Initial Rapid Growth Research Articles

Characterization of the Epidermis and Cuticle of the Cashew Pseudofruit during Its Development and Maturation

The epidermis and cuticle play an important role in reducing dehydration and protecting the cashew pseudofruit in both the production environment and the postharvest stage. This study analyzes the alterations on the epidermis and cuticle of CCP 76 cashew pseudofruits harvested in five developmental and maturation stages (S1, S2, S3, S4, and S5). The epidermis and cuticle of the samples were analyzed under light microscopy (LM) (quantitative analysis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The epidermal cells at S3 reached maximum outer periclinal wall thickness, which reduced during ripening (S4 and S5), while the cuticle increased in thickness during the same period. These changes coincided with the rapid initial growth of the cashew pseudofruit when the epidermis and cuticle need to accompany the expansion of internal tissues. At the ultrastructural level, lipid material is transported via vesicles through the cell wall to the cuticle, increasing its thickness. Epicuticular waxes, previously deposited as plates and globules, began to develop an amorphous shape during maturation. This process possibly occurs due to changes in wax composition that can be related to the development of greasiness on the fruit skin. These findings provide a better understanding of cashew pseudofruit skin, which will aid future studies and strategies to preserve quality during the postharvest stage.

Oral expressions and functional analyses of the extracellular calcium-sensing receptor (CaSR) in chicken

In vertebrates, the extracellular calcium-sensing receptor (CaSR) plays a key role in calcium homeostasis by sensing slight changes in extracellular Ca2+. CaSR is also expressed in mammals including rodent taste cells and is involved in sensing kokumi, a rich, savory quality that enhances the intensities of salty, sweet, and umami tastes. In this study, we focused on chicken CaSR (cCaSR) since calcium is an essential nutrient that is necessary for making eggshell and for the extremely rapid initial growth of bones. First we confirmed that cCaSR is expressed in taste cells. Next we cloned the cCaSR gene from kidney and transiently transfected human embryonic kidney 293 T (HEK293T) cells with the recombinant cCaSR, or empty vector and looked for the agonists and allosteric modulators (including kokumi substances) of cCaSR by Ca2+ imaging. We found that cCaSR was activated by extracellular Ca2+ and Mg2+ in a dose dependent manner. Several L-amino acids and kokumi substances such as glutathione enhanced the response of cCaSR. In addition, NPS2143 as a negative allosteric modulator of human CaSR negatively modulated the response of cCaSR. These results suggest that cCaSR can sense extracellular Ca2+ and Mg2+ as well as positive and negative allosteric modulators. Taken together, the results imply that CaSR might be a multifunctional receptor for calcium, amino acids, and kokumi substances in chicken. The present finding that functional CaSR is expressed in the chicken oral tissues will allow us to further elucidate the physiological role of CaSR in the chickens' taste sense, and to create new feeds that will contribute to the poultry industry.

Patterns of biogeographic and regional life-history trait variation in four large-bodied tropical wrasses

Ectotherms display substantial demographic variation across latitudinal gradients of temperature. Higher temperatures are often associated with smaller size, rapid initial growth rates, and early maturation, generally described as the Temperature-Size Rule (TSR). The longevity of most ectotherms also declines at warmer, lower latitudes. However, these patterns may be modified by increases in food resources that can flow on to continuous growth and large adult size. The present study estimates age-based demographic parameters of large-bodied tropical wrasses (Hemigymnus melapterus, H. fasciatus, Cheilinus fasciatus, and Oxycheilinus digramma) collected from Philippine fish markets (9–11°N) and sampled from Palm (18.53–18.70°S) and Whitsunday (20.05–20.21°S) reefs on the Great Barrier Reef, Australia (GBR). Differences in longevity, initial growth rates, and the age at sexual maturation at a biogeographic scale, between the Philippines and GBR, conformed to predictions of the TSR. However, Philippine specimens exhibited greater relative body condition and sustained periods of growth beyond sexual maturity resulting in larger adult size than GBR samples. Size-structure data from Philippine marine reserves and fished sites indicated that these differences were not confounded by fishery-dependent sampling. Moreover, latitudinal length–weight relationships could not be explained by lower densities of the focal wrasses in the Philippines or by relative gonad size. Less pronounced patterns of demographic variation that differed across species were evident at a regional scale, among Palm and Whitsunday reefs. Patterns of demographic variation between the Philippines and GBR strongly suggest that differences in food resource levels will be important in explaining the observed geographic variation.

The Transition from Practical to Intrinsic Predictability of Midlatitude Weather

Abstract This study investigates the transition from current practical predictability of midlatitude weather to its intrinsic limit. For this purpose, estimates of the current initial condition uncertainty of 12 real cases are reduced in several steps from 100% to 0.1% and propagated in time with a global numerical weather prediction model (ICON at 40 km resolution) that is extended by a stochastic convection scheme to better represent error growth from unresolved motions. With the provision that the perfect model assumption is sufficiently valid, it is found that the potential forecast improvement that could be obtained by perfecting the initial conditions is 4–5 days. This improvement is essentially achieved with an initial condition uncertainty reduction by 90% relative to current conditions, at which point the dominant error growth mechanism changes: With respect to physical processes, a transition occurs from rotationally driven initial error growth to error growth dominated by latent heat release in convection and due to the divergent component of the flow. With respect to spatial scales, a transition from large-scale up-amplitude error growth to a very rapid initial error growth on small scales is found. Reference experiments with a deterministic convection scheme show a 5%–10% longer predictability, but only if the initial condition uncertainty is small. These results confirm that planetary-scale predictability is intrinsically limited by rapid error growth due to latent heat release in clouds through an upscale-interaction process, while this interaction process is unimportant on average for current levels of initial condition uncertainty. Significance Statement Weather predictions provide high socioeconomic value and have been greatly improved over the last decades. However, it is widely believed that there is an intrinsic limit to how far into the future the weather can be predicted. Using numerical simulations with an innovative representation of convection, we are able to confirm the existence of this limit and to demonstrate which physical processes are responsible. We further provide quantitative estimates for the limit and the remaining improvement potential. These results make clear that our current weather prediction capabilities are not yet maxed out and could still be significantly improved with advancements in atmospheric observation and simulation technology in the upcoming decades.

Growth and shedding of harbor seal (Phoca vitulina) whiskers

Accurate and precise estimates of the timing of whisker growth and shedding are necessary to interpret biochemical information stored in whiskers. This fine-scale examination of harbor seal ( Phoca vitulina Linnaeus, 1758) whisker growth and shedding identified an asymptotic growth pattern with initial rapid growth that decays over time that can be defined with the von Bertalanffy curve. Initial growth rates were similar among whiskers, but estimated growth coefficients ( K) and asymptotic lengths ( L∞) differed by follicle positions suggesting that differences in total whisker lengths result from dissimilarly shaped growth curves. In other words, longer whisker length is attained by delaying the growth rate decay. There was substantial intra- and interseal variation in shedding dates; whisker shedding began at the caudal margin of the whisker bed and progressed toward the nose. Shedding of marked whiskers from the three study seals took from 78 to 133 days; however, selecting whiskers only from the most caudal follicle of the bottom three rows constrained the period of whisker shedding to 7–43 days. These differences in growth and shedding of harbor seal whiskers emphasize the importance of considering follicle position to select whiskers that are the most similar for analyses of information stored in whiskers.

Community Vital Signs: Measuring Wikipedia Communities’ Sustainable Growth and Renewal

Wikipedia is an undeniably successful project, with unprecedented numbers of online volunteer contributors. After 2007, researchers started to observe that the number of active editors for the largest Wikipedias declined after rapid initial growth. Years after those announcements, researchers and community activists still need to understand how to measure community health. In this paper, we study patterns of growth, decline and stagnation, and we propose the creation of 6 sets of language-independent indicators that we call “Vital Signs”. Three focus on the general population of active editors creating content: retention, stability, and balance; the other three are related to specific community functions: specialists, administrators, and global community participation. We borrow the analogy from the medical field, as these indicators represent a first step in defining the health status of a community; they can constitute a valuable reference point to foresee and prevent future risks. We present our analysis for eight Wikipedia language editions, and we show that communities are renewing their productive force even with stagnating absolute numbers; we observe a general lack of renewal in positions related to special functions or administratorship. Finally, we evaluate our framework by discussing these indicators with Wikimedia affiliates to support them in promoting the necessary changes to grow the communities.

Cyclic Voltammetric Experiment-Simulation Comparisons of the Complex Zr4+ to Zr0 Reduction Mechanism at a Molybdenum Electrode in LiF-CaF2 Eutectic Molten Salt

Nuclear energy represents an important option for generating largely clean CO2-free electricity. Zirconium is a fission product in the nuclear reaction that needs to be extracted from irradiated fuels used in Gen-IV molten salt reactors. The present investigation addresses the electrochemical reduction of solution soluble Zr4+ (soln) to surface confined Zro (s−c) at a molybdenum electrode in a LiF—CaF2 eutectic molten salt at 840 °C using DC cyclic, square-wave and AC voltammetry. Cyclic voltammograms simulated by the reaction scheme: Zr4+ (soln) + 4e− → Zro (soln); Zro (soln) ↔ Zr*(s−c); Zr*(s−c) → Zr4+*(s−c) + 4e−; Zr4+*(s−c) → Zr4+ (soln); Zr*(s−c) + Zr4+ (soln) ↔ 2Zr2+ (soln); Zr2+ (soln) ↔ Zr2+*(s−c) and Zr2+*(s−c) → Zr4+*(s−c) + 2e− provided excellent agreement with experimental data over the scan rate range of 50 to 500 mV s−1. The interpretation of the simulation is that the reduction of Zr4+ (soln) to Zro (metal) takes place via a transiently soluble Zro (soln) in an overall 4-electron essentially reversible diffusion-controlled process having a reversible formal potential (Eo f) of −1.22 V (vs Pt). A minor oxidation process observed at −0.455 V (vs Pt) on the reversing the potential scan direction is simulated via the reaction step Zr(s−c) + Zr4+ (soln) ↔ 2Zr2+ (s−c) followed by Zr2+ (s−c) → Zr4+ (sol) + 2e−. The sharply rising initial component where reduction of Zr4+ (sol) commences, contains evidence of a nucleation-growth mechanism associated with the electrocrystallisation of zirconium metal. This initial rapid growth of current is not fully accommodated in the simulations, but all features found beyond the peak potential are supported by the theory. A comparison with theory based on a direct reduction of Zr4+ (soln) to the metallic state having unit activity is provided. It is proposed that an analogous mechanism applies at a Ni electrode, except that a Ni-Zr alloy formation occurs instead of Zr metal.

Control of roughness-induced transition under the influence of inflow disturbance

Control of roughness-induced transition influenced by two- or three-dimensional inflow disturbances using spanwise-uniform wall blowing is investigated from the perspective of unstable modal growth with direct numerical simulations. Visualization of flow structures for two-dimensional disturbances indicates that the counter-rotating vortex pair in the wake bends the high-shear layer, which is related to both symmetric and antisymmetric unstable modes. The interaction of these structures is found to be responsible for the initial growth of the symmetric mode, which dominates the transition process. Both upstream and downstream position wall blowing are effective for transition control. Upstream position blowing works by lifting up the boundary layer and diminishing the wake structures, resulting in inhibition of the symmetric mode. Downstream position blowing has an even better effect, attributable to reconfiguration of the streamwise vorticity field in the wake and further distortion of the high-shear layer. When the inflow disturbance is a three-dimensional wave, the antisymmetric mode becomes dominant in the near-wake region, resulting in more rapid initial growth of the symmetric mode. As oblique waves have higher growth rates in a compressible boundary layer, the background disturbance is obviously stronger. Therefore, transition occurs earlier than for two-dimensional disturbances. When upstream position blowing is introduced, the spanwise shear related to the antisymmetric mode is reduced, and the background disturbance is suppressed as the disturbed boundary layer is pushed away from the roughness. Downstream position blowing can still inhibit the symmetric mode, but the antisymmetric mode is barely influenced, since this blowing is less effective in suppressing the counter-rotating vortex pair.

Supporting Growth and Transpiration of Newly Planted Street Trees With Passive Irrigation Systems

AbstractSolutions that use stormwater runoff to rapidly establish tree canopy cover in cities have received significant attention. Passive irrigation systems that direct stormwater to trees have the potential to increase growth and transpiration and may limit drought stress. However, little data from the field demonstrates this, and we lack robust and reliable designs which achieve it. Here, we quantified growth and transpiration for trees: (a) in infiltration pits receiving stormwater, with a raised underdrain and internal water storage (drained), (b) next to infiltration pits receiving stormwater but without an underdrain and internal water storage (adjacent), and (c) planted in standard pits, not receiving stormwater (control). Trees in drained pits grew twice as fast as control trees in the first 2 years, but fast initial growth rates were not sustained in years three and four. Trees outgrowing the small infiltration pits, rather than a lack of water, was most likely responsible for growth rates slowing down. Despite this, rapid initial growth for trees in drained pits meant trees were larger by year three and transpired more than twice as much (5.1 L d−1) as trees adjacent to pits (2.4 L d−1) or control trees (2.3 L d−1). No trees showed drought stress during the study. However, some trees planted adjacent to infiltration pits showed waterlogging stress, suggesting caution installing infiltration pits adjacent to establishing trees in fine‐textured soils. Overall, our results suggest passive irrigation systems can substantially increase initial tree growth, thereby facilitating greater cooling and runoff reduction through increased transpiration.

Aqueous Extracts of Medicinal Mushrooms Ganoderma lucidum and Pleurotus eryngii (Agaricomycetes) Can Affect Seed Germination and Seedling Survival.

Rapid and complete seed germination results in the rapid initial growth of plants. In this study, aqueous extracts (boiling, maceration + filtration, and maceration + autoclave) of Ganoderma lucidum and Pleurotus eryngii were used to improve seed germination of three crops (maize, clover, and alfalfa). The results revealed that boiled water extractions of G. lucidum positively affected seed germination of clover and alfalfa. Moreover, P. eryngii boiling extract could increase the vigor index II in alfalfa. The results achieved are comparable with those gained by phytohormones and in some cases were even better. From these findings, it can be concluded that the existing metabolites in aqueous extracts of G. lucidum and P. eryngii can be used to enhance seed germination effectively and even increase the leaf area of crop plants.

Visual experimental study on bubble behavior from nucleation site in vertical rectangular channel

The bubble behavior is a fundamental issue to deep understanding the boiling heat transfer, especially in rectangular channels where the bubble may be confined by the channel walls. In this paper experiment is performed and the bubble behavior is studied by a high-speed camera in the rectangular upward flow channels with a gap of 3.2 mm. The characteristics of bubble growth, bubble sliding velocity and coalescence are discussed in detail by analyzing the captured boiling behavior, including the effect of heat flux and system pressure. It is found that bubble originating from a single nucleation site experiences two stages, the namely initial rapid growth stage and the subsequent coalescence stage. The effect of heat flux on the growth rate of sliding bubble looks insignificant before coalescence, but it has an important impact on bubble growth rate at nucleation site. The bubble is easier to coalesce under higher heat flux, and also higher heat flux results in higher sliding bubble velocity. Besides, the system pressure has a significant effect on the bubble growth and coalescence. Under higher system pressure, bubble departing from the nucleation site slides along the heated wall and frequently coalesces with the previous bubble. The sliding bubble velocity after coalescence is approximately twice than before. A predictive correlation for sliding bubble velocity is presented in this paper and good agreement is achieved when comparing with experimental results.

Dynamic equilibrium of β-conglycinin/lysozyme heteroprotein complex coacervates

Complex coacervate is a classic charged polymer material in food science, personal care, and cellular biology. Nevertheless, time is often an important factor that is overlooked in the study of complex coacervates. This study analyzed the dynamic equilibrium/relaxation behavior of β-conglycinin/lysozyme (β-CG/LYS) heteroprotein coacervates after mixing, especially the effect of NaCl concentration, total protein concentration, and pH on this equilibrium behavior, only using two simple but effective methods (turbidity kinetics and bright-field microscopy). Although the turbidity kinetics of the β-CG/LYS coacervates experienced rapid initial growth like soluble complexes and amorphous precipitates, it subsequently showed a unique decline behavior. Through bright-field microscopy, we found that the drop in turbidity was closely related to the dynamic equilibrium of β-CG/LYS coacervates, including the shape-transformation from non-spherical clusters to spherical coacervates and the gradual merging of small coacervates. Adding NaCl (0, 20, and 40 mM), increasing the total protein concentration (1 and 5 mg/mL), and lowering pH (6 and 8) all accelerated the dynamic equilibrium of the β-CG/LYS coacervate and reduced the relaxation time. Turbidity kinetics can be used as a screening method to evaluate the effect of various factors on the dynamic equilibrium/relaxation behavior of coacervates.

Native mammals lack resilience to invasive generalist predator

Invasive predators have caused catastrophic declines in native wildlife across the globe. Though research has focused on the initial establishment, rapid growth, and spread of invasive predators, our understanding of prey resilience to established invasive predators remains limited. As a direct result of invasive Burmese pythons (Python molurus bivittatus), medium- to large-bodied native mammals decreased drastically across much of southern Florida as early as 2003. By 2014, most of these mammal species were exceedingly rare within the core invasion area, while pythons expanded outward to newly invaded areas. We used python observations to delineate the core python invasion area from the more recently invaded invasion front, and we compared changes in mammal occurrence from 2014 to 2019 between these two areas. We surveyed mammal communities using camera traps and scat surveys and used these observations to quantify the changes in occurrence among mammal species. As expected, occurrence of medium- and large-bodied mammals declined within the invasion front. However, contrary to our expectation, we observed little evidence of resilience among mammals within the invasion core. Of the 15 species detected in 2019, invasive black rats were the only species to increase in occurrence within the invasion core. Additionally, we observed declines in occurrence among native rodents within the invasion core, which were previously thought to be resistant to the effects of pythons. The continued presence of invasive pythons appears to be shifting the diverse mammal communities of southern Florida to one primarily composed of invasive species.

Examining the growth trajectories and cognitive predictors of reading in a consistent orthography: Evidence from a 10-year longitudinal study

AbstractWe examined the growth trajectories of reading in a consistent orthography (Greek) in two developmental periods (from Grade 1 to Grade 4 and from Grade 4 to Grade 10) and what cognitive skills predict the growth patterns. Seventy-five Greek-speaking children were assessed in Grades 1, 2, 4, 6, and 10 on word-, nonword-, and text-reading fluency. In Grades 1 and 4, they were also assessed on phonological awareness, rapid naming, phonological memory, orthographic knowledge, and articulation rate. Results of growth curve modeling showed that during the first developmental period, there was a rapid initial growth from Grade 1 to Grade 2 followed by a less rapid growth from Grade 2 to Grade 4. In the second developmental period, the slow growth continued. In both developmental periods, rapid naming and orthographic knowledge predicted the initial status of all reading outcomes and phonological memory predicted the initial status of nonword-reading fluency. Phonological awareness predicted the initial status of nonword-reading fluency in the first developmental period and the initial status of word- and text-reading fluency in the second developmental period. None of the cognitive skills predicted the growth rate in reading skills. Theoretical and practical implications of these findings are discussed.

Many-body localization in tilted and harmonic potentials

We discuss nonergodic dynamics of interacting spinless fermions in a tilted optical lattice as modeled by XXZ spin chain in magnetic (or electric) field changing linearly across the chain. The time dynamics is studied using exact propagation for small chains and matrix product states techniques for larger system sizes. We consider both the initial N\'eel separable state as well as the quantum quench scenario in which the initial state may be significantly entangled. We show that the entanglement dynamics is significantly different in both cases. In the former a rapid initial growth is followed by a saturation for sufficiently large tilt, $F$. In the latter case the dynamics seems to be dominated by pair tunneling and the effective tunneling rate scales as $1/F^2$. In the presence of an additional harmonic potential the imbalance is found to be entirely determined by a local effective tilt, $F_{\text{loc}}$, the entanglement entropy growth is modulated with frequency that follows $1/F_{loc}^2$ scaling first but at long time the dynamics is determined rather by the curvature of the harmonic potential. Only for large tilts or sufficiently large curvatures, corresponding to the deeply localized regime, we find the logarithmic entanglement growth for N\'eel initial state. The same curvature determines long-time imbalance for large $F$ which reveals strong revival phenomena associated with the manifold of equally spaced states, degenerate in the absence of the harmonic potential.

Development and Validation of Methodology for Estimating Potato Canopy Structure for Field Crop Phenotyping and Improved Breeding.

Traditional phenotyping techniques have long been a bottleneck in breeding programs and genotype- phenotype association studies in potato, as these methods are labor-intensive and time consuming. In addition, depending on the trait measured and metric adopted, they suffer from varying degrees of user bias and inaccuracy, and hence these challenges have effectively prevented the execution of large-scale population-based field studies. This is true not only for commercial traits (e.g., yield, tuber size, and shape), but also for traits strongly associated with plant performance (e.g., canopy development, canopy architecture, and growth rates). This study demonstrates how the use of point cloud data obtained from low-cost UAV imaging can be used to create 3D surface models of the plant canopy, from which detailed and accurate data on plant height and its distribution, canopy ground cover and canopy volume can be obtained over the growing season. Comparison of the canopy datasets at different temporal points enabled the identification of distinct patterns of canopy development, including different patterns of growth, plant lodging, maturity and senescence. Three varieties are presented as exemplars. Variety Nadine presented the growth pattern of an early maturing variety, showing rapid initial growth followed by rapid onset of senescence and plant death. Varieties Bonnie and Bounty presented the pattern of intermediate to late maturing varieties, with Bonnie also showing early canopy lodging. The methodological approach used in this study may alleviate one of the current bottlenecks in the study of plant development, paving the way for an expansion in the scale of future genotype-phenotype association studies.

Directly modelling population dynamics in the South American Arid Diagonal using 14C dates.

Large anthropogenic 14C datasets are widely used to generate summed probability distributions (SPDs) as a proxy for past human population levels. However, SPDs are a poor proxy when datasets are small, bearing little relationship to true population dynamics. Instead, more robust inferences can be achieved by directly modelling the population and assessing the model likelihood given the data. We introduce the R package ADMUR which uses a continuous piecewise linear (CPL) model of population change, calculates the model likelihood given a 14C dataset, estimates credible intervals using Markov chain Monte Carlo, applies a goodness-of-fit test, and uses the Schwarz Criterion to compare CPL models. We demonstrate the efficacy of this method using toy data, showing that spurious dynamics are avoided when sample sizes are small, and true population dynamics are recovered as sample sizes increase. Finally, we use an improved 14C dataset for the South American Arid Diagonal to compare CPL modelling to current simulation methods, and identify three Holocene phases when population trajectory estimates changed from rapid initial growth of 4.15% per generation to a decline of 0.05% per generation between 10 821 and 7055 yr BP, then gently grew at 0.58% per generation until 2500 yr BP. This article is part of the theme issue 'Cross-disciplinary approaches to prehistoric demography'.

Response to COVID-19 in South Korea and implications for lifting stringent interventions

BackgroundAfter experiencing a sharp growth in COVID-19 cases early in the pandemic, South Korea rapidly controlled transmission while implementing less stringent national social distancing measures than countries in Europe and the USA. This has led to substantial interest in their “test, trace, isolate” strategy. However, it is important to understand the epidemiological peculiarities of South Korea’s outbreak and characterise their response before attempting to emulate these measures elsewhere.MethodsWe systematically extracted numbers of suspected cases tested, PCR-confirmed cases, deaths, isolated confirmed cases, and numbers of confirmed cases with an identified epidemiological link from publicly available data. We estimated the time-varying reproduction number, Rt, using an established Bayesian framework, and reviewed the package of interventions implemented by South Korea using our extracted data, plus published literature and government sources.ResultsWe estimated that after the initial rapid growth in cases, Rt dropped below one in early April before increasing to a maximum of 1.94 (95%CrI, 1.64–2.27) in May following outbreaks in Seoul Metropolitan Region. By mid-June, Rt was back below one where it remained until the end of our study (July 13th). Despite less stringent “lockdown” measures, strong social distancing measures were implemented in high-incidence areas and studies measured a considerable national decrease in movement in late February. Testing the capacity was swiftly increased, and protocols were in place to isolate suspected and confirmed cases quickly; however, we could not estimate the delay to isolation using our data. Accounting for just 10% of cases, individual case-based contact tracing picked up a relatively minor proportion of total cases, with cluster investigations accounting for 66%.ConclusionsWhilst early adoption of testing and contact tracing is likely to be important for South Korea’s successful outbreak control, other factors including regional implementation of strong social distancing measures likely also contributed. The high volume of testing and the low number of deaths suggest that South Korea experienced a small epidemic relative to other countries. Caution is needed in attempting to replicate the South Korean response in populations with larger more geographically widespread epidemics where finding, testing, and isolating cases that are linked to clusters may be more difficult.

Heavy quark diffusion in an overoccupied gluon plasma

We extract the heavy-quark diffusion coefficient κ and the resulting momentum broadening 〈p2〉 in a far-from-equilibrium non-Abelian plasma. We find several features in the time dependence of the momentum broadening: a short initial rapid growth of 〈p2〉, followed by linear growth with time due to Langevin-type dynamics and damped oscillations around this growth at the plasmon frequency. We show that these novel oscillations are not easily explained using perturbative techniques but result from an excess of gluons at low momenta. These oscillation are therefore a gauge invariant confirmation of the infrared enhancement we had previously observed in gauge-fixed correlation functions. We argue that the kinetic theory description of such systems becomes less reliable in the presence of this IR enhancement.

Simulation of flow boiling in micro-channels: Effects of inlet flow rate and hot-spots

This paper presents the findings of a numerical study on the flow boiling in a micro-channel heat sink. The Navier-Stokes equations, energy equation, and the continuity equation are solved in a finite-volume framework using the front-tracking method. The numerical method is validated by comparison with the experimental results for a slug bubble growth, and vertical flow boiling. The numerical method is then used to study the effect of changing the inflow mass-velocity on the heat transfer coefficient, bubble size distribution, and the bubble nucleation frequency for a constant heat flux. The mean heat transfer coefficient of all the cases is found to be nearly twice that of the single-phase heat transfer coefficient. The bubble nucleation frequency is found to increase monotonically with the inflow mass-velocity. The bubble size distribution along the channel is found to become flatter as the mass-velocity is increased. We identify three distinct phases of the bubble evolution, namely the initial rapid growth phase, the boiling dominant phase, and finally the condensation dominant phase. Subsequently, the numerical method is used to study the effect of having a hot-spot near the bubble nucleation site on the heat transfer characteristics. It is found that the bubble nucleation frequency increases and the bubbles’ maximum volume decreases as the intensity of the hot-spot is increased for a fixed inlet flow rate. It is also observed that the average heat transfer coefficient does not change significantly with changing the intensity of the hot-spot, and that the bubble size distribution along the channel becomes flatter as the intensity of the hot-spot is increased.