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Pulsed Laser (pulsed + laser)
Terms modified by Pulsed Laser Selected AbstractsNoncontact photo-acoustic defect detection in drug tabletsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2007Ivin Varghese Abstract Quality assurance monitoring is of great importance in the pharmaceutical industry for the reason that if defects such as coating layer irregularities, internal cracks, and delamination are present in a drug tablet, the desired dose delivery and bioavailability can be compromised. The U.S. Food and Drug Administration (FDA) established the Process Analytical Technology (PAT) initiative, in order to ensure efficient quality monitoring at each stage of the manufacturing process by the integration of analysis systems into the evaluation procedure. Improving consistency and predictability of tablet action by improving quality and uniformity of tablet coatings as well as ensuring core integrity is required. An ideal technique for quality monitoring would be noninvasive, nondestructive, have a short measurement time, intrinsically safe, and relatively inexpensive. In the proposed acoustic system, a pulsed laser is utilized to generate noncontact mechanical excitations and interferometric detection of transient vibrations of the drug tablets is employed for sensing. Two novel methods to excite vibrational modes in drug tablets are developed and employed: (i) a vibration plate excited by a pulsed-laser and (ii) pulsed laser-induced plasma generated shockwave expansion. Damage in coat and/or core of a tablet weakens its mechanical stiffness and, consequently, affects its acoustic response to an external dynamic force field. From the analysis of frequency spectra and the time,frequency spectrograms obtained under both mechanisms, it can be concluded that defective tablets can be effectively differentiated from the defect-free ones and the proposed proof-of-concept techniques have potential to provide a technology platform to be used in the greater PAT effort. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:2125,2133, 2007 [source] Surface-enhanced resonance Raman scattering using pulsed and continuous-wave laser excitationJOURNAL OF RAMAN SPECTROSCOPY, Issue 6-7 2005Rachael E. Littleford Abstract Pulsed and continuous-wave (CW) lasers were compared as excitation sources for surface-enhanced resonance Raman scattering (SERRS). CW excitation provided SERRS spectra with a greater signal-to-noise ratio and more sensitive detection by a factor of ,50 compared with the high peak power, low repetition rate pulsed configuration used. The SERRS intensity using a pulsed laser produced a non-linear response with respect to changes in power of the laser. At powers of less than ,0.012 mW, the absolute intensity under the peaks of the CW and pulsed SERRS spectra converged, suggesting that lower peak power, high repetition rate systems may be more effective excitation sources for SERRS. Transmission electron microscopy of pulsed laser-irradiated silver particles showed significant sample damage and morphological changes. This problem was overcome with the use of a recirculating large-volume flow cell system, providing a fresh sample for each measurement. A picosecond-resolved time delay experiment found that SERRS intensity decreased by ,60% when exposed to a 400 nm pump pulse and probed with a 529 nm pulse. As the time delay between pump and probe increased the system recovered gradually to ,60% of the original SERRS intensity after 50 ps, where it remained constant. This suggests that the surface bonding between the silver and the dye is significantly perturbed, with some nanoscale diffusion occurring of the dye away from the metal surface. Hence chemical enhancement is temporarily prevented and electromagnetic enhancement is reduced as a function of 1/r3 as the dye moves away from the surface. Additionally, transient heating of the colloidal particles caused by the pulsed laser may also lead to plasmon shifts and changes in absorption intensity. Other factors such as surface annealing or decomposition of the silver particle or dye due the extreme temperature conditions may account for the permanent loss in SERRS intensity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Generation and interrogation of a pure nuclear spin state by parahydrogen-enhanced NMR spectroscopy: a defined initial state for quantum computationMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2005D. Blazina Abstract We describe a number of studies used to establish that parahydrogen can be used to prepare a two-spin system in a pure state, which is suitable for implementing NMR quantum computation. States are generated by pulsed and continuous-wave (CW) UV laser initiation of a chemical reaction between Ru(CO)3(L2) [where L2 = dppe = 1,2-bis(diphenylphosphino)ethane or L2 = dpae = 1,2-bis(diphenylarsino)ethane] with pure parahydrogen (generated at 18 K). This process forms Ru(CO)2(dppe)(H)2 and Ru(CO)2(dpae)(H)2 on a sub-microsecond time-scale. With the pulsed laser, the spin state of the hydride nuclei in Ru(CO)2(dppe)(H)2 has a purity of 89.8 ± 2.6% (from 12 measurements). To achieve comparable results by cooling would require a temperature of 6.6 mK, which is unmanageable in the liquid state, or an impractical magnetic field of 0.44 MT at room temperature. In the case of CW initiation, reduced state purities are observed due to natural signal relaxation even when a spin-lock is used to prevent dephasing. When Ru(CO)3(dpae) and pulsed laser excitation are utilized, the corresponding dihydride product spin state purity was determined as 106 ± 4% of the theoretical maximum. In other words, the state prepared using Ru(CO)3(dpae) as the precursor is indistinguishable from a pure state. Copyright © 2004 John Wiley & Sons, Ltd. [source] Textured growth and microstructure of pulsed laser deposited Nb/Cr/SmCo5 hybrid structuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010R. Schaarschuch Abstract Hybrid structures based on superconducting Nb and highly coercive ferromagnetic SmCo5 films grown on MgO(100) substrates were fabricated by pulsed laser deposition under UHV conditions. Thin film architectures of SmCo5 on Nb and the reversed system both with and without Cr spacer layer between superconductor and ferromagnet were examined by transmission electron microscopy and X-ray diffraction concerning their microstructure and epitaxial relationship, respectively. For SmCo5 on Nb with thick intermediate Cr spacer the epitaxial relationship MgO(001)[100]//Cr(001)[110]//Nb(001)[110]//Cr(001)[110]//SmCo5(11,,,20)[0001]//Cr(001)[110] was found. With decreasing thickness of the Cr spacer layer the strength of the texture decreases and finally crystallinity of SmCo5 is lost. In the reversed layer system, Nb on Cr on SmCo5, with decreasing thickness of the Cr spacer layer the epitaxial relationships change from SmCo5(11,,,20)[0001]//Nb(001)[110] to local SmCo5(11,,,20) [0001]//Nb(110)[1,,,11] and the Nb texture changes from the (001)[110] component to a ,110, fibre. The orientation relationships observed are discussed with regard to elastic strain energy minimization. [source] Tuneable Femtosecond Fiber Lasers , Ultra-short laser pulses from green to IRLASER TECHNIK JOURNAL, Issue 2 2005Jan Posthumus Dr. There is a wealth of applications for ultra-short, pulsed lasers in many areas of science and technology, material processing and also in medicine. However, their widespread use is severely hampered by the size and cost of these lasers, both in terms of acquisition and maintenance. This implies that there could be a large market for affordable, turn-key femtosecond lasers (1 fs = 10,15 s). A technical solution is now possible with a new generation of fiber lasers, which are made of standard telecom components. These fiber lasers are compact (A4 size) and scalable in cost and performance. They can also be produced in large volumes. They render water cooling methods and large power supplies obsolete. [source] | |||||||||||||