Electrical discharges in long air gaps, referred to as 'leader discharges', usually propagate with transient thermal plasma channels. The gas temperature evolution of the channels plays a key role in the inception and development of leader discharges. This paper is aimed at investigating the use of quantitative Schlieren techniques in temperature measurement of the leader discharge channels. To do this, a calibrated Toepler's lens-type Schlieren system was set up to measure the radial temperature profile of leader discharge channels. The measurements were compared with the simulation results from a detailed numerical model which describes the thermalhydrodynamic properties of the channel. The comparison shows that although a good agreement is obtained when the leader is propagating in a stable manner, the measurements of the temperature evolution at the axis of leader channel deviate significantly from the numerical simulation during the leader initiation stage. Apart from the limited spatial and temporal resolution of the Schlieren system, the deviation is also caused by the non-isobaric gas heating during leader inception. Based on the theoretical analysis and numerical simulation, we proposed several suggestions to the application of quantitative Schlieren techniques to measure the temperature of leader channels.

Abstract. Lasers have shown great advantages in enhancing transdermal drug delivery. However, the physical or physiological mechanisms are not clear, which limits the application in clinical medicine. Here, 1064 nm-Nd:YAG lasers with long-pulsed (LP, 15 J∕cm 2 ) and Q-switched (QS, 0.5 J∕cm 2 ) output modes inducing short-and long-term effects on the stratum corneum (SC) of skin are investigated. Infrared thermography is applied to monitor the dynamical temperature distribution of the skin surface, while histopathological analysis and two-photon fluorescence microscopy are employed to examine changes in the microstructure of skin and molecular constitution of SC, respectively. Results have shown that the LP laser irradiation increases skin temperature evidently and loosens keratin, making corneocytes fragile or exfoliative, whereas the QS laser irradiation disrupts the keratin or corneocytes completely, perforating some micropores on the SC. It can be concluded that the mechanisms of enhancing transdermal delivery caused by lasers depends on the output modes. The LP laser irradiation produces thermal effects on skin, which loosens the SC, while the QS laser induces mechanical effects on skin, which punches micropores on the SC. Moreover, the laser-induced enhancing effects on transdermal glycerol delivery can last for one week to wait for the recovery of SC. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Shortcomings in the dynamic range and the frequency bandwidth of current diagnostic methods mean that measurement of the time-resolved discharge current in a long air gap discharge is still a serious problem. This work presents data from a novel discharge current sensor that takes the parameters required to determine the accuracy of the current measurement into account. The design of a coaxial current sensor with ±0.7% accuracy and a bandwidth of 75 MHz is presented. A digital optical fiber transmission system with a bandwidth that exceeds 100 MHz is used to transmit the signal. To demonstrate the efficiency of the whole system, experiments using a rod-plane discharge geometry with 2 m and 4 m air gap lengths are performed to analyze the measured current data in comparison with that taken from synchronized high-speed photographs. The results demonstrate that the investigated experimental set-up improves substantially the understanding of the fundamental mechanisms of long air gap discharges.

Lightweight and head-mountable scanning nonlinear fiberscope technologies offer an exciting opportunity for enabling mechanistic exploration of ensemble neural activities with subcellular resolution on freely behaving rodents. The tether of the fiberscope, consisting of an optical fiber and scanner drive wires, however, restricts the mouse’s movement and consequently precludes free rotation and limits the freedom of walking. Here we present the first twist-free two-photon fiberscope technology for enabling neuroimaging on freely rotating/walking mice. The technology equips a scanning fiberscope with active rotational tracking and compensation capabilities through an optoelectrical commutator (OEC) to allow the animal to rotate and walk in arbitrary patterns during two-photon fluorescence (TPF) imaging of neural activities. The OEC provides excellent optical coupling stability ( <2016