Visitors   Views   Downloads
"PeerJ Preprints" is a venue for early communication or feedback before peer review. Data may be preliminary.

A peer-reviewed article of this Preprint also exists.

View peer-reviewed version

Supplemental Information

Additional Information

Competing Interests

The authors declare they have no competing interests.

Author Contributions

Sphiwe Madiba conceived and designed the experiments, analyzed the data, wrote the paper, prepared figures and/or tables.

Mathildah Mokgatle conceived and designed the experiments, analyzed the data, prepared figures and/or tables, reviewed drafts of the paper.

Human Ethics

The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):

Ethical clearance was obtained from the Medunsa Research Ethics Committee (MREC/H/168/2012: IR) of the University of Limpopo


The study was funded by the University of Limpopo research grants. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Add your feedback

Before adding feedback, consider if it can be asked as a question instead, and if so then use the Question tab. Pointing out typos is fine, but authors are encouraged to accept only substantially helpful feedback.

Some Markdown syntax is allowed: _italic_ **bold** ^superscript^ ~subscript~ %%blockquote%% [link text](link URL)
By posting this you agree to PeerJ's commenting policies