* Cobalt carbide (Co2C) was monitored using novel in situ magnetometer. * The formation of cobalt carbide was confirmed by means of in situ XRD and synchrotron XRD measurements. * Cobalt carbide, ...once formed, is very stable at realistic Fischer-Tropsch conditions. * The formation of cobalt carbide is inversely proportional to H2/CO ratio and FT reaction temperature. * The carbide formation is thermodynamically feasible, but only small amounts form at realistic FT conditions. While carbides are always present in iron-based Fischer-Tropsch synthesis, very little is known about the presence and the role of carbides in cobalt-based CO hydrogenation. Cobalt carbide, Co2C, has been reported in catalysts where operational upsets occurred and it is associated with low catalyst activity and increased methane selectivity. In this study, a novel in situ magnetometer was used to study the formation and the stability of cobalt carbide during the Fischer-Tropsch synthesis at fully relevant conditions. The formation of cobalt carbide was confirmed by means of in situ XRD and synchrotron XRD measurements. Cobalt carbide is relatively stable at typical reaction conditions, but a rapid decomposition into hcp cobalt occurs in hydrogen above 150°C. Cobalt carbide formation is inversely proportional to the H2/CO ratio and the reaction temperature. However, the amounts of cobalt carbide formed are small and the impact on deactivation at realistic Fischer-Tropsch conditions should generally be negligible.
In the summer of 2020, dozens of high-profile influencers in videogaming entertainment were accused of sexual harassment and predatory behavior. Among them, popular gaming YouTuber Craig Thompson ...(username Mini Ladd) confessed on Twitter to sexting minors but resumed uploading content to his YouTube channel one month later, resulting in public outcry. Thompson's return to YouTube, as a case study, illustrates how predatory influencers can manipulate technical affordances across social media platforms to insulate themselves from accountability and maintain their revenue and audience. Drawing on data scraped from Twitter (34k tweets) and YouTube (62k comments and video network data), this article uses a mixed-methods social network analysis (Burgess & Matamoros-Fernández, 2016) to map the public effort to deplatform Mini Ladd. This case study explores issues of cross-platform insulation and audience manipulation by demonstrating how a predatory influencer: 1) censored keywords in his comments to obfuscate criticism; 2) optimized YouTube's video algorithms to avoid references to his scandal; and 3) upheld harassment towards his young fanbase. Ultimately, I argue that YouTube's policies are ill-equipped to manage the networked practices of predatory influencers and that the platform's reliance on morally motivated networked harassment (Marwick, 2021) as a substitute is troubling and ineffective.
Control allocation problems can be formulated as optimization problems, where the objective is typically to minimize the use of control effort (or power) subject to actuator rate and position ...constraints, and other operational constraints. Here we consider the additional objective of singularity avoidance, which is essential to avoid loss of controllability in some applications, leading to a nonconvex nonlinear program. We suggest a sequential quadratic programming approach, solving at each sample a convex quadratic program approximating the nonlinear program. The method is illustrated by simulated maneuvers for a marine vessel equipped with azimuth thrusters. The example indicates reduced power consumption and increased maneuverability as a consequence of the singularity-avoidance.
Discord, a popular community chat application, has rhetorically distanced itself from its associations with white supremacist content through a public commitment to proactive moderation. However, ...Discord relies extensively on third-party services (like bots and server bulletins), which have been overlooked in their role in facilitating hateful networks. This study notes how Discord offloads searchability to server bulletin sites like Disboard, to deleterious effect. This study involves two parts: (1) we use critical technoculture discourse analysis to examine Discord’s blogs, policies, and application programming interface and (2) we present data scraped from 2741 Discord servers listed on Disboard, revealing networks of hateful and white supremacist communities that openly use “edgy,” raiding-oriented, and toxic messaging. These servers exploit Discord’s moderation tools and affordances to proliferate within Discord’s distributed ecology. We argue that Discord’s policies fail to address its reliance on unmoderated third-party services or the networked practices of its toxic communities.
Sintering of supported cobalt nanoparticles is one of the main deactivation mechanisms in the Fischer–Tropsch synthesis. In this study, crystallite growth was studied with an alumina-supported ...catalyst in real time and as a function of process conditions using a novel in situ magnetometer. It could be shown that sintering with this catalyst occurred via a combination of high CO and high water partial pressures. It is proposed that particle growth proceeds via cobalt subcarbonyl migration over the hydroxylated support surface.
Coverage dependence adsorption of intermediates typical for syngas conversion is studied theoretically on
fcc-cobalt surfaces. The
fcc structure is relevant for cobalt particles active in this ...reaction. Emphasis on the analysis is on the thermodynamics of surface reconstruction as a function of surface adsorbate and surface coverage. An important result is the finding that only adsorbed carbon induced reconstruction of
fcc-Co(1
1
1) to
fcc-Co(1
0
0) as well as the clock reconstruction for the two surfaces.
The production by enzymatic treatment of fish protein hydrolysates (FPH) is a promising route to add value to fisheries proteinic co-products (fish frames, heads etc.). Indeed, FPH possess good ...nutritional properties and biological activities for food and feed uses. Pressure-driven membrane separations such as ultrafiltration (UF) and nanofiltration (NF) can be used after the hydrolysis to increase the specific activities of the FPH. This paper discusses the impact of a two-step UF/NF process producing four different fractions on two industrial FPH with different hydrolysis degrees. Fractionation is carried out in “realistic” conditions for an industrial process, on highly concentrated FPH solutions (about 100 g of dry matter/L) at a high volume reduction factor. For each step, UF or NF, the variation of the permeation flux in the course of the fractionation is discussed according to the FPH hydrolysis degree and the membranes cut-offs. The values of performance indicators defined in terms of nitrogen content are also examined, including the concentration factor (
CF), the relative recovery in the retentate (η
R
) and the mean and final retention factors (
RF
m
and
RF
f
). Computed values of these indicators are validated through the setting of volume and mass balances around each step. The impact of fractionation on the FPH peptidic population is shown. Peptidic populations are described in terms of chromatographic profiles (SEC–FPLC). The UF fractionation produces a permeate enriched with respect to the FPH smaller than a molecular weight of about 600–750 Dalton, and a retentate enriched in large peptides (above the same MW). A similar behaviour is found for the NF fractionation. Comparing the impact of the UF fractionation on the two hydrolysates allows to conclude that the membrane cut-off is well-suited when comprised between the MWs of the biggest and the most abundant peptides in the FPH.
The quality of gilthead sea bream from distinct production systems and geographical locations in Southern Europe was evaluated to differentiate aquaculture products from extensive, integrated and ...semi-intensive systems from the ones produced intensively. This work analysed the external appearance of fish, yields after filleting as well as nutritional, sensory and histological characteristics of the muscle. The results showed that the yellow-golden line between eyes and the shiny red spot on the gill cover can be important and easy criteria to discriminate aquaculture products. Trimming losses are higher in fish from intensive systems. Lipid content of fish from extensive systems was significantly lower than values observed for fish reared intensively. Samples from the integrated and extensive systems showed the best n-3/n-6 ratio, contrarily to intensive systems, but it is difficult to establish clear quality markers to differentiate gilthead sea bream according to the rearing system. Regarding sensory characteristics, the sea bream flesh from intensive systems seems firmer and denser, having smaller white fibres and higher density of fibres in the dorsal muscle. The taste and odour of fatty fish was less strong in fish reared in non-intensive conditions, but extensive rearing in earthen pond is more propitious to the development of certain characteristics related to the environment.
The oxidation of nanosized metallic cobalt to cobalt oxide during Fischer-Tropsch synthesis has long been postulated as a major deactivation mechanism apparently related to cobalt crystallite size. ...To establish a connection between cobalt crystallite size and oxidation behaviour, well-defined spherical Co/SiO 2 model catalysts with average cobalt crystallites sizes of 4, 13, and 28 nm were synthesised. The crystallite size distribution of the spherical Co/SiO2 model catalysts was characterised with high-resolution transmission electron microscopy and in situ X-ray diffraction. The oxidation behaviour of the reduced spherical Co/SiO2 model catalysts of differing cobalt crystallite size was studied using in situ X-ray absorption fine structure under model oxidation conditions (H2 O/He, PH2O = 0.04 bar). Surprisingly, it was found that the spherical Co/SiO2 model catalyst with small cobalt crystallites (i.e., 4 nm) did not show oxidation under H2 O/He mixtures (PH2O = 0.04 0.3 bar) up to 400°C, which is against bulk thermodynamic calculations for the oxidation of cobalt metal to cobalt oxide. This was attributed to the encapsulation of the cobalt crystallites with silica after reduction at 500°C in hydrogen. The encapsulation was verified with high-resolution transmission electron microscopy. The spherical Co/SiO 2 model catalysts with medium-sized cobalt crystallites (i.e., 13 nm) did oxidize at 100°C and reached a maximum oxidation of 30% at 300°C (H2 O/He; PH2O = 0.04 bar). The spherical Co/SiO2 model catalysts with large cobalt crystallites (i.e., 28 nm) was found to undergo very little oxidation, <2% at 300°C under a H2 O/He (PH2O = 0.04 bar) environment. In general, it could be concluded that the oxidation of spherical Co/SiO2 model catalysts with water is difficult and is size-dependent.
Background Lower extremity arterial revascularization (LEAR) is the gold-standard for critical lower limb ischemia (CLI). The goal of this study was twofold. First, we evaluated the long-term ...functional status of patients undergoing primary LEAR for CLI. Second, prognostic factors of long-term functional status and survival after primary LEAR for CLI were assessed. Methods All primary LEAR procedures were analyzed. Patients were stratified by preoperative functional status: ambulatory (group I) vs nonambulatory (group II). Patients were followed-up after 3 and 6 years. Adverse events (AEs) were categorized according to predefined standards: minor, surgical, failed revascularization, and systemic. Associated patient demographic/clinical data were analyzed using univariate and multivariate methods. Results There were 106 LEAR patients (group I: n = 42, 40% vs group II: n = 64, 60%). Group II patients were significantly older (75 vs 62 years; P = .00), were classified ASA 3-4 more frequently (78% vs 52%; P < .02), had more cardiac disease (n = 42, 66% vs n = 10, 24%; P = .00), renal disease (n = 26, 41% vs n = 7, 17%; P = .00), diabetes (n = 36, 56% vs n = 8, 19%; P = .00), hypertension (n = 47, 73% vs n = 13, 31%; P = .00) and severe CLI (n = 42, 66% vs n = 18, 38%; P < .01). Group II patients had a higher incidence of death (65.6% vs 14.3%; P = .00), minor AEs (n = 38, 26% vs n = 10, 22%; P = .00), surgical AEs (n = 48, 33% vs n = 12, 26%; P < .02) and systemic AEs (n = 24, 86% vs n = 4, 9%; P < .02). Also more unplanned reinterventions occurred in group II (n = 148, 76% vs n = 47, 24%; P = .00). Nonambulatory status was a multivariate independent predictor of nonambulatory status after LEAR during 6 years follow-up (odds ration OR: 21.47; 95% confidence interval CI: 2.76-166.77; P = .00). Pulmonary disease (OR: 7.49; 95% CI: 2.17-25.80; P = .00), not prescribing β-blockers (OR: 4.67; 95% CI: 1.28-17.03; P < .02), nonambulatory status (OR: 22.99; 95% CI: 6.27-84.24; P = .00), and systemic AEs (OR: 9.66; 95% CI: 1.84-50.57; P < .01) were independent predictors of death. Functional status was not improved in group II after long-term follow-up. Conclusion Nonambulatory patients suffer from extensive comorbid conditions. They are accompanied with an increased occurrence of AEs, unplanned reinterventions, and poor long-term survival rates. Successful LEAR did not improve their functional status after 6 years. This emphasizes that attempts for limb salvage must be carefully considered in these patients.
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