Rapid fabrication of poly(ε‐caprolactone) nanofibers using needleless alternating current electrospinning

Poly(ε‐caprolactone) ( PCL) biopolymer nanofibers and micro‐fibers have been fabricated for the first time at the rates up to 14.0 g per hour using a needleless and collectorless alternating current electrospinning technique. By combining the ac‐voltage, “green” low toxicity glacial acetic acid (AA) as the solvent and sodium acetate (NaAc) as an additive, beadless PCL fibers with diameters tunable from 150 nm to 2000 nm, varying surface morphology and degree of self‐bundling are obtained. In this new approach, the addition of NaAc plays a crucial role in improving the spinnability of PCL solution and fiber morphology. NaAc reveals the concentration‐dependent effect on charge transfer and rheological properties of the PCL/AA precursor, which results in broader ranges of spinnable PCL concentrations and ac‐voltages suitable for rapid manufacturing of PCL‐based fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43232.     

Kinetic study of the depolymerization of Bruceton coal

The depolymerization of coals using phenol and p-toluenesulphonic acid, was studied.In this reaction the acid ‘catalyst’ is destroyed, its rate of destruction being different for different coals. A kinetic study of the depolymerization of Bruceton coal under conditions of gradually declining acid concentration has been carried out. Parameters which were monitored include the weight increase of the products, the solubility of the products in benzene-ethanol, the extractability of the products into pyridine, the amount of colloidal material present in the pyridine-extractables, and the molecular weight distribution of the pyridine-soluble products. Under the conditions used, the reaction produces primarily polymeric products from coal. The molecular weight distribution of the pyridine-soluble material seems to undergo no major changes with reaction time.     

Multimerization behaviour of single chain Fv variants for the tumour-binding antibody B72.3

A systematic study has been performed on the relationship betweenlinker length, relative orientation of variable domains, multimerizationbehaviour and antigen binding activity for single chain Fvs(scFvs) of the tumour-binding antibody B72.3. Thirteen scFvvariants with linkers comprising up to six repeats of the motifGly-Gly-Gry-Gly-Ser were studied. All these scFvs showed a tendencyto form dimers or higher molecular weight species, and thistendency decreased with increasing linker length. The dimersand higher molecular weight forms may arise from head to tailintermolecular association of V_H and V_L domains. For each linkerlength, scFvs with the organization VL-linker-VH showed greaterbinding activity than those with the organization VH-linker-VL.In fact, for the latter organization only the variant with a30 amino acid linker showed good binding activity, suggestingthat (0 for B72.3 the C-tenninus of VH or the N-tenninus ofVL makes a structural contribution to antigen binding, and (ii)shorter linkers interfere with this contribution. Antigen bindingstudies on scFvs should be interpreted with caution becauseof their tendency to multlmerize. Such multimerization can beminimized by using linkers longer than those in common use     

The design of serpentine-mode converters for high-power microwaveapplications

In this paper, we report the design methodology and numerical results for two mode converters that are suitable for high-power microwave applications. Both converters are designed to operate at 11.424 GHz and utilize periodic serpentine structures to convert between modes with different azimuthal-mode indexes. The first converts about 98.5% of an incident linearly polarized TE₁₂ mode to the TE ₀₁ mode when oriented as an H-plane bend, but has just 1% mode conversion to all modes when oriented as an E-plane bend. The second device converts a linearly polarized TE₁₁ mode to a TM ₀₁ mode with over 99.99% effectiveness. The performance of both devices with respect to parametric variations is detailed. Experimental measurements of the radiation patterns from the TE₁₂ -to-TE₀₁-mode converter are consistent with the theoretical predictions     

Initial and boundary conditions in multidimensional wave digital filter algorithms for plate vibration

Recently, multidimensional wave digital filter (MDWDF) structures have been proposed for the modeling of plate vibration problems. In this paper, we discuss how initial and boundary conditions may be properly embedded into such an algorithm in terms of the state quantities that are an integral part of the algorithm. Due to the essential feature of fully-local interconnectivity in the MDWDF model, different types of boundary conditions can be easily satisfied in a very simple and efficient manner. Instead of remodifying the whole algorithm, usually required by finite elements based methods, boundary conditions in terms of state outputs are simply attached to the model. This feature is especially useful when dealing with the mixed-edges boundary conditions frequently encountered in practice. Graphical results obtained from implementing the MDWDF algorithm are given to further demonstrate the capacities of the method in efficiently handling a fourth-order Mindlin plate vibration system with various types of boundary conditions.     

On development of a finite dynamic element and solution of associated eigenproblem by a block Lanczos procedure

The paper first presents the details of the development of a new six-noded plane triangular finite dynamic element. A block Lanczos algorithm is developed next for the accurate and efficient solution of the quadratic matrix eigenvalue problem associated with the finite dynamic element formulation. The resulting computer program fully exploits matrix sparsity inherent in such a discretization and proves to be most efficient for the extraction of the usually required first few roots and vectors, including repeated ones. Most importantly, the present eigenproblem solution effort is shown to be comparable to that of the corresponding finite element analysis, thereby rendering the associated dynamic element method rather attractive owing to superior convergence characteristics of such elements, presented herein.     

Metal concentrations in rural topsoil in South Carolina: potential for human health impact

Rural areas are often considered to have relatively uncontaminated soils; however few studies have measured metals in surface soil from low population areas. Many metals, i.e., arsenic (As), lead (Pb), and mercury (Hg), have well-documented negative neurological effects, and the developing fetus and young children are particularly at risk. Using a Medicaid database, two areas were identified: one with no increased prevalence of mental retardation and developmental delay (MR/DD) (Strip 1) and one with significantly higher prevalence of MR/DD (Strip 2) in children compared to the state-wide average. These areas were mapped and surface soil samples were collected from 0-5 cm depths from nodes of a uniform grid laid out across the sampling areas. Samples were analyzed for As, barium (Ba), beryllium (Be), chromium (Cr), copper (Cu), Pb, manganese (Mn), nickel (Ni), and Hg. Inverse distance weighting (IDW) was used to estimate concentrations throughout each strip area, and a principal component analysis (PCA) was used to identify common sources. All metal concentrations in Strip 2, the MR/DD cluster area, were significantly greater than those in Strip 1 and similar to those found in more urban and highly agricultural areas. Both Strips 1 and 2 had a high number of significant correlations between metals (33 for Strip 1 and 25 for Strip 2), suggesting possible similar natural or anthropogenic sources which was corroborated by PCA. While exposures were not assessed and direct causation between environmental soil metal concentrations and MR/DD cannot be concluded, the high metal concentrations in areas with an elevated prevalence of MR/DD warrants further consideration.     

Indoor mold levels and current asthma among school‐aged children in Saskatchewan,Canada

Current knowledge regarding the association between indoor mold exposures and asthma is still limited. The objective of this case–control study was to investigate the relationship between objectively measured indoor mold levels and current asthma among school‐aged children. Parents completed a questionnaire survey of health history and home environmental conditions. Asthma cases had a history of doctor‐diagnosed asthma or current wheeze without a cold in the past 12 months. Controls were age‐ and sex‐matched to cases. Vacuumed dust samples were collected from the child's indoor play area and mattress. Samples were assessed for mold levels and quantified in colony‐forming units (CFU). Sensitization to mold allergens was also determined by skin testing. Being a case was associated with family history of asthma, pet ownership, and mold allergy. Mold levels (CFU/m²) in the dust samples of children's mattress and play area floors were moderately correlated (r = 0.56; P < 0.05). High mold levels (≥30 000 CFU/m²) in dust samples from play [adjusted odds ratio (aOR) = 2.6; 95% CI: 1.03–6.43] and mattress (aOR) = 3.0; 95% CI: 1.11–8.00) areas were significantly associated with current asthma. In this study high levels of mold are a risk factor for asthma in children.     

Homotopy Path Spaces for Families of Admissible Paths

Motivated by the search for universal orbits in geometric control theory and universal topological semigroups over local semigroups in topological groups, particularly Lie groups, we introduce a very general axiomatic notion of “trajectory,” namely a topological space equipped with a family of paths satisfying certain properties that make it what we call an “admissible family.” Considering one-parameter families of these paths as a homotopy allows us to construct a homotopy path space, our main object of consideration. We identify a distinguished subfamily of admissible paths via what we call a selection or partial selection and show how this insures collapses in the homotopy path space structure. We establish sufficient conditions to identify the homotopy path space as the simply connected covering or as residing in the simply connected covering and point out certain of its universal properties in this setting. We close by applying and illustrating our results in the setting of Lie groups and semigroups.     

Approximate methods in Bayesian point process spatial models

A range of point process models which are commonly used in spatial epidemiology applications for the increased incidence of disease are compared. The models considered vary from approximate methods to an exact method. The approximate methods include the Poisson process model and methods that are based on discretization of the study window. The exact method includes a marked point process model, i.e., the conditional logistic model. Apart from analyzing a real dataset (Lancashire larynx cancer data), a small simulation study is also carried out to examine the ability of these methods to recover known parameter values. The main results are as follows. In estimating the distance effect of larynx cancer incidences from the incinerator, the conditional logistic model and the binomial model for the discretized window perform relatively well. In explaining the spatial heterogeneity, the Poisson model (or the log Gaussian Cox process model) for the discretized window produces the best estimate.