An investigation of paper based microfluidic devices for size based separation and extraction applications.

Conventional microfluidic devices are typically complex and expensive. The devices require the use of pneumatic control systems or highly precise pumps to control the flow in the devices. This work investigates an alternative method using paper based microfluidic devices to replace conventional microfluidic devices. Size based separation and extraction experiments conducted were able to separate free dye from a mixed protein and dye solution. Experimental results showed that pure fluorescein isothiocyanate could be separated from a solution of mixed fluorescein isothiocyanate and fluorescein isothiocyanate labeled bovine serum albumin. The analysis readings obtained from a spectrophotometer clearly show that the extracted tartrazine sample did not contain any amount of Blue-BSA, because its absorbance value was 0.000 measured at a wavelength of 590nm, which correlated to Blue-BSA. These demonstrate that paper based microfluidic devices, which are inexpensive and easy to implement, can potentially replace their conventional counterparts by the use of simple geometry designs and the capillary action. These findings will potentially help in future developments of paper based microfluidic devices.

Effects of fluid flow on the oligonucleotide folding in single-walled carbon nanotubes.

This paper presents molecular-dynamics (MD) simulations of DNA oligonucleotide and water molecules translocating through carbon nanotube (CNT) channels. An induced pressure difference is applied to the system by pushing a layer of water molecules toward the flow direction to drive the oligonucleotide and other molecules. This MD simulation investigates the changes that occur in the conformation of the oligonucleotide due to water molecules in nanochannels while controlling the temperature and volume of the system in a canonical ensemble. The results show that the oligonucleotide in the (8,8)-(12,12) CNT channel forms a folded state at a lower pressure, whereas the oligonucleotide in the (10,10)-(14,14) CNT channel forms a folded state at a higher pressure instead. The van der Waals forces between the water molecules and the oligonucleotide suggest that the attraction between these two types of molecules results in the linear arrangements of the bases of the oligonucleotide. For a larger nanotube channel, the folding of the oligonucleotide is mainly dependent on the solvent (water molecules), whereas pressure, the size of the nanotube junction, and water molecules are the considering factors of the folding of the oligonucleotide at a smaller nanotube channel. For a folded oligonucleotide, the water distribution around the oligonucleotide is concentrated at a smaller range than that for the distribution around an unfolded oligonucleotide.

Improving the system stability of a digital Shack-Hartmann wavefront sensor with a special lenslet array.

There has been very limited study on the stability of a Shack-Hartmann wavefront sensor (SHWS) since its emergence in the early 1970s. In this paper, through experimental study of the system stability of a digital SHWS, a special lenslet array with long focal range is designed and implemented with a spatial light modulator to improve the system performance. Diffractive lenses with long focal length range can provide pseudo-nondiffracting beams and a long range of focusing plane. The performance and effect of the modified SHWS with this lenslet array are investigated, and the experimental results show that the system stability and measurement repeatability are not sensitive to the sensing distance and stay at an acceptable level.

Quantitative analysis of the tracking of blood pressure and relative factors in childhood: Shimane Heart Study.

1. In order to clarify the predictive factors of cardiovascular diseases caused by hypertension and hypercholesterolaemia in adults, a longitudinal epidemiological study was started in 1978. 2. This paper reports the results of research carried out from a quantitative analysis of the tracking of blood pressure and anthropometric parameters in children and adolescents using a tracking index. The index was calculated according to the changes in blood pressure quintiles for the whole population during the observation period. 3. The study population consisted of 5148 Japanese children living in the city of Izumo, who were examined every 3 years between the ages of 6 and 15 years old. 4. Although systolic blood pressure tracked weakly during childhood and adolescence, there was no significant relation between the tracking of systolic blood pressure and a family history of hypertension. 5. The tracking indices of the anthropometric parameters were better than those of systolic blood pressure, but the index of the left ventricular mass was similar to that of systolic blood pressure. 6. In conclusion the tracking of blood pressure might be determined by the tracking of bodyweight and height.