Reactive oxygen species (ROS) are highly reactive molecules produced in cells. So far, they have mostly been connected to diseases and pathological conditions. More recent results revealed a somewhat unexpected role of ROS in control of developmental processes. In this review, we elaborate on ROS in development, focussing on their connection to epithelial tissue morphogenesis. After briefly summarising unique characteristics of epithelial cells, we present some characteristic features of ROS species, their production and targets, with a focus on proteins important (...) for epithelial development and function. Finally, we provide examples of regulation of epithelial morphogenesis by ROS, and also of developmental genes that regulate the overall redox status. We conclude by discussing future avenues of research that will further elucidate ROS regulation in epithelial development. (shrink)

No overarching hypotheses tie the basic mechanisms of mitochondrial reactive oxygen species (ROS) production to activity dependent synapse pruning—a fundamental biological process in health and disease. Neuronal activity divergently regulates mitochondrial ROS: activity decreases whereas inactivity increases their production, respectively. Placing mitochondrial ROS as innate synaptic activity sentinels informs the novel hypothesis that: (1) at an inactive synapse, increased mitochondrial ROS production initiates intrinsic apoptosis dependent pruning; and (2) at an active synapse, decreased mitochondrial ROS production masks intrinsic apoptosis dependent (...) pruning. Immature antioxidant defense may enable the developing brain to harness mitochondrial ROS to prune weak synapses. Beyond development, endogenous antioxidant defense constrains mitochondrial (ROS) to mask pruning. Unwanted age‐related synapse loss may arise when mitochondrial ROS aberrantly recapitulate developmental pruning. Placing mitochondrial ROS with their hands on the shears is beneficial in early but deleterious in later life. (shrink)

Osama bin Laden means well. This is evident from his declarations, juridical decrees, lectures, epistles, and written reminders, which Bruce Lawrence has made available in Messages to the World: The Statements of Osama Bin Laden a single volume. Duty, Osama claims, compels Muslims' support for jihad against the???Crusader???Jewish Alliance???. But many attack his goals and behavior as immoral. Initiatives he has supported or directed represent his strategy for fulfilling his duty and demonstrate its apparent immorality at the same time: notably, (...) attacks on U.S. embassies, the 9/11 attacks, and more recently an alleged plot to detonate hydrogen peroxide bombs in public transportation venues. Moreover, his willingness to kill innocents generally is self-evidently wrong, as is his blanket hatred of Jews, Americans, and Christians ; although on one occasion he has declared that???many in the West are polite and good people???. (shrink)

Arbuscular mycorrhizal fungi are considered as a potential biotechnological tool for improving phytostabilization efficiency and plant tolerance to heavy metal-contaminated soils. However, the mechanisms through which AMF help to alleviate metal toxicity in plants are still poorly understood. A greenhouse experiment was conducted to evaluate the effects of two AMF species on the growth, Pb accumulation, photosynthesis and antioxidant enzyme activities of a leguminous tree at Pb addition levels of 0, 500, 1000 and 2000 mg kg-1 soil. AMF symbiosis decreased (...) Pb concentrations in the leaves and promoted the accumulation of biomass as well as photosynthetic pigment contents. Mycorrhizal plants had higher gas exchange capacity, non-photochemistry efficiency, and photochemistry efficiency compared with non-mycorrhizal plants. The enzymatic activities of superoxide dismutase, ascorbate peroxidases and glutathione peroxidase were enhanced, and hydrogen peroxide and malondialdehyde contents were reduced in mycorrhizal plants. These findings suggested that AMF symbiosis could protect plants by alleviating cellular oxidative damage in response to Pb stress. Furthermore, mycorrhizal dependency on plants increased with increasing Pb stress levels, indicating that AMF inoculation likely played a more important role in plant Pb tolerance in heavily contaminated soils. Overall, both F. mosseae and R. intraradices were able to maintain efficient symbiosis with R. pseudoacacia in Pb polluted soils. AMF symbiosis can improve photosynthesis and reactive oxygen species scavenging capabilities and decrease Pb concentrations in leaves to alleviate Pb toxicity in R. pseudoacacia. Our results suggest that the application of the two AMF species associated with R. pseudoacacia could be a promising strategy for enhancing the phytostabilization efficiency of Pb contaminated soils. (shrink)

Rho GTPases are critically important and are centrally positioned regulators of the actomyosin cytoskeleton. By influencing the organization and architecture of the cytoskeleton, Rho proteins play prominent roles in many cellular processes including adhesion, migration, intra‐cellular transportation, and proliferation. The most important method of Rho GTPase regulation is via the GTPase cycle; however, post‐translational modifications (PTMs) also play critical roles in Rho protein regulation. Relative to other PTMs such as lipidation or phosphorylation that have been extensively characterized, protein oxidation is (...) a regulatory PTM that has been poorly studied. Protein oxidation primarily occurs from the reaction of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), with amino acid side chain thiols on cysteine (Cys) and methionine (Met) residues. The versatile redox modifications of cysteine residues exemplify their integral role in cell signalling processes. Here we review prominent members of the Rho GTPase family and discuss how lipidation, phosphorylation, and oxidation on conserved cysteine residues affects their regulation and function. (shrink)

Although the generation of reactive oxygen species is an activity normally associated with phagocytic leucocytes, mammalian spermatozoa were, in fact, the first cell type in which this activity was described. In recent years it has become apparent that spermatozoa are not the only nonphagocytic cells to exhibit a capacity for reactive oxygen species production, because this activity has been detected in a wide variety of different cells including fibroblasts, mesangial cells, oocytes, Leyding cells endothelial cells, thryroid cells, adipocytes, tumour cell (...) and platelets. Since the capacity to generate reactive oxygen species is apparently so widespread, the risk‐benefit equation for these potentially pernicious molecules becomes a matter of intese interest. In the case of human spermatozoa, the risk of manufacturing reactive oxygen metabolites is considerable because these cells are particularly vulnerable to lipid peroxidation. Indeed, there is now good evidence to indicate that oxygen radicals are involved in the initiation of peroxidative damage to the sperm plasma membrane, seen in many cases of male infertility. This risk is off‐set by recent data suggesting that superoxide anions and hydrogen peroxide also participate in the induction of key biological events such as hyperactiavated motility and the acrosome reaction. Thus, human spermatozoa appear to use reactive oxygen species for a physiological purpose and have the difficult task of ensuring the balanced generation of these potentially harmful, but biologically important, modulators of cellular function. (shrink)

Introduction of O2 to Earth's early biosphere stimulated remarkable evolutionary adaptations, and a wide range of electron acceptors allowed diverse, energy-yielding metabolic pathways. Enzymatic reduction of O2 yielded a several-fold increase in energy production, enabling evolution of multi-cellular animal life. However, utilization of O2 also presented major challenges as O2 and many of its derived reactive oxygen species are highly toxic, possibly impeding multicellular evolution after the Great Oxidation Event. Remarkably, ROS, and especially hydrogen peroxide, seem to play (...) a major part in early diversification and further development of cellular respiration and other oxygenic pathways, thus becoming an intricate part of evolution of complex life. Hence, although harnessing of chemical and thermo-dynamic properties of O2 for aerobic metabolism is generally considered to be an evolutionary milestone, the ability to use ROS for cell signaling and regulation may have been the first true breakthrough in development of complex life. The importance of Earth's oxygen cycle and reactive oxygen species produced on the evolution of complex life. The ability to detoxify oxygen species is not a trait that emerged as a response to increased O2 levels but rather crucial adaptation to the early Earth's weakly oxic microenvironments. (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)

Reactive oxygen species (ROS) are known as toxic metabolic products in plants and other aerobic organisms. An elaborate and highly redundant plant ROS network, composed of antioxidant enzymes, antioxidants and ROS-producing enzymes, is responsible for maintaining ROS levels under tight control. This allows ROS to serve as signaling molecules that coordinate an astonishing range of diverse plant processes. The specificity of the biological response to ROS depends on the chemical identity of ROS, intensity of the signal, sites of production, plant (...) developmental stage, previous stresses encountered and interactions with other signaling molecules such as nitric oxide, lipid messengers and plant hormones. Although many components of the ROS signaling network have recently been identified, the challenge remains to understand how ROS-derived signals are integrated to eventually regulate such biological processes as plant growth, development, stress adaptation and programmed cell death. (shrink)

Hydrogen is troublesome in any periodic table classification. This being so it may as well be placed in a position that confers desirable attributes to the arrangement of the elements, while notionally recognising its lineage to the group 1 alkali metals and the group 17 halogens. Since the noble gases bridge the halogens and the alkali metals, and hydrogen encompasses the transition from the alkali metals to the halogens, there is more to the idea of hydrogen over (...) helium. (Meyer 1870, p. 357) (Proust 1927, p. 559). (shrink)

The history of the hydrogen bond provides a good example of the of an important chemical concept. It illustrates the interplay between empirical and theoretical approaches to the problem of delimiting what has proved to be quite an elusive notion, with chemists whittling away at the particular sorts of case with a view to obtaining a precise, unitary concept. Even though there is a return to a more theoretically inspired notion in more recent research, empirical characterisations remain a feature (...) of the report of a Task Group recently set up by the IUPAC to reconsider the definition of the hydrogen bond, and this situation—by no means unusual for chemical concepts and principles—is unlikely to change in the foreseeable future. These developments are reviewed in this paper, which includes an extended discussion of the enormous significance hydrogen bonding has for the philosopher’s standard example of a “natural kind”, water. There is little to suggest a reduction to what philosophers of physics are pleased to call fundamental principles, and the details raise further questions about what essentialists could possibly have in mind when talking about the microscopic essence of water. (shrink)

The hydrogen economy is a technological bluff in its implied assurance that, despite the accelerating pace at which we are depleting the remaining half of our fossil fuels, our energy future is secure. Elementary thermodynamic considerations are developed to show that a hydrogen economy is about as feasible as a perpetual motion machine. Hydrogen is not an energy source but an energy carrier, and when produced renewably, it is an energy carrier to the second degree, with electricity (...) being the energy carrier to the first degree. As such, it greatly elongates the chain of energy transformations required to deliver a desired service from a primary source of energy. There will undoubtedly be applications in which hydrogen may be essential, but they will be limited because the services it delivers will come at a substantial energy premium. (shrink)

Relatively few thinkers have attempted to develop a systematic ‘ethics of expertise’ (EOE) that can guide scientists and other technical experts in providing information to the public. This paper argues that the prima facie duty to disseminate information in a manner that does not damage the self-determination of decision makers could fruitfully serve as one of the core principles of an EOE. Moreover, this duty can be fleshed out in promising ways by drawing on the concept of informed consent, which (...) guides medical clinicians in preserving the self-determination of their patients. The paper applies the resulting ethical framework to recent policy discussions about hydrogen fuel-cell (HFC) vehicles, both because they have received a good deal of research funding and because their merits have been hotly debated. It concludes that technical experts providing information about HFC vehicles should be especially cognizant of three issues: (1) important alternatives to hydrogen technology that need to be addressed, (2) major false beliefs that should be prevented or corrected, and (3) significant framing effects that could influence the recipients of information. (shrink)

(1983). Hydrogen production for ballooning during the French Revolution: An early example of chemical process development. Annals of Science: Vol. 40, No. 6, pp. 531-558.

Hydrogen is a very important industrial gas in chemical processes. It is very volatile; therefore, it can escape from the process units and its mass balance is not always correct. In many industrial processes where hydrogen is reacted, kinetics are often related to hydrogen pressure. The right thermodynamic properties of hydrogen can be found for a process simulation and optimization; they can be estimated by the Grayson-Streed model. In the case studied, a methanol plant with a (...) capacity of 150,000 tons/year, the flow rate of hydrogen (H2) can be optimized using nonlinear programming, but good estimates of thermodynamic properties of hydrogen had to be found. In the case study, the model is in relatively good agreement with experimental measurements in the existing methanol production plant. An additional flow rate of hydrogen can increase the methanol production by 1.2%. Total potential profit increase of the additional methanol production was estimated to be 30 kEUR/a (or 103 euros/year). (shrink)

The hydrogen economy has received increasing attention recently. Common reasons cited for investigating hydrogen energy options are improved energy security, reduced environmental impacts, and its contribution to a transition to sustainable energy sources. In anticipation of these benefits, national and local initiatives have been launched in the United States, creating pilot “roadmaps” and technology partnerships to explore hydrogen economy platforms. Although hydrogen can provide several positive improvements over a carbon- or uranium-based energy system, several problems are (...) also likely. As well, competitive technologies (e.g., hybrid vehicles) may offer comparatively greater economic and/or environmental advantages. Before policies to advance a hydrogen energy economy proceed, it is vital that all aspects of hydrogen be compared with other available alternatives. Important questions to ask in this regard are whether a hydrogen economy can fulfill key energy needs and whether there are appropriate roles for hydrogen to play in a sustainable energy future. (shrink)

In a recent paper the authors studied numerically the hydrogen ground state in stochastic electrodynamics within the the non-relativistic approximation. In quantum theory the leading non-relativistic corrections to the ground state energy dominate the Lamb shift related to the photon cloud that should cause the quantum-like behaviour of SED. The present work takes these corrections into account in the numerical modelling. It is found that they have little effect; the self-ionisation that occurs without them remains present. It is speculated (...) that the point-charge approximation for the electron is the cause of the failure. (shrink)

The development of a reliable and relatively simple micro‐assay for lipid peroxides in serum or plasma has made it possible to conduct clinical surveys of lipid peroxide levels in man. From many studies made in Japan, those suggesting a relationship between the elevation of lipid peroxide level plasma serum and the occurrence of vascular disorders are discussed here.The data described in this paper show that the elevation of the serum lipid peroxide level over the normal value is (...) a direct cause of the initiation of atherogenesis. Therefore, any factor bringing about the elevation of serum lipid peroxide levels, such as irradiation, would be an indirect cause of atherogenesis. In fact, irradiation is known to provoke this disorder and to elevate serum lipid peroxide levels. (shrink)

Summary The balloon mania between 1783 and 1785 put an extraordinary strain on the Paris Academy of Sciences, threatening its status as the highest tribunal of European science. Faced with repeated royal directives and public frenzy, the Academy manoeuvred carefully to steer the research toward the hydrogen balloon and thereby to maintain its scientific superiority. Antoine-Laurent Lavoisier seized this moment when the promise of ?the empire of airs? brought science to the centre of public attention to push his theoretical (...) reform for chemistry. He utilized the established protocol of the Academy and the resources of the Republic of Letters to broadly publicize his first decomposition of water in April 1784. Once he attained the publicity and the balloon fever began to cool, he staged a much more elaborate experiment for the experts in February 1785. Although this second, large-scale experiment cost much expense and effort, Lavoisier never published a full account. The differential care given to the two experiments can only be understood in their divergent rhetorical contexts. The written accounts in 1784 addressed the court of public opinion, while the exclusive performance in 1785 aimed at the court of experts to inaugurate the collaborative phase of the Chemical Revolution. (shrink)

The placement of hydrogen in the periodic table has unique implications for fundamental questions of chemical behavior. Recent arguments in favor of placing hydrogen either separately at the top of the table or as a member of the carbon family are shown to have serious defects. A Coulombic model, in which all compounds of hydrogen are treated as hydrides, places hydrogen exclusively as the first member of the halogen family and forms the basis for reconsideration of (...) fundamental concepts in bonding and structures. The model provides excellent descriptive and predictive ability for structures and reactivities of a wide range of substances. (shrink)

Summary The balloon mania between 1783 and 1785 put an extraordinary strain on the Paris Academy of Sciences, threatening its status as the highest tribunal of European science. Faced with repeated royal directives and public frenzy, the Academy manoeuvred carefully to steer the research toward the hydrogen balloon and thereby to maintain its scientific superiority. Antoine-Laurent Lavoisier seized this moment when the promise of ‘the empire of airs’ brought science to the centre of public attention to push his theoretical (...) reform for chemistry. He utilized the established protocol of the Academy and the resources of the Republic of Letters to broadly publicize his first decomposition of water in April 1784. Once he attained the publicity and the balloon fever began to cool, he staged a much more elaborate experiment for the experts in February 1785. Although this second, large-scale experiment cost much expense and effort, Lavoisier never published a full account. The differential care given to the two experiments can only be understood in their divergent rhetorical contexts. The written accounts in 1784 addressed the court of public opinion, while the exclusive performance in 1785 aimed at the court of experts to inaugurate the collaborative phase of the Chemical Revolution. (shrink)

Until the 1860s, science in Russia was principally conducted in Latin, French, and German. In the years leading up to and following the creation of the Russian Chemical Society in 1868, Russian chemists – treated in this article as both a representative sample of Russian scientists and also practitioners of the flagship science of the period – debated both the merits of developing a nomenclature that would enable Russian to “hold” modern inorganic and organic chemistry, and the practicability of doing (...) so. The article explores debates over whether Russian syntax could be adapted to represent chemical compounds according to emerging western conventions or in a sui generis manner, as well as the struggles of Russian scientists to use French and German to communicate with their foreign counterparts, arguing that the details of these debates highlight both the fruitfulness and the limits of using “standardization” as a framework for linguistic codification. (shrink)

The status of the chemical bond has long been a controversial issue with the increasing distance between quantum chemists’ theoretical understanding of molecular stability and the ideas of experimental chemists. Some aspects of the development of the concept of a hydrogen bond are discussed with a view to assessing its import on the general question.

In this new edition of his pioneering book "Tomorrow's Energy," Peter Hoffmann makes the case for hydrogen as the cornerstone of a new energy economy.

An economically viable and environmental friendly method of generating hydrogen for fuel cells is by the reaction of certain metals with steam, called metalsteam reforming (MSR). This technique does not generate any toxic by-products nor contributes to the undesirable greenhouse effect. From the standpoint of favorable thermodynamics, total environmental benignity, and attractive economics, iron appears to be the metal of choice for such a process. An inexpensive source of iron for the MSR is the steel industry's mill-scale waste via (...) hydrogen and carbothermic reduction, both of which are energy-intensive processes. These have been eliminated by a novel, solution-based room temperature technique producing nanoscale iron, thus obviating the sintering of iron or iron oxide and deactivation during the cyclic operation of MSR. Some preliminary results are presented of an investigation aimed at converting the mill-scale waste into nanoscale iron, which was subsequently used in generating hydrogen for proton exchange membrane fuel cells. (shrink)

Niels Bohr’s model of the hydrogen atom is widely cited as an example of an inconsistent scientific theory because of its reliance on classical electrodynamics together with assumptions about interactions between matter and electromagnetic radiation that could not be reconciled with CED. This view of Bohr’s model is controversial, but we believe a recently proposed approach to reasoning with inconsistent commitments offers a promising formal reading of how Bohr’s model worked. In this paper we present this new way of (...) reasoning with inconsistent commitments and compare it with other approaches before applying it to Bohr’s model and offering some suggestions for how it might be extended to account for subsequent developments in old quantum theory. (shrink)

Interest in a hydrogen economy has grown significantly in the past decade. However, the success of old technologies that are being re-engineered to work on hydrogen, as well as the creation of new hydrogenbased technologies, hinges upon public interest in and demand for such technologies. With increasing investments in the research and development of hydrogen technologies, there exists a need to monitor public attitudes toward hydrogen to ensure its success as an alternative energy carrier. To address (...) this need, two surveys were conducted. The results of the first survey give insights about how colored information influences the public acceptance of hydrogen, and the results of the second survey elucidate what trade-offs the public is willing to accept during the transition to a hydrogen economy. Furthermore, the research highlights how hydrogen knowledge and acceptance differ among age, education, and gender groups. (shrink)

The consequences of a generalized Dirac equation are discussed for the energy levels of the hydrogen atom. Apart from the usual generalizations of the Dirac equation by adding new interaction terms, we generalize the anticommutation rule of the Dirac matrices, which leads to spin-dependent propagation properties. Such a theory can be looked at as a model theory for testing Lorentz invariance or as an outcome of pregeometric dynamical induction schemes for space-time structure.For special examples of generalized Dirac matrices including (...) perturbation terms with respect to the SRT Dirac matrices, we derive the energy level of the hydrogen atom and find a hyperfine splitting due to these perturbations. A comparison of this additional splitting with Lamb shift measurements gives us upper limits for possible perturbations, which turn out to be of measurable magnitude. Spin precession experiments give much more restrictive limits. So, it turns out that the hydrogen atom is not such a sensitive indicator for the Lorentz invariance as widely believed. (shrink)

A modification of the regular medium-form periodic table is presented in which certain elements are placed in more than one position. H is included at the top of both the alkali metals and the halogens; He is above Be and above Ne. The column of noble gases is duplicated as Groups O and 18. The elements of the second and third periods are duplicated above the transition metals. This arrangement displays more patterns and connections between the elements than are seen (...) in the regular format. It fits more facts and so gives better guidance to useful predictions. (shrink)