222 research outputs found
Effect of cyclic loading on hydrogen diffusion in low carbon steels
Carbon steels or low-alloyed steels may be affected by damaging phenomena due to Hydrogen Embrittlement (HE), which is a particular form of Environmental Assisted Cracking (EAC). The insurgence of HE depends on the intrinsic susceptibility of the steel, the applied stress, and the concentration of hydrogen inside the metal. It occurs by a mechanism of absorption and subsequent diffusion of atomic hydrogen through the metal lattice.
On steels with a yield strength lower than 700 MPa, HE occurs in the plastic deformation field, in the presence of dynamic loading at slow strain rates or cyclic fatigue loading at very low frequencies. Although several important studies were carried out on the effect of loading conditions on hydrogen diffusion into the metal and HE mechanism, HE phenomena are not fully understood. In this work, the effect of the application of cyclic loads on hydrogen diffusion parameters was studied both in the elastic and in the plastic deformation field. The influence of mean load and amplitude was analyzed. Hydrogen permeation tests were performed on API 5L X65 steel, in accordance with ISO 17081:2014. The specimen behaved as bi-electrode between the two compartments of a Devanathan-Stachurski cell. The anodic side of the specimen was polarized at +340 mV vs Ag/AgCl in a 0.1 M NaOH aerated solution, while the cathodic compartment was filled with an aerated borate solution. A controller enabled temperature adjustment at 20±0.5°C. Once the passivity current registered in the anodic side reached values of 0.05 µA/cm2, a cathodic current density of 0.50 mA/cm2 was applied to charging cathodic side. The study included tests with sine waveform cycling loading, with a maximum level equal to 110% TYS, at a frequency of 10-2 Hz.
The results confirmed the values of hydrogen diffusion coefficient usually indicated for low-alloyed steels with a sorbitic microstructure. Strain hardened specimens - stretched above yield strength - showed an increase of steady state current and an extension of the time lag, denoting a slight decrease in the apparent hydrogen diffusion coefficient due to traps effect in the cold deformed steel matrix.
Under cyclic loading, an instantaneous peak of current with a subsequent significant transient decrease occurred after cyclic load application, whereas no relevant variation of permeation curve compared to unloaded specimens was observed if specimens were already loaded before hydrogen charging.
The instantaneous current peak reached values much higher than the steady state current. This is ascribed to the rupture of the passive film – caused by loading – and its subsequent reformation; in fact, this can also be noted during tests performed on specimens without hydrogen permeation.
The following transient, in which the permeation current decreases below the steady state and then returns to it, denotes a relevant trapping effect that causes the instantaneous reduction of mobile hydrogen concentration in the lattice. This becomes more significant for loads closer and closer to the yield strength, mainly beyond this, and can only be noted at the first loading step. Subsequent unloading and loading step at the same mean value showed no transient in the permeation curren
Recurrence of Mitotically Active Cellular Fibroma of the Ovary
Background. 10% of ovarian fibromatous tumours typically exhibit increased cellularity, mitotic activity, and less frequently nuclear atypia. Therefore, the classification within the group of fibromatous tumours may represent some difficulties, thus, one or several of these features should appear. Case. We introduce the clinical and pathologic features based on one case of recurrence of a mitotically active cellular ovarian fibroma (MACF) in the pararectal fossa. This recurrence took place six years after primary surgery. Macroscopically, the tumour was firm, fibrous, well delimited, yellow-white without gross necrosis. On microscopic examination, it was composed of a densely cellular proliferation of fibrolastic-like cells with bland nuclear features and arranged in a fascicular pattern. There was no sign of significant atypia or necrosis. Conclusion. Recently, this case is the first report of a recurrence of MACF, following primary surgery with no tumoral rupture or surgical difficulty. The clinical outcome of ovarian cellular fibromas (CFs) and MACFs is typically uneventful. This case, however, strongly suggests maintaining a long-term clinical follow-up even though the principal tumour was surgically treated without tumour rupture or in the absence of adherence or any surgical difficulty
Detecting Gluino-Containing Hadrons
When SUSY breaking produces only dimension-2 operators, gluino and photino
masses are of order 1 GeV or less. The gluon-gluino bound state has mass
1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and
lifetime is largely unconstrained because missing energy and beam dump
techniques are ineffective. With only small modifications, upcoming K^0 decay
experiments can study most of the interesting range. The lightest
gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to
find it and the uud-gluino are also discussed.Comment: 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295,
hep-ph/9508291, and hep-ph/9508292, focused on experimental search
techniques. To be published in Phys Rev Let
Tattoo-Paper Transfer as a Versatile Platform for All-Printed Organic Edible Electronics
The use of natural or bioinspired materials to develop edible electronic
devices is a potentially disruptive technology that can boost point-of-care
testing. The technology exploits devices which can be safely ingested, along
with pills or even food, and operated from within the gastrointestinal tract.
Ingestible electronics could potentially target a significant number of
biomedical applications, both as therapeutic and diagnostic tool, and this
technology may also impact the food industry, by providing ingestible or
food-compatible electronic tags that can smart track goods and monitor their
quality along the distribution chain. We hereby propose temporary tattoo-paper
as a simple and versatile platform for the integration of electronics onto food
and pharmaceutical capsules. In particular, we demonstrate the fabrication of
all-printed Organic Field-Effect Transistors (OFETs) on untreated commercial
tattoo-paper, and their subsequent transfer and operation on edible substrates
with a complex non-planar geometry
Nanoscale effects on the ionic conductivity of highly doped bulk nanometric cerium oxide
Nanometric ceria powders doped with 30 mol % samaria are consolidated by a high-pressure spark plasma sintering (HP-SPS) method to form > 99 % dense samples with a crystallite size as small as 16.5 nm. A conductivity dependence on grain size was noted: when the grain size was less than 20 nm, only one semicircle in the AC impedance spectra was observed and was attributed to bulk conductivity. In contrast to previous observations on pure ceria, the disappearance of the grain-boundary blocking effect is not associated with mixed conductivity. With annealing and concomitant grain growth, the samples show the presence of a grain-boundary effect
Impact of D0-D0bar mixing on the experimental determination of gamma
Several methods have been devised to measure the weak phase gamma using
decays of the type B+- --> D K+-, where it is assumed that there is no mixing
in the D0-D0bar system. However, when using these methods to uncover new
physics, one must entertain the real possibility that the measurements are
affected by new physics effects in the D0-D0bar system. We show that even
values of x_D and/or y_D around 10^{-2} can have a significant impact in the
measurement of sin^2{gamma}. We discuss the errors incurred in neglecting this
effect, how the effect can be checked, and how to include it in the analysis.Comment: 18 pages, Latex with epsfig, 8 figure
Hydrogen Embrittlement and Diffusion in High Strength Low Alloyed Steels with Different Microstructures
The paper deals with the effect of microstructure on the hydrogen diffusion in traditional ferritic-pearlitic HSLA steels and new high strength steels, with tempered martensite microstructures or banded ferritic-bainitic-martensitic microstructures. Diffusivity was correlated to the hydrogen embrittlement resistance of steels, evaluated by means of slow strain rate tests. </p
Tau and Charm physics highlights
In tau physics, we are at the frontier between the completion of the LEP
program and the start of analyses from b-factories, which are expected to
produce results in the coming years. Nice results from CLEO are steadily
delivered in the meantime. For charm, impressive progress have been achieved by
fixed target experiments in the search for CP violation and D^0 - \bar D^0
oscillations. First results from b-factories demonstrate the power of these
facilities in such areas. The novel measurement of the D* width by CLEO happens
to be rather different from current expectations. The absence of a charm
factory explains the lack or the very slow progress in the absolute scale
determinations for charm decays.Comment: "Typos corrected and references added
Experiments to Find or Exclude a Long-Lived, Light Gluino
Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter
gluinos are allowed, except for certain ranges of lifetime. Only small parts of
the mass-lifetime parameter space are excluded for larger masses unless the
lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and
lifetime estimates for R-hadrons are given, present direct and indirect
experimental constraints are reviewed, and experiments to find or definitively
exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies
discussion of some points and corresponds to version for Phys. Rev.
Leptogenesis and low energy observables in left-right symmetric models
In the context of left-right symmetric models we study the connection of
leptogenesis and low energy parameters such as neutrinoless double beta decay
and leptonic CP violation. Upon imposition of a unitarity constraint, the
neutrino parameters are significantly restricted and the Majorana phases are
determined within a narrow range, depending on the kind of solar solution. One
of the Majorana phases gets determined to a good accuracy and thereby the
second phase can be probed from the results of neutrinoless double beta decay
experiments. We examine the contributions of the solar and atmospheric mass
squared differences to the asymmetry and find that in general the solar scale
dominates. In order to let the atmospheric scale dominate, some finetuning
between one of the Majorana phases and the Dirac CP phase is required. In this
case, one of the Majorana phases is determined by the amount of CP violation in
oscillation experiments.Comment: 18 pages, 6 figures. Matches version to appear in PR
- …