High-Statistics Measurement of Neutrino Quasielasticlike Scattering at 6 GeV on a Hydrocarbon Target.

We measure neutrino charged-current quasielasticlike scattering on hydrocarbon at high statistics using the wideband Neutrinos at the Main Injector beam with neutrino energy peaked at 6 GeV. The double-differential cross section is reported in terms of muon longitudinal (p_{∥}) and transverse (p_{⊥}) momentum. Cross section contours versus lepton momentum components are approximately described by a conventional generator-based simulation, however, discrepancies are observed for transverse momenta above 0.5 GeV/c for longitudinal momentum ranges 3-5 and 9-20 GeV/c. The single differential cross section versus momentum transfer squared (dσ/dQ_{QE}^{2}) is measured over a four-decade range of Q^{2} that extends to 10 GeV^{2}. The cross section turnover and falloff in the Q^{2} range 0.3-10 GeV^{2} is not fully reproduced by generator predictions that rely on dipole form factors. Our measurement probes the axial-vector content of the hadronic current and complements the electromagnetic form factor data obtained using electron-nucleon elastic scattering. These results help oscillation experiments because they probe the importance of various correlations and final-state interaction effects within the nucleus, which have different effects on the visible energy in detectors.

Aversive stimulus differentially triggers subsecond dopamine release in reward regions.

Aversive stimuli have a powerful impact on behavior and are considered to be the opposite valence of pleasure. Recent studies have determined some populations of ventral tegmental area (VTA) dopaminergic neurons are activated by several types of aversive stimuli, whereas other distinct populations are either inhibited or unresponsive. However, it is not clear where these aversion-responsive neurons project, and whether alterations in their activity translate into dopamine release in the terminal field. Here we show unequivocally that the neurochemical and anatomical substrates responsible for the perception and processing of pleasurable stimuli within the striatum are also activated by tail pinch, a classical painful and aversive stimulus. Dopamine release is triggered in the dorsal striatum and nucleus accumbens (NAc) core by tail pinch and is time locked to the duration of the stimulus, indicating that the dorsal striatum and NAc core are neural substrates, which are involved in the perception of aversive stimuli. However, dopamine is released in the NAc shell only when tail pinch is removed, indicating that the alleviation of aversive condition could be perceived as a rewarding event.

Fast vesicle transport in PC12 neurites: velocities and forces.

Although the mechanical behavior of single-motor protein molecules such as kinesin has been carefully studied in buffer, the mechanical behavior of motor-driven vesicles in cells is much less understood. We have tracked single vesicles in neurites of PC12 cells with a spatial precision of +/-30 nm and a time resolution of 120 ms. Because the neurites are thin, long, straight, and attached to the surface of planar cover glasses, the velocity of individual vesicles could be measured for times as long as 15 s and distances as long as 15 mum. The velocity of anterograde vesicles was in most cases constant for periods of 1-2 s, then changed in a step-like fashion to a new constant velocity. The viscoelastic modulus felt by the vesicles within live PC12 cells was determined from the Brownian motion, using Mason's generalization of the Stokes-Einstein equation. From Stokes' law, the drag force at the smallest sustained velocity was 4.2+/-0.6 pN for vesicles of radius 0.30-0.40 mum, about half the maximum force which conventional kinesin can develop during bead assays in buffer. We interpret the observed velocity steps as changes of +/-1 or occasionally +/-2 in the number of active motor proteins dragging that vesicle along a microtubule. Assuming that the motor is conventional kinesin, which hydrolyzes one ATP per 8 nm step along the microtubule, the motor protein efficiency in PC12 neurites is approximately 35%.

Absolute two-photon cross section of Rb measured by differential absorption.

We applied a simple, sensitive differential absorption technique to measure the two-photon cross section for the 5(2)S((1/2))(F(g) = 2) ? 5(2)D(5/2)(F(e) = 4) hyperfine transition in (85)Rb [sigma((2)) = (1.2 +/- 0.5) x 10(-18) cm(4)/W]. The detection circuit permitted straightforward measurements close to the shot-noise limit. Detailed quantitative analysis of the measurements shows excellent agreement with theory.

Simple diffuser for production of laser speckle.

A passive optical element that is a simple, inexpensive, and effective way for producing laser speckle is described. The optical element, a random phase plate, was developed in our laboratory. The statistics of the speckle pattern it produces were measured and are discussed in this paper. The phase plate was used to produce a speckled beam using a 5-mW cw He-Ne laser with a Gaussian beam profile and using a pulsed Nd:YAG laser with a nonuniform intensity profile for which the mean intensity was 10(9) W/cm(2).

Two-photon resonant upconversion in xenon.

Coherent radiation at various VUV wavelengths, e.g., 125.9, 126.1, and 125.4 nm, has been generated through fourwave mixing processes enhanced by two-photon resonances in xenon. Maximum efficiencies of the order of 10(-4) were achieved. Maximum output intensities of difference generation (2omega(1) - omega(2)) for 7p[0 (1/2)](0), 7p[1 (1/2)](2), and 6p' [1 (1/2)](2) resonant states occurred at xenon pressures of 24, 12.5, and 4 Torr, corresponding to values of phase mismatch per atom of 1.2 x 10(-18), 2.3 x 10(-18), and 7.1 x 10(-18) esu, respectively. Parametric generation at 117.0 nm through the 7s[1(1/2)](0)(1) state was also observed.