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The purpose of this study is to suggest sound biofeedback, which is a new technique of early stress relief effect by observing change in the heart rate variability (HRV). The sound biofeedback imitating heart rate of the comfortable and stress state is termed parasympathetic stimulation sound (PSS) and sympathetic stimulation sound (SSS), respectively. Twelve subjects were selected without previous history of cardiovascular diseases and mental illness, such as arrhythmia, myocardial infarction, depression and panic disorder. To confirm the changes in the low-frequency (LF), high-frequency (HF) and LF/HF values of HRV as stress evaluation indicators, the HRV of subjects was measured by photoplethysmogram. Signals were processed using the peak detect algorithm, and fast Fourier transform. Results were obtained using power specific densities. During the PSS stimulation, the LF/HF tended to decrease generally. On the other hand, during the SSS stimulation, LF/HF tended to increase. The LF/HF Mean change value ($P<0.05$) using the PSS stimulation is similar to the effect of Transcutaneous Vagal Nerve Stimulation (tVNS). In addition, the quantitative effect of sound biofeedback was confirmed by judging changes in the parasympathetic and sympathetic nerves in the autonomic nervous system (ANS) through $Z$-score normalized data. These experimental results suggest that sound biofeedback has the same stimulation location and clinical applicability as tVNS. As a result, sound biofeedback may be used as a new method for stress reduction.

An analysis of heterophase states was carried out for ferro-active solid solutions of the system ($1-x-y$)NaNbO${}_3-x$KNbO${}_3-y$CdNb₂O₆. A complete stress relief at interfaces between phases in solid solutions with $y=0.05$ and $x=0.10$, 0.40, and 0.45 is realized at the single-domain state of the tetragonal and orthorhombic phases. In solid solutions with $y=0.05$ and $x=0.05$ and 0.20, as well as with $y=0.075$ and 0.10, and $x=0.15$, the formation of a planar interphase boundary being parallel to a zero-net-strain plane occurs at the elastic matching of the single-domain tetragonal and polydomain orthorhombic phases. In contrast to this, at $y=0.05$ and $x=0.25$, 0.30, and 0.35, the complete stress relief is associated with a co-existence of the single-domain orthorhombic and polydomain tetragonal phases, however in some cases, the tetragonal phase aims at a monodomainization.

Yoga is an ancient Indian way of life which includes specific practices, postures, voluntarily regulated breathing, meditation and philosophical principles. In India research on the effects of yoga began in the 1920s and continues today. While studies on the physiological effects of different practices are the most numerous (but have not been described here as they do not have direct applications), there is also research on the applications of yoga. The most common application is as a form of add-on therapy for a wide range of disorders. These studies have attempted to assess whether yoga is useful or not, and in some cases possible mechanisms have also been studied. Other applications (for example in adaptation to unusually stressful environments) and the use of yoga for stress management are also mentioned. This review has attempted to cover a wide range of applications of yoga practice in different parts of the country. Though there is a possibility that some studies may have been omitted the review shows that the applications of yoga in health are many and varied and are being actively explored.