Turbulent combustion models can be divided into two broad classes: models that make no assumption about the underlying combustion processes and models that constrain the underlying combustion ...processes to some a priori presumed reduced-order manifold. The former class of models, including the Transported PDF (TPDF) approach and the Linear Eddy Model (LEM), is by nature more general but comes at increased computational cost. The latter class of models, including “flamelet”-like models and Conditional Moment Closure (CMC), is computationally more efficient albeit with the need to assume something about the underlying combustion processes a priori, traditionally limiting combustion processes to a single asymptotic mode. In this work, a new turbulent combustion model is developed that breaks this inherent trade-off and enables a computationally efficient description of multi-modal combustion. The model is constructed by first postulating that all (adiabatic, isobaric, two-stream) combustion processes can be described with a two-dimensional space whose coordinates are a mixture fraction and a generalized progress variable. The governing equations for the species mass fractions and temperature are then projected onto this two-dimensional manifold through a coordinate transformation to provide the evolution equations for the thermochemical state on the manifold; this approach results in an equilibrium manifold formulation. An explicit transport equation for the generalized progress variable is derived through the choice of a (set of weighted) arbitrary reference species and the functional dependence of the reference species on the generalized progress variable. The approach can accommodate both unity Lewis numbers and differential diffusion without issue. The mode of combustion is encoded into three scalar dissipation rates (the mixture fraction dissipation rate, the generalized progress variable dissipation rate, and the cross-dissipation rate), and the asymptotic modes of combustion are recovered under appropriate limits. However, the relative ease at which the nonpremixed limit is recovered depends on the reference species. Alternatively, the evolution of the thermochemical state on the manifold can be derived by conditionally filtering (or averaging) the governing equations with respect to the manifold coordinates, resulting in a non-equilibrium manifold formulation. Simplification of the non-equilibrium manifold formulation to the equilibrium manifold formulation reveals the implicit assumptions inherent to the equilibrium manifold formulation. A new solver PDRs is developed for solving the manifold equations, and example solutions demonstrate the ability of the model to describe general multi-modal combustion phenomena as the scalar dissipation rates are varied including not only the asymptotic modes of combustion but also partially premixed and stratified premixed combustion coupled or uncoupled with autoignition. The paper concludes with a discussion of open challenges for integrating the model with Large Eddy Simulation (LES) and Reynolds-Averaged Navier–Stokes (RANS) approaches.
In this work, an integrated Large Eddy Simulation (LES) model is developed for sooting turbulent nonpremixed flames and validated in a laboratory scale flame. The integrated approach leverages ...state-of-the-art developments in both soot modeling and turbulent combustion modeling and gives special consideration to the small-scale interactions between turbulence, soot, and chemistry. The oxidation of the fuel and the formation of gas-phase soot precursors is described by the Flamelet/Progress Variable model, which has been previously extended to account for radiation losses. However, previous DNS studies have shown that Polycyclic Aromatic Hydrocarbons (PAH), the immediate precursors of soot particles, exhibit significant unsteady effects due to relatively slow chemistry. To model these unsteady effects, a transport equation is solved for a lumped PAH species. In addition, due to the removal of PAH from the gas-phase, alternative definitions of the mixture fraction, progress variable, and enthalpy are proposed. The evolution of the soot population is modeled with the Hybrid Method of Moments (HMOM), an efficient statistical model requiring the solution of only a few transport equations describing statistics of the soot population. The filtered source terms in these equations that describe the various formation, growth, and destruction processes are closed with a recently developed presumed subfilter PDF approach that accounts for the high spatial intermittency of soot. The integrated LES model is validated in a piloted natural gas turbulent jet diffusion flame and is shown to predict the magnitude of the maximum soot volume fraction in the flame relatively accurately, although the maximum soot volume fraction is shown to be rather sensitive to the subfilter scalar dissipation rate model.
•People’s beliefs can have subtle influences on their judgments of learning.•Fluency beliefs can influence their JOLs despite no differences in processing fluency.•To judge learning, people search ...for cues that are relevant to memory.
According to analytic-processing theory, when people are asked to judge their future memory performance, they search for cues that will help them reduce their uncertainty for how well they will remember each item. For instance, many people believe that more fluently performing a task is related to better task performance. Thus, when studying items for an upcoming test, items that are believed to be more easily processed are expected to be judged as more memorable. To test this prediction, we had participants judge their learning of words presented for study in two colors (blue or green), because these colors were not expected to differentially impact processing fluency or memory. During the task instructions, some participants were led to believe that one color was easier to process than another, but nothing was mentioned about whether color was related to memory. Across multiple experiments, color did not consistently influence final test performance, whereas people’s judgments were significantly higher for words printed in the color that had been associated with more fluent processing. In a final experiment, a different instruction was used in which one color was associated with being more calming when read. For participant’s who believed that calming was associated with better memory, JOLs were higher for the words presented in the allegedly calming color. This evidence supports analytic-processing theory and further highlights the central (and sometimes subtle) role of people’s beliefs as they judge their learning.
Individualized therapy in endometrial cancer, the most common gynaecologic cancer in the developed world, focuses on identifying specific molecular subtypes. Mutations in the exonuclease domain of ...the DNA polymerase epsilon (POLE) gene define one such subtype, which causes an ultra-mutated tumour phenotype. These tumours may have an improved progression-free survival and may be receptive to specific therapies. However, the clinical phenotype of these tumours is unknown. The objective of this study was to evaluate the clinical and genetic features of POLE-mutated tumours from a large cohort of women whose cases are characterized by: (1) the availability of detailed clinical and lifestyle data; (2) mutation analysis; and (3) long-term follow-up.
A total of 604 patients with endometrial cancer were included in the study. Data from a detailed questionnaire, including lifestyle and family history information, provided extensive pertinent information on the patients. Sequencing of exons 9-14 of the POLE gene was performed. Follow-up data were gathered and analysed.
Hotspot pathogenic POLE mutations were identified in N = 38/599 patients (6.3%). Patients with a POLE-mutated tumour were significantly younger, were more often nulliparous, and had a history of smoking. POLE-mutated tumours were more frequently aneuploid. Prognosis for patients with hotspot POLE-mutated tumours was significantly better in comparison with patients with non-mutated tumours; however careful selection of pathogenic mutations is essential to the definition of this prognostically favourable group.
This study demonstrates that POLE-mutated endometrial cancer is significantly associated with previously unknown clinicopathologic characteristics. Outcome in POLE-mutated tumours was excellent in cases with hotspot mutations. Our results suggest that prediction of excellent outcome in cases of POLE-mutated EMCA should be restricted to cases of EMCA with hotspot mutations until further data are available on the rising number of mutations with unknown significance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Clinicians and patients face a dilemma in understanding how best to resume walking after a healed diabetic neuropathic ulcer. The objectives of this brief review are to: provide context for the ...patient's health and mobility status; propose 5 suggestions to safely and effectively progress mobility following a healed foot ulcer; and to consider topics for future research to improve care in this area. Rates of ulcer recurrence and mortality are high, and activity is low following a diabetic foot wound. Medical and rehabilitation approaches have emphasized protection of the insensitive, fragile foot with the hope to prevent subsequent harm to the foot and person. In particular, the 1–2 months following wound unloading and “healing” have the greatest risk for ulcer recurrence. While early protection should be emphasized, a growing body of evidence suggests that over‐protection of the foot and limited walking can be harmful, presumably because of the negative effects of prolonged immobility and stress protection. Multiple recent studies report the ability of exercise and walking to have a positive effect on various diabetic foot outcomes without additional harm. Much less is known about how an ulcerated foot can resume walking after the wound is healed. This review integrates available guidelines, evidence, and precautions to suggest advice on how best to resume and progress walking in this population at high risk for ulcer recurrence.
Introduction and hypothesis
The objective was to demonstrate the surgical procedure of laparoscopic mesh removal after sacrocolpopexy to aid clinicians facing mesh complications.
Methods
Video ...footage shows the laparoscopic management of mesh failure and mesh erosion after sacrocolpopexy with narrated video sequences of two patients.
Results
Laparoscopic sacrocolpopexy represents the gold standard in advanced prolapse repair. Mesh complications occur infrequently but infections, failure of prolapse repair and mesh erosions necessitate mesh removal and repeat sacrocolpopexy if applicable.
The video deals with two women referred to our tertiary referral urogynecology unit in the University Women’s Hospital of Bern, Switzerland, after laparoscopic sacrocolpopexies that were carried out in remote hospitals. Both patients were asymptomatic more than 1 year after surgery.
Conclusions
Complete mesh removal after sacrocolpopexy and repeat prolapse surgery can be challenging but is feasible and is aimed at improving patients’ complaints and symptoms.
A Direct Numerical Simulation (DNS) of soot formation in an
n-heptane/air turbulent nonpremixed flame has been performed to investigate unsteady strain effects on soot growth and transport. For the ...first time in a DNS of turbulent combustion, Polycyclic Aromatic Hydrocarbons (PAH) are included via a validated, reduced chemical mechanism. A novel statistical representation of soot aggregates based on the Hybrid Method of Moments is used M.E. Mueller, G. Blanquart, H. Pitsch, Combust. Flame 156 (2009) 1143–1155, which allows for an accurate state-of-the-art description of soot number density, volume fraction, and morphology of the aggregates. In agreement with previous experimental studies in laminar flames, Damköhler number effects are found to be significant for PAH. Soot nucleation and growth from PAH are locally inhibited by high scalar dissipation rate, thus providing a possible explanation for the experimentally observed reduction of soot yields at increasing levels of mixing in turbulent sooting flames. Furthermore, our data indicate that soot growth models that rely on smaller hydrocarbon species such as acetylene as a proxy for large PAH molecules ignore or misrepresent the effects of turbulent mixing and hydrodynamic strain on soot formation due to differences in the species Damköhler number. Upon formation on the rich side of the flame, soot is displaced relative to curved mixture fraction iso-surfaces due to differential diffusion effects between soot and the gas-phase. Soot traveling towards the flame is oxidized, and aggregates displaced away from the flame grow primarily by condensation of PAH on the particle surface. In contrast to previous DNS studies based on simplified soot and chemistry models, surface reactions are found to contribute barely to the growth of soot, for nucleation and condensation processes occurring in the fuel stream are responsible for the most of soot mass generation. Furthermore, the morphology of the soot aggregates is found to depend on the location of soot in mixture fraction space. Aggregates having the largest primary particles populate the region closest to the location of peak soot growth. On the contrary, the aggregates with the largest number of primary particles are located much further into the fuel stream.
The formation, growth, and transport of soot is investigated via large scale numerical simulation in a three-dimensional turbulent non-premixed n-heptane/air jet flame at a jet Reynolds number of ...15,000. For the first time, a detailed chemical mechanism, which includes the soot precursor naphthalene and a high-order method of moments are employed in a three-dimensional simulation of a turbulent sooting flame. The results are used to discuss the interaction of turbulence, chemistry, and the formation of soot. Compared to temperature and other species controlled by oxidation chemistry, naphthalene is found to be affected more significantly by the scalar dissipation rate. While the mixture fraction and temperature fields show fairly smooth spatial and temporal variations, the sensitivity of naphthalene to turbulent mixing causes large inhomogeneities in the precursor fields, which in turn generate even stronger intermittency in the soot fields. A strong correlation is apparent between soot number density and the concentration of naphthalene. On the contrary, while soot mass fraction is usually large where naphthalene is present, pockets of fluid with large soot mass are also frequent in regions with very low naphthalene mass fraction values. From the analysis of Lagrangian statistics, it is shown that soot nucleates and grows mainly in a layer close to the flame and spreads on the rich side of the flame due to the fluctuating mixing field, resulting in more than half of the total soot mass being located at mixture fractions larger than 0.6. Only a small fraction of soot is transported towards the flame and is completely oxidized in the vicinity of the stoichiometric surface. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames. Finally, given the difficulties in obtaining quantitative data in experiments of turbulent sooting flames, this simulation provides valuable data to guide the development of models for Large Eddy Simulation and Reynolds Average Navier Stokes approaches.
Plant induced responses to environmental stressors are increasingly studied in a behavioral ecology context. This is particularly true for plant induced responses to herbivory that mediate direct and ...indirect defenses, and tolerance. These seemingly adaptive alterations of plant defense phenotypes in the context of other environmental conditions have led to the discussion of such responses as intelligent behavior. Here we consider the concept of plant intelligence and some of its predictions for chemical information transfer in plant interaction with other organisms. Within this framework, the flow, perception, integration, and storage of environmental information are considered tunable dials that allow plants to respond adaptively to attacking herbivores while integrating past experiences and environmental cues that are predictive of future conditions. The predictive value of environmental information and the costs of acting on false information are important drivers of the evolution of plant responses to herbivory. We identify integrative priming of defense responses as a mechanism that allows plants to mitigate potential costs associated with acting on false information. The priming mechanisms provide short- and long-term memory that facilitates the integration of environmental cues without imposing significant costs. Finally, we discuss the ecological and evolutionary prediction of the plant intelligence hypothesis.
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