Intracerebral Implantation of Ionic Synthetic Hydrogels: Effect of Polar Substrata on Astrocytosis and Axons

In previous studies, hyperporous synthetic hydrogels of poly(glyceryl methacrylate) or p(GMA), containing bioadhesive substrates of collagen, were implanted into rat cerebral tissue in order to provide systems of oriented guidance channels for directing the growth of the scar and axons /28/. In the present study, ionic p(GMA)- collagen hydrogels containing polar chemical groups, either basic amino groups or acidic carboxyl groups, were evaluated for their tolerance and their effects on the brain scarring response and axonal reactivity after long-term implantation in the cerebral cortex. In all animals, the implants were well tolerated. Although both types of gels influenced the astroglial reaction near the bioimplant, hydrogels carrying carboxyl groups had the strongest influence on the elongation, the direction and the organization of astrocytic processes so that a glial matrix could form in regions of the gel. Extracellular material (e.g. reticulin) was also deposited into the gels carrying carboxyl groups. Although cortical nerve fibers .in the surrounding tissue showed a regenerative response, extending onto or into the matrices, this behavior seemed to depend more on the organization of the .astrocytic scar imposed by the gel than on the type of gel. We conclude that matrices carrying negatively charged groups influence favorably the astrocytosis and the deposition of connective tissue, and that this approach represents a new avenue in attempting to modulate the brain scar formation

L'hydrologie urbaine: nouvelles problématiques, nouvelles approches de solutions

La pratique de l'hydrologie, appliquée au milieu urbain, a beaucoup évolué depuis les années 1960. De nouveaux outils scientifiques, méthodologiques et technologiques ont été mis au point. En ce qui concerne les eaux pluviales urbaines, un changement de philosophie complet s'est produit. Aujourd'hui, des développements rapides continuent à se produire pour faire face de la meilleure manière possible aux graves problèmes qui se posent en zone urbaine : inondation et pollution du milieu naturel. Deux approches récentes illustrent ces développements : la gestion des risques et l'approche globale sur le bassin versant. Une évaluation de plus en plus précise de l'aléa et de la vulnérabilité s'avère nécessaire ainsi qu'une planification hydrologique bassin versant par bassin versant. Celle-ci devrait conduire à définir et à hiérarchiser les principaux objectifs que l'on se fixe dans les domaines du contrôle des inondations, du contrôle de l'érosion, de l'amélioration du milieu naturel et de la protection de l'environnement. Les actions à mener doivent utiliser les outils de modélisation des phénomènes hydrologiques sur les bassins versants. L'efficacité de ces approches est illustrée par un exemple pris sur le bassin versant de la rivière Beauport au Québec.Urban hydrology practice has evolved a great deal, keeping up with the evolution of urban problems. Thus, professional engineers have had to keep up with this evolution, in order to understand the effects of urbanization on the hydrological behavior of the systems for which they have to recommend best solutions. Engineers have also had to evolve from the traditional approach of a limited vision of the problem, of its extent and of its impacts on the system. A global vision of the entire system, grouping every watershed element, such as forestry, agriculture or urbanization, is necessary if one is to circumscribe the problem, to analyze it and to reach to the best long-lasting solution. This article represents a synthesis of the hydrological disturbance phenomenon caused by uncontrolled urbanization, not properly planned, which is often characterized by numerous short-term solutions, often ineffective in the context of a long-lasting approach.Examples of natural disasters caused by meteorological events are more and more frequent. Take the case of Vaison-la-Romaine, in September 1992, where the Groseau devastated the Vaison community. More recently, the 1996 summer floods in the Saguenay region, in Québec, demonstrate once more that water always tends to return to its original bed, now occupied by artificial structures. When these types of events are analyzed in detail, we notice that meteorological phenomena are not always the main cause of the disaster cause and that often part of the responsibility lies with the occurrence of human activity in the catchment. This observation shows the importance of using wisdom and humility towards these natural forces and of anticipating, during design, a "secure" passage for the inevitable flows that one day will exceed the structure capacity. Knowing all the interactions that exist in the heart of the stormwater management problems, it is risky to intervene in isolation without analyzing the impact of the action. The approach must then be global and coherent; the tool necessary for success is the stormwater master plan made on a watershed basis. The master plan allows us to properly describe the problematical elements, to identify the real causes and to optimize the location of the control solutions. It also allows us to manage the increase in stormwater due to urbanization, with the "flow set point" concept of each watercourse tributary.This article presents an application example where the global analysis approach is used and where the solution involves different interventions and developments, which, when combined, effectively treat backwater effects, flooding and erosion in the presented area. The master plan of the watershed containing this sector had already been conceived and the specific flows of each of its tributaries had been identified; the global approach method therefore allowed us to settle the local problems in the studied area while respecting the flow granted by the master plan. Finally, a floodable plain, containing marshes, completes the intervention plan by combining the restoration of certain watercourse ecological characteristics with the need for flood control. This example demonstrates the necessity and the advantages of approaching urban drainage problems at the watershed level. However, watershed management concepts lead planners and designers to deal with antagonisms: urbanization or renaturalization? Obviously, in urban areas, the return to natural conditions is impossible and the disturbances to watercourses generated by urbanization cannot all be compensated for. Rather, we must aspire to the establishment of a balanced environment by controlling inflows produced by the watershed and by supporting the system to receive them. The notion of feasibility must always occupy the thoughts of the master plan designers and planners. The credibility and the continuity of the master plan depend on all these considerations; any unrealistic flow order, on an implementation level, can compromise the balance of the management plan and its applicability, which in turn can lead to a confused plan, possibly having disastrous consequences. The ultimate consequence of the management plan is the protection of the watercourse, the development of which can be designed to meet different criteria, such as flood control, erosion control, ecological potential enhancement, etc. It is at this stage that management becomes most complex: flood control, for example, does not apply to the same type of events as erosion control. The former requires management of major hydrological events, whereas the second needs implies control of frequent flows, which are at the origin of bank undermining caused by differential volume excesses. The management scheme must then handle multiple events and multiple criteria; consequently, it becomes more complex but also grows in value and justifies itself more adequately. Furthermore, the whole question of watercourse quality, in the broad sense of the term, must be managed from a frequent-event point of view, as this yields the best physical, ecological and aesthetic image of the aquatic environment. To this effect, present efforts in the control of combined sewage network overflows can be seen as a predecessor of what will later be extended to the entire stormwater network. This whole aspect of management has not been treated in this paper, as many others are dedicated to doing so. The evolution of the situation is similar in France and in Québec; coherent watershed management must rest on clear political goals regarding environmental use, risk protection and urban development. The stormwater master plan must, permanently, become part of the water resource master plan for the whole watershed, with its objectives of flood control, erosion control and maintenance of acceptable physical-chemical and biochemical water quality, as well as assured resource use (drinking water--, hydroelectricity, agriculture, industrial waters, etc.). This water resource master plan will have to be integrated in the same way as the French Water Agencies do today, and as Québec is preparing to do so

What promotes or prevents greater use of appropriate compression in people with venous leg ulcers? A qualitative interview study with nurses in the north of England using the Theoretical Domains Framework

OBJECTIVES: To investigate factors that promote and prevent the use of compression therapy in people with venous leg ulcers. DESIGN: Qualitative interview study with nurses using the Theoretical Domains Framework (TDF). SETTING: Three National Health Service Trusts in England. PARTICIPANTS: Purposive sample of 15 nurses delivering wound care. RESULTS: Nurses described factors which made provision of compression therapy challenging. Organisational barriers (TDF domains environmental context and resources/knowledge, skills/behavioural regulation) included heavy/increasing caseloads; lack of knowledge/skills and the provision of training; and prescribing issues (variations in bandaging systems/whether nurses could prescribe). Absence of specialist leg ulcer services to refer patients into was perceived as a barrier to providing optimal care by some community-based nurses. Compression use was perceived to be facilitated by clinics for timely initial assessment; continuity of staff and good liaison between vascular/leg ulcer clinics and community teams; clear local policies and care pathways; and opportunities for training such as ‘shadowing’ in vascular/leg ulcer clinics. Patient engagement barriers (TDF domains goals/beliefs about consequences) focused on getting patients ‘on board’ with compression, and supporting them in using it. Clear explanations were seen as key in promoting compression use. CONCLUSIONS: Rising workload pressures present significant challenges to enhancing leg ulcer services. There may be opportunities to develop facilitated approaches to enable community nursing teams to make changes to practice, enhancing quality of patient care. The majority of venous leg ulcers could be managed in the community without referral to specialist community services if issues relating to workloads/skills/training are addressed. Barriers to promoting compression use could also be targeted, for example, through the development of clear patient information leaflets. While the patient engagement barriers may be easier/quicker to address than organisational barriers, unless organisational barriers are addressed it seems unlikely that all people who would benefit from compression therapy will receive it

Method for fabricating submicron silicide structures on silicon using a resistless electron beam lithography process

Abstract : A novel resistless lithography process using a conventional electron beam system is presented. Metallic lines with widths of less than 50 nm were produced on silicon substrates. The process is based on localized heating with a focused electron beam of thin platinum layers deposited on silicon. It is demonstrated that silicide formation occurs at the Pt-Si interface. By using a dilute solution of aqua regia, it is possible to obtain a sufficient difference in etch rates between exposed and unexposed regions of the platinum thin film to selectively remove only the unexposed areas

Magma mixing enhanced by bubble segregation

In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be expected at the filament-host melt interface, due to the repetitive nature of the process. However, previously magmatic filaments were tacitly assumed to be of single-pulse origin. Consequently, the potential for multi-pulse filaments has to be considered in outcrop analyses. As compositional profiles alone may remain ambiguous for constraining the origin of filaments, and as 3-D visual evidence demonstrates that filaments may have experienced multiple bubbles passages even when featuring standard diffusion gradients, therefore, the calculation of diffusive timescales may be inadequate for constraining timescales in cases where bubbles have played an essential role in magma mixing. Data analysis employing concentration variance relaxation in natural samples can distinguish conventional single-pulse filaments from advection via multiple bubble ascent advection in natural samples, raising the prospect of yet another powerful application of this novel petrological tool

Image-derived input function in dynamic human PET/CT: methodology and validation with 11C-acetate and 18F-fluorothioheptadecanoic acid in muscle and 18F-fluorodeoxyglucose in brain

International audienc

Transcriptional Basis of Mouse and Human Dendritic Cell Heterogeneity

Dendritic cells (DCs) play a critical role in orchestrating adaptive immune responses due to their unique ability to initiate T cell responses and direct their differentiation into effector lineages. Classical DCs have been divided into two subsets, cDC1 and cDC2, based on phenotypic markers and their distinct abilities to prime CD8 and CD4 T cells. While the transcriptional regulation of the cDC1 subset has been well characterized, cDC2 development and function remain poorly understood. By combining transcriptional and chromatin analyses with genetic reporter expression, we identified two principal cDC2 lineages defined by distinct developmental pathways and transcriptional regulators, including T-bet and RORgt, two key transcription factors known to define innate and adaptive lymphocyte subsets. These novel cDC2 lineages were characterized by distinct metabolic and functional programs. Extending our findings to humans revealed conserved DC heterogeneity and the presence of the newly defined cDC2 subsets in human cancer

Absorbing boundary and free-surface conditions in the phononic lattice solid by interpolation

We have recently developed a new lattice-Boltzmann-based approach for modelling compressional wave propagation in heterogeneous media, which we call the phononic lattice solid by interpolation (PLSI). In this paper, we propose an absorbing boundary condition for the PLSI method in which the microscopic reflection coefficients at the boundaries of a model are set to zero and viscous layers are added to the boundaries. Numerical simulation examples using the PLSI method and comparisons with exact solutions demonstrate that artificial boundary reflections can be almost completely eliminated when the incidence angle is less than approximately 70°. Beyond this angle, remanent artificial boundary reflections become visible. We propose four methods for modelling free-surface reflections in PLSI simulations. In the first three methods, special collision rules at a free surface are specified to take into account the effect of a free surface on quasi-particle movements (i.e. wave propagation). They are termed the specular bouncing, backward bouncing I, and combined bouncing methods. They involve quasi-particle reflections with a coefficient of - 1 and require the free surface to be located exactly along lattice nodes. For the fourth method, we modify the backward bouncing I model for the case when a free surface is located at any position along lattice links and thus term it the backward bouncing II model. It uses the reflection coefficient at the free surface to calculate the reflected number densities during PLSI simulations. Hence, the free surface is handled in the same way as an interface within a model. Numerical examples and comparisons with exact solutions show that these four methods used at the microscopic scale are all appropriate for modelling macroscopic waves reflected from free surfaces

Absolute Paleointensity Study of Miocene Tiva Canyon Tuff, Yucca Mountain, Nevada: Role of Fine‐Particle Grain‐Size Variations

Fine‐grained, Ti‐poor titanomagnetite in the ~12.7 Ma Tiva Canyon (TC) Tuff systematically increases in grain size from superparamagnetic (SP) at the flow base to single domain (SD) at a few meters height. This allows us to examine the role of grain‐size variation on paleointensity, within the transition from SP to stable SD. We present magnetic properties from two previously unreported sections of the TC Tuff, as well as Thellier‐type paleointensity estimates from the lowermost ~7.0 m of the flow. Magnetic hysteresis, frequency‐dependent susceptibility, and thermomagnetic data show that sample grain‐size distribution is dominated by SP in the lower ~3.6 m, transitioning upwards to mostly stable SD. Paleointensity results are closely tied to stratigraphic height and to magnetic properties linked to domain state. SD samples have consistent absolute paleointensity values of 28.5 ± 1.94 μT (VADM of 51.3 ZAm2) and behaved ideally during paleointensity experiments. The samples including a significant SP fraction have consistently higher paleointensities and less ideal behavior but would likely pass many traditional quality‐control tests. We interpret the SD remanence to be a primary thermal remanent magnetization but discuss the possibility of a partial thermal‐chemical remanent magnetization if microcrystal growth continued at T \u3c Tc and/or the section is affected by post‐emplacement vapor‐phase alteration. The link between paleointensity and domain state is stronger than correlations with water content or other evidence of alteration and suggests that the presence of a significant SP population may adversely impact paleointensity results, even in the presence of a stable SD fraction