Magnetotactic bacteria used to generate electricity based on Faraday's law of electromagnetic induction

Magnetotactic bacteria (MTB) have the unique ability to produce magnetic particles surrounded by a biomembrane to form the magnetosome organelle. Therefore, MTB have novel physical and magnetic properties and have consequently been used in several biotechnological applications. The magnetic properties of these micro-organisms and their magnetosomes have, however, never been used for the generation of electricity as described in this letter. Comparisons were made between, firstly, the electricity generated from purified magnetosomes, MTB culture (bacterial cells with magnetosomes) and sterile, liquid growth medium (control). Secondly, the electricity generated by a dilution series of purified magnetosomes were compared. A statistically significant difference was found between the voltage measured from the purified magnetosomes (highest voltage), MTB culture (lower voltage) and liquid growth medium (lowest voltage). In the dilution series, the voltage measured increased as the magnetosome concentration increased, but only up to an optimum concentration (0·0376 mg ml^-1 ). In this study, we have demonstrated that a significantly higher voltage than that of the control could be measured when MTB or purified magnetosomes were pumped through a solenoid by applying Faraday's law of electromagnetic induction.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides proof-of-concept of electromagnetic induction using magnetosomes or magnetotactic bacteria in an experimental setup based on the law of Faraday. The concept of using these bacteria or their biomineralized magnetic nanoparticles as a biological alternative in low voltage electricity generation has the potential to be further explored and developed.

Personnel Psychology

On reading the table of contents it is already clear that the authors of this book covered the field of personnel psychology very fully and extensively.

Differential item functioning in the figure classification test

The elimination of unfair discrimination and cultural bias of any kind, is a contentious workplace issue in contemporary South Africa. To ensure fairness in testing, psychometric instruments are subjected to empirical investigations for the detection of possible bias that could lead to selection decisions constituting unfair discrimination. This study was conducted to explore the possible existence of differential item functioning (DIF), or potential bias, in the Figure Classification Test (A121) by means of the Mantel-Haenszel chi-square technique. The sample consisted of 498 men at a production company in the Western Cape. Although statistical analysis revealed significant differences between the mean test scores of three racial groups on the test, very few items were identified as having statistically significant DIF. The possibility is discussed that, despite the presence of some DIF, the differences between the means may not be due to the measuring instrument itself being biased/ but rather to extraneous sources of variation, such as the unequal education and socio-economic backgrounds of the racial groups. It was concluded that there is very little evidence of item bias in the test. Opsomming Die uitskakeling van onregverdige diskriminasie en kultuursydigheid van enige aard, is tans 'n omstrede kwessie in die werkpiek in Suid-Afrika. Ten einde regverdigheid in toetsing te verseker, word psigomefrriese toetse onderwerp aan empiriese ondersoeke na die moontlikheid van sydigheid wat kan lei tot keuringsbesluite wat onregverdige diskriminasie meebring. Hierdie ondersoek is ondemeem om die moontlikheid van differensiele itemfunksionering (DIF), of potensiële sydigheid, in die Figuurindelingtoets (A121), met behulp van die Mantel-Haenszel chikwadraattegniek, te ondersoek. Die steekproef het bestaan uit 498 mans by 'n produksiemaatskappy in die Wes-Kaap. Alhoewel statistiese ontleding beduidende verskille in gemiddelde toetstellings van drie rassegroepe op die toets aangedui het, is bate min items aangedui wat statistics beduidende DIF bevat. Die moontlikheid word bespreek dat, hoewel sommige DIF in die toets teenwoordig is, die verskille tussen die gemiddeldes nie die gevolg is van 'n sydige meetinstrument per se nie, maar eerder die gevolg van eksteme bronne van variasie, soos byvoorbeeld die ongelyke opvoedkundige- en sosio-ekonomiese agtergronde van die rassegroepe. Die gevolgtrekking was dat daar bate min getuienis van itemsydigheid in die toets is.