Industrial paper recycling process. Suitable micronization for additive polymer application

The traditional paper recycling process has problems related to the disposal of sludge and waste, the use of incinerators and water treatment. Because of that, an interesting alternative proposed from dep. of chemical and materials engineering of Sapienza University of Rome to Carlucci industrial typography, is using paper as filler in thermoplastics or recycled thermoplastic matrix composite. In this way it’s possible re-use paper, but it also possible reduces the amount of polymer with equal volume. The paper has to be subjected by grinding. The chosen grinding process is fundamental to obtain a suitable product for composite. After a pre-grinding process obtaining 5-10 mm of paper fragments, the charge have to be subjected to a micronization process. In this study are selected two different type of micronization: the superfine grinding mill SF, a micronization process based on system that uses simultaneously the impact and friction action, and a knife mill that uses instead the cutting and friction action. Thanks to the first process, it is possible obtaining fibres with diameters of about 15-20 microns and lengths of the order of 250-500micron: a product therefore suitable for the application of filler in composites. This process unfortunately causes the production of fluff, as will shown in figure 2, because of the interfibrillar bonds between the fibers: an optimal dispersion of the fibers is necessary to avoid agglomerates which would decrease the composite properties. From the second process it is possible to obtain both fiber than particles as illustrated in figure 3. This morphologies mix allows to achieve a higher fluency preventing agglomerates. The turbomixer equipment realizes the production process of the composite, this process allows to introduce a higher percentage of filler respect the traditional injection moulding technique. The resulting composite is subjected by a morphological and mechanical characterization: look at the SEM analysis of the fracture surface, the fiber-matrix interface is weak, in spite of this, however, from the tensile test there is a constant elastic modulus and in some cases growing respect to the matrix devoid of fibres. From these results, the importance of optimize the grinding and micronization processes is clear and there is the opportunity of additives introduction to improve fiber-matrix interface

Eco-friendly approach and potential biodegradable polymer matrix for WPC composite materials in outdoor application

Blends based on high density polyethylene (HDPE) and poly(lactic) acid (PLA) with different ratios of both polymers were produced: a blend with equal amounts of HDPE and PLA, hence 50 wt.% each, proved to be a useful compromise, allowing a high amount of bio-derived charge without this being too detrimental for mechanical properties and considering its possibility to biodegradation behaviour in outdoor application. In this way, an optimal blend suitable to produce a composite with cellulosic fillers is proposed. In the selected polymer blend, wood flour (WF) was added as natural filler in the proportion of 20, 30 and 40 wt.%, considering as 100 the weight of the polymer blend matrix. Two compatibilizers to modify both HDPE-PLA blend and wood-flour/polymer interfaces i.e. polyethylene grafted maleic anhydride and a random copolymer of ethylene and glycidyl methacrylate. The most suitable percentage of compatibilizer for HDPE-PLA blends appears to be 3 wt.%, which was selected also for use with wood flour. In order to evaluate properties of blends and composites tensile tests, scanning electron microscopy, differential scanning calorimetry, thermo-gravimetric analyses and infrared spectroscopy have been performed. Wood flour seems to affect heavy blend behaviour in process production of material suggesting that future studies are needed to reduce defectiveness

Dual morphology (fibres and particles) cellulosic filler for WPC materials

Wood-plastic composites (WPC) were fabricated by using a polyethylene (PE) matrix and filling it with wood flour in the amount of 30 wt.%, and compared with the same composites with further amount of 10 wt.% of cellulosic recycled fibres added. The materials were produced by turbomixing and subsequent moulding under pressure. Mechanical properties of both WPC and WPC with cellulosic recycled fibres were evaluated through mechanical and physical-chemical tests. Tensile tests clarified that a moderate reduction is strength is observed with the bare introduction of wood flour with respect to the neat PE matrix, whilst some recovery is offered by the addition of recycled cellulose fibres. Even more promisingly, the elastic modulus of PE matrix is substantially improved by the addition of wood flour (around 8% on average) and much more so with the further addition of recycled cellulose (around 20% on average). The fracture surfaces from the tensile test were analysed by scanning electron microscope (SEM) indicating a reduction in microporosity as an effect of added cellulose. The water absorption test and the hardness measure (Shore D) were also performed. SEM analysis underlined the weak interface between both wood particle and cellulosic recycled fibres and matrix. The water absorption test showed a higher mass variation for pure WPC than WPC with cellulosic recycled fibres. The hardness measurement showed that the presence of cellulosic recycled fibres improves both superficial hardness of the composite and temperature resistance. © 2016 Author(s)

Optimization of thermoplastic blend matrix HDPE/PLA with different types and levels of coupling agents

High-density polyethylene (HDPE) and poly(lactic) acid (PLA) blends with different ratios of both polymers, namely, 30:70, 50:50, and 70:30, were produced. Polyethylene-grafted maleic anhydride and a random copolymer of ethylene and glycidyl methacrylate were also considered as compatibilizers to modify HDPE/PLA optimal blends and were added in the amounts of 1, 3, and 5 wt.%. Different properties of the blends were evaluated by performing tensile tests and scanning electron microscopy to analyze blend and interfaces morphology. Moreover, thermomechanical analysis through differential scanning calorimetry, thermo-gravimetric analysis, and infrared spectroscopy were also performed. The blend containing equal amounts of HDPE and PLA seemed to present a good balance between amount of bio-derived charge and acceptable mechanical properties. This suggests that these blends have a good potential for the production of composites with lingo-cellulosic fillers

Social-Emotional Climate in the Community College Classroom: An Action Research Study Investigating the Impact of Real-Time Student Feedback to Instructors

Community college students often have obligations outside the classroom (supporting dependents or working part-or full-time jobs), preventing them from participating in extracurricular activities and fulfilling their social-emotional needs on campus. As a result, they rely heavily on classroom interactions with their instructors to gain a sense of belonging and motivation necessary for optimal cognitive growth. This action research study was conducted at a rural community college in New England to learn if an informal feedback tool, given to students, could provide real-time data to instructors to enhance the social-emotional classroom environment. An inquiry group (IG) comprised of the researcher and instructors met four times over the course of a semester. The IG reflected on the student data, spoke in-depth about their reactions to the data, offered feedback about the assessment, and discussed the changes they would make in response to the real-time, course-level data in their courses. Thematic analysis was utilized to analyze and interpret the qualitative data from the inquiry group and student assessments. Four themes rose to prominence: True Feelings, Engaging Students, Instructor Approachability, and Remote Learning. At the close of the study instructors completed a summative evaluation and met again to review the synthesized data. This study showed how a more reflective and transformational view of classroom assessment with a focus on engagement benefited students and instructors. This dissertation is available in open access at AURA: Antioch University Repository and Archive, http://aura.antioch.edu/and OhioLINK ETD Center, https://etd.ohiolink.edu/

Optimal Tuning of AGDs Parameters and a Technique for Testing the Correct Mounting of Heatsinks on Power Transistors

L'abstract è presente nell'allegato / the abstract is in the attachmen

Neuronal nicotinic receptors modulate glutamatergic transmission on neonatal rat hypoglossal motoneurons

In the neonate the muscles of the tongue, which are exclusively innervated by the XII cranial nerves originating from the brainstem nucleus hypoglossus, must contract rhythmically in coincidence with breathing, suckling and swallowing. These motor commands are generated by hypoglossal motoneurons excited by glutamatergic inputs. Since in forebrain areas the efficiency of glutamatergic transmission is modulated by neuronal nicotinic receptors (nAChRs), the role and identity of nAChRs within the nucleus hypoglossus of the neonatal rat were explored using an in vitro brainstem slice preparation. This area expressed immunoreactivity for a4, a7 and b2 subunits. Whole cell patch clamp recording from hypoglossal motoneurons showed lack of spontaneous cholinergic events mediated by nAChRs even in the presence of a cholinesterase inhibitor. However, pharmacological antagonism of a7 or b2 containing receptors depressed glutamatergic currents arising either spontaneously or by electrical stimulation of the reticular formation. Hypoglossal motoneurons expressed functional nAChRs with characteristics of a4b2 and a7 receptor subunits, and displaying fast desensitization (time constant of 200 ms) from which full recovery developed within one min. Low (0.5 \ub5M) concentration of nicotine first facilitated glutamatergic transmission on motoneurons and later depressed it through receptor desensitization. When 0.1 \ub5M nicotine was used, only depression of synaptic transmission occurred, in keeping with the suggestion that nAChRs can be desensitized without prior activation. These results highlight the role of tonic nAChR activity in shaping excitatory inputs to hypoglossal motoneurons and suggest that their desensitization by ambient nicotine could contribute to disorders of tongue muscle movements

Lightweight metallic matrix composites. Development of new composites material reinforced with carbon structures

Carbon nano/micro-structures used as fillers in metallic lightweight alloys matrix composites are receiving considerable attention in scientific research and industrial applications. Aluminum and magnesium are the most studied light metals used as matrices in metal composites materials principally for their low density (respectively 2.7 g/cm3 and 1.7 g/cm3) and low melting temperature (around 660 °C for both metals). A good interaction between matrix and fillers is the first step to obtain an increase in bulk properties; furthermore, the manufacturing procedure of the composite is fundamental in terms of quality of fillers dispersion. In this work the influence of surface modifications for three classes of carbon fillers for aluminum and magnesium alloy (AZ63) as matrices is studied. In particular, the selected fillers are short carbon micro fibres (SCMFs), carbon woven fabrics (CWF) and unidirectional yarn carbon fibres (UYFs). The surface modification was carried out by a direct coating of pure nickel on fibres. The electroless pure nickel plating was chosen as coating technique and the use of hydrazine as reducing agent has prevented the co-deposition of other elements (such as P or B). SEM and EDS analyses were performed to study the effect of surface modifications. The mechanical properties of manufactured composites were evaluated by four point flexural tests according to ASTM C1161 (room temperature). Results confirm improved interactions between matrix and fillers, and the specific interaction was studied for any chosen reinforcement

Clinical Picture of Gastroesophageal Reflux Disease in Children

Gastroesophageal reflux (GER), defined as the passage of gastric contents into the esophagus, is a normal physiologic process occurring several times per day in healthy infants, children, and adults. The majority of GER episodes occur in the postprandial period, last in <3 min, and cause few or no symptoms. Conversely, when the reflux of gastric contents into the esophagus causes troublesome symptoms and/or complications, we talk about “gastroesophageal reflux disease (GERD).” Distinguishing physiologic GER from GERD may often be tricky for clinicians, especially in infants. The typical presentation of GERD includes the following symptoms: recurrent regurgitation, vomiting, weight loss or poor weight gain, excessive crying and irritability in infants, heartburn or chest pain, ruminative behavior, hematemesis, and dysphagia. Besides these esophageal symptoms, there is a set of extra-esophageal symptoms, mainly respiratory, which may occur along with typical symptoms or may represent the only clinical picture of GERD: odynophagia, wheezing, stridor, cough, hoarseness, dental erosions, and apnea/apparent life-threatening events (ALTEs). While infantile GER tends to resolve spontaneously and does not deserve pharmacological treatment, GERD management includes lifestyle changes, pharmacologic therapy, and surgery. Therefore, a proper diagnosis of these two conditions, besides other possible conditions mimicking reflux, is crucial in order to target the treatment, avoiding the overuse of antacid drugs that currently represents a major source of concern

A SPICE model of Operational Amplifiers for Electromagnetic Compatibility Analysis

This article proposes a macromodel to predict the nonlinear behavior of operational amplifiers having their baseband signal affected by out-of-band disturbances, such as those caused by electromagnetic interference. Like any opamp macromodel, the one proposed in this work was developed with the purpose of not sharing neither the technology parameters nor the circuit topology of the real device. Besides the baseband macromodel, the proposed solution comprises a high frequency equivalent circuit that propagates the out-of-band signals, and a nonlinear model to account for their demodulation. The proposed solution is suitable for any SPICE-like simulator. It does not affect the simulation performance, meaning the simulation time, the simulation accuracy and it does not cause any convergence issue. This article shows in detail the macromodel, the method to calculate its parameters as well as its experimental validation, which was obtained comparing the model predictions with the results of the measurements carried out on a commercial device