We report on the observation of quantized conductance up to 10 K in epitaxially regrown, heterostructurally defined, 100-nm-wide Ga0.25In0.75As/InP quantum wires. In addition to the plateaus at integer steps of 2e2/h, we observe plateaus at 0.2(2e2/h), 0.7(2e2/h), and 1.5(2e2/h), indicating spin polarization at zero magnetic field. Of these, the first two plateaus appear to evolve into one at around 0.5(2e2/h) when the sample is subjected to a magnetic field parallel to the quantum wire. The observation of quantized conductance is made possible by the substantial improvement in the quality of the interface by regrowth.

Gastrointestinal tract failure may be involved in the development of systemic septic complications in acute pancreatitis. Systemic and intestinal circulation, intestinal permeability and absorptive function were evaluated in the early course of acute pancreatitis induced in rats by retrograde intraductal injection of 0.2 ml of 5 per cent sodium taurodeoxycholate and 0.4 nmol trypsin. A decrease in systemic arterial pressure and intestinal blood flow and an increase in intestinal permeability as measured by the leakage of 125I-labelled human serum albumin from blood to lumen were noted in the distal ileum and colon, reaching statistically significant differences 6 h after induction of pancreatitis. The transport of small molecular markers (sodium fluorescein and 51Cr-labelled ethylenediamine tetra-acetic acid) through the distal ileum and colon in vitro from the mucosal to the serosal site in Ussing chambers significantly increased in the early periodic (20-60 min) of incubation, while the passage of a macromolecular marker (ovalbumin) demonstrated a definite increase at 60-120 min of incubation. D-Xylose absorption from the gut lumen to the portal vein was significantly less in acute pancreatitis than after sham operation. Intravenous administration of the hydroxyl radical scavenger dimethylsulphoxide prevented the compromised intestinal permeability and gut absorptive capacity induced by acute pancreatitis, but did not affect the reduced arterial pressure and intestinal microcirculation. Cytotoxic oxygen-derived free radicals may contribute to the development of alterations in intestinal permeability and absorptive function found in the early stage of acute pancreatitis in the rat.

We report on edge state transport in a ternary material, a modulation-doped InP/Ga0.25In0.75As/InP quantum well, where the electron transport takes place in the highly strained Ga0.25In0.75As layer. The electron mobility is, even though fundamentally limited by alloy-disorder scattering, determined by the two-dimensional electron concentration. By varying the distance between the modulation-doped layer and the two-dimensional electron gas we influence the single particle relaxation time but not the electron mobility. Special attention is paid to the effect of dislocation formation in the conducting Ga0.25In0.75As layer. In addition to the quantum Hall and the Shubnikov–de Haas effect a strong, nonlocal transport behavior, which is maintained after illumination, is observed. This effect is explained by the low defect density and the Fermi level pinning on the etched Ga0.25In0.75As surface, at an energy close to the same as the Fermi energy of the two-dimensional electron gas. Furthermore, overshoot effects of the quantum Hall plateaus introduced by the high and varying effective (many-body) g value are investigated. The g value is further addressed in an experiment on a wet etched quantum wire in which values enhanced up to around 45 were found.

Experimental colitis was induced in the rat, by ethanol-oxazolone injections into the distal colon, resulting in diarrhea together with edema, ulcers, and cell infiltration in the exposed colon. Colitic rats showed an elevated urinary recovery of the permeability marker [51Cr]EDTA after intragastric feeding, 19 +/- 10%, compared to 2.9 +/- 0.7% for control rats (P < 0.001). An increased retention of [51Cr]EDTA in the intestines and a decreased discharge in feces suggested an increased intestinal transit time in colitic rats. The in vitro permeability to [51Cr]EDTA and ovalbumin was not elevated in the severely inflamed distal colon, but was in the proximal, unaffected colon to ovalbumin (P < 0.05) and in the distal small intestine, to both [51Cr]EDTA (P < 0.01) and ovalbumin (P < 0.05), indicating that an inflammation in one part of the intestine could have permeability effects in other remote parts. In conclusion, the increased [51Cr]EDTA absorption in vivo during colitis was probably due to both an increased permeability and an increased intestinal transit time.

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