bluuebunny/crossref_metadata_2025 huggingface dataset:
PREDICTING CLEANING OF EQUIPMENT USING COMPUTATIONAL FLUID DYNAMICS
Authors: ASTERIADOU KONSTANTIA , HASTING TONY , BIRD MICHAEL , MELROSE JOHN
Published: January 2007

In the food industry, production lines are ideally run for very long time periods without the need for cleaning. A prerequisite is that the equipment and the line are hygienically designed. This means that there are no stagnant areas, crevices or other parts of the flow domain that may cause entrapment of the product that can subsequently lead to bacterial growth. However, unhygienic geometries such as those described are frequently encountered in practice, and more frequent cleaning is a necessity. This article reported modeling results validated with experimental work. Computational fluid dynamics was used to assess the cleanability of a T‐junction. Electrical conductivity measurements of a salt solution of known concentration before and after the T‐junction is cleaned using deionized water were reported. This comparison gives an acceptable qualitative agreement with finite volume‐based calculations that involve both steady‐state and transient operations. This approach is a necessary prerequisite for the development of models that will ultimately include bacterial growth and deactivation kinetics under processing conditions.
Dilution Tests in a Low‐Permeability Fractured Aquifer: Matrix Diffusion Effect
Authors: Bernstein Anat , Adar Eilon , Yakirevich Alexander , Nativ Ronit
Published: January 2007

A point dilution test is commonly used in single‐borehole tracer experiments designed to determine the Darcy velocity of a formation. This method is based on the concept that, in a borehole, a tracer’s concentration declines as a consequence of the water flux. Based on theoretical simulations and field observations, this study indicates that for low‐permeability, yet highly porous fractured formations, the common practice of excluding the effect of diffusive mass flux between the dissolved tracer within the borehole and the surrounding matrix may lead to significant errors in the assessment of the Darcy velocity. This conclusion was confirmed by a model adapted to simulate experimental data collected from a tracer test performed in a vertical, large‐diameter (25‐cm) borehole drilled along a subvertical fracture intersecting a chalk formation.
Heat, Chloride, and Specific Conductance as Ground Water Tracers near Streams
Authors: Cox Marisa H. , Su Grace W. , Constantz Jim
Published: January 2007

Commonly measured water quality parameters were compared to heat as tracers of stream water exchange with ground water. Temperature, specific conductance, and chloride were sampled at various frequencies in the stream and adjacent wells over a 2‐year period. Strong seasonal variations in stream water were observed for temperature and specific conductance. In observation wells where the temperature response correlated to stream water, chloride and specific conductance values were similar to stream water values as well, indicating significant stream water exchange with ground water. At sites where ground water temperature fluctuations were negligible, chloride and/or specific conductance values did not correlate to stream water values, indicating that ground water was not significantly influenced by exchange with stream water. Best‐fit simulation modeling was performed at two sites to derive temperature‐based estimates of hydraulic conductivities of the alluvial sediments between the stream and wells. These estimates were used in solute transport simulations for a comparison of measured and simulated values for chloride and specific conductance. Simulation results showed that hydraulic conductivities vary seasonally and annually. This variability was a result of seasonal changes in temperature‐dependent hydraulic conductivity and scouring or clogging of the streambed. Specific conductance fits were good, while chloride data were difficult to fit due to the infrequent (quarterly) stream water chloride measurements during the study period. Combined analyses of temperature, chloride, and specific conductance led to improved quantification of the spatial and temporal variability of stream water exchange with shallow ground water in an alluvial system.
Seepage Face Height, Water Table Position, and Well Efficiency at Steady State
Authors: Chenaf Djaouida , Chapuis Robert P.
Published: January 2007

When a fully penetrating well pumps an ideal unconfined aquifer at steady state, the water table usually does not join the water level in the well. There is a seepage face inside the well, which is a key element in evaluating the well performance. This problem is analyzed using the finite‐element method, solving the complete equations for saturated and unsaturated flow. The seepage face position is found to be almost independent of the unsaturated zone properties. The numerical results are used to test the validity of several analytic approximations. Equations are proposed to predict the seepage face position at the pumping well for any well drawdown, and the water table position at any distance from the pumping well for any in‐well drawdown. Practical hints are provided for installing monitoring wells and evaluating well efficiency.
Ground Water Sustenance of Nebraska’s Unique Sand Hills Peatland Fen Ecosystems
Authors: Harvey F. Edwin , Swinehart James B. , Kurtz Tina M.
Published: January 2007

Many ecosystems have evolved under conditions where ground water is critical to the survival of the unique species contained therein. One example is Nebraska’s Sand Hills fens. The Sand Hills region comprises lush interdunal valleys amid grass‐stabilized dunes. One valley type, fens, are ground water‐fed wetlands that have several meters of saturated, organic soils comprising peat formed under anaerobic conditions where plant growth exceeds decomposition. These fens support unique flora and fauna such as rush aster and northern redbelly dace that are typically found in more boreal regions of North America. This study characterized the hydrogeology of a representative fen in the Jumbo Valley to explore how these relict species survive in a hot, arid climate and to understand present and historical relations between ground water and these unique ecosystems. Results indicate that ground water’s present role in sustaining the fens is twofold: (1) wetland plant transpiration of shallow ground water across the valley creates a cooler, humid microclimate that sustains the fens in the region’s hot, arid climate and (2) the large volume of ground water pumped through the fens by plant transpiration transports necessary nutrients to the root zone. Results suggest that, in the past, in addition to its sustaining role, ground water also played a vital role in fen development and in fen preservation through nearly 15,000 years of existence. Thus, as with like ecosystems, the role of ground water must be considered in future Sand Hills fen protection, restoration, and management.
Effects of Sea‐Level Rise on Ground Water Flow in a Coastal Aquifer System
Authors: Masterson John P. , Garabedian Stephen P.
Published: January 2007

The effects of sea‐level rise on the depth to the fresh water/salt water interface were simulated by using a density‐dependent, three‐dimensional numerical ground water flow model for a simplified hypothetical fresh water lens that is similar to shallow, coastal aquifers found along the Atlantic coast of the United States. Simulations of sea‐level rise of 2.65 mm/year from 1929 to 2050 resulted in an increase in water levels relative to a fixed datum, yet a net decrease in water levels relative to the increased sea‐level position. The net decrease in water levels was much greater near a gaining stream than farther from the stream. The difference in the change in water levels is attributed to the dampening effect of the stream on water level changes in response to sea‐level rise. In response to the decreased water level altitudes relative to local sea level, the depth to the fresh water/salt water interface decreased. This reduction in the thickness of the fresh water lens varied throughout the aquifer and was greatly affected by proximity to a ground water fed stream and whether the stream was tidally influenced. Away from the stream, the thickness of the fresh water lens decreased by about 2% from 1929 to 2050, whereas the fresh water lens thickness decreased by about 22% to 31% for the same period near the stream, depending on whether the stream was tidally influenced. The difference in the change in the fresh water/salt water interface position is controlled by the difference in the net decline in water levels relative to local sea level.
On the Use and Error of Approximation in the Domenico (1987) Solution
Authors: West Michael R. , Kueper Bernard H. , Ungs Michael J.
Published: January 2007

A mathematical solution for solute transport in a three‐dimensional porous medium with a patch source under steady‐state, uniform ground water flow conditions was developed by Domenico (1987). The solution derivation strategy used an approximate approach to solve the boundary value problem, resulting in a nonexact solution. Variations of the Domenico (1987) solution are incorporated into the software programs BIOSCREEN and BIOCHLOR, which are frequently used to evaluate subsurface contaminant transport problems. This article mathematically elucidates the error in the approximation and presents simulations that compare different versions of the Domenico (1987) solution to an exact analytical solution to demonstrate the potential error inherent in the approximate expressions. Results suggest that the accuracy of the approximate solutions is highly variable and dependent on the selection of input parameters. For solute transport in a medium‐grained sand aquifer, the Domenico (1987) solution underpredicts solute concentrations along the centerline of the plume by as much as 80% depending on the case of interest. Increasing the dispersivity, time, or dimensionality of the system leads to increased error. Because more accurate exact analytical solutions exist, we suggest that the Domenico (1987) solution, and its predecessor and successor approximate solutions, need not be employed as the basis for screening tools at contaminated sites.
Domenico Solution—Is It Valid?
Authors: Srinivasan V. , Clement T.P. , Lee K.K.
Published: January 2007

The Domenico solution is widely used in several analytical models for simulating ground water contaminant transport scenarios. Unfortunately, many textbook as well as journal article treatments of this approximate solution are full of empirical statements that are developed without mathematical rigor. For this reason, a rigorous analysis of this solution is warranted. In this article, we present a mathematical method to derive the Domenico solution and explore its limits. Our analysis shows that the Domenico solution is a true analytical solution when the value of longitudinal dispersivity is zero. For nonzero longitudinal dispersivity values, the Domenico solution will introduce a finite amount of error. We use an example problem to quantify the nature of this error and suggest some general guidelines for the appropriate use of this solution.
Did Manufacturing Matter? The Experience of Yesterdays Second Generation: A Reassessment
Authors: Waldinger Roger
Published: February 2007

Research on the “new second generation” takes the success of the earlier second generation of southern and eastern Europeans as its point of departure, but with little empirical basis. The hypothesis of “segmented assimilation” asserts that the children of the 1880–1920 immigration moved ahead due to the availability of well-paying, relatively low-skilled jobs in manufacturing. By contrast, defenders of the conventional approach to assimilation accent diffusionary processes, while conceding that the specific means by which the children of immigrants improved on their parents' condition remains a matter about which relatively little is known. This article returns to the world of the last second generation, just before it disappeared, to inquire into the extent and nature of the economic differences separating the adult immigrant offspring of the time from their third-generation-plus counterparts. Using data from the 1970 Census of Population, this article shows that manufacturing mattered, but in ways neither expected nor consistent with either of today's prevailing, theoretical approaches.
Early Child Care and the School Readiness of Children from Mexican Immigrant Families
Authors: Crosnoe Robert
Published: February 2007

Combining conceptual models from immigration and educational research, this study investigated whether a normative antecedent to the transition to formal schooling in the contemporary U.S. – early child care – links Mexican immigrant status to various aspects of school readiness. Regression models with nationally representative data revealed that children from Mexican immigrant families were overrepresented in parental care and underrepresented in center-based care compared to their native peers from other race/ethnic populations, which helped to explain a significant but small portion of their generally lower rates of both math achievement and externalizing symptoms in kindergarten. This mediating role of early child care, however, paled in comparison to family socioeconomic circumstances.
Immigrant Transnational Organizations and Development: A Comparative Study
Authors: Portes Alejandro , Escobar Cristina , Radford Alexandria Walton
Published: February 2007

This article explores how ninety Colombian, Dominican, and Mexican transnational immigrant organizations pursue philanthropic projects that aid in the development of their country or community of origin. We find that each nationality's context of exit and reception affects the origin, strength, and character of their organizations. We produce “maps” of the interaction of transnational organizations with each country of origin and conduct multivariate regressions to establish determinants of key organizational characteristics, including their degree of formalization and form of creation. Generally, Colombian organizations assume more middle-class forms, Dominican organizations stem largely from politics in the country of origin, and Mexican organizations are primarily hometown associations with greater involvement of the national state. We observe that regardless of nationality, transnational immigrant organizations' members are older, better-established, and possess above-average levels of education, suggesting that participation in transnational activities and assimilation are not incompatible. The character of proactive activities by each national state are examined. Theoretical implications for immigrant adaptation and community/national development are discussed.
Effects of Short‐Chain Nitrocompounds against Campylobacter jejuni and Campylobacter coli in vitro
Authors: Horrocks S.M. , Jung Y.S. , Huwe J.K. , Harvey R.B. , Ricke S.C. , Carstens G.E. , Callaway T.R. , Anderson R.C. , Ramlachan N. , Nisbet D.J.
Published: January 2007

ABSTRACT:  Effects of 2‐nitro‐1‐propanol, 2‐nitroethanol, nitroethane, and 2‐nitro‐methyl‐propionate (0, 10, and 20 mM) on growth of Campylobacter jejuni were tested during culture in Bolton broth adjusted to pH 5.6, 7.0, or 8.2. The nitrocompounds were similarly tested against C. coli but at pH 8.2 only. Viable cell counts measured during incubation revealed main effects (P < 0.05) of all nitrocompounds on the survivability of C. jejuni. An effect of pH (P < 0.05) on the survivability of C. Jejuni during incubation with nitrocompounds was observed, with greater inhibition observed at pH 8.2 than at pH 5.6 or 7.0 for nitroethane, 2‐nitro‐l‐propanol, and 2‐nitroethanol, but not for 2‐nitro‐methyl‐propionate, which showed greatest inhibition at pH 5.6. Except for 2‐nitro‐methyl‐propionate, which was ineffective, all nitrocompounds elicited similar effects on C. coli. The effect of nitroethane and 2‐nitro‐l‐propanol (10 mM) on naturally occurring Campylobacter was investigated during incubation of porcine fecal suspensions, where Campylobacter concentrations decreased more rapidly (P < 0.05) in suspensions with added 2‐nitro‐l‐propanol than in unsupplemented or nitroethane‐supplemented suspensions, thus reiterating the superior inhibitory effect of 2‐nitro‐l‐propanol.
Acceptance and Purchase Intent of US Consumers for Nonwheat Rice Butter Cakes
Authors: Sae‐Eaw A. , Chompreeda P. , Prinyawiwatkul W. , Haruthaithanasan V. , Suwonsichon T. , Saidu J.E. , Xu Z.
Published: January 2007

ABSTRACT: This study evaluated consumer acceptance and purchase intent of nonwheat butter cake formulations prepared with Thai jasmine rice flour. Three nonwheat rice butter cakes were prepared with varying amounts of powdered emulsifier (propylene glycol ester:diacetyl tartaric acid ester of monoglyceride, 8:2) at 0% (product A), 7.5% (product B), and 15% (product C) of the margarine content (15%) in the cake formulation. A commercial wheat‐based butter cake served as the control. Consumers (n= 400) evaluated acceptability of 9 sensory attributes using a 9‐point hedonic scale. Overall acceptance and purchase intent were determined with a binomial (yes/no) scale. At least 81% of consumers accepted products B and C, of which 42.1% and 47%, respectively, would purchase the products if commercially available. Product A was neither liked nor disliked with an overall liking score of 5.39. The butter cake products were differentiated by textural acceptability (overall texture, softness, and moistness) with a canonical correlation of 0.71 to 0.79. Overall liking and taste influenced overall acceptance and purchase intent. Odor influenced purchase intent (P= 0.0014), but not overall acceptance. The odds ratio of overall liking was 3.462 for purchase intent, indicating the probability of the product being purchased is 3.462 times higher (than not being purchased,P< 0.0001) with every 1‐unit increase of the overall liking score. Based on the logit model, overall acceptance and purchase intent could be predicted with 89.3% and 83.3% accuracy, respectively. The study demonstrated feasibility of completely substituting wheat flour with Thai jasmine rice flour for production of butter cake products acceptable to American consumers.
Improvement of Moistness and Texture of High Omega‐3 Fatty Acid Mackerel Nuggets by Inclusion of Moisture‐Releasing Ingredients
Authors: Lee K.H. , Joaquin H. , Lee C.M.
Published: January 2007

ABSTRACT:  In developing mince‐based nugget products using mackerel, an abundant, underutilized, high omega‐3 fatty acid species, attention was given to moistness and texture improvement with moisture‐releasing ingredients. Three basic approaches were used: added water level variation (0 to 35%), varying added water–moisture‐releasing vegetable combination (28/0, 21/7, 14/14, 7/21, 0/28), and varying milk–water combination (0/21, 7/14, 14/7, 21/0). Main ingredients of nugget included mackerel mince, mild cheddar cheese, and hydrated textured soy protein concentrate. The formulated products were molded, lightly battered, flash fried, and frozen until tested. Frozen nuggets were cooked to 65 °C and subjected to the Instron texture analysis (compressive force CF at 70% deformation, expressible fluid EF) and sensory analysis (firmness F, moistness M, overall desirability OD). The 28% added water, 7% moisture‐releasing vegetable at 21% water, and 14:7 and 21:0 milk‐water combinations were preferred (P < 0.05). Among the vegetables, onion and mushroom were preferred. Positive correlations were M‐OD (r= 0.82), EF‐OD (r= 0.54), and EF‐M (r= 0.49), and negative correlations were F‐OD (r=−0.83) and CF‐OD (r=−0.34). Milk was more effective than water in rendering moistness and tender texture. The vegetable was effective in forming and making the cooked product moist with less liquid added by holding moisture release during forming and liquid cells after cooking. During warming under the lamps, the least decreases in sensory score, compressive force, and expressible fluid were observed in nuggets made with vegetable and milk.
The Influence of Processing and Preservation on the Retention of Health‐Promoting Compounds in Broccoli
Authors: Galgano F. , Favati F. , Caruso M. , Pietrafesa A. , Natella S.
Published: January 2007

ABSTRACT:  In this work the effects of common household practices such as chilling, freezing, and cooking on vitamin C retention in broccoli (Marathon cv.), as well as their influence on the release of sulforaphane upon enzymatic hydrolysis of glucoraphanin by the endogenous enzyme myrosinase, were investigated. When chilled at 6 °C and 95% R.H. for 35 d, broccoli showed a vitamin C and sulforaphane loss of about 39% and 29%, respectively, while storage at –18 °C for 60 d resulted in similar losses, but mainly due to the blanching step. Boiling, steaming, microwaving, pressure‐cooking, and the combined use of pressure and microwaves were the cooking methods investigated. Boiling and steaming caused significant vitamin C losses, 34% and 22%, respectively, while with the other treatments more than 90% retention was observed. Sulforaphane was no more detectable after boiling or steaming, while pressure/microwave cooking did not cause any significant loss. The quantitative distribution of these moieties in the florets and stems of fresh and chilled broccoli was also investigated.
Change in Mutagenicity in White Rice after Accelerated and Long‐Term Storage
Authors: Pahulu H.F. , Davidson R.T. , Dunn M.L. , Ogden L.V. , Steele F.M. , Pike O.A.
Published: January 2007

ABSTRACT:  Certain reactions that occur in food during storage, such as nonenzymatic browning and lipid oxidation, form compounds that have been shown to be mutagenic. It is possible that over long storage periods, significant amounts of these products could be formed. Although some research has been published concerning the mutagenicity of foods due to processing or cooking, little research has been done regarding mutagenicity of foods stored for an extended time. The objective of this research was to determine the potential mutagenicity of white rice held in accelerated and long‐term storage using the Ames Salmonella/microsome assay. Fresh long‐grain white rice was packaged in foil laminate pouches and held at 60 °C for 18 wk. Rice stored for > 25 y in an oxygen‐free environment at or below room temperature in size number 10 cans was obtained from residential storage. The standard plate‐incorporation method was used to evaluate the mutagenic potential of all treatments using Salmonella typhimurium tester strains TA97a, TA98, TA100, and TA102. Samples were plated at 5 dilutions with and without rat liver S9 enzyme. A solvent control was also plated for each strain. Treatments yielding counts at least double the solvent control level were considered mutagenic. Plate counts for all treatments fell well below the required doubling of the solvent control value. White rice held in accelerated and long‐term storage appears not to increase in mutagenic compounds as measured by the Ames assay, supporting its use for long‐term storage purposes such as emergency preparedness and humanitarian food aid.
A Comparative Study on Phenolic Profiles and Antioxidant Activities of Legumes as Affected by Extraction Solvents
Authors: Xu B.J. , Chang S.K.C.
Published: January 2007

ABSTRACT:  The objective of this study was to investigate how 6 commonly used solvent systems affected the yields of phenolic substances and the antioxidant capacity of extracts from 8 major classes of food legumes. Several antioxidant‐related phytochemical compositions, namely, total phenolic content (TPC), total flavonoids content (TFC), and condensed tannins content (CTC), were investigated. In addition, antioxidant activities were tested using 2,2‐diphenyl‐1‐picryhydrazyl (DPPH) free radical scavenging, ferric‐reducing antioxidant power (FRAP), and the oxygen radical absorbance capacity (ORAC). The results showed that the 50% acetone extracts exhibited the highest TPC for yellow pea, green pea, chickpea, and yellow soybean. Acidic 70% acetone (+0.5% acetic acid) extracts exhibited the highest TPC, TFC, and FRAP values for black bean, lentil, black soybean, and red kidney bean. The 80% acetone extracts exhibited the highest TFC, CTC, and DPPH‐free radical scavenging activity for yellow pea, green pea, chickpea, and yellow soybean. The 70% ethanol extracts exhibited the greatest ORAC value for all selected legumes. These results indicated that solvents with different polarity had significant effects on total phenolic contents, extracted components, and antioxidant activities. High correlations between phenolic compositions and antioxidant activities of legume extracts were observed. The information is of interest to the nutraceutical food/ingredient industries since legumes are a rich source of antioxidants.
Instantaneous Behavior of Streamwise Vortices for Turbulent Boundary Layer Separation Control
Authors: Angele K. P. , Grewe F.
Published: February 2007

The present study investigates turbulent boundary layer separation control by means of streamwise vortices with focus on the instantaneous vortex behavior. A turbulent boundary layer is exposed to a pressure gradient that generates a separation bubble with substantial backflow. The separation bubble is controlled by conventional passive vortex generators creating pairs of counterrotating vortices. Quantitative information is achieved by applying Particle Image Velocimetry (PIV) to the cross-stream plane of the vortices. The characteristics of a pair of counter-rotating vortices shed from a vortex generator is investigated in the near-field downstream of the vortex generator. The vortices were found to grow with the boundary layer in the downstream direction, and the maximum vorticity decreases as the circulation is conserved. The vortices are nonstationary, and the movements in the spanwise direction are larger than those in the wall-normal direction, due to the presence of the wall. The vortices fluctuate substantially and move over a spanwise distance, which is approximately equal to their size. The most probable instantaneous separation between the two vortices shed from one vortex generator equals the difference between their mean positions. The unsteadiness of the vortices contributes to the observed maxima in the Reynolds stresses around the mean vortex centers. The instantaneous vortex size and the instantaneous maximum vorticity are also fluctuating properties, and the instantaneous vortex is generally smaller and stronger than the mean vortex. A correlation was found between a large instantaneous vortex size and a low instantaneous maximum vorticity (and vice versa), suggesting that the vortices are subjected to vortex stretching.
Particle Image Velocimetry Evaluation of a Novel Oscillatory-Flow Flexible Chamber Mixer
Authors: Shipman Thomas N. , Prasad Ajay K. , Davidson Scott L. , Cohee Donald R.
Published: February 2007

This paper describes a novel oscillatory-flow mixer consisting of a pair of flexible chambers connected by a perforated plate, or septum. During operation, the septum undergoes reciprocating motion such that the two chambers are alternately compressed and expanded. During compression, fluid is forced from one chamber to the other through the septum holes, creating an array of jets that drive the mixing process. Flow characterization within the mixer was conducted using particle image velocimetry. Tests were performed for Reynolds numbers ranging from 4 to 23,000, which encompass the creeping, laminar, and turbulent flow regimes. Results include mean and rms velocity maps, shear rate maps, vertical velocity profiles, and flow development data. The results suggest that the mixer is capable of gentle, continuous stirring (important for biological applications), as well as vigorous agitation. Finally, a comparison between this mixer and other existing mixing technologies is presented.
Characterization of the Content of the Cavity Behind a High-Speed Supercavitating Body
Authors: Wu Xiongjun , Chahine Georges L.
Published: February 2007

A high speed/high flow test facility was designed and implemented to study experimentally the supercavitating flow behind a projectile nose in a controlled laboratory setting. The simulated projectile nose was held in position in the flow and the cavity interior was made visible by having the walls of the visualization facility “cut through” the supercavity. Direct visualization of the cavity interior and measurements of the properties of the cavity contents were made. Transducers were positioned in the test section within the supercavitation volume to enable measurement of the sound speed and attenuation as a function of the flow and geometry parameters. These characterized indirectly the content of the cavity. Photography, high speed videos, and acoustic measurements were used to investigate the contents of the cavity. A side sampling cell was also used to sample in real time the contents of the cavity and measure the properties. Calibration tests conducted in parallel in a vapor cell enabled confirmation that, in absence of air injection, the properties of the supercavity medium match those of a mixture of water vapor and water droplets. Such a mixture has a very high sound speed with strong sound attenuation. Injection of air was also found to significantly decrease sound speed and to increase transmission.
CFD-Based Design Optimization for Hydro Turbines
Authors: Wu Jingchun , Shimmei Katsumasa , Tani Kiyohito , Niikura Kazuo , Sato Joushirou
Published: February 2007

A computational fluid dynamics-based design system with the integration of three blade design approaches, automatic mesh generator and CFD codes enables a quick and efficient design optimization of turbine components. It is applied to a Francis turbine rehabilitation project with strict customer requirements to provide over 3% increase in peak efficiency, 13% upgrade in power, and improved cavitation characteristics. Extensive turbulent flow simulations are performed for both the existing and new turbines at design and off design conditions. In order to take into account the interactions between different components, particularly the effects between the rotating and stationary parts, coupling calculations based on the implicit coupling method under multiple frames of reference are carried out for the entire turbine model. As a result, the runner and guide vanes are optimized to the greatest extent, and the stay vanes are locally modified with a possible minimum cost under the geometrical constraints of the existing machine. The performance of the new design is verified by model tests, and exceeds required improvements.
Molecular Dynamics Simulation of Thermal Cycling Test in Electronic Packaging
Authors: Fan Hai Bo , Chan Edward K. L. , Wong Cell K. Y. , Yuen Matthew M. F.
Published: February 2007

Interfacial failure under thermal cycling conditions is one of the main concerns in package design. To minimize such failure in multi-layered electronic assemblies and packages, it is important to develop a better understanding of the reliability at a molecular level. In this paper, molecular dynamics (MD) simulations were conducted to investigate the interfacial energy of the epoxy molding compound (EMC) cuprous oxide system during the thermal cycling test. In order to investigate the effect of the cuprous oxide content in the copper substrate on the interfacial adhesion, two kinds of MD models were examined in this study. The results revealed that the cuprous oxide content in the copper substrate had a large effect on the interfacial adhesion between the EMC and copper, which is consistent with the experimental observation.
Experimental Observation of Correlation Between Creep and Uniaxial Ratchetting of Sn∕37Pb and Sn∕3Ag∕0.5Cu Solder Alloys
Authors: Sasaki Katsuhiko , Kobayashi Takuji , Ohguchi Ken-ichi
Published: February 2007

Time-dependent deformations such as creep and ratchetting of solder alloys are significant deformation phenomena that need to be understood to ensure the safety and reliability of solder joints in electronic packaging. There is much research on creep deformation of solder alloys, but ratchetting deformation, especially the correlation between creep and ratchetting deformation of solder alloys has not been investigated. This paper discusses the correlation between creep and uniaxial ratchetting deformation to establish the differences in the time-dependent deformation of lead-free and lead-containing solder alloys. Uniaxial ratchetting tests were conducted by cyclic tension–compression tests or cyclic tension–unloading tests at several ratios of the maximum to minimum stresses. Additional creep tests following the uniaxial ratchetting were also conducted to observe the effect of the uniaxial ratchetting on creep deformation. An empirical method to select an optimal lead-free solder alloy is discussed by defining a uniaxial ratchetting strain rate. The additional creep tests also show that the uniaxial ratchetting deformation has a strong correlation to the creep deformation and that the correlation is different for lead-free and lead-containing solder alloys.
Investigations of Board-Level Drop Reliability of Wafer-Level Chip-Scale Packages
Authors: Lai Yi-Shao , Yeh Chang-Lin , Wang Ching-Chun
Published: February 2007

We present in this paper parametric studies of board-level reliability of wafer-level chip-scale packages subjected to a specific pulse-controlled drop test condition. Eighteen experiment cells, constructed by varying joint pitch, die thickness, and die size, are proposed and examined numerically. The transient analysis follows the support excitation scheme and incorporates an implicit time integration solver. Numerical results indicate that the drop reliability of the package enhances as the die thickness as well as the die size decreases. Moreover, the package with smaller solder joints and a smaller joint pitch suffers a greater drop reliability concern.
Improved Fluorescent In Situ Hybridization Method for Detection of Bacteria from Activated Sludge and River Water by Using DNA Molecular Beacons and Flow Cytometry
Authors: Lenaerts Jeremy , Lappin-Scott Hilary M. , Porter Jonathan
Published: February 2007

Fluorescent in situ hybridization (FISH) remains a key technique in microbial ecology. Molecular beacons (MBs) are self-reporting probes that have potential advantages over linear probes for FISH. MB-FISH strategies have been described using both DNA-based and peptide nucleic acid (PNA)-based approaches. Although recent reports have suggested that PNA MBs are superior, DNA MBs have some advantages, most notably cost. The data presented here demonstrate that DNA MBs are suitable for at least some FISH applications in complex samples, providing superior discriminatory power compared to that of corresponding linear DNA-FISH probes. The use of DNA MBs for flow cytometric detection of
Pseudomonas putida
resulted in approximately double the signal-to-noise ratio of standard linear DNA probes when using laboratory-grown cultures and yielded improved discrimination of target cells in spiked environmental samples, without a need for separate washing steps. DNA MBs were also effective for the detection and cell sorting of both spiked and indigenous
P. putida
from activated sludge and river water samples. The use of DNA MB-FISH presents another increase in sensitivity, allowing the detection of bacteria in environmental samples without the expense of PNA MBs or multilaser flow cytometry.
Spatial and Temporal Population Dynamics of a Naturally Occurring Two-Species Microbial Community inside the Digestive Tract of the Medicinal Leech
Authors: Kikuchi Yoshitomo , Graf Joerg
Published: February 2007

The medicinal leech,
Hirudo verbana
, is one of the simplest naturally occurring models for digestive-tract symbioses, where only two bacterial species,
Aeromonas veronii
bv. sobria (γ-
Proteobacteria
) and a
Rikenella
-like bacterium (
Bacteroidetes
), colonize the crop, the largest compartment of the leech digestive tract. In this study, we investigated spatial and temporal changes of the localization and microcolony structure of the native symbionts in the crop, after ingestion of a sterile blood meal, by fluorescence in situ hybridization. The population dynamics differed between the two symbiotic bacteria.
A. veronii
was detected mainly as individual cells inside the intraluminal fluid (ILF) during 14 days after feeding (daf) unless it was found in association with
Rikenella
microcolonies. The
Rikenella
-like bacteria were observed not only inside the ILF but also in association with the luminal surface of the crop epithelium. The sizes of
Rikenella
microcolonies changed dynamically through the 14-day period. From 3 daf onward, mixed microcolonies containing both species were frequently observed, with cells of both species tightly associating with each other. The sizes of the mixed microcolonies were consistently larger than the size of either single-species microcolony, suggesting a synergistic interaction of the symbionts. Lectin staining with succinylated wheat germ agglutinin revealed that the planktonic microcolonies present in the ILF were embedded in a polysaccharide matrix containing
N
-acetylglucosamine. The simplicity, symbiont-symbiont interaction, and mixed microcolonies of this naturally occurring, digestive-tract symbiosis lay the foundation for understanding the more complex communities residing in most animals.
Multiplex PCR Assay for Detection of
Vibrio vulnificus
Biotype 2 and Simultaneous Discrimination of Serovar E Strains
Authors: Sanjuán Eva , Amaro Carmen
Published: February 2007

In the present work we develop a multiplex PCR assay for the detection and identification of the fish pathogen
Vibrio vulnificus
biotype 2 with discriminating potential for zoonotic strains (serovar E). The PCR assay allowed the identification of two new biotype 2 serovar E human isolates from culture collections. Finally, the multiplex was successfully applied to both diagnosis and carrier detection in field samples.
Universal Sample Preparation Method for Characterization of Bacteria by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry
Authors: Liu Haihong , Du Zongmin , Wang Jin , Yang Ruifu
Published: February 2007

Mass spectrometry has been a very useful method to rapidly identify microorganisms associated with infectious diseases, detect bioterrorism threats, and discriminate among different subtypes of a pathogen. In this study, we developed a universal method for bacterial identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry. The effects on the mass spectrum of different experimental conditions, including the amount of bacterial cells used and treatment procedures with different solutions, matrix species, and solvents, were examined, and an optimized protocol was developed. Several different bacterial species, including
Yersinia pestis
,
Escherichia coli
,
Burkholderia cepacia
,
Bacillus anthracis
, and
Staphylococcus aureus
, which covered the gram-negative and -positive species and spore-producing and non-spore-producing species, were analyzed to evaluate the utility of the protocol. The results showed that five different species and different strains of the same species (9 strains of
S. aureus
and 10 strains of
E. coli
) could be discriminated clearly by their peak profiles in a mass range of 1,000 to 20,000 Da. This protocol is simple, rapid, and easy to perform; has excellent reproducibility; and is suitable for the construction of a mass spectrum fingerprinting database, which helps in fast bacterial identification via database searching.
Transposon Mutagenesis To Improve the Growth of Recombinant
Saccharomyces cerevisiae
on
d
-Xylose
Authors: Ni Haiying , Laplaza José M. , Jeffries Thomas W.
Published: February 2007

Saccharomyces cerevisiae
L2612 transformed with genes for xylose reductase and xylitol dehydrogenase (
XYL1
and
XYL2
) grows well on glucose but very poorly on
d
-xylose. When a gene for
d
-xylulokinase (
XYL3
or
XKS1
) is overexpressed, growth on glucose is unaffected, but growth on xylose is blocked. Spontaneous or chemically induced mutants of this engineered yeast that would grow on xylose could, however, be obtained. We therefore used insertional transposon mutagenesis to identify two loci that can relieve this xylose-specific growth inhibition. One is within the open reading frame (ORF) of
PHO13
, and the other is approximately 500 bp upstream from the
TAL1
ORF. Deletion of
PHO13
or overexpression of
TAL1
resulted in a phenotype similar to the insertional mutation events. Quantitative PCR showed that deletion of
PHO13
increased transcripts for
TAL1
, indicating that the growth inhibition imposed by the overexpression of
XYL3
on xylose can be relieved by an overexpression of transcripts for downstream enzymes. These results may be useful in constructing better xylose-fermenting
S. cerevisiae
strains.
Characterization of an
Escherichia coli
O157:H7 Plasmid O157 Deletion Mutant and Its Survival and Persistence in Cattle
Authors: Lim Ji Youn , Sheng Haiqing , Seo Keun Seok , Park Yong Ho , Hovde Carolyn J.
Published: February 2007

Escherichia coli
O157:H7 causes hemorrhagic colitis and hemolytic-uremic syndrome in humans, and its major reservoir is healthy cattle. An F-like 92-kb plasmid, pO157, is found in most
E. coli
O157:H7 clinical isolates, and pO157 shares sequence similarities with plasmids present in other enterohemorrhagic
E. coli
serotypes. We compared wild-type (WT)
E. coli
O157:H7 and an isogenic ΔpO157 mutant for (i) growth rates and antibiotic susceptibilities, (ii) survival in environments with various acidity, salt, or heat conditions, (iii) protein expression, and (iv) survival and persistence in cattle following oral challenge. Growth, metabolic reactions, and antibiotic resistance of the ΔpO157 mutant were indistinguishable from those of its complement and the WT. However, in cell competition assays, the WT was more abundant than the ΔpO157 mutant. The ΔpO157 mutant was more resistant to acidic synthetic bovine gastric fluid and bile than the WT. In vivo, the ΔpO157 mutant survived passage through the bovine gastrointestinal tract better than the WT but, interestingly, did not colonize the bovine rectoanal junction mucosa as well as the WT. Many proteins were differentially expressed between the ΔpO157 mutant and the WT. Proteins from whole-cell lysates and membrane fractions of cell lysates were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. Ten differentially expressed ∼50-kDa proteins were identified by quadrupole-time of flight mass spectrometry and sequence matching with the peptide fragment database. Most of these proteins, including tryptophanase and glutamate decarboxylase isozymes, were related to survival under salvage conditions, and expression was increased by the deletion of pO157. This suggested that the genes on pO157 regulate some chromosomal genes.
Consumption of Methane and CO
2
by Methanotrophic Microbial Mats from Gas Seeps of the Anoxic Black Sea
Authors: Treude Tina , Orphan Victoria , Knittel Katrin , Gieseke Armin , House Christopher H. , Boetius Antje
Published: February 2007

The deep anoxic shelf of the northwestern Black Sea has numerous gas seeps, which are populated by methanotrophic microbial mats in and above the seafloor. Above the seafloor, the mats can form tall reef-like structures composed of porous carbonate and microbial biomass. Here, we investigated the spatial patterns of CH
4
and CO
2
assimilation in relation to the distribution of ANME groups and their associated bacteria in mat samples obtained from the surface of a large reef structure. A combination of different methods, including radiotracer incubation, beta microimaging, secondary ion mass spectrometry, and catalyzed reporter deposition fluorescence in situ hybridization, was applied to sections of mat obtained from the large reef structure to locate hot spots of methanotrophy and to identify the responsible microbial consortia. In addition, CO
2
reduction to methane was investigated in the presence or absence of methane, sulfate, and hydrogen. The mat had an average δ
13
C carbon isotopic signature of −67.1‰, indicating that methane was the main carbon source. Regions dominated by ANME-1 had isotope signatures that were significantly heavier (−66.4‰ ± 3.9 ‰ [mean ± standard deviation;
n
= 7]) than those of the more central regions dominated by ANME-2 (−72.9‰ ± 2.2 ‰;
n
= 7). Incorporation of
14
C from radiolabeled CH
4
or CO
2
revealed one hot spot for methanotrophy and CO
2
fixation close to the surface of the mat and a low assimilation efficiency (1 to 2% of methane oxidized). Replicate incubations of the mat with
14
CH
4
or
14
CO
2
revealed that there was interconversion of CH
4
and CO
2.
The level of CO
2
reduction was about 10% of the level of anaerobic oxidation of methane. However, since considerable methane formation was observed only in the presence of methane and sulfate, the process appeared to be a rereaction of anaerobic oxidation of methane rather than net methanogenesis.
Selective Phylogenetic Analysis Targeting 16S rRNA Genes of Hyperthermophilic Archaea in the Deep-Subsurface Hot Biosphere
Authors: Kimura Hiroyuki , Ishibashi Jun-Ichiro , Masuda Harue , Kato Kenji , Hanada Satoshi
Published: February 2007

International drilling projects for the study of microbial communities in the deep-subsurface hot biosphere have been expanded. Core samples obtained by deep drilling are commonly contaminated with mesophilic microorganisms in the drilling fluid, making it difficult to examine the microbial community by 16S rRNA gene clone library analysis. To eliminate mesophilic organism contamination, we previously developed a new method (selective phylogenetic analysis [SePA]) based on the strong correlation between the guanine-plus-cytosine (G+C) contents of the 16S rRNA genes and the optimal growth temperatures of prokaryotes, and we verified the method's effectiveness (H. Kimura, M. Sugihara, K. Kato, and S. Hanada, Appl. Environ. Microbiol.72:21-27, 2006). In the present study we ascertained SePA's ability to eliminate contamination by archaeal rRNA genes, using deep-sea hydrothermal fluid (117°C) and surface seawater (29.9°C) as substitutes for deep-subsurface geothermal samples and drilling fluid, respectively. Archaeal 16S rRNA gene fragments, PCR amplified from the surface seawater, were denatured at 82°C and completely digested with exonuclease I (Exo I), while gene fragments from the deep-sea hydrothermal fluid remained intact after denaturation at 84°C because of their high G+C contents. An examination using mixtures of DNAs from the two environmental samples showed that denaturation at 84°C and digestion with Exo I completely eliminated archaeal 16S rRNA genes from the surface seawater. Our method was quite useful for culture-independent community analysis of hyperthermophilic archaea in core samples recovered from deep-subsurface geothermal environments.
Efficient Synthesis of Simvastatin by Use of Whole-Cell Biocatalysis
Authors: Xie Xinkai , Tang Yi
Published: February 2007

Simvastatin is a semisynthetic derivative of the fungal polyketide lovastatin and is an important drug for lowering cholesterol levels in adults. We have developed a one-step, whole-cell biocatalytic process for the synthesis of simvastatin from monacolin J. By using an
Escherichia coli
strain overexpressing the previously discovered acyltransferase LovD (X. Xie, K. Watanabe, W. A. Wojcicki, C. C. Wang, and Y. Tang, Chem. Biol. 13:1161-1169, 2006), we were able to achieve >99% conversion of monacolin J to simvastatin without the use of any chemical protection steps. The key finding was a membrane-permeable substrate, α-dimethylbutyryl-
S
-methyl-mercaptopropionate, that was efficiently utilized by LovD as the acyl donor. The process was scaled up for gram-scale synthesis of simvastatin. We also demonstrated that simvastatin synthesized via this method can be readily purified from the fermentation broth with >90% recovery and >98% purity as determined by high-performance liquid chromatography. Bioconversion using high-cell-density, fed-batch fermentation was also examined. The whole-cell biocatalysis can therefore be an attractive alternative to currently used multistep semisynthetic transformations.