Development of Tensile Properties and Crystalline Conformation of Recycled Polypropylene by Re-Extrusion Using a Twin-Screw Extruder with an Additional Molten Resin Reservoir Unit

Plastic mechanical recycling is an attractive method for reducing the amounts of waste plastics. However, the alterations in the mechanical properties (degradation) in recycled plastics is a limitation to the material’s mechanical recycling. In this study, the mechanical recycling was enhanced by the addition of a “molten resin reservoir” unit at the end of the twin-screw extruder. Recycled polypropylene (RPP) obtained from a household was re-extruded with this developed extrusion unit. The tensile properties, type of crystalline, and conformation of polypropylene polymorphs were evaluated and compared for virgin polypropylene (VPP), recycled polypropylene (RPP) without extrusion (RPP-original), and RPP with extrusion by using a new type of extruder (RPP-extrusion). It could be found that the tensile properties of RPP-extrusion were improved, so as to be similar to those of VPP. In addition, the conformation of RPP-extrusion was similar to that of VPP by increasing the ratio between the helix and parallel band. This study succeeded in regenerating the tensile properties and inner structures in recycled PP, which could prolong the used lifetime and decrease the amount of waste from single-use plastic.

Differentiating Subchondral Insufficiency Fracture from Osteonecrosis May Help Avoid Unnecessary Total Hip Arthroplasty

Differentiation of subchondral insufficiency fracture (SIF) from osteonecrosis (ON) is clinically important. The purpose of this study is to correlate the X-ray and magnetic resonance imaging (MRI) findings in cases that have been diagnosed histopathologically as SIF or ON, define features on X-ray and MRI analysis, and identify clinical features that may aid in the diagnosis of SIF from ON. Two blinded radiologists evaluated 104 femoral heads that were diagnosed on histopathology as either ON or SIF. Radiographs and MRIs were evaluated for pertinent radiologic features. If a low signal intensity band was present on MRI, size/depth, shape (parallel/concave/serpentine), and consistency (fatty/edematous/fibrous/mixed) were characterized. About 48.1% of SIF cases were misdiagnosed on X-ray. On MRI, SIF was associated with the presence of a parallel band (p < 0.001), while ON was associated with a serpentine band (p < 0.001). Fifty-eight percent of SIF cases had low intensity signal bands that were fibrous (p < 0.001), while 86% of ON cases had mixed signal bands (p < 0.001). Mean depth for SIF and ON patients was 1.56 mm and 15.36 mm, respectively. Women with bone mineral density < − 1, and age > 50 years had higher odds of SIF (p = 0.047, p = 0.014, p = 0.034, respectively). SIF is often misdiagnosed on X-ray, and the presence, shape, quality, and depth of the band on MRI can help distinguish SIF from ON. Patients with inconclusive X-ray findings with clinical features that match potential SIF should be considered for MRI. It is reasonable to allow for nonoperative management before recommending operative procedures in patients suspected of having SIF, as these fractures may be possibly managed conservatively.

Nanocavity crossbar arrays for parallel electrochemical sensing on a chip

We introduce a novel device for the mapping of redox-active compounds at high spatial resolution based on a crossbar electrode architecture. The sensor array is formed by two sets of 16 parallel band electrodes that are arranged perpendicular to each other on the wafer surface. At each intersection, the crossing bars are separated by a ca. 65 nm high nanocavity, which is stabilized by the surrounding passivation layer. During operation, perpendicular bar electrodes are biased to potentials above and below the redox potential of species under investigation, thus, enabling repeated subsequent reactions at the two electrodes. By this means, a redox cycling current is formed across the gap that can be measured externally. As the nanocavity devices feature a very high current amplification in redox cycling mode, individual sensing spots can be addressed in parallel, enabling high-throughput electrochemical imaging. This paper introduces the design of the device, discusses the fabrication process and demonstrates its capabilities in sequential and parallel data acquisition mode by using a hexacyanoferrate probe.

Pattern Center Determination in Electron Backscatter Diffraction Microscopy

The pattern center of an electron backscatter diffraction (EBSD) image indicates the relative position of the image with reference to the interaction volume of the sample. As interest grows in high-resolution EBSD techniques, accurate knowledge of this position is essential for precise interpretation of the EBSD features. In a typical EBSD framework, Kikuchi bands are recorded on a phosphor screen. If the flat phosphor were instead shaped as a sphere, with its center at the specimen's electron interaction volume, then the incident backscattered electrons would form Kikuchi bands on that sphere with parallel band edges centered on great circles. In this article, the authors present a method of pattern center (PC) refinement that maps bands from the planar phosphor onto a virtual spherical screen and measures the deviation of bands from a great circle and from possessing parallel edges. Potential sources of noise and error, as well as methods for reducing these, are discussed. Finally, results are presented on the application of the PC algorithm to two types of simulated EBSD patterns and two experimental setups, and the resolution of the method is discussed.

EPR INVESTIGATIONS OF CuO-B2O3-PbO-Ag2O GLASSES

Glasses of the x CuO · (100 - x)[3 B 2 O 3· 0.9 PbO · 0.1 Ag 2 O ] system, with 0.5 ≤ x ≤ 10 mol %, were prepared and investigated by means of electron paramagnetic resonance (EPR) measurements. Structural details of different diamagnetic vitreous systems may be revealed by the Cu 2+ ions, frequently used as paramagnetic probes in EPR experiments. The shape and the intensity of the recorded EPR lines are dependent on the CuO content. The EPR spectra are asymmetric, with characteristics for Cu 2+ (3d9) ions in axially-distorted octahedral symmetric sites. Due to the interaction of the unpaired electron spin (s = 1/2) with the nuclear one (I = 3/2) of Cu 2+ ions, the characteristic hyperfine structure (hfs) is visible for small concentrations of CuO in both spectra bands (parallel and perpendicular). The increasing of copper content in the samples generates the EPR absorption spectra modification, the hfs being resolved in the parallel band of the spectra in whole compositional range, while in the perpendicular band, hfs disappear for x > 3 mol %. This fact indicates the structural modification in Cu 2+ vicinity and possible magnetic interactions.