bluuebunny/crossref_metadata_2025 huggingface dataset:
Topology evolution of composite structures based on a phase field model
Authors: Wulf Jan Bernd , Muench Ingo
Published: January 2021

The composition of fibers and matrix is of great importance in several fields of engineering, such as steel reinforcement in concrete for civil engineering or lightweight applications in the automotive and aviation industry, as it allows combining the advantages of both materials. If the bond between fibers and matrix is ideally strong enough, the mechanical deformation can be assumed to be equal in both materials. With this assumption we set up a phase field model evolving the topology of reinforcement. The phase field parameter represents regions of reinforcement in the sense of averaged increased stiffness since we do not intend to simulate single fibers. A similar model but for topology optimization based on equivalent stresses was introduced by Muench et al. [1]. In many matrix materials, viscoelastic behavior is observed. Therefore, we also consider viscoelasticity in our model for the matrix.
A multifield computational model explains the underlying mechanisms of cortical malformations in the developing brain
Authors: Zarzor M. S. , Kaessmair S. , Steinmann P. , Budday S.
Published: January 2021

The convoluted macroscopic shape of the mammalian brain plays an important role for brain function. To date, the link between the cellular processes during brain development and normal or abnormal cortical folding remains insufficiently understood. In the early stages of development, progenitor cells divide symmetrically and asymmetrically in the inner layers of our brain. The newly generated neurons then migrate from the inner layers towards the outer surface to form the cortex. After about 20 weeks of gestation, the neuronal cells in the cortex start to interconnect, which causes a significant expansion of the outer brain layers. As this expansion is constrained by slower growing inner layers, compressive stresses emerge, which eventually induce mechanical instabilities and cortical folding. Disruption of cellular division, migration, or connectivity may lead to malformations of cortical development associated with neurological disorders like schizophrenia, autism, or epilepsy. Here we present a computational model describing cellular division and migration on the cellular scale, as well as growth and cortical folding on the tissue or organ scale, in a continuous way by a coupled finite growth and advection‐diffusion model. We introduce the cell density as independent field controlling the volumetric growth. This allow us to study the influence of the migration velocity, the cell diffusivity, the local stiffness, and the local connectivity of cells on the cortical folding process during normal and abnormal brain development numerically. We show how disrupted cell migration leads to a thickened cortex and the absence of normal folds in patients with the malformation lissencephaly. When calibrated using clinical data, the presented model can help to understand and diagnose neurological disorders arising from abnormal cellular development and cortical malformations.
A deep learning driven uncertain full‐field homogenization method
Authors: Henkes Alexander , Caylak Ismail , Mahnken Rolf
Published: January 2021

This work is directed to uncertainty quantification of homogenized effective properties of composite materials with a complex, three dimensional microstructure. The uncertainties arise in the material parameters of the single constituents as well as in the fiber volume fraction. They are taken into account by multivariate random variables. Uncertainty quantification is carried out by an efficient surrogate model based on pseudospectral polynomial chaos expansion and artificial neural networks, which is trained on a fast Fourier transformation based homogenization method. The numerical example deals with the comparison of the presented method to Monte Carlo‐type simulation for uncertain homogenization of spherical inclusions in a matrix material.
Forced harmonic vibrations of multi‐span Euler‐Bernoulli beams carrying spring‐damper‐mass systems
Authors: Klanner Michael , Ellermann Katrin
Published: January 2021

A spring‐damper‐mass system can be used as a passive vibration absorber, which can reduce the vibration amplitudes of a system at certain frequencies or in a broad band. In this paper, a highly efficient computational method called Numerical Assembly Technique (NAT) is extended to vibration problems of beams under arbitrarily distributed loads carrying spring‐damper‐mass systems, to identify the optimal set of parameters of the passive vibration absorbers. The method is quasi‐analytical in the sense that the governing equations are fulfilled exactly and only minor numerical errors due to double‐precision arithmetic are introduced in the boundary and interface conditions.
Experimental investigations on rising bubbles in vertical capillaries
Authors: Grünendahl Sabrina , Brandner Dean Martin , Ehrhard Peter
Published: January 2021

We investigate how the walls of cylindrical capillaries affect the velocity of rising gas bubbles of various diameters. Of course, as the capillary diameter increases, the velocity of the rising bubble will approach the case of free rising. Such systematic experiments on bubble rise in capillaries, in which the ratio of bubble diameter and capillary diameter is varied from one towards smaller values, can hardly be found in literature. First orienting experiments within the system water/air have been conducted and will be discussed in this paper.
Projection Methods in Adaptive Isogeometric Analysis and its Application to Topology Optimization
Authors: Hennig Paul , Heindel Leonhard , Carraturo Massimo , Reali Alessandro , Auricchio Ferdinando , Kästner Markus
Published: January 2021

In this contribution, we apply adaptive isogeometric analysis to a phase‐field model for topology optimization. To increase the efficiency of the computation, we perform local mesh refinement and coarsening between the time increments of the simulation. To provide a trial solution for the iterative solver of the next increment, state variables have to be transferred from the old to the new mesh. We therefore compare the application of a discrete least squares fit with an L2‐projection in well known two‐ and three‐dimensional benchmarks and analyze the influence of these methods on the quality of the results.
Ritz‐type surface homogenization: from atomistic to continuum surface models of copper despite imperfect bulk models
Authors: Kurzeja Patrick , Sievers Christian , Brendel Lothar , Mosler Jörn
Published: January 2021

Surfaces possess mechanical features on smaller scales that stand out against bulk phases, e.g., scaling of stiffness, curvature‐dependence, surfactant control and anchoring‐induced anisotropy. Continuum properties for the respective scales are often derived from ab initio simulations. This scale‐bridging however bears conceptual challenges and we highlight three aspects for the example of pure copper. First, free surface atoms relax and alter the boundary region in terms of interatomistic distances and resulting initital stresses. Second, eliminating the influence of finite thickness on the two‐dimensional continuum surface can be achieved by different averages or limit definitions, not all being physically consistent. Third, the continuum model of the surface is usually coupled to a continuum model of the bulk, which causes an approximation error itself. However, the bulk phase can not be eliminated direclty from the examination and simple averaging may even mask the aforementioned influences on the surface mechanics. A thermodynamically sound parameter identification across the scales is hence required. We present a Ritz‐type modeling approach for surfaces that ensures energy equivalence between atmostic and continuum simulations. The influences of relaxation, finite thickness and bulk approximation are identified by a mismatch in the energy contributions and accounted for by using appropriate homogenization limits.
Experimental investigations of viscoelastic and ferroelectric heating in PZT–5H
Authors: Warkentin Andreas , Ricoeur Andreas
Published: January 2021

This contribution focuses on the separation of two effects causing a temperature change in experiments with electrically loaded ferroelectrics. These materials are often subjected to cyclic loading, where viscoelasticity prevails at lower electric fields, whereas dissipative heating by domain switching governs the heating above the coercive field. Different frequencies and load amplitudes are investigated experimentally.
Advancements in multi‐phase unsaturated porous media fracture
Authors: Heider Yousef , Sun WaiChing , Markert Bernd
Published: January 2021

The focus in this research is on introducing an accurate and stable numerical modeling framework and to compare the numerical results with experimental data from the literature for desiccation‐induced fracturing of unsaturated porous materials. The macroscopic modeling approach is based on combined continuum porous media mechanics and a diffusive phase‐field method (PFM). In the case of unsaturated porous media, one has to deal with more than one pore fluid (e.g. water and air). In this, the mechanical behavior can be expressed via using the Bishop's effective stress principle, which considers the total stress, the capillary pressure (air pressure minus water pressure), and saturation degree. The onset of desiccation‐induced fracturing is driven by the capillary pressure, which leads to degradation not only in the effective stresses but also in the capillary pressure itself. In this contribution, we discuss via a numerical example the effect of considering the air pressure variation on the cracking process and numerical stability. Besides, we briefly discuss the potential inclusion of machine‐learning material laws, such as for retention curves and anisotropic permeability, using, e.g., deep recurrent neural networks (RNN) to improve the model accuracy.
Efficient modeling of 3D geometries using octree‐meshes combined with SBFEM and transfinite elements
Authors: Gravenkamp Hauke , Saputra Albert A. , Eisenträger Sascha
Published: January 2021

Hierarchical octree‐meshes constitute an extremely efficient approach to representing complicated three‐dimensional structures. This is due to their capability to refine meshes locally and adjust the cell size over several orders of magnitude very effectively. As octree‐meshes consist solely of cuboid cells, the mapping of the geometry is trivial. On the other hand, exploiting these advantages in the context of finite‐element‐based modeling strategies is not straightforward due to the presence of hanging nodes. Recently, it has been demonstrated that the scaled boundary finite element method (SBFEM) provides a promising tool for creating discretizations based on such octree‐meshes. In this approach, each cell of the mesh is treated as a three‐dimensional SBFEM subdomain whose boundary is discretized using two‐dimensional finite elements. However, in previous work, an additional triangulation was still required to create conforming meshes on some of the subdomains' faces. In the current contribution, we improve this technique by combining the SBFEM with particular transition elements based on transfinite mappings. The combined approach requires only quadrilateral elements and circumvents any hanging nodes from the beginning. Furthermore, the utilization of transfinite mappings allows for local p‐ and h‐refinement and even combining different classes of shape functions without introducing additional constraints.
Numerical methods in Jost Bürgi's “Coss”
Authors: Ullrich Peter
Published: January 2021

From 1579 to 1604 Jost Bürgi (1552–1632) worked at the court of the landgraves at Kassel both as constructor of scientific instruments and astronomical desk clocks and as astronomer and mathematician who analyzed the data gained by astronomical observations in order to design the technical devices that he constructed. Generally, little is known about the numerical methods which were used by craftsmen and engineers at that time. Bürgi, however, wrote up a manuscript on “Coss”, i. e., elementary algebra, in which he discusses several numerical methods to approximate zeros of polynomials.
A numerical study of the effect of phase evolution on residual stresses during cooling
Authors: Uebing Sonja , Brands Dominik , Scheunemann Lisa , Schröder Jörg
Published: January 2021

The consideration of residual stresses in forming processes is a promising opportunity to influence the final component's properties in a positive manner. Instead of their minimization, a targeted application of residual stresses can extend life time or durability and enhance manufacturability of metallic components. For this reason, detailed experimental and numerical analyses are an object of current research. Here, the cooling process is simulated in order to analyze the influence of the microscopic phase evolution on the macroscopic stress distribution in a cylinder with eccentric hole made of steel 100Cr6.
Data‐Driven simulation of inelastic materials using structured data sets and tangential transition rules
Authors: Ciftci Kerem , Hackl Klaus
Published: January 2021

Data‐driven computational mechanics replaces phenomenological constitutive functions by performing numerical simulations based on data sets of representative samples in stress‐strain space. The distance of modeling values, e.g. stresses and strains in Gauss‐points of a finite element calculation, from the data set is minimized with respect to an appropriate metric, subject to equilibrium and compatibility constraints, see [1]. Although this method operates well for non‐linear elastic problems, there are challenges dealing with history‐dependent materials, since one point in stress‐strain space might correspond to different material behaviour. In [2], this issue is treated by including local histories into the data set. However, there is still the necessity to include models for the evolution of internal variables. Thus, a mixed formulation is obtained consisting of a combination of classical and data‐driven modeling.

In the presented approach, the data set is augmented with directions in the tangent space of points in stress‐strain space. Moreover, the data set is classified into subsets corresponding to different material behaviour, e.g. elastic and inelastic. Based on the classification, transition rules map the modeling points to the various subsets. The approach and its performance will be demonstrated by applying it to a model of small strain elasto‐plasticity with isotropic hardening.
Computational aspects of the weak micro‐periodicity saddle point problem
Authors: Bharali Ritukesh , Larsson Fredrik , Jänicke Ralf
Published: January 2021

The finite element implementation of the weak micro‐periodicity problem in computational homogenisation requires special preconditioning techniques owing to the saddle point formulation. The saddle point nature arises from enforcing periodicity constraints using Lagrange multipliers. This manuscript addresses the solution techniques and preconditioning options for the aforementioned problem in a monolithic setting. Furthermore, an alternative technique is proposed, based on a linear multi‐point constraints strategy. The latter approach eliminates the Lagrange multiplier Degrees of Freedom (DOFs), thereby preventing the break‐down of conventional incomplete LU (ILU) variants and multi‐grid method based preconditioners.
Numerical Simulation of Viscoelastic Fluid‐Structure Interaction Problems and Drug Therapy in the Eye
Authors: Drobny Alexander , Friedmann Elfriede
Published: January 2021

The vitreous is a fluid‐like viscoelastic transparent medium located in the center of the human eye and is surrounded by hyperelastic structures like the sclera, lens and iris. This naturally gives rise to a fluid‐structure interaction (FSI) problem. While the healthy vitreous is viscoelastic and described by a viscoelastic Burgers‐type equation, the aging vitreous liquefies and is therefore modeled by the Navier‐Stokes equations. We derive a monolithic variational formulation employing the arbitrary Lagrangian Eulerian framework which is solved using the finite element method. To allow large 3D simulations the implementation is parallelized. Furthermore we study the vascular endothelial growth factor (VEGF) therapy in the vitreous which is modeled by four coupled convection‐diffusion‐reaction equations with an additional coupling to the underlying flow.
Parameter study on a phase‐field model for fatigue fracture
Authors: Seiler Martha , Kästner Markus
Published: January 2021

Recently, the problem of modelling fatigue fracture has been approached by the phase‐field method. The approach of Seiler et al. [1] focusses on a reduction of computational cost by combing the phase‐field method for fracture with a classic fatigue concept. For this model, we perform a parameter study analysing the influence of the fatigue degradation function and the crack propagation behaviour under cyclic loads with different mean loads. Eventually, we compare the results to a cyclic compact tension test.
On the Computation of Convergence Regions for Sequential Nonlinear Programming Problems
Authors: Mykhailiuk Ivan , Schäfer Kai , Flaßkamp Kathrin , Büskens Christof
Published: January 2021

In this work, we formulate and solve the problem of finding the ball of maximum radius around a local minimum of a nonlinear optimization problem, which is invariant with respect to the gradient descent method. This problem arises in the context of solving sequences of nonlinear optimization problems, in which one usually strives to converge to qualitatively similar solutions. We illustrate our idea with an example of a nonlinear function of two variables.
Simulation of weak‐inertia single‐phase flow in porous materials using Smoothed Particle Hydrodynamics
Authors: Krach David , Steeb Holger
Published: January 2021

Intrinsic permeability of a porous material is a crucial material parameter in various application fields like e.g. geosciences, materials science, biological sciences and mechanical engineering. In contrast to the permeability often used in purely linear models, however, it is also a (nonlinear) function of the Reynolds number (Re) with the onset of the influence of inertial forces. In coarse‐grained continuum models the Forchheimer equation describes this incipient influence of viscous momentum exchange but it is based on the adaptation of experimentally obtained data and its range of validity remains a subject for discussion. Performing three‐dimensional Direct Numerical Simulations for single‐phase flow through porous media this work aims to show a smooth transition of effective intrinsic permeability within the interval 0.1 < Re < 1000. We use the fully‐Lagrangian meshless Smoothed Particle Hydrodynamics method (SPH) to solve the weakly compressible Navier‐Stokes equations for pore‐scale resolved flow in the so‐called weak‐inertia regime. Our implementation utilizes HOOMD‐blue thus allows us to perform massively parallel computations which are crucial for these applications.
A phase field approach to study of transformation induced micro–cracking in a martensitic phase transformation
Authors: Borzabadi Farahani Ehsan , Juhre Daniel
Published: January 2021

In this study, a coupled phase field (PF) method for the simulation of crack propagation and martensitic phase transformations is developed. In order to investigate the crack field and martensitic microstructure evolution the concept of the thermodynamic driving force, interfacial energy, the elastic energy, and the kinetic of phase field equations are introduced (time dependent Ginzburg Landau equation) [1]. The weak form and an algorithm for the solution of corresponding equations are implemented in the finite element program (FEAP). Since the phase transformation can form during the application of high amount of stresses, the influence of microcrack propagation on the formation of the martensitic phase has been studied. The crack tip produces high amount of concentrated stresses, which lead to a change in the distribution of the martensitic phases and it can also deviate the crack direction [2].
A machine learning enhanced structural response prediction strategy due to seismic excitation
Authors: Thaler Denny , Bamer Franz , Markert Bernd
Published: January 2021

In this contribution, we present a fast prediction approach to estimate response statistics of the crude Monte Carlo simulation using artificial neural networks. Hereby, the neural network is trained within an initial response subset, based on which a forecast can be evaluated in an early state of the Monte Carlo simulation.
An artificial intelligence approach to model nonlinear continua by intelligent meta‐elements
Authors: Koeppe Arnd , Bamer Franz , Markert Bernd
Published: January 2021

A data‐driven “intelligent” meta‐element that reduces the dimensionality and accelerates nonlinear finite element computations is demonstrated on an elastoplastic continuum frame.
The influence of compatibility equations of non‐linear elasticity on convergence for spectral method solutions
Authors: Flajs Rado
Published: January 2021

In structural mechanics the stresses are of a primary interest. Due to the required regularity of the approximation it is often inconvenient to obtain the stresses from the displacement methods. Mixed and hybrid methods are thus proposed to avoid this obstacle. The compatibility conditions should be fulfilled in order to obtain a unique solution.

In this paper the compatibility equations of non‐linear elasticity are considered. Despite its very long history, this issue has not been satisfactorily resolved for non‐simply‐connected bodies until recently [1]. Its well known however, that the compatibility conditions are linearly dependent.

The aim of the present contribution is to include the spectral methods [2] in order to improve the finite element solution procedure for the reversible elastodynamics problem [3], formulated for a large strain deformation with the deformation gradient tensor as one of the basic unknowns. In the case of the small strains the components of the deformation gradient tensor are of different magnitude. The main contribution is the derivation of the solution strategy in order to take this information into account. Applying this strategy to the implicit time integration method the exponent decrease of the condition numbers of the iteration matrices was achieved. Consequently the accuracy of the calculations should increase and the convergence for spectral method solutions should considerably improve. The theoretical findings are confirmed by a selected numerical example from structural mechanics.
On Spray Modeling with Quadrature‐Based Moment Methods
Authors: Pütz Michele , Pollack Martin , Hasse Christian , Oevermann Michael
Published: January 2021

Spray modeling requires a proper representation of the dispersed phase and involves models for a variety of physical phenomena. On the population scale, a properly formulated population balance equation provides a complete statistical description of the particle system. However, in most cases the high dimensionality entails prohibitive computational costs. Quadrature‐based moment methods (QBMM) limit the description of particle populations to a set of only a few moments and thus considerably reduce computational complexity. In order to apply QBMM to sprays, models for many involved physical processes must be formulated consistently in the QBMM‐context. We study secondary droplet breakup with QBMM using a simple well‐established spray breakup model and simplified setups.
Model order reduction with dynamically transformed modes for the wave equation
Authors: Black Felix , Schulze Philipp , Unger Benjamin
Published: January 2021

In this contribution, we apply a recently introduced nonlinear model reduction framework based on dynamically transformed modes to the linear wave equation with periodic boundary conditions. We demonstrate that under reasonable assumptions, the reduced‐order model can be evaluated efficiently. Consequently, we obtain that the state variables of the reduced‐order model are constant or linear functions with respect to time.
On A Hybrid Concept for Approximating Self‐Excited Periodic Oscillations of Large‐Scaled Dynamical Systems
Authors: Kappauf Jonas , Hetzler Hartmut
Published: January 2021

Concerning the approximation of self‐excited periodic oscillations in large‐scaled mechanical systems involving strong nonlinearities, this contribution suggests a concept for an efficient treatment. The presented Hybrid FD‐HB method takes the advantages of both schemes Harmonic Balance and Finite Difference to enhance the ratio of computational cost and accuracy for mechanical systems with many degrees of freedom. Within this contribution the residual equations, required when applying a NEWTON‐RAPHSON‐scheme, are derived and the method is applied to a stiff nonlinear mechanical system.
Computational Stability Analysis of Diffusion‐Deformation Processes at Finite Strains
Authors: Sriram Siddharth , Polukhov Elten , Keip Marc-André
Published: January 2021

In the present work, we investigate the onset of structural instabilities occuring in soft hydrophilic elastomers undergoing geometrically constrained swelling, which is characterized by large elastic deformations coupled with transient fluid diffusion. We model this phenomenon using a minimization‐based variational formulation having the deformation map and the fluid flux as the independent variables [1,3]. The space‐time‐discrete form of the variational problem is implemented using a conforming Raviart–Thomas‐type finite element formulation, which yields a symmetric and positive definite global tangent matrix for a stable deformation state. The onset of instability is captured as the point where the tangent matrix loses its positive definiteness [4,5]. To validate the proposed theoretical framework, we consider the surface wrinkling phenomenon observed in constrained hydrogel bilayers subjected to fluid diffusion. Variations in the critical buckling load and the corresponding mode number with respect to the geometry and material parameters of the bilayer are studied. These studies could, for instance, serve as potential design guidelines for applications of such materials in microsensors or in the fabrication of soft microgears for actuators, where the buckling modes are exploited to produce a desired mechanical output [8].
Efficient Simulation of Random Fields by Trigonometric Polynomial and Low‐rank Tensor
Authors: Liu Dishi , Vondřejc Jaroslav , Matthies Hermann
Published: January 2021

We propose a fast and economic representation of stationary random fields in trigonometric polynomial, utilizing the prowess of fast Fourier transform (FFT) and low‐rank tensor approximation. With the method we are able to generate large random fields with discretization size up to 220 which are otherwise well beyond the capacity of PCs. We also illustrate the approach to the specified property of random field by increasing rank in the tensor approximation.
Material optimization for controlling interfacial damage in composite structures
Authors: Singh Sukhminder , Stingl Michael
Published: January 2021

Advances in the computational modeling of fracture in solid structures have opened up possibilities for structural design optimization. The rate‐independent structural problem considering damage in its original form is ill‐posed due to the non‐unique nature of the solution, that poses difficulty in using gradient‐based algorithms for material optimization. To overcome this issue, this work introduces a viscosity parameter in the governing state equations and, thus renders the structural problem well‐posed. Material interfaces are modeled using an exponential, initially‐elastic cohesive law and linear elasticity is assumed throughout the structural domain. The time‐dependent fracture problem is solved via incremental variational approach with finite element discretization of the displacement field. Finally, the effectiveness of the method is illustrated by a material optimization example using a smooth gradient‐based solver with first‐order material sensitivities.
Inheritance mode and metabolic mechanism of the sulfoximine insecticide sulfoxaflor resistance in Oxycarenus hyalinipennis (Costa)
Authors: Wazir Shabana , Shad Sarfraz A
Published: January 2021

BACKGROUND

Dusky cotton bug (DCB), Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae), is a key insect pest of cotton. It causes huge losses to cotton and many other economically important crops. Sulfoxaflor is a newly introduced systemic insecticide that is effective against many sap‐feeding insect pests such as aphids, whiteflies and true bugs. The present study was designed to characterize the inheritance of sulfoxaflor resistance in DCB. Moreover, the role of synergists in reducing sulfoxaflor resistance in DCB was also assessed.

RESULTS

A field population of DCB has developed 1132.0‐fold resistance to sulfoxaflor after 11 selected generations in the laboratory. Nonsignificant difference of reciprocal crosses was observed depending on the LC50 (median lethal concentration) values (95% confidence intervals overlapped), suggesting an autosomal mode of sulfoxaflor resistance inheritance. The degree of dominance of 0.7 for F1 (Sulfo‐Sel Pop ♀ × Lab‐Pop♂) and 0.6 for F1'(Sulfo‐Sel Pop ♂ × Lab‐Pop♀), respectively, suggested that sulfoxaflor resistance was incompletely dominant. According to the monogenic model, the number of genes involved to induce sulfoxaflor resistance revealed that sulfoxaflor resistance was polygenic in nature. The realized heritability (h2) value for sulfoxaflor resistance was 0.2. The synergists experiment indicated that esterases were involved in the sulfoxaflor resistance mechanism in DCB.

CONCLUSIONS

The current results indicate that there is autosomal, incompletely dominant and polygenic inheritance of sulfoxaflor resistance in DCB. Our results would be helpful in delaying sulfoxaflor resistance against DCB in the field. © 2021 Society of Chemical Industry
Peptide‐based hydrogels as delivery systems for doxorubicin
Authors: Diaferia Carlo , Rosa Elisabetta , Accardo Antonella , Morelli Giancarlo
Published: January 2021

Hydrogels (HGs) and nanogels (NGs) have been recently identified as innovative supramolecular materials for many applications in biomedical field such as in tissue engineering, optoelectronic, and local delivery of active pharmaceutical ingredients (APIs). Due to their in vivo biocompatibility, synthetic accessibility, low cost, and tunability, peptides have been used as suitable building blocks for preparation of HGs and NGs formulations. Peptide HGs have shown an outstanding potential to deliver small drugs, protein therapeutics, or diagnostic probes, maintaining the efficacy of their loaded molecules, preventing degradation phenomena, and responding to external physicochemical stimuli. In this review, we discuss the possible use of peptide‐based HGs and NGs as vehicles for the delivery of the anticancer drug doxorubicin (Dox). This anthracycline is clinically used for leukemia, stomach, lung, ovarian, breast, and bladder cancer therapy. The loading of Dox into supramolecular systems (liposomes, micelles, hydrogels, and nanogels) allows reducing its cardiotoxicity. According to a primary sequence classification of the constituent peptide, doxorubicin‐loaded systems are here classified in short and ultra‐short peptide‐based HGs, RGD, or RADA‐peptide‐based HGs and peptide‐based NGs.
Immigrants and legal status: Do personal contacts matter?
Authors: Cremaschi Simone , Devillanova Carlo
Published: January 2021

Using unique Italian survey data on both documented and undocumented immigrants, we empirically quantify the correlation between different types of personal contacts and immigrants' documentation probability, while also uncovering the contacts' indirect associations via immigrant labour market outcomes (employment status and job characteristics). Our results indicate that contacts with both natives and family members have a positive and quantitatively large effect on immigrant documentation probability, conditional on a large set of covariates. Contacts with members of the same ethnic group, by contrast, increase documentation probability only moderately, an effect explainable by these co‐ethnics' association with employment probability. Moreover, our findings support the hypothesis that native contacts can connect immigrants with jobs that favour documentation.
Negative Pulse and Compliance Current Dependent Negative Differential Resistance in ZnO/Nb:SrTiO3 Heterojunctions
Authors: Li Qinxuan , Jia Caihong , Ren Yong , Zhang Ying , Zhang Weifeng
Published: January 2021

The negative differential resistance (NDR) in ZnO/Nb:SrTiO3 heterojunctions is found to be strongly dependent on negative pulse amplitude/width and compliance current. When a small or short negative pulse is applied, the NDR feature remains almost the same. With the negative pulse amplitude or width increasing, the NDR feature gradually fades down and shifts to a larger negative bias. Meanwhile, the NDR intensity increases markedly without significant shift with increase of the compliance current. Interestingly, the low‐resistance state and NDR location are found to exhibit exactly the same trend when varying the negative pulse amplitude, width, and compliance current. The dependence of the NDR intensity and location on the pulse amplitude/width and compliance current can be well understood from the variance of concentration of ionized oxygen vacancies and the depletion layer width, respectively. This will promote the application of NDR devices.
Effects of garlic supplementation on oxidative stress and antioxidative capacity biomarkers: A systematic review and meta‐analysis of randomized controlled trials
Authors: Askari Mohammadreza , Mozaffari Hadis , Darooghegi Mofrad Manije , Jafari Alireza , Surkan Pamela J. , Amini Mohammad Reza , Azadbakht Leila
Published: January 2021

Evidence suggests that garlic supplementation may have an effect on oxidative stress by augmenting the rate of enzymatic and non‐enzymatic antioxidants and diminishing pro‐oxidant enzymes. Given inconsistencies across studies, we aimed to systematically review the current literature and quantify the effects of garlic supplementation on oxidative stress. We conducted a systematic search with multiple databases (Scopus, PubMed, and Web of Science) to find relevant articles published prior to October 2020. Results were reported as bias‐corrected standardized mean difference (Hedges' g) with 95% confidence intervals (CI) using random‐effects models. Cochrane's Q and I squared (I2) tests were used to determine heterogeneity among the studies included. Twelve randomized controlled trials (RCTs) were included. Garlic doses ranged from 80 to 4,000 mg/day, and intervention duration varied between 2 and 24 weeks. Garlic supplementation increased serum level of total antioxidant capacity (TAC) (Hedges' g: 2.77, 95% CI: 1.37 to 4.17, p < 0.001) and superoxide dismutase (SOD) (Hedges' g: 13.76, 95% CI: 4.24 to 23.29, p = 0.004), while it reduced the malondialdehyde serum level (MDA) (Hedges' g: ‐1.94, 95% CI: −3.17 to −0.70, p = 0.002). Due to limited data available, glutathione (GSH) was not considered for the current meta‐analysis. The nonlinear dose‐response effect of garlic supplementation was not observed with regard to serum TAC and MDA levels (TAC: p‐nonlinearity = 0.398; MDA: p‐nonlinearity = 0.488). Garlic supplementation appears to improve serum levels of TAC, MDA, and SOD. Garlic supplementation may be useful to reduce oxidative stress and related diseases. Future studies with large sample sizes and longer duration are required to confirm these findings.
Water quality impacts of small hydroelectric power plants in a tributary to the Pantanal floodplain, Brazil
Authors: da Cruz Rúbia Fantin , Hamilton Stephen K. , Tritico Hans M. , Fantin‐Cruz Ibraim , de Figueiredo Daniela Maimoni , Zeilhofer Peter
Published: January 2021

Small hydroelectric power (SHP) facilities are proliferating around the world, including in Brazil where legislation encourages SHP over other hydropower development, defining SHP as facilities with installed capacities of 3–30 MW and reservoirs <13 km2. SHP facilities are often diversion designs with small or no reservoirs, while other SHPs have more conventional dams that create extensive reservoirs. This study seeks to understand the relative impacts of these two different designs on downstream water quality, comparing a conventional SHP system on the main stem to a complex of smaller SHPs with diversion designs in lower‐order reaches of the São Lourenço River. This river delivers nutrients and sediments to the Pantanal, one of the world's largest floodplain ecosystems. Samples collected upstream and downstream of each set of facilities over a range of flows revealed that the conventional SHP reservoir significantly reduced pH, dissolved oxygen, total iron, suspended solids, and turbidity consistent with observations in many other reservoirs. In contrast, water quality changes downstream of the smaller SHPs were less pronounced and could be attributable to natural variability. An analysis of energy production versus water quality impacts suggests that SHPs on the smaller tributaries are favorable compared to the conventional SHP in terms of water quality impacts. With the proposed addition of dozens of new facilities in the upland watersheds draining into the Pantanal, this study improves our understanding of the relative impacts of different designs of SHPs on downstream water quality, while recognizing that water quality is just one of several potential impacts to be considered.
Link predictions for incomplete network data with outcome misclassification
Authors: Wu Qiong , Zhang Zhen , Ma Tianzhou , Waltz James , Milton Donald , Chen Shuo
Published: January 2021

Link prediction is a fundamental problem in network analysis. In a complex network, links can be unreported and/or under detection limits due to heterogeneous sources of noise and technical challenges during data collection. The incomplete network data can lead to an inaccurate inference of network based data analysis. We propose a parametric link prediction model and consider latent links as misclassified binary outcomes. We develop new algorithms to optimize model parameters and yield robust predictions of unobserved links. Theoretical properties of the predictive model are also discussed. We apply the new method to a partially observed social network data and incomplete brain network data. The results demonstrate that our method outperforms the existing latent‐link prediction methods.
Seaweed Mediated Fabrication of Zinc Oxide Nanoparticles and their Antibacterial, Antifungal and Anticancer Applications
Authors: Anjali K. P. , Sangeetha B. M. , Raghunathan R. , Devi Geetha , Dutta Susmita
Published: January 2021

Synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous extracts of seaweeds, Ulva lactuca, and Stoechospermum marginatum and their antibacterial, antifungal and anticancer activity have been reported. The UV absorption peaks at 310 nm and 345 nm confirmed the formation of ZnO NPs using U.lactuca (Ul‐ZnO) and S.marginatum (Sm‐ZnO), respectively. The XRD patterns indicated the crystalline nature of ZnO NPs with hexagonal wurtzite structure. The transmission electron microscopic analysis revealed that the ZnO NPs contain spherical and round‐shaped particles with a size range of 12–17 nm for Ul‐ZnO and 6–11 nm for Sm‐ZnO NPs. The antibacterial activity and antifungal activity of both the NPs (Sm‐ZnO and Ul‐ZnO) were comparable. The results of the cytotoxicity assay of Ul‐ZnO and Sm‐ZnO NPs revealed that Ul‐ZnO NPs recorded the maximum mortality rate of 97.34 % with an IC50 value of 91.18 μg/ml.
Benzopyranyl Phosphonate and β‐Phosphono Malonates Derivatives: An Exciting Breakthrough in Chemistry
Authors: Deshmukh Satish U. , Sangshetti Jaiprakash N. , Bhosale Sidhanath V. , Pawar Rajendra P.
Published: January 2021

In this review, we paid attention to the reported methods and recent advances in the development of 2‐amino‐3‐cyano‐4H‐chromen‐4‐yl‐phosphonates and functionalized β‐phosphonomalonates heterocyclic compound. Small‐molecular architectures are considered with the highlighting on their structural design and synthesis approach. The scope of the 2‐amino‐3‐cyano‐4H‐chromen‐4‐yl‐phosphonates and functionalized β‐phosphonomalonates heterocyclic compound via reactions like Knoevenagel, Pinner‐cyclisation and advanced phospha‐Michael addition reactions using different catalyst for synthesis is listed up to 2020.
Direct Synthesis, Characterization and Theoretical Studies of N‐(6‐Amino‐1,3‐dimethyl‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐5‐yl)benzamide Derivatives
Authors: Das Tushar , Ranjan Amit , Sieroń Lesław , Maniukiewicz Waldemar , Das Subrata
Published: January 2021

With the far‐flung importance of uracil and amides in innumerable fields of chemistry and biology, a coherent synthesis that nullifies the use of prodigal reagents, methods and catalysts are hugely accepted. From the present outcomes, we report a highly atom profitable nucleophilic addition reaction of aromatic aldehydes and heterocyclic amines for the generation of amides having an excellent yield and high reproducibility. The main force responsible for the forward reaction is the presence of the nitroso group at the C‐5 position on uracil scaffold, which drives the formation of formidable range products. The conclusive mechanism is based on the dehydrogenation reaction of the carbinolamine product formed during the nucleophilic addition reaction of the aromatic aldehyde with the free heterocyclic amino group to yield the corresponding amides. The synthesized compounds were predicated for biological properties and proved it to be an ideal G protein‐coupled receptor kinase2 (GRK2) inhibitor. Out of all, the compound 3 f showed the most preeminent properties when compared to Paroxetine, studied using molecular docking. At the same time, computed ADME analysis proved them as an ideal drug candidate. Our findings not only prophesize new methods for the synthesis of bioactive‐amides using a cross‐coupling strategy but also demonstrates their novel applications as a human GRK2 inhibitor.
Self‐perceived acute psychological stress and risk of mortality, recurrence and disability after stroke: Mashhad Stroke Incidence Study
Authors: Mokhber Naghmeh , Sheikh Andalibi Mohammad Sobhan , Morovatdar Negar , Thrift Amanda G. , Kapral Moira K. , Stranges Saverio , Saber Hamidreza , Farzadfard Mohammad Taghi , Amiri Amin , Akbarzadeh Farzad , Ghanei Neda , Khorram Bita , Azarpazhooh Mahmoud Reza
Published: January 2021

This longitudinal study was designed to evaluate the association between acute pre‐stroke stress and the severity stroke and its outcomes including mortality, recurrence, disability and functional dependency. Patients with first‐ever stroke (FES) were recruited from the Mashhad Stroke Incidence Study. Patients were asked about any acute severe pre‐stroke stress in the 2 weeks prior to index stroke. Disability and functional disability were defined using modified the Rankin Scale and Barthel Index, respectively. We used logistic and ordinal regression tests to assess the association between acute pre‐stroke stress and study outcomes. Among 624 patients with FES, 169 reported acute pre‐stroke stress. Patients with acute pre‐stroke stress were younger than those without stress (60.7 ± 14.4 vs. 66.2 ± 14.7; p < 0.001). The frequency of traditional vascular risk factors was not different in patients with and without acute pre‐stroke stress. We did not find any association between acute pre‐stroke stress and stroke outcomes. Although acute stress was common in our cohort, our results did not support an association between acute pre‐stroke stress and the severity of stroke at admission and long‐term stroke outcomes.
Understanding the Development, Standardization, and Validation Process of Alternative In Vitro Test Methods for Regulatory Approval from a Researcher Perspective
Authors: Bas Aurora , Burns Nicole , Gulotta Andrew , Junker James , Drasler Barbara , Lehner Roman , Aicher Lothar , Constant Samuel , Petri‐Fink Alke , Rothen‐Rutishauser Barbara
Published: January 2021

Due to economic, practical, ethical, and scientific reasons, researchers, among others, are pushing for alternative in vitro test methods to replace or reduce existing animal experiments. In order for these tests to be more broadly used by the industrial sector and regulatory bodies, orchestrated efforts are required to show the robustness and reliability of in vitro methods, which can accelerate the use for early screening testing. Another way of increasing the use of alternatives is to coordinate validation studies, that is, multi‐laboratory trials, and to gain regulatory approval and instatement as test guidelines or standard method. However, awareness of the exact standardization, validation, and approval process has been a major obstacle for many researchers. Herein, the process has been broken down into three main phases: i) test method development; ii) intra‐ and inter‐laboratory validation; and iii) regulatory acceptance. This general process applies to all alternative methods seeking validation and approval, although the intricacies of different toxicological endpoints and/or chemical sectors may lead to additional work, particularly in the validation stage. The authors’ aim is to provide insight in the development process of alternative methods with a focus on in vitro cell culture methods over validation to regulatory acceptance.
Study 3D Endothelial Cell Network Formation under Various Oxygen Microenvironment and Hydrogel Composition Combinations Using Upside‐Down Microfluidic Devices
Authors: Hsu Heng‐Hua , Ko Ping‐Liang , Wu Hsiao‐Mei , Lin Hsi‐Chieh , Wang Chien‐Kai , Tung Yi‐Chung
Published: January 2021

Formation of 3D networks is a crucial process for endothelial cells during development of primary blood vessels under both normal and pathological conditions. In order to investigate effects of oxygen microenvironment and matrix composition on the 3D network formation, an upside‐down microfluidic cell culture device capable of generating oxygen gradients is developed in this paper. In cell experiments, network formation of human umbilical vein endothelial cells (HUVECs) within fibrinogen‐based hydrogels with different concentrations of hyaluronic acid (HA) is systematically studied. In addition, five different oxygen microenvironments (uniform normoxia, 5%, and 1% O2; oxygen gradients under normoxia and 5% O2) are also applied for the cell culture. The generated oxygen gradients are characterized based on fluorescence lifetime measurements. The experimental results show increased 3D cell network length when the cells are cultured under the oxygen gradients within the hydrogels with the HA addition suggesting their roles in promoting network formation. Furthermore, the formed networks tend to align along the direction of the oxygen gradients indicating the presence of gradient‐driven cellular response. The results demonstrate that the developed upside‐down microfluidic device can provide an advanced platform to investigate 3D cell culture under the controlled oxygen microenvironments for various biomedical studies in vitro.