bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uncertainty quantification of parenchymal tracer distribution using random diffusion and convective velocity fields
Authors: Croci Matteo , Vinje Vegard , Rognes Marie E. 
Published: June 2019

ABSTRACTBackgroundInflux and clearance of substances in the brain parenchyma occur by a combination of diffusion and convection, but the relative importance of thiese mechanisms is unclear. Accurate modeling of tracer distributions in the brain relies on parameters that are partially unknown and with literature values varying up to 7 orders of magnitude. In this work, we rigorously quantified the variability of tracer enhancement in the brain resulting from uncertainty in diffusion and convection model parameters.MethodsIn a mesh of a human brain, using the convection-diffusion-reaction equation, we simulated tracer enhancement in the brain parenchyma after intrathecal injection. Several models were tested to assess the uncertainty both in type of diffusion and velocity fields and also the importance of their magnitude. Our results were compared with experimental MRI results of tracer enhancement.ResultsIn models of pure diffusion, the expected amount of tracer in the gray matter reached peak value after 15 hours, while the white matter does not reach peak within 24 hours with high likelihood. Models of the glymphatic system behave qualitatively similar as the models of pure diffusion with respect to expected time to peak but display less variability. However, the expected time to peak was reduced to 11 hours when an additional directionality was prescribed for the glymphatic circulation. In a model including drainage directly from the brain parenchyma, time to peak occured after 6-8 hours for the gray matter.ConclusionEven when uncertainties are taken into account, we find that diffusion alone is not sufficient to explain transport of tracer deep into the white matter as seen in experimental data. A glymphatic velocity field may increase transport if a directional structure is included in the glymphatic circulation.
Somatic drift and rapid loss of heterozygosity suggest small effective population size of stem cells and high somatic mutation rate in asexual planaria
Authors: Asgharian Hosseinali , Dunham Joseph , Marjoram Paul , Nuzhdin Sergey V. 
Published: June 2019

AbstractPlanarian flatworms have emerged as highly promising models of body regeneration due to the many stem cells scattered through their bodies. Currently, there is no consensus as to the number of stem cells active in each cycle of regeneration or the equality of their relative contributions. We approached this problem with a population genetic model of somatic genetic drift. We modeled the fissiparous life cycle of asexual planarians as an asexual population of cells that goes through repeated events of splitting into two subpopulations followed by population growth to restore the original size. We sampled a pedigree of obligate asexual clones ofGirardia cf. tigrinaat multiple time points encompassing 14 generations. Effective population size of stem cells was inferred from the magnitude of temporal fluctuations in the frequency of somatic variants and under most of the examined scenarios was estimated to be in the range of a few hundreds. Average genomic nucleotide diversity was 0.00398. Assuming neutral evolution and mutation-drift equilibrium, the somatic mutation rate was estimated in the 10−5− 10−7range. Alternatively, we estimatedNeand somaticμfrom temporal changes in nucleotide diversityπwithout the assumption of equilibrium. This second method suggested even smallerNeand largerμ. A key unknown parameter in our model on which estimates ofNeandμdepend isg, the ratio of cellular to organismal generations determined by tissue turnover rate. Small effective number of propagating stem cells might contribute to reducing reproductive conflicts in clonal organisms.
Heading choices of flyingDrosophilaunder changing angles of polarized light
Authors: Mathejczyk Thomas F. , Wernet Mathias F. 
Published: June 2019

SummaryMany navigating insects include the celestial polarization pattern as an additional visual cue to orient their travels. Spontaneous orientation responses of both walking and flying fruit flies (Drosophila melanogaster) to linearly polarized light have previously been demonstrated. Using newly designed modular flight arenas consisting entirely of off-the-shelf parts and 3D-printed components we present individual flying flies with a slow and continuous rotational change in the incident angle of linear polarization. Under such open-loop conditions, single flies choose arbitrary headings with respect to the angle of polarized light and show a clear tendency to maintain those chosen headings for several minutes, thereby adjusting their course to the slow rotation of the incident stimulus. Importantly, flies show the tendency to maintain a chosen heading even when two individual test periods under a linearly polarized stimulus are interrupted by an epoch of unpolarized light lasting several minutes. Finally, we show that these behavioral responses are wavelength-specific, existing under polarized UV stimulus while being absent under polarized green light. Taken together, these findings provide further evidence supporting Drosophila’s abilities to use celestial cues for visually guided navigation and course correction.
Left prefrontal impact links subthalamic stimulation with depressive symptoms
Authors: Irmen Friederike , Horn Andreas , Mosley Philip , Perry Alistair , Petry-Schmelzer Jan Niklas , Dafsari Haidar S. , Barbe Michael , Visser-Vandewalle Veerle , Schneider Gerd-Helge , Li Ningfei , Kübler Dorothee , Wenzel Gregor , Kühn Andrea 
Published: June 2019

AbstractObjectiveSubthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson’s Disease (PD) not only stimulates focal target structures but also affects distributed brain networks. The impact this network modulation has on non-motor DBS effects is not well characterized. By focusing on the affective domain, we systematically investigate the impact of electrode placement and associated structural connectivity on changes in depressive symptoms following STN-DBS which have been reported to improve, worsen or remain unchanged.MethodsDepressive symptoms before and after STN-DBS surgery were documented in 116 PD patients from three DBS centers (Berlin, Queensland, Cologne). Based on individual electrode reconstructions, the volumes of tissue activated (VTA) were estimated and combined with normative connectome data to identify structural connections passing through VTAs. Berlin and Queensland cohorts formed a training and cross-validation dataset used to identify structural connectivity explaining change in depressive symptoms. The Cologne data served as test-set for which depressive symptom change was predicted.ResultsStructural connectivity was linked to depressive symptom change under STN-DBS. An optimal connectivity map trained on the Berlin cohort could predict changes in depressive symptoms in Queensland patients and vice versa. Furthermore, the joint training-set map predicted changes in depressive symptoms in the independent test-set. Worsening of depressive symptoms was associated with left prefrontal connectivity.InterpretationFibers linking the STN electrode with left prefrontal areas predicted worsening of depressive symptoms. Our results suggest that for the left STN-DBS lead, placement impacting fibers to left prefrontal areas should be avoided to maximize improvement of depressive symptoms.
Quickly fading afterimages: hierarchical adaptations in human perception
Authors: Klinger Madeline E. , Kell Christian A. , Nikolić Danko 
Published: June 2019

AbstractAfterimages result from a prolonged exposure to still visual stimuli. They are best detectable when viewed against uniform backgrounds and can persist for multiple seconds. Consequently, the dynamics of afterimages appears to be slow by their very nature. To the contrary, we report here that about 50% of an afterimage intensity can be erased rapidly—within less than a second. The prerequisite is that subjects view a rich visual content to erase the afterimage; fast erasure of afterimages does not occur if subjects view a blank screen. Moreover, we find evidence that fast removal of afterimages is a skill learned with practice as our subjects were always more effective in cleaning up afterimages in later parts of the experiment. These results can be explained by a tri-level hierarchy of adaptive mechanisms, as has been proposed by the theory of practopoiesis.
Is it Time to Switch Your T1W Sequence? Assessing the Impact of Prospective Motion Correction on the Reliability and Quality of Structural Imaging
Authors: Ai Lei , Craddock R. Cameron , Tottenham Nim , Dyke Jonathan P , Lim Ryan , Colcombe Stanley , Milham Michael , Franco Alexandre R. 
Published: June 2019

AbstractNew large neuroimaging studies, such as the Adolescent Brain Cognitive Development study (ABCD) and Human Connectome Project (HCP) Development studies are adopting a new T1-weighted imaging sequence with prospective motion correction (PMC) in favor of the more traditional 3-Dimensional Magnetization-Prepared Rapid Gradient-Echo Imaging (MPRAGE) sequence. Here, we used a developmental dataset (ages 5-21, N=348) from the Healthy Brain Network (HBN) Initiative to directly compare two widely used MRI structural sequences: one based on the Human Connectome Project (MPRAGE) and another based on the ABCD study (MPRAGE+PMC). We aimed to determine if the morphometric measurements obtained from both protocols are equivalent or if one sequence has a clear advantage over the other. The sequences were also compared through quality control measurements. Inter- and intra-sequence reliability were assessed with another set of participants (N=71) from HBN that performed two MPRAGE and two MPRAGE+PMC sequences within the same imaging session, with one MPRAGE (MPRAGE1) and MPRAGE+PMC (MPRAGE+PMC1) pair at the beginning of the session and another pair (MPRAGE2 and MPRAGE+PMC2) at the end of the session. Intraclass correlation coefficients (ICC) scores for morphometric measurements such as volume and cortical thickness showed that intra-sequence reliability is the highest with the two MPRAGE+PMC sequences and lowest with the two MPRAGE sequences. Regarding inter-sequence reliability, ICC scores were higher for the MPRAGE1 - MPRAGE+PMC1 pair at the beginning of the session than the MPRAGE1 - MPRAGE2 pair, possibly due to the higher motion artifacts in the MPRAGE2 run. Results also indicated that the MPRAGE+PMC sequence is robust, but not impervious, to high head motion. For quality control metrics, the traditional MPRAGE yielded better results than MPRAGE+PMC in 5 of the 8 measurements. In conclusion, morphometric measurements evaluated here showed high inter-sequence reliability between the MPRAGE and MPRAGE+PMC sequences, especially in images with low head motion. We suggest that studies targeting hyperkinetic populations use the MPRAGE+PMC sequence, given its robustness to head motion and higher reliability scores. However, neuroimaging researchers studying non-hyperkinetic participants can choose either MPRAGE or MPRAGE+PMC sequences, but should carefully consider the apparent tradeoff between relatively increased reliability, but reduced quality control metrics when using the MPRAGE+PMC sequence.
Edifying role of corporate reputation in new issue market: Indian evidence
Authors: Kaur Amanpreet , Singh Balwinder 
Published: June 2019

PurposeThe purpose of this paper is to examine the relationship between corporate reputation and initial public offering (IPO) underpricing for a sample of 269 IPOs hitting the Indian capital market for the first time during the period ranging from April 1, 2007 to November 8, 2016.Design/methodology/approachThe study is based on secondary data (of 269 Indian companies going public) obtained from websites of capital market, Chittorgarh and Securities and Exchange Board of India (from where prospectus of each company was downloaded individually to extract data on financial variables). The study devises the technique of multivariate regression analysis to arrive at the results.FindingsThe results of the study reveal that corporate reputation serves as a signal to naive investors that assures them of issuer company’s credibility, resulting in lower underpricing. In addition to it, the study also observes the level of gender diversity on Indian boards. It is disappointing to notice low level of female representation on Indian boards and the improvement if any made in the number of female directors on Indian boards is due to provisions of new companies’ act, 2013 that mandates at least one women director on the board of every listed company. Thus, females do not constitute a critical mass on Indian boards.Research limitations/implicationsThe current study scrutinizes the impact of corporate reputation on IPO underpricing only. Furthermore, the study analyzes the underpricing of only book built IPOs. Incorporating both book built and fixed price IPOs could have provided better insights into the issue.Practical implicationsThe study outlines significant implications for managers of issuer company to portray company’s own reputation as a signal instead of showcasing borrowed reputation of external agents at the crucial juncture of going public.Originality/valueMany signals portraying quality of the offering are sent by issuer company in public arena to make IPO launch a successful event. Among many such signals like underwriting reputation, auditor reputation, director’s and CEO’s reputation, the corporate audience has started giving more impetus to issuer company’s own reputation. Thus, financial academia witnessed a paradigm shift from external agents reputation to internal agent’s reputation and now the loci of interest has shifted to company’s own reputation. Giving emphasis to corporate reputation seems more relevant in emerging economies like India where naive investors rely on their own judgments while making investment decision who take clue from various signals to infer quality of the offer. It is momentous to observe whether reputation of the company acts as a conspicuous signal to decipher IPO quality. Furthermore, there hardly exists any empirical research directly examining the impact of corporate reputation on IPO underpricing in the Indian context. Hence, the present study is a modest attempt to fill this gap in literature.
Diversification-based learning simulated annealing algorithm for hub location problems
Authors: Rathore Himanshu , Nandi Shirsendu , Pandey Peeyush , Singh Surya Prakash 
Published: June 2019

Purpose
The purpose of this paper is to examine the efficacy of diversification-based learning (DBL) in expediting the performance of simulated annealing (SA) in hub location problems.

Design/methodology/approach
This study proposes a novel diversification-based learning simulated annealing (DBLSA) algorithm for solving p-hub median problems. It is executed on MATLAB 11.0. Experiments are conducted on CAB and AP data sets.

Findings
This study finds that in hub location models, DBLSA algorithm equipped with social learning operator outperforms the vanilla version of SA algorithm in terms of accuracy and convergence rates.

Practical implications
Hub location problems are relevant in aviation and telecommunication industry. This study proposes a novel application of a DBLSA algorithm to solve larger instances of hub location problems effectively in reasonable computational time.

Originality/value
To the best of the author’s knowledge, this is the first application of DBL in optimisation. By demonstrating its efficacy, this study steers research in the direction of learning mechanisms-based metaheuristic applications.
A rapid stress calculation method for short flexspline harmonic drive
Authors: Wang Shuang , Jiang Gedong , Mei Xuesong , Zou Chuang , Zhang Xian , Zhang Hao 
Published: June 2019

Purpose
Because of the compact structure, short flexspline (FS) harmonic drive (HD) is increasingly used. The stress calculation of FS is very important in design and optimization of HD system. This paper aims to study the stress calculation methods for short FS, based on mechanics analysis and finite element method (FEM).

Design/methodology/approach
A rapid stress calculation method, based on mechanics analysis, is proposed for the short FS of HD. To verify the stress calculation precision of short FS, a complete finite element model of HD is established. The results of stress and deformation of short FS in different lengths are solved by FEM.

Findings
Through the rapid calculation method, the analytical relationship between circumferential stress and length of cylinder was obtained. And the circumferential stress has proportional relation with the reciprocal of squared length. The FEM results verified that the rapid stress calculation method could obtain accurate results.

Research limitations/implications
The rapid mechanics analysis method is practiced to evaluate the strength of FS at the design stage of HD. And the complete model of HD could contribute to improving the accuracy of FEM results.

Originality/value
The rapid calculation method is developed based on mechanics analysis method of cylinder and equivalent additional bending moment model, through which the analytical relationship between circumferential stress and length of cylinder was obtained. The complete three-dimensional finite element model of HD takes the stiffness of bearing into consideration, which can be used in the numerical simulation in the future work to improve the accuracy.
A novel scheme for imposing periodic boundary conditions on RVE in second-order computational homogenization for granular material
Authors: Li Xikui , Zhang Songge , Duan Qinglin 
Published: June 2019

Purpose
This paper aims to present a novel scheme for imposing periodic boundary conditions with downscaled macroscopic strain measures of gradient Cosserat continuum on the representative volume element (RVE) of discrete particle assembly in the frame of the second-order computational homogenization methods for granular materials.

Design/methodology/approach
The proposed scheme is based on the generalized Hill’s lemma of gradient Cosserat continuum and the incremental non-linear constitutive relation condensed to the peripheral particles of the RVE of discrete particle assembly. The generalized Hill’s lemma conducts to downscale the macroscopic strain or stress measures and to impose the periodic boundary conditions on the RVE boundary so that the Hill-Mandel energy equivalence condition is ensured. Because of the incremental non-linear constitutive relation condensed to the peripheral particles of the RVE, the periodic boundary displacement and traction constraints together with the downscaled macroscopic strains and strain gradients, micro-rotations and curvatures are imposed in the point-wise sense without the need of introducing the Lagrange multipliers for enforcing the periodic boundary displacement and traction constraints in a weak sense.

Findings
Numerical results demonstrate that the applicability and effectiveness of the proposed scheme in imposing the periodic boundary conditions on the RVE. The results of the RVE subjected to the periodic boundary conditions together with the displacement boundary conditions in the second-order computational homogenization for granular materials provide the desired estimations, which lie between the upper and the lower bounds provided by the displacement and the traction boundary conditions imposed on the RVE respectively.

Research limitations/implications
Each grain in the particulate system under consideration is assumed to be rigid and circular.

Practical implications
The proposed scheme for imposing periodic boundary conditions on the RVE can be adopted solely for estimating the effective mechanical properties of granular materials and/or integrated into the frame of the second-order computational homogenization method with a nested finite element method-discrete element method solution procedure for granular materials. It will tend to provide, at least theoretically, more reasonable results for effective material properties and solutions of a macroscopic boundary value problem simulated by the computational homogenization method.

Originality/value
This paper presents a novel scheme for imposing periodic boundary conditions with downscaled macroscopic strain measures of gradient Cosserat continuum on the RVE of discrete particle assembly for granular materials without need of introducing Lagrange multipliers for enforcing periodic boundary conditions in a weak (integration) sense.
Work-to-family and family-to-work conflicts among employed single parents in Germany
Authors: Reimann Mareike , Marx Charlotte Katharina , Diewald Martin 
Published: June 2019

PurposeThe purpose of this paper is to examine whether and how employed single-parents differ from parents in two-parent families in their experience of work-to-family conflict (WFC) and family-to-work conflict (FWC). Looking at job-related as well as family-related demands and resources, this research investigated to what degree these demands and resources contribute to differences in WFC and FWC, how their relevance in predicting conflicts varies between single parents and other parents and the role of compositional differences in work and family demands and resources.Design/methodology/approachCross-sectional linear regression analyses were applied to analyze a random sample of employees in large work organizations in Germany. The sample included 3,581 parents with children up to the age of 25, of whom 346 were single parents.FindingsThe results indicated that single parents face more FWC, but not more WFC, than other parents. For all parents, job demands such as overtime, supervising responsibilities and availability expectations were associated with higher levels of WFC, whereas job resources such as job autonomy, support from supervisors and flexible working hours were associated with lower levels of WFC. In predicting FWC, family demands and resources played only a minor role. However, results provide only scant evidence of differences between single parents and other parents in terms of the effects of job and family demands and resources.Originality/valueThis study offers interesting insights into the diversity of WFC and FWC experiences in Germany. It provides first evidence of the impact of job and family demands and resources on both directions of work–family conflicts among employed single parents as a specific social group.