Improved imaging techniques within the last 20 years have enabled the preoperative diagnosis of one quarter of patients with gallbladder torsion. With prompt surgical intervention, the condition has an excellent prognosis.
There is controversy as to whether a one-dimensional (1D) electron gas can spin polarize in the absence of a magnetic field. Together with a simple model, we present conductance measurements on ultra-low-disorder quantum wires supportive of a spin polarization at B=0. A spin energy gap is indicated by the presence of a feature in the range (0.5-0.7)x2e(2)/h in conductance data. Importantly, it appears that the spin gap is not constant but a function of the electron density. Data obtained using a bias spectroscopy technique are consistent with the spin gap widening further as the Fermi level is increased.
Zero length quantum wires (or point contacts) exhibit unexplained conductance structure close to 0.7 × 2e 2 /h in the absence of an applied magnetic field. We have studied the density-and temperature-dependent conductance of ultra-low-disorder GaAs/AlGaAs quantum wires with nominal lengths l=0 and 2µm, fabricated from structures free of the disorder associated with modulation doping. In a direct comparison we observe structure near 0.7 × 2e 2 /h for l=0 whereas the l = 2µm wires show structure evolving with increasing electron density to 0.5 × 2e 2 /h in zero magnetic field, the value expected for an ideal spin-split sub-band. Our results suggest the dominant mechanism through which electrons interact can be strongly affected by the length of the 1D region.73.61.-r, 73.23.Ad, 73.61.Ey III-V
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