Sine-Gordon Soliton on a Cnoidal Wave Background

The method of Darboux transformation, which is applied on cnoidal wave solutions of the sine-Gordon equation, gives solitons moving on a cnoidal wave background. Interesting characteristics of the solution, i.e., the velocity of solitons and the shift of crests of cnoidal waves along a soliton, are calculated. Solutions are classified into three types (Type-1A, Type-1B, Type-2) according to their apparent distinct properties.Comment: 11 pages, 5 figures, Contents change

Pairing without Superfluidity: The Ground State of an Imbalanced Fermi Mixture

Radio-frequency spectroscopy is used to study pairing in the normal and superfluid phases of a strongly interacting Fermi gas with imbalanced spin populations. At high spin imbalances the system does not become superfluid even at zero temperature. In this normal phase full pairing of the minority atoms is observed. This demonstrates that mismatched Fermi surfaces do not prevent pairing but can quench the superfluid state, thus realizing a system of fermion pairs that do not condense even at the lowest temperature

Tomographic RF Spectroscopy of a Trapped Fermi Gas at Unitarity

We present spatially resolved radio-frequency spectroscopy of a trapped Fermi gas with resonant interactions and observe a spectral gap at low temperatures. The spatial distribution of the spectral response of the trapped gas is obtained using in situ phase-contrast imaging and 3D image reconstruction. At the lowest temperature, the homogeneous rf spectrum shows an asymmetric excitation line shape with a peak at 0.48(4)$\epsilon_F$ with respect to the free atomic line, where $\epsilon_F$ is the local Fermi energy

A theoretical and numerical approach to "magic angle" of stone skipping

We investigate oblique impacts of a circular disk and water surface. An experiment [ Clanet, C., Hersen, F. and Bocquet, L., Nature 427, 29 (2004) ] revealed that there exists a "magic angle" of 20 [deg.] between a disk face and water surface which minimize the required speed for ricochet. We perform 3-dimensional simulation of the water impacts using the Smoothed Particle Hydrodynamics (SPH) and analyze the results with an ordinal differential equation (ODE) model. Our simulation is in good agreement with the experiment. The analysis with the ODE model give us a theoretical insight for the ``magic angle" of stone skipping.Comment: 4 pages, 4figure

Comparison of satellite-derived sea surface temperatures with in situ skin measurements

Sea surface temperatures (SSTs), computed from sensor systems on the National Oceanographic and Atmospheric Administration (NOAA) polar-orbiting satellites, are compared with surface skin temperatures (from an infrared radiometer mounted on a ship) and subsurface temperature measurements. Three split window retrieval methods using channels 4 and 5 of the NOAA 7 advanced very high resolution radiometer (AVHRR) sensor were investigated. These methods were (1) using AVHRR alone, (2) using AVHRR with atmospheric temperature and water vapor profiles from the TIROS operational vertical sounder (TOVS), and (3) using AVHRR and data from the high-resolution infrared sounder (HIRS). TOVS sensors (including HIRS) are carried by the same satellite as the AVHRR and provide simultaneous corrections for the AVHRR-based SST estimates. The importance of scan angle correction to define the correct atmospheric path is discussed, and the improvement of SST retrievals using sensor combinations is demonstrated with satellite versus ship skin temperature mean differences ranging from 0.55° to 0.73°C for AVHRR alone, from -0.39°to 0.71°C for AVHRR plus TOVS, and from 0.22°to 0.33°C for AVHRR plus HIRS. The improved SST accuracy by AVHRR plus HIRS is due to additional correction for the atmospheric water vapor and temperature structures, made possible with some of the HIRS channels. Significant differences between ship skin and subsurface temperatures were observed, with the mean deviation being 0.2°C for a range of temperature differences between -0.25°and 0.6°C. © Copyright 1987 by the American Geophysical Union

Degeneration and impaired regeneration of gray matter oligodendrocytes in amyotrophic lateral sclerosis.

Oligodendrocytes associate with axons to establish myelin and provide metabolic support to neurons. In the spinal cord of amyotrophic lateral sclerosis (ALS) mice, oligodendrocytes downregulate transporters that transfer glycolytic substrates to neurons and oligodendrocyte progenitors (NG2(+) cells) exhibit enhanced proliferation and differentiation, although the cause of these changes in oligodendroglia is unknown. We found extensive degeneration of gray matter oligodendrocytes in the spinal cord of SOD1 (G93A) ALS mice prior to disease onset. Although new oligodendrocytes were formed, they failed to mature, resulting in progressive demyelination. Oligodendrocyte dysfunction was also prevalent in human ALS, as gray matter demyelination and reactive changes in NG2(+) cells were observed in motor cortex and spinal cord of ALS patients. Selective removal of mutant SOD1 from oligodendroglia substantially delayed disease onset and prolonged survival in ALS mice, suggesting that ALS-linked genes enhance the vulnerability of motor neurons and accelerate disease by directly impairing the function of oligodendrocytes

Observation of Phase Separation in a Strongly-Interacting Imbalanced Fermi Gas

We have observed phase separation between the superfluid and the normal component in a strongly interacting Fermi gas with imbalanced spin populations. The in situ distribution of the density difference between two trapped spin components is obtained using phase-contrast imaging and 3D image reconstruction. A shell structure is clearly identified where the superfluid region of equal densities is surrounded by a normal gas of unequal densities. The phase transition induces a dramatic change in the density profiles as excess fermions are expelled from the superfluid.Comment: 5 pages, 7 figure