RATE-DEPENDENT COMPACTION AND RELAXATION RESPONSE OF UNCURED PREPREGS UNDER HIGH-PRESSURE CONDITIONS

The compaction-relaxation response at different compaction rates and fiber volume fractions plays a key role in understanding the viscoelastic response of uncured prepregs. Hence, this study characterizes the time-dependent behavior of un-cured 4- layer prepregs subjected to compaction-stress relaxation test at different displacement rates i.e., 0.1 mm/min, 1.0 mm/min, and 10 mm/min, at 0.65 fiber volume fraction and allowed to relax for two hours. In this study, the complete deformation history of the Hexply M26T multilayer prepregs is measured from a stress-free state to the cured state. The effects of rate-dependent compaction-relaxation at different rates on percentages of compaction, recovery, stress change during relaxation, and permanent deformation of prepregs are computed. It was concluded that the 0.1 / displacement rate showed the lowest peak stress level and the lowest stress relaxation and permanent deformation. A viscoelastic model was used to fit the experimental data and the results showed a good agreement. The void content was determined analytically and from the XCT-aided geometrical model. It was observed that for a given test condition, the void content increases as the displacement rate increases, due to the high applied pressure. This study highlights the importance of rate-dependent compaction-relaxation behavior and the need to determine the suitable process parameters and models to manufacture high-quality aerospace composite structures.

The Effect Of Breathing Relaxation And Lavender Aromatherapy On Insomnia In The Elderly

Background: The elderly experience insomnia in the form of problems with symptoms of sleep disorders in the form of repeated difficulties in sleeping or maintaining sleep even though there is an opportunity to sleep. The objective of research was to analyze the effect of Breathing Relaxation Aromatherapy Combination Lavandula Angustifolia on Insomnia in the Elderly. Methods: The design was a pre-experiment with approach the one group pretest-posttest design. The research population was elderly insomnia in elderly Posyandu and the sample was 21 peoples. The sampling research was total sampling. Variabel independent was Breathing Relaxation combination with lavender aromatherapy is relaxation using breathing techniques slowly and deeply, variabel dependen was insomnia level. Statistic test use Wilcoxon Signed Ranks Test Results: The results showed that The Wilcoxon Signed Ranks Test ρ value = 0,000, H1 is accepted, meaning that there is an effect of the Breathing Relaxation and lavender aromatherapy on insomnia in the elderly. The combination of Breathing Relaxation and lavender aromatherapy increases the relaxation response in the elderly. Conclusion: Effect of Breathing Relaxation combination of lavender aromatherapy (Lavandula angustifolia) is more effective in reducing insomnia levels in the elderly and is highly recommended and safe for the elderly)

Relaxation Response in Stressed Volunteers: Psychometric Tests and Neurotrophin Changes in Biological Fluids

Background: To evaluate the beneficial effects of relaxation response (RR) training in adult stressed subjects by evaluating the psychometric response recorded at relaxation session. Cortisol as well as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) mediators were quantified in both saliva and tears, and their levels were related to each other and to the psychometric response.Methods: Stressed subjects (n = 23; 10M/13F; age range 21–53 years old) were voluntarily enrolled in the study. RR training sessions were carried out for 2 months, 1 day per week, at the same time (3–5 p.m.). Two different psychological questionnaires, the Perceived Stress Scale-10 (PSS-10) and the Beck Depression Inventory - Short Form (BDI-SF) and Ocular Surface Disease Index (OSDI) tests, were administered before each session. Saliva and tears were sampled for cortisol (EIA), NGF (ELISA), and BDNF (ELISA) quantifications. Questionnaires' data were analyzed and compared to biochemical ones.Results: All subjects reported beneficial effects from training. RR significantly reduced the psychological stress indexes (p = 0.039 for PSS-10 and p = 0.001 for BDI-SF). Specifically, RR training lowered the perception of Perceived Helplessness (items 1, 3, 10; p < 0.05) in PSS-10 and increased the Perceived Self-Efficacy (p < 0.05). OSDI score was in the normal range (0–25). Biochemically, a decrease in cortisol, a trend to a decrease in NGF, and an increase in BDNF levels were observed in saliva samples after RR treatment. Furthermore, a trend to a decrease in NGF and an increase in BDNF were quantified in tear samples. A correlation between PSS-10 total score and saliva NGF variation (%) as well as between BDI-SF total score and BDNF tear levels were also observed.Conclusion: RR training appeared useful to lowering psychological, mental, and physical stress, as supported by both psychological total and single scores. The finding on biochemical levels of BDNF in saliva and tears are sustained by previous studies while those of NGF require further investigation. Overall, these data on a small population highlight the potential use of RR training and potential neurotrophic changes in biological fluids, in stressed volunteers.

Von Willebrand Factor Multimers and the Relaxation Response: A One-Year Study

Background and aim: Mental stress represents a pivotal factor in cardiovascular diseases. The mechanism by which stress produces its deleterious ischemic effects is still under study but some of the most explored pathways are inflammation, endothelial function and balancing of the thrombotic state. In this scenario, von Willebrand factor (vWF) is a plasma glycoprotein best known for its crucial hemostatic role, also acting as key regulatory element of inflammation, being released by the activated vascular endothelium. Antistress techniques seem to be able to slow down inflammation. As we have recently verified how the practice of the Relaxation Response (RR), which counteracts psychological stress, causes favorable changes in some inflammatory genes’ expressions, neurotransmitters, hormones, cytokines and inflammatory circulating microRNAs with coronary endothelial function improvement, we aimed to verify a possible change even in serum levels of vWF. Experimental procedure: We measured vWF multimers and the total protein carbonyl contents in the sera of 90 patients with ischemic heart disease (and 30 healthy controls) immediately before and after an RR session, three times (baseline, 6 months, 12 months), during a one-year follow-up study. Results: According to our data, large vWF multimers decrease during the RR, as does the plasma total carbonyl content. Conclusion: vWF levels seem to vary rapidly between anti-inflammatory and antithrombotic behaviors dependent on psychological activity, leading to relaxation and also possibly changes in its quaternary structure.