disk to a Single Fluid Stream
Authors: Mitchell J. W. , Metzger D. E.
Published: February 2012

This paper presents the initial results of a model study to determine the heat-transfer characteristics of radial-flow gas turbines. A test facility was constructed and several unconventional experimental techniques were developed for use in the facility. An idealized model consisting of a shrouded rotating disk with a single radially inward airflow was studied. The flow pattern and heat-transfer behavior were analytically and experimentally determined. The experimentally determined heat transfer is correlated by an algebraic expression over the range of nondimensional parameters characteristic of radial-flow gas-turbine operation.
Heat Conduction From Circular Cylinders in Rarefied Gases
Authors: Springer G. S. , Ratonyi R.
Published: February 2012

A method is presented for calculating the conductive heat transfer through gases contained between two concentric cylinders. The method of Lees and Liu is extended to include incomplete thermal accommodation at the inner cylindrical surface, and a comparison is made between the two methods. These results are then compared to those of the low pressure and temperature jump methods. On the basis of this analysis, limits are obtained for the free-molecule, transition, temperature jump, and continuum regimes.
Heat and Mass Transfer to a Cryosurface in Free Convection
Authors: Barron R. F. , Han L. S.
Published: February 2012

Heat and mass transfer rates were measured experimentally and compared with analytically developed correlations for frost formation on a vertical flat plate in free convection. The plate was cooled internally to cryogenic temperatures (−310 F or liquid nitrogen temperatures), and both the laminar and turbulent flow regimes were investigated. In the laminar flow correlation, the effects of thermal diffusion and diffusion thermoeffect were included. The analytical and experimental heat transfer rates were in good agreement; however, the mass transfer results were affected by the presence of macromolecules of frost within the boundary layer.
Resonant Pulsating Flow and Convective Heat Transfer
Authors: Jackson T. W. , Purdy K. R.
Published: February 2012

The results of experiments on the behavior of a simple convective heat exchanger which was subjected to a resonant pulsating flow are described. A 3.86-in. ID horizontal, isothermal tube, 10 ft long, through which air was blown at Reynolds numbers from 2000 to 200,000, was used as the heat exchanger. Both the thermal and the hydrodynamic boundary layers started at the same position in the apparatus. Local heat transfer coefficients were obtained experimentally and compared to equations derived, using a superposition technique, for both the laminar and turbulent regimes.
Turbulent Heat Transfer in the Separated, Reattached, and Redevelopment Regions of a Circular Tube
Authors: Krall K. M. , Sparrow E. M.
Published: February 2012

Experiments were performed to determine the effect of flow separation on the heat-transfer characteristics of a turbulent pipe flow. The flow separation was induced by an orifice situated at the inlet of an electrically heated circular tube. The degree of flow separation was varied by employing orifices of various bore diameters. Water was the working fluid. The Reynolds number and the Prandtl number, respectively, ranged from 10,000 to 130,000 and from 3 to 6. The measurements show that the local heat-transfer coefficients in the separated, reattached, and redevelopment regions are several times as large as those for a fully developed flow. For instance, at the point of reattachment, the coefficients were 3 to 9 times greater than the corresponding fully developed values. In general, the increase of the heat-transfer coefficient owing to flow separation is accentuated as the Reynolds number decreases. The point of flow reattachment, which corresponds to a maximum in the distribution of the heat-transfer coefficient, was found to occur from 1.25 to 2.5 pipe dia from the onset of separation.
Dynamic Analysis and Experimental Measurements for a Single Fluid Heat Exchanger
Authors: Lall P. S. , Schoenhals R. J.
Published: February 2012

The Lagrangian method of description was used, as opposed to the Eulerian coordinate system, in studying the dynamic response of a single fluid heat exchanger. Experimental measurements are reported for a heated thin walled stainless steel tube. Comparison of the analytical and experimental results is given.
Heat Transfer During Film Condensation of a Liquid Metal Vapor
Authors: Sukhatme S. P. , Rohsenow W. M.
Published: February 2012

The object of this investigation is to resolve the discrepancy between theory and experiment for the case of heat transfer during film condensation of liquid metal vapors. Calculations from kinetic theory show that with liquid metals a significant thermal resistance can exist at the liquid-vapor interface. This resistance increases with decreasing vapor pressure and is dependent on the value of an accommodation coefficient, named the “condensation coefficient” in this case. Experimental work verifying this hypothesis of a liquid-vapor interfacial resistance is presented here for mercury condensing at low pressures in the absence of noncondensable gases on a vertical nickel surface.
Sudden Contraction Losses in Two-Phase Flow
Authors: Geiger G. E. , Rohrer W. M.
Published: February 2012

The experimentally determined pressure drops due to a sudden contraction in two-phase flow in round pipes is given as a function of system pressure, flowing mixture quality, contraction area ratio, and mass velocity. The theoretical equation derived for the resulting pressure drop is ΔPc=G322gcρ¯[1−σ2+K¯TPC] where KTPC is a parameter independent of mass velocity. This parameter was evaluated for three different two-phase flow models. It is shown that the fog-flow (homogeneous) model gives the best correlation of data over the whole range of conditions studied. The range of pressures studied was 200–500 psia; the area ratios varied from 0.144 to 0.398; the mass velocity varied from 0.52 × 106 to 4.82 × 106 lb/hr-ft2. The fluid used in this study was water.
Radiative Exchange Among Non-Lambert Surfaces
Authors: Sarofim A. F. , Hottel H. C.
Published: February 2012

A method is presented for calculating radiative exchange in enclosures the reflectance of whose surfaces can be approximated by the sum of a diffuse and a specular component. As illustrations of application of the method, the radiative fluxes between the surfaces of two concentric spheres (or infinitely long concentric cylinders) and among the faces of a cube are calculated.
Heat Transfer and Flow Characteristics of Porous Matrices With Radiation as a Heat Source
Authors: Chiou J. P. , El-Wakil M. M.
Published: February 2012

A theoretical and experimental study of the heat transfer and flow friction characteristics of matrices of high porosity, with incident radiation from one side resulting in an exponential heat source, and with air as a coolant, is reported. In the theory, a transient solution of simultaneous convection and radiation heat transfer equations has been worked out. Used with experimental data taken in the unsteady state, it resulted in the calculation of volumetric heat transfer coefficients by convection in the matrices. Correlations with Reynolds numbers, based on a characteristic length obtained by equating pressure drops to the sum of viscous and inertia resistance terms, were obtained. Using the more familiar hydraulic radius did not result in reducing the relationships to a unified form. The matrices used in the experiments were formed from slit-and-expanded aluminum foils, blackened to high radiant absorptivity. The results of the investigation are believed useful in many solar, nuclear, and space applications.
The Relation Between Bubble Diameter and Frequency of Removal From a Sphere During Film Boiling
Authors: Frederking T. H. K. , Daniels D. J.
Published: February 2012

The kinematics of vapor removal from a sphere has been investigated during film boiling in saturated liquid nitrogen. New experimental data are presented concerning the bubble frequency f and diameter D. In spite of film boiling conditions, the results may be correlated with the nucleate boiling relation, f(D)1/2 ≈ 17.5 (cm)1/2 sec, proposed by McFadden and Grassmann.
Laminar Forced Convection of a Dissipative Fluid in a Channel
Authors: Tyagi V. P.
Published: February 2012

In the present study, the steady laminar forced convection problem of heat transfer in the fully developed constant property flow of liquids through a certain class of channels is analyzed by considering the contribution of heat due to viscosity. The effects of viscous dissipation on the heat transfer are emphasized. A class of sufficiently long straight channels with uniform cross-sectional area is chosen such that the solutions for velocity and temperature fields are deducible directly from the equations of the boundary curves. The wall temperature is allowed to vary linearly in the axial direction, and some heat-source distribution, other than that due to viscosity, is imagined to be present in the flow field. The general solution of the problem for the given class of channels is given directly by avoiding the details of the mathematical treatment of the governing equations. To illustrate the general mathematical derivations and to visualize the effects of viscous dissipation, some basic examples have been investigated and the graphical representation of several relevant results is given in a number of figures. In the last section of this study, various relevant results and figures have been discussed from the point of view of viscous dissipation phenomena.
Analog Solution of Laminar Heat Transfer in Noncircular Ducts by Moire´ Method and Point-Matching
Authors: Cheng K. C.
Published: February 2012

The problem of fully developed laminar flow heat transfer in polygonal ducts with axially uniform wall heat flux is considered. The well-known analogy between laminar heat transfer in ducts and simply supported thin flat plates of the same shape under uniform lateral loading is used to obtain heat transfer characteristics. It is shown that both the fully developed laminar flow characteristics in noncircular ducts and the steady temperature distribution in infinitely long prismatical bars with uniform internal heat generation can also be obtained by the plate analogy based on the Dirichlet problem. The plate problem may be solved by the Moire´ method and point-matching technique, and it is pointed out that the former can be applied to ducts of any shape. For a square duct, the results from these two approximate methods are given, and comparisons are made which show good agreement with the exact solution.
The Interaction of Radiation and Convection in the Laminar Boundary Layer
Authors: Oliver Calvin C. , McFadden P. W.
Published: February 2012

The problem of simultaneous convection and radiation in the laminar boundary layer on a flat plate is formulated and solved. The plate surface is assumed black and the fluid medium is a perfect gas for which the mass absorption coefficient for radiation is considered to be independent of frequency and temperature. The solution is of the iterative type and includes effects of viscous dissipation, secondary emission and absorption, and incident external radiative fluxes. Illustrative examples of temperature profiles and local and average heat transfer rates are presented.
Internal Low Reynolds-Number Turbulent and Transitional Gas Flow With Heat Transfer
Authors: McEligot D. M. , Ormand L. W. , Perkins H. C.
Published: February 2012

The results of a semitheoretical and experimental investigation of the heat-transfer and frictional effects in air, nitrogen, and helium in steady flow in the downstream region of round tubes are presented. The constant-properties analysis for low Reynolds-number turbulent flow is evolved from an improved description of the adiabatic velocity profile, without modifying the Reynolds analogy assumption of equal eddy diffusivities. Data cover peak wall-to-bulk temperature ratios from near unity to 4.8 and entering Reynolds numbers from 1450 to 45,000. Low and moderate temperature-ratio data are used to confirm and to extend the analysis, while high temperature-ratio results are utilized for classification of flow regimes at high heating rates in the low Reynolds-number range.
Prediction of Heat Transfer From Laminar Boundary Layers, With Emphasis on Large Free-Stream Velocity Gradients and Highly Cooled Walls
Authors: Back L. H. , Witte A. B.
Published: February 2012

Laminar boundary-layer heat transfer and shear-stress predictions from existing similarity solutions are extended in an approximate way to perfect gas flows with a large free-stream velocity gradient parameter β and variable density-viscosity product ρμ across the boundary layer resulting from a highly cooled wall. The dimensionless enthalpy gradient at the wall gw′, to which the heat flux is related, is found not to vary appreciably with β. Thus the application of similarity solutions on a local basis to predict heat transfer from accelerated flows to an arbitrary surface may be a reasonable approximation involving a minimum amount of calculation time. Unlike gw′, the dimensionless velocity gradient at the wall fw″, to which the shear stress is related, is strongly dependent on β.
Radiative Heat Transfer Through an Absorbing Boundary Layer
Authors: Fritsch C. A. , Grosh R. J. , Wildin M. W.
Published: February 2012

In this study, an analytical investigation is made of a method of shielding a surface from parallel beams of thermal radiation by distributed injection of a fluid containing absorbing particles into the boundary-layer flow over the surface near the stagnation point. Superposition of various solutions is used to obtain results for a wide range of parameter values from a relatively small number of functions. Three optical conditions of the surface are considered: Specular reflection, diffuse reflection, and black. It is found that injection of absorbing particles helps to shield the surface if the injection rate is relatively high.
Direct Monte Carlo Calculation of Radiative Heat Transfer in Vacuum
Authors: Corlett R. C.
Published: February 2012

A flexible digital-computer program, intended for engineering calculation of thermal radiation in real enclosures, is described. The method is a simple Monte Carlo application, which can be interpreted as direct mathematical simulation of photon histories. The formulation is based on possible specification of general biangular reflectance. Examples are presented for four simple configurations of surfaces with mixed specular-diffuse reflectivity. An advantage of this type of program is that complex formulations can be rapidly input for solution in a single pass. A disadvantage is the high direct computer cost of precise results.
Turbulent Free Convection in Near-Critical Water
Authors: Larson J. R. , Schoenhals R. J.
Published: February 2012

Heat transfer from a vertical flat plate by turbulent free convection to water near its thermodynamic critical point was studied analytically and experimentally. The analytical method of solution involved an integral technique as well as assumptions dealing with Reynolds analogy, the Blasius wall shear stress, and suitable velocity and temperature profiles. Measurements were made of the heat flux from a platinum ribbon suspended in a pressure vessel containing the test water. The ribbon was heated electrically by direct current. Its temperature was determined by resistance measurement combined with a previously obtained resistance-temperature calibration. The experimental results indicate reasonable agreement with the analytical prediction but could be improved with a better method of evaluating the Prandtl number. A correlation of the experimental data was developed and is given in terms of the usual dimensionless parameters.
PTEN Protein Phosphatase Activity Correlates with Control of Gene Expression and Invasion, a Tumor-Suppressing Phenotype, But Not with AKT Activity
Authors: Tibarewal Priyanka , Zilidis Georgios , Spinelli Laura , Schurch Nick , Maccario Helene , Gray Alexander , Perera Nevin M. , Davidson Lindsay , Barton Geoffrey J. , Leslie Nick R.
Published: February 2012

The lipid and protein phosphatase activities of PTEN are both required for glioma cell invasion and many of its effects on gene expression.
Winging It
Authors: Zahn Laura M.
Published: February 2012

The comparison of two closely related parasitoid wasps reveals the genetic bases for differences in size and shape of male
Nasonia
wings.
Curbing the Other Side
Authors: Stern Peter R.
Published: February 2012

Coordinating the right and left sides of the brain is mediated by the inhibition of activation in neuronal dendrites.
Quality Assessment of U.S. Marketplace Vancomycin for Injection Products Using High-Resolution Liquid Chromatography-Mass Spectrometry and Potency Assays
Authors: Hadwiger Michael E. , Sommers Cynthia D. , Mans Daniel J. , Patel Vikram , Boyne Michael T.
Published: February 2012

In response to a published concern about the potency and quality of generic vancomycin products, the United States Food and Drug Administration investigated a small sampling of the vancomycin products available in North America with regard to purity, content, and potency. To facilitate identification of impurities, a new liquid chromatography method was developed using high-resolution mass spectrometry in addition to diode array detection to characterize impurities in several commercial products. Furthermore, a microbiological assay was utilized to link the analytical profiles with an
in vitro
potency. All products tested met the quality specifications outlined in the United States Pharmacopeia (USP) (vancomycin hydrochloride for injection monograph) for impurities and potency (USP, Vancomycin hydrochloride for injection. United States Pharmacopeia and National Formulary, vol USP 34-NF 29, 2011).
Chromosomal Mutations Responsible for Fluoroquinolone Resistance in Ureaplasma Species in the United States
Authors: Xiao Li , Crabb Donna M. , Duffy Lynn B. , Paralanov Vanya , Glass John I. , Waites Ken B.
Published: February 2012

We sequenced the full lengths of the
gyrA
,
gyrB
,
parC
, and
parE
genes in 13 fluoroquinolone-resistant
Ureaplasma
isolates (levofloxacin MICs, 4 to 32 μg/ml) and 10 susceptible isolates (MICs ≤ 2 μg/ml). Mutations were detected in all resistant isolates but in none of the susceptible isolates. The most prevalent mutation was the S83L substitution in the ParC protein. No plasmid-mediated fluoroquinolone resistance genes were detected.
Expression of the Resistance-Nodulation-Cell Division Pump AdeIJK in Acinetobacter baumannii Is Regulated by AdeN, a TetR-Type Regulator
Authors: Rosenfeld Nicolas , Bouchier Christiane , Courvalin Patrice , Périchon Bruno
Published: February 2012

Resistance-nodulation-division efflux system AdeIJK contributes to intrinsic resistance to various drug classes inAcinetobacter baumannii. By whole-genome sequencing, we have identified in clinical isolate BM4587 theadeNgene, located 813 kbp upstream fromadeIJK, which encodes a TetR transcriptional regulator. In one-step mutant BM4666 overexpressingadeIJK, the deletion of cytosine 582 (C582) in the 3′ portion of this gene was responsible for a frameshift mutation resulting in the deletion of the seven C-terminal residues.trans-Complementation of this BM4587 derivative with a plasmid expressingadeNrestored antibiotic susceptibility to the host associated with the loss ofadeJoverexpression. The inactivation ofadeNin BM4587 led to a diminished susceptibility to antibiotics that are substrates for AdeIJK and to a 5-fold increase inadeJexpression. Taken together, these results indicate that AdeN represses AdeIJK expression. Quantitative reverse transcription-PCR (qRT-PCR) demonstrated that AdeN is constitutively expressed in BM4587 and does not regulate its own expression. Deletion of cytosine 582 and a 394-bp deletion of the 3′ part ofadeNwere found in independent one-stepadeIJK-overexpressing mutants selected from clinical isolates BM4667 and BM4651, respectively. The corresponding alterations were located in the α9 helix, which is known to be involved in dimerization, a process essential for the activity of TetR regulators. TheadeNgene was detected in all of the 30A. baumanniistrains tested and inAcinetobacter calcoaceticus,Acinetobacter nosocomialis, andAcinetobacter pittii.
Vitamin B
12
-Mediated Restoration of Defective Anaerobic Growth Leads to Reduced Biofilm Formation in Pseudomonas aeruginosa
Authors: Lee Kang-Mu , Go Junhyeok , Yoon Mi Young , Park Yongjin , Kim Sang Cheol , Yong Dong Eun , Yoon Sang Sun
Published: February 2012

Pseudomonas aeruginosa
undergoes cell elongation and forms robust biofilms during anaerobic respiratory growth using nitrate (NO
3
−
) as an alternative electron acceptor. Understanding the mechanism of cell shape change induced upon anaerobiosis is crucial to the development of effective treatments against
P. aeruginosa
biofilm infection. Here, we uncovered the molecular basis of anaerobiosis-triggered cell elongation and identified vitamin B
12
to be a molecule that can reinstate defective anaerobic growth of
P. aeruginosa
. The ratio of total cellular DNA content to protein content was significantly decreased in the PAO1 strain grown under anaerobic conditions, indicating that DNA replication is impaired during anaerobic growth. Anaerobic growth of PAO1 reached a higher cell density in the presence of vitamin B
12
, an essential coenzyme of class II ribonucleotide reductase. In addition, cell morphology returned to a normal rod shape and transcription of stress-response genes was downregulated under the same anaerobic growth conditions. These results suggest that vitamin B
12
, the production of which was suppressed during anaerobic growth, can restore cellular machineries for DNA replication and therefore facilitate better anaerobic growth of
P. aeruginosa
with normal cell division. Importantly, biofilm formation was substantially decreased when grown with vitamin B
12
, further demonstrating that anaerobiosis-induced cell elongation is responsible for robust biofilm formation. Taken together, our data reveal mechanistic details of a morphological change that naturally occurs during anaerobic growth of
P. aeruginosa
and illustrates the ability of vitamin B
12
to modulate the biofilm-forming capacity of
P. aeruginosa
under such condition.
Genome Sequence of Sphingomonas sp. Strain PAMC 26605, Isolated from Arctic Lichen (Ochrolechia sp.)
Authors: Shin Seung Chul , Ahn Do Hwan , Lee Jong Kyu , Kim Su Jin , Hong Soon Gyu , Kim Eun Hye , Park Hyun
Published: February 2012

The endosymbiotic bacterium
Sphingomonas
sp. strain PAMC 26605 was isolated from Arctic lichens (
Ochrolechia
sp.) on the Svalbard Islands. Here we report the draft genome sequence of this strain, which could provide further insights into the symbiotic mechanism of lichens in extreme environments.
Genome Sequence of Streptomyces sp. Strain TOR3209, a Rhizosphere Microecology Regulator Isolated from Tomato Rhizosphere
Authors: Hu Dong , Li Xiaozhi , Chang Yueli , He Huan , Zhang Cuimian , Jia Nan , Li Hongtao , Wang Zhanwu
Published: February 2012

Streptomyces
sp. strain TOR3209, isolated from tomato rhizosphere, can regulate the rhizosphere microecology of a variety of crops. Strain TOR3209 could improve plant systemic resistance and promote plant growth. Here, the genome sequence of strain TOR3209 is reported, providing the molecular biological basis of the regulation mechanism of rhizosphere microecology.
Draft Genome Sequence of Marine Streptomyces sp. Strain W007, Which Produces Angucyclinone Antibiotics with a Benz[a]anthracene Skeleton
Authors: Qin Song , Zhang Hongyu , Li Fuchao , Zhu Benwei , Zheng Huajun
Published: February 2012

A series of angucyclinone antibiotics have been isolated from marineStreptomycessp. strain W007 and identified. Here, a draft genome sequence ofStreptomycessp. W007 is presented. The genome contains an intact biosynthetic gene cluster for angucyclinone antibiotics, which provides insight into the combinatorial biosynthesis of angucyclinone antibiotics produced by marine streptomycetes.
Complete Genome Sequence of the Highly Hemolytic Strain Bacillus cereus F837/76
Authors: Auger Sandrine , Galleron Nathalie , Ségurens Béatrice , Dossat Carole , Bolotin Alexander , Wincker Patrick , Sorokin Alexei
Published: February 2012

Highly hemolytic strain
Bacillus cereus
F837/76 was isolated in 1976 from a contaminated prostate wound. The complete nucleotide sequence of this strain reported here counts nearly 36,500 single-nucleotide differences from the closest sequenced strain,
Bacillus thuringiensis
Al Hakam. F827/76 also contains a 10-kb plasmid that was not detected in the Al Hakam strain.
Genome Sequence of the Soybean Symbiont Sinorhizobium fredii HH103
Authors: Weidner Stefan , Becker Anke , Bonilla Ildefonso , Jaenicke Sebastian , Lloret Javier , Margaret Isabel , Pühler Alfred , Ruiz-Sainz José E. , Schneiker-Bekel Susanne , Szczepanowski Rafael , Vinardell José María , Zehner Susanne , Göttfert Michael
Published: February 2012

Sinorhizobium fredii
HH103 is a fast-growing rhizobial strain that is able to nodulate legumes that develop determinate nodules, e.g., soybean, and legumes that form nodules of the indeterminate type. Here we present the genome of HH103, which consists of one chromosome and five plasmids with a total size of 7.22 Mb.
Draft Genome Sequence of Clostridium sporogenes PA 3679, the Common Nontoxigenic Surrogate for Proteolytic Clostridium botulinum
Authors: Bradbury Mark , Greenfield Paul , Midgley David , Li Dongmei , Tran-Dinh Nai , Vriesekoop Frank , Brown Janelle L.
Published: February 2012

Clostridium sporogenes
PA 3679 is widely used as a nontoxigenic surrogate for proteolytic strains of
Clostridium botulinum
in the derivation and validation of thermal processes in food. Here we report the draft assembly and annotation of the
C. sporogenes
PA 3679 genome. Preliminary analysis demonstrates a high degree of relatedness between
C. sporogenes
PA 3679 and sequenced strains of proteolytic
C. botulinum
.
Draft Genome Sequence of Pseudomonas psychrotolerans L19, Isolated from Copper Alloy Coins
Authors: Espírito Santo Christophe , Lin Yanbing , Hao Xiuli , Wei Gehong , Rensing Christopher , Grass Gregor
Published: February 2012

We report the draft genome sequence of
Pseudomonas psychrotolerans
strain L19, isolated from a European 50-cent copper alloy coin. Multiple genes potentially involved in copper resistance were identified; however, it is unknown if these copper ion resistance determinants contribute to prolonged survival of this strain on dry metallic copper.
Genome Sequence of the Facultative Anaerobic Arsenite-Oxidizing and Nitrate-Reducing Bacterium Acidovorax sp. Strain NO1
Authors: Huang Yinyan , Li Hang , Rensing Christopher , Zhao Kai , Johnstone Laurel , Wang Gejiao
Published: February 2012

Acidovorax
sp. strain NO1, isolated from gold mine soil, was shown to be a facultative anaerobic arsenite-oxidizing and nitrate-reducing bacterium. The reported draft genome predicts the presence of genes involved in arsenic metabolism, nitrate reduction, phosphate transport, and multiple metal resistances and indicates putative horizontal gene transfer events.
Genome Sequence of the Cycloprodigiosin-Producing Bacterial Strain Pseudoalteromonas rubra ATCC 29570
T
Authors: Xie Bin-Bin , Shu Yan-Li , Qin Qi-Long , Rong Jin-Cheng , Zhang Xi-Ying , Chen Xiu-Lan , Zhou Bai-Cheng , Zhang Yu-Zhong
Published: February 2012

The cycloprodigiosin biosynthetic gene cluster has not been reported. We sequenced the genome of a cycloprodigiosin-producing bacterial strain,
Pseudoalteromonas rubra
ATCC 29570
T
. Analysis revealed a probable cycloprodigiosin biosynthetic cluster, providing a good model for the study of cycloprodigiosin synthesis and regulation.
Draft Genome Sequence of Vibrio fischeri SR5, a Strain Isolated from the Light Organ of the Mediterranean Squid Sepiola robusta
Authors: Gyllborg Mattias C. , Sahl Jason W. , Cronin David C. , Rasko David A. , Mandel Mark J.
Published: February 2012

Here, we describe the draft genome sequence of
Vibrio fischeri
SR5, a squid symbiotic isolate from
Sepiola robusta
in the Mediterranean Sea. This 4.3-Mbp genome sequence represents the first
V. fischeri
genome from an
S. robusta
symbiont and the first from outside the Pacific Ocean.
Two new genera of fungal trichomycetes, Bactromyces and Laculus (Harpellales), from Nova Scotia, Canada
Authors: William R.T. , Strongman D.B.
Published: February 2012

The gut lumen of immature aquatic insects is colonized by a unique community of protistan and fungal organisms, collectively called trichomycetes. The species diversity of fungal trichomycetes appears to be high, with new taxa published regularly. Bactromyces fluminalis and Laculus insecticola , species belonging to two new genera of fungal trichomycetes, are described from stonefly and mayfly nymphs, respectively. Bactromyces fluminalis was collected from a stream habitat in Long Lake Provincial Park, Halifax, Nova Scotia, Canada, while Laculus insecticola was found in a lentic environment (Governor Lake) in Timberlea, Nova Scotia, a suburb within the Halifax Regional Municipality. In addition to these new taxa, a new species, Pteromaktron timberleaense , in this previously monotypic genus is described from the hindgut of a mayfly collected from a stream in Timberlea, Nova Scotia. This discovery makes new material available for study, since it appears the type specimen for this genus is lost.
Dendrochronological evidence of shrub growth suppression by trees in a subarctic lichen woodland
Authors: Boudreau Stéphane , Villeneuve-Simard Marie-Pascale
Published: February 2012

Expansion of deciduous shrub species in open subarctic landscapes has been reported at several locations around the circumpolar region. However, few data are available to evaluate the response of shrub species in forested ecosystems. For this study, we conducted a dendrochronological analysis to compare the establishment and growth of Betula glandulosa Michx. individuals prior to and after an experimental removal of tree cover (1987) in a lichen woodland located at the boreal forest – tundra ecotone. Tree removal was followed by a B. glandulosa recruitment pulse. It is likely that the newly established seedlings benefited more from heavy trampling during tree removal, which destroyed the lichen cover, than from tree removal itself. A strong growth increase after tree removal suggests that the black spruce tree cover suppressed B. glandulosa growth prior to 1987. Moreover, while radial growth for the period prior to tree removal was not a function of the number of growing degree-days during the growing season, the same climatic variable explained 46% of the growth variability in the second period. These results suggest that the presence of a tree cover might limit the response of shrub species to climate change in forested ecosystems.
Experimental evidence of size effect in soil cracking
Authors: Lakshmikantha M.R. , Prat Pere C. , Ledesma Alberto
Published: February 2012

Results of an experimental study on the formation of crack patterns during drying of a soil paste are presented. The objective is to ascertain whether fracture mechanics plays a significant role in explaining the process of formation and propagation of cracks during drying of soils due to changes in environmental conditions such as temperature and humidity. The experiments consist of five geometrically similar rectangular specimens in two series of different thicknesses, subjected to drying conditions in an environment-controlled laboratory. Cracking initiates shortly before the soil reaches a near-solid quasi-brittle consistency. Although crack initiation can be explained by classical soil mechanics effective stress theory, crack development and propagation appear to be energy-driven. The results prove that cracking stress does depend on the size of the specimen and suggest that fracture mechanics might be applicable to soil cracking, at least in the context of the present research. Fracture toughness of the soil used was determined using compact tension tests at different water contents. Its tensile strength was also determined by a direct method for two natural specific weights (bulk density) and two dry specific weights with different water contents.
Interpreting pore-water pressure changes induced by water table fluctuations and mechanical loading due to soil moisture changes
Authors: Anochikwa Collins Ifeanyichukwu , van der Kamp Garth , Barbour S. Lee
Published: February 2012

Pore pressures within saturated subsurface formations respond to stress changes due to loading as well as to changes in pore pressure at the boundaries of the formation. The pore-pressure dynamics within a thick aquitard in response to water table fluctuations and mechanical loading due to soil moisture changes have been simulated using a coupled stress–strain and groundwater flow finite element formulation. This modelling approach isolates the component of pore-pressure response of soil moisture loading from that caused by water table fluctuations, by using a method of superposition. In this manner, the contributions to pore-pressure fluctuations that occur as a result of surface moisture loading (e.g., precipitation, evapotranspiration) can be isolated from the pore-pressure record. The required elastic stress–strain properties of the aquitard were obtained from the measured pore-pressure response to barometric pressure changes. Subsequently, the numerical simulations could be calibrated to the measured response by adjusting only the hydraulic conductivity. This paper highlights the significance of moisture loading effects in pore-pressure observations and describes an efficient technique for obtaining in situ stress–strain and hydraulic properties of near-surface aquitards.
AN ACTIVE ACCESS-POINT SELECTION APPROACH FOR DEPENDABLE WIRELESS MESH NETWORKS
Authors: FUNABIKI NOBUO , SHIMIZU JUNKI , HATA MASAHARU , TOMISATO SHIGERU , NAKANISHI TORU , WATANABE KAN
Published: February 2012

As an inexpensive, flexible, and scalable Internet-access wireless network, we have studied the architecture, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET) that adopts multiple access-points (APs) connected through wireless links. WIMNET can improve the dependability to failures of APs and/or their links by allocating APs redundantly in the network field. Because redundant APs may increase the operational cost and degrade the throughput due to increasing radio interferences, only the necessary APs for connectivity between the hosts and the Internet gateway should be activated in communications. In this paper, we first define the active AP selection problem of selecting the minimum number of active APs, and prove the NP-completeness of its decision version through reduction from the known minimum set cover problem. Then, we propose an active AP selection algorithm of deactivating APs one by one until no more AP can be deactivated. Due to the limited transmission capacity in WIMNET, we further present an algorithm extension for throughput maximization. We verify the effectiveness of our proposal through simulations in three instances, where the number of active APs is reduced by more than 40% and the throughput is improved by more than 10% from the original in any instance.
ON THE FOUNDATIONS OF MATHEMATICAL ECONOMICS
Authors: ROSSER J. BARKLEY
Published: February 2012

Kumaraswamy Vela Velupillai74 presents a constructivist perspective on the foundations of mathematical economics, praising the views of Feynman in developing path integrals and Dirac in developing the delta function. He sees their approach as consistent with the Bishop constructive mathematics and considers its view on the Bolzano-Weierstrass, Hahn-Banach, and intermediate value theorems, and then the implications of these arguments for such "crown jewels" of mathematical economics as the existence of general equilibrium and the second welfare theorem. He also relates these ideas to the weakening of certain assumptions to allow for more general results as shown by Rosser51 in his extension of Gödel's incompleteness theorem in his opening section. This paper considers these arguments in reverse order, moving from the matters of economics applications to the broader issue of constructivist mathematics, concluding by considering the views of Rosser on these matters, drawing both on his writings and on personal conversations with him.
REFLECTIONS ON MATHEMATICAL ECONOMICS IN THE ALGORITHMIC MODE
Authors: VELUPILLAI K. VELA
Published: February 2012

Non-standard analysis can be harnessed by the recursion theorist. But as a computable economist, the conundrums of the Löwenheim-Skolem theorem and the associated Skolem paradox, seem to pose insurmountable epistemological difficulties against the use of algorithmic non-standard analysis. Discontinuities can be tamed by recursive analysis. This particular kind of taming may be a way out of the formidable obstacles created by the difficulties of Diophantine Decision Problems. Methods of existence proofs, used by the "classical" mathematician — even if not invoking the axiom of choice — cannot be shown to be equivalent to the exhibition of an instance in the sense of a constructive proof. These issues were prompted by the fertile and critical contributions to this special issue.