1,337 research outputs found
Nonlinear fractional waves at elastic interfaces
We derive the nonlinear fractional surface wave equation that governs compression waves at an elastic interface that is coupled to a viscous bulk medium. The fractional character of the differential equation comes from the fact that the effective thickness of the bulk layer that is coupled to the interface is frequency dependent. The nonlinearity arises from the nonlinear dependence of the interface compressibility on the local compression, which is obtained from experimental measurements and reflects a phase transition at the interface. Numerical solutions of our nonlinear fractional theory reproduce several experimental key features of surface waves in phospholipid monolayers at the air-water interface without freely adjustable fitting parameters. In particular, the propagation distance of the surface wave abruptly increases at a threshold excitation amplitude. The wave velocity is found to be of the order of 40 cm/s in both experiments and theory and slightly increases as a function of the excitation amplitude. Nonlinear acoustic switching effects in membranes are thus shown to arise purely based on intrinsic membrane properties, namely, the presence of compressibility nonlinearities that accompany phase transitions at the interface
Concepts, Developments and Advanced Applications of the PAX Toolkit
The Physics Analysis eXpert (PAX) is an open source toolkit for high energy
physics analysis. The C++ class collection provided by PAX is deployed in a
number of analyses with complex event topologies at Tevatron and LHC. In this
article, we summarize basic concepts and class structure of the PAX kernel. We
report about the most recent developments of the kernel and introduce two new
PAX accessories. The PaxFactory, that provides a class collection to facilitate
event hypothesis evolution, and VisualPax, a Graphical User Interface for PAX
objects
Crystallization and preliminary X-ray analysis of sulfite dehydrogenase from Stargeya novella
Crystals of purified heterodimeric sulfite dehydrogenase from Starkeya novella have been grown using vapour diffusion. X-ray diffraction data have been collected from crystals of the native protein at lambda=1.0 Angstrom and close to the iron absorption edge at lambda=1.737 Angstrom. The crystals belong to space group P2(1)2(1)2, with unit-cell parameters a=97.5, b=92.5, c=55.9 Angstrom. Native data have been recorded to 1.8 Angstrom resolution and Fe-edge data to 2.5 Angstrom
Immune mechanisms of protection: can adjuvants rise to the challenge?
For many diseases vaccines are lacking or only partly effective. Research on protective immunity and adjuvants that generate vigorous immune responses may help generate effective vaccines against such pathogens
Physics Analysis Expert PAX: First Applications
PAX (Physics Analysis Expert) is a novel, C++ based toolkit designed to
assist teams in particle physics data analysis issues. The core of PAX are
event interpretation containers, holding relevant information about and
possible interpretations of a physics event. Providing this new level of
abstraction beyond the results of the detector reconstruction programs, PAX
facilitates the buildup and use of modern analysis factories. Class structure
and user command syntax of PAX are set up to support expert teams as well as
newcomers in preparing for the challenges expected to arise in the data
analysis at future hadron colliders.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, LaTeX, 10 eps figures. PSN
THLT00
Development and applications of the Gas Electron Multiplier
The Gas Electron Multiplier (GEM) has been recently developed to cope with the severe requirements of high luminosity particle physics experimentation. With excellent position accuracy and very high rate capability, GEM devices are robust and easy to manufacture. The possibility of cascading two or more multipliers permits to achieve larger gains and more stable operation. We discuss major performances of the new detectors, particularly in view of possible use for high rate portal imaging and medical diagnostics
Optimisation of the Gas Electron Multiplier for high rate application
The construction and performance of large size GEM~detectors for the COMPASS~experiment is described. Based on the experience gained during the operation of these detectors in high rate muon, proton, and pion beams we discuss the suitability of their use in harsh radiation environments
Development of a Time Projection Chamber Using Gas Electron Multipliers (GEM-TPC)
We developed a prototype time projection chamber using gas electron
multipliers (GEM-TPC) for high energy heavy ion collision experiments. To
investigate its performance, we conducted a beam test with 3 kinds of gases
(Ar(90%)-CH4(10%), Ar(70%)-C2H6(30%) and CF4). Detection efficiency of 99%, and
spatial resolution of 79 m in the pad-row direction and 313 m in the
drift direction were achieved. The test results show that the GEM-TPC meets the
requirements for high energy heavy ion collision experiments. The configuration
and performance of the GEM-TPC are described.Comment: 18 pages, 12 figures, published online in Nucl. Instr. and Meth.
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