This review discusses the main developments in the systematics of coccoid green algae over the last three decades. The relationships of key groups of planktonic coccoid green algae are shown in the ...phylogenetic trees of Chlorophyceae and Trebouxiophyceae. The trees clearly show that the morphology of these algae do not adequately reflect their phylogenetic position. Different phylogenetic species can be hidden under one and the same morphotype. As most of the genera have a polyphyletic origin, they are in need of a systematic re-evaluation. Species classification using the phylogenetic species concept resulted in the establishment of new genera with smaller numbers of species and the description of new species that are not distinguishable by light microscopy. An overview of genera is given in tables and the revised designations of species as contained in the harmonized taxon list of the European Water Framework Directive lists is provided. In this transitional phase from an artificial to a more natural systematics of algae, field biologists and ecologists as well as molecular biologists must strengthen their interdisciplinary cooperation. The alignment of eco-functional groups of algae with true species identities using the barcoding conception will provide a better understanding of the interaction between organisms and their environment.
The demand for lithium-ion batteries (LIBs) with high mass-specific capacities, high rate capabilities and long-term cyclabilities is driving the research and development of LIBs with nickel-rich NMC ...(LiNi
x
Mn
y
Co
1−
x
−
y
O
2
,
x
⩾
0.5
) cathodes and graphite (Li
x
C
6
) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid electrolyte interfaces are also reviewed, and trade-offs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.
Graphic Abstract
The demand for lithium-ion batteries (LIBs) with high mass specific capacities, high rate capabilities and longterm cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNi
x
Mn
y
Co
1−
x
−
y
O
2
,
x
≥ 0.5) cathodes and graphite (Li
x
C
6
) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid-electrolyte interfaces (SEIs) are also reviewed and tradeoffs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.
This work establishes a new method to measure the electrochemically active surface area (AECSA) of nickel electrodes, in situ. The addition of 0.08 mol L−1 of an oxalate salt to an alkaline ...electrolyte solution shifts the half-wave potential of the Ni(II)/Ni(III) redox pair by about −80 mV. Further, these peaks are very narrow. The sharpest peak in this work has a full width at half maximum (FWHM) of just 11 mV. This unusual sharpness is attributed to the layered structure of nickel hydroxides and the adsorption of oxalate from the solution on the (001) surface. This is supported by attenuated total reflectance infrared (ATR-IR) peaks measured at 1265 cm−1, 1655 cm−1, and 1713 cm−1, which correspond to mononuclear bidentate oxalate bonded to nickel. At sufficiently fast potential scan rates (≥150 mV s−1), the adsorbed oxalate limits growth of the surface hydroxide to a single layer. During the reverse scan, the surface NiOOH/Ni(OH)2 reduction peak is well-separated from other electrochemical processes and may be used to accurately and precisely measure the AECSA. The error of this method is estimated at < 10%.
The present work utilizes Raman and infrared (IR) spectroscopy, supported by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to re-examine the fine structural details of Ni(OH)2, ...which is a key material in many energy-related applications. This work also unifies the large body of literature on the topic. Samples were prepared by the galvanostatic basification of nickel salts and by aging the deposits in hot KOH solutions. A simplified model is presented consisting of two fundamental phases (α and β) of Ni(OH)2 and a range of possible structural disorder arising from factors such as impurities, hydration, and crystal defects. For the first time, all of the lattice modes of β-Ni(OH)2 have been identified and assigned using factor group analysis. Ni(OH)2 films can be rapidly identified in pure and mixed samples using Raman or IR spectroscopy by measuring their strong O–H stretching modes, which act as fingerprints. Thus, this work establishes methods to measure the phase, or phases, and disorder at a Ni(OH)2 sample surface and to correlate desired chemical properties to their structural origins.
One of the first steps in optimizing future prevention and appropriately allocating resources to future diagnosis and treatment of Gestational diabetes (GDM) is to quantify its burden. The aim of ...this study was therefore to conduct a systematic review of current international literature on the prevalence of GDM with a focus on advanced economies.
Based on literature searches with the database “PubMed” we included studies with a publication date between 2000 and 2011. All studies were classified independently by two authors. In accordance with the PRISMA Statement we identified 27 original studies.
The prevalence of GDM varies substantially between populations with a range of 1.7–11.6%. Patient self-reports yield higher prevalence estimates than values that are based on medical diagnosis or clinical diagnostic tests. Prevalence seems to vary considerably within Europe with higher prevalence values being observed in Southern Europe than in Northern and Central Europe. Prevalence values from studies from Australia and North America were within this range.
This review provides a comprehensive and sound summary of the current state of research on the prevalence of GDM in advances economies as a first step in identifying starting points for future interventions.
Shifts in the nutritional mode between phototrophy, mixotrophy and heterotrophy are a widespread phenomenon in the evolution of eukaryotic diversity. The transition between nutritional modes is ...particularly pronounced in chrysophytes and occurred independently several times through parallel evolution. Thus, chrysophytes provide a unique opportunity for studying the molecular basis of nutritional diversification and of the accompanying pathway reduction and degradation of plastid structures. In order to analyze the succession in switching the nutritional mode from mixotrophy to heterotrophy, we compared the transcriptome of the mixotrophic Poterioochromonas malhamensis with the transcriptomes of three obligate heterotrophic species of Ochromonadales. We used the transcriptome of P. malhamensis as a reference for plastid reduction in the heterotrophic taxa. The analyzed heterotrophic taxa were in different stages of plastid reduction. We investigated the reduction of several photosynthesis related pathways e.g. the xanthophyll cycle, the mevalonate pathway, the shikimate pathway and the tryptophan biosynthesis as well as the reduction of plastid structures and postulate a presumable succession of pathway reduction and degradation of accompanying structures.
Graphene was prepared by excimer laser irradiation reduction of graphite oxide dissolved in an aqueous solution at different laser energies and irradiation time. The morphologies and structure of the ...laser reduced graphene were characterized using scanning electron microscopy, low angle X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. The XRD results confirm that the deoxygenation of the graphite oxide sheets occurred almost completely for all laser irradiation conditions used. The graphene fabricated by laser irradiation reduction appears to be randomly aggregated, crumpled, disordered and small sheet solid material. The total amount of oxygen functional groups reduced significantly and the CC/CO intensity ratio increased, however, the atomic percentages of the CO double bond were increased after laser reduction. The laser reduced graphene was used as the electrode active material for supercapacitors and its specific capacitance was evaluated in a two electrode cell in either a 0.5 M Na2SO4 aqueous or a 1 M Tetraethylammoniumtetrafluoroborate acetonitrile based electrolyte. The specific capacitance of the laser fabricated graphene was found to depend on the energy and irradiation time of the laser. The highest specific capacitance was determined to be 141 F/g at 1.04 A/g and 84 F/g at 1.46 A/g in the aqueous and ACN electrolytes, respectively.
•Excimer laser photo-reduction of graphite oxide to form graphene.•XRD, XPS and SEM characterization of laser reduced graphene.•Supercapacitance performance of laser reduced graphene.•Specific current and capacitance determined by electrochemical measurements.
A rapid synthesis method for the preparation of PtRu colloids and their subsequent deposition on high surface area carbons is presented. The reaction mechanism is shown to involve the oxidation of ...the solvent, ethylene glycol, to mainly glycolic acid or, depending on the pH, its anion, glycolate, while the Pt(+IV) and Ru(+III) precursor salts are reduced. Glycolate acts as a stabilizer for the PtRu colloids and the glycolate concentration, and hence the size of the resulting noble metal colloids is controlled via the pH of the synthesis solution. Carbon-supported PtRu catalysts of controlled size can be prepared within the range of 0.7−4 nm. Slow scan X-ray diffraction and high-resolution transmission electron microscopy show the PtRu catalysts to be crystalline. The Ru is partly dissolved in the face-centered cubic Pt lattice, but the catalysts also consist of a separate, hexagonal Ru phase. The PtRu catalysts appear to be of the same composition independent of the catalyst size in the range of 1.2−4 nm. Particular PtRu catalysts prepared in this work display enhanced activities for the CH3OH electro-oxidation reaction when compared to two commercial catalysts.
PDF
