A nonlinear viscoelastic approach to durability predictions for polymer based composite structures

Current industry approaches for the durability assessment of metallic structures are briefly reviewed. For polymer based composite structures, it is suggested that new approaches must be adopted to include memory or viscoelastic effects which could lead to delayed failures that might not be predicted using current techniques. A durability or accelerated life assessment plan for fiber reinforced plastics (FRP) developed and documented over the last decade or so is reviewed and discussed. Limitations to the plan are outlined and suggestions to remove the limitations are given. These include the development of a finite element code to replace the previously used lamination theory code and the development of new specimen geometries to evaluate delamination failures. The new DCB model is reviewed and results are presented. Finally, it is pointed out that new procedures are needed to determine interfacial properties and current efforts underway to determine such properties are reviewed. Suggestions for additional efforts to develop a consistent and accurate durability predictive approach for FRP structures is outlined

Iowa\u27s First Steam Tractor

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2012-201

13-year mortality trends among hospitalized patients with inflammatory bowel disease

BACKGROUND: Studies document increasing rates of hospitalization among patients with inflammatory bowel disease, but temporal trends for in-hospital mortality among patients with inflammatory bowel disease are not characterized. We sought to determine whether in-hospital mortality changed over a 13-year period among nationwide hospitalizations associated with inflammatory bowel disease. We additionally sought to identify factors correlated with mortality. METHODS: We used the National Hospital Discharge Survey, a large nationally representative database, for the years 1994 through 2006. Age- and mortality-adjusted rates of in-hospital mortality and standardized mortality ratios were calculated for four time periods. Logistic regression analysis was used to assess associations between advancing time and mortality in adjusted analyses. RESULTS: 150 (0.9%) of 17,393 hospitalizations for patients with inflammatory bowel disease ended in death. Age-adjusted in-hospital mortality decreased from 3.6 deaths per 1,000 hospital days in 1994–96 to 2.4 per 1,000 in 2003–06; standardized mortality ratio decreased from 0.33 to 0.27. Similar trends were seen for patients with ulcerative colitis, but mortality did not change over time among patients with Crohn’s disease. Multivariable logistic regression analysis confirmed the significance of these changes in mortality, with 17% decreased odds of in-hospital death per three-year period (P = 0.012). Subject age (OR 1.06 per year, P < 0.001), Charlson comorbidity index (OR 1.29 per 1-point increase, P < 0.001), and diagnosis of ulcerative colitis (versus Crohn’s disease, OR 1.41, P = .042) were also associated with in-hospital mortality. CONCLUSIONS: The odds of in-hospital mortality among hospitalized patients with inflammatory bowel disease decreased by 17% per 3-year period from 1994 to 2006 in analysis adjusted for age and comorbidity status, in this large, nationally representative database. Multiple factors likely contribute to these trends

A study of the relationships between personality as indicated by the Myers Briggs Type Indicator and leadership strengths and weaknesses as identified by Skillscope

The purpose of this study was to improve the quality of information used in leadership assessment and development programs. The study determined the relationships between personality type, as indicated by the Myers-Briggs Type Indicator (MBTI), and leadership strengths and developmental needs as measured by Skillscope. The study also determined the relationships between personality type and congruence between self-awareness of strengths and developmental needs and ratings by knowledgeable observers. The discriminate analysis of the Skillscope leadership feedback instrument compared with the selected personality types revealed that personal management was a strength for both ISTJs and ESTJs. The decision-making skill was a strength for ISTJs, and power/influence was determined to be a strength for ESTJs. The high energy/results oriented skill was determined to be a developmental need for ISTJs. There was agreement between ENTJs and other raters as they both saw interpersonal relationships as a strength for that type. INTJs underrated themselves in interpersonal relationships, and ISTJs underrated themselves in decision-making. Further study is recommended to expand the general body of knowledge of leadership development research. Of particular concern are methods to identify and explore developmental needs of leaders and how those needs can be addressed in training programs. Three hundred sixty degree feedback instruments should be further analyzed in an effort to explain the differences between raters. Of concern is the high percentage of ISTJ types, which reveals a need to expand research to include significant numbers of other personality types. Consideration should be given to studies that identify the unique contributions of gender to leadership skills and development, and the impact culture has on leadership in organizations. Although statistically significant research is difficult to obtain in the behavioral sciences, the effort is worthwhile as it provides information that allows leadership development decisions to be made based on dependable data

Actin turnover is required to prevent axon retraction driven by endogenous actomyosin contractility

Growth cone motility and guidance depend on the dynamic reorganization of filamentous actin (F-actin). In the growth cone, F-actin undergoes turnover, which is the exchange of actin subunits from existing filaments. However, the function of F-actin turnover is not clear. We used jasplakinolide (jasp), a cell-permeable macrocyclic peptide that inhibits F-actin turnover, to study the role of F-actin turnover in axon extension. Treatment with jasp caused axon retraction, demonstrating that axon extension requires F-actin turnover. The retraction of axons in response to the inhibition of F-actin turnover was dependent on myosin activity and regulated by RhoA and myosin light chain kinase. Significantly, the endogenous myosin-based contractility was sufficient to cause axon retraction, because jasp did not alter myosin activity. Based on these observations, we asked whether guidance cues that cause axon retraction (ephrin-A2) inhibit F-actin turnover. Axon retraction in response to ephrin-A2 correlated with decreased F-actin turnover and required RhoA activity. These observations demonstrate that axon extension depends on an interaction between endogenous myosin-driven contractility and F-actin turnover, and that guidance cues that cause axon retraction inhibit F-actin turnover

Gaussian stationary processes over graphs, general frame and maximum likelihood identification

In this paper, using spectral theory of Hilbertian operators, we study ARMA Gaussian processes indexed by graphs. We extend Whittle maximum likelihood estimation of the parameters for the corresponding spectral density and show their asymptotic optimality