Subsurface melting of nylon by friction-induced vibrations

Dry sliding of nylon on steel may lead to subsurface recrystallization of the polymer. This phenomenon is described and explained by subsurface melting due to internal heating as a result of the dissipation of frictioninduced vibrations at frequencies above 10 kHz. A vibration model relating the distribution of stress and temperature is proposed. Calculations based on this model show reasonable agreement with experimental observations

A running-in model for the reciprocating sliding of Nylon 6.6 against stainless steel

Results are presented of investigations of the running-in period in reciprocating sliding of a semicrystalline polymer, Nylon 6.6, on metal. A correlation was established between the changes in transfer film geometry and both the friction coefficient and the wear rate variations during a single stroke, as well as with sliding time. The role of wear products in running-in was found to be the determining factor. In order to avoid any unspecified influence of frictional heat variation on the sliding process, the counter specimen temperature was kept constant. Significant correlations, between both local and mean coefficients of friction and local and total areas of transfer film respectively, were found. The latter relation shows the existence of two different types of running-in process which depend on whether, initially, adhesive or abrasive wear mechanisms prevail. In both cases, the building up of the transfer film together with roll-like wear particles create several types of interactions between the rubbing bodies. These interactions, subsequently called subprocesses, have their own different specific coefficients of friction and can exist on the sliding track solely or in combination. They also change their distribution over the track and finally create a variation in the mean friction coefficient with time. This variation is expressed as a function of the total area fraction of transfer film spreading with time. It is also shown that changes in wear rate coincide with variations in mean friction coefficient. The presented model can also be extended qualitatively to other semicrystalline polymers

Statistics of the structure components in S0s: implications for bar induced secular evolution

The fractions and dimension of bars, rings and lenses are studied in the Near-IR S0 galaxy Survey (NIRS0S). We find evidence that multiple lenses in some barred S0s are related to bar resonances in a similar manner as the inner and outer rings, for which the outer/inner length ratio 2. Inner lenses in the non-barred galaxies normalized to galaxy diameter are clearly smaller than those in the barred systems. Interestingly, these small lenses in the non-barred galaxies have similar sizes as barlenses (lens-like structures embedded in a bar), and therefore might actually be barlenses in former barred galaxies, in which the outer, more elongated bar component, has been destroyed. We also find that fully developed inner lenses are on average a factor 1.3 larger than bars, whereas inner rings have similar sizes as bars. The fraction of inner lenses is found to be constant in all family classes (A, AB, B). Nuclear bars appear most frequently among the weakly barred (AB) galaxies, which is consistent with the theoretical models by Maciejewski & Athanassoula (2008). Similar sized bars as the nuclear bars were detected in seven 'non-barred' S0s. Galaxy luminosity does not uniquely define the sizes of bars or bar-related structures, neither is there any upper limit in galaxy luminosity for bar formation. Although all the family classes cover the same range of galaxy luminosity, the non-barred (A) galaxies are on average 0.6 mag brighter than the strongly barred (B) systems. Overall, our results are consistent with the idea that bars play an important role in the formation of the structure components of galaxies. The fact that multiple lenses are common in S0s, and that at least the inner lenses can have very old stellar populations, implies that the last destructive merger, or major gas accretion event, must have taken place at a fairly high redshift.Comment: 36 pages (include 13 figures, 11 tables). Accepted to MNRAS 2013 Jan 2

Radical learning through semantic transformation: capitalizing on novelty

YesThat organizations exist in a fluid environment of unprecedented and discontinuous change seems beyond debate. We seem to find ourselves immersed in a world in which events have a tendency to unfold and overtake us in unforeseeable and novel ways that defy comprehension; a crisis of meaning takes place and conventional sensemaking is disrupted. Our need to imaginatively construct new meanings that allow us to understand what is going on and to work out how to respond becomes ever more pressing. We do live in interesting times. The emergence of the new, however, challenges current established ways of knowing and opens a creative space for radical learning to take place. Novelty stimulates the generative process by which organizations and individuals learn, adapt to and cope with the exigencies they face in order to survive and progress. Such radical learning occurs when creative linguistic interventions in dialogue opens up semantic spaces whereby new terms are coined and old ones broken up, combined and/or redeployed in novel ways, in an effort to give expression to the fresh circumstances experienced or new phenomena observed. We call this kind of imaginative linguistic intervention semantic transformation. In this paper we argue that it is this semantic transformation that promotes radical transformational learning. Such semantic transformation is predicated on the improvisatory character of dialogue as a form of communication. We explore how, through this dialogical process of semantic transformation, we discover the resources and means to respond to the vagueness and equivocality experienced, by exploiting language in novel ways in our attempts to make sense of and account for such experiences

Huisvestingskosten van ComfortClass voor varkensbedrijven

The project Varkens in ComfortClass (Pigs in Comfort Class) is searching for a system of stalls which respects the needs of the fattening pig as much as possible yet is still economically viable for the pig farmer. This study analyses the housing costs of both existing stalls and new stalls built in accordance with the ComfortClass approac

L4Fe2As2Te1-xO4-yFy (L = Pr, Sm, Gd): a layered oxypnictide superconductor with Tc up to 45 K

The synthesis, structural and physical properties of iron lanthanide oxypnictide superconductors, L4Fe2As2Te1-xO4 (L = Pr, Sm, Gd), with transition temperature at ~ 25 K are reported. Single crystals have been grown at high pressure using cubic anvil technique. The crystal structure consists of layers of L2O2 tetrahedra separated by alternating layers of chains of Te and of Fe2As2 tetrahedra: -L2O2-Te-L2O2-Fe2As2-L2O2-Te-L2O2- (space group: I4/mmm, a ~ 4.0, c ~ 29.6 {\AA}). Substitution of oxygen by fluorine increases the critical temperature, e.g. in Gd4Fe2As2Te1-xOyF4-y up to 45 K. Magnetic torque measurements reveal an anisotropy of the penetration depths of ~31.Comment: 8 figures, 4 table

Halo Geometry and Dark Matter Annihilation Signal

We study the impact of the halo shape and geometry on the expected weakly interacting massive particle (WIMP) dark matter annihilation signal from the galactic center. As the halo profile in the innermost region is still poorly constrained, we consider different density behaviors like flat cores, cusps and spikes, as well as geometrical distortions. We show that asphericity has a strong impact on the annihilation signal when the halo profile near the galactic center is flat, but becomes gradually less significant for cuspy profiles, and negligible in the presence of a central spike. However, the astrophysical factor is strongly dependent on the WIMP mass and annihilation cross-section in the latter case.Comment: 5 pages, 4 figures, PR