bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous In Vitro Transformation of Adult Neural Precursors into Stem‐Like Cancer Cells
Authors: Siebzehnrubl Florian A. , Jeske Ina , Müller Dorit , Buslei Rolf , Coras Roland , Hahnen Eric , Huttner Hagen B. , Corbeil Denis , Kaesbauer Johanna , Appl Thomas , Von Hörsten Stephan , Blümcke Ingmar
Published: July 2008

Recent studies have found that cellular self‐renewal capacity in brain cancer is heterogeneous, with only stem‐like cells having this property. A link between adult stem cells and cancer stem cells remains, however, to be shown. Here, we describe the emergence of cancer stem‐like cells from in vitro cultured brain stem cells. Adult rat subventricular zone (SVZ) stem cells transformed into tumorigenic cell lines after expansion in vitro. These cell lines maintained characteristic features of stem‐like cells expressing Nestin, Musashi‐1 and CD133, but continued to proliferate upon differentiation induction. Karyotyping detected multiple acquired chromosomal aberrations, and syngeneic transplantation into the brain of adult rats resulted in malignant tumor formation. Tumors revealed streak necrosis and displayed a neural as well as an undifferentiated phenotype. Deficient downregulation of platelet‐derived growth factor (PDGF) receptor alpha was identified as candidate mechanism for tumor cell proliferation, and its knockdown by siRNA resulted in a reduction of cell growth. Our data point to adult brain precursor cells to be transformed in malignancies. Furthermore, in vitro expansion of adult neural stem cells, which will be mandatory for therapeutic strategies in neurological disorders, also harbors the risk for amplifying precursor cells with acquired genetic abnormalities and induction of malignant tumors after transplantation.
Influence of Visual Masking Technique on the Assessment of 2 Red Wines by Trained and Consumer Assessors
Authors: Ross C.F. , Bohlscheid J. , Weller K.
Published: July 2008

ABSTRACT: During sensory evaluation assessments, visual masking techniques are frequently employed to disguise color differences between samples and minimize perceptual bias. Particularly in wine, the impact of these masking techniques on panelist evaluations has not been well studied. The objective of this study was to study the influence of visual masking techniques on the aroma and flavor assessment of 2 red wines and observe the impact of these techniques on trained and consumer sensory panels. Specific masking techniques included (1) blue wine glass/white illumination; (2) clear glass/red illumination; and (3) clear glass/white illumination. Ten panelists were trained to recognize 7 aroma and flavor attributes, while consumer panelists (n= 80) evaluated attributes and liking. For the trained panel, the visual masking technique affected only perceived spicy flavor of Syrah (P≤ 0.05), with the clear glass/red illumination resulting in more intense spicy flavor compared to the other 2 conditions. Principal components analysis showed that for the 2 red wines evaluated by the trained panel, red illumination resulted in higher spicy attributes and perceived astringency while wines served in blue wine glasses were higher in perceived astringency. For the consumer panel, red illumination resulted in wines higher in perceived astringency and blue wine glasses resulted in wines higher in perceived flavor liking. These results indicated that the visual masking techniques may influence both trained and consumer panel evaluation of aroma and flavor attributes of red wine. However, beyond red wine, this study makes the larger point that the choice of masking technique does impact sensory evaluations.
Effect of Home Freezing and Italian Style of Cooking on Antioxidant Activity of Edible Vegetables
Authors: Danesi F. , Bordoni A.
Published: July 2008

ABSTRACT:  In this study, we analyzed the modifications of antioxidant activity consequent to 3 typical home cooking practices (steaming, boiling, and microwave cooking) in fresh and home frozen vegetables. Six different vegetable species were examined: carrots (Daucus carota L.), zucchini (Cucurbita pepo L.), tomatoes (Solanum lycopersicum L.), green beans (Phaseolus vulgaris L.), peas (Pisum sativum L.), and yellow peppers (Capsicum annuum L.). All vegetables were conventional products and were analyzed in season to minimize differences due to agricultural practice and storage. Cooking and freezing are generally regarded as destructive to antioxidants, and this has fostered a belief among many consumers that raw vegetables are nutritionally superior to their frozen and/or cooked forms. In the current study, we provide evidence that this is not always the case.
Hydrodynamic Cavitation: Characterization of a Novel Design with Energy Considerations for the Inactivation of Saccharomyces cerevisiae in Apple Juice
Authors: Milly P.J. , Toledo R.T. , Kerr W.L. , Armstead D.
Published: July 2008

ABSTRACT:  A Shockwave Power™ Reactor consisting of an annulus with a rotating pock‐marked inner cylinder was used to induce hydrodynamic cavitation in calcium‐fortified apple juice flowing in the annular space. Lethality on Saccharomyces cerevisiae was assessed at processing temperatures of 65 and 76.7 °C. Details of the novel equipment design were presented and energy consumption was compared to conventional and pulsed electric fields processing technologies. The mean log cycle reduction of S. cerevisiae was 6.27 CFU/mL and all treatments resulted in nonrecoverable viable cells. Induced lethality from hydrodynamic cavitation on S. cerevisiae exceeded the predicted values based on experimentally determined thermal resistance. Rotation of 3000 and 3600 rpm at flow rates greater than 1.0 L/min raised product temperature from 20 to 65.6 or 76.7 °C, respectively, and energy input was less than 220 kJ/kg. Conversion efficiency from electrical to thermal was 55% to 84%. Hydrodynamic cavitation enhanced lethality of spoilage microorganisms in minimally processed juices and reduced energy usage.
Microbial Assessment in School Foodservices and Recommendations for Food Safety Improvement
Authors: Yoon Y. , Kim S.‐R. , Kang D.‐H. , Shim W.‐B. , Seo E. , Chung D.‐H.
Published: July 2008

ABSTRACT:  This study evaluated microbial food safety in school foodservices. Five school foodservices were randomly selected, and samples from water, cooking utensils, tableware, foodservice surroundings, and linen were collected in summer and winter (N= 420). Tap and drinking water samples were collected, samples of food contact surfaces were collected by swab‐kit, and samples for foodservice workers' hands and gloves were prepared by glove juice method. Aerobic plate count (APC) and coliform bacterial populations were enumerated on plate count agar (PCA) and desoxycholate lactose agar, respectively. The presence of Escherichia coli, Salmonella, Listeria monocytogenes, and Staphylococcus aureus was also examined by biochemical identification tests. In addition, PCA agar for APCs and Baird‐Parker agar for S. aureus were used to enumerate airborne microorganisms. Higher APCs (< 0 to 5.1 log CFU/mL) than acceptable level were generally observed in water samples, while low coliform counts were found in the samples. High APCs were enumerated in cooking utensils, foodservice workers, tableware, and foodservice surroundings, and coliforms were also found in the samples for both seasons. The presence of Salmonella was found from only 10% of plastic glove samples (summer), and the presence of L. monocytogenes was not observed in all samples. S. aureus was detected in some of water, cooking utensils, tableware, employees, and foodservice surroundings, and E. coli was observed in cooking utensils (10% to 20%; summer). No obvious airborne bacteria were detected. These results showed that sanitation practice in school foodservices should be improved, and the results may be useful in microbial assessment of school foodservices.
Effect of Xylose on Sheepmeat Flavors in Casserole‐Style Cooking
Authors: Young O.A. , Cummings T.L.
Published: July 2008

ABSTRACT: Five‐carbon sugars affect cooked meat flavor by the Maillard reaction. This research extends to the effects of pH and cooking temperature on meaty and species flavor, sweetness, barnyard, and rancid flavor in sheepmeat. Glucose and xylose were each blended into groundlongissimusmeat to 0%, 0.5%, or 1% and heated to 75 °C. Xylose treatments browned more than glucose treatments, and xylose flavor effects were more marked. With xylose, sheepmeat flavor declined significantly, but meaty flavor also declined. Differences were marked between pH 5.93 and 6.52, but pH effects at lower pHs were more subtle. Sweetness increased in many treatments, suggesting that 75 °C did not fully exploit the Maillard reaction. Therefore, pressure‐cooked casserole treatments, chilled and frozen, were used to study the effects of xylose, packaging, and storage time on flavor. There were no flavor differences due to chill packaging (foil laminate compared with barrier bag) (not significant). Xylose addition reduced sheepmeat flavor by 24% on the 1 to 9 intensity scale (P< 0.001), while meaty flavor and sweetness were unaffected. Rancid flavor was reduced by xylose addition (P< 0.01), and the reduction in barnyard flavor approached significance (P= 0.07). Chilled storage time to 29 d did not affect any attribute. In the frozen casserole trial (stored exposed to air), xylose had no significant flavor effects (allP≥ 0.38). However, storage to 71 d increased the rancid flavor score from a negligible 0.06 to 0.60 (P= 0.04), suggesting that rancidity development swamped more subtle effects.
Sweet Taste in Man: A Review
Authors: Meyers B. , Brewer M.S.
Published: July 2008

ABSTRACT:  A greater understanding of the molecular mechanisms of sweet taste has profound significance for the food industry as well as for consumers. Understanding the mechanism by which sweet taste is elicited by saccharides, peptides, and proteins will assist science and industry in their search for sweet substances with fewer negative health effects. The original AH‐B theories have been supplanted by detailed structural models. Recent identification of the human sweet receptor as a dimeric G‐protein coupled receptor comprising T1R2 and T1R3 subunits has greatly increased the understanding of the mechanisms involved in sweet molecule binding and sweet taste transduction. This review discusses early theories of the sweet receptor, recent research of sweetener chemoreception of nonprotein and protein ligands, homology modeling, the transduction pathway, the possibility of the sweet receptor functioning allosterically, as well as the implications of allelic variation.
Modeling Surface Transfer of Listeria monocytogenes on Salami during Slicing
Authors: Sheen S.
Published: July 2008

ABSTRACT:  Listeria monocytogenes has been implicated in several listeriosis outbreaks linked to the consumption of presliced ready‐to‐eat (RTE) deli meats, which has drawn considerable attention in regard to possible cross‐contamination during slicing operation at retail and food service environments. Salami with 15% fat (a moderate fat content deli item) was used to investigate the transfer of L. monocytogenes between a meat slicer and salami slices and to understand its impact on food safety. A 6‐strain cocktail of L. monocytogenes was inoculated onto a slicer blade to an initial level of approximately 3, 5, 6, 7, or 9 log CFU/blade (or approximately 2, 4, 5, 6, or 8 log CFU/cm2 of the blade edge area), and then the salami was sliced to a thickness of 1 to 2 mm (case I). For another cross‐contamination scenario, a clean blade was first used to slice salami loaf that was previously surface‐inoculated with L. monocytogenes (approximately 3, 5, 6, 7, 8, or 9 log CFU/100 cm2 area), followed by slicing the uninoculated salami loaf (case II). The salami slicing rate was maintained at an average of 3 to 4 slices per minute in all the tests. The results showed that the empirical models developed in this study were reasonably accurate in describing the transfer trend/pattern of L. monocytogenes between the blade and salami slices if the inoculum level was > 5 log CFU on the salami or blade. With an initial inoculum at 3 or 4 log CFU, the experimental data seemed to suggest a rather random pattern of bacterial transfer between blade and salami. The currently developed models are microbial load (n), sequential slice index (X), and contamination route dependent, which might limit their applications to certain conditions. However, the models may be further applied to predict the 3 or 4 log CFU level (and below) cross‐contamination of salami slicing process. Considering only few data are available in the literature regarding food pathogen surface transfer, the empirical models may provide a useful tool in building risk assessment procedures.
Purification, Thermal Stability, and Antigenicity of the Immunodominant Soybean Allergen P34 in Soy Cultivars, Ingredients, and Products
Authors: Wilson S. , Martinez‐Villaluenga C. , De Mejia E.G.
Published: July 2008

ABSTRACT:  Protein P34 (Gly m Bd 30K) is the immunodominant allergen in soybean (Glycine max L.). The objectives of this study were (1) to study the effect of thermal treatment on P34 antigenicity and secondary structure after isolation and purification of P34 from soybean by chromatographic techniques; (2) to identify the variability of P34 allergen within 138 accessions from a diverse USDA soybean germplasm collection by ELISA; and (3) to quantify P34 immunoreactivity in various commercial soy ingredients and products. Thermal processing decreased P34 antigenicity. Soybean accessions with the highest P34 content were ancestral (12 mg/g defatted flour) followed by modern (10 mg/g defatted flour) and exotic (8 mg/g defatted flour). The cultivar that emerged as the lowest‐expressing P34 accession was PI548657 (2.3 mg/g defatted flour). Among commercial soy ingredients, soy flour yielded the highest P34 antigenicity (32 mg/g extracted protein) followed by soy protein isolate (29 mg/g extracted protein) and soy protein concentrate (24 mg/g extracted protein). Among soy consumer products, soymilk presented the highest P34 antigenicity, ranging from 7 to 23 mg/g extracted protein, followed by tempeh (8 mg/g extracted protein), soy infant formula (3.4 mg/g extracted protein), soy powder (2 mg/g extracted protein), and soy cheese products (0.50 mg/g extracted protein). Korean miso, soy sauce, soy chili mix, soy nuts, soy cream cheese, soy meat patty, texturized soy protein, and soy cereal exhibited undetectable P34 antigenicity (detection limit = 0.45 ng). Selecting soybean varieties with low levels of this allergen, or via processing, could potentially make soybean products less antigenic.
Optimization of Medium Composition for Nisin Fermentation with Response Surface Methodology
Authors: Zhou X.‐X. , Pan Y.‐J. , Wang Y.‐B. , Li W.‐F.
Published: July 2008

ABSTRACT:  Nisin is an effective food biopreservative widely used in food industry. However, 1 problem of concern is limited production rate and final nisin concentration. A nisin‐producing strain, L. lactis Lac2, a mutant strain with high yield of nisin, was obtained in our laboratory recently. In the present study, a fractional factorial design was applied to investigate the main factors that affect the yield of L. lactis Lac2. Central composite experimental design and response surface methodology were adopted to derive a statistical model for optimizing the composition of the medium. The results showed that the optimum medium for nisin production of L. lactis Lac2 was composed of 2.68% sucrose (w/v), 0.5% tryptone (w/v), 1% yeast extract (w/v), 0.3% Tween‐80 (w/v), 0.02% MgSO4·7H2O (w/v), 0.81% NaCl (w/v), 1.91% K2HPO4 (w/v), 0.05% ascorbic acid (w/v), and 2% agar (w/v) (if necessary) at pH 6.5. When cultured in the optimum medium, the nisin yield is an average of 3381.81 IU/mL, which nearly doubled the yield when incubated in the initial medium. Also, the concentration of tryptone was decreased while that of the sucrose was increased when compared with CM broth, which means a reduction of the fermentation cost.
Growth Inhibition and Induction of Apoptosis in U937 Cells by Coptis chinensis Extract
Authors: Ma C.‐Y. , Shen S.‐C. , Huang D.‐W. , Chang H.‐M. , Wu J.S.‐B.
Published: July 2008

ABSTRACT:  Dried Coptidis Rizoma was extracted with boiling water. Conditioned medium was prepared by stimulating human peripheral blood mononuclear cells with Coptidis Rizoma extract (CR). The conditioned medium was then added to human leukemic U937 cells suspension for investigating the antiproliferation effect and the induction of apoptosis. Apparent DNA fragmentation and morphological changes occurred in U937 cells after incubating for 48 h to 72 h with the conditioned medium that had been prepared with 400 μg CR solids/mL. Flow cytometric analysis revealed that the percentage of apoptotic U937 cells increased in a time‐ and concentration‐dependent manner. The upregulation of Bax expression, the downregulation of Bcl‐2 and procaspase‐3 expression, and the release of cytochrome c from the mitochondria in U937 cells were all observed. Reverse transcription–polymerase chain reaction detected cytokine‐related mRNA expressions in human mononuclear cells incubated with CR. An increase in the concentration of CR in culturing medium downregulated granulocyte macrophage colony‐stimulatory factor mRNA expression while upregulated interleuken‐2 mRNA expression. All the above‐mentioned evidences suggest that CR induces the apoptosis of human leukemic U937 cells via the changes in cytokine profile and protein expressions in mitochondria pathway and that CR has the potential to be used in the therapy of leukemia due to its strong apoptosis‐promoting effect.
Safety of Polyethylene Terephthalate Food Containers Evaluated by HPLC, Migration Test, and Estimated Daily Intake
Authors: Park H.‐J. , Lee Y.J. , Kim M.‐R. , Kim K.M.
Published: July 2008

ABSTRACT:  A comparative high‐pressure liquid chromatography (HPLC) analysis of monomers, terephthalic acid (TPA), isophthalic acid (IPA), and dimethyl terephthalate (DMT) from polyethylene terephthalate (PET) food containers was conducted. Monomer linearities and sensitivities were calibrated between established and novel HPLC analyses. Safety of PET containers was evaluated with newly established detection methods for TPA, IPA, and DMT. Migration of the 3 monomers into food simulants (water, 4% acetic acid, 20% alcohol, and n‐heptane) from 56 PET containers collected from open markets was monitored. Migrated monomers were not detected over 0.1 ppm of detection limit. The corresponding estimated daily intake was measured to confirm the safety of these publicly available PET containers and to permit comparison to the specific migration limit of the European Union. The estimated daily intake of 3 monomers migrating from PET was 0.0384 mg/kg each. This represented only 0.6% of the European Union's specific migration limit, confirming the safety of the examined containers.
Changes in Postharvest Quality of Swiss Chard Grown Using 3 Organic Preharvest Treatments
Authors: Daiss N. , Lobo M.G. , Gonzalez M.
Published: July 2008

ABSTRACT:  Using storage conditions recommended for conventional chard (4 °C, 90% RH and 7 d), the chard treated with some organic preharvest treatments [effective microorganisms, a fermented mixture of effective microorganisms with organic matter (EM–Bokashi + EM), and an auxiliary soil product] lost considerable water (> 2%) and weight (> 25%). These results indicate that organic methods tested produce a vegetable that can not sustain its quality when commercialized through the conventional supply chain. Nevertheless, respiration, color, pH, and titratable acidity practically remained constant during conservation. Ascorbic acid content was constant in chard treated with the different preharvest treatments and collected at 8 wk after sowing (normal harvest). However, the ascorbic acid content of the control chard decreased 60% after 7 d of storage. This vitamin diminished (35%) in chard collected after 19 wk after sowing (late harvest) during the postharvest conservation. The greatest difference in chard quality was registered between sampling dates since chard collected during the late harvest had higher levels of dry matter, sugars, acids, proteins, and ascorbic acid than chard collected during the normal harvest.
Saltiness Enhancement by the Characteristic Flavor of Dried Bonito Stock
Authors: Manabe M.
Published: July 2008

ABSTRACT:  There is a pressing need for the development of ways of preparing palatable salt‐reduced foods to reduce the salt intake of the Japanese population. The salt‐reducing effect of the characteristic flavors other than umami of dried bonito stock, which is widely used in everyday Japanese food, was examined by sensory evaluation. In the 1st sensory evaluation, the effect was evaluated in a model solution. The saltiness of 0.80% NaCl solution was equivalent to that of 0.12% monosodium glutamate (MSG) solution containing 0.81% NaCl and dried bonito stock containing 0.68% NaCl. Saltiness enhancement could not be found when MSG solution was used, but was found with 6% dried bonito stock. The 2nd evaluation examined whether the effect was valid for 2 everyday Japanese foods—traditional Japanese clear soup (sumashi‐jiru) and steamed egg custard (tamagodoufu). Although enhancement of saltiness by dried bonito stock could not be clearly demonstrated in the soup, a change in NaCl concentration within 15% did not affect the palatability of the soup. However, dried bonito stock not only enhanced the saltiness but also improved the palatability of steamed egg custard. These findings are expected to be useful for improving the palatability of salt‐reduced food.
Changes of Anthocyanins, Anthocyanidins, and Antioxidant Activity in Bilberry Extract during Dry Heating
Authors: Yue X. , Xu Z.
Published: July 2008

ABSTRACT:  Thermal stability of 10 anthocyanins found in a bilberry extract was studied at different heating temperatures and times. Degradation of the 10 anthocyanins, delphinidin, cyanidin, petunidin, peonidin, and malvidin derivatives with different conjugated sugars, followed 1st‐order reaction kinetics at heating temperatures 80, 100, and 125 °C. Though the degradation rate constants of anthocyanins were not significantly different from each other at the same heating temperature, they increased drastically when heating temperature was increased to 125 °C. At that temperature, the half‐lives for all anthocyanins were less than 8 min. The degradation rate constants followed the Arrhenius equation. The trend of lower activation energy of the anthocyanins with arabinoside than with galactoside or glucoside was observed. These conjugated sugars were cleaved from the anthocyanins to produce their corresponding anthocyanidins or aglycones during heating. The production of anthocyanidins increased constantly and was converted from approximately 30% of the degraded anthocyanins when heated at 100 °C for up to 30 min. At 125 °C, the increase of anthocyanidins lasted for 10 min, after which the degradation rate of anthocyanidins exceeded the production rate. Antioxidant activities of the heated extracts were estimated by measuring DPPH (2, 2′‐diphenyl‐1‐picrylhydrazyl) free radical scavenging activity. The extracts heated at 80 °C for 30 min, 100 °C for 10 and 20 min, and 125 °C for 10 min had higher free radical scavenging capability than unheated extract.
Femtosecond Laser Disruption of Filamentous Cyanobacteria Unveils Dissimilar Cellular Stability Between Heterocysts and Vegetative Cells
Authors: Arellano Juan B. , Vázquez de Aldana Javier R. , Méndez Cruz , González‐Pérez Sergio , Moreno Pablo , Roso Luis
Published: July 2008

Filamentous cyanobacteria develop heterocysts in response to deprivation for combined nitrogen under aerobic conditions. The most prominent structural change in heterocysts is the biosynthesis of an envelope that restricts gas permeability, providing an appropriate micro‐oxic environment for N2 fixation inside. The additional thickness of the differentiated cells, when compared to vegetative cells, makes filamentous cyanobacteria an attractive biological system to investigate cellular response against femtosecond laser processing. By irradiating the cyanobacterial filaments with 120 fs, 795 nm, 1 kHz pulses focused through a 100× microscope objective with a numerical aperture of 0.85, we have determined that the pulse energy threshold for an apparent disruption of the cell wall of vegetative cells is 13 ± 4 nJ per pulse. A further increase in the pulse energy to 43 ± 13 nJ causes the complete removal of vegetative cells. In contrast, the pulse energy threshold has to be augmented about three‐fold for heterocyst envelope disruption or two‐fold for complete removal of heterocysts. We propose that the singular cross‐linked structure of the glycolipid multilayer of the envelope, required to restrict gas permeability, accounts for the remarked difference in the ablation energy threshold between vegetative cells and heterocysts.
A Numerical Study on the Effect of Water Addition on NO Formation in Counterflow CH4/Air Premixed Flames
Authors: Guo Hongsheng , Neill W. Stuart , Smallwood Gregory J.
Published: July 2008

The effect of water addition on NO formation in counterflow CH4/air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to flame temperature drop. Among a lean, a stoichiometric, and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame. The addition of water also reduces the formation of NO in a flame because of the chemical effect. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.
Optimization of the Flow in the Catalytic Converter of Internal Combustion Engines by Means of Screens
Authors: Arantes Eduardo M. R. , Medeiros Marcello A. F.
Published: July 2008

The flow in the automotive catalytic converter is, in general, not uniform. This significantly affects cost, service life, and performance, in particular, during cold startup. The current paper reports on a device that provided a large improvement in flow uniformity. The device is to be placed in the converter inlet diffuser and is constructed out of ordinary screens. It is cheap and easy to install. Moreover, the device does not present most of the undesired effects, such as increase in pressure drop and time to light off, often observed in other devices developed for the same purpose.
Asynchronous Dynamic Coefficients of a Three-Lobe Air Bearing
Authors: Ruiz Rafael O. , Di Liscia Marcelo H. , Medina Luis U. , Díaz Sergio E.
Published: July 2008

The study of dynamic whirl behavior of air bearings is fundamental for an adequate rotordynamic analysis and future validation of numerical predictions. This work shows the dynamic response of the air film on a three-lobe bearing under asynchronous whirl motion. One-dimensional multifrequency orbits are used to characterize the bearing rotordynamic coefficients. The test rig uses two magnetic bearing actuators to impose any given orbits to the journal. The dynamic forces are measured on the test bearing housing by three load cells. Journal whirling excitation is independent of the rotating speed, thus allowing asynchronous excitations. The multifrequency excitation is applied at each rotating speed up to 11,000rpm, allowing the asynchronous characterization of the air film. The experimental procedure requires two linearly independent excitation sets. Thus, vertical and horizontal one-dimensional multifrequency orbits are applied as perturbations. Results show the synchronous and asynchronous dynamic coefficients of the air bearing. Asynchronous experimental results are compared to numerical estimation of the bearing force coefficients through solution of the isotropic ideal gas journal bearing Reynolds equation. Numerical dynamic coefficients are obtained as the effective coefficient values of the bearing when subject to a given orbit. A full characterization of the asynchronous rotordynamics coefficients of the bearing is presented in three-dimensional maps.
A Musculoskeletal Model of the Equine Forelimb for Determining Surface Stresses and Strains in the Humerus—Part I. Mathematical Modeling
Authors: Pollock Sarah , Hull M. L. , Stover Susan M. , Galuppo Larry D.
Published: July 2008

Knowledge of the forces that act upon the equine humerus while the horse is standing and the resulting strains experienced by the bone is useful for the prevention and treatment of fractures and for assessing the proximolateral aspect of the bone as a site for obtaining autogenous bone graft material. The first objective was to develop a mathematical model to predict the loads on the proximal half of the humerus created by the surrounding musculature and ground reaction forces while the horse is standing. The second objective was to calculate surface bone stresses and strains at three cross sections on the humerus corresponding to the donor site for bone grafts, a site predisposed to stress fracture, and the middle of the diaphysis. A three-dimensional mathematical model employing optimization techniques and asymmetrical beam analysis was used to calculate shoulder muscle forces and surface strains on the proximal and mid-diaphyseal aspects of the humerus. The active shoulder muscles, which included the supraspinatus, infraspinatus, subscapularis, and short head of the deltoid, produced small forces while the horse is standing; all of which were limited to 4.3% of their corresponding maximum voluntary contraction. As a result, the strains calculated at the proximal cross sections of the humerus were small, with maximum compressive strains of −104με at the cranial aspect of the bone graft donor cross section. The middle of the diaphysis experienced larger strain magnitudes with compressive strains at the lateral and the caudal aspects and tensile strains at the medial and cranial aspects (−377με and 258με maximum values, respectively) while the horse is standing. Small strains at the donor bone graft site do not rule out using this location to harvest bone graft tissue, although strains while rising to a standing position during recovery from anesthesia are unknown. At the site common to stress fractures, small strains imply that the stresses seen by this region while the horse is standing, although applied for long periods of time, are not a cause of fracture in this location. Knowing the specific regions of the middle of the diaphysis of the humerus that experience tensile and compressive strains is valuable in determining optimum placement of internal fixation devices for the treatment of complete fractures.
A Musculoskeletal Model of the Equine Forelimb for Determining Surface Stresses and Strains in the Humerus—Part II. Experimental Testing and Model Validation
Authors: Pollock Sarah , Stover Susan M. , Hull M. L. , Galuppo Larry D.
Published: July 2008

The first objective of this study was to experimentally determine surface bone strain magnitudes and directions at the donor site for bone grafts, the site predisposed to stress fracture, the medial and cranial aspects of the transverse cross section corresponding to the stress fracture site, and the middle of the diaphysis of the humerus of a simplified in vitro laboratory preparation. The second objective was to determine whether computing strains solely in the direction of the longitudinal axis of the humerus in the mathematical model was inherently limited by comparing the strains measured along the longitudinal axis of the bone to the principal strain magnitudes and directions. The final objective was to determine whether the mathematical model formulated in Part I [Pollock et al., 2008, ASME J. Biomech. Eng., 130, p. 041006] is valid for determining the bone surface strains at the various locations on the humerus where experimentally measured longitudinal strains are comparable to principal strains. Triple rosette strain gauges were applied at four locations circumferentially on each of two cross sections of interest using a simplified in vitro laboratory preparation. The muscles included the biceps brachii muscle in addition to loaded shoulder muscles that were predicted active by the mathematical model. Strains from the middle grid of each rosette, aligned along the longitudinal axis of the humerus, were compared with calculated principal strain magnitudes and directions. The results indicated that calculating strains solely in the direction of the longitudinal axis is appropriate at six of eight locations. At the cranial and medial aspects of the middle of the diaphysis, the average minimum principal strain was not comparable to the average experimental longitudinal strain. Further analysis at the remaining six locations indicated that the mathematical model formulated in Part I predicts strains within ±2 standard deviations of experimental strains at four of these locations and predicts negligible strains at the remaining two locations, which is consistent with experimental strains. Experimentally determined longitudinal strains at the middle of the diaphysis of the humerus indicate that tensile strains occur at the cranial aspect and compressive strains occur at the caudal aspect while the horse is standing, which is useful for fracture fixation.
Comparison of Particle Image Velocimetry and Phase Contrast MRI in a Patient-Specific Extracardiac Total Cavopulmonary Connection
Authors: Kitajima Hiroumi D. , Sundareswaran Kartik S. , Teisseyre Thomas Z. , Astary Garrett W. , Parks W. James , Skrinjar Oskar , Oshinski John N. , Yoganathan Ajit P.
Published: July 2008

Particle image velocimetry (PIV) and phase contrast magnetic resonance imaging (PC-MRI) have not been compared in complex biofluid environments. Such analysis is particularly useful to investigate flow structures in the correction of single ventricle congenital heart defects, where fluid dynamic efficiency is essential. A stereolithographic replica of an extracardiac total cavopulmonary connection (TCPC) is studied using PIV and PC-MRI in a steady flow loop. Volumetric two-component PIV is compared to volumetric three-component PC-MRI at various flow conditions. Similar flow structures are observed in both PIV and PC-MRI, where smooth flow dominates the extracardiac TCPC, and superior vena cava flow is preferential to the right pulmonary artery, while inferior vena cava flow is preferential to the left pulmonary artery. Where three-component velocity is available in PC-MRI studies, some helical flow in the extracardiac TCPC is observed. Vessel cross sections provide an effective means of validation for both experiments, and velocity magnitudes are of the same order. The results highlight similarities to validate flow in a complex patient-specific extracardiac TCPC. Additional information obtained by velocity in three components further describes the complexity of the flow in anatomic structures.
Active Control of Pressure Oscillations in a Liquid-Fueled Sector Combustor
Authors: Cohen J. M. , Banaszuk A. , Hibshman J. R. , Anderson T. J. , Alholm H. A.
Published: July 2008

A system for the active control of combustor pressure oscillations in liquid-fueled, lean, premixed combustors was demonstrated in a three-nozzle sector combustor, using full-scale engine hardware. Modulation of a portion of the premixed fuel flow led to a reduction of 6.5 dB (2.1 times) in the amplitude of the dominant pressure oscillations mode. Combustor emissions were not adversely affected by the control.
Mechanical Performance of Generic and Proprietary Enema Bottles
Authors: Walsh Donna L. , Schroeder R. Jason , Stewart Sandy F. C.
Published: July 2008

Enemas containing the anti-inflammatory drug mesalamine are an effective treatment for a distal form of inflammatory bowel disease (IBD). An IBD patient discovered that a generic mesalamine enema was more difficult and painful to use than the proprietary version. A study was initiated to determine whether these differences were measurable in the laboratory using conventional mechanical test equipment. Differences among three bottle types (the proprietary brand and two generic versions) were quantified by mechanical testing. The compressive force required to squeeze the drug from each bottle was measured, tensile testing was performed on the bottle wall, and stiffness of the nozzle tips was studied via bend testing. The thickness of the bottle walls and the inner diameter (ID) of the nozzles were also recorded. The work required to expel the drug from the generic versions during bottle compression was significantly greater than for the proprietary (p<0.01). This was likely due to the wall thickness being greater in the generics; the elastic moduli of the three bottles were similar. The ID of the nozzles was smaller for the generic bottles, suggesting additional resistance to flow. Increased flow resistance was also observed for bottles in which lubricant obstructed the nozzle opening. The work required to bend the nozzle was greater in the generics than in the proprietary (p<0.01). These differences between the generic and proprietary bottles are consistent with the patient’s subjective experience. Poor bottle performance may adversely affect patient compliance with this treatment. Improved bottle design (such as tighter tolerances for wall thickness, nozzle ID, and nozzle stiffness) and manufacturing controls (e.g., preventing the nozzle lubricant from impeding delivery of the drug) could be achieved through the development of a standard specification for enema bottles. An optimal bottle design is suggested.
A Novel Low NOx Lean, Premixed, and Prevaporized Combustion System for Liquid Fuels
Authors: Gokulakrishnan P. , Ramotowski M. J. , Gaines G. , Fuller C. , Joklik R. , Eskin L. D. , Klassen M. S. , Roby R. J.
Published: July 2008

Dry low emission (DLE) systems employing lean, premixed combustion have been successfully used with natural gas in combustion turbines to meet stringent emission standards. However, the burning of liquid fuels in DLE systems is still a challenging task due to the complexities of fuel vaporization and air premixing. Lean, premixed, and prevaporized (LPP) combustion has always provided the promise of obtaining low pollutant emissions while burning liquid fuels, such as kerosene and fuel oil. Because of the short ignition delay times of these fuels at elevated temperatures, the autoignition of vaporized higher hydrocarbons typical of most practical liquid fuels has been proven difficult to overcome when burning in a lean, premixed mode. To avoid this autoignition problem, developers of LPP combustion systems have focused mainly on designing premixers and combustors that permit rapid mixing and combustion of fuels before spontaneous ignition of the fuel can occur. However, none of the reported works in the literature has looked at altering fuel combustion characteristics in order to delay the onset of ignition in lean, premixed combustion systems. The work presented in this paper describes the development of a patented low NOx LPP system for combustion of liquid fuels, which modifies the fuel rather than the combustion hardware in order to achieve LPP combustion. In the initial phase of the development, laboratory-scale experiments were performed to study the combustion characteristics, such as ignition delay time and NOx formation, of the liquid fuels that were vaporized into gaseous form in the presence of nitrogen diluent. In the second phase, a LPP combustion system was commissioned to perform pilot-scale tests on commercial turbine combustor hardware. These pilot-scale tests were conducted at typical compressor discharge temperatures and at both atmospheric and high pressures. In this study, vaporization of the liquid fuel in an inert environment has been shown to be a viable method for delaying autoignition and for generating a gaseous fuel stream with characteristics similar to natural gas. Tests conducted in both atmospheric and high pressure combustor rigs utilizing swirl-stabilized burners designed for natural gas demonstrated an operation similar to that obtained when burning natural gas. Emission levels were similar for both the LPP fuels (fuel oils 1 and 2) and natural gas, with any differences ascribed to the fuel-bound nitrogen present in the liquid fuels. An extended lean operation was observed for the liquid fuels as a result of the wider lean flammability range for these fuels compared to natural gas.
Comparative Study of Two Low CO2 Emission Power Generation System Options With Natural Gas Reforming
Authors: Zhang Na , Lior Noam
Published: July 2008

Two power plant schemes that reduce CO2 emission and employ natural gas reforming were analyzed and discussed. The first one integrates natural gas reforming technology for efficiency improvement with an oxy-fuel combined power system (OXYF-REF), with water as the main work fluid. The reforming heat is obtained from the available turbine exhaust heat, and the produced syngas is used as fuel with oxygen as the oxidizer. The turbine working fluid can expand down to a vacuum, producing a high-pressure ratio and thus more net work. The second system integrates natural gas reforming in a precombustion decarbonization scheme using chemical absorption technology for the CO2 removal (PCD-REF). The gas turbine is the conventional air-based one with compressor intercooling. Supplementary combustion is employed to elevate the turbine exhaust temperature and thus achieve a much higher methane conversion rate (96.9%). Both systems involve internal heat recuperation from gas turbine exhausts, and particular attention has been paid to the integration of the heat recovery chain to reduce the related exergy destruction. The systems are simulated and their thermal efficiency, overall and component exergy losses, and CO2 removal capacity are compared. The OXYF-REF system has a higher energy efficiency, of 51.4%, and higher CO2 removal, but the product CO2 has lower purity, of 84%. The PCD-REF system has a thermal efficiency of 46%, the captured CO2 is 99% pure, and the CO2 specific emission is 58.5g∕kWh.
A Study of the Transition Between Lean Conventional Diesel Combustion and Lean, Premixed, Low-Temperature Diesel Combustion
Authors: Busch Stephen , Bohac Stanislav V. , Assanis Dennis N.
Published: July 2008

New diesel combustion modes face difficult challenges with respect to engine-out emissions and transient behavior. Transitions between lean conventional diesel combustion and lean, premixed, low-temperature diesel combustion are investigated with an automotive diesel engine. Effects of fuel pressure on transitional cycles are investigated. Cycle-by-cycle heat release analysis is performed and an exhaust mass flow model is used to obtain cycle-averaged NO concentrations. The behavior of combustion progression and NO emissions during the transitions is discussed. Observed cool-flame behavior is identified and explained.
Investigation of the Effect of Incomplete Droplet Prevaporization on NOx Emissions in LDI Combustion Systems
Authors: Beck Christian H. , Koch Rainer , Bauer Hans-Jörg
Published: July 2008

The influence of incomplete liquid fuel prevaporization on the emissions of nitric oxides in a swirl stabilized model gas turbine combustor is investigated experimentally and numerically. The design of the model combustor enables the variation of the degree of prevaporization. This is achieved by using two liquid fuel injectors. One injector is located far upstream of the combustor and generates a fully prevaporized and premixed air fuel mixture. The second injector is located at the combustor inlet. Consequently, the liquid fuel mass flow split between the two injectors determines the fraction of nonprevaporized fuel present in the reaction zone. The NO∕NO2 measurements were performed with a chemoluminescence analyzer. In accordance to the findings of other researchers, the present experimental study revealed that the influence of prevaporization on nitric oxide emissions is of significance for practical applications. The experimental studies were accompanied by numerical studies of partially prevaporized lean combustion in an abstracted configuration. The purpose of this numerical study is to gain a detailed understanding of the influence of droplet slip on droplet flame position and peak temperature. The droplet slip velocity was found to have a significant impact on the peak temperature of the droplet flame and, therefore, NO formation rates within the droplet flame. The combustion system used for the experimental investigation was characterized regarding droplet slip velocities with an extended laser Doppler anemometry technique. The comparison between numerical and experimental results shows that the droplet slip velocities in the macroscopic reaction zone are within the transition range from an envelope to a wake flame. It is concluded that small-scale mixing effects play a significant role in the formation of nitric oxides in spray combustion systems with incomplete prevaporization.
Characterization of Particulate Matter Emissions From a Four-Stroke, Lean-Burn, Natural Gas Engine
Authors: Quillen Kris , Bennett Maren , Volckens John , Stanglmaier Rudolf H.
Published: July 2008

Regulatory agencies are becoming increasingly concerned with particulate emissions as the health and environmental effects are becoming better understood. While much research has been performed on diesel engines, little is known about particulate matter (PM) emissions from natural gas internal combustion engines. In this project, tests were conducted on a Waukesha VGF F18 natural gas engine running at full load. PM10 combustion emissions were collected on teflon and quartz filters and a scanning mobility particle sizer was used to determine the particle size distribution. Tests were performed at 4–7% exhaust oxygen (O2) levels. Overall, it was found that a large number of small particles were emitted from this engine. The total mass based PM emissions were found to be 0.0148gm∕bkWh, which is slightly greater than the Tier-4 nonroad diesel particulate emission standard. Particle distributions revealed that the geometric mean diameter of the natural gas particles was approximately 30nm and did not change with air to fuel ratio. Particulate concentrations were found to decrease at leaner engine operating conditions. Results showed a strong correlation between the NOx and particle concentrations, while an inverse correlation between CO and particle concentrations was revealed.
A Numerical Study on the Effect of CO Addition on Flame Temperature and NO Formation in Counterflow CH4/Air Diffusion Flames
Authors: Guo Hongsheng , Neill W. Stuart
Published: July 2008

A numerical study was carried out to understand the effect of CO enrichment on flame temperature and NO formation in counterflow CH4/air diffusion flames. The results indicate that when CO is added to the fuel, both flame temperature and NO formation rate are changed due to the variations in adiabatic flame temperature, fuel Lewis number, and chemical reaction. At a low strain rate, the addition of carbon monoxide causes a monotonic decrease in flame temperature and peak NO concentration. However, NO emission index first slightly increases, and then decreases. At a moderate strain rate, the addition of CO has negligible effect on flame temperature and leads to a slight increase in both peak NO concentration and NO emission index, until the fraction of carbon monoxide reaches about 0.7. Then, with a further increase in the fraction of added carbon monoxide, all three quantities quickly decrease. At a high strain rate, the addition of carbon monoxide causes increase in flame temperature and NO formation rate, until a critical carbon monoxide fraction is reached. After the critical fraction, the further addition of carbon monoxide leads to decrease in both flame temperature and NO formation rate.