Determining optimal laser-beam cutting equipment investment through a robust optimization modeling approach.

The acquisition of Advanced Manufacturing Technologies (AMT), such as high-power fiber or CO2 laser cutting equipment, generally involves high investment levels. Its payback period is usually more extended, and there is a moderate-to-high risk involved in adopting these technologies. In this work, we present a robust model that optimizes equipment investing decisions, considers the process's technical constraint and finds an optimal production plan based on the available machinery. We propose a linear investment model based on historical demand information and take physical process parameters for a LASER cutting equipment, such as cutting speed and gas consumption. The model is then transformed into a robust optimization model which considers demand uncertainty. Second, we determine the optimal production plan based on the results of the robust optimization model and assuming that demand follows a normal distribution. As a case study, we decided on the investment and productive plan for a company that offers Laser-Beam Cutting (LBC) services. The case study validates the effectiveness of the proposed model and proves the robustness of the solution. For this specific application of the model, results showed that the optimal robust solution could increase the company's expected profits by 6.4%.

Isoflavonoid-Antibiotic Thin Films Fabricated by MAPLE with Improved Resistance to Microbial Colonization.

Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) bacteria represent major infectious threats in the hospital environment due to their wide distribution, opportunistic behavior, and increasing antibiotic resistance. This study reports on the deposition of polyvinylpyrrolidone/antibiotic/isoflavonoid thin films by the matrix-assisted pulsed laser evaporation (MAPLE) method as anti-adhesion barrier coatings, on biomedical surfaces for improved resistance to microbial colonization. The thin films were characterized by Fourier transform infrared spectroscopy, infrared microscopy, and scanning electron microscopy. In vitro biological assay tests were performed to evaluate the influence of the thin films on the development of biofilms formed by Gram-positive and Gram-negative bacterial strains. In vitro biocompatibility tests were assessed on human endothelial cells examined for up to five days of incubation, via qualitative and quantitative methods. The results of this study revealed that the laser-fabricated coatings are biocompatible and resistant to microbial colonization and biofilm formation, making them successful candidates for biomedical devices and contact surfaces that would otherwise be amenable to contact transmission.

Simple way to correct the drift in surface-coupled optical tweezers using the laser reflection pattern.

The surface-coupled optical tweezers are widely used to resolve small units of motion in biology. However, such motions could readily be interfered by the drift between the trap and surface. We present a simple and low-cost method to correct the drift both actively and passively based on video tracking the distance between the laser reflection pattern and the reference bead. As a result, we achieved sub-nanometer resolution and stability for the stuck bead over a broad range of averaging time (0.002-100 s) as demonstrated by the Allan deviation analysis. The sub-nanometer resolution was further manifested with step measurement. Finally, in double-stranded DNA and DNA hairpin stretching experiments, an extension resolution of 1-2 nm with the stability over 120 s has been demonstrated under a constant force. This work thus provides an easy way to bring the benefit of nanometer resolution and long-term stability to the surface-coupled optical tweezers.

Laser spectroscopic technique for direct identification of a single virus I: FASTER CARS.

From the famous 1918 H1N1 influenza to the present COVID-19 pandemic, the need for improved viral detection techniques is all too apparent. The aim of the present paper is to show that identification of individual virus particles in clinical sample materials quickly and reliably is near at hand. First of all, our team has developed techniques for identification of virions based on a modular atomic force microscopy (AFM). Furthermore, femtosecond adaptive spectroscopic techniques with enhanced resolution via coherent anti-Stokes Raman scattering (FASTER CARS) using tip-enhanced techniques markedly improves the sensitivity [M. O. Scully, et al, Proc. Natl. Acad. Sci. U.S.A. 99, 10994-11001 (2002)].

Laser safety: the need for protocols.

Lasers are being used in ever-expanding roles in dermatology. As our understanding of laser energy grew, the need for safety guidelines became apparent. The US Food and Drug Administration (FDA) published the first safety guidelines in 1984, which are updated on a regular basis. However, these are just guidelines, and their implementation is voluntary by the laser practitioner. In this article, we discuss the 4 regulatory entities for laser safety in the United States, laser principles in general, ocular hazards, laser-generated airborne contaminants (LGACs), fires, and unintended laser beam injuries. We also review the use of checklists in reducing adverse outcomes and the need for safety protocols for laser practitioners. We provide a modifiable checklist, which pertains specifically to lasers and can be customized to meet the needs of the individual laser practitioner.

Simple Lithography-Free Single Cell Micropatterning using Laser-Cut Stencils.

Micropatterning techniques have been widely used in cell biology to study effects of controlling cell shape and size on cell fate determination at single cell resolution. Current state-of-the-art single cell micropatterning techniques involve soft lithography and micro-contact printing, which is a powerful technology, but requires trained engineering skills and certain facility support in microfabrication. These limitations require a more accessible technique. Here, we describe a simple alternative lithography-free method: stencil-based single cell patterning. We provide step-by-step procedures including stencil design, polyacrylamide hydrogel fabrication, stencil-based protein incorporation, and cell plating and culture. This simple method can be used to pattern an array of as many as 2,000 cells. We demonstrate the patterning of cardiomyocytes derived from single human induced pluripotent stem cells (hiPSC) with distinct cell shapes, from a 1:1 square to a 7:1 adult cardiomyocyte-like rectangle. This stencil-based single cell patterning is lithography-free, technically robust, convenient, inexpensive, and most importantly accessible to those with a limited bioengineering background.

Real-Time Measurement of the Liquid Amount in Cryo-Electron Microscopy Grids Using Laser Diffraction of Regular 2-D Holes of the Grids.

Cryo-electron microscopy (cryo-EM) is now the first choice to determine the high-resolution structures of huge protein complexes. Grids with two-dimensional arrays of holes covered with a carbon film are typically used in cryo-EM. Although semi-automatic plungers are available, notable trial-and-error is still required to obtain a suitable grid specimen. Herein, we introduce a new method to obtain thin ice specimens using real-time measurement of the liquid amounts in cryo-EM grids. The grids for cryo-EM strongly diffracted laser light, and the diffraction intensity of each spot was measurable in real-time. The measured diffraction patterns represented the states of the liquid in the holes due to the curvature of the liquid around them. Using the diffraction patterns, the optimal time point for freezing the grids for cryo-EM was obtained in real-time. This development will help researchers rapidly determine highresolution protein structures using the limited resource of cryo-EM instrument access.

Standardization of Sandwich-Structured Cu-Glass Substrates Embedded in a Flexible Diode Laser-Plasma Interface for the Detection of Cholesterol.

This study introduced sandwich-structured copper-glass substrates for standardization of laser desorption and plasma ionization. For standardized quantitative analysis, cavities were constructed which allow better reproducibility in droplet deposition and for laser application. Applying the diode laser, molten substrate material is incorporated into the glass, being trapped inside. Therefore, this method can be separated from laser ablation, achieving high ion signals without ablating material from the surface. Flexible microtube plasma (FµTP) was selected as the ionization source, this being the first time that laser desorption and FµTP ionization are coupled. This laser-plasma interface was applied to the detection of cholesterol, which showed a significantly improved limit of detection of 0.46 ng and linear dynamic range of 3 orders of magnitude in positive ion mode compared to other (ambient air mass spectrometry) methods. The main reason was the change of phase on the copper surface. The dehydrated molecule [M-H2O+H]+ was the base peak of the spectrum and no further dissociation or fragmentation was observed. Blood plasma was spiked with cholesterol. In a 1:100 chloroform dilution, the presence of the plasma was neglectable and led to the same detection limits and linear dynamic range as in the cholesterol standard. No sample preparation or internal standards were needed for calibration. The physical effects of the surface modification were investigated, including the calculation of the laser beam waist to simplify the comparison and reproducibility of results.

Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats.

Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about microbial-mediated carbon fluxes in extreme environments. Hence, the methodology of sample acquisition described in the very few studies available implies two major problems: A) high resolution data require a large number of samples, which is difficult to obtain in remote areas; B) unavoidable sample manipulation such as cutting, sawing, and melting of ice cores that leads to a misunderstanding of in situ conditions. In this study, a prototype device that requires neither sample preparation nor sample destruction is presented. The device can be used for in situ measurements with a high spectral and spatial resolution in terrestrial and ice ecosystems and is based on the Laser-Induced Fluorescence Emission (L.I.F.E.) technique. Photoautotrophic supraglacial communities can be identified by the detection of L.I.F.E. signatures in photopigments. The L.I.F.E. instrument calibration for the porphyrin derivates chlorophylla (chla) (405 nm laser excitation) and B-phycoerythrin (B-PE) (532 nm laser excitation) is demonstrated. For the validation of this methodology, L.I.F.E. data were ratified by a conventional method for chla quantification that involved pigment extraction and subsequent absorption spectroscopy. The prototype applicability in the field was proven in extreme polar environments. Further testing on terrestrial habitats took place during Mars analog simulations in the Moroccan dessert and on an Austrian rock glacier. The L.I.F.E. instrument enables high resolution scans of large areas with acceptable operation logistics and contributes to a better understanding of the ecological potential of supraglacial communities in the context of global change.

A guide to sample delivery systems for serial crystallography.

Crystallography has made a notable contribution to our knowledge of structural biology. For traditional crystallography experiments, the growth of crystals with large size and high quality is crucial, and it remains one of the bottlenecks. In recent years, the successful application of serial femtosecond crystallography (SFX) provides a new choice when only numerous microcrystals can be obtained. The intense pulsed radiation of X-ray free-electron lasers (XFELs) enables the data collection of small-sized crystals, making the size of crystals no longer a limiting factor. The ultrafast pulses of XFELs can achieve 'diffraction before destruction', which effectively avoids radiation damage and realizes diffraction near physiological temperatures. More recently, the SFX has been expanded to serial crystallography (SX) that can additionally employ synchrotron radiation as the light source. In addition to the traditional ones, these techniques provide complementary opportunities for structural determination. The development of SX experiments strongly relies on the advancement of hardware including the sample delivery system, the X-ray source, and the X-ray detector. Here, in this review, we categorize the existing sample delivery systems, summarize their progress, and propose their future prospectives.

Technological Advances in Surgical Equipment in Exotic Pet Medicine.

Surgery can be challenging in exotic pets owing to their small size and blood volume, and their increased anesthetic risk compared with small animals. Various devices are available to facilitate suturing, cutting, and hemostasis in the human and veterinary fields. These surgical equipment improve the simplicity, rapidity, and effectiveness of surgery. Vessel-sealing devices, radiosurgery, lasers, and ultrasound devices are commonly used because of their ease of use and increase in surgical efficiency. Other surgical devices are available (eg, stapling devices) but are not discussed in this article.

Exploring light confinement in laser-processed LYSO:Ce for photon counting CT application.

With the goal of developing a low-cost scintillator-based photon counting detector (PCD) with high dose efficiency suitable for CT, the light transport characteristics in LYSO:Ce detectors containing laser induced optical barriers (LIOB) are simulated. Light confinement and light collection efficiencies (LCE) are studied for a variety of optical barrier patterns and properties (refractive index (RI) and barrier/crystal interface roughness). Up to 80% confinement is achievable with a simple pixel pattern with one barrier wall separating each pixel coupled one-to-one to a photodetector (PD) pixel. Confinement is heavily dependent on barrier properties, and rough interfaces and higher RI results in increased cross-talk. Three approaches to enhance performance beyond the basic pattern are explored: (1) Multiple barrier walls separating each crystal pixel. (2) Introduction of long and short range confinement by having multiple crystal pixels per PD pixel. (3) Combination of LIOB and laser ablation (LA). (1) Is effective for rough interfaces where confinement can be increased by up to 24% for double compared to single walls. (2) Results in high confinement in the pixel centered on the PD pixel, but lower confinement closer to the PD edge. This feature may be explored to achieve spatial resolution beyond the PD pixel size using light sharing based positioning algorithms. (3) Can increase confinement for smooth interfaces using a smooth ablation in the bottom part of the crystal. A general trend across all configurations is a trade-off between light confinement and LCE. The LCE attainable is found comparable to that for mechanically pixelated arrays. While the confinement achievable with LIOB is always lower compared to a mechanically pixelated array, the former may offer a high level of flexibility in terms of detector design. This, in combination with the possibility to fabricate sub-mm pixels in a cost-effective manner, makes LIOB a promising technology for scintillator-based PCDs.

Improving High Viscosity Extrusion of Microcrystals for Time-resolved Serial Femtosecond Crystallography at X-ray Lasers.

High-viscosity micro-extrusion injectors have dramatically reduced sample consumption in serial femtosecond crystallographic experiments (SFX) at X-ray free electron lasers (XFELs). A series of experiments using the light-driven proton pump bacteriorhodopsin have further established these injectors as a preferred option to deliver crystals for time-resolved serial femtosecond crystallography (TR-SFX) to resolve structural changes of proteins after photoactivation. To obtain multiple structural snapshots of high quality, it is essential to collect large amounts of data and ensure clearance of crystals between every pump laser pulse. Here, we describe in detail how we optimized the extrusion of bacteriorhodopsin microcrystals for our recent TR-SFX experiments at the Linac Coherent Light Source (LCLS). The goal of the method is to optimize extrusion for a stable and continuous flow while maintaining a high density of crystals to increase the rate at which data can be collected in a TR-SFX experiment. We achieve this goal by preparing lipidic cubic phase with a homogenous distribution of crystals using a novel three-way syringe coupling device followed by adjusting the sample composition based on measurements of the extrusion stability taken with a high-speed camera setup. The methodology can be adapted to optimize the flow of other microcrystals. The setup will be available for users of the new Swiss Free Electron Laser facility.

Impacto do tratamento com laser fracionado de CO2 em cicatrizes hipertróficas e queloides: uma revisão sistemática / Impact of fractional CO2 laser treatment on hypertrophic scars and keloids: a systematic review

Introdução: Cicatrizes hipertróficas e queloides causam dano estético e funcional e são de difícil tratamento. O objetivo desta revisão foi identificar estudos prospectivos do tratamento com o laser fracionado de CO2, mostrando as alterações clínicas e histológicas e a metodologia utilizada para a avaliação das cicatrizes antes e após intervenção. Métodos: Foi realizada uma revisão eletrônica (LILACS, Medline e SciELO) de estudos publicados entre janeiro de 2004 e dezembro de 2017, com os termos "keloid/queloide", "hypertrophic scar/cicatriz hipertrófica" e "laser CO2", de acordo com o PRISMA Statement, sendo selecionados os estudos que comparassem as cicatrizes antes e depois de tratamento isolado com laser fracionado de CO2. Os dados foram analisados por dois revisores independentes. Resultados: Foram analisados 102 artigos, sendo que 7 cumpriam os critérios estabelecidos. Destes, os 7 analisaram cicatrizes hipertróficas, 2 deles também analisaram queloides, e 3 estudaram alterações histológicas. Houve diferença estatística entre os escores clínicos medidos antes e após tratamento de cicatrizes hipertróficas na maioria dos estudos, com melhora nos sintomas, na flexibilidade e altura da cicatriz. Entre os 2 estudos que analisaram os queloides, 1 deles demonstrou diferença clínica após tratamento. Nas alterações histológicas, houve diferença na orientação e densidade das fibras de colágeno e na espessura da epiderme. Conclusão: O laser fracionado de CO2 deve ser considerado como opção promissora no tratamento de cicatrizes patológicas, visto que melhora os sinais e sintomas clínicos como cor, espessura e prurido.

Introduction: Hypertrophic scars and keloids cause aesthetic and functional damages, and are difficult to treat. This review aimed to identify prospective studies on fractional CO2 laser to present the clinical and histological changes and the methodology used for the evaluation of scars before and after intervention. Methods: We conducted an electronic review (LILACS, Medline, and SciELO) of studies published between January 2004 and December 2017, using the search terms "keloid/queloide," "hypertrophic scar/cicatriz hipertrófica," and "CO2 laser ," according to the PRISMA Statement. Studies that compared scars before and after isolated treatment with fractional CO2 laser were selected. Two independent reviewers analyzed the data. Results: One hundred two articles were analyzed, of which 7 met the inclusion criteria. Of the 7 articles, all analyzed hypertrophic scars, 2 analyzed keloids in addition to hypertrophic scars, and 3 analyzed histological changes. Most studies showed a statistically significant difference in clinical scores between before and after treatment of hypertrophic scars, with improvement in symptoms, flexibility, and scar height. Between the 2 studies that analyzed keloids, 1 reported a clinical difference after treatment. The histological changes showed significant differences in the orientation and density of the collagen fibers, and in the thickness of the epidermis. Conclusion: The use of fractional CO2 laser should be considered as a promising treatment option for pathological scars, as it improves clinical signs and symptoms such as color, thickness, and pruritus.

Shaping the Amplitude and Phase of Laser Beams by Using a Phase-only Spatial Light Modulator.

The aim of this article is to visually demonstrate the utilization of an interferometric method for encoding complex fields associated with coherent laser radiation. The method is based on the coherent sum of two uniform waves, previously encoded into a phase-only spatial light modulator (SLM) by spatial multiplexing of their phases. Here, the interference process is carried out by spatial filtering of light frequencies at the Fourier plane of certain imaging system. The correct implementation of this method allows arbitrary phase and amplitude information to be retrieved at the output of the optical system. It is an on-axis, rather than off-axis encoding technique, with a direct processing algorithm (not an iterative loop), and free from coherent noise (speckle). The complex field can be exactly retrieved at the output of the optical system, except for some loss of resolution due to the frequency filtering process. The main limitation of the method might come from the inability to operate at frequency rates higher than the refresh rate of the SLM. Applications include, but are not limited to, linear and non-linear microscopy, beam shaping, or laser micro-processing of material surfaces.

Choosing a laser for laser speckle contrast imaging.

The use of laser speckle contrast imaging (LSCI) has expanded rapidly for characterizing the motion of scattering particles. Speckle contrast is related to the dynamics of the scattering particles via a temporal autocorrelation function, but the quality of various elements of the imaging system can adversely affect the quality of the signal recorded by LSCI. While it is known that the laser coherence affects the speckle contrast, it is generally neglected in in vivo LSCI studies and was not thoroughly addressed in a practical matter. In this work, we address the question of how the spectral width of the light source affects the speckle contrast both experimentally and through numerical simulations. We show that commonly used semiconductor laser diodes have a larger than desired spectral width that results in a significantly reduced speckle contrast compared with ideal narrow band lasers. This results in a reduced signal-to-noise ratio for estimating changes in the motion of scattering particles. We suggest using a volume holographic grating stabilized laser diode or other diodes that have a spectrum of emitted light narrower than ≈1 nm to improve the speckle contrast.

Electrode placement accuracy in robot-assisted epilepsy surgery: A comparison of different referencing techniques including frame-based CT versus facial laser scan based on CT or MRI.

BACKGROUND: Precise robotic or stereotactic implantation of stereoelectroencephalography (sEEG) electrodes relies on the exact referencing of the planning images in order to match the patient's anatomy to the stereotactic device or robot. We compared the accuracy of sEEG electrode implantation with stereotactic frame versus laser scanning of the face based on computed tomography (CT) or magnetic resonance imaging (MRI) datasets for referencing. METHODS: The accuracy was determined by calculating the Euclidian distance between the planned trajectory and the postoperative position of the sEEG electrode, defining the entry point error (EPE) and the target point error (TPE). The sEEG electrodes (n = 171) were implanted with the robotic surgery assistant (ROSA) in 19 patients. Preoperative trajectory planning was performed on three-dimensional (3D) MRI datasets. Referencing was accomplished either by performing (A) 1.25-mm slice CT with the patient's head fixed in a Leksell stereotactic frame (CT-frame, n = 49), fused with a 3D-T1-weighted, contrast enhanced- and T2-weighted 1.5 Tesla (T) MRI; (B) 1.25 mm CT (CT-laser, n = 60), fused with 3D-3.0-T MRI; (C) 3.0-T MRI T1-based laser scan (3.0-T MRI-laser, n = 56) or (D) in one single patient, because of a pacemaker, 3D-1.5-T MRI T1-based laser scan (1.5-T MRI-laser, n = 6). RESULTS: In (A) CT-frame referencing, the mean EPE amounted to 0.86 mm and the mean TPE amounted to 2.28 mm (n = 49). In (B) CT-laser referencing, the EPE amounted to 1.85 mm and the TPE to 2.41 mm (n = 60). In (C) 3.0-T MRI-laser referencing, the mean EPE amounted to 3.02 mm and the mean TPE to 3.51 mm (n = 56). In (D) 1.5-T MRI, surprisingly the mean EPE amounted only to 0.97 mm and the TPE to 1.71 mm (n = 6). In 3 cases using CT-laser and 1 case using 3.0 T MRI-laser for referencing, small asymptomatic intracerebral hemorrhages were detected. No further complications were observed. CONCLUSION: Robot-guided sEEG electrode implantation using CT-frame referencing and CT-laser-based referencing is most accurate and can serve for high precision placement of electrodes. In contrast, 3.0-T MRI-laser-based referencing is less accurate, but saves radiation. Most trajectories can be reached if alternative routes over less vascularized brain areas are used. This article is part of the Special Issue "Individualized Epilepsy Management: Medicines, Surgery and Beyond".

Overview of Lasers for Flow Cytometry.

Lasers are critical elements of all flow cytometers. Instrument capabilities are dictated by the wavelengths and characteristics of its laser sources. In this chapter, we review the lasers available for flow cytometry, and provide guidance in choosing laser wavelengths and characteristics to best match the analytical needs of biomedical research laboratories.

Guideline Implementation: Energy-Generating Devices, Part 2-Lasers.

Lasers have been used in the OR for many years and are essential tools in many different types of procedures. However, laser beams that come into contact with unintended targets directly or via reflection can cause injury to patients or personnel or pose other hazards, such as fires. The new AORN "Guideline for safe use of energy-generating devices" provides guidance on the use of all energy-generating devices in the OR. This article focuses on key points of the guideline that address the safe use of lasers. These include the components of the laser safety program, the responsibilities of the personnel in roles specific to use of a laser, laser safety measures, and documentation of laser use. Perioperative RNs should review the complete guideline for additional information and for guidance when writing and updating policies and procedures.