8,894 research outputs found

### A Dependence of Hadron Production in Inelastic Muon Scattering and Dimuon Production by Protons

The A dependence of the production of hadrons in inelastic muon scattering
and of the production of dimuons in high $Q^2$ proton interactions are simply
related. Feynman x distributions and z scaling distributions in nuclei are
compared with energy loss models. Suggestions for new data analyses are
presented.Comment: 14pp +13 figures, UPR report 607T (available from
ftp://dept.physics.upenn.edu/muhad

### Low frequency gyro-synchrotron radio noise from the earth's outer radiation belt

The problem of detecting cyclotron and synchrotron noise from superthermal electrons is analyzed for the frequency range 30 kHz 300 kHz. Due to the earth's ionosphere, ground based observation of this noise is improbable. Therefore, the calculations are made for an observer in the interplanetary medium. In particular, the location is chosen in the geomagnetic equatorial plane at a geocentric distance of 32 earth radii. This position of the observer allows the theoretical results to be compared directly with data obtained from the radio astronomy experiment aboard the IMP-6 spacecraft

### Corrosion Inhibition of AA2024-T3 by Vanadates

The speciation of vanadate solutions and the resultinginhibition of oxygen reduction and corrosion of AA2024-T3 wereinvestigated. 51V NMR is very useful for assessing vanadatespeciation. Clear metavanadate solutions contain nodecavanadate, which forms whenever the pH was decreased by theaddition of acid. Orange decavanadate solutions contain nomonovanadate, even when the pH is adjusted to high values.Monovanadate is a potent inhibitor in contrast to decavanadate. Inhibition by monovanadate seems to result from an adsorptionmechanism rather than reduction. Monovanadate effectivelyprotects S phase particles. Aging of high-pH decavanadatesolutions does not improve the inhibition performance or resultin complete depolymerization of the decavanadate

### Aluminum Alloy Corrosion Inhibition by Vanadates

The inhibition of Al alloy corrosion by vanadates was studied in this work. Vanadium speciation is very complicated and vital to the inhibition efficacy. Critical conditions for decavanadate polymerization from clear metavanadate solutions were investigated. Decavanadate only formed when metavanadate was added to solutions of pH 3 or less. It was not possible to change the pH of a metavanadate solution without forming decavanadates, creating an orange-colored solution. According to ^51 V nuclear magnetic resonance, monovanadates were present only in clear metavanadate solutions; orange solutions always contained decavanadates and never contained monovanadates. Orange decavanadate solutions containing 0.5 M NaCl at pH 8.71 exhibited no significant inhibition of the oxygen reduction reaction and increasing decavanadate concentration was detrimental. In contrast, clear metavanadate solutions containing monovanadate exhibited strong inhibition of the oxygen reduction reaction, to a level similar to chromate. At a fixed pH, increased NaVO3 concentration in clear metavanadate solutions increased inhibition efficiency.This work was partially funded by AFOSR under award F 49620-02-0321, Major J. Gresham, Ph.D.,
contract monitor

### Massive spinor fields in flat spacetimes with non-trivial topology

The vacuum expectation value of the stress-energy tensor is calculated for
spin $1\over 2$ massive fields in several multiply connected flat spacetimes.
We examine the physical effects of topology on manifolds such as $R^3 \times
S^1$, $R^2\times T^2$, $R^1 \times T^3$, the Mobius strip and the Klein bottle.
We find that the spinor vacuum stress tensor has the opposite sign to, and
twice the magnitude of, the scalar tensor in orientable manifolds. Extending
the above considerations to the case of Misner spacetime, we calculate the
vacuum expectation value of spinor stress-energy tensor in this space and
discuss its implications for the chronology protection conjecture.Comment: 18 pages, Some of the equations in section VI as well as
typographical errors corrected, 5 figures, Revtex

### A study of the mechanisms of corrosion inhibition of AA2024-T3 by vanadates using the split cell technique

The mechanisms of corrosion inhibition of AA2024-T3 by vanadates were studied in this work using the split cell technique and polarization curves. The electrochemical behavior of clear solutions containing metavanadates and orange solutions containing decavanadates was clearly distinctive. Injection of metavanadates to the cathode side of the different split cell setups greatly reduced the galvanic current, indicating a potent inhibition of the oxygen reduction kinetics. The galvanic current never exhibited a transient current peak, suggesting that metavanadates inhibit AA2024-T3 corrosion by a mechanism that does not involve electrochemical reduction. Injection of metavanadate to the anode side of the different split cells had no effect on the galvanic current. Injection of orange decavanadate to the cathode side of the AA2024-T3 split cell resulted in a large current peak, associated with the electrochemical reduction of decavanadate. However, decavanadates did not impart significant corrosion protection.This work was partially funded by AFOSR under award F 49620-02-0321, Major J. Gresham, PhD, contract monitor. JKâ€™s travel expenses were paid by NATO under grant PST.CLG.979370

### Electromagnetic wormholes and virtual magnetic monopoles

We describe new configurations of electromagnetic (EM) material parameters,
the electric permittivity $\epsilon$ and magnetic permeability $\mu$, that
allow one to construct from metamaterials objects that function as invisible
tunnels. These allow EM wave propagation between two points, but the tunnels
and the regions they enclose are not detectable to EM observations. Such
devices function as wormholes with respect to Maxwell's equations and
effectively change the topology of space vis-a-vis EM wave propagation. We
suggest several applications, including devices behaving as virtual magnetic
monopoles.Comment: 4 pages, 3 figure

### A Morse-theoretical analysis of gravitational lensing by a Kerr-Newman black hole

Consider, in the domain of outer communication of a Kerr-Newman black hole, a
point (observation event) and a timelike curve (worldline of light source).
Assume that the worldline of the source (i) has no past end-point, (ii) does
not intersect the caustic of the past light-cone of the observation event, and
(iii) goes neither to the horizon nor to infinity in the past. We prove that
then for infinitely many positive integers k there is a past-pointing lightlike
geodesic of (Morse) index k from the observation event to the worldline of the
source, hence an observer at the observation event sees infinitely many images
of the source. Moreover, we demonstrate that all lightlike geodesics from an
event to a timelike curve in the domain of outer communication are confined to
a certain spherical shell. Our characterization of this spherical shell shows
that in the Kerr-Newman spacetime the occurrence of infinitely many images is
intimately related to the occurrence of centrifugal-plus-Coriolis force
reversal.Comment: 14 pages, 2 figures; REVTEX; submitted to J. Math. Phy

### Taylor dispersion of gyrotactic swimming micro-organisms in a linear flow

The theory of generalized Taylor dispersion for suspensions of Brownian particles is developed to study the dispersion of gyrotactic swimming micro-organisms in a linear shear flow. Such creatures are bottom-heavy and experience a gravitational torque which acts to right them when they are tipped away from the vertical. They also suffer a net viscous torque in the presence of a local vorticity field. The orientation of the cells is intrinsically random but the balance of the two torques results in a bias toward a preferred swimming direction. The micro-organisms are sufficiently large that Brownian motion is negligible but their random swimming across streamlines results in a mean velocity together with diffusion. As an example, we consider the case of vertical shear flow and calculate the diffusion coefficients for a suspension of the alga <i>Chlamydomonas nivalis</i>. This rational derivation is compared with earlier approximations for the diffusivity

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