Effect of Corrosion and Wall Textures on Wettability and Heat Flux at Non-Isothermal Conditions

The corrosion behavior, evaporation and heat transfer of aluminum alloy during droplet evaporation of an aggressive solution of NaCl and hydrogen peroxide in water have been studied experimentally. To date, the effect of corrosion on the evaporation and heat transfer of droplet salt solutions on textured surfaces remains insufficiently explored. The corrosion resistance of the material and the contact angle increase with an increase in the number of laser penetrations after laser texturing. Studies conducted using an electron microscope and Energy-Dispersive X-ray Spectroscopy (EDS) mapping show that the maximum amount of adsorbed hydrocarbon impurities falls on areas with a large number of pits. In the process of metal corrosion, wettability and heat transfer change. In spite of the fact that laser exposure significantly increases the corrosion resistance, the wettability of the wall changes significantly due to corrosion. The wetted diameter of a droplet changes over time, which leads to an increase in the evaporation rate and heat flux. The heat flux during evaporation of a droplet on a heated wall depends on the water droplet diameter, the texture of the wall and the corrosion resistance.

Self-assembled tocopherol-albumin nanoparticles with full biocompatibility for chemo-photothermal therapy against breast cancer

Background:: The combination of photothermal therapy (PTT) and chemotherapy has proven to be a promising strategy for cancer treatment. Various nanomaterials have shown great potential in combination therapy, including gold, graphene oxide, iron oxide, and other nanoparticles. However, their undefinable toxicity in vivo greatly slowed down their development for clinical applications. Objective: The present work aimed to develop a multifunctional nanoparticle for chemo-photothermal therapy composed of acknowledged biocompatible materials. Methods: A novel biocompatible nanoparticle (HIT-NPs) was self-assembled through the intrinsic interaction between D-α-tocopherol Succinate (TOS), human serum albumin (HSA) and indocyanine green (ICG). Doxorubicin (DOX) was then loaded due to the ion pairing between DOX and TOS. The feasibility of combined chemo-photothermal therapy induced by DOX-loaded HIT-NPs was carefully evaluated. Results: In vitro, HIT-NPs showed no cytotoxicity on human normal liver cells (HL-7702 cells) but obvious killing effects murine breast cancer cells (4T1 cells). The combined chemo-photothermal therapeutic effect on 4T1 cells was successfully obtained. DOX-loaded HIT-NPs could effectively accumulate in 4T1 subcutaneous tumors after intravenous injection, and the tumor temperature rapidly increased under laser exposure, indicating the feasibility of PTT in vivo. Conclusion: The self-assembled HIT-NPs could provide a promising platform for combined chemo-photothermal cancer therapy with full biocompatibility.

Multi-Scale Modeling of Residual Stresses Evolution in Laser Powder Bed Fusion of Inconel 625

Laser powder bed fusion exhibits many advantages for manufacturing complex geometries from hard to machine alloys such as IN625. However, a major drawback is the formation of high tensile residual stresses, and the complex relationship between the process parameters and the residual stresses has not been fully investigated. The current study presents multi-scale models to examine the variation of process parameters on melt pool dimensions, cyclic temperature evolutions, cooling rate, and cyclic stress generation and how they affect the stress end state. In addition, the effect of the same energy density, which is often overlooked, on the generated residual stresses is investigated. Multi-level validation is performed based on melt pool dimensions, temperature measurements with a two-color pyrometer, and finally, in-depth residual stress measurement. The results show that scan speed has the strongest effect on residual stresses, followed by laser power and hatch spacing. The results are explained in light of the non-linear temperature evolution, temperature gradient, and cooling rate during laser exposure, cooling time, and the rate during recoating time.

Raman analysis of the crystallinity degree for the local regions in Ge2Sb2Te5 films after laser exposure at different parameters

The evaluation of the crystallinity degree for the local regions in Ge2Sb2Te5 (GST) thin films after phase state transformation by laser pulses at 405 nm wavelength was analyzed using the Raman spectroscopy. The modes of laser radiation for controlling the reflectivity and transmissivity at 1550 nm telecommunication wavelength of the local regions in the GST film were established. The results obtained make it possible to implement the method of the completely optical control of the multilevel modulation of the optical signals for the integrated optics devices.

Analysis of occupational risk factors causing diseases of the circulatory system in medical workers: Literature review

The review focuses on analysis of domestic and foreign literature sources concentrating on influence exerted by occupa-tional factors and factors related to labor process on prevalence of diseases of the circulatory system (CSD) among medical workers. At present, specific features typical for occupational activities performed by medical workers are proven to be among major causes of high CSD prevalence among them. Experts have established most common occupational factors and labor-related factors that are able to induce and stimulate development of cardiovascular pathology. Labor intensity associated with neuro-emotional loads, high responsibility, round-the-clock working regime and night shifts (hazard category 3.2–3.3) is estab-lished to have a leading role among adverse labor-related factors for medical workers. Other significant contributions are made by adverse chemicals and biological agents, noise and ultrasound, laser exposure and ionizing radiation. Some authors showed that CSD prevalence was considerably higher among medical workers than among people employed in other industries. The highest CSD prevalence was detected among medical workers with the most adverse working conditions (hazard category 3.2–3.3). A high degree of occupational conditionality for CSD is typical for surgeons, therapists, and phthisiatricians. Emergency doctors run the highest risk of CSD (RR = 3.1; EF = 67.7 %). Assessment cardiovascular risks according to the SCORE system revealed that approximately 15 % medical workers older than 40 ran moderate cardiovascular risks; medical workers older than 50, high (20.0–22.0 %) or extremely high (10.0–12.5 %) total risks of death due to CSD.

Photodynamic Therapy 405 nm Diode Laser as Antibacterial for Cavity and Root Canal Sterilization

Background: The goals of caries restoration and endodontic treatment are to repair and prevent the infection fromgetting worse and if possible, heal the damaged tissue. To achieve this goal, it is necessary to control the presence ofmicrobes in the cavity or root canals with chemo mechanics prior to filling or obturation of the root canals. Disinfectionmethods using disinfectants with effective bactericidal activity are mostly used at subtoxic levels and at concentrationswhere their toxicity is a significant factor. In addition, the disinfection method is considered unable to achieve thoroughcavity cleaning and causes secondary infection. A new method to provide better disinfection without cytotoxic effectshas recently been discovered using the photodynamic method of 405 nm diode laser therapy. Research continues and isprogressing with the existence of various factors that affect the effectiveness of the 405nm diode laser as an antibacterial.Purpose: To evaluate the results of research on photodynamic diode laser therapy with a wavelength of 405 nm as acombination antibacterial therapy in cavity and root canal sterilization techniques. Review(s): Literature study in the formof narrative review using libraries obtained through the PubMed and Google Scholar databases. The optimal bacterialmortality was influenced by the form factor of the target bacteria, the energy dose and duration of laser exposure, and thetype of photosensitizer used. Conclusion: The use of a 405 nm diode laser with an energy power of 50 mW with a distanceof 20 mm can degrade biofilms Streptococcus mutans up to 100% using erythrosine photosensitizer, for 75 seconds. Andwith the same power and distance, it can degrade the biofilm of bacteria Enterococcus fecalis up to 97.51%, using aphotosensitizer chlorophyll, for 120 seconds.

Development a Method for Estimating a Safe Distance between Coagulates to Automatically Plan Retinal Laser Coagulation in Diabetic Retinopathy Treatment

Introduction. Diabetes mellitus is a common endocrine disease that can lead to retinal vascular damage caused by the spread of macular edema and the development of diabetic retinopathy. Currently, diabetic retinopathy is treated using retinal laser coagulation. However, since even modern systems do not demonstrate sufficient treatment efficacy, methods for providing laser coagulation support on the basis of patient data analysis are required.Aim. This paper aims to develop and study a method for estimating a safe distance between coagulates via the mathematical modeling of coagulation in order to provide laser coagulation support.Materials and methods. The problem of thermal conductivity is numerically modeled for laser action in a multilayer medium.Results. A method for estimating a safe distance between coagulates has been developed via the mathematical modeling of the thermal conductivity problem. An algorithm was established for reconstructing a three-dimensional fundus structure from OCT images. It was demonstrated that the convergence rate of the integro-interpolation method is higher than that of the finite difference method. The study revealed that the retina heats up to 45 ºС due to heat redistribution from the epithelial layer, as well as laser exposure. According to the study results, the developed method yields a safe distance of 180 µm. By increasing the delay between laser pulses by more than 10 ms, this distance can be reduced to 160 μm.Conclusion. The developed method can calculate distance corresponding to that used in medical practice. Besides safe distance, the use of this method will allow other laser coagulation parameters to be determined non-invasively: laser power and pulse duration recommended to achieve a therapeutic effect. These estimates can be used to automatically produce a preliminary laser coagulation plan to support diabetic retinopathy treatment.

Prevention of The Development of Postoperative Complications and Their Treatment in The Surgery of Duedenal Purpose

The authors analyze various degrees of physiological anastomositis in 131 patients, and conclude that for the treatment of late anastomositis after surgical interventions on the stomach and duodenum, it is recommended to include the laser action of the anastomosis zone with two types of low-energy lasers in the complex program. The authors argue that the combined use of low-energy laser exposure through endoscopic and percutaneous irradiation will improve the effectiveness of the treatment of late anastomositis.

Mathematical simulation of the processes of two-beam laser controlled thermal-splitting of quartz glass

The paper presents the results of modeling the processes of controlled thermal cracking of quartz glass under the parallel action of two infrared laser beams of different geometries on the material: with maximum intensity in the center and with zero intensity in the center (annular section). To calculate the temperature distribution in the material, the method of Green's functions was used, which allows us to obtain a well-interpreted solution for almost any type of function of surface heat sources. Further, taking into account the quasi-static approach, using the methods of the classical theory of thermoelasticity, thermoelastic microstresses were calculated, both on the surface and in the depth of the material. It is established that the simultaneous use of these two types of laser exposure makes it possible to control the temperature field more efficiently, and create prerequisites for the most stable formation of a microcrack. The simulation results show that with a bi-beam effect, the micromechanical stresses necessary for the formation of a microcrack are realized in shorter time intervals, both on the surface and in the depth of the material, which allows increasing the processing speed by up to 30 %. Strengthening control over the process of controlled thermal cracking can significantly reduce the percentage of defects and improve the quality of the resulting microeletronics products.

Interferometric imaging of thermal expansion for temperature control in retinal laser therapy

Precise control of the temperature rise is a prerequisite for proper photothermal therapy. In retinal laser therapy, the heat deposition is primarily governed by the melanin concentration, which can significantly vary across the retina and from patient to patient. In this work, we present a method for determining the optical and thermal properties of layered materials, directly applicable to the retina, using low-energy laser heating and phase-resolved optical coherence tomography (pOCT). The method is demonstrated on a polymer-based tissue phantom heated with a laser pulse focused onto an absorbing layer buried below the phantom's surface. Using a line-scan spectral-domain pOCT, optical path length changes induced by the thermal expansion were extracted from sequential B-scans. The material properties were then determined by matching the optical path length changes to a thermo-mechanical model developed for fast computation. This method determined the absorption coefficient with a precision of 2.5% and the temperature rise with a precision of about 0.2°C from a single laser exposure, while the peak did not exceed 8°C during 1 ms pulse, which is well within the tissue safety range and significantly more precise than other methods.