bluuebunny/crossref_metadata_2025 huggingface dataset:
An 8-week resistance training protocol is effective in adapting quadriceps but not patellar tendon shear modulus measured by Supersonic Shearwave Imaging
Authors: Mannarino P. , Matta T. T. , Oliveira F. O.
Published: October 2018

Habitual loading and resistance training (RT) can determine changes in muscle and tendon morphology but also in its mechanical properties. Conventional ultrasound (US) evaluation of these mechanical properties present limitations that can now be overcome with the advent of Supersonic Shearwave Imaging (SSI). The objective of this study was to analyze the Vastus Lateralis (VL) and patellar tendon (PT) mechanical properties adaptations to an 8-week RT protocol using SSI. We submitted 15 untrained health young men to an 8-week RT directed knee extensor mechanism. VL and PT shear modulus (μ) was assessed pre and post intervention with SSI. VL muscle thickness (VL MT) and knee extension torque (KT) was also measure pre and post intervention to ensure the RT efficiency. Significant increases were observed in VL MT and KT (pre= 2.40 ± 0.40 cm and post= 2.63 ± 0.35 cm, p = 0.0111, and pre= 294.66 ± 73.98 Nm and post= 338.93 ± 76.39 Nm, p = 0.005, respectively). The 8-week RT was also effective in promoting VL μ adaptations (pre= 4.87 ± 1.38 kPa and post= 9.08.12 ± 1.86 kPa, p = 0.0105), but not in significantly affecting PT μ (pre= 78.85 ± 7.37 kPa and post= 66.41 ± 7.25 kPa, p = 0.1287). The present study showed that an 8-week resistance training protocol was effective in adapting VL μ but not PT μ. Further investigation should be conducted with special attention to longer interventions, to possible PT differential individual responsiviness and to the muscle-tendon resting state tension environment.
Cadherin-7 mediates proper neural crest cell-placodal neuron interactions during trigeminal ganglia assembly
Authors: Wu Chyong-Yi , Taneyhill Lisa A.
Published: October 2018

The cranial trigeminal ganglia play a vital role in the peripheral nervous system through their relay of sensory information from the vertebrate head to the brain. These ganglia are generated from the intermixing and coalescence of two distinct cell populations: cranial neural crest cells and placodal neurons. Trigeminal ganglia assembly requires the formation of cadherin-based adherens junctions within the neural crest cell and placodal neuron populations; however, the molecular composition of these adherens junctions is still unknown. Herein, we aimed to define the spatio-temporal expression pattern and function of Cadherin-7 during early chick trigeminal ganglia formation. Our data reveal that Cadherin-7 is expressed exclusively in migratory cranial neural crest cells and is absent from trigeminal neurons. Using molecular perturbation experiments, we demonstrate that modulation of Cadherin-7 in neural crest cells influences trigeminal ganglia assembly, including the organization of neural crest cells and placodal neurons within the ganglionic anlage. Moreover, alterations in Cadherin-7 levels lead to changes in the morphology of trigeminal neurons. Taken together, these findings provide additional insight into the role of cadherin-based adhesion in trigeminal ganglia formation, and, more broadly, the molecular mechanisms that orchestrate the cellular interactions essential for cranial gangliogenesis.
Automatic Inference of Sound Correspondence Patterns Across Multiple Languages
Authors: List Johann-Mattis
Published: October 2018

Sound correspondence patterns play a crucial role for linguistic reconstruction. Linguists use them to prove language relationship, to reconstruct proto-forms, and for classical phylogenetic reconstruction based on shared innovations. Cognate words which fail to conform with expected patterns can further point to various kinds of exceptions in sound change, such as analogy or assimilation of frequent words. Here we present an automatic method for the inference of sound correspondence patterns across multiple languages based on a network approach. The core idea is to represent all columns in aligned cognate sets as nodes in a network with edges representing the degree of compatibility between the nodes. The task of inferring all compatible correspondence sets can then be handled as the well-known minimum clique cover problem in graph theory, which essentially seeks to split the graph into the smallest number of cliques in which each node is represented by exactly one clique. The resulting partitions represent all correspondence patterns which can be inferred for a given dataset. By excluding those patterns which occur in only a few cognate sets, the core of regularly recurring sound correspondences can be inferred. Based on this idea, the paper presents a method for automatic correspondence pattern recognition, which is implemented as part of a Python library which supplements the paper. To illustrate the usefulness of the method, we present how the inferred patterns can be used to predict words that have not been observed before.
A high-throughput screen identifies small molecule modulators of alternative splicing by targeting RNA G-quadruplexes
Authors: Zhang Jing , Harvey Samuel E. , Cheng Chonghui
Published: October 2018

RNA secondary structures have been increasingly recognized to play an important regulatory role in post-transcriptional gene regulation. We recently showed that RNA G-quadruplexes, which serve as cis-elements to recruit splicing factors, play a critical role in regulating alternative splicing during the epithelial-mesenchymal transition. In this study, we performed a high-throughput screen using a dual-color splicing reporter to identify chemical compounds capable of regulating G-quadruplex-dependent alternative splicing. We identify emetine and its analog cephaeline as small molecules that disrupt RNA G-quadruplexes, resulting in inhibition of G-quadruplex-dependent alternative splicing. Transcriptome analysis reveals that emetine globally regulates alternative splicing, including splicing of variable exons that contain splice site-proximal G-quadruplexes. These data suggest the use of emetine and cephaeline for investigating mechanisms of G-quadruplex-associated alternative splicing.
Evolutionary superscaffolding and chromosome anchoring to improve Anopheles genome assemblies
Authors: Waterhouse Robert M. , Aganezov Sergey , Anselmetti Yoann , Lee Jiyoung , Ruzzante Livio , Reijnders Maarten J.M.F. , Feron Romain , Bérard Sèverine , George Phillip , Hahn Matthew W. , Howell Paul I. , Kamali Maryam , Koren Sergey , Lawson Daniel , Maslen Gareth , Peery Ashley , Phillippy Adam M. , Sharakhova Maria V. , Tannier Eric , Unger Maria F. , Zhang Simo V. , Alekseyev Max A. , Besansky Nora J. , Chauve Cedric , Emrich Scott J. , Sharakhov Igor V.
Published: October 2018

Background

New sequencing technologies have lowered financial barriers to whole genome sequencing, but resulting assemblies are often fragmented and far from ‘finished’. Updating multi-scaffold drafts to chromosome-level status can be achieved through experimental mapping or re-sequencing efforts. Avoiding the costs associated with such approaches, comparative genomic analysis of gene order conservation (synteny) to predict scaffold neighbours (adjacencies) offers a potentially useful complementary method for improving draft assemblies.

Results

We employed three gene synteny-based methods applied to 21 Anopheles mosquito assemblies to produce consensus sets of scaffold adjacencies. For subsets of the assemblies we integrated these with additional supporting data to confirm and complement the synteny-based adjacencies: six with physical mapping data that anchor scaffolds to chromosome locations, 13 with paired-end RNA sequencing (RNAseq) data, and three with new assemblies based on re-scaffolding or Pacific Biosciences long-read data. Our combined analyses produced 20 new superscaffolded assemblies with improved contiguities: seven for which assignments of non-anchored scaffolds to chromosome arms span more than 75% of the assemblies, and a further seven with chromosome anchoring including an 88% anchored Anopheles arabiensis assembly and, respectively, 73% and 84% anchored assemblies with comprehensively updated cytogenetic photomaps for Anopheles funestus and Anopheles stephensi.

Conclusions

Experimental data from probe mapping, RNAseq, or long-read technologies, where available, all contribute to successful upgrading of draft assemblies. Our comparisons show that gene synteny-based computational methods represent a valuable alternative or complementary approach. Our improved Anopheles reference assemblies highlight the utility of applying comparative genomics approaches to improve community genomic resources.
Dissociable mechanisms govern when and how strongly reward attributes affect decisions
Authors: Maier Silvia U. , Beharelle Anjali Raja , Polanía Rafael , Ruff Christian C. , Hare Todd A.
Published: October 2018

Theories and computational models of decision making usually focus on how strongly different attributes are weighted in choice, e.g., as a function of their importance or salience to the decision-maker. However, when different attributes impact on the decision process is a question that has received far less attention. Here, we investigated whether attribute consideration timing has a unique influence on decision making using a time-varying drift diffusion model and data from four separate experiments. Experimental manipulations of attention and neural activity demonstrated that we can dissociate the processes that determine the relative weighting strength and timing of attribute consideration. Thus, the processes determining either the weighting strengths or the timing of attributes in decision making can adapt independently to changes in the environment or goals. Quantifying these separate influences of timing and weighting on choice improves our understanding and predictions of individual differences in decision behaviour.
Triose phosphate utilization and beyond: from photosynthesis to end-product synthesis
Authors: McClain Alan M. , Sharkey Thomas D.
Published: October 2018

During photosynthesis plants fix CO2from the atmosphere onto ribulose-bisphosphate producing 3-phosphoglycerate, which is reduced to triose phosphates (TPs). The TPs are then converted into the end products of photosynthesis. When a plant is photosynthesizing very quickly it may not be possible to commit photosynthate to end product as fast as it is produced, causing a decrease in available phosphate and limiting the rate of photosynthesis to the rate of triose phosphate utilization (TPU). The occurrence of an observable TPU limitation is highly variable based on species and especially growth conditions, with TPU capacity seemingly regulated to be in just slight excess of the likely photosynthetic rate. The physiological effects of TPU limitation are discussed with an emphasis on interactions between the Calvin-Benson cycle and the light reactions. Methods for detecting TPU-limited data from gas exchange data are detailed, and the impact on modeling of some physiological effects are shown. Special consideration is given to common misconceptions about TPU.

Highlight

Photosynthetic triose phosphate utilization limitation is discussed, highlighting misleading points in physiology and focusing on regulation.
Time calibrated morpho-molecular classification of Nassellaria (Radiolaria)
Authors: Sandin Miguel M. , Pillet Loic , Biard Tristan , Poirier Camille , Bigeard Estelle , Romac Sarah , Suzuki Noritoshi , Not Fabrice
Published: October 2018

Nassellaria are marine radiolarian protists belonging to the Rhizaria lineage. Their skeleton, made of opaline silica, exhibit an excellent fossil record, extremely valuable in micro-paleontological studies for paleo-environmental reconstruction. Yet, to date very little is known about the extant diversity and ecology of Nassellaria in contemporary oceans, and most of it is inferred from their fossil record. Here we present an integrative classification of Nassellaria based on taxonomical marker genes (18S and 28S ribosomal DNA) and morphological characteristics obtained by optical and scanning electron microscopy imaging. Our phylogenetic analyses distinguished 11 main morpho-molecular clades relying essentially on the overall morphology of the skeleton and not on internal structures as previously considered. Using fossil calibrated molecular clock we estimated the origin of Nassellaria among radiolarians primitive forms in the Devonian (ca. 420 Ma), that gave rise to living nassellarian groups in the Triassic (ca. 250 Ma), during the biggest diversification event over their evolutionary history. This morpho-molecular framework provides both a new morphological classification easier to identify under light microscopy and the basis for future molecular ecology surveys. Altogether, it brings a new standpoint to improve our scarce understanding of the ecology and worldwide distribution of extant nassellarians.
Snapshots of single particles from single cells using electron microscopy
Authors: Yi Xiunan , Verbeke Eric J. , Chang Yiran , Dickinson Daniel J. , Taylor David W.
Published: October 2018

Cryo-electron microscopy has become an indispensable tool for structural studies of biological macromolecules. There are two predominant methods for studying the architectures of multi-protein complexes: (1) single particle analysis of purified samples and (2) tomography of whole cells or cell sections. The former can produce high-resolution structures but is limited to highly purified samples, while the latter can capture proteins in their native state but is hindered by a low signal-to-noise ratio and results in lower-resolution structures. Here, we present a method combining microfluidic single cell extraction with single particle analysis by electron microscopy to characterize protein complexes from individual C. elegans embryos. Using this approach, we uncover three-dimensional structures of ribosomes directly from single embryo extracts. In addition, we investigate structural dynamics during development by counting the number of ribosomes per polysome in early and late embyros. This approach has significant potential applications for counting protein complexes and studying protein architectures from single cells in developmental, evolutionary and disease contexts.
Relative biological effect of alpha particle radiation on low dose phenomena: lethal mutation, hyper-radiosensitivity and increased radioresistance
Authors: Fernando Chandula , Shi Xiaopei , Byun Soo Hyun , Seymour Colin B. , Mothersill Carmel E.
Published: October 2018

At high doses, the current recommended radiation weighting factors advise a significantly higher effectiveness of alpha particles relative to gamma radiation. However, at lower doses, the ratio of effectiveness between radiations of varying linear energy transfer values is complicated due to the relative importance of low dose phenomena such as genomic instability, bystander effects, low dose hyper-radiosensitivity and increased radioresistance (HRS/IRR). Radium is the most common source of alpha radiation exposure to humans, but the dosimetry is complicated by the decay chain which involves gamma exposure due to radon daughters. This study aimed to isolate the relative biological effect of alpha particles after low doses of radium to cells and their progeny. This was done by subtracting the survival values of a human keratinocyte cell line (HaCaT) and an embryonic Chinook salmon cell line (CHSE-214) exposed to gamma irradiation, from survival of the same cell lines exposed to mixed alpha and gamma radiation through chronic exposure to Ra-226 and its decay products. The human cell line showed increased radioresistance when exposed to low doses of alpha particles. In contrast the fish cell line, which demonstrated radioresistance to low dose gamma energy, demonstrated increased lethality when exposed to low doses of alpha particles. The results confirm the need to consider the dose-response relationship when developing radiation weighting factors for low dose exposures, as well as the need to be aware of possible cell line and species differences.
The seven transmembrane domain protein MoRgs7 functions in surface perception and undergoes coronin MoCrn1-dependent endocytosis in complex with Gα subunit MoMagA to promote cAMP signaling and appressorium formation in Magnaporthe oryzae
Authors: Li Xiao , Zhong Kaili , Yin Ziyi , Hu Jiexiong , Li Lianwei , Zhang Haifeng , Zheng Xiaobo , Wang Ping , Zhang Zhengguang
Published: October 2018

Regulator of G-protein signaling (RGS) proteins primarily function as GTPase-accelerating proteins (GAPs) to promote GTP hydrolysis of Gα subunits, thereby regulating G-protein mediated signaling. RGS proteins could also contain additional domains such as GoLoco to inhibit GDP dissociation. The rice blast fungus Magnaporthe oryzae encodes eight RGS and RGS-like proteins (MoRgs1 to MoRgs8) that have shared and distinct functions in growth, appressorium formation and pathogenicity. Interestingly, MoRgs7 and MoRgs8 contain a C-terminal seven-transmembrane domain (7-TM) motif typical of G-protein coupled receptor (GPCR) proteins, in addition to the conserved RGS domain. We found that MoRgs7, together with Gα MoMagA but not MoRgs8, undergoes endocytic transport from the plasma membrane to the endosome upon sensing of surface hydrophobicity. We also found that MoRgs7 can interact with hydrophobic surfaces via a hydrophobic interaction, leading to the perception of environmental hydrophobic cues. Moreover, we found that MoRgs7-MoMagA endocytosis is regulated by actin patch-associated protein MoCrn1, linking it to cAMP signaling. Our studies provided evidence suggesting that MoRgs7 could also function in a GPCR-like manner to sense environmental signals and it, together with additional proteins of diverse functions, promotes cAMP signaling required for developmental processes underlying appressorium function and pathogenicity.

Author summary

The 7-TM domain is considered the hallmark of GPCR proteins, which activate G proteins upon ligand binding and undergo endocytosis for regeneration or recycling. Among eight RGS and RGS-like proteins of M. oryzae, MoRgs7 and MoRgs8 contain the 7-TM domain in addition to the RGS domain. We found that MoRgs7 can form hydrophobic interactions with the hydrophobic surface. This interaction is important in sensing hydrophobic cues by the fungus. We also found that, in response to surface hydrophobicity, MoRgs7 couples with Gα subunit MoMagA to undergo endocytosis leading to the activation of cAMP signaling. Moreover, we found that such an endocytic event requires functions of the actin-binding protein MoCrn1. Our results revealed MoRgs7 functions as a GPCR-like receptor protein to sense surface cues and activate signaling required for pathogenesis, providing new insights into G-protein regulatory mechanisms in this and other pathogenic fungi.
An accurate theory of X-ray coplanar multiple SRMS diffractometry
Authors: Kohn V. G.
Published: October 2018

The article reports an accurate theory of X-ray coplanar multiple diffraction for an experimental setup that consists of a generic synchrotron radiation (SR) source, double-crystal monochromator (M) and slit (S). It is called for brevity the theory of X-ray coplanar multiple SRMS diffractometry. The theory takes into account the properties of synchrotron radiation as well as the features of diffraction of radiation in the monochromator crystals and the slit. It is shown that the angular and energy dependence (AED) of the sample reflectivity registered by a detector has the form of a convolution of the AED in the case of the monochromatic plane wave with the instrumental function which describes the angular and energy spectrum of radiation incident on the sample crystal. It is shown that such a scheme allows one to measure the rocking curves close to the case of the monochromatic incident plane wave, but only using the high-order reflections by monochromator crystals. The case of four-beam (220)(331)({\overline {11}}1) diffraction in Si is considered in detail.
Selective harmonic elimination in direct torque controlled permanent magnet synchronous motor drive
Authors: Asadzadeh Vahid , Dastfan Ali , Darabi Ahmad
Published: October 2018

Purpose

The purpose of this paper is to describe a new method for selective harmonic elimination in a two-level three-phase inverter-fed direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drive to suppress unwanted resonant frequencies.

Design/methodology/approach

The design methodology is based on random space vector pulse-width modulation (RSVPWM) of PMSM drives. MATLAB simulations support the validity of suggested structure.

Findings

The simulation results of the proposed algorithm exhibit the development of a proper gap at the selected frequency in the frequency spectra of the motor input currents and voltages as well as lowering the ripples in the PMSM electromagnetic torque, stator current and flux linkage responses in compared with traditional DTC.

Originality/value

The proposed algorithm is a revised form of the RSVPWM technique used in a closed-loop structure along with a sliding mode speed controller which is capable to deal with nonlinear motor loads in an online manner. This study can be beneficial for the designers of AC motor drive system who attempt to find a modulation method that can create a selective gap in the power spectrum density of the motor input voltages and currents, therefore, promote an acoustically pleasant drive or alleviate unwanted motor vibrations.
The employability skills of graduates and employers’ options in Portugal
Authors: Suleman Fátima , Laranjeiro Ana Maria Costa
Published: October 2018

Purpose

Available literature overlooks the factors that affect employers’ opinions of the skills graduates bring to the labour market. The purpose of this paper is to examine the relationship between the perception of graduates’ skills and the employers’ anticipative and remedial strategies.

Design/methodology/approach

A qualitative multiple case study is used and data were gathered from interviews with human resource managers in ten firms in Portugal. The data set includes information on perceptions of graduates’ skills, solutions for the acquisition of skills, hiring and training policies, and practices associated with university–industry linkages.

Findings

Almost all the employers sampled are unsatisfied with graduates’ preparation in soft skills and other personal traits. Some report skill shortages and gaps in technical skills that result in training costs. The perception of technical skills varies according to anticipative and remedial strategies.

Research limitations/implications

This is an explorative study with a very small sample of firms. However, it is a first step towards further research into whether the perception of graduates’ skills is affected by anticipative and remedial strategies implemented by firms within a particular human resource development system.

Practical implications

It is argued that the responsibility for graduates’ employability should be shared. Practitioners should learn how to interact with higher education, researchers should profit from insights into typologies of employers’ strategies on skill formation, and policy makers should understand that employers are heterogeneous and there is no one-size-fits-all solution.

Social implications

Universities, employers and policy makers should understand that the employability of graduates presupposes shared responsibility.

Originality/value

The relationship between the strategies employers adopt to access skills and their perception of graduates’ skills is a quite underexplored topic.
Predicting hotel attractiveness via personality traits of applicants
Authors: Bellou Victoria , Stylos Nikolaos , Rahimi Roya
Published: October 2018

Purpose

Despite the fact that hotels rely heavily upon frontline employees, extant evidence on what makes a hotel attractive in the eyes of job applicants is scarce. Thus, this paper aims to incorporate the Big Five personality traits model to identify what potential hotel job applicants are likely to seek in their prospective employers.

Design/methodology/approach

Applicants for non-managerial, frontline posts at upscale hotels were approached via three branches of a career agency located in England, UK; their responses were gathered via a self-administered questionnaire. The 522 usable responses were used in a covariance-based, multi-group structural equation modeling scheme to investigate three main research propositions with regards to the applicants’ personality traits’ influence on their perceptions of a hotel’s attractiveness as a potential employer.

Findings

Analysis of responses indicates significant differences regarding the impact of extraversion, conscientiousness and openness on perceived facets of employer attractiveness. Additionally, findings suggest that high self-esteem does make applicants more demanding, while work experience also influences their preferences regarding the hotels’ profiles as an employer.

Research limitations/implications

The results of this study are limited to applicants for non-managerial, frontline job positions in upscale hotels in the UK.

Practical implications

Practically, this study offers practitioners valuable feedback regarding the potential applicant’s personality profile that grants the best fit with an upscale hotel.

Originality/value

While different studies tried to identify the organizations’ attributes that attract potential applicants, evidence on what attracts individuals to a hotel is very limited. Hence, the present study tries to address this gap and link potential applicants’ personality profiles with that of hotels as employers.
Does corporate governance influence earnings management in listed companies in Bahrain Bourse?
Authors: Alareeni Bahaaeddin
Published: October 2018

Purpose

This paper aims to consider data for listed companies in Bahrain Bourse to determine whether companies practice earnings management (EM). Further, the effect of a set of corporate governance characteristics on EM practices is examined.

Design/methodology/approach

The EM level was measured using discretionary accruals (DA) [calculated using the Modified Jones (1995) Model]. The study sample consisted of 20 companies listed during the period 2011-2015. Panel regression model was used to test the study hypotheses and achieve the study aims.

Findings

EM is negatively correlated with board size, confirming that a larger board is associated with a lower level of EM practices. Further, board independence is positively correlated with EM, suggesting that the larger the number of independent directors, the higher the level of EM practices. In addition, internal ownership is positively related to EM, confirming that the higher level of internal ownership increases EM practices. CEO duality does not appear to have any effect on EM in Bahrain Bourse. More interestingly, the findings reveal that companies practice EM through income-increasing DA.

Research limitations/implications

Financial data and data related to other corporate governance characteristics are lacking.

Practical implications

The results of this study provide empirical support for the development of new regulations and amendments and necessary corrective decisions regarding the effectiveness of applying corporate governance code in Bahrain Bourse. More specifically, this study reveals an urgent need for new amendments to restrict EM practices in Bahrain Bourse.

Originality/value

This study enriches the EM literature by covering Bahrain as an Asian country, which has not been sufficiently examined in relation to this topic. Further, this study provides a clear picture of the level of EM practices in Bahrain Bourse to multiple parties.
Effect of the performance of physical and non-physical facilities on higher institutional facilities
Authors: Abdullahi Isa , Wan Yusoff Wan Zahari
Published: October 2018

Purpose

The role of institutional facilities is of paramount importance to ensure quality of teaching and learning with respect to achieving quality of education in any given higher educational institutions (HEIs). The purpose of this paper is to determine the performance of physical and non-physical facilities of higher institutional facilities.

Design/methodology/approach

The data were collected from respondents using a closed-end questionnaire. In total, 1,000 questionnaires were administered to students and 735 were returned and valid for analysis. Partial least squares-structural equation modelling was adopted for analysis.

Findings

It was found that the exogenous constructs [physical facilities (PPE) and non-physical facilities (PNE)] scored 32.7 per cent (R2 = 0.327) of the variance of the facility’s performance. It was also found that the physical facility is the most significant factor that determines facility performance.

Research limitations/implications

This paper is limited to investigating the performance of physical and non-physical facilities; it is not in any way a measure for the students’ views about other services offered by the institutions. Future research is needed to use relevant information from HEIs’ facilities for validating factors that determine the facility’s performance.

Practical implications

Physical facility was identified as the most influencing factor that determines the facility performance based on the information provided by respondents. This research should help the facility management department at HEIs when designing the academic facility management. The study will also serve as a yardstick for the Federal Ministry of Education, the National University Commission in academic facility accreditation. This paper contributes to both the body of knowledge in facility management by considering the performance of facilities at HEIs.

Originality/value

This paper demonstrates the duality of HEIs’ facilities into physical and non-physical facilities and their distinct contribution to the overall facility’s performance.
A novel method of preparing Ti powder for 3D printing
Authors: Zhang Yajuan , Song Xiaoyan , Wang Haibin , Nie Zuoren
Published: October 2018

Purpose

The purpose of this paper is to propose a novel method to prepare pure Ti powder for 3D printing with tailorable particle size distribution.

Design/methodology/approach

The main procedures of the present method consist of gas state reaction to synthesize TiH2 nanoparticles, agglomeration to obtain micronscale powder particles by spray drying, and densification of particle interior by heat treatment.

Findings

The prepared Ti powder has a specific bimodal particle size distribution in a range of small sizes, good sphericity and high flowability. Particularly, this new technique is capable of controlling powder purity and adjusting particle size.

Originality/value

To the best knowledge of the authors, the approach for preparing 3D printing metallic powders from nanoparticles has not been reported in the literature so far. This work provides a novel method that is particularly applicable to prepare 3D printing metallic powders which have small initial particle sizes and high reactivity in the air.
A review of slicing methods for directed energy deposition based additive manufacturing
Authors: Xu Jing , Gu Xizhi , Ding Donghong , Pan Zengxi , Chen Ken
Published: October 2018

Purpose

The purpose of this paper is to systematically review the published slicing methods for additive manufacturing (AM), especially the multi-direction and non-layerwise slicing methods, which are particularly suitable for the directed energy deposition (DED) process to improve the surface quality and eliminate the usage of support structures.

Design/methodology/approach

In this paper, the published slicing methods are clarified into three categories: the traditional slicing methods (e.g. the basic and adaptive slicing methods) performed in the powder bed fusion (PBF) system, the multi-direction slicing methods and non-layerwise slicing methods used in DED systems. The traditional slicing methods are reviewed only briefly because a review article already exists for them, and the latter two slicing methods are reviewed comprehensively with further discussion and outlook.

Findings

A few traditional slicing approaches were developed in the literature, including basic and adaptive slicing methods. These methods are efficient and robust when they are performed in the PBF system. However, they are retarded in the DED process because costly support structures are required to sustain overhanging parts and their surface quality and contour accuracy are not satisfactory. This limitation has led to the development of various multi-direction and non-layerwise slicing methods to improve the surface quality and enable the production of overhangs with minimum supports.

Originality/value

An original review of the AM slicing methods is provided in this paper. For the traditional slicing methods and the multi-direction and non-layerwise slicing method, the published slicing strategies are discussed and compared. Recommendations for future slicing work are also provided.
The Role of Spiritual Capital in Innovation and Performance: Evidence from Developing Economies
Authors: Neubert Mitchell J. , Bradley Steven W. , Ardianti Retno , Simiyu Edward M.
Published: October 2018

Forms of capital play a significant role in the innovation and performance of start–up firms. Current entrepreneurial research has focused on the role of financial, human, and social forms of capital. We build on a large body of theory and research in sociology and economics, proposing spiritual capital as an additional influence where institutional voids are greater in the development contexts studied. Results from microcredit entrepreneurs in Kenya and Indonesia indicate significant relationships between entrepreneurs’ spiritual capital and business innovation and performance, even after accounting for other forms of capital.
Michel Kripalani and Oceanhouse Media: Journey of a Serial Entrepreneur
Authors: Varaiya Nikhil P.
Published: October 2018

This case describes Michel Kripalani's entrepreneurial journey culminating in his third start–up, Oceanhouse Media. Oceanhouse Media, ranked 114 in the 2013 Inc. 5,000 list of the fastest growing companies, offers desktop and digital applications, for iOS, Android, and other platforms with digital book applications for children comprising half of annual revenues. It explores: (1) Kripalani's evolution as an entrepreneur, (2) the operating strategy of Oceanhouse Media, (3) the economics and structure of the digital applications market and the children's segment within that market, and (4) key decisions—structural, organizational, and financial—as Kripalani maps out Oceanhouse Media's future growth path and exit strategy.
Entrepreneurs’ Exploratory Perseverance in Learning Settings
Authors: Muehlfeld Katrin , Urbig Diemo , Weitzel Utz
Published: October 2018

We introduce “exploratory perseverance” as a novel construct that captures perseverant behavior in settings in which several alternatives can be explored and evaluated. We suggest that entrepreneurs display exploratory perseverance reflected by a tendency to keep exploring broader sets of alternatives, to adopt a parallel rather than sequential approach to trial‐and‐error learning, and, after negative experiences with some alternatives, to be more inclined to give them a second chance. The results from an experimental study of 449 individuals participating in the Iowa Gambling Task indicate that more entrepreneurially experienced individuals display greater exploratory perseverance than those with little to no entrepreneurial experience.
Temporal Change Patterns of Entrepreneurial Orientation: A Longitudinal Investigation of CEO Successions
Authors: Grühn Bastian , Strese Steffen , Flatten Tessa C. , Jaeger Nikolai A. , Brettel Malte
Published: October 2018

This study investigates the temporal change patterns of entrepreneurial orientation (EO) subsequent to chief executive officer (CEO) successions. Integrating prior research, we hypothesize that CEO successions lead to a change in EO and that this change exhibits an inverse U‐shape over time. Based on data collected for 67 CEO successions, our empirical results support our hypotheses, showing that successions effectuate changes in EO and tend to increase the level of EO in firms. Changes in EO peak in the second to fourth year of a new CEO's tenure, with less change before and after. We also demonstrate that changes in EO occur later but are more pronounced if the newly appointed firm leader is an outside CEO.
Study on Optimization of Pressure Ratio Distribution in Multistage Compressed Air Energy Storage System
Authors: Chen Shang , Zhu Tong , Zhang Huayu
Published: October 2018

Compressed air energy storage is an effective energy storage technology to solve the instability of wind power in distributed energy resources. In this paper, a multistage compressed air energy storage system optimization model is constructed based on the energy conservation equation. Then the system is optimized by differential evolution to improve the system efficiency. Optimal pressure ratios are proposed to distribute the pressures of compressors and expanders. The impact of pressure ratio distribution curve on the system energy efficiency suggests that the change curve of the characteristics vary in different heat exchanger performance. Results show that the change of thermal transfer reactor performance leads to the variety of optimal distribution pressure ratio and energy efficiency of the system. In addition, the differential ratio distribution factor can be effective on the pressure ratio of reasonable allocation. System efficiency optimization results increased by about 1% compared mean value.
Fuel Cell Backup Power System for Grid-Service and Micro-Grid in Telecommunication Applications
Authors: Ma Zhiwen , Eichman Josh , Kurtz Jennifer
Published: October 2018

This paper presents the feasibility and economics of using fuel cell backup power systems in telecommunication cell towers to provide grid services (e.g., ancillary services, demand response). The fuel cells are able to provide power for the cell tower during emergency conditions. This study evaluates the strategic integration of clean, efficient, and reliable fuel cell systems with the grid for improved economic benefits. The backup systems have potential as enhanced capability through information exchanges with the power grid to add value as grid services that depend on location and time. The economic analysis has been focused on the potential revenue for distributed telecommunications fuel cell backup units to provide value-added power supply. This paper shows case studies on current fuel cell backup power locations and regional grid service programs. The grid service benefits and system configurations for different operation modes provide opportunities for expanding backup fuel cell applications responsive to grid needs.

The objective of this work primarily focuses on how fuel cells can become a significant part of the telecom backup power to reduce system costs, environmental impact, and dependence on fossil fuels, while ensuring continuity of indispensable service for mobile users. The study identifies the approaches on the fuel cell application through nano/microgrids for an extensive network of fuel cells as distributed energy resources. The possibilities of various application scenarios extend the fuel cell technologies and microgrid for reliable power supply.
Analysis of Solar Receiver Performance for Chemical-Looping Integration With a Concentrating Solar Thermal System
Authors: Ma Zhiwen , Martinek Janna
Published: October 2018

This paper introduces a chemical-looping configuration integrated with a concentrating solar thermal (CST) system. The CST system uses an array of mirrors to focus sunlight, and the concentrated solar flux is applied onto a solar receiver to collect and convert solar energy into thermal energy. The thermal energy then drives a thermal power cycle for electricity generation or provides an energy source to chemical processes for material or fuel production. Considerable interest in CST has been driven by power generation with its capability to store thermal energy for continuous electricity supply or peak shaving. However, CST systems have other potential to convert solar energy into fuel or support thermochemical processes. The chemical-looping configuration integrated with the CST system can be a platform for implementing various solar-thermochemical processes. The chemical-looping configuration integrated with a CST system has potential applications for thermochemical energy storage and solar thermochemical hydrogen production. To use the solar energy efficiently and effectively, a high-temperature reactor receiver is a key component in the chemical-looping system. This paper shows a novel planar-cavity receiver design and its performance analyzed by solar-tracing and thermal-modeling methods for solar integration in a CST system.
Simulation of Inverted Perovskite Solar Cells
Authors: Gong Jiawei , Krishnan Sumathy
Published: October 2018

A planar perovskite solar cell (PSC) with p-i-n inverted structure was modeled and simulated to determine the power output characteristics under illumination. The performance of inverted PSC device was correlated to the thickness of the absorber layer, band alignment, and electrical properties of the hole transport materials (HTMs). Our simulation indicates that, with an optimized absorber layer thickness ∼300 nm, an efficiency of 18% can be achieved. This baseline device was further utilized to investigate the role of band offset between the HTM and absorber layer. Results show that the device efficiency can be improved to 24% when the work function of HTM is reduced to 0.1 eV lower than the valence band edge of perovskite. Parametric studies were carried out to compare the feasibility of five different HTMs including spiro-OMeTAD, Cu2O, CuSCN, NiO, and CuI. Among them, NiO is the most promising candidate with a theoretical efficiency limit up to 27%. This work would serve as a modeling frame to simulate and interpret the performance of inverted PSCs and suggest further device optimization strategies.
Optimization of a Rainbow Piezoelectric Energy Harvesting System for Tire Monitoring Applications
Authors: Esmaeeli Roja , Aliniagerdroudbari Haniph , Nazari Ashkan , Hashemi Seyed Reza , Alhadri Muapper , Zakri Waleed , Mohammed Abdul Haq , Batur Celal , Farhad Siamak
Published: October 2018

Ambient energy harvesting using piezoelectric transducers is becoming popular to provide power for small microelectronics devices. The deflection of tires during rotation is an example of the source of energy for electric power generation. This generated power can be used to feed tire self-powering sensors for bicycles, cars, trucks, and airplanes. The aim of this study is to optimize the energy efficiency of a rainbow shape piezoelectric transducer mounted on the inner layer of a pneumatic tire for providing enough power for microelectronics devices required to monitor tires. For this aim a rainbow shape piezoelectric transducer is adjusted with the tire dimensions and excited based on the car speed and strain. The geometry and load resistance effects of the piezoelectric transducer is optimized using Multiphysics modeling and finite element analysis.
On-Sun Testing of a High Temperature Bladed Solar Receiver and Transient Efficiency Evaluation Using Air
Authors: Ortega Jesus D. , Khivsara Sagar D. , Christian Joshua M. , Dutta Pradip , Ho Clifford K.
Published: October 2018

Prior research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Previous test results and models of the bladed receiver showed a receiver efficiency increase over a flat receiver panel of ∼ 5–7% over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 °C with no issues.

The bladed receiver is being tested at various peak heat fluxes ranging 75–150 kW/m2 under transient conditions using Air as a heat transfer fluid at inlet pressure ∼250 kPa (∼36 psi) using a regulating flow loop. The flow loop was designed and tested to maintain a steady mass flow rate for ∼15 minutes using pressurized bottles as gas supply. Due to the limited flow-time available, a novel transient methodology to evaluate the thermal efficiencies is presented in this work. Computational fluid dynamics (CFD) models are used to predict the temperature distribution and the resulting transient receiver efficiencies. The CFD simulations results using air as heat transfer fluid have been validated experimentally at the National Solar Thermal Test Facility in Sandia National Labs.
Cooling of Concentrator Photovoltaic Cells Using Mini-Scale Jet Impingement Heat Sinks
Authors: Radwan Ali , Hawi Meshack , Ahmed Mahmoud
Published: October 2018

In this study, an efficient cooling technique for concentrator photovoltaic (CPV) cells is proposed to enhance the system electrical efficiency and extend its lifetime. To do this, a comprehensive three-dimensional conjugate heat transfer model of CPV cells layers coupled with the heat transfer and fluid flow model inside jet impingement heat sink is developed. Four different jet impingement designs are compared. The investigated designs are (A) central inlet jet, (B) Hypotenuse inlet jet, (C) staggered inlet jet, and (D) conventional jet impingement design with side drainage. The effect of coolant flowrate on the CPV/T system performance is investigated. The model is numerically simulated and validated using the available experiments. The performance of CPV system is investigated at solar concentration ratios of 20 and coolant flowrate up to 6000g/min. It is found that increasing the flowrate from 60 g/min to 600 g/min decrease the maximum cell temperature by 31°C for the configuration D while increasing the flowrate from 600 g/min to 6000 g/min reduce the cell temperature by 20.2°C. It is also concluded that at a higher flowrate of 6000g/min, all the investigated configurations relatively achieve better temperature uniformity with maximum temperature differences of 0.9 °C, 2.1 °C, 3.6 °C, and 3.9 °C for configurations A, B, C, and D respectively.
Structural Analysis of Small Scale Radial Turbine for Solar Powered Brayton Cycle Application
Authors: Daabo Ahmed Mahmood , Mahmoud Saad , Al-Dadah Raya K.
Published: October 2018

Developing small scale turbines pauses challenges in terms of increased stresses due to high rotational speed leading to increase in component thicknesses and turbine overall weight. Therefore this study assesses both; the structural and aerodynamic performance of a Small Scale Radial Turbine SSRT by integrating finite-element methods FEM and Computational Fluid Dynamic CFD. Using Vista preliminary design model in ANSYS and detailed 3D CFD optimization, SSRT with 1–5 kW power for solar powered Brayton cycle was developed with high efficiency of 89.2%. Then both; the turbine’s hub and blades were structurally analysed under various loading conditions to investigate the effect of various rotational speeds and blade shapes on the stress distribution and deformation of the blades. The results of the current study showed that a maximum increment of 65% stress and 57% deformation was noticed when reaching the maximum studied rotational speed at inlet air temperature of 450 K.