Chain Architecture Research Articles

Characterizing long-chain branching in commercial HDPE samples via linear viscoelasticity and extensional rheology

It is well established that polymer chain architecture and the distribution of molecular weight play a key role in the flow behavior (processing) and performance of a given polymer material. Long-chain branching (LCB) in particular is known to strongly affect the processability and the material performance of polymers. Often branching is a result of the polymerization process and therefore must be quantified in every sample. We study four commercial high-density polyethylene (HDPE) samples with unknown degrees of polydispersity and LCB. We first use size-exclusion chromatography and linear shear rheology to identify differences in molecular weight, polydispersity, and LCB. Each material is then tested in constant rate and constant stress uniaxial extension using a filament stretching rheometer to quantify extensional viscosity and strain hardening. Correlations between nonlinear extensional rheology, LCB and polydispersity are discussed. We show that the combination of the van Gurp-Palmen plot and extensional rheology allows for a full characterization of the LCB fraction and their effect on extensional rheology.

The structure and function of deubiquitinases: lessons from budding yeast.

Protein ubiquitination is a key post-translational modification that regulates diverse cellular processes in eukaryotic cells. The specificity of ubiquitin (Ub) signalling for different bioprocesses and pathways is dictated by the large variety of mono-ubiquitination and polyubiquitination events, including many possible chain architectures. Deubiquitinases (DUBs) reverse or edit Ub signals with high sophistication and specificity, forming an integral arm of the Ub signalling machinery, thus impinging on fundamental cellular processes including DNA damage repair, gene expression, protein quality control and organellar integrity. In this review, we discuss the many layers of DUB function and regulation, with a focus on insights gained from budding yeast. Our review provides a framework to understand key aspects of DUB biology.

Combined Molecular Dynamics Simulation and Rouse Model Analysis of Static and Dynamic Properties of Unentangled Polymer Melts with Different Chain Architectures

Chain architecture effect on static and dynamic properties of unentangled polymers is explored by molecular dynamics simulation and Rouse mode analysis based on graph theory. For open chains, although they generally obey ideal scaling in chain dimensions, local structure exhibits nonideal behavior due to the incomplete excluded volume (EV) screening, the reduced mean square internal distance (MSID) can be well described by Wittmer’ theory for linear chains and the resulting chain swelling is architecture dependent, i.e., the more branches a bit stronger swelling. For rings, unlike open chains they are compact in term of global sizes. Due to EV effect and nonconcatenated constraints their local structure exhibits a quite different non-Gaussian behavior from open chains, i.e., reduced MSID curves do not collapse to a single master curve and fail to converge to a chain-length-independent constant, which makes the direct application of Wittmer’s theory to rings quite questionable. Deviation from ideality is further evidenced by limited applicability of Rouse prediction to mode amplitude and relaxation time at high modes as well as the non-constant and mode-dependent scaled Rouse mode amplitudes, while the latter is architecture-dependent and even molecular weight dependent for rings. The chain relaxation time is architecture-dependent, but the same scaling dependence on chain dimensions does hold for all studied architectures. Despite mode orthogonality at static state, the role of cross-correlation in orientation relaxation increases with time and the time-dependent coupling parameter rises faster for rings than open chains even at short time scales it is lower for rings.

A Survey on Supply Chain Security: Application Areas, Security Threats, and Solution Architectures

The rapid improvement in the global connectivity standards has escalated the level of trade taking place among different parties. Advanced communication standards are allowing the trade of all types of commodities and services. Furthermore, the goods and services developed in a particular region are transcending boundaries to enter into foreign markets. Supply chains play an essential role in the trade of these goods. To be able to realize a connected world with no boundary restrictions in terms of goods and services, it is imperative to keep the associated supply chains transparent, secure, and trustworthy. Therefore, some fundamental changes in the current supply chain architecture are essential to achieve a secure trade environment. This article discusses the supply chain's security-critical application areas and presents a detailed survey of the security issues in the existing supply chain architecture. Various emerging technologies, such as blockchain, machine learning (ML), and physically unclonable functions (PUFs) as solutions to the vulnerabilities in the existing infrastructure of the supply chain have also been discussed. Recent studies reviewed in this work reveal a growing sentiment in the industry toward new and emerging technologies, such as Internet of Things (IoT), blockchain, and ML. While many organizations have already adopted IoT applications and artificial intelligence systems in their businesses, widespread adoption of blockchain remains distant. It has also been found that over the past decade, PUF-based authentication systems have gained much ground. However, a proper reference model for their implementation in complex supply chains is still missing.

Differential flexibility leading to crucial microelastic properties of asymmetric lipid vesicles for cellular transfection: A combined spectroscopic and atomic force microscopy studies

The role of microscopic elasticity of nano-carriers in cellular uptake is an important aspect in biomedical research. Herein we have used AFM nano-indentation force spectroscopy and Förster resonance energy transfer (FRET) measurements to probe microelastic properties of three novel cationic liposomes based on di-alkyl dihydroxy ethyl ammonium chloride based lipids having asymmetry in their hydrophobic chains (Lip1818, Lip1814 and Lip1810). AFM data reveals that symmetry in hydrophobic chains of a cationic lipid (Lip1818) imparts higher rigidity to the resulting liposomes than those based on asymmetric lipids (Lip1814 and Lip1810). The stiffness of the cationic liposomes is found to decrease with increasing asymmetry in the hydrophobic lipid chains in the order of Lip1818 > Lip1814 > lip1810. FRET measurements between Coumarin 500 (Donor) and Merocyanine 540 (Acceptor) have revealed that full width at half-maxima (hw) of the probability distribution (P(r)) of donor-acceptor distance (r), increases in an order Lip1818 < Lip1814 < Lip1810 with increasing asymmetry of the hydrophobic lipid chains. This increase in width (hw) of the donor-acceptor distance distributions is reflective of increasing flexibility of the liposomes with increasing asymmetry of their constituent lipids. Thus, the results from AFM and FRET studies are complementary to each other and indicates that an increase in asymmetry of the hydrophobic lipid chains increases elasticity and or flexibility of the corresponding liposomes. Cell biology experiments confirm that liposomal flexibility or rigidity directly influences their cellular transfection efficiency, where Lip1814 is found to be superior than the other two liposomes manifesting that a critical balance between flexibility and rigidity of the cationic liposomes is key to efficient cellular uptake. Taken together, our studies reveal how asymmetry in the molecular architecture of the hydrophobic lipid chains influences the microelastic properties of the liposomes, and hence, their cellular uptake efficiency.

Impact of bottlebrush chain architecture on Tg‐confinement and fragility‐confinement effects enabled by thermo‐cleavable bottlebrush polymers synthesized by radical coupling and atom transfer radical polymerization

AbstractThermo‐cleavable bottlebrush polymers were synthesized by a facile grafting‐to method via radical coupling and atom transfer radical polymerization (ATRP) without small‐molecule synthesis involved. Bottlebrushes were achieved by coupling backbones of poly(4‐methacryloyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl), which contain nitroxide radicals, and ATRP‐synthesized side chains, which can be halogen‐abstracted to generate carbon‐centered radicals. Bottlebrushes were prepared using homopolymer or block copolymer side chains. Alkoxyamine covalent bonds resulting from radical coupling are thermo‐reversible at high temperature, and grafting density may be tuned by annealing of post‐synthesis bottlebrush, with the bottlebrush regime going from loose bottlebrush to dense comb and loose comb. The effects of confinement on the Tg and fragility of films of polystyrene bottlebrush were studied by ellipsometry; comparisons were made to thermally cleaved linear components obtained directly after annealing. Relative to linear polymer, bottlebrush topology reduces bulk fragility and suppresses Tg‐ and fragility‐confinement effects. The correlation between the strengths of the confinement effects is consistent with other film studies of linear and non‐linear polymers and supports the notion that fragility is a fundamental property underlying perturbations to Tg. Besides providing a platform for advancing fundamental scientific understanding, our synthetic strategy may afford novel applications of bottlebrushes via incorporated dynamic chemistry.

Multivalent Assembly of Flexible Polymer Chains into Supramolecular Nanofibers.

Polymeric materials in nature regularly employ ordered, hierarchical structures in order to perform unique and precise functions. Importantly, these structures are often formed and stabilized by the cooperative summation of many weak interactions as opposed to the independent association of a few strong bonds. Here, we show that synthetic, flexible polymer chains with periodically placed and directional dynamic bonds collectively assemble into supramolecular nanofibers when the overall molecular weight is below the polymer's critical entanglement molecular weight. This causes bulk films of long polymer chains to have faster dynamics than films of shorter polymer chains of identical chemical composition. The formation of nanofibers increases the bulk film modulus by over an order of magnitude and delays the onset of terminal flow by more than 100 °C, while still remaining solution processable. Systematic investigation of different polymer chain architectures and dynamic bonding moieties along with coarse-grained molecular dynamics simulations illuminate governing structure-function relationships that determine a polymer's capacity to form supramolecular nanofibers. This report of the cooperative assembly of multivalent polymer chains into hierarchical, supramolecular structures contributes to our fundamental understanding of designing biomimetic functional materials.

Technical report: Targeted proteomic analysis reveals enrichment of atypical ubiquitin chains in contractile murine tissues

SummaryUbiquitylation is an elaborate post-translational modification involved in all biological processes. Its pleotropic effect is driven by the ability to form complex polyubiquitin chain architectures that can influence biological functions. In this study, we optimised sample preparation and chromatographic separation of Ubiquitin peptides for Absolute Quantification by Parallel Reaction Monitoring (Ub-AQUA-PRM). Using this refined Ub-AQUA-PRM assay, we were able to quantify all ubiquitin chain types in 10-min LC-MS/MS runs. We used this method to determine the ubiquitin chain-linkage composition in murine bone marrow-derived macrophages and different mouse tissues. We could show tissue-specific differences in ubiquitin levels in murine tissues, with polyubiquitin chain types contributing a small proportion to the total pool of ubiquitin. Interestingly, we observed enrichment of atypical (K33) ubiquitin chains in heart and muscle. Our approach enabled high-throughput screening of ubiquitin chain-linkage composition in different murine tissues and highlighted a possible role for atypical ubiquitylation in contractile tissues.SignificanceLarge knowledge gaps exist in our understanding of ubiquitin chain-linkage composition in mammalian tissues. Defining this in vivo ubiquitin chain-linkage landscape could reveal the functional importance of different ubiquitin chain types in tissues. In this study, we refined the previously described Ub-AQUA-PRM assay to enable quantification of all ubiquitin chain types in a high-throughput manner. Using this assay, we provided new data on the ubiquitin chain-linkage composition in primary murine macrophages and tissues, and revealed an enrichment of atypical ubiquitin chains in contractile tissues. Our approach should thus enable rapid, high-throughput screening of ubiquitin chain-linkage composition in different sample types, as demonstrated in murine primary cells and tissues.

Research on Supply Chain Architecture Oflogistics Network Platform Based on Blockchain Technology

With the development of productivity, supply chaincame into being. This study briefly introduced the blockchain andsupply chain technology, constructed the blockchain-based supplychain logistics platform for managing the information of the supplychain, carried out the interface test on the logistics platform system inthe laboratory, and made an analysis by taking XX flour factory inSichuan province as an example. The laboratory interface test resultsshowed that the system platform could be normally applied to the flourfactory’s supply chain management. The case analysis results showedthat the supply chain that applied blockchain technology couldeffectively resist abnormal data modification to ensure the reliability ofsupply chain information and quickly trace the supply chain problemsto improve the efficiency of supply chain management.

Mechanism and inhibition of the papain-like protease, PLpro, of SARS-CoV-2.

The SARS‐CoV‐2 coronavirus encodes an essential papain‐like protease domain as part of its non‐structural protein (nsp)‐3, namely SARS2 PLpro, that cleaves the viral polyprotein, but also removes ubiquitin‐like ISG15 protein modifications as well as, with lower activity, Lys48‐linked polyubiquitin. Structures of PLpro bound to ubiquitin and ISG15 reveal that the S1 ubiquitin‐binding site is responsible for high ISG15 activity, while the S2 binding site provides Lys48 chain specificity and cleavage efficiency. To identify PLpro inhibitors in a repurposing approach, screening of 3,727 unique approved drugs and clinical compounds against SARS2 PLpro identified no compounds that inhibited PLpro consistently or that could be validated in counterscreens. More promisingly, non‐covalent small molecule SARS PLpro inhibitors also target SARS2 PLpro, prevent self‐processing of nsp3 in cells and display high potency and excellent antiviral activity in a SARS‐CoV‐2 infection model.

From Architectures to Cutting-Edge Properties, the Blooming World of Hydrophobically Modified Ethoxylated Urethanes (HEURs)

Hydrophobically modified ethoxylated urethanes (HEURs) are associative polymers that, compare to others, are far less sensitive to solution parameters, especially pH and ionic strength. Therefore, they are widely used as rheology modifiers in many different waterborne systems such as inks, coatings, emulsions, etc. In solutions, HEURs form transient networks through molecular associations between their hydrophobic groups. The transient network formation and its characteristics are responsible for the rheological properties and depend on the HEUR chains architecture. Many parameters such as molecular weight, size and nature of hydrophobic groups, polymer concentration, etc must be controlled to tune the several physicochemical properties of HEUR solutions. This article aims to give an overview of the HEUR studies reported in the literature in order to highlight the structure/rheological properties relationship. The article also draws attention to new trends in HEURs with innovative architectures and stimuli-responsive properties.

Understanding of strain-induced crystallization developments scenarios for polyesters: Comparison of poly(ethylene furanoate), PEF, and poly(ethylene terephthalate), PET

Specific conditions of strain, stretching, strain rate and temperature are known to be necessary for the strain induced crystallization phenomenon (SIC) to occur. It leads to the formation of a crystal in different amorphous polymers, stretched above their glassy transition. This phenomenon was intensively documented in case of poly(ethylene terephthalate), PET. More recently, some studies focused on SIC development in biobased poly(ethylene furandicarboxylate), PEF. Comparison of these crystallization abilities and crystallization kinetics upon stretching in the two materials allows to describe main differences between them, and to enlighten the role of chain architecture on SIC. To achieve that point, different mechanical tensile tests were conducted using well controlled loading paths to explore the different steps of the microstructural changes induced by the stretching and their correlation with mechanical behaviour.Several macroscopic equivalence in the effects of SIC were found, such as increase in modulus, appearance of organized phase, increase I n α−relaxation temperature despite some differences in chain architecture. Combining both loading-unloading tests and quenching protocols, it was found that inducing more or less strong interactions between constitutive units, and more or less stable crystalline phases, leads to differences in apparent strain induced crystallization kinetics:• PET stretching can induce, prior to main strain hardening step, the formation of re-enforcing intermediate phases (or imperfect crystal) being stable upon unloading and able to be improved upon relaxation or thermal treatments;• PEF stretching exhibits a more “simple” two-steps path with no intermediate phases stable upon unloading.This can be related with the weaker stability of PEF crystal compared to PET (PEF quiescent crystallization temperature and melting temperature are very close to each other), and to the more complex crystalline lattice in PEF (two units are needed instead of one due to furanic cycle). In addition, for PET, Young modulus increases more gradually during strain hardening than for PEF. The final microstructure after stretching is therefore more dependent on thermomechanical treatments (annealing or relaxation steps) in PET in comparison to PEF.

Role of endogenous glucose on natural rubber molecular chains and natural network architecture based on biological action and chelation

Natural rubber (NR) is widely applied in automobile industry, surgical rubber goods, and daily necessities due to its outstanding comprehensive properties originated from the unique non-rubber component and network architecture. Glucose as an endogenous component virtually exert an important influence during the microorganism or spontaneous coagulation of natural latex. However, such role of glucose on the reconstruction of NR molecular chains and corresponding network has not been paid wide attention to. Hence, we here examined the difference of molecular chain parameters and molecular chains network composition of raw NR coagulated by different glucose content. The results demonstrated that glucose exerted an important role on the molecular chain and molecular chain architecture via two main related action of glucose: metabolism and chelation. In this work, a possible mechanism was proposed to reveal the role of glucose on the reconstruction of natural network in raw NR from spontaneous coagulation assisted by glucose.

Tax Differences and Global Supply Chain Architecture

This paper examines the influence of tax rate differences and international transfer pricing regulations on the profit-maximizing supply chain structure of a multinational firm (MNF). We show how an MNF that sells its products in multiple markets and manufactures multiple inputs used for its own production can optimize its tax strategy by jointly selecting its transfer pricing approach and the location of the manufacturing divisions. The optimal choice of transfer pricing and supply chain structure balances the gains from locating input production in the low-tax country to enable profit-shifting with the losses that occur due to distorted quantity choices in the high-tax country. First, in contrast to existing literature, we find that the MNF should always fully exploit its profit-shifting opportunities by selecting the maximum admissible arm's length transfer price for international transactions. Second, for products that use multiple complementary inputs there is a close connection between the national and international transfer prices: the MNF's trade-off between the gains or losses can be moderated by setting an adjusted domestic transfer price for transactions between the divisions in the high-tax country. Third and finally, we also point out circumstances where the MNF should use the market price for a base product sold on an external market as an internal arm's length standard.

Supply chain spiral dynamics

The article is devoted to the research of modern tendencies of defining the essence of supply chain management as an innovative philosophy of spiral business dynamics. The research is based on the generalization and application of the basic principles of wave theory of development, classical theory of marketing, modern provisions of the theory of TQM and conceptual provisions of the theory of spiral dynamics. A new look at supply chain architecture, from identifying growing needs for specific products and ending with utilization, namely the emergence of new links in the chain of transformation of resources such as the stage of intelligent innovation processes to create modifications and upgrades or design a new product to meet growing needs. A multicomponent process of change is considered in view of current trends. The application of the theory of the spiral dynamics of the supply chains is a logical and predictable extrapolation of the general tendencies of the development of the life support system and the growing needs of society, starting from the “subsistence economy” and to the creation of modern global economic associations such as transnational corporations and international transport corridors. economic associations of countries and international programs of scientific search in the field of artificial intelligence and development of the cosmos.

FPGA Logic Block Architectures for Efficient Deep Learning Inference

Reducing the precision of deep neural network (DNN) inference accelerators can yield large efficiency gains with little or no accuracy degradation compared to half or single precision floating-point by enabling more multiplication operations per unit area. A wide range of precisions fall on the pareto-optimal curve of hardware efficiency vs. accuracy with no single precision dominating, making the variable precision capabilities of FPGAs very valuable. We propose three types of logic block architectural enhancements and fully evaluate a total of six architectures that improve the area efficiency of multiplications and additions implemented in the soft fabric. Increasing the LUT fracturability and adding two adders to the ALM (4-bit Adder Double Chain architecture) leads to a 1.5× area reduction for arithmetic heavy machine learning (ML) kernels, while increasing their speed. In addition, this architecture also reduces the logic area of general applications by 6%, while increasing the critical path delay by only 1%. However, our highest impact option, which adds a 9-bit shadow multiplier to the logic clusters, reduces the area and critical path delay of ML kernels by 2.4× and 1.2×, respectively. These large gains come at a cost of 15% logic area increase for general applications.

Development and Evaluation of Matrices Composed of β-cyclodextrin and Biodegradable Polyesters in the Controlled Delivery of Pindolol.

Polymer-drug conjugates are currently being more widely investigated for the treatment of hypertension. In view of the above, in the first stage of our work, we used nontoxic β-cyclodextrin (β-CD) as effective, simple, inexpensive, and safe for the human body initiator for the synthesis of biocompatible and biodegradable functionalized polymers suitable for the medical and pharmaceutical applications. The obtained polymeric products were synthesized through a ring-opening polymerization (ROP) of ε-caprolactone (CL), d,l-, and l,l-lactide (LA and LLA). The chemical structures of synthesized materials were elucidated based on 1H NMR and solid-state carbon-13 cross-polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) analysis, while the incorporation of β-CD molecule into the polymer chain was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Furthermore, molecular modeling has been applied to investigate the intrachain rigidities and chain architectures for several representative structures. The obtained and thoroughly characterized branched matrices were then used to generate the first β-cyclodextrin/biodegradable polymer/β-blocker conjugate through the successful conjugation of pindolol. The conjugates were fabricated by carbodiimide-mediated coupling reaction. The branched biodegradable materials released the drug in vitro in a sustained manner and without “burst release” and thus have the ability to treat different heart diseases.

Synthesis of (hard-soft-hard)x multiblock copolymers via RAFT emulsion polymerization and mechanical enhancement via block architectures

A large variety of block copolymers have become accessible due to the advances in controlled/living radical polymerization. However, it remains scarcely explored that how one can improve the properties of block copolymers via the chain architectures. Herein, three sets of well-defined multiblock copolymers (SBAS)x (S for poly(styrene)180 and BA for poly(n-butyl acrylate) blocks) with 25, 33, and 50 wt% PS are synthesized via RAFT emulsion polymerization. All three sets of (SBAS)x are weak/mild phase separated. Compared with their SBAS counterparts, all tensile properties of (SBAS)2 are enhanced. Particularly interestingly, both the tensile strength and toughness are simultaneously much enhanced but the modulus is less influenced. It is suggested that a soft yet strong and tough elastomer could be synthesized via changing widely-applied hard-soft-hard triblock copolymers to (hard-soft-hard)2 pentablock copolymers. The enhancement of mechanical properties increases as the increase of PnBA composition. In the case of 75 wt% PnBA, the tensile strength, toughness, and modulus of (SBAS)2 are enhanced by a factor of 2.73, 2.51 and 1.30. (SBAS)2 also show better mechanical properties than its counterpart of triblock copolymer S2BA2S2 with close molecular weight which is strongly phase separated. It is suggested that the combination of pulling-out end PS blocks and bridging middle PS blocks might contribute to the mechanical enhancement of (SBAS)2, simultaneously in toughness and tensile strength.

Mechanisms Regulating the UPS-ALS Crosstalk: The Role of Proteaphagy.

Protein degradation is tightly regulated inside cells because of its utmost importance for protein homeostasis (proteostasis). The two major intracellular proteolytic pathways are the ubiquitin-proteasome and the autophagy-lysosome systems which ensure the fate of proteins when modified by various members of the ubiquitin family. These pathways are tightly interconnected by receptors and cofactors that recognize distinct chain architectures to connect with either the proteasome or autophagy under distinct physiologic and pathologic situations. The degradation of proteasome by autophagy, known as proteaphagy, plays an important role in this crosstalk since it favours the activity of autophagy in the absence of fully active proteasomes. Recently described in several biological models, proteaphagy appears to help the cell to survive when proteostasis is broken by the absence of nutrients or the excess of proteins accumulated under various stress conditions. Emerging evidence indicates that proteaphagy could be permanently activated in some types of cancer or when chemoresistance is observed in patients.

A new ZnII metallocryptand with unprecedented diflexure helix induced by V-shaped diimidazole building blocks.

Taking advantage of V-shaped ligands, a ZnII metallocryptand, namely {[Zn2(didp)2(m-bdc)2]}n, (1) [didp = 2,8-di(1H-imidazol-1-yl)-dibenzothiophene and m-H2bdc = isophthalic acid], has been hydrothermally synthesized. Single-crystal X-ray diffraction analysis reveals a 26-membered butterfly-type metallomacrocycle [Zn2(didp)2]. One m-bdc2- ligand bridges [Zn2(didp)2] units to form a laterally non-symmetric [Zn2(didp)2(m-bdc)] metallocryptand with an exo-exo conformation. Another crystallographically independent m-bdc2- functions as a secondary synthon to bridge discrete metallocryptands into a 1D zigzag chain architecture. Undoubtedly, the choice of two matched ligands in this work is crucial for metallocryptand construction and structure expansion. Interestingly, a rare helical chain with two flexures in one single L and/or R strand is observed. Another important feature is the C-O...π interactions, by which the dimensionality extension of (1) can be induced. Fluorescence measurements and density functional theory (DFT) calculations illustrate that the emission of (1) can probably be attributed to ligand-to-ligand charge transfer (LLCT).