Quantum dislocations: the fate of multiple vacancies in two dimensional solid 4He

Defects are believed to play a fundamental role in the supersolid state of 4He. We have studied solid 4He in two dimensions (2D) as function of the number of vacancies n_v, up to 30, inserted in the initial configuration at rho = 0.0765 A^-2, close to the melting density, with the exact zero temperature Shadow Path Integral Ground State method. The crystalline order is found to be stable also in presence of many vacancies and we observe two completely different regimes. For small n_v, up to about 6, vacancies form a bound state and cause a decrease of the crystalline order. At larger n_v, the formation energy of an extra vacancy at fixed density decreases by one order of magnitude to about 0.6 K. In the equilibrated state it is no more possible to recognize vacancies because they mainly transform into quantum dislocations and crystalline order is found almost independent on how many vacancies have been inserted in the initial configuration. The one--body density matrix in this latter regime shows a non decaying large distance tail: dislocations, that in 2D are point defects, turn out to be mobile, their number is fluctuating, and they are able to induce exchanges of particles across the system mainly triggered by the dislocation cores. These results indicate that the notion of incommensurate versus commensurate state loses meaning for solid 4He in 2D, because the number of lattice sites becomes ill defined when the system is not commensurate. Crystalline order is found to be stable also in 3D in presence of up to 100 vacancies

Mars Observer Radar Altimeter Radiometer (MORAR)

The Mars Observer Project will permit the advancement of the state of the topographic and hypsometric knowledge of Mars to a level of 10 m or better over the surface of the planet Mars, the measurement of microwave surface brightness temperature of Mars with an accuracy of 15 to 20 K over 24 hours, and the measurement, globally, of surface returned power related to radar cross section with an accuracy of 1 dB and a repeatability of .5 dB. The MORAR Hardware Development, Ground Data Processing, and the Mission Operations will allow the accomplishment of these scientific objectives to define globally the topography of Mars at sufficient vertical resolution and spatial scale to address both large-scale geophysical and small-scale geologic problems, and to obtain global surface electrical and scattering properties of the upper several centimeters of the Martian surface for assessment of the composition, physical state, and volatile distribution of the surface

Universal conductance fluctuations in Dirac materials in the presence of long-range disorder

We study quantum transport in Dirac materials with a single fermionic Dirac cone (strong topological insulators and graphene in the absence of intervalley coupling) in the presence of non-Gaussian long-range disorder. We show, by directly calculating numerically the conductance fluctuations, that in the limit of very large system size and disorder strength, quantum transport becomes universal. However, a systematic deviation away from universality is obtained for realistic system parameters. By comparing our results to existing experimental data on 1/f noise, we suggest that many of the graphene samples studied to date are in a non-universal crossover regime of conductance fluctuations.Comment: 5 pages, 3 figures. Published versio

Characteristics of a betatron core for extraction in a proton-ion medical synchrotron

Medical synchrotrons for radiation therapy require a very stable extraction of the beam over a period of about one second. The techniques for applying resonant extraction to achieve this long spill can be classified into two groups, those that move the resonance and those that move the beam. The latter has the great advantage of keeping all lattice functions, and hence the resonance conditions, constant. The present report examines the possibility of using a betatron core to accelerate the waiting ion beam by induction into the resonance. The working principle, the proposed characteristics and the expected performances of this device are discussed. The betatron core is a smooth high-inductance device compared to the small quadrupole lenses that are normally used to move the resonance and is therefore better suited to delivering a very smooth spill. The large stored energy in a betatron core compared to a small quadrupole is also a safety feature since it responds less quickly to transients that could send large beam spikes to the patient

STOICHIOMETRY OF RESPIRATORY STIMULATION, ACCUMULATION OF CA++ AND PHOSPHATE, AND OXIDATIVE PHOSPHORYLATION IN RAT LIVER MITOCHONDRIA.

n/

Transmission Power Measurements for Wireless Sensor Nodes and their Relationship to the Battery Level

In this work we focus on the new generation EYESIFXv2 [1] wireless sensor nodes by carrying out experimental measurements on power related quantities. In particular, our aim is to characterize the relationship between the level of the battery and the transmission power radiated by the node. The present results point out the non linear and non trivial effects due to the output potentiometer which can be used to tune the transmission power. It shall be observed that a thorough study of how battery and/or potentiometer settings translate to actual transmitted power levels is crucial to e.g. design correct power control algorithms, which can effectively operate under any operational condition of the wireless sensor device

Quantized vortices in two dimensional solid 4He

Diagonal and off-diagonal properties of 2D solid 4He systems doped with a quantized vortex have been investigated via the Shadow Path Integral Ground State method using the fixed-phase approach. The chosen approximate phase induces the standard Onsager-Feynman flow field. In this approximation the vortex acts as a static external potential and the resulting Hamiltonian can be treated exactly with Quantum Monte Carlo methods. The vortex core is found to sit in an interstitial site and a very weak relaxation of the lattice positions away from the vortex core position has been observed. Also other properties like Bragg peaks in the static structure factor or the behavior of vacancies are very little affected by the presence of the vortex. We have computed also the one-body density matrix in perfect and defected 4He crystals finding that the vortex has no sensible effect on the off-diagonal long range tail of the density matrix. Within the assumed Onsager Feynman phase, we find that a quantized vortex cannot auto-sustain itself unless a condensate is already present like when dislocations are present. It remains to be investigated if backflow can change this conclusion.Comment: 4 pages, 3 figures, LT26 proceedings, accepted for publication in Journal of Physics: Conference Serie