Numerical Analysis of Cold Injury of Skin in Cryogen Spray Cooling for Laser Dermatologic Surgery

In laser dermatologic surgery, cryogen spray cooling (CSC) is used to avoid unwanted thermal damage such as scars from skin burning due to the melanin absorption of the laser beam. As the cryogen is fully atomized from the nozzle, temperature of the droplets can quickly drop below -60 oC because of evaporation. Such low temperature may lead to cold injury of skin. Therefore, spray cooling process should be accurately controlled during clinical practice to achieve sufficient protection and avoid cold injury. This study presents a numerical analysis for cold injury of skin in cryogen spray cooling for dermatologic laser surgery by a newly developed hest transfer model. For the freezing of skin cells, heat conduction equation was used to describe frozen and unfrozen zones, and heat capacity method was utilized for mushy zone to consider the phase change of tissue. A realistic boundary condition was implemented to simulate the cooling effect during cryogen spray cooling by a generalized correlation for the dynamic heat transfer coefficient. By tracking the front of the tissue phase change, the model can be used to predict the movement of the harmful isothermals. With this model, the severity of cold injury is quantified under various clinical conditions and the effects of initial temperature as well as the spurt duration on possible cold injury of skin are investigated. The results show that 100~150ms spray cooling duration is appropriate to avoid non-uniform cooling along the radial direction and also prevent potential cold injury. Lower room temperature (10~20oC) is recommended to achieve a deep penetration protection. Further development of new candidate cryogens with lower boiling point (e.g. R407C or R404a) are highly recommended to achieved a better cooling effect

An Overview of Three Promising Mechanical, Optical, and Biochemical Engineering Approaches to Improve Selective Photothermolysis of Refractory Port Wine Stains

During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion)

ESARDA 39th Annual Meeting: 2017 Symposium

The 39th ESARDA symposium on Safeguards and Nuclear Non-Proliferation was held in Düsseldorf, Germany from 16-18 May, 2017. The Symposium has been preceded by meetings of the ESARDA Working Groups on 15 May 2017. The event has once again been an opportunity for research organisations, safeguards authorities and nuclear plant operators to exchange information on new aspects of international safeguards and non-proliferation, as well as recent developments in nuclear safeguards and non-proliferation related research activities and their implications for the safeguards community.JRC.G.II.7-Nuclear securit

Large space structures and systems in the space station era: A bibliography with indexes

Bibliographies and abstracts are listed for 1219 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1990 and December 31, 1990. The purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

Synthesis of new pyrazolium based tunable aryl alkyl ionic liquids and their use in removal of methylene blue from aqueous solution

In this study, two new pyrazolium based tunable aryl alkyl ionic liquids, 2-ethyl-1-(4-methylphenyl)-3,5- dimethylpyrazolium tetrafluoroborate (3a) and 1-(4-methylphenyl)-2-pentyl-3,5-dimethylpyrazolium tetrafluoroborate (3b), were synthesized via three-step reaction and characterized. The removal of methylene blue (MB) from aqueous solution has been investigated using the synthesized salts as an extractant and methylene chloride as a solvent. The obtained results show that MB was extracted from aqueous solution with high extraction efficiency up to 87 % at room temperature at the natural pH of MB solution. The influence of the alkyl chain length on the properties of the salts and their extraction efficiency of MB was investigated