Deep Pool Research Articles

Measurement of Amniotic Fluid Volume in 2nd and 3rd Trimesters of Normal Pregnancies

The important implication of obstetric care is the assessment of amniotic fluid volume. This assessment can prevent anomalies that are associated with oligohydramnios and polyhydramnios. Objective: To evaluate normal amniotic fluid volume in the 2nd and 3rd trimesters with the correlation of gestational age. Methods: It was a cross-sectional study and data were collected from a private health care setup in Gujrat, Pakistan. After informed consent data were collected in four months. A sample size of 75 patients was calculated conveniently using a mean from previous related studies. The women with singleton gestation from 20 to 40 years of age group were included in this research. The data were entered and analyzed on SPSS version 20. Results: This study showed that 47(62.7%) of women were multigravida and 28(37.3%) were primigravida. The most frequent maternal age group was 26-30(38.7%) years and the gestational age group was 31 to 35(42.7%) weeks. At the gestational age of 21-25 weeks, the mean of AFI was 14.38 and the mean of SDP was 5.69, while at the age of 26-30 weeks the estimated mean of AFI was 12.12 and the mean of SDP was 5.11. The mean of AFI and SDP at the age of 31-35 weeks were calculated at 11.48 and 4.26 respectively. At the age of 36-40 weeks, the estimated mean of AFI and SDP were calculated 10.22 and 3.73 correspondingly. Conclusions: This study concluded that amniotic fluid volume measured by amniotic fluid index and the single deep pool was increased in the 2nd trimester from 21-25 weeks of gestation and then progressively reduced in the third trimester as the pregnancy advances.

Freshwater fish diversity in hill streams of Saberi River in Eastern Ghats of Odisha, India

Freshwater fish diversity of the hill streams of Saberi River (a major tributary of the Godavari River system) in Koraput district in Eastern Ghats of southern Odisha was studied from September 2017 to August 2019. Sites for the present study were located between Gupteswar Proposed Reserve Forest (PRF) of Odisha on the eastern side, and Kanger Valley National Park of Chhattisgarh on the western side. A total of 36 species of freshwater fish belonging to 24 genera, 13 families and six orders were recorded from the study sites, of which two species are exotic. Family Cyprinidae dominated with 14 species. Species richness and diversity is greater during the pre-monsoon months followed by post-monsoon and monsoon months respectively. The physico-chemical parameters of water in the study sites during all seasons are within prescribed limits for fish culture. Among the four major types of fish habitats identified in the study sites (riffles, runs, pools and logs), pools were the most preferred, and logs the least preferred habitat for the fishes. Habitat analysis indicated that deep pools and runs are the primary habitats contributing to the maximum species diversity, and therefore, protection of these particular habitats is recommended for conservation and management of ichthyodiversity.

Status and distribution of Mugger Crocodile Crocodylus palustris in the southern stretch of river Cauvery in Melagiris, India

A study was conducted to examine the population estimate and spatial distribution of Mugger Crocodile in the southern stretch of river Cauvery, Hosur Forest Division from February 2019 to May 2019. In total, 53 basking sites and 45 Muggers were encountered by direct sighting in the 24-km river stretch using daytime ground based survey approach. N-mixture models estimated an average Mugger density of 2.05 individuals per kilometre for daytime survey. A night spotlight survey across the seven segments of river stretch was also conducted which yielded direct sightings of 54 Muggers with an average encounter rate of 2.25 individuals per kilometre. Two crocodile nests with hatched egg shells were also observed on the sand banks of the river. We concluded that a potential healthy and breeding population of Mugger inhabits the studied stretch of the river. Multiple corresponding analysis was also performed, which demonstrated that Mugger responds to sandy banks alongside deep water pools for basking in contrast to river segments with shallow depth and dense riparian cover.

An experimental study on steam explosion of a small melt jet falling into a water pool

To address the mechanisms and influential factors of steam explosions which may occur during severe accidents in a nuclear power plant (NPP), the VULCAN apparatus is designed and built to investigate the characteristics of a steam explosion when molten material falls into a water pool. The test facility is composed of a high-speed measurement system and an induction furnace which enables preparation and delivery a small melt jet at temperature up to 1500 ℃. In the first campaign of tests, tin is employed as the simulant of melt material, and the steam explosion process and pressure signals of a small molten tin jet falling into a deep water pool are recorded by a high-speed camera and a high-frequency pressure sensor, respectively. Debris particles from part test are collected and sieved for analysis of morphology and size distribution of the particles. Multiple occurrences of steam explosion are observed during the traveling of the melt jet into the water pool, with several cycles of expansion–contraction in each occurrence of steam explosion. The time interval between two occurrences is around 80 ms and between two cycles is around 4 ms. For the melt mass ranging from 20 to 140 g in the present study, it is found that the number of steam explosion occurrences increases with the melt mass. Both the pressure impulse and the conversion ratio of steam explosion increase with melt mass. However, the pressure impulse and conversion ratio do not have a monotonic relation with melt superheat, and the conversion ratio increase with melt superheat when it is below a threshold (370℃), but decrease above the threshold.

Dendrite-resolved, full-melt-pool phase-field simulations to reveal non-steady-state effects and to test an approximate model

We study the epitaxial, columnar growth of (multiply oriented) dendrites/cells for a spot melt in a polycrystalline Al–Cu substrate using two-dimensional, phase-field, direct numerical simulations (DNS) at the full-melt-pool scale. Our main objective is to compare the expensive DNS model to a much cheaper but approximate “line” model in which a single-crystal phase-field simulation is confined to a narrow rectangular geometry. To perform this comparison, we develop algorithms that automatically extract quantities of interest (QoIs) from both DNS and line models. These QoIs allow us to quantitatively assess the assumptions in the line model and help us analyze its discrepancy with the DNS model. We consider four sets of heat source parameters, mimicking welding and additive manufacturing conditions, that create a combination shallow and deep melt pools. Our largest DNS simulation used 16K × 14K grid points in space. Our main findings can be summarized as follows. Under AM conditions, the QoIs of line models are in excellent agreement with the full DNS results for both shallow and deep melt pools. Under welding conditions, the primary spacing of the DNS model is smaller than the prediction of line model. We identify a geometric crowding effect that accounts for the discrepancies between the DNS and line models. We propose two potential mechanisms that determine the response of the microstructure to geometric crowding.

Cavity and jet formation after immiscible droplet impact into deep water pool

The impact behavior of a droplet in a liquid pool is of fundamental importance in nature and industrial applications. While there are several reports on using the same fluid type for the droplet and liquid pool, there are a few reports on the use of different liquids. Moreover, the mixing process of the droplet and liquid pool is yet to be fully quantified. Herein, we present an experimental setup to study the effect of droplet solubility in water on the impact characteristics of a deep-water pool. In this study, we used three droplets (water, ethanol, and silicone oil) with different densities, surface tensions, viscosities, and solubilities in water and visualized the impact process using a high-speed camera. The diameter of the droplets ranged from 2.0 to 3.4 mm, and the impact velocities ranged from 1.4 to 3.2 m/s. The depth of the droplet pool was fixed at 30 mm. To better understand the impact characteristics, the obtained images were processed to quantify the created cavity and the subsequent liquid jet formed by the droplet impact. Energy analysis performed during the droplet impact process for the 1000 cSt silicone oil droplet revealed that approximately 70% of the impact energy was converted into cavity energy, and the remaining 30% was converted into flow loss. These experimental results provide physical insight into the immiscibility effect on droplet impact dynamics in a deep pool and pave the way for practical applications.

Effects of Stream Enhancement Structures on Water Temperature in South Sister Creek, Oregon

We evaluated commonly used methods for monitoring stream restorations to inform and improve restoration monitoring and evaluation, using a headwater stream in the Oregon Coast Range as a case-study example. In-stream restoration projects are seldom monitored both pre- and post-restoration. In addition, frequently used low-cost methods may not provide sufficient data to effectively assess trends in stream temperature. Here, we examined what can be learned from temperature loggers installed in the same locations over multiple years in a restored stream. In-stream structures were installed between 2007 and 2011 along a 10-km length of South Sister Creek, Oregon for the purpose of enhancing in-stream habitat. Summer stream temperature data were collected using Hobo Pro-V temperature-logging thermistors at four locations in 2006, prior to restoration, as well as in 2012 and 2013. In 2013, additional temperature loggers were placed within 80 m of the four original loggers to investigate within-reach variability. Although median stream temperatures were highest in 2013 at all four multi-year sites, 7-day maximum temperatures were 4 to 5 °C cooler in post-treatment years than in 2006. Inter-annual variability in stream temperature was more closely linked to inter-annual variability in air temperature and solar radiation than presence of in-stream structures. Thermal heterogeneity was greater in reaches with deeper pools than in bedrock-dominated reaches. Although in-stream structures can create cool microhabitats, they have little influence on mean stream temperature. Longer pre-restoration monitoring and sensor deployment in more varied in-stream habitats would improve our ability to evaluate restoration impacts.

Morpho-dynamic evolution due to inertia-mediated impact of a compound drop on a deep liquid pool

A compound drop impacting on a liquid pool exhibits intriguing coalescence patterns that are primarily attributable to the complicated interplay of inertia with other physical parameters such as radius ratio of core to shell drop and density and viscosity contrasts of the two fluids. By executing comprehensive numerical investigations, here, we identify three different regimes based on the radius ratio of compound drop, viz., secondary drop pinch-off without bubble bursting, secondary drop pinch-off after bubble bursting, and compound breakage. Our findings also depict a transition in the shape of a secondary droplet from prolate to oblate or vice versa, a phenomenon non-trivially culminated by secondary drop pinch-off timing, neck radius, and amplitude and wavelength of capillary wave propagation. Our results bring out the fact that higher wavelength and amplitude of capillary waves are responsible for secondary drop pinch-off without bubble bursting. Furthermore, in the case of highly viscous core drop and surrounding fluid, we observe both complete and partial coalescence phenomena, which are critically dictated by the confluence of inertia and radius ratio of a compound drop leading to three different regimes, viz., complete coalescence without bubble bursting, complete coalescence with bubble bursting, and partial coalescence with bubble bursting, distinctively different from the observations for single droplet based investigations reported in earlier studies. These implications are likely to be beneficial in illustrating the physical functionalities accompanying the targeted release of encapsulated biological or pathological entities when they are transmitted under the action of an inertial force into another fluidic medium, a paradigm that has hitherto remained unexplored.

Covariation in width and depth in bedrock rivers

AbstractThe width and depth of rivers are generally inversely related. For a given discharge, wider rivers tend to be shallower than narrower rivers, which are correspondingly deeper. This is particularly true in bedrock and mixed bedrock–alluvial channels, where deep pools occur downstream of lateral constrictions, downstream of which the channel becomes wider and shallower. However, covariation of width and depth in bedrock and mixed bedrock–alluvial rivers has never been explored due to the lack of field measurements. Here we present a 375 km survey of width and depth measurements in the Fraser Canyon, British Columbia, which alternates irregularly among alluvial (no bedrock exposed on either bank), bedrock‐constrained (bedrock exposed on one bank), and bedrock‐bound (bedrock exposed on both banks) sections. We find that bedrock‐bound reaches have the deepest and narrowest sections, followed by bedrock‐constrained reaches and alluvial reaches, which feature the shallowest and widest sections of channel. There is an inverse relation between width and depth for all the channels, with alluvial channels having the highest correlation between these two variables, and thus the greatest covariance. We further explore the relation between width and depth and the downstream hydraulic geometry of 42 individual bedrock‐bound canyons. There is an inverse relation between canyon width and depth, with substantial variation within individual canyons. The downstream hydraulic geometry for these bedrock‐bound canyons does not follow that typical of alluvial channels; depth is the only variable that adjusts substantially as a response to increasing discharge and upstream basin area.

Rayleigh–Taylor instability in impact cratering experiments

When a liquid drop strikes a deep pool of a target liquid, an impact crater opens while the liquid of the drop decelerates and spreads on the surface of the crater. When the density of the drop is larger than the target liquid, we observe mushroom-shaped instabilities growing at the interface between the two liquids. We interpret this instability as a spherical Rayleigh–Taylor instability due to the deceleration of the interface, which exceeds the ambient gravity. We investigate experimentally the effect of the density contrast and the impact Froude number, which measures the importance of the impactor kinetic energy to gravitational energy, on the instability and the resulting mixing layer. Using backlighting and planar laser-induced fluorescence methods, we obtain the position of the air–liquid interface, an estimate of the instability wavelength, and the thickness of the mixing layer. We derive a model for the evolution of the crater radius from an energy conservation. We then show that the observed dynamics of the mixing layer results from a competition between the geometrical expansion of the crater, which tends to thin the layer, and entrainment related to the instability, which increases the layer thickness. The mixing caused by this instability has geophysical implications for the impacts that formed terrestrial planets. Extrapolating our scalings to planets, we estimate the mass of silicates that equilibrates with the metallic core of the impacting bodies.

The Effect of Laser Focus Shift on the Morphology of Melt Pool and Microstructure in Selective Laser Melting AlSi10Mg

Selective Laser Melting (SLM) enables to fabricate complex freeform geometries parts from computer models. In this paper, the effect of laser focus shift on the morphology, surface quality, grain size and texture of the SLMed AlSi10Mg was studied. Deep melt pool was found in 0 mm laser focus shift, while shallow and wide melt pool were found in-1.5 mm and +1.5 mm laser focus shift. The proportion of high angle grain boundaries in 0mm laser focus shift sample is the biggest han that in-1.5mm and +1.5mm. Height has a maximum value of 338 μm in +1.5 mm laser focus shift. The maximum Arithmetic average height is 33.5 μm in +1.5 mm laser focus shift. When the laser focus shift is 0 mm, the average grain diameter has a minimum grain diameter of 4.9 μm. {001}<100> cubic texture was found in sample fabricated by +1.5 mm laser focus shift rather than 0 mm and-1.5 mm laser focus shift.

Preliminary study on thermal–hydraulic behavior of loss-of-flow accident in deep pool-type nuclear reactor

Deep pool nuclear reactor (DPNR) is a novel pool-type reactor, which has shown great potential in seawater desalination and district heating. In this paper, the thermal–hydraulic behavior of loss-of-flow accident (LOFA) in DPNR were investigated by RELAP5. The parametric analyses were also carried out to reveal the effects of flow resistance coefficient (FRC) in connection pipe and flap valve opening criteria on thermal–hydraulic behavior of LOFA in DPNR. The results showed that the LOFA process could be divided into coast-down phase, oscillation phase and natural circulation phase, and two peaks of clad peak temperature appeared. Besides, the parametric analysis showed that increasing FRC in connection pipe and failure of flap valve can make the first and second peak of clad peak temperature larger, respectively. The decrease of flap valve opening criteria made flap valve open earlier, and inertia tank performance was weakened when flap valve opened in coast-down phase.

Droplet impact dynamics onto a deep liquid pool of wavy free surface

The impact of a droplet on a deep pool of water with a flat-free surface results in a deep cavity followed by the emergence of a thick jet with a secondary drop when the Froude number and Weber number of the impacting droplet are 220 and 252, respectively. The disturbances in the free surface of the liquid pool modify the crater and the jet dynamics under identical drop impact conditions. Here, we present the simulations of the water drop impact on a deep liquid pool having various wavy profiles mimicking the free surface ripples. Long slender jets with the formation of multiple secondary droplets are observed when the droplet impacts the trough of an axisymmetric wavy surface. The influence of wave number on the wavy profile becomes more pronounced at large wave amplitudes. While capillary-inertia instability governs the pinch-off of thick Worthington jets, the pinch-off of these slender jets is found to be mainly inertia driven. However, if the drop impacts the crest of an axisymmetric wave, a short thick jet forms with one or two secondary droplets. Axisymmetric waves with radially outward moving interface, as in ripples, showed the occurrence of complete coalescence when droplet impacted on the crest; but the dynamics remain mostly the same as that of a stationary wave for the droplet impact on a trough. Entrainment of air bubbles after cavity collapse and bent jet occurred for an impact on a sinusoidal planar wave when the impact location was in between the two consecutive extremes.

Evolution of jets during drop impact on a deep liquid pool

The impact of a liquid drop on a liquid pool has been widely investigated. The transition regimes between coalescence and splashing of drops include jet formation with single or multiple secondary drops. One of the main features in this regime is the formation of a central liquid jet followed by breakup of the jet in the form of drops. Earlier studies have shown that the diameter of the secondary drop lies between 0.58 and 0.94 times the diameter of the impacting drop. We perform investigations based on a coupled level-set and volume-of-fluid method to elucidate the earlier observations. The investigations reveal the creation of a variety of secondary drops depending on the impact conditions. The present study also reveals that secondary drops larger than the initial drop can be obtained at higher impact velocities. We identify the importance of cavity shapes on the formation of jets and the pertaining parameters that are responsible for drop ejection.

The New Public/Private Equilibrium and the Regulation of Public Companies

This Symposium Article examines how the public/private divide works today and maps out some of the potential implications for major issues in securities law. Classic debates in securities law were often predicated on the idea that public companies are a coherent class of firms that differ markedly from private companies. For more than fifty years after the adoption of the federal securities laws, this view was justified. During that period, the vast majority of successful and growing private firms eventually accepted the regulatory obligations of being public in order to access a wider and deeper pool of capital, among other benefits. This was a descriptive reality, but it had important normative implications as well. An identifiable class of large, growing firms went public, and they generally went public for a reason they shared: raising capital. As a result, regulatory interventions imposed on the category of “public companies” had a coherent target. 
 We argue that firms’ going public decisions are now shaped by a much larger and more varied set of factors. These factors are complex, cross-cutting, and impact firms considering going public in very heterogeneous ways. This complexity results from several developments and we emphasize two. First, it is a result of the fact that while the public/private divide was created by securities law, public and private markets now provide two widely different ecologies for firms, which profoundly shape firms’ governance as well as the issuance and trading of their shares. Second, long-term advances in the ease of capital raising in private markets have made it possible for firms to remain private indefinitely and have diminished or eliminated the capital-raising advantages of public markets. The result of this latter change has been rightly called a “new equilibrium.” In that equilibrium, fewer and older firms go public, while other successful firms remain private indefinitely. In this equilibrium, capital raising is no longer the primary reason firms go public. Rather, we argue, firms go public due to one or more of the many other features of the public market’s ecology. 
 The normative implication of this new equilibrium is to reduce the coherency of the regulation of public companies. The benefits and costs of being public (or private) apply unevenly to firms eligible to go public. Instead, to a greater degree firms now face idiosyncratic, company-specific tradeoffs between being public or private, and they often go public for reasons unrelated to the original design of the public/private divide. Regulations imposed on public firms are likely to not only be increasingly under- and over-inclusive, but also to apply to a class of companies whose coherency as an economic phenomenon may be increasingly suspect.

Crater Depth after the Impact of Multiple Drops into Deep Pools

Many studies have been devoted to single drop impacts onto liquid films and pools, while just a few are available about double drop or drop train impacts, despite the fact that the latter are more realistic situations. Thus, computational fluid dynamics with a volume-of-fluid approach was used here to simulate the impact of multiple drops into deep pools. The aim was to verify if multiple drop impacts significantly differ from single drops ones, and if the models available in the literature for the crater depth in the case of single impacts are reliable also for the multiple drop cases. After validation against experimental data for single and double drop impacts, simulations for four to 30 drops, with a diameter of 2.30 mm, impact velocities 1.0, 1.4, 1.8, and 2.2 m/s, and random initial positions in the domain were performed. The results showed that the time evolution of the crater depth for multiple impacts is similar to the single drop case during the inertial phase, while the following behavior is very different. Consequently, the available models for the maximum crater depth during single drop impacts can still predict the upper and lower bounds of the values of the crater depth during multiple drop impacts within 5% deviation.

Band-gap structure of the spectrum of the water-wave problem in a shallow canal with a periodic family of deep pools

We consider the linear water-wave problem in a periodic channel Pi ^h subset {{mathbb {R}}}^3, which is shallow except for a periodic array of deep potholes in it. Motivated by applications to surface wave propagation phenomena, we study the band-gap structure of the essential spectrum in the linear water-wave system, which includes the spectral Steklov boundary condition posed on the free water surface. We apply methods of asymptotic analysis, where the most involved step is the construction and analysis of an appropriate boundary layer in a neighborhood of the joint of the potholes with the thin part of the channel. Consequently, the existence of a spectral gap for small enough h is proven.

An appreciation: Matthew Alastair Parkes (1961–2020)

An appreciation:Matthew Alastair Parkes (1961–2020) Nigel T. Monaghan, Michael J. Simms, Patrick N. Wyse Jackson, and John Murray Matthew Parkes was a highly respected geologist and good friend to many who knew him. His legacy is his enduring scientific research, published in many popular articles, journals and books. It was important to him that geology was not only thoroughly researched and published for the scientific community, but that it should also be made fully accessible for the general public, particularly for any budding geologist. Once Matthew discovered geology as a teenager, the fascination never waned, and his work covered a wide expanse of geoscience topics across many countries. Click for larger view View full resolution The geologist Matthew was born 8 July 1961 and grew up in Hertfordshire. At school he focused on sciences, culminating with A levels in Geology and Geography in 1981. He worked at the Soil Survey of England and Wales, then studied geology at Sheffield University and was awarded his BSc in 1985. He then came to Ireland to study for his PhD at University College Galway (UCG; now University of Galway) as a recipient of an Anglo-Irish Postgraduate Exchange Scholarship. With typical careful dedication Matthew studied small areas of rocks of Ordovician and Silurian age on the south-eastern margin of the Iapetus Ocean, from Meath to Waterford, under the supervision of David Harper. These island relics with their endemic brachiopod faunas are poorly exposed and it took considerable determination to get decent fossils out of the scrappy outcrops. His good friend in UCG Eamon Doyle, now geologist for the Burren Geopark in County Clare, studied the other side of that ocean, but from the same office. Even before he completed his PhD in 1990, Matthew was working as an Assistant Lecturer and looking after overseas students on summer programmes. A post-doctoral appointment in Trinity College to work on the Irish-Italian EU-funded project 'Silurian ecostratigraphy in Ireland and Sardinia' organised by Charles Holland brought Matthew to Dublin in 1990 where he shared an office with Mike Simms. He was involved in leading student field trips in Ireland and overseas to the Mendip Hills and Devon and Dorset coasts. In 1997 he was awarded a Sylvester-Bradley Award by the Palaeontological Association. [End Page 1] Geologists will appreciate the quality and diversity of Matthew's contributions to our science. He produced well over a hundred publications, many as collaborations with experts in Ordovician rocks in other countries. His output ranged from the Geological Society's correlation of the Ordovician (Fortey et al. 2000), to books on Irish geology county by county and much more besides (see bibliography). Matthew produced high quality papers on Irish Paleozoic faunas that included studies on brachiopods (Parkes 1990; Harper et al. 1990, 2010), trilobites (Parkes and Owen 1994; Owen and Parkes 1996, 2000), Caradoc and Telychian faunas of south east and north west Ireland respectively (Parkes et al. 2017; Parkes 1993), and he also contributed to an assessment of elements of the significant Pennsylvanian Jarrow fauna (Orr et al. 1996). Matthew's publications on the Ordovician and Silurian faunas of Ireland, based on his PhD studies and subsequent research, have provided a significant volume of data that informs our current understanding of Lower Paleozoic geology in this part of the globe. The caver Matthew's time at Galway allowed him to indulge his love of caves and karst landscapes, something he maintained for the rest of his life, and caving led to many great friendships. Exploring Horse Discovery, near Cong, his height proved an advantage. The deep pool just inside was easily negotiated by Matthew (at six feet, seven and a half inches) but, as recalled by Mike Simms, it was a swim for the others in the group. Caving together became a lifelong activity, renewed in Wales when they found themselves working together in Cardiff, and again back in Ireland with Matthew based in Dublin and Mike in Belfast. The coast at Portrane, Dublin, with its Ordovician limestone shelly faunas was a great attraction and featured in Matthew's research. It was also a place where Mike found caves and Matthew discovered palaeokarst features...

An Appreciation: Matthew Alastair Parkes (1961-2020)

AN APPRECIATION: MATTHEW ALASTAIR PARKES (1961–2020) NIGEL T. MONAGHAN, MICHAEL J. SIMMS, PATRICK N. WYSE JACKSON and JOHN MURRAY Matthew Parkes was a highly respected geologist and good friend to many who knew him. His legacy is his enduring scientific research, published in many popular articles, journals and books. It was important to him that geology was not only thoroughly researched and published for the scientific community, but that it should also be made fully accessible for the general public, particularly for any budding geologist. Once Matthew discovered geology as a teenager, the fascination never waned, and his work covered a wide expanse of geoscience topics across many countries. The geologist Matthew was born 8 July 1961 and grew up in Hertfordshire. At school he focused on sciences, culminating with A levels in Geology and Geography in 1981. He worked at the Soil Survey of England and Wales, then studied geology at Sheffield University and was awarded his BSc in 1985. He then came to Ireland to study for his PhD at University College Galway (UCG; now University of Galway) as a recipient of an Anglo-Irish Postgraduate Exchange Scholarship. With typical careful dedication Matthew studied small areas of rocks of Ordovician and Silurian age on the south-eastern margin of the Iapetus Ocean, from Meath to Waterford, under the supervision of David Harper. These island relics with their endemic brachiopod faunas are poorly exposed and it took considerable determination to get decent fossils out of the scrappy outcrops. His good friend in UCG Eamon Doyle, now geologist for the Burren Geopark in County Clare, studied the other side of that ocean, but from the same office. Even before he completed his PhD in 1990, Matthew was working as an Assistant Lecturer and looking after overseas students on summer programmes. A post-doctoral appointment in Trinity College to work on the Irish-Italian EU-funded project ‘Silurian ecostratigraphy in Ireland and Sardinia’ organised by Charles Holland brought Matthew to Dublin in 1990 where he shared an office with Mike Simms. He was involved in leading student field trips in Ireland and overseas to the Mendip Hills and Devon and Dorset coasts. In 1997 he was awarded a Sylvester-Bradley Award by the Palaeontological Association. Irish Journal of Earth Sciences 40 (2022), 1–9 © 2022 Royal Irish Academy 2 Irish Journal of Earth Sciences (2022) Geologists will appreciate the quality and diversity of Matthew’s contributions to our science. He produced well over a hundred publications, many as collaborations with experts in Ordovician rocks in other countries. His output ranged from the Geological Society’s correlation of the Ordovician (Fortey et al. 2000), to books on Irish geology county by county and much more besides (see bibliography ). Matthew produced high quality papers on Irish Paleozoic faunas that included studies on brachiopods (Parkes 1990; Harper et al. 1990, 2010), trilobites (Parkes and Owen 1994; Owen and Parkes 1996, 2000), Caradoc and Telychian faunas of south east and north west Ireland respectively (Parkes et al. 2017; Parkes 1993), and he also contributed to an assessment of elements of the significant Pennsylvanian Jarrow fauna (Orr et al. 1996). Matthew’s publications on the Ordovician and Silurian faunas of Ireland, based on his PhD studies and subsequent research, have provided a significant volume of data that informs our current understanding of Lower Paleozoic geology in this part of the globe. The caver Matthew’s time at Galway allowed him to indulge his love of caves and karst landscapes, something he maintained for the rest of his life, and caving led to many great friendships. Exploring Horse Discovery, near Cong, his height proved an advantage . The deep pool just inside was easily negotiated by Matthew (at six feet, seven and a half inches) but, as recalled by Mike Simms, it was a swim for the others in the group. Caving together became a lifelong activity, renewed in Wales when they found themselves working together in Cardiff, and again back in Ireland with Matthew based in Dublin and Mike in Belfast. The coast at Portrane, Dublin, with its Ordovician limestone shelly faunas was a great attraction and featured in Matthew’s research. It was also a...

Life at the borderline: Responses of Ganges river dolphins to dry‐season flow regulation of river and canal habitats by the Farakka barrage

Abstract Modification of river flows by dams and barrages has fragmented riverine habitats and threatened the survival of Indian subcontinental river dolphins. In this study, habitat use by endangered Ganges river dolphins in response to dry‐season operations (December‐March) of the Farakka barrage on the Ganga River, located about 20 km upstream of the India–Bangladesh border, was assessed. Ten surveys were conducted in: (i) the Ganga River below the barrage, where rapid changes in water levels were expected owing to barrage operations; (ii) the Farakka feeder canal with stable water levels; and (iii) the Hooghly River downstream of the canal. Dolphin distribution, water depth, fishing boat count and temperature were recorded in all surveys and the data were analysed in a dynamic occupancy modelling framework. Temporal trends in river discharge, primary productivity and fish availability were also estimated to explain river dolphin responses. Occupancy and colonization by dolphins increased in all stretches by spring/March, correlated with rising water temperature and increased fishing intensity, which was related to upstream migration of hilsa fish. In the Ganga River, dolphin occupancy in deep river pools remained stable, but resulted in increased overlap with fisheries as river flow declined. The feeder canal, with stable flows, witnessed increased colonization by dolphins, but also greater risk of bycatch in fishing nets. The canal that appeared as a hydrological refuge thus became an ‘ecological trap’. The findings highlight the need for integration of flow maintenance and fishery regulations in the monitoring and management of canals as effective refuges for riverine species. We advocate the inclusion of ecological flow criteria and fishery regulations to reduce dolphin bycatch mortality, in the context of establishing river dolphin conservation plans and transboundary water‐sharing guidelines. The revision of the India–Bangladesh water‐sharing treaty in 2026 could incorporate the above considerations.