Bounds on strain in large Tertiary shear zones of SE Asia from boudinage restoration

NASA Astrophysics Data System (ADS)

Lacassin, R.; Leloup, P. H.; Tapponnier, P.

1993-06-01

We have used surface-balanced restoration of stretched, boudinaged layers to estimate minimum amounts of finite strain in the mylonitic gneisses of the Oligo-Miocene Red River-Ailao Shan shear zone (Yunnan, China) and of the Wang Chao shear zone (Thailand). The layer-parallel extension values thus obtained range between 250 and 870%. We discuss how to use such extension values to place bounds on amounts of finite shear strain in these large crustal shear zones. Assuming simple shear, these values imply minimum total and late shear strains of, respectively, 33 ± 6 and 7 ± 3 at several sites along the Red River-Ailao Shan shear zone. For the Wang Chao shear zone a minimum shear strain of 7 ± 4 is deduced. Assuming homogeneous shear would imply that minimum strike-slip displacements along these two left-lateral shear zones, which have been interpreted to result from the India-Asia collision, have been of the order of 330 ± 60 km (Red River-Ailao Shan) and 35 ± 20 km (Wang Chao).

Elevated temperature creep and fracture properties of the 62Cu-35Au-3Ni braze alloy

NASA Astrophysics Data System (ADS)

Stephens, J. J.; Greulich, F. A.

1995-06-01

The Cu-Au-Ni braze alloys are used for metal/ceramic brazes in electronic assemblies because of their good wetting characteristics and low vapor pressure. We have studied the tensile creep properties of annealed 62Cu-35Au-3Ni alloy over the temperature range 250 °C to 750 °C. Two power-law equations have been developed for the minimum creep rate as a function of true stress and temperature. At the highest temperatures studied (650 °C and 750 °C), the minimum creep rate is well described with a stress exponent of 3.0, which can be rationalized in the context of Class I solid solution strengthening. The inverted shape of the creep curves observed at these temperatures is also consistent with Class I alloy behavior. At lower temperatures, power-law creep is well described with a stress exponent of 7.5, and normal three-stage creep curves are observed. Intergranular creep damage, along with minimum values of strain to fracture, is most apparent at 450 °C and 550 °C. The lower stress exponent in the Class I alloy regime helps to increase the strain to fracture at higher temperatures (650 °C and 750 °C). The minimum creep rate behavior of the 62Cu-35Au-3Ni alloy is also compared with those of the 74.2Cu-25. 8Au alloy and pure Cu. This comparison indicates that the 62Cu-35Au-3Ni has considerably higher creep strength than pure Cu. This fact suggests that the 62Cu-35Au-3Ni braze alloy can be used in low mismatch metal-to-ceramic braze joints such as Mo to metallized alumina ceramic with few problems. However, careful joint design may be essential for the use of this alloy in high thermal mismatch metal-to-ceramic braze joints.

Attenuated Virulence and Biofilm Formation in Staphylococcus aureus following Sublethal Exposure to Triclosan

PubMed Central

Latimer, Joe; Forbes, Sarah

2012-01-01

Subeffective exposure of Staphylococcus aureus to the biocide triclosan can reportedly induce a small-colony variant (SCV) phenotype. S. aureus SCVs are characterized by low growth rates, reduced pigmentation, and lowered antimicrobial susceptibility. While they may exhibit enhanced intracellular survival, there are conflicting reports regarding their pathogenicity. The current study reports the characteristics of an SCV-like strain of S. aureus created by repeated passage on sublethal triclosan concentrations. S. aureus ATCC 6538 (the passage 0 [P0] strain) was serially exposed 10 times to concentration gradients of triclosan to generate strain P10. This strain was then further passaged 10 times on triclosan-free medium (designated strain ×10). The MICs and minimum bactericidal concentrations of triclosan for P0, P10, and ×10 were determined, and growth rates in biofilm and planktonic cultures were measured. Hemolysin, DNase, and coagulase activities were measured, and virulence was determined using a Galleria mellonella pathogenicity model. Strain P10 exhibited decreased susceptibility to triclosan and characteristics of an SCV phenotype, including a considerably reduced growth rate and the formation of pinpoint colonies. However, this strain also had delayed coagulase production, had impaired hemolysis (P < 0.01), was defective in biofilm formation and DNase activity, and displayed significantly attenuated virulence. Colony size, hemolysis, coagulase activity, and virulence were only partially restored in strain ×10, whereas the planktonic growth rate was fully restored. However, ×10 was at least as defective in biofilm formation and DNase production as P10. These data suggest that although repeated exposure to triclosan may result in an SCV-like phenotype, this is not necessarily associated with increased virulence and adapted bacteria may exhibit other functional deficiencies. PMID:22430975

Feasibility and reproducibility of a standard protocol for 2D speckle tracking and tissue Doppler-based strain and strain rate analysis of the fetal heart.

PubMed

Crispi, Fàtima; Sepulveda-Swatson, Eduardo; Cruz-Lemini, Monica; Rojas-Benavente, Juan; Garcia-Posada, Raul; Dominguez, Jesus Maria; Sitges, Marta; Bijnens, Bart; Gratacós, Eduard

2012-01-01

Assessment of cardiac function in the fetal heart is challenging because of its small size and high heart rate, restricted physical access to the fetus, and impossibility of fetal ECG recording. We aimed to standardize the acquisition and postprocessing of fetal echocardiography for deformation analysis and to assess its feasibility, reproducibility, and correlation for longitudinal strain and strain rate measurements by tissue Doppler imaging (TDI) and 2D speckle tracking (2D-strain) during pregnancy. Echocardiography was performed in 56 fetuses. 2D and color TDI in apical or basal four-chamber views were recorded for subsequent analysis. Caution was taken to achieve a frame rate >70 Hz for speckle tracking and >150 Hz for TDI analysis. For each acquisition, 7.5 s of noncompressed data were stored in cine loop format and analyzed offline. Since fetal ECG information is by definition not available, aortic valve closure was marked from aortic flow and the onset of each cardiac cycle was manually indicated in the 2D images. Sample volume length was standardized at the minimum size. Two observers measured the left and right ventricular peak systolic longitudinal strain and strain-rate. Strain and strain rate measurements were feasible in 93% of the TDI and 2D-strain acquisitions. The mean time spent on analyzing TDI images was 18 min, with an intraclass agreement coefficient of 0.86 (95% CI 0.77-0.92), 0.83 (95% CI 0.72-0.90), 0.96 (95% CI 0.93-0.98), and 0.86 (95% CI 0.76-0.92) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers using tissue Doppler also showed high reliability. The mean time spent for 2D-strain analysis was 15 min, with an intraclass agreement coefficient of 0.97 (95% CI 0.95-0.98), 0.94 (95% CI 0.89-0.96), 0.96 (95% CI 0.93-0.98), and 0.84 (95% CI 0.73-0.90) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers also showed a high reliability that was similar for TDI and 2D-strain. There was a weak correlation between TDI and 2D-strain measurements. A standard protocol with fixed acquisition and processing settings, including manual indication of the timing events of the cardiac cycle to correct for the lack of ECG, was feasible and reproducible for the evaluation of longitudinal ventricular strain and strain rate of the fetal heart by TDI as well as 2D-strain analysis. However, both techniques are not interchangeable as the correlation between them is relatively poor. Copyright © 2012 S. Karger AG, Basel.

Flexible heartbeat sensor for wearable device.

PubMed

Kwak, Yeon Hwa; Kim, Wonhyo; Park, Kwang Bum; Kim, Kunnyun; Seo, Sungkyu

2017-08-15

We demonstrate a flexible strain-gauge sensor and its use in a wearable application for heart rate detection. This polymer-based strain-gauge sensor was fabricated using a double-sided fabrication method with polymer and metal, i.e., polyimide and nickel-chrome. The fabrication process for this strain-gauge sensor is compatible with the conventional flexible printed circuit board (FPCB) processes facilitating its commercialization. The fabricated sensor showed a linear relation for an applied normal force of more than 930 kPa, with a minimum detectable force of 6.25Pa. This sensor can also linearly detect a bending radius from 5mm to 100mm. It is a thin, flexible, compact, and inexpensive (for mass production) heart rate detection sensor that is highly sensitive compared to the established optical photoplethysmography (PPG) sensors. It can detect not only the timing of heart pulsation, but also the amplitude or shape of the pulse signal. The proposed strain-gauge sensor can be applicable to various applications for smart devices requiring heartbeat detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of High Strain-Rate Deformation and Aging Temperature on the Evolution of Structure, Microhardness, and Wear Resistance of Low-Alloyed Cu-Cr-Zr Alloy

NASA Astrophysics Data System (ADS)

Kheifets, A. E.; Khomskaya, I. V.; Korshunov, L. G.; Zel'dovich, V. I.; Frolova, N. Yu.

2018-04-01

The effect of the preliminary high strain-rate deformation, performed via the method of dynamic channel-angular pressing (DCAP), and subsequent annealings on the tribological properties of a dispersionhardened Cu-0.092 wt % Cr-0.086 wt % Zr alloy has been investigated. It has been shown that the surfacelayer material of the alloy with a submicrocrystalline (SMC) structure obtained by the DCAP method can be strengthened using severe plastic deformation by sliding friction at the expense of creating a nanocrystalline structure with crystallites of 15-60 nm in size. It has been shown that the SMC structure obtained by the high strain-rate DCAP deformation decreases the wear rate of the samples upon sliding friction by a factor of 1.4 compared to the initial coarse-grained state. The maximum values of the microhardness and minimum values of the coefficient of friction and shear strength have been obtained in the samples preliminarily subjected to DCAP and aging at 400°C. The attained level of microhardness is 3350 MPa, which exceeds the microhardness of the alloy in the initial coarse-grained state by five times.

Right ventricular diastolic performance in children with pulmonary arterial hypertension associated with congenital heart disease: correlation of echocardiographic parameters with invasive reference standards by high-fidelity micromanometer catheter.

PubMed

Okumura, Kenichi; Slorach, Cameron; Mroczek, Dariusz; Dragulescu, Andreea; Mertens, Luc; Redington, Andrew N; Friedberg, Mark K

2014-05-01

Right ventricular diastolic dysfunction influences outcomes in pulmonary arterial hypertension (PAH), but echocardiographic parameters have not been investigated in relation to invasive reference standards in pediatric PAH. We investigated echocardiographic parameters of right ventricular diastolic function in children with PAH in relation to simultaneously measured invasive reference measures. We prospectively recruited children undergoing a clinically indicated cardiac catheterization for evaluation of PAH and pulmonary vasoreactivity testing. Echocardiography was performed simultaneously with invasive reference measurements by high-fidelity micromanometer catheter. For analysis, patients were divided into shunt and nonshunt groups. Sixteen children were studied. In the group as a whole, significant correlations were found among τ and tricuspid deceleration time, E', E/E', TimeE-E', A wave velocity, and global early and late diastolic strain rate. dp/dt minimum correlated significantly with late diastolic tricuspid annular velocity (A'), tissue Doppler imaging-derived systolic:diastolic duration ratio, and global late diastolic strain rate. End-diastolic pressure correlated significantly with tissue Doppler imaging-derived systolic:diastolic duration ratio. On multivariate analysis, tricuspid deceleration time, TimeE-E', and global early diastolic strain rate were independent predictors of τ, whereas tissue Doppler imaging-derived systolic:diastolic duration ratio was an independent predictor of dp/dt minimum. In general, correlations between echocardiographic and invasive parameters were better in the shunt group than in the nonshunt group. Echocardiography correlates with invasive reference measures of right ventricular diastolic function in children with PAH, although it does not differentiate between early versus late diastolic abnormalities. Newer echocardiographic techniques may have added value to assess right ventricular diastolic dysfunction in this population. © 2014 American Heart Association, Inc.

Right Atrial Deformation in Predicting Outcomes in Pediatric Pulmonary Hypertension.

PubMed

Jone, Pei-Ni; Schäfer, Michal; Li, Ling; Craft, Mary; Ivy, D Dunbar; Kutty, Shelby

2017-12-01

Elevated right atrial (RA) pressure is a risk factor for mortality, and RA size is prognostic of adverse outcomes in pulmonary hypertension (PH). There is limited data on phasic RA function (reservoir, conduit, and pump) in pediatric PH. We sought to evaluate (1) the RA function in pediatric PH patients compared with controls, (2) compare the RA deformation indices with Doppler indices of diastolic dysfunction, functional capacity, biomarkers, invasive hemodynamics, and right ventricular functional indices, and (3) evaluate the potential of RA deformation indices to predict clinical outcomes. Sixty-six PH patients (mean age 7.9±4.7 years) were compared with 36 controls (7.7±4.4 years). RA and right ventricular deformation indices were obtained using 2-dimensional speckle tracking (2DCPA; TomTec, Germany). RA strain, strain rates, emptying fraction, and right ventricular longitudinal strain were measured. RA function was impaired in PH patients versus controls ( P <0.001). There were significant associations between RA function with invasive hemodynamics ( P <0.01). RA reservoir, pump function, the rate of RA filling, and atrial minimum volume predicted adverse clinical outcomes (hazard ratio [HR], 0.15; confidence interval [CI], 0.03-0.73; P <0.01; HR, 0.05; CI, 0.003-0.43; P <0.004; HR, 0.04; CI, 0.006-0.56; P <0.01; and HR, 8.6; CI, 1.6-37.2; P <0.01, respectively). RA deformation properties are significantly altered in pediatric PH patients. Progressive worsening of RA reservoir and conduit functions is related to changes in right ventricular diastolic dysfunction. RA reservoir function, pump function, the rate of atrial filling, and atrial minimum volume emerged as outcome predictors in pediatric PH. © 2017 American Heart Association, Inc.

Elongational flow of polymer melts at constant strain rate, constant stress and constant force

NASA Astrophysics Data System (ADS)

Wagner, Manfred H.; Rolón-Garrido, Víctor H.

2013-04-01

Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.

Continuous Cultivation for Apparent Optimization of Defined Media for Cellulomonas sp. and Bacillus cereus

PubMed Central

Summers, R. J.; Boudreaux, D. P.; Srinivasan, V. R.

1979-01-01

Steady-state continuous culture was used to optimize lean chemically defined media for a Cellulomonas sp. and Bacillus cereus strain T. Both organisms were extremely sensitive to variations in trace-metal concentrations. However, medium optimization by this technique proved rapid, and multifactor screening was easily conducted by using a minimum of instrumentation. The optimized media supported critical dilution rates of 0.571 and 0.467 h−1 for Cellulomonas and Bacillus, respectively. These values approximated maximum growth rate values observed in batch culture. PMID:16345417

Impact of primary antibiotic resistance on the effectiveness of sequential therapy for Helicobacter pylori infection: lessons from a 5-year study on a large number of strains.

PubMed

Gatta, L; Scarpignato, C; Fiorini, G; Belsey, J; Saracino, I M; Ricci, C; Vaira, D

2018-05-01

The increasing prevalence of strains resistant to antimicrobial agents is a critical issue in the management of Helicobacter pylori (H. pylori) infection. (1) To evaluate the prevalence of primary resistance to clarithromycin, metronidazole and levofloxacin (2) to assess the effectiveness of sequential therapy on resistant strains (3) to identify the minimum number of subjects to enrol for evaluating the effectiveness of an eradication regimen in patients harbouring resistant strains. Consecutive 1682 treatment naïve H. pylori-positive patients referred for upper GI endoscopy between 2010 and 2015 were studied and resistances assessed by E-test. Sequential therapy was offered, effectiveness evaluated and analysed. H. pylori-primary resistance to antimicrobials tested was high, and increased between 2010 and 2015. Eradication rates were (estimates and 95% CIs): 97.3% (95.6-98.4) in strains susceptible to clarithromycin and metronidazole; 96.1% (91.7-98.2) in strains resistant to metronidazole but susceptible to clarithromycin; 93.4% (88.2-96.4) in strains resistant to clarithromycin but susceptible to metronidazole; 83.1% (77.7-87.3) in strains resistant to clarithromycin and metronidazole. For any treatment with a 75%-85% eradication rate, some 98-144 patients with resistant strains need to be studied to get reliable information on effectiveness in these patients. H. pylori-primary resistance is increasing and represents the most critical factor affecting effectiveness. Sequential therapy eradicated 83% of strains resistant to clarithromycin and metronidazole. Reliable estimates of the effectiveness of a given regimen in patients harbouring resistant strains can be obtained only by assessing a large number of strains. © 2018 John Wiley & Sons Ltd.

[Isolation and Identification of Petroleum Degradation Bacteria and Interspecific Interactions Among Four Bacillus Strains].

PubMed

Wang, Jia-nan; Shi, Yan-yun; Zheng, Li-yan; Wang, Zhe; Cai, Zhang; Liu, Jie

2015-06-01

Six petroleum-degrading strains were isolated from oil-contaminated soil at Dagang oil field and oil sewage on Bohai offshore drilling platform in Tianjin using enrichment culture and isolation method. The physiological biochemical test together with 16S rDNA sequencing analysis indicated that they belonged to Bacillus (S1, S2, S3, S4), Pseudomonas (W1) and Ochrobactrum (W2), respectively. The strain S3 had the maximum degradation rate of alkane (41.3%) and aromatic hydrocarbon (30.9%) among all isolated strains showing the better degradation efficiency by endogenous bacteria when compared to that by the exogenous bacteria. The four Bacillus strains were used to construct microbiome, thereafter subjected to petroleum degradation efficiency test and analyzed. The results showed that microbiome F3 consisting of S1 and S4 had the maximum degradation rates of alkane (50.5%) and aromatic hydrocarbon (54.0%), which were 69.9% and 156.1% higher than those by single bacterium, respectively. Furthermore, they were 22.1% and 74.6% respectively higher than those by the most optimal degradation bacterium S3. Microbiome F4 consisting of S2 and S3 had the minimum degradation rates of alkane (18.5%) and aromatic hydrocarbon (18.9%) which were 55.3% and 39.0% lower than the degradation rates of single bacterium, respectively. The results also demonstrated that there were both microbial synergy promotion and antagonism inhibition among bacteria of the same genus in the petroleum degradation period. Bacteria with close affinity in Bacillus genus displayed mainly promoted petroleum degradation effect.

[Study of marine actinomycetes isolated from the central coast of Peru and their antibacterial activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis].

PubMed

León, Jorge; Aponte, Juan José; Rojas, Rosario; Cuadra, D'Lourdes; Ayala, Nathaly; Tomás, Gloria; Guerrero, Marco

2011-06-01

To determine the antimicrobial potential of marine actinomycetes against drug-resistant pathogens represented by strains of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE). Strains of actinomycetes (29) isolated from marine sediment were evaluated by their characteristics in two culture media and by testing their inhibitory capacity by in vitro antagonism against multi-drug resistant (MDR) pathogenic bacteria for MRSA and VRE. Organic extracts of 3 selected actinomicetes were processed to determine the minimum inhibitory concentration (MIC) of the active compound. Most isolated actinomycetes belong to a homogeneous group of write-gray actinomycetes with a good growth in Marine Agar. The inhibitory rates of the isolates were above 85% for both pathogens with inhibition zones greater than 69 and 78 mm in diameter for MRSA and VRE respectively. Dichloromethane extracts of 3 isolates (I-400A, B1-T61, M10-77) showed strong inhibitory activity of both pathogens, M10-77 being the highest actinomycete strain with antibiotic activity against methicillin-resistant S. aureus ATCC 43300 and vancomycin-resistant E. faecalis ATCC 51299 with a minimum inhibitory concentrations (MIC) of 7.9 and 31.7 μg/ml respectively. Phylogenetic analysis of M10-77 strain showed 99% similarity with the marine species Streptomyces erythrogriseus. Marine sediments of the central coast of Peru, are a source of actinomycetes strains showing high capacity to produce bioactive compounds able to inhibit pathogens classified as multi-drug-resistant such as methicillin-resistant S. aureus and vancomycin-resistant E. faecalis.

Comparison of patella bone strain between females with and without patellofemoral pain: a finite element analysis study.

PubMed

Ho, Kai-Yu; Keyak, Joyce H; Powers, Christopher M

2014-01-03

Elevated bone principal strain (an indicator of potential bone injury) resulting from reduced cartilage thickness has been suggested to contribute to patellofemoral symptoms. However, research linking patella bone strain, articular cartilage thickness, and patellofemoral pain (PFP) remains limited. The primary purpose was to determine whether females with PFP exhibit elevated patella bone strain when compared to pain-free controls. A secondary objective was to determine the influence of patella cartilage thickness on patella bone strain. Ten females with PFP and 10 gender, age, and activity-matched pain-free controls participated. Patella bone strain fields were quantified utilizing subject-specific finite element (FE) models of the patellofemoral joint (PFJ). Input parameters for the FE model included (1) PFJ geometry, (2) elastic moduli of the patella bone, (3) weight-bearing PFJ kinematics, and (4) quadriceps muscle forces. Using quasi-static simulations, peak and average minimum principal strains as well as peak and average maximum principal strains were quantified. Cartilage thickness was quantified by computing the perpendicular distance between opposing voxels defining the cartilage edges on axial plane magnetic resonance images. Compared to the pain-free controls, individuals with PFP exhibited increased peak and average minimum and maximum principal strain magnitudes in the patella. Additionally, patella cartilage thickness was negatively associated with peak minimum principal patella strain and peak maximum principal patella strain. The elevated bone strain magnitudes resulting from reduced cartilage thickness may contribute to patellofemoral symptoms and bone injury in persons with PFP. © 2013 Published by Elsevier Ltd.

Strain Recovery by TiNi Element Under Fast Heating

NASA Astrophysics Data System (ADS)

Volkov, Aleksandr E.; Miszuris, Wiktoria; Volkova, Natalia A.

2018-03-01

A theoretical and experimental study of strain recovery under fast heating of a shape memory alloy (SMA) rod preliminarily stretched in the martensitic state is carried out. Two theoretical models are considered: instantaneous heating and heating with temperature variation during a finite time. In the first case, it is supposed that the straight SMA rod experiences an instantaneous reverse martensitic transformation, and in the second the transformation is supposed to progress at a rate corresponding to the temperature rate. Analytical expression for the time dependence of the rod free-end displacement is obtained. In the experiment, a wire specimen made of titanium-nickel SMA was heated by a short impulse of electric current. The variation of the specimen length in time was registered. Thus, it has been shown that the minimum operation time of an SMA actuator (time needed for the strain recovery) can be reduced to 20 µs. Comparison of the theoretical results with the experimental ones leads to the conclusion that the displacement variation in time is controlled by the rate of heating and the inertia of the specimen. The incubation time of the martensitic transformation on the microscale apparently is estimated as less than 1 µs.

Strain Recovery by TiNi Element Under Fast Heating

NASA Astrophysics Data System (ADS)

Volkov, Aleksandr E.; Miszuris, Wiktoria; Volkova, Natalia A.

2018-01-01

A theoretical and experimental study of strain recovery under fast heating of a shape memory alloy (SMA) rod preliminarily stretched in the martensitic state is carried out. Two theoretical models are considered: instantaneous heating and heating with temperature variation during a finite time. In the first case, it is supposed that the straight SMA rod experiences an instantaneous reverse martensitic transformation, and in the second the transformation is supposed to progress at a rate corresponding to the temperature rate. Analytical expression for the time dependence of the rod free-end displacement is obtained. In the experiment, a wire specimen made of titanium-nickel SMA was heated by a short impulse of electric current. The variation of the specimen length in time was registered. Thus, it has been shown that the minimum operation time of an SMA actuator (time needed for the strain recovery) can be reduced to 20 µs. Comparison of the theoretical results with the experimental ones leads to the conclusion that the displacement variation in time is controlled by the rate of heating and the inertia of the specimen. The incubation time of the martensitic transformation on the microscale apparently is estimated as less than 1 µs.

Thermomechanical coupling and dynamic strain ageing in ductile fracture

NASA Astrophysics Data System (ADS)

Delafosse, David

1995-01-01

This work is concerned with plastic deformation at the tip of a ductile tearing crack during propagation. Two kinds of effects are investigated: the thermomechanical coupling at the tip of a mobile ductile crack, and the influence of Dynamic Strain Aging (DSA) on ductile fracture. Three alloys are studied: a nickel based superalloy (N18), a soft carbon steel, and an Al-Li light alloy (2091). The experimental study of the thermo mechanical coupling effects by means of infrared thermography stresses the importance of plastic dissipation in the energy balance of ductile fracture. Numerical simulations involving plastic deformation as the only dissipation mechanism account for the main part of the measured heating. The effects of DSA on ductile tearing are investigated in the 2091 Al-Li alloy. Based on the strain rate/temperature dependence predicted by the standard model of DSA, an experimental procedure is set up for this purpose. Three main effects are evidenced. A maximum in tearing resistance is shown to be associated with the minimum of strain rate sensitivity. Through a simple model, this peak in tearing resistance is attributed to an increase in plastic dissipation as the strain rate sensitivity is decreased. Heterogenous plastic deformation is observed in the crack tip plastic zone. Comparison with uniaxial testing allows us to identify the observed strain heterogeneities as Portevin-Le Chatelier instabilities in the crack tip plastic zone. We perform a simplified numerical analysis of the effect of strain localization on crack tip screening. Finally, small crack propagation instabilities appear at temperatures slightly above that of the tearing resistance peak. These are interpreted as resulting from a positive feed-back between the local heating at the tip of a moving crack and the decrease in tearing resistance with increasing temperature.

The association of bacterial C9-based TTX-like compounds with Prorocentrum minimum opens new uncertainties about shellfish seafood safety.

PubMed

Rodríguez, Inés; Alfonso, Amparo; Alonso, Eva; Rubiolo, Juan A; Roel, María; Vlamis, Aristidis; Katikou, Panagiota; Jackson, Stephen A; Menon, Margassery Lekha; Dobson, Alan; Botana, Luis M

2017-01-20

In 2012, Tetrodotoxin (TTX) was identified in mussels and linked to the presence of Prorocentrum minimum (P. minimum) in Greece. The connexion between TTX and P. minimum was further studied in this paper. First, the presence of TTX-producer bacteria, Vibrio and Pseudomonas spp, was confirmed in Greek mussels. In addition these samples showed high activity as inhibitors of sodium currents (I Na ). P. minimum was before associated with neurotoxic symptoms, however, the nature and structure of toxins produced by this dinoflagellate remains unknown. Three P. minimum strains, ccmp1529, ccmp2811 and ccmp2956, growing in different conditions of temperature, salinity and light were used to study the production of toxic compounds. Electrophysiological assays showed no effect of ccmp2811 strain on I Na , while ccmp1529 and ccmp2956 strains were able to significantly reduce I Na in the same way as TTX. In these samples two new compounds, m/z 265 and m/z 308, were identified and characterized by liquid chromatography tandem high-resolution mass spectrometry. Besides, two TTX-related bacteria, Roseobacter and Vibrio sp, were observed. These results show for the first time that P. minimum produce TTX-like compounds with a similar ion pattern and C9-base to TTX analogues and with the same effect on I Na .

High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part 1: Narloy Z

NASA Technical Reports Server (NTRS)

Conway, J. B.; Stentz, R. H.; Berling, J. T.

1974-01-01

Short-term tensile and low-cycle fatigue data are reported for Narloy Z, a centrifugally cast, copper-base alloy. Tensile tests were performed at room temperature in air and in argon at 482, 538 and 593 C using an axial strain rate of .002/sec to the -1 power. In addition tensile tests were performed at 538 C in an evaluation of tensile properties at strain rates of .004 and .01/sec to the -1 power. Ultimate and yield strength values of about 315 and 200 MN/sq m respectively were recorded at room temperature and these decreased to about 120 and 105 respectively as the temperature was increased to 593 C. Reduction in area values were recorded in the range from 40 to 50% with some indication of a minimum ductility point at 538 C.

Preliminary investigation of the kinetics of primary creep of a two phase gamma TiAl alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, R.W.

1993-11-01

It is the intent of this communication to present and discuss some data regarding the kinetics of primary creep of a two phase gamma TiAl alloy which had been studied previously to determine the mechanisms giving rise to the minimum strain rate. In order to study the kinetics of primary creep of the present gamma TiAl alloy an approach previously taken by Dorn et al and also recently employed by Argon and Bhattacharya was taken. Dorn et al demonstrated that at a given constant stress, the strain rate during primary creep is governed by a combined time-temperature parameter [Theta] =more » t exp([minus]Q/RT) where Q is the activation energy for self diffusion which many times also governs the process of steady-state creep. It was shown that at the same constant stress level all primary creep curves were found to collapse on one another when the primary creep strain is plotted as a function of [Theta][sup (9)].« less

Stress corrosion behavior of Ru-enhanced alpha-beta titanium alloys in methanol solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schutz, R.W.; Horrigan, J.M.; Bednarowicz, T.A.

1998-12-31

Conservative, practical guidelines for the minimum water content required to prevent methanolic stress corrosion cracking (SCC) of Ti-6Al-4V-Ru and Ti-3Al-2.5V-Ru alloy tubulars have been developed from slow strain rate testing in plain and acidified NaCl-saturated methanol-water solutions at 25 C. A minimum methanol water content of 10 wt.% is proposed for Ti-6Al-4V-Ru, whereas 2-3 wt.% is sufficient for the lower strength Ti-3Al-2.5V-Ru alloy. Although HCl-acidification aggravated methanolic SCC, intermixing of methanol with crude oil or pure hydrocarbons, H{sub 2}S gas saturation, and/or increasing temperature diminished cracking susceptibility in these alloy tubulars.

Quasi-static responses and variational principles in gradient plasticity

NASA Astrophysics Data System (ADS)

Nguyen, Quoc-Son

2016-12-01

Gradient models have been much discussed in the literature for the study of time-dependent or time-independent processes such as visco-plasticity, plasticity and damage. This paper is devoted to the theory of Standard Gradient Plasticity at small strain. A general and consistent mathematical description available for common time-independent behaviours is presented. Our attention is focussed on the derivation of general results such as the description of the governing equations for the global response and the derivation of related variational principles in terms of the energy and the dissipation potentials. It is shown that the quasi-static response under a loading path is a solution of an evolution variational inequality as in classical plasticity. The rate problem and the rate minimum principle are revisited. A time-discretization by the implicit scheme of the evolution equation leads to the increment problem. An increment of the response associated with a load increment is a solution of a variational inequality and satisfies also a minimum principle if the energy potential is convex. The increment minimum principle deals with stables solutions of the variational inequality. Some numerical methods are discussed in view of the numerical simulation of the quasi-static response.

Temporal variations in extension rate on the Lone Mountain fault and strain distribution in the eastern California shear zone-Walker Lane

NASA Astrophysics Data System (ADS)

Hoeft, J. S.; Frankel, K. L.

2010-12-01

The eastern California shear zone (ECSZ) and Walker Lane represent an evolving segment of the Pacific-North America plate boundary. Understanding temporal variations in strain accumulation and release along plate boundary structures is critical to assessing how deformation is accommodated throughout the lithosphere. Late Pleistocene displacement along the Lone Mountain fault suggests the Silver Peak-Lone Mountain (SPLM) extensional complex is an important structure in accommodating and transferring strain within the ECSZ and Walker Lane. Using geologic and geomorphic mapping, differential global positioning system surveys, and terrestrial cosmogenic nuclide (TCN) geochronology, we determined rates of extension across the Lone Mountain fault in western Nevada. The Lone Mountain fault displaces the northwestern Lone Mountain and Weepah Hills piedmonts and is the northeastern component of the SPLM extensional complex, a series of down-to-the-northwest normal faults. We mapped seven distinct alluvial fan deposits and dated three of the surfaces using 10Be TCN geochronology, yielding ages of 16.5 ± 1.2 ka, 92 ± 9 ka, and 137 ± 25 ka for the Q3b, Q2c, and Q2b deposits, respectively. The ages were combined with scarp profile measurements across the displaced fans to obtain minimum rates of extension; the Q2b and Q2c surfaces yield an extension rate between 0.1 ± 0.1 and 0.2 ± 01 mm/yr and the Q3b surface yields a rate of 0.2 ± 0.1 to 0.4 ± 0.1 mm/yr, depending on the dip of the fault. Active extension on the Lone Mountain fault suggests that it helps partition strain off of the major strike-slip faults in the northern ECSZ and transfers deformation to the east around the Mina Deflection and northward into the Walker Lane. Combining our results with estimates from other faults accommodating dextral shear in the northern ECSZ reveals an apparent discrepancy between short- and long-term rates of strain accumulation and release. If strain rates have remained constant since the late Pleistocene, this could reflect transient strain accumulation, similar to the Mojave segment of the ECSZ. However, our data also suggest a potential increase in strain rates between ~92 ka and ~17 ka, and possibly to present day, which may also help explain the mismatch between long- and short-term rates of deformation in the region.

Repeatability of strain magnitude and strain rate measurements in the periodontal ligament using fibre Bragg gratings: An ex vivo study in a swine model.

PubMed

Romanyk, Dan L; Guan, Raymond; Major, Paul W; Dennison, Christopher R

2017-03-21

Measurement of periodontal ligament (PDL) strain in an ex vivo or in vivo setting of a complete tooth-PDL-bone complex (TPBC) has yet to be achieved in the literature. The objective of this study was to investigate inter- and intra-TPBC PDL strain measurement using fibre Bragg grating (FBG) strain sensors. Second and third premolars from the left and the right side of four swine mandibles were removed to yield sixteen TPBC samples. Samples were secured in a miniature load-frame equipped with a digital actuator used to apply apical-directed displacement to the tooth. The same tooth on left and right sides of the mouth were exposed to the same loading condition over ten trials allowing for comparisons in a split-mouth study. Displacements of 0.2 and 0.3mm were considered along with displacement rates of 0.025, 0.05, and 0.1mm/s, yielding six loading combinations. Hypothesis testing between left and right teeth revealed FBGs did not always measure the same strain between left and right TPBCs. For all strain measures, the average coefficient of variation (CV) (all data collected) was 2.16 (range: 0.274-10.71). For repeated measures in single TPBCs, the minimum CV ranged from 0.037 to 0.449, and generally coincided with the time of maximum strain measured over the test duration. Based on the findings of this study, it is suggested that FBGs can provide repeatable ex vivo strain measures in the PDL of complete TPBCs. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Ciprofloxacin Impact on Biofilm Formation by Proteus Mirabilis and P. Vulgaris Strains

PubMed Central

Kwiecinska-Pirog, Joanna; Skowron, Krzysztof; Bartczak, Wojciech; Gospodarek-Komkowska, Eugenia

2016-01-01

Background Proteus spp. bacilli belong to opportunistic human pathogens, which are primarily responsible for urinary tract and wound infections. An important virulence factor is their ability to form biofilms that greatly reduce the effectiveness of antibiotics in the site of infection. Objectives The aim of this study was to determine the value of the minimum concentration of ciprofloxacin that eradicates a biofilm of Proteus spp. strains. Materials and Methods A biofilm formation of 20 strains of P. mirabilis and 20 strains of P. vulgaris were evaluated by a spectrophotometric method using 0.1% 2, 3, 5-Triphenyl-tetrazolium chloride solution (TTC, AVANTORTM). On the basis of the results of the absorbance of the formazan, a degree of reduction of biofilm and minimum biofilm eradication (MBE) values of MBE50 and MBE90 were determined. Results All tested strains formed a biofilm. A value of 1.0 μg/mL ciprofloxacin is MBE50 for the strains of both tested species. An MBE90 value of ciprofloxacin for isolates of P. vulgaris was 2 μg/mL and for P. mirabilis was 512 μg/mL. Conclusions Minimum biofilm eradication values of ciprofloxacin obtained in the study are close to the values of the minimal inhibition concentration (MIC). PMID:27303616

Epidemiological and molecular characterization of Staphylococcus haemolyticus strains, from a hematology ward, with decreased susceptibility to glycopeptides.

PubMed

Ma, Xiao Xue; Sun, Dan Dan; Hu, Jian; Wang, En Hua; Luo, En Jie

2011-06-01

In the present study, we report on the reduced susceptibility to teicoplanin among clinical isolates of Staphylococcus haemolyticus in a hematology ward of a teaching hospital. The molecular characterization of 17 S. haemolyticus strains was performed using mec gene complex classification, pulsed-field gel electrophoresis analysis, and minimum inhibitory concentration examination. Pulsotype A strains carrying a class C2 mec gene complex were the most prevalent strains, at 64.7%. In vivo selection of stepwise increase in resistance to vancomycin and teicoplanin was observed in three S. haemolyticus strains serially isolated from a case patient. The results of the present study suggest the regional spread of certain S. haemolyticus clones with diminished susceptibility to glycopeptides, emphasizing the need for continuous monitoring of minimum inhibitory concentration levels of vancomycin and teicoplanin in S. haemolyticus strains, and the importance of infection control practices to prevent its transmission.

Constraints on the subsurface structure of Europa

NASA Astrophysics Data System (ADS)

Golombek, M. P.; Banerdt, W. B.

1990-02-01

The wedge-shaped bands appearing near the anti-Jovian point on Europa are tension cracks which, after formation on an intact lithosphere, have facilitated the rotation of ice-lithosphere sections decoupled from the silicate interior. Such factors as fluid pressure, surface temperature, silicate impurities in the ice, and strain rates, would have affected the processes in question. A minimum degree of differentiation is required for Europa to mechanically decouple the rotated ice lithosphere from the underlying, predominantly silicate mantle.

Emerging Helicobacter pylori levofloxacin resistance and novel genetic mutation in Nepal.

PubMed

Miftahussurur, Muhammad; Shrestha, Pradeep Krishna; Subsomwong, Phawinee; Sharma, Rabi Prakash; Yamaoka, Yoshio

2016-11-04

The prevalence of Helicobacter pylori antibiotic susceptibility in the Nepalese strains is untracked. We determined the antibiotic susceptibility for H. pylori and analyzed the presence of genetic mutations associated with antibiotic resistance in Nepalese strains. This study included 146 consecutive patients who underwent gastroduodenal endoscopy in Kathmandu, Nepal. Among 42 isolated H. pylori, there was no resistance to amoxicillin and tetracycline. In contrast, similar with typical South Asian patterns; metronidazole resistance rate in Nepalese strains were extremely high (88.1 %, 37/42). Clarithromycin resistance rate in Nepalese strains were modestly high (21.4 %, 9/42). Most of metronidazole resistant strains had highly distributed rdxA and frxA mutations, but were relative coincidence without a synergistic effect to increase the minimum inhibitory concentration (MIC). Among strains with the high MIC, 63.6 % (7/11) were associated with frameshift mutation at position 18 of frxA with or without rdxA involvement. However, based on next generation sequencing data we found that one strain with the highest MIC value had a novel mutation in the form of amino acid substituted at Ala-212, Gln-382, Ile-485 of dppA and Leu-145, Thr-168, Glu-117, Val-121, Arg-221 in dapF aside from missense mutations in full-length rdxA. Mutations at Asn-87 and/or Asp-91 of the gyrA were predominantly in levofloxacin-resistant strains. The gyrB mutation had steady relationship with the gyrA 87-91 mutations. Although three (44.4 %) and two (22.2 %) of clarithromycin resistant strains had point mutation on A2143G and A2146G, we confirmed the involvement of rpl22 and infB in high MIC strains without an 23SrRNA mutation. The rates of resistance to clarithromycin, metronidazole and levofloxacin were high in Nepalese strains, indicating that these antibiotics-based triple therapies are not useful as first-line treatment in Nepal. Bismuth or non-bismuth-based quadruple regimens, furazolidone-based triple therapy or rifabutin-based triple therapy may become alternative strategy in Nepal.

Short communication: Roles of outer membrane protein W (OmpW) on survival and biofilm formation of Cronobacter sakazakii under neomycin sulfate stress.

PubMed

Ye, Yingwang; Ling, Na; Gao, Jina; Zhang, Maofeng; Zhang, Xiyan; Tong, Liaowang; Ou, Dexin; Wang, Yaping; Zhang, Jumei; Wu, Qingping

2018-04-01

Cronobacter sakazakii is associated with severe infections including sepsis, neonatal meningitis, and necrotizing enterocolitis. Antibiotic resistance in Cronobacter species has been documented in recent years, but the genes involved in resistance in Cronobacter strains are poorly understood. In this study, we determined the role of outer membrane protein W (OmpW) on survival rates, morphologic changes, and biofilm formation between wild type (WT) and an OmpW mutant strain (ΔOmpW) under neomycin sulfate stress. Results indicated that the survival rates of ΔOmpW were significantly reduced after half minimum inhibitory concentration (½ MIC) treatment compared with the WT strain. Filamentation of C. sakazakii cells was observed after ½ MIC treatment in WT and ΔOmpW, and morphologic injury, including cell disruption and leakage of cells, was more predominant in ΔOmpW. Under ½ MIC stress, the biofilms of WT and ΔOmpW were significantly decreased, but decreasing rates of biofilm formation in mutant strain were more predominant compared with WT strain. This is the first report to determine the role of OmpW on survival, morphological changes, and biofilm formation in C. sakazakii under neomycin sulfate stress. The findings indicated that OmpW contributed to survival and reduction of morphological injury under neomycin sulfate stress. In addition, enhancing biofilm formation in ΔOmpW may be an alternative advantage for adaptation to neomycin sulfate stress. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

An improved Armstrong-Frederick-Type Plasticity Model for Stable Cyclic Stress-Strain Responses Considering Nonproportional Hardening

NASA Astrophysics Data System (ADS)

Li, Jing; Zhang, Zhong-ping; Li, Chun-wang

2018-03-01

This paper modified an Armstrong-Frederick-type plasticity model for investigating the stable cyclic deformation behavior of metallic materials with different sensitivity to nonproportional loadings. In the modified model, the nonproportionality factor and nonproportional cyclic hardening coefficient coupled with the Jiang-Sehitoglu incremental plasticity model were used to estimate the stable stress-strain responses of the two materials (1045HR steel and 304 stainless steel) under various tension-torsion strain paths. A new equation was proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range were presented for general multiaxial loadings. Then, the modified model requires only the cyclic strain hardening exponent and cyclic strength coefficient to determine the material constants. It is convenient for predicting the stable stress-strain responses of materials in engineering application. Comparisons showed that the modified model can reflect the effect of nonproportional cyclic hardening well.

Laboratory Transmission of Venezuelan Equine Encephalomyelitis Virus by the Tick Hyalomma Truncatum

DTIC Science & Technology

1994-01-01

equine On day 21 after infestation of the first guinea-pig, none encephalomyelitis virus by the tick of 95 unfed nv mphs sampled contained virus...Epi/ootic strains oft Venezuelan equine encephalo- nymphs [minimum infection rate =2 200 1% I"( 1 contained inveliti. \\EE’ virus Alp/tavirus. family...Togaviridae virus mean titre= 102 1 1PFU ’. About 200 unfed nymphs ý:iuse serious disease tin horse % and humans throughout were placed on a guinea-pig at

Investigation of a Coupled Arrhenius-Type/Rossard Equation of AH36 Material.

PubMed

Qin, Qin; Tian, Ming-Liang; Zhang, Peng

2017-04-13

High-temperature tensile testing of AH36 material in a wide range of temperatures (1173-1573 K) and strain rates (10 -4 -10 -2 s -1 ) has been obtained by using a Gleeble system. These experimental stress-strain data have been adopted to develop the constitutive equation. The constitutive equation of AH36 material was suggested based on the modified Arrhenius-type equation and the modified Rossard equation respectively. The results indicate that the constitutive equation is strongly influenced by temperature and strain, especially strain. Moreover, there is a good agreement between the predicted data of the modified Arrhenius-type equation and the experimental results when the strain is greater than 0.02. There is also good agreement between the predicted data of the Rossard equation and the experimental results when the strain is less than 0.02. Therefore, a coupled equation where the modified Arrhenius-type equation and Rossard equation are combined has been proposed to describe the constitutive equation of AH36 material according to the different strain values in order to improve the accuracy. The correlation coefficient between the computed and experimental flow stress data was 0.998. The minimum value of the average absolute relative error shows the high accuracy of the coupled equation compared with the two modified equations.

Pharmacodynamic studies of vancomycin, metronidazole and fusidic acid against Clostridium difficile.

PubMed

Odenholt, Inga; Walder, Mats; Wullt, Marlene

2007-01-01

Pharmacodynamic studies of antibiotics have attracted great interest in recent years. However, studies on the pharmacodynamics of different antibiotics against Clostridium difficile are scarce. The postantibiotic effects (PAE) and the postantibiotic sub-minimum inhibitory concentration (MIC) effects (PA SME) of vancomycin, metronidazole and fusidic acid were investigated by viable counts against three different strains of C. difficile. The killing rate and extent of the three antibiotics against the same strains were also studied by adding 2, 4, 8, 16 and 32x MIC of the three antibiotics, respectively. Metronidazole exerted a very rapid bactericidal effect at concentrations of 8x MIC and above against all three strains investigated. Vancomycin gave overall less kill in comparison to metronidazole and was bacteriostatic against two of the three strains. Fusidic acid exerted a concentration-dependent killing against two of the strains. Vancomycin exerted short PAEs and PA SMEs against all three strains. Significantly longer PAEs and PA SMEs were noted for fusidic acid. Metronidazole gave similar short PAEs like vancomycin but longer PA SMEs were noted against two of the investigated strains. Metronidazole exerted the most prominent bactericidal effect greater than fusidic acid and greater than vancomycin. Fusidic acid gave overall the longest PAEs and PA SMEs greater than metronidazole and greater than vancomycin. Copyright 2007 S. Karger AG, Basel.

Life cycle and population growth rate of Caenorhabditis elegans studied by a new method.

PubMed

Muschiol, Daniel; Schroeder, Fabian; Traunspurger, Walter

2009-05-16

The free-living nematode Caenorhabditis elegans is the predominant model organism in biological research, being used by a huge number of laboratories worldwide. Many researchers have evaluated life-history traits of C. elegans in investigations covering quite different aspects such as ecotoxicology, inbreeding depression and heterosis, dietary restriction/supplement, mutations, and ageing. Such traits include juvenile growth rates, age at sexual maturity, adult body size, age-specific fecundity/mortality, total reproduction, mean and maximum lifespan, and intrinsic population growth rates. However, we found that in life-cycle experiments care is needed regarding protocol design. Here, we test a recently developed method that overcomes some problems associated with traditional cultivation techniques. In this fast and yet precise approach, single individuals are maintained within hanging drops of semi-fluid culture medium, allowing the simultaneous investigation of various life-history traits at any desired degree of accuracy. Here, the life cycles of wild-type C. elegans strains N2 (Bristol, UK) and MY6 (Münster, Germany) were compared at 20 degrees C with 5 x 10(9) Escherichia coli ml-1 as food source. High-resolution life tables and fecundity schedules of the two strains are presented. Though isolated 700 km and 60 years apart from each other, the two strains barely differed in life-cycle parameters. For strain N2 (n = 69), the intrinsic rate of natural increase (r m d(-1)), calculated according to the Lotka equation, was 1.375, the net reproductive rate (R 0) 291, the mean generation time (T) 90 h, and the minimum generation time (T min) 73.0 h. The corresponding values for strain MY6 (n = 72) were r m = 1.460, R0 = 289, T = 84 h, and T min = 67.3 h. Peak egg-laying rates in both strains exceeded 140 eggs d(-1). Juvenile and early adulthood mortality was negligible. Strain N2 lived, on average, for 16.7 d, while strain MY6 died 2 days earlier; however, differences in survivorship curves were statistically non-significant. We found no evidence that adaptation to the laboratory altered the life history traits of C. elegans strain N2. Our results, discussed in the light of earlier studies on C. elegans, demonstrate certain advantages of the hanging drop method in investigations of nematode life cycles. Assuming that its reproducibility is validated in further studies, the method will reduce the inter-laboratory variability of life-history estimates and may ultimately prove to be more convenient than the current standard methods used by C. elegans researchers.

Life cycle and population growth rate of Caenorhabditis elegans studied by a new method

PubMed Central

Muschiol, Daniel; Schroeder, Fabian; Traunspurger, Walter

2009-01-01

Background The free-living nematode Caenorhabditis elegans is the predominant model organism in biological research, being used by a huge number of laboratories worldwide. Many researchers have evaluated life-history traits of C. elegans in investigations covering quite different aspects such as ecotoxicology, inbreeding depression and heterosis, dietary restriction/supplement, mutations, and ageing. Such traits include juvenile growth rates, age at sexual maturity, adult body size, age-specific fecundity/mortality, total reproduction, mean and maximum lifespan, and intrinsic population growth rates. However, we found that in life-cycle experiments care is needed regarding protocol design. Here, we test a recently developed method that overcomes some problems associated with traditional cultivation techniques. In this fast and yet precise approach, single individuals are maintained within hanging drops of semi-fluid culture medium, allowing the simultaneous investigation of various life-history traits at any desired degree of accuracy. Here, the life cycles of wild-type C. elegans strains N2 (Bristol, UK) and MY6 (Münster, Germany) were compared at 20°C with 5 × 109 Escherichia coli ml-1 as food source. Results High-resolution life tables and fecundity schedules of the two strains are presented. Though isolated 700 km and 60 years apart from each other, the two strains barely differed in life-cycle parameters. For strain N2 (n = 69), the intrinsic rate of natural increase (rmd-1), calculated according to the Lotka equation, was 1.375, the net reproductive rate (R0) 291, the mean generation time (T) 90 h, and the minimum generation time (Tmin) 73.0 h. The corresponding values for strain MY6 (n = 72) were rm = 1.460, R0 = 289, T = 84 h, and Tmin = 67.3 h. Peak egg-laying rates in both strains exceeded 140 eggs d-1. Juvenile and early adulthood mortality was negligible. Strain N2 lived, on average, for 16.7 d, while strain MY6 died 2 days earlier; however, differences in survivorship curves were statistically non-significant. Conclusion We found no evidence that adaptation to the laboratory altered the life history traits of C. elegans strain N2. Our results, discussed in the light of earlier studies on C. elegans, demonstrate certain advantages of the hanging drop method in investigations of nematode life cycles. Assuming that its reproducibility is validated in further studies, the method will reduce the inter-laboratory variability of life-history estimates and may ultimately prove to be more convenient than the current standard methods used by C. elegans researchers. PMID:19445697

An Axial-Torsional, Thermomechanical Fatigue Testing Technique

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

1995-01-01

A technique for conducting strain-controlled, thermomechanical, axial-torsional fatigue tests on thin-walled tubular specimens was developed. Three waveforms of loading, namely, the axial strain waveform, the engineering shear strain waveform, and the temperature waveform were required in these tests. The phasing relationships between the mechanical strain waveforms and the temperature and axial strain waveforms were used to define a set of four axial-torsional, thermomechanical fatigue (AT-TMF) tests. Real-time test control (3 channels) and data acquisition (a minimum of 7 channels) were performed with a software program written in C language and executed on a personal computer. The AT-TMF testing technique was used to investigate the axial-torsional thermomechanical fatigue behavior of a cobalt-base superalloy, Haynes 188. The maximum and minimum temperatures selected for the AT-TMF tests were 760 and 316 C, respectively. Details of the testing system, calibration of the dynamic temperature profile of the thin-walled tubular specimen, thermal strain compensation technique, and test control and data acquisition schemes, are reported. The isothermal, axial, torsional, and in- and out-of-phase axial-torsional fatigue behaviors of Haynes 188 at 316 and 760 C were characterized in previous investigations. The cyclic deformation and fatigue behaviors of Haynes 188 in AT-TMF tests are compared to the previously reported isothermal axial-torsional behavior of this superalloy at the maximum and minimum temperatures.

Dynamic strain aging in stress controlled creep-fatigue tests of 316L stainless steel under different loading conditions

NASA Astrophysics Data System (ADS)

Jiang, Huifeng; Chen, Xuedong; Fan, Zhichao; Dong, Jie; Jiang, Heng; Lu, Shouxiang

2009-08-01

Stress controlled fatigue-creep tests were carried out for 316L stainless steel under different loading conditions, i.e. different loading levels at the fixed temperature (loading condition 1, LC1) and different temperatures at the fixed loading level (loading condition 2, LC2). Cyclic deformation behaviors were investigated with respect to the evolutions of strain amplitude and mean strain. Abrupt mean strain jumps were found during cyclic deformation, which was in response to the dynamic strain aging effect. Moreover, as to LC1, when the minimum stress is negative at 550 °C, abrupt mean strain jumps occur at the early stage of cyclic deformation and there are many jumps during the whole process. While the minimum stress is positive, mean strain only jumps once at the end of deformation. Similar results were also found in LC2, when the loading level is fixed at -100 to 385 MPa, at higher temperatures (560, 575 °C), abrupt mean strain jumps occur at the early stage of cyclic deformation and there are many jumps during the whole process. While at lower temperature (540 °C), mean strain only jumps once at the end of deformation.

Micro-mechanical model for the tension-stabilized enzymatic degradation of collagen tissues

NASA Astrophysics Data System (ADS)

Nguyen, Thao; Ruberti, Jeffery

We present a study of how the collagen fiber structure influences the enzymatic degradation of collagen tissues. Experiments of collagen fibrils and tissues show that mechanical tension can slow and halt enzymatic degradation. Tissue-level experiments also show that degradation rate is minimum at a stretch level coincident with the onset of strain-stiffening in the stress response. To understand these phenomena, we developed a micro-mechanical model of a fibrous collagen tissue undergoing enzymatic degradation. Collagen fibers are described as sinusoidal elastica beams, and the tissue is described as a distribution of fibers. We assumed that the degradation reaction is inhibited by the axial strain energy of the crimped collagen fibers. The degradation rate law was calibrated to experiments on isolated single fibrils from bovine sclera. The fiber crimp and properties were fit to uniaxial tension tests of tissue strips. The fibril-level kinetic and tissue-level structural parameters were used to predict tissue-level degradation-induced creep rate under a constant applied force. We showed that we could accurately predict the degradation-induce creep rate of the pericardium and cornea once we accounted for differences in the fiber crimp structure and properties.

Strain rates estimated by geodetic observations in the Borborema Province, Brazil

NASA Astrophysics Data System (ADS)

Marotta, Giuliano Sant'Anna; França, George Sand; Monico, João Francisco Galera; Bezerra, Francisco Hilário R.; Fuck, Reinhardt Adolfo

2015-03-01

The strain rates for the Borborema Province, located in northeastern Brazil, were estimated in this study. For this purpose, we used GNSS tracking stations with a minimum of two years data. The data were processed using the software GIPSY, version 6.2, provided by the JPL of the California Institute of Technology. The PPP method was used to process the data using the non-fiducial approach. Satellite orbits and clock were supplied by the JPL. Absolute phase center offsets and variations for both the receiver and the satellite antennaes were applied, together with ambiguity resolution; corrections of the first and second order effects of the ionosphere and troposphere models adopting the VMF1 mapping function; 10° elevation mask; FES2004 oceanic load model and terrestrial tide WahrK1 PolTid FreqDepLove OctTid. From a multi annual solution, involving at least 2 years of continuous data, the coordinates and velocities as well as their accuracies were estimated. The strain rates were calculated using the Delaunay triangulation and the Finite Element Method. The results show that the velocity direction is predominantly west and north, with maximum variation of 4.0 ± 1.5 mm/year and 4.1 ± 0.5 mm/year for the x and y components, respectively. The highest strain values of extension and contraction were 0.109552 × 10-6 ± 3.65 × 10-10/year and -0.072838 × 10-6 ± 2.32 × 10-10/year, respectively. In general, the results show that the highest strain and variation of velocity values are located close to the Potiguar Basin, region that concentrates seismic activities of magnitudes of up to 5.2 mb. We conclude that the contraction direction of strain is consistent with the maximum horizontal stress derived from focal mechanism and breakout data. In addition, we conclude that the largest strain rates occur around the Potiguar Basin, an area already recognized as one of the major sites of seismicity in intraplate South America.

Dynamics of Diffusion Flames in von Karman Swirling Flows Studied

NASA Technical Reports Server (NTRS)

Nayagam, Vedha; Williams, Forman A.

2002-01-01

Von Karman swirling flow is generated by the viscous pumping action of a solid disk spinning in a quiescent fluid media. When this spinning disk is ignited in an oxidizing environment, a flat diffusion flame is established adjacent to the disk, embedded in the boundary layer (see the preceding illustration). For this geometry, the conservation equations reduce to a system of ordinary differential equations, enabling researchers to carry out detailed theoretical models to study the effects of varying strain on the dynamics of diffusion flames. Experimentally, the spinning disk burner provides an ideal configuration to precisely control the strain rates over a wide range. Our original motivation at the NASA Glenn Research Center to study these flames arose from a need to understand the flammability characteristics of solid fuels in microgravity where slow, subbuoyant flows can exist, producing very small strain rates. In a recent work (ref. 1), we showed that the flammability boundaries are wider and the minimum oxygen index (below which flames cannot be sustained) is lower for the von Karman flow configuration in comparison to a stagnation-point flow. Adding a small forced convection to the swirling flow pushes the flame into regions of higher strain and, thereby, decreases the range of flammable strain rates. Experiments using downward facing, polymethylmethacrylate (PMMA) disks spinning in air revealed that, close to the extinction boundaries, the flat diffusion flame breaks up into rotating spiral flames (refs. 2 and 3). Remarkably, the dynamics of these spiral flame edges exhibit a number of similarities to spirals observed in biological systems, such as the electric pulses in cardiac muscles and the aggregation of slime-mold amoeba. The tail of the spiral rotates rigidly while the tip executes a compound, meandering motion sometimes observed in Belousov-Zhabotinskii reactions.

Effect of welding on creep damage evolution in P91B steel

NASA Astrophysics Data System (ADS)

Baral, J.; Swaminathan, J.; Chakrabarti, D.; Ghosh, R. N.

2017-07-01

Study of creep behavior of base metal (without weld) and welded specimens of P91B steel over a range of temperatures (600-650 °C) and stresses (50-180 MPa) showed similar values of minimum creep-rates for both specimens at higher stress regime (>100 MPa) whilst, significantly higher creep rates in the case of welded specimens at lower stress regime. Considering that welded specimen is comprised of two distinct structural regimes, i.e. weld affected zone and base metal, a method has been proposed for estimating the material parameters describing creep behavior of those regimes. Stress-strain distribution across welded specimen predicted from finite element analysis based on material parameters revealed preferential accumulation of stress and creep strain at the interface between weld zone and base metal. This is in-line with the experimental finding that creep rupture preferentially occurs at inter-critical heat affected zone in welded specimens owing to ferrite-martensite structure with coarse Cr23C6 particles.

Mutations in the tacF gene of clinical strains and laboratory transformants of Streptococcus pneumoniae: impact on choline auxotrophy and growth rate.

PubMed

González, Ana; Llull, Daniel; Morales, María; García, Pedro; García, Ernesto

2008-06-01

The nutritional requirement that Streptococcus pneumoniae has for the aminoalcohol choline as a component of teichoic and lipoteichoic acids appears to be exclusive to this prokaryote. A mutation in the tacF gene, which putatively encodes an integral membrane protein (possibly, a teichoic acid repeat unit transporter), has been recently identified as responsible for generating a choline-independent phenotype of S. pneumoniae (M. Damjanovic, A. S. Kharat, A. Eberhardt, A. Tomasz, and W. Vollmer, J. Bacteriol. 189:7105-7111, 2007). We now report that Streptococcus mitis can grow in choline-free medium, as previously illustrated for Streptococcus oralis. While we confirmed the finding by Damjanovic et al. of the involvement of TacF in the choline dependence of the pneumococcus, the genetic transformation of S. pneumoniae R6 by using S. mitis SK598 DNA and several PCR-amplified tacF fragments suggested that a minimum of two mutations were required to confer improved fitness to choline-independent S. pneumoniae mutants. This conclusion is supported by sequencing results also reported here that indicate that a spontaneous mutant of S. pneumoniae (strain JY2190) able to proliferate in the absence of choline (or analogs) is also a double mutant for the tacF gene. Microscopic observations and competition experiments during the cocultivation of choline-independent strains confirmed that a minimum of two amino acid changes were required to confer improved fitness to choline-independent pneumococcal strains when growing in medium lacking any aminoalcohol. Our results suggest complex relationships among the different regions of the TacF teichoic acid repeat unit transporter.

Report - Susceptibility of avian pathogenic Escherichia coli from Zoo birds in Indonesia to antibiotics and disinfectants.

PubMed

Umar, Sajid; Maiyah, Ana Triana; Shareef, Mehwish; Qadir, Hajra; Nisa, Qamarun; Abbas, Seema

2018-03-01

Antibiotic resistance in avian pathogenic Escherichia coli (APEC) is a common problem in the Indonesian poultry industry. Zoo birds have been postulated as sentinels, reservoirs, and potential spreaders of antibiotic resistance, although much is still unknown about the strains of zoo birds. Disinfection can reduce the infection burden. However, little is known about the presence of resistance against these products. Sixty one APEC strains were isolated from Indonesian zoo birds. The resistance to different classes of antibiotics as well as the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of five disinfectants most often used in the poultry industry was determined. Resistance to tetracycline (42.6%), sulfonamides (24.5%), ampicillin (22.9%), gentamicin (19.6), nalidixic acid (18.03%) and streptomycin (16.3%) was high, but resistance to other tested antibiotics was low and none of the isolates were resistant to extended spectrum beta-lactamase (ESBL) producers. Sixteen strains (26.2%) were found positive for multi drug resistance. The MIC of the disinfectants for the APEC strains showed normal distribution, indicating that there was no acquired resistance. MBCs were similar to MICs using the broth dilution method, showing the bactericidal effect of the disinfectants. Phenotypic resistance to commonly used disinfectants could not be found, indicating that the current use of disinfectants in the zoo and aviaries did not select for resistance. Significantly high resistance rates against commonly used antibiotics in Indonesian zoos is worrisome and indicates that widespread use of antibiotics could have negative implications for animal health and the environment. Proper use of antibiotics and surveillance programs to monitor antimicrobial resistance in pathogenic bacteria are warranted.

Characterizing the Constitutive Properties of AA7075 for Hot Forming

NASA Astrophysics Data System (ADS)

Omer, K.; Kim, S.; Butcher, C.; Worswick, M.

2017-09-01

The work presented herein investigates the constitutive properties of AA7075 as it undergoes a hot stamping/die quenching process. Tensile specimens were solutionized inside a heated furnace set to 470°C. Once solutionized, the samples were quenched to an intermediate temperature using a vortex air chiller at a minimum rate of 52°C/s. Tensile tests were conducted at steady state temperatures of 470, 400, 300, 200, 115 and 25°C. This solutionizing and subsequent quenching process replicated the temperature cycle and quench rates representative of a die quenching operation. The results of the tensile test were analyzed with digital imaging correlation using an area reduction approach. The area reduction approach approximated the cross-sectional area of the tensile specimen as it necked. The approach allowed for the true stress-strain response to be calculated well past the initial necking point. The resulting true stress-strain curves showed that the AA7075 samples experienced almost no hardening at 470°C. As steady state temperature decreased, the rate of hardening as well as overall material strength increased. The true stress strain curves were fit to a modified version of the extended Voce constitutive model. The resulting fits can be used in a finite element model to predict the behaviour of an AA7075 blank during a die quenching operation.

[Evaluation of antibiotic susceptibilities and VISA-VRSA rates among MRSA strains isolated from hospitalized patients in intensive care units of hospitals in seven provinces of Turkey].

PubMed

Cesur, Salih; Irmak, Hasan; Simşek, Hüsniye; Cöplü, Nilay; Kılıç, Hasan; Arslan, Uğur; Bayramoğlu, Gülçin; Baysan, Betil Ozhak; Gülay, Zeynep; Hoşoğlu, Salih; Berktaş, Mustafa; Gencer, Serap; Demiröz, Ali Pekcan; Esen, Berrin; Karabiber, Nihal; Aydın, Faruk; Yalçın, Ata Nevzat

2012-07-01

The aim of this study was to determine whether vancomycin resistant Staphylococcus aureus (VRSA) and vancomycin intermediate susceptible S.aureus (VISA) strains were present among methicillin-resistant S.aureus (MRSA) strains isolated from patients hospitalised at intensive care units (ICU) of hospitals located at different regions of Turkey and to determine the minimum inhibitory concentration (MIC) values of teicoplanin, linezolid, tigecycline, quinupristin-dalfopristin and daptomycin, which are alternative drugs for the treatment of MRSA infections. A total of 260 MRSA clinical strains (isolated from 113 lower respiratory tract, 90 blood, 24 wound, 17 catheter, 13 nasal swabs, two urine and one CSF sample) were collected from nine health-care centers in eight provinces [Ankara (n= 52), Konya (n= 49), Antalya (n= 40), Istanbul (n= 7), Izmir (37), Diyarbakir (n= 15), Van (n= 12), Trabzon (n= 48)] selected as representatives of the seven different geographical regions of Turkey. Methicillin resistance was determined by cefoxitin disk diffusion in the hospitals where the strains were isolated and confirmed by oxacillin salt agar screening at the Refik Saydam National Public Health Agency. Screening for VISA and VRSA was conducted using the agar screening test and E-test. Susceptibility of the MRSA strains to other antibiotics was also determined by E-test method. None of the 260 MRSA strains were determined to be VRSA or VISA. All were susceptible to teicoplanin and linezolid, and susceptibility rates to daptomycin, tigecycline and quinupristin-dalfopristin were 99.6%, 96.9%, and 95%, respectively. Absence of VISA and VRSA among the MRSA strains surveyed currently seemed hopeful, however, continuous surveillance is necessary. In order to prevent the development of VISA and VRSA strains the use of linezolid, tigecycline, quinupristin-dalfopristin and daptomycin should be encouraged as alternative agents of treatment of MRSA infections.

Deformation modeling and constitutive modeling for anisotropic superalloys

NASA Technical Reports Server (NTRS)

Milligan, Walter W.; Antolovich, Stephen D.

1989-01-01

A study of deformation mechanisms in the single crystal superalloy PWA 1480 was conducted. Monotonic and cyclic tests were conducted from 20 to 1093 C. Both (001) and near-(123) crystals were tested, at strain rates of 0.5 and 50 percent/minute. The deformation behavior could be grouped into two temperature regimes: low temperatures, below 760 C; and high temperatures, above 820 to 950 C depending on the strain rate. At low temperatures, the mechanical behavior was very anisotropic. An orientation dependent CRSS, a tension-compression asymmetry, and anisotropic strain hardening were all observed. The material was deformed by planar octahedral slip. The anisotropic properties were correlated with the ease of cube cross-slip, as well as the number of active slip systems. At high temperatures, the material was isotropic, and deformed by homogeneous gamma by-pass. It was found that the temperature dependence of the formation of superlattice-intrinsic stacking faults was responsible for the local minimum in the CRSS of this alloy at 400 C. It was proposed that the cube cross-slip process must be reversible. This was used to explain the reversible tension-compression asymmetry, and was used to study models of cross-slip. As a result, the cross-slip model proposed by Paidar, Pope and Vitek was found to be consistent with the proposed slip reversibility. The results were related to anisotropic viscoplastic constitutive models. The model proposed by Walter and Jordan was found to be capable of modeling all aspects of the material anisotropy. Temperature and strain rate boundaries for the model were proposed, and guidelines for numerical experiments were proposed.

Investigation of a Coupled Arrhenius-Type/Rossard Equation of AH36 Material

PubMed Central

Qin, Qin; Tian, Ming-Liang; Zhang, Peng

2017-01-01

High-temperature tensile testing of AH36 material in a wide range of temperatures (1173–1573 K) and strain rates (10−4–10−2 s−1) has been obtained by using a Gleeble system. These experimental stress-strain data have been adopted to develop the constitutive equation. The constitutive equation of AH36 material was suggested based on the modified Arrhenius-type equation and the modified Rossard equation respectively. The results indicate that the constitutive equation is strongly influenced by temperature and strain, especially strain. Moreover, there is a good agreement between the predicted data of the modified Arrhenius-type equation and the experimental results when the strain is greater than 0.02. There is also good agreement between the predicted data of the Rossard equation and the experimental results when the strain is less than 0.02. Therefore, a coupled equation where the modified Arrhenius-type equation and Rossard equation are combined has been proposed to describe the constitutive equation of AH36 material according to the different strain values in order to improve the accuracy. The correlation coefficient between the computed and experimental flow stress data was 0.998. The minimum value of the average absolute relative error shows the high accuracy of the coupled equation compared with the two modified equations. PMID:28772767

Efficacy of 10-day Sitafloxacin-Containing Third-Line Rescue Therapies for Helicobacter pylori Strains Containing the gyrA Mutation.

PubMed

Mori, Hideki; Suzuki, Hidekazu; Matsuzaki, Juntaro; Tsugawa, Hitoshi; Fukuhara, Seiichiro; Miyoshi, Sawako; Hirata, Kenro; Seino, Takashi; Matsushita, Misako; Masaoka, Tatsuhiro; Kanai, Takanori

2016-08-01

Sitafloxacin-containing Helicobacter pylori eradication therapy is a promising third-line therapeutic approach, but there is no previous studies between gyrA mutation status of H. pylori strains and the efficacy of 10-day sitafloxacin-containing regimens. Here, we assessed the efficacy of 2 different 10-day sitafloxacin-containing rescue regimens. Patients who failed first- and second-line eradication therapies were enrolled. The minimum inhibitory concentrations (MICs) of sitafloxacin, amoxicillin, and metronidazole and the gyrA mutation status of the H. pylori strains were determined before treatment. The patients were randomized to receive a 10-day triple therapy containing either esomeprazole (20 mg, b.i.d.), amoxicillin (500 mg, q.i.d.), and sitafloxacin (100 mg, b.i.d.) (EAS regimen) or esomeprazole (20 mg, b.i.d.), metronidazole (250 mg, b.i.d.), and sitafloxacin (100 mg, b.i.d.) (EMS regimen). Eradication rates were evaluated by the [13C] urea breath test or the H. pylori stool antigen test. All patients with gyrA mutation-negative strains (24 in EAS and 16 in EMS) showed successful eradication, irrespective of the regimen they received. In patients with gyrA mutation-positive strains, we found eradication rates of 70.3% (26/37) and 66.7% (26/39) in the EAS and EMS groups in per-protocol population, respectively (p = .81). According to logistic regression analyses, the MICs of sitafloxacin, which were strongly associated with gyrA mutation status, were independently associated with successful eradication in both groups. This study was registered in the UMIN Clinical Trials Registry as UMIN000006483. There is no significant difference in the eradication rates between EAS and EMS, regardless of the gyrA mutation status of the H. pylori strains. GyrA mutation status was an important factor in predicting successful eradication with sitafloxacin-containing rescue therapies. © 2015 John Wiley & Sons Ltd.

Predictors for traumatic brain injuries evaluated through accident reconstructions.

PubMed

Kleiven, Svein

2007-10-01

The aim of this study is to evaluate all the 58 available NFL cases and compare various predictors for mild traumatic brain injuries using a detailed and extensively validated finite element model of the human head. Global injury measures such as magnitude in angular and translational acceleration, change in angular velocity, head impact power (HIP) and HIC were also investigated with regard to their ability to predict the intracranial pressure and strains associated with injury. The brain material properties were modeled using a hyperelastic and viscoelastic constitutive law. Also, three different stiffness parameters, encompassing a range of published brain tissue properties, were tested. 8 tissue injury predictors were evaluated for 6 different regions, covering the entire cerebrum, as well as for the whole brain. In addition, 10 head kinematics based predictors were evaluated both for correlation with injury as well as with strain and pressure. When evaluating the results, a statistical correlation between strain, strain rate, product of strain and strain rate, Cumulative Strain Damage Measure (CSDM), strain energy density, maximum pressure, magnitude of minimum pressure, as well as von Mises effective stress, with injury was found when looking into specific regions of the brain. However, the maximal pressure in the gray matter showed a higher correlation with injury than other evaluated measures. On the other hand, it was possible, through the reconstruction of a motocross accident, to re-create the injury pattern in the brain of the injured rider using maximal principal strain. It was also found that a simple linear combination of peak change in rotational velocity and HIC showed a high correlation (R=0.98) with the maximum principal strain in the brain, in addition to being a significant predictor of injury. When applying the rotational and translational kinematics separately for one of the cases, it was found that the translational kinematics contribute very little to the intracranial distortional strains while the rotational kinematics contributes insignificantly to the pressure response. This study underlines that the strain based brain tissue injury predictors are very sensitive to the choice of stiffness for the brain tissue.

Differences in antimicrobial susceptibility breakpoints for Pseudomonas aeruginosa, isolated from blood cultures, set by the Clinical and Laboratory Standards Institute (CLSI) and the Japanese Society of Chemotherapy.

PubMed

Nakamura, Tatsuya; Shimizu, Chihiro; Kasahara, Mayumi; Nakata, Chiyo; Munakata, Machiko; Takahashi, Hakuo

2007-02-01

A study was made of the antimicrobial susceptibility to and efficacy of various kinds of antimicrobial agents against 179 strains of Pseudomonas aeruginosa that were isolated from blood cultures at Kansai Medical University Hospital from 1990 through 2004. The annual detection rate was highest in 1994, at 22 strains (6.5%). There were 9 multidrug resistant strains of Pseudomonas aeruginosa (5.0%). Among 14 antimicrobial agents tested for measurements, ciprofloxacin (CPFX) showed the best minimum inhibitory concentration (MIC) 50 value, of 0.25 microg/ml, followed by pazufloxacin (PZFX) and biapenem (BIPM), each at 0.5 microg/ml. When the period of 15 years was divided into three stages, the MIC50 value for each antimicrobial agent was highest in the middle stage (1995 to 1999). Assuming that the percentage of sensitive strains according to the breakpoints set by the Clinical and Laboratory Standards Institute (CLSI) represents the antimicrobial susceptibility rate, amikacin (AMK) showed the best value, of 85.5%. According to the sepsis breakpoint set by the Japanese Society of Chemotherapy (JSC), the efficacy of CPFX showed the highest rate (77.1%) of all the antimicrobial agents tested. Among beta-lactams, BIPM showed the highest efficacy rate, of 67.0%. When the efficacy rates were compared with each other, the difference in efficacy rate between the breakpoint set by the CLSI and the sepsis breakpoint set by the JSC was large for beta-lactams. Comparisons made based on the CLSI criteria showed no difference in cross-resistance rates between CPFX, meropenem (MEPM), and BIPM. However, when comparisons were made using the JSC sepsis breakpoint, MEPM showed a cross-resistance rate of 87.8%, while the rate for BIPM was lower, at 56.1%, with the chi2 test showing a significant difference, at P = 0.0014. In accordance with the pharmacokinetics/pharmacodynamics theory that has been advocated, breakpoints which are more suitable for the clinical setting in Japan should be set so that more effective and more appropriate treatment can be carried out.

Hydrogen Induced Stress Cracking of Materials Under Cathodic Protection

NASA Astrophysics Data System (ADS)

LaCoursiere, Marissa P.

Hydrogen embrittlement of AISI 4340, InconelRTM 718, Alloy 686 and Alloy 59 was studied using slow strain rate tests of both smooth and notched cylindrical specimens. Two heat treatments of the AISI 4340 material were used as a standard for two levels of yield strength: 1479 MPa, and 1140 MPa. A subset of the 1140 MPa AISI 4340 material also underwent plasma nitriding. The InconelRTM 718 material was hardened following AMS 5663M to obtain a yield strength of 1091 MPa. The Alloy 686 material was obtained in the Grade 3 condition with a minimum yield strength of 1034 MPa. The Alloy 59 material was obtained with a cold worked condition similar to the Alloy 686 and with a minimum yield strength of 1034 MPa. Ninety-nine specimens were tested, including smooth cylindrical tensile test specimens and smooth and notched cylindrical slow strain rate tensile tests specimens. Testing included specimens that had been precharged with hydrogen in 3.5% NaCl at 50°C for 2 weeks (AISI 4340), 4 weeks (InconelRTM 718, Alloy 686, Alloy 59) and 16 weeks (InconelRTM 718, Alloy 686, Alloy 59) using a potentiostat to deliver a cathodic potential of -1100 mV vs. SCE. The strain rate over the gauge section for the smooth specimens and in the notch root for the notched specimens was 1 x 10-6 /s. It was found that the AISI 4340 was highly embrittled in simulated ocean water when compared to the nickel based superalloys. The higher strength AISI 4340 showed much more embrittlement, as expected. Testing of the AISI 4340 at both 20°C and 4°C showed that the temperature had no effect on the hydrogen embrittlement response. The InconelRTM 718 was highly embrittled when precharged, although it only showed low levels of embrittlement when unprecharged. Both the Alloy 686 and Alloy 59 showed minimal embrittlement in all conditions. Therefore, for the materials examined, the use of Alloy 686 and Alloy 59 for components in salt water environments when under a cathodic potential of -1100 mV vs. SCE is recommended.

Population analysis of clinical and environmental Vibrio parahaemolyticus isolated from eastern provinces in China by removing the recombinant SNPs in the MLST loci.

PubMed

Lu, Xin; Zhou, Haijian; Du, Xiaoli; Liu, Sha; Xu, Jialiang; Cui, Zhigang; Pang, Bo; Kan, Biao

2016-11-01

Vibrio parahaemolyticus is a common seafood-borne pathogenic bacterium which causes gastroenteritis in humans. Continuous surveillance on the molecular characters of the clinical and environmental V. parahaemolyticus strains needs to be conducted for the epidemiological and genetic purposes. To generate a picture of the population distribution of V. parahaemolyticus in eastern China isolated from clinical cases of gastroenteritis and environmental samples, we investigated the genetic and evolutionary relationships of the strains using the commonly used multi-locus sequence typing (MLST, in which seven house-keeping genes are used in the protocol). A highly genetic diversity within the V. parahaemolyticus population was observed but ST3 was still dominant in the clinical strains, and 103 new sequence types (ST) were found in the clinical strains by searching in the global V. parahaemolyticus MLST database. With these genetically diverse strains, we estimated the recombination rates of the loci in MLST analysis. The locus recA was found to be subject to exceptionally high rate of recombination, and the recombinant single nucleotide polymorphisms (SNPs) were also identified within the seven loci. The phylogenetic tree of the strains was re-constructed using the maximum likelihood method by removing the recombination SNPs of the seven loci, and the minimum spanning tree was re-constructed with the six loci without recA. Some changes were observed in comparison with the previously used methods, suggesting that the homologous recombination has roles in shaping the clonal structure of V. parahaemolyticus. We propose the recombination-free SNPs strategy in the clonality analysis of V. parahaemolyticus, especially when using the maximum likelihood method. Copyright © 2016. Published by Elsevier B.V.

Inheritance and fitness costs of Spodoptera frugiperda (Lepidoptera: Noctuidae) resistance to spinosad in Brazil.

PubMed

Okuma, Daniela M; Bernardi, Daniel; Horikoshi, Renato J; Bernardi, Oderlei; Silva, Aline P; Omoto, Celso

2018-06-01

Spodoptera frugiperda is a pest of economically important crops in South America. In Brazil, this species is considered the most destructive pest of maize. Use of spinosyn insecticides in insect resistance management (IRM) has been one strategy to control this pest. In this study, we selected a strain of S. frugiperda resistant to spinosad and evaluated the inheritance and fitness costs of the resistance. Estimated LC 50 (concentration required to kill 50% of larvae) values were 0.011 and 9.80 µg cm -2 for the spinosad-susceptible (Sus) and -resistant (Spin-res) strains, respectively. This represents an 890-fold resistance ratio. LC 50 values for reciprocal crosses were 0.18 and 0.14 µg cm -2 , indicating that resistance to spinosad is an autosomal incompletely recessive trait. Backcrosses of the F 1 progeny from reciprocal crosses with the parental Spin-res strain showed a polygenic effect. The estimated minimum number of independent segregations was ∼ 2.45, indicating that resistance to spinosad is associated with multiple genes. In greenhouse assays, third-instar larvae from the Spin-res strain showed >92% survival on spinosad-treated maize. By contrast Sus and reciprocal crosses exhibited 0% and <5% survival, respectively, indicating that resistance is recessive. Life history studies to investigate the fitness cost of resistance revealed a 41% reduction in the rate of survival to adulthood and a 49% lower reproductive rate in the Spin-res strain compared with the Sus strain. The autosomal, incompletely recessive and polygenic resistance to spinosad in S. frugiperda and the fitness costs associated with this resistance can be exploited in IRM strategies to preserve the lifetime of spinosad for control of S. frugiperda in Brazil. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Geodetic Constraints on Fault Slip Rates and Seismic Hazard in the Greater Las Vegas Area

NASA Astrophysics Data System (ADS)

Hammond, W. C.; Kreemer, C.; Blewitt, G.; Broermann, J.; Bennett, R. A.

2014-12-01

We address fundamental questions about how contemporary tectonic deformation of the crust in the southern Great Basin occurs in the region around Las Vegas (LV) Nevada, western Arizona and eastern California. This area lies in the intersection of the eastern Walker Lane Belt, southern Great Basin and western Colorado Plateau (CP), sharing features of transtensional and extensional deformation associated with Pacific/North America relative motion. We use GPS data collected from 48 stations of the MAGNET semi-continuous network and 77 stations from continuous networks including BARGEN and EarthScope Plate Boundary Observatory. MAGNET stations have been observed for a minimum of 7 years, while most continuous stations have longer records. From these data we estimate the velocity of crustal motion for all stations with respect to the stable North America reference frame NA12. To correct for transients from recent large earthquakes including the 1999 Hector Mine and 2010 El Mayor-Cucapah events we use models of co- and post-seismic deformation, subtracting the predicted motions from the time series before estimating interseismic stain rates. We find approximately 2 mm/yr of relative motion distributed over 200 km centered on Las Vegas, with a mean strain accumulation rate of 10 × 10-9 yr-1, with lower rates of predominantly extensional strain to the east and higher rates of predominantly shear deformation to the west. The mean strain rate is lower than that of the western Walker Lane but about twice that of eastern Nevada where e.g., the Wells, NV MW 6.0 earthquake occurred in 2008. From this new velocity field we generated a horizontal tensor strain rate map and a crustal block motion model to portray the transition of active strain from the CP into the Walker Lane. For faults in the Las Vegas Valley, including the Eglington Fault and Frenchman Mountain Fault, the observed velocity gradients and model results are consistent with normal slip rates of 0.2 mm/yr, which are typical for the region. The Stateline Fault system experiences dextral slip of at least 0.4 mm/yr while normal faults south of LV collectively accommodate 0.9 mm/yr of east-west extension across a zone ~150 km wide. We see no evidence for concentrations of deformation or isolated rigid microplates within this zone.

Establishment of a nested-ASP-PCR method to determine the clarithromycin resistance of Helicobacter pylori.

PubMed

Luo, Xiao-Feng; Jiao, Jian-Hua; Zhang, Wen-Yue; Pu, Han-Ming; Qu, Bao-Jin; Yang, Bing-Ya; Hou, Min; Ji, Min-Jun

2016-07-07

To investigate clarithromycin resistance positions 2142, 2143 and 2144 of the 23SrRNA gene in Helicobacter pylori (H. pylori) by nested-allele specific primer-polymerase chain reaction (nested-ASP-PCR). The gastric tissue and saliva samples from 99 patients with positive results of the rapid urease test (RUT) were collected. The nested-ASP-PCR method was carried out with the external primers and inner allele-specific primers corresponding to the reference strain and clinical strains. Thirty gastric tissue and saliva samples were tested to determine the sensitivity of nested-ASP-PCR and ASP-PCR methods. Then, clarithromycin resistance was detected for 99 clinical samples by using different methods, including nested-ASP-PCR, bacterial culture and disk diffusion. The nested-ASP-PCR method was successfully established to test the resistance mutation points 2142, 2143 and 2144 of the 23SrRNA gene of H. pylori. Among 30 samples of gastric tissue and saliva, the H. pylori detection rate of nested-ASP-PCR was 90% and 83.33%, while the detection rate of ASP-PCR was just 63% and 56.67%. Especially in the saliva samples, nested-ASP-PCR showed much higher sensitivity in H. pylori detection and resistance mutation rates than ASP-PCR. In the 99 RUT-positive gastric tissue and saliva samples, the H. pylori-positive detection rate by nested-ASP-PCR was 87 (87.88%) and 67 (67.68%), in which there were 30 wild-type and 57 mutated strains in gastric tissue and 22 wild-type and 45 mutated strains in saliva. Genotype analysis showed that three-points mixed mutations were quite common, but different resistant strains were present in gastric mucosa and saliva. Compared to the high sensitivity shown by nested-ASP-PCR, the positive detection of bacterial culture with gastric tissue samples was 50 cases, in which only 26 drug-resistant strains were found through analyzing minimum inhibitory zone of clarithromycin. The nested-ASP-PCR assay showed higher detection sensitivity than ASP-PCR and drug sensitivity testing, which could be performed to evaluate clarithromycin resistance of H. pylori.

Establishment of a nested-ASP-PCR method to determine the clarithromycin resistance of Helicobacter pylori

PubMed Central

Luo, Xiao-Feng; Jiao, Jian-Hua; Zhang, Wen-Yue; Pu, Han-Ming; Qu, Bao-Jin; Yang, Bing-Ya; Hou, Min; Ji, Min-Jun

2016-01-01

AIM: To investigate clarithromycin resistance positions 2142, 2143 and 2144 of the 23SrRNA gene in Helicobacter pylori (H. pylori) by nested-allele specific primer-polymerase chain reaction (nested-ASP-PCR). METHODS: The gastric tissue and saliva samples from 99 patients with positive results of the rapid urease test (RUT) were collected. The nested-ASP-PCR method was carried out with the external primers and inner allele-specific primers corresponding to the reference strain and clinical strains. Thirty gastric tissue and saliva samples were tested to determine the sensitivity of nested-ASP-PCR and ASP-PCR methods. Then, clarithromycin resistance was detected for 99 clinical samples by using different methods, including nested-ASP-PCR, bacterial culture and disk diffusion. RESULTS: The nested-ASP-PCR method was successfully established to test the resistance mutation points 2142, 2143 and 2144 of the 23SrRNA gene of H. pylori. Among 30 samples of gastric tissue and saliva, the H. pylori detection rate of nested-ASP-PCR was 90% and 83.33%, while the detection rate of ASP-PCR was just 63% and 56.67%. Especially in the saliva samples, nested-ASP-PCR showed much higher sensitivity in H. pylori detection and resistance mutation rates than ASP-PCR. In the 99 RUT-positive gastric tissue and saliva samples, the H. pylori-positive detection rate by nested-ASP-PCR was 87 (87.88%) and 67 (67.68%), in which there were 30 wild-type and 57 mutated strains in gastric tissue and 22 wild-type and 45 mutated strains in saliva. Genotype analysis showed that three-points mixed mutations were quite common, but different resistant strains were present in gastric mucosa and saliva. Compared to the high sensitivity shown by nested-ASP-PCR, the positive detection of bacterial culture with gastric tissue samples was 50 cases, in which only 26 drug-resistant strains were found through analyzing minimum inhibitory zone of clarithromycin. CONCLUSION: The nested-ASP-PCR assay showed higher detection sensitivity than ASP-PCR and drug sensitivity testing, which could be performed to evaluate clarithromycin resistance of H. pylori. PMID:27433095

Isolation and characterization of Dehalobacter sp. strain UNSWDHB capable of chloroform and chlorinated ethane respiration.

PubMed

Wong, Yie K; Holland, Sophie I; Ertan, Haluk; Manefield, Mike; Lee, Matthew

2016-09-01

Dehalobacter sp. strain UNSWDHB can dechlorinate up to 4 mM trichloromethane at a rate of 0.1 mM per day to dichloromethane and 1,1,2-trichloroethane (1 mM, 0.1 mM per day) with the unprecedented product profile of 1,2-dichloroethane and vinyl chloride. 1,1,1-trichloroethane and 1,1-dichloroethane were slowly utilized by strain UNSWDHB and were not completely removed, with minimum threshold concentrations of 0.12 mM and 0.07 mM respectively under growth conditions. Enzyme kinetic experiments confirmed strong substrate affinity for trichloromethane and 1,1,2-trichloroethane (Km  = 30 and 62 µM respectively) and poor substrate affinity for 1,1,1-trichloroethane and 1,1-dichloroethane (Km  = 238 and 837 µM respectively). Comparison of enzyme kinetic and growth data with other trichloromethane respiring organisms (Dehalobacter sp. strain CF and Desulfitobacterium sp. strain PR) suggests an adaptation of strain UNSWDHB to trichloromethane. The trichloromethane RDase (TmrA) expressed by strain UNSWDHB was identified by BN-PAGE and functionally characterized. Amino acid comparison of homologous RDases from all three organisms revealed only six significant amino acid substitutions/deletions, which are likely to be crucial for substrate specificity. Furthermore, strain UNSWDHB was shown to grow without exogenous supply of cobalamin confirming genomic-based predictions of a fully functional cobalamin synthetic pathway. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Influence of temperature and conductivity on the life-history characteristics of a pampean strain of Brachionus plicatilis.

PubMed

Ferrando, Noelia S; Claps, María C; Benítez, Hernán H; Gabellone, Néstor A

2018-05-14

In the present work, we provide the first approach about the life-history of Brachionus plicatilis in South America. We tested with laboratory experiments the response of the pampean strain of B. plicatilis for two of its main stressors (conductivity and temperature). We evaluated the effects of eight conductivity values from 1 to 17 mS.cm-1 and two temperatures (15 and 25 °C) to compare its abundance with those obtained in the pampean lotic and lentic environments, where this rotifer is frequent or dominant. The results demonstrated that the increase in population-growth rate and the peak of abundance occurred at the highest temperature and at medium conductivity. Minimum values were obtained at the lowest temperature and conductivities analyzed, but the final density attained was nevertheless similar to those recorded in the pampean environments at the optimum conductivity and during the spring and summer seasons. Males, mictic females, and resting eggs were observed at the minimum and maximum conductivities, revealing the strategy of this species for maintaining dominance in environments with fluctuating salinity. The experiments also indicated the possible behavior of this relevant member of the zooplankton community within a scenario of increasing temperature and salinity related to the climate changes occurring in the pampean region.

The Slip Behavior and Source Parameters for Spontaneous Slip Events on Rough Faults Subjected to Slow Tectonic Loading

NASA Astrophysics Data System (ADS)

Tal, Yuval; Hager, Bradford H.

2018-02-01

We study the response to slow tectonic loading of rough faults governed by velocity weakening rate and state friction, using a 2-D plane strain model. Our numerical approach accounts for all stages in the seismic cycle, and in each simulation we model a sequence of two earthquakes or more. We focus on the global behavior of the faults and find that as the roughness amplitude, br, increases and the minimum wavelength of roughness decreases, there is a transition from seismic slip to aseismic slip, in which the load on the fault is released by more slip events but with lower slip rate, lower seismic moment per unit length, M0,1d, and lower average static stress drop on the fault, Δτt. Even larger decreases with roughness are observed when these source parameters are estimated only for the dynamic stage of the rupture. For br ≤ 0.002, the source parameters M0,1d and Δτt decrease mutually and the relationship between Δτt and the average fault strain is similar to that of a smooth fault. For faults with larger values of br that are completely ruptured during the slip events, the average fault strain generally decreases more rapidly with roughness than Δτt.

Pharmacodynamics of oxytetracycline administered alone and in combination with carprofen in calves.

PubMed

Brentnall, C; Cheng, Z; McKellar, Q A; Lees, P

2012-09-15

The pharmacodynamics (PD) of oxytetracycline was investigated against a strain of Mannheimia haemolytica. In vitro measurements, comprising minimum inhibitory concentration (MIC), minimum bactericidal concentration and time-kill curves, were conducted in five matrices; Mueller Hinton Broth (MHB), cation-adjusted MHB (CAMHB) and calf serum, exudate and transudate. MICs were much higher in the biological fluids than in MHB and CAMHB. Ratios of MIC were, serum: CAMHB 19 : 1; exudate:CAMHB 16.1; transudate:CAMHB 14 : 1. Ex vivo data, generated in the tissue cage model of inflammation, demonstrated that oxytetracycline, administered to calves intramuscularly at a dose rate of 20 mg/kg, did not inhibit the growth of M haemolytica in serum, exudate and transudate, even at peak concentration. However, using in vitro susceptibility in CAMHB and in vivo-determined pharmacokinetic (PK) variables, average and minimum oxytetracycline concentrations relative to MIC (C(av)/MIC and C(min)/MIC) predicted achievement of efficacy for approximately 48 hours after dosing. Similar C(av)/MIC and C(min)/MIC data were obtained when oxytetracycline was administered in the presence of carprofen. PK-PD integration of data for oxytetracycline, based on MICs determined in the three biological fluids, suggests that it possesses, at most, limited direct killing activity against M haemolytica. These data raise questions concerning the mechanism(s) of action of oxytetracycline, when administered at clinically recommended dose rates.

Analysis of fracture in sheet bending and roll forming

NASA Astrophysics Data System (ADS)

Deole, Aditya D.; Barnett, Matthew; Weiss, Matthias

2018-05-01

The bending limit or minimum bending radius of sheet metal is conventionally measured in a wiping (swing arm) or in a vee bend test and reported as the minimum radius of the tool over which the sheet can be bent without fracture. Frequently the material kinks while bending so that the actual inner bend radius of the sheet metal is smaller than the tool radius giving rise to inaccuracy in these methods. It has been shown in the previous studies that conventional bend test methods may under-estimate formability in bending dominated processes such as roll forming. A new test procedure is proposed here to improve understanding and measurement of fracture in bending and roll forming. In this study, conventional wiping test and vee bend test have been performed on martensitic steel to determine the minimum bend radius. In addition, the vee bend test is performed in an Erichsen sheet metal tester equipped with the GOM Aramis system to enable strain measurement on the outer surface during bending. The strain measurement before the onset of fracture is then used to determine the minimum bend radius. To compare this result with a technological process, a vee channel is roll formed and in-situ strain measurement carried out with the Vialux Autogrid system. The strain distribution at fracture in the roll forming process is compared with that predicted by the conventional bending tests and by the improved process. It is shown that for this forming operation and material, the improved procedure gives a more accurate prediction of fracture.

Antimicrobial effect of Dinoponera quadriceps (Hymenoptera: Formicidae) venom against Staphylococcus aureus strains.

PubMed

Lima, D B; Torres, A F C; Mello, C P; de Menezes, R R P P B; Sampaio, T L; Canuto, J A; da Silva, J J A; Freire, V N; Quinet, Y P; Havt, A; Monteiro, H S A; Nogueira, N A P; Martins, A M C

2014-08-01

Dinoponera quadriceps venom (DqV) was examined to evaluate the antibacterial activity and its bactericidal action mechanism against Staphylococcus aureus. DqV was tested against a standard strain of methicillin-sensitive Staphylococcus aureus (MSSA), Staph. aureus ATCC 6538P and two standard strains of methicillin-resistant Staphylococcus aureus (MRSA), Staph. aureus ATCC 33591 and Staph. aureus CCBH 5330. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the rate of kill and pH sensitivity of the DqV were determined by microdilution tests. Bactericidal and inhibitory concentrations of DqV were tested to check its action on Staph. aureus membrane permeability and cell morphology. The MIC and MBC of DqV were 6·25 and 12·5 μg ml(-1) for Staph. aureus ATCC 6538P, 12·5 and 50 μg ml(-1) for Staph. aureus CCBH 5330 and 100 and 100 μg ml(-1) for Staph. aureus ATCC 33591, respectively. Complete bacterial growth inhibition was observed after 4 h of incubation with the MBC of DqV. A lowest MIC was observed in alkaline pH. Alteration in membrane permeability was observed through the increase in crystal violet uptake, genetic material release and morphology in atomic force microscopy. The results suggest antibacterial activity of DqV against Staph. aureus and that the venom acts in the cell membrane. Alteration in membrane permeability may be associated with the antimicrobial activity of hymenopteran venoms. © 2014 The Society for Applied Microbiology.

Permeability of compacting porous lavas

NASA Astrophysics Data System (ADS)

Ashwell, P. A.; Kendrick, J. E.; Lavallée, Y.; Kennedy, B. M.; Hess, K.-U.; von Aulock, F. W.; Wadsworth, F. B.; Vasseur, J.; Dingwell, D. B.

2015-03-01

The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability of lava domes and shallow conduits. Lava domes generally consist of a porous outer carapace surrounding a denser lava core with internal shear zones of variable porosity. Here we examine densification using uniaxial compression experiments on variably crystalline and porous rhyolitic dome lavas from the Taupo Volcanic Zone. Experiments were conducted at 900°C and an applied stress of 3 MPa to 60% strain, while monitoring acoustic emissions to track cracking. The evolution of the porous network was assessed via X-ray computed tomography, He-pycnometry, and relative gas permeability. High starting connected porosities led to low apparent viscosities and high strain rates, initially accompanied by abundant acoustic emissions. As compaction ensued, the lavas evolved; apparent viscosity increased and strain rate decreased due to strain hardening of the suspensions. Permeability fluctuations resulted from the interplay between viscous flow and brittle failure. Where phenocrysts were abundant, cracks had limited spatial extent, and pore closure decreased axial and radial permeability proportionally, maintaining the initial anisotropy. In crystal-poor lavas, axial cracks had a more profound effect, and permeability anisotropy switched to favor axial flow. Irrespective of porosity, both crystalline samples compacted to a threshold minimum porosity of 17-19%, whereas the crystal-poor sample did not achieve its compaction limit. This indicates that unconfined loading of porous dome lavas does not necessarily form an impermeable plug and may be hindered, in part by the presence of crystals.

[Analysis of resistant genes of beta-lactam antibiotics from Pseudomonas aeruginosa in pediatric patients].

PubMed

Dong, Fang; Xu, Xi-wei; Song, Wen-qi; Lü, Ping; Yang, Yong-hong; Shen, Xu-zhuang

2008-11-18

To analyze the antibiotic resistance of the Pseudomonas aeruginosa (PA) isolated from pediatric patients and the resistant genes of beta-lactam antibiotics thereof. 146 PA strains were isolated from pediatric patients. Agar dilution method recommended by the Clinical and Laboratory Standards Institute was used to examine the minimum inhibitory concentrations (MICs) of 12 antimicrobial agents, including the penicillins, third and fourth genet ration cephalosporins, carbapenemase, Aztreonam, beta-lactamase inhibitors, quinolones, and aminoglycosides. PCR was used to detect the expression of the genes TEM, SHV, OXA, PER, GES, CTX-M, IMP, VIM, DHA, MIR, FOX, and oprD2. The multi-drug resistance rates against different antibiotic were high among the 146 PA strains. The rates of imipenem and meropenem resistance were 41.1% and 35.6% respectively. Among the 146 PA strains, 46 (31.5%) were positive for the MBL genotype; 38 (82.6%) carried the blaIMP gene, 8 (17.4%) carried the blaVIM gene, and 114 (78.1%) were oprD2 negative. The genes TEM, SHV, OXA, CTX-M, PER, VEB, GES, FOX, MIR, and DHA were not found in all strains. Many PA isolated from pediatric patients carry the genes IMP or VIM and losses oprD2 gene related to the expression of the outer membrane porin OprD2. The loss of the gene oprD2 is essential mechanism of beta-lactam antibiotics resistance in PA.

Thermal design and analysis of a hydrogen-burning wind tunnel model of an airframe-integrated scramjet

NASA Technical Reports Server (NTRS)

Guy, R. W.; Mueller, J. N.; Pinckney, S. Z.; Lee, L. P.

1976-01-01

An aerodynamic model of a hydrogen burning, airframe integrated scramjet engine has been designed, fabricated, and instrumented. This model is to be tested in an electric arc heated wind tunnel at an altitude of 35.39 km (116,094 ft.) but with an inlet Mach number of 6 simulating precompression on an aircraft undersurface. The scramjet model is constructed from oxygen free, high conductivity copper and is a heat sink design except for water cooling in some critical locations. The model is instrumented for pressure, surface temperature, heat transfer rate, and thrust measurements. Calculated flow properties, heat transfer rates, and surface temperature distributions along the various engine components are included for the conditions stated above. For some components, estimates of thermal strain are presented which indicate significant reductions in plastic strain by selective cooling of the model. These results show that the 100 thermal cycle life of the engine was met with minimum distortion while staying within the 2669 N (600 lbf) engine weight limitation and while cooling the engine only in critical locations.

Strain gage attachment by spot welding reduces the fatigue strength of Ti-6Al-4V, Rene 41, and Inconel X

NASA Technical Reports Server (NTRS)

Imig, L. A.

1972-01-01

Fatigue tests were conducted with constant-amplitude axial stresses in the ratio of minimum to maximum stress of 0.05 (R=0.05). Specimens with and without strain gages were tested at 21 C, and superalloy specimens with and without strain gages were tested at 21 C and 815 C.

DFB fiber laser static strain sensor based on beat frequency interrogation with a reference fiber laser locked to a FBG resonator.

PubMed

Huang, Wenzhu; Feng, Shengwen; Zhang, Wentao; Li, Fang

2016-05-30

We report on a high-resolution static strain sensor developed with distributed feedback (DFB) fiber laser. A reference FBG resonator is used for temperature compensation. Locking another independent fiber laser to the resonator using the Pound-Drever-Hall technique results in a strain power spectral density better than S_ε(f) = (4.6 × 10^-21) ε²/Hz in the frequency range from 1 Hz to 1 kHz, corresponding to a minimum dynamic strain resolution of 67.8 pε/√Hz. This frequency stabilized fiber laser is proposed to interrogate the sensing DFB fiber laser by the beat frequency principle. As a reasonable DFB fiber laser setup is realized, a narrow beat frequency line-width of 3.23 kHz and a high beat frequency stability of 0.036 MHz in 15 minutes are obtained in the laboratory test, corresponding to a minimum static strain resolution of 270 pε. This is the first time that a sub-0.5 nε level for static strain measurement using DFB fiber laser is demonstrated.

Water intrusion in thin-skinned composite honeycomb sandwich structures

NASA Technical Reports Server (NTRS)

Jackson, Wade C.; O'Brien, T. Kevin

1988-01-01

Thin-skinned composite honeycomb sandwich structures from the trailing edge of the U.S. Army's Apache and Chinook helicopters have been tested to ascertain their susceptibility to water intrusion as well as such intrusions' effects on impact damage and cyclic loading. Minimum-impact and fatigue conditions were determined which would create microcracks sufficiently large to allow the passage of water through the skins; damage sufficient for this to occur was for some skins undetectable under a 40X-magnification optical microscope. Flow rate was a function of moisture content, damage, applied strain, and pressure differences.

An Approximate Solution to the Plastic Indentation of Circular Sandwich Panels

NASA Astrophysics Data System (ADS)

Xie, Z.

2018-05-01

The plastic indentation response of circular sandwich panels loaded by the flat end of a cylinder is investigated employing a velocity field model. Using the principles of virtual velocities and minimum work, an expression for the indenter load in relation to the indenter displacement and displacement field of the deformed face sheet is derived. The analytical solutions obtained are in good agreement with those found by simulations using the ABAQUS code. The radial tensile strain of the deformed face sheet and the ratio of energy absorption rate of the core to that of the face sheet are discussed.

Non-preserved 1% lidocaine solution has less antibacterial properties than currently available anaesthetic eye-drops.

PubMed

Labetoulle, Marc; Frau, Eric; Offret, Hervé; Nordmann, Patrice; Naas, Thierry

2002-08-01

Some anaesthetics inhibit bacterial growth, and thus may lead to low rates of positive cultures from bacterial keratitis. Antibacterial properties of lidocaine were compared with those of oxybuprocaine or tetracaine, either in current commercial eye lotions or in extemporaneous solutions. Forty-eight bacterial strains were used to determine the minimum inhibitory and bactericidal concentrations of four commercial eye lotions containing oxybuprocaine or tetracaine, of a non-ophthalmic 1% lidocaine commercial solution and of extemporaneously prepared solutions of oxybuprocaine, tetracaine, lidocaine and benzalkonium. Most strains had their growth inhibited by 0.2% oxybuprocaine or 0.4% tetracaine, which corresponds to a 1/2 dilution of the commercial eye-drops. Bacterial growth was still observed with a 1% lidocaine solution. Currently available anaesthetic eye-drops that are used before corneal specimen collection may lead to false-negative bacterial cultures. Conversely, a non-preserved 1% lidocaine solution might be more appropriate in corneal specimen collection.

29 CFR 520.409 - When will authority to pay apprentices special minimum wages become effective and what is the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... wages become effective and what is the special minimum wage rate? 520.409 Section 520.409 Labor... apprentices special minimum wages become effective and what is the special minimum wage rate? (a) An... Division. (b) The wage rate specified by the apprenticeship program becomes the special minimum wage rate...

Antimicrobial activity of gallic acid against thermophilic Campylobacter is strain specific and associated with a loss of calcium ions.

PubMed

Sarjit, Amreeta; Wang, Yi; Dykes, Gary A

2015-04-01

Gallic acid has been suggested as a potential antimicrobial for the control of Campylobacter but its effectiveness is poorly studied. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of gallic acid against Campylobacter jejuni (n = 8) and Campylobacter coli (n = 4) strains was determined. Gallic acid inhibited the growth of five C. jejuni strains and three C. coli strains (MIC: 15.63-250 μg mL(-1)). Gallic acid was only bactericidal to two C. coli strains (MBC: 125 and 62.5 μg mL(-1)). The mechanism of the bactericidal effect against these two strains (and selected non-susceptible controls) was investigated by determining decimal reduction times and by monitoring the loss of cellular content and calcium ions, and changes in cell morphology. Gallic acid did not result in a loss of cellular content or morphological changes in the susceptible strains as compared to the controls. Gallic acid resulted in a loss of calcium ions (0.58-1.53 μg mL(-1) and 0.54-1.17 μg mL(-1), respectively, over a 180 min period) from the susceptible strains but not the controls. Gallic acid is unlikely to be an effective antimicrobial against Campylobacter in a practical sense unless further interventions to ensure an effective bactericidal mode of action against all strains are developed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interatrial septum pacing decreases atrial dyssynchrony on strain rate imaging compared with right atrial appendage pacing.

PubMed

Yasuoka, Yoshinori; Abe, Haruhiko; Umekawa, Seiko; Katsuki, Keiko; Tanaka, Norio; Araki, Ryo; Imanaka, Takahiro; Matsutera, Ryo; Morisawa, Daisuke; Kitada, Hirokazu; Hattori, Susumu; Noda, Yoshiki; Adachi, Hidenori; Sasaki, Tatsuya; Miyatake, Kunio

2011-03-01

Interatrial septum pacing (IAS-P) decreases atrial conduction delay compared with right atrial appendage pacing (RAA-P). We evaluate the atrial contraction with strain rate of tissue Doppler imaging (TDI) during sinus activation or with IAS-P or RAA-P. Fifty-two patients with permanent pacemaker for sinus node disease were enrolled in the study. Twenty-three subjects were with IAS-P and 29 with RAA-P. The time from end-diastole to peak end-diastolic strain rate was measured and corrected with RR interval on electrocardiogram. It was defined as the time from end-diastole to peak end-diastolic strain rate (TSRc), and the balance between maximum and minimum TSRc at three sites (ΔTSRc) was compared during sinus activation and with pacing rhythm in each group. There were no significant differences observed in general characteristics and standard echocardiographic parameters except the duration of pacing P wave between the two groups. The duration was significantly shorter in the IAS-P group compared with the RAA-P group (95 ± 34 vs 138 ± 41; P = 0.001). TSRc was significantly different between sinus activation and pacing rhythm (36.3 ± 35.7 vs 61.6 ± 36.3; P = 0.003) in the RAA-P group, whereas no significant differences were observed in the IAS-P group (25.4 ± 12.1 vs 27.7 ± 14.7; NS). During the follow-up (mean 2.4 ± 0.7 years), the incidence of paroxysmal atrial fibrillation (AF) conversion to permanent AF was not significantly different between the two groups. IAS-P decreased the contraction delay on atrial TDI compared to RAA-P; however, it did not contribute to the reduction of AF incidence in the present study. ©2010, The Authors. Journal compilation ©2010 Wiley Periodicals, Inc.

The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density

PubMed Central

Rubin, Clinton T.; Seeherman, Howard; Qin, Yi-Xian; Gross, Ted S.

2013-01-01

Distributions of normal strain, shear strain, and strain energy density (SED) were determined across the midshaft of the third metacarpal (MCIII, or cannon bone) of 3 adult thoroughbred horses as a function of speed and gait. A complete characterization of the mechanical demands of the bone made through the stride and from mild through the extremes of locomotion was possible by using three 3-element rosette strain gauges bonded at the diaphyseal midshaft of the MCIII and evaluating the strain output with beam theory and finite element analysis. Mean ± sd values of normal strain, shear strain, and SED increased with speed and peaked during a canter (−3560±380 microstrain, 1760±470 microstrain, and 119±23 kPa, respectively). While the location of these peaks was similar across animals and gaits, the resulting strain distributions across the cortex were consistently nonuniform, establishing between a 73-fold (slow trot) to a 330-fold (canter) disparity between the sites of maximum and minimum SED for each gait cycle. Using strain power density as an estimate of strain history across the bone revealed a 154-fold disparity between peak and minimum at the walk but fell to ∼32-fold at the canter. The nonuniform, minimally varying, strain environment suggests either that bone homeostasis is mediated by magnitude-independent mechanical signals or that the duration of stimuli necessary to establish and maintain tissue integrity is relatively brief, and thus the vast majority of strain information is disregarded.—Rubin, C. T., Seeherman, H., Qin, Y.-X., Gross, T. S., The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density. PMID:23355269

[Effect of the development phase and growth rate of a Shigella sonnei population on the reproduction of homologous bacteriophage].

PubMed

Voroshilova, N N; Kazakova, T B

1983-04-01

This study showed that the minimum latent period (20 minutes) of the intracellular multiplication of dysentery bacteriophage S-9 in the population of S. sonnei substrate strain under the conditions of static heterogeneous surface batch cultivation was observed at the end of the lag phase and at the growth acceleration phase, in the first and second thirds of the exponential curve, while the maximum latent period (35-40 minutes) was observed at the stationary phase. The maximum yield of phage S-9 from one infected bacterial cell (628.3 +/- 116.8) was registered during the first third of the phase of the exponential growth of the bacterial population and the minimum yield (18.66 +/- 6.6), at the beginning of the lag phase. The significant direct correlation between the specific growth rate of the bacterial population and the yield of the phage from one infected bacterial cell at the end of the lag phase, at the growth acceleration and deceleration phases, as well as the significant inverse correlation between the yield of the phage and the time of the generation of the bacterial population at the growth acceleration phase were established.

Stem bark extract and fraction of Persea americana (Mill.) exhibits bactericidal activities against strains of bacillus cereus associated with food poisoning.

PubMed

Akinpelu, David A; Aiyegoro, Olayinka A; Akinpelu, Oluseun F; Okoh, Anthony I

2014-12-30

The study investigates the in vitro antibacterial potentials of stem bark extracts of Persea americana on strains of Bacillus cereus implicated in food poisoning. The crude stem bark extracts and butanolic fraction at a concentration of 25 mg/mL and 10 mg/mL, respectively, exhibited antibacterial activities against test isolates. The zones of inhibition exhibited by the crude extract and the fraction ranged between 10 mm and 26 mm, while the minimum inhibitory concentration values ranged between 0.78 and 5.00 mg/mL. The minimum bactericidal concentrations ranged between 3.12 mg/mL-12.5 mg/mL and 1.25-10 mg/mL for the extract and the fraction, respectively. The butanolic fraction killed 91.49% of the test isolates at a concentration of 2× MIC after 60 min of contact time, while a 100% killing was achieved after the test bacterial cells were exposed to the butanolic fraction at a concentration of 3× MIC after 90 min contact time. Intracellular protein and potassium ion leaked out of the test bacterial cells when exposed to certain concentrations of the fraction; this is an indication of bacterial cell wall disruptions by the extract's butanolic fraction and, thus, caused a biocidal effect on the cells, as evident in the killing rate test results.

Modeling of the minimum variable blank holder force based on forming limit diagram (FLD) in deep drawing process

NASA Astrophysics Data System (ADS)

Candra, S.; Batan, I. M. L.; Berata, W.; Pramono, A. S.

2017-11-01

This paper presents the mathematical approach of minimum blank holder force to prevent wrinkling in deep drawing process of the cylindrical cup. Based on the maximum of minor-major strain ratio, the slab method was applied to determine the modeling of minimum variable blank holder force (VBHF) and it compared to FE simulation. The Tin steel sheet of T4-CA grade, with the thickness of 0.2 mm was used in this study. The modeling of minimum VBHF can be used as a simple reference to prevent wrinkling in deep drawing.

Antifungal Activity of Essential Oils against Candida albicans Strains Isolated from Users of Dental Prostheses

PubMed Central

Júnior, José Klidenberg de Oliveira; Silva, Daniele de Figueredo; de Sousa, Janiere Pereira; Guerra, Felipe Queiroga Sarmento; de Oliveira Lima, Edeltrudes

2017-01-01

Objective The objective of this study was to analyze the antifungal activity of citral, selected by screening natural products, against Candida albicans isolates from subjects who use dental prostheses. Methodology Screening of essential oils, including those from Mentha piperita L. (Briq), Origanum vulgare, and Zingiber officinale L., and the phytoconstituents citral and limonene, to select an appropriate natural product. Citral, which mediated the best antifungal response, was selected for biological assays. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) for citral and nystatin were determined by the microdilution method. Micromorphological analyses, time-kill curve, and modulation tests were performed. Results The MIC and MFC of citral were established as 32 μg/mL, consistent with fungicidal activity. The clinical strains were resistant to nystatin. Citral caused micromorphological alteration in the strains. In the time-kill curve, the growth of the clinical strain was reduction in growth equal to 3 log10 colony-forming units per milliliter after exposure to the MIC and MIC × 2 of citral for 2 h. Citral did not modulate the resistance of the studied strains to nystatin. Conclusion This study revealed the potential of citral as a fungicidal agent and highlighted the resistance of clinical strains of C. albicans to nystatin. PMID:29234423

Growth and fermentation patterns of Saccharomyces cerevisiae under different ammonium concentrations and its implications in winemaking industry.

PubMed

Mendes-Ferreira, A; Mendes-Faia, A; Leão, C

2004-01-01

To study the effects of assimilable nitrogen concentration on growth profile and on fermentation kinetics of Saccharomyces cerevisiae. Saccharomyces cerevisiae was grown in batch in a defined medium with glucose (200 g l(-1)) as the only carbon and energy source, and nitrogen supplied as ammonium sulphate or phosphate forms under different concentrations. The initial nitrogen concentration in the media had no effect on specific growth rates of the yeast strain PYCC 4072. However, fermentation rate and the time required for completion of the alcoholic fermentation were strongly dependent on nitrogen availability. At the stationary phase, the addition of ammonium was effective in increasing cell population, fermentation rate and ethanol. The yeast strain required a minimum of 267 mg N l(-1) to attain complete dryness of media, within the time considered for the experiments. Lower levels were enough to support growth, although leading to sluggish or stuck fermentation. The findings reported here contribute to elucidate the role of nitrogen on growth and fermentation performance of wine yeast. This information might be useful to the wine industry where excessive addition of nitrogen to prevent sluggish or stuck fermentation might have a negative impact on wine stability and quality. Copyright 2004 The Society for Applied Microbiology

Combining the Sterile Insect Technique with Wolbachia-Based Approaches: II- A Safer Approach to Aedes albopictus Population Suppression Programmes, Designed to Minimize the Consequences of Inadvertent Female Release

PubMed Central

Zhang, Dongjing; Lees, Rosemary Susan; Xi, Zhiyong; Gilles, Jeremie R. L.; Bourtzis, Kostas

2015-01-01

Due to the absence of a perfect method for mosquito sex separation, the combination of the sterile insect technique and the incompatible insect technique is now being considered as a potentially effective method to control Aedes albopictus. In this present study first we examine the minimum pupal irradiation dose required to induce complete sterility in Wolbachia triple-infected (HC), double-infected (GUA) and uninfected (GT) female Ae. albopictus. The HC line is a candidate for Ae. albopictus population suppression programmes, but due to the risk of population replacement which characterizes this triple infected line, the individuals to be released need to be additionally irradiated. After determining the minimum irradiation dose required for complete female sterility, we test whether sterilization is sufficient to prevent invasion of the triple infection from the HC females into double-infected (GUA) populations. Our results indicate that irradiated Ae. albopictus HC, GUA and GT strain females have decreased fecundity and egg hatch rate when irradiated, inversely proportional to the dose, and the complete sterilization of females can be acquired by pupal irradiation with doses above 28 Gy. PCR-based analysis of F1 and F2 progeny indicate that the irradiated HC females, cannot spread the new Wolbachia wPip strain into a small cage GUA population, released at a 1:5 ratio. Considering the above results, we conclude that irradiation can be used to reduce the risk of population replacement caused by an unintentional release of Wolbachia triple-infected Ae. albopictus HC strain females during male release for population suppression. PMID:26252474

Inferring fault rheology from low-frequency earthquakes on the San Andreas

USGS Publications Warehouse

Beeler, Nicholas M.; Thomas, Amanda; Bürgmann, Roland; Shelly, David R.

2013-01-01

Families of recurring low-frequency earthquakes (LFEs) within nonvolcanic tremor (NVT) on the San Andreas fault in central California show strong sensitivity to shear stress induced by the daily tidal cycle. LFEs occur at all levels of the tidal shear stress and are in phase with the very small, ~400 Pa, stress amplitude. To quantitatively explain the correlation, we use a model from the existing literature that assumes the LFE sources are small, persistent regions that repeatedly fail during shear of a much larger scale, otherwise aseismically creeping fault zone. The LFE source patches see tectonic loading, creep of the surrounding fault which may be modulated by the tidal stress, and direct tidal loading. If the patches are small relative to the surrounding creeping fault then the stressing is dominated by fault creep, and if patch failure occurs at a threshold stress, then the resulting seismicity rate is proportional to the fault creep rate or fault zone strain rate. Using the seismicity rate as a proxy for strain rate and the tidal shear stress, we fit the data with possible fault rheologies that produce creep in laboratory experiments at temperatures of 400 to 600°C appropriate for the LFE source depth. The rheological properties of rock-forming minerals for dislocation creep and dislocation glide are not consistent with the observed fault creep because strong correlation between small stress perturbations and strain rate requires perturbation on the order of the ambient stress. The observed tidal modulation restricts ambient stress to be at most a few kilopascal, much lower than rock strength. A purely rate dependent friction is consistent with the observations only if the product of the friction rate dependence and effective normal stress is ~ 0.5 kPa. Extrapolating the friction rate strengthening dependence of phyllosilicates (talc) to depth would require the effective normal stress to be ~50 kPa, implying pore pressure is lithostatic. If the LFE source is on the order of tens of meters, as required by the model, rate-weakening friction rate dependence (e.g., olivine) at 400 to 600°C requires that the minimum effective pressure at the LFE source is ~ 2.5 MPa.

Assessing the antibiotic potential of essential oils against Haemophilus ducreyi.

PubMed

Lindeman, Zachary; Waggoner, Molly; Batdorff, Audra; Humphreys, Tricia L

2014-05-27

Haemophilus ducreyi is the bacterium responsible for the genital ulcer disease chancroid, a cofactor for the transmission of HIV, and it is resistant to many antibiotics. With the goal of exploring possible alternative treatments, we tested essential oils (EOs) for their efficacy as antimicrobial agents against H. ducreyi. We determine the minimum inhibitory concentration (MIC) of Cinnamomum verum (cinnamon), Eugenia caryophyllus (clove) and Thymus satureioides (thyme) oil against 9 strains of H. ducreyi using the agar dilution method. We also determined the minimum lethal concentration for each oil by subculturing from the MIC plates onto fresh agar without essential oil. For both tests, we used a 2-way ANOVA to evaluate whether antibiotic-resistant strains had a different sensitivity to the oils relative to non-resistant strains. All 3 oils demonstrated excellent activity against H. ducreyi, with MICs of 0.05 to 0.52 mg/mL and MLCs of 0.1-0.5 mg/mL. Antibiotic-resistant strains of H. ducreyi were equally susceptible to these 3 essential oils relative to non-resistant strains (p=0.409). E. caryophyllus, C. verum and T. satureioides oils are promising alternatives to antibiotic treatment for chancroid.

[Group B Streptococcus carriers among pregnant women].

PubMed

García, S D; Eliseth, M Cora; Lazzo, M J; Copolillo, E; Barata, A D; de Torres, R; Vay, C A; Famiglietti, A M

2003-01-01

Streptococcus agalactiae--group B streptococci (GBS)--is a main cause of severe neonatal infections with a high mortality rate. The detection of pregnant GBS carriers (5-35%) allows intrapartum administration of antibiotic prophylaxis to these women and prevents perinatal infection. We studied the prevalence of GBS in 259 patients between 28 and 37 weeks gestation from April 2000 to March 2002. The anorectum (AR) and vaginal introitus swabs (VI) were cultured in selective Todd-Hewitt broth containing colistin (10 micrograms/ml) and nalidixic acid (15 micrograms/ml) while vaginal swabs (VFS) were cultured following conventional methods. A total of 47 strains of EGB were isolated from 259 patients (18.15%). The prevalence in different samples were: 5.40% in VFS, 13.51% in VI, 11.58% in AR and 17.76% in VI + AR (reference method). The isolates were tested against penicillin, ceftriaxone, erythromycin, clindamycin, vancomycin, gentamicin and streptomycin to determine the minimum inhibitory concentration. The resistance phenotypes of erythromycin-resistant GBS were determined by the double-disk test. All strains were susceptible to penicillin, ceftriaxone and vancomycin, only one strain was erythromycin and clindamycin resistant by IMLSB mechanism. None of the isolated strains had a high resistant level to aminoglycosides. The sensitivity of cultures increased when selective broths were used as the primary detection method.

5 CFR 9701.324 - Treatment of employees whose rate of basic pay does not fall below the minimum rate of their band.

Code of Federal Regulations, 2013 CFR

2013-01-01

... basic pay does not fall below the minimum rate of their band. 9701.324 Section 9701.324 Administrative... basic pay does not fall below the minimum rate of their band. An employee who does not receive a pay... fall below the minimum rate of his or her band as a result of that rating will receive such an increase...

5 CFR 9701.324 - Treatment of employees whose rate of basic pay does not fall below the minimum rate of their band.

Code of Federal Regulations, 2011 CFR

2011-01-01

... basic pay does not fall below the minimum rate of their band. 9701.324 Section 9701.324 Administrative... basic pay does not fall below the minimum rate of their band. An employee who does not receive a pay... fall below the minimum rate of his or her band as a result of that rating will receive such an increase...

5 CFR 9701.324 - Treatment of employees whose rate of basic pay does not fall below the minimum rate of their band.

Code of Federal Regulations, 2012 CFR

2012-01-01

... basic pay does not fall below the minimum rate of their band. 9701.324 Section 9701.324 Administrative... basic pay does not fall below the minimum rate of their band. An employee who does not receive a pay... fall below the minimum rate of his or her band as a result of that rating will receive such an increase...

5 CFR 9701.324 - Treatment of employees whose rate of basic pay does not fall below the minimum rate of their band.

Code of Federal Regulations, 2014 CFR

2014-01-01

... basic pay does not fall below the minimum rate of their band. 9701.324 Section 9701.324 Administrative... basic pay does not fall below the minimum rate of their band. An employee who does not receive a pay... fall below the minimum rate of his or her band as a result of that rating will receive such an increase...

Comparative production of channel catfish and channel x blue hybrid catfish subjected to two minimum dissolved oxygen concentrations

USDA-ARS?s Scientific Manuscript database

The effect of daily minimum dissolved oxygen concentration on growth and yield (kg/ha) of the channel catfish (Ictalurus punctatus) and the channel x blue hybrid catfish (I. punctatus female x I. furcatus male), which shared the Jubilee strain of channel catfish as the maternal parent, was evaluated...

Cosmogenic 10Be and 36Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications for transient strain in the eastern California shear zone

USGS Publications Warehouse

Frankel, K.L.; Brantley, K.S.; Dolan, J.F.; Finkel, R.C.; Klinger, R.E.; Knott, J.R.; Machette, M.N.; Owen, L.A.; Phillips, F.M.; Slate, J.L.; Wernicke, B.P.

2007-01-01

The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right-lateral strike-slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high-resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ???297 ?? 9 m of right-lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36C1 geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/-20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ?? 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/-1.1 mm yr-1, whereas the 36Cl data indicate 4.7 +0.9/-0.6 mm yr-1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ???8.5 to 10 mm yr-1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant. Copyright 2007 by the American Geophysical Union.

Cosmogenic 10Be and 36Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications for transient strain in the eastern California shear zone

NASA Astrophysics Data System (ADS)

Frankel, Kurt L.; Brantley, Katherine S.; Dolan, James F.; Finkel, Robert C.; Klinger, Ralph E.; Knott, Jeffrey R.; Machette, Michael N.; Owen, Lewis A.; Phillips, Fred M.; Slate, Janet L.; Wernicke, Brian P.

2007-06-01

The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right-lateral strike-slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high-resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ˜297 ± 9 m of right-lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36Cl geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/-20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ± 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/-1.1 mm yr-1, whereas the 36Cl data indicate 4.7 +0.9/-0.6 mm yr-1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ˜8.5 to 10 mm yr-1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant.

Shear-strain energy rate distribution caused by the interplate locking along the Nankai Trough, southwest Japan: An integration analysis using stress tensor inversion and slip deficit inversion

NASA Astrophysics Data System (ADS)

Saito, T.; Noda, A.; Yoshida, K.; Tanaka, S.

2017-12-01

In the Nankai Trough, southwest Japan, the Philippine Sea Plate descends beneath the Eurasian plate. The locking, or the slip deficit, on the plate interface causes stress fluctuation in the inland area. The interplate locking does not always result in stress accumulation but also causes stress release. The stress increase/decrease is not determined only from the stress fluctuation but also depends on the background stress, in particular, its orientation. This study proposes a method to estimate the shear-strain energy increase/decrease distribution caused by the interplate locking. We at first investigated the background stress field in and around the Nankai Trough. The spatial distribution of the principal stress orientations and the stress ratio were estimated by analysis of 130,000 focal mechanisms of small earthquakes (e.g., Yoshida et al. 2015 Tectonophysics). For example, in an area called Chugoku region, the maximum and minimum compression axes were E-W and N-S directions, respectively. We also estimated the slip-deficit rate at the plate interface by analyzing GNSS data and calculated the stress fluctuation due to the deficit (e.g., Noda et al. 2013 GJI). The interplate locking causes the maximum compression in the direction of plate convergence. This is significantly different from the orientations of the background stress characterized by the E-W compressional strike-slip stress regime.. By combining the results of the background stress and the stress fluctuation, we made a map indicating the shear-strain energy change due to the interplate locking. In the Chugoku region, the shear-strain energy decreases due to the interplate locking. This is because the N-S compressional stress caused by the interplate locking compensates the N-S extensional stress in the background. The shear-strain energy increases in some parts of the analyzed areas. By statistically comparing the shear strain energy rate with the seismicity in the inland area, we found that the seismicity tends to be high where the interplate locking increases the shear-strain energy. Our results suggest that the stress fluctuation due to the interplate locking is not dominant in the background stress but surely contributes to the inland seismicity in southwest Japan.

Root-Zone-Specific Oxygen Tolerance of Azospirillum spp. and Diazotrophic Rods Closely Associated with Kallar Grass.

PubMed

Hurek, T; Reinhold, B; Fendrik, I; Niemann, E G

1987-01-01

The effect of oxygen on N(2)-dependent growth of two Azospirillum strains and two diazotrophic rods closely associated with roots of Kallar grass (Leptochloa fusca) was studied. To enable precise comparison, bacteria were grown in dissolved-oxygen-controlled batch and continuous cultures. Steady states were obtained from about 1 to 30 muM O(2), some of them being carbon limited. All strains needed a minimum amount of oxygen for N(2)-dependent growth. Nitrogen contents between 10 and 13% of cell dry weight were observed. The response of steady-state cultures to increasing O(2) concentrations suggested that carbon limitation shifted to internal nitrogen limitation when N(2) fixation became so low that the bacteria could no longer meet their requirements for fixed nitrogen. For Azospirillum lipoferum Rp5, increase of the dilution rate resulted in decreased N(2) fixation in steady-state cultures with internal nitrogen limitation. Oxygen tolerance was found to be strain specific in A. lipoferum with strain Sp59b as a reference organism. Oxygen tolerance of strains from Kallar grass was found to be root zone specific. A. halopraeferens Au 4 and A. lipoferum Rp5, predominating on the rhizoplane of Kallar grass, and strains H6a2 and BH72, predominating in the endorhizosphere, differed in their oxygen tolerance profiles. Strains H6a2 and BH72 still grew and fixed nitrogen in steady-state cultures at O(2) concentrations exceeding those which absolutely inhibited nitrogen fixation of both Azospirillum strains. It is proposed that root-zone-specific oxygen tolerance reflects an adaptation of the isolates to the microenvironments provided by the host plant.

In vitro transfer of multiple resistance observed in vivo during a Salmonella london epidemic.

PubMed

Lantos, J; Marjai, E

1980-01-01

Between 1976 and 1978, waves of Salmonella london infections conveyed by raw meat and meat products were observed. The strains isolated during the epidemic were first susceptible then developed multiple antibiotic resistance. The identical antibiotic resistance patterns of the strain and their more frequent occurrence in hospital environments indicated plasmid-mediated resistance. R-plasmid transfer, minimum inhibition concentration and resistance elimination were studied in representative strains. The resistant S. london strain and transconjugants of Escherichia coli rendered resistant were compared. The results proved that multiple resistance was plasmid-mediated.

The effect of inbreeding and larval feeding regime on immature development of Aedes albopictus.

PubMed

Jong, Zheng-Wei; Kassim, Nur Faeza A; Naziri, Muhammad Aiman; Webb, Cameron E

2017-06-01

The fundamental approach to the biological control of Aedes albopictus requires the mass rearing of mosquitoes and the release of highly competitive adults in the field. As the fitness of adults is highly dependent on the development of immatures, we aimed to identify the minimum feeding regime required to produce viable and competitive adults by evaluating three response parameters: development duration, immature mortality, and adult wing length. Our study suggests at least 0.60 mg/larva/day of larval diet composed of dog food, dried beef liver, yeast, and milk powder in a weight ratio of 2:1:1:1 is required to maximize adult fitness. With standardized protocols in mass rearing, intensive studies can be readily conducted on mosquito colonies to facilitate comparisons across laboratories. This study also evaluated the differences in response of laboratory and field strains under different feeding regimes. We found that strain alone did not exert substantial effects on all response parameters. However, the field strain exhibited significantly lower immature mortality than the laboratory strain under the minimum feeding regime. Females and males of the laboratory strain had longer wing lengths under nutritional constraint due to the higher mortality that resulted in reduced interactions with the remaining larvae. Meanwhile, the field strain exhibited heterogeneous duration of immature development compared with the laboratory strain. The disparities demonstrated by the two strains in this study suggest the effect of inbreeding surfaced after a long term of laboratory colonization. Despite the trade-offs resulting from laboratory colonization, the competitiveness of the laboratory strain of Ae. albopictus is comparable to the field strain, provided the larvae are fed optimally. © 2017 The Society for Vector Ecology.

Microstructure stability during creep deformation of hard-oriented polysynthetically twinned crystal of TiAl alloy

NASA Astrophysics Data System (ADS)

Kim, Hee Y.; Maruyama, K.

2003-10-01

The hard-orientated polysynthetically twinned (PST) crystal with the lamellar plates oriented parallel to the compression axis was deformed at 1150 K under the applied stress of 158 to 316 MPa. Microstructural changes were examined quantitatively for the PST crystal during creep deformation. In the as-grown PST crystal of the present study, proportions of α 2/ γ, true twin, pseudotwin, and 120 deg rotational fault interfaces were 12, 59, 12, and 17 pct, respectively. After creep deformation, lamellar coarsening by dissolution of α 2 lamellae and migration of γ/γ interfaces were observed. The acceleration of creep rate after the minimum strain rate in the creep curve was attributed to the lamellar coarsening and destruction of lamellar structure during the creep deformation. Thirty-two percent of α 2/ γ interfaces, 51 pct of true twin interfaces, 74 pct of pseudotwin interfaces, and 80 pct of 120 deg rotational faults disappeared after 4 pct creep strain at 1150 K. The α 2/ γ interface was more stable than γ/γ interfaces during the creep deformation. The pseudotwin interface and 120 deg rotational fault were less thermally stable than the true twin interface for γ/γ interfaces.

Antibacterial, antifungal and cytotoxic evaluation of some new quinazolinone derivatives

PubMed Central

Hassanzadeh, F.; Jafari, E.; Hakimelahi, G.H.; Khajouei, M. Rahmani; Jalali, M.; Khodarahmi, G.A.

2012-01-01

Quinazolinone ring system is renown because of its wide spectrum of pharmacological activities due to various substitutions on this ring system. In this study, the minimum inhibitory concentration of the synthesized compounds in our laboratory was determined by micro dilution Alamar Blue® Assay against six strains of bacteria (three Gram-positive and three Gram-negative) and three strains of fungi. Following a broth micro dilution minimum inhibitory concentration (MIC) test, Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC) tests were performed. Cytotoxic effects of the compounds were measured using the MTT colorimetric assay on HeLa cell line. Results of antimicrobial screening showed that compounds had better bacteriostatic activity against Gram-negative bacteria. Results from MBC revealed that these compounds had more significant bacteriostatic than bactericidal activities. Nearly all screened compounds showed good activity against C. albicans and A. niger. Results from MFC indicated that these compounds had better fungistatic rather than fungicidal activities. The synthesized target molecules were found to exhibit different cytotoxicity in the range of 10 to 100 μM on HeLa cell line. Compounds 6 and 7 exhibited acceptable cytotoxicity approximately 50% at 10 μM concentration. PMID:23181085

5 CFR 532.249 - Minimum rates for hard-to-fill positions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Minimum rates for hard-to-fill positions. 532.249 Section 532.249 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS Prevailing Rate Determinations § 532.249 Minimum rates for hard-to-fill...

5 CFR 532.249 - Minimum rates for hard-to-fill positions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Minimum rates for hard-to-fill positions. 532.249 Section 532.249 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS Prevailing Rate Determinations § 532.249 Minimum rates for hard-to-fill...

5 CFR 532.249 - Minimum rates for hard-to-fill positions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Minimum rates for hard-to-fill positions. 532.249 Section 532.249 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS Prevailing Rate Determinations § 532.249 Minimum rates for hard-to-fill...

Anti-Candida activity of fluoxetine alone and combined with fluconazole: a synergistic action against fluconazole-resistant strains.

PubMed

Oliveira, Ana S; Gaspar, Carlos A; Palmeira-de-Oliveira, Rita; Martinez-de-Oliveira, José; Palmeira-de-Oliveira, Ana

2014-07-01

The purpose of this work was to determine the antimicrobial activity of fluoxetine, alone and combined with fluconazole, against 29 Candida strains isolated from patients with vulvovaginal candidiasis. MIC and minimum lethal concentration values ranged from 9.8 to 625 μg/ml for all strains tested. The combination of fluconazole with fluoxetine resulted in synergistic activity against six Candida strains, with fractional inhibitory index (FIX) values between 0.15 and 0.31. An indifferent effect was found for the remaining strains, with FIX values between 0.63 and 1. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Antimicrobial susceptibility of Clostridium perfringens strains isolated from broiler chickens

PubMed Central

Silva, R. O. S.; Salvarani, F.M.; Assis, R.A.; Martins, N.R.S.; Pires, P.S.; Lobato, F.C.F.

2009-01-01

Clostridium perfringens is a normal inhabitant of the intestinal tract of chickens as well as a potential pathogen that causes necrotic enteritis and colangio hepatitis. The minimum inhibitory concentration (MIC) of seven different compounds used for therapy, growth promotion or prevention of coccidiosis was determined by agar dilution method for 55 C. perfringens strains isolated from the intestines of broiler chickens. All strains showed high susceptibility to penicillin, avilamycin, monensin and narasin. Only 7.3% of the strains showed an intermediated sensitivity to lincomycin, and 49 (89.1%) were considered susceptible. For tetracycline and bacitracin, 41.8% and 47.3% of strains, respectively, were considered resistant. PMID:24031355

Plastic strain arrangement in copper single crystals in sliding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chumaevskii, Andrey V., E-mail: tch7av@gmail.com; Lychagin, Dmitry V., E-mail: dvl-tomsk@mail.ru; Tarasov, Sergei Yu., E-mail: tsy@ispms.tsc.ru

2014-11-14

Deformation of tribologically loaded contact zone is one of the wear mechanisms in spite of the fact that no mass loss may occur during this process. Generation of optimal crystallographic orientations of the grains in a polycrystalline materials (texturing) may cause hardening and reducing the deformation wear. To reveal the orientation dependence of an individual gain and simplify the task we use copper single crystals with the orientations of the compression axis along [111] and [110]. The plastic deformation was investigated by means of optical, scanning electron microscopy and EBSD techniques. It was established that at least four different zonesmore » were generated in the course of sliding test, such as non-deformed base metal, plastic deformation layer sliding, crystalline lattice reorientation layer and subsurface grain structure layer. The maximum plastic strain penetration depth was observed on [110]-single crystals. The minimum stability of [111]-crystals with respect to rotation deformation mode as well as activation of shear in the sliding contact plane provide for rotation deformation localization below the worn surface. The high-rate accumulation of misorientations and less strain penetration depth was observed on [111]-crystals as compared to those of [110]-oriented ones.« less

An investigation of vancomycin minimum inhibitory concentration creep among methicillin-resistant Staphylococcus aureus strains isolated from pediatric patients and healthy children in Northern Taiwan.

PubMed

Chang, Chia-Ning; Lo, Wen-Tsung; Chan, Ming-Chin; Yu, Ching-Mei; Wang, Chih-Chien

2017-06-01

The phenomenon of vancomycin minimum inhibitory concentration (MIC) creep is an increasingly serious problem in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. In this study, we investigated the vancomycin and daptomycin MIC values of MRSA strains isolated from pediatric patients and MRSA colonized healthy children. Then, we assessed whether there was evidence of clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL. We collected clinical MRSA isolates from pediatric patients and from healthy children colonized with MRSA during 2008-2012 at a tertiary medical center in northern Taiwan and obtained vancomycin and daptomycin MIC values using the Etest method. Pulse-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome (SCCmec) typing were used to assess clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL. A total 195 MRSA strains were included in this study; 87 were isolated patients with a clinical MRSA infection, and the other 108 strains from nasally colonized healthy children. Vancomycin MIC≥1.5 μg/mL was seen in more clinical isolates (60/87, 69%) than colonized isolates (32/108, 29.6%), p < 0.001. The PFGE typing of both strains revealed multiple pulsotypes. Vancomycin MIC creeps existed in both clinical MRSA isolates and colonized MRSA strains. Great diversity of PFGE typing was in both strains collected. There was no association between the clinical and colonized MRSA isolates with vancomycin MIC creep. Copyright © 2016. Published by Elsevier B.V.

Minimum inhibitory (MIC) and minimum microbicidal concentration (MMC) of polihexanide and triclosan against antibiotic sensitive and resistant Staphylococcus aureus and Escherichia coli strains

PubMed Central

Assadian, Ojan; Wehse, Katrin; Hübner, Nils-Olaf; Koburger, Torsten; Bagel, Simone; Jethon, Frank; Kramer, Axel

2011-01-01

Background: An in-vitro study was conducted investigating the antimicrobial efficacy of polihexanide and triclosan against clinical isolates and reference laboratory strains of Staphylococcus aureus and Escherichia coli. Methods: The minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC) were determined following DIN 58940-81 using a micro-dilution assay and a quantitative suspension test following EN 1040. Polihexanide was tested in polyethylene glycol 4000, triclosan in aqueous solutions. Results: Against all tested strains the MIC of polihexanide ranged between 1–2 µg/mL. For triclosan the MICs varied depending on strains ranging between 0.5 µg/mL for the reference strains and 64 µg/mL for two clinical isolates. A logRF >5 without and logRF >3 with 0.2% albumin burden was achieved at 0.6 µg/mL triclosan. One exception was S. aureus strain H-5-24, where a triclosan concentration of 0.6 µg/mL required 1 minute without and 10 minutes with albumin burden to achieve the same logRFs. Polihexanide achieved a logRF >5 without and logRF >3 with albumin burden at a concentration of 0.6 µg/mL within 30 sec. The exception was the North-German epidemic MRSA strain, were an application time of 5 minutes was required. Conclusion: The clinical isolates of E. coli generally showed higher MICs against triclosan, both in the micro-dilution assay as well in the quantitative suspension test than comparable reference laboratory strains. For polihexanide and triclosan strain dependant susceptibility was shown. However, both antimicrobial compounds are effective when used in concentrations common in practice. PMID:22242087

New insights into the capacity of commercial wine yeasts to grow on sparkling wine media. Factor screening for improving wine yeast selection.

PubMed

Borrull, Anna; Poblet, Montse; Rozès, Nicolas

2015-06-01

During the production of sparkling wine, wine yeasts are subjected to many stress factors apart from ethanol, which lead to the need to achieve their acclimation in line with various industrial protocols. In the present work, 44 commercial wine Saccharomyces cerevisiae strains and one laboratory strain (BY4742) were firstly subjected to the influence of increasing concentrations of ethanol to cluster the yeasts using discriminant function analysis. Afterwards, non-inhibitory concentration (NIC) and minimum inhibitory concentration (MIC) were estimated, revealing some differences between 24 of these strains. Meanwhile, this study confirms the negative synergistic effect of low pH with ethanol on the maximum specific growth rate (μmax) and lag phase time. Moreover, a negative effect of increasing levels of glycerol in the growth medium was observed. Interestingly enough, an interactive positive effect was found between cysteine and medium-chain fatty acids (MCFA). While cysteine did not have a really significant effect in comparison to the control, it was able to restore the damage caused by MCFA, making the growth rate of cells recover and even reducing the formation of reactive oxygen species. Adequate culture aeration is also crucial for the composition of the cell fatty acid. The final results showed that few differences were observed between NIC and MIC estimations with respect to cells pre-cultured in the presence or absence of oxygen. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of solar radiation on multidrug resistant E. coli strains and antibiotic mixture photodegradation in wastewater polluted stream.

PubMed

Rizzo, L; Fiorentino, A; Anselmo, A

2012-06-15

The effect of solar radiation on the inactivation of multidrug resistant Escherichia coli (MDR) strains selected from an urban wastewater treatment plant (UWWTP) effluent and the change of their resistance to a mixture of three antibiotics (evaluated in terms of minimum inhibit concentration (MIC)) in wastewater polluted stream were investigated. The solar photodegradation of the mixture of the three target antibiotics (amoxicillin (AMX), ciprofloxacin (CPX), and sulfamethoxazole (SMZ)) was also evaluated. Additionally, since UWWTP effluents are possible sources of antibiotics and antibiotic resistant bacteria, the disinfection by conventional chlorination process of the UWWTP effluent inoculated with MDR strains was investigated too. Solar radiation poorly affected the inactivation of the two selected antibiotic resistant E. coli strains (40 and 60% after 180 min irradiation). Moreover, solar radiation did not affect strain resistance to AMX (MIC>256 μg/mL) and SMZ (MIC>1024 μg/mL), but affected resistance of the lower resistance strain to CPX (MIC decreased by 33% but only after 180 min of irradiation). Chlorination of wastewater sample strongly decreased the number of the two selected antibiotic resistant E. coli strains (99.667 and 99.999%), after 60 min of contact time at 2.0 mg/L initial chlorine concentration, but the resistance of survived colonies to antibiotics was unchanged. Finally, the solar photodegradation rate of the antibiotic mixture (1mg/L initial concentration respectively) resulted in the following order (half-life time): CPX (t(1/2)=24 min)

Frequency, pressure and strain dependence of nonlinear elasticity in Berea Sandstone

DOE PAGES

Riviere, Jacques; Johnson, Paul Allan; Marone, Chris; ...

2016-04-14

Acoustoelasticity measurements in a sample of room dry Berea sandstone are conducted at various loading frequencies to explore the transition between the quasi-static ( f → 0) and dynamic (few kilohertz) nonlinear elastic response. We carry out these measurements at multiple confining pressures and perform a multivariate regression analysis to quantify the dependence of the harmonic content on strain amplitude, frequency, and pressure. The modulus softening (equivalent to the harmonic at 0f) increases by a factor 2–3 over 3 orders of magnitude increase in frequency. Harmonics at 2f, 4f, and 6f exhibit similar behaviors. In contrast, the harmonic at 1fmore » appears frequency independent. This result corroborates previous studies showing that the nonlinear elasticity of rocks can be described with a minimum of two physical mechanisms. This study provides quantitative data that describes the rate dependency of nonlinear elasticity. Furthermore, these findings can be used to improve theories relating the macroscopic elastic response to microstructural features.« less

Drosophila geotaxis as a tool for the study of aging

NASA Technical Reports Server (NTRS)

Schnebel, Edgar M.; Hoffmann, R. Nicholas; Grossfield, Joe

1988-01-01

Age dependent changes in geotaxis profiles were examined in 27 wild-type populations of Drosophila, representing a diversity of species, semispecies and strains. In addition, four strains of D. melanogaster were tested. Tests were carried out at a minimum of three test ages, and involve the use of a calibrated, adjustable inclined plane that can be set at any angle between 0 and 85 deg. Among selected lines, decline in geotactic response occurs later in the long lived flies than in the controls. Longer lived flies continue to show an increase in negative geotactic response through age 14 days. These results suggest that common processes may be influencing the rate of decline in geotactic response and longevity. Further analysis of the mechanisms underlying age dependent changes in geotaxis may reveal factors which influence the aging process itself. The use of geotaxis aging markers in a broad range of Drosophila species reflecting varying degrees of genetic relatedness is proposed to test the universality vs. specificity of aging processes.

5 CFR 9701.337 - Treatment of employees whose rate of pay falls below the minimum adjusted rate of their band.

Code of Federal Regulations, 2011 CFR

2011-01-01

... falls below the minimum adjusted rate of their band. 9701.337 Section 9701.337 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.337 Treatment of employees whose rate of pay falls... (including a locality or special rate supplement) falls below the minimum adjusted rate of his or her band as...

5 CFR 9701.337 - Treatment of employees whose rate of pay falls below the minimum adjusted rate of their band.

Code of Federal Regulations, 2012 CFR

2012-01-01

... falls below the minimum adjusted rate of their band. 9701.337 Section 9701.337 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.337 Treatment of employees whose rate of pay falls... (including a locality or special rate supplement) falls below the minimum adjusted rate of his or her band as...

5 CFR 9701.337 - Treatment of employees whose rate of pay falls below the minimum adjusted rate of their band.

Code of Federal Regulations, 2014 CFR

2014-01-01

... falls below the minimum adjusted rate of their band. 9701.337 Section 9701.337 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.337 Treatment of employees whose rate of pay falls... (including a locality or special rate supplement) falls below the minimum adjusted rate of his or her band as...

5 CFR 9701.337 - Treatment of employees whose rate of pay falls below the minimum adjusted rate of their band.

Code of Federal Regulations, 2013 CFR

2013-01-01

... falls below the minimum adjusted rate of their band. 9701.337 Section 9701.337 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.337 Treatment of employees whose rate of pay falls... (including a locality or special rate supplement) falls below the minimum adjusted rate of his or her band as...

46 CFR 280.5 - Criteria for determining whether or not civilian preference cargo is carried at a premium rate.

Code of Federal Regulations, 2010 CFR

2010-10-01

... conference tariff or at the stated minimum level or floor rate for an open-rated commodity published in a..., stated minimum level, or floor rate has at least one foreign-flag carrier as a voting member, or (b) At a rate or tariff agreement rate, or at the stated minimum level or floor rate for an open-rated commodity...

Evaluation of expression of NorA efflux pump in ciprofloxacin resistant Staphylococcus aureus against hexahydroquinoline derivative by real-time PCR.

PubMed

Pourmand, Mohammad Reza; Yousefi, Masoud; Salami, Seyed Alireza; Amini, Mohsen

2014-01-01

Staphylococcus aureus causes a wide variety of infections worldwide. Methicillin-resistant S. aureus is one of most common causes of nosocomial and community acquired infections. The fluoroquinolones are an important class of antibiotics that used to treat infections caused by S. aureus. Today, a significant increase in the rate of ciprofloxacin resistance in methicillin-resistant S. aureus strains is concerning. The norA efflux pump is considered as contributors to antibiotic resistance. Here, we aimed to evaluate the expression of norA efflux pump in the presence of hexahydroquinoline derivative in methicillin and ciprofloxacin resistant S. aureus. We were determined minimum inhibitory concentration of ciprofloxacin and hexahydroquinoline derivative and their combination by broth microdilution method against ciprofloxacin resistant S. aureus. The expression of the norA efflux pump gene was evaluated by quantitative Real-time PCR. This study showed that minimum inhibitory concentrations of ciprofloxacin in the presence of hexahydroquinoline derivative in comparison to ciprofloxacin were decreased. Quantitative Real-time PCR identified the increased expression of norA efflux pump gene in methicillin and ciprofloxacin resistant S. aureus strain. The increased expression of norA efflux pump gene may have resulted in the effort of S. aureus to survive. The results showed that the hexahydroquinoline derivative enhanced the antibacterial effect of ciprofloxacin against methicillin and ciprofloxacin resistant S. aureus. Therefore, the derivatives may be used as inhibitors of antibiotic resistance for combination therapy.

Efficacy of some colloidal silver preparations and silver salts against Proteus bacteria, one possible cause of rheumatoid arthritis.

PubMed

Disaanayake, D M B T; Faoagali, Joan; Laroo, Hans; Hancock, Gerald; Whitehouse, Michael

2014-04-01

There has been increased interest in the role of anti-Proteus antibodies in the aetiology of rheumatoid arthritis (RA) and whether chemotherapeutic agents active against Proteus species might reduce the risk and/or exacerbations of RA. We examined the in vitro antibacterial effects of ten different silver preparations which were either ionic silver [Ag(I)] solutions or nanoparticulate silver (NPS) (Ag(0)) suspensions against ATCC and two wild (clinical) strains of Proteus. The data establish the low minimum inhibitory concentration and minimum bactericidal concentration of all the silver formulations tested against these four Proteus strains. In a pilot study, a potent NPS preparation ex vivo showed long-lasting anti-Proteus activity in a normal human volunteer.

On a Minimum Problem in Smectic Elastomers

NASA Astrophysics Data System (ADS)

Buonsanti, Michele; Giovine, Pasquale

2008-07-01

Smectic elastomers are layered materials exhibiting a solid-like elastic response along the layer normal and a rubbery one in the plane. Balance equations for smectic elastomers are derived from the general theory of continua with constrained microstructure. In this work we investigate a very simple minimum problem based on multi-well potentials where the microstructure is taken into account. The set of polymeric strains minimizing the elastic energy contains a one-parameter family of simple strain associated with a micro-variation of the degree of freedom. We develop the energy functional through two terms, the first one nematic and the second one considering the tilting phenomenon; after, by developing in the rubber elasticity framework, we minimize over the tilt rotation angle and extract the engineering stress.

Method and apparatus for determination of material residual stress

NASA Technical Reports Server (NTRS)

Chern, Engmin J. (Inventor); Flom, Yury (Inventor)

1993-01-01

A device for the determination of residual stress in a material sample consisting of a sensor coil, adjacent to the material sample, whose resistance varies according to the amount of stress within the material sample, a mechanical push-pull machine for imparting a gradually increasing compressional and tensional force on the material sample, and an impedance gain/phase analyzer and personal computer (PC) for sending an input signal to and receiving an input signal from the sensor coil is presented. The PC will measure and record the change in resistance of the sensor coil and the corresponding amount of strain of the sample. The PC will then determine, from the measurements of change of resistance and corresponding strain of the sample, the point at which the resistance of the sensor coil is at a minimum and the corresponding value and type of strain of the sample at that minimum resistance point, thereby, enabling a calculation of the residual stress in the sample.

Cloning of genes involved in the biosynthesis of pseudobactin, a high-affinity iron transport agent of a plant growth-promoting Pseudomonas strain.

PubMed Central

Moores, J C; Magazin, M; Ditta, G S; Leong, J

1984-01-01

A gene bank of DNA from plant growth-promoting Pseudomonas sp. strain B10 was constructed using the broad host-range conjugative cosmid pLAFR1. The recombinant cosmids contained insert DNA averaging 21.5 kilobase pairs in length. Nonfluorescent mutants of Pseudomonas sp. strain B10 were obtained by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine, ethyl methanesulfonate, or UV light and were defective in the biosynthesis of its yellow-green, fluorescent siderophore (microbial iron transport agent) pseudobactin. No yellow-green, fluorescent mutants defective in the production of pseudobactin were identified. Nonfluorescent mutants were individually complemented by mating the gene bank en masse and identifying fluorescent transconjugants. Eight recombinant cosmids were sufficient to complement 154 nonfluorescent mutants. The pattern of complementation suggests that a minimum of 12 genes arranged in four gene clusters is required for the biosynthesis of pseudobactin. This minimum number of genes seems reasonable considering the structural complexity of pseudobactin. Images PMID:6690426

Performance measures for lower gastrointestinal endoscopy: a European Society of Gastrointestinal Endoscopy (ESGE) quality improvement initiative

PubMed Central

Thomas-Gibson, Siwan; Bugajski, Marek; Bretthauer, Michael; Rees, Colin J; Dekker, Evelien; Hoff, Geir; Jover, Rodrigo; Suchanek, Stepan; Ferlitsch, Monika; Anderson, John; Roesch, Thomas; Hultcranz, Rolf; Racz, Istvan; Kuipers, Ernst J; Garborg, Kjetil; East, James E; Rupinski, Maciej; Seip, Birgitte; Bennett, Cathy; Senore, Carlo; Minozzi, Silvia; Bisschops, Raf; Domagk, Dirk; Valori, Roland; Spada, Cristiano; Hassan, Cesare; Dinis-Ribeiro, Mario; Rutter, Matthew D

2017-01-01

The European Society of Gastrointestinal Endoscopy and United European Gastroenterology present a short list of key performance measures for lower gastrointestinal endoscopy. We recommend that endoscopy services across Europe adopt the following seven key performance measures for lower gastrointestinal endoscopy for measurement and evaluation in daily practice at a center and endoscopist level: 1 rate of adequate bowel preparation (minimum standard 90%); 2 cecal intubation rate (minimum standard 90%); 3 adenoma detection rate (minimum standard 25%); 4 appropriate polypectomy technique (minimum standard 80%); 5 complication rate (minimum standard not set); 6 patient experience (minimum standard not set); 7 appropriate post-polypectomy surveillance recommendations (minimum standard not set). Other identified performance measures have been listed as less relevant based on an assessment of their importance, scientific acceptability, feasibility, usability, and comparison to competing measures. PMID:28507745

Pathogenicity, Ovicidal Action, and Median Lethal Concentrations (LC50) of Entomopathogenic Fungi against Exotic Spiralling Whitefly, Aleurodicus dispersus Russell

PubMed Central

Palaniappan, Karuppuchamy; Manickavasagam Pillai, Kalyanasundaram; Subbarayalu, Mohankumar; Madhaiyan, Ravi

2013-01-01

Biological control using entomopathogenic fungi could be a promising alternative to chemical control. Entomopathogenic fungi, Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin, Lecanicillium lecanii (Zimmerm.) Zare and Gams, and Paecilomyces fumosoroseus (Wize) Brown and Smith, were tested for their pathogenicity, ovicidal effect, and median lethal concentrations (LC50) against exotic spiralling whitefly, Aleurodicus dispersus Russell. The applications were made at the rate of 2 × 109 conidia mL−1 for evaluating the pathogenicity and ovicidal effect of entomopathogenic fungi against A. dispersus. The results of pathogenicity test showed that P. fumosoroseus (P1 strain) was highly pathogenic to A. dispersus recording 100% mortality at 15 days after treatment (DAT). M. anisopliae (M2 strain) had more ovicidal effect causing 37.3% egg mortality at 8 DAT. However, L. lecanii (L1 strain) caused minimum egg hatchability (23.2%) at 10 DAT as compared to control (92.6%). The lowest LC50 produced by P. fumosoroseus (P1 strain) as 8.189 × 107 conidia mL−1 indicated higher virulence against A. dispersus. Hence, there is potential for use of entomopathogenic fungi in the field conditions as an alternate control method in combating the insect pests and other arthropod pests since they are considered natural mortality agents and are environmentally safe. PMID:24455279

Characterization of the Metabolically Modified Heavy Metal-Resistant Cupriavidus metallidurans Strain MSR33 Generated for Mercury Bioremediation

PubMed Central

Rojas, Luis A.; Yáñez, Carolina; González, Myriam; Lobos, Soledad; Smalla, Kornelia; Seeger, Michael

2011-01-01

Background Mercury-polluted environments are often contaminated with other heavy metals. Therefore, bacteria with resistance to several heavy metals may be useful for bioremediation. Cupriavidus metallidurans CH34 is a model heavy metal-resistant bacterium, but possesses a low resistance to mercury compounds. Methodology/Principal Findings To improve inorganic and organic mercury resistance of strain CH34, the IncP-1β plasmid pTP6 that provides novel merB, merG genes and additional other mer genes was introduced into the bacterium by biparental mating. The transconjugant Cupriavidus metallidurans strain MSR33 was genetically and biochemically characterized. Strain MSR33 maintained stably the plasmid pTP6 over 70 generations under non-selective conditions. The organomercurial lyase protein MerB and the mercuric reductase MerA of strain MSR33 were synthesized in presence of Hg2+. The minimum inhibitory concentrations (mM) for strain MSR33 were: Hg2+, 0.12 and CH3Hg+, 0.08. The addition of Hg2+ (0.04 mM) at exponential phase had not an effect on the growth rate of strain MSR33. In contrast, after Hg2+ addition at exponential phase the parental strain CH34 showed an immediate cessation of cell growth. During exposure to Hg2+ no effects in the morphology of MSR33 cells were observed, whereas CH34 cells exposed to Hg2+ showed a fuzzy outer membrane. Bioremediation with strain MSR33 of two mercury-contaminated aqueous solutions was evaluated. Hg2+ (0.10 and 0.15 mM) was completely volatilized by strain MSR33 from the polluted waters in presence of thioglycolate (5 mM) after 2 h. Conclusions/Significance A broad-spectrum mercury-resistant strain MSR33 was generated by incorporation of plasmid pTP6 that was directly isolated from the environment into C. metallidurans CH34. Strain MSR33 is capable to remove mercury from polluted waters. This is the first study to use an IncP-1β plasmid directly isolated from the environment, to generate a novel and stable bacterial strain useful for mercury bioremediation. PMID:21423734

Crustal strain accumulation on Southern Basin and Range Province faults modulated by distant plate boundary earthquakes? Evidence from geodesy, seismic imaging, and paleoseismology

NASA Astrophysics Data System (ADS)

Bennett, R. A.; Shirzaei, M.; Broermann, J.; Spinler, J. C.; Holland, A. A.; Pearthree, P.

2014-12-01

GPS in Arizona reveals a change in the pattern of crustal strain accumulation in 2010 and based on viscoelastic modeling appears to be associated with the distant M7.2 El Mayor-Cucapah (EMC) earthquake in Baja California, Mexico. GPS data collected between 1999 and 2009 near the Santa Rita normal fault in SE Arizona reveal a narrow zone of crustal deformation coincident with the fault trace, delineated by W-NW facing Pleistocene fault scarps of heights 1 to 7 m. The apparent deformation zone is also seen in a preliminary InSAR interferogram. Total motion across the zone inferred using an elastic block model constrained by the pre-2010 GPS measurements is ~1 mm/yr in a sense consistent with normal fault motion. However, continuous GPS measurements throughout Arizona reveal pronounced changes in crustal velocity following the EMC earthquake, such that the relative motion across the Santa Rita fault post-2010 is negligible. Paleoseismic evidence indicates that mapped Santa Rita fault scarps were formed by two or more large magnitude (M6.7 to M7.6) surface rupturing normal-faulting earthquakes 60 to 100 kyrs ago. Seismic refraction and reflection data constrained by deep (~800 m) well log data provide evidence of progressive, possibly intermittent, displacement on the fault through time. The rate of strain accumulation observed geodetically prior to 2010, if constant over the past 60 to 100 kyrs, would imply an untenable minimum slip rate deficit of 60 to 100 m since the most recent earthquake. One explanation for the available geodetic, seismic, and paleoseismic evidence is that strain accumulation is modulated by viscoelastic relaxation associated with frequent large magnitude earthquakes in the Salton Trough region, episodically inhibiting the accumulation of elastic strain required to generate large earthquakes on the Santa Rita and possibly other faults in the Southern Basin and Range. An important question is thus for how long the postseismic velocity changes will persist relative to the recurrence interval of large Salton Trough earthquakes. Understanding the influence of far-field postseismic deformation on the southern Arizona strain rate field could have implications for other regions of diffuse intracontinental deformation in proximity to frequently rupturing large magnitude plate boundary faults.

Composite-cavity-based Fabry-Perot interferometric strain sensors.

PubMed

Zhang, Jianzhong; Peng, G D; Yuan, Libo; Sun, Weimin

2007-07-01

A composite-cavity-based Fabry-Perot interferometric strain sensor system is proposed to gain the minimum cross sensitivity to temperature and a high multiplexing capability at the same time. The interrogation of the sensor system is based on a white-light interferometric technology, and the demodulation is achieved by analyzing the coherence spectra. A demonstration system with two sensors is presented and tested.

20 CFR 229.41 - When a spouse can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2010 CFR

2010-04-01

... RETIREMENT BOARD REGULATIONS UNDER THE RAILROAD RETIREMENT ACT SOCIAL SECURITY OVERALL MINIMUM GUARANTEE When... annuity rate under the overall minimum. A spouse's inclusion in the computation of the overall minimum...

5 CFR 532.205 - The use of Federal, State, and local minimum wage requirements in determining prevailing rates.

Code of Federal Regulations, 2010 CFR

2010-01-01

... minimum wage requirements in determining prevailing rates. 532.205 Section 532.205 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS Prevailing Rate Determinations § 532.205 The use of Federal, State, and local minimum wage requirements in determining prevailing...

77 FR 75896 - Alcohol and Drug Testing: Determination of Minimum Random Testing Rates for 2013

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-26

...-11213, Notice No. 16] Alcohol and Drug Testing: Determination of Minimum Random Testing Rates for 2013... from FRA's Management Information System, the rail industry's random drug testing positive rate has... therefore determined that the minimum annual random drug testing rate for the period January 1, 2013...

The Effect of Minimum Wage Rates on High School Completion

ERIC Educational Resources Information Center

Warren, John Robert; Hamrock, Caitlin

2010-01-01

Does increasing the minimum wage reduce the high school completion rate? Previous research has suffered from (1. narrow time horizons, (2. potentially inadequate measures of states' high school completion rates, and (3. potentially inadequate measures of minimum wage rates. Overcoming each of these limitations, we analyze the impact of changes in…

Production and characterization of streptomycin dependent mutants of Pasteurella multocida from bovine haemorrhagic septicaemia.

PubMed Central

de Alwis, M C; Carter, G R; Chengappa, M M

1980-01-01

A large number of streptomycin dependent mutants were produced from bovine haemorrhagic septicaemia strains of Pasteurella multocida. The mutants required a minimum concentration of 25-50 microgram/mL streptomycin for growth and tolerated a concentration of 200 mg/mL. These mutants were avirulent to mice, when inoculated alone, but some mutants killed mice when inoculated with streptomycin. Biochemically all mutants were uniform and similar to the wild type. Most mutants were stable, but a few produced streptomycin independent revertants. The rate of reversion varied with each mutant. Most revertants were highly virulent for mice, some totally avirulant and a few relatively avirulent. PMID:6778598

Flow and pressure regulation in the cardiovascular system. [engineering systems model

NASA Technical Reports Server (NTRS)

Iberall, A.

1974-01-01

Principles and descriptive fragments which may contribute to a model of the regulating chains in the cardiovascular system are presented. Attention is given to the strain sensitivity of blood vessels, the law of the autonomy of the heart beat oscillator, the law of the encapsulation of body fluids, the law of the conservation of protein, the law of minimum 'arterial' pressure, the design of the 'mammalian' kidney, questions of homeokinetic organization, and the development of self-regulatory chains. Details concerning the development program for the heart muscle are considered along with the speed of response of the breathing rate and the significance of the pulmonary vascular pressure-flow characteristics.

Creep rupture of polymer-matrix composites

NASA Technical Reports Server (NTRS)

Brinson, H. F.; Morris, D. H.; Griffith, W. I.

1981-01-01

The time-dependent creep-rupture process in graphite-epoxy laminates is examined as a function of temperature and stress level. Moisture effects are not considered. An accelerated characterization method of composite-laminate viscoelastic modulus and strength properties is reviewed. It is shown that lamina-modulus master curves can be obtained using a minimum of normally performed quality-control-type testing. Lamina-strength master curves, obtained by assuming a constant-strain-failure criterion, are presented along with experimental data, and reasonably good agreement is shown to exist between the two. Various phenomenological delayed failure models are reviewed and two (the modified rate equation and the Larson-Miller parameter method) are compared to creep-rupture data with poor results.

The effect of temperature and moisture on electrical resistance, strain sensitivity and crack sensitivity of steel fiber reinforced smart cement composite

NASA Astrophysics Data System (ADS)

Teomete, Egemen

2016-07-01

Earthquakes, material degradations and other environmental factors necessitate structural health monitoring (SHM). Metal foil strain gages used for SHM have low durability and low sensitivity. These factors motivated researchers to work on cement based strain sensors. In this study, the effects of temperature and moisture on electrical resistance, compressive and tensile strain gage factors (strain sensitivity) and crack sensitivity were determined for steel fiber reinforced cement based composite. A rapid increase of electrical resistance at 200 °C was observed due to damage occurring between cement paste, aggregates and steel fibers. The moisture—electrical resistance relationship was investigated. The specimens taken out of the cure were saturated with water and had a moisture content of 9.49%. The minimum electrical resistance was obtained at 9% moisture at which fiber-fiber and fiber-matrix contact was maximum and the water in micro voids was acting as an electrolyte, conducting electrons. The variation of compressive and tensile strain gage factors (strain sensitivities) and crack sensitivity were investigated by conducting compression, split tensile and notched bending tests with different moisture contents. The highest gage factor for the compression test was obtained at optimal moisture content, at which electrical resistance was minimum. The tensile strain gage factor for split tensile test and crack sensitivity increased by decreasing moisture content. The mechanisms between moisture content, electrical resistance, gage factors and crack sensitivity were elucidated. The relations of moisture content with electrical resistance, gage factors and crack sensitivities have been presented for the first time in this study for steel fiber reinforced cement based composites. The results are important for the development of self sensing cement based smart materials.

Effect of Strengthening Mechanism on Strain-Rate Related Tensile Properties of Low-Carbon Sheet Steels for Automotive Application

NASA Astrophysics Data System (ADS)

Das, Anindya; Biswas, Pinaki; Tarafder, S.; Chakrabarti, D.; Sivaprasad, S.

2018-05-01

In order to ensure crash resistance of the steels used in automotive components, the ensile deformation behavior needs to be studied and predicted not only under quasi-static condition, but also under dynamic loading rates. In the present study, tensile tests have been performed on four different automobile grade sheet steels, namely interstitial free steel, dual-phase 600 and 800, and a carbon manganese steel over the strain rate regime of 0.001-800/s. Apart from the variation in strength (which always increased with strain rate), the effect of strengthening mechanism on strain rate sensitivity and strain hardening behavior has been evaluated. Strain rate sensitivity was found to increase at high-strain rate regime for all the steels. Contribution of solid solution hardening on strain rate sensitivity at lower plastic strains was found to be higher compared to dislocation strengthening and second-phase hardening. However, precipitation hardening coupled with solid solution hardening produced the highest strain rate sensitivity, in C-Mn-440 steel at high strain rates. Different strain-rate-sensitive models which take into account the change in yield stress and strain hardening behavior with strain rate for ductile materials were used to predict the flow behavior of these sheet steels at strain rates up to 800/s.

Antimicrobial Potential of Momordica charantia L. against Multiresistant Standard Species and Clinical Isolates.

PubMed

Lucena Filho, José Hardman Sátiro de; Lima, Rennaly de Freitas; Medeiros, Ana Claudia Dantas de; Pereira, Jozinete Vieira; Granville-Garcia, Ana Flávia; Costa, Edja Maria Melo de Brito

2015-11-01

The aim of the present study was to evaluate the antibacterial and antifungal potential in vitro of Momordica charantia L. against the microorganisms of clinical interest (standard strains and multiresistant isolates) in order to aggregate scientific information in relation to its use as a therapeutic product. M. charantia L. plant material was acquired in municipality of Malta, Paraiba, Brazil. The extract was obtained through maceration, filtration and then concentrated under reduced pressure in a rotary evaporator, resulting in a dough, and was then dried in an oven for 72 hours at 40°C. Antimicrobial action of ethanolic extract of seed M. charantia L. was evaluated based on the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) against standard strains of bacteria, isolates multiresistant bacteria and Candida species, by microdilution in broth method. All organisms were sensitive to the extract, being considered strong antimicrobial activity (MIC and MBC/MFC < 0.125 mg/ml). The M. charantia L. showed strong antimicrobial potential, with bactericidal and fungicidal profile, there is the prospect to constitute a new therapeutic strategy for the control of infections, particularly in multiresistant strains. The use of medicinal plants in treatment of infectious processes have an important function nowadays, due to the limitations of the use of synthetic antibiotics available, related specifically to the microbial resistance emergence.

Isoflavone formononetin from red propolis acts as a fungicide against Candida sp.

PubMed

das Neves, Michelline Viviane Marques; da Silva, Tânia Maria Sarmento; Lima, Edeltrudes de Oliveira; da Cunha, Emídio Vasconcelos Leitão; Oliveira, Eduardo de Jesus

2016-01-01

A bioassay-guided fractionation of two samples of Brazilian red propolis (from Igarassu, PE, Brazil, hereinafter propolis 1 and 2) was conducted in order to determine the components responsible for its antimicrobial activity, especially against Candida spp. Samples of both the crude powdered resin and the crude ethanolic extract of propolis from both locations inhibited the growth of all 12 tested Candida strains, with a minimum inhibitory concentration of 256μg/mL. The hexane, acetate and methanol fractions of propolis 1 also inhibited all strains with minimum inhibitory concentration values ranging from 128 to 512μg/mL for the six bacteria tested and from 32 to 1024μg/mL for the yeasts. Similarly, hexane and acetate fractions of propolis sample 2 inhibited all microorganisms tested, with minimum inhibitory concentration values of 512μg/mL for bacteria and 32μg/mL for yeasts. The extracts were analyzed by HPLC and their phenolic profile allowed us to identify and quantitate one phenolic acid and seven flavonoids in the crude ethanolic extract. Formononetin and pinocembrin were the major constituents amongst the identified compounds. Formononetin was detected in all extracts and fractions tested, except for the methanolic fraction of sample 2. The isolated isoflavone formononetin inhibited the growth of all the microorganisms tested, with a minimum inhibitory concentration of 200μg/mL for the six bacteria strains tested and 25μg/mL for the six yeasts. Formononetin also exhibited fungicidal activity against five of the six yeasts tested. Taken together our results demonstrate that the isoflavone formononetin is implicated in the reported antimicrobial activity of red propolis. Copyright © 2015 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Isoflavone formononetin from red propolis acts as a fungicide against Candida sp

PubMed Central

das Neves, Michelline Viviane Marques; da Silva, Tânia Maria Sarmento; Lima, Edeltrudes de Oliveira; da Cunha, Emídio Vasconcelos Leitão; Oliveira, Eduardo de Jesus

2016-01-01

A bioassay-guided fractionation of two samples of Brazilian red propolis (from Igarassu, PE, Brazil, hereinafter propolis 1 and 2) was conducted in order to determine the components responsible for its antimicrobial activity, especially against Candida spp. Samples of both the crude powdered resin and the crude ethanolic extract of propolis from both locations inhibited the growth of all 12 tested Candida strains, with a minimum inhibitory concentration of 256 μg/mL. The hexane, acetate and methanol fractions of propolis 1 also inhibited all strains with minimum inhibitory concentration values ranging from 128 to 512 μg/mL for the six bacteria tested and from 32 to 1024 μg/mL for the yeasts. Similarly, hexane and acetate fractions of propolis sample 2 inhibited all microorganisms tested, with minimum inhibitory concentration values of 512 μg/mL for bacteria and 32 μg/mL for yeasts. The extracts were analyzed by HPLC and their phenolic profile allowed us to identify and quantitate one phenolic acid and seven flavonoids in the crude ethanolic extract. Formononetin and pinocembrin were the major constituents amongst the identified compounds. Formononetin was detected in all extracts and fractions tested, except for the methanolic fraction of sample 2. The isolated isoflavone formononetin inhibited the growth of all the microorganisms tested, with a minimum inhibitory concentration of 200 μg/mL for the six bacteria strains tested and 25 μg/mL for the six yeasts. Formononetin also exhibited fungicidal activity against five of the six yeasts tested. Taken together our results demonstrate that the isoflavone formononetin is implicated in the reported antimicrobial activity of red propolis. PMID:26887239

Theoretical analysis of the cost of antagonistic activity for aquatic bacteria in oligotrophic environments.

PubMed

Aguirre-von-Wobeser, Eneas; Eguiarte, Luis E; Souza, Valeria; Soberón-Chávez, Gloria

2015-01-01

Many strains of bacteria produce antagonistic substances that restrain the growth of others, and potentially give them a competitive advantage. These substances are commonly released to the surrounding environment, involving metabolic costs in terms of energy and nutrients. The rate at which these molecules need to be produced to maintain a certain amount of them close to the producing cell before they are diluted into the environment has not been explored so far. To understand the potential cost of production of antagonistic substances in water environments, we used two different theoretical approaches. Using a probabilistic model, we determined the rate at which a cell needs to produce individual molecules in order to keep on average a single molecule in its vicinity at all times. For this minimum protection, a cell would need to invest 3.92 × 10(-22) kg s(-1) of organic matter, which is 9 orders of magnitude lower than the estimated expense for growth. Next, we used a continuous model, based on Fick's laws, to explore the production rate needed to sustain minimum inhibitory concentrations around a cell, which would provide much more protection from competitors. In this scenario, cells would need to invest 1.20 × 10(-11) kg s(-1), which is 2 orders of magnitude higher than the estimated expense for growth, and thus not sustainable. We hypothesize that the production of antimicrobial compounds by bacteria in aquatic environments lies between these two extremes.

Effect of dissolved oxygen on redox potential and milk acidification by lactic acid bacteria isolated from a DL-starter culture.

PubMed

Larsen, Nadja; Werner, Birgit Brøsted; Vogensen, Finn Kvist; Jespersen, Lene

2015-03-01

Milk acidification by DL-starter cultures [cultures containing Lactococcus lactis diacetylactis (D) and Leuconostoc (L) species] depends on the oxidation-reduction (redox) potential in milk; however, the mechanisms behind this effect are not completely clear. The objective of this study was to investigate the effect of dissolved oxygen on acidification kinetics and redox potential during milk fermentation by lactic acid bacteria (LAB). Fermentations were conducted by single strains isolated from mixed DL-starter culture, including Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris, and Leuconostoc mesenteroides ssp. cremoris, by the DL-starter culture, and by the type strains. High and low levels of oxygen were produced by flushing milk with oxygen or nitrogen, respectively. The kinetics of milk acidification was characterized by the maximum rate and time of acidification (Vamax and Tamax), the maximum rate and time of reduction (Vrmax and Trmax), the minimum redox potential (Eh7 final), and time of reaching Eh7 final (Trfinal). Variations in kinetic parameters were observed at both the species and strain levels. Two of the Lc. lactis ssp. lactis strains were not able to lower redox potential to negative values. Kinetic parameters of the DL-starter culture were comparable with the best acidifying and reducing strains, indicating their additive effects. Acidification curves were mostly diauxic at all oxygen levels, displaying 2 maxima of acidification rate: before (aerobic maximum) and after (anaerobic maximum) oxygen depletion. The redox potential decreased concurrently with oxygen consumption and continued to decrease at slower rate until reaching the final values, indicating involvement of both oxygen and microbiological activity in the redox state of milk. Oxygen flushing had a negative effect on reduction and acidification capacity of tested LAB. Reduction was significantly delayed at high initial oxygen, exhibiting longer Trmax, Trfinal, or both. Concurrently, anaerobic acidification rate maximum Vamax was decreased and Tamax was extended. Fermentation kinetics in nitrogen-flushed milk was not statistically different from that in untreated milk except for Lc. lactis ssp. lactis CHCC D2, which showed faster reduction time after nitrogen flushing. This study clarifies the relationship between the redox state in milk and acidification kinetics of the predominant subspecies in DL-starter cultures. This knowledge is important for dairies to ensure optimized, fast, and controlled milk fermentations, leading to greater standardization of dairy products. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

5 CFR 9701.336 - Treatment of employees whose pay does not fall below the minimum adjusted rate of their band.

Code of Federal Regulations, 2012 CFR

2012-01-01

... fall below the minimum adjusted rate of their band. 9701.336 Section 9701.336 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.336 Treatment of employees whose pay does not fall... or special rate supplement) does not fall below the minimum adjusted rate of his or her band as a...

5 CFR 9701.336 - Treatment of employees whose pay does not fall below the minimum adjusted rate of their band.

Code of Federal Regulations, 2013 CFR

2013-01-01

... fall below the minimum adjusted rate of their band. 9701.336 Section 9701.336 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.336 Treatment of employees whose pay does not fall... or special rate supplement) does not fall below the minimum adjusted rate of his or her band as a...

5 CFR 9701.336 - Treatment of employees whose pay does not fall below the minimum adjusted rate of their band.

Code of Federal Regulations, 2014 CFR

2014-01-01

... fall below the minimum adjusted rate of their band. 9701.336 Section 9701.336 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.336 Treatment of employees whose pay does not fall... or special rate supplement) does not fall below the minimum adjusted rate of his or her band as a...

5 CFR 9701.336 - Treatment of employees whose pay does not fall below the minimum adjusted rate of their band.

Code of Federal Regulations, 2011 CFR

2011-01-01

... fall below the minimum adjusted rate of their band. 9701.336 Section 9701.336 Administrative Personnel... Administration Locality and Special Rate Supplements § 9701.336 Treatment of employees whose pay does not fall... or special rate supplement) does not fall below the minimum adjusted rate of his or her band as a...

The minimum or natural rate of flow and droplet size ejected by Taylor cone-jets: physical symmetries and scaling laws

NASA Astrophysics Data System (ADS)

Gañán-Calvo, A. M.; Rebollo-Muñoz, N.; Montanero, J. M.

2013-03-01

We aim to establish the scaling laws for both the minimum rate of flow attainable in the steady cone-jet mode of electrospray, and the size of the resulting droplets in that limit. Use is made of a small body of literature on Taylor cone-jets reporting precise measurements of the transported electric current and droplet size as a function of the liquid properties and flow rate. The projection of the data onto an appropriate non-dimensional parameter space maps a region bounded by the minimum rate of flow attainable in the steady state. To explain these experimental results, we propose a theoretical model based on the generalized concept of physical symmetry, stemming from the system time invariance (steadiness). A group of symmetries rising at the cone-to-jet geometrical transition determines the scaling for the minimum flow rate and related variables. If the flow rate is decreased below that minimum value, those symmetries break down, which leads to dripping. We find that the system exhibits two instability mechanisms depending on the nature of the forces arising against the flow: one dominated by viscosity and the other by the liquid polarity. In the former case, full charge relaxation is guaranteed down to the minimum flow rate, while in the latter the instability condition becomes equivalent to the symmetry breakdown by charge relaxation or separation. When cone-jets are formed without artificially imposing a flow rate, a microjet is issued quasi-steadily. The flow rate naturally ejected this way coincides with the minimum flow rate studied here. This natural flow rate determines the minimum droplet size that can be steadily produced by any electrohydrodynamic means for a given set of liquid properties.

20 CFR 229.42 - When a child can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false When a child can no longer be included in... Entitlement Under the Overall Minimum Ends § 229.42 When a child can no longer be included in computing an annuity rate under the overall minimum. A child's inclusion in the computation of the overall minimum rate...

20 CFR 229.42 - When a child can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false When a child can no longer be included in... Entitlement Under the Overall Minimum Ends § 229.42 When a child can no longer be included in computing an annuity rate under the overall minimum. A child's inclusion in the computation of the overall minimum rate...

20 CFR 229.42 - When a child can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true When a child can no longer be included in... Entitlement Under the Overall Minimum Ends § 229.42 When a child can no longer be included in computing an annuity rate under the overall minimum. A child's inclusion in the computation of the overall minimum rate...

20 CFR 229.42 - When a child can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true When a child can no longer be included in... Entitlement Under the Overall Minimum Ends § 229.42 When a child can no longer be included in computing an annuity rate under the overall minimum. A child's inclusion in the computation of the overall minimum rate...

Chromosomally mediated intrinsic resistance to penicillin of penicillinase producing strains of Neisseria gonorrhoeae isolated in Sydney: guide to treatment with Augmentin.

PubMed Central

Tapsall, J W; Phillips, E A; Morris, L M

1987-01-01

Single dose Augmentin treatment fails to cure an appreciable proportion of patients infected with penicillinase producing Neisseria gonorrhoeae (PPNG) strains in parts of the world where high levels of chromosomally mediated intrinsic resistance are also present in gonococci. The levels of intrinsic resistance to penicillin of 31 PPNG strains isolated in Sydney were assessed by obtaining beta lactamase negative variants of these strains and measuring the minimum inhibitory concentration of penicillin by agar plate dilution techniques. The levels of intrinsic resistance found in these imported PPNG strains were higher than those recorded for local isolates of non-PPNG strains, which indicates that caution should be exercised in the use of single dose Augmentin treatment of infections with PPNG strains in Sydney. PMID:3119461

Smart absorbing property of composites with MWCNTs and carbonyl iron as the filler

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Yuan, Liming; Cai, Jun; Zhang, Deyuan

2013-10-01

A smart absorbing composite was prepared by mixing silicone rubber, multi-walled carbon nanotubes (MWCNTs) and flaky carbonyl iron particles (CIPs) in a two-roll mixer. The complex permittivity and permeability of composites with variable compression strain was measured by the transmission method and dc electric conductivity was measured by the standard four-point contact method, then the reflection loss (RL) could be calculated to evaluate the microwave absorbing ability. The results showed that the applied compression strain made the complex permittivity decrease but not obviously due to the broken original conductive network. The enforcement of the strain on the complex permeability was attributed to the orientation of flaky CIPs. With the compressing strain applied on the composites with thickness 1 mm or 1.5 mm, the RL value decreased (minimum -13.2 dB and -25.1 dB) and the absorbing band (RL<-10 dB) was widened (5.2-10.6 GHz and 4.0-8.4 GHz). While as the composite thickness decreased caused by the compression strain, the RL value still decreased (minimum -12.4 dB and -18.6 dB) and the absorbing band was also broadened (6.5-10.7 GHz and 4.4-10.0 GHz). Thus the smart absorbing property was effective on preparing absorbers with wide absorption band and high absorption ratio.

Desulfovibrio oceani subsp. oceani sp. nov., subsp. nov. and Desulfovibrio oceani subsp. galateae subsp. nov., novel sulfate-reducing bacteria isolated from the oxygen minimum zone off the coast of Peru.

PubMed

Finster, Kai W; Kjeldsen, Kasper U

2010-03-01

Two deltaproteobacterial sulfate reducers, designated strain I.8.1(T) and I.9.1(T), were isolated from the oxygen minimum zone water column off the coast of Peru at 400 and 500 m water depth. The strains were Gram-negative, vibrio-shaped and motile. Both strains were psychrotolerant, grew optimally at 20 degrees C at pH 7.0-8.0 and at 2.5-3.5% NaCl (w/v). The strains grew by utilizing hydrogen/acetate, C(3-4) fatty acids, amino acids and glycerol as electron acceptors for sulfate reduction. Fumarate, lactate and pyruvate supported fermentative growth. Sulfate, sulfite, thiosulfate and taurin supported growth as electron acceptors. Both strains were catalase-positive and highly oxygen-tolerant, surviving 24 days of exposure to atmospheric concentrations. MK6 was the only respiratory quinone. The most prominent cellular fatty acid was iso-17:1-omega9c (18%) for strain I.8.1(T) and iso-17:0-omega9c (14%) for strain I.9.1(T). The G+C contents of their genomic DNA were 45-46 mol%. Phylogenetic analysis of 16S rRNA and dsrAB gene sequences showed that both strains belong to the genus Desulfovibrio. Desulfovibrio acrylicus DSM 10141(T) and Desulfovibrio marinisediminis JCM 14577(T) represented their closest validly described relatives with pairwise 16S rRNA gene sequence identities of 98-99%. The level of DNA-DNA hybridization between strains I.8.1(T) and I.9.1(T) was 30-38%. The two strains shared 10-26% DNA-DNA relatedness with D. acrylicus. Based on a polyphasic investigation it is proposed that strains I.8.1(T) and I.9.1(T) represent a novel species for which the name Desulfovibrio oceani sp. nov. is proposed with the two subspecies D. oceani subsp. oceani (type strain, I.8.1(T) = DSM 21390(T) = JCM 15970(T)) and D. oceani subsp. galateae (type strain, I.9.1(T) = DSM 21391(T) = JCM 15971(T)).

Non-linear properties of metallic cellular materials with a negative Poisson's ratio

NASA Technical Reports Server (NTRS)

Choi, J. B.; Lakes, R. S.

1992-01-01

Negative Poisson's ratio copper foam was prepared and characterized experimentally. The transformation into re-entrant foam was accomplished by applying sequential permanent compressions above the yield point to achieve a triaxial compression. The Poisson's ratio of the re-entrant foam depended on strain and attained a relative minimum at strains near zero. Poisson's ratio as small as -0.8 was achieved. The strain dependence of properties occurred over a narrower range of strain than in the polymer foams studied earlier. Annealing of the foam resulted in a slightly greater magnitude of negative Poisson's ratio and greater toughness at the expense of a decrease in the Young's modulus.

Loading Configurations and Ground Reaction Forces During Treadmill Running in Weightlessness

NASA Technical Reports Server (NTRS)

DeWitt, John; Schaffner, Grant; Blazine, Kristi; Bentley, Jason; Laughlin, Mitzi; Loehr, James; Hagan, Donald

2003-01-01

Studies have shown losses in bone mineral density of 1-2% per month in critical weight bearing areas such as the proximal femur during long-term space flight (Grigoriev, 1998). The astronauts currently onboard the International Space Station (ISS) use a treadmill as an exercise countermeasure to bone loss that occurs as a result of prolonged exposure to weightlessness. A crewmember exercising on the treadmill is attached by a harness and loading device. Ground reaction forces are obtained through the loading device that pulls the crewn1ember towards the treadmill surface during locomotion. McCrory et al. (2002) found that the magnitude of the peak ground reaction force (pGRF) during horizontal suspension running, or simulated weightlessness, was directly related to the load applied to the subject. It is thought that strain magnitude and strain rate affects osteogenesis, and is a function of the magnitude and rate of change of the ground reaction force. While it is not known if a minimum stimulus exists for osteogenesis, it has been hypothesized that in order to replicate the bone formation occurring in normal gravity (1 G), the exercise in weightlessness should mimic the forces that occur on earth. Specifically, the pGRF obtained in weightlessness should be comparable to that achieved in 1 G.

Uniform Foam Crush Testing for Multi-Mission Earth Entry Vehicle Impact Attenuation

NASA Technical Reports Server (NTRS)

Patterson, Byron W.; Glaab, Louis J.

2012-01-01

Multi-Mission Earth Entry Vehicles (MMEEVs) are blunt-body vehicles designed with the purpose of transporting payloads from outer space to the surface of the Earth. To achieve high-reliability and minimum weight, MMEEVs avoid use of limited-reliability systems, such as parachutes and retro-rockets, instead using built-in impact attenuators to absorb energy remaining at impact to meet landing loads requirements. The Multi-Mission Systems Analysis for Planetary Entry (M-SAPE) parametric design tool is used to facilitate the design of MMEEVs and develop the trade space. Testing was conducted to characterize the material properties of several candidate impact foam attenuators to enhance M-SAPE analysis. In the current effort, four different Rohacell foams are tested at three different, uniform, strain rates (approximately 0.17, approximately 100, approximately 13,600%/s). The primary data analysis method uses a global data smoothing technique in the frequency domain to remove noise and system natural frequencies. The results from the data indicate that the filter and smoothing technique are successful in identifying the foam crush event and removing aberrations. The effect of strain rate increases with increasing foam density. The 71-WF-HT foam may support Mars Sample Return requirements. Several recommendations to improve the drop tower test technique are identified.

20 CFR 229.42 - When a child can no longer be included in computing an annuity rate under the overall minimum.

Code of Federal Regulations, 2010 CFR

2010-04-01

... annuity rate under the overall minimum. A child's inclusion in the computation of the overall minimum rate... second month after the month the child's disability ends, if the child is 18 years old or older, and not...

Nonlinear crack analysis with finite elements

NASA Technical Reports Server (NTRS)

Armen, H., Jr.; Saleme, E.; Pifko, A.; Levine, H. S.

1973-01-01

The application of finite element techniques to the analytic representation of the nonlinear behavior of arbitrary two-dimensional bodies containing cracks is discussed. Specific methods are proposed using which it should be possible to obtain information concerning: the description of the maximum, minimum, and residual near-tip stress and strain fields; the effects of crack closure on the near-tip behavior of stress and strain fields during cyclic loading into the plastic range; the stress-strain and displacement field behavior associated with a nonstationary crack; and the effects of large rotation near the crack tip.

The Phage Lysin PlySs2 Decolonizes Streptococcus suis from Murine Intranasal Mucosa.

PubMed

Gilmer, Daniel B; Schmitz, Jonathan E; Thandar, Mya; Euler, Chad W; Fischetti, Vincent A

2017-01-01

Streptococcus suis infects pigs worldwide and may be zoonotically transmitted to humans with a mortality rate of up to 20%. S. suis has been shown to develop in vitro resistance to the two leading drugs of choice, penicillin and gentamicin. Because of this, we have pursued an alternative therapy to treat these pathogens using bacteriophage lysins. The bacteriophage lysin PlySs2 is derived from an S. suis phage and displays potent lytic activity against most strains of that species including serotypes 2 and 9. At 64 μg/ml, PlySs2 reduced multiple serotypes of S. suis by 5 to 6-logs within 1 hour in vitro and exhibited a minimum inhibitory concentration (MIC) of 32 μg/ml for a S. suis serotype 2 strain and 64 μg/ml for a serotype 9 strain. Using a single 0.1-mg dose, the colonizing S. suis serotype 9 strain was reduced from the murine intranasal mucosa by >4 logs; a 0.1-mg dose of gentamicin reduced S. suis by <3-logs. A combination of 0.05 mg PlySs2 + 0.05 mg gentamicin reduced S. suis by >5-logs. While resistance to gentamicin was induced after systematically increasing levels of gentamicin in an S. suis culture, the same protocol resulted in no observable resistance to PlySs2. Thus, PlySs2 has both broad and high killing activity against multiple serotypes and strains of S. suis, making it a possible tool in the control and prevention of S. suis infections in pigs and humans.

The Phage Lysin PlySs2 Decolonizes Streptococcus suis from Murine Intranasal Mucosa

PubMed Central

Gilmer, Daniel B.; Schmitz, Jonathan E.; Thandar, Mya; Euler, Chad W.; Fischetti, Vincent A.

2017-01-01

Streptococcus suis infects pigs worldwide and may be zoonotically transmitted to humans with a mortality rate of up to 20%. S. suis has been shown to develop in vitro resistance to the two leading drugs of choice, penicillin and gentamicin. Because of this, we have pursued an alternative therapy to treat these pathogens using bacteriophage lysins. The bacteriophage lysin PlySs2 is derived from an S. suis phage and displays potent lytic activity against most strains of that species including serotypes 2 and 9. At 64 μg/ml, PlySs2 reduced multiple serotypes of S. suis by 5 to 6-logs within 1 hour in vitro and exhibited a minimum inhibitory concentration (MIC) of 32 μg/ml for a S. suis serotype 2 strain and 64 μg/ml for a serotype 9 strain. Using a single 0.1-mg dose, the colonizing S. suis serotype 9 strain was reduced from the murine intranasal mucosa by >4 logs; a 0.1-mg dose of gentamicin reduced S. suis by <3-logs. A combination of 0.05 mg PlySs2 + 0.05 mg gentamicin reduced S. suis by >5-logs. While resistance to gentamicin was induced after systematically increasing levels of gentamicin in an S. suis culture, the same protocol resulted in no observable resistance to PlySs2. Thus, PlySs2 has both broad and high killing activity against multiple serotypes and strains of S. suis, making it a possible tool in the control and prevention of S. suis infections in pigs and humans. PMID:28046082

Study of strains of Candida spp. Isolated from catheters in UHC of Oran (Algeria): Identification and antifungal susceptibility.

PubMed

Bendjelloul, M; Boucherit-Otmani, Z; Boucherit, K

2016-09-01

The increasing incidence of Candida spp., and the vital prognosis often compromise for patients with Candida species make urgent the exact knowledge of their distribution worldwide and exhaust action antifungals currently used in clinical. That why we carry out an epidemiological study of Candida species and testing their susceptibility against two antifungals: amphotericin B and caspofungin. Samplings of peripheral venous catheters (PVC) were carried out from during 8months on the services of Internal medicine, Surgery A and Neonatology of Oran's University Hospital Center (UHC). The study of the susceptibility of Candida species to antifungal agents was performed according to the Clinical Laboratory Standards Institute (CLSI 2008). From 300 samples, 25 yeasts were isolated. The rate of colonization PVC was 8.33% by Candida spp. The most isolated strains were Candida parapsilosis with 64% of cases, followed by Candida albicans (12%) then 8% for Candida glabrata and Candida krusei. However, only 4% of isolates were Candida famata or Candida lusitaniae. Furthermore all isolated strains were susceptible to amphotericin B with Minimum Inhibitory Concentrations (MIC) ranging from 0.25 to 1μg/mL. MIC obtained with caspofungin vary from 0.0625 to 2μg/mL for all strains. Moreover, one strain of C. krusei is resistant to caspofungin with a MIC superior to 8μg/mL. All though caspofungin is at least as effective as amphotericin B, it is better tolerated for the treatment of invasive fungal infections. Copyright © 2016. Published by Elsevier Masson SAS.

7 CFR 201.76 - Minimum Land, Isolation, Field, and Seed Standards.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) 100 1.0 Flax 7 1 23 0 5,000 0.05 7 1 23 0 2,000 0.1 7 1 23 0 1,000 0.2 Grasses: Cross-pollinated 57 5....76m). The minimum isolation from grass sorghum or broomcorn with the same chromosome number shall be 1... not apply to Helianthus similes, H. ludens, or H. agrestis. 42 The ratio of male sterile (A) strains...

7 CFR 201.76 - Minimum Land, Isolation, Field, and Seed Standards.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) 100 1.0 Flax 7 1 23 0 5,000 0.05 7 1 23 0 2,000 0.1 7 1 23 0 1,000 0.2 Grasses: Cross-pollinated 57 5....76m). The minimum isolation from grass sorghum or broomcorn with the same chromosome number shall be 1... not apply to Helianthus similes, H. ludens, or H. agrestis. 42 The ratio of male sterile (A) strains...

HIGH-RATE FORMABILITY OF HIGH-STRENGTH ALUMINUM ALLOYS: A STUDY ON OBJECTIVITY OF MEASURED STRAIN AND STRAIN RATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upadhyay, Piyush; Rohatgi, Aashish; Stephens, Elizabeth V.

2015-02-18

Al alloy AA7075 sheets were deformed at room temperature at strain-rates exceeding 1000 /s using the electrohydraulic forming (EHF) technique. A method that combines high speed imaging and digital image correlation technique, developed at Pacific Northwest National Laboratory, is used to investigate high strain rate deformation behavior of AA7075. For strain-rate sensitive materials, the ability to accurately model their high-rate deformation behavior is dependent upon the ability to accurately quantify the strain-rate that the material is subjected to. This work investigates the objectivity of software-calculated strain and strain rate by varying different parameters within commonly used commercially available digital imagemore » correlation software. Except for very close to the time of crack opening the calculated strain and strain rates are very consistent and independent of the adjustable parameters of the software.« less

Left atrial phasic function and heart rate variability in asymptomatic diabetic patients.

PubMed

Tadic, Marijana; Vukomanovic, Vladan; Cuspidi, Cesare; Suzic-Lazic, Jelena; Stanisavljevic, Dejana; Celic, Vera

2017-03-01

We evaluated left atrial (LA) phasic function and heart rate variability (HRV) in asymptomatic diabetic patients, and the relationship between HRV indices and LA phasic function assessed by volumes and speckle tracking imaging. This cross-sectional study included 55 asymptomatic patients with type 2 diabetes and 50 healthy controls without cardiovascular risk factors. All study subjects underwent laboratory analyses, complete two-dimensional echocardiography examination (2DE) and 24-h Holter monitoring. Maximum, minimum LA and pre-A LA volumes and volume indexes are significantly higher in diabetic patients. Total and passive LA emptying fractions (EF), representing the LA reservoir and conduit function, are significantly lower in diabetic subjects. Active LA EF, the parameter of the LA booster pump function, is compensatory increased in diabetic patients. Similar results were obtained by 2DE strain analysis. Cardiac autonomic function, assessed by HRV, is significantly deteriorated in diabetic patients. Time and frequency-domain HRV measures are significantly lower in diabetic subjects than in controls. HbA1c, LV mass index and HRV are associated with total LA EF and longitudinal LA strain independently of age, body mass index and LV diastolic function in the whole study population. LA phasic function and cardiac autonomic nervous system assessed by HRV are impacted by diabetes. HbA1c and HRV are independently associated with LA reservoir function evaluated by volumetric and strain methods in the whole study population. This study emphasizes the importance of determination of LA function and HRV as important markers of preclinical cardiac damage and autonomic function impairment in diabetic patients.

Effect of reinforcement morphology on matrix microcracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sridhar, N.; Srolovitz, D.J.; Rickman, J.M.

1996-03-01

The authors quantitatively examine the conditions under which a particle matrix misfit leads to matrix crack growth as a function of inclusion shape. Such misfit stresses and cracks can be generated by thermal expansion mismatch, generated by cooling a brittle matrix containing ductile inclusions. Using fracture mechanics and perturbation theory, they analyze the case of a penny-shaped crack interacting with a misfitting spheroidal inclusion. A simple and direct relationship is established between the strain energy release rate and the physical and geometrical properties of the system including: the thermal expansion mismatch, temperature change, the crack and inclusion sizes, the elasticmore » properties of the medium and the shape of the inclusion. In particular, the effects of inclusion shape on the stress intensity factors and strain energy release rate are analytically determined for nearly spherical inclusions. The authors use this information to determine the minimum crack size for crack growth to occur and the maximum size to which cracks may grown. The maximum crack size corresponds to the case where the elastic strain energy released upon crack growth is no longer sufficient to compensate for energy expended in extending the crack as the crack is growing into the rapidly decreasing stress field. The authors employ a nominally exact numerical procedure to study the effects of whiskers and platelets (i.e. spheroids very different from spheres) on matrix cracking. It is found that upon cooling a composite containing ductile inclusions, the propensity for matrix cracking is maximized for reinforcement shapes close to that of a sphere.« less

Rapid emergence of high-level tigecycline resistance in Escherichia coli strains harbouring blaNDM-5 in vivo.

PubMed

Li, Xi; Mu, Xinli; Yang, Yunxing; Hua, Xiaoting; Yang, Qing; Wang, Nanfei; Du, Xiaoxing; Ruan, Zhi; Shen, Xiaoqiang; Yu, Yunsong

2016-04-01

Tigecycline (TIG) resistance is a growing concern because this antibiotic is regarded as one of the last resorts to treat infections caused by multidrug-resistant and extensively drug-resistant (XDR) bacteria. Information regarding TIG-resistant Escherichia coli isolates is scarce. In this study, we report the emergence of high-level TIG resistance in a longitudinal series of XDR E. coli isolates collected during TIG treatment. Whole-genome sequencing was performed for six E. coli strains harbouring bla(NDM-5) and genomic comparison revealed two amino acid substitutions. Mutation in rpsJ could be a significant factor conferring TIG resistance in these isolates. The fitness cost of TIG resistance in resistant strains was evaluated by determining the relative growth rate, indicating that TIG resistance reduced fitness by ca. 7%. This study is the first report to demonstrate high-level TIG resistance in E. coli in vivo. In addition, we report the first treatment-emergent minimum inhibitory concentration (MIC) development of TIG from 1mg/L to 64 mg/L in E. coli. Clinicians should be aware of the risk of an increase in the MIC of TIG under therapy. Copyright © 2016 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

20 CFR 10.406 - What are the maximum and minimum rates of compensation in disability cases?

Code of Federal Regulations, 2011 CFR

2011-04-01

... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false What are the maximum and minimum rates of... Impairment § 10.406 What are the maximum and minimum rates of compensation in disability cases? (a... monthly pay does not include locality adjustments.) Compensation for Death ...

20 CFR 10.406 - What are the maximum and minimum rates of compensation in disability cases?

Code of Federal Regulations, 2014 CFR

2014-04-01

... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true What are the maximum and minimum rates of... Impairment § 10.406 What are the maximum and minimum rates of compensation in disability cases? (a... monthly pay does not include locality adjustments.) Compensation for Death ...

20 CFR 10.406 - What are the maximum and minimum rates of compensation in disability cases?

Code of Federal Regulations, 2013 CFR

2013-04-01

... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true What are the maximum and minimum rates of... Impairment § 10.406 What are the maximum and minimum rates of compensation in disability cases? (a... monthly pay does not include locality adjustments.) Compensation for Death ...

20 CFR 10.406 - What are the maximum and minimum rates of compensation in disability cases?

Code of Federal Regulations, 2012 CFR

2012-04-01

... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false What are the maximum and minimum rates of... Impairment § 10.406 What are the maximum and minimum rates of compensation in disability cases? (a... monthly pay does not include locality adjustments.) Compensation for Death ...

20 CFR 10.406 - What are the maximum and minimum rates of compensation in disability cases?

Code of Federal Regulations, 2010 CFR

2010-04-01

... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false What are the maximum and minimum rates of... Impairment § 10.406 What are the maximum and minimum rates of compensation in disability cases? (a... monthly pay does not include locality adjustments.) Compensation for Death ...

Strain-rate dependence of ramp-wave evolution and strength in tantalum

DOE PAGES

Lane, J. Matthew D.; Foiles, Stephen M.; Lim, Hojun; ...

2016-08-25

We have conducted molecular dynamics (MD) simulations of quasi-isentropic ramp-wave compression to very high pressures over a range of strain rates from 10 11 down to 10 8 1/s. Using scaling methods, we collapse wave profiles from various strain rates to a master profile curve, which shows deviations when material response is strain-rate dependent. Thus, we can show with precision where, and how, strain-rate dependence affects the ramp wave. We find that strain rate affects the stress-strain material response most dramatically at strains below 20%, and that above 30% strain the material response is largely independent of strain rate. Wemore » show good overall agreement with experimental stress-strain curves up to approximately 30% strain, above which simulated response is somewhat too stiff. We postulate that this could be due to our interatomic potential or to differences in grain structure and/or size between simulation and experiment. Strength is directly measured from per-atom stress tensor and shows significantly enhanced elastic response at the highest strain rates. As a result, this enhanced elastic response is less pronounced at higher pressures and at lower strain rates.« less

High-resolution spatiotemporal strain mapping reveals non-uniform deformation in micropatterned elastomers

NASA Astrophysics Data System (ADS)

Aksoy, B.; Rehman, A.; Bayraktar, H.; Alaca, B. E.

2017-04-01

Micropatterns are generated on a vast selection of polymeric substrates for various applications ranging from stretchable electronics to cellular mechanobiological systems. When these patterned substrates are exposed to external loading, strain field is primarily affected by the presence of microfabricated structures and similarly by fabrication-related defects. The capturing of such nonhomogeneous strain fields is of utmost importance in cases where study of the mechanical behavior with a high spatial resolution is necessary. Image-based non-contact strain measurement techniques are favorable and have recently been extended to scanning tunneling microscope and scanning electron microscope images for the characterization of mechanical properties of metallic materials, e.g. steel and aluminum, at the microscale. A similar real-time analysis of strain heterogeneity in elastomers is yet to be achieved during the entire loading sequence. The available measurement methods for polymeric materials mostly depend on cross-head displacement or precalibrated strain values. Thus, they suffer either from the lack of any real-time analysis, spatiotemporal distribution or high resolution in addition to a combination of these factors. In this work, these challenges are addressed by integrating a tensile stretcher with an inverted optical microscope and developing a subpixel particle tracking algorithm. As a proof of concept, the patterns with a critical dimension of 200 µm are generated on polydimethylsiloxane substrates and strain distribution in the vicinity of the patterns is captured with a high spatiotemporal resolution. In the field of strain measurement, there is always a tradeoff between minimum measurable strain value and spatial resolution. Current noncontact techniques on elastomers can deliver a strain resolution of 0.001% over a minimum length of 5 cm. More importantly, inhomogeneities within this quite large region cannot be captured. The proposed technique can overcome this challenge and provides a displacement measurement resolution of 116 nm and a strain resolution of 0.04% over a gage length of 300 µm. Similarly, the ability to capture inhomogeneities is demonstrated by mapping strain around a thru-hole. The robustness of the technique is also evaluated, where no appreciable change in strain measurement is observed despite the significant variations imposed on the measurement mesh. The proposed approach introduces critical improvements for the determination of displacement and strain gradients in elastomers regarding the real-time nature of strain mapping with a microscale spatial resolution.

In vitro susceptibility of rabbit strains of Clostridium spiroforme to antimicrobial agents.

PubMed

Carman, R J; Wilkins, T D

1991-08-30

Using an agar dilution method we measured the minimum inhibitory concentration (MIC) of 12 antimicrobial agents against 11 strains of iota-toxigenic strains of Clostridium spiroforme. Each strain was isolated from a separate outbreak of toxic diarrhoea of rabbits. Vancomycin and bacitracin, both agents used to treat intestinal clostridioses of humans and other animals, had a relatively high MIC (8 micrograms/ml or more). Metronidazole was uniformly active against C. spiroforme. With MIC of 8 micrograms/ml or more, both lincomycin (11 strains) and erythromycin (9 strains) were relatively inactive against C. spiroforme, conversely, penicillin G was active (MIC for 8 strains was 0.5 micrograms/ml or less). Exposure to any one of these drugs has been implicated as a predisposing factor for C. spiroforme mediated diarrhoea of rabbits. The greatest variation in MIC was seen for erythromycin (8-fold), penicillin G (8-fold) and tetracycline (16-fold).

Progress in high temperature speckle-shift strain measurement system

NASA Technical Reports Server (NTRS)

Lant, Christian T.; Barranger, John P.

1990-01-01

A fast, easy to use speckle tracking system is under development for the speckle-shift strain measurement technique. Preliminary correlation tests on wire specimens show strong correlations of well-developed speckle patterns. Stable cross-correlations were obtained from a tungsten filament at 2480 C. An analysis of the optical system determines the minimum required sampling frequency of the speckle pattern to be 2.55 pixels per speckle.

Optical Method for Detecting Displacements and Strains at Ultra-High Temperatures During Thermo-Mechanical Testing

NASA Technical Reports Server (NTRS)

Roth, Mark C. (Inventor); Smith, Russell W. (Inventor); Sikora, Joseph G. (Inventor); Rivers, H. Kevin (Inventor); Johnston, William M. (Inventor)

2016-01-01

An ultra-high temperature optical method incorporates speckle optics for sensing displacement and strain measurements well above conventional measurement techniques. High temperature pattern materials are used which can endure experimental high temperature environments while simultaneously having a minimum optical aberration. A purge medium is used to reduce or eliminate optical distortions and to reduce, and/or eliminate oxidation of the target specimen.

Antibacterial activity of different honeys against pathogenic bacteria.

PubMed

Voidarou, C; Alexopoulos, A; Plessas, S; Karapanou, A; Mantzourani, I; Stavropoulou, E; Fotou, K; Tzora, A; Skoufos, I; Bezirtzoglou, E

2011-12-01

To study the antimicrobial activity of honey, 60 samples of various botanical origin were evaluated for their antimicrobial activities against 16 clinical pathogens and their respective reference strains. The microbiological quality of honeys and the antibiotic susceptibility of the various isolates were also examined. The bioassay applied for determining the antimicrobial effect employs the well-agar diffusion method and the estimation of minimum active dilution which produces a 1mm diameter inhibition zone. All honey samples, despite their origin (coniferous, citrus, thyme or polyfloral), showed antibacterial activity against the pathogenic and their respective reference strains at variable levels. Coniferous and thyme honeys showed the highest activity with an average minimum dilution of 17.4 and 19.2% (w/v) followed by citrus and polyfloral honeys with 20.8 and 23.8% respectively. Clinical isolates of Staphylococcus aureus subsp. aureus, Escherichia coli, Salmonella enterica subsp. Enterica, Streptococcus pyogenes, Bacillus cereus and Bacillus subtilis were proven to be up to 60% more resistant than their equal reference strains thus emphasizing the variability in the antibacterial effect of honey and the need for further research. Copyright © 2011 Elsevier Ltd. All rights reserved.

Tolerance response of multidrug-resistant Salmonella enterica strains to habituation to Origanum vulgare L. essential oil

PubMed Central

Monte, Daniel F. M.; Tavares, Adassa G.; Albuquerque, Allan R.; Sampaio, Fábio C.; Oliveira, Tereza C. R. M.; Franco, Octavio L.; Souza, Evandro L.; Magnani, Marciane

2014-01-01

Multidrug-resistant Salmonella enterica isolates from human outbreaks or from poultry origin were investigated for their ability to develop direct-tolerance or cross-tolerance to sodium chloride, potassium chloride, lactic acid, acetic acid, and ciprofloxacin after habituation in subinhibitory amounts ( of the minimum inhibitory concentration – (MIC) and of the minimum inhibitory concentration – MIC) of Origanum vulgare L. essential oil (OVEO) at different time intervals. The habituation of S. enterica to OVEO did not induce direct-tolerance or cross-tolerance in the tested strains, as assessed by the modulation of MIC values. However, cells habituated to OVEO maintained or increased susceptibility to the tested antimicrobials agents, with up to fourfold double dilution decrease from previously determined MIC values. This study reports for the first time the non-inductive effect of OVEO on the acquisition of direct-tolerance or cross-tolerance in multidrug-resistant S. enterica strains to antimicrobial agents that are largely used in food preservation, as well as to CIP, the therapeutic drug of salmonellosis. PMID:25566231

Activity of Aristolochia bracteolata against Moraxella catarrhalis

PubMed Central

Khedr, Amgad I. M.; Abd AlGadir, Haidar; Takeshita, Satoshi; Shah, Mohammad Monir; Ichinose, Yoshio; Maki, Toshihide

2014-01-01

A bioassay-guided fractionation of methanol extract of Aristolochia bracteolata whole plant was carried out in order to evaluate its antimicrobial activity and to identify the active compounds in this extract. Antibacterial and antifungal activities of methanol extract against gram-positive, gram-negative, and fungal strains were investigated by the agar disk diffusion method. Among the strains tested, Moraxella catarrhalis and sea urchin-derived Bacillus sp. showed the highest sensitivity towards the methanol extract and hence they are used as test organisms for the bioassay-guided fractionation. From this extract, aristolochic acid 1 (AA-1) has been isolated and has showed the greatest antibacterial activity against both standard strain and clinical isolates of Moraxella catarrhalis with equal minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 25 and 50 μg/mL. Modification of the AA-1 to AA-1 methyl ester completely abolished the antibacterial activity of the compound and the piperonylic acid moiety of AA-1 which suggested that the coexistence of phenanthrene ring and free carboxylic acid is essential for AA-1 antibacterial activity. PMID:26904734

Antibacterial properties of parasitic mistletoe - Scurrula ferruginea (Jack) Danser of Brunei Darussalam

NASA Astrophysics Data System (ADS)

David, Sheba R.; Amni Adam, Amira; Rajabalaya, Rajan

2017-12-01

Natural products especially from plants have become subject of much interest in drug discovery. Scurrula ferruginea is parasitic mistletoe used traditionally to treat various illnesses. The aim of this study is to investigate the potential antibacterial effect of Scurrula ferruginea native to Brunei Darussalam. The plants were collected from Brunei-Muara district air-dried, pulverized into powder, extracted by water maceration and freeze dried. Later, the extract was screened by disc-diffusion assay for two bacterial strains. The positive controls were Gentamycin and Ampicillin for Staphylococcus aureus while Sulphamethoxazole was used for Escherichia coli. Dimethyl sulfoxide was the negative control for both strains. 100, 200 and 500 mg/ml of the extract were used for the assays. The extracts did not show any inhibition activity against Escherichia coli, while sulphamethoxazole, showed inhibition of 24 mm. Ampicillin, Gentamycin, 100 and 500 mg/ml extract exhibited 29, 20, 8.3 and 10.7 mm inhibition zone, respectively against Staphylococcus aureus. There was an increase in zone of inhibition on Staphylococcus aureus strain with increase in extract concentration. Further investigations including Minimum Inhibition Concentration and Minimum Bactericidal Concentration methods as well as investigation on additional bacterial strains will be conducted for confirmation of antibacterial effect of the extract.

Habituation of enterotoxigenic Staphylococcus aureus to Origanum vulgare L. essential oil does not induce direct-tolerance and cross-tolerance to salts and organic acids

PubMed Central

Tavares, Adassa Gama; do Monte, Daniel Farias Marinho; Albuquerque, Allan dos Reis; Sampaio, Fábio Correia; Magnani, Marciane; de Siqueira, José Pinto; de Souza, Evandro Leite

2015-01-01

Enterotoxigenic Staphylococcus aureus strains that were isolated from foods were investigated for their ability to develop direct-tolerance and cross-tolerance to sodium chloride (NaCl), potassium chloride (KCl), lactic acid (LA) and acetic acid (AA) after habituation in sublethal amounts (1/2 of the minimum inhibitory concentration - 1/2 MIC and 1/4 of the minimum inhibitory concentration - 1/4 MIC) of Origanum vulgare L. essential oil (OVEO). The habituation of S. aureus to 1/2 MIC and 1/4 MIC of OVEO did not induce direct-tolerance or cross-tolerance in the tested strains, as assessed by modulation of MIC values. Otherwise, exposing the strains to OVEO at sublethal concentrations maintained or increased the sensitivity of the cells to the tested stressing agents because the MIC values of OVEO, NaCl, KCl, LA and AA against the cells that were previously habituated to OVEO remained the same or decreased when compared with non-habituated cells. These data indicate that OVEO does not have an inductive effect on the acquisition of direct-tolerance or cross-tolerance in the tested enterotoxigenic strains of S. aureus to antimicrobial agents that are typically used in food preservation. PMID:26413067

Environmental and genetic influences on flight metabolic rate in the honey bee, Apis mellifera.

PubMed

Harrison, Jon F; Fewell, Jennifer H

2002-10-01

Flying honey bees demonstrate highly variable metabolic rates. The lowest reported values (approximately 0.3 Wg(-1)) occur in tethered bees generating the minimum lift to support their body weight, free-flying 2-day old bees, winter bees, or bees flying at high air temperatures (45 degrees C). The highest values (approximately 0.8 Wg(-1)) occur in foragers that are heavily loaded or flying in low-density air. In different studies, flight metabolic rate has increased, decreased, or remained constant with air temperature. Current research collectively suggests that this variation occurs because flight metabolic rates decrease at thorax temperatures above or below 38 degrees C. At 30 degrees C, approximately 30% of colonial energy is spent during typical foraging, so variation in flight metabolic rate can strongly affect colony-level energy balance. Higher air temperatures tend to increase colonial net gain rates, efficiencies and honey storage rates due to lower metabolic rates during flight and in the hive. Variation in flight metabolism has a clear genetic basis. Different genetic strains of honey bees often differ in flight metabolic rate, and these differences in flight physiology can be correlated with foraging effort, suggesting a possible pathway for selection effects on flight metabolism.

[Clinical studies on flomoxef in acute tonsillitis].

PubMed

Tomiyama, M

1994-09-01

To objectively evaluate the clinical efficacy and safety in acute tonsillitis, flomoxef (FMOX) was examined for the distribution of sensitivity of clinical strains to it and for its clinical usefulness. 1. The 80% minimum inhibitory concentration of 11 clinical strains of Gram-positive bacteria, 6 of Gram-negative bacteria and 5 of anaerobic bacteria was 0.39 microgram/ml. FMOX showed the strongest, most comprehensive antibacterial action among the drugs tested. 2. Thirty patients received FMOX. Clinical effectiveness was evaluated in 28 patients, and clinical usefulness and safety in 30. 3. The clinical efficacy rate ('excellent' and 'good') was 75% (21/28). 4. As for bacteriological response, bacterial elimination rates were 67% for Gram-positive bacteria, 100% for Gram-negative bacteria, 100% for anaerobic bacteria and 100% for mixed infections. 5. Side effects occurred in 2 (6%) patients: drug eruption and diarrhea in 1 patient each. These symptoms improved rapidly after discontinuation of the drug. 6. Although abnormal clinical test results were found in 7 (23%) patients, i.e., increases in GOT and GPT in 2, in GPT in 4 and in BUN in 1, they were transient. 7. The usefulness of FMOX was assessed in light of its efficacy and safety. It was highly satisfactory in 14 patients, satisfactory in 11, relatively satisfactory in 1, unsatisfactory in 2 and highly unsatisfactory in 2, and rate of usefulness was 83%. FMOX is considered to be highly useful for the treatment of severe acute tonsillitis.

Design and Study of Efflux Function of EGFP Fused MexAB-OprM Membrane Transporter in Pseudomonas aeruginosa Using Fluorescence Spectroscopy

PubMed Central

Ding, Feng; Lee, Kerry J.; Vahedi-Faridi, Ardeschir; Yoneyama, Hiroshi; Osgood, Christopher J.; Xu, Xiao-Hong Nancy

2014-01-01

Multidrug membrane transporters (efflux pumps) can selectively extrude a variety of structurally and functionally diverse substrates (e.g., chemotoxics, antibiotics), leading to multidrug resistance (MDR) and ineffective treatment of a wide variety of diseases. In this study, we have designed and constructed fusion gene (egfp-mexB) of N-terminal mexB with C-terminal egfp, inserted it into a plasmid vector (pMMB67EH), and successfully expressed it in ΔMexB (MexB deletion) strain of Pseudomonas aeruginosa to create a new strain that expresses MexA-(EGFP-MexB)-OprM. We characterized the fusion gene using gel electrophoresis and DNA sequencing, and determined their expression in live cells by measuring the fluorescence of EGFP in single live cells using fluorescence microscopy. Efflux function of the new strain was studied by measuring its accumulation kinetics of ethidium bromide (EtBr, a pump substrate) using fluorescence spectroscopy, which was compared with the cells (WT, ΔMexM, ΔABM, and nalB1) with various expression levels of MexAB-OprM. The new strain shows 6-fold lower accumulation rates of EtBr (15 μM) than ΔABM, 4-fold lower than ΔMexB, but only 1.1-fold higher than WT. As EtBr concentration increases to 40 μM, the new strain has nearly the same accumulation rate of EtBr as ΔMexB, but 1.4-fold higher than WT. We observed the nearly same level of inhibitory effect of CCCP (carbonyl cyanide-m-chlorophenylhydrazone) on the efflux of EtBr by the new strain and WT. Antibiotic susceptibility study shows that the minimum inhibitory concentrations (MICs) of aztreonam (AZT) and chloramphenicol (CP) for the new strain are 6-fold or 3-fold lower than WT, respectively, and 2-fold higher than those of ΔMexB. Taken together, the results suggest that the fusion protein partially retains the efflux function of MexAB-OprM. Modeled structure of the fusion protein shows that the position and orientation of the N-terminal fused EGFP domain may either partially block the translocation pore or restrict the movement of the individual pump domains, which leads to partially restrict efflux activity. PMID:24781334

New Variational Formulations of Hybrid Stress Elements

NASA Technical Reports Server (NTRS)

Pian, T. H. H.; Sumihara, K.; Kang, D.

1984-01-01

In the variational formulations of finite elements by the Hu-Washizu and Hellinger-Reissner principles the stress equilibrium condition is maintained by the inclusion of internal displacements which function as the Lagrange multipliers for the constraints. These versions permit the use of natural coordinates and the relaxation of the equilibrium conditions and render considerable improvements in the assumed stress hybrid elements. These include the derivation of invariant hybrid elements which possess the ideal qualities such as minimum sensitivity to geometric distortions, minimum number of independent stress parameters, rank sufficient, and ability to represent constant strain states and bending moments. Another application is the formulation of semiLoof thin shell elements which can yield excellent results for many severe test cases because the rigid body nodes, the momentless membrane strains, and the inextensional bending modes are all represented.

Natural Strain

NASA Technical Reports Server (NTRS)

Freed, Alan D.

1995-01-01

The purpose of this paper is to present a consistent and thorough development of the strain and strain-rate measures affiliated with Hencky. Natural measures for strain and strain-rate, as I refer to them, are first expressed in terms of of the fundamental body-metric tensors of Lodge. These strain and strain-rate measures are mixed tensor fields. They are mapped from the body to space in both the Eulerian and Lagrangian configurations, and then transformed from general to Cartesian fields. There they are compared with the various strain and strain-rate measures found in the literature. A simple Cartesian description for Hencky strain-rate in the Lagrangian state is obtained.

Temperature affects the morphology and calcification of Emiliania huxleyi strains

NASA Astrophysics Data System (ADS)

Rosas-Navarro, Anaid; Langer, Gerald; Ziveri, Patrizia

2016-05-01

The global warming debate has sparked an unprecedented interest in temperature effects on coccolithophores. The calcification response to temperature changes reported in the literature, however, is ambiguous. The two main sources of this ambiguity are putatively differences in experimental setup and strain specificity. In this study we therefore compare three strains isolated in the North Pacific under identical experimental conditions. Three strains of Emiliania huxleyi type A were grown under non-limiting nutrient and light conditions, at 10, 15, 20 and 25 °C. All three strains displayed similar growth rate versus temperature relationships, with an optimum at 20-25 °C. Elemental production (particulate inorganic carbon (PIC), particulate organic carbon (POC), total particulate nitrogen (TPN)), coccolith mass, coccolith size, and width of the tube element cycle were positively correlated with temperature over the sub-optimum to optimum temperature range. The correlation between PIC production and coccolith mass/size supports the notion that coccolith mass can be used as a proxy for PIC production in sediment samples. Increasing PIC production was significantly positively correlated with the percentage of incomplete coccoliths in one strain only. Generally, coccoliths were heavier when PIC production was higher. This shows that incompleteness of coccoliths is not due to time shortage at high PIC production. Sub-optimal growth temperatures lead to an increase in the percentage of malformed coccoliths in a strain-specific fashion. Since in total only six strains have been tested thus far, it is presently difficult to say whether sub-optimal temperature is an important factor causing malformations in the field. The most important parameter in biogeochemical terms, the PIC : POC ratio, shows a minimum at optimum growth temperature in all investigated strains. This clarifies the ambiguous picture featuring in the literature, i.e. discrepancies between PIC : POC-temperature relationships reported in different studies using different strains and different experimental setups. In summary, global warming might cause a decline in coccolithophore's PIC contribution to the rain ratio, as well as improved fitness in some genotypes due to fewer coccolith malformations.

13 CFR 301.4 - Investment rates.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Investment rates. 301.4 Section... ELIGIBILITY, INVESTMENT RATE AND PROPOSAL AND APPLICATION REQUIREMENTS Investment Rates and Matching Share Requirements § 301.4 Investment rates. (a) Minimum Investment Rate. There is no minimum Investment Rate for a...

13 CFR 301.4 - Investment rates.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Investment rates. 301.4 Section... ELIGIBILITY, INVESTMENT RATE AND APPLICATION REQUIREMENTS Investment Rates and Matching Share Requirements § 301.4 Investment rates. (a) Minimum Investment Rate. There is no minimum Investment Rate for a Project...

13 CFR 301.4 - Investment rates.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Investment rates. 301.4 Section... ELIGIBILITY, INVESTMENT RATE AND APPLICATION REQUIREMENTS Investment Rates and Matching Share Requirements § 301.4 Investment rates. (a) Minimum Investment Rate. There is no minimum Investment Rate for a Project...

13 CFR 301.4 - Investment rates.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 13 Business Credit and Assistance 1 2013-01-01 2013-01-01 false Investment rates. 301.4 Section... ELIGIBILITY, INVESTMENT RATE AND APPLICATION REQUIREMENTS Investment Rates and Matching Share Requirements § 301.4 Investment rates. (a) Minimum Investment Rate. There is no minimum Investment Rate for a Project...

13 CFR 301.4 - Investment rates.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 13 Business Credit and Assistance 1 2014-01-01 2014-01-01 false Investment rates. 301.4 Section... ELIGIBILITY, INVESTMENT RATE AND APPLICATION REQUIREMENTS Investment Rates and Matching Share Requirements § 301.4 Investment rates. (a) Minimum Investment Rate. There is no minimum Investment Rate for a Project...

Electro-mechanical Properties of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Anantram, M. P.; Yang, Liu; Han, Jie; Liu, J. P.; Saubum Subhash (Technical Monitor)

1998-01-01

We present a simple picture to understand the bandgap variation of carbon nanotubes with small tensile and torsional strains, independent of chirality. Using this picture, we are able to predict a simple dependence of d(Bandoap)$/$d(strain) on the value of $(N_x-N_y)*mod 3$, for semiconducting tubes. We also predict a novel change in sign of d(Bandgap)$/$d(strain) as a function of tensile strain arising from a change in the value of $q$ corresponding to the minimum bandgap. These calculations are complemented by calculations of the change in bandgap using energy minimized structures, and some important differences are discussed. The calculations are based on the $i$ electron approximation.

Measurements of Local Strain Variation in Si(1-x)Ge(x)/Si Heterostructures

NASA Technical Reports Server (NTRS)

Bell, L. D.; Kaiser, W. J.; Manion, S. J.; Milliken, S. J.; Pike, W. T.; Fathauer, R. W.

1995-01-01

The energy splitting of the conduction-band minimum of Si(1-x), Ge(x), due to strain has been directly measured by the application of ballistic-electron-emission microscope (BEEM) spectroscopy to Ag/Si(1-x), Ge(x) structures. Experimental values for this conduction-band splitting agree well with calculations. For Au/Si(1-x), Ge(x), however, heterogeneity in the strain of the Si(1-x), Ge(x) layer is introduced by deposition of the Au. This variation is attributed to species interdiffusion, which produces a rough Si(1-x)Ge(x) surface. Preliminary modeling indicates that the observed roughness is consistent with the strain variation measured by BEEM.

Comparative Study of Hydroalcoholic Extracts of Momordica charantia L. against Foodborne Pathogens

PubMed Central

Rakholiya, Kalpna; Vaghela, P.; Rathod, T.; Chanda, Sumitra

2014-01-01

The antimicrobial effect of 24 different hydroalcoholic extracts (100, 75, 50 and 25% methanol and water) obtained from four parts (leaf+stem (aerial), peel, pulp and seed) of Momordica charantia L. were investigated against five Gram-positive, six Gram-negative and four fungal strains. The extraction was done by individual cold percolation method using hexane, different hydroalcoholic solvent (100, 75, 50 and 25% methanol) and water. The antimicrobial activity was done by agar well diffusion assay. The extracts, which showed >15 mm zone of inhibition, were further screened to determine minimum inhibitory concentration and minimum bactericidal concentration using a broth dilution method performed in 96-well microtitre plate. The extractive yield was highest in aqueous extracts of all the four parts closely followed by 25% methanol. Micrococcus flavus was the most susceptible Gram-positive bacteria and Pseudomonas testosteroni was the most susceptible Gram-negative bacteria. The highest antibacterial activity was shown by 100% methanol. The Gram-negative Pseudomonas spp. was more susceptible towards all the extracts than the Gram-positive bacteria or fungal strains investigated. One hundred percent and 50% methanol extracts of seed showed lowest minimum inhibitory concentration and minimum bactericidal concentration values, that is <39 and 625 μg/ml, respectively, against Pseudomonas pictorum. Therefore, these extracts would be of interest in the control of Pseudomonas spp. in food industry as well as used for therapeutic purposes. PMID:24843188

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Zhang, Xingyi, E-mail: zhangxingyi@lzu.edu.cn; Liu, Cong

We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strandmore » is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.« less

Left atrial physiology and pathophysiology: Role of deformation imaging

PubMed Central

Kowallick, Johannes Tammo; Lotz, Joachim; Hasenfuß, Gerd; Schuster, Andreas

2015-01-01

The left atrium (LA) acts as a modulator of left ventricular (LV) filling. Although there is considerable evidence to support the use of LA maximum and minimum volumes for disease prediction, theoretical considerations and a growing body of literature suggest to focus on the quantification of the three basic LA functions: (1) Reservoir function: collection of pulmonary venous return during LV systole; (2) Conduit function: passage of blood to the left ventricle during early LV diastole; and (3) Contractile booster pump function (augmentation of ventricular filling during late LV diastole. Tremendous advances in our ability to non-invasively characterize all three elements of atrial function include speckle tracking echocardiography (STE), and more recently cardiovascular magnetic resonance myocardial feature tracking (CMR-FT). Corresponding imaging biomarkers are increasingly recognized to have incremental roles in determining prognosis and risk stratification in cardiac dysfunction of different origins. The current editorial introduces the role of STE and CMR-FT for the functional assessment of LA deformation as determined by strain and strain rate imaging and provides an outlook of how this exciting field may develop in the future. PMID:26131333

Fracture toughness and fracture behavior of SA508-III steel at different temperatures

NASA Astrophysics Data System (ADS)

Liu, Jia-hua; Wang, Lei; Liu, Yang; Song, Xiu; Luo, Jiong; Yuan, Dan

2014-12-01

The fracture toughness of SA508-III steel was studied in the temperature range from room temperature to 320°C using the J-integral method. The fracture behavior of the steel was also investigated. It was found that the conditional fracture toughness ( J Q) of the steel first decreased and then increased with increasing test temperature. The maximum and minimum values of J Q were 517.4 kJ/m2 at 25°C and 304.5 kJ/m2 at 180°C, respectively. Dynamic strain aging (DSA) was also observed to occur when the temperature exceeded 260°C with a certain strain rate. Both the dislocation density and the number of small dislocation cells effectively increased because of the occurrence of DSA; as a consequence, crack propagation was more strongly inhibited in the steel. Simultaneously, an increasing number of fine carbides precipitated under high stress at temperatures greater than 260°C. Thus, the deformation resistance of the steel was improved and the J Q was enhanced.

Creep deformation and mechanisms in Haynes 230 at 800 °C and 900 °C

NASA Astrophysics Data System (ADS)

Pataky, Garrett J.; Sehitoglu, Huseyin; Maier, Hans J.

2013-11-01

Creep was studied in Haynes 230, a material candidate for the very high temperature reactor's intermediate heat exchanger, at 800 °C and 900 °C. This study focused on the differences between the behavior at the two elevated temperature, and using the microstructure, grain boundary serrations and triple junction strain concentrations were quantitatively identified. There was significant damage in the 900 °C samples and the creep was almost entirely tertiary. In contrast, the 800 °C sample exhibited secondary creep. Using an Arrhenius equation, the minimum creep rate exponents were found to be n ≈ 3 and n ≈ 5 for 900 °C and 800 °C, respectively. The creep mechanisms were identified as solute drag for n ≈ 3 and dislocation climb for n ≈ 5. Strain concentrations were identified at triple junctions and grain boundary serrations using high resolution digital image correlation overlaid on the microstructure. The grain boundary serrations restrict grain boundary sliding which may reduce the creep damage at triple junctions and extend the creep life of Haynes 230 at elevated temperatures.

Early Impairment of Cardiac Function and Asynchronization of Systemic Amyloidosis with Preserved Ejection Fraction Using Two-Dimensional Speckle Tracking Echocardiography.

PubMed

Huang, He; Jing, Xian-chao; Hu, Zhang-xue; Chen, Xi; Liu, Xiao-qin

2015-12-01

To observe the ventricular global and regional function of the patients with systemic amyloidosis using two-dimensional speckle tracking echocardiography. The study enrolled 31 consecutive biopsy-proved patients with systemic amyloidosis who underwent echocardiographic examination and EF ≥ 55% and 37 age- and gender-matched healthy controls. We compared systolic strain and strain rate, diastolic strain rate, time to peak strain, peak delay time in longitudinal, radial, circumferential directions in 16 left ventricular segments. The global peak systolic longitudinal and radial strain of left ventricle, peak systolic longitudinal strain and strain rate, diastolic strain rate of right ventricular free wall were also compared. (1) Global peak systolic longitudinal strain (GPSLS), peak systolic longitudinal strain (PSLS) and strain rate (PSLSR), peak early diastolic longitudinal strain rate (PELSR) in 16 segments were decreased in case (P < 0.05). (2) Peak systolic radial strain and strain rate of inferoseptum and inferolateral at the level of papillary muscle were lower (P < 0.05), and peak early diastolic radial strain rate (PERSR) was reduced (P < 0.05). (3) Peak early diastolic circumferential strain rate was lower (P < 0.05). (4) Time to peak systolic longitudinal, radial, circumferential strain was longer, and peak delay time at the same level retarded (P < 0.05). (5) Into right ventricular wall, PSLS and PSLSR at mid-segment, and PSLSR, PELSR, peak atrial systolic longitudinal strain rate (PALSR) at basal were reduced (P < 0.05). (6) Inverse correlation between interventricular septum (IVS) thickness and GPSLS and GPSRS was found (P < 0.05). Systolic and diastolic dysfunction existed in systemic amyloidosis with preserved EF. Mechanical contraction disorder may be one reason for systolic dysfunction. GPLSR and GPRSR were negatively related to IVS thickness. © 2015, Wiley Periodicals, Inc.

Evaluating the antimicrobial potential of green cardamom essential oil focusing on quorum sensing inhibition of Chromobacterium violaceum.

PubMed

Abdullah; Asghar, Ali; Butt, Masood Sadiq; Shahid, Muhammad; Huang, Qingrong

2017-07-01

Spices are well known for their taste and flavor imparting properties. Green cardamom ( Elletaria cardamomum ), a herb spice belongs to family Zingiberaceae . In current study, GC-MS analysis of green cardamom essential oil (CEO) resulted in identification of twenty-six compounds with α -terpinyl acetate (38.4%), 1,8-cineole (28.71%), linalool acetate (8.42%), sabinene (5.21%), and linalool (3.97%) as major bioactive components. Present study also described the antimicrobial properties like zone of inhibition, minimum inhibitory concentration against microbial strains with special emphasis on quorum sensing inhibition. Disk diffusion assay showed that C. albicans and S. mutans were the most sensitive microorganisms followed by S. aureus , L. monocytogenes , B. cereus and S. typhimurium sensor strains, respectively. Whilst P. aeruginosa was found most resistant strain as CEO did not inhibited its growth. The minimum inhibitory concentration (MIC) values of CEO against tested strains were 10 ± 0.00 mg/mL against S. typhimurium , S. aureus and 5 ± 0.00 mg/mL against S. mutans , C. albicans strains, respectively. Regarding quorum sensing inhibition the tested concentrations 0.625 and 0.313 mg/mL of CEO inhibited violacein production with very little effect on growth of C. violaceum . Conclusively, study proved that quorum sensing inhibition values of CEO were much lower compared to MIC revealed values. Hence, cardamom bioactive constituents can effectively be used to develop novel antimicrobial drugs against conventional antibiotics.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus.

PubMed

Mohammadinia, M; Rahmani, S; Eslami, G; Ghassemi-Broumand, M; Aghazadh Amiri, M; Aghaie, Gh; Tabatabaee, S M; Taheri, S; Behgozin, A

2012-02-01

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines. Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated. All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosa and S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosa and S. aureus were acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount. Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosa and S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

PubMed Central

Mohammadinia, M; Rahmani, S; Eslami, G; Ghassemi-Broumand, M; Aghazadh Amiri, M; Aghaie, Gh; Tabatabaee, S M; Taheri, S; Behgozin, A

2012-01-01

Purpose To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosaand Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines. Methods Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated. Results All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosaand S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosaand S. aureuswere acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount. Conclusions Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosaand S. aureus, their efficacy may be insufficient against clinical isolates of these organisms. PMID:22094301

Helical coil buckling mechanism for a stiff nanowire on an elastomeric substrate

NASA Astrophysics Data System (ADS)

Chen, Youlong; Liu, Yilun; Yan, Yuan; Zhu, Yong; Chen, Xi

2016-10-01

When a stiff nanowire is deposited on a compliant soft substrate, it may buckle into a helical coil form when the system is compressed. Using theoretical and finite element method (FEM) analyses, the detailed three-dimensional coil buckling mechanism for a silicon nanowire (SiNW) on a polydimethylsiloxane (PDMS) substrate is studied. A continuum mechanics approach based on the minimization of the strain energy in the SiNW and elastomeric substrate is developed. Due to the helical buckling, the bending strain in SiNW is significantly reduced and the maximum local strain is almost uniformly distributed along SiNW. Based on the theoretical model, the energy landscape for different buckling modes of SiNW on PDMS substrate is given, which shows that both the in-plane and out-of-plane buckling modes have the local minimum potential energy, whereas the helical buckling model has the global minimum potential energy. Furthermore, the helical buckling spacing and amplitudes are deduced, taking into account the influences of the elastic properties and dimensions of SiNWs. These features are verified by systematic FEM simulations and parallel experiments. As the effective compressive strain in elastomeric substrate increases, the buckling profile evolves from a vertical ellipse to a lateral ellipse, and then approaches to a circle when the effective compressive strain is larger than 30%. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and 3D complex nano-structures.

Relationship of compressive stress-strain response of engineering materials obtained at constant engineering and true strain rates

DOE PAGES

Song, Bo; Sanborn, Brett

2018-05-07

In this paper, a Johnson–Cook model was used as an example to analyze the relationship of compressive stress-strain response of engineering materials experimentally obtained at constant engineering and true strain rates. There was a minimal deviation between the stress-strain curves obtained at the same constant engineering and true strain rates. The stress-strain curves obtained at either constant engineering or true strain rates could be converted from one to the other, which both represented the intrinsic material response. There is no need to specify the testing requirement of constant engineering or true strain rates for material property characterization, provided that eithermore » constant engineering or constant true strain rate is attained during the experiment.« less

Relationship of compressive stress-strain response of engineering materials obtained at constant engineering and true strain rates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Sanborn, Brett

In this paper, a Johnson–Cook model was used as an example to analyze the relationship of compressive stress-strain response of engineering materials experimentally obtained at constant engineering and true strain rates. There was a minimal deviation between the stress-strain curves obtained at the same constant engineering and true strain rates. The stress-strain curves obtained at either constant engineering or true strain rates could be converted from one to the other, which both represented the intrinsic material response. There is no need to specify the testing requirement of constant engineering or true strain rates for material property characterization, provided that eithermore » constant engineering or constant true strain rate is attained during the experiment.« less

Electronic and optical properties of α-InX (X = S, Se and Te) monolayer: Under strain conditions

NASA Astrophysics Data System (ADS)

Jalilian, Jaafar; Safari, Mandana

2017-04-01

Using ab initio study, the structural, electronic and optical properties of α-InX (X = S, Se and Te) are investigated under tensile and compressive strain conditions. The results illustrate that exerting biaxial tensile and compressive strain conditions can lead to a tunable energy gap with a linear trend. The shape of valence band maximum (VBM) and conduction band minimum (CBM) is so sensitive to applying tensile and compressive strain. Besides, a shift in optical spectra toward shorter wavelength (blue shift) occurs under compression. The exerting tensile strain, on the other hand, gives rise to a red shift in optical spectra correspondingly. The results have been presented that InX monolayers can be good candidates for optoelectronic applications as well.

Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

NASA Technical Reports Server (NTRS)

Padula, II, Santo A (Inventor)

2013-01-01

Methods and apparatuses for stabilizing the strain-temperature response for a shape memory alloy are provided. To perform stabilization of a second sample of the shape memory alloy, a first sample of the shape memory alloy is selected for isobaric treatment and the second sample is selected for isothermal treatment. When applying the isobaric treatment to the first sample, a constant stress is applied to the first sample. Temperature is also cycled from a minimum temperature to a maximum temperature until a strain on the first sample stabilizes. Once the strain on the first sample stabilizes, the isothermal treatment is performed on the second sample. During isothermal treatment, different levels of stress on the second sample are applied until a strain on the second sample matches the stabilized strain on the first sample.

Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

NASA Technical Reports Server (NTRS)

Padula, Santo A., II (Inventor)

2016-01-01

Methods and apparatuses for stabilizing the strain-temperature response for a shape memory alloy are provided. To perform stabilization of a second sample of the shape memory alloy, a first sample of the shape memory alloy is selected for isobaric treatment and the second sample is selected for isothermal treatment. When applying the isobaric treatment to the first sample, a constant stress is applied to the first sample. Temperature is also cycled from a minimum temperature to a maximum temperature until a strain on the first sample stabilizes. Once the strain on the first sample stabilizes, the isothermal treatment is performed on the second sample. During isothermal treatment, different levels of stress on the second sample are applied until a strain on the second sample matches the stabilized strain on the first sample.

EFFECT OF STRAIN FIELD ON THRESHOLD DISPLACEMENT ENERGY OF TUNGSTEN STUDIED BY MOLECULAR DYNAMICS SIMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, D.; Gao, Ning; Setyawan, Wahyu

The influence of hydrostatic strain on point defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten was studied with molecular dynamics simulations. Two different tungsten potentials (Fikar and Juslin) were used. The minimum Ed direction calculated with the Fikar-potential was <100>, but with the Juslin-potential it was <111>. The most stable self-interstitial (SIA) configuration was a <111>-crowdion for both potentials. The stable SIA configuration did not change with applied strain. Varying the strain from compression to tension increased the vacancy formation energy but decreased the SIA formation energy. The SIA formation energy changed more significantly thanmore » for a vacancy such that Ed decreased with applied strain from compression to tension.« less

20 CFR 10.411 - What are the maximum and minimum rates of compensation in death cases?

Code of Federal Regulations, 2011 CFR

2011-04-01

... maximum and minimum rates of compensation in death cases? (a) Compensation for death may not exceed the... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false What are the maximum and minimum rates of compensation in death cases? 10.411 Section 10.411 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...

20 CFR 10.411 - What are the maximum and minimum rates of compensation in death cases?

Code of Federal Regulations, 2013 CFR

2013-04-01

... maximum and minimum rates of compensation in death cases? (a) Compensation for death may not exceed the... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true What are the maximum and minimum rates of compensation in death cases? 10.411 Section 10.411 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...

20 CFR 10.411 - What are the maximum and minimum rates of compensation in death cases?

Code of Federal Regulations, 2012 CFR

2012-04-01

... maximum and minimum rates of compensation in death cases? (a) Compensation for death may not exceed the... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false What are the maximum and minimum rates of compensation in death cases? 10.411 Section 10.411 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...

20 CFR 10.411 - What are the maximum and minimum rates of compensation in death cases?

Code of Federal Regulations, 2014 CFR

2014-04-01

... maximum and minimum rates of compensation in death cases? (a) Compensation for death may not exceed the... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true What are the maximum and minimum rates of compensation in death cases? 10.411 Section 10.411 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...

20 CFR 10.411 - What are the maximum and minimum rates of compensation in death cases?

Code of Federal Regulations, 2010 CFR

2010-04-01

... maximum and minimum rates of compensation in death cases? (a) Compensation for death may not exceed the... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false What are the maximum and minimum rates of compensation in death cases? 10.411 Section 10.411 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...

In vitro and in vivo anti-MRSA activities of nosokomycins.

PubMed

Uchida, Ryuji; Hanaki, Hideaki; Matsui, Hidenori; Hamamoto, Hiroshi; Sekimizu, Kazuhisa; Iwatsuki, Masato; Kim, Yong Pil; Tomoda, Hiroshi

2014-12-01

The anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of nosokomycins A to D discovered in the silkworm-MRSA infection screening was investigated. The minimum inhibitory concentration (MIC) values of nosokomycins for authentic MRSA and S. aureus strains were calculated to be 0.06 to 2.0 μg/mL. They also showed potent inhibitory activity against 54 clinically isolated MRSA strains. Furthermore, nosokomycin A proved effective in the mouse-MRSA infection model.

Bifidobacterium mongoliense sp. nov., from airag, a traditional fermented mare's milk product from Mongolia.

PubMed

Watanabe, Koichi; Makino, Hiroshi; Sasamoto, Masae; Kudo, Yuko; Fujimoto, Junji; Demberel, Shirchin

2009-06-01

Two novel micro-organisms, designated strains YIT 10443(T) and YIT 10738, were isolated from airag, a traditional fermented mare's milk from Mongolia. The two strains were Gram-positive-staining, non-motile, asporogenous, catalase-negative, facultatively anaerobic rods of various shapes. Comparative analyses of 16S rRNA and ClpC ATPase (clpC) gene sequences and the presence of fructose-6-phosphate phosphoketolase (F6PPK) demonstrated that the novel strains were members of the genus Bifidobacterium. On the basis of 16S rRNA gene sequence similarity, the type strains of Bifidobacterium minimum (96.6 %) and Bifidobacterium psychraerophilum (95.7 %) were the closest neighbours of the novel strains, and DNA-DNA reassociation values with these strains were found to be lower than 15 %. The phenotypic and genotypic features demonstrated that the two strains represent a single, novel Bifidobacterium species, for which the name Bifidobacterium mongoliense sp. nov. is proposed. The type strain is YIT 10443(T) (=JCM 15461(T) =DSM 21395(T)).

Strain engineering on electronic structure and carrier mobility in monolayer GeP3

NASA Astrophysics Data System (ADS)

Zeng, Bowen; Long, Mengqiu; Zhang, Xiaojiao; Dong, Yulan; Li, Mingjun; Yi, Yougen; Duan, Haiming

2018-06-01

Using density functional theory coupled with the Boltzmann transport equation with relaxation time approximation, we have studied the strain effect on the electronic structure and carrier mobility of two-dimensional monolayer GeP3. We find that the energies of valence band maximum and conduction band minimum are nearly linearly shifted with a biaxial strain in the range of  ‑4% to 6%, and the band structure experiences a remarkable transition from semiconductor to metal with the appropriate compression (‑5% strain). Under biaxial strain, the mobility of the electron and hole in monolayer GeP3 reduces and increases by more than one order of magnitude, respectively. It is suggested that it is possible to perform successive transitions from an n-type semiconductor (‑4% strain) to a good performance p-semiconductor (+6% strain) by applying strain in monolayer GeP3, which is potentially useful for flexible electronics and nanosized mechanical sensors.

40 CFR Table 3 to Subpart Ec of... - Operating Parameters To Be Monitored and Minimum Measurement and Recording Frequencies

Code of Federal Regulations, 2011 CFR

2011-07-01

... scrubber followed by fabric filter Wet scrubber Dry scrubber followed by fabric filter and wet scrubber... flow rate Hourly 1×hour ✔ ✔ Minimum pressure drop across the wet scrubber or minimum horsepower or amperage to wet scrubber Continuous 1×minute ✔ ✔ Minimum scrubber liquor flow rate Continuous 1×minute...

The Effect of Minimum Wages on Adolescent Fertility: A Nationwide Analysis.

PubMed

Bullinger, Lindsey Rose

2017-03-01

To investigate the effect of minimum wage laws on adolescent birth rates in the United States. I used a difference-in-differences approach and vital statistics data measured quarterly at the state level from 2003 to 2014. All models included state covariates, state and quarter-year fixed effects, and state-specific quarter-year nonlinear time trends, which provided plausibly causal estimates of the effect of minimum wage on adolescent birth rates. A $1 increase in minimum wage reduces adolescent birth rates by about 2%. The effects are driven by non-Hispanic White and Hispanic adolescents. Nationwide, increasing minimum wages by $1 would likely result in roughly 5000 fewer adolescent births annually.

Rheology of welding: experimental constraints

NASA Astrophysics Data System (ADS)

Quane, S. L.; Russell, J. K.; Kennedy, L. A.

2003-04-01

The rheological behavior of pyroclastic deposits during welding is incompletely understood and is based on a surprisingly small number of experimental studies. Previous pioneering experimental studies were done on small (1 cm thick) samples of ash/crystal mixtures under constant load. They established minimum welding temperatures between 600 and 700^oC under loads of 0.7 MPa (˜40 m of ignimbrite) to 3.6 MPa (˜250 m depth of ignimbrite). However, these data are neither sufficiently comprehensive nor coherent enough to fully describe the rheology of pyroclastic mixtures. In addition, previous studies did not examine the microstructural and geometric changes associated with welding compaction. Our goal is to provide accurate and comprehensive constitutive relationships between material properties, temperature, load and strain rate for pyroclastic material undergoing welding. Here we present results from a newly designed experimental apparatus. The experimental apparatus consists of a LoadTrac II fully automated uniaxial compression load frame manufactured by Geocomp Corporation. The load frame has a built in displacement transducer and can run both constant strain rate (10-6 to 0.25 cm/s) and constant load (up to 1150 kg) tests to a maximum displacement of 7.5 cm. The sample assembly comprises 5 cm diameter cylindrical upper and lower pistons (insulating ceramic with steel conductive ends) housed in a copper jacket. Samples are 5 cm diameter cores and can vary in length from 1 to 15 cm depending on experimental needs. A fiber insulated tube furnace capable of reaching temperatures ≈1000^oC surrounds the sample assembly. Temperature is measured using a thermocouple located inside the sample through the bottom piston; the furnace controller is capable of maintaining temperature fluctuations to <5^oC. Deformation experiments are performed on pre-fabricated cylinders of soda-lime glass beads and rhyolitic volcanic ash, as well as, cores of pumiceous rhyodacite. Experimental runs use strain rates of 10-4 and 10-5 cm/s and loads of ˜0 to 4.5 MPa. Experiments are run at temperatures between 400 and 850^oC corresponding to below and above the calorimetric glass transition temperatures of the respective materials. Data deriving from constant load and constant strain rate experiments are being used to constrain rheological models for welding of pyroclastic material.

Microbial recycling of glycerol to biodiesel.

PubMed

Yang, Liu; Zhu, Zhi; Wang, Weihua; Lu, Xuefeng

2013-12-01

The sustainable supply of lipids is the bottleneck for current biodiesel production. Here microbial recycling of glycerol, byproduct of biodiesel production to biodiesel in engineered Escherichia coli strains was reported. The KC3 strain with capability of producing fatty acid ethyl esters (FAEEs) from glucose was used as a starting strain to optimize fermentation conditions when using glycerol as sole carbon source. The YL15 strain overexpressing double copies of atfA gene displayed 1.7-fold increase of FAEE productivity compared to the KC3 strain. The titer of FAEE in YL15 strain reached to 813 mg L(-1) in minimum medium using glycerol as sole carbon source under optimized fermentation conditions. The titer of glycerol-based FAEE production can be significantly increased by both genetic modifications and fermentation optimization. Microbial recycling of glycerol to biodiesel expands carbon sources for biodiesel production. Copyright © 2013 Elsevier Ltd. All rights reserved.

Does water content or flow rate control colloid transport in unsaturated porous media?

PubMed

Knappenberger, Thorsten; Flury, Markus; Mattson, Earl D; Harsh, James B

2014-04-01

Mobile colloids can play an important role in contaminant transport in soils: many contaminants exist in colloidal form, and colloids can facilitate transport of otherwise immobile contaminants. In unsaturated soils, colloid transport is, among other factors, affected by water content and flow rate. Our objective was to determine whether water content or flow rate is more important for colloid transport. We passed negatively charged polystyrene colloids (220 nm diameter) through unsaturated sand-filled columns under steady-state flow at different water contents (effective water saturations Se ranging from 0.1 to 1.0, with Se = (θ - θr)/(θs - θr)) and flow rates (pore water velocities v of 5 and 10 cm/min). Water content was the dominant factor in our experiments. Colloid transport decreased with decreasing water content, and below a critical water content (Se < 0.1), colloid transport was inhibited, and colloids were strained in water films. Pendular ring and water film thickness calculations indicated that colloids can move only when pendular rings are interconnected. The flow rate affected retention of colloids in the secondary energy minimum, with less colloids being trapped when the flow rate increased. These results confirm the importance of both water content and flow rate for colloid transport in unsaturated porous media and highlight the dominant role of water content.

From brittle to ductile fracture in disordered materials.

PubMed

Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

2010-10-08

We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

Antibacterial potential assessment of jasmine essential oil against e. Coli.

PubMed

Rath, C C; Devi, S; Dash, S K; Mishra, R K

2008-01-01

The antibacterial activity of Jasmine (Jasminum sambac L.) flower hydro steam distilled essential oil, synthetic blends and six major individual components was assessed against Escherichia coli (MTCC-443) strain. The activity was bactericidal. Minimum inhibitory concentration was determined by tube dilution technique, and the Minimum inhibitory concentration ranged between 1.9-31.25 mul/ml. Phenolcoefficient of the oil, synthetic blends and components varied between 0.6-1.7. The activity of the chemicals was possibly due to the inhibition of cell membrane synthesis.

Structure for identifying, locating and quantifying physical phenomena

DOEpatents

Richardson, John G.

2006-10-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Method and apparatus for identifying, locating and quantifying physical phenomena and structure including same

DOEpatents

Richardson, John G.

2006-01-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Surveillance of Helicobacter pylori Antibiotic Susceptibility in Indonesia: Different Resistance Types among Regions and with Novel Genetic Mutations

PubMed Central

Miftahussurur, Muhammad; Syam, Ari Fahrial; Nusi, Iswan Abbas; Makmun, Dadang; Waskito, Langgeng Agung; Zein, Lukman Hakim; Akil, Fardah; Uwan, Willy Brodus; Simanjuntak, David; Wibawa, I Dewa Nyoman; Waleleng, Jimmy Bradley; Saudale, Alexander Michael Joseph; Yusuf, Fauzi; Mustika, Syifa; Adi, Pangestu; Maimunah, Ummi; Maulahela, Hasan; Rezkitha, Yudith Annisa Ayu; Subsomwong, Phawinee; Nasronudin; Rahardjo, Dadik; Suzuki, Rumiko; Akada, Junko; Yamaoka, Yoshio

2016-01-01

Information regarding Helicobacter pylori antibiotic resistance in Indonesia was previously inadequate. We assessed antibiotic susceptibility for H. pylori in Indonesia, and determined the association between virulence genes or genetic mutations and antibiotic resistance. We recruited 849 dyspeptic patients who underwent endoscopy in 11 cities in Indonesia. E-test was used to determine the minimum inhibitory concentration of five antibiotics. PCR-based sequencing assessed mutations in 23S rRNA, rdxA, gyrA, gyrB, and virulence genes. Next generation sequencing was used to obtain full-length sequences of 23S rRNA, infB, and rpl22. We cultured 77 strains and identified 9.1% with clarithromycin resistance. Low prevalence was also found for amoxicillin and tetracycline resistance (5.2% and 2.6%, respectively). In contrast, high resistance rates to metronidazole (46.7%) and levofloxacin (31.2%) were demonstrated. Strains isolated from Sumatera Island had significantly higher metronidazole resistance than those from other locations. Metronidazole resistant strains had highly distributed rdxA amino acid substitutions and the 23S rRNA A2143G mutation was associated with clarithromycin resistance (42.9%). However, one strain with the highest MIC value had a novel mutation in rpl22 without an A2143G mutation. Mutation at Asn-87 and/or Asp-91 of gyrA was associated with levofloxacin-resistance and was related to gyrB mutations. In conclusions, although this is a pilot study for a larger survey, our current data show that Indonesian strains had the high prevalence of metronidazole and levofloxacin resistance with low prevalence of clarithromycin, amoxicillin, and tetracycline resistance. Nevertheless, clarithromycin- or metronidazole-based triple therapy should be administered with caution in some regions of Indonesia. PMID:27906990

Surveillance of Helicobacter pylori Antibiotic Susceptibility in Indonesia: Different Resistance Types among Regions and with Novel Genetic Mutations.

PubMed

Miftahussurur, Muhammad; Syam, Ari Fahrial; Nusi, Iswan Abbas; Makmun, Dadang; Waskito, Langgeng Agung; Zein, Lukman Hakim; Akil, Fardah; Uwan, Willy Brodus; Simanjuntak, David; Wibawa, I Dewa Nyoman; Waleleng, Jimmy Bradley; Saudale, Alexander Michael Joseph; Yusuf, Fauzi; Mustika, Syifa; Adi, Pangestu; Maimunah, Ummi; Maulahela, Hasan; Rezkitha, Yudith Annisa Ayu; Subsomwong, Phawinee; Nasronudin; Rahardjo, Dadik; Suzuki, Rumiko; Akada, Junko; Yamaoka, Yoshio

2016-01-01

Information regarding Helicobacter pylori antibiotic resistance in Indonesia was previously inadequate. We assessed antibiotic susceptibility for H. pylori in Indonesia, and determined the association between virulence genes or genetic mutations and antibiotic resistance. We recruited 849 dyspeptic patients who underwent endoscopy in 11 cities in Indonesia. E-test was used to determine the minimum inhibitory concentration of five antibiotics. PCR-based sequencing assessed mutations in 23S rRNA, rdxA, gyrA, gyrB, and virulence genes. Next generation sequencing was used to obtain full-length sequences of 23S rRNA, infB, and rpl22. We cultured 77 strains and identified 9.1% with clarithromycin resistance. Low prevalence was also found for amoxicillin and tetracycline resistance (5.2% and 2.6%, respectively). In contrast, high resistance rates to metronidazole (46.7%) and levofloxacin (31.2%) were demonstrated. Strains isolated from Sumatera Island had significantly higher metronidazole resistance than those from other locations. Metronidazole resistant strains had highly distributed rdxA amino acid substitutions and the 23S rRNA A2143G mutation was associated with clarithromycin resistance (42.9%). However, one strain with the highest MIC value had a novel mutation in rpl22 without an A2143G mutation. Mutation at Asn-87 and/or Asp-91 of gyrA was associated with levofloxacin-resistance and was related to gyrB mutations. In conclusions, although this is a pilot study for a larger survey, our current data show that Indonesian strains had the high prevalence of metronidazole and levofloxacin resistance with low prevalence of clarithromycin, amoxicillin, and tetracycline resistance. Nevertheless, clarithromycin- or metronidazole-based triple therapy should be administered with caution in some regions of Indonesia.

40 CFR 60.37e - Compliance, performance testing, and monitoring guidelines.

Code of Federal Regulations, 2010 CFR

2010-07-01

... requirements: (1) Establish maximum charge rate and minimum secondary chamber temperature as site-specific... above the maximum charge rate or below the minimum secondary chamber temperature measured as 3-hour... below the minimum secondary chamber temperature shall constitute a violation of the established...

76 FR 44339 - Office of Biotechnology Activities; Recombinant DNA Research: Action Under the NIH Guidelines for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-25

...) classification for several common attenuated strains of bacteria and viruses that are frequently used in... establishes the minimum containment level required for experiments subject to the NIH Guidelines. The...

76 FR 62816 - Office of Biotechnology Activities; Recombinant DNA Research: Action Under the NIH Guidelines for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-11

... specify the risk group (RG) classification for several common attenuated strains of bacteria and viruses... minimum containment level required for experiments subject to the NIH Guidelines. The classification of...

Efficient synthesis of new 2,3-dihydrooxazole-spirooxindoles hybrids as antimicrobial agents.

PubMed

Tiwari, Shailendra; Pathak, Poonam; Sagar, Ram

2016-05-15

Two series of new 2,3-dihydrooxazole-spirooxindole derivatives were efficiently synthesized starting from N'-(2-oxoindolin-3-ylidene) benzohydrazide/N'-(2-oxoindolin-3-ylidene)-2-phenoxyacetohydrazide using designed synthetic route. Newly synthesized 2,3-dihydrooxazole-spirooxindole derivatives were screened for their antibacterial and antifungal activity against different pathogenic strain of bacteria and fungi. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) were determined for the test compounds as well as for reference standards. Compounds 4e, 4g, 7g have shown good antibacterial activity whereas compounds 4f, 7b, 7d have displayed better antifungal activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of the in vitro activity of levornidazole, its metabolites and comparators against clinical anaerobic bacteria.

PubMed

Hu, Jiali; Zhang, Jing; Wu, Shi; Zhu, Demei; Huang, Haihui; Chen, Yuancheng; Yang, Yang; Zhang, Yingyuan

2014-12-01

This study evaluated the in vitro anti-anaerobic activity and spectrum of levornidazole, its metabolites and comparators against 375 clinical isolates of anaerobic bacteria, including Gram-negative bacilli (181 strains), Gram-negative cocci (11 strains), Gram-positive bacilli (139 strains) and Gram-positive cocci (44 strains), covering 34 species. Minimum inhibitory concentrations (MICs) of levornidazole, its five metabolites and three comparators against these anaerobic isolates were determined by the agar dilution method. Minimum bactericidal concentrations (MBCs) of levornidazole and metronidazole were measured against 22 strains of Bacteroides fragilis. Levornidazole showed good activity against B. fragilis, other Bacteroides spp., Clostridium difficile, Clostridium perfringens and Peptostreptococcus magnus, evidenced by MIC90 values of 0.5, 1, 0.25, 2 and 1mg/L, respectively. The activity of levornidazole and the comparators was poor for Veillonella spp. Generally, levornidazole displayed activity similar to or slightly higher than that of metronidazole, ornidazole and dextrornidazole against anaerobic Gram-negative bacilli, Gram-positive bacilli and Gram-positive cocci, especially B. fragilis. Favourable anti-anaerobic activity was also seen with levornidazole metabolites M1 and M4 but not M2, M3 or M5. For the 22 clinical B. fragilis strains, MBC50 and MBC90 values of levornidazole were 2mg/L and 4mg/L, respectively. Both MBC50/MIC50 and MBC90/MIC90 ratios of levornidazole were 4, similar to those of metronidazole. Levornidazole is an important anti-anaerobic option in clinical settings in terms of its potent and broad-spectrum in vitro activity, bactericidal property, and the anti-anaerobic activity of its metabolites M1 and M4. Copyright © 2014 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Evaluation of Antimicrobial Activity of the Methanol Extracts from 8 Traditional Medicinal Plants

PubMed Central

Kang, Chang-Geun; Hah, Dae-Sik; Kim, Chung-Hui; Kim, Young-Hwan; Kim, Euikyung

2011-01-01

The methanol extract of 12 medicinal plants were evaluated for its antibacterial activity against Gram-positive (5 strains) and Gram-negative bacteria (10 strains) by assay for minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) . The antibacterial activity was determined by an agar dilution method (according to the guidelines of Clinical and Laboratory Standard Institute) . All the compounds (12 extracts) of the 8 medicinal plants (leaf or root) were active against both Gram-negative and Gram-positive bacteria. Gram-negative showed a more potent action than Gram positive bacteria. The MIC concentrations were various ranged from 0.6 μg/ml to 5000 μg/ml. The lowest MIC (0.6 μg/ml) and MBC (1.22 μg/ml) values were obtained with extract on 4 and 3 of the 15 microorganisms tested, respectively. PMID:24278548

Impact of heat release on strain rate field in turbulent premixed Bunsen flames

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coriton, Bruno Rene Leon; Frank, Jonathan H.

2016-08-10

The effects of combustion on the strain rate field are investigated in turbulent premixed CH 4/air Bunsen flames using simultaneous tomographic PIV and OH LIF measurements. Tomographic PIV provides three-dimensional velocity measurements, from which the complete strain rate tensor is determined. The OH LIF measurements are used to determine the position of the flame surface and the flame-normal orientation within the imaging plane. This combination of diagnostic techniques enables quantification of divergence as well as flame-normal and tangential strain rates, which are otherwise biased using only planar measurements. Measurements are compared in three lean-to-stoichiometric flames that have different amounts ofmore » heat release and Damköhler numbers greater than unity. The effects of heat release on the principal strain rates and their alignment relative to the local flame normal are analyzed. The extensive strain rate preferentially aligns with the flame normal in the reaction zone, which has been indicated by previous studies. The strength of this alignment increases with increasing heat release and, as a result, the flame-normal strain rate becomes highly extensive. These effects are associated with the gas expansion normal to the flame surface, which is largest for the stoichiometric flame. In the preheat zone, the compressive strain rate has a tendency to align with the flame normal. Away from the flame front, the flame – strain rate alignment is arbitrary in both the reactants and products. The flame-tangential strain rate is on average positive across the flame front, and therefore the turbulent strain rate field contributes to the enhancement of scalar gradients as in passive scalar turbulence. As a result, increases in heat release result in larger positive values of the divergence as well as flame-normal and tangential strain rates, the tangential strain rate has a weaker dependence on heat release than the flame-normal strain rate and the divergence.« less

Minimum airflow reset of single-duct VAV terminal boxes

NASA Astrophysics Data System (ADS)

Cho, Young-Hum

Single duct Variable Air Volume (VAV) systems are currently the most widely used type of HVAC system in the United States. When installing such a system, it is critical to determine the minimum airflow set point of the terminal box, as an optimally selected set point will improve the level of thermal comfort and indoor air quality (IAQ) while at the same time lower overall energy costs. In principle, this minimum rate should be calculated according to the minimum ventilation requirement based on ASHRAE standard 62.1 and maximum heating load of the zone. Several factors must be carefully considered when calculating this minimum rate. Terminal boxes with conventional control sequences may result in occupant discomfort and energy waste. If the minimum rate of airflow is set too high, the AHUs will consume excess fan power, and the terminal boxes may cause significant simultaneous room heating and cooling. At the same time, a rate that is too low will result in poor air circulation and indoor air quality in the air-conditioned space. Currently, many scholars are investigating how to change the algorithm of the advanced VAV terminal box controller without retrofitting. Some of these controllers have been found to effectively improve thermal comfort, indoor air quality, and energy efficiency. However, minimum airflow set points have not yet been identified, nor has controller performance been verified in confirmed studies. In this study, control algorithms were developed that automatically identify and reset terminal box minimum airflow set points, thereby improving indoor air quality and thermal comfort levels, and reducing the overall rate of energy consumption. A theoretical analysis of the optimal minimum airflow and discharge air temperature was performed to identify the potential energy benefits of resetting the terminal box minimum airflow set points. Applicable control algorithms for calculating the ideal values for the minimum airflow reset were developed and applied to actual systems for performance validation. The results of the theoretical analysis, numeric simulations, and experiments show that the optimal control algorithms can automatically identify the minimum rate of heating airflow under actual working conditions. Improved control helps to stabilize room air temperatures. The vertical difference in the room air temperature was lower than the comfort value. Measurements of room CO2 levels indicate that when the minimum airflow set point was reduced it did not adversely affect the indoor air quality. According to the measured energy results, optimal control algorithms give a lower rate of reheating energy consumption than conventional controls.

Isolation and characterization of Sphingomonas sp. Y2 capable of high-efficiency degradation of nonylphenol polyethoxylates in wastewater.

PubMed

Bai, Naling; Wang, Sheng; Abuduaini, Rexiding; Zhu, Xufen; Zhao, Yuhua

2016-06-01

Nonylphenol polyethoxylates (NPEOs), although banned for decades, are still widely used in manufactories and thus affect human lives. In this study, a highly efficient NPEO-degrading bacterium, Sphingomonas sp. Y2, was isolated from sewage sludge by enrichment culture. Strain Y2 ensured the complete removal of NPEO in 48 h and degraded 99.2 % NPEO (1,000 mg L(-1)) within 30 h at a specific growth rate of 0.73 h(-1) in minimum salt medium. To date, this degradation efficiency is the highest reported for NPEO metabolism by a pure bacterium under this condition. Furthermore, the application of this bacterium to wastewater treatment demonstrated that it metabolized 98.5 % NPEO (1,000 mg L(-1)) within 5 days with a specific growth rate of 2.03 day(-1). The degradation intermediates, identified as nonylphenol, short-chain NPEOs and short-chain nonylphenol polyethoxycarboxylates by high-performance liquid chromatography and gas chromatography-mass spectrometry, indicated the sequential exo-cleavage of the EO chain. Additionally, the enzymes involved in the biodegradation were inducible rather than constitutive. Considering that strain Y2 exhibits prominent biodegradation advantages in industrial wastewater treatment, it might serve as a promising potential candidate for in situ bioremediation of contamination by NPEOs and other structurally similar compounds.

Effect of strain rate on bake hardening response of BH220 steel

NASA Astrophysics Data System (ADS)

Das, Anindya; Tarafder, Soumitro; Sivaprasad, S.; Chakrabarti, Debalay

2015-09-01

This study aims at understanding the bake hardening ability of ultra low carbon BH220 steel at different strain rates. The as-received material has been pre-strained to four different levels and then deformed in tension under (a) as pre-strained state and (b) after baking at 170 ∘C for 20 minutes, at three different strain rates of 0.001, 0.1 and 100/s. In both the conditions, yield stress increased with pre-strain and strain rate, but bake hardening ability was found to decrease when strain rate was increased. The strain rate sensitivity of the material was also found to decrease with bake hardening. Generation of dislocation forests and their subsequent immobility during baking treatment enables them to act as long range obstacles during further deformation. At higher strain rates, less amount of dislocations are produced which can interact with themselves and produce hardening, because of which bake hardening ability and the strain rate drops. A dislocation based strengthening model, as proposed by Larour et al. 2011 [7], was used to predict the yield stress values obtained at different conditions. The equation produced excellent co-relation with the experimental data.

Earthquake nucleation on faults with rate-and state-dependent strength

USGS Publications Warehouse

Dieterich, J.H.

1992-01-01

Dieterich, J.H., 1992. Earthquake nucleation on faults with rate- and state-dependent strength. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 115-134. Faults with rate- and state-dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability. Calculations with a plane-strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch. The dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip. The critical length is a function of normal stress, loading conditions and constitutive parameters which include Dc, the characteristic slip distance. If slip starts on a patch that exceeds the critical size, the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches. Solutions have been obtained for a uniform, fixed-patch model that are in good agreement with results from the plane-strain model. Over a wide range of conditions, above the steady-state stress, the logarithm of the time to instability linearly decreases as the initial stress increases. Because nucleation patch length and premonitory displacement are proportional to Dc, the moment of premonitory slip scales by D3c. The scaling of Dc is currently an open question. Unless Dc for earthquake faults is significantly greater than that observed on laboratory faults, premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods. Excluding the possibility that Dc in the nucleation zone controls the magnitude of the subsequent earthquake, then the source dimensions of the smallest earthquakes in a region provide an upper limit for the size of the nucleation patch. ?? 1992.

Strong antimicrobial activity of xanthohumol and other derivatives from hops (Humulus lupulus L.) on gut anaerobic bacteria.

PubMed

Cermak, Pavel; Olsovska, Jana; Mikyska, Alexandr; Dusek, Martin; Kadleckova, Zuzana; Vanicek, Jiri; Nyc, Otakar; Sigler, Karel; Bostikova, Vanda; Bostik, Pavel

2017-11-01

Anaerobic bacteria, such as Bacteroides fragilis or Clostridium perfringens, are part of indigenous human flora. However, Clostridium difficile represents also an important causative agent of nosocomial infectious antibiotic-associated diarrhoea. Treatment of C. difficile infection is problematic, making it imperative to search for new compounds with antimicrobial properties. Hops (Humulus lupulus L.) contain substances with antibacterial properties. We tested antimicrobial activity of purified hop constituents humulone, lupulone and xanthohumol against anaerobic bacteria. The antimicrobial activity was established against B. fragilis, C. perfringens and C. difficile strains according to standard testing protocols (CLSI, EUCAST), and the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBC) were calculated. All C. difficile strains were toxigenic and clinically relevant, as they were isolated from patients with diarrhoea. Strongest antimicrobial effects were observed with xanthohumol showing MIC and MBC values of 15-107 μg/mL, which are close to those of conventional antibiotics in the strains of bacteria with increased resistance. Slightly higher MIC and MBC values were obtained with lupulone followed by higher values of humulone. Our study, thus, shows a potential of purified hop compounds, especially xanthohumol, as alternatives for treatment of infections caused by select anaerobic bacteria, namely nosocomial diarrhoea caused by resistant strains. © 2017 APMIS. Published by John Wiley & Sons Ltd.

Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

PubMed Central

Min, Fanlu; Yao, Zhanhu; Jiang, Teng

2014-01-01

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1 to 10−4 s−1 in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates. PMID:24883355

The strain-rate sensitivity of high-strength high-toughness steels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dilmore, M.F.; Crenshaw, Thomas B.; Boyce, Brad Lee

2006-01-01

The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate.more » Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.« less

Prevalence of current patterns and predictive trends of multidrug-resistant Salmonella Typhi in Sudan.

PubMed

Elshayeb, Ayman A; Ahmed, Abdelazim A; El Siddig, Marmar A; El Hussien, Adil A

2017-11-14

Enteric fever has persistence of great impact in Sudanese public health especially during rainy season when the causative agent Salmonella enterica serovar Typhi possesses pan endemic patterns in most regions of Sudan - Khartoum. The present study aims to assess the recent state of antibiotics susceptibility of Salmonella Typhi with special concern to multidrug resistance strains and predict the emergence of new resistant patterns and outbreaks. Salmonella Typhi strains were isolated and identified according to the guidelines of the International Standardization Organization and the World Health Organization. The antibiotics susceptibilities were tested using the recommendations of the Clinical Laboratories Standards Institute. Predictions of emerging resistant bacteria patterns and outbreaks in Sudan were done using logistic regression, forecasting linear equations and in silico simulations models. A total of 124 antibiotics resistant Salmonella Typhi strains categorized in 12 average groups were isolated, different patterns of resistance statistically calculated by (y = ax - b). Minimum bactericidal concentration's predication of resistance was given the exponential trend (y = n e x ) and the predictive coefficient R 2  > 0 < 1 are approximately alike. It was assumed that resistant bacteria occurred with a constant rate of antibiotic doses during the whole experimental period. Thus, the number of sensitive bacteria decreases at the same rate as resistant occur following term to the modified predictive model which solved computationally. This study assesses the prediction of multi-drug resistance among S. Typhi isolates by applying low cost materials and simple statistical methods suitable for the most frequently used antibiotics as typhoid empirical therapy. Therefore, bacterial surveillance systems should be implemented to present data on the aetiology and current antimicrobial drug resistance patterns of community-acquired agents causing outbreaks.

In Situ Biosurfactant Production by Bacillus Strains Injected into a Limestone Petroleum Reservoir▿

PubMed Central

Youssef, N.; Simpson, D. R.; Duncan, K. E.; McInerney, M. J.; Folmsbee, M.; Fincher, T.; Knapp, R. M.

2007-01-01

Biosurfactant-mediated oil recovery may be an economic approach for recovery of significant amounts of oil entrapped in reservoirs, but evidence that biosurfactants can be produced in situ at concentrations needed to mobilize oil is lacking. We tested whether two Bacillus strains that produce lipopeptide biosurfactants can metabolize and produce their biosurfactants in an oil reservoir. Five wells that produce from the same Viola limestone formation were used. Two wells received an inoculum (a mixture of Bacillus strain RS-1 and Bacillus subtilis subsp. spizizenii NRRL B-23049) and nutrients (glucose, sodium nitrate, and trace metals), two wells received just nutrients, and one well received only formation water. Results showed in situ metabolism and biosurfactant production. The average concentration of lipopeptide biosurfactant in the produced fluids of the inoculated wells was about 90 mg/liter. This concentration is approximately nine times the minimum concentration required to mobilize entrapped oil from sandstone cores. Carbon dioxide, acetate, lactate, ethanol, and 2,3-butanediol were detected in the produced fluids of the inoculated wells. Only CO2 and ethanol were detected in the produced fluids of the nutrient-only-treated wells. Microbiological and molecular data showed that the microorganisms injected into the formation were retrieved in the produced fluids of the inoculated wells. We provide essential data for modeling microbial oil recovery processes in situ, including growth rates (0.06 ± 0.01 h−1), carbon balances (107% ± 34%), biosurfactant production rates (0.02 ± 0.001 h−1), and biosurfactant yields (0.015 ± 0.001 mol biosurfactant/mol glucose). The data demonstrate the technical feasibility of microbial processes for oil recovery. PMID:17172458

In vitro inhibitory activities of magnolol against Candida spp.

PubMed

Zhou, Peiru; Fu, Jingya; Hua, Hong; Liu, Xiaosong

2017-01-01

Candida spp. cause various infections involving the skin, mucosa, deep tissues, and even life-threatening candidemia. They are regarded as an important pathogen of nosocomial bloodstream infection, with a high mortality rate. As a result of prolonged exposure to azoles, the therapeutic failure associated with azoles resistance has become a serious challenge in clinical situations. Therefore, novel, alternative antifungals are required urgently. In the present study, the CLSI M-27A broth microdilution method and the 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay were used to evaluate the antifungal effects of magnolol against various standard Candida strains in planktonic mode and biofilm formation, respectively. The antifungal activity of magnolol was demonstrated in planktonic C. albicans and non-albicans Candida species, especially fluconazole-resistant Candida krusei , with the minimum inhibitory concentrations ranging from 10 to 40 μg/mL. The BMIC 90 (minimum concentration with 90% Candida biofilm inhibited) values of magnolol ranged from 20 to 160 μg/mL, whereas the BMIC 90 values of fluconazole were more than 128 μg/mL. As an alternative and broad-spectrum antifungal agent, magnolol might be of benefit to the treatment of refractory Candida infection.

Comparison of strain rates of dart impacted plaques and pendulum impacted bumpers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scammell, K.L.

1987-01-01

The difference in strain rates prevailing during pendulum impact of bumpers versus high speed dart impact of plaques was investigated. Uni-axial strain gages were applied to the tension side of the plaques and bumpers directly opposite the point of impact. The plaques were impacted with an instrumented high rate dart impact tester and the bumpers impacted with a full scale bumper pendulum impact tester. Theoretical calculations and actual strain rate data support the conclusion that the strain rate of a plaque during dart impact significantly exceeds that of bumper strain rate during pendulum impact.

Power-law viscous materials for analogue experiments: New data on the rheology of highly-filled silicone polymers

NASA Astrophysics Data System (ADS)

Boutelier, D.; Schrank, C.; Cruden, A.

2008-03-01

The selection of appropriate analogue materials is a central consideration in the design of realistic physical models. We investigate the rheology of highly-filled silicone polymers in order to find materials with a power-law strain-rate softening rheology suitable for modelling rock deformation by dislocation creep and report the rheological properties of the materials as functions of the filler content. The mixtures exhibit strain-rate softening behaviour but with increasing amounts of filler become strain-dependent. For the strain-independent viscous materials, flow laws are presented while for strain-dependent materials the relative importance of strain and strain rate softening/hardening is reported. If the stress or strain rate is above a threshold value some highly-filled silicone polymers may be considered linear visco-elastic (strain independent) and power-law strain-rate softening. The power-law exponent can be raised from 1 to ˜3 by using mixtures of high-viscosity silicone and plasticine. However, the need for high shear strain rates to obtain the power-law rheology imposes some restrictions on the usage of such materials for geodynamic modelling. Two simple shear experiments are presented that use Newtonian and power-law strain-rate softening materials. The results demonstrate how materials with power-law rheology result in better strain localization in analogue experiments.

Antimicrobial susceptibilities and molecular typing of neisseria gonorrhoeae isolates at a medical centre in Taiwan, 2001-2013 with an emphasis on high rate of azithromycin resistance among the isolates.

PubMed

Liu, Yen-Hung; Huang, Yu-Tsung; Liao, Chun-Hsing; Hsueh, Po-Ren

2018-05-01

A high prevalence of gonococcal resistance to various antimicrobials and Neisseria gonorrhoeae isolates exhibiting resistance to extended-spectrum cephalosporins have been reported in the past few decades. A total of 226 N. gonorrhoeae isolates obtained from the National Taiwan University Hospital from 2001 to 2013 were evaluated. The minimum inhibitory concentrations (MICs) of the isolates to antimicrobials were determined by the agar dilution method and interpreted using the 2017 clinical breakpoints or epidemiological cut-off values recommended by the Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST). The genetic relatedness of these isolates was determined by multilocus sequence typing. None of the isolates was resistant to ceftriaxone and cefotaxime, and the resistance rates to cefixime, spectinomycin, cefpodoxime, ciprofloxacin, and penicillin were 0.4%, 0.4%, 13.3%, 91.6%, and 87.6%, respectively. The rate of isolates resistant to azithromycin was 14.6% (EUCAST criteria), which is higher than in previous surveillance studies. A total of 57 sequence types (ST) were identified, and ST1901, ST7365, and ST1927 prevailed. Isolates of ST8143 emerged after 2011. ST1901 isolates had relatively higher MIC values for ceftriaxone and azithromycin than those of the other STs. In conclusion, ceftriaxone remains an effective drug of choice for gonorrhoeal management in Taiwan. High rates of azithromycin resistance among N. gonorrhoeae isolates were found. The circulating ST1901 strains with high MIC values for ceftriaxone and azithromycin and the emerging ST8143 strains were alarming. Copyright © 2018 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Evaluation of the antimicrobial efficacy of Minthostachys verticillata essential oil and limonene against Streptococcus uberis strains isolated from bovine mastitis.

PubMed

Montironi, Ivana D; Cariddi, Laura N; Reinoso, Elina B

Bovine mastitis is a disease that causes great economic losses per year, being Streptococcus uberis the main environmental pathogen involved. The aim of the present study was to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of Minthostachys verticillata essential oil and limonene for S. uberis strains isolated from bovine mastitis. In addition, the effect of MIC on biofilm formation was analyzed. MIC values for the essential oil ranged from 14.3 to 114.5mg/ml (1.56-12.5%v/v) and MBC between 114.5 and 229mg/ml (12.5-25%v/v). MICs for limonene ranged from 3.3 to 52.5mg/ml (0.39-6.25%v/v) and MBC was 210mg/ml (25%v/v). Both compounds showed antibacterial activity and affected the biofilm formation of most of the strains tested. In conclusion, these compounds could be used as an alternative and/or complementary therapy for bovine mastitis caused by S. uberis. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Rate-compatible protograph LDPC code families with linear minimum distance

NASA Technical Reports Server (NTRS)

Divsalar, Dariush (Inventor); Dolinar, Jr., Samuel J (Inventor); Jones, Christopher R. (Inventor)

2012-01-01

Digital communication coding methods are shown, which generate certain types of low-density parity-check (LDPC) codes built from protographs. A first method creates protographs having the linear minimum distance property and comprising at least one variable node with degree less than 3. A second method creates families of protographs of different rates, all having the linear minimum distance property, and structurally identical for all rates except for a rate-dependent designation of certain variable nodes as transmitted or non-transmitted. A third method creates families of protographs of different rates, all having the linear minimum distance property, and structurally identical for all rates except for a rate-dependent designation of the status of certain variable nodes as non-transmitted or set to zero. LDPC codes built from the protographs created by these methods can simultaneously have low error floors and low iterative decoding thresholds, and families of such codes of different rates can be decoded efficiently using a common decoding architecture.

Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of Strain Rate and Temperature

PubMed Central

Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Luo, Wen-Zhen

2011-01-01

A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under strain rates ranging from 1 × 103 s−1 to 5 × 103 s−1 and temperatures between 25°C and 800°C. The results indicate that the flow stress, work-hardening rate, strain rate sensitivity, and thermal activation energy are all significantly dependent on the strain, strain rate, and temperature. For a constant temperature, the flow stress, work-hardening rate, and strain rate sensitivity increase with increasing strain rate, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a strain rate of 5 × 103 s−1 and temperatures of 25°C or 200°C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing strain rate. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of 800°C. PMID:22216015

Automatic procedure for stable tetragonal or hexagonal structures: application to tetragonal Y and Cd

NASA Astrophysics Data System (ADS)

Marcus, P. M.; Jona, F.

2005-05-01

A simple effective procedure (MNP) for finding equilibrium tetragonal and hexagonal states under pressure is described and applied. The MNP procedure finds a path to minima of the Gibbs free energy G at T=0 K (G=E+pV, E=energy per atom, p=pressure, V=volume per atom) for tetragonal and hexagonal structures by using the approximate expansion of G in linear and quadratic strains at an arbitrary initial structure to find a change in the strains which moves toward a minimum of G. Iteration automatically proceeds to a minimum within preset convergence criteria on the calculation of the minimum. Comparison is made with experimental results for the ground states of seven metallic elements in hexagonal close-packed (hcp), face- and body-centered cubic structures, and with a previous procedure for finding minima based on tracing G along the epitaxial Bain path (EBP) to a minimum; the MNP is more easily generalized than the EBP procedure to lower symmetry and more atoms in the unit cell. Comparison is also made with a molecular-dynamics program for crystal equilibrium structures under pressure and with CRYSTAL, a program for crystal equilibrium structures at zero pressure. Application of MNP to the elements Y and Cd, which have hcp ground states at zero pressure, finds minima of E at face-centered cubic (fcc) structure for both Y and Cd. Evaluation of all the elastic constants shows that fcc Y is stable, hence a metastable phase, but fcc Cd is unstable.

Candida parapsilosis as a Potent Biocontrol Agent against Growth and Aflatoxin Production by Aspergillus Species

PubMed Central

Niknejad, F; Zaini, F; Faramarzi, MA; Amini, M; Kordbacheh, P; Mahmoudi, M; Safara, M

2012-01-01

Background: Aflatoxin contamination of food and feed stuff is a serious health problem and significant economic concerns. In the present study, the inhibitory effect of Candida parapsilosis IP1698 on mycelial growth and aflatoxin production in aflatoxigenic strains of Aspergillus species was investigated. Methods: Mycelial growth inhibitions of nine strains of aflatoxigenic and non-aflatoxigenic Aspergillus species in the presence of C. parapsilosis investigated by pour plate technique at different pH, temperature and time of incubation. Reduction of aflatoxin was evaluated in co-cultured fungi in yeast extract sucrose broth after seven days of incubation using HPLC method. The data were analyzed by SPSS 11.5. Results: The presence of the C. parapsilosis at different pH did not affect significantly the growth rate of Aspergillus isolates. On the other hand, temperature and time of incubation showed to be significantly effective when compared to controls without C. parapsilosis (P≤0.05). In aflatoxigenic strains, minimum percentage of reductions in total aflatoxin and B1, B2, G1, G2 fractions were 92.98, 92.54, 77.48, 54.54 and 72.22 and maximum percentage of reductions were 99.59, not detectable, 94.42, and not detectable in both G1 and G2, respectively. Conclusion: C. parapsilosis might employ as a good biocontrol agent against growth and aflatoxin production by aflatoxigenic Aspergillus species PMID:23308351

Antibiotic susceptibility of probiotic strains: Is it reasonable to combine probiotics with antibiotics?

PubMed

Neut, C; Mahieux, S; Dubreuil, L J

2017-11-01

The main goal of this study was to determine the in vitro susceptibility of strains collected from marketed probiotics to antibiotics used to treat community-acquired infections. The minimum inhibitory concentrations (MICs) of 16 antibiotics were determined using a gradient strip (E test) or the agar dilution method for fidaxomicin. The probiotics demonstrated various antibiotic patterns. Bacterial probiotics are generally susceptible to most prescribed antibiotics orally administered, whereas yeast probiotics, such as Saccharomyces boulardii, are resistant. Special attention must be paid to co-prescriptions of antibiotics and probiotics to ensure that the probiotic strain is not susceptible. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Antimicrobial activity of LBM415 (NVP PDF-713) tested against pathogenic Neisseria spp. (Neisseria gonorrhoeae and Neisseria meningitidis).

PubMed

Jones, Ronald N; Sader, Helio S; Fritsche, Thomas R

2005-02-01

LBM415 (NVP PDF-713), a novel peptide deformylase inhibitor, was tested by reference methods against 2 collections of pathogenic Neisseria, N. gonorrhoeae (157 strains) and N. meningitidis (100 strains). The collection included strains resistant to penicillin, tetracycline, and fluoroquinolones and were also tested against ceftriaxone, ciprofloxacin, penicillin, and tetracycline. The 50% and 90% minimum inhibitory concentration values for LBM415 were 1 and 2 microg/mL, and 4 and 8 microg/mL for N. meningitidis and N. gonorrhoeae, respectively. All comparison agents were more active than this peptide deformylase inhibitor against this genus.

Synthesis, antibacterial and cytotoxic activities of new biflorin-based hydrazones and oximes.

PubMed

da S Souza, Luciana G; Almeida, Macia C S; Lemos, Telma L G; Ribeiro, Paulo R V; de Brito, Edy S; Silva, Vera L M; Silva, Artur M S; Braz-Filho, Raimundo; Costa, José G M; Rodrigues, Fábio F G; Barreto, Francisco S; de Moraes, Manoel O

2016-01-15

Biflorin 1 is a biologically active quinone, isolated from Capraria biflora. Five new biflorin-based nitrogen derivatives were synthesized, of which two were mixtures of (E)- and (Z)- isomers: (Z)-2a, (Z)-2b, (Z)-3a, (Z)- and (E)-3b, (Z)- and (E)-3c. The antibacterial activity was investigated using the microdilution method for determining the minimum inhibitory concentration (MIC) against six bacterial strains. Tests have shown that these derivatives have potential against all bacterial strains. The cytotoxic activity was also evaluated against three strains of cancer cells, but none of the derivatives showed activity. Copyright © 2015. Published by Elsevier Ltd.

12 CFR Appendix A to Subpart A of... - Minimum Capital Components for Interest Rate and Foreign Exchange Rate Contracts

Code of Federal Regulations, 2011 CFR

2011-01-01

... interest rate and foreign exchange rate contracts are computed on the basis of the credit equivalent amounts of such contracts. Credit equivalent amounts are computed for each of the following off-balance... Equivalent Amounts a. The minimum capital components for interest rate and foreign exchange rate contracts...

Elastic strain relaxation in interfacial dislocation patterns: I. A parametric energy-based framework

NASA Astrophysics Data System (ADS)

Vattré, A.

2017-08-01

A parametric energy-based framework is developed to describe the elastic strain relaxation of interface dislocations. By means of the Stroh sextic formalism with a Fourier series technique, the proposed approach couples the classical anisotropic elasticity theory with surface/interface stress and elasticity properties in heterogeneous interface-dominated materials. For any semicoherent interface of interest, the strain energy landscape is computed using the persistent elastic fields produced by infinitely periodic hexagonal-shaped dislocation configurations with planar three-fold nodes. A finite element based procedure combined with the conjugate gradient and nudged elastic band methods is applied to determine the minimum-energy paths for which the pre-computed energy landscapes yield to elastically favorable dislocation reactions. Several applications on the Au/Cu heterosystems are given. The simple and limiting case of a single set of infinitely periodic dislocations is introduced to determine exact closed-form expressions for stresses. The second limiting case of the pure (010) Au/Cu heterophase interfaces containing two crossing sets of straight dislocations investigates the effects due to the non-classical boundary conditions on the stress distributions, including separate and appropriate constitutive relations at semicoherent interfaces and free surfaces. Using the quantized Frank-Bilby equation, it is shown that the elastic strain landscape exhibits intrinsic dislocation configurations for which the junction formation is energetically unfavorable. On the other hand, the mismatched (111) Au/Cu system gives rise to the existence of a minimum-energy path where the fully strain-relaxed equilibrium and non-regular intrinsic hexagonal-shaped dislocation rearrangement is accompanied by a significant removal of the short-range elastic energy.

Building Finite Element Models to Investigate Zebrafish Jaw Biomechanics.

PubMed

Brunt, Lucy H; Roddy, Karen A; Rayfield, Emily J; Hammond, Chrissy L

2016-12-03

Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical strain. Skeletal joints are subjected to dynamic mechanical loading. Finite element analysis (FEA) is a computational method, frequently used in engineering that can predict how a material or structure will respond to mechanical input. By dividing a whole system (in this case the zebrafish jaw skeleton) into a mesh of smaller 'finite elements', FEA can be used to calculate the mechanical response of the structure to external loads. The results can be visualized in many ways including as a 'heat map' showing the position of maximum and minimum principal strains (a positive principal strain indicates tension while a negative indicates compression. The maximum and minimum refer the largest and smallest strain). These can be used to identify which regions of the jaw and therefore which cells are likely to be under particularly high tensional or compressional loads during jaw movement and can therefore be used to identify relationships between mechanical strain and cell behavior. This protocol describes the steps to generate Finite Element models from confocal image data on the musculoskeletal system, using the zebrafish lower jaw as a practical example. The protocol leads the reader through a series of steps: 1) staining of the musculoskeletal components, 2) imaging the musculoskeletal components, 3) building a 3 dimensional (3D) surface, 4) generating a mesh of Finite Elements, 5) solving the FEA and finally 6) validating the results by comparison to real displacements seen in movements of the fish jaw.

Growth Inhibition and Morphological Alterations of Trichophyton Rubrum Induced by Essential oil from Cymbopogon Winterianus Jowitt Ex Bor

PubMed Central

de Oliveira Pereira, Fillipe; Alves Wanderley, Paulo; Cavalcanti Viana, Fernando Antônio; Baltazar de Lima, Rita; Barbosa de Sousa, Frederico; de Oliveira Lima, Edeltrudes

2011-01-01

Trichophyton rubrum is one of the most common fungi causer of dermatophytosis, mycosis that affect humans and animals around the world. Researches aiming new products with antifungal activity become necessary to overcome difficulties on treatment of these infections. Accordingly, this study aimed to investigate the antifungal activity of essential oil from Cymbopogon winterianus against the dermatophyte T. rubrum. The antifungal screening was performed by solid medium diffusion method with 16 T. rubrum strains, minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) were determined using the microdilution method. The effects on mycelial dry weight and morphology were also observed. Screening showed essential oil in natura inhibited all the tested strains, with inhibition zones between 24-28 mm diameter. MIC50 and MIC90 values of the essential oil were 312 μg/mL for nearly all the essayed strains (93.75 %) while the MFC50 and MFC90 values were about eight times higher than MIC for all tested strains. All tested essential oil concentrations managed to inhibit strongly the mycelium development. Main morphological changes on the fungal strains observed under light microscopy, which were provided by the essential oil include loss of conidiation, alterations concerning form and pigmentation of hyphae. In the oil presence, colonies showed folds, cream color and slightly darker than the control, pigment production was absent on the reverse and with evident folds. It is concluded that C. winterianus essential oil showed activity against T. rubrum. Therefore, it could be known as potential antifungal compound especially for protection against dermatophytosis. PMID:24031626

Predicting the compressibility behaviour of tire shred samples for landfill applications.

PubMed

Warith, M A; Rao, Sudhakar M

2006-01-01

Tire shreds have been used as an alternative to crushed stones (gravel) as drainage media in landfill leachate collection systems. The highly compressible nature of tire shreds (25-47% axial strain on vertical stress applications of 20-700 kPa) may reduce the thickness of the tire shred drainage layer to less than 300 mm (minimum design requirement) during the life of the municipal solid waste landfill. There hence exists a need to predict axial strains of tire shred samples in response to vertical stress applications so that the initial thickness of the tire shred drainage layer can be corrected for compression. The present study performs one-dimensional compressibility tests on four tire shred samples and compares the results with stress/strain curves from other studies. The stress/strain curves are developed into charts for choosing the correct initial thickness of tire shred layers that maintain the minimum thickness of 300 mm throughout the life of the landfill. The charts are developed for a range of vertical stresses based on the design height of municipal waste cell and bulk unit weight of municipal waste. Experimental results also showed that despite experiencing large axial strains, the average permeability of the tire shred sample consistently remained two to three orders of magnitude higher than the design performance criterion of 0.01cm/s for landfill drainage layers. Laboratory experiments, however, need to verify whether long-term chemical and bio-chemical reactions between landfill leachate and the tire shred layer will deteriorate their mechanical functions (hydraulic conductivity, compressibility, strength) beyond permissible limits for geotechnical applications.

Antimicrobial potential and taxonomic investigation of piezotolerant Streptomyces sp. NIOT-Ch-40 isolated from deep-sea sediment.

PubMed

Padmanaban, Vishnu Priya; Verma, Pankaj; Venkatabaskaran, Srividhyalakshmi; Keppayan, Thirupathi; Gopal, Dharani; Sekar, Ashok Kumar; Ramalingam, Kirubagaran

2017-02-01

Microbial-derived natural products from extreme niches such as deepsea are known to possess structural and functional novelty. With this background, the present study was designed to investigate the bioprospecting potential and systematics of a deep-sea derived piezotolerant bacterial strain NIOT-Ch-40, showing affiliation to the genus Streptomyces based on 16S RNA gene similarity. Preliminary screening for the presence of biosynthetic genes like polyketide synthase I, polyketide synthase II, non ribosomal peptide synthase, 3-amino-5-hydroxybenzoic acid synthase and spiroindimicin followed by antibacterial activity testing confirmed the presence of potent bioactivity. The secondary metabolites produced during fermentation in Streptomyces broth at 28 °C for 7 days were extracted with ethyl acetate. The extract exhibited a specific inhibitory activity against Gram-positive bacteria and was significantly effective (p < 0.0001) against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration and minimum bactericidal concentration against MRSA was 1.5 µg/mL, which was statistically significant in comparison with erythromycin. A multifaceted analysis of the Streptomyces spp. was carried out to delineate the strain NIOT-Ch-40 at a higher resolution which includes morphological, biochemical and molecular studies. Piezotolerance studies and comparison of fatty acid profiles at high pressures revealed that it could be considered as one of the taxonomic markers, especially for the strains isolated from the deep sea environments. In conclusion, the observation of comparative studies with reference strains indicated towards the strain NIOT-Ch-40 as an indigenous marine piezotolerant Streptomyces sp. with a higher probability of obtaining novel bioactive metabolites.

PHAGE FORMATION IN STAPHYLOCOCCUS MUSCAE CULTURES

PubMed Central

Price, Winston H.

1950-01-01

1. Four strains of Staphylococcus muscae have been isolated which differ in their growth rates and phage syntheses in Fildes' synthetic medium. 2. Two of the strains when singly infected cannot release phage in Fildes' synthetic medium unless a substance present in certain acid-hydrolyzed proteins is added to the medium. One of these strains also requires other substance(s) present in acid-hydrolyzed proteins in order to grow in Fildes' medium. 3. The two strains which do not require the addition of the phage-stimulating factor have been found either to synthesize this substance, or one similar to it. One of these strains will not grow in Fildes' medium unless substance(s) present in acid-hydrolyzed proteins is added to the medium. 4. The purified acid-hydrolyzed protein factor necessary for virus liberation does not affect the multiplication rate of uninfected S. muscae cells in Fildes' synthetic medium. 5. The substance is not needed for the adsorption or the invasion of the host cell by the virus. In the absence of the factor, the virus is adsorbed to the cell and "kills" it. 6. An analysis carried out by means of the one-step growth curve technique has indicated that the substance is not concerned simply with the mechanism of virus release, but is necessary for some initial stage in virus synthesis. 7. With one bacterial strain not requiring the AHPF, aspartic acid had to be present at least during the minimum latent period for the cell to form virus. 8. In the absence of aspartic acid, the virus was adsorbed to the cell and killed it, but no virus was released from singly infected bacteria. 9. If the cells were grown in a medium containing aspartic acid and then resuspended in the medium minus aspartic acid, no virus was released, although such cells contained at least two times the amount of aspartic acid necessary for the burst size in the complete medium. 10. Aspartic acid, a constituent of the virus particle, appears from an analysis of one-step growth curves to take part in the initial phase of phage synthesis. 11. The effect of amino acids on virus formation is discussed in relation to the time sequence of virus protein and desoxyribonucleic acid synthesis. PMID:14824494

Selection of Lecanicillium Strain with High Virulence against Developmental Stages of Bemisia tabaci

PubMed Central

Park, Heeyong

2010-01-01

Selection of fungal strains with high virulence against the developmental stages of Bemisia tabaci was performed using internal transcribed spacer regions. The growth rate of hyphae was measured and bioassay of each developmental stage of B. tabaci was conducted for seven days. All of the fungal strains tested were identified as Lecanicillium spp., with strain 4078 showing the fastest mycelium growth rate (colony diameter, 16.3 ± 0.9 mm) among the strains. Compared to strain 4075, which showed the slowest growth rate, the growth rate of strain 4078 was increased almost 2-fold after seven days. Strains 4078 and Btab01 were most virulent against the egg and larva stages, respectively. The virulence of fungal strains against the adult stage was high, except for strains 41185 and 3387. Based on the growth rate of mycelium and level of virulence, strains 4078 and Btab01 were selected as the best fungal strains for application to B. tabaci, regardless of developmental stage. PMID:23956657

Strain Rate Sensitivity of Graphite/Polymer Laminate Composites

NASA Astrophysics Data System (ADS)

Syed, Izhar H.; Brar, N. S.

2002-07-01

Strain rate sensitivities of Graphite/Epoxy and Graphite/Peek laminate composites are investigated by measuring their stress-strain response at strain rates of 0.001/s, 0.1/s, and 400/s. Tension specimens of the composite laminates are fabricated in a dog-bone shape. Stress-strain data at quasi-static rates of 0.001/s and 0.1/s are obtained using a servohydraulic test system. High strain rate data are produced with a Direct Tension Split Hopkinson Bar (DTSHB). A tensile stress pulse is generated in the DTSHB by impacting a stopper flange at the end of the incident bar with an aluminum/polymeric tube launched around the incident bar. The failure (flow) tensile stress of Graphite/Epoxy increases from 240 MPa to 280±10 MPa (ɛ = 0.06) when the strain rate is raised from 0.001/s to 400/s. For Graphite/Peek, failure (flow) tension stress increases from 175 MPa at a strain rate of 0.001/s to 270±20 MPa at a strain rate of 400/s.

76 FR 80781 - Alcohol and Drug Testing: Determination of Minimum Random Testing Rates for 2012

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-27

...-11213, Notice No. 15] RIN 2130-AA81 Alcohol and Drug Testing: Determination of Minimum Random Testing.... According to data from FRA's Management Information System, the rail industry's random drug testing [[Page... Administrator (Administrator) has therefore determined that the minimum annual random drug testing rate for the...

Stress Corrosion Cracking Behavior of Interstitial Free Steel Via Slow Strain Rate Technique

NASA Astrophysics Data System (ADS)

Murkute, Pratik; Ramkumar, J.; Mondal, K.

2016-07-01

An interstitial free steel is subjected to slow strain rate tests to investigate the stress corrosion cracking (SCC) behavior at strain rates ranging from 10-4 to 10-6s-1 in air and 3.5 wt.% NaCl solution. The ratios of time to failure, failure strain, and ultimate tensile stress at different strain rates in air to that in corrosive were considered as SCC susceptibility. Serrated stress-strain curve observed at lowest strain rate is explained by the Portevin-Le Chatelier effect. Maximum susceptibility to SCC at lowest strain rate is attributed to the soluble γ-FeOOH in the rust analyzed by Fourier Transformed Infrared spectroscopy. Mechanism for SCC relates to the anodic dissolution forming the groove, where hydrogen embrittlement can set in and finally fracture happens due to triaxiality.

Molecular epidemiology of Mycobacterium tuberculosis in Baja California, Mexico: A result of human migration?

PubMed

Flores-López, Carlos A; Zenteno-Cuevas, Roberto; Laniado-Laborín, Rafael; Reynaud, Yann; García-Ortiz, Rosa Alejandra; González-Y-Merchand, Jorge A; Rivera, Sandra; Vázquez-Chacón, Carlos A; Vaughan, Gilberto; Martínez-Guarneros, José Armando; Victoria-Cota, Nelva Lorena; Cruz-Rivera, Mayra; Rastogi, Nalin; Muñiz-Salazar, Raquel

2017-11-01

The State of Baja California (BC) exhibits the highest incidence and prevalence rates of tuberculosis (TB), and multidrug-resistant TB (MDR-TB) in Mexico. However information about the circulation of M. tuberculosis lineages in BC and Mexico as a whole is limited. Here, we describe the genetic relationship and genetic diversity among M. tuberculosis clinical isolates (n=140) collected in BC between October 2009 and April 2011 with other regions of Mexico, the United States, and Latin America. All specimens were genotyped based on 24 mycobacterial interspersed repetitive units (MIRU)-variable number of tandem repeats (VNTR) loci. Population structure and minimum spanning tree (MST) analyses were used to assess the genetic diversity and distribution of BC isolates in comparison to USA and South America strains. Among the nine lineages observed, LAM, Haarlem and S were the most frequent identified in BC. Population structure analysis clustered most BC isolates (41%) into three distinctive groups that included strains from San Diego and South America, whereas other BC strains (22%) clustered with other Mexican strains. A subset of isolates (12%) seemed to be autochthonous of BC, while 25% were cosmopolitan and grouped into multiple clusters. It is highly likely that the TB genetic structure observed in BC is due to human migration. Additional studies are required to determine the mechanism involved in the phylogeographic distribution of M. tuberculosis in Mexico. Implementation of domestic molecular TB surveillance programs is required to better understand the molecular epidemiology of TB not only in the region but at the national level. Copyright © 2016 Elsevier B.V. All rights reserved.

The antibiotic polymyxin B exhibits novel antifungal activity against Fusarium species.

PubMed

Hsu, Li-Hang; Wang, Hsuan-Fu; Sun, Pei-Lun; Hu, Fung-Rong; Chen, Ying-Lien

2017-06-01

The genus Fusarium comprises many species, including Fusarium oxysporum, Fusarium solani, Fusarium graminearum and Fusarium verticillioides, and causes severe infections in plants and humans. In clinical settings, Fusarium is the third most frequent mould to cause invasive fungal infections after Aspergillus and the Mucorales. F. solani and F. oxysporum are the most prevalent Fusarium spp. causing clinical disease. However, few effective antifungal drugs are available to treat human and plant Fusarium infections. The cationic peptide antibiotic polymyxin B (PMB) exhibits antifungal activity against the human fungal pathogens Candida albicans and Cryptococcus neoformans, but its efficacy against Fusarium spp. is unknown. In this study, the antifungal activity of PMB was tested against 12 Fusarium strains that infect humans and plants (banana, tomato, melon, pea, wheat and maize). PMB was fungicidal against all 12 Fusarium strains, with minimum fungicidal concentrations of 32 µg/mL or 64 µg/mL for most strains tested, as evidenced by broth dilution, methylene blue staining and XTT reduction assays. PMB can reduce the germination rates of conidia, but not chlamydospores, and can cause defects in cell membrane integrity in Fusarium strains. PMB exhibits synergistic activity with posaconazole and can potentiate the effect of fluconazole, voriconazole or amphotericin B against Fusarium spp. However, PMB does not show synergistic effects with fluconazole against Fusarium spp. as it does against Candida glabrata and C. neoformans, indicating evolutionary divergence of mechanisms between yeast pathogens and the filamentous fungus Fusarium. Copyright © 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Three regimens of procaine penicillin G, Augmentin, and probenecid compared for treating acute gonorrhoea in men.

PubMed Central

Lim, K B; Thirumoorthy, T; Lee, C T; Sng, E H; Tan, T

1986-01-01

The efficacy of three penicillin regimens in treating uncomplicated gonorrhoea in men was evaluated. The regimens consisted of: Augmentin 3.25 g plus probenecid 1 g orally: aqueous procaine penicillin G 4.5 MIU intramuscularly and probenecid 1 g plus one tablet of Augmentin 375 mg orally; or aqueous procaine penicillin G 4.5 MIU intramuscularly and probenecid 1 g plus two tablets of Augmentin 375 mg orally. Cure rates for infections caused by penicillinase (beta lactamase) producing Neisseria gonorrhoeae (PPNG) were 87% (20/23) for regimen 1, 97% (28/29) for regimen 2, and 95% (19/20) for regimen 3. Thus the addition of one or two tablets of Augmentin 375 mg to aqueous procaine penicillin G and probenecid cured 96% (47/49) of infections caused by PPNG strains. All three regimens were 100% effective in eradicating infections caused by non-PPNG strains. Post gonococcal urethritis occurred in 24% of cases treated with regimen 1, 14% of cases treated with regimen 2, and 15% of cases treated with regimen 3. The geometric minimum inhibitory concentrations (MIC90) of Augmentin for 72 PPNG and 162 non-PPNG isolates of N gonorrhoeae obtained before treatment were 1.98 and 0.55 mg/l, respectively. Regimen 2, besides being effective against infections caused by PPNG or non-PPNG strains, has the advantage of cost effectiveness and low toxicity. This regimen may be useful in treating gonorrhoea in areas of high prevalence of PPNG strains, such as South East Asia and Africa. PMID:3721514

Stoichiometry as key to ferroelectricity in compressively strained SrTiO{sub 3} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haislmaier, R. C.; Engel-Herbert, R.; Gopalan, V.

2016-07-18

While strain is a powerful tuning parameter for inducing ferroelectricity in thin film oxides, the role of stoichiometry control is critical, but far less explored. A series of compressively strained SrTiO{sub 3} films on (001) (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} substrates were grown by hybrid molecular beam epitaxy where the Ti cation was supplied using a metal-organic titanium tetraisopropoxide molecule that helps systematically and precisely control Sr:Ti stoichiometry in the resulting films. A stoichiometric growth window is located through X-ray diffraction and in-situ reflection high-energy electron diffraction measurements, which show a minimum out-of-plane lattice parameter as well as constantmore » growth rate within the stoichiometric growth window range. Using temperature dependent optical second harmonic generation (SHG) characterization, a ferroelectric-to-paraelectric transition at T ∼ 180 K is observed for a stoichiometric SrTiO{sub 3} film, as well as a higher temperature structural transition at T ∼ 385 K. Using SHG polarimetry modeling, the polar point group symmetry is determined to be tetragonal 4mm with the polarization pointing out-of-plane of the film. The SHG coefficients, d{sub 31}/d{sub 15}=3 and d{sub 33}/d{sub 15}=21, were determined at 298 K. The ferroelectric transition disappears in films grown outside the growth window, thus proving the critical role of stoichiometry control in realizing strain-induced ferroelectricity.« less

Multicenter cross-sectional observational study of antibiotic resistance and the genotypes of Propionibacterium acnes isolated from Chinese patients with acne vulgaris.

PubMed

Fan, Yukun; Hao, Fei; Wang, Weizhen; Lu, Yonghong; He, Li; Wang, Gang; Chen, Wenchieh

2016-04-01

Antibiotics are widely applied in management of acne vulgaris, which raises the issue of antibiotic resistance. Due to improper application and supervision of antibiotics, antibiotic resistance has become a serious problem in China. So, the efficacy of antimicrobial therapy in acne is unclear without an objective monitor of antibiotic resistance of Propionibacterium acnes. This cross-sectional, multicenter observational study is aimed at understanding the status of antibiotic resistance in P. acnes, investigating the measures of acne management in China and analyzing the genotypes of antibiotic-resistant strains of P. acnes. Altogether, 312 strains of P. acnes were collected from patients in five medical centers across central China after reviewing the corresponding medical history in detail. The samples underwent antibiotic susceptibility assays by agar dilution method with a total of 11 classes of antibiotics being tested. The antibiotic-resistant strains were screened and further analyzed by investigation of the genotypes regarding 23S rRNA, 16S rRNA and erm(X). The predominant resistance occurred in macrolides and lincomycin with an overall resistance rate of 47.8%. The resistance to tetracyclines was scarce with only two cases identified. The emergence of minimum inhibitory concentration elevation for tetracyclines is associated with its application history (P < 0.005). The genotypes of the reported macrolide-lincosamide-streptogramin B resistance strains were also spotted in Chinese subjects while other resistance determinants may also exist. The tetracyclines have been proved to be vastly susceptible while macrolides and lincomycin face a serious resistance status in China. © 2015 Japanese Dermatological Association.

Bactericidal activity and post-antibiotic effect of ozenoxacin against Propionibacterium acnes.

PubMed

Kanayama, Shoji; Okamoto, Kazuaki; Ikeda, Fumiaki; Ishii, Ritsuko; Matsumoto, Tatsumi; Hayashi, Naoki; Gotoh, Naomasa

2017-06-01

Ozenoxacin, a novel non-fluorinated topical quinolone, is used for the treatment of acne vulgaris in Japan. We investigated bactericidal activity and post-antibiotic effect (PAE) of ozenoxacin against Propionibacterium acnes, a major causative bacterium of acne vulgaris. The minimum inhibitory concentrations (MICs) of ozenoxacin against 3 levofloxacin-susceptible strains (MIC of levofloxacin; ≤4 μg/mL) and 3 levofloxacin-resistant strains (MIC of levofloxacin; ≥8 μg/mL) ranged from 0.03 to 0.06 μg/mL and from 0.25 to 0.5 μg/mL, respectively. These MICs of ozenoxacin were almost the same or lower than nadifloxacin and clindamycin. The minimum bactericidal concentrations (MBCs) of ozenoxacin against the levofloxacin-susceptible and -resistant strains were from 0.06 to 8 μg/mL and from 0.5 to 4 μg/mL, respectively. These MBCs were lower than those of nadifloxacin and clindamycin. In time-kill assay, ozenoxacin at 1/4, 1 and 4 times the respective MIC against both levofloxacin-susceptible and -resistant strains showed a concentration-dependent bactericidal activity. Ozenoxacin at 4 times the MICs against the levofloxacin-susceptible strains showed more potent and more rapid onset of bactericidal activity compared to nadifloxacin and clindamycin at 4 times the respective MICs. The PAEs of ozenoxacin at 4 times the MICs against the levofloxacin-susceptible strains were from 3.3 to 17.1 h, which were almost the same or longer than nadifloxacin and clindamycin. In contrast, the PAEs were hardly induced by any antimicrobial agents against the levofloxacin-resistant strains. The present findings suggest that ozenoxacin has a potent bactericidal activity against both levofloxacin-susceptible and -resistant P. acnes, and a long-lasting PAE against levofloxacin-susceptible P. acnes. Copyright © 2017 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Autonomous Sensor Motes Employing Liquid-Bearing Rotary Stages

DTIC Science & Technology

2014-03-06

breaks off (Fig. 27d) as shown in the sudden change in force, indicating rotor pull off. The minimum of each curve indicates the maximum tensile load...configuration, with marks on the curves at the minimum energy positions are shown in Fig. 39. The minimum energy positions from Fig. 39are plotted as...rates between 5 and 17 Hz rotation rate plotted vs. rotor eccentricity. The minimum energy positions are indicated on each curve . 3.3 Discussion

State-level minimum wage and heart disease death rates in the United States, 1980-2015: A novel application of marginal structural modeling.

PubMed

Van Dyke, Miriam E; Komro, Kelli A; Shah, Monica P; Livingston, Melvin D; Kramer, Michael R

2018-07-01

Despite substantial declines since the 1960's, heart disease remains the leading cause of death in the United States (US) and geographic disparities in heart disease mortality have grown. State-level socioeconomic factors might be important contributors to geographic differences in heart disease mortality. This study examined the association between state-level minimum wage increases above the federal minimum wage and heart disease death rates from 1980 to 2015 among 'working age' individuals aged 35-64 years in the US. Annual, inflation-adjusted state and federal minimum wage data were extracted from legal databases and annual state-level heart disease death rates were obtained from CDC Wonder. Although most minimum wage and health studies to date use conventional regression models, we employed marginal structural models to account for possible time-varying confounding. Quasi-experimental, marginal structural models accounting for state, year, and state × year fixed effects estimated the association between increases in the state-level minimum wage above the federal minimum wage and heart disease death rates. In models of 'working age' adults (35-64 years old), a $1 increase in the state-level minimum wage above the federal minimum wage was on average associated with ~6 fewer heart disease deaths per 100,000 (95% CI: -10.4, -1.99), or a state-level heart disease death rate that was 3.5% lower per year. In contrast, for older adults (65+ years old) a $1 increase was on average associated with a 1.1% lower state-level heart disease death rate per year (b = -28.9 per 100,000, 95% CI: -71.1, 13.3). State-level economic policies are important targets for population health research. Copyright © 2018 Elsevier Inc. All rights reserved.

Stretch-rate relationships for turbulent premixed combustion LES subgrid models measured using temporally resolved diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steinberg, Adam M.; Driscoll, James F.

2010-07-15

Temporally resolved measurements of turbulence-flame interaction were used to experimentally determine relationships for the strain-rate and curvature stretch-rate exerted on a premixed flame surface. These relationships include a series of transfer functions that are analogous to, but not equal to, stretch-efficiency functions. The measurements were obtained by applying high-repetition-rate particle image velocimetry in a turbulent slot Bunsen flame and were able to resolve the range of turbulent scales that cause flame surface straining and wrinkling. Fluid control masses were tracked in a Lagrangian manner as they interacted with the flame surface. From each interaction, the spatially and temporally filtered subgridmore » strain-rate and curvature stretch-rate were measured. By analyzing the statistics of thousands of turbulence-flame interactions, relationships for the strain-rate and curvature stretch-rate were determined that are appropriate for Large Eddy Simulation. It was found that the strain-rate exerted on the flame during these interactions was better correlated with the strength of the subgrid fluid-dynamic strain-rate field than with previously used characteristic strain-rates. Furthermore, stretch-efficiency functions developed from simplified vortex-flame interactions significantly over-predict the measurements. Hence, the proposed relationship relates the strain-rate on the flame to the filtered subgrid fluid-dynamic strain-rate field during real turbulence-flame interactions using an empirically determined Strain-Rate Transfer function. It was found that the curvature stretch-rate did not locally balance the strain-rate as has been proposed in previous models. A geometric relationship was found to exist between the subgrid flame surface wrinkling factor and subgrid curvature stretch-rate, which could be expressed using an empirically determined wrinkling factor transfer function. Curve fits to the measured relationships are provided that could be implemented in numerical simulations of turbulent premixed combustion. (author)« less

78 FR 4855 - Random Drug Testing Rate for Covered Crewmembers

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-23

... DEPARTMENT OF HOMELAND SECURITY Coast Guard [Docket No. USCG-2009-0973] Random Drug Testing Rate for Covered Crewmembers AGENCY: Coast Guard, DHS. ACTION: Notice of minimum random drug testing rate. SUMMARY: The Coast Guard has set the calendar year 2013 minimum random drug testing rate at 25 percent of...

76 FR 79204 - Random Drug Testing Rate for Covered Crewmembers

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-21

... DEPARTMENT OF HOMELAND SECURITY Coast Guard [Docket No. USCG-2009-0973] Random Drug Testing Rate for Covered Crewmembers AGENCY: Coast Guard, DHS. ACTION: Notice of minimum random drug testing rate. SUMMARY: The Coast Guard has set the calendar year 2012 minimum random drug testing rate at 50 percent of...

76 FR 1448 - Random Drug Testing Rate for Covered Crewmembers

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-10

... DEPARTMENT OF HOMELAND SECURITY Coast Guard [Docket No. USCG-2009-0973] Random Drug Testing Rate for Covered Crewmembers AGENCY: Coast Guard, DHS. ACTION: Notice of minimum random drug testing rate. SUMMARY: The Coast Guard has set the calendar year 2011 minimum random drug testing rate at 50 percent of...

The effect of hold-times on the fatigue life of 20% cold-worked Type 316L stainless steel under deuteron irradiation

NASA Astrophysics Data System (ADS)

Scholz, R.

1995-09-01

Strain-controlled fatigue tests have been performed in torsion on 20% cold-worked Type 316L stainless steel specimens during irradiation with 19 MeV deuterons. A hold-time was imposed at the minimum strain value in the loading cycle. The irradiation creep induced stress relaxation led to the buildup of a mean stress. The number of cycles to failure may be significantly reduced in comparison to analogous continuous cycling tests under thermal conditions.

Fatigue behavior of a cross-ply ceramic matrix composite at elevated temperature under tension-tension loading. Master`s thesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steiner, C.D.

This study investigated the fatigue behavior and damage mechanisms of a (0/90)4s SiC/MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

Bending energy of buckled edge dislocations

NASA Astrophysics Data System (ADS)

Kupferman, Raz

2017-12-01

The study of elastic membranes carrying topological defects has a longstanding history, going back at least to the 1950s. When allowed to buckle in three-dimensional space, membranes with defects can totally relieve their in-plane strain, remaining with a bending energy, whose rigidity modulus is small compared to the stretching modulus. In this paper we study membranes with a single edge dislocation. We prove that the minimum bending energy associated with strain-free configurations diverges logarithmically with the size of the system.

5 CFR 9701.325 - Treatment of employees whose rate of basic pay falls below the minimum rate of their band.

Code of Federal Regulations, 2014 CFR

2014-01-01

... basic pay falls below the minimum rate of their band. 9701.325 Section 9701.325 Administrative Personnel... Administration Setting and Adjusting Rate Ranges § 9701.325 Treatment of employees whose rate of basic pay falls... under § 9701.323 because of an unacceptable rating of record and whose rate of basic pay falls below the...

5 CFR 9701.325 - Treatment of employees whose rate of basic pay falls below the minimum rate of their band.

Code of Federal Regulations, 2011 CFR

2011-01-01

... basic pay falls below the minimum rate of their band. 9701.325 Section 9701.325 Administrative Personnel... Administration Setting and Adjusting Rate Ranges § 9701.325 Treatment of employees whose rate of basic pay falls... under § 9701.323 because of an unacceptable rating of record and whose rate of basic pay falls below the...

5 CFR 9701.325 - Treatment of employees whose rate of basic pay falls below the minimum rate of their band.

Code of Federal Regulations, 2012 CFR

2012-01-01

... basic pay falls below the minimum rate of their band. 9701.325 Section 9701.325 Administrative Personnel... Administration Setting and Adjusting Rate Ranges § 9701.325 Treatment of employees whose rate of basic pay falls... under § 9701.323 because of an unacceptable rating of record and whose rate of basic pay falls below the...

5 CFR 9701.325 - Treatment of employees whose rate of basic pay falls below the minimum rate of their band.

Code of Federal Regulations, 2013 CFR

2013-01-01

... basic pay falls below the minimum rate of their band. 9701.325 Section 9701.325 Administrative Personnel... Administration Setting and Adjusting Rate Ranges § 9701.325 Treatment of employees whose rate of basic pay falls... under § 9701.323 because of an unacceptable rating of record and whose rate of basic pay falls below the...

Isolation and characterization of cyclo-(tryptophanyl-prolyl) and chloramphenicol from Streptomyces sp. SUK 25 with antimethicillin-resistant Staphylococcus aureus activity

PubMed Central

Alshaibani, Muhanna M; Jalil, Juriyati; Sidik, Nik M; Edrada-Ebel, Ruangelie; Zin, Noraziah M

2016-01-01

Background Zingiber spectabile, commonly known as Beehive Ginger, is used as an ethnobotanical plant in many countries as an appetizer or to treat stomachache, toothache, muscle sprain, and as a cure for swelling, sores and cuts. This is the first report of isolation of Streptomyces strain from the root of this plant. Strain Universiti Kebangsaan 25 (SUK 25) has a very high activity to produce secondary metabolites against methicillin-resistant Staphylococcus aureus (MRSA), which is associated with high morbidity and mortality rates due to acquired multidrug resistance genes and causes medication failure in some clinical cases worldwide. Phylogenetic analysis based on the 16S ribosomal RNA gene sequence exhibited that the most closely related strain was Streptomyces omiyaensis NBRC 13449T (99.0% similarity). Aim This study was conducted to carry out the extraction, identification, and biological evaluation of active metabolites isolated from SUK 25 against three MRSA strains, namely, MRSA ATCC 43300, MRSA ATCC 33591, and MRSA ATCC 49476. Materials and methods The production of secondary metabolites by this strain was optimized through Thronton’s media. Isolation, purification, and identification of the bioactive compounds were carried out using reversed-phase high-performance liquid chromatography, high-resolution mass spectrometry, Fourier transform infrared, and one-dimensional and two-dimensional nuclear magnetic resonance. Results During screening procedure, SUK 25 exhibited good antimicrobial potential against several strains of MRSA. The best biological activity was shown from fraction number VII and its subfractions F2 and F3 with minimum inhibitory concentration values at 16 µg/mL and 8 µg/mL, respectively. These two subfractions were identified as diketopiperazine cyclo-(tryptophanyl-prolyl) and chloramphenicol. Conclusion On the basis of obtained results, SUK 25 isolated from Z. spectabile can be regarded as a new valuable source to produce secondary metabolites against bacteria, especially MRSA. PMID:27330275

In vitro effect of bergamot (Citrus bergamia) juice against cagA-positive and-negative clinical isolates of Helicobacter pylori.

PubMed

Filocamo, Angela; Bisignano, Carlo; Ferlazzo, Nadia; Cirmi, Santa; Mandalari, Giuseppina; Navarra, Michele

2015-07-30

Helicobacter pylori infection has been associated with chronic gastritis, peptic ulcer and gastric carcinoma as over half of the world's population is colonized with this gram-negative bacterium. Due to the increasing antibiotic resistance, its eradication rates fails in a great portion of patients. A number of studies showed that molecules largely distributed in commonly consumed fruits and vegetables may have antimicrobial activity. The aim of the present study was to investigate the effect of bergamot juice (BJ) against Helicobacter pylori in vitro. The potential therapeutic combination between BJ and the antibiotics amoxicillin (AMX), clarithromycin (CLA) and metronidazole (MTZ) has also been evaluated. The minimum inhibitory concentration (MIC) of BJ, AMX, CLA and MTZ against 2 ATCC and 32 clinical isolates of H. pylori was assayed according to CLSI. The checkerboard method was used to determine the efficacy of the association BJ with the three reference antibiotics. Killing curves were performed on the two cagA-positive ATCC strains of H. pylori (ATCC 43504 and ATCC 49503), on the clinical isolate cagA-positive HP6 strain of H. pylori and on the clinical isolate cagA-negative HP61 strain of H. pylori. BJ (2.5%, v/v) inhibited the growth of 50% of the H. pylori clinical isolates, whereas 5% (v/v) inhibited 90%. AMX was the most effective antibiotic against the reference strains and the clinical isolates, followed by CLA and MTZ. In the combination assays, synergism was observed between BJ and AMX and between BJ and MTZ against both the reference strains and the clinical isolates. Indifference was observed between BJ and CLA. BJ was effective in vitro against H. pylori and the genotype status of the clinical strains may have an impact on its susceptibility. The synergistic combination of BJ and antibiotics could be used to prevent or treat resistance.

Electronic structure in 1T-ZrS2 monolayer by strain

NASA Astrophysics Data System (ADS)

Xin, Qianqian; Zhao, Xu; Ma, Xu; Wu, Ninghua; Liu, Xiaomeng; Wei, Shuyi

2017-09-01

We report electronic structure of 1T-ZrS2 monolayer with biaxial strain from -10% to 15%, basing the first principles calculations. Our calculation results indicate that the band structure of ZrS2 monolayer was changed clearly. The location of conduction band minimum (CBM) and valence band maximum (VBM) changed with the variation of isotropic strain. At compressive strain, the location of CBM and VBM retains at M and Γ point, respectively. The band gap of ZrS2 monolayer decreases from 1.111 eV to 0 eV when compressive strain increases from 0% to -8%, which means that the ZrS2 monolayer turns to metal at -8% compressive strain. Under the tensile strain, the ZrS2 monolayer also retains be an indirect band gap semiconductor. The location of CBM moves from M to Γ point and the location of VBM moves along Γ-A-K-Γ direction. The band gap of ZrS2 monolayer firstly increases and then decreases and the biggest band gap is 1.577 eV at tensile strain 6%. We can see the compression strain is more effective than tensile strain in modulating band gap of 1T-ZrS2 monolayer.

Tensile Strength of Carbon Nanotubes Under Realistic Temperature and Strain Rate

NASA Technical Reports Server (NTRS)

Wei, Chen-Yu; Cho, Kyeong-Jae; Srivastava, Deepak; Biegel, Bryan (Technical Monitor)

2002-01-01

Strain rate and temperature dependence of the tensile strength of single-wall carbon nanotubes has been investigated with molecular dynamics simulations. The tensile failure or yield strain is found to be strongly dependent on the temperature and strain rate. A transition state theory based predictive model is developed for the tensile failure of nanotubes. Based on the parameters fitted from high-strain rate and temperature dependent molecular dynamics simulations, the model predicts that a defect free micrometer long single-wall nanotube at 300 K, stretched with a strain rate of 1%/hour, fails at about 9 plus or minus 1% tensile strain. This is in good agreement with recent experimental findings.

Shrinkage strain-rates of dental resin-monomer and composite systems.

PubMed

Atai, Mohammad; Watts, David C; Atai, Zahra

2005-08-01

The purpose of this study was to investigate the shrinkage strain rate of different monomers, which are commonly used in dental composites and the effect of monomer functionality and molecular mass on the rate. Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage strain of the samples photopolymerised at Ca. 550 mW/cm2 and 23 degrees C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788-794), and initial shrinkage-strain rates were obtained by numerical differentiation. Shrinkage-strain rates rose rapidly to a maximum, and then fell rapidly upon vitrification. Strain and initial strain rate were dependent upon monomer functionality, molecular mass and viscosity. Strain rates were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75-80 w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower rates. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage strain rate (P < 0.05). Shrinkage strain rate, related to polymerization rate, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.

Mechanical Properties of Transgenic Silkworm Silk Under High Strain Rate Tensile Loading

NASA Astrophysics Data System (ADS)

Chu, J.-M.; Claus, B.; Chen, W.

2017-12-01

Studies have shown that transgenic silkworm silk may be capable of having similar properties of spider silk while being mass-producible. In this research, the tensile stress-strain response of transgenic silkworm silk fiber is systematically characterized using a quasi-static load frame and a tension Kolsky bar over a range of strain-rates between 10^{-3} and 700/s. The results show that transgenic silkworm silk tends to have higher overall ultimate stress and failure strain at high strain rate (700/s) compared to quasi-static strain rates, indicating rate sensitivity of the material. The failure strain at the high strain rate is higher than that of spider silk. However, the stress levels are significantly below that of spider silk, and far below that of high-performance fiber. Failure surfaces are examined via scanning electron microscopy and reveal that the failure modes are similar to those of spider silk.

Clear distinction between Burkholderia mallei and Burkholderia pseudomallei using fluorescent motB primers.

PubMed

Schmoock, Gernot; Elschner, Mandy; Sprague, Lisa D

2015-03-07

A frame-shift mutation in the flagellum motor gene motB coding for the chemotaxis MotB protein of Burkholderia mallei has been utilized to design a conventional duplex PCR assay with fluorescent labelled primers. Species specificity was tested with a panel of 13 Burkholderia type strains. A total of 41 B. mallei field strains, 36 B. pseudomallei field strains, and 1 B. thailandensis field strain from different geographic regions were tested and correctly identified. Testing of 55 non-Burkholderia bacterial species revealed 100% specificity of the assay. The minimum detection limit was 1 pg DNA or 160 GE for B. mallei and 130 GE for B. pseudomallei, respectively. This assay enables the clear distinction between B. mallei and B. pseudomallei/B. thailandensis.

In vitro activity of selected antimicrobial agents against penicillinase producing Neisseria gonorrhoeae (PPNG) and non-PPNG strains.

PubMed

Waghorn, D J; Azadian, B S; Talboys, C

1986-12-01

One hundred and twelve penicillinase producing Neisseria gonorrhoeae (PPNG) isolates and the same number of non-PPNG isolates were obtained from patients attending the genitourinary department of this hospital. Susceptibilities to six beta lactam antibiotics--ceftriaxone, cefotaxime, cefuroxime, ceftazidime, amoxycillin, and temocillin--to the combined formulation of amoxycillin and clavulanic acid, Augmentin, and to the aminocyclitol, spectinomycin, were compared by assessing their minimum inhibitory concentrations (MICs). Results showed that all the cephalosporins used in this study had good in vitro activity against both PPNG and non-PPNG strains, and ceftriaxone had the lowest MICs. Temocillin and Augmentin also showed good activity against both types of strain. Spectinomycin resistance was shown in about 4% of the PPNG isolates but was not found in any non-PPNG strains.

Development of strain gages for use to 1311 K (1900 F)

NASA Technical Reports Server (NTRS)

Lemcoe, M. M.

1974-01-01

A high temperature electric resistance strain gage system was developed and evaluated to 1366 K (2000 F) for periods of at least one hour. Wire fabricated from a special high temperature strain gage alloy (BCL-3), was used to fabricate the gages. Various joining techniques (NASA butt welding, pulse arc, plasma needle arc, and dc parallel gap welding) were investigated for joining gage filaments to each other, gage filaments to lead-tab ribbons, and lead-tab ribbons to lead wires. The effectiveness of a clad-wire concept as a means of minimizing apparent strain of BCL-3 strain gages was investigated by sputtering platinum coatings of varying thicknesses on wire samples and establishing the optimum coating thickness--in terms of minimum resistivity changes with temperature. Finally, the moisture-proofing effectiveness of barrier coatings subjected to elevated temperatures was studied, and one commercial barrier coating (BLH Barrier H Waterproofing) was evaluated.

Fatigue data for polyether ether ketone (PEEK) under fully-reversed cyclic loading

PubMed Central

Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima

2016-01-01

In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK), a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1) strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2) strain-controlled fatigue tests with various frequencies, (3) load-controlled fatigue tests without step loadings, and (4) load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak) and minimum (valley) stress–strain responses for each cycle, and the hysteresis stress–strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given. PMID:26937465

Fatigue data for polyether ether ketone (PEEK) under fully-reversed cyclic loading.

PubMed

Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima

2016-03-01

In this article, the data obtained from the uniaxial fully-reversed fatigue experiments conducted on polyether ether ketone (PEEK), a semi-crystalline thermoplastic, are presented. The tests were performed in either strain-controlled or load-controlled mode under various levels of loading. The data are categorized into four subsets according to the type of tests, including (1) strain-controlled fatigue tests with adjusted frequency to obtain the nominal temperature rise of the specimen surface, (2) strain-controlled fatigue tests with various frequencies, (3) load-controlled fatigue tests without step loadings, and (4) load-controlled fatigue tests with step loadings. Accompanied data for each test include the fatigue life, the maximum (peak) and minimum (valley) stress-strain responses for each cycle, and the hysteresis stress-strain responses for each collected cycle in a logarithmic increment. A brief description of the experimental method is also given.

Bioremediation of Mercury by Vibrio fluvialis Screened from Industrial Effluents

PubMed Central

Saranya, Kailasam; Shekhar, Sudhanshu; Swaminathan, Sankaran; Balasubramanian, Thangavel

2017-01-01

Thirty-one mercury-resistant bacterial strains were isolated from the effluent discharge sites of the SIPCOT industrial area. Among them, only one strain (CASKS5) was selected for further investigation due to its high minimum inhibitory concentration of mercury and low antibiotic susceptibility. In accordance with 16S ribosomal RNA gene sequences, the strain CASKS5 was identified as Vibrio fluvialis. The mercury-removal capacity of V. fluvialis was analyzed at four different concentrations (100, 150, 200, and 250 μg/ml). Efficient bioremediation was observed at a level of 250 μg/ml with the removal of 60% of mercury ions. The interesting outcome of this study was that the strain V. fluvialis had a high bioremediation efficiency but had a low antibiotic resistance. Hence, V. fluvialis could be successfully used as a strain for the ecofriendly removal of mercury. PMID:28626761

Bioremediation of Mercury by Vibrio fluvialis Screened from Industrial Effluents.

PubMed

Saranya, Kailasam; Sundaramanickam, Arumugam; Shekhar, Sudhanshu; Swaminathan, Sankaran; Balasubramanian, Thangavel

2017-01-01

Thirty-one mercury-resistant bacterial strains were isolated from the effluent discharge sites of the SIPCOT industrial area. Among them, only one strain (CASKS5) was selected for further investigation due to its high minimum inhibitory concentration of mercury and low antibiotic susceptibility. In accordance with 16S ribosomal RNA gene sequences, the strain CASKS5 was identified as Vibrio fluvialis . The mercury-removal capacity of V. fluvialis was analyzed at four different concentrations (100, 150, 200, and 250  μ g/ml). Efficient bioremediation was observed at a level of 250  μ g/ml with the removal of 60% of mercury ions. The interesting outcome of this study was that the strain V. fluvialis had a high bioremediation efficiency but had a low antibiotic resistance. Hence, V. fluvialis could be successfully used as a strain for the ecofriendly removal of mercury.

Susceptibility of Haemophilus influenzae Isolates from Blood and Cerebrospinal Fluid to Ampicillin, Chloramphenicol, and Trimethoprim-Sulfamethoxazole

PubMed Central

McGowan, John E.; Terry, Pamela M.; Nahmias, Andre J.

1976-01-01

Susceptibility to ampicillin and chloramphenicol in vitro has been determined for Haemophilus influenzae strains isolated from blood and/or cerebrospinal fluid cultures of patients admitted to two Atlanta hospitals from 1 January 1974 to 31 March 1975. Since the appearance of ampicillin-resistant strains of this organism in early 1974, chloramphenicol has been used in these hospitals as initial therapy for severe infection due to H. influenzae. Strains from five of 94 patients were resistant to ampicillin (minimum inhibitory concentration [MIC] ≥ 12.5 μg/ml), but all strains were susceptible to chloramphenicol (MIC < 2 μg/ml). The first 35 strains studied, including three resistant to ampicillin, were also tested for in vitro susceptibility to trimethoprim-sulfamethoxazole; all were highly susceptible (MIC ≤ 0.0312 μg of trimethoprim and 0.625 μg of sulfamethoxazole per ml). PMID:1083198

Characterization of a Strain Rate Transient Along the San Andreas and San Jacinto Faults Following the October 1999 Hector Mine Earthquake.

NASA Astrophysics Data System (ADS)

Hernandez, D.; Holt, W. E.; Bennett, R. A.; Dimitrova, L.; Haines, A. J.

2006-12-01

We are continuing work on developing and refining a tool for recognizing strain rate transients as well as for quantifying the magnitude and style of their temporal and spatial variations. We determined time-averaged velocity values in 0.05 year epochs using time-varying velocity estimates for continuous GPS station data from the Southern California Integrated GPS Network (SCIGN) for the time period between October 1999 and February 2004 [Li et al., 2005]. A self-consistent model velocity gradient tensor field solution is determined for each epoch by fitting bi-cubic Bessel interpolation to the GPS velocity vectors and we determine model dilatation strain rates, shear strain rates, and the rotation rates. Departures of the time dependent model strain rate and velocity fields from a master solution, obtained from a time-averaged solution for the period 1999-2004, with imposed plate motion constraints and Quaternary fault data, are evaluated in order to best characterize the time dependent strain rate field. A particular problem in determining the transient strain rate fields is the level of smoothing or damping that is applied. Our current approach is to choose a damping that both maximizes the departure of the transient strain rate field from the long-term master solution and achieves a reduced chi-squared value between model and observed GPS velocities of around 1.0 for all time epochs. We observe several noteworthy time-dependent changes. First, in the Eastern California Shear Zone (ECSZ) region, immediately following the October 1999 Hector Mine earthquake, there occurs a significant spatial increase of relatively high shear strain rate, which encompasses a significant portion of the ECSZ. Second, also following the Hector Mine event, there is a strain rate corridor that extends through the Pinto Mt. fault connecting the ECSZ to the San Andreas fault segment in the Salton Trough region. As this signal slowly decays, shear strain rates on segments of the San Andreas fault, just east of Palm Springs, and the San Jacinto fault increase during 2001-2004. During this period shear strain rates increase by roughly 20 nanostrain per year on the San Andreas fault and 20-30 nanostrain per year on the San Jacinto fault (over a zone approximately 20 km wide). Lastly, a further investigation into this strain rate recovery reveals a power law flow mechanism during the first six months after the earthquake for the Anza segment, after which strain rates appear to reach a steady state for the remainder of the data. Moreover, seismicity rates increase along these segments following the period of shear strain rate increase. These results quantify the spatial coverage of the strain rate changes and provide some bounds on their magnitude and confidence, as well as constraints on the associated regional rheology and interseismic cycle strain rate pattern. The compiled epoch solution "movies" may be viewed at the additional resources site.

Investigating the Sensitivity of Model Intraseasonal Variability to Minimum Entrainment

NASA Astrophysics Data System (ADS)

Hannah, W. M.; Maloney, E. D.

2008-12-01

Previous studies have shown that using a Relaxed Arakawa-Schubert (RAS) convective parameterization with appropriate convective triggers and assumptions about rain re-evaporation produces realistic intraseasonal variability. RAS represents convection with an ensemble of clouds detraining at different heights, each with different entrainment rate, the highest clouds having the lowest entrainment rates. If tropospheric temperature gradients are weak and boundary layer moist static energy is relatively constant, then by limiting the minimum entrainment rate deep convection is suppressed in the presence of dry tropospheric air. This allows moist static energy to accumulate and be discharged during strong intraseasonal convective events, which is consistent with the discharge/recharge paradigm. This study will examine the sensitivity of intra-seasonal variability to changes in minimum entrainment rate in the NCAR-CAM3 with the RAS scheme. Simulations using several minimum entrainment rate thresholds will be investigated. A frequency-wavenumber analysis will show the improvement of the MJO signal as minimum entrainment rate is increased. The spatial and vertical structure of MJO-like disturbances will be examined, including an analysis of the time evolution of vertical humidity distribution for each simulation. Simulated results will be compared to observed MJO events in NCEP-1 reanalysis and CMAP precipitation.

Antibacterial Potential Assessment of Jasmine Essential Oil Against E. Coli

PubMed Central

Rath, C. C.; Devi, S.; Dash, S. K.; Mishra, R. K.

2008-01-01

The antibacterial activity of Jasmine (Jasminum sambac L.) flower hydro steam distilled essential oil, synthetic blends and six major individual components was assessed against Escherichia coli (MTCC-443) strain. The activity was bactericidal. Minimum inhibitory concentration was determined by tube dilution technique, and the Minimum inhibitory concentration ranged between 1.9-31.25 μl/ml. Phenolcoefficient of the oil, synthetic blends and components varied between 0.6-1.7. The activity of the chemicals was possibly due to the inhibition of cell membrane synthesis. PMID:20046722

Influence of strain rate and temperature on tensile properties and flow behaviour of a reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Vanaja, J.; Laha, K.; Sam, Shiju; Nandagopal, M.; Panneer Selvi, S.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

2012-05-01

Tensile strength and flow behaviour of a Reduced Activation Ferritic-Martensitic (RAFM) steel (9Cr-1W-0.06Ta-0.22V-0.08C) have been investigated over a temperature range of 300-873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.

Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction

PubMed Central

Aiello, B. R.; Iriarte-Diaz, J.; Blob, R. W.; Butcher, M. T.; Carrano, M. T.; Espinoza, N. R.; Main, R. P.; Ross, C. F.

2015-01-01

Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar–canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction. PMID:26063842

Tissue Doppler, strain, and strain rate echocardiography for the assessment of left and right systolic ventricular function

PubMed Central

Pellerin, D; Sharma, R; Elliott, P; Veyrat, C

2003-01-01

Tissue Doppler (TDE), strain, and strain rate echocardiography are emerging real time ultrasound techniques that provide a measure of wall motion. They offer an objective means to quantify global and regional left and right ventricular function and to improve the accuracy and reproducibility of conventional echocardiography studies. Radial and longitudinal ventricular function can be assessed by the analysis of myocardial wall velocity and displacement indices, or by the analysis of wall deformation using the rate of deformation of a myocardial segment (strain rate) and its deformation over time (strain). A quick and easy assessment of left ventricular ejection fraction is obtained by mitral annular velocity measurement during a routine study, especially in patients with poor endocardial definition or abnormal septal motion. Strain rate and strain are less affected by passive myocardial motion and tend to be uniform throughout the left ventricle in normal subjects. This paper reviews the underlying principles of TDE, strain, and strain rate echocardiography and discusses currently available quantification tools and clinical applications. PMID:14594870

Dynamic Tensile Properties of Iron and Steels for a Wide Range of Strain Rates and Strain

NASA Astrophysics Data System (ADS)

Kojima, Nobusato; Hayashi, Hiroyuki; Yamamoto, Terumi; Mimura, Koji; Tanimura, Shinji

The tensile stress-strain curves of iron and a variety of steels, covering a wide range of strength level, over a wide strain rate range on the order of 10-3 ~ 103 s-1, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the strain rate sensitivity of the flow stress for the large strain region, including the viscous term at high strain rates, the true fracture strength and the true fracture strain were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide strain rate range.

Final Report Auto/Steel Partnership Phase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cady, C.M.; Chen, S.R.; Gray, G.T. III

1999-06-09

This is the final report in which effects of strain-rate, temperature, and stress-state on the yield stress and the strain hardening behavior of many common steels used in automobile construction were investigated. The yield and flow stresses were found to exhibit very high rate sensitivities for most of the steels while the hardening rates were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependencemore » of the yield stress on temperature and strain rate was found to decrease while the strain hardening rate increased. The Mechanical Threshold Stress (MTS) model was adopted to model the stress-strain behavior of the steels. Parameters for the constitutive relations were derived for the MTS model and also for the Johnson-Cook (JC) and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of these materials. The JC and ZA models, however, due to their use of a power strain hardening law were found to yield constitutive relations for the materials which are strongly dependent on the range of strains for which the models were optimized.« less

The dynamic compressive behavior and constitutive modeling of D1 railway wheel steel over a wide range of strain rates and temperatures

NASA Astrophysics Data System (ADS)

Jing, Lin; Su, Xingya; Zhao, Longmao

The dynamic compressive behavior of D1 railway wheel steel at high strain rates was investigated using a split Hopkinson pressure bar (SHPB) apparatus. Three types of specimens, which were derived from the different positions (i.e., the rim, web and hub) of a railway wheel, were tested over a wide range of strain rates from 10-3 s-1 to 2.4 × 103 s-1 and temperatures from 213 K to 973 K. Influences of the strain rate and temperature on flow stress were discussed, and rate- and temperature-dependent constitutive relationships were assessed by the Cowper-Symonds model, Johnson-Cook model and a physically-based model, respectively. The experimental results show that the compressive true stress versus true strain response of D1 wheel steel is strain rate-dependent, and the strain hardening rate during the plastic flow stage decreases with the elevation of strain rate. Besides, the D1 wheel steel displays obvious temperature-dependence, and the third-type strain aging (3rd SA) is occurred at the temperature region of 673-973 K at a strain rate of ∼1500 s-1. Comparisons of experimental results with theoretical predictions indicate that the physically-based model has a better prediction capability for the 3rd SA characteristic of the tested D1 wheel steel.

Strain rate dependent calcite microfabric evolution - an experiment carried out by nature

NASA Astrophysics Data System (ADS)

Rogowitz, A.; Huet, B.; Grasemann, B.; Habler, G.

2013-12-01

The deformation behaviour of calcite has been studied extensively in a number of experiments. Different strain rates and pressure and temperature conditions have been used to investigate a wide range of deformation regimes. However, a direct comparison with natural fault rocks remains difficult because of extreme differences between experimental and natural strain rates. A secondary shear zone (flanking structure) developed in almost pure calcite marble on Syros (Greece). Due to rotation of an elliptical inclusion (crack) a heterogeneous strain field in the surrounding area occurred resulting in different strain domains and the formation of the flanking structure. Assuming that deformation was active continuously during the development of the flanking structure, the different strain domains correspond to different strain-rate domains. The outcrop thus represents the final state of a natural experiment and gives us a great opportunity to get natural constraints on strain rate dependent deformation behaviour of calcite. Comparing the microfabrics in the 1 to 2.5 cm thick shear zone and the surrounding host rocks, which formed under the same metamorphic conditions but with different strain rates, is the central focus of this study. Due to the extreme variation in strain and strain rate, different microstructures and textures can be observed corresponding to different deformation mechanisms. With increasing strain rate we observe a change in dominant deformation mechanism from dislocation glide to dislocation creep and finally diffusion creep. Additionally, a change from subgrain rotation (SGR) to bulging (BLG) recrystallization can be observed in the dislocation creep regime. Textures and the degree of intracrystalline deformation have been measured by electron back scatter diffraction (EBSD). At all strain rates clear CPOs developed leading to the assumption that calcite preferentially deforms within the dislocation creep field. However, we can also find clear evidence for grain size sensitive deformation mechanisms at smaller grain sizes (3.6 μm) consistent with experimental observations and determined flaw laws. Although mylonitic layers evolve at high (10^-10 s^-1) and intermediate strain rates (10^-11 s^-1) by SGR recrystallization we observe variations in texture leading to the assumption that at varying strain rates different gliding systems were active. The results of this study are compared with experimental data, closing the gap between experimental and natural geological strain rates.

Forming limit curves of DP600 determined in high-speed Nakajima tests and predicted by two different strain-rate-sensitive models

NASA Astrophysics Data System (ADS)

Weiß-Borkowski, Nathalie; Lian, Junhe; Camberg, Alan; Tröster, Thomas; Münstermann, Sebastian; Bleck, Wolfgang; Gese, Helmut; Richter, Helmut

2018-05-01

Determination of forming limit curves (FLC) to describe the multi-axial forming behaviour is possible via either experimental measurements or theoretical calculations. In case of theoretical determination, different models are available and some of them consider the influence of strain rate in the quasi-static and dynamic strain rate regime. Consideration of the strain rate effect is necessary as many material characteristics such as yield strength and failure strain are affected by loading speed. In addition, the start of instability and necking depends not only on the strain hardening coefficient but also on the strain rate sensitivity parameter. Therefore, the strain rate dependency of materials for both plasticity and the failure behaviour is taken into account in crash simulations for strain rates up to 1000 s-1 and FLC can be used for the description of the material's instability behaviour at multi-axial loading. In this context, due to the strain rate dependency of the material behaviour, an extrapolation of the quasi-static FLC to dynamic loading condition is not reliable. Therefore, experimental high-speed Nakajima tests or theoretical models shall be used to determine the FLC at high strain rates. In this study, two theoretical models for determination of FLC at high strain rates and results of experimental high-speed Nakajima tests for a DP600 are presented. One of the theoretical models is the numerical algorithm CRACH as part of the modular material and failure model MF GenYld+CrachFEM 4.2, which is based on an initial imperfection. Furthermore, the extended modified maximum force criterion considering the strain rate effect is also used to predict the FLC. These two models are calibrated by the quasi-static and dynamic uniaxial tensile tests and bulge tests. The predictions for the quasi-static and dynamic FLC by both models are presented and compared with the experimental results.

Construction of Protograph LDPC Codes with Linear Minimum Distance

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Dolinar, Sam; Jones, Christopher

2006-01-01

A construction method for protograph-based LDPC codes that simultaneously achieve low iterative decoding threshold and linear minimum distance is proposed. We start with a high-rate protograph LDPC code with variable node degrees of at least 3. Lower rate codes are obtained by splitting check nodes and connecting them by degree-2 nodes. This guarantees the linear minimum distance property for the lower-rate codes. Excluding checks connected to degree-1 nodes, we show that the number of degree-2 nodes should be at most one less than the number of checks for the protograph LDPC code to have linear minimum distance. Iterative decoding thresholds are obtained by using the reciprocal channel approximation. Thresholds are lowered by using either precoding or at least one very high-degree node in the base protograph. A family of high- to low-rate codes with minimum distance linearly increasing in block size and with capacity-approaching performance thresholds is presented. FPGA simulation results for a few example codes show that the proposed codes perform as predicted.

Behavioral and physiological significance of minimum resting metabolic rate in king penguins.

PubMed

Halsey, L G; Butler, P J; Fahlman, A; Woakes, A J; Handrich, Y

2008-01-01

Because fasting king penguins (Aptenodytes patagonicus) need to conserve energy, it is possible that they exhibit particularly low metabolic rates during periods of rest. We investigated the behavioral and physiological aspects of periods of minimum metabolic rate in king penguins under different circumstances. Heart rate (f(H)) measurements were recorded to estimate rate of oxygen consumption during periods of rest. Furthermore, apparent respiratory sinus arrhythmia (RSA) was calculated from the f(H) data to determine probable breathing frequency in resting penguins. The most pertinent results were that minimum f(H) achieved (over 5 min) was higher during respirometry experiments in air than during periods ashore in the field; that minimum f(H) during respirometry experiments on water was similar to that while at sea; and that RSA was apparent in many of the f(H) traces during periods of minimum f(H) and provides accurate estimates of breathing rates of king penguins resting in specific situations in the field. Inferences made from the results include that king penguins do not have the capacity to reduce their metabolism to a particularly low level on land; that they can, however, achieve surprisingly low metabolic rates at sea while resting in cold water; and that during respirometry experiments king penguins are stressed to some degree, exhibiting an elevated metabolism even when resting.

Modeling of Impression Testing to Obtain Mechanical Properties of Lead-Free Solders Microelectronic Interconnects

DTIC Science & Technology

2005-12-01

hardening exponent and Cimp is the impression strain-rate hardening coefficient. The strain-rate hardening exponent m is a parameter that is...exponent and Cimp is the impression strain-rate hardening coefficient. The strain-rate hardening exponent m is a parameter that is related to the creep

Development of constitutive models for cyclic plasticity and creep behavior of super alloys at high temperature

NASA Technical Reports Server (NTRS)

Haisler, W. E.

1983-01-01

An uncoupled constitutive model for predicting the transient response of thermal and rate dependent, inelastic material behavior was developed. The uncoupled model assumes that there is a temperature below which the total strain consists essentially of elastic and rate insensitive inelastic strains only. Above this temperature, the rate dependent inelastic strain (creep) dominates. The rate insensitive inelastic strain component is modelled in an incremental form with a yield function, blow rule and hardening law. Revisions to the hardening rule permit the model to predict temperature-dependent kinematic-isotropic hardening behavior, cyclic saturation, asymmetric stress-strain response upon stress reversal, and variable Bauschinger effect. The rate dependent inelastic strain component is modelled using a rate equation in terms of back stress, drag stress and exponent n as functions of temperature and strain. A sequence of hysteresis loops and relaxation tests are utilized to define the rate dependent inelastic strain rate. Evaluation of the model has been performed by comparison with experiments involving various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy X.

The response of equine cortical bone to loading at strain rates experienced in vivo by the galloping horse.

PubMed

Evans, G P; Behiri, J C; Vaughan, L C; Bonfield, W

1992-03-01

The behaviour of cortical bone under load is strain rate-dependent, i.e. it is dependent on the rate at which the load is applied. This is particularly relevant in the galloping horse since the strain rates experienced by the bone are far in excess of those recorded for any other species. In this study the effect of strain rates between 0.0001 and 1 sec-1 on the mechanical properties of equine cortical bone were assessed. Initially, increasing strain rates resulted in increased mechanical properties. Beyond a critical value, however, further increases in strain rate resulted in lower strain to failure and energy absorbing capacity. This critical rate occurred around 0.1 sec-1 which is within the in vivo range for a galloping racehorse. Analysis of the stress-strain curves revealed a transition in the type of deformation at this point from pseudo-ductile to brittle. Bones undergoing brittle deformation are more likely to fail under load, leading to catastrophic fracture and destruction of the animal.

29 CFR 511.2 - Initiation of proceedings; notices of hearings.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., giving notice of hearings by industry committees to recommend the minimum rate or rates of wages to be... the minimum rate or rates of wages for all industry in American Samoa. All such orders will make... Section 511.2 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR...

Antibiotic resistance assessment in S. aureus strains isolated from raw sheep's milk cheese.

PubMed

Spanu, V; Virdis, S; Scarano, C; Cossu, F; De Santis, E P L; Cosseddu, A M

2010-06-01

In vitro activities of 16 antibiotics were tested against 36 Staphylococcus aureus (SA) strains isolated from raw sheep's milk cheese from six dairies. The minimum inhibitory concentration (MIC) was determined using a broth microdilution method (CLSI). All 36 isolates were analyzed for the presence of the accessory gene regulator gene, agr (I-IV), and genes encoding resistance to methicillin (mecA), erythromycin (ermA), penicillin (blaZ), and vancomycin (vanA-B). The isolates were also analyzed for similarities in pulsed-field gel electrophoresis (PFGE) patterns. SA strains showed resistance to ampicillin (36.1%), penicillin (33.3%), tetracycline (11.1%), and cloxacillin (2.8%) but were susceptible (>or=94.4%) to 12 out of 16 tested antimicrobials. The overall susceptibility of the strains to oxacillin, vancomycin, and erythromycin was confirmed by the absence of the mecA, vanA-B, and ermA genes. The PFGE results showed that 32 strains belonged to 10 different clusters (P1-P10) while four strains were untypeable.

In vitro susceptibility of Helicobacter pullorum strains to different antimicrobial agents.

PubMed

Ceelen, Liesbeth; Decostere, Annemie; Devriese, Luc A; Ducatelle, Richard; Haesebrouck, Freddy

2005-01-01

The in vitro activity of 13 antimicrobial agents against 23 Helicobacter pullorum strains from poultry (21) and human (two) origin, and one human H. canadensis strain was tested by the agar dilution method. With the H. pullorum strains, monomodal distributions of Minimum Inhibitory Concentrations (MICs) were seen with lincomycin, doxycycline, gentamicin, tobramycin, erythromycin, tylosin, metronidazole, and enrofloxacin in concentration ranges considered as indicating susceptibility in other bacteria. The normal susceptibility level for nalidixic acid was situated at or slightly above the MIC breakpoints proposed for Campylobacteriaceae. Ampicillin, ceftriaxone, and sulphamethoxazole-trimethoprim showed poor activity against H. pullorum. For the H. canadensis strain, a similar susceptibility pattern was seen, except for nalidixic acid and enrofloxacin, whose MIC of >512 and 8 microg/ml, respectively, indicated resistance of this agent. With spectinomycin, a bimodal distribution of the MICs was noted for the tested strains; eight H. pullorum isolates originating from one flock showed acquired resistance (MIC>512 microg/ml).

Earthquake potential in California-Nevada implied by correlation of strain rate and seismicity

USGS Publications Warehouse

Zeng, Yuehua; Petersen, Mark D.; Shen, Zheng-Kang

2018-01-01

Rock mechanics studies and dynamic earthquake simulations show that patterns of seismicity evolve with time through (1) accumulation phase, (2) localization phase, and (3) rupture phase. We observe a similar pattern of changes in seismicity during the past century across California and Nevada. To quantify these changes, we correlate GPS strain rates with seismicity. Earthquakes of M > 6.5 are collocated with regions of highest strain rates. By contrast, smaller magnitude earthquakes of M ≥ 4 show clear spatiotemporal changes. From 1933 to the late 1980s, earthquakes of M ≥ 4 were more diffused and broadly distributed in both high and low strain rate regions (accumulation phase). From the late 1980s to 2016, earthquakes were more concentrated within the high strain rate areas focused on the major fault strands (localization phase). In the same time period, the rate of M > 6.5 events also increased significantly in the high strain rate areas. The strong correlation between current strain rate and the later period of seismicity indicates that seismicity is closely related to the strain rate. The spatial patterns suggest that before the late 1980s, the strain rate field was also broadly distributed because of the stress shadows from previous large earthquakes. As the deformation field evolved out of the shadow in the late 1980s, strain has refocused on the major fault systems and we are entering a period of increased risk for large earthquakes in California.

Earthquake Potential in California-Nevada Implied by Correlation of Strain Rate and Seismicity

NASA Astrophysics Data System (ADS)

Zeng, Yuehua; Petersen, Mark D.; Shen, Zheng-Kang

2018-02-01

Rock mechanics studies and dynamic earthquake simulations show that patterns of seismicity evolve with time through (1) accumulation phase, (2) localization phase, and (3) rupture phase. We observe a similar pattern of changes in seismicity during the past century across California and Nevada. To quantify these changes, we correlate GPS strain rates with seismicity. Earthquakes of M > 6.5 are collocated with regions of highest strain rates. By contrast, smaller magnitude earthquakes of M ≥ 4 show clear spatiotemporal changes. From 1933 to the late 1980s, earthquakes of M ≥ 4 were more diffused and broadly distributed in both high and low strain rate regions (accumulation phase). From the late 1980s to 2016, earthquakes were more concentrated within the high strain rate areas focused on the major fault strands (localization phase). In the same time period, the rate of M > 6.5 events also increased significantly in the high strain rate areas. The strong correlation between current strain rate and the later period of seismicity indicates that seismicity is closely related to the strain rate. The spatial patterns suggest that before the late 1980s, the strain rate field was also broadly distributed because of the stress shadows from previous large earthquakes. As the deformation field evolved out of the shadow in the late 1980s, strain has refocused on the major fault systems and we are entering a period of increased risk for large earthquakes in California.

Impact of Rate Design Alternatives on Residential Solar Customer Bills: Increased Fixed Charges, Minimum Bills and Demand-Based Rates

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLaren, Joyce; Davidson, Carolyn; Miller, John

Utilities are proposing changes to residential rate structures to address concerns about lost revenue due to increased adoption of distributed solar generation. An investigation of the impacts of increased fixed charges, minimum bills and residential demand charges on PV and non-PV customer bills suggests that minimum bills more accurately capture utilities' revenue requirement than fixed charges, while not acting as a disincentive to efficiency or negatively impacting low-income customers.

Advancements in dynamic kill calculations for blowout wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kouba, G.E.; MacDougall, G.R.; Schumacher, B.W.

1993-09-01

This paper addresses the development, interpretation, and use of dynamic kill equations. To this end, three simple calculation techniques are developed for determining the minimum dynamic kill rate. Two techniques contain only single-phase calculations and are independent of reservoir inflow performance. Despite these limitations, these two methods are useful for bracketing the minimum flow rates necessary to kill a blowing well. For the third technique, a simplified mechanistic multiphase-flow model is used to determine a most-probable minimum kill rate.

THE EFFECT OF STRAIN RATE ON FRACTURE TOUGHNESS OF HUMAN CORTICAL BONE: A FINITE ELEMENT STUDY

PubMed Central

Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

2011-01-01

Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08 to 18 s−1). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of microcomputed tomography-based compact tension specimens. The simulation results showed that bone’s resistance against the propagation of fracture decreased sharply with increase in strain rates up to 1 s−1 and attained an almost constant value for strain rates larger than 1 s−1. On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone’s resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture. PMID:21783112

Dynamic strain aging in the high-temperature low-cycle fatigue of SA508 Cl. 3 forging steel

NASA Astrophysics Data System (ADS)

Lee, Byung Ho; Kim, In Sup

1995-10-01

The effect of dynamic strain aging on cyclic stress response and fatigue resistance of ASME SA508 Cl.3 forging steel for nuclear reactor pressure vessels has been evaluated in the temperature range of room temperature to 500°C. Total strain ranges and strain rates were varied from 0.7 to 2.0% and from 4 × 10 -4 to 1 × 10 -2 s -1, respectively. The cyclic stress response depended on the testing temperature, strain rate, and range. Generally, the initial cyclic hardening was immediately followed by cyclic softening at all strain rates. However, at 300°C, the operating temperature of nuclear reactor pressure vessels, the variation of cyclic stress amplitude showed the primary and secondary hardening stages dependent on the strain rate and strain range. Dynamic strain aging was manifested by enhanced cyclic hardening, distinguished secondary hardening, and negative strain rate sensitivity. A modified cell shutting model was described for the onset of the secondary hardening due to the dynamic strain aging and it was in good agreement with the experimental results. Fatigue life increased in strain rate at all testing temperatures. Specifically the fatigue life was longer at the dynamic strain aging temperature. Further, the dynamic strain aging was easy to initiate the crack, while crack propagation was retarded by crack branching and suppression of plastic zone, hence the dynamic strain aging caused the improvement of fatigue resistance.

A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields

NASA Astrophysics Data System (ADS)

Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

2016-07-01

We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields.

PubMed

Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

2016-07-01

We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

Ultra High Strain Rate Nanoindentation Testing.

PubMed

Sudharshan Phani, Pardhasaradhi; Oliver, Warren Carl

2017-06-17

Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition rates (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high strain rates. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation strain rates approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of strain rate dependence of hardness spanning over seven orders of magnitude in strain rate is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of strain rate.

Creep Strain and Strain Rate Response of 2219 Al Alloy at High Stress Levels

NASA Technical Reports Server (NTRS)

Taminger, Karen M. B.; Wagner, John A.; Lisagor, W. Barry

1998-01-01

As a result of high localized plastic deformation experienced during proof testing in an International Space Station connecting module, a study was undertaken to determine the deformation response of a 2219-T851 roll forging. After prestraining 2219-T851 Al specimens to simulate strains observed during the proof testing, creep tests were conducted in the temperature range from ambient temperature to 107 C (225 F) at stress levels approaching the ultimate tensile strength of 2219-T851 Al. Strain-time histories and strain rate responses were examined. The strain rate response was extremely high initially, but decayed rapidly, spanning as much as five orders of magnitude during primary creep. Select specimens were subjected to incremental step loading and exhibited initial creep rates of similar magnitude for each load step. Although the creep rates decreased quickly at all loads, the creep rates dropped faster and reached lower strain rate levels for lower applied loads. The initial creep rate and creep rate decay associated with primary creep were similar for specimens with and without prestrain; however, prestraining (strain hardening) the specimens, as in the aforementioned proof test, resulted in significantly longer creep life.

Interseismic Strain Accumulation Across Metropolitan Los Angeles: Puente Hills Thrust

NASA Astrophysics Data System (ADS)

Argus, D.; Liu, Z.; Heflin, M. B.; Moore, A. W.; Owen, S. E.; Lundgren, P.; Drake, V. G.; Rodriguez, I. I.

2012-12-01

Twelve years of observation of the Southern California Integrated GPS Network (SCIGN) are tightly constraining the distribution of shortening across metropolitan Los Angeles, providing information on strain accumulation across blind thrust faults. Synthetic Aperture Radar Interferometry (InSAR) and water well records are allowing the effects of water and oil management to be distinguished. The Mojave segment of the San Andreas fault is at a 25° angle to Pacific-North America plate motion. GPS shows that NNE-SSW shortening due to this big restraining bend is fastest not immediately south of the San Andreas fault across the San Gabriel mountains, but rather 50 km south of the fault in northern metropolitan Los Angeles. The GPS results we quote next are for a NNE profile through downtown Los Angeles. Just 2 mm/yr of shortening is being taken up across the San Gabriel mountains, 40 km wide (0.05 micro strain/yr); 4 mm/yr of shortening is being taken up between the Sierra Madre fault, at the southern front of the San Gabriel mountains, and South Central Los Angeles, also 40 km wide (0.10 micro strain/yr). We find shortening to be more evenly distributed across metropolitan Los Angeles than we found before [Argus et al. 2005], though within the 95% confidence limits. An elastic models of interseismic strain accumulation is fit to the GPS observations using the Back Slip model of Savage [1983]. Rheology differences between crystalline basement and sedimentary basin rocks are incorporated using the EDGRN/EDCMP algorithm of Wang et al. [2003]. We attempt to place the Back Slip model into the context of the Elastic Subducting Plate Model of Kanda and Simons [2010]. We find, along the NNE profile through downtown, that: (1) The deep Sierra Madre Thrust cannot be slipping faster than 2 mm/yr, and (2) The Puente Hills Thrust and nearby thrust faults (such as the upper Elysian Park Thrust) are slipping at 9 ±2 mm/yr beneath a locking depth of 12 ±5 km (95% confidence limits). Incorporating sedimentary basin rock either reduces the slip rate by 10 per cent or increases the locking rate by 20 per cent. The 9 mm/yr rate for the Puente Hills Thrust and nearby faults exceeds the cumulative 3-5 mm/yr rate estimated using paleoseismology along the Puente Hills Thrust (1.2-1.6 mm/yr, Dolan et al. 2003), upper Elysian Park Thrust (0.6-2.2 mm/yr, Oskin et al. 2000), and western Compton Thrust (1.2 mm/yr, Leon et al. 2009], though all the paleoseismic estimates are minimums. We infer that M 7 earthquakes in northern metropolitan Los Angeles may occur more frequently that previously thought.

Relating rheology to geometry in large-scale natural shear zones

NASA Astrophysics Data System (ADS)

Platt, John

2016-04-01

The geometry and width of the ductile roots of plate boundary scale faults are very poorly understood. Some field and geophysical data suggests widths of tens of km in the lower crust, possibly more in the upper mantle. Other observations suggest they are much narrower. Dip slip shear zones may flatten out and merge into zones of subhorizontal lower crustal or asthenospheric flow. The width of a ductile shear zone is simply related to relative velocity and strain rate. Strain rate is related to stress through the constitutive relationship. Can we constrain the stress, and do we understand the rheology of materials in ductile shear zones? A lot depends on how shear zones are initiated. If they are localized by pre-existing structures, width and/or rheology may be inherited, and we have too many variables. If shear zones are localized primarily by shear heating, initial shear stress has to be very high (> 1 GPa) to overcome conductive heat loss, and very large feedbacks (both positive and negative) make the system highly unstable. Microstructural weakening requires a minimum level of stress to cause deformation and damage in surrounding rock, thereby buffering the stress. Microstructural weakening leads to grain-size sensitive creep, for which we have constitutive laws, but these are complicated by phase mixing in polyphase materials, by viscous anisotropy, by hydration, and by changes in mineral assemblage. Here are some questions that need to be addressed. (1) If grain-size reduction by dynamic recrystallization results in a switch to grain-size sensitive creep (GSSC) in a stress-buffered shear zone, does dynamic recrystallization stop? Does grain growth set in? If grain-size is still controlled by dislocation processes, then the effective stress exponent for GSSC is 4-5, even though the dominant mechanism may be diffusion and/or grain-boundary sliding (GBS). (2) Is phase mixing in ultramylonites primarily a result of GBS + neighbour switching, creep cavitation and diffusion, or metamorphic reactions? (3) In two-phase / polyphase mixtures, does the strong phase generally form a load-bearing framework, favoring constant strain-rate (Voigt) bound behavior, or does the weak phase form through-going strain pathways, favoring constant stress (Reuss) bound behavior, or do the phases remain well mixed, favoring an intermediate behavior (e.g., Tullis et al model)? (4) How do we deal with the rheological effect of water? Is it simply an unconstrained variable in nature? Is the water fugacity model in flow laws adequate? (5) How can we better relate experimental results (often carried out at constant strain-rate, and not reaching microstructural steady state) to deformation in natural shear zones? Rheological observations on well-constrained natural shear zones are helping us answer some of these questions.

Relationships of left ventricular strain and strain rate to wall stress and their afterload dependency.

PubMed

Murai, Daisuke; Yamada, Satoshi; Hayashi, Taichi; Okada, Kazunori; Nishino, Hisao; Nakabachi, Masahiro; Yokoyama, Shinobu; Abe, Ayumu; Ichikawa, Ayako; Ono, Kota; Kaga, Sanae; Iwano, Hiroyuki; Mikami, Taisei; Tsutsui, Hiroyuki

2017-05-01

Whether and how left ventricular (LV) strain and strain rate correlate with wall stress is not known. Furthermore, it is not determined whether strain or strain rate is less dependent on the afterload. In 41 healthy young adults, LV global peak strain and systolic peak strain rate in the longitudinal direction (LS and LSR, respectively) and circumferential direction (CS and CSR, respectively) were measured layer-specifically using speckle tracking echocardiography (STE) before and during a handgrip exercise. Among all the points before and during the exercise, all the STE parameters significantly correlated linearly with wall stress (LS: r = -0.53, p < 0.01, LSR: r = -0.28, p < 0.05, CS in the inner layer: r = -0.72, p < 0.01, CSR in the inner layer: r = -0.47, p < 0.01). Strain more strongly correlated with wall stress than strain rate (r = -0.53 for LS vs. r = -0.28 for LSR, p < 0.05; r = -0.72 for CS vs. r = -0.47 for CSR in the inner layer, p < 0.05), whereas the interobserver variability was similar between strain and strain rate (longitudinal 6.2 vs. 5.2 %, inner circumferential 4.8 vs. 4.7 %, mid-circumferential 7.9 vs. 6.9 %, outer circumferential 10.4 vs. 9.7 %), indicating that the differences in correlation coefficients reflect those in afterload dependency. It was thus concluded that LV strain and strain rate linearly and inversely correlated with wall stress in the longitudinal and circumferential directions, and strain more strongly depended on afterload than did strain rate. Myocardial shortening should be evaluated based on the relationships between these parameters and wall stress.

Assessment of myocardial mechanics in patients with end-stage renal disease and renal transplant recipients using speckle tracking echocardiography.

PubMed

Pirat, Bahar; Bozbas, Huseyin; Simsek, Vahide; Sade, L Elif; Sayin, Burak; Muderrisoglu, Haldun; Haberal, Mehmet

2015-04-01

Velocity vector imaging allows quantitation of myocardial strain and strain rate from 2-dimensional images based on speckle tracking echocardiography. The aim of this study was to analyze the changes in myocardial strain and strain rate patterns in patients with end-stage renal disease and renal transplant recipients. We studied 33 patients with end-stage renal disease on hemodialysis (19 men; mean age, 36 ± 8 y), 24 renal transplant recipients with functional grafts (21 men; mean age, 36 ± 7 y) and 26 age- and sex-matched control subjects. Longitudinal peak systolic strain and strain rate for basal, mid, and apical segments of the left ventricular wall were determined by velocity vector imaging from apical 4- and 2-chamber views. The average longitudinal strain and strain rate for the left ventricle were noted. From short-axis views at the level of papillary muscles, average circumferential, and radial strain, and strain rate were assessed. Mean heart rate and systolic and diastolic blood pressure during imaging were similar between the groups. Longitudinal peak systolic strain and strain rate at basal and mid-segments of the lateral wall were significantly higher in renal transplant recipients and control groups than endstage renal disease patients. Average longitudinal systolic strain from the 4-chamber view was highest in control subjects (-14.5% ± 2.9%) and was higher in renal transplant recipients (-12.5% ± 3.0%) than end-stage renal disease patients (-10.2% ± 1.6%; P ≤ .001). Radial and circumferential strain and strain rate at the level of the papillary muscle were lower in patients with end-stage renal disease than other groups. Differences in myocardial function in patients with end-stage renal disease, renal transplant recipients, and normal controls can be quantified by strain imaging. Myocardial function is improved in renal transplant recipients compared with end-stage renal disease patients.

Phytochemical, antimicrobial, and antioxidant activities of different citrus juice concentrates.

PubMed

Oikeh, Ehigbai I; Omoregie, Ehimwenma S; Oviasogie, Faith E; Oriakhi, Kelly

2016-01-01

The search for new antimicrobial compounds is ongoing. Its importance cannot be overemphasized in an era of emerging resistant pathogenic organisms. This study therefore investigated the phytochemical composition and antioxidant and antimicrobial activities of different citrus juice concentrates. Fruit juices of Citrus tangerine (tangerine), Citrus paradisi (grape), Citrus limon (lemon), and Citrus aurantifolia (lime) were evaluated. Antimicrobial activities against five bacterial and three fungal strains were evaluated. The results revealed the presence of alkaloids, flavonoids, steroids, terpenoids, saponins, cardiac glycosides, and reducing sugars in all the juice concentrates. DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging capacities varied with tangerine and grape juices having better scavenging capacities than lemon and lime juices. Grape juice was observed to have a significantly higher (P < 0.05) ferric-reducing antioxidant potential (FRAP) value (364.2 ± 10.25 μmol/L Fe(II)/g of the extract) than the reference antioxidant, ascorbic acid (312.88 ± 5.61 μmol/L). Antimicrobial studies revealed differential antimicrobial activities against different microbial strains. Zones of inhibition ranging from 4 to 26 mm were observed for the antibacterial tests with 0-24 mm for antifungal test. Minimum inhibitory concentrations (MIC) and minimum bacteriostatic concentrations (MBC) for concentrates against bacterial strains ranged from 12.5 to 200 μg/mL. Lemon and lime juice concentrates had lower MIC and MBC values with orange and tangerine having the highest values. Minimum fungicidal concentrations ranged from 50 to 200 μg/mL. The results of this study suggest that these juice concentrates may have beneficial antimicrobial roles that can be exploited in controlling unwanted microbial growth.

Silver nanoparticles from Pilimelia columellifera subsp. pallida SL19 strain demonstrated antifungal activity against fungi causing superficial mycoses.

PubMed

Wypij, Magdalena; Czarnecka, Joanna; Dahm, Hanna; Rai, Mahendra; Golinska, Patrycja

2017-09-01

In this study, we present the in vitro antifungal activity of silver nanoparticles (AgNPs) synthesized from acidophilic actinobacterium Pilimelia columellifera subsp. pallida SL19 strain, alone and in combination with antibiotics viz., amphotericin B, fluconazole, and ketoconazole against pathogenic fungi, namely Candida albicans, Malassezia furfur, and Trichophyton erinacei. The minimum inhibitory concentration (MIC) and minimum biocidal concentration (MBC) of AgNPs against test fungi were evaluated. The fractional inhibitory concentration (FIC) index was determined to estimate antifungal activity of AgNPs combined with antibiotics. Antifungal activity of AgNPs varied among the tested fungal strains. M. furfur was found to be most sensitive to biogenic silver nanoparticles, followed by C. albicans and T. erinacei. The lowest MIC of AgNPs was noticed against M. furfur (16 μg ml -1 ). Synergistic effect was observed on C. albicans when AgNP were combined with amphotericin B and ketoconazole and on M. furfur with fluconazole and ketoconazole (FIC index of 0.5). Cytotoxic effect of AgNPs on HeLa and 3T3 cell lines was evaluated. The IC 50 values were found to be 55 and 25 μg ml -1 , respectively. The present study indicates that silver nanoparticles from P. columellifera subsp. pallida SL19 strain have antifungal activity, both alone and in combination with antibiotics, and offer a valuable contribution to nanomedicine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

5 CFR 551.301 - Minimum wage.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for all...

Characteristic systolic waveform of left ventricular longitudinal strain rate in patients with hypertrophic cardiomyopathy.

PubMed

Okada, Kazunori; Kaga, Sanae; Mikami, Taisei; Masauzi, Nobuo; Abe, Ayumu; Nakabachi, Masahiro; Yokoyama, Shinobu; Nishino, Hisao; Ichikawa, Ayako; Nishida, Mutsumi; Murai, Daisuke; Hayashi, Taichi; Shimizu, Chikara; Iwano, Hiroyuki; Yamada, Satoshi; Tsutsui, Hiroyuki

2017-05-01

We analyzed the waveform of systolic strain and strain-rate curves to find a characteristic left ventricular (LV) myocardial contraction pattern in patients with hypertrophic cardiomyopathy (HCM), and evaluated the utility of these parameters for the differentiation of HCM and LV hypertrophy secondary to hypertension (HT). From global strain and strain-rate curves in the longitudinal and circumferential directions, the time from mitral valve closure to the peak strains (T-LS and T-CS, respectively) and the peak systolic strain rates (T-LSSR and T-CSSR, respectively) were measured in 34 patients with HCM, 30 patients with HT, and 25 control subjects. The systolic strain-rate waveform was classified into 3 patterns ("V", "W", and "√" pattern). In the HCM group, T-LS was prolonged, but T-LSSR was shortened; consequently, T-LSSR/T-LS ratio was distinctly lower than in the HT and control groups. The "√" pattern of longitudinal strain-rate waveform was more frequently seen in the HCM group (74 %) than in the control (4 %) and HT (20 %) groups. Similar but less distinct results were obtained in the circumferential direction. To differentiate HCM from HT, the sensitivity and specificity of the T-LSSR/T-LS ratio <0.34 and the "√"-shaped longitudinal strain-rate waveform were 85 and 63 %, and 74 and 80 %, respectively. In conclusion, in patients with HCM, a reduced T-LSSR/T-LS ratio and a characteristic "√"-shaped waveform of LV systolic strain rate was seen, especially in the longitudinal direction. The timing and waveform analyses of systolic strain rate may be useful to distinguish between HCM and HT.

Orientations of dendritic growth during solidification

NASA Astrophysics Data System (ADS)

Lee, Dong Nyung

2017-03-01

Dendrites are crystalline forms which grow far from the limit of stability of the plane front and adopt an orientation which is as close as possible to the heat flux direction. Dendritic growth orientations for cubic metals, bct Sn, and hcp Zn, can be controlled by thermal conductivity, Young's modulus, and surface energy. The control factors have been elaborated. Since the dendrite is a single crystal, its properties such as thermal conductivity that influences the heat flux direction, the minimum Young's modulus direction that influences the strain energy minimization, and the minimum surface energy plane that influences the crystal/liquid interface energy minimization have been proved to control the dendritic growth direction. The dendritic growth directions of cubic metals are determined by the minimum Young's modulus direction and/or axis direction of symmetry of the minimum crystal surface energy plane. The dendritic growth direction of bct Sn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction. The primary dendritic growth direction of hcp Zn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction and the secondary dendrite arm direction of hcp Zn is normal to the primary dendritic growth direction.

Effect of Strain Rate on Hot Ductility Behavior of a High Nitrogen Cr-Mn Austenitic Steel

NASA Astrophysics Data System (ADS)

Wang, Zhenhua; Meng, Qing; Qu, Minggui; Zhou, Zean; Wang, Bo; Fu, Wantang

2016-03-01

18Mn18Cr0.6N steel specimens were tensile tested between 1173 K and 1473 K (900 °C and 1200 °C) at 9 strain rates ranging from 0.001 to 10 s-1. The tensile strained microstructures were analyzed through electron backscatter diffraction analysis. The strain rate was found to affect hot ductility by influencing the strain distribution, the extent of dynamic recrystallization and the resulting grain size, and dynamic recovery. The crack nucleation sites were primarily located at grain boundaries and were not influenced by the strain rate. At 1473 K (1200 °C), a higher strain rate was beneficial for grain refinement and preventing hot cracking; however, dynamic recovery appreciably occurred at 0.001 s-1 and induced transgranular crack propagation. At 1373 K (1100 °C), a high extent of dynamic recrystallization and fine new grains at medium strain rates led to good hot ductility. The strain gradient from the interior of the grain to the grain boundary increased with decreasing strain rate at 1173 K and 1273 K (900 °C and 1000 °C), which promoted hot cracking. Grain boundary sliding accompanied grain rotation and did not contribute to hot cracking.

In vitro anti-mycobacterial activities of three species of Cola plant extracts (Sterculiaceae).

PubMed

Adeniyi, B A; Groves, M J; Gangadharam, P R J

2004-05-01

Extracts obtained from three Nigerian Sterculiaceae plants: Cola accuminata, C. nitida and C. milleni were screened for anti-mycobacterium properties using a slow growing Mycobacterium bovis ATCC 35738 (designated BCG Mexican and known to have some virulence in mouse and guinea pig) at 1000 microg/ml using the radiometric (BACTEC) method. The extracts were also tested against six fast growing ATCC strains of M. vaccae using the broth microdilution method. The methanol extracts from both leaves, stem bark and root bark of Cola accuminata and from the leaves and stem bark of C. nitida and C. milleni were not active at the highest concentration of 1000 microg/ml. Only the methanol extract of root bark for both C. nitida and C. milleni were found to be potent against both M. bovis and strains of M. vaccae. The minimum inhibitory concentration (MIC) of C. nitida against M. bovis is 125 microg/ml while the MIC of C. milleni against M. bovis is 62.5 microg/ml after at least 6 days of inhibition with growth index (GI) units lesser than or equal to the change in GI units inoculated with a 1/100 of the BACTEC inoculum for a control vial. The minimum inhibitory concentration of C. milleni against the six ATCC strain of M. vaccae ranged from 62.5 microg/ml to 250 microg/ml while for C. nitida ranged from 500 microg/ml to above 1000microg/ml. Evidently, C. milleni has the highest inhibitory activity against both M. bovis and strains of M. vaccae used. Rifampicin, the positive control used has strong activity against M. bovis at the tested concentration of 5 microg and 10 microg/ml and 4 to 8 microg/ml against the six strains of M. vaccae. Copyright 2004 John Wiley & Sons, Ltd.

Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into Strain Rate Dependent Analyses of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.

2004-01-01

A numerical procedure has been developed to investigate the nonlinear and strain rate dependent deformation response of polymer matrix composite laminated plates under high strain rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain rate dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed strain rate dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain rate loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.

Constitutive behavior of tantalum and tantalum-tungsten alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, S.R.; Gray, G.T. III

1996-10-01

The effects of strain rate, temperature, and tungsten alloying on the yield stress and the strain-hardening behavior of tantalum were investigated. The yield and flow stresses of unalloyed Ta and tantalum-tungsten alloys were found to exhibit very high rate sensitivities, while the hardening rates in Ta and Ta-W alloys were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependence of yield stress on temperaturemore » and strain rate was found to decrease, while the strain-hardening rate increased with tungsten alloying content. The mechanical threshold stress (MTS) model was adopted to model the stress-strain behavior of unalloyed Ta and the Ta-W alloys. Parameters for the constitutive relations for Ta and the Ta-W alloys were derived for the MTS model, the Johnson-Cook (JC), and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of Ta and Ta-W alloys. The JC and ZA models, however, due to their use of a power strain-hardening law, were found to yield constitutive relations for Ta and Ta-W alloys that are strongly dependent on the range of strains for which the models were optimized.« less

A new analytical method for estimating lumped parameter constants of linear viscoelastic models from strain rate tests

NASA Astrophysics Data System (ADS)

Mattei, G.; Ahluwalia, A.

2018-04-01

We introduce a new function, the apparent elastic modulus strain-rate spectrum, E_{app} ( \\dot{ɛ} ), for the derivation of lumped parameter constants for Generalized Maxwell (GM) linear viscoelastic models from stress-strain data obtained at various compressive strain rates ( \\dot{ɛ}). The E_{app} ( \\dot{ɛ} ) function was derived using the tangent modulus function obtained from the GM model stress-strain response to a constant \\dot{ɛ} input. Material viscoelastic parameters can be rapidly derived by fitting experimental E_{app} data obtained at different strain rates to the E_{app} ( \\dot{ɛ} ) function. This single-curve fitting returns similar viscoelastic constants as the original epsilon dot method based on a multi-curve global fitting procedure with shared parameters. Its low computational cost permits quick and robust identification of viscoelastic constants even when a large number of strain rates or replicates per strain rate are considered. This method is particularly suited for the analysis of bulk compression and nano-indentation data of soft (bio)materials.

Screening for unicellular algae as possible bioassay organisms for monitoring marine water samples.

PubMed

Millán de Kuhn, Rosmary; Streb, Christine; Breiter, Roman; Richter, Peter; Neesse, Thomas; Häder, Donat-Peter

2006-08-01

ECOTOX is an automatic early warning system to monitor potential pollution of freshwater, municipal or industrial waste waters or aquatic ecosystems. It is based on a real time image analysis of the motility and orientation parameters of the unicellular, photosynthetic flagellate Euglena gracilis. In order to widen the use of the device to marine habitats and saline waters nine marine flagellates were evaluated as putative bioassay organisms, viz. Dunaliella salina, Dunaliella viridis, Dunaliella bardawil, Prorocentrum minimum Kattegat, P. minimum Lissabon, Tetraselmis suecica, Heterocapsa triquetra, Gyrodinium dorsum and Cryptomonas maculata. Because of their slow growth the last three strains were excluded from further evaluation. Selection criteria were ease of culture, density of cell suspension, stability of motility and gravitactic orientation. The sensitivity toward toxins was tested using copper(II) ions. The instrument allows the user to automatically determine effect-concentration (EC) curves from which the EC(50) values can be calculated. For the interpretation of the EC curves a sigmoid logistic model was proposed which proved to be satisfactory for all tested strains. The inhibition of the motility was considered as the most appropriate movement parameter as an endpoint. The Dunaliella species had the lowest sensitivity to copper with EC(50) values of 220, 198 and 176 mg/L for D. salina, D. bardawil and D. viridis, respectively, followed by T. suecica with an EC(50) value of 40 mg/L. The Prorocentrum species were found to be the most sensitive with an EC(50) value of 13.5 mg/L for P. minimum Lissabon and 7.5 mg/L for P. minimum Kattegat.

Strain rate dependent calcite microfabric evolution - An experiment carried out by nature

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard; Huet, Benjamin; Habler, Gerlinde

2014-12-01

A flanking structure developed along a secondary shear zone in calcite marbles, on Syros (Cyclades, Greece), provides a natural laboratory for directly studying the effects of strain rate variations on calcite deformation at identical pressure and temperature conditions. The presence and rotation of a fracture during progressive deformation caused extreme variations in finite strain and strain rate, forming a localized ductile shear zone that shows different microstructures and textures. Textures and the degree of intracrystalline deformation were measured by electron backscattered diffraction. Marbles from the host rocks and the shear zone, which deformed at various strain rates, display crystal-preferred orientation, suggesting that the calcite preferentially deformed by intracrystalline-plastic deformation. Increasing strain rate results in a switch from subgrain rotation to bulging recrystallization in the dislocation-creep regime. With increasing strain rate, we observe in fine-grained (3 μm) ultramylonitic zones a change in deformation regime from grain-size insensitive to grain-size sensitive. Paleowattmeter and the paleopiezometer suggest strain rates for the localized shear zone around 10-10 s-1 and for the marble host rock around 10-12 s-1. We conclude that varying natural strain rates can have a first-order effect on the microstructures and textures that developed under the same metamorphic conditions.

Phonon dispersion evolution in uniaxially strained aluminum crystal

NASA Astrophysics Data System (ADS)

Parthasarathy, Ranganathan; Misra, Anil; Aryal, Sitaram; Ouyang, Lizhi

2018-04-01

The influence of loading upon the phonon dispersion of crystalline materials could be highly nonlinear with certain particular trends that depend upon the loading path. In this paper, we have calculated the influence of [100] uniaxial strain on the phonon dispersion and group velocities in fcc aluminum using second moments of position obtained from molecular dynamics (MD) simulation at 300 K. In contrast to nonlinear monotonic variation of both longitudinal and transverse phonon frequencies along the Δ , Λ and Σ lines of the first Brillouin zone under tension, transverse phonon branches along the Λ line show inflection at specific wavevectors when the compressive strain exceeds 5%. Further, the longitudinal group velocities along the high-symmetry Δ line vary non-monotonically with strain, reaching a minimum at 5% compressive strain. Throughout the strain range studied, the equilibrium positions of atoms displace in an affine manner preserving certain static structural symmetry. We attribute the anomalies in the phonon dispersion to the non-affine evolution of second moments of atomic position, and the associated plateauing of force constants under the applied strain path.

Mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the in-plane biaxial strain

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2017-11-01

Recently, a new two-dimensional (2D) material, the 2D BC3 crystal, has been synthesized. Here, the mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the biaxial strain is investigated. The electronic structure calculations showed that the strain-free monolayer and bilayer BC3 are indirect band-gap semiconductors with band gap of 0.62 and 0.29 eV, respectively, where the conduction band minimum (CBM) is at the M point whereas the valence band maximum (VBM) is at the Γ point. The doubly degenerated bands in the monolayer BC3 are splitted in the bilayer BC3 due to the interlayer interactions. Both monolayer and bilayer BC3 remain indirect gap semiconductor under biaxial tensile strain and their band gaps increases with strain. On the other hand, by increasing the magnitude of tensile strain, the optical spectra shift to the lower energies and the static dielectric constant increases. These findings suggest the potential of strain-engineered 2D BC3 in electronic and optoelectronic device applications.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-05-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-04-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Suppression and Structure of Low Strain Rate Nonpremixed Flames

NASA Technical Reports Server (NTRS)

Hamins, Anthony; Bundy, Matthew; Park, Woe Chul; Lee, Ki Yong; Logue, Jennifer

2003-01-01

The agent concentration required to achieve suppression of low strain rate nonpremixed flames is an important fire safety consideration. In a microgravity environment such as a space platform, unwanted fires will likely occur in near quiescent conditions where strain rates are very low. Diffusion flames typically become more robust as the strain rate is decreased. When designing a fire suppression system for worst-case conditions, low strain rates should be considered. The objective of this study is to investigate the impact of radiative emission, flame strain, agent addition, and buoyancy on the structure and extinction of low strain rate nonpremixed flames through measurements and comparison with flame simulations. The suppression effectiveness of a suppressant (N2) added to the fuel stream of low strain rate methane-air diffusion flames was measured. Flame temperature measurements were attained in the high temperature region of the flame (T greater than 1200 K) by measurement of thin filament emission intensity. The time varying temperature was measured and simulated as the flame made the transition from normal to microgravity conditions and as the flame extinguished.

Variation of strain rate sensitivity index of a superplastic aluminum alloy in different testing methods

NASA Astrophysics Data System (ADS)

Majidi, Omid; Jahazi, Mohammad; Bombardier, Nicolas; Samuel, Ehab

2017-10-01

The strain rate sensitivity index, m-value, is being applied as a common tool to evaluate the impact of the strain rate on the viscoplastic behaviour of materials. The m-value, as a constant number, has been frequently taken into consideration for modeling material behaviour in the numerical simulation of superplastic forming processes. However, the impact of the testing variables on the measured m-values has not been investigated comprehensively. In this study, the m-value for a superplastic grade of an aluminum alloy (i.e., AA5083) has been investigated. The conditions and the parameters that influence the strain rate sensitivity for the material are compared with three different testing methods, i.e., monotonic uniaxial tension test, strain rate jump test and stress relaxation test. All tests were conducted at elevated temperature (470°C) and at strain rates up to 0.1 s-1. The results show that the m-value is not constant and is highly dependent on the applied strain rate, strain level and testing method.

Interactions between creep, fatigue and strain aging in two refractory alloys

NASA Technical Reports Server (NTRS)

Sheffler, K. D.

1972-01-01

The application of low-amplitude, high-frequency fatigue vibrations during creep testing of two strain-aging refractory alloys (molybdenum-base TZC and tantalum-base T-111) significantly reduced the creep strength of these materials. This strength reduction caused dramatic increases in both the first stage creep strain and the second stage creep rate. The magnitude of the creep rate acceleration varied directly with both frequency and A ratio (ratio of alternating to mean stress), and also varied with temperature, being greatest in the range where the strain-aging phenomenon was most prominent. It was concluded that the creep rate acceleration resulted from a negative strain rate sensitivity which is associated with the strain aging phenomenon in these materials. (A negative rate sensitivity causes flow stress to decrease with increasing strain rate, instead of increasing as in normal materials). By combining two analytical expressions which are normally used to describe creep and strain aging behavior, an expression was developed which correctly described the influence of temperature, frequency, and A ratio on the TZC creep rate acceleration.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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-ratemore » independent within the experimental accuracy.« less

Prediction of Mechanical Behaviour of Low Carbon Steel at High Strain Rate Using Thermal Activation Theory and Static Data

NASA Astrophysics Data System (ADS)

Ogawa, Kinya; Kobayashi, Hidetoshi; Sugiyama, Fumiko; Horikawa, Keitaro

Thermal activation theory is well-known to be a useful theory to explain the mechanical behaviour of various metals in the wide range of temperature and strain-rate. In this study, a number of trials to obtain the lower yield stress or flow stress at high strain rates from quasi-static data were carried out using the data shown in the report titled “The final report of research group on high-speed deformation of steels for automotive use”. A relation between the thermal component of stress and the strain rate obtained from experiments for αFe and the temperature-strain rate parameter were used with thermal activation theory. The predictions were successfully performed and they showed that the stress-strain behaviour at high strain rates can be evaluated from quasi-static data with good accuracy.

Bauschinger effect in haynes 230 alloy: Influence of strain rate and temperature

NASA Astrophysics Data System (ADS)

Thakur, Aniruddha; Vecchio, Kenneth S.; Nemat-Nasser, Sia

1996-07-01

Quasistatic and dynamic Bauschinger behavior in HAYNES 230 alloy is examined. At low strain rate (10-3/s), the as- received 230 alloy does not show a drop in flow stress, i.e., no Bauschinger effect is displayed. At high strain rate (103/s), a drop in flow stress of 240 MPa was observed upon stress reversal. In contrast, the precipitation- strengthened condition exhibited a Bauschinger effect in both low and high strain rate stress-reversal experiments. The magnitude of the Bauschinger effect was found to increase with increasing strain rate, forward strain, and decreasing temperature. The substructure evolution accompanying the forward loading cycles was investigated by transmission electron microscopy and is related to the back stresses that developed. The increased Bauschinger stress drop observed at high strain rate and/or low temperature was correlated to an increased degree of planar slip under these conditions.

Hibiscus sabdariffa extract inhibits in vitro biofilm formation capacity of Candida albicans isolated from recurrent urinary tract infections.

PubMed

Alshami, Issam; Alharbi, Ahmed E

2014-02-01

To explore the prevention of recurrent candiduria using natural based approaches and to study the antimicrobial effect of Hibiscus sabdariffa (H. sabdariffa) extract and the biofilm forming capacity of Candida albicans strains in the present of the H. sabdariffa extract. In this particular study, six strains of fluconazole resistant Candida albicans isolated from recurrent candiduria were used. The susceptibility of fungal isolates, time-kill curves and biofilm forming capacity in the present of the H. sabdariffa extract were determined. Various levels minimum inhibitory concentration of the extract were observed against all the isolates. Minimum inhibitory concentration values ranged from 0.5 to 2.0 mg/mL. Time-kill experiment demonstrated that the effect was fungistatic. The biofilm inhibition assay results showed that H. sabdariffa extract inhibited biofilm production of all the isolates. The results of the study support the potential effect of H. sabdariffa extract for preventing recurrent candiduria and emphasize the significance of the plant extract approach as a potential antifungal agent.

Synthesis and biological evaluation of 1,3-diaryl pyrazole derivatives as potential antibacterial and anti-inflammatory agents.

PubMed

Li, Ya-Ru; Li, Chao; Liu, Jia-Chun; Guo, Meng; Zhang, Tian-Yi; Sun, Liang-Peng; Zheng, Chang-Ji; Piao, Hu-Ri

2015-11-15

Three series of 1,3-diaryl pyrazole derivatives bearing aminoguanidine or furan-2-carbohydrazide moieties have been synthesized, characterized and evaluated for antibacterial and anti-inflammatory activities. Most of the synthesized compounds showed potent inhibition of several Gram-positive bacterial strains (including multidrug-resistant clinical isolates) and Gram-negative bacterial strains with minimum inhibitory concentration values in the range of 1-64 μg/mL. Compounds 6g, 6l and 7l presented the most potent inhibitory activity against Gram-positive bacteria (e.g. Staphylococcus aureus 4220), Gram-negative bacteria (e.g. Escherichia coli 1924) and the fungus, Candida albicans 7535, with minimum inhibitory concentration values of 1 or 2 μg/mL. Compared with previous studies, these compounds exhibited a broad spectrum of inhibitory activity. Furthermore, compound 7l showed the greatest anti-inflammatory activity (93.59% inhibition, 30 min after intraperitoneal administration), which was more potent than the reference drugs ibuprofen and indomethacin. Copyright © 2015 Elsevier Ltd. All rights reserved.

Slime production and proteinase activity of Candida species isolated from blood samples and the comparison of these activities with minimum inhibitory concentration values of antifungal agents.

PubMed

Ozkan, Semiha; Kaynak, Fatma; Kalkanci, Ayse; Abbasoglu, Ufuk; Kustimur, Semra

2005-05-01

Slime and proteinase activity of 54 strains consisting of 19 Candida parapsilosis and 35 C. albicans strains isolated from blood samples were investigated in this study. Ketoconazole, amphothericin B, and fluconazole susceptibility of Candida species were compared with slime production and proteinase activity of these species. For both Candida species, no correlation was detected between the slime activity and minimum inhibitory concentration (MIC) values of the three antifungal agents. For both Candida species no correlation was detected between the proteinase activity and the MIC values of amphothericin B, and fluconazole however, statistically significant difference, was determined between the proteinase activity and MIC values of ketoconazole (p = 0.007). Slime production was determined by using modified Christensen macrotube method and proteinase activity was measured by the method of Staib. Antifungal susceptibility was determined through the guidelines of National Committee for Laboratory Standards (NCCLS M27-A).

Biological and surface-active properties of double-chain cationic amino acid-based surfactants.

PubMed

Greber, Katarzyna E; Dawgul, Małgorzata; Kamysz, Wojciech; Sawicki, Wiesław; Łukasiak, Jerzy

2014-08-01

Cationic amino acid-based surfactants were synthesized via solid phase peptide synthesis and terminal acylation of their α and ε positions with saturated fatty acids. Five new lipopeptides, N-α-acyl-N-ε-acyl lysine analogues, were obtained. Minimum inhibitory concentration and minimum bactericidal (fungicidal) concentration were determined on reference strains of bacteria and fungi to evaluate the antimicrobial activity of the lipopeptides. Toxicity to eukaryotic cells was examined via determination of the haemolytic activities. The surface-active properties of these compounds were evaluated by measuring the surface tension and formation of micelles as a function of concentration in aqueous solution. The cationic surfactants demonstrated diverse antibacterial activities dependent on the length of the fatty acid chain. Gram-negative bacteria and fungi showed a higher resistance than Gram-positive bacterial strains. It was found that the haemolytic activities were also chain length-dependent values. The surface-active properties showed a linear correlation between the alkyl chain length and the critical micelle concentration.

Strain Anomalies during an Earthquake Sequence in the South Iceland Seismic Zone

NASA Astrophysics Data System (ADS)

Arnadottir, T.; Haines, A. J.; Geirsson, H.; Hreinsdottir, S.

2017-12-01

The South Iceland Seismic Zone (SISZ) accommodates E-W translation due to oblique spreading between the North American/Hreppar microplate and Eurasian plate, in South Iceland. Strain is released in the SISZ during earthquake sequences that last days to years, at average intervals of 80-100 years. The SISZ is currently in the midst of an earthquake sequence that started with two M6.5 earthquakes in June 2000, and continued with two M6 earthquakes in May 2008. Estimates of geometric strain accumulation, and seismic strain release in these events indicate that they released at most only half of the strain accumulated since the last earthquake cycle in 1896-1912. Annual GPS campaigns and continuous measurements during 2001-2015 were used to calculate station velocities and strain rates from a new method using the vertical derivatives of horizontal stress (VDoHS). This new method allows higher resolution of strain rates than other (older) approaches, as the strain rates are estimated by integrating VDoHS rates obtained by inversion rather than differentiating interpolated GPS velocities. Estimating the strain rates for eight 1-2 year intervals indicates temporal and spatial variation of strain rates in the SISZ. In addition to earthquake faulting, the strain rates in the SISZ are influenced by anthropogenic signals due to geothermal exploitation, and magma movements in neighboring volcanoes - Hekla and Eyjafjallajökull. Subtle signals of post-seismic strain rate changes are seen following the June 2000 M6.5 main shocks, but interestingly, much larger strain rate variations are observed after the two May 2008 M6 main shocks. A prominent strain anomaly is evident in the epicentral area prior to the May 2008 earthquake sequence. The strain signal persists over at least 4 years in the epicentral area, leading up to the M6 main shocks. The strain is primarily extension in ESE-WNW direction (sub-parallel to the direction of plate spreading), but overall shear across the N-S faults that subsequently ruptured, increases with time. The pre-2008 strain anomaly and large post-2008 strain variations are enigmatic, but may signify crustal fluids and/or differences in rheology and crustal thickness between the 2000 and 2008 epicentral areas.

Microstructure and critical strain of dynamic recrystallization of 6082 aluminum alloy in thermal deformation

NASA Astrophysics Data System (ADS)

Ren, W. W.; Xu, C. G.; Chen, X. L.; Qin, S. X.

2018-05-01

Using high temperature compression experiments, true stress true strain curve of 6082 aluminium alloy were obtained at the temperature 460°C-560°C and the strain rate 0.01 s-1-10 s-1. The effects of deformation temperature and strain rate on the microstructure are investigated; (‑∂lnθ/∂ε) ‑ ε curves are plotted based on σ-ε curve. Critical strains of dynamic recrystallization of 6082 aluminium alloy model were obtained. The results showed lower strain rates were beneficial to increase the volume fraction of recrystallization, the average recrystallized grain size was coarse; High strain rates are beneficial to refine average grain size, the volume fraction of dynamic recrystallized grain is less than that by using low strain rates. High temperature reduced the dislocation density and provided less driving force for recrystallization so that coarse grains remained. Dynamic recrystallization critical strain model and thermal experiment results can effectively predict recrystallization critical point of 6082 aluminium alloy during thermal deformation.

[Epidemiological characteristics of typhoid fever and antibiotic susceptibility testing of Salmonella Typhi isolates in Guangxi, 1994-2013].

PubMed

Wang, Mingliu; Kan, Biao; Yang, Jin; Lin, Mei; Yan, Meiying; Zeng, Jun; Quan, Yi; Liao, Hezhuang; Zhou, Lingyun; Jiang, Zhenling; Huang, Dehui

2014-08-01

Through analyzing the typhoid epidemics and to determine and monitor regional resistance characteristics of the shift of drug resistant profile on Salmonella (S.) Typhi, to understand the related epidemiological characteristics of typhoid fever and to provide evidence for the development of strategies, in Guangxi. Data of typhoid fever from surveillance and reporting system between 1994 to 2013 was collected and statistically analyzed epidemiologically. The susceptibility of 475 S. Typhi isolates from patients on ten antibiotics was tested by broth micro-dilution method and minimum inhibition concentration was obtained and interpreted based on the CLSI standard. From 1994 to 2013, a total of 57 928 cases of typhoid fever were reported in Guangxi province with an annual incidence of 6.29/100 000 and mortality as 0.03%. The higher incidence was observed in the population under 20 years of age. There was no significant difference on incidence between male and female, but farmers and students were among the hardest hit groups. More cases were seen from the northern part of the province. Cases appeared all year round with the peak from May to October. A total of 13 major outbreaks during 2001 to 2013 were reported and the main transmission route was water-borne. All the strains were sensitive to third generation cephalosporins cefotaxime and fluoroquinolones norfloxacin. The susceptibility rates to tetracycline, chloramphenicol, ampicillin and gentamicin was around 98% but relative lower susceptible rate to ciprofloxacin was seen as 89.89% . The lowest susceptibility was found for streptomycin and sulfamethoxazole agents, with the rates as 67.73% and 65.89% , respectively. One strain was found to have been resistant to ciprofloxacin and another 47 isolates with reduced susceptibility to ciprofloxacin. Twenty eight isolates were found to be resistant to multiple antibiotics and one displayed ampicillin, chloramphenicol, streptomycin, sulfamethoxazole tetracycline and nalidixic acid (ACSSxT-NAL) resistance profile. This was the first report in China. Multi-drug resistant strains were frequently isolated from small scale outbreaks of typhoid fever. The incidence of typhoid fever in Guangxi was still high and some strains showed multi-drug resistance and reduced susceptibility to ciprofloxacin, indicating that the surveillance and monitor programs on drug resistance of S. Typhi should be strengthened, to prevent large scale outbreaks of typhoid fever in this province.

On the use of a split Hopkinson pressure bar in structural geology: High strain rate deformation of Seeberger sandstone and Carrara marble under uniaxial compression

NASA Astrophysics Data System (ADS)

Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael H.; Nau, Siegfried; Hess, Sebastian

2017-04-01

There is increasing evidence that seismogenic fractures can propagate faster than the shear wave velocity of the surrounding rocks. Strain rates within the tip region of such super-shear earthquake ruptures can reach deformation conditions similar to impact processes, resulting in rock pulverization. The physical response of brittle rocks at high strain rates changes dramatically with respect to quasi-static conditions. Rocks become stiffer and their strength increases. A measure for the dynamic behavior of a rock and its strain dependency is the dynamic increase factor (DIF) which is the ratio of the dynamic compressive strength to the quasi-static uniaxial compressive strength. To investigate deformation in the high strain rate regime experimentally, we introduce the split Hopkinson pressure bar technology to the structural geology community, a method that is frequently used by rock and impact engineers. We measure the stress-strain response of homogeneous, fine-grained Seeberger sandstone and Carrara marble in uniaxial compression at strain rates ranging from 10+1 to 10+2 s-1 with respect to tangent modulus and dynamic uniaxial compressive strength. We present full stress-strain response curves of Seeberger sandstone and Carrara marble at high strain rates and an evaluation method to determine representative rates of deformation. Results indicate a rate-dependent elastic behavior of Carrara marble where an average increase of ∼18% could be observed at high strain rates of about 100 s-1. DIF reaches a factor of 2.2-2.4. Seeberger sandstone does not have a rate-dependent linear stress-strain response at high strain rates. Its DIF was found to be about 1.6-1.7 at rates of 100 s-1. The onset of dynamic behavior is accompanied with changes in the fracture pattern from single to multiple fractures to pervasive pulverization for increasing rates of deformation. Seismogenic shear zones and their associated fragment-size spectra should be carefully revisited in the light of dynamic deformation.

A novel method for the accurate evaluation of Poisson's ratio of soft polymer materials.

PubMed

Lee, Jae-Hoon; Lee, Sang-Soo; Chang, Jun-Dong; Thompson, Mark S; Kang, Dong-Joong; Park, Sungchan; Park, Seonghun

2013-01-01

A new method with a simple algorithm was developed to accurately measure Poisson's ratio of soft materials such as polyvinyl alcohol hydrogel (PVA-H) with a custom experimental apparatus consisting of a tension device, a micro X-Y stage, an optical microscope, and a charge-coupled device camera. In the proposed method, the initial positions of the four vertices of an arbitrarily selected quadrilateral from the sample surface were first measured to generate a 2D 1st-order 4-node quadrilateral element for finite element numerical analysis. Next, minimum and maximum principal strains were calculated from differences between the initial and deformed shapes of the quadrilateral under tension. Finally, Poisson's ratio of PVA-H was determined by the ratio of minimum principal strain to maximum principal strain. This novel method has an advantage in the accurate evaluation of Poisson's ratio despite misalignment between specimens and experimental devices. In this study, Poisson's ratio of PVA-H was 0.44 ± 0.025 (n = 6) for 2.6-47.0% elongations with a tendency to decrease with increasing elongation. The current evaluation method of Poisson's ratio with a simple measurement system can be employed to a real-time automated vision-tracking system which is used to accurately evaluate the material properties of various soft materials.

Phenolic content, antibacterial and antioxidant activities of Erica herbacea L.

PubMed

Vucić, Dragana M; Petković, Miroslav R; Rodić-Grabovac, Branka B; Stefanović, Olgica D; Vasić, Sava M; Comić, Ljiljana R

2013-01-01

Antibacterial and antioxidant activity, total phenolic and flavonoid concentrations of aqueous, ethanol and ethyl acetate extracts from the leaves and flowers of Erica herbacea L. were studied. In vitro antibacterial activity of the extracts was determined by macrodilution method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) have been determined. Testing was performed on 30 clinical isolates, including different strains of Escherichia coli, Enterococcus faecalis and Proteus vulgaris. The values for MIC were in the range from 2.5 mg/mL to 40 mg/mL. The most sensitive bacterial strains were Proteus vulgaris strains. The aqueous extract from E. herbacea was found the most active. The total phenolic content was determined using Folin-Ciocalteu reagent and ranged between 14.98 and 119.88 mg GA/g. The concentration of flavonoids in extracts was determined using spectrophotometric method with aluminium chloride and obtained results varied from 16.19 to 26.90 mg RU/g. Antioxidant activity was monitored spectrophotometrically using DPPH reagent. The highest capacity to neutralize DPPH radicals was found in the aqueous extract from E. herbacea. The results of the total phenolic content determination of the examined extracts indicate that E. herbacea extracts are a rich source of phenolic compounds and also possess a significant antioxidant activity and moderate antibacterial activity.

Effect of Strain Rate on Mechanical Properties of Wrought Sintered Tungsten at Temperatures above 2500 F

NASA Technical Reports Server (NTRS)

Sikora, Paul F.; Hall, Robert W.

1961-01-01

Specimens of wrought sintered commercially pure tungsten were made from 1/8-inch swaged rods. All the specimens were recrystallized at 4050 F for 1 hour prior to testing at temperatures from 2500 to 4000 F at various strain rates from 0.002 to 20 inches per inch per minute. Results showed that, at a constant temperature, increasing the strain rate increased the ultimate tensile strength significantly. The effects of both strain rate and temperature on the ultimate tensile strength of tungsten may be correlated by the linear parameter method of Manson and Haferd and may be used to predict the ultimate tensile strength at higher temperatures, 4500 and 5000 F. As previously reported, ductility, as measured by reduction of area in a tensile test, decreases with increasing temperature above about 3000 F. Increasing the strain rate at temperatures above 3000 F increases the ductility. Fractures are generally transgranular at the higher strain rates and intergranular at the lower strain rates.

Strain rate dependent activation of slip systems in calcite marbles from Syros (Cyclades, Greece)

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard; Morales, Luiz F. G.; Huet, Benjamin; White, Joseph C.

2017-04-01

The activation of certain slip systems in calcite has been experimentally proven to be highly temperature dependent, but also the strain rate plays an important role on the activation of the dominant slip system. In this study, observations from a flanking structure (i.e. shear zone) that developed under lower greenschist-facies conditions, in an almost pure calcite marble (Syros Island, Greece) are presented. The shear zone is characterized by a strain gradient from the slightly deformed tips (γ ˜ 50) to the highly strained centre (γ up to 1000) while the host rock is moderately deformed (γ ˜ 3). During the shear zone development, the strain gradient coincided with a strain rate gradient with strain rate varying from 10-13 to 10-9 s-1. The studied outcrop thus represents the final state of a natural experiment and gives us a great opportunity to get natural constraints on strain rate dependent mechanical behaviour in a calcite marble. Detailed microstructural analyses have been performed via optical microscopy, electron microscopy, electron backscatter diffraction mapping and transmission electron microscopy, on samples from the highly strained shear zone and the host rock. The analyses show that the calcite microfabric varies depending on position within the shear zone, indicating activation of different deformation, recrystallization mechanisms and slip systems at different strain rates. Up to strain rates of ˜10-10 s-1 the marble deformed exclusively within the dislocation creep field, showing a change in recrystallization mechanism and dominant active slip system. While the marble preferentially recrystallized by grain boundary migration at relatively low strain rates (˜10-13 s-1), subgrain rotation recrystallization seems to be the dominant mechanism at higher strain rates (˜10-12 to 10-10 s-1). At higher strain rates (˜10-9 s-1), the recrystallization mechanism is bulging, resulting in the development of an extremely fine grained ultramylonite (average grain size ˜3 μm) accompanied by a switch in deformation mechanism from dislocation creep to a combined deformation by grain boundary sliding and dislocation activity. Constraints on dominant active slip system depending on deformation strain rate have been made by a combination of misorientation analyses and viscoplastic self-consistent modelling.

Effect of Loading Rate and Orientation on the Compressive Response of Human Cortical Bone

DTIC Science & Technology

2014-05-01

use thereof. Destroy this report when it is no longer needed. Do not return it to the originator. Army Research Laboratory Aberdeen Proving...quasi-static (0.001/s), intermediate (1/s), and dynamic (1000–2000/s) strain rates using a split-Hopkinson pressure bar to determine the strain rate...6 Figure 5. Strain rate and strain histories of human cortical bone specimen at high rate using bar signals

Fundamental mechanisms in premixed flame propagation via vortex-flame interactions: Numerical simulations

NASA Technical Reports Server (NTRS)

Mantel, Thierry

1994-01-01

The goal of the present study is to assess numerically the ability of single-step and two-step chemical models to describe the main features encountered during the interaction between a two-dimensional vortex pair and a premixed laminar flame. In the two-step mechanism, the reaction kinetics are represented by a first chain branching reaction A + X yields 2X and a second chain termination reaction X + X yields P. This paper presents the fundamental mechanisms occurring during vortex-flame interactions and the relative impact of the major parameters encountered in turbulent premixed flames and suspected of playing a role in quenching mechanism: (1) Influence of stretch is investigated by analyzing the contribution of curvature and tangential strain on the local structure of the flame. The effect of Lewis number on the flame response to a strained field is analyzed. (2) Radiative heat losses which are suspected to be partially or totally responsible for quenching are also investigated. (3) The effect of the diffusion of the radicals is studied using a two-step mechanism in which an intermediate species is present. The parameters of the two-step mechanism are entirely determined from physical arguments. (4) Precise quantitative comparisons between the DNS and the experimental results of Samaniego et al are performed. These comparisons concern the evolution of the minimum heat release rate found along the flame front during the interaction and the distribution of the heat release rate along the flame front.

Critical cracking potentials of 26Cr-1 Mo ferritic stainless steels in boiling 42% LiCl solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, H.S.; Troiano, A.R.; Hehemann, R.F.

This paper reports that the critical cracking potentials (E[sub cc] for 26Cr-1Mo ferritic stainless steels (UNS S44627), above which stress corrosion cracking (SCC) does occur, have been measured at constant load in a hot chloride solution. Various factors affecting E[sub cc] for the low interstitial 26Cr-1Mo alloy (E-Brite) is shown to be a potential for crack initiation and is determined by the competing rates of generation of new surface by slip-induced film breakdown and repassivation. E[sub cc] for E-Brite is very sensitive to the microstructural conditions developed by prior thermal and mechanical treatments; varying in the range of -485 mVmore » for the mill annealed to -625 mV for the grain coarsened. On the other hand, the minimum potential permitting crack growth is insensitive to these treatments and corresponds to the most active value of E[sub cc] -625 mV. When strained at a constant strain rate (2.5 [times] 10[sup [minus]6]/S), the critical potential above which E-Brite is susceptible to SCC corresponds to the most active value of E[sub cc] measured at constant load. Thus, it appears that the most active value of E[sub cc](-625 mV) is a repassivation potential for growing cracks, and E[sub cc] approaches that for crack propagation as a limiting condition.« less

Finite Element Modeling of Dieless Tube Drawing of Strain Rate Sensitive Material with Coupled Thermo-Mechanical Analysis

NASA Astrophysics Data System (ADS)

Furushima, Tsuyoshi; Sakai, Takashi; Manabe, Ken-ichi

2004-06-01

Dieless drawing is a unique deformation process without conventional dies, which can achieve a great reduction of wire and tube metals in single pass by means of local heating and cooling approach. In this study, for microtube forming, the dieless drawing process applying superplastic behavior was analyzed by finite element method (FEM) in order to clarify the effect of dieless tube drawing conditions such as tensile speed, moving speed of heating and cooling system, and material properties on deformation behavior of the tube. In the calculation, the material properties were dealt in a special subroutine, whose constitutive equation was defined as σ = Kɛnɛ˙m, and was linked to the solver. A coupled thermo-mechanical analysis was performed for the dieless tube drawing using the FEM. In the thermal analysis of dieless tube drawing, heat transfer was introduced to calculate the heat flux between heating coil and tube surface, and heat conduction in a tube. The influence of dieless tube drawing conditions on deformation behavior was clarified. As a result, for the strain rate sensitive material, the maximum reduction of area and the minimum outer diameter in single pass attain to 90.9% and 2.56mm, respectively. From the result, it is concluded that the dieless tube drawing is essential to produce an extrafine microtube by reason of keeping cylindrical tube diameter ratio constant with extremely high reduction.

Elevated temperature fracture of RS/PM alloy 8009; Part 1: Fracture mechanics behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Porr, W.C. Jr.; Gangloff, R.P.

1994-02-01

Increasing temperature and decreasing loading rate degrade the planes strain initiation (K[sub ICi] from the J integral) and growth (tearing modulus, T[sub R]) fracture toughnesses of RS/PM 8009 (Al-8.5Fe-1.3V-1.7Si, wt pct). K[sub ICi] decreases with increasing temperature from 25[degree]C to 175[degree]C (33 to 15 MPa[radical]m at 316[degree]C) without a minimum. T[sub R] is greater than zero at all temperatures and is minimized at 200[degree]C. A four order-of-magnitude decrease in loading rate, at 175[degree]C, results in a 2.5-fold decrease in K[sub ICi] and a 5-fold reduction in T[sub R]. K[sub ICi] and T[sub R] are anisotropic for extruded 8009 but aremore » isotropic for cross-rolled plate. Cross rolling does not improve the magnitude or adverse temperature dependence of toughness. Delamination occurs along oxide-decorated particle boundaries for extruded but not cross-rolled 8009. Delamination toughening plays no role in the temperature dependence of K[sub ICi], however, T[sub R] is increased by this mechanism. Macroscopic work softening and flow localization do not occur for notch-root deformation; such uniaxial tensile phenomena may not be directly relevant to crack-tip fracture. Micromechanical modeling, employing temperature-dependent flow strength, modulus, and constrained fracture strain, reasonably predicts the temperature dependencies of K[sub ICi] and T[sub R] for 8009.« less

In vitro activity of selected antimicrobial agents against penicillinase producing Neisseria gonorrhoeae (PPNG) and non-PPNG strains.

PubMed Central

Waghorn, D J; Azadian, B S; Talboys, C

1986-01-01

One hundred and twelve penicillinase producing Neisseria gonorrhoeae (PPNG) isolates and the same number of non-PPNG isolates were obtained from patients attending the genitourinary department of this hospital. Susceptibilities to six beta lactam antibiotics--ceftriaxone, cefotaxime, cefuroxime, ceftazidime, amoxycillin, and temocillin--to the combined formulation of amoxycillin and clavulanic acid, Augmentin, and to the aminocyclitol, spectinomycin, were compared by assessing their minimum inhibitory concentrations (MICs). Results showed that all the cephalosporins used in this study had good in vitro activity against both PPNG and non-PPNG strains, and ceftriaxone had the lowest MICs. Temocillin and Augmentin also showed good activity against both types of strain. Spectinomycin resistance was shown in about 4% of the PPNG isolates but was not found in any non-PPNG strains. PMID:2950043

Strain rate dependent calcite microfabric evolution at natural conditions

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard; Huet, Benjamin; Habler, Gerlinde

2014-05-01

Crystal plastic deformational behaviour of calcite has been the focus of many experimental studies. Different strain rates, pressure and temperature conditions have been addressed to investigate a wide range of deformation regimes. However, a direct comparison with natural fault rocks remains difficult because of extreme differences between experimental and natural strain rates. A flanking structure developed in almost pure calcite marble on Syros (Cyclades, Greece). Due to rotation of a planar feature (crack) a heterogeneous strain field in the surrounding area occurred resulting in different strain domains and the formation of the flanking structure. Assuming that deformation was active continuously during the development of the flanking structure, the different strain domains correspond to different strain-rate domains. The outcrop thus represents the final state of a natural experiment and gives us a great opportunity to get natural constraints on strain rate dependent deformation behaviour of calcite. Comparing the microfabrics in the 1 to 2.5 cm thick shear zone and the surrounding host rocks, which formed under the same metamorphic conditions but with different strain rates, is the central focus of this study. Due to the extreme variation in strain and strain rate, different microstructures and textures can be observed corresponding to different deformation mechanisms. With increasing strain rate we observe a change in dominant deformation mechanism from dislocation glide to dislocation creep and finally diffusion creep. Additionally, a change from subgrain rotation to bulging recrystallization can be observed in the dislocation creep regime. Crystallographic preferred orientations (CPO) and the grade of intracrystalline deformation were measured on a FEI Quanta 3D FEG instrument equipped with an EDAX Digiview IV EBSD camera. At all strain rates clear CPOs developed leading to the assumption that calcite preferentially deforms within the dislocation creep field. However, we can also find clear evidence for grain size sensitive deformation mechanisms at smaller grain sizes (3.6 μm) consistent with experimental observations and determined flaw laws. The results of this study are compared with experimental data, closing the gap between experimental and natural geological strain rates.

The Kinematics of Central American Fore-Arc Motion in Nicaragua: Geodetic, Geophysical and Geologic Study of Magma-Tectonic Interactions

NASA Astrophysics Data System (ADS)

La Femina, P. C.; Geirsson, H.; Saballos, A.; Mattioli, G. S.

2017-12-01

A long-standing paradigm in plate tectonics is that oblique convergence results in strain partitioning and the formation of migrating fore-arc terranes accommodated on margin-parallel strike-slip faults within or in close proximity to active volcanic arcs (e.g., the Sumatran fault). Some convergent margins, however, are segmented by margin-normal faults and margin-parallel shear is accommodated by motion on these faults and by vertical axis block rotation. Furthermore, geologic and geophysical observations of active and extinct margins where strain partitioning has occurred, indicate the emplacement of magmas within the shear zones or extensional step-overs. Characterizing the mechanism of accommodation is important for understanding short-term (decadal) seismogenesis, and long-term (millions of years) fore-arc migration, and the formation of continental lithosphere. We investigate the geometry and kinematics of Quaternary faulting and magmatism along the Nicaraguan convergent margin, where historical upper crustal earthquakes have been located on margin-normal, strike-slip faults within the fore arc and arc. Using new GPS time series, other geophysical and geologic data, we: 1) determine the location of the maximum gradient in forearc motion; 2) estimate displacement rates on margin-normal faults; and 3) constrain the geometric moment rate for the fault system. We find that: 1) forearc motion is 11 mm a-1; 2) deformation is accommodated within the active volcanic arc; and 3) that margin-normal faults can have rates of 10 mm a-1 in agreement with geologic estimates from paleoseismology. The minimum geometric moment rate for the margin-normal fault system is 2.62x107 m3 yr-1, whereas the geometric moment rate for historical (1931-2006) earthquakes is 1.01x107 m3/yr. The discrepancy between fore-arc migration and historical seismicity may be due to aseismic accommodation of fore-arc motion by magmatic intrusion along north-trending volcanic alignments within the volcanic arc.

20 CFR 225.15 - Overall Minimum PIA.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Security Act based on combined railroad and social security earnings. The Overall Minimum PIA is used in computing the social security overall minimum guaranty amount. The overall minimum guaranty rate annuity... INSURANCE AMOUNT DETERMINATIONS PIA's Used in Computing Employee, Spouse and Divorced Spouse Annuities § 225...

Strain rate effects on mechanical properties of fiber composites, part 3

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1976-01-01

An experimental investigation was conducted to determine the strain rate effects in fiber composites. Unidirectional composite specimens of boron/epoxy, graphite/epoxy, S-glass/epoxy and Kevlar/epoxy were tested to determine longitudinal, transverse and intralaminar (in-plane) shear properties. In the Longitudinal direction the Kevlar/epoxy shows a definite increase in both modulus and strength with strain rate. In the transverse direction, a general trend toward higher strength with strain rate is noticed. The intralaminar shear moduli and strengths of boron/epoxy and graphite/epoxy show a definite rise with strain rate.

Image Data Compression Having Minimum Perceptual Error

NASA Technical Reports Server (NTRS)

Watson, Andrew B. (Inventor)

1997-01-01

A method is presented for performing color or grayscale image compression that eliminates redundant and invisible image components. The image compression uses a Discrete Cosine Transform (DCT) and each DCT coefficient yielded by the transform is quantized by an entry in a quantization matrix which determines the perceived image quality and the bit rate of the image being compressed. The quantization matrix comprises visual masking by luminance and contrast technique all resulting in a minimum perceptual error for any given bit rate, or minimum bit rate for a given perceptual error.

Effect of Catechins, Green tea Extract and Methylxanthines in Combination with Gentamicin Against Staphylococcus aureus and Pseudomonas aeruginosa

PubMed Central

Fazly Bazzaz, Bibi Sedigheh; Sarabandi, Sahar; Khameneh, Bahman; Hosseinzadeh, Hossein

2016-01-01

Objectives: Bacterial resistant infections have become a global health challenge and threaten the society’s health. Thus, an urgent need exists to find ways to combat resistant pathogens. One promising approach to overcoming bacterial resistance is the use of herbal products. Green tea catechins, the major green tea polyphenols, show antimicrobial activity against resistant pathogens. The present study aimed to investigate the effect of catechins, green tea extract, and methylxanthines in combination with gentamicin against standard and clinical isolates of Staphylococcus aureus (S. aureus) and the standard strain of Pseudomonas aeruginosa (P. aeruginosa). Methods: The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values of different agents against bacterial strains were determined. The interactions of green tea extract, epigallate catechin, epigallocatechin gallate, two types of methylxanthine, caffeine, and theophylline with gentamicin were studied in vitro by using a checkerboard method and calculating the fraction inhibitory concentration index (FICI). Results: The MICs of gentamicin against bacterial strains were in the range of 0.312 - 320 μg/mL. The MIC values of both types of catechins were 62.5 - 250 μg/ mL. Green tea extract showed insufficient antibacterial activity when used alone. Methylxanthines had no intrinsic inhibitory activity against any of the bacterial strains tested. When green tea extract and catechins were combined with gentamicin, the MIC values of gentamicin against the standard strains and a clinical isolate were reduced, and synergistic activities were observed (FICI < 1). A combination of caffeine with gentamicin did not alter the MIC values of gentamicin. Conclusion: The results of the present study revealed that green tea extract and catechins potentiated the antimicrobial action of gentamicin against some clinical isolates of S. aureus and standard P. aeruginosa strains. Therefore, combinations of gentamicin with these natural compounds might be a promising approach to combat microbial resistance. PMID:28097041

Radiation-induced polymerization of glass-forming systems. IV. Effect of the homogeneity of polymerization phase and polymer concentration on temperature dependence of initial polymerization rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-06-01

The effect of homogeneity of polymerization phase and monomer concentration on the temperature dependence of initial polymerization rate was studied in the radiation-induced radical polymerization of binary systems consisting of glass-forming monomer and solvent. In the polymerization of a completely homogeneous system such as HEMA-propylene glycol, a maximum and a minimum in polymerization rates as a function of temperature, characteristic of the polymerization in glass-forming systems, were observed for all monomer concentrations. However, in the heterogeneous polymerization systems such as HEMA-triacetin and HEMAisoamyl acetate, maximum and minimum rates were observed in monomer-rich compositions but not at low monomer concentrations. Furthermore,more » in the HEMA-dioctyl phthalate polymerization system, which is extremely heterogeneous, no maximum and minimum rates were observed at any monomer concentration. The effect of conversion on the temperature dependence of polymerization rate in homogeneous bulk polymerization of HEMA and GMA was investigated. Maximum and minimum rates were observed clearly in conversions less than 10% in the case of HEMA and less than 50% in the case of GMA, but the maximum and minimum changed to a mere inflection in the curve at higher conversions. A similar effect of polymer concentration on the temperature dependence of polymerization rate in the GMA-poly(methyl methacrylate) system was also observed. It is deduced that the change in temperature dependence of polymerization rate is attributed to the decrease in contribution of mutual termination reaction of growing chain radicals to the polymerization rate. (auth)« less

Feasibility and reproducibility of feature-tracking-based strain and strain rate measures of the left ventricle in different diseases and genders.

PubMed

Maceira, Alicia M; Tuset-Sanchis, Luis; López-Garrido, Miguel; San Andres, Marta; López-Lereu, M Pilar; Monmeneu, Jose V; García-González, M Pilar; Higueras, Laura

2018-05-01

The measurement of myocardial deformation by strain analysis is an evolving tool to quantify regional and global myocardial function. To assess the feasibility and reproducibility of myocardial strain/strain rate measurements with magnetic resonance feature tracking (MR-FT) in healthy subjects and in patient groups. Prospective study. Sixty patients (20 hypertensives with left ventricular (LV) hypertrophy (H); 20 nonischemic dilated cardiomyopathy (D); 20 ischemic heart disease (I); as well as 20 controls (C) were included, 10 men and 10 women in each group. A 1.5T MR protocol including steady-state free precession (SSFP) cine sequences in the standard views and late enhancement sequences. LV volumes, mass, global and regional radial, circumferential, and longitudinal strain/strain rate were measured using CVI42 software. The analysis time was recorded. Intraobserver and interobserver agreement and intraclass correlation coefficients (ICC) were obtained for reproducibility assessment as well as differences according to gender and group of pertinence. Strain/strain rate analysis could be achieved in all subjects. The average analysis time was 14 ± 3 minutes. The average intraobserver ICC was excellent (ICC >0.90) for strain and good (ICC >0.75) for strain rate. Reproducibility of strain measurements was good to excellent (ICC >0.75) for all groups of subjects and both genders. Reproducibility of strain measurements was good for basal segments (ICC >0.75) and excellent for middle and apical segments (ICC >0.90). Reproducibility of strain rate measurements was moderate for basal segments (ICC >0.50) and good for middle and apical segments. MR-FT for strain/strain rate analysis is a feasible and highly reproducible technique. CVI42 FT analysis was equally feasible and reproducible in various pathologies and between genders. Better reproducibility was seen globally for middle and apical segments, which needs further clarification. 3 Technical Efficacy Stage 2 J. Magn. Reson. Imaging 2018;47:1415-1425. © 2017 International Society for Magnetic Resonance in Medicine.

Step width alters iliotibial band strain during running.

PubMed

Meardon, Stacey A; Campbell, Samuel; Derrick, Timothy R

2012-11-01

This study assessed the effect of step width during running on factors related to iliotibial band (ITB) syndrome. Three-dimensional (3D) kinematics and kinetics were recorded from 15 healthy recreational runners during overground running under various step width conditions (preferred and at least +/- 5% of their leg length). Strain and strain rate were estimated from a musculoskeletal model of the lower extremity. Greater ITB strain and strain rate were found in the narrower step width condition (p < 0.001, p = 0.040). ITB strain was significantly (p < 0.001) greater in the narrow condition than the preferred and wide conditions and it was greater in the preferred condition than the wide condition. ITB strain rate was significantly greater in the narrow condition than the wide condition (p = 0.020). Polynomial contrasts revealed a linear increase in both ITB strain and strain rate with decreasing step width. We conclude that relatively small decreases in step width can substantially increase ITB strain as well as strain rates. Increasing step width during running, especially in persons whose running style is characterized by a narrow step width, may be beneficial in the treatment and prevention of running-related ITB syndrome.

The change of macrolide resistance rates in group A Streptococcus isolates from children between 2002 and 2013 in Asahikawa city.

PubMed

Sakata, Hiroshi

2015-05-01

This study targeted patients in the Department of Pediatrics, Asahikawa Kosei Hospital, between January 2002 and December 2013. In patients suspected of having hemolytic streptococcal infection, Group A Streptococcus (GAS) strains isolated from a throat swab were examined for antimicrobial susceptibility testing. The MICs were measured by the broth microdilution method. The annual number of GAS strains examined for antimicrobial susceptibility testing ranged from 28 to 65 strains, for a total of 574 strains. Some of the isolates obtained from 2006 to 2009 and from 2011 to 2013 were analyzed to determine their emm types. An erythromycin (EM) resistant strain was not detected until 2004, but one EM-resistant strain appeared in 2005. Subsequently, EM-resistant strains rapidly increased, and 48 of 65 strains (73.8%) examined in 2009 were resistant. In 2010, the number of EM-resistant strains decreased to 12 of 36 strains (33.3%). However, it gradually increased afterwards, and 37 of 60 strains (61.7%) were resistant in 2013. Out of 574 strains examined, 184 exhibited EM-resistance, and the overall resistance rate was 31.9%. Partitioning the 124 strains examined between 2006 and 2008 according to emm types, only emm28 strains, which exhibited a high resistance rate, and emm12 strains demonstrated resistance. For the 142 strains examined between 2011 and 2013, the resistance rate of emm28 strains was similarly high; the resistance of emm12 strains significantly increased, and emm1 strains exhibited a high resistance rate. The number of emm types associated with the resistant strains increased. Copyright © 2015 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Effects of grain size on the quasi-static mechanical properties of ultrafine-grained and nanocrystalline tantalum

NASA Astrophysics Data System (ADS)

Ligda, Jonathan Paul

The increase in strength due to the Hall-Petch effect, reduced strain hardening capacity, a reduced ductility, and changes in deformation mechanisms are all effects of reducing grain size (d) into the ultrafine-grained (UFG, 100 < d < 1000 nm) and nanocrystalline (NC, d<100 nm) state. However, most of the studies on the mechanical behavior of UFG/NC metals have been on face-centered cubic (FCC) metals. Of the few reports on UFG/NC body-centered cubic (BCC) metals, the interest is related to their increase in strength and reduced strain rate sensitivity. This combination increases their propensity to deform via adiabatic shear bands (ASBs) at high strain rates, which is a desired response for materials being considered as a possible replacement for depleted uranium in kinetic energy penetrators. However, an ideal replacement material must also plastically deform in tension under quasi-static rates to survive initial launch conditions. This raises the question: if the material forms ASBs at dynamic rates, will it also form shear bands at quasi-static isothermal rates? As well as, is there a specific grain size for a material that will plastically deform in tension at quasi-static rates but form adiabatic shear bands at dynamic rates? Using high pressure torsion, a polycrystalline bulk tantalum disk was refined into the UFG/NC regime. Using microscale mechanical testing techniques, such as nanoindentation, microcompression, and microtension, it is possible to isolate locations with a homogeneous grain size within the disk. Pillars are compressed using a nanoindenter with a flat punch tip, while "dog-bone" specimens were pulled in tension using a custom built in-situ tension stage within a scanning electron microscope (SEM). The observed mechanical behavior is related to the microstructure by using transmission electron microscopy (TEM) on the as-processed material and tested specimens. Synchrotron X-ray based texture analysis was also conducted on the disk to determine if any changes in the deformation texture occur during HPT processing. Nanoindentation data shows a trend of increasing hardness with radial position that saturates at 4.5 GPa near the edge, and decreasing strain rate sensitivity. The micromechanical tests show two distinct regions on a processed circular disk, a non-shearing region and a shearing region. Microcompression/tension tests in the region of 1.0< X < 5.3 mm (X is the radial distance from the disk center) show limited strain hardening, homogeneous plastic deformation, and tensile elongation that varies from 0.3--4.0%. Tests performed at X > 5.3 mm show a drastic switch to localized plastic deformation in the form of shear bands, with evidence of grain rotation as the active deformation mechanism, and a measureable tension-compression asymmetry. Grains are elongated at all locations, and while the minimum diameters are consistent between regions, the elongated diameter in the shearing region is reduced. The transition to localized deformation is attributed to this reduced dimension. A larger percentage of grains in the shearing region have an elongated diameter below the critical grain size necessary to activate the grain rotation mechanism. The tension-compression asymmetry is due to an increased dependence on the normal stress for yielding, meaning NC Ta would follow a Mohr-Coulomb criterion over the traditional Tresca or von Mises.

Mapping strain rate dependence of dislocation-defect interactions by atomistic simulations

PubMed Central

Fan, Yue; Osetskiy, Yuri N.; Yip, Sidney; Yildiz, Bilge

2013-01-01

Probing the mechanisms of defect–defect interactions at strain rates lower than 106 s−1 is an unresolved challenge to date to molecular dynamics (MD) techniques. Here we propose an original atomistic approach based on transition state theory and the concept of a strain-dependent effective activation barrier that is capable of simulating the kinetics of dislocation–defect interactions at virtually any strain rate, exemplified within 10−7 to 107 s−1. We apply this approach to the problem of an edge dislocation colliding with a cluster of self-interstitial atoms (SIAs) under shear deformation. Using an activation–relaxation algorithm [Kushima A, et al. (2009) J Chem Phys 130:224504], we uncover a unique strain-rate–dependent trigger mechanism that allows the SIA cluster to be absorbed during the process, leading to dislocation climb. Guided by this finding, we determine the activation barrier of the trigger mechanism as a function of shear strain, and use that in a coarse-graining rate equation formulation for constructing a mechanism map in the phase space of strain rate and temperature. Our predictions of a crossover from a defect recovery at the low strain-rate regime to defect absorption behavior in the high strain-rate regime are validated against our own independent, direct MD simulations at 105 to 107 s−1. Implications of the present approach for probing molecular-level mechanisms in strain-rate regimes previously considered inaccessible to atomistic simulations are discussed. PMID:24114271

Effect of rifampicin and gentamicin on Shiga toxin 2 expression level and the SOS response in Escherichia coli O104:H4.

PubMed

Fadlallah, Sukayna M; Rahal, Elias A; Sabra, Ahmad; Kissoyan, Kohar A B; Matar, Ghassan M

2015-01-01

A novel pathotype, Shiga toxin-producing Escherichia coli O104:H4, was the cause of a severe outbreak that affected European countries, mainly Germany, in 2011. The effect of different regimens of rifampicin and gentamicin were evaluated to determine possible treatment modes for the novel strain, and to evaluate the SOS response and its effect on toxin release. Pulsed-field gel electrophoresis (PFGE) was performed on the novel E. coli O104:H4 pathotype and two pre-outbreak E. coli O104:H4 CDC strains. Transcript levels of the stx2 and recA gene (SOS response inducer) were evaluated using quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) in the novel E. coli O104:H4 samples subjected to different regimens of rifampicin and gentamicin. Consequently, reverse passive latex agglutination (RPLA) was used to determine the Stx2 titers in these samples. Western blot was performed to determine the LexA levels (SOS response repressor) in E. coli O104:H4. The efficacy of treatment with antimicrobial agents was assessed in BALB/c mice. The outbreak and pre-outbreak strains are closely related as shown by PFGE, which demonstrated slight genomic differences between the three strains. The transcription level of the stx2 gene in the new pathotype was 1.41- and 1.75-fold that of the 2009 EL-2050 and 2009 EL-2071 pre-outbreak strains, respectively. Moreover, the transcription level of the stx2 gene in the new pathotype was substantially decreased as a result of treatment with the different concentrations of the antimicrobial agents, but was enhanced when the antibiotics were administered at two subinhibitory levels. RPLA data were in accordance with the qRT-PCR results. E. coli O104:H4 exposed to gentamicin at both sub-minimum inhibitory concentration (MIC) levels led to high transcription levels of the recA gene and lack of expression of the LexA protein, implying that the SOS response was activated. Rifampicin at both sub-MIC levels resulted in low transcript levels of the recA gene, indicating that the SOS response was not induced. In vivo, the highest survival rate in BALB/c mice was observed in the group that was treated with the minimum bactericidal concentration (MBC) of gentamicin. The use of antimicrobial agents in E. coli O104:H4 infection seems to be effective at the MIC and MBC levels. This provides a promising ground for treatment of E. coli O104:H4.

Effects of Recovery Behavior and Strain-Rate Dependence of Stress-Strain Curve on Prediction Accuracy of Thermal Stress Analysis During Casting

NASA Astrophysics Data System (ADS)

Motoyama, Yuichi; Shiga, Hidetoshi; Sato, Takeshi; Kambe, Hiroshi; Yoshida, Makoto

2017-06-01

Recovery behavior (recovery) and strain-rate dependence of the stress-strain curve (strain-rate dependence) are incorporated into constitutive equations of alloys to predict residual stress and thermal stress during casting. Nevertheless, few studies have systematically investigated the effects of these metallurgical phenomena on the prediction accuracy of thermal stress in a casting. This study compares the thermal stress analysis results with in situ thermal stress measurement results of an Al-Si-Cu specimen during casting. The results underscore the importance for the alloy constitutive equation of incorporating strain-rate dependence to predict thermal stress that develops at high temperatures where the alloy shows strong strain-rate dependence of the stress-strain curve. However, the prediction accuracy of the thermal stress developed at low temperatures did not improve by considering the strain-rate dependence. Incorporating recovery into the constitutive equation improved the accuracy of the simulated thermal stress at low temperatures. Results of comparison implied that the constitutive equation should include strain-rate dependence to simulate defects that develop from thermal stress at high temperatures, such as hot tearing and hot cracking. Recovery should be incorporated into the alloy constitutive equation to predict the casting residual stress and deformation caused by the thermal stress developed mainly in the low temperature range.

Genetic diversity analysis of Leuconostoc mesenteroides from Korean vegetables and food products by multilocus sequence typing.

PubMed

Sharma, Anshul; Kaur, Jasmine; Lee, Sulhee; Park, Young-Seo

2018-06-01

In the present study, 35 Leuconostoc mesenteroides strains isolated from vegetables and food products from South Korea were studied by multilocus sequence typing (MLST) of seven housekeeping genes (atpA, groEL, gyrB, pheS, pyrG, rpoA, and uvrC). The fragment sizes of the seven amplified housekeeping genes ranged in length from 366 to 1414 bp. Sequence analysis indicated 27 different sequence types (STs) with 25 of them being represented by a single strain indicating high genetic diversity, whereas the remaining 2 were characterized by five strains each. In total, 220 polymorphic nucleotide sites were detected among seven housekeeping genes. The phylogenetic analysis based on the STs of the seven loci indicated that the 35 strains belonged to two major groups, A (28 strains) and B (7 strains). Split decomposition analysis showed that intraspecies recombination played a role in generating diversity among strains. The minimum spanning tree showed that the evolution of the STs was not correlated with food source. This study signifies that the multilocus sequence typing is a valuable tool to access the genetic diversity among L. mesenteroides strains from South Korea and can be used further to monitor the evolutionary changes.

Plant growth-promoting rhizobacteria allow reduced application rates of chemical fertilizers.

PubMed

Adesemoye, A O; Torbert, H A; Kloepper, J W

2009-11-01

The search for microorganisms that improve soil fertility and enhance plant nutrition has continued to attract attention due to the increasing cost of fertilizers and some of their negative environmental impacts. The objectives of this greenhouse study with tomato were to determine (1) if reduced rates of inorganic fertilizer coupled with microbial inoculants will produce plant growth, yield, and nutrient uptake levels equivalent to those with full rates of the fertilizer and (2) the minimum level to which fertilizer could be reduced when inoculants were used. The microbial inoculants used in the study were a mixture of plant growth-promoting rhizobacteria (PGPR) strains Bacillus amyloliquefaciens IN937a and Bacillus pumilus T4, a formulated PGPR product, and the arbuscular mycorrhiza fungus (AMF), Glomus intraradices. Results showed that supplementing 75% of the recommended fertilizer rate with inoculants produced plant growth, yield, and nutrient (nitrogen and phosphorus) uptake that were statistically equivalent to the full fertilizer rate without inoculants. When inoculants were used with rates of fertilizer below 75% of the recommended rate, the beneficial effects were usually not consistent; however, inoculation with the mixture of PGPR and AMF at 70% fertility consistently produced the same yield as the full fertility rate without inoculants. Without inoculants, use of fertilizer rates lower than the recommended resulted in significantly less plant growth, yield, and nutrient uptake or inconsistent impacts. The results suggest that PGPR-based inoculants can be used and should be further evaluated as components of integrated nutrient management strategies.

Protograph LDPC Codes with Node Degrees at Least 3

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Jones, Christopher

2006-01-01

In this paper we present protograph codes with a small number of degree-3 nodes and one high degree node. The iterative decoding threshold for proposed rate 1/2 codes are lower, by about 0.2 dB, than the best known irregular LDPC codes with degree at least 3. The main motivation is to gain linear minimum distance to achieve low error floor. Also to construct rate-compatible protograph-based LDPC codes for fixed block length that simultaneously achieves low iterative decoding threshold and linear minimum distance. We start with a rate 1/2 protograph LDPC code with degree-3 nodes and one high degree node. Higher rate codes are obtained by connecting check nodes with degree-2 non-transmitted nodes. This is equivalent to constraint combining in the protograph. The condition where all constraints are combined corresponds to the highest rate code. This constraint must be connected to nodes of degree at least three for the graph to have linear minimum distance. Thus having node degree at least 3 for rate 1/2 guarantees linear minimum distance property to be preserved for higher rates. Through examples we show that the iterative decoding threshold as low as 0.544 dB can be achieved for small protographs with node degrees at least three. A family of low- to high-rate codes with minimum distance linearly increasing in block size and with capacity-approaching performance thresholds is presented. FPGA simulation results for a few example codes show that the proposed codes perform as predicted.

Time-dependent rheological behavior of natural polysaccharide xanthan gum solutions in interrupted shear and step-incremental/reductional shear flow fields

NASA Astrophysics Data System (ADS)

Lee, Ji-Seok; Song, Ki-Won

2015-11-01

The objective of the present study is to systematically elucidate the time-dependent rheological behavior of concentrated xanthan gum systems in complicated step-shear flow fields. Using a strain-controlled rheometer (ARES), step-shear flow behaviors of a concentrated xanthan gum model solution have been experimentally investigated in interrupted shear flow fields with a various combination of different shear rates, shearing times and rest times, and step-incremental and step-reductional shear flow fields with various shearing times. The main findings obtained from this study are summarized as follows. (i) In interrupted shear flow fields, the shear stress is sharply increased until reaching the maximum stress at an initial stage of shearing times, and then a stress decay towards a steady state is observed as the shearing time is increased in both start-up shear flow fields. The shear stress is suddenly decreased immediately after the imposed shear rate is stopped, and then slowly decayed during the period of a rest time. (ii) As an increase in rest time, the difference in the maximum stress values between the two start-up shear flow fields is decreased whereas the shearing time exerts a slight influence on this behavior. (iii) In step-incremental shear flow fields, after passing through the maximum stress, structural destruction causes a stress decay behavior towards a steady state as an increase in shearing time in each step shear flow region. The time needed to reach the maximum stress value is shortened as an increase in step-increased shear rate. (iv) In step-reductional shear flow fields, after passing through the minimum stress, structural recovery induces a stress growth behavior towards an equilibrium state as an increase in shearing time in each step shear flow region. The time needed to reach the minimum stress value is lengthened as a decrease in step-decreased shear rate.

Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

NASA Astrophysics Data System (ADS)

Wang, Peng; Zheng, Zhijun; Liao, Shenfei; Yu, Jilin

2018-02-01

The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored. The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

37 CFR 385.13 - Minimum royalty rates and subscriber-based royalty floors for specific types of services.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., and Copyrights COPYRIGHT ROYALTY BOARD, LIBRARY OF CONGRESS RATES AND TERMS FOR STATUTORY LICENSES... PHYSICAL AND DIGITAL PHONORECORDS Interactive Streaming and Limited Downloads § 385.13 Minimum royalty...

Effect of biofilm formation by clinical isolates of Helicobacter pylori on the efflux-mediated resistance to commonly used antibiotics.

PubMed

Attaran, Bahareh; Falsafi, Tahereh; Ghorbanmehr, Nassim

2017-02-21

To evaluate the role of biofilm formation on the resistance of Helicobacter pylori ( H. pylori ) to commonly prescribed antibiotics, the expression rates of resistance genes in biofilm-forming and planktonic cells were compared. A collection of 33 H. pylori isolates from children and adult patients with chronic infection were taken for the present study. The isolates were screened for biofilm formation ability, as well as for polymerase chain reaction (PCR) reaction with HP1165 and hp1165 efflux pump genes. Susceptibilities of the selected strains to antibiotic and differences between susceptibilities of planktonic and biofilm-forming cell populations were determined. Quantitative real-time PCR (qPCR) analysis was performed using 16S rRNA gene as a H. pylori -specific primer, and two efflux pumps-specific primers, hp1165 and hefA . The strains were resistant to amoxicillin, metronidazole, and erythromycin, except for one strain, but they were all susceptible to tetracycline. Minimum bactericidal concentrations of antibiotics in the biofilm-forming cells were significantly higher than those of planktonic cells. qPCR demonstrated that the expression of efflux pump genes was significantly higher in the biofilm-forming cells as compared to the planktonic ones. The present work demonstrated an association between H. pylori biofilm formation and decreased susceptibility to all the antibiotics tested. This decreased susceptibility to antibiotics was associated with enhanced functional activity of two efflux pumps: hp1165 and hefA .

Antimicrobial Activity and Possible Mechanism of Action of Citral against Cronobacter sakazakii.

PubMed

Shi, Chao; Song, Kaikuo; Zhang, Xiaorong; Sun, Yi; Sui, Yue; Chen, Yifei; Jia, Zhenyu; Sun, Huihui; Sun, Zheng; Xia, Xiaodong

2016-01-01

Citral is a flavor component that is commonly used in food, beverage and fragrance industries. Cronobacter sakazakii is a food-borne pathogen associated with severe illness and high mortality in neonates and infants. The objective of the present study was to evaluate antimicrobial effect of citral against C. sakazakii strains. The minimum inhibitory concentration (MIC) of citral against C. sakazakii was determined via agar dilution method, then Gompertz models were used to quantitate the effect of citral on microbial growth kinetics. Changes in intracellular pH (pHin), membrane potential, intracellular ATP concentration, and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also examined using a field emission scanning electron microscope. The MICs of citral against C. sakazakii strains ranged from 0.27 to 0.54 mg/mL, and citral resulted in a longer lag phase and lower growth rate of C. sakazakii compared to the control. Citral affected the cell membrane of C. sakazakii, as evidenced by decreased intracellular ATP concentration, reduced pHin, and cell membrane hyperpolarization. Scanning electron microscopy analysis further confirmed that C. sakazakii cell membranes were damaged by citral. These findings suggest that citral exhibits antimicrobial effect against C. sakazakii strains and could be potentially used to control C. sakazakii in foods. However, how it works in food systems where many other components may interfere with its efficacy should be tested in future research before its real application.

Antimicrobial Activity and Possible Mechanism of Action of Citral against Cronobacter sakazakii

PubMed Central

Shi, Chao; Song, Kaikuo; Zhang, Xiaorong; Sun, Yi; Sui, Yue; Chen, Yifei; Jia, Zhenyu; Sun, Huihui; Sun, Zheng; Xia, Xiaodong

2016-01-01

Citral is a flavor component that is commonly used in food, beverage and fragrance industries. Cronobacter sakazakii is a food-borne pathogen associated with severe illness and high mortality in neonates and infants. The objective of the present study was to evaluate antimicrobial effect of citral against C. sakazakii strains. The minimum inhibitory concentration (MIC) of citral against C. sakazakii was determined via agar dilution method, then Gompertz models were used to quantitate the effect of citral on microbial growth kinetics. Changes in intracellular pH (pHin), membrane potential, intracellular ATP concentration, and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also examined using a field emission scanning electron microscope. The MICs of citral against C. sakazakii strains ranged from 0.27 to 0.54 mg/mL, and citral resulted in a longer lag phase and lower growth rate of C. sakazakii compared to the control. Citral affected the cell membrane of C. sakazakii, as evidenced by decreased intracellular ATP concentration, reduced pHin, and cell membrane hyperpolarization. Scanning electron microscopy analysis further confirmed that C. sakazakii cell membranes were damaged by citral. These findings suggest that citral exhibits antimicrobial effect against C. sakazakii strains and could be potentially used to control C. sakazakii in foods. However, how it works in food systems where many other components may interfere with its efficacy should be tested in future research before its real application. PMID:27415761

Identification of Group G Streptococcal Isolates from Companion Animals in Japan and Their Antimicrobial Resistance Patterns.

PubMed

Tsuyuki, Yuzo; Kurita, Goro; Murata, Yoshiteru; Goto, Mieko; Takahashi, Takashi

2017-07-24

In this study, we conducted a species-level identification of group G streptococcal (GGS) isolates from companion animals in Japan and analyzed antimicrobial resistance (AMR) patterns. Strains were isolated from sterile and non-sterile specimens collected from 72 animals with clinical signs or symptoms in April-May, 2015. We identified the strain by 16S rRNA sequencing, mass spectrometry (MS), and an automated method based on their biochemical properties. Antimicrobial susceptibility was determined using the broth microdilution method and E-test. AMR determinants (erm(A), erm(B), mef(A), tet(M), tet(O), tet(K), tet(L), and tet(S)) in corresponding resistant isolates were amplified by PCR. The 16S rRNA sequencing identified the GGS species as Streptococcus canis (n = 68), Streptococcus dysgalactiae subsp. equisimilis (n = 3), and S. dysgalactiae subsp. dysgalactiae (n = 1). However, there were discrepancies between the sequencing data and both the MS and automated identification data. MS and the automated biochemical technique identified 18 and 37 of the 68 sequencing-identified S. canis strains, respectively. The AMR rates were 20.8% for tetracycline and 5.6% for clarithromycin, with minimum inhibitory concentrations (MIC) 50 -MIC 90 of 2-64 and ≤ 0.12-0.25μg/mL, respectively. AMR genotyping showed single or combined genotypes: erm(B) or tet(M)-tet(O)-tet(S). Our findings show the unique characteristics of GGS isolates from companion animals in Japan in terms of species-level identification and AMR patterns.

Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae isolated from pigs with swine erysipelas in Japan, 1988-1998.

PubMed

Yamamoto, K; Kijima, M; Yoshimura, H; Takahashi, T

2001-03-01

The susceptibility to 21 antimicrobial agents of 214 strains of Erysipelothrix rhusiopathiae isolated from pigs affected with swine erysipelas in Japan between 1988 and 1998 was determined. Ampicillin, cloxacillin, benzylpenicillin, ceftiofur, tylosin, enrofloxacin and danofloxacin were the most active agents [minimum inhibitory concentrations (MICs); < or = 0.025-0.78 microgram/ml], followed by cefazolin, virginiamycin, tiamulin, chloramphenicol, florphenicol and oxolinic acid (MICs; 0.1-25 micrograms/ml). Activity was poor or absent with kanamycin and sulfadimethoxine. Strains resistant to dihydrostreptomycin, erythromycin, clindamycin, lincomycin, oxytetracycline and doxycycline were detected. The susceptibilities to dihydrostreptomycin and oxytetracycline tended to decrease. Investigation of the differences in antimicrobial susceptibility of the 214 strains according to their serotypes, sources, isolation years and regions, showed that the strains resistant to dihydrostreptomycin were most frequently found in the strains of serotype 1a and in strains from septicaemic cases. Strains resistant to oxytetracycline were detected in all serotypes and all sources, and most of the strains resistant to erythromycin were detected in the strains of serotype 2. The frequency of strains resistant to dihydrostreptomycin gradually increased from 1988 to 1996, but then decreased between 1997 and 1998. The frequency of strains resistant to oxytetracycline was remained more than 38% from 1988 to 1998. It was suggested that the strains resistant to dihydrostreptomycin and oxytetracycline were distributed over almost all districts of Japan.

Extension of Viscoplasticity Based on Overstress to Capture the Effects of Prior Aging on the Time Dependent Deformation Behavior of a High-Temperature Polymer: Experiments and Modeling

DTIC Science & Technology

2008-10-01

the standard model characterization procedure is based on creep and recovery tests, where loading and unloading occurs at a fast rate of 1.0 MPa/s...σ − g[ǫ] and on d̊g[ǫ] dǫ = E, where g̊ is defined as the equilibrium stress g[ ] for extremely fast loading. For this case, the stress-strain curves...Strain S tr es s Strain Rate Slow Strain Rate Medium Strain Rate Fast Plastic Flow Fully Established Figure 2.10: Stress Strain Curve Schematic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Nelson, Kevin; Lipinski, Ronald J.

Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzedmore » the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 – 10000 s -1) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.« less

TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

NASA Astrophysics Data System (ADS)

Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

2016-10-01

The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

Creep crack growth by grain boundary cavitation under monotonic and cyclic loading

NASA Astrophysics Data System (ADS)

Wen, Jian-Feng; Srivastava, Ankit; Benzerga, Amine; Tu, Shan-Tung; Needleman, Alan

2017-11-01

Plane strain finite deformation finite element calculations of mode I crack growth under small scale creep conditions are carried out. Attention is confined to isothermal conditions and two time histories of the applied stress intensity factor: (i) a monononic increase to a plateau value subsequently held fixed; and (ii) a cyclic time variation. The crack growth calculations are based on a micromechanics constitutive relation that couples creep deformation and damage due to grain boundary cavitation. Grain boundary cavitation, with cavity growth due to both creep and diffusion, is taken as the sole failure mechanism contributing to crack growth. The influence on the crack growth rate of loading history parameters, such as the magnitude of the applied stress intensity factor, the ratio of the applied minimum to maximum stress intensity factors, the loading rate, the hold time and the cyclic loading frequency, are explored. The crack growth rate under cyclic loading conditions is found to be greater than under monotonic creep loading with the plateau applied stress intensity factor equal to its maximum value under cyclic loading conditions. Several features of the crack growth behavior observed in creep-fatigue tests naturally emerge, for example, a Paris law type relation is obtained for cyclic loading.

Cyclic tensile response of a pre-tensioned polyurethane

NASA Astrophysics Data System (ADS)

Nie, Yizhou; Liao, Hangjie; Chen, Weinong W.

2018-05-01

In the research reported in this paper, we subject a polyurethane to uniaxial tensile loading at a quasi-static strain rate, a high strain rate and a jumping strain rate where the specimen is under quasi-static pre-tension and is further subjected to a dynamic cyclic loading using a modified Kolsky tension bar. The results obtained at the quasi-static and high strain rate clearly show that the mechanical response of this material is significantly rate sensitive. The rate-jumping experimental results show that the response of the material behavior is consistent before jumping. After jumping the stress-strain response of the material does not jump to the corresponding high-rate curve. Rather it approaches the high-rate curve asymptotically. A non-linear hyper-viscoelastic (NLHV) model, after having been calibrated by monotonic quasi-static and high-rate experimental results, was found to be capable of describing the material tensile behavior under such rate jumping conditions.

High-Strain-Rate Compression Testing of Ice

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Prakash, Vikas; Lerch, Bradley A.

2006-01-01

In the present study a modified split Hopkinson pressure bar (SHPB) was employed to study the effect of strain rate on the dynamic material response of ice. Disk-shaped ice specimens with flat, parallel end faces were either provided by Dartmouth College (Hanover, NH) or grown at Case Western Reserve University (Cleveland, OH). The SHPB was adapted to perform tests at high strain rates in the range 60 to 1400/s at test temperatures of -10 and -30 C. Experimental results showed that the strength of ice increases with increasing strain rates and this occurs over a change in strain rate of five orders of magnitude. Under these strain rate conditions the ice microstructure has a slight influence on the strength, but it is much less than the influence it has under quasi-static loading conditions. End constraint and frictional effects do not influence the compression tests like they do at slower strain rates, and therefore the diameter/thickness ratio of the samples is not as critical. The strength of ice at high strain rates was found to increase with decreasing test temperatures. Ice has been identified as a potential source of debris to impact the shuttle; data presented in this report can be used to validate and/or develop material models for ice impact analyses for shuttle Return to Flight efforts.

a Study on Strain Rate Effect in Collision Analysis of Rolling STOCK

NASA Astrophysics Data System (ADS)

Kim, Seung Rok; Koo, Jeong Seo

In this paper, the strain rate effect of energy absorption members in rolling stock is studied using the virtual testing model (VTM) for Korean high speed train (KHST). The VTM of KHST was simulated for two different strain rate conditions. The VTM is composed of FE models for structures, and nonlinear spring/damper models for dynamic components. To simplify numerical model for the full rake KHST, the first three units consist of full flexible multi-body dynamic models, and the remainder does 1-D spring/damper/mass models. To evaluate the strain rate effect of KHST, the crash simulation was performed under the accident scenario for a collision with a rigid mass of 15 tons at 110kph. The numerical results show that the overall crash response of the train is not largely affected as much as expected, but individual components have some different deformations according to strain rate. The deformation of the front end structure without strain rate effect is larger than that with it. However, the deformation of the rear end structure without strain rate effect is smaller than that with it. Finally, the intrusion of the driver's cabin is overestimated for no strain rate effect when compared to the case with it.

14 CFR 29.49 - Performance at minimum operating speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Performance at minimum operating speed. 29... minimum operating speed. (a) For each Category A helicopter, the hovering performance must be determined... than helicopters, the steady rate of climb at the minimum operating speed must be determined over the...

14 CFR 29.49 - Performance at minimum operating speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Performance at minimum operating speed. 29... minimum operating speed. (a) For each Category A helicopter, the hovering performance must be determined... than helicopters, the steady rate of climb at the minimum operating speed must be determined over the...

Characterization of a New Fully Recycled Carbon Fiber Reinforced Composite Subjected to High Strain Rate Tension

NASA Astrophysics Data System (ADS)

Meftah, H.; Tamboura, S.; Fitoussi, J.; BenDaly, H.; Tcharkhtchi, A.

2017-08-01

The aim of this study is the complete physicochemical characterization and strain rate effect multi-scale analysis of a new fully recycled carbon fiber reinforced composites for automotive crash application. Two composites made of 20% wt short recycled carbon fibers (CF) are obtained by injection molding. The morphology and the degree of dispersion of CF in the matrixes were examined using a new ultrasonic method and SEM. High strain tensile behavior up to 100 s-1 is investigated. In order to avoid perturbation due to inertial effect and wave propagation, the specimen geometry was optimized. The elastic properties appear to be insensitive to the strain rate. However, a high strain rate effect on the local visco-plasticity of the matrix and fiber/matrix interface visco-damageable behavior is emphasized. The predominant damage mechanisms evolve from generalized matrix local ductility at low strain rate regime to fiber/matrix interface debonding and fibers pull-out at high strain rate regime.

Cyclic strain rate effects in fatigued face-centred and body-centred cubic metals

NASA Astrophysics Data System (ADS)

Mughrabi, Haël

2013-09-01

The present work deals mainly with the effect and the use of strain rate and temperature changes during cyclic deformation as a means to obtain valuable information on the thermally activated dislocation glide processes, based on the assessment of reversible changes of the thermal effective stress and of transient changes of the athermal stress. The importance of closed-loop testing in true plastic strain control with constant cyclic plastic strain rate throughout the cycle is explained and emphasized, especially with respect to the case of strain rate sensitive materials. Stress responses of face-centred cubic and body-centred cubic (bcc) metals to cyclic strain rate changes are presented to illustrate that the deformation modes of these two classes of materials differ characteristically at temperatures below that the so-called knee temperature of bcc metals. When such tests are performed in cyclic saturation, the temperature and strain rate dependence of bcc metals can be measured very accurately on one and the same specimen, permitting a thorough analysis of thermal activation.

Characterization of a New Fully Recycled Carbon Fiber Reinforced Composite Subjected to High Strain Rate Tension

NASA Astrophysics Data System (ADS)

Meftah, H.; Tamboura, S.; Fitoussi, J.; BenDaly, H.; Tcharkhtchi, A.

2018-06-01

The aim of this study is the complete physicochemical characterization and strain rate effect multi-scale analysis of a new fully recycled carbon fiber reinforced composites for automotive crash application. Two composites made of 20% wt short recycled carbon fibers (CF) are obtained by injection molding. The morphology and the degree of dispersion of CF in the matrixes were examined using a new ultrasonic method and SEM. High strain tensile behavior up to 100 s-1 is investigated. In order to avoid perturbation due to inertial effect and wave propagation, the specimen geometry was optimized. The elastic properties appear to be insensitive to the strain rate. However, a high strain rate effect on the local visco-plasticity of the matrix and fiber/matrix interface visco-damageable behavior is emphasized. The predominant damage mechanisms evolve from generalized matrix local ductility at low strain rate regime to fiber/matrix interface debonding and fibers pull-out at high strain rate regime.

Abnormal Strain Rate Sensitivity Driven by a Unit Dislocation-Obstacle Interaction in bcc Fe

NASA Astrophysics Data System (ADS)

Bai, Zhitong; Fan, Yue

2018-03-01

The interaction between an edge dislocation and a sessile vacancy cluster in bcc Fe is investigated over a wide range of strain rates from 108 down to 103 s-1 , which is enabled by employing an energy landscape-based atomistic modeling algorithm. It is observed that, at low strain rates regime less than 105 s-1 , such interaction leads to a surprising negative strain rate sensitivity behavior because of the different intermediate microstructures emerged under the complex interplays between thermal activation and applied strain rate. Implications of our findings regarding the previously established global diffusion model are also discussed.

Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

NASA Technical Reports Server (NTRS)

Porr, William C., Jr.; Gangloff, Richard P.

1990-01-01

Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging may play a role. Fractography showed that microvoid coalescence was the microscopic mode of fracture in FVS0812 under all testing conditions. However, the nature of the microvoids varied with test temperature and loading rate, and is complex for the fine grain and dipersoid sizes of FVS0812.

The Effect of Strain Rate on the Evolution of Plane Wakes Subjected to Irrotational Strains

NASA Technical Reports Server (NTRS)

Rogers, Michael M.; Merriam, Marshal (Technical Monitor)

1996-01-01

Direct numerical simulations of time-evolving turbulent plane wakes developing in the presence of irrotational plane strain applied at three different strain rates have been generated. The strain geometry is such that the flow is compressed in the streamwise direction and expanded in the cross-stream direction with the spanwise direction being unstrained. This geometry is the temporally evolving analogue of a spatially evolving wake in an adverse pressure gradient. A pseudospectral numerical method with up to 16 million modes is used to solve the equations in a reference frame moving with the irrotational strain. The initial condition for each simulation is taken from a previous turbulent self-similar plane wake direct numerical simulation at a velocity deficit Reynolds number, Re, of about 2,000. Although the evolutions of many statistics are nearly collapsed when plotted against total strain, there are some differences owing to the different strain rate histories. The impact of strain-rate on the wake spreading rate, the peak velocity deficit, the Reynolds stress profiles, and the flow structure is examined.

Residual thermal and moisture influences on the strain energy release rate analysis of edge delamination

NASA Technical Reports Server (NTRS)

Obrien, T. K.; Raju, I. S.; Garber, D. P.

1985-01-01

A laminated plate theory analysis is developed to calculate the strain energy release rate associated with edge delamination growth in a composite laminate. The analysis includes the contribution of residual thermal and moisture stresses to the strain energy released. The strain energy release rate, G, increased when residual thermal effects were combined with applied mechanical strains, but then decreased when increasing moisture content was included. A quasi-three-dimensional finite element analysis indicated identical trends and demonstrated these same trends for the individual strain energy release rate components, G sub I and G sub II, associated with interlaminar tension and shear. An experimental study indicated that for T300/5208 graphite-epoxy composites, the inclusion of residual thermal and moisture stresses did not significantly alter the calculation of interlaminar fracture toughness from strain energy release rate analysis of edge delamination data taken at room temperature, ambient conditions.

Hot Deformation and Dynamic Recrystallization Behavior of the Cu-Cr-Zr-Y Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yi; Huili, Sun; Volinsky, Alex A.; Tian, Baohong; Chai, Zhe; Liu, Ping; Liu, Yong

2016-03-01

To study the workability and to optimize the hot deformation processing parameters of the Cu-Cr-Zr-Y alloy, the strain hardening effect and dynamic softening behavior of the Cu-Cr-Zr-Y alloy were investigated. The flow stress increases with the strain rate and stress decreases with deformation temperature. The critical conditions, including the critical strain and stress for the occurrence of dynamic recrystallization, were determined based on the alloy strain hardening rate. The critical stress related to the onset of dynamic recrystallization decreases with temperature. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Dynamic recrystallization appears at high temperatures and low strain rates. The addition of Y can refine the grain and effectively accelerate dynamic recrystallization. Dislocation generation and multiplication are the main hot deformation mechanisms for the alloy. The deformation temperature increase and the strain rate decrease can promote dynamic recrystallization of the alloy.

Paleomagnetic evidence for rapid vertical-axis rotations during thrusting in an active collision zone, northeastern Papua New Guinea

NASA Astrophysics Data System (ADS)

Weiler, Peter D.; Coe, Robert S.

1997-06-01

A paleomagnetic study of three thrust sheets of the fold and thrust belt north of the Ramu-Markham Fault Zone (RMFZ) indicates very rapid vertical-axis rotations, with differential declination anomalies related to tectonic transport of thrust units. Data from this investigation indicate depositional ages straddling the Brunhes-Matuyama reversal (780 ka) for the Leron Formation in Erap Valley. Net counterclockwise, vertical-axis rotations as great as 90° since 1 Ma have occurred locally in the Erap Valley area. These rotations appear to be kinematically related to shear across a tear fault within the foreland fold and thrust belt of the colliding Finisterre Arc, which in turn is aligned with and may be structurally controlled by a major fault in the lower plate. These data indicate that vertical-axis rotations occurred during thrusting; consequently, the actual rotation rate is likely several times higher than the calculated minimum rate. Such very rapid rotations during thrust sheet emplacement may be more common in fold and thrust belts than is presently recognized. Anisotropy of magnetic susceptibility data yields foliated fabrics with subordinate, well-grouped lineations that differ markedly in azimuth in the three thrust sheets. The susceptibility lineations are rendered parallel by the same bedding-perpendicular rotations used to restore the paleomagnetic remanence to N-S thus independently confirming the rapid rotations. The restored lineations are perpendicular to the direction of tectonic transport, and the minimum susceptibility axes are streaked perpendicular to the lineation. We interpret these anisotropy of magnetic susceptibility data as primary sedimentary fabrics modified by weak strain accompanying foreland thrusting.

Microstructure characterization of 316L deformed at high strain rates using EBSD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yvell, K., E-mail: kyv@du.se

2016-12-15

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s{sup −1} at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneousmore » and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain. - Highlights: •Only changes in strain, not strain rate, gave differences in the microstructure. •A bimodal lognormal size distribution was found to describe the size distribution. •Variation of the subgrain fraction sizes agrees with models for heterogeneous slip. •Variation of subgrain size with strain describes part of the stress strain curve.« less

The Effect Analysis of Strain Rate on Power Transmission Tower-Line System under Seismic Excitation

PubMed Central

Wang, Wenming

2014-01-01

The effect analysis of strain rate on power transmission tower-line system under seismic excitation is studied in this paper. A three-dimensional finite element model of a transmission tower-line system is created based on a real project. Using theoretical analysis and numerical simulation, incremental dynamic analysis of the power transmission tower-line system is conducted to investigate the effect of strain rate on the nonlinear responses of the transmission tower and line. The results show that the effect of strain rate on the transmission tower generally decreases the maximum top displacements, but it would increase the maximum base shear forces, and thus it is necessary to consider the effect of strain rate on the seismic analysis of the transmission tower. The effect of strain rate could be ignored for the seismic analysis of the conductors and ground lines, but the responses of the ground lines considering strain rate effect are larger than those of the conductors. The results could provide a reference for the seismic design of the transmission tower-line system. PMID:25105157

Dynamic Behavior of AA2519-T8 Aluminum Alloy Under High Strain Rate Loading in Compression

NASA Astrophysics Data System (ADS)

Olasumboye, A. T.; Owolabi, G. M.; Odeshi, A. G.; Yilmaz, N.; Zeytinci, A.

2018-06-01

In this study, the effects of strain rate on the dynamic behavior, microstructure evolution and hence, failure of the AA2519-T8 aluminum alloy were investigated under compression at strain rates ranging from 1000 to 3500 s-1. Cylindrical specimens of dimensions 3.3 mm × 3.3 mm (L/D = 1) were tested using the split-Hopkinson pressure bar integrated with a digital image correlation system. The microstructure of the alloy was assessed using optical and scanning electron microscopes. Results showed that the dynamic yield strength of the alloy is strain rate dependent, with the maximum yield strength attained by the material being 500 MPa. The peak flow stress of 562 MPa was attained by the material at 3500 s-1. The alloy also showed a significant rate of strain hardening that is typical of other Al-Cu alloys; the rate of strain hardening, however, decreased with increase in strain rate. It was determined that the strain rate sensitivity coefficient of the alloy within the range of high strain rates used in this study is approximately 0.05 at 0.12 plastic strain; a more significant value than what was reported in literature under quasi-static loading. Micrographs obtained showed potential sites for the evolution of adiabatic shear band at 3500 s-1, with a characteristic circular-shaped surface profile comprising partially dissolved second phase particles in the continuous phase across the incident plane of the deformed specimen. The regions surrounding the site showed little or no change in the size of particles. However, the constituent coarse particles were observed as agglomerations of fractured pieces, thus having a shape factor different from those contained in the as-received alloy. Since the investigated alloy is a choice material for military application where it can be exposed to massive deformation at high strain rates, this study provides information on its microstructural and mechanical responses to such extreme loading condition.

Dynamic Behavior of AA2519-T8 Aluminum Alloy Under High Strain Rate Loading in Compression

NASA Astrophysics Data System (ADS)

Olasumboye, A. T.; Owolabi, G. M.; Odeshi, A. G.; Yilmaz, N.; Zeytinci, A.

2018-02-01

In this study, the effects of strain rate on the dynamic behavior, microstructure evolution and hence, failure of the AA2519-T8 aluminum alloy were investigated under compression at strain rates ranging from 1000 to 3500 s-1. Cylindrical specimens of dimensions 3.3 mm × 3.3 mm (L/D = 1) were tested using the split-Hopkinson pressure bar integrated with a digital image correlation system. The microstructure of the alloy was assessed using optical and scanning electron microscopes. Results showed that the dynamic yield strength of the alloy is strain rate dependent, with the maximum yield strength attained by the material being 500 MPa. The peak flow stress of 562 MPa was attained by the material at 3500 s-1. The alloy also showed a significant rate of strain hardening that is typical of other Al-Cu alloys; the rate of strain hardening, however, decreased with increase in strain rate. It was determined that the strain rate sensitivity coefficient of the alloy within the range of high strain rates used in this study is approximately 0.05 at 0.12 plastic strain; a more significant value than what was reported in literature under quasi-static loading. Micrographs obtained showed potential sites for the evolution of adiabatic shear band at 3500 s-1, with a characteristic circular-shaped surface profile comprising partially dissolved second phase particles in the continuous phase across the incident plane of the deformed specimen. The regions surrounding the site showed little or no change in the size of particles. However, the constituent coarse particles were observed as agglomerations of fractured pieces, thus having a shape factor different from those contained in the as-received alloy. Since the investigated alloy is a choice material for military application where it can be exposed to massive deformation at high strain rates, this study provides information on its microstructural and mechanical responses to such extreme loading condition.

Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dong; Gao, Ning; Setyawan, W.

The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten (W) has been studied with molecular dynamics simulations. Two different W potentials (Fikar and Juslin) were compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affects the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar-potential is <100> and with the Juslin-potential is <111>. Nevertheless, the most stable self-interstitial configuration is found to be a <111>-crowdion for both potentials. This stable configuration doesmore » not change with applied strain. Varying the strain from compression to tension increases the vacancy formation energy but decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with applied hydrostatic strain from compression to tension.« less

Sub-inhibitory stress with essential oil affects enterotoxins production and essential oil susceptibility in Staphylococcus aureus.

PubMed

Turchi, Barbara; Mancini, Simone; Pistelli, Luisa; Najar, Basma; Cerri, Domenico; Fratini, Filippo

2018-03-01

Fourteen wild strains of Staphylococcus aureus positive for gene sea were tested for enterotoxins production and the minimum inhibitory concentration of Leptospermum scoparium, Origanum majorana, Origanum vulgare, Satureja montana and Thymus vulgaris essential oils (EOs) were determined. After this trial, bacteria stressed with sub-inhibitory concentration of each EO were tested for enterotoxins production by an immunoenzymatic assay and resistance to the same EO. Oregano oil exhibited the highest antibacterial activity followed by manuka and thyme oils. After the exposure to a sub-inhibitory concentration of EOs, strains displayed an increased sensitivity in more than 95% of the cases. After treatment with oregano and marjoram EOs, few strains showed a modified enterotoxins production, while 43% of the strains were no longer able to produce enterotoxins after treatment with manuka EO. The results obtained in this study highlight that exposure to sub-inhibitory concentration of EO modifies strains enterotoxins production and EOs susceptibility profile.

Mycobacterium massiliense BRA100 strain recovered from postsurgical infections: resistance to high concentrations of glutaraldehyde and alternative solutions for high level disinfection.

PubMed

Lorena, Nádia Suely de Oliveira; Pitombo, Marcos Bettini; Côrtes, Patrícia Barbur; Maya, Maria Cristina Araújo; Silva, Marlei Gomes da; Carvalho, Ana Carolina da Silva; Coelho, Fábrice Santana; Miyazaki, Neide Hiromi Tokumaru; Marques, Elizabeth Andrade; Chebabo, Alberto; Freitas, Andréa D'Avila; Lupi, Otília; Duarte, Rafael Silva

2010-10-01

To evaluate the minimum inhibitory concentration (MIC) of GTA against these microorganisms and alternative disinfectants for high-level disinfection (HLD). Reference mycobacteria and clinical M. massiliense strains were included in this study. Active cultures were submitted to susceptibility qualitative tests with GTA dilutions (ranging from 1.5% to 8%), and commercial orthophthaldehyde (OPA) and peracetic acid (PA)-based solutions, during the period of exposure as recommended by National Agency of Sanitary Surveillance for HLD. All reference and M. massiliense non-BRA100 strains, recovered from sputum, were susceptible to any GTA concentration, OPA and PA solutions. M. massiliense BRA100 strains presented MIC of 8% GTA and were susceptible to OPA and PA. M. massiliense BRA100 strain is resistant to high GTA concentrations (up to 7%), which proves that this product is non-effective against specific rapidly growing mycobacteria and should be substituted by OPA or PA-based solutions for HLD.

Strain-rate/temperature behavior of high density polyethylene in compression

NASA Technical Reports Server (NTRS)

Clements, L. L.; Sherby, O. D.

1978-01-01

The compressive strain rate/temperature behavior of highly linear, high density polyethylene was analyzed in terms of the predictive relations developed for metals and other crystalline materials. For strains of 5 percent and above, the relationship between applied strain rate, dotted epsilon, and resulting flow stress, sigma, was found to be: dotted epsilon exp times (Q sub f/RT) = k'(sigma/sigma sub c) to the nth power; the left-hand side is the activation-energy-compensated strain rate, where Q sub f is activation energy for flow, R is gas constant, and T is temperature; k is a constant, n is temperature-independent stress exponent, and sigma/sigma sub c is structure-compensated stress. A master curve resulted from a logarithmic plot of activation-energy-compensated strain rate versus structure-compensated stress.

Effects of strain rate, mixing ratio, and stress-strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications.

PubMed

Khanafer, Khalil; Duprey, Ambroise; Schlicht, Marty; Berguer, Ramon

2009-04-01

Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.

Analytical Modeling of the High Strain Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2003-01-01

The results presented here are part of an ongoing research program to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric matrix materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical 5 plasticity theory definitions of effective stress and effective plastic strain are modified by applying variations of the Drucker-Prager yield criterion. To verify the revised formulation, the shear and tensile deformation of a representative toughened epoxy is analyzed across a wide range of strain rates (from quasi-static to high strain rates) and the results are compared to experimentally obtained values. For the analyzed polymers, both the tensile and shear stress-strain curves computed using the analytical model correlate well with values obtained through experimental tests. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. In the micromechanics, the unit cell is divided up into a number of independently analyzed slices, and laminate theory is then applied to obtain the effective deformation of the unit cell. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite (composed using the representative polymer analyzed for the correlation of the polymer constitutive equations) for several fiber orientation angles across a variety of strain rates. The computed values compare favorably to experimentally obtained results.

The Effect of Ivermectin in Seven Strains of Aedes aegypti (Diptera: Culicidae) Including a Genetically Diverse Laboratory Strain and Three Permethrin Resistant Strains

PubMed Central

Deus, K. M.; Saavedra-rodriguez, K.; Butters, M. P.; Black, W. C.; Foy, B. D.

2014-01-01

Seven different strains of Aedes aegypti (L.), including a genetically diverse laboratory strain, three laboratory-selected permethrin-resistant strains, a standard reference strain, and two recently colonized strains were fed on human blood containing various concentrations of ivermectin. Ivermectin reduced adult survival, fecundity, and hatch rate of eggs laid by ivermectin-treated adults in all seven strains. The LC50 of ivermectin for adults and the concentration that prevented 50% of eggs from hatching was calculated for all strains. Considerable variation in adult survival after an ivermectin-bloodmeal occurred among strains, and all three permethrin-resistant strains were significantly less susceptible to ivermectin than the standard reference strain. The hatch rate after an ivermectin bloodmeal was less variable among strains, and only one of the permethrin-resistant strains differed significantly from the standard reference strain. Our studies suggest that ivermectin induces adult mortality and decreases the hatch rate of eggs through different mechanisms. A correlation analysis of log-transformed LC50 among strains suggests that permethrin and ivermectin cross-resistance may occur. PMID:22493855

Changes in Speckle Tracking Echocardiography Measures of Ventricular Function after Percutaneous Implantation of the Edwards SAPIEN Transcatheter Heart Valve in the Pulmonary Position

PubMed Central

Chowdhury, Shahryar M.; Hijazi, Ziyad M.; Rhodes, John F.; Kar, Saibal; Makkar, Raj; Mullen, Michael; Cao, Qi-Ling; Mandinov, Lazar; Buckley, Jason; Pietris, Nicholas P.; Shirali, Girish S.

2015-01-01

Background Patients with free pulmonary regurgitation or mixed pulmonary stenosis and regurgitation and severely dilated right ventricles (RV) show little improvement in ventricular function after pulmonary valve replacement when assessed by traditional echocardiographic markers. We evaluated changes in right and left ventricular (LV) function using speckle tracking echocardiography in patients after SAPIEN transcatheter pulmonary valve (TPV) placement. Methods Echocardiograms were evaluated at baseline, discharge, 1 and 6 months after TPV placement in 24 patients from 4 centers. Speckle tracking measures of function included peak longitudinal strain, strain rate, and early diastolic strain rate. RV fractional area change, tricuspid annular plane systolic excursion, and left ventricular LV ejection fraction were assessed. Routine Doppler and tissue Doppler velocities were measured. Results At baseline, all patients demonstrated moderate to severe pulmonary regurgitation; this improved following TPV placement. No significant changes were detected in conventional measures of RV or LV function at 6 months. RV longitudinal strain (−16.9% vs. −19.6%, P < 0.01), strain rate (−0.87 s−1 vs. −1.16 s−1, P = 0.01), and LV longitudinal strain (−16.2% vs. −18.2%, P = 0.01) improved between baseline and 6 month follow-up. RV early diastolic strain rate, LV longitudinal strain rate and early diastolic strain rate showed no change. Conclusion Improvements in RV longitudinal strain, strain rate, and LV longitudinal strain are seen at 6 months post-TPV. Diastolic function does not appear to change at 6 months. Speckle tracking echocardiography may be more sensitive than traditional measures in detecting changes in systolic function after TPV implantation. (Echocardiography 2015;32:461–469) PMID:25047063

Preliminary phytochemical screening and in vitro anti-helicobacter pylori activity of extracts of the stem bark of Bridelia micrantha (Hochst., Baill., Euphorbiaceae).

PubMed

Okeleye, Benjamin I; Bessong, Pascal O; Ndip, Roland N

2011-07-25

Helicobacter pylori is a major risk factor for gastritis, ulcers and gastric cancer. This study was aimed to determine the antimicrobial activity of the stem bark of Bridelia. micrantha on H. pylori isolated in South Africa. Extracts and clarithromycin were tested against 31 clinical strains, including a standard strain (NCTC 11638) of H. pylori, by measuring the diameters of the corresponding inhibition zones, followed by determination of the Minimum Inhibitory Concentration (MIC) (using metronidazole, and amoxicillin as control antibiotics) and the rate of kill. Preliminary phytochemical screening was also done. Inhibition zone diameters which ranged from 0-23 mm were observed for all five of the extracts and 0-35 mm for clarithromycin. Marked susceptibility of strains (100%) was noted for the acetone extract (P < 0.05), followed by ethyl acetate extract (93.5%). The MIC₅₀ values ranged from 0.0048 to 0.156 mg/mL for the ethyl acetate extract and 0.0048 to 0.313 mg/mL for the acetone extract. The MIC₉₀ values ranged from 0.0048 to 2.5 mg/mL for the ethyl acetate extract and 0.078 to > 0.625 mg/mL for the acetone extract, respectively. Insignificant statistical difference in potency was observed when comparing the crude ethyl acetate extract to metronidazole and amoxicillin (P > 0.05). Complete killing of strain PE430C by the ethyl acetate extract was observed at 0.1 mg/mL (2 × MIC) and 0.2 mg/mL (4 × MIC) at 66 and 72 h. For strain PE369C, 100% killing was observed at 0.1 mg/mL (2 × MIC) in 66 and 72 h. The ethyl acetate extract could thus be a potential source of lead molecules for the design of new anti-Helicobacter pylori therapies as this study further confirmed the presence of phytochemicals including alkaloids, flavonoids, steroids, tannins and saponins.

Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

NASA Technical Reports Server (NTRS)

Paglietti, A.

1982-01-01

At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.

Advanced Nanoindentation Testing for Studying Strain-Rate Sensitivity and Activation Volume

NASA Astrophysics Data System (ADS)

Maier-Kiener, Verena; Durst, Karsten

2017-11-01

Nanoindentation became a versatile tool for testing local mechanical properties beyond hardness and modulus. By adapting standard nanoindentation test methods, simple protocols capable of probing thermally activated deformation processes can be accomplished. Abrupt strain-rate changes within one indentation allow determining the strain-rate dependency of hardness at various indentation depths. For probing lower strain-rates and excluding thermal drift influences, long-term creep experiments can be performed by using the dynamic contact stiffness for determining the true contact area. From both procedures hardness and strain-rate, and consequently strain-rate sensitivity and activation volume can be reliably deducted within one indentation, permitting information on the locally acting thermally activated deformation mechanism. This review will first discuss various testing protocols including possible challenges and improvements. Second, it will focus on different examples showing the direct influence of crystal structure and/or microstructure on the underlying deformation behavior in pure and highly alloyed material systems.

Spall response of single-crystal copper

NASA Astrophysics Data System (ADS)

Turley, W. D.; Fensin, S. J.; Hixson, R. S.; Jones, D. R.; La Lone, B. M.; Stevens, G. D.; Thomas, S. A.; Veeser, L. R.

2018-02-01

We performed a series of systematic spall experiments on single-crystal copper in an effort to determine and isolate the effects of crystal orientation, peak stress, and unloading strain rate on the tensile spall strength. Strain rates ranging from 0.62 to 2.2 × 106 s-1 and peak shock stresses in the 5-14 GPa range, with one additional experiment near 50 GPa, were explored as part of this work. Gun-driven impactors, called flyer plates, generated flat top shocks followed by spall. This work highlights the effect of crystal anisotropy on the spall strength by showing that the spall strength decreases in the following order: [100], [110], and [111]. Over the range of stresses and strain rates explored, the spall strength of [100] copper depends strongly on both the strain rate and shock stress. Except at the very highest shock stress, the results for the [100] orientation show linear relationships between the spall strength and both the applied compressive stress and the strain rate. In addition, hydrodynamic computer code simulations of the spall experiments were performed to calculate the relationship between the strain rate near the spall plane in the target and the rate of free surface velocity release during the pullback. As expected, strain rates at the spall plane are much higher than the strain rates estimated from the free surface velocity release rate. We have begun soft recovery experiments and molecular dynamics calculations to understand the unusual recompression observed in the spall signature for [100] crystals.

Optimal control approach for establishing wMelPop Wolbachia infection among wild Aedes aegypti populations.

PubMed

Campo-Duarte, Doris E; Vasilieva, Olga; Cardona-Salgado, Daiver; Svinin, Mikhail

2018-06-01

Wolbachia-based biocontrol has recently emerged as a potential method for prevention and control of dengue and other vector-borne diseases. Major vector species, such as Aedes aegypti females, when deliberately infected with Wolbachia become less capable of getting viral infections and transmitting the virus to human hosts. In this paper, we propose an explicit sex-structured population model that describes an interaction of uninfected (wild) male and female mosquitoes and those deliberately infected with wMelPop strain of Wolbachia in the same locality. This particular strain of Wolbachia is regarded as the best blocker of dengue and other arboviral infections. However, wMelPop strain of Wolbachia also causes the loss of individual fitness in Aedes aegypti mosquitoes. Our model allows for natural introduction of the decision (or control) variable, and we apply the optimal control approach to simulate wMelPop Wolbachia infestation of wild Aedes aegypti populations. The control action consists in continuous periodic releases of mosquitoes previously infected with wMelPop strain of Wolbachia in laboratory conditions. The ultimate purpose of control is to find a tradeoff between reaching the population replacement in minimum time and with minimum cost of the control effort. This approach also allows us to estimate the number of Wolbachia-carrying mosquitoes to be released in day-by-day control action. The proposed method of biological control is safe to human health, does not contaminate the environment, does not make harm to non-target species, and preserves their interaction with mosquitoes in the ecosystem.

Assessment of Low Cycle Fatigue Behavior of Powder Metallurgy Alloy U720

NASA Technical Reports Server (NTRS)

Gabb, Tomothy P.; Bonacuse, Peter J.; Ghosn, Louis J.; Sweeney, Joseph W.; Chatterjee, Amit; Green, Kenneth A.

2000-01-01

The fatigue lives of modem powder metallurgy disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary as functions of variables the different steps of materials/component processing: powder atomization, consolidation, extrusion, forging, heat treating, and machining. It is important to understand the relationship between the statistical variations in life and these variables, as well as the change in life distribution due to changes in fatigue loading conditions. The objective of this study was to investigate these relationships in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were performed at 538 C (1000 F) at limited sets of test conditions. Analyses were performed to: (1) assess variations of microstructure, mechanical properties, and LCF failure initiation sites as functions of disk processing and loading conditions; and (2) compare mean and minimum fatigue life predictions using different approaches for modeling the data from assorted test conditions. Significant variations in life were observed as functions of the disk processing variables evaluated. However, the lives of all specimens could still be combined and modeled together. The failure initiation sites for tests performed at a strain ratio R(sub epsilon) = epsilon(sub min)/epsilon(sub max) of 0 were different from those in tests at a strain ratio of -1. An approach could still be applied to account for the differences in mean and maximum stresses and strains. This allowed the data in tests of various conditions to be combined for more robust statistical estimates of mean and minimum lives.

Presence of antiseptic resistance genes in porcine methicillin-resistant Staphylococcus aureus.

PubMed

Wong, T Z; Zhang, M; O'Donoghue, M; Boost, M

2013-03-23

Numerous studies have documented the presence of methicillin-resistant Staphylococcus aureus (MRSA) in meat-producing animals, which has led to concern about its spread into the community. Disinfectants play an important role in reduction of contamination in both animal husbandry and food-preparation, helping control spread of organisms from foodstuffs, including raw meat. Plasmid-borne antiseptic resistance (AR) genes increasing tolerance to several disinfectants have been reported in S. aureus of human origin (qacA/B and smr) and from bovine, equine, and caprine staphylococcal isolates (qacG, qacH, and qacJ). This study investigated the presence of AR genes in porcine MRSA isolates. Plasmid DNA from 100 MRSA ST9 strains isolated from pig carcasses was amplified for the presence of AR genes. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) to benzalkonium chloride (BC) and chlorhexidine gluconate (CHX) were determined in AR gene-positive isolates. qacG was present in 45 strains, eight of which also harbored smr. No strains carried qacA/B, qacH or qacJ. Presence of smr increased MICs to both BC and CHX and MBCs of CHX, but qacG presence only resulted in elevated MBC for CHX. This is the first report of AR genes from a porcine source. AR gene positivity has previously been associated with methicillin resistance and AR gene presence in these strains may increase their ability to persist in the environment. Improved implementation of hygiene measures during transportation and pre- and post-slaughter should be considered to prevent spread in the community. Copyright © 2012 Elsevier B.V. All rights reserved.

Simultaneous multiscale measurements on dynamic deformation of a magnesium alloy with synchrotron x-ray imaging and diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, L.; Sun, T.; Fezzaa, K.

Dynamic split Hopkinson pressure bar experiments with in situ synchrotron x-ray imaging and diffraction are conducted on a rolled magnesium alloy at high strain rates of ~5500 s-1. High speed multiscale measurements including stress–strain curves (macroscale), strain fields (mesoscale), and diffraction patterns (microscale) are obtained simultaneously, revealing strong anisotropy in deformation across different length scales. {1012} extension twinning induces homogenized strain fields and gives rise to rapid increase in strain hardening rate, while dislocation motion leads to inhomogeneous deformation and a decrease in strain hardening rate. During the early stage of plastic deformation, twinning is dominant in dynamic compression, whilemore » dislocation motion prevails in quasi-static loading, manifesting a strain-rate dependence of deformation.« less

A new design approach to achieve a minimum impulse limit cycle in the presence of significant measurement uncertainties

NASA Technical Reports Server (NTRS)

Martin, M. W.; Kubiak, E. T.

1982-01-01

A new design was developed for the Space Shuttle Transition Phase Digital Autopilot to reduce the impact of large measurement uncertainties in the rate signal during attitude control. The signal source, which was dictated by early computer constraints, is characterized by large quantization, noise, bias, and transport lag which produce a measurement uncertainty larger than the minimum impulse rate change. To ensure convergence to a minimum impulse limit cycle, the design employed bias and transport lag compensation and a switching logic with hysteresis, rate deadzone, and 'walking' switching line. The design background, the rate measurement uncertainties, and the design solution are documented.

Antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish (Armoracia rusticana) root against oral microorganisms.

PubMed

Park, Ho-Won; Choi, Kyu-Duck; Shin, Il-Shik

2013-01-01

The antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish root was investigated against oral microorganisms: 6 strains of facultative anaerobic bacteria, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus casei, Staphylococcus aureus, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans; one strain of yeast, Candida albicans, and 3 strains of anaerobic bacteria, Fusobacterium nucleatum, Prevotella nigrescens, and Clostridium perfringens. The ITCs extracted from horseradish root showed antimicrobial activity against all oral microorganisms by the paper disk method. The minimum bactericidal concentration (MBC) of the ITCs extracted from horseradish root ranged from 1.25 to 5.00 mg/ml against 6 strains of facultative anaerobic bacteria and one strain of yeast, and 4.17 to 16.67 mg/ml against 3 strains of anaerobic bacteria. The ITCs extracted from horseradish root showed the strongest antimicrobial activity, with a MBC of 1.25 mg/ml, against C. albicans among facultative microorganisms, and 4.17 mg/ml against F. nucleatum among anaerobic bacteria. These results suggest that the ITCs extracted from horseradish root may be a candidate for use as an antimicrobial agent against oral microorganisms.

Lithology-dependent minimum horizontal stress and in-situ stress estimate

NASA Astrophysics Data System (ADS)

Zhang, Yushuai; Zhang, Jincai

2017-04-01

Based on the generalized Hooke's law with coupling stresses and pore pressure, the minimum horizontal stress is solved with assumption that the vertical, minimum and maximum horizontal stresses are in equilibrium in the subsurface formations. From this derivation, we find that the uniaxial strain method is the minimum value or lower bound of the minimum stress. Using Anderson's faulting theory and this lower bound of the minimum horizontal stress, the coefficient of friction of the fault is derived. It shows that the coefficient of friction may have a much smaller value than what it is commonly assumed (e.g., μf = 0.6-0.7) for in-situ stress estimate. Using the derived coefficient of friction, an improved stress polygon is drawn, which can reduce the uncertainty of in-situ stress calculation by narrowing the area of the conventional stress polygon. It also shows that the coefficient of friction of the fault is dependent on lithology. For example, if the formation in the fault is composed of weak shales, then the coefficient of friction of the fault may be small (as low as μf = 0.2). This implies that this fault is weaker and more likely to have shear failures than the fault composed of sandstones. To avoid the weak fault from shear sliding, it needs to have a higher minimum stress and a lower shear stress. That is, the critically stressed weak fault maintains a higher minimum stress, which explains why a low shear stress appears in the frictionally weak fault.

Colistin-resistant Escherichia coli clinical isolate harbouring the mcr-1 gene in Ecuador.

PubMed

Ortega-Paredes, D; Barba, P; Zurita, J

2016-10-01

Colistin resistance mediated by the mcr-1 gene has been reported worldwide, but to date not from the Andean region, South America. We report the first clinical isolate of Escherichia coli harbouring the mcr-1 gene in Ecuador. The strain was isolated from peritoneal fluid from a 14-year-old male with acute appendicitis, and subjected to molecular analysis. The minimum inhibitory concentration of colistin for the strain was 8 mg/ml and it was susceptible to carbapenems but resistant to tigecycline. The strain harboured mcr-1 and bla CTX-M-55 genes and was of sequence type 609. The recognition of an apparently commensal strain of E. coli harbouring mcr-1 serves as an alert to the presence in the region of this recently described resistance mechanism to one of the last line of drugs available for the treatment of multi-resistant Gram-negative infections.

Fabrication of comb-drive actuators for straining nanostructured suspended graphene.

PubMed

Goldsche, Matthias; Verbiest, G J; Khodkov, Tymofiy; Sonntag, Jens; von den Driesch, Nils; Buca, Dan; Stampfer, Christoph

2018-06-20

We report on the fabrication and characterization of an optimized comb-drive actuator design for strain-dependent transport measurements on suspended graphene. We fabricate devices from highly p-doped silicon using deep reactive ion etching with a chromium mask. Crucially, we implement a gold layer to reduce the device resistance from ≈51.6 kΩ to ≈236 Ω at room temperature in order to allow for strain-dependent transport measurements. The graphene is integrated by mechanically transferring it directly onto the actuator using a polymethylmethacrylate membrane. Importantly, the integrated graphene can be nanostructured afterwards to optimize device functionality. The minimum feature size of the structured suspended graphene is 30~nm, which allows for interesting device concepts such as mechanically-tunable nanoconstrictions. Finally, we characterize the fabricated devices by measuring the Raman spectrum as well as the a mechanical resonance frequency of an integrated graphene sheet for different strain values. © 2018 IOP Publishing Ltd.

Design, Optimization, and Evaluation of A1-2139 Compression Panel with Integral T-Stiffeners

NASA Technical Reports Server (NTRS)

Mulani, Sameer B.; Havens, David; Norris, Ashley; Bird, R. Keith; Kapania, Rakesh K.; Olliffe, Robert

2012-01-01

A T-stiffened panel was designed and optimized for minimum mass subjected to constraints on buckling load, yielding, and crippling or local stiffener failure using a new analysis and design tool named EBF3PanelOpt. The panel was designed for a compression loading configuration, a realistic load case for a typical aircraft skin-stiffened panel. The panel was integrally machined from 2139 aluminum alloy plate and was tested in compression. The panel was loaded beyond buckling and strains and out-of-plane displacements were extracted from 36 strain gages and one linear variable displacement transducer. A digital photogrammetric system was used to obtain full field displacements and strains on the smooth (unstiffened) side of the panel. The experimental data were compared with the strains and out-of-plane deflections from a high-fidelity nonlinear finite element analysis.

Optimization of Stability Constrained Geometrically Nonlinear Shallow Trusses Using an Arc Length Sparse Method with a Strain Energy Density Approach

NASA Technical Reports Server (NTRS)

Hrinda, Glenn A.; Nguyen, Duc T.

2008-01-01

A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.

Digital antimicrobial susceptibility testing using the MilliDrop technology.

PubMed

Jiang, L; Boitard, L; Broyer, P; Chareire, A-C; Bourne-Branchu, P; Mahé, P; Tournoud, M; Franceschi, C; Zambardi, G; Baudry, J; Bibette, J

2016-03-01

We present the MilliDrop Analyzer (MDA), a droplet-based millifluidic system for digital antimicrobial susceptibility testing (D-AST), which enables us to determine minimum inhibitory concentrations (MICs) precisely and accurately. The MilliDrop technology was validated by using resazurin for fluorescence readout, for comparison with standard methodology, and for conducting reproducibility studies. In this first assessment, the susceptibility of a reference Gram-negative strain Escherichia coli ATCC 25922 to gentamicin, chloramphenicol, and nalidixic acid were tested by the MDA, VITEK®2, and broth microdilution as a reference standard. We measured the susceptibility of clinically relevant Gram-positive strains of Staphylococcus aureus to vancomycin, including vancomycin-intermediate S. aureus (VISA), heterogeneous vancomycin-intermediate S. aureus (hVISA), and vancomycin-susceptible S. aureus (VSSA) strains. The MDA provided results which were much more accurate than those of VITEK®2 and standard broth microdilution. The enhanced accuracy enabled us to reliably discriminate between VSSA and hVISA strains.

Experimental Study on the Anisotropic Stress-Strain Behavior of Polycrystalline Ni-Mn-Ga in Directional Solidification

NASA Astrophysics Data System (ADS)

Teng, Yao; Shi, Tao; Zhu, Yuping; Li, Zongbin; Deng, Tao; Bai, Guonan

2016-03-01

A polycrystalline Ni-Mn-Ga ferromagnetic shape memory alloy produced by directional solidification is the subject of this research paper. The compressive stress-strain curves of the material for different cutting angles to the solidification direction are tested. The martensite Young's modulus, macroscopic reorientation strain, and phase transition critical stress are analyzed experimentally. The results show that mechanical behaviors in the loading-unloading cycle of the material present nonlinear and anisotropic characteristics, which are all closely related to the material's orientation to the solidification direction. The martensite Young's modulus, macroscopic reorientation strain, and phase transition critical stress achieve maximum values in the solidification direction. A 50° orientation to the solidification direction is the cut-off direction of the mechanical properties, where the martensite Young's modulus and reorientation start critical stress reach minimum values. The present study is expected to provide sound guidance for practical applications.

Influence of strain rate on indentation response of porcine brain.

PubMed

Qian, Long; Zhao, Hongwei; Guo, Yue; Li, Yuanshang; Zhou, Mingxing; Yang, Liguo; Wang, Zhiwei; Sun, Yifan

2018-06-01

Knowledge of brain tissue mechanical properties may be critical for formulating hypotheses about some specific diseases mechanisms and its accurate simulations such as traumatic brain injury (TBI) and tumor growth. Compared to traditional tests (e.g. tensile and compression), indentation shows superiority by virtue of its pinpoint and nondestructive/quasi-nondestructive. As a viscoelastic material, the properties of brain tissue depend on the strain rate by definition. However most efforts focus on the aspect of velocity in the field of brain indentation, rather than strain rate. The influence of strain rate on indentation response of brain tissue is taken little attention. Further, by comparing different results from literatures, it is also obvious that strain rate rather than velocity is more appropriate to characterize mechanical properties of brain. In this paper, to systematically characterize the influence of strain rate, a series of indentation-relaxation tests n = 210) are performed on the cortex of porcine brain using a custom-designed indentation device. The mechanical response that correlates with indenter diameters, depths of indentation and velocities, is revealed for the indentation portion, and elastic behavior of brain tissue is analyzed as the function of strain rate. Similarly, a linear viscoelastic model with a Prony series is employed for the indentation-relaxation portion, wherein the brain tissue shows more viscous and responds more quickly with increasing strain rate. Understanding the effect of strain rate on mechanical properties of brain indentation may be far-reaching for brain injury biomechanics and accurate simulations, but be important for bridging between indentation results of different literatures. Copyright © 2018 Elsevier Ltd. All rights reserved.

40 CFR Table 3 to Subpart Jjjjjj... - Operating Limits for Boilers With Emission Limits

Code of Federal Regulations, 2013 CFR

2013-07-01

... as defined in § 63.11237. 4. Dry sorbent or activated carbon injection control Maintain the 30-day rolling average sorbent or activated carbon injection rate at or above the minimum sorbent injection rate or minimum activated carbon injection rate as defined in § 63.11237. When your boiler operates at...

Major effect of inherited rheology weakening in the crust and mantle on continental intraplate strain and seismicity rates

NASA Astrophysics Data System (ADS)

Gueydan, Frédéric; Mazzotti, Stephane

2017-04-01

Stable Continental Regions (SCR, i.e., intraplate) are commonly viewed as non-deforming and very high resistance lithosphere domains, except in localized regions of higher strain and seismicity rates that often related to fossilized tectonic zones acting as weaker domains (e.g., Rhine Graben, New Madrid). Two main categories of models have been proposed to explain strain concentration in SCR: Local stress concentration (fault intersection, erosion pulse, …) and local lithosphere weakness (high geotherm, mantle anisotropy, …). In order to test the respective role of these various parameters of the stress - rheology - strain relationship, we propose a simple 1D model to quantify first-order continental strain rate variations using laboratory and field-based rheology laws for the crust and mantle. In particular, we include new strain-weakening rheologies in order to simulate tectonic heritage. Within the framework of near-failure equilibrium between tectonic forces and strain rates, we show that inherited rheology weakening plays a fundamental role in allowing for and explaining strain and seismicity concentration in intraplate weak zones. A comparison with empirical strain rate estimations in SCR and intraplate weak zones shows that inherited weakening rheologies can increase local strain rates by as much as three orders of magnitude, about one to two orders higher than that permitted by other processes such as stress concentration, thermal anomaly, etc.

Simulation study of the effect of strain rate on the mechanical properties and tensile deformation of gold nanowire

NASA Astrophysics Data System (ADS)

Shi, Guo-Jie; Wang, Jin-Guo; Hou, Zhao-Yang; Wang, Zhen; Liu, Rang-Su

2017-09-01

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, the stress-strain curve displays a periodic zigzag increase-decrease feature, and the plastic deformation is resulted from the slide of dislocation. The dislocations nucleate, propagate, and finally annihilate in every decreasing stages of stress, and the nanowire always can recover to FCC-ordered structure. At the medium strain rate, the stress-strain curve gently decreases during the plastic process, and the deformation is contributed from sliding and twinning. The dislocations formed in the yield stage do not fully propagate and further escape from the nanowire. At the high strain rate, the stress-strain curve wave-like oscillates during the plastic process, and the deformation is resulted from amorphization. The FCC atoms quickly transform into disordered amorphous structure in the yield stage. The relative magnitude between the loading velocity of strain and the propagation velocity of phonons determines the different deformation mechanisms. The mechanical behavior of Au nanowire is similar to Ni, Cu and Pt nanowires, but their deformation mechanisms are not completely identical with each other.

Echocardiographic strain and strain-rate imaging: a new tool to study regional myocardial function.

PubMed

D'hooge, Jan; Bijnens, Bart; Thoen, Jan; Van de Werf, Frans; Sutherland, George R; Suetens, Paul

2002-09-01

Ultrasonic imaging is the noninvasive clinical imaging modality of choice for diagnosing heart disease. At present, two-dimensional ultrasonic grayscale images provide a relatively cheap, fast, bedside method to study the morphology of the heart. Several methods have been proposed to assess myocardial function. These have been based on either grayscale or motion (velocity) information measured in real-time. However, the quantitative assessment of regional myocardial function remains an important goal in clinical cardiology. To do this, ultrasonic strain and strain-rate imaging have been introduced. In the clinical setting, these techniques currently only allow one component of the true three-dimensional deformation to be measured. Clinical, multidimensional strain (rate) information can currently thus only be obtained by combining data acquired using different transducer positions. Nevertheless, given the appropriate postprocessing, the clinical value of these techniques has already been shown. Moreover, multidimensional strain and strain-rate estimation of the heart in vivo by means of a single ultrasound acquisition has been shown to be feasible. In this paper, the new techniques of ultrasonic strain rate and strain imaging of the heart are reviewed in terms of definitions, data acquisition, strain-rate estimation, postprocessing, and parameter extraction. Their clinical validation and relevance will be discussed using clinical examples on relevant cardiac pathology. Based on these examples, suggestions are made for future developments of these techniques.

High-rate tensile properties of Si-reduced TRIP sheet steels

NASA Astrophysics Data System (ADS)

Choi, Ildong; Park, Yeongdo; Son, Dongmin; Kim, Sung-Joon; Moon, Manbeen

2010-02-01

There have been efforts to develop Si-reduced TRIP steels to improve the wettability of Zn coatings, since the conventional CMnSi-TRIP steels suffer from poor galvanizability. In addition, for the development of potential applications of Si-reduced TRIP steels in vehicle crash management, a better understanding of high strain rate properties is required. In the present study, the effects of alloying elements, such as Cu, Al, Si, and P, on the high-rate tensile properties of Si-reduced TRIP sheet steels were investigated. Tensile tests were performed with a servo-hydraulic tensile testing machine at strain rates ranging from 10-2 to 6 × 102 s-1, and the ultimate tensile strength, elongation, strain rate sensitivity, and absorbed energy were evaluated. The retained austenite volume fractions and carbon content of the specimens were measured using neutron diffraction. The UTS was increased with Cu, Al, Si, and P alloying throughout the strain rate range, and the alloying effect on UTS was considerable with Cu and P. The effects of alloying on the microstructure were not significant. All the steels tested in this study exhibited positive strain rate sensitivity, and the m value at strain rates higher than 10 s-1 was at least two times higher than that at lower strain rates.

High-speed polarized light microscopy for in situ, dynamic measurement of birefringence properties

NASA Astrophysics Data System (ADS)

Wu, Xianyu; Pankow, Mark; Shadow Huang, Hsiao-Ying; Peters, Kara

2018-01-01

A high-speed, quantitative polarized light microscopy (QPLM) instrument has been developed to monitor the optical slow axis spatial realignment during controlled medium to high strain rate experiments at acquisition rates up to 10 kHz. This high-speed QPLM instrument is implemented within a modified drop tower and demonstrated using polycarbonate specimens. By utilizing a rotating quarter wave plate and a high-speed camera, the minimum acquisition time to generate an alignment map of a birefringent specimen is 6.1 ms. A sequential analysis method allows the QPLM instrument to generate QPLM data at the high-speed camera imaging frequency 10 kHz. The obtained QPLM data is processed using a vector correlation technique to detect anomalous optical axis realignment and retardation changes throughout the loading event. The detected anomalous optical axis realignment is shown to be associated with crack initiation, propagation, and specimen failure in a dynamically loaded polycarbonate specimen. The work provides a foundation for detecting damage in biological tissues through local collagen fiber realignment and fracture during dynamic loading.

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing.

PubMed

Bazant, Zdenek P; Caner, Ferhun C

2013-11-26

Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the -2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the -1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow.

Implementation of an Associative Flow Rule Including Hydrostatic Stress Effects Into the High Strain Rate Deformation Analysis of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2003-01-01

A previously developed analytical formulation has been modified in order to more accurately account for the effects of hydrostatic stresses on the nonlinear, strain rate dependent deformation of polymer matrix composites. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical J2 plasticity theory definitions of effective stress and effective inelastic strain, along with the equations used to compute the components of the inelastic strain rate tensor, are appropriately modified. To verify the revised formulation, the shear and tensile deformation of two representative polymers are computed across a wide range of strain rates. Results computed using the developed constitutive equations correlate well with experimental data. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite for several fiber orientation angles across a variety of strain rates. The computed values compare well to experimentally obtained results.

48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

Code of Federal Regulations, 2011 CFR

2011-10-01

... be the highest applicable minimum weight which will result in the lowest freight rate (or per car... minimum weight, the Contractor agrees to ship such scheduled quantity in one shipment. The Contractor...

48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

Code of Federal Regulations, 2013 CFR

2013-10-01

... be the highest applicable minimum weight which will result in the lowest freight rate (or per car... minimum weight, the Contractor agrees to ship such scheduled quantity in one shipment. The Contractor...

48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

Code of Federal Regulations, 2014 CFR

2014-10-01

... be the highest applicable minimum weight which will result in the lowest freight rate (or per car... minimum weight, the Contractor agrees to ship such scheduled quantity in one shipment. The Contractor...

48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

Code of Federal Regulations, 2012 CFR

2012-10-01

... be the highest applicable minimum weight which will result in the lowest freight rate (or per car... minimum weight, the Contractor agrees to ship such scheduled quantity in one shipment. The Contractor...

Probing collagen-enzyme mechanochemistry in native tissue with dynamic, enzyme-induced creep

PubMed Central

Zareian, Ramin; Church, Kelli P.; Saeidi, Nima; Flynn, Brendan P.; Beale, John W.; Ruberti, Jeffrey W.

2012-01-01

Mechanical strain or stretch of collagen has been shown to be protective of fibrils against both thermal and enzymatic degradation. The details of this mechanochemical relationship could change our understanding of load-bearing tissue formation, growth, maintenance and disease in vertebrate animals. However, extracting a quantitative relationship between strain and the rate of enzymatic degradation is extremely difficult in bulk tissue due to confounding diffusion effects. In this investigation, we develop a dynamic, enzyme-induced creep assay and diffusion/reaction rate scaling arguments to extract a lower bound on the relationship between strain and the cutting rate of bacterial collagenase (BC) at low strains. The assay method permits continuous, forced probing of enzyme-induced strain which is very sensitive to degradation rate differences between specimens at low initial strain. The results, obtained on uniaxially-loaded strips of bovine corneal tissue (0.1, 0.25 or 0.5 N), demonstrate that small differences in strain alter the enzymatic cutting rate of the BC substantially. It was estimated that a change in tissue elongation of only 1.5% (at ~5% strain) reduces the maximum cutting-rate of the enzyme by more than half. Estimation of the average load per monomer in the tissue strips indicates that this protective “cutoff” occurs when the collagen monomers are transitioning from an entropic to an energetic mechanical regime. The continuous tracking of the enzymatic cleavage rate as a function of strain during the initial creep response indicates that the decrease in the cleavage rate of the BC is non-linear (initially-steep between 4.5 and 6.5% then flattens out from 6.5–9.5%). The high sensitivity to strain at low strain implies that even lightly-loaded collagenous tissue may exhibit significant strain-protection. The dynamic, enzyme-induced creep assay described herein has the potential to permit the rapid characterization of collagen/enzyme mechanochemistry in many different tissue types. PMID:20429513

Suppression of Low Strain Rate Nonpremixed Flames by an Agent

NASA Technical Reports Server (NTRS)

Hamins, A.; Bundy, M.; Puri, I. K.; McGrattan, K.; Park, W. C.

2001-01-01

The agent concentration required to achieve the suppression of low strain rate nonpremixed flames is an important consideration for fire protection in a microgravity environment such as a space platform. Currently, there is a lack of understanding of the structure and extinction of low strain rate (<20 s(exp -1)) nonpremixed flames. The exception to this statement is the study by Maruta et al., who reported measurements of low strain rate suppression of methane-air diffusion flames with N2 added to the fuel stream under microgravity conditions. They found that the nitrogen concentration required to achieve extinction increased as the strain rate decreased until a critical value was obtained. As the strain rate was further decreased, the required N2 concentration decreased. This phenomenon was termed "turning point" behavior and was attributed to radiation-induced nonpremixed flame extinction. In terms of fire safety, a critical agent concentration assuring suppression under all flow conditions represents a fundamental limit for nonpremixed flames. Counterflow flames are a convenient configuration for control of the flame strain rate. In high and moderately strained near-extinction nonpremixed flames, analysis of flame structure typically neglects radiant energy loss because the flames are nonluminous and the hot gas species are confined to a thin reaction zone. In counterflowing CH4-air flames, for example, radiative heat loss fractions ranging from 1 to 6 percent have been predicted and measured. The objective of this study is to investigate the impact of radiative emission, flame strain, agent addition, and buoyancy on the structure and extinction of low strain rate nonpremixed flames through measurements and comparison with flame simulations. The suppression effectiveness of a number of suppressants (N2, CO2, or CF3Br) was considered as they were added to either the fuel or oxidizer streams of low strain rate methane-air diffusion flames.

Strain rate sensitivity of a TRIP-assisted dual-phase high-entropy alloy

NASA Astrophysics Data System (ADS)

Basu, Silva; Li, Zhiming; Pradeep, K. G.; Raabe, Dierk

2018-05-01

Dual-phase high-entropy alloys (DP-HEAs) with transformation induced plasticity (TRIP) have an excellent strength-ductility combination. To reveal their strain-rate sensitivity and hence further understand the corresponding deformation mechanisms, we investigated the tensile behavior and microstructural evolution of a typical TRIP-DP-HEA (Fe50Mn30Co10Cr10, at. %) under different strain rates (i.e., 5 × 10-3 s-1, 1 × 10-3 s-1, 5 × 10-4 s-1 and 1 × 10-4 s-1) at room temperature. The strain rate range was confined to this regime in order to apply the digital image correlation technique for probing the local strain evolution during tensile deformation at high resolution and to correlate it to the microstructure evolution. Grain size effects of the face-centered cubic (FCC) matrix and the volume fractions of the hexagonal-close packed (HCP) phase prior to deformation were also considered. The results show that within the explored strain rate regime the TRIP-DP-HEA has a fairly low strain rate sensitivity parameter within the range from 0.004 to 0.04, which is significantly lower than that of DP and TRIP steels. Samples with varying grain sizes (e.g., 2.8 μm and 38 μm) and starting HCP phase fractions (e.g., 25% and 72%) at different strain rates show similar deformation mechanisms, i.e., dislocation plasticity and strain-induced transformation from the FCC matrix to the HCP phase. The low strain rate sensitivity is attributed to the observed dominant displacive transformation mechanism. Also, the coarse-grained alloy samples with a very high starting HCP phase fraction ( 72%) prior to deformation show very good ductility with a total elongation of 60%, suggesting that both, the initial and the transformed HCP phase in the TRIP-DP-HEA are ductile and deform further via dislocation slip at the different strain rates which were probed.

Interaction of rate- and size-effect using a dislocation density based strain gradient viscoplasticity model

NASA Astrophysics Data System (ADS)

Nguyen, Trung N.; Siegmund, Thomas; Tomar, Vikas; Kruzic, Jamie J.

2017-12-01

Size effects occur in non-uniform plastically deformed metals confined in a volume on the scale of micrometer or sub-micrometer. Such problems have been well studied using strain gradient rate-independent plasticity theories. Yet, plasticity theories describing the time-dependent behavior of metals in the presence of size effects are presently limited, and there is no consensus about how the size effects vary with strain rates or whether there is an interaction between them. This paper introduces a constitutive model which enables the analysis of complex load scenarios, including loading rate sensitivity, creep, relaxation and interactions thereof under the consideration of plastic strain gradient effects. A strain gradient viscoplasticity constitutive model based on the Kocks-Mecking theory of dislocation evolution, namely the strain gradient Kocks-Mecking (SG-KM) model, is established and allows one to capture both rate and size effects, and their interaction. A formulation of the model in the finite element analysis framework is derived. Numerical examples are presented. In a special virtual creep test with the presence of plastic strain gradients, creep rates are found to diminish with the specimen size, and are also found to depend on the loading rate in an initial ramp loading step. Stress relaxation in a solid medium containing cylindrical microvoids is predicted to increase with decreasing void radius and strain rate in a prior ramp loading step.

A Geodetic Strain Rate Model for the East African Rift System.

PubMed

Stamps, D S; Saria, E; Kreemer, C

2018-01-15

Here we describe the new Sub-Saharan Africa Geodetic Strain Rate Model v.1.0 (SSA-GSRM v.1.0), which provides fundamental constraints on long-term tectonic deformation in the region and an improved seismic hazards assessment in Sub-Saharan Africa. Sub-Saharan Africa encompasses the East African Rift System, the active divergent plate boundary between the Nubian and Somalian plates, where strain is largely accommodated along the boundaries of three subplates. We develop an improved geodetic strain rate field for sub-Saharan Africa that incorporates 1) an expanded geodetic velocity field, 2) redefined regions of deforming zones guided by seismicity distribution, and 3) updated constraints on block rotations. SSA-GSRM v.1.0 spans longitudes 22° to 55.5° and latitudes -52° to 20° with 0.25° (longitude) by 0.2° (latitude) spacing. For plates/sub-plates, we assign rigid block rotations as constraints on the strain rate calculation that is determined by fitting bicubic Bessel splines to a new geodetic velocity solution for an interpolated velocity gradient tensor field. We derive strain rates, velocities, and vorticity rates from the velocity gradient tensor field. A comparison with the Global Geodetic Strain Rate model v2.1 reveals regions of previously unresolved spatial heterogeneities in geodetic strain rate distribution, which indicates zones of elevated seismic risk.

Biventricular myocardial strain analysis in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) using cardiovascular magnetic resonance feature tracking.

PubMed

Heermann, Philipp; Hedderich, Dennis M; Paul, Matthias; Schülke, Christoph; Kroeger, Jan Robert; Baeßler, Bettina; Wichter, Thomas; Maintz, David; Waltenberger, Johannes; Heindel, Walter; Bunck, Alexander C

2014-10-07

Fibrofatty degeneration of myocardium in ARVC is associated with wall motion abnormalities. The aim of this study was to examine whether Cardiovascular Magnetic Resonance (CMR) based strain analysis using feature tracking (FT) can serve as a quantifiable measure to confirm global and regional ventricular dysfunction in ARVC patients and support the early detection of ARVC. We enrolled 20 patients with ARVC, 30 with borderline ARVC and 22 subjects with a positive family history but no clinical signs of a manifest ARVC. 10 healthy volunteers (HV) served as controls. 15 ARVC patients received genotyping for Plakophilin-2 mutation (PKP-2), of which 7 were found to be positive. Cine MR datasets of all subjects were assessed for myocardial strain using FT (TomTec Diogenes Software). Global strain and strain rate in radial, circumferential and longitudinal mode were assessed for the right and left ventricle. In addition strain analysis at a segmental level was performed for the right ventricular free wall. RV global longitudinal strain rates in ARVC (-0.68 ± 0.36 sec⁻¹) and borderline ARVC (-0.85 ± 0.36 sec⁻¹) were significantly reduced in comparison with HV (-1.38 ± 0.52 sec⁻¹, p ≤ 0.05). Furthermore, in ARVC patients RV global circumferential strain and strain rates at the basal level were significantly reduced compared with HV (strain: -5.1 ± 2.7 vs. -9.2 ± 3.6%; strain rate: -0.31 ± 0.13 sec(-1) vs. -0.61 ± 0.21 sec⁻¹). Even for patients with ARVC or borderline ARVC and normal RV ejection fraction (n=30) global longitudinal strain rate proved to be significantly reduced compared with HV (-0.9 ± 0.3 vs. -1.4 ± 0.5 sec(-1); p < 0.005). In ARVC patients with PKP-2 mutation there was a clear trend towards a more pronounced impairment in RV global longitudinal strain rate. On ROC analysis RV global longitudinal strain rate and circumferential strain rate at the basal level proved to be the best discriminators between ARVC patients and HV (AUC: 0.9 and 0.92, respectively). CMR based strain analysis using FT is an objective and useful measure for quantification of wall motion abnormalities in ARVC. It allows differentiation between manifest or borderline ARVC and HV, even if ejection fraction is still normal.

Appropriate antibiotic therapy improves Ureaplasma sepsis outcome in the neonatal mouse.

PubMed

Weisman, Leonard E; Leeming, Angela H; Kong, Lingkun

2012-11-01

Ureaplasma causes sepsis in human neonates. Although erythromycin has been the standard treatment, it is not always effective. No published reports have evaluated Ureaplasma sepsis in a neonatal model. We hypothesized that appropriate antibiotic treatment improves Ureaplasma sepsis in a neonatal mouse model. Two ATCC strains and two clinical strains of Ureaplasma were evaluated in vitro for antibiotic minimum inhibitory concentration (MIC). In addition, FVB albino mice pups infected with Ureaplasma were randomly assigned to saline, erythromycin, or azithromycin therapy and survival, quantitative blood culture, and growth were evaluated. MICs ranged from 0.125 to 62.5 µg/ml and 0.25 to 1.0 µg/ml for erythromycin and azithromycin, respectively. The infecting strain and antibiotic selected for treatment appeared to affect survival and bacteremia, but only the infecting strain affected growth. Azithromycin improved survival and bacteremia against each strain, whereas erythromycin was effective against only one of four strains. We have established a neonatal model of Ureaplasma sepsis and observed that treatment outcome is related to infecting strain and antibiotic treatment. We speculate that appropriate antibiotic selection and dosing are required for effective treatment of Ureaplasma sepsis in neonates, and this model could be used to further evaluate these relationships.

Applications of Displacement Transfer Functions to Deformed Shape Predictions of the G-III Swept-Wing Structure

NASA Technical Reports Server (NTRS)

Lung, Shun-Fat; Ko, William L.

2016-01-01

In support of the Adaptive Compliant Trailing Edge [ACTE] project at the NASA Armstrong Flight Research Center, displacement transfer functions were applied to the swept wing of a Gulfstream G-III airplane (Gulfstream Aerospace Corporation, Savannah, Georgia) to obtain deformed shape predictions. Four strainsensing lines (two on the lower surface, two on the upper surface) were used to calculate the deformed shape of the G III wing under bending and torsion. There being an insufficient number of surface strain sensors, the existing G III wing box finite element model was used to generate simulated surface strains for input to the displacement transfer functions. The resulting predicted deflections have good correlation with the finite-element generated deflections as well as the measured deflections from the ground load calibration test. The convergence study showed that the displacement prediction error at the G III wing tip can be reduced by increasing the number of strain stations (for each strain-sensing line) down to a minimum error of l.6 percent at 17 strain stations; using more than 17 strain stations yielded no benefit because the error slightly increased to 1.9% when 32 strain stations were used.

[Fundamental studies on legionellosis--the growth with in Acanthamoeba sp. and antibiotics susceptibility of Legionella spp. isolated from soil samples in Japan].

PubMed

Furuhata, Katsunori; Miyamoto, Hiroshi; Hara, Motonobu; Fukuyama, Masafumi

2003-02-01

As part of an epidemiological study of legionellosis, we investigated the growth within Acanthamoeba sp. and antibiotic susceptibility of 62 strains of Legionella spp. isolated from surface soils nationwide in 2001. 1) All strains tested grew in Acanthamoeba sp., suggesting that the strains were pathogenic. The minimum bacterial number required for the growth in the amoeba was 10(3)-10(8) CFU/ml and there were differences between the strains. 2) Susceptibility to 10 drugs was investigated using the Etest. The MIC90 values of imipenem, as a beta-lactam, and rifampicin, as an antitubercular agent, were 0.047 microgram/ml and 0.064 microgram/ml, respectively, showing high sensitivity. In contrast, sensitivity to minocycline, as a tetracycline, and piperacillin, as a beta-lactam, was low and the MIC90 values were 12 micrograms/ml and 16 micrograms/ml, respectively. Sensitivity to minocycline was particularly low, with a MIC value of 32 micrograms/ml, in two strains. The above findings suggested that all soil-derived strains were pathogenic, and susceptibility of the strains tended to be slightly lower than that of clinical isolates.

Occupational stress and strain in the Royal Navy 2007.

PubMed

Bridger, R S; Brasher, K; Dew, A; Kilminster, S

2008-12-01

Previous surveys of psychological strain in the Naval Service (NS) have shown higher than expected levels of strain when compared to the general population. To repeat the survey last carried out in 2004 and to obtain further information on the nature of the occupational stressors associated with strain. General Health Questionnaire-12 strain rates and job/life stressors were measured using a Work and Well-Being Questionnaire. Models of strain were developed for male and female personnel in the Royal Navy (RN) and males in the Royal Marines (RM). The response rate was 57%. The psychological strain rate was 31.5% overall. Personnel suffering from strain tended to be 'overcommitted' to work, had low levels of commitment to the NS and had suffered stressful life events (SLEs) in the previous 12 months. Strain rates declined with age and rank in males, but not in females. Strain was significantly positively correlated with levels of overcommitment, effort-reward imbalance (ERI), role conflict, work-family conflict, organizational commitment and exposure to SLEs. Models of strain in the males and females in the RN and in the RM accounted for between 37 and 44% of the variance in strain. The survey provides evidence for both the demand control and ERI models-components of these models contribute independently to strain. High levels of commitment to the organization were associated with lower strain and exposure to SLEs to higher strain.

Investigation of rolling variables on the structure of steel

NASA Astrophysics Data System (ADS)

Ekebuisi, Godwyn O.

The Literature pertaining to the present research has been critically reviewed. Hot deformation of Nb-free and Nb-containing stainless and C-Mn steels has been carried out by: upset-forging, rolling, and plane strain compression testing. Also, some gridded lead alloy and some mild steel containing Type I MnS inclusions as markers have been hot rolled. Subsequently investigations have been made into: barrelling and lubrication in upsetting; distributions of temperature and strain during thermomechanical working; microstructural processes associated with hot deformation of steel and the evolution of microstructures particularly recrystallised gamma-grain size; isothermal transformation of austenite to ferrite; and the mechanisms governing hot deformation of austenite.Barrelling during the hot upsetting of a solid cylinder arises from the combined effects of interface friction and inhomogeneous distribution of temperature. A barrelling factor, B[f], has been defined to quantify the degree of barrelling and hence of inhomogeneity of deformation in an upset-forged cylinder. Employing glass as a lubricant, an optimised lubrication technique, which ensures homogeneous deformation in upsetting, has been developed and a mechanism of lubrication proposed. The through-thickness temperature distribution of a deforming material, particularly during hot rolling, is inhomogeneous. Generally, the centre-plane temperature rises due to heat generation while the surface-plane temperature drops due to the cooling effects of the tools. Strain distribution during hot rolling is also inhomogeneous. In particular, the vertical strain (epsilon[z]) is minimum at the surface-plane of the material, maximum at the mid-plane and intermediate at the centre-plane.Hot deformation of the stainless steels leads to substructure formation and, at suitably high strains, dynamic and metadynamic recrystallisation. Only a small amount of static recovery precedes static recrystallisation. Nucleation for recrystallisation occurs at preferential sites, particularly serrated boundaries and triple junctions of the deformed prior gamma-grains.The nucleated gamma-grains grow anisotropically and link up to form chains of grains at the prior gamma-grain boundaries. Recrystallisation in hot-rolled samples is inhomogeneous at micro and macro-levels. Particularly, recrystallisation is accelerated at the centre-plane and retarded at the surface plane. This effect arises mainly from non-uniform distribution of temperature and is influenced by material and hot rolling variables. Nb retards recrystallisation by the combined effects of Nb carbide/ nitride particles and Nb atoms in solid solution, the particle effect predominating at 1100°C. Recrystallisation is accelerated by a higher strain, a higher deformation temperature, a higher strain rate, a decrease in the prior ?-grain size, and the presence of deformation bands and twins. A non-isothermal multiple deformation sequence increases the incubation time due to a large temperature drop but promotes a fast recrystallisation rate at the recrystallisation temperature. (Abstract shortened by ProQuest.).

Atomistic Simulation of the Rate-Dependent Ductile-to-Brittle Failure Transition in Bicrystalline Metal Nanowires.

PubMed

Tao, Weiwei; Cao, Penghui; Park, Harold S

2018-02-14

The mechanical properties and plastic deformation mechanisms of metal nanowires have been studied intensely for many years. One of the important yet unresolved challenges in this field is to bridge the gap in properties and deformation mechanisms reported for slow strain rate experiments (∼10 -2 s -1 ), and high strain rate molecular dynamics (MD) simulations (∼10 8 s -1 ) such that a complete understanding of strain rate effects on mechanical deformation and plasticity can be obtained. In this work, we use long time scale atomistic modeling based on potential energy surface exploration to elucidate the atomistic mechanisms governing a strain-rate-dependent incipient plasticity and yielding transition for face centered cubic (FCC) copper and silver nanowires. The transition occurs for both metals with both pristine and rough surfaces for all computationally accessible diameters (<10 nm). We find that the yield transition is induced by a transition in the incipient plastic event from Shockley partials nucleated on primary slip systems at MD strain rates to the nucleation of planar defects on non-Schmid slip planes at experimental strain rates, where multiple twin boundaries and planar stacking faults appear in copper and silver, respectively. Finally, we demonstrate that, at experimental strain rates, a ductile-to-brittle transition in failure mode similar to previous experimental studies on bicrystalline silver nanowires is observed, which is driven by differences in dislocation activity and grain boundary mobility as compared to the high strain rate case.

The Dynamic Flow and Failure Behavior of Magnesium and Magnesium Alloys

NASA Astrophysics Data System (ADS)

Eswar Prasad, K.; Li, B.; Dixit, N.; Shaffer, M.; Mathaudhu, S. N.; Ramesh, K. T.

2014-01-01

We review the dynamic behavior of magnesium alloys through a survey of the literature and a comparison with our own high-strain-rate experiments. We describe high-strain-rate experiments (at typical strain rates of 103 s-1) on polycrystalline pure magnesium as well as two magnesium alloys, AZ31B and ZK60. Both deformation and failure are considered. The observed behaviors are discussed in terms of the fundamental deformation and failure mechanisms in magnesium, considering the effects of grain size, strain rate, and crystallographic texture. A comparison of current results with the literature studies on these and other Mg alloys reveals that the crystallographic texture, grain size, and alloying elements continue to have a profound influence on the high-strain-rate deformation behavior. The available data set suggests that those materials loaded so as to initiate extension twinning have relatively rate-insensitive strengths up to strain rates of several thousand per second. In contrast, some rate dependence of the flow stress is observed for loading orientations in which the plastic flow is dominated by dislocation mechanisms.

High Strain Rate Tensile Testing of Silver Nanowires: Rate-Dependent Brittle-to-Ductile Transition.

PubMed

Ramachandramoorthy, Rajaprakash; Gao, Wei; Bernal, Rodrigo; Espinosa, Horacio

2016-01-13

The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here, we report in situ scanning electron microscope (SEM) tensile testing of bicrystalline silver nanowires at strain rates up to 2/s, which is 2 orders of magnitude higher than previously reported in the literature. The experiments are enabled by a microelectromechanical system (MEMS) with fast response time. It was identified that the nanowire plastic deformation has a small activation volume (<10b(3)), suggesting dislocation nucleation as the rate controlling mechanism. Also, a remarkable brittle-to-ductile failure mode transition was observed at a threshold strain rate of 0.2/s. Transmission electron microscopy (TEM) revealed that along the nanowire, dislocation density and spatial distribution of plastic regions increase with increasing strain rate. Furthermore, molecular dynamic (MD) simulations show that deformation mechanisms such as grain boundary migration and dislocation interactions are responsible for such ductility. Finally, the MD and experimental results were interpreted using dislocation nucleation theory. The predicted yield stress values are in agreement with the experimental results for strain rates above 0.2/s when ductility is pronounced. At low strain rates, random imperfections on the nanowire surface trigger localized plasticity, leading to a brittle-like failure.

Prediction of obliteration after gamma knife surgery for cerebral arteriovenous malformations.

PubMed

Karlsson, B; Lindquist, C; Steiner, L

1997-03-01

To define the factors of importance for the obliteration of cerebral arteriovenous malformations (AVMs), thus making a prediction of the probability for obliteration possible. In 945 AVMs of a series of 1319 patients treated with the gamma knife during 1970 to 1990, the relationship between patient, AVMs, and treatment parameters on the one hand and the obliteration of the nidus on the other was analyzed. The obliteration rate increased both with increased minimum (lowest periphery) and average dose and decreased with increased AVM volume. The minimum dose to the AVMs was the decisive dose factor for the treatment result. The higher the minimum dose, the higher the chance for total obliteration. The curve illustrating this relation increased logarithmically to a value of 87%. A higher average dose shortened the latency to AVM obliteration. For the obliterated cases, the larger the malformation, the lower the minimum dose used. This prompted us to relate the obliteration rate to the product minimum dose (AVM volume)1/3 (K index). The obliteration rate increased linearly with the K index up to a value of approximately 27, and for higher K values, the obliteration rate had a constant value of approximately 80%. For the group of 273 cases treated with a minimum dose of at least 25 Gy, the obliteration rate at the study end point (defined as 2-yr latency) was 80% (95% confidence interval = 75-85%). If obliterations that occurred beyond the end point are included, the obliteration rate increased to 85% (81-89%). The probability of obliteration of AVMs after gamma knife surgery is related both to the lowest dose to the AVMs and the AVM volume, and it can be predicted using the K index.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, K. C.; Tran, T. M.; Langer, J. S.

The statistical-thermodynamic dislocation theory developed in previous papers is used here in an analysis of high-temperature deformation of aluminum and steel. Using physics-based parameters that we expect theoretically to be independent of strain rate and temperature, we are able to fit experimental stress-strain curves for three different strain rates and three different temperatures for each of these two materials. Here, our theoretical curves include yielding transitions at zero strain in agreement with experiment. We find that thermal softening effects are important even at the lowest temperatures and smallest strain rates.

The effect of strain rate on the evolution of microstructure in aluminium alloys.

PubMed

Leszczyńska-Madej, B; Richert, M

2010-03-01

Intensive deformations influence strongly microstructure. The very well-known phenomenon is the diminishing dimension of grain size by the severe plastic deformation (SPD) methods. The nanometric features of microstructure were discovered after the SPD deformation of various materials, such as aluminium alloys, iron and others. The observed changes depended on the kind of the deformed material, amount of deformation, strain rate, existence of different phases and stacking fault energy. The influence of the strain and strain rate on the microstructure is commonly investigated nowadays. It was found that the high strain rates activate deformation in shear bands, microbands and adiabatic shear bands. It was observed that bands were places of the nucleation of nanograins in the material deformed by SPD methods. In the work, the refinement of microstructure of the aluminium alloys influenced by the high strain rate was investigated. The samples were compressed by a specially designed hammer to the deformation of phi= 0/0.62 with the strain rate in the range of [Formula in text]. The highest reduction of microbands width with the increase of the strain was found in the AlCu4Zr alloy. The influence of the strain rate on the microstructure refinement indicated that the increase of the strain rate caused the reduction of the microbands width in the all investigated materials (Al99.5, AlCu4Zr, AlMg5, AlZn6Mg2.5CuZr). A characteristic feature of the microstructure of the compressed material was large density of the shear bands and microbands. It was found that the microbands show a large misorientation to the surrounds and, except Al99.5, the large density of dislocation.

Maltotriose fermentation by Saccharomyces cerevisiae.

PubMed

Zastrow, C R; Hollatz, C; de Araujo, P S; Stambuk, B U

2001-07-01

Maltotriose, the second most abundant sugar of brewer's wort, is not fermented but is respired by several industrial yeast strains. We have isolated a strain capable of growing on a medium containing maltotriose and the respiratory inhibitor, antimycin A. This strain produced equivalent amounts of ethanol from 20 g l(-1) glucose, maltose, or maltotriose. We performed a detailed analysis of the rates of active transport and intracellular hydrolysis of maltotriose by this strain, and by a strain that does not ferment this sugar. The kinetics of sugar hydrolysis by both strains was similar, and our results also indicated that yeast cells do not synthesize a maltotriose-specific alpha-glucosidase. However, when considering active sugar transport, a different pattern was observed. The maltotriose-fermenting strain showed the same rate of active maltose or maltotriose transport, while the strain that could not ferment maltotriose showed a lower rate of maltotriose transport when compared with the rates of active maltose transport. Thus, our results revealed that transport across the plasma membrane, and not intracellular hydrolysis, is the rate-limiting step for the fermentation of maltotriose by these Saccharomyces cerevisiae cells.

Constitutive relations for determining the critical conditions for dynamic recrystallization behavior

NASA Astrophysics Data System (ADS)

Choe, J. I.

2016-04-01

A series mathematical model has been developed for the prediction of flow stress and microstructure evolution during the hot deformation of metals such as copper or austenitic steels with low stacking fault energies, involving features of both diffusional flow and dislocation motion. As the strain rate increases, multiple peaks on the stress-strain curve decrease. At a high strain rate, the stress rises to a single peak, while dynamic recrystallization causes an oscillatory behavior. At a low strain rate (when there is sufficient time for the recrystallizing grains to grow before they become saturated with high dislocation density with an increase in strain rate), the difference in stored stress between recrystallizing and old grains diminishes, resulting in reduced driving force for grain growth and rendering smaller grains in the alloy. The final average grain size at the steady stage (large strain) increases with a decrease in the strain rate. During large strain deformation, grain size reduction accompanying dislocation creep might be balanced by the grain growth at the border delimiting the ranges of realization (field boundary) of the dislocation-creep and diffusion-creep mechanisms.

Early Assessment of Right Ventricular Function in Systemic Lupus Erythematosus Patients using Strain and Strain Rate Imaging.

PubMed

Luo, Runlan; Cui, Hongyan; Huang, Dongmei; Sun, Lihua; Song, Shengda; Sun, Mengyao; Li, Guangsen

2018-06-11

Right ventricular function is a crucial factor of the prognosis of systemic lupus erythematosus (SLE). To evaluate the right ventricular function in SLE patients with different degrees of pulmonary hypertension (PH) by strain and strain rate imaging. A total of 102 SLE patients and 30 healthy volunteers were studied between October 2015 and May 2016. Patients were divided into three groups according to pulmonary artery systolic pressure (PASP) estimated by echocardiography: group control (A); PASP ≤ 30 mmHg (group B, n = 37); PASP 30-50 mmHg (mild PH; group C, n = 34); and PASP ≥ 50 mmHg (moderate-to-severe PH; group D, n = 31). Longitudinal peak systolic strain (ε) and strain rate (SR), including systolic strain rate (SRs), early diastolic strain rate (SRe) and late diastolic strain rate (SRa) were measured in the basal, middle and apical segments of the right ventricular free wall in participants by two-dimensional speckle tracking echocardiography (2D-STE) from the apical four-chamber view. A p < 0.05 was set for statistical significance. The parameters of ε, SRs, SRe, and SRa were significantly decreased in groups C and D compared with groups A and B. The ε of each segments was significantly lower in group D than in group C, while there were no differences in SRs, SRe and SRa between groups C and D. Strain and strain rate imaging could early detect the right ventricular dysfunction in SLE patients with PH, and provide important value for clinical therapy and prognosis of these patients. (Arq Bras Cardiol. 2018; [online].ahead print, PP.0-0).

An Examination of Sunspot Number Rates of Growth and Decay in Relation to the Sunspot Cycle

NASA Technical Reports Server (NTRS)

Wilson, Robert M.; Hathaway, David H.

2006-01-01

On the basis of annual sunspot number averages, sunspot number rates of growth and decay are examined relative to both minimum and maximum amplitudes and the time of their occurrences using cycles 12 through present, the most reliably determined sunspot cycles. Indeed, strong correlations are found for predicting the minimum and maximum amplitudes and the time of their occurrences years in advance. As applied to predicting sunspot minimum for cycle 24, the next cycle, its minimum appears likely to occur in 2006, especially if it is a robust cycle similar in nature to cycles 17-23.

Microstructural Evolution and Dynamic Softening Mechanisms of Al-Zn-Mg-Cu Alloy during Hot Compressive Deformation

PubMed Central

Shi, Cangji; Lai, Jing; Chen, X.-Grant

2014-01-01

The hot deformation behavior and microstructural evolution of an Al-Zn-Mg-Cu (7150) alloy was studied during hot compression at various temperatures (300 to 450 °C) and strain rates (0.001 to 10 s−1). A decline ratio map of flow stresses was proposed and divided into five deformation domains, in which the flow stress behavior was correlated with different microstructures and dynamic softening mechanisms. The results reveal that the dynamic recovery is the sole softening mechanism at temperatures of 300 to 400 °C with various strain rates and at temperatures of 400 to 450 °C with strain rates between 1 and 10 s−1. The level of dynamic recovery increases with increasing temperature and with decreasing strain rate. At the high deformation temperature of 450 °C with strain rates of 0.001 to 0.1 s−1, a partially recrystallized microstructure was observed, and the dynamic recrystallization (DRX) provided an alternative softening mechanism. Two kinds of DRX might operate at the high temperature, in which discontinuous dynamic recrystallization was involved at higher strain rates and continuous dynamic recrystallization was implied at lower strain rates. PMID:28788454

Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite.

PubMed

Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani

2017-01-28

This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

Yielding of tantalum at strain rates up to 10{sup 9 }s{sup −1}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowhurst, Jonathan C., E-mail: crowhurst1@llnl.gov; Armstrong, Michael R., E-mail: armstrong30@llnl.gov; Gates, Sean D.

2016-08-29

We have used a 45 μJ laser pulse to accelerate the free surface of fine-grained tantalum films up to peak velocities of ∼1.2 km s{sup −1}. The films had thicknesses of ∼1–2 μm and in-plane grain widths of ∼75–150 nm. Using ultrafast interferometry, we have measured the time history of the velocity of the surface at different spatial positions across the accelerated region. The initial part of the histories (assumed to correspond to the “elastic precursor” observed previously) exhibited measured strain rates of ∼0.6 to ∼3.2 × 10{sup 9 }s{sup −1} and stresses of ∼4 to ∼22 GPa. Importantly, we find that elastic amplitudes exhibit littlemore » variation with strain rate for a constant peak surface velocity, even though, via covariation of the strain rate with peak surface velocity, they vary with strain rate. Furthermore, by comparison with data obtained at lower strain rates, we find that amplitudes are much better predicted by peak velocities rather than by either strain rate or sample thickness.« less