Search Results (23)

Overhanging parapets are commonly adopted in vertical breakwaters to reduce wave overtopping. However, previous studies have shown that these structures may also be subjected to significant impulsive loads associated with the Confined-Crest Impact (C-CI) phenomenon. While the loading mechanisms of conventional recurved parapets have been extensively investigated, the influence of alternative overhanging geometries on both wave loading and overtopping reduction remains poorly understood. This study investigates the hydraulic efficiency and wave loading on rectilinear, recurved, and recurved crownwall under non-breaking wave conditions by means of Reynolds-Averaged Navier-Stokes (RANS) simulations coupled with a Volume of Fluid (VOF) approach. The results show that parapet geometry strongly influences both dynamic/impulsive wave loading and overtopping volumes. The recurved crownwall achieves the greatest overtopping reduction but also the highest force amplification. Conversely, the recurved parapet produces the lowest impulsive loads among the tested overhanging geometries, at the expense of hydraulic efficiency, although these loads remain higher than those experienced by the reference vertical parapet. These findings reveal a trade-off between overtopping mitigation and structural loading, indicating that the most hydraulically effective geometry is not necessarily the most structurally advantageous. Full article

Introduction: The genus Thorichthys comprises nine species of Central American freshwater cichlids, which are distributed along the eastern slopes of Mexico and Honduras. These species are grouped into two subgroups: “helleri” and “meeki”. While some analyses of the group’s ecomorphology and character evolution have been conducted, the skeletal structures of this genus remain to be described. Objective: This study provides an osteological description of the species in the genus Thorichthys. Methodology: The specimens were sectioned and stained with alizarin red, and the bone structures were analyzed and described. Results: The genus Thorichthys possesses 12 abdominal vertebrae and 12–13 caudal vertebrae. Species of “helleri” group are characterized by the following points: (1) there is a urohyal bone with a sharply concave dorsal margin and a spiniform, inclined process; (2) typically, there are a total of 14–15 gill rakers in the first gill arch; (3) the opercular bone bears a dorsally displaced, posterior protuberance; (4) a total of 12–13 anal pterygiophores; and (5) a slightly recurved cephalic profile. Meanwhile species of the “meeki” group exhibit the following characteristics: (1) a urohyal with a broad, unsharpened dorsal concavity and a small, blunt, nearly straight process; (2) a total of 15–21 gill spines; (3) a dorsally positioned protuberance in the middle of the opercular bone; (4) a total of 14–16 proximal anal pterygiophores; and (5) a straight cephalic profile. Conclusions: These bony elements are proposed as a complement to the taxonomic differentiation of the species in Thorichthys, and to contribute new morphological characteristics to the study of other cichlid genera. Full article

Greece and the eastern Mediterranean are among the regions that are most exposed to climate-driven natural hazards, with wildfires, floods, and extreme rainfall events consistently producing significant socioeconomic and environmental impacts. Although previous literature has addressed each hazard type individually, a systematic, comparative analysis of the atmospheric circulation regimes associated with all three hazard categories within a unified Lagrangian framework has not yet been conducted for Greece. In this study, a 96 h HYSPLIT back-trajectory analysis driven by ERA5 reanalysis data, combined with k-means clustering, is employed to characterise the air mass origins associated with extreme events in Greece from 2000 to 2020 at two atmospheric levels: 750 m and 3000 m above sea level. Wildfire events are predominantly linked to short-distance northeast airflow at 750 m, and are directly associated with the Etesian wind system and to a coherent northwest-west Mediterranean signal at 3000 m, reflecting the influence of the summer blocking anticyclone over Europe. Conversely, flood events are dominated by northerly flow at 750 m, driven by the eastern flank of Mediterranean depressions. These results indicate that flooding in Greece is primarily conditioned by surface cyclogenesis, regardless of the upper-level flow geometry. Extreme rainfall events exhibit the most complex structure, with a dominant upper-level cluster that describes a recurving trajectory consistent with cut-off low dynamics. Cross-hazard comparisons demonstrate that similar near-surface trajectory patterns may arise from different atmospheric drivers, underscoring the necessity of integrating Lagrangian trajectory classification with additional context, such as thermodynamic and seasonal, to enable robust multi-hazard attribution and enhance early warning capabilities in the eastern Mediterranean. Full article

Archery performance is substantially influenced by postural stability. Although archery is commonly practiced outdoors, most studies have focused on short-distance indoor environments. Accordingly, this study examined the correlation between postural stability and shooting accuracy in competitive recurve and compound archers on a standard outdoor field (70 m for recurve and 50 m for compound). This study included 37 archers. Each archer’s performance was recorded during a simulated competition. Measurements included muscle strength, body stability, and center of pressure. Postural stability data were analyzed at 0.5 s before and 0.1 s after arrow release. The results indicated that compared with compound archers, recurve archers had stronger upper-limb muscles and exhibited lower pre-release total center of pressure (51.9 mm; p = 0.022) and medial/lateral sway (1.1 mm; p = 0.043). The compound archers exhibited lower post-release anterior/posterior sway (3.2 mm; p = 0.001) and lower angular velocities in most body segments, except for the lower back. The recurve archers relied more on post-release stability, whereas the compound archers relied more on pre-release control. Linear regression analysis identified different predictors of scoring accuracy for each bow type. Our findings highlight the need for discipline-specific training strategies, such as enhancing bow-side stability for recurve archers and drawing-side control for compound archers. Full article

John Strong Newberry described three species of the lobe-fin fish Onychodus (Osteichthyes, Sarcopterygii, Onychodontida) based on parasymphysial teeth, or tusks. Two species, Onychodus sigmoides Newberry, 1857 (type species of the genus) and Onychodus hopkinsi Newberry, 1857, were described from the “fish beds” in the Delaware Limestone (Middle Devonian, Eifelian) of Delaware, Ohio, USA; and one species, Onychodus ortoni Newberry, 1889, was described from the Ohio Shale, Huron Member (Upper Devonian, Famennian) of Perry Township, Franklin County, Ohio. In 1873, Newberry replaced the original species-group definition of O. hopkinsi with a definition based on teeth of different morphology from the West Falls Group (Upper Devonian, Frasnian) of Franklin, New York. Specimens of Newberry’s original Onychodus material, including the primary types, which were long assumed to be lost, have been rediscovered in a 19th-century collection. They show O. hopkinsi to be a junior synonym of O. sigmoides and clarify the species definition of O. sigmoides. Onychodus sigmoides, which is recognized from Middle Devonian strata of the Appalachian Basin in the United States and Canada, shows two end-member shapes of teeth on the parasymphysial whorl: procurved (arcuate) or nearly so proximally and recurved distally (anteriorly). Small teeth are commonly more slender than large teeth, which are robust. Parasymphysial teeth from the Upper Devonian of Ohio and New York are referred to O. ortoni. Full article

Cyclone Mocha, classified as an Extremely Severe Cyclonic Storm (ESCS), followed an unusual northeastward trajectory while exhibiting a well-defined eyewall structure. It experienced rapid intensification (RI) before making landfall along the Myanmar coast. It caused heavy rainfall (~90 mm) and gusty winds (~115 knots) over the coastal regions of Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation (BIMSTEC) countries, such as the coasts of Bangladesh and Myanmar. The factors responsible for the RI of the cyclone in lower latitudes, such as sea surface temperature (SST), tropical cyclone heat potential (TCHP), vertical wind shear (VWS), and mid-tropospheric moisture content, are studied using the National Ocean and Atmospheric Administration (NOAA) SST and National Center for Medium-Range Weather Forecasting (NCMRWF) Unified Model (NCUM) global analysis. The results show that SST and TCHP values of 30 °C and 100 (KJ cm⁻²) over the Bay of Bengal (BoB) favored cyclogenesis. However, a VWS (ms⁻¹) and relative humidity (RH; %) within the range of 10 ms⁻¹ and >70% also provided a conducive environment for the low-pressure system to transform into the ESCS category. The physical mechanism of RI and recurvature of the Mocha cyclone have been investigated using forecast products and compared with Cooperative Institute for Research in the Atmosphere (CIRA) and Indian Meteorological Department (IMD) satellite observations. The key results indicate that a dry air intrusion associated with a series of troughs and ridges at a 500 hPa level due to the western disturbance (WD) during that time was very active over the northern part of India and adjoining Pakistan, which brought north-westerlies at the 200 hPa level. The existence of troughs at 500 and 200 hPa levels are significantly associated with a Rossby wave pattern over the mid-latitude that creates the baroclinic zone and favorable for the recurvature and RI of Mocha cyclone clearly represented in the NCUM analysis. Moreover the Q-vector analysis and steering flow (SF) emphasize the vertical motion and recurvature of the Mocha cyclone so as to move in a northeast direction, and this has been reasonably well represented by the NCUM model analysis and the 24, 7-, and 120 h forecasts. Additionally, a quantitative assessment of the system indicates that the model forecasts of TC tracks have an error of 50, 70, and 100 km in 24, 72, and 120 h lead times. Thus, this case study underscores the capability of the NCUM model in representing the physical mechanisms behind the recurving and RI over the BoB. Full article

An arrow’s attack angle continuously changes during its flight, which affects the position of the aerodynamic pressure center. To account for the offset between the aerodynamic pressure center and the center of mass of an arrow in recurve bow shooting, two equations for describing the variation of the aerodynamic pressure center with the attack angles were fitted via CFD simulation. On this basis, a new theoretical aerodynamic model was developed by integrating the above equations with the current model to predict the flight along the outer ballistic trajectory more accurately than ever. With regard to actual archery competition occasions, the distance, initial velocity, and attack angle were set to 70 m, 57 m/s, and −3° to 3°, respectively; the attitude and trajectory of the arrow flying details under background wind, such as crosswind, headwind, and tailwind, were numerically analyzed to reveal the accuracy deviation mechanism. A comparison was conducted with previous models, indicating that the model proposed in this study achieved improvements in accuracy of 15% under crosswind conditions and 8% under headwind/tailwind conditions. The results could, from a fluid physics perspective, provide valuable recommendations not only for archers and coaches but also for arrow manufacturers. Full article

The genus Rhamphempis gen. nov. (Diptera: Empididae: Empidinae: Empidini) is described and includes the following five new species from French Guiana and the USA: Rhamphempis concava sp. nov. (France: French Guiana, Roura); R. distincta sp. nov. (France: French Guiana, Roura); R. mirifica sp. nov. (France: French Guiana, Régina); R. montreuili sp. nov. (Type species, France: French Guiana, Mitaraka, Roura, St-Georges-de-l’Oyapock); and R. septentrionalis sp. nov. (USA: Maryland, College Park). The genus differs from other empidine genera by the following combination of characters: scape and postpedicel lengthened, proboscis long, strongly sclerotised with labella as long as prementum bearing annulations, wing with R₂₊₃ somewhat shortened, more or less recurved at pterostigma, R₄₊₅ unforked, base of abdomen yellowish in male, brownish to blackish in female, male pregenital segments strongly modified and postabdomen more or less downcurved, presence of large surstylus, very fine and long phallus. The genus is fully illustrated and keyed along with a discussion of its peculiar disjunct geographic distribution and its phylogenetic relationship within the tribe Empidini. Full article

The ECMWF‘s ensemble (ECEPS) predictions are documented for the lifecycles of six tropical cyclones (TCs) that formed during a long-lasting Rossby wave breaking event in the western North Pacific. All six TC tracks started between 20° N and 25° N, and between 136° E and 160° E. All five typhoons recurved north of 30° N, and the three typhoons that did not make landfall had long tracks to 50° N and beyond. The ECEPS weighted mean vector motion track forecasts from pre-formation onward are quite accurate, with track forecast spreads that are primarily related to initial position uncertainties. The ECEPS intensity forecasts have been validated relative to the Joint Typhoon Warning Center (JTWC) Working Best Track (WBT) intensities (when available). The key results for Tokage (11 W) were the ECEPS forecasts of the intensification to a peak intensity of 100 kt, and then a rapid decay as a cold-core cyclone. For Hinnamnor (12 W), the key result was the ECEPS intensity forecasts during the post-extratropical transition period when Hinnamnor was rapidly translating poleward through the Japan Sea. For Muifa (14 W), the key advantage of the ECEPS was that intensity guidance was provided for longer periods than the JTWC 5-day forecast. The most intriguing aspect of the ECEPS forecasts for post-Merbok (15 W) was its prediction of a transition to an intense, warm-core vortex after Merbok had moved beyond 50° N and was headed toward the Aleutian Islands. The most disappointing result was that the ECEPS over-predicted the slow intensification rate of Nanmadol (16 W) until the time-to-typhoon (T2TY), but then failed to predict the large rapid intensification (RI) following the T2TY. The tentative conclusion is that the ECEPS model‘s physics are not capable of predicting the inner-core spin-up rates when a small inner-core vortex is undergoing large RI. Full article

The wheat grain yields increased in EU from 4.98 t ha⁻¹ to 5.45 t ha⁻¹ in the periods from 2006 to 2014 to from 2015 to 2023. It is hypothesized that changes in specific morphological traits over the years resulted in grain yield increase due to the utilization of new wheat varieties in production. To highlight the current status and changes over time, we evaluated a comprehensive panel of 1322 wheat varieties that included testing of morphological traits of varieties recognized from period from 2006 till 2023. Positive relation of registration year with traits such as seed color, glaucosity of neck of culm, plant height, ear length, scurs and awns length, ear color, and shape of the beak of the lower glume was obtained. The most significant changes over time resulted in a darker color of the seed, decreased area of hairiness of the convex surface of the apical rachis segment, enhanced glaucosity of the neck of the culm and decreased frequency of the plants with recurved flag leaves. It was shown that traits such as the frequency of plants with recurved flag leaves, time of emergence, glaucosity of flag leaves, existence of scurs and awns, and area of the hairiness of the convex surface of the apical rachis segment had significant decreases over time. This research demonstrated the importance of twelve morphological traits in the varietal improvement of grain yield over the time from 2006 to 2023. Full article

U-shape steel sheet piles are widely used in deep and large excavation engineering due to their excellent soil-retaining and water-stopping performances. To achieve deformation control in excavations, an experimental investigation on the deformation characteristics of a strutted U-shape sheet pile flexible retaining structure was conducted. Single-layer and double-layer strutted retaining structure excavation indoor model tests in sand, where U-shape sheet piles were formed by 3D printing, were successfully accomplished. Deformation was monitored in real time during the test. The results show that the lateral displacement mode of the retaining structure transformed with the change in excavation from the “cantilever” to the “bulge” and finally developed into an intricate “recurve bow”. The average maximum lateral displacement was 0.756% of the excavation depth. With a maximum settlement of 0.375% of the excavation depth on average, the distribution of ground settlement behind walls changed from “exponential” to “triangular” before ultimately transforming into “trough” or “trapezoid” mode. The maximum settlement to maximum lateral displacement ratio (s_max/δ_max) on average was 0.54; the maximum settlement deformation rate was always less than the maximum lateral displacement deformation rate. Full article

Palaeozoic fern-like plants show great diversity in their morphology and/or anatomy. Within this group, a novel taxon, Xinhangia spina gen. et sp. nov., is now reported from the Upper Devonian (Famennian) Wutong Formation of Anhui Province, China. The primary and secondary branches are borne alternately and sometimes in a triseriate pattern. Spines are evident on the main axes or stems and on the primary branches. Vegetative ultimate appendages with recurved tips are alternate, usually dichotomous 1–2 times, and sometimes as an aphlebia located at the base of primary or secondary branches. Fertile ultimate appendages are alternate, usually dichotomous 1–2 times, and terminate in elongated and paired sporangia. The stele has a clepsydroid-like primary xylem with each end bearing a protoxylem strand. The secondary xylem surrounding the primary xylem illustrates uniseriate rays. With rare divisions in both the vegetative and fertile ultimate appendages, Xinhangia represents a morphologically primitive plant. It is of uncertain affinity at the class or order level. The stelar architecture suggests that the clepsydroid stele may not be emphasized in discussing the relationship among fern-like plants such as rhacophytaleans. Full article

It is more common to introduce the parapet/recurve/wave return wall over the existing structure, such as a vertical seawall or composite structure, to reduce the overtopping efficiently. The advantage of a recurve wall on top of the sea wall has been studied in the past in regards to wave interaction and overtopping. However, their efficiency in protecting the inland structure during extreme events such as flooding during a tsunami is unexplored. The present study addresses the effect of a vertical seawall with recurve in reducing the dam break surge simulating tsunami-induced forces on an inland structure. The study compares the momentum transferred on the landward structure behind a Vertical seaWall (VW) and a vertical wall with the Large ReCurve on the top (LRC) during overtopped conditions. The outcome from the numerical simulation shows an insignificant contribution due to the LRC in reducing the force on the inland structure compared to the VW, albeit delaying the impact time. However, the LRC performed slightly better in the case of a low-rise wall located near the inland structure than the VW. Furthermore, a low-rise VW increases the force and overturning moment on the inland structure compared to no-wall conditions. Both the LRC and the VW reduced the horizontal force on the structure linearly with the increase in height. An exponential decrease in the overturning moment was observed on the landward structure with the increase in the height of the VW or the LRC. Design equations are proposed for the forces and overturning moment reduction based on the height of the VW or the LRC. Full article

Typhoon Fitow (2013) took an unusual westward track deflection after a lengthy northward movement over the western North Pacific (WNP). Based on observation and wave analysis, it is found that the track deflection of Fitow is attributed to the transition of environmental flow from meridional to zonal orientation, which is closely associated with a low-frequency intra-seasonal oscillation (ISO). Furthermore, the impact of ISO on tropical cyclone (TC) unusual movement is investigated using the Advanced Research version of Weather Research and Forecasting (WRF-ARW) model. The control simulation (CTL) reproduces well the synoptic pattern and track deflection of the TC. The TC moves straightly westward and northwestward without track deflection in the sensitivity experiments with the removal of total ISOs and the west-propagating ISO component, while keeping the recurving track with the removal of east-propagating ISO, which suggests that the west-propagating ISO plays a dominant role in the westward track deflection. In the experiment of removing west-propagating ISOs, an anomalous southeast–northwest-oriented wave train around the TC is modified, the mid-latitude trough decays, and the enhanced zonally elongated subtropical high is responsible for the straight northwestward motion of the TC. However, after removing a weaker convection anomaly associated with east-propagating ISOs in the form of a southwest–northeast oriented dipole circulation, the TC is affected by a sustained shallow mid-latitude trough and a west-extended ridge of subtropical high to keep the cyclonic track turning analogous to the counterpart in CTL. The piecewise potential vorticity inversion diagnosis further assesses the contribution of the different ISO components to TC track deflection. Full article

This study investigates the variation of wave impact loads with the geometrical configurations of recurve retrofits mounted on the crest of a vertical seawall. Physical model tests were undertaken in a wave flume at the University of Warwick to investigate the effects of the geometrical properties of recurve on the pressure distribution, overall force, and overturning moment at the seawall, subject to both impulsive and non-impulsive waves. Additionally, the wave impact and quasi-static loads on the recurve portion of the retrofitted seawalls are investigated to understand the role of retrofitting on the structural integrity of the vertical seawall. Detailed analysis of laboratory measurements is conducted to understand the effects of overhang length and height of the recurve wall on the wave loading. It is found that the increase in both recurve height and overhang length lead to the increase of horizontal impact force at an average ratio of 1.15 and 1.1 times larger the reference case of a plain vertical wall for the tested configurations. The results also show that the geometrical shape changes in recurve retrofits, increasing the overturning moment enacted by the wave impact force. A relatively significant increase in wave loading (both impact and quasi-static loads) are observed for the higher recurve retrofits, while changes in the overturning moment are limited for the retrofits with longer overhang length. The data generated from the physical modelling measurements presented in this study will be particularly helpful for a range of relevant stakeholders, including coastal engineers, infrastructure designers, and the local authorities in coastal regions. The results of this study can also enable scientists to design and develop robust decision support tools to evaluate the performance of vertical seawalls with recurve retrofitting. Full article