Cold electron Josephson transistor

A superconductor-normal metal-superconductor mesoscopic Josephson junction has been realized in which the critical current is tuned through normal current injection using a symmetric electron cooler directly connected to the weak link. Both enhancement of the critical current by more than a factor of two, and supercurrent suppression have been achieved by varying the cooler bias. Furthermore, this transistor-like device demonstrates large current gain $\sim$20) and low power dissipation

Limitations in cooling electrons by normal metal - superconductor tunnel junctions

We demonstrate both theoretically and experimentally two limiting factors in cooling electrons using biased tunnel junctions to extract heat from a normal metal into a superconductor. Firstly, when the injection rate of electrons exceeds the internal relaxation rate in the metal to be cooled, the electrons do no more obey the Fermi-Dirac distribution, and the concept of temperature cannot be applied as such. Secondly, at low bath temperatures, states within the gap induce anomalous heating and yield a theoretical limit of the achievable minimum temperature.Comment: 4 pages, 4 figures, added Ref. [6] + minor correction

Transcranial light alters melanopsin and monoamine production in mouse (Mus musculus) brain

Abstract Background: The mammalian circadian system sets a rhythm for the appropriate occurrence of physiological and behavioral phenomena during a 24-h period. Since the duration of the circadian system is usually less or more than 24 h, it must be entrained regularly and light is the governing stimulus of the rhythm. The target for light stimulus is the master circadian clock, which is located in the suprachiasmatic nucleus in the hypothalamus. One of the key molecules transmitting light information and entraining the clock is melanopsin (OPN4), a G protein-coupled molecule that is found most abundantly in the retina and brain. Although light stimulus is usually mediated through the eyes, light has an ability to penetrate the skull. Here, we present the effect of transcranial light illumination on OPN4 and serotonin expression in the mouse brain. Methods: Male mice were randomly assigned to a control group, morning-light group and evening-light group, and animals were illuminated transcranially five times a week for 8 min for a total of 4 weeks. The concentrations of OPN4 and monoamines were analyzed with Western blot and high-performance liquid chromatography (HPLC) techniques, respectively. Results: Our results show that transcranial light illumination increases the amount of OPN4 in the hypothalamus and cerebellum. Additionally, the production of serotonin in the cortex was shown to decrease in the morning-light group. Conclusions: With this study, we provide novel information on the effects of light administration through the skull on transmitters regulating circadian rhythmicity by showing that transcranial light affects molecules involved in circadian rhythmicity

Architectural modifications for flexible supercapacitor performance optimization

We have developed material and architectural alternatives for flexible supercapacitors and investigated their effect on practical performance. The substrate alternatives include paperboard as well as various polyethylene terephthalate (PET) films and laminates, with aqueous NaCl electrolyte used in all devices. In all the supercapacitors, activated carbon is used as the active layer and graphite ink as the current collector, with various aluminium or copper structures applied to enhance the current collectors’ conductivity. The capacitance of the supercapacitors was between 0.05 F and 0.58 F and their equivalent series resistance (ESR) was from <1 Ω to 14 Ω, depending mainly on the current collector structure. Furthermore, leakage current and self- discharge rates were defined and compared for the various architectures. The barrier properties of the supercapacitor encapsulation have a clear correlation with leakage current, as was clearly shown by the lower leakage in devices with an aluminium barrier layer. A cycle life test showed that after 40000 charge-discharge cycles the capacitance decreases by less than 10%