Acceleration of Plasma Flows Due to Reverse Dynamo Mechanism

The "reverse-dynamo" mechanism - the amplification/generation of fast plasma flows by micro scale (turbulent) magnetic fields via magneto-fluid coupling is recognized and explored. It is shown that macro-scale magnetic fields and flows are generated simultaneously and proportionately from micro scale fields and flows. The stronger the micro-scale driver, the stronger are the macro-scale products. Stellar and astrophysical applications are suggested.Comment: 16 pages including 3 figures. The Astrophys. J. (accepted); additional material is given for clarification; terminology is change

Analysis of Biofilm Communities for Legionella pneumophila

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen

Radar backscatter and rocket probe measurements of electron temperature above Arecibo

Comparison of radar backscatter and rocket probe measurements of ionospheric electron temperatur

A New Lower Bound on the Maximum Number of Satisfied Clauses in Max-SAT and its Algorithmic Applications

A pair of unit clauses is called conflicting if it is of the form $(x)$, $(\bar{x})$. A CNF formula is unit-conflict free (UCF) if it contains no pair of conflicting unit clauses. Lieberherr and Specker (J. ACM 28, 1981) showed that for each UCF CNF formula with $m$ clauses we can simultaneously satisfy at least \pp m clauses, where \pp =(\sqrt{5}-1)/2. We improve the Lieberherr-Specker bound by showing that for each UCF CNF formula $F$ with $m$ clauses we can find, in polynomial time, a subformula $F'$ with $m'$ clauses such that we can simultaneously satisfy at least \pp m+(1-\pp)m'+(2-3\pp)n"/2 clauses (in $F$), where $n"$ is the number of variables in $F$ which are not in $F'$. We consider two parameterized versions of MAX-SAT, where the parameter is the number of satisfied clauses above the bounds $m/2$ and $m(\sqrt{5}-1)/2$. The former bound is tight for general formulas, and the later is tight for UCF formulas. Mahajan and Raman (J. Algorithms 31, 1999) showed that every instance of the first parameterized problem can be transformed, in polynomial time, into an equivalent one with at most $6k+3$ variables and $10k$ clauses. We improve this to $4k$ variables and $(2\sqrt{5}+4)k$ clauses. Mahajan and Raman conjectured that the second parameterized problem is fixed-parameter tractable (FPT). We show that the problem is indeed FPT by describing a polynomial-time algorithm that transforms any problem instance into an equivalent one with at most $(7+3\sqrt{5})k$ variables. Our results are obtained using our improvement of the Lieberherr-Specker bound above

Doping effects in the coupled, two-leg spin ladder BiCu2PO6

We report preparation, x-ray diffraction, magnetic susceptibility chi(T) and heat capacity Cp(T) measurements on the undoped samples as also samples with Zn-doped (S = 0) at Cu site, Ni doped (S = 1) at Cu site, and Ca-doped (holes) at Bi site in the coupled two-leg spin ladder system BiCu2PO6. While, Zn shows complete solid solubility, Ni could be doped to about 20% and Ca to about 15%. Magnetization and heat capacity data in the undoped compound point towards the existence of frustration effects. In all the samples, the chi(T) at low temperature increases with doping content. The Zn-induced susceptibility is smaller than that due to effective S=1/2 moments possibly due to frustrating next-nearest-neighbor interactions along the leg. For Zn content x > 0.01, chi(T) deviates from the Curie-law at low temperatures. The magnetic specific heat data Cm(T) for the Zn-doped samples show weak anomalies at low temperature in agreement with chi(T) behavior. The anomalies are suggestive of spin freezing at low-T. In contrast, prominent effects are observed in chi(T) and Cm(T) on Ni-doped samples. The zero-field-cooled (ZFC) and field-cooled (FC) chi(T) data are different from each other at low temperature unlike that for Zn doped samples, clearly indicating a transition to a spin-glass like phase. No anomalies were found in Ca- or Pb-doped samples.Comment: 16 pages, 9 figures, Submitted to J. Phy. Cond. Matte

CP violation in the decay mode B→πγγB\to \pi \gamma \gamma

Within the framework of Standard Model, the exclusive decay mode $B\to \pi \gamma \gamma$ is studied. Although the usual short distance contribution is small compared to the similar $B\to K\gamma\gamma$ mode, the process offers the possibility of studying the CP violation, a feature absent in the $B \to K$ counterpart.Comment: 11 page latex file including 2 ps figures. Typos corrected, minor changes. To appear in PR

Gyrokinetic analysis and simulation of pedestals, to identify the culprits for energy losses using fingerprints

Fusion performance in tokamaks hinges critically on the efficacy of the Edge Transport Barrier (ETB) at suppressing energy losses. The new concept of fingerprints is introduced to identify the instabilities that cause the transport losses in the ETB of many of today's experiments, from widely posited candidates. Analysis of the Gyrokinetic-Maxwell equations, and gyrokinetic simulations of experiments, find that each mode type produces characteristic ratios of transport in the various channels: density, heat and impurities. This, together with experimental observations of transport in some channel, or, of the relative size of the driving sources of channels, can identify or determine the dominant modes causing energy transport. In multiple ELMy H-mode cases that are examined, these fingerprints indicate that MHD-like modes are apparently not the dominant agent of energy transport; rather, this role is played by Micro-Tearing Modes (MTM) and Electron Temperature Gradient (ETG) modes, and in addition, possibly Ion Temperature Gradient (ITG)/Trapped Electron Modes (ITG/TEM) on JET. MHD-like modes may dominate the electron particle losses. Fluctuation frequency can also be an important means of identification, and is often closely related to the transport fingerprint. The analytical arguments unify and explain previously disparate experimental observations on multiple devices, including DIII-D, JET and ASDEX-U, and detailed simulations of two DIII-D ETBs also demonstrate and corroborate this

Dominant ferromagnetism in the spin-1/2 half-twist ladder 334 compounds, Ba3Cu3In4O12 and Ba3Cu3Sc4O12

The magnetic properties of polycrystalline samples of Ba3Cu3In4O12 (In-334) and Ba3Cu3Sc4O12 (Sc-334) are reported. Both 334 phases have a structure derived from perovskite, with CuO4 squares interconnected to form half-twist ladders along the c-axis. The Cu-O-Cu angles, ~ 90o, and the positive Weiss temperatures indicate the presence of significant ferromagnetic (FM) interactions along the Cu ladders. At low temperatures, T < 20 K, sharp transitions in the magnetic susceptibility and heat capacity measurements indicate three-dimensional (3D) antiferromagnetic (AFM) ordering at TN. TN is suppressed on application of a field and a complex magnetic phase diagram with three distinct magnetic regimes below the upper critical field can be inferred from our measurements. The magnetic interactions are discussed in relation to a modified spin-1/2 FM-AFM model and the 334 half-twist ladder is compared to other 2-rung ladder spin-1/2 systems.Comment: 20 pages, 7 figure

Persistence of Li Induced Kondo Moments in the Superconducting State of Cuprates

We measure the magnetic susceptibility nearby Li spinless impurities in the superconducting phase of the high Tc cuprate YBaCuO. The induced moment which was found to exist above Tc persists below Tc. In the underdoped regime, it retains its Curie law below Tc. In contrast, near optimal doping, the large Kondo screening observed above Tc (T_K=135 K) is strongly reduced below Tc as expected theoretically when the superconducting gap develops. This moment still extends essentially on its 4 near neighbour Cu, showing the persistence of AF correlations in the superconducting state. A direct comparison with recent STM results of Pan et al. is proposed.Comment: accepted for publication in Phys. Rev. Lett. (issue of 30 april 2001) Revised version : 8 pages including 4 pages of text and 4 figure