Energy and power characteristics of nanocatalyzed Belousov-Zhabotinsky reactions via bifurcation analyses

Active stimuli-responsive materials, intrinsically powered by chemical reactions, have immense capabilities that can be harnessed for designing synthetic systems for a variety of biomimetic applications. It goes without saying that the key aspect involved in the designing of such systems is to accurately estimate the amount of energy and power available for transduction through various mechanisms. Belousov-Zhabotinsky (BZ) reactions are dynamical systems, which exhibit self-sustained nonlinear chemical oscillations, as their catalyst undergoes periodic redox cycles in the presence of reagents. The unique feature of BZ reaction based active systems is that they can continuously perform mechanical work by transducing energy from sustained chemical oscillations. The objective of our work is to use bifurcation analyses to identify oscillatory regimes and quantify energy-power characteristics of the BZ reaction based on nanocatalyst activity and BZ reaction formulations. Our approach involves not only the computation of higher order Lyapunov and frequency coefficients but also Hamiltonian functions, through normal form reduction of the kinetic model of the BZ reaction. Ultimately, using these calculations, we determine amplitude, frequency, and energy-power densities, as a function of the nanocatalysts' activity and BZ formulations. As normal form representations are applicable to any dynamical system, we believe that our framework can be extended to other self-sustained active systems, including systems based on stimuli-responsive materials.

Dynamical attributes of nanocatalyzed self-oscillating reactions via bifurcation analyses

Self-oscillating chemical reactions that undergo reaction-diffusion (RD) phenomena have shown great potential for designing stimuli-responsive materials. Belousov-Zhabotinsky (BZ) reactions are one such class of reactions that exhibit nonlinear chemical oscillations due to redox cycles of the metal-ion catalyst by virtue of Hopf bifurcation. Using bifurcation analyses, here we investigate the BZ reactions, catalyzed by 0D-2D catalytic nanomats and bare nanosheets, which are known to exhibit enhanced dynamic response due to catalysts' heterogeneity. Specifically, we incorporate the nanocatalysts' activity in the kinetic model of the BZ reactions and, subsequently, use catalysts' activity as the bifurcation parameter for analyses. By computing higher-order Lyapunov and frequency coefficients, we have revealed new oscillatory regimes in the bifurcation diagram, including re-entrant regions where sustained oscillations are unexpectedly suppressed, even with high catalytic activity. In addition, we also calculate the amplitude and frequency of BZ oscillations in each of these regions as a function of nanocatalysts' activity. We believe that our current findings can be used to harness the nonlinearity of RD-based dynamical systems to provide unique functionalities to active stimuli-response systems.

<b>New distribution records of Elegant Water Shrew <I>Nectogale elegans</I> Milne-Edwards, 1870 (Mammalia: Eulipotyphla: Soricidae) from the western Himalaya, Uttarakhand, India</b>

Of the 13 known species of water shrews in the world, two water shrews are known from India, the Elegant Water Shrew Nectogale elegans and Himalayan Water Shrew Chimmarogale himalayica.  Of these, the Elegant Water Shrew was earlier reported only from streams of north Sikkim, and Arunachal Pradesh, India.  During the period 2014–2016, the Elegant Water Shrews were sighted at three different locations in Uttarakhand State in the western Himalayan region.  The present records are evidence for the broader range of distribution of Nectogale elegans in India indicating that the species is more widely distributed than previously thought.  We present the details of sightings, habitats and behavior of shrews that were recorded during our study on impact of climate change on the aquatic ecosystem of the Himalaya.

Chronic insomnia: a practical review

Insomnia has numerous, often concurrent etiologies, including medical conditions, medications, psychiatric disorders and poor sleep hygiene. In the elderly, insomnia is complex and often difficult to relieve because the physiologic parameters of sleep normally change with age. In most cases, however, a practical management approach is to first consider depression, medications, or both, as potential causes. Sleep apnea also should be considered in the differential assessment. Regardless of the cause of insomnia, most patients benefit from behavioral approaches that focus on good sleep habits. Exposure to bright light at appropriate times can help realign the circadian rhythm in patients whose sleep-wake cycle has shifted to undesirable times. Periodic limb movements during sleep are very common in the elderly and may merit treatment if the movements cause frequent arousals from sleep. When medication is deemed necessary for relief of insomnia, a low-dose sedating antidepressant or a nonbenzodiazepine anxiolytic may offer advantages over traditional sedative-hypnotics. Longterm use of long-acting benzodiazepines should, in particular, be avoided. Melatonin may be helpful when insomnia is related to shift work and jet lag; however, its use remains controversial.

Adult onset familial hemiplegic migraine

Familial hemiplegic migraine and its associated signs and symptoms have previously been well described. The condition demonstrates autosomal dominant inheritance and has been recently assigned to a locus on chromosome 19. Previous reports of familial hemiplegic migraine have indicated that expression always occurs early in life. We describe a patient who presented with multiple episodes of reversible hemiplegia followed by headache at the age of 75. Seven other family members were found to have been affected in a similar manner. We believe this case represents a unique description of familial hemiplegic migraine presenting in later life.