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Production planning and scheduling in the pulp and paper industry can be very challenging. In most cases, practitioners address the production planning process manually, which is time-consuming and sub-optimal. This study deals with production planning encountered in a pulp mill company involving different wood species, parallel heterogeneous lines, inventory limits, sequence-independent setup times and preventive maintenance. To tackle the problem, an efficient mixed-integer formulation is proposed that optimizes when, where and how much to produce of different wood species and schedules preventive maintenance to minimize the total setup times. Several computational experiments are conducted to solve a case study in a pulp mill company in Chile. The results show the capability of the model to support the decision-making process in the pulp and paper industry, providing an efficient tool for practitioners to solve the problem in a reasonable amount of time. [ABSTRACT FROM AUTHOR]

Results from the natural aging process of copy paper using emission fluorescence spectra are presented in this article. For the study, copy paper examples subjected to aging from 0 to 25 years were selected as test samples. Copy paper shows a well-defined fluorescence spectrum due to the cellulosic compounds used in its manufacture. By analysing each sample's fluorescence bands, relative intensities and the band shifts in the paper's fluorescence spectra, results provide information about the condition of the cellulosic compounds from which we can estimate the paper's age. Results show that the relative intensity of fluorescence emission bands of the copy paper exponentially decay as it ages. As such, fluorescence spectroscopy stands out as a suitable technique for evaluating the deterioration suffered by, for example, art works on copy paper. The effect of incorporating wood extracts on the fluorescence properties of aged copy paper was also studied. Wood extracts soluble in ethanol and acetone appear to enhance the fluorescence emissions, raising the prospect of a novel preservation process. [ABSTRACT FROM AUTHOR]

AbstractPer- and polyfluoroalkyl substances (PFAS) analysis has become crucial due to their presence in the environment, their persistence and potential health risks. These compounds are commonly used in food contact materials (FCM) as a coating to provide water and grease-repellent properties. One of the pathways for PFAS to enter the human body is either through direct consumption of contaminated food or indirectly through migration from FCM into food. The purpose of this study was to investigate where the initial contamination of paper FCM occurs. We analysed paper material consisting of fresh fibre and secondary materials, intended to produce food packaging for the presence of PFAS. The samples were extracted and analysed for 23 different PFAS substances using the targeted approach with LC tandem mass spectrometry (LC-MS/MS). This analytical technique detects specific, easily ionisable PFAS with high sensitivity. However, one drawback of this approach is that it allows the identification of less than 1% of the PFAS known today. For this reason, we used combustion ion chromatography (CIC) to determine the content of extractable organic fluorine compounds (EOF) and compare it to the total fluorine content. The targeted analysis using LC-MS/MS measured an average sum concentration of PFAS of 0.17 ng g−1 sample. Our research shows that the primary PFAS contamination happens during the recycling process since all of the samples in which the targeted PFAS were measured belonged to the secondary material. The most frequently detected analytes were PFOA and PFOS, detected in 90% and 62% of the samples, respectively, followed by PFBS (in 29% of the samples). CIC showed that measured PFAS via LC-MS/MS amount to an average of 2.7 × 10−4% of total fluorine content, whereas the EOF was under the LOD in all of the measured samples. This result highlights the complexity of the accurate determination of PFAS compounds, displaying what kind of information the chosen methods provide. [ABSTRACT FROM AUTHOR]

La transición hacia el uso del papel para la enseñanza de la escritura en las escuelas elementales públicas en México no fue sencilla. Al finalizar el siglo XIX, se había cuestionado el uso de las pizarras por el riesgo que representaban para la salud, pues muchas veces los estudiantes borraban sus escritos con saliva y el material con el que estaban fabricadas no siempre guardaba las especificaciones necesarias, además el ruido al escribir era insoportable. En cambio, el papel, desde el punto de vista higiénico, pedagógico y estético, fue considerado un material superior frente a la dureza de la pizarra, el brillo de la superficie y la poca precisión que se obtenía en el trazo de las letras. Derivado de este planteamiento, se vislumbró seriamente la posibilidad de la adopción de papel en las escuelas oficiales. Sin embargo, este material era escaso y muy caro. Hacia el cambio de siglo, sólo dos fábricas de papel podían surtir a las escuelas y era necesario que abarataran el precio, que el sistema de distribución garantizara el abastecimiento y que el suministro fuera continuo. Este artículo analiza el inicio del proceso de reconversión de una tecnología para la enseñanza como era la pizarra por el papel. Analizo el gasto que significó y cómo esta modificación fue resultado de una multiplicidad de relaciones sociales, culturales, económicas y políticas que se entrecruzaron para dar una nueva configuración del tiempo, el ruido y los valores establecidos en el salón de clases. The transition to the use of paper in public elementary schools in Mexico was not easy. At the end of the nineteenth century, the use of slates had been questioned due to the health risk they represented since students often erased their writing with saliva and the material with which the slates were made did not always meet the necessary specifications. On the other hand, paper, from a hygienic, pedagogical and aesthetic point of view, was considered a superior material compared to the hardness of the slate, the shine of the surface and the lack of precision obtained in the tracing of the letters. Derived from this approach, the possibility of changing materials in official schools was seriously envisioned. However, the paper represented a very high cost. Only two paper mills could supply the schools and it was necessary to lower the price, and guarantee the supply by enhancing the distribution system. This article analyses the beginning of the conversion process of a technology for learning to write such as the slate for paper. I analyse the expense that it meant for the authorities and families, how the change was the result of a multiplicity of social, cultural, economic and political relations that intersected to give a new configuration of time, noise and established values in the classroom. [ABSTRACT FROM AUTHOR]

This paper focuses on the Southern African Association for Research in Mathematics, Science and Technology Education's (SAARMSTE's) role as a platform supporting research dissemination and connecting researchers in early grades mathematics (EGM) in the Southern African region. A review of the Long Papers in SAARMSTE over the last 20 years supports the finding of the other review papers in this Special Issue: that there has been substantial growth of attention to EGM since 2013. However, two distinctions are marked when looking at conference papers rather than journal papers. Firstly, there is a particularly large expansion of work in the last 5 years, with a broadening base of participation in this work. Second, looking across all the formats of conference presentations indicates SAARMSTE's role in supporting and building EGM as a key focus of research attention, and bringing together regional and international groups with interests in this area. Given that conference proceedings usually offer a broader picture of emerging interests than journal papers, we reflect on the range of foci of attention within EGM in the SAARMSTE Proceedings, and trends within this. These trends also help us to point to areas that are likely to be of key interest in the next decade. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lead pollution may cause serious damage to environment safety and human health, especially to children's growth. In this work, by using double stranded DNA (dsDNA) as the recognition element, a simple and effective electrochemical DNA sensor has been developed on a full carbon-based substrate, reduced graphene oxide/carbon paper (rGO/CP), to accomplish the rapid, sensitive and selective determination of Pb2+. Carbon paper (CP) provides a suitable substrate for the sensor with high portability and low cost, while rGO is easily electrodeposited onto CP and serves as both the signal amplification element and the molecular bridge between DNA and CP. Because of its high specific surface area and unique conjugated giant π structure, rGO tightly binds with DNA through π-π stacking and hydrophobic interactions, thereby providing loading of high quantities of DNA. The specific coordination between DNA and Pb2+ further improves the sensitivity of the sensor. The results demonstrate that rapid electrochemical enrichment of Pb2+ is achieved using the constructed CP/rGO/DNA electrode with a linear relationship between the peak current and the concentration of Pb2+ from 1 pM to 100 pM and a detection limit of 1 pM. In addition, this approach shows good selectivity and satisfactory repeatability for river water analysis. A promising sensitive, low-cost, simply-fabricated, and portable full carbon-based electrochemical biosensing platform has been therefore provided for lead determination. [ABSTRACT FROM AUTHOR]

Michael Hillard's Shredding Paper: The Rise and Fall of Maine's Mighty Paper Industry is both a labor history of the paper industry and a political economy of corporate governance and class struggle in the United States. As a labor historian, Hillard has compiled thousands of hours of interviews with paper-industry workers and managers. As a political economist, he persuasively argues that contests over the distribution of surplus from the 1960s forward and shifts in paper-industry ownership led to the strike wave that began in the '60s and spread to every paper mill in Maine by the late 1980s. Rapacious practices by out-of-state owners challenged workers' moral compass as much as their material existence. Responding, paper workers developed a folk political economy and even a folk Marxism, creating the foundation for challenging working-class support for regressive economics. This review provides context for Hillard's claim while partially challenging it in a different context, the United States steel industry. [ABSTRACT FROM AUTHOR]

Gas chromatography – tandem mass spectrometry (GC-MS/MS) using formic acid as a protective agent is reported for the determination of acrylic resin monomers in food contact packaging paper. The analytes were extracted by ethanol mixed with formic acid with 2-phenylethyl propionate as the internal standard. The extract was separated by a 6% cyanopropylbenzene-94% dimethylsiloxane ultra-inert chromatographic column and analyzed by GC-MS/MS in multiple reaction monitoring (MRM) mode. 13 acrylic resin monomers including acrylic acid, styrene, and acrylic ester were separated. The procedure was successfully applied for the analysis of real samples. The procedure provided a linear calibration range with detection limits from 0.16 to 0.46 mg kg−1. The mean recoveries were from 88.1% to 100.9% with relative standard deviations less than 5.4%. The residual acrylic resin monomers in packaging paper were primarily from printing base paper and varnish. Of the acrylic resin monomers, the monomers except for butyl acrylate and 2-ethylhexyl acrylate showed low migration rates. The method provides high sensitivity and good reproducibility with simple pretreatment, demonstrating application for monitoring acrylic resin monomers in food contact packaging paper. [ABSTRACT FROM AUTHOR]