Ground Band and a Generalized GP-equation for Spinor Bose-Einstein Condensates

For the spinor Bose-Einstein condensates both the total spin $S$ and its Z-component $S_{Z}$ should be conserved. However, in existing theories, only the conservation of $S_{z}$ has been taken into account. To remedy, this paper is the first attempt to take the conservation of both $$ and $S_{Z}$ into account. For this purpose, a total spin-state with the good quantum numbers $S$ and $S_{Z}$ is introduced in the trial wave function, thereby a generalized Gross-Pitaevskii equation has been derived. With this new equation, the ground bands of the $^{23}$Na and $$Rb condensates have been studied, where the levels distinct in $S$ split. It was found that the level density is extremely dense in the bottom of the ground band of $^{23}$Na, i.e., in the vicinity of the ground state. On the contrary, for $^{87}$Rb, the levels are extremely dense in the top of the ground band,Comment: 7 page, 5 figure

An east-west asymmetry in the solar wind velocity

East-west asymmetry in solar wind velocit

First excited band of a spinor Bose-Einstein condensate

The analytical expression of the fractional parentage coefficients for the total spin-states of a spinor N-boson system has been derived. Thereby an S-conserved theory for the spinor Bose-Einstein condensation has been proposed. A set of equations has been established to describe the first excited band of the condensates. Numerical solution for $^{23}$Na has been given as an example.Comment: 6 pages, 3 figure

Measuring the eccentricity of the Earth orbit with a nail and a piece of plywood

I describe how to obtain a rather good experimental determination of the eccentricity of the Earth orbit, as well as the obliquity of the Earth rotation axis, by measuring, over the course of a year, the elevation of the Sun as a function of time during a day. With a very simple "instrument" consisting of an elementary sundial, first-year students can carry out an appealing measurement programme, learn important concepts in experimental physics, see concrete applications of kinematics and changes of reference frames, and benefit from a hands-on introduction to astronomy.Comment: 12 pages, 6 figure

AlGaAs heterojunction lasers

The characterization of 8300 A lasers was broadened, especially in the area of beam quality. Modulation rates up to 2 Gbit/sec at output powers of 20 mW were observed, waveform fidelity was fully adequate for low BER data transmission, and wavefront measurements showed that phase aberrations were less than lamda/50. Also, individually addressable arrays of up to ten contiguous diode lasers were fabricated and tested. Each laser operates at powers up to 30 mW CW in single spatial mode. Shifting the operating wavelength of the basic CSP laser from 8300 A to 8650 A was accomplished by the addition of Si to the active region. Output power has reached 100 mW single mode, with excellent far field wave front properties. Operating life is currently approx. 1000 hrs at 35 mW CW. In addition, laser reliability, for operation at both 8300 A and 8650 A, has profited significantly from several developments in the processing procedures

Observations of plasma dynamics in the coma of P/Halley by the Giotto Ion Mass Spectrometer

Observations in the coma of P/Halley by the Giotto Ion Mass Spectrometer (IMS) are reported. The High Energy Range Spectrometer (HERS) of the IMS obtained measurements of protons and alpha particles from the far upstream region to the near ionopause region and of ions from mass 12 to 32 at distances of about 250,000 to 40,000 km from the nucleus. Plasma parameters from the High Intensity Spectrometer (HIS) of the IMS obtained between 150,000 to 5000 km from the nucleus are also discussed. The distribution functions of water group ions (water group will be used to refer to ions of 16 to 18 m/q, where m is in AMU and q is in unit charges) are observed to be spherically symmetric in velocity space, indicating strong pitch angle scattering. The discontinuity known as the magnetic pile-up boundary (MPB) is apparent only in proton, alpha, and magnetometer data, indicating that it is a tangential discontinuity of solar wind origin. HERS observations show no significant change in the properties of the heavy ions across the MPB. A comparison of the observations to an MHD model is made. The plasma flow directions at all distances greater than 30,000 km from the nucleus are in agreement with MHD calculations. However, despite the agreement in flow direction, within 200,000 km of the nucleus the magnitude of the velocity is lower than predicted by the MHD model and the density is much larger (a factor of 4). Within 30,000 km of the nucleus there are large theoretical differences between the MHD model flow calculations for the plane containing the magnetic field and for the plane perpendicular to the magnetic field. The observations agreed much better with the pattern calculated for the plane perpendicular to the magnetic field. The data obtained by the High Energy Range Spectrometer (HERS) of the IMS that are published herein were provided to the International Halley Watch archive

Observations of solar wind ion charge exchange in the comet Halley coma

Giotto Ion Mass Spectrometer/High Energy Range Spectrometer (IMS/HERS) observations of solar wind ions show charge exchange effects and solar wind compositional changes in the coma of comet Halley. As the comet was approached, the He(++) to proton density ratio increased until about 1 hour before closest approach after which time it decreased. Abrupt increases in this ratio were also observed in the beginning and near the end of the so-called Mystery Region (8.6 - 5.5(10)(exp 5) km from the comet along the spacecraft trajectory). These abrupt increases in the density ratio were well correlated with enhanced fluxes of keV electrons as measured by the Giotto plasma electron spectrometer. The general increase and then decrease of the He(++) to proton density ratio is quantitatively consistent with a combination of the addition of protons of cometary origin to the plasma and loss of plasma through charge exchange of protons and He(++). In general agreement with the solar wind proton and He(++) observations, solar wind oxygen and carbon ions were observed to charge exchange from higher to lower charge states with decreasing distance to the comet. The more abrupt increases in the He(++) to proton and the He(++) to O(6+) density ratios in the mystery region require a change in the solar wind ion composition in this region while the correlation with energetic electrons indicates processes associated with the comet

Kinesin Light Chains Are Essential for Axonal Transport in Drosophila

Kinesin is a heterotetramer composed of two 115-kD heavy chains and two 58-kD light chains. The microtubule motor activity of kinesin is performed by the heavy chains, but the functions of the light chains are poorly understood. Mutations were generated in the Drosophila gene Kinesin light chain (Klc), and the phenotypic consequences of loss of Klc function were analyzed at the behavioral and cellular levels. Loss of Klc function results in progressive lethargy, crawling defects, and paralysis followed by death at the end of the second larval instar. Klc mutant axons contain large aggregates of membranous organelles in segmental nerve axons. These aggregates, or organelle jams (Hurd, D.D., and W.M. Saxton. 1996. Genetics. 144: 1075-1085), contain synaptic vesicle precursors as well as organelles that may be transported by kinesin, kinesin-like protein 68D, and cytoplasmic dynein, thus providing evidence that the loss of Klc function blocks multiple pathways of axonal transport. The similarity of the Klc and Khc ((Saxton et al. Cell 64:1093-1102; Hurd, D.D., and W.M. Saxton. 1996. Genetics 144: 1075-1085) mutant phenotypes indicates that KLC is essential for kinesin function, perhaps by tethering KHC to intracellular cargos or by activating the kinesin motor