Surface compositional gradients of InAs/GaAs quantum dots

With laterally resolved photoemission spectroscopy, we obtained In and Ga surface concentration maps of InAs/GaAs quantum dots. Our data demonstrate that the dot composition is neither pure InAs nor homogeneous InxGa1-xAs, but presents an In concentration increasing from the borders to the center of the dots. Besides, our observations suggest strong In segregation (x similar to 0.9) on the surface of the dots and of the surrounding wetting layer. Such segregation, well known for two-dimensional InAs/GaAs growth, had not been directly observed so far on the dots, and should be taken into account to model size and composition of GaAs-overgrown structures

On-line predilution hemofiltration versus ultrapure high-flux hemodialysis: a multicenter prospective study in 23 patients

The aims of the present prospective multicenter study were to assess the clinical tolerance and well being, the correlation between nPCr and Kt/V and the pretreatment β2-microglobulin level in patients sequentially treated with high-flux dialysis with ultrapure bicarbonate hemodialysis (HD; phase I) and predilution hemofiltration (HF) with on-line prepared bicarbonate substitution fluid (phase II). The same monitor (Gambro AK 100 ULTRA) and membrane (polyamide) were used. Twenty-three patients, all in a stable clinical condition, entered the study. The treatment was targeted to an equilibrated Kt/V (eqKt/V) of 1.4 for HD and 1.0 for HF. No mortality or relevant morbidity were observed. The number of hypotensive episodes was 1.78 ± 2.8 per patient and month during HD vs. 1.17 ± 3.1 during HF (p = 0.003) and the number of the hypertensive episodes 1.28 ± 2.8 during HD vs. 0.42 ± 0.8 during HF (p = 0.04). Incidences of arrhythmia, muscular cramps and headache were significantly less frequent during HF. Interdialytic cramps, arthralgia and fatigue were also significantly less frequent during the HF period. The average β2-microglobulin level was 27.1 ± 14.7 mg/dl at the start of the study, 22.9 ± 4.9 mg/dl at the beginning of phase II and 22.4 ± 4 mg/dl at the end of phase II (p = 0.01 compared to the start). A significant linear correlation between the normalized protein catabolic rate and eqKt/V was obtained faster during HD than during HF (45 vs. 120 days) indicating that HF affects the nutritional status with mechanisms different from HD. The present study is in agreement with the hypothesis that HF gives an adequate nutritional status with improved clinical stability and well being at a lower Kt/V compared to HD. Both therapies were efficient in controlling the pretreatment β2-microglobulin level.RH release