bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of scabies prevalence using simplified criteria and mapping procedures in three Pacific and southeast Asian countries
Authors: Tsoi Shu Ki , Lake Susanna J. , Thean Li Jun , Matthews Alexander , Sokana Oliver , Kama Mike , Amaral Salvador , Romani Lucia , Whitfeld Margot , Francis Joshua R. , Vaz Nery Susana , Marks Michael , Kaldor John M. , Steer Andrew C. , Engelman Daniel
Published: November 2021

Background

Scabies causes considerable morbidity in disadvantaged populations. The International Alliance for the Control of Scabies (IACS) published consensus criteria in 2020 to standardize scabies diagnosis. However, these criteria are complex, and a WHO informal consultation proposed simplified criteria for mapping, to identify regions of high prevalence as targets for mass drug administration. We aimed to investigate the accuracy of simplified criteria in determining scabies prevalence, compared to the 2020 IACS criteria.

Methods

We obtained data relating to demographics, relevant history and skin lesions from all-age prevalence surveys from Fiji (n = 3365) and Solomon Islands (n = 5239), as well as school-aged children in Timor-Leste (n = 1043). We calculated prevalence using the 2020 IACS criteria and simplified criteria and compared these disease estimates.

Results

There was no significant difference in the pooled prevalence using the two methods (2020 IACS criteria: 16.6%; simplified criteria: 15.6%; difference = 0.9, [95% CI -0.1, 2.0]). In Timor-Leste, the prevalence using simplified criteria was lower (26.5% vs 33.8%). Simplified criteria had a sensitivity of 82.3% (95% CI 80.2, 84.2) and specificity of 97.6% (95% CI 97.2, 97.9) compared to the 2020 IACS criteria.

Conclusions

The scabies prevalence estimation using simplified criteria was similar to using the 2020 IACS criteria in high prevalence, tropical countries. The prevalence estimation was lower in the school-based survey in Timor-Leste. Mapping using simplified criteria may be a feasible and effective public health tool to identify priority regions for scabies control. Further work assessing use of simplified criteria for mapping in a field setting should be conducted.
Comparative study of the functional outcomes of combined medial-lateral approach arthrolysis with or without external fixation for severe elbow stiffness
Authors: Xiao Dan , Gong Maoqi , Chen Chen , Zha Yejun , Li Ting , Ji Shangwei , Hua Kehan , Sun Weitong , Jiang Xieyuan
Published: November 2021

Background

To evaluate and compare the functional outcomes of combined medial-lateral approach open arthrolysis with and without hinged external fixation.

Methods

We retrospectively collected and analyzed the clinical data of patients with severe elbow stiffness who were treated in our institution from January 2018 to January 2019. All of them were treated with combined medial-lateral approach arthrolysis. There were 20 patients who had the hinged external fixation placed and 29 patients without the placement of the external fixation. Their baseline characteristics and functional outcomes were evaluated and compared.

Results

The average follow-up time was 28.4 ± 3.7 months. There were no significant differences in the ROM of the elbow, MEPS, VAS, DASH, or complications between the two groups. The operation time and treatment cost of the patients without external fixation were significantly lower than patients with external fixation.

Conclusion

Combined medial-lateral approach open elbow arthrolysis without external fixation is a safe and effective way to treat elbow stiffness.

Level of evidence

Therapeutic Level III; Retrospective Cohort Comparison; Treatment Study.
Periodontal results of different therapeutic approaches (open vs. closed technique) and timing evaluation (< 2 year vs. > 2 year) of palatal impacted canines: a systematic review
Authors: Guarnieri Rosanna , Bertoldo Serena , Cassetta Michele , Altieri Federica , Grenga Camilla , Vichi Maurizio , Di Giorgio Roberto , Barbato Ersilia
Published: November 2021

Background

This review evaluates, as a primary outcome, which surgical technique (open vs. closed) and which type of material used for the auxiliaries (elastic vs. metallic) were preferable in terms of periodontal results during the treatment of palatal-impacted canines. The timing of the evaluation of the results was also assessed as a secondary outcome.

Methods

An electronic search of the literature up to March 2021 was performed on Pubmed, MEDLINE (via Pubmed), EMBASE (via Ovid), Cochrane Reviews and Cochrane Register of Controlled Trials (RCTs) (CENTRAL). The risk of bias evaluation was performed using version 2 of the Cochrane risk of bias tool (RoB 2) for RCTs and the ACROBAT NRSI tool of Cochrane for non-RCTs.

Results

11 articles met the inclusion criteria. Only one RCT was assessed as having a low risk of bias and all the non-RCTs were assessed as having a serious risk of bias. This review revealed better periodontal results for the closed technique and metallic auxiliaries. In addition, it revealed that the timing of the evaluation of the results affects the periodontal results with better results obtained 2 years after the end of treatment.

Conclusion

In the treatment of a palatal-impacted canine, the closed technique and metallic auxiliaries should be preferred in terms of better periodontal results. The timing of the evaluation of the results affects the periodontal results.
The ethanol extract of Garcinia subelliptica Merr. induces autophagy
Authors: Kim Kyun Ha , Lee Ji Yeon , Li Wan Yi , Lee Sangwoo , Jeong Han-Sol , Choi Jun-Yong , Joo Myungsoo
Published: November 2021

Background

Garcinia subelliptica Merr. is a multipurpose coastal tree, the potential medicinal effects of which have been studied, including cancer suppression. Here, we present evidence that the ethanol extract of G. subelliptica Merr. (eGSM) induces autophagy in human lung adenocarcinoma cells.

Methods

Two different human lung adenocarcinoma cell lines, A549 and SNU2292, were treated with varying amounts of eGSM. Cytotoxicity elicited by eGSM was assessed by MTT assay and PARP degradation. Autophagy in A549 and SNU2292 was determined by western blotting for AMPK, mTOR, ULK1, and LC3. Genetic deletion of AMPKα in HEK293 cells was carried out by CRISPR.

Results

eGSM elicited cytotoxicity, but not apoptosis, in A549 and SNU2292 cells. eGSM increased LC3-II production in both A549 and, more extensively, SNU2292, suggesting that eGSM induces autophagy. In A549, eGSM activated AMPK, an essential autophagy activator, but not suppressed mTOR, an autophagy blocker, suggesting that eGSM induces autophagy by primarily activating the AMPK pathway in A549. By contrast, eGSM suppressed mTOR activity without activating AMPK in SNU2292, suggesting that eGSM induces autophagy by mainly suppressing mTOR in SNU2292. In HEK293 cells lacking AMPKα expression, eGSM increased LC3-II production, confirming that the autophagy induced by eGSM can occur without the AMPK pathway.

Conclusion

Our findings suggest that eGSM induces autophagy by activating AMPK or suppressing mTOR pathways, depending on cell types.
From chaos to control – experiences of healthcare workers during the early phase of the COVID-19 pandemic: a focus group study
Authors: Rücker Fredrik , Hårdstedt Maria , Rücker Sekai Chenai Mathabire , Aspelin Emma , Smirnoff Alexander , Lindblom Anders , Gustavsson Catharina
Published: November 2021

Background

The Coronavirus disease 2019 (COVID-19) pandemic has caused overwhelming challenges to healthcare systems worldwide. Healthcare workers (HCWs) have faced particular challenges: being exposed to the coronavirus SARS-CoV-2 and caring for patients having a new and potentially life-threatening disease. The aim of this study was to explore how HCWs in the Swedish healthcare system perceived their work situation during the first phase of the COVID-19 pandemic in 2020.

Methods

Focus group discussions and interviews with HCWs were performed from June to October 2020 in one Swedish healthcare region. A purposeful sampling approach was used to select a variety of professions (physicians, nurses, nurse aides and cleaners) and workplaces (hospital inpatient wards, emergency department, nursing home and home care service). Qualitative content analysis was used for data analysis.

Results

In total, 51 HCWs participated in eight focus group discussions and one HCW participated in an individual interview. The content analysis identified two main categories: ‘Concerns about the risk of infection and transmission of infection to others’, and ‘Transition from chaos to managing in a new and challenging work situation’. The findings revealed how HCWs perceived working conditions, including experiences of fear for personal health, confusion and uncertainty regarding personal protective equipment and infection prevention and control (PPE/IPC), and fear of infecting others. Both fearful and appreciating attitudes were achieved from the surrounding community. Helpful strategies for transition from chaos to control were lifted i.e. present and supportive leadership, and finding comfort and strength in the working team. Both helplessness and meaningfulness were described when caring for COVID-19 patients.

Conclusions

This study provides unique insights into HCWs experiences of an extremely challenging work situation during the first phase of the COVID-19 pandemic, including feelings of stress and insecurity in a chaotic and hazardous working environment. But there is also mitigation of these challenges and even positive experiences including feelings of safety and meaningfulness. To enhance safety among HCWs in healthcare crises such as the COVID-19 pandemic, the findings highlight the importance of avoiding confusion about PPE/IPC, having a supportive healthcare leadership and ensuring accurate information provision about virus transmission to the public.
Assessment of genetic diversity of Plasmodium falciparum circumsporozoite protein in Sudan: the RTS,S leading malaria vaccine candidate
Authors: Mohamed Nouh Saad , AbdElbagi Hanadi , Elsadig Ahad R. , Ahmed Abdalla Elssir , Mohammed Yassir Osman , Elssir Lubna Taj , Elnour Mohammed-Ahmed B. , Ali Yousif , Ali Mohamed S. , Altahir Omnia , Abubakr Mustafa , Siddig Emmanuel Edwar , Ahmed Ayman , Omer Rihab Ali
Published: November 2021

Background

The currently used malaria vaccine, RTS,S, is designed based on thePlasmodium falciparumcircumsporozoite protein (PfCSP). Thepfcspgene, besides having different polymorphic patterns, can vary betweenP. falciparumisolates due to geographical origin and host immune response. Such aspects are essential when considering the deployment of the RTS,S vaccine in a certain region. Therefore, this study assessed the genetic diversity ofP. falciparumin Sudan based on thepfcspgene by investigating the diversity at the N-terminal, central repeat, and the C-terminal regions.

Methods

A cross-sectional molecular study was conducted;P. falciparumisolates were collected from different health centres in Khartoum State between January and December 2019. During the study period, a total of 261 febrile patients were recruited. Malaria diagnosis was made by expert microscopists using Giemsa-stained thick and thin blood films. DNA samples were examined by the semi-nested polymerase chain reaction (PCR). Single clonal infection of the confirmedP. falciparumcases, were used to amplify thepfcspgene. The amplified amplicons ofpfcsphave been sequenced using the Sanger dideoxy method. The obtained sequences ofpfcspnucleotide diversity parameters including the numbers of haplotypes (Hap), haplotypes diversity (Hapd), the average number of nucleotide differences between two sequences (p), and the numbers of segregating sites (S) were obtained. The haplotype networks were constructed using the online tcsBU software. Natural selection theory was also tested onpfcspusing Fuand Li’s D, Fuand Li’s F statistics, and Tajima’s D test using DnaSP.

Results

In comparison with the differentpfcspreference strains, the Sudanese isolates showed high similarity with other African isolates. The results of the N-terminal region showed the presence of 2 different haplotypes with a Hapd of 0.425 ± 0.00727. The presence of the unique insertion of NNNGDNGREGKDEDKRDGNN was reported. The KLKQP motif was conserved in all the studied isolates. At the central repeat region, 11 haplotypes were seen with a Hapd of 0.779 ± 0.00097. The analysis of the genetic diversity in the C-terminal region showed the presence of 10 haplotypes with a Hapd of 0.457 ± 0.073. Several non-synonymous amino acids changes were also seen at the Th2R and the Th3R T-cell epitope regions including T317K, E317K, Q318E, K321N, I322K, T322K, R322K, K324Q, I327L, G352N, S354P, R355K, N356D, Q357E, and E361A.

Conclusions

In this study, the results indicated a high conservation at thepfcspgene. This may further contribute in understanding the genetic polymorphisms ofP. falciparumprior to the deployment of the RTS,S vaccine in Sudan.
Hiding in the dark: pan-cancer characterization of expression and clinical relevance of CD40 to immune checkpoint blockade therapy
Authors: Yan Chi , Richmond Ann
Published: November 2021

Highlights

CD40 expression correlates with the type I anti-tumor response and better survival.

Pan-cancer bioinformatics characterization reveals reduced CD40 expression in 11 cancer types, including RASmut melanoma compared to nevi.

RAS mutation correlates with reduced CD40 expression in malignant melanoma.

CD40 expression is associated with better response to immune checkpoint blockade therapy in melanoma.
Assessment of a website aimed at providing information on mental health to secondary school students in Can Tho city, Vietnam
Authors: Nguyen Dat Tan , Pham Tam Thi , Wright E. Pamela , Bunders Joske
Published: November 2021

Background

The stigmatization of mental health problems is a primary barrier for young people to approach mental health services when they suspect they might have such problems. Nevertheless, the internet has become a common platform on which they are likely to seek information on mental health. As such, this study aimed to explore responses from secondary school students in Can Tho city regardingsuckhoetre.vnwebsite. This website provided information on health and mental health, and this study assessed the potential relevance, appeal, accessibility, usefulness, and sustainability of the website.

Methods

A cross-sectional study included 643 secondary school students in Can Tho city selected by cluster sampling. Two weeks after the students were introduced to the website, they were invited to evaluate it using an anonymous questionnaire. The Chi-squared test was used to assess the significance of differences in the distribution of selected students’ sociodemographic characteristics.

Results

Most (98.6%) participants visited the website in the two-week period, 74% once or twice a week, the others more often, up to once a day. Their activities included reading information (85.8%), seeking help (17.7%), sharing information (15.5%), giving advice to others (11.0%), and chatting or giving comments (9.8%). Most students rated the website very highly in terms of appeal, relevance, accessibility, and usefulness, and wanted to have access to the website in the future. These findings are positive signals to pursue the possible use of a website on mental health for secondary school students to help raise awareness and support good mental health among adolescents in Can Tho city and beyond.

Conclusion

A website designed to provide information to secondary school students appeared to be a promising way to provide access to information on the topic of mental health. The website should be maintained and introduced widely to students, teachers and parents, with regular evaluation of the effectiveness of this website.
Community acquired Acinetobacter baumannii in pediatric patients under 1 year old with a clinical diagnosis of whooping cough in Lima, Peru
Authors: Peña-Tuesta Isaac , del Valle-Vargas Cristina , Petrozzi-Helasvuo Veronica , Aguilar-Luis Miguel Angel , Carrillo-Ng Hugo , Silva-Caso Wilmer , del Valle-Mendoza Juana
Published: November 2021

Objective

This study aimed to determine the prevalence of A. baumannii in children aged less than 1 year admitted with a clinical diagnosis of whooping cough.

Results

A total of 225 nasopharyngeal samples from children under 1 year old hospitalized with clinical diagnosis of whooping cough were studied from January 2010 to July 2012. The presence of A. baumannii was detected in 20.89% (47/225) of the nasopharyngeal swab samples. Among the 47 patients with A. baumannii: 5 were diagnosed with A. baumannii monoinfection, 17 co-infection with bacteria, 7 co-infection with virus and 18 co-infection with bacteria + virus. It was observed that 51.6% (116/225) were children between 29 days and 3 months old, this same group had the highest overall prevalence with 53.3%. The most common co-infecting pathogens were Bordetella pertussis in 55.3%, Adenovirus in 42.6% and Mycoplasma pneumoniae in 23.4%.
Comparison of the pre-treatment functional MRI metrics’ efficacy in predicting Locoregionally advanced nasopharyngeal carcinoma response to induction chemotherapy
Authors: Zhao Da-wei , Fan Wen-jun , Meng Ling-ling , Luo Yan-rong , Wei Jian , Liu Kun , Liu Gang , Li Jin-feng , Zang Xiao , Li Meng , Zhang Xin-xin , Ma Lin
Published: November 2021

Background

Functional MRI (fMRI) parameters analysis has been proven to be a promising tool of predicting therapeutic response to induction chemotherapy (IC) in nasopharyngeal carcinoma (NPC). The study was designed to identify and compare the value of fMRI parameters in predicting early response to IC in patients with NPC.

Methods

This prospective study enrolled fifty-six consecutively NPC patients treated with IC from January 2021 to May 2021. Conventional diffusion weighted imaging (DWI), diffusion kurtosis imaging (DKI), intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) protocols were performed before and after IC. Parameters maps (ADC, MD, MK, Dslow, Dfast, PF, Ktrans, Ve and Kep) of the primary tumor were calculated by the Functool post-processing software. The participants were classified as responding group (RG) and non-responding group (NRG) according to Response Evaluation Criteria in Solid Tumors 1.1. The fMRI parameters were compared before and after IC and between RG with NRG. Logistic regression analysis and ROC were performed to further identify and compare the efficacy of the parameters.

Results

After IC, the mean values of ADC(p < 0.001), MD(p < 0.001), Dslow(p = 0.001), PF(p = 0.030) and Ve(p = 0.003) significantly increased, while MK(p < 0.001), Dfast(p = 0.009) and Kep(p = 0.003) values decreased dramatically, while no significant difference was detected in Ktrans(p = 0.130). Compared with NRG, ADC-pre(p < 0.001), MD-pre(p < 0.001) and Dslow-pre(p = 0.002) values in RG were lower, while MK-pre(p = 0.017) values were higher. The areas under the ROC curves for the ADC-pre, MD-pre, MK-pre, Dslow-pre and PRE were 0.885, 0.855, 0.809, 0.742 and 0.912, with the optimal cutoff value of 1210 × 10− 6 mm2/s, 1010 × 10− 6 mm2/s, 832 × 10− 6, 835 × 10− 6 mm2/s and 0.799 respectively.

Conclusions

The pretreatment conventional DWI (ADC), DKI (MD and MK), and IVIM (Dslow) values derived from fMRI showed a promising potential in predicting the response of the primary tumor to IC in NPC patients.

Trial registration

This study was approved by ethics board of the Chinese PLA General Hospital, and registered on January 30, 2021, in Chinese Clinical Trial Registry (ChiCTR2100042863).
Uncertainty quantification in stochastic inversion with dimensionality reduction using variational autoencoder
Authors: Liu Mingliang , Grana Dario , de Figueiredo Leandro Passos
Published: November 2021

Estimating rock and fluid properties in the subsurface from geophysical measurements is a computationally and memory-intensive inverse problem. For nonlinear problems with non-Gaussian variables, analytical solutions are generally not available, and the solutions of those inverse problems must be approximated using sampling and optimization methods. To reduce the computational cost, model and data can be reparameterized into low-dimensional spaces where the solution of the inverse problem can be computed more efficiently. Among the potential dimensionality reduction methods, deep-learning algorithms based on deep generative models provide an efficient approach to reduce the dimension of the model and data vectors. However, such dimension reduction might lead to information loss in the reconstructed model and data, reduction of the accuracy and resolution of the inverted models, and under- or overestimation of the uncertainty of the predicted models. To comprehensively investigate the impact of model and data dimension reduction with deep generative models on uncertainty quantification, we compare the prediction uncertainty in nonlinear inverse problem solutions obtained from Markov chain Monte Carlo and ensemble-based data assimilation methods implemented in lower dimensional data and model spaces using a deep variational autoencoder. Our workflow is applied to two geophysical inverse problems for the prediction of reservoir properties: prestack seismic inversion and seismic history matching. The inversion results consist of the most likely model and a set of realizations of the variables of interest. The application of dimensionality reduction methods makes the stochastic inversion more efficient.
Quantification of Discordant Variant Interpretations in a Large Family-Based Study of Li-Fraumeni Syndrome
Authors: Frone Megan N. , Stewart Douglas R. , Savage Sharon A. , Khincha Payal P.
Published: November 2021

PURPOSE

The use of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines has improved germline variant classification concordance, but discrepancies persist, sometimes directly affecting medical management. We evaluated variant discordance between and within families with germline TP53 variants in the National Cancer Institute's Li-Fraumeni syndrome longitudinal cohort study.

MATERIALS AND METHODS

Germline TP53 genetic testing results were obtained from 421 individuals in 140 families. A discordant test result was defined as a report of pathogenicity that differed between two clinical testing laboratories, between a testing laboratory and the ClinVar database, or between either the laboratory or ClinVar database and variant classification by internal study review.

RESULTS

There were 141 variants in 140 families (one family had two different TP53 variants). Fifty-four families had discordant interpretations (54 of 140, 39%). Sixteen families had discordant classifications leading to clinically important differences in medical management (16 of 140, 11%). Interfamilial discordance was observed between four families (two different variants). Intrafamilial discordance was observed within six families. One family experienced both intrafamilial and interfamilial discordance.

CONCLUSION

This large single-gene study found discordant germline TP53 variant interpretations in 39% of families studied; 11% had a variant with the potential to significantly affect medical management. This finding is especially concerning in patients with Li-Fraumeni syndrome because of their exceedingly high risks of multiple cancers and intensive cancer screening and risk-reducing recommendations. Centralized data sharing, gene-specific variant curation guidelines, and provider education for consistent variant interpretation are essential for optimal patient care.
Ecology without Civilization
Authors: Dudley Jack
Published: November 2021

While Jeff VanderMeer’s Southern Reach Trilogy has been read through the uncanny human traumas and tropes of “contamination” in its first novel, Annihilation, the trilogy’s radical ecological thought emerges more clearly through cosmic and transformative trauma in the final novel, Acceptance. Rather than some contaminated space, Area X is restoring Earth’s ecosystems to a “pristine” state, but in a process of guided succession that traumatizes human life as lived under ecologically destructive neoliberal economies of extraction. Reading the twinned falls of Saul and Control, this article shows how Acceptance reimagines uncanny trauma for a new form that is painful but also familiar, human but also posthuman, and utterly necessary for planetary survival.
A conserved arginine in NS5 binds genomic 3′ stem–loop RNA for primer-independent initiation of flavivirus RNA replication
Authors: Wang Sai , Chan Kitti Wing Ki , Tan Min Jie Alvin , Flory Charlotte , Luo Dahai , Lescar Julian , Forwood Jade K. , Vasudevan Subhash G.
Published: November 2021

The commitment to replicate the RNA genome of flaviviruses without a primer involves RNA–protein interactions that have been shown to include the recognition of the stem–loop A (SLA) in the 5′ untranslated region (UTR) by the nonstructural protein NS5. We show that DENV2 NS5 arginine 888, located within the carboxy-terminal 18 residues, is completely conserved in all flaviviruses and interacts specifically with the top-loop of 3′SL in the 3′UTR which contains the pentanucleotide 5′-CACAG-3′ previously shown to be critical for flavivirus RNA replication. We present virological and biochemical data showing the importance of this Arg 888 in virus viability and de novo initiation of RNA polymerase activity in vitro. Based on our binding studies, we hypothesize that ternary complex formation of NS5 with 3′SL, followed by dimerization, leads to the formation of the de novo initiation complex that could be regulated by the reversible zipping and unzipping of cis-acting RNA elements.
Polymer tiles from polyethylene terephthalate (PET) wastes and fly ash: mechanical properties and durability
Authors: Omosebi Taiwo O. , Abass Noor Faisal
Published: November 2021

Background: Plastic waste (PW) is becoming increasingly hazardous to the environment as a result of its massive production, causing significant damage to both the ecosystem and its inhabitants. Managing plastic waste is a global concern due to its non-biodegradable nature. However, it is important to handle PWs properly to curtail the environmental emissions associated with their incineration and dumping into landfills. This research investigates the possibility of producing tiles from polyethylene terephthalate (PET) waste bottles and fly ash. The mechanical properties, as well as the chemical resistance of the manufactured PET polymer tiles, are reported in this study.

Methods: PET waste was used in varying proportions (from 30% to 100%) by sand weight. The shredded PET waste was heated at 230 oC before being suitably blended with fly ash. It was then poured into the designated mold, removed after one hour, and cooled for 24 hours before testing.

Results: The assessment of the physical and mechanical properties of the materials revealed that the tiles produced with 30% PET content performed better in terms of material density and strength compared to the samples with higher PET content. The highest compressive strength being 6.88 MPa. Based on the results of the tests, the produced PET tiles have a low water absorption efficiency of 80% lower when compare to cement and ceramic tiles (the water absorption values are between 0.98% and 0.09%).

Conclusions: The results from this study indicate that PET waste bottles can be used to produce long-lasting, durable, and extremely low water absorption eco-friendly tiles for both residential and commercial applications. This prospect of tile production using polyethylene terephthalate (PET) waste and fly ash would not only minimize the cost of building products but will also act as a waste diversion to mitigate environmental emissions caused by plastic waste disposal.
Evaluation of the effect of soft drinks on the surface roughness of dental enamel in natural human teeth
Authors: Al-Amri Ibrahim , Albounni Roula , Binalrimal Sultan
Published: November 2021

Background: Exposing enamel to soft drinks and beverages causes changes in the microscopical morphology. Changes in the physical characteristics, like hardness and surface roughness, were studied with various parameters. Factors such as pH, exposed duration, and other content of the soft drinks have different effects on the enamel.

Methods: Thirty-six human premolar teeth were randomly divided into three groups (n=12). Group 1 consisted of teeth which were immersed in artificial saliva (control), group 2 consisted of teeth which were immersed in Pepsi, and group 3 consisted of teeth which were immersed in Mirinda. After the preparation of samples and necessary measures, surface roughness was measured using the profilometer. Baseline measurements were taken. Reading two and reading three were taken after exposing the specimens for three days and 15 days, respectively. All of the collected data were compared statistically using SPSS and presented in tables and graphs.

Results: At the baseline, the surface roughness value was the same for all three groups. On the 3rd day, the Mirinda group showed more surface roughness compared to that of the test and Pepsi groups, which was statistically significant. On the 15th day, both the Pepsi and Mirinda groups showed increased surface roughness compared to that of the control, which was statistically significant.

Conclusions: Within the limitation of this study, it can be concluded that surface roughness increased when teeth were exposed to both soft drinks
Sustainable Development and Education: Challenges and Risks
Authors: Svistunov Vasiliy , Kovaleva I. , Lobachyev Vitaliy , Golyshkova I.
Published: November 2021

The article focuses on the main problems and risks associated with the global processes of abrupt transfer of learning processes to a distance format by several countries in the world during the COVID-19 pandemic. The features of the transformation of traditional education, considering new requirements, previously based on the principles of sustainable development, are considered. The problems of introducing online formats, distance technologies, digital educational environment, difficulties, and risks in the forced rapid transition to online learning are identified. The emphasis is placed on the need to identify the problems of digital and social inequality of students. Special attention is paid to measures to mitigate the consequences of distance education for socially unprotected categories of students, since they are the ones who faced serious obstacles of various types and found themselves in the zone of greatest risk.
EFFECT OF IMPACTOR MASS ON CFRP IN ARCTIC CONDITION UNDER LOW-VELOCITY IMPACT
Authors: BANIK ARNOB , ZHANG CHAO , TAN K. T.
Published: November 2021

This study investigates the impact response and damage characterization of carbon fiber reinforced polymer (CFRP) under low-velocity impact by impactors of different masses and velocities at 62J. Low-velocity impacts are conducted at room temperature (23ºC) as well as low temperature (-70ºC) conditions in the thermal chamber of the drop tower testing machine, Instron CEAST 9350. The aim is to observe composite behavior in the cold Arctic environment due to equal energy impacts. Moreover, a 3mm thickness of ice is created on the CFRP samples at -12ºC after 24 hours of freezing and impacted at -70ºC. The goal is to elucidate the contribution of surface ice on the overall impact damage of composites. X-ray micro-computed tomography is utilized to reveal the inner damages of the composite structures. Intralaminar damage in the form of fiber breakage is found as the dominant failure mode on the CFRP samples from 62J impacts. But differences in the delamination and matrix crack formation are identified for different mass-velocity configurations and environmental conditions. Results show that low mass impactors produce a larger damage initiation force on the composites at all temperatures, whereas no specific trend is observed in the peak force values due to severe fiber failure. Although higher mass impactors show longer impact duration, lower mass impactors develop greater damage on the CFRP, as seen by a greater reduction in specimen stiffness. Furthermore, the presence of ice is observed to have a minimal effect on the damage behavior of composites. But ice layer assists to reduce the amplitude of initial load drop by the low mass impactor and as such, less permanent displacement is identified in the CFRP specimens than both room temperature and low-temperature conditions. This study explores the understanding of the dynamic behavior of composites under low-temperature icy conditions.
A UNIQUE APPROACH TO EXPERIMENTAL CHARACTERIZATION OF A THERMOSETTING POLYMER MATRIX FOR ICME FRAMEWORKS
Authors: OLAYA MICHAEL N. , PATIL SAGAR , ODEGARD GREGORY M. , MAIARÙ MARIANNA
Published: November 2021

A novel approach for characterization of thermosetting epoxy resins as a function of the degree of cure is presented. Density, cure kinetics, tensile strength, and Young’s modulus are experimentally characterized across four mixing ratios of DGEBF/DETDA epoxy. Dynamic differential scanning calorimetry (DSC) is used to characterize parameters for a Prout-Thompkins kinetic model unique to each mixing ratio case through a data fitting procedure. Tensile strength and Young’s modulus are then characterized using stress-strain data extracted from quasi-static, uniaxial tension tests at room temperature. Strains are measured with the 2-D digital image correlation (DIC) optical strain measurement technique. Strength tends to increase as amine content use in the formulation increases. The converse trend is observed for Young’s modulus. Density measurements also reveal an inverse relationship with amine content.
ROBOTIC SEQUENTIAL ULTRASONIC WELDING OF THERMOPLASTIC COMPOSITES: PROCESS DEVELOPMENT AND TESTING
Authors: CHOUDHARY, ABHAS , FERNANDEZ IRENE
Published: November 2021

Multi-spot sequential ultrasonic welding is a promising joining technique for fibre-reinforced thermoplastic composites structures (TPC). In existing research on the multi-spot sequential ultrasonic welding process, welds are produced through the use of a static table-top welding machine, at a coupon level. However, in order to apply this joining technology to large structures, the welding process needs to be up-scaled through the use of a robotic platform. At the Smart Advanced Manufacturing (SAM|XL) automation field lab and TU Delft Aerospace Engineering, a robotic sequential ultrasonic welding system has been developed. The system consists of a welding end-effector (EEF) equipped with various sensors that enable online process monitoring and control, which can be mounted on an industrial robot arm to perform sequential multi-spot welds. The goal of this study was to assess the welding performance of the ultrasonic welding EEF, which was mounted on an industrial KUKA KR210 R2700 Extra 10-axis robot arm, by comparing it to the performance of welds produced through the static table-top machine. In this study, single and multi-spot welds were produced on thermoplastic composite coupons, based on welding conditions which were defined in a preliminary study. The robot and EEF deflections observed during the welding process were analysed to assess the deviation of the robotic process from the static one. The feedback obtained from the welding equipment in terms of consumed power and tool displacement in both processes was also compared. The weld quality was assessed though single lap shear testing of the welded joints as well as fractography of the failure surface. The results of this study indicate that the developed robotic welding process is quite robust and is capable of producing high-quality sequential welded joints despite significant system deflections observed during the welding process. Slightly lower welded area and weld strength was obtained which can be attributed to the system deflections. Finally, the results indicate that the use of a stiffer robotic platform as well as a stiffer EEF construction will result in better system rigidity and weld spot positioning accuracy, and through this the welding process shows promise for large-scale industrial applications.
REPRESENTATION, CHARACTERIZATION AND SIMULATION OF TOOL-PART INTERACTION AND ITS EFFECTS ON PROCESS-INDUCED DEFORMATIONS IN COMPOSITES
Authors: SCHOENHOLZ CALEB , SLADE DANIEL , ZAPPINO ENRICO , PETROLO MARCO , ZOBEIRY NAVID
Published: November 2021

The interaction between a tool and part during composites processing contributes to the formation of residual stresses and dimensional changes. A resultant mismatch of part geometries during assembly can cause a potential loss of mechanical performance in aerospace structures. Costly shimming steps are needed to compensate for processinduced deformations and satisfy specifications on mechanical performance. Due to difficulties associated with accurate measurement of interfacial shear stresses, current analysis methods fail to represent the interaction between a tool and part throughout processing. A combined approach to represent, characterize, and simulate tool-part interaction and its effects on dimensional changes is proposed. First, a characterization method was established using a custom Dynamic Mechanical Analysis (DMA) shear test setup to measure tool-part interfacial stress development in a simulated autoclave curing environment. Tool-part interfacial stresses were characterized for Toray T800S/3900-2 UD prepreg as a function of temperature, degree of cure, strain rate, and tool surface condition. Then, a previously developed numerical model was modified to include the effects of tool-part interaction in predicting dimensional changes of L-shape parts. For validation, composite parts were fabricated on tools with different surface conditions and successfully compared to simulation results. This paper demonstrates that tool-part interaction significantly impacts the spring-in of angled composite parts. The proposed method is a comprehensive and practical approach to study and simulate the effects of tool-part interaction. The results of this paper can be used to understand the complex interaction between a tool and part throughout processing and potentially mitigate processinduced deformations.
DYNAMIC PERFORMANCE OF ADHESIVELY BONDED SINGLE LAP JOINTS WITH DIFFERENT FIBER ANGLE ORIENTATIONS OF ADHERENDS
Authors: KARAAHMET S. BUSE , KADIOGLU FERHAT
Published: November 2021

This work aims to investigate the dynamic response of the adhesive bonding of Single Lap Joints (SLJs) using a free vibration technique. For this purpose, the joints with fixed-end conditions were subjected to the vibration test, and the results were compared with the numerical ones which were obtained from the Finite Element Method (FEM) via the ANSYS package program. The materials used in this study are an adhesive film, AF163 2K produced by 3M, and adherends, manufactured from a glass reinforced polymer matrix composite, produced by Hexcel. While four different adherends with different fiber orientations were used, the thickness of the adhesive layer in bonded region was kept constant, 0.2 mm. In doing so, the main concentration was given to the adherends as the energy dissipation was believed to come mainly from them. The main objective was to get high damping values without compromising any decrease in the structural performance of the joints. The experimental natural frequency, flexural rigidity and damping values of the joints were obtained as a parameter of the different adherend types. The results were also validated using numerical modal analysis.
MICROMECHANICAL FINITE ELEMENT MODELING OF UNIDIRECTIONAL COMPOSITES IN THREE DIMENSIONS: PREDICTION OF TRANSVERSE TENSILE & COMPRESSIVE, TRANSVERSE SHEAR & IN-PLANE SHEAR PROGRESSIVE DAMAGE BEHAVIOR
Authors: HAQUE BAZLE Z.(GAMA) , NGUYEN TAM , CATUGAS ISABEL , O’BRIEN DANIEL J. , GLLESPIE, JR. JOHN W.
Published: November 2021

Predicting the rate-dependent non-linear progressing damage behavior of unidirectional composites from the rate dependent properties of the constituents will enable computational materials-by-design and provide the fundamental understanding of the energy dissipating damage mechanisms. In this study, micromechanical finite element models of unidirectional glass-epoxy composites have been developed with fiber volume fractions, FVF = 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, & 0.70; respectively with zero thickness fiber-matrix cohesive interfaces between the fibers and the surrounding matrix. Experimentally determined rate dependent non-linear stress-strain behavior of DER353 epoxy resin [1] (Tamrakar 2019) has been used to model the large deformation matrix behavior in conjunction with a rate dependent fiber-matrix interface traction law obtained from S-2 Glass/DER353 micro-droplet experiments & simulations [2] (Tamrakar 2019). Transverse tension, compression, in-plane shear, and transverse shear loads have been applied in predicting the progressive damage behavior of unidirectional S-2 Glass/DER353 epoxy composites.
COMPUTATIONAL MODELING OF EPOXY-BASED HYBRID COMPOSITES REINFORCED WITH CARBON FIBERS AND FUNCTIONALIZED GRAPHENE NANOPLATELETS
Authors: MAHMUD HASHIM AL , RADUE , MATTHEW , PISANI WILLIAM , ODEGARD GREGORY
Published: November 2021

The impact on the mechanical properties of unidirectional carbon fiber (CF)/epoxy composites reinforced with pristine graphene nanoplatelets (GNP), highly concentrated graphene oxide (GO), and Functionalized Graphene Oxide (FGO) are investigated in this study. The localized reinforcing effect of each of the graphene nanoplatelet types on the epoxy matrix is predicted at the nanoscale-level by molecular dynamics. The bulk-level mechanical properties of unidirectional CF/epoxy hybrid composites are predicted using micromechanics techniques considering the reinforcing function, content, and aspect ratios for each of the graphene nanoplatelets. In addition, the effect of nanoplatelets dispersion level is also investigated for the pristine graphene nanoplatelets considering a lower dispersion level with four layers of graphene nanoplatelets (4GNP). The results indicate that the shear and transverse properties are significantly affected by the nanoplatelet type, loading and aspect ratio. The results of this study can be used in the design of hybrid composites to tailor specific laminate properties by adjusting nanoplatelet parameters.
INVESTIGATING STRESS TRANSFER AND FAILURE MECHANISMS IN GRAPHENE OXIDE-CELLULOSE NANOCRYSTALS FILMS
Authors: JAYATILAKA, GEHAN , MOHAMMADI MOHAMMAD MOEIN , TEHRANI MEHRAN
Published: November 2021

Graphene oxide (GO) films have great potential for aerospace, electronics, and renewable energy applications. GO sheets are low-cost and water-soluble and retain some of Graphene’s exceptional properties once reduced. GO or reduced GO (rGO) sheets within a film interact with each other via secondary bonds and cross-linkers. These interfacial interactions include non-covalent bonds such as hydrogen bonding, ionic bonding, and π-π stacking. Stress transfer and failure mechanisms in GO and rGO films, specifically how linkers affect them, are not well understood. The present study investigates the influence of inter-particle interactions and film structures, focusing on hydrogen bonds introduced via cellulose nanocrystals (CNC), on failure and stress-transfer of the GO and rGO films. To this end, GO films with CNC crosslinkers were made, followed by a chemical reduction. The few-micron thick films were characterized using tensile testing. All tested films exhibited a brittle failure and achieved tensile strengths and modulus in the ~40-85 MPa and ~3.5-9 GPa ranges, respectively. To reveal stress transfer mechanisms in each sample, tensile in-situ Raman spectroscopy testing was carried out. By monitoring the changes in bandwidth and position of Raman bands while stretching the film, useful information such as sheet slippage and cross-linker interactions were gathered. The addition of CNC enhanced modulus but degraded strength for both GO and rGO films. Interestingly, the Raman G-peak shift at failure, indicative of stress transfer to individual GO/rGO particles, is commensurate with the films’ strengths. Correlating these results with the structure and composition of different films reveals new understanding of stress transfer between GO/rGO particles, paving the way for the scalable manufacturing of strong and stiff GO-based films.
MULTIFUNCTIONAL CERAMIC COMPOSITE SYSTEM FOR SIMULTANEOUS THERMAL PROTECTION AND ELECTROMAGNETIC INTERFERENCE (EMI) SHIELDING FOR CARBON FIBER REINFORCED POLYMER COMPOSITES (CFRP)
Authors: AJAYI TOSIN D. , JIA YUJUN , XU CHERYL
Published: November 2021

Achieving high electrical conductivity while maintaining good thermal insulation are often contradictory in the material design for the goal of simultaneous thermal protection and electromagnetic interference (EMI) shielding. The reason is that materials with high electrical conductivity often pertain high thermal conductivity. To address this challenge, this study reports a multifunctional ceramic composite system for carbon fiber reinforced polymer (CFRP) composites. The fabricated multifunctional ceramic composite system has a multi-layer structure. The polymer derived SiCN ceramic reinforced with yttria stabilized zirconia fibers serves as the thermal protection and impedance matching layer, while the carbon nanotubes provide the EMI shielding. Thermal conductance of the multi-layered ceramic composite is about 22.5% lower compared to that of the carbon fiber reinforced polymer composites. Thermal insulation test during the steady-state condition shows that the hybrid composite can be used up to 300oC while keeping the temperature reaching the surface of carbon fiber reinforced polymer (CFRP) composites at around 167.8oC. Flame test was used to characterize the thermal protection capability under transient condition. The hybrid composite showed a temperature difference of 72.9oC and 280.7oC during the low and high temperature settings, respectively. The average total shielding efficiency per thickness of the fabricated four-layered ceramic composite system was 21.45 dB/mm, which showed high reflection dominant EMI shielding. The average total shielding efficiency per thickness of the eight-layered composite system was 16.57 dB/mm, revealing high absorption dominant EMI shielding. Typical CFRP composites reveal reflection dominant EMI shielding. Results of this study showed that materials with good thermal insulation and EMI shielding can be obtained simultaneously by confining the electron movement inside the materials and refraining their movement at the skin surface.