bluuebunny/crossref_metadata_2025 huggingface dataset:
Student Hits in an Internet‐Supported Course: How Can Instructors Use Them and What Do They Mean?
Authors: Baugher Varanelli Weisbord Dan, Andrew, Ellen
Published: December 2003

The world of education is changing as Web‐based technology and courseware are increasingly used for delivery of course material. In this environment, instructors may need new measures for determining student involvement, and ultimately student performance. This study examines whether hits to a Web site have any value for predicting student performance in a traditional course supported by Web activities. Total Hits at the end of the semester was used as one measure. Hit Consistency, determined by assigning a 0 when no hits occurred between class meetings and by assigning a 1 when one or more hits occurred between class meetings, was another. Hit Consistency was significantly correlated with course average (r= .37, p < .001) for 108 students in two course sections. Hit Consistency started to show a significant relationship with course average by the third week (or class). Total Hits was not found to significantly correlate with course average (r= .08, p > .05) at the end of the semester or during any week. These results suggest that students who consistently access a Web site will perform better than those who do not. When Hit Consistency and Total Hits were entered as independent variables into a stepwise regression with course average as the dependent variable, the model was enhanced by the addition of Total Hits after Hit Consistency was entered (R= .43, p < .001). Hierarchical regression analysis in which cumulative grade point average was entered as the first controlling variable suggested that online access may go beyond the predictive value of achievement alone for predicting course performance with Hit Consistency appearing to be the dominant causal variable.
Graduate Business Students Performance with Synchronous and Asynchronous Interaction e‐Learning Methods
Authors: Clouse Shawn F. , Evans Gerald E.
Published: December 2003

The effects of synchronous and asynchronous lectures and interaction formats were examined with graduate business students in on‐campus and off‐campus MBA programs. The dependent variables were scores on exams questions and learning styles and cognitive styles were used as covariates. The results indicated significant differences for discussion and lecture format and for on‐campus and off‐campus students. The results were discussed relative to learning in electronic environments.
Evaluation of a Computer‐Supported Learning System
Authors: Janicki Thomas , Steinberg Geoffrey
Published: December 2003

Educational content on the Internet is rapidly increasing. Academics and businesses are placing more course material online to supplement classroom and business training situations. In addition, significant increases in undergraduate enrollments in information system courses, and the rapid pace of new knowledge in the field, have led researchers to call for new innovative approaches to learning. Prior researchers have reported that this new Web‐based training technology (which has its foundation in computer‐based training) has not integrated sound pedagogical practices into the authoring process when developing new tutorials. This paper summarizes an experiment to evaluate the effect on posttest scores of a Web‐based authoring tool that prompts the developer to build multiple presentation styles into the learning module. Early results indicate that the tool is more effective than traditional HTML‐authoring tools and that the number of exercises affects posttest scores in a positive manner. No effect on posttest scores was observed for the number of examples in the learning module.
Perceived Role of Multimedia Instructional Materials on Multicriteria Technology and Engineering Decisions*
Authors: Mbarika Victor W. , Sankar Chetan S. , Raju P. K.
Published: December 2003

Studies have shown that it is difficult for people to deal with multicriteria decision‐making situations. Information technology tools such as decision‐support systems and expert systems have been developed in order to help them in such situations. Another tool that has been identified as helping managers understand complex engineering decision‐making situations is multimedia instructional materials. This research investigates the perceptions of business versus engineering students on improvement of their higher‐level cognitive skills when they participated in a multimedia‐based case study that used an expert system to model a complex engineering and technical problem. Two groups of students, business and engineering, participated in an experiment, where they analyzed the case study and made their recommendations. Two questionnaires measured their perceptions on the improvements achieved on different constructs. A structural equations model was developed in order to test the research hypotheses with business students being the experimental group and the engineering students as a control group. The major findings are no significant relationship between student major and higher‐order cognitive skills improvement, business students perceived more higher‐order skills improvement compared to engineering students, both groups perceived an improvement in learning‐driven factor, and business students valued learning‐driven factors more compared to engineering students. These results show that multimedia instructional materials were perceived to be very useful in making multicriteria engineering and technical decisions.
Using Statistical Control Charts to Analyze Data from Student Evaluations of Teaching
Authors: Marks and Neil B. , O'Connell Richard T.
Published: December 2003

In this paper, a method for analyzing data from student evaluations of teaching is presented. The first step of the process requires development of a regression model for teacher's summary rating as a function of student's expected grade. Then, two‐sigma control charts for individual evaluation scores (section averages) and residuals from the regression model are used to identify both excellent and poor outcomes. The performance of an individual whose scores are out of control on both charts cannot be explained by expected grade and therefore is worthy of note.
TradeSmith: An Exercise to Demonstrate the Illusion of Control in Decision Making
Authors: Martz Ben , Neil Thomas C. , Biscaccianti Alessandro
Published: December 2003

Resource allocation decisions are a fundamental class of problems common throughout a business and therefore are found throughout business school curricula. Entrepreneurs must allocate capital, financiers must allocation cash, and production managers must create the best mix of multiple‐use resources. Within this context, a business school's curriculum, instructional materials, and learning processes must consider the implications of individual decision making. Our traditional instructional content and delivery methods may effectively teach how to set up a decision “problem” and how to obtain an optimal answer. Yet, we may not be teaching a key underlying factor: that entrepreneurs, managers, and future leaders appear to have implicit cognitive biases, which discount information and skew individual decision making. The results of this study demonstrate that a phenomenon known as the “illusion of control” presents a fundamental challenge to the efficacy of formalized educational programs on decision making. TradeSmith was designed as a problem‐based learning exercise to elicit for the illusion of control in a basic, resource allocation, decision environment. The subjects in this study demonstrate a decision‐making pattern consistent with the “illusion of control” phenomenon. Finally, by revealing individuals' implicit design‐making paradigms, TradeSmith helps them experience key issues for managerial decision making.
Fluid Dynamics of a Pre-Swirl Rotor-Stator System
Authors: Yan Youyou , Gord Mahmood Farzaneh , Lock Gary D. , Wilson Michael , Owen J. Michael
Published: December 2003

In a “direct-transfer” pre-swirl supply system, cooling air flows axially across the wheel-space from stationary pre-swirl nozzles to receiver holes located at a similar radius in the rotating turbine disc. This paper describes a combined computational and experimental study of the fluid dynamics of such a system. Measurements of total and static pressures have been made using a purpose-built rotor-stator rig, with 24 pre-swirl nozzles on the stator and 60 receiver holes in the rotor. The number of pre-swirl nozzles could be reduced, and it was possible to calculate CD, the discharge coefficient of the receiver holes. Information on the flowfield was also obtained from three-dimensional, incompressible steady turbulent flow computations. The measurements showed that there was a significant loss of total pressure between the outlet from the pre-swirl nozzles and the rotating core of fluid in the wheel-space. This loss increased as the pre-swirl flow-rate and inlet swirl ratio increased, and as the number of nozzles decreased. CD increased as the swirl ratio at the receiver hole radius approached unity; also CD decreased as the number of nozzles decreased. Computed pressures and tangential velocities were in mainly good agreement with the measurements. The computations help to explain the reasons for the significant losses in total pressure and for the relatively low values of CD in this pre-swirl system.
An Overview of High-Temperature Electronics and Sensor Development at NASA Glenn Research Center
Authors: Hunter Gary W. , Neudeck Philip G. , Okojie Robert S. , Beheim Glenn M. , Powell J. A. , Chen Liangyu
Published: December 2003

This paper gives a brief overview of the status of high-temperature electronics and sensor development at NASA Glenn Research Center supported in part or in whole by the Ultra Efficient Engine Technology Program. These activities contribute to the long-term development of an intelligent engine by providing information on engine conditions even in high temperature, harsh environments. The technology areas discussed are: 1) high-temperature electronics, 2) sensor technology development (pressure sensor and high-temperature electronic nose), 3) packaging of harsh environment devices and sensors, and 4) improved silicon carbide electronic materials. A description of the state-of-the-art and technology challenges is given for each area. It is concluded that the realization of a future intelligent engine depends on the development of both hardware and software including electronics and sensors to make smart components. When such smart components become available, an intelligent engine composed of smart components may become a reality.title
Analysis of the Worst Mistuning Patterns in Bladed Disk Assemblies
Authors: Petrov E. P. , Ewins D. J.
Published: December 2003

The problem of determining the worst mistuning patterns is formulated and solved as an optimization problem. Maximum resonant amplitudes searched across the many nodes of a large-scale finite element model of a mistuned bladed disk and across all the excitation frequencies in a given range are combined into an objective function. Individual blade mistuning is controlled by varying design parameters, whose variation range is constrained by manufacture tolerances. Detailed realistic finite element models, which have so far only been used for analyzing tuned bladed disks, are used for calculation of the forced resonant response of mistuned assemblies and for determination of its sensitivity coefficients with respect to mistuning variation. Results of the optimum search of mistuning patterns for some practical bladed disks are analyzed and reveal higher worst cases than those found in previous studies.
Blade Count and Clocking Effects on Three-Bladerow Interaction in a Transonic Turbine
Authors: Li H. D. , He L.
Published: December 2003

A computational study of the multirow interaction mechanisms has been carried out for a one-and-a-half stage (NGV-rotor-stator) transonic turbine. In addition to measurable subharmonic unsteadiness on the rotor blades induced by two fundamental stator passing frequencies, a significant aperiodic (“mistuned”) circumferential variation of unsteady forcing magnitude by about three times has been observed in the downstream stator blades. Further parametric studies with various stator blade counts illustrate that the circumferential variation pattern of the unsteady forcing is dictated by the NGV-stator blade count difference, while the local stator forcing magnitude is affected by its circumferential clocking position relative to the upstream NGV blades. The present work suggests that the circumferential clocking together with the choice of blade count should be considered as an aeromechanical design parameter. For cases with stator-stator (or rotor-rotor) blade counts resulting in a tuned (or nearly tuned) unsteady forcing pattern, the clocking position should be chosen to minimize the unsteady forcing. On the other hand, if the choice of blade counts leads to a significant aerodynamic aperiodicity (mistuning), the clocking-forcing analysis can be used to identify the most vulnerable blade that is subject to the maximum forcing.
Heat Transfer and Friction Factors for Flows Inside Circular Tubes With Concavity Surfaces
Authors: Bunker Ronald S. , Donnellan Katherine F.
Published: December 2003

Heat transfer and friction coefficients measurements have been obtained for fully developed, turbulent internal flows in circular tubes with six different concavity (dimple) surface array geometries. Two different concavity depths and three different concavity array densities were tested using tube bulk flow Reynolds numbers from 20,000 to 90,000. Liquid-crystal thermography was used to measure the temperature distributions on the outside of the concavity tubes. Using the average heat transfer coefficient for the fully developed region, the overall heat transfer enhancements are compared to baseline smooth tube results. Friction coefficients are also compared to values for a smooth tube. Dimple depths of 0.2–0.4 relative to the dimple surface diameter were used, with surface area densities ranging from 0.3 to 0.7. Dimple arrays were all in-line geometries. The results showed that heat transfer enhancements for dimpled internal surfaces of circular passages can reach factors of 2 or more when the relative dimple depth is greater than 0.3 and the dimple array density is about 0.5 or higher. The associated friction factor multipliers for such configurations are in the range of 4–6. The present study provides a first insight into the heat transfer and friction effects of various concavity arrays for turbulent flows.
Turbulent Flow in a Rotating Two Pass Ribbed Rectangular Channel
Authors: Hsieh Shou-Shing , Chin Hsiang-Jung
Published: December 2003

Laser-Doppler anemometry has been applied to approximately two-dimensional turbulent air flow in rotating two pass channel with turbulator of rectangular cross section (AR=3:1). The axis of rotation is normal to the axis of the duct, and the flow is radially outward/inward. The duct is of finite length and the walls are isothermal. Two sided oppositely ribbed channel including one sided ribbed U bend of p/e=8 at e/DH=0.27 are experimentally conducted with ReD=5000 and 10,000. The main features of the flow, reattachment length, recirculation zone, and mean velocity as well as turbulent intensity and shear stress distributions are presented in ribbed ducts. The measured flow field is found to be quite complex, consisting of secondary cross-stream flows due to the Coriolis effects and centrifugal forces with rib-roughened surfaces.
Impact of Geometric Variability on Axial Compressor Performance
Authors: Garzon Victor E. , Darmofal David L.
Published: December 2003

A probabilistic methodology to quantify the impact of geometric variability on compressor aerodynamic performance is presented. High-fidelity probabilistic models of geometric variability are derived using a principal-component analysis of blade surface measurements. This probabilistic blade geometry model is then combined with a compressible, viscous blade-passage analysis to estimate the impact on the passage loss and turning using a Monte Carlo simulation. Finally, a mean-line multistage compressor model, with probabilistic loss and turning models from the blade-passage analysis, is developed to quantify the impact of the blade variability on overall compressor efficiency and pressure ratio. The methodology is applied to a flank-milled integrally bladed rotor. Results demonstrate that overall compressor efficiency can be reduced by approximately 1% due to blade-passage effects arising from representative manufacturing variability.
Experimental Investigation of Centrifugal Compressor Stabilization Techniques
Authors: Skoch Gary J.
Published: December 2003

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 6.5 points of additional surge margin over the baseline surge margin of 11.7 points.
Experimental Demonstration of Maximum Mistuned Bladed Disk Forced Response
Authors: Kenyon J. A. , Griffin J. H.
Published: December 2003

A theory was previously developed for predicting robust maximum forced response in mistuned bladed disks from distortion of a structural mode. This paper describes an experiment to demonstrate the theory. A bladed disk is designed to be sufficiently sensitive to mistuning to obtain maximum response. The maximum amplitude magnification from mistuning is predicted using the theory, 1.918. The bladed disk is intentionally mistuned to obtain the maximum response, and the response to an engine order traveling wave excitation is measured. The measured amplitude magnification is in close agreement with the theory. The robustness of the maximum response is demonstrated.
Experimental and Numerical Investigation of Impingement on a Rib-Roughened Leading-Edge Wall
Authors: Taslim M. E. , Bakhtari K. , Liu H.
Published: December 2003

Effective cooling of the airfoil leading edge is imperative in gas turbine designs. Among several methods of cooling the leading edge, impingement cooling has been utilized in many modern designs. In this method, the cooling air enters the leading edge cavity from the adjacent cavity through a series of crossover holes on the partition wall between the two cavities. The crossover jets impinge on a smooth leading-edge wall and exit through the film holes, and, in some cases, form a cross flow in the leading-edge cavity and move toward the end of the cavity. It was the main objective of this investigation to measure the heat transfer coefficient on a smooth as well as rib-roughened leading-edge wall. Experimental data for impingement on a leading-edge surface roughened with different conical bumps and radial ribs have been reported by the same authors previously. This investigation, however, deals with impingement on different horseshoe ribs and makes a comparison between the experimental and numerical results. Three geometries representing the leading-edge cooling cavity of a modern gas turbine airfoil with crossover jets impinging on (1) a smooth wall, (2) a wall roughened with horseshoe ribs, and (3) a wall roughened with notched-horseshoe ribs were investigated. The tests were run for a range of flow arrangements and jet Reynolds numbers. The major conclusions of this study were: (a) Impingement on the smooth target surface produced the highest overall heat transfer coefficients followed by the notched-horseshoe and horseshoe geometries. (b) There is, however, a heat transfer enhancement benefit in roughening the target surface. Among the three target surface geometries, the notched-horseshoe ribs produced the highest heat removal from the target surface, which was attributed entirely to the area increase of the target surface. (c) CFD could be considered as a viable tool for the prediction of impingement heat transfer coefficients on an airfoil leading-edge wall.
Influence of Clocking and Vane/Blade Spacing on the Unsteady Surface Pressure Loading for a Modern Stage and One-Half Transonic Turbine
Authors: Haldeman C. W. , Krumanaker M. L. , Dunn M. G.
Published: December 2003

This paper describes pressure measurements obtained for a modern one and one-half stage turbine. As part of the experimental effort, the position of the high-pressure turbine (HPT) vane was clocked relative to the downstream low-pressure turbine (LPT) vane to determine the influence of vane clocking on both the steady and unsteady pressure loadings on the LPT vane and the HPT blade. In addition, the axial location of the HPT vane relative to the HPT blade was changed to investigate the combined influence of vane/blade spacing and clocking on the unsteady pressure loading. Time-averaged and time-accurate surface-pressure results are presented for several spanwise locations on the vanes and blade. Results were obtained at four different HPT vane-clocking positions and at two different vane/blade axial spacings for three (of the four) clocking positions. For time-averaged results, the effect of clocking is small on the HPT blade and vane. The influence of clocking on the transition ducts and the LPT vane is slightly greater (on the order of ±1%). Reduced HPT vane/blade spacing has a larger effect than clocking on the HPT vanes and blades ±3% depending upon the particular surface. Examining the data at blade passing and the first fundamental frequency, the effect of spacing does not produce a dramatic influence on the relative changes that occur between clocking positions. The results demonstrate that clocking and spacing effects on the surface pressure loading are very complex and may introduce problems if the results of measurements or analysis made at one span or location in the machine are extrapolated to other sections.
Average Passage Flow Field and Deterministic Stresses in the Tip and Hub Regions of a Multistage Turbomachine
Authors: Uzol Oguz , Chow Yi-Chih , Katz Joseph , Meneveau Charles
Published: December 2003

This paper continues our effort to study the dynamics of deterministic stresses in a multistage turbomachine using experimental data. Here we focus on the tip and hub regions and compare them to midspan data obtained in previous studies. The analysis is based on data obtained in particle image velocimetry (PIV) measurements performed in the second stage of a two-stage turbomachine. A complete data set is obtained using blades and fluid with matched optical index of refraction. Previous measurements at midspan have shown that at midspan and close to design conditions, the deterministic kinetic energy is smaller than the turbulent kinetic energy. The primary contributor to the deterministic stresses at midspan is the interaction of a blade with the upstream wakes. Conversely, we find that the tip vortex is the dominant source of phase-dependent unsteadiness and deterministic stresses in the tip region. Along the trajectory of the tip vortex, the deterministic kinetic energy levels are more than one order of magnitude higher than the levels measured in the hub and midspan, and are of the same order of magnitude as the turbulent kinetic energy levels. Reasons for this trend are explained using a sample distribution of phase-averaged flow variables. Outside of the region affected by tip-vortex transport, within the rotor-stator gap and within the stator passages, the turbulent kinetic energy is still 3–4 times higher than the deterministic kinetic energy. The deterministic and turbulent shear stress levels are comparable in all spanwise locations, except for the wakes of the stator blades, where the turbulent stresses are higher. However, along the direction of tip-vortex transport, the deterministic shear stresses are about an order of magnitude higher than the turbulent shear stresses. The decay rates of deterministic kinetic energy in the hub and midspan regions are comparable to each other, whereas at the tip the decay rate is higher. The decay rates of turbulent kinetic energy are much smaller than those of the deterministic kinetic energy. The paper also examines terms in the deterministic kinetic energy transport equation. The data indicate that “deterministic production” and a new term, here called “dissipation due to turbulence,” are the dominant source/sink terms. Regions with alternating signs of deterministic production indicate that the energy transfer between the phase-averaged and average-passage flow fields can occur in both directions. The divergence of the pressure-velocity correlation, obtained from a balance of all the other terms, is dominant and appears to be much larger than the deterministic production (source/sink) term. This trend indicates that there are substantial deterministic pressure fluctuations in the flow field, especially within the rotor-stator gap and within the stator passage.
Heat Transfer in 1:4 Rectangular Passages With Rotation
Authors: Agarwal Peeyush , Acharya Sumanta , Nikitopoulos D. E.
Published: December 2003

The paper presents an experimental study of heat/mass transfer coefficient in 1:4 rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5000–40,000 and rotation numbers in the range of 0–0.12. Such passages are encountered close to the mid-chord sections of the turbine blade. Normal ribs (e/Dh=0.3125 and P/e=8) are placed on the leading and the trailing sides only. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. For purposes of comparison, selected measurements are also performed in a 1:1 cross section. The local mass-transfer data in the fully developed region is averaged to study the effect of the Reynolds and the rotation numbers. The spanwise mass transfer distributions in the smooth and the ribbed cases are also examined.
Heat Transfer Coefficients on the Squealer Tip and Near-Tip Regions of a Gas Turbine Blade With Single or Double Squealer
Authors: Kwak Jae Su , Ahn Jaeyong , Han Je-Chin , Lee C. Pang , Bunker Ronald S. , Boyle Robert , Gaugler Raymond
Published: December 2003

Detailed heat transfer coefficient distributions on a gas turbine squealer tip blade were measured using a hue detection based transient liquid-crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Squealer rims were located along (a) the camber line, (b) the pressure side, (c) the suction side, (d) the pressure and suction sides, (e) the camber line and the pressure side, and (f) the camber line and the suction side, respectively. Tests were performed on a five-bladed linear cascade with a blow down facility. The Reynolds number based on the cascade exit velocity and the axial chord length of a blade was 1.1×106 and the overall pressure ratio was 1.2. Heat transfer measurements were taken at the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span. Results show that the heat transfer coefficients on the blade tip and the shroud were significantly reduced by using a squealer tip blade. Results also showed that a different squealer geometry arrangement changed the leakage flow path and resulted in different heat transfer coefficient distributions. The suction side squealer tip provided the lowest heat transfer coefficient on the blade tip and near tip regions compared to the other squealer geometry arrangements.
Passive Flow Control on Low-Pressure Turbine Airfoils
Authors: Volino Ralph J.
Published: December 2003

Two-dimensional rectangular bars have been used in an experimental study to control boundary layer transition and reattachment under low-pressure turbine conditions. Cases with Reynolds numbers (Re) ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (8.5% inlet) free-stream turbulence levels. Three different bars were considered, with heights ranging from 0.2% to 0.7% of suction surface length. Mean and fluctuating velocity and intermittency profiles are presented and compared to results of baseline cases from a previous study. Bar performance depends on the bar height and the location of the bar trailing edge. Bars located near the suction surface velocity maximum are most effective. Large bars trip the boundary layer to turbulent and prevent separation, but create unnecessarily high losses. Somewhat smaller bars had no immediate detectable effect on the boundary layer, but introduced small disturbances that caused transition and reattachment to move upstream from their locations in the corresponding baseline case. The smaller bars were effective under both high and low free-stream turbulence conditions, indicating that the high free-stream turbulence transition is not simply a bypass transition induced by the free stream. Losses appear to be minimized when a small separation bubble is present, so long as reattachment begins far enough upstream for the boundary layer to recover from the separation. Correlations for determining optimal bar height are presented. The bars appear to provide a simple and effective means of passive flow control. Bars that are large enough to induce reattachment at low Re, however, cause higher losses at the highest Re. Some compromise would, therefore, be needed when choosing a bar height for best overall performance.
Separation Control on Low-Pressure Turbine Airfoils Using Synthetic Vortex Generator Jets
Authors: Volino Ralph J.
Published: December 2003

Oscillating vortex generator jets have been used to control boundary layer separation from the suction side of a low-pressure turbine airfoil. A low Reynolds number (Re=25,000) case with low free-stream turbulence has been investigated with detailed measurements including profiles of mean and fluctuating velocity and turbulent shear stress. Ensemble averaged profiles are computed for times within the jet pulsing cycle, and integral parameters and local skin friction coefficients are computed from these profiles. The jets are injected into the mainflow at a compound angle through a spanwise row of holes in the suction surface. Preliminary tests showed that the jets were effective over a wide range of frequencies and amplitudes. Detailed tests were conducted with a maximum blowing ratio of 4.7 and a dimensionless oscillation frequency of 0.65. The outward pulse from the jets in each oscillation cycle causes a disturbance to move down the airfoil surface. The leading and trailing edge celerities for the disturbance match those expected for a turbulent spot. The disturbance is followed by a calmed region. Following the calmed region, the boundary layer does separate, but the separation bubble remains very thin. Results are compared to an uncontrolled baseline case in which the boundary layer separated and did not reattach, and a case controlled passively with a rectangular bar on the suction surface. The comparison indicates that losses will be substantially lower with the jets than in the baseline or passively controlled cases.
Physiological and Community Responses of EstablishedGrassland Bacterial Populations to WaterStress
Authors: Griffiths Robert I. , Whiteley Andrew S. , O'Donnell Anthony G. , Bailey Mark J.
Published: December 2003

The
effects of water stress upon the diversity and culturable activity of
bacterial communities in the rhizosphere of an established upland
grassland soil have been investigated. Intact monoliths were subjected
to different watering regimens over a 2-month period to study community
adaptation to moisture limitation and subsequent response to stress
alleviation following rewetting. Genetic diversity was analyzed with
16S-based denaturing gradient gel electrophoresis (DGGE) of total
soil-extracted DNA (rRNA genes) and RNA (rRNA transcripts) in an
attempt to discriminate between total and active communities.
Physiological response was monitored by plate counts, total counts, and
BIOLOG-GN2 substrate utilization analyses. Controlled soil drying
decreased the total number of CFU on all the media tested and also
decreased the substrate utilization response. Following rewetting of
dried soil, culture-based analyses indicated physiological recovery of
the microbial population by the end of the experiment. In contrast,
DGGE analyses of community 16S rRNA genes, rRNA transcripts and
cultured communities did not reveal any changes relating to the
moisture regimens, despite the observed physiological effects. We
conclude that the imposed moisture regimen modulated the physiological
status of the bacterial community and that bacterial communities in
this soil are resistant to water stress. Further, we highlight the need
for a reexamination of rRNA transcript-based molecular profiling
techniques as a means of describing the active component of soil
bacterial
communities.
Cloning, Expression, and Cell Surface Localization of
Paenibacillus
sp. Strain W-61 Xylanase 5, a Multidomain Xylanase
Authors: Ito Yasuko , Tomita Toshio , Roy Narayan , Nakano Akito , Sugawara-Tomita Noriko , Watanabe Seiji , Okai Naoko , Abe Naoki , Kamio Yoshiyuki
Published: December 2003

We
have shown that a xylan-degrading bacterium, W-61, excretes multiple
xylanases, including xylanase 5 with a molecular mass of 140 kDa. Here,
we emend the previously used classification of the bacterium (i.e.,
Aeromonas caviae
W-61) to
Paenibacillus
sp. strain
W-61 on the basis of the nucleotide sequence of the 16S rRNA gene, and
we clone and express the
xyn5
gene encoding xylanase 5 (Xyn5)
in
Escherichia coli
and study the subcellular localization of
Xyn5.
xyn5
encodes 1,326 amino acid residues, including a
27-amino-acid signal sequence. Sequence analysis indicated that Xyn5
comprises two family 22 carbohydrate-binding modules (CBM), a family 10
catalytic domain of glycosyl hydrolases, a family 9 CBM, a domain
similar to the lysine-rich region of
Clostridium thermocellum
SdbA, and three S-layer-homologous (SLH) domains. Recombinant Xyn5
bound to a crystalline cellulose, Avicel PH-101, while an N-terminal
90-kDa fragment of Xyn5, which lacks the C-terminal half of the family
9 CBM, did not bind to Avicel PH-101. Xyn5 was cell bound, and the
cell-bound protein was digested by exogenous trypsin to produce
immunoreactive and xylanolytic fragments with molecular masses of 80
and 60 kDa. Xyn5 was exclusively distributed in the cell envelope
fraction consisting of a peptidoglycan-containing layer and an
associated S layer. Thus,
Paenibacillus
sp. strain W-61 Xyn5
is a cell surface-anchored modular xylanase possessing a functional
cellulose-binding module and SLH domains. Possible
cooperative action of multiple xylanases produced by strain W-61 is
discussed on the basis of the modular structure of
Xyn5.
Improvementof Foreign-Protein Production in
Aspergillus niger
var.
awamori
by Constitutive Induction of the Unfolded-ProteinResponse
Authors: Valkonen Mari , Ward Michael , Wang Huaming , Penttilä Merja , Saloheimo Markku
Published: December 2003

Unfolded-protein
response (UPR) denotes the upregulation of endoplasmic reticulum
(ER)-resident chaperone and foldase genes and numerous
other genes involved in secretory functions during the accumulation of
unfolded proteins into the ER. Overexpression of individual foldases
and chaperones has been used in attempts to improve protein production
in different production systems. We describe here a novel strategy to
improve foreign-protein production. We show that the constitutive
induction of the UPR pathway in
Aspergillus niger
var.
awamori
can be achieved by expressing the activated form of
the transcription factor
hacA
. This induction enhances the
production of
Trametes versicolor
laccase by up to sevenfold
and of bovine preprochymosin by up to 2.8-fold in this biotechnically
important fungus. The regulatory range of UPR was studied by analyzing
the mRNA levels of novel
A. niger
var.
awamori
genes
involved in different secretory functions. This revealed both
similarities and differences to corresponding studies in
Saccharomyces
cerevisiae
.
Investigation of Protein Export in
Bifidobacteriumbreve
UCC2003
Authors: MacConaill Laura E. , Fitzgerald Gerald F. , van Sinderen Douwe
Published: December 2003

The
molecular interactions between the bifidobacterial cell and its natural
environment, namely, the gastrointestinal tract of its host, are
particularly important in understanding the presumed positive effects
of
Bifidobacterium
on the health status of the host. In this
study an export-specific reporter system, designed for use in
gram-positive organisms and based on the use of the staphylococcal
nuclease (Nuc) as a reporter, was employed to identify exported
proteins in
Bifidobacterium breve
UCC2003. A
B. breve
genomic library of translational fusions to the Nuc-encoding gene
devoid of its own export signal was established in the shuttle vector
pFUN (I. Poquet, S. D. Ehrlich, and A. Gruss, J. Bacteriol.
180:
1904-1912, 1998) and screened for bifidobacterial
export signals. Sequence analysis of the fusion proteins obtained that
displayed a nuclease-producing phenotype in both
Lactococcus
lactis
and
B. breve
predicted the presence of a classical
signal peptide and/or single or multiple transmembrane domains, thus
indicating that some of the export signals in
B. breve
are
comparable to those used in
L. lactis
. Cell fractionation
studies, zymograms, nuclease assays, and Western blotting were employed
to confirm the function of the predicted signals and to determine the
location and activity of the exported fusion proteins in
B.
breve
and/or
L.
lactis
.
Identification and Distribution of Insertion Sequences of
Paracoccus solventivorans
Authors: Bartosik Dariusz , Szymanik Michal , Baj Jadwiga
Published: December 2003

Three
novel insertion sequences (ISs) (IS
Pso1
, IS
Pso2
, and
IS
Pso3
) of the soil bacterium
Paracoccus
solventivorans
DSM 11592 were identified by transposition into
entrapment vector pMEC1. IS
Pso1
(1,400 bp) carries one large
open reading frame (ORF) encoding a putative basic protein (with a DDE
motif conserved among transposases [Tnps] of elements
belonging to the IS
256
family) with the highest levels of
similarity with the hypothetical Tnps of
Rhodospirillum rubrum
and
Sphingopyxis macrogoltabida
. IS
Pso2
(832 bp)
appeared to be closely related to IS
Ppa2
of
Paracoccus
pantotrophus
DSM 11072 and IS
1248
of
Paracoccus
denitrificans
PdX22, both of which belong to the IS
427
group (IS
5
family). These elements contain two overlapping
ORFs and a putative frameshift motif (AAAAG) responsible for production
of a putative transframe Tnp. IS
Pso3
(1,286 bp) contains a
single ORF, whose putative product showed homology with Tnps of ISs
classified as members of a distinct subgroup of the IS
5
group
of the IS
5
family. The highest levels of similarity were
observed with IS
Ssp126
of
Sphingomonas
sp. and
IS
1169
of
Bacteroides fragilis
. Analysis of the
distribution of ISs of
P. solventivorans
revealed that
IS
Pso2
-like elements are the most widely spread of the
elements in nine species of the genus
Paracoccus
.
IS
Pso1
and IS
Pso3
are present in only a few
paracoccal strains, which suggests that they were acquired by lateral
transfer. Phylogenetic analysis of Tnps of the novel ISs and their
closest relatives showed their evolutionary relationships and possible
directions of lateral transfer between various bacterial
hosts.
Nitrate/NitriteAssimilation System of the Marine Picoplanktonic Cyanobacterium
Synechococcus
sp. Strain WH 8103: Effect of NitrogenSource and Availability on GeneExpression
Authors: Bird Clare , Wyman Michael
Published: December 2003

The
genes encoding the structural components of the nitrate/nitrite
assimilation system of the oceanic cyanobacterium
Synechococcus
sp. strain WH 8103 were cloned and
characterized. The genes encoding nitrate reductase (
narB
) and
nitrite reductase (
nirA
) are clustered on the chromosome but
are organized in separate transcriptional units. Upstream of
narB
is a homologue of
nrtP
that encodes a
nitrate/nitrite-bispecific permease rather than the components of an
ABC-type nitrate transporter found in freshwater cyanobacteria.
Unusually, neither
nirA
nor
ntcA
(encoding a positive
transcription factor of genes subject to nitrogen control) were found
to be tightly regulated by ammonium. Furthermore, transcription of
glnA
(encoding glutamine synthetase) is up-regulated in
ammonium-grown cells, highlighting significant differences in nitrogen
control in this cyanobacterium. Nitrogen depletion led to the transient
up-regulation of
ntcA
,
nirA
,
nrtP
,
narB
, and
glnA
in what appears to be an
NtcA-dependent manner. The NtcA-like promoters found upstream of
nirA
,
nrtP
, and
narB
all differ in sequence
from the canonical NtcA promoter established for other cyanobacteria,
and in the case of
nirA
, the NtcA-like promoter was functional
only in cells deprived of combined nitrogen. The ecological
implications of these findings are discussed in the context of the
oligotrophic nature of oceanic surface waters in which
Synechococcus
spp.
thrive.
Carbon Source-Induced Modifications in the MycolicAcid Content and Cell Wall Permeability of
Rhodococcuserythropolis
E1
Authors: Sokolovská Ivana , Rozenberg Raoul , Riez Christophe , Rouxhet Paul G. , Agathos Spiros N. , Wattiau Pierre
Published: December 2003

The
influence of the carbon source on cell wall properties was analyzed in
an efficient alkane-degrading strain of
Rhodococcus
erythropolis
(strain E1), with particular focus on the mycolic
acid content. A clear correlation was observed between the carbon
source and the mycolic acid profiles as estimated by high-performance
liquid chromatography and mass spectrometry. Two types of mycolic acid
patterns were observed after growth either on saturated linear alkanes
or on short-chain alkanoates. One type of pattern was characterized by
the lack of odd-numbered carbon chains and resulted from growth on
linear alkanes with even numbers of carbon atoms. The second type of
pattern was characterized by mycolic acids with both even- and
odd-numbered carbon chains and resulted from growth on compounds with
odd-numbered carbon chains, on branched alkanes, or on mixtures of
different compounds. Cellular short-chain fatty acids were twice as
abundant during growth on a branched alkane (pristane) as during growth
on acetate, while equal amounts of mycolic acids were found under both
conditions. More hydrocarbon-like compounds and less polysaccharide
were exposed at the cell wall surface during growth on alkanes.
Whatever the substrate, the cells had the same affinity for
aqueous-nonaqueous solvent interfaces. By contrast, bacteria displayed
completely opposite susceptibilities to hydrophilic and hydrophobic
antibiotics and were found to be strongly stained by hydrophobic dyes
after growth on pristane but not after growth on acetate. Taken
together, these data show that the cell wall composition of
R.
erythropolis
E1 is influenced by the nutritional regimen and that
the most marked effect is a radical change in cell wall
permeability.
Shigella dysenteriae
Type 1-SpecificBacteriophage from Environmental Waters inBangladesh
Authors: Faruque Shah M. , Chowdhury Nityananda , Khan Rasel , Hasan M. Rubayet , Nahar Jebun , Islam M. Johirul , Yamasaki Shinji , Ghosh A. N. , Nair G. Balakrish , Sack David A.
Published: December 2003

Shigella
dysenteriae
type 1 is the causative agent of the most severe form
of bacillary dysentery, which occurs as epidemics in many developing
countries. We isolated a bacteriophage from surface water samples from
Bangladesh that specifically lyses strains of
S. dysenteriae
type 1. This phage, designated SF-9, belongs to the
Podoviridae
family and has a 41-kb double-stranded DNA genome.
Further screening of water samples for the prevalence of the phage
revealed 9 of 71 (12.6%) water samples which were positive for
the phage. These water samples were also positive in PCR assays for one
or more
S. dysenteriae
type 1-specific genes, including
ipaBCD
and
stx1
, and live
S. dysenteriae
type 1 was isolated from three phage-positive samples. The results of
this study suggest that phage SF-9 may have epidemiological
applications in tracing the presence of
S. dysenteriae
type 1
in environmental
waters.
Compatible Solutes Protect against Chaotrope(Ethanol)-Induced, Nonosmotic WaterStress
Authors: Hallsworth John E. , Prior Bernard A. , Nomura Yoshiyuki , Iwahara Masayoshi , Timmis Kenneth N.
Published: December 2003

Water
stress is one of the major stresses experienced by cellular systems and
can take a number of distinct forms. In response to turgor-related
osmotic stress, cells produce compatible solutes that are macromolecule
protectants and also counteract the outflow of water from stressed
cells. In this report we show that the germination of conidia of
Aspergillus nidulans
, a sensitive indicator of water stress,
in the presence of ethanol is correlated with the intracellular
concentration of the compatible solutes glycerol and erythritol, which
protect against both osmotic and nonturgor forms of water
stress.
Role of Soil pH in the Development of EnhancedBiodegradation ofFenamiphos
Authors: Singh Brajesh K. , Walker Allan , Morgan J. Alun W. , Wright Denis J.
Published: December 2003

Repeated
treatment with fenamiphos (ethyl 4-methylthio-
m
-tolyl
isopropylphosphoramidate) resulted in enhanced biodegradation of this
nematicide in two United Kingdom soils with a high pH (≥7.7).
In contrast, degradation of fenamiphos was slow in three acidic United
Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result
in enhanced biodegradation. Rapid degradation of fenamiphos was
observed in two Australian soils (pH 6.7 to 6.8) in which it was no
longer biologically active against plant nematodes. Enhanced degrading
capability was readily transferred from Australian soil to United
Kingdom soils, but only those with a high pH were able to maintain this
capability for extended periods of time. This result was confirmed by
fingerprinting bacterial communities by 16S rRNA gene profiling of
extracted DNA. Only United Kingdom soils with a high pH retained
bacterial DNA bands originating from the fenamiphos-degrading
Australian soil. A degrading consortium was enriched from the
Australian soil that utilized fenamiphos as a sole source of carbon.
The 16S rRNA banding pattern (determined by denaturing gradient gel
electrophoresis) from the isolated consortium migrated to the same
position as the bands from the Australian soil and those from the
enhanced United Kingdom soils in which the Australian soil had been
added. When the bands from the consortium and the soil were sequenced
and compared they showed between 97 and 100% sequence identity,
confirming that these groups of bacteria were involved in degrading
fenamiphos in the soils. The sequences obtained showed similarity to
those from the genera
Pseudomonas
,
Flavobacterium
,
and
Caulobacter
. In the Australian soils, two different
degradative pathways operated simultaneously: fenamiphos was converted
to fenamiphos sulfoxide (FSO), which was hydrolyzed to the
corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos
phenol. In the United Kingdom soils in which enhanced degradation had
been induced, fenamiphos was oxidized to FSO and then hydrolyzed to
FSO-OH, but direct conversion to fenamiphos phenol did not
occur.