Simulations of elastoinertial turbulence (EIT) of a polymer solution at low Reynolds number are shown to display localized polymer stretch fluctuations. These are very similar to structures arising ...from linear stability (Tollmien-Schlichting modes) and resolvent analyses, i.e., critical-layer structures localized where the mean fluid velocity equals the wave speed. Computations of self-sustained nonlinear Tollmien-Schlichting waves reveal that the critical layer exhibits stagnation points that generate sheets of large polymer stretch. These kinematics may be the genesis of similar structures in EIT.
Direct simulations of two-dimensional plane channel flow of a viscoelastic fluid at Reynolds number
$Re=3000$
reveal the existence of a family of attractors whose structure closely resembles the ...linear Tollmien–Schlichting (TS) mode, and in particular exhibits strongly localized stress fluctuations at the critical layer position of the TS mode. At the parameter values chosen, this solution branch is not connected to the nonlinear TS solution branch found for Newtonian flow, and thus represents a solution family that is nonlinearly self-sustained by viscoelasticity. The ratio between stress and velocity fluctuations is in quantitative agreement for the attractor and the linear TS mode, and increases strongly with Weissenberg number,
$\mathit{Wi}$
. For the latter, there is a transition in the scaling of this ratio as
$\mathit{Wi}$
increases, and the
$\mathit{Wi}$
at which the nonlinear solution family comes into existence is just above this transition. Finally, evidence indicates that this branch is connected through an unstable solution branch to two-dimensional elastoinertial turbulence (EIT). These results suggest that, in the parameter range considered here, the bypass transition leading to EIT is mediated by nonlinear amplification and self-sustenance of perturbations that excite the TS mode.
BACKGROUND The Centers for Disease Control and Prevention has shifted policy away from using ventilator-associated pneumonia (VAP) and toward using ventilator-associated conditions (VACs) as a marker ...of ICU quality. To date, limited prospective data regarding the incidence of VAC among medical and surgical ICU patients, the ability of VAC criteria to capture patients with VAP, and the potential clinical preventability of VACs are available. METHODS This study was a prospective 12-month cohort study (January 2013 to December 2013). RESULTS We prospectively surveyed 1,209 patients ventilated for ≥ 2 calendar days. Sixty-seven VACs were identified (5.5%), of which 34 (50.7%) were classified as an infection-related VAC (IVAC) with corresponding rates of 7.0 and 3.6 per 1,000 ventilator days, respectively. The mortality rate of patients having a VAC was significantly greater than that of patients without a VAC (65.7% vs 14.4%, P < .001). The most common causes of VACs included IVACs (50.7%), ARDS (16.4%), pulmonary edema (14.9%), and atelectasis (9.0%). Among IVACs, 44.1% were probable VAP and 17.6% were possible VAP. Twenty-five VACs (37.3%) were adjudicated to represent potentially preventable events. Eighty-six episodes of VAP occurred in 84 patients (10.0 of 1,000 ventilator days) during the study period. The sensitivity of the VAC criteria for the detection of VAP was 25.9% (95% CI, 16.7%-34.5%). CONCLUSIONS Although relatively uncommon, VACs are associated with greater mortality and morbidity when they occur. Most VACs represent nonpreventable events, and the VAC criteria capture a minority of VAP episodes.
Chemerin is an adipose-derived signaling protein (adipokine) that regulates adipocyte differentiation and function, immune function, metabolism, and glucose homeostasis through activation of ...chemokine-like receptor 1 (CMKLR1). A second chemerin receptor, G protein-coupled receptor 1 (GPR1) in mammals, binds chemerin with an affinity similar to CMKLR1; however, the function of GPR1 in mammals is essentially unknown. Herein, we report that expression of murine Gpr1 mRNA is high in brown adipose tissue and white adipose tissue (WAT) and skeletal muscle. In contrast to chemerin (Rarres2) and Cmklr1, Gpr1 expression predominates in the non-adipocyte stromal vascular fraction of WAT. Heterozygous and homozygous Gpr1-knockout mice fed on a high-fat diet developed more severe glucose intolerance than WT mice despite having no difference in body weight, adiposity, or energy expenditure. Moreover, mice lacking Gpr1 exhibited reduced glucose-stimulated insulin levels and elevated glucose levels in a pyruvate tolerance test. This study is the first, to our knowledge, to report the effects of Gpr1 deficiency on adiposity, energy balance, and glucose homeostasis in vivo. Moreover, these novel results demonstrate that GPR1 is an active chemerin receptor that contributes to the regulation of glucose homeostasis during obesity.
Campylobacter jejuni is a microaerophilic foodborne pathogen that is sensitive to stress conditions. However, it is not yet understood how this stress-sensitive pathogen may cause a significant ...number of cases of human gastroenteritis worldwide. In this study, we examined stress tolerance in 70 C. jejuni strains isolated from retail chicken under several stress conditions related to food safety. Compared to oxygen-sensitive (OS) strains of C. jejuni, C. jejuni strains with increased aerotolerance, such as hyper-aerotolerant (HAT) and aerotolerant (AT) strains, were more tolerant to peracetic acid, refrigeration and freeze-thaw stresses. However, the levels of thermotolerance and hyper-osmotolerance were not associated with the aerotolerance level of C. jejuni. The HAT and AT strains of C. jejuni exhibited significantly increased activities of catalase and superoxide dismutase (SOD), compared to the OS strains. Consistently, the HAT and AT strains were highly tolerant to oxidants, such as hydrogen peroxide, cumene hydroperoxide and menadione, compared to the OS strains. The AT and HAT strains that were tolerant to stresses, particularly peracetic acid and refrigeration, predominantly belonged to multilocus sequence typing (MLST) clonal complex (CC)-21. This study shows that oxidative stress resistance plays a role in determining the differential level of aerotolerance in C. jejuni and that AT and HAT strains of C. jejuni are more tolerant to oxidants and low temperatures than OS strains.
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•A chitosan/CNC/PAAm hybrid hydrogel is developed via double-network.•The hydrogel has superior tensile and compressive properties.•The hydrogel exhibits high self-recovery rate ...(81.3% after 12 h at room temperature).•The hydrogel is biocompatible and have potential for controlled drug release.
As medical practitioners’ interest in hydrogels continues to grow, their new expectations in terms of mechanical properties, biocompatibility and durability are changed. Here, we demonstrated a new strategy to improve both mechanical properties and self-recovery of double network (DN) hydrogels by introducing a self-healing network, consisting of carboxymethyl chitosan (CMC) and dialdehyde cellulose nanocrystals (DACNC). Notably, the hydrogel could be repeatedly stretched to 4 times its initial length and has tensile strength of 244 kPa, and completely recovered its shape when compressed by 90% and had the compressive strength up to 8 MPa. In addition, the deformed hydrogel recovered 81.3% of its dissipated energy at room temperature without any external stimuli. The hydrogel also exhibited good biocompatibility. We have developed a new method to fabricate stretchable and tough hydrogels that could spontaneously self-repair following mechanical deformation. They are promising for controlled drug release and dye adsorption.
Low water activity (aW) foods permit the survival of low-infectious dose pathogens including Escherichia coli and Salmonella. Desiccation of non-heat resistant E. coli and Salmonella enterica ...increases their heat resistance; therefore, alternative methods are necessary to ensure the safety of low aW foods. High-pressure carbon dioxide (HPCD) reduced microbial contaminants in high aW foods. This study aimed to identify HPCD conditions that reduce pathogenic E. coli and Salmonella in low aW conditions. Four strains of Shiga toxin-producing E. coli (STEC) and one strain of enteropathogenic E. coli were treated as a cocktail, and five strains of Salmonella were treated individually. The suitability of E. coli AW1.7, Pediococcus acidilactici FUA 3072, Enterococcus faecium NRRL B-2354 and Staphylococcus carnosus R6 FUA 2133 as surrogate organisms was evaluated. Treatments were validated in beef jerky. Samples were equilibrated to aW 0.75 and treated with heat, HPCD or pressurized N2. Treatment of desiccated E. coli AW1.7 and the STEC cocktail with dry gaseous CO2 (5.7 MPa and 65 °C) did not reduce cell counts; however, treatment with gaseous CO2 saturated with water reduced cell counts of all strains of E. coli. Treatment of beef jerky inoculated with E. coli and Salmonella with saturated gaseous CO2 resulted in >5-log reductions for all strains. E. faecium NRRL B-2354 and S. carnosus R6 were suitable surrogates for Salmonella on beef jerky treated with HPCD. Treatment of beef jerky with water-saturated gaseous CO2 was more effective than treatment with supercritical CO2 or treatments with N2 at the same temperature and pressure. Overall, the treatment of low aW foods with water-saturated gaseous HPCD can meet industry standards by achieving a >5-log reductions of E. coli and Salmonella. Additionally, surrogate organisms representing pathogenic E. coli and Salmonella have been validated.
•High pressure CO2 reduced cells counts of Salmonella on beef jerky by 5 log.•Salmonella is more resistant to treatment than STEC.•Gas-phase CO2 is more effective than supercritical CO2 or supercritical N2.•Treatment lethality is dependent on the water activity of the treatment medium.•Enterococcus faecalis is a suitable surrogate strain for Salmonella.
The effects of propiconazole, prothioconazole, tebuconazole, metconazole, and prothioconazole+tebuconazole (as a tank mix or a formulated premix) on the control of Fusarium head blight index (IND; ...field or plot-level disease severity) and deoxynivalenol (DON) in wheat were determined. A multivariate random-effects meta-analytical model was fitted to the log-transformed treatment means from over 100 uniform fungicide studies across 11 years and 14 states, and the mean log ratio (relative to the untreated check or tebuconazole mean) was determined as the overall effect size for quantifying fungicide efficacy. Mean log ratios were then transformed to estimate mean percent reduction in IND and DON relative to the untreated check (mean percent control: IND and mean percent control DON) and relative to tebuconazole. All fungicides led to a significant reduction in IND and DON (P < 0.001), although there was substantial between-study variability. Prothioconazole+tebuconazole was the most effective fungicide for IND, with a mean percent control IND of 52%, followed by metconazole (50%), prothioconazole (48%), tebuconazole (40%), and propiconazole (32%). For DON, metconazole was the most effective treatment, with a mean percent control DON of 45%; prothioconazole+tebuconazole and prothioconazole showed similar efficacy, with mean percent control DON values of 42 and 43%, respectively; tebuconazole and propiconazole were the least effective, with mean percent control DON values of 23 and 12%, respectively. All fungicides, with the exception of propiconazole, were significantly more effective than tebuconazole for control of both IND and DON (P < 0.001). Relative to tebuconazole, prothioconazole, metconazole, and tebuconzole+prothioconzole reduced disease index a further 14 to 20% and DON a further 25 to 29%. In general, fungicide efficacy was significantly higher for spring wheat than for soft winter wheat studies; depending on the fungicide, the difference in percent control between spring and soft winter wheat was 5 to 20% for mean percent control IND and 7 to 16% for mean percent control DON. Based on the mean log ratios and between-study variances, the probability that IND or DON in a treated plot from a randomly selected study was lower than that in the check by a fixed margin was determined, which confirmed the superior efficacy of prothioconazole, metconazole, and tebuconzole+prothioconzole for Fusarium head blight disease and toxin control.
The prophage-encoded Shiga toxin is a major virulence factor in Stx-producing
(STEC). Toxin production and phage production are linked and occur after induction of the RecA-dependent SOS response. ...However, food-related stress and Stx-prophage induction have not been studied at the single-cell level. This study investigated the effects of abiotic environmental stress on
expression by single-cell quantification of gene expression in STEC O104:H4 Δ
::
::
In addition, the effect of stress on production of phage particles was determined. The lethality of stressors, including heat, HCl, lactic acid, hydrogen peroxide, and high hydrostatic pressure, was selected to reduce cell counts by 1 to 2 log CFU/ml. The integrity of the bacterial membrane after exposure to stress was measured by propidium iodide (PI). The fluorescent signals of green fluorescent protein (GFP) and PI were quantified by flow cytometry. The mechanism of prophage induction by stress was evaluated by relative gene expression of
and cell morphology. Acid (pH < 3.5) and H
O
(2.5 mM) induced the expression of
in about 18% and 3% of the population, respectively. The mechanism of prophage induction by acid differs from that of induction by H
O
H
O
induction but not acid induction corresponded to production of infectious phage particles, upregulation of
, and cell filamentation. Pressure (200 MPa) or heat did not induce the Stx2-encoding prophage (Stx2-prophage). Overall, the quantification method developed in this study allowed investigation of prophage induction and physiological properties at the single-cell level. H
O
and acids mediate different pathways to induce Stx2-prophage.
Induction of the Stx-prophage in STEC results in production of phage particles and Stx and thus relates to virulence as well as the transduction of virulence genes. This study developed a method for a detection of the induction of Stx-prophages at the single-cell level; membrane permeability and an indication of SOS response to environmental stress were additionally assessed. H
O
and mitomycin C induced expression of the prophage and activated a SOS response. In contrast, HCl and lactic acid induced the Stx-prophage but not the SOS response. The lifestyle of STEC exposes the organism to intestinal and extraintestinal environments that impose oxidative and acid stress. A more thorough understanding of the influence of food processing-related stressors on Stx-prophage expression thus facilitates control of STEC in food systems by minimizing prophage induction during food production and storage.
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