Doubly Differential Ionization In Proton-helium Collisions At Intermediate Energies: Energy Distribution Of Emitted Electrons As A Function Of Scattered-projectile Angle

Differential studies of the proton-helium scattering problem using the two-center wave-packet convergent close-coupling approach is extended to the calculation of the ionization cross section differential in the electron emission energy and the projectile scattering angle. The results obtained using the correlated two-electron and effective one-electron methods are in reasonably good agreement with experiment. While the shape of the doubly differential cross section generally agrees with the results of the experiment, at some emission energies its magnitude does not. This appears consistent with similar disagreement seen in the singly differential cross section at the same emission energies

The cleaning of burned and contaminated archaeological maize prior to 87Sr/86Sr analysis

Accurate trace-metal and strontium-isotope analyses of archaeological corn cobs require that metal contaminants be removed prior to chemical analysis. Archaeological cobs are often coated with construction debris, dust, or soilwhich contains mineral particles. In addition, most archaeological cobs are partially or completely burned and the burned parts incorporate mineral debris in their hardened residual structures. Unburned cobs are weak ion exchangers and most metals within a cob are not firmly bound to cob organic matter; therefore, immersing cobs in acids and rinsing them in deionized water to remove mineral contaminants may result in the undesirable loss of metals, including strontium, from the cob. In this paper we show that some cob metal-pair ratios are not substantially changed when the cob is ‘‘cleaned’’ with deionized water, if the water-cob contact time does not exceed five minutes. Additionally, we introduce a method for eliminating mineral contaminants in both burned and unburned cobs, thus rendering them acceptable for strontium-isotope analysis. However, the decontamination procedure results in the rapid non-stoichiometric leaching of trace metals from the unburned cobs and it is possible that most metals will be extracted from the cobs during the lengthy decontamination process. Trace metals, in particular Al and Ca, should be analyzed in order to determine the presence and level of mineral contamination after cleaning

Cholesterol-sensitive Cdc42 activation regulates actin polymerization for endocytosis via the GEEC pathway

Glycosyl-phosphatidylinositol (GPI)-anchored proteins (GPI-APs) are present at the surface of living cells in cholesterol dependent nanoscale clusters. These clusters appear to act as sorting signals for the selective endocytosis of GPI-APs via a Cdc42-regulated, dynamin and clathrin-independent pinocytic pathway called the GPI-AP-enriched early endosomal compartments (GEECs) pathway. Here we show that endocytosis via the GEECs pathway is inhibited by mild depletion of cholesterol, perturbation of actin polymerization or overexpression of the Cdc42/Rac-interactive-binding (CRIB) motif of neural Wiskott-Aldrich syndrome protein (N-WASP). Consistent with the involvement of Cdc42-based actin nanomachinery, nascent endocytic vesicles containing cargo for the GEEC pathway co-localize with fluorescent protein-tagged isoforms of Cdc42, CRIB domain, N-WASP and actin; high-resolution electron microscopy on plasma membrane sheets reveals Cdc42-labelled regions rich in green fluorescent protein-GPI. Using total internal reflection fluorescence microscopy at the single-molecule scale, we find that mild cholesterol depletion alters the dynamics of actin polymerization at the cell surface by inhibiting Cdc42 activation and consequently its stabilization at the cell surface. These results suggest that endocytosis into GEECs occurs through a cholesterol-sensitive, Cdc42-based recruitment of the actin polymerization machinery

Radical Change Accidentally: The Emergence and Amplification of Small Change

A decision to offer breakfast to homeless people led to radical change in a church and its environment. Existing theories of change do not fully explain observations from our qualitative study; however, complexity theory constructs suggest how and why such change emerged. We offer four key findings. First, the radical change was unintended, emergent, and slow. Second, destabilizing conditions helped small changes to emerge and become radical. Third, subsequent actions amplified an initial small change and, though not intended to do so, promoted radical change. Finally, the dynamic interaction of amplifying actions, contextual conditions, and small changes led to continuous radical change

Radical Change Accidentally: The Emergence and Amplification of Small Change

A decision to offer breakfast to homeless people led to radical change in a church and its environment. Existing theories of change do not fully explain observations from our qualitative study; however, complexity theory constructs suggest how and why such change emerged. We offer four key findings. First, the radical change was unintended, emergent, and slow. Second, destabilizing conditions helped small changes to emerge and become radical. Third, subsequent actions amplified an initial small change and, though not intended to do so, promoted radical change. Finally, the dynamic interaction of amplifying actions, contextual conditions, and small changes led to continuous radical change

Children, play and computers in pre-school education

The paper reports a study designed to inform the development of an information and communication technology strategy for the pre-school years of education. The main methods of collecting evidence were observations at seven pre-school settings and interviews with at least two practitioners and a number of children at each site. Practitioners generally referred to children “playing with the computer”. We describe some of the problems to be found in the emphasis on free play in nurseries and play groups when this means children are using computers as complete novices. There were few examples of peer support; adults rarely intervened or offered guidance and the most common form of intervention was reactive supervision. Interaction with a computer was therefore a limited experience for most children, but we provide examples of guided interaction that suggest a way forward for professional development

Outcome of children with resistant and relapsed Hodgkin's disease.

During the period 1974-89, 169 children with Hodgkin's disease were treated in the Paediatric Oncology Units of the Royal Marsden and St Bartholomew's Hospitals. The overall actuarial survival for the whole group was 81% at 10 years. Thirty-five of the 169 children either did not achieve a complete remission or subsequently relapsed. The estimated actuarial survival from initial relapse or failure of primary treatment was 60% at 5 years and 45% at 10 years. Over half of the patients requiring salvage therapy had declared themselves within 2 years and only 3 relapses occurred more than 3 years from diagnosis. Very few patients remain disease free long term after failure of primary and initial salvage therapy. Patients relapsing within a year of diagnosis or not achieving a complete response to primary therapy and those with disseminated relapse had a poor response to salvage therapy. A significant subgroup of patients had prolonged survival despite multiple relapses. Neither initial histology nor stage affected survival from relapse although numbers in each subgroup were small

H-Ras Nanocluster Stability Regulates the Magnitude of MAPK Signal Output

H-Ras is a binary switch that is activated by multiple co-factors and triggers several key cellular pathways one of which is MAPK. The specificity and magnitude of downstream activation is achieved by the spatio-temporal organization of the active H-Ras in the plasma membrane. Upon activation, the GTP bound H-Ras binds to Galectin-1 (Gal-1) and becomes transiently immobilized in short-lived nanoclusters on the plasma membrane from which the signal is propagated to Raf. In the current study we show that stabilizing the H-Ras-Gal-1 interaction, using bimolecular fluorescence complementation (BiFC), leads to prolonged immobilization of H-Ras.GTP in the plasma membrane which was measured by fluorescence recovery after photobleaching (FRAP), and increased signal out-put to the MAPK module. EM measurements of Raf recruitment to the H-Ras.GTP nanoclusters demonstrated that the enhanced signaling observed in the BiFC stabilized H-Ras.GTP nanocluster was attributed to increased H-Ras immobilization rather than to an increase in Raf recruitment. Taken together these data demonstrate that the magnitude of the signal output from a GTP-bound H-Ras nanocluster is proportional to its stability

Exploring the quotidian in young children's lives at home

The challenges of conducting research in the home, especially with preschool children, mean that the role of the home as a site for research is often overlooked by educationalists. Our repeat visits to fourteen families that included a three- or four-year-old child over more than a year as part of our study “Young Children Learning with Toys and Technology at Home” enabled us to develop research relationships that resulted in a 100 percent retention rate. We summarize the ecocultural framework that informed the design of our study and describe two methods for collecting data (“toy tours” and “mobile phone diaries”) that highlight issues relating to the rules of engagement when conducting research that generates insights into children’s everyday lives at home