Ultrafine polystyrene nanofibers prepared by electrospinning

Ultrafine polystyrene (PS) nanofibers were prepared via the simple electrospinning technique. Uniform and smooth PS nanofibers were obtained with adding the organic salt BTEAC into the PS solutions and adjusting the concentration of PS solutions. Without the addition of BTEAC, PS fibers with few beads could be achieved with a PS mass fraction of 20%, and the average diameter of the fibers was 280 nm. The addition of the organic salt BTEAC could lower the critical concentration for the fiber formation and reduce the amount of beads on the fibers. Unltrafine PS fibers without any beads were obtained with a PS mass fraction of 10% and an ionic salt mass fraction of 0.5%. The average diameter of the fiber was successfully reduced to 100 nm. The influence of the salt concentration on the morphology and diameter of the PS fibers was also investigated. The viscosity and surface tension changes were measured with changing the concentration of BTEAC. The results show that the changes were so small that these factors could be ignored. It was suggested that variations of the fiber diameter should be mainly resulted from the changes of conductivity and conformation of the polymer chain as the concentration of BTEAC is varied.

Ultra-wideline 14N solid-state NMR as a method for differentiating polymorphs: glycine as a case study

Nitrogen-14 solid-state NMR (SSNMR) is utilized to differentiate three polymorphic forms and a hydrochloride (HCl) salt of the amino acid glycine. Frequency-swept Wideband, Uniform Rate, Smooth Truncated (WURST) pulses were used in conjunction with Carr-Purcell Meiboom-Gill refocusing, in the form of the WURST-CPMG pulse sequence, for all spectral acquisitions. The ¹⁴N quadrupolar interaction is shown to be very sensitive to variations in the local electric field gradients (EFGs) about the ¹⁴N nucleus; hence, differentiation of the samples is accomplished through determination of the quadrupolar parameters CQ and ηQ, which are obtained from analytical simulations of the ¹⁴N SSNMR powder patterns of stationary samples (i.e., static NMR spectra). Additionally, differentiation of the polymorphs is also possible via the measurement of ¹⁴N effective transverse relaxation time constants, T^eff2(¹⁴N). Plane-wave density functional theory (DFT) calculations, which exploit the periodicity of crystal lattices, are utilized to confirm the experimentally determined quadrupolar parameters as well as to determine the orientation of the ¹⁴N EFG tensors in the molecular frames. Several signal-enhancement techniques are also discussed to help improve the sensitivity of the ¹⁴N SSNMR acquisition method, including the use of selective deuteration, the application of the BRoadband Adiabatic INversion Cross-Polarization (BRAIN-CP) technique, and the use of variable-temperature (VT) experiments. Finally, we examine several cases where ¹⁴N VT experiments employing Carr-Purcell-Meiboom-Gill (CPMG) refocusing are used to approximate the rotational energy barriers for RNH3⁺ groups.

The right to convert exploration licences to mining leases in Australia: a proposed national uniform model

In this article, the authors raise an important proposal for reform to Australia's mining legislation: a nationally-consistent model providing exploration licence holders with a legislative right to be granted a mining lease. This proposed national model will be designed to reflect the present Western Australian system - Western Australia being the only jurisdiction to provide exploration licence holders with the express right to be granted a mining lease on application. The authors believe that the Western Australian system should provide the basis for a national legislative model, given that it is designed to balance appropriately the interests of companies wanting a right to mine to recoup the costs involved in exploring for minerals, and the interests of the public in ensuring that exploration and mining is conducted
reasonably.

Non-uniform bird assemblages in urban environments : the influence of streetscape vegetation

The urban landscape encompasses a broad spectrum of variable environments ranging from remnant patches to highly modified streetscapes. Despite the expansion of urban environments, few studies have examined the influence of urbanization on faunal diversity, particularly in the Southern Hemisphere. In this study, four broad habitat types were recognized in the urban environment, representing a continuum of modification ranging from parks with remnant vegetation to streetscapes dominated by native vegetation and those dominated by exotic vegetation to recently developed streetscapes. Bird censuses were conducted at 36 sites throughout urban Melbourne, with nine sites surveyed in each habitat type. The four habitat types supported significantly different bird communities based on species richness, abundance and composition suggesting that bird assemblages of urban environments are non-uniform. Parks and native streetscapes generally supported fewer introduced species than exotic and recently developed streetscapes. Overall abundance and richness of species were lower in the exotic and recently developed streetscapes than in parks and native streetscapes. Significant differences were also observed in foraging guilds within the four habitat types, with parks having the most foraging guilds and recently developed streetscapes having the fewest. The transition from native to exotic streetscapes saw the progressive loss of insectivorous and nectarivorous species reflecting a reliance by these species on structurally diverse and/or native vegetation for both shelter and food resources. The implementation of effective strategies and incentives which encourage the planting of structurally diverse native vegetation in streetscapes and gardens should be paramount if avian biodiversity is to be retained and enhanced in urban environments. It is also critical to encourage the maintenance of the existing remnant vegetation in the urban environment.

Texture, twinning and uniform elongation of wrought magnesium

A small number of crystal plasticity simulations and tensile tests are carried out with the aim of demonstrating that control of twinning can improve the uniform elongation of magnesium based alloys, It is suggested that this can be accomplished through texture manipulation because texture influences both the fraction of grains that undergo twinning and the strain required for the twinning reaction to go to completion.

Parallelization of the discrete gradient method of non-smooth optimization and its applications

We investigate parallelization and performance of the discrete gradient method of nonsmooth optimization. This derivative free method is shown to be an effective optimization tool, able to skip many shallow local minima of nonconvex nondifferentiable objective functions. Although this is a sequential iterative method, we were able to parallelize critical steps of the algorithm, and this lead to a significant improvement in performance on multiprocessor computer clusters. We applied this method to a difficult polyatomic clusters problem in computational chemistry, and found this method to outperform other algorithms.

Modeling the tensile strains of non-uniform fibers

The maximum strain experienced by the thinnest segment of a non-uniform fiber governs fiber breakage, yet this maximum strain can not be obtained from a normal single fiber test. Only the average strain of the whole fiber specimen can be obtained from a normal single fiber tensile test. This study has examined the relationship between the average strain, the maximum strain and the degree of fiber non-uniformity, expressed in coefficient of variation (CV) of fiber diameters along fiber length. The tensile strain of irregular fibers has been simulated using the finite element method (FEM). Using this method, average and maximum tensile strains of non-uniform fibers were calculated. The results indicate that for irregular fibers such as wool, there is an exponential relationship (i.e.ɛ _ave ɛ _max=ae ^{−b CV} ) between the ratio of average breaking strain and maximum breaking strain (ɛ _ave ɛ _max) and the along-fiber diameter variation (CV). The strain ratio decreases with the increase of the along-fiber diameter variation.

Socialisation and the work-related norms of marketing practitioners

This paper empirically describes the influences of professional and organisational socialisation on the norms of marketers. Based on a survey of 5,000 practitioners, it finds that the socialisation of marketers into their profession and organisations positively influences their marketing-related norms. This research appears to be the first investigation in the marketing ethics literature of the relationships among these constructs. The paper explains how the learning of professional and organisational rules, guidelines, and values influence the work-related norms of marketers. The findings have important implications for marketing managers and managers of professional associations.

Discordance between lung function of Chinese university students of 20-year-old established norms

Objective: We examined the validity of the 20-year-old established Asian norms for pulmonary function in a contemporary cohort of Hong Kong Chinese university students. Design and participants: Pulmonary function testing was conducted in university students (n = 805). Setting: A university campus in Hong Kong. Measurements and results: Parameters recorded included gender, age, height, weight, standard lung function variables (ie, FEV1, FVC, and peak expiratory flow rate [PEFR]), and exhaled carbon monoxide (CO) level. Subjects completed a questionnaire on pulmonary health, smoking history, and their dietary and exercise habits within 3 months of the study. Data were compared with the established norms for lung function for Chinese persons from Hong Kong. On average, subjects were taller than those reported in the original cohort, on whom the established norms are based; however, FEV1, FVC, and PEFR were lower. As predicted, the exhaled CO level was higher in smokers. Those who exercised regularly had a higher FEV1 and FVC, and reported fewer respiratory complaints. Conclusions: Our findings support the idea that lung function norms not only differ across ethnic groups, but that they may be susceptible to change over a single generation within an ethnic group living in the same geographic region. Assuming the equivalence of our testing methods and those on which established norms are based, our findings shed further insight into the dynamic nature of lung function, and have implications regarding the definition of normal pulmonary function and its variance over the short term.