A statistical analysis of some non-linear optical effects

Statistical analysis of some nonlinear optical effects including scattering light from rotating glass and second harmonic light generated by pseudo-thermal sourc

1^{1}H-NMR spin-echo measurements of the static and dynamic spin properties in λ\lambda-(BETS)2_{2}FeCl4_{4}

$^{1}$H-NMR spin-echo measurements of the spin-echo decay $M(2\tau)$ with a decay rate 1/$T_{2}$ and the frequency shift $\Delta\nu/\nu_{0}$ under applied magnetic field $\mathbf{B}$$_{0}$ = 9 T along the a-axis over a temperature range 2.0$-$180 K are reported for a single crystal of the organic conductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$. It provides the spin dynamic and static properties in the paramagnetic metal (PM) and antiferromagnetic insulator (AFI) states as well as across the PM$-$AFI phase transition. A large slow beat structure in the spin-echo decay is observed with a typical beat frequency of $f$ $\sim$ 7 kHz and it varies across the spectrum. Its origin is attributed to the $^{1}$H$-$$^{1}$H dipole interactions rather than to the much larger dipolar field contribution from the Fe$^{3+}$ electrons (spin $S$ = 5/2). A simple phenomenological model provides an excellent fit to the data. The dominant $^{1}$H-NMR frequency shift comes from the dipolar field from the 3d Fe$^{3+}$ ions, and the Fe$^{3+}$ $-$ Fe$^{3+}$ exchange interactions ($J_{0}$) ($J_{0}$ includes the d$-$d exchange interactions through the $\pi-$electrons) have a substantial effect to the local field at the proton sites expecially at low temperatures. A good fit is obtained with $J_{0}$ = - 1.7 K. The data of the spin-echo decay rate 1/$T_{2}$ indicates that there is a significant change in the slow fluctuations of the local magnetic field at the $^{1}$H-sites on traversing the PM to AFI phase. This evidence supports earlier reports that the PM$-$AFI phase transition in $\lambda$-(BETS)$_{2}$FeCl$_{4}$ is driven magnetically and first order.Comment: 9 pages, 10 figures, resubmitted to Phys. Rev. B in response to comments of Editor and reviewers on March 23, 200

Description and catalog of ionospheric F-region data, Jicamarca Radar Observatory, November 1966 - April 1969

Equatorial ionospheric F-region data reduced from the Jicamarca Radar Observatory (JRO) incoherent scatter observations for particular periods is described. It lists in catalog form the times of the observations made during those periods. These F-region data include the electron concentration and the electron and ion temperatures. The data were inferred from the incoherent scatter observations of JRO

Imaging the phase of an evolving Bose-Einstein condensate wavefunction

We demonstrate a spatially resolved autocorrelation measurement with a Bose-Einstein condensate (BEC) and measure the evolution of the spatial profile of its quantum mechanical phase. Upon release of the BEC from the magnetic trap, its phase develops a form that we measure to be quadratic in the spatial coordinate. Our experiments also reveal the effects of the repulsive interaction between two overlapping BEC wavepackets and we measure the small momentum they impart to each other

Use of ERTS-1 data in identification, classification, and mapping of salt-affected soils in California

There are no author-identified significant results in this report

Proton NMR measurements of the local magnetic field in the paramagnetic metal and antiferromagnetic insulator phases of λ\lambda-(BETS)2_{2}FeCl4_{4}

Measurements of the $^{1}$H-NMR spectrum of a small ($\sim$ 4 $\mu$g) single crystal of the organic conductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$ are reported with an applied magnetic field $\bf{B}$$_{0}$ = 9 T parallel to the a-axis in the $ac$-plane over a temperature $(T)$ range 2.0 $-$ 180 K. They provide the distribution of the static local magnetic field at the proton sites in the paramagnetic metal (PM) and antiferromagnetic insulator (AFI) phases, along with the changes that occur at the PM$-$AFI phase transition. The spectra have six main peaks that are significantly broadened and shifted at low $T$. The origin of these features is attributed to the large dipolar field from the 3d Fe$^{3+}$ ion moments (spin $S_{\rm{d}}$ = 5/2). Their amplitude and $T-$dependence are modeled using a modified Brillouin function that includes a mean field approximation for the total exchange interaction ($J_{0}$) between one Fe$^{3+}$ ion and its two nearest neighbors. A good fit is obtained using $J_{0}$ = $-$ 1.7 K. At temperatures below the PM$-$AFI transition temperature $T_{MI}$ = 3.5 K, an extra peak appears on the high frequency side of the spectrum and the details of the spectrum become smeared. Also, the rms linewidth and the frequency shift of the spectral distribution are discontinuous, consistent with the transition being first-order. These measurements verify that the dominant local magnetic field contribution is from the Fe$^{3+}$ ions and indicate that there is a significant change in the static local magnetic field distribution at the proton sites on traversing the PM to AFI phase transition.Comment: 11 pages, 7 figures. Revised version of cond-mat/0605044 resubmitted to Phys. Rev. B in response to comments of Editor and reviewer

A gravity exercise system

An effective method for muscle conditioning during weightlessness flight is derived from isometric exercise. The basic principle of gravity exercise is to periodically displace the human body upon reactionless rollers so that spacial equilibrium can only be maintained by the proper tension and relaxation of the body's muscles. A rotating platform mounted upon two degrees of freedom rollers provides such a condition of gravitational reaction stress throughout each of its 360 deg rotation

The Wilson Effective K\"ahler Potential For Supersymmetric Nonlinear Sigma Models

Renormalization group methods are used to determine the evolution of the low energy Wilson effective action for supersymmetric nonlinear sigma models in four dimensions. For the case of supersymmetric $CP^{(N-1)}$ models, the K\"ahler potential is determined exactly and is shown to exhibit a nontrivial ultraviolet fixed point in addition to a trivial infrared fixed point. The strong coupling behavior of the theory suggests the possible existence of additional relevant operators or nonperturbative degrees of freedom.Comment: 9 pages, LaTeX, 1 eps figur

Measurement of vertical velocity using clear-air Doppler radars

A new clear air Doppler radar was constructed, called the Flatland radar, in very flat terrain near Champaign-Urbana, Illinois. The radar wavelength is 6.02 m. The radar has been measuring vertical velocity every 153 s with a range resolution of 750 m almost continuously since March 2, 1987. The variance of vertical velocity at Flatland is usually quite small, comparable to the variance at radars located near rough terrain during periods of small background wind. The absence of orographic effects over very flat terrain suggests that clear air Doppler radars can be used to study vertical velocities due to other processes, including synoptic scale motions and propagating gravity waves. For example, near rough terrain the shape of frequency spectra changes drastically as the background wind increases. But at Flatland the shape at periods shorter than a few hours changes only slowly, consistent with the changes predicted by Doppler shifting of gravity wave spectra. Thus it appears that the short period fluctuations of vertical velocity at Flatland are alsmost entirely due to the propagating gravity waves