Development of Decibel Stepped Attenuator for Automated Sound Level Meter Calibration

MAPAN - Parameter testing in the sound level meter calibration, such as frequency weighting and linearity, needs precise adjustment of sound level in the decibel (dB) unit. In the...     

Effects of propentofylline on CNS remyelination in the rat brainstem

Propentofylline (PPF) is a xanthine derivative with pharmacological effects distinct from those of the classical methylxanthines. It depresses activation of microglial cells and astrocytes which is associated with neuronal damage during neural inflammation and hypoxia. The aim of this study was to evaluate whether PPF had the capacity of affecting glial cells behavior during the process of demyelination and remyelination following ethidium bromide (EB) gliotoxic injury. EB injection into the CNS is commonly used as an experimental demyelinating model inducing local oligodendroglial and astrocytic death, which results in primary demyelination, blood–brain barrier and glia limitans disruption and Schwann cells invasion. Sixty Wistar rats were divided into four different groups receiving 10 microlitres of 0.1% EB or 0.9% saline solution into the cisterna pontis and treated or not with the xanthine. PPF treatment was done using 12.5 mg/kg/day by the intraperitonial route for 31 days of the experimental period. The rats were euthanized from 7 to 31 days after EB injection and brainstem sections were collected and processed for light and transmission electron microscopy studies. Results from both groups were compared by using a semi‐quantitative method developed for documenting in semithin sections the extent and nature of remyelination of demyelinating lesions. Results showed that PPF administration after EB injection significantly increased both oligodendroglial and Schwann cell remyelination at 31 days (mean remyelination scores of 3.67 ± 0.5 for oligodendrocytes and 1.27 ± 0.49 for Schwann cells) compared to untreated animals (scores of 3.19 ± 0.57 and 0.90 ± 0.33, respectively). Microsc. Res. Tech. 77:23–30, 2014. © 2013 Wiley Periodicals, Inc.     

Cyclosporine improves remyelination in diabetic rats submitted to a gliotoxic demyelinating model in the brainstem

The use of cyclosporine (CsA) has shown to induce an increase in density of oligodendrocytes near remyelinating areas following the injection of ethidium bromide (EB), a demyelinating agent, in the rat brainstem. It is also known that diabetes mellitus was capable of delaying remyelination by both oligodendrocytes and Schwann cells in this gliotoxic model. This study was designed to assess whether CsA had the capacity to improve remyelination in streptozotocin‐induced (50 mg/kg, intraperitoneal route) diabetic rats. Diabetic Wistar rats were divided in different groups receiving 10 microlitres of 0.1% EB or 0.9% saline solution into the cisterna pontis and were treated or not with CsA. During 7 days and, thereafter, three times a week, 10 mg/kg/day of CsA were given by intraperitoneal route. The rats were euthanized from 7 to 31 days after EB or saline injection and brainstem sections were collected and processed for light and transmission electron microscopy studies. Results from different groups were compared by using a semi‐quantitative method developed for documenting the extent and nature of remyelination in semithin sections following gliotoxic lesions. Results showed that CsA administration to diabetic rats after EB injection stimulate both oligodendroglial and Schwann cell remyelination (mean remyelination scores of 3.15 ± 0.5 for oligodendrocytes and 1.36 ± 0.58 for Schwann cells) compared to untreated animals (2.52 ± 0.71 for oligodendrocytes and 0.73 ± 0.47 for Schwann cells, respectively). CsA given to diabetic rats was capable of reversing some of the deleterial effects of diabetes on remyelination. Microsc. Res. Tech. 76:714–722, 2013. © 2013 Wiley Periodicals, Inc.     

Influence of dynamic crosslinking on the morphology,crystallization, and dynamic mechanical properties of PA6,12/EVA blends

This study investigated the effect of dynamic crosslinking of polyamide 6,12 and random copolymers of ethylene and vinyl acetate blends (PA6,12/EVA) on the morphology, crystallinity, and dynamic mechanical properties. The crosslinking agent was dicumyl peroxide (DCP), and the blends were processed in a torque rheometer. The morphology depended on the DCP content, and all blends exhibited the same crystallinity index. However, with increasing crosslinking degree, the interfacial tackiness (E) values increased from 1.8 to 2.7 nm. The lamellar structures of all blends started forming at approximately 160 °C, close to the temperature of pure polyamide. The crosslinked phase enhanced the pseudo‐elastic behavior of the blends and increased their molecular mobility activation energy. Samples with higher crosslinking degree exhibited smaller permanent deformation (0.01%) than those with low crosslinking. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44206.     

Structure and properties relationship of melt reacted polyamide 6/malenized soybean oil

In this work, a maleinized soybean oil (SOMA) was melt reacted with polyamide 6 and the thermal, rheological, and morphological properties were evaluated. It was observed that the maleinized soybean oil reacted with polyamide chains, increasing the molecular weight of the polymer. Addition of SOMA also promoted an increase in the amount of α crystalline phase as well as in the crystallinity index. The average amorphous layer thickness (L_a) was enhanced with the addition of 1 wt % of SOMA, while the average crystalline layer thickness (L_c) were significantly enlarged with the increase in SOMA content, indicating that SOMA structures were located at the interfacial region between amorphous and crystalline. The addition of 5 wt % of SOMA plasticized the PA6, reducing its glass transition temperature. However, the sample containing 5 wt % of SOMA showed an accentuated pseudoplastic behavior as compared to other samples. Addition of SOMA also reduced the tensile strength and increased the elongation at break. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43050.     

Beyond VNFM: Filling the gaps of the ETSI VNF manager to fully support VNF life cycle operations

One of the main challenges to use network functions virtualization (NFV) is to properly manage the life cycle of the virtualized network functions (VNFs). Current solutions based on the ETSI standard NFV architectural framework are complex and require the knowledge of a myriad of details of the underlying infrastructure. This work proposes a VNF manager (VNFM) specification that supports different platforms and VNF utilization scenarios. The proposed VNFM specification defines a set of APIs, modules, and components, for both the end user and the back-end that provide the fundamental set of operations required to fully manage the VNF life cycle. Our primary goal is to simplify the operations, in particular reducing the need for the network operator to know the details of the virtualized infrastructure. Note that the proposed solution fills a gap and complements the ETSI VNFM module. A prototype was implemented, and experimental results show the effectiveness and low overhead of the proposed solution.     

Integrating dynamic spectrum access and device‐to‐device via cloud radio access networks and cognitive radio

Dynamic Spectrum Access (DSA) can be integrated with Device‐to‐Device (D2D) communications to enable the exploitation of unused spectrum portions and to address the spectrum scarcity problem. Spectrum management mechanisms integrated into DSA and D2D allow low‐power communications between User Equipments without interfering with licensed primary users. However, these mechanisms tend to be energy and processing intensive, being unfeasible to implement in User Equipments with strict battery and processing limitations. On the other hand, Cloud Radio Access Networks already leverage the virtually unlimited computing capacity of clouds for baseband processing functions. Thus, in this article, we propose the Cognitive Radio Device‐to‐Device (CRD2D) approach aiming to offload spectrum management functionality to the cloud taking advantage of Cloud Radio Access Networks architecture to support the integration of DSA and D2D.     

Effect of dynamic cross-linking on phase morphology and dynamic mechanical properties of polyamide 12/ethylene vinyl acetate copolymer blends

Dynamic cross-linking of polyamide 12 (PA12) and ethylene vinyl acetate copolymer (EVA) blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively cross-linked within the PA12 phase through free radical reactions using dicumyl peroxide. The torque level and temperature in the torque rheometer chamber were monitored to follow the evolution of the EVA cross-linking during the dynamic cross-linking process. The degree of cross-linking of EVA in the PA12/EVA materials was estimated based on the gel content (insoluble EVA fraction). The PA12/EVA phase morphology was investigated by scanning electron microscopy. The solid viscoelastic properties were investigated by dynamic mechanical thermal analysis (DMTA). The morphology, interfacial tension and viscoelastic results showed the immiscible nature of this system. The morphology of the blends was observed and the results revealed a two-phase system. The PA12/EVA 70/30 showed disperse-phase morphology, however a co-continuous phase was observed in blend ratios of 50/50 and 60/40. The dynamic cross-linking process resulted in a more stable EVA phase morphology with disperse and interconnected structures in the thermoplastic PA12 domains.