Evaluation of imbedded fiber retraction phenomenological models for determining interfacial tension between molten polymers

In this work, the interfacial tension for several polymer pairs, namely polypropylene/polystyrene (PP/PS), PP/polycarbonate (PC), PP/polyamide 6 (PA-6) and low density polyethylene (LDPE) and ethylene vinyl alcohol copolymer (EVOH) was evaluated as a function of temperature using the imbedded fiber retraction method (IFR). Two phenomenological models were used and compared to infer the interfacial tension from the evolution of the imbedded fiber back into a sphere: [Carriere CJ, Cohen A, Arends CB. J Rheol 1989;33:681-9. [1] and Tjahjadi M, Ottino JM, Stone HA. AIChE J 1994;40:385-94. [2]]. It was shown that Carriere et al.'s model overestimates the value of interfacial tension whereas Tjahjadi et al.'s model leads to results that corroborate the ones obtained using other experimental methods. A method to further increase the accuracy of Tjahjadi et al.'s model was proposed. Using this method the interfacial tension for the different polymer pairs studied was evaluated and shown to decrease linearly with increasing temperature.     

Three-channel solar radiometer for the determination of atmospheric columnar water vapor

The design of a three-channel solar radiometer used to determine total columnar atmospheric water-vapor amounts is presented. The main channel is located in the 0.94-μm water-vapor band, and two other channels are located in adjacent nonabsorption regions of the solar spectrum and are used to remove scattering effects from the main channel. Water-vapor transmittance is determined by means of a modified Langley approach, and these transmittances are converted to columnar water vapor by means of a band model developed at the University of Arizona. Several cases are presented in which columnar water-vapor amounts are determined through the use of the instrument and method described here. These results are compared with sounding-balloon results. Tests of the method indicate that columnar water vapor may be retrieved with an uncertainty of less than 10%.     

Domain structure of the Fib-1 and Fib-2 regions of human fibronectin. Thermodynamic properties of the type I finger module

The stability of the Fib-1 (29 kDa) and Fib-2 (19 kDa) fragments of human fibronectin as well as several different subfragments and isolated type I "finger" modules were studied under various solvent conditions by differential scanning calorimetry and fluorescence spectroscopy. It was established that all fibronectin fingers constitute independently folded domains whose melting temperatures range from 54 to 108 degrees C. The difference between heat capacities of the native and denatured states (delta Cp) is low, about 0.03 cal/K-g, which is consistent with the relatively low percentage of hydrophobic amino acids and the consequent small change in non-polar surface area exposed to the solvent upon denaturation. The free energy of unfolding at 25 degrees, as calculated from the calorimetric data or measured directly by titration with GdmSCN is also small, in the range of 2.4 to 6.7 kcal/mol. The small delta G value and its flat dependence on temperature (determined by delta Cp) translates the small variations in delta G between fingers into large variations in tm. The small value of delta G also indicates that finger modules are structurally rather fragile which may account for their sensitivity to proteolysis; almost any cleavage within either of the two disulfide loops destroys the cooperative structure and abolishes the corresponding melting transition. The fact that some fingers exhibit large decreases in tm upon separation from more stable neighbors with which they interact can also be viewed as a consequence of the low values of delta G and delta Cp.     

Infective endocarditis complicated with rapidly progressive glomerulonephritis: a case report

Despite a general national decline in criminal activities in the 1990s, juvenile criminal offenses continue to increase, (including violent, property, and delinquency acts). In addition increased numbers of children are being held in juvenile jails. It is all but impossible for pediatric health providers to think that "their patients" and "their practices" are immune from the epidemic of crime that affects and is caused by "just kids."     

Examining student satisfaction with wholly online learning

Learner satisfaction has been shown to be positively correlated with quality of learning outcomes. An understanding of the factors that influence student satisfaction with online learning in a particular context can be used as an input to the appropriate design of learning environments, and for the provision of targeted support to students, with an aim to positively influence the student online learning experience. Following the mandatory inclusion of at least one wholly online unit of study in all undergraduate programs at Deakin University, a large 'experiences of learning online' (ELO) survey was undertaken to gauge students' perceptions of studying in the wholly online mode. A multivariate linear regression of all the questionnaire items was performed against an overall satisfaction item. Five items were found to significantly contribute to a model that explained approximately 70% of reported student satisfaction. Factors that were found to positively influence student satisfaction with studying a wholly online unit primarily related to how confident they felt about their ability to communicate and learn online, having a clear understanding of what was required to succeed in the unit and how well they thought they were performing in the unit. Other results are also reported.     

Photolithography of amorphous films of (η5-C5H5)2Ti(N3)2 on silicon (111) resulting in TiO2: The mechanism of the photodeposition reaction

Photolithography to produce TiO₂ patterns from amorphous films of (⁵-C₅H₅)₂Ti(N₃)₂ has been demonstrated. The efficiency of the reaction has been measured yielding a quantum yield of 0.025. The mechanism of the photoreactions of (⁵-C₅H₅)₂Ti(N₃)₂ has been studied using Fourier transform-infrared spectroscopy in both a low-temperature 1,2-epoxyethylbenzene glass and as surface films. In each case the primary photochemical process was found to be loss of a single azido group. The result of subsequent photolysis was found to be dependent upon medium and temperature. In the low-temperature glass no further photochemistry was observed. The exhaustive photolysis of films at 20 K, or room temperature, under a vacuum or in air led to loss of all ligands and the formation of TiO₂.     

Low-density properties of gaseous,spin-aligned atomic hydrogen

The ground-state properties of bulk atomic hydrogen are calculated for the low-density gas, assuming that the atoms interact via the ³ _u ⁺ pair potential. The Monte Carlo technique is applied to a system consisting of 32 hydrogen atoms in a box, with periodic boundary conditions. These results are compared with those derived from the hard-sphere Bose-Einstein gas model.Work supported by NASA Grant No. NGR 06-002-159.     

Evaluation of the effects of sodium chloride,potassium sorbate,nisin and lysozyme on the probability of growth of Clostridium sporogenes

The aim of this study was to evaluate the combined effect of salt (sodium chloride, 0–8% w/v), sorbate (potassium sorbate, 0–4.5% w/v), nisin (0–500 ppm) and lysozyme (0–500 ppm) on the survival of Clostridium sporogenes as a non‐toxigenic surrogate of Clostridium botulinum in terms of the probability of growth by using a central composite rotatable design. The results indicated that salt and sorbate were the most effective factors in preventing the growth of Cl. sporogenes in high‐moisture (>95%) and low‐acid conditions. The probability of growth of Cl. sporogenes in broth was reduced by combinations of salt and sorbate. Nisin and lysozyme had insignificant effects on the probability of growth of Cl. sporogenes (P > 0.05). Lysozyme individually and in combination with nisin had no inhibitory effect on Cl. sporogenes. Overall, the addition of sorbate and lysozyme may allow the salt concentration to be reduced while preventing growth.