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Sample records for aleaciones al-6si-3cu-xmg t6

  1. Quench sensitivity of hot extruded 6061-T6 and 6069-T6 aluminum alloys

    SciTech Connect

    Bergsma, S C; Kassner, M E; Li, X; Rosen, R S

    2000-08-08

    The purpose of this study is to investigate the quench sensitivity of mechanical properties of hot extruded 6061 and 6069 aluminum alloys. The relationship between mechanical properties and quench delzty time at various temperatures between 200-500 C was determined. It was concluded that the 6069-T6 was somewhat more quench sensitive than 6061, which may be consistent with the composition difference.

  2. Electron beam welding of 6061-T6 covers to A356-T6 machined cast housings: Final report

    SciTech Connect

    Miller, G.P.

    1988-03-01

    An electron beam welding process was developed to replace the manual gas tungsten arc welding process for welding 6061-T6 aluminum covers to the A356-T6 cast aluminum machined housing for a Filter Pack Assembly. Design change recommendations must be incorporated prior to implementation of the electron beam welding process. 3 refs., 9 figs., 5 tabs.

  3. Advanced Colloids Experiment (Temperature Controlled) - ACE-T6

    NASA Technical Reports Server (NTRS)

    Meyer, William V.; Sicker, Ronald J.; Bailey, Kelly; Eustace, John; Lynch, Matthew

    2017-01-01

    Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-T6) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  4. Advanced Colloids Experiment (Temperature Controlled) - ACE-T6

    NASA Technical Reports Server (NTRS)

    Meyer, William V.; Sicker, Ron; Bailey, Kelly; Eustace, John; Abbott-Hearn, Amber; Lynch, Matthew

    2016-01-01

    Increment 51 - 52 Science Symposium presentation of Advanced Colloids Experiment (ACE-T6) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  5. Performance Evaluation of the T6 Ion Engine

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Goebel, Dan M.; Hofer, Richard R.; Polk, James E.; Wallace, Neil C.; Simpson, Huw

    2010-01-01

    The T6 ion engine is a 22-cm diameter, 4.5-kW Kaufman-type ion thruster produced by QinetiQ, Ltd., and is baselined for the European Space Agency BepiColombo mission to Mercury and is being qualified under ESA sponsorship for the extended range AlphaBus communications satellite platform. The heritage of the T6 includes the T5 ion thruster now successfully operating on the ESA GOCE spacecraft. As a part of the T6 development program, an engineering model thruster was subjected to a suite of performance tests and plume diagnostics at the Jet Propulsion Laboratory. The engine was mounted on a thrust stand and operated over its nominal throttle range of 2.5 to 4.5 kW. In addition to the typical electrical and flow measurements, an E x B mass analyzer, scanning Faraday probe, thrust vector probe, and several near-field probes were utilized. Thrust, beam divergence, double ion content, and thrust vector movement were all measured at four separate throttle points. The engine performance agreed well with published data on this thruster. At full power the T6 produced 143 mN of thrust at a specific impulse of 4120 seconds and an efficiency of 64%; optimization of the neutralizer for lower flow rates increased the specific impulse to 4300 seconds and the efficiency to nearly 66%. Measured beam divergence was less than, and double ion content was greater than, the ring-cusp-design NSTAR thruster that has flown on NASA missions. The measured thrust vector offset depended slightly on throttle level and was found to increase with time as the thruster approached thermal equilibrium.

  6. Performance Evaluation of the T6 Ion Engine

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Goebel, Dan M.; Hofer, Richard R.; Polk, James E.; Wallace, Neil C.; Simpson, Huw

    2010-01-01

    The T6 ion engine is a 22-cm diameter, 4.5-kW Kaufman-type ion thruster produced by QinetiQ, Ltd., and is baselined for the European Space Agency BepiColombo mission to Mercury and is being qualified under ESA sponsorship for the extended range AlphaBus communications satellite platform. The heritage of the T6 includes the T5 ion thruster now successfully operating on the ESA GOCE spacecraft. As a part of the T6 development program, an engineering model thruster was subjected to a suite of performance tests and plume diagnostics at the Jet Propulsion Laboratory. The engine was mounted on a thrust stand and operated over its nominal throttle range of 2.5 to 4.5 kW. In addition to the typical electrical and flow measurements, an E x B mass analyzer, scanning Faraday probe, thrust vector probe, and several near-field probes were utilized. Thrust, beam divergence, double ion content, and thrust vector movement were all measured at four separate throttle points. The engine performance agreed well with published data on this thruster. At full power the T6 produced 143 mN of thrust at a specific impulse of 4120 seconds and an efficiency of 64%; optimization of the neutralizer for lower flow rates increased the specific impulse to 4300 seconds and the efficiency to nearly 66%. Measured beam divergence was less than, and double ion content was greater than, the ring-cusp-design NSTAR thruster that has flown on NASA missions. The measured thrust vector offset depended slightly on throttle level and was found to increase with time as the thruster approached thermal equilibrium.

  7. Effect of service usage on tensile, fatigue, and fracture properties of 7075-T6 and 7178-T6 aluminum alloys

    NASA Technical Reports Server (NTRS)

    Everett, R. A., Jr.

    1975-01-01

    A study has been made to determine the effects of extensive service usage on some basic material properties of 7075-T6 and 7178-T6 aluminum alloy materials. The effects of service usage were determined by comparing material properties for new material (generally obtained from the literature) with those for material cut from the center wing box of a C-130B transport airplane with 6385 flight-hours of service. The properties investigated were notched and unnotched fatigue strengths, fatigue-crack-growth rate, fracture toughness, and tensile properties. For the properties investigated and the parameter ranges considered (crack length, stress ratio, etc.), the results obtained showed no significant difference between service and new materials.

  8. Effect of specimen thickness of fatigue-crack-growth behavior and fracture toughness of 7075-T6 and 7178-T6 aluminum alloys

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.; Newman, J. C., Jr.

    1973-01-01

    A study was made to determine the effects of specimen thickness on fatigue crack growth and fracture behavior of 7075-T6 and 7178-T6 aluminum alloy sheet and plate. Specimen thicknesses ranged from 5.1 to 12.7 mm (0.20 to 0.50 in.) for 7075-T6 and from 1.3 to 6.4 mm (0.05 to 0.25 in.) for 7178-T6. The stress ratios R used in the crack growth experiments were 0.02 and 0.50. For 7075-T6, specimen thickness had relatively little effect on fatigue-crack growth. However, the fracture toughness of the thickness of the thickest gage of 7075-T6 was about two-thirds of the fracture toughness of the thinner gages of 7075-T6. For 7178-T6, fatigue cracks generally grew somewhat faster in the thicker gages than in the thinnest gage. The fracture toughness of the thickest gage of 7178-T6 was about two-thirds of the fracture toughness of the thinner gages of 7178-T6. Stress intensity methods were used to analyze the experimental results. For a given thickness and value of R, the rate of fatigue crack growth was essentially a single-valued function of the stress intensity range for 7075-T6 and 7178-T6. An empirical equation developed by Forman, Kearney, and Engle fit the 7075-T6 and 7178-T6 crack growth data reasonably well.

  9. Fatigue design curves for 6061-T6 aluminum

    SciTech Connect

    Yahr, G.T.

    1993-01-01

    A request has been made to the ASME Boiler and Pressure Vessel Committee that 6061-T6 aluminum be approved for use in the construction of Class 1 welded nuclear vessels so it can be used for the pressure vessel of the Advanced Neutron Source research reactor. Fatigue design curves with and without mean stress effects have been proposed. A knock-down factor of two is applied to the design curve for evaluation of welds. The basis of the curves is explained. The fatigue design curves are compared to fatigue data from base metal and weldments.

  10. Fatigue design curves for 6061-T6 aluminum

    SciTech Connect

    Yahr, G.T.

    1993-06-01

    A request has been made to the ASME Boiler and Pressure Vessel Committee that 6061-T6 aluminum be approved for use in the construction of Class 1 welded nuclear vessels so it can be used for the pressure vessel of the Advanced Neutron Source research reactor. Fatigue design curves with and without mean stress effects have been proposed. A knock-down factor of two is applied to the design curve for evaluation of welds. The basis of the curves is explained. The fatigue design curves are compared to fatigue data from base metal and weldments.

  11. Quantitative image analysis of WE43-T6 cracking behavior

    NASA Astrophysics Data System (ADS)

    Ahmad, A.; Yahya, Z.

    2013-06-01

    Environment-assisted cracking of WE43 cast magnesium (4.2 wt.% Yt, 2.3 wt.% Nd, 0.7% Zr, 0.8% HRE) in the T6 peak-aged condition was induced in ambient air in notched specimens. The mechanism of fracture was studied using electron backscatter diffraction, serial sectioning and in situ observations of crack propagation. The intermetallic (rare earthed-enriched divorced intermetallic retained at grain boundaries and predominantly at triple points) material was found to play a significant role in initiating cracks which leads to failure of this material. Quantitative measurements were required for this project. The populations of the intermetallic and clusters of intermetallic particles were analyzed using image analysis of metallographic images. This is part of the work to generate a theoretical model of the effect of notch geometry on the static fatigue strength of this material.

  12. The ubiquitin ligase CHIP prevents SirT6 degradation through noncanonical ubiquitination.

    PubMed

    Ronnebaum, Sarah M; Wu, Yaxu; McDonough, Holly; Patterson, Cam

    2013-11-01

    The ubiquitin ligase CHIP (carboxyl terminus of Hsp70-interacting protein) regulates protein quality control, and CHIP deletion accelerates aging and reduces the life span in mice. Here, we reveal a mechanism for CHIP's influence on longevity by demonstrating that CHIP stabilizes the sirtuin family member SirT6, a lysine deacetylase/ADP ribosylase involved in DNA repair, metabolism, and longevity. In CHIP-deficient cells, SirT6 protein half-life is substantially reduced due to increased proteasome-mediated degradation, but CHIP overexpression in these cells increases SirT6 protein expression without affecting SirT6 transcription. CHIP noncanonically ubiquitinates SirT6 at K170, which stabilizes SirT6 and prevents SirT6 canonical ubiquitination by other ubiquitin ligases. In CHIP-depleted cells, SirT6 K170 mutation increases SirT6 half-life and prevents proteasome-mediated degradation. The global decrease in SirT6 expression in the absence of CHIP is associated with decreased SirT6 promoter occupancy, which increases histone acetylation and promotes downstream gene transcription in CHIP-depleted cells. Cells lacking CHIP are hypersensitive to DNA-damaging agents, but DNA repair and cell viability are rescued by enforced expression of SirT6. The discovery of this CHIP-SirT6 interaction represents a novel protein-stabilizing mechanism and defines an intersection between protein quality control and epigenetic regulation to influence pathways that regulate the biology of aging.

  13. The Ubiquitin Ligase CHIP Prevents SirT6 Degradation through Noncanonical Ubiquitination

    PubMed Central

    Ronnebaum, Sarah M.; Wu, Yaxu; McDonough, Holly

    2013-01-01

    The ubiquitin ligase CHIP (carboxyl terminus of Hsp70-interacting protein) regulates protein quality control, and CHIP deletion accelerates aging and reduces the life span in mice. Here, we reveal a mechanism for CHIP's influence on longevity by demonstrating that CHIP stabilizes the sirtuin family member SirT6, a lysine deacetylase/ADP ribosylase involved in DNA repair, metabolism, and longevity. In CHIP-deficient cells, SirT6 protein half-life is substantially reduced due to increased proteasome-mediated degradation, but CHIP overexpression in these cells increases SirT6 protein expression without affecting SirT6 transcription. CHIP noncanonically ubiquitinates SirT6 at K170, which stabilizes SirT6 and prevents SirT6 canonical ubiquitination by other ubiquitin ligases. In CHIP-depleted cells, SirT6 K170 mutation increases SirT6 half-life and prevents proteasome-mediated degradation. The global decrease in SirT6 expression in the absence of CHIP is associated with decreased SirT6 promoter occupancy, which increases histone acetylation and promotes downstream gene transcription in CHIP-depleted cells. Cells lacking CHIP are hypersensitive to DNA-damaging agents, but DNA repair and cell viability are rescued by enforced expression of SirT6. The discovery of this CHIP-SirT6 interaction represents a novel protein-stabilizing mechanism and defines an intersection between protein quality control and epigenetic regulation to influence pathways that regulate the biology of aging. PMID:24043303

  14. Essentiality of threonylcarbamoyladenosine (t6A), a universal tRNA modification, in bacteria

    PubMed Central

    Thiaville, Patrick C.; Yacoubi, Basma El; Köhrer, Caroline; Thiaville, Jennifer J.; Deutsch, Chris; Iwata-Reuyl, Dirk; Bacusmo, Jo Marie; Armengaud, Jean; Bessho, Yoshitaka; Wetzel, Collin; Cao, Xiaoyu; Limbach, Patrick A.; RajBhandary, Uttam L.; de Crécy-Lagard, Valérie

    2016-01-01

    Threonylcarbamoyladenosine (t6A) is a modified nucleoside universally conserved in tRNAs in all three kingdoms of life. The recently discovered genes for t6A synthesis, including tsaC and tsaD, are essential in model prokaryotes but not essential in yeast. These genes had been identified as antibacterial targets even before their functions were known. However, the molecular basis for this prokaryotic-specific essentiality has remained a mystery. Here, we show that t6A is a strong positive determinant for aminoacylation of tRNA by bacterial-type but not by eukaryotic-type isoleucyl-tRNA synthetases and might also be a determinant for the essential enzyme tRNAIle-lysidine synthetase. We confirm that t6A is essential in Escherichia coli and a survey of genome-wide essentiality studies shows that genes for t6A synthesis are essential in most prokaryotes. This essentiality phenotype is not universal in Bacteria as t6A is dispensable in Deinococcus radiodurans, Thermus thermophilus, Synechocystis PCC6803 and Streptococcus mutans. Proteomic analysis of t6A- D. radiodurans strains revealed an induction of the proteotoxic stress response and identified genes whose translation is most affected by the absence of t6A in tRNAs. Thus, although t6A is universally conserved in tRNAs, its role in translation might vary greatly between organisms. PMID:26337258

  15. The Pseudomonas putida T6SS is a plant warden against phytopathogens.

    PubMed

    Bernal, Patricia; Allsopp, Luke P; Filloux, Alain; Llamas, María A

    2017-04-01

    Bacterial type VI secretion systems (T6SSs) are molecular weapons designed to deliver toxic effectors into prey cells. These nanomachines have an important role in inter-bacterial competition and provide advantages to T6SS active strains in polymicrobial environments. Here we analyze the genome of the biocontrol agent Pseudomonas putida KT2440 and identify three T6SS gene clusters (K1-, K2- and K3-T6SS). Besides, 10 T6SS effector-immunity pairs were found, including putative nucleases and pore-forming colicins. We show that the K1-T6SS is a potent antibacterial device, which secretes a toxic Rhs-type effector Tke2. Remarkably, P. putida eradicates a broad range of bacteria in a K1-T6SS-dependent manner, including resilient phytopathogens, which demonstrates that the T6SS is instrumental to empower P. putida to fight against competitors. Furthermore, we observed a drastically reduced necrosis on the leaves of Nicotiana benthamiana during co-infection with P. putida and Xanthomonas campestris. Such protection is dependent on the activity of the P. putida T6SS. Many routes have been explored to develop biocontrol agents capable of manipulating the microbial composition of the rhizosphere and phyllosphere. Here we unveil a novel mechanism for plant biocontrol, which needs to be considered for the selection of plant wardens whose mission is to prevent phytopathogen infections.

  16. Hydroxyeicosatetraenoic acids released through the cytochrome P-450 pathway regulate 3T6 fibroblast growth.

    PubMed

    Nieves, Diana; Moreno, Juan José

    2006-12-01

    Eicosanoids participate in the regulation of cellular proliferation. Thus, we observed that prostaglandin E(2) interaction with membrane receptors is involved in the control of 3T6 fibroblast growth induced by serum. However, our results suggested that another arachidonic acid pathway might be implicated in these events. Our results show that 3T6 fibroblasts synthesized hydroxyeicosatetraenoic acids (HETEs) such as 12-HETE through the cytochrome P-450 (CYP450) pathway. However, 3T6 fibroblasts did not produce leukotriene B(4) (LTB(4)), and lipoxygenase inhibitors and LT antagonists failed to inhibit 3T6 fibroblast growth induced by FBS. In contrast, we observed that CYP450 inhibitors such as SKF-525A, 17-octadecynoic acid, 1-aminobenzotriazole, and 6-(2-propargyloxyphenyl)hexanoic acid reduced 12(S)-HETE levels, 3T6 fibroblast growth, and DNA synthesis induced by FBS. The impairment of DNA synthesis and 3T6 fibroblast growth induced by SKF-525A were reversed by exogenous addition of HETEs. Moreover, we report that 5-HETE, 12(S)-HETE, and 15(S)-HETE are mitogenic on 3T6 fibroblast in the absence of another growth factor, and this effect was dependent on the activation of the phosphatidylinositol-3-kinase pathway. In conclusion, our results show that HETEs, probably produced by CYP450, are involved in the control of 3T6 fibroblast growth.

  17. The Variability of Fatigue Crack Growth Life of Aluminum Casting Alloy A357-T6

    DTIC Science & Technology

    1986-07-01

    34,FWAL-TR-86-4115 . A THE VARIABILITY OF FATIGUE CRACK GROWTH LIFE OF ALUMINUM CASTING ALLOY A357 -T6 .D. TIRPAK, CAPT, USAF Materials Engineering...Fatigue Crack Growth Life of Aluminum Casting Alloy A357 -T6 17 COSATI CODES 18. SUBJECT 1%iRMS (Continue on reverse if necessary and identify by...fContinue on reverse if necessary and identify by block number) "This investigation considers the variability of fatigue crack growth (FCG) life of A357 -T6

  18. MIX and match: mobile T6SS MIX-effectors enhance bacterial fitness.

    PubMed

    Salomon, Dor

    2016-01-01

    Protein secretion systems that mediate interbacterial competition secret a wide repertoire of antibacterial toxins. A major player in these competitions is the newly discovered bacterial type VI secretion system (T6SS). We recently found that a subset of polymorphic MIX-effectors, which are a widespread class of effectors secreted by T6SSs, are horizontally shared between marine bacteria and are used to diversify their T6SS effector repertoires, thus enhancing their environmental fitness. In this commentary, I expand on the ideas that were introduced in the previous report, and further speculate on the possible mobility of other MIX-effectors. In addition, I discuss the possible role of horizontal gene transfer in the dissemination of MIX-effectors through bacterial genomes, as well as its possible role in diversifying the T6SS effector repertoire.

  19. New backup-bar groove configuration improves heliarc welding of 2014-T6 aluminum

    NASA Technical Reports Server (NTRS)

    Black, F. J.

    1966-01-01

    Backup chill bar with new grooved dimensions improve welding of 2014-T6 aluminum. This groove geometry affords optimum chilling characteristics, reduces shrinkage and the weld bead is narrower and consistently free from impurities or voids.

  20. Formability Evaluation of Aluminum Alloy 6061-T6 Sheet at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Chen, Zhu; Fang, Gang; Zhao, Jia-Qing

    2017-09-01

    The formability of aluminum alloy 6061-T6 sheet was evaluated, and the effects of temperature and strain rate on the formability were analyzed. Uniaxial tension tests and Nakajima tests were conducted at room temperature to obtain the constitutive parameters of AA 6061-T6 and establish the forming limit diagram (FLD), respectively. Moreover, uniaxial tension tests were performed at the temperatures ranging between 180 and 380 °C and the strain rates ranging between 0.0005 and 0.05 s-1, and the constitutive equations of AA 6061-T6 were established. Nakajima tests at temperature 330 °C and two forming speeds (15 and 150 mm/min) were carried out to evaluate the formability of AA6061-T6 at elevated temperatures. In consequence, FLDs under different forming conditions were established and compared. Experimental results showed that the forming limit of AA 6061-T6 increased with the increasing temperature and the decreasing forming speed. The present investigation presented the formability of AA 6061-T6 under different forming conditions, which provided a guidance to design the warm/hot forming of AA 6061 sheet. The FLDs and constitutive equations established through these experiments will be used to predict the forming defects in the forming process design.

  1. A visual assay to monitor T6SS-mediated bacterial competition.

    PubMed

    Hachani, Abderrahman; Lossi, Nadine S; Filloux, Alain

    2013-03-20

    Type VI secretion systems (T6SSs) are molecular nanomachines allowing Gram-negative bacteria to transport and inject proteins into a wide variety of target cells(1,2). The T6SS is composed of 13 core components and displays structural similarities with the tail-tube of bacteriophages(3). The phage uses a tube and a puncturing device to penetrate the cell envelope of target bacteria and inject DNA. It is proposed that the T6SS is an inverted bacteriophage device creating a specific path in the bacterial cell envelope to drive effectors and toxins to the surface. The process could be taken further and the T6SS device could perforate other cells with which the bacterium is in contact, thus injecting the effectors into these targets. The tail tube and puncturing device parts of the T6SS are made with Hcp and VgrG proteins, respectively(4,5). The versatility of the T6SS has been demonstrated through studies using various bacterial pathogens. The Vibrio cholerae T6SS can remodel the cytoskeleton of eukaryotic host cells by injecting an "evolved" VgrG carrying a C-terminal actin cross-linking domain(6,7). Another striking example was recently documented using Pseudomonas aeruginosa which is able to target and kill bacteria in a T6SS-dependent manner, therefore promoting the establishment of bacteria in specific microbial niches and competitive environment(8,9,10). In the latter case, three T6SS-secreted proteins, namely Tse1, Tse2 and Tse3 have been identified as the toxins injected in the target bacteria (Figure 1). The donor cell is protected from the deleterious effect of these effectors via an anti-toxin mechanism, mediated by the Tsi1, Tsi2 and Tsi3 immunity proteins(8,9,10). This antimicrobial activity can be monitored when T6SS-proficient bacteria are co-cultivated on solid surfaces in competition with other bacterial species or with T6SS-inactive bacteria of the same species(8,11,12,13). The data available emphasized a numerical approach to the bacterial

  2. Differential Role of the T6SS in Acinetobacter baumannii Virulence

    PubMed Central

    Foucault-Grunenwald, Marie-Laure; Borges, Vitor; Charpentier, Xavier; Limansky, Adriana S.; Gomes, João Paulo; Viale, Alejandro M.; Salcedo, Suzana P.

    2015-01-01

    Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner. PMID:26401654

  3. Composition, function, and regulation of T6SS in Pseudomonas aeruginosa.

    PubMed

    Chen, Lihua; Zou, Yaru; She, Pengfei; Wu, Yong

    2015-03-01

    Bacterial cells can communicate with their surrounding environment through secretion systems. Type VI secretion system (T6SS) is one of the most recently discovered secretion systems, which is distributed widely in Gram-negative bacteria such as Pseudomonas aeruginosa (P. aeruginosa), an important opportunistic pathogen. This protein secretion system shares similarity with the puncturing device of bacteriophages in structure. P. aeruginosa is an important opportunistic pathogen and distributes widely in diverse environment. T6SS is beneficial to survival advantage of P. aeruginosa by delivering toxins to its neighboring pathogens and translocating protein effectors into the host cells. T6SS is also the virulence factor and takes part in biofilm formation of P. aeruginosa. The functions of T6SS in P. aeruginosa are regulated at transcriptional, posttranscriptional and posttranslational levels by diverse mechanisms. This article reviews the latest progress in the structure, effector proteins, biological function, and regulation mechanisms of P. aeruginosa T6SS. Copyright © 2015 Elsevier GmbH. All rights reserved.

  4. Corrosion behaviors of Al-Si-Cu-based filler metals and 6061-T6 brazements

    NASA Astrophysics Data System (ADS)

    Su, T. L.; Wang, S. S.; Tsao, L. C.; Chang, S. Y.; Chuang, T. H.; Yeh, M. S.

    2002-04-01

    The corrosion behaviors of a series of Al-Si-Cu-based filler metals and the 6061-T6 butt joints brazed with these filler metals are evaluated by polarization tests and immersion tests in a 3.5% NaCl aqueous solution. For comparison, a traditional Al-12Si filler metal is also employed. The results indicate that the Al-Si-Cu-based filler metals before brazing possess much higher corrosion current densities and pitting tendencies than the Al-12Si filler metal. However, brazing of the 6061-T6 alloy with an Al-12Si filler metal produces a wider butt joint, which, in this case, creates a more extensive corrosion region. Severe galvanic corrosion occurs at the 6061-T6 joints when brazed with Al-Si-Cu-based filler metals. However, in the case of the 6061-T6/Al-12Si brazements, selective corrosion of the Al-12Si eutectic phase can be observed. The bonding strengths of the 6061-T6 butt joints brazed with various filler metals are also measured before and after the immersion tests.

  5. High strength and high ductility behavior of 6061-T6 alloy after laser shock processing

    NASA Astrophysics Data System (ADS)

    Gencalp Irizalp, Simge; Saklakoglu, Nursen

    2016-02-01

    The plastic deformation behavior of 6061-T6 alloy which was subjected to severe plastic deformation (SPD) at high strain rates during laser shock processing (LSP) was researched. In LSP-treated materials, the near surface microstructural change was examined by TEM and fracture surfaces after tensile testing were examined by SEM. An increase in strength of metallic materials brings about the decrease in ductility. In this study, the results showed that LSP-treated 6061-T6 alloy exhibited both high strength and high ductility. TEM observation showed that stacking fault (SF) ribbon enlarged, deformation twins formed and twin boundary increased in LSP-treated 6061-T6 alloy. This observation was an indication of stacking fault energy (SFE) decrease. Work hardening capability was recovered after LSP impacts.

  6. Numerical investigation on friction welding of alumina / AA 6063 T6 joints

    NASA Astrophysics Data System (ADS)

    Hynes, N. Rajesh Jesudoss; Velu, P. Shenbaga; Tharmaraj, R.; Kumar, R.

    2016-05-01

    Friction welding is the most suitable candidate for joining the dissimilar materials such as AA 6063 T6 alloy/Alumina for critical situations in high temperature and high corrosion resistance applications. In the present work, the numerical simulation was carried out to understand the mechanism of joining of AA 6063 T6 alloy/ Alumina rod by friction welding process. The developed thermo mechanical model is a highly nonlinear due to the interaction between the temperature fields and time dependent of the material properties. The developed numerical tool could be used to predict the temperature distribution, stress, strain and deformation of the dissimilar joints.

  7. Multi-Objective Optimization of Friction Stir Welding Process Parameters of AA6061-T6 and AA7075-T6 Using a Biogeography Based Optimization Algorithm

    PubMed Central

    Tamjidy, Mehran; Baharudin, B. T. Hang Tuah; Paslar, Shahla; Matori, Khamirul Amin; Sulaiman, Shamsuddin; Fadaeifard, Firouz

    2017-01-01

    The development of Friction Stir Welding (FSW) has provided an alternative approach for producing high-quality welds, in a fast and reliable manner. This study focuses on the mechanical properties of the dissimilar friction stir welding of AA6061-T6 and AA7075-T6 aluminum alloys. The FSW process parameters such as tool rotational speed, tool traverse speed, tilt angle, and tool offset influence the mechanical properties of the friction stir welded joints significantly. A mathematical regression model is developed to determine the empirical relationship between the FSW process parameters and mechanical properties, and the results are validated. In order to obtain the optimal values of process parameters that simultaneously optimize the ultimate tensile strength, elongation, and minimum hardness in the heat affected zone (HAZ), a metaheuristic, multi objective algorithm based on biogeography based optimization is proposed. The Pareto optimal frontiers for triple and dual objective functions are obtained and the best optimal solution is selected through using two different decision making techniques, technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon’s entropy. PMID:28772893

  8. Parametric studies on tensile strength in joining AA6061- T6 and AA7075-T6 by gas metal arc welding process

    NASA Astrophysics Data System (ADS)

    Ishak, M.; Noordin, N. F. M.; Shah, L. H.

    2015-12-01

    Proper selection of the welding parameters can result in better joining. In this study, the effects of various welding parameters on tensile strength in joining dissimilar aluminum alloys AA6061-T6 and AA7075-T6 were investigated. 2 mm thick samples of both base metals were welded by semi-automatic gas metal arc welding (GMAW) using filler wire ER5356. The welding current, arc voltage and welding speed were chosen as variables parameters. The strength of each specimen after the welding operations were tested and the effects of these parameters on tensile strength were identified by using Taguchi method. The range of parameter for welding current were chosen from 100 to 115 A, arc voltage from 17 to 20 V and welding speed from 2 to 5 mm/s. L16 orthogonal array was used to obtained 16 runs of experiments. It was found that the highest tensile strength (194.34 MPa) was obtained with the combination of a welding current of 115 A, welding voltage of 18 V and welding speed of 4 mm/s. Through analysis of variance (ANOVA), the welding voltage was the most effected parameter on tensile strength with percentage of contribution at 41.30%.

  9. Multi-Objective Optimization of Friction Stir Welding Process Parameters of AA6061-T6 and AA7075-T6 Using a Biogeography Based Optimization Algorithm.

    PubMed

    Tamjidy, Mehran; Baharudin, B T Hang Tuah; Paslar, Shahla; Matori, Khamirul Amin; Sulaiman, Shamsuddin; Fadaeifard, Firouz

    2017-05-15

    The development of Friction Stir Welding (FSW) has provided an alternative approach for producing high-quality welds, in a fast and reliable manner. This study focuses on the mechanical properties of the dissimilar friction stir welding of AA6061-T6 and AA7075-T6 aluminum alloys. The FSW process parameters such as tool rotational speed, tool traverse speed, tilt angle, and tool offset influence the mechanical properties of the friction stir welded joints significantly. A mathematical regression model is developed to determine the empirical relationship between the FSW process parameters and mechanical properties, and the results are validated. In order to obtain the optimal values of process parameters that simultaneously optimize the ultimate tensile strength, elongation, and minimum hardness in the heat affected zone (HAZ), a metaheuristic, multi objective algorithm based on biogeography based optimization is proposed. The Pareto optimal frontiers for triple and dual objective functions are obtained and the best optimal solution is selected through using two different decision making techniques, technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon's entropy.

  10. Corrosion Fatigue Crack Growth Behavior at Notched Hole in 7075-T6 Under Biaxial and Uniaxial Fatigue with Different Phases

    DTIC Science & Technology

    2015-09-17

    Assigning the Material Type which is Aluminum Alloy 7075-T6 to the Specimen...T6 alloy [3]. ......................................... 32 Table 3.2: Mechanical properties of AA 7075-T6 [3...The proper understanding of the type of corrosion is the key to choose which method is appropriate to control it [31, 35]. Aluminum alloy is the

  11. Initial, Cockpit Anthropometric Assessment of U.S. Navy T-6 Life Support Equipment

    DTIC Science & Technology

    2007-11-05

    dimension interaction for normal and emergency functionality and immediate ejection safety , the T-6A didn’t fully (safely) accommodate the full...anthropometric accommodation and straight forward cockpit functionality. But, the following anthropometrical dimension interactions present safety ...restrictions, limitations, interference of cockpit functions for safety of flight for the specified anthropometric range of operators. The

  12. Strength of the aluminium alloy 6082-T6 under high strain-rate conditions

    SciTech Connect

    Harrigan, J. J.; Millett, J. C. F.; Bourne, N. K.

    2007-12-12

    The measurement of shear strength via the use of lateral stress gauges has been shown to be a viable technique in a number of materials. An experimental investigation on the intermediate-rate behaviour and shock response of the aluminium alloy, 6082-T6, is reported here. Results obtained using the lateral stress gauge technique show that the shear strength increases with impact stress. The lateral stress behind the shock front is seen to be relatively flat, unlike many other face-centred cubic metals and alloys, where a decrease in lateral stress indicates an increase in shear strength. This unusal response may be a reflection of the high stacking fault energy of aluminium and its alloys resulting in a reduction of the work hardening (i.e. increases in dislocation and/or twin density). Further plate impact results show that the Hugoniot of 6082-T6 is in effect identical to that of the more widely known 6061-T6. Split Hopkinson pressure bar results are used to provide a fuller picture of the rate-dependant behaviour of 6082-T6 over a range of loading rates and conditions.

  13. Precipitate evolution in friction stir welding of 2219-T6 aluminum alloys

    SciTech Connect

    Chen, Y.C.; Feng, J.C.; Liu, H.J.

    2009-06-15

    Precipitate evolution in friction stir welding of 2219-T6 aluminum alloys was characterized by transmission electron microscopy. In the weld nugget zone and the thermo-mechanically affected zone some metastable precipitates overaged to equilibrium phase while others solutionized into the aluminum solid solution. In the heat-affected zone the precipitates coarsened.

  14. Involvement of Trichoderma asperellum strain T6 in regulating iron acquisition in plants.

    PubMed

    Zhao, Lei; Wang, Fei; Zhang, Yaqing; Zhang, Jiaojiao

    2014-07-01

    Iron (Fe) deficiency is a major plant nutritional disorder in many parts of the world, particularly in areas with saline soils. Among the numerous root-associated microbes that are beneficial for plant nutrient uptake, Trichoderma spp. are the most effective rhizosphere fungi for enhancing plant growth and plant resistance to biotic and abiotic stresses. To investigate the potential mechanisms of action of Trichoderma on insoluble Fe in the soil, which is difficult for plants to absorb and utilize, a high siderophore-producing strain of Trichoderma T6, was isolated from the rhizosphere of cucumber plants. The strain was identified as T. asperellum based on the morphological features and molecular phylogenetic analyses. Applying strain T6 to sterile soil could increase soil levels of Fe(2+) and siderophores, as well as increase Fe(2+) and Fe(3+)-chelate reductase (FCR) activity in cucumber tissues. Purified siderophore eluent (PSE) increased plant growth, thus confirming its role in plant growth promotion. Moreover, extracellular Fe(3+) reducing activity and three kinds of organic acids were detected in the culture filtrate of strain T6. These results indicate that strain T6 influences plant Fe absorption in several ways. Siderophore-based Fe chelation is effective in providing Fe to plants, organic acids, and Fe(3+) reducing enzymes may participate in the solubilization and reduction of insoluble Fe(3+) to Fe(2+).

  15. Cavitation pitting and erosion of Al 6061-T6 in mineral oil and water

    NASA Technical Reports Server (NTRS)

    Rao, B. C. S.; Buckley, D. H.

    1983-01-01

    The authors are currently carrying out a study of the cavitation erosion of different bearing metals and alloys in mineral oils were studied. The variations of weight loss, the pit diameter and depth due to cavitation erosion on Al 6061-T6 in mineral oil and water are presented.

  16. Severe oligospermia associated with a unique balanced reciprocal translocation t(6;12)(q23;q24.3): male infertility related to t(6;12).

    PubMed

    Bianco, B; Christofolini, D; Gava, M; Mafra, F; Moraes, E; Barbosa, C

    2011-04-01

    The prevalence of chromosome abnormalities is increased in infertile men, the incidence of a chromosomal factor being estimated to be about 8%. We report two brothers, a 38-year-old man with 10 years' primary infertility and severe oligospermia, but otherwise healthy, and a 35-year-old man with primary infertility and a history of mumps during puberty. Semen and karyotype analysis, and investigation of Y-chromosome microdeletions were performed. An apparently unique reciprocal translocation t(6;12)(q23;q24.3) was found in both infertile brothers. Semen analyses showed severe oligospermia. No Y-chromosome microdeletions were found. These two cases support the relationship between both environmental and chromosomal abnormalities, combined or separated, with male infertility. Investigation of genetic alterations in infertile males has to be performed prior to performing any assisted reproduction technique. © 2010 Blackwell Verlag GmbH.

  17. The T6SSs of Pseudomonas aeruginosa Strain PAO1 and Their Effectors: Beyond Bacterial-Cell Targeting.

    PubMed

    Sana, Thibault G; Berni, Benjamin; Bleves, Sophie

    2016-01-01

    Pseudomonas aeruginosa is an opportunistic pathogen responsible for many diseases such as chronic lung colonization in cystic fibrosis patients and acute infections in hospitals. The capacity of P. aeruginosa to be pathogenic toward several hosts is notably due to different secretion systems. Amongst them, P. aeruginosa encodes three Type Six Secretion Systems (T6SS), named H1- to H3-T6SS, that act against either prokaryotes and/or eukaryotic cells. They are independent from each other and inject diverse toxins that interact with different components in the host cell. Here we summarize the roles of these T6SSs in the PAO1 strain, as well as the toxins injected and their targets. While H1-T6SS is only involved in antiprokaryotic activity through at least seven different toxins, H2-T6SS and H3-T6SS are also able to target prokaryotic as well as eukaryotic cells. Moreover, recent studies proposed that H2- and H3-T6SS have a role in epithelial cells invasion by injecting at least three different toxins. The diversity of T6SS effectors is astounding and other effectors still remain to be discovered. In this review, we present a table with other putative P. aeruginosa strain PAO1 T6SS-dependent effectors. Altogether, the T6SSs of P. aeruginosa are important systems that help fight other bacteria for their ecological niche, and are important in the pathogenicity process.

  18. Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 High Strength Aluminum Alloy

    DTIC Science & Technology

    2013-06-01

    Date Date AFIT-ENY-13-J-01 Abstract Research on fatigue crack formation from two types corrosion pits tangent to a circular hole in a 7075-T6 aluminum...37 3.9 The original corner crack model created using Solidworks . This model was too complex for Abaqus to...conducted with regard to corrosion and pitting. The formation of pitting due to corrosion may seem more like an art than a science at times because of

  19. Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction

    SciTech Connect

    Zhang, Yuan; Babu, Suresh; Zhang, P; Kenik, Edward A; Daehn, Glenn

    2008-01-01

    The grain boundary crystallographic misorientations of magnetic-pulse-welded (MPW) aluminum alloy (AA) 6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique. A refined structure of heavily deformed grains with higher grain boundary angles was observed in linear welds. Significant spalling was observed away from the joints, in the interior of tubular welds. The results show the complex interaction of shock waves with the materials during this impact welding process.

  20. Excess APP O-glycosylation by GalNAc-T6 decreases Aβ production.

    PubMed

    Akasaka-Manya, Keiko; Kawamura, Masaki; Tsumoto, Hiroki; Saito, Yuko; Tachida, Yuriko; Kitazume, Shinobu; Hatsuta, Hiroyuki; Miura, Yuri; Hisanaga, Shin-Ichi; Murayama, Shigeo; Hashimoto, Yasuhiro; Manya, Hiroshi; Endo, Tamao

    2017-01-01

    Alterations of the structure and/or amount of glycans present on proteins are associated with many diseases. We previously demonstrated that changes in N-glycans alter Aβ production. In the present study, we focused on the relationship between Alzheimer's disease (AD) and O-glycan, another type of glycan. The UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-T) family functions in the first step of mucin-type O-glycan synthesis. Analysis of the expression of GalNAc-Ts in the human brain using real-time PCR revealed that the expression of several GalNAc-Ts was altered with sporadic AD progression. Three of these GalNAc-Ts (GalNAc-T1, GalNAc-T4 and GalNAc-T6) were transfected into HEK293T cells to examine their impact on Aβ production. Transfection of GalNAc-T6 significantly reduced both Aβ1-40 and Aβ1-42 generation, but GalNAc-T1 and GalNAc-T4 only reduced Aβ1-40 generation. Although these three GalNAc-Ts exhibited enzymatic activities on soluble amyloid precursor protein (APP), the GalNAc transferase activity of GalNAc-T6 to APP was most prominent. The expression of α-secretase and β-secretase was slightly altered in the transfected cells, but the activities of α-secretase and β-secretase were not significantly altered. These data suggest that excess O-glycosylation on APP by GalNAc-T6 inhibits Aβ production. © The Authors 2016. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

  1. Cleidocranial dysplasia associated with a t(6;18)(p12;q24) translocation

    SciTech Connect

    Narahara, Kouji; Tsuji, Kazushiro; Yokoyama, Yuji

    1995-03-13

    Cleidocranial displasia (CCD) is an autosomal-dominant, generalized skeletal disorder. The gene locus for this syndrome has not yet been mapped. The presence of rare chromosome rearrangements in Mendelian disorders has facilitated the localization or positional cloning of these disease genes. We report on another patient with autosomal-dominant CCD who had a balanced t(6;8) translocation. 3 refs., 2 figs.

  2. Deformation behavior and microstructural evolution of 7075-T6 aluminum alloy at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Lee, Woei-Shyan; Lin, Ching-Rong

    2016-10-01

    The impact deformation behavior and associated microstructural evolution of 7075-T6 aluminum alloy at cryogenic temperatures are investigated using a compressive split-Hopkinson pressure bar (SHPB) system. Cylindrical specimens are deformed at strain rates of 1 × 103 s-1, 2 × 103 s-1, 3 × 103 s-1 and 5 × 103 s-1 and temperatures of 0 °C, -100 °C and -196 °C. It is shown that the flow stress is strongly dependent on the strain rate and temperature. For a given temperature, the flow stress varies with the strain rate in accordance with a power law relation with an average exponent of 0.157 and an activation energy of 0.7 kJ/mol. Moreover, the coupled effects of the strain rate and temperature on the flow stress are adequately described by the Zener-Hollomon parameter (Z). For all test temperatures, catastrophic failure occurs only under the highest strain rate of 5 × 103 s-1, and is the result of adiabatic shear. An increasing strain rate or reducing temperature leads to a greater dislocation density and a smaller grain size. Finally, the dependence of the flow stress on the microstructural properties of the impacted 7075-T6 specimens is well described by a specific Hall-Petch constitutive model with constants of K = 108.3 MPa μm1/2 and K‧ = 16.1 MPa μm, respectively. Overall, the results presented in this study provide a useful insight into the combined effects of strain rate and temperature on the flow resistance and deformability of 7075-T6 alloy and confirm that 7075-T6 is well suited to the fabrication of fuel tanks and related structural components in the aerospace field.

  3. Constitutive Model Constants for Al7075-T651 and Al7075-T6

    NASA Astrophysics Data System (ADS)

    Brar, Nachhatter; Joshi, Vasant; Harris, Bryan

    2009-06-01

    Aluminum 7075-T651 and 7075-T6 are characterized at quasi-static and high strain rates to determine Johnson-Cook (J-C) strength and fracture model constants. Constitutive model constants are required as input to computer codes to simulate projectile (fragment) impact or similar impact events on structural components made of these material. J-C strength model constants (A, B, n, C, and m) for the two alloys are determined from tension stress-strain data at room and high temperature to 250^oC. J-C strength model constants for Al7075-T651 are: A=527 MPa, B=676 MPa, n=0.71, C=0.017, and m=1.61 and for Al7075-T6: A = 546 MPa, B = 674 MPa, n = 0.72, C = 0.059, and m =1.56. J-C fracture model constants are determined form quasi-static and high strain rate/high temperature tests on notched and smooth tension specimens. J-C fracture model constants for the two alloys are: Al7075-T651; D1 = 0.110, D2 = 0.573, D3= -3.4446, D4 = 0.016, and D 5= 1.099 and Al7075-T6; D1= 0.451 D2= -0.952 D3= -.068, D4 =0.036, and D5 = 0.697.

  4. Effect of the layer of anodized 7075-T6 aluminium corrosion properties

    NASA Astrophysics Data System (ADS)

    Montoya Z, R. D.; L, E. Vera; Pineda T, Y.; Cedeño, M. L.

    2017-01-01

    Aluminium alloys are widely used in various sectors of industry. The 7075-T6 alloy corresponding to an Al-Zn T6, is mostly used as structural component in the aviation industry, due to the good relationship between weight and mechanical properties. However, the negative point of this alloys is the resistance to corrosion, which is why they need to be coated with an anodic film. Different surface treatments, such as anodizing, are used to improve corrosion resistance. Anodizing is an electrolytic process by which a protective layer on aluminium known as “alumina” is formed, this is formed by the passage of an electric current in an acidic electrolyte. This investigation presents a study of the effect of the thickness of layers of alumina deposited by anodized method, in the corrosion resistance of 7075-T6 aluminium. This study was performed by using in a solution of tartaric acid - sulfuric acid and an inorganic salt. To evaluate the influence alumina layer thickness on the corrosion properties some tests were carried out by using the electrochemical spectroscopy impedances (EIS) technique and Tafel polarization curves. It was found that the grown of the thickness of film favourably influences in the corrosion resistance.

  5. Functional performance of the T-6A Texan (JPATS) CFIS laser detonator

    NASA Astrophysics Data System (ADS)

    Blachowski, Thomas J.; Thom, Travis

    2010-08-01

    The Indian Head Division, Naval Surface Warfare Center (IHD NSWC) CAD Engineering Division is conducting a program to evaluate the laser and energetic components which comprise the Canopy Fracturing Initiation System (CFIS). This system is currently installed on the T-6A Texan II or JPATS (Joint Primary Aircraft Training System) aircraft. The T-6A Texan II is the first aircraft used by the military to train future pilots. The CFIS is an element of the pilot emergency escape system which weakens the canopy in the path of the ejection seat. The CFIS is comprised of three differing laser configurations (Internal, External, and Seat Motion) which generate a pulse that is distributed through a fiber optic energy transmission system. This pulse, in turn, initiates one of the system's explosive components, a detonator (specifically, the CCU-158/A Laser Initiated Detonator). This detonator transfers the signal to the remaining energetic components that, in turn, function to weaken their respective canopies. All of the CFIS laser types are flashlamp-pumped, neodymium glass lasers which are located at various positions in the aircraft cockpit area. This paper builds on the previous SPIE papers (2008 - Conference 7070 and 2009 - Conference 7434, respectively) and presents the initial functional test results for the CFIS Laser Detonator. These functional test results provide the technical support to justify the useful lifetime of this energetic component while being installed in the T-6A Texan II aircraft under operational conditions.

  6. Corrosion of type 6061-T6 aluminum in mercury and mercury vapor

    NASA Astrophysics Data System (ADS)

    Pawel, S. J.; Manneschmidt, E. T.

    2003-05-01

    To examine potential corrosion of aluminum maintenance equipment in environments periodically containing mercury vapor and droplets of liquid mercury, c-rings of 6061-T6 aluminum have been exposed to a series of screening tests. The tests included vapor phase exposures as well as immersion of stressed and unstressed c-rings in the as-received condition and with chemical treatments to modify the passive film. Test conditions included the temperature range 0-160 °C, times of 3-30 days and, in addition to liquid Hg, various Hg vapor environments including residual air, residual helium and condensing conditions. The results indicate 6061-T6 is quite susceptible to pitting and cracking when immersed in Hg for even a brief time, but at least one chemical treatment was shown to improve corrosion resistance under immersion conditions. Type 6061-T6 was found to be essentially immune to vapor phase corrosion for the conditions examined, with only very minor development of pits or pit precursors.

  7. Spectrum Fatigue Crack Growth Rate Characteristics of Cast Aluminum Alloys A201-T7 and A357-T6.

    DTIC Science & Technology

    The spectrum fatigue crack growth characteristics of cast aluminum alloys A201-T7 and A357 -T6 were evaluated and compared with wrought aluminum 7050...T76 data. For specimens tested at three different spectrum stress levels, A357 -T6 consistently possessed the longest fatigue life, nearly double that...Further analysis of the a vs. N record of each sample to obtain the crack growth rate (FCGR) vs. the corresponding stress intensity indicated that A357 -T6

  8. Shock-loading response of 6061-T6 aluminum metal-matrix composites

    SciTech Connect

    Vecchio, K.S.; Gray, G.T. III

    1995-10-01

    The purpose of this research was to systematically study the influence of peak-shock pressure and second-phase reinforcement on the structure/property response of shock-loaded 6061-T6 Al, used as a baseline for comparison, showed no increased shock hardening compared to the unshocked material deformed to an equivalent strain. The reload stress-strain response of the shock-loaded 6061-T6 Al-alumina composites exhibit a lower reload yield strength than the flow stress of the starting composites. The degrees of strength loss was found to increase with increasing shock pressure. Wavespeed measurements of shock-prestrained specimens showed no degradation compared to unshocked specimens, indicating that particle cracking had not occurred under shock. This result was supported by optical metallography, which did not reveal cracked particles or particle decohesion in the shock-prestrained samples. The reload stress-strain response of the shock-prestrained composites, after resolutionizing and T6 reaging, showed that the composites recovered their full as-received preshock stress-strain responses. This result supports the finding that degradation in reload strength was attributable to matrix microstructural changes resulting from the shock. Transmission electron microscopy (TEM) examination of the shock-loaded microstructures revealed that the matrix regions adjacent to the particle/matrix interface had undergone significant recovery and partial recrystallization resulting from the shock. This type of near-interface substructure is in stark contrast to the heavily dislocated near-interface dislocation substructure of the as-received composites. The loss of dislocation density (i.e., strain hardening) in the near-interface matrix region, resulting from the shock, highlights the importance of the thermally introduced dislocation substructure changes in establishing the strength of metal-matrix composites (MMCs).

  9. Modeling of microstructure evolution, residual stresses and distortions in 6082-T6 aluminum weldments

    SciTech Connect

    Myhr, O.R.; Kluken, A.O.; Klokkehaug, S.; Fjaer, H.G.; Grong, O.

    1998-07-01

    This article illustrates the applications of process modeling for prediction of microstructure evolution, residual stresses and distortions in welding of hollow AA6082-T6 extrusions. The model consists of three components, i.e., a numerical heat flow model, a microstructure model and a mechanical model that are sequentially coupled. It is shown that the model adequately predicts the temperature and local strength distribution. The calculated distortions were found to depend strongly on the welding sequence. Moreover, the local softening of the heat-affected zone was shown to have a significant effect on the simulated residual stress distribution.

  10. The thrust generated by a T6 ion engine hollow cathode

    NASA Astrophysics Data System (ADS)

    Gessini, Paolo; Coletti, Michele; Gabriel, Stephen B.

    2014-09-01

    The thrust produced by a T6 ion engine main discharge hollow cathode was characterized using different propellants with a target-based measurement system, for discharge current values of 5-25 A and a wide range of mass flow rates. The calculated values of specific impulse are far in excess of those that could be attributed to the heating of a gas to thermal equilibrium with the walls, as in a resistojet. This would suggest an operation mechanism more similar to that of an arcjet. The main scaling parameter for the specific impulse appears to be the discharge power per unit mass flow rate (specific power).

  11. An infinite square lattice of super-supertetrahedral T(6)-like tin oxyselenide clusters.

    PubMed

    Lin, Qipu; Bu, Xianhui; Feng, Pingyun

    2014-04-21

    A new super-supertetrahedral cluster, resembling a coreless supertetrahedral T6 cluster, was made as a tin oxyselenide by integrating hard and soft Lewis bases (O(2-) and Se(2-)) into the tetravalent system. Its hierarchical architecture, built from supertetrahedral T3-[Sn10O4Se20] and Sn2Se6 clusters, represents a new level of complexity in the cluster-based construction. Compared to pure tin selenides, the new tin oxyselenide material in this work shows much enhanced stability and size-dependent band energy level.

  12. Supernova Simulations from the T-6 Group at Los Alamos National Laboratory (LANL)

    DOE Data Explorer

    Woosley, Stanford

    LANL's primary effort to numerically model supernova explosions is based in the Theoretical Astrophysics Group (T-6). Both thermonuclear supernovae and core- collapse supernovae are studied, with special emphasis placed on multi-dimensional simulations. Both types of supernova require a wide range of input physics, which is provided by research efforts throughout the lab. In particular this research benefits from other LANL efforts studying massive star evolution, equations of state and aspects of neutrino physics. [From http://laastro.lanl.gov/science/computation.html

  13. Global translational impacts of the loss of the tRNA modification t(6)A in yeast.

    PubMed

    Thiaville, Patrick C; Legendre, Rachel; Rojas-Benítez, Diego; Baudin-Baillieu, Agnès; Hatin, Isabelle; Chalancon, Guilhem; Glavic, Alvaro; Namy, Olivier; de Crécy-Lagard, Valérie

    2016-01-01

    The universal tRNA modification t(6)A is found at position 37 of nearly all tRNAs decoding ANN codons. The absence of t(6)A37 leads to severe growth defects in baker's yeast, phenotypes similar to those caused by defects in mcm(5)s(2)U34 synthesis. Mutants in mcm(5)s(2)U34 can be suppressed by overexpression of tRNA(Lys)UUU, but we show t(6)A phenotypes could not be suppressed by expressing any individual ANN decoding tRNA, and t(6)A and mcm(5)s(2)U are not determinants for each other's formation. Our results suggest that t(6)A deficiency, like mcm(5)s(2)U deficiency, leads to protein folding defects, and show that the absence of t(6)A led to stress sensitivities (heat, ethanol, salt) and sensitivity to TOR pathway inhibitors. Additionally, L-homoserine suppressed the slow growth phenotype seen in t(6)A-deficient strains, and proteins aggregates and Advanced Glycation End-products (AGEs) were increased in the mutants. The global consequences on translation caused by t(6)A absence were examined by ribosome profiling. Interestingly, the absence of t(6)A did not lead to global translation defects, but did increase translation initiation at upstream non-AUG codons and increased frame-shifting in specific genes. Analysis of codon occupancy rates suggests that one of the major roles of t(6)A is to homogenize the process of elongation by slowing the elongation rate at codons decoded by high abundance tRNAs and I34:C3 pairs while increasing the elongation rate of rare tRNAs and G34:U3 pairs. This work reveals that the consequences of t(6)A absence are complex and multilayered and has set the stage to elucidate the molecular basis of the observed phenotypes.

  14. The tensile strength of 339 aluminum reinforced with Kaowool fibers: A comparison of T5 and T6 heat treatments

    SciTech Connect

    Baxter, W.J.; Sachdev, A.K.

    1999-07-01

    This study compares the effects of T5 and T6 heat treatment on the tensile strengths of both KAOWOOL fiber reinforced and unreinforced 339 aluminum. The 339 Al-T6 is stronger than 339 AL-T5 (as expected), but for a KAOWOOL/339 Al composite, the T5 condition is substantially stronger than the T6. The controlling parameter is the strength of the aluminum dendrites, which in turn is proportional to the concentration of magnesium retained in the dendrites. In the T5 condition, more than half of the magnesium is in the form of large intermetallics in both the unreinforced alloy and the KAOWOOL/339 Al composite. During a T6 heat treatment, magnesium in the intermetallics is redissolved. In the unreinforced T6 alloy, this additional magnesium is retained in and strengthens the dendrites. But in the T6 composite, the magnesium segregates extensively to the KAOWOOL/aluminum interfaces depleting and softening the dendrites. This factor along is sufficient to account for the low strength of the T6 composites. The tensile strengths of both the T5 and T6 composites correspond to the calculated values for a perfectly bonded system.

  15. Investigations on the long-term stability of 6013-T6 sheet

    SciTech Connect

    Braun, Reinhold . E-mail: reinhold.braun@dlr.de

    2006-03-15

    Sheet material of the Al-Mg-Si-Cu alloy 6013-T6 was additionally aged at 191 deg. C for up to 100 h and thermally exposed at temperatures ranging from 85 to 150 deg. C for time periods up to 3000 h. Microstructure, tensile properties and corrosion behaviour were investigated in the different heat treatment conditions using differential scanning calorimetry and transmission electron microscopy as well as performing tensile tests and various corrosion tests. Hardening precipitates present in the peak-aged microstructure were the metastable {beta}'' and Q' phases. Alloy 6013-T6 exhibited sensitivity to pitting and intergranular corrosion when immersed in chloride solutions, but was immune to intergranular stress corrosion cracking. Increasing aging at 191 deg. C resulted in progress in the precipitation sequence and coarsening of the precipitates. However, the degradation of tensile properties due to overaging was slight, and no change in corrosion behaviour was observed. Prolonged thermal exposure at temperatures between 85 and 120 deg. C did not cause significant alterations in microstructure, tensile properties, and corrosion performance of peak-aged 6013 sheet, indicating thermal stability of this alloy when used in fuselage applications.

  16. Stress-strain response of a cast 319-T6 aluminum under thermomechanical loading

    SciTech Connect

    Sehitoglu, H.; Qing, X.; Smith, T.; Maier, H.J.; Allison, J.A.

    2000-01-01

    The stress-strain behavior of cast 319-T6 aluminum-copper alloys with three different secondary dendrite arm spacings (SDASs) was studied at high temperatures and under thermomechanical deformation, exposing marked cyclic softening. A two state-variable unified inelastic constitutive model proposed earlier was modified to describe the stress-strain responses of these alloys by considering the variation of hardening and recovery functions of back-stress and drag stress. The SDAS was incorporated in the model as a length-scale parameter, and the materials constants were determined systematically from experiments on a cast 319-T6 aluminum with small and large SDASs. The capabilities of the constitutive model were checked by the comparisons of simulations to experiments in the small-strain regime (< 0.005). The results show that the model provides successful simulations for material response after thermal exposure at high temperature and cyclic transient stress-strain behavior. The causes of mechanical behaviors at the macro scale are discussed based on microstructural changes during thermal exposure.

  17. Purification and characterization of a thermostable xylanase from Bacillus stearothermophilus T-6.

    PubMed

    Khasin, A; Alchanati, I; Shoham, Y

    1993-06-01

    Bacillus stearothermophilus T-6 produces an extracellular xylanase that was shown to optimally bleach pulp at pH 9 and 65 degrees C. The enzyme was purified and concentrated in a single adsorption step onto a cation exchanger and is made of a single polypeptide with an apparent M(r) of 43,000 (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Xylanase T-6 is an endoxylanase that completely degrades xylan to xylose and xylobiose. The pIs of the purified protein were 9 and 7 under native and denaturing conditions, respectively. The optimum activity was at pH 6.5; however, 60% of the activity was still retained at pH 10. At 65 degrees C and pH 7, the enzyme was stable for more than 10 h; at 65 degrees C and pH 9, the half-life of the enzyme was approximately 6 h. Kinetic experiments at 55 degrees C gave Vmax and Km values of 288 U/mg and 1.63 mg/ml, respectively. The enzyme had no apparent requirement for cofactors, and its activity was strongly inhibited by Zn2+, Cd2+, and Hg2+. Xylan completely protected the protein from inactivation by N-bromosuccinimide. The N-terminal sequence of the first 45 amino acids of the enzyme showed high homology with the N-terminal region of xylanase A from the alkalophilic Bacillus sp. strain C-125.

  18. A Pseudomonas T6SS effector recruits PQS-containing outer membrane vesicles for iron acquisition

    PubMed Central

    Lin, Jinshui; Zhang, Weipeng; Cheng, Juanli; Yang, Xu; Zhu, Kaixiang; Wang, Yao; Wei, Gehong; Qian, Pei-Yuan; Luo, Zhao-Qing; Shen, Xihui

    2017-01-01

    Iron sequestration by host proteins contributes to the defence against bacterial pathogens, which need iron for their metabolism and virulence. A Pseudomonas aeruginosa mutant lacking all three known iron acquisition systems retains the ability to grow in media containing iron chelators, suggesting the presence of additional pathways involved in iron uptake. Here we screen P. aeruginosa mutants defective in growth in iron-depleted media and find that gene PA2374, proximal to the type VI secretion system H3 (H3-T6SS), functions synergistically with known iron acquisition systems. PA2374 (which we have renamed TseF) appears to be secreted by H3-T6SS and is incorporated into outer membrane vesicles (OMVs) by directly interacting with the iron-binding Pseudomonas quinolone signal (PQS), a cell–cell signalling compound. TseF facilitates the delivery of OMV-associated iron to bacterial cells by engaging the Fe(III)-pyochelin receptor FptA and the porin OprF. Our results reveal links between type VI secretion, cell–cell signalling and classic siderophore receptors for iron acquisition in P. aeruginosa. PMID:28348410

  19. Differentiation of A31T6 proadipocytes to adipocytes: A flow cytometric analysis

    SciTech Connect

    Smyth, M.J.; Wharton, W. )

    1992-03-01

    A flow cytometric assay has been developed which provides precise, quantitative information on the accumulation of cytoplasmic triglycerides in individual A31T6 proadipocytes as they differentiate into adipocytes. The opportunity to measure multiple optical parameter on a cell-by-cell basis has enabled us to monitor phenotypic aspects of differentiation with a greater level of sensitivity than was previously possible. Using the fluorescent hydrophobic probe, Nile red, they have found that as a cell proceeds along the differentiation pathway, the gold fluorescence signal from the cell increases, reflecting the accumulation of cytoplasmic lipid droplets. They have determined (1) the presence of an undifferentiated population of cells whose existence is not detected by conventional phase microscopy, (2) that insulin is no required to drive differentiation in this system, (3) that exposure to a combination of insulin and dexamethasone results in a lower accumulation of lipid in a cell than does exposure to either agent alone, and (4) that A31T6 cells show the same response to differentiation-promoting agents whether applied at the time of plating or at confluence.

  20. Constitutive Model Constants for Al7075-T651 and Al7075-T6

    NASA Astrophysics Data System (ADS)

    Brar, N. S.; Joshi, V. S.; Harris, B. W.

    2009-12-01

    Aluminum 7075-T651 and 7075-T6 are characterized at quasi-static and high strain rates to determine Johnson-Cook (J-C) strength and fracture model constants. Constitutive model constants are required as input to computer codes to simulate projectile (fragment) impact or similar impact events on structural components made of these materials. Although the two tempers show similar elongation at breakage, the ultimate tensile strength of T651 temper is generally lower than the T6 temper. Johnson-Cook strength model constants (A, B, n, C, and m) for the two alloys are determined from high strain rate tension stress-strain data at room and high temperature to 250°C. The Johnson-Cook fracture model constants are determined from quasi-static and medium strain rate as well as high temperature tests on notched and smooth tension specimens. Although the J-C strength model constants are similar, the fracture model constants show wide variations. Details of the experimental method used and the results for the two alloys are presented.

  1. An evaluation of the T-6A Texan (JPATS) functional performance of the CFIS laser assemblies

    NASA Astrophysics Data System (ADS)

    Blachowski, Thomas J.; Eccard, George

    2008-08-01

    The Indian Head Division, Naval Surface Warfare Center (IHDIV, NSWC) CAD Engineering Division is conducting a program to evaluate the laser components which comprise the Canopy Fracturing Initiation System (CFIS) currently installed on the T-6A Texan or JPATS (Joint Primary Aircraft Training System) aircraft. The T-6A Texan is the first aircraft used by the military to train future pilots. The CFIS is an element of the pilot emergency escape system which weakens the canopy in the path of the ejection seat. The CFIS is comprised of three differing configurations (Internal, External, and Seat Motion) which generate a laser pulse that is distributed through a fiber optic energy transmission system. This pulse, in turn, initiates explosive components which weaken the respective canopies. All of the CFIS laser types are flashlamp-pumped, neodymium glass lasers which are located at various positions in the aircraft cockpit area. This paper presents the CAD Engineering Division effort to evaluate the functional performance of the three CCFIS laser signal generators after their being in fleet use for a period of time.

  2. Mechanical characterization and fracture toughness of electroplated cadmium coating of Al -Zn alloy, T6

    NASA Astrophysics Data System (ADS)

    Mohan Kumar, S.; Ravi Kumar, V.; Shashi Kumar, M. E.; Govindaraju, H. K.

    2017-07-01

    Fracture toughness, Hardness and Tensile Strength of the Aluminum alloy 7075-T6 coated with Cadmium with varying thickness of 10µ and 20µ were investigated. Electroplating Cadmium coating process gives excellent corrosion resistance, provides low coefficient of friction which increases the surface hardness of the material. It also provides a uniform and dense coating, in many cases, maintains surface finish as it was before plating. The specimens prepared in line with ASTM E-8M and E-399 standard were subjected to various tests. The results shows thatthe hardness of the EC coted specimens has increased by 10% and increases with increase in thickness, butthe thicker the EC coating, more brittle is the material. The Ultimate Tensile Strength also increased by 5% compared to the uncoated counterpart. There was a steep increase in plain strain fracture toughness with the increase in the coating thickness for the Aluminum 7075-T6 alloy in TL orientation. The crack growth was Unstable due to the strong adhesion between the EC coating and the alloy.

  3. The corrosion protection of 6061-T6 aluminum by a polyurethane-sealed anodized coat

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1990-01-01

    The corrosion protection of 6061-T6 anodized aluminum afforded by a newly patented polyurethane seal was studied using the ac impedance technique. Values of the average corrosion rates over a 27-day exposure period in 3.5 percent NaCl solutions at pH 5.2 and pH 9.5 compared very favorably for Lockheed-prepared polyurethane-sealed and dichromate-sealed coats of the same thickness. Average corrosion rates for both specimens over the first 7 days of exposure compared well with those for a hard anodized, dichromate-sealed coat, but rose well above those for the hard anodized coat over the entire 27-day period. This is attributed both to the greater thickness of the hard anodized coat, and possibly to its inherently better corrosion protective capability.

  4. Supersymmetric Intersecting Branes on the Type IIA T6/Bbb Z4 Orientifold

    NASA Astrophysics Data System (ADS)

    Blumenhagen, Ralph; Görlich, Lars; Ott, Tassilo

    2003-01-01

    We study supersymmetric intersecting D6-branes wrapping 3-cycles in the Type IIA T6/Z4 orientifold background. As a new feature, the 3-cycles in this orbifold space arise both from the untwisted and the Z2 twisted sectors. We present an integral basis for the homology lattice, H3(M,Z), in terms of fractional 3-cycles, for which the intersection form involves the Cartan matrix of E8. We show that these fractional D6-branes can be used to construct supersymmetric brane configurations realizing a three generation Pati-Salam model. Via brane recombination processes preserving supersymmetry, this GUT model can be broken down to a standard-like model.

  5. D-brane instantons on the T6/Bbb Z3 orientifold

    NASA Astrophysics Data System (ADS)

    Bianchi, Massimo; Fucito, Francesco; Morales, Jose F.

    2007-07-01

    We give a detailed microscopic derivation of gauge and stringy instanton generated superpotentials for gauge theories living on D3-branes at Bbb Z3-orientifold singularities. Gauge instantons are generated by D(-1)-branes and lead to Affleck, Dine and Seiberg (ADS) like superpotentials in the effective Script N = 1 gauge theories with three generations of bifundamental and anti/symmetric matter. Stringy instanton effects are generated by Euclidean ED3-branes wrapping four-cycles on T6/Bbb Z3. They give rise to Majorana masses, Yukawa couplings or non-renormalizable superpotentials depending on the gauge theory. Finally we determine the conditions under which ADS like superpotentials are generated in Script N = 1 gauge theories with adjoints, fundamentals, symmetric and antisymmetric chiral matter.

  6. A Micro-Electrochemical Study of Friction Stir Welded Aluminum 6061-T6

    NASA Technical Reports Server (NTRS)

    Hintze, Paul E.; Calle, Luz M.

    2005-01-01

    The corrosion behavior of friction stir welded Aluminum alloy 606 1-T6 was studied using a micro-electrochemical cell. The micro-electrochemical cell has a measurement area of about 0.25 square mm which allows for measurement of corrosion properties at a very small scale. The corrosion and breakdown potentials were measured at many points inside and outside the weld along lines perpendicular to the weld. The breakdown potential is approximately equal inside and outside the weld; however, it is lower in the narrow border between the weld and base material. The results of electrochemical measurements were correlated to micro-structural analysis. The corrosion behavior of the friction stir welded samples was compared to tungsten inert gas (TIG) welded samples of the same material.

  7. Experimental Investigation of Turning Parameters on AA 6061-T6 Material

    NASA Astrophysics Data System (ADS)

    Parthiban, A.; Pugazhenthi, R.; Ravikumar, R.; Vivek, P.

    2017-03-01

    Turning is a broadly used material removal process to manufacture cylindrical products. The effects of various process parameters on turning like spindle speed, feed rate and depth of cut have been investigated to Impact on Material Removal Rate (MRR) and surface roughness (Ra) by using Response Surface Methodology. Experimental plan is performed by a Box-behenken design. The main purpose of this work is to study the effect of process parameters on Aluminium alloy AA6061-T6 surface, and to develop the mathematical model for Material removal rate and surface roughness on milling process. The quadratic model is best agreement with experimental data; finally the numerical optimization technique has been used to find out best optimum milling parameters. The optimal set of process parameters has also been predicted to maximize the MRR and minimize the surface roughness.

  8. Residual strength of cracked 7075 T6 Al-alloy sheets under high loading rates

    NASA Astrophysics Data System (ADS)

    Vasek, A.; Schijve, J.

    1995-04-01

    Dynamic tests were carried out on long sheet specimens with two collinear cracks. First the ligament between the two cracks fails, which implies that the cracks are linked up to a single crack. Linking up did increase the loading rate (dK/dt) of the outer crack tips up to 2 x 10(exp 4) MPa (sq root) m/s. COD measurements during the fast running crack were made. The residual strength was decreased by about 10 percent as compared to the quasi-static result. Fractographic evidence indicates that a high dK/dt has some effect on the shear lips. It promotes some plane-strain influence, associated with an increased yield stress, due to the high plastic strain rate in the crack tip zone. The results were evaluated in terms of fracture mechanics. The results are bearing on the damage tolerance of aircraft structures built up from 7075-T6 sheet material.

  9. Fatigue Behavior of Oil Jet Peened Aluminum Alloy, AA 6063-T6

    NASA Astrophysics Data System (ADS)

    Grinspan, Alphonse Sahaya; Gnanamoorthy, Rajappa

    Oil jet peening is a new surface modification process developed for the introduction of compressive residual stresses. This paper describes the effect of oil jet peening on the fatigue performance of aluminum alloy, AA 6063-T6. Specimens were peened at an oil injection pressure of 40 MPa with various nozzle-traveling velocities. Each impact of oil droplet generates an indentation on the surface of specimen. The surface roughness increases with decreasing nozzle-traveling velocity. The maximum compressive residual stress developed is about 75% of yield strength. Fatigue life depends on the compressive residual stress as well as surface roughness of oil jet peened specimens. Fracture mechanism of unpeened and oil jet peened specimens were studied using optical and scanning electron microscopes.

  10. Prevention of non-ductile fracture in 6061-T6 aluminum nuclear pressure vessels

    SciTech Connect

    Yahr, G.T.

    1995-06-01

    The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Committee has approved rules for the use of 6061-T6 and 6061-T651 aluminum for the construction of Class 1 welded nuclear pressure vessels for temperatures not exceeding 149 C (300 F). Nuclear Code Case N-519 allows the use of this aluminum in the construction of low temperature research reactors such as the Advanced Neutron Source. The rules for protection against non-ductile fracture are discussed. The basis for a value of 25.3 MPa {radical}m (23 ksi {radical}in.) for the critical or reference stress intensity factor for use in the fracture analysis is presented. Requirements for consideration of the effects of neutron irradiation on the fracture toughness are discussed.

  11. Cavitation pitting and erosion of aluminum 6061-T6 in mineral oil water

    NASA Technical Reports Server (NTRS)

    Rao, B. C. S.; Buckley, D. H.

    1983-01-01

    Cavitation erosion studies of aluminum 6061-T6 in mineral oil and in ordinary tap water are presented. The maximum erosion rate (MDPR, or mean depth of penetration rate) in mineral oil was about four times that in water. The MDPR in mineral oil decreased continuously with time, but the MDPR in water remained approximately constant. The cavitation pits in mineral oil were of smaller diameter and depth than the pits in water. Treating the pits as spherical segments, we computed the radius r of the sphere. The logarithm of h/a, where h is the pit depth and 2a is the top width of the pit, was linear when plotted against the logarithm of 2r/h - 1.

  12. Investigation of aluminum 6061-T6 strength properties to 160 GPa

    NASA Astrophysics Data System (ADS)

    Reinhart, William; Alexander, Scott; Asay, James; Chhabildas, Lalit

    2009-06-01

    Shock compression experiments were performed on aluminum 6061-T6 up to 160 GPa to probe aluminum strength through the melt regime. A careful set of experiments, using established two and three stage flyer plate launch techniques were conducted using symmetric impact loading conditions to compress the aluminum through the solid to liquid phase boundary. Velocity interferometry provides the fine structure almost as an in-situ particle velocity wave profile at the aluminum/lithium-fluoride window interface. Results will be detailed in terms of wave speeds in the shocked state for estimates of strength of the material. Results of these experiments will be discussed in detail. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  13. Effect of turning parameters on A16351 T6 by using Design of Experiments

    NASA Astrophysics Data System (ADS)

    Annigeri, Ulhas K.; Charan, M.; Vishnu Sai, M.; Ram Charan, T.; Rahul Sai, L.

    2016-09-01

    Aluminium is a well known lightest engineering metals. It is the most productive element on the earth crust. It can be extracted from bauxite, kaolinite or nepheline. It can be used in making aeroplane bodies, automobile parts etc. It is mostly used in multiple applications in order to reduce the weight of the component and it has fancy corrosion resistance. In the present study Al 6351 T6 is selected and a plain turning operation is performed on it with the help of design of experiments. The surface roughness of the samples are tested by varying the cutting parameters such as speed, feed, and depth of cut. A mathematical model is developed and the parameter which affects the surface roughness is determined.

  14. Salmonella Typhimurium utilizes a T6SS-mediated antibacterial weapon to establish in the host gut

    PubMed Central

    Flaugnatti, Nicolas; Lugo, Kyler A.; Lam, Lilian H.; Jacobson, Amanda; Baylot, Virginie; Durand, Eric; Journet, Laure; Cascales, Eric; Monack, Denise M.

    2016-01-01

    The mammalian gastrointestinal tract is colonized by a high-density polymicrobial community where bacteria compete for niches and resources. One key competition strategy includes cell contact-dependent mechanisms of interbacterial antagonism, such as the type VI secretion system (T6SS), a multiprotein needle-like apparatus that injects effector proteins into prokaryotic and/or eukaryotic target cells. However, the contribution of T6SS antibacterial activity during pathogen invasion of the gut has not been demonstrated. We report that successful establishment in the gut by the enteropathogenic bacterium Salmonella enterica serovar Typhimurium requires a T6SS encoded within Salmonella pathogenicity island-6 (SPI-6). In an in vitro setting, we demonstrate that bile salts increase SPI-6 antibacterial activity and that S. Typhimurium kills commensal bacteria in a T6SS-dependent manner. Furthermore, we provide evidence that one of the two T6SS nanotube subunits, Hcp1, is required for killing Klebsiella oxytoca in vitro and that this activity is mediated by the specific interaction of Hcp1 with the antibacterial amidase Tae4. Finally, we show that K. oxytoca is killed in the host gut in an Hcp1-dependent manner and that the T6SS antibacterial activity is essential for Salmonella to establish infection within the host gut. Our findings provide an example of pathogen T6SS-dependent killing of commensal bacteria as a mechanism to successfully colonize the host gut. PMID:27503894

  15. Sperm FISH and chromatin integrity in spermatozoa from a t(6;10;11) carrier.

    PubMed

    Olszewska, Marta; Huleyuk, Nataliya; Fraczek, Monika; Zastavna, Danuta; Wiland, Ewa; Kurpisz, Maciej

    2014-05-01

    Complex chromosome rearrangements (CCRs) are structurally balanced or unbalanced aberrations involving more than two breakpoints on two or more chromosomes. CCRs can be a potential reason for genomic imbalance in gametes, which leads to a drastic reduction in fertility. In this study, the meiotic segregation pattern, aneuploidy of seven chromosomes uninvolved in the CCR and chromatin integrity were analysed in the ejaculated spermatozoa of a 46,XY,t(6;10;11)(q25.1;q24.3;q23.1)mat carrier with asthenozoospermia and a lack of conception. The frequency of genetically unbalanced spermatozoa was 78.8% with a prevalence of 4:2 segregants of 38.2%, while the prevalence of the adjacent 3:3 mode was 35.3%. Analysis of the aneuploidy of chromosomes 13, 15, 18, 21, 22, X and Y revealed an approximately fivefold increased level in comparison with that of the control group, indicating the presence of an interchromosomal effect. Sperm chromatin integrity status was evaluated using chromomycin A3 and aniline blue staining (deprotamination), acridine orange test and TUNEL assay (sperm DNA fragmentation). No differences were found when comparisons were made with a control group. We suggest that the accumulation of genetically unbalanced spermatozoa, significantly increased sperm aneuploidy level and decreased sperm motility (20%, progressive) were not responsible for the observed lack of reproductive success in the analysed infertile t(6;10;11) carrier. Interestingly, in the case described herein, a high level of sperm chromosomal imbalance appears not to be linked to sperm chromatin integrity status.

  16. Early state damage detection of aluminum 7075-T6 plate based on acoustic emission

    NASA Astrophysics Data System (ADS)

    Ozevin, Didem; Li, Zhong; Heidary, Zahra

    2011-04-01

    Aluminum alloy 7075-T6 is a commonly used material in aircraft industry. A crack usually initiates at the edge of a fastener hole, and it can affect the maintenance schedule and reduce the life of an aircraft structure significantly. The fatigue property of the material has been researched widely to develop methods and models for predicting fatigue crack growth under random loading. From the point of damage tolerance design, the inspection technique of a crack for an aircraft structure is very important because it can be used to determine the inspection period of the aircraft structure. The acoustic emission (AE) technique is a nondestructive testing (NDT) method that is able to monitor damage initiation and progression in real time. Understanding the early stage of AE signature due to the damage progression using small scale laboratory samples requires non-traditional data analysis approaches. In this study, 1mm thick Al-7075-T6 plates were tested under monotonic and fatigue loading. The initiation of damage progression using AE data was identified based on improved linear location algorithm and the result was verified using elasto-plastic finite element model. The improved location algorithm integrates dispersive characteristics of flexural waves and threshold independent approach to pick up the wave arrival time. In this paper, AE results in comparison with FE model under monotonic and fatigue loading will be presented. The comparison of traditional and improved location approaches will be shown. The approach for implementing the laboratory scale results in the large scale field testing will be discussed.

  17. Mitigating Diminishing Manufacturing Sources Material Shortages (DMS/MS) and Obsolescence for the T-6 Canopy Fracturing Initiation System (CFIS)

    DTIC Science & Technology

    2012-03-01

    6 CANOPY FRACTURING INITIATION SYSTEM (CFIS) THESIS Richard P. Carrano, DP-5, USN AFIT/GSE/ENV/12-M01DL DEPARTMENT OF THE AIR FORCE AIR...SOURCES/MATERIAL SHORTAGES (DMS/MS) AND OBSOLESCENCE FOR THE T-6 CANOPY FRACTURING INITIATION SYSTEM (CFIS) THESIS Presented to the Faculty...DIMINISHING MANUFACTURING SOURCES/MATERIAL SHORTAGES (DMS/MS) AND OBSOLESCENCE FOR THE T-6 CANOPY FRACTURING INITIATION SYSTEM (CFIS

  18. Experiments and simulation for 6061-T6 aluminum alloy resistance spot welded lap joints

    NASA Astrophysics Data System (ADS)

    Florea, Radu Stefanel

    This comprehensive study is the first to quantify the fatigue performance, failure loads, and microstructure of resistance spot welding (RSW) in 6061-T6 aluminum (Al) alloy according to welding parameters and process sensitivity. The extensive experimental, theoretical and simulated analyses will provide a framework to optimize the welding of lightweight structures for more fuel-efficient automotive and military applications. The research was executed in four primary components. The first section involved using electron back scatter diffraction (EBSD) scanning, tensile testing, laser beam profilometry (LBP) measurements, and optical microscopy(OM) images to experimentally investigate failure loads and deformation of the Al-alloy resistance spot welded joints. Three welding conditions, as well as nugget and microstructure characteristics, were quantified according to predefined process parameters. Quasi-static tensile tests were used to characterize the failure loads in specimens based upon these same process parameters. Profilometer results showed that increasing the applied welding current deepened the weld imprints. The EBSD scans revealed the strong dependency between the grain sizes and orientation function on the process parameters. For the second section, the fatigue behavior of the RSW'ed joints was experimentally investigated. The process optimization included consideration of the forces, currents, and times for both the main weld and post-heating. Load control cyclic tests were conducted on single weld lap-shear joint coupons to characterize the fatigue behavior in spot welded specimens. Results demonstrate that welding parameters do indeed significantly affect the microstructure and fatigue performance for these welds. The third section comprised residual strains of resistance spot welded joints measured in three different directions, denoted as in-plane longitudinal, in-plane transversal, and normal, and captured on the fusion zone, heat affected zone

  19. Chemically short-crack behavior of the 7075-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Dolley, Evan Jarrett, Jr.

    Commercial and military aircraft are exposed to deleterious environments (such as salt spray) that can enhance the fatigue-crack-growth (FCG) rates in structural components. This phenomenon, generically termed corrosion fatigue (CF) can have a large effect on their fatigue lives. CFCG behavior may be separated into two regimes: a chemically long-crack regime and a chemically short-crack regime. FCG rates in the chemically long-crack regime for the 7075-T6 aluminum alloy are approximately one order of magnitude greater than those in a dehumidified environment and exhibit growth rate similitude under a constant crack driving force ( D K). FCG rates in the chemically short-crack regime exhibit a breakdown in growth rate similitude at crack lengths shorter than 7 mm. The growth rates at 0.5 mm are 2 times greater than those in the long-crack regime and decay with increasing crack length to the long-crack rates at approximately 7 mm. The extent of the chemically short-crack behavior in the 7075-T6 aluminum alloy depends on D K, crack length and dissolved oxygen concentration in the aqueous solution. Mathematical modeling of the mass transport of dissolved oxygen to the crack tip region shows a good correlation between the chemically short-crack behavior and the amount of dissolved oxygen at the crack tip. The short-crack behavior is not observed in a deaerated solution. The enhanced growth rates are caused by hydrogen embrittlement. Fracture in dehumidified air occurs along the 100 fracture plane while cracking in the chemically short and long-crack regimes occur on 100 and 110 (flat brittle type fracture) planes with the fractional area of the 110 fracture decreasing with increasing crack length in the chemically short-crack regime. Predicted and actual FCG rates correlate well showing that the enhancement of growth rates in the deleterious environment depends on the amount of 110 fracture. The chemically short-crack behavior may reduce the FCG life of a structure by

  20. The Glucuronic Acid Utilization Gene Cluster from Bacillus stearothermophilus T-6

    PubMed Central

    Shulami, Smadar; Gat, Orit; Sonenshein, Abraham L.; Shoham, Yuval

    1999-01-01

    A λ-EMBL3 genomic library of Bacillus stearothermophilus T-6 was screened for hemicellulolytic activities, and five independent clones exhibiting β-xylosidase activity were isolated. The clones overlap each other and together represent a 23.5-kb chromosomal segment. The segment contains a cluster of xylan utilization genes, which are organized in at least three transcriptional units. These include the gene for the extracellular xylanase, xylanase T-6; part of an operon coding for an intracellular xylanase and a β-xylosidase; and a putative 15.5-kb-long transcriptional unit, consisting of 12 genes involved in the utilization of α-d-glucuronic acid (GlcUA). The first four genes in the potential GlcUA operon (orf1, -2, -3, and -4) code for a putative sugar transport system with characteristic components of the binding-protein-dependent transport systems. The most likely natural substrate for this transport system is aldotetraouronic acid [2-O-α-(4-O-methyl-α-d-glucuronosyl)-xylotriose] (MeGlcUAXyl3). The following two genes code for an intracellular α-glucuronidase (aguA) and a β-xylosidase (xynB). Five more genes (kdgK, kdgA, uxaC, uxuA, and uxuB) encode proteins that are homologous to enzymes involved in galacturonate and glucuronate catabolism. The gene cluster also includes a potential regulatory gene, uxuR, the product of which resembles repressors of the GntR family. The apparent transcriptional start point of the cluster was determined by primer extension analysis and is located 349 bp from the initial ATG codon. The potential operator site is a perfect 12-bp inverted repeat located downstream from the promoter between nucleotides +170 and +181. Gel retardation assays indicated that UxuR binds specifically to this sequence and that this binding is efficiently prevented in vitro by MeGlcUAXyl3, the most likely molecular inducer. PMID:10368143

  1. Lessons from an aged, dried crystal of T(6) human insulin.

    PubMed

    Smith, G David; Blessing, Robert H

    2003-08-01

    The structure of the T(6) hexameric form of human insulin has been determined at both room temperature and 100 K from a single air-dried crystal. At 100 K, the space group is R3 and the asymmetric unit consists of a dimer, as has been observed previously in hydrated structures. At room temperature, the space group is P1 and the unit cell contains a quasi-threefold-symmetric hexamer. In the absence of stabilizing water interactions, the N-termini of all six A chains in the room-temperature structure appear to have undergone partial unfolding, but the N-termini of these chains are well ordered in the 100 K structure. Other differences between the room-temperature and 100 K structures involve the coordination around the zinc ions. At 100 K, both zinc ions clearly exhibit dual coordination: zinc is octahedrally coordinated in one half of the zinc sites but tetrahedrally coordinated in the other half; at room temperature, the electron densities suggest tetrahedral coordination but the bond distances to the fourth ligands are longer than expected. Contrary to what has been observed to date in all other T(6) insulin structures, there are no contacts between pairs of GluB13 residues, either at room temperature or at 100 K, that would suggest the presence of a hydrogen bond. At room temperature, three of the six independent GluB13 side chains are disordered; at 100 K, both independent side chains are disordered. The disorder in the GluB13 side chains and the lack of contacts between carboxylate groups suggests that as a result of disruption of the hydration structure in the central core of the hexamer, all six B13 carboxylates bear a negative charge. This in turn suggests that in the hydrated structures the well ordered water structure in the central core is involved in stabilizing the B13 side-chain conformations and modulating charge repulsions among the six B13 glutamates if they are not protonated, or that, as is considered more likely, the water structure plays an

  2. Overexpression of a Homeobox Gene, LeT6, Reveals Indeterminate Features in the Tomato Compound Leaf1

    PubMed Central

    Janssen, Bart-Jan; Lund, Lance; Sinha, Neelima

    1998-01-01

    The cultivated tomato (Lycopersicon esculentum) has a unipinnate compound leaf. In the developing leaf primordium, major leaflet initiation is basipetal, and lobe formation and early vascular differentiation are acropetal. We show that engineered alterations in the expression of a tomato homeobox gene, LeT6, can cause dramatic changes in leaf morphology. The morphological states are variable and unstable and the phenotypes produced indicate that the tomato leaf has an inherent level of indeterminacy. This is manifested by the production of multiple orders of compounding in the leaf, by numerous shoot, inflorescence, and floral meristems on leaves, and by the conversion of rachis-petiolule junctions into “axillary” positions where floral buds can arise. Overexpression of a heterologous homeobox transgene, kn1, does not produce such phenotypic variability. This indicates that LeT6 may differ from the heterologous kn1 gene in the effects manifested on overexpression, and that 35S-LeT6 plants may be subject to alterations in expression of both the introduced and endogenous LeT6 genes. The expression patterns of LeT6 argue in favor of a fundamental role for LeT6 in morphogenesis of leaves in tomato and also suggest that variability in homeobox gene expression may account for some of the diversity in leaf form seen in nature. PMID:9662520

  3. Si doped T6 carbon structure as an anode material for Li-ion batteries: An ab initio study

    NASA Astrophysics Data System (ADS)

    Rajkamal, A.; Kumar, E. Mathan; Kathirvel, V.; Park, Noejung; Thapa, Ranjit

    2016-11-01

    First-principles calculations are performed to identify the pristine and Si doped 3D metallic T6 carbon structure (having both sp2 and sp3 type hybridization) as a new carbon based anode material. The π electron of C2 atoms (sp2 bonded) forms an out of plane network that helps to capture the Li atom. The highest Li storage capacity of Si doped T6 structure with conformation Li1.7Si1C5 produces theoretical specific capacity of 632 mAh/g which substantially exceeding than graphite. Also, open-circuit voltage (OCV) with respect to Li metal shows large negative when compared to the pristine T6 structure. This indicates modifications in terms of chemical properties are required in anode materials for practical application. Among various doped (Si, Ge, Sn, B, N) configuration, Si doped T6 structure provides a stable positive OCV for high Li concentrations. Likewise, volume expansion study also shows Si doped T6 structure is more stable with less pulverization and substantial capacity losses in comparison with graphite and silicon as an anode materials. Overall, mixed hybridized (sp2 + sp3) Si doped T6 structure can become a superior anode material than present sp2 hybridized graphite and sp3 hybridized Si structure for modern Lithium ion batteries.

  4. Si doped T6 carbon structure as an anode material for Li-ion batteries: An ab initio study

    PubMed Central

    Rajkamal, A.; Kumar, E. Mathan; Kathirvel, V.; Park, Noejung; Thapa, Ranjit

    2016-01-01

    First-principles calculations are performed to identify the pristine and Si doped 3D metallic T6 carbon structure (having both sp2 and sp3 type hybridization) as a new carbon based anode material. The π electron of C2 atoms (sp2 bonded) forms an out of plane network that helps to capture the Li atom. The highest Li storage capacity of Si doped T6 structure with conformation Li1.7Si1C5 produces theoretical specific capacity of 632 mAh/g which substantially exceeding than graphite. Also, open-circuit voltage (OCV) with respect to Li metal shows large negative when compared to the pristine T6 structure. This indicates modifications in terms of chemical properties are required in anode materials for practical application. Among various doped (Si, Ge, Sn, B, N) configuration, Si doped T6 structure provides a stable positive OCV for high Li concentrations. Likewise, volume expansion study also shows Si doped T6 structure is more stable with less pulverization and substantial capacity losses in comparison with graphite and silicon as an anode materials. Overall, mixed hybridized (sp2 + sp3) Si doped T6 structure can become a superior anode material than present sp2 hybridized graphite and sp3 hybridized Si structure for modern Lithium ion batteries. PMID:27892532

  5. Erosion of aluminum 6061-T6 under cavitation attack in mineral oil and water

    NASA Technical Reports Server (NTRS)

    Rao, B. C. S.; Buckley, D. H.

    1985-01-01

    Studies of the erosion of aluminum 6061-T6 under cavitation attack in distilled water, ordinary tap water and a viscous mineral oil are presented. The mean depth of penetration for the mineral oil was about 40 percent of that for water at the end of a 40 min test. The mean depth of penetration and its rate did not differ significantly for distilled and tap water. The mean depth of penetration rate for both distilled and tap water increased to a maximum and then decreased with test duration, while that for mineral oil had a maximum during the initial period. The ratio h/2a of the pit depth h to the pit diameter 2a varied from 0.04 to 0.13 in water and from 0.06 to 0.20 in mineral oil. Scanning electron microscopy indicates that the pits are initially formed over the grain boundaries and precipitates while the surface grains are deformed under cavitation attack.

  6. The effects of pitting on fatigue crack nucleation in 7075-T6 aluminum alloy

    NASA Technical Reports Server (NTRS)

    Ma, LI; Hoeppner, David W.

    1994-01-01

    A high-strength aluminum alloy, 7075-T6, was studied to quantitatively evaluate chemical pitting effects of its corrosion fatigue life. The study focused on pit nucleation, pit growth, and fatigue crack nucleation. Pitting corrosion fatigue experiments were conducted in 3.5 percent NaCl aqueous solution under constant amplitude sinusoidal loading at two frequencies, 5 and 20 Hz. Smooth and unnotched specimens were used in this investigation. A video recording system was developed to allow in situ observation of the surface changes of the specimens during testing. The results indicated that pitting corrosion considerably reduces the fatigue strength by accelerating fatigue crack nucleation. A metallographic examination was conducted on the specimens to evaluate the nature of corrosion pits. First, the actual shapes of the corrosion pits were evaluated by cross-sectioning the pits. Secondly, the relation between corrosion pits and microstructure was also investigated. Finally, the possibility of another corrosion mechanism that might be involved in pitting was explored in this investigation. The fractography of the tested specimens showed that corner corrosion pits were responsible for fatigue crack nucleation in the material due to the associated stress concentration. The pits exhibited variance of morphology. Fatigue life for the experimental conditions appeared to be strongly dependent on pitting kinetics and the crack nucleation stage.

  7. Vertical Compensation Friction Stir Welding of 6061-T6 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Ji, Shude; Meng, Xiangchen; Xing, Jingwei; Ma, Lin; Gao, Shuangsheng

    2016-09-01

    Vertical compensation friction stir welding (VCFSW) was proposed in order to solve the adverse effect caused by a big gap at the interface between two welded workpieces. VCFSW was successfully applied to weld 6061-T6 aluminum alloy with the thickness of 4 mm, while 2024-T4 aluminum alloy was selected as a rational compensation material. The results show that VCFSW is difficult to get a sound joint when the width of strip is no less than 1.5 mm. Decreasing the welding speed is beneficial to break compensation strip into pieces and then get higher quality joint. When the width of strip is 1 mm, the tensile strength and elongation of joint at the welding speed of 50 mm/min and rotational velocity of 1,800 rpm reach the maximum values of 203 MPa and 5.2%, respectively. Moreover, the addition of 2024-T4 alloy plays a strengthening effect on weld zone (WZ) of VCFSW joint. The fracture surface morphology of joint consisting of amounts of dimples exhibits ductile fracture.

  8. Electrochemical behavior of anodized AA6063-T6 alloys affected by matrix structures

    NASA Astrophysics Data System (ADS)

    Huang, Yung-Sen; Shih, Teng-Shih; Wu, Chen-En

    2013-01-01

    AA 6063 alloys were cold-rolled (CR) either before or after solution treatment (S) and then different samples were artificially aged (T6) to obtain different samples (CRST6 and SCRT6). The highest dislocation density was observed in the SCRT6 sample which also showed the lowest particle count among the three samples; ST6, CRST6 and SCRT6. Subsequently, all samples were anodized in a 15 wt% sulfuric acid solution for different time spans to obtain anodic aluminum oxide (AAO) films. The anodized samples were further analyzed with X-ray Photoelectron Spectroscopy (XPS) analysis. We determined that the constituent phases in the AAO film were composed of hydrated amorphous alumina, hydrated oxide (Al(OH)3) and oxyhydroxide (AlOOH) phases together with some silicon-containing particles trapped in the films on all samples. In the electrochemical test, the silicon-containing particles and hydrated Al(OH)3 oxide that existed at the electrolyte/film (e/f) interface were found to inversely influence the corrosion resistance of the anodized samples.

  9. Mechanical properties of dissimilar metal joints composed of DP 980 steel and AA 7075-T6

    DOE PAGES

    Squires, Lile; Lim, Yong Chae; Miles, Michael; ...

    2015-03-18

    In this study, a solid state joining process, called friction bit joining, was used to spot weld aluminium alloy 7075-T6 to dual phase 980 steel. Lap shear failure loads for specimens without adhesive averaged ~10kN, while cross-tension specimens averaged 2·8 kN. Addition of adhesive with a thickness up to 500 μm provided a gain of ~50% to lap shear failure loads, while a much thinner layer of adhesive increased cross-tension failure loads by 20%. Microstructures of the welds were martensitic, but the hardness of the joining bit portion was greater than that of the DP 980, owing to its highermore » alloy content. Softening in the heat affected zone of a welded joint appeared to be relatively small, though it was enough to cause nugget pullout failures in some lap shear tension specimens. Finally, other failures in lap shear tension were interfacial, while all of the failures in cross-tension were interfacial.« less

  10. Mechanical properties of dissimilar metal joints composed of DP 980 steel and AA 7075-T6

    SciTech Connect

    Squires, Lile; Lim, Yong Chae; Miles, Michael; Feng, Zhili

    2015-03-18

    In this study, a solid state joining process, called friction bit joining, was used to spot weld aluminium alloy 7075-T6 to dual phase 980 steel. Lap shear failure loads for specimens without adhesive averaged ~10kN, while cross-tension specimens averaged 2·8 kN. Addition of adhesive with a thickness up to 500 μm provided a gain of ~50% to lap shear failure loads, while a much thinner layer of adhesive increased cross-tension failure loads by 20%. Microstructures of the welds were martensitic, but the hardness of the joining bit portion was greater than that of the DP 980, owing to its higher alloy content. Softening in the heat affected zone of a welded joint appeared to be relatively small, though it was enough to cause nugget pullout failures in some lap shear tension specimens. Finally, other failures in lap shear tension were interfacial, while all of the failures in cross-tension were interfacial.

  11. Effect of Laser Shock Peening on surface properties and residual stress of Al6061-T6

    NASA Astrophysics Data System (ADS)

    Salimianrizi, A.; Foroozmehr, E.; Badrossamay, M.; Farrokhpour, H.

    2016-02-01

    The purpose of this study is to investigate the effects of Laser Shock Peening (LSP) on Al 6061-T6. The confined LSP regime using Nd: YAG laser with 1200 mJ of energy per pulse and 8 ns of pulse width were applied. The treated specimens were evaluated by means of surface integrity with optical microscopy, scanning electron microscope, microhardness, surface roughness and induced residual stress using an X-ray diffraction method. Results showed that by the use of LSP, compressive residual stress could effectively be induced on the surface of treated material. It was also revealed that the hardened depth of the material, up to a maximum depth of 1875 μm, could be achieved due to work hardening and grain refinement. In addition, surface roughness measurements showed that the LSP could deteriorate surface quality depending on the LSP parameters. The influences of beam overlap rates, number of laser shots and scanning pattern on microhardness as well as surface roughness are discussed.

  12. Built-up edge investigation in vibration drilling of Al2024-T6.

    PubMed

    Barani, A; Amini, S; Paktinat, H; Fadaei Tehrani, A

    2014-07-01

    Adding ultrasonic vibrations to drilling process results in an advanced hybrid machining process, entitled "vibration drilling". This study presents the design and fabrication of a vibration drilling tool by which both rotary and vibrating motions are applied to drill simultaneously. High frequency and low amplitude vibrations were generated by an ultrasonic transducer with frequency of 19.65 kHz. Ultrasonic transducer was controlled by a MPI ultrasonic generator with 3 kW power. The drilling tool and workpiece material were HSS two-flute twist drill and Al2024-T6, respectively. The aim of this study was investigating on the effect of ultrasonic vibrations on built-up edge, surface quality, chip morphology and wear mechanisms of drill edges. Therefore, these factors were studied in both vibration and ordinary drilling. Based on the achieved results, vibration drilling offers less built-up edge and better surface quality compared to ordinary drilling. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Description of plastic anisotropy in AA6063-T6 using the crystal plasticity finite element method

    NASA Astrophysics Data System (ADS)

    Dumoulin, S.; Engler, O.; Hopperstad, O. S.; Lademo, O. G.

    2012-07-01

    The crystal plasticity finite element method has been used in combination with crystallographic texture data to predict the plastic anisotropy of the extruded aluminium alloy AA6063 in temper T6. The results are compared with experimental data from tensile tests at different angles between the tensile and extrusion directions. Inverse modelling based on the tensile test in a reference direction is used to identify the parameters of the work-hardening model at slip system level. To investigate the influence of grain interactions, various discretizations of the grains are applied in the representative volume element modelled with finite elements. In addition, alternative homogenization schemes, such as the full-constraint Taylor and viscoplastic self-consistent methods, are used to model the behaviour of the polycrystal. It is found that the grain discretization and the homogenization scheme have only minor influence on the predicted plastic anisotropy. While the crystal plasticity-based methods all give reasonable predictions of the directional variations of flow stresses and plastic strain ratios measured experimentally, there are still significant deviations, indicating there are other sources to the plastic anisotropy than crystallographic texture.

  14. Microstructure and Mechanical Behavior of Al 7075-T6 Subjected to Shallow Cryogenic Treatment

    NASA Astrophysics Data System (ADS)

    Mohan, K.; Suresh, J. A.; Ramu, Palaniappan; Jayaganthan, R.

    2016-06-01

    The effect of shallow cryogenic treatment (SCT) on the microstructure and mechanical properties of Al7075-T6 is investigated in the present work. The alloy was subjected to shallow CT at -80 °C for 72 h. Mechanical tests such as Vickers hardness test, tensile, and fatigue tests were performed on both native and treated samples. It was observed that the mechanical properties such as hardness, yield strength, and ultimate tensile strength increased by about 30, 17, and 7%, respectively, for the treated sample. The treated alloy was characterized by using the techniques such as optical microscopy, electron back scattered diffraction (EBSD), energy-dispersive x-ray spectroscopy (EDS), and transmission electron microscopy (TEM) to observe the changes in the microstructural features. EBSD results show precipitation, better distribution of second-phase particles, and higher dislocation density in the treated alloy as compared to the untreated alloy. The treatment imparts improved hardness and strength to the alloy due to precipitation hardening and high dislocation density. Fracture morphologies of the treated and the native samples were characterized by using scanning electron microscopy and it was observed that the striations were denser in the treated sample justifying the higher fatigue strength.

  15. Microstructure, hardness profile and tensile strength in welds of AA6013 T6 extrusions

    SciTech Connect

    Guitterez, L.A.; Neye, G.; Zschech, E.

    1996-04-01

    Alloy AA6013 is easily welded by conventional arc welding processes as well as by high-energy-density processes. However, some physical properties, which are inherent to all aluminum alloys, have to be considered during welding. In comparison to steel, the high thermal conductivity of aluminum alloys requires the use of higher heat input for welding. This is realized by a greater welding current during GTAW of aluminum alloys. One of the main problems associated with LBW of aluminum alloys is the high surface reflectivity. In particular, the threshold intensity for the development of a keyhole is much higher for aluminum than for steel. Finally, aluminum alloys, and particularly the heat-treatable alloys, are sensitive to weld cracking. This phenomenon can be avoided by proper filler and base metal alloy selection and adequate filler metal dilution. In order to improve the mechanical integrity of Al-Mg-Si weldments, it would be desirable to study the microstructure of the FZ and of the HAZ, as well as the residual stress distribution. The present study was performed in order to show differences in microstructure, hardness profile and tensile strength of gas tungsten arc (GTA) and laser beam (LB) welded AA6013-T6 extrusions. In addition, grain boundary liquations and hot tearing are discussed.

  16. Design and Analysis of Wind Turbine Blade Hub using Aluminium Alloy AA 6061-T6

    NASA Astrophysics Data System (ADS)

    Ravikumar, S.; Jaswanthvenkatram, V.; Sai kumar, Y. J. N. V.; Sohaib, S. Md.

    2017-05-01

    This work presents the design and analysis of horizontal axis wind turbine blade hub using different material. The hub is very crucial part of the wind turbine, which experience the loads from the blades and the loads were transmitted to the main shaft. At present wind turbine is more expensive and weights more than a million pounds, with the nacelle, rotor hub and blades accounting for most of the weight. In this work Spheroidal graphite cast iron GGG 40.3 is replaced by aluminium alloy 6061-T6 to enhance the casting properties and also to improve the strength-weight ratio. This transition of material leads to reduction in weight of the wind turbine. All the loads caused by wind and extreme loads on the blades are transferred to the hub. Considering the IEC 61400-1 standard for defining extreme loads on the hub the stress and deflection were calculated on the hub by using Finite element Analysis. Result obtained from ANSYS is compared and discussed with the existing design.

  17. CO2 laser beam welding of 6061-T6 aluminum alloy thin plate

    NASA Astrophysics Data System (ADS)

    Hirose, Akio; Kobayashi, Kojiro F.; Todaka, Hirotaka

    1997-12-01

    Laser beam welding is an attractive welding process for age-hardened aluminum alloys, because its low heat input minimizes the width of weld fusion and heat-affected zones (HAZs). In the present work, 1-mm-thick age-hardened Al-Mg-Si alloy, 6061-T6, plates were welded with full penetration using a 2.5-kW CO2 laser. Fractions of porosity in the fusion zones were less than 0.05 pct in bead-on-plate welding and less than 0.2 pct in butt welding with polishing the groove surface before welding. The width of a softened region in the-laser beam welds was less than 1/4 times that of a tungsten inert gas (TIG) weld. The softened region is caused by reversion of strengthening β″ (Mg2Si) precipitates due to weld heat input. The hardness values of the softened region in the laser beam welds were almost fully recovered to that of the base metal after an artificial aging treatment at 448 K for 28.8 ks without solution annealing, whereas those in the TIG weld were not recovered in a partly reverted region. Both the bead-on-plate weld and the butt weld after the postweld artificial aging treatment had almost equivalent tensile strengths to that of the base plate.

  18. Variable and Polarized Radio Emission from a T6 Brown Dwarf

    NASA Astrophysics Data System (ADS)

    Williams, Peter K. G.; Gizis, John; Berger, Edo

    2017-01-01

    Route & Wolszczan (2016) recently detected five radio bursts from the T6 brown dwarf WISEP J112254.7+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ~17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission possibly with a period of 116 minutes, although our observation lasted only 162 minutes and so more data are needed to confirm it. Our proposed periodicity is typical of other radio-active ultracool dwarfs. The handedness of the circular polarization alternates with time and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object’s magnetic dipole axis may be highly misaligned relative to its rotation axis.

  19. Experimental Research on Fatigue Failure for 2219-T6 Aluminum Alloy Friction Stir-Welded Joints

    NASA Astrophysics Data System (ADS)

    Sun, Guo-Qin; Niu, Jiang-Pei; Chen, Ya-Jing; Sun, Feng-Yang; Shang, De-Guang; Chen, Shu-Jun

    2017-08-01

    The fatigue experiment was executed for the 2219-T6 aluminum alloy friction stir-welded joints at the rotation speed of 800 r/min and the welding velocity of 150 mm/min. Most fatigue failures occurred in the weld nugget zone (WNZ), the thermo-mechanical affected zone and the nearby areas. The experimental results demonstrated that the sudden hardness gradient increases sites corresponding to the fatigue failure locations. The high-angle grain boundaries with the highest concentration were scattered within the WNZ. The microcracks initiated at the intersection of the soft grains. More than one crack initiation site was observed within the WNZ and the thermo-mechanical affected zone, when the fracture occurred in these areas. The rough surface of the welding area should be one of the main reasons for the fatigue failure occurrence. The fatigue crack growth rate in the WNZ at the first stage was fastest in comparison with the fatigue crack growth rate in the other areas of the joint.

  20. Erosion of aluminum 6061-T6 under cavitation attack in mineral oil and water

    NASA Technical Reports Server (NTRS)

    Rao, B. C. S.; Buckley, D. H.

    1985-01-01

    Studies of the erosion of aluminum 6061-T6 under cavitation attack in distilled water, ordinary tap water and a viscous mineral oil are presented. The mean depth of penetration for the mineral oil was about 40 percent of that for water at the end of a 40 min test. The mean depth of penetration and its rate did not differ significantly for distilled and tap water. The mean depth of penetration rate for both distilled and tap water increased to a maximum and then decreased with test duration, while that for mineral oil had a maximum during the initial period. The ratio h/2a of the pit depth h to the pit diameter 2a varied from 0.04 to 0.13 in water and from 0.06 to 0.20 in mineral oil. Scanning electron microscopy indicates that the pits are initially formed over the grain boundaries and precipitates while the surface grains are deformed under cavitation attack.

  1. Thermal-mechanical modeling and experimental validation of weld solidification cracking in 6061-T6 aluminum

    SciTech Connect

    Dike, J.J.; Brooks, J.A.; Bammann, D.J.; Li, M.

    1997-12-31

    Finite element simulation using an internal state variable constitutive model coupled with a void growth and damage model are used to study weld solidification cracking of 6061-T6 aluminum. Calculated results are compared with data from an experimental program determining the locations of failure as a function of weld process parameters and specimen geometry. Two types of weld solidification cracking specimen were studied. One specimen, in which cracking did not occur, was used to evaluate finite element simulations of the thermal response and calculations of average strain across the weld. The other specimen type was used to determine the location of crack initiation as a function of weld process parameters. This information was used to evaluate the finite element simulations of weld solidification cracking. A solidification model which includes dendrite tip and eutectic undercooling was used in both thermal and mechanical finite element analyses. A strain rate and temperature history dependent constitutive model is coupled with a ductile void growth damage model in the mechanical analyses. Stresses near the weld pool are examined to explain results obtained in the finite element analyses and correlated with experimental observations. Good agreement is obtained between simulation and experiment for locations of crack initiation and extent of cracking. Some effects of uncertainties in material parameters are discussed.

  2. Identification of modes of fracture in a 2618-T6 aluminum alloy using stereophotogrammetry

    SciTech Connect

    Salas Zamarripa, A.; Mata, M.P. Guerrero; Morales, M. Castillo; Beber-Solano, T.P.

    2011-12-15

    The identification and the development of a quantification technique of the modes of fracture in fatigue fracture surfaces of a 2618-T6 aluminum alloy were developed during this research. Fatigue tests at room and high temperature (230 Degree-Sign C) were carried out to be able to compare the microscopic fractographic features developed by this material under these testing conditions. The overall observations by scanning electron microscopy (SEM) of the fracture surfaces showed a mixture of transgranular and ductile intergranular fracture. The ductile intergranular fracture contribution appears to be more significant at room temperature than at 230 Degree-Sign C. A quantitative methodology was developed to identify and to measure the contribution of these microscopic fractographic features. The technique consisted of a combination of stereophotogrammetry and image analysis. Stereo-pairs were randomly taken along the crack paths and were then analyzed using the profile module of MeX software. The analysis involved the 3-D surface reconstruction, the trace of primary profile lines in both vertical and horizontal directions within the stereo-pair area, the measurements of the contribution of the modes of fracture in each profile, and finally, the calculation of the average contribution in each stereo-pair. The technique results confirmed a higher contribution of ductile intergranular fracture at room temperature than at 230 Degree-Sign C. Moreover, there was no indication of a direct relationship between this contribution and the strain amplitudes range applied during the fatigue testing. - Highlights: Black-Right-Pointing-Pointer Stereophotogrammetry and image analysis as a measuring tool of modes of fracture in fatigue fracture surfaces. Black-Right-Pointing-Pointer A mixture of ductile intergranular and transgranular fracture was identified at room temperature and 230 Degree-Sign C testing. Black-Right-Pointing-Pointer Development of a quantitative methodology to

  3. Ratcheting fatigue behaviour of Al-7075 T6 alloy: Influence of stress parameters

    NASA Astrophysics Data System (ADS)

    Amarnath, Lala; Bhattacharjee, Antara; Dutta, K.

    2016-02-01

    The use of aluminium and aluminium based alloys are increasing rapidly on account of its high formability, good thermal and electrical conductivity, high strength and lightness. Aluminium alloys are extensively used in aerospace, automobile, marine and space research industries and are also put into structural applications where chances of fatigue damage cannot be ruled out. In the current work, it is intended to study the ratcheting fatigue behavior of 7075-T6 aluminium alloy at room temperature. This Al alloy is potentially used in aviation, marine and automotive components as well as in bicycle parts, rock mounting equipment and parts of ammunition where there is every chance of failure of the parts due to deformation caused by ratcheting. Ratcheting is the process of accruement of plastic stain produced when a component is subjected to asymmetric cyclic loading under the influence of low cycle fatigue. To accomplish the requirements of the projected research, stress-controlled cyclic loading experiments were done using a ±250 kN servo-hydraulic universal testing machine (Instron: 8800R). The effect of stress parameters such as mean stress and stress amplitude were investigated on the ratcheting behavior of the selected aluminium alloy. It was observed that, ratcheting strain increased with increase in the value of stress amplitude at any constant mean stress while a saturation in strain accumulation attained in the investigated material after around 10-20 cycles, under all test conditions. The analyses of hysteresis loop generated during cyclic loading indicate that the material exhibits cyclic hardening in the initial fifty cycles which gets softened in further loading up to about 70-80 cycles and finally attains a steady state. The increase in the ratcheting strain value with stress parameters happens owing to increased deformation domain during cycling. The cyclic hardening accompanied by softening is correlated with characteristic precipitation features of

  4. Sensitivity of polycrystal plasticity to slip system kinematic hardening laws for Al 7075-T6

    DOE PAGES

    Hennessey, Conor; Castelluccio, Gustavo M.; McDowell, David L.

    2017-02-01

    The prediction of formation and early growth of microstructurally small fatigue cracks requires use of constitutive models that accurately estimate local states of stress, strain, and cyclic plastic strain. However, few research efforts have attempted to systematically consider the sensitivity of overall cyclic stress-strain hysteresis and higher order mean stress relaxation and plastic strain ratcheting responses introduced by the slip system back-stress formulation in crystal plasticity, even for face centered cubic (FCC) crystal systems. This paper explores the performance of two slip system level kinematic hardening models using a finite element crystal plasticity implementation as a User Material Subroutine (UMAT)more » within ABAQUS, with fully implicit numerical integration. The two kinematic hardening formulations aim to reproduce the cyclic deformation of polycrystalline Al 7075-T6 in terms of both macroscopic cyclic stress-strain hysteresis loop shape, as well as ratcheting and mean stress relaxation under strain- or stress-controlled loading with mean strain or stress, respectively. The first formulation is an Armstrong-Frederick type hardening-dynamic recovery law for evolution of the back stress. This approach is capable of reproducing observed deformation under completely reversed uniaxial loading conditions, but overpredicts the rate of cyclic ratcheting and associated mean stress relaxation. The second formulation corresponds to a multiple back stress Ohno-Wang type hardening law with nonlinear dynamic recovery. The adoption of this back stress evolution law greatly improves the capability to model experimental results for polycrystalline specimens subjected to cycling with mean stress or strain. As a result, the relation of such nonlinear dynamic recovery effects are related to slip system interactions with dislocation substructures.« less

  5. Structural insights into methanol-stable variants of lipase T6 from Geobacillus stearothermophilus.

    PubMed

    Dror, Adi; Kanteev, Margarita; Kagan, Irit; Gihaz, Shalev; Shahar, Anat; Fishman, Ayelet

    2015-11-01

    Enzymatic production of biodiesel by transesterification of triglycerides and alcohol, catalyzed by lipases, offers an environmentally friendly and efficient alternative to the chemically catalyzed process while using low-grade feedstocks. Methanol is utilized frequently as the alcohol in the reaction due to its reactivity and low cost. However, one of the major drawbacks of the enzymatic system is the presence of high methanol concentrations which leads to methanol-induced unfolding and inactivation of the biocatalyst. Therefore, a methanol-stable lipase is of great interest for the biodiesel industry. In this study, protein engineering was applied to substitute charged surface residues with hydrophobic ones to enhance the stability in methanol of a lipase from Geobacillus stearothermophilus T6. We identified a methanol-stable variant, R374W, and combined it with a variant found previously, H86Y/A269T. The triple mutant, H86Y/A269T/R374W, had a half-life value at 70 % methanol of 324 min which reflects an 87-fold enhanced stability compared to the wild type together with elevated thermostability in buffer and in 50 % methanol. This variant also exhibited an improved biodiesel yield from waste chicken oil compared to commercial Lipolase 100L® and Novozyme® CALB. Crystal structures of the wild type and the methanol-stable variants provided insights regarding structure-stability correlations. The most prominent features were the extensive formation of new hydrogen bonds between surface residues directly or mediated by structural water molecules and the stabilization of Zn and Ca binding sites. Mutation sites were also characterized by lower B-factor values calculated from the X-ray structures indicating improved rigidity.

  6. Recovery of Mechanical Properties of a 6061-T6 Aluminum Weld by Heat Treatment After Welding

    NASA Astrophysics Data System (ADS)

    Pérez, Javier Serrano; Ambriz, Ricardo Rafael; López, Francisco Fernando Curiel; Vigueras, David Jaramillo

    2016-07-01

    The dilution effects in welds of a 6061-T6 (Al-Si-Mg) alloy obtained by the modified indirect electric arc (MIEA), using an ER4043 filler metal (Al-Si), and postweld heat treatment (PWHT) were analyzed. The soft zone (55 to 70 HV0.1) formed by the microstructural transformation in the heat-affected zone (HAZ) was eliminated. The hardness measurements were presented on a traditional microhardness profile and mapping representation. A hardening effect of the fusion zone was observed; the hardness values were above 120 HV0.1 and tended to be uniform. This behavior could be attributed to the chemical composition of the filler metal, the Mg migration from the base to the weld metal, and the reversible process of the PWHT, which promotes precipitation hardening. Improvement for yield (260 MPa) and tensile strength (310 MPa) of the MIEA joints was observed; these values were similar to those obtained for the base metal. However, the presence of porosity in the fusion zone limits the ductility of the joints (4.3 pct). Even though the yield and tensile strengths of the base metal and welded joints were similar, the stress concentration due to porosity in the weld metal generated data dispersion in fatigue life. As a consequence, the high-cycle fatigue life decreases with respect to the base metal. In contrast, when the crack propagates under elastic conditions, the crack-tip singularity is affected by the porosity in the weld metal (stress liberator). This aspect, in conjunction with the hardening effect in joints subjected to PWHT, improves the fatigue crack growth rate when compared to the as-welded condition.

  7. Multistage Fatigue Modeling of Cast A356-T6 and A380-F Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Xue, Y.; Burton, C. L.; Horstemeyer, M. F.; McDowell, D. L.; Berry, J. T.

    2007-08-01

    This article presents a microstructure-based multistage fatigue (MSF) model extended from the model developed by McDowell et al.[1,2] to an A380-F aluminum alloy to consider microstructure-property relations of descending order, signifying deleterious effects of defects/discontinuities: (1) pores or oxides greater than 100 μm, (2) pores or oxides greater than 50 μm near the free surface, (3) a high porosity region with an area greater than 200 μm, and (4) oxide film of an area greater than 10,000 μm2. These microconstituents, inclusions, or discontinuities represent different casting features that may dominate fatigue life at stages of fatigue damage evolutions. The incubation life is estimated using a modified Coffin Mansion law at the microscale based on the microplasticity at the discontinuity. The microstructurally small crack (MSC) and physically small crack (PSC) growth was modeled using the crack tip displacement as the driving force, which is affected by the porosity and dendrite cell size (DCS). When the fatigue damage evolves to several DCSs, cracks behave as long cracks with growth subject to the effective stress intensity factor in linear elastic fracture mechanics. Based on an understanding of the microstructures of A380-F and A356-T6 aluminum alloys, an engineering treatment of the MSF model was introduced for A380-F aluminum alloys by tailoring a few model parameters based on the mechanical properties of the alloy. The MSF model is used to predict the upper and lower bounds of the experimental fatigue strain life and stress life of the two cast aluminum alloys.

  8. The structure of T6 human insulin at 1.0 A resolution.

    PubMed

    Smith, G David; Pangborn, Walter A; Blessing, Robert H

    2003-03-01

    The structure of T(6) human insulin has been determined at 120 K at a resolution of 1.0 A and refined to a residual of 0.183. As a result of cryofreezing, the first four residues of the B chain in one of the two crystallographically independent AB monomers in the hexameric [Zn(1/3)(AB)(2)Zn(1/3)](3) complex undergo a conformational shift that displaces the C(alpha) atom of PheB1 by 7.86 A relative to the room-temperature structure. A least-squares superposition of all backbone atoms of the room-temperature and low-temperature structures yielded a mean displacement of 0.422 A. Omitting the first four residues of the B chain reduced the mean displacement to 0.272 A. At 120 K, nine residues were found to exhibit two discrete side-chain conformations, but only two of these residues are in common with the seven residues found to have disordered side chains in the room-temperature structure. As a result of freezing, the disorder observed at room temperature in both ArgB22 side chains is eliminated. The close contact between pairs of O( epsilon 2) atoms in GluB13 observed at room temperature is maintained at cryotemperature and suggests that a carboxylate-carboxylic acid centered hydrogen bond exists [-C(=O)-O.H.O-C(=O)-] such that the H atom is equally shared between the two partially charged O atoms.

  9. Sensitivity of polycrystal [local] plasticity to slip system kinematic hardening laws for Al 7075-T6

    DOE PAGES

    Hennessey, Conor; Castelluccio, Gustavo M.; McDowell, David L.

    2017-01-22

    The prediction of formation and early growth of microstructurally small fatigue cracks requires use of constitutive models that accurately estimate local states of stress, strain, and cyclic plastic strain. However, few research efforts have attempted to systematically consider the sensitivity of overall cyclic stress-strain hysteresis and higher order mean stress relaxation and plastic strain ratcheting responses introduced by the slip system back-stress formulation in crystal plasticity, even for face centered cubic (FCC) crystal systems. This paper explores the performance of two slip system level kinematic hardening models using a finite element crystal plasticity implementation as a User Material Subroutine (UMAT)more » within ABAQUS, with fully implicit numerical integration. The two kinematic hardening formulations aim to reproduce the cyclic deformation of polycrystalline Al 7075-T6 in terms of both macroscopic cyclic stress-strain hysteresis loop shape, as well as ratcheting and mean stress relaxation under strain- or stress-controlled loading with mean strain or stress, respectively. The first formulation is an Armstrong-Frederick type hardening-dynamic recovery law for evolution of the back stress. This approach is capable of reproducing observed deformation under completely reversed uniaxial loading conditions, but overpredicts the rate of cyclic ratcheting and associated mean stress relaxation. The second formulation corresponds to a multiple back stress Ohno-Wang type hardening law with nonlinear dynamic recovery. The adoption of this back stress evolution law greatly improves the capability to model experimental results for polycrystalline specimens subjected to cycling with mean stress or strain. As a result, the relation of such nonlinear dynamic recovery effects are related to slip system interactions with dislocation substructures.« less

  10. [Effects of blueberry on apoptosis and expression of Bcl-2 and Bax in HSC-T6].

    PubMed

    Lu, Shuang; Cheng, Mingliang; Yang, Demeng; Liu, Yang; Guan, Li; Wu, Jun

    2015-08-18

    To investigate the effects of blueberry on the apoptosis, expression of Bcl-2 and Bax in rat hepatic stellate cell (HSC-T6). 10% blueberry serum at low, middle and high dose, 10% Fu-Fang-Bie-Jia-Ruan-Gan tablet serum and 10% saline serum were prepared by method of serum pharmacology. Subcultured HSC-T6 was divided into saline serum control group, blueberry serum at low, middle, high dose and Fu-Fang-Bie-Jia-Ruan-Gan tablet serum group, and then was respectively incubated at different dose of 10% blueberry serum, 10% Fu-Fang-Bie-Jia-Ruan-Gan tablet serum and 10% saline serum for 72 hours.Apoptosis of HSC-T6 was detected using flow cytometry with annexin V FITC/PI double staining. The expression of Bcl-2 and Bax in HSC-T6 were examined using immunocytochemistry and Western blotting, respectively. There was no significant difference for HSC-T6 Bax protein expression in the low, middle and high dose blueberry serum groups, compared with saline serum control group, respectively.In the high-dose blueberry serum group HSC-T6 early and total apoptosis rate increased significantly compared with the saline serum control group (5.55% ± 0.98% vs 2.53% ± 0.46%, 7.01% ± 1.05% vs 2.96% ± 0.81%, both P<0.05); Bcl-2 protein expression was significantly decreased (A value, 82 ± 35 vs 51 ± 13, P<0.05); Bcl-2/Bax ratio was significantly decreased (0.26 ± 0.02 vs 0.46 ± 0.03, P<0.05); HSC-T6 early and total apoptosis rate, Bcl-2 expression and Bcl-2/Bax ratio in the low and the middle dose blueberry serum group showed no significant difference with the saline serum control group. Blueberry can induce HSC-T6 apoptosis by down-regulating Bcl-2 expression and decreasing the ratio of Bcl-2/Bax in HSC-T6 cells, so it may have potential interference effects on hepatic fibrosis.

  11. Diversity of the biosynthesis pathway for threonylcarbamoyladenosine (t6A), a universal modification of tRNA

    PubMed Central

    Thiaville, Patrick C; Iwata-Reuyl, Dirk; de Crécy-Lagard, Valérie

    2014-01-01

    The tRNA modification field has a rich literature covering biochemical analysis going back more than 40 years, but many of the corresponding genes were only identified in the last decade. In recent years, comparative genomic-driven analysis has allowed for the identification of the genes and subsequent characterization of the enzymes responsible for N6-threonylcarbamoyladenosine (t6A). This universal modification, located in the anticodon stem-loop at position 37 adjacent to the anticodon of tRNAs, is found in nearly all tRNAs that decode ANN codons. The t6A biosynthesis enzymes and synthesis pathways have now been identified, revealing both a core set of enzymes and kingdom-specific variations. This review focuses on the elucidation of the pathway, diversity of the synthesis genes, and proposes a new nomenclature for t6A synthesis enzymes. PMID:25629598

  12. Investigating the presence of predatory bacteria on algal bloom samples using a T6SS gene marker.

    NASA Astrophysics Data System (ADS)

    Hendricks, J.; Sison-Mangus, M.; Mehic, S.; McMahon, E.

    2015-12-01

    Predation is considered to be a major driving force in evolution and ecology, which has been observed affecting individual organisms, communities, and entire ecosystems. The type VI secretion system (T6SS) is an intermembranal protein complex identified in certain bacteria, which appears to have evolved strictly as a mechanism of predation. The effects of bacteria on phytoplankton physiology are still understudied, however, studies have shown that the interactions between bacteria that inhabit the phycosphere of phytoplankton can possibly result in coevolution of native host and microbiota. It is unclear if bacteria can prey upon other bacteria to gain advantages during periods of high phytoplankton density. Here, we investigate the predatory interactions between bacteria and analyze environmental samples for the presence of predatory bacterial genes in an effort to understand bacteria-bacteria and phytoplankton interactions during algal blooms. DNA were extracted from bacterial samples collected weekly from size-fractionated samples using 3.0 um and 0.2 um membrane filters at the Santa Cruz wharf. PCR amplification and gel visualization for the presence of T6SS gene was carried out on bloom and non-bloom samples. Moreover, we carried out a lab- based experiment to observe bacteria-bacteria interaction that may hint for the presence of predatory behavior between bacterial taxa. We observed what appeared to be a predatory biofilm formation between certain bacterial species. These bacteria, however, did not contain the T6SS genes. On the contrary the T6SS gene was discovered in some of the bloom samples gathered from the Santa Cruz wharf. It is still unclear if the predatory mechanisms facilitate the abundance of certain groups of bacteria that contain the T6SS genes during algal blooms, but our evidence suggest that bacterial predation through T6SS mechanism is present during bloom events.

  13. Flow and fracture behavior of aluminum alloy 6082-T6 at different tensile strain rates and triaxialities.

    PubMed

    Chen, Xuanzhen; Peng, Yong; Peng, Shan; Yao, Song; Chen, Chao; Xu, Ping

    2017-01-01

    This study aims to investigate the flow and fracture behavior of aluminum alloy 6082-T6 (AA6082-T6) at different strain rates and triaxialities. Two groups of Charpy impact tests were carried out to further investigate its dynamic impact fracture property. A series of tensile tests and numerical simulations based on finite element analysis (FEA) were performed. Experimental data on smooth specimens under various strain rates ranging from 0.0001~3400 s-1 shows that AA6082-T6 is rather insensitive to strain rates in general. However, clear rate sensitivity was observed in the range of 0.001~1 s-1 while such a characteristic is counteracted by the adiabatic heating of specimens under high strain rates. A Johnson-Cook constitutive model was proposed based on tensile tests at different strain rates. In this study, the average stress triaxiality and equivalent plastic strain at facture obtained from numerical simulations were used for the calibration of J-C fracture model. Both of the J-C constitutive model and fracture model were employed in numerical simulations and the results was compared with experimental results. The calibrated J-C fracture model exhibits higher accuracy than the J-C fracture model obtained by the common method in predicting the fracture behavior of AA6082-T6. Finally, the Scanning Electron Microscope (SEM) of fractured specimens with different initial stress triaxialities were analyzed. The magnified fractographs indicate that high initial stress triaxiality likely results in dimple fracture.

  14. Draft Genome Sequence of Geobacillus sp. Isolate T6, a Thermophilic Bacterium Collected from a Thermal Spring in Argentina

    PubMed Central

    Ortiz, Elio M.; Berretta, Marcelo F.; Benintende, Graciela B.; Zandomeni, Rubén O.

    2015-01-01

    Geobacillus sp. isolate T6 was collected from a thermal spring in Salta, Argentina. The draft genome sequence (3,767,773 bp) of this isolate is represented by one major scaffold of 3,46 Mbp, a second one of 207 kbp, and 20 scaffolds of <13 kbp. The assembled sequences revealed 3,919 protein-coding genes. PMID:26184933

  15. Flow and fracture behavior of aluminum alloy 6082-T6 at different tensile strain rates and triaxialities

    PubMed Central

    Chen, Xuanzhen; Peng, Shan; Yao, Song; Chen, Chao; Xu, Ping

    2017-01-01

    This study aims to investigate the flow and fracture behavior of aluminum alloy 6082-T6 (AA6082-T6) at different strain rates and triaxialities. Two groups of Charpy impact tests were carried out to further investigate its dynamic impact fracture property. A series of tensile tests and numerical simulations based on finite element analysis (FEA) were performed. Experimental data on smooth specimens under various strain rates ranging from 0.0001~3400 s-1 shows that AA6082-T6 is rather insensitive to strain rates in general. However, clear rate sensitivity was observed in the range of 0.001~1 s-1 while such a characteristic is counteracted by the adiabatic heating of specimens under high strain rates. A Johnson-Cook constitutive model was proposed based on tensile tests at different strain rates. In this study, the average stress triaxiality and equivalent plastic strain at facture obtained from numerical simulations were used for the calibration of J-C fracture model. Both of the J-C constitutive model and fracture model were employed in numerical simulations and the results was compared with experimental results. The calibrated J-C fracture model exhibits higher accuracy than the J-C fracture model obtained by the common method in predicting the fracture behavior of AA6082-T6. Finally, the Scanning Electron Microscope (SEM) of fractured specimens with different initial stress triaxialities were analyzed. The magnified fractographs indicate that high initial stress triaxiality likely results in dimple fracture. PMID:28759617

  16. Epoxyeicosatrienoic acids induce growth inhibition and calpain/caspase-12 dependent apoptosis in PDGF cultured 3T6 fibroblast.

    PubMed

    Nieves, Diana; Moreno, Juan J

    2007-11-01

    Previous studies have demonstrated that arachidonic acid (AA) metabolites released by the cyclooxygenase pathway is involved in serum-induced 3T6 fibroblast cycle progression and proliferation. However, these results also suggest that other AA cascade pathways might be involved. Recently, we also described the role of hydroxyeicosatetraenoic acids, which are produced by cytochrome P450 monooxygenases (CYP), in 3T6 fibroblast growth. AA can be also metabolized by the epoxygenase activity of CYP-producing epoxyeicosatrienoic acids (EETs). Finally, the cytosolic epoxide hydrolases catalyze the hydration of the EETs, transforming them into dihydroxyeicosatetraenoic acids (DHETEs). In this work, we have studied the role of the EETs/DHETEs on 3T6 fibroblasts growth. Our results show that PDGF stimulates 3T6 fibroblast proliferation and [3H]thymidine incorporation, while the addition of 5,6-EET, 8,9-EET, 11,12-EET or 14,15-EET (0.1-1 microM) inhibit these processes. Furthermore, 5,6-DHETE and 11,12-DHETE (0.1-1 microM) also inhibit cell proliferation and DNA synthesis. Interestingly, this growth inhibition was correlated with an induction of apoptosis. Thus, we observed that in the presence of PDGF, EETs or DHETEs (0.1-1 microM) induce phosphatidylserine externalization (as measured by annexin V-binding) and DNA fragmentation (as quantified using a TUNEL assay). Our results show that calpain, as well as caspase-12 and caspase-3, are involved in these events. Therefore, EETs and DHETEs have anti-proliferative and pro-apoptotic effects on PDGF-stimulated 3T6 fibroblasts.

  17. Estudio numerico y experimental del proceso de soldeo MIG sobre la aleacion 6063--T5 utilizando el metodo de Taguchi

    NASA Astrophysics Data System (ADS)

    Meseguer Valdenebro, Jose Luis

    improvement on mechanical properties in aluminum metal joint. Los procesos de soldadura por arco electrico representan unas de las tecnicas mas utilizadas en los procesos de fabricacion de componentes mecanicos en la industria moderna. Los procesos de soldeo por arco se han adaptado a las necesidades actuales, haciendose un modo de fabricacion flexible y versatil. Los resultados obtenidos numericamente en el proceso de soldadura son validados experimentalmente. Los principales metodos numericos mas empleados en la actualidad son tres, metodo por diferencias finitas, metodos por elementos finitos y metodo por volumenes finitos. El metodo numerico mas empleado para el modelado de uniones soldadas, es el metodo por elementos finitos, debido a que presenta una buena adaptacion a las condiciones geometricas y de contorno ademas de que existe una diversidad de programas comerciales que utilizan el metodo por elementos finitos como base de calculo. Este trabajo de investigacion presenta un estudio experimental de una union soldada mediante el proceso MIG de la aleacion de aluminio 6063-T5. El metodo numerico se valida experimentalmente aplicando el metodo de los elementos finitos con el programa de calculo ANSYS. Los resultados experimentales obtenidos son: las curvas de enfriamiento, el tiempo critico de enfriamiento t4/3, geometria del cordon, microdurezas obtenidas en la union soldada, zona afectada termicamente y metal base, dilucion del proceso, areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Los resultados numericos son: las curvas del ciclo termico, que representan tanto el calentamiento hasta alcanzar la temperatura maxima y un posterior enfriamiento. Se calculan el tiempo critico de enfriamiento t4/3, el rendimiento termico y se representa la geometria del cordon obtenida experimentalmente. La zona afectada termicamente se obtiene diferenciando las zonas que se encuentran a diferentes temperaturas, las areas criticas intersecadas entre las

  18. Determination of the dynamic stress intensity factors for 7075-T6 aluminum alloy using the reflected caustic method

    SciTech Connect

    Tsukagoshi, Seiji; Takahashi, Susumu; Shimamoto, Akira

    1996-12-31

    Dynamic fracture initiation and propagation in Al 7075-T6 was investigated experimentally using the optical method of reflected caustics combined with a simplified high speed photography. A crack propagation testing configuration consisting of a three point bending specimen loaded In a drop weighting was used. It was found that prior to crack initiation the stress intensity factor time record calculated using the dynamic impact load and a static formula disagrees with the actual stress Intensity factor measured by caustics. The impact fracture tests are performed. With use of Al 7075-T6 band plate test specimens with a V-notch on their one side. The dynamic stress intensity factor K{sub id} are given. With this, the authors experimentally calculated the dynamic fracture toughness K{sub ID}.

  19. Over-aging of aluminum alloys. Final report. [7050-T736; 7075-T6; 9021-T4; 9052-F

    SciTech Connect

    Ulitchny, M.G.

    1983-12-01

    The effects of short-time over-aging on the mechanical properties of aluminum alloys 7050-T736, 7075-T6, 9021-T4, and 9052-F have been evaluated. Test results show that when subjected to a temperature of 600/sup 0/F for short periods of time, the 7XXX series alloys lose almost all of the tensile strength they received through heat treatment; alloy 9021-T4 loses less of its strength; and 9052-F loses almost none of its strength. Tensile tests carried out on 7050-T736 and 7075-T6 in both the as-received and stress-relief-annealed conditions have confirmed that the stress relief anneal has little or no effect on tensile strength.

  20. Effect of microstructural factors on fracture toughness of a 2124-T6 Al-SiC(w) composite

    SciTech Connect

    Kim, Young-Hwan; Lee, Sunghak; Kwon, Dongil Changwon National University, )

    1992-05-01

    The effect of microstructure on the fracture toughness of 2124-T6 aluminum reinforced with 15 vol pct SiC whiskers was investigated using results of fracture toughness tests and SEM observations. In order to analyze fracture behavior of the composite, a micromechanical fracture model involving ductile fracture initiation was adopted, from which the critical characteristic distance and the critical equivalent strain were calculated to be 14 microns and 0.07, respectively. The computed critical distance agreed well with the average size of secondary roughness on fracture surfaces and with the spacing of large scale microstuctural parameters such as coarse Mn-containing particles, which significantly affect the fracture behavior of the 2124-T6 Al/SiC(w) composite. 14 refs.

  1. Enhancement of methotrexate resistance and dihydrofolate reductase gene amplification by treatment of mouse 3T6 cells with hydroxyurea.

    PubMed Central

    Brown, P C; Tlsty, T D; Schimke, R T

    1983-01-01

    We investigated various parameters associated with the initial selection of mouse 3T6 cells for resistance to single concentrations of methotrexate and characterized resistant colonies for the presence of additional (amplified) copies of the dihydrofolate reductase gene. Our results indicate that the frequency of occurrence of dihydrofolate reductase gene amplification varies with the selecting concentration of methotrexate and is highly variable between clonally derived sublines of mouse 3T6 cells. Second, we increased the frequency of occurrence of cells with amplified dihydrofolate reductase genes by transiently inhibiting DNA synthesis with hydroxyurea before the selection of cells in single concentrations of methotrexate. This effect was dependent on the concentration of hydroxyurea, the time of exposure to the drug, and the time interval between the removal of hydroxyurea and the selection of cells in methotrexate. Images PMID:6877240

  2. Characterization of Retrogression and Re-Aging Heat Treatment of AA7075-T6 Using Nonlinear Acoustics and Eddy Current

    SciTech Connect

    Ananthula, Rajeshwar; Ko, Ray T.; Sathish, Shamachary; Blodgett, Mark

    2004-02-26

    Nonlinear acoustic parameter and eddy current methods have been utilized to characterize the heat treatment process of retrogression and re-aging of aluminum 7075-T6. The results of nonlinear acoustic parameter measurements show two distinct peaks at 30 minutes and 45 minutes of retrogression time. The phase of the through-thickness eddy current signal shows a minimum at 42 minutes of retrogression time. Application of combined methods for identifying the optimized properties in the material is discussed.

  3. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; Brown, D. W.; Clausen, B; An, Ke; Choo, Hahn; Hubbard, Camden R; David, Stan A

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in-situ, time-resolved neutron diffraction technique. A method is developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  4. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Feng, Zhili; Wang, Xun-Li; David, Stan A; Choo, Hahn; Hubbard, Camden R; Woo, Wan Chuck; Brown, D. W.; Clausen, B; An, Ke

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in situ, time resolved neutron diffraction technique. A method was developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  5. Microstructure and Mechanical Properties of Welded Joints of Aluminum Alloy AA7020-T6 Obtained by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Srinivasa Rao, G.; Subba Rao, V. V.; Rao, S. R. K.

    2017-07-01

    Plates from alloy AA7020 (Al - Zn - Mg) with a thickness of 4.5 mm are studied after T6 heat treatment and friction stir welding. Tensile and bending tests are performed. The hardness of the welds is measured in transverse direction. The microstructure over cross section of a weld is studied by the methods of light and transmission electron microscopy. The weldability of alloy AA7020 by friction stir welding is shown to be high.

  6. Structural and functional characterization of KEOPS dimerization by Pcc1 and its role in t6A biosynthesis

    PubMed Central

    Wan, Leo C.K.; Pillon, Monica C.; Thevakumaran, Neroshan; Sun, Yulong; Chakrabartty, Avi; Guarné, Alba; Kurinov, Igor; Durocher, Daniel; Sicheri, Frank

    2016-01-01

    KEOPS is an ancient protein complex required for the biosynthesis of N6-threonylcarbamoyladenosine (t6A), a universally conserved tRNA modification found on all ANN-codon recognizing tRNAs. KEOPS consist minimally of four essential subunits, namely the proteins Kae1, Bud32, Cgi121 and Pcc1, with yeast possessing the fifth essential subunit Gon7. Bud32, Cgi121, Pcc1 and Gon7 appear to have evolved to regulate the central t6A biosynthesis function of Kae1, but their precise function and mechanism of action remains unclear. Pcc1, in particular, binds directly to Kae1 and by virtue of its ability to form dimers in solution and in crystals, Pcc1 was inferred to function as a dimerization module for Kae1 and therefore KEOPS. We now present a 3.4 Å crystal structure of a dimeric Kae1–Pcc1 complex providing direct evidence that Pcc1 can bind and dimerize Kae1. Further biophysical analysis of a complete archaeal KEOPS complex reveals that Pcc1 facilitates KEOPS dimerization in vitro. Interestingly, while Pcc1-mediated dimerization of KEOPS is required to support the growth of yeast, it is dispensable for t6A biosynthesis by archaeal KEOPS in vitro, raising the question of how precisely Pcc1-mediated dimerization impacts cellular biology. PMID:27302132

  7. Exploring the catalytic activity of pristine T6[100] surface for oxygen reduction reaction: A first-principles study

    NASA Astrophysics Data System (ADS)

    Banerjee, Paramita; Chakrabarty, Soubhik; Thapa, Ranjit; Das, G. P.

    2017-10-01

    The electrocatalytic activity of T6[100] surface containing both sp3 (C1) and sp2 (C2) hybridized carbon atoms is explored using first-principles density functional theory based approach. The top layered C1 atom of the surface is found to be more active towards the oxygen reduction reaction (ORR), as compared to that of C2 atom. This is attributed to the presence of dangling σ bond in the corresponding C1 atom, leading to the high electron density near the Ferrmi level. Whereas, the π electron in the top layered C2 atom forms a weak out of plane network. As estimated from free energy profile, the overpotential is much lower when C1 is considered as the active site and the final step i.e desorption of final OH- ion is found to be the potential determining step. We have also reported the effect of Si dopant on the catalytic activity of T6[100] surface and explained the origin of high overpotential value in this case. Thus in this report, we propose a new metal-free catalyst i.e T6[100] surface, having both sp2 (maintains the high metallicity needed to reduce ohmic loss) and sp3 (helps in capturing the upcoming molecules) hybridized carbon atoms, as a potential candidate for ORR.

  8. UV spectroscopic identification and thermodynamic analysis of protonated third strand deoxycytidine residues at neutrality in the triplex d(C(+)-T)6:[d(A-G)6.d(C-T)6]; evidence for a proton switch.

    PubMed Central

    Lavelle, L; Fresco, J R

    1995-01-01

    Near-UV difference spectral analysis of the triplex formed from d(C-T)6 and d(A-G)6.d(C-T)6 in neutral and acidic solution shows that the third strand dC residues are protonated at pH 7.0, far above their intrinsic pKa. Additional support for ion-dipole interactions between the third strand dC residues and the G.C target base pairs comes from reduced positive dependence of triplet stability on ionic strength below 0.9 M Na+, inverse dependence above 0.9 M Na+ and strong positive dependence on hydrogen ion concentration. Molecular modeling (AMBER) of C:G.C and C+:G.C base triplets with the third strand base bound in the Hoogsteen geometry shows that only the C+:G.C triplet is energetically feasible. van't Hoff analysis of the melting of the triplex and target duplex shows that between pH 5.0 and 8.5 in 0.15 M NaCl/0.005 M MgCl2 the enthalpy of melting (delta H degree obs) varies from 5.7 to 6.6 kcal.mol-1 for the duplex in a duplex mixture and from 7.3 to 9.7 kcal.mol-1 for third strand dissociation in the triplex mixture. We have extended the condensation-screening theory of Manning to pH-dependent third strand binding. In this development we explicitly include the H+ contribution to the electrostatic free energy and obtain [formula: see text]. The number of protons released in the dissociation of the third strand from the target duplex at pH 7.0, delta n2, is thereby calculated to be 5.5, in good agreement with approximately six third strand dc residues per mole of triplex. This work shows that when third strand binding requires protonated residues that would otherwise be neutral, triplex formation and dissociation are mediated by proton uptake and release, i.e., a proton switch. As a by-product of this study, we have found that at low pH the Watson-Crick duplex d(A-G)6.d(C-T)6 undergoes a transition to a parallel Hoogsteen duplex d(A-G)6.d(C(+)-T)6. PMID:7651830

  9. The identification of the acid-base catalyst of alpha-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycoside hydrolase.

    PubMed

    Shallom, Dalia; Belakhov, Valery; Solomon, Dmitry; Gilead-Gropper, Sara; Baasov, Timor; Shoham, Gil; Shoham, Yuval

    2002-03-13

    The alpha-L-arabinofuranosidase from Geobacillus stearothermophilus T-6 (AbfA T-6) belongs to the retaining family 51 glycoside hydrolases. The conserved Glu175 was proposed to be the acid-base catalytic residue. AbfA T-6 exhibits residual activity towards aryl beta-D-xylopyranosides. This phenomenon was used to examine the catalytic properties of the putative acid-base mutant E175A. Data from kinetic experiments, pH profiles, azide rescue, and the identification of the xylopyranosyl azide product provide firm support to the assignment of Glu175 as the acid-base catalyst of AbfA T-6.

  10. A Williams syndrome patient with a familial t(6;7) translocation and deletion of the elastin gene

    SciTech Connect

    Pober, B.R.; Gibson, L.H.; Yang-Feng, T.L.

    1994-09-01

    Discovery of a {open_quotes}balanced{close_quotes} reciprocal translocation [46,XX,t(6;7)(q11.2;q11.23)] on routine amniocentesis prompted clinical and cytogenetic study of additional family members. The same t(6;7) translocation was found in the clincally normal father and in a sibling with Williams syndrome (WS). WS had been diagnosed previously according to clinical criteria including distinctive facial features, supravalvar aortic stenosis requiring surgical repair, dental abnormalties and developmental delay. A clinically normal female was delivered and the translocation was confirmed with a cord blood specimen. Hemizygosity for the gene, elastin, (which has been mapped to the chromosome 7 translocation breakpoint, 7q11.23, in this family) appears to be a cause of WS. We therefore investigated whether the t(6;7) in the phenotypically normal father represented more than a simple reciprocal translocation. FISH using a chromosome 7 specific library revealed no differences between the cytogenetically identical, yet phenotypically distinct, father and son. Hybridization with a cosmid MR127D4 containing elastin sequence showed that the WS patient was missing one allele from the derivative chromosome 7 whereas both his mother and father had two copies of the elastin gene. This family indicates that the de novo loss of one copy of the elastin gene produces the recognizable phenotype of Williams syndrome. Molecular characterization (with additional probes) of the extent of this de novo deletion near the translocation breakpoint is in progress. This information will be valuable for defining the WS-critical region and will lead to a better understanding of the molecular basis for WS.

  11. Electrochemical investigation on the hydrogen permeation behavior of 7075-T6 Al alloy and its influence on stress corrosion cracking

    NASA Astrophysics Data System (ADS)

    Zheng, Chuan-bo; Yan, Bing-hao; Zhang, Ke; Yi, Guo

    2015-07-01

    The hydrogen permeation behavior and stress corrosion cracking (SCC) susceptibility of precharged 7075-T6 Al alloy were investigated in this paper. Devanthan-Stachurski (D-S) cell tests were used to measure the apparent hydrogen diffusivity and hydrogen permeation current density of specimens immersed in 3.5wt% NaCl solution. Electrochemical experiment results show that the SCC susceptibility is low during anodic polarization. Both corrosion pits and hydrogen-induced cracking are evident in scanning electron microscope images after the specimens have been charging for 24 h.

  12. Free Energy of the Three-Dimensional Spin-12 Quantum Heisenberg Model to O[T6

    NASA Astrophysics Data System (ADS)

    Chang, Chih-chun

    2001-11-01

    By applying the Friedberg-Lee-Ren's theorem (Ann. Phys. (N.Y.) 228, 52 (1993)) to the spin-12 three-dimensional isotropic quantum Heisenberg system, we obtain the low-temperature expansion of the free energy through a field theoretical calculation done in the equivalent lattice boson system. We reproduced Dyson's result and also extended it from T5 to T6. Nevertheless, because of the peculiar property of the spin operator being neither bosonic nor fermionic, the extension is not easy to obtain by other method.

  13. Caffeic acid phenethyl ester up-regulates antioxidant levels in hepatic stellate cell line T6 via an Nrf2-mediated mitogen activated protein kinases pathway

    PubMed Central

    Yang, Ning; Shi, Juan-Juan; Wu, Feng-Ping; Li, Mei; Zhang, Xin; Li, Ya-Ping; Zhai, Song; Jia, Xiao-Li; Dang, Shuang-Suo

    2017-01-01

    AIM To investigate the antioxidant effect of caffeic acid phenethyl ester (CAPE) in hepatic stellate cell-T6 (HSC-T6) cells cultured in vitro and the potential mechanisms. METHODS HSC-T6 cells were cultured in vitro and treated with various concentrations of CAPE for 24, 48 and 72 h, respectively. Cell proliferation was investigated using the MTT assay, and cell ultrastructural alterations were observed by transmission electron microscopy. Flow cytometry was employed to investigate the effects of CAPE on apoptosis and the levels of reactive oxygen species in HSC-T6 cells cultured in vitro. An enzyme immunoassay instrument was used to evaluate antioxidant enzyme expression. The effect on α-smooth muscle actin was shown using immunofluorescence. Gene and protein levels of Nrf2, related factors, and mitogen activated protein kinases (MAPKs), in HSC-T6 cells were detected using RT-PCR and Western blot, respectively. RESULTS CAPE inhibited the proliferation and activation of HSC-T6 cells cultured in vitro. CAPE increased the antioxidant levels and the translocation of Nrf2 from the cytoplasm to the nucleus in HSC-T6 cells. Moreover, the phosphorylation of MAPKs in cells decreased in response to CAPE. Interestingly, CAPE-induced oxidative stress in the cells was significantly attenuated by pretreatment with MAPKs inhibitors. CONCLUSION CAPE inhibits cell proliferation and up-regulates the antioxidant levels in HSC-T6 cells partly through the Nrf2-MAPKs signaling pathway. PMID:28275300

  14. A study of fatigue and fracture in 7075-T6 aluminum alloy in vacuum and air environments

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.

    1973-01-01

    Axial load fatigue life, fatigue-crack propagation, and fracture toughness experiments were conducted on sheet specimens made of 7075-T6 aluminum alloy. These experiments were conducted at pressures ranging from atmospheric to 5 x 10 to the minus 8th torr. Analysis of the results from the fatigue life experiments indicated that for a given stress level, lower air pressures produced longer fatigue lives. At a pressure of 5 x 10 to the minus 8th torr fatigue lives were 15 or more times as long as at atmospheric pressure. Analysis of the results from the fatigue crack propagation experiments indicated that for small stress intensity factor ranges the fatigue crack propagation rates were up to twice as high at atmospheric pressure as in vacuum. The fracture toughness of 7075-T6 was unaffected by the vacuum environment. Fractographic examination showed that specimens tested in both vacuum and air developed fatigue striations. Considerably more striations developed on specimens tested at atmospheric pressure, however.

  15. The anti-hepatic fibrosis activity of ergosterol depended on upregulation of PPARgamma in HSC-T6 cells.

    PubMed

    Tai, Chen-Jei; Choong, Chen-Yen; Lin, Yu-Chun; Shi, Yeu-Ching; Tai, Cheng-Jeng

    2016-04-01

    Advanced glycation endproducts (AGEs) were shown to play an important role in metabolic syndrome and were suggested to contribute to the development of hepatic fibrosis. Evidence indicates that AGEs resulted in hepatic fibrosis coupled to the activation of the receptor for AGEs (RAGE) in hepatic stellate cells (HSCs). NADPH oxidase is downstream of the RAGE signaling pathway, resulting in an increase in reactive oxygen species (ROS), alpha-smooth muscle actin (alpha-SMA), RAGE, and matrix metalloproteinase-9 (MMP-9). This study was designed to evaluate the effects of ergosterol on RAGE signaling in HSC-T6 cells. Ergosterol suppressed the activation of HSC-T6 cells induced by AGEs, and attenuated overexpressions of alpha-SMA, MMP-9, and epithelial-mesenchymal transition (EMT) markers, including N-cadherin and vimentin. We also found that these inhibitory effects of ergosterol on the activation of HSCs were dependent on peroxisome proliferator-activated receptor-gamma (PPARgamma) confirmed by PPARgamma reporter assay and PPARgamma knockdown. In addition, ergosterol also showed an inhibitory effect on the generation of AGEs, fructosamine, and α-dicarbonyl compounds in this study. Our results show that ergosterol can be used as a protective agent against hepatic fibrosis caused by induction of AGEs.

  16. An analytical electron microscopy study of constituent particles in commercial 7075-T6 and 2024-T3 alloys

    SciTech Connect

    Gao, M.; Feng, C.R.; Wei, R.P.

    1998-04-01

    To better understand the role of constituent particles in pitting corrosion, analytical electron microscopic studies were performed on the constituent particles in commercial 7075-T6 and 2024-T3 alloys. Five phases, namely, Al{sub 23}CuFe{sub 4} and amorphous SiO{sub 2} in 7075-T6 and Al{sub 2}CuMg, Al{sub 2}Cu, and (Fe,Mn){sub x}Si(Al,Cu){sub y} in 2024-T3, were identified. The crystal structure and chemistry of the Al{sub 23}CuFe{sub 4}, Al{sub 2}CuMg, and Al{sub 2}Cu phases in these alloys are in good agreement with the published data. Small deviations from their stoichiometric compositions were observed and are attributed to the influence of alloy composition on the phase chemistry. For the (Fe,Mn){sub x}Si(Al,Cu){sub y} (approximately, x = 3 and y = 11) phase, a rhombohedral structure, with lattice parameter a = b = c = 1.598 nm and {alpha} = {beta} = {gamma} = 75 deg, was identified and is believed to be a modified form of either Al{sub 8}Fe{sub 2}Si or Al{sub 10}Mn{sub 3}Si. Information from this study provided technical support for studying the electrochemical interactions between the individual particles (or phases) and the matrix. The corrosion results are reported in a companion article.

  17. An evaluation of the T-6A Texan (JPATS) initial functional performance of the CFIS laser assemblies

    NASA Astrophysics Data System (ADS)

    Blachowski, Thomas J.; Eccard, George; Thom, Travis

    2009-08-01

    The Indian Head Division, Naval Surface Warfare Center (IHDIV, NSWC) CAD Engineering Division is conducting a program to evaluate the laser components which comprise the Canopy Fracturing Initiation System (CFIS) currently installed on the T-6A Texan or JPATS (Joint Primary Aircraft Training System) aircraft. The T-6A Texan is the first aircraft used by the military to train future pilots. The CFIS is an element of the pilot emergency escape system which weakens the canopy in the path of the ejection seat. The CFIS is comprised of three differing configurations (Internal, External, and Seat Motion) which generate a laser pulse that is distributed through a fiber optic energy transmission system. This pulse, in turn, initiates explosive components which weaken the respective canopies. All of the CFIS laser types are flashlamp-pumped, neodymium glass lasers which are located at various positions in the aircraft cockpit area. This paper builds on the previous 2008 SPIE paper (Conference 7070) and presents further CAD Engineering Division test results and analysis which were utilized to evaluate the functional performance of the three CFIS laser signal generators after their being installed fleet applications over a period of time.

  18. The t(6)A modification acts as a positive determinant for the anticodon nuclease PrrC, and is distinctively nonessential in Streptococcus mutans.

    PubMed

    Bacusmo, Jo Marie; Orsini, Silvia S; Hu, Jennifer; DeMott, Michael; Thiaville, Patrick C; Elfarash, Ameer; Paulines, Mellie June; Rojas-Benítez, Diego; Meineke, Birthe; Deutsch, Chris; Iwata-Reuyl, Dirk; Limbach, Patrick A; Dedon, Peter C; Rice, Kelly C; Shuman, Stewart; Crécy-Lagard, Valérie de

    2017-07-20

    Endoribonuclease toxins (ribotoxins) are produced by bacteria and fungi to respond to stress, eliminate non-self competitor species, or interdict virus infection. PrrC is a bacterial ribotoxin that targets and cleaves tRNA(Lys)UUU in the anticodon loop. In vitro studies suggested that the post-transcriptional modification threonylcarbamoyl adenosine (t(6)A) is required for PrrC activity but this prediction had never been validated in vivo. Here, by using t(6)A-deficient yeast derivatives, it is shown that t(6)A is a positive determinant for PrrC proteins from various bacterial species. Streptococcus mutans is one of the few bacteria where the t(6)A synthesis gene tsaE (brpB) is dispensable and its genome encodes a PrrC toxin. We had previously shown using an HPLC-based assay that the S. mutans tsaE mutant was devoid of t(6)A. However, we describe here a novel and a more sensitive hybridization-based t(6)A detection method (compared to HPLC) that showed t(6)A was still present in the S. mutans ΔtsaE, albeit at greatly reduced levels (93% reduced compared with WT). Moreover, mutants in 2 other S. mutans t(6)A synthesis genes (tsaB and tsaC) were shown to be totally devoid of the modification thus confirming its dispensability in this organism. Furthermore, analysis of t(6)A modification ratios and of t(6)A synthesis genes mRNA levels in S. mutans suggest they may be regulated by growth phase.

  19. An extensive allelic series of Drosophila kae1 mutants reveals diverse and tissue-specific requirements for t6A biogenesis

    PubMed Central

    Lin, Ching-Jung; Smibert, Peter; Zhao, Xiaoyu; Hu, Jennifer F.; Ramroop, Johnny; Kellner, Stefanie M.; Benton, Matthew A.; Govind, Shubha; Dedon, Peter C.; Sternglanz, Rolf; Lai, Eric C.

    2015-01-01

    N6-threonylcarbamoyl-adenosine (t6A) is one of the few RNA modifications that is universally present in life. This modification occurs at high frequency at position 37 of most tRNAs that decode ANN codons, and stabilizes cognate anticodon–codon interactions. Nearly all genetic studies of the t6A pathway have focused on single-celled organisms. In this study, we report the isolation of an extensive allelic series in the Drosophila ortholog of the core t6A biosynthesis factor Kae1. kae1 hemizygous larvae exhibit decreases in t6A that correlate with allele strength; however, we still detect substantial t6A-modified tRNAs even during the extended larval phase of null alleles. Nevertheless, complementation of Drosophila Kae1 and other t6A factors in corresponding yeast null mutants demonstrates that these metazoan genes execute t6A synthesis. Turning to the biological consequences of t6A loss, we characterize prominent kae1 melanotic masses and show that they are associated with lymph gland overgrowth and ectopic generation of lamellocytes. On the other hand, kae1 mutants exhibit other phenotypes that reflect insufficient tissue growth. Interestingly, whole-tissue and clonal analyses show that strongly mitotic tissues such as imaginal discs are exquisitely sensitive to loss of kae1, whereas nonproliferating tissues are less affected. Indeed, despite overt requirements of t6A for growth of many tissues, certain strong kae1 alleles achieve and sustain enlarged body size during their extended larval phase. Our studies highlight tissue-specific requirements of the t6A pathway in a metazoan context and provide insights into the diverse biological roles of this fundamental RNA modification during animal development and disease. PMID:26516084

  20. An extensive allelic series of Drosophila kae1 mutants reveals diverse and tissue-specific requirements for t6A biogenesis.

    PubMed

    Lin, Ching-Jung; Smibert, Peter; Zhao, Xiaoyu; Hu, Jennifer F; Ramroop, Johnny; Kellner, Stefanie M; Benton, Matthew A; Govind, Shubha; Dedon, Peter C; Sternglanz, Rolf; Lai, Eric C

    2015-12-01

    N(6)-threonylcarbamoyl-adenosine (t6A) is one of the few RNA modifications that is universally present in life. This modification occurs at high frequency at position 37 of most tRNAs that decode ANN codons, and stabilizes cognate anticodon-codon interactions. Nearly all genetic studies of the t6A pathway have focused on single-celled organisms. In this study, we report the isolation of an extensive allelic series in the Drosophila ortholog of the core t6A biosynthesis factor Kae1. kae1 hemizygous larvae exhibit decreases in t6A that correlate with allele strength; however, we still detect substantial t6A-modified tRNAs even during the extended larval phase of null alleles. Nevertheless, complementation of Drosophila Kae1 and other t6A factors in corresponding yeast null mutants demonstrates that these metazoan genes execute t6A synthesis. Turning to the biological consequences of t6A loss, we characterize prominent kae1 melanotic masses and show that they are associated with lymph gland overgrowth and ectopic generation of lamellocytes. On the other hand, kae1 mutants exhibit other phenotypes that reflect insufficient tissue growth. Interestingly, whole-tissue and clonal analyses show that strongly mitotic tissues such as imaginal discs are exquisitely sensitive to loss of kae1, whereas nonproliferating tissues are less affected. Indeed, despite overt requirements of t6A for growth of many tissues, certain strong kae1 alleles achieve and sustain enlarged body size during their extended larval phase. Our studies highlight tissue-specific requirements of the t6A pathway in a metazoan context and provide insights into the diverse biological roles of this fundamental RNA modification during animal development and disease. © 2015 Lin et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  1. Effect of T6 heat treatment on the microstructural and mechanical properties of Al-Si-Cu-Mg alloys

    NASA Astrophysics Data System (ADS)

    Patel, Dhruv; Davda, Chintan; Solanki, P. S.; Keshvani, M. J.

    2016-05-01

    In this communication, it is aimed to optimize the conditions for T6 heat treatment of permanent die cast Al-Si-Cu-Mg alloys. Various solutionizing temperatures, aging treatments and soaking times were used to improve / modify the mechanical properties of presently studied alloys. Formation mechanism of the particles was understood by carrying out optical microscopy and energy dispersive X-ray (EDX) spectroscopy measurements. Spherical particles of alloys were studied for their microstructural properties using scanning electron microscopy (SEM). Microhardness test was performed to investigate their mechanical properties. Dependence of cluster formation and microhardness of the alloys on the adequate solutionizing temperature, aging treatment and soaking time has been discussed in detail.

  2. Effect of laser peening with different energies on fatigue fracture evolution of 6061-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Sheng, J.; Huang, S.; Zhou, J. Z.; Lu, J. Z.; Xu, S. Q.; Zhang, H. F.

    2016-03-01

    To deeply understand the effect of laser peening (LP) with different laser pulse energies on 6061-T6 aluminum alloy, the fatigue fracture morphologies evolution process at various fatigue crack growth (FCG) stages and the corresponding strengthen mechanism were investigated. At the initial stage of FCG, more fatigue micro-cliffs were found after LP, while the fatigue striation spacing simultaneously reduced. A "stop-continue" phenomenon of crack propagation was discovered for laser peened samples. The fatigue striation spacing at the middle stage of FCG increased significantly while compared with that at the initial stage, in addition, the fatigue striation spacing decreased with an increase in laser pulse energy. Fracture morphologies in transition region of laser peened samples exhibit a mixing fracture characteristic of striations and dimples. The laser peened sample with laser pulse energy of 7 J presents more circuitous growing paths. Due to the complex stress state induced by LP, dimples with different sizes appeared in the final fracture region.

  3. Effect of T6 heat treatment on the microstructural and mechanical properties of Al–Si–Cu–Mg alloys

    SciTech Connect

    Patel, Dhruv Davda, Chintan; Keshvani, M. J.; Solanki, P. S.

    2016-05-06

    In this communication, it is aimed to optimize the conditions for T6 heat treatment of permanent die cast Al–Si–Cu–Mg alloys. Various solutionizing temperatures, aging treatments and soaking times were used to improve / modify the mechanical properties of presently studied alloys. Formation mechanism of the particles was understood by carrying out optical microscopy and energy dispersive X–ray (EDX) spectroscopy measurements. Spherical particles of alloys were studied for their microstructural properties using scanning electron microscopy (SEM). Microhardness test was performed to investigate their mechanical properties. Dependence of cluster formation and microhardness of the alloys on the adequate solutionizing temperature, aging treatment and soaking time has been discussed in detail.

  4. Accidental finding of Hashimoto-like thyroiditis in male B.U.T. 6 turkeys at slaughter.

    PubMed

    Plesch, P; Schade, B; Breithaupt, A; Bellof, G; Kienzle, E

    2014-10-01

    In the context of a study on the tolerance of rapeseed meal in B.U.T. 6 turkeys, thyroid glands were histologically and immunohistochemically examined because of potential thyreostatic effects. In all groups including the controls with no rapeseed meal in their food, there was a high incidence of lymphocytic infiltration and thyroiditis (14% of thyroids with moderate to severe lymphocytic thyroiditis). Thirty per cent of mononuclear inflammatory cells were immunohistochemically identified as T cells. There were occasional accumulations of PAX-5 labelled cells, indicating germinal centre development. These lesions resemble Hashimoto's disease in humans. The effect on thyroid function is unknown. Mild hypothyreosis might enhance productivity but also explain dispositions towards diseases seen in context with thyroid dysfunction such as skin diseases (foot pad disease?) and cardiovascular problems. Further studies on thyroid function in these turkeys are needed. Journal of Animal Physiology and Animal Nutrition © 2013 Blackwell Verlag GmbH.

  5. Corrosion behaviour of friction-bit-joined and weld-bonded AA7075-T6/galvannealed DP980

    SciTech Connect

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; Miles, Michael; Keum, Jong Kahk; Song, Guang-Ling; Wang, Yanli; Feng, Zhili

    2016-12-22

    Joining of aluminium alloys 7075-T6 and galvannealed dual phase 980 steel was achieved by friction bit joining (FBJ) and weld-bonding (FBJ + adhesive) processes. Accelerated laboratory-scale corrosion tests were performed on both FBJ only and weld-bonded specimens to study joint strength under a corrosive environment. Static lap shear tests showed that both FBJ only and weld-bonded cases generally retained more than 80% of the joint strength of non-corroded specimens at the end of corrosion testing. The presence of Zn/Fe coating on the steel substrate resulted in improved corrosion resistance for FBJ specimens, compared to joints produced with bare steel. Finally, an optical microscopy was used for cross-sectional analysis of corroded specimens. Some corrosion on the joining bit was observed near the bit head. However, the joining bit was still intact on the steel substrate, indicating that the primary bond was sound.

  6. Effect of Welding Speeds on Mechanical Properties of Level Compensation Friction Stir Welded 6061-T6 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Wen, Quan; Yue, Yumei; Ji, Shude; Li, Zhengwei; Gao, Shuangsheng

    2016-04-01

    In order to eliminate the flash, arc corrugation and concave in weld zone, level compensation friction stir welding (LCFSW) was put forward and successfully applied to weld 6061-T6 aluminum alloy with varied welding speed at a constant tool rotational speed of 1,800 rpm in the present study. The glossy joint with equal thickness of base material can be attained, and the shoulder affected zone (SAZ) was obviously reduced. The results of transverse tensile test indicate that the tensile strength and elongation reach the maximum values of 248 MPa and 7.1% when the welding speed is 600 mm/min. The microhardness of weld nugget (WN) is lower than that of base material. The tensile fracture position locates at the heat affected zone (HAZ) of the advancing side (AS), where the microhardness is the minimum. The fracture surface morphology represents the typical ductile fracture.

  7. Mechanical Properties of SiC, Al2O3 Reinforced Aluminium 6061-T6 Hybrid Matrix Composite

    NASA Astrophysics Data System (ADS)

    Murugan, S. Senthil; Jegan, V.; Velmurugan, M.

    2017-06-01

    This paper contains the investigation of tensile, compression and impact characterization of SiC, Al2O3 reinforced Aluminium 6061-T6 matrix hybrid composite. Hybrid matrix composite fabrication was done by stir casting method. An attempt has been made by keeping Al2O3 percentage (7%) constant and increasing SiC percentage (10, 15, and 20%). After fabricating, the samples were prepared and tested to find out the various mechanical properties like tensile, compressive, and impact strength of the developed composites of different weight % of silicon carbide and Alumina in Aluminium alloy. The main objective of the study is to compare the values obtained and choose the best composition of the hybrid matrix composite from the mechanical properties point of view.

  8. Corrosion behavior of the friction-stir-welded joints of 2A14-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Qin, Hai-long; Zhang, Hua; Sun, Da-tong; Zhuang, Qian-yu

    2015-06-01

    The corrosion behavior of friction-stir-welded 2A14-T6 aluminum alloy was investigated by immersion testing in immersion exfoliation corrosion (EXCO) solution. Electrochemical measurements (open circuit potential, potentiodynamic polarization curves, and electrochemical impedance spectroscopy), scanning electron microscopy, and energy dispersive spectroscopy were employed for analyzing the corrosion mechanism. The results show that, compared to the base material, the corrosion resistance of the friction-stir welds is greatly improved, and the weld nugget has the highest corrosion resistance. The pitting susceptibility originates from the edge of Al-Cu-Fe-Mn-Si phase particles as the cathode compared to the matrix due to their high self-corrosion potential. No corrosion activity is observed around the θ phase (Al2Cu) after 2 h of immersion in EXCO solution.

  9. Mechanical Characteristics of Welded Joints of Aluminum Alloy 6061 T6 Formed by Arc and Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Astarita, A.; Squillace, A.; Nele, L.

    2016-01-01

    Butt welds formed by arc welding in inert gas with nonconsumable electrode (tungsten inert gas (TIG) welding) and by friction stir welding (FSW) from aluminum alloy AA6061 T6 are studied. Comparative analysis of the structures and mechanical properties of the welded joints is performed using the results of optical and electron microscopy, tensile tests, tests for residual bending ductility, and measurements of microhardness. The changes in the microstructure in different zones and the degrees of degradation of the mechanical properties after the welding are determined. It is shown that the size of the tool for the friction stir welding affects the properties of the welds. Quantitative results showing the relation between the microscopic behavior of the alloy and the welding-induced changes in the microstructure are obtained. Friction stir welding is shown to provide higher properties of the welds.

  10. Crystallization and preliminary X-ray analysis of alpha-D-glucuronidase from Bacillus stearothermophilus T-6.

    PubMed

    Teplitsky, A; Shulami, S; Moryles, S; Zaide, G; Shoham, Y; Shoham, G

    1999-04-01

    alpha-D-Glucuronidases cleave the alpha-1,2-glycosidic bond of the 4-O-methyl-alpha-D-glucuronic acid side chain in xylan. Of the xylan-debranching hydrolases, these enzymes are the least studied and characterized. The alpha-glucuronidase gene (aguA) from Bacillus stearothermophilus T-6 has been cloned, sequenced and overproduced in Escherichia coli. The gene encodes for a protein of 679 amino acids with a calculated molecular weight of 78480 and a pI of 5.42. alpha-Glucuronidase T-6 shows high homology to the alpha-glucuronidases of Thermotoga maritima (60% identity) and of Tri-choderma reesei (44% identity). Based on the amino-acid sequence similarity, it is likely that these enzymes represent a new class of glycosyl hydrolases. Crystallographic studies of alpha-glucuronidase T-6 were initiated to study the mechanism of catalysis, as well as to provide a structural basis for rational introduction of enhanced thermostability by site-specific mutagenesis. In this report, the crystallization and preliminary crystallographic characterization of the native alpha-glucuronidase T-6 enzyme is described. Two crystal forms were found suitable for detailed crystal structure analysis. The T1 form was obtained by the vapour-diffusion method using PEG 4000 as a precipitant and 2-propanol as an organic additive. The crystals belong to a primitive tetragonal crystal system (space group P41212 or P43212) with unit-cell dimensions a = b = 76.1 and c = 331.2 A. These crystals are mechanically strong, are stable in the X--ray beam and diffract X-rays to better than 2.4 A resolution. A full 3.0 A resolution diffraction data set (97.3% completeness, Rmerge 9.8%) has recently been collected on one crystal at room temperature using a rotating-anode X-ray source and an R-AXIS IIc imaging-plate detector. The M1 form was obtained and characterized by similar techniques. The best crystallization occurred at a slightly lower pH and a lower concentration of 2-propanol. The crystals belong to

  11. Investigation of Hot Cracking Behavior in Transverse Mechanically Arc Oscillated Autogenous AA2014 T6 TIG Welds

    NASA Astrophysics Data System (ADS)

    Biradar, N. S.; Raman, R.

    2012-09-01

    Hot cracking studies on autogenous AA2014 T6 TIG welds were carried out. Significant cracking was observed during linear and circular welding test (CWT) on 4-mm-thick plates. Weld metal grain structure and amount of liquid distribution during the terminal stages of solidification were the key cause for hot cracking in aluminum welds. Square-wave AC TIG welding with transverse mechanical arc oscillation (TMAO) was employed to study the cracking behavior during linear and CWT. TMAO welds with amplitude = 0.9 mm and frequency = 0.5 Hz showed significant reduction in cracking tendency. The increase in cracking resistance in the arc-oscillated weld was attributed to grain refinement and improved weld bead morphology, which improved the weld metal ductility and uniformity, respectively, of residual tensile stresses that developed during welding. The obtained results were comparable to those of reported favorable results of electromagnetic arc oscillation.

  12. A molecular dynamics investigation into the size-dependent buckling behavior of a novel three-dimensional metallic carbon nanostructure (T6)

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Ajori, S.; Hassani, R.

    2016-09-01

    The buckling behavior of a novel three-dimensional metallic carbon nanostructure known as T6 is investigated herein employing the molecular dynamics (MD) simulations. The models are prepared on the basis of two beam- and plate-like structures to study the effects of size and geometry on the critical buckling force and critical strain. It is observed that the range of critical force for the beam-like and plate-like T6 with different geometrical parameters is approximately identical. Moreover, it is demonstrated that the critical buckling force decreases and increases by increasing the length and the width of T6, respectively. Moreover, it is shown that critical strain of beam-like T6 decreases by increasing the length, whereas, in the case of plate-like T6, the critical strain only fluctuates around 2% by increasing the width. It is further found that the buckling parameters of T6 are not comparable with those of single-walled carbon nanotubes (SWCNTs) and graphene with a relatively similar dimension. The critical buckling force and critical strain of T6 are considerably smaller than those of SWCNT and larger than those of graphene.

  13. Effect of the Zener-Hollomon parameter on the formability of AA6082-T6 formed at elevated temperature

    NASA Astrophysics Data System (ADS)

    Novella, Michele F.; Ghiotti, Andrea; Bruschi, Stefania

    2016-10-01

    Material formability is one of the main research topics in metal forming, but it is usually regarded as a secondary concern in processes carried out at high temperature. Though usually entailing higher material ductility, the high temperature used in hot forging can lead to the phenomenon of hot shortness, with fall of material formability due to the microstructural changes during the deformation. Hot metal formability modelling can imply three main issues: (i) the lack of models expressly developed for high temperatures, (ii) the exponential increase of the experimental effort which is needed for the model calibration, since different thermo-mechanical conditions need to be tested, according to the process window parameters, and consequently (iii) the more complex model calibration, especially if inverse analysis techniques are used. In this work the formability of the AA6082-T6 aluminum alloy is investigated by means of tensile tests carried out at different temperatures and strain rates. The hot shortness onset is identified as well as the negative strain rate influence on the material maximum strain at fracture. A linear dependency of the material formability on the Zener-Hollomon parameter is established for temperatures below the hot shortness point, allowing a significant simplification of the experiments needed for the calibration. A new formability model is proposed to overcome the limits of the linear correlation thanks to the introduction of a critical value of the Zener-Hollomon parameter. The Oyane-Sato damage criterion is then extended to hot conditions using the afore mentioned Zener-Hollomon dependency. Finally, the approach is validated on the reference industrial case: the cross wedge rolling of AA6082-T6 round bars carried out at elevated temperature showing axial cracking due to Mannesmann effect.

  14. Crystallization and preliminary crystallographic analysis of a family 43 β-d-xylosidase from Geobacillus stearothermophilus T-6

    SciTech Connect

    Brüx, Christian; Niefind, Karsten; Ben-David, Alon; Leon, Maya; Shoham, Gil; Shoham, Yuval; Schomburg, Dietmar

    2005-12-01

    The crystallization and preliminary X-ray analysis of a β-d-xylosidase from G. stearothermophilus T-6, a family 43 glycoside hydrolase, is described. Native and catalytic inactive mutants of the enzymes were crystallized in two different space groups, orthorhombic P2{sub 1}2{sub 1}2 and tetragonal P4{sub 1}2{sub 1}2 (or the enantiomorphic space group P4{sub 3}2{sub 1}2), using a sensitive cryoprotocol. The latter crystal form diffracted X-rays to a resolution of 2.2 Å. β-d-Xylosidases (EC 3.2.1.37) are hemicellulases that cleave single xylose units from the nonreducing end of xylooligomers. In this study, the crystallization and preliminary X-ray analysis of a β-d-xylosidase from Geobacillus stearothermophilus T-6 (XynB3), a family 43 glycoside hydrolase, is described. XynB3 is a 535-amino-acid protein with a calculated molecular weight of 61 891 Da. Purified recombinant native and catalytic inactive mutant proteins were crystallized and cocrystallized with xylobiose in two different space groups, P2{sub 1}2{sub 1}2 (unit-cell parameters a = 98.32, b = 99.36, c = 258.64 Å) and P4{sub 1}2{sub 1}2 (or the enantiomorphic space group P4{sub 3}2{sub 1}2; unit-cell parameters a = b = 140.15, c = 233.11 Å), depending on the detergent. Transferring crystals to cryoconditions required a very careful protocol. Orthorhombic crystals diffract to 2.5 Å and tetragonal crystals to 2.2 Å.

  15. Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Bonomo, A. S.; Pagano, I.; Leto, G.; Messina, S.; Cutispoto, G.; Moutou, C.; Aigrain, S.; Alonso, R.; Barge, P.; Deleuil, M.; Fridlund, M.; Silva-Valio, A.; Auvergne, M.; Baglin, A.; Collier Cameron, A.

    2011-01-01

    Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days. Aims: We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. Methods: We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of ~ 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts. Results: Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation for which a lower limit of ΔΩ/Ω = 0.12 ± 0.02 is obtained. Several active regions show a maximum of activity at a longitude lagging the subplanetary point by ~ 200° with the probability of a chance occurrence being smaller than 1 percent. Conclusions: Our spot modelling indicates that the photospheric activity of CoRoT-6 could be partially modulated by some kind of star-planet magnetic interaction, while an interaction related to tides is highly unlikely because of the weakness of the tidal force. Based on observations obtained with CoRoT, a space project operated by the French Space Agency, CNES, with partecipation of the Science Programme of ESA, ESTEC/RSSD, Austria, Belgium, Brazil, Germany, and Spain.

  16. Application of Plant-Growth-Promoting Fungi Trichoderma longibrachiatum T6 Enhances Tolerance of Wheat to Salt Stress through Improvement of Antioxidative Defense System and Gene Expression

    PubMed Central

    Zhang, Shuwu; Gan, Yantai; Xu, Bingliang

    2016-01-01

    Soil salinity is a serious problem worldwide that reduces agricultural productivity. Trichoderma longibrachiatum T6 (T6) has been shown to promote wheat growth and induce plant resistance to parasitic nematodes, but whether the plant-growth-promoting fungi T6 can enhance plant tolerance to salt stress is unknown. Here, we determined the effect of plant-growth-promoting fungi T6 on wheat seedlings’ growth and development under salt stress, and investigated the role of T6 in inducing the resistance to NaCl stress at physiological, biochemical, and molecular levels. Wheat seedlings were inoculated with the strain of T6 and then compared with non-inoculated controls. Shoot height, root length, and shoot and root weights were measured on 15 days old wheat seedlings grown either under 150 mM NaCl or in a controlled setting without any NaCl. A number of colonies were re-isolated from the roots of wheat seedlings under salt stress. The relative water content in the leaves and roots, chlorophyll content, and root activity were significantly increased, and the accumulation of proline content in leaves was markedly accelerated with the plant growth parameters, but the content of leaf malondialdehyde under saline condition was significantly decreased. The antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in wheat seedlings were increased by 29, 39, and 19%, respectively, with the application of the strain of T6 under salt stress; the relative expression of SOD, POD, and CAT genes in these wheat seedlings were significantly up-regulated. Our results indicated that the strain of T6 ameliorated the adverse effects significantly, protecting the seedlings from salt stress during their growth period. The possible mechanisms by which T6 suppresses the negative effect of NaCl stress on wheat seedling growth may be due to the improvement of the antioxidative defense system and gene expression in the stressed wheat plants. PMID:27695475

  17. Application of Plant-Growth-Promoting Fungi Trichoderma longibrachiatum T6 Enhances Tolerance of Wheat to Salt Stress through Improvement of Antioxidative Defense System and Gene Expression.

    PubMed

    Zhang, Shuwu; Gan, Yantai; Xu, Bingliang

    2016-01-01

    Soil salinity is a serious problem worldwide that reduces agricultural productivity. Trichoderma longibrachiatum T6 (T6) has been shown to promote wheat growth and induce plant resistance to parasitic nematodes, but whether the plant-growth-promoting fungi T6 can enhance plant tolerance to salt stress is unknown. Here, we determined the effect of plant-growth-promoting fungi T6 on wheat seedlings' growth and development under salt stress, and investigated the role of T6 in inducing the resistance to NaCl stress at physiological, biochemical, and molecular levels. Wheat seedlings were inoculated with the strain of T6 and then compared with non-inoculated controls. Shoot height, root length, and shoot and root weights were measured on 15 days old wheat seedlings grown either under 150 mM NaCl or in a controlled setting without any NaCl. A number of colonies were re-isolated from the roots of wheat seedlings under salt stress. The relative water content in the leaves and roots, chlorophyll content, and root activity were significantly increased, and the accumulation of proline content in leaves was markedly accelerated with the plant growth parameters, but the content of leaf malondialdehyde under saline condition was significantly decreased. The antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in wheat seedlings were increased by 29, 39, and 19%, respectively, with the application of the strain of T6 under salt stress; the relative expression of SOD, POD, and CAT genes in these wheat seedlings were significantly up-regulated. Our results indicated that the strain of T6 ameliorated the adverse effects significantly, protecting the seedlings from salt stress during their growth period. The possible mechanisms by which T6 suppresses the negative effect of NaCl stress on wheat seedling growth may be due to the improvement of the antioxidative defense system and gene expression in the stressed wheat plants.

  18. Variable and Polarized Radio Emission from the T6 Brown Dwarf WISEP J112254.73+255021.5

    NASA Astrophysics Data System (ADS)

    Williams, P. K. G.; Gizis, J. E.; Berger, E.

    2017-01-01

    Route & Wolszczan recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ∼17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission. Assuming that the radio emission of this T dwarf is periodically variable on ∼hour timescales, like other radio-active ultracool dwarfs, we infer a likely period of 116 minutes. However, our observation lasted only 162 minutes and so more data are needed to test this hypothesis. The handedness of the circular polarization switches twice and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object’s magnetic dipole axis may be highly misaligned relative to its rotation axis.

  19. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    NASA Astrophysics Data System (ADS)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-09-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  20. ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6.

    PubMed

    Eichmann, Thomas O; Grumet, Lukas; Taschler, Ulrike; Hartler, Jürgen; Heier, Christoph; Woblistin, Aaron; Pajed, Laura; Kollroser, Manfred; Rechberger, Gerald; Thallinger, Gerhard G; Zechner, Rudolf; Haemmerle, Günter; Zimmermann, Robert; Lass, Achim

    2015-10-01

    Lipid droplets (LDs) of hepatic stellate cells (HSCs) contain large amounts of vitamin A [in the form of retinyl esters (REs)] as well as other neutral lipids such as TGs. During times of insufficient vitamin A availability, RE stores are mobilized to ensure a constant supply to the body. To date, little is known about the enzymes responsible for the hydrolysis of neutral lipid esters, in particular of REs, in HSCs. In this study, we aimed to identify LD-associated neutral lipid hydrolases by a proteomic approach using the rat stellate cell line HSC-T6. First, we loaded cells with retinol and FAs to promote lipid synthesis and deposition within LDs. Then, LDs were isolated and lipid composition and the LD proteome were analyzed. Among other proteins, we found perilipin 2, adipose TG lipase (ATGL), and comparative gene identification-58 (CGI-58), known and established LD proteins. Bioinformatic search of the LD proteome for α/β-hydrolase fold-containing proteins revealed no yet uncharacterized neutral lipid hydrolases. In in vitro activity assays, we show that rat (r)ATGL, coactivated by rat (r)CGI-58, efficiently hydrolyzes TGs and REs. These findings suggest that rATGL and rCGI-58 are LD-resident proteins in HSCs and participate in the mobilization of both REs and TGs.

  1. Investigation of the effect of vacuum environment on the fatigue and fracture behavior of 7075-T6.

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.

    1972-01-01

    Axial-load fatigue-life, fatigue-crack propagation, and fracture-toughness experiments were conducted on sheet specimens made of 7075-T6 aluminum alloy. These experiments were conducted at air pressures ranging from 101 kN/sq m to 7 micronewtons/sq m to determine the effect of air pressure on fatigue behavior. Analysis of the results from the fatigue-life experiments indicated that for a given stress level, the lower the air pressure was the longer the fatigue life. At a pressure of 7 micronewtons/sq m, fatigue lives were 15 to 30 times longer than at 101 kN/sq m. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue-crack-growth rates were approximately twice as high at atmospheric pressure as in vacuum. However, at higher values of stress-intensity range, the fatigue-crack-growth rates were nominally the same in vacuum and at atmospheric pressure.

  2. Corrosion behaviour of friction-bit-joined and weld-bonded AA7075-T6/galvannealed DP980

    DOE PAGES

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; ...

    2016-12-22

    Joining of aluminium alloys 7075-T6 and galvannealed dual phase 980 steel was achieved by friction bit joining (FBJ) and weld-bonding (FBJ + adhesive) processes. Accelerated laboratory-scale corrosion tests were performed on both FBJ only and weld-bonded specimens to study joint strength under a corrosive environment. Static lap shear tests showed that both FBJ only and weld-bonded cases generally retained more than 80% of the joint strength of non-corroded specimens at the end of corrosion testing. The presence of Zn/Fe coating on the steel substrate resulted in improved corrosion resistance for FBJ specimens, compared to joints produced with bare steel. Finally,more » an optical microscopy was used for cross-sectional analysis of corroded specimens. Some corrosion on the joining bit was observed near the bit head. However, the joining bit was still intact on the steel substrate, indicating that the primary bond was sound.« less

  3. Angular distortion and through-thickness residual stress distribution in the friction-stir processed 6061-T6 aluminum alloy

    SciTech Connect

    Woo, Wan Chuck; Choo, Hahn; Brown, D. W.; Feng, Zhili; Liaw, Peter K; Hubbard, Camden R

    2006-01-01

    Residual stresses were measured through the thickness of friction-stir processed (FSP) 6061-T6 aluminum-alloy plates using neutron diffraction. Two different specimens were prepared to study the relationship between residual stress distributions through the thickness of the plate and angular distortion: (Case 1) a plate processed with both stirring pin and tool shoulder, i.e., a typical FSP plate subjected to both plastic deformation and frictional heat, and (Case 2) a plate processed only with the tool shoulder, i.e., subjected mainly to the frictional heating. The measured residual stress profiles show relatively small through-thickness residual stress variations in Case 1, while there is a significant through-thickness residual stress variations in Case 2. The main cause of the geometric angular distortion could be related to the non-uniform distribution of the frictional heat generated by the tool shoulder leading to the asymmetric distributions of the residual stress through the thickness of the FSP plate.

  4. Dislocation density evolution of AA 7020-T6 investigated by in-situ synchrotron diffraction under tensile load

    SciTech Connect

    Zhong, Z.Y.; Brokmeier, H.-G.; Gan, W.M.; Maawad, E.; Schwebke, B.; Schell, N.

    2015-10-15

    The dislocation density evolution along the loading axis of a textured AA 7020-T6 aluminum alloy during uniaxial tension was investigated by in-situ synchrotron diffraction. The highly parallel synchrotron beam at the High Energy Materials Science beamline P07 in PETRA III, DESY, offers excellent conditions to separate different influences for line broadening from which micro-strains are obtained using the modified Williamson–Hall method which is also for defect density investigations. During tensile loading the dislocation density evolution was documented from the as-received material (initial micro-strain state) to the relaxation of the strains during elastic deformation. After yield, the increasing rate of dislocation density growth was relatively fast till half-way between yield and UTS. After that, the rate started to decrease and the dislocation density fluctuated as the elongation increased due to the generation and annihilation of dislocations. When dislocation generation is dominant, the correlation between the flow stress and dislocation density satisfies the Taylor equation. Besides, a method to correct the thickness effect on peak broadening is developed in the present study. - Highlights: • In-situ synchrotron diffraction was applied to characterize peak broadening. • Dislocation evolution along the loading axis during uniaxial tension was investigated. • A method to correct the sample thickness effect on peak broadening was developed. • Dislocation density and flow stress satisfy the Taylor equation at a certain range. • The texture before load and after sample fracture was analyzed.

  5. Plastic Stress-strain Relations for 75S-T6 Aluminum Alloy Subjected to Biaxial Tensile Stresses

    NASA Technical Reports Server (NTRS)

    Marin, Joseph; Ulrich, B H; Hughes, W P

    1951-01-01

    In this investigation, the material tested was a 75S-T6 aluminum alloy and the stresses were essentially biaxial and tensile. The biaxial tensile stresses were produced in a specially designed testing machine by subjecting a thin-walled tubular specimen to axial tension and internal pressure. Plastic stress-strain relations for various biaxial stress conditions were obtained using a clip-type SR-4 strain gage. Three types of tests were made: Constant-stress-ratio tests, variable-stress-ratio tests, and special tests. The constant-stress-ratio test results gave control data and showed the influence of biaxial stresses on the yield, fracture, and ultimate strength of the material. By means of the variable-stress-ratio tests, it is possible to determine whether there is any significant difference between the flow and deformation type of theory. Finally, special tests were conducted to check specific assumptions made in the theories of plastic flow. The constant-stress-ratio tests show that the deformation theory based on the octahedral, effective; or significant stress-strain relations is in approximate agreement with the test results. The variable-stress-ratio tests show that both the deformation and flow theory are in equally good agreement with the test results.

  6. Effects of Different Filler Metals on the Mechanical Behaviors of GTA Welded AA7A52(T6)

    NASA Astrophysics Data System (ADS)

    Shu, Fengyuan; Lv, Yaohui; Liu, Yuxin; Lin, Jianjun; Sun, Zhe; Xu, Binshi; He, Peng

    2014-06-01

    ER4043, ER5356, and AA7A52 on behalf of the Al-Si, Al-Mg, and Al-Zn-Mg-based welding material, respectively, were chosen as the filler metal to weld AA7A52(T6) plates by GTAW. The variance in mechanical performances of the joints caused by the various filler materials was investigated with reference to the SEM and EDS test results for the weld seam and the fracture surface. Failure was found in the seam for all the welded joints. With regard to the joint obtained with ER4043 welding wire, the total elongation was limited by the brittle intergranular compound Mg2Si of which Mg was introduced by convection mass transfer. As for the other two welds, the content ratio of Zn and Mg was found to play the dominant role in deciding the mechanical properties of the intergranular Mg-Zn compounds which were responsible for the tensile behavior of the joints. The content ratio (wt.%) of beyond 2:1 gave birth to the strengthening phase MgZn2 leading to a ductile fracture. Cr in the seam obtained with AA7A52 filler metal was found to enhance the strength of the joint through isolated particles.

  7. A study on ultra-precision machining technique for Al6061-T6 to fabricate space infrared optics

    NASA Astrophysics Data System (ADS)

    Ryu, Geun-man; Lee, Gil-jae; Hyun, Sang-won; Sung, Ha-yeong; Chung, Euisik; Kim, Geon-hee

    2014-08-01

    In this paper, analysis of variance on designed experiments with full factorial design was applied to determine the optimized machining parameters for ultra-precision fabrication of the secondary aspheric mirror, which is one of the key elements of the space cryogenic infrared optics. A single point diamond turning machine (SPDTM, Nanotech 4μpL Moore) was adopted to fabricate the material, AL6061-T6, and the three machining parameters of cutting speed, feed rate and depth of cut were selected. With several randomly assigned experimental conditions, surface roughness of each condition was measured by a non-contact optical profiler (NT2000; Vecco). As a result of analysis using Minitab, the optimum cutting condition was determined as following; cutting speed: 122 m/min, feed rate: 3 mm/min and depth of cut: 1 μm. Finally, a 120 mm diameter aspheric secondary mirror was attached to a particularly designed jig by using mixture of paraffin and wax and successfully fabricated under the optimum machining parameters. The profile of machined surface was measured by a high-accuracy 3-D profilometer(UA3P; Panasonic) and we obtained the geometrical errors of 30.6 nm(RMS) and 262.4 nm(PV), which satisfy the requirements of the space cryogenic infrared optics.

  8. EN AW-4032 T6 Piston Alloy After High-Temperature Exposure: Residual Strength and Microstructural Features

    NASA Astrophysics Data System (ADS)

    Balducci, Eleonora; Ceschini, Lorella; Morri, Alessandro; Morri, Andrea

    2017-08-01

    This study aims to evaluate the effects of prolonged thermal exposure on both microstructural evolution and mechanical properties of the EN AW-4032 T6 piston alloy. For the purpose, the experimental activities have been carried out on samples machined from forged and heat-treated automotive pistons. The effects of overaging have been investigated in the temperature range of 140-290 °C, firstly by evaluating the time-temperature-hardness curves and then by carrying out room-temperature tensile tests on overaged samples. The material softening was substantial and extremely rapid when the soaking temperature exceeded 250 °C. During overaging, both the tensile strength and the residual hardness considerably decreased, and a relationship between these parameters has been established. The alloy behavior in the plastic field has been modeled according to the Hollomon's equation, showing that both the strain hardening exponent and the strength coefficient are a function of the residual hardness. The results were finally related to the corresponding microstructural changes: OM and FEG-SEM metallographic and fractographic analyses on overaged samples gave evidence of coarsened precipitates along the grain boundaries.

  9. High strain rate properties of an SiC{sub W}/2124-T6 aluminum composite at elevated temperatures

    SciTech Connect

    Guden, M.; Hall, I.W.

    1998-07-03

    Metal matrix composites, (MMC`s) provide several important advantages over unreinforced metals and alloys. Among these, higher moduli and yield stresses and enhanced thermo-mechanical properties are normally considered important in structural applications of MMC`s. It is also possible that MMC`s may be exposed to loading conditions involving high strain rates during service, for example, components of a car in collision with another or turbine blades hit by ingestion of foreign objects. In such situations of rapidly increasing loading conditions, the material property response may be considerably different from that which applies during slow loading of normal quasi-static testing and, consequently, dynamic mechanical properties are of increasing interest and importance. Several studies involving dynamic deformation of a SiC{sub W}/2124-T6 Al MMC have already been conducted using tension, shear, compression and projectile impact testing. The purpose of the present study was to extend the high strain rate data to include high temperature effects. Mechanical test results and microstructural observations of features of dynamic deformation have been compared with data from the unreinforced alloy to obtain more complete information on the dynamic response of the composite.

  10. Prediction of hardness minimum locations during natural aging in an aluminum alloy 6061-T6 friction stir weld

    SciTech Connect

    Woo, Wan Chuck; Choo, Hahn; Feng, Zhili; Withers, Prof Philip

    2009-01-01

    This study describes a simple model that can predict the evolution of hardness distribution as a function of natural aging time in a heat-treatable 6061-T6 Al alloy plate subjected to friction stir welding (FSW). First, two dimensional thermal distributions were simulated as a function of time in the FSW plate by finite element modeling. Second, the hardness changes during natural aging were measured as a function of aging time for a number of Al specimens that had been previously isothermally heat-treated to different hold temperatures in order to determine the natural aging kinetics. Finally, the simulated temperature profiles and the natural aging kinetics were correlated to predict the hardness profiles in the FSW plate. The predicted hardness variations are consistent with measured hardness profiles in that the location of minimum hardness moves away from the centerline as the aging time and/or heat input increases. The hardness variation was also related to the location of failure in cross-weld tensile samples.

  11. Modeling of Residual Stresses and Property Distributions in Friction Stir Welds of Aluminum Alloy 6061-T6

    SciTech Connect

    Feng, Zhili; David, Stan A; Wang, Xun-Li; Sklad, Philip S

    2007-01-01

    An integrated thermal-metallurgical-mechanical model is used to analyze and provide insights into the formation of the residual stress and the changes in microstructure and property of Al6061-T6 friction stir welds. The simulations were conducted by means of a three-dimensional finite element model that accounts for the phenomena of frictional heating, weld microstructure and strength changes due to dissolution and reprecipitation of the hardening precipitate particles, and the mechanical workpiece/tool contact during the friction stir welding (FSW) process. The model predictions were confirmed by experimental measurement data from previous studies. For the friction stir welds investigated, it was found that the residual stress distribution is strongly dependent on the welding process parameters and the degree of material softening caused by welding. The recovery of material strength from natural aging does not increase the residual stress in the weld. The failure of friction stir weld under tensile load is controlled by the combination of the reduction in strength and the residual stresses in the heat affected zone (HAZ).

  12. Crystallization and preliminary crystallographic analysis of a family 43 β-d-xylosidase from Geobacillus stearothermophilus T-6

    PubMed Central

    Brüx, Christian; Niefind, Karsten; Ben-David, Alon; Leon, Maya; Shoham, Gil; Shoham, Yuval; Schomburg, Dietmar

    2005-01-01

    β-d-Xylosidases (EC 3.2.1.37) are hemicellulases that cleave single xylose units from the nonreducing end of xylooligomers. In this study, the crystallization and preliminary X-ray analysis of a β-d-xylosidase from Geobacillus stearothermophilus T-6 (XynB3), a family 43 glycoside hydrolase, is described. XynB3 is a 535-amino-acid protein with a calculated molecular weight of 61 891 Da. Purified recombinant native and catalytic inactive mutant proteins were crystallized and cocrystallized with xylobiose in two different space groups, P21212 (unit-cell parameters a = 98.32, b = 99.36, c = 258.64 Å) and P41212 (or the enantiomorphic space group P43212; unit-cell parameters a = b = 140.15, c = 233.11 Å), depending on the detergent. Transferring crystals to cryoconditions required a very careful protocol. Orthorhombic crystals diffract to 2.5 Å and tetragonal crystals to 2.2 Å. PMID:16511233

  13. ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6[S

    PubMed Central

    Eichmann, Thomas O.; Grumet, Lukas; Taschler, Ulrike; Hartler, Jürgen; Heier, Christoph; Woblistin, Aaron; Pajed, Laura; Kollroser, Manfred; Rechberger, Gerald; Thallinger, Gerhard G.; Zechner, Rudolf; Haemmerle, Günter; Zimmermann, Robert; Lass, Achim

    2015-01-01

    Lipid droplets (LDs) of hepatic stellate cells (HSCs) contain large amounts of vitamin A [in the form of retinyl esters (REs)] as well as other neutral lipids such as TGs. During times of insufficient vitamin A availability, RE stores are mobilized to ensure a constant supply to the body. To date, little is known about the enzymes responsible for the hydrolysis of neutral lipid esters, in particular of REs, in HSCs. In this study, we aimed to identify LD-associated neutral lipid hydrolases by a proteomic approach using the rat stellate cell line HSC-T6. First, we loaded cells with retinol and FAs to promote lipid synthesis and deposition within LDs. Then, LDs were isolated and lipid composition and the LD proteome were analyzed. Among other proteins, we found perilipin 2, adipose TG lipase (ATGL), and comparative gene identification-58 (CGI-58), known and established LD proteins. Bioinformatic search of the LD proteome for α/β-hydrolase fold-containing proteins revealed no yet uncharacterized neutral lipid hydrolases. In in vitro activity assays, we show that rat (r)ATGL, coactivated by rat (r)CGI-58, efficiently hydrolyzes TGs and REs. These findings suggest that rATGL and rCGI-58 are LD-resident proteins in HSCs and participate in the mobilization of both REs and TGs. PMID:26330055

  14. Ultrasonic Fatigue Endurance of Aluminum Alloy AISI 6061-T6 on Pre-corroded and Non-corroded Specimens

    NASA Astrophysics Data System (ADS)

    Domínguez Almaraz, Gonzalo M.; Dueñas Aburto, Antonio; Correa Gómez, Erasmo

    2014-01-01

    Ultrasonic fatigue tests are carried out on aluminum alloy 6061-T6 in order to analyze the fatigue endurance behavior under artificial pre-corrosion attack by hydrochloric acid for the pH concentrations of 0.47 and 0.80. The pre-corrosion attack is used to simulate the long-time environmental effect and the corresponding decay of fatigue life in regard to non-corroded specimens. Experimental results show that ultrasonic fatigue endurance under these two degrees of pre-corrosion attack decreases dramatically. Furthermore, it is observed that crack initiation is frequently associated with one or several pre-corrosion pitting holes at the specimen surface. Pitting holes are assumed to be semi-hemispherical and the stress concentration factors are evaluated taking into account the size and proximity of two crack initiation pitting holes. The crack growth rates are obtained for the pre-corroded specimens and compared to the non-corroded specimen. Finally, conclusions are listed concerning ultrasonic fatigue endurance of testing specimens, together with the fracture surfaces, crack paths, and crack growth rates.

  15. Effect of laser shot peening on precipitation hardened aluminum alloy 6061-T6 using low energy laser

    NASA Astrophysics Data System (ADS)

    Sathyajith, S.; Kalainathan, S.

    2012-03-01

    Mechanical properties of engineering material can be improved by introducing compressive residual stress on the material surface and refinement of their microstructure. Variety of mechanical process such as shot peening, water jet peening, ultrasonic peening, laser shot peening were developed in the last decades on this contrast. Among these, lasers shot peening emerged as a novel industrial treatment to improve the crack resistance of turbine blades and the stress corrosion cracking (SCC) of austenic stainless steel in power plants. In this study we successfully performed laser shot peening on precipitation hardened aluminum alloy 6061-T6 with low energy (300 mJ, 1064 nm) Nd:YAG laser using different pulse densities of 22 pulses/mm 2 and 32 pulses/mm 2. Residual stress evaluation based on X-ray diffraction sin 2 ψ method indicates a maximum of 190% percentage increase on surface compressive stress. Depth profile of micro-hardness shows the impact of laser generated shock wave up to 1.2 mm from the surface. Apart from that, the crystalline size and micro-strain on the laser shot peened surfaces have been investigated and compared with the unpeened surface using X-ray diffraction in conjunction with line broadening analysis through the Williamson-Hall plot.

  16. Artificial neural networks application for modeling of friction stir welding effects on mechanical properties of 7075-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Maleki, E.

    2015-12-01

    Friction stir welding (FSW) is a relatively new solid-state joining technique that is widely adopted in manufacturing and industry fields to join different metallic alloys that are hard to weld by conventional fusion welding. Friction stir welding is a very complex process comprising several highly coupled physical phenomena. The complex geometry of some kinds of joints makes it difficult to develop an overall governing equations system for theoretical behavior analyse of the friction stir welded joints. Weld quality is predominantly affected by welding effective parameters, and the experiments are often time consuming and costly. On the other hand, employing artificial intelligence (AI) systems such as artificial neural networks (ANNs) as an efficient approach to solve the science and engineering problems is considerable. In present study modeling of FSW effective parameters by ANNs is investigated. To train the networks, experimental test results on thirty AA-7075-T6 specimens are considered, and the networks are developed based on back propagation (BP) algorithm. ANNs testing are carried out using different experimental data that they are not used during networks training. In this paper, rotational speed of tool, welding speed, axial force, shoulder diameter, pin diameter and tool hardness are regarded as inputs of the ANNs. Yield strength, tensile strength, notch-tensile strength and hardness of welding zone are gathered as outputs of neural networks. According to the obtained results, predicted values for the hardness of welding zone, yield strength, tensile strength and notch-tensile strength have the least mean relative error (MRE), respectively. Comparison of the predicted and the experimental results confirms that the networks are adjusted carefully, and the ANN can be used for modeling of FSW effective parameters.

  17. Creep properties of forged 2219 T6 aluminum alloy shell of general-purpose heat source-radioisotope thermoelectric generator

    SciTech Connect

    Hammond, J.P.

    1981-12-01

    The shell (2219 T6 aluminum forging) of the General Purpose Heat Source-Radioisotope Thermoelectric Generator was designed to retain the generator under sufficient elastic stress to secure it during space flight. A major concern was the extent to which the elastic stress would relax by creep. To determine acceptability of the shell construction material, the following proof tests simulating service were performed: 600 h of testing at 270/sup 0/C under 24.1 MPa stress followed by 10,000 h of storage at 177/sup 0/C under 55.1 MPa, both on the ground; and 10,000 h of flight in space at 270/sup 0/C under 34.4 MPa stress. Additionally, systematic creep testing was performed at 177 and 260/sup 0/C to establish creep design curves. The creep tests performed at 177/sup 0/C revealed comparatively large amounts of primary creep followed by small amounts of secondary creep. The early creep is believed to be abetted by unstable substructures that are annealed out during testing at this temperature. The creep tests performed at 270/sup 0/C showed normal primary creep followed by large amounts of secondary creep. Duplicate proof tests simulating the ground exposure conditions gave results that were in good agreement. The proof test simulating space flight at 270/sup 0/C gave 0.11% primary creep followed by 0.59% secondary creep. About 10% of the second-stage creep was caused by four or five instantaneous strains, which began at the 4500-h mark. One or two of these strain bursts, occurred in each of several other tests at 177 and 260/sup 0/C but were assessed as very moderate in magnitude. The effect is attributable to a slightly microsegregated condition remaining from the original cast structure.

  18. Effect of caffeine on motility and vitality of sperm and in vitro fertilization of outbreed mouse in T6 and M16 media

    PubMed Central

    Nabavi, Narges; Todehdehghan, Fatemeh; Shiravi, Abdollhossein

    2013-01-01

    Background: Caffeine increases the CAMP production that stimulates spermatozoa movement. Caffeine is also used for induction of in vitro acrosome reaction in mammalian spermatozoa, an important step in achieving fertilization. Objective: The aim of this study was to assess the effect of caffeine on sperm's motility, vitality and laboratory fertilization rates in mouse in two T6 and M16 media. Materials and Methods: Epididymal mouse sperms were collected and treated by caffine in T6 and M16 media and their motility and vitality rates were evaluated. The pretreated sperms were added to oocytes in T6 and M16 media with and without caffeine and fertilization rates were recorded after 24 hours incubation. Results: Sperm's motility (81.7±1.67%) and vitality (88.7±1.33%) rates and percentage of fertilized oocytes (67.52±8.16%) in T6 medium plus caffeine compare to control group have increased and shown significant differences at p≤0.01. While the percentages of these parameters in M16 medium supplemented with caffeine were 68.3±6.01%, 78±6.11%, and 42.6±12.96 respectively and in comparison to control group (M16 without caffeine) have not shown significant differences. Conclusion: Addition of caffeine to T6 medium promotes the sperm's motility and vitality and enhances fertilization and early in vitro development of mouse embryos. This article extracted from M.Sc. thesis. (Narges Navabi) PMID:24639814

  19. Effect of caffeine on motility and vitality of sperm and in vitro fertilization of outbreed mouse in T6 and M16 media.

    PubMed

    Nabavi, Narges; Todehdehghan, Fatemeh; Shiravi, Abdollhossein

    2013-09-01

    Caffeine increases the CAMP production that stimulates spermatozoa movement. Caffeine is also used for induction of in vitro acrosome reaction in mammalian spermatozoa, an important step in achieving fertilization. The aim of this study was to assess the effect of caffeine on sperm's motility, vitality and laboratory fertilization rates in mouse in two T6 and M16 media. Epididymal mouse sperms were collected and treated by caffine in T6 and M16 media and their motility and vitality rates were evaluated. The pretreated sperms were added to oocytes in T6 and M16 media with and without caffeine and fertilization rates were recorded after 24 hours incubation. Sperm's motility (81.7±1.67%) and vitality (88.7±1.33%) rates and percentage of fertilized oocytes (67.52±8.16%) in T6 medium plus caffeine compare to control group have increased and shown significant differences at p≤0.01. While the percentages of these parameters in M16 medium supplemented with caffeine were 68.3±6.01%, 78±6.11%, and 42.6±12.96 respectively and in comparison to control group (M16 without caffeine) have not shown significant differences. Addition of caffeine to T6 medium promotes the sperm's motility and vitality and enhances fertilization and early in vitro development of mouse embryos. This article extracted from M.Sc. thesis. (Narges Navabi).

  20. Human epidermal Langerhans cells cointernalize by receptor-mediated endocytosis "nonclassical" major histocompatibility complex class I molecules (T6 antigens) and class II molecules (HLA-DR antigens).

    PubMed Central

    Hanau, D; Fabre, M; Schmitt, D A; Garaud, J C; Pauly, G; Tongio, M M; Mayer, S; Cazenave, J P

    1987-01-01

    HLA-DR and T6 surface antigens are expressed only by Langerhans cells and indeterminate cells in normal human epidermis. We have previously demonstrated that T6 antigens are internalized in Langerhans cells and indeterminate cells by receptor-mediated endocytosis. This process is induced by the binding of BL6, a monoclonal antibody directed against T6 antigens. In the present study, using a monoclonal antibody directed against HLA-DR antigens, on human epidermal cells in suspension, we show that the surface HLA-DR antigens are also internalized by receptor-mediated endocytosis in Langerhans and indeterminate cells. Moreover, using immunogold double labeling, we demonstrate that T6 and HLA-DR antigens are internalized through common coated regions of the membrane of Langerhans or indeterminate cells. The receptor-mediated endocytosis that is induced involves coated pits and vesicles, receptosomes, lysosomes, and also, in Langerhans cells, the Birbeck granules. Thus, T6 antigens, which are considered to be "unusual" or "nonclassical" major histocompatibility complex class I molecules, and the major histocompatibility complex class II molecules, HLA-DR, are internalized in Langerhans and indeterminate cells through common receptor-mediated endocytosis organelles. Images PMID:3106979

  1. Novel Gene Clusters and Metabolic Pathway Involved in 3,5,6-Trichloro-2-Pyridinol Degradation by Ralstonia sp. Strain T6

    PubMed Central

    Li, Jingquan; Huang, Yan; Hou, Ying; Li, Xiangmin; Cao, Hui

    2013-01-01

    3,5,6-Trichloro-2-pyridinol (TCP) is a widespread pollutant. Some bacteria and fungi have been reported to degrade TCP, but the gene clusters responsible for TCP biodegradation have not been characterized. In this study, a fragment of the reduced flavin adenine dinucleotide (FADH2)-dependent monooxygenase gene tcpA was amplified from the genomic DNA of Ralstonia sp. strain T6 with degenerate primers. The tcpA disruption mutant strain T6-ΔtcpA could not degrade TCP but could degrade the green intermediate metabolite 3,6-dihydroxypyridine-2,5-dione (DHPD), which was generated during TCP biodegradation by strain T6. The flanking sequences of tcpA were obtained by self-formed adaptor PCR. tcpRXA genes constitute a gene cluster. TcpR and TcpX are closely related to the LysR family transcriptional regulator and flavin reductase, respectively. T6-ΔtcpA-com, the complementation strain for the mutant strain T6-ΔtcpA, recovered the ability to degrade TCP, and the strain Escherichia coli DH10B-tcpRXA, which expressed the tcpRXA gene cluster, had the ability to transform TCP to DHPD, indicating that tcpA is a key gene in the initial step of TCP degradation and that TcpA dechlorinates TCP to DHPD. A library of DHPD degradation-deficient mutants of strain T6 was obtained by random transposon mutagenesis. The fragments flanking the Mariner transposon were amplified and sequenced, and the dhpRIJK gene cluster was cloned. DhpJ could transform DHPD to yield an intermediate product, 5-amino-2,4,5-trioxopentanoic acid (ATOPA), which was further degraded by DhpI. DhpR and DhpK are closely related to the AraC family transcriptional regulator and the MFS family transporter, respectively. PMID:24056464

  2. Molecular identification of natural hybrids between Trichinella nativa and Trichinella T6 provides evidence of gene flow and ongoing genetic divergence.

    PubMed

    La Rosa, G; Marucci, G; Zarlenga, D S; Casulli, A; Zarnke, R L; Pozio, E

    2003-02-01

    To date, there are no data available on the population genetics of Trichinella due to the lack of genetic markers and the difficulty of working with such small parasites. In the Arctic region of North America and along the Rocky Mountains, there exist two genotypes of Trichinella, Trichinella nativa and Trichinella T6, respectively, which are well differentiated by biochemical and molecular characters. However, both are resistant to freezing, show other common biological characters (e.g. low or no infectivity to rodents and swine) and produce fertile F1 offspring upon interbreeding. To data, these two genotypes have been considered allopatric. In this study, we detected both genotypes in wolves of the same wolf packs in Alaska, suggesting sympatry. A single GTT trinucleotide present in the ITS-2 sequence of T. nativa but not in Trichinella T6 was used as a genetic marker to study gene flow for this character in both a murine infection model and in larvae from naturally-infected Alaskan wolves. Only F1 larvae originating from a cross between T. nativa male and Trichinella T6 female were able to produce F2 offspring. Larvae (F1) originating from a cross between Trichinella T6 male and T. nativa female were not reproductively viable. As expected, all F1 larvae showed a heterozygote pattern for the GTT character upon heteroduplex analysis; however, within the F2 population, the number of observed heterozygotes (n=52) was substantially higher than expected (n=39.08), as supported by the F(is) index, and was not in the Hardy-Weinberg equilibrium. Larvae from two of the 16 Trichinella positive Alaskan wolves, showed the Trichinella T6 pattern or the T. nativa/Trichinella T6 hybrid pattern. Our data demonstrate that T. nativa and Trichinella T6 live in sympatry at least in Alaskan wolves, where T. nativa occurs more frequently (69%) than Trichinella T6 (31%). One explanation for this phenomenon is that glacial periods may have caused a geographical relocation, colonisation

  3. Functional anticodon architecture of human tRNALys3 includes disruption of intraloop hydrogen bonding by the naturally occurring amino acid modification, t6A.

    PubMed

    Stuart, J W; Gdaniec, Z; Guenther, R; Marszalek, M; Sochacka, E; Malkiewicz, A; Agris, P F

    2000-11-07

    The structure of the human tRNA(Lys3) anticodon stem and loop domain (ASL(Lys3)) provides evidence of the physicochemical contributions of N6-threonylcarbamoyladenosine (t(6)A(37)) to tRNA(Lys3) functions. The t(6)A(37)-modified anticodon stem and loop domain of tRNA(Lys3)(UUU) (ASL(Lys3)(UUU)- t(6)A(37)) with a UUU anticodon is bound by the appropriately programmed ribosomes, but the unmodified ASL(Lys3)(UUU) is not [Yarian, C., Marszalek, M., Sochacka, E., Malkiewicz, A., Guenther, R., Miskiewicz, A., and Agris, P. F., Biochemistry 39, 13390-13395]. The structure, determined to an average rmsd of 1.57 +/- 0.33 A (relative to the mean structure) by NMR spectroscopy and restrained molecular dynamics, is the first reported of an RNA in which a naturally occurring hypermodified nucleoside was introduced by automated chemical synthesis. The ASL(Lys3)(UUU)-t(6)A(37) loop is significantly different than that of the unmodified ASL(Lys3)(UUU), although the five canonical base pairs of both ASL(Lys3)(UUU) stems are in the standard A-form of helical RNA. t(6)A(37), 3'-adjacent to the anticodon, adopts the form of a tricyclic nucleoside with an intraresidue H-bond and enhances base stacking on the 3'-side of the anticodon loop. Critically important to ribosome binding, incorporation of the modification negates formation of an intraloop U(33).A(37) base pair that is observed in the unmodified ASL(Lys3)(UUU). The anticodon wobble position U(34) nucleobase in ASL(Lys3)(UUU)-t(6)A(37) is significantly displaced from its position in the unmodified ASL and directed away from the codon-binding face of the loop resulting in only two anticodon bases for codon binding. This conformation is one explanation for ASL(Lys3)(UUU) tendency to prematurely terminate translation and -1 frame shift. At the pH 5.6 conditions of our structure determination, A(38) is protonated and positively charged in ASL(Lys3)(UUU)-t(6)A(37) and the unmodified ASL(Lys3)(UUU). The ionized carboxylic acid moiety

  4. Identification of a t(6;19)(p21;q13) translocation in a t(9;22)(q34;q11) Ph-positive CML by FISH

    SciTech Connect

    Elizalde, A.M.; Abdelaal, A.; Gogineni, S.K.

    1994-09-01

    More than 90% of the reported cases of chronic myelogenous leukemia (CML) have the typical t(9;22)(q34;q11) translocation as the only abnormality. Approximately 5 to 8% of CML cases have so-called variant translocations where either one or more chromosomes is involved with the t(9;22) or an additional translocation has arisen. What is most unusual is that, clinically, these cases do not differ from standard CML. We report a case of CML who presented with typical clinical symptoms and the standard t(9;22) plus a t(6;19)(p21;q13) translocation. We used the FISH technique with whole chromosome 6 painting probe (GIBCO/BRL, Gaithersburg, MD) and whole chromosome 19 painting probe (Oncor, Gaithersburg, MD) to verify the unusual tanslocation. We then applied the two color ABL/BCR probe (Oncor) to establish that the ABL gene had translocated to the BCR gene on chromosome 22 and was not involved in the separate t(6;19) translocation. The t(6;19) has been reported in three previous cases; however, in all three, there was at least one additional translocation besides the t(9;22) and the t(6;19). The 6p21 breakpoint is frequently involved in variant translocations with chromosomes 9 and 22, and chromosome 19 is one of the most frequent aberrations detected in blast crisis. It is obvious that molecular characterization of these unusual cases should help to further elucidate this disease.

  5. Ligustrazine-Oleanolic Acid Glycine Derivative, G-TOA, Selectively Inhibited the Proliferation and Induced Apoptosis of Activated HSC-T6 Cells.

    PubMed

    Bi, Siling; Chu, Fuhao; Wang, Mina; Li, Bi; Mao, Pei; Zhang, Huazheng; Wang, Penglong; Guo, Wenbo; Xu, Liang; Ren, Liwei; Lei, Haimin; Zhang, Yuzhong

    2016-11-23

    Hepatic fibrosis is a naturally occurring wound-healing reaction, with an imbalance of extracellular matrix (ECM) during tissue repair response, which can further deteriorate to hepatocellular carcinoma without timely treatment. Inhibiting activated hepatic stellate cell (HSC) proliferation and inducing apoptosis are the main methods for the treatment of liver fibrosis. In our previous study, we found that the TOA-glycine derivative (G-TOA) had exhibited more significant inhibitory activity against HepG2 cells and better hydrophilicity than TOA, ligustrazine (TMP), and oleanolic acid (OA). However, inhibiting activated HSC proliferation and inducing apoptosis by G-TOA had not been reported. In this paper, the selective cytotoxicity of G-TOA was evaluated on HSC-T6 cells and L02 cells, and apoptosis mechanisms were explored. It was found that G-TOA could selectively inhibit the proliferation of activated HSC-T6 cells, induce morphological changes, early apoptosis, and mitochondrial membrane potential depolarization, increase intracellular free calcium levels, downregulate the expression of NF-κB/p65 and COX-2 protein, and decrease the ratio of Bcl-2/Bax, thereby inducing HSC-T6 cell apoptosis. Thence, G-TOA might be a potential antifibrosis agent for the therapy of hepatic fibrosis, provided that it exerts anti-fibrosis effects on activated HSC-T6 cells.

  6. H-NS binding to evpB and evpC and repressing T6SS expression in fish pathogen Edwardsiella piscicida.

    PubMed

    Cui, Shilei; Xiao, Jingfan; Wang, Qiyao; Zhang, Yuanxing

    2016-09-01

    Edwardsiella piscicida is an important causative agent of hemorrhagic septicemia in fish and infects both cultured and wild fish species. Type VI secretion system (T6SS) was proved to play important roles in pathogenesis of E. piscicida. In this study, it was demonstrated that the expression of T6SS genes evpB and evpC was under control of the global regulator H-NS in E. piscicida and the transcriptional level of evpB and evpC was significantly down-regulated by H-NS. Compared to the wild type, the transcriptional levels of evpB and evpC were up-regulated in hns null mutant, while down-regulated in hns overexpression strain. The results of EMSA and DNase I footprinting revealed that H-NS protein directly bound to upstream region of evpC at multiple sites. A high-affinity motif with a 9-nucleotide sequence 5'-ATATAAAAT-3' was defined for H-NS preferential recognition based on the feature of the binding sites. These results indicated that H-NS acted cooperatively to form extended nucleoprotein filaments on target DNA. Site-directed mutagenesis of H-NS further showed that R86 played an essential role in T6SS gene binding. These findings highlighted the mechanisms underlying the complex regulation network of T6SS by H-NS in E. piscicida.

  7. Functional assignment of KEOPS/EKC complex subunits in the biosynthesis of the universal t6A tRNA modification

    PubMed Central

    Perrochia, Ludovic; Guetta, Dorian; Hecker, Arnaud; Forterre, Patrick; Basta, Tamara

    2013-01-01

    N6-threonylcarbamoyladenosine (t6A) is a universal tRNA modification essential for normal cell growth and accurate translation. In Archaea and Eukarya, the universal protein Sua5 and the conserved KEOPS/EKC complex together catalyze t6A biosynthesis. The KEOPS/EKC complex is composed of Kae1, a universal metalloprotein belonging to the ASHKA superfamily of ATPases; Bud32, an atypical protein kinase and two small proteins, Cgi121 and Pcc1. In this study, we investigated the requirement and functional role of KEOPS/EKC subunits for biosynthesis of t6A. We demonstrated that Pcc1, Kae1 and Bud32 form a minimal functional unit, whereas Cgi121 acts as an allosteric regulator. We confirmed that Pcc1 promotes dimerization of the KEOPS/EKC complex and uncovered that together with Kae1, it forms the tRNA binding core of the complex. Kae1 binds l-threonyl-carbamoyl-AMP intermediate in a metal-dependent fashion and transfers the l-threonyl-carbamoyl moiety to substrate tRNA. Surprisingly, we found that Bud32 is regulated by Kae1 and does not function as a protein kinase but as a P-loop ATPase possibly involved in tRNA dissociation. Overall, our data support a mechanistic model in which the final step in the biosynthesis of t6A relies on a strictly catalytic component, Kae1, and three partner proteins necessary for dimerization, tRNA binding and regulation. PMID:23945934

  8. Full Field Measurement of The Dynamic Response of AA6061-T6 Aluminum Alloy under High Strain Rate Compression and Torsion Loads

    NASA Astrophysics Data System (ADS)

    Odoh, Daniel Oghenekewhe Oluwatobi

    The dynamic response of AA6061-T6 aluminum alloy under high strain rate loading in compression and torsion loading conditions was studied using the split Hopkinson pressure bar, the Kolsky torsion bar, and the high speed digital image correlation system. AA6061-T6 alloy, the most widely used in the AA6000 series, is a multi-purpose Al-Mg-Si-Cu alloy containing about 0.4 % wt. of Cu and other alloying additives. The properties of AA6061-T6 aluminum alloy including medium to high strength, good fracture toughness, and high corrosion resistance make it to find application in high performance structures such as the automotive parts, panels, and armored carriers. In this work, the effect of strain rate during dynamic test on formation of adiabatic shear bands in AA6061-T6 alloy was investigated. A post deformation analysis of the tested specimen was performed in order to determine the damage evolution and strain localization along the narrow adiabatic shear bands within the specimen. The formation of an adiabatic shear band in the aluminum alloy tested was found to depend on the strain rate at which the test was conducted. Stress, strain, and strain rate data obtained from the elastic waves in the compression and torsion bar tests were also compared with those obtained using the high speed digital cameras. Results show good agreement between both measurement techniques with the 3D digital image correlation technique giving a slightly lower result. Scanning and electron microscopy results show that both deformed and transformed bands can be formed in AA6061-T6 alloy during dynamic loading. The type of adiabatic shear band formed depends on the strain rate at which test was performed.

  9. Tensile Properties of 7075-T6 and 2024-T3 Aluminum-alloy Sheet Heated at Uniform Temperature Rates Under Constant Load

    NASA Technical Reports Server (NTRS)

    Heimerl, George J; Inge, John E

    1955-01-01

    Results are presented of tests to determine the effect of heating at uniform temperature rates from 0.2 degrees to 100 degrees F. per second on the tensile properties of 7075-T6 d(75s-T6) and 2024-T3 (24s-T3) aluminum-alloy sheet under constant-load conditions. Yield and rupture stresses, obtained under rapid-heating conditions, are compared with results of elevated-temperature stress-strain tests for 1/2-hour exposure. Master yield-and-rupture-stress curves based on linear temperature-rate parameter are presented. Yield and rupture stresses and temperatures may be predicted by means of master curves and the parameter.

  10. Examination of irradiated 304L stainless steel to 6061-T6 aluminum inertia welded transition joints after irradiation in a spallation neutron

    SciTech Connect

    Dunn, K.A.

    2000-04-28

    The Savannah River Technology Center (SRTC) designed and fabricated tritium target/blanket assemblies which were irradiated for six months at the Los Alamos Neutron Science Center (LANSCE). Cooling water was supplied to the assemblies through 1 inch diameter 304L Stainless Steel (SS) tubing. To attach the 304L SS tubing to the modules a 304L SS to 6061-T6 Aluminum (Al) inertia welded transition joint was used. These SS/Al inertia weld transition joints simulate expected transition joints in the Accelerator Production of Tritium (APT) Target/Blanket where as many as a thousand SS/Al weld transition joints will be used. Materials compatibility between the 304L SS and the 6061-T6 Al in the spallation neutron environment is a major concern as well as the corrosion associated with the cooling water flowing through the piping. The irradiated inertia weld examination will be discussed.

  11. The Effect of Some Water-Displacing Corrosion Preventives on Corrosion of Aluminium Alloys 7075-T651 and 2024-T6,

    DTIC Science & Technology

    1983-08-01

    AIR 82/138 4. Title 5. Security 6. No. Pages THE EFFECT OF SOME WATER- DISPLACING a. document 8 CORROSION PREVENTIVES ON CORROSION Unclassifiedb. title...LABORATORIES MELBOURNE, VICTORIA MATERIALS REPORT 115 THE EFFECT OF SOME WATER- DISPLACING CORROSION PREVENTIVES ON CORROSION OF ALUMINIUM ALLOYS 7075-T651 AND... DISPLACING CORROSION PREVENTIVES ON CORROSION OF ALUMINIUM ALLOYS 7075-T651 AND 2024-T6 by L. WILSON and R. S. G. DEVEREUX SUMMARY The effectiveness

  12. Direct-reading design charts for 75S-T6 aluminum-alloy flat compression panels having longitudinal extruded Z-section stiffeners

    NASA Technical Reports Server (NTRS)

    Hickman, William A; Dow, Norris F

    1951-01-01

    Direct-reading design charts are presented for 75S-T6 aluminum-alloy flat compression panels having longitudinal extruded Z-section stiffeners. These charts, which cover a wide range of proportions, make possible the direct determination of the stress and all panel dimensions required to carry a given intensity of loading with a given skin thickness and effective length of panel.

  13. The influence of hypermodified nucleosides lysidine and t(6)A to recognize the AUA codon instead of AUG: a molecular dynamics simulation study.

    PubMed

    Sonawane, Kailas D; Sambhare, Susmit B

    2015-11-01

    Hypermodified nucleosides lysidine (L) and N(6)-threonylcarbamoyladenosine (t(6)A) influence codon-anticodon interactions during the protein biosynthesis process. Lysidine prevents the misrecognition of the AUG codon as isoleucine and that of AUA as methionine. The structural significance of these modified bases has not been studied in detail at the atomic level. Hence, in the present study we performed multiple molecular dynamics (MD) simulations of anticodon stem loop (ASL) of tRNA(Ile) in the presence and absence of modified bases 'L' and 't(6)A' at the 34th and 37th positions respectively along with trinucleotide 'AUA' and 'AUG' codons. Hydrogen bonding interactions formed by the tautomeric form of lysidine may assist in reading the third base adenine of the 'AUA' codon, unlike the guanine of the 'AUG' codon. Such interactions might be useful to restrict codon specificity to recognize isoleucine tRNA instead of methionine tRNA. The t(6)A side chain interacts with the purine ring of the first codon nucleotide adenine, which might provide base stacking interactions and could be responsible for restricting extended codon-anticodon recognition. We found that ASL tRNA(Ile) in the absence of modifications at the 34th and 37th positions cannot establish proper hydrogen bonding interactions to recognize the isoleucine codon 'AUA' and subsequently disturbs the anticodon loop structure. The binding free energy calculations revealed that tRNA(Ile) ASL with modified nucleosides prefers the codon AUA over AUG. Thus, these findings might be useful to understand the role of modified bases L and t(6)A to recognize the AUA codon instead of AUG.

  14. Genomic analysis of the biocontrol strain Pseudomonas fluorescens Pf29Arp with evidence of T3SS and T6SS gene expression on plant roots.

    PubMed

    Marchi, Muriel; Boutin, Morgane; Gazengel, Kévin; Rispe, Claude; Gauthier, Jean-Pierre; Guillerm-Erckelboudt, Anne-Yvonne; Lebreton, Lionel; Barret, Matthieu; Daval, Stéphanie; Sarniguet, Alain

    2013-06-01

    Several bacterial strains of the Pseudomonas genus provide plant growth stimulation, plant protection against pests or bioremediation. Among these bacteria, P. fluorescens Pf29Arp reduces the severity of take-all, a disease caused by the pathogenic fungus Gaeumannomyces graminis var. tritici (Ggt) on wheat roots. In this study, we obtained a draft genome of Pf29Arp and subsequent comparative genomic analyses have revealed that this bacterial strain is closely related to strains of the 'P. brassicacearum-like' subgroup including P. brassicacearum ssp. brassicacearum NFM421 and P. fluorescens F113. Despite an overall chromosomal organization similar to these strains, a number of features including antibiotic synthesis gene clusters from secondary metabolism are not found in the Pf29Arp genome. But Pf29Arp possesses different protein secretion systems including type III (T3SS) and type VI (T6SS) secretion systems. Pf29Arp is the first Pseudomonas sp. strain described with four T6SS clusters (cluster I, II, III and IV). In addition, some protein-coding genes involved in the assembly of these secretion systems are basally expressed during Pf29Arp colonization of healthy wheat roots and display different expression patterns on necrotized roots caused by Ggt. These data suggest a role of T3SS and T6SS in the Pf29Arp adaptation to different root environments.

  15. Time exposure studies on stress corrosion cracking of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651, and titanium 6Al-4V

    NASA Technical Reports Server (NTRS)

    Terrell, J.

    1973-01-01

    The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651 and titanium 6Al-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 7) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity), and demineralized distilled water. Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, titanium stressed specimens showed no reactions to its environment. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 and aluminum 2014-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl), while aluminum 2219-T87 seem to resist stress corrosion cracking in sodium chloride at three levels of stress (25%, 50%, and 75% Y.S.). In organic fluids of methyl, ethyl, and iso-propyl alcohol, 2014-T6 and 7075-T651 did not fail by SCC; but 2014-T651 was susceptible to SCC in methly alcohol, but resistant in ethyl alcohol, iso-propyl alcohol and demineralized distilled water.

  16. Galvanic coupling between D6AC steel, 6061-T6 aluminum, Inconel 718 and graphite-epoxy composite material: Corrosion occurrence and prevention

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Higgins, R. H.

    1983-01-01

    The effects of galvanic coupling between D6AC steel, 6061-T6 aluminum, Inconel 718, and graphite-epoxy composite material (G/E) in 3.5% NaCl were studied. Measurements of corrosion potentials, galvanic currents and corrosion rates of the bare metals using weight-loss methods served to establish the need for corrosion protection in cases where D6AC steel and 6061-T6 aluminum are galvanically coupled to G/E in salt water while Inconel 718 was shown to be compatible with G/E. Six tests were made to study corrosion protective methods for eliminating galvanic corrosion in the cases of D6AC steel and 6061-T6 aluminum coupled to G/E. These results indicate that, when the G/E is completely coated with paint or a paint/polyurethane resin combination, satisfactory protection of the D6AC steel is achieved with either a coat of zinc-rich primer or a primer/topcoat combination. Likewise, satisfactory corrosion protection of the aluminum is achieved by coating it with an epoxy coating system.

  17. Surface Characterizations of Fretting Fatigue Damage in Aluminum Alloy 7075-T6 Clamped Joints: The Beneficial Role of Ni–P Coatings

    PubMed Central

    Oskouei, Reza H.; Barati, Mohammad Reza; Ibrahim, Raafat N.

    2016-01-01

    This paper aims to characterize the surface damage as a consequence of fretting fatigue in aluminum alloy 7075-T6 plates in double-lap bolted joints through XRD, surface profilometry, and SEM analyses. The main focus was on the surface roughness and chemical phase composition of the damaged zone along with the identification of fretting fatigue crack initiations over the surface of the material. The surface roughness of the fretted zone was found to increase when the joint was clamped with a higher tightening torque and tested under the same cyclic loading. Additionally, MgZn2 (η/ή) precipitates and ZnO phase were found to form onto the surface of uncoated aluminum plate in the fretted and worn zones. The formation of the ZnO phase was understood to be a result of frictional heat induced between the surface of contacting uncoated Al 7075-T6 plates during cyclic loading and exposure to the air. The beneficial role of electroless nickel-phosphorous (Ni–P) coatings in minimizing the fretting damage and thus improving the fretting fatigue life of the aluminum plates was also studied. The results showed that the surface roughness decreased by approximately 40% after applying Ni–P coatings to the Al 7075-T6 plates. PMID:28773267

  18. The potential of species-specific tagatose-6-phosphate (T6P) pathway in Lactobacillus casei group for galactose reduction in fermented dairy foods.

    PubMed

    Wu, Qinglong; Shah, Nagendra P

    2017-04-01

    Residual lactose and galactose in fermented dairy foods leads to several industrial and health concerns. There is very little information pertaining to manufacture of fermented dairy foods that are low in lactose and galactose. In the present study, comparative genomic survey demonstrated the constant presence of chromosome-encoded tagatose-6-phosphate (T6P) pathway in Lactobacillus casei group. Lactose/galactose utilization tests and β-galactosidase assay suggest that PTS(Gal) system, PTS(Lac) system and T6P pathway are major contributors for lactose/galactose catabolism in this group of organisms. In addition, it was found than lactose catabolism by Lb. casei group accumulated very limited galactose in the MRS-lactose medium and in reconstituted skim milk, whereas Streptococcus thermophilus and Lb. delbrueckii subsp. bulgaricus (Lb. bulgaricus) strains secreted high amount of galactose extracellularly. Moreover, co-culturing Lb. casei group with Str. thermophilus showed significant reduction in galactose content, while co-culturing Lb. casei group with Lb. bulgaricus showed significant reduction in lactose content but significant increase in galactose content in milk. Overall, the present study highlighted the potential of Lb. casei group for reducing galactose accumulation in fermented milks due to its species-specific T6P pathway.

  19. Tn-Seq analysis of Vibrio cholerae intestinal colonization reveals a role for T6SS-mediated antibacterial activity in the host.

    PubMed

    Fu, Yang; Waldor, Matthew K; Mekalanos, John J

    2013-12-11

    Analysis of genes required for host infection will provide clues to the drivers of evolutionary fitness of pathogens like Vibrio cholerae, a mounting threat to global heath. We used transposon insertion site sequencing (Tn-seq) to comprehensively assess the contribution of nearly all V. cholerae genes toward growth in the infant rabbit intestine. Four hundred genes were identified as critical to V. cholerae in vivo fitness. These included most known colonization factors and several new genes affecting the bacterium's metabolic properties, resistance to bile, and ability to synthesize cyclic AMP-GMP. Notably, a mutant carrying an insertion in tsiV3, encoding immunity to a bacteriocidal type VI secretion system (T6SS) effector VgrG3, exhibited a colonization defect. The reduced in vivo fitness of tsiV3 mutants depends on their cocolonization with bacterial cells carrying an intact T6SS locus and VgrG3 gene, suggesting that the V. cholerae T6SS is functional and mediates antagonistic interbacterial interactions during infection. Copyright © 2013 Elsevier Inc. All rights reserved.

  20. The structural basis of the Tle4-Tli4 complex reveals the self-protection mechanism of H2-T6SS in Pseudomonas aeruginosa.

    PubMed

    Lu, Defen; Zheng, Youshi; Liao, Naishun; Wei, Ling; Xu, Bo; Liu, Xiaolong; Liu, Jingfeng

    2014-12-01

    The type VI secretion system (T6SS) has recently been demonstrated to mediate interbacterial competition and to discriminate between self and nonself. T6SS(+) bacteria employ toxic effectors to inhibit rival cells and concurrently use effector cognate immunity proteins to protect their sibling cells. The effector and immunity pairs (E-I pairs) endow the bacteria with a great advantage in niche competition. Tle4-Tli4 (PA1510-PA1509) is a newly identified E-I pair that is controlled by H2-T6SS in Pseudomonas aeruginosa. Tle4 exhibits phospholipase activity, which destroys the cell membrane of rival cells, and the periplasm-located Tli4 in donor cells eliminates this toxic effect of Tle4. In this paper, the structure of the Tle4-Tli4 complex is reported at 1.75 Å resolution. Tle4 consists of two domains: a conserved α/β-hydrolase domain and an unusual cap domain in which two lid regions (lid1 and lid2) display a closed conformation that buries the catalytic triad in a deep funnel. Tli4 also displays a two-domain structure, in which a large lobe and a small lobe form a crab claw-like conformation. Tli4 uses this crab claw to grasp the cap domain of Tle4, especially the lid2 region, which prevents the interfacial activation of Tle4 and thus causes enzymatic dysfunction of Tle4 in sister cells.

  1. INFLUENCE OF URETHANE AND OF HYDROSTATIC PRESSURE ON THE GROWTH OF BACTERIOPHAGES T2, T5, T6, AND T7

    PubMed Central

    Foster, Ruth A. C.; Johnson, Frank H.

    1951-01-01

    In 0.5 per cent NaCl, nutrient broth at 35°C., urethane in a concentration of 0.4 M stops the reproduction of Escherichia coli, strain B. On dilution with 20 volumes of sterile medium, growth is resumed at its former rate after a short lag. In the one-step growth of T2, 15, T6, or T7, in the same medium at the same temperature, 0.4 M urethane, when added at the time of infection, had no apparent effect on adsorption and caused no decrease in titer throughout the latent period of the control, but completely prevented a rise in titer. If diluted 1:20 with sterile medium prior to a certain critical time in the latent period, however, bacteriophage was liberated at the same time, and in the same amount as in the control. The initial stage of apparent insensitivity to the drug lasts from the time of infection until the approximate critical times of 7 minutes with T7, T2, or T6, or 13 minutes with T5. Under the conditions described, the normal latent periods were 14, 23, 30, and 44 minutes for T7, T2, T6, and T5, respectively. At the critical times referred to above, there begins a stage characterized by complete sensitivity, rather than complete insensitivity, to 0.4 M urethane, in the sense that no active phage is subsequently liberated in continued presence of the drug. The length of this completely sensitive stage, as judged by addition of the drug at successive intervals during the latent period, extends from approximately 7 until 9 minutes after infection with T7, 7 until 15 minutes with T2 or T6, or 13 until 25 minutes with T5. When the urethane is added late in this stage of T2, a decrease in initial titer takes place as judged by assays made 40 minutes after infection, the maximum effect occurring when the drug is added between 14 and 15 minutes after infection. When added subsequently to the completely sensitive stage of each type, i.e. subsequently to 9 minutes after infection with T7, 15 minutes with T2 or T6, or 25 minutes with T5, liberation of the

  2. The structures of T6, T3R3 and R6 bovine insulin: combining X-ray diffraction and absorption spectroscopy.

    PubMed

    Frankær, Christian Grundahl; Knudsen, Marianne Vad; Norén, Katarina; Nazarenko, Elena; Ståhl, Kenny; Harris, Pernille

    2012-10-01

    The crystal structures of three conformations, T(6), T(3)R(3) and R(6), of bovine insulin were solved at 1.40, 1.30 and 1.80 Å resolution, respectively. All conformations crystallized in space group R3. In contrast to the T(6) and T(3)R(3) structures, different conformations of the N-terminal B-chain residue PheB1 were observed in the R(6) insulin structure, resulting in an eightfold doubling of the unit-cell volume upon cooling. The zinc coordination in each conformation was studied by X-ray absorption spectroscopy (XAS), including both EXAFS and XANES. Zinc adopts a tetrahedral coordination in all R(3) sites and an octahedral coordination in T(3) sites. The coordination distances were refined from XAS with a standard deviation of <0.01 Å. In contrast to the distances determined from the medium-resolution crystal structures, the XAS results were in good agreement with similar coordination geometries found in small molecules, as well as in other high-resolution insulin structures. As the radiation dose for XRD experiments is two orders of magnitude higher compared with that of XAS experiments, the single crystals were exposed to a higher degree of radiation damage that affected the zinc coordination in the T(3) sites in particular. Furthermore, XANES spectra for the zinc sites in T(6) and R(6) insulin were successfully calculated using finite difference methods and the bond distances and angles were optimized from a quantitative XANES analysis.

  3. STAT activation status differentiates leukemogenic from non-leukemogenic stem cells in AML and is suppressed by arsenic in t(6;9)-positive AML.

    PubMed

    Oancea, Claudia; Rüster, Brigitte; Brill, Boris; Roos, Jessica; Heinssmann, Maria; Bug, Gesine; Mian, Afsar Ali; Guillen, Nathalie Andrea; Kornblau, Steven M; Henschler, Reinhard; Ruthardt, Martin

    2014-11-01

    Acute myeloid leukemia (AML) is characterized by an aberrant self-renewal of hematopoietic stem cells (HSC) and a block in differentiation. The major therapeutic challenge is the characterization of the leukemic stem cell as a target for the eradication of the disease. Until now the biology of AML-associated fusion proteins (AAFPs), such as the t(15;17)-PML/RARα, t(8;21)-RUNX1/RUNX1T1 and t(6;9)-DEK/NUP214, all able to induce AML in mice, was investigated in different models and genetic backgrounds, not directly comparable to each other. To avoid the bias of different techniques and models we expressed these three AML-inducing oncogenes in an identical genetic background and compared their influence on the HSC compartment in vitro and in vivo. These AAFPs exerted differential effects on HSCs and PML/RARα, similar to DEK/NUP214, induced a leukemic phenotype from a small subpopulation of HSCs with a surface marker pattern of long-term HSC and characterized by activated STAT3 and 5. In contrast the established AML occurred from mature populations in the bone marrow. The activation of STAT5 by PML/RARα and DEK/NUP214 was confirmed in t(15;17)(PML/RARα) and t(6;9)(DEK/NUP214)-positive patients as compared to normal CD34+ cells. The activation of STAT5 was reduced upon the exposure to Arsenic which was accompanied by apoptosis in both PML/RARα- and DEK/NUP214-positive leukemic cells. These findings indicate that in AML the activation of STATs plays a decisive role in the biology of the leukemic stem cell. Furthermore we establish exposure to arsenic as a novel concept for the treatment of this high risk t(6;9)-positive AML.

  4. Detection and serogroup differentiation of Salmonella spp. in food within 30 hours by enrichment-immunoassay with a T6 monoclonal antibody capture enzyme-linked immunosorbent assay.

    PubMed Central

    Ng, S P; Tsui, C O; Roberts, D; Chau, P Y; Ng, M H

    1996-01-01

    We previously described an antigen capture enzyme-linked immunosorbent assay which makes use of monoclonal antibody T6, which recognizes an epitope on the outer core polysaccharide of Salmonella lipopolysaccharide molecules that is common to almost all Salmonella serovars. In this paper, we show that this assay can detect between 10(5) and 10(7) Salmonella cells per ml even in the presence of excess Escherichia coli. A total of 153 of 154 (99%) serogroup A to E strains and 51 of 78 (71%) serogroup F to 67 strains were reactive as determined by this assay. This corresponds to a detection rate of approximately 98% of all salmonellae known to affect humans. None of the 65 strains of non-Salmonella bacteria tested positive. Taking advantage of the O-factor polysaccharides also present on the antigen captured by the immobilized T6 antibody, we showed that 136 of 154 Salmonella serogroup A to E strains (88%) were correctly differentiated according to their serogroups by use of enzyme conjugates of a panel of O-factor-specific monoclonal antibodies. We evaluated this assay for the detection and serogroup differentiation of salmonellae directly from enrichment cultures of simulated food, eggs, pork, and infant formula milk. All 26 samples which had been contaminated with Salmonella spp. were detected by T6 (100% sensitivity), with only one false-positive result from 101 samples not contaminated by Salmonella spp. (99% specificity). The detection time was substantially reduced to between 17 and 29 h, depending on the enrichment methods used. Since there were no false-negative results, we concluded that this enrichment-immunoassay method can afford rapid screening for Salmonella spp. in food samples. PMID:8779567

  5. Recording triggered EMG thresholds from axillary chest wall electrodes: a new refined technique for accurate upper thoracic (T2-T6) pedicle screw placement.

    PubMed

    Regidor, Ignacio; de Blas, Gema; Barrios, Carlos; Burgos, Jesús; Montes, Elena; García-Urquiza, Sergio; Hevia, Edurado

    2011-10-01

    This study was aimed at evaluating the sensitivity and safety of a new technique to record triggered EMG thresholds from axillary chest wall electrodes when inserting pedicle screws in the upper thoracic spine (T2-T6). A total of 248 (36.6%) of a total of 677 thoracic screws were placed at the T2-T6 levels in 92 patients with adolescent idiopathic scoliosis. A single electrode placed at the axillary midline was able to record potentials during surgery from all T2-T6 myotomes at each side. Eleven screws were removed during surgery because of malposition according to intraoperative fluoroscopic views. Screw position was evaluated after surgery in the remaining 237 screws using a CT scan. Malposition was detected in 35 pedicle screws (14.7%). Pedicle medial cortex was breached in 24 (10.1%). Six screws (2.5%) were located inside the spinal canal. Mean EMG threshold was 24.44 ± 11.30 mA in well-positioned screws, 17.98 ± 8.24 mA (p < 0.01) in screws violating the pedicle medial cortex, and 10.38 ± 3.33 mA (p < 0.005) in screws located inside the spinal canal. Below a threshold of 12 mA, 33.4% of the screws (10/30) were malpositioned. Furthermore, 36% of the pedicle screws with t-EMG stimulation thresholds within the range 6-12 mA were malpositioned. In conclusion, assessment of upper thoracic pedicle screw placement by recording tEMG at a single axillary electrode was highly reliable. Thresholds below 12 mA should alert surgeons to suspect screw malposition. This technique simplifies tEMG potential recording to facilitate safe placement of pedicle screws at upper thoracic levels.

  6. Analysis of five presumptive protein-coding sequences clustered between the primosome genes, 41 and 61, of bacteriophages T4, T2, and T6.

    PubMed Central

    Selick, H E; Stormo, G D; Dyson, R L; Alberts, B M

    1993-01-01

    In bacteriophage T4, there is a strong tendency for genes that encode interacting proteins to be clustered on the chromosome. There is 1.6 kb of DNA between the DNA helicase (gene 41) and the DNA primase (gene 61) genes of this virus. The DNA sequence of this region suggests that it contains five genes, designated as open reading frames (ORFs) 61.1 to 61.5, predicted to encode proteins ranging in size from 5.94 to 22.88 kDa. Are these ORFs actually genes? As one test, we compared the DNA sequence of this region in bacteriophages T2, T4, and T6 and found that ORFs 61.1, 61.3, 61.4, and 61.5 are highly conserved among the three closely related viruses. In contrast, ORF 61.2 is conserved between phages T4 and T6 yet is absent from phage T2, where it is replaced by another ORF, T2 ORF 61.2, which is not found in the T4 and T6 genomes. As a second, independent test for coding sequences, we calculated the codon base position preferences for all ORFs in this region that could encode proteins that contain at least 30 amino acids. Both the T4/T6 and T2 versions of ORF 61.2, as well as the other ORFs, have codon base position preferences that are indistinguishable from those of known T4 genes (coefficients of 0.81 to 0.94); the six other possible ORFs of at least 90 bp in this region are ruled out as genes by this test (coefficients less than zero). Thus, both evolutionary conservation and codon usage patterns lead us to conclude that ORFs 61.1 to 61.5 represent important protein-coding sequences for this family of bacteriophages. Because they are located between the genes that encode the two interacting proteins of the T4 primosome (DNA helicase plus DNA primase), one or more may function in DNA replication by modulating primosome function. Images PMID:8383243

  7. Quasi-steady state principle and in-situ real-time investigation of transient strains in 6061-T6 Al alloy using neutron diffraction

    SciTech Connect

    Woo, Wan Chuck; Brown, D. W.; Choo, Hahn; Clausen, B; David, Stan A; Feng, Zhili; Hubbard, Camden R; Wang, Xun-Li

    2007-01-01

    Neutron diffraction research has been limited to the "static" behavior of materials since the number of collected neutrons is insufficient to reach the adequate neutron counts in rapid changes of material state. In order to achieve the desired precision for the study of the transient material behavior, we propose an in-situ neutron-diffraction measurement method based on the quasi-steady state (QSS) phenomenon. The QSS principle was applied for the measurement of transient lattice spacing changes in a 6061-T6 aluminum alloy plate during thermo-mechanical processing.

  8. Effect of Quenching Medium on Mechanical Properties of Alloy Al7049-T6 and Lowering of its After-Machining Warpage

    NASA Astrophysics Data System (ADS)

    Sani, Saeed Aliakbari; Feizabadi, Javad; Pourgharibshahi, Mohammad; Hashemi, Seyed Hamidreza

    2017-07-01

    Aluminum alloy Al 7049 is studied in state T6. Heat treatment of the specimens is performed in different quenching media (cold water, boiling water, aqueous polymer solutions). The mechanical properties and the Brinell hardness of the alloy are determined after different modes of heat treatment. Comparative analysis is used to find the maximum residual stresses responsible for warpage of the alloy after machining. The relation between the warpage and the dimensionless Biot number is obtained. Quenching modes removing the warpage in billets of Al7049 are determined.

  9. Time exposure studies on stress corrosion cracking of aluminum 2014-T6, aluminum 7075-T651, and titanium 6Al-4V

    NASA Technical Reports Server (NTRS)

    Terrell, J.

    1972-01-01

    The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 7075-T651 and titanium 6A1-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 6) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity). Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, a similar observation was not noted for titanium stressed specimens. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl); while they (both alloys) seem to resist stress corrosion cracking in methyl alcohol, ethyl alcohol, iso-propyl alcohol, and demineralized distilled water. Titanium 6A1-4V showed some evidence of susceptibility to SCC in methanol, while no such susceptibility was exhibited in ethanol, iso-propyl alcohol and demineralized distilled water.

  10. RADIO FLARING FROM THE T6 DWARF WISEPC J112254.73+255021.5 WITH A POSSIBLE ULTRA-SHORT PERIODICITY

    SciTech Connect

    Route, Matthew; Wolszczan, Alexander E-mail: alex@astro.psu.edu

    2016-04-20

    We present new results from a continuing 5 GHz search for flaring radio emission from a sample of L and T brown dwarfs, conducted with the 305 m Arecibo radio telescope. In addition to the previously reported flaring from the T6.5 dwarf 2MASS J10475385+212423, we have detected and confirmed circularly polarized flares from another T6 dwarf, WISEPC J112254.73+255021.5. Although the flares are sporadic, they appear to occur at a stable period of 0.288 hr. Given the current constraints, periods equal to its second and third subharmonic cannot be ruled out. The stability of this period over the eight-month timespan of observations indicates that, if real, it likely reflects the star’s rapid rotation. If confirmed, any of the three inferred periodicities would be much shorter than the shortest, 1.41 hr, rotation period of a brown dwarf measured so far. This finding would place a new observational constraint on the angular momentum evolution and rotational stability of substellar objects. The detection of radio emission from the sixth ∼1000 K dwarf further demonstrates that the coolest brown dwarfs and, possibly, young giant planets, can be efficiently investigated using radio observations at centimeter wavelengths as a tool.

  11. The mechanical response of a 6061-T6 Al/Al{sub 2}O{sub 3} metal matrix composite at high rates of deformation

    SciTech Connect

    Yadav, S.; Chichili, D.R.; Ramesh, K.T.

    1995-12-01

    The mechanical properties of a 6061-T6 aluminum alloy reinforced with a 20 vol% fraction of alumina particles and of an unreinforced 6061-T6 alloy are studied over a range of strain rates (10{sup {minus}4} to 6 {times} 10{sup 5} s{sup {minus}1}) using quasistatic compression, compression and torsion Kolsky Bars, and high strain rate pressure-shear plate impact. At a given strain rate the composite displays increased strength but essentially the same strain hardening as the matrix. However, the composite displays a stronger rate-sensitivity than does the unreinforced alloy at high rates of deformation (> 10{sup 3} s{sup {minus}1}). The rate-sensitivity of the unreinforced alloy is shown to be largely the result of the imposed strain rate rather than of the rate history. For quasistatic deformations, a model proposed by Bao et al. (1991) describes the behavior of the composite fairly accurately given the behavior of the unreinforced alloy. This paper presents an extension of the model that is able to predict the dynamic behavior of the composite given the dynamic response of the monolithic alloy.

  12. RUNX1 truncation resulting from a cryptic and novel t(6;21)(q25;q22) chromosome translocation in acute myeloid leukemia: A case report

    PubMed Central

    Panagopoulos, Ioannis; Torkildsen, Synne; Gorunova, Ludmila; Ulvmoen, Aina; Tierens, Anne; Zeller, Bernward; Heim, Sverre

    2016-01-01

    Fluorescence in situ hybridization examination of a pediatric AML patient whose bone marrow cells carried trisomy 4 and FLT3-ITD mutation, demonstrated that part of the RUNX1 probe had unexpectedly moved to chromosome band 6q25 indicating a cryptic t(6;21)(q25;q22) translocation. RNA sequencing showed fusion of exon 7 of RUNX1 with an intergenic sequence of 6q25 close to the MIR1202 locus, something that was verified by RT-PCR together with Sanger sequencing. The RUNX1 fusion transcript encodes a truncated protein containing the Runt homology domain responsible for both heterodimerization with CBFB and DNA binding, but lacking the proline-, serine-, and threonine-rich (PST) region which is the transcription activation domain at the C terminal end. Which genetic event (+4, FLT3-ITD, t(6;21)-RUNX1 truncation or other, undetected acquired changes) was more pathogenetically important in the present case of AML, remains unknown. The case illustrates that submicroscopic chromosomal rearrangements may accompany visible numerical changes and perhaps should be actively looked for whenever a single trisomy is found. An active search for them may provide both pathogenetic and prognostic novel information. PMID:27667292

  13. Production, crystallization and X-ray diffraction analysis of a complex between a fragment of the TssM T6SS protein and a camelid nanobody

    PubMed Central

    Nguyen, Van Son; Spinelli, Silvia; Desmyter, Aline; Le, Thi Thu Hang; Kellenberger, Christine; Cascales, Eric; Cambillau, Christian; Roussel, Alain

    2015-01-01

    The type VI secretion system (T6SS) is a machine evolved by Gram-negative bacteria to deliver toxin effectors into target bacterial or eukaryotic cells. The T6SS is functionally and structurally similar to the contractile tail of the Myoviridae family of bacteriophages and can be viewed as a syringe anchored to the bacterial membrane by a transenvelope complex. The membrane complex is composed of three proteins: the TssM and TssL inner membrane components and the TssJ outer membrane lipoprotein. The TssM protein is central as it interacts with both TssL and TssJ, therefore linking the membranes. Using controlled trypsinolysis, a 32.4 kDa C-terminal fragment of enteroaggregative Escherichia coli TssM (TssM32Ct) was purified. A nanobody obtained from llama immunization, nb25, exhibited subnanomolar affinity for TssM32Ct. Crystals of the TssM32Ct–nb25 complex were obtained and diffracted to 1.9 Å resolution. The crystals belonged to space group P64, with unit-cell parameters a = b = 95.23, c = 172.95 Å. Molecular replacement with a model nanobody indicated the presence of a dimer of TssM32Ct–nb25 in the asymmetric unit. PMID:25760699

  14. Crack Initiation and Growth from Pre-corroded Pits in Aluminum 7075-T6 Under Laboratory Air and Salt Water Environments

    NASA Astrophysics Data System (ADS)

    Joshi, G.; Mall, S.

    2017-05-01

    Small crack growth behavior, including the pit-to-crack transition, of pre-corroded aluminum alloy 7075-T6 was investigated under ambient air and saltwater environments. Through pit and corner crack pits were created prior to constant stress amplitude fatigue testing. The small crack growth life (SCGL) and crack initiation life (CIL) under salt water condition were about 5-8 times less when compared to those under ambient air. The ratio of SCGL to CIL was significantly smaller with large uncertainty (variation) under salt water environment. The small crack growth rates under salt water were 2-12 times larger than corresponding rates under laboratory air at identical stress amplitude and crack length. The crack lengths required to attain Paris region growth rates (Paris region threshold crack lengths) were about 1-3 mm for stress amplitudes less than 45 MPa. Sub-millimeter cracks attained 10-4 mm/cycle fatigue crack growth rates (FCGR) for stress amplitudes greater than 45 MPa. The crack growth rates of 0.25-mm-long cracks were about 2 times higher for salt water environment when compared to identical stress conditions in ambient air. Empirical crack growth rate versus stress intensity factor range equations similar to Paris law were developed for small crack growth and crack initiation under ambient air and salt water condition, for fatigue crack prognostics applications. For the design applications, a modified Kitagawa-Takahashi (K-T) diagram for corrosion-pitted aluminum 7075-T6 is presented.

  15. Application of high-speed counter-current chromatography for isolation of triterpenes from Schisandra Chinensis (Turcz.) Baill and induction apoptosis mechanism of HSC-T6.

    PubMed

    Li, Bin; Meng, Xianjun; Zhu, Lijie; Jiao, Xinyao; Zhang, Jiachen

    2014-01-01

    Triterpenes have shown many beneficial activities in researches, but their separation and preparation usually require multiple methods. Following an initial cleaning-up step on the AB-8 macroporous resin, a preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system comprising chloroform-n-butyl alcohol-methanol-water (10:1:7:4, v/v/v/v) was used to isolate and separate triterpenes from caculis of Schisandra Chinensis (Turcz.) baill. A total of 89 mg corosolic acid with purities of 98.5% were obtained from 400 mg crude extract in one-step elution and less than 4 h, and the structure identification was performed by UV, IR, MS, 1H NMR and 13C NMR. The inhibition on liver fibrosis activities of the triterpenes against HSC-T6 in vitro were studied by cell culture methods. The results showed that the corosolic acid have better inhibitory effects on HSC-T6 cells with the IC50 value of 5~25 μg/mL and the study also indicated that corosolic acid might be a potential Chinese medical component to inhibit liver fibrosis.

  16. Assessment of abdominal muscle function in individuals with motor-complete spinal cord injury above T6 in response to transcranial magnetic stimulation.

    PubMed

    Bjerkefors, Anna; Squair, Jordan W; Chua, Romeo; Lam, Tania; Chen, Zhen; Carpenter, Mark G

    2015-02-01

    To use transcranial magnetic stimulation and electromyography to assess the potential for preserved function in the abdominal muscles in individuals classified with motor-complete spinal cord injury above T6. Five individuals with spinal cord injury (C5-T3) and 5 able-bodied individuals. Transcranial magnetic stimulation was delivered over the abdominal region of primary motor cortex during resting and sub-maximal (or attempted) contractions. Surface electromyography was used to record motor-evoked potentials as well as maximal voluntary (or attempted) contractions in the abdominal muscles and the diaphragm. Responses to transcranial magnetic stimulation in the abdominal muscles occurred in all spinal cord injury subjects. Latencies of muscle response onsets were similar in both groups; however, peak-to-peak amplitudes were smaller in the spinal cord injury group. During maximal voluntary (or attempted) contractions all spinal cord injury subjects were able to elicit electromyography activity above resting levels in more than one abdominal muscle across tasks. Individuals with motor-complete spinal cord injury above T6 were able to activate abdominal muscles in response to transcranial magnetic stimulation and during maximal voluntary (or attempted) contractions. The activation was induced directly through corticospinal pathways, and not indirectly by stretch reflex activations of the diaphragm. Transcranial magnetic stimulation and electromyography measurements provide a useful method to assess motor preservation of abdominal muscles in persons with spinal cord injury.

  17. Radio Flaring from the T6 Dwarf WISEPC J112254.73+255021.5 with a Possible Ultra-short Periodicity

    NASA Astrophysics Data System (ADS)

    Route, Matthew; Wolszczan, Alexander

    2016-04-01

    We present new results from a continuing 5 GHz search for flaring radio emission from a sample of L and T brown dwarfs, conducted with the 305 m Arecibo radio telescope. In addition to the previously reported flaring from the T6.5 dwarf 2MASS J10475385+212423, we have detected and confirmed circularly polarized flares from another T6 dwarf, WISEPC J112254.73+255021.5. Although the flares are sporadic, they appear to occur at a stable period of 0.288 hr. Given the current constraints, periods equal to its second and third subharmonic cannot be ruled out. The stability of this period over the eight-month timespan of observations indicates that, if real, it likely reflects the star’s rapid rotation. If confirmed, any of the three inferred periodicities would be much shorter than the shortest, 1.41 hr, rotation period of a brown dwarf measured so far. This finding would place a new observational constraint on the angular momentum evolution and rotational stability of substellar objects. The detection of radio emission from the sixth ˜1000 K dwarf further demonstrates that the coolest brown dwarfs and, possibly, young giant planets, can be efficiently investigated using radio observations at centimeter wavelengths as a tool.

  18. Protective effects of Cinnamomum cassia Blume in the fibrogenesis of activated HSC-T6 cells and dimethylnitrosamine-induced acute liver injury in SD rats.

    PubMed

    Lim, Chang-Shin; Kim, Eun-Young; Lee, Hyun-Sam; Soh, Yunjo; Sohn, Youngjoo; Kim, Sun Yeou; Sohn, Nak-Won; Jung, Hyuk-Sang; Kim, Yoon-Bum

    2010-01-01

    Cinnamomum cassia Blume (CC) is one of the world's oldest natural spices, and is commonly used in traditional oriental medicine. We investigated the protective effect of ethanol extract from Cinnamomum cassia Blume (CCE) on the activation of hepatic stellate cells (HSCs). In addition, we examined the effects of CC powder in Sprague-Dawley rats with acute liver injury induced by dimethylnitrosamine (DMN). In vitro, HSC-T6 cells exhibit an activated phenotype, as reflected in their fibroblast-like morphology. CCE significantly reduced the expression of alpha-smooth muscle actin (alpha-SMA), connective tissue growth factor (CTGF), transforming growth factor beta (TGF-beta1), and tissue inhibitor of metalloproteinase-1 (TIMP-1). In vivo, the results were significantly protected by CC powder in the serum total protein, albumin, total-bilirubin, direct-bilirubin, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and alkaline phosphatase (ALP). We suggest that CC inhibits fibrogenesis, followed by HSC-T6 cell activation and increased restoration of liver function, ultimately resulting in acute liver injury.

  19. Investigation of Microstructure and Microhardness in Self-Reacting Friction Stir Welded AA2014-T6 and AA2219-T87

    NASA Technical Reports Server (NTRS)

    Horton, K. Renee; McGill, Preston; Barkey, Mark

    2011-01-01

    Friction stir welding (FSW) is a solid state welding process with potential advantages for aerospace and automotive industries dealing with light alloys. Self-reacting friction stir welding (SR-FSW) is one variation of the FSW process being developed at the National Aeronautics and Space Administration (NASA) for use in the fabrication of propellant tanks. This work reports on the microstructure and microhardness of SR-FSW between two dissimilar aluminum alloys. Specifically, the study examines the cross section of the weld joint formed between an AA2014-T6 plate on the advancing side and an AA2219-T87 plate on the retreating side. The microstructural analysis shows an irregularly displaced weld seam from the advancing side past the thermo-mechanical affected zone (TMAZ) into the weld nugget region. There are sharp variations in the microhardness across the weld. These variations are described in the paper and mechanisms for their formation are discussed.

  20. Study of mechanical joint strength of aluminum alloy 7075-T6 and dual phase steel 980 welded by friction bit joining and weld-bonding under corrosion medium

    SciTech Connect

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; Miles, Michael; Song, Guang-Ling; Wang, Yanli; Feng, Zhili

    2014-12-30

    We have employed a unique solid-sate joining process, called friction bit joining (FBJ), to spot weld aluminum alloy (AA) 7075-T6 and dual phase (DP) 980 steel. Static joint strength was studied in the lap shear tension configuration. In addition, weld-bonding (adhesive + FBJ) joints were studied in order to evaluate the ability of adhesive to mitigate the impact of corrosion on joint properties. Accelerated laboratory cyclic corrosion tests were carried out for both FBJ only and weld-bonding joints. Furthermore, the FBJ only joints that emerged from corrosion testing had lap shear failure loads that were significantly lower than freshly prepared joints. However, weld-bonding specimens retained more than 80% of the lap shear failure load of the freshly prepared weld-bonding specimens. Moreover, examination of joint cross sections confirmed that the presence of adhesive in the weld-bonding joints mitigated the effect of the corrosion environment, compared to FBJ only joints.

  1. Craniosynostosis and hemizygosity for D7S135 caused by a de novo and apparently balanced t(6;7) translocation

    SciTech Connect

    Tsuji, Kazushiro; Narahara, Kouji; Kikkawa, Kiyoshi; Murakami, Masae; Yokoyama, Yuji; Ninomiya, Shinsuke; Seino, Yoshiki

    1994-01-01

    Craniosynostosis (CRS) is frequently seen in the del(7p) syndrome, and the gene for this cranial anomaly (CRS1) has been assigned to 7p21. The authors present a 3-year-old boy with CRS involving the sagittal and coronal sutures, who had a de novo and apparently balanced translocation, t(6;7)(q16.2;p15.3). Southern blot analysis of several loci on 7p14{yields}pter showed that the patient was heterozygous for HOX1I and IL6, possibly homozygous for D7S149, but hemizygous for D7S135 with a loss of the paternal allele. These findings suggest the localization of a candidate gene for CRS1 to be on 7p15.3 in the close proximity to the D7S135 locus. 19 refs., 5 figs., 2 tabs.

  2. The young's modulus of 1018 steel and 67061-T6 aluminum measured from quasi-static to elastic precursor strain-rates

    SciTech Connect

    Rae, Philip J; Trujillo, Carl; Lovato, Manuel

    2009-01-01

    The assumption that Young's modulus is strain-rate invariant is tested for 6061-T6 aluminium alloy and 1018 steel over 10 decades of strain-rate. For the same billets of material, 3 quasi-static strain-rates are investigated with foil strain gauges at room temperature. The ultrasonic sound speeds are measured and used to calculate the moduli at approximately 10{sup 4} s{sup -1}. Finally, ID plate impact is used to generate an elastic pre-cursor in the alloys at a strain-rate of approximately 10{sup 6} s{sup -1} from which the longitudinal sound speed may be obtained. It is found that indeed the Young's modulus is strain-rate independent within the experimental accuracy.

  3. Influences of post weld heat treatment on tensile strength and microstructure characteristics of friction stir welded butt joints of AA2014-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Rajendran, C.; Srinivasan, K.; Balasubramanian, V.; Balaji, H.; Selvaraj, P.

    2016-08-01

    Friction stir welded (FSWed) joints of aluminum alloys exhibited a hardness drop in both the advancing side (AS) and retreating side (RS) of the thermo-mechanically affected zone (TMAZ) due to the thermal cycle involved in the FSW process. In this investigation, an attempt has been made to overcome this problem by post weld heat treatment (PWHT) methods. FSW butt (FSWB) joints of Al-Cu (AA2014-T6) alloy were PWHT by two methods such as simple artificial aging (AA) and solution treatment followed by artificial aging (STA). Of these two treatments, STA was found to be more beneficial than the simple aging treatment to improve the tensile properties of the FSW joints of AA2014 aluminum alloy.

  4. Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

    NASA Astrophysics Data System (ADS)

    Peng, Dong; Shen, Jun; Tang, Qin; Wu, Cui-ping; Zhou, Yan-bing

    2013-03-01

    Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

  5. The Young's Modulus of 1018 Steel and 6061-T6 Aluminium Measured from Quasi-Static to Elastic Precursor Strain-Rates

    NASA Astrophysics Data System (ADS)

    Rae, Philip J.; Trujillo, Carl P.; Lovato, Manuel L.

    2009-12-01

    The assumption that Young's modulus is strain-rate invariant is tested for 6061-T6 aluminium alloy and 1018 steel over 10 decades of strain-rate. For the same billets of material, 3 quasi-static strain-rates are investigated with foil strain gauges at room temperature. The ultrasonic sound speeds are measured and used to calculate the moduli at approximately 104 s-1. Finally, 1D plate impact is used to generate an elastic pre-cursor in the alloys at a strain-rate of approximately 106 s1 from which the longitudinal sound speed may be obtained. It is found that indeed the Young's modulus is strain-rate independent within the experimental accuracy.

  6. Experimental comparison of the MIG, friction stir welding, cold metal transfer and hybrid laser-MIG processes for AA 6005-T6 aluminium alloy

    NASA Astrophysics Data System (ADS)

    Caruso, Serafino; Sgambitterra, Emanuele; Rinaldi, Sergio; Gallone, Antonello; Viscido, Lucio; Filice, Luigino; Umbrello, Domenico

    2016-10-01

    In this study, the mechanical properties of welded joints of AA 6005-T6 aluminum alloy obtained with hybrid laser-MIG and cold metal transfer (CMT) welding were analyzed. The performance of hybrid laser-MIG and CMT welded joints were identified using tensile, bending, shear and fatigue life tests. Taking into account the process conditions and requirements, hybrid laser-MIG and CMT welding processes were compared with friction stir welding (FSW) and conventional metal inert gas (MIG) welding processes, shown in a previous work, to understand the advantages and disadvantages of the processes for welding applications of studied Al alloy. Better tensile, bending and shear strength and fatigue life behavior were obtained with hybrid laser-MIG and FSW welded joints compared with conventional MIG processes.

  7. Internalization of Pseudomonas aeruginosa Strain PAO1 into Epithelial Cells Is Promoted by Interaction of a T6SS Effector with the Microtubule Network.

    PubMed

    Sana, Thibault G; Baumann, Christoph; Merdes, Andreas; Soscia, Chantal; Rattei, Thomas; Hachani, Abderrahman; Jones, Cerith; Bennett, Keiryn L; Filloux, Alain; Superti-Furga, Giulio; Voulhoux, Romé; Bleves, Sophie

    2015-06-02

    Invasion of nonphagocytic cells through rearrangement of the actin cytoskeleton is a common immune evasion mechanism used by most intracellular bacteria. However, some pathogens modulate host microtubules as well by a still poorly understood mechanism. In this study, we aim at deciphering the mechanisms by which the opportunistic bacterial pathogen Pseudomonas aeruginosa invades nonphagocytic cells, although it is considered mainly an extracellular bacterium. Using confocal microscopy and immunofluorescence, we show that the evolved VgrG2b effector of P. aeruginosa strain PAO1 is delivered into epithelial cells by a type VI secretion system, called H2-T6SS, involving the VgrG2a component. An in vivo interactome of VgrG2b in host cells allows the identification of microtubule components, including the γ-tubulin ring complex (γTuRC), a multiprotein complex catalyzing microtubule nucleation, as the major host target of VgrG2b. This interaction promotes a microtubule-dependent internalization of the bacterium since colchicine and nocodazole, two microtubule-destabilizing drugs, prevent VgrG2b-mediated P. aeruginosa entry even if the invasion still requires actin. We further validate our findings by demonstrating that the type VI injection step can be bypassed by ectopic production of VgrG2b inside target cells prior to infection. Moreover, such uncoupling between VgrG2b injection and bacterial internalization also reveals that they constitute two independent steps. With VgrG2b, we provide the first example of a bacterial protein interacting with the γTuRC. Our study offers key insight into the mechanism of self-promoting invasion of P. aeruginosa into human cells via a directed and specific effector-host protein interaction. Innate immunity and specifically professional phagocytic cells are key determinants in the ability of the host to control P. aeruginosa infection. However, among various virulence strategies, including attack, this opportunistic bacterial

  8. A transmission electron microscopy study of constituent-particle-induced corrosion in 7075-T6 and 2024-T3 aluminum alloys

    SciTech Connect

    Wei, R.P.; Liao, C.M.; Gao, M.

    1998-04-01

    To better understand particle-induced pitting corrosion in aluminum alloys, thin foil specimens of 7075-T6 and 2024-T3 aluminum alloys, with identified constituent particles, were immersed in aerated 0.5M NaCl solution and then examined by transmission electron microscopy (TEM). The results clearly showed matrix dissolution around the iron- and manganese-containing particles (such as Al{sub 23}CuFe{sub 4}), as well as the Al{sub 2}Cu particles. While Al{sub 2}CuMg particles tended to dissolve relative to the matrix, limited local dissolution of the matrix was also observed around these particles. These results are consistent with scanning electron microscopy (SEM) observations of pitting corrosion and are discussed in terms of the electrochemical characteristics of the particles and the matrix.

  9. Ultrasonic measurement of anisotropy and temperature dependence of elastic parameters by a dry coupling method applied to a 6061-T6 alloy.

    PubMed

    Augereau, F; Laux, D; Allais, L; Mottot, M; Caes, C

    2007-03-01

    A pulse-echo ultrasonic method is presented to measure elastic parameter variations during thermal loading with high accuracy. Using a dry coupling configuration dedicated to high temperature investigation, this technique has been applied on 6061-T6 aluminium samples up to 220 degrees C. Experimental settings are described to assess the measurement reproducibility estimated at a value of 0.2%. Consequently, the anisotropy of this aluminium between the rolling direction and two orthogonal axes has been clearly detected and also measured versus temperature. As regards the temperature dependence of these elastic parameters, these results are compared with the estimations of the Young's modulus obtained during mechanical tests in conditions of low cycle fatigue (LCF). The same linear variation versus temperature is found but with a shift of 7GPa. This difference has been classically attributed to systematic experimental error sources and to the distinction existing between dynamic and static elastic modulus.

  10. Effects of Cyclic Loading on Mechanical Behavior of 24S-T4 and 75S-T6 Aluminum Alloys and SAE 4130 Steel

    NASA Technical Reports Server (NTRS)

    Macgregor, C W; Grossman, N

    1952-01-01

    An investigation was conducted to determine the effects of cyclic loading on the mechanical behavior of 24S-T4 and 75S-T6 aluminum alloys and SAE 4130 steel. Specimens of the three materials were subjected to various numbers of prior fatigue cycles both below and above the fatigue limits. Special slow-bend tests were employed to show the effects of prior cycles of fatigue stressing on the transition temperature to brittle fracture for SAE 4130 steel and on the energy-absorption capacity of the aluminum alloys. Micrographic studies were made to observe and measure crack formation and propagation and additional special tests were conducted to supplement the results of the slow-bend tests. These included Charpy impact tests, mirohardness surveys, tension tests, and fretting-corrosion studies.

  11. 3D finite element prediction of chip flow, burr formation, and cutting forces in micro end-milling of aluminum 6061-T6

    NASA Astrophysics Data System (ADS)

    Davoudinejad, A.; Parenti, P.; Annoni, M.

    2017-06-01

    Predictive models for machining operations have been significantly improved through numerous methods in recent decades. This study proposed a 3D finite element modeling (3D FEM) approach for the micro end-milling of Al6061-T6. Finite element (FE) simulations were performed under different cutting conditions to obtain realistic numerical predictions of chip flow, burr formation, and cutting forces. FE modeling displayed notable advantages, such as capability to easily handle any type of tool geometry and any side effect on chip formation, including thermal aspect and material property changes. The proposed 3D FE model considers the effects of mill helix angle and cutting edge radius on the chip. The prediction capability of the FE model was validated by comparing numerical model and experimental test results. Burr dimension trends were correlated with force profile shapes. However, the FE predictions overestimated the real force magnitude. This overestimation indicates that the model requires further development.

  12. Diagnostic accuracy of common clinical tests for assessing abdominal muscle function after motor-complete spinal cord injury above T6.

    PubMed

    Bjerkefors, A; Squair, J W; Malik, R; Lam, T; Chen, Z; Carpenter, M G

    2015-02-01

    Diagnostic study. The objective of this study was to compare patterns of electromyography (EMG) recordings of abdominal muscle function in persons with motor-complete spinal cord injury (SCI) above T6 and in able-bodied controls, and to determine whether manual examination or ultrasound measures of muscle activation can be accurate alternatives to EMG. Research center focused on SCI and University laboratory, Vancouver, Canada. Thirteen people with SCI (11 with American Spinal Injury Association Impairment Scale (AIS) A and 2 AIS B; C4-T5), and 13 matched able-bodied participants volunteered for the study. Participants completed trunk tasks during manual examination of the abdominal muscles and then performed maximal voluntary isometric contractions, while EMG activity and muscle thickness changes were recorded. The frequency of muscle responses detected by manual examination and ultrasound were compared with detection by EMG (sensitivity and specificity). All individuals with SCI were able to elicit EMG activity above resting levels in at least one abdominal muscle during one task. In general, the activation pattern was task specific, confirming voluntary control of the muscles. Ultrasound, when compared with EMG, showed low sensitivity but was highly specific in its ability to detect preserved abdominal muscle function in persons with SCI. Conversely, manual examination was more sensitive than ultrasound but showed lower specificity. The results from this study confirm preserved voluntary abdominal muscle function in individuals classified with motor-complete SCI above T6 and highlight the need for further research in developing more accurate clinical measures to diagnose the level of trunk muscle preservation in individuals with SCI.

  13. Switching from antiferromagnetic to ferromagnetic coupling in heptanuclear [M(t)6M(c)](n+) complexes by going from an achiral to a chiral triplesalen ligand.

    PubMed

    Mukherjee, Chandan; Hoeke, Veronika; Stammler, Anja; Bögge, Hartmut; Schnack, Jürgen; Glaser, Thorsten

    2014-07-07

    The chiral triplesalen ligand H6chand(RR) has been used to synthesize the chiral heptanuclear complexes [{(chand(RR))Mn(III)3}2{Fe(II)(CN)6}](ClO4)2 ((RR)[Mn(III)6Fe(II)](ClO4)2) and [{(chand(RR))Fe(III)3}2{Fe(II)(CN)6}](ClO4)2 ((RR)[Fe(III)6Fe(II)](ClO4)2), which have been characterized by single-crystal X-ray diffraction, mass spectrometry, elemental analysis, FT-IR, Mössbauer, and UV-vis spectroscopies, electrochemistry, as well as DC and AC magnetic susceptibility measurements. The half-wave potential of the Fe(III)/Fe(II) couple in (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+) is E1/2 = +0.21 and +0.75 V vs. Fc(+)/Fc, respectively, which (i) corresponds to a strong stabilization of the reduced Fe(II) species compared to the redox couple of free [Fe(II/III)(CN)6](4-/3-) and (ii) indicates a significant difference of the electronic coupling with the {(chand(RR))M(t)}(3+) units (M(t) = Mn(III), Fe(III)). Analysis of the DC magnetic data (μeffvs. T, VTVH) of both complexes by a full-matrix diagonalization of the spin-Hamiltonian including isotropic exchange, zero-field splitting with full consideration of the relative orientation of the D tensors and Zeeman interactions reveals ferromagnetic interactions of JMn-Mn = +0.17 ± 0.02 cm(-1) with DMn = -3.4 ± 0.3 cm(-1) for (RR)[Mn(III)6Fe(II)](2+) and JFe-Fe = +0.235 ± 0.005 cm(-1) with DFe = 0 for (RR)[Fe(III)6Fe(II)](2+). The comparison of the molecular structures of (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+) with those of the heptanuclear complexes [M(t)6M(c)](n+) using the achiral triplesalen ligand (talen(t-Bu2))(6-) reveals significant differences in the ligand folding, smaller C-C bond distances in the central phloroglucinol ring and larger HOMA values. This indicates more aromatic character and less heteroradialene contribution in (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+), which explains the switching from antiferromagnetic coupling in [M(t)6M(c)](n+) to ferromagnetic

  14. Molecular confirmation of t(6;11)(p21;q12) renal cell carcinoma in archival paraffin-embedded material using a break-apart TFEB FISH assay expands its clinicopathologic spectrum.

    PubMed

    Argani, Pedram; Yonescu, Raluca; Morsberger, Laura; Morris, Kerry; Netto, George J; Smith, Nathan; Gonzalez, Nilda; Illei, Peter B; Ladanyi, Marc; Griffin, Constance A

    2012-10-01

    A subset of renal cell carcinomas (RCCs) is characterized by t(6;11)(p21;q12), which results in fusion of the untranslated Alpha (MALAT1) gene to the TFEB gene. Only 21 genetically confirmed cases of t(6;11) RCCs have been reported. This neoplasm typically demonstrates a distinctive biphasic morphology, comprising larger epithelioid cells and smaller cells clustered around basement membrane material; however, the full spectrum of its morphologic appearances is not known. The t(6;11) RCCs differ from most conventional RCCs in that they consistently express melanocytic immunohistochemical (IHC) markers such as HMB45 and Melan A and the cysteine protease cathepsin K but are often negative for epithelial markers such as cytokeratins. TFEB IHC has been proven to be useful to confirm the diagnosis of t(6;11) RCCs in archival material, because native TFEB is upregulated through promoter substitution by the gene fusion. However, IHC is highly fixation dependent and has been proven to be particularly difficult for TFEB. A validated fluorescence in situ hybridization (FISH) assay for molecular confirmation of the t(6;11) RCC in archival formalin-fixed, paraffin-embedded material has not been previously reported. We report herein the development of a break-apart TFEB FISH assay for the diagnosis of t(6;11)(p21;q12) RCCs. We validated the assay on 4 genetically confirmed cases and 76 relevant expected negative control cases and used the assay to report 8 new cases that expand the clinicopathologic spectrum of t(6;11) RCCs. An additional previously reported TFEB IHC-positive case was confirmed by TFEB FISH in 46-year-old archival material. In conclusion, TFEB FISH is a robust, clinically validated assay that can confirm the diagnosis of t(6;11) RCC in archival material and should allow a more comprehensive clinicopathologic delineation of this recently recognized neoplastic entity.

  15. Severe mental retardation in six generations of a large South African family carrying a translocation t(6;10)(q27;q25.2).

    PubMed Central

    Brusnický, J; van Heerden, K M; de Jong, G; Cronjé, A S; Retief, A E

    1986-01-01

    Partial monosomy 10q25.2----qter, detected in a newborn baby with multiple congenital abnormalities, was found to be derived from a balanced maternal translocation t(6;10)(q27;q25.2). The pedigree of six generations of the family is presented. In an extensive cytogenetic study of this family, the chromosome complements of 57 subjects, potentially capable of carrying some form of this translocation, were analysed. A total of 14 male carriers (four obligatory) and 14 female carriers (three obligatory) of this translocation was found. Partial trisomy 10q25.2----qter, associated with severe mental retardation, occurred in nine cases, eight males and one female. Two of these eight males were detected prenatally and subsequently therapeutically aborted. The phenotypes of the family members with partial trisomy 10q25.2----qter are compared to each other and to those reported in publications. No further cases of partial monosomy 10q25.2----qter were encountered. A review of published reports of partial monosomy and partial trisomy 10qter is given. The apparent absence of infertility, the occurrence of many first trimester miscarriages, and the marked sex ratio are discussed. Images PMID:3783620

  16. Influence of MC3T3-E1 preosteoblast culture on the corrosion of a T6-treated AZ91 alloy

    PubMed Central

    Brooks, Emily K.; Tobias, Menachem E.; Yang, Shuying; Bone, Lawrence B.; Ehrensberger, Mark T.

    2015-01-01

    This study investigated the corrosion of artificially aged T6 heat-treated Mg-9%Al-1%Zn (AZ91) for biomedical applications. Corrosion tests and surface analysis were completed both with and without a monolayer of mouse preosteoblast MC3T3-E1 cells cultured on the sample. Electrochemical impedance spectroscopy (EIS) and inductively coupled plasma mass spectroscopy (ICPMS) were used to explore the corrosion processes after either 3 or 21 days of AZ91 incubation in cell culture medium (CCM). The EIS showed both the inner layer resistance (Rin) and outer layer resistance (Rout) were lower for samples without cells cultured on the surface at 3 days (Rin = 2.64 e4 Ω/cm2, Rout = 140 Ω/cm2) compared to 21 days (Rin = 3.60 e4 Ω/cm2, Rout = 287 Ω/cm2) due to precipitation of magnesium and calcium phosphates over time. Samples with preosteoblasts cultured on the surface had a slower initial corrosion (3 day, Rin = 1.88 e5 Ω/cm2, Rout = 1060 Ω/cm2) which was observed to increase over time (21 day, Rin = 2.99 e4 Ω/cm2, Rout = 287 Ω/cm2). Changes in the corrosion processes were thought to be related to changes in the coverage provided by the cell layer. Our results reveal that the presence of cells and biological processes are able to significantly influence the corrosion rate of AZ91. PMID:25715925

  17. Study of mechanical joint strength of aluminum alloy 7075-T6 and dual phase steel 980 welded by friction bit joining and weld-bonding under corrosion medium

    DOE PAGES

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; ...

    2014-12-30

    We have employed a unique solid-sate joining process, called friction bit joining (FBJ), to spot weld aluminum alloy (AA) 7075-T6 and dual phase (DP) 980 steel. Static joint strength was studied in the lap shear tension configuration. In addition, weld-bonding (adhesive + FBJ) joints were studied in order to evaluate the ability of adhesive to mitigate the impact of corrosion on joint properties. Accelerated laboratory cyclic corrosion tests were carried out for both FBJ only and weld-bonding joints. Furthermore, the FBJ only joints that emerged from corrosion testing had lap shear failure loads that were significantly lower than freshly preparedmore » joints. However, weld-bonding specimens retained more than 80% of the lap shear failure load of the freshly prepared weld-bonding specimens. Moreover, examination of joint cross sections confirmed that the presence of adhesive in the weld-bonding joints mitigated the effect of the corrosion environment, compared to FBJ only joints.« less

  18. Critical assessment of precracked specimen configuration and experimental test variables for stress corrosion testing of 7075-T6 aluminum alloy plate

    NASA Technical Reports Server (NTRS)

    Domack, M. S.

    1985-01-01

    A research program was conducted to critically assess the effects of precracked specimen configuration, stress intensity solutions, compliance relationships and other experimental test variables for stress corrosion testing of 7075-T6 aluminum alloy plate. Modified compact and double beam wedge-loaded specimens were tested and analyzed to determine the threshold stress intensity factor and stress corrosion crack growth rate. Stress intensity solutions and experimentally determined compliance relationships were developed and compared with other solutions available in the literature. Crack growth data suggests that more effective crack length measurement techniques are necessary to better characterize stress corrosion crack growth. Final load determined by specimen reloading and by compliance did not correlate well, and was considered a major source of interlaboratory variability. Test duration must be determined systematically, accounting for crack length measurement resolution, time for crack arrest, and experimental interferences. This work was conducted as part of a round robin program sponsored by ASTM committees G1.06 and E24.04 to develop a standard test method for stress corrosion testing using precracked specimens.

  19. Determination of forming limit diagrams of AA6013-T6 aluminum alloy sheet using a time and position dependent localized necking criterion

    NASA Astrophysics Data System (ADS)

    Dicecco, S.; Butcher, C.; Worswick, M.; Boettcher, E.; Chu, E.; Shi, C.

    2016-11-01

    The forming limit behaviour of AA6013-T6 aluminium alloy sheet was characterized under isothermal conditions at room temperature (RT) and 250°C using limiting dome height (LDH) tests. Full field strain measurements were acquired throughout testing using in situ stereoscopic digital image correlation (DIC) techniques. Limit strain data was generated from the resulting full field strain measurements using two localized necking criteria: ISO12004- 2:2008 and a time and position dependent criterion, termed the “Necking Zone” (NZ) approach in this paper, introduced by Martinez-Donaire et al. (2014). The limit strains resulting from the two localization detection schemes were compared. It was found that the ISO and NZ limit strains at RT are similar on the draw-side of the FLD, while the NZ approach yields a biaxial major limit strain 14.8% greater than the ISO generated major limit strain. At 250°C, the NZ generated major limit strains are 31-34% greater than the ISO generated major limit strains for near uniaxial, plane strain and biaxial loading conditions, respectively. The significant variance in limit strains between the two methodologies at 250°C highlights the need for a validation study regarding warm FLC determination.

  20. Effect of Welding Parameters on Microstructure, Thermal, and Mechanical Properties of Friction-Stir Welded Joints of AA7075-T6 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Lotfi, Amir Hossein; Nourouzi, Salman

    2014-06-01

    A high-strength Al-Zn-Mg-Cu alloy AA7075-T6 was friction-stir welded with various process parameter combinations incorporating the design of the experiment to investigate the effect of welding parameters on the microstructure and mechanical properties. A three-factors, five-level central composition design (CCD) has been used to minimize the number of experimental conditions. The friction-stir welding parameters have significant influence on the heat input and temperature profile, which in turn regulates the microstructural and mechanical properties of the joints. The weld thermal cycles and transverse distribution of microhardness of the weld joints were measured, and the tensile properties were tested. The fracture surfaces of tensile specimens were observed by a scanning electron microscope (SEM), and the formation of friction-stir processing zone has been analyzed macroscopically. Also, an equation was derived to predict the final microhardness and tensile properties of the joints, and statistical tools are used to develop the relationships. The results show that the peak temperature during welding of all the joints was up to 713 K (440 °C), which indicates the key role of the tool shoulder diameter in deciding the maximum temperature. From this investigation, it was found that the joint fabricated at a rotational speed of 1050 rpm, welding speed of 100 mm/min, and shoulder diameter of 14 mm exhibited higher mechanical properties compared to the other fabricated joints.

  1. Microstructure and mechanical properties of twin-wire arc sprayed Ni-Al composite coatings on 6061-T6 aluminum alloy sheet

    NASA Astrophysics Data System (ADS)

    Wang, Ji-xiao; Liu, Jing-shun; Zhang, Lun-yong; Sun, Jian-fei; Wang, Zhi-ping

    2014-05-01

    We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coatings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear behavior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treatment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers microhardness of NiAl and Ni3Al intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth exponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550°C, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.

  2. In-situ Time-Resolved Neutron Diffraction Measurements of Microstructure Variations during Friction Stir Welding in a 6061-T6 Aluminum Alloy

    SciTech Connect

    Woo, Wan Chuck; Wang, Xun-Li; Ungar, Prof Tomas; Feng, Zhili; David, Stan A; Clausen, B; Hubbard, Camden R

    2008-01-01

    The microstructure change is one of the most important research areas in the friction stir welding (FSW). However, direct observation of microstructure changes during FSW has been extremely challenging because many measurement techniques are inapplicable. Recently developed in-situ time-resolved neutron diffraction methodology, which drastically improves the temporal resolution of neutron diffraction, enables to observe the transient microstructure changes during FSW. We installed a portable FSW system in the Spectrometer for MAterials Research at Temperature and Stress (SMARTS) at Los Alamos Neutron Science Center and the FSW was made on 6.35mm-thickness 6061-T6 Al alloy plate. At the same time, the neutron beam was centered on the mid-plane of the Al plate at 8 mm from the tool center (underneath the tool shoulder) and the diffraction peak was continuously measured during welding. The peak broadening analysis has been performed using the Williamson-Hall Method. The result shows that the dislocation density of about 3.2 x 10^15 m-2 duing FSW, which is the significant increse compared to the before (4.5 x 10^14 m-2) and after (4.0 x 10^14 m-2) the FSW. The quantitatively analysis of the grain structure can provide an insight to understand the transient variation of the microstructure during FSW.

  3. An Investigation of Mechanical Properties of Shielded Metal Arc Welding and Friction Stir Welding in 7020-T6 A1 Alloy

    NASA Astrophysics Data System (ADS)

    Jalal, Shawnim R.; Saeed, Mohammedtahir M.; Khider, Gawhar I.

    2014-06-01

    Two different types of welds, shielded metal arc (SMA) welding and friction stir welding (FSW) have been used to weld Aluminum alloy 7020-T6.Investigation has been carried out on mechanical properties such as (yield and tensile strength, impact, harnesses, ductility ,and microstructure) . The result shows that both method could be used to weld such alloy although FSW weld show higher mechanical properties comparison to SMA with joint efficiency equal to 97% compared to 58% in SMA .The extension of the heat affected zone is higher in SMA method in comparison to the FSW and localized grain size for FSW in the stirred zone was 15-18 micron and it was 37- 39 micron for SMA, while it was 32-35 micron for the base metal.In general decay of mechanical properties of SMA joints, was due to high temperature experienced by the material, but in FSW joint lower temperature are involved in the process due to sever plastic deformation induced by the tool motion.

  4. Critical assessment of precracked specimen configuration and experimental test variables for stress corrosion testing of 7075-T6 aluminum alloy plate

    NASA Technical Reports Server (NTRS)

    Domack, M. S.

    1985-01-01

    A research program was conducted to critically assess the effects of precracked specimen configuration, stress intensity solutions, compliance relationships and other experimental test variables for stress corrosion testing of 7075-T6 aluminum alloy plate. Modified compact and double beam wedge-loaded specimens were tested and analyzed to determine the threshold stress intensity factor and stress corrosion crack growth rate. Stress intensity solutions and experimentally determined compliance relationships were developed and compared with other solutions available in the literature. Crack growth data suggests that more effective crack length measurement techniques are necessary to better characterize stress corrosion crack growth. Final load determined by specimen reloading and by compliance did not correlate well, and was considered a major source of interlaboratory variability. Test duration must be determined systematically, accounting for crack length measurement resolution, time for crack arrest, and experimental interferences. This work was conducted as part of a round robin program sponsored by ASTM committees G1.06 and E24.04 to develop a standard test method for stress corrosion testing using precracked specimens.

  5. Design, fabrication and test of a hydrogen heat pipe. [extruding and grooving 6063-T6 aluminum tubes for cryogenic heat pipes

    NASA Technical Reports Server (NTRS)

    Alario, J.

    1979-01-01

    Re-entrant groove technology was extended to hydrogen heat pipes. Parametric analyses are presented which optimize the theoretical design while considering the limitations of state-of-the-art extrusion technology. The 6063-T6 aluminum extrusion is 14.6 mm OD with a wall thickness of 1.66 mm and contains 20 axial grooves which surround a central 9.3 mm diameter vapor core. Each axial groove is 0.775 mm diameter with a 0.33 mm opening. An excess vapor reservoir is provided at the evaporator to minimize the pressure containment hazard during ambient storage. Modifications to the basic re-entrant groove profile resulted in improved overall performance. While the maximum heat transport capacity decreased slightly to 103 w-m the static wicking height increased markedly to 4.5 cm. The heat pipe became operational between 20 and 30 K after a cooldown from 77 K without any difficulty. Steady state performance data taken over a 19 to 23 K temperature range indicated: (1) maximum heat transport capacity of 5.4 w-m; (2) static wicking height of 1.42 cm; and (3) overall heat pipe conductance of 1.7 watts/deg C.

  6. Influence of MC3T3-E1 preosteoblast culture on the corrosion of a T6-treated AZ91 alloy.

    PubMed

    Brooks, Emily K; Tobias, Menachem E; Yang, Shuying; Bone, Lawrence B; Ehrensberger, Mark T

    2016-02-01

    This study investigated the corrosion of artificially aged T6 heat-treated Mg-9%Al-1%Zn (AZ91) for biomedical applications. Corrosion tests and surface analysis were completed both with and without a monolayer of mouse preosteoblast MC3T3-E1 cells cultured on the sample. Electrochemical impedance spectroscopy (EIS) and inductively coupled plasma mass spectroscopy (ICPMS) were used to explore the corrosion processes after either 3 or 21 days of AZ91 incubation in cell culture medium (CCM). The EIS showed both the inner layer resistance (Rin ) and outer layer resistance (Rout ) were lower for samples without cells cultured on the surface at 3 days (Rin  = 2.64 e4 Ω/cm(2) , Rout  = 140 Ω/cm(2) ) compared to 21 days (Rin  = 3.60 e4 Ω/cm(2) , Rout  = 287 Ω/cm(2) ) due to precipitation of magnesium and calcium phosphates over time. Samples with preosteoblasts cultured on the surface had a slower initial corrosion (3 day, Rin  = 1.88 e5 Ω/cm(2) , Rout  = 1060 Ω/cm(2) ) which was observed to increase over time (21 day, Rin  = 2.99 e4 Ω/cm(2) , Rout  = 287 Ω/cm(2) ). Changes in the corrosion processes were thought to be related to changes in the coverage provided by the cell layer. Our results reveal that the presence of cells and biological processes are able to significantly influence the corrosion rate of AZ91.

  7. Protein Engineering by Random Mutagenesis and Structure-Guided Consensus of Geobacillus stearothermophilus Lipase T6 for Enhanced Stability in Methanol

    PubMed Central

    Dror, Adi; Shemesh, Einav; Dayan, Natali

    2014-01-01

    The abilities of enzymes to catalyze reactions in nonnatural environments of organic solvents have opened new opportunities for enzyme-based industrial processes. However, the main drawback of such processes is that most enzymes have a limited stability in polar organic solvents. In this study, we employed protein engineering methods to generate a lipase for enhanced stability in methanol, which is important for biodiesel production. Two protein engineering approaches, random mutagenesis (error-prone PCR) and structure-guided consensus, were applied in parallel on an unexplored lipase gene from Geobacillus stearothermophilus T6. A high-throughput colorimetric screening assay was used to evaluate lipase activity after an incubation period in high methanol concentrations. Both protein engineering approaches were successful in producing variants with elevated half-life values in 70% methanol. The best variant of the random mutagenesis library, Q185L, exhibited 23-fold-improved stability, yet its methanolysis activity was decreased by one-half compared to the wild type. The best variant from the consensus library, H86Y/A269T, exhibited 66-fold-improved stability in methanol along with elevated thermostability (+4.3°C) and a 2-fold-higher fatty acid methyl ester yield from soybean oil. Based on in silico modeling, we suggest that the Q185L substitution facilitates a closed lid conformation that limits access for both the methanol and substrate excess into the active site. The enhanced stability of H86Y/A269T was a result of formation of new hydrogen bonds. These improved characteristics make this variant a potential biocatalyst for biodiesel production. PMID:24362426

  8. UKIDSS detections of cool brown dwarfs. Proper motions of 14 known >T5 dwarfs and discovery of three new T5.5-T6 dwarfs

    NASA Astrophysics Data System (ADS)

    Scholz, R.-D.; Bihain, G.; Schnurr, O.; Storm, J.

    2012-05-01

    Aims: We contribute to improving the census of cool brown dwarfs (late-T and Y dwarfs) in the immediate solar neighbourhood. Methods: By combining near-infrared (NIR) data of UKIDSS with mid-infrared WISE and other available NIR (2MASS) and red optical (SDSS z-band) multi-epoch data we detected high proper motion (HPM) objects with colours typical of late spectral types (>T5). We used NIR low-resolution spectroscopy for the classification of new candidates. Results: We determined new proper motions for 14 known T5.5-Y0 dwarfs, many of which are significantly (>2-10 times) more accurate than previous ones. We detected three new candidates, ULAS J0954+0623, ULAS J1152+0359, and ULAS J1204-0150, by their HPMs and colours. Using previously published and new UKIDSS positions of the known nearby T8 dwarf WISE J0254+0223 we improved its trigonometric parallax to 165 ± 20 mas. For the three new objects we obtained NIR spectroscopic follow-up with LBT/LUCIFER classifying them as T5.5 and T6 dwarfs. With their estimated spectroscopic distances of about 25-30 pc, their proper motions of about 430-650 mas/yr lead to tangential velocities of about 50-80 km s-1, typical of the Galactic thin-disk population. Based on observations with the Large Binocular Telescope (LBT)Tables 1-5 are available in electronic form at http://www.aanda.org

  9. Prediction of low-cycle fatigue-life by acoustic emission—1: 2024-T3 aluminum alloy, and —2: 7075-T6 aluminum alloy

    SciTech Connect

    Baram, J.; Rosen, M.

    1981-01-01

    1: In this paper, low-cycle fatigue tests were conducted by tension-tension until rupture, on a 2024-T3 aluminum alloy sheet. Initial crack sizes and orientations in the fatigue specimens were found to be randomly distributed. Acoustic emission was continuously monitored during the tests. Every few hundred cycles, the acoustic signal having the highest peak-amplitude, was recorded as an extremal event for the elapsed period. This high peak-amplitude is related to a fast crack propagation rate through a phenomenological relationship. The extremal peak amplitudes are shown by an ordered statistics treatment, to be extremally distributed. The statistical treatment enables the prediction of the number of cycles left until failure. Predictions performed a posteriori based on results gained early in each fatigue test are in good agreement with actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress appears to be a promising nondestructive method of predicting fatigue life. 2: In this paper, low cycle high stress fatigue tests were conducted by tension-tension on an Alclad 7075-T6 aluminum sheet alloy, until rupture. Initial crack sizes and orientations in the fatigue specimens were randomly distributed. Acoustic emission was continuously monitored during the tests. Extremal peak-amplitudes, equivalent to extremal crack-propagation rates, are shown to be extremally Weibull distributed. The prediction of the number of cycles left until failure is made possible, using an ordered statistics treatment and an experimental equipment parameter obtained in previous experiments (Part 1). The predicted life-times are in good agreement with the actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress has been proven to be a feasible nondestructive method of predicting fatigue life.

  10. Comparison of three mobile devices for measuring R-R intervals and heart rate variability: Polar S810i, Suunto t6 and an ambulatory ECG system.

    PubMed

    Weippert, Matthias; Kumar, Mohit; Kreuzfeld, Steffi; Arndt, Dagmar; Rieger, Annika; Stoll, Regina

    2010-07-01

    The first aim of this study was to compare an ambulatory five-lead ECG system with the commercially available breast belt measuring devices; Polar S810i and Suunto t6, in terms of R-R interval measures and heart rate variability (HRV) indices. The second aim was to compare different HRV spectral analysis methods. Nineteen young males (aged between 22 and 31 years, median 24 years) underwent simultaneous R-R interval recordings with the three instruments during supine and sitting rest, moderate dynamic, and moderate to vigorous static exercise of the upper and lower limb. For each subject, 17 R-R interval series of 3-min length were extracted from the whole recordings and then analyzed in frequency domain using (1) a fast Fourier transform (FFT), (2) an autoregressive model (AR), (3) a Welch periodogram (WP) and (4) a continuous wavelet transform (CWT). Intra-class correlation coefficients (ICC) and Bland-Altman limits of agreement (LoA) method served as criteria for measurement agreement. Regarding the R-R interval recordings, ICC (lower ICC 95% confidence interval >0.99) as well as LoA (maximum LoA: -15.1 to 14.3 ms for ECG vs. Polar) showed an excellent agreement between all devices. Therefore, the three instruments may be used interchangeably in recording and interpolation of R-R intervals. ICCs for HRV frequency parameters were also high, but in most cases LoA analysis revealed unacceptable discrepancies between the instruments. The agreement among the different frequency transform methods can be taken for granted when analyzing the normalized power in low and high frequency ranges; however, not when analyzing the absolute values.

  11. Study on the 8He ground state via 8He(p, d)7He and 8He(p, t)6He reaction at 82.3 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Lou, J. L.; Ye, Y. L.; Pang, D. Y.; Cao, Z. X.; Jiang, D. X.

    2013-03-01

    The differential cross sections for reactions 8He(p, d)7Heg.s and 8He(p, t)6He2+ were measured by the coincidence of d + 6 He and t + 4He in a wide angular range from 15 to 130 degree in the center-of-mass system. The cross sections of the 8He(p, t)6Heg.s reaction were extremely lower than that of 8He(p, t)6He2+ reaction, and was not obtained from the present data. The experimental results were compared to the preliminary theoretical calculations in the frame of adiabatic distorted-wave approximation with the code Fresco. The results show that the configuration of (1p3/2)2(1p1/2)2 may have some probability in the ground state wave function of 8He. The cluster structure of 8He = 5H + 3H could not be neglected.

  12. The dual transcriptional regulator RovM regulates the expression of AR3- and T6SS4-dependent acid survival systems in response to nutritional status in Yersinia pseudotuberculosis.

    PubMed

    Song, Yunhong; Xiao, Xiao; Li, Changfu; Wang, Tietao; Zhao, Ruoxi; Zhang, Weipeng; Zhang, Lei; Wang, Yao; Shen, Xihui

    2015-11-01

    Coordinated regulation of various acid survival systems in response to environmental stimuli is crucial for the adaptation of enteropathogenic bacteria to acidic environments such as the stomach. In this study, we demonstrated that the RovM protein, a central regulator of the CsrABC-RovM-RovA cascade, conversely regulates the expression of two acid survival systems in Yersinia pseudotuberculosis by acting as a dual transcriptional regulator. RovM activated the expression of T6SS4, which is essential for bacterial survival under mild acidic conditions, by binding upstream of the T6SS4 promoter. On the contrary, RovM repressed the expression of a functional arginine-dependent acid resistance system (AR3), which is crucial for bacterial survival under strong acidic conditions, by directly binding to the -35 element in the AR3 promoter. Consistent with previous findings that rovM expression responds to the availability of nutrients, the expression of T6SS4 and AR3 was differentially regulated by nutritional status. Based on these results, a dynamic model whereby RovM coordinately regulates the expression of AR3 and T6SS4 in response to the availability of nutrients in the environment was proposed.

  13. Francisella tularensis IglG Belongs to a Novel Family of PAAR-Like T6SS Proteins and Harbors a Unique N-terminal Extension Required for Virulence

    PubMed Central

    Mosnier, Amandine; Hologne, Maggy; Martin, Amandine; Lindgren, Lena; Punginelli, Claire; Lays, Claire; Walker, Olivier; Charbit, Alain; Telouk, Philippe; Conlan, Wayne; Terradot, Laurent; Sjöstedt, Anders; Henry, Thomas

    2016-01-01

    The virulence of Francisella tularensis, the etiological agent of tularemia, relies on an atypical type VI secretion system (T6SS) encoded by a genomic island termed the Francisella Pathogenicity Island (FPI). While the importance of the FPI in F. tularensis virulence is clearly established, the precise role of most of the FPI-encoded proteins remains to be deciphered. In this study, using highly virulent F. tularensis strains and the closely related species F. novicida, IglG was characterized as a protein featuring a unique α-helical N-terminal extension and a domain of unknown function (DUF4280), present in more than 250 bacterial species. Three dimensional modeling of IglG and of the DUF4280 consensus protein sequence indicates that these proteins adopt a PAAR-like fold, suggesting they could cap the T6SS in a similar way as the recently described PAAR proteins. The newly identified PAAR-like motif is characterized by four conserved cysteine residues, also present in IglG, which may bind a metal atom. We demonstrate that IglG binds metal ions and that each individual cysteine is required for T6SS-dependent secretion of IglG and of the Hcp homologue, IglC and for the F. novicida intracellular life cycle. In contrast, the Francisella-specific N-terminal α-helical extension is not required for IglG secretion, but is critical for F. novicida virulence and for the interaction of IglG with another FPI-encoded protein, IglF. Altogether, our data suggest that IglG is a PAAR-like protein acting as a bi-modal protein that may connect the tip of the Francisella T6SS with a putative T6SS effector, IglF. PMID:27602570

  14. t(6;9)(p23;q34) presenting acute myeloid leukemia in a child with an unsuspected 45,X/46,X,derY [?t(Yp;Yq)] chromosomal constitution: yet another Y chromosome overdosage and malignancy association.

    PubMed

    Ogur, Gönül; Duru, Feride; Ozyurek, Emel; Fisgin, Tunc

    2012-08-01

    Development of leukemia in patients with sexual chromosome abnormalities is relatively rare and mostly involves cases of monosomy X, Turner syndrome. Here, we report on a child having a 45,X/46,X,derY [?t(Yp;Yq)] chromosomal constitution (variant Turner syndrome) presenting with concordant acute myeloid leukemia and a rarely seen clonal neoplasic cell lineage-related karyotype, t(6;9)(p23;q34).

  15. Enantioselective effect of 12(S)-hydroxyeicosatetraenoic acid on 3T6 fibroblast growth through ERK 1/2 and p38 MAPK pathways and cyclin D1 activation.

    PubMed

    Nieves, Diana; Moreno, Juan J

    2008-09-01

    Hydroxyeicosatetraenoic acids (HETEs) have numerous physiological effects, including modulation of cell proliferation and differentiation. However, little is known about the selective effects of HETE enantiomers on cell proliferation and cell signalling pathways involved in the regulation of cell growth. Furthermore, information on epithelial and endothelial cells growth is controversial. Recently, we demonstrated that 5-, 12-, and 15-HETE are involved in the control of 3T6 fibroblast growth though serine/treonine Akt/PKB (Akt) pathway. Here we examined the participation of both enantiomers (S and R) of HETEs in the control of 3T6 fibroblast growth. Our results show that HETEs (5-, 12-, and 15-HETE) are enantioselective on protein and DNA synthesis and 3T6 fibroblast growth. Furthermore, we observed that 12(S)-HETE induces the enhancement of cAMP and intracellular calcium concentration, whereas 12(R)-HETE was uneffective. Our findings also demonstrated that 12(S)-HETE exerts these effects through enantiospecific interactions with a cellular element, probably a plasma membrane receptor coupling to a pertussis toxin-sensitive protein G. Moreover, these elements may be involved in the activation of mitogen-activated protein kinase pathways which induce the enhancement of cyclin D(1) levels.

  16. An Experimental Investigation of the Effects of Vacuum Environment on the Fatigue Life, Fatigue-Crack-Growth Behavior, and Fracture Toughness of 7075-T6 Aluminum Alloy. Ph.D. Thesis - North Carolina State Univ.

    NASA Technical Reports Server (NTRS)

    Hudson, C. M.

    1972-01-01

    Axial load fatigue life, fatigue-crack propagation, and fracture toughness tests were conducted on 0.090-inch thick specimens made of 7075-T6 aluminum alloy. The fatigue life and fatigue-crack propagation experiments were conducted at a stress ratio of 0.02. Maximum stresses ranged from 33 to 60 ksi in the fatigue life experiments, and from 10 to 40 ksi in the fatigue-crack propagation experiments, and fatigue life experiments were conducted at gas pressures of 760, 0.5, 0.05, and 0.00000005 torr. Fatigue-crack-growth and fracture toughness experiments were conducted at gas pressures of 760 and 5 x 10 to the minus 8th power torr. Residual stress measurements were made on selected fatigue life specimens to determine the effect of such stresses on fatigue life. Analysis of the results from the fatigue life experiments indicated that fatigue life progressively increased as the gas pressure decreased. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue crack growth rates were approximately twice as high in air as in vacuum. Fracture toughness data showed there was essentially no difference in the fracture toughness of 7075-T6 in vacuum and in air.

  17. The effect of strain rate on the tensile properties of an Al[sub 2]O[sub 3p]/6061-T6 aluminum metal-matrix composite at low temperatures

    SciTech Connect

    Chia Chaw Perng; Jiun Ren Hwang; Ji Liang Doong )

    1993-08-01

    Alumina (Al[sub 2]O[sub 3]) particles reinforced aluminum matrix composites have recently become candidates for structural materials because of their good specific modulus and strength, and are considered to be valuable materials for aerospace and automobile industry applications. In view of such application, they might be processed or applied in high strain rate loading conditions, such as explosive forming, blast loading and metalworking, etc. Knowledge of the mechanical behavior of the metal matrix composites under high strain rate loading is a prerequisite. However, not much work related to this topic has been done. The objective of this study was to investigate the effect of the strain rate on the tensile properties of the Al[sub 2]O[sub 3p]/6061-T6 composite at low temperatures.

  18. Effect of shot peening and grain refinement on the fatigue life and strength of commercially pure Al and two of its alloys: Al-2024-T3 and Al-7075-T6

    NASA Astrophysics Data System (ADS)

    Qandil, A.; Zaid, Adnan I. O.

    2016-08-01

    Aluminum and its alloys are widely used materials in automobile, aircraft and space craft industries due to their high strength- to- weight ratio and corrosion resistance beside their other useful properties. They are the second materials in use after steel alloys. Most of the failures in parts of aircrafts and space vehicles are mainly caused by fatigue and stress corrosion cracking. In this paper, the effect of shot peening on the fatigue life of commercially pure aluminumand two of its alloys namely:Al-2024 and Al-7075-T6 is presented and discussed. Furthermore, the effect of addition of vanadium to Al and Al grain refined by Ti and Ti+Bon Its fatigue life and strengthis also presented and discussed using scanning electron microscope, SEM. It was that shot peening and the addition of V toAl and Al onAl grain refined by Ti and Ti+B have resulted in enhancement of the fatigue life and strength. Ffinally, the effect of shot peening on the surface quality of the peened parts is also presented and discussed.

  19. A high incidence of adjacent-1 meiotic segregation pattern, revealed by multicolor sperm FISH, in a carrier boar of a new reciprocal translocation t(6;16)(p13;q23).

    PubMed

    Kociucka, B; Szczerbal, I; Bugaj, S; Orsztynowicz, M; Switonski, M

    2014-01-01

    Reciprocal translocations pose a serious problem in pig breeding due to the reduced fertility of the carriers. This paper presents a new reciprocal translocation in a phenotypically normal, but hypoprolific (20% reduction) boar. Chromosome banding as well as the FISH technique with the use of BAC and telomeric probes was applied for a detailed characterization of this chromosome rearrangement. The karyotype of the studied boar was described as 38,XY,t(6;16)(p13;q23). The meiotic segregation of the quadrivalent was studied in 1,071 sperms by multicolor FISH. The most frequent segregation patterns were alternate (47.5%) and adjacent 1 (41.9%), while adjacent 2 and 3:1 were less frequent at 1.2 and 9.2%, respectively. Surprisingly, the frequency of the adjacent-1 segregation appeared to be relatively high, when compared with human and pig reciprocal translocations studied by sperm FISH. Our study, along with a review of the literature, shows that a reduction of fertility in the carriers and the incidence of different segregation patterns of the quadrivalent may vary within a broad range, and both aspects seem to be unrelated. A need for obligatory karyotype screening programs of artificial insemination boars is emphasized.

  20. A 10-year wildlife survey of 15 species of Canadian carnivores identifies new hosts or geographic locations for Trichinella genotypes T2, T4, T5, and T6.

    PubMed

    Gajadhar, Alvin A; Forbes, Lorry B

    2010-02-26

    A survey of wild carnivores in Canada was conducted over a 10-year period to determine the prevalence and genotypes of Trichinella. Muscle samples collected from 1409 animals representing 15 hosts species were enzymatically digested to recover Trichinella larvae. Larvae were recovered from a total of 287 (20.4%) animals and PCR identified four genotypes of Trichinella. Trichinella nativa was found in 5 host species and was the most commonly found genotype. Trichinella T6 was present in 7 species of carnivores, and coyote and badger are new host records for this genotype. The recovery of T. pseudospiralis and T. murrelli from cougars is the first documentation of these species in Canada and in cougars. The cougar was also the only host species in which all four genotypes of Trichinella were identified. Black bears and walruses had the highest tissue levels of larvae in this study and are also the species most frequently associated with human trichinellosis in Canada. This work identifies additional host species and expanded geographic ranges for 4 genotypes of Trichinella in North America. Failure to demonstrate T. spiralis in wildlife and continued negative results from ongoing surveillance activities in swine provide additional evidence that T. spiralis is not present in Canada.

  1. [Clinical results of tinted aspheric multifocal toric intraocular lens (SND1T3, SND1T4, SND1T5, SND1T6) for eyes following cataract extraction].

    PubMed

    Nakamura, Kunihiko; Bissen-Miyajima, Hiroko; Hayashi, Ken; Yoshino, Mami; Hirasawa, Manabu; Masumoto, Miki; Takimoto, Minehiro; Horikawa, Kumi; Maeda, Naoyuki

    2015-01-01

    The efficacy and safety of tinted aspheric multifocal toric intraocular lens (IOL) (SND1T3, SND1T4, SND1T5, SND1T6 : Alcon) were evaluated in 130 eyes of 65 patients following cataract removal. Visual acuities (VAs) at distance, near (40 cm) and intermediate (50 cm, 1 m), IOL rotation, contrast sensitivity, spectacle usage and glare/halo were examined up to 1 year postoperatively. The mean bilateral uncorrected distance VA was -0.04 ± 0.10 logMAR, near VA was 0.00 ± 0.11 logMAR, intermediate VA at 50 cm was -0.00 ± 0.11 logMAR, intermediate VA at 1 m was 0.11 ± 0.15 logMAR. IOL rotation was 5.73 ± 4.36 degrees, photopic contrast sensitivities were within normal range, and 76.9% of the patients did not require any spectacles. None of the patients complained of either serious glare or halo. The multifocal toric IOL provides better VA from distance to near at 40 cm.

  2. Autonomic dysreflexia in a tetraplegic patient due to a blocked urethral catheter: spinal cord injury patients with lesions above T-6 require prompt treatment of an obstructed urinary catheter to prevent life-threatening complications of autonomic dysreflexia

    PubMed Central

    2012-01-01

    Background The Manchester Triage System is commonly used as the triage system in emergency departments of the UK. As per the Manchester Triage System, patients presenting with retention of urine to the accident and emergency department are categorized to yellow, which denotes that the ideal maximum time to first contact with a treating clinician will be 60 min. Cervical spinal cord injury patients, in whom urinary catheter is blocked, may develop suddenly headache, sweating, high blood pressure, cardiac dysrhythmia, convulsions, intracranial bleed, and acute neurogenic pulmonary oedema as a result of autonomic dysreflexia due to a distended bladder. Case presentation A 46-year-old male with C-6 tetraplegia developed urinary retention because of a blocked catheter. He was seen immediately on arrival in the spinal injuries unit. The blocked catheter was removed and a new catheter was about to be inserted. Then this patient said that the ceiling lights were very bright and glaring. Five milligrams of Nifedipine was given sublingually. This patient started having fits involving his head, face, neck and shoulders with loss of consciousness. A 14-French silicone Foley catheter was inserted per urethra without any delay and 300 ml of clear urine was drained. This patient recovered consciousness within 5 min. Computed tomography of the brain revealed no focal cerebral or cerebellar abnormality. There was no intra-cranial haemorrhage. Conclusion This case illustrates that spinal cord injury patients with lesion above T-6, who develop retention of urine because of a blocked catheter, may look apparently well, but these patients can develop suddenly life-threatening autonomic dysreflexia. Therefore, spinal cord injury patients, who present to the accident and emergency department or spinal units with a blocked urinary catheter, should be seen urgently although their vital signs may be stable on arrival. Increasing the awareness of staff in emergency departments regarding

  3. Mapping of the Pim-1 oncogene in mouse t-haplotypes and its use to define the relative map positions of the tcl loci t0(t6) and tw12 and the marker tf (tufted).

    PubMed

    Ark, B; Gummere, G; Bennett, D; Artzt, K

    1991-06-01

    Pim-1 is an oncogene activated in mouse T-cell lymphomas induced by Moloney and AKR mink cell focus (MCF) viruses. Pim-1 was previously mapped to chromosome 17 by somatic cell hybrids, and subsequently to the region between the hemoglobin alpha-chain pseudogene 4 (Hba-4ps) and the alpha-crystalline gene (Crya-1) by Southern blot analysis of DNA obtained from panels of recombinant inbred strains. We have now mapped Pim-1 more accurately in t-haplotypes by analysis of recombinant t-chromosomes. The recombinants were derived from Tts6tf/t12 parents backcrossed to + tf/ + tf, and scored for recombination between the loci of T and tf. For simplicity all t-complex lethal genes properly named tcl-tx are shortened to tx. The Pim-1 gene was localized 0.6 cM proximal to the tw12 lethal gene, thus placing the Pim-1 gene 5.2 cM distal to the H-2 region in t-haplotypes. Once mapped, the Pim-1 gene was used as a marker for further genetic analysis of t-haplotypes. tw12 is so close to tf that even with a large number of recombinants it was not possible to determine whether it is proximal or distal to tf. Southern blot analysis of DNA from T-tf recombinants with a separation of tw12 and tf indicated that tw12 is proximal to tf. The mapping of two allelic t-lethals, t0 and t6 with respect to tw12 and tf has also been a problem.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Double partial trisomy of 6p23-pter and 9pter-q21.2 in a neonate resulting from 4:2 meiotic segregation of a maternal complex t(6;7;9)(p23;p15;q21.2) translocation.

    PubMed

    Cetin, Z; Mihci, E; Keser, I; Karaali, K; Berker, S; Luleci, G

    2012-01-01

    We report, a newborn presenting multiple congenital abnormalities with karyotype; 47,XY,der(7)t(6;7)(pter-p23::p15-->qter),+der(9)t(7;9)(pter-->p15::q21.2--> pter)t(6;7;9)(p23;p15;q21.2)mat[20]. The mother and her phenotypically normal daughter were carriers of a complex chromosomal rearrangement with karyotypes; 46,XX,t(6;7;9)(p23;p15;q21.2)[20]. Paternal chromosomes were normal. In our case the extra derivative chromosome was the result of a 4:2 segregation of the chromosomes involved in translocation during oogenesis. Double partial trisomy in newborns resulting from 4:2 segregation is a rare event, and double partial trisomies of the 6p23-pter and trisomy 9pter-q22 regions have not reported to date.

  5. T-6A Texan II Systems Engineering Case Study

    DTIC Science & Technology

    2010-01-01

    IFR Certified Instrumentation IFR Certified (Selectable EADI/EHSI) All digital except backups Visual System for IFT/OFT Provide a visual field...subject matter expert ( SME ), signifying that the requirement had been verified. Some requirements also required the systems safety and program manager’s...Engineering Plan SLEP Structural Life Extension Program SME Subject Matter Expert SON Statement of Need SoS System-of-Systems SOW Statement of Work

  6. Environmental Assessment: T-6 Aircraft Basing and Operation

    DTIC Science & Technology

    2004-06-01

    AQCR 5 includes Baldwin, Escambia and Mobile counties in Alabama. The AQCR includes Bay, Calhoun, Escambia, Gulf , Holmes, Jackson, Okaloosa...American badger X Brazilian free-tailed bat X Buttermilk racer X Cerulean warbler X Desert shrew X Green water snake X Gulf crayfish snake X...Louisiana milk snake X Northern scarlet snake X Osprey X Ozark big-eared bat X Plains harvest mouse X Rafinesque’s big-eared bat X Ringtail X

  7. Impact properties of A356-T6 alloys

    NASA Astrophysics Data System (ADS)

    Shivkumar, S.; Wang, L.; Keller, C.

    1994-02-01

    The Charpy impact energy of A356 alloys has been measured. Instrumented Charpy impact tests have been conducted at 25,100,150, and 200 °C. The Charpy specimens were machined from plate castings ortapered cylindrical castings. The plates were produced in sand molds, and tapered cylinders were produced in water-cooled copper molds. Both unmodified and strontium-modified castings were tested. The results indicate that strontium modification improves the impact properties of sand and permanent mold castings. The impact energy increases with solution treatment time. Strontium modification reduces the solution treatment time for attaining a specific impact property level in the casting.

  8. Fatigue Strengths of Aircraft Materials: Axial-Load Fatigue Tests on Edge-Notched Sheet Specimens of 2024-T3 and 7075-T6 Aluminum Alloys and of SAE 4130 Steel with Notch Radii of 0.004 and 0.070 inch

    NASA Technical Reports Server (NTRS)

    Grover, H. J.; Hyler, W. S.; Jackson, L. R.

    1959-01-01

    The present report gives results of axial-load fatigue tests on notched specimens of three sheet materials: 2024-T3 and 7075-T6 aluminum alloys and normalized SAE 4130 steel. Two edge-notched specimens were designed and tested, each having a theoretical stress-concentration factor K(sub t) = 4.0. The radii of the notches were 0.004 and 0.070 inch. Tests of these specimens were run at two levels of nominal mean stress: 0 and 20,000 psi. Results of these studies extended information previously reported on tests of specimens with varying notch severity. They afford data on the variation of fatigue-strength reduction with notch radius and on the potential usefulness of Neuber's technical stress-concentration factor K(sub n).

  9. Characterization of mechanical shock waves in aluminum 6061-T6 using a high power laser pulse

    NASA Astrophysics Data System (ADS)

    Gonzalez Romero, J. R.; García-Torales, G.; Gómez Rosas, G.; Ocaña, J. L.; Flores, Jorge L.

    2016-09-01

    Strengthening techniques allows enhance metal physical properties. Laser shock peening (LSP) technique consist in a surface treatment which a high power laser pulse induces a compressive residual stress field through mechanical shock waves, increasing hardness, corrosion resistance, fatigue resistance. In comparison with the shot peening technique, LSP is a method that allows precision controlling the laser incidence on the surface under treatment increasing the surface quality in the surface under treatment. In this work, mechanical shock waves are induced in aluminum and measure using two different experimental approaches. First, using a PVDZ sensors and secondly, strain gauges are used. Experimental results are presented.

  10. Low cost corrosion damage mitigation and improved fatigue performance of low plasticity burnished 7075-T6

    NASA Astrophysics Data System (ADS)

    Prevéy, Paul S.; Cammett, John

    2001-10-01

    Low plasticity burnishing (LPB) has been investigated as a surface enhancement process and corrosion mitigation method for aging aircraft structural applications. Compressive residual stresses reaching the alloy yield strength and extending to a depth of 1.25 mm (0.050 in.) deeper than typical corrosion damage is achievable. Excellent surface finish can be achieved with no detectable metallurgical damage to surface and subsurface material. Salt fog exposures of 100 and 500 h reduced the fatigue strength at 2×106 cycles by 50%. The LPB of the corroded surface, without removal of the corrosion product or pitted material, restored the 2×106 fatigue strength to greater than that of the original machined surface. The fatigue strength of the corroded material in the finite life regime (104 to 106 cycles) after LPB was 140 MPa (20 ksi) higher than the original uncorroded alloy and increased the life by an order of magnitude. Ease of adaptation to computer numerical control (CNC) machine tools allows LPB processing at costs and speeds comparable to machining operations. Low plasticity burnishing offers a promising new technology for mitigation of corrosion damage and improved fatigue life of aircraft structural components with significant cost and time savings over current practices.

  11. 7075-T6 and 2024-T351 Aluminum Alloy Fatigue Crack Growth Rate Data

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; Wright, Christopher W.; Johnston, William M., Jr.

    2005-01-01

    Experimental test procedures for the development of fatigue crack growth rate data has been standardized by the American Society for Testing and Materials. Over the past 30 years several gradual changes have been made to the standard without rigorous assessment of the affect these changes have on the precision or variability of the data generated. Therefore, the ASTM committee on fatigue crack growth has initiated an international round robin test program to assess the precision and variability of test results generated using the standard E647-00. Crack growth rate data presented in this report, in support of the ASTM roundrobin, shows excellent precision and repeatability.

  12. Recreation Expenditures by U. S. Consumers, 1929-l979. Publication T-6-135.

    ERIC Educational Resources Information Center

    Kitchen, James W.; And Others

    This study explored trends in how Americans spent disposable personal income (DPI) on recreational activities from 1929 to 1979. Statistics were compiled from the Economic Report of the President and the United States Department of Commerce. Twelve classifications of recreation expenditures are presented: (1) books and maps; (2) magazines,…

  13. Experimental measurement of the principal isentrope for aluminum 6061-T6 to 240 GPa.

    SciTech Connect

    Davis, Jean-Paul

    2005-02-01

    Using a magnetic pressure drive, an absolute measurement of stress and density along the principal compression isentrope is obtained for solid aluminum to 240 GPa. Reduction of the free-surface velocity data relies on a backward integration technique, with approximate accounting for unknown systematic errors in experimental timing. Maximum experimental uncertainties are {+-}4.7% in stress and {+-}1.4% in density, small enough to distinguish between different equation-of-state (EOS) models. The result agrees well with a tabular EOS that uses an empirical universal zero-temperature isotherm.

  14. Experimental measurement of the principal isentrope for aluminum 6061-T6 to 240 GPa.

    SciTech Connect

    Davis, Jean-Paul

    2006-02-01

    Using a magnetic pressure drive, an absolute measurement of stress and density along the principal compression isentrope is obtained for solid aluminum to 240 GPa. Reduction of the free-surface velocity data relies on a backward integration technique, with approximate accounting for unknown systematic errors in experimental timing. Maximum experimental uncertainties are +/-4.7% in stress and +/-1.4% in density, small enough to distinguish between different equation-of-state (EOS) models. The result agrees well with a tabular EOS that uses an empirical universal zero-temperature isotherm.

  15. Equation of state for two flavor QCD at N{sub t}=6

    SciTech Connect

    Bernard, C.; Blum, T.; DeTar, C.; Gottlieb, S.; Rummukainen, K.; Heller, U.M.; Hetrick, J.E.; Toussaint, D.; Kaerkkaeinen, L.; Sugar, R.L.; Wingate, M.

    1997-06-01

    We calculate the two flavor equation of state for QCD on lattices with lattice spacing a=(6T){sup {minus}1} and find that cutoff effects are substantially reduced compared to an earlier study using a=(4T){sup {minus}1}. However, it is likely that significant cutoff effects remain. We fit the lattice data to expected forms of the free energy density for a second order phase transition at zero-quark mass, which allows us to extrapolate the equation of state to m{sub q}=0 and to extract the speed of sound. We find that the equation of state depends weakly on the quark mass for small quark mass. {copyright} {ital 1997} {ital The American Physical Society}

  16. Environmental Assessment T-1, T-6, and T-37 Aircraft Operations at Perry Municipal Airport

    DTIC Science & Technology

    2006-04-01

    whooping crane ( Grus americana). The closest known sightings of the bald eagle are around Kaw Lake and Sooner Lake, which are outside the airspace...region of influence (ROI) within an approximate 5-mile radius of PMA. The closest known sighting of the whooping crane are on the Great Salt Plains...shortness of breath, coughing , wheezing, headaches, nausea, eye and throat irritations, and lung damage. There are two categories of particulate matter

  17. The Effectiveness of T-6A Instrument Flying Training as Compared to T-37B Training

    DTIC Science & Technology

    2004-12-01

    manual of the American Psychological Association (5th ed.). Washington, DC: Author. Microsoft Access 2002 SP3 [Computer software]. (2001). Redmond, WA...San Antonio, TX: Air Education and Training Command. 38 APPENDIX A BIBLIOGRAPHY American Psychological Association. (2001). Publication

  18. Effects of Applied Load on 6061-T6 Aluminum Joined Employing a Novel Friction Bonding Process

    SciTech Connect

    Douglas E. Burkes; Neil P. Hallinan; Karen L. Shropshire; Peter B. Wells

    2008-12-01

    Friction bonding is under consideration for use in mass production of plate-type nuclear fuels for research reactors. This article discusses the effects of applied load (the most important process parameter for fabrication of these fuels) on temperature distribution, microstructure, and mechanical properties. Friction bonding experiments showed that tool geometry caused temperature gradients across the tool surface. Temperatures at the joint interface suggested the advancing side of the tool produced a majority of the frictional heat, while the retreating side of the tool mainly forged the plasticized material while bonding increased with applied load. The microstructure across the tool surface was also altered and, as a function of applied load, affected the mechanical properties. The 6061 aluminum alloy had mechanical properties close to a T4 temper after processing. Results documented in this article will aid in continual enhancement of friction bonding for nuclear fuel plate fabrication, and will hopefully contribute to continued advancement of friction stir welding (FSW) state of the art.

  19. An Investigation of Residual Stress Characterization of 7075-T6 Aluminum for Application in Fatigue Analysis

    DTIC Science & Technology

    1978-12-01

    machine and loaded to give a 10,000 psi nominal stress (applied load/reduced cross-section). A Photolastic Inc. Model 031 Reflection Polariscope , equipped...1971. 9. Photolastic Inc., Instruction Manual for 030 Series Reflection Polariscope . 10. Blakely, F. M., Design of Software Package for Incorporation...level to cause yielding at the notch tip. The largest localized strain at the notch was measured with the polariscope . The compensator reading and load

  20. A damage tolerance comparison of 7075-T6 aluminum alloy and IM7/977-2 carbon/epoxy

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Lance, David G.; Hodge, Andrew J.

    1991-01-01

    A comparison of low velocity impact damage between one of the strongest aluminum alloys, to a new, damage tolerant resin system as a matrix for high strength carbon fibers was examined in this study. The aluminum and composite materials were used as face sheets on a 0.13 g/cu cm aluminum honeycomb. Four levels of impact energy were used; 2.6 J, 5.3 J, 7.8 J and 9.9 J. The beams were compared for static strength and fatique life by use of the four-point bend flexure test. It was found that in the undamaged state the specific strength of the composite face sheets was about twice that of the aluminum face sheets. A sharp drop in strength was observed for the composite specimens impacted at the lowest (2.6J) energy level, but the overall specific strength was still higher than for the aluminum specimens. At all impact energy levels tested, the static specific strength of the composite face sheets were significantly higher than the aluminum face sheets. The fatigue life of the most severely damaged composite specimen was about 17 times greater than the undamaged aluminum specimens when cycled at 1 Hz between 20 percent and 85 percent of ultimate breaking load.

  1. Discernible but limited introgression has occurred where Trichinella nativa and the T6 genotype occur in sympatry

    USDA-ARS?s Scientific Manuscript database

    The genetic diversity within and among parasite populations provides clues to their evolutionary history. Here, we sought to determine whether mitochondrial and microsatellite variation could be used to evaluate the extent of differentiation, gene flow and historical reproductive isolation among the...

  2. Multiscale Study of Interfacial Intermetallic Compounds in a Dissimilar Al 6082-T6/Cu Friction-Stir Weld

    NASA Astrophysics Data System (ADS)

    Avettand-Fenoël, M. N.; Taillard, R.; Ji, G.; Goran, D.

    2012-12-01

    The objective of this work was to characterize the Al x Cu y intermetallic compounds (IMCs) formed at the abutting interface during solid-state friction-stir welding (FSW) of 6082 aluminum alloy and pure copper. As IMCs are potential sources of flaws in case of mechanical loading of welds, their study is essential at various scale lengths. In the present case, they have been identified by neutron diffraction, electron backscattered diffraction, and transmission electron microscopy. Neutron diffraction analyses have shown that a shift of the tool from the interface, in particular towards the Cu part, generates an increase of the IMCs' volume fraction. In accordance with an exacerbation of its kinetics of formation by FSW, a 4- μm-thick layer has precipitated at the interface despite the shortness of the thermal cycle. This layer is composed of two sublayers with the Al4Cu9 and Al2Cu stoichiometry, respectively. Convergent beam electron diffraction analyses have, however, disclosed that the crystallography of the current Al2Cu compound does not comply with the usual tetragonal symmetry of this phase. The Al2Cu phase formation results from both the local chemical composition and thermodynamics, whereas the development of Al4Cu9 is rather due to both the local chemical composition and the shortness of the local FSW thermal cycle.

  3. On binding specificity of (6-4) photolyase to a T(6-4)T DNA photoproduct*

    NASA Astrophysics Data System (ADS)

    Jepsen, Katrine Aalbæk; Solov'yov, Ilia A.

    2017-06-01

    Different factors lead to DNA damage and if it is not repaired in due time, the damaged DNA could initiate mutagenesis and cancer. To avoid this deadly scenario, specific enzymes can scavenge and repair the DNA, but the enzymes have to bind first to the damaged sites. We have investigated this binding for a specific enzyme called (6-4) photolyase, which is capable of repairing certain UV-induced damage in DNA. Through molecular dynamics simulations we describe the binding between photolyase and the DNA and reveal that several charged amino acid residues in the enzyme, such as arginines and lysines turn out to be important. Especially R421 is crucial, as it keeps the DNA strands at the damaged site inside the repair pocket of the enzyme separated. DNA photolyase is structurally highly homologous to a protein called cryptochrome. Both proteins are biologically activated similarly, namely through flavin co-factor photoexcitation. It is, however, striking that cryptochrome cannot repair UV-damaged DNA. The present investigation allowed us to conclude on the small but, apparently, critical differences between photolyase and cryptochrome. The performed analysis gives insight into important factors that govern the binding of UV-damaged DNA and reveal why cryptochrome cannot have this functionality.

  4. Identifying Combination of Friction Stir Welding Parameters to Maximize Strength of Lap Joints of AA2014-T6 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Rajendrana, C.; Srinivasan, K.; Balasubramanian, V.; Balaji, H.; Selvaraj, P.

    2017-01-01

    AA2014 aluminum alloy (Al-Cu alloy) has been widely utilized in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimize process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminum alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminum alloys. Hence, in this investigation, an attempt has been made to optimize friction stir lap welding (FSLW) parameters to attain maximum tensile strength using statistical tools such as design of experiment (DoE), analysis of variance (ANOVA), response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

  5. Effect of Preexisting Corrosion on Fatigue Cracking of Aluminum Alloys 2024-T3 and 7075-T6

    DTIC Science & Technology

    1995-08-01

    play a dominant role, although a possible 93 effect of hydrogen should not be ruled out. Doerfler et al.41 and Bucci et al.47 proposed to...WL/FIBE, Wright-Patterson Air Force Base, OH, July 1994. 41. M. T. Doerfler , A. F. Grandt, Jr., R. J. Bucci, and M. Kulak, "A Fracture Mechanics

  6. The effects of maintaining temperature in annealing heat treatment for an FSWed 6061-T6 Al alloy.

    PubMed

    Lee, Seung-Jun; Han, Min-Su; Kim, Seong-Jong

    2013-08-01

    The technological development of all kinds of lightweight transportation devices including vehicles, aircraft, ships, etc. has progressed markedly with the demand for energy saving and environmental protection. Aluminum alloy is in the spotlight as it is a suitable environmentally friendly material. However, deformation is a major problem during the welding process because aluminum alloy has a large thermal expansion coefficient. In addition, it is known that its corrosion resistance is excellent; nevertheless, in practice, considerable corrosion is generated and this is a major problem. To solve this problem, the friction stir welding (FSW) technology is applied extensively at various industrial fields as a new welding technique. This method involves a process in which materials are joined by frictional heat and physical force. Therefore, we evaluated improvements in mechanical properties and corrosion resistance through annealing heat treatment after FSW. The electrochemical experiment did not show a significant difference. However, the microstructure observation showed defectless, fine crystal particles, indicating excellent properties at 200-225°C.

  7. Corrosion Fatigue Crack Growth Behavior at Notched Hole in 7075 T6 Under Different Biaxial Stress Ratios

    DTIC Science & Technology

    2016-08-18

    constant for Paris law (unit less) CF corrosion fatigue da/dN rate of crack growth per cycle (mm/cycle) DOD Department of Defense G...31]. When these different factors failure modes are combined, the failure occurs sooner. Corrosion fatigue ( CF ) occurs when the crack generated by...Intrusion and Extrusion of Fatigue Crack Initiation [30]. 2.2 Corrosion Fatigue Corrosion fatigue ( CF ) is one of the most complicated topics of

  8. Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 Under Biaxial and Uniaxial Fatigue

    DTIC Science & Technology

    2014-06-19

    evolution in Al - Zn -Mg- Cu ". Corrosion Science, 52:498–508, 2010. [8] Castro, P.M.S.T., P.F.P. Matos, G.P. Moreira, and L.F.M. Silva. "An overview on... alloys . The heterogeneous microstructures of aluminum alloys such as 2024 and 7075, which are widely used in aircraft structures, make them extremely...presence of corrosion pits notably reduces the fatigue life of the aluminum alloy by a factor of 10–100. Sankaran et al . found this factor as 6 to 8 [45

  9. External And Internal Work Of A T-6 Paraplegic Propelling A Wheelchair And Arm Cranking A Cycle Ergometer: Case Study

    NASA Astrophysics Data System (ADS)

    Novak, Charles W.

    1982-02-01

    In this, the International Year of the Disabled, attention is directed among other areas toward rehabilitation and sports participation of wheelchair users. As an application of movement analysis in medicine and rehabilitation and as an application of sports research using biomechanics, this investigation was performed to compare the results of two methods of gathering data on the stress of wheelchair propelling at equivalent work loads and to account for differences in physiological responses with a mechanical analysis of wheelchair propelling. Physiological data collected were heart rate, systolic blood pressure, and rate-pressure product. A biomechanical cinematography analysis was used to determine external work in wheelchair propelling and to determine the extent to which modifications in segment actionsoccurred during increasing magnitude of work. A cycle ergometer was adjusted to replicate external work loads performed during wheelchair propelling. A t-test of equivalent external work loads indicated that heart rate was not different between the two exercise modes at the .05 level of significance. The t-test did indicate a significant difference in systolic blood pressure and rate-pressure product at the .05 level of significance. The biomechanical analysis of wheelchair propelling established that an increase in external work was accomplished by a decrease in the range of motion and an increase in the speed of movement. During cycle ergometry the range and speed of movement remained the same while resistance was increased. Results of the study established that while heart rate for equivalent external work loads was the same for wheelchair propelling and arm cranking cycle ergometry, systolic blood pressure and rate-pressure product were not the same. The suggestion was that some means of propelling a wheelchair other than that which is con-sidered "standard" might be considered which produces less stressful responses in wheelchair users.

  10. Mixed Mode Stable Tearing of Thin Sheet Al 6061-T6 Specimens: Experimental Measurements and Finite Element Simulations using a Modified Mohr-Coulomb Fracture Criterion

    DTIC Science & Technology

    2010-11-01

    grounding. Oliver (1996a,b), Teng (2008) andXue (2007a) reported on successful application of contin- uum damage mechanics in simulating initiation and...the accumulated damage should reach the critical value and the load carrying capacity must vanish in the post-initiate range. It should be noted that...specimen using fracture coupled with damage plastic- ity approach. Different from Mode I, little thickness reduction is observed for Mode III loading, as

  11. Cytotoxic and antiproliferative effects induced by a non terpenoid polar extract of A. indica seeds on 3T6 murine fibroblasts in culture.

    PubMed

    Di Ilio, Vincenzo; Pasquariello, Nicoletta; van der Esch, Andrew S; Cristofaro, Massimo; Scarsella, Gianfranco; Risuleo, Gianfranco

    2006-07-01

    Neem oil is a natural product obtained from the seeds of the tree Azadirachta indica. Its composition is very complex and the oil exhibits a number of biological activities. The most studied component is the terpenoid azadirachtin which is used for its insecticidal and putative antimicrobial properties. In this report we investigate the biological activity of partially purified components of the oil obtained from A. indica. We show that the semi-purified fractions have moderate to strong cytotoxicity. However, this is not attributable to azadirachtin but to other active compounds present in the mixture. Each fraction was further purified by appropriate extraction procedures and we observed a differential cytotoxicity in the various sub-fractions. This led us to investigate the mode of cell death. After treatment with the oil fractions we observed positivity to TUNEL staining and extensive internucleosomal DNA degradation both indicating apoptotic death. The anti-proliferative properties of the neem oil-derived compounds were also assayed by evaluation of the nuclear PCNA levels (Proliferating Cell Nuclear Antigen). PCNA is significantly reduced in cells treated with a specific fraction of neem oil. Finally, our results strongly suggest a possible involvement of the mitochondrial pathway in the apoptotic death.

  12. Spin Forming of an Aluminum 2219-T6 Aft Bulkhead for the Orion Multi-Purpose Crew Vehicle: Phase II Supplemental Report

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Squire, Michael D.; Domack, Marcia S.; Hoffman, Eric K.

    2015-01-01

    The principal focus of this project was to assist the Orion Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the aft bulkhead of the pressure vessel. The spin forming process will enable a single piece aluminum (Al) 2219 aft bulkhead which will eliminate the current multiple piece welded construction, simplify fabrication, and lead to an enhanced design that will reduce vehicle weight by eliminating welds. Phase I of this assessment explored spin forming the single-piece forward pressure vessel bulkhead from aluminum-lithium 2195.

  13. Effect of Stress Ratio on Fatigue Crack Growth Rate at Notched Hole in 7075-T6 Aluminum Alloy Under Biaxial Fatigue

    DTIC Science & Technology

    2016-08-18

    and corrosion. This approach has been used to delay crack in structure in aerospace field [26]. In addition, laterally many studies have described...loading conditions. And it is a link between previous studies and future studies in the field . II. Background 2.1 Fatigue Since fracture mechanics...steady, but other forms of stresses such as rotation, torsion , pending can lead to fatigue failure [5,34]. Fatigue crack start as invisible microcrack

  14. 22q11.2 Deletion Syndrome due to a Translocation t(6;22) in a Patient Conceived via in vitro Fertilization

    PubMed Central

    Gollo Dantas, Anelisa; Bortolai, Adriana; Moysés-Oliveira, Mariana; Takeno Herrero, Sylvia; Azoubel Antunes, Adriana; Tavares Costa-Carvalho, Beatriz; Ayres Meloni, Vera; Melaragno, Maria Isabel

    2016-01-01

    We report on a patient conceived via in vitro fertilization (IVF) with a 22q11.2 deletion due to an unusual unbalanced translocation involving chromosomes 6 and 22 in a karyotype with 45 chromosomes. Cytogenomic studies showed that the patient has a 3.3-Mb deletion of chromosome 22q and a 0.4-Mb deletion of chromosome 6p, which resulted in haploinsufficiency of the genes responsible for the 22q11.2 deletion syndrome and also of the IRF4 gene, a member of the interferon regulatory factor family of transcription factors, which is expressed in the immune system cells. The rearrangement could be due to the manipulation of the embryo or as a sporadic event unrelated to IVF. Translocation involving chromosome 22 in a karyotype with 45 chromosomes is a rare event, with no previous reports involving chromosomes 6p and 22q. PMID:26997945

  15. Effect of Precipitation During Quenching on the Prediction of the Mechanical Properties of Al-5 Pct Cu Alloy After T6 Treatment

    NASA Astrophysics Data System (ADS)

    Hu, Yisen; Wang, Gang; Wang, Wenguang; Rong, Yiming

    2017-08-01

    The mechanical properties of Al-5 pct Cu cast alloy, one of the heat-treatable aluminum alloys, depend on the quenching rate and aging conditions. The effect of precipitation during quenching cannot be ignored for large and thick-walled components, although it is generally assumed that no precipitates form during cooling. In this article, a non-isokinetic model, considering the strengthening effects of precipitation during quenching and aging, was proposed to describe the evolution of minimum strength based on fully precipitating tests and transmission electron microscopy observations. Moreover, a comprehensive quench factor analysis, integrated with the non-isokinetic model, was conducted for the Al-5 pct Cu cast alloy using isothermal quench tests. Finally, the integrated model of the mechanical property was validated under various quenching conditions, including water at 353 K (80 °C), air at room temperature and furnace cooling. It was shown that the prediction can be extended to an 85 pct loss of property.

  16. Enhancing Friction Stir Weldability of 6061-T6 Al and AZ31B Mg Alloys Assisted by External Non-rotational Shoulder

    NASA Astrophysics Data System (ADS)

    Ji, Shude; Huang, Ruofei; Meng, Xiangchen; Zhang, Liguo; Huang, Yongxian

    2017-05-01

    In order to increase cooling rate and then reduce the amounts of intermetallic compounds, external non-rotational shoulder tool system derived from traditional tool in friction stir welding was used to join dissimilar Al and Mg alloys. In this study, based on the external non-rotational shoulder, the weldability of Al and Mg alloys was significantly improved. The non-rotational shoulder tool is propitious to make more materials into weld, increase cooling rate and then reduce material adhesion of rotational pin, obtaining sound joint with smaller flashes and smooth surface. Importantly, the thickness of intermetallic compounds layer is reduced compared with traditional tool. Meanwhile, hardness values of dissimilar joint present uneven distribution, resulting from complex intercalated structures in nugget zone (NZ) featured by intermetallic compound layers and fine recrystallized Mg and Al grains. Compared with traditional tool, non-rotational shoulder is beneficial to higher tensile properties of joint. Due to the intermetallic compound layer formed in the interface of Al-Mg, the welding joint easily fractures at the NZ, presenting the typical brittle fracture mode.

  17. Modelisation numerique des phenomenes physiques du soudage par friction-malaxage et comportement en fatigue de joints soudes en aluminium 7075-T6

    NASA Astrophysics Data System (ADS)

    Gemme, Frederic

    The aim of the present research project is to increase the amount of fundamental knowledge regarding the process by getting a better understanding of the physical phenomena involved in friction stir welding (FSW). Such knowledge is required to improve the process in the context of industrial applications. In order to do so, the first part of the project is dedicated to a theoretical study of the process, while the microstructure and the mechanical properties of welded joints obtained in different welding conditions are measured and analyzed in the second part. The combination of the tool rotating and translating movements induces plastic deformation and heat generation of the welded material. The material thermomechanical history is responsible for metallurgical phenomena occurring during FSW such as recrystallization and precipitate dissolution and coarsening. Process modelling is used to reproduce this thermomechanical history in order to predict the influence of welding on the material microstructure. It is helpful to study heat generation and heat conduction mechanisms and to understand how joint properties are related to them. In the current work, a finite element numerical model based on solid mechanics has been developed to compute the thermomechanical history of the welded material. The computation results were compared to reference experimental data in order to validate the model and to calibrate unknown physical parameters. The model was used to study the effect of the friction coefficient on the thermomechanical history. Results showed that contact conditions at the workpiece/tool interface have a strong effect on relative amounts of heat generated by friction and by plastic deformation. The comparison with the experimental torque applied by the tool for different rotational speeds has shown that the friction coefficient decreases when the rotational speed increases. Consequently, heat generation is far more important near the material/tool interface and the material deformation is shallower, increasing the lack of penetration probability. The variation of thermomechanical conditions with regards to the rotational speed is responsible for the variation of the nugget shape, as recrystallization conditions are not reached in the same volume of material. The second part of the research project was dedicated to a characterization of the welded joints microstructure and mechanical properties. Sound joints were obtained by using a manufacturing procedure involving process parameters optimization and quality control of the joint integrity. Five different combinations of rotational and advancing speeds were studied. Microstructure observations have shown that the rotational speed has an effect on recrystallization conditions because of the variation of the contact conditions at the material/tool interface. On the other hand, the advancing speed has a strong effect on the precipitation state in the heat affected zone (HAZ). The heat input increases when the advancing speed decreases. The material softening in the HAZ is then more pronounced. Mechanical testing of the welded joints showed that the fatigue resistance increases when the rotational speed increases and the advancing speed decreases. The fatigue resistance of FSW joints mainly depends on the ratio of the advancing speed on the rotational speed, called the welding pitch k. When the welding pitch is high (k ≥ 0,66 mm/rev), the fatigue resistance depends on crack initiation at the root of circular grooves left by the tool on the weld surface. The size of these grooves is directly related to the welding pitch. When the welding pitch is low (k ≤ 0,2 mm/rev), the heat input is high and the fatigue resistance is limited by the HAZ softening. The fatigue resistance is optimized when k stands in the 0,25-0,30 mm/rev range. Outside that range, the presence of small lateral lips is critical. The results of the characterization part of the project showed that the effects of the applied vertical force on the formation of lateral lips should be submitted to further investigations. The elimination of the lateral lip, which could be achieved with a more precise adjustment of the vertical force, could lead to an improved fatigue resistance. The elimination of lateral lips, but also the circular grooves left by the tool, may be obtained by developing an appropriate surfacing technique and could lead to an improved fatigue resistance without reducing the advancing speed. (Abstract shortened by UMI.)

  18. Effects of the FLASHJET Paint Removal Process on the Fatigue Properties of Al 7075-T6 and Al 2024-T3

    DTIC Science & Technology

    2005-09-01

    Acknowledgments The authors wish to extend their appreciation to Mr. Marty Munsell and Mr. Ray Rolen of Boeing-St. Louis. Mr. Munsell , an engineer...FLASHJET is the result of color and proximity sensors that control the pulse rate, travel speed, distance, and power to the xenon lamp. By...of 1.0–1.5 mil, which was followed by a polyurethane coating (MIL- PRF-85285, Color Chip 17925 White) to a dry film thickness of 2.0–2.5 mil. After

  19. Experimental Investigation of Effects of Random Loading on the Fatigue Life of Notched Cantilever-Beam Specimens of 7075-T6 Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Fralich, Robert W.

    1959-01-01

    Results of random-loading fatigue tests on 125 notched cantilever-beam specimens and constant-amplitude fatigue tests on 46 similar specimens are presented in terms of the root-mean-square value of peak stresses. The results from the two sets of tests are compared on the basis of time to failure, where the results from the constant-amplitude tests are expressed in terms of an equivalent time to failure based on the natural period of vibration. Compared on this basis, failure at the lower stress levels occurred in a shorter time for the random loading than for the constant-amplitude loading, whereas at the higher stress levels failure occurred in the reverse order. A theoretical result for random loading is also presented and compared with the experimental results. The theoretical result shows good agreement with experiment for low values of stress but underestimates the time to failure at the higher stresses.

  20. Draft Genome Sequence of Pseudomonas azotifigens Strain DSM 17556T (6H33bT), a Nitrogen Fixer Strain Isolated from a Compost Pile.

    PubMed

    Busquets, Antonio; Peña, Arantxa; Gomila, Margarita; Mulet, Magdalena; Mayol, Joan; García-Valdés, Elena; Bennasar, Antonio; Huntemann, Marcel; Han, James; Chen, I-Min; Mavromatis, Konstantinos; Markowitz, Victor; Palaniappan, Krishnaveni; Ivanova, Natalia; Schaumberg, Andrew; Pati, Amrita; Reddy, T B K; Nordberg, Henrik; Woyke, Tanja; Klenk, Hans-Peter; Kyrpides, Nikos; Lalucat, Jorge

    2013-10-31

    Pseudomonas azotifigens strain 6H33b(T) is a nitrogen fixer isolated from a hyperthermal compost pile in 2005 by Hatayama and collaborators. Here we report the draft genome, which has an estimated size of 5.0 Mb, exhibits an average G+C content of 66.73%, and is predicted to encode 4,536 protein-coding genes and 100 RNA genes.

  1. Draft Genome Sequence of Pseudomonas azotifigens Strain DSM 17556T (6H33bT), a Nitrogen Fixer Strain Isolated from a Compost Pile

    PubMed Central

    Busquets, Antonio; Peña, Arantxa; Gomila, Margarita; Mulet, Magdalena; Mayol, Joan; García-Valdés, Elena; Bennasar, Antonio; Huntemann, Marcel; Han, James; Chen, I-Min; Mavromatis, Konstantinos; Markowitz, Victor; Palaniappan, Krishnaveni; Ivanova, Natalia; Schaumberg, Andrew; Pati, Amrita; Reddy, T. B. K.; Nordberg, Henrik; Woyke, Tanja; Klenk, Hans-Peter; Kyrpides, Nikos

    2013-01-01

    Pseudomonas azotifigens strain 6H33bT is a nitrogen fixer isolated from a hyperthermal compost pile in 2005 by Hatayama and collaborators. Here we report the draft genome, which has an estimated size of 5.0 Mb, exhibits an average G+C content of 66.73%, and is predicted to encode 4,536 protein-coding genes and 100 RNA genes. PMID:24179119

  2. Nuclear Repositioning of the Non-Translocated HLXB9 Allele in the Leukaemia Cell Line GDM-1 Harbouring a t(6;7)(q23;q36).

    PubMed

    Federico, Concetta; Leotta, Claudia G; Bruno, Francesca; Longo, Anna M; Owoka, Temitayo; Tosi, Sabrina; Saccone, Salvatore

    2017-09-29

    Transcriptionally active and inactive topologically associated domains (TADs) occupy different areas in the cell nucleus, and chromosomal rearrangements relocating TADs could determine ectopic expression of the repositioned genes. In this study, we investigated the HLXB9 gene in a myeloid leukaemia cell line, GDM-1, known to harbour a rearrangement involving chromosome 7 with a breakpoint distal to HLXB9, highly expressed in these cells. We used FISH to target the regions involved in the translocation and to distinguish the translocated chromosome from the non-translocated one in interphase nuclei. Two-dimensional analysis of the interphase FISH data indicated that the 2 HLXB9 alleles had a different localisation in the cell nuclei, with the translocated allele consistently positioned in the nuclear periphery and the normal one in the more internal portion of the nucleus, known as the transcriptionally active compartment. Our data may indicate that HLXB9 transcripts in the GDM-1 cell line do not arise from the allele located in rearranged chromosome 7, suggesting that regulation of gene expression in cancer cells harbouring chromosomal translocations might be more complex than previously thought, paving the path to further investigations on mechanisms of gene expression. © 2017 S. Karger AG, Basel.

  3. Galvanic Corrosion of Al-7075-T6 and Steel-4340 Coupled to Brass QQ-B- 626,360 and Al-7075-T6 Coupled to Steel-4130 and Steel-4340: Exposure to Aqueous NaCl and Salt-Fog Environments

    DTIC Science & Technology

    1986-06-30

    between the copper plates fail. Reboul (3) and Mansfeld et al. (4) provide excellent reviews on the galvanic corrosion behavior of aluminum coupled to...A.S.T.M., STP 576, 1976), p. 20. 2. Baboian, R,, ibid., p. 5. 3. Reboul , M. C., Corrosion, Vol. 35, No. 9, 1979, p. 423, 4. Nansfeld, F., lIcngstenbcrg

  4. Application of in situ thermography for evaluating the high-cycle and very high-cycle fatigue behaviour of cast aluminium alloy AlSi7Mg (T6).

    PubMed

    Krewerth, D; Weidner, A; Biermann, H

    2013-12-01

    The present paper illustrates the application of infrared thermal measurements for the investigation of crack initiation point and crack propagation in the high-cycle and the very high-cycle fatigue range of cast AlSi7Mg alloy (A356). The influence of casting defects, their location, size and amount was studied both by fractography and thermography. Besides internal and surface fatigue crack initiation as a further crack initiation type multiple fatigue crack initiation was observed via in situ thermography which can be well correlated with the results from fractography obtained by SEM investigations. In addition, crack propagation was studied by the development of the temperature measured via thermography. Moreover, the frequency influence on high-cycle fatigue behaviour was investigated. The presented results demonstrate well that the combination of fractography and thermography can give a significant contribution to the knowledge of crack initiation and propagation in the VHCF regime. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Transiting exoplanets from the CoRoT space mission. IX. CoRoT-6b: a transiting ``hot Jupiter'' planet in an 8.9d orbit around a low-metallicity star

    NASA Astrophysics Data System (ADS)

    Fridlund, M.; Hébrard, G.; Alonso, R.; Deleuil, M.; Gandolfi, D.; Gillon, M.; Bruntt, H.; Alapini, A.; Csizmadia, Sz.; Guillot, T.; Lammer, H.; Aigrain, S.; Almenara, J. M.; Auvergne, M.; Baglin, A.; Barge, P.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Deeg, H. J.; de La Reza, R.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Guenther, E.; Gondoin, P.; den Hartog, R.; Hatzes, A.; Jorda, L.; Léger, A.; Llebaria, A.; Magain, P.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Shporer, A.; Stecklum, B.; Tingley, B.; Weingrill, J.; Wuchterl, G.

    2010-03-01

    The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations - photometric and spectroscopic - carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a “hot Jupiter” planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high 7Li abundance. While the light curve indicates a much higher level of activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Ca ii] H&K lines. The CoRoT space mission, launched on December 27, 2006, has been developed and is being operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, The Research and Scientific Support Department of ESA, Germany and Spain.

  6. Established Microbial Colonies Can Survive Type VI Secretion Assault

    PubMed Central

    Borenstein, David Bruce; Ringel, Peter; Basler, Marek; Wingreen, Ned S.

    2015-01-01

    Type VI secretion (T6S) is a cell-to-cell injection system that can be used as a microbial weapon. T6S kills vulnerable cells, and is present in close to 25% of sequenced Gram-negative bacteria. To examine the ecological role of T6S among bacteria, we competed self-immune T6S+ cells and T6S-sensitive cells in simulated range expansions. As killing takes place only at the interface between sensitive and T6S+ strains, while growth takes place everywhere, sufficiently large domains of sensitive cells can achieve net growth in the face of attack. Indeed T6S-sensitive cells can often outgrow their T6S+ competitors. We validated these findings through in vivo competition experiments between T6S+ Vibrio cholerae and T6S-sensitive Escherichia coli. We found that E. coli can survive and even dominate so long as they have an adequate opportunity to form microcolonies at the outset of the competition. Finally, in simulated competitions between two equivalent and mutually sensitive T6S+ strains, the more numerous strain has an advantage that increases with the T6S attack rate. We conclude that sufficiently large domains of T6S-sensitive individuals can survive attack and potentially outcompete self-immune T6S+ bacteria. PMID:26485125

  7. Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts

    PubMed Central

    2014-01-01

    The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SSSPI-6 and T6SSSPI-19. This study has determined the contribution of T6SSSPI-6 and T6SSSPI-19 to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SSSPI-6/∆T6SSSPI-19) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SSSPI-6 mutant, suggesting that this serotype requires a functional T6SSSPI-6 for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SSSPI-19 was not necessary for colonization of either chickens or mice. Transfer of T6SSSPI-6, but not T6SSSPI-19, restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SSSPI-6 for efficient colonization of mice and chickens, and that the T6SSSPI-6 and T6SSSPI-19 are not functionally redundant. PMID:24405577

  8. Vibrio parahaemolyticus Type VI Secretion System 1 Is Activated in Marine Conditions to Target Bacteria, and Is Differentially Regulated from System 2

    PubMed Central

    Salomon, Dor; Gonzalez, Herman; Updegraff, Barrett L.; Orth, Kim

    2013-01-01

    Vibrio parahaemolyticus is a marine bacterium that thrives in warm climates. It is a leading cause of gastroenteritis resulting from consumption of contaminated uncooked shellfish. This bacterium harbors two putative type VI secretion systems (T6SS). T6SSs are widespread protein secretion systems found in many Gram-negative bacteria, and are often tightly regulated. For many T6SSs studied to date, the conditions and cues, as well as the regulatory mechanisms that control T6SS activity are unknown. In this study, we characterized the environmental conditions and cues that activate both V. parahaemolyticus T6SSs, and identified regulatory mechanisms that control T6SS gene expression and activity. We monitored the expression and secretion of the signature T6SS secreted proteins Hcp1 and Hcp2, and found that both T6SSs are differentially regulated by quorum sensing and surface sensing. We also showed that T6SS1 and T6SS2 require different temperature and salinity conditions to be active. Interestingly, T6SS1, which is found predominantly in clinical isolates, was most active under warm marine-like conditions. Moreover, we found that T6SS1 has anti-bacterial activity under these conditions. In addition, we identified two transcription regulators in the T6SS1 gene cluster that regulate Hcp1 expression, but are not required for immunity against self-intoxication. Further examination of environmental isolates revealed a correlation between the presence of T6SS1 and virulence of V. parahaemolyticus against other bacteria, and we also showed that different V. parahaemolyticus isolates can outcompete each other. We propose that T6SS1 and T6SS2 play different roles in the V. parahaemolyticus lifestyles, and suggest a role for T6SS1 in enhancing environmental fitness of V. parahaemolyticus in marine environments when competing for a niche in the presence of other bacterial populations. PMID:23613791

  9. Comparative genomics of type VI secretion systems in strains of Pantoea ananatis from different environments

    PubMed Central

    2014-01-01

    Background The Type VI secretion system (T6SS) has been identified in several different bacteria, including the plant pathogenPantoea ananatis. Previous in silico analyses described three different T6SS loci present in the pathogenic strain of P. ananatis LMG 20103. This initial investigation has been extended to include an additional seven sequenced strains of P. ananatis together with 39 strains from different ecological niches. Comparative and phylogenetic analyses were used to investigate the distribution, evolution, intra-strain variability and operon structure of the T6SS in the sequenced strains. Results Three different T6SS loci were identified in P. ananatis strain LMG 20103 and designated PA T6SS 1-3. PA T6SS-1 was present in all sequenced strains of P. ananatis and in all 39 additional strains examined in this study. In addition, PA T6SS-1 included all 13 core T6SS genes required for synthesis of a functional T6SS. The plasmid-borne PA T6SS-2 also included all 13 core T6SS genes but was restricted to only 33% (15/46) of the strains examined. In addition, PA T6SS-2 was restricted to strains of P. ananatis isolated from symptomatic plant material. This finding raises the possibility of an association between PA T6SS-2 and either pathogenicity or host specificity. The third cluster PA T6SS-3 was present in all strains analyzed in this study but lacked 11 of the 13 core T6SS genes suggesting it may not encoded a functional T6SS. Inter-strain variability was also associated with hcp and vgrG islands, which are associated with the T6SS and encode a variable number of proteins usually of unknown function. These proteins may play a role in the fitness of different strains in a variety of ecological niches or as candidate T6SS effectors. Phylogenetic analysis indicated that PA T6SS-1 and PA T6SS-2 are evolutionarily distinct. Conclusion Our analysis indicates that the three T6SSs of P. ananatis appear to have been independently acquired and may play different

  10. 49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure. Each facility performing eddy... ring and probe for each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

  11. 49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure. Each facility performing eddy... ring and probe for each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

  12. 49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure. Each facility performing eddy... ring and probe for each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

  13. 49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure. Each facility performing eddy... ring and probe for each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

  14. 49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure. Each facility performing eddy... ring and probe for each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

  15. Pantoea ananatis Utilizes a Type VI Secretion System for Pathogenesis and Bacterial Competition.

    PubMed

    Shyntum, Divine Y; Theron, Jacques; Venter, Stephanus N; Moleleki, Lucy N; Toth, Ian K; Coutinho, Teresa A

    2015-04-01

    Type VI secretion systems (T6SSs) are a class of macromolecular machines that are recognized as an important virulence mechanism in several gram-negative bacteria. The genome of Pantoea ananatis LMG 2665(T), a pathogen of pineapple fruit and onion plants, carries two gene clusters whose predicted products have homology with T6SS-associated gene products from other bacteria. Nothing is known regarding the role of these T6SS-1 and T6SS-3 gene clusters in the biology of P. ananatis. Here, we present evidence that T6SS-1 plays an important role in the pathogenicity of P. ananatis LMG 2665(T) in onion plants, while a strain lacking T6SS-3 remains as pathogenic as the wild-type strain. We also investigated the role of the T6SS-1 system in bacterial competition, the results of which indicated that several bacteria compete less efficiently against wild-type LMG 2665(T) than a strain lacking T6SS-1. Additionally, we demonstrated that these phenotypes of strain LMG 2665(T) were reliant on the core T6SS products TssA and TssD (Hcp), thus indicating that the T6SS-1 gene cluster encodes a functioning T6SS. Collectively, our data provide the first evidence demonstrating that the T6SS-1 system is a virulence determinant of P. ananatis LMG 2665(T) and plays a role in bacterial competition.

  16. Zeolite Coating System for Corrosion Control to Eliminate Hexavalent Chromium from DoD Applications

    DTIC Science & Technology

    2009-08-01

    7075-T6, and steels (S1008, S4130, SS304 ) With support from US EPA, UCR has so far focused on 2x3 cm coupons to demonstrate that high-silica...Production of 3x6 ZSM-5 on AA-5052-H32, AA-6065-T6, AA-7075-T6 and S1008, (UCR 10/1/04) COMPLETED and expanded to include ZSM-5 on S4130 and SS304 - 2b...14) Quality Control testing method by DC Polarization on 3x6 inch zeolite coatings on AAs(2024-T3, 5052-H32, 6061-T6, 7075-T6) and steels ( SS304

  17. NASA TEERM Hexavalent Chrome Alternatives Projects

    DTIC Science & Technology

    2011-08-18

    T6 2024-T3 2195-T8 2219 -T87 Average Average Across Coatings 6Mo...T8 2219 -T87 7075- T6 2024-T3 2195-T8 2219 -T87 7075- T6 2024-T3 2195-T8 2219 -T87 S1 S2 S3 18 Months Exposure (S1-S3) Launch Pad Beach Site...National Aeronautics and Space Administration (NASA) 41 0 1 2 3 4 5 6 7 8 9 10 7075- T6 2024-T3 2195-T8 2219 -T87 7075- T6

  18. Marker for type VI secretion system effectors

    PubMed Central

    Salomon, Dor; Kinch, Lisa N.; Trudgian, David C.; Guo, Xiaofeng; Klimko, John A.; Grishin, Nick V.; Mirzaei, Hamid; Orth, Kim

    2014-01-01

    Bacteria use diverse mechanisms to kill, manipulate, and compete with other cells. The recently discovered type VI secretion system (T6SS) is widespread in bacterial pathogens and used to deliver virulence effector proteins into target cells. Using comparative proteomics, we identified two previously unidentified T6SS effectors that contained a conserved motif. Bioinformatic analyses revealed that this N-terminal motif, named MIX (marker for type six effectors), is found in numerous polymorphic bacterial proteins that are primarily located in the T6SS genome neighborhood. We demonstrate that several MIX-containing proteins are T6SS effectors and that they are not required for T6SS activity. Thus, we propose that MIX-containing proteins are T6SS effectors. Our findings allow for the identification of numerous uncharacterized T6SS effectors that will undoubtedly lead to the discovery of new biological mechanisms. PMID:24927539

  19. Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts.

    PubMed

    Pezoa, David; Blondel, Carlos J; Silva, Cecilia A; Yang, Hee-Jeong; Andrews-Polymenis, Helene; Santiviago, Carlos A; Contreras, Inés

    2014-01-09

    The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SS(SPI-6) and T6SS(SPI-19). This study has determined the contribution of T6SS(SPI-6) and T6SS(SPI-19) to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SS(SPI-6)/∆T6SS(SPI-19)) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SS(SPI-6) mutant, suggesting that this serotype requires a functional T6SS(SPI-6) for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SS(SPI-19) was not necessary for colonization of either chickens or mice. Transfer of T6SS(SPI-6), but not T6SS(SPI-19), restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SS(SPI-6) for efficient colonization of mice and chickens, and that the T6SS(SPI-6) and T6SS(SPI-19) are not functionally redundant.

  20. H-NS regulates the Vibrio parahaemolyticus type VI secretion system 1

    PubMed Central

    Salomon, Dor; Klimko, John A.

    2014-01-01

    The marine bacterium Vibrio parahaemolyticus, a major cause of food-borne gastroenteritis, employs a type VI secretion system 1 (T6SS1), a recently discovered protein secretion system, to combat competing bacteria. Environmental signals such as temperature, salinity, cell density and surface sensing, as well as the quorum-sensing master regulator OpaR, were previously reported to regulate T6SS1 activity and expression. In this work, we set out to identify additional transcription regulators that control the tightly regulated T6SS1 activity. To this end, we determined the effect of deletions in several known virulence regulators and in two regulators encoded within the T6SS1 gene cluster on expression and secretion of the core T6SS component Hcp1 and on T6SS1-mediated anti-bacterial activity. We report that VP1391 and VP1407, transcriptional regulators encoded within the T6SS1 gene cluster, are essential for T6SS1 activity. Moreover, we found that H-NS, a bacterial histone-like nucleoid structuring protein, which mediates transcription silencing of horizontally acquired genes, serves as a repressor of T6SS1. We also show that activation of surface sensing and high salt conditions alleviate the H-NS-mediated repression. Our results shed light on the complex network of environmental signals and transcription regulators that govern the tight regulation over T6SS1 activity. PMID:24987102

  1. Trehalose 6-Phosphate Is Required for the Onset of Leaf Senescence Associated with High Carbon Availability1[W][OA

    PubMed Central

    Wingler, Astrid; Delatte, Thierry L.; O’Hara, Liam E.; Primavesi, Lucia F.; Jhurreea, Deveraj; Paul, Matthew J.; Schluepmann, Henriette

    2012-01-01

    Trehalose 6-phosphate (T6P) is an important regulator of plant metabolism and development. T6P content increases when carbon availability is high, and in young growing tissue, T6P inhibits the activity of Snf1-related protein kinase (SnRK1). Here, strong accumulation of T6P was found in senescing leaves of Arabidopsis (Arabidopsis thaliana), in parallel with a rise in sugar contents. To determine the role of T6P in senescence, T6P content was altered by expressing the bacterial T6P synthase gene, otsA (to increase T6P), or the T6P phosphatase gene, otsB (to decrease T6P). In otsB-expressing plants, T6P accumulated less strongly during senescence than in wild-type plants, while otsA-expressing plants contained more T6P throughout. Mature otsB-expressing plants showed a similar phenotype as described for plants overexpressing the SnRK1 gene, KIN10, including reduced anthocyanin accumulation and delayed senescence. This was confirmed by quantitative reverse transcription-polymerase chain reaction analysis of senescence-associated genes and genes involved in anthocyanin synthesis. To analyze if the senescence phenotype was due to decreased sugar sensitivity, the response to sugars was determined. In combination with low nitrogen supply, metabolizable sugars (glucose, fructose, or sucrose) induced senescence in wild-type and otsA-expressing plants but to a smaller extent in otsB-expressing plants. The sugar analog 3-O-methyl glucose, on the other hand, did not induce senescence in any of the lines. Transfer of plants to and from glucose-containing medium suggested that glucose determines senescence during late development but that the effects of T6P on senescence are established by the sugar response of young plants. PMID:22247267

  2. Molecular detection identified a type six secretion system in Campylobacter jejuni from various sources but not from human cases.

    PubMed

    Siddiqui, F; Champion, O; Akram, M; Studholme, D; Eqani, S A M A S; Wren, B W; Titball, R; Bokhari, H

    2015-05-01

    To determine the presence of the T6SS in Campylobacter jejuni from diverse sources. The recently identified type VI secretion system (T6SS) is a bacterial injection machinery that plays a role in virulence, symbiosis, bacterial interactions and environmental stress responses. This system has been recently discovered in the major enteric pathogen Camp. jejuni. In this study, we used multiplex PCR (mPCR), based on conserved genetic markers of the T6SS, to screen 366 Pakistani Camp. jejuni isolates from humans, poultry, cattle, wildlife or waste-water sources. We identified the T6SS in isolates from all of these sources except humans. The overall prevalence of the T6SS among the isolates was 17/366 (4·6%) and the T6SS positive isolates clustered into four different groups. Transcription of the T6SS genes, determined using RT-PCR, was observed in bacteria cultured at 37 or 42°C but not in 37°C cultures adjusted to pH3. Campylobacter jejuni isolates harbouring T6SS markers genes were identified in livestock and non-livestock sources but in this study we did not identify human diarrhoeal isolates which possessed the T6SS. We demonstrated down-regulation of T6SS in an acidic environment. This study questions the role of the T6SS in human diarrhoeal disease. Moreover this study did not identify a clear association of Camp. jejuni isolates harbouring T6SS with any of the niches tested. Our study highlights the need to establish the role of the T6SS in environmental survival or virulence. © 2015 The Society for Applied Microbiology.

  3. Dual Expression Profile of Type VI Secretion System Immunity Genes Protects Pandemic Vibrio cholerae

    PubMed Central

    Miyata, Sarah T.; Unterweger, Daniel; Rudko, Sydney P.; Pukatzki, Stefan

    2013-01-01

    The Vibrio cholerae type VI secretion system (T6SS) assembles as a molecular syringe that injects toxic protein effectors into both eukaryotic and prokaryotic cells. We previously reported that the V. cholerae O37 serogroup strain V52 maintains a constitutively active T6SS to kill other Gram-negative bacteria while being immune to attack by kin bacteria. The pandemic O1 El Tor V. cholerae strain C6706 is T6SS-silent under laboratory conditions as it does not produce T6SS structural components and effectors, and fails to kill Escherichia coli prey. Yet, C6706 exhibits full resistance when approached by T6SS-active V52. These findings suggested that an active T6SS is not required for immunity against T6SS-mediated virulence. Here, we describe a dual expression profile of the T6SS immunity protein-encoding genes tsiV1, tsiV2, and tsiV3 that provides pandemic V. cholerae strains with T6SS immunity and allows T6SS-silent strains to maintain immunity against attacks by T6SS-active bacterial neighbors. The dual expression profile allows transcription of the three genes encoding immunity proteins independently of other T6SS proteins encoded within the same operon. One of these immunity proteins, TsiV2, protects against the T6SS effector VasX which is encoded immediately upstream of tsiV2. VasX is a secreted, lipid-binding protein that we previously characterized with respect to T6SS-mediated virulence towards the social amoeba Dictyostelium discoideum. Our data suggest the presence of an internal promoter in the open reading frame of vasX that drives expression of the downstream gene tsiV2. Furthermore, VasX is shown to act in conjunction with VasW, an accessory protein to VasX, to compromise the inner membrane of prokaryotic target cells. The dual regulatory profile of the T6SS immunity protein-encoding genes tsiV1, tsiV2, and tsiV3 permits V. cholerae to tightly control T6SS gene expression while maintaining immunity to T6SS activity. PMID:24348240

  4. H-NS Silencing of the Salmonella Pathogenicity Island 6-Encoded Type VI Secretion System Limits Salmonella enterica Serovar Typhimurium Interbacterial Killing

    PubMed Central

    Brunet, Yannick R.; Khodr, Ahmad; Logger, Laureen; Aussel, Laurent; Mignot, Tâm; Rimsky, Sylvie

    2015-01-01

    The secretion of bacterial toxin proteins is achieved by dedicated machineries called secretion systems. The type VI secretion system (T6SS) is a widespread versatile machine used for the delivery of protein toxins to both prokaryotic and eukaryotic cells. In Salmonella enterica serovar Typhimurium, the expression of the T6SS genes is activated during macrophage or mouse infection. Here, we show that the T6SS gene cluster is silenced by the histone-like nucleoid structuring H-NS protein using a combination of reporter fusions, electrophoretic mobility shift assays, DNase footprinting, and fluorescence microscopy. We further demonstrate that derepression of the S. Typhimurium T6SS genes induces T6SS-dependent intoxication of competing bacteria. Our results suggest that relieving T6SS H-NS silencing may be used as a sense-and-kill mechanism that will help S. Typhimurium to homogenize and synchronize the microbial population to gain efficiency during infection. PMID:25916986

  5. Altering Trehalose-6-Phosphate Content in Transgenic Potato Tubers Affects Tuber Growth and Alters Responsiveness to Hormones during Sprouting1[C][W

    PubMed Central

    Debast, Stefan; Nunes-Nesi, Adriano; Hajirezaei, Mohammad R.; Hofmann, Jörg; Sonnewald, Uwe; Fernie, Alisdair R.; Börnke, Frederik

    2011-01-01

    Trehalose-6-phosphate (T6P) is a signaling metabolite that regulates carbon metabolism, developmental processes, and growth in plants. In Arabidopsis (Arabidopsis thaliana), T6P signaling is, at least in part, mediated through inhibition of the SNF1-related protein kinase SnRK1. To investigate the role of T6P signaling in a heterotrophic, starch-accumulating storage organ, transgenic potato (Solanum tuberosum) plants with altered T6P levels specifically in their tubers were generated. Transgenic lines with elevated T6P levels (B33-TPS, expressing Escherichia coli osmoregulatory trehalose synthesis A [OtsA], which encodes a T6P synthase) displayed reduced starch content, decreased ATP contents, and increased respiration rate diagnostic for high metabolic activity. On the other hand, lines with significantly reduced T6P (B33-TPP, expressing E. coli OtsB, which encodes a T6P phosphatase) showed accumulation of soluble carbohydrates, hexose phosphates, and ATP, no change in starch when calculated on a fresh weight basis, and a strongly reduced tuber yield. [14C]Glucose feeding to transgenic tubers indicated that carbon partitioning between starch and soluble carbohydrates was not altered. Transcriptional profiling of B33-TPP tubers revealed that target genes of SnRK1 were strongly up-regulated and that T6P inhibited potato tuber SnRK1 activity in vitro. Among the SnRK1 target genes in B33-TPP tubers, those involved in the promotion of cell proliferation and growth were down-regulated, while an inhibitor of cell cycle progression was up-regulated. T6P-accumulating tubers were strongly delayed in sprouting, while those with reduced T6P sprouted earlier than the wild type. Early sprouting of B33-TPP tubers correlated with a reduced abscisic acid content. Collectively, our data indicate that T6P plays an important role for potato tuber growth. PMID:21670224

  6. Altering trehalose-6-phosphate content in transgenic potato tubers affects tuber growth and alters responsiveness to hormones during sprouting.

    PubMed

    Debast, Stefan; Nunes-Nesi, Adriano; Hajirezaei, Mohammad R; Hofmann, Jörg; Sonnewald, Uwe; Fernie, Alisdair R; Börnke, Frederik

    2011-08-01

    Trehalose-6-phosphate (T6P) is a signaling metabolite that regulates carbon metabolism, developmental processes, and growth in plants. In Arabidopsis (Arabidopsis thaliana), T6P signaling is, at least in part, mediated through inhibition of the SNF1-related protein kinase SnRK1. To investigate the role of T6P signaling in a heterotrophic, starch-accumulating storage organ, transgenic potato (Solanum tuberosum) plants with altered T6P levels specifically in their tubers were generated. Transgenic lines with elevated T6P levels (B33-TPS, expressing Escherichia coli osmoregulatory trehalose synthesis A [OtsA], which encodes a T6P synthase) displayed reduced starch content, decreased ATP contents, and increased respiration rate diagnostic for high metabolic activity. On the other hand, lines with significantly reduced T6P (B33-TPP, expressing E. coli OtsB, which encodes a T6P phosphatase) showed accumulation of soluble carbohydrates, hexose phosphates, and ATP, no change in starch when calculated on a fresh weight basis, and a strongly reduced tuber yield. [¹⁴C]glucose feeding to transgenic tubers indicated that carbon partitioning between starch and soluble carbohydrates was not altered. Transcriptional profiling of B33-TPP tubers revealed that target genes of SnRK1 were strongly up-regulated and that T6P inhibited potato tuber SnRK1 activity in vitro. Among the SnRK1 target genes in B33-TPP tubers, those involved in the promotion of cell proliferation and growth were down-regulated, while an inhibitor of cell cycle progression was up-regulated. T6P-accumulating tubers were strongly delayed in sprouting, while those with reduced T6P sprouted earlier than the wild type. Early sprouting of B33-TPP tubers correlated with a reduced abscisic acid content. Collectively, our data indicate that T6P plays an important role for potato tuber growth.

  7. Concepts for Design of Lightweight Track for the U.S. Marine Landing Vehicle Assault (LVA)

    DTIC Science & Technology

    1976-02-20

    used on MSO Hawk Missile Loader Vehicle (sectioned through the centerguide). Track block is 2014- T6 aluminum forging integral centerguide is bonded to...resistance to ical equipment. Catle clamps for corrosion , electrical industry. 2014 - T6 High tensile and yield strength Widcly used for aircraft and -T61... 2219 - T6 Good mechanical properties at room Tankage tor liquid fuel rockets. -T852 temperatures. Ability to retain Structural parts which must 3per

  8. Electro-Deposited Primer Development and Low-Polluting Primer Evaluation

    DTIC Science & Technology

    1989-08-01

    on 2024-T81 and 7075- T6 Aluminum ..................................... 4-52 4-5 Six-Gallon Electrodeposition Cell Facility with Dialysis Setup...Shear Strength Using AF-131 Adhesive on Phosphoric Acid Anodized/XEA-9289 (Water-Base) Primed 2024-T81 and 7075- T6 Aluminum .................... 4-9...7075- T6 Aluminum .................... 4-10 4-5 Lap Shear Strength Using AF-131 and RB-398 Adhesives on Chromic Acid Anodized/XEA-9289 (Water-Base

  9. Durability and Damage Tolerance of Aluminum Castings

    DTIC Science & Technology

    1991-10-01

    OF DEFECTS ON THE MECHANICAL PROPERTIES OF D357-T6 TYPE AND NUMBER OF TESTS S/N CONST. SPECTRUM DEFECT/ FATIGUE AMPL. FATIGUE FRACTURE GRADE LEVEL...microstructure, and mechanical properties were investigated using multiple regression analyses. Sr (silicon modifier) and Ag had the most significant...castings. The effect of intentionally-added defects (D357-T6) and nonoptimnum miscrostructure (D357-T6 and B20l-.T7) on mechanical properties was

  10. The type VI secretion system gene cluster of Salmonella typhimurium: required for full virulence in mice.

    PubMed

    Liu, Ji; Guo, Ji-Tao; Li, Yong-Guo; Johnston, Randal N; Liu, Gui-Rong; Liu, Shu-Lin

    2013-07-01

    Type VI secretion system (T6SS) has increasingly been believed to participate in the infection process for many bacterial pathogens, but its role in the virulence of Salmonella typhimurium remains unclear. To look into this, we deleted the T6SS cluster from the genome of S. typhimurium 14028s and analyzed the phenotype of the resulting T6SS knockout mutant (T6SSKO mutant) in vitro and in vivo. We found that the T6SSKO mutant exhibited reduced capability in colonizing the spleen and liver in an in vivo colonization competition model in BALB/c mice infected by the oral route. Additionally, infection via intraperitoneal administration also showed that the T6SSKO mutant was less capable of colonizing the mouse spleen and liver than the wild-type strain. We did not detect significant differences between the T6SSKO and wild-type strains in epithelial cell invasion tests. However, in the macrophage RAW264.7 cell line, the T6SSKO mutant survived and proliferated significantly more poorly than the wild-type strain. These findings indicate that T6SS gene cluster is required for full virulence of S. typhimurium 14028s in BALB/c mice, possibly due to its roles in bacterial survival and proliferation in macrophages.

  11. Bile Salts Modulate the Mucin-Activated Type VI Secretion System of Pandemic Vibrio cholerae

    PubMed Central

    Unterweger, Daniel; Diaz-Satizabal, Laura; Ogg, Stephen; Pukatzki, Stefan

    2015-01-01

    The causative agent of cholera, Vibrio cholerae, regulates its diverse virulence factors to thrive in the human small intestine and environmental reservoirs. Among this pathogen’s arsenal of virulence factors is the tightly regulated type VI secretion system (T6SS). This system acts as an inverted bacteriophage to inject toxins into competing bacteria and eukaryotic phagocytes. V. cholerae strains responsible for the current 7th pandemic activate their T6SS within the host. We established that T6SS-mediated competition occurs upon T6SS activation in the infant mouse, and that this system is functional under anaerobic conditions. When investigating the intestinal host factors mucins (a glycoprotein component of mucus) and bile for potential regulatory roles in controlling the T6SS, we discovered that once mucins activate the T6SS, bile acids can further modulate T6SS activity. Microbiota modify bile acids to inhibit T6SS-mediated killing of commensal bacteria. This interplay is a novel interaction between commensal bacteria, host factors, and the V. cholerae T6SS, showing an active host role in infection. PMID:26317760

  12. T3 expression by human thymocytes in culture.

    PubMed Central

    Aiello, F B; Musiani, P; Maggiano, N; Larocca, L M; Piantelli, M

    1985-01-01

    By panning procedures employing T6 and T3 monoclonal antibody, human thymocytes were fractionated into two subpopulations depleted of T6- or T3-positive (T6+, T3+) cells. Unfractionated thymocytes and T6- and T3-depleted subpopulations were separately cultured for 48 h in RPMI 1640 medium with 10% FCS or in HB 101 serum-free medium. Determining the phenotype of unfractionated thymocytes at various time intervals, a time-dependent increase of T3+ cells was observed. An inverse relationship was found between the percentage of T3+ cells and the T6 and peanut agglutinin (PNA) reactive thymocytes. When the surface antigen expression in the T3-depleted population (greater than 95% T6+ and PNA+ cells) was analysed, a strong increase of T3+ cells and a complementary reduction of T6+ and PNA+ cells was evidenced. During that time the surface phenotype of the T6-depleted population (greater than 80% T3+ cells) showed the same trend of differentiation, as the other thymocyte preparations. These results indicate that a conspicuous fraction of human thymocytes and particularly of those characterized by a cortical phenotype (PNA+ and T6+ cells), are able to express mature T-cell antigens when cultured in vitro in the absence of the thymic microenvironment influence. However, the in vitro acquisition of a mature phenotype is not accompanied by a parallel achievement of the capacity to respond to mitogens such as PHA or T3 monoclonal antibody. PMID:3876184

  13. Some observations on loss of static strength due to fatigue cracks

    NASA Technical Reports Server (NTRS)

    Illg, Walter; Hardrath, Herbert F

    1955-01-01

    Static tensile tests were performed on simple notched specimens containing fatigue cracks. Four types of aluminum alloys were investigated: 2024-T3(formerly 24S-T3) and 7075-T6(formerly 75S-T6) in sheet form, and 2024-T4(formerly 24S-T4) and 7075-T6(formerly 75S-T6) in extruded form. The cracked specimens were tested statically under four conditions: unmodified and with reduced eccentricity of loading by three methods. Results of static tests on C-46 wings containing fatigue cracks are also reported.

  14. The delay of leukaemia in tetraparental ovum fusion-derived AKR chimaeras

    PubMed Central

    Barnes, R. D.; Tuffrey, Maureen; Kingman, Jean

    1972-01-01

    The development of thymic lymphomas in inbred AKR mice is well established. Ovum fusion of the AKR with a normal and relatively tumour resistant strain has been achieved to obtain AKR:CBA/H/T6T6 chimaeras. The fact that unlike the parental AKR, three of six AKR:CBA/H/T6T6 chimaeras are alive and well at more than 68 weeks of age, records the delay and suggests the possible inhibition of lymphomas in this situation. PMID:4650371

  15. A Comparison of Microstructure and Properties of Equivalent Strength Ingot Metallurgy and Powder Metallurgy 7XXX Aluminum Alloys.

    DTIC Science & Technology

    1981-08-01

    conjunction with other corrosion susceptibility evaluations. Rockwell B hardness testing was performed in accordance with ASTM Standard E18 -74 (Reference 286...M-T6 89 I/M-T73 85 P/M-T6 88 P/M-T73 84 (average of five tests) * ASTM E18 -74 TABLE 16 CONDUCTIVITY* DATA Material % IACS I/M-T6 32 I/M-T73 37 P/M-T6...282. 6. Dieter, op. cit., 409. 283. D. Voss, op. cit., 83. 284. W. Neenning, Int’l J. of Fract., 11, (1), (1975), 123. 286. ASTM STD E18 -74. Amer. Soc

  16. The Trehalose 6-Phosphate/SnRK1 Signaling Pathway Primes Growth Recovery following Relief of Sink Limitation1[W][OA

    PubMed Central

    Nunes, Cátia; O’Hara, Liam E.; Primavesi, Lucia F.; Delatte, Thierry L.; Schluepmann, Henriette; Somsen, Govert W.; Silva, Anabela B.; Fevereiro, Pedro S.; Wingler, Astrid; Paul, Matthew J.

    2013-01-01

    Trehalose 6-P (T6P) is a sugar signal in plants that inhibits SNF1-related protein kinase, SnRK1, thereby altering gene expression and promoting growth processes. This provides a model for the regulation of growth by sugar. However, it is not known how this model operates under sink-limited conditions when tissue sugar content is uncoupled from growth. To test the physiological importance of this model, T6P, SnRK1 activities, sugars, gene expression, and growth were measured in Arabidopsis (Arabidopsis thaliana) seedlings after transfer to cold or zero nitrogen compared with sugar feeding under optimal conditions. Maximum in vitro activities of SnRK1 changed little, but T6P accumulated up to 55-fold, correlating with tissue Suc content in all treatments. SnRK1-induced and -repressed marker gene expression strongly related to T6P above and below a threshold of 0.3 to 0.5 nmol T6P g−1 fresh weight close to the dissociation constant (4 µm) of the T6P/ SnRK1 complex. This occurred irrespective of the growth response to Suc. This implies that T6P is not a growth signal per se, but through SnRK1, T6P primes gene expression for growth in response to Suc accumulation under sink-limited conditions. To test this hypothesis, plants with genetically decreased T6P content and SnRK1 overexpression were transferred from cold to warm to analyze the role of T6P/SnRK1 in relief of growth restriction. Compared with the wild type, these plants were impaired in immediate growth recovery. It is concluded that the T6P/SnRK1 signaling pathway responds to Suc induced by sink restriction that enables growth recovery following relief of limitations such as low temperature. PMID:23735508

  17. Comparative genomics of the type VI secretion systems of Pantoea and Erwinia species reveals the presence of putative effector islands that may be translocated by the VgrG and Hcp proteins

    PubMed Central

    2011-01-01

    Background The Type VI secretion apparatus is assembled by a conserved set of proteins encoded within a distinct locus. The putative effector proteins Hcp and VgrG are also encoded within these loci. We have identified numerous distinct Type VI secretion system (T6SS) loci in the genomes of several ecologically diverse Pantoea and Erwinia species and detected the presence of putative effector islands associated with the hcp and vgrG genes. Results Between two and four T6SS loci occur among the Pantoea and Erwinia species. While two of the loci (T6SS-1 and T6SS-2) are well conserved among the various strains, the third (T6SS-3) locus is not universally distributed. Additional orthologous loci are present in Pantoea sp. aB-valens and Erwinia billingiae Eb661. Comparative analysis of the T6SS-1 and T6SS-3 loci showed non-conserved islands associated with the vgrG and hcp, and vgrG genes, respectively. These regions had a G+C content far lower than the conserved portions of the loci. Many of the proteins encoded within the hcp and vgrG islands carry conserved domains, which suggests they may serve as effector proteins for the T6SS. A number of the proteins also show homology to the C-terminal extensions of evolved VgrG proteins. Conclusions Extensive diversity was observed in the number and content of the T6SS loci among the Pantoea and Erwinia species. Genomic islands could be observed within some of T6SS loci, which are associated with the hcp and vgrG proteins and carry putative effector domain proteins. We propose new hypotheses concerning a role for these islands in the acquisition of T6SS effectors and the development of novel evolved VgrG and Hcp proteins. PMID:22115407

  18. New secreted toxins and immunity proteins encoded within the Type VI secretion system gene cluster of Serratia marcescens

    PubMed Central

    English, Grant; Trunk, Katharina; Rao, Vincenzo A; Srikannathasan, Velupillai; Hunter, William N; Coulthurst, Sarah J

    2012-01-01

    Protein secretion systems are critical to bacterial virulence and interactions with other organisms. The Type VI secretion system (T6SS) is found in many bacterial species and is used to target either eukaryotic cells or competitor bacteria. However, T6SS-secreted proteins have proven surprisingly elusive. Here, we identified two secreted substrates of the antibacterial T6SS from the opportunistic human pathogen, Serratia marcescens. Ssp1 and Ssp2, both encoded within the T6SS gene cluster, were confirmed as antibacterial toxins delivered by the T6SS. Four related proteins encoded around the Ssp proteins (‘Rap’ proteins) included two specifically conferring self-resistance (‘immunity’) against T6SS-dependent Ssp1 or Ssp2 toxicity. Biochemical characterization revealed specific, tight binding between cognate Ssp–Rap pairs, forming complexes of 2:2 stoichiometry. The atomic structures of two Rap proteins were solved, revealing a novel helical fold, dependent on a structural disulphide bond, a structural feature consistent with their functional localization. Homologues of the Serratia Ssp and Rap proteins are found encoded together within other T6SS gene clusters, thus they represent founder members of new families of T6SS-secreted and cognate immunity proteins. We suggest that Ssp proteins are the original substrates of the S. marcescens T6SS, before horizontal acquisition of other T6SS-secreted toxins. Molecular insight has been provided into how pathogens utilize antibacterial T6SSs to overcome competitors and succeed in polymicrobial niches. PMID:22957938

  19. Genetic Dissection of the Type VI Secretion System in Acinetobacter and Identification of a Novel Peptidoglycan Hydrolase, TagX, Required for Its Biogenesis

    PubMed Central

    Weber, Brent S.; Hennon, Seth W.; Wright, Meredith S.; Scott, Nichollas E.; de Berardinis, Véronique; Foster, Leonard J.; Ayala, Juan A.; Adams, Mark D.

    2016-01-01

    ABSTRACT The type VI secretion system (T6SS) is a widespread secretory apparatus produced by Gram-negative bacteria that has emerged as a potent mediator of antibacterial activity during interbacterial interactions. Most Acinetobacter species produce a genetically conserved T6SS, although the expression and functionality of this system vary among different strains. Some pathogenic Acinetobacter baumannii strains activate this secretion system via the spontaneous loss of a plasmid carrying T6SS repressors. In this work, we compared the expression of T6SS-related genes via transcriptome sequencing and differential proteomics in cells with and without the plasmid. This approach, together with the mutational analysis of the T6SS clusters, led to the determination of the genetic components required to elaborate a functional T6SS in the nosocomial pathogen A. baumannii and the nonpathogen A. baylyi. By constructing a comprehensive combination of mutants with changes in the T6SS-associated vgrG genes, we delineated their relative contributions to T6SS function. We further determined the importance of two effectors, including an effector-immunity pair, for antibacterial activity. Our genetic analysis led to the identification of an essential membrane-associated structural component named TagX, which we have characterized as a peptidoglycan hydrolase possessing l,d-endopeptidase activity. TagX shows homology to known bacteriophage l,d-endopeptidases and is conserved in the T6SS clusters of several bacterial species. We propose that TagX is the first identified enzyme that fulfills the important role of enabling the transit of T6SS machinery across the peptidoglycan layer of the T6SS-producing bacterium. PMID:27729508

  20. The archetype Pseudomonas aeruginosa proteins TssB and TagJ form a novel subcomplex in the bacterial type VI secretion system.

    PubMed

    Lossi, Nadine S; Manoli, Eleni; Simpson, Pete; Jones, Cerith; Hui, Kailyn; Dajani, Rana; Coulthurst, Sarah J; Freemont, Paul; Filloux, Alain

    2012-10-01

    In Pseudomonas aeruginosa three type VI secretion systems (T6SSs) coexist, called H1- to H3-T6SSs. Several T6SS components are proposed to be part of a macromolecular complex resembling the bacteriophage tail. The T6SS protein HsiE1 (TagJ) is unique to the H1-T6SS and absent from the H2- and H3-T6SSs. We demonstrate that HsiE1 interacts with a predicted N-terminal α-helix in HsiB1 (TssB) thus forming a novel subcomplex of the T6SS. HsiB1 is homologous to the Vibrio cholerae VipA component, which contributes to the formation of a bacteriophage tail sheath-like structure. We show that the interaction between HsiE1 and HsiB1 is specific and does not occur between HsiE1 and HsiB2. Proteins of the TssB family encoded in T6SS clusters lacking a gene encoding a TagJ-like component are often devoid of the predicted N-terminal helical region, which suggests co-evolution. We observe that a synthetic peptide corresponding to the N-terminal 20 amino acids of HsiB1 interacts with purified HsiE1 protein. This interaction is a common feature to other bacterial T6SSs that display a TagJ homologue as shown here with Serratia marcescens. We further show that hsiE1 is a non-essential gene for the T6SS and suggest that HsiE1 may modulate incorporation of HsiB1 into the T6SS.

  1. Constitutive type VI secretion system expression gives Vibrio cholerae intra- and interspecific competitive advantages.

    PubMed

    Unterweger, Daniel; Kitaoka, Maya; Miyata, Sarah T; Bachmann, Verena; Brooks, Teresa M; Moloney, Jessica; Sosa, Oscar; Silva, David; Duran-Gonzalez, Jorge; Provenzano, Daniele; Pukatzki, Stefan

    2012-01-01

    The type VI secretion system (T6SS) mediates protein translocation across the cell membrane of Gram-negative bacteria, including Vibrio cholerae - the causative agent of cholera. All V. cholerae strains examined to date harbor gene clusters encoding a T6SS. Structural similarity and sequence homology between components of the T6SS and the T4 bacteriophage cell-puncturing device suggest that the T6SS functions as a contractile molecular syringe to inject effector molecules into prokaryotic and eukaryotic target cells. Regulation of the T6SS is critical. A subset of V. cholerae strains, including the clinical O37 serogroup strain V52, express T6SS constitutively. In contrast, pandemic strains impose tight control that can be genetically disrupted: mutations in the quorum sensing gene luxO and the newly described regulator gene tsrA lead to constitutive T6SS expression in the El Tor strain C6706. In this report, we examined environmental V. cholerae isolates from the Rio Grande with regard to T6SS regulation. Rough V. cholerae lacking O-antigen carried a nonsense mutation in the gene encoding the global T6SS regulator VasH and did not display virulent behavior towards Escherichia coli and other environmental bacteria. In contrast, smooth V. cholerae strains engaged constitutively in type VI-mediated secretion and displayed virulence towards prokaryotes (E. coli and other environmental bacteria) and a eukaryote (the social amoeba Dictyostelium discoideum). Furthermore, smooth V. cholerae strains were able to outcompete each other in a T6SS-dependent manner. The work presented here suggests that constitutive T6SS expression provides V. cholerae with an advantage in intraspecific and interspecific competition.

  2. Comparative genomics of the Type VI secretion systems of Pantoea and Erwinia species reveals the presence of putative effector islands that may be translocated by the VgrG and Hcp proteins.

    PubMed

    De Maayer, Pieter; Venter, Stephanus N; Kamber, Tim; Duffy, Brion; Coutinho, Teresa A; Smits, Theo H M

    2011-11-24

    The Type VI secretion apparatus is assembled by a conserved set of proteins encoded within a distinct locus. The putative effector proteins Hcp and VgrG are also encoded within these loci. We have identified numerous distinct Type VI secretion system (T6SS) loci in the genomes of several ecologically diverse Pantoea and Erwinia species and detected the presence of putative effector islands associated with the hcp and vgrG genes. Between two and four T6SS loci occur among the Pantoea and Erwinia species. While two of the loci (T6SS-1 and T6SS-2) are well conserved among the various strains, the third (T6SS-3) locus is not universally distributed. Additional orthologous loci are present in Pantoea sp. aB-valens and Erwinia billingiae Eb661. Comparative analysis of the T6SS-1 and T6SS-3 loci showed non-conserved islands associated with the vgrG and hcp, and vgrG genes, respectively. These regions had a G+C content far lower than the conserved portions of the loci. Many of the proteins encoded within the hcp and vgrG islands carry conserved domains, which suggests they may serve as effector proteins for the T6SS. A number of the proteins also show homology to the C-terminal extensions of evolved VgrG proteins. Extensive diversity was observed in the number and content of the T6SS loci among the Pantoea and Erwinia species. Genomic islands could be observed within some of T6SS loci, which are associated with the hcp and vgrG proteins and carry putative effector domain proteins. We propose new hypotheses concerning a role for these islands in the acquisition of T6SS effectors and the development of novel evolved VgrG and Hcp proteins.

  3. Two Functional Type VI Secretion Systems in Avian Pathogenic Escherichia coli Are Involved in Different Pathogenic Pathways

    PubMed Central

    Ma, Jiale; Bao, Yinli; Sun, Min; Dong, Wenyang; Pan, Zihao; Zhang, Wei; Lu, Chengping

    2014-01-01

    Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. The VgrG protein, a core component and effector of T6SS, has been demonstrated to perform diverse functions. The N-terminal domain of VgrG protein is a homologue of tail fiber protein gp27 of phage T4, which performs a receptor binding function and determines the host specificity. Based on sequence analysis, we found that two putative T6SS loci exist in the genome of the avian pathogenic Escherichia coli (APEC) strain TW-XM. To assess the contribution of these two T6SSs to TW-XM pathogenesis, the crucial clpV clusters of these two T6SS loci and their vgrG genes were deleted to generate a series of mutants. Consequently, T6SS1-associated mutants presented diminished adherence to and invasion of several host cell lines cultured in vitro, decreased pathogenicity in duck and mouse infection models in vivo, and decreased biofilm formation and bacterial competitive advantage. In contrast, T6SS2-associated mutants presented a significant decrease only in the adherence to and invasion of mouse brain microvascular endothelial cell (BMEC) line bEnd.3 and brain tissue of the duck infection model. These results suggested that T6SS1 was involved in the proliferation of APEC in systemic infection, whereas VgrG-T6SS2 was responsible only for cerebral infection. Further study demonstrated that VgrG-T6SS2 was able to bind to the surface of bEnd.3 cells, whereas it did not bind to DF-1 (chicken embryo fibroblast) cells, which further proved the interaction of VgrG-T6SS2 with the surface of BMECs. PMID:24980972

  4. The Versatile Type VI Secretion System

    PubMed Central

    Alteri, Christopher J.; Mobley, Harry L.T.

    2016-01-01

    Summary Bacterial Type VI Secretion Systems (T6SS) function as contractile nanomachines to puncture target cells and deliver lethal effectors. In the ten years since the discovery of the T6SS, much has been learned about the structure and function of this versatile protein secretion apparatus. Most of the conserved protein components that comprise the T6SS apparatus itself have been identified and ascribed specific functions. In addition, numerous effector proteins that are translocated by the T6SS have been identified and characterized. These protein effectors usually represent toxic cargoes that are delivered by the attacker cell to a target cell. The field is beginning to better understand the lifestyle or physiology that dictates when bacteria normally express their T6SS. In this Chapter, we consider what is known about the structure and regulation of the T6SS, the numerous classes of antibacterial effector T6SS substrates, and how the action of the T6SS relates to a given lifestyle or behavior in certain bacteria. PMID:27227310

  5. Metabolic phenotypes of Saccharomyces cerevisiae mutants with altered trehalose 6-phosphate dynamics.

    PubMed

    Walther, Thomas; Mtimet, Narjes; Alkim, Ceren; Vax, Amélie; Loret, Marie-Odile; Ullah, Azmat; Gancedo, Carlos; Smits, Gertien J; François, Jean Marie

    2013-09-01

    In Saccharomyces cerevisiae, synthesis of T6P (trehalose 6-phosphate) is essential for growth on most fermentable carbon sources. In the present study, the metabolic response to glucose was analysed in mutants with different capacities to accumulate T6P. A mutant carrying a deletion in the T6P synthase encoding gene, TPS1, which had no measurable T6P, exhibited impaired ethanol production, showed diminished plasma membrane H⁺-ATPase activation, and became rapidly depleted of nearly all adenine nucleotides which were irreversibly converted into inosine. Deletion of the AMP deaminase encoding gene, AMD1, in the tps1 strain prevented inosine formation, but did not rescue energy balance or growth on glucose. Neither the 90%-reduced T6P content observed in a tps1 mutant expressing the Tps1 protein from Yarrowia lipolytica, nor the hyperaccumulation of T6P in the tps2 mutant had significant effects on fermentation rates, growth on fermentable carbon sources or plasma membrane H⁺-ATPase activation. However, intracellular metabolite dynamics and pH homoeostasis were strongly affected by changes in T6P concentrations. Hyperaccumulation of T6P in the tps2 mutant caused an increase in cytosolic pH and strongly reduced growth rates on non-fermentable carbon sources, emphasizing the crucial role of the trehalose pathway in the regulation of respiratory and fermentative metabolism.

  6. The corrosion protection of several aluminum alloys by chromic acid and sulfuric acid anodizing

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1994-01-01

    The corrosion protection afforded 7075-T6, 7075-T3, 6061-T6, and 2024-T3 aluminum alloys by chromic acid and sulfuric acid anodizing was examined using electrochemical techniques. From these studies, it is concluded that sulfuric acid anodizing provides superior corrosion protection compared to chromic acid anodizing.

  7. Cold Spray Technology for Repair of Magnesium Rotorcraft Components (Briefing Charts)

    DTIC Science & Technology

    2007-01-01

    Hardened steel landing structures (Boeing) - Iron brake components (Delphi) 2. Corrosion protection and restoration of magnesium -Repair ZE41& AZ91 ...41A magnesium substrate) Hardness: 57 Brinell Hardness Yield Strength: 22ksi comparable to ZE41A-T6 and AZ91E -T6 magnesium Density: >99% with oxide

  8. 27 CFR 9.230 - Ballard Canyon.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Los Olivos map, to a marked, unnamed large structure located within a circular-shaped 920-foot contour... located within the 760-foot contour line, T6N/R31W; then (7) Proceed west-southwesterly in a straight line... intersection with the 400-foot contour line, T6N/R31W; then (10) Proceed southerly and then northwesterly...

  9. Identification of Possible Virulence Marker from Campylobacter jejuni Isolates

    PubMed Central

    Harrison, James W.; Dung, Tran Thi Ngoc; Siddiqui, Fariha; Korbrisate, Sunee; Bukhari, Habib; Tra, My Phan Vu; Hoang, Nguyen Van Minh; Carrique-Mas, Juan; Bryant, Juliet; Campbell, James I.; Studholme, David J.; Wren, Brendan W.; Baker, Stephen; Titball, Richard W.

    2014-01-01

    A novel protein translocation system, the type-6 secretion system (T6SS), may play a role in virulence of Campylobacter jejuni. We investigated 181 C. jejuni isolates from humans, chickens, and environmental sources in Vietnam, Thailand, Pakistan, and the United Kingdom for T6SS. The marker was most prevalent in human and chicken isolates from Vietnam. PMID:24856088

  10. Type VI Secretion System Transports Zn2+ to Combat Multiple Stresses and Host Immunity

    PubMed Central

    Zhu, Wenhan; Gao, Fen; Wang, Yao; Zhang, Lei; Zhang, Weipeng; Wei, Gehong; Luo, Zhao-Qing; Shen, Xihui

    2015-01-01

    Type VI secretion systems (T6SSs) are widespread multi-component machineries that translocate effectors into either eukaryotic or prokaryotic cells, for virulence or for interbacterial competition. Herein, we report that the T6SS-4 from Yersinia pseudotuberculosis displays an unexpected function in the transportation of Zn2+ to combat diverse stresses and host immunity. Environmental insults such as oxidative stress induce the expression of T6SS-4 via OxyR, the transcriptional factor that also regulates many oxidative response genes. Zinc transportation is achieved by T6SS-4-mediated translocation of a novel Zn2+-binding protein substrate YezP (YPK_3549), which has the capacity to rescue the sensitivity to oxidative stress exhibited by T6SS-4 mutants when added to extracellular milieu. Disruption of the classic zinc transporter ZnuABC together with T6SS-4 or yezP results in mutants that almost completely lost virulence against mice, further highlighting the importance of T6SS-4 in resistance to host immunity. These results assigned an unconventional role to T6SSs, which will lay the foundation for studying novel mechanisms of metal ion uptake by bacteria and the role of this process in their resistance to host immunity and survival in harmful environments. PMID:26134274

  11. High-Speed Blade Vibration in a Transonic Compressor

    DTIC Science & Technology

    2008-06-01

    x THIS PAGE INTENTIONALLY LEFT BLANK xi LIST OF TABLES Table 1. Material Properties AL7075 -T6 [From 6...compressor rig at the Naval Postgraduate School Table 1. Material Properties AL7075 -T6 [From 6] Attribute Value Units Young’s Modulus 71.75 GPa

  12. Non-Chromate Aluminum Pretreatments, Phase 2

    DTIC Science & Technology

    2004-09-01

    September 2004 78 ALUMINUM AL2024-T3 ALUMINUM AL7075 -T6 PNL ID 4 Control 5...ALUMINUM - AL2024-T3 192 ALUMINUM - AL7075 -T6 112 Table 5.13: AMCOM – NAVAIR PANEL TEST MATRIX OCTOBER 2003 NCAP Phase II Interim Report

  13. Independent Regulation of Type VI Secretion in Vibrio cholerae by TfoX and TfoY.

    PubMed

    Metzger, Lisa C; Stutzmann, Sandrine; Scrignari, Tiziana; Van der Henst, Charles; Matthey, Noémie; Blokesch, Melanie

    2016-05-03

    Type VI secretion systems (T6SSs) are nanomachines used for interbacterial killing and intoxication of eukaryotes. Although Vibrio cholerae is a model organism for structural studies on T6SSs, the underlying regulatory network is less understood. A recent study showed that the T6SS is part of the natural competence regulon in V. cholerae and is activated by the regulator TfoX. Here, we identify the TfoX homolog TfoY as a second activator of the T6SS. Importantly, despite inducing the same T6SS core machinery, the overall regulons differ significantly for TfoX and TfoY. We show that TfoY does not contribute to competence induction. Instead, TfoY drives the production of T6SS-dependent and T6SS-independent toxins, together with an increased motility phenotype. Hence, we conclude that V. cholerae uses its sole T6SS in response to diverse cues and for distinctive outcomes: either to kill for the prey's DNA, leading to horizontal gene transfer, or as part of a defensive escape reaction. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  14. 27 CFR 9.223 - Coombsville.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... T6N/T5N common line, to the intersection of the Napa River with Milliken Creek, T6N/R4W; then (11) Proceed north (upstream) along Milliken Creek for 0.75 mile to the intersection of Milliken Creek with...

  15. 27 CFR 9.223 - Coombsville.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... T6N/T5N common line, to the intersection of the Napa River with Milliken Creek, T6N/R4W; then (11) Proceed north (upstream) along Milliken Creek for 0.75 mile to the intersection of Milliken Creek with...

  16. Chemical Intervention: New Tools to Dissect Metabolic Signaling.

    PubMed

    Ramon, Matthew; Rolland, Filip

    2017-05-01

    The metabolic intermediate trehalose-6-P (T6P) has emerged as a key regulator of plant growth and development, but the underlying mechanisms remain largely elusive. A recent publication reported a new chemical intervention strategy, providing a powerful tool to dissect T6P-mediated metabolic signaling. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Identification of possible virulence marker from Campylobacter jejuni isolates.

    PubMed

    Harrison, James W; Dung, Tran Thi Ngoc; Siddiqui, Fariha; Korbrisate, Sunee; Bukhari, Habib; Tra, My Phan Vu; Hoang, Nguyen Van Minh; Carrique-Mas, Juan; Bryant, Juliet; Campbell, James I; Studholme, David J; Wren, Brendan W; Baker, Stephen; Titball, Richard W; Champion, Olivia L

    2014-06-01

    A novel protein translocation system, the type-6 secretion system (T6SS), may play a role in virulence of Campylobacter jejuni. We investigated 181 C. jejuni isolates from humans, chickens, and environmental sources in Vietnam, Thailand, Pakistan, and the United Kingdom for T6SS. The marker was most prevalent in human and chicken isolates from Vietnam.

  18. Type VI Secretion Systems of Erwinia amylovora Contribute to Bacterial Competition, Virulence, and Exopolysaccharide Production.

    PubMed

    Tian, Yanli; Zhao, Yuqiang; Shi, Linye; Cui, Zhongli; Hu, Baishi; Zhao, Youfu

    2017-06-01

    The type VI secretion system (T6SS) plays a major role in mediating interbacterial competition and might contribute to virulence in plant pathogenic bacteria. However, the role of T6SS in Erwinia amylovora remains unknown. In this study, 33 deletion mutants within three T6SS clusters were generated in E. amylovora strain NCPPB1665. Our results showed that all 33 mutants displayed reduced antibacterial activities against Escherichia coli as compared with that of the wild-type (WT) strain, indicating that Erwinia amylovora T6SS are functional. Of the 33 mutants, 19 exhibited reduced virulence on immature pear fruit as compared with that of the WT strain. Among them, 6, 1, and 12 genes belonged to T6SS-1, T6SS-2, and T6SS-3 clusters, respectively. Interestingly, these 19 mutants also produced less amylovoran or levan or both. These findings suggest that E. amylovora T6SS play a role in bacterial competition and virulence possibly by influencing exopolysaccharide production.

  19. Type VI secretion requires a dynamic contractile phage tail-like structure

    PubMed Central

    Basler, M.; Pilhofer, M.; Henderson, P.G.; Jensen, J. G.; Mekalanos, J.

    2012-01-01

    Type VI Secretion Systems (T6SS) are bacterial virulence-associated nanomachines composed of proteins that are evolutionarily related to components of bacteriophage tails. Here we show that protein secretion by the T6SS of Vibrio cholerae requires the action of a dynamic intracellular tubular structure that is structurally and functionally homologous to contractile phage tail sheath. Time-lapse fluorescence light microscopy revealed that T6SS sheaths cycle between assembly, quick contraction, disassembly and re-assembly. Whole-cell electron cryotomography further showed that T6SS sheaths appear as long tubular structures in either extended or contracted conformations that are connected to the inner membrane by a distinct basal structure. These data support a model in which the contraction of the T6SS sheath provides the energy needed to translocate proteins out of effector cells and into adjacent target cells. PMID:22367545

  20. Type VI Secretion Effectors: Methodologies and Biology

    PubMed Central

    Lien, Yun-Wei; Lai, Erh-Min

    2017-01-01

    The type VI secretion system (T6SS) is a nanomachine deployed by many Gram-negative bacteria as a weapon against eukaryotic hosts or prokaryotic competitors. It assembles into a bacteriophage tail-like structure that can transport effector proteins into the environment or target cells for competitive survival or pathogenesis. T6SS effectors have been identified by a variety of approaches, including knowledge/hypothesis-dependent and discovery-driven approaches. Here, we review and discuss the methods that have been used to identify T6SS effectors and the biological and biochemical functions of known effectors. On the basis of the nature and transport mechanisms of T6SS effectors, we further propose potential strategies that may be applicable to identify new T6SS effectors. PMID:28664151

  1. Multicellular Bacteria Deploy the Type VI Secretion System to Preemptively Strike Neighboring Cells

    PubMed Central

    Pickens, Shannon R.; Lindner, Jonathon R.; Zora, Jonathan S.; Miller, Jessa E.; Arno, Peter D.; Straight, Samuel W.; Mobley, Harry L. T.

    2013-01-01

    The Type VI Secretion System (T6SS) functions in bacteria as a contractile nanomachine that punctures and delivers lethal effectors to a target cell. Virtually nothing is known about the lifestyle or physiology that dictates when bacteria normally produce their T6SS, which prevents a clear understanding of how bacteria benefit from its action in their natural habitat. Proteus mirabilis undergoes a characteristic developmental process to coordinate a multicellular swarming behavior and will discriminate itself from another Proteus isolate during swarming, resulting in a visible boundary termed a Dienes line. Using transposon mutagenesis, we discovered that this recognition phenomenon requires the lethal action of the T6SS. All mutants identified in the genetic screen had insertions within a single 33.5-kb region that encodes a T6SS and cognate Hcp-VrgG-linked effectors. The identified T6SS and primary effector operons were characterized by killing assays, by construction of additional mutants, by complementation, and by examining the activity of the type VI secretion system in real-time using live-cell microscopy on opposing swarms. We show that lethal T6SS-dependent activity occurs when a dominant strain infiltrates deeply beyond the boundary of the two swarms. Using this multicellular model, we found that social recognition in bacteria, underlying killing, and immunity to killing all require cell-cell contact, can be assigned to specific genes, and are dependent on the T6SS. The ability to survive a lethal T6SS attack equates to “recognition”. In contrast to the current model of T6SS being an offensive or defensive weapon our findings support a preemptive mechanism by which an entire population indiscriminately uses the T6SS for contact-dependent delivery of effectors during its cooperative mode of growth. PMID:24039579

  2. Multicellular bacteria deploy the type VI secretion system to preemptively strike neighboring cells.

    PubMed

    Alteri, Christopher J; Himpsl, Stephanie D; Pickens, Shannon R; Lindner, Jonathon R; Zora, Jonathan S; Miller, Jessa E; Arno, Peter D; Straight, Samuel W; Mobley, Harry L T

    2013-01-01

    The Type VI Secretion System (T6SS) functions in bacteria as a contractile nanomachine that punctures and delivers lethal effectors to a target cell. Virtually nothing is known about the lifestyle or physiology that dictates when bacteria normally produce their T6SS, which prevents a clear understanding of how bacteria benefit from its action in their natural habitat. Proteus mirabilis undergoes a characteristic developmental process to coordinate a multicellular swarming behavior and will discriminate itself from another Proteus isolate during swarming, resulting in a visible boundary termed a Dienes line. Using transposon mutagenesis, we discovered that this recognition phenomenon requires the lethal action of the T6SS. All mutants identified in the genetic screen had insertions within a single 33.5-kb region that encodes a T6SS and cognate Hcp-VrgG-linked effectors. The identified T6SS and primary effector operons were characterized by killing assays, by construction of additional mutants, by complementation, and by examining the activity of the type VI secretion system in real-time using live-cell microscopy on opposing swarms. We show that lethal T6SS-dependent activity occurs when a dominant strain infiltrates deeply beyond the boundary of the two swarms. Using this multicellular model, we found that social recognition in bacteria, underlying killing, and immunity to killing all require cell-cell contact, can be assigned to specific genes, and are dependent on the T6SS. The ability to survive a lethal T6SS attack equates to "recognition". In contrast to the current model of T6SS being an offensive or defensive weapon our findings support a preemptive mechanism by which an entire population indiscriminately uses the T6SS for contact-dependent delivery of effectors during its cooperative mode of growth.

  3. The Type VI Secretion System Encoded in Salmonella Pathogenicity Island 19 Is Required for Salmonella enterica Serotype Gallinarum Survival within Infected Macrophages

    PubMed Central

    Blondel, Carlos J.; Jiménez, Juan C.; Leiva, Lorenzo E.; Álvarez, Sergio A.; Pinto, Bernardo I.; Contreras, Francisca; Pezoa, David; Santiviago, Carlos A.

    2013-01-01

    Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells. PMID:23357385

  4. The Methyl Group of the N6-Methyl-N6-Threonylcarbamoyladenosine in tRNA of Escherichia coli Modestly Improves the Efficiency of the tRNA

    PubMed Central

    Qian, Qiang; Curran, James F.; Björk, Glenn R.

    1998-01-01

    tRNA species that read codons starting with adenosine (A) contain N6-threonylcarbamoyladenosine (t6A) derivatives adjacent to and 3′ of the anticodons from all organisms. In Escherichia coli there are 12 such tRNA species of which two (tRNAGGUThr1 and tRNAGGUThr3) have the t6A derivative N6-methyl-N6-threonylcarbamoyladenosine (m6t6A37). We have isolated a mutant of E. coli that lacks the m6t6A37 in these two tRNAGGUThr species. These tRNA species in the mutant are likely to have t6A37 instead of m6t6A37. We show that the methyl group of m6t6A37 originates from S-adenosyl-l-methionine and that the gene (tsaA) which most likely encodes tRNA(m6t6A37)methyltransferase is located at min 4.6 on the E. coli chromosomal map. The growth rate of the cell, the polypeptide chain elongation rate, and the selection of Thr-tRNAGGUThr to the ribosomal A site programmed with either of the cognate codons ACC and ACU were the same for the tsaA1 mutant as for the congenic wild-type strain. The expression of the threonine operon is regulated by an attenuator which contains in its leader mRNA seven ACC codons that are read by these two m6t6A37-containing tRNAGGUThr species. We show that the tsaA1 mutation resulted in a twofold derepression of this operon, suggesting that the lack of the methyl group of m6t6A37 in tRNAGGUThr slightly reduces the efficiency of this tRNA to read cognate codon ACC. PMID:9537379

  5. Biochemical analysis of TssK, a core component of the bacterial Type VI secretion system, reveals distinct oligomeric states of TssK and identifies a TssK–TssFG subcomplex

    PubMed Central

    English, Grant; Byron, Olwyn; Cianfanelli, Francesca R.; Prescott, Alan R.; Coulthurst, Sarah J.

    2014-01-01

    Gram-negative bacteria use the Type VI secretion system (T6SS) to inject toxic proteins into rival bacteria or eukaryotic cells. However, the mechanism of the T6SS is incompletely understood. In the present study, we investigated a conserved component of the T6SS, TssK, using the antibacterial T6SS of Serratia marcescens as a model system. TssK was confirmed to be essential for effector secretion by the T6SS. The native protein, although not an integral membrane protein, appeared to localize to the inner membrane, consistent with its presence within a membrane-anchored assembly. Recombinant TssK purified from S. marcescens was found to exist in several stable oligomeric forms, namely trimer, hexamer and higher-order species. Native-level purification of TssK identified TssF and TssG as interacting proteins. TssF and TssG, conserved T6SS components of unknown function, were required for T6SS activity, but not for correct localization of TssK. A complex containing TssK, TssF and TssG was subsequently purified in vitro, confirming that these three proteins form a new subcomplex within the T6SS. Our findings provide new insight into the T6SS assembly, allowing us to propose a model whereby TssK recruits TssFG into the membrane-associated T6SS complex and different oligomeric states of TssK may contribute to the dynamic mechanism of the system. PMID:24779861

  6. The Type VI Secretion System Modulates Flagellar Gene Expression and Secretion in Citrobacter freundii and Contributes to Adhesion and Cytotoxicity to Host Cells.

    PubMed

    Liu, Liyun; Hao, Shuai; Lan, Ruiting; Wang, Guangxia; Xiao, Di; Sun, Hui; Xu, Jianguo

    2015-07-01

    The type VI secretion system (T6SS) as a virulence factor-releasing system contributes to virulence development of various pathogens and is often activated upon contact with target cells. Citrobacter freundii strain CF74 has a complete T6SS genomic island (GI) that contains clpV, hcp-2, and vgr T6SS genes. We constructed clpV, hcp-2, vgr, and T6SS GI deletion mutants in CF74 and analyzed their effects on the transcriptome overall and, specifically, on the flagellar system at the levels of transcription and translation. Deletion of the T6SS GI affected the transcription of 84 genes, with 15 and 69 genes exhibiting higher and lower levels of transcription, respectively. Members of the cell motility class of downregulated genes of the CF74ΔT6SS mutant were mainly flagellar genes, including effector proteins, chaperones, and regulators. Moreover, the production and secretion of FliC were also decreased in clpV, hcp-2, vgr, or T6SS GI deletion mutants in CF74 and were restored upon complementation. In swimming motility assays, the mutant strains were found to be less motile than the wild type, and motility was restored by complementation. The mutant strains were defective in adhesion to HEp-2 cells and were restored partially upon complementation. Further, the CF74ΔT6SS, CF74ΔclpV, and CF74Δhcp-2 mutants induced lower cytotoxicity to HEp-2 cells than the wild type. These results suggested that the T6SS GI in CF74 regulates the flagellar system, enhances motility, is involved in adherence to host cells, and induces cytotoxicity to host cells. Thus, the T6SS plays a wide-ranging role in C. freundii.

  7. Discovery of the β-barrel–type RNA methyltransferase responsible for N6-methylation of N6-threonylcarbamoyladenosine in tRNAs

    PubMed Central

    Kimura, Satoshi; Miyauchi, Kenjyo; Ikeuchi, Yoshiho; Thiaville, Patrick C.; de Crécy-Lagard, Valérie; Suzuki, Tsutomu

    2014-01-01

    Methylation is a versatile reaction involved in the synthesis and modification of biologically active molecules, including RNAs. N6-methyl-threonylcarbamoyl adenosine (m6t6A) is a post-transcriptional modification found at position 37 of tRNAs from bacteria, insect, plants, and mammals. Here, we report that in Escherichia coli, yaeB (renamed as trmO) encodes a tRNA methyltransferase responsible for the N6-methyl group of m6t6A in tRNAThr specific for ACY codons. TrmO has a unique single-sheeted β-barrel structure and does not belong to any known classes of methyltransferases. Recombinant TrmO employs S-adenosyl-L-methionine (AdoMet) as a methyl donor to methylate t6A to form m6t6A in tRNAThr. Therefore, TrmO/YaeB represents a novel category of AdoMet-dependent methyltransferase (Class VIII). In a ΔtrmO strain, m6t6A was converted to cyclic t6A (ct6A), suggesting that t6A is a common precursor for both m6t6A and ct6A. Furthermore, N6-methylation of t6A enhanced the attenuation activity of the thr operon, suggesting that TrmO ensures efficient decoding of ACY. We also identified a human homolog, TRMO, indicating that m6t6A plays a general role in fine-tuning of decoding in organisms from bacteria to mammals. PMID:25063302

  8. TagR promotes PpkA-catalysed type VI secretion activation in Pseudomonas aeruginosa.

    PubMed

    Hsu, FoSheng; Schwarz, Sandra; Mougous, Joseph D

    2009-06-01

    Type VI secretion systems (T6SSs) contribute to interactions of bacterial pathogens and symbionts with their hosts. Previously, we showed that Pseudomonas aeruginosa T6S is posttranslationally activated upon phosphorylation of Fha1, an FHA domain protein, by PpkA, a membrane-spanning threonine kinase. Herein, additional structural, enzymatic and genetic requirements for PpkA-catalysed T6SS activation are identified. We found that PpkA plays an essential structural role in the T6SS, and that this role is intimately linked to its ability to promote secretion and phosphorylate Fha1. Protein localization and protein-protein interaction studies show that a complex containing Fha1 and the T6S ATPase, ClpV1 is recruited to the T6S apparatus in a phosphorylation-dependent manner. The mechanism of PpkA activation was also investigated. We identified critical PpkA autophosphorylation sites and showed that small molecule-induced dimerization of the extracellular domains of PpkA is sufficient to activate the T6SS. Finally, we discovered TagR, a component of the T6S posttranslational regulatory pathway that functions upstream of PpkA to promote kinase activity. We present a model whereby an unknown cue causes dimerization of the extracellular domains of PpkA, leading to its autophosphorylation, recruitment of the Fha1-ClpV1 complex, phosphorylation of Fha1, and T6SS activation. Our findings should facilitate approaches for identifying physiological activators of T6S.

  9. Estudio del comportamiento tribologico y de las interacciones de superficie de nuevos nanofluidos ionicos

    NASA Astrophysics Data System (ADS)

    Espinosa Rodriguez, Tulia

    tribocorrosion processes. The formation of a coating layer on magnesium alloys from phosphonate imidazolium ionic liquids by immersion and by chronoamperometry has been described. The new coatings reduce the abrasive wear in the magnesium-aluminium alloy but they are not effective in the magnesium-zinc alloy, which prevent the formation of continuous coatings. Los liquidos ionicos son sales liquidas a temperatura ambiente o bajas temperaturas que presentan excelentes propiedades fisico-quimicas. En el presente trabajo se estudian como lubricantes en problemas tribologicos complejos como la lubricacion de metales contra si mismos, el desarrollo de lubricantes base agua y de nuevas superficies autolubricadas. Cuando no es posible reducir la friccion y desgaste mediante lubricacion, como en las aleaciones de magnesio, los liquidos ionicos se han estudiado como precursores de recubrimientos protectores. Se han determinado las interacciones superficiales y los procesos de corrosion sobre cobre y sobre acero con diferentes liquidos ionicos proticos y aproticos para desarrollar nuevos lubricantes y aditivos. En el contacto cobre/cobre, excepto el liquido ionico protico derivado del oleato, todos los liquidos ionicos estudiados presentan mejor comportamiento tribologico que el lubricante comercial Polialfaolefina 6. En el contacto acero/zafiro, los nuevos liquidos ionicos proticos son buenos lubricantes cuando se utilizan en estado puro, y, como aditivos en agua, generan peliculas adsorbidas sobre la superficie del metal reduciendo la friccion y el desgaste tras la evaporacion del agua. Para evitar el periodo de alta friccion inicial en presencia de agua, se han generado peliculas superficiales de liquido ionico sobre el acero en condiciones estaticas. El mejor comportamiento lubricante tanto en el contacto cobre/cobre como en el contacto acero/zafiro se obtiene para el liquido ionico protico derivado del anion adipato, con dos grupos carboxilicos. Las interacciones de los grupos

  10. The type VI secretion system: a multipurpose delivery system with a phage-like machinery.

    PubMed

    Records, Angela R

    2011-07-01

    Whether they live in the soil, drift in the ocean, survive in the lungs of human hosts or reside on the surfaces of leaves, all bacteria must cope with an array of environmental stressors. Bacteria have evolved an impressive suite of protein secretion systems that enable their survival in hostile environments and facilitate colonization of eukaryotic hosts. Collectively, gram-negative bacteria produce six distinct secretion systems that deliver proteins to the extracellular milieu or directly into the cytosol of host cells. The type VI secretion system (T6SS) was discovered recently and is encoded in at least one fourth of all sequenced gram-negative bacterial genomes. T6SS proteins are evolutionarily and structurally related to phage proteins, and it is likely that the T6SS apparatus is reminiscent of phage injection machinery. Most studies of T6SS function have been conducted in the context of host-pathogen interactions. However, the totality of data suggests that the T6SS is a versatile tool with roles in virulence, symbiosis, interbacterial interactions, and antipathogenesis. This review gives a brief history of T6SS discovery and an overview of the pathway's predicted structure and function. Special attention is paid to research addressing the T6SS of plant-associated bacteria, including pathogens, symbionts and plant growth-promoting rhizobacteria.

  11. Type VI Secretion System Toxins Horizontally Shared between Marine Bacteria

    PubMed Central

    Salomon, Dor; Klimko, John A.; Trudgian, David C.; Kinch, Lisa N.; Grishin, Nick V.; Mirzaei, Hamid; Orth, Kim

    2015-01-01

    The type VI secretion system (T6SS) is a widespread protein secretion apparatus used by Gram-negative bacteria to deliver toxic effector proteins into adjacent bacterial or host cells. Here, we uncovered a role in interbacterial competition for the two T6SSs encoded by the marine pathogen Vibrio alginolyticus. Using comparative proteomics and genetics, we identified their effector repertoires. In addition to the previously described effector V12G01_02265, we identified three new effectors secreted by T6SS1, indicating that the T6SS1 secretes at least four antibacterial effectors, of which three are members of the MIX-effector class. We also showed that the T6SS2 secretes at least three antibacterial effectors. Our findings revealed that many MIX-effectors belonging to clan V are “orphan” effectors that neighbor mobile elements and are shared between marine bacteria via horizontal gene transfer. We demonstrated that a MIX V-effector from V. alginolyticus is a functional T6SS effector when ectopically expressed in another Vibrio species. We propose that mobile MIX V-effectors serve as an environmental reservoir of T6SS effectors that are shared and used to diversify antibacterial toxin repertoires in marine bacteria, resulting in enhanced competitive fitness. PMID:26305100

  12. How do sugars regulate plant growth and development? New insight into the role of trehalose-6-phosphate.

    PubMed

    O'Hara, Liam E; Paul, Matthew J; Wingler, Astrid

    2013-03-01

    Plant growth and development are tightly controlled in response to environmental conditions that influence the availability of photosynthetic carbon in the form of sucrose. Trehalose-6-phosphate (T6P), the precursor of trehalose in the biosynthetic pathway, is an important signaling metabolite that is involved in the regulation of plant growth and development in response to carbon availability. In addition to the plant's own pathway for trehalose synthesis, formation of T6P or trehalose by pathogens can result in the reprogramming of plant metabolism and development. Developmental processes that are regulated by T6P range from embryo development to leaf senescence. Some of these processes are regulated in interaction with phytohormones, such as auxin. A key interacting factor of T6P signaling in response to the environment is the protein kinase sucrose non-fermenting related kinase-1 (SnRK1), whose catalytic activity is inhibited by T6P. SnRK1 is most likely involved in the adjustment of metabolism and growth in response to starvation. The transcription factor bZIP11 has recently been identified as a new player in the T6P/SnRK1 regulatory pathway. By inhibiting SnRK1, T6P promotes biosynthetic reactions. This regulation has important consequences for crop production, for example, in the developing wheat grain and during the growth of potato tubers.

  13. Chimeric adaptor proteins translocate diverse type VI secretion system effectors in Vibrio cholerae.

    PubMed

    Unterweger, Daniel; Kostiuk, Benjamin; Ötjengerdes, Rina; Wilton, Ashley; Diaz-Satizabal, Laura; Pukatzki, Stefan

    2015-08-13

    Vibrio cholerae is a diverse species of Gram-negative bacteria, commonly found in the aquatic environment and the causative agent of the potentially deadly disease cholera. These bacteria employ a type VI secretion system (T6SS) when they encounter prokaryotic and eukaryotic competitors. This contractile puncturing device translocates a set of effector proteins into neighboring cells. Translocated effectors are toxic unless the targeted cell produces immunity proteins that bind and deactivate incoming effectors. Comparison of multiple V. cholerae strains indicates that effectors are encoded in T6SS effector modules on mobile genetic elements. We identified a diverse group of chimeric T6SS adaptor proteins required for the translocation of diverse effectors encoded in modules. An example for a T6SS effector that requires T6SS adaptor protein 1 (Tap-1) is TseL found in pandemic V. cholerae O1 serogroup strains and other clinical isolates. We propose a model in which Tap-1 is required for loading TseL onto the secretion apparatus. After T6SS-mediated TseL export is completed, Tap-1 is retained in the bacterial cell to load other T6SS machines. © 2015 The Authors. Published under the terms of the CC BY NC ND 4.0 license.

  14. A view to a kill: the bacterial type VI secretion system.

    PubMed

    Ho, Brian T; Dong, Tao G; Mekalanos, John J

    2014-01-15

    The bacterial type VI secretion system (T6SS) is an organelle that is structurally and mechanistically analogous to an intracellular membrane-attached contractile phage tail. Recent studies determined that a rapid conformational change in the structure of a sheath protein complex propels T6SS spike and tube components along with antibacterial and antieukaryotic effectors out of predatory T6SS(+) cells and into prey cells. The contracted organelle is then recycled in an ATP-dependent process. T6SS is regulated at transcriptional and posttranslational levels, the latter involving detection of membrane perturbation in some species. In addition to directly targeting eukaryotic cells, the T6SS can also target other bacteria coinfecting a mammalian host, highlighting the importance of the T6SS not only for bacterial survival in environmental ecosystems, but also in the context of infection and disease. This review highlights these and other advances in our understanding of the structure, mechanical function, assembly, and regulation of the T6SS. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Tensile and compressive stress-strain behavior of heat treated boron-aluminum

    NASA Technical Reports Server (NTRS)

    Kennedy, J. M.; Tenney, D. R.; Herakovich, C. T.

    1978-01-01

    An experimental study was conducted to assess the effects of heat treatment and cyclic mechanical loading on the tensile and compressive stress-strain behavior of six boron-aluminum composites having different laminate orientations and being subjected to different heat treatments. The heat treatments were as-fabricated, T6, and T6N consisting of T6 treatment followed by cryogenic quench in liquid nitrogen prior to testing. All laminates were tested in monotonic and cyclic compression, while the tensile-test data are taken from the literature for comparison purposes. It is shown that the linear elastic range of the T6- and T6N-condition specimens is larger than that of the as-fabricated specimens, and that cyclic loading in tension or compression strain hardens the specimens and extends the linear elastic range. For laminates containing 0-deg plies, the stress-strain behavior upon unloading is found to be nonlinear, whereas the other laminates exhibit a linear behavior upon unloading. Specimens in the T6 and T6N conditions show higher strain hardening than the as-fabricated specimens.

  16. Structure/property relations of aluminum under varying rates and stress states

    SciTech Connect

    Tucker, Matthew T; Horstemeyer, Mark F; Whittington, Wilburn R; Solanki, Kiran N

    2010-11-19

    In this work we analyze the plasticity, damage, and fracture characteristics of three different processed aluminum alloys (rolled 5083-H13, cast A356-T6, and extruded 6061-T6) under varying stress states (tension, compression, and torsion) and strain rates (0.001/, 1/s., and 1000/s). The stress state difference had more of a flow stress effect than the applied strain rates for those given in this study (0.001/sec up to 1000/sec). The stress state and strain rate also had a profound effect on the damage evolution of each aluminum alloy. Tension and torsional straining gave much greater damage nucleation rates than compression. Although the damage of all three alloys was found to be void nucleation dominated, the A356-T6 and 5083-H131 aluminum alloys incurred void damage via micron scale particles where the 6061-T6 aluminum alloy incurred void damage from two scales, micron-scale particles and nanoscale precipitates. Having two length scales of particles that participated in the damage evolution made the 6061-T6 incur a strain rate sensitive damage rate that was different than the other two aluminum alloys. Under tension, as the strain rate increased, the 6061-T6 aluminum alloy's void nucleation rate decreased, but the A356-T6 and 5083-H131 aluminum alloys void nucleation rate increased.

  17. An ERP study of good production vis-à-vis poor perception of tones in Cantonese: implications for top-down speech processing.

    PubMed

    Law, Sam-Po; Fung, Roxana; Kung, Carmen

    2013-01-01

    This study investigated a theoretically challenging dissociation between good production and poor perception of tones among neurologically unimpaired native speakers of Cantonese. The dissociation is referred to as the near-merger phenomenon in sociolinguistic studies of sound change. In a passive oddball paradigm, lexical and nonlexical syllables of the T1/T6 and T4/T6 contrasts were presented to elicit the mismatch negativity (MMN) and P3a from two groups of participants, those who could produce and distinguish all tones in the language (Control) and those who could produce all tones but specifically failed to distinguish between T4 and T6 in perception (Dissociation). The presence of MMN to T1/T6 and null response to T4/T6 of lexical syllables in the dissociation group confirmed the near-merger phenomenon. The observation that the control participants exhibited a statistically reliable MMN to lexical syllables of T1/T6, weaker responses to nonlexical syllables of T1/T6 and lexical syllables of T4/T6, and finally null response to nonlexical syllables of T4/T6, suggests the involvement of top-down processing in speech perception. Furthermore, the stronger P3a response of the control group, compared with the dissociation group in the same experimental conditions, may be taken to indicate higher cognitive capability in attention switching, auditory attention or memory in the control participants. This cognitive difference, together with our speculation that constant top-down predictions without complete bottom-up analysis of acoustic signals in speech recognition may reduce one's sensitivity to small acoustic contrasts, account for the occurrence of dissociation in some individuals but not others.

  18. The opportunistic pathogen Serratia marcescens utilizes type VI secretion to target bacterial competitors.

    PubMed

    Murdoch, Sarah L; Trunk, Katharina; English, Grant; Fritsch, Maximilian J; Pourkarimi, Ehsan; Coulthurst, Sarah J

    2011-11-01

    The type VI secretion system (T6SS) is the most recently described and least understood of the protein secretion systems of Gram-negative bacteria. It is widely distributed and has been implicated in the virulence of various pathogens, but its mechanism and exact mode of action remain to be defined. Additionally there have been several very recent reports that some T6SSs can target bacteria rather than eukaryotic cells. Serratia marcescens is an opportunistic enteric pathogen, a class of bacteria responsible for a significant proportion of hospital-acquired infections. We describe the identification of a functional T6SS in S. marcescens strain Db10, the first report of type VI secretion by an opportunist enteric bacterium. The T6SS of S. marcescens Db10 is active, with secretion of Hcp to the culture medium readily detected, and is expressed constitutively under normal growth conditions from a large transcriptional unit. Expression of the T6SS genes did not appear to be dependent on the integrity of the T6SS. The S. marcescens Db10 T6SS is not required for virulence in three nonmammalian virulence models. It does, however, exhibit dramatic antibacterial killing activity against several other bacterial species and is required for S. marcescens to persist in a mixed culture with another opportunist pathogen, Enterobacter cloacae. Importantly, this antibacterial killing activity is highly strain specific, with the S. marcescens Db10 T6SS being highly effective against another strain of S. marcescens with a very similar and active T6SS. We conclude that type VI secretion plays a crucial role in the competitiveness, and thus indirectly the virulence, of S. marcescens and other opportunistic bacterial pathogens.

  19. An ERP Study of Good Production vis-à-vis Poor Perception of Tones in Cantonese: Implications for Top-Down Speech Processing

    PubMed Central

    Law, Sam-Po; Fung, Roxana; Kung, Carmen

    2013-01-01

    This study investigated a theoretically challenging dissociation between good production and poor perception of tones among neurologically unimpaired native speakers of Cantonese. The dissociation is referred to as the near-merger phenomenon in sociolinguistic studies of sound change. In a passive oddball paradigm, lexical and nonlexical syllables of the T1/T6 and T4/T6 contrasts were presented to elicit the mismatch negativity (MMN) and P3a from two groups of participants, those who could produce and distinguish all tones in the language (Control) and those who could produce all tones but specifically failed to distinguish between T4 and T6 in perception (Dissociation). The presence of MMN to T1/T6 and null response to T4/T6 of lexical syllables in the dissociation group confirmed the near-merger phenomenon. The observation that the control participants exhibited a statistically reliable MMN to lexical syllables of T1/T6, weaker responses to nonlexical syllables of T1/T6 and lexical syllables of T4/T6, and finally null response to nonlexical syllables of T4/T6, suggests the involvement of top-down processing in speech perception. Furthermore, the stronger P3a response of the control group, compared with the dissociation group in the same experimental conditions, may be taken to indicate higher cognitive capability in attention switching, auditory attention or memory in the control participants. This cognitive difference, together with our speculation that constant top-down predictions without complete bottom-up analysis of acoustic signals in speech recognition may reduce one’s sensitivity to small acoustic contrasts, account for the occurrence of dissociation in some individuals but not others. PMID:23342146

  20. Inhibiting Corrosion Cracking: Crack Tip Chemistry and Physics.

    DTIC Science & Technology

    1986-03-14

    8217.. MacDill Fcrmula See Table 2. Erny Supply Co. Tampa, FL MBT C7H5NS 2 Eastman Kodak Co. -.... Rochester, NY Boric Acid H3B 3 Fisher Scientific Co. Fairlawn...alloy in 3 wt% NaCI 37 solution. 5. Anodic polarization of 7075-T6 Al alloy in 1 wt% NaCl andi 38 nitrite/ borax Inhibitor. 6. Anodic polarization of...polarization of 7075-T6 Al alloy ]n 1 wt% Naed and 42 * sodium oxalate. 9. Anodic polarization of 7075-T6 Al alloy in 1 wt* N&Cl, 45 - " * nitrite/ borax

  1. Acrylic Plastic Spherical Pressure Hull for Continental Shelf Depths

    DTIC Science & Technology

    1993-03-01

    29 7. Aluminum 7075-T6 alloy hatch plate for Model AA 30 8. The 15-inch OD x 10.7-inch ID Model BB acrylic sphere with single penetration 30 9...Dimensions of Model BB acrylic sphere 31 10. Removable hatch assembly for Model BB 31 11. Removable aluminum 6061-T6 alloy hatch plate for Models BB and CC...32 12. Aluminum 6061-T6 alloy hatch seat for removable hatches on Models BB and CC 32 13. Plastic bearing gasket for Models BB and CC 33 14. Hatch

  2. Analysis of Liquid Rocket Tankage

    DTIC Science & Technology

    1975-04-01

    48 a. Detail Analysi.s of Corrosion and Leakage 0:curring on Inlet Tube Weld (4043 Filler Alloy) of 20Pl- T6 Aluminum Alloy Martin 10-Gallon Tank S... Corrosion Observed on A 2014- T6 Aluminum Alloy Alcoa One Quart Container Exposed to ClF5 Propellant ...... 67 (1) Test History ................... 67 2...CIF5 Propellant for 42 Months ...... 5 n. 70 Pitting Corrosion Observed on Internal Surface of 201.4.- T6 Aluminum Alloy One-quart Container S/N 24

  3. Corrosion characterization of aluminum alloys treated with a new sealing process -- Part 2

    SciTech Connect

    Banerjee, G.; Miller, A.E.; Vasanth, K.L.

    1999-07-01

    Continuing an earlier investigation a new sealing solution that contains catalytic amount of chromium (1--10{micro}g) was developed. Aluminum alloys 2024-T6 and 6061-T6 coupons were anodized and sealed with the new sealing formulation. Passivation characteristics of these samples were evaluated using potentiodynamic anodic polarization tests. Al 6061-T6 coupons were further subjected to prohesion tests. In this paper, the results obtained from these tests are compared to those obtained by aluminum alloy treated with standard chromate conversion coating.

  4. Manufacturing Methods for Process Effects on Aluminum Casting Allowables

    DTIC Science & Technology

    1985-03-01

    YS 5% elongation Hardness per ASTM E18 Minimum of HRB 70 Electrical conductivity Minimum of 31% TACS per MIL-STD-1537 In addition, each foundry was...Min ( ASTM E18 ) A357-T6: 90HRB Min A Solidification A357-T6 A357-T6 Rate - DAS Control DAS Evaluation Max DAS (A357 Only) Per Proposed Det. by...defined in ASTM B557. 3.8.2 Hardness of Castings: Castings, should have hardness of ERE 90 minimum determined in accordance with ASTM E18 , but

  5. Crystal structure of YwpF from Staphylococcus aureus reveals its architecture comprised of a β-barrel core domain resembling type VI secretion system proteins and a two-helix pair.

    PubMed

    Lee, Sang Jae; Lee, Kyu-Yeon; Lee, Ki-Young; Kim, Dong-Gyun; Kim, Soon-Jong; Lee, Bong-Jin

    2015-04-01

    The ywpF gene (SAV2097) of the Staphylococcus aureus strain Mu50 encodes the YwpF protein, which may play a role in antibiotic resistance. Here, we report the first crystal structure of the YwpF superfamily from S. aureus at 2.5-Å resolution. The YwpF structure consists of two regions: an N-terminal core β-barrel domain that shows structural similarity to type VI secretion system (T6SS) proteins (e.g., Hcp1, Hcp3, and EvpC) and a C-terminal two-helix pair. Although the monomer structure of S. aureus YwpF resembles those of T6SS proteins, the dimer/tetramer model of S. aureus YwpF is distinct from the functionally important hexameric ring of T6SS proteins. We therefore suggest that the S. aureus YwpF may have a different function compared to T6SS proteins.

  6. Development of a Dynamic Biomechanical Model for Load Carriage: Phase II Part A: Initial Development of a Novel Strap Tension Sensor

    DTIC Science & Technology

    2005-08-01

    Aluminium 6061 -T6 Ffailure 28.7 Kg 281.547 N L 0.999 in 25.375 Mm t 0.068 in 1.727 mm d 0.0582 in 1.478 mm Sample 2... Aluminium 6061 -T6 Ffailure 11.5 kg 112.815 N L 0.997 in 25.324 mm t 0.039 in 0.991 mm d 0.05 in 1.27 mm Sample 3 Aluminium 6061 -T6 Ffailure 9.0 kg...88.29 N L 0.995 in 25.273 mm t 0.076 in 1.930 mm d 0.05 in 1.27 mm Sample 4 Aluminium 6061 -T6 Ffailure 21.0 kg 206.01 N Table B1: Aluminium

  7. 26 CFR 31.3231(e)-1 - Compensation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... to a less remunerative position or occupation as well as pay for time lost. (5) For rules regarding... regarding the inclusion of fringe benefits in compensation, see § 31.3121(a)-1T. (6) Split-dollar...

  8. Aim, Load, Fire: The Type VI Secretion System, a Bacterial Nanoweapon.

    PubMed

    Cianfanelli, Francesca R; Monlezun, Laura; Coulthurst, Sarah J

    2016-01-01

    Bacteria utilise specialised protein secretion systems to interact with host organisms, competitor bacteria, and the environment. The Type VI secretion system (T6SS) is a versatile weapon deployed by many bacterial species to target either host cells or rival bacteria. The widespread occurrence and significance of the T6SS is becoming increasingly appreciated, as is its intriguing mode of action. The T6SS delivers multiple, diverse effector proteins directly into target cells using a dynamic 'firing' mechanism related to the action of contractile bacteriophage tails. Here, we summarise the contribution of recent findings to our developing picture of how the T6SS assembles and fires, how it is loaded with different types of effectors, and how it can be aimed towards an incoming assault.

  9. Effects of Initial Temper Condition and Postweld Heat Treatment on the Properties of Dissimilar Friction-Stir-Welded Joints between AA7075 and AA6061 Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    İpekoğlu, Güven; Çam, Gürel

    2014-06-01

    In this study, dissimilar AA7075-O/6061-O and AA7075-T6/6061-T6 butt joints were produced by friction stir welding (FSW), and postweld heat treatment (PWHT) was applied to the joints obtained. The effects of initial temper condition and PWHT on the microstructure and mechanical properties of the dissimilar joints were thus investigated. It was demonstrated that sound dissimilar joints can be produced for both temper conditions. A hardness increase in the joint area ( i.e., strength overmatching) was obtained in the joints produced in the O-temper condition, whereas a hardness loss was observed in the joint area of the joints obtained in the T6 temper condition. It was also well demonstrated that PWHT could be used in order to improve the joint properties for both O and T6 joints provided that the joint is defect-free prior to subsequent heat treatment.

  10. 12 CFR 165.4 - Capital measures and capital category definitions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... directive, or prompt corrective action directive issued by the OCC or OTS under section 8 of the FDI Act....C. 1464(t)(6)(A)(ii)), or section 38 of the FDI Act, or any regulation thereunder, to meet...

  11. Improved pregnancy rate in human in vitro fertilization with the use of a medium based on the composition of human tubal fluid.

    PubMed

    Quinn, P; Kerin, J F; Warnes, G M

    1985-10-01

    Significantly more mouse zygotes developed to blastocysts in culture in a medium formulated on the composition of human tubal fluid (HTF) than in modified Tyrode's medium (T6). In a randomized 2 X 2 factorial trial of human in vitro fertilization that compared the two media and culture under oil versus culture in loosely capped tubes, significantly more clinical pregnancies (30% of 60 transfers) were obtained with HTF medium than with T6 medium (11% of 53 transfers). Decreasing the K+ content of HTF medium to that present in T6 medium significantly decreased the number of mouse zygotes that developed in culture. Modifying Ca++ levels had no effect. It is therefore likely that the higher K+ content in HTF medium is primarily responsible for the superiority of HTF medium over T6 medium, but other differences in the composition of the two media could contribute to the results observed.

  12. Evaluation of the roles played by Hcp and VgrG type 6 secretion system effectors in Aeromonas hydrophila SSU pathogenesis.

    PubMed

    Sha, Jian; Rosenzweig, Jason A; Kozlova, Elena V; Wang, Shaofei; Erova, Tatiana E; Kirtley, Michelle L; van Lier, Christina J; Chopra, Ashok K

    2013-06-01

    Aeromonas hydrophila, a Gram-negative bacterium, is an emerging human pathogen equipped with both a type 3 and a type 6 secretion system (T6SS). In this study, we evaluated the roles played by paralogous T6SS effector proteins, hemolysin co-regulated proteins (Hcp-1 and -2) and valine glycine repeat G (VgrG-1, -2 and -3) protein family members in A. hydrophila SSU pathogenesis by generating various combinations of deletion mutants of the their genes. In addition to their predicted roles as structural components and effector proteins of the T6SS, our data clearly demonstrated that paralogues of Hcp and VgrG also influenced bacterial motility, protease production and biofilm formation. Surprisingly, there was limited to no observed functional redundancy among and/or between the aforementioned T6SS effector paralogues in multiple assays. Our data indicated that Hcp and VgrG paralogues located within the T6SS cluster were more involved in forming T6SS structures, while the primary roles of Hcp-1 and VgrG-1, located outside of the T6SS cluster, were as T6SS effectors. In terms of influence on bacterial physiology, Hcp-1, but not Hcp-2, influenced bacterial motility and protease production, and in its absence, increases in both of the aforementioned activities were observed. Likewise, VgrG-1 played a major role in regulating bacterial protease production, while VgrG-2 and VgrG-3 were critical in regulating bacterial motility and biofilm formation. In an intraperitoneal murine model of infection, all Hcp and VgrG paralogues were required for optimal bacterial virulence and dissemination to mouse peripheral organs. Importantly, the observed phenotypic alterations of the T6SS mutants could be fully complemented. Taking these results together, we have further established the roles played by the two known T6SS effectors of A. hydrophila by defining their contributions to T6SS function and virulence in both in vitro and in vivo models of infection.

  13. Source/sink interactions underpin crop yield: the case for trehalose 6-phosphate/SnRK1 in improvement of wheat

    PubMed Central

    Lawlor, David W.; Paul, Matthew J.

    2014-01-01

    Considerable interest has been evoked by the analysis of the regulatory pathway in carbohydrate metabolism and cell growth involving the non-reducing disaccharide trehalose (TRE). TRE is at small concentrations in mesophytes such as Arabidopsis thaliana and Triticum aestivum, excluding a role in osmoregulation once suggested for it. Studies of TRE metabolism, and genetic modification of it, have shown a very wide and more important role of the pathway in regulation of many processes in development, growth, and photosynthesis. It has now been established that rather than TRE, it is trehalose 6-phosphate (T6P) which has such profound effects. T6P is the intermediary in TRE synthesis formed from glucose-6-phosphate and UDP-glucose, derived from sucrose, by the action of trehalose phosphate synthase. The concentration of T6P is determined both by the rate of synthesis, which depends on the sucrose concentration, and also by the rate of breakdown by trehalose-6-phosphate phosphatase which produces TRE. Changing T6P concentrations by genetically modifying the enzymes of synthesis and breakdown has altered photosynthesis, sugar metabolism, growth, and development which affect responses to, and recovery from, environmental factors. Many of the effects of T6P on metabolism and growth occur via the interaction of T6P with the SnRK1 protein kinase system. T6P inhibits the activity of SnRK1, which de-represses genes encoding proteins involved in anabolism. Consequently, a large concentration of sucrose increases T6P and thereby inhibits SnRK1, so stimulating growth of cells and their metabolic activity. The T6P/SnRK1 mechanism offers an important new view of how the distribution of assimilates to organs, such as developing grains in cereal plants, is achieved. This review briefly summarizes the factors determining, and limiting, yield of wheat (particularly mass/grain which is highly conserved) and considers how T6P/SnRK1 might function to determine grain yield and might be

  14. Evaluation of the roles played by Hcp and VgrG type 6 secretion system effectors in Aeromonas hydrophila SSU pathogenesis

    PubMed Central

    Sha, Jian; Rosenzweig, Jason A.; Kozlova, Elena V.; Wang, Shaofei; Erova, Tatiana E.; Kirtley, Michelle L.; van Lier, Christina J.

    2013-01-01

    Aeromonas hydrophila, a Gram-negative bacterium, is an emerging human pathogen equipped with both a type 3 and a type 6 secretion system (T6SS). In this study, we evaluated the roles played by paralogous T6SS effector proteins, hemolysin co-regulated proteins (Hcp-1 and -2) and valine glycine repeat G (VgrG-1, -2 and -3) protein family members in A. hydrophila SSU pathogenesis by generating various combinations of deletion mutants of the their genes. In addition to their predicted roles as structural components and effector proteins of the T6SS, our data clearly demonstrated that paralogues of Hcp and VgrG also influenced bacterial motility, protease production and biofilm formation. Surprisingly, there was limited to no observed functional redundancy among and/or between the aforementioned T6SS effector paralogues in multiple assays. Our data indicated that Hcp and VgrG paralogues located within the T6SS cluster were more involved in forming T6SS structures, while the primary roles of Hcp-1 and VgrG-1, located outside of the T6SS cluster, were as T6SS effectors. In terms of influence on bacterial physiology, Hcp-1, but not Hcp-2, influenced bacterial motility and protease production, and in its absence, increases in both of the aforementioned activities were observed. Likewise, VgrG-1 played a major role in regulating bacterial protease production, while VgrG-2 and VgrG-3 were critical in regulating bacterial motility and biofilm formation. In an intraperitoneal murine model of infection, all Hcp and VgrG paralogues were required for optimal bacterial virulence and dissemination to mouse peripheral organs. Importantly, the observed phenotypic alterations of the T6SS mutants could be fully complemented. Taking these results together, we have further established the roles played by the two known T6SS effectors of A. hydrophila by defining their contributions to T6SS function and virulence in both in vitro and in vivo models of infection. PMID:23519162

  15. Source/sink interactions underpin crop yield: the case for trehalose 6-phosphate/SnRK1 in improvement of wheat.

    PubMed

    Lawlor, David W; Paul, Matthew J

    2014-01-01

    Considerable interest has been evoked by the analysis of the regulatory pathway in carbohydrate metabolism and cell growth involving the non-reducing disaccharide trehalose (TRE). TRE is at small concentrations in mesophytes such as Arabidopsis thaliana and Triticum aestivum, excluding a role in osmoregulation once suggested for it. Studies of TRE metabolism, and genetic modification of it, have shown a very wide and more important role of the pathway in regulation of many processes in development, growth, and photosynthesis. It has now been established that rather than TRE, it is trehalose 6-phosphate (T6P) which has such profound effects. T6P is the intermediary in TRE synthesis formed from glucose-6-phosphate and UDP-glucose, derived from sucrose, by the action of trehalose phosphate synthase. The concentration of T6P is determined both by the rate of synthesis, which depends on the sucrose concentration, and also by the rate of breakdown by trehalose-6-phosphate phosphatase which produces TRE. Changing T6P concentrations by genetically modifying the enzymes of synthesis and breakdown has altered photosynthesis, sugar metabolism, growth, and development which affect responses to, and recovery from, environmental factors. Many of the effects of T6P on metabolism and growth occur via the interaction of T6P with the SnRK1 protein kinase system. T6P inhibits the activity of SnRK1, which de-represses genes encoding proteins involved in anabolism. Consequently, a large concentration of sucrose increases T6P and thereby inhibits SnRK1, so stimulating growth of cells and their metabolic activity. The T6P/SnRK1 mechanism offers an important new view of how the distribution of assimilates to organs, such as developing grains in cereal plants, is achieved. This review briefly summarizes the factors determining, and limiting, yield of wheat (particularly mass/grain which is highly conserved) and considers how T6P/SnRK1 might function to determine grain yield and might be

  16. Hcp family proteins secreted via the type VI secretion system coordinately regulate Escherichia coli K1 interaction with human brain microvascular endothelial cells.

    PubMed

    Zhou, Yan; Tao, Jing; Yu, Hao; Ni, Jinjing; Zeng, Lingbing; Teng, Qihui; Kim, Kwang Sik; Zhao, Guo-Ping; Guo, Xiaokui; Yao, Yufeng

    2012-03-01

    Type VI secretion systems (T6SSs) are involved in the pathogenicity of several gram-negative bacteria. Based on sequence analysis, we found that a cluster of Escherichia coli virulence factors (EVF) encoding a putative T6SS exists in the genome of the meningitis-causing E. coli K1 strain RS218. The T6SS-associated deletion mutants exhibited significant defects in binding to and invasion of human brain microvascular endothelial cells (HBMEC) compared with the parent strain. Hcp family proteins (the hallmark of T6SS), including Hcp1 and Hcp2, were localized in the bacterial outer membrane, but the involvements of Hcp1 and Hcp2 have been shown to differ in E. coli-HBMEC interaction. The deletion mutant of hcp2 showed defects in the bacterial binding to and invasion of HBMEC, while Hcp1 was secreted in a T6SS-dependent manner and induced actin cytoskeleton rearrangement, apoptosis, and the release of interleukin-6 (IL-6) and IL-8 in HBMEC. These findings demonstrate that the T6SS is functional in E. coli K1, and two Hcp family proteins participate in different steps of E. coli interaction with HBMEC in a coordinate manner, e.g., binding to and invasion of HBMEC, the cytokine and chemokine release followed by cytoskeleton rearrangement, and apoptosis in HBMEC. This is the first demonstration of the role of T6SS in meningitis-causing E. coli K1, and T6SS-associated Hcp family proteins are likely to contribute to the pathogenesis of E. coli meningitis.

  17. Demonstrate a Low Biochemical Oxygen Demand Aircraft Deicing Fluid

    DTIC Science & Technology

    2013-03-04

    steels . Water spray endurance time (WSET) represents the ability of the fluid to prevent ice formation when exposed to a water spray for a short...each test category. Table 2. Substrate Materials Tested per Category Test Category Substrate Material Metallic Materials 4140 Steel (AMS 6395...9Ni-4 Co steel (AMS 6523) 7075-T6 Bare Aluminum Alloy (AMS 4045H) AZ91E-T6 Cast Magnesium Alloy (AMS 4446A) C63200 Aluminum-Nickel-Bronze (AMS

  18. Durability and Damage Tolerance of Aluminum Castings

    DTIC Science & Technology

    1988-09-01

    casting alloys A357 and A201. On completion of the program, revisions to material, process, and DADT specifications will be recommended, if necessary...and the effects of process variables on the properties of A357 -T6 and A201-T7 castings were described. This second interim report covers additional...damage tolerance properties of A357 -T6 and A201-T7 produced using the specifications selected earlier [1] in Task 2 were determined. These alloys were

  19. Report on Sediment Transport Events on Shelf and Slope (STRESS) Field Season 1: Winter 1988-1989 Benthic Acoustic Stress Sensor (BASS) Component

    DTIC Science & Technology

    1989-12-01

    Analog measurements T7- - T8- - TR1- TR2- PTCH ROLL 0 minutes / 30 minutes TI-- T2-- T3-- T4-- T5--T6-- T7- - T8- - TR1- TR2- PTCH ROLL 10 minutes...40 minutes TI-- T2-- T3-- T4-- T--T6-- T7- - T8- - TRI- TR2- PTCH ROLL 20 minutes / 50 minutes 11 Table 4: BASS Tattletale Spectra Record Data Format

  20. Systematic dissection of the agrobacterium type VI secretion system reveals machinery and secreted components for subcomplex formation.

    PubMed

    Lin, Jer-Sheng; Ma, Lay-Sun; Lai, Erh-Min

    2013-01-01

    The type VI secretion system (T6SS) is widely distributed in pathogenic Proteobacteria. Sequence and structural analysis of T6SS reveals a resemblance to the T4 bacteriophage tail, in which an outer sheath structure contracts an internal tube for injecting nucleic acid into bacterial cells. However, the molecular details of how this phage tail-like T6SS structure is assembled in vivo and executed for exoprotein or effector secretion remain largely unknown. Here, we used a systematic approach to identify T6SS machinery and secreted components and investigate the interaction among the putative sheath and tube components of Agrobacterium tumefaciens. We showed that 14 T6SS components play essential roles in the secretion of the T6SS hallmark exoprotein Hcp. In addition, we discovered a novel T6SS exoprotein, Atu4347, that is dispensable for Hcp secretion. Interestingly, Atu4347 and the putative tube components, Hcp and VgrG, are mainly localized in the cytoplasm but also detected on the bacterial surface. Atu4342 (TssB) and Atu4341 (TssC41) interact with and stabilize each other, which suggests that they are functional orthologs of the sheath components TssB (VipA) and TssC (VipB), respectively. Importantly, TssB interacts directly with the three exoproteins (Hcp, VgrG, and Atu4347), in which Hcp also interacts directly with VgrG-1 on co-purification from Escherichia coli. Further co-immunoprecipitation and pulldown assays revealed these subcomplex(es) in A. tumefaciens and thereby support T6SS functioning as a contractile phage tail-like structure.

  1. Fatigue Performance of Fluidized Bed Heat Treated 319 Alloy Diesel Cylinder Heads

    NASA Astrophysics Data System (ADS)

    Chaudhury, Sujoy K.; Apelian, Diran; Meyer, Philippe; Massinon, Denis; Morichon, Julien

    2015-07-01

    Effects of various heat treatment tempers on fatigue performance of 319 alloy diesel cylinder heads were investigated. Castings were heat treated to T5, T6, and T7 tempers. Castings were solution heat treated and quenched using fluidized beds and aged using both conventional air convective furnace and fluidized bed for T6 and T7 tempers; while they were aged after casting for T5 temper using conventional furnace. Fatigue tests were performed at 373 K (100 °C) and stress ratio equal to -1. Results show that heat treatment has significant effect on the fatigue behavior of 319 alloy. The fatigue strength of T6 tempered 319 alloy is greater than T5 and T7 treatments. Weibull analysis shows that the Weibull modulus and characteristic fatigue life of castings treated (using conventional forced air circulation electrical resistance furnace) to T6 and T7 tempers are greater than T5 temper. This implies that castings treated to T6 and T7 tempers have greater reliability vis-à-vis T5 temper. Fractographic analyses reveal three distinct regions. These are: (I) crack initiation region from the surface, (II) crack propagation region, and (III) catastrophic or monotonic failure region. The relative size of the crack propagation region in T6 and T7 treated samples is greater than T5 treated samples. In general, the monotonic failure region shows typical dimple morphology, which implies significant plastic deformation prior to failure. Dimples on the fractured surface of T5 treated alloy are relatively more faceted than those treated to T6 and T7 tempers. This implies that the 319 alloy treated to T6 and T7 tempers underwent higher degree of plasticity prior to failure than that in the T5 condition.

  2. Manganese scavenging and oxidative stress response mediated by type VI secretion system in Burkholderia thailandensis

    PubMed Central

    Si, Meiru; Zhao, Chao; Burkinshaw, Brianne; Zhang, Bing; Wei, Dawei; Wang, Yao; Dong, Tao G.; Shen, Xihui

    2017-01-01

    Type VI secretion system (T6SS) is a versatile protein export machinery widely distributed in Gram-negative bacteria. Known to translocate protein substrates to eukaryotic and prokaryotic target cells to cause cellular damage, the T6SS has been primarily recognized as a contact-dependent bacterial weapon for microbe–host and microbial interspecies competition. Here we report contact-independent functions of the T6SS for metal acquisition, bacteria competition, and resistance to oxidative stress. We demonstrate that the T6SS-4 in Burkholderia thailandensis is critical for survival under oxidative stress and is regulated by OxyR, a conserved oxidative stress regulator. The T6SS-4 is important for intracellular accumulation of manganese (Mn2+) under oxidative stress. Next, we identified a T6SS-4–dependent Mn2+-binding effector TseM, and its interacting partner MnoT, a Mn2+-specific TonB-dependent outer membrane transporter. Similar to the T6SS-4 genes, expression of mnoT is regulated by OxyR and is induced under oxidative stress and low Mn2+ conditions. Both TseM and MnoT are required for efficient uptake of Mn2+ across the outer membrane under Mn2+-limited and -oxidative stress conditions. The TseM–MnoT-mediated active Mn2+ transport system is also involved in contact-independent bacteria–bacteria competition and bacterial virulence. This finding provides a perspective for understanding the mechanisms of metal ion uptake and the roles of T6SS in bacteria–bacteria competition. PMID:28242693

  3. Integrated Hypersonic Aerothermoelastic Methodology for Trans Atmospheric Vehicle (TAV)/Thermal Protection System (TPS) Structural Design and Optimization. Thermal Protection System Optimization (TPSOPT)

    DTIC Science & Technology

    2006-01-01

    thickness parts of the five layers are 221 (HRSI COATING), 103 ( ALUMINUM 7075-T6), 114 (INCONEL 617), and 101 ( ALUMINUM 2024-T4). This set of thermal...RTV-560), and 101 ( ALUMINUM 2024-T4). This set of thermal structures is defined for patches 3-8 and 10-14. 2-10 2.5 Output Information The...0.12000 in. ALUMINUM 7075-T6 i ------------------------------------------------------------ i i i i

  4. Bacteroides fragilis type VI secretion systems use novel effector and immunity proteins to antagonize human gut Bacteroidales species.

    PubMed

    Chatzidaki-Livanis, Maria; Geva-Zatorsky, Naama; Comstock, Laurie E

    2016-03-29

    Type VI secretion systems (T6SSs) are multiprotein complexes best studied in Gram-negative pathogens where they have been shown to inhibit or kill prokaryotic or eukaryotic cells and are often important for virulence. We recently showed that T6SS loci are also widespread in symbiotic human gut bacteria of the order Bacteroidales, and that these T6SS loci segregate into three distinct genetic architectures (GA). GA1 and GA2 loci are present on conserved integrative conjugative elements (ICE) and are transferred and shared among diverse human gut Bacteroidales species. GA3 loci are not contained on conserved ICE and are confined to Bacteroides fragilis Unlike GA1 and GA2 T6SS loci, most GA3 loci do not encode identifiable effector and immunity proteins. Here, we studied GA3 T6SSs and show that they antagonize most human gut Bacteroidales strains analyzed, except for B. fragilis strains with the same T6SS locus. A combination of mutation analyses,trans-protection analyses, and in vitro competition assays, allowed us to identify novel effector and immunity proteins of GA3 loci. These proteins are not orthologous to known proteins, do not contain identified motifs, and most have numerous predicted transmembrane domains. Because the genes encoding effector and immunity proteins are contained in two variable regions of GA3 loci, GA3 T6SSs of the species B. fragilis are likely the source of numerous novel effector and immunity proteins. Importantly, we show that the GA3 T6SS of strain 638R is functional in the mammalian gut and provides a competitive advantage to this organism.

  5. Bacteroides fragilis type VI secretion systems use novel effector and immunity proteins to antagonize human gut Bacteroidales species

    PubMed Central

    Chatzidaki-Livanis, Maria; Geva-Zatorsky, Naama; Comstock, Laurie E.

    2016-01-01

    Type VI secretion systems (T6SSs) are multiprotein complexes best studied in Gram-negative pathogens where they have been shown to inhibit or kill prokaryotic or eukaryotic cells and are often important for virulence. We recently showed that T6SS loci are also widespread in symbiotic human gut bacteria of the order Bacteroidales, and that these T6SS loci segregate into three distinct genetic architectures (GA). GA1 and GA2 loci are present on conserved integrative conjugative elements (ICE) and are transferred and shared among diverse human gut Bacteroidales species. GA3 loci are not contained on conserved ICE and are confined to Bacteroides fragilis. Unlike GA1 and GA2 T6SS loci, most GA3 loci do not encode identifiable effector and immunity proteins. Here, we studied GA3 T6SSs and show that they antagonize most human gut Bacteroidales strains analyzed, except for B. fragilis strains with the same T6SS locus. A combination of mutation analyses, trans-protection analyses, and in vitro competition assays, allowed us to identify novel effector and immunity proteins of GA3 loci. These proteins are not orthologous to known proteins, do not contain identified motifs, and most have numerous predicted transmembrane domains. Because the genes encoding effector and immunity proteins are contained in two variable regions of GA3 loci, GA3 T6SSs of the species B. fragilis are likely the source of numerous novel effector and immunity proteins. Importantly, we show that the GA3 T6SS of strain 638R is functional in the mammalian gut and provides a competitive advantage to this organism. PMID:26951680

  6. Enhancement of toxicity and enzyme-repressing activity of p-dioxane by chlorination: stereoselective effects.

    PubMed

    Woo, Y T; Neuburger, B J; Arcos, J C; Argus, M F; Nishiyama, K; Griffin, G W

    1980-01-01

    The acute toxicity of p-dioxane may be enhanced up to 1000-fold by chlorination of the compound. The effect was stereoselective. Of the stereoisomers tested, tetrachloro-p-dioxane, isomer I (2r, 3t, 5t, 6c) was over 80 times more toxic than isomer II (2r, 3c, 5t, 6t). The latter compound was also a potent repressor of hepatic dimethylnitrosamine-demethylase I (DMN-d) and aryl hydrocarbon hydroxylase (AHH).

  7. Thermomechanical Processing of Al Alloy 2090 for Grain Refinement and Superplasticity.

    DTIC Science & Technology

    1987-12-01

    introduced as a replacement for the 7075 -T6 alloy. The ouroose of this research is to investigate the applicability of thermmechanical processing...effect of the processing on microstructural evolution and the super- cla~tic behavior of this material. ~ - 20 DiSTRiBLTrON ’AVAILABILITY OF ABSTRAC’ 2...percent lower density and 10 percent ".>iqher elastic modulus, has been introduced as a ronlacment for the 7075 -T6 alloy. The purpose of this research is

  8. Corrosion and Fatigue Study of JSTARS Aircraft. Volume 1

    DTIC Science & Technology

    1997-04-01

    are made of 7075- T6 aluminum Corrosion resistant steel borders are used around door and window cutouts, The tail skin panels aft of BS 1440 are made...and vertical stabilizers utilize similar materials. The leading edge is made of 7075- T6 aluminum . The skin panels are made of either 2024-T3 or 2024...2024 - T3 aluminum planks removes material in the fastener holes and develops initiation sites for fatigue cracking. Corrosion damage and material loss

  9. Assessment of Accelerated Tests Compared to Beachfront Test and Proposed Evaluation Method

    DTIC Science & Technology

    2009-09-03

    corrosion tests to beachfront test NCAP Data Assessment Data set includes: – 4 aluminum alloys: 2024, 7075, 2219 , 5083 – 9 conversion coatings...2024-T3 Alodine 1600 2024-T3 TCP-IC 7075- T6 Alodine 1600 7075- T6 TCP-IC 18 Months Exposure at KSC 20X view of surface As is Cleaned Unpainted Corrosion ...Certification Program (ESTCP) funded project entitled “Non-Chromate Aluminum Pretreatments” (NCAP) – Funding began in 2000, ended 2004 for Phase I

  10. Survey - Monomethylhydrazine Propellant/Material Compatibility

    DTIC Science & Technology

    1977-07-01

    Alloys Martin Marietta (Refs.l0, 20) rated 1100-0, 2014- T6 , and 2219 -T87 compatible with MMH for 300 hours at 135’C, no corrosion or MMH decomposition...Ti, 6061- T6 Al. The aluminum alloys show no susceptibility. The order of decreasing stress corrosion cracking promotion for the fuels is hydrazine...decomposition of propellant and no noticeable corrosion of the metal surfaces. The metals were aluminum alloys 1100, 2014, 6061; corrosion -resistant steels

  11. Manganese scavenging and oxidative stress response mediated by type VI secretion system in Burkholderia thailandensis.

    PubMed

    Si, Meiru; Zhao, Chao; Burkinshaw, Brianne; Zhang, Bing; Wei, Dawei; Wang, Yao; Dong, Tao G; Shen, Xihui

    2017-03-14

    Type VI secretion system (T6SS) is a versatile protein export machinery widely distributed in Gram-negative bacteria. Known to translocate protein substrates to eukaryotic and prokaryotic target cells to cause cellular damage, the T6SS has been primarily recognized as a contact-dependent bacterial weapon for microbe-host and microbial interspecies competition. Here we report contact-independent functions of the T6SS for metal acquisition, bacteria competition, and resistance to oxidative stress. We demonstrate that the T6SS-4 in Burkholderia thailandensis is critical for survival under oxidative stress and is regulated by OxyR, a conserved oxidative stress regulator. The T6SS-4 is important for intracellular accumulation of manganese (Mn(2+)) under oxidative stress. Next, we identified a T6SS-4-dependent Mn(2+)-binding effector TseM, and its interacting partner MnoT, a Mn(2+)-specific TonB-dependent outer membrane transporter. Similar to the T6SS-4 genes, expression of mnoT is regulated by OxyR and is induced under oxidative stress and low Mn(2+) conditions. Both TseM and MnoT are required for efficient uptake of Mn(2+) across the outer membrane under Mn(2+)-limited and -oxidative stress conditions. The TseM-MnoT-mediated active Mn(2+) transport system is also involved in contact-independent bacteria-bacteria competition and bacterial virulence. This finding provides a perspective for understanding the mechanisms of metal ion uptake and the roles of T6SS in bacteria-bacteria competition.

  12. Polypeptide N-acetylgalactosaminyltransferase 6 expression in pancreatic cancer is an independent prognostic factor indicating better overall survival

    PubMed Central

    Li, Z; Yamada, S; Inenaga, S; Imamura, T; Wu, Y; Wang, K-Y; Shimajiri, S; Nakano, R; Izumi, H; Kohno, K; Sasaguri, Y

    2011-01-01

    Background: The family of polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts) is responsible for the altered glycosylation in cancer. The purpose of our study was to investigate the clinical significance of two isoforms, GalNAc-T6 and -T3, and their correlation with the prognosis of pancreatic cancer. Methods: Immunohistochemistry was used to analyse GalNAc-T6 and -T3 expressions in 70 clinicopathologically characterised pancreatic cancer cases. Results: Positive expressions of GalNAc-T6 and -T3 were immunohistochemically identified in 51% (36 of 70) and in 77% (54 of 70) of patients, respectively. A close relationship was noted between GalNAc-T6 positive expression and pathological well/moderate differentiated type (P=0.001), small tumour size (P=0.044), absence of vascular invasion (P=0.009), and low stage of the American Joint Committee on Cancer systems (P=0.043). The expression of GalNAc-T3 significantly correlated with good differentiation (P=0.001), but not with other clinicopathologic features. Furthermore, univariate and multivariate analyses revealed that GalNAc-T6 expression was an independent prognosis indicator for the disease, whereas GalNAc-T3 expression had no impact on clinical outcome, even though 33 of 36 GalNAc-T6-positive cases also had a positive expression of GalNAc-T3 (P=0.001, r=0.356). Conclusion: Both GalNAc-T6 and -T3 expressions correlated significantly with tumour differentiation, whereas only GalNAc-T6 expression predicted prognosis in pancreatic cancer. PMID:21587259

  13. A Study of Notch Fatigue. Part III. Plastic Stress Analysis of Notches.

    DTIC Science & Technology

    1981-09-01

    strain expressions reflecting the calibrated parameters of the polariscope in the Aeronautical Engineering laboratory at NPS are( 4 ) e.4O= 3 ~j-7(Ii...stress and strain values for 7075-T6 aluminum were obtained via finite elements and reflection photoelasticity in the plastic zone, and residual stress...strain values for 7075-T6 aluminum were obtained via finite elements and reflection photoelasticity in the plastic zone, and residual stress and

  14. Expression, secretion and bactericidal activity of type VI secretion system in Vibrio anguillarum.

    PubMed

    Tang, Lei; Yue, Shu; Li, Gui-Yang; Li, Jie; Wang, Xiao-Ran; Li, Shu-Fang; Mo, Zhao-Lan

    2016-10-01

    The type VI secretion system (T6SS) was recently shown to modulate quorum sensing and the stress response in Vibrio anguillarum serotype O1 strain NB10. It is not known whether there is a functionally active T6SS in other serotypes of V. anguillarum. Here, homologues to T6SS cluster VtsEFGH and hemolysin-coregulated protein (Hcp)-encoding genes were found to be prevalent and conserved in clinical isolates of V. anguillarum from fish, including four O1 and five non-O1 serotype strains. Unexpectedly, only the non-O1 serotype strains expressed VtsEFGH and Hcp under laboratory and marine-like conditions, in contrast to the serotype O1 strains. This suggested that the V. anguillarum non-O1 serotype strains tested have constitutive expression of T6SS. Examination of a representative non-O1 strain, MHK3, showed that Hcp production was growth phase dependent and that maximum Hcp production was observed in the exponential growth phase. Moreover, Hcp production by MHK3 was most active under warm marine-like conditions. Further examination revealed a correlation of the constitutive expression of T6SS with bactericidal activity against Escherichia coli and Edwardsiella tarda. The work presented here suggests that the constitutive expression of T6SS provides V. anguillarum with advantage in microbial competition in marine environments.

  15. The Vibrio cholerae type VI secretion system displays antimicrobial properties.

    PubMed

    MacIntyre, Dana L; Miyata, Sarah T; Kitaoka, Maya; Pukatzki, Stefan

    2010-11-09

    The acute diarrheal disease cholera is caused by the marine bacterium Vibrio cholerae. A type VI secretion system (T6SS), which is structurally similar to the bacteriophage cell-puncturing device, has been recently identified in V. cholerae and is used by this organism to confer virulence toward phagocytic eukaryotes, such as J774 murine macrophages and Dictyostelium discoideum. We tested the interbacterial virulence of V. cholerae strain V52, an O37 serogroup with a constitutively active T6SS. V52 was found to be highly virulent toward multiple Gram-negative bacteria, including Escherichia coli and Salmonella Typhimurium, and caused up to a 100,000-fold reduction in E. coli survival. Because the T6SS-deficient mutants V52ΔvasK and V52ΔvasH showed toxicity defects that could be complemented, virulence displayed by V. cholerae depends on a functional T6SS. V. cholerae V52 and strains of the O1 serogroup were resistant to V52, suggesting that V. cholerae has acquired immunity independently of its serogroup. We hypothesize that the T6SS, in addition to targeting eukaryotic host cells, confers toxicity toward other bacteria, providing a means of interspecies competition to enhance environmental survival. Thus, the V. cholerae T6SS may enhance the survival of V. cholerae in its aquatic ecosystem during the transmission of cholera and between epidemics.

  16. Shifts in microbial community composition and function in the acidification of a lead/zinc mine tailings.

    PubMed

    Chen, Lin-Xing; Li, Jin-Tian; Chen, Ya-Ting; Huang, Li-Nan; Hua, Zheng-Shuang; Hu, Min; Shu, Wen-Sheng

    2013-09-01

    In an attempt to link the microbial community composition and function in mine tailings to the generation of acid mine drainage, we simultaneously explored the geochemistry and microbiology of six tailings collected from a lead/zinc mine, i.e. primary tailings (T1), slightly acidic tailings (T2), extremely acidic tailings (T3, T4 and T5) and orange-coloured oxidized tailings (T6). Geochemical results showed that the six tailings (from T1 to T6) likely represented sequential stages of the acidification process of the mine tailings. 16S rRNA pyrosequencing revealed a contrasting microbial composition between the six tailings: Proteobacteria-related sequences dominated T1-T3 with relative abundance ranging from 56 to 93%, whereas Ferroplasma-related sequences dominated T4-T6 with relative abundance ranging from 28 to 58%. Furthermore, metagenomic analysis of the microbial communities of T2 and T6 indicated that the genes encoding key enzymes for microbial carbon fixation, nitrogen fixation and sulfur oxidation in T2 were largely from Thiobacillus and Acidithiobacillus, Methylococcus capsulatus, and Thiobacillus denitrificans respectively; while those in T6 were mostly identified in Acidithiobacillus and Leptospirillum, Acidithiobacillus and Leptospirillum, and Acidithiobacillus respectively. The microbial communities in T2 and T6 harboured more genes suggesting diverse metabolic capacities for sulfur oxidation/heavy metal detoxification and tolerating low pH respectively. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

  17. Structure and specificity of the Type VI secretion system ClpV-TssC interaction in enteroaggregative Escherichia coli

    PubMed Central

    Douzi, Badreddine; Brunet, Yannick R.; Spinelli, Silvia; Lensi, Valentine; Legrand, Pierre; Blangy, Stéphanie; Kumar, Anant; Journet, Laure; Cascales, Eric; Cambillau, Christian

    2016-01-01

    The Type VI secretion system (T6SS) is a versatile machine that delivers toxins into either eukaryotic or bacterial cells. It thus represents a key player in bacterial pathogenesis and inter-bacterial competition. Schematically, the T6SS can be viewed as a contractile tail structure anchored to the cell envelope. The contraction of the tail sheath propels the inner tube loaded with effectors towards the target cell. The components of the contracted tail sheath are then recycled by the ClpV AAA+ ATPase for a new cycle of tail elongation. The T6SS is widespread in Gram-negative bacteria and most of their genomes carry several copies of T6SS gene clusters, which might be activated in different conditions. Here, we show that the ClpV ATPases encoded within the two T6SS gene clusters of enteroaggregative Escherichia coli are not interchangeable and specifically participate to the activity of their cognate T6SS. Here we show that this specificity is dictated by interaction between the ClpV N-terminal domains and the N-terminal helices of their cognate TssC1 proteins. We also present the crystal structure of the ClpV1 N-terminal domain, alone or in complex with the TssC1 N-terminal peptide, highlighting the commonalities and diversities in the recruitment of ClpV to contracted sheaths. PMID:27698444

  18. Remodelling of VipA/VipB tubules by ClpV-mediated threading is crucial for type VI protein secretion.

    PubMed

    Bönemann, Gabriele; Pietrosiuk, Aleksandra; Diemand, Alexander; Zentgraf, Hanswalter; Mogk, Axel

    2009-02-18

    The recently identified type VI secretion systems (T6SS) have a crucial function in the virulence of various proteobacteria, including the human pathogen Vibrio cholerae. T6SS are encoded by a conserved gene cluster comprising approximately 15 open reading frames, mediating the appearance of Hcp and VgrG proteins in cell culture supernatants. Here, we analysed the function of the V. cholerae T6SS member ClpV, a specialized AAA+ protein. ClpV is crucial for a functional T6SS and interacts through its N-terminal domain with the VipA/VipB complex that is composed of two conserved and essential members of T6SS. Transferring ClpV substrate specificity to a distinct AAA+ protein involved in proteolysis caused degradation of VipA but not Hcp or VgrG2, suggesting that VipA rather than Hcp/VgrG2 functions as a primary ClpV substrate. Strikingly, VipA/VipB form tubular, cogwheel-like structures that are converted by a threading activity of ClpV into small complexes. ClpV-mediated remodelling of VipA/VipB tubules represents a crucial step in T6S, illuminating an unexpected role of an ATPase component in protein secretion.

  19. Chelation of Membrane-Bound Cations by Extracellular DNA Activates the Type VI Secretion System in Pseudomonas aeruginosa

    PubMed Central

    Wilton, Mike; Wong, Megan J. Q.; Tang, Le; Liang, Xiaoye; Moore, Richard; Parkins, Michael D.; Lewenza, Shawn

    2016-01-01

    Pseudomonas aeruginosa employs its type VI secretion system (T6SS) as a highly effective and tightly regulated weapon to deliver toxic molecules to target cells. T6SS-secreted proteins of P. aeruginosa can be detected in the sputum of cystic fibrosis (CF) patients, who typically present a chronic and polymicrobial lung infection. However, the mechanism of T6SS activation in the CF lung is not fully understood. Here we demonstrate that extracellular DNA (eDNA), abundant within the CF airways, stimulates the dynamics of the H1-T6SS cluster apparatus in Pseudomonas aeruginosa PAO1. Addition of Mg2+ or DNase with eDNA abolished such activation, while treatment with EDTA mimicked the eDNA effect, suggesting that the eDNA-mediated effect is due to chelation of outer membrane-bound cations. DNA-activated H1-T6SS enables P. aeruginosa to nonselectively attack neighboring species regardless of whether or not it was provoked. Because of the importance of the T6SS in interspecies interactions and the prevalence of eDNA in the environments that P. aeruginosa inhabits, our report reveals an important adaptation strategy that likely contributes to the competitive fitness of P. aeruginosa in polymicrobial communities. PMID:27271742

  20. Chelation of Membrane-Bound Cations by Extracellular DNA Activates the Type VI Secretion System in Pseudomonas aeruginosa.

    PubMed

    Wilton, Mike; Wong, Megan J Q; Tang, Le; Liang, Xiaoye; Moore, Richard; Parkins, Michael D; Lewenza, Shawn; Dong, Tao G

    2016-08-01

    Pseudomonas aeruginosa employs its type VI secretion system (T6SS) as a highly effective and tightly regulated weapon to deliver toxic molecules to target cells. T6SS-secreted proteins of P. aeruginosa can be detected in the sputum of cystic fibrosis (CF) patients, who typically present a chronic and polymicrobial lung infection. However, the mechanism of T6SS activation in the CF lung is not fully understood. Here we demonstrate that extracellular DNA (eDNA), abundant within the CF airways, stimulates the dynamics of the H1-T6SS cluster apparatus in Pseudomonas aeruginosa PAO1. Addition of Mg(2+) or DNase with eDNA abolished such activation, while treatment with EDTA mimicked the eDNA effect, suggesting that the eDNA-mediated effect is due to chelation of outer membrane-bound cations. DNA-activated H1-T6SS enables P. aeruginosa to nonselectively attack neighboring species regardless of whether or not it was provoked. Because of the importance of the T6SS in interspecies interactions and the prevalence of eDNA in the environments that P. aeruginosa inhabits, our report reveals an important adaptation strategy that likely contributes to the competitive fitness of P. aeruginosa in polymicrobial communities.

  1. The Levels of a Universally Conserved tRNA Modification Regulate Cell Growth*

    PubMed Central

    Rojas-Benitez, Diego; Thiaville, Patrick C.; de Crécy-Lagard, Valérie; Glavic, Alvaro

    2015-01-01

    N6-Threonylcarbamoyl-adenosine (t6A) is a universal modification occurring at position 37 in nearly all tRNAs that decode A-starting codons, including the eukaryotic initiator tRNA (tRNAiMet). Yeast lacking central components of the t6A synthesis machinery, such as Tcs3p (Kae1p) or Tcs5p (Bud32p), show slow-growth phenotypes. In the present work, we show that loss of the Drosophila tcs3 homolog also leads to a severe reduction in size and demonstrate, for the first time in a non-microbe, that Tcs3 is required for t6A synthesis. In Drosophila and in mammals, tRNAiMet is a limiting factor for cell and animal growth. We report that the t6A-modified form of tRNAiMet is the actual limiting factor. We show that changing the proportion of t6A-modified tRNAiMet, by expression of an un-modifiable tRNAiMet or changing the levels of Tcs3, regulate target of rapamycin (TOR) kinase activity and influences cell and animal growth in vivo. These findings reveal an unprecedented relationship between the translation machinery and TOR, where translation efficiency, limited by the availability of t6A-modified tRNA, determines growth potential in eukaryotic cells. PMID:26063805

  2. Polypeptide N-acetylgalactosaminyltransferase-6 expression independently predicts poor overall survival in patients with lung adenocarcinoma after curative resection

    PubMed Central

    Li, Zhi; Yamada, Sohsuke; Wu, Ying; Wang, Ke-Yong; Liu, Yun-Peng; Uramoto, Hidetaka; Kohno, Kimitoshi; Sasaguri, Yasuyuki

    2016-01-01

    Background Polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts) are important glycosyltransferases in cancer, but the clinical role of its individual isoforms is unclear. We investigated the clinical significance and survival relevance of one isoform, GalNAc-T6 in lung adenocarcinoma after curative resection. Results GalNAc-T6 was identified in 27.8% (55/198) of patients, and statistically indicated advanced TNM stage (P = 0.069). Multivariate analysis showed GalNAc-T6 to be an independent predictor for reduced overall survival of patients (P = 0.027), and the result was confirmed with bootstraping techniques, and on line “Kaplan-Meier Plotter” and “SurvExpress” database analysis, respectively. Moreover, ROC curve demonstrated that GalNAc-T6 expression significantly improved the accuracy of survival prediction. Methods With 198 paraffin-embedded tumor samples from lung adenocarcinoma patients, GalNAc-T6 expression was immunohistochemically assessed for the association with clinicopathological parameters. The prognostic significance was evaluated by Cox proportional hazards regression analysis with 1000 bootstraping. “Kaplan-Meier Plotter”, “SurvExpress” database analysis, and receiver-operating characteristic (ROC) curve were performed to provide further validation. Conclusions GalNAc-T6 expression correlated significantly with advanced TNM stage, and independently predicted worse OS for lung adenocarcinoma. PMID:27276675

  3. Type VI secretion system: secretion by a contractile nanomachine

    PubMed Central

    Basler, Marek

    2015-01-01

    The type VI secretion systems (T6SS) are present in about a quarter of all Gram-negative bacteria. Several key components of T6SS are evolutionarily related to components of contractile nanomachines such as phages and R-type pyocins. The T6SS assembly is initiated by formation of a membrane complex that binds a phage-like baseplate with a sharp spike, and this is followed by polymerization of a long rigid inner tube and an outer contractile sheath. Effectors are preloaded onto the spike or into the tube during the assembly by various mechanisms. Contraction of the sheath releases an unprecedented amount of energy, which is used to thrust the spike and tube with the associated effectors out of the effector cell and across membranes of both bacterial and eukaryotic target cells. Subunits of the contracted sheath are recycled by T6SS-specific unfoldase to allow for a new round of assembly. Live-cell imaging has shown that the assembly is highly dynamic and its subcellular localization is in certain bacteria regulated with a remarkable precision. Through the action of effectors, T6SS has mainly been shown to contribute to pathogenicity and competition between bacteria. This review summarizes the knowledge that has contributed to our current understanding of T6SS mode of action. PMID:26370934

  4. Satellite tobacco mosaic virus sequence variants with only five Nucleotide differences can interfere with each other in a cross protection-like phenomenon in plants

    USGS Publications Warehouse

    Kurath, Gael; Dodds, J. Allan

    1994-01-01

    The type strain of satellite tobacco mosaic virus (STMV) contains two major variants, designated type 5 (T5) and type 6 (T6), which can be easily distinguished by RNase protection analyses. Clones containing cDNA of representative T5 and T6 STMV genomes have only five single-base differences in the entire 1059-nucleotide genome, and RNA transcribed from each clone is highly infectious when inoculated onto tobacco plants. The different RNase protection assay patterns can be used as genetic markers to identify individual STMV variants and to follow the interactions of variants and their progeny during coinfections in plants. The study described here investigated the effects of coinoculation and various delayed inoculations of T5 and T6 variants on the composition of the progeny STMV populations in systemically infected tobacco tissues. When T5 and T6 STMV RNAs were coinoculated or inoculated with 1-hr delays, the progeny from individual plants most often contained a mixture of T5 and T6 genomes. However, when there was a 24-hr delay between inoculations, the balance of T5 and T6 components in the progeny populations shifted toward predominance of the first variant inoculated. With delays of 3 or 7 days only the first variant was evident in the progeny populations, indicating that established replication of one STMV variant interferes with replication of another in a manner similar to the cross protection phenomenon.

  5. Methanogenic activity inhibition by increasing the linear alkylbenzene sulfonate (LAS) concentration.

    PubMed

    Souza, Luiza F C; Florencio, Lourdinha; Gavazza, Savia; Kato, Mario T

    2016-07-02

    The effect of the initial concentration of linear alkylbenzene sulfonate (LAS) on specific methanogenic activity (SMA) was investigated in this work. Six anaerobic flasks reactors with 1 L of total volume were inoculated with anaerobic sludge (2 g VSS L(-1)). The reactors were assayed for 42 days, and fed with volatile fatty acids, nutrients, and LAS. The initial LAS concentrations were 0, 10, 30, 50, 75, and 100 mg L(-1) for the treatment flasks T1 (control), T2, T3, T4, T5, and T6, respectively. When compared with T1, T2 exhibited a 30% reduction in maximum SMA and total methane production (TMP). In treatment T3 through T6, the reductions were 44-97% (T3-T6) for SMA, and 30-90% (T3-T6) for TMP. Total LAS removal increased following the increase in the initial LAS concentration (from 36% at T1 to 76% at T6), primarily due to the high degree of sludge adsorption. LAS biodegradation also occurred (32% in all treatments), although this was most likely associated with the formation of non-methane intermediates. Greater removal by adsorption was observed in long-chain homologues, when compared to short-chain homologues (C13 > C10), whereas the opposite occurred for biodegradation (C10 > C13). The C13 homologue was adsorbed to a great extent (in mass) in T4, T5 and T6, and may also have inhibited methane formation in these treatments.

  6. A multidrug resistance plasmid contains the molecular switch for type VI secretion in Acinetobacter baumannii

    PubMed Central

    Weber, Brent S.; Ly, Pek Man; Irwin, Joshua N.; Pukatzki, Stefan; Feldman, Mario F.

    2015-01-01

    Infections with Acinetobacter baumannii, one of the most troublesome and least studied multidrug-resistant superbugs, are increasing at alarming rates. A. baumannii encodes a type VI secretion system (T6SS), an antibacterial apparatus of Gram-negative bacteria used to kill competitors. Expression of the T6SS varies among different strains of A. baumannii, for which the regulatory mechanisms are unknown. Here, we show that several multidrug-resistant strains of A. baumannii harbor a large, self-transmissible resistance plasmid that carries the negative regulators for T6SS. T6SS activity is silenced in plasmid-containing, antibiotic-resistant cells, while part of the population undergoes frequent plasmid loss and activation of the T6SS. This activation results in T6SS-mediated killing of competing bacteria but renders A. baumannii susceptible to antibiotics. Our data show that a plasmid that has evolved to harbor antibiotic resistance genes plays a role in the differentiation of cells specialized in the elimination of competing bacteria. PMID:26170289

  7. Anticytoproliferative effect of Vitamin C on rat hepatic stellate cell

    PubMed Central

    Su, Min; Chao, Guo; Liang, Minqing; Song, Jianhua; Wu, Ka

    2016-01-01

    This study was conducted to investigate the potential therapeutical benefit of Vitamin (VC), a potent antioxidant, on suppressing proliferation of immortalized rat liver stellate cell line (HSC-T6) in vitro, and to discuss the underlying mechanism. HSC-T6 was co-treated with different concentrations of VC (50, 100, 200 μmol/L) on designed time points. Then, cell viability was assessed by using MTT analysis, and the changes of cytomorphology was observed with apoptosis-specific TUNEL and immunohistochemical stains, as well as the intracellular target genes was determined by using RT-PCR, respectively. As the outcomes, VC-treated HSC-T6 showed significantly inhibited cell growth in a dose-dependent manner when compared to the vehicle control. Cytologically, VC increased TUNEL-labeled positive cells in cultured HSC-T6, which the cell count was greater than vehicle control. Meanwhile, VC-treated HSC-T6 showed elevated immunoreactive for TGF-β1-labeled cells. Moreover, VC contributed to down-regulated expressions of intracellular c-myc, cyclin D1, mTOR mRNAs in HSC-T6. Collectively, these preliminary findings have demonstrated that VC-mediated anti-proliferative effect on HSCs is involved in molecular mechanisms of promoting apoptosis and blocking endogenous collagenation. PMID:27398165

  8. Identifying Beneficial Qualities of Trichoderma parareesei for Plants

    PubMed Central

    Rubio, M. Belén; Quijada, Narciso M.; Pérez, Esclaudys; Domínguez, Sara; Hermosa, Rosa

    2014-01-01

    Trichoderma parareesei and Trichoderma reesei (teleomorph Hypocrea jecorina) produce cellulases and xylanases of industrial interest. Here, the anamorphic strain T6 (formerly T. reesei) has been identified as T. parareesei, showing biocontrol potential against fungal and oomycete phytopathogens and enhanced hyphal growth in the presence of tomato exudates or plant cell wall polymers in in vitro assays. A Trichoderma microarray was used to examine the transcriptomic changes in T6 at 20 h of interaction with tomato plants. Out of a total 34,138 Trichoderma probe sets deposited on the microarray, 250 showed a significant change of at least 2-fold in expression in the presence of tomato plants, with most of them being downregulated. T. parareesei T6 exerted beneficial effects on tomato plants in terms of seedling lateral root development, and in adult plants it improved defense against Botrytis cinerea and growth promotion under salt stress. Time course expression patterns (0 to 6 days) observed for defense-related genes suggest that T6 was able to prime defense responses in the tomato plants against biotic and abiotic stresses. Such responses undulated, with a maximum upregulation of the jasmonic acid (JA)/ethylene (ET)-related LOX1 and EIN2 genes and the salt tolerance SOS1 gene at 24 h and that of the salicylic acid (SA)-related PR-1 gene at 48 h after T6 inoculation. Our study demonstrates that the T. parareesei T6-tomato interaction is beneficial to both partners. PMID:24413597

  9. Gene Expression of Type VI Secretion System Associated with Environmental Survival in Acidovorax avenae subsp. avenae by Principle Component Analysis.

    PubMed

    Cui, Zhouqi; Jin, Guoqiang; Li, Bin; Kakar, Kaleem Ullah; Ojaghian, Mohammad Reza; Wang, Yangli; Xie, Guanlin; Sun, Guochang

    2015-09-11

    Valine glycine repeat G (VgrG) proteins are regarded as one of two effectors of Type VI secretion system (T6SS) which is a complex multi-component secretion system. In this study, potential biological roles of T6SS structural and VgrG genes in a rice bacterial pathogen, Acidovorax avenae subsp. avenae (Aaa) RS-1, were evaluated under seven stress conditions using principle component analysis of gene expression. The results showed that growth of the pathogen was reduced by H₂O₂ and paraquat-induced oxidative stress, high salt, low temperature, and vgrG mutation, compared to the control. However, pathogen growth was unaffected by co-culture with a rice rhizobacterium Burkholderia seminalis R456. In addition, expression of 14 T6SS structural and eight vgrG genes was significantly changed under seven conditions. Among different stress conditions, high salt, and low temperature showed a higher effect on the expression of T6SS gene compared with host infection and other environmental conditions. As a first report, this study revealed an association of T6SS gene expression of the pathogen with the host infection, gene mutation, and some common environmental stresses. The results of this research can increase understanding of the biological function of T6SS in this economically-important pathogen of rice.

  10. The type VI protein secretion system contributes to biofilm formation and seed-to-seedling transmission of Acidovorax citrulli on melon.

    PubMed

    Tian, Yanli; Zhao, Yuqiang; Wu, Xinrong; Liu, Fengquan; Hu, Baishi; Walcott, Ronald R

    2015-01-01

    The type VI protein secretion system (T6SS) is essential for the virulence of several Gram-negative bacteria. In this study, we identified a T6SS gene cluster in Acidovorax citrulli, a plant-pathogenic bacterium that causes bacterial fruit blotch (BFB) of cucurbits. One T6SS cluster, of approximately 25 kb in length and comprising 17 genes, was found in the A. citrulli AAC00-1 genome. Seventeen A. citrulli mutants were generated, each with a deletion of a single T6SS core gene. There were significant differences in BFB seed-to-seedling transmission between wild-type A. citrulli strain, xjl12, and ΔvasD, ΔimpK, ΔimpJ and ΔimpF mutants (71.71%, 9.83%, 8.41%, 7.15% and 5.99% BFB disease index, respectively). In addition, we observed that these four mutants were reduced in melon seed colonization and biofilm formation; however, they were not affected in virulence when infiltrated into melon seedling tissues. There were no significant differences in BFB seed-to-seedling transmission, melon tissue colonization and biofilm formation between xjl12 and the other 13 T6SS mutants. Overall, our results indicate that T6SS plays a role in seed-to-seedling transmission of BFB on melon.

  11. Identifying beneficial qualities of Trichoderma parareesei for plants.

    PubMed

    Rubio, M Belén; Quijada, Narciso M; Pérez, Esclaudys; Domínguez, Sara; Monte, Enrique; Hermosa, Rosa

    2014-03-01

    Trichoderma parareesei and Trichoderma reesei (teleomorph Hypocrea jecorina) produce cellulases and xylanases of industrial interest. Here, the anamorphic strain T6 (formerly T. reesei) has been identified as T. parareesei, showing biocontrol potential against fungal and oomycete phytopathogens and enhanced hyphal growth in the presence of tomato exudates or plant cell wall polymers in in vitro assays. A Trichoderma microarray was used to examine the transcriptomic changes in T6 at 20 h of interaction with tomato plants. Out of a total 34,138 Trichoderma probe sets deposited on the microarray, 250 showed a significant change of at least 2-fold in expression in the presence of tomato plants, with most of them being downregulated. T. parareesei T6 exerted beneficial effects on tomato plants in terms of seedling lateral root development, and in adult plants it improved defense against Botrytis cinerea and growth promotion under salt stress. Time course expression patterns (0 to 6 days) observed for defense-related genes suggest that T6 was able to prime defense responses in the tomato plants against biotic and abiotic stresses. Such responses undulated, with a maximum upregulation of the jasmonic acid (JA)/ethylene (ET)-related LOX1 and EIN2 genes and the salt tolerance SOS1 gene at 24 h and that of the salicylic acid (SA)-related PR-1 gene at 48 h after T6 inoculation. Our study demonstrates that the T. parareesei T6-tomato interaction is beneficial to both partners.

  12. DotU expression is highly induced during in vivo infection and responsible for virulence and Hcp1 secretion in avian pathogenic Escherichia coli

    PubMed Central

    Wang, Shaohui; Dai, Jianjun; Meng, Qingmei; Han, Xiangan; Han, Yue; Zhao, Yichao; Yang, Denghui; Ding, Chan; Yu, Shengqing

    2014-01-01

    Type VI secretion systems (T6SSs) contribute to pathogenicity in many pathogenic bacteria. Three distinguishable T6SS loci have been discovered in avian pathogenic Escherichia coli (APEC). The sequence of APEC T6SS2 locus is highly similar to the sequence of the newborn meningitis Escherichia coli (NMEC) RS218 T6SS locus, which might contribute to meningitis pathogenesis. However, little is known about the function of APEC T6SS2. We showed that the APEC T6SS2 component organelle trafficking protein (DotU) could elicit antibodies in infected ducks, suggesting that DotU might be involved in APEC pathogenicity. To investigate DotU in APEC pathogenesis, mutant and complemented strains were constructed and characterized. Inactivation of the APEC dotU gene attenuated virulence in ducks, diminished resistance to normal duck serum, and reduced survival in macrophage cells and ducks. Furthermore, deletion of the dotU gene abolished hemolysin-coregulated protein (Hcp) 1 secretion, leading to decreased interleukin (IL)-6 and IL-8 gene expression in HD-11 chicken macrophages. These functions were restored for the complementation strain. Our results demonstrated that DotU plays key roles in the APEC pathogenesis, Hcp1 secretion, and intracellular host response modulation. PMID:25426107

  13. The icmF3 locus is involved in multiple adaptation- and virulence-related characteristics in Pseudomonas aeruginosa PAO1

    PubMed Central

    Lin, Jinshui; Cheng, Juanli; Chen, Keqi; Guo, Chenghao; Zhang, Weipeng; Yang, Xu; Ding, Wei; Ma, Li; Wang, Yao; Shen, Xihui

    2015-01-01

    The type VI secretion system (T6SS) is widely distributed in Gram-negative bacteria. Three separate T6SSs called H1-, H2-, and H3-T6SS have been discovered in Pseudomonas aeruginosa PAO1. Recent studies suggest that, in contrast to the H1-T6SS that targets prokaryotic cells, H2- and H3-T6SS are involved in interactions with both prokaryotic and eukaryotic cells. However, the detailed functions of T6SS components are still uncharacterized. The intracellular multiplication factor (IcmF) protein is conserved in type VI secretion systems (T6SS) of all different bacterial pathogens. Bioinformatic analysis revealed that IcmF3 in P. aeruginosa PAO1 is different from other IcmF homologs and may represent a new branch of these proteins with distinct functions. Herein, we have investigated the function of IcmF3 in this strain. We have shown that deletion of the icmF3 gene in P. aeruginosa PAO1 is associated with pleiotropic phenotypes. The icmF3 mutant has variant colony morphology and an hypergrowth phenotype in iron-limiting medium. Surprisingly, this mutant is also defective for the production of pyoverdine, as well as defects in swimming motility and virulence in a C. elegans worm model. The icmF3 mutant exhibits higher conjugation frequency than the wild type and increased biofilm formation on abiotic surfaces. Additionally, expression of two phenazine biosynthetic loci is increased in the icmF3 mutant, leading to the overproduction of pyocyanin. Finally, the mutant exhibits decreased susceptibility to aminoglycosides such as tobramycin and gentamicin. And the detected phenotypes can be restored completely or partially by trans complementation of wild type icmF3 gene. The pleiotropic effects observed upon icmF3 deletion demonstrate that icmF3 plays critical roles in both pathogenesis and environmental adaptation in P. aeruginosa PAO1. PMID:26484316

  14. The involvement of the anticodon adjacent modified nucleoside N-(9-(BETA-D-ribofuranosyl) purine-6-ylcarbamoyl)-threonine in the biological function of E. coli tRNAile.

    PubMed Central

    Miller, J P; Hussain, Z; Schweizer, M P

    1976-01-01

    tRNAile was isolated from E. coli Cp 79 (leu-, arg-, thr-, his-, thiamin-, RCrel) which had been grown on a sub-optimal concentration of thr and was found to contain an average of 50% less N-[9-(beta-D-ribofuranosyl)- purin-6-ylcarbamoyl]threonine, t6Ado, than tRNAile from cells grown on an optimum concentration of thr and containing a normal complement of t6Ado. The two tRNA's were identical in their ability to be aminoacylated, to accept the 3'-terminal dinucleotide, and to form an ile-tRNAile-Tu-GTP complex. In contrast, the t6Ado-deficient-tRNA was significantly less efficient in binding to ribosomes compared to the normal tRNA. This difference was seen in the binding of deacylated tRNA and in the nonenzymatic and enzymatic binding of ile-tRNA, all in response to poly AUC. The t6Ado-deficient ile-tRNA demonstrated no binding at Mg2+ concentrations less than or equal to 10 mM, while the normal ile-tRNA bound at low Mg2+ concentrations. Tetracycline had the same effect on the normal as on the t6Ado-deficient ile-tRNA binding. As a control, the binding of phe-tRNA (which does not contain t6Ado) from normal and thr-starved cells in response to poly U was identical. It was concluded that t6Ado is required for proper codon-anticodon interaction. PMID:781621

  15. Role of the Genes of Type VI Secretion System in Virulence of Rice Bacterial Brown Stripe Pathogen Acidovorax avenae subsp. avenae Strain RS-2.

    PubMed

    Masum, Md Mahidul Islam; Yang, Yingzi; Li, Bin; Olaitan, Ogunyemi Solabomi; Chen, Jie; Zhang, Yang; Fang, Yushi; Qiu, Wen; Wang, Yanli; Sun, Guochang

    2017-09-21

    The Type VI secretion system (T6SS) is a class of macromolecular machine that is required for the virulence of gram-negative bacteria. However, it is still not clear what the role of T6SS in the virulence of rice bacterial brown stripe pathogen Acidovorax avenae subsp. avenae (Aaa) is. The aim of the current study was to investigate the contribution of T6SS in Aaa strain RS2 virulence using insertional deletion mutation and complementation approaches. This strain produced weak virulence but contains a complete T6SS gene cluster based on a genome-wide analysis. Here we compared the virulence-related phenotypes between the wild-type (RS-2) and 25 T6SS mutants, which were constructed using homologous recombination methods. The mutation of 15 T6SS genes significantly reduced bacterial virulence and the secretion of Hcp protein. Additionally, the complemented 7 mutations ΔpppA, ΔclpB, Δhcp, ΔdotU, ΔicmF, ΔimpJ, and ΔimpM caused similar virulence characteristics as RS-2. Moreover, the mutant ΔpppA, ΔclpB, ΔicmF, ΔimpJ and ΔimpM genes caused by a 38.3~56.4% reduction in biofilm formation while the mutants ΔpppA, ΔclpB, ΔicmF and Δhcp resulted in a 37.5~44.6% reduction in motility. All together, these results demonstrate that T6SS play vital roles in the virulence of strain RS-2, which may be partially attributed to the reductions in Hcp secretion, biofilm formation and motility. However, differences in virulence between strain RS-1 and RS-2 suggest that other factors may also be involved in the virulence of Aaa.

  16. Hybridization is limited between two lineages of freeze-resistant Trichinella during coinfection in a mouse model.

    PubMed

    Hecht, Luke B B; Thompson, Peter C; Lavin, Elizabeth S; Zarlenga, Dante S; Rosenthal, Benjamin M

    2016-03-01

    Hybridization between two closely related but distinct genetic lineages may lead to homogenization of the two lineages with potentially novel phenotypes, or selective pressure to avoid hybridization if the two lineages are truly distinct. Trichinella nativa and Trichinella T6 are zoonotic nematode parasites which can be distinguished genetically despite occasional hybridization. Here, using an experimental murine model, we attempt to determine whether there are barriers to hybridization when sizeable numbers of each lineage are allowed to coinfect a host. Two mice were independently infected with equal numbers of T. nativa and T6. The offspring of these coinfections were genotyped at two microsatellite loci and one mitochondrial locus capable of distinguishing T. nativa from T6 genotypes. Among larvae in the F1 generation, offspring of every possible mating were encountered. Most larvae (63.6%) derived from T. nativa×T. nativa matings, while 21.1% of offspring were the product of T6×T6 matings, and only 15.3% were hybrid offspring of T. nativa×T6 crosses, differing markedly from null expectations. In this experimental model, T. nativa and Trichinella T6 were able to mate, but ratios of offspring indicated pre- or post-zygotic barriers to hybridization that may include assortative mating, genetic incompatibilities, and/or differences in the fitness of offspring. These barriers would limit gene flow between these two lineages in a natural setting, serving as a barrier to their homogenization and promoting their persistence as distinct and separate entities. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  17. The icmF3 locus is involved in multiple adaptation- and virulence-related characteristics in Pseudomonas aeruginosa PAO1.

    PubMed

    Lin, Jinshui; Cheng, Juanli; Chen, Keqi; Guo, Chenghao; Zhang, Weipeng; Yang, Xu; Ding, Wei; Ma, Li; Wang, Yao; Shen, Xihui

    2015-01-01

    The type VI secretion system (T6SS) is widely distributed in Gram-negative bacteria. Three separate T6SSs called H1-, H2-, and H3-T6SS have been discovered in Pseudomonas aeruginosa PAO1. Recent studies suggest that, in contrast to the H1-T6SS that targets prokaryotic cells, H2- and H3-T6SS are involved in interactions with both prokaryotic and eukaryotic cells. However, the detailed functions of T6SS components are still uncharacterized. The intracellular multiplication factor (IcmF) protein is conserved in type VI secretion systems (T6SS) of all different bacterial pathogens. Bioinformatic analysis revealed that IcmF3 in P. aeruginosa PAO1 is different from other IcmF homologs and may represent a new branch of these proteins with distinct functions. Herein, we have investigated the function of IcmF3 in this strain. We have shown that deletion of the icmF3 gene in P. aeruginosa PAO1 is associated with pleiotropic phenotypes. The icmF3 mutant has variant colony morphology and an hypergrowth phenotype in iron-limiting medium. Surprisingly, this mutant is also defective for the production of pyoverdine, as well as defects in swimming motility and virulence in a C. elegans worm model. The icmF3 mutant exhibits higher conjugation frequency than the wild type and increased biofilm formation on abiotic surfaces. Additionally, expression of two phenazine biosynthetic loci is increased in the icmF3 mutant, leading to the overproduction of pyocyanin. Finally, the mutant exhibits decreased susceptibility to aminoglycosides such as tobramycin and gentamicin. And the detected phenotypes can be restored completely or partially by trans complementation of wild type icmF3 gene. The pleiotropic effects observed upon icmF3 deletion demonstrate that icmF3 plays critical roles in both pathogenesis and environmental adaptation in P. aeruginosa PAO1.

  18. Trehalose-6-Phosphate-Mediated Toxicity Determines Essentiality of OtsB2 in Mycobacterium tuberculosis In Vitro and in Mice

    PubMed Central

    Koliwer-Brandl, Hendrik; Hartman, Travis; Jacobs, William R.; Ioerger, Thomas R.; Ehrt, Sabine

    2016-01-01

    Trehalose biosynthesis is considered an attractive target for the development of antimicrobials against fungal, helminthic and bacterial pathogens including Mycobacterium tuberculosis. The most common biosynthetic route involves trehalose-6-phosphate (T6P) synthase OtsA and T6P phosphatase OtsB that generate trehalose from ADP/UDP-glucose and glucose-6-phosphate. In order to assess the drug target potential of T6P phosphatase, we generated a conditional mutant of M. tuberculosis allowing the regulated gene silencing of the T6P phosphatase gene otsB2. We found that otsB2 is essential for growth of M. tuberculosis in vitro as well as for the acute infection phase in mice following aerosol infection. By contrast, otsB2 is not essential for the chronic infection phase in mice, highlighting the substantial remodelling of trehalose metabolism during infection by M. tuberculosis. Blocking OtsB2 resulted in the accumulation of its substrate T6P, which appears to be toxic, leading to the self-poisoning of cells. Accordingly, blocking T6P production in a ΔotsA mutant abrogated otsB2 essentiality. T6P accumulation elicited a global upregulation of more than 800 genes, which might result from an increase in RNA stability implied by the enhanced neutralization of toxins exhibiting ribonuclease activity. Surprisingly, overlap with the stress response caused by the accumulation of another toxic sugar phosphate molecule, maltose-1-phosphate, was minimal. A genome-wide screen for synthetic lethal interactions with otsA identified numerous genes, revealing additional potential drug targets synergistic with OtsB2 suitable for combination therapies that would minimize the emergence of resistance to OtsB2 inhibitors. PMID:27936238

  19. Hcp and VgrG1 are secreted components of the Helicobacter hepaticus type VI secretion system and VgrG1 increases the bacterial colitogenic potential.

    PubMed

    Bartonickova, Lucie; Sterzenbach, Torsten; Nell, Sandra; Kops, Friederike; Schulze, Jessika; Venzke, Annika; Brenneke, Birgit; Bader, Sophie; Gruber, Achim D; Suerbaum, Sebastian; Josenhans, Christine

    2013-06-01

    The enterohepatic Epsilonproteobacterium Helicobacter hepaticus persistently colonizes the intestine of mice and causes chronic inflammatory symptoms in susceptible mouse strains. The bacterial factors causing intestinal inflammation are poorly characterized. A large genomic pathogenicity island, HHGI1, which encodes components of a type VI secretion system (T6SS), was previously shown to contribute to the colitogenic potential of H. hepaticus. We have now characterized the T6SS components Hcp, VgrG1, VgrG2 and VgrG3, encoded on HHGI1, including the potential impact of the T6SS on intestinal inflammation in a mouse T-cell transfer model. The H. hepaticus T6SS components were expressed during the infection and secreted in a T6SS-dependent manner, when the bacteria were cultured either in the presence or in the absence of mouse intestinal epithelial cells. Mutants deficient in VgrG1 displayed a significantly lower colitogenic potential in T-cell-transferred C57BL/6 Rag2(-/-) mice, despite an unaltered ability to colonize mice persistently. Intestinal microbiota analyses demonstrated only minor changes in mice infected with wild-typeH. hepaticus as compared with mice infected with VgrG1-deficient isogenic bacteria. In addition, competitive assays between both wild-type and T6SS-deficient H. hepaticus, and between wild-type H. hepaticus and Campylobacter jejuni or Enterobacteriaceae species did not show an effect of the T6SS on interbacterial competitiveness. Therefore, we suggest that microbiota alterations did not play a major role in the changes of pro-inflammatory potential mediated by the T6SS. Cellular innate pro-inflammatory responses were increased by the secreted T6SS proteins VgrG1 and VgrG2. We therefore concluded that the type VI secretion component VgrG1 can modulate and specifically exacerbate the innate pro-inflammatory effect of the chronic H. hepaticus infection.

  20. VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System

    PubMed Central

    Cianfanelli, Francesca R.; Alcoforado Diniz, Juliana; Guo, Manman; De Cesare, Virginia; Trost, Matthias; Coulthurst, Sarah J.

    2016-01-01

    The Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria and eukaryotic hosts by delivering toxic effector proteins directly into target cells. The T6SS utilises a bacteriophage-like contractile machinery to expel a puncturing device based on a tube of Hcp topped with a VgrG spike, which can be extended by a final tip from a PAAR domain-containing protein. Effector proteins are believed to be delivered by specifically associating with particular Hcp, VgrG or PAAR proteins, either covalently (‘specialised’) or non-covalently (‘cargo’ effectors). Here we used the T6SS of the opportunistic pathogen Serratia marcescens, together with integratecd genetic, proteomic and biochemical approaches, to elucidate the role of specific VgrG and PAAR homologues in T6SS function and effector specificity, revealing new aspects and unexpected subtleties in effector delivery by the T6SS. We identified effectors, both cargo and specialised, absolutely dependent on a particular VgrG for delivery to target cells, and discovered that other cargo effectors can show a preference for a particular VgrG. The presence of at least one PAAR protein was found to be essential for T6SS function, consistent with designation as a ‘core’ T6SS component. We showed that specific VgrG-PAAR combinations are required to assemble a functional T6SS and that the three distinct VgrG-PAAR assemblies in S. marcescens exhibit distinct effector specificity and efficiency. Unexpectedly, we discovered that two different PAAR-containing Rhs proteins can functionally pair with the same VgrG protein. Showing that accessory EagR proteins are involved in these interactions, native VgrG-Rhs-EagR complexes were isolated and specific interactions between EagR and cognate Rhs proteins identified. This study defines an essential yet flexible role for PAAR proteins in the T6SS and highlights the existence of distinct versions of the

  1. A type VI secretion system is involved in Pseudomonas fluorescens bacterial competition.

    PubMed

    Decoin, Victorien; Barbey, Corinne; Bergeau, Dorian; Latour, Xavier; Feuilloley, Marc G J; Orange, Nicole; Merieau, Annabelle

    2014-01-01

    Protein secretion systems are crucial mediators of bacterial interactions with other organisms. Among them, the type VI secretion system (T6SS) is widespread in Gram-negative bacteria and appears to inject toxins into competitor bacteria and/or eukaryotic cells. Major human pathogens, such as Vibrio cholerae, Burkholderia and Pseudomonas aeruginosa, express T6SSs. Bacteria prevent self-intoxication by their own T6SS toxins by producing immunity proteins, which interact with the cognate toxins. We describe here an environmental P. fluorescens strain, MFE01, displaying an uncommon oversecretion of Hcp (hemolysin-coregulated protein) and VgrG (valine-glycine repeat protein G) into the culture medium. These proteins are characteristic components of a functional T6SS. The aim of this study was to attribute a role to this energy-consuming overexpression of the T6SS. The genome of MFE01 contains at least two hcp genes (hcp1 and hcp2), suggesting that there may be two putative T6SS clusters. Phenotypic studies have shown that MFE01 is avirulent against various eukaryotic cell models (amebas, plant or animal cell models), but has antibacterial activity against a wide range of competitor bacteria, including rhizobacteria and clinical bacteria. Depending on the prey cell, mutagenesis of the hcp2 gene in MFE01 abolishes or reduces this antibacterial killing activity. Moreover, the introduction of T6SS immunity proteins from S. marcescens, which is not killed by MFE01, protects E. coli against MFE01 killing. These findings suggest that the protein encoded by hcp2 is involved in the killing activity of MFE01 mediated by effectors of the T6SS targeting the peptidoglycan of Gram-negative bacteria. Our results indicate that MFE01 can protect potato tubers against Pectobacterium atrosepticum, which causes tuber soft rot. Pseudomonas fluorescens is often described as a major PGPR (plant growth-promoting rhizobacterium), and our results suggest that there may be a connection between

  2. A Type VI Secretion System Is Involved in Pseudomonas fluorescens Bacterial Competition

    PubMed Central

    Decoin, Victorien; Barbey, Corinne; Bergeau, Dorian; Latour, Xavier; Feuilloley, Marc G. J.; Orange, Nicole; Merieau, Annabelle

    2014-01-01

    Protein secretion systems are crucial mediators of bacterial interactions with other organisms. Among them, the type VI secretion system (T6SS) is widespread in Gram-negative bacteria and appears to inject toxins into competitor bacteria and/or eukaryotic cells. Major human pathogens, such as Vibrio cholerae, Burkholderia and Pseudomonas aeruginosa, express T6SSs. Bacteria prevent self-intoxication by their own T6SS toxins by producing immunity proteins, which interact with the cognate toxins. We describe here an environmental P. fluorescens strain, MFE01, displaying an uncommon oversecretion of Hcp (hemolysin-coregulated protein) and VgrG (valine-glycine repeat protein G) into the culture medium. These proteins are characteristic components of a functional T6SS. The aim of this study was to attribute a role to this energy-consuming overexpression of the T6SS. The genome of MFE01 contains at least two hcp genes (hcp1 and hcp2), suggesting that there may be two putative T6SS clusters. Phenotypic studies have shown that MFE01 is avirulent against various eukaryotic cell models (amebas, plant or animal cell models), but has antibacterial activity against a wide range of competitor bacteria, including rhizobacteria and clinical bacteria. Depending on the prey cell, mutagenesis of the hcp2 gene in MFE01 abolishes or reduces this antibacterial killing activity. Moreover, the introduction of T6SS immunity proteins from S. marcescens, which is not killed by MFE01, protects E. coli against MFE01 killing. These findings suggest that the protein encoded by hcp2 is involved in the killing activity of MFE01 mediated by effectors of the T6SS targeting the peptidoglycan of Gram-negative bacteria. Our results indicate that MFE01 can protect potato tubers against Pectobacterium atrosepticum, which causes tuber soft rot. Pseudomonas fluorescens is often described as a major PGPR (plant growth-promoting rhizobacterium), and our results suggest that there may be a connection between

  3. Action of antimicrobial substances produced by different oil reservoir Bacillus strains against biofilm formation.

    PubMed

    Korenblum, E; Sebastián, G V; Paiva, M M; Coutinho, C M L M; Magalhães, F C M; Peyton, B M; Seldin, L

    2008-05-01

    Microbial colonization of petroleum industry systems takes place through the formation of biofilms, and can result in biodeterioration of the metal surfaces. In a previous study, two oil reservoir Bacillus strains (Bacillus licheniformis T6-5 and Bacillus firmus H(2)O-1) were shown to produce antimicrobial substances (AMS) active against different Bacillus strains and a consortium of sulfate-reducing bacteria (SRB) on solid medium. However, neither their ability to form biofilms nor the effect of the AMS on biofilm formation was adequately addressed. Therefore, here, we report that three Bacillus strains (Bacillus pumilus LF4 -- used as an indicator strain, B. licheniformis T6-5, and B. firmus H(2)O-1), and an oil reservoir SRB consortium (T6lab) were grown as biofilms on glass surfaces. The AMS produced by strains T6-5 and H(2)O-1 prevented the formation of B. pumilus LF4 biofilm and also eliminated pre-established LF4 biofilm. In addition, the presence of AMS produced by H(2)O-1 reduced the viability and attachment of the SRB consortium biofilm by an order of magnitude. Our results suggest that the AMS produced by Bacillus strains T6-5 and H(2)O-1 may have a potential for pipeline-cleaning technologies to inhibit biofilm formation and consequently reduce biocorrosion.

  4. Type VI Secretion System Substrates Are Transferred and Reused among Sister Cells.

    PubMed

    Vettiger, Andrea; Basler, Marek

    2016-09-22

    Bacterial type VI secretion system (T6SS) is a nanomachine that works similarly to a speargun. Rapid contraction of a sling (sheath) drives a long shaft (Hcp) with a sharp tip and associated effectors through the target cell membrane. We show that the amount and composition of the tip regulates initiation of full-length sheath assembly and low amount of available Hcp decreases sheath length. Importantly, we show that both tip and Hcp are exchanged by T6SS among by-standing cells within minutes of initial cell-cell contact. The translocated proteins are reused for new T6SS assemblies suggesting that tip and Hcp reach the cytosol of target cells. The efficiency of protein translocation depends on precise aiming of T6SS at the target cells. This interbacterial protein complementation can support T6SS activity in sister cells with blocked protein synthesis and also allows cooperation between strains to increase their potential to kill competition. VIDEO ABSTRACT.

  5. Quorum sensing control of Type VI secretion factors restricts the proliferation of quorum-sensing mutants.

    PubMed

    Majerczyk, Charlotte; Schneider, Emily; Greenberg, E Peter

    2016-05-16

    Burkholderia thailandensis uses acyl-homoserine lactone-mediated quorum sensing systems to regulate hundreds of genes. Here we show that cell-cell contact-dependent type VI secretion (T6S) toxin-immunity systems are among those activated by quorum sensing in B. thailandensis. We also demonstrate that T6S is required to constrain proliferation of quorum sensing mutants in colony cocultures of a BtaR1 quorum-sensing signal receptor mutant and its parent. However, the BtaR1 mutant is not constrained by and outcompetes its parent in broth coculture, presumably because no cell contact occurs and there is a metabolic cost associated with quorum sensing gene activation. The increased fitness of the wild type over the BtaR1 mutant during agar surface growth is dependent on an intact T6SS-1 apparatus. Thus, quorum sensing activates B. thailandensis T6SS-1 growth inhibition and this control serves to police and constrain quorum-sensing mutants. This work defines a novel role for T6SSs in intraspecies mutant control.

  6. Type VI secretion and bacteriophage tail tubes share a common assembly pathway

    PubMed Central

    Brunet, Yannick R; Hénin, Jérôme; Celia, Hervé; Cascales, Eric

    2014-01-01

    The Type VI secretion system (T6SS) is a widespread macromolecular structure that delivers protein effectors to both eukaryotic and prokaryotic recipient cells. The current model describes the T6SS as an inverted phage tail composed of a sheath-like structure wrapped around a tube assembled by stacked Hcp hexamers. Although recent progress has been made to understand T6SS sheath assembly and dynamics, there is no evidence that Hcp forms tubes in vivo. Here we show that Hcp interacts with TssB, a component of the T6SS sheath. Using a cysteine substitution approach, we demonstrate that Hcp hexamers assemble tubes in an ordered manner with a head-to-tail stacking that are used as a scaffold for polymerization of the TssB/C sheath-like structure. Finally, we show that VgrG but not TssB/C controls the proper assembly of the Hcp tubular structure. These results highlight the conservation in the assembly mechanisms between the T6SS and the bacteriophage tail tube/sheath. PMID:24488256

  7. Type VI secretion and bacteriophage tail tubes share a common assembly pathway.

    PubMed

    Brunet, Yannick R; Hénin, Jérôme; Celia, Hervé; Cascales, Eric

    2014-03-01

    The Type VI secretion system (T6SS) is a widespread macromolecular structure that delivers protein effectors to both eukaryotic and prokaryotic recipient cells. The current model describes the T6SS as an inverted phage tail composed of a sheath-like structure wrapped around a tube assembled by stacked Hcp hexamers. Although recent progress has been made to understand T6SS sheath assembly and dynamics, there is no evidence that Hcp forms tubes in vivo. Here we show that Hcp interacts with TssB, a component of the T6SS sheath. Using a cysteine substitution approach, we demonstrate that Hcp hexamers assemble tubes in an ordered manner with a head-to-tail stacking that are used as a scaffold for polymerization of the TssB/C sheath-like structure. Finally, we show that VgrG but not TssB/C controls the proper assembly of the Hcp tubular structure. These results highlight the conservation in the assembly mechanisms between the T6SS and the bacteriophage tail tube/sheath.

  8. Chemical intervention in plant sugar signalling increases yield and resilience

    NASA Astrophysics Data System (ADS)

    Griffiths, Cara A.; Sagar, Ram; Geng, Yiqun; Primavesi, Lucia F.; Patel, Mitul K.; Passarelli, Melissa K.; Gilmore, Ian S.; Steven, Rory T.; Bunch, Josephine; Paul, Matthew J.; Davis, Benjamin G.

    2016-12-01

    The pressing global issue of food insecurity due to population growth, diminishing land and variable climate can only be addressed in agriculture by improving both maximum crop yield potential and resilience. Genetic modification is one potential solution, but has yet to achieve worldwide acceptance, particularly for crops such as wheat. Trehalose-6-phosphate (T6P), a central sugar signal in plants, regulates sucrose use and allocation, underpinning crop growth and development. Here we show that application of a chemical intervention strategy directly modulates T6P levels in planta. Plant-permeable analogues of T6P were designed and constructed based on a ‘signalling-precursor’ concept for permeability, ready uptake and sunlight-triggered release of T6P in planta. We show that chemical intervention in a potent sugar signal increases grain yield, whereas application to vegetative tissue improves recovery and resurrection from drought. This technology offers a means to combine increases in yield with crop stress resilience. Given the generality of the T6P pathway in plants and other small-molecule signals in biology, these studies suggest that suitable synthetic exogenous small-molecule signal precursors can be used to directly enhance plant performance and perhaps other organism function.

  9. A Pseudomonas aeruginosa type VI secretion phospholipase D effector targets both prokaryotic and eukaryotic cells.

    PubMed

    Jiang, Feng; Waterfield, Nicholas R; Yang, Jian; Yang, Guowei; Jin, Qi

    2014-05-14

    Widely found in animal and plant-associated proteobacteria, type VI secretion systems (T6SSs) are potentially capable of facilitating diverse interactions with eukaryotes and/or other bacteria. Pseudomonas aeruginosa encodes three distinct T6SS haemolysin coregulated protein (Hcp) secretion islands (H1, H2, and H3-T6SS), each involved in different aspects of the bacterium's interaction with other organisms. Here we describe the characterization of a P. aeruginosa H3-T6SS-dependent phospholipase D effector, PldB, and its three tightly linked cognate immunity proteins. PldB targets the periplasm of prokaryotic cells and exerts an antibacterial activity. Surprisingly, PldB also facilitates intracellular invasion of host eukaryotic cells by activation of the PI3K/Akt pathway, revealing it to be a trans-kingdom effector. Our findings imply a potentially widespread T6SS-mediated mechanism, which deploys a single phospholipase effector to influence both prokaryotic cells and eukaryotic hosts.

  10. Crystal structure of trehalose-6-phosphate phosphatase–related protein: Biochemical and biological implications

    PubMed Central

    Rao, Krishnamurthy N.; Kumaran, Desigan; Seetharaman, Jayaraman; Bonanno, Jeffrey B.; Burley, Stephen K.; Swaminathan, Subramanyam

    2006-01-01

    We report here the crystal structure of a trehalose-6-phosphate phosphatase–related protein (T6PP) from Thermoplasma acidophilum, TA1209, determined by the dual-wavelength anomalous diffraction (DAD) method. T6PP is a member of the haloacid dehalogenase (HAD) superfamily with significant sequence homology with trehalose-6-phosphate phosphatase, phosphoserine phosphatase, P-type ATPases and other members of the family. T6PP possesses a core domain of known α/β-hydrolase fold, characteristic of the HAD family, and a cap domain, with a tertiary fold consisting of a four-stranded β-sheet with two α-helices on one side of the sheet. An active-site magnesium ion and a glycerol molecule bound at the interface between the two domains provide insight into the mode of substrate binding by T6PP. A trehalose-6-phosphate molecule modeled into a cage formed by the two domains makes favorable interactions with the protein molecule. We have confirmed that T6PP is a trehalose phosphatase from amino acid sequence, three-dimensional structure, and biochemical assays. PMID:16815921

  11. Quorum sensing control of Type VI secretion factors restricts the proliferation of quorum-sensing mutants

    PubMed Central

    Majerczyk, Charlotte; Schneider, Emily; Greenberg, E Peter

    2016-01-01

    Burkholderia thailandensis uses acyl-homoserine lactone-mediated quorum sensing systems to regulate hundreds of genes. Here we show that cell-cell contact-dependent type VI secretion (T6S) toxin-immunity systems are among those activated by quorum sensing in B. thailandensis. We also demonstrate that T6S is required to constrain proliferation of quorum sensing mutants in colony cocultures of a BtaR1 quorum-sensing signal receptor mutant and its parent. However, the BtaR1 mutant is not constrained by and outcompetes its parent in broth coculture, presumably because no cell contact occurs and there is a metabolic cost associated with quorum sensing gene activation. The increased fitness of the wild type over the BtaR1 mutant during agar surface growth is dependent on an intact T6SS-1 apparatus. Thus, quorum sensing activates B. thailandensis T6SS-1 growth inhibition and this control serves to police and constrain quorum-sensing mutants. This work defines a novel role for T6SSs in intraspecies mutant control. DOI: http://dx.doi.org/10.7554/eLife.14712.001 PMID:27183270

  12. A widespread bacterial type VI secretion effector superfamily identified using a heuristic approach.

    PubMed

    Russell, Alistair B; Singh, Pragya; Brittnacher, Mitchell; Bui, Nhat Khai; Hood, Rachel D; Carl, Mike A; Agnello, Danielle M; Schwarz, Sandra; Goodlett, David R; Vollmer, Waldemar; Mougous, Joseph D

    2012-05-17

    Sophisticated mechanisms are employed to facilitate information exchange between interfacing bacteria. A type VI secretion system (T6SS) of Pseudomonas aeruginosa was shown to deliver cell wall-targeting effectors to neighboring cells. However, the generality of bacteriolytic effectors and, moreover, of antibacterial T6S remained unknown. Using parameters derived from experimentally validated bacterial T6SS effectors we identified a phylogenetically disperse superfamily of T6SS-associated peptidoglycan-degrading effectors. The effectors separate into four families composed of peptidoglycan amidase enzymes of differing specificities. Effectors strictly co-occur with cognate immunity proteins, indicating that self-intoxication is a general property of antibacterial T6SSs and effector delivery by the system exerts a strong selective pressure in nature. The presence of antibacterial effectors in a plethora of organisms, including many that inhabit or infect polymicrobial niches in the human body, suggests that the system could mediate interbacterial interactions of both environmental and clinical significance.

  13. BcsKC is an essential protein for the type VI secretion system activity in Burkholderia cenocepacia that forms an outer membrane complex with BcsLB.

    PubMed

    Aubert, Daniel; MacDonald, Douglas K; Valvano, Miguel A

    2010-11-12

    The type VI secretion system (T6SS) contributes to the virulence of Burkholderia cenocepacia, an opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis. BcsK(C) is a highly conserved protein among the T6SSs in Gram-negative bacteria. Here, we show that BcsK(C) is required for Hcp secretion and cytoskeletal redistribution in macrophages upon bacterial infection. These two phenotypes are associated with a functional T6SS in B. cenocepacia. Experiments employing a bacterial two-hybrid system and pulldown assays demonstrated that BcsK(C) interacts with BcsL(B), another conserved T6SS component. Internal deletions within BcsK(C) revealed that its N-terminal domain is necessary and sufficient for interaction with BcsL(B). Fractionation experiments showed that BcsK(C) can be in the cytosol or tightly associated with the outer membrane and that BcsK(C) and BcsL(B) form a high molecular weight complex anchored to the outer membrane that requires BcsF(H) (a ClpV homolog) to be assembled. Together, our data show that BcsK(C)/BcsL(B) interaction is essential for the T6SS activity in B. cenocepacia.

  14. TssB is essential for virulence and required for type VI secretion system in Ralstonia solanacearum.

    PubMed

    Zhang, Liqing; Xu, Jingsheng; Xu, Jin; Zhang, Hao; He, Liyuan; Feng, Jie

    2014-09-01

    The type VI secretion system (T6SS) is recently discovered machinery in Gram-negative bacteria for translocation of proteins and also is required for full virulence. TssB is a highly conserved protein among the T6SSs, and indispensable for composition and function of T6S. The plant pathogenic bacterium Ralstonia solanacearum also harbours T6SS gene clusters, and a homologue of TssB, hereafter designated as TssBRS, but up to date its characterization and function remain unclear. In this study, we showed that TssBRS of R. solanacearum was required for secretion of Hcp, the haemolysin coregulated protein and a hallmark of T6S pathway. Deletion of tssBRS in R. solanacearum GMI1000 strain resulted in defect of biofilm formation, and the expression of the flagella operon is decreased, leading to decreased motility. More importantly, tssBRS mutant strain had significantly attenuated its virulence on tomato plants. TssB is essential for virulence and required for type VI secretion system in R. solanacearum. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Francisella requires dynamic type VI secretion system and ClpB to deliver effectors for phagosomal escape

    PubMed Central

    Brodmann, Maj; Dreier, Roland F.; Broz, Petr; Basler, Marek

    2017-01-01

    Francisella tularensis is an intracellular pathogen that causes the fatal zoonotic disease tularaemia. Critical for its pathogenesis is the ability of the phagocytosed bacteria to escape into the cell cytosol. For this, the bacteria use a non-canonical type VI secretion system (T6SS) encoded on the Francisella pathogenicity island (FPI). Here we show that in F. novicida T6SS assembly initiates at the bacterial poles both in vitro and within infected macrophages. T6SS dynamics and function depends on the general purpose ClpB unfoldase, which specifically colocalizes with contracted sheaths and is required for their disassembly. T6SS assembly depends on iglF, iglG, iglI and iglJ, whereas pdpC, pdpD, pdpE and anmK are dispensable. Importantly, strains lacking pdpC and pdpD are unable to escape from phagosome, activate AIM2 inflammasome or cause disease in mice. This suggests that PdpC and PdpD are T6SS effectors involved in phagosome rupture. PMID:28621333

  16. Promoter swapping unveils the role of the Citrobacter rodentium CTS1 type VI secretion system in interbacterial competition.

    PubMed

    Gueguen, Erwan; Cascales, Eric

    2013-01-01

    The type VI secretion system (T6SS) is a versatile secretion machine dedicated to various functions in Gram-negative bacteria, including virulence toward eukaryotic cells and antibacterial activity. Activity of T6SS might be followed in vitro by the release of two proteins, Hcp and VgrG, in the culture supernatant. Citrobacter rodentium, a rodent pathogen, harbors two T6SS gene clusters, cts1 and cts2. Reporter fusion and Hcp release assays suggested that the CTS1 T6SS was not produced or not active. The cts1 locus is composed of two divergent operons. We therefore developed a new vector allowing us to swap the two divergent endogenous promoters by P(tac) and P(BAD) using the λ red recombination technology. Artificial induction of both promoters demonstrated that the CTS1 T6SS is functional as shown by the Hcp release assay and confers on C. rodentium a growth advantage in antibacterial competition experiments with Escherichia coli.

  17. Fatigue Properties of Cast Magnesium Wheels

    NASA Astrophysics Data System (ADS)

    Li, Zhenming; Luo, Alan A.; Wang, Qigui; Peng, Liming; Zhang, Peng

    2016-08-01

    This paper investigates the fatigue properties and deformation behavior of a newly developed Mg-2.96Nd-0.21Zn-0.39Zr magnesium alloy wheel in both as-cast and T6 conditions. Compared with the as-cast alloy, the T6-treated alloy shows a significant increase in fatigue strength and cyclic stress amplitude. This is believed to be attributed to the change of defect type from porosity to oxides and the increased matrix strength in the T6 (peak-aged) condition. For the as-cast alloy wheel, fatigue failure mainly originated from the cast defects including porosity, oxide film, and inclusion at or near the sample surface. In the T6-treated alloy, however, oxides and inclusions or slip bands initiate the fatigue cracks. Solution treatment appears to reduce or eliminate the shrinkage porosity because of grain growth and dissolution of as-cast eutectic phases in the grain boundaries. The cyclic stress amplitude of the as-cast alloy increases with increasing the number of cycles, while the T6-treated alloy shows cyclic softening after the stress reaches a maximum value. The Coffin-Manson law and Basquin equation can be used to evaluate the life of low cycle fatigue. The developed long crack model and multi-scale fatigue (MSF) models can be used to predict high-cycle fatigue life of the Mg-2.96Nd-0.21Zn-0.39Zr alloys with or without casting defects.

  18. Synthesis of a Trichoderma chitinase which affects the Sclerotium rolfsii and Rhizoctonia solani cell walls.

    PubMed

    Lima, L H; De Marco, J L; Ulhoa, C J; Felix, C R

    1999-01-01

    A Trichoderma sp. isolate, hereafter called T6, produces a 46-kDa endochitinase (CHIT 46) which had been shown to drastically affect in vitro the cell walls of the phytopathogens Sclerotium rolfsii and Rhizoctonia solani. We attempted to gain insight into its properties. The CHIT 46 N-terminal amino acid sequence shares a very high homology with other fungal chitinases. Western blot analysis using polyclonal antibodies anti-CHIT 46 revealed that this enzyme is immunologically distinct from other proteins produced by the same Trichoderma isolate T6, but is immunologically identical with proteins having equivalent molar mass, probably chitinases, produced by other Trichoderma spp. isolates. In addition, the antibodies revealed also that a substantial amount of this enzyme is secreted into the culture medium 2 d after the Trichoderma isolate T6 comes into contact with chitin.

  19. Influence of overaging treatment on localized corrosion of Al 6056

    SciTech Connect

    Gullaumin, V.; Mankowski, G.

    2000-01-01

    The influence of T78 overaging treatment on the corrosion behavior of AL 6056 (UNS A96056) in 1 M sodium chloride (NaCl) solution was investigated. The overaged alloy presented the same localized corrosion mechanisms as Al 6056-T6. However, Al 6056-T78 coarse intermetallic Al-Mg-Si-containing particles were found to be more reactive than those in the Al 6056-T6 alloy and were nucleation sites for pits. Pitting and intergranular corrosion were dependent upon each other; intergranular corrosion nucleated on pit walls. A quantitative study showed that T78 overaging of Al 6056 offered a better resistance to intergranular corrosion compared to T6 peak-aging treatment. The overaged alloy will be able to replace the traditional Al 2024 because of the efficiency of this overaging treatment.

  20. Type VI secretion apparatus and phage tail-associated protein complexes share a common evolutionary origin

    SciTech Connect

    Leiman, Petr G.; Basler, Marek; Ramagopal, Udupi A.; Bonanno, Jeffrey B.; Sauder, J. Michael; Pukatzki, Stefan; Burley, Stephen K.; Almo, Steven C.; Mekalanos, John J.

    2009-04-22

    Protein secretion is a common property of pathogenic microbes. Gram-negative bacterial pathogens use at least 6 distinct extracellular protein secretion systems to export proteins through their multilayered cell envelope and in some cases into host cells. Among the most widespread is the newly recognized Type VI secretion system (T6SS) which is composed of 15--20 proteins whose biochemical functions are not well understood. Using crystallographic, biochemical, and bioinformatic analyses, we identified 3 T6SS components, which are homologous to bacteriophage tail proteins. These include the tail tube protein; the membrane-penetrating needle, situated at the distal end of the tube; and another protein associated with the needle and tube. We propose that T6SS is a multicomponent structure whose extracellular part resembles both structurally and functionally a bacteriophage tail, an efficient machine that translocates proteins and DNA across lipid membranes into cells.

  1. CHEMICAL STUDIES IN HOST-VIRUS INTERACTIONS

    PubMed Central

    Cohen, Seymour S.; Arbogast, Rachel

    1950-01-01

    Various chemical and physiological aspects of the reproductive cycles of r+ and r strains of T2, T4, and T6 viruses have been examined and compared. These include the ultraviolet absorption spectra in which differences between r and r+ strains were not observed, though they were obtained in the case of T2, T4, and T6. Adsorption of T4 and T6 was found to require the adsorption cofactor l-tryptophane. Among the r and r+ strains of these viruses limiting tryptophane requirements for adsorption were found to be different. Some differences were observed in the one-step growth curves of these viruses under conditions of single and multiple infection. The turbidity-time relations of infected cultures were characteristically different. The rates of DNA and protein synthesis in the infected cells were found to be independent of the viruses used. Certain implications of the data have been discussed. PMID:15422088

  2. Type VI secretion effectors: poisons with a purpose

    PubMed Central

    Russell, Alistair B.; Peterson, S. Brook; Mougous, Joseph D.

    2014-01-01

    The type VI secretion system (T6SS) mediates interactions between a diverse range of Gram-negative bacterial species. Recent studies have led to a drastic increase in the number of characterized T6SS effector proteins and produced a more complete and nuanced view of the adaptive significance of the system. While the system is most often implicated in antagonism, in this review we consider the case for its involvement in both antagonistic and non-antagonistic behaviors. Clarifying the roles that T6S plays in microbial communities will contribute to broader efforts to understand the importance of microbial interactions in maintaining human and environmental health, and will inform efforts to manipulate these interactions for therapeutic or environmental benefit. PMID:24384601

  3. Antifibrotic constituents from Garcinia mangostana.

    PubMed

    Chin, Young-Won; Shin, Eunjin; Hwang, Bang Yeon; Lee, Mi Kyeong

    2011-09-01

    From the CHCl3-soluble fraction of the fruits of Garcinia mangostana (Clusiaceae), six xanthone derivatives, alpha-mangostin (1), gamma-mangostin (2), gartanin (3), deoxygartanin (4), 1-isomangstanin (5) and garcinone E (6), were isolated. All these compounds significantly inhibited HSC-T6 viability as assessed by employing HSC-T6 hepatic stellate cells as an in vitro assay system. Among them, compounds 1 and 2, the most potent and major constituents of G. mangostana, inhibited HSC-T6 viability in dose- and time-dependent manners. In addition, compounds 1 and 2 significantly reduced collagen content, a pathological characteristic of liver fibrosis. Taken together, G. mangostana and its constituents might be beneficial for the treatment of liver fibrosis.

  4. Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment

    NASA Astrophysics Data System (ADS)

    Bai, J. Y.; Fan, C. L.; Lin, S. B.; Yang, C. L.; Dong, B. L.

    2017-04-01

    2219-Al parts were produced by gas tungsten arc-additive manufacturing and sequentially processed by an especial heat treatment. In order to investigate the effects of heat treatment on its mechanical properties, multiple tests were conducted. Hardness tests were carried out on part scale and layer scale along with tensile tests which were performed on welding and building directions. Results show that compared to conventional casting + T6 2219-Al, the current deposit + T6 2219-Al exhibits satisfying properties with regard to strength but unsatisfying results in plasticity. Additionally, anisotropy is significant. Fractures were observed and the cracks' propagating paths in both directional specimens are described. The effects of heat treatment on the cracks' initiation and propagation were also investigated. Ultimately, a revised formula was developed to calculate the strength of the deposit + T6 2219-Al. The aforementioned formula, which takes into consideration the belt-like porosities-distributing feature, can scientifically describe the anisotropic properties in the material.

  5. Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment

    NASA Astrophysics Data System (ADS)

    Bai, J. Y.; Fan, C. L.; Lin, S. B.; Yang, C. L.; Dong, B. L.

    2017-03-01

    2219-Al parts were produced by gas tungsten arc-additive manufacturing and sequentially processed by an especial heat treatment. In order to investigate the effects of heat treatment on its mechanical properties, multiple tests were conducted. Hardness tests were carried out on part scale and layer scale along with tensile tests which were performed on welding and building directions. Results show that compared to conventional casting + T6 2219-Al, the current deposit + T6 2219-Al exhibits satisfying properties with regard to strength but unsatisfying results in plasticity. Additionally, anisotropy is significant. Fractures were observed and the cracks' propagating paths in both directional specimens are described. The effects of heat treatment on the cracks' initiation and propagation were also investigated. Ultimately, a revised formula was developed to calculate the strength of the deposit + T6 2219-Al. The aforementioned formula, which takes into consideration the belt-like porosities-distributing feature, can scientifically describe the anisotropic properties in the material.

  6. The Galvanic Corrosion of Graphite Epoxy Composite Materials Coupled with Alloys

    DTIC Science & Technology

    1975-12-01

    301, Borderline-Aluminum Graphite, MA-87, SS- 440C , A1-2024-TG, A1-2024 T3, 1020, Al-70󈨏-T6, 4130, Unacceptable-lO Ni Mod, 300M, Al-2020-T651, and...1020 Steel/GECM Couples in 3.5% NaCl Solution at Ambient Temperature ........ .................... 71 31 Galvanic Current vs Time for SS- 440C Stainless...Borderline-Aluminum- Graphite, MA-87, SS- 440C , Al-2024-T6, Al-2024-T3, 1020, Al-7075-T6, 4130, x GkE/MC/7.rD--8 Unacceptable-lO Ni Mod, 300M, Al-2020-T651

  7. Influence of volume fraction of component materials and interlayer bond strength on fracture toughness of multi-layer Al 6090-25 vol % SiCp and Al 5182 laminates

    SciTech Connect

    Syn, C.K.; Stoner, S.; Lesuer, D.R.; Sherby, O.D.

    1993-11-01

    Multilayer laminates of Al 6090/SiC/25p MMC and Al 5182 were prepared by hot pressing alternating layers of the component materials at 450{degree}C in an argon gas atmosphere. Tensile properties, interlayer normal and shear bond strengths, and fracture toughness were measured in the T6-treated and untreated conditions. Fracture toughness was also measured as a function of the volume fraction of the MMC component. Yield and tensile strengths increased substantially by the T6 treatment while the total-elongation and interlayer bond strengths decreased even more substantially. Fracture toughness, on the other hand, did not change appreciably by the T6 treatment. The fracture toughness increased perceptibly with an increase in the volume percent of the MMC component.

  8. Aluminum alloy 6013 sheet for new U. S. Navy aircraft

    SciTech Connect

    Kaneko, R.S.; Bakow, L.; Lee, E.W. Naval Air Development Center, Warminster, PA )

    1990-05-01

    The recently developed aluminum alloy 6013-T6 has been selected for the fuselage skin and other applications on the U.S. Navy's P-7A airplane, in place of the traditional 2024-T3 clad sheet. Alloy 6013-T6 is naturally corrosion resistant, like the well-established alloy 6061, and hence is used unclad. Its fatigue strength, fatigue crack growth and fracture toughness compare favorably with 2024-T3. Replacement of alloy 2024 with alloy 6013 also reduces manufacturing costs for formed parts, because 6013 is readily formed in the T4 temper, then simply aged to T6, thus avoiding the costly heat treatments and straightening required for alloy 2024. 5 refs.

  9. The analysis of aluminum alloy structure beams under static load

    NASA Astrophysics Data System (ADS)

    Ho, Minghsiung; Wang, Pinning; Yeh, Jungpeng

    2017-04-01

    The Aluminum alloy had been applications in many areas. In this study, the models with four type's cross-section were designed and analyzed. Analyses of the use of aluminum alloy materials are 5086-H32, 6061-T6, 7005-T6 and 7075-T6. The materials selected are based on the recommendations of the casting plant. The boundary conditions are set according to the actual conditions of use. Force and torsion are used to apple on models under different conditions. The results of stress and deformation are discussed. The stress results were shown that 40x80 model with hollow cross-section under two end fixed middle beam load had the highest stresses of 41.177 MPa nearby fixed end position. The beam model of 40x80 hollow cross-section under boundary condition of one end fixed and one end force load like a cantilever beam has the maximum deformation 1.587 mm.

  10. Prevalence of Type VI Secretion System in Spanish Campylobacter jejuni Isolates.

    PubMed

    Ugarte-Ruiz, M; Stabler, R A; Domínguez, L; Porrero, M C; Wren, B W; Dorrell, N; Gundogdu, O

    2015-11-01

    Infections from Campylobacter jejuni pose a serious public health problem and are now considered the leading cause of foodborne bacterial gastroenteritis throughout the world. Sequencing of C. jejuni genomes has previously allowed a number of loci to be identified, which encode virulence factors that aid survival and pathogenicity. Recently, a Type VI secretion system (T6SS) consisting of 13 conserved genes was described in C. jejuni strains and recognised to promote pathogenicity and adaptation to the environment. In this study, we determined the presence of this T6SS in 63 Spanish C. jejuni isolates from the food chain and urban effluents using whole-genome sequencing. Our findings demonstrated that nine (14%) strains harboured the 13 ORFs found in prototype strain C. jejuni 108. Further studies will be necessary to determine the prevalence and importance of T6SS-positive C. jejuni strains. © 2014 The Authors. Zoonoses and Public Health Published by Blackwell Verlag GmbH.

  11. Advanced neutron source materials surveillance program

    SciTech Connect

    Heavilin, S.M.

    1995-01-01

    The Advanced Neutron Source (ANS) will be composed of several different materials, one of which is 6061-T6 aluminum. Among other components, the reflector vessel and the core pressure boundary tube (CPBT), are to be made of 6061-T6 aluminum. These components will be subjected to high thermal neutron fluences and will require a surveillance program to monitor the strength and fracture toughness of the 6061-T6 aluminum over their lifetimes. The purpose of this paper is to explain the steps that were taken in the summer of 1994 toward developing the surveillance program. The first goal was to decide upon standard specimens to use in the fracture toughness and tensile testing. Second, facilities had to be chosen for specimens representing the CPBT and the reflector vessel base, weld, and heat-affected-zone (HAZ) metals. Third, a timetable had to be defined to determine when to remove the specimens for testing.

  12. Killing by Type VI secretion drives genetic phase separation and correlates with increased cooperation

    NASA Astrophysics Data System (ADS)

    McNally, Luke; Bernardy, Eryn; Thomas, Jacob; Kalziqi, Arben; Pentz, Jennifer; Brown, Sam P.; Hammer, Brian K.; Yunker, Peter J.; Ratcliff, William C.

    2017-02-01

    By nature of their small size, dense growth and frequent need for extracellular metabolism, microbes face persistent public goods dilemmas. Genetic assortment is the only general solution stabilizing cooperation, but all known mechanisms structuring microbial populations depend on the availability of free space, an often unrealistic constraint. Here we describe a class of self-organization that operates within densely packed bacterial populations. Through mathematical modelling and experiments with Vibrio cholerae, we show how killing adjacent competitors via the Type VI secretion system (T6SS) precipitates phase separation via the `Model A' universality class of order-disorder transition mediated by killing. We mathematically demonstrate that T6SS-mediated killing should favour the evolution of public goods cooperation, and empirically support this prediction using a phylogenetic comparative analysis. This work illustrates the twin role played by the T6SS, dealing death to local competitors while simultaneously creating conditions potentially favouring the evolution of cooperation with kin.

  13. The Hcp proteins fused with diverse extended-toxin domains represent a novel pattern of antibacterial effectors in type VI secretion systems.

    PubMed

    Ma, Jiale; Pan, Zihao; Huang, Jinhu; Sun, Min; Lu, Chengping; Yao, Huochun

    2017-01-06

    The type VI secretion system (T6SS) is a widespread molecular weapon deployed by many bacterial species to target eukaryotic host cells or rival bacteria. Using a dynamic injection mechanism, diverse effectors can be delivered by T6SS directly into recipient cells. Here, we report a new family of T6SS effectors encoded by extended Hcps carrying diverse toxin domains. Bioinformatic analyses revealed that these Hcps with C-terminal extension toxins, designated as Hcp-ET, exist widely in the Enterobacteriaceae. To verify our findings, Hcp-ET1 was tested for its antibacterial effect, and showed effective inhibition of target cell growth via the predicted HNH-DNase activity by T6SS-dependent delivery. Further studies showed that Hcp-ET2 mediated interbacterial antagonism via a Tle1 phospholipase (encoded by DUF2235 domain) activity. Notably, comprehensive analyses of protein homology and genomic neighborhoods revealed that Hcp-ET3-4 is fused with 2 toxin domains (Pyocin S3 and Colicin-DNase) C-terminally, and its encoding gene is followed 3 duplications of the cognate immunity genes. However, some bacteria encode a separated hcp-et3 and an orphan et4 (et4O1) genes caused by a termination-codon mutation in the fusion region between Pyocin S3 and Colicin-DNase encoding fragments. Our results demonstrated that both of these toxins had antibacterial effects. Further, all duplications of the cognate immunity protein contributed to neutralize the DNase toxicity of Pyocin S3 and Colicin, which has not been reported previously. In conclusion, we propose that Hcp-ET proteins are polymorphic T6SS effectors, and thus present a novel encoding pattern of T6SS effectors.

  14. tRNA N6-adenosine threonylcarbamoyltransferase defect due to KAE1/TCS3 (OSGEP) mutation manifest by neurodegeneration and renal tubulopathy.

    PubMed

    Edvardson, Simon; Prunetti, Laurence; Arraf, Aiman; Haas, Drago; Bacusmo, Jo Marie; Hu, Jennifer F; Ta-Shma, Asas; Dedon, Peter C; de Crécy-Lagard, Valérie; Elpeleg, Orly

    2017-03-08

    Post-transcriptional tRNA modifications are numerous and require a large set of highly conserved enzymes in humans and other organisms. In yeast, the loss of many modifications is tolerated under unstressed conditions; one exception is the N(6)-threonyl-carbamoyl-adenosine (t(6)A) modification, loss of which causes a severe growth phenotype. Here we aimed at a molecular diagnosis in a brother and sister from a consanguineous family who presented with global developmental delay, failure to thrive and a renal defect manifesting in proteinuria and hypomagnesemia. Using exome sequencing, the patients were found to be homozygous for the c.974G>A (p.(Arg325Gln)) variant of the KAE1 gene. KAE1 is a constituent of the KEOPS complex, a five-subunit complex that catalyzes the second biosynthetic step of t(6)A in the cytosol. The yeast KAE1 allele carrying the equivalent mutation did not rescue the t(6)A deficiency of the kae1Δ yeast strain as efficiently as the WT allele; furthermore, t(6)A levels quantified by LC-MS/MS were lower in the kae1Δ strain which was complemented by the mutation than in the kae1Δ strain, which was complemented by the WT allele. We conclude that homozygosity for c.974G>A (p.(Arg325Gln)) in KAE1 likely exerts its pathogenic effect by perturbing t(6)A synthesis, thereby interfering with global protein production. This is the first report of t(6)A biosynthesis defect in human. KAE1 joins the growing list of cytoplasmic tRNA modification enzymes, all associated with severe neurological disorders.European Journal of Human Genetics advance online publication, 8 March 2017; doi:10.1038/ejhg.2017.30.

  15. PAAR-Rhs proteins harbor various C-terminal toxins to diversify the antibacterial pathways of type VI secretion systems.

    PubMed

    Ma, Jiale; Sun, Min; Dong, Wenyang; Pan, Zihao; Lu, Chengping; Yao, Huochun

    2017-01-01

    The type VI secretion system (T6SS) of bacteria plays a key role in competing for specific niches by the contact-dependent killing of competitors. Recently, Rhs proteins with polymorphic C-terminal toxin-domains that inhibit or kill neighboring cells were identified. In this report, we identified a novel Rhs with an MPTase4 (Metallopeptidase-4) domain (designated as Rhs-CT1) that showed an antibacterial effect via T6SS in Escherichia coli. We managed to develop a specific strategy by matching the diagnostic domain-architecture of Rhs-CT1 (Rhs with an N-terminal PAAR-motif and a C-terminal toxin domain) for effector retrieval and discovered a series of Rhs-CTs in E. coli. Indeed, the screened Rhs-CT3 with a REase-3 (Restriction endonuclease-3) domain also mediated interbacterial antagonism. Further analysis revealed that vgrGO1 and eagR/DUF1795 (upstream of rhs-ct) were required for the delivery of Rhs-CTs, suggesting eagR as a potential T6SS chaperone. In addition to chaperoned Rhs-CTs, neighborless Rhs-CTs could be classified into a distinct family (Rhs-Nb) sharing close evolutionary relationship with T6SS2-Rhs (encoded in the T6SS2 cluster of E. coli). Notably, the Rhs-Nb-CT5 was confirmed bioinformatically and experimentally to mediate interbacterial antagonism via Hcp2B-VgrG2 module. In a further retrieval analysis, we discovered various toxin/immunity pairs in extensive bacterial species that could be systematically classified into eight referential clans, suggesting that Rhs-CTs greatly diversify the antibacterial pathways of T6SS.

  16. Anti-LFA-1 antibodies enhance metastasis of ocular lymphoma to the brain and contralateral eye

    PubMed Central

    Shen, DeFen; Gottesman, Michael M.

    2012-01-01

    Previously we demonstrated that intraperitoneal (IP) inoculation of Rev-2-T-6 mouse lymphoma into syngeneic Balb/c hosts resulted in brain metastasis, migration along the optic nerve sheath, and ocular infiltration. In a second model: intravitreal inoculation of Rev-2-T-6 cells, the developing lymphoma was largely confined within the eye, seldom breaching the retinal pigment epithelium to reside in the choroid and sclera. There was no retrograde infiltration into the brain. Here, we describe a third, complementary model, whereby intravitreal inoculation of Rev-2-T-6 cells into Balb/c mice, followed by repeated IP inoculations of anti-LFA-1/CD11a monoclonal antibodies, results in extensive infiltration of the choroid, sclera, conjunctiva, eyelids and orbit. Furthermore, the lymphoma cells metastasize along the optic nerve sheath into the brain, and through the contralateral optic nerve tract into the contralateral eye. There is no systemic involvement of the lymphoma. Furthermore, anti-LFA-1 treatment results in elevated levels of serum anti-Rev-2-T-6 antibodies. Inoculation of Rev-2-T-6 cells into the vitreous of severe combined immune deficient mice demonstrates a course of clinical signs and histopathological findings similar to those in immune-competent mice treated with anti-LFA-1 antibodies, including invasion of the contralateral eye. Taken together, these findings suggest that confinement of Rev-2-T-6 lymphoma cells to the eye depends on active immune surveillance using a population of effector cells expressing the cell surface integrin LFA-1. Impairing this protection enhances tumor aggressiveness within the eye, and the likelihood of early retrograde lymphoma metastasis into the brain and the contralateral eye. PMID:22865235

  17. Structure of the Trehalose-6-phosphate Phosphatase from Brugia malayi Reveals Key Design Principles for Anthelmintic Drugs

    PubMed Central

    Farelli, Jeremiah D.; Galvin, Brendan D.; Li, Zhiru; Liu, Chunliang; Aono, Miyuki; Garland, Megan; Hallett, Olivia E.; Causey, Thomas B.; Ali-Reynolds, Alana; Saltzberg, Daniel J.; Carlow, Clotilde K. S.; Dunaway-Mariano, Debra; Allen, Karen N.

    2014-01-01

    Parasitic nematodes are responsible for devastating illnesses that plague many of the world's poorest populations indigenous to the tropical areas of developing nations. Among these diseases is lymphatic filariasis, a major cause of permanent and long-term disability. Proteins essential to nematodes that do not have mammalian counterparts represent targets for therapeutic inhibitor discovery. One promising target is trehalose-6-phosphate phosphatase (T6PP) from Brugia malayi. In the model nematode Caenorhabditis elegans, T6PP is essential for survival due to the toxic effect(s) of the accumulation of trehalose 6-phosphate. T6PP has also been shown to be essential in Mycobacterium tuberculosis. We determined the X-ray crystal structure of T6PP from B. malayi. The protein structure revealed a stabilizing N-terminal MIT-like domain and a catalytic C-terminal C2B-type HAD phosphatase fold. Structure-guided mutagenesis, combined with kinetic analyses using a designed competitive inhibitor, trehalose 6-sulfate, identified five residues important for binding and catalysis. This structure-function analysis along with computational mapping provided the basis for the proposed model of the T6PP-trehalose 6-phosphate complex. The model indicates a substrate-binding mode wherein shape complementarity and van der Waals interactions drive recognition. The mode of binding is in sharp contrast to the homolog sucrose-6-phosphate phosphatase where extensive hydrogen-bond interactions are made to the substrate. Together these results suggest that high-affinity inhibitors will be bi-dentate, taking advantage of substrate-like binding to the phosphoryl-binding pocket while simultaneously utilizing non-native binding to the trehalose pocket. The conservation of the key residues that enforce the shape of the substrate pocket in T6PP enzymes suggest that development of broad-range anthelmintic and antibacterial therapeutics employing this platform may be possible. PMID:24992307

  18. Identification of an Inhibitory Alcohol Binding Site in GABAA ρ1 Receptors

    PubMed Central

    Borghese, Cecilia M.; Ruiz, Carlos I.; Lee, Ui S.; Cullins, Madeline A.; Bertaccini, Edward J.; Trudell, James R.; Harris, R. Adron

    2016-01-01

    Alcohols inhibit γ-aminobutyric acid type A ρ1 receptor function. After introducing mutations in several positions of the second transmembrane helix in ρ1, we studied the effects of ethanol and hexanol on GABA responses using two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. The 6′ mutations produced the following effects on ethanol and hexanol responses: small increase or no change (T6′M), increased inhibition (T6′V) and small potentiation (T6′Y and T6′F). The 5′ mutations produced mainly increases in hexanol inhibition. Other mutations produced small (3′ and 9′) or no changes (2′ and L277 in the first transmembrane domain) in alcohol effects. These results suggest an inhibitory alcohol binding site near the 6′ position. Homology models of ρ1 receptors based on the X-ray structure of GluCl showed that the 2′, 5′, 6’ and 9′ residues were easily accessible from the ion pore, with 5′ and 6′ residues from neighboring subunits facing each other; L3′ and L277 also faced the neighboring subunit. We tested ethanol through octanol on single and double mutated ρ1 receptors [ρ1(I15′S), ρ1(T6′Y) and ρ1(T6′Y,I15′S)] to further characterize the inhibitory alcohol pocket in the wild-type ρ1 receptor. The pocket can only bind relatively short-chain alcohols and is eliminated by introducing Y in the 6’ position. Replacing the bulky 15′ residue with a smaller side chain introduced a potentiating binding site, more sensitive to long-chain than to short-chain alcohols. In conclusion, the net alcohol effect on the ρ1 receptor is determined by the sum of its actions on inhibitory and potentiating sites. PMID:26571107

  19. An ABC-transporter and an outer membrane lipoprotein participate in posttranslational activation of type VI secretion in Pseudomonas aeruginosa

    PubMed Central

    Casabona, Maria G.; Silverman, Julie M.; Sall, Khady M.; Boyer, Frédéric; Couté, Yohann; Poirel, Jessica; Grunwald, Didier; Mougous, Joseph D.; Elsen, Sylvie; Attree, Ina

    2012-01-01

    Pseudomonas aeruginosa is capable of injecting protein toxins into other bacterial cells through one of its three type VI secretion systems (T6SS). The activity of this T6SS is tightly regulated on the posttranslational level by phosphorylation-dependent and -independent pathways. The phosphorylation-dependent pathway consists of a Thr kinase/phosphatase pair (PpkA/PppA) that acts on a forkhead domain-containing protein Fha1, and a periplasmic protein, TagR, that positively regulates PpkA. In the present work, we biochemically and functionally characterize three additional proteins of the phosphorylation-dependent regulatory cascade that controls T6S activation: TagT, TagS and TagQ. We show that similar to TagR, these proteins act upstream of the PpkA/PppA checkpoint and influence phosphorylation of Fha1 and export of Hcp1 and Tse1. Localization studies demonstrate that TagQ is an outer membrane lipoprotein and TagR is associated with the outer membrane. Consistent with their homology to lipoprotein outer membrane localization (Lol) components, TagT and TagS form a stable inner membrane complex with ATPase activity. However, we find that outer membrane association of T6SS lipoproteins TagQ and TssJ1, and TagR, is unaltered in a ΔtagTS background. Notably, we found that TagQ is indispensible for anchoring of TagR to the outer membrane fraction. As T6S-dependent fitness of P. aeruginosa requires TagT, S, R and Q, we conclude that these proteins likely participate in a trans-membrane signaling pathway that promotes H1-T6SS activity under optimal environmental conditions. PMID:22765374

  20. Identification of an Inhibitory Alcohol Binding Site in GABAA ρ1 Receptors.

    PubMed

    Borghese, Cecilia M; Ruiz, Carlos I; Lee, Ui S; Cullins, Madeline A; Bertaccini, Edward J; Trudell, James R; Harris, R Adron

    2016-01-20

    Alcohols inhibit γ-aminobutyric acid type A ρ1 receptor function. After introducing mutations in several positions of the second transmembrane helix in ρ1, we studied the effects of ethanol and hexanol on GABA responses using two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. The 6' mutations produced the following effects on ethanol and hexanol responses: small increase or no change (T6'M), increased inhibition (T6'V), and small potentiation (T6'Y and T6'F). The 5' mutations produced mainly increases in hexanol inhibition. Other mutations produced small (3' and 9') or no changes (2' and L277 in the first transmembrane domain) in alcohol effects. These results suggest an inhibitory alcohol binding site near the 6' position. Homology models of ρ1 receptors based on the X-ray structure of GluCl showed that the 2', 5', 6', and 9' residues were easily accessible from the ion pore, with 5' and 6' residues from neighboring subunits facing each other; L3' and L277 also faced the neighboring subunit. We tested ethanol through octanol on single and double mutated ρ1 receptors [ρ1(I15'S), ρ1(T6'Y), and ρ1(T6'Y,I15'S)] to further characterize the inhibitory alcohol pocket in the wild-type ρ1 receptor. The pocket can only bind relatively short-chain alcohols and is eliminated by introducing Y in the 6' position. Replacing the bulky 15' residue with a smaller side chain introduced a potentiating binding site, more sensitive to long-chain than to short-chain alcohols. In conclusion, the net alcohol effect on the ρ1 receptor is determined by the sum of its actions on inhibitory and potentiating sites.

  1. Effect of heat treatment on tensile and fatigue deformation behavior of extruded Al-12 wt%Si alloy

    NASA Astrophysics Data System (ADS)

    Ham, Gi-Su; Baek, Min-Seok; Kim, Jong-Ho; Lee, Si-Woo; Lee, Kee-Ahn

    2017-01-01

    This study investigated the effect of heat treatment on tensile and high-cycle fatigue deformation behavior of extruded Al-12 wt%Si alloy. The material used in this study was extruded at a ratio of 17.7: 1 through extrusion process. To identify the effects of heat treatment, T6 heat treatment (515 °C/1 h, water quenching, and then 175 °C/10 h) was performed. Microstructural observation identified Si phases aligned in the extrusion direction in both extruded alloy (F) and heat treated alloy (T6). The average grain size of F alloy was 8.15 °C, and that of T6 alloy was 8.22 °C. Both alloys were composed of Al matrix, Si, Al2Cu, Al3Ni and AlFeSi phases. As T6 heat treatment was applied, Al2Cu phases became more finely and evenly distributed. Tensile results confirmed that yield strength increased from 119.0 MPa to 329.0 MPa, ultimate tensile strength increased from 226.8 MPa to 391.4 MPa, and the elongation decreased from 16.1% to 5.0% as T6 heat treatment was applied. High-cycle fatigue results represented F alloy's fatigue limit as 185 MPa and T6 alloy's fatigue limit as 275 MPa, indicating that high-cycle fatigue properties increased significantly as heat treatment was conducted. Through tensile and fatigue fracture surface analysis, this study considered the deformation behaviors of extruded and heat treated Al-Si alloys in relation to their microstructures.

  2. Contribution of the Type VI Secretion System Encoded in SPI-19 to Chicken Colonization by Salmonella enterica Serotypes Gallinarum and Enteritidis

    PubMed Central

    Blondel, Carlos J.; Yang, Hee-Jeong; Castro, Benjamín; Chiang, Sebastián; Toro, Cecilia S.; Zaldívar, Mercedes; Contreras, Inés; Andrews-Polymenis, Helene L.; Santiviago, Carlos A.

    2010-01-01

    Salmonella Gallinarum is a pathogen with a host range specific to poultry, while Salmonella Enteritidis is a broad host range pathogen that colonizes poultry sub-clinically but is a leading cause of gastrointestinal salmonellosis in humans and many other species. Despite recent advances in our understanding of the complex interplay between Salmonella and their hosts, the molecular basis of host range restriction and unique pathobiology of Gallinarum remain largely unknown. Type VI Secretion System (T6SS) represents a new paradigm of protein secretion that is critical for the pathogenesis of many Gram-negative bacteria. We recently identified a putative T6SS in the Salmonella Pathogenicity Island 19 (SPI-19) of Gallinarum. In Enteritidis, SPI-19 is a degenerate element that has lost most of the T6SS functions encoded in the island. In this work, we studied the contribution of SPI-19 to the colonization of Salmonella Gallinarum strain 287/91 in chickens. Non-polar deletion mutants of SPI-19 and the clpV gene, an essential T6SS component, colonized the ileum, ceca, liver and spleen of White Leghorn chicks poorly compared to the wild-type strain after oral inoculation. Return of SPI-19 to the ΔSPI-19 mutant, using VEX-Capture, complemented this colonization defect. In contrast, transfer of SPI-19 from Gallinarum to Enteritidis resulted in transient increase in the colonization of the ileum, liver and spleen at day 1 post-infection, but at days 3 and 5 post-infection a strong colonization defect of the gut and internal organs of the experimentally infected chickens was observed. Our data indicate that SPI-19 and the T6SS encoded in this region contribute to the colonization of the gastrointestinal tract and internal organs of chickens by Salmonella Gallinarum and suggest that degradation of SPI-19 T6SS in Salmonella Enteritidis conferred an advantage in colonization of the avian host. PMID:20661437

  3. A novel sensor kinase-response regulator hybrid controls biofilm formation and type VI secretion system activity in Burkholderia cenocepacia.

    PubMed

    Aubert, Daniel F; Flannagan, Ronald S; Valvano, Miguel A

    2008-05-01

    Burkholderia cenocepacia is an important opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis (CF). Adaptation of B. cenocepacia to the CF airways may play an important role in the persistence of the infection. We have identified a sensor kinase-response regulator (BCAM0379) named AtsR in B. cenocepacia K56-2 that shares 19% amino acid identity with RetS from Pseudomonas aeruginosa. atsR inactivation led to increased biofilm production and a hyperadherent phenotype in both abiotic surfaces and lung epithelial cells. Also, the atsR mutant overexpressed and hypersecreted an Hcp-like protein known to be specifically secreted by the type VI secretion system (T6SS) in other gram-negative bacteria. Amoeba plaque assays demonstrated that the atsR mutant was more resistant to Dictyostelium predation than the wild-type strain and that this phenomenon was T6SS dependent. Macrophage infection assays also demonstrated that the atsR mutant induces the formation of actin-mediated protrusions from macrophages that require a functional Hcp-like protein, suggesting that the T6SS is involved in actin rearrangements. Three B. cenocepacia transposon mutants that were found in a previous study to be impaired for survival in chronic lung infection model were mapped to the T6SS gene cluster, indicating that the T6SS is required for infection in vivo. Together, our data show that AtsR is involved in the regulation of genes required for virulence in B. cenocepacia K56-2, including genes encoding a T6SS.

  4. Monoclonal origin of B lymphocyte colony-forming cells in spleen colonies formed by multipotential hemopoietic stem cells

    PubMed Central

    Lala, PK; Johnson, GR

    1978-01-01

    Spleen colonies produced by transplanting lethally irradiated mice with either 12 day fetal liver or adult bone marrow cells were found to contain B- lymphocyte colony-forming cells (BL-CFC) . The proportion of BL-CFC positive spleen colonies did not increase substantially between 8 and 14 days after transplantation, the range being 18-45 percent. However, the absolute number of BL-CFC per spleen colony varied considerably (between 1 and 10,318), although the majority of colonies contained less than 200 BL-CFC. Irrespective of the time after transplantation, smaller spleen colonies were found to have a higher frequency of BL-CFC than larger spleen colonies. To determine the possible clonal origin of BL-CFC from spleen colony- forming unit (CFU-S), CBA mice were injected with equal numbers of CBA and CBA T(6)/T(6) fetal liver or adult bone marrow cells. Analysis of 7-15-day spleen colonies demonstrated that 90 percent were either exclusively T(6) positive or T(6) negative and approximately equal numbers ofboth colony types were observed. B-lymphocyte colonies were grown and successfully karyotyped from 19 spleen colonies. When compared with the original spleen colony karyotype the B-lymphocyte colony cells karyotype was identical in all 19 cases. In 3 of the 19 colonies analyzed a mixture of T(6) positive and T(6) negative karyotypes was present and identical proportions of the karyotypes were present in the pooled B-lymphocyte colony cells and spleen colony cells. The data indicate that the B-lymphocyte colony-forming cells detected in spleen colonies are genuine members of the hemopoietic clone derived from the initiating hemopoietic stem cell (CFU-S). PMID:309918

  5. A Novel Sensor Kinase-Response Regulator Hybrid Controls Biofilm Formation and Type VI Secretion System Activity in Burkholderia cenocepacia▿

    PubMed Central

    Aubert, Daniel F.; Flannagan, Ronald S.; Valvano, Miguel A.

    2008-01-01

    Burkholderia cenocepacia is an important opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis (CF). Adaptation of B. cenocepacia to the CF airways may play an important role in the persistence of the infection. We have identified a sensor kinase-response regulator (BCAM0379) named AtsR in B. cenocepacia K56-2 that shares 19% amino acid identity with RetS from Pseudomonas aeruginosa. atsR inactivation led to increased biofilm production and a hyperadherent phenotype in both abiotic surfaces and lung epithelial cells. Also, the atsR mutant overexpressed and hypersecreted an Hcp-like protein known to be specifically secreted by the type VI secretion system (T6SS) in other gram-negative bacteria. Amoeba plaque assays demonstrated that the atsR mutant was more resistant to Dictyostelium predation than the wild-type strain and that this phenomenon was T6SS dependent. Macrophage infection assays also demonstrated that the atsR mutant induces the formation of actin-mediated protrusions from macrophages that require a functional Hcp-like protein, suggesting that the T6SS is involved in actin rearrangements. Three B. cenocepacia transposon mutants that were found in a previous study to be impaired for survival in chronic lung infection model were mapped to the T6SS gene cluster, indicating that the T6SS is required for infection in vivo. Together, our data show that AtsR is involved in the regulation of genes required for virulence in B. cenocepacia K56-2, including genes encoding a T6SS. PMID:18316384

  6. Understanding the sequential activation of Type III and Type VI Secretion Systems in Salmonella typhimurium using Boolean modeling

    PubMed Central

    2013-01-01

    Background Three pathogenicity islands, viz. SPI-1 (Salmonella pathogenicity island 1), SPI-2 (Salmonella pathogenicity island 2) and T6SS (Type VI Secretion System), present in the genome of Salmonella typhimurium have been implicated in the virulence of the pathogen. While the regulation of SPI-1 and SPI-2 (both encoding components of the Type III Secretion System - T3SS) are well understood, T6SS regulation is comparatively less studied. Interestingly, inter-connections among the regulatory elements of these three virulence determinants have also been suggested to be essential for successful infection. However, till date, an integrated view of gene regulation involving the regulators of these three secretion systems and their cross-talk is not available. Results In the current study, relevant regulatory information available from literature have been integrated into a single Boolean network, which portrays the dynamics of T3SS (SPI-1 and SPI-2) and T6SS mediated virulence. Some additional regulatory interactions involving a two-component system response regulator YfhA have also been predicted and included in the Boolean network. These predictions are aimed at deciphering the effects of osmolarity on T6SS regulation, an aspect that has been suggested in earlier studies, but the mechanism of which was hitherto unknown. Simulation of the regulatory network was able to recreate in silico the experimentally observed sequential activation of SPI-1, SPI-2 and T6SS. Conclusions The present study integrates relevant gene regulatory data (from literature and our prediction) into a single network, representing the cross-communication between T3SS (SPI-1 and SPI-2) and T6SS. This holistic view of regulatory interactions is expected to improve the current understanding of pathogenesis of S. typhimurium. PMID:24079299

  7. Interaction of Tumor Necrosis Factor Receptor-associated Factor 6 (TRAF6) and Vav3 in the Receptor Activator of Nuclear Factor κB (RANK) Signaling Complex Enhances Osteoclastogenesis.

    PubMed

    Yu, Jiyeon; Yun, Hyeongseok; Shin, Bongjin; Kim, Yongjin; Park, Eui-Soon; Choi, Seunga; Yu, Jungeun; Amarasekara, Dulshara Sachini; Kim, Sumi; Inoue, Jun-Ichiro; Walsh, Matthew C; Choi, Yongwon; Takami, Masamichi; Rho, Jaerang

    2016-09-23

    The signaling pathway downstream of stimulation of receptor activator of nuclear factor κB (RANK) by RANK ligand is crucial for osteoclastogenesis. RANK recruits TNF receptor-associated factor 6 (TRAF6) to TRAF6-binding sites (T6BSs) in the RANK cytoplasmic tail (RANKcyto) to trigger downstream osteoclastogenic signaling cascades. RANKcyto harbors an additional highly conserved domain (HCR) that also activates crucial signaling during RANK-mediated osteoclastogenesis. However, the functional cross-talk between T6BSs and the HCR in the RANK signaling complex remains unclear. To characterize the cross-talk between T6BSs and the HCR, we screened TRAF6-interacting proteins using a proteomics approach. We identified Vav3 as a novel TRAF6 binding partner and evaluated the functional importance of the TRAF6-Vav3 interaction in the RANK signaling complex. We demonstrated that the coiled-coil domain of TRAF6 interacts directly with the Dbl homology domain of Vav3 to form the RANK signaling complex independent of the TRAF6 ubiquitination pathway. TRAF6 is recruited to the RANKcyto mutant, which lacks T6BSs, via the Vav3 interaction; conversely, Vav3 is recruited to the RANKcyto mutant, which lacks the IVVY motif, via the TRAF6 interaction. Finally, we determined that the TRAF6-Vav3 interaction resulting from cross-talk between T6BSs and the IVVY motif in RANKcyto enhances downstream NF-κB, MAPK, and NFATc1 activation by further strengthening TRAF6 signaling, thereby inducing RANK-mediated osteoclastogenesis. Thus, Vav3 is a novel TRAF6 interaction partner that functions in the activation of cooperative signaling between T6BSs and the IVVY motif in the RANK signaling complex. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Corrosion Properties of Rapidly Solidified Copper Base Alloys for Marine Service

    DTIC Science & Technology

    1988-02-01

    les alliages de cuivre sont utilis~s lorsqu’il faut i la fois une grande solidit6 et une excellente r6sistance i la corrosion. Dans le but d’am~liorer...les propri~t6s de certains alliages de cuivre , on a eu recours i la solidification rapide pour affiner les microstructures et pour augmenter la...30), a du fer (90/10 - 8 Fe) ainsi que du bronze d’aluminiun. La resistance A la corrosion des alliages S ainsi trait~s a 6t6 compar6e i celle

  9. A Preliminary Report on the Strength and Metallography of a Bimetallic Friction Stir Weld Joint Between AA6061 and MIL-DTL-46100E High Hardness Steel Armor

    DTIC Science & Technology

    2012-11-26

    plates of 6061-T6 aluminum alloy and High Hardness steel armor (MIL-STD-46100) were successfully joined by the friction stir welding ( FSW ) process using a...b 124 c FSW 194 d High Hardness Steel (HHS) base material 1034 e GMAW f tbd g AA6061/HHS FSW joint 176 8 a Kaiser Aluminum Certified Test...bimetallic friction stir weld joint between AA6061 and MIL-DTL-46100E High Hardness steel armor. ABSTRACT One half inch thick plates of 6061-T6 aluminum

  10. Bridge Fatigue Monitoring Device

    DTIC Science & Technology

    1990-11-01

    T6 aluminum parent coupon in Assemblies D and F,