Single Breakup Research Articles

Reinterpretation of Marine Magnetic Anomalies in the Bay of Bengal: Implications for Plate Tectonics During the Mid‐Cretaceous

AbstractThe breakup of India from Antarctica in the Early Cretaceous and subsequent seafloor spreading in the NW‐SE direction initiated the formation of the Bay of Bengal and its conjugate Enderby Basin. Two hypotheses are proposed to explain the evolutionary tectonics between India and Antarctica. One involves a single breakup, while the second invokes another breakup episode. Further, a major reorganization of the plate boundaries in the mid‐Cretaceous caused the spreading center to align E‐W by Late Cretaceous. The tectonics involved in this spreading direction change is unknown and difficult to understand as it occurred in the mid‐Cretaceous, coincident with the Cretaceous Normal Superchron. In the present study, we have generated a revised magnetic isochron map of the Bay of Bengal and used the modulus of its analytic signal to understand the evolutionary tectonics between the two plates, India and Antarctica. Mesozoic magnetic anomalies M12n to M0, and mid‐Cretaceous incursion Q2 (108 Ma) are identified in the western basin of the Bay of Bengal, while Q2, Q1 (92 Ma) and Late Cretaceous isochron A34 are inferred in its eastern basin. Gravity grid reconstructions demonstrate asymmetrical crustal accretion in the conjugate corridors. Fan‐shaped spreading and a southward ridge jump between 108 and 92 Ma in the eastern basin, aided the ∼40° clockwise rotation of the spreading center. The presence of volcanic basement beneath the additional crust suggests on‐axis mode of formation for the Ninetyeast Ridge by 100 Ma. The present study favors the two‐phase breakup model for the evolution of these plates.

Trajectory of depressive symptoms in the context of romantic relationship breakup: Characterizing the "natural course" of response and recovery in young adults.

Young adults face stressful role transitions as well as increased risk for poor mental health, but little is known about a "natural course" of response to such events. We used the PHQ-2 to characterize the trajectory of depressive symptoms before, during, and after relationship breakup and examined subjective appraisal and sense of control as moderators. In our sample of participants reporting a single breakup during the 2-year study period (N=156), breakup was associated with a temporary increase in depressive symptoms that returned to pre-breakup levels within three months. We observed increased symptoms among negatively appraised, but not positive or neutral, events. A general low sense of control was associated with higher depressive symptoms at all time points. Our results suggest that a natural course of response to young adult breakups is characterized by recovery within three months and that subjective appraisal and sense of control contribute to this adaptive response.

Preliminary debris risk assessment for mega-constellations in low and medium earth orbit due to satellite breakup

This paper presents a theoretical analysis of the potential risk posed by artificial debris clouds in low Earth orbit (LEO) from mega-constellations, modeled after current communication constellations such as Starlink and OneWeb with 750 satellites each. The analysis examines three different constellation designs: a low-altitude LEO, a high-altitude LEO, and a medium Earth orbit (MEO) constellation, which will be positioned using the Walker-Delta design. The study is based on physics-based digital mission engineering and a Monte Carlo simulation framework. The simulation involves debris generated from a single breakup of one randomly selected satellite per run, but does not consider cascading debris events. This debris cloud is propagated for 1 week and how it interacts with the mega-constellation is recorded. The results show an average of 705.65 potential conjunctions within the LEO constellation, with 14.40% of those being considered catastrophic, and an average of 165.5 conjunctions in the MEO constellation, with 0.72% considered catastrophic.

Deformation dynamics and breakup criteria of confined fluid threads in motion

Experiments are carried out to study the breakup of moving fluid threads tightly confined in circular microchannels. A configuration with two flow-focusing channel junctions is used to control lengths and deformations of fluid threads at the first and second junctions, respectively. As fluid threads move and deform simultaneously at the second junction, the final outcomes (nonbreakup, single breakup, and double breakup) depend on the combination of three flow rates. The regime diagram for different outcomes is obtained, and the critical geometrical condition for the transition between nonbreakup and breakup is then identified from the deformation dynamics of the neck section. A theoretical analysis is then carried out to predict critical values of characteristic geometries for the transition between nonbreakup and breakup. The predictions of the critical initial thread length and the length of the first thread after breakup show good agreement with experimental measurements.

Evaluating interfacial shear and strain stress during droplet deformation in micro-pores

The formulation of high quality emulsions is a key challenge in many industrial applications. The premix emulsification process in porous membranes enables the generation of tailored emulsions with fine and narrow droplet size distributions under low shear and energy input. However, the droplet deformation and breakup process within porous structures is a complex mechanism and single breakup events are hard to relate to the local stress conditions and the pore geometry. This relation however is required for the proper design of membrane structures with specific emulsification behavior (i.e., avoidance of stress peaks). Thus, in this contribution, the stress residence time behavior of single droplets during deformation and breakup in idealized micro-pores is investigated for different Capillary numbers and droplet sizes. The interface stress induced droplet deformation and breakup process is to be analyzed in a generic flow configuration. The results show that interface stresses are applied by the wall interface (wall-droplet interface) and by the liquid-liquid (continuous-droplet interface) interface and that both stress contributions have to be considered separately in order to understand the droplet deformation and breakup process. Only at the liquid-liquid interface, stress induced deformation is possible. The analysis of the stress conditions delivers a correlation between the stress residence time behavior and the interface deformation, which can be directly related to the pore geometry. As a result, main deformation and breakup trends are derived. This enables better opportunities for proper membrane design and handling of shear sensitive media in the premix emulsification process.

Study of Impingement Types and Printing Quality during Laser Printing of Viscoelastic Alginate Solutions.

Laser-induced forward transfer-based laser printing has been being implemented as a promising orifice-free direct-write strategy for different printing applications. The printing quality during laser printing is largely affected by the jet and droplet formation process and subsequential impingement. The objective of this study is to investigate the impingement-based printing type and resulting printing quality during the laser printing of viscoelastic alginate solutions, which are representative inks for soft structure printing such as bioprinting. Three printing types are identified: droplet-impingement printing, jet-impingement printing with multiple breakups, and jet-impingement printing with a single breakup. Printing quality, in terms of printed droplet morphology and size, has been investigated as a function of alginate concentration, laser fluence, and direct-writing height based on a time-resolved imaging approach and microarrays of printed droplets. Of these, the best printing quality is achieved with single-breakup jet-impingement printing, followed by multiple-breakup jet-impingement printing, with droplet-impingement printing producing the lowest quality printing. The printing quality can be improved by using high-concentration alginate solutions. The increase of laser fluence may lead to a well-defined primary droplet for low-concentration alginate solutions; however, this can cause the droplet diameter to increase, which may not be desirable. The direct-writing height (i.e., ribbon coating-receiving substrate distance) also influences the print quality. For example, an increase in direct-writing height can cause the printing type to change from the ideal jet-impingement with a single breakup, to the jet-impingement with multiple breakups, and even the least desired droplet-impingement printing, with only slight variations in droplet diameter.

An operational calculus framework to characterize droplet size populations from turbulent breakup by a small number of parameters

A systematic operational calculus framework that characterizes droplet/bubble size distributions resulting from turbulent breakup of an immiscible fluid into a carrier one is presented. The proposed formulation is derived from dynamical arguments; a finite-difference formulation of the integro-differential continuous coagulation and fragmentation equation is shown to exhibit the same structure as a discrete sequence of Mellin convolutions between the probability distribution of the evolving dispersed phase and a generic kernel. This kernel may have its physical correspondence with the probability distribution resulting from a single breakup event, e.g. a liquid ligament breakup in a ligament-mediated spray formation. The number of convolution steps in the sequence can be reduced to a single parameter. As an illustration, this procedure is applied to the exponential and the gamma distributions, obtaining as a result the Fréchet distribution earlier used by Rosin and Rammler (1934 Kolloid-Zeitschrift 67 16–26), and by Nukiyama and Tanasawa (1939 Trans. Soc. Mech. Eng. Japan 5 62–7). Thus, the framework introduced in this work provides a physical foundation for the success of the Fréchet distribution in accurately fitting experimentally measured droplet size distributions in sprays and emulsions.

Molecular phylogenetics reveal multiple tertiary vicariance origins of the African rain forest trees

BackgroundTropical rain forests are the most diverse terrestrial ecosystems on the planet. How this diversity evolved remains largely unexplained. In Africa, rain forests are situated in two geographically isolated regions: the West-Central Guineo-Congolian region and the coastal and montane regions of East Africa. These regions have strong floristic affinities with each other, suggesting a former connection via an Eocene pan-African rain forest. High levels of endemism observed in both regions have been hypothesized to be the result of either 1) a single break-up followed by a long isolation or 2) multiple fragmentation and reconnection since the Oligocene. To test these hypotheses the evolutionary history of endemic taxa within a rain forest restricted African lineage of the plant family Annonaceae was studied. Molecular phylogenies and divergence dates were estimated using a Bayesian relaxed uncorrelated molecular clock assumption accounting for both calibration and phylogenetic uncertainties.ResultsOur results provide strong evidence that East African endemic lineages of Annonaceae have multiple origins dated to significantly different times spanning the Oligocene and Miocene epochs. Moreover, these successive origins (c. 33, 16 and 8 million years – Myr) coincide with known periods of aridification and geological activity in Africa that would have recurrently isolated the Guineo-Congolian rain forest from the East African one. All East African taxa were found to have diversified prior to Pleistocene times.ConclusionMolecular phylogenetic dating analyses of this large pan-African clade of Annonaceae unravels an interesting pattern of diversification for rain forest restricted trees co-occurring in West/Central and East African rain forests. Our results suggest that repeated reconnections between the West/Central and East African rain forest blocks allowed for biotic exchange while the break-ups induced speciation via vicariance, enhancing the levels of endemicity. These results provide an explanation for present day distribution patterns and origins of endemicity for African rain forest trees. Moreover, given the pre-Pleistocene origins of all the studied endemic East African genera and species, these results also offer important insights for setting conservation priorities in these highly diversified but threatened ecosystems.

L‐chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40Ar‐39 Ar dating

Abstract— Radiochronometry of L chondritic meteorites yields a rough age estimate for a major collision in the asteroid belt about 500 Myr ago. Fossil meteorites from Sweden indicate a highly increased influx of extraterrestrial matter in the Middle Ordovician ∼480 Myr ago. An association with the L‐chondrite parent body event was suggested, but a definite link is precluded by the lack of more precise radiometric ages. Suggested ages range between 450 ± 30 Myr and 520 ± 60 Myr, and can neither convincingly prove a single breakup event, nor constrain the delivery times of meteorites from the asteroid belt to Earth. Here we report the discovery of multiple 40Ar‐39Ar isochrons in shocked L chondrites, particularly the regolith breccia Ghubara, that allow the separation of radiogenic argon from multiple excess argon components. This approach, applied to several L chondrites, yields an improved age value that indicates a single asteroid breakup event at 470 ± 6 Myr, fully consistent with a refined age estimate of the Middle Ordovician meteorite shower at 467.3 ± 1.6 Myr (according to A Geologic Time Scale 2004). Our results link these fossil meteorites directly to the L‐chondrite asteroid destruction, rapidly transferred from the asteroid belt. The increased terrestrial meteorite influx most likely involved larger projectiles that contributed to an increase in the terrestrial cratering rate, which implies severe environmental stress.

Anisotropy and breakup of extended droplets in immiscible blends

A frame-invariant constitutive model is developed to describe the changes in droplet anisotropy and stress in a dilute blend of Newtonian droplets in a Newtonian matrix after imposition of a large step strain. The model, based on the Tomotika theory [Proc. R. Soc. London, Ser. A 150 (1935) 322], describes the evolution of components of the anisotropy tensor from values consistent with a cylindrical shape with undulations to values consistent with a series of fragmented spherical droplets. This model is compared to experimental measurements of droplet shape anisotropy for single droplets that were deformed to various degrees and then allowed to relax. Here, the droplet shape anisotropy is defined using the Doi–Ohta anisotropy tensor [J. Chem. Phys. 95 (1991) 1242], which is obtained by integrating over the droplet interfacial position as determined by microscopic image analysis. For moderately extended droplets, the anisotropy is affected by the ends of the droplet, and thus does not agree with breakup model predictions based on the Tomotika theory, which neglects contributions from the ends of the droplet. When droplet end-effects are subtracted, and only the effects of undulations in the droplet center remain, good agreement between theory and experiment is achieved. Data at various strains also superimpose on a single breakup line when end-effects are neglected.

Generalized isoscaling of isotopic distributions

At incident energies in excess of about E/A530 MeV, a rapid collective expansion of the combined system may occur during the later stages of a central collision between heavy nuclei @1,2#. At densities less than about 1 3 of the saturation density, such systems disassemble into a mixture of fragments and light particles; the duration of fragment emission is of the order of 100 fm/c @3,4#. Even though the emission time is short, statistical models such as bulk multifragmentation models, which assume equilibrium at a single breakup density and temperature, have been used successfully to describe many experimental observables such as fragment multiplicities, charge distributions, and energy spectra of the emitted fragments @2,5–7#. These descriptions require careful, though not necessarily obvious, choices for the source size, excitation energy, and collective velocity of expansion @2,6–8#. Many of these statistical models display a phase transition in nuclear matter with subsaturation density @9,10#; such models have been employed to extract the caloric curve, i.e., the relationship between excitation energy and temperature for the nuclear liquid-gas phase transition @5,11–17# and to address whether finite nuclear systems may display negative heat capacities in analogy to those deduced for finite metallic clusters @18#. The success of thermal models raises the fundamental

Temperature measurements in central collisions

At incident energies in excess of about E/A=50 MeV, a rapid collective expansion of the combined system may occur during the later stages of a central collision between heavy nuclei. The emission of the observed particle species occurs after initial overlap and before the density of the system passes below about 0.1Po, corresponding to an expansion rate dependent on the total emission time which is less than 100 fm/c. The short emission times motivate the description of such collisions via dynamical models or via statistical models which assume equilibrium at a single breakup density and temperature. This latter class of models includes bulk multifragmentation models such as the Statistical Multifragmentation Model (SMM) which displays a phase transition in sub-saturation density [1]. Calculations predict enhanced heat capacities for finite nuclear systems at temperatures of the order of 4-6 MeV due to the transformation from the Fermi liquid which can be found in the interior of large nuclei in their ground and low excited states to a gas phase consisting of free nucleons and light clusters.

Transient liquid jet breakup model and comparison with phase doppler measurements

A new liquid jet breakup model is developed based on the transient breakup mechanism and incorporated into the KIVA-II code. Liquid column is considered as a chain of balls. Rayleigh-Taylor instability and Kelvin-Helmholtz instability was applied to the liquid jet column. Liquid jet column is continuously surveyed to apply breakup mechanisms. Once liquid droplets are separated from the main liquid jet column, these droplets are subjected to the single breakup mechanism. When Bond number is greater than a critical Bond number, single droplets continue to break up by Rayleigh-Taylor instability or Kelvin-Helmholtz instability. Computational results were compared with the PDPA measurement data. Gross behavior of the spray and detailed droplet sizes and velocities predicted by KIVA calculations which include proposed drop breakup model are compared with those produced from droplet size/velocity measurements.

The number of daughter drops formed per breakup of a highly viscous mother-drop in turbulent flow.

We have attempted to quantify the relation of the number of daughter drops to the physical properties of the mother drop, its size, and the intensity of turbulence, during a single breakup of a mother drop having a high viscosity

Predicting spatial density characteristics from breakup models

Simulations are used to predict regions of increased density in the debris cloud resulting from a single breakup. Secondary conjunctions are assumed to be correlated with increased spatial density of debris. The probability of secondary conjunctions is shown to be greatest at the extreme latitudes of the debris cloud, at the height of the breakup, and in the predicted plane of the parent object. Density is shown to vary by orders of magnitude within the cloud. This result gives some insight into the complex structure of the debris environment.

A model for stationary heterogeneous detonation in a gas-droplet mixture

1. A model has been constructed for a stationary heterogeneous detonation in a gasdroplet medium with allowance for chemical equilibrium and losses at the tube walls. The calculations are in good agreement with the available experimental data. 2. Wall loss has a decisive effect on the detonation parameters for hydrocarbon-oxygen mixtures. The residual unburned droplet fraction tends to zero as the loss decreases. 3. There is good agreement with experiment for DECH-O2 mixtures given by the conditions for the absence of droplet breakup or the conditions for single breakup of large droplets into a small number of parts. 4. There is found to be a considerable effect from variation in the heat of reaction and gas molecular mass in the reaction zone. 5. If a hydrocarbon-oxygen mixture is not very heavily diluted with nitrogen and has a combination close to stoichiometric, then the length of the induction zone is much less than the distance to the Chapman-Jouguet surface. 6. There is found to be substantial velocity disequilibrium in the phases in the Chapman-Jouguet plane in a hydrogen-oxygen mixture and also for small droplets in hydrocarbon-oxygen mixtures.

Double spectator poles and quasi-free inelastic scattering in the [formula omitted] reaction

We have searched for double spectator pole events in the reaction 6Li + 6Li → 2α + 2d, such that the deuteron from the projectile goes forward with the beam velocity while α or d from the target remains at rest. Triple coincidence studies of the reaction show such events, but with the 0° deuteron energy spectrum peaked at slightly higher velocities. Similar effects are seen in d-6Li double coincidence spectra from the single breakup reaction 6Li → 6Li + α + d. Quasi-free inelastic scattering, where the d from the projectile receives no momentum transfer while the α excites the target to its first excited state, is also shown to be an important mechanism.