Laser-based Tools Research Articles

Rectification of a large vertical wall surface for flatness

This paper describes the efforts made in rectifying a large prestressed, L-shaped, vertical reaction wall with circular cavities and the lessons learnt. The wall was to be constructed with a certain flatness requirement, which it later turned out was not met. Though various studies have been undertaken in the past describing rectification of horizontal concrete floors, the present study discusses a novel approach to determine the extent of non-compliance and then re-surfacing of the vertical wall to achieve required flatness. The paper discusses in detail the applicability of various instruments like profilometers, water level manometers, and laser-based tools in determining the extent of undulations. It was found that the rotating laser-based tool best served the purpose for defect identification and that placing a layer of micro concrete along with a bonding agent using a novel construction method helped to achieve the desired level of flatness.

Neurochemical assessment of identified phrenic motor neurons via flow cytometry

Flow cytometry (FCM) utilizes high powered, laser‐based tools to perform multi‐parametric analyses on cell populations. Although FCM is routinely utilized in immunology and cancer biology fields, it is rarely used in the study of neurobiology. Here, we show a novel use of FCM to identify and isolate phrenic motor neurons, a small, but critical pool of respiratory motor neurons innervating the diaphragm. Rat phrenic motor neurons were retrogradely labeled via bilateral intrapleural injections of fluorescently‐conjugated cholera toxin fragment B (CtB‐AlexaFluor 647). After 72 hours, rats were perfused and the cervical spinal cords dissected, dissociated, fixed in a modified zinc‐based fixative, and stained with DAPI to discriminate intact cells from debris. Using FCM, a clearly defined group of intact cells were identified as CtB‐AlexaFluor 647 positive, corresponding closely with available estimates of phrenic motor neuron numbers in rats. These cells were confirmed to be neurons by co‐staining with the neuronal marker NeuN. Our results demonstrate the feasibility of using FCM to identify, characterize, and sort phrenic motor neurons. Coupling FCM with neurophysiology provides an innovative approach to the study of phrenic motor neuron biology, while lending new insights into mechanisms of spinal respiratory neuroplasticity in models of traumatic or neurodegenerative injury.

Influence of the hydration state on the ultrashort laser ablation of dental hard tissues

Since about 40 years, laser-based surgical tools have been used in medicine and dentistry to improve clinical protocols. In dentistry, femtosecond lasers have been claimed to be a potential ablation tool. It would, however, be good to perform a more fundamental investigation to understand ablation interaction mechanisms and possible side effects, depending on different specific components of the target tissue. The goal of this study is to show the changes of ablation characteristics in the femtosecond regime at different levels of structural water within dental hard tissues. Thirty human teeth samples were split into three hydration groups and subdivided into dentin and enamel groups (n = 5). The specimens were irradiated using a 70-fs Ti:sapphire laser (with a 1-kHz repetition rate and a 801-nm wavelength output). Ablation was performed using five different power levels and three exposure times. The results clearly show an inversely proportional dependence of the ablation threshold to the hydration level of the tissues. A known mathematical model was adapted in order to include the influence of the changes on the relative fractional composition of dental hard tissues. This analysis was consistent with the experimental results regarding the ablation threshold. High thermal and mechanical damages were observed as a high repetition rate had been applied. Macroscopic images and scanning electron microscopy images were used to preliminarily analyze both the thermal and mechanical damage thresholds, and their variations according to the hydration level present. By manipulating the hydration states, the modifications in the proportions of the molecules that build dental hard tissues clearly shift, and therefore, the characteristics of a plasma-induced ablation change.

High‐Efficiency Silicon Solar Cells Demand New Process Tools

AbstractLaser‐based tools are becoming an essential part of new crystalline silicon cell lines which are configured for high‐efficiency performance. Different tooling types are required on a case‐by‐case basis, depending on the level of process development undertaken and how fast cell producers move to implement the laserbased tools within high‐throughput production lines.

Robert Feulgen Prize Lecture. Laser tweezers and multiphoton microscopes in life sciences.

Near infrared (NIR) laser microscopy enables optical micromanipulation, piconewton force determination, and sensitive fluorescence studies by laser tweezers. Otherwise, fluorescence images with high spatial and temporal resolution of living cells and tissues can be obtained via non-resonant fluorophore excitation with multiphoton NIR laser scanning microscopes. Furthermore, NIR femtosecond laser pulses at TW/cm2 intensities can be used to realize non-invasive contact-free surgery of nanometer-sized structures within living cells and tissues. Applications of these novel versatile NIR laser-based tools for the determination of motility forces, coenzyme and chlorophyll imaging, three-dimensional multigene detection, non-invasive optical sectioning of tissues ("optical biopsy"), functional protein imaging, and nanosurgery of chromosomes are described.