ICE SLURRY PRODUCTION IN A TUBULAR HEAT EXCHANGER

International audienceOne of the challenges of ice slurry generation using a heat exchanger is to overcome the risk of choking. The nucleation usually appears after a supercooling state that remains a key aspect of this technology. In order to focus on this crucial problem, the crystallization of a water ethanol solution was studied in a transparent tubular heat exchanger. Our experiments consisted in cooling the solution until ice slurry formation. Flow visualization permitted mainly to determine the conditions of crystallization according to the flow rate. A limited range of flow rate permitted to obtain the desired ice slurry quality. The heterogeneous crystallization appeared on the wall and dendrites began to develop before being carried away by the solution. Experiments also indicated that dendrites growth from the freezing front upstream in the counter flow direction. The velocity of this retro-propagation phenomenon was estimated using an image analysis tool. Temperature measurements also provided important information on this retro-propagation. Selected process parameters have to be properly adjusted (flow rate, wall properties …). This technology has been patented by the CNRS in selected European countries and in the USA

7,9-Bis(hy­droxy­meth­yl)-7H-purine-2,6,8(1H,3H,9H)trione

The structure of the title uric acid derivative, C7H8N4O5, from human kidney stones, is characterized by the C and O atoms of one of the two hy­droxy­methyl groups being disordered nearly equally over three different sites. In the crystal, mol­ecules are connected by a three-dimensional hydrogen-bonding scheme though they look stacked in planes nearly parallel to (04)

Conformational changes of polymers in model batter systems

Cake batters - made of flour, egg, sugar and fat - are complex systems. Ingredients interactions and their impact on protein secondary structure and starch conformational structures were studied in model batter systems using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. The results showed the possibility of using the pregelatinized starch without affecting protein conformation. The estimation of protein secondary structure highlighted the prevalence of \u3b1-helical structures in the model batter system, while \u3b2-sheets are predominant in flour systems as known in dough systems. The protein conformation in batter system is related to fat-protein interactions and could explain fat functionality in the final product. Starch crystallinity increased when each ingredient - except for pregelatinized starches - was added to the flour. Changes in starch conformation could be related to the redistribution of water between the batter ingredients. The overall results highlighted the importance of ingredients on the structural conformation of the batter polymers - starch and proteins - which could be the key factor to understand the functional properties of the batter

Sur les frontières de la reconnaissance

Faisant appel aux études récentes portant sur la reconnaissance et l’identité sociale, nous analysons les changements dans la catégorisation de l’identité collective des groupes stigmatisés en Israël, en Irlande du Nord, au Québec et au Brésil. Alors que la littérature sur la reconnaissance tend à présumer une opposition nette entre « nous » et « eux », l’analyse de la littérature empirique démontre la complexification et la multiplication des catégories d’identité. Dans les quatre cas nous avons observé le processus de reconnaissance, en explorant les transformations de la signification des frontières internes et externes de l’identité collective pour ses membres ainsi que pour ceux qui lui sont extérieurs. Nous soutenons que la nature conditionnelle de la reconnaissance devrait conduire les chercheurs à considérer non seulement les composantes normatives du conflit ethnique mais aussi, en leur accordant une importance particulière, le langage et la catégorisation qui fondent ce type de débat.On the Boundaries of Recognition. Internal and External Categories of Collective Identity.Drawing upon recent advances in the study of recognition and social identity, we trace changes in the categorization of collective identity among stigmatized groups in Israel, Northern reland, Québec, and Brazil. While the recognition literature commonly assumes an opposition between « Us » and « Them », a review of these empirical cases illustrates the full complexity of identity categories in each of the four cases. We focus on the process of recognition in each case while highlighting the significance of internal and external boundaries of collective identity. We argue that the contingent nature of recognition should lead scholars to consider not only the normative components of ethnic conflict, but more importantly the language and categories which form the basis for such debates.En las fronteras del reconocimiento. Las categorías internas y externas de la identidad colectiva.Fundándonos en estudios recientes sobre el reconocimiento y la identidad social analizamos los cambios de categorización de la identidad colectiva de grupos estigmatizados en Israel, en Irlanda del Norte, en el Québec canadiense y en Brasil. Cuando la literatura sobre reconocimiento presume una oposición neta entre “nosotros” y “ellos” el análisis de los estudios empíricos demuestra la complicación y la multiplicación de las categorías de identidad. En los cuatro casos que hemos observado el proceso de reconocimiento, explorando las transfor­maciones la significación de la las fronteras internas y externas de la identidad colectiva para sus miembros como para los que son exteriores a ella. Consideramos que la naturaleza condicional del reconocimiento debe llevar a los investigadores a analizar no solo a los componentes normativos des conflicto étnico sino también, dándoles una importancia particular, el lenguaje y la categorización que fundan este tipo de debate

The Effect of a Type I Photoinitiator on Cure Kinetics and Cell Toxicity in Projection-Microstereolithography

AbstractProjection-microstereolithography is an additive manufacturing technique based on the spatially controlled solidification of a liquid photopolymer on exposure to digitally manipulated light patterns. This study presents a methodology to evaluate the effect of a type-I photoinitiator on the reaction kinetics in the process and the cytocompatibility of the produced components. While the reaction speed and degree of conversion were heavily dependent on the applied amount of the initiator, a clear toxic effect was observed with all tested concentrations, and a post-processing step of 7 days was required to leach out the initiator residues

The myth of agency and the misattribution of blame in collective imaginaries of the future

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149565/1/bjos12662_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149565/2/bjos12662.pd

An online experiment during the 2020 US-Iran crisis shows that exposure to common enemies can increase political polarization

A longstanding theory indicates that the threat of a common enemy can mitigate conflict between members of rival groups. We tested this hypothesis in a pre-registered experiment where 1670 Republicans and Democrats in the United States were asked to complete an online social learning task with a bot that was labeled as a member of the opposing party. Prior to this task, we exposed respondents to primes about (a) a common enemy (involving Iran and Russia); (b) a patriotic event; or (c) a neutral, apolitical prime. Though we observed no significant differences in the behavior of Democrats as a result of priming, we found that Republicans-and particularly those with very strong conservative views-were significantly less likely to learn from Democrats when primed about a common enemy. Because our study was in the field during the 2020 Iran Crisis, we were able to further evaluate this finding via a natural experiment-Republicans who participated in our study after the crisis were even less influenced by the beliefs of Democrats than those Republicans who participated before this event. These findings indicate common enemies may not reduce inter-group conflict in highly polarized societies, and contribute to a growing number of studies that find evidence of asymmetric political polarization in the United States. We conclude by discussing the implications of these findings for research in social psychology, political conflict, and the rapidly expanding field of computational social science

Determination of the high-pressure crystal structure of BaWO4 and PbWO4

We report the results of both angle-dispersive x-ray diffraction and x-ray absorption near-edge structure studies in BaWO4 and PbWO4 at pressures of up to 56 GPa and 24 GPa, respectively. BaWO4 is found to undergo a pressure-driven phase transition at 7.1 GPa from the tetragonal scheelite structure (which is stable under normal conditions) to the monoclinic fergusonite structure whereas the same transition takes place in PbWO4 at 9 GPa. We observe a second transition to another monoclinic structure which we identify as that of the isostructural phases BaWO4-II and PbWO4-III (space group P21/n). We have also performed ab initio total energy calculations which support the stability of this structure at high pressures in both compounds. The theoretical calculations further find that upon increase of pressure the scheelite phases become locally unstable and transform displacively into the fergusonite structure. The fergusonite structure is however metastable and can only occur if the transition to the P21/n phases were kinetically inhibited. Our experiments in BaWO4 indicate that it becomes amorphous beyond 47 GPa.Comment: 46 pages, 11 figures, 3 table

Alginates along the filament of the brown alga Ectocarpus help cells cope with stress.

Ectocarpus is a filamentous brown alga, which cell wall is composed mainly of alginates and fucans (80%), two non-crystalline polysaccharide classes. Alginates are linear chains of epimers of 1,4-linked uronic acids, β-D-mannuronic acid (M) and α-L-guluronic acid (G). Previous physico-chemical studies showed that G-rich alginate gels are stiffer than M-rich alginate gels when prepared in vitro with calcium. In order to assess the possible role of alginates in Ectocarpus, we first immunolocalised M-rich or G-rich alginates using specific monoclonal antibodies along the filament. As a second step, we calculated the tensile stress experienced by the cell wall along the filament, and varied it with hypertonic or hypotonic solutions. As a third step, we measured the stiffness of the cell along the filament, using cell deformation measurements and atomic force microscopy. Overlapping of the three sets of data allowed to show that alginates co-localise with the stiffest and most stressed areas of the filament, namely the dome of the apical cell and the shanks of the central round cells. In addition, no major distinction between M-rich and G-rich alginate spatial patterns could be observed. Altogether, these results support that both M-rich and G-rich alginates play similar roles in stiffening the cell wall where the tensile stress is high and exposes cells to bursting, and that these roles are independent from cell growth and differentiation

Sense of coherence moderates job demand‐resources and impact on burnout among nurses and midwives in the context of the COVID ‐19 pandemic: a cross‐sectional survey.

This study aimed to test the propositions using the job demands‐resources (JD‐R) model for main/moderation/mediation effects of a sense of coherence and practice environment support on mental well-being (anxiety, depression and burnout) outcomes in nurses and midwives in Australia during the COVID-19 pandemic. Cross-sectional quantitative survey. The study was a cross-sectional design using self-report questionnaires reported as per the Reporting of Observational Studies in Epidemiology Guidelines. Following human research ethics approval (2020.ETH.00121) participants were recruited to take part in an online anonymous survey using self-report instruments to test the JD-R model in Australia. 156 participant nurses and midwives experienced anxiety, depression and emotional burnout during COVID-19. While a considerable proportion of participants indicated high levels of emotional exhaustion, their responses showed low levels of depersonalization (detached response to other people) and high levels of personal accomplishment (high levels of work performance and competence). A sense of coherence was a significant protective factor for mental health well-being for the participants, which is to say, high levels of sense of coherence were predictive of lower levels of anxiety, depression and burnout in this study sample. It is evident that both nursing and midwifery professions require psychosocial support to preserve their health both in the short and long term. Ensuring individualized tailored support will require a layered response within organizations aimed at individual self-care and collegial peer support. There was no patient or public contribution in this study, as the focus was on nurses and midwives