bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Career Adaptability on Employee Performance: The Moderating Role of HR Practices
Authors: Chouhan Vikram Singh
Published: April 2023

The research aims to observe the impact of career adaptability on employee performance using organizational commitment as the mediator. This study also attempts to investigate human resource practices as a moderator in the association between career adaptability and organizational commitment. The survey was conducted among employees working in different Indian firms. Findings of this research reveal that organizational commitment acted as a mediator in the positive association of organizational commitment with career adaptability. Employee performance is found to be positively influenced by organizational commitment while organizational commitment is found to be positively influenced by career adaptability. The findings of this research present testimony for the hypothesized moderating role of human resource practices only in the case of opportunity-enhancing human resource practices. The connection of career adaptability with organizational commitment is found to be positive only for high and medium opportunity-enhancing HR practices.
Emotional Labour During the COVID-19 Pandemic—Current Inquiry and Suggested Future Research Directions
Authors: Das Debaraj , Pal Suchitra , Jena Lalatendu Kesari
Published: April 2023

The objective of this article is to examine the impact of macro-extreme emotional experience (MEEE) and the new societal norms during the COVID-19 pandemic on health and well-being and their situational consequences on emotional labour of frontline employees. The vast literature on emotional labour in the past has focused on several situational cues, and individual and organizational factors as antecedents. We did a systematic review of available literature on emotional labour, literature on sentiment analysis and emotional experience during the pandemic and analysed COVID-19 related blogs using Natural Language Processing (NLP) in RStudio. At the same time, we attempted to look at the possible intervention of individual factors of MEEEs and social aspects of the new societal norms as antecedents on emotion regulation process and its outcome and propose a conceptual framework for future research on emotional labour under the ‘new normal’. It was concluded that perceived risk, fear and anxiety are extreme emotions that individuals are experiencing during the pandemic.
L1-transfer effects and the role of computational complexity in L2 pronoun interpretation
Authors: Kim Eun Hee
Published: April 2023

This study investigates pronoun interpretation by second language (L2) learners of English, focusing on whether first language (L1) transfer and/or processing difficulty affect L2 learners’ pronoun resolution. It is hypothesized that L2 learners’ non-target performance in L2-pronoun interpretation is attributable to two sources. The first is the computational complexity required for pronoun resolution, as argued in L1 acquisition by Grodzinsky and Reinhart and L2 acquisition by Slabakova et al. The second is how pronoun interpretation operates in L1. The hypothesis is tested by comparing Korean and Spanish L2-English learners’ interpretation of English pronouns using a Truth Value Judgment Task. Both groups had difficulty rejecting pronouns with local-referential antecedents when their proficiency levels were low. Additionally, Korean speakers showed more non-target responses than Spanish speakers due to their knowledge of pronoun interpretation in Korean. These results indicate that both L1 transfer and processing difficulty may be sources of L2 learners’ non-target pronoun interpretation, supporting the hypothesis of the study.
What drives the creation of green jobs, products and technologies in cities and regions? Insights from recent research on green industrial transitions
Authors: Froy Francesca , Heroy Samuel , Uyarra Elvira , O’Clery Neave
Published: April 2023

Given the global imperative to meet ‘net zero’, and growing interest in the potential for green jobs growth, there is an urgent need to better understand the drivers and processes underlying green structural economic transitions. How should we in fact define ‘green’ products, jobs and technologies? How do local economies transition into greener jobs – is this generally an incremental process or does it require more radical innovation? Building on nascent green definitions, recent work emerging from the literature in Evolutionary Economic Geography suggests that there is a degree of path dependency to green transitions, with regions benefiting from existing capabilities which are somehow related to newer green tasks and technologies. On the other hand, having diverse, frequently unrelated, skills and competencies also helps local economies to make the recombinations necessary for the emergence of new green activities. These drivers are moderated by factors such as the local institutional environment, IT skills and the degree of maturity of the local industrial base. This article summarises the recent literature in order to provide an overview of emerging findings of relevance to local policy delivery, while also highlighting future research directions.
Isoflurane and ketamine-xylazine modify pharmacokinetics of [18F]SynVesT-1 in the mouse brain
Authors: Miranda Alan , Bertoglio Daniele , De Weerdt Caro , Staelens Steven , Verhaeghe Jeroen
Published: April 2023

We investigated the effect of isoflurane and ketamine-xylazine anesthesia on the positron emission tomography (PET) tracer [18F]SynVesT-1 in the mouse brain. [18F]SynVesT-1 PET scans were performed in C57BL/6J mice in five conditions: isoflurane anesthesia (ANISO), ketamine-xylazine (ANKX), awake freely moving (AW), awake followed by isoflurane administration (AW/ANISO) or followed by ketamine-xylazine (AW/ANKX) 20 min post tracer injection. ANISO, ANKX and AW scans were also performed in mice administered with levetiracetam (LEV, 200 mg/kg) to assess non-displaceable binding. Metabolite analysis was performed in ANISO, ANKX and AW mice. Finally, in vivo autoradiography in ANISO, ANKX and AW mice at 30 min post-injection was performed for validation. Kinetic modeling, with a metabolite corrected image derived input function, was performed to calculate total and non-displaceable volume of distribution ( VT(IDIF)). VT(IDIF) was higher in ANISO compared to AW (p < 0.0001) while VT(IDIF) in ANKX was lower compared with AW (p < 0.0001). Non-displaceable VT(IDIF) was significantly different between ANISO and AW, but not between ANKX and AW. Change in the TAC washout was observed after administration of either isoflurane or ketamine-xylazine. Observed changes in tracer kinetics and volume of distribution might be explained by physiological changes due to anesthesia, as well as by induced cellular effects.
Untangling the Association Between Goal Clarity and Public Service Motivation With the Moderating Role of Value Congruence
Authors: Kim Gook Jin , Ki Namhoon , Yoon Taewon
Published: April 2023

Drawing on the socialization aspect of public service motivation (PSM) and the internalization process of organizational values, this study empirically tests the argument that goal clarity leads to higher PSM, with a specific focus on the moderating role of value congruence between them. Using data from 4,133 Korean public employees in the 2021 Public Employee Perception Survey, the current study finds that individuals’ perception of goal clarity generally has a positive relationship with their PSM, especially among those who have high individual–organization value congruence. We also discovered that certain matched levels of both goal clarity and value congruence are crucial for the positive relationship between clear goal perception and PSM to exist. This study concludes that the relationship between goal clarity and PSM is not straightforward, but instead follows a U-shaped pattern, characterized by a decrease followed by an increase. This implies that perceiving clearer goals may have a demotivating effect on some employees; those with relatively low levels of goal clarity and, therefore, low goal congruence (i.e., lack of internalization of clear organizational goals) would instead be demotivated as they perceive clearer goals.
Intraoperative computed tomography during fenestrated and branched endovascular aortic repair: a feasibility study
Authors: Schrøder-Aasen Anne Marte , Carling Ulrik , Aaløkken Trond Mogens , Rasmussen Margrethe Kallestad , Dorenberg Eric
Published: April 2023

Background

Endovascular aortic repair with fenestrated or branched endografts is technically challenging, and proper intraoperative assessment of all stent graft components with only angiography and fluoroscopy can be difficult. Intraoperative computed tomography (CT) imaging can be a valuable aid for the operators in the evaluation of stent grafting results prior to completion of surgery.

Purpose

To examine the feasibility of performing intraoperative CT imaging during fenestrated and branched endovascular aortic repair (f-bEVAR) under sterile conditions and with patients under general anesthesia.

Material and Methods

Intraoperative CT imaging was performed in 10 patients undergoing elective aortic repair with fenestrated or branched endografts. Adverse events, time consumption for CT set-up and image acquisition, and additional radiation dose to the patient were recorded. CT image quality was graded. Immediate corrective maneuvers performed based on the CT findings was registered.

Results

There were no adverse events related to intraoperative CT imaging. The median additional operating time by including intraoperative CT was 16 min (interquartile range [IQR] = 12–19), comprising 7% of the median total operating time. The median estimated additional radiation dose to the patient was 4.8 mSv (IQR = 3.8–4.9). All intraoperative CT examinations were considered to be of sufficient quality for stent graft evaluation. No immediate corrective procedures were performed on the basis of CT findings in this study cohort.

Conclusion

CT imaging intraoperatively during f-bEVAR is feasible with an acceptable increase in operating time and radiation dose.
Management of chronic Stanford type A aortic dissection combined with Neri type C coronary occlusion: a case report and literature review
Authors: Tang Tiansheng , Wang Ziao , Zhou Wei , Wang Hai , Zhang Hanjun , Sun Ayu , Wei Jun , Sheng Weiyong , Zhang Dafa
Published: April 2023

While there are many reports on partial aortic root remodelling, it is rarely performed for chronic aortic dissection of the coronary artery. This case report describes a 71-year-old male patient with chronic aortic dissection who was admitted to hospital due to repeated palpitations and chest distress. He had a long-term occlusion of the right coronary artery and an abnormal origin of the left vertebral artery. A carefully planned surgical strategy was arranged for this patient, and the surgical experience is described and discussed herein. Briefly, the patient was treated by aortic root repair plus ascending aorta replacement plus Sun's procedure plus left vertebral artery graft implantation plus coronary artery bypass graft (right coronary artery to saphenous vein to innominate artery). At approximately 6 months following surgery, the patient had returned to normal living conditions without any reports of discomfort.
Oral vinorelbine in young patients with desmoid-type fibromatosis
Authors: Kornreich Laure , Orbach Daniel , Nicolas Nayla , Brisse Hervé J , Berlanga Pablo , Defachelles Anne-Sophie , Mansuy Ludovic , Verite Cécile , Saumet Laure , Karanian Marie , Corradini Nadège
Published: April 2023

Background:

Desmoid-type fibromatosis are rare intermediate tumors in children and adolescents. Owing to local aggressiveness and relapse, systemic treatment for symptomatic advanced or progressive forms is recommended. Following promising results in adult patients, oral vinorelbine is investigated in young patients.

Methods:

A retrospective review of young patients (<25 years old) with advanced or progressive desmoid type fibromatosis treated with oral vinorelbine in eight large centers of the Société Française des Cancers de l’Enfant was performed. In addition to tumor assessment according to RECIST 1.1, pre-treatment and during-treatment imagery were reviewed centrally to assess tumor volume and estimate fibrosis score through the change in percentage in hypoT2 signal intensity.

Results:

From 2005 to 2020, 24 patients (median age 13.9 years [range, 1.0-23.0]) received oral vinorelbine. Median number of prior systemic lines of treatment was 1 (range, 0-2), mainly based on intravenous low dose methotrexate and vinblastine. Before vinorelbine initiation, all patients had a progressive disease: radiological for 19, radiological and clinical (pain) for three and only clinical for two. Oral vinorelbine was delivered for a median duration of 12 months (range, 1-42). The toxicity profile was favorable, with no grade 3-4 event. Overall response estimated on 23 evaluable patients according to RECIST 1.1 criteria was three partial responses (13%), 18 stabilization (78%) and two progressive disease (9%). Overall progression-free survival was 89.3% (95% confidential intervals 75.2-100) at 24 months. Four stable tumors according to standard RECIST criteria displayed a partial response with > 65% tumor volume reduction. Among 21 informative patients, the estimated fibrosis score decreased for 15 patients, was stable for four patients and increased for two patients.

Conclusion:

Oral vinorelbine seems to be effective to control advanced or progressive desmoid type fibromatosis in young patients, with a well-tolerated profile. These results support testing this drug as first-line alone or in combination to improve response rate while preserving quality of life.
South African academic libraries as contributors to social justice and ubuntu through community engagement
Authors: Bangani Siviwe , Dube Luyanda
Published: April 2023

The purpose of this article is to assess the role of academic libraries as social justice and ubuntu advocates, promoters and contributors within a community engagement framework. This was a qualitative study that utilised interviews with 20 library heads and 8 focus group discussions with librarians from South African university libraries to gather data. The findings reflect that South African academic libraries’ community engagement approaches can be grouped into several themes. These include contributions to quality education, health and wellness, work and employment, food security, addressing the digital divide, environmental concerns, equality and gender equality, the preservation of national heritage and food security. With regard to social justice, there were four themes that emerged from the participants’ narratives: (1) they stated that community engagement is a deliberate social justice action; (2) community engagement was associated with a contribution to the rights to education and information access, among others; (3) they pointed to the social-redress actions of their libraries as contributing to social justice; and (4) they associated community engagement with ubuntu, which they argued is itself a social justice concept. The findings support community engagement activities as a contribution to a socially just society and ubuntu. The results confirm the need for academic libraries (and universities in general) to go beyond their traditional role of teaching, learning and research support, and participate in community engagement not only as an expected social responsibility but also as a contribution to a socially just society and development. Based on the results, this article considers social justice and ubuntu as inherent to, and not an accidental notion of, community engagement.
Beyond Greenland: Other aspects of Georgian Liverpool's whaling trade
Authors: Hill Simon
Published: April 2023

Most of the existing research on Georgian Liverpool's whaling activities has focused on the northern whaling trade around the Arctic and Greenland. However, this article sheds new light by exploring the port's other whaling activities – namely, the southern whale fishery. In doing so, this short research note expands the geography of Liverpool's whaling industry and suggests that it may have had ties to the port's most notorious activity – transatlantic slavery.
Use of Invasive Brain-Computer Interfaces in Pediatric Neurosurgery: Technical and Ethical Considerations
Authors: Bergeron David , Iorio-Morin Christian , Bonizzato Marco , Lajoie Guillaume , Orr Gaucher Nathalie , Racine Éric , Weil Alexander G.
Published: April 2023

Invasive brain-computer interfaces hold promise to alleviate disabilities in individuals with neurologic injury, with fully implantable brain-computer interface systems expected to reach the clinic in the upcoming decade. Children with severe neurologic disabilities, like quadriplegic cerebral palsy or cervical spine trauma, could benefit from this technology. However, they have been excluded from clinical trials of intracortical brain-computer interface to date. In this manuscript, we discuss the ethical considerations related to the use of invasive brain-computer interface in children with severe neurologic disabilities. We first review the technical hardware and software considerations for the application of intracortical brain-computer interface in children. We then discuss ethical issues related to motor brain-computer interface use in pediatric neurosurgery. Finally, based on the input of a multidisciplinary panel of experts in fields related to brain-computer interface (functional and restorative neurosurgery, pediatric neurosurgery, mathematics and artificial intelligence research, neuroengineering, pediatric ethics, and pragmatic ethics), we then formulate initial recommendations regarding the clinical use of invasive brain-computer interfaces in children.
Bagasse fiber reinforced chemically functionalized polystyrene composites
Authors: Verma Harsha , Palsule Sanjay
Published: April 2023

This study develops bagasse fiber (BGSEF) reinforced chemically functionalized polystyrene (CF-PS) composites (BGSEF/CF-PS) using CF-PS as a matrix, that has higher amount of functionality and requires processing upto 210°C. BGSEF/CF-PS have been processed by extrusion and injection moulding, retaining the stability of the thermally sensitive BGSEF. Relative to the CF-PS, all the BGSEF/CF-PS composite compositions show higher tensile and flexural properties, that increase with increasingly higher amounts of BGSEF in them. Relative to the CF-PS, the 10/90, 20/80 and 30/70 BGSEF/CF-PS composites show approx. 9.5%, 45% and 63% higher tensile strength, approx. 19%, 31% and 45% higher tensile modulus and approx. 20.5%, 22%, and 23% lower tensile elongation at break respectively, and show approx. 5%, 10%, and 16% higher flexural strength respectively, and approx. 6.5%, 16%, and 24% higher flexural modulus respectively. Upon water absorption saturation, the tensile and flexural properties of the wet composites decrease, relative to the dry composites. Adhesion between BGSEF and CF-PS in the composites, results from ester bonds and hydrogen bonds. The composites are thermally stable upto 290°C. These BGSEF/CF-PS composites by Palsule process show better performance than the BGSEF/PS composites by fiber treatment process.
Later-Life Functionality in Married Women: The Mediating Role of Self-Perpetuating BMI and Pain Trajectories
Authors: Wickrama Kandauda (A. S.)
Published: April 2023

The current study investigated how pain and BMI trajectories mediate the influence of family stress (1991–1994) on later-life impaired functionality (2017) in women. The study used prospective data from 244 mid-older rural Midwest Caucasian women who were in long-term marriages over a span of 27 years. Within the structural equation framework, the analytical model used latent constructs of family stress and trajectories of pain and BMI to predict later-life functionality. BMI and pain trajectories mutually influenced each other in forming a self-perpetuating cycle over time in mid-older women. Further, midlife family stress shaped BMI and pain trajectories, and these trajectories had consequences for later-life functionality, as defined by three kinds of impairments: physical, cognitive (subjective memory), and social (loneliness). The findings emphasize the need for policies and interventions that focus on reducing women’s stressful family circumstances in middle years to weaken and redirect their association with BMI and pain trajectories.
Could a Conscious Machine Deliver Pastoral Care?
Authors: Proudfoot Andrew
Published: April 2023

Could Artificial Intelligence (AI) play an active role in delivering pastoral care? The question rests not only on whether an AI could be considered an autonomous agent, but on whether such an agent could support the depths of relationship with humans which is essential to genuine pastoral care. Theological consideration of the status of human-AI relations is heavily influenced by Noreen Herzfeld, who utilises Karl Barth's I-Thou encounters to conclude that we will never be able to relate meaningfully to a computer since it would not share our relationship to God. In this article, I look at Barth's anthropology in greater depth to establish a more comprehensive and permissive foundation for human-machine encounter than Herzfeld provides—with the key assumption that, at some stage, computers will become conscious. This work allows discussion to shift focus to the challenges that the alterity of the conscious computer brings, rather than dismissing it as a non-human object. If we can relate as an I to a Thou with a computer, then this allows consideration of the types of pastoral care they could provide.
Prediction of thermal errors in a motorized spindle in CNC machine tools by applying loads based on heat flux
Authors: Haoshuo Wang , Guangsheng Chen , Yushan Sun
Published: April 2023

The thermal errors of a motorized spindle are seen as a source of significant errors in computer numerical control (CNC) machine tools, and motion errors, geometrical errors, among others, that are consequences of the thermal errors in the spindle. A predictive model of the thermal errors of a motorized spindle is proposed using a loading method based on heat flux. At first, a finite element model for the steady-state and transient thermal-structure coupling analysis of a motorized spindle is established, in which the loading method based on heat flux is adopted to assign the total amount of heat to the ball, an inner race, and an outer race of angular-contact ball bearing proportionally. The response values of sample points are obtained by simulation, and then a response surface model for the prediction of the steady-state elongation of the spindle thermal deformation under the influences of four factors including rotational speed of a bearing, coolant temperature, ambient temperature, and preload is constructed. The simulation and experimental results indicate that predictive error of the steady-state elongation of the spindle thermal deformation is only 3.81 μm, and the thermal equilibrium time in the transient thermal-structure coupling analysis is almost same to the experimental result. The response surface model can predict steady-state errors arising from the changes in working conditions and corresponding changes of the spindle.
Study of the time-varying mesh stiffness of two-stage planetary gear train considering tooth surface wear
Authors: Mo Shuai , Wang Lei , Liu Meng , Hu Qingsen , Bao Heyun , Cen Guojian , Huang Yunsheng
Published: April 2023

Due to the complex structure of the planetary gear train, the influence of early fault on the dynamic characteristics of the planetary gear train is complex and changeable. This paper proposes a time-varying meshing stiffness (TVMS) calculation model of internal meshing considering the coupling effect between teeth; and a multi-tooth coupling stiffness calculation model of the planetary gear train. The Archard equation is used to calculate the wear depth; moreover, the potential energy method calculated The TVMS of the planetary gear train under the wear state. The wear fault will cause the TVMS of the gear to decrease. In the two-stage planetary gear train, the TVMS of the first-stage sun-planet gear decreases more obviously. In addition, there is a specific coupling effect between the sun, ring, and planetary gear. The influence of the wear fault on the two-stage planetary gear train is analyzed by calculating the synthetic stiffness considering the meshing phase difference. The results show that under the same wear fault condition, the more teeth involved in meshing, the more significant the decrease in coupling stiffness.
Lost in the crowd? An investigation into where microwork is conducted and classifying worker types
Authors: Morgan Ryan A , van Zoonen Ward , ter Hoeven Claartje
Published: April 2023

The global expansion of the platform economy raised questions about where and by whom different forms of platform work are performed in Europe. This study focuses on microworking – that is, where an anonymous ‘crowd’ completes piecemeal digital work. Specifically, we address two questions about microworking in the EU-27: Where is microworking performed? Who is performing it? Based on the geolocation of 5,239 workers active on six prominent microworking platforms, we identify variation in the relative prevalence of microworking across the EU. Furthermore, we build on existing research to provide a more granular understanding of different classes of microworkers, in terms of diversity and (income) dependency. Four distinct classes of microworkers emerge through statistical modelling of eight relevant diversity and dependency indicators: age, gender, education, citizenship, experience, hours per week, personal income earned, household income. We label these classes Explorers, Enthusiasts, Supplementers, and Dependents. The identification of these emergent classes and varied prevalence of microworking across the EU, suggest the importance of heterogeneity to both the future study and regulation of microwork.
Imputation and missing indicators for handling missing data in the development and deployment of clinical prediction models: A simulation study
Authors: Sisk Rose , Sperrin Matthew , Peek Niels , van Smeden Maarten , Martin Glen Philip
Published: April 2023

Background: In clinical prediction modelling, missing data can occur at any stage of the model pipeline; development, validation or deployment. Multiple imputation is often recommended yet challenging to apply at deployment; for example, the outcome cannot be in the imputation model, as recommended under multiple imputation. Regression imputation uses a fitted model to impute the predicted value of missing predictors from observed data, and could offer a pragmatic alternative at deployment. Moreover, the use of missing indicators has been proposed to handle informative missingness, but it is currently unknown how well this method performs in the context of clinical prediction models. Methods: We simulated data under various missing data mechanisms to compare the predictive performance of clinical prediction models developed using both imputation methods. We consider deployment scenarios where missing data is permitted or prohibited, imputation models that use or omit the outcome, and clinical prediction models that include or omit missing indicators. We assume that the missingness mechanism remains constant across the model pipeline. We also apply the proposed strategies to critical care data. Results: With complete data available at deployment, our findings were in line with existing recommendations; that the outcome should be used to impute development data when using multiple imputation and omitted under regression imputation. When missingness is allowed at deployment, omitting the outcome from the imputation model at the development was preferred. Missing indicators improved model performance in many cases but can be harmful under outcome-dependent missingness. Conclusion: We provide evidence that commonly taught principles of handling missing data via multiple imputation may not apply to clinical prediction models, particularly when data can be missing at deployment. We observed comparable predictive performance under multiple imputation and regression imputation. The performance of the missing data handling method must be evaluated on a study-by-study basis, and the most appropriate strategy for handling missing data at development should consider whether missing data are allowed at deployment. Some guidance is provided.
A comparative study of analytical and numerical models of mechanical properties of composites and hybrid composites reinforced with natural reinforcements
Authors: Chichane Assia , Boujmal Radouane , El Barkany Abdellah
Published: April 2023

This present research aims to predict the mechanical behavior of the composite and hybrid composites based on a polypropylene matrix (PP) reinforced by organic/inorganic naturally occurring fillers using analytical and numerical models. It also aims to demonstrate the effect of hybridization on the global stiffness of the material. In this study, Voigt-Reuss models, Halpin-Tsai equations, the Hirsch model, and numerical simulation are applied to predict the effective elastic moduli of hybrid composites/composites with clay and other alfa fillers. The results obtained are compared with experimental data. Hirsch’s results match well with the experimental results for the alfa/PP composite. However, the values of the Halpin-Tsai model showed a good agreement with the experimental results for the alfa-clay/PP hybrid composite. The numerical results show good accordance with the experimental results with higher accuracy. The overall results provided a good indication of the effects of hybridization on the stiffness of the final hybrid composites.
The Application of Vibrational Spectroscopy to the Research and Development of Polymeric Materials: III. Instrumentation and Experimental Techniques in Raman Spectroscopy
Authors: Ellis G. , Marco C. , Fatou J.M. Gómez
Published: April 2023

Raman spectroscopy has developed significantly over the last twenty-five years, and its applications in the polymer field are growing on a daily basis, due to the considerable advances in Raman instrumentation, like for example the FT-Raman technique. This article is intended to provide a perspective on the use of conventional Raman spectroscopy, and present some of the more important developments.
Mesostructures and the Tensile Strength and Fatigue Endurance of Aligned Fibre Composites
Authors: Piggott M.R. , Loken D.
Published: April 2023

Mesostructures are structures which are middle rank in size, and usually unintentional. They provide a direct link between production processing and final properties of a composite. In this study an orientation mesostructure, i.e. fibre waviness, was artificially introduced into aligned carbon fibre composites using optical fibres (80–250 μm in diameter) oriented at right angles to the carbon. Although this caused severe curvature of the fibres, it was over very short lengths (a few microns) and appeared not to be the cause of the reduction in tensile strength of these composites. Instead it was concluded that the fibre crowding effect in the cross section of the optical fibre caused fibre contacts, and hence fibre damage, which weakened the composite. The tensile strengths of the composites without the optical fibres were higher than values quoted by the manufacturers, but were still less than theoretical values, probably due to stress concentrations in the end tabs. Better tensile testing methods therefore appear to be needed before embarking on a more detailed examination of the effect of mesostructures on tensile strength of unidirectional composites. Fibre waviness has also been suggested as a possible initiator of damage during the fatigue of aligned fibre composites. In this work, the presence of the optical fibres induced “ply cutting”. This could have resulted from the fibres in the regions of high fibre volume fraction rubbing against each other. The largest optical fibre caused, in addition, massive splitting of the specimen, in agreement with a mechanism previously proposed for the early stages of fatigue failure of these composites.
A Review of 129Xe NMR as a Probe of Polymer Morphology
Authors: Walton Jeffrey H.
Published: April 2023

129 Xe NMR is a new tool for probing the morphology of polymers and polymer blends. Recent developments of the NMR of 129 Xe gas dissolved in polymers are reviewed. This technique yields information on polymer morphology via the NMR lineshape and the isotropic chemical shift and their temperature dependencies. Polymer glass transition temperatures are plainly evident. The miscibility of polymer blends is easily determined and thus phase diagrams may be mapped out. Of particular use is the potential ability to measure domain sizes in immiscible polymer blends by 2-D NMR techniques. Domain sizes from 0.1 micrometers to 25 micrometers should easily be measurable.
Carbon Fibres from Partially Oriented Polyethylene Precursors
Authors: Zhang Dong
Published: April 2023

Earlier work has shown that carbon fibres can be produced from highly oriented polyethylene precursors (1). Polyethylene fibres are attractive as carbon fiber precursors due to their high carbon content and ease of manufacture. In this research, an effort is made to produce carbon fiber from a partially oriented polyethylene fiber. Stabilisation of the fibres was carried out using sulphonation by crosslinking. Being a diffusion controlled process, stabilisation of partially oriented polyethylene precursors can be achieved in less time than that of highly oriented polyethylene fibres. The progress of reactions and the extent of stabilisation was studied by thermal analyses (Differential Scanning Calorimetry and Thermogravimetric Analysis) and other techniques. The structure and properties of the carbon fibres produced from partially oriented polyethylene precursors were investigated.
Interferometric Studies on Polymer Fibres II. Application of Multiple-Beam Fizeau Method for the Characterisation of Multilayer Fibres
Authors: Hamza A.A. , Fouda I.M. , Sokkar T.Z.N. , Shahin M.M. , Seisa E.A.
Published: April 2023

A modified method using multiple-beam Fizeau fringes is used to measure refractive indices of immersion liquids. In this case, there is no need for making corrections for the temperature and dispersion of these liquids. This method is applied to determine the refractive index profile of a cylindrical multilayer fibre. A mathematical formula is derived in the case of the shape of multiple-beam Fizeau fringes crossing a cylindrical multilayer fibre, as well as equations to determine the refractive index profile for fibre having irregular cross section. Similar mathematical formulas are derived for the case of fibre having skin-core structure. This method with the derived equations is applied to determine the optical properties of “Terylene” and polypropylene fibres. Microinterferograms are given for illustrations.
Agricultural Wastes as a Base for Synthesis of Vinyl Polymer-Cellulose Composites
Authors: Hebeish A. , El-Sisi F. , El-Halwagy A. , El-Kashouti M. , Omar H.
Published: April 2023

Cellulose pulps prepared from bagasse, rice straw, cotton stalk and wood sawdust were polymerized in the presence of acrylic acid(AA) and acrylonitrile(AN) with binary mixtures. Potassium persulphate was used as the initiating system. The treatment was carried out under different conditions including concentration of AA and AN, composition of AA/AN binary mixture, potassium persulphate concentration, material to liquor ratio, time and temperature of polymerization. Based on the results obtained, appropriate conditions for the preparation of vinyl polymer-cellulose composites were established. The maximum total conversion occurred at 0.5% K2S2O8 along with 5% AA and 5% AN at 70°C for 60 minutes using a material-to-liquor ratio of 1:20. The treated samples were monitored for polymer yield, carboxyl and nitrogen contents as well as swellability and solubility. Results indicated that the total conversion (grafting and homopolymerization) increased by increasing K2S2O8 concentration irrespective of the land of cellulose pulp used. Nevertheless the percent polymer yield and percent graft yield follow the order: > Bagasse > rice straw > cotton stalk ≥ wood sawdust. The nitrogen content is higher the higher the concentration of AN in the AA/AN binary mixtures regardless of the kind of agricultural waste. Carboxyl content is higher, the higher the concentration of AA in the AA/AN binary mixture. The swellability of the composite is governed by the composition of the AA/AN binary mixture and it is higher, the higher the concentration of AN in the AA/AN binary mixture irrespective of the kind of cellulose source, but with the certainty that swellability of the composites follows the order: Bagasse > rice straw > cotton stalk > wood sawdust. The solubility of the composite is also governed by the composition of AA/AN binary mixture and it is higher the higher the concentration of the AA in the mixture and follow the order: Rice straw ≥ wood sawdust > cotton stalk ≥ bagasse
Viscoelastic and Mechanical Properties of Epoxy/Mixed Amine Systems. Influence of Stoichiometry and Cure Conditions
Authors: Garmendia J. , Alcorta C. , Llano-Ponte R. , Mondragon I. , Rubio A.
Published: April 2023

Epoxy networks based on the diglycidyl ether of bisphenol A (DGEBA) and a mixture of an aliphatic triamine and a difunctional cycloaliphatic diamine were studied. The glass transition temperatures of mixtures with different stoichiometric ratios were analysed by differential scanning calorimetry and dynamic mechanical techniques. The influence of the cure schedule was also studied for all mixtures, post-cured and not fully cured. Differences in crosslink densities were studied in the glass transition region. By using the average molecular weight between crosslinks, calculated using the rubber elasticity theory, the correlation between the glass transition temperature of cured systems and that corresponding to the unreacted system was determined. The variation of the glass transition temperatures was interpreted in terms of the macromolecular chain motions. Flexural properties such as modulus, strength, and strain to break were measured for the post-cured mixtures with different stoichiometrics.
Epoxy Resin - Cyclic Carbonate Oligomer Compositions Cured with BF3·Et2O
Authors: Rokicki Gabriel , Nguyen Thinh X.
Published: April 2023

The properties of bisphenol A epoxy resins containing bidentate cyclic carbonate oligomers cured with BF3 complexes by cationic polymerisation are presented. The effect of cyclic carbonate content on the gel time, peak exotherm temperature and degree of crosslinking of the epoxide-cyclic carbonate compositions were investigated. It was found that for the range of 0–30 wt. % the amount of energy released during crosslinking rises with increasing cyclic carbonate concentration. The reaction mechanism, and the reason for the higher enthalpy of polymerisation of epoxide-cyclic carbonate compositions in comparison with the epoxy resin, are discussed. The cured compositions exhibited good mechanical properties, especially the impact resistance and the tensile strength.
Lapinus Fibre Reinforced Phenolic Composites: Flexural and Friction Properties
Authors: Dong Feng , Blum Frank D. , Dharani L.R.
Published: April 2023

The flexural and frictional properties of Lapinus fibre-reinforced phenolic friction materials at different fibre loadings have been studied via three point bend tests and SAE J661a friction tests, respectively. A positive correlation was observed between flexural moduli and fibre volume fraction for these materials. The empirical constant in the Halpin-Tsai model is about 0.22 for this material compared with 0.375 for some other fibre reinforced structural composites with randomly distributed fibres in a plane. The coefficient of friction of the composites fell in the range of 0.1 to 0.5 and the minimum friction was found in materials with volume fraction of 0.024 to 0.05 fibre loading. These two fibre loadings also showed a more stable coefficient of friction than the other fibre loadings did over the wide range of temperatures in the second fade test. A minimum volumetric wear was found in the material with 0.05 fibre loading during the wear test. The wear mechanisms at different fibre loadings have also been discussed.
Control of Polymer Layer Thickness in Coating of Monodispersed Colloidal Silica
Authors: Yoshinaga K. , Iwasaki M. , Teramoto M. , Karakawa H.
Published: April 2023

Two methods for the polymer coating of monodispersed colloidal silica and for the control of layer thickness by radical polymerization were examined. Consecutive radical polymerization of styrene on the prepolymer-coated silica by periodic addition of 2,2′-azobis(isobutyronitrile) in ethanolic solution induced the aggregation of the composite particles. The radical polymerization in the surface hydrophobic layer, formed by the reaction of surface silanol with a silane coupling agent on the colloidal silica, gave monodispersed composite particles having surface polymer layers, the thickness of which was dependent on the molecular size and polarity of the silane modifier. It is suggested that the polymer coating layer is controllable in the range of about two times to five times the modifier size.
Effect of Matrix Toughening on the Mechanical Properties of Glass Fibre Reinforced Composite
Authors: Kang Tae Jin , Hwang Seong Deok
Published: April 2023

Changes in morphology and mechanical properties of glass fibre reinforced composites fabricated using a polyvinylbutyral (PVB) modified phenolic resol resin were studied. The PVB modified phenolic resin systems possessed discrete spheres of PVB evenly dispersed in a phenolic resin matrix at low thermoplastic content. However, at higher concentrations, phase inversion resulted, and the morphology consisted of discrete spheres of phenolic resin embedded in a PVB matrix. The mechanical properties of neat resin films showed maximum values with PVB content of 66.7 phr. But the tensile and flexural properties of the glass fibre composite showed the highest values with PVB 25-42.9 phr, lower PVB levels than those of neat resin films. The tensile and flexural moduli were significantly improved and showed maxima at about 25-42.9 phr, unlike the neat resin films which showed a continuous decrease. The reason is that the interfacial bond between fibre and matrix plays an important role and has been altered by the addition of the PVB to the glass fibre reinforced composite. The composite with increased PVB content showed increased toughness and a smaller damaged area after a drop-weight impact test.
Miscibility of Tertiary Amide Polymers with Poly(styrene-co-acrylonitrile)
Authors: Yeo Y.T. , Goh S.H. , Lee S.Y.
Published: April 2023

The miscibility of poly(N-vinyl-2-pyrrolidone) (PVP), poly(N-methyl-N-vinylacetamide) (PMVAc) and poly(N,N-dimethylacrylamide) (PDMA) with poly(styrene-co-acrylonitrile) (SAN) was studied. The three tertiary amide polymers are miscible with SAN, having a sufficiently high acrylonitrile (AN) content. The critical AN contents are 62, 65 and 68 wt% for PVP, PMVAc and PDMA, respectively. The miscibility behaviour is discussed in terms of a binary interaction model.
Radiation Vulcanisation of Short-Carbon Fibre-Reinforced Styrene-Butadiene Rubber Composites
Authors: Abdel-Aziz M.M. , Youssef H.A. , Miligy A.A. El , Yoshii F. , Makuuchi K.
Published: April 2023

The effects of short-carbon fibres on the anisotropy swelling, mechanical and electrical properties of radiation vulcanized styrene-butadiene rubber (SBR) composites have been studied. The effect of radiation on the crosslinking density as well as the fracture mode of the composites have also been studied. It has been found that carbon fibre improves the reinforcement of SBR due to good adhesion between the fibre and the rubber matrix. However, increasing fibre loading leads to decrease the strength in spite of increasing the crosslinking density. Moreover, tensile fracture surfaces of the composites have been studied using scanning electron microscopy (SEM) in order to assess the failure criteria. SEM studies indicate that the fracture mode depends mainly on the adhesion between the fibre and the matrix.
A Review of Microporous Composite Polymeric Membrane Technology for Air-Separation
Authors: Chung Tai-Shung
Published: April 2023

A detailed review of the fabrication technology of microporous composite polymeric membranes has been conducted. We believe that this type of membrane has greater potential than the traditional asymmetric-composite membranes to be used for the development of the third generation of gas-separation membranes. However, there are four major challenges when preparing a high-performance microporous composite membrane: namely, eliminating pore intrusion, reducing coating thickness, improving interfacial adhesion and enhancing separation performance. In this article, we review and identify those approaches that have overcome or can potentially overcome these difficulties.
Lignocellulosic Materials in Building Elements. Part II. Cement Light-Weight Building Bricks
Authors: Basta Altaf H. , Fadl Nairn A. , Gabra Usama I.
Published: April 2023

Wood processing and agricultural wastes (spruce wood, bagasse and cotton stalk) were used for the production of cemented lignocellulosic bricks. Pretreatment with 50% linseed oil, followed by hardening at 120°C was carried out to improve water repellency.

Several variables were investigated during the formation of the bricks, such as the mesh size of the lignocellulosic waste, the cement to wood ratio and the use of some additives, e.g. urea formaldehyde, aluminium oxide powder, emulsion acrylic (Nitobond AR), hemihydrate gypsum and polyvinyl alcohol. The results obtained indicate that bricks prepared by adding Nitobond AR to cement-wood mixtures have higher strength than those obtained using other additives. Also, bricks produced by blending treated wood waste with cement have better properties than those produced from blends of treated agricultural wastes (bagasse and barked cotton stalk) with cement. The field of application of the product was considered. A plant for the production of cemented lignocellulosic bricks was also designed.
The Development and Appraisal of 3D Fully Integrated Woven Structures for Textile Reinforced Composites
Authors: Hill B.J. , McIlhagger R.
Published: April 2023

A method of estimating the proportions of fibre in three mutually perpendicular directions in 3D fully integrated woven structures is described. This is based on simple geometrical relationships. This method is validated using woven structures in glass yarns. The areal density, thickness and fibre proportions are predicted within acceptable limits (viz. + 29% to -13%) which in turn assists with the prediction of composite performance.
Synthesis of Polyarylates with Allylic Side Groups. Part 3. Polyarylates Based on 1,3-bis(3-allyl-4-hydroxybenzylidene) Acetone
Authors: Zadrozna I. , Brzozowski Z.K. , Noniewicz K. , Dyrda M.
Published: April 2023

Several UV-sensitive polyarylates based on 1,3-bis(3-allyl-4-hydroxybenzylidene)acetone were obtained by interfacial poly-condensation foruse as potential photo-sensitive polymers. The structures of the UV-sensitive monomers and polymers obtained were confirmed using 1R, 1HNMR and UV spectroscopies. Their physical, chemical and mechanical properties were determined.

The investigations show that some of the new polymers possessing allylic groups as photosensitive side chains conjugated with bisbenzylideneketone groups exhibit different behaviour under UV light exposure from polyarylates based only on bisbenzylideneketone bisphenols presented in our previous work.