Alternatives to convenience sampling (CS) are needed for HIV/STI surveillance of most-at-risk populations in Latin America. We compared CS, time space sampling (TSS), and respondent driven sampling (RDS) for recruitment of men who have sex with men (MSM) and transgender women (TW) in Lima, Peru. During concurrent 60-day periods from June-August, 2011, we recruited MSM/TW for epidemiologic surveillance using CS, TSS, and RDS. A total of 748 participants were recruited through CS, 233 through TSS, and 127 through RDS. The TSS (...) sample included the largest proportion of TW (30.7 %) and the lowest percentage of subjects who had previously participated in HIV/STI research (14.9 %). The prevalence of newly diagnosed HIV infection, according to participants' self-reported previous HIV diagnosis, was highest among TSS recruits (17.9 %) compared with RDS (12.6 %) and CS (10.2 %). TSS identified diverse populations of MSM/TW with higher prevalences of HIV/STIs not accessed by other methods. (shrink)

Decision support systems, which incorporate artificial intelligence and big data, are receiving significant attention in the public sector. Decision support systems are sociocultural artefacts that are subject to a mix of technical and political choices, and critical investigation of these choices and the rationales they reflect are paramount since they are inscribed into and may cause harm, violate fundamental rights and reproduce negative social patterns. Applying and merging the concepts of sense-making and translation, this article investigates the rationales, translations and (...) critical reflections that shape the development of a decision support system to support social workers assessing referrals concerning child neglect. It presents findings from a qualitative case study conducted in 2019–2020 at the Citizen Centre Children and Young People, Copenhagen Municipality, Denmark. The analysis shows how key actors through processes of translation construct, negotiate and readjust problem definitions, roles, interests, responsibilities and ideas of ambiguity and accountability. Although technological solutionism is present in these processes, it is not the only rationale invested. Rather, technological and data-driven rationales are adjusted to and merged with rationales of efficiency, return on investment and child welfare. Through continuous renegotiation of roles, responsibilities and problems according to these rationales, the key actors attempt to orchestrate ways of managing the complexity facing child welfare services by projecting images of future potentials of the decision support system that are yet to be realised. (shrink)

All projects take place within a context of uncertainty. That is especially noticeable in complex hydroelectric power generation projects, which are affected by factors such as the large number of multidisciplinary tasks to be performed in parallel, long execution times, or the risks inherent in various fields like geology, hydrology, and structural, electrical, and mechanical engineering, among others. Such factors often lead to cost overruns and delays in projects of this type. This paper analyzes the efficiency of the Earned Value (...) Management technique and its Earned Schedule extension, as means of forecasting costs and deadlines when applied to complex hydroelectric power production projects. It is worth noting that this analysis was based on simulation models applied to real-life projects. The results showed that cost forecasting becomes very accurate over time, whereas duration forecasting is not reliably accurate. (shrink)

Ensuring the trustworthiness of autonomous systems and artificial intelligence is an important interdisciplinary endeavour. In this position paper, we argue that this endeavour will benefit from technical advancements in capturing various forms of responsibility, and we present a comprehensive research agenda to achieve this. In particular, we argue that ensuring the reliability of autonomous system can take advantage of technical approaches for quantifying degrees of responsibility and for coordinating tasks based on that. Moreover, we deem that, in certifying the legality (...) of an AI system, formal and computationally implementable notions of _responsibility_, _blame_, _accountability_, and _liability_ are applicable for addressing potential responsibility gaps (i.e. situations in which a group is responsible, but individuals’ responsibility may be unclear). This is a call to enable AI systems themselves, as well as those involved in the design, monitoring, and governance of AI systems, to represent and reason about who can be seen as responsible in prospect (e.g. for completing a task in future) and who can be seen as responsible retrospectively (e.g. for a failure that has already occurred). To that end, in this work, we show that across all stages of the design, development, and deployment of trustworthy autonomous systems (TAS), responsibility reasoning should play a key role. This position paper is the first step towards establishing a road map and research agenda on how the notion of responsibility can provide novel solution concepts for ensuring the _reliability_ and _legality_ of TAS and, as a result, enables an effective embedding of AI technologies into society. (shrink)

Aworkshop was held August 26–28, 2015, by the Earth- Life Science Institute (ELSI) Origins Network (EON, see Appendix I) at the Tokyo Institute of Technology. This meeting gathered a diverse group of around 40 scholars researching the origins of life (OoL) from various perspectives with the intent to find common ground, identify key questions and investigations for progress, and guide EON by suggesting a roadmap of activities. Specific challenges that the attendees were encouraged to address included the following: What key (...) questions, ideas, and investigations should the OoL research community address in the near and long term? How can this community better organize itself and prioritize its efforts? What roles can particular subfields play, and what can ELSI and EON do to facilitate research progress? (See also Appendix II.) The present document is a product of that workshop; a white paper that serves as a record of the discussion that took place and a guide and stimulus to the solution of the most urgent and important issues in the study of the OoL. This paper is not intended to be comprehensive or a balanced representation of the opinions of the entire OoL research community. It is intended to present a number of important position statements that contain many aspirational goals and suggestions as to how progress can be made in understanding the OoL. The key role played in the field by current societies and recurring meetings over the past many decades is fully acknowledged, including the International Society for the Study of the Origin of Life (ISSOL) and its official journal Origins of Life and Evolution of Biospheres, as well as the International Society for Artificial Life (ISAL). (shrink)

We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released (...) DR9 and DR10 samples. Assuming a concordance Λ cold dark matter cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28 Mpc in our fiducial cosmology. We find DV = at z = 0.32 and DV = at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = and H =. Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant. © 2014 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society. (shrink)

© 2015 Elsevier Inc.Toxoplasma gondii is a protozoan pathogen in the phylum Apicomplexa that resides within an intracellular parasitophorous vacuole that is selectively permeable to small molecules through unidentified mechanisms. We have identified GRA17 as a Toxoplasma-secreted protein that localizes to the parasitophorous vacuole membrane and mediates passive transport of small molecules across the PVM. GRA17 is related to the putative Plasmodium translocon protein EXP2 and conserved across PV-residing Apicomplexa. The PVs of GRA17-deficient parasites have aberrant morphology, reduced permeability to (...) small molecules, and structural instability. GRA17-deficient parasites proliferate slowly and are avirulent in mice. These GRA17-deficient phenotypes are rescued by complementation with Plasmodium EXP2. GRA17 functions synergistically with a related protein, GRA23. Exogenous expression of GRA17 or GRA23 alters the membrane conductance properties of Xenopus oocytes in a manner consistent with a large non-selective pore. Thus, GRA17 and GRA23 provide a molecular basis for PVM permeability and nutrient access. (shrink)

The 1996 European Summer Meeting of the Association of Symbolic Logic was held held the University of the Basque Country, at Donostia Spain, on July 9-15, 1996. It was organised by the Institute for Logic, Cognition, Language and Information and the Department of Logic and Philosophy of Sciences of the University of the Basque Coun try. It was supported by: the University of Pais Vasco/Euskal Herriko Unib ertsitatea, the Ministerio de Education y Ciencia, Hezkuntza Saila, Gipuzkoako Foru Aldundia, and Kuxta (...) Fun dazioa. The main topics of the meeting were Model Theory, Proof Theory, Re cursion and Complexity Theory, Models of Arithmetic, Logic for Artifi cial Intelligence, Formal Semantics of Natural Language and Philosophy of Contemporary Logic. The Program Committee consisted of K. Ambos Spies, J.L. Balcazar, J.E. Fenstad, D. Israel, H. Kamp, R. Kaye, J.M. Larrazabal, D. Lascar, A. Marcja, G. Mints, M. Otero, S. Ronchi della Rocca, K. Segerberg and L. Vega. The organizing Committee consisted of X. Arrazola, A. Arrieta, R. Beneyeto, B. Carrascal, K. Korta, J.M. Larrazabal, J.C. Martinez, J.M. Mendez, F. Migura and J. Perez. (shrink)

Short description: Part A : Philosophy, Literature, and Knowledge – Chapter I : Idealism and the Absolute – A. J. B. Hampton: “Herzen schlagen und doch bleibet die Rede zurück?” Philosophy, poetry, and Hölderlin’s development of language suffi cient to the Absolute – P. Sabot: L’absolu au miroir de la littérature. Versions de l’Hégélianisme’ chez Villiers de l’Isle Adam et chez Mallarmé – P. Gordon: Nietzsche’s Critique of the Kantian Absolute – Chapter II: Philosophy and Style – J.-P. Larthomas: Le (...) cas Kierkegaard (1813-1855) ou l’écriture comme dialectique de l’écoute – S. Hüsch: Style et signifi cation. Intériorité et communication indirecte chez Søren Kierkegaard – A. Milon: La question du style en philosophie: la grammaire non-style – C. Van Lerberghe: La question du style dans la phénoménologie asubjective de Jan Patocka – Chapter III: Poetry and Philosophy – J.-B. Dussert: Martin Heidegger en ses poèmes – C. de Roche: The poem and the monad: On the reception of Leibniz‘ monadology in Paul Celan’s poetics – M. de Jesus Cabral: Entre théâtre et philosophie : notes sur la poétique de Maurice Maeterlinck – Chapter IV : Literature, Philosophy, and (new) Mythology – A. Martinengo: La raison hors de soi. Herméneutique et mythe chez Paul Ricoeur – G. Boggio Marzet Tremoloso: Démythologisation comme acte mythopoïétique: le cas de Jason de Elisabeth Porquerol. – G. Coulter: Jean Baudrillard: The Literary / Poetic Philosopher – Chapter V : Literature and Ethics – J. Azoulai: L’Éthique de Spinoza dans Bouvard et Pécuchet: un vertige philosophique et littéraire – I. Vendrell: Can Literature be Moral Philosophy? A sceptical view on the Ethics of Literary Empathy – F. Picon: Envisager Todorov: Poétique, éthique et humanisme contemporain – Chapter VI : Philosophy and Textuality – E. Lecler: La littérature : la mort de la philosophie – J. A. Gosetti- Ferencei: Writing in Philosophy and the Literature and Philosophy of Writing (Plato, Mann, Blanchot) –W. Cristaudo: Bringing Back Character and Grammar: Freeing Literature from Excessive Reliance on Philosophy and Theory – C. Alfano: Parenthesising Cracks into the Ground of Philosophy: The Textuality of Stanley Cavell’s Philosophical Writing – Part B: Perspectives of a Dialogue between Philosophy and Literature: Philosophical Refl ections in Literary Creation – Chapter VII : Philosophical Dialogue and Literature – A. Baillot: Tieck et Solger, un dialogue philosophicolittéraire – V. Altachina: Le dialogue philosophique chez Diderot et chez Dostoïevski – Chapter XIII : Bergsonien Infl uences in Literature – C. Dewas: Bergson et Katzantzakis. Les limites du langage comme condition d’une métaphysique de la littérature – E. Pesenti Rossi: La philosophie à l’épreuve de la poésie : Bergson et Ungaretti – Chapter IX : Wittgenstein and Literature – G. Valdemarca: La revanche du sens commun : Wittgenstein, Musil et la chute de la certitude – A. Leaker: From the ‘numinous glow’ to ‘gut squalor’: Transcendence and the Ordinary in Wittgenstein and Don DeLillo’s Underworld – A. den Dulk: Wallace and Wittgenstein: Literature as Dialogue Concerning the Real World – Chapter X: Borges and Semprun: Writers and Philosophers – J.-F. Mattéi: Borges et la philosophie – T. Capmartin: Voyage au bout de la représentation dans Fictions: Quelques remarques ménardiennes sur Borges et le stoïcisme – V. Capdevielle- Hounieu: Jorge Semprún et l’hybridation du littéraire et du philosophique : pour une ‘fi ction essayistique’ – Chapter XI : Literary (Mis-) Readings of Philosophy – P. Lasarte: Misreadings of Arthur Schopenhauer in Sin Rumbo by Eugenio Cambaceres – S. Roldan: Qu’est-ce qui est fort comme la mort selon Maupassant? La détermination ultime d’Olivier Vertin vue sous l’angle de Schopenhauer – B. Nickel: L’infl uence de Ludwig Wittgenstein (1889–1951) sur la poésie concrète – Chapter XII: The Impact of Philosophy on 20th Century Literature and Poetry – B. Ertugrul: Walter Benjamin et Ingeborg Bachmann entre littérature et philosophie – J. Leclercq / M. Watthee-Delmotte: Michel Henry : pour un langage de la subjectivité. La pensée du roman Le Fils du roi – J. Hobus: “The happiness of the concentration camps”: Reading Imre Kertész’ Novel Fatelessness with Albert Camus’ Concept of the Absurd – S. Frogel: Man without God: Nietzsche, Kafka and Camus Der Herausgeber Sébastian Hüsch, Studium der Philosophie, Geschichte,. (shrink)

A classicist, philosopher, and poet, Poul Martin Møller was an important figure in the Danish Golden Age. The traumatic event of the death of his wife led him to think more profoundly about the question of the immortality of the soul. In 1837 he published his most important philosophical treatise, "Thoughts on the Possibility of Proofs of Human Immortality," presented here in English for the first time. It was read and commented upon by the leading figures of the Golden Age, (...) such as Søren Kierkegaard. It proved to be the last important work that Møller wrote before his death in March of 1838 at the age of 43. (shrink)

This translation of Gregor Malantschuk's Den kontroversielle Kierkegaard again illustrates his ability to state clearly "what Kierkegaard said." The title is slightly misleading because we are not really shown the "controversial" Kierkegaard in any real sense even though a number of themes in his writings are treated in a kind of random way. The first part of this thin volume is promising: Kierkegaard is said to be an opponent of communism and to have written Works of Love largely as a (...) protest against the notion of worldly or natural "equality." The defense of "the single individual" is urged against all social movements that would pretend to eliminate human differences. This is shown to be parallel to his attack, in Two Ages, on the "leveling" tendencies of the age which, earlier, Poul Møller had characterized as "nihilism." So specifically are Kierkegaard's criticisms against "mass man" and "the crowd" directed to communism that Malantschuk points out that Kierkegaard had, in all likelihood, read an essay entitled "Luther as Judge between Strauss and Feuerbach". In addition to such interesting and novel bits of scholarship, Malantschuk includes a summary of Fear and Trembling that does not fit too well into the overall point of the book. A discussion of Kierkegaard's attitudes towards women is interesting insofar as it points out that Christianity emphasizes the equality of men and women before God and that the religious orientation requires a synthesis of the feminine and the masculine: "An eminently masculine intellectuality joined to a feminine submissiveness." It is shown that Kierkegaard sees women as attuned to "finitude," as sensitive, imaginative, and aesthetically involved in life. Before Schopenhauer, he averred that romantic love serves "nature" and its ends. Before Baudelaire and Nietzsche, he emphasized that, as compared to men, women are more deeply rooted in the "natural world." Naturally, as Malantschuk points out, he was ambivalent on this issue: his later pronouncements are quite bitter and picture women as luring men from their "tasks" and inhibiting their daring, their expressions of "spirit," domesticating them. Of all the opinions on women laid out by Malantschuk, one is curious enough to sound valid: women, unlike men, are intolerant of "paradox" and find "reduplication" impossible. Throughout this set of thinly related essays, there are sprinkled biographical details that, by now, are quite familiar. Even though it is mentioned that Kierkegaard was influenced by one Madame Gyllenbourg in regard to Two Ages and paid tribute to the actress, Johanne Heiberg, in A Crisis in the Life of an Actress, an opportunity is missed to note that this essay was perhaps the first attempt to touch upon the question of the "passages" through which individuals pass in life. This brief study is not a sustained analysis of any one issue in Kierkegaard's corpus nor is it a full account of his decided anti-communism. An interpretation of Kierkegaard along these lines would be interesting and provocative. Curiously absent from Malantschuk's work is any reference to Kierkegaard's rather reactionary attachment to monarchy and some of the more cutting remarks about the communist ideal and the leveling of all individuals that can be found in the Journals and Papers. Fortunately, we are told that unless there is an inner transformation of each person, no social system of legislated "equality" will ever achieve its ends. Finally, it should be mentioned that Malantschuk placidly accepts Kierkegaard's concerns for the average man even though it is quite clear that the description of ethical individuality and "becoming a Christian" indicate a very strong defense of "spiritual aristocracy."--George J. Stack, SUNY at Brockport. (shrink)

This is the collection of essays presented to Bochenski on his 60th birthday, and it contains, as a mirror of Bochenski's own work, a broad spectrum of studies ranging from formal logic and history of logic, to the philosophy of logic and language, and to the methodology of explanation in Greek philosophy. Of the seventeen articles, these are some of the more important to the reviewer: "Betrachtungen zum Sequenzen Kalkül" by Paul Bernays, which is an extensive study of Gentzen-type formulations (...) of logic; "Remarks on Formal Deduction," H. B. Curry, a further discussion of sequenzen-logics; "Marginalia on Gentzen's Sequenzen Kalkül" by Hughes Leblanc; "Method and Logic in Presocratic Explanation," Jerry Stannard; "On the Logic of Preference and Choice," H. S. Houthakker, a suggestive presentation of decision and utility theory in logical form; "Leibniz's Law in Belief Contexts," Chisholm; "On Ontology and the Province of Logic," R. M. Martin; and "N. A. Vasilev and the Development of Many-valued Logics," G. L. Kline, an important addition to the history of logic. Other contributors are: Storrs McCall, Albert Menne, E. W. Beth, Benson Mates, Ivo Thomas, J. F. Staal, F. R. Barbò, A.-T. Tymieniecka, and N. M. Luyten. There is a bibliography of Bochenski's writings through 1962.—P. J. M. (shrink)

Malthus did not leave us with a systematic treatment of colonization, but from remarks scattered throughout his publications and correspondence it is possible to assemble a fairly coherent account of his views on the advantages and disadvantages of colonies, and on the reasons why some have failed and others succeeded. Included in these scattered remarks are some comparisons between his own views on colonies and those of Adam Smith. The question of the relationship between Malthus and Adam Smith is a (...) rather complex and subtle one, and cannot be given the full consideration it deserves in one short paper. But, as a general summary, it can be said that Malthus had a high regard for Smith and considered himself a follower and disciple of Smith, by contrast with Ricardo, James Mill, and McCulloch etc., whom he considered as exponents of a ‘New System of Political Economy”. His own Principles of Political Economy was conceived as a collection of ‘tracts or essays”, not as a new systematic treatise replacing the Wealth of Nations, Joseph Gamier in his article ‘Malthus” in the Dictionnaire de l'Economie Politique, 1852, saw that the title of the Principles was in fact a misnomer: ‘Malgré son titre, le livre sur les Principes n'est point un traité complet, mais seulement une collection de dissertations.” In what was probably intended as a criticism of Ricardo's Principles of Political Economy and Taxation, 1817, Malthus stated that the ‘present period … seems to be unpropitious to the publication of a new systematic treatise on political economy”, and, referring to Smith's work, stated that ‘the treatise which we already possess is still of the very highest value”. Nevertheless, despite professing his affiliation, Malthus did not hesitate to criticize Smith when he disagreed with him. He recognized that the Wealth of Nations contained ‘controverted points” and that it would require some ‘additions … which the more advanced stage of the science has rendered necessary”. (shrink)

Kant's Critique of Pure Reason, his main work of theoretical philosophy, frequently uses metaphors from law. In this first book-length study in English of Kant's legal metaphors and their role in the first Critique, Sofie Møller shows that they are central to Kant's account of reason. Through an analysis of the legal metaphors in their entirety, she demonstrates that Kant conceives of reason as having a structure mirroring that of a legal system in a natural right framework. Her study shows (...) that Kant's aim is to make cognisers become similar to authorized judges within such a system, by proving the legitimacy of the laws and the conditions under which valid judgments can be pronounced. These elements consolidate her conclusion that reason's systematicity is legal systematicity. (shrink)

En este trabajo se presentan criterios que permiten estimar parámetros de desinfección mediante el uso de luz ultravioleta UV-C de onda corta, en agua, aire y superficies. Se indican métodos para evaluar la dosificación en función de la potencia de la lámpara empleada. Este tipo de estrategia permiten resultados de hasta 99.9% de desinfección, inactivando diferentes tipos de microorganismos. Estas referencias sirven de base para el diseño de dispositivos de utilidad en la presente emergencia por COVID-19, cuyo origen, al ser (...) viral, es susceptible al mismo método de desinfección debido al proceso de dimerización del ADN, donde el daño producido en la estructura celular, afecta la capacidad de reproducción y de funcionalidad. Palabras Clave: luz UV-C o germicida, desinfección UV, dimerización del ADN. Referencias [1]R. Wallace, M. Ouellette and J. Jean, "Effect of UV‐C light or hydrogen peroxide wipes on the inactivation of methicillin resistant Staphylococcus aureus, Clostridium difficile spores and norovirus surrogate", Journal of Applied Microbiology, vol. 127, no. 2, pp. 586-597, 2019. [2]J. Vargas, "Efecto de la radiación gamma sobre las características físico - químicas, sensoriales y microbiológicas en páprika en polvo ", Revista ECIPeru, pp. 68-71, 2019. [3]M. Ángeles García y P. Fernández, "Luz ultravioleta e inmunidad", Piel, vol. 21, no. 8, pp. 367-368, 2016. [4]W. Pachuau y R. Tiwari, " Deep Ultraviolet Light Emitting Diodes: Physics, Performance, and Applications", ECS Meetings, 2014. [5]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 1-13. [6]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 17-47. [7]"Germicidal Ultraviolet ", Media.ies.org, 2020. [En línea]. Disponible en: https://media.ies.org/docs/standards/IES%20CR-2-20-V1a-20200507.pdf. [Último acceso: 16 de junio de 2020]. [8]J. Bolton y C. Cotton, The ultraviolet disinfection handbook, 3rd ed. Denver, Colo.: American Water Works Association, 2008, pp. 13-33. [9]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 8-9. [10]P. Aguirre, J. García y R. Mujeriego Sahuquillo, "Desinfección con cloro y luz UV en un proceso convencional de regeneración de agua", Ingeniería del agua, vol. 11, no. 1, p. 75, 2004. (shrink)

In this article I assess the Invariance Principle, which states that only quantities that are invariant under the symmetries of our theories are physically real. I argue, contrary to current orthodoxy, that the variance of a quantity under a theory’s symmetries is not a sufficient basis for interpreting that theory as being uncommitted to the reality of that quantity. Rather, I argue, the variance of a quantity under symmetries only ever serves as a motivation to refrain from any commitment to (...) the quantity in question. (shrink)

This article explores yet another paradox – aside from the privacy paradox – related to the datafication of media: citizens trust least the media they use most It investigates the role that daily life plays in shaping the trust that citizens place in datafied media. The study reveals five sets of heuristics guiding the trust assessments of citizens: characteristics of media organisations, old media standards, context of use and purpose, experiences of datafication and understandings of datafication. The article discusses the (...) use of these heuristics and the value that everyday life holds in assessing trust in datafied media. It concludes that, guided by a partial ‘structure of perception’ and enticed into trusting datafied media in the context of their daily lives, citizens may be highly concerned by the datafication of media but use them nevertheless. (shrink)

There exists a common view that for theories related by a ‘duality’, dual models typically may be taken ab initio to represent the same physical state of affairs, i.e. to correspond to the same possible world. We question this view, by drawing a parallel with the distinction between ‘interpretational’ and ‘motivational’ approaches to symmetries.