Статті в журналах з теми "KPg boundary"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: KPg boundary.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 статей у журналах для дослідження на тему "KPg boundary".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте статті в журналах для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Liu, Liang, Jin Zhang, Frank E. Rheindt, Fumin Lei, Yanhua Qu, Yu Wang, Yu Zhang, et al. "Genomic evidence reveals a radiation of placental mammals uninterrupted by the KPg boundary." Proceedings of the National Academy of Sciences 114, no. 35 (August 14, 2017): E7282—E7290. http://dx.doi.org/10.1073/pnas.1616744114.
Анотація:
The timing of the diversification of placental mammals relative to the Cretaceous–Paleogene (KPg) boundary mass extinction remains highly controversial. In particular, there have been seemingly irreconcilable differences in the dating of the early placental radiation not only between fossil-based and molecular datasets but also among molecular datasets. To help resolve this discrepancy, we performed genome-scale analyses using 4,388 loci from 90 taxa, including representatives of all extant placental orders and transcriptome data from flying lemurs (Dermoptera) and pangolins (Pholidota). Depending on the gene partitioning scheme, molecular clock model, and genic deviation from molecular clock assumptions, extensive sensitivity analyses recovered widely varying diversification scenarios for placental mammals from a given gene set, ranging from a deep Cretaceous origin and diversification to a scenario spanning the KPg boundary, suggesting that the use of suboptimal molecular clock markers and methodologies is a major cause of controversies regarding placental diversification timing. We demonstrate that reconciliation between molecular and paleontological estimates of placental divergence times can be achieved using the appropriate clock model and gene partitioning scheme while accounting for the degree to which individual genes violate molecular clock assumptions. A birth-death-shift analysis suggests that placental mammals underwent a continuous radiation across the KPg boundary without apparent interruption by the mass extinction, paralleling a genus-level radiation of multituberculates and ecomorphological diversification of both multituberculates and therians. These findings suggest that the KPg catastrophe evidently played a limited role in placental diversification, which, instead, was likely a delayed response to the slightly earlier radiation of angiosperms.
2
Rosado, Margarita, Ruslan Gabbasov, and Isaura Fuentes-Carrera. "Numerical Simulations of KPG 302 (NGC 3893/96)." Proceedings of the International Astronomical Union 6, S277 (December 2010): 259–62. http://dx.doi.org/10.1017/s1743921311022903.
Анотація:
AbstractWe present the results of numerical simulations on the M51-type galaxy pair KPG 302 (NGC 3893/96) taking as boundary conditions for these simulations the results of our observations on the kinematics of this pair. The observations allow us to deduce the different components of each galaxy in the pair (stellar disk and bulge, dark matter halo) as well as the geometry of the encounter at the present time. The numerical simulations were carried out using GADGET2 numerical code including gas. We describe in detail how the numerical simulations are being done. We succeeded to reproduce the actual conditions of the pair, in particular, the grand-design spiral arms of NGC 3893 (the main galaxy of the pair) when the numerical simulations include gas, consider a parabolic direct collision and multiple passages.
3
DePalma, Robert A., Jan Smit, David A. Burnham, Klaudia Kuiper, Phillip L. Manning, Anton Oleinik, Peter Larson, et al. "A seismically induced onshore surge deposit at the KPg boundary, North Dakota." Proceedings of the National Academy of Sciences 116, no. 17 (April 1, 2019): 8190–99. http://dx.doi.org/10.1073/pnas.1817407116.
Анотація:
The most immediate effects of the terminal-Cretaceous Chicxulub impact, essential to understanding the global-scale environmental and biotic collapses that mark the Cretaceous–Paleogene extinction, are poorly resolved despite extensive previous work. Here, we help to resolve this by describing a rapidly emplaced, high-energy onshore surge deposit from the terrestrial Hell Creek Formation in Montana. Associated ejecta and a cap of iridium-rich impactite reveal that its emplacement coincided with the Chicxulub event. Acipenseriform fish, densely packed in the deposit, contain ejecta spherules in their gills and were buried by an inland-directed surge that inundated a deeply incised river channel before accretion of the fine-grained impactite. Although this deposit displays all of the physical characteristics of a tsunami runup, the timing (<1 hour postimpact) is instead consistent with the arrival of strong seismic waves from the magnitude Mw∼10 to 11 earthquake generated by the Chicxulub impact, identifying a seismically coupled seiche inundation as the likely cause. Our findings present high-resolution chronology of the immediate aftereffects of the Chicxulub impact event in the Western Interior, and report an impact-triggered onshore mix of marine and terrestrial sedimentation—potentially a significant advancement for eventually resolving both the complex dynamics of debris ejection and the full nature and extent of biotic disruptions that took place in the first moments postimpact.
4
Bininda-Emonds, Olaf R. P., and Andy Purvis. "Comment on “Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification”." Science 337, no. 6090 (July 5, 2012): 34.1–34. http://dx.doi.org/10.1126/science.1220012.
Анотація:
Meredith et al. (Reports, 28 October 2011, p. 521) question three findings of our delayed-rise hypothesis for present-day mammals made with reference to the Cretaceous-Paleogene (KPg) boundary, based on their new time tree of the group. We show that their own data do not support their objections and that the macroevolutionary patterns from the respective phylogenies are not statistically different.
5
Baas, Pieter, Steven R. Manchester, Elisabeth A. Wheeler, and Rashmi Srivastava. "Fossil wood with dimorphic fibers from the Deccan Intertrappean Beds of India – the oldest fossil Connaraceae?" IAWA Journal 38, no. 1 (February 13, 2017): 124–33. http://dx.doi.org/10.1163/22941932-20170162.
Анотація:
Wood of Connaroxylon dimorphum (Connaraceae, Oxalidales) from the Deccan Intertrappean Beds of India (KPg Boundary 65–67 MY BP) is described. It is characterized by parenchyma-like fiber bands alternating with normal fibers, septate and nonseptate fibers, vessel-ray pits with strongly reduced borders, uniseriate rays of square and upright cells, and radial tubules in the center of ray cells that are arranged in a herringbone pattern. The overall wood anatomy strongly resembles Melastomataceae p. p., Lagerstroemia p. p. (Lythraceae) and Connarus (Connaraceae). However, the shared radial tubules of Connarus and the fossil strongly tilt the evidence of botanical affinities towards this genus. This would represent the second and by far the oldest fossil wood record of the Connaraceae, also considerably older than the earliest fossil records of the family’s other plant parts, and one of the oldest fossils of the order Oxalidales.
6
Maruoka, Teruyuki, Yoshiro Nishio, Tetsu Kogiso, Katsuhiko Suzuki, Takahito Osawa, Yuichi Hatsukawa, and Yasuko Terada. "Enrichment of chalcophile elements in seawater accompanying the end-Cretaceous impact event." GSA Bulletin 132, no. 9-10 (February 5, 2020): 2055–66. http://dx.doi.org/10.1130/b35403.1.
Анотація:
Abstract Chalcophile elements are enriched in the Cretaceous–Paleogene (KPg) boundary clays from Stevns Klint, Denmark. As the concentrations of Cu, Ag, and Pb among several chalcophile elements such as Cu, Zn, Ga, As, Ag, and Pb are correlated with those of Ir, we suggest that these elements were supplied to the oceans by processes related to the end-Cretaceous asteroid impact. Synchrotron X-ray fluorescence images revealed that Cu and Ag exist as trace elements in pyrite grains or as 1–10-µm-sized discrete phases specifically enriched in Cu or Ag. The difference in carrier phases might depend on the materials that transported these elements to the seafloor. Based on their affinities with Cu, Ag, and Ir, iron oxides/hydroxides and organic matter were identified as the potential carrier phases that supplied these elements to the seafloor. Chalcophile elements adsorbed on iron oxides/hydroxides might have been released during reductive dissolution of iron oxides/hydroxides and incorporated into the pyrite produced simultaneously with the reductive dissolution of iron oxides/hydroxides. Both iron oxides/hydroxides and chalcophile elements were possibly released from the KPg target rocks (i.e., sedimentary rocks and/or basement crystalline rocks) by impact heating. Elements with a high affinity to organic matter would have been released upon its degradation and then converted into discrete minerals because of the deficiency in Fe ions. As such discrete minerals include the elements that form acid soluble sulfides such as Cu, Ag, and Pb, enrichment of these elements might have been induced by the intense acid rain just after the end-Cretaceous asteroid impact.
7
Umbarger, Keelan F., and John W. Snedden. "Delineation of post-KPg carbonate slope deposits as a sedimentary record of the Paleogene linkage of De Soto Canyon and Suwannee Strait, northern Gulf of Mexico." Interpretation 4, no. 1 (February 1, 2016): SC51—SC61. http://dx.doi.org/10.1190/int-2015-0086.1.
Анотація:
Seismicity generated from the Chicxulub impact has been postulated as the cause for the dramatic alteration of basin margin morphology and catastrophic movement of sediments in the Gulf of Mexico (GOM). Immediately following the impact, the formation of the Cretaceous-Paleogene boundary deposit (KPBD) was widespread and caused considerable erosion as portions of the Florida Escarpment collapsed, inducing sediment failure on the northern Florida Platform and formation of the ancestral De Soto Canyon. Overlying the more prominent KPBD existed a distinct, younger, post-Cretaceous/Paleogene carbonate slope deposit (CSD) confined within the De Soto Canyon bathymetric feature. Presence of this discrete unit provided insight into the post-impact history of De Soto Canyon and its long-duration connection to the Suwannee Strait, which linked the GOM with the Atlantic Ocean for almost 40 ma. We have postulated that the bathymetric low of the De Soto Canyon acted as a conduit for west to east sediment movement from nearby carbonate-dominated shorelines into the canyon in episodic sediment transport events from the Danian to the earliest Miocene. Closure of the Suwannee Strait, due to sediment infilling, terminated deposition of the De Soto Canyon CSD. This was followed by major siliciclastic influx as the paleo-Tennessee drainage system began to enter the Mississippi Canyon area.
8
Breiter, Karel, Jaromír Tvrdý, and Pavel Jedlička. "Petrological diversity of leucocratic rocks at the sodium-potassium feldspar deposit Krásno – Vysoký kámen." Geoscience Research Reports 56, no. 1 (May 9, 2023): 14–20. http://dx.doi.org/10.3140/zpravy.geol.2023.03.
Анотація:
The presented study aims to reevaluate the geological structure of the Krásno-Vysoký Kámen feldspar deposit and its relationship to the surrounding rocks using chemical and imaging methods. For this purpose, we have documented in detail all the preserved fragments of drill cores from the survey in the 1960s and 1970s years, and 21 exploratory boreholes of the KP series (Fig. 1) realized in 2021, including about 600 chemical XRF bulk-rocks analyzes of rocks from these drillings. The Krásno-Vysoký Kámen open pit is located about 1 km northwest of the Krásno village, western Bohemia. Subject of mining is a complex of leucocratic, feldspar-rich granitoids consisting of predominant medium-grained leucogranite with mainly subhorizontal intercalations of syenite, aplite-pegmatite and feldspar-rich metasomatites. Both the immediate bedrock and the exposed overburden of the leucogranite complex consist of biotite granites. The leucogranite complex forms a lenticular body, the lower boundary of which decreases from N and NW towards E and S (Fig. 5). Especially on the western side of the open pit, the contact of the two rocks is relatively steep, further to the east it flattens. Medium-grained leucocratic granite makes up most of the volume of the deposit. It has a magmatic texture (Fig. 2a) with euhedral, short columnar albite crystals, subhedral orthoclase grains, irregular late quartz grains and low mica content (Tab. 2); apatite and rare topaz and niobium rutile are also present. In the SW edge of the quarry, contact facies of the leucogranite with several layers of oriented crystallization of quartz is exposed. Locally, leucogranite changes to leucosyenite (Fig. 2b). The leucosyenite is still a medium-grained rock with a magmatic texture, but the quartz content decreases (<10%) and the mica is only accessory. Several flat veins of virtually mica-free aplite (Fig. 2c), from several dm to 5 m thick, are lined along the upper contact by a zone of oriented K-feldspar and quartz crystallization (i.e. stockscheider). Alkaline metasomatites (Fig. 2d) are medium to fine grained. Medium-grained varieties are macroscopically hardly distinguishable from igneous syenites; fine-grained varieties are similar to aplites. Feldspars in metasomatites already have a completely irregular worm-like shape, while the ratio of both feldspars fluctuates strongly. The underlying biotite granite is currently well exposed in the NW part of the quarry and was reached by wells KP4, KP5, KP6, and KP7. It is medium-grained granite with Li-biotite and topaz. The contact between this granite and the overlying leucocratic complex was interpreted as rapid transition in old boreholes (Pácal and Pavlů 1979), but sharp contact was found in the borehole KP4. The overlying biotite granite was exposed in the SW parts of the quarry and confirmed by 2 boreholes (KP2, KP3). Both types of biotite granite differ statistically in Fe, Na and K contents. The medians of the chemical composition of all rock types defined above are shown in Tab. 3, relationships between some elements in Fig. 3. While both types of biotite granites and aplite have a relatively homogeneous chemical composition, the composition of leucogranite, syenite and metasomatites is very variable, especially in terms of SiO2 and alkalis. When comparing both alkalis, a significantly greater variability of K2O contents (<1 to 9 wt. %) compared to Na2O (mostly 1-6 wt. %, but fewer samples with marginal values) is evident. Extreme samples containing almost only one of the feldspars can be found in the case of syenite, metasomatites and leucogranite. The total content of feldspars varies mainly between 40 and 70 wt. % in leucogranite, 70–90 wt. % in syenite, 50–70 wt. % in aplite and 50–90 wt. % in metasomatites. Significant vertical changes in the chemistry of macroscopically homogeneous leucocratic rocks are well documented in boreholes KP13 and KP14 (Fig. 4).
9
Al Ahmar, Rudy, and Joseph Majdalani. "On the Kármán momentum-integral approach and the Pohlhausen paradox: Extension to a cylinder in crossflow with a potential farfield motion." Physics of Fluids 34, no. 6 (June 2022): 063107. http://dx.doi.org/10.1063/5.0096780.
Анотація:
In this work, the Kármán–Pohlhausen (KP) momentum-integral approach based on optimized fourth-order (MX4) polynomial approximations of the velocity and temperature profiles is applied to a classical benchmark problem, namely, that of a cylinder in crossflow with a variable pressure gradient. This enables us to extract closed-form expressions for both hydrodynamic and thermal boundary-layer parameters and then compare the newly found solutions to their counterparts obtained using Pohlhausen's cubic (KP3) and quartic (KP4) polynomials. As usual, the farfield around the cylinder is modeled using potential flow theory and the momentum-integral analysis is paired with Walz's empirical expression for the momentum thickness, which is based on a wide collection of experiments. This procedure permits retrieving explicit relations for the pressure-sensitive KP3, KP4, and MX4 velocity profiles across the boundary layer; one also obtains accurate approximations for the pressure distribution around the cylinder as well as an improved prediction of the separation point, namely, to within 0.87% of the actual location. In this process, refined estimates are produced for several characteristic parameters whose distributions are found to be in favorable agreement with experimental measurements and numerical simulations. These include the disturbance, momentum, and displacement thicknesses as well as the skin friction, pressure, and total drag coefficients. Finally, the thermal analysis is undertaken using both isothermal and isoflux boundary conditions. For each of these cases, closed-form analytical solutions are obtained for the local Nusselt number distribution around the cylinder, and these distributions are found to exhibit noticeably reduced errors relative to their classical values.
10
Sarajedini, Ata. "The Formation Chronology of Local Group Spiral Galaxies." Symposium - International Astronomical Union 207 (2002): 73–82. http://dx.doi.org/10.1017/s0074180900223401.
Анотація:
The ‘Second Parameter Effect’ (2ndPE) has long been recognized as an important probe into the formation of spiral galaxies. The concept that the horizontal branch morphologies of globular clusters are primarily affected by metal abundance in the inner halo (RGC<8 kpc) of the Galaxy but require an additional parameter (probably cluster age) to explain their behavior in the outer halo (RGC > 8 kpc), suggests that the former experienced a rapid monotonic collapse while the latter underwent a slower chaotic formation scenario. As such, in the Milky Way, the so-called second parameter boundary is located at 8 kpc. We find that, in the other Local Group spirals — M31 and M33 — this boundary lies at ∼40 kpc and ∼0 kpc, respectively. We therefore speculate that the boundary delimiting rapid monotonic halo collapse from the chaotic accretion of dwarf galaxy fragments is inversely related to the mass of the spiral galaxy.
11
Berry, Keith, and Ganesh K. Jaganathan. "Did selection for seed traits across the Cretaceous/Paleogene boundary sort plants based on ploidy?" Acta Palaeobotanica 62, no. 2 (2022): 182–95. http://dx.doi.org/10.35535/acpa-2022-0012.
Анотація:
Paleobotanists debate whether the Cretaceous/Paleogene boundary (KPB) event was selective. As the hypothesis that the KPB event selected for plants with fast-return leaf economic traits (e.g. deciduousness) has lost empirical support in recent investigations, researchers have turned to alternative hypotheses to explain an abrupt decline in primary productivity across the KPB. Two contemporary hypotheses designed to explain selectivity among plants across the KPB are that (1) polyploids exhibited greater survivorship than their diploid progenitors or counterparts (i.e. the KPB-whole genome duplication or WGD hypothesis) and that (2) plants with desiccation-tolerant (DT), i.e. orthodox, seeds exhibited greater survivorship than plants with desiccationsensitive (DS), also known as recalcitrant, seeds. Late embryogenesis abundant (LEA) protein gene families are perceived to confer DT and seed longevity among vascular plants. Non-parametric Wilcoxon signed-rank test for matched pairs and a Mann-Whitney U test reveal that plant lineages perceived to have undergone WGD across the KPB exhibit significantly greater numbers of LEA genes than those that did not. On the basis of these data, this investigation elicits a merger between the KPB-WGD and KPB-seed traits concepts. However, emphasis is shifted from the concept of WGD as an immediate adaptation to climatic stress at the KPB (the KPB-WGD hypothesis) to the concept that WGD was an exaptation, which, by definition, fortuitously enhanced the survival of vascular plants across the KPB but that probably evolved initially in other climatic contexts.
12
Sprain, Courtney J., Paul R. Renne, Loÿc Vanderkluysen, Kanchan Pande, Stephen Self, and Tushar Mittal. "The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary." Science 363, no. 6429 (February 21, 2019): 866–70. http://dx.doi.org/10.1126/science.aav1446.
Анотація:
Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes in the magmatic plumbing system. We also found that the DT did not erupt in three discrete large pulses and that >90% of DT volume erupted in <1 million years, with ~75% emplaced post-KPB. Late Cretaceous records of climate change coincide temporally with the eruption of the smallest DT phases, suggesting that either the release of climate-modifying gases is not directly related to eruptive volume or DT volcanism was not the source of Late Cretaceous climate change.
13
Kim, Eun Jeong. "The Role of Parents for Boundary Formation and Separation-Individuation of Adolescents." Association for Studies in Parents and Guardians 6, no. 3 (November 30, 2019): 1–19. http://dx.doi.org/10.56034/kjpg.2019.6.3.1.
14
Tao, Gui Lan, and Li Zhang. "Dynamic Response Analysis of Docking Chamber Structure Considering Viscoelastic Boundary Condition." Applied Mechanics and Materials 405-408 (September 2013): 1939–44. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.1939.
Анотація:
Spring-damper units were set on the boundaries to absorb incident waves and reflected scattering waves to realize viscoelastic artificial boundary (VAB). The equivalent node load input method was used to simulate the VAB and viscoelastic boundary element wave input. Programming is based on APDL secondary development language with ANSYS finite element software. Considering the interaction between chamber structure and the surrounding soil, docking chamber structure dynamic model is established based on the VAB. The linear elastic model was used for concrete structure. The D-P nonlinear model was used for the back soil calculation. Docking chamber structure dynamic analysis under conditions of fixed boundaries and viscoelastic boundaries were conducted. The result indicated that under the viscoelastic boundary conditions, dynamic acceleration response is significant on the top of the lock wall, which is approximately 2.5 times of the value on the bottom of the lock wall. The maximum response stress appears near the cross point of the lock wall and the bottom floor with value of approximately 5620 kPa;.The chamber bottom floor is subjected to tension and maximum stress with the value of approximately 6180 kPa. Usually, the structure response under the fixed boundary conditions is higher than the structure response under the viscoelastic boundary conditions.
15
Brachman, R. WI, I. D. Moore, and R. K. Rowe. "The design of a laboratory facility for evaluating the structural response of small-diameter buried pipes." Canadian Geotechnical Journal 37, no. 2 (April 1, 2000): 281–95. http://dx.doi.org/10.1139/t99-104.
Анотація:
The design of a new laboratory facility for evaluating the structural response of small-diameter buried pipes (e.g., leachate collection pipes in landfills) is presented. The pipe is tested within a 2.0 m wide, 2.0 m long, and 1.6 m high prism of soil, subject to large vertical pressures (1000 kPa), with only minimal roughness and deflection of the lateral boundaries. Results from finite element analyses are presented to examine the effect of proximity, roughness, and stiffness of the lateral boundary on the soil and pipe response and how reasonable the laboratory idealizations are relative to the deep burial conditions expected to prevail in the field. Shear stresses arising from the roughness of the lateral boundaries alter the stresses acting around the pipe and reduce the proportion of the applied surcharge reaching the pipe. Outward deflection of the lateral boundaries also alters the stress state around the pipe, predominantly resulting from decreases in horizontal stresses within the soil. Reducing boundary friction to less than 5° and limiting the boundary deformation to less than 1 mm at a vertical surcharge of 1000 kPa provide a good idealization of field conditions for a deeply buried pipe.Key words: buried pipes, soil-structure interaction, laboratory testing, boundary friction.
16
Premović, Pavle I. "Cretaceous-Paleogene Boundary Clays from Spain and New Zealand: Arsenic Anomaly and the Deccan Traps." International Letters of Natural Sciences 55 (June 2016): 1–8. http://dx.doi.org/10.18052/www.scipress.com/ilns.55.1.
Анотація:
High arsenic (As) contents have been reported in numerous Cretaceous-Paleogene boundary (KPB) clays worldwide including that from Spain (at Caravaca and Agost) and N. Zealand (at Woodside Creek). The Deccan Traps (India) enormous volcanism is one of the interpretations which have been offered to explain this anomaly. This report shows that the estimated surface densities of As in the boundary clays in Spain and New Zealand strongly contradict that anomalous As was sourced by this volcanic event.
17
Premović, Pavle I. "Cretaceous-Paleogene Boundary Clays from Spain and New Zealand: Arsenic Anomaly and the Deccan Traps." International Letters of Natural Sciences 55 (June 3, 2016): 1–8. http://dx.doi.org/10.56431/p-zqqiro.
Анотація:
High arsenic (As) contents have been reported in numerous Cretaceous-Paleogene boundary (KPB) clays worldwide including that from Spain (at Caravaca and Agost) and N. Zealand (at Woodside Creek). The Deccan Traps (India) enormous volcanism is one of the interpretations which have been offered to explain this anomaly. This report shows that the estimated surface densities of As in the boundary clays in Spain and New Zealand strongly contradict that anomalous As was sourced by this volcanic event.
18
Feder, M. E., R. J. Gonzalez, T. Robbins, and C. R. Talbot. "Bulk flow of the medium and cutaneous sodium uptake in frogs: potential significance of sodium and oxygen boundary layers." Journal of Experimental Biology 174, no. 1 (January 1, 1993): 235–46. http://dx.doi.org/10.1242/jeb.174.1.235.
Анотація:
To examine the potential impact of fluid dynamic boundary layers on cutaneous ion exchange, we investigated how bulk flow of dilute Na+ solutions (< or = 1.0 mmol l-1) over the skin of intact frogs (Rana catesbeiana and Rana pipiens) affects cutaneous Na+ uptake (JNa(in)) and transepithelial potential (TEP). Cessation of stirring resulted in a 14-35% decrease in TEP and a 14-65% decrease in JNa(in). Two weeks' acclimation to an unstirred bath increased JNa(in) to levels 70% greater than in frogs acclimated to a continuously stirred bath and to levels comparable to those of frogs acclimated to deionized water. These effects are consistent with depletion of Na+ in the boundary layer, but are also consistent with depletion of O2 in the boundary layer, which might limit generation of ATP consumed by ATPases responsible for cutaneous Na+ uptake. To investigate this latter possibility, we measured TEP and JNa(in) while manipulating the PO2 of well-stirred external media at constant [Na+]. Hyperoxia (PO2 > or = 97 kPa) increased JNa(in) by 28% and had little or no effect on TEP. Hypoxia (PO2 < or = 1.5 kPa) reduced JNa(in) by 48% and decreased TEP by 22%. These results suggest that ionic and gaseous boundary layers may interact to affect cutaneous ion transport.
19
PINDER, ALAN W., and MARTIN E. FEDER. "Effect of Boundary Layers on Cutaneous Gas Exchange." Journal of Experimental Biology 154, no. 1 (November 1, 1990): 67–80. http://dx.doi.org/10.1242/jeb.154.1.67.
Анотація:
Boundary layers may offer significant resistance to cutaneous oxygen uptake by amphibians in water. This hypothesis was tested by measuring resistance to oxygen uptake as a function of water velocity in bullfrogs submerged at 5 °C and by direct measurements of the boundary layer with oxygen microelectrodes. The oxygen diffusion boundary layer was easily measurable with oxygen microelectrodes. The proportion of the total resistance to oxygen uptake represented by the boundary layer increased from 35 % at a water velocity of 5 cms−1 1 to over 90% at 0.1 cms−1. At water velocities below lcms−1 oxygen uptake was limited by the resistance of the boundary layer. At 0.1 cms−1, the partial pressure of oxygen immediately adjacent to the skin was only 2 kPa (15 mmHg); placing an immobilized frog in still water was tantamount to placing it in anoxic water. Body movements disrupted boundary layers efficiently; even occasional small movements by the animal (1 min−1) were sufficient to maintainoxygen uptake in still water.
20
Zuo, Zheng, Guangqing Yang, Zhijie Wang, He Wang, and Jing Jin. "Effect of Boundary Conditions on the Mechanical Behavior of the Geogrid–Soil Interface." Applied Sciences 11, no. 21 (October 25, 2021): 9942. http://dx.doi.org/10.3390/app11219942.
Анотація:
Geogrid-reinforced structures are extensively adopted in various engineering fields. At present, the influence of boundary conditions was not considered in design methods, bringing hidden dangers to the safety of the structure. In the current study, a series of pullout tests were carried out on high-density polyethylene (HDPE) geogrid-reinforced coarse sand. The magnitude and growth pattern of pullout resistance and the variation laws of interfacial shear strength indexes under four types of boundary conditions were analyzed. Additionally, the boundary reduction coefficient (BRC) was introduced to establish the relationship between rigid and flexible boundary for the design of the structure. The tests results showed that the boundary conditions cannot be ignored in the design of structures, especially in the front. When the normal loading was up to 120 kPa, the BRC-top and BRC-positive could be taken as 0.9 and 0.5, respectively, and verified by fitting results. The boundary conditions affected the pullout resistance, while the vertical loading corresponding to the maximum pullout resistance was not related to boundary conditions. Investigating the interaction of the geogrid–soil under different boundary conditions can help to improve the understanding of the behavior of reinforced soil structure, and to achieve a more efficient and economical design.
21
Chidambaranathan, Manisankar, Shashi B. Verma, and Ethirajan Rathakrishnan. "Control of incident shock-induced boundary-layer separation using steady micro-jet actuators at M∞ = 3.5." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 4 (January 2, 2018): 1284–306. http://dx.doi.org/10.1177/0954410017749868.
Анотація:
Experiments were carried out to control an incident shock-induced separation associated with 22° shock generator in a Mach 3.5 flow using an array of steady micro-jet actuators. Four micro-jet actuator configurations based on the variation in their pitch angle [Formula: see text], skew angle [Formula: see text] and span-wise spacing were used. Each of these configurations were placed 14 δ upstream of the interaction and operated with injection pressures ( Poj) varying from 140 to 643 kPa. While no major variations in separation characteristics were observed for Poj < 140 kPa, significant modifications were observed beyond [Formula: see text] of 140 kPa and until 208.5 kPa. Amongst all the four control configurations, micro-jet vortex generator 2 ([Formula: see text] showed the best control with a 2 δ downstream shift in separation point location relative to no-control. The shift is also accompanied with a change in maximum zero-crossing frequency towards higher frequency (almost twice), a reduction in the intermittency length and an increase in the correlation value between the boundary layer just upstream of the interaction and the intermittent region. These results indicate that the effectiveness of micro-jet vortex generator 2 is probably due to the improved entrainment levels in the shear layer induced by the micro-vortices which are generated downstream of these devices. The increase of the skew angle [Formula: see text] from 180° to 270° for the same pitch angle of β = 45° (micro-jet vortex generator 3) seems to have no major impact on the separation characteristics. The reduction in the span-wise spacing (micro-jet vortex generator 4) resulted in deterioration of the flow field due to the jet-to-jet interaction with increasing injection pressures.
22
Premović, Pavle I. "Experimental evidence for the global acidification of surface ocean at the Cretaceous–Palaeogene boundary: the biogenic calcite-poor spherule layers." International Journal of Astrobiology 8, no. 3 (July 2009): 193–206. http://dx.doi.org/10.1017/s1473550409990139.
Анотація:
AbstractThe massive amount of impact-generated atmospheric CO2at the Cretaceous-Palaeogene boundary (KPB) would have accumulated globally in the surface ocean, leading to acidification and CaCO3undersaturation. These chemical changes would have caused a crisis of biocalcification of calcareous plankton and enhanced dissolution of their shells; these factors together may have played a crucial role in forming the biogenic calcite-poor KPB spherule layers observed at numerous oceanic sites and marine (now on land) sites in Europe and Africa. Experimental data and observations indicate that the deposition spherule layer probably lasted only a few decades at most.
23
Premović, P. I. "Distal “impact” layers and global acidification of ocean water at the Cretaceous-Paleogene boundary (KPB)." Geochemistry International 49, no. 1 (January 2011): 55–65. http://dx.doi.org/10.1134/s0016702911010095.
24
Балакирева, В. Б., В. П. Горелов, Л. А. Дунюшкина та А. В. Кузьмин. "Влияние влажности на электроперенос протонпроводящих перовскитов AZr-=SUB=-0.95-=/SUB=-Sc-=SUB=-0.05-=/SUB=-O-=SUB=-3-alpha-=/SUB=- (A=Ca, Sr, Ba) в окислительной атмосфере". Физика твердого тела 61, № 4 (2019): 645. http://dx.doi.org/10.21883/ftt.2019.04.47406.266.
Анотація:
AbstractThe total, bulk, and grain boundary conductivities of proton-conducting zirconates of general formula AZr_0.95Sc_0.05O_3 – α (AZS), where A = Ca, Sr, Ba, are measured in air with different humidity levels. The conductivity is measured using the four-probe dc method (600–900°C) and impedance spectroscopy (30–800°C). The impact of humid atmosphere on the total, bulk, and grain boundary conductivities of the AZS system is studied at different humidity levels: $${{p}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 0.04, 0.61, and 2.5 kPa. Humidity is found to have a considerable effect on the conductivity of our CaZS and BaZS at lower temperatures, suggesting the likelihood of hydronium ion-mediated transport.
25
Costa, Roberto D. D., Oscar Cavichia, and Walter J. Maciel. "Planetary nebulae and determination of the bulge–disk boundary." Proceedings of the International Astronomical Union 8, S289 (August 2012): 375–78. http://dx.doi.org/10.1017/s1743921312021746.
Анотація:
AbstractIn this paper, a sample of planetary nebulae in the Galaxy's inner-disk and bulge is used to find the galactocentric distance that optimally separates these two populations in terms of their abundances. Statistical distance scales were used to investigate the distribution of abundances across the disk–bulge interface, while a Kolmogorov–Smirnov test was used to find the distance at which the chemical properties of these regions separate optimally. The statistical analysis indicates that, on average, the inner population is characterized by lower abundances than the outer component. Additionally, for the α-element abundances, the inner population does not follow the disk's radial gradient toward the Galactic Center. Based on our results, we suggest a bulge–disk interface at 1.5 kpc, marking the transition between the bulge and the inner disk of the Galaxy as defined by the intermediate-mass population.
26
Adamenko, N. A., G. V. Agafonova, D. A. An, A. V. Kazurov, and V. S. Pirozhenko. "RESEARCH OF THERMOMECHANICAL PROPERTIES OF UHMWPE AND ITS COMPOSITE WITH QGP AFTER EXPLOSIVE COMPRESSION." IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, no. 2(249) (February 25, 2021): 30–33. http://dx.doi.org/10.35211/1990-5297-2021-2-249-30-33.
Анотація:
To develop the technology of explosive pressing of ultrahigh molecular weight polyethylene (UHMWPE) and its powder composite mixtures with inorganic fillers, the thermomechanical properties of an unfilled polymer and a composite containing 3% coke graphite powder (KGP) after explosive pressing were studied. It was found that explosive pressing with a pressure of 0.25-1.3 gpa provides high heat resistance of UHMWPE and the studied composite (154-156 °C), and the filler restrains the thermal deformation expansion of the polymer, which is associated with increased intermolecular and adhesive interaction at the phase boundary. Thus, the method of explosive pressing can be recommended for industrial processing of UHMWPE and its composite mixture with 3 % KGP.
27
Bajdak, Marjana. "Obraz życia i śmierci w kobiecych narracjach Wielkiej Wojny na podstawie materiałów z Galicji Wschodniej." Krakowskie Pismo Kresowe 9 (September 30, 2018): 73–89. http://dx.doi.org/10.12797/kpk.09.2017.09.03.
Анотація:
Images of Life and Death in Women’s Discourse on the Great War (Based on Materials from Eastern Galicia)´The First World War changed the relatively stable and comprehensible life of women in Eastern Galicia. It made everyone ponder over the concepts of life and death. Women hardly thought about life in the war in philosophical categories. For them it was an everyday struggle. ´The war manifested the contrast of life and death, and at the same time, immediately led the women to assert that the boundary between being and non-existence was too blurry, almost unreal, and could be crossed at any moment. The fear of death was usually greater when women obtained higher education and their living conditions were better, and the attitude to death depended on what place it occupied in the system of values of the whole society, as well as that of the individual, and on women’s subjective perception of the phenomenon of death. Life became more valuable at the end of the war.
28
Mohr, Rachel C., Thomas S. Tobin, Sierra V. Petersen, Andrea Dutton, and Elizabeth Oliphant. "Subannual stable isotope records reveal climate warming and seasonal anoxia associated with two extinction intervals across the Cretaceous-Paleogene boundary on Seymour Island, Antarctica." Geology 48, no. 11 (July 21, 2020): 1131–36. http://dx.doi.org/10.1130/g47758.1.
Анотація:
Abstract High-resolution stable isotope (δ18O and δ13C) sclerochronology of accretionary carbonate bivalve shells can provide subannual environmental records useful for understanding intervals of extinction, which are commonly periods of rapid change and instability. Here, we present results from high-resolution serial sampling of Lahillia larseni bivalve shells across the Cretaceous-Paleogene boundary (KPB) on Seymour Island, Antarctica. These data highlight two intervals of anomalous δ18O and δ13C values that coincide with condensed fossil last occurrences: one at the KPB and one at an apparent extinction event 150 k.y. earlier. We interpret these two intervals to represent periods of both climate warming, as indicated by lower δ18O, and seasonal anoxia or euxinia, as evidenced by anomalously low (−21.6‰ to −3.0‰ VPDB [Vienna Peedee belemnite]) δ13C values with high (2‰ to 19‰ in magnitude) seasonal variation. Low-oxygen conditions may have acted as a kill mechanism at the earlier extinction interval and possibly prolonged recovery from the KPB extinction.
29
Zeng, Qingyun, Silvestre Roberto Gonzalez-Avila, Rory Dijkink, Phoevos Koukouvinis, Manolis Gavaises, and Claus-Dieter Ohl. "Wall shear stress from jetting cavitation bubbles." Journal of Fluid Mechanics 846 (May 4, 2018): 341–55. http://dx.doi.org/10.1017/jfm.2018.286.
Анотація:
The collapse of a cavitation bubble near a rigid boundary induces a high-speed transient jet accelerating liquid onto the boundary. The shear flow produced by this event has many applications, examples of which are surface cleaning, cell membrane poration and enhanced cooling. Yet the magnitude and spatio-temporal distribution of the wall shear stress are not well understood, neither experimentally nor by simulations. Here we solve the flow in the boundary layer using an axisymmetric compressible volume-of-fluid solver from the OpenFOAM framework and discuss the resulting wall shear stress generated for a non-dimensional distance, $\unicode[STIX]{x1D6FE}=1.0$ ($\unicode[STIX]{x1D6FE}=h/R_{max}$, where $h$ is the distance of the initial bubble centre to the boundary, and $R_{max}$ is the maximum spherical equivalent radius of the bubble). The calculation of the wall shear stress is found to be reliable once the flow region with constant shear rate in the boundary layer is determined. Very high wall shear stresses of 100 kPa are found during the early spreading of the jet, followed by complex flows composed of annular stagnation rings and secondary vortices. Although the simulated bubble dynamics agrees very well with experiments, we obtain only qualitative agreement with experiments due to inherent experimental challenges.
30
Stawarz, Ł., and M. Ostrowski. "High Energy Radiation Generated at Boundary Shear Layers of Relativistic Jets." Publications of the Astronomical Society of Australia 19, no. 1 (2002): 22–25. http://dx.doi.org/10.1071/as01092.
Анотація:
AbstractA simple model of cosmic ray electron acceleration at the jet boundary yields a power law particle energy distribution of ultra-relativistic electrons with an energy cut-off growing with time, and, finally, a growing particle bump at the energy where energy gains equal radiation losses. For such electron distribution, in tens-of-kpc scale jets, we derived the observed time-varying spectra of synchrotron and inverse Compton radiation, including Comptonisation of synchrotron and cosmic microwave background photons. Slowly varying spectral index along the jet in the ‘low frequency’ spectral range is a natural consequence of boundary layer acceleration. Variations of the high energy bump of the electron distribution can give rise to anomalous behaviour in the X-ray band in comparison to the lower frequencies.
31
Deng, Wei, and Ken-ichi Tsubota. "Numerical Modeling and Simulation of Blood Flow in a Rat Kidney: Coupling of the Myogenic Response and the Vascular Structure." Processes 10, no. 5 (May 18, 2022): 1005. http://dx.doi.org/10.3390/pr10051005.
Анотація:
A numerical simulation was carried out to investigate the blood flow behavior (i.e., flow rate and pressure) and coupling of a renal vascular network and the myogenic response to various conditions. A vascular segment and an entire kidney vascular network were modeled by assuming one single vessel as a straight pipe whose diameter was determined by Murray’s law. The myogenic response was tested on individual AA (afferent artery)–GC (glomerular capillaries)–EA (efferent artery) systems, thereby regulating blood flow throughout the vascular network. Blood flow in the vascular structure was calculated by network analysis based on Hagen–Poiseuille’s law to various boundary conditions. Simulation results demonstrated that, in the vascular segment, the inlet pressure Pinlet and the vascular structure act together on the myogenic response of each individual AA–GC–EA subsystem, such that the early-branching subsystems in the vascular network reached the well-regulated state first, with an interval of the inlet as Pinlet = 10.5–21.0 kPa, whereas the one that branched last exhibited a later interval with Pinlet = 13.0–24.0 kPa. In the entire vascular network, in contrast to the Pinlet interval (13.0–20.0 kPa) of the unified well-regulated state for all AA–GC–EA subsystems of the symmetric model, the asymmetric model exhibited the differences among subsystems with Pinlet ranging from 12.0–17.0 to 16.0–20.0 kPa, eventually achieving a well-regulated state of 13.0–18.5 kPa for the entire kidney. Furthermore, when Pinlet continued to rise (e.g., 21.0 kPa) beyond the vasoconstriction range of the myogenic response, high glomerular pressure was also related to vascular structure, where PGC of early-branching subsystems was 9.0 kPa and of late-branching one was 7.5 kPa. These findings demonstrate how the myogenic response regulates renal blood flow in vascular network system that comprises a large number of vessel elements.
32
Sun, Jiulun, Di Jin, Shengfang Huang, Kai Zhang, Weiqi Chen, and Xinyao Cheng. "The Characteristics of Gliding Arc Plasma and Its Activating Effect for Ramjet Combustion." Energies 15, no. 12 (June 9, 2022): 4260. http://dx.doi.org/10.3390/en15124260.
Анотація:
In order to improve the combustion performance of a ramjet under low temperature and pressure, a gliding arc plasma actuator was designed based on a typical evaporation flameholder. The discharge characteristics, as well as the activating effect of single-channel and three-channel gliding arc plasma under different carrier gas flow rates, were studied. Results show that with the increase in the carrier gas flow rate, the average duration of the gliding arc discharge becomes shorter, while the average power increases, and the specific input energy decreases. Compared with single-channel discharge, three-channel discharge has higher discharge power and energy injection rate, which makes a bigger actuated space. Through gliding arc plasma, the kerosene is cracked and H2, CH4, C2H2, C2H4, C3H6 and other small molecule components are produced. For three-channel gliding arc discharge, the effective cracking rate and the production rate of each component are higher than those of the single-channel discharge; both of them gradually increase with the increase in the carrier gas flow rate. The experiment results indicate that three-channel gliding arc plasma can effectively widen the ignition boundary and improve the combustion efficiency of ramjet combustion. The ignition pressure boundary is expanded from 60 kPa to 50 kPa under 390 K; the combustion efficiency is increased from 76% to 82%.
33
Zhang, Yuqi. "Model computation and biomechanical measurements of running shoes." Theoretical and Natural Science 10, no. 1 (November 17, 2023): 148–53. http://dx.doi.org/10.54254/2753-8818/10/20230333.
Анотація:
The design of running shoes is mainly to reduce mechanical stress through the deformation of the viscoelastic midsole, which is usually made of ethylene vinyl acetate (EVA) foam. This study aims to analyze and compute the heel pad stresses through simulated strikes. For stresses and strains, a non-linear model and its dierential equation (Eq.1) is reported. Through repeated measure ANOVAs, analyses and comparisons of the three methods for non-linear computation are made. Then detailed numerical approximations of a dierential equation are derived using Eulers method. In addition, Dinato reported biomechanical measures results for Air (Nike), Gel (Asics), and Adiprene (Adidas). The results are compared to simulated data correspondingly. The measured stresses (peak pressure, kPa) are 242.7 40.8, 239.5 420.0, and 246.5 51.6 respectively. The computed boundary stress is 55 kPa. These show signicant associations between the simulated and measured stress.
34
Hernandez Nava, Andres, Benjamin A. Black, Sally A. Gibson, Robert J. Bodnar, Paul R. Renne, and Loÿc Vanderkluysen. "Reconciling early Deccan Traps CO2 outgassing and pre-KPB global climate." Proceedings of the National Academy of Sciences 118, no. 14 (March 29, 2021): e2007797118. http://dx.doi.org/10.1073/pnas.2007797118.
Анотація:
A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous–Paleogene boundary (KPB) mass extinction at 66.05 ± 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO2 concentrations and trace-element proxies for CO2 to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO2 concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO2 concentrations range up to 0.23 to 1.2 wt% CO2 for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO2 concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO2 prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO2 rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO2 outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO2.
35
Suchan, Jared, and Shahid Azam. "Influence of Saline Pore Fluid on Soil Behavior during Evaporation." Geotechnics 2, no. 3 (September 2, 2022): 754–64. http://dx.doi.org/10.3390/geotechnics2030036.
Анотація:
Saline conditions govern soil behavior during evaporation, thereby affecting the water budget in semi-arid regions. This research examined the effects of saline pore fluid on soil behavior during evaporation. The results indicated volumetric reductions of about 5% for silty sand and about 15% for lean clay. The evaporative flux for silty sand decreased from 26 mg/m2∙s to 22 mg/m2∙s in StageII, remained at a constant flux in StageIII, and decreased to 13 mg/m2∙s in StageIV. The air entry and residual suction values were found to be 5 kPa and 100 kPa, respectively, and the total suction of about 5000 kPa merged with matric suction near the Stage II/Stage III boundary. The swell–shrink curve (SSC) was J-shaped with the only void ratio decrease in Stage II. In contrast, the evaporative flux for lean clay decreased from 30 mg/m2∙s to 15 mg/m2∙s in StageII, to 10 mg/m2∙s in StageIII, and then to 5 mg/m2∙s in StageIV. The air entry and residual suction values were 5 kPa and 2000 kPa, respectively, and the total suction during Stage II and Stage III ranged from 1000 kPa to 6000 kPa, with an average value of 3500 kPa. The SSC showed a major void ratio decrease in Stage II, marginal decrease in Stage III, and no decrease in Stage IV. Under high demand, the evaporative flux for silty sand was constant at 180 mg/m2∙s in StageIII and decreased to 50 mg/m2∙s in Stage IV, whereas it decreased for the lean clay from 230 mg/m2∙s to 145 mg/m2∙s in StageII, to 95 mg/m2∙s in StageIII, and then to 25 mg/m2∙s in StageIV. For both soils, the total water loss was found to be six times higher than that under low demand.
36
Jeong, Il-Gyo, and Bon-Chul Koo. "SRAO CO Observation of Supernova Remnants in l = 70° to 190°." Proceedings of the International Astronomical Union 9, S296 (January 2013): 183–87. http://dx.doi.org/10.1017/s1743921313009447.
Анотація:
AbstractWe present the results 12CO J = 1–0 line observations of eleven Galactic supernova remnants (SNRs) between l = 70° and 190° obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. We detected CO emission towards most of the remnants. In seven SNRs, molecular clouds show a good spatial relation with their radio morphology: G73.9+0.9, G84.2−0.8, G85.4+0.7, G85.9−0.6, G93.3+6.9 (DA530), 94.0+1.0 (3C 434.1), and G182.4+4.3. Two SNRs are particularly interesting. In G85.4+0.7, there is a filamentary molecular cloud aligned along the south-east boundary of the remnant. This cloud extends to the nearby Hii region G84.9+0.5. If the molecular cloud is associated with both the Hii region and the SNR, the distance to the SNR would be 5–7 kpc. In 3C 434.1, there is a large molecular cloud blocking the western half of the remnant where the radio continuum emission is faint. The cloud shows a very good spatial correlation with radio continuum features, which strongly suggests the physical association of the cloud with the SNR. This gives a distance of 3 kpc to the SNR. We performed 12CO J = 2–1 line observations of this cloud using Kölner Observatorium für Sub-Millimeter Astronomie (KOSMA) 3-m telescope and found a region where the 12CO J = 2–1/1–0 line ratio is high. We present a hydrodynamic model showing that 3C434.1 could have resulted from a SN explosion occurred just outside the boundary of a thin, molecular cloud.
37
Feng, Yan-Jie, David C. Blackburn, Dan Liang, David M. Hillis, David B. Wake, David C. Cannatella, and Peng Zhang. "Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary." Proceedings of the National Academy of Sciences 114, no. 29 (July 3, 2017): E5864—E5870. http://dx.doi.org/10.1073/pnas.1704632114.
Анотація:
Frogs (Anura) are one of the most diverse groups of vertebrates and comprise nearly 90% of living amphibian species. Their worldwide distribution and diverse biology make them well-suited for assessing fundamental questions in evolution, ecology, and conservation. However, despite their scientific importance, the evolutionary history and tempo of frog diversification remain poorly understood. By using a molecular dataset of unprecedented size, including 88-kb characters from 95 nuclear genes of 156 frog species, in conjunction with 20 fossil-based calibrations, our analyses result in the most strongly supported phylogeny of all major frog lineages and provide a timescale of frog evolution that suggests much younger divergence times than suggested by earlier studies. Unexpectedly, our divergence-time analyses show that three species-rich clades (Hyloidea, Microhylidae, and Natatanura), which together comprise ∼88% of extant anuran species, simultaneously underwent rapid diversification at the Cretaceous–Paleogene (K–Pg) boundary (KPB). Moreover, anuran families and subfamilies containing arboreal species originated near or after the KPB. These results suggest that the K–Pg mass extinction may have triggered explosive radiations of frogs by creating new ecological opportunities. This phylogeny also reveals relationships such as Microhylidae being sister to all other ranoid frogs and African continental lineages of Natatanura forming a clade that is sister to a clade of Eurasian, Indian, Melanesian, and Malagasy lineages. Biogeographical analyses suggest that the ancestral area of modern frogs was Africa, and their current distribution is largely associated with the breakup of Pangaea and subsequent Gondwanan fragmentation.
38
Zhang, Xiao, Yang Chen, Hui Li та Xin Zhou. "On the hadronic γ-ray emission from Tycho's Supernova Remnant". Proceedings of the International Astronomical Union 9, S296 (січень 2013): 358–59. http://dx.doi.org/10.1017/s1743921313009812.
Анотація:
AbstractTycho is one of nearly a dozen Galactic supernova remnants which are suggested to emit hadronic γ-ray emission. Among them, however, it is the only one in which the hadronic emission is proposed to arise from the interaction with low-density ambient medium. Based on the multi-band observations, we suggest that Tycho is encountering dense cloud at the northeastern boundary. The γ-ray emissions can be explained by hadronic process with self-consistent parameters, such as a modest energy conversion efficiency. In this SNR-cloud association scenario, the distance can be estimated as ~2.5 kpc.
39
Suchan, Jared, and Shahid Azam. "Influence of Desaturation and Shrinkage on Evaporative Flux from Soils." Geotechnics 2, no. 2 (May 22, 2022): 412–26. http://dx.doi.org/10.3390/geotechnics2020019.
Анотація:
An assessment of evaporation losses from soils is critical for sustainable agriculture in semi-arid regions. The purpose of this research was to determine the effect of desaturation and shrinkage on evaporative flux from representative soils. Results indicated that the surface area did not change for silty sand (6% volume reduction) and substantially increased for lean clay (17% volume reduction). The evaporative flux for silty sand decreased from 31 to 25 mg/m2∙s in Stage II, remained constant during Stage III, and decreased to 11 mg/m2∙s in Stage IV. In contrast, the lean clay showed a longer Stage II (34 to 14 mg/m2∙s), a near constant Stage III, albeit a similar Stage IV (13 to 3 mg/m2∙s). The air entry and residual suction values were 1 kPa and 100 kPa for silty sand and 5 kPa and 1400 kPa for lean clay. In both soils, the total suction merged with the matric suction at Stage II–Stage III boundary. Furthermore, the shrinkage curve was J-shaped for silty sand with the only void ratio decrease in Stage II, whereas that for the lean clay showed a significant void ratio decrease in Stage II, marginal decrease in Stage III, and no decrease in Stage IV. Under high demand, the silty sand exhibited Stage III and Stage IV evaporation, whereas the lean clay also showed significant flux during Stage II. For the investigated range of water content, the total water loss under high demand was found to be 7 times that under low demand.
40
Nickerson, David, Nicolas Smith, and Peter Hunter. "New developments in a strongly coupled cardiac electromechanical model." EP Europace 7, s2 (January 1, 2005): S118—S127. http://dx.doi.org/10.1016/j.eupc.2005.04.009.
Анотація:
Abstract Aim The aim of this study is to develop a coupled three-dimensional computational model of cardiac electromechanics to investigate fibre length transients and the role of electrical heterogeneity in determining left ventricular function. Methods A mathematical model of cellular electromechanics was embedded in a simple geometric model of the cardiac left ventricle. Electrical and mechanical boundary conditions were applied based on Purkinje fibre activation times and ventricular volumes through the heart cycle. The mono-domain reaction diffusion equations and finite deformation elasticity equations were solved simultaneously through the full pump cycle. Simulations were run to assess the importance of cellular electrical heterogeneity on myocardial mechanics. Results Following electrical activation, mechanical contraction moves out through the wall to the circumferentially oriented mid-wall fibres, producing a progressively longitudinal and twisting deformation. This is followed by a more spherical deformation as the inclined epicardial fibres are activated. Mid-way between base and apex peak tensions and fibre shortening of 40 kPa and 5%, respectively, are generated at the endocardial surface with values of 18 kPa and 12% at the epicardial surface. Embedding an electrically homogeneous cell model for the same simulations produced equivalent values of 36.5 kPa, 4% at the endocardium and 14 kPa, 13.5% at the epicardium. Conclusion The substantial redistribution of fibre lengths during the early pre-ejection phase of systole may play a significant role in preparing the mid-wall fibres to contract. The inclusion of transmural heterogeneity of action potential duration has a marked effect on reducing sarcomere length transmural dispersion during repolarization.
41
Caproni, Anderson, Gustavo A. Lanfranchi, Amâncio C. S. Friaça, and Jennifer F. Soares. "Boundary Conditions in Hydrodynamic Simulations of Isolated Galaxies and Their Impact on the Gas-loss Processes." Astrophysical Journal 944, no. 1 (February 1, 2023): 11. http://dx.doi.org/10.3847/1538-4357/acae85.
Анотація:
Abstract Three-dimensional hydrodynamic simulations are commonly used to study the evolution of the gaseous content in isolated galaxies, besides its connection with galactic star formation histories. Stellar winds, supernova blasts, and black hole feedback are mechanisms usually invoked to drive galactic outflows and decrease the initial galactic gas reservoir. However, any simulation imposes the need of choosing the limits of the simulated volume, which depends, for instance, on the size of the galaxy and the required numerical resolution, besides the available computational capability to perform it. In this work, we discuss the effects of boundary conditions on the evolution of the gas fraction in a small-sized galaxy (tidal radius of ∼1 kpc), like classical spheroidal galaxies in the Local Group. We found that open boundaries with sizes smaller than approximately 10 times the characteristic radius of the galactic dark-matter halo become unappropriated for this kind of simulation after ∼0.6 Gyr of evolution, since they act as an infinity reservoir of gas due to dark-matter gravity. We also tested two different boundary conditions that avoid gas accretion from numerical frontiers: closed and selective boundary conditions. Our results indicate that the later condition (that uses a velocity threshold criterion to open or close frontiers) is preferable since it minimizes the number of reversed shocks due to closed boundaries. Although the strategy of putting computational frontiers as far as possible from the galaxy itself is always desirable, simulations with a selective boundary condition can lead to similar results at lower computational costs.
42
XIAO, YINGNI, HELAI HUANG, YONG PENG, and XINGHUA WANG. "A STUDY ON MOTORCYCLISTS HEAD INJURIES IN CAR–MOTORCYCLE ACCIDENTS BASED ON REAL-WORLD DATA AND ACCIDENT RECONSTRUCTION." Journal of Mechanics in Medicine and Biology 18, no. 04 (June 2018): 1850036. http://dx.doi.org/10.1142/s0219519418500367.
Анотація:
Accident data had shown that as one of the most vulnerable road users, the risk of motorcyclist casualties due to head injuries is extremely high in motorcycle accidents. The objective of this study was to analyze motorcyclist head injury based on epidemiological statistical analysis and car–motorcycle accident reconstruction using real world accident data, and obtain a comprehensive understanding about safety effects of helmets on motorcyclists head injury. In epidemiological data analysis of this study, odds ratios (ORs) was applied to identify differences in injuries between helmeted and unhelmeted motorcyclists. Two vehicle–motorcycle collisions with detailed information were reconstructed by using PC-Crash simulation and MADYMO reconstruction. Furthermore, the head injury reconstruction using MADYMO outputs as boundary conditions was accomplished and analyzed with respect to 1st principal strain, Von Mises stress, coup pressure, countercoup pressure at the cerebrum. The results indicated that unhelmeted motorcyclists were more likely to suffer head injury, serious and fatal injury, and tend to take equal responsibility or more. 1st principal strain was reduced from 0.44 to 0.25 for Case 1, and from 0.16 to 0.10 for case 2 when including a helmet. Von Mises stress were reduced from 30.37[Formula: see text]kpa to 19.51[Formula: see text]kpa for Case 1 and from 3.42[Formula: see text]kpa to 3.03[Formula: see text]kpa for case when including a helmet, which meant a reduction of the risk of concussion. But the motorcyclist in Case 2 experienced a lower percentage increase in coup pressure and countercoup pressure. This study provided comprehensive knowledge on motorcyclists head injuries and the effectiveness of helmets as well as contributing to develop the injury prevention measures and protection devices of motorcyclists.
43
SIVARAMAKRISHNAN, S. "Meso-scale convergence rainfall and surface fluxes during the Indian summer monsoon." MAUSAM 54, no. 3 (January 18, 2022): 631–44. http://dx.doi.org/10.54302/mausam.v54i3.1554.
Анотація:
Meso-scale convergence and vertical velocity were computed using Bellamy technique from rawindsonde and pibal data obtained from three stations. These stations formed the vertices of a meso-scale triangle around Kharagpur (22.3° N, 87.2° E) - a region of moist convection located near the eastern end of the monsoon trough, where the monsoon trough boundary layer experiment (MONTBLEX), was conducted during the Indian summer monsoon 1990. We find that the total rainfall over the meso-triangle depends on the proximity and intensity of the large-scale pressure system forming in the head Bay and moving W/NW towards the land during the onset and active phase of the monsoon. When the large-scale flow showed cyclic circulation extending to mid-troposphere, the rainfall over the triangle does not seem to be affected by the meso-scale divergence. However the rainfall at Kalaikonda (KKA) -an airforce station near Kharagpur (KGP) correlates with meso-scale divergence/convergence. Surface heat flux estimated using sonic anemometer at 8m AGL at KGP was large during meso-scale convergence. It increased with wind speed while the momentum flux showed large variation.
44
Bourgès-Gastaud, Sébastien, Guillaume Stoltz, Patricia Dolez, Éric Blond, and Nathalie Touze-Foltz. "Laboratory device to characterize electrokinetic geocomposites for fluid fine tailings dewatering." Canadian Geotechnical Journal 52, no. 4 (April 2015): 505–14. http://dx.doi.org/10.1139/cgj-2014-0031.
Анотація:
The oil sands industry usually leads to the production of large quantities of mineral waste, such as fluid fine tailings (FFT), whose disposal is often challenging. Electrokinetic geocomposites (eGCPs) installed into the FFT disposal area may improve in situ dewatering, as eGCPs can drain water expulsed during FFT consolidation as well as impose a voltage across FFT to displace water by electro-osmosis. This paper presents a laboratory device specifically developed to evaluate eGCP performance for sludge dewatering. Based on the oedometer principle, the device aims at studying sludge consolidation as a function of boundary conditions (mechanical stress and (or) voltage), with drainage and electrical conduction ensured by two eGCPs positioned on both sides of the sludge layer. Preliminary results obtained with one particular eGCP are presented: the solids content was increased from 42% to 66%, which led to a significant improvement of the shear strength from nearly 0 kPa to a mean value of 40 kPa. The energy required for this experiment was 71 W·h (3.5 kW·h/(m3 of sludge)). The filtration performance remained satisfactory; the sludge particles were retained upstream of the filter, with clean water flowing through.
45
Beers, Timothy C., Masashi Chiba, Tsuyoshi Sakamoto, Ron Wilhelm, Carlos Allende Prieto, Jesper Sommer-Larsen, Heidi J. Newberg, Brian Yanny, Brian Marsteller, and Jeffrey R. Pier. "The Mass of the Galaxy from Large Samples of Field Horizontal-Branch Stars in the SDSS Early Data Release." Symposium - International Astronomical Union 220 (2004): 195–200. http://dx.doi.org/10.1017/s0074180900183202.
Анотація:
We present a new estimate of the mass of the Milky Way, making use of a large sample of 955 field horizontal-branch (FHB) stars from the Early Data Release of the Sloan Digital Sky Survey. This sample of stars has been classified on the basis of an automated analysis approach, in combination with other methods, in order to obtain estimates of the physical parameters of the stars, i.e., Teff, log g, [Fe/H], and should be relatively free of contamination from halo blue stragglers. the stars all have measured radial velocities and photometric distance estimates, and the sample includes objects as distant as ~ 75 kpc from the Galactic center. Application of a Bayesian likelihood method, for a specific model of the Galaxy, indicates that the total mass of the Galaxy lies in the range 1.5 − 4.0 × 1012 M⊙. Our sample appears to reveal a clear signature of a dual halo population of FHB stars, with the boundary between the inner and outer halo around 20 kpc, and the possibility of rather striking differences in the rotational properties of the Galaxy at low metallicity.
46
Jalal, Fazal E., Babak Jamhiri, Ahsan Naseem, Muhammad Hussain, Mudassir Iqbal, and Kennedy Onyelowe. "Isolated Effect and Sensitivity of Agricultural and Industrial Waste Ca-Based Stabilizer Materials (CSMs) in Evaluating Swell Shrink Nature of Palygorskite-Rich Clays." Advances in Civil Engineering 2021 (November 1, 2021): 1–17. http://dx.doi.org/10.1155/2021/7752007.
Анотація:
This paper evaluates the suitability of sugarcane bagasse ash (SCBA) and waste marble dust (WMD) on the geotechnical properties of Palygorskite-rich expansive clays located in northwest Pakistan. These problematic soils exhibit undesirable characteristics which greatly affect the pavements, boundary walls, slab-on-grade members, and other civil engineering infrastructures. A series of geotechnical tests were performed on soil specimens using prescribed percentages of the aforementioned Ca-based stabilizer materials (CSMs). The investigation includes X-Ray Diffraction (XRD) Analysis, Scanning Electron Microscopy (SEM), X-Ray Fluorescence (XRF) tests, and physicomechanical properties such as moisture-density relationship, Atterberg’s limits, swell pressure, and an ANN-based sensitivity analyses of overall swell pressure development. The outcomes of these experimental investigations showed that the addition of CSMs into the expansive soils increased to 4% SCBA and 10% WMD, the plasticity index reduced by 30% and 49%, the volumetric swell decreased from approximately 49% to 86% and 63%, and the swelling pressure reduction was from 189 kPa to 120 kPa and 160 kPa (about 15% and 36%), respectively. It is interesting to note that replacement with specified CSM accelerated the strength of soil at extended curing periods and the optimum improvement in the strength behavior of the soil was also recorded. Moreover, with addition of the respective CSMs, the compactability and strength characteristics were ameliorated, while plasticity was significantly lowered. Given the amount of SCBA and WMD produced annually, their utilization for the stabilization of problematic soils, even in relatively low concentrations, could potentially have a substantial impact on the sustainable reuse of these waste materials.
47
Malpas, Amber, Michael D. Albrow, Jennifer C. Yee, Andrew Gould, Andrzej Udalski, Antonio Herrera Martin, Charles A. Beichman, et al. "OGLE-2017-BLG-1038: A Possible Brown-dwarf Binary Revealed by Spitzer Microlensing Parallax." Astronomical Journal 164, no. 3 (August 18, 2022): 102. http://dx.doi.org/10.3847/1538-3881/ac7d4c.
Анотація:
Abstract We report the analysis of microlensing event OGLE-2017-BLG-1038, observed by the Optical Gravitational Lensing Experiment, Korean Microlensing Telescope Network, and Spitzer telescopes. The event is caused by a giant source star in the Galactic Bulge passing over a large resonant binary-lens caustic. The availability of space-based data allows the full set of physical parameters to be calculated. However, there exists an eightfold degeneracy in the parallax measurement. The four best solutions correspond to very-low-mass binaries near ( M 1 = 170 − 50 + 40 M J and M 2 = 110 − 30 + 20 M J ), or well below ( M 1 = 22.5 − 0.4 + 0.7 M J and M 2 = 13.3 − 0.3 + 0.4 M J ) the boundary between stars and brown dwarfs. A conventional analysis, with scaled uncertainties for Spitzer data, implies a very-low-mass brown-dwarf binary lens at a distance of 2 kpc. Compensating for systematic Spitzer errors using a Gaussian process model suggests that a higher mass M-dwarf binary at 6 kpc is equally likely. A Bayesian comparison based on a galactic model favors the larger-mass solutions. We demonstrate how this degeneracy can be resolved within the next 10 years through infrared adaptive-optics imaging with a 40 m class telescope.
48
Rampino, C., C. Mancuso, and F. Vinale. "Laboratory testing on an unsaturated soil: equipment, procedures, and first experimental results." Canadian Geotechnical Journal 36, no. 1 (August 8, 1999): 1–12. http://dx.doi.org/10.1139/t98-093.
Анотація:
This paper describes two new apparatuses recently developed at the Università di Napoli Federico II (Italy) in order to test soils under unsaturated conditions. The related experimental procedures and the first results obtained on a dynamically compacted silty sand are also discussed. The devices mentioned are a Bishop and Wesley stress-path cell and a Wissa oedometer, modified to control matric suction and to measure all the stress-strain variables relevant to unsaturated soil mechanics. Specific experimental procedures were established to perform tests under general conditions and were carefully verified during several tests. Using the triaxial cell, isotropic and anisotropic compression stages were carried out under constant suction levels of 0, 100, 200, and 300 kPa. Furthermore, two deviator stages were performed following different stress paths and water drainage conditions. Using the oedometer, an additional suction level (400 kPa) was investigated during compression tests driven up to 5 MPa of vertical net stress (sigmav - ua). This research is a part of a major project in progress at the Dipartimento di Ingegneria Geotecnica of Naples; it is aimed at the experimental analysis of the behaviour of several dynamically compacted soils and at the numerical modelling of boundary problems related to earth structures.Key words: unsaturated soils, equipment layout, silty sand, matric suction.
49
Shibuya, Toshio, Akihito Sugimoto, Yoshiaki Kitaya, and Makoto Kiyota. "High Plant Density of Cucumber (Cucumis sativus L.) Seedlings Mitigates Inhibition of Photosynthesis Resulting from High Vapor-pressure Deficit." HortScience 44, no. 6 (October 2009): 1796–99. http://dx.doi.org/10.21273/hortsci.44.6.1796.
Анотація:
To evaluate the effects of plant density on gas exchanges under water stress resulting from high vapor-pressure deficit (VPD), we measured net photosynthetic rate (Pn), transpiration rate, and leaf conductance (gl) of cucumber (Cucumis sativus L.) seedlings before and after raising the VPD at different plant densities. Measurements were conducted continuously using a chamber and weighing method. Five, nine, or 12 seedlings with leaf area index (LAI) of 0.39, 0.73, and 1.10, respectively, were placed in the assimilation chamber. The average VPD in the chamber was raised from 1.1 to 3.7 kPa 30 min after the starting measurement. The Pn and gl decreased after raising the VPD above the plant community from 1.1 to 3.7 kPa. The VPD near the leaf surface (measured with 3-mm diameter humidity sensors) decreased with increasing LAI of the plant community, whereas average VPD in the whole chamber did not change with LAI. We noted significant negative correlations between the VPD near the leaf surface and Pn and gl. These results indicate that higher plant density mitigates the inhibition of photosynthesis resulting from high VPD by maintaining a lower VPD near the leaf surface with the development of a thicker boundary layer above the canopy.
50
Lou, Chenhui, Junfeng Ni, Jingchun Chai, Hongtao Fu, Xiuqing Hu, Donghai Xu, Youchang Lyu, Zhi Guan, Zhengde Xia, and Qiang Ye. "Consolidation Effect of Prefabricated Vertical Drains with Different Lengths for Soft Subsoil under Vacuum Preloading." Advances in Civil Engineering 2019 (August 19, 2019): 1–12. http://dx.doi.org/10.1155/2019/7428595.
Анотація:
The application of vacuum preloading to prefabricated vertical drains (PVDs) with different lengths is widely used in practical engineering to investigate their consolidation at the same depths of even and multilayer subsoils from the seabed. In a laboratory, model experiment was conducted using even subsoil and embedded PVDs with lengths of 0.6 and 1.2 m. The obtained results showed that in the even subsoil, the 1.2 m PVDs maintained a higher vacuum pressure in the shallow layer and demonstrated better consolidation behavior as compared to those of the 0.6 m PVDs. In the upper subsoil layer, the average vane shear strengths of these two systems increased to 18.2 and 22.6 kPa, respectively. The degree of consolidation of the upper subsoil layers in the two model experiments calculated from the pore water pressures under boundary drainage conditions were 51% and 68%, respectively. For practical verification purposes, similar experiments were conducted for multilayer subsoil by inserting PVDs with lengths of 6 and 15 m into different test sites. As a result, the vane shear strengths of the upper 6 m subsoil layers increased to 26.3 and 33 kPa, while the degree of consolidation were 72.1% and 80.9%, respectively, although some irregularities were observed at different depths.