2,315 research outputs found
Investigation to define the propagation characteristics of a finite amplitude acoustic pressure wave Final report
Aerodynamic noise generation by finite amplitude pressure wave propagation through entropy producing region
Investigation to define the propagation characteristics of a finite amplitude acoustic pressure wave
A theoretical analysis of the propagation characteristics of a finite amplitude pressure wave is presented. The analysis attempts to study the contribution of entropy-producing regions to the mechanism of aerodynamic noise generation. It results in a nonlinear convective wave equation in terms of entropy and a thermodynamic 'J' function. A direct analogy between the derived governing equation and those used in classical literature is obtained. An idealization of the processes considered permits the uncoupling of the equations of motion with a consequent construction of an acoustic analogy treating shock wave emission of finite amplitude acoustic waves. An engineering approach is reflected in the concept of an extended plug nozzle whose function is to facilitate aerodynamic noise attenuation by modifying the entropy-producing regions
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
Thermodynamic theory of dislocation-enabled plasticity
The thermodynamic theory of dislocation-enabled plasticity is based on two
unconventional hypotheses. The first of these is that a system of dislocations,
driven by external forces and irreversibly exchanging heat with its
environment, must be characterized by a thermodynamically defined effective
temperature that is not the same as the ordinary temperature. The second
hypothesis is that the overwhelmingly dominant mechanism controlling plastic
deformation is thermally activated depinning of entangled pairs of
dislocations. This paper consists of a systematic reformulation of this theory
followed by examples of its use in analyses of experimentally observed
phenomena including strain hardening, grain-size (Hall-Petch) effects, yielding
transitions, and adiabatic shear banding
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
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 âmobsâ of four cattle allocated to either a âcontrolâ (no electric goads used preslaughter) or a âstressâ (six prods given with an electric goad over 5â10 min) treatment at 15 min preslaughter. Cattle undergoing the âstressâ 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 âstressâ 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). âStressâ cattle produced longissimus lumborum muscle with similar sarcomere lengths andWarnerâBratzler shear force at 2, 6 and 21 days , compared to âcontrolâ cattle (P\u3c0.05 for all). The longissimus lumborum muscle of cattle undergoing the âstressâ treatment was rated less tender, less juicy, with a less acceptable flavour, a lower âlikingâ and a lower MQ4 score (P\u3c0.05 for all). The âbloomedâ surface colour (CIE L*, a*, b*) of the longissimus lumborum muscle at 2, 6 and 21 days postslaughter was similar between the âstressâ and âcontrolâ 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 Aitkenâmode particles were observed during a sampling campaign (13â29 September 2004) at the Duke University FreeâAir CO2 Enrichment facility, a forested field site located in suburban central North Carolina. Aerosol growth rates between 1.2 and 4.9 nm hrâ1 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. Campaignâaverage aerosol mass concentrations measured by an Aerodyne quadrupole aerosol mass spectrometer (QâAMS) were 1.9 ± 1.6 (Ï), 1.6 ± 1.9, 0.1 ± 0.1, and 0.4 ± 0.4 ÎŒg mâ3 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 QâAMS spectra, OM was apportioned to hydrocarbonâlike organic aerosol (HOA, likely representing primary organic aerosol) and two types of oxidized organic aerosol (OOAâ1 and OOAâ2), which constituted on average 6%, 58%, and 36%, respectively, of the apportioned OM. OOAâ1 probably represents aged, regional secondary organic aerosol (SOA), while OOAâ2 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 OOAâ2 to overall OM levels was enhanced, indicating the likelihood of less aged SOA formation. Statistical analyses investigate the relationships between HOA, OOAâ1, OOAâ2, other aerosol components, gasâphase species, and meteorological data during the campaign and individual events. No single variable clearly controls the occurrence of a particle growth event
AGB subpopulations in the nearby globular cluster NGC 6397
It has been well established that Galactic Globular clusters (GCs) harbour
more than one stellar population, distinguishable by the anti-correlations of
light element abundances (C-N, Na-O, and Mg-Al). These studies have been
extended recently to the asymptotic giant branch (AGB). Here we investigate the
AGB of NGC 6397 for the first time. We have performed an abundance analysis of
high-resolution spectra of 47 RGB and 8 AGB stars, deriving Fe, Na, O, Mg and
Al abundances. We find that NGC 6397 shows no evidence of a deficit in Na-rich
AGB stars, as reported for some other GCs - the subpopulation ratios of the AGB
and RGB in NGC 6397 are identical, within uncertainties. This agrees with
expectations from stellar theory. This GC acts as a control for our earlier
work on the AGB of M 4 (with contrasting results), since the same tools and
methods were used.Comment: 10 pages, 7 figures, 8 tables (2 online-only). Accepted for
publication in MNRA
FGFR2 amplification in colorectal adenocarcinoma
FGFR2 is recurrently amplified in 5% of gastric cancers and 1%â4% of breast cancers; however, this molecular alteration has never been reported in a primary colorectal cancer specimen. Preclinical studies indicate that several FGFR tyrosine-kinase inhibitors (TKIs), such as AZD4547, have in vitro activity against the FGFR2-amplified colorectal cell line, NCI-H716. The efficacy of these inhibitors is currently under investigation in clinical trials for breast and gastric cancer. Thus, better characterizing colorectal tumors for FGFR2 amplification could identify a subset of patients who may benefit from FGFR TKI therapies. Here, we describe a novel FGFR2 amplification identified by clinical next-generation sequencing in a primary colorectal cancer. Further characterization of the tumor by immunohistochemistry showed neuroendocrine differentiation, similar to the reported properties of the NCI-H716 cell line. These findings demonstrate that the spectrum of potentially clinically actionable mutations detected by targeted clinical sequencing panels is not limited to only single-nucleotide polymorphisms and insertions/deletions but also to copy-number alterations.</jats:p
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