Elastic properties of carbon nanotubes and their heterojunctions

Comprehensive studies on the modelling and numerical simulation of the mechanical behaviour under tension, bending and torsion of single-walled carbon nanotubes and their heterojunctions are performed. It is proposed to deduce the mechanical properties of the carbon nanotubes heterojunctions from the knowledge of the mechanical properties of the single-walled carbon nanotubes, which are their constituent key unit

Same Program, Different Outcomes: Understanding Differential Effects from Access to Free, High-Quality Early Care

The Infant Health and Development Program (IHDP) was designed to promote the development of low-birth weight (up to 2,500 grams) and premature (up to 37 weeks gestational age) infants. There is evidence that the IHDP intervention, a randomly-assigned bundle of services including primarily free, high-quality child care from 12 to 36 months, boosted cognitive and behavioral outcomes by the time participants at the end of the intervention. The literature has established that the intervention was more effective among the subsample of heavier low birth weight (2,000-2,500 grams) than among those born lighter. Among the heavier group, it was more effective for children from lower-income families. Families who participated in the intervention were diverse in key observable characteristics like income, race or ethnicity. In addition, families reallocated their time in different ways when then had the opportunity to use the free services provided by the IHDP. The goal of this paper is to understand the economic decisions and constraints faced by households who gained access to the IHDP and explain their differential behavior. In order to do so, we propose an economic model, construct measures of theoretically-relevant drivers of postnatal investment decisions, and explore patterns of heterogeneity in parental response and child development along these dimensions

The North American Plums (<em>Prunus</em> Spp.): A Review of the Taxonomic and Phylogenetic Relationships

North America is a center of diversity for Prunus species. Tree architecture, chilling requirement, heat requirement, fruit development period, fruit size, fruit texture, disease resistance, and adaptive changes to multiple environmental conditions are a few examples of the traits of which tremendous genetic variability is available in the native plum species. Wild native Prunus species constitute an important potential source of genetic diversity for stone fruit breeding and selection. A review of the North American plum taxonomic treatment and phylogenetic studies is described. Various studies have been done with three major groups being identified: Americana series, Chickasaw series, and Beach series

Final Report: Review of the FITS Program: Program Tasks, Goals and Pilot Training Initiatives

In 2002 the FAA, academic and industry partners established the FAA/Industry Training Standards (FITS) program whose purpose is to modernize General Aviation (GA) pilot training. The FAA recognized the need to modernize training standards for pilots who would use new avionics technology that integrate the GPS (Global Positioning Systems) with the autopilot along with multifunction displays capable of depicting flight path, weather, terrain and traffic information. These avionics and displays are touted as improving safety by enhancing pilot Situational Awareness and reducing pilot workload. The new technology has highlighted the need for programs to train and certify pilots to use the avionics suites. The instrumentation places new demands on pilots including changes in the level and distribution of pilot workload during a flight, the need to manage and integrate information from multiple displays, navigate complex menu structures, and program navigation computers. The literature describing the FITS program argues that the current structure and content of GA pilot training programs will not adequately prepare pilots for the challenges of using these technologies (FAA, 2003a; Glista, 2003b; Wright, 2002). The FITS curriculum attempts to address these issues by stressing training of risk management (RM), situational awareness (SA), aeronautical decision making (ADM) and single-pilot resource management (SRM). It also proposes to change pilot instruction to make it more relevant to real world flying by relying on scenario-based training (SBT). FITS proposes to emphasize the use of scenarios as a means to practice the integration of individual skills as they might occur in the real world. For instance, a student pilot might be instructed to plan a flight from Wichita, KS to Kansas City, MO. The student would perform all the tasks necessary to plan the flight including preflight checks, route planning, checking the weather reroute etc. During the flight the student would demonstrate individual flight skills including turns, climbs, navigation, and communication while executing the scenario. The purpose of this project was to review research related to the proposed initiatives and to identify future research needs to support the long-term objectives of FITS. In addition to reviewing pertinent academic and government literature, the objectives of FITS were reviewed with representatives of the FAA, academic and industry partners. At present FITS materials provide few details regarding important components of the training initiative including decision making, the training requirements of advanced avionics technology and its effects on situation awareness. Future work should draw on an extensive academic literature and on lessons learned from prior industry experience when similar avionics technologies were introduced to commercial aviation. Also, clear distinctions should be made between SBT as employed in FITS and SBT used by the military and in commercial aviation. These are very different programs

Classification and Analysis of Errors Reported in Aircraft Maintenance Manuals

Previous research has identified maintenance information as one of the primary causal factors of maintenance error. Incorrect maintenance information has also been cited as a contributing factor in a number of recent aircraft mishaps. To date no one has studied the types of errors found in aircraft maintenance manuals published by manufacturers. The purpose of this research is to analyze Publication Change Requests (PCRs) to document the most frequently reported types of errors found in aircraft maintenance manual, to identify how errors vary across Air Transport Association (ATA) chapters, and identify the corrective actions required to address the cited problem. The most common request was for additional procedural information followed by requests to add or change the language to improve clarity. The results show that the majority of PCRs (42%) cited procedures found in Chapters 27 (Flight controls), 32 (Landing gear), and 71 (Powerplant)

Trends of Non-Fatal HEMS Accident-Related Injuries

We conducted an investigation into non-fatal helicopter emergency medical service accidents from January 26, 1991 to April 26, 2018 via the National Transportation Safety Board aviation accident database. Over this 28-year timeframe 247 accidents results in 251 fatalities and 179 non-fatal injuries. Exploratory analysis of the data indicate that more non-fatal injuries occurred in September compared to any other month during the study timeframe. Exploratory correlational analysis via elastic net logistic regression concluded that no linear relationship of NTSB accident database data provide insights into what factors are correlated with an increased likelihood of non-fatal injuries. Further, no linear relationships of available variables provide insights into the increased number of non-fatal injuries in September during this investigation’s timeframe. Future research should identify if these null results are due to a true lack or no relationship between available data and non-fatal injuries or if these results are due to inaccessibility to relevant data

Editorial: Teaching history in the era of globalization: epistemological and methodological challenges

The COVID-19 pandemic has highlighted the need of several changes within the field of History Education. Firstly, the need of a methodological change that integrates active learning methods, digital resources, and emerging technologies in order to attend the non-presential lessons for the students. Secondly, the need of a multicultural approach on teaching history, social, and gender equality moving away from supremacists' dogma. It is necessary for teachers to change their conception of why and for what reasons they teach history. This need has become more acute with the COVID-19 pandemic: fighting vs. hate speeches through argumentation and critical analysis of sources to avoid fake news and to develop a learning perception evidences. This Research Topic is focused both on Primary and Secondary Education, but also on Higher Education, considering History teachers training courses. Particularly, this book focuses to know the development of the skills of active and future History teachers who are trained at programs at universities to bring a profound methodological and content change in the way History is taught..

Diagnosis and outcome of oesophageal Crohn's disease

BACKGROUND AND AIMS: Crohn's disease (CD) can involve any part of the gastrointestinal tract. We aimed to characterize clinical, endoscopic, histologic features and treatment outcomes of CD patients with oesophageal involvement. METHODS: We collected cases through a retrospective multicentre European Crohn's and Colitis Organisation CONFER [COllaborative Network For Exceptionally Rare case reports] project. Clinical data were recorded in a standardized case report form. RESULTS: A total of 40 patients were reported [22 males, mean (±SD, range) age at oesophageal CD diagnosis: 25 (±13.3, 10-71) years and mean time of follow-up: 67 (±68.1, 3-240) months]. Oesophageal involvement was established at CD diagnosis in 26 patients (65%) and during follow-up in 14. CD was exclusively located in the oesophagus in 2 patients. Thirteen patients (32.2%) were asymptomatic at oesophageal disease diagnosis. Oesophageal strictures were present in 5 patients and fistulizing oesophageal disease in one. Eight patients exhibited granulomas on biopsies. Proton-pump inhibitors (PPIs) were administered in 37 patients (92.5%). Three patients underwent endoscopic dilation for symptomatic strictures and none oesophageal-related surgery. Diagnosis in pre-established CD resulted in treatment modifications in 9/14 patients. Clinical remission of oesophageal disease was seen in 33/40 patients (82.5%) after a mean time of 7 (±5.6, 1-18) months. Follow-up endoscopy was performed in 29/40 patients and 26/29 (89.7%) achieved mucosal healing. CONCLUSION: In this case series the endoscopic and histologic characteristics of isolated oesophageal CD were similar to those reported in other sites of involvement. Treatment was primarily conservative, with PPIs administered in the majority of patients and modifications in pre-existing IBD-related therapy occurring in two thirds of them. Clinical and endoscopic remission was achieved in more than 80% of the patients.info:eu-repo/semantics/publishedVersio

A new approach for reverse analyses in depth-sensing indentation using numerical simulation

This paper seeks to present a new approach to reverse analysis in depth-sensing indentation which makes use of numerical simulation. This methodology allows the results of experimental hardness tests acquired with single indenter geometry to be used to determine the plastic properties of materials. Forward and reverse analyses of high deformation three-dimensional numerical simulations of Vickers indentation tests are used to determine different mechanical properties of materials: Young's modulus, yield stress and strain-hardening exponent. The Vickers indenter used in the numerical simulations is formulated as a rigid body and takes into account the presence of the most common imperfection of the tip, so-called offset. The contact friction between the Vickers indenter and the deformable body is also considered. The forward analysis uses materials with Young's modulus values from 50 to 600 GPa, yield stress values from 0.3 to 10 GPa and strain-hardening exponents from 0 to 0.6; the Poisson ratio did not vary from 0.3. The representative plastic strain [epsilon]r and the correspondent stress [sigma]r, as previously defined by other authors [Dao M, Chollacoop N, Vliet KJ, Venkatesh TA, Suresh S. Acta Mater 2001;49:3899], were identified by an independent numerical method. The values of the representative plastic strain [epsilon]r obtained for the Vickers indenter confirm those of the above-mentioned authors, despite showing a slight influence from the Young's modulus values. The forward study enables the production of a unique plot of the hardness HIT vs. representative stress [sigma]r, where both are normalized by the Young's modulus E. The proposed reverse analysis provides a unique solution to the representative stress [sigma]r and the strain-hardening exponent, n, given that the Young's modulus is predetermined from the experimental hardness test. Depending on the material properties, the value of n can be more or less sensitive to the scatter of the experimental results obtained using the depth-sensing equipment, particularly the stiffness of the unloading curve. The validity of the proposed reverse analysis method is checked using three real materials: stamping quality steel (DC 06), stainless AISI 304 steel and BK7 glass.http://www.sciencedirect.com/science/article/B6TW8-4M69JXG-1/1/ffe1726f3b7df73e4e01c941d6c4cbe