Effects of boron doping on the grain growth behaviour of γ/γ nickel-aluminium alloy

Effects of 0.5 at. 9c boron doping on Nigs Al y/f superalloys were investigated for the first !ime. yielding a number of observations not previously observed in the literature. First, the grant growth kinetics of both the doped and undoped alloys were found to disobey the simple Nielsen law d = Of. but instead follow an equation of the type d = C ln(r) + C0. The constants C and Co were found to be respectively 10.2 and 23.2 for the boron-free alloy, and 6.2 and 14.2 for ire boron-doped alloy, i.e., the grain growth rate was retarded significantly upon boron doping. Such a retarding effect is thought to be due to the formation of a boron-nickel cosegregated zone observed at the grain boundaries of the doped alloy: the width of the zone, in juni's, is two to three orders of magnitude larger than the boron induced disordered layer found in nickel rich Ni3Al. compounds doped with boron. Other associated effects of the cosegregated zone include a -harp increase in toughness, much better slip transmission across grains and reduced workhardening rates. Another intriguing point is that the Y precipitates were found to segregate to the grain boundaries in the boron-free alloy after cold rolling, but no such segregation of y precipitates, has been observed in the boron-doped alloy. The different deformation microstructures and the retarded grain growth rates upon boron doping will be discussed.published_or_final_versionlink_to_subscribed_fulltex

Probing the critical stress intensity factor for slip transfer across grain boundaries by subgranular indentation

By analysing the relevant results in the literature, we have found that, when identation is made on a subgranular level, the hardness varies roughly inversely with the square root of the distance between the indent and the grian boundary. This effect is analogous to the Hall-Petch effect for macroscopic deformation.published_or_final_versio

The effects of a new grain boundary phase in Ni-Al alloy

In a γ/γ nickel-aluminum alloy, a new phase has been identified along grain boundaries by conventional transmission electron microscopy. This phase is identified to be of the C6Cr23 type structure with lattice parameter 10.48Å, which is approximately three times that of Ni3Al or nickel. This grain boundary precipitate is found to be coherent with the γ phase in one grain. The chemical composition of this grain boundary precipitate is determined by energy dispersive x-ray spectroscopy and parallel electron energy loss spectroscopy. The deformation mechanism of this grain boundary precipitate is investigated on post-mortem specimens which have been carefully deformed by nanoindentation after jet-polishing.published_or_final_versio

Childhood acute lymphoblastic leukaemia masquerading as primary skeletal problem

Acute lymphobiastic leukaemia (ALL) usually presents with signs of bone marrow failure, Occasionally ALL in children may present with non-specific or misleading clinical features. In a retrospect analysis of 25 consecutive cases of childhood ALL, we identified three children who were initially managed and discharged as acute osteomyelitis, juvenile chronic arthritis and postinfectious arthralgia respectively. They had mild normochromic, normocytic anaemia and two had transient leucopenia. Their platelet counts were normal and none had circulating blasts. The severity of their skeletal symptoms was out of proportion to the clinical and radiological finding. They failed to respond to the initial management and diagnosis was delayed for an average of 42 days and eventually confirmed on the marrow aspirate. Complete remission was attained in all cases with standard chemotherapy and had been maintained for an average of 29 months. ALL should be considered as a differential diagnosis in children complaining of multiple or persistent joint pains, especially in the presence of atypical clinical features or poor response to treatment.published_or_final_versio

An alternative method for continuous property measurement during depth-sensing indentation

Based on the Oliver-Pharr framework, an iteration scheme is proposed to continuously evaluate the hardness during monotonic loading in nanoindentation. The new method was applied to measure the hardness of various crystalline materials including Al, Cu, Ni3Al(Cr,B) and MgO, where an obvious Indentation Size Effect (ISE) was observed. In a-Se and PP, no ISE was observed when using exponential loading schemes at constant strain rates. The new method therefore produced the correct ISE behaviours in various materials under different loading situations.postprin

The effects of job demands, control, and social support on hospital clinical nurses' intention to turn over

[[abstract]]Nursing turnovers may cause a serious setback to the quality of health delivery system. In addition, this turnover increases direct and indirect labor costs. This study examined the influence of job demand, job control, and social support on clinical nurses' turnover intention based on the job strain model. In total, 373 hospital clinical nurses in northern, central, and southern Taiwan were surveyed. The results show that nurses in high job demand and low-control work situations reveal the highest turnover intention. Job-related social support may decrease this turnover rate

The process of telepractice implementation during the COVID-19 pandemic: a narrative inquiry of preschool speech-language pathologists and assistants from one center in Canada

Background: Many professional services were pressed to adopt telepractice in response to the global coronavirus SARS-CoV-2 (COVID-19) pandemic. The need to adopt a new service delivery approach quickly created different implementation challenges. This study explored the lived experiences of frontline clinicians who successfully transitioned their in-person speech-language therapy services to telepractice through an implementation science lens. Methods: The study was conducted in partnership with one publicly funded program in Ontario, Canada that offers services to preschoolers with speech, language and communication disorders. Sixteen frontline speech-language pathologists and assistants at this organization shared their lived experience transitioning to telepractice during the pandemic during videoconference interviews. A narrative inquiry approach was used to analyze interview transcripts to identify the processes (or steps) this program took to implement telepractice and to understand the facilitators and barriers to telepractice implementation during the pandemic. Results: The following six stages were identified from clinicians\u27 narratives: abrupt lockdown; weeks of uncertainty; telepractice emerged as an option; preparation for telepractice; telepractice trials; and finally, full implementation of telepractice. The stages of events offered significant insights into how government public health measures influenced clinicians\u27 decisions and their processes of adopting telepractice. In terms of barriers, clinicians reported a lack of knowledge, skills and experience with telepractice and a lack of technological support. The organization\u27s learning climate and team approach to transitioning services were identified as the main facilitator of implementation. Conclusions: Findings suggest a need for better coordination of public health measures and professional services, which would have eased clinicians\u27 stress and facilitated an earlier transition to telepractice. Fostering an organization\u27s learning climate may improve organization\u27s resilience in response to emergency situations

Changes in nasopharyngeal carriage and serotype distribution of antibiotic-resistant Streptococcus pneumoniae before and after the introduction of 7-valent pneumococcal conjugate vaccine in Hong Kong

This study assessed the changes in serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolates in children before and after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Hong Kong. Nasopharyngeal specimens were collected from 1978 and 2211 children (ages, 2 to 6 years) attending day care centers or kindergartens in period 1 (1999-2000) and period 2 (2009-2010), respectively. Carriage of PCV7 serotypes decreased from 12.8% to 8.6% (P < 0.01). The relative contribution of PCV7 serotypes 14 and 18C had decreased, whereas that for non-PCV7 serotypes 19A, 6A, 6C, 23A, and 15B had increased. In period 2, PCV7 penetration rate (at least 1 dose) for children aged 2, 3, 4, and 5 years was 43%, 35.7%, 26.7%, and 20.4%, respectively. In multivariate analysis, PCV7 use was the only independent variable associated with fewer PCV7 serotype carriages (odds ratio 0.5; P = 0.001). In period 2, high rates of dual penicillin/erythromycin nonsusceptibility were found in serotypes 6B (77.3%), 14 (100%), 19F (100%), 23F (78%), 19A (75%), 6A (87.8%), 6C (59.3%), and 23A (78.9%).postprin

The need of policies and legislative changes for tobacco control in Hong Kong: Letter of recommendations to Hong Kong Legislative Council

Recommendations on Anti-smoking Policy in Hong Kong, in response to the discussion on increasing tobacco taxation for the Legislative Council Subcommittee on Public Revenue Protection (Dutiable Commodities) Order 2011published_or_final_versio

Molecular epidemiology and nasal carriage of Staphylococcus aureus and methicillin-resistant S. aureus among young children attending day care centers and kindergartens in Hong Kong

OBJECTIVES: To investigate the prevalence and molecular epidemiology of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) nasal carriage in children. METHODS: We collected nasal and nasopharyngeal swabs from 2211 children aged 2-5 years attending 79 day care centers (DCCs) and 113 kindergartens (KGs) in all 18 geographical districts in Hong Kong. RESULTS: The overall carriage rates of S. aureus and MRSA were 27.6% (95% confidence interval [CI], 24.8-28.5%) and 1.3% (95% CI, 0.8-1.8%), respectively. Molecular typing (staphylococcal cassette chromosome mec [SCCmec], sequence type [ST], clonal cluster [CC]) showed that all the 28 MRSA isolates had SCCmec IV (n = 13) or V (n = 15) including 12 isolates with community-associated-MRSA genotypes (ST59-IV/V, ST30-IV and ST88-V), 10 isolates with healthcare-associated-MRSA genotypes (ST45-IV/V, CC5-IV and ST630-V) and six isolates with novel genotypes (ST10-V and CC1-IV). Spa typing indicated that there was some within and between DCCs/KGs transmission of certain MRSA and methicillin-sensitive S. aureus strains but this was not extensive. CONCLUSION: Our findings indicate the potential for DCCs to be a reservoir for emerging MRSA genotypes and highlight the need to enhance education and infection control measures to reduce their cross-transmission in this population.postprin