bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Characterization of Composite Poly(1.8 Octanediol-co-Citrate) (POC)/Nano-Hydroxyapatite as Candidate Biodegradable Bone Screw
Authors: Qulub Fitriyatul , Widiyanti Prihartini , Ady Jan
Published: May 2016

The high number of bone fractures, around 300-400 cases per month, are treated with orthopedic surgery method using internal fixation by bone screw which is aimed at accelerating patients’ mobilization. There is a necessity to invent biomaterial which possesses two main characteristics: biocompatible and biofunctional, as well as having an important element of biodegradable without conducting reoperation. A research focused on the various composition of nano-hydroxyapatite (HA) derived from extracted snapper fish scales on Poly (1,8-octanediol-Co-Citrate (POC) as Biodegradable Bone screw. This research is purported to synthesize Poly (1,8-Octanediol-co-Citrate (POC) and characterize the influence of HA compositions against mechanical properties and compatibility of POC-HA composite that enable it to be used as Biodegradable Bone screw material. The condensation polymerization method is applied in synthesizing POC to produce POC pre-polymer by the formation of an ester bond group C=O stretch at 1731 cm-1 through a test of functional groups (FTIR). POC pre-polymer is composited with nano-HA compositions of 62%, 65%, 68% and 71% and followed by post-polymerization treatment. POC-HA composites formed were tested on hardness and biodegradability. The results obtained indicate that the composition of HA nanoparticles influences the mechanical properties and biocompatibility of the material. Best results were from 62% HA composition in which the hardness value was of 885.57 MPa, close to that of bone hardness which is 150-664 MPa. Results also showed that the rate of biodegradation reached 3.42% (4 weeks) which is in accordance to fracture bone grafting period of 21 months. Based on the characteristics result indicated in this study, the composite of Poly (1,8-Octanediol-co-Citrate) (POC)-Nano Hydroxyapatite is a potential candidate for biodegradable bone screw material.
Cyclic Tension Test of AZ31 Magnesium Alloy at Elevated Temperature Realized in a Miniaturized Uniaxial Tensile Test Setup
Authors: Suttner Sebastian , Merklein Marion
Published: May 2016

The use of new materials, e.g. aluminum and magnesium alloys, in the automotive and aviation sector is becoming increasingly important to reach the global aim of reduced emissions. Especially magnesium alloys with their low density offer great potential for lightweight design. However, magnesium alloys are almost exclusively formable at elevated temperatures. Therefore, material characterization methods need to be developed for determining the mechanical properties at elevated temperatures. In particular, cyclic tests at elevated temperatures are required to identify the isotropic-kinematic hardening behavior, which is important for numerically modeling the springback behavior. In this contribution, a characterization method for determining the cyclic behavior of the magnesium alloy AZ31B at an elevated temperature of 200 °C is presented. The setup consists of a miniaturized tensile specimen and stabilization plates to prevent buckling under compressive load. The temperature in the relevant area is introduced with the help of conductive heating. Moreover, the complex kinematic model according to Chaboche and Rousselier is identified, to map the transient hardening behavior of AZ31B after load reversal, which cannot be modeled with a single Bauschinger coefficient.
Effects of Process Parameter Variation on the Bonding Strength in Clad Steel Strips by Twin-Roll Strip Casting
Authors: Münster Dennis , Vidoni Michele , Hirt Gerhard
Published: May 2016

Twin-roll strip casting represents a promising alternative production route for clad steel strips. The main idea behind the presented research is the introduction of a prefabricated strip into the melt pool of a twin-roll casting process to exploit the heat of the melt to create bonding between the cast strip and the prefabricated strip. Prior investigations proved the general feasibility of this concept for steel-steel combinations and described the bonding of the two layers. This concept is now further investigated with the aim to understand the influence of the process parameters on the bonding. For the experiments an austenitic high manganese steel is cladded with an austenitic stainless steel. Beginning from a starting point determined in numerical simulations, a process window for the introduction of a 0.3 mm thick strip of 1.4301 was identified by process parameter variation during casting experiments. Up to 25 m long clad strips with a thickness ratio between introduced strip and cast strip ranging from 1:6 to 1:10 were produced this way. Micrographic examinations of the clad strips’ cross sections were carried out to describe the influence of the casting parameters on the joining interface. Higher element diffusion was found in strips with bigger thickness ratios, indicating a stronger bonding of the two layers. Afterwards the observations from the micrographic examination were compared to the results of bonding strength which were obtained by a customised shear test. Supporting the findings of the micrographic examinations the average bonding strength rose from around 100 MPa for a ratio of 1:7 to over 300 MPa for the ratio of 1:10. Although the process parameters with the main influence on the bonding strength, the contact time and the thickness ratio, have been identified more research is needed to quantify their influence.
Modelling the Temperature Evolution During Hot Reversing Strip Rolling of Magnesium Alloys
Authors: Nam Alexander , Prüfert Uwe , Eiermann Michael , Kawalla Rudolf
Published: May 2016

The paper proposes the approach for the thermal through process modelling of the strip hot rolling chain of magnesium alloys. This strip hot rolling chain comprises the coil reheating after the Twin-Roll Casting (TRC) process, storage or transport operations and reversing hot rolling. The modelling of reversing rolling is implemented in connection with the simultaneous un-/coiling process of a coil. The numerical calculation is based on an object-oriented FEM tool kit written in MATLAB™ and is carried out in three spatial dimensions and time.
A New FE-Model for the Investigation of Bond Formation and Failure in Roll Bonding Processes
Authors: Pietryga Michael , Lohmar Johannes , Hirt Gerhard
Published: May 2016

Roll bonding is a process to join two or more different materials permanently in a rolling process. A typical industrial application is the manufacturing of aluminum sheets for heat exchangers in cars where the solder is joined onto a base layer by roll bonding. From a modelling point of view the challenge is to describe the bond formation and failure of the different material layers within a FE-process model. Most methods established today either tie the different layers together or treat them as completely separate. The problem for both assumptions is that they are not applicable to describe the influence of tangential stresses that can cause layer shifting and occur in addition to the normal stresses within the roll gap. To overcome these restrictions in this paper a 2D FE-model is presented that integrates an adapted contact formulation being able to join two bodies that are completely separated at the start of the simulation. The contact formulation is contained in a user subroutine that models bond formation by adhesion in dependence of material flow and load. Additionally if the deformation conditions are detrimental already established bonds can fail. This FE-model is then used to investigate the process boundaries of the first passes of a typical rolling schedule in terms of achievable height reductions. The results show that passes with unfavorable height reduction introduce tensile and shear stresses that can lead to incomplete bonding or can even destroy the bond entirely. It is expected that, with adequate calibration, the developed FE-model can be used to identify conditions that are profitable for bond formation in roll bonding prior to production and hence can lead to shorter rolling schedules with higher robustness.
Computer Model STAN 2000 and its Use in Practice of Steels Hot Rolling on Mill 2000 of Severstal
Authors: Ogoltcov Alexey , Sokolov Dmitry , Sokolov Semen , Vasilyev Alexander
Published: May 2016

An integral computer model/program STAN 2000 for simulation of steels hot rolling on mill 2000 of SEVERSTAL was developed. The capacity of the model includes, for example, the following features:‒ control of power parameters and prediction of hot strip temperature for a given rolling and accelerated cooling regimes;‒ follow-up of the evolution of steel microstructure at all stages of strip production and prediction of ultimate mechanical properties (yield stress, ultimate tensile stress and relative elongation);‒ optimization of rolling regimes for existing steel grades and developing them for a new ones.The STAN 2000 program is written in С++ programming language and can work on all modern Microsoft Windows family operating systems. The program has a well-designed and user-friendly interface facilitating its practical use.The integral model was calibrated using an extensive data base on rolling regimes and forces, measured temperatures and final mechanical properties for a number of steel grades rolled on mill 2000 of SEVERSTAL with chemical compositions covering the following ranges of alloying elements content (mass.%): С(≤0.65); Mn(≤2.0); Si(≤1.0); Cr(≤0.9); Ni(≤0.6); Cu(≤0.5); Mo(≤0.4); Nb(≤0.05); V(≤0.065); Ti(≤0.06); B(≤0.003).Some results of calculations performed with STAN 2000 program for temperatures, rolling forces and mechanical properties are presented and compared with experimental data. Some examples of the program utilization in hot strip production on mill 2000 of SEVERSTAL are presented and discussed.
On the Correlation between Microstructure Homogeneity and Formability in Two Multi Phase Steels Treated with Different Cooling Strategies
Authors: Bechtold Marion , Witte Marco , Kluge Sascha
Published: May 2016

In the scope of the optimization of multi phase steels, e.g. for the automotive industry, control of the microstructure is essential to tailor the mechanical properties. In this study, two cold rolled steels varying in carbon content were annealed and cooled under different laboratory conditions. The microstructure is investigated using optical and electron microscopy and EBSD. The results are correlated to the mechanical properties obtained from tensile, hole expansion and bending test. It is found that tensile strength and elongation are mainly dependent on martensite volume fraction, while yield strength is less affected by chemical composition or annealing treatment. In contrast, hole expansion capacity and maximum bending angle are significantly improved by the homogenization of the microstructure which is independent of strength and elongation. The microstructure homogeneity is expressed by analyzing the Lorenz curves derived from the kernel average misorientation from EBSD measurements.
Substitution of Rare Earth Elements in Hot Rolled Magnesium Alloys with Improved Mechanical Properties
Authors: Neh Kristina , Ullmann Madlen , Kawalla Rudolf
Published: May 2016

Magnesium alloys containing rare earth elements offer excellent strength at room temperature as well as at elevated temperatures and are distinguished by a high ignition-resistance. However, with regard to cost efficiency and the conversation of resources, these alloys are not suitable for commercial industrial applications. Therefore, the research project SubSEEMag at the Institute of Metal Forming/Technische Universität Bergakademie Freiberg focusses on the development of alternative alloy compositions, which meet the requirements on materials properties of magnesium alloys for industrial applications and production costs. Several magnesium alloys containing zinc, aluminum, manganese and calcium were poured in cylindrical molds at the Helmholtz-Zentrum Geesthacht. The characterization of the as-cast condition was carried out by light and scanning electron microscopy. Phase compositions were determined using EDX analysis. The Mg alloys were homogenized at different temperatures. Afterwards, hot rolling to a final thickness of 2.7 mm was conducted. The influence of temperature and time of the annealing on the microstructure and the mechanical properties of the hot rolled condition have been investigated. The results were discussed in comparison to commercial available Mg-RE alloys.
Investigation of Texture Structure and Mechanical Properties Evolution during Hot Deformation of 1565 Aluminum Alloy
Authors: Rushchits S.V. , Aryshenskii Evgenii V. , Kawalla Rudolf , Serebryany Vladimir
Published: May 2016

The article is devoted to study of mechanical properties and texture evolution during thermal mechanical treatment of new aluminum 5XXX series alloy (1565 ch in Russian naming system). For the investigation of deformation behavior of 1565ch alloy a Gleeble axial compression mode is used. The expression for steady flow stress as the functions of temperature of deformation and strain rate is obtained. For texture evolution investigation industrial mills is used. Texture evaluation is performed using the orientation distribution function (ODF) calculated from the X-ray direct pole figures
Rolling of Flat Aluminum Strips with Tailored Mechanical Properties
Authors: Grydin Olexandr , Bondarenko Serhii , Stolbchenko Mykhailo , Schaper Mirko
Published: May 2016

In this study, the possibility of producing of flat aluminum strips with tailored mechanical properties across their width by means of rolling was examined. The aim of the work was an experimental analysis of the effect of cold rolling of the strips with a pre-profiled cross-section in flat rolls. Because of different work hardening of the various elements of the pre-profiled strips a characteristic profile of mechanical properties over the strips cross-section was created. The performed tensile tests and hardness measurements proved the possibility of setting of tailored properties in flat strips by means of rolling. The difference between the mechanical characteristics of various strip’s elements for the selected aluminum alloy can reach 40%.
Skin Pass Rolling of High Manganese Steels
Authors: Köhler Kai , Kwiaton Norbert , Bretschneider Martin
Published: May 2016

Applying a specific roughness on steel sheets, to ensure paintability and sufficient lubrication, is a crucial point for the metal forming processes. Due to the strength of high manganese HSD® steels (X70MnAlSi 15-2.5-2.5), special actions are necessary to obtain the required roughness. At Salzgitter Mannesmann Forschung GmbH skin-pass rolling experiments on high manganese HSD® steels with different PRETEX® textured work-rolls were performed to investigate the influence of roll-surface-texture and skin-pass rolling force on the roughness transfer. The roughness and texture parameters of the steel sheets and roll surfaces were determined using optical confocal microscopy measurements. It is clearly shown that the work-roll surface texture has a major influence on the roughness transfer from work-rolls to steel sheet surfaces.
A New Strategy for Manufacturing Tailored Blanks by a Flexible Rolling Process
Authors: Hildenbrand Philipp , Lechner Michael , Merklein Marion
Published: May 2016

Applying bulk forming processes on sheet metals enables the manufacturing of functional components with local wall thickness distributions. Using tailored blanks improves the forming of the functional components and increases the material efficiency. One process for manufacturing tailored blanks with defined sheet thickness distributions is a flexible rolling process. However, this process requires a complex process strategy. Additionally, tailored blanks out of high-strength steels from this process have failed in subsequent forming. Thus, a new rolling concept with a defined shaping of the material into a die cavity has been developed. This new concept requires the development of a new process strategy. In this paper, the general qualification and first results of the new concept are presented.
Study of Mechanical Properties on Bi-Directional E-Glass Fiber with Epoxy Resin Multi Walled CNT Nanoсomposite
Authors: Nallusamy S.
Published: May 2016

Now a days composite material plays an important role in many industrial applications due to their excellent mechanical properties. Presently researchers are making composite materials using various filler materials to characterize the wear behavior of the composite which is used as a machine component in various industrial applications and in machine house hold articles for daily use to highly sophisticated applications. This is due to the proven fact that composite materials acquire higher strength to weight ratio. In this investigation Nano composites of E-Glass fiber/Multi walled carbon nano tube were prepared by the technique of hand layup. The glass fiber used for current investigation is E-glass fiber bi-directional of 45 degree orientation. The composite material samples were prepared in the form of a plate with a thickness of 4 mm. The fabricated composite materials were cut into analogous profiles as per ASTM for tensile and flexural testing analysis. This investigation reveals that the growth of Multi Walled Carbon Nano Tube (MWCNT) particles improves considerably the mechanical properties even if the fabrication is done by manual method like the technique of hand layup.
RIPK1 and PGAM5 Control Leishmania Replication through Distinct Mechanisms
Authors: Farias Luz Nivea , Balaji Sakthi , Okuda Kendi , Barreto Aline Silva , Bertin John , Gough Peter J. , Gazzinelli Ricardo , Almeida Roque P. , Bozza Marcelo T. , Borges Valeria M. , Chan Francis Ka-Ming
Published: May 2016

Leishmaniasis is an important parasitic disease found in the tropics and subtropics. Cutaneous and visceral leishmaniasis affect an estimated 1.5 million people worldwide. Despite its human health relevance, relatively little is known about the cell death pathways that control Leishmania replication in the host. Necroptosis is a recently identified form of cell death with potent antiviral effects. Receptor interacting protein kinase 1 (RIPK1) is a critical kinase that mediates necroptosis downstream of death receptors and TLRs. Heme, a product of hemoglobin catabolism during certain intracellular pathogen infections, is also a potent inducer of macrophage necroptosis. We found that human visceral leishmaniasis patients exhibit elevated serum levels of heme. Therefore, we examined the impact of heme and necroptosis on Leishmania replication. Indeed, heme potently inhibited Leishmania replication in bone marrow–derived macrophages. Moreover, we found that inhibition of RIPK1 kinase activity also enhanced parasite replication in the absence of heme. We further found that the mitochondrial phosphatase phosphoglycerate mutase family member 5 (PGAM5), a putative downstream effector of RIPK1, was also required for inhibition of Leishmania replication. In mouse infection, both PGAM5 and RIPK1 kinase activity are required for IL-1β expression in response to Leishmania. However, PGAM5, but not RIPK1 kinase activity, was directly responsible for Leishmania-induced IL-1β secretion and NO production in bone marrow–derived macrophages. Collectively, these results revealed that RIPK1 and PGAM5 function independently to exert optimal control of Leishmania replication in the host.
Cholesterol Crystals Activate the Lectin Complement Pathway via Ficolin-2 and Mannose-Binding Lectin: Implications for the Progression of Atherosclerosis
Authors: Pilely Katrine , Rosbjerg Anne , Genster Ninette , Gal Peter , Pál Gábor , Halvorsen Bente , Holm Sverre , Aukrust Pål , Bakke Siril Skaret , Sporsheim Bjørnar , Nervik Ingunn , Niyonzima Nathalie , Bartels Emil D. , Stahl Gregory L. , Mollnes Tom Eirik , Espevik Terje , Garred Peter
Published: May 2016

Cholesterol crystals (CC) play an essential role in the formation of atherosclerotic plaques. CC activate the classical and the alternative complement pathways, but the role of the lectin pathway is unknown. We hypothesized that the pattern recognition molecules (PRMs) from the lectin pathway bind CC and function as an upstream innate inflammatory signal in the pathophysiology of atherosclerosis. We investigated the binding of the PRMs mannose-binding lectin (MBL), ficolin-1, ficolin-2, and ficolin-3, the associated serine proteases, and complement activation products to CC in vitro using recombinant proteins, specific inhibitors, as well as deficient and normal sera. Additionally, we examined the deposition of ficolin-2 and MBL in human carotid plaques by immunohistochemistry and fluorescence microscopy. The results showed that the lectin pathway was activated on CC by binding of ficolin-2 and MBL in vitro, resulting in activation and deposition of complement activation products. MBL bound to CC in a calcium-dependent manner whereas ficolin-2 binding was calcium-independent. No binding was observed for ficolin-1 or ficolin-3. MBL and ficolin-2 were present in human carotid plaques, and binding of MBL to CC was confirmed in vivo by immunohistochemistry, showing localization of MBL around CC clefts. Moreover, we demonstrated that IgM, but not IgG, bound to CC in vitro and that C1q binding was facilitated by IgM. In conclusion, our study demonstrates that PRMs from the lectin pathway recognize CC and provides evidence for an important role for this pathway in the inflammatory response induced by CC in the pathophysiology of atherosclerosis.
Multiple IgH Isotypes Including IgD, Subclasses of IgM, and IgY Are Expressed in the Common Ancestors of Modern Birds
Authors: Han Binyue , Yuan Hui , Wang Tao , Li Bo , Ma Li , Yu Shuyang , Huang Tian , Li Yan , Fang Dongming , Chen Xiaoli , Wang Yongsi , Qiu Si , Guo Ying , Fei Jing , Ren Liming , Pan-Hammarström Qiang , Hammarström Lennart , Wang Jun , Wang Jian , Hou Yong , Pan Qingjie , Xu Xun , Zhao Yaofeng
Published: May 2016

Although evolutionarily just as ancient as IgM, it has been thought for many years that IgD is not present in birds. Based on the recently sequenced genomes of 48 bird species as well as high-throughput transcriptome sequencing of immune-related tissues, we demonstrate in this work that the ostrich (Struthio camelus) possesses a functional δ gene that encodes a membrane-bound IgD H chain with seven CH domains. Furthermore, δ sequences were clearly identified in many other bird species, demonstrating that the δ gene is widely distributed among birds and is only absent in certain bird species. We also show that the ostrich possesses two μ genes (μ1, μ2) and two υ genes (υ1, υ2), in addition to the δ and α genes. Phylogenetic analyses suggest that subclass diversification of both the μ and υ genes occurred during the early stages of bird evolution, after their divergence from nonavian reptiles. Although the positions of the two υ genes are unknown, physical mapping showed that the remaining genes are organized in the order μ1-δ-α-μ2, with the α gene being inverted relative to the others. Together with previous studies, our data suggest that birds and nonavian reptile species most likely shared a common ancestral IgH gene locus containing a δ gene and an inverted α gene. The δ gene was then evolutionarily lost in selected birds, whereas the α gene lost in selected nonavian reptiles. The data obtained in this study provide significant insights into the understanding of IgH gene evolution in tetrapods.
Groundwater level monitoring near Killarney and Cartwright, Manitoba, 2010-2014
Authors: Hinton M J
Published: May 2016

The Geological Survey of Canada (GSC) is investigating the hydrogeology of the Spiritwood buried valley aquifer in southwestern Manitoba as part of its Groundwater Geosciences Program. This Open File Report presents hourly groundwater level and temperature data
collected between November 2010 and November 2014 from eight piezometers installed by the GSC at four sites located near Killarney and Cartwright, Manitoba.
Effects of Various Kynurenine Metabolites on Respiratory Parameters of Rat Brain, Liver and Heart Mitochondria
Authors: Baran* Halina , Staniek Katrin , Bertignol-Spörr Melanie , Attam Martin , Kronsteiner Carina , Kepplinger Berthold
Published: May 2016

Previously, we demonstrated that the endogenous glutamate receptor antagonist kynurenic acid dose-dependently and significantly affected rat heart mitochondria. Now we have investigated the effects of L-tryptophan, L-kynurenine, 3-hydroxykynurenine and kynurenic, anthranilic, 3-hydroxyanthranilic, xanthurenic and quinolinic acids on respiratory parameters (ie, state 2, state 3), respiratory control index (RC) and ADP/oxygen ratio in brain, liver and heart mitochondria of adult rats. Mitochondria were incubated with glutamate/malate (5 mM) or succinate (10 mM) and in the presence of L-tryptophan metabolites (1 mM) or in the absence, as control. Kynurenic and anthranilic acids significantly reduced RC values of heart mitochondria in the presence of glutamate/malate. Xanthurenic acid significantly reduced RC values of brain mitochondria in the presence of glutamate/malate. Furthermore, 3-hydroxykynurenine and 3-hydroxyanthranilic acid decreased RC values of brain, liver and heart mitochondria using glutamate/malate. In the presence of succinate, 3-hydroxykynurenine and 3-hydroxyanthranilic acid affected RC values of brain mitochondria, whereas in liver and heart mitochondria only 3-hydroxykynurenine lowered RC values significantly. Furthermore, lowered ADP/oxygen ratios were observed in brain mitochondria in the presence of succinate with 3-hydroxykynurenine and 3-hydroxyanthranilic acid, and to a lesser extent with glutamate/malate. In addition, 3-hydroxyanthranilic acid significantly lowered the ADP/oxygen ratio in heart mitochondria exposed to glutamate/malate, while in the liver mitochondria only a mild reduction was found. Tests of the influence of L-tryptophan and its metabolites on complex I in liver mitochondria showed that only 3-hydroxykynurenine, 3-hydroxyanthranilic acid and L-kynurenine led to a significant acceleration of NADH-driven complex I activities. The data indicate that L-tryptophan metabolites had different effects on brain, liver and heart mitochondria. Alterations of L-tryptophan metabolism might have an impact on the bioenergetic activities of brain, liver and/or heart mitochondria and might be involved in the development of clinical symptoms such as cardiomyopathy, hepatopathy and dementia.
Near-field Imaging Point-like Scatterers and Extended Elastic Solid in a Fluid
Authors: Yin Tao , Hu Guanghui , Xu Liwei
Published: May 2016

Consider the time-harmonic acoustic scattering from an extended elastic body surrounded by a finite number of point-like obstacles in a fluid. We assume point source waves are emitted from arrayed transducers and the signals of scattered near-field data are recorded by receivers not far away from the scatterers (compared to the incident wavelength). The forward scattering can be modeled as an interaction problem between acoustic and elastic waves together with a multiple scattering problem between the extend solid and point scatterers. We prove a necessary and sufficient condition that can be used simultaneously to recover the shape of the extended elastic solid and to locate the positions of point scatterers. The essential ingredient in our analysis is the outgoing-to-incoming (OtI) operator applied to the resulting near-field response matrix (or operator). In the first part, we justify the MUSIC algorithm for locating point scatterers from near-field measurements. In the second part, we apply the factorization method, the continuous analogue of MUSIC, to the two-scale scattering problem for determining both extended and point scatterers. Numerical examples in 2D are demonstrated to show the validity and accuracy of our inversion algorithms.
A Dimensional Splitting of ETD Schemes for Reaction-Diffusion Systems
Authors: Asante-Asamani E. O. , Wade Bruce A.
Published: May 2016

Novel dimensional splitting techniques are developed for ETD Schemes which are second-order convergent and highly efficient. By using the ETD-Crank-Nicolson scheme we show that the proposed techniques can reduce the computational time for nonlinear reaction-diffusion systems by up to 70%. Numerical tests are performed to empirically validate the superior performance of the splitting methods.
Application of Lie Algebra in Constructing Volume-Preserving Algorithms for Charged Particles Dynamics
Authors: Zhang Ruili , Liu Jian , Qin Hong , Tang Yifa , He Yang , Wang Yulei
Published: May 2016

Volume-preserving algorithms (VPAs) for the charged particles dynamics is preferred because of their long-term accuracy and conservativeness for phase space volume. Lie algebra and the Baker-Campbell-Hausdorff (BCH) formula can be used as a fundamental theoretical tool to construct VPAs. Using the Lie algebra structure of vector fields, we split the volume-preserving vector field for charged particle dynamics into three volume-preserving parts (sub-algebras), and find the corresponding Lie subgroups. Proper combinations of these subgroups generate volume preserving, second order approximations of the original solution group, and thus second order VPAs. The developed VPAs also show their significant effectiveness in conserving phase-space volume exactly and bounding energy error over long-term simulations.
A Numerical Thermal-Hydraulic Model to Simulate the Fast Transients in a Supercritical Water Channel Subjected to Sharp Pressure Variations
Authors: Dutta Goutam , Jiang Jin , Maitri Rohit , Zhang Chao
Published: May 2016

The present work demonstrates the extension of a thermal-hydraulic model, THRUST, with an objective to simulate the fast transient flow dynamics in a supercritical water channel of circular cross section. THRUST is a 1-D model which solves the nonlinearly coupled mass, axial momentum and energy conservation equations in time domain based on a characteristics-dependent fully implicit finite difference scheme using an Eulerian approach. The model developed accounts for the compressibility of the supercritical flow by considering the finite value of acoustic speed in the solution algorithm and treats the boundary conditions naturally. A supercritical water channel of circular cross section, for which the experimental data is available at steady state operating conditions, is chosen for the transient simulations to start with. Two different case studies are undertaken with a purpose to assess the capability of the model to analyze the fast transient processes caused by the large reduction in system pressure. The first transient case study is where the initial exit pressure is reduced by 1MPaexponentially in a time span of 5s. In the second case study, the transient is initiated with a sudden step decrease in the exit pressure by the same amount. Results obtained for both the case studies show the desired performance from the model developed.
Entropy Stable Scheme on Two-Dimensional Unstructured Grids for Euler Equations
Authors: Ray Deep , Chandrashekar Praveen , Fjordholm Ulrik S. , Mishra Siddhartha
Published: May 2016

We propose an entropy stable high-resolution finite volume scheme to approximate systems of two-dimensional symmetrizable conservation laws on unstructured grids. In particular we consider Euler equations governing compressible flows. The scheme is constructed using a combination of entropy conservative fluxes and entropy-stable numerical dissipation operators. High resolution is achieved based on a linear reconstruction procedure satisfying a suitable sign property that helps to maintain entropy stability. The proposed scheme is demonstrated to robustly approximate complex flow features by a series of benchmark numerical experiments.
Parameter-Free Time Adaptivity Based on Energy Evolution for the Cahn-Hilliard Equation
Authors: Luo Fuesheng , Tang Tao , Xie Hehu
Published: May 2016

It is known that large time-stepping method are useful for simulating phase field models. In this work, an adaptive time-stepping strategy is proposed based on numerical energy stability and equi-distribution principle. The main idea is to use the energy variation as an indicator to update the time step, so that the resulting algorithm is free of user-defined parameters, which is different from several existing approaches. Some numerical experiments are presented to illustrate the effectiveness of the algorithms.
Landscape Fragmentation as a Risk Factor for Buruli Ulcer Disease in Ghana
Authors: Wu Jianyong , Smithwick Erica A. H.
Published: May 2016

Land cover and its change have been linked to Buruli ulcer (BU), a rapidly emerging tropical disease. However, it is unknown whether landscape structure affects the disease prevalence. To examine the association between landscape pattern and BU presence, we obtained land cover information for 20 villages in southwestern Ghana from high resolution satellite images, and analyzed the landscape pattern surrounding each village. Eight landscape metrics indicated that landscape patterns between BU case and reference villages were different (P < 0.05) at the broad spatial extent examined (4 km). The logistic regression models showed that landscape fragmentation and diversity indices were positively associated with BU presence in a village. Specifically, for each increase in patch density and edge density by 100 units, the likelihood of BU presence in a village increased 2.51 (95% confidence interval [CI] = 1.36–4.61) and 4.18 (95% CI = 1.63–10.76) times, respectively. The results suggest that increased landscape fragmentation may pose a risk to the emergence of BU.
Historical Review: Problematic Malaria Prophylaxis with Quinine
Authors: Shanks G. Dennis
Published: May 2016

Quinine, a bitter-tasting, short-acting alkaloid drug extracted from cinchona bark, was the first drug used widely for malaria chemoprophylaxis from the 19th century. Compliance was difficult to enforce even in organized groups such as the military, and its prophylaxis potential was often questioned. Severe adverse events such as blackwater fever occurred rarely, but its relationship to quinine remains uncertain. Quinine prophylaxis was often counterproductive from a public health viewpoint as it left large numbers of persons with suppressed infections producing gametocytes infective for mosquitoes. Quinine was supplied by the first global pharmaceutical cartel which discouraged competition resulting in a near monopoly of cinchona plantations on the island of Java which were closed to Allied use when the Japanese Imperial Army captured Indonesia in 1942. The problems with quinine as a chemoprophylactic drug illustrate the difficulties with medications used for prevention and the acute need for improved compounds.
Are We Ready to investigate Cognitive Function of Fetal Brain? The Role of Advanced Four-dimensional Sonography
Authors: Kadic Aida Salihagic , Barisic Lara Spalldi
Published: May 2016

ABATRACT

Human brain is fascinating organ in so many ways. Some of its cognitive functions, such as ability to learn, memorize, think, percept different sensations, such as pain, to have emotion, process audio-visual inputs, and to coordinate reaction and movements have been subjects of studies for many years. Yet, till recently, we could only make assumptions about prenatal activities, interactions and its construction of complex structures in the time frame of antenatal life. With the prenatal assessment (sonoembryology, neurosonoembryology, KANET test, etc.) by latest advanced HDlive, Silhouette and Flow 3D/4D imaging there is possibility to follow in continuity normal structural and functional development from the early beginnings of “life” and on the other hand consider what might be different (not necessarily abnormal) and deviate from normal development and behavior.

On this way, we are able to supplement knowledge of fundamental building blocks of development of fetal cognitive functions, to pay more attention and follow up fetuses at higher risk and finally find some of the possible origins of cognitive dysfunctions which may manifest in childhood or later in life.82 With the introduction of different 3D/4D ultrasound modes we have ability to observe all of this in vivo while emerging, and make “time-lapse” of fetal neurodevelopment and behavior in correlation to its cognitive functional development

How to cite this article

Kurjak A, Spalldi Barisic L, Stanojevic M, Salihagic Kadic A, Porovic S. Are We Ready to investigate Cognitive Function of Fetal Brain? The Role of Advanced Fourdimensional Sonography. Donald School J Ultrasound Obstet Gynecol 2016;10(2):116-124.
Prevention of Retinopathy of Prematurity: A Perinatal approach
Authors: Vidyasagar Dharmapuri
Published: May 2016

Retinopathy of prematurity (ROP) is a multifactorial vasoproliferative retinal disorder in the premature infant exposed to high oxygen therapy. Retinopathy of prematurity is a major contributor to childhood blindness. Whereas ROP in high-income countries is decreasing, it is increasing in the low and middle-income countries, such as India. On the other hand, ROP is also a preventable disease. So far, preventive programs have focused on pediatric, neonatal, and nursing practices: Minimizing exposure to oxygen of premature babies admitted to neonatal intensive care unit (NICU) in respiratory distress (RDS) and early detection of ROP and treatment by the ophthalmologists.

Prematurity is the major risk factor for ROP. Decreasing the risk of prematurity requires a perinatal approach. Evidence shows that good antenatal care, managing preterm labor, and administration of antenatal steroids decrease respiratory complication and the need for oxygen therapy in the premature infants. There is also a need for decreasing the elective cesarean sections (ECS) which add to iatrogenic preterm births and associated respiratory complications. New research shows that inflammatory factors that lead to premature labor also make the premature retinal vessels susceptible to developing ROP. These scientific findings lay ground for a stronger perinatal approach to prevent ROP in future. This article attempts to highlight the perinatal approach to prevent ROP.

How to cite this article

Vidyasagar D. Prevention of Retinopathy of Prematurity: A Perinatal Approach. Donald School J Ultrasound Obstet Gynecol 2016;10(2):185-188.
Implementation of Bessel's method for solar eclipses prediction in the WRF-ARW model
Authors: Montornès Alex , Codina Bernat , Zack John W. , Sola Yolanda
Published: May 2016

Abstract. Solar eclipses are predictable astronomical events that abruptly reduce the incoming solar radiation into the Earth's atmosphere, which frequently results in non-negligible changes in meteorological fields. The meteorological impacts of these events have been analyzed in many studies since the late 1960s. The recent growth in the solar energy industry has greatly increased the interest in providing more detail in the modeling of solar radiation variations in numerical weather prediction (NWP) models for the use in solar resource assessment and forecasting applications. The significant impact of the recent partial and total solar eclipses that occurred in the USA (23 October 2014) and Europe (20 March 2015) on solar power generation have provided additional motivation and interest for including these astronomical events in the current solar parameterizations.Although some studies added solar eclipse episodes within NWP codes in the 1990s and 2000s, they used eclipse parameterizations designed for a particular case study. In contrast to these earlier implementations, this paper documents a new package for the Weather Research and Forecasting–Advanced Research WRF (WRF-ARW) model that can simulate any partial, total or hybrid solar eclipse for the period 1950 to 2050 and is also extensible to a longer period. The algorithm analytically computes the trajectory of the Moon's shadow and the degree of obscuration of the solar disk at each grid point of the domain based on Bessel's method and the Five Millennium Catalog of Solar Eclipses provided by NASA, with a negligible computational time. Then, the incoming radiation is modified accordingly at each grid point of the domain.This contribution is divided in three parts. First, the implementation of Bessel's method is validated for solar eclipses in the period 1950–2050, by comparing the shadow trajectory with values provided by NASA. Latitude and longitude are determined with a bias lower than 5  ×  10−3 degrees (i.e.,  ∼  550 m at the Equator) and are slightly overestimated and underestimated, respectively. The second part includes a validation of the simulated global horizontal irradiance (GHI) for four total solar eclipses with measurements from the Baseline Surface Radiation Network (BSRN). The results show an improvement in mean absolute error (MAE) from 77 to 90 % under cloudless skies. Lower agreement between modeled and measured GHI is observed under cloudy conditions because the effect of clouds is not included in the simulations for a better analysis of the eclipse outcomes. Finally, an introductory discussion of eclipse-induced perturbations in the surface meteorological fields (e.g., temperature, wind speed) is provided by comparing the WRF–eclipse outcomes with control simulations.
Organic nitrate chemistry and its implications for nitrogen budgets in an isoprene- and monoterpene-rich atmosphere: constraints from aircraft (SEAC4RS) and ground-based (SOAS) observations in the Southeast US
Authors: Fisher Jenny A. , Jacob Daniel J. , Travis Katherine R. , Kim Patrick S. , Marais Eloise A. , Chan Miller Christopher , Yu Karen , Zhu Lei , Yantosca Robert M. , Sulprizio Melissa P. , Mao Jingqiu , Wennberg Paul O. , Crounse John D. , Teng Alex P. , Nguyen Tran B. , St. Clair Jason M. , Cohen Ronald C. , Romer Paul , Nault Benjamin A. , Wooldridge Paul J. , Jimenez Jose L. , Campuzano-Jost Pedro , Day Douglas A. , Hu Weiwei , Shepson Paul B. , Xiong Fulizi , Blake Donald R. , Goldstein Allen H. , Misztal Pawel K. , Hanisco Thomas F. , Wolfe Glenn M. , Ryerson Thomas B. , Wisthaler Armin , Mikoviny Tomas
Published: May 2016

Abstract. Formation of organic nitrates (RONO2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry of RONO2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO2) in the GEOS-Chem global chemical transport model with  ∼  25  ×  25 km2 resolution over North America. We evaluate the model using aircraft (SEAC4RS) and ground-based (SOAS) observations of NOx, BVOCs, and RONO2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas- and particle-phase RONO2 species measured during the campaigns. Gas-phase isoprene nitrates account for 25–50 % of observed RONO2 in surface air, and we find that another 10 % is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10 % of observed boundary layer RONO2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO3 accounts for 60 % of simulated gas-phase RONO2 loss in the boundary layer. Other losses are 20 % by photolysis to recycle NOx and 15 % by dry deposition. RONO2 production accounts for 20 % of the net regional NOx sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NOx emissions. This segregation implies that RONO2 production will remain a minor sink for NOx in the Southeast US in the future even as NOx emissions continue to decline.
In Vitro Exposure to Isoprene-Derived Secondary Organic Aerosol by Direct Deposition and its Effects on COX-2 and IL-8 Gene Expression
Authors: Arashiro Maiko , Lin Ying-Hsuan , Sexton Kenneth G. , Zhang Zhenfa , Jaspers Ilona , Fry Rebecca C. , Vizuete William G. , Gold Avram , Surratt Jason D.
Published: May 2016

Abstract. Atmospheric oxidation of isoprene, the most abundant non-methane hydrocarbon emitted into Earth’s atmosphere primarily from terrestrial vegetation, is now recognized as a major contributor to the global secondary organic aerosol (SOA) burden. Anthropogenic pollutants significantly enhance isoprene SOA formation through acid-catalyzed heterogeneous chemistry of epoxide products. Since isoprene SOA formation as a source of fine aerosol is a relatively recent discovery, research is lacking on evaluating its potential adverse effects on human health. The objective of this study was to examine the effect of isoprene-derived SOA on inflammation-associated gene expression in human lung cells using a direct deposition exposure method. We assessed altered expression of inflammation-related genes in human bronchial epithelial cells (BEAS-2B) exposed to isoprene-derived SOA generated in an outdoor chamber facility. Measurements of gene expression of known inflammatory biomarkers interleukin 8 (IL-8) and cyclooxygenase 2 (COX-2) in exposed cells, together with complementary chemical measurements, showed that a dose of 0.067 µg cm−2 of SOA from isoprene photooxidation leads to statistically significant increases in IL-8 and COX-2 mRNA levels. Resuspension exposures using aerosol filter extracts corroborated these findings, supporting the conclusion that isoprene-derived SOA constituents induce the observed changes in mRNA levels. Future studies are needed to systematically examine the molecular mechanisms of toxicity.
An optical particle size spectrometer for aircraft-borne measurements in IAGOS-CARIBIC
Authors: Hermann Markus , Weigelt Andreas , Assmann Denise , Pfeifer Sascha , Müller Thomas , Conrath Thomas , Voigtländer Jens , Heintzenberg Jost , Wiedensohler Alfred , Martinsson Bengt G. , Deshler Terry , Brenninkmeijer Carl A. M. , Zahn Andreas
Published: May 2016

Abstract. The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new optical particle size spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region on board a passenger aircraft (IAGOS-CARIBIC observatory: In-service Aircraft for a Global Observing System – Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container). A modified KS93 particle sensor from RION Co., Ltd., together with a new airflow system and a dedicated data acquisition system, is the key component of the CARIBIC OPSS. The instrument records individual particle pulse signal curves in the particle size range 130–1110 nm diameter (for a particle refractive index of 1.47-i0.006) together with a time stamp and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instrument's measurement performance shows no pressure dependency and no particle coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of 2 in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.