Wetting behavior of thermally bonded polyester nonwoven fabrics: The importance of porosity

The wetting properties of thermally bonded polyester nonwoven fabrics with different basis weights were studied. These nonwovens had the same composition: 85% poly(ethylene terephthalate) and 15% poly(butylene terephthalate) fibers. Two techniques, the 3S wicking test and sessile drop method, yielded similar water contact angles for all the nonwovens, but these results differed from the values obtained with the single fibers. In the nonwoven fabrics, the pore structure played a dominant role in the wetting properties: the existence of large pores in the thinner nonwovens reduced the dimensions of the liquid–solid interfacial perimeter. Compared with the water contact angle of the constituent single fibers, the contact angle of the fabrics was increased. A crenellated surface model was created to quantify the influence of pores on the wettability of nonwovens. It was possible to deduce the surface porosity of the fabric with this model, but only in the case of contact with nonwetting liquids such as water: this surface porosity corresponded only to the outermost layers of the fabric structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 387–394, 2006     

Bidirectional axial transmission can improve accuracy and precision of ultrasonic velocity measurement in cortical bone: a validation on test materials

The axial transmission technique uses a linear arrangement of ultrasonic emitters and receivers placed on a same side of a cortical bone site in contact with the skin, involving ultrasonic propagation along the axis of bone. The velocity of the waves radiated from bone has been shown to reflect bone status. The thickness and composition of soft tissue may vary along the length of the bone, between different skeletal sites, or between subjects. Hence, accurate estimates of velocity require first to eliminate the effect of the overlying soft tissue that is traversed by the ultrasound wave. To correct for such bias without measuring soft tissue properties, we designed new ultrasonic probes in the 1-2 MHz frequency range. It is based on propagation along the bone surface in two opposite directions from two sources placed on both sides of a unique group of receivers. The aim is to obtain an unbiased estimate of the velocity without any intermediate calculation of soft tissue properties, such as thickness variation or velocity. Validation tests were performed on academic material such as Perspex or aluminium. We found that head wave velocity values could be biased by more than 10% for inclination of a few degrees between the test specimen surface and the probe. On test materials, the compensation procedure implemented in our probe led to a relative precision error on velocity measurement lower than 0.2 to 0.3%. These results suggest that the correction procedure allows measuring in vivo velocities independently of soft tissue properties.     

Simple identification of a cross-linked hemoglobin by tandem mass spectrometry in human serum

Hemoglobin-based oxygen therapeutics are prepared by reaction of hemoglobin with cross-linking molecules and are utilized as blood substitutes. They can be used as doping agents to increase the oxygen-carrying capacity of hemoglobin. We have compared a glutaraldehyde-polymerized bovine hemoglobin (Oxyglobin, Biopure Corp.) with natural bovine hemoglobin by mass spectrometry in order to detect specific fragment ions of the cross-linked protein for further potential applications in doping control of human blood samples. HCl acid (6 N) hydrolysis was performed in parallel on both proteins. Hydrolysates were then analyzed by direct infusion electrospray mass spectrometry (ESIMS) using a triple quadrupole mass spectrometer. Confirmation and precision were obtained by LC-ESIMS(n) experiments performed on an ion trap mass spectrometer. Chromatographic and mass spectrometry data allowed detection of two potential Oxyglobin-specific ions--m/z 299 and 399--that were shown to lose a 159 u neutral fragment under collision-induced dissociation conditions. Thus, monitoring of constant neutral loss of 159 u on acid hydrolysates of human serum samples spiked with different amounts of Oxyglobin has proved to be an efficient screening method to specifically detect and identify Oxyglobin. LC-MS of the spiked serum sample hydrolysates enabled detection of Oxyglobin at a detection limit of 4 g x L(-1).     

Properties and drug release profile of poly(N-isopropylacrylamide) microgels functionalized with maleic anhydride and alginate

This study highlights the advantages of functionalized poly(N-isopropylacrylamide) (PNIPAAm) microgels over pure PNIPAAm microgels in terms of polymer network properties and drug release profiles. PNIPAAm network was modified by addition of maleic anhydride (MA) as a comonomer and by formation of interpenetrating polymer network in the presence of alginate. The functionalized thermosensitive microgels in the size range from 20 to 80 μm and with better performance in comparison with pure PNIPAAm microgels were prepared by inverse suspension polymerization. The impact of MA and alginate on the PNIPAAm microgel structure was evaluated through analysis of microgel size, size distribution, volume phase transition temperature (VPTT), equilibrium swelling ratio as well as morphology of the system. It was shown that the controlled modification of PNIPAAm network could result in microgels of considerably improved swelling capacity with unchanged thermosensitivity and maintained open pore morphology. In addition, drug release behavior of microgels could be markedly altered. Release of procaine hydrochloride from the selected microgels was studied using Franz diffusion cell at temperatures below and above VPTT of the microgels. Temperature-controlled drug release pattern was dependent on the type of functionalization of PNIPAAm network. According to drug loading properties and drug release mechanism, PNIPAAm/MA copolymer microgels demonstrated the optimal performances.     

Electromagnetic metamaterials

This paper proposes a review of electromagnetic metamaterials based on the idea that these are composite materials, their properties depending of the type and dimensions of the structural elements as well as the dimensions of unit cell. From the multitude of structural elements, only few that could present negative permittivity and negative or very high permeability in the range of radio and microwave frequency were chosen. The method of determination for the constitutive parameters (μ_eff and ?_eff) of metamaterials based on the S parameters or transmission and reflection coefficients is presented. Moreover, some applications of metamaterials are described, the attention being focused on perfect lenses and novel structures, namely conical Swiss rolls, electromagnetic cloaks and sensors for nondestructive evaluation of materials. Given that the spatial resolution of these sensors can be substantially improved in comparison to classical sensors, the metamaterial lenses are used for the manipulation of evanescent waves.