Models describing how fillers affect the barrier properties of polymers remain an important research topic to improve applications such as hydrogen storage or food preservation. The Nielsen model, ...one of the earliest models for such predictions, is still one of the most widely used in the literature. However, it does not provide quantitative information on arrangements of fillers inside a polymer matrix, which is crucial for the definition of suitable filler distributions in barrier materials. Therefore, the channel model was developed in this work, which extends the Nielsen model by determining the relative distances between the fillers in regular filler arrangements in polymer matrices. This allows us to relate the permeation properties of filled polymer membranes to the geometric properties of the filler arrangement in simulations and experimental measurements. Simulations with geometries defined according to the channel model showed good agreement with the predictions of the Nielsen model. This demonstrated that the channel model can be a valuable tool for predicting at least mean geometric distances in studied polymer membranes. The validity range of the channel model was limited to a value range of the filler volume fraction 0.01≤ϕf≤0.5 based on theoretical considerations.
Conventional textbook wisdom portrays the skin as an organ that literally enwraps whatever each of us stands for as a more or less functional, individual member of the mammalian species, and has it ...that the skin primarily establishes, controls and transmits contacts with the external world. In addition, the skin has long been recognized to protect the organism from deleterious environmental impacts (physical, chemical,microbiological), and is well-known as crucial for the maintenance of temperature, electrolyte and fluid balance. Now, ever more studies are being published that show the skin to also operate as a huge and highly active biofactory for the synthesis,processing and/or metabolism of an astounding range of e.g. structural proteins, glycans, lipids and signaling molecules. Increasingly, it becomes appreciated that the skin, furthermore, is an integral component of the immune, nervous and endocrine systems, with numerous lines of cross-talk between these systems established intracutaneously (e.g. Ann NY Acad Sci Vol 885, 1999; Endocrine Rev 21:457-487, 2000; Physiol Rev 80:980-1020, 2001; Exp Dermatol 10: 349-367, 2001). All these emerging cutaneous functions beyond the classical image of the skin as a barrier and sensory organ are immediately relevant for many of the quandaries that clinical dermatology, dermatopathology, and dermatopharmacology are still struggling with to-date, and offer the practising dermatologist attractive new targets for therapeutic intervention. Yet, many of these skin functions are not even mentioned in dermatology textbooks and await systematic therapeutic targeting. Following a suggestion by Enno Christophers, the current 'Controversies' feature brings together an unusually diverse council of biologists and clinicians, who share their thought-provoking views with the readers and allow us to peek into the future of research in cutaneous biology, not the least by reminding us of the -- often ignored -- evolutionary and embryonal origins of our favorite organ. Hopefully, this unique discussion feature will foster an understanding of the 'true' skin functions that is both more comprehensive and more profound than conventional teaching on this topic, and will stimulate more than 'skin-deep' reflections on the full range of skin functions.
To reduce loss of hydrogen in storage vessels with high energy-to-weight-ratio, new materials, especially polymers, have to be developed as barrier materials. Very established methods for ...characterization of barrier materials with permeation measurements are the time-lag and flow rate method along with the differential pressure method, which resembles the nature of hydrogen vessel systems very well. Long measurement durations are necessary to gain suitable measurement data for these evaluation methods, and often restrictive conditions have to be fullfilled. For these reasons, common models for hydrogen permeation through single-layer and multi-layer membranes, as well as models for hydrogen gas properties were collected and reviewed. Using current computer power together with these models can reduce measurement time for characterization of the barrier properties of materials, while additional information about the quality of the measurement results is obtained.
•Review of models for single- and multi-layered membrane permeation.•Recommendation of curve fitting instead of time lag or flow rate measurements.•Empirical equations of state for viscosity and density of hydrogen.•Discussion of the influence of porous plates on permeation measurements.
What Are PVDF-Based Backsheets Made Of? Barretta, Chiara; Helfer, Eric; Macher, Astrid E. ...
2022 IEEE 49th Photovoltaics Specialists Conference (PVSC),
2022-June-5
Conference Proceeding
It is important to have a deep knowledge of a material's formulation to understand the degradation mechanisms taking place when the materials are exposed to external stresses. In the last years, ...cracking of backsheets with polyvinylidene fluoride (PVDF) has become an issue. PVDF based backsheets are widely used, but there is still quite some uncertainty regarding their exact formulation and the mechanisms behind the degradation. In this study seven PVDF films were investigated to get a deeper knowledge regarding their formulations and their principal properties.
Progression of human melanoma is associated with changes in antigenic phenotypes of tumor cells. To establish whether inflammatory infiltrates in progressing melanoma also change, we studied 146 ...cutaneous melanomas at different stages of progression. Monoclonal antibodies (MAbs) against lymphocyte and macrophage subpopulations, interleukin-2 receptor (IL-2 R), immune interferon (IFN-gamma), and the IFN-gamma-inducible, progression-associated melanoma antigens HLA-DR and gp89 were applied in situ. During the course of melanoma progression, decreased amounts of peritumoral T cells, IL-2 R-expressing lymphocytes and dermal T6+ dendritic cells were found, while increased numbers of intratumoral T cells, inflammatory (27E10+) and mature (25F9+) macrophages were associated with local progression of primary melanomas. In metastases, most infiltrate components except 25F9+ macrophages were rare. Positive correlations were observed between: (1) dermal T6+ cells and IL-2 R+ lymphocytes, and (2) presence of IFN-gamma in the infiltrate and HLA-DR and gp89 antigens on tumor cells. In all stages, HLA-DR expression on tumor cells was correlated with: (1) a shift towards T8+ lymphocytes in the infiltrates and (2) a loss of IL-2 R expression. Our data suggest mutual influences between melanoma cells and mononuclear cell infiltrates in situ.
The study presents a degradation analysis carried out on photovoltaic modules with the same bill of materials exposed in different climates: moderate (Germany) and tropical (the Caribbean). The ...modules exposed in tropical climate experienced severe power degradation after about 7 years of exposure, mainly due to the occurrence of acetic acid-related degradation modes. Evidence of acetic acid presence could be seen in the electroluminescence images and ion chromatography. Reduction of molar mass could be detected by means of differential scanning calorimetry, but thermogravimetric analysis and infrared spectroscopy were proven to be not suitable methods to detect chain scission phenomena.
The therapeutic effect of thalidomide in chronic discoid lupus erythematosus (CDLE) was studied in sixty patients who were followed up for 2 years. In fifty-four patients (90%) a complete or marked ...regression of the disease was observed, but when the thalidomide was stopped, thirty out of forty-one (71%) patients relapsed. Patients undergoing a second course of thalidomide treatment again responded well. Nine of the patients in whom the disease recurred after successful treatment with thalidomide and who had been unresponsive to intermittent treatment with antimalarials, showed a good response to a second or third course with thalidomide. Mild side-effects were common and 25% of patients complained of slight to moderate polyneuritic symptoms. Since electroneurological examinations had not been performed before the thalidomide therapy, the frequency of neurological side-effects cannot be accurately calculated but we recommend neurological examinations before and periodically during thalidomide treatment. Thalidomide is a very effective drug in CDLE, but in most cases it exerts its effect only whilst treatment is continued. Its use should be restricted to patients resistant to topical steroids and systemic antimalarials.
Normal skin is permeable to low molecular hydrophobic substances, including allergenic chemicals. Whereas such foreign matter appears to enter the skin naturally, it rarely induces contact ...hypersensitivity. This suggests that immunological tolerance would be the normal state of affairs. In search of a suitable model, we painted picryl chloride or oxazolone once or repeatedly on normal skin of BALB/c or C57B1/6 mice and found subsensitizing doses to be tolerogenic. The most effective doses in inducing tolerance were doses between those at the point of inflection from no responses to threshold sensitivity. But even doses three orders of magnitude lower than these suppressed subsequent sensitization if applied repeatedly. C57B1/6 mice (low responders) were consistently easier to make tolerant than BALB/c mice (high responders). The tolerant state established by a single painting was found to be fully developed at 48 h after initiation and long-lasting (>14 d). It could be adoptively transferred by intravenous injection of total spleen cells (SC), lymph node cells (LNC), or purified T cells and shown to be hapten specific. Pretreatment with cyclophosphamide (Cy) prevented tolerization. The T cells capable of transferring suppressive activity were found to be generated irrespective of the dose applied. On day 2 after painting, tolerance could be transferred with LNC from both tolerant and sensitized animals. On day 5, however, only cells from tolerant donors transferred tolerance. But by action of Cy, suppression was shown to be part of every sensitization, although masked. Production of hapten-specific antibodies was suppressed as well. Through depletion by monoclonal antibody in vitro the T suppressor cells were shown to belong to the murine CD8+ subset (Lyt2+). Upon restimulation in vitro by haptenized and irradiated normal SC, LNC from tolerant donors produced predominantly interleukin (IL)-4, IL-5, and IL-10. In contrast, LNC from sensitized donors produced preferentially IL-2 and interferon-gamma. Thus we demonstrate that painting subsensitizing doses of contact sensitizers on normal murine skin generates CD8+ Th2-like cells that give rise to hapten-specific tolerance. The model may have broader significance and apply to other species, including humans.
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