Rational Design of Novel Materials From Polymer Microrheology

2010 ◽  
Author(s):  
Rodrigo E. Teixeira ◽  
Richard S. Graham
Keyword(s):  
Rational Design ◽  
Molecular Level ◽  
Pressure Vessels ◽  
Novel Materials ◽  
Entangled Polymers ◽  
Stochastic Fluctuations ◽  
Safety Margins ◽  
Polymer Liquids ◽  
Entangled Polymer ◽  
High Degree

The visco-elastic properties of entangled polymer liquids arise from molecular-scale topological interactions and stochastic fluctuations under flow. Here, the evolutions of individual entangled polymers were observed in rheologically relevant shear flow histories. We uncover a high degree of molecular individualism and broad conformational distributions resulting from incessant stretch-collapse cycles. The data and insights of the present study may lead to improved molecular-level models and constitutive equations. These tools, in turn, may enable the rational design of novel materials with properties tailored to accomplish specific tasks such as high-pressure vessels and piping with greater safety margins and cost-effectiveness.

In situ nanoscale visualization of solvent effects on molecular crystal surfaces

CrystEngComm ◽  
2021 ◽  
Author(s):  
Mikkel Herzberg ◽  
Anders Støttrup Larsen ◽  
Tue Hassenkam ◽  
Anders Østergaard Madsen ◽  
Jukka Rantanen
Keyword(s):  
Solid Solution ◽  
Solvent Effects ◽  
Molecular Crystal ◽  
Rational Design ◽  
Molecular Level ◽  
Molecular Crystals ◽  
Crystal Surfaces ◽  
Solution Interface ◽  
Atomic Force

Solvents can dramatically affect molecular crystals. Obtaining favorable properties for these crystals requires rational design based on molecular level understanding of the solid-solution interface. Here we show how atomic force...

Relaxation dynamics of entangled polymer liquids in steady shear flow

2003 ◽  
Vol 47 (2) ◽  
pp. 469-482 ◽  
Author(s):  
Javier Sanchez-Reyes ◽  
Lynden A. Archer
Keyword(s):  
Shear Flow ◽  
Steady Shear ◽  
Relaxation Dynamics ◽  
Steady Shear Flow ◽  
Polymer Liquids ◽  
Entangled Polymer

Rational Design of Solid-Acid Catalysts for Cellulose Hydrolysis Using Colloidal Theory

2021 ◽  
Author(s):  
Ziyang Zhang ◽  
Geoffrey A Tompsett ◽  
Christopher Lambert ◽  
Sergio Granados-Focil ◽  
Michael T. Timko
Keyword(s):  
Rational Design ◽  
Solid Acid ◽  
Molecular Level ◽  
Cellulose Hydrolysis ◽  
Solid Acid Catalysts ◽  
Acid Catalysts

Solid-acid catalysts functionalized with catalytic groups have attracted intense interests for hydrolyzing cellulose into fermentable compounds. However, the solid-acid catalysts design has been guided by molecular level of interactions and...

scholarly journals Nitrone Modified Gold Nanoparticles: Synthesis, Characterization and Their Potential as 18F-Labeled PET Probes via I-SPANC

2019 ◽  
Author(s):  
Sara Ghiassian ◽  
Lihai Yu ◽  
Pierangelo Gobbo ◽  
Ali nazemi ◽  
Tommaso Romagnoli ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Nmr Spectroscopy ◽  
Gold Nanoparticle ◽  
Molecular Level ◽  
Prosthetic Group ◽  
H Nmr ◽  
Nanoparticles Synthesis ◽  
Interfacial Strain ◽  
Pet Probes ◽  
High Degree

A bioorthogonal gold nanoparticle template displaying interfacial nitrone functional groups for bioorthogonal interfacial strain-promoted alkyne-nitrone cycloaddition (I-SPANC) reactions has been synthesized. The Nitrone-AuNPs were characterized in detail using <sup>1</sup>H NMR spectroscopy, TEM, TGA, and XPS and a nanoparticle raw formula was calculated. The ability to control the conjugation of molecules of interest at the molecular level onto the Nitrone-AuNPs template allowed us to create a methodology for the synthesis of AuNP-based radiolabeled probes with a high degree of loading using copper free, strained-promoted cycloaddition. To this end, we also describe the synthesis of a new prosthetic group containing a strained-alkyne capable of clicking hot <sup>18</sup>F-label onto complementary azide or nitrone labelled agents.

scholarly journals Progress in the rational design of an AIDS vaccine

2011 ◽  
Vol 366 (1579) ◽  
pp. 2759-2765 ◽  
Author(s):  
Gary J. Nabel ◽  
Peter D. Kwong ◽  
John R. Mascola
Keyword(s):  
Structural Biology ◽  
Neutralizing Antibodies ◽  
Rational Design ◽  
Computational Modelling ◽  
Effective Vaccine ◽  
Aids Vaccine ◽  
Immunodeficiency Virus ◽  
High Degree ◽  
Hiv 1 ◽  
Human Immunodeficiency Virus 1

Human immunodeficiency virus-1 (HIV-1) has a high degree of genetic and antigenic diversity that has impeded the development of an effective vaccine using traditional methods. We are attempting to develop an AIDS vaccine by employing strategies that include structural biology and computational modelling, in an effort to develop immunogens capable of eliciting neutralizing antibodies of the requisite breadth and potency against circulating strains of HIV-1.

ORNL Evaluation of Safety Cases for Two Belgian Reactor Pressure Vessels Containing Quasi-Laminar Defects

2017 ◽  
Author(s):  
Hilda B. Klasky ◽  
B. Richard Bass ◽  
Terry L. Dickson ◽  
Sarma B. Gorti ◽  
Randy K. Nanstad ◽  
...  
Keyword(s):  
New York ◽  
Finite Element ◽  
Structural Integrity ◽  
National Laboratory ◽  
Relevant Literature ◽  
Pressure Vessels ◽  
Oak Ridge ◽  
Safety Margins ◽  
Safety Cases ◽  
Reactor Pressure

The Oak Ridge National Laboratory (ORNL) performed a detailed technical review of the 2015 Electrabel (EBL) Safety Cases prepared for the Belgium reactor pressure vessels (RPVs) at Doel 3 and Tihange 2 (D3/T2). The Federal Agency for Nuclear Control (FANC) in Belgium commissioned ORNL to provide a thorough assessment of the existing safety margins against cracking of the RPVs due to the presence of almost laminar flaws found in each RPV. Initial efforts focused on surveying relevant literature that provided necessary background knowledge on the issues related to the quasi-laminar flaws observed in D3/T2 reactors. Next, ORNL proceeded to develop an independent quantitative assessment of the entire flaw population in the two Belgian reactors according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, Appendix G, “Fracture Toughness Criteria for Protection Against Failure,” New York (both 1992 and 2004 versions). That screening assessment of the EBL-characterized flaws in D3/T2 used ORNL tools, methodologies, and the ASME Code Case N-848, “Alternative Characterization Rules for Quasi-Laminar Flaws”. Results and conclusions derived from comparisons of the ORNL flaw acceptance assessments of D3/T2 with those from the 2015 EBL Safety Cases are presented in the paper. The ORNL screening analyses identified fewer flaws than EBL that were not compliant with the ASME Section XI (1992) criterion; the EBL criterion imposed additional conservatisms not included in ASME Section XI. Furthermore, ORNL’s application of the updated ASME Section XI (2004) criterion produced only four non-compliant flaws, all due to design-basis loss-of-coolant loading transients. Among the latter, only one flaw remained non-compliant when analyzed using the warm-prestress (WPS) cleavage fracture model typically applied in USA flaw assessments. ORNL’s independent refined analysis of that flaw (#1660, which was also non-compliant in the EBL screening assessments) rendered it compliant when modeled as a more realistic individual quasi-laminar flaw using a 3-dimensional XFEM (eXtended Finite Element Method) approach available in the ABAQUS© finite element code. Taken as a whole, the ORNL-specific results and conclusions confirmed the structural integrity of Doel 3 and Tihange 2 under all design transients with ample margin in the presence of the 16,196 detected flaws.

scholarly journals Contraction of Entangled Polymers After Large Step Shear Deformations in Slip-Link Simulations

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 370 ◽  
Author(s):  
Yuichi Masubuchi
Keyword(s):  
Dynamics Simulation ◽  
Uniaxial Deformation ◽  
Single Chain ◽  
Orientational Relaxation ◽  
Entangled Polymers ◽  
Constraint Release ◽  
Large Step ◽  
Entangled Polymer ◽  
Convective Constraint Release ◽  
Chain Contraction

Although the tube framework has achieved remarkable success to describe entangled polymer dynamics, the chain motion assumed in tube theories is still a matter of discussion. Recently, Xu et al. [ACS Macro Lett. 2018, 7, 190–195] performed a molecular dynamics simulation for entangled bead-spring chains under a step uniaxial deformation and reported that the relaxation of gyration radii cannot be reproduced by the elaborated single-chain tube model called GLaMM. On the basis of this result, they criticized the tube framework, in which it is assumed that the chain contraction occurs after the deformation before the orientational relaxation. In the present study, as a test of their argument, two different slip-link simulations developed by Doi and Takimoto and by Masubuchi et al. were performed and compared to the results of Xu et al. In spite of the modeling being based on the tube framework, the slip-link simulations excellently reproduced the bead-spring simulation result. Besides, the chain contraction was observed in the simulations as with the tube picture. The obtained results imply that the bead-spring results are within the scope of the tube framework whereas the failure of the GLaMM model is possibly due to the homogeneous assumption along the chain for the fluctuations induced by convective constraint release.

Uncertainties in Pressurized Thermal Shock Analyses

2019 ◽  
Author(s):  
M. Niffenegger ◽  
O. Costa Garrido ◽  
D. F. Mora ◽  
G. Qian ◽  
R. Mukin ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Thermal Shock ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Pressurized Water Reactor ◽  
Ansys Fluent ◽  
Pressurized Water ◽  
Integrity Assessment ◽  
Safety Margins ◽  
Pressurized Thermal Shock

Abstract Integrity assessment of reactor pressure vessels (RPVs) can be performed either by deterministic fracture mechanics (DFM) or/and by probabilistic fracture mechanics (PFM) analyses. In European countries and Switzerland, only DFM analyses are required. However, in order to establish the probabilistic approach in Switzerland, the advantages and shortcomings of the PFM are investigated in the frame of a national research project. Both, the results from DFM and PFM depend strongly on the previous calculated thermal-hydraulic boundary conditions. Therefore, complete integrity analyses involving several integrated numerical codes and methods were performed for a reference pressurized water reactor (PWR) RPV subjected to pressurized thermal shock (PTS) loads. System analyses were performed with the numerical codes RELAP5 and TRACE, whereas for structural and fracture mechanics calculations, the FAVOR and ABAQUS codes were applied. Additional computational fluid dynamics analyses were carried out with ANSYS/FLUENT, and the plume cooling effect was alternatively considered with GRS-MIX. The results from the different analyses tools are compared, to judge the expected overall uncertainty and reliability of PTS safety assessments. It is shown that the scatter band of the stress intensities for a fixed crack configuration is rather significant, meaning that corresponding safety margins should be foreseen. The conditional probabilities of crack initiation and RPV failure might also differ, depending on the considered random parameters and applied rules.

Use of a CFD-Tool for Assessment of the Reactor Pressure Vessel Integrity in Pressurised Thermal Shock Conditions: Thermal-Hydraulic Studies of a Safety Injection in a PWR Plant — Methodology and Present Limitation

2007 ◽  
Author(s):  
A. Martin ◽  
S. Bosse ◽  
F. Lestang
Keyword(s):  
Heat Transfer ◽  
Thermal Shock ◽  
Thermal Loading ◽  
Development Program ◽  
Pressure Vessels ◽  
Surveillance Program ◽  
Fluid Temperature ◽  
Two Phase ◽  
Safety Margins ◽  
Reactor Pressure

Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behaviour of cracks under PTS loading conditions due to the emergency cooling during PTS transient like SBLOCA. This paper explains the Research and Development program started at Electricite´ De France about the cooling phenomena of a PWR vessel after a Pressurised Thermal Shock. The numerical results are obtained with the E.D.F ThermalHydraulic code (Code_Saturne) coupled with the thermal-solid code SYRTHES to take into account the conjugate heat transfer on the cooling of the vessel. We first explain the global methodology with a progress report on the state of the art of the tools available to simulate the different scenari displayed within the frame of the plant life project in order to reassess the integrity of the RPV, taking into account the evolution of some input data, such as the new value of end of life (EOL) fluence, the feedback results of surveillance program and the evolution of the functional requirements. The main results are presented and are related to the evaluation of the RPV integrity during a Small Break Loss Of Coolant Accident transient for 900 and 1300 MWe nuclear plant. On the whole, the main purpose of the numerical CFD studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margins. In a second time, a new analysis is performed to assess an accurate temperature distribution in the RPV. Indeed, from a physical phenomena point of view, the EDF thermalhydraulic tool Code_Saturne is now qualified in order to assess single phase transient but in the case where the cold legs are partially filled with steam, it becomes a two-phase problem and new important effects occur, such as condensation due to the emergency core cooling injections of sub-cooled water. Thus, an advanced prediction of RPV thermal loading during these transients requires sophisticated two-phase, local scale, 3D codes. In that purpose, a program has been set up to extend the capabilities of the Neptune_CFD two-phase solver which is the tool able to solve two phase flow configuration. In a same time, A simplified approach has showed that for a type of transient weakly uncovered, a free surface calculation was sufficient to respect the necessary criteria of safety. A Qualification study was carried out on the Hybiscus experimental E.D.F facility, representing a cold leg with ECC injection and a third down comer. Temperature profiles have been compared and are presented and analysed here, showing encouraging results.

Template-Directed Syntheses of Catenanes

1997 ◽  
Vol 62 (4) ◽  
pp. 527-557 ◽  
Author(s):  
Martin Bělohradský ◽  
Françisco M. Raymo ◽  
J. Fraser Stoddart
Keyword(s):  
Self Assembly ◽  
Molecular Level ◽  
Covalent Bonds ◽  
Topological Features ◽  
Multistep Synthesis ◽  
Chance Event ◽  
Degree Of Control ◽  
High Degree ◽  
Acyclic Precursor ◽  
Molecular Compounds

The art and science of introducing mechanical-interlocking at the molecular level in order to generate catenanes - molecules composed of two or more macrocyclic components - offers the opportunity of constructing a new range of molecular compounds possessing intriguing properties. However, the topological features displayed by catenanes has rendered the syntheses of such molecular compounds an extremely challenging task for synthetic chemists to address. Their early syntheses were based upon either statistical approaches - the threading of a small amount of a macrocycle on to an acyclic precursor as a chance event - or directed approaches, relying upon the temporary introduction of covalent bonds in the multistep synthesis of a so-called precatenane, followed by its conversion ultimately into a catenane. These approaches afforded catenanes in very low yields overall and only after following tedious and laborious synthetic procedures. Fortunately, however, with the advent of supramolecular chemistry, template-directed methods that allow us to self-assemble [n]catenanes much more efficiently have become available. Numerous successful template-directed syntheses have now emerged - some by chance and others by design. These methods have been based upon (i) metal coordinating, (ii) hydrogen bonding, (iii) solvophobic, and/or (iv) π-π stacking interactions which have been found to govern self-assembly processes to catenated compounds from appropriate precursors. Their relative simplicity, the high degree of control with which they can be employed, and the remarkable efficiency with which they proceed has already provided the opportunity to synthetic chemists to self-assemble a series of [n]catenanes, incorporating from two up to five mechanically-interlocked macrocyclic components.

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