Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. A variety of materials including cyclodextrins, metal complexes, porphyrins, polymers, dendrimers and biomolecules have been extensively explored to mimic the structures and functions of naturally occurring enzymes. Recently, some nanomaterials have been found to exhibit unexpected enzyme-like activities, and great advances have been made in this area due to the tremendous progress in nano-research and the unique characteristics of nanomaterials. To highlight the progress in the field of nanomaterial-based artificial enzymes (nanozymes), this review discusses various nanomaterials that have been explored to mimic different kinds of enzymes. We cover their kinetics, mechanisms and applications in numerous fields, from biosensing and immunoassays, to stem cell growth and pollutant removal. We also summarize several approaches to tune the activities of nanozymes. Finally, we make comparisons between nanozymes and other catalytic materials (other artificial enzymes, natural enzymes, organic catalysts and nanomaterial-based catalysts) and address the current challenges and future directions (302 references).

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes

Polycyclic Hydrocarbons Vol. 1. Pp. xxvi + 487. 126S. (With a chapter on carcinogenesis by Regina Schoental.) Vol. 2. Pp. lvii + 487. 140s. By E. Clar. (London and New York: Academic Press; Berlin: Springer-Verlag, 1964.)

Polycyclic Aromatic Hydrocarbons

The new tectonic map of the Alps is based on the combination of purely structural data with criteria regarding paleogeographical affiliation and/or tectono-metamorphic evolution. The orogenic evolution of the Alps is discussed using a combination of maps and paleogeographical reconstructions. It is proposed that the Alps are the product of two orogenies, a Cretaceous followed by a Tertiary one. While the former is related to the closure of an embayment of the Meliata ocean into Apulia, the latter is due to the closure of the Alpine Tethys between Apulia and Europe. The along-strike changes in the overall architecture, as for example revealed by geophysical-geological transects, are by far more substantial than hitherto believed. It appears that the Alps are still far from being over-investigated, as is demonstrated by many surprising recent findings based on field geology, laboratory results and geophysical methods of deep sounding.

/pdf/tectonic-map-and-overall-architecture-of-the-alpine-orogen-23efh3jp0j.pdf

Tectonic map and overall architecture of the Alpine orogen

Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of biogeochemical redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms coupled to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe, Mn, C, P, N, S, Cr, Cu, Co, As, Sb, Se, Hg, Tc, a...

http://pubs.acs.org/doi/pdf/10.1021/es9026248

Biogeochemical Redox Processes and their Impact on Contaminant Dynamics

This review provides a comprehensive evaluation of the state-of-knowledge of radiation effects in crystalline ceramics that may be used for the immobilization of high-level nuclear waste and plutonium. The current understanding of radiation damage processes, defect generation, microstructure development, theoretical methods, and experimental methods are reviewed. Fundamental scientific and technological issues that offer opportunities for research are identified. The most important issue is the need for an understanding of the radiation-induced structural changes at the atomic, microscopic, and macroscopic levels, and the effect of these changes on the release rates of radionuclides during corrosion.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/09D70E1FB1A625EC09BB98883C3A5ED3/S0884291400044411a.pdf/div-class-title-radiation-effects-in-crystalline-ceramics-for-the-immobilization-of-high-level-nuclear-waste-and-plutonium-div.pdf

Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium

Traffic-related non-exhaust particulate matter mainly consists of tire wear, brake wear, and road wear. For this study, passive-samplers were placed near highly frequented roads in industrial, agricultural, and urban environments with the aim of collecting and characterizing super-coarse (> 10 µm) airborne particles. Single-particle analysis using SEM-EDX was conducted on more than 500 particles with nearly 1500 spectra to determine their size, shape, volume, and chemical composition. The ambient aerosol near all studied roads is dominated by traffic-related abrasion particles, amounting to approximately 90 vol%. The majority of the particles were composites of tire-, road-, and brake-abrasion material. The particle assemblages differed in size distribution, composition, and structure depending on driving speed, traffic flow, and traffic fleet. Our study documents that tire wear significantly contributes to the flux of microplastics into the environment. A decrease in the release of this abrasion material, however, is unlikely in the near future.

/pdf/tire-abrasion-as-a-major-source-of-microplastics-in-the-5aef4hjt3l.pdf

Tire Abrasion as a Major Source of Microplastics in the Environment

Epidote-group minerals rich in rare earth elements (REE), in particular allanite, are common accessory phases in igneous, metamorphic, metasomatic, and sedimentary rocks. Small amounts of REE are present in most epidote-group minerals, but in allanite—and the related minerals dissakisite, ferriallanite, dollaseite, khristovite and androsite—the REE are essential structural constituents. An important characteristic of REE-rich epidote-group minerals is that their octahedrally coordinated M sites contain major amounts of divalent cations. This paper summarizes literature data for these minerals and discusses their chemistry, occurrence, phase relations, and petrologic and geologic significance. The chapter emphasizes allanite, because it is the most common and best-studied of the REE-rich epidote-group minerals.

Epidote-group minerals contain isolated silicon tetrahedra and corner-sharing groups of two tetrahedra, and are thus assigned to the disilicate or sorosilicate structural family (for a detailed description of the structure, see Franz and Liebscher 2004). The epidote-group structural formula is A2M3(SiO4)(Si2O7)(O,F)(OH), or in a simplified form A2M3Si3O11(O,F)(OH), in which A = Ca, Sr, Pb2+, Mn2+, Th, REE3+, and U, and M = Al, Fe3+, Fe2+, Mn3+, Mn2+, Mg, Cr3+, and V3+ (Deer et al. 1986). There are two structurally different A sites, A(1) and A(2), with different coordination numbers, and there are three different M sites, M(1), M(2), and M(3), which are all octahedrally coordinated (Ueda 1955; Dollase 1971).

In epidote-group minerals, trivalent REE are accommodated in the A sites, which in endmember epidote both contain Ca. The incorporation of REE3+ is commonly charge balanced by a divalent cation (Fe2+, Mn2+, Mg) substituted for a trivalent one in the M sites (Table 1 …

Allanite and Other REE-Rich Epidote-Group Minerals

Epidote-group minerals are monoclinic in symmetry and have topology consistent with space group P21/m and the general formula A2M3(T2O7)(TO4)(O,F)(OH,O). Zoisite is an orthorhombic polymorph of clinozoisite Ca2Al3(Si2O7)(SiO4)O(OH) and is thus not considered a member of the epidote-group. Epidote-group minerals are divided into three subgroups. (1) Members of the clinozoisite subgroup are derived from the mineral clinozoisite Ca2Al3(Si2O7)(SiO4)O(OH) by homovalent substitutions only. The key cation- and anion-sites are A1 = M2+, A2 = M2+, M1 = M3+, M2 = M3+, M3 = M3+, O4 = O2-, O10 = (OH)-. In other words, the dominant valence as listed above must be maintained. (2) Members of the allanite subgroup are REE-rich minerals typified by the eponymous mineral "allanite". This subgroup may be derived from clinozoisite by homovalent substitutions and one coupled heterovalent substitution of the type A2(REE)3+ + M3M2+ → A2Ca2+ + M3M3+. Thus the valences on the key sites are: A1 = M2+, A2 = M3+, M1 = M3+, M2 = M3+, M3 = M2+, O4 = O2-, O10 = (OH)-. (3) Members of the dollaseite subgroup are REE-rich minerals typified by the eponymous mineral "dollaseite". This subgroup may be derived from clinozoisite by homovalent substitutions and two coupled heterovalent substitutions of the type A2(REE)3+ + M3M2+ → A2Ca2+ + M3M3+ and M1M2+ + O4F - → M1M3+ + O4O-2. Thus the valences on the key sites are: A1 = M2+, A2 = M3+, M1 = M2+, M2 = M3+, M3 = M2+, O4 = F-, O10 = (OH)-. The key cation-sites M3 and A1 (and, in principle, M2) determine the root name. In both clinozoisite and allanite subgroups no prefix is added to the root name if M1 = Al. The prefixes ferri, mangani, chromo, and vanado indicate dominant Fe3+, Mn3+, Cr3+, and V3+ on M1, respectively. In the dollaseite subgroup no prefix is added to the root name if M1 = Mg. Otherwise a proper prefix must be attached; the prefixes ferro and mangano indicate dominant Fe2+ and Mn2+ at M1, respectively. The dominant cation on A2 (other than Ca) is treated according to the Extended Levinson suffix designation. This simple nomenclature requires renaming of the following approved species: Niigataite (old) = clinozoisite-(Sr) (new), hancockite (old) = epidote-(Pb) (new), tweddillite (old) = manganipiemontite-(Sr) (new). Minor modifications are necessary for the following species: Strontiopiemontite (old) = piemon- tite-(Sr) (new), androsite-(La) (old) = manganiandrosite-(La) (new). Before a mineral name can be assigned, the proper subgroup has to be determined. The determination of a proper subgroup is made by the dominating valence at M3, M1, and A2 expressed as M2+ and or M3+, not by a single, dominant ion (i.e., Fe2+, or Mg, or Al). In addition, the dominant valence on O4: X - or X 2- must be ascertained. (M2+)A2 > 0.50, (M3+)M3 > 0.50 → clinozoisite subgroup, (M3++ M4+)A2 > 0.50, (M2+)M3 > 0.50 → allanite subgroup, {(M2+)M3+M1 - (M3++ M4+)A2 } > 0.50 and (X - )O4 > 0.5 → dollaseite subgroup. Coupled heterovalent substitutions in epidote-group minerals require a special application of the so-called 50 % rule in solid-solution series. (1) Clinozoisite subgroup: The dominant trivalent cation on M3 determines the name, whereas the A2 cation appearing in the suffix has to be selected from among the diva- lent cations. (2) Allanite and dollaseite subgroups: For the sites involved in the charge compensation of a heterovalent substitution in A2 and O4 (i.e. M3 in the allanite subgroup; M3 and M1 in the dollaseite subgroup), identification of the relevant end-member formula must take into account the dominant divalent charge-compensating octahedral cation (M2+) and not the dominant cation

Recommended nomenclature of epidote-group minerals

A new scheme of nomenclature for the pyrochlore supergroup, approved by the CNMNC-IMA, is based on the ions at the A, B and Y sites. What has been referred to until now as the pyrochlore group should be referred to as the pyrochlore supergroup, and the subgroups should be changed to groups. Five groups are recommended, based on the atomic proportions of the B atoms Nb, Ta, Sb, Ti, and W. The recommended groups are pyrochlore, microlite, rom£ite, betafite, and elsmoreite, respectively. The new names are composed of two prefixes and one root name (identical to the name of the group). The first prefix refers to the dominant anion (or cation) of the dominant valence [or HO or □] at the Y site. The second prefix refers to the dominant cation of the dominant valence [or HO or □] at the A site. The prefix "keno-" represents "vacancy". Where the first and second prefixes are equal, then only one prefix is applied. Complete descriptions are missing for the majority of the pyrochlore-supergroup species. Only seven names refer to valid species on the grounds of their complete descriptions: oxycalciopyrochlore, hydropyrochlore, hydroxykenomicrolite, oxystannomicrolite, oxystibiomicrolite, hydroxycalciorom6ite, and hydrokenoelsmoreite. Fluornatromicrolite is an IMA-approved mineral, but the complete description has not yet been published. The following 20 names refer to minerals that need to be completely described in order to be approved as valid species: hydroxycalciopyrochlore, fiuornatropyrochlore, fluorcalciopyrochlore, fluorstrontiopyrochlore, fluorkenopyrochlore, oxynatropyrochlore, oxyplumbopyrochlore, oxyyttropyrochlore-(Y), kenoplumbopyrochlore, fluorcalciomicrolite, oxycalciomicrolite, kenoplumbomicrolite, hydromicrolite, hydrokenomicrolite, oxycalciobetafite, oxyuranobetafite, fluornatroromite, fluorcalcioromeite, oxycalcioromdite, and oxyplumborom£ite. For these, there are only chemical or crystal-structure data. Type specimens need to be defined. Potential candidates for several other species exist, but are not sufficiently well characterized to grant them any official status. Ancient chemical data refer to wet-chemical analyses and commonly represent a mixture of minerals. These data were not used here. All data used represent results of electron-microprobe analyses or were obtained by crystal-structure refinement. We also verified the scarcity of crystal-chemical data in the literature. There are crystal-structure determinations published for only nine pyrochlore-supergroup minerals: hydropyrochlore, hydroxykenomicrolite, hydroxycalcioromite, hydrokenoelsmoreite, hydroxycalciopyrochlore, fluorcalciopyrochlore, kenoplumbomicrolite, oxycalciobetafite, and fluornatrorom£ite. The following mineral names are now discarded: alumotungstite, bariomicrolite, bariopyrochlore, bindheimite, bismutomicrolite, bismutopyrochlore, bismutostibiconite, calciobetafite, ceriopyrochlore-(Ce), cesstibtantite, ferritungstite, jixianite, kalipyrochlore, monimolite, natrobistantite, partzite, plumbobetafite, plumbomicrolite, plumbopyrochlore, stannomicrolite, stetefeldtite, stibiconite, stibiobetafite, stibiomicrolite, strontiopyrochlore, uranmicrolite, uranpyrochlore, yttrobetafite-(Y), and yttropyrochlore-(Y).

Reto Gieré

Papers

Tire Abrasion as a Major Source of Microplastics in the Environment

Allanite and Other REE-Rich Epidote-Group Minerals

Recommended nomenclature of epidote-group minerals

The pyrochlore supergroup of minerals: nomenclature

The role of secondary minerals in controlling the migration of arsenic and metals from high-sulfide wastes (Berikul gold mine, Siberia)