3,482 research outputs found
Experimental determination and control of prepreg tack for automated manufacture
No full textThe automated tape laying (ATL) process has been examined and found to be sensitive to tack and stiffness properties of the prepreg material being laid. A comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feedrate. Examination of constituent resin rheology has found that tack, and the two observed failure modes, are somewhat dependent upon viscoelastic stiffness. Observation of temperature and feedrate response revealed a time–temperature superposition relationship. The Williams–Landel–Ferry equation was utilised to make predictions of the temperature response based on the feedrate response. Tack levels were stabilised over the feedrate range by making temperature adjustments. Results from the peel test, where mould conditions at lay-up were recreated, were found transferable to the ATL, where a suitable lay-up feedrate under ambient conditions was predicted
The experimental determination of prepreg tack and dynamic stiffness
No full textA new peel test has been developed which quantifies the tack and dynamic stiffness of uncured prepreg. The test is designed to simulate the automated tape lay-up (ATL) and automated fibre placement (AFP) processes. It includes a pressure controlled application stage, where contact time is inversely proportional to peel rate. The use of a thin film allows stiffness to be isolated from peel resistance in a continuous two stage test. A repeatability study revealed consistent results with 16% standard deviation. Tack and stiffness variability has been observed across roll width and between faces in commercial hand lay-up prepregs. The overall tack and stiffness values for commercial hand lay-up prepregs were found to be inconsistent with the levels specified by manufacturers. A temperature increase revealed inconsistent effects on tack between materials. The contradictory results were rationalised by observing failure modes. The two failure modes observed appeared equivalent to those found in pressure sensitive adhesive (PSA) peel. The shear storage modulus of the prepreg resin was compared to the PSA Dahlquist criterion and found to support the principle of contact efficiency. However, the actual value for the criterion is expected to be a function of prepreg specific conditions such as resin content, fibre distribution and surface pattern
Clinical trial design in adult reflux disease: a methodological workshop
No full textBackground: The development of well-tolerated acid suppressant drugs has stimulated substantial growth in the number of trials assessing therapy options for gastro-oesophageal reflux disease (GERD). Aim: To develop consensus statements to inform clinical trial design in adult patients with GERD. Methods: Draft statements were developed employing a systematic literature review. A modified Delphi process including three rounds of voting was used to reach consensus. Between voting, statements were revised based on feedback from the Working Group and additional literature reviews. The final vote was at a face-to-face meeting that included discussion time. Voting was conducted using a six-point scale. Results: At the last vote, 93% of the final 102 statements achieved consensus (defined a priori as being supported by ‡75% of the votes). The Working Group strongly supported the development of validated patientreported outcome instruments. Symptom assessments carried out by the investigator were considered unacceptable. There was agreement that exclusion from clinical trials should be minimized to improve generalizability, that prospective evaluation ideally requires electronic timed ⁄ dated methods and that endoscopists should be blinded to patient symptom status. Conclusions: Implementation of the consensus statements will improve the quality and comparability of trials, and make them compatible with regulatory requirements.J . Dent, P. J . Kahrilas, N. Vakil, S. Veldhuyzen Van Zanten, P. Bytzer, B. Delaney, K. Haruma, J. Hatlebakk, E. McColl, P. Moayyedi, V. Stanghellini, J . Tack and M. Vaezihttp://www3.interscience.wiley.com/journal/120088380/issu
Gastroparesis: separate entity or just a part of dyspepsia?
No full textGastroparesis is defined by the presence of delayed gastric emptying (GE) in the absence of mechanical obstruction. Symptoms that have been attributed to gastroparesis include postprandial fullness, early satiation nausea and vomiting. Gastroprokinetic drugs are the preferred treatment option. A number of problems with the concept of gastroparesis have been identified recently. Major overlap exists with the symptom complex of the functional dyspepsia subtype of postprandial distress syndrome. The distinguishing feature of gastroparesis is delayed GE, but the correlation between delayed emptying and symptom pattern or severity in gastroparesis is modest and the stability of delayed emptying over time is poor. Other pathophysiological mechanisms such as hypersensitivity or impaired accommodation may also underlie symptoms in patients with gastroparesis. Moreover, symptomatic response to prokinetic therapy is variable and cannot be predicted based on the degree of enhancing GE. A number of approaches have been proposed to increase clinical usefulness of a diagnosis of gastroparesis, including a higher threshold of abnormal emptying and selection of patients with a specific symptom pattern more likely to be associated with delayed emptying
Translational molecular biomarker validation in diabetes
No full textContains fulltext :
220322.pdf (Publisher’s version ) (Open Access)Radboud University, 04 september 2020Promotores : Gool, A.J. van, Tack, C.J.J. Co-promotores : Gloerich, J., Wessels, J.C.T
Design for Tack or Nail.
No full textDesign patent for a tack or nail that is both useful and ornamental
Visceral hypersensitivity in functional disorders of the upper gastrointestinal tract.
No full textVisceral hypersensitivity is now recognised as a major pathophysiological mechanism in functional gastrointestinal disorders of the upper gastrointestinal tract. In patients with non-cardiac chest pain and functional dyspepsia, a high prevalence of visceral hypersensitivity has been indeed observed. In these patients, luminal physiological stimuli can be perceived as unpleasant or even painful. Although the fine mechanisms underlying such “aberrant perceptions” are yet not fully clarified, it is thought that an altered activation of the gut-wall receptors, an altered conduction of sensory inputs at the level of neural pathways, or an impaired processing of the sensations at the level of brain, may occur along the brain–gut axis. So far, drugs able to reduce hypersensitivity, that target each of the constituents of the stimuli–perception chain, have the therapeutic potential to reduce visceral hypersensitivity and, thus, to improve the symptoms. In this context, the availability of new agonists/antagonists to neurotransmitters offers a new exciting tool for the treatment of functional disorders of the upper gastrointestinal tract
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