bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of an Algebraic Reynolds Stress Model for Simulation of Wall-Bounded Turbulent Flows With and Without Buoyancy Effects
Authors: Jamal Tausif , Walters D. Keith
Published: October 2020

Complex turbulent flows such as those encountered in nuclear reactor cooling systems pose considerable challenges for computational fluid dynamics (CFD) simulation using traditional Reynolds-averaged Navier-Stokes (RANS) models based on the linear eddy-viscosity modeling (LEVM) framework. One particular difficulty is the use of low Prandtl number (Pr) fluids such as liquid metal coolants, which considerably alters the fluctuating thermal field and violates the Reynolds analogy upon which turbulent heat flux modeling in LEVMs is based. Although previous studies have shown that Reynolds Stress Models (RSM) offer some improvements over traditional LEVMs for flows containing complex inter-component interaction and Reynolds stress anisotropy, the added complexity, increased computational requirements, and the lack of robustness introduced by traditional RSMs do not always result in an overall improvement. This study evaluates the performance of a newly proposed Algebraic Reynolds Stress Model (ARSM) including an Algebraic Heat Flux Model (AHFM) against two industry standard RANS models, standard k-ε and realizable k-ε model, for a set of canonical test cases relevant to nuclear reactor cooling applications. Numerical simulations using the spectral element code Nek5000 are performed for fully developed channel flows with varying values of Reynolds number (Re) and Pr, both with and without the effects of buoyancy. Results are compared to Direct Numerical Simulation (DNS) data in terms of the velocity and thermal statistics. For all cases investigated, the ARSM model consistently outperforms the other RANS models in this study and it is concluded that the new ARSM model can be a suitable alternative to traditional LEVMs for complex turbulent flows without significant penalty to efficiency and robustness that are commonly associated with traditional RSMs.
Airflow Characterization Combined With 3D Reconstruction of Rabbit Vocal Cord Based on In-Vivo Phonatory Experiments
Authors: Lou Zhipeng , Wang Junshi , Daniero James J. , Dong Haibo , Xi Jinxiang
Published: October 2020

In this paper, a numerical approach combined with experiments is employed to characterize the airflow through the vocal cord. Rabbits are used to perform in vivo magnetic resonance imaging (MRI) experiments and the MRI scan data are directly imposed for the three-dimensional (3D) reconstruction of a 3D high-fidelity model. The vibration modes are observed via the in vivo high-speed videoendoscopy (HSVM) technique, and the time-dependent glottal height is evaluated dynamically for the validation of the 3D reconstruction model. 72 sets of rabbit in vivo high-speed recordings are evaluated to achieve the most common vibration mode. The reconstruction is mainly based on MRI data and the HSVM records are supporting and validate the 3D model. A sharp-interface immersed-boundary-method (IBM)-based compressible flow solver is employed to compute the airflow. The primary purpose of the computational effort is to characterize the influence of the vocal folds that applied to the airflow and the airflow-induced phonation. The vocal fold kinematics and the vibration modes are quantified and the vortex structures are analyzed under the influence of vocal folds. The results have shown significant effects of the vocal fold height on the vortex structure, vorticity and velocity. The reconstructed 3D model from this work helps to bring insight into further understanding of the rabbit phonation mechanism. The results provide potential improvement for diagnosis of human vocal fold dysfunction and phonation disorder.
MPI Parallelization for Two-Way Coupled Euler-Lagrange Simulation of Microbubble Enhanced HIFU
Authors: Ma Jingsen , Gnanaskandan Aswin , Hsiao Chao-Tsung , Chahine Georges L.
Published: October 2020

Microbubble enhanced High Intensity Focused Ultrasound (HIFU) is of great interest to tissue ablation for tumor treatment such as in liver and brain cancers, in which ultrasonic contrast agent microbubbles are injected to the targeted region to promote local heating while reducing pre-focal damage. To accurately characterize the acoustic and thermal fields during this process, a compressible Euler-Lagrange model is used. The non-linear ultrasound field is modeled using compressible N-S equations on an Eulerian grid, while the microbubbles are tracked as discrete singularities in a Lagrangian fashion with their dynamics computed. Their intimate coupling is realized through the local void fraction, which is computed from the instantaneous bubble volumes and locations, and then fed to the fluid continuum model.

Owing to demanding computational cost in real applications, schemes for significant speedup are highly desirable. We present here a MPI parallelization scheme based on domain decomposition for both the continuum fluid and the discrete bubbles. The Eulerian computational domain is subdivided into several subdomains having each the same number of grids, while the bubbles are subdivided based on their locations corresponding to each subdomain. During each computation time step, MPI processors, each handling one subdomain, are 1) first used to execute the fluid computation, and 2) then to execute the bubble computations, 3) followed by the coupling procedure, which maps the void fraction from the Lagrangian bubble solutions into the Eulerian grids.

Steps 1) and 2) are relatively straightforward by routinely following regular MPI procedures. However, step 3) becomes challenging as the effect of the bubbles through the void fraction at an Eulerian point near a subdomain border will require information from bubbles located in different subdomains. Similarly, a bubble near a border between subdomains will spread its contribution to the void fraction of different subdomains. This is addressed by a special utilization of ghost cells surrounding each fluid subdomain, which allows bubbles to spread their void fraction effects across subdomain edges without the need of exchanging directly bubble information between subdomains and significantly increasing overhead. This void fraction implementation is verified by gas volume conservation before and after spreading the bubble effects. Other bubble effects such as thermal effects are handled in a similar way.

This parallelization scheme is validated and illustrated on a typical microbubble enhanced HIFU problem, followed by parallelization scaling tests and efficiency analysis.
Application of Advanced RANS Turbulence Models for the Prediction of Turbomachinery Flows
Authors: Casartelli Ernesto , Mangani Luca , Roos David , Del Rio Armando
Published: October 2020

The simulation models used in the design process of modern turbo-machines are becoming increasingly complex. Nevertheless, the steady-state RANS approach is still the mostly used method for CFD computations. However, detailed flow information is more and more required for further improving the performance and extend the operating range. Turbulence modeling has becoming therefore a key issue in this context. The increased computer power already available would enable the use of more sophisticated turbulence models than standard two equation ones, such as SST k-omega and k-epsilon. These, despite their shortcomings, are still predominant in the field, since more advanced models often lead to numerical instabilities in the simulations. The most important shortcomings can be related to either boundary layer effects or mixing process in the channels. In order to improve the predictions considering boundary layer effects, like impingement or large pressure gradients in flow direction, various derivations of four equations models were investigated. Using an additional transport equation for the wall normal Reynolds-stress component and an elliptic equation for near-wall effects, they improve the results for this kind of flows. Considering the accurate prediction of mixing processes, like (1) the interaction of tip-clearance vortices with the main flow or (2) off-design conditions, the focus was oriented to the anisotropy present in the turbulent structures. Standard models are often not sufficient to predict accurately vortices, which can have a huge impact on the performance, since based on the assumption of isotropic turbulence. Accordingly, they tend to dissipate and diffuse the vortices too quickly. Improved models, which take the anisotropic nature of the Reynolds-stresses into account, can help in this context. The models can thereby introduce the additional anisotropy via an explicit algebraic expression, or model directly the transport equations for the Reynolds-stresses. In order to improve the predictions using advanced turbulence models a particularly robust framework based on a pressure-based fully coupled approach was used.

The goal of this work is the development and testing of improved models for the application in turbo-machinery. The focus lies thereby on near-wall behavior and mixing / vortex dissipation. The assessment of the models is exemplarily used on the centrifugal compressor open-case Radiver with vaned diffuser.
Predicting Solid Particle Erosion and Uncertainty in Elbows by Artificial Intelligence Methods
Authors: Karimi Soroor , Xu Bohan , Asgharpour Alireza , Shirazi Siamack A. , Sen Sandip
Published: October 2020

AI approaches include machine learning algorithms in which models are trained from existing data to predict the behavior of the system for previously unseen cases. Recent studies at the Erosion/Corrosion Research Center (E/CRC) have shown that these methods can be quite effective in predicting erosion. However, these methods are not widely used in the engineering industries due to the lack of work and information in this area. Moreover, in most of the available literature, the reported models and results have not been rigorously tested. This fact suggests that these models cannot be fully trusted for the applications for which they are trained. Therefore, in this study three machine learning models, including Elastic Net, Random Forest and Support Vector Machine (SVM), are utilized to increase the confidence in these tools. First, these models are trained with a training data set. Next, the model hyper-parameters are optimized by using nested cross validation. Finally, the results are verified with a test data set. This process is repeated several times to assure the accuracy of the results. In order to be able to predict the erosion under different conditions with these three models, six main variables are considered in the training data set. These variables include material hardness, pipe diameter, particle size, liquid viscosity, liquid superficial velocity, and gas superficial velocity. All three studied models show good prediction performances. The Random Forest and SVM approaches, however, show slightly better results compared to Elastic Net. The performance of these models is compared to both CFD erosion simulation results and also to Sand Production Pipe Saver (SPPS) results, a mechanistic erosion prediction software developed at the E/CRC. The comparison shows SVM prediction has a better match with both CFD and SPPS. The application of AI model to determine the uncertainty of calculated erosion is also discussed.
Multiphase Flow Development on Single Particle Migration in Low Reynolds Number Fluid Domains
Authors: Pourghasemi Mahyar , Fathi Nima , Vorobieff Peter , Ahmadi Goodarz , Anderson Kevin R.
Published: October 2020

Here we present the results of the newly developed Eulerian-Lagrangian model to simulate both the primary and the secondary phases coupled in a transient analysis. A set of two a-dimensional, transient linear shear flow at low Reynolds numbers was considered, and the effect of shearing rate on a suspended buoyant spherical solid particle was analyzed. The rotation and displacement of the solid particle are considered in the model, and the effect of the secondary phase on the primary phase is also evaluated at each time step without any simplification. In order to overcome the existing discontinuity at the interface between secondary and primary phases in this Eulerian-Lagrangian approach, the interface between the solid particle and the fluid phase is replaced by a kernel function creating a smooth profile from the solid into the liquid with a predefined thickness. Several simulations were performed, and the reliability of the developed model was assessed. The global deviation grid convergence index (GCI) approach was employed to perform solution verification. The observed order of accuracy of the primary phase solver approaches 2, consistent with the formal order of accuracy of the applied discretization scheme. The obtained velocity profiles from the computational analyses show excellent agreement with the analytical solution confirming the reliability of the single-phase flow solver. To validate the computational results for the multiphase flow solver, we used the experimental data from our newly developed linear shear flow apparatus with suspended buoyant particles.
Effects of Taper Configurations on Heat Transfer and Pressure Drop in Single-Phase Flows in Microgaps
Authors: Moreira Debora C. , Ribatski Gherhardt , Kandlikar Satish G.
Published: October 2020

This paper presents a comparison of heat transfer and pressure drop during single-phase flows inside diverging, converging, and uniform microgaps using distilled water as the working fluid. The microgaps were created on a plain heated copper surface with a polysulfone cover that was either uniform or tapered with an angle of 3.4°. The average gap height was 400 microns and the length and width dimensions were 10 mm × 10 mm, resulting in an average hydraulic diameter of approximately 800 microns for all configurations. Experiments were conducted at atmospheric pressure and the inlet temperature was set to 30 °C. Heat transfer and pressure drop data were acquired for flow rates varying from 57 to 485 ml/min and the surface temperature was monitored not to exceed 90 °C to avoid bubble nucleation, so the heat flux varied from 35 to 153 W/cm2 depending on the flow rate. The uniform configuration resulted in the lowest pressure drop, and the diverging one showed slightly higher pressure drop values than the converging configuration, possibly because the flow is most constrained at the inlet section, where the fluid is colder and presents higher viscosity. In addition, a minor dependence of pressure drop with heat flux was observed due to temperature dependent properties. The best heat transfer performance was obtained with the converging configuration, which was especially significant at low flow rates. This behavior could be explained by an increase in the heat transfer coefficient due to flow acceleration in converging gaps, which compensates the decrease in temperature difference between the fluid and the surface due to fluid heating along the gap. Overall, the comparison between the three configurations shows that converging microgaps have better performance than uniform or diverging ones for single-phase flows, and such effect is more pronounced at lower flow rates, when the fluid experiences higher temperature changes.
Evolution of Heat Transfer in Pool Boiling in Contaminated Water
Authors: Graham Jacob , Hawa Angelo , Weisensee Patricia
Published: October 2020

Boiling heat transfer serves as an efficient mechanism to dissipate large amounts of thermal energy due to the latent heat of phase change. In academic studies, typically ultra-pure deionized (DI) water is used to avoid contamination. However, in industrial and commercial settings, the working fluid might be contaminated with sediments, dust, salts, or organic matter. Long-term boiling processes in non-DI water cause substantial build-up of a stable layer of deposit that dramatically reduces the heat transfer coefficient. Therefore, heating applications in a contaminated medium demand strategies to prevent such fouling. Here, we studied the use of lubricant infused surfaces (LIS) and their ability to possibly minimize the deposition of calcium sulfate. Aluminum samples were infused with Krytox 102 oil and the heat transfer coefficient was investigated at a vertical and horizontal surface orientation. Fouling effects were introduced by pool boiling for 7.5 hours in a 6.97 mM calcium sulfate solution at constant heat flux. Heat flux curves for both plain aluminum and LIS were calibrated before contamination. Initially, the LIS was unable to support a nucleate phase and transitioned directly from liquid convection to film boiling heat transfer. Upon partial degradation of the lubricant layer during long-run experiments, nucleate boiling ensued. Over 7.5 hours, the heat transfer coefficient of each sample (Al and LIS) degraded between 5.4% and 7.9% with no significant correlation with either lubricant treatment or surface orientation. Post boiling profilometry was conducted on each sample to characterize the thickness and distribution of the calcium sulfate layer. In these experiments, the plain aluminum surface outperformed the LIS at both orientations in minimizing calcium layer thickness. The LIS oriented vertically outperformed the LIS oriented horizontally.
A General Correlation for Frictional Pressure Drop of Flow Boiling in Plate Heat Exchangers
Authors: Tang Weiyu , Lv Tong , Zheng Boren , Li Wei
Published: October 2020

Plate heat exchangers are widely used in various industries for many years. The corrugated channels on the plates effectively enhance the turbulence of flow boiling and complicate the prediction of pressure drop. This paper presents a brief review about the influence factors of frictional pressure drop during flow boiling in plate heat exchangers. Experimental data points of frictional pressure drop were collected from previous literatures to develop a general correlation. The database contained 454 data points, covering eight refrigerants, mass flux range 5.5–137 kg m-2 s-1, heat flux 0–30 kW m-2, vapor quality 0.07–0.95, saturation pressure 0.11–2.7 MPa, chevron angle 30°–70° and hydraulic diameter 1.7–5.4 mm. In this work, several existing correlations were compared with the database, and all of them seem fail to give an acceptable prediction. A new correlation was proposed with multiple regression analysis in terms of two-phase Fanning friction factor. The new method showed good agreement and predicted 63.2% and 92.9% of data points within ±30% and ±50% errors, respectively.
Steam Flow Condensation on Superhydrophobic Surfaces in a High Aspect Ratio Microchannel
Authors: Mohammadpour Chehrghani Mirvahid , Abbasiasl Taher , Gharib Ghazaleh , Kosar Ali , Khalili Sadaghiani Abdolali
Published: October 2020

Steam flow condensation has a wide range of applications in the industry such as in air conditioning, refrigeration, and thermal power plants. Condensation of steam on highly hydrophobic surfaces has resulted in notable heat transfer improvement compared to conventional hydrophilic surfaces. Dropwise condensation and increased droplet mobility are the main reason for thermal performance enhancement of superhydrophobic surfaces. Although there are considerable reports of enhanced thermal transport behavior of highly hydrophobic surfaces on steam condensation, the literature lacks sufficient investigation on flow condensation of steam, such as the effect of average vapor quality change on heat transfer rate.

Unlike gravity-driven droplet departure in quiescent dropwise condensation, droplet departure sizes in flow condensation are governed by flow-droplet shear forces and droplet-surface adhesive forces. This work experimentally investigates steam flow condensation on nanotextured highly hydrophobic and slightly hydrophobic surfaces. The experimental setup consists of a reservoir, boiler, superheater, condensation chamber (test section), pre-condenser (to adjust the inlet quality), a post condenser, and a pump. A high aspect ratio microchannel was used as the test section. Different mass fluxes and inlet vapor qualities were used for the experimentations. Visualization studies were performed to analyze droplet dynamics such as droplet departure and coalescence in flow condensation. It is shown that for both surfaces increase condensation heat transfer coefficient were a function of both average quality and mass flux. Increase in mass flux from G = 8 kg/m2s to G = 14 kg/m2s, resulted in 65% and 60% enhancement in condensation heat transfer coefficient of slightly hydrophobic and highly hydrophobic surfaces respectively.
Numerical Prediction of Dropwise Condensation Performances Over Hybrid Surfaces, Under the Action of Gravity and Vapor Shear
Authors: Suzzi Nicola , Croce Giulio , D’Agaro Paola
Published: October 2020

A Lagrangian model following the history of every droplet belonging to an evolving droplets population, originally developed to simulate pattern evolution in the framework of in-flight icing phenomenon, is used in order to simulate dropwise condensation over different shaped micro-structured surfaces. Both the mechanical and the thermal energy balances are solved for every droplet, allowing to predict droplet velocity and condensing flow rate. Coalescence phenomenon is also implemented. The model in the present form is an evolution of the code presented at ICNMM 2019, introducing the effect of vapor shear, a physical model of the evolution of the dynamic contact angle during droplet growth and a prediction of condensing flow rate through the solution of thermal energy balance, thus taking into account the influence of the droplet size. Shared memory parallelization is also carried out decomposing the computational domain into different subdomains, allowing the efficient simulation of a larger number of droplets.

Here, the model is validated and used to predict the heat transfer performance of hybrid condensation surfaces, both plane and curved, under the action of both gravity and vapor shear. Starting from literature proposals, several patterns, each characterized by a complex composition of patches with different wettabilities, are numerically investigated and the configuration ensuring the best heat transfer performance and liquid drainage is identified. The sensitivity of the solution with respect to the uncertainty on the estimate of some parameters, such as nucleation density, is also discussed.
From People to
Panthera
: Natural SARS-CoV-2 Infection in Tigers and Lions at the Bronx Zoo
Authors: McAloose Denise , Laverack Melissa , Wang Leyi , Killian Mary Lea , Caserta Leonardo C. , Yuan Fangfeng , Mitchell Patrick K. , Queen Krista , Mauldin Matthew R. , Cronk Brittany D. , Bartlett Susan L. , Sykes John M. , Zec Stephanie , Stokol Tracy , Ingerman Karen , Delaney Martha A. , Fredrickson Richard , Ivančić Marina , Jenkins-Moore Melinda , Mozingo Katie , Franzen Kerrie , Bergeson Nichole Hines , Goodman Laura , Wang Haibin , Fang Ying , Olmstead Colleen , McCann Colleen , Thomas Patrick , Goodrich Erin , Elvinger François , Smith David C. , Tong Suxiang , Slavinski Sally , Calle Paul P. , Terio Karen , Torchetti Mia Kim , Diel Diego G.
Published: October 2020

The human-animal-environment interface of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important aspect of the coronavirus disease 2019 (COVID-19) pandemic that requires robust One Health-based investigations. Despite this, few reports describe natural infections in animals or directly link them to human infections using genomic data. In the present study, we describe the first cases of natural SARS-CoV-2 infection in tigers and lions in the United States and provide epidemiological and genetic evidence for human-to-animal transmission of the virus. Our data show that tigers and lions were infected with different genotypes of SARS-CoV-2, indicating two independent transmission events to the animals. Importantly, infected animals shed infectious virus in respiratory secretions and feces. A better understanding of the susceptibility of animal species to SARS-CoV-2 may help to elucidate transmission mechanisms and identify potential reservoirs and sources of infection that are important in both animal and human health.
Ancestral Reconstructions Decipher Major Adaptations of Ammonia-Oxidizing Archaea upon Radiation into Moderate Terrestrial and Marine Environments
Authors: Abby Sophie S. , Kerou Melina , Schleper Christa
Published: October 2020

Unlike all other archaeal lineages, ammonia-oxidizing archaea (AOA) of the phylum
Thaumarchaeota
are widespread and abundant in all moderate and oxic environments on Earth. The evolutionary adaptations that led to such unprecedented ecological success of a microbial clade characterized by highly conserved energy and carbon metabolisms have, however, remained underexplored. Here, we reconstructed the genomic content and growth temperature of the ancestor of all AOA, as well as the ancestors of the marine and soil lineages, based on 39 available complete or nearly complete genomes of AOA.
Single-Inclusion Kinetics of
Chlamydia trachomatis
Development
Authors: Chiarelli Travis J. , Grieshaber Nicole A. , Omsland Anders , Remien Christopher H. , Grieshaber Scott S.
Published: October 2020

Chlamydia trachomatis
is an obligate intracellular bacterium that can cause trachoma, cervicitis, urethritis, salpingitis, and pelvic inflammatory disease. To establish infection in host cells,
Chlamydia
must complete a multiple-cell-type developmental cycle. The developmental cycle consists of specialized cells, the EB cell, which mediates infection of new host cells, and the RB cell, which replicates and eventually produces more EB cells to mediate the next round of infection. By developing and testing mathematical models to discriminate between two competing hypotheses for the nature of the signal controlling RB-to-EB cell type switching, we demonstrate that RB-to-EB development follows a cell-autonomous program that does not respond to environmental cues. Additionally, we show that RB-to-EB development is a function of chlamydial growth and division. This study serves to further our understanding of the chlamydial developmental cycle that is central to the bacterium’s pathogenesis.
Effect of birth order on stereoacuity in Chinese preschool children: a cross-sectional study
Authors: Han Shu , Zhang Xiaohan , Li Rui , Tong Haohai , Zhao Xiaoyan , Wang Yue , Hao Qingfeng , Huang Dan , Zhu Hui , Zhang Xiaojun , Liu Hu
Published: October 2020

Objective

This study aimed to investigate the relationship between birth order and stereoacuity among Chinese children aged 60–72 months.

Design

Cross-sectional.

Participants

1342 children with complete data on the questionnaire, stereoacuity and refraction were included.

Results

The mean stereoacuity was 53.2±1.7, 56.9±1.9 and 60.9±1.5 s of arc in the first-born group, second-born group and third-born group, respectively. Lower birth order was significantly correlated with better stereoacuity (p=0.036). Third-borns (OR=3.02, p=0.027) were at higher risk of having subnormal stereoacuity compared with first-borns in the multivariate analysis.

Conclusion

Later-borns had poorer stereoacuity than first-borns.
Population-based rapid assessment of avoidable blindness survey in Sohag governorate in Egypt
Authors: AlSawahli Heba , McCormick Ian , Mpyet Caleb D , Ezzelarab Gamal , Shalaby Mohammad
Published: October 2020

Objectives

To determine the prevalence and causes of blindness and vision impairment, and the coverage and quality of cataract surgical services, among population aged 50 years and older in Sohag governorate in Egypt.

Design

A population-based cross-sectional survey using two-stage cluster random sampling following the rapid assessment of avoidable blindness methodology.

Setting

A community-based survey conducted by six teams of ophthalmologists, assistants and local guides. Enrolment and examination were door-to-door in selected clusters.

Participants

Using 2016 census data, 68 population units were randomly selected as clusters (of 60 people) with probability proportionate to population size. Anyone aged 50 years and older, residing in a non-institutional setting in a cluster for at least 6 months, was eligible to participate.

Primary and secondary outcome measures

The prevalence and causes of blindness and vision impairment. Secondary outcomes were CSC and effectiveness and participant-reported barriers to cataract surgery.

Results

Of 4078 participants enrolled, 4033 (98.9%) were examined. The age-adjusted and sex-adjusted prevalence of blindness, severe vision impairment and moderate vision impairment were 5.9% (95% CI 4.8% to 6.9%), 4.7% (95% CI 3.8% to 5.7%) and 18.9% (95% CI 16.8% to 21.0%), respectively. Cataract caused most of blindness (41.6%), followed by non-trachomatous corneal opacity (15.7%) and posterior segment diseases (14.5%). Cataract surgical coverage (CSC) for persons for visual acuity <3/60 was 86.8%, the proportion of cataract surgeries with poor visual outcome was 29.5% and effective CSC (eCSC) was 44.9%. eCSC was lower in women than men. The most frequently reported barrier to surgery was cost (51.5%).

Conclusions

The prevalence of blindness in Sohag governorate is higher than districts in other middle-income countries in the region. CSC was high; however, women suffer worse quality-corrected CSC than men. The quality of cataract surgery needs to be addressed, while health system strengthening across government and private settings could alleviate financial barriers.
Asymmetric crypt fission in sessile serrated lesions
Authors: Rubio Carlos A , Schmidt Peter T
Published: October 2020

Objective

Sessile serrated lesions without dysplasia (SSL-ND) are epitomised by dilated crypts with epithelial serrations and architectural distortions portraying boot-shapes, L-shapes or inverted-T shapes. Recently, crypts in asymmetric fission were detected in SSL-ND. The purpose was to assess the frequency of crypts in asymmetric fission in a cohort of SSL-ND.

Methods

The frequency of crypts in fission was assessed in 60 SSL-ND, the distribution of cell proliferation in 48 SSL-ND and the expression of maspin, a tumour-suppressor protein, in 29 SSL-ND.

Results

Out of the 60 SSL-ND, 40 (66.7%) showed crypts in fission: 39 (65%) SSL-ND had crypts in asymmetric fission and one SSL-ND (1.7%), in symmetric fission (p<0.05). Of 1495 crypts recorded in the 60 SSL-ND, 73 (4.9%) were in asymmetric fission but only one (0.06%), in symmetric fission (p<0.05). Out of the 48 Ki67-immunostained SSL-ND,15 (31%) showed randomly distributed proliferating cell-domains. All 29 SSL-ND revealed maspin-upregulation (including crypts in asymmetric and symmetric fission). In contrast, the normal colon mucosa showed occasional single crypts in symmetric fission, proliferating cell-domains limited to the lower thirds of the crypts, absence of crypts in asymmetric fission and remained maspin negative.

Conclusions

SSL-ND thrive with crypts in asymmetric fission displaying randomly distributed proliferating cell-domains and maspin-upregulation. These histo-biological aberrations disclose pathological cryptogenesis and suggest possibly unfolding somatic mutations in SSL-ND. The present findings may open new vistas on the parameters pertinent to the susceptibility of SSL-ND to develop dysplasia and carcinoma.
Fair allocation of scarce medical resources in the time of COVID-19: what do people think?
Authors: Fallucchi Francesco , Faravelli Marco , Quercia Simone
Published: October 2020

The COVID-19 pandemic has placed an enormous burden on health systems, and guidelines have been developed to help healthcare practitioners when resource shortage imposes the choice on who to treat. However, little is known on the public perception of these guidelines and the underlying moral principles. Here, we assess on a sample of 1033 American citizens’ moral views and agreement with proposed guidelines. We find substantial heterogeneity in citizens’ moral principles, often not in line with the guidelines recommendations. As the guidelines are likely to directly affect a considerable number of citizens, our results call for policy interventions to inform people on the ethical rationale behind physicians or triage committees decisions to avoid resentment and feelings of unfairness.
F-theory and heterotic duality, Weierstrass models from Wilson lines
Authors: Chabrol Lilian
Published: October 2020

We present how to construct elliptically fibered K3 surfaces via Weierstrass models which can be parametrized in terms of Wilson lines in the dual heterotic string theory. We work with a subset of reflexive polyhedras that admit two fibers whose moduli spaces contain the ones of the $$E_{8}\times E_{8}$$

E
8

×

E
8

or $$\frac{Spin(32)}{{\mathbb {Z}}_{2}}$$

S
p
i
n
(
32
)

Z
2

heterotic theory compactified on a two torus without Wilson lines. One can then interpret the additional moduli as a particular Wilson line content in the heterotic strings. A convenient way to find such polytopes is to use graphs of polytopes where links are related to inclusion relations of moduli spaces of different fibers. We are then able to map monomials in the defining equations of particular K3 surfaces to Wilson line moduli in the dual theories. Graphs were constructed developing three different programs which give the gauge group for a generic point in the moduli space, the Weierstrass model as well as basic enhancements of the gauge group obtained by sending coefficients of the hypersurface equation defining the K3 surface to zero.
FINANCIAL DEVELOPMENT IN DEVELOPING COUNTRIES
Authors: EZEIBEKWE OBINNA FRANKLIN
Published: October 2020

What are the economic, political, institutional, socio-cultural, and geographical determinants of financial development in developing countries? This paper uses the two-way fixed effects (with clustered standard errors) and annual panel data from 1980 to 2018 for 69 developing countries in sub-Saharan Africa, Middle East and North Africa, East and South Asia, Latin America, and the Caribbean to address this question. The principal component analysis is employed to construct a financial development index based on three financial development indicators. This study builds on the previous studies by introducing new potential determinants of financial development such as the perception of corruption, and by exploring important quadratic and interaction effects. The results show that national income, trade openness, indices of political stability and Polity2 (a democracy score), perception of corruption, the predominant religion in the countries, and geographical factors such as territorial access to the sea explain the differences in the levels of financial development across countries and regions. A rise in national income leads to a higher level of financial development and countries with a high perceived level of corruption have a lower level of financial development. There is strong evidence of threshold effects as trade openness has a diminishing marginal effect on financial development while the auxiliary growth regressions show that financial development has an increasing marginal effect on national income. Of the five regions studied, East and South Asia and sub-Saharan Africa have the highest and lowest levels of financial development, respectively. Also, fuel-exporting countries, least developed countries, and landlocked countries tend to have lower levels of financial development. These results have relevant policy implications for developing countries in their continued efforts to achieve better financial development and ultimately, sustainable economic development.
Data-Mining Homogeneous Subgroups in Multiple Regression When Heteroscedasticity, Multicollinearity, and Missing Variables Confound Predictor Effects
Authors: Francoeur Richard B.
Published: October 2020

Multiple regression is not reliable to recover predictor slopes within homogeneous subgroups from heterogeneous samples. In contrast to Monte Carlo analysis, which assigns completely to the first-specified predictor the variation it shares with the remaining predictors, multiple regression does not assign this shared variation to any predictor, and it is sequestered in the residual term. This unassigned and confounding variation may correlate with specified predictors, lead to heteroscedasticity, and distort multicollinearity. I develop and test an iterative, sequential algorithm to estimate a two-part series of weighted least-square (WLS) multiple regressions for recovering the Monte Carlo predictor slopes in three homogeneous subgroups (each generated with 500 observations) of a heterogeneous sample [Formula: see text]. Each variable has a different nonnormal distribution. The algorithm mines each subgroup and then adjusts bias within it from 1) heteroscedasticity related to one, some, or all specified predictors and 2) “nonessential” multicollinearity. It recovers all three specified predictor slopes across the three subgroups in two scenarios, with one influenced also by two unspecified predictors. The algorithm extends adaptive analysis to discover and appraise patterns in field research and machine learning when predictors are inter-correlated, and even unspecified, in order to reveal unbiased outcome clusters in heterogeneous and homogeneous samples with nonnormal outcome and predictors.
Summary of the 1st ICSSP-ICGSE Joint Event
Authors: Tell Paolo , Raffo David , Huang Liguo , Steinmacher Igor , Britto Ricardo , Tüzün Eray , Clarke Paul
Published: October 2020

Having the common objective of bringing together researchers and industry practitioners to share their research ndings, experiences, and new ideas as well as sharing topics of interest, the organizing committees of the 14th International Conference on Software and System Processes (ICSSP) and the 15th International Conference on Global Software Engineering (ICGSE) ceased the opportunity to explore the idea of bringing together the two communities once it was clear that the International Conference on Software Engineering and all its co-located events had to be redesigned as online events.
Cholic Acid Protects In Vitro Neurovascular Units against Oxygen and Glucose Deprivation-Induced Injury through the BDNF-TrkB Signaling Pathway
Authors: Li Changxiang , Wang Xueqian , Yan Juntang , Cheng Fafeng , Ma Xiaona , Chen Congai , Wang Wei , Wang Qingguo
Published: October 2020

Ischemic stroke (IS) can disrupt various types of brain cells in the neurovascular unit (NVU) at both the structural and functional levels. Therefore, NVU is considered to be a more comprehensive target for the treatment of IS. It is necessary to develop drugs which targeted multiple mechanisms and cell types on NVU against IS. As a component of bile acid, cholic acid has been reported to be able to diffuse across phospholipid bilayers and further cross the blood-brain barrier (BBB). However, the effects exerted by cholic acid (CA) on the NVU after stroke remain unclear. Based on our previous research, we established and further supplemented the characteristics of the functional in vitro NVU model and its oxygen-glucose deprivation and reoxygenation (OGD/R) model. Then, we investigated the effect of CA on the maintenance of the in vitro NVU after OGD/R and further discussed the specific molecular targets that CA played a role in. For the first time, we found that CA significantly maintained BBB integrity, downregulated apoptosis, and mitigated oxidative stress and inflammation damage after OGD/R. Meanwhile, CA obviously increased the levels of brain-derived neurotrophic factor (BDNF), which were mainly secreted from astrocytes, in the coculture system after OGD/R. The results demonstrated that CA significantly increased the expression of TrkB, PI3K/Akt, MAPK/Erk, and CREB in neurons. These positive effects on the downstream proteins of BDNF were suppressed by treatment with ANA12 which is an inhibitor of TrkB. In conclusion, the present study demonstrates that CA exerted multiple protective effects on the NVU, mediated by increasing the release of BDNF and further stimulating the BDNF-TrkB-PI3K/Akt and BDNF-TrkB-MAPK/Erk signaling pathways in the context of OGD/R-induced injury. These findings indicate that CA possesses the effect of antagonizing multiple mechanisms of IS and protecting multiple cell types in NVU and may be useful as a treatment for IS.
The Association between Neutrophil‐to‐Lymphocyte Ratio and Diabetic Depression in U.S. Adults with Diabetes: Findings from the 2009‐2016 National Health and Nutrition Examination Survey (NHANES)
Authors: Wang Jie , Zhou Depu , Li Xiaokun
Published: October 2020

Objective. To determine the association between neutrophil‐to‐lymphocyte ratio (NLR) and clinically relevant depressive symptoms in people with diabetes. Methods. This cross‐sectional study was conducted among adults (age >18) with diabetes in the National Health and Nutrition Examination Survey (NHANES) between 2009 and 2016. NLR was calculated from complete blood count. Nine‐item Patient Health Questionnaire (PHQ‐9) was used to measure depression, with scores ≥10 indicating the presence of clinically relevant symptoms. Multivariable logistic regression was used to calculate the odds ratio (OR) with 95% confidence interval (CI) of clinically relevant depressive symptoms in relation to the NLR. We performed the smooth curve fitting and established a weighted generalized additive model to identify the nonlinearity of NLR and depression in diabetes patients. To account for the nonlinear relationship between NLR and depression in diabetes patients, weighted two‐piecewise linear model was applied. Results. We included 2,820 eligible participants, of which 371 (12.4%) had clinically relevant depressive symptoms. In the unadjusted model, the OR (95% CI) of clinically relevant depressive symptoms for the second (NLR 1.75‐2.57) and third (NLR >2.57) were 1.24 (0.90, 1.70) and 1.68 (1.23, 2.30), respectively, compared to the reference group (NLR < 1.75). After controlling for potential confounding factors, NLR was significantly associated with clinically relevant symptoms (odds ratio = 1.57, 95% confidence interval: 1.13–1.87; P for trend = .0078). Nonlinear relationships were observed, and a two‐piecewise linear regression model was established. The inflection point of NLR was 2.87. To the left of the inflection point (NLR ≤ 2.87), the OR (95% CIs) was 1.33 (1.07–1.66) (P < .031). Conclusions. Elevated levels of NLR are independently associated with increased odds of clinically relevant depressive symptoms in people with diabetes. Prospective study is needed to further analyze the role of NLR in depression in diabetic patients.
Esophageal Gastrointestinal Stromal Tumor with Rare Intracranial Metastasis
Authors: Carvalho José , Teixeira Margarida , Silva Francisco Teixeira , Esteves Alexandra , Ribeiro Carlos , Guerra Diana
Published: October 2020

Introduction. Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors and constitute the largest group of nonepithelial digestive neoplasms. However, they do not represent more than 1% of primary digestive tumors. They commonly metastasize to the liver and peritoneum, but brain metastases are extremely rare. Clinical Case. A 76-year-old woman with a diagnosis of esophageal GIST with liver and lung metastases for 13 years, medicated with imatinib, is presented. She was brought to the emergency department after falling and due to changes in behavior and vertigo with 24 hours of evolution. On physical examination, she presented changes in behavior, dysarthria, dysmetria on the right, gait imbalance, and no motor or sensory deficits. On brain computed tomography and posteriorly on magnetic resonance, 2 lesions were observed, left frontal and right cerebellar, compatible with metastatic lesions. After contribution of neurosurgery, histology was obtained that confirmed the lesions were GIST metastases. Imatinib was maintained, and whole brain radiotherapy was performed. After 6 months, she died. Discussion. The rarity of GIST brain metastases is noteworthy, and because of that, there is not enough experience to be certain of the best treatment. Our patient lived for 13 years with excellent disease control with imatinib, but the fact that it does not cross the blood-brain barrier makes it not useful in preventing or treating brain lesions. New tyrosine kinase inhibitors that may cross the blood-brain barrier could be the answer to these cases.
Functional Precision Medicine Identifies New Therapeutic Candidates for Medulloblastoma
Authors: Rusert Jessica M. , Juarez Edwin F. , Brabetz Sebastian , Jensen James , Garancher Alexandra , Chau Lianne Q. , Tacheva-Grigorova Silvia K. , Wahab Sameerah , Udaka Yoko T. , Finlay Darren , Seker-Cin Huriye , Reardon Brendan , Gröbner Susanne , Serrano Jonathan , Ecker Jonas , Qi Lin , Kogiso Mari , Du Yuchen , Baxter Patricia A. , Henderson Jacob J. , Berens Michael E. , Vuori Kristiina , Milde Till , Cho Yoon-Jae , Li Xiao-Nan , Olson James M. , Reyes Iris , Snuderl Matija , Wong Terence C. , Dimmock David P. , Nahas Shareef A. , Malicki Denise , Crawford John R. , Levy Michael L. , Van Allen Eliezer M. , Pfister Stefan M. , Tamayo Pablo , Kool Marcel , Mesirov Jill P. , Wechsler-Reya Robert J.
Published: October 2020

Medulloblastoma is among the most common malignant brain tumors in children. Recent studies have identified at least four subgroups of the disease that differ in terms of molecular characteristics and patient outcomes. Despite this heterogeneity, most patients with medulloblastoma receive similar therapies, including surgery, radiation, and intensive chemotherapy. Although these treatments prolong survival, many patients still die from the disease and survivors suffer severe long-term side effects from therapy. We hypothesize that each patient with medulloblastoma is sensitive to different therapies and that tailoring therapy based on the molecular and cellular characteristics of patients' tumors will improve outcomes. To test this, we assembled a panel of orthotopic patient-derived xenografts (PDX) and subjected them to DNA sequencing, gene expression profiling, and high-throughput drug screening. Analysis of DNA sequencing revealed that most medulloblastomas do not have actionable mutations that point to effective therapies. In contrast, gene expression and drug response data provided valuable information about potential therapies for every tumor. For example, drug screening demonstrated that actinomycin D, which is used for treatment of sarcoma but rarely for medulloblastoma, was active against PDXs representing Group 3 medulloblastoma, the most aggressive form of the disease. Functional analysis of tumor cells was successfully used in a clinical setting to identify more treatment options than sequencing alone. These studies suggest that it should be possible to move away from a one-size-fits-all approach and begin to treat each patient with therapies that are effective against their specific tumor.

Significance:

These findings show that high-throughput drug screening identifies therapies for medulloblastoma that cannot be predicted by genomic or transcriptomic analysis.