Adhesively-bonded repair proposal for wood members damaged by horizontal shear using carbon-epoxy patches

In this work, a repair technique with adhesively bonded carbon-epoxy patches is proposed for wood members damaged by horizontal shear and under bending loads. This damage is characterized by horizontal crack growth near the neutral plane of the wood beam, normally originating from checks and shakes. The repair consists of adhesively bonded carbon-epoxy patches on the vertical side faces of the beam at the cracked region to block sliding between the beam arms. An experimental and numerical parametric analysis was performed on the patch length. The numerical analysis used the finite element method (FEM) and cohesive zone models (CZMs), with an inverse modelling technique for the characterization of the adhesive layer. Trapezoidal cohesive laws in each pure mode were used to account for the ductility of the adhesive used. To fully reproduce the tests, horizontal damage propagation within the wood beam was also simulated. A good correlation with the experiments was found. Regarding the effectiveness of the repair, for the conditions selected for this work, a full strength recovery was achieved for the bigger value of patch length tested.

Strap repairs using embedded patches: numerical analysis and experimental results

Adhesively bonded repairs offer an attractive option for repair of aluminium structures, compared to more traditional methods such as fastening or welding. The single-strap (SS) and double-strap (DS) repairs are very straightforward to execute but stresses in the adhesive layer peak at the overlap ends. The DS repair requires both sides of the damaged structures to be reachable for repair, which is often not possible. In strap repairs, with the patches bonded at the outer surfaces, some limitations emerge such as the weight, aerodynamics and aesthetics. To minimize these effects, SS and DS repairs with embedded patches were evaluated in this work, such that the patches are flush with the adherends. For this purpose, in this work standard SS and DS repairs, and also with the patches embedded in the adherends, were tested under tension to allow the optimization of some repair variables such as the overlap length (LO) and type of adhesive, thus allowing the maximization of the repair strength. The effect of embedding the patch/patches on the fracture modes and failure loads was compared with finite elements (FE) analysis. The FE analysis was performed in ABAQUS® and cohesive zone modelling was used for the simulation of damage onset and growth in the adhesive layer. The comparison with the test data revealed an accurate prediction for all kinds of joints and provided some principles regarding this technique.

Augmentation cystoplasty using pedicled and de-epithelialized gastric patches in the mini-pig model.

PURPOSE: The most common methods of bladder augmentation are gastrocystoplasty and enterocystoplasty. Gastrocystoplasty is advantageous due to minimal mucous secretion and a well developed muscular wall as well as good urodynamic properties of the patch. However, the permanent contact of urine with the gastric mucosa is not free of complications. We report the urodynamic, macroscopic and histological outcomes of a pedicled de-epithelialized gastric patch incorporated in the bladder. We compared the results to those of our previous study, which sought to analyze these techniques of patch coverage using sigmoid patches. MATERIALS AND METHODS: We performed 20 augmentation cystoplasties in the mini-pig model using a pedicled de-epithelialized gastric patch and 5 techniques of patch coverage. RESULTS: Three months after surgery all bladders had an increase in volume except those in which the auto-augmentation technique was used. However, all gastric patches were smaller compared to preoperative size. Many had irregular fibrosed inner surfaces and histological evaluation revealed a fibrosed newly formed submucosal layer with a complete urothelial coverage in every patch. No gastric mucosal remnant was found. CONCLUSIONS: De-epithelialized gastrocystoplasty is an attractive procedure that can increase bladder capacity as well as provide a complete urothelial lining without mucosal remnants. However, the success of this procedure seems to be limited by increased morbidity and fibrotic changes, and decreased surface of the patch.

Histological and ultrastructural studies of the marsupial Didelphis albiventris Peyer's patches

Differing from the studied Eutheria the white belly opossum Peyer"s patches do not present a conspicous dome. M cells are located in the inmer layer of bilaminal invaginations formed at the bottom of the villi. A great variation in the morphology of M cells was observed. The enterocytes located at the epithelial inner layer may present endocytic vesicles, and the microvilli are shorter tha the microvilli of enterocytes lining the small intestine. As these morphological aspects have been described to exist in the enterocytes of the lancet opossum small intstine it was surmised that the opossum Peyer's patches special epithelium could represent the persistence in adult animals of a cellular pattern established before the intestinal maturation had occurred.

Antigen-secretory IgA immune complexes are retro-transported into mouse Peyer's patches: immunotargeting to dendritic cells

RÉSUMÉ Les plaques de Peyer (PP) représentent le site d'entrée majeur des pathogènes au niveau des muqueuses intestinales. Après avoir traversé la cellule M, l'antigène est pris en charge par les cellules dendritiques (DC) de la région sub-épithéliale du dôme des PP. Ces dernières activent une réponse immunitaire qui conduit à la production de l'IgA de sécrétion (SIgA), l'anticorps majeur au niveau muqueux. Des études précédentes dans notre laboratoire ont démontré qu'après administration de SIgA dans des anses intestinales de souris, les SIgA se lient spécifiquement aux cellules M, entrent dans les PP, et sont éventuellement internalisées par les DC. Le but de ce travail est de comprendre la relevance biologique de l'entrée des SIgA dans les PP et leur relevance physiologique dans l'homéostasie mucosale. Dans un premier temps, nous avons montré en utilisant une méthode de purification optimisée basée sur une isolation magnétique, que, en plus des DC myéloïdes (CD11c+/CD11b+) et des DC lymphoïdes (CD11c+/CD8+), les PP de souris contiennent un nouveau sous-type de DC exprimant les marqueurs CD11c et CD19. L'utilisation de la microscopie confocale nous a permis de démontrer que les DC myéloïdes internalisent des SIgA, contrairement aux DC lymphoïdes qui n'interagissent pas avec les SIgA, alors que le nouveau sous-type de DC exprimant CD19 lie les SIgA. En plus, nous avons démontré qu'aucune des DC de rate, de ganglion bronchique ou de ganglion inguinal interagit avec les SIgA. Dans le but d'explorer si les SIgA peuvent délivrer des antigènes aux DC des PP in vivo, nous avons administré des complexes immunitaires formés de Shigella flexneri complexées à des SIgA, dans des anses intestinales de souris. Nous avons observé une entrée dans les PP, suivie d'une migration vers les ganglions mésentériques drainants, contrairement aux Shigella flexneri seules, qui n'infectent pas la souris par la voie intestinale. Shigella flexneri délivrée par SIgA n'induit pas de destruction tissulaire au niveau de l'intestin. En plus de l'exclusion immunitaire, ces résultats suggèrent un nouveau rôle des SIgA, qui consiste à transporter des antigènes à l'intérieur des PP dans un contexte non-inflammatoire. RÉSUMÉ DESTINÉ À UN LARGE PUBLIC L'intestin a pour rôle principal d'absorber les nutriments digérés tout au long du tube digestif, et de les faire passer dans le compartiment intérieur sanguin. Du fait de son exposition chronique avec un monde extérieur constitué d'aliments et de bactéries, l'intestin est un endroit susceptible aux infections et a donc besoin d'empêcher l'entrée de microbes. Pour cela, l'intestin est tapissé de "casernes" appelées les plaques de Peyer, qui appartiennent à un système de défense appelé système immunitaire muqueux. Les plaques de Peyer sont composées de différents types de cellules, ayant pour rôle de contrôler l'entrée de microbes et de développer une réaction immunitaire lors d'infection. Cette réaction immunitaire contre les microbes (antigènes) débute par la prise en charge de l'antigène par des sentinelles, les cellules dendritiques. L'antigène est préparé de façon à être reconnu par d'autres cellules appelées lymphocytes T capables d'activer d'autres cellules, les lymphocytes B. La réaction immunitaire résulte dans la production par les lymphocytes B d'un anticorps spécifique appelé IgA de sécrétion (SIgA) au niveau de la lumière intestinale. De manière classique, le rôle de SIgA au niveau de la lumière intestinale consiste à enrober les microbes et donc exclure leur entrée dans le compartiment intérieur. Dans ce travail, nous avons découvert une nouvelle fonction des SIgA qui consiste à introduire des antigènes dans les plaques de Peyer, et de les diriger vers les cellules dendritiques. Sachant que les SIgA sont des anticorps qui ne déclenchent pas de réactions de défense violentes dites inflammatoires, l'entrée des antigènes via SIgA serait en faveur d'une défense intestinale maîtrisée sans qu'il y ait d'inflammation délétère. Ces résultats nous laissent supposer que l'entrée d'antigènes via SIgA pourrait conduire le système immunitaire muqueux à reconnaître ces antigènes de manière appropriée. Ce mécanisme pourrait expliquer les désordres immunitaires de types allergiques et maladies auto-immunitaires que l'on rencontre chez certaines personnes déficientes en IgA, chez qui cette lecture d'antigènes de manière correcte serait inadéquate. ABSTRACT Peyer's patches (PP) represent the primary site for uptake and presentation of ingested antigens in the intestine. Antigens are sampled by M cells, which pass them to underlying antigen-presenting cells including dendritic cells (DC). This leads to the induction of mucosal T cell response that is important for the production of secretory IgA (SIgA), the chief antibody at mucosal surfaces. Previous studies in the laboratory have shown that exogenous SIgA administrated into mouse intestinal loop binds specifically to M cells, enter into PP, and is eventually internalized by DC. The aim of this work is to understand the biological significance of the SIgA uptake by PP DC and its physiological relevance for mucosal homeostasis. As a first step, we have shown by using an optimized MACS method that, in addition to the CD11c+/CD11b+ (myeloid DC) and CD11c+/CD8+ (lymphoid DC) subtypes, mouse PP contain a novel DC subtype exhibiting both CD11c and CD19 markers. By using a combination of MACS isolation and confocal microscopy, we have demonstrated that in contrast to the lymphoid DC which do not interact with SIgA, the myeloid DC internalize SIgA, while the CD19+ subtype binds SIgA on its surface. Neither spleen DC, nor bronchial-lymph node DC, nor inguinal lymph node DC exhibit such a binding specificity. To test whether SIgA could deliver antigens to PP DC in vivo, we administered SIgA-Shigella flexneri immune complexes into mouse intestinal loop containing a PP. We found that (i) SIgA-Shigella flexneri immune complexes enter the PP and are internalized by sub-epithelial dome PP DC, in contrast to Shigella flexneri alone that does not penetrate the intestinal epithelia in mice, (ii) immune complexes migrate to the draining mesenteric lymph node, (iii) Shigella flexneri carried via SIgA do not induce intestinal tissue destruction. Our results suggest that in addition to immune exclusion, SIgA transports antigens back to the PP under non-inflammatory conditions.

Complex suicide with homemade nicotine patches.

Suicide by self-poisoning is rather common around the world. This paper presents an exceptional complex suicide in which nicotine was applied in the form of self-made patches soaked with an extraction from fine-cut tobacco. In addition, the 51-year-old suicide victim took a lethal dose of diphenhydramine. Toxicological analysis also revealed the presence of tetrazepam in subtherapeutic concentrations. The scene of death suggested an autoerotic accident at first, as the body was tied with tapes, cables and handcuffs. As a result of the entire investigations, the fatality had to be classified as a suicidal intoxication by nicotine and diphenhydramine.

Enterocystoplasty using modified pedicled, detubularized, de-epithelialized sigmoid patches in the mini-pig model.

Enterocystoplasty and gastrocystoplasty have been developed to restore adequate bladder capacity but they still result in the undesired harmful contact of urine with the intestinal mucosa. In an attempt to prevent this nonphysiological interface we performed several modified enterocystoplasties in the mini-pig model using a pedicled, detubularized, de-epithelialized sigmoid patch. Five techniques of patch coverage were used to evaluate urothelial growth or survival on the sigmoid patch. All but 1 patch had intestinal mucosa remnants with mucocele formation. When no coverage was applied or a biodegradable polyglactin mesh was temporarily covering the pedicled, detubularized, de-epithelialized sigmoid patch, severe shrinkage occurred. Partial cover with autologous urothelium islets seemed to decrease shrinkage. Adequate urothelium survival and satisfactory elastic properties of the patch were observed when total cover of the sigmoid patch was achieved with a sheet of homologous urothelium recovering autologous urothelial islets or when the patch was applied to protruding urothelium obtained following sagittal posterior detrusor myotomy.

Direct observations of the evolution of polar cap ionization patches

Patches of ionization are common in the polar ionosphere where their motion and associated density gradients give variable disturbances to High Frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a “tongue” of ionization (TOI).

Automated identification and tracking of polar-cap plasma patches at solar minimum

A method of automatically identifying and tracking polar-cap plasma patches, utilising data inversion and feature-tracking methods, is presented. A well-established and widely used 4-D ionospheric imaging algorithm, the Multi-Instrument Data Assimilation System (MIDAS), inverts slant total electron content (TEC) data from ground-based Global Navigation Satellite System (GNSS) receivers to produce images of the free electron distribution in the polar-cap ionosphere. These are integrated to form vertical TEC maps. A flexible feature-tracking algorithm, TRACK, previously used extensively in meteorological storm-tracking studies is used to identify and track maxima in the resulting 2-D data fields. Various criteria are used to discriminate between genuine patches and "false-positive" maxima such as the continuously moving day-side maximum, which results from the Earth's rotation rather than plasma motion. Results for a 12-month period at solar minimum, when extensive validation data are available, are presented. The method identifies 71 separate structures consistent with patch motion during this time. The limitations of solar minimum and the consequent small number of patches make climatological inferences difficult, but the feasibility of the method for patches larger than approximately 500 km in scale is demonstrated and a larger study incorporating other parts of the solar cycle is warranted. Possible further optimisation of discrimination criteria, particularly regarding the definition of a patch in terms of its plasma concentration enhancement over the surrounding background, may improve results.

Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate

Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin- Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the companion paper by Lockwood et al. (2005). It is shown that the poleward-moving, high-concentration plasma patches observed in the ionosphere by EISCAT on 23 November 1999, as reported by Davies et al. (2002), were often associated with corresponding reconnection rate pulses. However, not all such pulses generated a patch and only within a limited MLT range (11:00–12:00 MLT) did a patch result from a reconnection pulse. Three proposed mechanisms for the production of patches, and of the concentration minima that separate them, are analysed and evaluated: (1) concentration enhancement within the patches by cusp/cleft precipitation; (2) plasma depletion in the minima between the patches by fast plasma flows; and (3) intermittent injection of photoionisation-enhanced plasma into the polar cap. We devise a test to distinguish between the effects of these mechanisms. Some of the events repeat too frequently to apply the test. Others have sufficiently long repeat periods and mechanism (3) is shown to be the only explanation of three of the longer-lived patches seen on this day. However, effect (2) also appears to contribute to some events. We conclude that plasma concentration gradients on the edges of the larger patches arise mainly from local time variations in the subauroral plasma, via the mechanism proposed by Lockwood et al. (2000).