bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine mapping chromatin contacts in capture Hi-C data
Authors: Eijsbouts Christiaan , Burren Oliver , Newcombe Paul , Wallace Chris
Published: January 2018

Hi-C and capture Hi-C (CHi-C) are used to map physical contacts between chromatin regions in cell nuclei using high-throughput sequencing. Analysis typically proceeds considering the evidence for contacts between each possible pair of fragments independent from other pairs. This can produce long runs of fragments which appear to all make contact with the same baited fragment of interest. We hypothesised that these long runs could result from a smaller subset of direct contacts and propose a new method, based on a Bayesian sparse variable selection approach, which attempts to fine map these direct contacts.

Our model is conceptually novel, exploiting the spatial pattern of counts in CHi-C data, and prioritises fragments with biological properties that would be expected of true contacts. For bait fragments corresponding to gene promoters, we identify contact fragments with active chromatin and contacts that correspond to edges found in previously defined enhancer-target networks; conversely, for intergenic bait fragments, we identify contact fragments corresponding to promoters for genes expressed in that cell type. We show that long runs of apparently co-contacting fragments can typically be explained using a subset of direct contacts consisting of < 10% of the number in the full run, suggesting that greater resolution can be extracted from existing datasets. Our results appear largely complementary to the those from a per-fragment analytical approach, suggesting that they provide an additional level of interpretation that may be used to increase resolution for mapping direct contacts in CHi-C experiments.
Efficacy and dynamics of self-targeting CRISPR/Cas constructs for gene editing in the retina
Authors: Li Fan , Hung Sandy S.C. , Wang Jiang-Hui , Chrysostomou Vicki , Wong Vickie H.Y. , Bender James A. , Tu Leilei , Pébay Alice , King Anna E , Cook Anthony L. , Wong Raymond C.B. , Bui Bang V. , Hewitt Alex W. , Liu Guei-Sheung
Published: January 2018

Safe delivery of CRISPR/Cas endonucleases remains one of the major barriers to the widespread application ofin vivogenome editing including the anticipatory treatment of monogenic retinal diseases. We previously reported the utility of adeno-associated virus (AAV)-mediated CRISPR/Cas genome editing in the retina; however, with this type of viral delivery system, active endonucleases will remain in the retina for an extended period, making genotoxicity a significant consideration in clinical applications. To address this issue, we have designed a self-destructing “kamikaze” CRISPR/Cas system that disrupts the Cas enzyme itself following expression. Four guide RNAs (sgRNAs) were designed to targetStreptococcus pyogenesCas9 (SpCas9), afterin situvalidation, the selected sgRNAs were cloned into a dual AAV vector. One construct was used to deliver SpCas9 and the other delivered sgRNAs directed against SpCas9 and the target locus (yellow fluorescent protein, YFP), in the presence of mCherry. Both constructs were packaged into AAV2 vector and intravitreally administered in C57BL/6 andThy1-YFPtransgenic mice. After 8 weeks the expression of SpCas9, the efficacy ofYFPgene disruption was quantified. A reduction of SpCas9 mRNA was found in retinas treated with AAV2-mediated-YFP/SpCas9 targeting CRISPR/Cas compared to those treated with YFP targeting CRISPR/Cas alone. We also show that AAV2-mediated delivery of YFP/SpCas9 targeting CRISPR/Cas significantly reduced the number of YFP fluorescent cells among mCherry-expressing cells (~85.5% reduction compared to LacZ/SpCas9 targeting CRISPR/Cas) in transfected retina ofThy1-YFPtransgenic mice. In conclusion, our data suggest that a self-destructive “kamikaze” CRISPR/Cas system can be used as a robust tool for refined genome editing in the retina, without compromising on-target efficiency.
CCA based multi-view feature selection for multi-omics data integration
Authors: El-Manzalawy Yasser
Published: January 2018

Recent technological advances in high-throughput omics technologies and their applications in genomic medicine have opened up outstanding opportunities for individualized medicine. However, several challenges arise in the integrative analysis of such data including heterogeneity and high dimensionality of the omics data. In this study, we present a novel multi-view feature selection algorithm based on the well-known canonical correlation analysis (CCA) statistical method for jointly selecting discriminative features from multi-omics data sources (multi-views). Our results demonstrate that models for predicting kidney renal clear cell carcinoma (KIRC) survival using our proposed method for jointly selecting discriminative features from copy number alteration (CNA), gene expression RNA-Seq, and reverse-phase protein arrays (RPPA) views outperform models trained using single-view data as well as three integrated models developed using data fusion approaches including CCA-based feature fusion.
Impacts of Simultaneous Multislice Acquisition on Sensitivity and Specificity in fMRI
Authors: Risk Benjamin B. , Kociuba Mary C. , Rowe Daniel B.
Published: January 2018

Simultaneous multislice (SMS) acquisition can be used to decrease the time between acquisition of fMRI volumes, which can increase sensitivity by facilitating the removal of higher-frequency artifacts and boosting effective sample size. The technique requires an additional processing step in which the slices are separated, or unaliased, to recover the whole brain volume. However, this may result in signal “leakage” between aliased locations, i.e., slice “leakage,” and lead to spurious activation (decreased specificity). SMS can also lead to noise amplification, which can reduce the benefits of decreased repetition time. In this study, we evaluate the original slice-GRAPPA (no leak block) reconstruction algorithm and acquisition scenarios used in the young adult Human Connectome Project (HCP), as well as split slice-GRAPPA (leak block). In addition to slice leakage, signal leakage can result from spatial smoothing, i.e., smoothing leakage, which leads to inflated regions of activation. Previous studies have generally found that SMS acquisition results in higher test statistics and/or a greater number of activated voxels. Here, we use simulations to disentangle this phenomenon into true positives (sensitivity) and false positives (decreased specificity). Slice leakage was greatly decreased by split slice-GRAPPA. Noise amplification was decreased by using moderate acceleration factors (AF = 4). We examined slice leakage in unprocessed fMRI motor task data from the HCP, which used the original slice-GRAPPA. When data were smoothed, we found evidence of slice leakage in some, but not all, subjects. We also found evidence of SMS noise amplification in unprocessed task and processed resting-state HCP data.
The histone variant H2A.Z and chromatin remodeler BRAHMA act coordinately and antagonistically to regulate transcription and nucleosome dynamics in Arabidopsis
Authors: Torres E. Shannon , Deal Roger B.
Published: January 2018

Plants adapt to changes in their environment by regulating transcription and chromatin organization. The histone H2A variant H2A.Z and the SWI2/SNF2 ATPase BRAHMA have overlapping roles in positively and negatively regulating environmentally responsive genes in Arabidopsis, but the extent of this overlap was uncharacterized. Both have been associated with various changes in nucleosome positioning and stability in different contexts, but their specific roles in transcriptional regulation and chromatin organization need further characterization. We show that H2A.Z and BRM act both cooperatively and antagonistically to contribute directly to transcriptional repression and activation of genes involved in development and response to environmental stimuli. We identified 8 classes of genes that show distinct relationships between H2A.Z and BRM and their roles in transcription. We found that H2A.Z contributes to a range of different nucleosome properties, while BRM stabilizes nucleosomes where it binds and destabilizes and/or repositions flanking nucleosomes. H2A.Z and BRM contribute to +1 nucleosome destabilization, especially where they coordinately regulate transcription. We also found that at genes regulated by both BRM and H2A.Z, both factors overlap with the binding sites of light-regulated transcription factors PIF4, PIF5, and FRS9, and that some of the FRS9 binding sites are dependent on H2A.Z and BRM for accessibility. Collectively, we comprehensively characterized the antagonistic and cooperative contributions of H2A.Z and BRM to transcriptional regulation, and illuminated their interrelated roles in chromatin organization. The variability observed in their individual functions implies that both BRM and H2A.Z have more context-specific roles within diverse chromatin environments than previously assumed.
Contribution of the axon initial segment to action potentials recorded extracellularly
Authors: Teleńczuk Maria , Brette Romain , Destexhe Alain , Teleńczuk Bartosz
Published: January 2018

Action potentials (APs) are electric phenomena that are recorded both intracellularly and extracellularly. APs are usually initiated in the short segment of the axon called the axon initial segment (AIS). It was recently proposed that at onset of an AP the soma and the AIS form a dipole. We study the extracellular signature (the extracellular action potential, EAP) generated by such a dipole. First, we demonstrate the formation of the dipole and its extracellular signature in detailed morphological models of a reconstructed pyramidal neuron. Then, we study the EAP waveform and its spatial dependence in models with axonal AP initiation and contrast it with the EAP obtained in models with somatic AP initiation. We show that in the models with axonal AP initiation the dipole forms between somatodendritic compartments and the AIS, and not between soma and dendrites as in the classical models. Soma-dendrites dipole is present only in models with somatic AP initiation. Our study has consequences for interpreting extracellular recordings of single-neuron activity and determining electrophysiological neuron types, but also for better understanding the origins of the high-frequency macroscopic electric fields recorded in the brain.

New & Noteworthy

We studied the consequences of the action potential (AP) initiation site on the extracellular signatures of APs. We show that: (1) at the time of AP initiation the action initial segment (AIS) forms a dipole with the soma, (2) the width but not (3) amplitude of the extracellular AP generated by this dipole increases with the soma-AIS distance. This may help to monitor dynamic changes in the AIS position in experimental in vivo recordings.
epiTAD: a web application for visualizing high throughput chromosome conformation capture data in the context of genetic epidemiology
Authors: Creed Jordan H. , Aden-Buie Garrick , Monteiro Alvaro N. , Gerke Travis A.
Published: January 2018

The increasing availability of public data resources coupled with advancements in genomic technology has created greater opportunities for researchers to examine the genome on a large and complex scale. To meet the need for integrative genome wide exploration, we present epiTAD. This web-based tool enables researchers to compare genomic structures and annotations across multiple databases and platforms in an interactive manner in order to facilitate in silico discovery. epiTAD can be accessed at https://apps.gerkelab.com/epiTAD/.
BOFdat: generating biomass objective function stoichiometric coefficients from experimental data
Authors: Lachance Jean-Christophe , Monk Jonathan M. , Lloyd Colton J. , Seif Yara , Palsson Bernhard O. , Rodrigue Sébastien , Feist Adam M. , King Zachary A. , Jacques Pierre-Étienne
Published: January 2018

Genome-scale models (GEMs) rely on a biomass objective function (BOF) to predict phenotype from genotype. Here we present BOFdat, a Python package that offers functions to generate biomass objective function stoichiometric coefficients (BOFsc) from macromolecular cell composition and relative abundances of macromolecules obtained from omic datasets. Growth-associated and non-growth associated maintenance (GAM and NGAM) costs can also be calculated by BOFdat.

BOFdat is freely available on the Python Package Index (pip install BOFdat). The source code and an example usage (Jupyter Notebook and example files) are available on GitHub (https://github.com/jclachance/BOFdat). The documentation and API are available through ReadTheDocs (https://bofdat.readthedocs.io).

Contact

jean-christophe.lachance@usherbrooke.ca, zaking@eng.ucsd.edu, pierre-etienne.jacques@usherbrooke.ca
Differential impact of reward and punishment on functional connectivity after skill learning
Authors: Steel Adam , Silson Edward H. , Stagg Charlotte J. , Baker Chris I.
Published: January 2018

Reward and punishment shape behavior, but the mechanisms underlying their effect on skill learning are not well understood. Here, we tested whether the functional connectivity of premotor cortex (PMC), a region known to be critical for learning of sequencing skills, is altered after training by reward or punishment given during training. Resting-state fMRI was collected in two experiments before and after participants trained on either a serial reaction time task (SRTT; n = 36) or force-tracking task (FTT; n = 36) with reward, punishment, or control feedback. In each experiment, training-related change in PMC functional connectivity was compared across feedback groups. In both tasks, reward and punishment differentially affected PMC functional connectivity. On the SRTT, participants trained with reward showed an increase in functional connectivity between PMC and cerebellum as well as PMC and striatum, while participants trained with punishment showed an increase in functional connectivity between PMC and medial temporal lobe connectivity. After training on the FTT, subjects trained with control and reward showed increases in PMC connectivity with parietal and temporal cortices after training, while subjects trained with punishment showed increased PMC connectivity with ventral striatum. While the results from the two experiments overlapped in some areas, including ventral pallidum, temporal lobe, and cerebellum, these regions showed diverging patterns of results across the two tasks for the different feedback conditions. These findings suggest that reward and punishment strongly influence spontaneous brain activity after training, and that the regions implicated depend on the task learned.
Transcriptome assembly and annotation of johnsongrass (Sorghum halepense) rhizomes identifies candidate rhizome-specific genes
Authors: Ryder Nathan , Dorn Kevin M. , Huitsing Mark , Adams Micah , Ploegstra Jeff , DeHaan Lee , Larson Steve , Tintle Nathan L.
Published: January 2018

Rhizomes facilitate the wintering and vegetative propagation of many perennial grasses. Sorghum halepense (johnsongrass) is an aggressive perennial grass that relies on a robust rhizome system to persist through winters and reproduce asexually from its rootstock nodes. This study aimed to sequence and assemble expressed transcripts within the johnsongrass rhizome. A de novo transcriptome assembly was generated from a single johnsongrass rhizome meristem tissue sample. A total of 141,176 probable protein-coding sequences from the assembly were identified and assigned gene ontology terms using Blast2GO. The johnsongrass assembly was compared to Sorghum bicolor, a related non-rhizomatous species, along with an assembly of similar rhizome tissue from the perennial grain crop Thinopyrum intermedium. The presence/absence analysis yielded a set of 259 johnsongrass contigs that are likely associated with rhizome development.
A computational framework for converting high-throughput DNA sequencing data into neural circuit connectivity
Authors: Oyibo Hassana , Cao Cang , Ferrante Daniel D. , Zhan Huiqing , Koulakov Alex , Enquist Lynn , Dubnau Joshua , Zador Anthony
Published: January 2018

There is growing interest in determining the connectivity of neural circuits—the “connectome”—at single neuron resolution. Most approaches to circuit mapping rely on either microscopy or physiology, but these approaches have very limited throughput. We have recently proposed BOINC (Barcoding of Individual Neuronal Connectivity), a radically different approach to connectivity mapping based on high-throughput DNA sequencing. Here we describe the set of computational algorithms that serve to convert sequencing data into neural connectivity. We apply our computational pipeline to the results of proof-of-principle experiments illustrating an implementation of BOINC based on pseudorabies virus (PRV). PRV is capable of traversing individual synapses and carry DNA barcodes from one cell to another. Using this high-throughput sequencing data, we obtain 456-by-486 connectivity matrix between putative neurons. An inexpensive high-throughput technique for establishing circuit connectivity at single neuron resolution would represent a major advance in neuroscience.
A de novo nonsense mutation in ASXL3 shared by siblings with Bainbridge–Ropers syndrome
Authors: Koboldt Daniel C. , Mihalic Mosher Theresa , Kelly Benjamin J. , Sites Emily , Bartholomew Dennis , Hickey Scott E. , McBride Kim , Wilson Richard K. , White Peter
Published: January 2018

Two sisters (ages 16 yr and 15 yr) have been followed by our clinical genetics team for several years. Both girls have severe intellectual disability, hypotonia, seizures, and distinctive craniofacial features. The parents are healthy and have no other children. Oligo array, fragile X testing, and numerous single-gene tests were negative. All four family members underwent research exome sequencing, which revealed a heterozygous nonsense mutation in ASXL3 (p.R1036X) that segregated with disease. Exome data and independent Sanger sequencing confirmed that the variant is de novo, suggesting possible germline mosaicism in one parent. The p.R1036X variant has never been observed in healthy human populations and has been previously reported as a pathogenic mutation. Truncating de novo mutations in ASXL3 cause Bainbridge–Ropers syndrome (BRPS), a developmental disorder with similarities to Bohring–Opitz syndrome. Fewer than 30 BRPS patients have been described in the literature; to our knowledge, this is the first report of the disorder in two related individuals. Our findings lend further support to intellectual disability, absent speech, autistic traits, hypotonia, and distinctive facial appearance as common emerging features of Bainbridge–Ropers syndrome.
The deduced role of a chitinase containing two nonsynergistic catalytic domains
Authors: Liu Tian , Zhu Weixing , Wang Jing , Zhou Yong , Duan Yanwei , Qu Mingbo , Yang Qing
Published: January 2018

The glycoside hydrolase family 18 chitinases degrade or alter chitin. Multiple catalytic domains in a glycoside hydrolase family 18 chitinase function synergistically during chitin degradation. Here, an insect group III chitinase from the agricultural pestOstrinia furnacalis(OfChtIII) is revealed to be an arthropod-conserved chitinase that contains two nonsynergistic GH18 domains according to its catalytic properties. Both GH18 domains are active towards single-chained chitin substrates, but are inactive towards insoluble chitin substrates. The crystal structures of each unbound GH18 domain, as well as of GH18 domains complexed with hexa-N-acetyl-chitohexaose or penta-N-acetyl-chitopentaose, suggest that the two GH18 domains possess endo-specific activities. Physiological data indicated that the developmental stage-dependent gene-expression pattern ofOfChtIII was the same as that of the chitin synthaseOfChsA but significantly different from that of the chitinaseOfChtI, which is indispensable for cuticular chitin degradation. Additionally, immunological staining indicated thatOfChtIII was co-localized withOfChsA. Thus,OfChtIII is most likely to be involved in the chitin-synthesis pathway.
The folate-binding module ofThermus thermophiluscobalamin-dependent methionine synthase displays a distinct variation of the classical TIM barrel: a TIM barrel with a `twist'
Authors: Yamada Kazuhiro , Koutmos Markos
Published: January 2018

Methyl transfer between methyltetrahydrofolate and corrinoid molecules is a key reaction in biology that is catalyzed by a number of enzymes in many prokaryotic and eukaryotic organisms. One classic example of such an enzyme is cobalamin-dependent methionine synthase (MS). MS is a large modular protein that utilizes an SN2-type mechanism to catalyze the chemically challenging methyl transfer from the tertiary amine (N5) of methyltetrahydrofolate to homocysteine in order to form methionine. Despite over half a century of study, many questions remain about how folate-dependent methyltransferases, and MS in particular, function. Here, the structure of the folate-binding (Fol) domain of MS fromThermus thermophilusis reported in the presence and absence of methyltetrahydrofolate. It is found that the methyltetrahydrofolate-binding environment is similar to those of previously described methyltransferases, highlighting the conserved role of this domain in binding, and perhaps activating, the methyltetrahydrofolate substrate. These structural studies further reveal a new distinct and uncharacterized topology in the C-terminal region of MS Fol domains. Furthermore, it is found that in contrast to the canonical TIM-barrel β8α8fold found in all other folate-binding domains, MS Fol domains exhibit a unique β8α7fold. It is posited that these structural differences are important for MS function.
A DNA structural alphabet provides new insight into DNA flexibility
Authors: Schneider Bohdan , Božíková Paulína , Nečasová Iva , Čech Petr , Svozil Daniel , Černý Jiří
Published: January 2018

DNA is a structurally plastic molecule, and its biological function is enabled by adaptation to its binding partners. To identify the DNA structural polymorphisms that are possible in such adaptations, the dinucleotide structures of 60 000 DNA steps from sequentially nonredundant crystal structures were classified and an automated protocol assigning 44 distinct structural (conformational) classes called NtC (for Nucleotide Conformers) was developed. To further facilitate understanding of the DNA structure, the NtC were assembled into the DNA structural alphabet CANA (Conformational Alphabet of Nucleic Acids) and the projection of CANA onto the graphical representation of the molecular structure was proposed. The NtC classification was used to define a validation score called confal, which quantifies the conformity between an analyzed structure and the geometries of NtC. NtC and CANA assignment were applied to analyze the structural properties of typical DNA structures such as Dickerson–Drew dodecamers, guanine quadruplexes and structural models based on fibre diffraction. NtC, CANA and confal assignment, which is accessible at the website https://dnatco.org, allows the quantitative assessment and validation of DNA structures and their subsequent analysis by means of pseudo-sequence alignment. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:Acta_Cryst_D:2.
Numerical analysis of compact plate-fin heat exchangers for aerospace applications
Authors: Chennu Ranganayakulu
Published: January 2018

Purpose

The purpose of this study is to find the thermo-hydraulic performances of compact heat exchangers (CHE’s), which are strongly depending upon the prediction of performance of various types of heat transfer surfaces such as offset strip fins, wavy fins, rectangular fins, triangular fins, triangular and rectangular perforated fins in terms of Colburn “j” and Fanning friction “f” factors.

Design/methodology/approach

Numerical methods play a major role for analysis of compact plate-fin heat exchangers, which are cost-effective and fast. This paper presents the on-going research and work carried out earlier for single-phase steady-state heat transfer and pressure drop analysis on CHE passages and fins. An analysis of a cross-flow plate-fin compact heat exchanger, accounting for the individual effects of two-dimensional longitudinal heat conduction through the exchanger wall, inlet fluid flow maldistribution and inlet temperature non-uniformity are carried out using a Finite Element Method (FEM).

Findings

The performance deterioration of high-efficiency cross-flow plate-fin compact heat exchangers have been reviewed with the combined effects of wall longitudinal heat conduction and inlet fluid flow/temperature non-uniformity using a dedicated FEM analysis. It is found that the performance deterioration is quite significant in some typical applications due to the effects of wall longitudinal heat conduction and inlet fluid flow non-uniformity on cross-flow plate-fin heat exchangers. A Computational Fluid Dynamics (CFD) program FLUENT has been used to predict the design data in terms of “j” and “f” factors for plate-fin heat exchanger fins. The suitable design data are generated using CFD analysis covering the laminar, transition and turbulent flow regimes for various types of fins.

Originality/value

The correlations for the friction factor “f” and Colburn factor “j” have been found to be good. The correlations can be used by the heat exchanger designers and can reduce the number of tests and modification of the prototype to a minimum for similar applications and types of fins.
A roadmap for driving customer word-of-mouth
Authors: Keiningham Timothy Lee , Rust Roland T. , Lariviere Bart , Aksoy Lerzan , Williams Luke
Published: January 2018

Purpose

Managers seeking to manage customer word-of-mouth (WOM) behavior need to understand how different attitudinal drivers (e.g. satisfaction, positive and negative emotion, commitment, and self-brand connection) relate to a range of WOM behaviors. They also need to know how the effects of these drivers are moderated by customer characteristics (e.g. gender, age, income, country). The paper aims to discuss these issues.

Design/methodology/approach

To investigate these issues a built a large-scale multi-national database was created that includes attitudinal drivers, customer characteristics, and a full range of WOM behaviors, involving both the sending and receiving of both positive and negative WOM, with both strong and weak ties. The combination of sending-receiving, positive-negative and strong ties-weak ties results in a typology of eight distinct WOM behaviors. The investigation explores the drivers of those behaviors, and their moderators, using a hierarchical Bayes model in which all WOM behaviors are simultaneously modeled.

Findings

Among the many important findings uncovered are: the most effective way to drive all positive WOM behaviors is through maximizing affective commitment and positive emotions; minimizing negative emotions and ensuring that customers are satisfied lowers all negative WOM behaviors; all other attitudinal drivers have lower or even mixed effects on the different WOM behaviors; and customer characteristics can have a surprisingly large impact on how attitudes affect different WOM behaviors.

Practical implications

These findings have important managerial implications for promotion (which attitudes should be stimulated to produce the desired WOM behavior) and segmentation (how should marketing efforts change, based on segments defined by customer characteristics).

Originality/value

This research points to the myriad of factors that enhance positive and reduce negative word-of-mouth, and the importance of accounting for customer heterogeneity in assessing the likely impact of attitudinal drivers on word-of-mouth behaviors.
Customer engagement behaviours in social media: capturing innovation opportunities
Authors: Carlson Jamie , Rahman Mohammad , Voola Ranjit , De Vries Natalie
Published: January 2018

Purpose

Social media brand pages have become instrumental in enabling customers to voluntarily participate in providing feedback/ideas for improvement and collaboration with others that contribute to the innovation effort of brands. However, research on mechanisms which harness these specific customer engagement behaviours (CEB) in branded social media platforms is limited. Based on the stimulus–organism–response paradigm, this study investigates how specific online-service design characteristics in social media brand pages induce customer-perceived value perceptions, which in turn, stimulate feedback and collaboration intentions with customers.

Design/methodology/approach

Data collected from 654 US consumers of brand pages on Facebook were used to empirically test the proposed framework via structural equation modelling.

Findings

The theoretical framework found support for most hypothesized relationships showing how online-service design characteristics induce an identified set of customer value perceptions that influence customer feedback and collaboration intentions.

Research limitations/implications

The sample is restricted to customer evaluations of brand pages on Facebook in the USA. Practitioners are advised to maximize online-service design characteristics of content quality, brand page interactivity, sociability and customer contact quality as stimulants that induce brand learning value, entitativity value and hedonic value. This then translates to customer feedback and collaboration intentions towards the brand page.

Originality/value

The findings have important implications for the design and optimization of online services in the customer engagement-innovation interface to harness CEBs for innovation performance.
Preparation and properties of polyimide/Fe3O4 composite foams
Authors: Weng Ling , Wang Ting , Ju Pei-Hai , Liu Li-Zhu
Published: January 2018

Purpose

This paper aims to develope the electromagnetic interference shielding materials with high performance. To develop advanced polymer-based electromagnetic interference shielding materials with rather high temperature stability, good processability and moderate mechanical properties, the authors chose the polyimide (PI) foam as matrix and ferriferrous oxide (Fe3O4) as fillers to prepare the composite foams with lightweight and rather good electromagnetic interference shielding performance.

Design/methodology/approach

Some polyimide nanocomposite foams with Fe3O4 as fillers have been prepared by in situ dispersion and foaming with pyromellitic dianhydride (PMDA) and isocyanate (PAPI) as raw materials and water as foaming agent. By varying the Fe3O4 contents, a series of PI/Fe3O4 nanocomposite foams with fine microstructures and high thermal stability were obtained. The structure and performances of nanocomposite foams were examined, and the effects of Fe3O4 on the microstructure and properties of composite foams were investigated.

Findings

This work demonstrates that PI/Fe3O4 foams could be fabricated by thermally treating the polyimide foam intermediates with Fe3O4 nanoparticles through a blending reaction of precursors. The final PI/Fe3O4 composite foams maintained the excellent thermal property and showed a super paramagnetic behaviour, which has a positive effect on the improvement of electromagnetic shielding performance.

Research limitations/implications

In this paper, the effects of Fe3O4 on the performances of PI/Fe3O4 composite foam were reported. It provided an effective methodology for the preparation of polymer/Fe3O4 nanocomposite foams, which hold great promise towards the potential application in the areas of electromagnetic shielding materials.

Originality/value

A series of PI/Fe3O4 composite foams with different contents of Fe3O4 were prepared by blending reaction of the precursors. The effects of Fe3O4 on the structures and properties of PI/Fe3O4 composite foam were discussed in detail.
Synthesis of polyurethane dispersion from polyesteramide polyol
Authors: More Aarti P. , Mhaske Shashank T.
Published: January 2018

Purpose

The study aims to synthesise polyurethane dispersion from polyesteramide polyol. The polyesteramide polyol is a novel polyol for the synthesis of polyurethane dispersion.

Design/methodology/approach

Polyesteramide polyol has been synthesised from phthalic anhydride and fatty amide of mustard oil. Aminolysis of mustard oil had been carried out with diethanolamine. The novel polyurethane dispersion had been synthesised using a polyesteramide polyol as a precursor. Isophorone diisocyanate was used as an isocyanate component and polyurethane dispersion (PUDs) had been synthesised by an anionic method where DMPA was introduced to introduce –COOH groups as via grafting to the resin backbone. Triethylamine was used for neutralisation and, hence, for further dispersion in water. Hydroxyl ethyl methacrylate was used for the synthesis to introduce unsaturation in the backbone of PUDs. The coating was made by an UV curing process. The coating was characterised for mechanical properties, chemical properties, thermal properties as well as stain resistance.

Findings

The polyurethane dispersion formed through it has ester and amide linkage present in it. The acetone process is used for its synthesis. The nuclear magnetic resonance spectroscopy confirms the successful formation of polyesteramide polyol and PUDs. Even though long aliphatic chains present in polyol which may impart hydrophobicity the synthesis PUDs well dispersed in water. It is observed as the coating made from it have hardness and scratch resistance properties. The coating also exhibits good stain resistance properties.

Practical implications

The method is an easy one to synthesise polyurethane dispersion from polyesteramide polyol, which is based on ester and amide linkage.

Originality/value

To the best of the authors’ knowledge, this is the first report on synthesised polyurethane dispersion from polyesteramide polyol. The polyesteramide resin already proves its excellence and upcoming technology in the coating industry. Here, they are incorporated into the synthesis of polyurethane dispersion.
Pre-concentration and determination of fluorescence quenching of CdS quantum dots of Pb ions by dispersive liquid–liquid microextraction in the presence of the ionic liquids
Authors: Jafarnejad Ehsan , Abolhasani Jafar , Derakhshan Arezoo
Published: January 2018

Purpose

This study aims to develop a new simple and sensitive method for the microextraction of trace levels of lead in environmental samples. It is based on the use of ionic liquids based dispersive liquid–liquid microextraction (IL–DLLME) before spectrofluorometry.

Design/methodology/approach

Cadmium sulphide quantum dots have been synthesised using thioglycolic acid as capping agent through a one-step process with stability and excellent water-solubility, and have strong affinity for lead (Pb). This probe is based on the fluorescence quenching effect of functionalised cadmium sulphide quantum dots.

Findings

Factors affecting the extraction efficiency and fluorescence quenching of metals, such as the amount of ionic liquid, amount of metanol, microextraction and centrifugation time, volume of quantum dots and buffer pH, were investigated. Under optimum conditions, the calibration graph was linear in the range of 0.01-3 µg.L-1, with the detection limit of 0.004 µg.L-1 for Pb2+. The relative standard deviation (RSD%, n = 5) of 5.4 per cent at 1 µg.L-1 of Pb2+ was obtained.

Originality/value

This method for pre-concentration of the Pb ions by dispersive liquid–liquid microextraction is novel and could be used for various applications in the synthesis of a wide variety of determination of fluorescence quenching of cadmium sulphide quantum dots.
Fabrication of renewable myristic acid based polyurethane nano zinc phosphate hybrid coatings to mitigate corrosion of mild steel
Authors: Rajput Sandip D. , Patil Chandrashekhar K. , Gite Vikas V.
Published: January 2018

Purpose

The present study aims to demonstrate the use of renewable source in the preparation of polyurethane (PU) coatings and mitigation of corrosion of mild steel using nano zinc phosphate. Results indicated improvement in the properties of the PU coatings, especially anticorrosive properties by the addition of nano zinc phosphate.

Design/methodology/approach

Renewable-source-based polyestermyristamide polyol was synthesized using myristic acid as a starting material. The synthesis of polyol was carried by amidation as well as by esterification by a one-pot route. The structure of the prepared polyestermyristamide was confirmed with the support of end-group analysis and spectral study. PU coatings were prepared from synthesized polyestermyristamide polyol and used to protect metal substrate against corrosion. Corrosion properties of the prepared PU were found to be lower; hence, to improve the performance of these coatings, nano zinc phosphate was added to the coatings. The nano zinc phosphate was synthesized in the laboratory by reported sonication method and analyzed for morphology by scanning electron microscopy. Performance of coatings was studied with respect to effect of percentage nano zinc phosphate on thermal stability, mechanical properties and chemical resistances of PU coatings.

Findings

The combination of zinc phosphate nano rods and particles in myristic acid-based PU coatings provided substantial corrosion barrier properties to the coatings. Different per cent of the synthesized zinc phosphate nano rods and particles were loaded into the matrix, and corresponding coatings were estimated for corrosion resistance, thermal and chemical properties. Immersion study of the coated panels in 3.5 per cent NaCl solution showed good corrosion resistance for both PU coatings containing 2 and 3 per cent nano zinc phosphate.

Practical implications

This paper has provided the solution to replace existing petroleum-based raw materials with myristic acid as a renewable source in preparing PU coatings. Conventional coatings act as physical barriers against aggressive species but do not have ability to perform as permanent impassable to corrosive species. Hence, nano-sized zinc phosphate is used as corrosion inhibitor in to the synthesized PU coatings for enhancing anticorrosive performance.

Originality/value

In the paper, polyesteramide polyol is synthesized using renewable-source-based material, i.e. myristic acid to replace existing petroleum-based acid as a greener approach. Normally, vegetable oils are preferred as they have such kinds of polyols. The polyesteramide reaction is one pot that avoids the extra steps required in the synthesis. Further, it has been found that the pristine renewable coatings are unable to fully protect subtract from corrosion, whereas an addition of the nano-size zinc phosphate has enhanced the corrosion properties of the coatings.
Design, development and performance evaluation of pressure sensor using eddy current displacement sensing coil
Authors: K. Gobi , B. Kannapiran , D. Devaraj , K. Valarmathi
Published: January 2018

Purpose

The conventional strain gauge type pressure sensor suffers in static testing of engines due to the contact transduction method. This paper aims to focus on the concept of non-contact transduction-based pressure sensor using eddy current displacement sensing coil (ECDS) to overcome the temperature limitations of the strain gauge type pressure sensor. This paper includes the fabrication of prototypes of the proposed pressure sensor and its performance evaluation by static calibration. The fabricated pressure sensor is proposed to measure pressure in static test environment for a short period in the order of few seconds. The limitations of the fabricated pressure sensor related to temperature problems are highlighted and the suitable design changes are recommended to aid the future design.

Design/methodology/approach

The design of ECDS-based pressure sensor is aimed to provide non-contact transduction to overcome the limitations of the strain gauge type of pressure sensor. The ECDS is designed and fabricated with two configurations to measure deflection of the diaphragm corresponding to the applied pressure. The fabricated ECDS is calibrated using a standard micro meter to ensure transduction within limits. The fabricated prototypes of pressure sensors are calibrated using dead weight tester, and the calibration results are analyzed to select the best configuration. The proposed pressure sensor is tested at different temperatures, and the test results are analyzed to provide recommendations to overcome the shortcomings.

Findings

The performance of the different configurations of the pressure sensor using ECDS is evaluated using the calibration data. The analysis of the calibration results indicates that the pressure sensor using ECDS (coil-B) with the diaphragm as target is the best configuration. The accuracy of the fabricated pressure sensor with best configuration is ±2.8 per cent and the full scale (FS) output is 3.8 KHz. The designed non-contact transduction method extends the operating temperature of the pressure sensor up to 150°C with the specified accuracy for the short period.

Originality/value

Most studies of eddy current sensing coil focus on the displacement and position measurement but not on the pressure measurement. This paper is concerned with the design of the pressure sensor using ECDS to realize the non-contact transduction to overcome the limitations of strain gauge type pressure sensors and evaluation of the fabricated prototypes. It is shown that the accuracy of the proposed pressure sensor is not affected by the high temperature for the short period due to non-contact transduction using ECDS.
Analysis of Heat Transfer and Entropy Generation in a Channel Partially Filled With N-Layer Porous Media
Authors: Yang Kun , Chen Hao , Wang Jiabing
Published: January 2018

Convective heat transfer in a channel partially filled with porous medium has received a lot of attention due to its wide engineering applications. However, most researches focused on a channel partially filled with single layer porous medium. In this paper, we will analyze the heat transfer and entropy generation inside a channel partially filled with N-layer porous media. The flow and the heat transfer in the porous region are described by the Darcy–Brinkman model and the local thermal nonequilibrium model, respectively. At the porous-free fluid interface, the momentum and the heat transfer are described by the stress jump boundary condition and the heat flux jump boundary condition, respectively; while at the interface between two different porous layers, the momentum and the heat transfer are described by the stress continuity boundary condition and the heat flux continuity boundary condition, respectively. The analytical solutions for the velocity and temperature in the channel are derived and used to calculate the overall Nusselt number, the total entropy generation rate, the Bejan number, and the friction factor. Furthermore, the performances of the flow and heat transfer of a channel partially filled with third-layer porous media are studied.
Numerical Study of Heat Transfer Enhancement of Roll-to-Roll Microchannel Heat Exchangers
Authors: Wang Heng , Balasubramaniam Lakshmi , Marshall Samuel D. , Jin Xin , Arayanarakool Rerngchai , Seng Lee Poh , Chen Peter C. Y.
Published: January 2018

The heat transfer performance of two roll-to-roll microchannel heat exchangers with square cross section and side length ranging from 0.2 mm to 0.5 mm were investigated via numerical studies. In order to assess the heat transfer enhancement, equivalent straight channel heat exchangers were also researched numerically as comparisons. For the roll-to-roll devices, numerical studies demonstrated that there were two reasons for heat transfer enhancement. First, when the average Dean number of the fluid was greater than approximately 10, Dean vortices started to form within the roll-to-roll microchannels, enhancing the convective heat transfer between channels. Second, the compact roll-to-roll structure of the heat exchangers increased the area of heat transfer compared with straight microchannel equivalents, and thus promoted the conductive heat transfer. Numerical simulations noted both higher Nusselt numbers and higher thermal performance factors (TPF) for roll-to-roll microchannel heat exchangers compared with equivalent straight channels and were employed to optimize both the microchannel cross section dimensions and the wall thickness between channels. In addition, the swirling strength and the heat transfer area were also calculated to characterize the convective and conductive heat transfer, respectively, allowing for a comparison between two roll-to-roll microchannel heat exchanger designs.
Optimizing the Performance of Swirl Recovery Vane on Fokker 29 Propeller Using Design of Experiments Method
Authors: Wang Yangang , Chen Nanshu , Li Qingxi , Eitelberg Georg
Published: January 2018

The swirl recovery vane (SRV) oriented in the slipstream of the propeller can in principle recover the swirl effect and thus would improve the propulsion performance in terms of thrust production and propulsive efficiency. The present study employs the design of experiments (DoEs) method to optimize the geometry of the specific SRV for Fokker 29 propeller for the sake of further enhancing the thrust generation and swirling recovery. First, orthogonal experiment was employed to identify the most significant factors, which directly influence the thrust production. Second, steepest ascent method was used to search the optimum range of target factors through climbing and factorial experiments. The resulting optimal solution was evaluated by the center composite experiment. Results show that the thrust generated by the SRV has been increased significantly (11.78%) after optimization at the design point, and a 0.66% increment in the total efficiency of the propeller–SRV system has been obtained. For the off-design point, an increment of the total efficiency (2.10%) can be observed at low rotating speed. Additionally, the optimized SRV is able to correct the out-flow behavior at the tip region of the vane, where the tip vortex and swirl kinetic energy loss is weaken, and the thrust distribution along the spanwise direction tends to be more uniform.