bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mechanistic model for reward prediction and extinction learning in the fruit fly
Authors: Springer Magdalena , Nawrot Martin Paul 
Published: December 2020

AbstractExtinction learning, the ability to update previously learned information by integrating novel contradictory information, is a key mechanism for adapting our behavior and of high clinical relevance for therapeutic approaches to the modulation of maladaptive memories. Insect models have been instrumental in uncovering fundamental processes of memory formation and memory update. Recent experimental results inDrosophila melanogastersuggest that, after the behavioral extinction of a memory, two parallel but opposing memory traces coexist, residing at different sites within the mushroom body. Here we propose a minimalistic circuit model of theDrosophilamushroom body that supports classical appetitive and aversive conditioning and memory extinction. The model is tailored to the existing anatomical data and involves two circuit motives of central functional importance. It employs plastic synaptic connections between Kenyon cells and mushroom body output neurons (MBONs) in separate and mutually inhibiting appetitive and aversive learning pathways. Recurrent modulation of plasticity through projections from MBONs to reinforcement-mediating dopaminergic neurons implements a simple reward prediction mechanism. A distinct set of four MBONs encodes odor valence and predicts behavioral model output. Subjecting our model to learning and extinction protocols reproduced experimental results from recent behavioral and imaging studies. Simulating the experimental blocking of synaptic output of individual neurons or neuron groups in the model circuit confirmed experimental results and allowed formulation of testable predictions. In the temporal domain, our model achieves rapid learning with a step-like increase in the encoded odor value after a single pairing of the conditioned stimulus with a reward or punishment, facilitating single-trial learning.
31P NMR Spectroscopy Demonstrates Large Amounts of Phosphohistidine in Mammalian Cells
Authors: Makwana Mehul V. , van Meurs Sandra , Hounslow Andrea M. , Williamson Mike P. , Jackson Richard F. W. , Muimo Richmond 
Published: December 2020

AbstractProtein phosphorylation plays a key role in many cellular processes but there is presently no accurate information or reliable procedure to determine the relative abundance of many phosphoamino acids in cells. At pH ≤ 8, phosphohistidine is unstable compared to the extensively studied phosphoserine, phosphothreonine and phosphotyrosine. This study reports the absolute quantitative analysis of histidine phosphorylation of proteins from a human bronchial epithelial cell (16HBE14o-) lysate using31P NMR spectroscopic analysis. The method was designed to minimize loss of the phosphohistidine phosphoryl group. Phosphohistidine was determined on average to be approximately one third as abundant as phosphoserine and phosphothreonine combined (and thus roughly 20 times more abundant than phosphotyrosine). The amount of phosphohistidine, and phosphoserine/phosphothreonine per gram of protein from a cell lysate was determined to be 23 μmol/g and 68 μmol/g respectively. The amount of phosphohistidine, and phosphoserine/phosphothreonine per cell was determined to be 1.8 fmol/cell, and 5.8 fmol/cell respectively. After tryptic digest of proteins from the16HBE14o- cell lysate, the phosphohistidine signal was abolished and increasing phosphoserine/phosphothreonine signal was observed, which has implications for mass spectrometry investigations. The31P NMR spectroscopic analysis not only highlights the abundance of phosphohistidine, which likely reflects its importance in mammalian cells, but also provides a way of measuring and comparing levels of phosphorylated amino acids in cells.
Seizure localisation with attention-based graph neural networks
Authors: Grattarola Daniele , Livi Lorenzo , Alippi Cesare , Wennberg Richard , Valiante Taufik A. 
Published: December 2020

AbstractIn this paper, we introduce a machine learning methodology for localising the seizure onset zone in subjects with epilepsy. We represent brain states as functional networks obtained from intracranial electroen-cephalography recordings, using correlation and the phase locking value to quantify the coupling between different brain areas.Our method is based on graph neural networks (GNNs) and the attention mechanism, two of the most significant advances in artificial intelligence in recent years. Specifically, we train a GNN to distinguish between functional networks associated with interictal and ictal phases. The GNN is equipped with an attention-based layer that automatically learns to identify those regions of the brain (associated with individual electrodes) that are most important for a correct classification. The localisation of these regions does not require any prior information regarding the seizure onset zone.We show that the regions of interest identified by the GNN strongly correlate with the localisation of the seizure onset zone reported by electroencephalographers. We report results both for human patients and for simulators of brain activity. We also show that our GNN exhibits uncertainty on those patients for which the clinical localisation was unsuccessful, highlighting the robustness of the proposed approach.
Fossils improve phylogenetic analyses of morphological characters
Authors: Koch Nicolás Mongiardino , Garwood Russell J. , Parry Luke A. 
Published: December 2020

AbstractFossils provide our only direct window into evolutionary events in the distant past. Incorporating them into phylogenetic hypotheses of living clades can help elucidate macroevolutionary patterns and processes, such as ancestral states and diversification dynamics. However, the effect fossils have on phylogenetic inference from morphological data remains controversial. Previous studies have highlighted their strong impact on topologies inferred from empirical data, but have not demonstrated that they improve accuracy. The consequences of explicitly incorporating the stratigraphic ages of fossils using tip-dated inference are also unclear. Here we employ a simulation approach to explore how fossil sampling and missing data affect tree reconstruction across a range of inference methods. Our results show that fossil taxa improve phylogenetic analysis of morphological datasets, even when highly fragmentary. Irrespective of inference method, fossils improve the accuracy of phylogenies and increase the number of resolved nodes. They also induce the collapse of ancient and highly uncertain relationships that tend to be incorrectly resolved when sampling only extant taxa. Furthermore, tip-dated analyses which simultaneously infer tree topology and divergence times outperform all other methods of inference, demonstrating that the stratigraphic ages of fossils contain vital phylogenetic information. Fossils help to extract true phylogenetic signals from morphology, an effect that is mediated by both their unique morphology and their temporal information, and their incorporation in total-evidence phylogenetics is necessary to faithfully reconstruct evolutionary history.
Structure of the mature Rous sarcoma virus lattice reveals a role for IP6 in the formation of the capsid hexamer
Authors: Obr Martin , Ricana Clifton L. , Nikulin Nadia , Feathers Jon-Philip R. , Klanschnig Marco , Thader Andreas , Johnson Marc C. , Vogt Volker M. , Schur Florian K.M. , Dick Robert A. 
Published: December 2020

AbstractInositol hexakisphosphate (IP6) is an assembly cofactor for HIV-1. We report here that IP6 is also used for assembly of Rous sarcoma virus (RSV), a retrovirus from a different genus. IP6 was ∼100-fold more potent at promoting RSV mature CA assembly than observed for HIV-1 and removal of IP6in vivoreduced infectivity by 100-fold. By cryo-electron tomography and subtomogram averaging, mature virus-like particles (VLPs) showed an IP6-like density in the CA hexamer, coordinated by rings of six lysines and six arginines. Phosphate and IP6 had opposing effects on CAin vitroassembly, inducing formation of T=1 icosahedrons and tubes, respectively, implying that phosphate promotes pentamer and IP6 hexamer formation. Subtomogram averaging and classification optimized for analysis of pleomorphic retrovirus particles revealed that the heterogeneity of mature RSV CA polyhedrons results from an unexpected, intrinsic CA hexamer flexibility. In contrast, the CA pentamer forms rigid units organizing the local architecture. These different features of hexamers and pentamers determine the structural mechanism to form CA polyhedrons of variable shape in mature RSV particles.
Uniparental nuclear inheritance following bisexual mating in fungi
Authors: Yadav Vikas , Sun Sheng , Heitman Joseph 
Published: December 2020

AbstractSome remarkable animal species require an opposite-sex partner for their sexual development but discard the partner’s genome before gamete formation, generating hemi-clonal progeny in a process called hybridogenesis. Here, we discovered a similar phenomenon, termed pseudosexual reproduction, in a basidiomycete human fungal pathogen,Cryptococcus neoformans, where exclusive uniparental inheritance of nuclear genetic material was observed during bisexual reproduction. Analysis of strains expressing fluorescent reporter proteins revealed instances where only one of the parental nuclei was present in the terminal sporulating basidium. Whole-genome sequencing revealed the nuclear genome of the progeny was identical with one or the other parental genome. Pseudosexual reproduction was also detected in natural isolate crosses where it resulted in mainlyMATα progeny, a bias observed inCryptococcusecological distribution as well. The meiotic recombinase Dmc1 was found to be critical for pseudosexual reproduction. These findings reveal a novel, and potentially ecologically significant, mode of eukaryotic microbial reproduction that shares features with hybridogenesis in animals.
Stimulus-selective lateral signaling between olfactory afferents enables parallel encoding of distinct CO2dynamics
Authors: Zocchi Dhruv , Ye Emily S. , Hong Elizabeth J. 
Published: December 2020

SUMMARYAn important problem in sensory processing is how lateral interactions that mediate the integration of information across sensory channels function with respect to stimulus tuning. We demonstrate a novel form of selective crosstalk between specific olfactory channels that occurs between primary olfactory receptor neurons (ORNs). Neurotransmitter release from ORNs can be driven by two distinct sources of excitation, feedforward activity derived from the odorant receptor and lateral input originating from specific subsets of other ORNs. Consequently, levels of presynaptic release can become dissociated from firing rate. Stimulus-selective lateral signaling results in the distributed representation of CO2, a behaviorally important environmental cue that elicits spiking in only a single ORN class, in multiple olfactory channels. Different CO2-responsive channels preferentially transmit distinct stimulus dynamics, thereby expanding the coding bandwidth for CO2. These results generalize to additional odors and olfactory channels, revealing a subnetwork of lateral interactions between ORNs that reshape the spatial and temporal structure of odor representations in a stimulus-specific manner.One Sentence SummaryA novel subnetwork of stimulus-selective lateral interactions between primary olfactory sensory neurons enables new sensory computations.
Superradiant Cherenkov–wakefield radiation as THz source for FEL facilities
Authors: Floettmann Klaus , Lemery Francois , Dohlus Martin , Marx Michaela , Tsakanov Vasili , Ivanyan Mikayel 
Published: December 2020

An electron beam passing through a tube of small inner diameter which is lined on the inside with a dielectric layer will radiate energy in the THz range due to the interaction with the boundary. The resonant enhancement of certain frequencies is conditioned by structure parameters such as tube radius and the permittivity and thickness of the dielectric layer. In low-loss structures narrow-band radiation is generated which can be coupled out by suitable antennas. For higher frequencies, the coupling to the resistive outer metal layer becomes increasingly important. The losses in the outer layer prohibit reaching higher frequencies with narrow-band conditions. Instead, short broad-band pulses can be generated with still attractive power levels. In the first section of the paper, a general theory of the impedance of a two-layer structure is presented and the coupling to the outer resistive layer is discussed. Approximate relations for the radiated energy, power and pulse length for a set of structure parameters are derived and compared with numerical results in the following section. Finally, the first numerical result of the out-coupling of the radiation by means of a Vlasov antenna and estimates of the achieved beam quality are presented.
Understanding the spread of prevention and cessation messages on social media for substance use in youth
Authors: Mandal Soumik , Shah Chirag , Peña-Alves Stephanie , Hecht Michael L. , Glenn Shannon D. , Ray Anne E. , Greene Kathryn 
Published: December 2020

PurposeEngagement is a critical metric to the effectiveness of online health messages. This paper explores how people engage in youth-generated prevention messages in social media.Design/methodology/approachThe data sample consisted of engagement measures of 82 youth-generated messages hosted in a social media channel and a follow-up survey on content creators' motivation for promoting their messages and their dissemination strategies. A comparative analysis of engagement metrics along with qualitative analysis of the message types was performed.FindingsTwo types of messages were considered: stop messages and prevent messages. Our analyses found that people interacted with stop messages on social media more frequently than prevent messages. On analyzing the youth's motivation and promotion strategies, no significant difference was observed between stop message creators and prevent message creators.Social implicationsThis work has implications for programs promoting prevention and health information in social media.Originality/valueThis is the first study in social media-based prevention programs the authors are aware of that differentiated between the strategies of youth-produced prevention messages.
STEM faculty members and their perceptions of mentoring: “I do not want to be a role model”
Authors: Olson Joann S. , Nayar-Bhalerao Sneha 
Published: December 2020

PurposeThe purpose of this case study is to explore the perceptions of science, technology, engineering and mathematics (STEM) faculty members toward mentoring undergraduates.Design/methodology/approachWithin the context of a student scholarship and faculty development project, funded by the National Science Foundation (NSF), STEM faculty members were interviewed at a small teaching-focused university in South Texas, United States. This research study utilized a qualitative case study approach based on semi-structured interviews with nine Mathematics and Computer Science faculty members. Transcripts were coded thematically, beginning with open coding and continuing with repeated rounds of comparison leading to the identification of four themes.FindingsFour themes were identified in the data: describing settings where mentoring occurs, identifying the tasks of mentoring, developing skills for mentoring others and inhabiting the identity of a mentor. These findings suggest that increasing faculty engagement and effectiveness in mentoring STEM students may be a matter of broadening the definition of mentoring and helping faculty members develop the identity of a mentor.Practical implicationsIn an effort to promote retention of students, specifically within STEM fields, many initiatives highlight the importance of faculty mentoring for undergraduate students. This research suggests that faculty members' perceptions of the role and structure of a mentoring relationship will shape this relationship and have an impact on student persistence and success.Originality/valueWhile most studies of faculty–student mentoring focus on the experiences of students, this study explored faculty members' perceptions of that relationship.
Identifying factors affecting the value of advertisements on football clubs' and players' social media: a discrete choice analysis
Authors: Balliauw Matteo , Onghena Evy , Mulkens Simon 
Published: December 2020

PurposeAdvertisers frequently use social media for interactive and customer-oriented relationship marketing (RM) purposes. Moreover, sports clubs and players have been using their social media accounts to post content of their sponsors and other advertising companies. Such posts create visibility and have value for these advertising companies, something which has not been empirically quantified in the existing literature. Hence, this paper's purpose is to identify the factors or attributes that influence the value of such advertisement posts.Design/methodology/approachA discrete choice approach is used to empirically estimate the utility that sponsorship managers derive from a post advertising their company or product on football clubs' and players' social media.FindingsThe results indicate that more followers, better on-field performance and a lower price significantly increase the advertising company's utility. Moreover, the used social media channel has a significant influence too, since Facebook and Instagram are preferred over Twitter, due to the latter's limited degrees of freedom for advertisers.Research limitations/implicationsConsidering additional factors such as the image fit between sponsor and sponsee and presence on the Chinese social media market offers an interesting avenue for future research.Practical implicationsThe empirical estimates allow commercial managers of clubs and players to derive companies' relative willingness to pay (WTP) for changes in characteristics of advertisements on their social media from the calculated utilities. This information can be used in the pricing decision when social media posts are sold or included in sponsorship packages.Originality/valueThis is the first study applying discrete choice modelling to link social media marketing (SMM) and sports marketing.
Blockchain platforms in supply chains
Authors: Vivaldini Mauro 
Published: December 2020

PurposeThe purpose of this study is to analyze blockchain (Bc) platforms in order to expand knowledge about the functionalities applied to supply chains (SCs). Therefore, this research seeks to address what these functionalities are and whether they are aligned with the theory.Design/methodology/approachThe research utilizes a literature review on Bc in SC (Bc-SC) and an exploratory study focusing on the developers of Bc platforms.FindingsThe research maps and synthesizes concepts and applications of the platforms for SC. The platforms involved with the development of solutions with Bc technology are relatively representative (138 found by this research, and 47 offer solutions in SC), as well as the diversity of solutions and application (101 applications), covering different activities and areas of the SC.Research limitations/implicationsDespite extensive research and data analysis, there may be other platforms and solutions not analyzed in this paper.Practical implicationsThe narrative and the different examples provided contribute to managers' understanding of the different possibilities for Bc-SC. Studying the services offered by the various platforms also enables managers to better understand what options exist and could potentially be utilized.Originality/valueThis is one of the first papers in a leading international OSCM (operations and supply chain management) journal to analyze the Bc platforms in SC and thereby has its relevance by synthesizing the knowledge that is dispersed in software developers (platforms).
The impact of termination severity on customers' emotional, attitudinal and behavioral reactions
Authors: Nazifi Amin , El-Manstrly Dahlia , Tregear Angela , Auxtova Kristina 
Published: December 2020

PurposeThis paper empirically examines the direct and indirect effects of perceived termination severity on customers' behavioral reactions via betrayal and justice. It also examines the moderating effects of attitude toward complaining (ATC).Design/methodology/approachThis paper employs a quantitative method approach using a scenario-based experiment in a banking setting.FindingsThe results show that a more severe termination approach results in higher customer negative reactions. Betrayal is shown to be a key driver of customers' behavioral reactions, and ATC moderates these effects.Research limitations/implicationsFuture studies should examine the effects of different termination strategies in markedly different cultures and should also examine other boundary conditions such as prior warning, relationship quality and service importance in influencing customers' negative behavioral responses.Originality/valueThis paper contributes to the service termination literature by shedding light on the impact of termination severity on customers' reactions. It also unveils the mechanism that explains customers' reactions to service termination. Further, it reveals that ATC moderates customers' public (but not private) complaining behaviors.
Climate influences the value of a plant structural defence against browsing
Authors: Lusk Christopher H. , Wiser Susan K. , Laughlin Daniel C. 
Published: December 2020

Abstract

The circumstances that select for plant anti‐herbivore defences are not well understood. In New Zealand, the ‘divaricate’ cage‐like architecture of many woody plants may have arisen as a defence against avian browsing; it also has some ability to deter browsing by introduced deer. Its prominence on alluvial soils in frosty and droughty areas led us to hypothesize that structural defences are of most value where fertile soils coincide with climatic constraints that prevent plants from quickly growing out of the browse zone.

We tested this hypothesis by growing seedlings of three divaricate species and their broadleaved congeners on fenced and unfenced plots beneath tree‐fall gaps at three humid frost‐free sites in the North Island of New Zealand, and at three colder and drier sites in the South Island. Soil total phosphorus levels were moderate to high at all sites (344–961 ppm), and pellet counts indicated similar average deer densities at North and South Island sites, enabling us to attribute variation in seedling growth and survival primarily to climatic differences between our sites.

On fenced plots, average relative height growth rates in the North Island exceeded those on the southern sites by 64%, and growth of broadleaved species averaged 132% and 99% greater than that of divaricate congeners at North and South Island sites, respectively. On the northern sites, broadleaved species also held a large (137%) net height growth advantage over divaricates even on unfenced plots. In contrast, exposure to browsing on the coldest sites resulted in complete loss of the broadleaved net height growth advantage.

Synthesis. Even in the presence of deer, divaricate plants were overgrown on humid frost‐free sites, but not on colder and drier sites, where browsing neutralized the superior growth potential of broadleaved species. The cost of structural defences therefore paid off only on sites where climatic adversity reduces the ability of plants lacking such defences to grow quickly out of the browse zone, in agreement with our hypothesis.