Technical University of Dortmund

About: Technical University of Dortmund is a education organization based out in Dortmund, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Context (language use) & Large Hadron Collider. The organization has 13028 authors who have published 27666 publications receiving 615557 citations. The organization is also known as: Dortmund University & University of Dortmund.

Measurement of inclusive jet and dijet cross sections in proton-proton collisions at 7 TeV centre-of-mass energy with the ATLAS detector

Abstract: Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector. The measurement uses an integrated luminosity of 17 nb-1 recorded at the Large Hadron Collider. The anti-kt algorithm is used to identify jets, with two jet resolution parameters, R = 0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variable $\chi$. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation of the theory in a new kinematic regime.

Analytical properties of polaron systems or: Do polaronic phase transitions exist or not?

Abstract: For more than 40 years it was thought that polaron- and exciton-phonon systems exhibited unexpected localization properties. Particular attention was paid to the so-called phonon-induced self-trapping transition, which, it was believed, should manifest itself as a point of nonanalyticity in the ground-state energy as a function of the electron-phonon coupling parameter. It will be demonstrated for a large class of (generalized Fr\"ohlich) models that no such transition exists. The dimensionality of space has no qualitative influence; insofar, an application of the authors' results to problems in lower dimensions (e.g., polarons in quantum wells) is straightforward. The same holds true if homogeneous external fields are involved; for example, a discontinuous mass stripping for magnetopolarons can be excluded. On the other hand, a phase-transition-like behavior will be found, if a polaron or exciton is exposed to a short-range potential, allowing a so-called pinning transition. The authors emphasize, however, that even in this case the transition is only modified, and not induced, by phonons.

Enzymatic mineralization generates ultrastiff and tough hydrogels with tunable mechanics

Abstract: The cartilage and skin of animals, which are made up of more than fifty per cent water, are rather stiff (having elastic moduli of up to 100 megapascals) as well as tough and hard to break (with fracture energies of up to 9,000 joules per square metre). Such features make these biological materials mechanically superior to existing synthetic hydrogels. Lately, progress has been made in synthesizing tough hydrogels, with double-network hydrogels achieving the toughness of skin and inorganic-organic composites showing even better performance. However, these materials owe their toughness to high stretchability; in terms of stiffness, synthetic hydrogels cannot compete with their natural counterparts, with the best examples having elastic moduli of just 10 megapascals or less. Previously, we described the enzyme-induced precipitation and crystallization of hydrogels containing calcium carbonate, but the resulting materials were brittle. Here we report the enzyme-induced formation of amorphous calcium phosphate nanostructures that are homogenously distributed within polymer hydrogels. Our best materials have fracture energies of 1,300 joules per square metre even in their fully water-swollen state-a value superior to that of most known water-swollen synthetic materials. We are also able to modulate their stiffness up to 440 megapascals, well beyond that of cartilage and skin. Furthermore, the highly filled composite materials can be designed to be optically transparent and to retain most of their stretchability even when notched. We show that percolation drives the mechanical properties, particularly the high stiffness, of our uniformly mineralized hydrogels.