Morphological evolution of nanofibers during electrospinning

Electrospinning is a very useful technique to produce polymeric nanofibers. It involves fast-drawing a polymer fluid into nanofibers under a strong electric filed, and depositing randomly on an electrode collector to form non-woven nanofiber mat in most cases [1]. The fibre stretching during electrospinning is a fast and incessant process which can be divided into three consecutive stages: jet initiation, whipping instability and fibre deposition. From the initial jet to dry fibres, the fibre stretching takes place in milliseconds, so it has been hardly so far to observe fiber morphology changes by any normal methods, such as high speed photography [2-5]. In this study, we used a facile and practical approach to realize the observation of nanofiber morphology changes during electrospinning. Through a special collection device with coagulation bath, newly electrospun nanofibers can be solidified at different electro spinning distances, and by associating the fiber morphology with the electrospinning distance (d), the morphological evolution of nanofibers can be established. We used polyacrylonitrile (PAN) and polystyrene (PS) as two model polymers to demonstrate this method in present research. From experimental results, we found the massive jet-thinning happens at the initial stage of the process. The formation of uniform PAN nanofibers (7%) and the beads structure changes on beads-on-string PAN nanofibers (5%) have also been successful observed. Using the same method, we also observed PS nanofiber (10%) morphology changes to understand the beads formation 011 nanofibers during electrospinning process, and how the beads was eliminated when ionic surfactant is added into the PS solution for electrospinning.

Stability and convergence analysis of transform-domain LMS adaptive filters with second-order autoregressive process

In this paper, the stability and convergence properties of the class of transform-domain least mean square (LMS) adaptive filters with second-order autoregressive (AR) process are investigated. It is well known that this class of adaptive filters improve convergence property of the standard LMS adaptive filters by applying the fixed data-independent orthogonal transforms and power normalization. However, the convergence performance of this class of adaptive filters can be quite different for various input processes, and it has not been fully explored. In this paper, we first discuss the mean-square stability and steady-state performance of this class of adaptive filters. We then analyze the effects of the transforms and power normalization performed in the various adaptive filters for both first-order and second-order AR processes. We derive the input asymptotic eigenvalue distributions and make comparisons on their convergence performance. Finally, computer simulations on AR process as well as moving-average (MA) process and autoregressive-moving-average (ARMA) process are demonstrated for the support of the analytical results.

On performance of transform domain adaptive filters with Markov-2 inputs

In this paper, the analysis for the performance of the discrete Fourier transform LMS adaptive filter (DFT-LMS) and the discrete cosine transform LMS adaptive filter (DCT-LMS) for the Markov-2 inputs is presented. To improve the convergence property of the least mean squares (LMS) adaptive filter, the DFT-LMS and DCT-LMS preprocess the inputs with the fixed orthogonal transforms and power normalization. We derive the asymptotic results for the eigenvalues and eigenvalue distributions of the preprocessed input autocorrelation matrices with DFT-LMS and DCT-LMS for Markov-2 inputs. These results explicitly show the superior decorrelation property of DCT-LMS over that of DFT-LMS, and also provide the upper bounds for the eigenvalue spreads of the finite-length DFT-LMS and DCT-LMS adaptive filters. Simulation results are demonstrated to support the analytic results.

Morphological signals of sex and status in spotted bowerbirds

The Spotted Bowerbird, Chlamydera maculata, appears to be sexually monomorphic. We caught and marked 118 birds in central Queensland, and sexed 88 using molecular methods. We found that our catch was strongly male-biased, both at bower sites and at non-bower feeding sites. We continued to observe the bird's behaviour after their release and so sub-divided males into sexual status groups as either bower-owners or non-owners. We searched for morphological measures, subjectively judged colour differences and quantitatively collected spectral measures of the visual properties of the crest feathers that would allow us to separate birds of differing sex and status. We found that bower owners had larger crests than non-owner males or females and that crest area provided the most accurate predictor of a bird's sex and status in a discriminant function analysis. We studied a cohort of seven males who went from non-owners to bower owners over three years, and found that their change in status was accompanied by a change in crest size – the only significant change in their morphology. Crest size did not relate to the mating success of a bower-owner. Instead, we suggest why the crest may differ between status groups and the implications that this may have for the sexual behaviour of male and female Spotted Bowerbirds.

The effects of phonological and morphological training on speech perception scores and grammatical judgments in deaf and hard-of-hearing children

Seventeen primary school deaf and hard-of-hearing children were given two types of training for 9 weeks each. Phonological training involved practice of /s, z, t, d/ in word final position in monomorphemic words. Morphological training involved learning and practicing the rules for forming third-person singular, present tense, past tense, and plurals. The words used in the two training types were different (monomorphemic or polymorphemic) but both involved word final /s, z, t, d/. Grammatical judgments were tested before and after training using short sentences that were read aloud by the child (or by the presenter if the child was unable to read them). Perception was tested with 150 key words in sentences using the trained morphemes and phonemes in word final position. Grammatical judgments for sentences involving the trained morphemes improved significantly after each type of training. Both types of training needed to be completed before a significant improvement was found for speech perception scores. The results suggest that both phonological and morphological training are beneficial in improving speech perception and grammatical performance of deaf and hard-of-hearing children and that both types of training were required to obtain the maximum benefit.

Design and optimization of LNA topologies with image rejection filters

An important problem in designing RFIC in CMOS technology is the parasitic elements of passive and active devices that complicate design calculations. This article presents three LNA topologies including cascode, folded cascade, and differential cascode and then introduces image rejection filters for low-side and high-side injection. Then, a new method for design and optimization of the circuits based on a Pareto-based multiobjective genetic algorithm is proposed. A set of optimum device values and dimensions that best match design specifications are obtained. The optimization method is layout aware, parasitic aware, and simulation based. Circuit simulations are carried out based on TSMC 0.18 um CMOS technology by using Hspice.

Application of floating medium filters for aquaculture wastewater treatment

Filtration is an effective process in removing particles of various nature and sizes that are present in water and wastewater. It has been used as a final clarifying step in water treatment since the19th century. It is becoming increasingly important in the tertiary treatment step of wastewater to produce effluent of superior quality for the purpose of reuse. Filtration is particularly applied when high flow rates of water with relatively low contents of suspended solids have to be treated. In a conventional water or wastewater treatment system, the filters are usually placed after sedimentation units to remove suspended particles, which escape without settling in the sedimentation units. When chemically pretreated and flocculated water is applied to a filter without a prior-solid liquid separation it is called direct filtration.

Kinetic effects of halide ions on the morphological evolution of silver nanoplates

Time-resolved extinction spectroscopy is employed to study the reaction kinetics in the shape-conversion reaction involving halide ions (including Cl-, Br- and I-) etching (sculpturing) silver nanoplates. A series of time-resolved extinction spectra are obtained during the in situ etching process and the evolution of surface plasmon resonance (SPR) of the silver nanoparticles is analyzed. Spectral analysis indicates that the conversion of nanoprisms starts simultaneously with the emergence of nanodisks when the halide ions are added. The etching rate of different halide ions is evaluated through the in-plane dipole resonance peak intensity of silver nanoplates vs. the reaction time (dI/dt). The relationship between the etching rate and the halide ion concentration shows that the halide ion etching reaction can be considered as a pseudo-first-order reaction. The effect of different halide ions on the shape-conversion of silver nanoplates is compared in detail. The activation energy of the etching reaction is calculated, which indicates that the etching ability of different halide ions is on the order of Cl - < I- < Br-.

The use of molecular phylogenetic and morphological tools to identify cryptic and paraphyletic species : examples from the diminutive long-fingered bats (Chiroptera : Miniopteridae : Miniopterus) on Madagascar

Based on nearly complete (1125 bp) cytochrome-b sequence data and morphological characters, two new endemic species of Miniopterus are described from Madagascar that were previously identified as M. manavi. Using phylogenetic analysis, the basal nodes of major lineages in the Malagasy members of this genus are weakly supported, while, in most cases, the branches leading to each of the clades are well resolved. Miniopterus mahafaliensis, new species, occurs in the southwestern semidesert areas and M. brachytragos, new species, has a broad distribution across the northern half of the island, ranging across several different biomes. Phylogenetic inference indicates that these two new taxa are not closely related to M. manavi sensu stricto, with average genetic distances of 9.2% and 5.7% from this taxon, respectively. On the basis of this and previous revisions, the former M. manavi complex is now recognized to represent at least five taxa, which do not form a monophyletic group with respect to one another, and represent extraordinary examples of convergent evolution. Miniopterus brachytragos is closely related to the recently named M. aelleni, while M. mahafaliensis is not closely associated with any of these species. Molecular phylogenetic analysis was imperative to resolve the species limits of these taxa and morphology then provided the means to corroborate the recovered clades. There are localities on the island, specifically limestone karstic zones, where four species of the former M. manavi sensu lato complex occur in strict sympatry. These species often use the same day-roost caves and have similar external and craniodental measurements. This raises intriguing questions as to how these animals divide their worlds with regard to dietary regimes and foraging strategies, as well as their speciation history.