Strong coupling between two resonance modes leads to the formation of new hybrid modes exhibiting disparate characteristics owing to the reversible exchange of information between different uncoupled ...modes. Here, we realize the strong coupling between the localized surface plasmon resonance and surface plasmon polariton Bloch wave using multilayer nanostructures. An anticrossing behavior with a splitting energy of 144 meV can be observed from the far-field spectra. More importantly, we investigate the near-field properties in both the frequency and time domains using photoemission electron microscopy. In the frequency domain, the near-field spectra visually demonstrate normal-mode splitting and display the extent of coupling. Importantly, the variation of the dephasing time of the hybrid modes against the detuning is observed directly in the time domain. These findings signify the evolution of the dissipation and the exchange of information in plasmonic strong coupling systems and pave the way to manipulate the dephasing time of plasmon modes, which can benefit many applications of plasmonics.
Reperfusion injury, the paradoxical tissue response that is manifested by blood flow-deprived and oxygen-starved organs following the restoration of blood flow and tissue oxygenation, has been a ...focus of basic and clinical research for over 4-decades. While a variety of molecular mechanisms have been proposed to explain this phenomenon, excess production of reactive oxygen species (ROS) continues to receive much attention as a critical factor in the genesis of reperfusion injury. As a consequence, considerable effort has been devoted to identifying the dominant cellular and enzymatic sources of excess ROS production following ischemia-reperfusion (I/R). Of the potential ROS sources described to date, xanthine oxidase, NADPH oxidase (Nox), mitochondria, and uncoupled nitric oxide synthase have gained a status as the most likely contributors to reperfusion-induced oxidative stress and represent priority targets for therapeutic intervention against reperfusion-induced organ dysfunction and tissue damage. Although all four enzymatic sources are present in most tissues and are likely to play some role in reperfusion injury, priority and emphasis has been given to specific ROS sources that are enriched in certain tissues, such as xanthine oxidase in the gastrointestinal tract and mitochondria in the metabolically active heart and brain. The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source (e.g., Nox) to activate and enhance ROS production by a second source (e.g., mitochondria). This review provides a synopsis of the evidence implicating ROS in reperfusion injury, the clinical implications of this phenomenon, and summarizes current understanding of the four most frequently invoked enzymatic sources of ROS production in post-ischemic tissue.
Respirometry is the gold standard measurement of mitochondrial oxidative function, as it reflects the activity of the electron transport chain complexes working together. However, the requirement for ...freshly isolated mitochondria hinders the feasibility of respirometry in multi‐site clinical studies and retrospective studies. Here, we describe a novel respirometry approach suited for frozen samples by restoring electron transfer components lost during freeze/thaw and correcting for variable permeabilization of mitochondrial membranes. This approach preserves 90–95% of the maximal respiratory capacity in frozen samples and can be applied to isolated mitochondria, permeabilized cells, and tissue homogenates with high sensitivity. We find that primary changes in mitochondrial function, detected in fresh tissue, are preserved in frozen samples years after collection. This approach will enable analysis of the integrated function of mitochondrial Complexes I to IV in one measurement, collected at remote sites or retrospectively in samples residing in tissue biobanks.
Synopsis
Freeze‐thawing events cause mitochondrial membrane permeabilization and disrupt mitochondrial functionality in cells and tissues. Reconstitution of maximal mitochondrial respiration allows the analysis of mitochondrial bioenergetics in frozen and thawed crude samples, thus overcoming limitations associated with the current methods.
Following reconstitution, mitochondrial maximal respiration can be assessed in frozen isolated mitochondria or total tissue lysate.
Respiratory rate measurements from tissue lysates reduce by an order of magnitude the minimal mass of tissue required.
Maximal respiration rates in reconstituted frozen samples are comparable to those in fresh ones.
Respiratory rates can be normalized per cell, per total protein or per mitochondrial content in frozen specimens.
Respiratory rates can be measured in stored samples from clinical and animal studies, and drug toxicity assays.
Reconstitution of maximal mitochondrial respiration circumvents the limitations associated with current methods for assessing mitochondrial bioenergetics in frozen clinical samples.
•A novel calibration method of the modified Mohr-Coulomb fracture model is presented.•Localization analyses and two material tests are used in the model calibration.•Experiments on AA6016 specimens ...covering a range of stress states are performed.•FE simulations predict crack initiation and propagation with good accuracy.
This paper presents a novel calibration procedure of the modified Mohr-Coulomb (MMC) fracture model by use of localization analyses and applies it for three tempers of an AA6016 aluminium alloy. The localization analyses employ the imperfection band approach, where metal plasticity is assigned outside the band and porous plasticity is assigned inside the band. Ductile failure is thus assumed to occur when the deformation localizes into a narrow band. The metal plasticity model is calibrated from notch tension tests using inverse finite element modelling. The porous plasticity model is calibrated by use of localization analyses where the deformation histories from finite element simulations of notch and plane-strain tension tests are prescribed as boundary conditions. Subsequently, localization analyses are used to establish the failure locus in stress space for proportional loading conditions and thus to determine the parameters of the MMC fracture model. Finite element simulations of notch tension and in-plane simple shear tests as well as two load cases of the modified Arcan test are used to validate the calibrated fracture model. The predictions by the simulations are in good agreement with the experiments, even though some deviations are seen for each temper. The results demonstrate that localization analyses are a cost-effective and reliable tool for predicting ductile failure, reducing the number of mechanical tests required to calibrate the MMC fracture model compared to the hybrid experimental-numerical approach usually applied.
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•Feedstocks govern PHA production schemes and enrichment conditions.•Synergistic impact of OLR, cycle length and SRT on enrichment conditions.•Nitrogen supplement associates with ...growth of PHA accumulators in the MC.•Uncoupled C/N supply and extended cultivation are strategies to improve PHA productivity.•Future work focusing in impact of F/F regime combined nitrogen supply on PHA production.
PHA production using a combination of mixed culture and carbon wastes has been demonstrated as a cost-reducing solution compared to the use of expensive pure culture process. Continuous research has been conducted with the aim to further reduce the production cost by simplifying the production scheme, as well as enhancing the performance of mixed culture in PHA production. Selection of the carbon feedstock and enrichment strategies needs to be essentially considered to obtain a culture enriched with PHA accumulators for a stable PHA production. Most of the studies implementing mixed culture process applied the feast-famine regime with periodical supply of carbon for culture enrichment. Results have revealed that the enriched culture showed a comparable performance with pure culture, in terms of PHA content (30–80%) and yield (0.4–0.8 g PHA/g S). However, a low productivity is the hindering factor to produce PHA at industrial scale by using mixed culture, which could be overcome by improvising the enrichment strategies. This review zooms into the evaluation of two step and three step processes in PHA production by utilising different feedstocks. Critical parameters to be considered for PHA production such as the suitable feedstocks, enrichment conditions, stability of the enriched culture and nutrient supplementation are being highlighted. The possible enrichment strategies that include uncoupled C and N supply and extended cultivation in overcoming the issue of low productivity are presented. The impact of different enrichment strategies on microbial community, characteristics of PHA produced as well as PHA production performance is worth investigating in future.
Understanding and controlling modal coupling in micro/nanomechanical devices is integral to the design of high-accuracy timing references and inertial sensors. However, insight into specific physical ...mechanisms underlying modal coupling, and the ability to tune such interactions is limited. Here, we demonstrate that tuneable mode coupling can be achieved in capacitive microelectromechanical devices with dynamic electrostatic fields enabling strong coupling between otherwise uncoupled modes. A vacuum-sealed microelectromechanical silicon ring resonator is employed in this work, with relevance to the gyroscopic lateral modes of vibration. It is shown that a parametric pumping scheme can be implemented through capacitive electrodes surrounding the device that allows for the mode coupling strength to be dynamically tuned, as well as allowing greater flexibility in the control of the coupling stiffness. Electrostatic pump based sideband coupling is demonstrated, and compared to conventional strain-mediated sideband operations. Electrostatic coupling is shown to be very efficient, enabling strong, tunable dynamical coupling.
•The concept of the charge structure with the uncoupled shell was proposed.•A typical casing with the uncoupled shell was tested and numerically studied.•The influence of different structural ...parameters on fragment velocity was obtained.•The modified formula for calculating the fragments velocity was proposed.
The demand for uncoupled charge structures has risen alongside advancements in warheads and protective design technologies in defense and public security sectors. Consequently, this work investigates the fragment dispersion characteristics of uncoupled charge structures and the impact of different structural parameters through numerical simulations. A modified equation derived from the Gurney formula is proposed using numerical simulation and the smoothed particle hydrodynamics method, tailored to the uncoupled charge concept and the foundational theory of the Gurney formula. To validate the fragment velocity prediction model for uncoupled charge structures, explosion experiments and other testing methods were utilized. By examining the theoretical underpinnings and the application of numerical simulation methods, this paper provides a robust foundation for the uncoupled charge structure, offering a crucial reference for designing protective measures against improvised explosive devices.
•3D fracture loci of uncoupled ductile fracture models were calibrated for 2024-T351 aluminum alloy and DP600 steel.•The type and number of calibration tests has a marginal influence in the fracture ...locus and predictive ability of the models.•Quite different shapes of the fracture locus are observed for between both materials.•The models present different levels of prediction accuracy in the high range of stress triaxiality, for both materials.•It is difficult to select the most appropriate model based only on the objective function value.
The prediction of ductile failure is crucial for the progress of metal forming industries. Therefore, uncoupled fracture models have been proposed and continuously extended, trying to improve their forecasting abilities. However, without an assessment analysis of their predictive ability, it is difficult to establish the most suitable model, for describing the onset of failure under a wide range of loading conditions. Actually, a fair comparison of models’ predictive ability requires the use of an extensive experimental database and a similar calibration procedure. In this context, seven uncoupled fracture models are chosen and revisited to study the effect of the type and number of tests used for calibration on their predictive ability. Experimental datasets available in literature were considered for 2024-T351 aluminium alloy and for DP600 steel. For each material, the experimental dataset was split in two subsets. The first one includes tests that were carried out under plane stress conditions that were used in the calibration procedure. For the aluminium alloy, different groups of 6 tests, covering distinct stress states, were elicited from the experimental subset and applied in the calibration of the seven models. The remaining tests were used to assess the predictive ability and their sensibility regarding the group used in models’ calibration. Different trends of the fracture loci are observed, depending on the selected models and the tests used in their calibration. However, the analysis of the results indicates that a set of at least 6 experimental tests is appropriate to calibrate fracture models, providing that they enable covering a wide range for the stress triaxiality and Lode parameter. Finally, the conclusions provide some recommendations for the improvement of the calibration procedure.
A methodology for computer simulation of ductile fracture in engineering structures using the eXtended Finite Element Method (XFEM) is presented. Crack initiation is modeled using an ...instability-based failure criterion derived from the micromechanics of void coalescence. The criterion depends on the state of stress at failure, strain hardening and the void volume fraction, whose evolution as a function of plastic strain is obtained using a physics-based void growth law. Material separation is modeled using the cohesive zone method, where cohesive surface elements are dynamically inserted into continuum elements that satisfy the failure criterion. The methodology is illustrated by comparing the model predictions with experimental data on uncracked and pre-cracked 316LN stainless steel specimens. It is shown that, using a set of parameters calibrated from standard tests, the model is able to quantitatively predict fracture in a variety of specimens. In contrast, widely used continuum damage models are unable to predict fracture in the different specimen types using a single set of material parameters.
•Ductile fracture of SS316LN is studied using experiments and XFEM simulations.•Specimens used encompass a wide range of stress triaxiality at crack initiation.•Crack initiation in XFEM is modeled using an instability-based fracture criterion.•The model quantitatively predicts the load–deflection response of all specimens.•Advantages of the instability-based model for ductile fracture are highlighted.
Forty-eight specimens with four notch specimen configurations have been extracted from three structural steel grades used in the Indian construction industry. The extracted specimen simulates stress ...states of ductile fracture initiation similar to the sacrificial element installed in seismic-resistant steel structures. All the specimens are monotonically tested under a displacement-controlled loading protocol. With the help of a universal testing machine and digital image correlation, the load versus notch elongation until the point of ductile fracture initiation has been captured for all the specimens. A validated numerical model is then developed to extract the ductile fracture initiation parameters, namely stress Triaxiality (T), Lode function (L - ξ or θ or Lp), and Equivalent Plastic Strain (PEEQ). The extracted T, L, and PEEQ are then used to construct a three-dimensional fracture locus for all three study grades. In addition, a new uncoupled ductile fracture model named the Exponential based Lode parameter Void Growth Model (ELVGM) is proposed to predict the point of ductile fracture initiation and is then compared with six well-established existing uncoupled ductile fracture models using eight error measures. The proposed ELVGM with two free parameters is observed to provide better prediction accuracy for both low and high-yield strength steel corresponding to the considered stress states.
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•Fracture locus database is created for three Indian steel grades (E250, E350, E450).•Isotropic hardening and free parameters are calibrated using 48 monotonic results.•New model (ELVGM) shows better prediction accuracy compared to six existing models.
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