Cellulose: from biocompatible to bioactive material

International audienceSince the papyri, cellulose has played a significant role in human culture, especially as paper. Nowadays, this ancient product has found new scientific applications in the expanding sector of paper-based technology. Among paper-based devices, paper-based biosensors raise a special interest. The high selectivity of biomolecules for target analytes makes these sensors efficient. Moreover, simple paper-based detection devices do not require hardware or specific technical skill. They are inexpensive, rapid, user-friendly and therefore highly promising for providing resource-limited settings with point-of-care diagnostics. The immobilization of biomolecules onto cellulose is a key step in the development of these sensing devices. Following an overview of cellulose structural features and physicochemical properties, this article reviews current techniques for the immobilization of biomolecules on paper membranes. These procedures are categorized into physical, biological and chemical approaches. There is no universal method for biomolecule immobilization. Thus, for a given paper-based biochip, each strategy can be considered

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

T is associated with severe dyspepsia

Contains fulltext : 96333.pdf (publisher's version ) (Open Access

Centrifuge modelling of spoil slopes within pit-lake mine reclamations

Pit lakes are a common form of reclamation of areas where open pit mining activities have taken place. The development of these lakes often uses previous overburden materials, or “spoils”, that are readily available. Depending on the local geology, these spoil materials can contain large proportions of high-plasticity clays, which poses challenges in terms of the analysis and design of the sloped banks constructed to form new lakes. This paper describes a study in which geotechnical centrifuge modelling was used to investigate the stability and performance, in terms of accumulated displacements over cycles of lowering and raising the lake water elevation, of slopes constructed with a high-plasticity clay. A “replica-spoil” material was used in the tests to replicate key characteristics of spoil materials from known spoil heaps in Europe. The paper describes the centrifuge models and testing procedure developed for the tests, as well as the challenges encountered with the use of the high-plasticity clay. Two slope angles were tested: a 15 slope to match the typical slopes at a known field site, and a steeper 24 slope. Pore pressures within the slope were measured over several cycles of lake water elevation change. Slope displacements were measured using local transducers placed at the slope crest and toe, as well as using a PIV image analysis technique. The slopes were shown to experience plastic deformations, with displacements accumulating over subsequent cycles of lake water level change. The 24 slope developed slightly larger accumulated displacements than the 15 slope, though neither slope showed signs of ultimate collapse. Results from the centrifuge tests provide invaluable data which can be used for the verification of numerical models considering similar stability scenarios

Wpływ przestrzennego zróżnicowania właściwości materiału zwałowego na przemieszczenia zboczy w warunkach gwałtownego spiętrzenia wód zbiorników poeksploatacyjnych

In many European countries, lignite or brown coal is used as a fuel source in steam-electric power generation. Upon completion of mining activities, a reclamation plan is imperative to ensure environmental and social prosperity of local areas. Abandoned mine pits are often reclaimed by creating a pit lake. Reclamation of large lignite open pit mine sites may use large amounts of previous overburden materials or “spoils” to create the slopes of the pit lake. Spoils are anthropogenic materials with large spatial variation in properties, hence, considering mean values of shear strength and hydraulic parameters to assess stability and seasonal displacements will not fully simulate actual field conditions. This paper considers the effect of spatial variation on slope stability and ground movements during rapid drawdown events (a critical case) using coupled flow-deformation 2D finite element analyses, incorporating unsaturated soil suctions above the phreatic surface. Effects of heterogeneity and randomness of spoils on the response of the slope are considered through random field modelling and the Monte-Carlo simulation technique. Four lognormally distributed random variables (spoil cohesion, friction angle, void ratio, and permeability coefficient) are examined. The effect of spatial variability of spoils is shown to be important; a significant number of the random field analyses resulted in larger displacements compared to a benchmark deterministic analysis adopting uniform mean parameter values.W wielu krajach europejskich węgiel brunatny jest wykorzystywany jako źródło paliwa w energetyce parowo-elektrycznej. Po zakończeniu działalności górniczej konieczne jest opracowanie planu rekultywacji w celu zapewnienia środowiskowego i społecznego dobrostanu okolicznych obszarów. Opuszczone wyrobiska górnicze są często rekultywowane poprzez utworzenie w nich zbiorników wodnych. W rekultywacji dużych kopalni odkrywkowych węgla brunatnego do tworzenia zboczy zbiornika można wykorzystać duże ilości wcześniejszych materiałów nadkładowych lub „odpadowych”. Materiał zwałowy jest materiałem antropogenicznym o dużej przestrzennej zmienności właściwości, dlatego też przyjęcie średnich wartości wytrzymałości na ścinanie i parametrów hydraulicznych w celu oceny stabilności i sezonowych przemieszczeń nie będzie w pełni odzwierciedlać rzeczywistych warunków terenowych. W niniejszej pracy rozważano wpływ zmienności przestrzennej na stabilność zboczy i przemieszczenia gruntu podczas gwałtownego obniżenia poziomu wody (przypadek krytyczny), stosując sprzężone analizy 2D metodą elementów skończonych typu przepływ-deformacja, z uwzględnieniem ssania gruntów nienasyconych powyżej powierzchni freatycznej. Wpływ heterogeniczności i losowości materiału na zachowanie zbocza rozważany jest poprzez modelowanie pola losowego i technikę symulacji Monte-Carlo. Badane są cztery zmienne losowe (kohezja materiału, kąt tarcia, wskaźnik porowatości i współczynnik przepuszczalności) w rozkładach log-normalnych. Wykazano, że wpływ przestrzennej zmienności materiału zwałowego jest istotny; znaczna liczba analiz z wykorzystaniem pola losowego skutkowała większymi przemieszczeniami w porównaniu z wzorcową analizą deterministyczną, w której przyjęto jednolite średnie wartości parametrów

Systemy fundamentowania w zrównoważonej rewitalizacji terenów zwałowisk pogórniczych

The design of foundations systems is well established in the literature and codes of practice. However, these are generally applicable to well characterised, homogenous ground conditions. Spoil materials represent a significant challenge when implementing these design procedures due to their time-dependent characteristics, their spatial variability , and the likelihood that they will consist of low strength/stiffness materials. As such, careful consideration is required when designing foundation systems on spoil materials, especially for sensitive structures such as wind turbines. Physical modelling experiments using a geotechnical centrifuge were conducted to study the spoil-foundation system interaction. In these tests, an equivalent spoil was used that provided satisfactory reproduction of key physical and mechanical characteristics of a real spoil material. Three types of foundation systems were considered in the centrifuge tests: (1) raft foundation, (2) pile-group foundation, and (3) pile-raft foundation. The long-term cyclic loading of 87kN, 171kN and 460kN maximum cyclic load were used for the raft foundation. A higher cyclic load of 501kN was applied to the pile-group and pile-raft foundations. To evaluate the effect of climatic condition variations on spoil-foundation interactions, the centrifuge tests were carried out at different water table levels within the spoil material. The experimental results were analysed in terms of foundation rotation and foundation vertical settlement. The raft foundation rotated around 0.1-0.2 degrees and vertically displaced by 5-10 mm, whereas the pile-group rotated about 0.6-0.8 degrees and vertically displaced by 20-30 mm due to long-term cyclic loading. The pile-raft foundation displayed better response as compared to pile-group foundation.Projektowanie systemów fundamentowych jest dobrze ugruntowane w literaturze i w praktyce. Systemy te mają jednak zastosowanie do dobrze scharakteryzowanych, jednorodnych warunków gruntowych. Materiały zwałowe stanowią poważne wyzwanie przy wdrażaniu procedur projektowych ze względu na ich charakterystykę zależną od czasu, ich zmienność przestrzenną oraz duże prawdopodobieństwo, że będą się składać z materiałów o niskiej wytrzymałości/sztywności. W związku z tym, projektowanie systemów fundamentowych na zwałowiskach, szczególnie w przypadku wrażliwych konstrukcji, takich jak turbiny wiatrowe, wymaga starannego podejścia. W celu zbadania interakcji pomiędzy materiałem zwałowym a systemem fundamentowym przeprowadzono eksperymenty modelowania fizycznego z wykorzystaniem wirówki geotechnicznej. W badaniach tych zastosowano materiał równoważny, który zapewniał zadowalające odzwierciedlenie kluczowych cech fizycznych i mechanicznych rzeczywistego materiału. W badaniach wirówkowych rozpatrywano trzy rodzaje systemów fundamentowych: (1) fundamenty płytowe, (2) fundamenty wielopalowe oraz (3) fundamenty palowo-płytowe. Dla fundamentów płytowych zastosowano długotrwałe obciążenie cykliczne o maksymalnej wartości 87kN, 171kN i 460kN. Dla fundamentów wielopalowych i palowo-płytowych zastosowano większe obciążenie cykliczne - 501kN. W celu oceny wpływu zmienności warunków klimatycznych na interakcje zwałowisko-fundamenty, przeprowadzono badania wirówkowe przy różnych poziomach zwierciadła wody w obrębie zwałowiska. Wyniki eksperymentów analizowano pod kątem rotacji fundamentu i jego osiadania pionowego. W wyniku długotrwałego obciążenia cyklicznego fundament płytowy obrócił się o około 0,1-0,2 stopnia i przesunął w pionie o 5-10 mm, natomiast fundament wielopalowy obrócił się o około 0,6-0,8 stopnia i przesunął w pionie o 20-30 mm. Fundamenty palowo-płytowe odznaczały się lepszą reakcją w porównaniu do fundamentu wielopalowego