Showing papers by "Laval University published in 2022"

Microglia modulate hippocampal synaptic transmission and sleep duration along the light/dark cycle

Abstract: Microglia, the brain's resident macrophages, actively contributes to the homeostasis of cerebral parenchyma by sensing neuronal activity and supporting synaptic remodeling and plasticity. While several studies demonstrated different roles for astrocytes in sleep, the contribution of microglia in the regulation of sleep/wake cycle and in the modulation of synaptic activity in the different day phases has not been deeply investigated. Using light as a zeitgeber cue, we studied the effects of microglial depletion with the colony stimulating factor-1 receptor antagonist PLX5622 on the sleep/wake cycle and on hippocampal synaptic transmission in male mice. Our data demonstrate that almost complete microglial depletion increases the duration of NREM sleep and reduces the hippocampal excitatory neurotransmission. The fractalkine receptor CX3CR1 plays a relevant role in these effects, because cx3cr1GFP/GFP mice recapitulate what found in PLX5622-treated mice. Furthermore, during the light phase, microglia express lower levels of cx3cr1 and a reduction of cx3cr1 expression is also observed when cultured microglial cells are stimulated by ATP, a purinergic molecule released during sleep. Our findings suggest that microglia participate in the regulation of sleep, adapting their cx3cr1 expression in response to the light/dark phase, and modulating synaptic activity in a phase-dependent manner.

15 W monolithic fiber laser at 3.55 µm

Abstract: We report a dual-wavelength-pumped all-fiber continuous-wave (CW) laser operating at 3.55 µm that reached an output power of 14.9 W, which is, to the best of our knowledge, a record. The laser cavity, made of an erbium-doped fluoride fiber and bounded by two fiber Bragg gratings (FBGs), operates at an overall optical efficiency of 17.2% and a slope efficiency of 51.3% with respect to the 1976 nm launched pump power. The all-fiber design of the cavity not only allows for significant power scaling of the laser output, but also improves its long-term stability at high output power. The cavity design was set according to a numerical optimization that showed very good agreement with the experimental results.

Nanoplastics: From Model Materials To Colloidal Fate

Abstract: Nanoplastics are pieces of plastic debris of mixed shape and chemical composition, which can be present in the air, soil, freshwater bodies, seas, biota, and our diet. We know little about the prevalence of nanoplastics and the risks they pose to the health of living organisms; recent studies of plastics in the environment have not significantly contributed information about this crucial topic. In this article, nanoplastics are presented as colloids. Analysing their colloidal properties shows that their fate is governed by interfacial properties, Trojan horse properties, and their stability in aqueous media. Their hazards, however, are as yet unknown.

Nanoplastics: From model materials to colloidal fate

Abstract: Nanoplastics are pieces of plastic debris of mixed shape and chemical composition, which can be present in the air, soil, freshwater bodies, seas, biota, and our diet. We know little about the prevalence of nanoplastics and the risks they pose to the health of living organisms; recent studies of plastics in the environment have not significantly contributed information about this crucial topic. In this article, nanoplastics are presented as colloids. Analysing their colloidal properties shows that their fate is governed by interfacial properties, Trojan horse properties, and their stability in aqueous media. Their hazards, however, are as yet unknown.

A framework for ensemble modelling of climate change impacts on lakes worldwide: the ISIMIP Lake Sector

Abstract: Abstract. Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a single model forced with limited scenario-driven projections of future climate for a relatively small number of lakes. As a result, our understanding of the effects of climate change on lakes is fragmentary, based on scattered studies using different data sources and modelling protocols, and mainly focused on individual lakes or lake regions. This has precluded identification of the main impacts of climate change on lakes at global and regional scales and has likely contributed to the lack of lake water quality considerations in policy-relevant documents, such as the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Here, we describe a simulation protocol developed by the Lake Sector of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) for simulating climate change impacts on lakes using an ensemble of lake models and climate change scenarios for ISIMIP phases 2 and 3. The protocol prescribes lake simulations driven by climate forcing from gridded observations and different Earth system models under various representative greenhouse gas concentration pathways (RCPs), all consistently bias-corrected on a 0.5∘ × 0.5∘ global grid. In ISIMIP phase 2, 11 lake models were forced with these data to project the thermal structure of 62 well-studied lakes where data were available for calibration under historical conditions, and using uncalibrated models for 17 500 lakes defined for all global grid cells containing lakes. In ISIMIP phase 3, this approach was expanded to consider more lakes, more models, and more processes. The ISIMIP Lake Sector is the largest international effort to project future water temperature, thermal structure, and ice phenology of lakes at local and global scales and paves the way for future simulations of the impacts of climate change on water quality and biogeochemistry in lakes.

Ni-based catalysts supported on acid/alkali-activated coal fly ash residue for improved glycerol steam reforming

Abstract: Application of coal fly ash (FA) residues as catalyst support is mainly restricted because of low surface area and high sulfur content. In the present work, the physicochemical properties of a low-efficiency FA were significantly improved via simple acid/alkali treatments consisting of one-step (HNO3 or NaOH) or two-step (NaOH/HNO3 or HNO3/NaOH) leaching-partial-dissolution (LPD). As a result, as compared to Ni-FA, the catalytic activity of the Ni-FA(treated) catalysts for glycerol steam reforming was considerably enhanced. Alkali-LPD is more effective than acid-LPD in simultaneously improving FA’s surface area and regulating FA’s elemental distribution. Ni-FA(HNO3/NaOH) has the best performance with high glycerol conversion to gas (99.2%) and H2 yield (74.5%), attributed to i) removal of sulfur-containing species by acid-LPD, ii) upgrading specific surface area, iron-exposure, and Ni dispersion via alkali-LPD, iii) diminishment of coke using acid/alkali-LPD sequence treatment, and iv) enhancement of catalytic stability due to the formation of NiFe alloys.

Ni-based catalysts supported on acid/alkali-activated coal fly ash residue for improved glycerol steam reforming

Abstract: Application of coal fly ash (FA) residues as catalyst support is mainly restricted because of low surface area and high sulfur content. In the present work, the physicochemical properties of a low-efficiency FA were significantly improved via simple acid/alkali treatments consisting of one-step (HNO3 or NaOH) or two-step (NaOH/HNO3 or HNO3/NaOH) leaching-partial-dissolution (LPD). As a result, as compared to Ni-FA, the catalytic activity of the Ni-FA(treated) catalysts for glycerol steam reforming was considerably enhanced. Alkali-LPD is more effective than acid-LPD in simultaneously improving FA’s surface area and regulating FA’s elemental distribution. Ni-FA(HNO3/NaOH) has the best performance with high glycerol conversion to gas (99.2%) and H2 yield (74.5%), attributed to i) removal of sulfur-containing species by acid-LPD, ii) upgrading specific surface area, iron-exposure, and Ni dispersion via alkali-LPD, iii) diminishment of coke using acid/alkali-LPD sequence treatment, and iv) enhancement of catalytic stability due to the formation of NiFe alloys.

Crosslinked polyethylene: A review on the crosslinking techniques, manufacturing methods, applications, and recycling

Abstract: One of the most used resins in the plastics industry is polyethylene (PE). Although PE has good impact resistance and ductility, its low maximum use temperature and mechanical strength limit some commercial development, especially for load-bearing applications. To get better overall performances, crosslinking is performed to improve the chemical, mechanical, and thermal properties of PE. Although PE can be crosslinked by using various chemical and physical methods, this makes the resulting polymers more difficult to recycle since a three-dimensional (3D) network is created. In this review, we first describe the different crosslinking techniques for PE to manufacture crosslinked PE (XLPE) parts. Then, as more than half of the XLPE-based products are disposed directly after use, we present several options to reuse and recycle these products to overcome this environmental issue and find a sustainable solution. A focus is made on mechanical recycling and de-crosslinking techniques for XLPE to generate recycled-XLPE (r-XLPE). Finally, a conclusion is presented on the current situation and research gaps that must be filled by future works.

Time trends in social contacts before and during the COVID-19 pandemic: the CONNECT study

Abstract: Since the beginning of the COVID-19 pandemic, many countries, including Canada, have adopted unprecedented physical distancing measures such as closure of schools and non-essential businesses, and restrictions on gatherings and household visits. We described time trends in social contacts for the pre-pandemic and pandemic periods in Quebec, Canada.CONNECT is a population-based study of social contacts conducted shortly before (2018/2019) and during the COVID-19 pandemic (April 2020 - February 2021), using the same methodology for both periods. We recruited participants by random digit dialing and collected data by self-administered web-based questionnaires. Questionnaires documented socio-demographic characteristics and social contacts for two assigned days. A contact was defined as a two-way conversation at a distance ≤ 2 m or as a physical contact, irrespective of masking. We used weighted generalized linear models with a Poisson distribution and robust variance (taking possible overdispersion into account) to compare the mean number of social contacts over time and by socio-demographic characteristics.A total of 1291 and 5516 Quebecers completed the study before and during the pandemic, respectively. Contacts significantly decreased from a mean of 8 contacts/day prior to the pandemic to 3 contacts/day during the spring 2020 lockdown. Contacts remained lower than the pre-COVID period thereafter (lowest = 3 contacts/day during the Christmas 2020/2021 holidays, highest = 5 in September 2020). Contacts at work, during leisure activities/in other locations, and at home with visitors showed the greatest decreases since the beginning of the pandemic. All sociodemographic subgroups showed significant decreases of contacts since the beginning of the pandemic. The mixing matrices illustrated the impact of public health measures (e.g. school closure, gathering restrictions) with fewer contacts between children/teenagers and fewer contacts outside of the three main diagonals of contacts between same-age partners/siblings and between children and their parents.Physical distancing measures in Quebec significantly decreased social contacts, which most likely mitigated the spread of COVID-19.

Engineered feldspar-based ceramics: A review of their potential in ceramic industry

Abstract: Feldspars are the most abundant mineral in the earth’s crust, however, their interest in ceramic industry goes beyond their abundancy. The unique compositional and structural features as well as the many outstanding properties that feldspars own, make them to be widely used as raw material for the ceramic industry. Moreover, multiple works have demonstrated that engineered feldspar-based ceramics are very promising for their use in applications such as ceramic tiles, dielectrics or phosphors, among others, and therefore, in this article, a comprehensive review on their dielectric, mechanical, optical and thermal properties is presented. This review intends to provide an up-to-date outlook of the possibilities that engineered feldspars offer to their application in ceramic industry, discussing future prospects and challenges that might ease the opening up of new horizons for future applications in ceramic sector.

<i>In Vitro</i> Selection of Remdesivir-Resistant SARS-CoV-2 Demonstrates High Barrier to Resistance

Abstract: In vitro selection of remdesivir-resistant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) revealed the emergence of a V166L substitution, located outside of the polymerase active site of the Nsp12 protein, after 9 passages of a single lineage. V166L remained the only Nsp12 substitution after 17 passages (10 μM remdesivir), conferring a 2.3-fold increase in 50% effective concentration (EC50). When V166L was introduced into a recombinant SARS-CoV-2 virus, a 1.5-fold increase in EC50 was observed, indicating a high in vitro barrier to remdesivir resistance.

A three-organelle complex made by wrappER contacts with peroxisomes and mitochondria responds to liver lipid flux changes

Abstract: Hepatic lipid homeostasis depends on intracellular pathways that respire fatty acid in peroxisomes and mitochondria, and on systemic pathways that secrete fatty acid into the bloodstream, either free or condensed in very-low-density lipoprotein (VLDL) triglycerides. These systemic and intracellular pathways are interdependent, but it is unclear whether and how they integrate into a single cellular circuit. Here, we report that mouse liver wrappER, a distinct endoplasmic reticulum (ER) compartment with apparent fatty acid- and VLDL-secretion functions, connects peroxisomes and mitochondria. Correlative light electron microscopy, quantitative serial section electron tomography and three-dimensional organelle reconstruction analysis show that the number of peroxisome-wrappER-mitochondria complexes changes throughout fasting-to-feeding transitions and doubles when VLDL synthesis stops following acute genetic ablation of Mttp in the liver. Quantitative proteomic analysis of peroxisome-wrappER-mitochondria complex-enriched fractions indicates that the loss of Mttp upregulates global fatty acid β-oxidation, thereby integrating the dynamics of this three-organelle association into hepatic fatty acid flux responses. Therefore, liver lipid homeostasis occurs through the convergence of systemic and intracellular fatty acid-elimination pathways in the peroxisome-wrappER-mitochondria complex.

Human Smuggling Under Canadian Refugee Law: Protecting a System, Not Persons

Abstract: This article examines the legal regime applying to asylum seekers arriving irregularly and categorised as ‘designated foreign nationals’ in Canadian refugee law. Our main contention is that changes to the Immigration and Refugee Protection Act have created a new regime for a category of asylum seekers whom the Canadian government considers with suspicion and mistrust. This article highlights some of the most striking features of the legal regime applying to designated foreign nationals under the Immigration and Refugee Protection Act. It is followed by a discussion of how the regime for designated foreign nationals fares with Canada’s obligations under international law, the rule of law, and the principles of justice and humanity.

<scp>EEG</scp> power spectral measures of cognitive workload: A meta‐analysis

Abstract: Cognitive workload (CWL) is a fundamental concept in the assessment and monitoring of human performance during cognitive tasks. Numerous studies have attempted to objectively and continuously measure the CWL using neuroimaging techniques. Although the electroencephalogram (EEG) is a widely used technique, the impact of CWL on the spectral power of brain frequencies has shown inconsistent results. The present review aimed to synthesize the results of the literature and quantitatively assess which brain frequency is the most sensitive to CWL. A systematic literature search following PRISMA recommendations highlighted three main frequency bands used to measure CWL: theta (4-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz). Three meta-analyses were conducted to quantitatively examine the effect of CWL on these frequencies. A total of 45 effect sizes from 24 studies involving 723 participants were computed. CWL was associated with significant effects on theta (g = 0.68, CI [0.41, 0.95]), alpha (g = -0.25, CI [-0.45, 0.04]), and beta (g = 0.50, CI [0.21, 0.79]) power. Our results suggests that theta, especially the frontal theta, is the best index of CWL. Alpha and beta power were also significantly impacted by CWL; however, their association seemed less straightforward. These results are critically analyzed considering the literature on cerebral oscillations. We conclude by emphasizing the need to investigate the interaction between CWL and other factors that may influence spectral power (e.g., emotional load), and to combine this measure with other methods of analysis of the central and peripheral nervous system (e.g., functional connectivity, heart rate).