Chemical Laser Research Articles

Laser-joined aluminium–polypropylene sheets: the effect of the surface preparation of aluminium

The aim of this paper is to determine the effect of aluminium surface preparation on the load-bearing capacity of laser-joined aluminium–polypropylene (Al-PP) specimens. The surface of the aluminium is prepared by chemical cleaning and laser engraving. The effect of pulse frequency, engraving speed and repetition number during laser engraving is investigated on the geometric parameters of the structure (straight groove) created on the surface of AA6082 aluminium alloy. Quasi-static shear testing of Al-PP joints is performed to determine how the amount and distance of the grooves affect the load-bearing capacity of the joints. The highest ultimate shear force (1250 ± 35 N) was achieved when many (21) grooves were formed with a laser engraving frequency of 20 kHz, a slow engraving speed (5 mm s−1) and many engraving repetitions (10) in the aluminium specimen. This corresponds to a shear strength of 3.1 MPa, which is 72.5% of the shear strength of the PP material used. Microscopic evaluation of joint cross-sections confirmed that the molten PP completely filled the grooves on the aluminium surface.Graphical abstract

Efficacy of cysteamine and methimazole in treating melasma: A comparative narrative review.

Melasma is a chronic and acquired pigmentary condition that primarily affects women and undermines patient satisfaction and confidence. Melasma mostly affects females, accounting for 90% of all cases. It affects people of all races, particularly those with skin types IV and V who live in areas with lots of UV radiation. According to the studies, Melasma lesions are seen throughout the face in centrofacial, malar, and mandibular patterns. Melasma lesions on the forehead, cheeks, nose, upper lip, and/or chin are the most prevalent centrofacial pattern. Melasma lesions can also be detected along the periorbital area, especially in Asian people. Melasma is notably resistant to treatment, with many patients experiencing only temporary relief and relapses. Combining therapies that target numerous pathologic components, including photodamage, inflammation, aberrant vascularity, and abnormal pigmentation, generally results in the most dramatic therapeutic improvements. Treatments for dark circles include topical depigmenting medicines like hydroquinone, kojic acid, azelaic acid, and topical retinoic acid, and physical treatments such as chemical peels, surgical adjustments, and laser therapy. The objective of therapy should be to figure out what is causing the hyperpigmentation and what is contributing to it. This article provides an overview of melasma therapies and the efficacy of methimazole and cysteamine for melasma therapy.

Contemporary review on carbon nanotube (CNT) composites and their impact on multifarious applications

Abstract Since their discovery in 1991, carbon nanotubes (CNTs) have found widespread use in various industries, from aerospace to energy, due to their excellent mechanical, thermal, electrical, and tribological properties. Their lightweight nature, small size, incredible tensile strength, and conductivity have made them very popular as reinforcements in metals, polymers, and even finding employment in additive manufacturing. In this review, we provide a rundown of these structures and discuss in detail the numerous methods used to process CNT-reinforced materials, such as chemical vapor deposition (CVD), ball milling, hot pressing, and selective laser melting. The limitations of manufacturing and processing these composites are also discussed, strengthened by the support of different published works. To understand the changes in the properties of these composites in terms of varying parameters such as temperature, CNT length, diameter, etc., an extensive summary is provided, describing several techniques to perform experimental analysis and giving plausible reasons for attributing these changes. Consequently, we explore the specific areas of applications for these CNT-reinforced composites in fields such as aerospace, energy, biomedical, and automobile, and how they can be further processed and changed to allow for more affordable and efficient solutions in the future.

Dermatology: how to manage facial hyperpigmentation in skin of colour.

Hyperpigmentation disorders, such as post-inflammatory hyperpigmentation and melasma, are common conditions affecting all skin types. These conditions are largely benign and are influenced by numerous endogenous and exogenous factors impacting melanocyte activity and melanin production. Current treatment modalities for these conditions fall into broad categories, including photoprotection, topical and systemic therapies, chemical peels, and laser or light-based therapies. Biological differences in skin of colour require additional consideration when deciding on treatment and management. This narrative review provides an inclusive summary of these conditions and compares the current treatment options with a specific focus on skin of colour. Photoprotection and sunscreens protective against both UV and visible light are recommended for all individuals. Topical therapy is the recommended first-line treatment, with the gold standard being hydroquinone, which can be used alone or in combination with other agents. Chemical peels and laser or light-based therapies are also effective adjunctive methods of treatment; however, caution should be taken when used in patients with richly pigmented skin due to the increased risk of post-inflammatory hyperpigmentation.

Excited Electronic State Cross Sections for Group 3 Halide and Oxide Production: Evaluating Relative Excited-State Quantum Yields

The cross sections for excited-state formation from the reactions of the group 3 metals, Sc, Y, and La, with F2 and NO2, are evaluated from experimental data. Detailed calibrations indicate that the cross sections for MF formation greatly exceed those for MO formation. The experimentally determined cross sections are compared to upper bounds for total reactive cross sections. Based on this comparison, the ratios of excited state to ground state product formation (quantum yield) are evaluated. The reactions of Sc and Y with F2, which produce excited states selectively, may represent candidates to create a population inversion for use in a chemical laser.

Xeroderma pigmentosum: an updated review.

BackgroundEarly recognition of xeroderma pigmentosum is important to minimize the complications arising from the harmful effects of exposure to ultraviolet radiation. This narrative review aims to familiarize physicians with the clinical features, diagnosis and management of xeroderma pigmentosum.MethodsA search was conducted in December 2021 in PubMed Clinical Queries using the key term “xeroderma pigmentosum”. The search strategy included all clinical trials, observational studies and reviews published within the past 10 years. The information retrieved from the search was used in the compilation of this article.ResultsXeroderma pigmentosum is a condition of abnormal DNA repair of ultraviolet radiation-induced and oxidative DNA damage, which leads to increased skin cancer susceptibility. Approximately 50% of patients with xeroderma pigmentosum have increased photosensitivity and certain types of xeroderma pigmentosum are more prone to ocular disease and progressive neurodegeneration depending on the causative mutation. The diagnosis should be suspected in patients with increased photosensitivity and characteristic cutaneous, ophthalmological and neurological findings. A definite diagnosis can be made by the identification of biallelic mutation in one of the causative genes. Strict and consistent sun avoidance and protection and early detection and treatment of premalignant and malignant skin lesions are the mainstays of management. Treatment options for actinic keratosis include cryotherapy, topical imiquimod, topical 5-fluorouracil, chemical peeling, excision, CO2 laser resurfacing, fractional/pulsed laser therapy, and photodynamic therapy. Cutaneous malignancy can be treated by photodynamic therapy, curettage and electrodesiccation, or surgical excision. Oral isotretinoin, oral niacinamide, topical imiquimod and topical fluorouracil can be used for the prevention of skin malignancy. Treatment options for poikiloderma include chemical peeling, dermabrasion and laser resurfacing. Methylcellulose eyedrops and soft ultraviolet-protective contact lenses may be used to keep the cornea moist and protect against the harmful effects of keratitis sicca. Investigational therapies include the use of T4 endonuclease-V liposome lotion and oral nicotinamide to reduce the rate of actinic keratoses and non-melanoma skin cancers and gene therapy for radical cure of this condition.ConclusionAlthough currently there is no cure for xeroderma pigmentosum, increased awareness and early diagnosis of the condition, followed by rigorous sun avoidance and protection and optimal management, can dramatically improve the quality of life and life expectancy.

Control of the wetting properties of stainless steel by ultrashort laser texturing using multi-parallel beam processing

The laser surface microtexturing is increasingly used for the production of surfaces with desired wetting characteristics (i.e., superhydrophobicity). For this not only precise but also fast laser processing is needed. Microtextures not based entirely on laser induced material self-organization require relatively tight focusing of the laser beam which can not be achieved using fast beam scanning systems. Therefore, in this work, the possibility to use parallel laser processing by multi-beam array for control of the EN 1.4301 (AISI 304) stainless steel surface was investigated. High-energy picosecond laser pulses were used to pattern the polished steel surface using 8 × 8 beam array with two different patterning strategies: mesh and dot. The multi-beam patterning inevitably brings some irregularities due to variation of properties of the beams in the array. However, after the investigation of the influence of laser patterning parameters on the wetting properties of the steel surface, it was determined that multi-beam mesh patterning allows obtaining superhydrophobic surface properties through the right combination of texture depth, surface chemical properties and laser induced surface ripples. The dot patterning was even more promising and was found suitable for obtaining a broad spectrum of wetting states ranging from superhydrophobic to superhydrophilic, when appropriate patterning parameters were used, mostly by controlling self-organized surface structure shape by changing texture period (laser spot overlap).

Experimental study on liquid nitrogen flash evaporation spray on super-hydrophilic microstructured surface

Flash evaporation spray is an efficient heat transfer method. Changes in the microstructure and wettability of the cooling surface have important effects on its heat transfer. In this paper, four kinds of cooling surfaces, including a smooth copper surface, a square-column microstructured surface, a superhydrophilic smooth surface, and a superhydrophilic square-column surface, were prepared by chemical corrosion and laser etching. Using liquid nitrogen as the cooling medium, we conducted transient flash evaporation spray experiments on these four types of cooling surfaces. The experimental results show that surface superhydrophilic treatment can substantially enhance the flash evaporation spray of liquid nitrogen. It can more than double the cooling rate for both smooth copper surfaces and square-column microstructured surfaces. In addition, the combination of a microcolumn structure and superhydrophilicity on the cooling surface can provide double reinforcement for the liquid nitrogen flash evaporation spray. Its average cooling rate can reach 131,046 °C/min, and the maximum heat flux is 173 W/cm2. This study sheds some lights on heat transfer mechanism of superhydrophilic microstructure on the flash evaporation spray and contributes to the development of a new method for cell vitrification.

Thermal and Electron Plasma Effects on Phase Separation Dynamics Induced by Ultrashort Laser Pulses

During ultrafast laser-induced crystallization from glass with a non-congruent composition, a phase separation occurs. The morphology of the crystallized area, inside the heat-affected zone (HAZ), is spectacular showing a bouquet-like structure, under some specific conditions related to glass chemical composition and laser parameters. In this work, we investigate this HAZ along a written line through a set of high-resolution electron microscopy techniques to probe both the morphology and the chemical distribution at the nanoscale. Based on these findings, we demonstrate that the bouquet-like structure arises from poorly textured nanocrystals between two regions that have probably accumulated elastic strain. From that analysis, we also provide insights into the chemical separation process during this complex light-matter transformation in which the induced plasma structure guides the spatial distribution of SiO2 and LiNbO3. We suggest a model based on an electric field modulation produced by the inhomogeneous plasma electron trapping, that modifies the electrochemical potentials of the constituents.

The Influence of Surface Iron Contamination on the Localized Corrosion Resistance of Austenitic and Duplex Stainless Steel, Studied with a Novel Rust Deposition Method

The influence of iron contamination on a stainless steel surface was evaluated based on a novel rust deposition procedure. The main variables that control the corrosion process and the influence of iron contamination on localized corrosion resistance of austenitic and super duplex stainless steel were investigated. Cyclic potentiodynamic polarization tests and environmental exposure with different rust surface contamination degrees were performed. Potentiodynamic polarization curves showed that iron contamination deteriorated the local corrosion resistance of both stainless steels. Environmental salt-spray exposure results indicated that the alloy resistance to rust contamination increased with the materials’ pitting resistance equivalent. Likewise, the extent of localized corrosion decreased with the rust contamination degree. These findings suggested that preferential corrosion from rust contamination was associated with the occluded solution chemistry. Environmentally friendly cleaning methods, including chemical treatments and laser cleaning, were evaluated as alternatives to hazardous pickling based on hydrofluoric-nitric acid. Last, practical recommendations for rust contamination of stainless steel are addressed.

Management of post-inflammatory hyperpigmentation in skin of color: A short review.

Post-inflammatory hyperpigmentation (PIH) is a common cosmetic complaint affecting patient quality of life. PIH has been proven to disproportionately affect skin of color. While several treatment options exist, special consideration must be given when managing PIH in patients of color, as topical treatments and aesthetic procedures, such as chemical peels and lasers, may either exacerbate or prove ineffective against PIH.

Frontispiece: Fluorescence Colour Control in Perylene‐Labeled Polymer Chains Trapped by Nanotextured Silicon

Laser Chemistry In their Research Article (e202117227), Yasuyuki Tsuboi et al. report an optical tweezer technique using nanotextured Si that can efficiently trap polymer chains. The fluorescence color of the perylene-labeled polymer chains can be controlled by changing the laser intensity.

P-Type carrier concentration enhancement analysis of 4H–SiC by wet chemical laser doping

Al was laser doped in semi-insulating 4H–SiC showing highly enhanced impurity diffusion via 660 μm AlCl3 aqueous layer by optimization of maximum power delivered by KrF-Excimer Laser at substrate. Due to optimized laser fluence, modifications in surface stoichiometry and residual bands formation were expected to occur. Irradiation induces p-type carrier concentration up to 1015 cm-2 having low surface loss with no damage to substrate. Analysis shows c-Si out diffusion at surface and some residual a-Si without any carbonization accompanying variety of complexes formation followed via irradiation thermal environment. Processing did not show any negative impact on the substrate quality and defect formation altering carrier concentration at a large scale. Minor change in Raman mode has been observed due to increasing Al doping concentration and irradiation.

Giant Congenital Melanocytic Nevi of the Head and Neck: Clinical Update and Advances in Treatment

Introduction: Giant congenital melanocytic nevi are rare lesions of various size, shape, color, and location with potential complications including malignant and neurocutaneous melanoma. Here we discuss the etiology and epidemiology of giant congenital melanocytic nevi, the indications and options for treatment, and current data regarding outcomes, as well as our preferred approach to patient management. Methods: Full text case reports, retrospective studies, prospective studies, clinical trials, and review articles regarding giant congenital melanocytic nevi in English were included in this analysis utilizing PubMed, MEDLINE, EMBASE, and Google scholar databases. Results: Giant congenital melanocytic nevi pose a difficult diagnostic and reconstructive challenge for the plastic surgeon. Indications for treatment depend on the size of the nevus, pigmentation, established melanoma, persistent symptoms, maintenance of function, and psychological burden. A multidisciplinary approach should be applied to establish an individualized treatment plan for patients with giant congenital melanocytic nevi. Numerous surgical and nonexcisional options have been illustrated for the management of these lesions. Chemical peels and laser ablation are among the most common non-surgical approaches. When considering surgical treatment for lesions with malignant potential, a multimodal approach is generally employed, including serial excision, excision with skin grafting and/or skin substitutes, and tissue expansion. Conclusion: A proper understanding of the disease’s histology, natural history, complications, and treatment options are essential in the management of these complex lesions.

Piezoelectric benders with strain sensing electrodes: Sensor design for position control and force estimation

Piezoelectric benders are widely used in industrial applications due to their low-cost and compact size. However, due to the large relative size and cost of displacement sensors, bender actuators are often operated in open-loop or with feed-forward control, which can limit positioning accuracy to 20% of full-scale. To improve the positioning accuracy of piezoelectric benders, this article proposes integrating resistive strain gauges into the electrode surface by chemical etching or laser ablation. These strain sensors are then used to measure and control the tip displacement. The proposed sensors are shown to suffer from significant cross-coupling between the actuator voltage and measured signal; however, this can be mitigated by judicious choice of the sensor location and actuator driving scheme. In addition to position sensing, a method is also presented for simultaneous estimation of the contact force between the actuator tip and load. The proposed methods are validated experimentally by controlling the tip position of a piezoelectric bender while simultaneously estimating the force applied to a reference load cell.

Real Time Flow Control System for Precise Gas Feed in COIL

This paper reports development of a real time flow control system for precise, controlled and uniform gas feed to a flowing medium Chemical Oxygen Iodine Laser (COIL). The optimal operation of this prominent laser depends upon the desired supply of gas constituents such as nitrogen (N2), chlorine (Cl2) and iodine (I2) to achieve adequately mixed laser gas. The laser also demands real time variation of flow rates during gas constituent transitions in order to maintain stabilized pressures in critical subsystems. Diluent nitrogen utilized for singlet oxygen transport is termed as primary buffer gas and that for iodine transport is termed as secondary buffer gas (with main and bypass components). Also, nitrogen in precise flows is used for mirror blowing, nozzle curtain, cavity bleed and diffuser startup. A compact hybrid data acquisition system (Hybrid DAS) for precise flow control using LabVIEW 2014 platform has been developed. The supported flow ranges may vary from few mmole.s-1 to few hundred mmole.s-1. The estimated relative uncertainty in the largest gas component i.e. primary buffer gas feed is nearly 0.7%. The implementation of in-operation variation using flow ramp enables swift stabilization of singlet oxygen generator pressures critical for successful COIL operation. The performance of Hybrid DAS is at par with fully wired DAS providing the crucial benefit of remote field operation at distances of nearly 80m in line of sight and 35m with obstacles

Evaluation of Electrosurgery and Diode Laser in Gingival Depigmentation.

Introduction:Gingival depigmentation is a surgical procedure done to eliminate or reduce gingival hyperpigmentation. Various techniques are employed such as scalpel de-epithelization, gingivectomy, electrosurgery, use of chemical agents, cryosurgery, and lasers. The present study was conducted to assess the efficacy of laser and electrosurgical procedure in reducing gingival pigmentation in terms of pain, wound healing, and recurrence of melanin pigmentation.Methodology:A prospective study was conducted on 40 subjects affected by melanin pigmentation. Group I patients were treated with electrosurgery and Group II patients with diode laser procedure. Evaluation for pain was done intraoperatively, 24 hours and 7 days using VAS. Wound healing and recurrence of pigmentation was assessed at one month and three months.Results:No significant difference was noted between the two groups for pain assessment at 7 days with P > 0.001. Both electrosurgery and laser group showed significant differences between intraoperative time period to 24 hours and 24 hours to 7 days at P < 0.001 for pain.Conclusion:Esthetic demands necessitate cosmetic gingival depigmentation procedure. Laser diode photoablation proves to be an effective and reliable technique in achieving the same.

STATE OF THE ART OF SURFACE TEXTURING FOR BIOTRIBOLOGY APPLICATIONS

Surface texturing can be defined as a technique that consists of creating micro cavities in the surface of a material. There are different texturing techniques such as chemical etching, electromechanical micromachining, diamond embossing, electric discharge, pellet-pressing and laser surface, the last being the most common. For years, these surface texturing techniques have been used in tribological applications because microcavities can store oils or fluids and constantly lubricate the surfaces that are subjected to wear; they can also be used to trap wear particles (debris) that would otherwise act as abrasive particles (three body abrasive wear). This literature review seeks to analyse and compare the advantages that the use of surface texturing techniques can offer in reducing the wear of prosthetic components and therefore lengthening their useful life, to provide a better quality of life to patients. The results of this review showed a growing interest in the scientific community in the use of surface texturing for biotribogical applications, using to a greater extent the Laser Surface Texturing (LST) technique and the surface pattern composed by dimples.

Impacts of oxygen source on band alignment of ALD Al2O3/(α-, ε-)Ga2O3 interface

Al2O3 films were deposited on α- and ε-Ga2O3 films by atomic layer deposition (ALD) in different plasma oxygen source (H2O, O3, O2 plasma). The α- and ε-Ga2O3 films were epitaxially grown on sapphire substrates by mist chemical vapor deposition (Mist-CVD) and pulsed laser deposition (PLD), respectively. The epilayer characteristics were investigated by high resolution X-ray diffraction (HRXRD), atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM). Furthermore, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 were investigated by X-ray photoelectron spectroscopy (XPS). On the basis of Ga 3d and Al 2p core-level spectra as well as α- and ε-Ga2O3 valence band spectra, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 interface were determined. And the conduction band offset of Al2O3/α-Ga2O3 interfaces were estimated to be 1.21/1.31/1.27 eV for oxidant of H2O, O3 and O2 plasma, respectively, while that of Al2O3/ε-Ga2O3 were 1.61/1.72/1.7 eV, the conduction band offsets of Al2O3 grown by O3 and O2 plasma were higher than those grown by H2O. And, the conduction band offsets of all samples were greater than 1 eV, indicating that Al2O3 grown by ALD can be used as gate dielectric in (α-, ε-) Ga2O3 power device.

Vibrational and Rotational Gaussian Binning selections on QCT calculations for the OH + D2 → HOD((vHO’, vHOD’, vOD’), J’) + D reaction

Abstract A large sample has been employed to obtain total reaction cross sections and product state distributions (translational, vibrational and rotational) for the title reaction. Quasi-Classical Trajectory (QCT) calculations and the Gaussian Binning (GB) methodology have been used on Wu-Schatz-Lendvay-Fang-Harding (WSLFH) and Neural Networks (NN) potential energy surfaces. After a first selection, Vibrational-Gaussian Binning (V-GB), (vHO’, vHOD’, vOD’), and a second selection, Rotational-Gaussian Binning (R-GB), although the preference observed (odd or even J') is not exactly followed by each vibrational excitation of HOD, there is a similar behavior to the physical laser phenomenon observed in another triatomic molecule utilized in the gas laser of CO2. The dynamics of polyatomic chemical reactions (e.g., OH + D2 → HOD* + D and its isotopic variants), of relevance in the excitation/emission processes of current and future chemical lasers, could be studied theoretically from the results obtained in this article.