The production of alkali-activated materials and geopolymers from the finer fraction of tailings is being increasingly investigated, as they could be used for building and public works, or to retain ...heavy metals in a consolidated solid matrix. The present study proposes a Pitzer-based geochemical model to reproduce the alkaline leaching for two mine tailing samples and the polymerization reactions. The model fits the results of the leaching tests quite well over the reaction duration and up to NaOH 10 M and 60 °C. Discrepancy for the dissolved Mg concentration indicates that the database can handle ionic strength up to 5 mol.kg−1. A geopolymer solid solution was developed for setting reactions modeling. The results compare favorably with compressive strength tests results, with C-S-H, M-S-H and geopolymers as the main hydration products. The study proposes an innovative application of Pitzer database developments with application to the mining industry.
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•Pitzer database for geopolymer hydration modeling•Kinetic dissolution rate laws for mafic minerals•Geochemical modeling of the alkaline leaching.•Empirical relation between the amount of binder mineral and compressive strength•Predicting compressive strength test result
Background
Medical devices made of polydioxanone (a synthetic biodegradable polymer) have been available since the early 1980s. However, no review regarding their performance and safety has been ...published.
Objective
This systematic review intends to review and assess commercially available polydioxanone implants and their safety and performance in patients.
Methods
We searched for approved polydioxanone implants in several Food and Drug Administration databases. Then, we performed a literature search for publications and clinical trials where polydioxanone devices were implanted in patients. This search was performed on MEDLINE, Embase, Scopus and other databases. Safety and performance of polydioxanone implants in patients were assessed and compared with the implantation of non-polydioxanone devices, when possible, based on scoring systems developed by the authors that analyse surgical site infection rates, inflammatory reaction rates, foreign body response, postoperative pain and fever.
Results
Food and Drug Administration databases search revealed that 48 implants have been approved since 1981, with 1294 adverse reactions or product malfunction in the last decade and 16 recalls. A total of 49 clinical trials and 104 scientific publications were found. Polydioxanone sutures and meshes/plates had low rates of surgical site infection, inflammatory reaction, foreign body response and postoperative fever. Polydioxanone clips/staples reported high rates of surgical site infection, postoperative fever and pain, with sub-optimal clinical performance and poor safety rates. The remaining implants identified showed high levels of safety and performance. Safety scores of polydioxanone implants and non-polydioxanone alternatives are similar. Polydioxanone monofilament sutures perform better than non-polydioxanone alternatives but performance did not differ with remaining polydioxanone implant types.
Conclusions
Although polydioxanone clips/staples should be implanted with caution and monitored carefully, in general, safety and performance scores of other polydioxanone implants did not differ from non-polydioxanone alternatives. This review will be a useful reference for researchers and industries developing new polydioxanone medical devices.
Electrospun filaments are leading to a new generation of medical yarns that have the ability to enhance tissue healing through their biophysical cues. We have recently developed a technology to ...fabricate continuous electrospun filaments by depositing the submicron fibres onto a thin wire. Here we investigate the influence of pyridine on the fibre deposition. We have added pyridine to polydioxanone solutions at concentrations ranging from 0 to 100 ppm, increasing the conductivity of the solutions almost linearly from 0.04 uS/cm to 7 uS/cm. Following electrospinning, this led to deposition length increasing from 1 cm to 14 cm. The samples containing pyridine easily underwent cold drawing. The strength of drawn filaments increased from 0.8 N to 1.5 N and this corresponded to a decrease in fibre diameter, with values dropping from 2.7 μm to 1 μm. Overall, these findings are useful to increase the reliability of the manufacturing process of continuous electrospun filaments and to vary their biophysical properties required for their application as medical yarns such as surgical sutures.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Chronic tendinopathy represents a growing healthcare burden in the ageing global population. Curative therapies remain elusive as the mechanisms that underlie chronic inflammation in tendon disease ...remain unclear. Identifying and isolating key pathogenic and reparative cells is essential in developing precision therapies and implantable materials for improved tendon healing. Multiple discrete human tendon cell populations have been previously described ex vivo. To determine if these populations persist in vitro, healthy human hamstring tenocytes were cultured for 8 d on either tissue culture plastic or aligned electrospun fibres of absorbable polydioxanone. Novel single-cell surface proteomics combined with unbiased single-cell transcriptomics (CITE-Seq) was used to identify discrete tenocyte populations. 6 cell populations were found, 4 of which shared key gene expression determinants with ex vivo human cell clusters: PTX3_PAPPA, POSTN_SCX, DCN_LUM and ITGA7_NES. Surface proteomics found that PTX3_PAPPA cells were CD10+CD26+CD54+. ITGA7_NES cells were CD146+ and POSTN_SCX cells were CD90+CD95+CD10+. Culture on the aligned electrospun fibres favoured 3 cell subtypes (DCN_LUM, POSTN_SCX and PTX3_ PAPPA), promoting high expression of tendon-matrix-associated genes and upregulating gene sets enriched for TNF-a and IL-6/STAT3 signalling. Discrete human tendon cell subpopulations persisted in in vitro culture and could be recognised by specific gene and surface-protein signatures. Aligned polydioxanone fibres promoted the survival of 3 clusters, including pro-inflammatory PTX3-expressing CD10+CD26+CD54+ cells found in chronic tendon disease. These results improved the understanding of preferred culture conditions for different tenocyte subpopulations and informed the development of in vitro models of tendon disease.
There exists large uncertainty in the literature as to the pK
of medium-chain fatty acids at the air-water interface. Via surface tension titration, the surface-pK
values of octanoic (C
), nonanoic ...(C
), and decanoic (C
) fatty acids are determined to be 4.9, 5.8, and 6.4, respectively. The surface-pK
determined with surface tension differs from the bulk value obtained during a standard acid-base titration. Near the surface-pK
of the C
and C
systems, surface tension minima are observed and are attributed to the formation of surface-active acid-soap complexes. The direction of the titration is shown to affect the surface-pK
of the C
system, as the value shifts to 5.2 with NaOH titrant due to a higher concentration of Na
ions at pH values close to the surface-pK
. As the reactivity and climate-relevant properties of sea spray aerosols (SSA) are partially dictated by the charge and surface activity of the organics at the aerosol-atmosphere interface, the results presented here on SSA-identified C
-C
fatty acids can be used to better predict the health and climate impact of particles with significant concentrations of medium-chain fatty acids.
This reflective essay describes steps taken by Business faculty in a U.S. Midwestern mid-sized regional university to assist faculty in making the rapid transition to 100% online teaching. These ...steps include the development of an online course template within the university’s course management system made available to all faculty with tips and video tutorials specifically tailored to business courses. The coronavirus pandemic forced faculty members at institutions across the world into teaching online in about two weeks. Many tenure-track professors and full-time instructors, who were required to complete extensive training prior to teaching online courses, were relatively well-prepared. In spite of this training, some instructors felt overwhelmed when the pandemic forced an immediate transition online. Adjunct instructors and some junior faculty were particularly affected. Consistent with the conservation of resources theory which suggests that individuals conserve their limited resources (e.g., time, money, etc.) to ensure availability when they are most needed, many instructors, particularly adjunct and junior faculty, were constrained by competing demands. Adjunct instructors often teach limited courses while maintaining full-time employment in their respective fields. Junior faculty also have limited resources due to service and publishing demands. The availability of a special online course helped these vulnerable faculty members make the rapid transition to emergency online teaching. This reflective essay also describes the results of a survey about this transition among both faculty and center for teaching and learning (CTL) staff. Lastly, we recommend strategies for CTLs and academic departments to prepare for future crises. “Deputizing” power-users in each academic unit to redistribute workloads during emergencies and sharing tips and tricks customized for their departments is one such strategy. Creating annual online training modules is another strategy to allow seamless transition to unexpected online teaching.
There exists large uncertainty in the literature as to the pKa of medium-chain fatty acids at the air-water interface. Via surface tension titration, the surface-pKa values of octanoic (C8), nonanoic ...(C9), and decanoic (C10) fatty acids are determined to be 4.9, 5.8, and 6.4, respectively. The surface-pKa determined with surface tension differs from the bulk value obtained during a standard acid-base titration. Near the surface-pKa of the C8 and C9 systems, surface tension minima are observed and are attributed to the formation of surface-active acid-soap complexes. The direction of the titration is shown to affect the surface-pKa of the C9 system, as the value shifts to 5.2 with NaOH titrant due to a higher concentration of Na+ ions at pH values close to the surface-pKa. As the reactivity and climate-relevant properties of sea spray aerosols (SSA) are partially dictated by the charge and surface activity of the organics at the aerosol-atmosphere interface, the results presented here on SSA-identified C8-C10 fatty acids can be used to better predict the health and climate impact of particles with significant concentrations of medium-chain fatty acids.
This empirical study evaluates the impact of faculty training in online teaching on perceived comfort, perceived effectiveness, and stress during the Emergency Transition to Online Learning (ETOL) ...caused by COVID‐19. Survey data revealed a positive relationship between training in online teaching and perceived effectiveness during the ETOL. However, this relationship is fully mediated by perceived comfort in teaching online, meaning training in online teaching significantly increased faculty perceived comfort, which in turn increased perceived effectiveness. Relative to their counterparts, faculty who agreed that the ETOL was stressful were significantly more likely to cite working from home distractions and a lack of physical resources as the greatest challenges. Going forward, our results suggest faculty should be trained in best practices in online teaching as a regular part of their development. Doing so would not only benefit online courses, but the tools used in online courses can also benefit faculty teaching in‐person courses. The emerging tools used in online courses can also serve to enhance teaching in emerging, technology‐based disciplines in business, such as digital marketing or business analytics. In addition to ongoing training, another best practice to prepare for a future ETOL would be to allow business school faculty to share what they have learned with other business faculty.
We find that individuals are confused by the titles used by investment professionals and
cannot distinguish between investment advisers and brokers. This confusion persists even
among those with ...investment industry experience, a college degree, or a high level of
perceived knowledge (one's self-assessment or feeling of knowing the information).
Surveyed individuals better identified the brokerage responsibilities of "an
investment sales representative" (an alternate title for broker) than the more
ambiguous titles brokers often use, such as "financial advisor."
Disclosure: One of the authors, Patrick Lach, owns and operates an independent investment
advisory firm.
Editor's Note
Submitted 17 January 2019
Accepted 13 March 2019 by Stephen J. Brown
Understanding of the molecular basis of long‐term fear memory (fear LTM) formation provides targets in the treatment of emotional disorders. Ca2+/calmodulin‐dependent protein kinase II (CaMKII) is ...one of the key synaptic molecules involved in fear LTM formation. There are two endogenous inhibitor proteins of CaMKII, CaMKII Nα and Nβ, which can regulate CaMKII activity in vitro. However, the physiological role of these endogenous inhibitors is not known. Here, we have investigated whether CaMKII Nβ protein expression is regulated after contextual fear conditioning or exposure to a novel context. Using a novel CaMKII Nβ‐specific antibody, CaMKII Nβ expression was analysed in the naïve mouse brain as well as in the amygdala and hippocampus after conditioning and context exposure. We show that in naïve mouse forebrain CaMKII Nβ protein is expressed at its highest levels in olfactory bulb, prefrontal and piriform cortices, amygdala and thalamus. The protein is expressed both in dendrites and cell bodies. CaMKII Nβ expression is rapidly and transiently up‐regulated in the hippocampus after context exposure. In the amygdala, its expression is regulated only by contextual fear conditioning and not by exposure to a novel context. In conclusion, we show that CaMKII Nβ expression is differentially regulated by novelty and contextual fear conditioning, providing further insight into molecular basis of fear LTM.
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