bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensive study on structure transformation of muscovite single crystal under high-doseγ-ray irradiation and mechanism speculation
Authors: Wang Honglong , Sun Yaping , Chu Jian , Wang Xu , Zhang Ming
Published: July 2019

Intensive study on structure transformation of muscovite single crystal under high-doseγ-ray irradiation is essential for its use in irradiation detection and also beneficial for mechanism cognition on defect formation within a matrix of clay used in the disposal of high-level radioactive waste (HLRW). In this work, muscovite single crystal was irradiated with Co-60γray in air at a dose rate of 54 Gy min−1with doses of 0–1000 kGy. Then, structure transformation and mechanism were explored by Raman spectrum, Fourier-transform infrared spectrum, X-ray diffraction, thermogravimetric analysis, CA, scanning electron microscope and atomic force microscopy. The main results show that variations in the chemical/crystalline structure are dose-dependent. Low-dose irradiation sufficiently destroyed the structure, removing Si–OH, thus declining hydrophilicity. With dose increase up to 100 kGy, CA increased from 20° to 40°. Except for hydrophilicity variation, shrink occurred in the (004) lattice plane which later recovered; the variation range at 500 kGy irradiation was 0.5% close to 0.02 Å. The main mechanisms involved were framework break and H2O radiolysis. Framework break results in Si–OH removal and H2O radiolysis results in extra OH introduction. The extra introduced OH probably results in Si–OH bond regeneration, lattice plane shrink and recovered surface hydrophilicity. The importance of framework break and H2O radiolysis on structure transformation is dose-dependence. At low doses, framework break seems more important while at high doses H2O radiolysis is important. Generally, variations in the chemical structure and surface property are nonlinear and less at high doses. This indicates using the chemical structure or surface property variation to describe irradiation is correct at low doses but not at high doses. This finding is meaningful for realizing whether muscovite is suitable for detecting high-dose irradiation or not, and mechanism exploration is efficient for identifying the procedure for defect formation within the matrix of clay used in disposal HLRW in practice.
Simultaneous elastic shape optimization for a domain splitting in bone tissue engineering
Authors: Dondl Patrick , Poh Patrina S. P. , Rumpf Martin , Simon Stefan
Published: July 2019

This paper deals with the simultaneous optimization of a subset

O

0

of some domain
Ω
and its complement

O

1

=
Ω
∖

O

0

¯

both considered as separate elastic objects subject to a set of loading scenarios. If one asks for a configuration which minimizes the maximal elastic cost functional both phases compete for space since elastic shapes usually get mechanically more stable when being enlarged. Such a problem arises in biomechanics where a bioresorbable polymer scaffold is implanted in place of lost bone tissue and in a regeneration phase, new bone tissue grows in the scaffold complement via osteogenesis. In fact, the polymer scaffold should be mechanically stable to bear loading in the early stage regeneration phase and at the same time, the new bone tissue grown in the complement of this scaffold should as well bear the loading. Here, this optimal subdomain splitting problem with appropriate elastic cost functionals is introduced and the existence of optimal two-phase configurations is established for a regularized formulation. Furthermore, based on a phase-field approximation, a finite-element discretization is derived. Numerical experiments are presented for the design of optimal periodic scaffold microstructure.
The acoustic emission from asperity interactions in mixed lubrication
Authors: Hutt S. , Clarke A. , Pullin R. , Evans H. P.
Published: July 2019

Gears typically operate in mixed lubrication conditions, where the lubricant film is too thin to prevent opposing surface asperities from interacting with each other. The likelihood/intensity of interactions is indicated by the
Λ
ratio: the ratio of smooth surface film thickness to surface roughness. Researchers have asserted that asperity interactions are the predominant cause of acoustic emission (AE) in healthy gear contacts. However, direct experiments on gears have yet to yield a clear relationship between the Asperity AE (AAE) and
Λ
ratio, this is in part due to the complexity of gear tooth contacts. In this paper, a disc rig was used to simulate a simplified gear contact so that the fundamental relationship between AAE and
Λ
could be investigated more effectively. By varying oil temperature and entrainment speed, a wide spectrum of lubrication conditions was generated. In contrast to other published studies, an independent measurement technique, the contact voltage (CV), was used to verify the amount of interactions, and repeated roughness measurements were used to confirm minimal surface wear. A simple, consistent and precise relationship between AAE amplitude and
Λ
was identified and defined for changes from full-film to mixed lubrication. Within the mixed lubrication regime, the AAE amplitude increased exponentially as
Λ
decreased at all speeds tested. It was also observed that an increase in speed always resulted in an increase in AAE amplitude, independently of any changes in
Λ
. This direct effect of speed was modelled so that the AAE could be predicted for any combination of speed and
Λ
within the tested envelope. This paper links gear contact tribology and AE with new precision and clearly demonstrates the potential of using AAE as a sensitive monitoring technique for the lubrication condition of gears.
Sociality emerges from solitary behaviours and reproductive plasticity in the orchid beeEuglossa dilemma
Authors: Saleh Nicholas W. , Ramírez Santiago R.
Published: July 2019

The evolution of eusociality and sterile worker castes represents a major transition in the history of life. Despite this, little is known about the mechanisms involved in the initial transition from solitary to social behaviour. It has been hypothesized that plasticity from ancestral solitary life cycles was coopted to create queen and worker castes in insect societies. Here, we tested this hypothesis by examining gene expression involved in the transition from solitary to social behaviour in the orchid beeEuglossa dilemma. To this end, we conducted observations that allowed us to classify bees into four distinct categories of solitary and social behaviour. Then, by sequencing brain and ovary transcriptomes from these behavioural phases, we identified gene expression changes overlapping with socially associated genes across multiple eusocial lineages. We find that genes involved in solitaryE. dilemmaovarian plasticity overlap extensively with genes showing differential expression between fertile and sterile workers—or between queens and workers in other eusocial bees. We also find evidence that sociality inE. dilemmareflects gene expression patterns involved in solitary foraging and non-foraging nest care behaviours. Our results provide strong support for the hypothesis that eusociality emerges from plasticity found across solitary life cycles.
Sea urchins mediate the availability of kelp detritus to benthic consumers
Authors: Yorke Christie E. , Page Henry M. , Miller Robert J.
Published: July 2019

Detritus can fundamentally shape and sustain food webs, and shredders can facilitate its availability. Most of the biomass of the highly productive giant kelp,Macrocystis pyrifera, becomes detritus that is exported or falls to the seafloor as litter. We hypothesized that sea urchins process kelp litter through shredding, sloppy feeding and egestion, making kelp litter more available to benthic consumers. To test this, we conducted a mesocosm experiment in which an array of kelp forest benthic consumers were exposed to13C- and15N-labelledMacrocystiswith or without the presence of sea urchins,Strongylocentrotus purpuratus. Our results showed that several detritivore species consumed significant amounts of kelp, but only when urchins were present. Although they are typically portrayed as antagonistic grazers in kelp forests, sea urchins can have a positive trophic role, capturing kelp litter before it is exported and making it available to a suite of benthic detritivores.
Multi-species comparisons of snakes identify coordinated signalling networks underlying post-feeding intestinal regeneration
Authors: Perry Blair W. , Andrew Audra L. , Mostafa Kamal Abu Hena , Card Daren C. , Schield Drew R. , Pasquesi Giulia I. M. , Pellegrino Mark W. , Mackessy Stephen P. , Chowdhury Saiful M. , Secor Stephen M. , Castoe Todd A.
Published: July 2019

Several snake species that feed infrequently in nature have evolved the ability to massively upregulate intestinal form and function with each meal. While fasting, these snakes downregulate intestinal form and function, and upon feeding restore intestinal structure and function through major increases in cell growth and proliferation, metabolism and upregulation of digestive function. Previous studies have identified changes in gene expression that underlie this regenerative growth of the python intestine, but the unique features that differentiate this extreme regenerative growth from non-regenerative post-feeding responses exhibited by snakes that feed more frequently remain unclear. Here, we leveraged variation in regenerative capacity across three snake species—two distantly related lineages (CrotalusandPython) that experience regenerative growth, and one (Nerodia) that does not—to infer molecular mechanisms underlying intestinal regeneration using transcriptomic and proteomic approaches. Using a comparative approach, we identify a suite of growth, stress response and DNA damage response signalling pathways with inferred activity specifically in regenerating species, and propose a hypothesis model of interactivity between these pathways that may drive regenerative intestinal growth in snakes.
To see or not to see: molecular evolution of the rhodopsin visual pigment in neotropical electric fishes
Authors: Van Nynatten Alexander , Janzen Francesco H. , Brochu Kristen , Maldonado-Ocampo Javier A. , Crampton William G. R. , Chang Belinda S. W. , Lovejoy Nathan R.
Published: July 2019

Functional variation in rhodopsin, the dim-light-specialized visual pigment, frequently occurs in species inhabiting light-limited environments. Variation in visual function can arise through two processes: relaxation of selection or adaptive evolution improving photon detection in a given environment. Here, we investigate the molecular evolution of rhodopsin in Gymnotiformes, an order of mostly nocturnal South American fishes that evolved sophisticated electrosensory capabilities. Our initial sequencing revealed a mutation associated with visual disease in humans. As these fishes are thought to have poor vision, this would be consistent with a possible sensory trade-off between the visual system and a novel electrosensory system. To investigate this, we surveyed rhodopsin from 147 gymnotiform species, spanning the order, and analysed patterns of molecular evolution. In contrast with our expectation, we detected strong selective constraint in gymnotiform rhodopsin, with rates of non-synonymous to synonymous substitutions lower in gymnotiforms than in other vertebrate lineages. In addition, we found evidence for positive selection on the branch leading to gymnotiforms and on a branch leading to a clade of deep-channel specialized gymnotiform species. We also found evidence that deleterious effects of a human disease-associated substitution are likely to be masked by epistatic substitutions at nearby sites. Our results suggest that rhodopsin remains an important component of the gymnotiform sensory system alongside electrolocation, and that photosensitivity of rhodopsin is well adapted for vision in dim-light environments.
Biodiversity–ecosystem functioning relationships in fish communities: biomass is related to evenness and the environment, not to species richness
Authors: Maureaud Aurore , Hodapp Dorothee , van Denderen P. Daniël , Hillebrand Helmut , Gislason Henrik , Spaanheden Dencker Tim , Beukhof Esther , Lindegren Martin
Published: July 2019

The relationship between biodiversity and ecosystem functioning (BEF) is a topic of considerable interest to scientists and managers because a better understanding of its underlying mechanisms may help us mitigate the consequences of biodiversity loss on ecosystems. Our current knowledge of BEF relies heavily on theoretical and experimental studies, typically conducted on a narrow range of spatio-temporal scales, environmental conditions, and trophic levels. Hence, whether a relationship holds in the natural environment is poorly understood, especially in exploited marine ecosystems. Using large-scale observations of marine fish communities, we applied a structural equation modelling framework to investigate the existence and significance of BEF relationships across northwestern European seas. We find that ecosystem functioning, here represented by spatial patterns in total fish biomass, is unrelated to species richness—the most commonly used diversity metric in BEF studies. Instead, community evenness, differences in species composition, and abiotic variables are significant drivers. In particular, we find that high fish biomass is associated with fish assemblages dominated by a few generalist species of a high trophic level, who are able to exploit both the benthic and pelagic energy pathway. Our study provides a better understanding of the mechanisms behind marine ecosystem functioning and allows for the integration of biodiversity into management considerations.
Burkholderia cepacia complex bacteremia outbreaks among non-cystic fibrosis patients in the pediatric unit of the university hospital
Authors: Tüfekci Sinan , Şafak Birol , Kızılca Özgür , Nalbantoğlu Ayşin , Nalbantoğlu Burçin , Samancı Nedim , Kiraz Nuri
Published: July 2019

Introduction

Burkholderia cepacia complex (Bcc) leads to severe nosocomial infections particularly in the patients who have intravascular catheters and cystic fibrosis. The present study aims at investigation of Bcc outbreaks in non-cystic fibrosis patients.

Material and Methods

A total of 6 patients who were hospitalized at General Pediatrics Department were included in the study. Blood cultures which yielded positive signals were incubated at 5% blood sheep agar, chocolate agar and Eosin Methylene Blue agar. All fields which could be the source of the infection at the clinic were examined. Isolates confirmation with Pulsed-Field Gel Electrophoresis (PFGE) tests were performed.

Results

The first patient aged 14.5 years was hospitalized due to left renal agenesis, urinary tract infection and renal failure. Bcc growing was detected in blood culture which was obtained due to high fever at the 3rd day of hospitalization. New patient hospitalizations were stopped due to Bcc growing in blood cultures which was obtained due to high fever in the remaining five patients. No growing was detected in samples obtained from the clinic and the patient rooms. PFGE patterns were similar in all clinical isolates of Bcc indicating that the outbreak had originated from the same origin.

Conclusions

Bcc infection should always be kept in mind in nosocomial outbreaks due to multi-drug resistance and the need for hospitalization at intensive care unit. Control measures should be taken for prevention of nosocomial infections and required investigations should be done for detection of the source of the infection.
Dose-Dependent Effects of Transcranial Alternating Current Stimulation on Spike Timing in Awake Nonhuman Primates
Authors: Johnson Luke , Alekseichuk Ivan , Krieg Jordan , Doyle Alex , Yu Ying , Vitek Jerrold , Johnson Matthew , Opitz Alexander
Published: July 2019

Weak extracellular electric fields can influence spike timing in neural networks. Approaches to impose such fields on the brain in a noninvasive manner have high potential for novel treatments of neurological and psychiatric disorders. One of these methods, transcranial alternating current stimulation (TACS), is hypothesized to affect spike timing and cause neural entrainment. However, the conditions under which these effects occur in-vivo are unknown. Here, we show that TACS modulates spike timing in awake nonhuman primates (NHPs) in a dose-dependent fashion. Recording single-unit activity from pre-and post-central gyrus regions in NHPs during TACS, we found that a larger population of neurons became entrained to the stimulation waveform for higher stimulation intensities. Performing a cluster analysis of changes in interspike intervals, we identified two main types of neural responses to TACS – increased burstiness and phase entrainment. Our results demonstrate the ability of TACS to affect spike-timing in the awake primate brain and identify fundamental neural mechanisms. Concurrent electric field recordings demonstrate that spike-timing changes occur with stimulation intensities readily achievable in humans. These results suggest that novel TACS protocols tailored to ongoing brain activity may be a potent tool to normalize spike-timing in maladaptive brain networks and neurological disease.
Increased expression of mitochondrial dysfunction stimulon genes affects chloroplast redox status and photosynthetic electron transfer in Arabidopsis
Authors: Shapiguzov Alexey , Nikkanen Lauri , Fitzpatrick Duncan , Vainonen Julia P. , Tiwari Arjun , Gossens Richard , Alseekh Saleh , Aarabi Fayezeh , Blokhina Olga , Panzarová Klará , Benedikty Zuzana , Tyystjärvi Esa , Fernie Alisdair R. , Trtílek Martin , Aro Eva-Mari , Rintamäki Eevi , Kangasjärvi Jaakko
Published: July 2019

Mitochondrial retrograde signals control expression of nuclear mitochondrial dysfunction stimulon (MDS) genes. Although MDS gene products mostly affect mitochondrial functions, they also influence production of reactive oxygen species (ROS) and redox status of chloroplasts. To study this inter-organellar interaction, we analysed the response of the Arabidopsis MDS-overexpressor mutantrcd1to methyl viologen (MV), which catalyses electron transfer from Photosystem I (PSI) to molecular oxygen, generating ROS in Mehler’s reaction. The response of plants to MV was investigated by imaging chlorophyll fluorescence in aerobic and hypoxic environments, and by membrane inlet mass spectrometry. Hypoxic treatment abolished the effect of MV on photosynthetic electron transfer inrcd1, but not in wild type. A similar reaction to hypoxia was observed in other MDS-activating lines and treatments. This suggests that MDS gene products contribute to oxygen depletion at the PSI electron-acceptor side. In unstressed growth conditions this MDS-related effect is likely masked by endogenous oxygen evolution and gas exchange with the atmosphere. Inrcd1, altered Mehler’s reaction coincided with more reduced state of the chloroplast NADPH-thioredoxin oxidoreductase C (NTRC) and its targets, suggesting that NTRC performs feedback control of photosynthesis. This regulation may represent a novel mechanism whereby mitochondrial retrograde signalling affects chloroplast functions.
Comparison of the full distribution of fitness effects of new amino acid mutations across great apes
Authors: Castellano David , Macià Moisès Coll , Tataru Paula , Bataillon Thomas , Munch Kasper
Published: July 2019

The distribution of fitness effects (DFE) is central to many questions in evolutionary biology. However, little is known about the differences in DFEs between closely related species. We use more than 9,000 coding genes orthologous one-to-one across great apes, gibbons, and macaques to assess the stability of the DFE across great apes. We use the unfolded site frequency spectrum of polymorphic mutations (n = 8 haploid chromosomes per population) to estimate the DFE. We find that the shape of the deleterious DFE is strikingly similar across great apes. We confirm that effective population size (Ne) is a strong predictor of the strength of negative selection, consistent with the Nearly Neutral Theory. However, we also find that the strength of negative selection varies more than expected given the differences inNebetween species. Across species, mean fitness effects of new deleterious mutations co-varies withNe, consistent with positive epistasis among deleterious mutations. We find that the strength of negative selection for the smallest populations: bonobos and western chimpanzees, is higher than expected given theirNe. This may result from a more efficient purging of strongly deleterious recessive variants in these populations. Forward simulations confirm that these findings are not artifacts of the way we are inferringNeand DFE parameters. All findings are replicated using only GC-conservative mutations, thereby confirming that GC-biased gene conversion is not affecting our conclusions.
Phytochromes measure photoperiod in Brachypodium
Authors: Gao Mingjun , Geng Feng , Klose Cornelia , Staudt Anne-Marie , Huang He , Nguyen Duy , Lan Hui , Mockler Todd C. , Nusinow Dmitri A. , Hiltbrunner Andreas , Schäfer Eberhard , Wigge Philip A. , Jaeger Katja E.
Published: July 2019

Daylength is a key seasonal cue for animals and plants. In cereals, photoperiodic responses are a major adaptive trait, and alleles of clock genes such asPHOTOPERIOD DEPENDENT1 (PPD1)andEARLY FLOWERING3 (ELF3)have been selected for in breeding barley and wheat for more northern latitudes (Faure et al., 2012; Turner, Beales, Faure, Dunford, & Laurie, 2005). How monocot plants sense photoperiod and integrate this information into growth and development is not well understood. We show that inBrachypodium distachyon, phytochrome C (phyC) acts as a molecular timer, directly communicating information to the circadian clock protein ELF3. In this way, ELF3 levels integrate night length information. ELF3 is a central regulator of photoperiodism in Brachypodium, andelf3mutants display a constitutive long day transcriptome. Conversely, conditions that result in higher levels of ELF3 suppress long day responses. We are able to show that these effects are direct, as ELF3 and phyC occur in a common complex, and they associate with the promoters of a number of conserved regulators of photoperiodism, includingPPD1. Consistent with observations in barley, we are able to show thatPPD1overexpression accelerates flowering in SD and is necessary for rapid flowering in response to LD. These findings provide a conceptual framework for understanding observations in the photoperiodic responses of key crops, including wheat, barley and rice.
Revealing the Assembly of Filamentous Proteins with Scanning Transmission Electron Microscopy
Authors: Martinez-Torres Cristina , Burla Federica , Alkemade Celine , Koenderink Gijsje H.
Published: July 2019

Filamentous proteins are responsible for the superior mechanical strength of our cells and tissues. The remarkable mechanical properties of protein filaments are tied to their complex molecular packing structure. However, since these filaments have widths of several to tens of nanometers, it has remained challenging to quantitatively probe their molecular mass density and three-dimensional packing order. Scanning transmission electron microscopy (STEM) is a powerful tool to perform simultaneous mass and morphology measurements on filamentous proteins at high resolution, but its applicability has been greatly limited by the lack of automated image processing methods. Here, we demonstrate a semi-automated tracking algorithm that is capable of analyzing the molecular packing density of intra- and extracellular protein filaments over a broad mass range from STEM images. We prove the wide applicability of the technique by analyzing the mass densities of two cytoskeletal proteins (actin and microtubules) and of the main protein in the extracellular matrix, collagen. The high-throughput and spatial resolution of our approach allow us to quantify the internal packing of these filaments and their polymorphism by correlating mass and morphology information. Moreover, we are able to identify periodic mass variations in collagen fibrils that reveal details of their axially ordered longitudinal self-assembly. STEM-based mass mapping coupled with our tracking algorithm is therefore a powerful technique in the characterization of a wide range of biological and synthetic filaments.
Cardiac valve regeneration in adult zebrafish: importance of TGFß signaling in new tissue formation
Authors: Bensimon-Brito Anabela , Ramkumar Srinath , Boezio Giulia L. M. , Guenther Stefan , Kuenne Carsten , Sánchez-Iranzo Héctor , Iloska Dijana , Piesker Janett , Pullamsetti Soni , Mercader Nadia , Beis Dimitris , Stainier Didier Y. R.
Published: July 2019

Cardiac valve disease can lead to severe cardiac dysfunction and is thus a frequent cause of morbidity and mortality. Its main treatment is valve replacement, which is currently greatly limited by the poor recellularization and tissue formation potential of the implanted valves. As we still lack suitable animal models to identify modulators of these processes, here we used the adult zebrafish and found that, upon valve decellularization, they initiate a striking regenerative program that leads to the formation of new functional valves. After injury, endothelial and kidney marrow-derived cells undergo cell cycle re-entry and differentiate into new extracellular matrix-secreting valve cells. The Transforming Growth Factor beta (TGFβ) signaling pathway promotes this process by enhancing progenitor cell proliferation as well as valve cell differentiation. These findings reveal a key role for TGFβ signaling in valve regeneration and also establish the zebrafish as a model to identify and test factors promoting valve recellularization and growth.
TRF1 prevents permissive DNA damage response, recombination and Break Induced Replication at telomeres
Authors: Porreca Rosa Maria , Law Pui Pik , Herrera-Moyano Emilia , Gonzalez-Franco Roser , Montoya Alex , Faull Peter , Kramer Holger , Vannier Jean-Baptiste
Published: July 2019

Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that telomeres lacking TRF1 undergo protein composition reorganisation associated with a DNA damage response and chromatin remodelers. Surprisingly, TRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Recombination (HR) and TERRA transcription. We uncovered a previously unappreciated role for TRF1 in the suppression of telomere recombination, dependent on SMC5 and also POLD3 dependent Break Induced Replication at telomeres. We propose that TRF1 facilitates S-phase telomeric DNA synthesis to prevent illegitimate mitotic DNA recombination and chromatin rearrangement.
An annotation dataset facilitates automatic annotation of whole-brain activity imaging ofC. elegans
Authors: Toyoshima Yu , Wu Stephen , Kanamori Manami , Sato Hirofumi , Jang Moon Sun , Oe Suzu , Murakami Yuko , Teramoto Takayuki , Park ChanHyun , Iwasaki Yuishi , Ishihara Takeshi , Yoshida Ryo , Iino Yuichi
Published: July 2019

Annotation of cell identity is an essential process in neuroscience that allows for comparing neural activities across different animals. InC. elegans, although unique identities have been assigned to all neurons, the number of annotatable neurons in an intact animal is limited in practice and comprehensive methods for cell annotation are required. Here we propose an efficient annotation method that can be integrated with the whole-brain imaging technique. We systematically identified neurons in the head region of 311 adult worms using 35 cell-specific promoters and created a dataset of the expression patterns and the positions of the neurons. The large positional variations illustrated the difficulty of the annotation task. We investigated multiple combinations of cell-specific promoters to tackle this problem. We also developed an automatic annotation method with human interaction functionality that facilitates annotation for whole-brain imaging.
A mathematical model of ephaptic interactions in neuronal fiber pathways: could there be more than transmission along the tracts?
Authors: Sheheitli Hiba , Jirsa Viktor K.
Published: July 2019

In the past several decades, there has been numerous experimental and modeling efforts to study ephaptic interactions in neuronal systems. While studies on the matter have looked at either axons of the peripheral nervous system or cortical neuronal structures, no attention has be given to the possibility of ephaptic interactions in the white matter tracts of the brain. Inspired by the highly organized and tightly packed geometry of axons in neuronal fiber pathways, we aim to theoretically investigate the potential effects of ephaptic interactions along these structures that are resilient to experimental probing. For that end, we use axonal cable theory to derive a minimal model of a sheet of N ephaptically coupled axons. We numerically solve the equations and explore the dynamics of the system as the ephaptic coupling parameter is varied. We demonstrate that ephaptic interactions can lead to local phase locking between impulses traveling along adjacent axons. As ephaptic coupling is increased, traveling impulses trigger new impulses along adjacent axons resulting in finite size traveling fronts. For strong enough coupling, impulses propagate laterally and backwards, resulting in complex spatio-temporal patterns. While it is common for large scale brain network models to assume the role of brain fiber pathways to be that of mere transmission of signals between different brain regions, our work calls for a closer re-examination of the validity of such a view. The results suggest that in the presence of significant ephaptic interactions the brain fiber tracts can act as a dynamic active medium.

Author summary

Starting from local circuit theory and the Fitzhugh-Nagumo cable model of an axon, we derive a system of nonlinear coupled partial differential equations (PDE’s) to model a sheet of N ephaptically coupled axons. We also put forward a continuous limit approximation that transforms the model into a field equation in the form of a two-dimensional PDE that allows for the extension of the model to a 3D domain. We numerically solve the equations and explore the dynamic responses as the ephaptic coupling strength is varied. We observe that ephaptic interaction allows for phase locking of adjacent impulses and coordination of subthreshold dynamics. In addition, when strong enough, ephaptic interaction can lead to the generation of new impulses along the axons as well as lateral and backward propagation in the form of traveling fronts and complex spatio-temporal patterns. The transition between different dynamic regimes happens abruptly at critical values of the parameter. We also compare the dynamics of the two models and find good qualitative correspondence in certain parameter regimes. The results put into question the validity of assuming the role of fiber pathways to be that of mere interneuronal transmission and calls for further investigation of the matter.
Rag1D600A, a novel catalytically inactive RAG mouse model
Authors: Wong Jason B , Skok Jane A
Published: July 2019

The RAG complex (RAG1 and RAG2) can bind to recombination signal sequences of antigen receptor loci gene segments and coordinate V(D)J recombination which is the primary method of generating antigen receptor diversity. Previous biochemistry studies discovered RAG1 D600, D708 and E962 residues as essential for catalytic DNA nicking and hairpin forming activity of the RAG complex. Neutralization of each of the acidic residues does not impair DNA binding to recombination signal sequence containing DNA substrates, but cleavage of the substrates is severely compromised. These three acidic residues are thought to comprise a DDE motif that is responsible for binding to a divalent cation that is necessary for cleavage activity. Although a Rag1-/-; RAG1-D708A transgenic mouse model system has been used to study dynamics of RAG activity, transgenic expression may not precisely mimic expression from the endogenous locus. In order to improve upon this model, we created Rag1D600A mice that lack B and T cells and demonstrate a developmental block at the pro-B and DN stages, respectively. Thus, Rag1D600A mice provide a novel mouse model system for studying the poorly understood noncanonical functions of RAG1.
Mapping Cumulative Impacts to Coastal Ecosystem Services in British Columbia
Authors: Singh Gerald G. , Eddy Ian M.S. , Halpern Benjamin S. , Neslo Rabin , Satterfield Terre , Chan Kai M.A.
Published: July 2019

Ecosystem services are impacted through restricting service supply, through limiting people from accessing services, and by affecting the quality of services. We map cumulative impacts to 8 different ecosystem services in coastal British Columbia using InVEST models, spatial data, and expert elicitation to quantify risk to each service from anthropogenic activities. We find that impact to service access and quality as well as impact to service supply results in greater severity of impact and a greater diversity of causal processes of impact than only considering impact to service supply. This suggests that limiting access to services and impacts to service quality may be important and understanding these kinds of impacts may complement our knowledge of impacts to biophysical systems that produce services. Some ecosystem services are at greater risk from climate stressors while others face greater risk from local activities. Prominent causal pathways of impact include limiting access and affecting quality. Mapping cumulative impacts to ecosystem services can yield rich insights, including highlighting areas of high impact and understanding causes of impact, and should be an essential management tool to help maintain the flow of services we benefit from.
Monitoring and characterizing soluble and membrane-bound ectonucleotidases CD73 and CD39
Authors: Goueli Said A. , Hsiao Kevin
Published: July 2019

The success of immunotherapy treatment in oncology ushered a new modality for treating a wide variety of cancers. However, lack of effect in some patients made it imperative to identify other pathways that are exploited by cancer cells to circumvent immune surveillance, and possibly synergize immune checkpoint treatment in those cases. It has been recently recognized that adenosine levels increased significantly in the tumor microenvironment and that adenosine/adenosine receptors play a powerful role as immunosuppressant and attenuating several effector T cell functions. The two main enzymes responsible for generating adenosine in the microenvironment are the ectonucleotidases CD39 and CD73, the former utilizes both ATP and ADP and producing AMP while the latter utilizes AMP and generates adenosine. Thus, these two enzymes combined are the major source for the bulk of adenosine produced in the microenvironment. They were shown to be validated targets in oncology leading to several clinical trials that include small molecules as well as antibodies, showing positive and encouraging results in the preclinical arena. Towards the development of novel drugs to target these enzymes, we have developed a platform that can be utilized to monitor the activities of both enzymes in vitro (biochemical) as well as in cells (cell based) assays. We have developed very sensitive and homogenous assays that enabled us to monitor the activity of both enzymes and demonstrate selectivity of known inhibitors as well as monoclonal antibodies. This should speed up screening for novel inhibitors leading to more effective cancer therapy
Effect of pulsed light on postharvest disease control-related metabolomic variation in melon (Cucumis melo) artificially inoculated with Fusarium pallidoroseum
Authors: Filho Francisco Oiram , de Oliveira Silva Ebenézer , de Almeida Lopes Mônica Maria , Vasconselos Ribeiro Paulo Riceli , Oster Andréia Hansen , Carvalho Guedes Jhonyson Arruda , Nascimento Bordallo Patrícia do , Zocolo Guilherme Julião
Published: July 2019

Pulsed light, as a postharvest technology, is an alternative to traditional fungicides, and can be used on a wide variety of fruit and vegetables for sanitization or pathogen control. In addition to these applications, other effects also are detected in vegetal cells, including changes in metabolism and production of secondary metabolites, which directly affect disease control response mechanisms. This study aimed to evaluate the possible applications of pulsed ultraviolet light in controlling postharvest rot, mainly caused by Fusarium pallidoroseum in yellow melon ‘Goldex’, in natura, and its implications in the disease control as a function of metabolomic expression to effect fungicidal or fungistatic. The dose of pulsed light (PL) that inhibited F. pallidoroseum growth in melons (Cucumis melo var. Spanish) was 9 KJ m-2. Ultra performance liquid chromatography (UPLC) coupled to a quadrupole time-of-flight (QTOF) mass analyzer identified 12 compounds based on the MS/MS fragmentation patterns. Chemometric analysis by Principal Components Analysis (PCA) and Orthogonal Partial Least Squared Discriminant Analysis (OPLS-DA and S-plot) were used to evaluate the changes in fruit metabolism. PL technology provided protection against postharvest disease in melons, directly inhibiting the growth of F. pallidoroseum through upregulation of specific fruit biomarkers such as pipecolic acid (11), saponarin (7), and orientin (3), which acted as major markers for the defense system against pathogens. PL can thus be proposed as a postharvest technology to avoid chemical fungicides and may be applied to reduce the decay of melon quality during its export and storage.
Agents of alienation: accountants and the land grab of Papua New Guinea
Authors: Finau Glenn , Jacobs Kerry , Chand Satish
Published: July 2019

Purpose

The purpose of this paper is to explore and examine the role of accounting and accountants in customary land transactions between Indigenous peoples and foreign corporate entities. The paper uses the case of two accountants who utilised accounting technologies in lease agreements to alienate customary land from Indigenous landowners in Papua New Guinea (PNG).

Design/methodology/approach

Employing a case study methodology, the paper draws on contemporary data sets of transcripts related to a Commission of Inquiry established in 2011 to investigate PNG’s Special Agricultural Business Lease system. Analysis of other publicly available data and semi-structured interviews with PNG landowners and other stakeholders supplement and triangulate data from the inquiry transcripts. A Bourdieusian lens was adopted to conceptualise how accounting was used in the struggles for customary land between foreign developers and Indigenous landowners within the wider capitalist field and the traditional Melanesian field.

Findings

This paper reveals how accountants exploited PNG’s customary land registration system, the Indigenous peoples’ lack of financial literacy and their desperation for development to alienate customary land from landowners. The accountants employed accounting technologies in the sublease agreements to reduce their royalty obligations to the landowners and to impose penalty clauses that made it financially impossible for the landowners to cancel the leases. The accountants used accounting to normalise, legitimise and rationalise these exploitative arrangements in formal lease contracts.

Originality/value

This paper responds to the call for research on accounting and Indigenous peoples that is contemporary rather than historic; examines the role of accountants in Indigenous relations, and examines the emancipatory potential of accounting.
In-flight thrust monitoring: an acoustics-based approach
Authors: Lowe K. Todd , Otero Raul , Ng Wing
Published: July 2019

Purpose

The purpose of this paper is to present an acoustics-based method for measuring turbofan nozzle exhaust thrust, while assessing the potential of scaling the methods for in-flight measurements.

Design/methodology/approach

Although many methods proposed for achieving in-flight thrust measurements involve complicated, sensitive and expense instruments, an acoustics-based approach is discussed that greatly simplifies the technology development pathway to in-flight applications.

Findings

Results are provided for a minimum set of sensors applied in the exhaust of a research turbofan engine at Virginia Tech, showing the difference in acoustics-measured thrust and nozzle thrust found by integrating thermocouple and Kiel probe measurements to be less than 6 per cent at the maximum fan speed examined.

Practical implications

Measuring accurate thrust values in flight will prove immediately valuable for installed thrust validation and engine health monitoring. Acoustics-based methodologies are attractive because of the robustness and low cost of sensors and sources. The value of in-flight thrust measurements, along with the benefits of acoustic approaches, makes the current topic of great interest for further development.

Originality/value

This paper presents unique applications of a time-of-flight acoustic thrust sensor, while providing an original assessment of technological challenges involved with the progression of the technique for in-flight measurements.
Thermal performance enhancement in a wedge duct with in-line pin fins combined with vortex generators
Authors: Hussain Safeer , Liu Jian , Wang Lei , Sunden Bengt Ake
Published: July 2019

Purpose

The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs).

Design/methodology/approach

This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers.

Findings

The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins.

Originality/value

VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.
Comparison of subgrid-scale models for large-eddy simulation of hydrodynamic and magnetohydrodynamic channel flows
Authors: Prinz Sebastian , Schumacher Jörg , Boeck Thomas
Published: July 2019

Purpose

This paper aims to address the performance of different subgrid-scale models (SGS) for hydro- (HD) and magnetohydrodynamic (MHD) channel flows within a collocated finite-volume scheme.

Design/methodology/approach

First, the SGS energy transfer is analyzed by a priori tests using fully resolved DNS data. Here, the focus lies on the influence of the magnetic field on the SGS energy transport. Second, the authors performed a series of 18 a posteriori model tests, using different grid resolutions and SGS models for HD and MHD channel flows.

Findings

From the a priori analysis, the authors observe a quantitative reduction of the SGS energy transport because of the action of the magnetic field depending on its orientation. The a posteriori model tests show a clear improvement because of the use of mixed-models within the numerical scheme.

Originality/value

This study demonstrates the necessity of improved SGS modeling strategies for magnetohydrodynamic channel flows within a collocated finite-volume scheme.
Research on transient aerodynamic characteristics of windshield wipers of vehicles
Authors: Chen Zhen , Gu Zhenqqi , Jiang Tao
Published: July 2019

Purpose

The main purpose of this paper is to gain a better understanding of the transient aerodynamic characteristics of moving windshield wipers. In addition, this paper also strives to illustrate and clarify how the wiper motion impacts the airflow structure; the aerodynamic interaction of two wipers is also discussed.

Design/methodology/approach

A standard vehicle model proposed by the Motor Industry Research Association and a pair of simplified bone wipers are introduced, and a dynamic mesh technique and user-defined functions are used to achieve the wiper motion. Finite volume methods and large eddy simulation (LES) are used to simulate the transient airflow field. The simulation results are validated through the wind tunnel test.

Findings

The results obtained from the study are presented graphically, and pressure, velocity distributions, airflow structures, aerodynamic drag and lift force are shown. Significant influences of wiper motion on airflow structures are achieved. The maximum value of aerodynamic lift and drag force exists when wipers are rotating and there is a certain change rule. The aerodynamic lift and drag force when wipers are rotating downward is greater than when wipers are rotating upward, and the force when rotating upward is greater than that when steady. The aerodynamic lift and drag forces of the driver-side wiper is greater than those of the passenger-side wiper.

Originality/value

The LES method in combination with dynamic mesh technique to study the transient aerodynamic characteristics of windshield wipers is relatively new.