Bacterial cells can vary greatly in size, from a few hundred nanometers to hundreds of micrometers in diameter. Filamentous cable bacteria also display substantial size differences, with filament diameters ranging from 0.4 to 8 µm. We analyzed the genomes of cable bacterium filaments from 11 coastal environments of which the resulting 23 new genomes represent 10 novel species-level clades of Candidatus Electrothrix and two clades that putatively represent novel genus-level diversity. Fluorescence in situ hybridization with a species-level probe showed that large-sized cable bacteria belong to a novel species with the proposed name Ca. Electrothrix gigas. Comparative genome analysis suggests genes that play a role in the construction or functioning of large cable bacteria cells: the genomes of Ca. Electrothrix gigas encode a novel actin-like protein as well as a species-specific gene cluster encoding four putative pilin proteins and a putative type II secretion platform protein, which are not present in other cable bacteria. The novel actin-like protein was also found in a number of other giant bacteria, suggesting there could be a genetic basis for large cell size. This actin-like protein (denoted big bacteria protein, Bbp) may have a function analogous to other actin proteins in cell structure or intracellular transport. We contend that Bbp may help overcome the challenges of diffusion limitation and/or morphological complexity presented by the large cells of Ca. Electrothrix gigas and other giant bacteria. IMPORTANCE In this study, we substantially expand the known diversity of marine cable bacteria and describe cable bacteria with a large diameter as a novel species with the proposed name Candidatus Electrothrix gigas. In the genomes of this species, we identified a gene that encodes a novel actin-like protein [denoted big bacteria protein (Bbp)]. The bbp gene was also found in a number of other giant bacteria, predominantly affiliated to Desulfobacterota and Gammaproteobacteria, indicating that there may be a genetic basis for large cell size. Thus far, mostly structural adaptations of giant bacteria, vacuoles, and other inclusions or organelles have been observed, which are employed to overcome nutrient diffusion limitation in their environment. In analogy to other actin proteins, Bbp could fulfill a structural role in the cell or potentially facilitate intracellular transport.

The propagation of dam-break waves on different rough beds was observed to be quasi-steady in the range < [CDATA[11.3 < x/h dam, where is measured from the dam position. These quasi-steady propagation speeds converge with the steady ideal fluids model of Stoker (Water Waves, 1957, Interscience) when the tailwater depth becomes greater than, in the range <[CDATA[0.001< k_s/h_{dam}, where is the roughness and the depth behind the dam. Hence, this convergence encourages the use of Stoker's steady, ideal fluid solution to develop more general models, including friction effects due to bed roughness and/or viscosity. The new experimental data support a MacLaurin series for the celerity, in analogy with the series in terms of, derived for Stoker's model, being the tailwater depth. Compared with the retarding effect of the tailwater, 1 mm of roughness is found to be equivalent to 13 mm of tailwater, and 1 m of viscous length (, where is the kinematic viscosity and g the acceleration due to gravity) is equivalent to 1700 m of tailwater. While the MacLaurin series quantifies the similar effects of small roughness and small tailwater depths acting separately, the new data illustrate for the first time the complex interplay between tailwater and roughness on 'wet beds' with many details yet to be investigated. In particular, it was shown that a small amount of tailwater on a rough bed acts as a lubricant, so that is an increasing function of for <[CDATA[h 2.

The circular economy demands waste utilization for the production of high-value products, and this requires the development of novel processing routes. In this study, rare earth (La and Ce) oxides were completely (>99%) recovered from polishing waste by a combined novel reductive acid leaching and alkali treatment process. About 70% of rare earths were dissolved during the first leaching step. The undissolved rare earth compounds are converted to oxides/hydroxides by alkali treatment and dissolved in the acid solution – the 2nd leaching step – for the complete recovery of rare earths. The recovered rare earth oxides were used for producing in-situ high-value Al-La-Ce alloys with fused salt electrolysis. Mechanical properties of our Al-La-Ce alloys are similar to the known high temperature Al-Ce alloys. This development of new alloys by our novel process helps in utilization of both overproduced primary La and Ce oxides as well as La and Ce recovered from polishing waste.

Shear plates have previously been used to measure bed shear stresses under swash and dam-break waves. The present study has been focused on the large bed shear stresses near the tip and even at distances less than one plate length from the tip. In order to resolve this rapid stress variation, the shear plate was calibrated with respect to its step response as well as statically. Step response calibration enables the effects of the time lag and the natural frequency of the shear plate system to be removed. Thus, the initial variation of the bed shear stress during and just after the rise of the water level is resolved and opens the opportunity to investigate the boundary layer development close to the tip where other measurements have not previously succeeded. The bed shear stress τ_bed(t) initially increases almost linearly with time to a maximum, which occurs about 0.2 s after the passage of the contact point, while it takes about 2.0 s for the water surface level h(t) to rise to a quasi-steady level under the present experimental conditions. Thus, with h(t) and τ_bed(t) varying with different timescales, the simple assumption of τbed=τbed(roughnessdepth) is not supported. For a given dam-break, the peak bed shear stress depends on the tailwater level. In our tests with initial dam depth 400 mm and bed roughness 84 mm, τ_bed peaks at 210 Pa ± 20 Pa on dry beds decreases to peak values of the order 40 Pa with 98 mm tailwater depths. Quasi-steady τ_bed-values reached while the water surface is still quasi-steady, which are of the order 5–10 Pa. For dry beds, τ_bed shows a single peak followed by a smooth monotonical decay, while tailwater depths above 40 mm may lead to two almost equal, successive τ_bed-peaks and an oscillating decay. Graphic abstract: [Figure not available: see fulltext.]

One of the main applications of ceria (CeO ₂ ) is its use in glass polishing. About 16,000 tonnes of rare earth oxides, which is about 10% of total rare earth production, are used for polishing applications. The waste generated in glass polishing contains rare earths, along with other impurities. In this study, two different glass polishing waste samples were characterized and two different processes were proposed for the complete recovery of rare earths from polishing waste, i.e., an acid-based process and an alkali-based process. The polishing waste samples were characterized with inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA) and particle size analysis. Chemical analysis showed that sample A (CeO ₂ -rich waste from plate glass polishing) contained a high amount of impurities compared to sample B (CeO ₂ -rich waste from mirror polishing). XRD analysis showed that sample B contained CeO ₂ , LaO _0.65 F _1.7 and LaPO ₄ compounds, whereas sample A contained CaCO ₃ in addition to rare earth compounds. SEM-EDX analysis showed the presence of alumino-silicates in sample A. Leaching experiments were carried out at 75 ^◦ C at different acid concentrations for the recovery of rare earths from polishing waste samples. The leaching results showed that it is difficult to dissolve rare earths completely in acid solutions due to the presence of fluorides and phosphates. Hence, undissolved rare earths in the leach residue were further recovered by an alkali treatment with NaOH. In another approach, polishing waste samples were directly treated with NaOH at 500 ^◦ C. After alkali treatment followed by water leaching, rare earths can be completely dissolved during acid leaching. Rare earths from polishing waste can be recovered completely by both the acid-based process and the alkali-based process.

Electron transport within living cells is essential for energy conservation in all respiring and photosynthetic organisms. While a few bacteria transport electrons over micrometer distances to their surroundings, filaments of cable bacteria are hypothesized to conduct electric currents over centimeter distances. We used resonance Raman microscopy to analyze cytochrome redox states in living cable bacteria. Cable-bacteria filaments were placed in microscope chambers with sulfide as electron source and oxygen as electron sink at opposite ends. Along individual filaments a gradient in cytochrome redox potential was detected, which immediately broke down upon removal of oxygen or laser cutting of the filaments. Without access to oxygen, a rapid shift toward more reduced cytochromes was observed, as electrons were no longer drained from the filament but accumulated in the cellular cytochromes. These results provide direct evidence for long-distance electron transport in living multicellular bacteria.