Total Strains Research Articles

Bifidobacterium bifidum prevents the IL-1B induced increase in intestinal permeability by a novel mechanism: TLR-2 dependent activation of PPAR-gamma and inhibition of NF-kB signaling pathway

Background: Bifidobacterium bifidum (BB) is one of the most common probiotic bacteria strains that have been shown to have protective effects against intestinal inflammation, primarily by enhancing the intestinal epithelial tight junction (TJ) barrier function. IL-1β contributes to the development of intestinal inflammation in inflammatory bowel disease (IBD) in part by causing an increase in intestinal permeability. The IL-1β induced increase in intestinal epithelial TJ permeability is mediated by an NF-κB-dependent activation of myosin light chain kinase (MLCK) gene and disruption of the intestinal TJ barrier. The peroxisome proliferator-activated receptor gamma (PPAR-γ) is an important nuclear receptor in enterocytes which is known to have anti-inflammatory activity by interfering with NF-κB activation. However, the role of BB/PPAR-γ (and the possible mechanism involved) in protecting against IL-1β increase in intestinal permeability remain unclear. Aims: The major purpose of this study was to delineate the protective effect of BB against the IL-1β induced increase in intestinal TJ permeability and the intracellular mechanism involved. Methods: Filter-grown Caco-2 monolayers ( in vitro) and recycling intestinal perfusion of live mice ( in vivo) were used to assess intestinal permeability by using a paracellular marker (dextran-10kDa). Results: IL-1β caused a rapid activation of NF-κB and NF-κB and MLCK-dependent increase in intestinal epithelial TJ permeability in vitro and in vivo. A specific strain of BB (1x108 CFU/ml) referred to as BB1 strain inhibited the IL-1β increase in intestinal TJ permeability while strain BB4 had no effect. Other BB strains examined (5 total strains including BB4) did not inhibit the IL-1β increase in intestinal TJ permeability, suggesting that the BB enhancement of Caco-2 TJ barrier function was strain-specific. BB1, not BB4 enhancement of the TJ barrier was associated with an increase in TLR-2 expression, and PPAR-γ activation; BB1 also inhibited NF-kB activation and MLCK activity in Caco-2 monolayers and in mouse enterocyte. The inhibitory effect of BB on 1L-1β induced increase intestinal permeability, NF-κB activation, MLCK expression and activity was blocked by siRNA-induced knockdown of TLR-2 or PPAR-γ in Caco-2 monolayers. We also generated Villin-cre intestinal epithelial specific PPAR-γ knockout mice to study the involvement of enterocytes TLR-2/PPAR-γ on BB1 effect. BB1 did not inhibit the IL-1β-induced activation of NF-κB, increase in MLCK expression and increase in mouse intestinal permeability in TLR-2 or PPAR-γ intestinal deficient mice. Conclusion: These studies provide a novel insight into the BB the protective mechanism against the IL-1β-induced increase in intestinal TJ permeability in -vitro and in-vivo. Our data show that BB protects against the IL-1β induced increase in intestinal TJ permeability by a novel mechanism involving TLR-2/PPAR-g mediated inhibition of NF-kB and MLCK gene activatiation. NIH funding This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Transient Strain Monitoring of Weldments Using Distributed Fiber Optic System

The primary objective of this study was to evaluate the capability of a distributed fiber optic sensor to capture in situ dynamic transient strain formation during and post-weldment on the surface of a steel plate. The study involved a vertical manual weld of a bead on a plate on a 300 mm × 300 mm × 6.35 mm A36 steel plate (European equivalent S235J2; Chinese equivalent Q235B) clamped at the corners. A fiber optic distributed sensor was used to measure the surface total and thermal strains on the welded side of the plate adjacent to the weld path. Experimental results show a complex behavior of strain changes during the welding process and the residual strain formation post-welding. This study aims to document the use of distributed fiber optic sensing techniques in welding applications. Validations of the experimental data were performed using VrWeld, a commercial software framework for computational weld mechanics, and an iPhone FLIR One Pro. thermographic camera. The experimental results demonstrated that although distributed fiber optic sensing based on Rayleigh backscattering is an appropriate and useful technique for total strain measurements, the manufacturing and the materials used for the thermal sensors are critical in obtaining optimal results. Finally, this study highlights the challenges encountered in synchronizing large experimental data sets captured with different instruments with computational welding mechanic (CWM) models.

Effect of thermal strain on the formation of the nanostructure in YBCO films with doped nanorods

For superconducting YBCO coated films, introducing artificial nanopinning has been proven to be the effective methodologies to effectively enhance the critical current density (Jc). In order to precisely control the nanostructure of YBCO-nanopinning composite films, it is most important to accurately understand the mismatch strain and its effect in YBCO nanocomposite films. In this article, on the base of elastic theory we derived a theoretical model of describing the elastic energy of the superconducting YBCO film doped with artificial nanorods (usually BZO nanorods) due to the temperature change during the cooling process. On this model, the total strains of the film and nanorods were analytically calculated through solving the equilibrium equations, and further the thermal strain and its influence on the diameter of nanorods arranged along the c-axis in the YBCO film were comprehensively discussed by calculating the elastic energy density of the YBCO film and nanorods. These calculated results show that the thermal strain due to temperature change has a great effect on the YBCO nanocomposite structure, while this effect gradually weakens when the dopant concentration increases to a certain value.

Comparative Study of Creep and Stress Relaxation Behaviour during Ageing of 7050 Aluminum Alloy

This work focuses on quantitatively investigating the relationship between creep and stress relaxation of 7050 aluminum alloy at ageing temperatures. The creep strain rates, creep exponent, n, and activation energy were extracted from both the creep and stress relaxation curves to explore the creep mechanisms. Results showed that higher applied stress promotes the creep and stress relaxation extents. The calculated creep strain rates from creep and stress relaxation curves located in similar ranges and share similar n values (n = 3.7 for creep and n = 3.5 for stress relaxation), indicating that both tests are dominated by the dislocation slip mechanism. Additionally, the n value for creep tests is a constant throughout the tests, indicating that the dominant creep mechanism is unchanged. However, the activation energy changes from 123 kJ/mol to 139 kJ/mol, possibly due to evolved dislocations. Such a new finding could provide a supporting mechanism for building constitutive equations depending on the evolved A value. Furthermore, compared to the single-stage creep ageing, no primary creep was observed in T74 multi-stage creep ageing while similar amount of total creep strains was achieved. This suggests an alternative loading sequence for creep age forming of 7050 aluminum alloy, i.e., loading at the second stage to avoid prolonged exposure to high temperatures, extend the tool life, and achieve similar amounts of inelastic deformations. Based on all the above studies, creep and stress relaxation have a certain relationship. This paper provides a theoretical basis for future research on creep ageing forming of 7050 aluminum alloy.

An enhanced damaged plasticity model for concrete under cyclic and monotonic triaxial compression

The concrete damaged plasticity model (CDPM) in ABAQUS has been widely used to capture the damage behavior and nonlinear deformation characteristics of concrete structures. However, there are no available guidelines for defining the damage variables in this model. Modeling the behavior of concrete under high hydrostatic pressure (HP) is also beyond the scope of the CDPM. As a result, an enhanced model within the CDPM theoretical framework for modeling concrete under monotonic and cyclic triaxial compression (TC) was developed in this paper. Based on the 3-parameter Menétrey-Willam strength criterion (MWSC), the constant aspect ratio Kc, which dominates the shape of the failure surface in the deviatoric plane, of the original yield criterion was modified to be an HP-dependent variable to account for concrete behavior under high confining pressures. Besides, a corresponding confining pressure-dependent compression hardening/softening rule was developed based on the modified failure criterion. Moreover, both the compressive and tensile damage variables were explicitly derived as functions of the inelastic strain since improved relationships between the total strains and the corresponding plastic strains, as well as the effect of the lateral confining pressure on the compressive damage variable, was established. Furthermore, the predictive capability of the enhanced CDPM for concrete was demonstrated through comparisons of numerical simulations and experimental tests. The numerical predictions were in satisfactory agreement with the experimental results reported in the technical literature. Therefore, the enhanced CDPM in ABAQUS can properly capture the strength and ductility behavior of concrete under cyclic and monotonic TC.

Antibodies to oral pathobionts and colon cancer risk in the CLUE I cohort study.

Periodontitis has been associated with an increased risk for gastrointestinal cancers. The objective of our study was to investigate the association of antibodies to oral bacteria and the risk of colon cancer in a cohort setting. Using the CLUE I cohort, a prospective cohort initiated in 1974 in Washington County, Maryland, we conducted a nested case-control study to examine the association of levels of IgG antibodies to 11 oral bacterial species (13 total strains) with risk of colon cancer diagnosed a median of 16 years later (range: 1-26 years). Antibody response was measured using checkerboard immunoblotting assays. We included 200 colon cancer cases and 200 controls matched on age, sex, cigarette smoking status, time of blood draw and pipe or cigar smoking status. Controls were selected using incidence density sampling. Conditional logistic regression models were used to assess the association between antibody levels and colon cancer risk. In the overall analysis, we observed significant inverse associations for 6 of the 13 antibodies measured (P-trends <.05) and one positive association for antibody levels to Aggregatibacter actinomycetemcomitans (ATCC 29523; P-trend = .04). While we cannot rule out a role for periodontal disease in colon cancer risk, findings from our study suggest that a strong adaptive immune response may be associated with a lower risk of colon cancer. More studies will need to examine whether the positive associations we observed with antibodies to A. actinomycetemcomitans reflect a true causal association for this bacterium.

Antimicrobial Resistance and β-Lactamase Production in Clinically Significant Gram-Negative Bacteria Isolated from Hospital and Municipal Wastewater.

Hospital and municipal wastewater contribute to the spread of antibiotic-resistant bacteria and genes in the environment. This study aimed to examine the antibiotic resistance and β-lactamase production in clinically significant Gram-negative bacteria isolated from hospital and municipal wastewater. The susceptibility of bacteria to antibiotics was tested using the disk diffusion method, and the presence of extended-spectrum β-lactamases (ESBL) and carbapenemases was determined using an enzyme inhibitor and standard multiplex PCR. Analysis of antimicrobial resistance of total bacterial strains (n = 23) revealed that most of them were resistant to cefotaxime (69.56%), imipenem (43.47%), meropenem (47.82%) and amoxicillin-clavulanate (43.47%), gentamicin (39.13%), cefepime and ciprofloxacin (34.78%), trimethoprim-sulfamethoxazole (30.43%). A total of 8 of 11 phenotypically confirmed isolates were found to have ESBL genes. The blaTEM gene was present in 2 of the isolates, while the blaSHV gene was found in 2 of the isolates. Furthermore, the blaCTX-M gene was found in 3 of the isolates. In one isolate, both the blaTEM and blaSHV genes were identified. Furthermore, of the 9 isolates that have been phenotypically confirmed to have carbapenemase, 3 were confirmed by PCR. Specifically, 2 isolates have the blaOXA-48 type gene and 1 have the blaNDM-1 gene. In conclusion, our investigation shows that there is a significant rate of bacteria that produce ESBL and carbapenemase, which can promote the spread of bacterial resistance. Identifying ESBL and carbapenemase production genes in wastewater samples and their resistance patterns can provide valuable data and guide the development of pathogen management strategies that could potentially help reduce the occurrence of multidrug resistance.

Experimental and numerical investigation of sandstone deformation under cycling loading relevant for underground energy storage

Considering the storage capacity and already existing infrastructures, underground porous reservoirs are highly suitable to store green energy, for example, in the form of green gases such as hydrogen and compressed air. Depending on the energy demand and supply, the energy-rich fluids are injected and produced, which induces cyclic change of state-of-the-stress in the reservoir and its surrounding. Detailed analyses of the geo-mechanical deformations under variable storage conditions i.e., storage frequency and fluid fluctuating pressures, are crucially important for safe and efficient operations. The present work presents an integrated analysis, based on experimental and constitutive modeling aspects, to investigate sandstones’ geomechanical response to cyclic loading relevant to underground energy storage (UES). To this end, sandstone rock samples were subjected to cyclic loading above and below the onset of dilatant cracking under different frequencies and loading amplitudes. Axial strains and Acoustic Emissions (AE) were measured in both regimes to quantify the total deformation (strain) of the rock and its AE characteristics. It is found that the inelastic strain and number of AE events is the highest in the first cycle and reduce subsequently cycle after cycle. Moreover, cyclic inelastic deformations are affected by the mean stress, amplitude, and frequency of the stress waveform. On the one hand, the higher the mean stress and the amplitude, the higher the total inelastic strains. On the other hand, the lower the frequency, the higher the total inelastic strain. From the modeling perspectives, five types of deformation mechanisms were identified based on the governing physics: elastic, viscoelastic, compaction-based cyclic inelastic, inelastic brittle creep, and dilatation-based inelastic deformation. To model elastic, viscoelastic, and brittle creep, the Nishihara model was used. A cyclic modified cam clay model (MCC) and hardening–softening model were applied to capture plastic deformation. The results show a very good fit of the constitutive model with the experimental results, which could help in studying the response of reservoirs to injection and production.

Ab initio prediction of temperature-dependent stability of heterogeneous B19′ phase in TiNi alloy using atomistically informed Eshelby’s ellipsoidal inclusion

In this study, we energetically predicted the temperature-dependent stability of the heterogeneous B19′ phase in the B2 matrix of TiNi alloys using density functional theory (DFT) and phonon analysis informed Eshelby’s ellipsoidal inclusion. The temperature-dependent eigenstrains and elastic constants for Eshelby’s ellipsoidal inclusion were calculated using DFT and phonon analysis under a quasi-harmonic approximation. The stable orientation of the disk-shaped B19′ phase in the B2 matrix and its total strains were evaluated with respect to temperature using Eshelby’s ellipsoidal inclusion analysis. Using the total strains, the elastically deformed atomic structure of the heterogeneous B19′ phase in the B2 matrix was determined, and its temperature-dependent free energy was calculated using DFT calculations and phonon analysis. Comparing the temperature-dependent free energies of the B2 and elastically deformed B19′ structures, we successfully predicted that the transformation between the two phases occurs at 300 K, which agrees with experimental observations. Moreover, it is shown that the temperature-dependent difference in the elastic constants between the B19′ phase and B2 matrix influences the phase transformation, which is the origin of the shape-memory effect of TiNi alloy.

Influence of antibiotic-resistance and exudate on peroxyacetic acid tolerance in O157 and non-O157 Shiga toxin producing E. coli

Shiga toxin producing Escherichia coli (STEC) continues to cause foodborne outbreaks associated with beef and beef products despite consistent use of antimicrobial interventions. In this study, the influence of antibiotic resistance (ABR) in E. coli O157:H7 H1730, O157:H7 43,895, O121:H19 and O26:H11 on tolerance to peroxyacetic acid (PAA) was evaluated. Further, bactericidal concentrations of PAA in the presence of nutrient rich media (Tryptic Soy Broth, TSB and beef exudates) and nutrient deficient media (Sterile Deionized Water, SDW and Phosphate Buffered Saline, PBS) were evaluated for all bacterial strains. Antibiotic resistance to ampicillin (amp C), or ampicillin and streptomycin (amp P strep C) was generated in each bacterial strain through incremental exposure to the antibiotics or by plasmid transformation (n = 12 total strains). The mean bactericidal concentrations of PAA were higher (p ≤ 0.05) in nutrient rich media (205.55 ± 31.11 in beef exudate and 195.83 ± 25.00 ppm in TSB) than in nutrient deficient media (57.91 ± 11.97 ppm in SDW and 56.66 ± 9.56 ppm in PBS). Strain O157: H7 ampP strepC was the most tolerant to PAA (p ≤ 0.05). At 200 ppm in nutrient rich media and 60 ppm in nutrient deficient media, all bacterial strains declined in population to below the limit of detection. Analysis of the beef exudates indicated the presence of diverse amino acids that have been associated with acid tolerance. The results from this study indicate that beef exudates could contribute to acid tolerance and suggest that some STEC bacterial strains with certain ABR profiles might be more tolerant to PAA.

Clinical and Environmental Vibrio cholerae Non-O1, Non-O139 Strains from Australia Have Similar Virulence and Antimicrobial Resistance Gene Profiles.

Cholera caused by pathogenic Vibrio cholerae is still considered one of the major health problems in developing countries including those in Asia and Africa. Australia is known to have unique V. cholerae strains in Queensland waterways, resulting in sporadic cholera-like disease being reported in Queensland each year. We conducted virulence and antimicrobial genetic characterization of O1 and non-O1, non-O139 V. cholerae (NOVC) strains (1983 to 2020) from Queensland with clinical significance and compared these to environmental strains that were collected as part of a V. cholerae monitoring project in 2012 of Queensland waterways. In this study, 87 V. cholerae strains were analyzed where O1 (n = 5) and NOVC (n = 54) strains from Queensland and international travel-associated NOVC (n = 2) (61 in total) strains were sequenced, characterized, and compared with seven previously sequenced O1 strains and 18 other publicly available NOVC strains from Australia and overseas to visualize the genetic context among them. Of the 61 strains, three clinical and environmental NOVC serogroup strains had cholera toxin-producing genes, namely, the CTX phage (identified in previous outbreaks) and the complete Vibrio pathogenicity island 1. Phylogenetic analysis based on core genome analysis showed more than 10 distinct clusters and interrelatedness between clinical and environmental V. cholerae strains from Australia. Moreover, 30 (55%) NOVC strains had the cholix toxin gene (chxA) while only 11 (20%) strains had the mshA gene. In addition, 18 (34%) NOVC strains from Australia had the type three secretion system and discrete expression of type six secretion system genes. Interestingly, four NOVC strains from Australia and one NOVC strain from Indonesia had intSXT, a mobile genetic element. Several strains were found to have beta-lactamase (blaCARB-9) and chloramphenicol acetyltransferase (catB9) genes. Our study suggests that Queensland waterways can harbor highly divergent V. cholerae strains and serve as a reservoir for various V. cholerae-associated virulence genes which could be shared among O1 and NOVC V. cholerae strains via mobile genetic elements or horizontal gene transfer. IMPORTANCE Australia has its own V. cholerae strains, both toxigenic and nontoxigenic, that are associated with cholera disease. This study aimed to characterize a collection of clinical and environmental NOVC strains from Australia to understand their virulence and antimicrobial resistance profile and to place strains from Australia in the genetic context of international strains. The findings from this study suggest the toxigenic V. cholerae strains in the Queensland River water system are of public health concern. Therefore, ongoing monitoring and genomic characterization of V. cholerae strains from the Queensland environment are important and would assist public health departments to track the source of cholera infection early and implement prevention strategies for future outbreaks. Understanding the genomics of V. cholerae could also inform the natural ecology and evolution of this bacterium in natural environments.

Influence of implant design and length on stress distribution in immediately loaded implants in posterior maxilla - A two-dimensional finite element analysis.

The aim of this two dimensional (2D) finite element analysis study was to evaluate the influence of implant design (step and tapered) and length on stress distribution at bone implant interface, when placed in maxillary posterior bone under immediate loading protocol. 2D finite element models were developed to simulate the two types of implant designs, i.e., Tapered and step implants of 3.75-mm - Diameter and 6 and 10 mm lengths, respectively. Maxillary posterior bone quality (D4 bone) was simulated with a very thin cortical bone (0.5 mm) for the placement of implants. The respective material properties were assigned. The implant designs incorporated microthreads at the crestal part and rest of the implant body incorporated Acme threads. Forces of 100 Newtons were applied vertically and in oblique direction (at an angle of 45°) to long axis of the implants. Total deformation (micromovements), stresses and strains were evaluated at the bone implant interface. The results of micromovements, stresses and strains were found to be lower for long implants as compared to short implants. Also, all the values were found to be higher for oblique loads as compared to vertical loads. The von mises stress values were highest for 6 mm step implants and lowest for 10 mm step implants. In the presence of low bone density with optimal bone height, standard diameter long step implants can be used. Incorporation of microthreads at the crestal portion and acme threads for body portion of the implant presents a good option to be used under immediate loading protocol.

Comparative evaluation of variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element (FE) method: An in-vitro analysis.

While using preadjusted brackets, the position of the bracket on the crown is one of the deciding factors that determine the tooth's final tip, torque, height, and rotation. The final tooth position is not optimal if the bracket is placed incorrectly or if the varying crown morphology does not correspond with the bracket design. The present study was conducted to evaluate and compare the variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element method. For the present study, three-dimensional models of maxillary right central incisor and canine were made using CREO version 4.0 software. CREO is a powerful three-dimensional (3-D) computer-based, computer-aided design (CAD) software developed by Parametric Technology Corporation (PTC) to aid in design processes. Simulation was done to replicate the clinical situation of an active palatal root torque acting on the incisor and canine. The induced palatal movement of root tips and labial movement of crowns tips, overall stress, and von Mises stress generated in the brackets and the total equivalent strains developed in the periodontal ligament (PDL) were calculated, while the values obtained were tabulated and subjected to statistical analysis. Based on the findings of the present study, the average maximum stress produced in the bracket was calculated as 265.069 Mpa in incisor and 166.742 Mpa in the canine. Likewise, the average of the maximum displacement of root apex observed in the present study was calculated as 0.01401 mm in the incisor and 0.00421 mm in the canine, while the average strain developed in the PDL was calculated as 0.0587 for incisor and 0.0498 for the canine. Furthermore, it was, also, observed that the magnitude of strain developed in the PDL increased with increase in the stress produced by the bracket prescription for both incisor and canine. Within the limitations of the present study, it was concluded that the magnitude of displacement of root apex was significantly influenced by bracket prescription and bracket position. Also, the stress developed in the bracket was influenced by bracket prescription and position, while the variation in crown morphology in the incisor and canine played a significant role in the eventual strain developed in the PDL after torque application.

Global emergence of carbapenem-resistant Klebsiella pneumoniae co-carrying multiple carbapenemases

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) co-carrying multiple carbapenemases is complicating clinical treatment. This study aimed to investigate the global dissemination trends of CRKP strains that co-carry multiple carbapenemases. The CRKP isolate KP424 co-carrying blaNDM-1 and blaKPC-2, recovered from a stool specimen, was identified by the NG-Test Carba 5 test, and the genome sequence was further determined by using Nanopore MinION and Illumina NovaSeq 6000 technologies. The genome sequences of the CRKP strains carrying multiple carbapenemase genes were further retrieved from the NCBI GenBank database. Thirteen antimicrobial resistance genes, including blaNDM-1 and blaKPC-2, have been identified in KP424, with blaNDM-1 and blaKPC-2 located on different plasmids. In total, 832 genome sequences of CRKP strains co-carrying two carbapenemase genes were retrieved from the NCBI database. Strains carrying both blaNDM and blaOXA-48-like accounted for 665 (79.9 %) of the total strains, ranking first, and those carrying both blaKPC and blaNDM accounted for 103 (12.4 %), ranking second. The prevalence of CRKP strains co-carrying two carbapenemase genes increased significantly over time, from 0.40 % in 2010 to 9.67 % in 2021. The proportion of strains carrying both blaKPC and blaNDM has also increased, from 0.00 % in 2010 to 4.40 % in 2021. The strains carrying both blaKPC and blaNDM had the highest prevalence (66.7 %, 52/78) in China, while those carrying both blaNDM and blaOXA-48-like had the highest prevalence worldwide. Multiple-carbapenemase producers pose a great threat to public health; further research on the mechanisms underlying multiple carbapenemase gene occurrence is required to prevent their global dissemination.

Elastic investigation for the existence of B33 phase in TiNi shape memory alloys using atomistically informed Eshelby’s ellipsoidal inclusion

The existence of the B33 phase in TiNi alloys, which was reported to be a stable phase using density functional theory calculations but not confirmed experimentally, is controversial. Using Eshelby’s ellipsoidal inclusion, which was atomistically informed by density functional theory calculations, we investigated the existence of the B33 phase in the TiNi shape memory alloy. The calculated total strains of the heterogeneously nucleated B33 phase were similar to the eigenstrains of the B19’ phase, which were also calculated using density functional theory calculations. Considering the similarity of the atomic structures of B33 and B19’, this indicates that the B33 phase was elastically suppressed and changed to the B19’ phase by the original B2 matrix. We confirmed that the elastic inhomogeneity between the B2 matrix and B33 phase plays a role in this change.

Hydrolytic enzyme screening and carotenoid production evaluation of halophilic archaea isolated from highly heavy metal-enriched solar saltern sediments.

This paper aimed to screen the enzymatic activities and evaluate the carotenoid production level of twenty-two halophilic archaea isolated from Sfax solar saltern sediments. The molecular identification performed by sequencing the 16S rRNA genes showed that all strains have a high similarity degree (99.7-100%) with Halobacterium salinarum NRC-1. The strains were screened for the presence of eight hydrolase activities using agar plate-based assays. The most detected enzyme was gelatinase (77.27% of total strains), followed by protease (63.63%) and amylase activities (50%). The carotenoid production yields of the strains ranged between 2.027 and 14.880mg/l. The UV-Visible spectroscopy of pigments revealed that it was a bacterioruberin type. When evaluated and compared to the standard β-carotene, the antioxidant capacities of these pigments showed a scavenging activity of more than 75% at a concentration of 5μg/ml for three strains (AS16, AS17, and AS18). Then a sequence of one-step optimization processes was performed, using the one-factor-at-a-time approach, to define the optimum conditions for growth and carotenoid production of the highest carotenoid producing strain (AS17). Different environmental factors and nutritional conditions were tested. Variations in these factors were found to deeply influence growth and carotenoid production. A maximum carotenoid production (16.490mg/l), higher than that of the control (14.880mg/l), was observed at 37°C, pH 7, 250g/l of salinity, with 80% air phase in the flask at 110rpm, in presence of light and in culture media containing (g/l) 10, yeast extract; 7.5, casamino acid; 20, MgSO4; 4, KCl; and 3, trisodium citrate.

Neutronographic Analysis of Load Partitioning and Micro Residual Stress Development in Duplex Stainless Steels

In the present work, neutronographic in situ diffraction stress analyses during uniaxial loading and subsequent unloading were carried out on the two duplex stainless steels X2CrNiMoN22-5-3 and X3CrNiMoN27-5-2 with nominal phase fractions for ferrite:austenite of 50:50% and 70:30%, respectively. In addition to the different phase fractions, the two steels also differed in their phase-specific crystallographic texture. The load-partitioning behaviour and the phase-specific micro (residual) stress evolution for total strains up to about 9% were investigated. The results indicated that for both materials under load, the phase-specific stress in the ferrite phase was significantly higher than in the austenite phase, while no texture development through the plastic deformation could be observed.

Creep-aging behaviors of Al-Cu-Li alloy with different grain sizes

The Al-Cu-Li alloys with different grain sizes were manufactured through different routes and treated with T34 before the creep aging process. Their creep-aging behaviors at 160 °C under 175 MPa were investigated and their corresponding mechanical properties were tested. Their microstructure was characterized by EBSD and HAADF-STEM. The results show that the total creep strains increase with increasing grain size. The creep strain of specimens with an average grain size of 53.4 µm is twice as that with an average grain size of 12.2 µm. However, their yield and tensile strengths are grain size independent. This appearance could be explained by the large creep strain achieved before the secondary primary creep stage, which is contributed by dislocation motion and increases with increasing grain size. When strengthening precipitates start to nucleate and grow, the creep resistance of dislocations sharply increases and Harper-Dorn creep becomes the main creep mechanism. The alloys with different grain sizes have similar precipitates and substructures in their peak-creep-aged state, leading to their similar yield and tensile strengths at room temperature. • A new thermomechanical treatment was used to fabricate sheets with fine grains. • The creep mechanism of the complex four-stage creep age test in the Al-Cu-Li alloy has been clarified. • Grain refinement was proven to have a negative influence on the total creep strain in this work. • GND densities was used to characterize the distribution evolution of dislocations during creep age test.

Universality in Anisotropic Linear Anelasticity

In linear elasticity, universal displacements for a given symmetry class are those displacements that can be maintained by only applying boundary tractions (no body forces) and for arbitrary elastic constants in the symmetry class. In a previous work, we showed that the larger the symmetry group, the larger the space of universal displacements. Here, we generalize these ideas to the case of anelasticity. In linear anelasticity, the total strain is additively decomposed into elastic strain and anelastic strain, often referred to as an eigenstrain. We show that the universality constraints (equilibrium equations and arbitrariness of the elastic constants) completely specify the universal elastic strains for each of the eight anisotropy symmetry classes. The corresponding universal eigenstrains are the set of solutions to a system of second-order linear PDEs that ensure compatibility of the total strains. We show that for three symmetry classes, namely triclinic, monoclinic, and trigonal, only compatible (impotent) eigenstrains are universal. For the remaining five classes universal eigenstrains (up to the impotent ones) are the set of solutions to a system of linear second-order PDEs with certain arbitrary forcing terms that depend on the symmetry class.

On strain-based rupture criterion for ascending aortic aneurysm: The role of fiber waviness

We propose a new approach for constructing strain-based rupture criterion for ascending thoracic aortic aneurysm. The rupture metric is formulated using an effective strain, which is a measure of net strain that the collagen bundles experience after fiber uncrimping. The effective strain is a function of the total strain and the waviness properties of the collagen fibers. In the present work, the waviness properties are obtained from fitting biaxial response data to constitutive models that explicitly consider the collagen waviness and fiber recruitment. Inflation test data from 10 ascending thoracic aortic aneurysm specimens are analyzed. For each specimen, tension-strain data at ∼2300 material points are garnered. The effective strain fields in the configuration immediately before rupture are computed. It is found that the hotspots of the effective strain match the rupture sites very well in all 10 samples. More importantly, the values of effective strain at the hotsopts are closely clustered around 0.1, in contrast to a much wider distribution of the total strain. The study underscores the importance of considering the fiber recruitment in formulating strain-based rupture metric, and suggests that ϵ¯≈0.1, where ϵ¯ is the effective strain metric defined in this work, can be considered as a criterion for assessing the imminent rupture risk of ascending aortic aneurysms. Statement of significanceWe advocate to use effective strain in ATAA rupture assessment. The effective strain is a measure of net strain in the collagen network after waviness uncrimping. We analyzed bulge inflation data of ATAA samples. It was found that, while the total strains at rupture varied from sample to sample, the effective strains were closely clustered around 0.1. And the hotspots of effective strain matched the rupture sites well. The work underlines the importance of considering collagen fiber waviness and recruitment when evaluating the rupture risk using strain, and suggests a new direction for developing sharper rupture metrics.