Chitosan adhesive for laser tissue repair: In vitro characterization

Background and Objectives Laser tissue repair usually relies on hemoderivate protein solders, based on serum albumin. These solders have intrinsic limitations that impair their widespread use, such as limited tensile strength of repaired tissue, poor solder solubility, and brittleness prior to laser denaturation. Furthermore, the required activation temperature of albumin solders (between 65 and 70°C) can induce significant thermal damage to tissue. In this study, we report on the design of a new polysaccharide adhesive for tissue repair that overcomes some of the shortcomings of traditional solders. Study Design/Materials and Methods Flexible and insoluble strips of chitosan adhesive (elastic modulus ~6.8 Mpa, surface area ~34 mm2, thickness ~20 µm) were bonded onto rectangular sections of sheep intestine using a diode laser (continuous mode, 120 ± 10 mW, = λ 808 nm) through a multimode optical fiber with an irradiance of ~15 W/cm2. The adhesive was based on chitosan and also included indocyanin green dye (IG). The temperature between tissue and adhesive was measured using a small thermocouple (diameter ~0.25 mm) during laser irradiation. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were cultured in extracted media from chitosan adhesive to assess cytotoxicity via cell growth inhibition in a 48 hours period. Results Chitosan adhesive successfully repaired intestine tissue, achieving a tensile strength of 14.7 ± 4.7 kPa (mean ± SD, n = 30) at a temperature of 60-65°C. Media extracted from chitosan adhesive showed negligible toxicity to fibroblast cells under the culture conditions examined here. Conclusion A novel chitosan-based adhesive has been developed, which is insoluble, flexible, and adheres firmly to tissue upon infrared laser activation.

Pt/Nanograined ZnO/SiC Schottky diode based hydrogen and propene sensor

A nanostructured Schottky diode was fabricated to sense hydrogen and propene gases in the concentration range of 0.06% to 1%. The ZnO sensitive layer was deposited on SiC substrate by pulse laser deposition technique. Scanning electron microscopy and X-ray diffraction characterisations revealed presence of wurtzite structured ZnO nanograins grown in the direction of (002) and (004). The nanostructured diode was investigated at optimum operating temperature of 260 °C. At a constant reverse current of 1 mA, the voltage shifts towards 1% hydrogen and 1% propene were measured as 173.3 mV and 191.8 mV, respectively.

Temperature dependent electrical characterisation of Pt/HfO2/n-GaN metal-insulator-semiconductor (MIS) Schottky diodes

This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO2 (5 nm) between the metal and semiconductor interface. The resulting Pt/HfO2/n-GaN metal-insulator-semiconductor (MIS) Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V), increase in barrier height (0.52 eV to 0.63eV) and a reduction in ideality factor (2.1 to 1.3) as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE). The crystalline and optical qualities of the films were confirmed using high resolution X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN) and metal-insulator-semiconductor (Pt/HfO2/n-GaN) Schottky diodes were fabricated. To gain further understanding of the Pt/HfO2/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV) and the ideality factor decreased (3.6 to 1.2) with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights. (C) 2015 Author(s).

Laser-surface-alloyed carbon nanotubes reinforced hydroxyapatite composite coatings

Carbon-nanotube sCNTd-reinforced hydroxyapatite composite coatings have been fabricated by laser surface alloying. Microstructural observation using high-resolution transmission electron microscopy showed that a large amount of CNTs remained with their or

Microstructure Evolution of Laser Pulse processed Ductile Iron Surface

Pulsed laser beam was used to modify surface processing for ductile iron. The microstructures of processed specimen were observed using optical microscope (OM). Nanoindentation and micro-hardness of microstructures were measured from surface to inner of sample. The experimental results show that, modification zone is consisted of light melted zone, phase transformation hardening area and transient area. The light melt area is made up of coarse dendrite crystalline with a thickness less than 20um, phase transformation hardening area mainly of laminal or acicular martensite, retained austenite and graphite, i.e. M+A prime+ G. The cow-eye microstructure around graphite sphere always is formed in phase transformation hardening area zone, which consisting of a variety structure with the distance from the surface. So, it maybe as a obvious sign distinguishing modification zone border. Finally, the microstructures evolution of laser pulse processed ductile iron was analyzed coupling with beam energy distribution in space and laser pulse heating procession characteristics. The analysis shows that energy distribution of laser pulse has an important effect on microstructure during laser pulse modified ductile iron. Multi-scale and interlace arrangement are the important features for laser pulse modified ductile iron. Of microstructure.

1ps passively mode-locked laser operation of Na, Yb : CaF2 crystal

Diode-pumped passively mode-locked laser operation of Yb3+,Na+:CaF2 single crystal has been demonstrated for the first time. By using a SESAM ( semiconductor saturable mirror), simultaneous transform-limited 1-ps passively mode-locked pulses, with the repetition rate of 183MHz, were obtained under the self-Q-switched envelope induced by the laser medium. The average output power of 360mW was attained at 1047nm for 3.34W of absorbed power at 976nm, and the corresponding pulse peak power arrived at 27kW, indicating the promising application of Yb3+,Na+-codoped CaF2 crystals in achieving ultra-short pulses and high pulse peak power. (c) 2005 Optical Society of America.

Aperiodic structures in optics and integrated optics and the transverse Bragg reflector laser

The first part of this work describes the uses of aperiodic structures in optics and integrated optics. In particular, devices are designed, fabricated, tested and analyzed which make use of a chirped grating corrugation on the surface of a dielectric waveguide. These structures can be used as input-output couplers, multiplexers and demultiplexers, and broad band filters.

Next, a theoretical analysis is made of the effects of a random statistical variation in the thicknesses of layers in a dielectric mirror on its reflectivity properties. Unlike the intentional aperiodicity introduced in the chirped gratings, the aperiodicity in the Bragg reflector mirrors is unintentional and is present to some extent in all devices made. The analysis involved in studying these problems relies heavily on the coupled mode formalism. The results are compared with computer experiments, as well as tests of actual mirrors.

The second part of this work describes a novel method for confining light in the transverse direction in an injection laser. These so-called transverse Bragg reflector lasers confine light normal to the junction plane in the active region, through reflection from an adjacent layered medium. Thus, in principle, it is possible to guide light in a dielectric layer whose index is lower than that of the surrounding material. The design, theory and testing of these diode lasers are discussed.

Study of the effect of alcohol on single human red blood cells using near-infrared laser tweezers Raman spectroscopy

The effect of alcohol solution on single human red blood Cells (RBCs) was investigated using near-infrared laser tweezers Raman spectroscopy (LTRS). In our system, a low-power diode laser at 785 nm was applied for the trapping of a living cell and the excitation of its Raman spectrum. Such a design could simultaneously reduce the photo-damage to the cell and suppress the interference from the fluorescence on the Raman signal. The denaturation process of single RBCs in 20% alcohol solution was investigated by detecting the time evolution of the Raman spectra at the single-cell level. The vitality of RBCs was characterized by the Raman band at 752 cm(-1), which corresponds to the porphyrin breathing mode. We found that the intensity of this band decreased by 34.1% over a period of 25 min after the administration of alcohol. In a further study of the dependence of denaturation on alcohol concentration, we discovered that the decrease in the intensity of the 752 cm(-1) band became more rapid and more prominent as the alcohol concentration increased. The present LTRS technique may have several potential applications in cell biology and medicine, including probing dynamic cellular processes at the single cell level and diagnosing cell disorders in real time. Copyright (c) 2005 John Wiley T Sons, Ltd.

Application of sample-and-hold circuits in the laser frequency-shifting

A new method of frequency-shifting for a diode laser is realized. Using a sample-and-hold circuit, the error signal can be held by the circuit during frequency shifting. It can avoid the restraint of locking or even lock-losing caused by the servo circuit when we input a step-up voltage into piezoelectric transition (PZT) to achieve laser frequency-shifting.