Nano-Modification for High Performance Cement Composites with Cellulose NanoCrystals and Carbon Nanotubes

One of the new engineering frontiers is the exploration of infrastructure materials with novel combinations of properties that break traditional paradigms. The goal of this study is to utilize two different nano-fibers, cellulose nanocrystals (CNCs) and carbon nanotubes (CNTs) to modify the nanoscale structures of cement composites and thereby improve the performance at the macro-level. This study also evaluates the mechanism behind the modification, since fiber bridging, the most common reinforcing mechanism for fiber-reinforced composites, cannot be simply applied because CNCs are too short to bridge cracks in cement composites. ^ The mechanical tests show an increase in the flexural strength of cement paste with modest CNC concentrations. It is found that the degree of hydration (DOH) of the cement paste is increased when CNCs are used, which is the fundamental reason for the strength improvement. Two mechanisms are confirmed for the increased DOH: steric stabilization and a new theory referred as short circuit diffusion (SCD), which is more dominant. SCD increases DOH by increasing the transport of water from the pores to the unhydrated cement core through the high density CSH shell. This study evaluates the agglomeration of CNCs at high concentration and it is found the strength of the cement paste with CNCs decreases when the agglomerates start prevailing. The sonication is employed to effectively reduce the agglomerates and the strength of the cement paste is improved significantly with sonicated CNCs. Due to the hygroscopic and hydrophilic nature of CNCs, the agglomerates may lead to larger and more pores around them. It is found that the elastic modulus at the high density CSH is increased when raw CNCs are added, and is increased even more with sonicated CNCs. The porosity study shows CNCs can reduce the total porosity of cement pastes, while after sonication the porosity reduction is even greater. ^ The CNTs are successfully dispersed with a combined approach of sonication and surfactant and the degree of dispersion is evaluated with SEM imaging and impedance spectroscopy (IS). The flexural and compressive strength of the cement paste increase significantly with the dispersed CNTs. It is verified that the fiber bridging is the mechanism for the strength improvement. The IS curve for cement paste with CNTs shows a dual-arc behavior, which is consistent with the frequency-switchable coating model

Ethical climate and intention to leave among critical care clinicians : an observational study in 68 intensive care units across Europe and the United States

PurposeApart from organizational issues, quality of inter-professional collaboration during ethical decision-making may affect the intention to leave one's job. To determine whether ethical climate is associated with the intention to leave after adjustment for country, ICU and clinicians characteristics.MethodsPerceptions of the ethical climate among clinicians working in 68 adult ICUs in 12 European countries and the US were measured using a self-assessment questionnaire, together with job characteristics and intent to leave as a sub-analysis of the Dispropricus study. The validated ethical decision-making climate questionnaire included seven factors: not avoiding decision-making at end-of-life (EOL), mutual respect within the interdisciplinary team, open interdisciplinary reflection, ethical awareness, self-reflective physician leadership, active decision-making at end-of-life by physicians, and involvement of nurses in EOL. Hierarchical mixed effect models were used to assess associations between these factors, and the intent to leave in clinicians within ICUs, within the different countries.ResultsOf 3610 nurses and 1137 physicians providing ICU bedside care, 63.1% and 62.9% participated, respectively. Of 2992 participating clinicians, 782 (26.1%) had intent to leave, of which 27% nurses, 24% junior and 22.7% senior physicians. After adjustment for country, ICU and clinicians characteristics, mutual respect OR 0.77 (95% CI 0.66- 0.90), open interdisciplinary reflection (OR 0.73 [95% CI 0.62-0.86]) and not avoiding EOL decisions (OR 0.87 [95% CI 0.77-0.98]) were all associated with a lower intent to leave.ConclusionThis is the first large multicenter study showing an independent association between clinicians' intent to leave and the quality of the ethical climate in the ICU. Interventions to reduce intent to leave may be most effective when they focus on improving mutual respect, interdisciplinary reflection and active decision-making at EOL

The effect of an educational intervention on information-seeking behaviors of new graduate nurses

Sound information-seeking processes are essential to nurses’ clinical decisions and the delivery of safe patient care. Research suggests that experienced nurses prefer to gain information verbally from colleagues over formal information sources, such as policies, procedures, and research. As technologies advance and options for accessing information proliferate, research is lacking on nurses’ information-seeking behaviors, especially of new nurses. Furthermore, no research has examined the effect of clinical simulations on informationseeking behaviors of new nurses. This study explored information-seeking behaviors before and after an educational intervention incorporated within simulated patient care scenarios for new nurses and compared new graduate nurses’ information-seeking behaviors to those of experienced nurses. Framed by Wilson’s (1999) decision-making model, this pre-test post-test single-site study was conducted with a convenience sample of registered nurses (n = 80). Participants reported sources of information for clinical decisions and frequency of usage before and after an educational intervention incorporating use of electronic and policy-based resources. Results illuminate an important element of the clinical decision-making processes of new nurses and guide educators and preceptors in shaping the information-seeking behaviors of new nurses.Thesis (M.S.)School of Nursin

Breast cancer risk associated with changes in mammographic density.

PhD ThesisBreast cancer is the most common cancer in the UK, and mammographic density (‘density’) is one of its strongest known risk factors. At present, most research focuses on static measures of density to determine population effects. The central hypothesis of this thesis is that repeated measures of density are more valuable for personalised breast cancer prevention. This hypothesis was tested through the following research. Study-I investigated within-women associations between body mass index (BMI) and density, to assess whether density (visual/Cumulus/volumetric ‘Stepwedge’) acts as a mediator for breast cancer risk reduction during a premenopausal weight-loss intervention (n=65). Study-II evaluated the benefit of using a woman’s longitudinal history of (BI-RADS) density to improve breast cancer risk estimation (n=132,439). Study-III was a Cochrane systematic review investigating the association between endocrine therapy-induced density reduction and breast cancer risk and mortality. Studies-IV and V (n=575) evaluated visually-assessed density reduction with prophylactic anastrozole during the International Breast Cancer Intervention Study-II, and its use as a biomarker for concurrent breast cancer risk reduction, respectively. In Study-I, change in BMI was associated with change in breast fat but not dense tissue, negating density reduction as a biomarker for risk reduction with weight-loss. In Study-II, longitudinal density provided approximately a quarter more statistical information than most recent density and improved discriminatory accuracy. Study-III found evidence that density reduction may be a biomarker for reduction in risk and mortality with tamoxifen, but the level of evidence was limited by some study quality issues. Study-IV indicated that preventive anastrozole might marginally reduce density, but statistical significance was not obtained. In Study-V, sample size was too small to draw definitive conclusions. Overall, changes in density were useful for the study of breast cancer risk and should be considered for personalised breast cancer prevention strategies

Stent-assisted reconstructive endovascular repair of intracranial aneurysms: long-term clinical and angiographic follow-up

Abstract Background and Purpose: The development of self-expanding stents dedicated to intracranial use has significantly widened the applicability of endovascular therapy to many intracranial aneurysms. The purpose of this study was to report the angiographic and clinical outcomes of wide-necked intracranial aneurysms treated with stent. Methods: Between January 2007 and October 2011 we deployed 22 stents in 20 patients with wide-necked cerebral aneurysms. Inclusion criteria restricted the group to adult patients with wide-necked intracranial aneurysms (ruptured and unruptured lesions). Immediate post-procedural angiographic studies were performed to evaluate successful occlusion of the aneurysm as well as patency of the parent vessel. We assessed long term angiography follow-up to detect in-stent stenosis, progressive thrombosis, recurrence and need for retreatment. Clinical outcome was assessed with the modifing Ranking Scale (mRS). Results: Technical success was obtained in all 22 (100%) cases. Angiography immediately after treatment procedure showed complete occlusion in 7 aneurysms (35%), neck remnant in 11 (55%), incomplete occlusion in 1 (5%) and partial occlusion in 1 (5%). During the endovascular embolization procedure no rupture of the sac or bleeding complication occurred; none of the patients needed undergoing surgical crossover. Procedure-related adverse events occurred in one (5%) patient: a brachial artery pseudoaneurysm. Three (15%) patients had neurological complications after procedure, whose 1 (5%) transitory complication spontaneusly resolved. Two patients (10%), had acute complete in-stent thrombosis which resolved after intraarterial administration of abciximab and placement of a new stent in-stent. Of the 20 patients treated with stent deployment, a follow-up imaging study was available in all 19 surviving patients (95%) at an average of 16.2 months (range, 6 to 50 months). The first follow-up DSA, compared with initial angiography, showed no changes in 14 aneurysms (73.7%), progressive thrombosis in 3 (15.7%), and major recurrence in 2 (10.5%). The overall rate of succesful procedure to 6 months is 89.5%; there was 1 case of asintomatic moderate endothelial hyperplasia. The further follow-up imaging study, showed no changes in 17 (89.5%) of the 19 surviving patients, 1 progressive thrombosis and 1 minor recurrence. One month- and long term (average of 16.2 months; range, 6 to 50 months) clinical follow-up showed no worsening in the mRS in 18 (90%) of 20 patients, 1 (5%) mRS 2 and 1 (5%) mRS 6. All the survived patients are alive and we did not observe periprocedural or long-term intracranial bleeding events or symptomatic stent related stenosis/occlusion complication. Conclusions: Our findings suggest that the endovascular treatment of intracranial aneurysms by stenting is feasible, effective and safe; follow-up results proved intact parent arteries and stable occlusion rates in the majority of treated aneurysms. Nevertheless, long-term data on safety and efficacy and larger patient groups are necessary

Ethical climate and intention to leave among critical care clinicians: an observational study in 68 intensive care units across Europe and the United States

Purpose: Apart from organizational issues, quality of inter-professional collaboration during ethical decision-making may affect the intention to leave one’s job. To determine whether ethical climate is associated with the intention to leave after adjustment for country, ICU and clinicians characteristics. Methods: Perceptions of the ethical climate among clinicians working in 68 adult ICUs in 12 European countries and the US were measured using a self-assessment questionnaire, together with job characteristics and intent to leave as a sub-analysis of the Dispropricus study. The validated ethical decision-making climate questionnaire included seven factors: not avoiding decision-making at end-of-life (EOL), mutual respect within the interdisciplinary team, open interdisciplinary reflection, ethical awareness, self-reflective physician leadership, active decision-making at end-of-life by physicians, and involvement of nurses in EOL. Hierarchical mixed effect models were used to assess associations between these factors, and the intent to leave in clinicians within I