bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating graph neural networks under graph sampling scenarios
Authors: Wei Qiang , Hu Guangmin
Published: March 2022

Background

It is often the case that only a portion of the underlying network structure is observed in real-world settings. However, as most network analysis methods are built on a complete network structure, the natural questions to ask are: (a) how well these methods perform with incomplete network structure, (b) which structural observation and network analysis method to choose for a specific task, and (c) is it beneficial to complete the missing structure.

Methods

In this paper, we consider the incomplete network structure as one random sampling instance from a complete graph, and we choose graph neural networks (GNNs), which have achieved promising results on various graph learning tasks, as the representative of network analysis methods. To identify the robustness of GNNs under graph sampling scenarios, we systemically evaluated six state-of-the-art GNNs under four commonly used graph sampling methods.

Results

We show that GNNs can still be applied on single static networks under graph sampling scenarios, and simpler GNN models are able to outperform more sophisticated ones in a fairly experimental procedure. More importantly, we find that completing the sampled subgraph does improve the performance of downstream tasks in most cases; however, completion is not always effective and needs to be evaluated for a specific dataset. Our code is available at https://github.com/weiqianglg/evaluate-GNNs-under-graph-sampling.
Awareness of Source of Radiation, Its Hazards and Protection among Final Year MBBS Students: A Cross-sectional Observational Study
Authors: Shastri Dipsa Digant , Diwanji Nehal Sanket , Shastri Mona Digant , Desai Ekta J , Patel Paresh Gordhanbhai , Kadwani Nirav Kishorbhai , Patidar Nipa , Bhatt Avani Yogeshbhai
Published: March 2022

Introduction: Increase availability of multi-detector high speed CT scan, digital radiography and various image guided interventional procedures has increased the total number of radiation related examinations in current era. These have lead to increase radiation exposure to patients as well as the radiologist. This situation has raised the concern about the potential side effects to patients, like radiation-related cancer and death. Aim: Evaluation of awareness of source of radiation, radiation hazards and radiation protection among final year medical students in Tertiary Care Medical College Hospital. Materials and Methods: This was a cross-sectional observational type of study in which total 136 final MBBS students were issued a questionnaire consisting of 12 multiple choice questions including demographic data, awareness about source of radiation, radiation hazard, protection issues and knowledge about radiation dose levels of common radiological examinations. All questions were multiple choice types with answers containing 2 to 9 choices having only one correct answer. The questionnaire was prepared by authors and their answers were validated by various faculties of Department of Radiodiagnosis by peer review methods. This questionnaire was given in a physical form. The obtained data were analysed using statistical software (descriptive statistics used). As homogenous group of final year medical students were analysed, no scoring and no statistical test were needed. Results: In present study 87.5 % (n=119) of students considered radiation knowledge important for them. Out of eight specific questions for checking their knowledge about radiation awareness, five questions were regarding safe radiation practice, radiation exposure, and radiation dose in common and radiological examination. Among these questions “Rule of 10”- question was correctly answered by 113 (83.1%) of students. Questions regarding “Radiological examination of pregnant patient”- was correctly answered by 114 (83.8 %) of students and “Radiation exposure to patients during diagnostic radiology” question was correctly answered by 115 (84.6%) of students. Conclusion: Medical students have good awareness about radiation protection, with a specific gap of knowledge concerning source of radiation, biological effect of radiation and radiation hazards. Undergraduate teaching curriculum must include comprehensive knowledge about radiation hazards and radiation safety.
A Study of Chromosomal Abnormality Patterns in Patients with Primary Amenorrhea in a Tertiary Care Referral Hospital
Authors: Shivaleela C , Prabha S Lakshmi , Bhat Meenakshi , Jayaram K , Harshal KL
Published: March 2022

Introduction: Congenital absence of uterus, inability of the ovary to produce the eggs and any malformations of ovary, fallopian tube, uterus and adnexal tissue may lead to Primary Amenorrhea (PA). The genetic and chromosomal abnormalities are the main cause of PA. Endocrine causes like abnormal function of pituitary gland and hypothalamus also lead to PA. Other causes like stress, extreme physical activity and psychological causes or a combination of these causes may lead to delayed onset of menarche. Aim: To study the frequency and type of chromosomal abnormalities in PA patients. Materials and Methods: In the present descriptive study, subjects included patients referred with PA for chromosomal analysis to Sri Siddhartha Medical College Genetic Laboratory. Pedigrees with details were drawn and in-depth clinical evaluation and clinical information were obtained from all subjects. Results: Of the 77 females with amenorrhea, 65 (84.4%) had a normal karyotype (46, XX) while 12 (15.58%) had abnormal karyotype. The age group of the patients with PA ranged from 16-27 years. Mean age of PA was 21 years. In the present study, among 12 abnormal karyotyping patients 7 (58,3%) patients showed XY, sex reversal. This study also identified a X chromosome homogeneous monosomy, (Turner’s) 45 X in one (8.3%) case. Turner’s mosaic 45, X/46, XX in three cases (25%), and one case (8.3%) showed inversion 46, XX, inv (11), (P15q11). Conclusion: A significant number of patients had sex chromosomal abnormalities; thus, early cytogenetic investigation is prudent to guide further management. Genetic counselling should include the risk of premature menopause for patients with Turner’s syndrome and the use of hormonal replacement therapy, the risk of gonadal malignancy for patients with XY gonadal dysgenesis and the possibility of infertility in the future children of patients with mosaic Turner.
Use of Shear Wave Elastography to Diagnose Acute Pancreatitis: A Cross-sectional Study
Authors: Basavaraju Umamaheshwari K , Kumar Narasipur Lingaiah Rajendra , Narayana Manupratap , Rashmi Kn , Prathibha Ps , Seetharam Mahesh , Sriviruthi B , Pious Rinu
Published: March 2022

Introduction: Acute inflammation process of the pancreas with or without involvement of surrounding tissues and remote organ systems is termed as Acute Pancreatitis (AP). Contrast Enhanced Computed Tomography (CECT) if performed immediately may underestimate the severity. Therefore, ultrasound examination remains the first imaging diagnostic method in suspected cases of AP. The sensitivity of B-mode sonography for the early diagnosis of AP can be increased by the detection of an increase in pancreatic tissue stiffness with Shear Wave Elastography (SWE). Aim: To evaluate the efficacy of SWE in the analysis of AP. Materials and Methods: A cross-sectional study was conducted in Tertiary Care Hospital attached to Mysore Medical College and Research Institute, Mysuru, Karnataka, India, from August 2019 to September 2019. The pancreatic parenchyma of 30 patients with symptoms of AP that included acute onset of severe central epigastric pain, poorly localised tenderness and pain increased by supine positioning radiating to the back. The study also included 40 healthy, asymptomatic volunteer who were examined using B-mode sonography and SWE. Computed Tomography (CT) was performed in all patients with AP with a SEIMENS SOMATOM DEFINITION EDGE 128 slice CT scanner. Elastographic measurements were performed and quantitative SWE values represented in kilopascal (kPa) of the patients and asymptomatic volunteers group were compared. Patients’ amylase and lipase levels were done by biochemical tests. Descriptive and Inferential statistical analysis was carried out in the present study. Student’s t-test (two tailed, independent), Leven’s test for homogeneity of variance and Chi-square test was used to find the significance of study parameters. Results: The mean SWE values for the asymptomatic volunteers with normal pancreatic parenchyma were 9.53±2.62 kPa. The mean SWE values for the pancreatic parenchyma of the patients with AP were 17.23±6.24 kPa. The mean SWE value for the patients with AP was significantly higher than the value for the control group (p<0.001). A SWE cut-off value of 13.5 kPa was associated with 70% sensitivity and 92.5% specificity for diagnosis of AP. Conclusion: For the diagnosis of AP at initial hospital admission, SWE can be used as it is a rapid, radiation-free, and non- invasive tool. It is a useful imaging method with high sensitivity and specificity for the diagnosis of AP.
Assessment of Knowledge, Attitude and Practice of C-shaped Root Canals among Dental Students and Dentists in the Makkah Region of Saudi ArabiaA Cross-sectional Study
Authors: Ahmed Siddiq , Aldughaysh Abdulrahaman Mohammed Ali , Alhazmi Baheej Ghazi Hamzah , Alsubhi Faisal Saud Mohammed , Ashour Zeyad Tariq Hilal
Published: March 2022

Introduction: Thorough management of root canal anatomy and its variants is important for good prognosis of endodontic treatment. C-shaped root canal is one such important variation in root canal anatomy. Due to the complex nature of C-shaped root canals the clinicians should be familiar with this variation to achieve better success rate in endodontic treatment. Aim: To assess Knowledge, Attitude and Practice (KAP) among dental students and dentists of the Makkah region of the Kingdom of Saudi Arabia towards C-shaped root canals. Materials and Methods: A cross-sectional questionnaire survey was conducted for a period of five months from 25th September 2020 to 25th February 2021 in Dentistry program of Ibn Sina National College for Medical Studies, Jeddah using a selfstructured, close-ended, multiple-choice questionnaire consisting of 21 questions. The questionnaire was sent using online to 503 Dental students and Dentists of Makkah region of Saudi Arabia. The study population was selected using convenient random sampling. The questionnaire was constructed and validated with the help of five endodontics with adequate teaching and clinical experience. The data were analysed using IBM Statistical Package for the Social Sciences (SPSS) version 22.0 and descriptive statistics followed by Chi-square test was applied to test of variables in the questionnaire. Results: In the study population ,68.4% (n=344) were males and 31.6% (n=159) were females, 25.2% (n=127) were undergraduate students and 74.7% (n=376) were graduate dentists, 63.2% (n=318) believe most commonly C-shaped root canals are found in mandibular second molars, 49.3% (n=248) have strongly agreed that they are proficient in diagnosing C-shaped root canals, 75.7% (n=381) have agreed that knowledge of canal anatomy will be helpful during access preparation of C-shaped root canals,48.5% (n=244) felt use of crown down technique will be effective in managing C-shaped root canals,72.8% (n=366) felt multiple visit endodontics is needed for successful management of C-shaped root canals and 25.8% (n=130) felt use of thermoplasticised gutta-percha compaction will be helpful in obturation. Conclusion: Knowledge of anatomical variations of root canal system and the use of advanced endodontic instruments and techniques will enable the dentists to handle difficult root canal cases thoroughly for good prognosis of dentition.
Retrograde Intubation for Airway Management of Firearm Injury in the Maxillofacial Region
Authors: Kumar Manoj , Yadav Jay Brijesh Singh , Singh Dheer , Kumar Vimal
Published: March 2022

Endotracheal intubation is one of the most important anaesthetic skills. Trauma to the maxillofacial region is challenging in terms of airway management. Airway management in such patients is difficult and decides the survival of the patient. Endotracheal intubation in patients with difficult ventilation and difficult intubation always remains a challenge, especially in the absence of a flexible fibreoptic bronchoscope. The retrograde catheter technique is an acceptable option for airway management in cases where oral intubation is not possible because of difficult airway or is not recommended because of fear of dislodgement of fractured segments of facial bones. The author here reports a case of a 30-year-old male with firearm injury in maxillofacial region posted for emergency surgery with anticipated difficult airway. Emergency retrograde intubation was done for the management of airway with successful outcome.
Analysis of Competitiveness Fisheries Processing Industry in West Java, Indonesia
Authors: Handaka Asep Agus , Lestari Rosiani Putri , Rizal Achmad
Published: March 2022

The fisheries sector is one of the leading sectors in Indonesia contributinge to the regional and national economy such as in West Java Province in the fishery processing sector which has advantages in each region and can lead to competitiveness. This study to analyze the competitiveness of fisheries processing industry in West Java Province. This research was carried out in January 2021 – July 2021. The method used was a literature survey method to determine the competitiveness of the fisheries processing industry in 24 Regencys/cities in West Java Province. All data are processed and analyzed descriptively. Primary data was obtained from expert judgment consisting of 12 people regarding the proportion of competitiveness of the fisheries processing industry. Secondary data is obtained from statistical data on the fisheries processing industry of West Java province from the marine and fisheries service from 2010 to 2018. The results showed that Depok City was ranked first with very high competitiveness with a final score of 28.76. Depok City has advantages in three variables, namely the facilities and infrastructure, production, and the application of science and technology. Meanwhile, Banjar City ranked last which had low competitiveness with a final score of 0.26. Banjar City does not have an advantage in each variable category because it is in the category of moderate and low competitiveness.
Overview of Causes, Risk Factors and Management of Sciatica: A Review
Authors: Ahmed Abukanna Abdelrahman Mohamed , Tinan Alenezi Atheer Ayed , Alanazi Naif Muhalhil , Hamoud Alotaibi Ahmed
Published: March 2022

Root pain in the sciatic nerve distribution area caused by one or more herniated lumbar discs is a common and often debilitating event. The lifetime incidence of this condition is estimated to be between 13% and 40%. Fortunately, most cases can heal on their own with simple pain relief and physical therapy. However, this situation can become chronic and stubborn, and have a major impact on the social economy. This review looks at the epidemiology, causes, risk factors, and management of sciatica. Factors that influence the incidence of sciatica include height, age, genetic predisposition, walking, jogging (if there is a history of sciatica), and specific physical occupations, including driving. The influence of the protruding nucleus pulposus and the possible inflammatory response mediated by cytokines in the lumbar and sacral nerve roots are discussed. Abnormal immune responses and possible mechanical factors are also considered factors that can mediate pain. The current topic of different treatment modalities is also discussed.
Assessment of the Hygiene Level of Street Food in the City of Beni in the Democratic Republic of Congo
Authors: Loïs Kavira Muhira , Franck Dimoke Okito , Raymond Assani Ramazani
Published: March 2022

Introduction: Street food is a cheap option for people in eastern DRC, but the unhygienic practices of street vendors and their customers create an environment that causes disease and other health problems, as well the introduction of food wastes into the environment is worrisome. The study objective is to assess the level of hygiene of the foodstuffs sold on Nyamwisi Boulevard in Beni City.

Methods: This is a descriptive cross-sectional study. It focused on food vendors and consumers in Nyamwisi Boulevard in 2021. The study population was infinite with a non-random sample whose number was fixed by the PEDUIZZI formula (n=K*10); K being the number of variables or 100 people.

Results: The study showed that 64% of the sellers are women while 58% of the consumers are men, the motivation for them being the creation of employment for 49% of the sellers, the home being far away for 40% of the consumers. The level of hygiene of the food sold on Nyamwisi Boulevard remains a concern with regard to elements such as 59% use well water, which could be the basis of food-borne diseases, 45% of the respondents are clean, only 8% used protective clothing, 12% wash their hands regularly before serving customers, 26% have dustbins, presence of rubbish at 38%; 36% protect against breath and flies, 55% of utensils are clean, 49% have workstations.

Conclusion: Generally speaking, the hygiene rules for food sold on the public highway on Nyamwisi Boulevard are not in place. Certain practices are said to be at the root of the lack of hygiene of food intended for consumption.
Prevalence of Hepatitis E Virus Infection among Pregnant Women Attending the Ante-Natal Clinic of a Tertiary Health Care Centre
Authors: Alao Jude Oluwapelumi , Bejide Ifeoluwa Opeyemi , Komolafe Omotosho Isaac , Alao Oluwaseyi Joy , Oyetunde Oluwapelumi Breakthrough , Oni Matthew Olujenyo
Published: March 2022

Hepatitis E virus (HEV) is the most common cause of viral hepatitis in developing countries. HEV is particularly problematic in pregnancy due to the vulnerability of pregnant women to infections and often causes spontaneous abortion, premature delivery, maternal (≤ 20%), and infant mortality. While pregnant women attending ante-natal clinics are mandatorily screened for some infections, Hepatitis E, except in endemic areas, is not included in the protocol, even though the prevalence of Hepatitis E globally is increasing. This study aimed to determine the presence and prevalence of Hepatitis E among ante-natal clinic attendees at the Ladoke Akintola Teaching Hospital, Osogbo, Osun State. A total of 100 consenting individuals were enrolled in the study between ages 20 and 45. Twenty-one percent of the participants enrolled were in the first trimester of their pregnancy, 33% in the second trimester, and 46% were in the third trimester of pregnancy. A structured questionnaire was administered to extract information on the participants’ demography and clinical history. A volume of 5ml of blood sample was collected from each consenting participant, and the obtained serum, stored at -20°C until ready for analysis. A double antibody sandwich HEV-ELISA technique was performed to analyze the sera for HEV antigen, using an ELISA Kit. Of the 100 samples analyzed, 8% (χ2=12.164, df=1, P=0.019) were positive for HEV Ag. The study only showed an association between the number of positive cases and a history of blood transfusion whereas, there was no such association with age, pregnancy stage, and educational status of the participants. Being an index study in Osun State, this study showed an 8% HEV prevalence rate, which is considered statistically significant.
Implant-Supported Hybrid Prosthesis using All on Six Concept for Atrophic Ridges with Severe Gag Reflex: A Case Report
Authors: Ahlawat Anamika , Rathee Manu , Divakar S. , Singh Sandeep , Chahal Sujata , Wakure Poonam
Published: March 2022

Aims: Edentulism is correlated to poor self-esteem and depression in both young and old individuals due to social rejection. For edentulous patients who are not interested in removable prosthesis, implant-supported fixed prosthesis might be an appropriate treatment modality. The aim of this case report is to rehabilitate the completely edentulous patient with severe gag reflex by maxillary implant supported hybrid prosthesis and mandibular conventional complete denture.

Presentation of case: A 58 years old female patient had reported to the outpatient wing of department of prosthodontics with chief complaint of missing teeth in maxillary and mandibular arches. Patient had a history of severe gagging and discomfort with old denture. The treatment progresses as six implant placed and hybrid prosthesis was fabricated in maxillary arch and conventional complete denture was fabricated in mandibular arch and delivered to the patient.

Discussion: Implant-supported complete arch rehabilitation can be accomplished with either a fixed or removable prosthesis. For a satisfactory outcome, proper patient selection, accurate surgical procedure, and meticulous prosthetic planning are required. Cement-retained implant restorations are becoming more popular because they are simple, aesthetic, and cost-effective. However, such restorations are hard to retrieve, and any residual cement in the soft tissue around the implant might cause peri-implant illness.

Conclusion: A screw retained fixed prosthesis was planned for this patient in maxillary arch and conventional complete denture in mandibular arch which gave a successful outcome and avoid gag reflex.
Capabilities of the T-Scan 10 Novus System in the Diagnosis of Occlusion
Authors: Bozhkova Tanya
Published: March 2022

The physiological restoration of occlusal relationships is important for the normal functioning of the masticatory system. Currently, qualitative and quantitative occlusal indicators are used in clinical practice for occlusion registration. In the past, articulation paper, foil, silk marks, waxes, etc. were the only tools available to access and balance the bite force. However, these methods do not detect simultaneous contact, nor do they quantify time and force. With the introduction of T-Scan, this changes. The evolution of T-Scan from the 1st generation to the 8th generation (1987-2016) has revolutionized the concept of occlusal analysis. The latest version of the T-Scan Novus system, is software version 10.0 that was released in 2018. The T-Scan Novus system is made up of hardware (handpiece, sensor) and Microsoft Windows-based software. 

Тhe registered occlusion is transformed by a computer into a dynamic film (dynamic occlusion video). Recorded occlusal contacts are then illustrated as 2- and 3-dimensional graphics. The improved features of the software provide detailed digital information about the occlusal relationships, which enhances the quality of their analysis.

T-Scan Novus helps to avoid errors in the subjective judgment of the dentist and to control changes in occlusal contacts.
Numerical Simulations of the Cabbeling Phenomenon in Surface Gravity Currents in Cold Fresh Water
Authors: George Alabodite Meipre , Kay Anthony
Published: March 2022

The behaviour of warm water discharge at a temperature higher then Tm horizontally into a homogeneous body of cold fresh water at a temperature lower then Tm was investigated by means of a numerical model. Water density here was taken to be a quadratic function of temperature. Thus cabbeling process was inevitable as positively buoyant water form surface current while penetrating the ambient water. The current halted as mixture became dense and sink. These results are very similar to the experimental study of warm discharge into cold water by Marmoush et al. [14] and Bukreev [22]. The results showed an initially sinking water at the point where the two water bodies meets within the first few time interval. Development of Rayleigh-Taylor instabilities was observed at the lower part of the surface current as lighter fluid penetrate further. The frontal head was found to being replenished by a surface flow of warm unadulterated water, but after much entrainment of ambient fluid and cabbeling then, this head halted and sink. On the floor, denser fluid advance in the same direction as the original surface current, with some degree of Kelvin-Helmholtz instability as it penetrates further. Relations were also drawn that describes the speed, the spread length of both surface current were obtained.

Relation were also drawn that describes the final spread length of the surface current Lsm and the time taken to reach that final spread length Tsm as a function ϕin. This work as presented here is practical and relevant to many fields of study and also enhances policy making towards the protection of the aquatic ecosystems.
Utilization of Various Starch Hydrolysates and Defatted Proteins by Bacillus cereus for Microbial Synthesis of Methionine in Submerged Medium
Authors: Ezemba C. C. , Ekwealor I. A.
Published: March 2022

Three of the methionine-producing bacteria previously isolated from different soil ecovars in Owerri, characterized as Bacillus cereus no: DS13, RS16 and AS9, based on 16s rRNA sequencing, were screened for utilization agricultural products for production of methionine. Experimental studies on the Bacillus strains were carried out to examine the use of various starch hydrolysates from different agricultural products: wheat, sorghum, cassava, cocoyam, yam, plantain, millet, corn, potato, rice and defatted plant proteins: pigeon pea, cowpea, bambaranut, groundnut and soybean meal as source of carbon and nitrogen, respectively for the production of methionine. The result of the influence of various carbon and nitrogen sources on methionine production showed that 2.32mg/ml methionine accumulation in the culture broth of B. cereus DS13 when corn-starch hydrolysate/defatted groundnut meal was used, while B. cereus RS16 and Bacillus cereus DS13 gave the same methionine yield of 2.22mg/ml with corn-starch hydrolysate/defatted groundnut meal and sorghum hydrolysate/soyabean meal respectively. Bacillus cereus AS9 utilized wheat starch hydrolysate/soaybean meal, followed by plaintain-starch hydrolysate/bambaranut to produced 1.79mg/ml and 1.78mg/ml methionine respectively. Methionine was accumulated in the fermentation broth of the Bacillus strains after a fermentation period of 96h. This study indicates the possible utilization of agricultural products as substrates for L-methionine production in submerged medium especially when considering the limitations of producing methionine by fermentation processes.
Quartz technology in Scottish prehistory
Authors: Ballin Torben Bjarke
Published: March 2022

The project Quartz Technology in Scottish Prehistory was initiated in the year 2000, and over the following five years a large number of quartz assemblages were examined from all parts of Scotland, and from all prehistoric periods. The general aim of the project was to shed light on quartz variability, that is, to define how quartz assemblages in different periods and areas of the Scottish quartz province (the north, north-west and Highland regions of Scotland) differ. Subsequently it was attempted to explain the observed variability, focusing on factors such as chronology, territoriality, access to lithic resources, technology and activity patterns. In the larger framework, the present paper forms part of international efforts to increase awareness of archaeological quartz as an important resource. It is hoped that the research put forward in this paper may prove useful to quartz researchers in other parts of the world.
Genetic diversity and origin of a fish population recently colonizing a reservoir: The case ofBasilichthys microlepidotus, central Chile
Authors: Cortes‐Miranda Jorge , Véliz David , Flores‐Prado Luis , Sallaberry Michel , Vega‐Retter Caren
Published: March 2022

Freshwater ecosystems are among those most affected by human activity. Constructing artificial reservoirs can change freshwater biodiversity, thereby impacting genetic diversity (GD), which is crucial to population‐level adaptation. The Maipo River basin, inhabited by the endemic silversideBasilichthys microlepidotus, is one of Chile's most impacted freshwater systems. In this basin, the species is divided into five populations. Recently, a new population was discovered in the reservoir Laguna Esmeralda (LE). We hypothesized that LE silversides possess less GD than other populations and originated from a single basin population. Our evidence shows that the LE is a genetically isolated population with evidence of low genetic variation, but not showing signals of bottleneck or significant reduction in GD. Results consistently identified two sites as unlikely to be the origin of the LE silverside population, suggesting that it was established by the immigration of many individuals from the other three populations.
Emerging Trends in Ring‐opening Metathesis Polymerization
Authors: Cao Edgar , Pichavant Loïc , Trinh Thi Kim Hoang , Chemtob Abraham , Quémener Damien , Pinaud Julien , Héroguez Valerie
Published: March 2022

This article presents the different techniques and strategies that have been explored over the last decade to overcome synthetic challenges and produce a wide range of new (nano)materials by ring‐opening metathesis polymerization (ROMP). In a first part, recent developments in photochemically activated ROMP are critically discussed. The second part is devoted to the synthesis of nanoparticles in dispersed media and by self‐assembly. The last two parts are dedicated to two interesting ROMP developments, the first in the medical field and the last part on different separation techniques.
Polymeric Dispersants
Authors: Pirrung Frank , Auschra Clemens
Published: March 2022

This article provides an overview on the numerous approaches that have been developed for several decades for a major class of coating and printing ink additives often referred to as polymeric pigment dispersants. The first part of this article will focus on the polymer architectures, the anchoring mechanisms, types of particle surfaces, the suitable anchoring groups, and explains how the different particle stabilization mechanisms have been realized in the design of the polymers. In the following chapters, the dispersants will be classified according to their main polymer chemistry, and details will be given on the building blocks and processes employed for industrial production for each class of pigment dispersants. It will be shown, how they can be adapted towards different end use applications ranging from solvent‐free, solvent‐based to aqueous systems. This article will address in detail the “classical” major dispersant classes of commercial importance in the coatings industry based on polyacrylates, polyesters, polyurethanes, and polyacids. In addition, we will especially review recent developments based on controlled polymerization techniques using GTP, ATRP, NMP, and RAFT, as such dispersants are gaining increasing importance for the most demanding applications like for nano‐sized pigments in applications such as inkjet or electronics.
Macromolecular Rheology
Authors: van Ruymbeke Evelyne , Vlassopoulos Dimitris
Published: March 2022

One of the most important features of polymeric systems is their response to weak external stimuli. Of utmost importance is their reaction to an imposed mechanical load, which reflects their viscoelasticity. The viscoelastic properties of polymers are central to their handling and are responsible for their wide‐ranging applications. In this article, we provide the basic elements of molecular rheology, the science of deformation and flow of matter, which is necessary for understanding polymer viscoelasticity and linking it to molecular characteristics of the studied macromolecules. The presentation is basic and does not require prior knowledge on the topic. It refers to amorphous flexible polymers with emphasis on melts. First, the fundamental aspects of rheological measurements are discussed, followed by a discussion on linear viscoelasticity. Then, the models for the linear viscoelastic response of both unentangled and entangled polymers are presented in detail for different architectures, linear, star, and well‐characterized branched polymers. Subsequently, we focus on the nonlinear viscoelastic regime with particular emphasis on the current state‐of‐the‐art and remaining challenges. Where appropriate, some applications of interest to the industrial practice are briefly discussed. Nonlinear phenomena such as flow instabilities, flow‐induced crystallization, and wall slip are not covered.
Additive Manufacturing of Polymers: 3D and 4D Printing, Methodologies, Type of Polymeric Materials, and Applications
Authors: González‐Henríquez Carmen M. , Sarabia‐Vallejos Mauricio A. , Sanz‐Horta Raul , Rodriguez‐Hernandez Juan
Published: March 2022

This article is devoted to the use of polymers in additive manufacturing (AM), also generally known as 3D printing or rapid prototyping. AM presents essential advantages in comparison to traditional fabrication methodologies since it allows the fabrication of wholly customized 3D parts and objects with astonishing levels of geometrical complexity. Moreover, AM entails a significant reduction in the fabrication time, and therefore, parts can be fabricated with a substantial cost reduction. While different materials can be employed for 3D printing, including metals and ceramics, polymers are without any doubt the most versatile, and their use is increasingly growing.

In this article, we aim to provide a clear overview of the principles in which are based the different AM technologies that employ polymers for the fabrication of 3D objects. The particularities of each technology including advantages/disadvantages and type of polymers used will be presented. Consequently, an extensive overview of the applications of the 3D‐printed structures will be provided, covering different areas ranging from biomedical purposes to the fabrication of microfluidic devices. This article also introduces the concept of 4D printing and presents some of the current analysis of the environmental aspects associated with AM and the future of this technology.
Tough Hydrogels Based on Sacrificial Bond Principle
Authors: Cui Kunpeng , Gong Jian P.
Published: March 2022

Hydrogels are swollen polymer networks in water and are usually considered as a type of mechanically weak materials. In recent years, by using sacrificial bond principle, many strong and tough hydrogels were developed, widely extending their application to various fields. The sacrificial bonds break preferentially during deformation, dissipating a significant amount of energy and giving a high toughness of the hydrogels. Diverse sacrificial structures have been used to toughen hydrogels, with structure length ranging from nanometer scale to millimeter scale. Different sacrificial structures cause very different specific molecular mechanisms and properties of hydrogels. In this article, the molecular mechanisms of various tough hydrogels are summarized, and the synergistic effect by combining multiple energy dissipation mechanisms to achieve super‐tough hydrogels is highlighted.
Flow‐Induced Crystallization of Semicrystalline Polymer
Authors: Chen Wei , Sheng Junfang , Yu Wancheng , Li Liangbin
Published: March 2022

This article summarizes our recent efforts to understand the fundamental mechanism of flow‐induced crystallization of semicrystalline polymers in the melt state. Three general experimental phenomena for polymer crystallization underflow are presented first, which are related to crystal morphology, polymorphism, and crystallization kinetics. Then, theoretical efforts to clarify the above phenomena are briefly summarized. The validation of coil‐stretch transition proposed by de Gennes and the stretched network model in flow‐induced crystallization of polymers is discussed. We proposed a new thermodynamics scenario to quantify the nucleation barrier through decoupling the contribution of conformational entropy and segmental orientation order of initial deformed melt. We also incorporated the crystal morphology and polymorphism into calculating the free energy of nuclei. The proposed model can well agree with the experimental observations. Finally, we present some recent synchrotron radiation X‐ray scattering and molecular dynamics simulation results, which challenge the classical one‐step nucleation model. These results suggest a multistep ordering of flow‐induced nucleation, which is discussed in detail.
Polymeric Membranes
Authors: Nunes Suzana P.
Published: March 2022

Polymeric membranes are constantly expanding their applications in separations going from desalination to hydrocarbon recovery and fractionation in the petrochemical industry. They are superior in terms of processability and scalability when compared to inorganic analogues. The diversity of chemistry allows to design membranes with tune porosity and functionality optimized for different applications. This article gives an overview of the main methods of membrane preparation and discusses the field challenges and opportunities. It considers how substituting the classical materials by more stable ones can open the door for applications in the chemical industry, how building blocks with preformed cavities can increase selectivity to level not demonstrated before, and how the criterion of sustainability is changing the strategies, materials, and solvents in the membrane fabrication.
Macromolecular Engineering by Photochemical Routes
Authors: Yılmaz Gorkem , Yagci Yusuf
Published: March 2022

Applications of photochemical processes have been revitalized and rapidly expanding, especially after its indisputable advantages in comparison to conventional methods have been realized. These advantages include low energy requirements, environmentally friendly processing, mildness, and modularity. As such, photochemical strategies meet the requirements of green chemistry, which is perhaps the most important demand as we move to a more sustainable world. The most important application of photochemistry to polymer synthesis is definitely photopolymerization, which is the typical process that transforms monomers into polymers through photon energy. The use of photoinitiators in such systems is of high priority as they lead to the generation of the reactive species responsible for initiation. Photopolymerization can be applied to both chain and step‐growth polymerizations, though the former is in more advanced state. For chain polymerizations, free radical and cationic photoinitiators can be employed.
Polymeric Materials for Additive Manufacturing
Authors: Weyhrich Cody W. , Scott Philip J. , Williams Christopher B. , Long Timothy E. , Hmeidat Nadim S. , Wimmer Madeline , Romberg Stian K. , Compton Brett G. , Levenhagen Neiko , Dadmun Mark
Published: March 2022

Additive manufacturing (AM), also known as 3D printing, is a promising technology to produce complex shapes with little waste material in a distributed fashion. AM can be implemented with various materials, but metal and polymer are dominant feedstocks. During the deposition process for polymeric AM, the polymer may encounter repetitive softening or melting, applied shear flow including multiple constrictions, cooling and solidification, solvent evaporation, polymerization and crosslinking, or coalescence across interfaces. This leads to the need to invoke polymer science principles to rationally predict the response of the polymeric feedstock to the shear fields, thermal gradients, and reaction fronts that they will encounter in the complex 3D printing process. Elucidating the fate of the macromolecules as they experience the 3D printing process provides a foundation to design new materials that are formulated to bias the formation of robust structures and interfaces. As such, polymers in AM offer a unique opportunity to apply polymer science principles to address shortcomings, offer potential solutions, and advance the technology. This article provides a focused discussion of how polymer science principles drive the growth of three common polymeric AM techniques, fused filament fabrication, direct‐ink write, and vat polymerization.
Polymer Nanocomposites
Authors: Alkhodairi Husam , Bilchak Connor , Chan Sophia Y. , Jhalaria Mayank , Kumar Sanat K. , Tannenbaum Robert J.
Published: March 2022

There has been significant interest in polymer nanocomposites (PNCs) because of their promising property enhancements – however, achieving these improvements are contingent on controlling the nanoparticle (NP) dispersion state in the polymer matrix. The inherent incompatibility between a hydrophilic filler and a hydrophobic polymer is the ultimate barrier for obtaining controlled NP spatial dispersion. We can mediate this unfavorable interaction by incorporating moieties on the chains that interact favorably with the NP surface, but preparation strategies typically used to prepare nanocomposites, e.g., casting from a common solvent or melt blending, frequently result in (far) out‐of‐equilibrium NP dispersion states with the degree of non‐equilibrium character sensitively dependent on the particular preparation technique employed. This is due to the energy landscape of even a simple PNC material being very highly complex with many local equilibria and large barriers. Most theoretical studies and our current understanding are based on the assumption that an equilibrium description of the nanocomposite applies, i.e., the system attains its global minimum state. However, different preparation conditions can place the system in different local basinsandthe extremely slow relaxation times of these systems to go from the “as cast” state to the equilibrium state imply that nanocomposites can end up in out‐of‐equilibrium conditions,including stateswhere properties might be favorable. These points, which are elaborated in this review, speak to the importance of preparation and annealing conditions in the NP dispersion state and hence the properties of this novel class of materials. This topic is the focus of this chapter.
Anionic Polymerization of Vinyl and Related Monomers
Authors: Fontanille Michel , Gnanou Yves
Published: March 2022

Vinyl, vinylidene, (meth)acrylic monomers, conjugated dienes can undergo polymerization upon repeated nucleophilic attacks and additions on to their carbon‐carbon double bonds, generating carbanionic growing species. In absence of protic impurities or molecular groups that can react with these propagating carbanionic centers, the latter can be preserved indefinitely. Besides describing the essential features of anionic polymerization, of its initiation and propagation steps, this review also focuses on the opportunities unleashed in macromolecular engineering by the “living” nature of anionic polymerization. Examples of well‐defined macromolecular architectures obtained by anionic polymerization are reported.
Epilogue: Sorting, Depolymerizing, and Recycling Polymers: The Long Road to a Circular Plastics Economy
Authors: Gnanou Yves
Published: March 2022

After Hermann Staudinger laid the foundations of polymer science 100 years ago, an extraordinary scientific, technological, and industrial saga has been written by a long list of academic and industrial scientists. As a result, polymers are present in practically all sectors of human activity, transforming human societies in terms of quality of life, safety, hygiene, etc. Yet the expansion in the production and use of polymeric materials comes at a price for the environment because the polymer economy has been organized since its inception under the “take, make, dispose” pattern. Such a linear organization of the polymer economy causes considerable damages to the environment, wastes resources, and harms wildlife. This article discusses the steps that need to be taken worldwide to turn a still linear polymer economy into a circular one. Questions such as the sorting of polymer waste, their mechanical recycling, their recycling through nonchemical processes, the depolymerization of some polymers into monomers, the pyrolysis of nondegradable polymers, the potential of biodegradation processes are critically reviewed. Recommendations are made in this article to dramatically reduce the carbon footprint of the whole production chain from monomer synthesis to the manufacture of polymers and build a truly circular polymer economy withreuse, repair, and recycleas its foundations.
Cardiac metabolic changes on 18F‐positron emission tomography after thoracic radiotherapy predict for overall survival in esophageal cancer patients
Authors: Zakem Sara J , Jones Bernard , Castillo Richard , Castillo Edward , Miften Moyed , Goodman Karyn A , Schefter Tracey , Olsen Jeffrey , Vinogradskiy Yevgeniy
Published: March 2022

Purpose

Heart doses have been shown to be predictive of cardiac toxicity and overall survival (OS) for esophageal cancer patients. There is potential for functional imaging to provide valuable cardiac information. The purpose of this study was to evaluate the cardiac metabolic dose–response using 18F‐deoxyglucose (FDG)–PET and to assess whether standard uptake value (SUV) changes in the heart were predictive of OS.

Methods

Fifty‐one patients with esophageal cancer treated with radiation who underwent pre‐ and post‐treatment FDG–PET scans were retrospectively evaluated. Pre‐ and post‐treatment PET‐scans were rigidly registered to the planning CT for each patient. Pre‐treatment to post‐treatment absolute mean SUV (SUVmean) changes in the heart were calculated to assess dose–response. A dose–response curve was generated by binning each voxel in the heart into 10 Gy dose‐bins and analyzing the SUVmean changes in each dose‐bin. Multivariate cox proportional hazard models were used to assess whether pre‐to‐post treatment cardiac SUVmean changes predicted for OS.

Results

The cardiac dose–response curve demonstrated a trend of increasing cardiac SUV changes as a function of dose with an average increase of 0.044 SUV for every 10 Gy dose bin. In multivariate analysis, disease stage and SUVmean change in the heart were predictive (p < 0.05) for OS.

Conclusions

Changes in pre‐ to post‐treatment cardiac SUV were predictive of OS with patients having a higher pre‐ to post‐treatment cardiac SUV change surviving longer.
Latent Mechanisms of Polarization Switching from In Situ Electron Microscopy Observations
Authors: Ignatans Reinis , Ziatdinov Maxim , Vasudevan Rama , Valleti Mani , Tileli Vasiliki , Kalinin Sergei V.
Published: March 2022

In situ scanning transmission electron microscopy enables observation of the domain dynamics in ferroelectric materials as a function of externally applied bias and temperature. The resultant data sets contain a wealth of information on polarization switching and phase transition mechanisms. However, identification of these mechanisms from observational data sets has remained a problem due to a large variety of possible configurations, many of which are degenerate. Here, an approach based on a combination of deep learning‐based semantic segmentation, rotationally invariant variational autoencoder (VAE), and non‐negative matrix factorization to enable learning of a latent space representation of the data with multiple real‐space rotationally equivalent variants mapped to the same latent space descriptors is introduced. By varying the size of training sub‐images in the VAE, the degree of complexity in the structural descriptors is tuned from simple domain wall detection to the identification of switching pathways. This yields a powerful tool for the exploration of the dynamic data in mesoscopic electron, scanning probe, optical, and chemical imaging. Moreover, this work adds to the growing body of knowledge of incorporating physical constraints into the machine and deep‐learning methods to improve learned descriptors of physical phenomena.