bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mesogenic Index: An Empirical Method for Predicting Polymeric Liquid Crystallinity
Authors: Dolden J G , Alder P T 
Published: August 2002

An empirical method for predicting the chemical compositions of random or partially ordered copolymers that exhibit mesophases was devised by the authors in 1989, while working on liquid crystal copolymer synthesis for BP Chemicals. A brief description of the method and its application to the chemical synthesis of amorphous thermotropic polyamides was given by the authors in a previous paper. Thermotropic polyimides were also synthesized by the authors as a result of the use of the predictive method. Subsequently, the method has been updated and applied to polycarbonates and polyimides. The new approach has been termed ‘the mesogenic index’ (MI) and has successfully been applied to 23 copolymer systems in which the critical compositions for mesophase formation have been established by means of varying constituent monomer concentrations. It is also consistent in predicting liquid crystalline behaviour in several hundred main-chain polymer systems containing amide, ester, carbonate, ether and urethane groups. It is inherent in the MI system that the mesogenic length is defined in terms of the number of monomer units for a given polymer class. From published work in the literature, it was first established that ester and amide groups need at least two and three aromatic rings in the mesogen respectively. Using these values to define mesogen length in polyester and polyamide copolymers, the condition MI > 10 has been determined for mesophase formation. This rule has been applied to other linking groups, such as carbonate or imide, with the surprising result that the corresponding mesogen lengths for these condensation polymers are simple numbers. Moreover, the rule has been applied successfully to mixed systems, by simply averaging the contributions of the different groups to the mesogen length in strictly molar proportions. The mesogenic index is based upon summing functional group contributions towards rigidity and/or resonance stabilization of the mesogen. To the best of our knowledge, this is the first simple method to be published that successfully correlates chemical composition with mesophase formation.
Increasing the Electrical Discharge Endurance of Acid Anhydride Cured DGEBA Epoxy Resin by Dispersion of Nanoparticle Silica
Authors: Henk P O , Kortsen T W , Kvarts T 
Published: August 2002

A fluid DGEBA/methyl nadicanhydride epoxy system has been filled with inorganic particles, cast as bubble-free plates and cured. The ability of both the pure network polymer and the polymer/particle composites to withstand partial electrical discharges has been investigated. Three types of particle combinations were used: (a) fumed nanoparticle silicon dioxide referred to as Aerosil, (b) equal volumes of Aerosil and nanoparticle anatase, and (c) Aerosil plus anatase in combination with coarse-particle filler grade calcium–magnesium carbonate dolomite. A test for endurance using the CIGRE method II electrode arrangement was applied, the test comprising the establishment of partial discharges running perpendicularly onto one face of a plate specimen for a period measured until breakdown Our results show that the endurance of the pure polymer is low. Increased loading with Aerosil increases the endurance by a factor of up to 20 as the Aerosil content goes from zero to 5.4 vol.%. Aerosil mixed with anatase has a similar effect. The high level of endurance is maintained with an additional high-volume (35 vol.%) filling of coarse-particle dolomite to an epoxy system already containing Aerosil and anatase. The results are discussed in the light of estimated interparticle spacings and interface areas.
High-Temperature Polymers for Advanced Microelectronics
Authors: Maier Gerhard , Banerjee Susanta , Haußmann Jörg , Sezi Recai 
Published: August 2002

Several series of aromatic polyethers and polybenzoxazoles with high thermal stability and low dielectric constant were prepared and characterized. The polyethers were synthesized by nucleophilic aromatic displacement of fluorine with phenoxides. In order to avoid strongly polar groups such as carbonyl and sulfone, trifluoromethyl groups were used to activate the fluorine for displacement. An additional benefit of the presence of the trifluoromethyl groups is the decreased dielectric constant, which fluorinated materials exhibit. This is attributed to two factors: the strong electronegativity of fluorine, resulting in very low polarizability of the C–F bonds, and the larger radius of a fluorine atom in comparison with a hydrogen atom, resulting in increased free volume. Trifluoromethyl substituted terphenyl and quadriphenyl poly(arylether)s prepared in this study exhibit decomposition temperatures far in excess of 500°C, even in air, dielectric constants below three, and mechanical properties comparable to engineering plastics such as polycarbonate and high-performance thermoplastics such as PEEK. Poly(benzoxazole)s were prepared with and without fluorine substituents. Since most of the poly(benzoxazole)s were insoluble, they were prepared via soluble poly(hydroxyamide) precursors, which were converted to the final polymers by thermal treatment. These materials had dielectric constants as low as 2.69 and also decomposition temperatures far above 500°C in air.
Smectic A structure in main-chain liquid crystalline polymers with two different spacers
Authors: Nakata Yasukazu , Shimizu Kazuya , Watanabe Junji 
Published: August 2002

We have prepared a homologous series of polymers, BP-CO4-On (n= 3-15). [ILLEGIBLE] The BP-CO4-On polymers are classified as a new type of main-chain liquid crystalline polymer, characterized by having the mesogenic biphenyl moieties and the two different aliphatic spacers incorporated in a regularly alternate fashion. All the polymers form a smectic A phase. The smectic behaviour and structure have been examined by differential scanning, optical microscopic and x-ray methods, concentrating on how the two spacers, which are different in length and of odd-even nature, are accommodated into a smectic layer structure.
Training and development for informal science learning
Authors: Crockett Jane Randall 
Published: August 2002

This exploratory study assessed the need for training and development of both administrators and education directors working in informal learning environments in the United States. Further, the study identified useful and feasible methods to meet these needs. Finally, it suggested that informal science learning is understood as a collective entity. This study triangulated, or coordinated, various research and data analysis methods to provide a more effective base for understanding the proposed activities. Phase 1 consisted of interviewing persons knowledgeable about informal science learning. These data were analysed qualitatively and used to develop the Phase 2 survey, which was administered to practitioners in these environments. Data from the Phase 2 survey were measured quantitatively. Although results suggest that some kind of training is necessary for administrators, significantly more people strongly agree that education directors need training specifically oriented towards informal science learning. Training for either administrators or education directors should include development of the following skills and attributes: personnel skills, fund-raising skills, financial skills, enthusiasm about doing science with others, knowledge of diverse publics, ability to interact with diverse publics, and volunteer interaction skills. Data indicate that several methods would be very useful and feasible for training both administrators and education directors. These methods include: on-the-job training, a yearly one-week training activity, a degree program in a related field combined with a specific internship, and a series of training courses or seminars. Data suggest that informal science learning can be understood as a collective entity using descriptors such as: industry, field, profession and discipline. However, this study suggests that using environmental characteristics of informal science learning contexts (instead of conceptualising them as the opposite of formal education) may be valuable for better understanding these environments. This understanding might increase the attention given to informal science learning environments as integral components in a holistic view of human learning.
Design of Fatigue‐Resistant Hydrogels
Authors: Han Zilong , Lu Yuchen , Qu Shaoxing 
Published: January 2024

AbstractHydrogels are made tough to resist crack propagation. However, for seamless integration into devices and machines, it necessitates robustness against cyclic loads. Central to this objective is enhancing fatigue resistance, an indispensable attribute facilitating the optimal performance of hydrogels within a multitude of biological contexts, spanning various plant and animal tissues, as well as diverse biomedical and engineering areas. In this review, recent research concerning the fatigue behavior of hydrogels, presenting a comprehensive consolidation of the inherent mechanisms that underpin diverse strategies aimed at fortifying fatigue resistance, is summarized. A critical facet in the architectural blueprint of fatigue‐resistant hydrogels is emphasized, involving the imposition of spatial constraints upon the main chains at the crack tips, thereby effectuating a protracted delay in their fracture initiation during prolonged cyclic loading. The integration of multiscale mechanisms encompassing networks, interactions, media, and structures stands as a pivotal factor in the design of fatigue‐resistant hydrogels. It is hoped that the review will considerably propel the pragmatic deployment of fatigue‐resistant hydrogels across a diverse array of applications, thus catalyzing advancements in multiple fields.
Revealing the Substrate Constraint Effect on the Thermodynamic Behaviour of the Pd–H through Capacitive‐Based Hydrogen‐Sorption Measurement
Authors: Kim Gwangmook , Lee Soomin , Lee Sang‐kil , Yu Han Jun , Cho Hunyoung , Chung Youngjun , Park Tae‐Eon , Lee Hyun‐Sook , Shim Wooyoung , Lee Kyu Hyoung , Park Jeong Young , Kim Yu Jin , Chun Dong Won , Lee Wooyoung 
Published: January 2024

AbstractMechanical constraints imposed on the Pd–H system can induce significant strain upon hydrogenation‐induced expansion, potentially leading to changes in the thermodynamic behavior, such as the phase‐transition pressure. However, the investigation of the constraint effect is often tricky due to the lack of simple experimental techniques for measuring hydrogenation‐induced expansion. In this study, a capacitive‐based measurement system is developed to monitor hydrogenation‐induced areal expansion, which allows us to control and evaluate the magnitude of the substrate constraint. By using the measurement technique, the influence of substrate constraint intensity on the thermodynamic behavior of the Pd–H system is investigated. Through experiments with different constraint intensities, it is found that the diffefrence in the constraint intensity minimally affects the phase‐transition pressure when the Pd–H system allows the release of constraint stress through plastic deformation. These experiments can improve the understanding of the substrate constraint behaviours of Pd–H systems allowing plastic deformation while demonstrating the potential of capacitive‐based measurement systems to study the mechanical–thermodynamic coupling of M–H systems.
Anti‐Fatigue Tandem Organic Photovoltaics for Indoor Illumination
Authors: Li Hao , Zheng Zhong , Yang Shiwei , Wang Tao , Yang Yi , Tang Yanjie , Zhang Shaoqing , Hou Jianhui 
Published: January 2024

AbstractThe ability of achieving high efficiency makes tandem organic photovoltaics (PVs) a competitive technique in potential indoor applications. Except high efficiency, reliable indoor energy supply also calls for outstanding stability. However, unavoidable unstable voltage supply from the circuit control system for indoor light sources like light emitting diodes (LED) and incandescent lamps would cause carrier density fluctuation and device fatigue driven by periodic light/dark switching. In this work, the strobing‐induced fatigue within the bulk heterojunction (BHJ)/interconnecting layer (ICL) interface is first revealed and overcome. Based on reliable and effective interfacial doping between conjugated acceptor and metal oxide, the interfacial capacitance that determines the strobing‐induced fatigue, has been significantly restrained. The imbalance carrier migration and fierce inter‐layer accommodating during the burn‐in stage caused by light strobing are substantially diminished. Benefit from this method, the stability of tandem devices is highly enhanced under strobing indoor illumination, and a champion efficiency (35.02%) is obtained. The method provides guidance for further material design for interconnecting layers in organic photovoltaics.
Injectable MSC Spheroid and Microgel Granular Composites for Engineering Tissue
Authors: Caprio Nikolas Di , Davidson Matthew D. , Daly Andrew C. , Burdick Jason A. 
Published: January 2024

AbstractMany cell types require direct cell–cell interactions for differentiation and function; yet, this can be challenging to incorporate into 3‐dimensional (3D) structures for the engineering of tissues. Here, a new approach is introduced that combines aggregates of cells (spheroids) with similarly‐sized hydrogel particles (microgels) to form granular composites that are injectable, undergo interparticle crosslinking via light for initial stabilization, permit cell–cell contacts for cell signaling, and allow spheroid fusion and growth. One area where this is important is in cartilage tissue engineering, as cell–cell contacts are crucial to chondrogenesis and are missing in many tissue engineering approaches. To address this, granular composites are developed from adult porcine mesenchymal stromal cell (MSC) spheroids and hyaluronic acid microgels and simulations and experimental analyses are used to establish the importance of initial MSC spheroid to microgel volume ratios to balance mechanical support with tissue growth. Long‐term chondrogenic cultures of granular composites produce engineered cartilage tissue with extensive matrix deposition and mechanical properties within the range of cartilage, as well as integration with native tissue. Altogether, a new strategy of injectable granular composites is developed that leverages the benefits of cell–cell interactions through spheroids with the mechanical stabilization afforded with engineered hydrogels.
Accounting for costs in attainable‐region‐based reactor–separation network synthesis: Models, tradeoffs, and insights
Authors: Pastore de Lima Arthur E. , Ryu Joonjae , Maravelias Christos T. 
Published: January 2024

AbstractIn reaction engineering, the attainable region defines the set of all possible states attainable in the outlet stream of any steady‐state reactor network, given specified feed and reaction kinetics. Costs in approaches that aim to determine the attainable region are often neglected, resulting in targets that require expensive processes. In this work, we propose modeling methods that allow us to account for costs in reactor–separation synthesis while accurately identifying the attainable region. Our goal is to holistically analyze cost trade‐offs within the attainable region as well as provide a method to obtain practical targets to be used as benchmarks. We generate the attainable region using the continuous stirred tank reactor (CSTR) equivalence principle and introduce separation models accounting for costs to perform the required separation tasks. Through several case studies, we show how some subregions, typically close to the attainable region boundary, are expensive to achieve.
Human‐like enamel growth in Homo naledi
Authors: Mahoney Patrick , McFarlane Gina , Taurozzi Alberto J. , Madupe Palesa P. , O'Hara Mackie C. , Molopyane Keneiloe , Cappellini Enrico , Hawks John , Skinner Matthew M. , Berger Lee 
Published: January 2024

AbstractObjectivesA modern pattern (rate and duration) of dental development occurs relatively recently during human evolution. Given the temporal overlap of Homo naledi with the first appearance of fossil Homo sapiens in Africa, this small‐bodied and small‐brained hominin presents an opportunity to elucidate the evolution of enamel growth in the hominin clade. Here we conduct the first histological study of two permanent mandibular canines and one permanent maxillary first molar, representing three individuals attributed to H. naledi. We reconstruct the rate and duration of enamel growth and compare these findings to those reported for other fossil hominins and recent humans.Materials and MethodsThin sections of each tooth were produced using standard histological methods. Daily and longer period incremental markings were measured to reconstruct enamel secretion and extension rates, Retzius periodicity, canine crown and molar cusp formation time.ResultsDaily enamel secretion rates overlapped with those from recent hominins. Canine crown formation time is similar to that observed in recent Europeans but is longer than canine formation times reported for most other hominins including Australopithecus and H. neanderthalensis. The extended period of canine formation appears to be due to a relatively tall enamel crown and a sustained slow rate of enamel extension in the cervical portion of the crown. A Retzius periodicity of 11 days for the canines, and nine days for the molar, in H. naledi parallel results found in recent humans. An 11‐day periodicity has not been reported for Late Pleistocene Homo (H. erectus, H. neanderthalensis) and is rarely found in Australopithecus and Paranthropus species.DiscussionEnamel growth of H. naledi is most similar to recent humans though comparative data are limited for most fossil hominin species. The high Retzius periodicity values do not follow expectations for a small‐brained hominin.
All‐Round Ionic Liquids for Shuttle‐Free Zinc‐Iodine Battery
Authors: Xiao Tao , Yang Jin‐Lin , Zhang Bao , Wu Jiawen , Li Jinliang , Mai Wenjie , Fan Hong Jin 
Published: January 2024

AbstractThe practical implementation of aqueous zinc‐iodine batteries (ZIBs) is hindered by the rampant Zn dendrites growth, parasite corrosion, and polyiodide shuttling. In this work, ionic liquid EMIM[OAc] is employed as an all‐round solution to mitigate challenges on both the Zn anode and the iodine cathode side. First, the EMIM+ embedded lean‐water inner Helmholtz plane (IHP) and inert solvation sheath modulated by OAc− effectively repels H2O molecules away from the Zn anode surface. The preferential adsorption of EMIM+ on Zn metal facilitates uniform Zn nucleation via a steric hindrance effect. Second, EMIM+ can reduce the polyiodide shuttling by hindering the iodine dissolution and forming an EMIM+‐I3− dominated phase. These effects holistically enhance the cycle life, which is manifested by both Zn || Zn symmetric cells and Zn‐I2 full cells. ZIBs with EAc deliver a capacity decay rate of merely 0.01 ‰ per cycle after over 18,000 cycles at 4 A g−1, and lower self‐discharge and better calendar life than the ZIBs without ionic liquid EAc additive.
Polydentate Ligand Reinforced Chelating to Stabilize Buried Interface toward High‐Performance Perovskite Solar Cells
Authors: Liu Baibai , Zhou Qian , Li Yong , Chen Yu , He Dongmei , Ma Danqing , Han Xiao , Li Ru , Yang Ke , Yang Yingguo , Lu Shirong , Ren Xiaodong , Zhang Zhengfu , Ding Liming , Feng Jing , Yi Jianhong , Chen Jiangzhao 
Published: January 2024

AbstractThe instability of the buried interface poses a serious challenge for commercializing perovskite photovoltaic technology. Herein, we report a polydentate ligand reinforced chelating strategy to strengthen the stability of buried interface by managing interfacial defects and stress. The bis(2,2,2‐trifluoroethyl) (methoxycarbonylmethyl)phosphonate (BTP) is employed to manipulate the buried interface. The C=O, P=O and two −CF3 functional groups in BTP synergistically passivate the defects from the surface of SnO2 and the bottom surface of the perovskite layer. Moreover, The BTP modification contributes to mitigated interfacial residual tensile stress, promoted perovskite crystallization, and reduced interfacial energy barrier. The multidentate ligand modulation strategy is appropriate for different perovskite compositions. Due to much reduced nonradiative recombination and heightened interface contact, the device with BTP yields a promising power conversion efficiency (PCE) of 24.63 %, which is one of the highest efficiencies ever reported for devices fabricated in the air environment. The unencapsulated BTP‐modified devices degrade to 98.6 % and 84.2 % of their initial PCE values after over 3000 h of aging in the ambient environment and after 1728 h of thermal stress, respectively. This work provides insights into strengthening the stability of the buried interface by engineering multidentate chelating ligand molecules.
Succinic acid production from softwood with genome‐edited Corynebacterium glutamicum using the CRISPR‐Cpf1 system
Authors: Lee Dae‐Seok , Cho Eun Jin , Nguyen Dinh‐Truong , Song Younho , Chang Jihye , Bae Hyeun‐Jong 
Published: January 2024

AbstractCorynebacterium glutamicum is a useful microbe that can be used for producing succinic acid under anaerobic conditions. In this study, we generated a knock‐out mutant of the lactate dehydrogenase 1 gene (ΔldhA‐6) and co‐expressed the succinic acid transporter (Psod:SucE‐ ΔldhA) using the CRISPR‐Cpf1 genome editing system. The highly efficient HPAC (hydrogen peroxide and acetic acid) pretreatment method was employed for the enzymatic hydrolysis of softwood (Pinus densiflora) and subsequently utilized for production of succinic acid.Upon evaluating a 1%–5% hydrolysate concentration range, optimal succinic acid production with the ΔldhA mutant was achieved at a 4% hydrolysate concentration. This resulted in 14.82 g L−1 succinic acid production over 6 h. No production of acetic acid and lactic acid was detected during the fermentation. The co‐expression transformant, [Psod:SucE‐ΔldhA] produced 17.70 g L−1 succinic acid in 6 h. In the fed‐batch system, 39.67 g L−1 succinic acid was produced over 48 h. During the fermentation, the strain consumed 100% and 73% of glucose and xylose, respectively. The yield of succinic acid from the sugars consumed was approximately 0.77 g succinic acid/g sugars. These results indicate that the production of succinic acid from softwood holds potential applications in alternative biochemical processes.
A versatile method for conjugating lipid nanoparticles on T cells through combination of click chemistry and metabolic glycoengineering
Authors: Li Xin , Weller Sven , Clergeaud Gael , Andresen Thomas L. 
Published: January 2024

AbstractCell‐mediated drug delivery by conjugating nanomedicine to the surface of living cells is a promising strategy for enhancing the efficacy of both drug delivery and cell therapy. It exploits the tissue homing properties of the specific cell types to overcome in vivo barriers and forms a drug depot by directly putting the therapeutic payload in target cells. An important concern of developing this system is the method to conjugate nanoparticles on cells. Herein, we developed a bioorthogonal T cell conjugation strategy using SPAAC click chemistry, which allows controllable and highly efficient conjugation without affecting the viability and functions of the cytotoxic T lymphocytes. Azide groups were incorporated on the surface of T cells through metabolic glycoengineering, followed by reacting with dibenzylcyclooctyne (DBCO) modified lipid nanoparticles (LNPs). LNPs can be conjugated to T cells, allowing for the loading of different drug molecules on the cells. The metabolic engineering and click reaction approach provides a simple and versatile strategy to conjugate NPs to living cells and enable the development of sophisticated therapeutic cell products.