We present the results of the first in-beam studies of a medium size (10\(\times\)10 cm\(^2\)) Resistive-Plate WELL (RPWELL): a single-sided THGEM coupled to a pad anode through a resistive layer of ...high bulk resistivity (\(\sim\)10\(^9 \Omega\)cm). The 6.2~mm thick (excluding readout electronics) single-stage detector was studied with 150~GeV muons and pions. Signals were recorded from 1\(\times\)1 cm\(^2\) square copper pads with APV25-SRS readout electronics. The single-element detector was operated in Ne\(5% \(\mathrm{CH_{4}}\)) at a gas gain of a few times 10\(^4\), reaching 99\(\%\) detection efficiency at average pad multiplicity of \(\sim\)1.2. Operation at particle fluxes up to \(\sim\)10\(^4\) Hz/cm\(^2\) resulted in \(\sim\)23\(\%\) gain drop leading to \(\sim\)5\(\%\) efficiency loss. The striking feature was the discharge-free operation, also in intense pion beams. These results pave the way towards robust, efficient large-scale detectors for applications requiring economic solutions at moderate spatial and energy resolutions.
The central question in the origin of life is to understand how structure can emerge from randomness. The Eigen theory of replication states, for sequences that are copied one base at a time, that ...the replication fidelity has to surpass an error threshold to avoid that replicated specific sequences become random because of the incorporated replication errors M. Eigen,
58 (10), 465-523 (1971). Here, we showed that linking short oligomers from a random sequence pool in a templated ligation reaction reduced the sequence space of product strands. We started from 12-mer oligonucleotides with two bases in all possible combinations and triggered enzymatic ligation under temperature cycles. Surprisingly, we found the robust creation of long, highly structured sequences with low entropy. At the ligation site, complementary and alternating sequence patterns developed. However, between the ligation sites, we found either an A-rich or a T-rich sequence within a single oligonucleotide. Our modeling suggests that avoidance of hairpins was the likely cause for these two complementary sequence pools. What emerged was a network of complementary sequences that acted both as templates and substrates of the reaction. This self-selecting ligation reaction could be restarted by only a few majority sequences. The findings showed that replication by random templated ligation from a random sequence input will lead to a highly structured, long, and nonrandom sequence pool. This is a favorable starting point for a subsequent Darwinian evolution searching for higher catalytic functions in an RNA world scenario.
•Salt marsh vegetation can reduce near-bed orbital velocities during storm surges.•Vegetation effect on orbital velocities varies with biophysical properties.•Flexible low-growing plant canopies show ...high resilience to storm surge conditions.•More rigid and tall plant canopies experience stem folding and breakage.•The contribution of vegetation to wave dissipation is plant species specific
Vegetation-wave interactions are critical in determining the capacity of coastal salt marshes to reduce wave energy (wave dissipation), enhance sedimentation and protect the shoreline from erosion. While vegetation-induced wave dissipation is increasingly recognized in low wave energy environments, little is known about: (i) the effect of vegetation on wave dissipation during storms when wave heights and water levels are highest; and (ii) the ability of different plant species to dissipate waves and to maintain their integrity under storm surge conditions. Experiments undertaken in one of the world’s largest wave flumes allowed, for the first time, the study of vegetation-wave interactions at near-field scale, under wave heights ranging from 0.1–0.9m (corresponding to orbital velocities of 2–91cms−1) and water depths up to 2m, in canopies of two typical NW European salt marsh grasses: Puccinellia maritima (Puccinellia) and Elymus athericus (Elymus). Results indicate that plant flexibility and height, as well as wave conditions and water depth, play an important role in determining how salt marsh vegetation interacts with waves. Under medium conditions (orbital velocity 42–63cms−1), the effect of Puccinellia and Elymus on wave orbital velocities varied with water depth and wave period. Under high water levels (2m) and long wave periods (4.1s), within the flexible, low-growing Puccinellia canopy orbital velocity was reduced by 35% while in the more rigid, tall Elymus canopy deflection and folding of stems occurred and no significant effect on orbital velocity was found. Under low water levels (1m) and short wave periods (2.9s) by contrast, Elymus reduced near-bed velocity more than Puccinellia. Under high orbital velocities (≥74cms−1), flattening of the canopy and an increase of orbital velocity was observed for both Puccinellia and Elymus. Stem folding and breakage in Elymus at a threshold orbital velocity≥42cms−1 coincided with a levelling-off in the marsh wave dissipation capacity, while Puccinellia survived even extreme wave forces without physical damage. These findings suggest a species-specific control of wave dissipation by salt marshes which can potentially inform predictions of the wave dissipation capacity of marshes and their resilience to storm surge conditions.
Proton gradients are essential for biological systems. They not only drive the synthesis of ATP, but initiate molecule degradation and recycling inside lysosomes. However, the high mobility and ...permeability of protons through membranes make pH gradients very hard to sustain in vitro. Here we report that heat flow across a water-filled chamber forms and sustains stable pH gradients. Charged molecules accumulate by convection and thermophoresis better than uncharged species. In a dissociation reaction, this imbalances the reaction equilibrium and creates a difference in pH. In solutions of amino acids, phosphate, or nucleotides, we achieve pH differences of up to 2 pH units. The same mechanism cycles biomolecules by convection in the created proton gradient. This implements a feedback between biomolecules and a cyclic variation of the pH. The finding provides a mechanism to create a self-sustained proton gradient to drive biochemical reactions.
The emergence of evermore complex entities from prebiotic building blocks is a key aspect of origins of life research. The RNA-world hypothesis posits that RNA oligomers known as ribozymes acted as ...the first self-replicating entities. However, the mechanisms governing the self-assembly of complex informational polymers from the shortest prebiotic building blocks were unclear. One open issue concerns the relation between concentration and oligonucleotide length, usually assumed to be exponentially decreasing. Here, we show that a competition of timescales in the self-assembly of informational polymers by templated ligation generically leads to nonmonotonic strand-length distributions with two distinct length scales. The first length scale characterizes the onset of a strongly nonequilibrium regime and is visible as a local minimum. Dynamically, this regime is governed by extension cascades, where the elongation of a “primer” with a short building block is more likely than its dehybridization. The second length scale appears as a local concentration maximum and reflects a balance between degradation and dehybridization of completely hybridized double strands in a heterocatalytic extension-reassembly process. Analytical arguments and extensive numerical simulations within a sequence-independent model allowed us to predict and control these emergent length scales. Nonmonotonic strand-length distributions confirming our theory were obtained in thermocycler experiments using random DNA sequences from a binary alphabet. Our work emphasizes the role of structure-forming processes already for the earliest stages of prebiotic evolution. The accumulation of strands with a typical length reveals a possible starting point for higher-order self-organization events that ultimately lead to a self-replicating, evolving system.
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