Saturation point model for the formation of metal nitrate in nitrogen tetroxide oxidizer

A model was developed for the formation of metal nitrate in nitrogen tetroxide (N2O4). The basis of this model is the saturation point of metal nitrate in N2O4. This basis is chosen mainly because of the White Sands Test Facility's metal nitrate in N2O4 experience. Means of reaching the saturation point are examined, and a relationship is made for the reaction/formation rate and diffusion rate of metal nitrate in N2O4

Numerical study of axisymmetric vortex breakdowns

Axisymmetric flow of rotating stream analyzed to determine conditions allowing isolated vortex breakdown to develo

Do sixth-grade writers need process strategies?

Background: Strategy-focussed writing instruction trains students both to set explicit product goals and to adopt specific procedural strategies, particularly for planning text. A number of studies have demonstrated that strategy-focussed writing instruction is effective in developing writing performance. Aim: The present study aimed to determine whether teaching process strategies provides additional benefit over teaching students to set product goals. Sample: 94 typically developing Spanish sixth-grade (upper primary) students. Method: Students received 10 hours of instruction in one of three conditions: Strategy-focussed training in setting product goals and in writing procedures (planning and revision; Product-and-Process), strategy-focussed training in setting product goals (Product-Only), and product-focussed instruction (Control). Students' writing performance was assessed before, during, and after intervention with process measures based on probed self-report and holistic and text-analytic measures of text quality. Results: Training that included process instruction was successful in changing students' writing processes, with no equivalent process changes in the Product-Only or control conditions. Both Process-and-Product and Product-Only conditions resulted in substantial improvements in the quality of students' texts relative to controls, but with no evidence of benefits of process instruction over those provided by the Product-Only condition. Teaching process substantially increased time-on-task. Conclusions: Our findings confirm the value of strategy-focussed writing instruction, but question the value of training specific process strategies

Effects of direct instruction and strategy modelling on upper-primary students' writing development

Strategy-focused instruction is one of the most effective approaches to improve writing skills. It aims to teach developing writers strategies that give them executive control over their writing processes. Programs under this kind of instruction tend to have multiple components that include direct instruction, modeling and scaffolded practice. This multi-component nature has two drawbacks: it makes implementation challenging due to the amount of time and training required to perform each stage, and it is difficult to determine the underlying mechanisms that contribute to its effectiveness. To unpack why strategy-focused instruction is effective, we explored the specific effects of two key components: direct teaching of writing strategies and modeling of strategy use. Six classes (133 students) of upper-primary education were randomly assigned to one of the two experimental conditions, in which students received instruction aimed at developing effective strategies for planning and drafting, or control group with no strategy instruction: Direct Instruction (N = 46), Modeling (N = 45), and Control (N = 42). Writing performance was assessed before the intervention and immediately after the intervention with two tasks, one collaborative and the other one individual to explore whether differential effects resulted from students writing alone or in pairs. Writing performance was assessed through reader-based and text-based measures of text quality. Results at post-test showed similar improvement in both intervention conditions, relatively to controls, in all measures and in both the collaborative and the individual task. No statistically significant differences were observed between experimental conditions. These findings suggest that both components, direct teaching and modeling, are equally effective in improving writing skills in upper primary students, and these effects are present even after a short training

Evaluating effects of different forms of revision instruction in upper-primary students

p. 1741-1767This study aimed to establish (a) whether teaching students revision skills provides beneft over and above teaching strategies for setting explicit goals for the communicative efect of their text, and (b) whether teaching students to adopt specifc revision strategies provides benefts over revision instruction that focusses on increasing students’ awareness of audience needs. Six classes of Spanish sixth-grade students (N=107, 11–12 years) were randomly assigned to one of three conditions. In all three conditions students were taught to set communicative goals. Students in the Strategy Focused condition were then taught a 6-step revision strategy. Students in the Reader Focused condition observed a reader trying to comprehend a text and suggesting ways in which it might be improved. Students in a control condition continued with goal-setting practice. Students’ writing performance was assessed through composition and revision tasks before and immediately after intervention, 2 months post-intervention, and for transfer to an untaught genre. Writing performance and revision skills improved more in the two revision-instruction conditions than for students in the control condition. The improvements were large, persistent and transferred to a diferent type of text. We found no statistically signifcant diferences between the two revision conditions. Findings suggest that specifc revision instruction benefts sixth-grade students’ writing performance and revision skills, but that strategy-focused and reader-focused approaches are similarly efectiveS

Effects of ADHD on writing composition product and process in school-age students

Objective: This study examined the relationship between ADHD and writing performance. Method: Students in Grades 3 to 7, 84 with ADHD and 135 age and gender-matched controls completed a writing task (including process logs), and measures of, working memory and attention. Results: Students with ADHD wrote texts of similar length but with poorer structure, coherence and ideation. 6.7% of the variance in writing quality was explained by whether or not the student had an ADHD diagnosis, after control for IQ and age-within-year, with students with ADHD producing text that was less coherent, well structured, and ideationally rich and to spend less time thinking about and reviewing their text. Half of the effect on text quality could be attributed to working memory and sustained attention effects. Conclusions: ADHD has some effect on writing performance which can, in part, be explained by working memory and attentional deficits

Post-operative immune suppression is reversible with interferon gamma and independent of IL-6 pathways

Introduction The post-operative period is characterised by increased IL-6 production and clinical features of immune suppression. In vitro anti-inflammatory actions of IL-6 are mediated through suppression of interferon gamma (IFNγ) [1]. The clinical significance of IL-6 in mediating post-operative immune suppression remains unclear. Objectives To evaluate the role of IL-6 pathways in post-operative immune suppression and the reversibility of this phenomenon. Methods Patients over 45 years old undergoing elective surgery involving the gastrointestinal tract and requiring at least an overnight hospital stay were recruited. The primary outcome was hospital-acquired infection. IL-6 and IFNγ levels were assayed using ELISA preoperatively and at 24 and 48 hours. Pooled healthy control peripheral blood mononuclear cells (PBMCs) were cultured in perioperative serum and CD14+HLA-DR (mHLA-DR) geometric mean florescent intensity (MFI) measured in the presence and absence of interferon gamma (IFNγ) and IL-6 neutralising antibody. Data were analysed with non-parametric statistics. Results 119 patients were recruited and 44 (37%) developed a post-operative infection a median of 9 (IQR 5-11) days postoperatively (Figure 1). IL-6 levels increased from baseline to 24 hours postoperatively (P < 0.0001, Figure 1A) but were then unchanged between 24 and 48 hours (P = 0.06, Figure 1B). Postoperative IL-6 levels correlated with the duration of the procedure (P = 0.009). Higher preoperative IL-6 levels were observed in patients with cancer (P = 0.02). IL-6 levels at 24 (P = 0.0002) and 48 hours (P = 0.003) were associated with the later occurrence of infectious complications. This pattern remained similar after adjustment for baseline characteristics. Healthy donor PBMCs incubated with postoperative serum downregulated mHLA-DR MFI when compared with serum from baseline (n = 8, p = 0.008). Culturing in the presence of IFNγ 250IU (n = 4) prevented this decrease whereas culturing in the presence of IL-6 neutralising antibody 15ng/ml (n = 8) did not. Conclusions IL-6 levels increase following major surgery and are associated with an increased susceptibility to post-operative infections. Serum obtained from post-operative patients induces an immunosuppressive response through an IL-6 independent pathways which is reversible with IFNγ treatment

From band insulator to Mott insulator in one dimension

We derive the phase diagram for the one-dimensional model of a ferroelectric perovskite recently introduced by Egami, Ishihara and Tachiki [Science, {\bf 261}, 1307 (1993)]. We show that the interplay between covalency, ionicity and strong correlations results in a spontaneously dimerized phase which separates the weak-coupling band insulator from the strong-coupling Mott insulator. The transition from the band insulator to the dimerized phase is identified as an Ising critical point. The charge gap vanishes at this single point with the optical conductivity diverging as $\sigma(\omega)\sim \omega^{-3/4}$. The spin excitations are gapless above the second transition to the Mott insulator phase.Comment: 4 pages LaTex (RevTex) and 1 postscript figure included by eps