Chain Units Research Articles

Influence of Cr2O3 on the Viscous Flow Behavior and Structure of Cr‐Containing Molten Titanium Slag

Herein, the influence of Cr2O3 on the viscous flow behavior and structure of Cr‐containing molten titanium slag is investigated in this work. The melting and viscosity properties are studied by hemisphere method and rotating cylinder method, respectively. In addition, the structure of Cr‐containing molten titanium slag is investigated by Raman spectroscopy. It is shown in the results that the melting temperature and viscosity both increase with the increase of Cr2O3 content. The activation energy for viscous flow increases with increasing Cr2O3 content, which is in the same trend as viscosity. When the Cr2O3 content increases from 0% to 3%, the simpler 6‐coordinated Ti4+ and TiO44− monomer unit transformed into more complex O–Ti–O deformation and Ti2O64− chain unit. Furthermore, the fraction of relatively complex silicate structural units shows an increasing trend. Cr2O3 behaves as a network former and enhances the degree of polymerization of network structure, and the variation of Cr‐containing molten titanium slag structure is consistent with the increasing trend of viscosity.

Recent application advances of covalent organic frameworks for solid-phase extraction

Covalent organic frameworks (COFs) are a type of crystalline porous polymers. It firstly prepared by thermodynamically controlled reversible polymerization to obtain chain units and connecting small organic molecular building units with a certain symmetry. These polymers are widely used in gas adsorption, catalysis, sensing, drug delivery, and many other fields. Solid-phase extraction (SPE) is a fast and simple sample pretreatment technology that can enrich analytes and improve the accuracy and sensitivity of analysis and detection; it is extensively employed in food safety detection, environmental pollutant analysis, and several other fields. How to improve the sensitivity, selectivity, and detection limit of the method during sample pretreatment have become a topic of great interest. COFs have recently been applied to sample pretreatment owing to their low skeleton density, large specific surface area, high porosity, good stability, facile design and modification, simple synthesis, and high selectivity. At present, COFs have also attracted extensive attention as new extraction materials in the field of SPE. These materials have been applied to the extraction and enrichment of diverse types of pollutants in food, environmental, and biological samples, such as heavy metal ions, polycyclic aromatic hydrocarbons, phenol, chlorophenol, chlorobenzene, polybrominated diphenyl ethers, estrogen, drug residues, pesticide residues, etc. COFs can be synthesized from different materials and exert different effects on different extracts. New types of COFs can also be synthesized via modification to achieve better extraction effects. In this work, the main types and synthesis methods of COFs are introduced, and the most important applications of COFs in the fields of food, environment and biology in recent years are highlighted. The development prospects of COFs in the field of SPE are also discussed.

Two-dimensional assemblies of saccharide-derived molecules on highly oriented pyrolytic graphite revealed by scanning tunneling microscopy

Saccharides play important roles as structural components of plants and for molecular recognition in living organisms, and they are increasingly being used as environmentally-friendly bio-based materials. In this study, two-dimensional (2D) assemblies of 1,5-anhydro-D-glucitol (AG) derivatives were examined by scanning tunneling microscopy at the highly oriented pyrolytic graphite (HOPG)/solvent interface. The effects of the solvent, alkyl chain linkage, and alkyl chain length on the 2D structures were investigated. Grid-like and columnar structures were periodically formed depending on the odd–even nature of the carbon atoms in the alkyl chain unit, highlighting the importance of in-plane intermolecular interactions between adsorbed molecules in determining the 2D molecular arrangement. The calculated adsorption energies for the alkyl chain and pyranose ring units with the graphene model indicated that the former was significantly greater than the latter. Despite the strong interactions between adsorbates and substrate, relatively weak in-plane interactions between adsorbates result in the 2D molecular arrangements of the AG derivatives.

Design and Synthesis of Amphiphilic Graft Polyphosphazene Micelles for Docetaxel Delivery.

The structural versatility of polydichlorophosphazene derived from the inestimable possibilities to functionalize the two halogens, attached to each phosphazene main chain unit, attracted increasing attention in the last decade. This uncountable chemical derivatization is doubled by the amphiphilic roleplay demonstrated by polyphosphazenes containing twofold side-chained hydrophilic and hydrophobic moieties. Thus, it is able to encapsulate specific bioactive molecules for various targeted nanomedicine applications. A new amphiphilic graft, polyphosphazenes (PPP/PEG-NH/Hys/MAB), was synthesized via the thermal ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a subsequent two-step substitution reaction of chlorine atoms with hydrophilic methoxypolyethylene glycol amine/histamine dihydrochloride adduct (PEG-NH2)/(Hys) and hydrophobic methyl-p-aminobenzoate (MAB), respectively. Fourier transform infrared spectroscopy (FTIR) and 1H and 31P-nuclear magnetic resonance spectroscopy (NMR) have been used to validate the expected architectural assembly of the copolymer. Docetaxel loaded micelles based on synthesized PPP/PEG-NH/Hys/MAB were designed by dialysis method. The micelles size was evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The drug release profiles from the PPP/PEG-NH/Hys/MAB micelles were established. In vitro cytotoxicity tests of PPP/PEG-NH/Hys/MAB micelles loaded with Docetaxel revealed that designed polymeric micelles exhibited an increased cytotoxic effect on MCF-7 cells.

Maldistribution of Chemical Bond Strength Inducing Exceptional Anisotropy of Thermal Conductivity in Non‐Layered Materials

AbstractCurrently, the efforts to find materials with high κ anisotropy ratios mainly focus on layered materials, however, the limited quantity and lower workability comparing to non‐layered ones boost the exploration of non‐layered materials with high κ anisotropy ratios. Here, taking PbSnS3, a typical non‐layered orthorhombic compound, as an example, we propose that maldistribution of chemical bond strength can lead to large anisotropy of κ in non‐layered materials. Our result reveals that the maldistribution of Pb−S bonds lead to obvious collective vibrations of dioctahedron chain units, resulting in an anisotropy ratio up to 7.1 at 200 K and 5.5 at 300 K, respectively, which is one of the highest ever reported in non‐layered materials and even surpasses many classical layered materials such as Bi2Te3 and SnSe. Our findings can not only broaden the horizon for exploring high anisotropic κ materials but also provide new opportunities for the application of thermal management.

Maldistribution of Chemical Bond Strength Inducing Exceptional Anisotropy of Thermal Conductivity in Non-Layered Materials.

Currently, the efforts to find materials with high κ anisotropy ratios mainly focus on layered materials, however, the limited quantity and lower workability comparing to non-layered ones boost the exploration of non-layered materials with high κ anisotropy ratios. Here, taking PbSnS3 , a typical non-layered orthorhombic compound, as an example, we propose that maldistribution of chemical bond strength can lead to large anisotropy of κ in non-layered materials. Our result reveals that the maldistribution of Pb-S bonds lead to obvious collective vibrations of dioctahedron chain units, resulting in an anisotropy ratio up to 7.1 at 200 K and 5.5 at 300 K, respectively, which is one of the highest ever reported in non-layered materials and even surpasses many classical layered materials such as Bi2 Te3 and SnSe. Our findings can not only broaden the horizon for exploring high anisotropic κ materials but also provide new opportunities for the application of thermal management.

A multiple criteria decision-making model for minimizing platelet shortage and outdating in blood supply chains under demand uncertainty

Uncertainty in blood supply and demand has proven to be a massive barrier to developing an efficient blood supply chain system. Recent literature has observed blood units’ profligacy and deficiency of approximately 20% and 14%, respectively, due to a limited donor pool, short shelf life, and emergency demand. Therefore, it is critical to develop inventory models to determine the number of units to order and the time between orders to minimize these criteria. The present study is one of the first to formulate a multi-criteria decision-making (MCDM) model for platelet inventory management along the blood supply chain that minimizes three conflicting measures: total supply chain costs, unit outdated, and unit shortage under demand uncertainty. The developed model is solved using three solution techniques: Preemptive goal programming (PGP), non-preemptive goal programming (NPGP), and weighted objective method (WOM). The results indicate that the desired goal for expected supply chain cost is achieved using the PGP model; however, the unit shortage and outdated exceeded by over 350% for each criterion. In contrast, the target value for outdated units is obtained by WOM and NPGP approaches, with WOM performing slightly better by six units when compared with NPGP. Sensitivity analysis is performed to analyze the impact of order priority and assigned weights on the three performance measures. The decision-makers can choose to implement a suitable inventory policy based on the results obtained from the three models.

Straightforward access to novel cytotoxic phytosphingosine-like aminotriols from l-erythrose chiron

A divergent approach to a small library of long-chain 6-amino-1,4,5-triols as novel phytosphingosine-type entities, together with their preliminary cytotoxic evaluation, was achieved. Construction of the target compounds addressed two key aspects. First, the installation of a carbon-nitrogen bond via two prototypes of [3,3]-sigmatropic rearrangements and second the introduction of an alkyl side chain unit by using a late stage olefin cross-metathesis process. As shown in cell viability experiments, the corresponding HCl salts proved to be the most cytotoxic derivatives among all the tested substances, with IC50 values in the lower micromolar range on the Jurkat, HeLa and HCT-116 cell lines.

Synthesis and Characterization of Aromatic Poly(ether ketone)s Bearing Perfluoroalkylene Units in the Main Chains

Nucleophilic aromatic substitution polymerization of perfluoroalkylene-α,ω-bisphenols with aromatic difluorides afforded a series of aromatic poly(ether ketone)s with perfluoroalkylene units in the main chains. The resulting poly(ether ketone)s have good heat-resistance, organosolubility, and water-repellency.

Alkylation of N,N-Dibenzylaminoacetonitrile: From Five- to Seven-Membered Nitrogen-Containing Heterocyclic Systems.

The syntheses of several alkaloids and nitrogen-containing compounds including N-Boc-coniine (14b), pyrrolizidine (1), δ-coniceine (2), and pyrrolo[1,2a]azepine (3) are described. New C-C bonds in the α position relative to the nitrogen atom were formed by the alkylation of metalated α-aminonitriles 4 and 6a-c with alkyl iodides possessing the requisite size and functionality. In all of the reported cases, the pyrrolidine ring was formed in the aqueous medium through a favorable 5-exo-tet process involving a primary or a secondary amino group and a terminal δ-leaving group. Conversely, the azepane ring was efficiently formed in N,N-dimethylformamide (DMF), as the preferred aprotic solvent, through an unreported 7-exo-tet cyclization process involving a more nucleophilic sodium amide and a terminal mesylate borne by a saturated six carbon chain unit. In this way, we successfully synthesized pyrrolo[1,2a]azepane 3 and 2-propyl-azepane 14c in good yields from inexpensive and readily available materials without tedious separation methods.

REARRANGEMENTS IN THE CONFORMATIONAL STRUCTURE OF POLYELECTROLYTES ON THE SURFACE OF A FLATTENED METAL NANOSPHEROID IN AN ALTERNATING ELECTRIC FIELD

A mathematical model has been presented for the formation of the conformational structure of chain units in a polyelectrolyte adsorbed on a flattened conducting charged nanospheroid polarized in an external electric field, which harmonically varies at a frequency much lower than the plasma frequency of the nanospheroid metal. Molecular dynamics has been employed to study the rearrangements in the conformational structure of uniformly charged polypeptides adsorbed on the surface of the oppositely charged flattened gold nanospheroid in an external alternating electric field, the strength vector of which varies along the rotation axis of the nanospheroid. One-dimensional density distributions along the rotation axis, as well as radial distributions, have been plotted for atoms of the polypeptides adsorbed on the nanospheroid surface. At a low temperature, a narrow ring-shaped polyelectrolyte fringe is formed in the equatorial region of the flattened metal nanospheroid, and the fringe density increases with the total charge of the nanospheroid and the number of charged units in polyelectrolyte macrochains. At a high temperature, the formed narrow macromolecular ring periodically shifts along the rotation axis of the nanospheroid with redirections of the polarizing electric field vector. The amplitude of the shifts increases with a decrease in the total charge of the nanospheroid and an increase in the fraction of charged units in a polyelectrolyte.

Synthesis and Applications of Single-Chain Atomic Crystal, LiMo3Se3

Among the currently available low-dimensional nanomaterials, single-chain atomic crystals (SCAC) exhibit unique physical and chemical properties because of their one-dimensional atomic structure. SCAC is the isolated molecular chain unit from bulk 1D chained materials, in which weak van der Waals or ionic interactions stack together SCACs with strong intra-chain bonding. They have one-dimensional fibrous morphology and sub-nanometer scale diameter similar to conventional organic polymers. Furthermore, unlike conventional organic polymers that consist only of organic elements such as C, H, N, O, and S, SCACs are composed of inorganic elements, such as transition metal, chalcogen, and halogen. Therefore, SCACs have novel additional properties, such as electrical, optical, mechanical, and electrochemical properties that conventional organic polymers do not.To investigate the properties of isolated SCAC, the preparation of bulk single crystal with high crystallinity, and strategy for exfoliation are required. In this review, the studies on synthesis, exfoliation and applications of the representative SCAC, LiMo3Se3 are described. These results demonstrate that solution processed SCACs are promising building block for future application.

Application of Internet of Things to Ensure Improved Performance within the Internal Supply Chain Unit of an Organization

With the rapidly changing business world, technology adapted for doing business has also undergone rapid transformation leading to use Internet of Things as an advanced technological innovation required to connect production units to internet devices for smooth production and operation, with enhanced ICT systems and infrastructure. Internet of Things is considered to be an advanced information and communication technology, whose applicability is highly needed to ensure smart performance of organizations in Indonesia. Indonesia, being a developing country, adapting to new ways of doing things, including the use of IoT takes time, hence affecting studies regarding the use of IoT in business units, such as the internal supply chain sector. Thus, there is no much studies from a localized perspective, measuring the importance and using IoT as well as supply chain performance of the country. The present paper applied an organizational capacity theory to establish the Internet of Things impact on varying dimensions of Supply Chain, which included supply chain integration process, organizational performance of supply chain and the capacity to the influence production. The research applied a survey of cross-section on several companies within the Greater Jakarta area as the research approach. Data was obtained from over 161 companies from across Jakarta. Finally, the data was analyzed with the help of the structural equation modelling (SEM-AMOS) for the development of an empirical structural model.

Near-Zero Thermal Expansion and High Heat-Resistance Polyimide Films Based on a Symmetric and Rigid Pyrazine Structure

Regarding the applications of polyimide (PI) films in emerging flexible devices and precision apparatus, their low coefficient of thermal expansion (CTE), especially near-zero expansion, is an urgent requirement for weakening the internal stress between the organic/inorganic layers. Other properties of PI films including the high heat-resistance and superior toughness are also demanded in actual scenarios. Herein, a set of PI films was developed by copolymerization of 2,5-bis(4-aminophenyl)pyrazine (PRZ) into a pyromellitic dianhydride (PMDA)/4,4′-oxydianiline (ODA) system. The monocrystal analysis of the PRZ monomer reveals its rigid, symmetric, and nearly coplanar steric structure. Thanks to the synergy and balance of flexible ODA and rigid PRZ units in PI chains, the near-zero expansion, high heat-resistance, and optimal mechanical properties of the PI films are simultaneously achieved. Particularly, the PI film with ODA/PRZ = 4.5/5.5 presents a near-zero CTE of −0.41 ppm/K, high glass transition temperature (Tg) of around 417 °C, superior fracture strength of 191 MPa, and initial modulus of 3.83 GPa. Interestingly, via adjusting the ODA/PRZ ratios, the precise control of CTE values can be realized, enabling the thermal expansion matching of PI films on broad types of device substrates, e.g., Cu (15–17 ppm/K) and Si (3–5 ppm/K).

Physicochemical effects of proton implantation doping on transparent nanoscale thin films of polyaniline emeraldine base covalently fabricated on organosilanized surfaces

Physicochemical effects of proton implantation doping on transparent nanoscale thin films of non-conductive polyaniline emeraldine base covalently fabricated on organosilanized surfaces were investigated in this study. Resistance measurement using the Au-electrode array coated with an initially non-conductive thin film of polyaniline emeraldine base showed that proton irradiation could first induce a drastic effect to decrease the resistance of polyaniline emeraldine base and then continue to act as a doping process to further exponentially reduce the resistance to yield a relatively stable conductive state for the proton-irradiated PANI EB. Analysis of experimental results obtained by X-ray photoelectron spectroscopy and Raman spectroscopy also revealed that (i) the proportion of bonding structures characterized as protonated amine/imine groups related to electrical conduction for polyaniline was increased after proton irradiation, (ii) nitro groups were introduced to the polymer by the applied proton beam propagating through the ambient air and (iii) crosslinking could be induced by proton irradiation through the formation of phenazine-like structures between polymer chains. With crosslinking and nitration, the proton-irradiated polyaniline exhibited electrical conductivity similar to that of polyaniline derivatives with N-alkylaniline and nitroaniline as co-monomer units in the polymer chains.

HOW BIG DATA WILL BE AN ADDED VALUE TO SCM?

It is the era of digital information technology where almost everything is going smart. Thus, organizations move towards digitalization that cause the emergent of Big Data. Analyzing big data is the big challenge today. Being smart puts the world under a big challenge to adapt, change, and upgrade systems to analyze the Big Data using the high technology. Challenges are growing with the market and appears in different forms. Many of these challenges can be hard or difficult to handle on your own if you are a small to medium size business without the help of supply chain management system. The main objective of this paper is to contribute and examine these research questions: What are the Big Data Analytical tools used in SCM? In addition to the Impact of Analyzing Big Data on Supply Chain Management? The methodology used was a systematic review over the existing literature including Big Data, supply chain, SCM, and the impact of BD analytical tools on SCM. Data collected and unsystematically interpreted and the findings summarized in a subjective way that describes and discusses the literature from a contextual or theoretical point of view. Big data can tremendously affect the supply chain units and can add values to the overall supply chain operations by improving the processes to be more effective and efficient based on the analysis results. Big data analytics become a core differentiation factor for any organization that acquire it in the last few years.

Linear Regulating of Polymer Acceptor Aggregation with Short Alkyl Chain Units Enhances All-Polymer Solar Cells' Efficiency.

The power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) has ascended rapidly arising from the development of polymerized small-molecule acceptor materials. However, numerous insulating long alkyl chains, which ensure the solubility of the polymer, result in inferior aggregation and charge mobility. Herein, this study proposes a facile random copolymerization strategy of two small molecule acceptor units with different lengths of alkyl side chains and synthesizes a series of polymer acceptors PYT-EHx, where x is the percentage of the short alkyl chain units. The aggregation strength and charge mobility of the acceptors rise linearly with increasing the proportion of short alkyl chain units. Thus, the PYT-EH20 reaches balanced aggregation with the star polymer donor PBDB-T, resulting in optimal morphology, fastest carrier transport, and reduced recombination and energy loss. Consequently, the PYT-EH20-based device yields a 14.8% PCE, a 16% improvement over the control PYT-EH0-based device, accompanied by an increase in open-circuit voltage (Voc ), short-circuit current density (Jsc ), and fill factor (FF). This work demonstrates that the random copolymerization strategy with short alkyl chain insertion is an effective avenue for developing high-performance polymer acceptors, which facilitates further advances in the efficiency of all-PSCs.

Synthesis of high regular poly(ethylene succinate) by adding oxalic acid in poly-condensation system: Suppressing etherification side reaction

Poly(ethylene succinate) (PES) with high chain regularity was synthesized by adding oxalic acid in the melt poly-condensation system. The molar ratios of diethylene glycol succinate (DEGS) units in the polymer chains were diminished from 3.8% to 0.6% when 17 mol% oxalic acid was added. Oxalic acid underwent esterification with ethylene glycol and decarboxylation, producing ethylene glycol monoformate and formate end-capped PES oligomers. The formate endcapping supressed the etherification side reactions. Ethylene glycol formate with a lower boiling point was more easily released by-production than ethylene glycol during the transesterification stage, resulting in a faster transesterification rate. Meanwhile, the molecular weights significantly increased. The high chain regularity endowed the PES with higher melting temperatures of 105 °C and remarkably increased crystallization rates. The mechanical properties, including tensile strength at break, were simultaneously improved for a high-molecular-weight PES sample (Mw = 100 kg/mol).

Interactions between Package Design, Airflow, Heat and Mass Transfer, and Logistics in Cold Chain Facilities for Horticultural Products

Homogeneity and temperature levels within a refrigerated facility are vital in preserving the quality of horticultural products throughout the cold chain to the consumer. These temperatures are affected by different factors at different scales, including the shape and thermal properties of the horticultural products, package design, pallet arrangement, or characteristics of the cold chain unit of operation. Therefore, airflow and heat transfer studies are valuable in evaluating these factors to optimize the cold chain and achieve and maintain an optimal product temperature. This paper provides an overview of the different scales of the numerical model and experimental setup used to assess the influence of the different factors on the cooling performance, as well as any challenges and limitations of each scale. The importance of considering other aspects in the cold chain studies, such as product quality, energy consumption, and package mechanical strength, will be discussed through an integrative approach. Finally, we propose new perspectives on how multi-scale modelling approaches can be helpful in tackling different challenges and how to investigate the effects of different factors on the cooling efficiency.

Oligomer formation from the gas-phase reactions of Criegee intermediates with hydroperoxide esters: mechanism and kinetics

Abstract. Hydroperoxide esters, formed in the reactions of carbonyl oxides (also called Criegee intermediates, CIs) with formic acid, play a crucial role in the formation of secondary organic aerosol (SOA) in the atmosphere. However, the transformation mechanism of hydroperoxide esters in the presence of stabilized Criegee intermediates (SCIs) is not well understood. Herein, the oligomerization reaction mechanisms and kinetics of distinct SCI (CH2OO, syn-CH3CHOO, anti-CH3CHOO, and (CH3)2COO) reactions, with their respective hydroperoxide esters and with hydroperoxymethyl formate (HPMF), are investigated in the gas phase using quantum chemical and kinetics modeling methods. The calculations show that the addition reactions of SCIs with hydroperoxide esters proceed through successive insertion of SCIs into hydroperoxide ester to form oligomers that involve SCIs as the repeated chain unit. The saturated vapor pressure and saturated concentration of the formed oligomers decrease monotonically as the number of SCIs is increased. The exothermicity of oligomerization reactions decreases significantly when the number of methyl substituents increases, and the exothermicity of anti-methyl substituted carbonyl oxides is obviously higher than that of syn-methyl substituted carbonyl oxides. The −OOH insertion reaction is energetically more feasible than the −CH insertion pathway in the SCI oligomerization reactions, and the barrier heights increase with increasing the number of SCIs added to the oligomer, except for syn-CH3CHOO. For the reactions of distinct SCIs with HPMF, the barrier of the −OOH insertion pathway shows a dramatic decrease when a methyl substituent occurs at the anti-position, while it reveals a significant increase when a methyl group is introduced at the syn-position and dimethyl substituent. Compared with the rate coefficients of the CH2OO + HPMF reaction, the rate coefficients increase by about 1 order of magnitude when a methyl substituent occurs at the anti-position, whereas the rate coefficients decrease by 1–2 orders of magnitude when a methyl group is introduced at the syn-position. These new findings advance our current understanding of the influence of Criegee chemistry on the formation and growth processes and the chemical compositions of SOA.