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Letters to the editor are an important part of democratic societies. In academic journals, letters serve as a form of postpublication review and thus permit continued discussion and debate of scientific ideas. However, letters and their importance are rarely taught to university students. Therefore, the aim of the present paper is to propose a lecture and an assignment that introduce the exercise physiology student to letters. The lecture includes an overview of the history of letters, the definition and purposes of letters, letter themes, examples of letters published in exercise physiology journals, and a search method for discovering letters. The student is then assigned a project comprised of two parts. Part 1 requires the student to independently discover a letter exchange in a scientific journal, including the original research article, the letter commenting on the article, and the reply to the letter. The student then writes a report that summarizes the exchange. The report includes an analysis of the letter's themes and the validity of the arguments made. Part 2 of the assignment requires the student to independently discover an article published in the past year that they believe requires comment. The student then writes a letter, commenting on the article. Students who write convincing letters can be encouraged to submit their letter to the journal. The assignment should help prepare the next generation of journal editors, reviewers, and readers for the task of preserving and participating in a practice that serves to refine knowledge.NEW & NOTEWORTHY Letters to the editor are a form of postpublication review and thus help to refine knowledge through discussion and debate, yet exercise physiology students are rarely introduced to letters in their formal education. Here, the author proposes a lecture and an assignment that the university educator can use to help students understand the importance of letters. In the assignment, the student, among other tasks, critiques an existing letter exchange and writes a letter for potential publication.

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Pakistan, one of the eight countries comprising South Asia, has more than 212.2 million people, making it the world's fifth most populous country after China, India, USA, and Indonesia. It has also the world's second-largest Muslim population. Eberhard et al. (Ethnologue: languages of the world, SIL International, 2020) report 77 languages used by people in Pakistan, although the only two official languages are Urdu and English. After its Independence from the British colonial rule in 1947, it took much deliberation for the country to make a shift from its monolingual Urdu orientation to a multilingual language policy in education in 2009. This entailed a shift from the dominant Urdu language policy for the masses (and English exclusively reserved for elite institutions), to a gradual and promising change that responded to the increasing social demand for English and for including regional languages in the curriculum. Yet English and Urdu dominate the present policy and exclude regional non-dominant languages in education that themselves are dynamic and unstable, and restructured continually due to the de facto multilingual and plurilingual repertoire of the country. Using Bourdieu's (Outline of a theory of practice Cambridge University Press, Cambridge, 1977a, The economics of linguistic exchanges. Soc Sci Inform 16:645-668, 1977b, The genesis of the concepts of habitus and field. Sociocriticism 2:11-24 1985, Language and symbolic power Polity Press, Cambridge, 1991) conceptualization of habitus, this study analyzes letters to the editor published between 2002-2009 and 2018-2020 in a leading English daily of Pakistan. The analysis unveils the linguistic dispositions that are discussed in the letters and their restructuring through market forces, demonstrating a continuity between the language policy discourse and public aspirations. The findings also indicate the ambivalences towards Urdu and English in relation to nationalistic ideologies, modernity and identity.

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Letters to the editor can provide useful scientific information and evaluation of published work as well as acting as an additional level of peer review. Furthermore, letters are good reading material, especially if they involve a debate between authors. Finally, letters are relatively short. Therefore, inexperienced career researchers can use such an opportunity to practice putting together a cogent argument. However, it is far from an ideal situation if letters are the only (or main) type of article on which to base an academic career.

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Short communications are an integral part of academic journal publishing since they serve as a forum for scholarly debate on recently published journal articles. Their prestige and popularity, however, have been declining in the present academic setting. In this short note, we offer several reasons for this phenomenon.

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OBJECTIVE: To conduct a bibliometric analysis of Letters to the Editor published on the Zika virus from 1952-2018. METHODS: A PubMed search was conducted using the terms (Zika OR ZIKV). Results were limited to 1952-2018 and Publication Type = Letter. Results were exported to EndNote, and the full text of each Letter examined. Each Letter was assigned to one of five categories: Reader Response, Author Reply, Observation, Case Report, or Research. Additional study parameters included number of authors, number of references, use of graphics, and funding. Citation reports were generated for each category and the entire dataset, producing lists sorted by Times Cited. RESULTS: Of 499 Letters, only 15 (3.0%) were published before 2016. In 2016, at the height of the Zika virus epidemic in the Americas, 244 (48.9%) Letters were published, dropping to 145 (29.1%) in 2017 and 95 (19.0%) in 2018. Letters included 149 (29.9%) Reader Responses, 56 (11.2%) Author Replies, 112 (22.4%) Observations, 70 (14.0%) Case Reports, and 112 (22.4%) Research. The Letters were written by 1-35 authors; 369 (74.0%) Letters had 1-5 authors, and 130 (26.0%) had 6 or more. The Letters cited 0-63 references, with an average of 7.0 per Letter. Graphics appeared in 192 (38.5%) Letters, and 77 (15.4%) Letters reported funding. An interesting anomaly was the 104 (20.8%) Letters authored or co-authored by 1 individual. CONCLUSION: Letters to the Editor remain an important component of scientific communication and may serve as a valuable source of clinical and research information.

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This paper addresses the subject of letters to the editor as one of the longest standing forums for public discussion and debate by ordinary citizens. To show how the voice of ordinary citizens is presented in letters to the editor during national election campaigns over a period of ten years (2008, 2013 & 2017), we are focusing on the Austrian Kronen Zeitung: A newspaper with an exceptionally high market share of up to 40% during the examination period, a heavy focus on the letters section with three pages per day, and a self-declared willingness to take a stance, especially during election periods. Based on a quantitative content analysis of 530 letters to the editor and 525 articles in the politics section as well as survey data from the Austrian national election study on the political positions of the Kronen Zeitung's readers, we find that letters to the editor in the Kronen Zeitung do not reflect, but complement the articles in the politics section. The tone of the letters is more negative than that of news articles, but the letters closely reflect the readers' political positions, therefore offering identification with the paper.

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Understanding attitudes towards science is crucial to safeguard the future of science, the application of its results and the inclusivity of decision-making processes related to science and technology. Most studies focus on attributes of social groups to explain attitudes towards science. In this study, we aim to move the discussion forward by focusing on perceived attributes of science itself by analysing over 300 letters to the editor in two Dutch national newspapers. The authors of these letters express a large degree of trust in science as a source of societal progress, if research is conducted according to a specific set of rules. Yet, they believe that these rules are under attack. The interests of universities as organizations and individual academics as well as the involvement of industry and government in research are perceived as conflicting with these rules. We conclude with recommendations for further research and practice.

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Gas micronuclei are gas-filled voids in liquids from which bubbles can form at low gas supersaturation. If water is depleted of gas micronuclei, high gas supersaturation is required for bubble formation. This high gas supersaturation is required in part to overcome the Laplace pressure at the point of transition from dissolved gas to a bubble of perhaps nanometer-scale radius. The sum of gas and vapour partial pressures inside a spherical bubble (Pbub) of radius r exceeds the ambient barometric pressure (Pamb) and is given by the Young-LaPlace equation: Pbub = Pamb + 2γ/r for a bubble not in contact with a solid surface. The second term on the right-hand side is the Laplace pressure across the gas-liquid interface due to surface tension (γ). For instance, for a surface tension characteristic of blood of 0.056 N·m⁻¹, de novo formation of a bubble of r = 10 nm requires gas supersaturation exceeding 2γ/r = 11.2 MPa. However, in humans, detectable venous gas bubbles follow decompression to sea level from as shallow as 138 kPa air saturation, implying gas supersaturation of only a few kPa are required for decompression bubble formation. It is widely accepted that bubbles that form at such low gas supersaturation grow from pre-existing, micron-scale gas micronuclei. For such gas micronuclei to already exist prior to gas supersaturation they cannot simply be small bubbles because positive feedback of Laplace pressure causes a micron radius bubble to dissolve in a fraction of a second. Theoretical candidates for gas micronuclei are bubbles coated in surfactants that counteract the Laplace pressure or crevices where gas voids assume shapes that negate the Laplace pressure. However, to date, the nature of gas micronuclei that underly decompression-induced bubbles and decompression sickness have yet to be identified. Consequently, I was intrigued that in two previous issues of Diving and Hyperbaric Medicine (2018 Volume 48, Issue 2, page 114 and Issue 3, page 197), letters from Ran Arieli to the Editor hypothesized a mechanism for decompression bubble formation in blood vessels and in the skin. Both letters stated "It is known that nanobubbles form spontaneously when a smooth hydrophobic surface is submerged in water containing dissolved gas. We have shown that nanobubbles are the gas micronuclei underlying decompression bubbles and decompression sickness". Surface nanobubbles have been extensively described in the physical chemistry literature, but the second sentence is supported by citation of an hypothesis article. The latter is based on experimental work (referenced therein) in which sections of large blood vessels from sheep were incubated in saline and compressed to 1.013 MPa for 18 hours then rapidly decompressed to the surface, whereupon macroscopic bubbles were photographed forming on the luminal surface of the vessels. The authors speculate that the bubbles were forming from surface nanobubbles on the vessel lumen, but no experimental or analytical evidence was presented that surface nanobubbles were present on the vessel lumen or were the precursors of the observed macroscopic bubbles. Surface nanobubbles form on atomically smooth, hard surfaces in gas supersaturated liquids and, imaged with atomic force microscopy, appear as spherical caps of gas. As far as I can determine, surface nanobubbles have not been reported on biological tissue surfaces. Surface nanobubbles typically have diameters less than 100 nanometers but have lifetimes that are orders of magnitude longer than would a bubble of similar dimensions. Surface nanobubbles do not grow into macroscopic bubbles when exposed to pressure waves sufficient to cause bubble formation from adventitious gas micronuclei elsewhere in the apparatus. This is surely not the last word in this new and active field of research into nanoscopic gas species; however, based on current evidence one must treat with skepticism speculation that unobserved surface nanobubbles are the gas micronuclei from which bubbles form in humans with low gas supersaturation and which underlie decompression sickness.

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In a study of the effect of a fatty diet on decompression bubbles, based on the responses to a questionnaire regarding daily food consumption, the approximate fat intake for each diver was calculated, taking into account the maximum recommended intake for a person doing his type of work. Following hyperbaric exposure, divers were divided into two groups: 'bubblers' (a minimum of the second level on the Kisman-Masurel scale) and 'non-bubblers'. Bubblers had higher fat consumption than non-bubblers (146 ± 39% versus 92 ± 18%). There was only a small difference in body mass index between the two groups: 26.3 ± 3.3 kg·m⁻² for bubblers and 24.9 ± 1.9 kg·m⁻² for non-bubblers. Cholesterol and triglycerides in serum were high in the bubblers (211 ± 39 mg·dl⁻¹ and 230 ± 129 mg∙dl⁻¹, respectively) compared with the non-bubblers (188 ± 34 mg∙dl⁻¹ and 153 ± 111 mg∙dl⁻¹, respectively). The authors concluded that a high-fat diet significantly increased the severity of decompression stress in hyperbaric air exposures. However, their explanation that the increased amount of fat in the serum contained more dissolved nitrogen, and that this was the cause of the increase in bubble production, was challenged in a subsequent letter. Decompression bubbles can expand and develop only from pre-existing gas micronuclei. It is known that nanobubbles form spontaneously when a smooth hydrophobic surface is submerged in water containing dissolved gas. We have shown that these nanobubbles are the gas micronuclei underlying decompression bubbles and decompression sickness. It has been suggested that hydrophobic multilayers of phospholipids on the luminal aspect of blood vessels, which we have termed active hydrophobic spots (AHS), were derived from lung surfactant. The essential components of lung surfactant required to construct the surfactant films, namely dipalmitoylphosphatidylcholine (DPPC) and surfactant proteins B and C, were found in the plasma of man and sheep, while DPPC was also found at the AHS. These findings have borne out the assumption that lung surfactants are the source of the AHS on the luminal aspect of blood vessels. These AHS seem to be stable, and their number and size increase with age as more DPPC settles. Bubbles may evolve at these AHS with decompression. The nanobubbles so formed on the surface of these lamellar layers of phospholipids in divers will expand into venous bubbles on decompression. The main surfactant in the lung is DPPC (40%), with the presence of additional components including other phospholipids, glycerides, and cholesterol. In the cited study, only serum triglycerides and cholesterol were measured, whereas it may well be that other phospholipids and fatty acids were carried by proteins in the plasma. We suggest that, as with the different elements which compose the layers of surfactant in the lung, some of the additional fatty components carried by the blood will attach themselves to the AHS, thus contributing further to their enlargement. We hypothesise that divers who consume food that is high in fat, and as a result have more fatty components in their blood, will develop more and larger AHS, subsequently becoming bubblers with a higher risk of decompression illness.

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