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Leuconostoc mesenteroides is a commercially important lactic acid bacterium currently used as a starter for kimchi and kefir. However, its sensitivity to acid stress limits its performance. L. mesenteroides was grown in a medium supplemented with 3.2 or 6.4 mM glutathione (GSH), and cell survival rates were measured during a long-term mild acid challenge (pH 4.0). As a result, GSH was imported by the cells and protected against acid stress; thereafter it was consumed as a nutrient. Acid stress resistance of starter cultures of this bacterium can thus be improved by cultivating it in media supplemented with GSH.

In the present study, toxicity of silver nanoparticles (AgNPs) was investigated in the nematode, Caenohabditis elegans focusing on the upstream signaling pathway responsible for regulating oxidative stress, such as mitogen-activated protein kinase (MAPK) cascades. Formation of reactive oxygen species (ROS) was observed in AgNPs exposed C.elegans, suggesting oxidative stress as an important mechanism in the toxicity of AgNPs towards C. elegans. Expression of genes in MAPK signaling pathways increased by AgNPs exposure in less than 2-fold compared to the control in wildtype C.elegans, however, those were increased dramatically in sod-3 (gk235) mutant after 48 h exposure of AgNPs (i.e. 4-fold for jnk-1 and mpk-2; 6-fold for nsy-1, sek-1, and pmk-1, and 10-fold for jkk-1). These results on the expression of oxidative stress response genes suggest that sod-3 gene expression appears to be dependent on p38 MAPK activation. The high expressions of the pmk-1 gene 48 h exposure to AgNPs in the sod-3 (gk235) mutant can also be interpreted as compensatory mechanisms in the absence of important stress response genes. Overall results suggest that MAPK-based integrated stress signaling network seems to be involved in defense to AgNPs exposure in C.elegans.

In the present study, a toxic mechanism of silver nanoparticles (AgNPs) was investigated in the nematode, Caenorhabditis elegans, focusing on the involvement of oxidative stress in reproduction toxicity. Initially, AgNPs were tested as potential oxidative stress inducers, and increased formation of reactive oxygen species (ROS) was observed in AgNP-exposed C. elegans. Subsequently, the potential upstream signaling pathway activated in response to AgNP exposure was investigated, paying special attention to the C. elegans PMK-1 p38 mitogen-activated protein kinase (MAPK). Increased PMK-1 p38 MAPK gene and protein expressions were observed in C. elegans exposed to AgNPs. Expression of the p38-dependent transcription factor genes and glutathione S-transferase (GST) enzyme activity was also investigated in wildtype (N2) and pmk-1 mutant (km25) C. elegans exposed to AgNPs. The results indicated that AgNP exposure led to increased ROS formation, increased expression of PMK-1 p38 MAPK and hypoxia-inducible factor (HIF-1), GST enzyme activity, and decreased reproductive potential in wildtype (N2) C. elegans; whereas in the AgNP-exposed pmk-1 (km25) mutant, ROS formation and HIF-1 and GST activation were not observed, and decreased reproductive potential was rescued. These results suggest that oxidative stress is an important mechanism of AgNP-induced reproduction toxicity in C. elegans, and that PMK-1 p38 MAPK plays an important role in it. The results also suggest that GST and HIF-1 activation by AgNP exposure are PMK-1 p38 MAPK-dependent, and that both play an important role in the PMK-1 p38 MAPK-mediated defense pathway to AgNP exposure in C. elegans., (Copyright © 2011 SETAC.)

Bifidobacterium longum subsp. infantis ATCC 15697 utilizes several small-mass neutral human milk oligosaccharides (HMOs), several of which are fucosylated. Whereas previous studies focused on endpoint consumption, a temporal glycan consumption profile revealed a time-dependent effect. Specifically, among preferred HMOs, tetraose was favored early in fermentation, with other oligosaccharides consumed slightly later. In order to utilize fucosylated oligosaccharides, ATCC 15697 possesses several fucosidases, implicating GH29 and GH95 α-L-fucosidases in a gene cluster dedicated to HMO metabolism. Evaluation of the biochemical kinetics demonstrated that ATCC 15697 expresses three fucosidases with a high turnover rate. Moreover, several ATCC 15697 fucosidases are active on the linkages inherent to the HMO molecule. Finally, the HMO cluster GH29 α-L-fucosidase possesses a crystal structure that is similar to previously characterized fucosidases.

The pCB42 plasmid from Leuconostoc citreum CB2567, a strain isolated from kimchi, was characterized, and a shuttle vector for Escherichia coli and lactic acid bacteria (LAB) was constructed. The pCB42 plasmid has a circular structure of 4312bp, a low G+C content, and no single-stranded DNA intermediates during replication, which indicates that pCB42 replicates via the theta-type replication mechanism. In silico analysis of this plasmid revealed 6 open reading frames: 1 transposase gene, 1 DNA-binding gene, 2 putative replication genes, and 2 unknown genes. The fragment encompassing ORF5 contains a functional plasmid replicon. This plasmid was capable of replicating in various LAB, including L. citreum, L. mesenteroides, Lactobacillus plantarum, Lb. reuteri, Lactococcus lactis, Streptococcus thermophilus, Weissella confusa, and Oenococcus oeni. The LAB-E. coli shuttle vector was constructed by ligating pCB42 and pEK104, and the resulting shuttle vector, pLeuCM42, showed a high segregational stability in L. citreum CB2567 after 100 generations of cell division. By using this shuttle vector, the β-gal gene from Lb. plantarum was successfully expressed in the host strain, L. citreum CB2567. The pLeuCM42 shuttle vector can serve as a useful gene-delivery and expression tool for the genetic study or metabolic engineering of various strains of LAB., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Leuconostoc genus, which comprise heterofermentative lactic acid bacteria, reduces fructose to mannitol by recycling intracellular NADH. To evaluate the mannitol productivities of different Leuconostoc species, 5 stock cultures and 4 newly isolated strains were cultivated in MRS and simplified media containing glucose and fructose (1:2 ratio). Among them, L. citreum KACC 91348P, which was isolated from kimchi, showed superior result in cell growth rate, mannitol production rate, and yield in both media. The optimal condition for mannitol production of this strain was pH 6.5 and 30°C. When L. citreum KACC was cultured in simplified medium in a 2 l batch fermenter under optimal conditions, the maximum volumetric productivity was 14.83 g·l(-1)h(-1) and overall yield was 86.6%. This strain is a novel and efficient mannitol producer originated from foods to be used for fermentation of fructose-containing foods.

Objectives: In this study, we investigated the potential harmful effect of the exposure to silicon dioxide (SiO(2)) nanoparticles through in vitro toxicity assay using human bronchial epithelial cell, Beas-2B with a focus on the involvement of oxidative stress as the toxic mechanism., Methods: SiO(2)-induced oxidative stress was assessed by examining formation of reactive oxygen species (ROS), the induction of superoxide dismutase (SOD) and heme oxygenase-1 (HO-1), as well as cytotoxicity effect was evaluation by cell viability. Subsequently, to understand the molecular mechanism of nanoparticle-induced oxidative stress, the involvement of oxidative stress-responding transcription factors, such as, nuclear factor-kappaB (NF-κB) and nuclear factor-E2-related factor-2 (Nrf-2), and mitogen-activated protein (MAP) kinase signal transduction pathway was also investigated., Results: 5-d i phenyltera zolium bromide (MTT) assay results show that decrease 20% in cell viability and the number of cells in the subG1 phase increased. The increase in ROS formation was observed in SiO(2) nanoparticle treated cells. The expression of SOD protein was not changed, whereas that of HO-1 was increased by SiO(2) nanoparticle exposure. transcription factors Nrf-2 and the expression of phosphorylated form of extracellular signal-regulating kinase (ERK) was strongly induced by SiO(2) nanoparticle exposure, Conclusions: SiO(2) nanoparticles exert their toxicity through oxidative stress as they cause the significant increase ROS level. SiO(2) nanoparticles induce induction of HO-1 via Nrf-2-ERK MAP kinase pathway. Our tested oxidative stress parameters are rather limited in terms of allowing the full understanding of oxidative stress and cellular response by SiO(2) nanoparticle exposure.

To identify potential harmful effects of silver nanoparticles (AgNPs) on human health, a comprehensive toxicity assay was conducted on human Jurkat T cells, using oxidative stress-related endpoint. The effect of Ag ions was also investigated and compared with that of AgNPs, as it is anticipated that Ag ions will be released from AgNPs, which may be responsible for their toxicity. Cell viability tests indicated high sensitivity of Jurkat T cells when exposed to AgNPs compared to Ag ions; however, both AgNPs and Ag ions induce similar levels of cellular reactive oxygen species during the initial exposure period and; after 24 h, they were increased on exposure to AgNPs compared to Ag ions, which suggest that oxidative stress may be an indirect cause of the observed cytotoxicity of AgNPs. AgNPs exposure activates p38 mitogen-activated protein kinase through nuclear factor-E2-related factor-2 and nuclear factor-kappaB signaling pathways, subsequently inducing DNA damage, cell cycle arrest and apoptosis. Selective toxicity of AgNPs on Jurkat T cells suggests that rigorous toxicity evaluation should be conducted using various different cell types and biological systems prior to the widespread use of AgNPs.

In this work, an analytical method for the characterization of the hygroscopic property, chemical composition, and morphology of individual aerosol particles is introduced. The method, which is based on the combined use of optical and electron microscopic techniques, is simple and easy to apply. An optical microscopic technique was used to perform the visual observation of the phase transformation and hygroscopic growth of aerosol particles on a single particle level. A quantitative energy-dispersive electron probe X-ray microanalysis, named low-Z particle EPMA, was used to perform a quantitative chemical speciation of the same individual particles after the measurement of the hygroscopic property. To validate the analytical methodology, the hygroscopic properties of artificially generated NaCl, KCl, (NH(4))(2)SO(4), and Na(2)SO(4) aerosol particles of micrometer size were investigated. The practical applicability of the analytical method for studying the hygroscopic property, chemical composition, and morphology of ambient aerosol particles is demonstrated.

Biodiesel is a renewable fuel which can be produced through an esterification reaction. The cost of feedstock which resulted in that of biodiesel is a large problem to be resolved. Dark oil from industrial process can be a better alternative for biodiesel production because of its low price. In spite of this, the study of biodiesel production using the dark oil has not been reported. This study provides technical information and catalytic properties on this system. Among the several catalysts, WO(3)/ZrO(2) catalyst was the most effective catalyst in the esterification of the dark oil to fatty acid methyl esters (FAMEs). The catalytic reaction parameters were optimized that 20 wt.% WO(3)/ZrO(2) has a high FFA conversion of 96% at 150 degrees C, 0.4 g/ml (oil), 1:9 (oil to alcohol, molar ratio) and 2h reaction time. The physical and chemical properties of the catalyst were characterized by XRD, Raman spectrometer, BET and NH(3)-TPD., ((c) 2010. Published by Elsevier Ltd. All rights reserved.)

This study investigates the buffering effects of calcium salts in kimchi on total acidity, microbial population, and dextransucrase activity. Calcium chloride or calcium carbonate was added in dongchimi-kimchi, a watery-radish kimchi, and their effects on various biochemical attributes were analyzed. The addition of 0.1% calcium chloride produced a milder decrease in the pH after 24 days of incubation, which allowed the lactic acid bacteria to survive longer than in the control. In particular, the heterofermentative Leuconostoc genus population was 10-fold higher than that in the control. When sucrose and maltose were also added along with the calcium salts, the dextransucrase activity in the kimchi was elevated and a higher concentration of isomaltooligosaccharides was synthesized when compared with the control. Calcium chloride was determined as a better activator compound of dextransucrase than calcium carbonate, probably because of its higher solubility. Therefore, the results of this study confirm the ability of the proposed approach to modulate the kimchi fermentation process and possibly enhance the quality of kimchi based on the addition of dietary calcium salts.

To develop a gene expression system for Leuconostoc genus, construction of expression vector and expression of a heterologus protein in Leuconostoc was performed. Alpha-amylase gene from Lactobacillus amylovorus was cloned into a Leuconostoc cloning vector, pLeuCM, with its own signal peptide. pLeuCMamy was introduced into Leuconostoc citreum CB2567 and a successful expression of alpha-amy gene was confirmed by enzyme activity assays. About 90% of alpha-amylase activity was detected in the culture broth, revealing most of expressed alpha-amylase was secreted out cells. The signal sequence of alpha-amy gene is a good candidate for the secretion of heterologous protein by using Leuconostoc host-vector system.

D-form lactate is often found in fermented foods and excessive dietary intake of D-lactate may cause metabolic stress in both infants and patients. Leuconostoc citreum is a major lactic acid bacterium that produces D-lactate in fermented foods. The aim of this study was to change the pyruvate carbon flux in L. citreum from D-lactate into L-lactate by heterologous expression of L-lactate dehydrogenase (ldhL) gene. For this, ldhL from Lactobacillus plantarum was cloned and introduced into L. citreum using a shuttle vector pLeuCM. In the transformant, ldhL was successfully transcribed and L-lactate dehydrogenase was expressed. As a consequence of transformation, the ratio between D- and L-isomers was changed due to the increment of L-lactate and the decrement of D-lactate, but no significant differences were found in total lactate concentration between the host and transformant cells. This is the first report of metabolic engineering in Leuconostoc by modulating the central carbon flux into health-favored way.

In this study, the potentially harmful effect of the exposure to fumed and porous silicon dioxide (silica) nanoparticles was investigated using human bronchial epithelial cell, Beas-2B, with a focus on the involvement of oxidative stress as the toxic mechanism. Silica nanoparticles-induced oxidative stress was assessed by examining the formation of reactive oxygen species (ROS) and induction of antioxidant enzymes, such as superoxide dismutase (SOD) and heme oxygenase-1 (HO-1). Subsequently, to understand the mechanism of nanoparticles-induced oxidative stress, the involvement of oxidative stress-responding transcription factors, such as, nuclear factor-kappaB (NF-kappaB) and nuclear factor-E2-related factor-2 (Nrf-2), as well as the mitogen-activated protein (MAP) kinase signal transduction pathway were investigated. From the overall results, silica nanoparticles exerted toxicity via oxidative stress, which lead to the induction of HO-1 via the Nrf-2-ERK MAP kinase signaling pathway; cells exposed to porous silica nanoparticles showed a more sensitive response than those exposed to fumed silica. Nevertheless, the parameters tested were rather limited in terms of gaining a full understanding of the oxidative stress and cellular response due to exposure to silica nanoparticles. Further studies on the mechanism by which silica nanoparticles induce the Nrf-2-ERK MAP kinase pathway, to more clearly elucidate the silica-induced oxidative stress, as well as on the relationship between the physico-chemical properties of nanoparticles and their cytotoxicity are warranted to gain an understanding of the phenomenon of different sensitivities between porous and fumed silica.

A dextransucrase (LcDS) gene from Leuconostoc citreum HJ-P4 has been amplified and cloned in E. coli. The LcDS gene consists of 4,431 nucleotides encoding 1,477 amino acid residues sharing 63-98% of amino acid sequence identities with other known dextransucrases from Leuc. mesenteroides. Interestingly, 0.1 mM of IPTG induction at 15 degrees remarkably increased the LcDS productivity to 19,187 U/l culture broth, which was over 330-fold higher than that induced at 37 degrees. Optimal reaction temperature and pH of LcDS were determined as 35 degrees and pH 5.5 in 20 mM sodium acetate buffer, respectively. Meanwhile, 0.1 mM CaCl(2) increased its activity to the maximum of 686 U/mg, which was 2.1-fold higher than that in the absence of calcium ion. Similar to the native Leuconostoc dextransucrase, recombinant LcDS could successfully produce a series of isomaltooligosaccharides from sucrose and maltose, on the basis of its transglycosylation activity.

To understand the molecular mechanism of previously observed cerium oxide (CeO(2)) nanoparticles-induced oxidative stress, an in vitro toxicity assay was conducted using human bronchial epithelial cell, Beas-2B, focusing on the involvement of the oxidative stress responding signal transduction pathway and transcription factors in the toxicity of CeO(2) nanoparticles. Extracellular signal-regulating kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) signaling pathways, along with nuclear factor-kappaB (NF-kappaB) and nuclear factor-E2-related factor-2 (Nrf-2), were investigated as the upstream events of oxidative stress from exposure to CeO(2) nanoparticles. The overall results suggest that CeO(2) nanoparticles may exert their toxicity through oxidative stress, as they cause significant increases in the cellular reactive oxygen species (ROS) concentrations, subsequently leading to the strong induction of heme oxygenase-1 (HO-1) via the p38-Nrf-2 signaling pathway. Further studies on the mechanism by which CeO(2) nanoparticles induce the p38-Nrf-2 signaling pathway are warranted for a better understanding of the CeO(2) nanoparticles-induced oxidative stress; studies with other signaling pathways, with concentration-response and time course experiments would also be justified.

Leuconostoc citreum (L. citreum) HJ-P4 (KACC 91035) is one of the major predominant species in kimchi fermentation in Korea. The purpose of the present study was to test the immunomodulatory capacity of L. citreum to modulate the IgE-mediated allergic response and to examine the involvement of NF-kappaB and MAPK in IL-12 production in macrophages. Balb/c mice were sensitized with OVA/alum and oral administration of L. citreum to the mice began before or after the OVA sensitization. Protein and mRNA expression of Th1 cytokines in splenocytes by L. citreum in vitro was measured. The role of NF-kappaB and MAPK such as p38, ERK1/2 and JNK in L. citreum-induced IL-12 was investigated in peritoneal macrophages and RAW264.7 cell lines. L. citreum inhibited the serum levels of total IgE, IgG1 and IgG2a altogether and increased OVA-specific IFN-gamma production in splenocytes from pre- and post-sensitized animals. However, the downregulation of IL-4 and IL-5 production was observed only in the pre-sensitization group. The ability of L. citreum to stimulate IFN-gamma was dependent on its induction of IL-12. NF-kappaB, p38 and JNK were mainly involved in L. citreum-induced IL-12 production. In conclusion, the current study demonstrated that L. citreum is able to regulate serum IgE generation at the induction and effector phases of allergic response through overall control over antibody production and that its involvement of IL-12 production was mediated through NF-kappaB and p38/JNK. Taken together, the use of L. citreum can be useful in preventing the development and progression of IgE production.

Leuconostoc mesenteroides subsp. mesenteroides (LMM) KCTC 3100, is one of the prominent species in the fermentation of kimchi, a traditional Korean food. In the present study, we investigated the capacity of this microorganism in inducing Th1 cytokines in the presence of Th2 signals in vitro and in vivo and the requirement of NF-kappaB and MAPK signaling. Stimulation with heat-killed LMM in mouse splenocytes induced the expression of IFN-gamma, which was dependent on IL-12 production by LMM. Pre-treatment with LMM in vitro augmented the production of IFN-gamma and IL-4 in response to anti-CD3 plus recombinant IL-4 (rIL-4). LMM administration to mice, beginning either before or after the development of OVA sensitization, increased OVA-restimulated IFN-gamma production in the splenocytes and reduced serum total and OVA-specific IgE levels. However, only the pre-sensitization treatment induced a slight reduction in IL-4 from the same cells, but the post-sensitization treatment did not. Induction of IL-12 by LMM in peritoneal macrophages involved NF-kappaB, p38 and JNK, but not ERK1/2. In conclusion, our data presented the upregulation of IFN-gamma by LMM under the pro-Th2 conditions and the requirement of NF-kappaB, p38 and JNK for IL-12 production. These observations suggest that this microorganism can be a useful Th1-inducing agent in modulating the Th1/Th2 imbalance.

To investigate the lactic acid bacterial population in Korean traditional rice wines, biotyping was performed using cell morphology and whole-cell protein pattern analysis by SDSPAGE, and then the isolates were identified by 16S rRNA sequencing analysis. Based on the morphological characteristics, 103 LAB isolates were detected in wine samples, characterized by whole-cell protein pattern analysis, and they were then divided into 18 patterns. By gene sequencing of 16S rRNA, the isolates were identified as Lactobacillus paracasei, Lb. arizonensis, Lb. plantarum, Lb. harbinensis, Lb. parabuchneri, Lb. brevis, and Lb. hilgardii when listed by their frequency of occurrence. It was found that the difference in bacterial diversity between rice and grape wines depends on the raw materials, especially the composition of starch and glucose.

In 2004, Leuconostoc mesenteroides DRC was first used as a starter culture for achieving higher organoleptic effects in Korean kimchi manufacture. For a better understanding of starter growth in a mixed culture system, and for predicting starter predominance in kimchi, a monitoring system for the starter was established. The chloramphenicol resistance marker gene (cat) was randomly integrated into chromosomal DNA of L. mesenteroides DRC using a viral transposon and transposase. The DRC mutant, tDRC2, had a similar growth pattern to the host strain, with no major alteration in phenotypic characteristics. The mutant strain was inoculated into real kimchi, and monitoring of the starter population was successfully achieved. The overall predominance of Leuconostoc in kimchi inoculated with DRC followed the general growth pattern of this genus during kimchi fermentation. Our results also demonstrate the competitive ability of the DRC starter against Leuconostoc from natural flora, maintaining its predominance above 88% during the whole fermentation period. Based on this experiment, the random gene integration method using a transposon was shown to be of utility in transferring any commercial starter into a selectable and monitorable strain for simulation purposes.

Isomaltooligosaccharide (IMO) is a promising dietary component with prebiotic effect, and the long-chain IMOs are preferred to short chain ones owing to the longer persistence in the colon. To establish the optimal process for synthesis of long-chain IMOs, we systematically examined the reaction condition of dextransucrase of Leuconostoc mesenteroides B-512F by changing the ratio of sucrose to maltose (varying as 1:4, 1:2, 1:1, and 2:1) and amount of each sugar (from 2% to 20%). As a result, a ratio of 2:1 (sucrose to maltose, 10:5% or 20:10%, w/v) was determined as an optimal condition for long-chain IMO synthesis (DP3-DP9) with relatively higher yields (70-90%, respectively).

Synthesis of oligosaccharides during milk fermentation was attempted by inoculating Leuconostoc citreum with Lactobacillus casei, Lb. delbrueckii subsp. bulgaricus, and Streptococcus thermophilus as starters. Dextransucrase of Ln. citreum worked as a catalyst for the transglycosylation reaction of sugars; sucrose was added as the glucose donor, and lactose or maltose acted as the acceptor compound for the reaction. When 4% sucrose was added in milk, glucosyl-lactose was synthesized (about 1%, w/v) after 1-2 days of fermentation at 15 or 25 degrees C. Alternatively, when sucrose and maltose (2% each, w/v) were added, panose (about 1%, w/v) and other isomaltooligosaccharides were made in a day at 15-35 degrees C. Growth patterns of lactobacilli and streptococci starters were not affected by the coculture of leuconostoc starter, but the rate of acid synthesis was slightly slowed at every temperature. Addition of sugars in milk did not give any adverse effect on the lactate fermentation. Accordingly, the use of leuconostoc starter and addition of sugars in milk allowed the production of oligosaccharides-containing fermented milk, and application of this method will facilitate the extensive development of synbiotic lactate foods.

Leuconostoc is the major bacterial genus in the initial phase of the lactate fermentation of vegetables. The dextransucrase elaborated from this bacterium is used to synthesize dextran polymers or prebiotic oligosaccharides. To use Leuconostoc as a starter culture in the manufacture of the kimchi-like fermented foods at low temperature, we isolated microbial flora that showed fast growth rates and high enzyme activity under the test conditions. Nine hundred colonies of Leuconostoc were collected from kimchi, sauerkraut, and pickled cucumber using three consecutive selection media; after batch culture and enzyme activity assays, four strains were selected. Sequencing of 16S rRNA genes of the strains revealed that HJ-S7 and HJ-S13 were Leuconostoc (Ln.) mesenteroides and HJ-P4 and HJ-P5 were Ln. citreum. When compared to the type strain, Ln. mesenteroides B-512F, HJ-P4 showed a more than twofold faster growth rate and 20-fold higher enzyme activity during cultivation at 8 degrees C. These strains are suitable as oligosaccharide-synthesizing starters for the fermentation of not only kimchi but also sauerkraut and pickled cucumbers.

Scattering of an obliquely incident plane wave by a general-shaped groove engraved on a perfectly conducting plane is rigorously solved. The scattered field is represented by a Fourier-integral representation. To analytically represent the fields in a general-shaped groove, the groove is divided into L number of layers. Fields are then expressed in each layer as summations of 2D spatial harmonic fields with unknown coefficients. Matching the boundary conditions between layers provides a linear set of equations connecting all the unknown harmonic coefficients. Judicious use of Fourier transform on the equations resulting from matching boundary conditions at the groove aperture provides a series representation of the scattered field in the spectral domain with unknown harmonic coefficients of the first layer in the groove. A stable solution is obtained by solving the complete system of equations with an adaptive choice for the number of modes in each layer.

A problem of acoustic wave scattering from two circular apertures in a thick hard plane is solved. The Hankel transform and mode matching is used to represent the scattered field in rapidly convergent series. The reflection coefficient, transmission coefficient, and far-zone field are rigorously derived and presented in numerically efficient forms. Numerical computations are performed to illustrate scattering behaviors in terms of aperture geometry.

Acoustic scattering from a hybrid junction in a rectangular waveguide is studied. The Fourier transform and mode matching is used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. A residue calculus is utilized to obtain a solution to the simultaneous equations in fast-converging series. Numerical computations are performed to show the behavior of transmission in terms of junction geometry and operating frequency. The utility of acoustic hybrid junction is discussed in terms of its decoupling characteristics.

The purpose of this study was to test the hypothesized factor structure of the Group Environment Questionnaire (GEQ) with confirmatory factor analysis and to ascertain the degree of factorial invariance across gender and across type of sport (team, individual). Additionally, the underlying theoretical structure on which the GEQ was developed was examined by fitting the data to alternative hierarchical factor structures. These models were tested with GEQ data collected on 740 high school varsity athletes (426 males, 314 females). It was shown that the males and females had different factor structures and that neither group exhibited the hypothesized structure. Attempts to fit the data to a two-factor and a second-order hierarchical factor model were unsuccessful. Finally, exploratory factor analysis did not produce a satisfactory four-factor solution. It was concluded that the data from this sample do not support the hypothesized four-factor structure of the GEQ and that further examination of the factor structure of this instrument is required.

The purpose of this study was to develop and test a method to analyze and evaluate sequential skill performances in a team sport. An on-line computerized system was developed to record and summarize the sequential skill performances in volleyball. Seventy-two sample games from the third Federation of International Volleyball Cup men's competition were videotaped and grouped into two categories according to the final team standing and game outcome. Log-linear procedures were used to investigate the nature and degree of the relationship in the first-order (pass-to-set, set-to-spike) and second-order (pass-to-spike) transition plays. Results showed that there was a significant dependency in both the first-order and second-order transition plays, indicating that the outcome of a skill performance is highly influenced by the quality of a preceding skill performance. In addition, the pattern of the transition plays was stable and consistent, regardless of the classification status: Game Outcome, Team Standing, or Transition Process. The methodology and subsequent results provide valuable aids for a thorough understanding of the characteristics of transition plays in volleyball. In addition, the concept of sequential performance analysis may serve as an example for sport scientists in investigating probabilistic patterns of motor performance.

The purpose of this study was to investigate the playing characteristics of team performance in international men's volleyball. The specific purposes were (a) to examine differences in playing characteristics (in particular, the set and spike) between the Attack Process and the Counterattack Process; (b) to examine changes in playing characteristics as a function of team success (as indicated by single-game outcomes and by final tournament standings); and (c) to determine the best predictor, or a set of predictors, of team success among the selected skill components. Seventy-two sample games from the Third Federation of International Volleyball Cup men's competition were recorded using a computerized recording system. Results showed that the significant differences between Team Standing and Game Outcome were due to better performances on those skills used in the Counterattack Process. Among the eight selected skills, the block and spike were the most important in determining team success. The methodology used in this study and the subsequent results provide valuable aids for the coach in the evaluation of team performance and ultimately in the preparation of training sessions in volleyball.