Developing an optimal river typology for biological elements within the Water Framework Directive

The Water Framework Directive requires a river classification based on environmental variables (a typology) to be created as a structure for reporting ecological status. A single permutation procedure, utilising the same variables repeatedly but with different categorical divisions, enabled both the choice of variables and the boundary divisions for these variables to be optimised simultaneously in the development of the typology. This, in addition to a data set which appropriately combined different biological elements, enabled a typology to be developed which was far more effective than a System A, CCA-derived or expert opinion-based typology in segregating communities. This optimal typology could be used to improve the performance of ecological quality assessment methods.     

Outstanding problems posed by nonpolymeric particulates in the synthesis of a well-structured geopolymeric material

In the conventional geopolymer synthesis of ternary reactants system of silicate anions [Na₂O·2SiO₂], metakaolin [Al₂O₃·2SiO₂] and aqueous alkali [Na₂O], the SiO₂/Al₂O₃ molar ratio can only be varied from ∼2 to 8. For geopolymerisation to occur, the minimum mole percentage of metakaolin reactant is about 25% and the maximum mole percentage of Na₂O content is about 30%. As the reduction of metakaolin and increase of alkali content is limited, the total conversion of metakaolin into polymeric material is uncertain. The identification of the presence or absence of metakaolin in the cured geopolymer product is not possible in this synthesis of a ternary reactant system even by ²⁹Si NMR, as the signal due to metakaolin is indistinguishable from a broad ²⁹Si NMR peak consisting of many resonance lines of polymer network of cross-linked Si/Al tetrahedra.With our modified synthesis method employing colloidal SiO₂ as an additional component, the metakaolin content is decreased while keeping an optimum amount of Na₂O, thereby increasing the compositional SiO₂/Al₂O₃ molar ratio. In this case, the signals related to Al-substituted SiO₄ tetrahedra are reduced, indicating the reduction of Al-substituted SiO₄ tetrahedra in the polymer network, resulting in better-resolved ²⁹Si NMR lines. The ²⁹Si NMR signal related to metakaolin is then distinguishable in the spectra of cured products by observing a series of samples with 11, 7, 5 and 3 mol% of metakaolin reactant. ²⁹Si NMR signal related to metakaolin was only absent in the spectra of cured product when metakaolin reactant content is ≤5 mol%; that is, the compositional SiO₂/Al₂O₃ molar ratio is ≥20.     

Digital sinusoidal PWMs for a micro-controller based single-phase inverter,Part 2: Performance assessment–experimental

The performance, including efficiency, harmonics and dead-time effect of the three major digital sinusoidal pulse width modulations (DSPWMs) presented in Part 1 are investigated in this study using a 2 kVA single-phase full-bridge inverter. Each DSPWM is implemented using a low-cost 8-bit micro-controller and the effect of different switching frequencies on the inverter performance is analysed and the inverter switching, conduction and transformer losses investigated. The experimental results confirm the validity of the mathematical and simulation analysis presented in Part 1. The work shows that the type of DSPWM used for a single-phase full-bridge inverter and the switching frequency selected can have a significant effect on the inverter performance and that switch and transformer losses make up the majority of the inverter losses.     

Frequency and clinical significance of cytogenetic abnormalities in pediatric T-lineage acute lymphoblastic leukemia: a report from the Children's Cancer Group

PURPOSE: Nonrandom chromosomal translocations are frequently observed in pediatric patients with acute lymphoblastic leukemia (ALL). Specific translocations, such as t(4;11) and t(9;22), identify subgroups of B-lineage ALL patients who have an increased risk of treatment failure. The current study was conducted to determine the prognostic significance of chromosomal translocations in T-lineage ALL patients. MATERIALS AND METHODS: The study included 169 children with newly diagnosed T-lineage ALL enrolled between 1988 and 1995 on risk-adjusted protocols of the Children's Cancer Group (CCG) who had centrally reviewed cytogenetics data. Outcome analyses used standard life-table methods. RESULTS: Presenting features for the current cohort were similar to those of concurrently enrolled patients for whom cytogenetic data were not accepted on central review. The majority of patients (80.5%) were assigned to CCG protocols for high-risk ALL and 86.4% had pseudodiploid (n = 80) or normal diploid (n = 66) karyotypes; modal chromosome number was not a significant prognostic factor. Overall, 103 of 169 (61%) patients had an abnormal karyotype, including 31 with del(6q), 29 with 14q11 breakpoints, 15 with del(9p), 11 with trisomy 8, nine with 11q23 breakpoints, nine with 14q32 translocations, and eight with 7q32-q36 breakpoints. Thirteen patients had the specific 14q11 translocation t(11;14)(p13;q11) and all were classified as poor risk. Patients with any of these translocations had outcomes similar to those with normal diploid karyotypes. CONCLUSION: Chromosomal abnormalities, including specific nonrandom translocations, were frequently observed in a large group of children with T-lineage ALL, but were not significant prognostic factors for this cohort. Thus, contemporary intensive treatment programs result in favorable outcomes for the majority of T-lineage ALL patients, regardless of karyotypic abnormalities, and such features do not identify patients at higher risk for relapse.     

Augmented Berlin-Frankfurt-Munster therapy abrogates the adverse prognostic significance of slow early response to induction chemotherapy for children and adolescents with acute lymphoblastic leukemia and unfavorable presenting features: a report from the Children's Cancer Group

PURPOSE: Compared with previous Children's Cancer Group (CCG) acute lymphoblastic leukemia (ALL) trials, therapy based on the Berlin-Frankfurt-Munster (BFM) 76 trial has effected an improvement in event-free survival (EFS). In an attempt to improve EFS further, CCG investigators formulated an augmented BFM (A-BFM) regimen that provides prolonged, intensified postinduction chemotherapy relative to the CCG-modified BFM regimen. PATIENTS AND METHODS: We tested A-BFM in 101 patients with ALL and unfavorable presenting features that showed slow early response (SER) to induction therapy who attained remission on day 28. Their outcome was compared with that of 251 concurrent patients with unfavorable presenting features, a rapid early response to therapy (RER), and remission by day 28, treated with CCG-BFM with or without cranial radiation (CRT). RESULTS: The 4-year EFS rate from the end of induction for SER patients treated with A-BFM was 70.8% +/- 4.6%. Seventeen patients remain in continuous remission beyond 5 years. Vincristine (VCR) neurotoxicity developed in 50% of patients, but was rarely debilitating. Allergies to Escherichia coli L-asparaginase (L-ASP) occurred in 35% of patients. Avascular necrosis of bone (AVN) developed in 9% of patients. In comparison, a concurrent RER group treated with standard BFM +/- CRT had a 4-year EFS rate of 73.1% +/- 4.6%. CONCLUSION: The toxicity of A-BFM is significant, but acceptable. Compared with historical control SER patients treated with CCG-modified BFM, A-BFM therapy appears to produce a significant improvement in EFS. This is the first study to show that intensive chemotherapy, as given in the A-BFM regimen, can abrogate the adverse prognostic significance of SER.     

Investigation of fluorescent lamp phosphors using the combined CL and EDS modes of the SEM

The phenomenon of cathodoluminescence (CL) potentially offers the ideal tool for studying the phosphor materials used in fluorescent lamps, since it can be used directly on processed or unprocessed powders, on coatings in tubes, or on sections cut from tubes. Using examples of both single component materials and multi-component blends, it is demonstrated how a relatively unsophisticated dispersive CL system attached to a scanning electron microscope (SEM) can be used expediently in the extensive study of such phosphors. These studies can be significantly enhanced when other complementary modes of the SEM (e. g. the energy-dispersive x-ray analysis facility) are combined with the CL mode. The strength of the combined technique lies in the major role it can play in materials and processing aspects of the powders themselves, in the processing of the lamps (e.g. by optimising such parameters as coating thickness, packing density etc.), and in diagnostic studies of poor materials or lamps (e.g. by locating rogue particles/components and identifying their origin). The technique also provides a convenient method of studying the temperature stability of selected phosphors.     

Impact of programming mechanisms on the performance and reliability of nonvolatile memory devices based on Si nanocrystals

A nonvolatile memory based on silicon nanocrystals (nc-Si) synthesized with very-low-energy Si/sup +/ implantation is fabricated, and the memory performance under the programming/erasing of either Fowler-Nordheim (FN)/FN or channel hot electron (CHE)/FN at both room temperature and 85/spl deg/C is investigated. The CHE programming has a larger memory window, a better endurance, and a longer retention time as compared to FN programming. In addition, the CHE programming yields less stress-induced leakage current than FN programming, suggesting that it produces less damage to the gate oxide and the oxide/Si interface. Detailed discussions on the impact of the programming mechanisms are presented.