Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams.

The creation and application of PET nanofibrils for PP composite reinforcement were studied. PET nanofibrils were fibrillated within a PP matrix using a spunbond process and then injection molded to test for the end-use properties. The nanofibril reinforcement helped to provide higher tensile and flexural performance in solid (unfoamed) injection molded parts. With foam injection molding, the nanofibrils also helped to improve and refine the microcellular morphology, which led to improved performance. Easily and effectively increasing the strength of a polymeric composite is a goal for many research endeavors. By creating nanoscale fibrils within the matrix itself, effective bonding and dispersion have already been achieved, overcoming the common pitfalls of fiber reinforcement. As blends of PP and PET are drawn in a spunbond system, the PET domains are stretched into nanoscale fibrils. By adapting the spunbonded blends for use in injection molding, both solid and foamed nanocomposites are created. The injection molded nanocomposites achieved increased in both tensile and flexural strength. The solid and foamed tensile strength increased by 50 and 100%, respectively. In addition, both the solid and foamed flexural strength increased by 100%. These increases in strength are attributed to effective PET nanofibril reinforcement.

Scalable Fabrication of Thermally Insulating Mechanically Resilient Hierarchically Porous Polymer Foams.

The requirement of energy efficiency demands materials with superior thermal insulation properties. Inorganic aerogels are excellent thermal insulators, but are difficult to produce on a large-scale, are mechanically brittle, and their structural properties depend strongly on their density. Here, we report the scalable generation of low-density, hierarchically porous, polypropylene foams using industrial-scale foam-processing equipment, with thermal conductivity lower than that of commercially available high-performance thermal insulators such as superinsulating Styrofoam. The reduction in thermal conductivity is attributed to the restriction of air flow caused by the porous nanostructure in the cell walls of the foam. In contrast to inorganic aerogels, the mechanical properties of the foams are less sensitive to density, suggesting efficient load transfer through the skeletal structure. The scalable fabrication of hierarchically porous polymer foams opens up new perspectives for the scalable design and development of novel superinsulating materials.

Ultralight Microcellular Polymer-Graphene Nanoplatelet Foams with Enhanced Dielectric Performance.

Dielectric polymer nanocomposites with high dielectric constant (ε') and low dielectric loss (tan δ) are extremely desirable in the electronics industry. Percolative polymer-graphene nanoplatelet (GnP) composites have shown great promise as dielectric materials for high-performance capacitors. Herein, an industrially-viable technique for manufacturing a new class of ultralight polymer composite foams using commercial GnPs with excellent dielectric performance is presented. Using this method, the high-density polyethylene (HDPE)-GnPs composites with a microcellular structure were fabricated by melt-mixing. This was followed by supercritical fluid (SCF) treatment and physical foaming in an extrusion process, which added an extra layer of design flexibility. The SCF treatment effectively in situ exfoliated the GnPs in the polymer matrix. Moreover, the generation of a microcellular structure produced numerous parallel-plate nanocapacitors consisting of GnP pairs as electrodes with insulating polymer as nanodielectrics. This significantly increased the real permittivity and decreased the dielectric loss. The ultralight extruded HDPE-1.08 vol % GnP composite foams, with a 0.15 g·cm-3 density, had an excellent combination of dielectric properties (ε' = 77.5, tan δ = 0.003 at 1 × 105 Hz), which were superior to their compression-molded counterparts (ε' = 19.9, tan δ = 0.15 and density of = 1.2 g·cm-3) and to those reported in the literature. This dramatic improvement resulted from in situ GnP's exfoliation and dispersion, as well as a unique GnP parallel-plate arrangement around the cells. Thus, this facile method provides a scalable method to produce ultralight dielectric polymer nanocomposites, with a microscopically tailored microstructure for use in electronic devices.

Enhanced Thermal Conductivity of Graphene Nanoplatelet-Polymer Nanocomposites Fabricated via Supercritical Fluid-Assisted in Situ Exfoliation.

As electronic devices become increasingly miniaturized, their thermal management becomes critical. Efficient heat dissipation guarantees their optimal performance and service life. Graphene nanoplatelets (GnPs) have excellent thermal properties that show promise for use in fabricating commercial polymer nanocomposites with high thermal conductivity. Herein, an industrially viable technique for manufacturing a new class of lightweight GnP-polymer nanocomposites with high thermal conductivity is presented. Using this method, GnP-high-density polyethylene (HDPE) nanocomposites with a microcellular structure are fabricated by melt mixing, which is followed by supercritical fluid (SCF) treatment and injection molding foaming, which adds an extra layer of design flexibility. Thus, the microstructure is tailored within the nanocomposites and this improves their thermal conductivity. Therefore, the SCF-treated HDPE 17.6 vol % GnP microcellular nanocomposites have a solid-phase thermal conductivity of 4.13 ± 0.12 W m-1 K-1. This value far exceeds that of their regular injection-molded counterparts (2.09 ± 0.03 W m-1 K-1) and those reported in the literature. This dramatic improvement results from in situ GnPs' exfoliation and dispersion, and from an elevated level of random orientation and interconnectivity. Thus, this technique provides a novel approach to the development of microscopically tailored structures for the production of lighter and more thermally conductive heat sinks for next generations of miniaturized electronic devices.

Dental histology of Coelophysis bauri and the evolution of tooth attachment tissues in early dinosaurs.

Studies of dinosaur teeth have focused primarily on external crown morphology and thus, use shed or in situ tooth crowns, and are limited to the enamel and dentine dental tissues. As a result, the full suites of periodontal tissues that attach teeth to the jaws remain poorly documented, particularly in early dinosaurs. These tissues are an integral part of the tooth and thus essential to a more complete understanding of dental anatomy, development, and evolution in dinosaurs. To identify the tooth attachment tissues in early dinosaurs, histological thin sections were prepared from the maxilla and dentary of a partial skull of the early theropod Coelophysis bauri from the Upper Triassic (Rhaetian- 209-201 Ma) Whitaker Quarry, New Mexico, USA. As one of the phylogenetically and geologically oldest dinosaurs, it is an ideal candidate for examining dental tissues near the base of the dinosaurian clade. The teeth of C. bauri exhibited a fibrous tooth attachment in which the teeth possessed five tissues: enamel, dentine, cementum, periodontal ligament (PDL), and alveolar bone. Our findings, coupled with those of more recent studies of ornithischian teeth, indicate that a tripartite periodontium, similar to that of crocodilians and mammals, is the plesiomorphic condition for dinosaurs. The occurrence of a tripartite periodontium in dinosaurs adds to the growing consensus that the presence of these tissues is the plesiomorphic condition for the major amniote clades. Furthermore, this study establishes the relative timing of tissue development and growth directions of periodontal tissues and provides the first comparative framework for future studies of dinosaur periodontal development, tooth replacement, and histology. J. Morphol. 277:916-924, 2016. © 2016 Wiley Periodicals, Inc.

Superhydrophobic and oleophilic open-cell foams from fibrillar blends of polypropylene and polytetrafluoroethylene.

Effective removal of oils from water is of global significance for environmental protection. In this study, we investigate the hydrophobicity and oleophilicity of open-cell polymer foams prepared in a continuous and scalable extrusion process. The material used to prepare the open-cell foams is a fibrillar blend of polypropylene (PP) and polytetrafluoroethylene (PTFE). Scanning electron microscopy (SEM) images of the morphology of the PP/PTFE fibrillar blend reveal that the PTFE has a fibrillar morphology in the PP matrix. SEM micrograph of the extruded foam shows the formation of an interconnected open-cell structure. Using nitrogen pycnometry, the open-cell content is estimated to be 97.7%. A typical bulk density of the open-cell foam is measured to be about 0.07 g cm(-3) corresponding to a void fraction of 92%. Thus, a large three-dimensional space is made available for oil storage. A drop of water on the cross-section of the extruded open-cell foam forms a contact angle of 160° suggesting that the open-cell foam exhibits superhydrophobicity. The open-cell foam can selectively absorb various petroleum products, such as octane, gasoline, diesel, kerosene, light crude oil, and heavy crude oil from water and the uptake capacities range from about 5 to 24 g g(-1). The uptake kinetics can be enhanced by exposing the open-cell foam to high intensity ultrasound which increases the surface porosity of the thin, impervious, foam "skin" layer. The reusability of the foam can be improved by using a matrix polymer which demonstrates superior elastic properties and prevents the foams from undergoing a large permanent deformation upon compression to "squeeze out" the oil. For example, when the PP homopolymer matrix is replaced with a PP random copolymer, the permanent deformation for 10 compressive cycles is reduced from about 30% to 10%. To the best of our knowledge, these PP-based open-cell foams outperform PP-based absorbents conventionally used for oil-spill cleanup applications such as nonwoven PP fibers or melt-blown PP pads.

Safety status of farm tractors that operate on public highways in four rural Kentucky counties.

Kentucky FFA students inspected 153 farm tractors for safety features that prevent operator injuries during tractor overturns, highway collisions, runovers, and power take-off (PTO) entanglements. Tractor mean age was 23.6 years (SD = 20.9). Rollover protective structures (ROPS) were present on 50.66% of tractors, but only 33.33% of these had functional seatbelts. Loose and damaged seats were found on 30.46% of tractors. In 38.99% of cases, tractor rear-wheel fenders exposed operators to moving tractor tires, and 48.67% of tractors had dangerously worn or damaged tires. Tractors with a narrow front-end stance comprised 16.11% of the total. Only 53.06% of the tractors had starters with secure hard cover by-pass starting shields that fully covered the starter terminals, and 37.37% had fully exposed terminals with no cover. PTO master shields with all parts present and undamaged were present on only 29.27% of the tractors, and in 39.02% of cases the entire shield was missing. Only 44.67% of the tractors had properly mounted and fully functional mounting and dismounting access steps and handholds. SMV emblems were missing on 53.64% of tractors and in the proper place and condition in only 25.83% of cases. Tractors with properly mounted and fully functional head and tail lights comprised 40.94% of the sample, and tractors with no functional lights comprised 24.16%. Properly mounted, clean, and functional rearview mirrors were present on only 19.87% of the tractors, and 69.54% had no rearview mirrors. The project increased farming and non-farming students' awareness of tractor safety issues, provided empirical data about the safety status of a sample of tractors that frequently travel public highways in four rural Kentucky farming counties, and promoted dialog about these issues with adult farmers and other community members with whom the students interacted.

Binding of ferric enterobactin by the Escherichia coli periplasmic protein FepB.

The periplasmic protein FepB of Escherichia coli is a component of the ferric enterobactin transport system. We overexpressed and purified the binding protein 23-fold from periplasmic extracts by ammonium sulfate precipitation and chromatographic methods, with a yield of 20%, to a final specific activity of 15,500 pmol of ferric enterobactin bound/mg. Periplasmic fluid from cells overexpressing the binding protein adsorbed catecholate ferric siderophores with high affinity: in a gel filtration chromatography assay the K(d) of the ferric enterobactin-FepB binding reaction was approximately 135 nM. Intrinsic fluorescence measurements of binding by the purified protein, which were more accurate, showed higher affinity for both ferric enterobactin (K(d) = 30 nM) and ferric enantioenterobactin (K(d) = 15 nM), the left-handed stereoisomer of the natural E. coli siderophore. Purified FepB also adsorbed the apo-siderophore, enterobactin, with comparable affinity (K(d) = 60 nM) but did not bind ferric agrobactin. Polyclonal rabbit antisera and mouse monoclonal antibodies raised against nearly homogeneous preparations of FepB specifically recognized it in solid-phase immunoassays. These sera enabled the measurement of the FepB concentration in vivo when expressed from the chromosome (4,000 copies/cell) or from multicopy plasmids (>100,000 copies/cell). Overexpression of the binding protein did not enhance the overall affinity or rate of ferric enterobactin transport, supporting the conclusion that the rate-limiting step of ferric siderophore uptake through the cell envelope is passage through the outer membrane.

[Prevalence study of biotinidase deficiency in newborns]. / Estudo de prevalência em recém-nascidos por deficiência de biotinidase.

INTRODUCTION: Biotinidase deficiency is an inheritable disorder of biotin metabolism. This disorder fulfills major criteria for consideration for newborn screening: the affected children do no show clinical signs in the newborn period; the disease is highly disabling; treatment is effective in preventing neurological sequelae if undertaken promptly. MATERIAL AND METHODS: Screening of 125,000 infants born in Paraná State was carried out to establish the prevalence of biotinidase deficiency. A simple colorimetric procedure was used to detect two infants with biotinidase deficiency (1:62,500), one of them with profound deficiency (1:125,000) and the other with partial deficiency (1:125,000) of the enzyme. RESULTS: There were no known false-negative test results and 0.12% were false-positive, defined by further blood samples which were negative upon repeated testing. Sensitivity was 100% and specificity was 99.88%. Repeat blood samples could not be obtained in 63 (30%) suspected cases. CONCLUSIONS: Newborn screening for biotinidase is useful in identifying affected children, is inexpensive and allows early intervention, which may prevent irreversible neurological damage.

The effect of light and darkness on the production of cercariae of Schistosoma haematobium from Bulinus globosus.

The cercariae of Schistosoma haematobium showed a diurnal periodicity of emergence from Bulinus globosus in a twelve hour light/dark cycle. Peak emission occurred at 11.00 hrs with a smaller peak at 20.00 hrs, following the start of the period of darkness. In continuous illumination this second peak was not seen, indicating that only the morning peak is circadian in origin. The evening peak occurs in response to dark treatment and can be produced by periods of darkness ranging from eight seconds to one hour. The longer the period of dark treatment the longer the rise in output is maintained on return to light conditions. Subjection of snails to periods of dark treatment during the normal light period caused a reduction in the evening peak with the largest effect seen following the longest period of darkness. An increased output of cercariae was seen following fifteen minutes exposure to a range of light intensities, the largest increase occurring at 10,000 and 7000 lux and complete darkness. The rapidity of this reaction to variations in light intensity suggests that the cercariae of S. haematobium are showing emergence in response to shadows.