In many cells, a nitric oxide (NO) synthase inducible by immunological stimuli produces a sustained flow of NO that lasts a long time. NO is a short‐lived molecule but it is a diffusibel ligand believed to be capable of reaching distal target sites. Further, several lines of evidence indicate that cysteine‐rich motifs of metal‐binding proteins, as well as redox‐sensitive metal clusters of metalloproteins, are natural sensors of bioradicals like NO. In metalloregulatory proteins, metals are often conveniently located (...) at binding sites and bound to cysteine residues. Accordingly, disruption of the metal‐thiolate polymetallic clusters should trigger significant remodelling of the protein structure involved in regulation. We can therefore postulate that the nitrosation reaction occurring at metal centres or cysteine‐rich motifs will preclude correct binding to regulatory sites. Several examples are given of metalloregulatory proteins whose metal is bound to thiols and may then become sensitive to NO. Recent observations indicate that in response to NO synthesis, iron regulatory protein, a eukaryotic bifunctional [Fe‐S] protein, switches from acting as aconitase to being an RNA‐binding regulator, and we suggest that the interplay between NO or a NO‐derived molecule and metal clusters at critical allosteric sites may be a crucial component of the cellular response to environmental stress. (shrink)

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)

The sporadic nature of Alzheimer's disease argues for an environmental link that may drive AD pathogenesis; however, the triggering factors and the period of their action are unknown. Recent studies in rodents have shown that exposure to lead during brain development predetermined the expression and regulation of the amyloid precursor protein and its amyloidogenic beta-amyloid product in old age. Here, we report that the expression of AD-related genes [APP, BACE1 ] as well as their transcriptional regulator were elevated in aged (...) monkeys exposed to Pb as infants. Furthermore, developmental exposure to Pb altered the levels, characteristics, and intracellular distribution of Abeta staining and amyloid plaques in the frontal association cortex. These latent effects were accompanied by a decrease in DNA methyltransferase activity and higher levels of oxidative damage to DNA, indicating that epigenetic imprinting in early life influenced the expression of AD-related genes and promoted DNA damage and pathogenesis. These data suggest that AD pathogenesis is influenced by early life exposures and argue for both an environmental trigger and a developmental origin of AD. (shrink)

Building upon Nancy Cartwright's discussion of models in How the Laws of Physics Lie, this paper addresses solid state research in transition metal oxides. Historical analysis reveals that in this domain models function both as the culmination of phenomenology and the commencement of theoretical explanation. Those solid state chemists who concentrate on the description of phenomena pertinent to specific elements or compounds assess models according to different standards than those who seek explanation grounded in approximate applications of the Schroedinger (...) equation. Accurate accounts of scientific debate in this field must include both perspectives. (shrink)

Recent work by historians and philosophers has called attention to the complexity of modern experimental physics and its intricate relation to interpretive and explanatory theory (Franklin 1987, Hacking 1983, Galison 1987 and 1989, Pickering 1984 and 1987). One point of general agreement has been that the contexts of discovery and justification often significantly overlap and do not uniformly correlate with experiment and theory. Instead, intended applications, instrumentation, experiment, phenomenological description, explicative models, and explanatory theory all act both as incentives and (...) as constraints during the production of scientific knowledge. The present paper investigates how one node of this network operates in the domain of solid state physics and chemistry. In particular, a case study analysis of how models function in transition metal oxide research provides ample support for several conclusions.First, it must be emphasized that the term “theory” can have misleading connotations in this domain if it is allowed to imply a single and foundational level of explanatory generality. (shrink)

The importance of watching and understanding color of chemical compounds and linking it to diverse physical and chemical properties is illustrated here using transition metal oxides at the highest achievable oxidation state of a metal. Analyses are based on qualitative thinking supported by Molecular Orbital theory in its simplest implementation. Graphic abstract.

During a period of about four decades following World War I, gasoline was often deodorized at refineries by treatment with alkaline solutions of lead oxide, a procedure generally denoted ‘doctor sweetening’. Contemporary accounts describe it as old, but are generally vague about its origin. This paper traces the early history of the treatment of petroleum distillate by alkaline plumbite solution, dating back to 1866 when it was introduced in Germany by Rudolf Wagner. After 1869, this procedure became the preferred (...) method for deodorizing Canadian kerosene and other petroleum products which were afflicted by unusually high sulphur content. Subsequently, Hermann Frasch improved on this method by distilling the afflicted petroleum in the presence of solid metal oxides. (shrink)

We present the resistive switching characteristics of Metal-Insulator-Metal devices based on amorphous Al2O3which is deposited by Atomic Layer Deposition. A maximum processing temperature for this memory device is 300°C, making it ideal for Back-End-of-Line processing. Although some variations in the forming, set, and reset voltages are obtained for many of the measured MIM devices, thememristoreffect has been obtained after cyclicI-Vmeasurements. These resistive transitions in the metal oxide occur for bothbipolarandunipolarconditions, while theIOFF/IONratio is around 4–6 orders of (...) magnitude and is formed at gate voltages ofVg<4 V. In unipolar mode, a gradual reduction inVSETis observed and is related to combined incomplete dissolution of conductive filaments which leaves some residuals and thickening of chemically reduced Al2O3during localized Joule heating. This is important because, by analyzing the macroscopic resistive switching behavior of this MIM structure, we could indirectly relate it to microscopic and/or nanoscopic phenomena responsible for the physical mechanism upon which most of these devices operate. (shrink)

The World Health Organisation recently listed air pollution as the most significant threat to human health. Air pollution comprises particulate matter (PM), metals, black carbon and gases such as ozone (O3), nitrogen dioxide (NO2) and carbon monoxide (CO). In addition to respiratory and cardiovascular disease, PM exposure is linked with increased risk of neurodegeneration as well as neurodevelopmental impairments. Critically, studies suggest that PM crosses the placenta, making direct in utero exposure a reality. Rodent models reveal that neuroinflammation, neurotransmitter imbalance (...) and oxidative stress are triggered following gestational/early life exposure to PM, and may be exacerbated by concomitant mitochondrial dysfunction. Gestational PM exposure (potentiated by mitochondrial impairment in the metabolically active neonatal brain) not only impacts neurodevelopment but may sensitise the brain to subsequent cognitive impairment. Having reviewed this field, we conclude that strategies are urgently required to reduce exposure to PM during this sensitive developmental period. (shrink)

Abstract This paper describes the early history of magnetochemistry: the search for chemical effects of magnetism in the nineteenth century. Some early researchers, such as Johann Wilhelm Ritter, attempted to reproduce with magnets the effects that had been produced by electricity and Volta’s battery. For several decades, researchers successively reported positive results and denied claims concerning the effect of magnetism in oxidation, electrolysis, reduction of metals from saline solutions, crystallisation, change of colour of vegetable tinctures and other chemical reactions. In (...) the two last decades of the nineteenth century some effects were accepted as real, and a thermodynamic theory of the influence of magnetic fields upon chemical reactions was developed. Finally, Dragomir Hurmuzescu was able to create reproducible experiments and measured the electromotive force between two electrodes, with or without the presence of magnetic fields, confirming the existence of the phenomenon and obtaining results compatible with the theoretical predictions. Afterwards, this magnetochemical effect was accepted as real, but the effect was weak and its practical importance was negligible. The subject was gradually forgotten. Content Type Journal Article Pages 1-26 DOI 10.1007/s10698-011-9127-8 Authors Roberto de Andrade Martins, Department of Physics, State University of Paraiba, Campina Grande, PB, Brazil Journal Foundations of Chemistry Online ISSN 1572-8463 Print ISSN 1386-4238. (shrink)

The present article is devoted to two issues. The first is the identification of lead and tin in medieval Arabic alchemy. The second is the investigation of whether Arabic alchemists differentiate between these problematic substances or not. These two issues are investigated in the light of a comparison which is made between the facts that are stated about the two problematic substances in the original Arabic alchemical works and those stated in modern chemical literature. It is proved that Arabic alchemists (...) made a sharp distinction between lead and tin. Also, it becomes clear that these two metals were used in a satisfactory purity in the era of medieval Arabic alchemy. As a consequence of the present study, some conclusions are drawn about the existence of some categories of ‘derivatives’ of fusible bodies in Arabic alchemy which are degenerate to modern categories of oxides, carbonates, etc. (shrink)

This chapter contains sections titled: Formation of Materials Carbon Nanomaterials Inorganic Nanomaterials.

A quick tour through an average U.S. hospital gives pause to anyone with even a rudimentary concern for environmental issues. To a careful observer, the typical U.S. hospital presents an array of challenges to the health of ecosystems. For example, hospitals consume vast quantities of natural resources. The most obvious of these are fossil fuels, which form the basic building blocks of the industrialized medical care industry. Aside from the worry that our healthcare systems are technologically and functionally dependent upon (...) nonrenewable, relatively scarce, and politically volatile resources, our heavy reliance on fossil fuels has important ill effects, including unfavorable health outcomes for humans. For example, the combustion of fossil fuels is the driving force behind global warming, which will likely result in increasing heat-related mortality and morbidity and may contribute to the spread and resurgence of infectious diseases around the world. Also, the combustion of coal and oil releases pollutants such as sulfur oxides, nitrogen oxides, and ground-level ozone that contribute to various respiratory ailments. In addition to being energy intensive, the modern hospital uses a great deal of water, wood, paper, metals, minerals, plastics, chemicals, food, and land. (shrink)

The present article is devoted to two issues. The first is the identification of lead and tin in medieval Arabic alchemy. The second is the investigation of whether Arabic alchemists differentiate between these problematic substances or not. These two issues are investigated in the light of a comparison which is made between the facts that are stated about the two problematic substances in the original Arabic alchemical works and those stated in modern chemical literature. It is proved that Arabic alchemists (...) made a sharp distinction between lead and tin. Also, it becomes clear that these two metals were used in a satisfactory purity in the era of medieval Arabic alchemy. As a consequence of the present study, some conclusions are drawn about the existence of some categories of ‘derivatives’ of fusible bodies in Arabic alchemy which are degenerate to modern categories of oxides, carbonates, etc. (shrink)

A major obstacel to the study of mammalian development, and to the practical application of knowledge gained from it in the clinic during therapeutic in vitro fertilisation and embryo transfer (IVF‐ET), is the propensity of embryos to become retarded or arrested during their culture in vitro. The precise developmental cell cycle in which embryos arrest or delay is characteristic for the species and coincides with the earliest period of embryonic gene expression. Much evidence reviewed here implicates free oxygen radicals (FORs) (...) in the process of arrest. Thus, studies on the development of mouse preimplantation embryos in vitro have shown that (i) FORs are elevated in vitro, but not in vivo, at the time at which embryos become arrested or delayed, (ii) systems for removing reactive oxygen species to limit the formation of hydroxy radicals are present, although they have not yet been assessed quantitatively and may differ qualitatively from those in adult cells, (iii) metabolic and possibly genetic adaptations to oxidative damage are evident, (iv) published procedures for overcoming in vitro arrest are explicable in terms of FOR‐mediated damage or responses and (v) the arrest or delay of most embryos in vitro can be reduced or prevented experimentally by addition of metal chelators to limit hydroxy radical formation and lipid hydroperoxidation. (shrink)

The frequency and temperature dependences of the ac conductivity and dielectric constant of the V 2 O 5 -MnO-TeO 2 system, containing two transition-metal ions, have been measured. The dc conductivity † dc measured in the high-temperature range decreases with addition of the oxide MnO. This is considered to be due to the formation of bonds such as V--O--Mn and Mn--O--Mn in the glass. The conductivity arises mainly from polaron hopping between V 4+ and V 5+ ions. It (...) is found that a mechanism of adiabatic small-polaron hopping is the most appropriate conduction model for these glasses. This is in sharp contrast with the behaviour of the Mn-free V 2 O 5 -TeO 2 glass, in which non-adiabatic hopping takes place. High-temperature conductivity data satisfy Mott's small-polaron hopping model and also a model proposed by Schnakenberg in 1968. A power-law behaviour † ac = A y s , with s < 1) is well exhibited by the ac conductivity † ac data of these glasses. Analysis of dielectric data indicates a Debye-type relaxation behaviour with a distribution of relaxation times. The MnO-concentration-dependent † ac data follow an overlapping large-polaron tunnelling model over the entire range of temperatures studied. The estimated model parameters are reasonable and consistent with changes in composition. (shrink)

In the yeast Saccharomyces cerevisiae three positive transcriptional control elements are activated by stress conditions: heat shock elements (HSEs), stress response elements (STREs) and AP‐1 responsive elements (AREs). HSEs bind heat shock transcription factor (HSF), which is activated by stress conditions causing accumulation of abnormal proteins. STREs mediate transcriptional activation by multiple stress conditions. They are controlled by high osmolarity via the HOG signal pathway, which comprises a MAP kinase module and a two‐component system homologous to prokaryotic signal transducers. AREs (...) bind the transcription factor Yap1p. The three types of control elements seem to have overlapping, but distinct functions. Some stress proteins encoded by HSE‐regulated genes are necessary for growth of yeast under moderate stress, products of STRE‐activated genes appear to be important for survival under severe stress and ARE‐controlled genes may mainly function during oxidative stress and in the response to toxic conditions, such as caused by heavy metal ions. (shrink)

Acidophilic autotrophic thiobacilli, which are able to oxidize metal and solubilize sulphide ores, are used industrially to leach metals from mineral ores. Genetic manipulation of the thiobacilli has the potential for the production of leaching bacteria with desirable characteristics for industry. In this review we examine the development of genetic systems in the thiobacilli and the present status of molecular genetics in the group.

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)

Similarities in properties among pairs of metallic elements and their compounds in the lower-right quadrant of the Periodic Table have been named the ‘Knight’s Move’ relationship. Here, we have undertaken a systematic study of the only two ‘double-pairs’ of ‘Knight’s Move’ elements within this region: copper-indium/indium-bismuth and zinc-tin/tin-polonium, focussing on: metal melting points; formulas and properties of compounds; and melting points of halides and chalcogenides. On the basis of these comparisons, we conclude that the systematic evidence for ‘Knight’s Move’ (...) relationships derives from similarities in formulas and properties of matching pairs of compounds in the same oxidation state. Physical properties, such as melting points, do not provide consistent patterns and trends and hence should not be considered as a common characteristic of this relationship. (shrink)

The Hubbard model is studied at half filling, using two complementary variational wave functions, the Gutzwiller ansatz for the metallic phase at small values of the interaction parameter U and its analog for the insulating phase at large values of U. The metallic phase is characterized by the Drude weight, which exhibits a jump at the critical point Uc. In the insulating phase the system behaves as a collection of dipoles which increase both in number and in size as (...) U gets smaller. The two wave functions are able to describe the two asymptotic regimes (small and large values of U, respectively), but they can no longer be trusted in the region of the Mott transition (U≈Uc). More powerful methods are needed to study, for instance, the divergence of the electric susceptibility for U→Uc. (shrink)

Nucleation and motion of kink pairs on partial dislocations are examined by elasticity theory for materials with a high Peierls stress. Two approaches are used: one considers the change in average stacking-fault energy due to alloying elements and the other considers the change in local SFE due to a nearby solute atom. Both approaches highlight the role of SFE on kink nucleation, propagation and annihilation and both furnish strain rate as a function of stress, temperature and SFE. Model predictions are (...) compared with yield stress data for two systems: firstly, an intermetallic, MoSi 2 , which softens for alloying elements that decrease the SFE and hardens for Re additions that increase the SFE; secondly, a ceramic oxide, MgO-Al 2 O 3 spinel, which softens with increasing addition of excess alumina and at the same time exhibits a decrease in SFE. The average SFE approach agrees qualitatively with the data while quantitative agreement is obtained with the local SFE approach. The possibility is considered that the model applies to other materials, such as TiAl, HfV 2 and Fe 3 Al, which show softening with certain alloying additions. One requirement is that the dislocations are dissociated more than a few atomic distances; otherwise kink nucleation occurs on the perfect dislocation . Hence the model does not apply to materials such as bcc metals which only have a core dissociation. Normal hardening effects of solutes from size and modulus misfits are additive with any softening effects from a decrease in SFE and so may mask the latter, as occurs for W additions to MoSi 2. (shrink)

This paper concentrates on the possible segregation of indium and gallium and competitive segregation of gallium and indium at atomically flat parallel {111}-oriented Cu-MnO interfaces. The segregation of gallium at Cu-MnO interfaces after introduction of gallium in the copper matrix of internally oxidized Cu-1 at.% Mn could be hardly detected with energy-dispersive spectrometry in a field emission gun transmission electron microscope. After a heat treatment to dissolve indium in the copper matrix, gallium has a weak tendency to segregate, that is (...) 2.5 at.% Ga per monolayer at the interface compared with 2 at.% in the copper matrix. The striking result is that this gallium segregation is observable because it does not occur at the metal side of the interface but in the first two monolayers at the oxide side. Using the same heat treatment as for introducing indium in the sample, but without indium present, gallium segregates strongly at the oxide side of the Cu-MnO interface with a concentration of about 14.3 at.% in each monolayer of the two. In contrast, the presence of gallium has no influence on the segregation of indium towards Cu-MnO interfaces, because the outermost monolayer at the metal side of the interface contains 17.6 at.% In, that is similar to previously found results. This leads to the intriguing conclusions, firstly, that, in contrast with antimony and indium, gallium segregates at the oxide side of the interface and, secondly, that the presence of indium strongly hampers gallium segregation. The results from analytical transmission electron microscopy on gallium segregation are supported by high-resolution transmission electron microscopy observations. (shrink)

The lanthanide elements from lanthanum to lutetium inclusive are incorporated into the body of the periodic table. They are subdivided into three sub-groups according to their important oxidation states: La to Sm, Eu to Tm, Yb and Lu, so that Eu and Yb fall directly below Ba; La, Gd, Lu form a column directly below Y; Ce and Tb fall in a vertical line between Zr and Hf. Pm falls below Tc; both are radioactive, and not naturally occurring. The elements (...) with easily attained 2+ and 4+ oxidation states are grouped and clearly differentiated. Gadolinium has an important position as the centre of four triads in the block of elements that surround it– La, Gd, Lu; Ba, Gd, Hf; Eu, Gd, Tb; Yb, Gd, Ce. This new arrangement has the advantages of compactness, simplicity and clarity – there are no tie lines; and important oxidation states of these metals are emphasized. The actinides are also accommodated within this system, and element 114 falls naturally below lead in Group 14. (shrink)

In the study of innovation institutions, it is important to consider how different institutional models can affect a research organization in conducting or funding successful work. As an industry collaborative, Semiconductor Research Corporation provides an example of a privately funded institution that leverages the inputs of several member companies, along with federal funding, to accomplish innovation in its mission area. SRC has several component programs, all attempting to find innovative solutions to semiconductor problems, but on different time scales, and in (...) different technology areas. But how does SRC use its resources to ensure these goals? Through data gathered from semi-structured qualitative interviews and SRC documentation, this paper addresses that question. SRC has found a way to leverage industry money to motivate and develop a robust field of university research for over 30 years. SRC uses several mechanisms for maintaining an application focused, member-centered decision process, institutional flexibility, and strong ties between industry contributors and university researchers. SRC has continued to keep its members satisfied by training thousands of graduate students for employment in their member companies, by focusing on precompetitive research that addresses industry requirements, and doing so in a manner that operates leanly, with low overhead to its funders. Given these successes, we identify aspects of SRC operations, such as a focus on its member company needs, frequent interactions between funders and researchers, flexible funding mechanisms, and focus on workforce development, that may be diffusible to innovation institutions, including federal research efforts. (shrink)

The environment can elicit biological responses such as oxidative stress (OS) and inflammation as a consequence of chemical, physical, or psychological changes. As population studies are essential for establishing these environment-organism interactions, biomarkers of OS or inflammation are critical in formulating mechanistic hypotheses. By using examples of stress induced by various mechanisms, we focus on the biomarkers that have been used to assess OS and inflammation in these conditions. We discuss the difference between biomarkers that are the result of a (...) chemical reaction (such as lipid peroxides or oxidized proteins that are a result of the reaction of molecules with reactive oxygen species) and those that represent the biological response to stress, such as the transcription factor NRF2 or inflammation and inflammatory cytokines. The high-throughput and holistic approaches to biomarker discovery used extensively in large-scale molecular epidemiological exposome are also discussed in the context of human exposure to environmental stressors. We propose to consider the role of biomarkers as signs and to distinguish between signs that are just indicators of biological processes and proxies that one can interact with and modify the disease process. (shrink)

The theory stating that oxidative stress is at the root of several diseases is extremely popular. However, so far, no antioxidant is recommended or offered by healthcare systems neither approved as therapy by regulatory agencies that base their decisions on evidence-based medicine. This is simply because, so far, despite many preclinical and clinical studies indicating a beneficial effect of antioxidants in many disease conditions, randomised clinical trials have failed to provide the evidence of efficacy required for drug approval. In this (...) review, we discuss the levels of evidence required to claim causality in preclinical research on OS, the weakness of the oversimplification associated with OS theory of disease and the importance of the narrative in its popularity. Finally, from a more translational perspective, we discuss the reasons why antioxidants acting by scavenging reactive oxygen species might not only prevent their detrimental effects but also interfere with essential signalling roles. We propose that ROS have a complex metabolism and are generated by different enzymes at diverse sites and with different timing. Aggregating this plurality of systems in a single theory of disease may not be the best way to develop new drugs, and future research may need to focus on specific oxygen-toxifying pathways rather than on non-specific ROS scavengers. Finally, similarly to what is nowadays required for clinical trials, we recommend making unpublished data available in repositories, as this will allow big data approaches or meta-analyses without the blinders of the publication bias. (shrink)