Analysis of formulas for calculating the main characteristics of backscattered electrons and how they compare to experimental results

Semiempirical relations for the following basic parameters of backscattered electrons in a scanning electron microscope are derived: reflection coefficient; average and most probable energies; energy spectra; and energy of backscattered electrons, depending on the angle of exit. The energy dependence is shown to have a maximum in the angular region of backscattered electrons Θ = 65°–75°.     

Spinal effects of acupuncture stimulation assessed by proton density-weighted functional magnetic resonance imaging at 0.2 T

Signal changes can be detected by proton density-weighted functional imaging in both the brain and the spinal cord. These are attributed to changes in extravascular water proton (signal enhancement by extravascular protons) density during neuronal activation. In this study, we used this technique to detect correlations between acupoint stimulation and neural activity in the spinal cord. Stimulation of acupoints associated with treatment of sensorimotor deficits (LI4 and LI11) was performed on 11 volunteers. During stimulation, 8 of the 11 subjects had consistent functional activations in C6/C7. A bilateral activation pattern was common. Our findings show that acupoint stimulation modulates activity in the spinal cord.     

Thickness dependence of exciton absorption in pure GaAs crystals at the “prequantum” limit

The optical absorption of GaAs crystals with thicknesses d=0.4−4.4 μm is measured in the exciton-polariton resonance region at a temperature of 1.7 K. As the thickness is reduced, both a broadening of the exciton line and increased absorption with a negligible Stark shift are observed. The way the absorption spectra vary with crystal thickness is examined in terms of a competition between two regions for light-exciton interactions in the crystal: in the field of surface charges and electric-field free. Fiz. Tverd. Tela (St. Petersburg) 40, 869–871 (May 1998)     

Suppressing ringing caused by large photomultiplier tube signals

We describe here the characteristic features of the ringing we observed following large PMT signals in the Daya Bay reactor antineutrino experiment. We conclude that the ceramic capacitors used in the circuitry of the PMT bases and the HV-signal decouplers are the primary cause for this ringing. We present some possible schemes to reduce the ringing when replacing these ceramic capacitors is not feasible.     

Influence of solute mobility on dislocation motion I. Basic model

Dislocation motion in the real lattice of alloys is highly complex. In a certain temperature range the dynamic strain ageing phenomena have been reported. In this paper the influence of mobile solute atoms (as obstacles) on the motion of dislocation is analysed. Both processes are assumed to be thermally activated. A new model based on this assumption is proposed. The dislocation velocity and the friction stress (due to solute-dislocation interactions) are calculated. A change in the friction stress caused by solute mobility is discussed.     

High-power optical parametric chirped-pulse amplifier system with a 1.55 microm signal and a 1.064 microm pump

We have designed and built a chirped-pulse parametric-amplifier system that utilizes a 10 Hz, 300 ps, Nd:YAG pump laser system; a 1.575 microm fiber oscillator and amplifier as the signal source; and rubidium titanyl phosphate and potassium titanyl arsenate nonlinear crystals. We obtained 260 fs, 30 mJ pulses centered at 1.550 microm, representing a gain of > 10(9) and a peak power of 100 GW. To our knowledge, these are the highest energy and peak power pulses ever produced in the 1.5-2.0 microm region     

First results from KamLAND: evidence for reactor antineutrino disappearance

KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.