Инновационный фактор совершенствования внешнеэкономической деятельности предприятий Украины: теоретический аспект

Infragravity waves (0.005–0.05 Hz) have recently been observed to dissipate a large part of their energy in the short-wave (0.05–1 Hz) surf zone, however, the underlying mechanism is not well understood. Here, we analyse two new field data sets of near-bed pressure and velocity at up to 13 cross-shore locations in View the MathML source depth on a ≈1:80 and a ≈1:30 sloping beach to quantify infragravity-wave dissipation close to the shoreline and to identify the underlying dissipation mechanism. A frequency-domain Complex Eigenfunction analysis demonstrated that infragravity-wave dissipation was frequency dependent. Infragravity waves with a frequency larger than View the MathML source were predominantly onshore progressive, indicative of strong dissipation of the incoming infragravity waves. Instead, waves with a lower frequency showed the classic picture of cross-shore standing waves with minimal dissipation. Bulk infragravity reflection coefficients at the shallowest position (water depth View the MathML source) were well below 1 (≈0.20), implying that considerable dissipation took place close to the shoreline. We hypothesise that for our data sets infragravity-wave breaking is the dominant dissipation mechanism close to the shoreline, because the reflection coefficient depends on a normalised bed slope, with the higher infragravity frequencies in the mild-sloping regime where breaking is known to dominate dissipation. Additional numerical modelling indicates that, close to the shoreline of a 1:80 beach, bottom friction contributes to infragravity-wave dissipation to a limited extent, but that non-linear transfer of infragravity energy back to sea–swell frequencies is unimportant

FIRRM/C1orf112 is synthetic lethal with PICH and mediates RAD51 dynamics

Joint DNA molecules are natural byproducts of DNA replication and repair. Persistent joint molecules give rise to ultrafine DNA bridges (UFBs) in mitosis, compromising sister chromatid separation. The DNA translocase PICH (ERCC6L) has a central role in UFB resolution. A genome-wide loss-of-function screen is performed to identify the genetic context of PICH dependency. In addition to genes involved in DNA condensation, centromere stability, and DNA-damage repair, we identify FIGNL1-interacting regulator of recombination and mitosis (FIRRM), formerly known as C1orf112. We find that FIRRM interacts with and stabilizes the AAA + ATPase FIGNL1. Inactivation of either FIRRM or FIGNL1 results in UFB formation, prolonged accumulation of RAD51 at nuclear foci, and impaired replication fork dynamics and consequently impairs genome maintenance. Combined, our data suggest that inactivation of FIRRM and FIGNL1 dysregulates RAD51 dynamics at replication forks, resulting in persistent DNA lesions and a dependency on PICH to preserve cell viability. </p

Infragravity-wave dynamics in shallow water : energy dissipation and role in sand suspension and transport

Infragravity waves (20-200 s) receive their energy from sea-swell waves (2-20 s), and are thought to be important to beach erosion during storms, when they can reach up to several meters in height. Numerous studies have observed that on sandy beaches infragravity waves can lose a large part of their energy close to shore. The causes of this energy dissipation are unclear and are currently considered to be either by nonlinear energy transfers back to sea-swell frequencies, by infragravity-wave breaking, or a combination of the two. In addition, the influence of infragravity waves on the suspension of sand, and the resulting cross-shore sand transport, are not well understood. The overarching aim of this thesis is to improve the understanding of infragravity wave dynamics in the nearshore zone of sandy beaches, with a focus on their energy dissipation and role in sand suspension and transport. New field data observations indicate that the infragravity waves dissipated up to 80% of their energy close to the shoreline (water depths < 0.7 m) and depended both on the particular infragravity-wave period and the local beach slope, with less dissipation on steeper beaches, and with longer-period infragravity waves. Overall, infragravity-wave breaking seems to be the main cause for the large energy losses, as it occurs in very shallow water, and non-linear energy transfers back to sea-swell waves were not observed. Energy transfers involving infragravity frequencies were investigated in more detail with a high-resolution lab dataset of wave fields propagating over a gently sloping beach. During infragravity-wave energy dissipation, infragravity-infragravity interactions dominated, and forced strongly asymmetrically shaped infragravity waves, leading to their breaking close to shore. The numerical model SWASH was subsequently used to study the various effects of beach steepness, profile shape and offshore wave conditions on the type of nonlinear energy transfer during infragravity-wave dissipation, and in particular beach steepness was seen to affect infragravity-wave energy loss. On gentle slopes, where infragravity-wave energy dominates the water motion close to shore, infragravity-infragravity interactions dominated and caused large infragravity energy losses. On the contrary, during infragravity-wave energy dissipation on steeper slopes, sea-swell energy dominated the water motion everywhere, and infragravity waves interacted with the sea-swell wave spectral peak, and relatively little infragravity-wave dissipation occurred. To study the effect of beach slope on cross-shore sand suspension and transport by infragravity waves, two field data sets were analyzed, obtained at beaches contrasting in bed slope. On the gently sloping beach the ratio of infragravity- to sea-swell wave height (H­IG/HSW) is typically larger than 0.4, and sand is suspended under offshore directed infragravity-wave velocities. The resulting offshore infragravity transport contributes up to 60% of the total cross-shore transport. On the steeper sloping beach, H­IG/HSW is typically lower than 0.4 and sand is suspended on the infragravity timescale by sea-swell waves. The correlation between the sea-swell wave group and infragravity orbital velocities (r0) then determines whether infragravity-wave sand transport is offshore or onshore directed. During these conditions, the infragravity-wave component contributes for less than 20% to the total cross-shore transport

Infragravity-wave dynamics in shallow water : energy dissipation and role in sand suspension and transport

Infragravity waves (20-200 s) receive their energy from sea-swell waves (2-20 s), and are thought to be important to beach erosion during storms, when they can reach up to several meters in height. Numerous studies have observed that on sandy beaches infragravity waves can lose a large part of their energy close to shore. The causes of this energy dissipation are unclear and are currently considered to be either by nonlinear energy transfers back to sea-swell frequencies, by infragravity-wave breaking, or a combination of the two. In addition, the influence of infragravity waves on the suspension of sand, and the resulting cross-shore sand transport, are not well understood. The overarching aim of this thesis is to improve the understanding of infragravity wave dynamics in the nearshore zone of sandy beaches, with a focus on their energy dissipation and role in sand suspension and transport. New field data observations indicate that the infragravity waves dissipated up to 80% of their energy close to the shoreline (water depths < 0.7 m) and depended both on the particular infragravity-wave period and the local beach slope, with less dissipation on steeper beaches, and with longer-period infragravity waves. Overall, infragravity-wave breaking seems to be the main cause for the large energy losses, as it occurs in very shallow water, and non-linear energy transfers back to sea-swell waves were not observed. Energy transfers involving infragravity frequencies were investigated in more detail with a high-resolution lab dataset of wave fields propagating over a gently sloping beach. During infragravity-wave energy dissipation, infragravity-infragravity interactions dominated, and forced strongly asymmetrically shaped infragravity waves, leading to their breaking close to shore. The numerical model SWASH was subsequently used to study the various effects of beach steepness, profile shape and offshore wave conditions on the type of nonlinear energy transfer during infragravity-wave dissipation, and in particular beach steepness was seen to affect infragravity-wave energy loss. On gentle slopes, where infragravity-wave energy dominates the water motion close to shore, infragravity-infragravity interactions dominated and caused large infragravity energy losses. On the contrary, during infragravity-wave energy dissipation on steeper slopes, sea-swell energy dominated the water motion everywhere, and infragravity waves interacted with the sea-swell wave spectral peak, and relatively little infragravity-wave dissipation occurred. To study the effect of beach slope on cross-shore sand suspension and transport by infragravity waves, two field data sets were analyzed, obtained at beaches contrasting in bed slope. On the gently sloping beach the ratio of infragravity- to sea-swell wave height (H­IG/HSW) is typically larger than 0.4, and sand is suspended under offshore directed infragravity-wave velocities. The resulting offshore infragravity transport contributes up to 60% of the total cross-shore transport. On the steeper sloping beach, H­IG/HSW is typically lower than 0.4 and sand is suspended on the infragravity timescale by sea-swell waves. The correlation between the sea-swell wave group and infragravity orbital velocities (r0) then determines whether infragravity-wave sand transport is offshore or onshore directed. During these conditions, the infragravity-wave component contributes for less than 20% to the total cross-shore transport

Intrawave sand suspension in the shoaling and surf zone of a field-scale laboratory beach

Short-wave sand transport in morphodynamic models is often based solely on the near-bedwave-orbital motion, thereby neglec ting the effect of ripple-induced and surface-induced turbulence onsand transport processes. Here sand stirring was studied using measurements of the wave-orbital motion,turbulence, ripple characteristics, and sand concentration collected on a field-scale laboratory beach underconditions ranging from irregular nonbreaking waves above vortex ripples to plunging waves and boresabove subdued bed forms. Turbulence and sand concentration were analyzed as individual events and ina wave phase-averaged sense. The frac tion of turbulence events related to suspension events is relativelyhigh (∼50%), especially beneath plunging waves. Beneath nonbreaking waves with vortex ripples, the sandconcentration close to the bed peaks right after the maximum positive wave-orbital motion and shows amarked phase lag in the vertical, although the peak in concentration at higher elevations does not shiftto beyond the positive to negative flow reversal. Under plunging waves, concentration peaks beneaththe wavefront without any notable phase lags in the vertical. In the inner-surf zone (bores), the sandconcentration remains phase coupled to positive wave-orbital motion, but the concentration decreaseswith distance toward the shoreline. On the whole, our observations demonstrate that the wave-drivensuspended load transport is onshore and largest beneath plunging waves, while it is small and can alsobe offshore beneath shoaling waves. To accurately predict wave-driven sand transport in morphodynamicmodels, the effect of surface-induced turbulence beneath plunging waves should thus be included

Cross-shore sand transport by infragravity waves as a function of beach steepness

Two field data sets of near-bed velocity, pressure, and sediment concentration are analyzed to study the influence of infragravity waves on sand suspension and cross-shore transport. On the moderately sloping Sand Motor beach (≈1:35), the local ratio of infragravity wave height to sea-swell wave height is relatively small (HIG/HSW0.4), most sand is suspended during negative infragravity velocities, and qIG is offshore directed. The infragravity contribution to the total sand flux is considerably larger and reaches up to ≈60% during energetic conditions. On the whole, HIG/HSW is a good indicator for the infragravity-related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance

Nonlinear infragravity–wave interactions on a gently sloping laboratory beach

A high-resolution dataset of three irregular wave conditions collected on a gently sloping laboratory beach is analyzed to study nonlinear energy transfers involving infragravity frequencies. This study uses bispectral analysis to identify the dominant, nonlinear interactions and estimate energy transfers to investigate energy flows within the spectra. Energy flows are identified by dividing transfers into four types of triad interactions, with triads including one, two, or three infragravity–frequency components, and triad interactions solely between short-wave frequencies. In the shoaling zone, the energy transfers are generally from the spectral peak to its higher harmonics and to infragravity frequencies. While receiving net energy, infragravity waves participate in interactions that spread energy of the short-wave peaks to adjacent frequencies, thereby cre- ating a broader energy spectrum. In the short-wave surf zone, infragravity–infragravity interactions develop, and close to shore, they dominate the interactions. Nonlinear energy fluxes are compared to gradients in total energy flux and are observed to balance nearly completely. Overall, energy losses at both infragravity and short-wave frequencies can largely be explained by a cascade of nonlinear energy transfers to high frequencies (say, f . 1.5 Hz) where the energy is presumably dissipated. Infragravity–infragravity interactions seem to induce higher harmonics that allow for shape transformation of the infragravity wave to symmetric. The largest decrease in infragravity wave height occurs close to the shore, where infragravity–infragravity in- teractions dominate and where the infragravity wave is asymmetric, suggesting wave breaking to be the dominant mechanism of infragravity wave dissipation.Hydraulic EngineeringCivil Engineering and Geoscience

Sand nourishments to mitigate the eco-morphological losses caused by storm surge barriers

Storm surge barriers (SSBs) protect the hinterland of estuaries against flooding, while in open state the tidal dynamics are maintained to some extent. Even when tidal dynamics are maintained, tidal conditions are inevitably affected by the confinement of the flow. As a result, intertidal flats – providing important ecosystem services – face losses through erosion. In this work, we integrated research on (1) morphological consequences of the Eastern Scheldt SSB (The Netherlands, 1987) and (2) intertidal flat nourishments mitigating these negative eco-morphological consequences. Through decades of data, we show that the SSB induced persistent erosion. We have demonstrated that sand nourishments on tidal flats can effectively mitigate SSB-induced erosion and ecological consequences. We have found that net lowering of tidal flats in systems as the Eastern Scheldt will proceed, also given accelerated sea level rise. Even though tidal flat nourishments are an effective mitigation strategy, we urge to steer first on minimizing irreversible hydromorphological changes caused by future SSB projects (e.g., considered for Galveston Bay). Through monitoring data on intertidal flat sand nourishments in this system, we identify the potential of these mitigation measures and provide recommendations for future SSB deployments and mitigation