Origin of the structural phase transition in Li7La3Zr2O12

Garnet-type Li7La3Zr2O12 (LLZO) is a solid electrolyte material with a low-conductivity tetragonal and a high-conductivity cubic phase. Using density-functional theory and variable cell shape molecular dynamics simulations, we show that the tetragonal phase stability is dependent on a simultaneous ordering of the Li ions on the Li sublattice and a volume-preserving tetragonal distortion that relieves internal structural strain. Supervalent doping introduces vacancies into the Li sublattice, increasing the overall entropy and reducing the free energy gain from ordering, eventually stabilizing the cubic phase. We show that the critical temperature for cubic phase stability is lowered as Li vacancy concentration (dopant level) is raised and that an activated hop of Li ions from one crystallographic site to another always accompanies the transition. By identifying the relevant mechanism and critical concentrations for achieving the high conductivity phase, this work shows how targeted synthesis could be used to improve electrolytic performance

Dynamic autonomous intelligent control of an asteroid lander

One of the future flagship missions of the European Space Agency (ESA) is the asteroid sample return mission Marco-Polo. Although there have been a number of past missions to asteroids, a sample has never been successfully returned. The return of asteroid regolith to the Earth's surface introduces new technical challenges. This paper develops attitude control algorithms for the descent phase onto an asteroid in micro-gravity conditions and draws a comparison between the algorithms considered. Two studies are also performed regarding the Fault Detection Isolation and Recovery (FDIR) of the control laws considered. The potential of using Direct Adaptive Control (DAC) as a controller for the surface sampling process is also investigated. Use of a DAC controller incorporates increased levels of robustness by allowing realtime variation of control gains. This leads to better response to uncertainties encountered during missions

Unstable Hadrons in Hot Hadron Gas in Laboratory and in the Early Universe

We study kinetic master equations for chemical reactions involving the formation and the natural decay of unstable particles in a thermal bath. We consider the decay channel of one into two particles, and the inverse process, fusion of two thermal particles into one. We present the master equations the evolution of the density of the unstable particles in the early Universe. We obtain the thermal invariant reaction rate using as an input the free space (vacuum) decay time and show the medium quantum effects on $\pi+\pi \leftrightarrow \rho$ reaction relaxation time. As another laboratory example we describe the $K+K \leftrightarrow \phi$ process in thermal hadronic gas in heavy-ion collisions. A particularly interesting application of our formalism is the $\pi^{0}\leftrightarrow \gamma +\gamma$ process in the early Universe. We also explore the physics of $\pi^{\pm}$ and $\mu^{\pm}$ freeze-out in the Universe.Comment: 13 pages, 9 figures, published in Physical Review

On the role of entanglement in quantum computational speed-up

For any quantum algorithm operating on pure states we prove that the presence of multi-partite entanglement, with a number of parties that increases unboundedly with input size, is necessary if the quantum algorithm is to offer an exponential speed-up over classical computation. Furthermore we prove that the algorithm can be classically efficiently simulated to within a prescribed tolerance \eta even if a suitably small amount of global entanglement (depending on \eta) is present. We explicitly identify the occurrence of increasing multi-partite entanglement in Shor's algorithm. Our results do not apply to quantum algorithms operating on mixed states in general and we discuss the suggestion that an exponential computational speed-up might be possible with mixed states in the total absence of entanglement. Finally, despite the essential role of entanglement for pure state algorithms, we argue that it is nevertheless misleading to view entanglement as a key resource for quantum computational power.Comment: Main proofs simplified. A few further explanatory remarks added. 22 pages, plain late

Weak Lensing Determination of the Mass in Galaxy Halos

We detect the weak gravitational lensing distortion of 450,000 background galaxies (20<R<23) by 790 foreground galaxies (R<18) selected from the Las Campanas Redshift Survey (LCRS). This is the first detection of weak lensing by field galaxies of known redshift, and as such permits us to reconstruct the shear profile of the typical field galaxy halo in absolute physical units (modulo H_0), and to investigate the dependence of halo mass upon galaxy luminosity. This is also the first galaxy-galaxy lensing study for which the calibration errors are negligible. Within a projected radius of 200 \hkpc, the shear profile is consistent with an isothermal profile with circular velocity 164+-20 km/s for an L* galaxy, consistent with typical disk rotation at this luminosity. This halo mass normalization, combined with the halo profile derived by Fischer et al (2000) from lensing analysis SDSS data, places a lower limit of (2.7+-0.6) x 10^{12}h^{-1} solar masses on the mass of an L* galaxy halo, in good agreement with satellite galaxy studies. Given the known luminosity function of LCRS galaxies, and the assumption that $M\propto L^\beta$ for galaxies, we determine that the mass within 260\hkpc of normal galaxies contributes $\Omega=0.16\pm0.03$ to the density of the Universe (for $\beta=1$) or $\Omega=0.24\pm0.06$ for $\beta=0.5$. These lensing data suggest that $0.6<\beta<2.4$ (95% CL), only marginally in agreement with the usual $\beta\approx0.5$ Faber-Jackson or Tully-Fisher scaling. This is the most complete direct inventory of the matter content of the Universe to date.Comment: 18 pages, incl. 3 figures. Submitted to ApJ 6/7/00, still no response from the referee after four months

Teaching varies with task complexity in wild chimpanzees

Understanding social influences on how apes acquire tool behaviors can help us model the evolution of culture and technology in humans. Humans scaffold novice tool skills with diverse strategies, including the transfer of tools between individuals. Chimpanzees transfer tools, and this behavior meets criteria for teaching. However, it is unclear how task complexity relates to this form of helping. Here, we find differences between 2 wild chimpanzee populations in rate, probability, and types of tool transfer during termite gathering. Chimpanzees showed greater helping in the population where termite gathering is a more complex tool task. In wild chimpanzees, as in humans, regular and active provisioning of learning opportunities may be essential to the cultural transmission of complex skills.Cumulative culture is a transformative force in human evolution, but the social underpinnings of this capacity are debated. Identifying social influences on how chimpanzees acquire tool tasks of differing complexity may help illuminate the evolutionary origins of technology in our own lineage. Humans routinely transfer tools to novices to scaffold their skill development. While tool transfers occur in wild chimpanzees and fulfill criteria for teaching, it is unknown whether this form of helping varies between populations and across tasks. Applying standardized methods, we compared tool transfers during termite gathering by chimpanzees in the Goualougo Triangle, Republic of Congo, and in Gombe, Tanzania. At Goualougo, chimpanzees use multiple, different tool types sequentially, choose specific raw materials, and perform modifications that improve tool efficiency, which could make it challenging for novices to manufacture suitable tools. Termite gathering at Gombe involves a single tool type, fishing probes, which can be manufactured from various materials. Multiple measures indicated population differences in tool-transfer behavior. The rate of transfers and probability of transfer upon request were significantly higher at Goualougo, while resistance to transfers was significantly higher at Gombe. Active transfers of tools in which possessors moved to facilitate possession change upon request occurred only at Goualougo, where they were the most common transfer type. At Gombe, tool requests were typically refused. We suggest that these population differences in tool-transfer behavior may relate to task complexity and that active helping plays an enhanced role in the cultural transmission of complex technology in wild apes

Efficacy of mupirocin nasal ointment in eradicating Staphylococcus aureus nasal carriage in chronic haemodialysis patients

Topical 2% mupirocin ointment eradicated chronic Staphylococcus aureus nasal carriage immediately post-therapy in 17 (77%) of 22 haemodialysis patients. Mean time to recurrence was 3.8 weeks. Similar pre-therapy and post-therapy phage types occurred in 12 (71%) of 17 patients. Staphylococcus aureus infections developed in none of 17 successfully treated patients, two of five treatment failures (P = 0.05), and 10 of 46 untreated patients studied concurrently (P = 0.03)

Maximum entropy controller synthesis for colocated and noncolocated systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77185/1/AIAA-21277-539.pd

The Size Distribution of Trans-Neptunian Bodies

[Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are discovered, roughly 25 times fewer than expected from extrapolation of the differential sky density Sigma(m) of brighter objects. The ACS and other recent TNO surveys show departures from a power law size distribution. Division of the TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals that Sigma(m) differs for the two populations at 96% confidence. A double power law adequately fits all data. Implications include: The total mass of the CKB is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the form of ~100 km bodies. The mass of Excited objects is perhaps a few times larger. The Excited class has a shallower bright-end size distribution; the largest objects, including Pluto, comprise tens of percent of the total mass whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the largest Excited body is close to the Pluto mass; the largest CKBO is ~60 times less massive. The deficit of small TNOs occurs for sizes subject to disruption by present-day collisions, suggesting extensive depletion by collisions. Both accretion and erosion appearing to have proceeded to more advanced stages in the Excited class than the CKB. The absence of distant TNOs implies that any distant (60 AU) population must have less than the CKB mass in the form of objects 40 km or larger. The CKB population is sparser than theoretical estimates of the required precursor population for short period comets, but the Excited population could be a viable precursor population.Comment: Revised version accepted to the Astronomical Journal. Numerical results are very slightly revised. Implications for the origins of short-period comets are substantially revised, and tedious material on statistical tests has been collected into a new Appendi

Pattern recognition on a quantum computer

By means of a simple example it is demonstrated that the task of finding and identifying certain patterns in an otherwise (macroscopically) unstructured picture (data set) can be accomplished efficiently by a quantum computer. Employing the powerful tool of the quantum Fourier transform the proposed quantum algorithm exhibits an exponential speed-up in comparison with its classical counterpart. The digital representation also results in a significantly higher accuracy than the method of optical filtering. PACS: 03.67.Lx, 03.67.-a, 42.30.Sy, 89.70.+c.Comment: 6 pages RevTeX, 1 figure, several correction