Adhesive properties of silicone resins

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (leaves 70-76).An experimental study on adhesive properties of Phase I rubber toughened rigid silicone resins was performed to determine the possibility of an application such as structural adhesives. Single-lap shear tests were used to study several parameters, such as the thickness of the joint, the overlap length, the behavior at high temperature and a comparison with different adhesives. Results suggest that a 10% KPE / 6% Cab-O-Sil® modified silicone resin shows optimal adhesion for sandblasted plates and a 0.1 mm thick joint, whereas such an optimum has not been observed for the untoughened resin. For small overlaps, the failure criterion is the shear strength of the resin, whereas for laps over 20 mm, it is the applied load. Toughened silicone resins behave well at high temperatures, as the strength of the joint is half as small between 150 and 250 °C as it is at room temperature. Furthermore, no degradation has been noticed for exposures up to 200°C and up to 500 hours, but the resin starts decomposing after 10 hours at 250°C. Last, comparison with other commercial glues proves that the studied toughened silicone resin provides a relatively strong bond, between the performance of epoxy glues and cyanoacrylate adhesives.by Bruno Chéron.S.M

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Deltaic and Coastal Sediments as Recorders of Mediterranean Regional Climate and Human Impact Over the Past Three Millennia

International audienc

A united statement of the global chiropractic research community against the pseudoscientific claim that chiropractic care boosts immunity.

BACKGROUND: In the midst of the coronavirus pandemic, the International Chiropractors Association (ICA) posted reports claiming that chiropractic care can impact the immune system. These claims clash with recommendations from the World Health Organization and World Federation of Chiropractic. We discuss the scientific validity of the claims made in these ICA reports. MAIN BODY: We reviewed the two reports posted by the ICA on their website on March 20 and March 28, 2020. We explored the method used to develop the claim that chiropractic adjustments impact the immune system and discuss the scientific merit of that claim. We provide a response to the ICA reports and explain why this claim lacks scientific credibility and is dangerous to the public. More than 150 researchers from 11 countries reviewed and endorsed our response. CONCLUSION: In their reports, the ICA provided no valid clinical scientific evidence that chiropractic care can impact the immune system. We call on regulatory authorities and professional leaders to take robust political and regulatory action against those claiming that chiropractic adjustments have a clinical impact on the immune system

Matching with Phantoms

WP online halshs-00472751v1International audienceSearching for partners involves informational persistence that reduces future traders’ matching probability. In this article, traders who are no longer available but who left tracks on the market are called phantoms. We examine a dynamic matching market in which phantoms are a by-product of search activity, no coordination frictions are assumed, and non-phantom traders may lose time trying to match with phantoms. The resulting aggregate matching technology features increasing returns to scale in the short run, but has constant returns to scale in the long run. We embed a generalized version of this matching function in the canonical continuous-time equilibrium search unemployment model. Long-run constant returns to scale imply there is a unique steady state, whereas short-run increasing returns generate excess volatility in the short run and endogenous fluctuations based on self-fulfilling prophecies

Role of molecular ions in plasmas of atmospheric and energetic interest

International audienc

Transformations du graphe des programmes SIGNAL

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Manuel SIGNAL

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Collisional-radiative model in air for earth re-entry problems

A nonlinear time-dependent two-temperature collisional-radiative model for air plasma has been developed for pressures between 1 kPa and atmospheric pressure to be applied to the flow conditions of space vehicle re-entry into the Earth's atmosphere. The model consists of 13 species: N-2, O-2, N, O, NO, N-2(+), O-2(+), N+, O+, NO+, O-2(-), O- in their ground state and major electronic excited states and of electrons. Many elementary processes are considered given the temperatures involved (up to 10 000 K). Time scales to reach the final nonequilibrium or equilibrium steady states are derived. Then we apply our model to two typical re-entry situations and show that O-2(-) and O- play an important role during the ionization phase. Finally, a comparison with existing reduced kinetic mechanisms puts forward significant discrepancies for high velocity flows when the flow is in chemical nonequilibrium and smaller discrepancies when the flow is close to chemical equilibrium. This comparison illustrates the interest of using a time-dependent collisional-radiative model to validate reduced kinetic schemes for the relevant time scales of the flows studied

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