Mechanical performance and environmental impact of normal strength concrete incorporating various levels of coconut fiber and recycled aggregates.

This study presents the fresh and mechanical properties of concrete made with recycled aggregates (RAs) and coconut fibers (CFs), with an emphasis on the development of sustainable and ductile cementitious composite through the valorization of coconut and construction wastes. For this purpose, the effect of different percentages of CF, i.e., 0%, 1%, 2%, and 3% by wt. of cement, was examined on the mechanical and physical properties of concrete incorporating RA (0%, 30%, 50%, and 100%). To avoid the negative effect of CF on workability, a plasticizer was used to achieve the target workability. The performance of mixes was evaluated based on the results of workability, density, compressive strength (CS), splitting-tensile strength (STS), flexural strength (FS), and water absorption. The results showed that incorporation of 1-2% CF improved the CS and STS of concrete for each constant level of RA. The addition of 2% CF is recommended for maximum mechanical performance. Concrete incorporating 50% coarse RA with 2% CF showed CS comparable to conventional concrete. Concrete made with 100% coarse RA and 2% CF showed STS and FS comparable to that of conventional concrete. This study recommends the use of 2% CF along with plasticizer to attain the best mechanical performance. Despite comparable STS and FS, 100% RA concrete with 2% CF produced 25% lower CO2 emissions than conventional concrete.

Illuminating the dark side--vitamin D status in different localities of Karachi.

This study was conducted to determine the association between place of residence (grouped into neighbourhoods), and 25-hydroxy D (25[OH]D) levels of individuals of Karachi. Addresses of 4788 individuals tested for 25[OH]D at the clinical laboratory of the Aga Khan University (AKU), Karachi, from January 2007 to June 2008 were reviewed. The neighbourhoods were categorized into ten, based on locality attributes. A high overall prevalence (74%) of vitamin D deficiency (VDD) was observed. There was a significant difference (p-value < 0.01) between mean log 25[OH]D levels amongst neighbourhoods grouped according to distinct housing structure attributes and localities. A high frequency of VDD in all the studied localities of an urban city warrant dietary vitamin D supplementation and food fortification.

What method of contact works best for recruiting participants in a study: lessons for health care researchers?

OBJECTIVES: To assess the various recruitment strategies used by medical researchers and their response rates. METHODS: The observational study, part of a larger retrospective cohort, was done at the Aga Khan University Hospital, Karachi, Pakistan, from May 2008-December 2010, covering a period from 1999 to 2005. We used a multi-mode contact approach for including participants in the study. This comprised an invitational letter that described the study sent along with a mail-back, postage-paid envelope and multiple phone calls for recruitment of participants. The response to each mode was noted and described as frequency and percentage. RESULTS: There were 1335 participants eligible for recruitment in the study. Of them, 1247 (93.4%) were sent mailouts to which only 84 (6.7%) responded. Besides, 1133 participants,whose phone numbers were available, were called. Overall, the number of people that we were able to contact was low. The response to postage paid mail was very poor whereas the majority of participants were contacted via phone calls. Out of such participants, 257 (19.25%) agreed to participate at the very first call and our results suggest that more than three calls made very little contribution to the consent rate. CONCLUSION: Recruiting subjects from contact information available in the medical records may not be the best method. Multiple and innovative approaches are required for approaching potential participants and requesting them to participate in a study.