Dynamic Trap Formation and Elimination in Colloidal Quantum Dots.

Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping.

Indolent T-cell large granular lymphocyte leukaemia after haematopoietic SCT: a clinicopathologic and molecular analysis.

Four women and three men after allogeneic (n=4) and autologous (n=3) haematopoietic SCT (HSCT) were observed to have an increase in T-cell large granular lymphocytes (T-LGLs) of CD3+CD8+ phenotype for a median of 41 (15-118) months. Clonal rearrangement of the T-cell receptor gene was verified by two PCR techniques and direct DNA sequencing, confirming that the cases were neoplastic and therefore classifiable as T-LGL leukaemia. In the allogeneic HSCT cases, T-LGL leukaemia was derived from donor T cells in three patients, as shown by DNA chimerism analysis, and recipient T cells in one patient who had graft failure previously. None of the patients showed cytopenia, autoimmune phenomenon or organ infiltration, which were features typical of de novo T-LGL leukaemia. Six patients had remained asymptomatic with stable large granular lymphocyte counts. One patient died from cerebral relapse of the original lymphoma. T-LGL leukaemias occurring post-HSCT are distinct from de novo T-LGL leukaemia and may have a different pathogenesis and clinical course. Patients did not require specific treatment, and the disease remained stable for long periods.

Quality monitoring of haemapheresis platelet concentrates: sampling in EDTA helps with the standardization and improves the consistency.

At the North London Blood Transfusion Centre, all haemapheresis platelet concentrates (PC) are tested in duplicate by a Technicon H-1 analyser to provide accurate information on the cell separator performance and on the cellular content of packs before issue. Repeated counting on fresh samples (within 4 h) reveals spontaneous aggregation (SA), which causes inconsistency in the estimated platelet yields and invalidates the cellular indices. Preliminary work showed that sampling into EDTA eliminated SA. Further studies on the effect of EDTA were undertaken as follows: (i) using the same PCS preparations (n = 7) stored conventionally and sampled daily in tubes with and without EDTA, and (ii) using fresh V50 and CS3000 PC to assess the difference on samples routinely collected in EDTA tubes for 2 months compared to those collected without EDTA in the previous 2 months. EDTA improved concordance of duplicate counts in fresh products. The increase in platelet yield in V50 and CS3000 preparations (12-22% respectively) was associated with a concomitant decrease (60-74%) in erythrocyte contamination. The variation in leucocyte count (3-5%) was less pronounced but the percentage differential was affected. There was also a systematic increase (8-11%) in mean platelet volume (MPV) due to EDTA. In PCS preparations the EDTA-induced variation in the cellular indices remained essentially in the same order (2-6%), while the MPV decreased progressively on storage. The difference in MPV can be used to assess the storage stability of various PC preparations. The implication of a double sampling technique (CPDA-1 and EDTA/CPDA-1) in the quality monitoring of haemapheresis procedures is substantial.

Characteristics of platelet concentrates, with particular reference to Autopheresis C Plateletcell: correlation between dMPV and other tests for platelet function.

The quality of platelet concentrates (PC) collected by the Autopheresis C cell separator was assessed in two Regional Transfusion Centres taking part in a multicentre study. This study also enabled the assessment of a new simple, rapid test of platelet function and comparison with more established tests, such as aggregation to adenosine diphosphate, as a tool for the quality testing of PC. The new test, based upon the measurement of mean platelet volume using automated haematological cell analysers, is rapid and uses the same samples as those used to estimate the platelet and leucocyte content of the concentrates. The high correlation between this test and the other tests of platelet function used in the study suggests that it is an ideal tool in the quality testing of platelet concentrates.