The predictive capabilities of turbulent flow simulations, critical for aerodynamic design and weather prediction, hinge on the choice of turbulence models. The abundance of data from experiments and ...simulations and the advent of machine learning have provided a boost to turbulence modeling efforts. However, simulations of turbulent flows remain hindered by the inability of heuristics and supervised learning to model the near-wall dynamics. We address this challenge by introducing scientific multi-agent reinforcement learning (SciMARL) for the discovery of wall models for large-eddy simulations (LES). In SciMARL, discretization points act also as cooperating agents that learn to supply the LES closure model. The agents self-learn using limited data and generalize to extreme Reynolds numbers and previously unseen geometries. The present simulations reduce by several orders of magnitude the computational cost over fully-resolved simulations while reproducing key flow quantities. We believe that SciMARL creates unprecedented capabilities for the simulation of turbulent flows.
A fundamental understanding of chemical sensing mechanisms in graphene-based chemical field-effect transistors (chemFETs) is essential for the development of next generation chemical sensors. Here we ...explore the hidden sensing modalities responsible for tailoring the gas detection ability of pristine graphene sensors by exposing graphene chemFETs to electron donor and acceptor trace gas vapors. We uncover that the sensitivity (in terms of modulation in electrical conductivity) of pristine graphene chemFETs is not necessarily intrinsic to graphene, but rather it is facilitated by external defects in the insulating substrate, which can modulate the electronic properties of graphene. We disclose a mixing effect caused by partial overlap of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of adsorbed gas molecules to explain graphene’s ability to detect adsorbed molecules. Our results open a new design space, suggesting that control of external defects in supporting substrates can lead to tunable graphene chemical sensors, which could be developed without compromising the intrinsic electrical and structural properties of graphene.
The Solitaire FR can be used not only as a tool for mechanical thrombectomy but also as a detachable permanent stent. Our aim was to assess the feasibility and safety of permanent stent placement ...with the Solitaire FR compared with other self-expanding stents for intracranial artery recanalization for acute ischemic stroke.
From January 2011 through January 2016, we retrospectively selected 2979 patients with acute ischemic stroke. Among them, 27 patients who underwent permanent stent placement (13 patients with the Solitaire FR Solitaire group and 14 patients with other self-expanding stents other stent group) were enrolled. The postprocedural modified TICI grade and angiographic and clinical outcomes were assessed. The safety and efficacy of permanent stent placement of the Solitaire FR for acute large-artery occlusion were evaluated.
Stent placement was successful in all cases. Modified TICI 2b-3 reperfusion was noted in 84.6% of the Solitaire group and in 78.6% of the other stent group. Procedural time was significantly shorter in the Solitaire group than in the other stent group (
= .022). Shorter procedural time was correlated with favorable outcome (ρ = 0.46,
= .035). No significant differences were found in the modified TICI grade, NIHSS score, mRS, and hemorrhagic transformation rate between the 2 groups. The acute in-stent thrombosis rate at discharge was significantly lower when a glycoprotein IIb/IIIa inhibitor was injected during the procedure (
= .013).
Permanent stent placement with the Solitaire FR compared with other self-expanding stents appears to be feasible and safe as a rescue tool for refractory intra-arterial therapy.
Iron is a crucial transition metal for virtually all life. Two major destinations of iron within mammalian cells are the cytosolic iron-storage protein, ferritin, and mitochondria. In mitochondria, ...iron is utilized in critical anabolic pathways, including: iron-storage in mitochondrial ferritin, heme synthesis, and iron–sulfur cluster (ISC) biogenesis. Although the pathways involved in ISC synthesis in the mitochondria and cytosol have begun to be characterized, many crucial details remain unknown. In this review, we discuss major aspects of the journey of iron from its initial cellular uptake, its modes of trafficking within cells, to an overview of its downstream utilization in the cytoplasm and within mitochondria. The understanding of mitochondrial iron processing and its communication with other organelles/subcellular locations, such as the cytosol, has been elucidated by the analysis of certain diseases e.g., Friedreich's ataxia. Increased knowledge of the molecules and their mechanisms of action in iron processing pathways (e.g., ISC biogenesis) will shape the investigation of iron metabolism in human health and disease.
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•Iron is a crucial transition metal for virtually all life.•Imported iron is stored or utilized with the cytoplasm or mitochondria.•Iron storage in ferritin involves iron chaperones (e.g., PCBPs).•Utilized iron is employed in anabolic pathways in cytoplasm/mitochondria.•Defects in iron trafficking lead to various human diseases.
The resolvent formulation of McKeon & Sharma (
J. Fluid Mech.
, vol. 658, 2010, pp. 336–382) is applied to supersonic turbulent boundary layers to study the validity of Morkovin’s hypothesis, which ...postulates that high-speed turbulence structures in zero-pressure-gradient turbulent boundary layers remain largely the same as their incompressible counterparts. Supersonic zero-pressure-gradient turbulent boundary layers with adiabatic wall boundary conditions at Mach numbers ranging from 2 to 4 are considered. Resolvent analysis highlights two distinct regions of the supersonic turbulent boundary layer in the wave parameter space: the relatively supersonic region and the relatively subsonic region. In the relatively supersonic region, where the flow is supersonic relative to the free-stream, resolvent modes display structures consistent with Mach wave radiation that are absent in the incompressible regime. In the relatively subsonic region, we show that the low-rank approximation of the resolvent operator is an effective approximation of the full system and that the response modes predicted by the model exhibit universal and geometrically self-similar behaviour via a transformation given by the semi-local scaling. Moreover, with the semi-local scaling, we show that the resolvent modes follow the same scaling law as their incompressible counterparts in this region, which has implications for modelling and the prediction of turbulent high-speed wall-bounded flows. We also show that the thermodynamic variables exhibit similar mode shapes to the streamwise velocity modes, supporting the strong Reynolds analogy. Finally, we demonstrate that the principal resolvent modes can be used to capture the energy distribution between momentum and thermodynamic fluctuations.
Aims
To evaluate the antimicrobial activities of an active compound isolated from the culture broth of Amphirosellinia nigrospora JS‐1675 against various plant pathogenic bacteria and fungi.
Methods ...and Results
While screening for bioactive secondary metabolites from endophytic fungi, we found that A. nigrospora JS‐1675 showed strong in vitro antibacterial activity against Ralstonia solanacearum. One compound (1) was isolated and identified as (4S, 5S, 6S)‐5,6‐epoxy‐4‐hydroxy‐3‐methoxy‐5‐methyl‐cyclohex‐2‐en‐1‐one. Growth of most of the tested phytopathogenic bacteria was inhibited by compound 1 and the ethyl acetate (EtOAc) layer except Pseudomonas syringae pv. lachrymans. Compound 1 also inhibited the mycelial growth of several plant pathogenic fungi. Both compound 1 and the EtOAc layer reduced bacterial leaf spot disease in detached peach leaves. They also suppressed the development of bacterial wilt on tomato seedlings quite effectively.
Conclusions
Amphirosellinia nigrospora JS‐1675 showed antimicrobial activity against plant pathogenic bacteria and fungi by producing compound 1.
Significance and Impact of the Study
This is the first report on the occurrence of compound 1 in A. nigrospora JS‐1675 and its efficacy against plant pathogenic bacteria and fungi. Their strong disease control efficacy against tomato bacterial wilt suggests that this fungus can be used as a microbial bactericide.
Asymptomatic hemorrhagic transformation (HT) is not associated with immediate deterioration of patients with acute ischemic stroke. However, it is unclear whether it is clinically innocuous with ...respect to long-term outcome. The aim of this study was to determine the impact of asymptomatic HT on 3-month outcome.
A consecutive series of 1,618 patients, hospitalized between January 2004 and August 2007 for ischemic stroke within 7 days from symptom onset were identified in a prospective stroke registry database. Those who had no evidence of acute cerebral ischemia on diffusion-weighted MRI, who did not undergo T2-weighted gradient echo MRI, whose modified Rankin Scale (mRS) score at 3 months after stroke onset was not available, or who had symptomatic HT were excluded. The odds ratio (OR) of asymptomatic HT was calculated for the full distribution of mRS score and adjusted for variables with p < 0.25 with respect to their associations with asymptomatic HT or functional outcome.
Of 1,412 patients eligible for the study, 100 (7.1%) had asymptomatic HT. Patients who experienced asymptomatic HT were more likely to have cardioembolic stroke, to receive thrombolytic therapy, to receive anticoagulation with heparin, and to have a higher initial NIH Stroke Scale score. The crude and adjusted ORs of asymptomatic HT for an increment of mRS score at 3 months were 2.94 (95% confidence interval 2.05-4.24) and 1.90 (1.27-2.82), respectively.
Our study shows that the odds of a worse outcome are increased by a factor of 2 in patients with asymptomatic HT compared with those without HT after acute ischemic stroke.
A wall model for large-eddy simulation (LES) is proposed by devising the flow as a combination of building blocks. The core assumption of the model is that a finite set of simple canonical flows ...contains the essential physics to predict the wall shear stress in more complex scenarios. The model is constructed to predict zero/favourable/adverse mean pressure gradient wall turbulence, separation, statistically unsteady turbulence with mean flow three-dimensionality, and laminar flow. The approach is implemented using two types of artificial neural networks: a classifier, which identifies the contribution of each building block in the flow, and a predictor, which estimates the wall shear stress via a combination of the building-block flows. The training data are obtained directly from wall-modelled LES (WMLES) optimised to reproduce the correct mean quantities. This approach guarantees the consistency of the training data with the numerical discretisation and the gridding strategy of the flow solver. The output of the model is accompanied by a confidence score in the prediction that aids the detection of regions where the model underperforms. The model is validated in canonical flows (e.g. laminar/turbulent boundary layers, turbulent channels, turbulent Poiseuille–Couette flow, turbulent pipe) and two realistic aircraft configurations: the NASA Common Research Model High-lift and NASA Juncture Flow experiment. It is shown that the building-block-flow wall model outperforms (or matches) the predictions by an equilibrium wall model. It is also concluded that further improvements in WMLES should incorporate advances in subgrid-scale modelling to minimise error propagation to the wall model.
We present a miniature Fabry-Perot pressure sensor fabricated at the tip of an optical fiber with a pre-written Bragg grating by using UV-molding polymer process. The mold is constructed by ...integrating an optical fiber of 80 μm diameter with a zirconia ferrule. The optical fiber based mold makes it possible to use optical aligning method to monitor the coupled intensity between the mold-side and replica-side fibers, rendering a maskless alignment process with a submicrometer accuracy. A polymer-metal composite thin diaphragm is employed as the pressure transducer. The overall sensor size is around 200 μm in diameter. Experimental study shows that the sensor exhibits a good linearity over a pressure range of 1.9-7.9 psi, with a sensitivity of 0.0106 μm/psi. The fiber Bragg grating is exploited for simultaneous temperature measurements or compensation for temperature effects in pressure readings. The sensor is expected to benefit many fronts that require miniature and inexpensive sensors for reliable pressure measurement, especially biomedical applications.
Background and purpose
We investigated the effect of celecoxib, a selective inhibitor of cyclo‐oxygenase 2, in patients with intracerebral hemorrhage (ICH).
Methods
We conducted a multicenter, ...randomized, controlled, and open with blinded end‐point trial of 44 Korean patients 18 years or older with ICH within 24 h of onset. The intervention group (n = 20) received celecoxib (400 mg twice a day) for 14 days. The control group (n = 24) received the standard medical treatment for ICH. The primary end‐point was the number of patients with a change in the volume of perihematomal edema (PHE) from the 1st to the 7th ± 1 day (cut‐off value, 20%).
Results
The time from onset to computed tomography scan slightly differed between groups (177 ± 160 min for control vs. 297 ± 305 min for the celecoxib group; P = 0.10). In the primary end‐point analysis using cut‐off values, there was a significant shift to reduced expansion of PHE in the celecoxib group (P = 0.005). With respect to the secondary end‐points, there was also a significant shift to reduced expansion of ICH in the celecoxib group (P = 0.046). In addition, the expansion rate of PHE at follow‐up tended to be higher in the control group than in the celecoxib group (90.6 ± 91.7% vs. 44.4 ± 64.9%; P = 0.058).
Conclusions
In our small, pilot trial, administration of celecoxib in the acute stage of ICH was associated with a smaller expansion of PHE than that observed in controls.
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