bluuebunny/crossref_metadata_2025 huggingface dataset:
Exogenous alginate protectsStaphylococcus aureusfrom killing byPseudomonas aeruginosa
Authors: Price Courtney E. , Brown Dustin G. , Limoli Dominique H. , Phelan Vanessa V. , O’Toole George A.
Published: August 2019

Cystic fibrosis (CF) patients chronically infected with bothPseudomonas aeruginosaandStaphylococcus aureushave worse health outcomes than patients who are mono-infected with eitherP. aeruginosaorS. aureus. We showed previously that mucoid strains ofP. aeruginosacan co-exist withS. aureus in vitrodue to transcriptional downregulation of several toxic exoproducts typically produced byP. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here we demonstrate that exogenous alginate protectsS. aureusfromP. aeruginosain both planktonic and biofilm co-culture models under a variety of nutritional conditions.S. aureusprotection in the presence of exogenous alginate is due to transcriptional downregulation ofpvdA, a gene required for the production of the iron scavenging siderophore pyoverdine, as well as down-regulation of the PQS (Pseudomonas quinolone signal; 2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that co-culture of mucoidP. aeruginosawith non-mucoidP. aeruginosacan mitigate the killing ofS. aureusby the non-mucoid strain ofP. aeruginosa, indicating that the mechanism we describe here may functionin vivoin the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability killS. aureusat late time points, and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the effects of mucoidy in a strain-specific manner.

IMPORTANCE

CF patients are chronically infected by polymicrobial communities of microorganisms. The two dominant bacterial pathogens that infect CF patient lungs areP. aeruginosaandS. aureus, with ∼30% of patients co-infected by both species. Patients infected with bothP. aeruginosaandS. aureushave worse outcomes than mono-infected patients, and both species persist within the same physical space in the lungs of CF patients. A variety of host and environmental factors have been demonstrated to promoteP. aeruginosa-S. aureusco-existence, despite evidence thatP. aeruginosakillsS. aureuswhen these organisms are co-culturedin vitro. Thus, a better understanding ofP. aeruginosa-S. aureusinteractions, particularly mechanisms by which these microorganisms are able to co-exist in proximal physical space, will lead to better informed treatments for chronic polymicrobial infections.
Higher order interactions and coexistence theory
Authors: Singh Pragya , Baruah Gaurav
Published: August 2019

Higher order interactions (HOIs) have been suggested to stabilize diverse ecological communities. However, their role in maintaining species coexistence from the perspective of modern coexistence theory is unknown. Here, using a three-species Lotka-Volterra model, we derive a general rule for species coexistence modulated by HOIs. We show that negative HOIs that intensify pairwise competition, can promote coexistence across a wide range of fitness differences, provided that HOIs strengthen intraspecific competition more than interspecific competition. In contrast, positive HOIs that alleviate pairwise competition can also stabilize coexistence across a wide range of fitness differences, irrespective of differences in strength of inter- and intraspecific competition. Furthermore, we extend our three-species analytical result to multispecies competitive community and show, using simulations, that feasible multispecies coexistence is possible provided that strength of negative intraspecific HOIs is higher than interspecific HOIs. In addition, multispecies communities, however, become unstable with positive HOIs as such higher-order interactions could lead to disproportionately infeasible growth rates. This work provides crucial insights on the underlying mechanisms that could maintain species diversity and links HOIs with modern coexistence theory.
Baroreceptor denervation reduces inflammatory status and worsens cardiovascular collapse during systemic inflammation
Authors: Amorim Mateus R. , de Deus Júnia L. , Pereira Camila A. , da Silva Luiz E. V. , Borges Gabriela S. , Ferreira Nathanne S. , Batalhão Marcelo E. , Antunes-Rodrigues José , Cárnio Evelin C. , Tostes Rita C. , Branco Luiz G. S.
Published: August 2019

Beyond the regulation of cardiovascular function, baroreceptor afferents play polymodal roles. We hypothesized that baroreceptor denervation affects lipopolysaccharide (LPS)-induced systemic inflammation (SI) and hemodynamic collapse in conscious rats, and that these parameters are interconnected. We combine: a) hemodynamic and thermoregulatory recordings after LPS administration at a septic-like dose b) analysis of the cardiovascular complexity, c) evaluation of vascular function in mesenteric resistance vessels, and d) measurements of inflammatory cytokines (plasma and spleen). LPS-induced drop in blood pressure was higher in sino-aortic denervated (SAD) rats. LPS-induced hemodynamic collapse was associated with SAD-dependent autonomic disbalance. LPS-induced vascular dysfunction was not affected by SAD. Surprisingly, SAD blunted LPS-induced surges of plasma and spleen cytokines. These data indicate that sino-aortic afferents are key to alleviate LPS-induced cardiovascular collapse, affecting the autonomic cardiovascular control, without affecting resistance blood vessels. Moreover, baroreflex modulation of the LPS-induced SI and hemodynamic collapse seem not to be interconnected.
Reassessing the validity of slow-wave dynamics as a proxy for NREM sleep homeostasis
Authors: Hubbard Jeffrey , Gent Thomas C. , Hoekstra Marieke M. B. , Emmenegger Yann , Mongrain Valerie , Landolt Hans-Peter , Adamantidis Antoine R. , Franken Paul
Published: August 2019

Sleep-wake driven changes in NREM sleep (NREMS) EEG delta (δ: ∼0.75-4.5Hz) power are widely used as proxy for a sleep homeostatic process. We noted frequency increases in δ-waves in sleep-deprived (SD) mice, prompting us to re-evaluate how slow-wave characteristics relate to prior sleep-wake history. We discovered two types of δ-waves; one responding to SD with high initial power and fast, discontinuous decay (δ2: ∼2.5-3.5Hz) and another unrelated to time-spent-awake with slow, linear decays (δ1: ∼0.75-1.75Hz). Human experiments confirmed this δ-band heterogeneity. Similar to SD, silencing of centromedial thalamus neurons boosted δ2-waves, specifically. δ2-dynamics paralleled that of temperature, muscle tone, heart-rate, and neuronal UP/DOWN state lengths, all reverting to characteristic NREMS levels within the first recovery hour. Thus, prolonged waking seems to necessitate a physiological recalibration before typical NREMS can be reinstated. These short-lasting δ2-dynamics challenge accepted models of sleep regulation and function based on the merged δ-band as sleep-need proxy.
Diversity amongst human cortical pyramidal neurons revealed via their sag currents and frequency preferences
Authors: Chameh Homeira Moradi , Rich Scott , Wang Lihua , Chen Fu-Der , Zhang Liang , Carlen Peter L. , Tripathy Shreejoy J. , Valiante Taufik A.
Published: August 2019

In the human neocortex coherent interlaminar theta oscillations are driven by deep cortical layers, suggesting neurons in these layers exhibit distinct electrophysiological properties. To characterize this potential distinctiveness, we use in vitro whole-cell recordings from cortical layers 2 and 3 (L2&3), layer 3c (L3c) and layer 5 (L5) of the human cortex. Across all layers we observe notable heterogeneity, indicating human cortical pyramidal neurons are an electrophysiologically diverse population. L5 pyramidal cells are the most excitable of these neurons and exhibit the most prominent sag current (abolished by blockade of the hyperpolarization activated cation current, Ih). While subthreshold resonance is more common in L3c and L5, we rarely observe this resonance at frequencies greater than 2Hz. However, the frequency dependent gain of L5 neurons reveals they are most adept at tracking both delta and theta frequency inputs, a unique feature that may indirectly be important for the generation of cortical theta oscillations.
Climatic sensitivity of species’ vegetative and reproductive phenology in a Hawaiian montane wet forest
Authors: Pau Stephanie , Cordell Susan , Ostertag Rebecca , Sack Lawren , Inman-Narahari Faith
Published: August 2019

Understanding the way tropical tree phenology (i.e., the timing and amount of seed and leaf production) responds to climate is vital for predicting how climate change may alter ecological functioning of tropical forests. We examined the effects of temperature, rainfall, and photosynthetically active radiation (PAR) on seed and leaf phenology in a montane wet forest on Hawaiʻi using monthly data collected over ∼6 years. We expected that species’ phenologies were more sensitive to temperature and PAR than to rainfall at this wet tropical site because rainfall is not limiting. Seed production declined with increasing temperatures for two foundational species in Hawaiian forests (Acacia koaandMetrosideros polymorpha). Seed production also declined with rainfall for two species, and greater PAR for one species. One species showed relatively flat responses to climate. Community-level leaf phenology was not strongly seasonal. Unlike seed phenology, we found no effect of temperature on leaf phenology. However, leaf fall increased with rainfall. Climatic factors explained a low to moderate proportion of variance for both seed and leaf litterfall, thus the impact of future climate change on this forest will depend on how climate change interacts with other factors such as daylength, biotic, and/or evolutionary constraints. Our results nonetheless provide insight into how climate change may differentially affect different species with potential consequences for shifts in species distributions and community composition.
Sensitivity in the antioxidant system of discus fish (Symphysodonspp.) to cold temperature: evidence for species-specific cold resistance
Authors: Jin Shi-Rong , Wen Bin , Chen Zai-Zhong , Gao Jian-Zhong , Wang Lei , Liu Ying , Liu Han-Peng
Published: August 2019

The discus fish (Symphysodonspp.) is an endemic species of the Amazon that is among the most popular ornamental fish around the world, and is usually used as the model animal for studying the diversification of Amazon fish. Here, a comparative analysis of two species of discus fish, i.e.,S. haraldiandS. aequifasciatus, based on several antioxidant indexes was conducted, to test the hypothesis that cold resistance might correlate with the diversification of discus fish. We set up a continuous sequence of three temperature programs, namely cooling (28 °C to 14 °C; -1 °C/h), cold maintenance (14 °C for 12 h) and recovery (14 °C to 28 °C; +1 °C/h). Subordinate function (SF) combined with principal component analysis (PCA) showed that the cold hardiness ofS. haraldiduring cold treatment was in the order of cooling > cold maintenance ≈ recovery, but the cold hardiness ofS. aequifasciatusduring cold treatment was in the order of cold maintenance > cooling > recovery. Specifically, the lowest cold hardiness was observed inS. aequifasciatusduring recovery, indicating that cold stress resulted in more seriously oxidative stress inS. aequifasciatusthan inS. haraldi. Overall, these results show a significant interspecific variation, indicating the correlation between environmental adaptation and the diversification of discus fish.
Novel Quorum Sensing Activity in East Antarctic Soil Bacteria
Authors: Wong Sin Yin , Charlesworth James C. , Benaud Nicole , Burns Brendan P. , Ferrari Belinda C.
Published: August 2019

Antarctica, being the coldest, driest and windiest continent on Earth, represents the most extreme environment a living organism can thrive in. Under constant exposure to harsh environmental threats, terrestrial Antarctica remains home to a great diversity of microorganisms, indicating that the soil bacteria must have adapted a range of survival strategies that require cell-to-cell communication. Survival strategies include secondary metabolite production, biofilm formation, bioluminescence, symbiosis, conjugation, sporulation and motility, all of which are often regulated by quorum sensing (QS), a type of bacterial communication. Up to now, such mechanisms have not been explored in terrestrial Antarctica. Here, for the first time, LuxI/LuxR-based quorum sensing (QS) activity was delineated in soil bacterial isolates recovered from Adams Flat, in the Vestfold Hills region of East Antarctica. Interestingly, we identified the production of potential homoserine lactones (HSLs) ranging from medium to long chain length in 19 bacterial species using three biosensors, namelyAgrobacterium tumefaciensNTL4,Chromobacterium violaceumCV026 andEscherichia coliMT102, in conjunction with thin layer chromatography (TLC). The majority of detectable HSLs were from gram-positive microorganisms not previously known to produce HSLs. This discovery further expands our understand of the microbial community capable of this type of communication, as well as providing insights into physiological adaptations of microorganisms that allow them to survive in the harsh Antarctic environment.

IMPORTANCE

Quorum sensing, a type of bacterial communication, is widely known to regulate many processes including those that confer survival advantage. However, little is known about communication by bacteria thriving within Antarctic soils. Employing a combination of bacteria biosensors, analytical techniques, and genome mining, we found a variety of Antarctic soil bacteria speaking a common language, via the LuxI/LuxR-based quorum sensing, thus potentially supporting survival in a mixed microbial community. This is the first report of quorum sensing activity in Antarctic soils and has provided a platform for studying physiological adaptations of microorganisms that allow them to not just survive but thrive in the harsh Antarctic environment.
A morphological analysis of activity-dependent myelination and myelin injury in transitional oligodendrocytes
Authors: Toth Eszter , Rassul Sayed Muhammed , Berry Martin , Fulton Daniel
Published: August 2019

Neuronal activity is established as a driver of oligodendrocyte (OL) differentiation and myelination. The concept of activity-dependent myelin plasticity, and its role in cognition and disease, is gaining support. Methods capable of resolving changes in the morphology of individual myelinating OL would advance our understanding of myelin plasticity and injury, thus we adapted a labelling approach involving Semliki Forest Virus (SFV) vectors to resolve and quantify the 3-D structure of OL processes and internodes in cerebellar slice cultures. We first demonstrate the utility of the approach by studying changes in OL morphology after complement-mediated injury. SFV vectors injected into cerebellar white matter labelled transitional OL (TOL), whose characteristic mixture of myelinating and non-myelinating processes exhibited significant degeneration after complement injury. The method was also capable of resolving finer changes in morphology related to neuronal activity. Prolonged suppression of neuronal activity, which reduced myelination, increased the number of TOL processes, while decreasing both the length of putative internodes, and the proportion of myelinating terminal branches. Overall this approach provides novel information on the morphology of TOL, and new opportunities to study the response of OL to conditions that alter circuit function or induce demyelination.
Rac1 is a downstream effector of PKCα in structural synaptic plasticity
Authors: Tu Xun , Yasuda Ryohei , Colgan Lesley A
Published: August 2019

Structural and functional plasticity of dendritic spines is the basis of animal learning. The calcium-dependent protein kinase C isoform, PKCα, has been suggested to be critical for this actin-dependent plasticity. However, mechanisms linking PKCα and structural plasticity of spines are unknown. Here, we examine the spatiotemporal activation of actin regulators, including small GTPases Rac1, Cdc42 and Ras, in the presence or absence of PKCα during single-spine structural plasticity. Removal of PKCα expression in the postsynapse attenuated Rac1 activation during structural plasticity without affecting Ras or Cdc42 activity. Moreover, disruption of a PDZ binding domain within PKCα led to impaired Rac1 activation and deficits in structural spine remodeling. These results demonstrate that PKCα positively regulates the activation of Rac1 during structural plasticity.
Cyclin N-Terminal Domain-Containing 1 (CNTD1) coordinates meiotic crossover formation with cell cycle progression in a cyclin-independent manner
Authors: Gray Stephen , Santiago Emerson R. , Chappie Joshua S. , Cohen Paula E.
Published: August 2019

During meiotic prophase I, programmed DNA double-strand breaks repair as non-crossover or crossover events, the latter predominantly occurring via the Class I crossover pathway and requiring the cyclin family member CNTD1. Using an epitope-taggedCntd1allele, we show that mouse CNTD1 existsin vivoas a short isoform that lacks the predicted N-terminal cyclin domain and does not bind cyclin-dependent kinases. Instead, we find that CNTD1 associates with Replication Factor C to drive crossover formation and the Skp1-Cullin1-F-Box complex to regulate ubiquitination and subsequent degradation of the WEE1 kinase, thereby indirectly modulating cell cycle progression. We propose that these interactions enable CNTD1 to orchestrate the steps of prophase I and coordinate crossover formation with cellular division.
Sex differences in the ability of corticostriatal oscillations to predict rodent alcohol consumption
Authors: Henricks Angela M. , Sullivan Emily D.K. , Dwiel Lucas L. , Keus Karina M. , Adner Ethan D. , Green Alan I. , Doucette Wilder T.
Published: August 2019

Background

Although male and female rats differ in their patterns of alcohol use, little is known regarding the neural circuit activity that underlies these differences in behavior. The current study used a machine learning approach to characterize sex differences in local field potential (LFP) oscillations that may relate to sex differences in alcohol drinking behavior.

Methods

LFP oscillations were recorded from the nucleus accumbens shell and the rodent medial prefrontal cortex of adult male and female Sprague-Dawley rats. Recordings occurred before rats were exposed to alcohol (n=10/sex X 2 recordings/rat) and during sessions of limited access to alcohol (n=5/sex X 5 recordings/rat). Oscillations were also recorded from each female rat in each phase of estrous prior to alcohol exposure. Using machine-learning, we built predictive models to classify rats based on: 1) biological sex; 2) phase of estrous; and 3) alcohol intake levels. We evaluated model performance from real data by comparing it to the performance of models built and tested on permutations of the data.

Results

Our data demonstrate that corticostriatal oscillations were able to predict alcohol intake levels in males (p<0.01), but not in females (p=0.45). The accuracies of models predicting biological sex and phase of estrous were related to fluctuations observed in alcohol drinking levels; females in diestrus drank more alcohol than males (p=0.052), and the male vs. diestrus female model had the highest accuracy (71.01%) compared to chance estimates.

Conversely, females in estrus drank similar amounts of alcohol to males (p=0.702), and the male vs. estrus female model had the lowest accuracy (56.14%) compared to chance estimates.

Conclusions

The current data demonstrate that oscillations recorded from corticostriatal circuits contain significant information regarding alcohol drinking in males, but not alcohol drinking in females. Future work will focus on identifying where to record LFP oscillations in order to predict alcohol drinking in females, which may help elucidate sex-specific neural targets for future therapeutic development.
HOPS recognizes each SNARE, assembling ternary trans-complexes for sudden fusion upon engagement with the 4th SNARE
Authors: Song Hongki , Orr Amy , Harner Max , Wickner William
Published: August 2019

Vacuole fusion requires SNAREs, Sec17/18, a Rab, and HOPS. We find that co-incubation of HOPS, proteoliposomes bearing the Rab and R-SNARE, and proteoliposomes with the Rab and any two Q-SNAREs yields a trans complex which includes these 3 SNAREs. The missing Q-SNARE then triggers a burst of fusion, indicating that each HOPS, R-, and QxQy-SNARE trans-complex is an activated intermediate for functional Qz-SNARE incorporation. HOPS can assemble activated fusion intermediates because it recognizes each of the four SNAREs, binding them independently. HOPS-dependent fusion is saturable for each Q-SNARE, indicating saturable functional sites on HOPS. Though a nonspecific tether allows fusion with pre-assembled Q-SNAREs, only HOPS catalyzes fusion when the Q-SNAREs are not pre-assembled by ushering each Q-SNARE into a functional complex. In contrast, there is little spontaneous functional assembly of the 3 Q-SNAREs. HOPS thus recognizes each of the 4 SNAREs to assemble a versatile set of activated fusion intermediates.
Structure of the dihydrolipoamide succinyltransferase catalytic domain fromEscherichia coliin a novel crystal form: a tale of a common protein crystallization contaminant
Authors: Andi Babak , Soares Alexei S. , Shi Wuxian , Fuchs Martin R. , McSweeney Sean , Liu Qun
Published: August 2019

The crystallization of amidase, the ultimate enzyme in the Trp-dependent auxin-biosynthesis pathway, fromArabidopsis thalianawas attempted using protein samples with at least 95% purity. Cube-shaped crystals that were assumed to be amidase crystals that belonged to space groupI4 (unit-cell parametersa=b= 128.6,c= 249.7 Å) were obtained and diffracted to 3.0 Å resolution. Molecular replacement using structures from the PDB containing the amidase signature fold as search models was unsuccessful in yielding a convincing solution. Using theSequence-Independent Molecular replacement Based on Available Databases(SIMBAD) program, it was discovered that the structure corresponded to dihydrolipoamide succinyltransferase fromEscherichia coli(PDB entry 1c4t), which is considered to be a common crystallization contaminant protein. The structure was refined to anRworkof 23.0% and anRfreeof 27.2% at 3.0 Å resolution. The structure was compared with others of the same protein deposited in the PDB. This is the first report of the structure of dihydrolipoamide succinyltransferase isolated without an expression tag and in this novel crystal form.
Investigations on strain distribution, stress-based fracture limit and corrosion behaviour of titanium Grade 2 sheets during single point incremental forming
Authors: Yoganjaneyulu G. , Ravikumar V.V. , Sathiya Narayanan C.
Published: August 2019

Purpose

The purpose of this paper is to investigate the strain distribution, stress-based fracture limit and corrosion behaviour of titanium Grade 2 sheets during single point incremental forming (SPIF) process, with various computerized numerical control (CNC) spindle rotational speeds and step depths. The development of corrosion pits in 3.5 (%) NaCl solution has also been studied during the SPIF process.

Design/methodology/approach

A potentiodynamic polarization (PDP) study was performed to investigate the corrosion behaviour of titanium Grade 2 deformed samples, with various spindle rotational speeds in 3.5 (%) NaCl solution. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis was carried out to study the fracture behaviour, dislocation densities and corrosion morphology of deformed samples.

Findings

The titanium Grade 2 sheets exhibited better strain distribution, fracture limit and corrosion resistance by increasing the CNC spindle rotational speeds, tool diameters and vertical step depths (VSD). It was recorded that varying the spindle speed affected plastic deformation which in turn affected corrosion rate.

Research limitations/implications

In this study, poor corrosion rate was observed for the as-received condition, and better corrosion rate was achieved at maximum speed of 600 rpm and 0.6 mm of VSD in the deformed sheet. This indicates that corrosion rate improved with increase in the plastic deformation. The EDS analysis report of corroded surface revealed the composition to be mainly of titanium and oxides.

Practical implications

This study discusses the strain distribution, stress-based fracture limit and corrosion behaviour by using titanium Grade 2 sheets during SPIF process.

Social implications

This study is useful in the field of automobile and industrial applications.

Originality/value

With an increase in the spindle rotational speeds and VSD, the titanium Grade 2 sheets showed better strain distribution, fracture limit and corrosion behaviour; the same is evidenced in fracture limit curve and PDP curves.
The rise of social networking sites
Authors: Naqvi Mishal , Li Shan , Jiang Yushi , Naqvi Muhammad Hasnain Abbas
Published: August 2019

Purpose

The purpose of this paper is to investigate the impact of the technology acceptance model, privacy concerns and demographic factors on intention to use (ITU) social networking sites (SNSs).

Design/methodology/approach

A questionnaire survey was developed and administered to a convenience sample of 838 university students.

Findings

The findings indicate that perceived privacy, demographic factors and perceived usefulness (PU) have a significant effect on the ITU SNSs, and that age does not moderate the relationship between perceived ease-of-use and PU.

Originality/value

This study confirms the growing importance of SNSs. It also provides social networking service providers with insights into user intentions towards such networks.
Women directors and performance: evidence from Malaysia
Authors: Lim Kwee Pheng , Lye Chun-Teck , Yuen Yee Yen , Teoh Wendy Ming Yen
Published: August 2019

Purpose

The purpose of this paper is to examine the relationship between women on board and the financial performance of Malaysian listed companies.

Design/methodology/approach

Panel generalised method of moments (GMM) analysis was used over 928 public-listed companies listed on the Malaysian Stock Exchange from 2010 to 2016. GMM overcomes the problem of endogeneity and simultaneity bias. The dependent variable was firm performance, measured by Tobin’sQ. The explanatory variable was gender diversity, proxied by the percentage of women on board, the presence of women and gender heterogeneity indices, Blau and Shannon indices.

Findings

More gender diversification leads to declining firm performance possibly due to issues of tokenism and gender stereotypes.

Research limitations/implications

Further studies should look into the impact of various types of ownership structures on firm value and also by sectors.

Practical implications

As women represent half the population in Malaysia, more positive affirmative policies must be introduced to enhance their contributions to society.

Social implications

As women progress in society, their contributions towards nation building will be significant. Women not only play a nurturing role, but also can shape the destiny of a country.

Originality/value

Studies on the relationship between board gender diversity and financial performance have been conducted in the context of a few developed economies. This study contributes to the literature by examining such an issue in a developing economy that has a different environment from that of developed economies.
Microaggression experiences of different marginalized identities
Authors: Nair Nisha , Good Deborah Cain , Murrell Audrey J.
Published: August 2019

Purpose

Given the nascent stage of research on microaggressions, the study is an attempt to better understand the experience of microaggressions and examine it from the point of view of different marginalized minority identities. The purpose of this paper is to report on the subjective experience of microaggressions from the lenses of gender, race, religion and sexual orientation.

Design/methodology/approach

To explore how microaggressions are experienced by different identities, the authors conducted four focus group studies with university students at a prominent Midwestern university. Each focus group focused on the experience of microaggressions for a particular identity group.

Findings

The authors discuss the nature and forms of exclusion that occur through microaggressions, and offer six microaggression themes that emerged as common across the marginalized identities studied. The authors add to the microaggression taxonomy and highlight the role of repetition in how microaggressions are perceived. The authors also discuss intersectional microaggressions.

Originality/value

While various studies have focused on reporting microaggression themes with regard to singular identities, this study is potentially the first that explores microaggression themes across different marginalized identities. The findings highlight novel forms of microaggressions such as the revealing or making visible of marginalized identities, and microaggressions emanating from within a minority group directed at other members within the same identity group, what the authors call as in-group microaggressions. The authors highlight and point to the need for more work on intersectional microaggressions.
Enhanced heat transfer in a labyrinth channels with ribs of different shape
Authors: Du Wei , Luo Lei , Wang Songtao , Liu Jian , Sunden Bengt Ake
Published: August 2019

Purpose

The purpose of this study is to enhance the thermal performance in the labyrinth channel by different ribs shape. The labyrinth channel is a relatively new cooling structure to decrease the temperature near the trailing region of gas turbine.

Design/methodology/approach

Based on the geometric similarity, a simplified geometric model is used. The k − ω turbulence model is used to close the Navier–Stokes equations. Five rib shapes (one rectangular rib, two arched ribs and two trapezoid ribs) and five Reynolds numbers (10,000 to 50,000) are considered. The Nusselt number, flow structure and friction factor are analyzed.

Findings

Nusselt number is tightly related to the rib shape in the labyrinth channel. The different shapes of the ribs result in different horseshoe vortex and wake region. In general, the arched rib brings the highest Nusselt number and friction factor. The Nusselt number is increased by 15.8 per cent compared to that of trapezoidal ribs. High Nusselt number is accompanied by the high friction factor in a labyrinth channels. The friction factor is increased by 64.6 per cent compared to rectangular ribs. However, the rib shape has a minor effect on the overall thermal performance.

Practical implications

This study is useful to protect the trailing region of advanced gas turbine.

Originality/value

This paper presents the flow structure and heat transfer characteristics in a labyrinth channel with different rib shapes.
Effects of magnetic field on the liquid gallium thermosyphon fluid flow; a numerical study
Authors: Teimouri Hamid , Behzadmehr Amin
Published: August 2019

Purpose

This paper aims to numerically study the laminar natural convection in a thermosyphon filled with liquid gallium exposed to a constant magnetic field. The left wall of the thermosyphon is at an uniformed hot temperature, whereas the right wall is at a uniform cold temperature. The top and bottom walls are considered to be adiabatic. All walls are electrically insulated. The effects of Hartmann number, in a wide range of Rayleigh number and aspect ratio combinations, on the natural convection throughout the thermosyphon, are investigated and discussed. Furthermore, different forces that influence the natural flow structure are studied.

Design/methodology/approach

A Fortran code is developed based on the finite volume method to solve the two-dimensional unsteady governing equations.

Findings

Imposing a magnetic field improves the stability of the fluid flow and thus reduces the Nusselt number. For a given Hartmann and Rayleigh number, there is an optimum aspect ratio for which the average velocity becomes maximum.

Research limitations/implications

This paper is a two-dimensional investigation.

Originality/value

To the best of the authors’ knowledge, the effect of the magnetic field on natural convection of liquid gallium in the considered thermosyphon has not been studied numerically in detail. The results of this paper would be helpful in considering the application of the low Prandtl number’s liquid metals in thermosyphon MHD generators and certain cooling devices.
Enhanced understanding of leakage in mechanical seals with elliptical dimples based on CFD simulation
Authors: Jiang Sen , Ji Hua , Wang Tianhao , Feng Donglin , Li Qian
Published: August 2019

Purpose

The shapes of surface textures have been designed to control the leakage of mechanical seals in recent years. The purpose of this paper is to demonstrate the influence of geometric properties of elliptical dimples on the leakage rate.

Design/methodology/approach

A new geometric feature point is expressed using an analytical solution to locate the high-pressure zones. Furthermore, a numerical model of the three-dimensional flow field for the mechanical seal with elliptical dimples is developed using ANSYS Fluent to demonstrate the influencing mechanism.

Findings

The location of the proposed geometric converging point coincides with the maximum pressure point under different orientation angles. An inward flow on the leakage section observed from the simulation results is responsible for decreasing the leakage rate.

Originality/value

The influencing mechanism of the elliptical dimple on the leakage rate is demonstrated, which can facilitate the design of surface textures.
Tribological properties of carbonized polydopamine/rGO composite coatings
Authors: Yang Ming , Jia Zhengfeng , Wei Denghu , Wang Yunxia , Pang Xianjuan , Zhen Jinming , Zhang Ran , Yu Bo
Published: August 2019

Purpose

The purpose of this paper is to investigate the tribological properties of carbonized polydopamine/reduced graphene oxide (CPDA/rGO) composite coatings.

Design/methodology/approach

CPDA/rGO composite coatings were prepared using the spray technique and subsequent pyrolysis under argon. The transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy revealed the conversion of PDA and GO into CPDA and rGO, respectively.

Findings

The results of tribological investigations show that the CPDA/rGO composite coatings with heat treatment at 300°C possess much better friction-reduction and anti-wear properties.

Originality/value

The worn surfaces of the PDA/GO composite films after heat treatment at 300°C were much smoother than that of the copper substrate. The tribofilms containing C, N, O and Cu played an important role on reducing friction and increasing wear resistance.
Bundling cloud software to fight piracy: an economic analysis
Authors: Zhang Xiong , Yue Wei T. , Hui Wendy
Published: August 2019

Purpose

The emergence of internet-enabled technology has led to the software service model in which the software firm, instead of the consumer, maintains software ownership. This model can curtail software piracy more effectively than the traditional on-premises software model. However, software firms are not abandoning traditional on-premises software but embracing both models simultaneously. In this study, the authors consider a firm’s software bundling decision in combination with its piracy deterrence strategy. The paper aims to discuss these issues.

Design/methodology/approach

The authors build three stylized models to analytically compare the bundling strategies under three scenarios: no piracy, piracy is present and piracy is present while the firm applies digital rights management (DRM).

Findings

The authors find pure bundling (PB) to be the optimal strategy due to the combination of competition and cannibalization effects in mixed bundling (MB). Simultaneously, consumers may enjoy greater surplus in PB than in MB, making PB the preferred strategy for both the firm and consumers. Interestingly, the win-win outcome coexists with some degree of piracy in the market.

Originality/value

The results provide important insights for firms and policy-makers and contribute to the literature on piracy and product bundling. First, the authors show piracy could be another driver for product bundling, which has never been discussed in prior literature. Second, the authors suggest an alternative perspective; that PB may be a desirable outcome for both firms and consumers when considering piracy and DRM. More surprisingly, this desirable outcome occurs with some level of piracy in the market. The presence of piracy leads to competition and cannibalization effects in MB, which eventually results in the win-win outcome in the software market for both the firm and the consumers.
Supply chain flexibility and mass personalization: a systematic literature review
Authors: R. Novais Luciano , Maqueira Juan M. , Bruque Sebastián
Published: August 2019

Purpose

This paper aims to explore the current state of research on supply chain flexibility (SCF) and mass personalization (MP) to identify the literature findings to date, research gaps and to provide guidelines for future research in this area.

Design/methodology/approach

A systematic literature review of 64 papers was undertaken to address the use of SCF as a productive response to MP environments. The methodology used is made up of five steps: formulation of the research questions, identification of studies, selection and evaluation of studies, analysis and synthesis and presentation of the results.

Findings

Three main research topics have been identified: personalization levels and flexible processes in supply chain, where flexible processes in supply chain are analysed as a productive response to high levels of MP; supply chain collaborative processes for SCF and MP, where product co-creation and relationships between supply chain members is analysed; and SCF and MP enabling technologies, in which technologies to support MP implementation and SCF are considered. Each of these three main topics have been divided into research lines and research sublines that allowed identifying a positive relationship between the SCF and the MP strategies.

Research limitations/implications

Systematic literature review is a methodology reliable and recommended by a large number of scientific papers. However, it depends on available and accessible research studies and the researcher’s criteria. The selection of certain criteria for inclusion and exclusion of papers introduces publication bias, which should be considered an intrinsic limitation to systematic literature review.

Originality/value

The main literature findings in each research line and subline related to the SCF-MP relationship are identified and analysed. Furthermore, research gaps and further research lines in the SCF-MP area are highlighted. The information presented in this paper improves the literature on the advances in the SCF use as a productive response to MP environments.
Environmental management in small and medium enterprises: the role of customer orientation and firm performance
Authors: Lee Euehun , Jo Sang Hyun , Jeong Haeyoung
Published: August 2019

Purpose

The purpose of this study is to explore the antecedents and effects of environmental management (EM) and its related factors on firm performance from the perspective of small and medium-sized enterprises (SMEs). Most previous studies have focused on determining the effects of environmental efforts on environmental performance. This study aims to illustrate that effective EM – along with other factors such as customer emphasis, recognition and capabilities – generates positive firm performance for SMEs. Additionally, the stdy aims to show evidence that EM is worth proactively pursuing rather than being viewed as a burden and being subject to reactive task by SMEs.

Design/methodology/approach

The authors collected data via a questionnaire from 300 SMEs through a professional research company. They then used the data to assess a model and determine the relationships between the different constructs using structural equation modeling.

Findings

The results testify to the optimal structure between the study’s constructs: customer emphasis on EM, recognition and implementation of EM, capabilities and the performance of SMEs that have implemented EM. The main finding is that EM has a positive relationship to firm performance.

Originality/value

This study’s findings could likely persuade SMEs and policymakers to more proactively engage in EM. It also contributes to offer evidence that customer orientation plays an important role in SMEs’ implementation of EM and its impact on firm performance.
Wanting it all – public perceptions of the effectiveness, cost, and privacy of surveillance technology
Authors: Cayford Michelle , Pieters Wolter , van Gelder P.H.A.J.M
Published: August 2019

Purpose

This study aims to explore how the public perceives the effectiveness of surveillance technology, and how people’s views on privacy and their views on effectiveness are related. Likewise, it looks at the relation between perceptions of effectiveness and opinions on the acceptable cost of surveillance technology.

Design/methodology/approach

For this study, surveys of Dutch students and their parents were conducted over three consecutive years.

Findings

A key finding of this paper is that the public does not engage in a trade-off neither with regard to privacy-effectiveness (exchanging more effectiveness for less privacy and vice versa) nor with effectiveness-cost, but rather expects all three elements to be achieved simultaneously. This paper also found that the correlation between perceived effectiveness and perceived privacy was stronger for parents than for students.

Research limitations/implications

Participants for this study were exclusively in The Netherlands. Survey questions on the effectiveness of surveillance technology focused on one type of technology, and on private mobile device use in two scenarios.

Social implications

The public’s perceptions of the effectiveness of surveillance technology potentially influence its acceptance of the technology, which, in turn, can affect the legitimacy and use of the technology.

Originality/value

Within the much-discussed privacy-security debate lies a less-heard debate – that of the effectiveness of the surveillance technology in question. The public is one actor in this debate. This study examines the public’s perceptions of this less-heard debate.
Mergers and acquisitions: the latest university fashion?
Authors: Czarniawska Barbara
Published: August 2019

Purpose

This paper aims to describe and explain a contemporary phenomenon.

Design/methodology/approach

This is an analysis of research reports and fiction texts.

Findings

Universities use mergers and acquisitions to improve their ranking positions, ignoring the effects on research and teaching.

Research limitations/implications

More attention should be paid to current managerial fashions.

Practical implications

An opposition to thoughtless fashion following may lead to positive changes.

Social implications

If you mean “societal implications”, the state of universities is very important to democratic societies.

Originality/value

These are not for the author to judge.
Network-based pricing for 3D printing services in two-sided manufacturing-as-a-service marketplace
Authors: Pahwa Deepak , Starly Binil
Published: August 2019

Purpose

This paper presents approaches to determine a network-based pricing for 3D printing services in the context of a two-sided manufacturing-as-a-service marketplace. The purpose of this study is to provide cost analytics to enable service bureaus to better compete in the market by moving away from setting ad hoc and subjective prices.

Design/methodology/approach

A data mining approach with machine learning methods is used to estimate a price range based on the profile characteristics of 3D printing service suppliers. The model considers factors such as supplier experience, supplier capabilities, customer reviews and ratings from past orders and scale of operations, among others, to estimate a price range for suppliers’ services. Data were gathered from existing marketplace websites, which were then used to train and test the model.

Findings

The model demonstrates an accuracy of 65 per cent for US-based suppliers and 59 per cent for Europe-based suppliers to classify a supplier’s 3D printer listing in one of the seven price categories. The improvement over baseline accuracy of 25 per cent demonstrates that machine learning-based methods are promising for network-based pricing in manufacturing marketplaces

Originality/value

Conventional methodologies for pricing services through activity-based costing are inefficient in strategically priced 3-D printing service offering in a connected marketplace. As opposed to arbitrarily determining prices, this work proposes an approach to determine prices through data mining methods to estimate competitive prices. Such tools can be built into online marketplaces to help independent service bureaus to determine service price rates.
Personalized design of part orientation in additive manufacturing
Authors: Yu Cong , Qie LongFei , Jing ShiKai , Yan Yan
Published: August 2019

Purpose

Orientation determination is an essential planning task in additive manufacturing (AM) because it directly affects the part quality, build time, geometric tolerance, fabrication cost, etc. This paper aims to propose a negative feedback decision-making (NFDM) model to realize the personalized design of part orientation in AM process.

Design/methodology/approach

NFDM model is constructed by integrating two sub-models: proportional–integral–derivative (PID) negative feedback control model and technique for order preference by similarity to an ideal solution (TOPSIS) decision-making model. With NFDM model, a desired target is first specified by the user. Then, the TOPSIS decision model calculates the “score” for the current part orientation. TOPSIS decision model is modified for ease of control. Finally, the PID controller automatically rotates the part based on the error between the user-specified target and the calculated “score”. Part orientation adjustment is completed when the error is eliminated. Five factors are considered in NFDM model, namely, surface roughness, support structure volume, geometric tolerance, build time and fabrication cost.

Findings

The case studies of turbine fan and dragon head indicate that the TOPSIS model can be perfectly integrated with the PID controller. This work extends the proposed model to different AM processes and investigates the feasibility of combining different decision-making models with PID controller and the effects of including various evaluation criteria in the integrated model.

Originality/value

The proposed model innovatively takes the TOPSIS decision-making model and the PID control model as a whole. In this way, the uncontrollable TOPSIS model becomes controllable, so the proposed model can control the TOPSIS model to achieve the user-specified targets.