Ab initio parametrised model of strain-dependent solubility of H in alpha-iron

The calculated effects of interstitial hydrogen on the elastic properties of alpha-iron from our earlier work are used to describe the H interactions with homogeneous strain fields using ab initio methods. In particular we calculate the H solublility in Fe subject to hydrostatic, uniaxial, and shear strain. For comparison, these interactions are parametrised successfully using a simple model with parameters entirely derived from ab initio methods. The results are used to predict the solubility of H in spatially-varying elastic strain fields, representative of realistic dislocations outside their core. We find a strong directional dependence of the H-dislocation interaction, leading to strong attraction of H by the axial strain components of edge dislocations and by screw dislocations oriented along the critical slip direction. We further find a H concentration enhancement around dislocation cores, consistent with experimental observations.Comment: part 2/2 from splitting of 1009.3784 (first part was 1102.0187), minor changes from previous version

Acute stress induced by the preslaughter use of electric prodders causes tougher beef meat

Adrenergic activation and hormone release preslaughter is an inevitable outcome of the systems used to move cattle to slaughter. The aim of this experiment was to investigate the effects of acute preslaughter stress in beef cattle on postmortem muscle metabolism and the meat quality, including consumer-assessed eating quality. Eighty-four cattle were used on three separate days, with ‘mobs’ of four cattle allocated to either a ‘control’ (no electric goads used preslaughter) or a ‘stress’ (six prods given with an electric goad over 5–10 min) treatment at 15 min preslaughter. Cattle undergoing the ‘stress’ treatment had higher plasma lactate at slaughter. The prerigor pH and temperature, ultimate pH and temperature at rigor of the longissimus thoracis muscle were similar between treatments (P\u3e0.05 for all). The water-holding capacity of the longissimus lumborum was reduced by the ‘stress’ treatment, as indicated by higher levels of water lost during suspension (drip loss), storage (purge) for 21 days and cooking (cooking loss at 1 day postslaughter) (P\u3c0.05 for all). ‘Stress’ cattle produced longissimus lumborum muscle with similar sarcomere lengths andWarner–Bratzler shear force at 2, 6 and 21 days , compared to ‘control’ cattle (P\u3c0.05 for all). The longissimus lumborum muscle of cattle undergoing the ‘stress’ treatment was rated less tender, less juicy, with a less acceptable flavour, a lower ‘liking’ and a lower MQ4 score (P\u3c0.05 for all). The ‘bloomed’ surface colour (CIE L*, a*, b*) of the longissimus lumborum muscle at 2, 6 and 21 days postslaughter was similar between the ‘stress’ and ‘control’ treatments (P\u3e0.05 for all). In conclusion, cattle subjected to acute preslaughter stress using electric goads produced meat which the consumer rated as tougher with inferior quality. The inferior quality induced by the acute stress treatment was associated with reduced water-holding capacity but was independent of muscle pH and temperature

Characterization of aerosol associated with enhanced small particle number concentrations in a suburban forested environment

Two elevated particle number/mass growth events associated with Aitken‐mode particles were observed during a sampling campaign (13–29 September 2004) at the Duke University Free‐Air CO2 Enrichment facility, a forested field site located in suburban central North Carolina. Aerosol growth rates between 1.2 and 4.9 nm hr−1 were observed, resulting in net increases in geometric mean diameter of 21 and 37 nm during events. Growth was dominated by addition of oxidized organic compounds. Campaign‐average aerosol mass concentrations measured by an Aerodyne quadrupole aerosol mass spectrometer (Q‐AMS) were 1.9 ± 1.6 (σ), 1.6 ± 1.9, 0.1 ± 0.1, and 0.4 ± 0.4 μg m−3 for organic mass (OM), sulfate, nitrate, and ammonium, respectively. These values represent 47%, 40%, 3%, and 10%, respectively, of the measured submicron aerosol mass. Based on Q‐AMS spectra, OM was apportioned to hydrocarbon‐like organic aerosol (HOA, likely representing primary organic aerosol) and two types of oxidized organic aerosol (OOA‐1 and OOA‐2), which constituted on average 6%, 58%, and 36%, respectively, of the apportioned OM. OOA‐1 probably represents aged, regional secondary organic aerosol (SOA), while OOA‐2 likely reflects less aged SOA. Organic aerosol characteristics associated with the events are compared to the campaign averages. Particularly in one event, the contribution of OOA‐2 to overall OM levels was enhanced, indicating the likelihood of less aged SOA formation. Statistical analyses investigate the relationships between HOA, OOA‐1, OOA‐2, other aerosol components, gas‐phase species, and meteorological data during the campaign and individual events. No single variable clearly controls the occurrence of a particle growth event

A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis

We present a mode identification based on new high-resolution time-series spectra of the non-radially pulsating Delta Scuti star FG~Vir (HD 106384, V = 6.57, A5V). From 2002 February to June a global Delta Scuti Network (DSN) campaign, utilizing high-resolution spectroscopy and simultaneous photometry has been conducted for FG~Vir in order to provide a theoretical pulsation model. In this campaign we have acquired 969 Echelle spectra covering 147 hours at six observatories. The mode identification was carried out by analyzing line profile variations by means of the Fourier parameter fit method, where the observational Fourier parameters across the line are fitted with theoretical values. This method is especially well suited for determining the azimuthal order m of non-radial pulsation modes and thus complementary with the method of Daszynska-Daszkiewicz (2002) which does best at identifying the degree l. 15 frequencies between 9.2 and 33.5 c/d were detected spectroscopically. We determined the azimuthal order m of 12 modes and constrained their harmonic degree l. Only modes of low degree (l <= 4) were detected, most of them having axisymmetric character mainly due to the relatively low projected rotational velocity of FG Vir. The detected non-axisymmetric modes have azimuthal orders between -2 and 1. We derived an inclination of 19 degrees, which implies an equatorial rotational rate of 66 km/s.Comment: 14 pages, 26 figure

Scaling Behaviour and Complexity of the Portevin-Le Chatelier Effect

The plastic deformation of dilute alloys is often accompanied by plastic instabilities due to dynamic strain aging and dislocation interaction. The repeated breakaway of dislocations from and their recapture by solute atoms leads to stress serrations and localized strain in the strain controlled tensile tests, known as the Portevin-Le Chatelier (PLC) effect. In this present work, we analyse the stress time series data of the observed PLC effect in the constant strain rate tensile tests on Al-2.5%Mg alloy for a wide range of strain rates at room temperature. The scaling behaviour of the PLC effect was studied using two complementary scaling analysis methods: the finite variance scaling method and the diffusion entropy analysis. From these analyses we could establish that in the entire span of strain rates, PLC effect showed Levy walk property. Moreover, the multiscale entropy analysis is carried out on the stress time series data observed during the PLC effect to quantify the complexity of the distinct spatiotemporal dynamical regimes. It is shown that for the static type C band, the entropy is very low for all the scales compared to the hopping type B and the propagating type A bands. The results are interpreted considering the time and length scales relevant to the effect.Comment: 35 pages, 6 figure

Impact of active and passive social facilitation on self paced endurance and sprint exercise: encouragement augments performance and motivation to exercise

Objective The positive effect of an audience on performance is anecdotally well known, but the impact of such social facilitation to both performance and the motivation to exercise have not been thoroughly explored. The aim of this study was therefore to investigate verbal encouragement as a means to promote positive behavioural adherence to exercise and augmented performance. Methods Twelve untrained but active individuals (seven female), age 24±3 years participated in this study. Exercise conditions with external verbal encouragement (EVE) and without external verbal encouragement (WEVE) were compared in both endurance (20 min) and sprint (2 × 30 s Wingate) cycling tasks in a randomised crossover design. Results were analysed by separate 2 (EVE/WEVE) × 2 (sprint/endurance) within-subjects analyses of variance for each dependent variable. Statistical significance was set at p≤0.05. Results EVE resulted in a significant increase, F (1,11)=15.37, p=0.002, η p 2=0.58 in the average power generated by participants in each exercise bout on the cycle ergometer. EVE also had a significant effect on reported motivation to exercise the next day, F (1,11)=5.5, p=0.04, η p 2 =0.33, which did not differ between type of exercise. Conclusion External encouragement in both sprint and endurance activities resulted in large improvements in performance and motivation to continue an exercise regimen the next day, which has important implications for health, adherence and maximising physical performance using a practical intervention

Use of ERTS-1 data to access and monitor change in the west side of the San Joaquin Valley and central coastal zone of California

There are no author-identified significant results in this report

Contact Modelling in Isogeometric Analysis: Application to Sheet Metal Forming Processes

Isogeometric Analysis (IGA) has been growing in popularity in the past few years essentially due to the extra exibility it introduces with the use of higher degrees in the basis functions leading to higher convergence rates. IGA also o ers the capability of easily reproducing discontinuous displacement and/or strain elds by just manipulating the multiplicity of the knot parametric coordinates. Another advantage of IGA is that it uses the Non-Uniform Rational B-Splines (NURBS) basis functions, that are very common in CAD solid modelling, and consequently it makes easier the transition from CAD models to numerical analysis. In this work it is explored the contact analysis in IGA for both implicit and explicit time integration schemes. Special focus will be given on contact search and contact detection techniques under NURBS patches for both the rigid tools and the deformed sheet blank

Critical Dynamics of Burst Instabilities in the Portevin-Le Chatelier Effect

We investigate the Portevin-Le Chatelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or "jerky") and "laminar" plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/\tau of the PLC effect exhibits large fluctuations, and "critical slowing down" (i.e., the number $\tau$ of bursts, or plastic instabilities, per unit time slows down considerably).Comment: the published 4-page version is in the PRL web sit