Genetic distance informs polygenic score predictive accuracy.

Polygenic scores (PGSs) aggregate the effects of variants across the genome to estimate genetic liability, but have lower performance in external study populations. A new study by Ding et al. has applied a novel framework to estimate the individual-level predictive accuracy of PGSs, and demonstrates that performance reduction occurs linearly with genetic distance.

Consensus Definitions of Cytomegalovirus (CMV) Infection and Disease in Transplant Patients Including Resistant and Refractory CMV for Use in Clinical Trials: 2024 Update From the Transplant Associated Virus Infections Forum.

Cytomegalovirus (CMV) infection and disease are important causes of morbidity and mortality in transplant recipients. For the purpose of developing consistent reporting of CMV outcomes in clinical trials, definitions of CMV infection and disease were developed and most recently published in 2017. Since then, there have been major developments, including registration of new antiviral agents. Therefore, the Transplant Associated Virus Infections Forum, which consists of scientists, clinicians, regulators, and industry representatives, has produced an updated version of these definitions that incorporates recent knowledge with the aim of supporting clinical research and drug development. This also includes an update regarding the definition of resistant and refractory CMV infections previously published in 2019. As the field evolves, the need for updates of these definitions is clear, and collaborative efforts among clinicians, scientists, regulators, and industry representatives can provide a platform for this work.

Exercise-induced pain within endurance exercise settings: Definitions, measurement, mechanisms and potential interventions.

Pain can be defined as an unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damage. Though consistent with this definition, different types of pain result in different behavioural and psychophysiological responses. For example, the transient, non-threatening, acute muscle pain element of exercise-induced pain (EIP) is entirely different from other pain types like delayed onset muscle soreness, muscular injury or chronic pain. However, studies often conflate the definitions or assume parity between distinct pain types. Consequently, the mechanisms through which pain might impact exercise behaviour across different pain subcategories may be incorrectly assumed, which could lead to interventions or recommendations that are inappropriate. Therefore, this review aims to distinguish EIP from other subcategories of pain according to their aetiologies and characteristics, thereby providing an updated conceptual and operational definition of EIP. Secondly, the review will discuss the experimental pain models currently used across several research domains and their relevance to EIP with a focus on the neuro-psychophysiological mechanisms of EIP and its effect on exercise behaviour and performance. Finally, the review will examine potential interventions to cope with the impact of EIP and support wider exercise benefits. HIGHLIGHTS: What is the topic of this review? Considerations for future research focusing on exercise-induced pain within endurance exercise settings. What advances does it highlight? An updated appraisal and guide of research concerning exercise-induced pain and its impact on endurance task behaviour, particularly with reference to the aetiology, measurement, and manipulation of exercise-induced pain.

Defining autopolyploidy: Cytology, genetics, and taxonomy.

Autopolyploidy is taxonomically defined as the presence of more than two copies of each genome within an organism or species, where the genomes present must all originate within the same species. Alternatively, "genetic" or "cytological" autopolyploidy is defined by polysomic inheritance: random pairing and segregation of the four (or more) homologous chromosomes present, with no preferential pairing partners. In this review, we provide an overview of methods used to categorize species as taxonomic and cytological autopolyploids, including both modern and obsolete cytological methods, marker-segregation-based and genomics methods. Subsequently, we also investigated how frequently polysomic inheritance has been reliably documented in autopolyploids. Pure or predominantly polysomic inheritance was documented in 39 of 43 putative autopolyploid species where inheritance data was available (91%) and in seven of eight synthetic autopolyploids, with several cases of more mixed inheritance within species. We found no clear cases of autopolyploids with disomic inheritance, which was likely a function of our search methodology. Interestingly, we found seven species with purely polysomic inheritance and another five species with partial or predominant polysomic inheritance that appear to be taxonomic allopolyploids. Our results suggest that observations of polysomic inheritance can lead to relabeling of taxonomically allopolyploid species as autopolyploid and highlight the need for further cytogenetic and genomic investigation into polyploid origins and inheritance types.

Equity in family planning policies and programs in Uganda: conceptualization, dimensions and implementation constraints.

BACKGROUND: Equity is at the core and a fundamental principle of achieving the family planning (FP) 2030 Agenda. However, the conceptualization, definition, and measurement of equity remain inconsistent and unclear in many FP programs and policies. This paper aims to document the conceptualization, dimensions and implementation constraints of equity in FP policies and programs in Uganda. METHODS: A review of Ugandan literature and key informant interviews with 25 key stakeholders on equity in FP was undertaken between April and July 2020. We searched Google, Google Scholar and PubMed for published and grey literature from Uganda on equity in FP. A total of 112 documents were identified, 25 met the inclusion criteria and were reviewed. Data from the selected documents were extracted into a Google master matrix in MS Excel. Data analysis was done across the thematic areas by collating similar information. Data were analyzed using thematic content analysis approach. RESULTS: A limited number of documents had an explicit definition of equity, which varied across documents and stakeholders. The definitions revolved around universal access to FP information and services. There was a limited focus on equity in FP programs in Uganda. The dimensions most commonly used to assess equity were either geographical location, or socio-demographics, or wealth quintile. Almost all the key informants noted that equity is a very important element, which needs to be part of FP programming. However, implementation constraints (e.g. lack of quality comprehensive FP services, duplicated FP programs and a generic design of FP programs with limited targeting of the underserved populations) continue to hinder effective implementation of equitable FP programs in Uganda. Clients' constraints (e.g. limited contraceptive information) and policy constraints (inadequate focus on equity in policy documents) also remain key challenges. CONCLUSIONS: There is lack of a common understanding and definition of equity in FP programs in Uganda. There is need to build consensus on the definitions and measurements of equity with a multidimensional lens to inform clear policy and programming focus on equity in FP programs and outcomes. To improve equitable access to and use of FP services, attention must be paid to addressing implementation, client and policy constraints.

The Conceptual Definition of Sarcopenia: Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS).

IMPORTANCE: Sarcopenia, the age-related loss of muscle mass and strength/function, is an important clinical condition. However, no international consensus on the definition exists. OBJECTIVE: The Global Leadership Initiative in Sarcopenia (GLIS) aimed to address this by establishing the global conceptual definition of sarcopenia. DESIGN: The GLIS steering committee was formed in 2019-21 with representatives from all relevant scientific societies worldwide. During this time, the steering committee developed a set of statements on the topic and invited members from these societies to participate in a two-phase International Delphi Study. Between 2022 and 2023, participants ranked their agreement with a set of statements using an online survey tool (SurveyMonkey). Statements were categorised based on predefined thresholds: strong agreement (>80%), moderate agreement (70-80%) and low agreement (<70%). Statements with strong agreement were accepted, statements with low agreement were rejected and those with moderate agreement were reintroduced until consensus was reached. RESULTS: 107 participants (mean age: 54 ± 12 years [1 missing age], 64% men) from 29 countries across 7 continents/regions completed the Delphi survey. Twenty statements were found to have a strong agreement. These included; 6 statements on 'general aspects of sarcopenia' (strongest agreement: the prevalence of sarcopenia increases with age (98.3%)), 3 statements on 'components of sarcopenia' (muscle mass (89.4%), muscle strength (93.1%) and muscle-specific strength (80.8%) should all be a part of the conceptual definition of sarcopenia)) and 11 statements on 'outcomes of sarcopenia' (strongest agreement: sarcopenia increases the risk of impaired physical performance (97.9%)). A key finding of the Delphi survey was that muscle mass, muscle strength and muscle-specific strength were all accepted as 'components of sarcopenia', whereas impaired physical performance was accepted as an 'outcome' rather than a 'component' of sarcopenia. CONCLUSION AND RELEVANCE: The GLIS has created the first global conceptual definition of sarcopenia, which will now serve to develop an operational definition for clinical and research settings.

Whose (germ) line is it anyway? Reproductive technologies and kinship.

Reproductive biotechnologies can separate concepts of parenthood into genetic, gestational and social dimensions, often leading to a fragmentation of heteronormative kinship models and posing a challenge to historical methods of establishing legal and/or moral parenthood. Using fictional cases, this article will demonstrate that the issues surrounding the intersection of current and emerging reproductive biotechnologies with definitions of parenthood are already leading to confusion regarding social and legal family ties for offspring, which is only expected to increase as new technologies develop. Rather than opposing these new technologies to reassert traditional concepts of the family, however, this article will explore the opportunities that these technologies represent for re-imagining various culturally cherished values of family-making in a way that is inclusive of diverse genders, sexualities and cultures. It will consider IVF, gametogenesis, mitochondrial donation, surrogacy, artificial gestation, CRISPR-Cas9 gene editing, foster care and adoption as some of many possible pathways to parenthood, including for members of the LGBTIAUQ+ community.

The role of champions in the implementation of technology in healthcare services: a systematic mixed studies review.

BACKGROUND: Champions play a critical role in implementing technology within healthcare services. While prior studies have explored the presence and characteristics of champions, this review delves into the experiences of healthcare personnel holding champion roles, as well as the experiences of healthcare personnel interacting with them. By synthesizing existing knowledge, this review aims to inform decisions regarding the inclusion of champions as a strategy in technology implementation and guide healthcare personnel in these roles. METHODS: A systematic mixed studies review, covering qualitative, quantitative, or mixed designs, was conducted from September 2022 to March 2023. The search spanned Medline, Embase, CINAHL, and Scopus, focusing on studies published from 2012 onwards. The review centered on health personnel serving as champions in technology implementation within healthcare services. Quality assessments utilized the Mixed Methods Appraisal Tool (MMAT). RESULTS: From 1629 screened studies, 23 were included. The champion role was often examined within the broader context of technology implementation. Limited studies explicitly explored experiences related to the champion role from both champions' and health personnel's perspectives. Champions emerged as promoters of technology, supporting its adoption. Success factors included anchoring and selection processes, champions' expertise, and effective role performance. DISCUSSION: The specific tasks and responsibilities assigned to champions differed across reviewed studies, highlighting that the role of champion is a broad one, dependent on the technology being implemented and the site implementing it. Findings indicated a correlation between champion experiences and organizational characteristics. The role's firm anchoring within the organization is crucial. Limited evidence suggests that volunteering, hiring newly graduated health personnel, and having multiple champions can facilitate technology implementation. Existing studies predominantly focused on client health records and hospitals, emphasizing the need for broader research across healthcare services. CONCLUSIONS: With a clear mandate, dedicated time, and proper training, health personnel in champion roles can significantly contribute professional, technological, and personal competencies to facilitate technology adoption within healthcare services. The review finds that the concept of champions is a broad one and finds varied definitions of the champion role concept. This underscores the importance of describing organizational characteristics, and highlights areas for future research to enhance technology implementation strategies in different healthcare settings with support of a champion.

The Language of the UDDA is Sufficiently Precise and Pragmatic.

We have a reason to value the Uniform Determination of Death Act (UDDA). Since enactment, the UDDA has been of paramount importance to US citizens, families of comatose patients, and the health care professionals who care for them. The UDDA sets forth two standards for determining death and leaves to the medical community to elaborate criteria by which physicians can determine when those standards have been met. Neurologists and neurocritical care experts always have been center stage in this effort. Perfectly established, why change it? What ignited the recent review of the UDDA were lawsuits questioning medical (neurological) authority leading to the wording and accuracy of the UDDA being revisited. The major objections to the language of the UDDA by several groups led a committee appointed by the Uniform Law Commission to consider several substantial changes in the Act. After several years of discussion without reaching a consensus, the committee's chair suspended the effort. Upending the UDDA will lead to a legal crisis and confusion across the states. We present our main arguments against revising this statute and argue that the committee's failure to revise the UDDA should actually be seen as a necessary success.

Measuring and increasing rates of self-isolation in the context of COVID-19: a systematic review with narrative synthesis.

OBJECTIVES: This study aimed to investigate (1) definitions of self-isolation used during the COVID-19 pandemic; (2) measures used to quantify adherence and their reliability, validity, and acceptability; (3) rates of self-isolation adherence; and (4) factors associated with adherence. STUDY DESIGN: This was a systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Synthesis Without Meta-analysis (PRISMA) guidelines (PROSPERO record CRD42022377820). METHODS: MEDLINE, PsycINFO, Embase, Web of Science, PsyArXiv, medRxiv, and grey literature sources were searched (1 January 2020 to 13 December 2022) using terms related to COVID-19, isolation, and adherence. Studies were included if they contained original, quantitative data of self-isolation adherence during the COVID-19 pandemic. We extracted definitions of self-isolation, measures used to quantify adherence, adherence rates, and factors associated with adherence. RESULTS: We included 45 studies. Self-isolation was inconsistently defined. Four studies did not use self-report measures. Of 41 studies using self-report, one reported reliability; another gave indirect evidence for the lack of validity of the measure. Rates of adherence to self-isolation for studies with only some concerns of bias were 51%-86% for COVID-19 cases, 78%-94% for contacts, and 16% for people with COVID-19-like symptoms. There was little evidence that self-isolation adherence was associated with sociodemographic or psychological factors. CONCLUSIONS: There was no consensus in defining, operationalising, or measuring self-isolation, resulting in significant risk of bias in included studies. Future definitions of self-isolation should state behaviours to be enacted and duration. People recommended to self-isolate should be given support. Public health campaigns should aim to increase perceived effectiveness of self-isolation and promote accurate information about susceptibility to infection.

What Is a Surgical Site Infection After Carpal Tunnel Release?

PURPOSE: Considerable variation exists in the literature on published rates of surgical site infection (SSI) after carpal tunnel release, ranging over 20-fold, from 0.28% to 6.4%. The reason for this variability is unknown. METHODS: A retrospective review was conducted on 748 open carpal tunnel releases performed under wide-awake local anesthetic no tourniquet in an in-office procedure room. The following three different definitions of infection were used for analysis: definition A: prescription of an oral antibiotic; Definition B: SSI definition by the Centers for Disease Control and Prevention; Definition C: infection that required reoperation. RESULTS: Infection rate by definition A was 8.9% (67/748), by definition B was 2.3% (17/748), and by definition C was 0.4% (3/748), resulting in a 22-fold range. CONCLUSIONS: The infection rate after carpal tunnel release is heavily influenced by the definition of SSI. The definition of SSI needs to be considered when making comparisons, either in research or quality assurance/quality improvement applications. CLINICAL RELEVANCE: When analyzing SSI rates, the exact definition of infection must be ascertained to accurately compare an individual's practice or institutional data to the literature.

Optimizing Antifungal Treatment Strategies to Prevent Invasive Pulmonary Aspergillosis Infection-Related Deaths in Intensive Care Unit Patients: The Need for Standardization of Research Definitions.

The clinical spectrum of invasive pulmonary aspergillosis (IPA) has expanded in recent decades. A large group of patients admitted to intensive care units (ICU) is indeed susceptible to the development of IPA. Although timely diagnosis and antifungal therapy of IPA in this expanding population is crucial to prevent IPA-related deaths, the magnitude of the favorable prognostic impact of antifungal therapy is difficult to measure precisely. In our opinion, the development of standardized research definitions could have favorable implications for further improving our ability both to measure the favorable effect of antifungal treatment and to prevent IPA-related death in ICU patients.

Does citing early SIDS research skew contemporary conclusions?

Research on infants who have allegedly succumbed to sudden infant death syndrome (SIDS) has been of variable quality over the years. Even now peer-reviewed papers are being published on cases termed 'SIDS' without autopsies having been performed, despite this being a requirement of the three major definitions for over five decades. Clearly cases used in earlier research studies could not have complied with the requirements of as-yet unpublished definitions/guidelines. For this reason care must be taken in citing initial papers as their results may have been skewed by the presence of non-SIDS cases. This may have particular relevance for meta analyses. Reviewing the literature on substance P and its relationship to SIDS provides an excellent example of how diametrically opposed conclusions were reached at different time points. Early studies on SIDS, and studies that use cases that were classified before the standard NICHD and San Diego definitions, should, therefore, be approached with a degree of scepticism and not cited in contemporary papers or at meetings as they have the potential to confuse rather than clarify.

[Emotional Maltreatment of Children and Adolescents - Definitions, Prevalences, Risk Factors and Psychological Consequences]. / Emotionale Misshandlung von Kindern und Jugendlichen ­ Definitionen, Häufigkeiten, Risikofaktoren und psychische Folgen.

The aim of this article is to provide an introductory overview of the phenomenon of emotional maltreatment of children and adolescents by presenting national and international literature and, in particular, to illustrate the consequences for the mental health of those affected. First, relevant definitions are made and forms of appearance of emotional child maltreatment are presented. A comparison of national and global prevalences shows that emotional child maltreatment is one of the most prevalent forms of child maltreatment. There are different risk factors that can exist at the level of the parents as well as at the level of the children or the environment. The risk that children and adolescents who have experienced emotional violence will have experienced other forms of childmaltreatment is high.There aremultiple consequences for victims of emotional child maltreatment which can result in different, longterm participatory impairments. Especially the psychological and somatic consequences of emotional childmaltreatment can be compared to the consequences of child sexual abuse and physical child maltreatment. Nevertheless, the significance of emotional maltreatment for affected children and adolescents is still underestimated in practice. Often, the effects of emotionalmaltreatment on those affected are not visible. Froma child and adolescent psychiatric/ psychotherapeutic perspective, the psychological consequences must therefore be clearly stated. Finally, there is a need for a broader understanding of emotional child maltreatment that also includes peer and sibling violence.

Performance of Existing and Novel Symptom- and Antigen Testing-Based COVID-19 Case Definitions in a Community Setting.

Point-of-care antigen tests are an important tool for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection, yet are less clinically sensitive than real-time reverse-transcription polymerase chain reaction (RT-PCR), affecting their efficacy as screening procedures. Our goal in this analysis was to see whether we could improve this sensitivity by considering antigen test results in combination with other relevant information, namely exposure status and reported symptoms. In November 2020, we collected 3,419 paired upper respiratory specimens tested by RT-PCR and the Abbott BinaxNOW (Abbott Laboratories, Abbott Park, Illinois) antigen test at 2 community testing sites in Pima County, Arizona. We used symptom, exposure, and antigen-testing data to evaluate the sensitivity and specificity of various symptom definitions in predicting RT-PCR positivity. Our analysis yielded 6 novel multisymptom case definitions with and without antigen test results, the best of which overall achieved a Youden's J index of 0.66, as compared with 0.53 for antigen testing alone. Using a random forest as a guide, we show that this definition, along with our others, does not lose the ability to generalize well to new data despite achieving optimal performance in our sample. Our methodology is broadly applicable, and our code is publicly available to aid public health practitioners in developing or fine-tuning their own case definitions.

Rio de Janeiro Global Consensus on Landmarks, Definitions, and Classifications in Barrett's Esophagus: World Endoscopy Organization Delphi Study.

BACKGROUND & AIMS: Despite the significant advances made in the diagnosis and treatment of Barrett's esophagus (BE), there is still a need for standardized definitions, appropriate recognition of endoscopic landmarks, and consistent use of classification systems. Current controversies in basic definitions of BE and the relative lack of anatomic knowledge are significant barriers to uniform documentation. We aimed to provide consensus-driven recommendations for uniform reporting and global application. METHODS: The World Endoscopy Organization Barrett's Esophagus Committee appointed leaders to develop an evidence-based Delphi study. A working group of 6 members identified and formulated 23 statements, and 30 internationally recognized experts from 18 countries participated in 3 rounds of voting. We defined consensus as agreement by ≥80% of experts for each statement and used the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) tool to assess the quality of evidence and the strength of recommendations. RESULTS: After 3 rounds of voting, experts achieved consensus on 6 endoscopic landmarks (palisade vessels, gastroesophageal junction, squamocolumnar junction, lesion location, extraluminal compressions, and quadrant orientation), 13 definitions (BE, hiatus hernia, squamous islands, columnar islands, Barrett's endoscopic therapy, endoscopic resection, endoscopic ablation, systematic inspection, complete eradication of intestinal metaplasia, complete eradication of dysplasia, residual disease, recurrent disease, and failure of endoscopic therapy), and 4 classification systems (Prague, Los Angeles, Paris, and Barrett's International NBI Group). In round 1, 18 statements (78%) reached consensus, with 12 (67%) receiving strong agreement from more than half of the experts. In round 2, 4 of the remaining statements (80%) reached consensus, with 1 statement receiving strong agreement from 50% of the experts. In the third round, a consensus was reached on the remaining statement. CONCLUSIONS: We developed evidence-based, consensus-driven statements on endoscopic landmarks, definitions, and classifications of BE. These recommendations may facilitate global uniform reporting in BE.

Biomass-Derived Carbonaceous Materials with Graphene/Graphene-Like Structures: Definition, Classification, and Environmental Applications.

Biomass-derived carbonaceous materials with graphene/graphene-like structures (BGS) have attracted tremendous attention in the field of environmental remediation. The introduction of graphene/graphene-like structures into raw biochars can effectively improve their properties, such as electrical conductivity, surface functional groups, and catalytic activity. In 2021, the International Organization for Standardization defined graphene as a "single layer of carbon atoms with each atom bound to three neighbours in a honeycomb structure". Considering this definition, several studies have incorrectly referred to BGS (e.g., biomass-derived few-layer graphene or porous graphene-like nanosheets) as "graphene". The definitions and classifications of BGS and their applications in environmental remediation have not been assessed critically thus far. Comprehensive analysis and sufficient and robust evidence are highly desired to accurately determine the specific structures of BGS. In this perspective, we provide a systematic framework to define and classify the BGS. The state-of-the-art methods currently used to determine the structural properties of BGS are scrutinized. We then discuss the design and fabrication of BGS and how their distinctive features could improve the applicability of biomass-derived carbonaceous materials, particularly in environmental remediation. The environmental applications of these BGS are highlighted, and future research opportunities and needs are identified. The fundamental insights in this perspective provide critical guidance for the further development of BGS for a wide range of environmental applications.

Redefining ARDS: a paradigm shift.

Although the defining elements of "acute respiratory distress syndrome" (ARDS) have been known for over a century, the syndrome was first described in 1967. Since then, despite several revisions of its conceptual definition, it remains a matter of debate whether ARDS is a discrete nosological entity. After almost 60 years, it is appropriate to examine how critical care has modeled this fascinating syndrome and affected patient's outcome. Given that the diagnostic criteria of ARDS (e.g., increased pulmonary vascular permeability and diffuse alveolar damage) are difficult to ascertain in clinical practice, we believe that a step forward would be to standardize the assessment of pulmonary and extrapulmonary involvement in ARDS to ensure that each patient can receive the most appropriate and effective treatment. The selection of treatments based on arbitrary ranges of PaO2/FiO2 lacks sufficient sensitivity to individualize patient care.

A longitudinal assessment of chronic periodontitis in Australian adults.

AIM: The study aimed to estimate the incidence/progression and reversal of chronic periodontitis and to identify factors associated with chronic periodontitis in Australian adults over a 12-year period. MATERIALS AND METHODS: Data were obtained from the longitudinal component of the National Study of Adult Oral Health (NSAOH) in 2004-2006, and repeated data, among the same adults, in 2017-2018. NSAOH 2004-2006 was a population-based study of Australian adults aged 15+ years. The American Academy of Periodontology/European Federation of Periodontology case definitions were used, and then compared with two other case definitions. Multivariable Poisson regression models were used to estimate incidence rate ratios (IRRs) and reversal rate ratio (RRRs) of periodontitis. RESULTS: A total of 775 dentate Australian adults had dental examinations at both times. The proportion of incidence/progression and reversal among Australian adults was 56.4% and 11.0%, respectively. Tobacco smokers presented with more than three times higher incidence (IRR: 3.32, 95% CI: 1.50-7.60) and lower reversals (RRR: 0.94, 95% CI: 0.39-0.98) than those who had never smoked. Cessation of smoking was positively associated with periodontitis reversal. The total incidence/progression was 471.7/10,000 person-years, with reversal being 107.5/10,000 person-years. The average number of teeth lost due to periodontal disease was 1.9 in 2017-2018. Being male and not having periodontal treatment were significant risk markers for the incidence/progression of periodontitis. CONCLUSION: Smoking is a risk factor for periodontitis. Cessation of smoking is an effective means of reducing the incidence and progression of chronic periodontitis, to reduce the risk of tooth loss, and to improve overall periodontal health.

Definition of the term asymmetric synthesis-History and revision.

The widely used term asymmetric synthesis was introduced by Emil Fischer in 1894 by demonstration with examples. An early definition by Marckwald was successful in applications involving enantiomeric reaction products. The term caused difficulties in cases of diastereomeric products, because of a lack of a clear definition of the term diastereoisomers, which in turn affected the introduction of the term diastereoselectivity. Clarity was reached only after Wheland had revived a definition by Victor Meyer of 1907. Today, a definition codified by the International Union of Pure and Applied Chemistry (IUPAC) is in use, which is slightly modified here.