Абляция кремния в воздухе моно- и бихроматическими импульсами лазерного излучения с длинами волн 355 и 532 nm

Ablation of silicon sample in air under irradiance of single and double laser pulses with wavelengths 355 and 532 nm was studied by means of optical and scanning electron microscopy, raman spectroscopy, profilometry of laser craters as well as video registration of plasma’s plume radiation in time. Dependence of specific sample’s material removal on laser fluence and time interval between coupled pulses of bichromatic laser irradiance was established. Spallation of silicon was found in broad range of irradiance parameters and parameters of craters formed by ablation and spallation under the action of bichromatic laser radiation were determined.

Kinetic Evolution of Laser Ablating Alloy Materials

Through the theoretical simulation and analysis of the whole process of laser ablating target and producing plasma with high spatio-temporal resolution, it is helpful for people to gain a more complete understanding of the ablation process of target and the evolution process of plasma parameters, which has an important guiding role for the improvement and optimization of laser ablation technology. Alloys are commonly used in daily life, but there are few researches on laser-induced alloy targets at present. Therefore, based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamic model, the process of laser ablating Al-Mg alloy under atmospheric pressure argon is theoretically simulated, and the ablation process of alloy target and the spatio-temporal evolution results of plasma parameters under different laser irradiances are compared. At high laser irradiance, the melt and evaporation depth, laser energy absorption and plasma characterization parameters are much greater than those at low laser irradiance, and the species energy distribution at different laser irradiance also presents different trends. In addition, the velocity of different species is calculated according to the position-time diagram of the maximum emission intensity, and they expand at a constant speed during the studied time. These results can provide some theoretical guidance for the early application of laser-induced breakdown spectroscopy in metallurgy.

DRUG POLYMORPHISM IDENTIFICATION USING FOURIER TRANSFORM-RAMAN SPECTROSCOPY: A COMPARATIVE STUDY OF LAMIVUDINE AND FINASTERIDE DRUGS

Objectives: Maintaining the quality of the pharmaceutical drug product during its shelf life is highly desirable. The crystalline form of the drug having the great thermodynamic stability is essential for the manufacturers in pharmaceutical industry in view of their profit and also for the safety of the customer. Many pharmaceutical drugs have the tendency to exhibit polymorphism which is unwanted for pharmaceutical companies, where they have experienced market shortages due to these unpredicted polymorphic and/or pseudomorphic changes. The property of a drug exhibiting more than one crystal form is considerably regarded as polymorphism and each of the crystalline form has its own physicochemical properties, namely, solubility, heat capacity, melting point, and sublimation point. To relieve this ultimate effect on the drug quality and stability, a prior detection of polymorphism in the final dosage form is highly recommended. Hence, many analytical techniques have been proposed for the detection of polymorphism in pharmaceutical drug products. Methods: Fourier transform (FT)-Raman spectrometer is used for the investigation of drug polymorphism and the instrument is advanced with charge coupled device detectors, ease of sample preparation and handling, mitigation of sub-sampling problems using different geometric laser irradiance patterns and having different optical components of Raman spectrometers. Results: In this work, we carefully studied the Raman spectral patterns for Lamivudine as well as Finasteride drug substances for the detection of polymorphism. Further, we have highlighted the advantages of FT-Raman spectroscopy over other polymorphism detection techniques. For example, Raman spectra showed invariably sharp, well resolved bands compare to IR spectra due to the minor contribution of overtone vibrations in Raman spectra, resulting in much less broadening and a better resolution of bands. Besides, Raman spectroscopy does not suffer from the sampling problems that are common in X-ray powder diffraction, where preferred orientation and specimen displacements are serious restrictions for the application of quantitative method. Conclusion: Here, in this paper, we are presented and compared the experimental results regarding the detection of polymorphism in Lamivudine and Finasteride drugs using FT-Raman spectroscopy, to illustrate the advantages of the technique in the detection of polymorphism over other techniques.

Spectroscopic Characterization of Laser Ablated Germanium Plasma

In the present study, the germanium (Ge) sample has been studied by laser induced breakdown spectroscopy which leads to the formation of plasma plume in the air. This research work comprises on pure Ge sample, and it has been studied using laser irradiance 1.831011 watt.cm-2 and Q-Switched Nd:YAG laser pulse (λ ~ 1064 nm wavelength and  ~ 5 ns pulse width). The spatially resolved plasma plume parameters are investigated, such as variation of electron temperature Te and electron number density ne as a function of detector position. These parameters show variation in the plasma plume and yield electron temperature Te from 12340 to 7640 ± 1200 K. Whereas electron number density ne varies from 3.61017 to 1.601017 cm-3 with the change in detector position is moving away from plasma plume from 0 to 3 mm. The results show that electron temperature Te and electron number density ne are estimated from the Boltzmann plot method and by using Lorentzian function at spectral line using FWHM full width at half maximum at 265.11 nm (4p5s 3 p2 → 4p 2 3 p2) wavelength of Ge (I) line, respectively.

An Investigation of Laser Produced Lead-Tin Alloy Plasmas between 10 and 18 nm

The results of a systematic study performed on Pb-Sn alloys of concentration 65–35% and 94–6% by weight along with spectra from pure Pb and Sn in the wavelength range of 9.8–18 nm are presented. The dynamics of the Nd:YAG laser produced plasma were changed by varying the focused spot size and input energy of the laser pulse; the laser irradiance at the target varied from 7.3 × 109 W cm−2 to 1.2 × 1012 W cm−2. The contributing ion stages and line emission are identified using the steady state collisional radiative model of Colombant and Tonon, and the Cowan suite of atomic structure codes. The Sn spectrum was dominated in each case by the well-known unresolved transition array (UTA) near 13.5 nm. However, a surprising result was the lack of any enhancement or narrowing of this feature at low concentrations of Sn in the alloy spectra whose emission was essentially dominated by Pb ions.

Initial treatment for patients with temporomandibular disorders: pain relief and muscle tone relief by photobiomodulation therapy using carbon dioxide laser

Purpose To investigate the efficacy of photobiomodulation therapy (PBMT) with a CO2 laser (Bel Laser, Takara Belmont, CO. Ltd., Osaka, Japan; wavelength 10.6 μm) (tissue surface absorption effects) in conjunction with mouth opening training in patients with temporomandibular disorders (TMDs). Methods This is a retrospective study on TMD patients with pre- and post-treatment assessments. The study included 36 patients (7 men and 29 women, mean age 58.2 years (SD 18.3)) (after excluding 4 patients due to dropouts, loss to follow up or refusal of treatment) with symptoms of pain and muscle tenderness during mouth opening. Treatment included Amfenac sodium (50 mg per day, thrice daily after meals) for 1–2 weeks for acute symptoms. Based on the diagnostic criteria for TMD, we identified the trigger point (muscle contracture site). We implemented muscle massage and stretching therapy as mouth opening training after PBMT. The laser irradiance conditions were as follows: output 1.5 W, on time 0.01 s, off time 0.05 s, and repeat pulse. Distance between the laser source and the skin was approximately 10 cm; irradiation time was 3 min (approximately 56.9 J/cm2). Mouth opening training involved massaging the areas of muscle contracture that were the trigger points, as well as muscle stretching to improve temporomandibular joint flexibility. One PBMT cycle and mouth opening training was conducted per week for four cycles. We determined the effects before and after intervention. A numeric rating scale (NRS; range 0–10) was used to evaluate pain, and maximum mouth opening (MMO) capacity was also assessed. Data were analyzed using the Wilcoxon signed-rank test. Results The mean (SD) pain levels, as determined via NRS, were 4.9(3.6) and 2.7 (3.0) (p < 0.001), before and after four treatment cycles, respectively. The mean (SD) of MMO was 39.6 (5.9) and 44.6 mm (4.8) (p < 0.001), before and after treatment, respectively. Conclusion The current study suggests that PBMT using a CO2 laser combined with mouth opening training is effective for the treatment of temporomandibular disorders.