bluuebunny/crossref_metadata_2025 huggingface dataset:
Antioxidant activity ofSanionia uncinata, a polar moss species from King George Island, Antarctica
Authors: Bhattarai Hari Datta , Paudel Babita , Lee Hyoung Seok , Lee Yoo Kyung , Yim Joung Han
Published: September 2008

Antioxidant agents counter reactive oxygen species (ROS) and can be used in cosmetic and medicinal applications. The goal of this study was to evaluate the antioxidant activity of an Antarctic moss species from King George Island (Antarctica), tentatively designated as KSJ‐M5. On the basis of morphological characteristics, KSJ‐M5 was identified asSanionia uncinata(Hedw.) Loeske (Amblystegiaceae). The identification was confirmed by comparing the partial sequence of the ITS (internal transcribed spacer) region with that in GenBank. The antioxidant activity of an ethanol extract of KSJ‐M5 was evaluated by analyzing its reducing power, superoxide scavenging activity, ABTS [2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid)] cation scavenging activity, and DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) free‐radical scavenging activity. The reducing power of 1 mg of KSJ‐M5 extract was equivalent to 31.9 ± 0.9 µg (Mean ± SD,n= 3) of the commercial standard, BHT (butylated hydroxytoluene). IC50values of the KSJ‐M5 extract for DPPH free‐radical scavenging activity, superoxide scavenging activity, and ABTS cation scavenging activity were found as 356 ± 26.8 µg/mL, 466.2 ± 43.4 µg/mL, and 181.3 ± 12.2 µg/mL, respectively. The total phenolic content in 1 mg of KSJM5 extract was equivalent to 12.7 ± 2.7 µg of pyrocatechol. These results clearly showed that KSJ‐M5 could be an important source of natural antioxidant agents for improved medicinal and cosmetic applications. Copyright © 2008 John Wiley & Sons, Ltd.
Antiaging effect of Cordyceps sinensis extract
Authors: Ji Deng‐Bo , Ye Jia , Li Chang‐Ling , Wang Yu‐Hua , Zhao Jiong , Cai Shao‐Qing
Published: September 2008

This experiment studied the effect of Cordyceps sinensis extract (CSE) on mice aged by d‐galactose and castrated rats to analyse its antiaging effect. Water maze and step‐down type avoidance tests were used to examine the effect of CSE on learning and memory. CSE shortened escape latency, prolonged step‐down latency and decreased the number of errors in mice aged by d‐galactose. The effect of CSE on the sexual function of castrated rats was evaluated by measuring the penis erection latency, mount latency and ejaculation latency. CSE appeared to shorten penis erection latency and mount latency in castrated rats. The study also measured the effect of CSE on the activity of age‐related enzymes. The results showed that CSE improved the activity of superoxide dismutase, glutathione peroxidase and catalase and lowered the level of lipid peroxidation and monoamine oxidase activity in the aged mice. The study demonstrated that CSE can improve the brain function and antioxidative enzyme activity in mice with d‐galactose‐induced senescence and promote sexual function in castrated rats. All of these findings suggest that CSE has an antiaging effect. Copyright © 2008 John Wiley & Sons, Ltd.
Inhibitory Activities of Cassia tora and its Anthraquinone Constituents on Angiotensin‐Converting Enzyme
Authors: Hyun Sook Kyung , Lee Hyang , Kang Sam Sik , Chung Hae Young , Choi Jae Sue
Published: September 2008

As a component of our program that pertains to the isolation of antihypertensive agents derived from natural products, we screened the bioactivity of seeds from raw and roasted Cassia tora via angiotensin converting enzyme (ACE) inhibitory assays. We found that both of the MeOH extracts from the raw and roasted C. tora exhibited significant inhibitory properties against ACE, demonstrating more than 50% inhibition at a concentration of 163.93 µg/mL. Emodin (3), alaternin (4), gluco‐obtusifolin (5), cassiaside (6), gluco‐aurantioobtusin (7), cassitoroside (8), toralactone gentiobioside (9), and chrysophanol triglucoside (10) had been previously isolated; however, questin (1) and 2‐hydroxyemodin 1‐methylether (2) were isolated from C. tora for the first time in this study. Among them, only anthraquinone glycoside (7) demonstrated marked inhibitory activity against ACE, with an IC50 value of 30.24 ± 0.20 µM. Conversely, aurantioobtusin (7a), obtained from the acid hydrolysis of 7, showed no activity. Further inhibitory kinetics analyzed from Lineweaver‐Burk plots showed 7 to be a competitive inhibitor with a Ki value of 8.3 × 10−5 M. Moreover, compound 7 showed marked inhibitory and scavenging activities with an IC50 value of 49.64 ± 0.37 µM (positive control; trolox: 26.07 ± 1.05 µM) for total reactive oxygen species generation, and 4.60 ± 1.12 µM (positive control; penicillamine: 0.24 ± 0.04 µM) for ONOO−. Copyright © 2008 John Wiley & Sons, Ltd.
Comparative analysis between Chamomilla recutita and corticosteroids on wound healing. An in vitro and in vivo study
Authors: Martins Manoela Domingues , Marques Márcia Martins , Bussadori Sandra Kalil , Martins Marco Antonio Trevizani , Pavesi Vanessa Christina Santos , Mesquita‐Ferrari Raquel Agnelli , Fernandes Kristianne Porta Santos
Published: September 2008

The comparison of chamomile and corticosteroids for treating ulcers was done in vitro and in vivo. The experimental groups were: control; chamomile recutita; triamcinolone acetonide and clobetasol propionate. For the in vitro study the cell viability of fibroblasts cultured for 24 h in media conditioned by the substances was obtained by the MTT reduction analysis. For the in vivo study, 125 male rats were submitted to experimental ulcers treated or not (control) by the substances tested. At 1, 3, 5, 7 and 14 days later 5 animals of each group were sacrificed. The lesions were analyzed by means of clinical observation and histological wound‐healing grading. Data were compared by ANOVA (p ≤ 0.05). All experimental groups presented positive cell viability in 24 h. The cultures treated with chamomile presented the smallest cell viability. All animals of the chamomile group exhibited complete wound healing 9 days before the other groups. Complete repaired lesions were observed after 5 days of treatment only in the chamomile group. Animals treated with chamomile presented significantly faster wound healing in comparison to those treated with corticosteroids. Based on the conditions of this study, we concluded that chamomile in comparison to corticosteroids promotes faster wound healing process. Copyright © 2008 John Wiley & Sons, Ltd.
Top management incentive compensation and knowledge sharing in multinational corporations
Authors: Fey Carl F. , Furu Patrick
Published: September 2008

Growing interest has emerged in viewing the multinational corporation as a knowledge creating and diffusing entity. The importance of sharing knowledge across organizational and national boundaries has been established in previous research. However, the question of which organizational policies lead to knowledge sharing between multinational units is still not fully understood. In particular, the link between compensation mechanisms and knowledge sharing has not received attention in previous studies. By studying 164 foreign‐owned subsidiaries located in Finland and China, this article attempts to identify the relationship between subsidiary bonus pay based on MNC‐wide performance and knowledge sharing between different units of the MNC. In line with the knowledge‐based perspective of the firm, the results suggest that incentive pay based on the collective performance of the MNC leads to greater knowledge sharing. Copyright © 2008 John Wiley & Sons, Ltd.
Institutions, resources, and entry strategies in emerging economies
Authors: Meyer Klaus E. , Estrin Saul , Bhaumik Sumon Kumar , Peng Mike W.
Published: September 2008

We investigate the impact of market‐supporting institutions on business strategies by analyzing the entry strategies of foreign investors entering emerging economies. We apply and advance the institution‐based view of strategy by integrating it with resource‐based considerations. In particular, we show how resource‐seeking strategies are pursued using different entry modes in different institutional contexts. Alternative modes of entry—greenfield, acquisition, and joint venture (JV)—allow firms to overcome different kinds of market inefficiencies related to both characteristics of the resources and to the institutional context. In a weaker institutional framework, JVs are used to access many resources, but in a stronger institutional framework, JVs become less important while acquisitions can play a more important role in accessing resources that are intangible and organizationally embedded. Combining survey and archival data from four emerging economies, India, Vietnam, South Africa, and Egypt, we provide empirical support for our hypotheses. Copyright © 2008 John Wiley & Sons, Ltd.
What passes as a rigorous case study?
Authors: Gibbert Michael , Ruigrok Winfried , Wicki Barbara
Published: September 2008

This article investigates the methodological sophistication of case studies as a tool for generating and testing theory by analyzing case studies published during the period 1995–2000 in 10 influential management journals. We find that case studies emphasized external validity at the expense of the two more fundamental quality measures, internal and construct validity. Comparing case studies published in the three highest‐ranking journals with the other seven, we reveal strategies that may be useful for authors wishing to conduct methodologically rigorous case study research. Copyright © 2008 John Wiley & Sons, Ltd.
Appropriability, preemption, and firm performance
Authors: Ceccagnoli Marco
Published: September 2008

The impact of strategies used to appropriate innovation rents on firm performance is analyzed using a sample of U.S. public manufacturing firms. Stronger appropriability at the firm level, achieved through patent protection or the ownership of specialized complementary assets, leads to superior economic performance, as measured by the stock market valuation of a firm's R& D assets. Among commonly used ‘nonconventional’ patent strategies, preemptive patenting allows incumbents to strengthen their market power. Consistent with theory, such effect is higher for incumbents with higher ex ante market power and facing a higher threat of entry, and lower when R& D competition is characterized by the discovery of drastic innovations. Copyright © 2008 John Wiley & Sons, Ltd.
Capacity rationalization and exit strategies
Authors: Wood Andrew
Published: September 2008

A case study of the response to chronic excess capacity in a small competitive industry (the manufacturing of clay bricks) permits a generalization of Bower's concentration hypothesis. Barriers to exit produced a free rider problem where only smaller and lower quality brick plants were shut when the efficient solution demanded major closures. The exit logjam was resolved by the strategic actions of growth‐maximizing managers. They used major acquisitions as the basis for substantial reductions in firm and industry capacity while growing their own market share. The fall in industry capacity enabled other firms to follow suit while maintaining their market share as predicted by prospect theory. Copyright © 2008 John Wiley & Sons, Ltd.
An introduction to social and historical factors affecting multiracial college students
Authors: Shang Paul
Published: September 2008

This chapter describes social and historical developments coinciding with the emergence of increasing numbers of biracial and multiracial college students. It thus sets the context for the chapters that follow on identity development, student experiences, student services, and policy.
The space in between: Issues for multiracial student organizations and advising
Authors: Ozaki C. Casey , Johnston Marc
Published: September 2008

This chapter reviews relevant literature on multiracial student organizations, highlights challenges faced by such groups, and provides suggestions for advisers who work with members and leaders of multiracial campus groups.
Bicultural faculty and their professional adaptation
Authors: Cuyjet Michael J.
Published: September 2008

This chapter expands the notion of biracial identity to include bicultural individuals and examines their adap‐tation to faculty culture in the United States.
Student affairs and higher education policy issues related to multiracial students
Authors: Kellogg Angela , Niskodé Amanda Suniti
Published: September 2008

This chapter describes how the emerging multiracial student population is influencing policy, procedures, and programs within higher education in the United States.
Promoting persistence and success of underrepresented students: Lessons for teaching and learning
Authors: Kinzie Jillian , Gonyea Robert , Shoup Rick , Kuh George D.
Published: September 2008

This chapter explores the relationships between indicators of student success such as persistence and student engagement in effective educational practices focusing on historically underrepresented populations.
Closing the gate: Part‐Time faculty instruction in gatekeeper courses and first‐year persistence
Authors: Eagan M. Kevin , Jaeger Audrey J.
Published: September 2008

This chapter reports the results of a large study on the effects of part‐time faculty on student persistence and suggests that administrators give careful consideration when trying to reduce expenses through the use of such faculty in large beginning courses.
The role of active learning in college student persistence
Authors: Braxton John M. , Jones Willis A. , Hirschy Amy S. , Hartley III Harold V.
Published: September 2008

The primary goal of this study was to examine the impact of active learning on a student's level of overall social integration and perception of his or her institution's commitment to student welfare.
Classroom practices at institutions with higher‐than‐expected persistence rates: What student engagement data tell us
Authors: Laird Thomas F. Nelson , Chen Daniel , Kuh George D.
Published: September 2008

This chapter discusses the finding that student retention benefits when the instruction increases the level of academic challenge and the amount of support provided to students.
Stress‐induced down‐regulation of tumor‐associated NADH oxidase during apoptosis in transformed cells
Authors: Mao Liang-Chi , Wang Hsi-Ming , Lin You-Yu , Chang Te-Kau , Hsin Yi-Hong , Chueh Pin Ju
Published: September 2008

Tumor‐associated NADH oxidase (tNOX) is a growth‐related protein expressed in transformed cells. tNOX knockdown using RNA interference leads to a significant reduction in HeLa cell proliferation and migration, indicating an important role for tNOX in growth regulation and the cancer phenotype. Here, we show that tNOX is down‐regulated during apoptosis in HCT116 cells. Treatment with diverse stresses induced a dose‐ and time‐dependent decrease in tNOX expression that was concurrent with apoptosis. Moreover, shRNA‐mediated tNOX knockdown rendered cells susceptible to apoptosis, whereas re‐expression of tNOX partially recovered cell proliferation. Our results indicate that tNOX is suppressed during apoptosis and demonstrate that tNOX down‐regulation sensitizes cells to stress‐induced growth reduction, suggesting that tNOX is required for transformed cell growth.
Functional implications of the proximal site hydrogen bonding network in Vitreoscilla hemoglobin (VHb): Role of Tyr95 (G5) and Tyr126 (H12)
Authors: Kaur Ramandeep , Ahuja Sandhya , Anand Arvind , Singh Balwinder , Stark Benjamin. C. , Webster Dale. A. , Dikshit Kanak L.
Published: September 2008

Although Vitreoscilla hemoglobin (VHb) carries a conventional globin fold, its proximal site geometry is unique in having a hydrogen‐bonding network between proximal site residues, HisF8‐TyrG5‐GluH23 and TyrG5‐TyrH12. TyrG5 and TyrH12 were mutated to study their relevance in VHb function. VHb G5 mutants (Tyr95Phe and Tyr95Leu showed no stable oxyform and nitric oxide dioxygenase activity, whereas, VHb H12 mutants (Tyr126Phe and Tyr126Leu) displayed little change in their oxygen affinity indicating a crucial role of Tyr95 in protein function. The VHb H12 mutant, Tyr126Leu, enhanced the intracellular pool of oxygen and cell growth better than VHb. Molecular modeling suggests that the replacement of tyrosine with leucine in Tyr126Leu creates an opening on the protein surface that may facilitate oxygen diffusion and accumulation.
Collagen‐binding motif peptide, a cleavage product of osteopontin, stimulates human neutrophil chemotaxis via pertussis toxin‐sensitive G protein‐mediated signaling
Authors: Kim Mi-Kyoung , Kim Sang Doo , Lee Ha Young , Lee Sun Young , Shim Jae Woong , Yun Jeanho , Kim Jong-Min , Min Do Sik , Yoo Young Hyun , Bae Yoe-Sik
Published: September 2008

The collagen‐binding motif (CBM) peptide, a cleavage product of osteopontin (OPN), stimulated intracellular calcium increase in human neutrophils. CBM peptide‐stimulated calcium was inhibited by pertussis toxin (PTX), suggesting the influence of PTX‐sensitive G‐proteins. In addition CBM peptide stimulated the chemotactic migration of human neutrophils and human monocytes. CBM peptide‐induced neutrophil chemotaxis was completely inhibited by PTX, once again indicating the influence of Gi proteins. CBM peptide was also found to induce mitogen activated protein kinase activation. CBM peptide‐induced neutrophil chemotaxis was mediated by p38 kinase as well as an extracellular signal‐regulated protein kinase. Taken together, the results suggest that a cleavage product of OPN, CBM peptide, initiates immune responses by inducing neutrophil trafficking via certain PTX‐sensitive cell surface receptors.
ANTI-COMMUTING REAL HYPERSURFACES IN COMPLEX TWO-PLANE GRASSMANNIANS
Authors: JEONG IMSOON , LEE HYUN JIN , SUH YOUNG JIN
Published: September 2008

In this paper we give a nonexistence theorem for real hypersurfaces in complex two-plane Grassmannians G2(ℂm+2) with anti-commuting shape operator.
Ethanol extract ofPsoralea corylifoliaL. and its main constituent, bakuchiol, reduce bone loss in ovariectomised Sprague–Dawley rats
Authors: Lim Sun-Hye , Ha Tae-Youl , Kim Sung-Ran , Ahn Jiyun , Park Hyun Jin , Kim Suna
Published: September 2008

The aim of the present study was to investigate whether ethanol extracts ofPsoralea corylifoliaL. (PCE) and its active component protect against bone loss in ovariectomised rats. We screened oestrogenic activities of the main extract fractions usingin vitroassays and identified bakuchiol as the most active oestrogenic component by HPLC and LC/MS, and then demonstrated that bakuchiol had strong binding affinity for oestrogen receptor (ER) α. Seventy female Sprague–Dawley rats were assigned to either a sham-operated group (n10) or an ovariectomised group (n60). The ovariectomised group was subdivided into six groups, each containing ten rats: vehicle group, two bakuchiol-treated groups (dose of 15 mg/kg per d or 30 mg/kg per d; ten rats for each group), two PCE-supplemented groups (0·25 % or 0·5 % extracts of diets; ten rats for each group) and a 17β-oestradiol (E2)-treated group (20 μg/kg per d). We recorded weight and feed intake every week, and killed all animals after 6 weeks. Blood was collected, and the uterus, kidneys and livers were removed. Bakuchiol has a three-fold higher binding affinity for ERα than for ERβ. Bakuchiol and PCE treatments had no uterotrophic activity even though they demonstrated oestrogenic activity in thein vitroassays. Bakuchiol and PCE treatments reduced postmenopausal bone loss by increasing alkaline phosphatase, Ca concentrations, serum E2 concentration and bone mineral density, and by decreasing the inorganic P level. The present study indicated that bakuchiol and PCE treatments could protect against bone loss.
Timing of volcanism and evolution of the northern Kenya Rift
Authors: McDOUGALL IAN , BROWN FRANCIS H.
Published: September 2008

The northern Kenya Rift is bounded on the west by uplands of Turkana which comprise horst-like blocks that include metamorphic basement rocks, locally overlain unconformably by the Cretaceous Lubur Sandstone, in turn overlain by predominantly volcanic sequences in which relatively thin sedimentary packages occur. Amphibolite facies crystalline rocks of the basement yield Early Palaeozoic K–Ar cooling ages reflecting the Pan-African Orogeny. Volcanism in Turkana was initiated through voluminous eruptions of transitional tholeiitic basalts commencing about 36 Ma ago in the Late Eocene, with some evidence for concomitant rhyolitic volcanism. Volcanism became dominantly rhyolitic in the interval from about 27 to 23 Ma ago, but remained bimodal as basaltic lavas are also known from this period. From about 19 to 15 Ma or younger, basaltic volcanism again dominated, often alkaline in nature, with thin but significant sedimentary sequences interleaved that have yielded important vertebrate faunal assemblages. Parallels exist between the volcanic history recorded in Turkana and that found in the Nabwal Hills east of Lake Turkana. In the southern Turkana region, oil exploration by seismic methods and deep drill holes has shown the existence of northerly-trending half-graben with up to 7 km of fill, and that these developed from at least Oligocene and possibly Late Eocene times. This suggests that the widespread basaltic volcanism at about 36 Ma ago (Late Eocene) heralds an earlier initiation of the Kenya Rift in northern Kenya than most workers have previously suggested.
Trajectory and flow properties for a rod spinning in a viscous fluid. Part 1. An exact solution
Authors: CAMASSA ROBERTO , LEITERMAN TERRY JO , MCLAUGHLIN RICHARD M.
Published: September 2008

An exact mathematical solution for the low-Reynolds-number quasi-steady hydrodynamic motion induced by a rod in the form of a prolate spheroid sweeping a symmetric double cone is developed, and the influence of the ensuing fluid motion upon passive particles is studied. The resulting fluid motion is fully three-dimensional and time varying. The advected particles are observed to admit slow orbits around the rotating rods and a fast epicyclic motion roughly commensurate with the rod rotation rate. The epicycle amplitudes, vertical fluctuations, arclengths and angle travelled per rotation are mapped as functions of their initial coordinates and rod geometry. These trajectories exhibit a rich spatial structure with greatly varying trajectory properties. Laboratory frame asymmetries of these properties are explored using integer time Poincaré sections and far-field asymptotic analysis. This includes finding a small cone angle invariant in the limit of large spherical radius whereas an invariant for arbitrary cone angles is obtained in the limit of large cylindrical radius. The Eulerian and Lagrangian flow properties of the fluid flow are studied and shown to exhibit complex structures in both space and time. In particular, spatial regions of high speed and Lagrangian velocities possessing multiple extrema per rod rotation are observed. We establish the origin of these complexities via an auxiliary flow in a rotating frame, which provides a generator that defines the epicycles. Finally, an additional spin around the major spheroidal axis is included in the exact hydrodynamic solution resulting in enhanced vertical spatial fluctuation as compared to the spinless counterpart. The connection and relevance of these observations with recent developments in nano-scale fluidics is discussed, where similar epicycle behaviour has been observed. The present study is of direct use to nano-scale actuated fluidics.
Analysis and flamelet modelling for spray combustion
Authors: BABA YUYA , KUROSE RYOICHI
Published: September 2008

The validity of a steady-flamelet model and a flamelet/progress-variable approach for gaseous and spray combustion is investigated by a two-dimensional direct numerical simulation (DNS) of gaseous and spray jet flames, and the combustion characteristics are analysed. A modified flamelet/progress-variable approach, in which total enthalpy rather than product mass fraction is chosen as a progress variable, is also examined. DNS with an Arrhenius formation, in which the chemical reaction is directly solved in the physical flow field, is performed as a reference to validate the combustion models. The results show that the diffusion flame is dominant in the gaseous diffusion jet flame, whereas diffusion and premixed flames coexist in the spray jet flame. The characteristics of the spray flame change from premixed–diffusion coexistent to diffusion-dominant downstream. Comparisons among the results from DNS with various combustion models show the modified flamelet/progress-variable approach to be superior to the other combustion models, particularly for the spray flame. Where the behaviour of the gaseous total enthalpy is strongly affected by the energy transfer (i.e. heat transfer and mass transfer) from the dispersed droplet, and this effect can be accounted for only by solving the conservation equation of the total enthalpy. However, even the DNS with the modified flamelet/progress-variable approach tends to underestimate the gaseous temperature in the central region of the spray jet flame. To increase the prediction accuracy, a combustion model for the partially premixed flame for the spray flame is necessary.
Turbulent spot flow topology and mechanisms for surface heat transfer
Authors: SABATINO D. R. , SMITH C. R.
Published: September 2008

The properties of artificially initiated turbulent spots over a heated plate were investigated in a water channel. The instantaneous velocity field and surface Stanton number were simultaneously established using a technique that combines particle image velocimetry and thermochromic liquid crystal thermography. Several characteristics of a spot are found to be similar to those of a turbulent boundary layer. The spacing of the surface heat transfer streak patterns within the middle or ‘body’ of a turbulent spot are comparable to the low-speed streak spacing within a turbulent boundary layer. Additionally, the surface shear stress in the same region of a spot is also found to be comparable to a turbulent boundary layer. However, despite these similarities, the heat transfer within the spot body is found to be markedly less than the heat transfer for a turbulent boundary layer. In fact, the highest surface heat transfer occurs at the trailing or calmed region of a turbulent spot, regardless of maturity. Using a modified set of similarity coordinates, instantaneous two-dimensional streamlines suggest that turbulent spots entrain and subsequently recirculate warm surface fluid, thereby reducing the effective heat transfer within the majority of the spot. It is proposed that energetic vortices next to the wall, near the trailing edge of the spot body, are able to generate the highest surface heat transfer because they have the nearest access to cooler free-stream fluid.
Slender-body theory for steady sheared plumes in very viscous fluid
Authors: WHITTAKER ROBERT J. , LISTER JOHN R.
Published: September 2008

A simple model based on slender-body theory is developed to describe the deflection of a steady plume by shear flow in very viscous fluid of the same viscosity. The key dimensionless parameters measuring the relative strengths of the shear, diffusion and source flux are identified, which allows a number of different dynamical regimes to be distinguished. The predictions of the model show good agreement with many, but not all, observations from previous experimental studies. Possible reasons for the discrepancies are discussed.
The stability of the variable-density Kelvin–Helmholtz billow
Authors: FONTANE JÉRÔME , JOLY LAURENT
Published: September 2008

We perform a three-dimensional stability analysis of the Kelvin–Helmholtz (KH) billow, developing in a shear layer between two fluids with different density. We begin with two-dimensional simulations of the temporally evolving mixing layer, yielding the unsteady base flow fields. The Reynolds number is 1500 while the Schmidt and Froude numbers are infinite. Then exponentially unstable modes are extracted from a linear stability analysis performed at the saturation of the primary mode kinetic energy. The spectrum of the least stable modes exhibits two main classes. The first class comprises three-dimensional core-centred and braid-centred modes already present in the homogeneous case. The baroclinic vorticity concentration in the braid lying on the light side of the KH billow turns the flow into a sharp vorticity ridge holding high shear levels. The hyperbolic modes benefit from the enhanced level of shear in the braid whereas elliptic modes remain quite insensitive to the modifications of the base flow. In the second class, we found typical two-dimensional modes resulting from a shear instability of the curved vorticity-enhanced braid. For a density contrast of 0.5, the wavelength of the two-dimensional instability is about ten times shorter than that of the primary wave. Its amplification rate competes well against those of the hyperbolic three-dimensional modes. The vorticity-enhanced braid thus becomes the preferred location for the development of secondary instabilities. This stands as the key feature of the transition of the variable-density mixing layer. We carry out a fully resolved numerical continuation of the nonlinear development of the two-dimensional braid-mode. Secondary roll-ups due to a small-scale Kelvin–Helmholtz mechanism are promoted by the underlying strain field and develop rapidly in the compression part of the braid. Originally analysed by Reinoud et al. (Phys. Fluids, vol. 12, 2000, p. 2489) from two-dimensional non-viscous numerical simulations, this instability is shown to substantially increase the mixing.
Shear-enhanced convection in a mushy layer
Authors: NEUFELD JEROME A. , WETTLAUFER J. S.
Published: September 2008

We investigate the effect of an external shear flow on the buoyant instabilities inherent in the directional solidification of a dendritic mushy layer. In the presence of an external shear flow, perturbations of the mush–liquid interface lead to perturbed flow in the bulk fluid that create pressure variations along the mush–liquid interface. These pressure variations drive flow in the mushy layer. A numerical analysis of the stability of the system provides the critical porous-medium Rayleigh number as a function of both the external flow speed and the wavenumber of the interfacial perturbations. In the limit of zero external flow we recover the so-called boundary and mushy layer modes of buoyancy-driven convection first established by Worster (J. Fluid Mech., vol. 237, 1992b, p. 649). We find that the application of an external flow can significantly reduce the stability of both the boundary and mushy layer modes. The resultant forced mushy layer mode gives rise to the formation of channels of reduced solid fraction perpendicular to the applied flow that are distinct from the planform found in the absence of an external flow. The stability of the system is examined as a function of the principal thermodynamic and dynamic parameters, and the results are applied to the solidification of sea ice in the presence of vigorous oceanic flow.
Bubble-induced skin-friction drag reduction and the abrupt transition to air-layer drag reduction
Authors: ELBING BRIAN R. , WINKEL ERIC S. , LAY KEARY A. , CECCIO STEVEN L. , DOWLING DAVID R. , PERLIN MARC
Published: September 2008

To investigate the phenomena of skin-friction drag reduction in a turbulent boundary layer (TBL) at large scales and high Reynolds numbers, a set of experiments has been conducted at the US Navy's William B. Morgan Large Cavitation Channel (LCC). Drag reduction was achieved by injecting gas (air) from a line source through the wall of a nearly zero-pressure-gradient TBL that formed on a flat-plate test model that was either hydraulically smooth or fully rough. Two distinct drag-reduction phenomena were investigated; bubble drag reduction (BDR) and air-layer drag reduction (ALDR).

The streamwise distribution of skin-friction drag reduction was monitored with six skin-friction balances at downstream-distance-based Reynolds numbers to 220 million and at test speeds to 20.0ms−1. Near-wall bulk void fraction was measured at twelve streamwise locations with impedance probes, and near-wall (0 <Y< 5mm) bubble populations were estimated with a bubble imaging system. The instrument suite was used to investigate the scaling of BDR and the requirements necessary to achieve ALDR.

Results from the BDR experiments indicate that: significant drag reduction (>25%) is limited to the first few metres downstream of injection; marginal improvement was possible with a porous-plate versus an open-slot injector design; BDR has negligible sensitivity to surface tension; bubble size is independent of surface tension downstream of injection; BDR is insensitive to boundary-layer thickness at the injection location; and no synergetic effect is observed with compound injection. Using these data, previous BDR scaling methods are investigated, but data collapse is observed only with the ‘initial zone’ scaling, which provides little information on downstream persistence of BDR.

ALDR was investigated with a series of experiments that included a slow increase in the volumetric flux of air injected at free-stream speeds to 15.3ms−1. These results indicated that there are three distinct regions associated with drag reduction with air injection: Region I, BDR; Region II, transition between BDR and ALDR; and Region III, ALDR. In addition, once ALDR was established: friction drag reduction in excess of 80% was observed over the entire smooth model for speeds to 15.3ms−1; the critical volumetric flux of air required to achieve ALDR was observed to be approximately proportional to the square of the free-stream speed; slightly higher injection rates were required for ALDR if the surface tension was decreased; stable air layers were formed at free-stream speeds to 12.5ms−1with the surface fully roughened (though approximately 50% greater volumetric air flux was required); and ALDR was sensitive to the inflow conditions. The sensitivity to the inflow conditions can be mitigated by employing a small faired step (10mm height in the experiment) that helps to create a fixed separation line.
Differential diffusion of high-Schmidt-number passive scalars in a turbulent jet
Authors: LAVERTU T. M. , MYDLARSKI L. , GASKIN S. J.
Published: September 2008

The separate evolution, or differential diffusion, of high-Schmidt-number passive scalars in a turbulent jet is studied experimentally. The two scalars under consideration are disodium fluorescein (Sc≡ ν/D= 2000) and sulforhodamine 101 (Sc= 5000). The objectives of the research are twofold: to determine (i) the Reynolds-number-dependence, and (ii) the radial distribution of differential diffusion effects in the self-similar region of the jet. Punctual laser-induced fluorescence (LIF) measurements were obtained 50 jet diameters downstream of the nozzle exit for five Reynolds numbers (Re≡uod/ν = 900, 2100, 4300, 6700 and 10600, whereu0is the jet exit velocity,dis the jet diameter, and ν is the kinematic viscosity) and for radial positions extending from the centreline to the edges of the jet cross-section (0 ≤r/d≤ 7.5). Statistics of the normalized concentration difference,Z, were used to quantify the differential diffusion. The latter were found to decay slowly with increasing Reynolds number, with the root mean square ofZscaling asZrms≡ 〈Z2〉1/2∝Re−0.1, (or alternatively 〈Z2〉 ∝Re−0.2). Regardless of Reynolds number, differential diffusion effects were found to increase away from the centreline. The increase in differential diffusion effects with radial position, along with their increase with decreasing Reynolds number, support the hypothesis of increased differential diffusion at interfaces between the jet and ambient fluids. Power spectral densities ofZwere also studied. These spectra decreased with increasing wavenumber – an observation attributed to the decay of the scalar fluctuations in a turbulent jet. Furthermore, these spectra showed that significant differential diffusion effects persist at scales larger than the Kolmogorov scale, even for moderately high Reynolds numbers.
An experimental study of shear-enhanced convection in a mushy layer
Authors: NEUFELD JEROME A. , WETTLAUFER J. S.
Published: September 2008

The influence of an external shear flow on the evolution of a solidifying array of dendritic crystals, termed a mushy layer, is investigated through controlled cooling of an aqueous ammonium chloride solution in a laboratory flume. The controlled cooling produces a mushy layer that grows at a constant rate from the base of the flume over which a laminar shear flow is applied. We find a critical flow speed above which a spatiotemporal variation of the solid fraction of the layer appears with a planform transverse to the flow direction. The presence of this distinctive pattern of spanwise crevasses is compared with a simplified stability analysis in which the motion of the external fluid over the corrugated mush–liquid interface produces a pressure perturbation that drives flow and phase change within the mushy layer. This flow leads to a pattern of solidification and dissolution that is compared to the experimental results. The physical mechanism underlying the pattern formation is confirmed by the agreement between the theoretical predictions and experimental results. Finally, the comparison between theory and experiment provides a value for the mushy layer permeability, the evolution of which is of relevance to a host of geophysical, biological and engineering systems.
Gonad development and spawning in one and two year old mussels (Mytilus edulis) from Western Norway
Authors: Duinker Arne , Håland Liv , Hovgaard Peter , Mortensen Stein
Published: September 2008

Sexual maturation and spawning was followed in one and two year old rope cultured mussels (Mytilus edulis) from April to December. Development of gonad and storage tissue was followed using descriptive categories from histology, and development of total soft tissue was followed using meat yield and condition index.

Both age groups were mature both during spring and autumn and had similar patterns of spawning and maturation. April and May were characterized by scattered spawning activity and accumulation of storage reserves at the same time, resulting in relative constant condition indices during this period. This was followed by ripening of the gonads and an increase in condition index that culminated in a spawning in late June. Parts of the population then entered a resting phase, while a part of the population underwent new maturation towards an autumn spawning in September. In December all the mussels had started the winter maturation.

Condition index and meat yield were higher throughout the season in the one year old mussels. This was probably due to the sum of several factors, including differences in specific feeding rates and biomass density, rather than spawning.

The present study is the first to compare the reproductive patterns over time of one and two year old mussels with reliable age determination, and provide information that there are no obvious differences in neither timing of gonad development nor spawning patterns between the age-classes.
Cephalopods in the diet of albacore, Thunnus alalunga, from the eastern Mediterranean
Authors: Salman Alp , Karakulak F. Saadet
Published: September 2008

In this study, the stomach contents of 116 albacore specimens, Thunnus alalunga were examined from the eastern Mediterranean Sea. Fifty-five of the 116 stomachs examined were empty. The occurrence of major prey categories in stomachs were 95.1% cephalopods, 47.5% teleosts and 39.3% crustaceans with a total of 633 individuals belonging to 14 species identified. Heteroteuthis dispar from the order Sepiolida constituted 56.40% of the main cephalopod prey followed by Onychoteuthis banksii from the order Teuthida.
Frequency and risk factors for toxoplasmosis in ovines of various regions of the State of Colima, Mexico
Authors: CABALLERO-ORTEGA H. , PALMA J. M. , GARCÍA-MÁRQUEZ L. J. , GILDO-CÁRDENAS A. , CORREA D.
Published: September 2008

Infection of ewes byToxoplasma gondiimay induce abortions, thus it has consequences for sheep production. Colima, Western State of Mexico, has favourable climatic conditions for transmission and both domestic and wild cats live there. The aim of this study was to determine the frequency of specific antibodies in sheep from the coast, a mountain, and a hill of Colima. Serum samples from 351 sheep were tested by a previously standardized indirect ELISA. The frequency of infection was estimated and the farm location and flock size, as well as the animals' age and sex were analysed as risk factors for toxoplasmosis. The frequency of antibodies depended on the altitude, being higher at sea level than at 1200 metres above sea level (OR=3·77, 95% CI=1·79–7·94,P<0·0001), and the size of the flock, being higher in the large ones (OR=2·23, 95% CI=1·35–3·71,P=0·002). Older animals were more frequently positive and with a stronger response than young ones (OR=1·77, 95% CI=1·07–2·93,P=0·016). No differences were observed between male and female sheep. In conclusion, toxoplasmosis is present in sheep of Colima with variations related to altitude, flock size and age.
Non-wandering sets of the powers of maps of the interval
Authors: Coven Ethan M. , Nitecki Zbigniew
Published: September 2008

We show that, for maps of the interval, the non-wandering set of the map coincides with the non-wandering set of each of its odd powers, while the nonwandering set of any of its even powers can be strictly smaller.
A proof of Pesin's formula
Authors: Mañé Ricardo
Published: September 2008

Let f: M → M be a diffeomorphism of a compact manifold M and let χ:M → R be defined by putting χ(x) equal to the sum of the non-negative characteristic exponents of f at x, each being counted with its multiplicity. If μ is an f-invariant probability of M which is absolutely continuous relative to Lebesgue measure, then Pesin has proved the entropy, hμ(f), is given by We prove this formula without using the theory of stable manifolds.
On the classification of Markov chains by finite equivalence
Authors: Parry William , Tuncel Selim
Published: September 2008

We consider a certain analytic function β (t) which is an invariant of finite equivalence between two finite state Markov chains. If two such chains P, Q have the same β-function we wish to prove that they are finitely equivalent. To this end we show that U(t)Pt = QtU (t) has a nontrivial matrix solution U over the ring (exp) of integral combinations of exponential functions. In fact we can force U(t) to be strictly positiveat any specified t0. If U(t) has entries from (exp), the sub-semi-ring of positive integral combinations of exponential functions, then P, Q are finitely equivalent. Many examples reinforce the conjecture that U(t) may always be chosen over (exp) when P, Q have the same β-function. We relate the β-function to topological entropy, measure entropy and information variance.
The modified Lax and two-dimensional Toda lattice equations associated with simple Lie algebras
Authors: Wilson George
Published: September 2008

We associate to each complex simple Lie algebra g a hierarchy of evolution equations; in the simplest case g = sl(2) they are the modified KdV equations. These new equations are related to the two-dimensional Toda lattice equations associated with g in the same way that the modified KdV equations are related to the sinh-Gordon equation.
Maximally highly proximal generators of minimal flows
Authors: Auslander Joseph , van der Woude Jaap
Published: September 2008

We study minimal flows and their extensions by means of the associated maximally highly proximal flows. These, in turn, can be represented by highly proximal generators, which are certain subsets of the universal minimal flow. From this point of view we obtain information on relative disjointness, coalescence, the Bronstein property, and RIC extensions.
An amenable equivalence relation is generated by a single transformation
Authors: Connes A. , Feldman J. , Weiss B.
Published: September 2008

We prove that for any amenable non-singular countable equivalence relation R⊂X×X, there exists a non-singular transformation T of X such that, up to a null set:

It follows that any two Cartan subalgebras of a hyperfinite factor are conjugate by an automorphism.
A relation between Lyapunov exponents, Hausdorff dimension and entropy
Authors: Manning Anthony
Published: September 2008

For an Axiom A diffeomorphism of a surface with an ergodic invariant measure we prove that the entropy is the product of the positive Lyapunov exponent and the Hausdorff dimension of the set of generic points in an unstable manifold.
An alternative approach to the ergodic theory of measured foliations on surfaces
Authors: Rees Mary
Published: September 2008

We consider measured foliations on surfaces, and interval exchanges. We give alternative proofs of the following theorems first proved by Masur and (independently) Veech. The action of the diffeomorphism group of the surface on the projective space of measured foliations (with respect to a natural ‘Lebesgue’ measure) is ergodic. Almost all measured foliations are uniquely ergodic. Almost all interval exchanges (again, with respect to a natural ‘Lebesgue’ measure) are uniquely ergodic.
Integrable geodesic flows on homogeneous spaces
Authors: Thimm A.
Published: September 2008

A method is exposed which allows the construction of families of first integrals in involution for Hamiltonian systems which are invariant under the Hamiltonian action of a Lie group G. This is applied to invariant Hamiltonian systems on the tangent bundles of certain homogeneous spaces M = G/K. It is proved, for example, that every such invariant Hamiltonian system is completely integrable if M is a real or complex Grassmannian manifold or SU(n + 1)/SO(n + 1) or a distance sphere in ℂPn+1. In particular, the geodesic flows of these homogeneous spaces are integrable.
The bifurcation of periodic orbits of one-dimensional maps
Authors: Block Louis , Hart David
Published: September 2008

The bifurcation of C1-continuous families of maps of the interval or circle is studied. It is shown, for example, that period-tripling cannot occur. This yields topological properties of the stratification of C1(I, I) induced by the Sarkovskii order, and corresponding bifurcation properties.
The bifurcation of homoclinic orbits of maps of the interval
Authors: Block Louis , Hart David
Published: September 2008

Relationships involving homoclinic orbits of various periods and the Sarkovskii stratification are given and corresponding bifurcation properties are derived. It is shown that if a continuous map has one homoclinic periodic orbit, it has infinitely many. In any family of C1 maps going from zero to positive entropy, infinitely many homoclinic bifurcations occur, involving periods which are successively smaller powers of two.
On uniformly distributed orbits of certain horocycle flows
Authors: Dani S. G.
Published: September 2008

Let

(where t ε ℝ) and let μ be the G-invariant probability measure on G/Γ. We show that if x is a non-periodic point of the flow given by the (ut)-action on G/Γ then the (ut)-orbit of x is uniformly distributed with respect to μ; that is, if Ω is an open subset whose boundary has zero measure, and l is the Lebesque measure on ℝ then, as T→∞, converges to μ(Ω).
Isentropic fitting of Anosov automorphisms
Authors: Fried David
Published: September 2008

In response to a question of Newhouse, we show that in many cases an Anosov automorphism can be uniformly approximated by a Smale diffeomorphism of the same topological entropy. We conjecture this can be done whenever the automorphism is sufficiently hyperbolic.

A three-dimensional example is given that suggests this approximation is not always possible.
Some remarks on Birkhoff and Mather twist map theorems
Authors: Katok A.
Published: September 2008

A recent result of J. Mather [1] about the existence of quasi-periodic orbits for twist maps is derived from an appropriately modified version of G. D. Birkhoff's classical theorem concerning periodic orbits. A proof of Birkhoff's theorem is given using a simplified geometric version of Mather's arguments. Additional properties of Mather's invariant sets are discussed.