Incomplete Bond Research Articles

Quantum confinement effect in nanotwinned diamond

The success in enhancing diamond by introducing nanotwins opens a new frontier in the development of superhard materials. However, the underlying hardening mechanism of nanotwinned diamond (nt-diamond) remains elusive and a persistent research focus. In this study, we employ first-principles calculations to unveil the performance enhancement in nt-diamond mediated by quantum confinement effect. This effect is characterized by the non-uniform valence charge density of C-C bonds near the twin boundary, leading to incomplete bond breakage at the onset of elastic instability and identified as the key factor in delaying cracking. These findings not only contribute to establishing the theory of hardness in superhard materials, but also suggest new avenues for enhancing their mechanical performance through the introduction of heterogeneous structures and dopant atoms aligned with the principle of quantum confinement effect.

Analysis and Governance of "Greenwashing" Behavior in China's Green Bond Market

With the Chinese government and leaders attaching great importance to the construction of ecological civilization and the green financial market, green bonds have become an important tool to promote green development. However, the problem of "green washing" in the market not only erodes investors' trust in the market, but also damages the credibility and actual effectiveness of green finance, posing a potential threat to the continuous promotion of ecological civilization construction. This article analyzes two typical behaviors of "greenwashing" in the Chinese green bond market: false labeling of green projects and opaque use of funds, and explores their causes, involving problems such as incomplete green bond standard formulation and certification system, weak regulatory crackdown, short-term interest driven corporate behavior, insufficient public green awareness and supervision. Targeted response strategies have been proposed: firstly, to improve the green bond standard formulation and certification system, ensuring the authenticity of green projects; Secondly, enhance regulatory efforts and punishment measures, and build a rigorous legal environment; The third is to improve the transparency of information disclosure, requiring enterprises to regularly disclose the progress of projects and the use of funds; The fourth is to establish a sound investor protection mechanism and safeguard the legitimate rights and interests of investors. Through these measures, it is possible to effectively regulate and curb "green washing" behavior, and promote the sustainable development of the green bond market.

Incomplete ionic interactions and hydrogen bonds constructing elastomers with water accelerated Self-Healing and self-healing strengthening capacities

Self-healing polymers with microphase separation structure typically require external stimuli to achieve self-healing, and their performance often degrades. To solve these issues, we introduce tertiary amine and carboxyl groups into polymer. The intermolecular ionic interactions and H-bonds contribute to the formation of microphase separation structures, endowing polyurethane elastomers (PU-n) outstanding mechanical properties with a maximum tensile strength and toughness of 20.61 MPa and 59.02 MJ/m3, respectively. The self-healing of the prepared PU-n can be achieved at room temperature and accelerated significantly by water because hard phases can be dissociated, resulting in enhanced molecular movement. After self-healing with water, the enhanced molecular movement and further ionization of ionic groups lead to stronger H-bonds and ionic interactions, promoting more distinct microphase separation. Thus, the mechanical strength is strengthened and the self-healing efficiency can reach 104.72 %. The enhanced molecular movement and strengthened intermolecular interactions when self-healing with water can also be verified through in-depth analysis of molecular dynamics (MD) simulations of the self-healing process. Furthermore, PU-n display remarkable shape memory and can be recycled through exposure to solvents and hot water. This study provides a novel and general method for preparing materials that can self-heal with water and self-strengthen after self-healing.

Micro X-ray computed tomography examination of mini plate fuel with hot isostatic pressed aluminum cladding

In order to minimize proliferation risks and improve security of nuclear material, the United States high performance research and test reactors (USHPRR) program is tasked with converting nuclear reactors that are fueled with highly enriched uranium (HEU) fuels to operate with low-enriched uranium (LEU) nuclear fuels. One favorable LEU fuel configuration is plate fuel with a metallic uranium-molybdenum foil clad within an aluminum alloy (AA 6061). In this fuel, the aluminum cladding is bonded with a hot isostatic pressing (HIP) method to seal the cladding around the fuel meat. However, the HIP process parameters influence the cladding performance, as a defective or incomplete bond can cause a pathway for corrosion. Micro X-ray computed tomography (XCT), a nondestructive technique that provides volumetric imaging, can be applied to inspect fuel plate cladding at the engineering scale. In this work, XCT methodology was developed and successfully utilized to not only observe the bond line of unirradiated mini fuel plates, but to also identify subsurface abnormalities in the plates’ cladding. In future work, this technique could be applied to fuel plates, pre- and post-irradiation, to quantify irradiation effects on cladding defects and bond line integrity.

T15 High Speed Steels Produced by High-Temperature Low-Pressure Short-Time Vacuum Hot-Pressing Combined with Subsequent Diffusion-Bonding Treatment

Currently, hot isostatic pressing (HIP) is widely used to produce highly alloyed high speed steels (HSSs) in an industrial scale; however, the HIP’s production cost is very high. Another powder consolidation approach with low production cost, namely vacuum hot-pressing (VHP), has hitherto received limited attention. The present work aims to develop an innovative solid-state VHP approach, producing HSSs with large cross-sectional sizes via a VHP facility having low loading capacity, thus further decreasing production cost. In doing so, VHP is performed at a sufficiently high temperature such that the pressure leading to full densification can be significantly reduced to a magnitude as low as several MPa; simultaneously, VHP is completed within a timeframe as short as several seconds to minutes, retaining fine carbide sizes; subsequently, the as-VHP HSS is diffusion-bonding treated (DBT-ed) at a relatively low temperature, achieving full metallurgical bond between powders while minimizing carbide growth. In the present work, T15 HSS was processed using the above VHP approach. The VHP temperature as high as 1200 °C was selected and consequently, the minimal pressure leading to full densification was decreased to ~7 MPa. By controlling displacement of pressing punch to a value corresponding to full densification, the VHP was competed for only 15 min. The almost fully dense as-VHP T15 HSS exhibits submicrometric carbide sizes smaller than those in the as-HIP counterpart, but incomplete metallurgical bond between powders. After diffusion bonding treatment at a relatively low temperature of 1100 °C for 2–4 h, the extent of metallurgical bond between powders is significantly enhanced with insignificant carbide growth. After regular quenching and tempering, the VHP plus DBT-ed T15 HSSs exhibit smaller average primary carbide sizes and similar hardness and three-point bend fracture strength, relative to those in the HIP counterpart after similar quenching and tempering.

Elucidating the impact mechanism of temperature and water content on thermal conductivity of hydrated Nafion membranes by molecular dynamics simulation

The thermal conductivity of the proton exchange membrane significantly affects the operating performance of the fuel cell. In this work, the impact of water content and temperature on thermal conductivity of hydrated Nafion membranes was investigated via molecular dynamics simulations and the influencing mechanism was explained from the perspective of interchain and intrachain heat transfer. The study shows that the thermal conductivity is mainly positively affected by water content, which is a result of the triple effect of hydrogen bonding acting as interchain heat transfer bridge, the stronger microphase separation allowing water to behave more like bulk water, and the decrease in the degree of chain torsion resulting in less phonon scattering along the chain. Particularly, we emphasized two crucial paths in which hydrogen bonding improves interchain heat transport. Furthermore, the temperature has little and slightly negative effects on thermal conductivity at low and high hydration levels, respectively. That is because, in low hydration levels, the incomplete hydrogen bond network is hardly influenced, but the bridging effect is suppressed and intrachain heat transfer capacity is reduced in high hydration levels. We believe this study can broaden the design basis of high temperature polymer electrolyte membranes.

A toolkit for recombinant production of seven human EGF family growth factors in active conformation

Epidermal growth factors (EGF) play a wide range of roles in embryogenesis, skin development, immune response homeostasis. They are involved in several pathologies as well, including several cancer types, psoriasis, chronic pain and chronic kidney disease. All members share the structural EGF domain, which is responsible for receptor interaction, thereby initiating transduction of signals. EGF growth factors have intense use in fundamental research and high potential for biotechnological applications. However, due to their structural organization with three disulfide bonds, recombinant production of these factors in prokaryotic systems is not straightforward. A significant fraction usually forms inclusion bodies. For the fraction remaining soluble, misfolding and incomplete disulfide bond formation may affect the amount of active factor in solution, which can compromise experimental conclusions and biotechnological applications. In this work, we describe a reliable procedure to produce seven human growth factors of the EGF family in Escherichia coli. Biophysical and stability analyses using limited proteolysis, light scattering, circular dichroism and nanoDSF show that the recombinant factors present folded and stable conformation. Cell proliferation and scratch healing assays confirmed that the recombinant factors are highly active at concentrations as low as 5 ng/ml.

Enhanced Interfacial Integrity of Amorphous Oxide Thin-Film Transistors by Elemental Diffusion of Ternary Oxide Semiconductors.

Low-temperature solution-processed oxide semiconductor and dielectric films typically possess a substantial number of defects and impurities due to incomplete metal-oxygen bond formation, causing poor electrical performance and stability. Here, we exploit a facile route to improve the film quality and the interfacial property of low-temperature solution-processed oxide thin films via elemental diffusion between metallic ion-doped InOx (M:InOx) ternary oxide semiconductor and AlOx gate dielectric layers. Particularly, it was revealed that metallic dopants such as magnesium (Mg) and hafnium (Hf) having a small ionic radius, a high Gibbs energy of oxidation, and bonding dissociation energy could successfully diffuse into the low-quality AlOx gate dielectric layer and effectively reduce the structural defects and residual impurities present in the bulk and at the semiconductor/dielectric interface. Through an extensive investigation on the compositional, structural, and electrical properties of M:InOx/AlOx thin-film transistors (TFTs), we provide direct evidences of elemental diffusion occurred between M:InOx and AlOx layers as well as its contribution to the electrical performance and operational stability. Using the elemental diffusion process, we demonstrate solution-processed Hf:InOx TFTs using a low-temperature (180 °C) AlOx gate dielectric having a field-effect mobility of 2.83 cm2 V-1·s-1 and improved bias stability. Based on these results, it is concluded that the elemental diffusion between oxide semiconductor and gate dielectric layers can play a crucial role in realizing oxide TFTs with enhanced structural and interfacial integrity.

What's Wrong with Annuity Markets?

The annuity market in the US has been historically small. What drives this fact? The annuity market could be small because of adverse selection or supply-side frictions in insurance markets. Identifying demand- and supply-side frictions is difficult without data separately measuring exogenous shocks and endogenous responses. In this paper, we provide a novel identification using annuity price data and regulatory capital requirements. Using publicly available data, we document a robust relationship between shocks originating in the corporate bond market and annuity price markups. We show that this relationship supports a standard model of adverse selection with an incomplete bond market.

Robust long-term interest rate risk hedging in incomplete bond markets

AbstractPricing ultra-long-dated pension liabilities under the market-consistent valuation is challenged by the scarcity of the long-term market instruments that match or exceed the terms of pension liabilities. We develop a robust self-financing hedging strategy which adopts a min–max expected shortfall hedging criterion to replicate the long-dated liabilities for agents who fear parameter misspecification. We introduce a backward robust least squares Monte Carlo method to solve this dynamic robust optimization problem. We find that both naive and robust optimal portfolios depend on the hedging horizon and the current funding ratio. The robust policy suggests taking more risk when the current funding ratio is low. The yield curve constructed by the robust dynamic hedging portfolio is always lower than the naive one but is higher than the model-based yield curve in a low-rate environment.

Quantum efficient fast UV photodetectors based on nanocrystalline Zn1-xPxO (x = 0.00, 0.03, 0.07) thin films deposited by pulsed laser deposition technique

Here, we demonstrate the effect of phosphorous doping concentration on the structural, electrical and optical properties of ZnO thin films deposited by pulse laser deposition technique. X-ray diffraction studies performed on the deposited films reveal the polycrystalline nature of films and confirm the deposition of ZnO films in wurtzite phase. However, the incorporation of phosphorous does not lead to originate new peak in XRD patterns of the doped films, negating the formation of new phase or the formation of P2O5 phase of phosphorous. But this doping influences the peak positions of pure ZnO film which suggests that phosphorous taking the interstitially positions of Zn and compensates the incomplete bonds. The electrical conductivity of the deposited films is found to significantly increases with phosphorous doping. The prepared photo-devices have shown exceptional UV-photodetection ability under UVA light for fixed illumination intensity of 3.3 mW/cm2 and varying intensities of ~ 0.367 to 3.3 mW/cm2. All the prepared devices have fast response and high sensitivity towards UV light. The response and recovery times for the deposited films are less than 200 ms, with sensitivity as high as ~ 85% at 3.3 mW/cm2 illumination intensity for the device with 7 wt% doping of phosphorous. The high responsivity and detectivity as compared to reported literature, confirms the superior device performance and photo-characteristic of the prepared devices.

Real-time monitoring of solid-phase peptide synthesis using a variable bed flow reactor

On-resin aggregation and incomplete amide bond formation are major challenges for solid-phase peptide synthesis that are difficult to be monitored in real-time. Incorporation of a pressure-based variable bed flow reactor into an automated solid-phase peptide synthesizer permitted real-time monitoring of resin swelling to determine amino acid coupling efficiency and on-resin aggregation.

The Criterion for Choosing an Insulator for Sili-con MOS Structures

Nowadays, MIS structures based on silicon dioxide films have become the most widely used. However, the desire to reduce the channel length and the nano-scaling in electronics showed, that SiO 2 can’t provide the specified MIS devices parameters and characteristics. This is due to the superfine insulator films problem. First of all, this can be solved by replacing SiO 2 with another insulator that meets certain requirements. Oxides of transition and rare-earth metals meets almost all of these requirements. However, the principle issue of insulator and semiconductor compatibility remains unsolved in terms of ensure theirs interface quality. Therefore, the researching purpose is to create a general approach to the selection of insulator which is an alternative to silicon dioxide. This insulator must provide a high quality of insulator-semiconductor interface. In MIS structures, the main indicator of semiconductor-insulator interface is its density of the electric charge. Low values of the charge density at the semiconductor-insulator interface are corresponds to high quality of the interface. This is due to the fact that low interface charge density has low affecting on threshold voltage and provide higher its stability. In the first approximation, the surface states density is identically equal to the incomplete bonds density at semiconductor-insulator interface. Therefore, this parameter is selected as the basis of the insulator choosing criterion for a particular semiconductor substrate. It is shown that the classical theory of crystalline lattice (site aspect) can't allow to obtain an analytical expression for the insulator choosing criterion for MIS structures. Therefore, a new form of description of a crystal lattice (intersite aspect) is proposed. Since the crystals differs not only by symmetry but also by the crystallographic orientation of their interface with the vacuum, then an infinite number of solutions about value of incomplete bonds density at the interface correspond to each pair of materials. For obtaining only the one solution by using insulator choosing criterion, a new characteristic parameter of the crystalline substance is introduced - the average bond length. To confirm the practical significance of the average bond length, the relationship between this parameter and electron work function is obtained. The experiment based on literary data of both electron work function and lattice constants was made. The experimental results proves both validity of the relationship and practical significance of the average bond length. On the basis of the intersite aspect and the average bond length, general insulator choosing criterion for MIS structures on certain semiconductor substrate was obtained. For replacement of silicon dioxide in silicon MIS devices, insulator was selected from suitable materials namely oxides of transition and rare-earth metals. The incomplete bonds density at the insulator-silicon interface was calculated for each of these materials. Analysis of the calculation results showed that, in accordance with the insulator choosing criterion, the most promising material is CeO 2 . The insulator choosing criterion for MIS structures on certain semiconductor substrate is proposed. Its allows, under other equal conditions, to choose the suitable insulator which will provide the least electric charge density at the insulator-semiconductor interface, in comparison with other pretenders. In case of a silicon substrate, such insulator is CeO 2 . A new characteristic parameter of a crystalline materials is introduced - the average bond length. The analytical expression, which get the relationship between this parameter and the electron work function, is obtained. The obtained results provide an opportunity to make choices insulator for MIS devices based on not only silicon substrates, but also any other semiconductor materials. The proposed insulator choosing criterion can serve as the basis for build new criteria. This ones can help in solving more complicated problems like choosing insulator for MIS devices based on semiconductor substrate with a certain crystallographic orientation. Bibl. 10, Fig. 9.

A gradient-based optimization approach for the detection of partially connected surfaces using vibration tests

The integrity of engineering structures is often compromised by embedded surfaces that result from incomplete bonding during the manufacturing process, or initiation of damage from fatigue or impact processes. Examples include delaminations in composite materials, incomplete weld bonds when joining two components, and internal crack planes that may form when a structure is damaged. In many cases the areas of the structure in question may not be easily accessible, thus precluding the direct assessment of structural integrity. In this paper, we present a gradient-based, partial differential equation (PDE)-constrained optimization approach for solving the inverse problem of interface detection in the context of steady-state dynamics. An objective function is defined that represents the difference between the model predictions of structural response at a set of spatial locations, and the experimentally measured responses. One of the contributions of our work is a novel representation of the design variables using a density field that takes values in the range [0,1] and raised to an integer exponent that promotes solutions to be near the extrema of the range. The density field is combined with the penalty method for enforcing a zero gap condition and realizing partially bonded surfaces. The use of the penalty method with a density field representation leads to objective functions that are continuously differentiable with respect to the unknown parameters, enabling the use of efficient gradient-based optimization algorithms. Numerical examples of delaminated plates are presented to demonstrate the feasibility of the approach.

Understanding double bond conversion using laser con-focus RAMAN spectroscopy

Abstract The oxygen inhibition in free radical photo-polymerization is one of the big issues, because it causes the incomplete double bond conversion (DBC) of the (meth)acrylate, especially on the surface which decreases the mechanical properties of the coatings. Until now, it is still difficult to measure the effect of oxygen, because the concentration of oxygen inside the coatings depends on the penetration of oxygen and the distance from surface exposed the air. In this research, laser Con-focus RAMAN Spectroscopy was used to investigate the double bond conversion in different distance from the surface of coatings, which could provide detail information of effect of oxygen concentration on double bond conversion. At the same time, the effect of light dosage and concentration of photo-initiators on double bond conversion was investigated as well. This data could guide the end use of UV coatings to overcome the oxygen inhibition.

Monitoring Ligand-Induced Protein Ordering in Drug Discovery

While the gene for p53 is mutated in many human cancers causing loss of function, many others maintain a wild-type gene but exhibit reduced p53 tumor suppressor activity through overexpression of the negative regulators, Mdm2 and/or MdmX. For the latter mechanism of loss of function, the activity of endogenous p53 can be restored through inhibition of Mdm2 or MdmX with small molecules. We previously reported a series of compounds based upon the Nutlin-3 chemical scaffold that bind to both MdmX and Mdm2 [Vara, B. A. et al. (2014) Organocatalytic, diastereo- and enantioselective synthesis of nonsymmetric cis-stilbene diamines: A platform for the preparation of single-enantiomer cis-imidazolines for protein–protein inhibition. J. Org. Chem. 79, 6913–6938]. Here we present the first solution structures based on data from NMR spectroscopy for MdmX in complex with four of these compounds and compare them with the MdmX:p53 complex. A p53-derived peptide binds with high affinity (Kd value of 150nM) and causes the formation of an extensive network of hydrogen bonds within MdmX; this constitutes the induction of order within MdmX through ligand binding. In contrast, the compounds bind more weakly (Kd values from 600nM to 12μM) and induce an incomplete hydrogen bond network within MdmX. Despite relatively weak binding, the four compounds activated p53 and induced p21Cip1 expression in retinoblastoma cell lines that overexpress MdmX, suggesting that they specifically target MdmX and/or Mdm2. Our results document structure–activity relationships for lead-like small molecules targeting MdmX and suggest a strategy for their further optimization in the future by using NMR spectroscopy to monitor small-molecule-induced protein order as manifested through hydrogen bond formation.

Optimum steepest descent higher level learning radial basis function network

Dynamically changing real world applications, demands for rapid and accurate machine learning algorithm. In neural network based machine learning algorithms, radial basis function (RBF) network is a simple supervised learning feed forward network. With its simplicity, this network is highly suitable to model and control the nonlinear systems. Existing RBF networks in literature are applied to static applications and also faces challenges such as increased model size, neuron removal, improper center selection etc leading to erroneous output. To overcome the challenges and handle complex real world problems, this paper proposes a new optimum steepest descent based higher level learning radial basis function network (OSDHL-RBFN). The proposed OSDHL-RBFN implements major components inspired from the human brain for efficient learning, adaptive structure and accurate classification. Higher level learning and thinking components of the proposed network are sample deletion, neuron addition, neuron migration, sample navigation and neuroplasticity. These components helps the classifier to think before learning the samples and regulates the learning strategy. The knowledge gained from the trained samples are used by the network to identify the incomplete sample, optimal center and bond strength of hidden & output neurons. Adaptive network structure is employed to minimize classification error. The proposed work also uses optimum steepest descent method for weight parameter update to minimize the sum square error. OSDHL-RBFN is tested and evaluated in both static and dynamic environments on nine benchmark classification (binary and multiclass) problems for balanced, unbalanced, small, large, low dimensional and high dimensional datasets. The overall and class wise efficiency of OSDHL-RBFN is improved when compared to other RBFN’s in the literature. The performance results clearly show that the proposed OSDHL-RBFN reduces the architecture complexity and computation time compared to other RBFN’s. Overall, the proposed OSDHL-RBFN is efficient and suitable for dynamic real world applications in terms of detection time and accuracy. As a case study, OSDHL-RBFN is implemented in real time remote health monitoring application for classifying the various abnormality levels in vital parameters.

Biodegradability of fluorinated fire-fighting foams in water

Fluorinated fire-fighting foams may be released into the environment during fire-fighting activities, raising concerns due to the potential environmental and health impacts for some fluorinated organics. The current study investigated (1) the biodegradability of three fluorinated fire-fighting foams, and (2) the applicability of current standard measures used to assess biodegradability of fluorinated fire-fighting foams.The biodegradability of three fluorinated fire-fighting foams was evaluated using a 28-day dissolved organic carbon (DOC) Die-Away Test. It was found that all three materials, diluted in water, achieved 77–96% biodegradability, meeting the criteria for “ready biodegradability”. Defluorination of the fluorinated organics in the foam during biodegradation was measured using ion chromatography. It was found that the fluorine liberated was 1–2 orders of magnitude less than the estimated initial amount, indicating incomplete degradation of fluorinated organics, and incomplete CF bond breakage.Published biodegradability data may utilize biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC) metrics to quantify organics. COD and TOC of four fluorinated compounds were measured and compared to the calculated carbon content or theoretical oxygen demand. It was found that the standard dichromate-based COD test did not provide an accurate measure of fluorinated organic content. Thus published biodegradability data using COD for fluorinated organics quantification must be critically evaluated for validity. The TOC measurements correlated to an average of 91% of carbon content for the four fluorinated test substances, and TOC is recommended for use as an analytical parameter in fluorinated organics biodegradability tests.

Zirconia-based dental crown to support a removable partial denture: a three-dimensional finite element analysis using contact elements and micro-CT data

Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core – MAu; zirconia core – MZi) and the quality of the veneer/core interface (complete bonded – MZi; incomplete bonded – MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface.

Robust Long-Term Interest Rate Risk Hedging in Incomplete Bond Markets

We introduce a robust investment strategy to hedge long dated liabilities under model misspecification and incomplete bond markets. A robust agent who worries about misspecified bond premia follows a min-max expected shortfall criterion to protect against model uncertainty. We employ a backward least squares Monte Carlo method to solve this dynamic robust optimization problem. We find that both naive and robust optimal portfolios depend on the hedging horizon and current funding ratio. The robust policy suggests to take more risk when the current funding ratio is low. The robust yield curve derived through the minimum assets required to eliminate shortfall risk is lower than the naive one.