9,875 research outputs found
Cross sections for the production of fragments with Z greater than or equal to 8 by fragmentation of Z greater than or equal to 9 and less than or equal to 26 nuclei
Charge changing nuclear collisions in plastic nuclear track detectors were studied using a new experimental technique of automatic track measurement for etched tracks in plastic detectors. Partial cross sections for the production of fragments of charge Z approximately 8 were measured for projectile nuclei of charge 9 approximately Z approximately 26 in the detector material CR39 and in silver. for this purpose three independent experiments were performed using Bevalac beams. The first one was an exposure of a stack of CR39 plastic plates to 1.8 GeV/nucl. Ar-40 nuclei. The second one was an exposure of another CR39 stack of 1.7 GeV/nucl. Fe-56 projectiles. In the third experiment a mixed stack of CR39 plates and silver foils was irradiated with 1.7 GeV/nucl. Fe-56 nuclei. Thus the measurement of nuclear cross sections in a light target (CR39 = C12H18O7) and as well in a heavy target (silver) was possible
Crack barriers improve the mechanical and thermal properties of non-metallic sinter materials
Means of improving the tensile strength of ceramic composites by introducing ductile intermediate layers capable of absorbing the elastic energy at the rupture front are studied. Tests with an Al203 laminate with niobium inclusions showed that crack propagation could be successfully precluded by dissipation of the energy by deformation and/or delamination at the inclusion/matrix interface
Classification of SUSY and non-SUSY Chiral Models from Abelian Orbifolds AdS/CFT
We classify compactifications of the type IIB superstring on AdS_{5} x
S^{5}/\Gamma, where \Gamma is an abelian group of order n<= 12. Appropriate
embedding of \Gamma in the isometry of S^5 yields both SUSY and non-SUSY chiral
models that can contain the minimal SUSY standard model or the standard model.
New non-SUSY three family models with \Gamma=Z_8 are introduced, which lead to
the right Weinberg angle for TeV trinification.Comment: 12 pages, no figur
A Charge and Spin Readout Scheme For Single Self-Assembled Quantum Dots
We propose an all optical spin initialization and readout concept for single
self assembled quantum dots and demonstrate its feasibility. Our approach is
based on a gateable single dot photodiode structure that can be switched
between charge and readout mode. After optical electron generation and storage,
we propose to employ a spin-conditional absorption of a circularly polarized
light pulse tuned to the single negatively charged exciton transition to
convert the spin information of the resident electron to charge occupancy.
Switching the device to the charge readout mode then allows us to probe the
charge state of the quantum dot (1e, 2e) using non-resonant luminescence. The
spin orientation of the resident electron is then reflected by the
photoluminescence yield of doubly and singly charged transitions in the quantum
dot. To verify the feasibility of this spin readout concept, we have applied
time gated photoluminescence to confirm that selective optical charging and
efficient non perturbative measurement of the charge state can be performed on
the same dot. The results show that, by switching the electric field in the
vicinity of the quantum dot, the charging rate can be switched between a regime
of efficient electron generation and a readout regime, where the charge
occupancy and, therefore, the spin state of the dot can be tested via PL over
millisecond timescales, without altering it.Comment: 20 Pages, 6 Figures, submitted to Phys. Rev.
From splashing to bouncing: the influence of viscosity on the impact of suspension droplets on a solid surface
We experimentally investigated the splashing of dense suspension droplets
impacting a solid surface, extending prior work to the regime where the
viscosity of the suspending liquid becomes a significant parameter. The overall
behavior can be described by a combination of two trends. The first one is that
the splashing becomes favored when the kinetic energy of individual particles
at the surface of a droplet overcomes the confinement produced by surface
tension. This is expressed by a particle-based Weber number . The second
is that splashing is suppressed by increasing the viscosity of the solvent.
This is expressed by the Stokes number , which influences the effective
coefficient of restitution of colliding particles. We developed a phase diagram
where the splashing onset is delineated as a function of both and .
A surprising result occurs at very small Stokes number, where not only
splashing is suppressed but also plastic deformation of the droplet. This leads
to a situation where droplets can bounce back after impact, an observation we
are able to reproduce using discrete particle numerical simulations that take
into account viscous interaction between particles and elastic energy
A novel ozone sensor for various environmental applications
A small, lightweight, and fast-response ozone sensor for various environmental applications is described. At a flow rate of 100 l/min(-1) the ozone sensor has a response time of significantly better than 0.1 s with a detection limit lower than 100 pptv. The ozone sensor was successfully tested in various environmental applications, i.e. in measuring directly the vertical ozone flux onto agricultural land utilizing the eddy correlation or covariance technique and in monitoring horizontal and vertical ozone profiles in the troposphere and stratosphere
Non-collinear magnetic structures: a possible cause for current induced switching
Current induced switching in Co/Cu/Co trilayers is described in terms of
ab-initio determined magnetic twisting energies and corresponding sheet
resistances. In viewing the twisting energy as an energy flux the
characteristic time thereof is evaluated by means of the
Landau-Lifshitz-Gilbert equation using ab-initio parameters. The obtained
switching times are in very good agreement with available experimental data. In
terms of the calculated currents, scalar quantities since a classical Ohm's law
is applied, critical currents needed to switch magnetic configurations from
parallel to antiparallel and vice versa can unambiguously be defined. It is
found that the magnetoresistance viewed as a function of the current is
essentially determined by the twisting energy as a function of the relative
angle between the orientations of the magnetization in the magnetic slabs,
which in turn can also explain in particular cases the fact that after having
switched off the current the system remains in the switched magnetic
configuration. For all ab-initio type calculations the fully relativistic
Screened Korringa-Kohn-Rostoker method and the corresponding Kubo-Greenwood
equation in the context of density functional theory are applied.Comment: 20 pages, 4 tables and 15 figures, submitted to PR
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