The Effect of Melt Extrusion Process Parameters on Rotary‐Evaporated Poly(propylene) Nanocomposites

Design of experiments is employed to investigate the interrelationships between processing and nanotube surface chemistry on the properties of PP nanocomposites. Statistically significant effects of nanomaterial type and concentration, extrusion temperature, screw speed, and recirculation time, and their interactions, on nanocomposite thermal properties and stability are isolated. The effects of these factors on the shear storage modulus, the low‐frequency slope of the shear storage modulus, decomposition temperature, and melt temperature are explored. Nanotube concentration has the most significant effect in enhancing the decomposition temperature of the nanocomposite, while long extrusion time and higher temperatures lead to deteriorated properties.

     

Poly(ethylene glycol) grafted polystyrene dendrimer resins: Novel class of supports for solid phase peptide synthesis

Poly(propyleneglycol)dimethacrylate cross-linked support using monomers Styrene and 4-chloromethyl styrene (PS-PPGDMA-VBC resin) was prepared by suspension polymerization method. Dendritic templates were synthesized from Schiff base and trimesic acid molecules and assembled independently on PS-PPGDMA-VBC support to the second generation. N,N-bischloro ethyl amine dendrimer was generated from Schiff base units and introduced to the chloromethyl groups uniquely through secondary amine. It was followed by acidolytic cleavage, diazotization and thionyl chloride reactions leading to first generation dendrimer. O-benzyl ether dendrimer was created using 1,3,5-tris(hydroxyl methyl)benzene unit which was produced by the LiAlH₄ reduction of carbonyl groups of trimesic acid molecule. The hydroxyl methyl groups formed were converted to chloro methyl groups by adding thionyl chloride that leads to first generation dendrimer. Similar synthetic routes were followed to produce second generation dendrimers too. Poly(ethylene glycol), M_n ≈ 1500) has been grafted to chlorine termini of both dendrimers and used to check various physical and chemical properties of different peptide synthetic conditions. Reactions were qualitatively analyzed by FTIR, ¹³C NMR, SEM and quantitatively analyzed by UV measurements and CHN analysis. Classically difficult ACP sequence was synthesized on both PEGylated dendrimer supports and compared to Tenta Gel. Biologically significant disulfide bonded endothelin class of peptides were also synthesized using novel supports using various literature reported methods.     

Effect of Microstructure on the Radioluminescence and Transparency of Ce-Doped Strontium Hafnate Ceramics

In this paper we report on the fabrication and characterization of SrHfO(3):Ce ceramics. Powders were prepared by solid-state synthesis using metal oxides and carbonates. X-ray diffraction measurements showed that phase-pure SrHfO(3) is formed at 1200°C. Inductively coupled plasma spectroscopy confirmed the purity and composition of each batch. SrHfO(3) exhibits several phase changes in the solid, but this does not appear to be detrimental to the ceramics. Microprobe experiments showed uniform elemental grain composition, whereas aluminum added as charge compensation for trivalent cerium congregated at grain boundaries and triple points. Radioluminescence spectra revealed that the light yield decreases when the concentration of excess Sr increases. The decrease in the light yield may be related to the change of Ce(3+) into Ce(4+) ions. For stoichiometric SrHfO(3):Ce, the light yield is about four times that of bismuth germanate (BGO), the conventional benchmark, indicating great potential for many scintillator applications.     

Intrinsic carrier multiplication in layered Bi2O2Se avalanche photodiodes with gain bandwidth product exceeding 1 GHz

Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities, strong light-matter interactions, and tunable optical absorption and emission. Here, metal-semiconductor-metal avalanche photodiodes (APDs) are fabricated from Bi₂O₂Se crystals, which consist of electrostatically bound [Bi₂O₂]²⁺ and [Se]²⁻ layers. The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of ~ 400 kHz at a visible wavelength of 515.6 nm, ultimately resulting in a gain bandwidth product exceeding 1 GHz. Due to exceptionally low dark currents, Bi₂O₂Se APDs also yield high detectivities up to 4.6 × 10¹⁴ Jones. A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi₂O₂Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of ~ 44 meV, in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors. In this manner, layered Bi₂O₂Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.

     

Fast, ultrasensitive virus detection using a Young interferometer sensor

We report the application of an integrated optical Young interferometer sensor for ultrasensitive, real-time, direct detection of viruses. We have validated the sensor by detecting herpes simplex virus type 1 (HSV-1), but the principle is generally applicable. Detection of HSV-1 virus particles was performed by applying the virus sample onto a sensor surface coated with a specific antibody against HSV-1. The performance of the sensor was tested by monitoring virus samples at clinically relevant concentrations. We show that the Young interferometer sensor can specifically and sensitively detect HSV-1 at very low concentrations (850 particles/mL). We have further demonstrated that the sensor can specifically detect HSV-1 suspended in serum. Extrapolation of the results indicates that the sensitivity of the sensor approaches the detection of a single virus particle binding, yielding a sensor of unprecedented sensitivity with wide applications for viral diagnostics.     

Biofunctionalized lipid-polymer hybrid nanocontainers with controlled permeability

We have successfully developed, for the first time, a novel polymer-lipid hybrid nanocontainer with controlled permeability functionality. The nanocontainer is made by nanofabricating holes with desired dimensions in an impermeable polymer scaffold by focused ion beam drilling and sealing them with lipid bilayers containing remote-controlled pore-forming channel proteins. This system allows exchange of solutions only after channel activation at will to form temporary pores in the container. Potential applications are foreseen in bionanosensors, nanoreactors, nanomedicine, and triggered delivery.     

Investigation into Surface Defects Arising in Hot-Rolled SUP 11A Grade Spring Billets

Silicomanganese grade billets are the most commonly used steels for manufacture of automobile leaf springs. However, Cr-Mn-B grade steel known by trade name of SUP 11A grade is replacing the conventional silicomanganese grades such as 60Si7 or 65Si7 steels because it has become a competitive alternative in the market. Three heats of SUP11A grade spring steel were made through BOF-VAD-CC route and continuously cast into 125 × 125 mm billets. Some of the billets contained blowholes and piping. Rolling of selected billets into 85 × 15 mm flats revealed occasional slivers, seams, and a few shallow hairline surface cracks. A detailed metallurgical investigation was carried out to understand the genesis of these defects. A pearlite-free ferritic microstructure near the cracks combined with the presence of dispersed inclusions resulting from internal oxidation in the vicinity of cracks and the presence of scales within the shallow discontinuous short-length longitudinal cracks indicated that these defects resulted from pre-existing subsurface blowholes lying within 1 mm of billet surface. Reduction of the gas content of liquid steel in the mold, optimization of electromagnetic stirring (EMS) current, and control of superheat are some of the broad measures identified to improve the cast quality of SUP 11A spring steel billets and minimize the rejection of rolled flats.     

Multifunctional composites using reinforced laminae with carbon-nanotube forests

Traditional fibre-reinforced composite materials with excellent in-plane properties fare poorly when out-of-plane through-thickness properties are important. Composite architectures with fibres designed orthogonal to the two-dimensional (2D) layout in traditional composites could alleviate this weakness in the transverse direction, but all of the efforts so far have only produced limited success. Here, we unveil an approach to the 3D composite challenge, without altering the 2D stack design, on the basis of the concept of interlaminar carbon-nanotube forests that would provide enhanced multifunctional properties along the thickness direction. The carbon-nanotube forests allow the fastening of adjacent plies in the 3D composite. We grow multiwalled carbon nanotubes on the surface of micro-fibre fabric cloth layouts, normal to the fibre lengths, resulting in a 3D effect between plies under loading. These nanotube-coated fabric cloths serve as building blocks for the multilayered 3D composites, with the nanotube forests providing much-needed interlaminar strength and toughness under various loading conditions. For the fabricated 3D composites with nanotube forests, we demonstrate remarkable improvements in the interlaminar fracture toughness, hardness, delamination resistance, in-plane mechanical properties, damping, thermoelastic behaviour, and thermal and electrical conductivities making these structures truly multifunctional.     

Are more senior academics really more research productive than junior academics? Evidence from Australian law schools

This study examines the relationship between academic seniority and research productivity through a study of a sample of academics at Australian law schools. To measure research productivity, we use both publications in top law journals, variously defined, and citation metrics. A feature of the study is that we pay particular attention to addressing the endogeneity of academic rank. To do so, we use a novel identification strategy, proposed by Lewbel (Journal of Business and Economic Statistics 30:67–80, 2012), which utilises a heteroscedastic covariance restriction to construct an internal instrumental variable. Our main finding is that once endogeneity of academic rank is addressed, more senior academics at Australian law schools do not publish more articles in top law journals (irrespective of how top law journals are defined) than their less senior colleagues. However, Professors continue to have greater impact than Lecturers when research productivity is measured in terms of total citations and common citation indices, such as the h-index and g-index.     

An investigation over the effect of the reducing agent on the properties of the ZnO-reinforced Ni–P coatings

Journal of Materials Science: Materials in Electronics - Electroless ZnO-reinforced Ni–P coatings are developed on mild steel substrates in the Electroless bath, which contains an optimum...