Contact Force Mediated Rapid Deposition of Colloidal Microspheres Flowing over Microstructured Barriers.

Deposition of particles while flowing past constrictions is a ubiquitous phenomenon observed in diverse systems. Some common examples are jamming of salt crystals near the orifice of salt shakers, clogging of filter systems, gridlock in vehicular traffic, etc. Our work investigates the deposition events of colloidal microspheres flowing over microstructured barriers in microfluidic devices. The interplay of DLVO, contact, and hydrodynamic forces in facilitating rapid deposition of microspheres is discussed. Noticeably, a decrease in the electrostatic repulsion among microspheres leads to linear chain formations, whereas an increase in roughness results in rapid deposition.

Swimming statistics of cargo-loaded single bacteria.

Burgeoning interest in the area of bacteria-powered micro robotic systems prompted us to study the dynamics of cargo transport by single bacteria. In this paper, we have studied the swimming behaviour of oil-droplets attached as cargo to the cell bodies of single bacteria. The oil-droplet loaded bacteria exhibit super-diffusive motion which is characterised by a high degree of directional persistence. Interestingly, bacteria could navigate with cargo size as large as 8 µm resulting in an increased rotational drag of more than 2 orders when compared to the free bacteria. The directional change of cargo loaded bacterial trajectories seems to be enhanced by steric hindrance from other oil-droplets present in the environment.

Rhesus genotype frequency in Bangladeshi population.

The prevalence of Rhesus genotypes in Bangladesh has been studied and several important findings were observed. This being the initial report, includes a population of 1600 only. By using five Rh antisera (Anti-C, Anti-D, Anti-E, Anti-c and Anti-e) a genotype can be deduced since anti-d is not available. More often only a probable genotype can be suggested after reference to the known chromosome frequencies in the population. By using family studies in conjunction, it may be possible to determine genotype with certainty. The prominent Rhesus genotype was CDe/cDE (R1R2), i.e., 39.75%, Rhesus genotype cde/cde (rr) was found to be only 1.75%. The genotype cdE/cde (r"r) was not detected in the present series of Bangladeshi population. These results have been compared with the English and the Indian Bengalee Hindu Population.