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Sample records for active media lasers

  1. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

    A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

  2. Active media for tunable lasers based on hybrid polymers

    SciTech Connect

    Kopylova, T N; Eremina, N S; Vaitulevich, E A; Samsonova, L G; Maier, G V; Tel'minov, E N; Solodova, T A; Solodov, A M

    2008-02-28

    The lasing properties of rhodamine 6G (chloride and perchlorate) in synthesised hybrid polymers based on an organic polymer (methyl methacrylate with hydroxyethyl methacrylate) and an inorganic precursor (tetraethoxysilane) are studied. Rhodamine 6G samples were transversely pumped by the second harmonic of a Nd{sup 3+}:YAG laser. It is found that the active media based on hybrid polymers have a considerably longer service life compared to the active media based on organic polymers. The structure of the hybrid polymer is studied by the methods of IR Fourier spectroscopy, X-ray diffraction, and thermogravimetry. It is shown that the longer service life of hybrid-polymer active media is explained by the formation of an inorganic nanostructure network in them, which improves the thermooptic properties of the material and reduces the efficiency of thermal decomposition of active molecules. (lasers. amplifiers)

  3. REVIEW: Excited states in the active media of oxygen — iodine lasers

    NASA Astrophysics Data System (ADS)

    Azyazov, V. N.

    2009-11-01

    A review of investigations of kinetic processes in active media oxygen — iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O2 and I2 molecules are considered, and dissociation mechanisms of I2 in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended.

  4. generation of picosecond pulses in solid-state lasers using new active media

    SciTech Connect

    Lisitsyn, V.N.; Matrosov, V.N.; Pestryakov, E.V.; Trunov, V.I.

    1986-07-01

    Results are reported of investigations aimed at generating nanosecond radiation pulses in solid-state lasers using new active media having broad gain lines. Passive mode locking is accomplished for the first time in a BeLa:Nd/sup 3/ laser at a wavelength 1.354 microm, and in a YAG:Nd/sup 3/ laser on a 1.32-microm transition. The free lasing and mode-locking regimes were investigated in an alexandrite (BeA1/sub 2/O/sub 4/:Cr/sup 3/) laser in the 0.72-0.78-microm range and in a synchronously pumped laser on F/sub 2//sup -/ centers in LiF in the 1.12-1.24-microm region. The features of nonlinear perception of IR radiation by the eye, using a developed picosecond laser on F/sub 2//sup -/ centers, are investigated for the first time.

  5. Active lamp pulse driver circuit. [optical pumping of laser media

    NASA Technical Reports Server (NTRS)

    Logan, K. E. (Inventor)

    1983-01-01

    A flashlamp drive circuit is described which uses an unsaturated transistor as a current mode switch to periodically subject a partially ionized gaseous laser excitation flashlamp to a stable, rectangular pulse of current from an incomplete discharge of an energy storage capacitor. A monostable multivibrator sets the pulse interval, initiating the pulse in response to a flash command by providing a reference voltage to a non-inverting terminal of a base drive amplifier; a tap on an emitter resistor provides a feedback signal sensitive to the current amplitude to an inverting terminal of amplifier, thereby controlling the pulse amplitude. The circuit drives the flashlamp to provide a squarewave current flashlamp discharge.

  6. Detachment instability of self-sustained volume discharge in active media of non-chain HF(DF) lasers

    SciTech Connect

    Belevtsev, A A; Kazantsev, S Yu; Kononov, I G; Firsov, K N

    2010-08-27

    The development of detachment instability in active media of electric-discharge non-chain HF(DF) lasers due to the electron-impact detachment of electrons from negative ions is considered. This instability is initiated in large volumes of SF{sub 6}-based gas mixtures, spatially separated from electrodes and heated by a pulsed CO{sub 2} laser. The self-organisation of self-sustained volume discharge upon laser heating, which results in the formation of quasi-periodic plasma structures within the discharge gap, is experimentally investigated. The evolution of these structures, depending on the gas temperature and specific deposition of electric energy, is analysed. The possible relationship between the self-organisation and detachment instability is discussed. A mechanism of development of single plasma channels in the working media of HF(DF) lasers, based on electron-impact destruction of negative ions is proposed. (active media)

  7. ACTIVE MEDIA: Dynamics of growth of inhomogeneities in the active medium of a liquid laser

    NASA Astrophysics Data System (ADS)

    Barikhin, B. A.; Ivanov, A. Yu; Kudryavkin, E. V.; Nedolugov, V. I.

    1991-07-01

    Fast cinematography of holograms and of shadow and interference patterns was combined with an acoustic method in a study of the dynamics of growth of inhomogeneities in the active medium of a coaxially pumped dye laser. The main mechanism of the formation of these inhomogeneities was related to acoustic waves created by the deformation of the walls of a dye cell created by electrical pulses applied to the pump flashlamp. Multipulse operation of this laser could be achieved and the off-duty factor could be reduced if the active medium was excited by the strongest possible pump pulses.

  8. ACTIVE MEDIA. LASERS: Study of a Nd3+:KGW crystal laser transversely pumped by laser diode bars

    NASA Astrophysics Data System (ADS)

    Abazadze, Aleksandr Yu; Zverev, Georgii M.; Kolbatskov, Yurii M.; Ustimenko, N. S.

    2004-01-01

    A Nd3+:KGW crystal laser transversely pumped by laser diode bars is studied experimentally. The optimisation of the laser parameters provided the maximum slope efficiency of ~50 % at 1.067 μm in the free running regime. Using the SRS self-conversion in a Nd3+: KWG laser, lasing was obtained in the eye-safe spectral region at 1.538 nm with the energy up to 5 mJ and a pulse repetition rate up to 20 Hz.

  9. Laser media based on coloured polyurethane

    SciTech Connect

    Bezrodnyi, V I; Ishchenko, Aleksandr A

    2000-12-31

    The advantages of a polyurethane matrix over other polymers, which are widely used as active media for dye lasers, are analysed. This matrix exhibits the photostability, service life, radiation resistance, conversion efficiency, and homogeneity of the dye distribution that surpass these properties for active media based on polyurethane acrylate, which has close physical and operation properties. These advantages result not only from the milder polymerisation conditions but also from a lower probability of the formation of ion pairs and dye aggregates. A substantial suppression of these processes in polyurethane is explained by its greater polarity and solvation ability compared to polyurethane acrylate. (active media)

  10. Loop laser cavities with self-pumped phase-conjugate mirrors in low-gain active media for phase-locked multichannel laser systems

    SciTech Connect

    Basiev, Tasoltan T; Gavrilov, A V; Ershkov, M N; Smetanin, Sergei N; Fedin, Aleksandr V; Bel'kov, K A; Boreysho, A S; Lebedev, V F

    2011-03-31

    It is proved that lasers with different loop cavities with self-pumped phase-conjugate mirrors in low-gain active media can operate under injection of external laser radiation and can be used for the development of diode-pumped phase-locked multichannel neodymium laser systems operating both on the fundamental laser transition with the wavelength {lambda} = 1.06 {mu}m and on the transition with {lambda} = 1.34 {mu}m. The phase-conjugate oscillation thresholds in the case of injection of an external signal are determined for a multiloop cavity configuration and an increased number of active elements in the cavity. It is shown that phase-conjugate oscillation can occur even if the single-pass gain of the active element is as low as only {approx}2. Under high-power side diode pumping of a multiloop Nd:YAG laser, single-mode output radiation was achieved at {lambda} = 1.064 {mu}m with a pulse energy up to 0.75 J, a pulse repetition rate up to 25 Hz, an average power up to 18.3 W, and an efficiency up to 20%. In a multiloop Nd:YAG laser with three active elements in the cavity, single-mode radiation at {lambda} = 1.34 {mu}m was obtained with a pulse energy up to 0.96 J, a pulse repetition rate up to 10 Hz, and an average power up to 8.5 W. (control of laser radiation parameters)

  11. ACTIVE MEDIA: Nonlinear thermally induced distortions of a laser beam in a cryogenic disk amplifier

    NASA Astrophysics Data System (ADS)

    Vyatkin, A. G.; Khazanov, Efim A.

    2009-09-01

    Taking into account the temperature dependences of the heat conductivity, the refractive index, and the thermal expansion coefficient, we calculated the temperature, elastic stresses, a thermally induced lens and depolarisation of a beam in a cryogenic disk amplifier (an Yb:YAG disk placed between a copper cylinder and a sapphire disk cooled by liquid nitrogen). When the active element (the thickness is 0.6 mm, the orientation is [001], the atomic concentration of Yb is 10%) is pumped by radiation from a diode laser (the beam diameter is 6 mm), the temperature does not exceed 140 K for the heat release power of 100 W. In this case, elastic stresses in the active element are six times lower than the maximum permissible value. The focal distance of the thermally induced lens is 5.5 m and the depolarisation rate is 0.038% per two passes through the active element. Although the heat conductivity of the active element rapidly decreases with temperature, the thermal load can be increased by 1.5-2 times when the dimensions of the active element remain constant.

  12. The development of polymer laser-active media with improved performances

    NASA Astrophysics Data System (ADS)

    Idrisov, R.; Serova, V.; Farukhshin, I.; Nizamutdinov, A.; Semashko, V.; Lovchev, A.; Naumov, A.

    2014-11-01

    The influence of modification of organic glass by additives new derivatives of thiazole and thiourea on the spectral-fluorescent and lasing characteristics of the Rhodamine 6G laser dye has been investigated. For the sample modified by additive - N-(4-carbomethoxy- 5-phenyl-thiazol-2-yl)-N'-phenylthiourea taken in amounts of 0.01 mol% the maximum rise of the absorption and fluorescence intensity to compare with the unmodified sample 1.3 and 2.3 times, respectively, was detected. The 8.3 times more lasing energy, and the 7.3 times higher laser photostability has been achieved.

  13. Active Media Studies for PASER

    SciTech Connect

    Antipov, Sergey P.; Kanareykin, Alexei; Schoessow, Paul; Schaechter, Levi

    2009-01-22

    The Particle Acceleration by Stimulated Emission of Radiation (PASER) is a concept that is based on the direct transfer of energy from active medium to a charged particle beam. The PASER was originally formulated and demonstrated for optical (laser) media; we are pursuing a PASER demonstration experiment based on an optically pumped paramagnetic medium active in the X-band. The activity in this case is produced via Zeeman Effect. We report on the development of an active medium based on fullerene (C{sub 60}). Various aspects like temperature dependence, concentration effects and the role of the host media are presented. Application of the technology to accelerators and microwave components will be discussed.

  14. Three-block model of the kinetics of vibrationally excited I{sub 2}(X) molecules in the active media of oxygen - iodine lasers

    SciTech Connect

    Pichugin, S Yu

    2012-09-30

    A three-block model of the kinetics of vibrationally excited I{sub 2}(X) molecules in the active media of chemical oxygen - iodine lasers is developed. Instead of the system of equations describing a change in the concentrations of I{sub 2}(X, u) (u=0 - 47) molecules, this model uses equations for the total concentrations of iodine molecules belonging to the blocks of vibrational levels with u {<=} 10, u = 11 - 24, and u {>=} 25. Effective deactivation rate constants of I{sub 2}(X, 11 {<=} u {<=} 24) molecules are found for laser media of different compositions. The results of calculations performed using the proposed model agree with experimental data and are close to the parameters calculated previously by using the total system of equations for populations of individual vibrational levels of I{sub 2}(X, u). (laser applications and other topics in quantum electronics)

  15. ACTIVE MEDIA: Specific features of thermal regimes in rectangular laser slabs under steady-state pumping

    NASA Astrophysics Data System (ADS)

    Alpat'ev, A. N.; Smirnov, V. A.; Shcherbakov, Ivan A.

    2010-01-01

    We continue to investigate the phenomena related to smoothing of temperature profiles in rectangular laser slabs and to an increase in the thresholds of their breakdown under optical pumping with variations in the slab optical density [the effect of smoothing of thermooptical inhomogeneities (STOI effect)]. It is found that the STOI effect is observed not only with increasing but also with decreasing optical density if this occurs due to a decrease in the sample thickness. The dependence of the maximum temperature difference inside the slab on its optical density at the instant of its thermal breakdown is calculated. It is shown that the variations in the optical density caused by variations in both the absorption coefficient and geometric dimensions of the slab differently affect the order of occurrence of two undesirable events — destruction of the slab or boiling of cooling water — with increasing pump power. The calculated relationships reveal two optical density regions corresponding to different orders of occurrence of these events. The maximum allowable temperatures in each region are determined.

  16. Blue laser inorganic write-once media

    NASA Astrophysics Data System (ADS)

    Chen, Bing-Mau; Yeh, Ru-Lin

    2004-09-01

    With the advantages of low cost, portability and compliance with ROM disc, write once disk has become the most popular storage media for computer and audio/video application. In addition, write once media, like CD-R and DVD-/+ R, are used to store permanent or nonalterable information, such as financial data transitions, legal documentation, and medical data. Several write once recording materials, such as TeO[1], TeOPd[2] and Si/Cu [3] have been proposed to realize inorganic write once media. Moreover, we propose AlSi alloy [4] to be used for recording layer of write once media. It had good recording properties in DVD system although the reflectivity is too low to be used for DVD-R disk. In this paper, we report the further results in blue laser system, such as the static and dynamic characteristics of write once media.

  17. Solid-state active media based on aminocoumarins

    SciTech Connect

    Kopylova, T N; Mayer, G V; Samsonova, L G; Svetlichnyi, Valerii A; Reznichenko, A V; Dolotov, S M; Ponomarenko, E P; Tavrizova, M A

    2003-06-30

    The lasing properties and photostability of eighteen aminocoumarins in polymethyl methacrylate, methyl methacrylate, and ethanol excited by an excimer XeCl laser are studied. It is shown that coumarins with a fluorinated methyl group and substituents in the third position of the molecule can be promising active media for lasers on polymer matrices doped with dyes. (lasers)

  18. Laser acceleration in novel media

    NASA Astrophysics Data System (ADS)

    Tajima, T.

    2014-05-01

    With newly available compact laser technology [1] we are capable of producing 100 PW-class laser pulses with a single-cycle duration on the femtosecond timescale. With this fs intense laser we can produce a coherent X-ray pulse that is also compressed, well into the hard X-ray regime (˜10 keV) and with a power up to as much as 10 Exawatts. We suggest utilizing these coherent X-rays to drive the acceleration of particles. Such X-rays are focusable far beyond the diffraction limit of the original laser wavelength and when injected into a crystal it forms a metallic-density electron plasma ideally suited for laser wakefield acceleration. If the X-ray field is limited by the Schwinger field at the focal size of ˜100 nm, the achievable energy is 1 PeV over 50 m. (If the X-rays are focused further, much higher energies beyond this are possible). These processes are not limited to only electron acceleration, and if ions are pre-accelerated to beyond GeV they are capable of being further accelerated using a LWFA scheme [2] to similar energies as electrons over the same distance-scales. Such high energy proton (and ion) beams can induce copious neutrons, which can also give rise to intense compact muon beams and neutrino beams that may be portable. High-energy gamma rays can also be efficiently emitted with a bril- liance many orders of magnitude above the brightest X-ray sources by this accelerating process, from both the betatron radiation as well as the dominant radiative-damping dynamics. With the exceptional conditions enabled by this technology we envision a whole scope of new physical phenomena, including: the possibility of laser self-focus in the vacuum, neutron manipulation by the beat of such lasers, zeptosecond spectroscopy of nuclei, etc. Further, we now introduce along with the idea of vacuum as a nonlinear medium, the Schwinger Fiber Accelerator. This is a self-organized vacuum fiber acceleration concept, in which the repeated process of self-focusing and

  19. Laser action in scattering gain media

    NASA Astrophysics Data System (ADS)

    Balachandran, Ram Mohan

    1997-12-01

    Since the discovery of narrow linewidth, isotropic laser emission from scattering gain media by Lawandy, Balachandran, Gomes and Sauvain in 1993, there has been growing interest in understanding the underlying mechanism responsible for the observed emission properties of the system. This thesis addresses the spectral, spatial and temporal characteristics of the emission. The experimental results show a well-defined threshold in the input-output of the emission with a corresponding collapse in the emission linewidth in the same way as a conventional reflective cavity laser. Furthermore, the threshold was found to decrease with an increase in the scatterer concentration. These results suggest a laser process as the underlying mechanism for the observed emission properties. A laser model is described using Monte Carlo simulation of the multiple scattering problem. Feedback is quantified by measuring the fraction of photons that leave and return to the gain volume. These quantities along with the average length traveled by the emission photon in the gain volume can be used to calculate the threshold gain necessary to initiate laser action in the system. The threshold gain was used in the time dependent laser equations for the population inversion and the laser intensity as a function of the wavelength. Numerical solution of these equations over the entire emission spectrum was carried out and found to be in good agreement with the observed emission characteristics. The laser model was also successfully used to explain the observed bichromatic emission at high pump energies. Injection locking, a process whereby the emission properties of a laser is controlled by that of a secondary seed laser, was also demonstrated in scattering gain media. The locking mechanism was found to be independent of the emission direction. The emission signal saturated with the seed intensity and was found to be limited by the pulsewidth of the seed source. Finally, applications in the area of

  20. ACTIVE MEDIA: Autowaves of the carrier density in PbS1-xSex injection lasers

    NASA Astrophysics Data System (ADS)

    Murashov, M. S.; Shotov, A. P.

    1989-12-01

    An investigation of time dependences of the spectral and spatial distributions of the radiation emitted by pulsed homojunction wide-contact PbS1-xSex lasers revealed excitation of autowaves (self-oscillatory waves) of the free carrier density at two similar frequencies (≲ 107 Hz). These autowaves resulted in simultaneous emission of laser radiation of two types, associated with modulation of the refractive index and of the optical gain. The width of the channels was governed by the thickness of the laser diode wafer, but was independent of the resonator width. The transverse (along with p-n junction plane) intermode spacing was governed by the amplitude and spatial period (channel width) of the autowaves. A study was made of the influence of the conditions of operation ofthe laser diodes on the autowave parameters. A strong scatter of the threshold current density in a batch of 30 injection lasers with a constant resonator length, formed freshly by four-sided cleaving from a single wafer, was attributed to changes in lateral optical confinement as a result of a change in the resonator width, which was a consequence of interference between the autowaves in the resonator induced by the lateral faces of the crystal.

  1. ACTIVE MEDIA: Electronic and thermal lensing in diode end-pumped Yb:YAG laser rods and discs

    NASA Astrophysics Data System (ADS)

    Antipov, Oleg L.; Anashkina, E. A.; Fedorova, K. A.

    2009-12-01

    The lensing effects in diode end-pumped Yb:YAG laser rods and discs are studied. Two mechanisms of refractive-index changes are taken into account, thermal and electronic (due to the difference between the excited- and ground-state Yb3+ polarisabilities), as well as pump-induced deformation of the laser crystal. Under pulsed pumping, the electronic lensing effect prevails over the thermal one in both rods and discs. In rods pumped by a highly focused cw beam, the dioptric power of the electronic lens exceeds that of the thermal lens, whereas in discs steady-state lensing is predominantly due to the thermal mechanism.

  2. Microbiologically active nanocomposite media

    NASA Astrophysics Data System (ADS)

    Petranovskii, Vitalii; Panina, Lyudmila; Bogomolova, Eugenia; Belostotskaya, Galina

    2003-07-01

    The most recent approach to the development of novel antimicrobial and antifungal agents is based on the application of synthetic and natural zeolites, because zeolites are known to be the carrier and slow releaser of the heavy metals with olygodynamic properties. The microbiological activity of the ion-exchanged zeolites is attributed to the ionic state of the metal sreleased from the zeolites by ion re-exchange. In the present work we used low cost natural clinoptilolite (Cli) as a substrate for copper and silver in different states. The state of oxidation of the exchanged metal in zeolite with supported Cu and Ag species (in the form of cations, small clusters, sub-coloidal particles, large particles) in order to fit them to fulfill the following criteria: to demonstrate their high protective abilities against fungi and long-term stability. The study of structure of samples with XRD, UV-visible spectroscopy, FTIR, their stability with temperature and during storage was carried out for obtaining the correct correlation with microbiological activity.

  3. LASER BIOLOGY: Laser spectroscopy technique for estimating the efficiency of photosensitisers in biological media

    NASA Astrophysics Data System (ADS)

    Ryabova, A. V.; Stratonnikov, Aleksandr A.; Loshchenov, V. B.

    2006-06-01

    A fast and highly informative method is presented for estimating the photodynamic activity of photosensitisers. The method makes it possible to determine the rate of photodegradation in erythrocyte-containing biological media in nearly in vivo conditions, estimate the degree of irreversible binding of oxygen dissolved in the medium during laser irradiation in the presence of photosensitisers, and determine the nature of degradation of photosensitisers exposed to light (photobleaching).

  4. Raising the efficiency of intracavity laser pumping of selectively absorbing media

    SciTech Connect

    Aubakirov, R.G.; Murzin, A.G.; Fromzel, V.A.

    1983-09-01

    Conditions providing for maximum efficiency during intracavity laser pumping of active media have been analyzed. It is shown that the occasional parasitic oscillation shift of the pumping laser can be eliminated without any loss of laser pumping efficiency. An experimental study has been made on two possible energetically efficient methods of stabilizing the oscillation spectrum of a neodymium glass laser with an intracavity load of ytterbium-erbium glass: introduction of a small-base Fabry-Perot etalon into the cavity and use of mirrors with a sharp drop of the spectral characteristic as laser cavity mirrors. An optimum variant of the multilayered coating of such mirrors has been selected.

  5. Studies of new media radiation induced laser

    NASA Technical Reports Server (NTRS)

    Han, K. S.; Shiu, Y. J.; Raju, S. R.; Hwang, I. H.; Tabibi, B.

    1984-01-01

    Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed.

  6. ACTIVE MEDIA: Chromium-activated forsterite crystal as the passive Q switch in the cavity of an Nd:YAG laser and as the active medium in an Nd:YAG—Cr:forsterite laser system

    NASA Astrophysics Data System (ADS)

    Skripko, G. A.; Tarazevich, I. G.

    1996-03-01

    An investigation was made of the generation and self-modulation of the λ = 1.064 and 1.25 μm radiation in an Nd:YAG—Cr:forsterite laser system. The advantages of this system over those with traditional methods were demonstrated. The feasibility of self-control of the rate of pumping of the Cr:forsterite crystal was revealed and recommendations on optimisation of the system were developed.

  7. ACTIVE MEDIA: Gain dynamics in a pulsed laser amplifier on CO-He, CO-N2 and CO-O2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Vetoshkin, S. V.; Ionin, Andrei A.; Klimachev, Yu M.; Kozlov, A. Yu; Kotkov, A. A.; Rulev, O. A.; Seleznev, L. V.; Sinitsyn, D. V.

    2007-02-01

    Small-signal gain (SSG) dynamics G(t) in the active medium of a pulsed laser amplifier operating on the v+1→vP(J) vibrational-rotational transitions of the CO molecule, including high (v > 15) vibrational transitions, is studied experimentally. It is demonstrated that as the vibrational number increases from 7 to 31, G changes with time slower, while Gmax decreases in this case by three times. It is found that at a fixed value of v the rate of the SSG rise increases with increasing the rotational number J > 6. It is shown that in oxygen-containing gas mixtures (CO:O2 = 1:19) the value of Gmax at low vibrational levels (for v < 13) can substantially exceed Gmax in mixtures containing nitrogen (CO:N2 = 1:19) instead of oxygen. It is found that the efficiency (47%) of a CO laser on mixtures with a high concentration of oxygen considerably exceeds the efficiency (30%) of a CO laser operating on a nitrogen-containing mixture.

  8. Laser spectroscopy technique for estimating the efficiency of photosensitisers in biological media

    SciTech Connect

    Ryabova, A V; Stratonnikov, Aleksandr A; Loshchenov, V B

    2006-06-30

    A fast and highly informative method is presented for estimating the photodynamic activity of photosensitisers. The method makes it possible to determine the rate of photodegradation in erythrocyte-containing biological media in nearly in vivo conditions, estimate the degree of irreversible binding of oxygen dissolved in the medium during laser irradiation in the presence of photosensitisers, and determine the nature of degradation of photosensitisers exposed to light (photobleaching). (laser biology)

  9. Semihumid gels as matrices for laser media

    NASA Astrophysics Data System (ADS)

    Larrue, Denis; Zarzycki, J.; Canva, Michael; Georges, Patrick M.; Brun, Alain

    1992-12-01

    Laser dyes were trapped in SiO2 xerogel host matrices to obtain a solid state dye laser. The evolution of the mechanical properties of two kinds of matrices, 'classic' and 'sono' gels, was followed during drying. A new impregnation process was performed on these xerogels: impregnation with a 'sono' sol. The influence of this treatment on certain physical and mechanical properties of the resulting impregnated gels was studied. The results indicate that impregnation substantially improves hardness, elastic modulus and fracture stress. The samples can then be easily polished to obtain optical quality surfaces and be used in a laser cavity. Moreover, optical properties related to laser emission of these materials such as efficiency, lifetime and longevity are better when the laser dye doped xerogels are impregnated. The organic dye molecule used was sulforhodamine 640, and results were obtained six months after their synthesis, with a pump beam working at a 5 Hz repetition rate with 450 (mu) J/pulse energy level. With the first pump shot on a fixed point of the samples, tunability from 600 to 650 nm, 60 (mu) J threshold, 2600 pump shots lifetime and a 10.5% slope efficiency were achieved using an impregnated 'sono' gel matrix.

  10. Pattern formation in transparent media using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Thomas, J.; Bernard, R.; Alti, K.; Dharmadhikari, A. K.; Dharmadhikari, J. A.; Bhatnagar, A.; Santhosh, C.; Mathur, D.

    2013-09-01

    We report results of a systematic study of the morphology of laser-written structures within transparent media like fused silica, borosilicate glass (BK7), and polymethylmethylacrylate (PMMA) using a high-energy, 5.1 MHz repetition rate, femtosecond laser oscillator. Depending on experimental conditions, both smooth channels as well as dot patterns can be laser-written. The periodicity of the written dots is readily controlled by the energy dose, a single parameter that encompasses laser energy, translation speed at fixed repetition rate, and focusing conditions. We discover the importance of the direction in which laser-writing is carried out: the periodicity of the dot patterns written at fixed energy dose but with opposite writing directions is significantly different. In PMMA, extremely large rod-like structures (˜200 µm) are observed whose formation is also dependent on writing direction. We quantify guidance of 632 nm and 830 nm light in structures written in BK7.

  11. Birefringence of solid-state laser media: broadband tuning discontinuities and application to laser line narrowing

    SciTech Connect

    Krasinski, J.S.; Band, Y.B.; Chin, T.; Heller, D.F.; Morris, R.C.; Papanestor, P.

    1989-04-15

    Spectral consequences that result from using birefringent media with broadband gain inside of laser cavities containing polarizing elements are described. We show that the laser intensity is modulated as a function of the output frequency unless the cavity elements are carefully aligned so that their polarization axis coincides with a principal optical axis of the gain medium. Analysis of the tuning characteristics of a birefringent polarization-dependent gain medium is exploited to provide a simple method for line narrowing the laser output. By introduction of an intracavity birefringent compensator the narrow-band output can be continuously tuned. Experimental results for alexandrite lasers are presented.

  12. Coupled-resonator vertical-cavity lasers with two active gain regions

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-05-20

    A new class of coupled-resonator vertical-cavity semiconductor lasers has been developed. These lasers have multiple resonant cavities containing regions of active laser media, resulting in a multi-terminal laser component with a wide range of novel properties.

  13. Highly concentrated active nonlinear media based on oxides

    SciTech Connect

    Bakin, D.V.; Dorozhkin, L.M.; Krasilov, Yu.I.; Kuznetsov, N.T.; Potemkin, A.V.; Tadzhi-Aglaev, K.S.; Shestakov, A.V.

    1987-07-01

    Important characteristics of highly concentrated active nonlinear media were studied which were based on oxide compounds of phosphates, niobates, tantalates, and titanates of neodymium with alkaline earth metals. Compounds of the indicated classes were synthesized and their spectral luminescent and nonlinear optical properties were studied. Single crystals were grown from the selected compounds (5-8mm) and preliminary measurements of the laser and nonlinear optical parameters were taken. Formulas are given for materials that demonstrated high nonlinear and luminescent properties simultaneously. Spectroscopic and nonlinear optical properties of some oxygen compounds of rare earth elements are shown.

  14. Stimulated Raman scattering of laser dye mixtures dissolved in multiple scattering media

    SciTech Connect

    Yashchuk, V P; Komyshan, A O; Tikhonov, E A; Olkhovyk, L A

    2014-10-31

    Stimulated Raman scattering (SRS) of a mixture of rhodamine 6G and pyrromethene 605 laser dyes in vesicular films is studied. It is shown that a peculiar interaction of dyes occurs under conditions of multiple scattering of light from vesicles. This interaction manifests itself as SRS excitation of one of the dyes by random lasing of the other dye, provided that the random lasing spectrum overlaps the Stokes lines of the first dye. In addition, there is energy transfer between molecules of these dyes if their luminescence and absorption spectra overlap. The results obtained confirm that the mechanism of SRS from laser dyes in multiple scattering media is similar to that in coherent-active Raman spectroscopy. These results extend the possibility of determining the vibrational spectrum of dye molecules from their secondary radiation in these media. (nonlinear optical phenomena)

  15. Laser refrigeration of hydrothermal nanocrystals in physiological media

    PubMed Central

    Roder, Paden B.; Smith, Bennett E.; Zhou, Xuezhe; Crane, Matthew J.; Pauzauskie, Peter J.

    2015-01-01

    Coherent laser radiation has enabled many scientific and technological breakthroughs including Bose–Einstein condensates, ultrafast spectroscopy, superresolution optical microscopy, photothermal therapy, and long-distance telecommunications. However, it has remained a challenge to refrigerate liquid media (including physiological buffers) during laser illumination due to significant background solvent absorption and the rapid (∼ps) nonradiative vibrational relaxation of molecular electronic excited states. Here we demonstrate that single-beam laser trapping can be used to induce and quantify the local refrigeration of physiological media by >10 °C following the emission of photoluminescence from upconverting yttrium lithium fluoride (YLF) nanocrystals. A simple, low-cost hydrothermal approach is used to synthesize polycrystalline particles with sizes ranging from <200 nm to >1 μm. A tunable, near-infrared continuous-wave laser is used to optically trap individual YLF crystals with an irradiance on the order of 1 MW/cm2. Heat is transported out of the crystal lattice (across the solid–liquid interface) by anti-Stokes (blue-shifted) photons following upconversion of Yb3+ electronic excited states mediated by the absorption of optical phonons. Temperatures are quantified through analysis of the cold Brownian dynamics of individual nanocrystals in an inhomogeneous temperature field via forward light scattering in the back focal plane. The cold Brownian motion (CBM) analysis of individual YLF crystals indicates local cooling by >21 °C below ambient conditions in D2O, suggesting a range of potential future applications including single-molecule biophysics and integrated photonic, electronic, and microfluidic devices. PMID:26589813

  16. Laser refrigeration of hydrothermal nanocrystals in physiological media.

    PubMed

    Roder, Paden B; Smith, Bennett E; Zhou, Xuezhe; Crane, Matthew J; Pauzauskie, Peter J

    2015-12-01

    Coherent laser radiation has enabled many scientific and technological breakthroughs including Bose-Einstein condensates, ultrafast spectroscopy, superresolution optical microscopy, photothermal therapy, and long-distance telecommunications. However, it has remained a challenge to refrigerate liquid media (including physiological buffers) during laser illumination due to significant background solvent absorption and the rapid (∼ ps) nonradiative vibrational relaxation of molecular electronic excited states. Here we demonstrate that single-beam laser trapping can be used to induce and quantify the local refrigeration of physiological media by >10 °C following the emission of photoluminescence from upconverting yttrium lithium fluoride (YLF) nanocrystals. A simple, low-cost hydrothermal approach is used to synthesize polycrystalline particles with sizes ranging from <200 nm to >1 μm. A tunable, near-infrared continuous-wave laser is used to optically trap individual YLF crystals with an irradiance on the order of 1 MW/cm(2). Heat is transported out of the crystal lattice (across the solid-liquid interface) by anti-Stokes (blue-shifted) photons following upconversion of Yb(3+) electronic excited states mediated by the absorption of optical phonons. Temperatures are quantified through analysis of the cold Brownian dynamics of individual nanocrystals in an inhomogeneous temperature field via forward light scattering in the back focal plane. The cold Brownian motion (CBM) analysis of individual YLF crystals indicates local cooling by >21 °C below ambient conditions in D2O, suggesting a range of potential future applications including single-molecule biophysics and integrated photonic, electronic, and microfluidic devices. PMID:26589813

  17. Media Literacy Art Education: Logos, Culture Jamming, and Activism

    ERIC Educational Resources Information Center

    Chung, Sheng Kuan; Kirby, Michael S.

    2009-01-01

    Critical media literacy art education teaches students to: (1) appreciate the aesthetic qualities of media; (2) critically negotiate meanings and analyze media culture as products of social struggle; and (3) use media technologies as instruments of creative expression and social activism. In concert with art education practices oriented toward…

  18. PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Kinetic model of the active medium of an XeCl laser pumped by an electron beam

    NASA Astrophysics Data System (ADS)

    Boĭchenko, A. M.; Derzhiev, V. I.; Zhidkov, A. G.; Yakovlenko, Sergei I.

    1989-02-01

    Kinetic models of active media of an XeCl laser are developed for the case when these media are diluted by various buffer gases (helium, neon, argon) and the laser is pumped by an electron beam. The results of the calculations are in satisfactory agreement with experimental data.

  19. Femtosecond laser ablation of brass in air and liquid media

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2013-06-01

    Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

  20. Compact laser sources for laser designation, ranging and active imaging

    NASA Astrophysics Data System (ADS)

    Goldberg, Lew; Nettleton, John; Schilling, Brad; Trussel, Ward; Hays, Alan

    2007-04-01

    Recent advances in compact solid sate lasers for laser designation, eye-safe range finding and active imaging are described. Wide temperature operation of a compact Nd:YAG laser was achieved by end pumping and the use of multi-λ diode stacks. Such lasers enabled construction of fully operational 4.7 lb laser designator prototypes generating over 50 mJ at 10-20 Hz PRF. Output pulse energy in excess of 100 mJ was demonstrated in a breadboard version of the end-pumped laser. Eye-safe 1.5 μm lasers based on flash-pumped, low PRF, Monoblock lasers have enabled compact STORM laser range finders that have recently been put into production. To achieve higher optical and electrical efficiency needed for higher PRF operation, Monoblock lasers were end-pumped by a laser diode stack. Laser diode end-pumped Monoblock lasers were operated at 10-20 Hz PRF over a wide temperature range (-20 to +50 °C). Compared with bulk compact solid state lasers, fiber lasers are characterized by lower pulse energy, higher PRF's, shorter pulses and higher electrical efficiency. An example of fiber lasers suitable for LIDAR, and atmospheric measurement applications is described. Eye-safe, low intensity diode pumped solid state green warning laser developed for US Army checkpoint and convoy applications is also described.

  1. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A.; Soules, Thomas F.; Fochs, Scott N.; Rotter, Mark D.; Letts, Stephan A.

    2011-02-22

    A novel method and apparatus for suppressing ASE and/or parasitic oscillation modes in a laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges to a predetermined electromagnetic absorbing material arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE, parasitic oscillation modes and/or residual pump energy can be effectively suppressed.

  2. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A.; Soules, Thomas F.; Fochs, Scott N.; Rotter, Mark D.; Letts, Stephan A.

    2008-12-09

    A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges using a substantially high index bonding elastomer or epoxy to a predetermined electromagnetic absorbing arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

  3. Optically pumped planar waveguide lasers: Part II: Gain media, laser systems, and applications

    NASA Astrophysics Data System (ADS)

    Grivas, Christos

    2016-01-01

    The field of optically pumped planar waveguide lasers has seen a rapid development over the last two decades driven by the requirements of a range of applications. This sustained research effort has led to the demonstration of a large variety of miniature highly efficient laser sources by combining different gain media and resonator geometries. One of the most attractive features of waveguide lasers is the broad range of regimes that they can operate, spanning from continuous wave and single frequency through to the generation of femtosecond pulses. Furthermore, their technology has experienced considerable advances to provide increased output power levels, deriving benefits from the relative immunity from the heat generated in the gain medium during laser operation and the use of cladding-pumped architectures. This second part of the review on optically pumped planar waveguide lasers provides a snapshot of the state-of-the-art research in this field in terms of gain materials, laser system designs, and as well as a perspective on the status of their application as real devices in various research areas.

  4. Envelope evolution of a laser pulse in an active medium

    SciTech Connect

    Fisher, D.L.; Tajima, T.; Downer, M.C.; Siders, C.W.

    1994-11-01

    The authors show that the envelope velocity, v{sub env}, of a short laser pulse can, via propagation in an active medium, be made less than, equal to, or even greater than c, the vacuum phase velocity of light. Simulation results, based on moving frame propagation equations coupling the laser pulse, active medium and plasma, are presented, as well as equations that determines the design value of super- and sub-luminous v{sub env}. In this simulation the laser pulse evolves in time in a moving frame as opposed to their earlier work where the profile was fixed. The elimination of phase slippage and pump depletion effects in the laser wakefield accelerator is discussed as a particular application. Finally they discuss media properties necessary for an experimental realization of this technique.

  5. Spatially and temporally resolved temperature measurement in laser media.

    PubMed

    Körner, Jörg; Yue, Fangxin; Hein, Joachim; Kaluza, Malte C

    2016-06-01

    A technique to measure the spatially resolved temperature distribution in a laser medium is presented. It is based on the temperature dependence of the absorption cross section close to the zero-phonon line of the active medium. Since other materials in the beam path exhibit a high (and constant) transmission at this wavelength, the method can easily be applied in realistic amplifier setups. The method was successfully tested on three different samples, which were pumped by a pulsed laser diode with up to 150 W average power: side-cooled Yb:YAG and Yb:fluoride-phosphate glass at room temperature and face-cooled Yb:CaF2 at 120 K. PMID:27244405

  6. Laser based analysis using a passively Q-switched laser employing analysis electronics and a means for detecting atomic optical emission of the laser media

    DOEpatents

    Woodruff, Steven D.; Mcintyre, Dustin L.

    2016-03-29

    A device for Laser based Analysis using a Passively Q-Switched Laser comprising an optical pumping source optically connected to a laser media. The laser media and a Q-switch are positioned between and optically connected to a high reflectivity mirror (HR) and an output coupler (OC) along an optical axis. The output coupler (OC) is optically connected to the output lens along the optical axis. A means for detecting atomic optical emission comprises a filter and a light detector. The optical filter is optically connected to the laser media and the optical detector. A control system is connected to the optical detector and the analysis electronics. The analysis electronics are optically connected to the output lens. The detection of the large scale laser output production triggers the control system to initiate the precise timing and data collection from the detector and analysis.

  7. Laser-Induced Fluorescence Analysis of Protein-Based Binding Media

    NASA Astrophysics Data System (ADS)

    Nevin, A.; Cather, S.; Anglos, D.; Fotakis, Costas

    Laser-induced fluorescence of intrinsic fluorophores of organic media found in paintings (casein, animal glue and egg proteins) provides a means of characterising general classes of media depending on the amino acid composition and presence of degradation cross-linkages. Wavelength dependence of spectra is investigated for non-destructive and non-invasive analyses of thin films of protein-based binding media.

  8. Laser Beam Propagation Through Inhomogeneous Media with Shock-Like Profiles: Modeling and Computing

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Ida, Nathan

    1997-01-01

    Wave propagation in inhomogeneous media has been studied for such diverse applications as propagation of radiowaves in atmosphere, light propagation through thin films and in inhomogeneous waveguides, flow visualization, and others. In recent years an increased interest has been developed in wave propagation through shocks in supersonic flows. Results of experiments conducted in the past few years has shown such interesting phenomena as a laser beam splitting and spreading. The paper describes a model constructed to propagate a laser beam through shock-like inhomogeneous media. Numerical techniques are presented to compute the beam through such media. The results of computation are presented, discussed, and compared with experimental data.

  9. Media-Smart Youth: Eat, Think, and Be Active!

    ERIC Educational Resources Information Center

    US Department of Health and Human Services, 2005

    2005-01-01

    This document provides an overview for the Media-Smart Youth Program, which is an education program that helps young people ages 11 to 13 understand the complex media world around them, and how it can influence their health--especially in regard to nutrition and physical activity. The following questions are answered in this document: (1) Why is…

  10. Laser heating of an absorbing and conducting media applied to laser flash property measurements

    SciTech Connect

    Gritzo, L.A.; Anderson, E.E.

    1993-12-31

    The laser flash technique is widely used for determining the thermal diffusivity of a sample. In this work, the temperature distribution throughout the sample is investigated, identifying localized, highly-heated regions near the front surface of the sample as a function of: (1) pulse duration, (2) incident beam uniformity, and (3) sample opacity. These high-temperature regions result in an increase in the uncertainty due to temperature-dependent properties, an increase in the heat loss from the sample, and an increased risk of sample damage. The temperature within a semi-transparent media is also investigated in order to establish a regime for which the media can reasonably be considered as opaque. This analysis illustrates that, for same total energy deposition, treatment of the incident energy as a continuous heat source, as opposed to an infinitesimal pulse of energy, results in a factor of 2 increase in the front surface temperature during heating. Also, for the same total energy deposition and approximate beam size, use of a Gaussian intensity distribution increases the front surface temperature during heating by more than a factor of 2 as compared to the use of a uniform temperature distribution. By analyzing the front surface temperature of an absorbing and conducting semi-transparent sample subjected to a Gaussian intensity distribution, it is concluded that the media can be treated as opaque, (i.e. the energy can be applied as a boundary condition) for {var_epsilon} = kd > 50, where k is the extinction coefficient and d is the beam diameter. For materials with a sufficiently small absorption coefficient and thermal diffusivity, a closed-form solution suitable for design use is presented for the front-surface temperature at a location coincident with the beam centerline.

  11. Dependence of gold nanoparticle production on pulse duration by laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Riabinina, Daria; Chaker, Mohamed; Margot, Joëlle

    2012-04-01

    The dependence on laser fluence and laser pulse duration of size, size distribution and concentration of gold nanoparticles synthesized by laser ablation in liquid media was investigated. It was demonstrated that increasing laser energy from 1 to 5 mJ/pulse enhances the ablation rate by a factor of 100. The behavior of the ablation rate, hence of the nanoparticle concentration, as a function of pulse duration (varied from 40 fs to 200 ps) was found to strongly differ from that in air, which can be explained by photoionization and important losses of laser energy in the femtosecond regime. The optimal pulse duration for maximum ablation rate in liquid media was found to be equal to 2 ps.

  12. Laser-Induced Nuclear Activation Studies

    NASA Astrophysics Data System (ADS)

    Simons, Andrew; Gardner, Matthew; Thompson, Peter; Allwork, Christopher; Rubery, Michael; Clarke, Robert

    2009-10-01

    A series of experimental campaigns, each designed to activated carefully selected materials, have been conducted with high- power short-pulse laser systems. These relatively new CPA laser systems can produce large bursts of X-rays, electrons, protons and other ions. Characterising the nature of these mixed radiation fields is neccessary for both physics experiments and facility safety. Three campaigns, two with the HELEN laser faility at AWE and one with the Vulcan Petawatt laser at the Rutherford Appleton laboratory, were designed to accelerate protons. These protons irradiated secondary activation targets of pure foils and various optical glasses, typically those used in target chamber environments such as those found at NIF, Omega and AWE's Orion laser facility. This talk discusses these experiments and covers the production of laser-produced radiation fields, the selection of activation targets, the interpretation the radioactive decay signals, the current status of the analysis and the future applications of this research.

  13. Solid state laser media driven by remote nuclear powered fluorescence

    SciTech Connect

    Prelas, M.A.

    1991-01-16

    An apparatus is provided for driving a solid state laser by a nuclear powered fluorescence source which is located remote from the fluorescence source. A nuclear reaction produced in a reaction chamber generates fluorescence or photons. The photons are collected from the chamber into a waveguide, such as a fiber optic waveguide. The waveguide transports the photons to the remote laser for exciting the laser.

  14. Solid state laser media driven by remote nuclear powered fluorescence

    DOEpatents

    Prelas, Mark A.

    1992-01-01

    An apparatus is provided for driving a solid state laser by a nuclear powered fluorescence source which is located remote from the fluorescence source. A nuclear reaction produced in a reaction chamber generates fluorescence or photons. The photons are collected from the chamber into a waveguide, such as a fiber optic waveguide. The waveguide transports the photons to the remote laser for exciting the laser.

  15. Nuclear fission fragment excitation of electronic transition laser media

    NASA Technical Reports Server (NTRS)

    Lorents, D. C.; Mccusker, M. V.; Rhodes, C. K.

    1976-01-01

    Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media.

  16. Comparative analysis of the use of various solid-state laser media for the self-starting of four-wave PCW generation in a loop laser resonator

    NASA Astrophysics Data System (ADS)

    Smetanin, Sergei N.

    2013-01-01

    A generalised theory has been used to carry out a comparative analysis of the use of various four-level and quasi-threelevel media for the self-starting of degenerate four-wave mixing PCW generation directly in a laser medium placed in a loop resonator. It has been shown that quasi-three-level media can compete with four-level media at long upper laser level lifetimes and increased pump intensities. The most attractive solid-state laser media for four-wave PCW generation have been identified that have the highest deposited energy at a given pump intensity. In addition to neodymium-doped crystals, which are already widely used for four-wave PCW generation, promising materials are fourlevel chromium-doped media, e.g. alexandrite and Cr : LiCAF, and quasi-three-level media with the longest upper laser level lifetime, such as Yb : YAG and Tm, Ho : YAG, at high pump intensities.

  17. Social media for Europlanet Public Engagement Activities

    NASA Astrophysics Data System (ADS)

    Giacomini, L.; Gröschl, M.; Media Centre, Europlanet; Node Network, National

    2011-10-01

    In this work we will present an overview of all social media developed and used by Europlanet EPO office as tools to popularize planetology topics to a larger public and create a network of European researchers interested in collaborating at the task. The presentation will include the "institutional" outreach website for Europlanet Research Infrastructure but also social tools as Facebook and Twitter accounts. We will attempt to analyze the local results of this web 2.0 approach in different countries all over Europe, studying different examples of social web tools developed and implemented in Europlanet member countries.

  18. Perfluorobutyl iodides as gain media for a solar-pumped laser amplifier

    NASA Technical Reports Server (NTRS)

    Lee, Ja H.; Weaver, Willard R.; Tabibi, Bagher M.

    1988-01-01

    Perfluorobutyl iodides were studied as media for an iodine photodissociation laser amplifier, and photoabsorption cross sections were measured. The results indicate superior performance for t-C4F9I compared to that for n-C4F9I. The gain of n-C4F9I is found to be equal to that of n-C3F7I. The implications of these findings for space-based solar-pumped lasers are discussed.

  19. Laser-induced local heating of moving multilayer media.

    PubMed

    Mansuripur, M; Connell, G A

    1983-03-01

    Earlier work on the local heating of stationary multilayer structures by focused laser light has been extended to deal with nonstationary situations. The numerical procedures described here are therefore applicable to many important technologies including optical recording, thermal marking, and laser annealing. We demonstrate this in two examples, namely, the effects of readout intensity on the readout signal from a quadrilayer magnetooptic disk and the writing threshold for ablative materials in single-layer and three-layer structures. PMID:18195853

  20. Active polarimeter optical system laser hazard analysis.

    SciTech Connect

    Augustoni, Arnold L.

    2005-07-01

    A laser hazard analysis was performed for the SNL Active Polarimeter Optical System based on the ANSI Standard Z136.1-2000, American National Standard for Safe Use of Lasers and the ANSI Standard Z136.6-2000, American National Standard for Safe Use of Lasers Outdoors. The Active Polarimeter Optical System (APOS) uses a pulsed, near-infrared, chromium doped lithium strontium aluminum fluoride (Cr:LiSAF) crystal laser in conjunction with a holographic diffuser and lens to illuminate a scene of interest. The APOS is intended for outdoor operations. The system is mounted on a height adjustable platform (6 feet to 40 feet) and sits atop a tripod that points the beam downward. The beam can be pointed from nadir to as much as 60 degrees off of nadir producing an illuminating spot geometry that can vary from circular (at nadir) to elliptical in shape (off of nadir). The JP Innovations crystal Cr:LiSAF laser parameters are presented in section II. The illuminating laser spot size is variable and can be adjusted by adjusting the separation distance between the lens and the holographic diffuser. The system is adjusted while platform is at the lowest level. The laser spot is adjusted for a particular spot size at a particular distance (elevation) from the laser by adjusting the separation distance (d{sub diffuser}) to predetermined values. The downward pointing angle is also adjusted before the platform is raised to the selected operation elevation.

  1. Effects of focusing on third-order nonlinear processes in isotropic media. [laser beam interactions

    NASA Technical Reports Server (NTRS)

    Bjorklund, G. C.

    1975-01-01

    Third-order nonlinear processes in isotropic media have been successfully used for tripling the efficiency of high-power laser radiation for the production of tunable and fixed-frequency coherent vacuum UV radiation and for up-conversion of IR radiation. The effects of focusing on two processes of this type are studied theoretically and experimentally.

  2. Activism or "Slacktivism?": Digital Media and Organizing for Social Change

    ERIC Educational Resources Information Center

    Glenn, Cerise L.

    2015-01-01

    The influence of social media and technological developments has changed how groups and organizations advocating for social change generate awareness and participation in their causes. In this single class activity students will (a) analyze notions of activism and "slacktivism" from scholarly and popular sources to apply these concepts…

  3. Physical activity in the mass media: an audience perspective.

    PubMed

    Smith, Ben J; Bonfiglioli, Catriona M F

    2015-04-01

    Physical activity's role in promoting health is highlighted in public health campaigns, news and current affairs, reality television and other programs. An investigation of audience exposure, beliefs and reactions to media portrayals of physical activity offers insights into the salience and influence of this communication. An audience reception study was conducted involving in-depth interviews with 46 adults in New South Wales, Australia. The sample was stratified by gender, age group, area of residence and body mass index. Most respondents could only recall media coverage of physical activity with prompting. Television was the primary channel of exposure, with reality television the dominant source, followed by news programs and sports coverage. The messages most readily recalled were the health risks of inactivity, especially obesity, and the necessity of keeping active. Physical activity was regarded as a matter of personal volition, or for children, parental responsibility. Respondents believed that the media had given physical activity inadequate attention, focused too heavily on risks and not provided practical advice. In Australia, there is a need to counter the framing of physical activity by reality television, and engage the media to generate understanding of the socioecological determinants of inactivity. Physical activity campaigns should deliver positive and practical messages. PMID:25697582

  4. Physical Activity in the Mass Media: An Audience Perspective

    ERIC Educational Resources Information Center

    Smith, Ben J.; Bonfiglioli, Catriona M. F.

    2015-01-01

    Physical activity's role in promoting health is highlighted in public health campaigns, news and current affairs, reality television and other programs. An investigation of audience exposure, beliefs and reactions to media portrayals of physical activity offers insights into the salience and influence of this communication. An audience reception…

  5. Developing Intercultural Competencies Using Activities with Different Media

    ERIC Educational Resources Information Center

    Marchis, Iuliana; Ciascai, Liliana; Saial, Joaquim

    2008-01-01

    The aim of this article is to present some activities with multimedia, which can be used in intercultural education. The first part of the article presents those intercultural competencies, which have to be developed by the teacher. The second part presents some activities using different types of media for intercultural education purposes. All of…

  6. Laser activated diffuse discharge switch

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    1988-01-01

    The invention is a gas mixture for a diffuse discharge switch which is capable of changing from a conducting state to an insulating state in the presence of electrons upon the introduction of laser light. The mixture is composed of a buffer gas such as nitrogen or argon and an electron attaching gas such as C.sub.6 H.sub.5 SH, C.sub.6 H.sub.5 SCH.sub.3, CH.sub.3 CHO and CF.sub.3 CHO wherein the electron attachment is brought on by indirect excitation of molecules to long-lived states by exposure to laser light.

  7. Refractive Index Matching for Planar Laser-Induced Fluorescence Imaging of Fluid Mixing in Porous Media

    NASA Astrophysics Data System (ADS)

    Roth, E. J.; Tigera, R. G.; Crimaldi, J. P.; Mays, D. C.

    2015-12-01

    Research in porous media is often hampered by the difficulty in making pore-scale observations. By selecting porous media that is refractive index matched (RIM) to the pore fluid, the media becomes transparent. This allows optical imaging techniques such as static light scattering (SLS), dynamic light scattering (DLS), confocal microscopy, and planar laser-induced fluorescence (PLIF) to be employed. RIM is particularly useful for research concerning contaminant remediation in the subsurface, permitting visual observation of plume dynamics at the pore scale. The goal of this research is to explore and assess candidate combinations of porous media, fluid, and fluorescent dye. The strengths and weaknesses of each combination will then be evaluated in terms of safety, cost, and optical quality in order to select the best combination for use with PLIF. Within this framework, top-ranked RIM combinations include Pyrex glass beads, water beads, or granular Nafion saturated in vegetable glycerin, deionized water, and an aqueous solution of 48% isopropanol, respectively. This research lays the groundwork for future efforts to build a flow chamber in which the selected RIM porous media, solution, and dye will be used in evaluating subsurface pumping strategies designed to impose chaotic plume spreading in porous media. Though the RIM porous media explored in this research are selected based on the specifications of a particular experiment, the methods developed for working with and evaluating RIM porous media should be of utility to a wide variety of research interests.

  8. Liquid heat capacity lasers

    DOEpatents

    Comaskey, Brian J.; Scheibner, Karl F.; Ault, Earl R.

    2007-05-01

    The heat capacity laser concept is extended to systems in which the heat capacity lasing media is a liquid. The laser active liquid is circulated from a reservoir (where the bulk of the media and hence waste heat resides) through a channel so configured for both optical pumping of the media for gain and for light amplification from the resulting gain.

  9. Improving Reading Comprehension by Using Media Literacy Activities.

    ERIC Educational Resources Information Center

    Hobbs, Renee

    2001-01-01

    Argues that media literacy activities in the English language arts classroom can promote the strategies of reflective thinking, self-monitoring, close observation, and visualization. Shows how one seventh-grade teacher develops students' understanding of character development by using a film excerpt, a graphic organizer for developing…

  10. Preparation of polyynes by laser ablation of graphite in aqueous media

    NASA Astrophysics Data System (ADS)

    Shin, Seung Keun; Song, Jae Kyu; Park, Seung Min

    2011-04-01

    Polyynes were prepared by liquid-phase laser ablation of a graphite target at 1064 nm and identified by analyzing UV absorption spectra in deionized water and various aqueous solutions. We observed that major UV absorption peaks coincide with the electronic transitions corresponding to linear hydrogen-capped polyynes (C nH 2: n = 6, 8, 10). The peak intensities increased when polyynes were produced by irradiating the target immersed in acidic media, while those were relatively weak in basic media. This leads us to conclude that OH - or H + ions play a certain role in the formation of polyynes.

  11. ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media.

    PubMed

    Honda, Mitsuhiro; Goto, Taku; Owashi, Tatsuki; Rozhin, Alex G; Yamaguchi, Shigeru; Ito, Tsuyohito; Kulinich, Sergei A

    2016-09-14

    ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures. PMID:27507010

  12. Transmission media appropriate laser-microwave solar power satellite system

    NASA Astrophysics Data System (ADS)

    Schäfer, C. A.; Gray, D.

    2012-10-01

    As a solution to the most critical problems with Solar power Satellite (SPS) development, a system is proposed which uses laser power transmission in space to a receiver high in the atmosphere that relays the power to Earth by either cable or microwave power transmission. It has been shown in the past that such hybrid systems have the advantages of a reduction in the mass of equipment required in geostationary orbit and avoidance of radio frequency interference with other satellites and terrestrial communications systems. The advantage over a purely laser power beam SPS is that atmospheric absorption is avoided and outages due to clouds and precipitation will not occur, allowing for deployment in the equatorial zone and guaranteeing year round operation. This proposal is supported by brief literature surveys and theoretical calculations to estimate crucial parameters in this paper. In relation to this concept, we build on a recently proposed method to collect solar energy by a tethered balloon at high altitude because it enables a low-cost start for bringing the first Watt of power to Earth giving some quick return on investment, which is desperately missing in the traditional SPS concept. To tackle the significant problem of GW-class SPSs of high launch cost per kg mass brought to space, this paper introduces a concept which aims to achieve a superior power over mass ratio compared to traditional satellite designs by the use of thin-film solar cells combined with optical fibres for power delivery. To minimise the aperture sizes and cost of the transmitting and receiving components of the satellite and high altitude receiver, closed-loop laser beam pointing and target tracking is crucial for pointing a laser beam onto a target area that is of similar size to the beam's diameter. A recently developed technique based on optical phase conjugation is introduced and its applicability for maintaining power transmission between the satellite and high altitude receiver is

  13. Actively mode-locked semiconductor lasers

    SciTech Connect

    Bowers, J.E.; Morton, P.A.; Mar, A.; Corzine, S.W.

    1989-06-01

    Measurements of actively mode-locked semiconductor lasers are described and compared to calculations of the mode-locking process using three coupled traveling wave rate equations for the electron and photon densities. The dependence of pulse width on the modulation current and frequency are described. A limitation to minimum achievable pulse widths in mode-locked semiconductor lasers is shown to be dynamic detuning due to gain saturation. Techniques to achieve subpicosecond pulses are described, together with ways to reduce multiple pulse outputs. The amplitude and phase noise of linear and ring cavity semiconductor lasers were measured and found to be tens of dB smaller than YAG and argon lasers and limited by the noise from the microwave oscillator. High-frequency phase noise is only measurable in detuned cavities, and is below -110 dBc (1 Hz) in optimally tuned cavities. The prospects for novel ways to achieve even shorter pulses are discussed.

  14. Connecting local active forces to macroscopic stress in elastic media.

    PubMed

    Ronceray, Pierre; Lenz, Martin

    2015-02-28

    In contrast with ordinary materials, living matter drives its own motion by generating active, out-of-equilibrium internal stresses. These stresses typically originate from localized active elements embedded in an elastic medium, such as molecular motors inside the cell or contractile cells in a tissue. While many large-scale phenomenological theories of such active media have been developed, a systematic understanding of the emergence of stress from the local force-generating elements is lacking. In this paper, we present a rigorous theoretical framework to study this relationship. We show that the medium's macroscopic active stress tensor is equal to the active elements' force dipole tensor per unit volume in both continuum and discrete linear homogeneous media of arbitrary geometries. This relationship is conserved on average in the presence of disorder, but can be violated in nonlinear elastic media. Such effects can lead to either a reinforcement or an attenuation of the active stresses, giving us a glimpse of the ways in which nature might harness microscopic forces to create active materials. PMID:25594831

  15. Advanced Laser Based Measurements in Porous Media Combustion

    NASA Technical Reports Server (NTRS)

    Tedder, Sarah A.

    2009-01-01

    We present measurements using dual-pump dual-broadband coherent anti-Stokes Raman scattering spectroscopy (DP-DBB-CARS) inside a porous media burner. This work continues our previous measurements in such combustion systems. The existing setup was significantly modified with the aim of providing improved data quality and data rate, reduction of interferences and additional species information. These changes are presented and discussed in detail. The CARS technique was expanded to a dual-pump dual-broadband CARS system which in principle enables acquisition of temperatures together with relative H2/N2- and O2/N2- species concentrations. Experimental complexity was reduced by the use of a modified spectrometer enabling the detection of both signals, vibrational and rotational CARS, with only one detection system.

  16. Rapid assessment of disaster damage using social media activity

    PubMed Central

    Kryvasheyeu, Yury; Chen, Haohui; Obradovich, Nick; Moro, Esteban; Van Hentenryck, Pascal; Fowler, James; Cebrian, Manuel

    2016-01-01

    Could social media data aid in disaster response and damage assessment? Countries face both an increasing frequency and an increasing intensity of natural disasters resulting from climate change. During such events, citizens turn to social media platforms for disaster-related communication and information. Social media improves situational awareness, facilitates dissemination of emergency information, enables early warning systems, and helps coordinate relief efforts. In addition, the spatiotemporal distribution of disaster-related messages helps with the real-time monitoring and assessment of the disaster itself. We present a multiscale analysis of Twitter activity before, during, and after Hurricane Sandy. We examine the online response of 50 metropolitan areas of the United States and find a strong relationship between proximity to Sandy’s path and hurricane-related social media activity. We show that real and perceived threats, together with physical disaster effects, are directly observable through the intensity and composition of Twitter’s message stream. We demonstrate that per-capita Twitter activity strongly correlates with the per-capita economic damage inflicted by the hurricane. We verify our findings for a wide range of disasters and suggest that massive online social networks can be used for rapid assessment of damage caused by a large-scale disaster. PMID:27034978

  17. Rapid assessment of disaster damage using social media activity.

    PubMed

    Kryvasheyeu, Yury; Chen, Haohui; Obradovich, Nick; Moro, Esteban; Van Hentenryck, Pascal; Fowler, James; Cebrian, Manuel

    2016-03-01

    Could social media data aid in disaster response and damage assessment? Countries face both an increasing frequency and an increasing intensity of natural disasters resulting from climate change. During such events, citizens turn to social media platforms for disaster-related communication and information. Social media improves situational awareness, facilitates dissemination of emergency information, enables early warning systems, and helps coordinate relief efforts. In addition, the spatiotemporal distribution of disaster-related messages helps with the real-time monitoring and assessment of the disaster itself. We present a multiscale analysis of Twitter activity before, during, and after Hurricane Sandy. We examine the online response of 50 metropolitan areas of the United States and find a strong relationship between proximity to Sandy's path and hurricane-related social media activity. We show that real and perceived threats, together with physical disaster effects, are directly observable through the intensity and composition of Twitter's message stream. We demonstrate that per-capita Twitter activity strongly correlates with the per-capita economic damage inflicted by the hurricane. We verify our findings for a wide range of disasters and suggest that massive online social networks can be used for rapid assessment of damage caused by a large-scale disaster. PMID:27034978

  18. Picosecond laser induced fragmentation of coarse Cu2O particles into nanoparticles in liquid media

    NASA Astrophysics Data System (ADS)

    Ali, Mokhtar; Remalli, Nagarjuna; Yehya, Fahem; Chaudhary, Anil Kumar; Srikanth, Vadali V. S. S.

    2015-12-01

    Micron sized cuprous oxide (Cu2O) particles are easily fragmented into nanosized (5-10 nm) particles using picosecond (ps) laser (wavelength = 532 nm) pulses. The coarse Cu2O particles are first synthesized by reducing copper chloride with the aid of honey. These particles are then dispersed in liquid media (double distilled water or ethanol) and exposed to ps laser pulses to obtain well-dispersed nanosized Cu2O particles. By using this method of fragmentation, morphology of the particles can be altered while retaining their crystal structure. The innate nature of this method allows continuous production of nanoparticles from coarser particles.

  19. Redox-active media for permeable reactive barriers

    SciTech Connect

    Sivavec, T.M.; Mackenzie, P.D.; Horney, D.P.; Baghel, S.S.

    1997-12-31

    In this paper, three classes of redox-active media are described and evaluated in terms of their long-term effectiveness in treating TCE-contaminated groundwater in permeable reactive zones. Zero-valent iron, in the form of recycled cast iron filings, the first class, has received considerable attention as a reactive media and has been used in about a dozen pilot- and full-scale subsurface wall installations. Criteria used in selecting commercial sources of granular iron, will be discussed. Two other classes of redox-active media that have not yet seen wide use in pilot- or full-scale installations will also be described: Fe(II) minerals and bimetallic systems. Fe(II) minerals, including magnetite (Fe{sub 3}O{sub 4}), and ferrous sulfide (troilite, FeS), are redox-active and afford TCE reduction rates and product distributions that suggest that they react via a reductive mechanism similar to that which operates in the FeO system. Fe(II) species within the passive oxide layer coating the iron metal may act as electron transfer mediators, with FeO serving as the bulk reductant. Bimetallic systems, the third class of redox-active media, are commonly prepared by plating a second metal onto zero-valent iron (e.g., Ni/Fe and Pd/Fe) and have been shown to accelerate solvent degradation rates relative to untreated iron metal. The long-term effectiveness of this approach, however, has not yet been determined in groundwater treatability tests. The results of a Ni-plated iron column study using site groundwater indicate that a change in reduction mechanism (to catalytic dehydrohalogenation/hydrogenation) accounts for the observed rate enhancement. A significant loss in media reactivity was observed over time, attributable to Ni catalyst deactivation or poisoning. Zero-valent iron systems have not shown similar losses in reactivity in long-term laboratory, pilot or field investigations.

  20. Blue luminescent silicon nanocrystals prepared by short pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Švrček, Vladimir; Kondo, Michio

    2009-09-01

    The pulsed laser processing in liquid media is an attractive alternative to produce room temperature luminescent silicon nanocrystals (Si-ncs). We report on a blue luminescent Si-ncs preparation by using nanosecond pulsed laser (Nd:YAG, KrF excimer) processing in transparent polymer and water. The Si-ncs fabrication is assured by ablation of crystalline silicon target immersed in liquids. During the processing and following aging in liquids, oxide based liquid media, induce shell formation around fresh nanocrystals that provides a natural and stable form of surface passivation. The stable room temperature blue-photoluminescent Si-ncs are prepared with maxima located around ˜440 nm with corresponding optical band gap around ˜2.8 eV (˜430 nm). Due to the reduction of surface defects, the Si-ncs preparation in water, leads to a narrowing of full-width-half-maxima of the photoluminescence spectra.

  1. Intelligent correction of laser beam propagation through turbulent media using adaptive optics

    NASA Astrophysics Data System (ADS)

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2014-10-01

    Adaptive optics methods have long been used by researchers in the astronomy field to retrieve correct images of celestial bodies. The approach is to use a deformable mirror combined with Shack-Hartmann sensors to correct the slightly distorted image when it propagates through the earth's atmospheric boundary layer, which can be viewed as adding relatively weak distortion in the last stage of propagation. However, the same strategy can't be easily applied to correct images propagating along a horizontal deep turbulence path. In fact, when turbulence levels becomes very strong (Cn 2>10-13 m-2/3), limited improvements have been made in correcting the heavily distorted images. We propose a method that reconstructs the light field that reaches the camera, which then provides information for controlling a deformable mirror. An intelligent algorithm is applied that provides significant improvement in correcting images. In our work, the light field reconstruction has been achieved with a newly designed modified plenoptic camera. As a result, by actively intervening with the coherent illumination beam, or by giving it various specific pre-distortions, a better (less turbulence affected) image can be obtained. This strategy can also be expanded to much more general applications such as correcting laser propagation through random media and can also help to improve designs in free space optical communication systems.

  2. Media.

    ERIC Educational Resources Information Center

    Allen, Lee E., Ed.

    1974-01-01

    Intended for secondary English teachers, the materials and ideas presented here suggest ways to use media in the classroom in teaching visual and auditory discrimination while enlivening classes and motivating students. Contents include "Media Specialists Need Not Apply," which discusses the need for preparation of media educators with…

  3. Subluminal optical pulse propagation in amplifying media and temperature controlled laser action in scattering media

    NASA Astrophysics Data System (ADS)

    Lee, Kijoon

    In the first half of the thesis, we investigated methods of controlling the group velocity of an optical probe pulse by another optical pulse. We focused on the gain linecenter region of an optical amplifier where group velocity can be very small due to the large dispersion. We made use of an optically pumped barium nitrate (Ba(NO3)2) Raman crystal to delay a probe pulse which is tuned to the Raman gain center, and measured the delay time as a function of pump pulse intensity. Within the intensity region where no significant amplified spontaneous emission (ASE) occurs, we observed pulse delays greater than the input pulse width and obtained predictions based on quasi-steady state Raman gain estimates. We also theoretically studied group velocity control in an optically pumped far-infrared (OPFIR) molecular gas amplifier system, where even larger group velocity reductions are expected due to the extremely narrow low-pressure gain linewidth. By using a 5-level model of a molecular gas, the change of group velocity was calculated as a function of pump beam intensity and gas pressure, and a minimum achievable value of the group velocity was estimated. Furthermore, the effect of static electric field was studied, where the selection rule-dependent level splitting by the DC Stark effect alters the gain lineshape, and hence the group velocity. In the second half, we experimentally and theoretically studied the emission characteristics from a novel random laser system where scattering power can be controlled by temperature. Our system is a laser dye-dissolved aqueous solution of hydroxypropyl cellulose (HPC) which has a lower critical solution temperature (LCST) at ˜41°C. When pumped with optical pulses, this system exhibits drastic spectral narrowing of emission with increasing temperature. A numerical calculation was performed by using a ring laser model developed for non-coherent random laser system, and the results were compared with the experimental linewidth vs

  4. Digital Media Use and Social Engagement: How Social Media and Smartphone Use Influence Social Activities of College Students.

    PubMed

    Kim, Yonghwan; Wang, Yuan; Oh, Jeyoung

    2016-04-01

    Social media and mobile phones have emerged as important platforms for college students' communication activities. This study examined how college students' psychological need to belong is associated with their use of social media and smartphones. In addition, it further investigated the effects of college students' digital media use on their social engagement. Findings revealed that students' need to belong was positively related with their use of social media and smartphones, which could further facilitate their social engagement. Moreover, the relationship between the need to belong and social engagement was mediated by college students' digital media use. This study offers empirical evidence of the positive effects of digital media on social behaviors and contributed to further understanding about the mechanisms by which need to belong leads to social engagement through digital media use. PMID:26991638

  5. Ranging performance of active laser detection

    NASA Astrophysics Data System (ADS)

    Sun, Huayan; Xiong, Fei; Gu, Suolin

    2006-06-01

    Ranging performance is described for photoelectric equipment reconnaissance using an active laser detection system that is based on the 'cat's eyes' effect of optical windows. Active laser detection systems have an advantage over passive systems because they can measure target velocity and spatial coordinates. However, there are several challenging problems here because of the great distances involved, the low returned power of the uncooperative target, and the optical aberrations induced by the atmosphere. In the design of this system, the principle of detection is based on the 'cat's eyes' effect according to which the optical windows of photoelectric equipments have a strong reflect character towards incident laser beam. With 'cat's eyes' effect, the detection of uncooperative target can be translated into one of a cooperative target, so the ratio of returned laser can be increased. In this paper, the ranging performance presented here takes into account all the various elements of the system, from the laser emission, target, atmospheric propagation to the detector. The characteristics of back-reflected laser and an estimate of the laser Cross Section (LCS) from 'cat's eyes target' are investigated in theory and simulation. The Signal-to-Noise Ratio (SNR) is calculated by combining the probability of detection of the system for given electronic characteristics of the system and for a given probability of false alarms. On the basis of analysis of SNR, minimum detectable signal power, operating distance of the system and factors affecting the ranging performance is analyzed. Results indicate that system has characters of long range, and high sensitivity. It can be used to detect the aerial targets such as reconnaissance drone, navigate missile, reconnaissance satellite etc.

  6. Experimental studies of light propagation in active scattering media

    NASA Astrophysics Data System (ADS)

    Perkins, Amy Elizabeth

    1998-10-01

    Over the past several years there has been a great deal of renewed interest in multiple scattering systems with gain. Laser action has been demonstrated in systems containing high gain laser dyes mixed with passive scattering particles. In these materials, known as photonic paint, the scatterers redirect the light and provide the feedback mechanism to initiate lasing. A method of decreasing the linewidth which has been used in conventional laser systems is injection locking, in which a seed at the desired wavelength is introduced into the cavity to initiate lasing. Experiments are presented which demonstrate injection locking of this new laser system. It is also of particular interest to study the phenomenon of weak localization of light in these photonic paint systems. The interference between scattered light paths increases the probability of light traveling opposite to the direction of the incident light, and produces a cone of enhanced reflected light in that direction. In the presence of amplification, the coherent backscattering cone narrows. In this high gain scattering system, an unstudied regime can be achieved in which significant amplification takes place over one scattering length. The results of the coherent backscattering experiment in a high gain scattering system is discussed. There are certain intrinsic problems with inversion gain systems, such as photonic paint, which makes the narrowing of the coherent backscattering cone less pronounced. In Raman materials, these effects are greatly reduced. Experimental studies of the amplification of a probe beam in a disordered Raman scattering medium, and the Monte Carlo simulations of this experiment, are presented. It is also of interest to study absorptive scattering systems which appear in a number of different situations, including the determination of the excitation volume in a scattering gain system and the modeling of biological tissue. The addition of an absorbing species into a scattering medium

  7. Resonant activation in bistable semiconductor lasers

    SciTech Connect

    Lepri, Stefano; Giacomelli, Giovanni

    2007-08-15

    We theoretically investigate the possibility of observing resonant activation in the hopping dynamics of two-mode semiconductor lasers. We present a series of simulations of a rate-equation model under random and periodic modulation of the bias current. In both cases, for an optimal choice of the modulation time scale, the hopping times between the stable lasing modes attain a minimum. The simulation data are understood by means of an effective one-dimensional Langevin equation with multiplicative fluctuations. Our conclusions apply to both edge-emitting and vertical cavity lasers, thus opening the way to several experimental tests in such optical systems.

  8. Polarization ray tracing in anisotropic optically active media

    NASA Technical Reports Server (NTRS)

    Mcclain, Stephen C.; Chipman, Russell A.

    1992-01-01

    Procedures for performing polarization ray tracing through birefringent media are presented in a form compatible with the standard methods of geometric ray tracing. The birefringent materials treated include the following: anisotropic optically active materials such as quartz, non-optically active uniaxial materials such as calcite, and isotropic optically active materials such as mercury sulfide or organic liquids. Refraction and reflection algorithms are presented which compute both ray directions and wave directions. Methods for computing polarization modes, refractive indices, optical path lengths, and Fresnel transmission and reflection coefficients are also specified.

  9. Modeling of mode locking in a laser with spatially separate gain media.

    PubMed

    Oldenbeuving, R M; Lee, C J; Van Voorst, P D; Offerhaus, H L; Boller, K-

    2010-10-25

    We present a novel laser mode locking scheme and discuss its unusual properties and feasibility using a theoretical model. A large set of single-frequency continuous-wave lasers oscillate by amplification in spatially separated gain media. They are mutually phase-locked by nonlinear feedback from a common saturable absorber. As a result, ultra-short pulses are generated. The new scheme offers three significant benefits: the light that is amplified in each medium is continuous-wave, thereby avoiding issues related to group-velocity dispersion and nonlinear effects that can perturb the pulse shape. The set of frequencies on which the laser oscillates, and therefore the pulse repetition rate, is controlled by the geometry of resonator-internal optical elements, not by the cavity length. Finally, the bandwidth of the laser can be controlled by switching gain modules on and off. This scheme offers a route to mode-locked lasers with high average output power, repetition rates that can be scaled into the THz range, and a bandwidth that can be dynamically controlled. The approach is particularly suited for implementation using semiconductor diode laser arrays. PMID:21164639

  10. Laser activated MTOS microwave device

    NASA Technical Reports Server (NTRS)

    Maserjian, J. (Inventor)

    1985-01-01

    A light-activated semiconductor device usable as an optoelectronic switch, pulse generator or optical detector is provided. A semiconductor device is disclosed which provides back-to-back metal-thin oxide-silicon (MTOS) capacitors. Each capacitor includes a thin, light-absorptive aluminum electrode which overlies a thin oxide layer and a lightly doped region implanted in an intrinsic silicon substrate.

  11. Actively mode-locked Raman fiber laser.

    PubMed

    Yang, Xuezong; Zhang, Lei; Jiang, Huawei; Fan, Tingwei; Feng, Yan

    2015-07-27

    Active mode-locking of Raman fiber laser is experimentally investigated for the first time. An all fiber connected and polarization maintaining loop cavity of ~500 m long is pumped by a linearly polarized 1120 nm Yb fiber laser and modulated by an acousto-optic modulator. Stable 2 ns width pulse train at 1178 nm is obtained with modulator opening time of > 50 ns. At higher power, pulses become longer, and second order Raman Stokes could take place, which however can be suppressed by adjusting the open time and modulation frequency. Transient pulse evolution measurement confirms the absence of relaxation oscillation in Raman fiber laser. Tuning of repetition rate from 392 kHz to 31.37 MHz is obtained with harmonic mode locking. PMID:26367642

  12. LASERS IN MEDICINE: Determination of the optical characteristics of turbid media by the laser optoacoustic method

    NASA Astrophysics Data System (ADS)

    Karabutov, Aleksander A.; Pelivanov, Ivan M.; Podymova, N. B.; Skipetrov, S. E.

    1999-12-01

    A method, based on the optoacoustic effect for determination of the spatial distribution of the light intensity in turbid media and of the optical characteristics of such media was proposed (and implemented experimentally). A temporal profile of the pressure of a thermo-optically excited acoustic pulse was found to be governed by the absorption coefficient and by the spatial distribution of the light intensity in the investigated medium. The absorption coefficient and the reduced light-scattering coefficient of model turbid water-like media were measured by the optoacoustic method. The results of a direct determination of the spatial light-intensity distribution agreed with a theoretical calculation made in the diffusion approximation.

  13. Rigrod laser-pumped-laser resonator model: II. Application to thin and optically-dilute laser media

    NASA Astrophysics Data System (ADS)

    Brown, D. C.

    2014-08-01

    In part I of this paper, and to set the foundation for this part II, we derived the resonator equations describing the normalized intensities, output power, gain, and extraction efficiency for a standard resonator incorporating two dielectric mirrors and a gain element. We then generalized the results to include an absorbing region representing a second laser crystal characterized by a small-signal transmission T0. Explicit expressions were found for the output power extracted into absorption by the second laser crystal and the extraction efficiency, and the limits to each were discussed. It was shown that efficient absorption by a thin or dilute second laser crystal can be realized in resonators in which the mirror reflectivities were high and in which the single-pass absorption was low, due to the finite photon lifetime and multi-passing of the absorbing laser element. In this paper, we apply the model derived in part I to thin or dilute laser materials, concentrating on a Yb, Er:glass intracavity pumped by a 946 nm Nd:YAG laser, a Yb, Er:glass laser-pumped intracavity by a 977 nm diode laser, and an Er:YAG laser-pumped intracavity to a 1530 nm diode laser. It is shown that efficient absorption can be obtained in all cases examined.

  14. Hypersensitivity reactions to radiocontrast media: the role of complement activation.

    PubMed

    Szebeni, Janos

    2004-01-01

    Although intravenous use of radiocontrast media (RCM) for a variety of radiographic procedures is generally safe, clinically significant acute hypersensitivity reactions still occur in a significant percentage of patients. The mechanism of these anaphylactoid, or "pseudoallergic," reactions is complex, involving complement activation, direct degranulation of mast cells and basophils, and modulation of enzymes and proteolytic cascades in plasma. In this review, basic information on different RCMs and their reactogenicity is summarized and updated, and the prevalence, pathomechanism, prediction, prevention, treatment, and economic impact of hypersensitivity reactions are discussed. Particular attention is paid to the in vitro and in vivo evidence supporting complement activation as an underlying cause of RCM reactions. PMID:14680617

  15. Comparative analysis of the use of various solid-state laser media for the self-starting of four-wave PCW generation in a loop laser resonator

    SciTech Connect

    Smetanin, Sergei N

    2013-01-31

    A generalised theory has been used to carry out a comparative analysis of the use of various four-level and quasi-threelevel media for the self-starting of degenerate four-wave mixing PCW generation directly in a laser medium placed in a loop resonator. It has been shown that quasi-three-level media can compete with four-level media at long upper laser level lifetimes and increased pump intensities. The most attractive solid-state laser media for four-wave PCW generation have been identified that have the highest deposited energy at a given pump intensity. In addition to neodymium-doped crystals, which are already widely used for four-wave PCW generation, promising materials are fourlevel chromium-doped media, e.g. alexandrite and Cr : LiCAF, and quasi-three-level media with the longest upper laser level lifetime, such as Yb : YAG and Tm, Ho : YAG, at high pump intensities. (nonlinear optical phenomena)

  16. Dynamics of self-propelled nanomotors in chemically active media

    NASA Astrophysics Data System (ADS)

    Thakur, Snigdha; Kapral, Raymond

    2011-07-01

    Synthetic chemically powered nanomotors often rely on the environment for their fuel supply. The propulsion properties of such motors can be altered if the environment in which they move is chemically active. The dynamical properties of sphere dimer motors, composed of linked catalytic and noncatalytic monomers, are investigated in active media. Chemical reactions occur at the catalytic monomer and the reactant or product of this reaction is involved in cubic autocatalytic or linear reactions that take place in the bulk phase environment. For these reactions, as the bulk phase reaction rates increase, the motor propulsion velocity decreases. For the cubic autocatalytic reaction, this net effect arises from a competition between a reduction of the nonequilibrium concentration gradient that leads to smaller velocity and the generation of fuel in the environment that tends to increase the motor propulsion. The role played by detailed balance in determining the form of the concentration gradient in the motor vicinity in the active medium is studied. Simulations are carried out using reactive multiparticle collision dynamics and compared with theoretical models to obtain further insight into sphere dimer dynamics in active media.

  17. Laser Pencil Beam Based Techniques for Visualization and Analysis of Interfaces Between Media

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Giles, Sammie, Jr.

    1998-01-01

    Traditional optical methods that include interferometry, Schlieren, and shadowgraphy have been used successfully for visualization and evaluation of various media. Aerodynamics and hydrodynamics are major fields where these methods have been applied. However, these methods have such major drawbacks as a relatively low power density and suppression of the secondary order phenomena. A novel method introduced at NASA Lewis Research Center minimizes disadvantages of the "classical" methods. The method involves a narrow pencil-like beam that penetrates a medium of interest. The paper describes the laser pencil beam flow visualization methods in detail. Various system configurations are presented. The paper also discusses interfaces between media in general terms and provides examples of interfaces.

  18. Laser Pencil Beam Based Techniques for Visualization and Analysis of Interfaces Between Media

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Giles, Sammie, Jr.

    1998-01-01

    Traditional optical methods that include interferometry, Schlieren, and shadowgraphy have been used successfully for visualization and evaluation of various media. Aerodynamics and hydrodynamics are major fields where these methods have been applied. However, these methods have such major drawbacks as a relatively low power density and suppression of the secondary order phenomena. A novel method introduced at NASA Lewis Research Center minimizes disadvantages of the 'classical' methods. The method involves a narrow pencil-like beam that penetrates a medium of interest. The paper describes the laser pencil beam flow visualization methods in detail. Various system configurations are presented. The paper also discusses interfaces between media in general terms and provides examples of interfaces.

  19. Modification of biological objects in water media by CO{sub 2}-laser radiation

    SciTech Connect

    Baranov, G A; Belyaev, A A; Onikienko, S B; Smirnov, S A; Khukharev, V V

    2005-09-30

    The modification of biological objects (polysaccharides and cells) by CO{sub 2}-laser radiation in water added drop by drop into the interaction region is studied theoretically and experimentally. Calculations are performed by using the models describing gas-dynamic and heterogeneous processes caused by absorption of laser radiation by water drops. It is found experimentally that the laser modification of polysaccharides leads to the formation of low-molecular derivatives with immunostimulating properties. A dose of the product of laser activation of the yeast culture Saccharamyces cerevisiae prevented the development of a toxic emphysema in mice and protected them against lethal grippe and also prevented a decrease of survival rate, increased the average life, and prevented the development of metabolic and immune disorders in mice exposed to sublethal gamma-radiation doses. (laser applications and other topics in quantum electronics)

  20. Laser Initiated Ordnance (LIO) activities in NASA

    NASA Technical Reports Server (NTRS)

    Schulze, Norman R.

    1994-01-01

    This technical report presents the summary of the 2nd NASA Aerospace Pyrotechnic Systems Workshop's discussion on Laser Initiated Ordnance (LIO). Laser initiated ordnance benefits, applications, advantage of laser ordnance, and disadvantage of laser diode initiated ordnance are discussed. In addition, the three LIO programs: NASA standard laser diode safe and arm, NASA standard laser detonators, and laser diode safe/arm performance are reviewed. Steps for the LIO implementation are also presented.

  1. Active laser tweezers microrheometry of microbial biofilms

    NASA Astrophysics Data System (ADS)

    Osterman, N.; Slapar, V.; Boric, M.; Stopar, D.; Babič, D.; Poberaj, I.

    2010-08-01

    Microbial biofilms are present on biotic and abiotic surfaces and have a significant impact on many fields in industry, health care and technology. Thus, a better understanding of processes that lead to development of biofilms and their chemical and mechanical properties is needed. In the following paper we report the results of active laser tweezers microrheology study of optically inhomogeneous extracellular matrix secreted by Visbrio sp. bacteria. One particle and two particle active microrheology were used in experiments. Both methods exhibited high enough sensitivity to detect viscosity changes at early stages of bacterial growth. We also showed that both methods can be used in mature samples where optical inhomogeneity becomes significant.

  2. Intense Laser Alignment in Dissipative Media as a Route to Solvent Dynamics

    SciTech Connect

    Ramakrishna, S.; Seideman, Tamar

    2005-09-09

    We extend the concept of alignment by short intense pulses to dissipative environments within a density matrix formalism and illustrate the application of this method as a probe of the dissipative properties of dense media. In particular, we propose a means of disentangling rotational population relaxation from decoherence effects via strong laser alignment. We illustrate also the possibility of suppressing rotational relaxation to prolong the alignment lifetime through choice of the field parameters. Implications to several disciplines and a number of potential applications are proposed.

  3. Specific imaging of caustics upon refraction of structured laser radiation in stratified media

    NASA Astrophysics Data System (ADS)

    Raskovskaya, I. L.

    2015-06-01

    Conditions for caustic formation upon longitudinal probing of stratified optically inhomogeneous media by structured laser beams that are visualized in the cross section as families of geometrical figures are studied. In the plane of observation at the exit from the medium, the projection of the caustic surface is imaged as an envelope of extrema of refractive deflection of beam-structure elements. This circumstance makes it possible to experimentally determine the caustic position in the absence of intensity measurements in the refraction image. The measured geometrical parameters of caustics are employed in the solution of the inverse problem of refraction to reconstruct physical parameters of the medium that control nonuniformity of refractive index.

  4. Advancements in quantum cascade laser-based infrared microscopy of aqueous media.

    PubMed

    Haase, K; Kröger-Lui, N; Pucci, A; Schönhals, A; Petrich, W

    2016-06-23

    The large mid-infrared absorption coefficient of water frequently hampers the rapid, label-free infrared microscopy of biological objects in their natural aqueous environment. However, the high spectral power density of quantum cascade lasers is shifting this limitation such that mid-infrared absorbance images can be acquired in situ within signal-to-noise ratios of up to 100. Even at sample thicknesses well above 50 μm, signal-to-noise ratios above 10 are readily achieved. The quantum cascade laser-based microspectroscopy of aqueous media is exemplified by imaging an aqueous yeast solution and quantifying glucose consumption, ethanol generation as well as the production of carbon dioxide gas during fermentation. PMID:27032367

  5. Comprehensive analytical model for CW laser induced heat in turbid media.

    PubMed

    Erkol, Hakan; Nouizi, Farouk; Luk, Alex; Unlu, Mehmet Burcin; Gulsen, Gultekin

    2015-11-30

    In this work, we present a new analytical approach to model continuous wave laser induced temperature in highly homogeneous turbid media. First, the diffusion equation is used to model light transport and a comprehensive solution is derived analytically by obtaining a special Greens' function. Next, the time-dependent bio-heat equation is used to describe the induced heat increase and propagation within the medium. The bio-heat equation is solved analytically utilizing the separation of variables technique. Our theoretical model is successfully validated using numerical simulations and experimental studies with agarose phantoms and ex-vivo chicken breast samples. The encouraging results show that our method can be implemented as a simulation tool to determine important laser parameters that govern the magnitude of temperature rise within homogenous biological tissue or organs. PMID:26698736

  6. Shock-wave generation in transparent media from ultra-fast lasers

    NASA Astrophysics Data System (ADS)

    Bernath, R.; Brown, C. G.; Aspiotis, J.; Fisher, M.; Richardson, M.

    2006-05-01

    Laser interactions with bulk transparent media have long been investigated for material processing applications involving ablation and shock wave generation in both the nanosecond and femtosecond pulse width regimes1. Shock waves have been studied in fused silica and other optical glasses but previously have been characterized by the morphology of the concurrent ablation. We perform ablation at distances of 30 meters using the non-linear self-channeling effect. Using silicon wafers as targets because of their clearly defined ablation zones, we examine the effect that the filament has on the thin SiO II layer coating the wafer's surface. It is observed that the surface layer experiences a shock wave resulting from the explosive forces produced by the plasma. The use of several laser pulses in burst mode operation leads to the observation of multiple shock fronts in the material, and the possibility of shock wave addition for higher damage. Optical interferometry will be used to characterize the shock wave dynamics, using both traditional means of focusing in the near field and at 30 meters using propagating self-channeled femtosecond pulses. The novelty of using self-channeling laser pulses for shock wave generation has many implications for military applications. These experiments are to be performed in our secure test range using intensities of 10 14W/cm2 and higher incident on various transparent media. Interferometry is performed using a harmonic of the pump laser frequency. Experiments also include burst-mode operation, where a train of ultra-fast pulses, closely spaced in time, and novel new beam distributions, strike the sample.

  7. Effect of laser annealing of pressure gradients in a diamond-anvil cell using common solid pressure media

    NASA Astrophysics Data System (ADS)

    Uts, Ilya; Glazyrin, Konstantin; Lee, Kanani K. M.

    2013-10-01

    Pressure media are one of the most effective deterrents of pressure gradients in diamond-anvil cell (DAC) experiments. The media, however, become less effective with increasing pressure, particularly for solid pressure media. One of the most popular ways of alleviating the increase in pressure gradients in DAC samples is through laser annealing of the sample. We explore the effectiveness of this technique for six common solid pressure media that include: alkali metal halides LiF, NaCl, KCl, CsCl, KBr, as well as amorphous SiO2. Pressure gradients are determined through the analysis of the first-order diamond Raman band across the sample before and after annealing the sample with a near-infrared laser to temperatures between ˜2000 and 3000 K. As expected, we find that in the absence of sample chamber geometrical changes and diamond anvil damage, laser annealing reduces pressure gradients, albeit to varying amounts. We find that under ideal conditions, NaCl provides the best deterrent to pressure gradients before and after laser annealing, at least up to pressures of 60 GPa and temperatures between ˜2000 and 3000 K. Amorphous SiO2, on the other hand, transforms in to harder crystalline stishovite upon laser annealing at high pressures resulting in increased pressure gradients upon further compression without laser annealing.

  8. Do Media Use and Physical Activity Compete in Adolescents? Results of the MoMo Study

    PubMed Central

    Spengler, Sarah; Mess, Filip; Woll, Alexander

    2015-01-01

    Purpose The displacement hypothesis predicts that physical activity and media use compete in adolescents; however, findings are inconsistent. A more differentiated approach at determining the co-occurrence of physical activity and media use behaviors within subjects may be warranted. The aim of this study was to determine the co-occurrence of physical activity and media use by identifying clusters of adolescents with specific behavior patterns including physical activity in various settings (school, sports club, leisure time) and different types of media use (watching TV, playing console games, using PC / Internet). Methods Cross-sectional data of 2,083 adolescents (11–17 years) from all over Germany were collected between 2009 and 2012 in the Motorik-Modul Study. Physical activity and media use were self-reported. Cluster analyses (Ward’s method and K-means analysis) were used to identify behavior patterns of boys and girls separately. Results Eight clusters were identified for boys and seven for girls. The clusters demonstrated that a high proportion of boys (33%) as well as girls (42%) show low engagement in both physical activity and media use, irrespective of setting or type of media. Other adolescents are engaged in both behaviors, but either physical activity (35% of boys, 27% of girls) or media use (31% of boys and girls) predominates. These adolescents belong to different clusters, whereat in most clusters either one specific setting of physical activity or a specific combination of different types of media predominates. Conclusion The results of this study support to some extent the hypothesis that media use and physical activity compete: Very high media use occurred with low physical activity behavior, but very high activity levels co-occurred with considerable amounts of time using any media. There was no evidence that type of used media was related to physical activity levels, neither setting of physical activity was related to amount of media use

  9. Optical pumping of generalized laser active materials.

    PubMed

    Fry, F H

    1967-11-01

    Results are presented of a computer-based study on the rate of excitation in the active cores of two types of optically pumped lasers as a function of a number of parameters of the active core. The absorption bands of the active materials are generated by Lorentzian and Gaussian functions. The excitation rate of the active core is proportional to the width of the absorption band at all depths of penetration. The plots of excitation rate as a function of frequency show curves similar to line reversal spectra and emphasize the importance of excitation some distance from the center of the absorption band in the slab model. In the cylindrical model, this wing pumping is even more important due to focusing. The effect of refractive index on the excitation rate is also described. PMID:20062337

  10. Fabrication of transparent ceramic laser media for high energy laser applications

    NASA Astrophysics Data System (ADS)

    Serivalsatit, Karn

    Sesquioxides of yttrium, scandium, and lutetium, i.e., Y2O 3, Sc2O3, and Lu2O3, have received a great deal of recent attention as potential high power solid state laser hosts. These oxides are receptive to lanthanide doping, including trivalent Er, Ho and Tm which have well known emissions at eye-safe wavelengths that can be excited using commercial diode lasers. These sesquioxides are considered superior to the more conventional yttrium aluminum garnet (YAG) due to their higher thermal conductivity, which is critical for high power laser system. Unfortunately, these oxides possess high melting temperatures, which make the growth of high purity and quality crystals using melt techniques difficult. Transparent ceramics are an attractive alternative route to laser hosts since the processing by-passes many of the challenges of refractory crystal melt growth. Moreover, transparent ceramics can possess added benefits relative to single crystals including faster production rates, the fabrication of larger sizes and composite laser structures, uniform doping concentrations, and better mechanical behavior. In order to fabricate highly transparent ceramics, the starting powders must have good dispersion and high reactivity. In this work, sesquioxide nanopowders with high sinterability were synthesized by solution precipitation techniques. For Y2O3, the nanopowders were prepared using yttrium nitrate and ammonium hydroxide with the addition of a small amount of ammonium sulfate. Doping sulfate ions was found to reduce the agglomeration of Y 2O3 nanopowders. The Y2O3 nanopowders with average particle size about 40 nm were obtained by calcining at 1050°C for 4 hours. Unfortunately, this method failed to prepare well-dispersed Sc 2O3 and Lu2O3 nanopowders. For Sc 2O3 and Lu2O3, the nanopowders were synthesized by using scandium or lutetium sulfate and hexamethylenetetramine (HMT). The precipitate precursors were calcined at 1100°C for 4 hours to yielded Sc2O3 and Lu2O3

  11. Active Vibration Control For Lasers And Spacecraft

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome

    1983-12-01

    The Active Control of Space Structures (ACOSS) program of the Defense Advanced Research Projects Agency has identified problems in active vibration control of structural modes in extremely flexible space structures and in precisely pointed optics. The Air Force Wright Aeronautical Laboratories programs are an outgrowth of the ACOSS program. They are aimed at the problems of sensors, actuators, and their dynamic interactions with the structure to be controlled, and at the problem of system identification by one-g laboratory experiments. The VCOSS-1 and VCOSS-2 programs (Vibration Control of Space Structures) address the dynamic interactions of the sensor-actuator-structure; the Benchless Laser program and the Airborne Laser Mirror-Control program address the active control of HEL mirrors; the Experimental Modal Analysis and Component Synthesis and the Large Space Structure Dynamics programs address the problems of system identification and testing. Closer coordination with NASA and DARPA is being sought in support of on-orbit dynamic testing using the Space Shuttle and in the development of a national facility for one-g dynamics testing of large space structures.

  12. Gas in Scattering Media Absorption Spectroscopy -- Laser Spectroscopy in Unconventional Environments

    NASA Astrophysics Data System (ADS)

    Svanberg, Sune

    2010-02-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. The GASMAS technique combines narrow-band diode-laser spectroscopy with optical propagation in diffuse media. Whereas solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures. These are typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. Molecular oxygen and water vapor have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied, demonstrating new possibilities for characterization and diagnostics. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen gas, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the human sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen, while breathing normally through the mouth. A clinical study comprising 40 patients has been concluded.

  13. Synthesis of Silver Nanoparticles Dispersed in Various Aqueous Media Using Laser Ablation

    PubMed Central

    Tajdidzadeh, M.; Azmi, B. Z.; Yunus, W. Mahmood M.; Talib, Z. Abidin; Sadrolhosseini, A. R.; Karimzadeh, K.; Gene, S. A.; Dorraj, M.

    2014-01-01

    The particle size, morphology, and stability of Ag-NPs were investigated in the present study. A Q-Switched Nd: YAG pulsed laser (λ = 532 nm, 360 mJ/pulse) was used for ablation of a pure Ag plate for 30 min to prepare Ag-NPs in the organic compound such as ethylene glycol (EG) and biopolymer such as chitosan. The media (EG, chitosan) permitted the making of NPs with well dispersed and average size of Ag-NPs in EG is about 22 nm and in chitosan is about 10 nm in spherical form. Particle size, morphology, and stability of NPs were compared with distilled water as a reference. The stability of the samples was studied by measuring UV-visible absorption spectra of samples after one month. The result indicated that the formation efficiency of NPs in chitosan was higher than other media and NPs in chitosan solution were more stable than other media during one month storage. This method for synthesis of silver NPs could be as a green method due to its environmentally friendly nature. PMID:25295298

  14. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Genc, Suzanne L.; Ma, Huan; Venugopalan, Vasan

    2014-08-01

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of Ep ≈ 4-5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (Rmax = 2-20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy EB. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (Ep = 11-20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1-2 orders of magnitude larger in size ( R max ≳ 100 μ m ) due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA.

  15. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

    PubMed Central

    Genc, Suzanne L.; Ma, Huan; Venugopalan, Vasan

    2014-01-01

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of Ep ≈ 4–5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (Rmax = 2–20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy EB. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (Ep = 11–20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1–2 orders of magnitude larger in size (Rmax≳100 μm) due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA. PMID:25278618

  16. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses.

    PubMed

    Genc, Suzanne L; Ma, Huan; Venugopalan, Vasan

    2014-08-11

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of E p ≈ 4-5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (R max = 2-20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy E B. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (E p = 11-20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1-2 orders of magnitude larger in size [Formula: see text] due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA. PMID:25278618

  17. Activation of lignin peroxidase in organic media by reversed micelles.

    PubMed

    Kimura, Masayuki; Michizoe, Junji; Oakazaki, Shin-Ya; Furusaki, Shintaro; Goto, Masahiro; Tanaka, Hiroo; Wariishi, Hiroyuki

    2004-11-20

    Activation of lignin peroxidase (LIP) in an organic solvent by reversed micelles was investigated. Bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) was used as a surfactant to form a reversed micelle. Lyophilized LIP from an optimized aqueous solution exhibited no enzymatic activity in any organic solvents examined in this study; however, LIP was catalytically active by being entrapped in the AOT reversed micellar solution. LIP activity in the reversed micelle was enhanced by optimizing either the preparation or the operation conditions, such as water content and pH in water pools of the reversed micelle and the reaction temperature. Stable activity was obtained in isooctane because of the stability of the reversed micelle. The optimal pH was 5 in the reversed micellar system, which shifted from pH 3 in the aqueous solution. The degradation reaction of several environmental pollutants was attempted using LIP hosted in the AOT reversed micelle. Degradation achieved after a 1-h reaction reached 81%, 50%, and 22% for p-nonylphenol, bisphenol A, and 2,4-dichlorophenol, respectively. This is the first report on the utilization of LIP in organic media. PMID:15459910

  18. Active laser system for sea ice control

    NASA Astrophysics Data System (ADS)

    Evtikhiev, Nickolay N.; Gaponov, Alexandr E.; Kuluba, Yury N.; Matous, Vladislav I.; Radominov, Oleg E.; Tuzikov, Vladimir Z.; Vargaftic, Vasiliy N.

    1997-01-01

    The airborne systems are used for complex investigations of coastline very successfully, for example it can be used to measure the depth of the sea, to discover the reefs and so on. Such information may be used in navigation too. The specific conditions of navigation in the North and Pole seas defines the necessity of exact knowledge about the ice cracks in order to find the possible direction of the ship movement. The active optical system, working in the near IR region, has many advantages before the passive one, especially if it is necessary to work during the polar night and at bad weather conditions. In this article we discuss the demands to the laser active airborne systems, that given the accurate picture of the ice with high resolution in the daytime and nighttime conditions. Such system based on the laser, mechanical scanner and avalanche photodiode is very compact, reliable and informative. The picture of the ice surface can be shown on the TV monitor, can be written to the memory and can be delivered to the processing center by the radiochannel. The experimental results are shown together with results of this system probing in the conditions of the North Pole Ocean.

  19. Laser perforated fuel cell diffusion media. Part I: Related changes in performance and water content

    NASA Astrophysics Data System (ADS)

    Manahan, M. P.; Hatzell, M. C.; Kumbur, E. C.; Mench, M. M.

    In this study, cathode-side, bi-layered diffusion media (DM) samples with micro-porous layer were perforated with 300 μm laser-cut holes (covering 15% of the surface area in a homogenous pattern) using a ytterbium fiber laser to investigate the effect of structural changes on the gas and water transport. Under reduced humidity conditions (50% inlet relative humidity on the anode and cathode), the perforated DM were observed to increase the potential by an average of 6% for current densities ranging from 0.2 to 1.4 A cm -2. However, the perforated DM showed reduced performance for current densities greater than 1.4 A cm -2 and at all currents under high-humidity conditions. Neutron radiography experiments were also performed to understand the changes in liquid water retention characteristics of DM due to the laser perforations. Significant water accumulation and water redistribution were observed in the perforated DM, which helps explain the observed performance behavior. The results indicate that the perforations act as water pooling and possible channeling locations, which significantly alter the water condensation, storage, and transport scheme within the fuel cell. These observations suggest that proper tailoring of fuel cell DM possesses significant potential to enable fuel cell operations with reduce liquid overhead and high performance.

  20. Effect of Laser Annealing of Common Solid Pressure Media on Pressure Gradients in a Diamond Anvil Cell

    NASA Astrophysics Data System (ADS)

    Uts, I.; Glazyrin, K.; Lee, K. K.

    2012-12-01

    Advances in experimental techniques allow for the studying of geophysics and planetary science related materials under high pressure and high temperature conditions. With the intrinsic limits of the multianvil apparatus, compression in a diamond anvil cell (DAC) has become the preferred method for creating the extreme conditions of planetary interiors. High pressures up to 1 Mbar can be routinely obtained in laboratories with the use of DACs. Additionally, as in situ laser heating is becoming progressively more affordable for DACs, it is becoming more common to find laser heating setups in many large scale facilities. After the sample material, the pressure medium is the second most important ingredient for a successful high pressure DAC experiment. Not every pressure medium is equally suitable for every experiment. For example, solid pressure media are more persistent than gaseous pressure media if high temperature heating is required. The melting point of the former is much higher, and melting of pressure media may induce undesirable sample shift in the pressure chamber. However, the most important characteristic of a pressure medium is its ability to maintain hydrostaticity in the DAC. The media, particularly solid pressure media, become less effective with increasing pressure. One of the most popular ways of alleviating pressure gradients is through laser annealing of the sample. We explore the effectiveness of this technique in relation to common pressure media, namely, alkali metal halides NaCl, CsCl, KCl, LiF, and oxide MgO. The samples were laser annealed at temperatures above 2000 K. Pressure gradients were determined through the analysis of diamond Raman and ruby fluorescence peaks before and after annealing the sample with a near-infrared laser. We find that the effect of annealing varies for different materials. For some (NaCl and KCl), it reduces pressure gradients considerably, but for the others (MgO), the effect of annealing is less profound.

  1. Stigma's Effect on Social Interaction and Social Media Activity.

    PubMed

    Boudewyns, Vanessa; Himelboim, Itai; Hansen, Derek L; Southwell, Brian G

    2015-01-01

    Stigmatized topics, such as HIV/STD, likely constrain related information sharing in ways that should be apparent in social interactions both on and off the Internet. Specifically, the authors predicted that the more people perceive an issue as stigmatized, the less likely they are to talk about the issue both privately (with sexual partners and peers) and publicly (on Twitter). Study 1 tested the effect of stigma on conversations at the individual level: The authors asked a group of participants (N = 138) about perceived STD-testing stigma, interactions with a sexual partner, and conversations with peers about STD testing. Study 2 assessed whether health conditions, in the aggregate, were less likely to generate social media activity as a function of current stigmatization. Using 259,758 archived Twitter posts mentioning 13 medical conditions, the authors tested whether level of stigma predicted the volume of relevant social media conversation, controlling for each condition's amount of advocacy and Google search popularity from a user's perspective. Findings supported our hypotheses. Individuals who reported perceiving a given health conditions in more stigmatic ways also reported interacting less with others about that topic; Twitter results showed a similar pattern. Results also suggest a more complex story of influence, as funding from the National Institutes of Health (i.e., each conditions amount of advocacy) associated with the examined health conditions also predicted Twitter activity. Overall, these results indicated that stigma had a similar, dampening effect on face-to-face and Twitter interactions. Findings hold theoretical and practical implications, which are discussed. PMID:26087307

  2. Green laser light activates the inner ear

    NASA Astrophysics Data System (ADS)

    Wenzel, Gentiana I.; Balster, Sven; Zhang, Kaiyin; Lim, Hubert H.; Reich, Uta; Massow, Ole; Lubatschowski, Holger; Ertmer, Wolfgang; Lenarz, Thomas; Reuter, Guenter

    2009-07-01

    The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices. Laser light can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. We sought to assess whether visible light with parameters that could induce an optoacoustic effect (532 nm, 10-ns pulses) would activate the cochlea. Auditory brainstem responses (ABRs) were recorded preoperatively in anesthetized guinea pigs to confirm normal hearing. After opening the bulla, a 50-μm core-diameter optical fiber was positioned in the round window niche and directed toward the basilar membrane. Optically induced ABRs (OABRs), similar in shape to those of acoustic stimulation, were elicited with single pulses. The OABR peaks increased with energy level (0.6 to 23 μJ/pulse) and remained consistent even after 30 minutes of continuous stimulation at 13 μJ, indicating minimal or no stimulation-induced damage within the cochlea. Our findings demonstrate that visible light can effectively and reliably activate the cochlea without any apparent damage. Further studies are in progress to investigate the frequency-specific nature and mechanism of green light cochlear activation.

  3. Improving Activity of Salt-Lyophilized Enzymes in Organic Media

    NASA Astrophysics Data System (ADS)

    Borole, Abhijeet P.; Davison, Brian H.

    Lyophilization with salts has been identified as an important method of activating enzymes in organic media. Using salt-activated enzymes to transform molecules tethered to solid surfaces in organic phase requires solubilization of enzymes in the solvents. Methods of improving performance of salt-lyophilized enzymes, further, via chemical modification, and use of surfactants and surfactants to create fine emulsions prior to lyophilization are investigated. The reaction system used is transesterification of N-acetyl phenylalanine ethyl ester with methanol or propanol. Initial rate of formation of amino acid esters by subtilisin Carlsberg (SC) was studied and found to increase two to sevenfold by either chemical modification or addition of surfactants in certain solvents, relative to the salt (only)-lyophilized enzyme. The method to prepare highly dispersed enzymes in a salt-surfactant milieu also improved activity by two to threefold. To test the effect of chemical modification on derivatization of drug molecules, acylation of bergenin was investigated using chemically modified SC.

  4. Muscle activity characterization by laser Doppler Myography

    NASA Astrophysics Data System (ADS)

    Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

    2013-09-01

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

  5. Actively Q-switched Raman fiber laser

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. G.; Podivilov, E. V.; Babin, S. A.

    2015-03-01

    A new scheme providing actively Q-switched operation of a Raman fiber laser (RFL) has been proposed and tested. The RFL consists of a 1 km single-mode fiber with a switchable loop mirror at one end and an angled cleaved output end. An 1080 nm pulse with microsecond duration is generated at the output by means of acousto-optic switching of the mirror at ~30 kHz in the presence of 6 W backward pumping at 1030 nm. In the proposed scheme, the generated pulse energy is defined by the pump energy distributed along the passive fiber, which amounts to 30 μJ in our case. The available pump energy may be increased by means of fiber lengthening. Pulse shortening is also expected.

  6. Enhancement of transmission of laser and other radiation by soft turbid physical and biological media

    NASA Astrophysics Data System (ADS)

    Askar'yan, G. A.

    1982-07-01

    An analysis is made and experimental results are reported of studies of the transmission of laser and other radiation by turbid physical and biological media, such as layers of a scattering medium or human tissue of thickness much greater than the characteristic attenuation length. It is reported that the transmission increases strongly as a result of depression and piercing of soft scattering media. A local pressure applied to a biological tissue produces a transmission enhancement considerably greater than compression of a layer of a physically turbid medium: this is due to the displacement of blood and of muscle out of the compressed region. A reduction in the scattering and absorption is expected to occur also in the case of rf and ionizing radiations, such as charged particles, x rays, gamma rays, etc. It is pointed out that this could be useful in deep irradiation carried out with the aim of inhibiting internal morbid processes (for example, in the spinal cord) and in treatment of neuroinfectious diseases (amyotrophic lateral sclerosis, multiple sclerosis, poliomyelitis, etc.), as well as in oncological conditions, ulcers, etc.

  7. Optodynamic Phenomena During Laser-Activated Irrigation Within Root Canals

    NASA Astrophysics Data System (ADS)

    Lukač, Nejc; Gregorčič, Peter; Jezeršek, Matija

    2016-07-01

    Laser-activated irrigation is a powerful endodontic treatment for smear layer, bacteria, and debris removal from the root canal. In this study, we use shadow photography and the laser-beam-transmission probe to examine the dynamics of laser-induced vapor bubbles inside a root canal model and compare ultrasonic needle irrigation to the laser method. Results confirm important phenomenological differences in the two endodontic methods with the laser method resulting in much deeper irrigation. Observations of simulated debris particles show liquid vorticity effects which in our opinion represents the major cleaning mechanism.

  8. Perfluorobutyl iodides as gain media for a solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher M.; Lee, Min H.; Lee, Ja H.; Weaver, Willard R.

    1987-01-01

    The effectiveness of t-C4F9I and n-C4F9I as gain media for a space-based solar-pumped iodine photodissociation laser is investigated experimentally. The optically coupled flashlamp/amplifier-tube apparatus described by Hwang et al. (1986) is employed, driving the amplifier with 4-microsec 4.2-mJ TEM(00) pulses from a flashlamp-pumped laser oscillator; the variation of amplification with energy-extraction time was monitored by inserting a delay of up to 1 msec between the firing of the two flashlamps and measuring the delay between the optical pulses. The results are presented graphically and briefly characterized. The performance of t-C4F9I is found to be better than that of n-C4F9I (or n-C3F7I), with an absorption band shifted toward the visible (for improved utilization of solar radiation), higher gain (by a factor of 2) at all delay times, and better chemical reversibility. The gain did not depend significantly on temperature in any of the iodides.

  9. Laser synthesis and stability of one-dimensional polyynic carbon chains in liquid media

    NASA Astrophysics Data System (ADS)

    Arutyunyan, Natalia R.; Fedotov, Pavel V.; Kononenko, Vitaly V.

    2016-03-01

    The results on femtosecond laser formation of polyynic linear carbon chains (LCCs) are reported. To reduce the oxidation and degradation of carbon chains, the synthesis of LCCs was performed in liquid media. The flakes of graphite were suspended in water or in hexane and ultrasonicated to obtain a suspension of micron-size graphite particles. This suspension was irradiated by pulses of Ti:sapphire laser. The spectral lines at 189, 199, 215, 225, 262, 276, 284, 299, 323, 342, and 368 nm in the optical absorption spectrum of the irradiated graphite suspension were clearly distinguished. They were attributed to the absorption of polyynic carbon chains CnH2, where n=2 to 20. The stability of the synthesized one-dimensional carbon chains suspended in water and hexane was defined based on the intensity of the optical absorption bands. Its half-life time was estimated to be 20 h at room temperature for water, and 7 and 25 days for hexane at 60°C and 5°C, respectively.

  10. Synthesis of silver nanoparticles and antimony oxide nanocrystals by pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Mendivil, M. I.; Krishnan, B.; Sanchez, F. A.; Martinez, S.; Aguilar-Martinez, J. A.; Castillo, G. A.; Garcia-Gutierrez, D. I.; Shaji, S.

    2013-03-01

    Pulsed laser ablation in liquid media (PLALM) is a prominent technique for the controlled fabrication of nanomaterials via rapid reactive quenching of ablated species at the interface between the plasma and liquid. Results on nanoparticles and nanocrystals formed by PLALM of silver (Ag) and antimony (Sb) solid targets in different liquid environments (Sodium Dodecyl Sulfate, distilled water) are presented. These experiments were done by irradiating solid targets of Ag and Sb with a nanosecond pulsed Nd:YAG laser output of wavelength 532 nm. Nanoparticles of silver and nanocrystals of antimony oxide (Sb2O3) obtained were characterized using UV-Vis spectrometry, Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), X-ray Energy Dispersion Analysis (EDAX) and X-ray diffractometry (XRD). The morphology of nanomaterials formed is studied as a function of surfactant environment. The silver nanoparticles obtained were spherical of size in the order of 10-35 nm in solution of SDS having different concentrations. In case of the Sb target, ablation was performed in two different molarities of SDS solution and distilled water. Nanocrystals of Sb2O3 in powder form having cubic and orthorhombic phases were formed in SDS solution and as fibers of nanocrystals of cubic Sb2O3 in distilled water.

  11. Generation of phase - matched coherent point source in plasma media by propagated X-ray laser seeded beam

    NASA Astrophysics Data System (ADS)

    Pikuz, T.; Faenov, A.; Magnitskiy, S.; Nagorskiy, N.; Tanaka, M.; Ishino, M.; Nishikino, M.; Kando, M.; Kato, Y.; Kawachi, T.

    2016-03-01

    There is a significant interest in developing the coherent table-top X-ray lasers. Advent of plasma-based transient collisional excitation x-ray laser and particular, injection of coherent seeded beam, especially high-order harmonics, has tremendously improved the spatial coherence of such lasers, what allowed them to be the same widely used as synchrotron sources. Here we report experimental founding of unknown interference structure in a spatial profile of the output beam of the two-stage plasma X-ray laser. That allowed us experimental and theoretical discovering a new phenomenon consisted in a generation of phase-matched coherent point source in a laser plasma media by propagated X-ray laser seeded beam. This phenomenon could extend the applications of such x-ray lasers. For explanation of the observed phenomenon a new method of solving the standard system of Maxwell-Bloch equations has been developed. It was found that the interference pattern in the output laser beam was formed due to an emergence of phase-matched coherent virtual point source in the XRL amplifier and could be treated as the first observation of mirage phenomenon, analogous to the optical mirage, but in X-rays. The obtained results bring new comprehension into the physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and opening new opportunities for X-ray interferometry, holography and other applications, which requiring multiple rigidly phased sources of coherent radiation.

  12. Multispectral angular domain optical tomography in scattering media with argon and diode laser sources

    NASA Astrophysics Data System (ADS)

    Chan, Paulman K. Y.; Vasefi, Fartash; Chapman, Glenn H.; Kaminska, Bozena; Pfeiffer, Nick

    2007-02-01

    Angular Domain Imaging (ADI) within highly scattering media employs micromachined angular filter tunnels to detect nonscattered photons which pass through the tunnels unattenuated while scattered photons collide with the tunnel walls. Each tunnel is micromachined approximately 51 μm wide by 10 mm long in silicon, giving a maximum acceptance angle of 0.29 degrees. The ADI technique is inherently independent of wavelength, and thus multispectral laser sources can be incorporated. Previous ADI experiments employed a 488-514 nm Argon ion laser source. This paper describes the construction of a new imaging system utilizing a high-power (up to 0.5 W) laser diode at the 670 nm wavelength, along with an aspheric and cylindrical lens system for shaping the beam into a collimated line of light. ADI results of biological samples (i.e. chicken breast tissue) are also presented. Image resolution is 204 μm or better in compressed chicken breast tissue approximately 3.8 mm in thickness. Digital image processing techniques are employed to improve image contrast, definition, and detectability of test structures. Because silicon is 40% reflective, scattered light at up to three times the acceptance angle is not sufficiently absorbed by the angular filter tunnels and contributes significant background noise, thus decreasing image contrast and detectability. Roughening of the tunnel surface using a NH4OH etchant solution scatters light hitting the walls, thus allowing it to be absorbed. Images after roughening show dramatic reductions in background scattered light levels between tunnels, suggesting that further experiments will make progress towards improved contrast and detectability of structures.

  13. Decreasing excessive media usage while increasing physical activity: a single-subject research study.

    PubMed

    Larwin, Karen H; Larwin, David A

    2008-11-01

    The Kaiser Family Foundation released a report entitled Kids and Media Use in the United States that concluded that children's use of media--including television, computers, Internet, video games, and phones--may be one of the primary contributor's to the poor fitness and obesity of many of today's adolescents. The present study examines the potential of increasing physical activity and decreasing media usage in a 14-year-old adolescent female by making time spent on the Internet and/or cell phone contingent on physical activity. Results of this investigation indicate that requiring the participant to earn her media-usage time did correspond with an increase in physical activity and a decrease in media-usage time relative to baseline measures. Five weeks after cessation of the intervention, the participant's new level of physical activity was still being maintained. One year after the study, the participant's level of physical activity continued to increase. PMID:18544746

  14. Social media activism and Egyptians' use of social media to combat sexual violence: an HiAP case study.

    PubMed

    Peuchaud, Sheila

    2014-06-01

    This paper represents a case study of how social media activists have harnessed the power of Facebook, Twitter and mobile phone networks to address sexual harassment in Egypt. HarassMap plots reports of sexual harassment on a Google Map and informs victims of support services. Tahrir Bodyguard and Operation Anti-Sexual Harassment (OpAntiSH) protect female protestors who have been vulnerable to sexual aggression at the hands of unruly mobs and by agents of the state. Activists have access to an Android app called 'I'm Getting Arrested' or 'Byt2ebed 3alia' in Egyptian Arabic. The app sends the time and GPS coordinates of an arrest to family, fellow activists, legal counsel and social media outlets. The hope is the initiatives described in this paper could inspire public health ministries and activist NGOs to incorporate crowdsourcing social media applications in the spirit of health in all policies (HiAP). To that end, this paper will begin by defining social media activism from the perspective of the communications discipline. This paper will then demonstrate the significance of sexual harassment as a public health issue, and describe several social media efforts to document incidents and protect victims. The paper will conclude with discussion regarding how these innovations could be integrated into the HiAP approach. PMID:25217347

  15. Laser-induced fluorescence method for on-line molecular isotopologues of iodine-127, iodine-129, iodine-131 detected in gaseous media using a tunable diode laser

    NASA Astrophysics Data System (ADS)

    Kireev, S. V.; Shnyrev, S. L.; Sobolevsky, I. V.

    2016-06-01

    The letter reports on the development of a laser-induced fluorescence method for on-line selective measurement of 127I2, 129I2, 131I2, 129I127I, 127I131I, 129I131I isotopologue concentrations in gaseous media. The method is based on the excitation of molecular iodine isotopologues’ fluorescence by tunable diode laser (632–637 nm) radiation at three or four wavelengths corresponding to the 127I2, 131I2, 129I127I, 129I131I absorption line centers. Boundary relations for concentrations of simultaneously measured iodine isotopologues is about 10‑5–10‑6.

  16. Pulsed actively mode-locked laser based on Nd{sup 3+}-doped disordered garnet and LiF:F{sub 2}{sup {minus}} crystal

    SciTech Connect

    Basiev, T.; Fedorov, V.; Karasik, A.; Senatorov, A.; Shubochkin, R.; Sobol, A.; Grudinin, A.

    1994-12-31

    It is well known that neodymium glasses are widely used as active media in powerful picosecond laser system. However, low thermal conductivity of glasses with broad bands of absorption and luminescence limits their use in pulsed lasers with high repetition rate. At the same time, disordered crystals having broad inhomogeneous bands of active ions and combining properties of both glasses and crystals may be reckoned as active media for ultrashort pulse lasers with high repetition rate. The aim of this work is to investigate the operation of actively mode-locked with LiNbO{sub 3} AOM laser on a calcium-lithium-niobium-gallium disordered garnet crystal doped with Nd{sup 3+} ions (CLNGG:Nd{sup 3+}) and a LiF:F{sub 2}{sup {minus}} passive Q-switch.

  17. MBBR system performance improvement for petroleum hydrocarbon removal using modified media with activated carbon.

    PubMed

    Sayyahzadeh, Amir Hossein; Ganjidoust, Hossein; Ayati, Bita

    2016-01-01

    Moving bed biofilm reactor (MBBR) system has a successful operation in the treatment of different types of wastewater. Since the media, i.e. the place of growth and formation of biofilm, play the main role in the treatment in this system, MBBR systems were operated in the present research with modified Bee-cell media. Activated carbon granules of almond or walnut shells were placed in media pores to improve the treatment of refinery oil wastewater and their operation with MBBR system was compared with the conventional Bee-cell media. In these experiments, the effects of organic loading rate, hydraulic retention time (HRT), media filling ratio (MFR), and activated carbon concentration (ACC) used in the media were investigated on the operation of MBBR systems. The analysis of results estimated the optimal values of HRT, MFR, and ACC used in the media between the studied levels, being equal to 22 h, 50%, and 7.5 g/L, respectively. Under these conditions, total petroleum hydrocarbons removal efficiencies for MBBR systems using Bee-cell media with carbon of almond, carbon of walnut shells, and a carbon-free system were 95 ± 1.17%, 91 ± 1.11%, and 57 ± 1.7%, respectively, which confirms the adsorption ability of systems with the media containing activated carbon in the removal of petroleum compounds from wastewater. PMID:27148731

  18. Laser based on dye-activated silica gel

    SciTech Connect

    Altshuler, G.B.; Bakhanov, V.A.; Dulneva, E.G.; Erofeev, A.V.; Mazurin, O.V.; Roskova, G.P.; Tsekhomskaya, T.S.

    1987-06-01

    Silica gel activated by a dye is used as a new laser medium. The lasin characteristics of rhodamine 6G in silica gel are reported. An important characteristic of the dye laser is its long service life, which is determined by the photostability of the dye in silic gel.(AIP)

  19. Media device ownership and media use: Associations with sedentary time, physical activity and fitness in English youth.

    PubMed

    Sandercock, Gavin R H; Alibrahim, Mohammed; Bellamy, Mark

    2016-12-01

    The aim of this study was to determine whether ownership and use of electronic media were associated with sedentary time and cardiorespiratory fitness (fitness) in youth. We also aimed to determine if associations were independent of physical activity (PA). Fitness was measured using the 20 m shuttle-run. PA, sedentary time, ownership of media devices and media use were self-reported. Participants (n = 678, age 10-15 years) reported daily sedentary time of 620 (± 210) min. Forty-one percent of participants had low PA and 50.4% had low fitness. Higher weekend sedentary time was associated with low fitness in girls (p = 0.005) and boys (p < 0.001) and remained significant when adjusted for PA in the latter (p = 0.006). Using social media was associated with higher sedentary time in both sexes and low fitness in girls. High sedentary time was more likely (OR = 5.3, 95%CI: 2.0-14.4) in boys who owned game consoles. Low fitness was more likely in boys who owned digital/satellite TV receivers (OR = 1.8, 95%CI: 1.8-3.2). Schoolchildren spent > 10 h or ~ 85% of each waking day sedentary. Use of social media was associated with higher sedentary time in both sexes and with low fitness in girls. Reducing social media use in youth offers one potential target for intervention. Behaviours associated with sedentary time differed from predictors of low fitness. The complex and often sex-specific interactions identified between sedentary time, PA and fitness suggest the need for carefully targeted interventions to reduce sedentary time and improve fitness in English youth. PMID:27413678

  20. Direct opto-acoustic in vitro measurement of the spatial distribution of laser radiation in biological media

    SciTech Connect

    Pelivanov, Ivan M; Belov, Sergej A; Solomatin, Vladimir S; Khokhlova, Tanya D; Karabutov, Aleksander A

    2006-12-31

    The problem of opto-acoustic (AO) diagnostics of light scattering and absorption in biological media is considered. The objects under study were milk, bovine and porcine liver, and bovine muscle tissue. The forward and backward schemes for recording acoustic signals were used in experiments. The spatial distribution of the light intensity was measured for each biological medium from the temporal profile of the excited OA pulse and the absorption coefficient and reduced scattering coefficient were determined. Opto-acoustic signals were excited by a 1064-nm pulsed Nd:YAG laser and a tunable Ti:sapphire laser at 779 nm. It is shown that the proposed method can be used for obtaining a priori information on a biological medium in problems of optical and AO tomography. (special issue devoted to multiple radiation scattering in random media)

  1. Social Media and the Idle No More Movement: Citizenship, Activism and Dissent in Canada

    ERIC Educational Resources Information Center

    Tupper, Jennifer

    2014-01-01

    This paper, informed by a critique of traditional understandings of citizenship and civic education, explores the use of social media as a means of fostering activism and dissent. Specifically, the paper explores the ways in which the Idle No More Movement, which began in Canada in 2012 marshalled social media to educate about and protest Bill…

  2. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  3. Study of closed-shell molecular complexes as possible laser media

    SciTech Connect

    Koepke, C.; Wojtowicz, A.J.; Lempicki, A.

    1995-08-01

    The authors have evaluated a series of blue-green emitting molecular-complex materials (d{degree} electronic system) from the point of view of their suitability as possible tunable laser media. All of them reveal a very strong, broad-band excited-state absorption (ESA), occurring between states of different configurations and positioned at the energy related to the crystal field parameter 10 Dq. The ESA strongly overlaps the luminescence spectra. Because of the nature of the terminal state of ESA, the high rate of ESA transitions can be ascribed to the efficient breaking of the Laporte selection rule, because of considerable admixture of p{sub {sigma}} orbitals of ligands and/or p-orbitals of the central ion into the d-orbitals of the central ion in the terminal configuration, and to the existence of triplet terms in this configuration. They survey the ESA characteristics and compare its cross sections to those of stimulated emission. They interpret the obtained results by means of a configuration-coordinate model. Some possible avenues of future work are indicated.

  4. High-energy laser activities at MBDA Germany

    NASA Astrophysics Data System (ADS)

    Mohring, Bernd; Dietrich, Stephan; Tassini, Leonardo; Protz, Rudolf; Geidek, Franz; Zoz, Jürgen

    2013-05-01

    At MBDA Germany a concept for a high-energy laser weapon system is investigated, which is based on existing industrial laser sources. Due to the enormous progress in the field of high-power fiber lasers, commercial industrial fiber lasers are now available delivering a nearly-diffraction limited beam quality with power levels of up to 10 kW. By using a geometric beam coupling scheme, a number of individual high-power fiber laser beams are combined together using one common beam director telescope. A total laser beam power of more than 100 kW can be achieved, which is sufficient for an operational laser weapon system. The individual beams from the different lasers are steered by servo-loops using fast tip-tilt mirrors. This principle enables the concentration of the total laser beam power at one common focal point on a distant target, also allowing fine tracking of target movements and first-order compensation of turbulence effects on laser beam propagation. The proposed beam combination concept was demonstrated by using different experimental set-ups. A number of experiments were performed successfully to investigate laser beam target interaction and target fine tracking, also at large distances and at moving targets. Content and results of these investigations are reported, which demonstrate the complete engagement sequence for a C-RAM scenario. This includes subsequent steps of target acquisition by radar and IR optics, followed by large angle coarse tracking, active fine tracking and destruction of the target by the laser system. This successful implementation of geometric beam combining is an important step for the realization of a laser weapon system in the near future.

  5. Physical Activity Mass Media Campaigns and Their Evaluation: A Systematic Review of the Literature 2003-2010

    ERIC Educational Resources Information Center

    Leavy, Justine E.; Bull, Fiona C.; Rosenberg, Michael; Bauman, Adrian

    2011-01-01

    Internationally, mass media campaigns to promote regular moderate-intensity physical activity have increased recently. Evidence of mass media campaign effectiveness exists in other health areas, however the evidence for physical activity is limited. The purpose was to systematically review the literature on physical activity mass media campaigns,…

  6. Effects of radiation reaction in the interaction between cluster media and high intensity lasers in the radiation dominant regime

    NASA Astrophysics Data System (ADS)

    Iwata, Natsumi; Nagatomo, Hideo; Fukuda, Yuji; Matsui, Ryutaro; Kishimoto, Yasuaki

    2016-06-01

    Interaction between media composed of clusters and high intensity lasers in the radiation dominant regime, i.e., intensity of 10 22 - 23 W / cm 2 , is studied based on the particle-in-cell simulation that includes the radiation reaction. By introducing target materials that have the same total mass but different internal structures, i.e., uniform plasma and cluster media with different cluster radii, we investigate the effect of the internal structure on the interaction dynamics, high energy radiation emission, and its reaction. Intense radiation emission is found in the cluster media where electrons exhibit non-ballistic motions suffering from strong accelerations by both the penetrated laser field and charge separation field of clusters. As a result, the clustered structure increases the energy conversion into high energy radiations significantly at the expense of the conversion into particles, while the total absorption rate into radiation and particles remains unchanged from the absorption rate into particles in the case without radiation reaction. The maximum ion energy achieved in the interaction with cluster media is found to be decreased through the radiation reaction to electrons into the same level with that achieved in the interaction with the uniform plasma. The clustered structure thus enhances high energy radiation emission rather than the ion acceleration in the considered intensity regime.

  7. Stability of higher-order Bragg interactions in active periodic media

    NASA Technical Reports Server (NTRS)

    Jaggard, D. L.

    1977-01-01

    The stability of waves in unbounded, longitudinally periodic media is studied for index and gain coupling. Time-independent periodic media are found to support both stable and absolutely unstable waves. The wave characteristics depend upon average gain or loss, coupling type, and Bragg order. The extended coupled waves equations provide explicit values of threshold, frequency, and temporal growth rate for instabilities at all Bragg resonances through the dispersion relation. Applications to multiharmonic periodicities and complex couplings are briefly discussed with particular note taken of possible reductions of the stability thresholds and removal of threshold degeneracies. Comparisons are made to the longitudinally bounded case of distributed feedback lasers.

  8. Iron-Catalyzed Activation of Chloride from Saline Media

    NASA Astrophysics Data System (ADS)

    Wittmer, Julian; Bleicher, Sergej; Ofner, Johannes; Zetzsch, Cornelius

    2015-04-01

    Iron (Fe) occurs in highly saline media (e.g. sea salt aerosol, salt brines etc.). High salinity, low pH, and organic constituents promote the dissolution of iron, forming photosensitive complexes that are responsible for a gaseous Cl production when irradiated by sunlight [1]. We studied the production of atomic Cl, Br and OH radicals from modeled salt pans [2] and artificial sea-salt aerosols containing Fe(III) ions or pyrogenic Fe2O3particles (Sicotrans Orange, BASF) at various compositions in a Teflon smog-chamber. The samples were either spread on a Teflon sheet or they were nebulized from dilute brines (most abundant particle diameter: ~0.4 μm, initial surface area: up to 3-10-2 cm2cm-3) and exposed to simulated sunlight at 60-90% relative humidity. The photochemical formation of Cl, OH and Br (if possible) in the gas phase was quantified by the radical clock method [3] resulting in time profiles of the radical-production rates and total productions. Simultaneous monitoring of the aerosol surface area enabled us to determine the initial Cl production rate per cm2 aerosol surface. Whereas no significant Cl production was detected employing a molar Cl-/Fe(III) ratio of 13, it increased to ~2.8-1017 atoms cm-2s-1 (at a ratio of 101), ~4.1-1017 atoms cm-2s-1(at a ratio of 53) and ~1.9-1018 atoms cm-2s-1(at a ratio of 13). The presence of NO2 (~20 ppb) or O3 (630 ppb) in the gas phase additionally increased the Fe(III)-induced chloride activation to ~7-1018 atoms cm-2s-1 and ~9-1018 atoms cm-2s-1(at a Cl-/Fe(III) ratio of 13), respectively. SO2 slightly restrained the Cl formation. Artificial sea salt aerosols doped with Fe2O3 (Cl-/Fetot ~13) did not result in detectable Cl concentrations. However, decreasing the pH below 2 favored the dissolution of Fe and led to Cl production rates comparable to the Fe(III) experiments. These observations are in accord with the speciation of the photolabile, aqueous Fe(III) complexes obtained from an equilibrium model (PHREEQC

  9. The aqueous-polyelectrolyte dye solution as an active laser medium

    SciTech Connect

    Akimov, A I; Saletskii, A M

    2000-11-30

    The spectral, luminescent, and lasing properties of aqueous solutions of a cationic dye rhodamine 6G with additions of anion polyelectrolytes - polyacrylic and polymethacrylic acids - are studied. It is found that the energy and spectral properties of lasing of these solutions depend on the ratio of concentrations of polyelectrolyte and molecules. It is also found that the lasing parameters of aqueous-polyelectrolyte dye solutions can be controlled by changing the structure of the molecular system. The variation in the structure of aqueous-polyelectrolyte dye solutions of rhodamine 6G resulted in an almost five-fold increase in the lasing efficiency compared to that in aqueous dye solutions. (lasers, active media)

  10. Behavior of piezoelectric wafer active sensor in various media

    NASA Astrophysics Data System (ADS)

    Kamas, Tuncay

    The dissertation addresses structural health monitoring (SHM) techniques using ultrasonic waves generated by piezoelectric wafer active sensors (PWAS) with an emphasis on the development of theoretical models of standing harmonic waves and guided waves. The focal objective of the research is to extend the theoretical study of electro-mechanical coupled PWAS as a resonator/transducer that interacts with standing and traveling waves in various media through electro-mechanical impedance spectroscopy (EMIS) method and guided wave propagation. The analytical models are developed and the coupled field finite element analysis (CF-FEA) models are simulated and verified with experiments. The dissertation is divided into two parts with respect to the developments in EMIS methods and GWP methods. In the first part, analytical and finite element models have been developed for the simulation of PWAS-EMIS in in-plane (longitudinal) and out-of-plane (thickness) mode. Temperature effects on free PWAS-EMIS are also discussed with respect to the in-plane mode. Piezoelectric material degradation on certain electrical and mechanical properties as the temperature increases is simulated by our analytical model for in-plane circular PWAS-EMIS that agrees well with the sets of experiments. Then the thickness mode PWAS-EMIS model was further developed for a PWAS resonator bonded on a plate-like structure. The latter analytical model was to determine the resonance frequencies for the normal mode expansion method through the global matrix method by considering PWAS-substrate and proof mass-PWAS-substrate models. The proof mass concept was adapted to shift the systems resonance frequencies in thickness mode. PWAS in contact with liquid medium on one of its surface has been analytically modeled and simulated the electro-mechanical response of PWAS with various liquids with different material properties such as the density and the viscosity. The second part discusses the guided wave propagation

  11. The Variable Influence of Audience Activity on Media Effects.

    ERIC Educational Resources Information Center

    Kim, JungKee; Rubin, Alan M.

    1997-01-01

    Hypothesizes that instrumental media motivation, selectivity, attention, and involvement are positive predictors of satisfaction, parasocial interaction, and cultivation effects from watching daytime television serials; avoidance, distraction, and skepticism were seen as negative predictors. Finds support for these expectations through three path…

  12. Activating Digital-Media-Global Literacies and Learning

    ERIC Educational Resources Information Center

    Jacobs, Heidi Hayes

    2014-01-01

    In this article, the author states: "It doesn't matter how many computer-related devices we have in school, what matters is how we employ technology toward a large learning goal, toward a new vision of education." She continues, "When I suggest the cultivation and integration of digital, media, and global literacies, I do so…

  13. Media Unit. ArtsEdge Curricula, Lessons and Activities.

    ERIC Educational Resources Information Center

    Robertson, Helen

    This "mini" curriculum unit introduces primary children (grades K-3) to the concept of images presented through the media, primarily advertising through print and on television. The unit is divided into three approximately 45-minute lessons. In the unit's first lesson, students will discuss why they like the particular toy they have chosen to…

  14. Laser stimulation can activate autophagy in HeLa cells

    SciTech Connect

    Wang, Yisen; Hu, Minglie; Wang, Chingyue; Lan, Bei; Cao, Youjia; He, Hao

    2014-10-27

    For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca{sup 2+} dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

  15. Laser stimulation can activate autophagy in HeLa cells

    NASA Astrophysics Data System (ADS)

    Wang, Yisen; Lan, Bei; He, Hao; Hu, Minglie; Cao, Youjia; Wang, Chingyue

    2014-10-01

    For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca2+ dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

  16. Extreme nonlinearities in InAs/InP nanowire gain media: the two-photon induced laser.

    PubMed

    Capua, Amir; Karni, Ouri; Eisenstein, Gadi; Reithmaier, Johann Peter; Yvind, Kresten

    2012-03-12

    We demonstrate a novel laser oscillation scheme in an InAs / InP wire-like quantum dash gain medium. A short optical pulse excites carriers by two photon absorption which relax to the energy levels providing gain thereby enabling laser oscillations. The nonlinear dynamic interaction is analyzed and quantified using multi-color pump-probe measurements and shows a highly efficient nonlinear two photon excitation process which is larger by more than an order of magnitude compared to common quantum well and bulk gain media. The dynamic response of the nonlinearly induced laser line is characterized by spectrally resolved temporal response measurements, while changes incurring upon propagation in the stimulating short pulse itself are characterized by frequency resolved optical gating (FROG). PMID:22418475

  17. Some results of the propagation of the high-power terawatt femtosecond laser radiation in different media

    NASA Astrophysics Data System (ADS)

    Babushkin, P. A.; Burnashov, A. V.; Iglakova, A. N.; Kovaleva, S. F.; Medvedenko, I. A.

    2015-12-01

    The results of laboratory experiments and numerical calculation of propagation of high-power terawatt femtosecond laser radiation via different media (air, glass and water) are represented. The experiments have been made on femtosecond Ti:Sa-laser system of IAO SB RAS. The spatial features of high-power terawatt femtosecond laser radiation are presented also. The ability of control of the position of the beginning of the field filamentation and angle of divergence of supercontinuum on high-power terawatt femtosecond laser radiation via plane parallel plate (glass) are found. The values of the location of the high value of the backscattering depending on filamentation conditions and the characteristics of supercontinuum and lidar system are obtained. The ability of the remote sensing of cirrus clouds with the help of high-power terawatt femtosecond laser radiation is discussed. The results of interactions of high-power terawatt femtosecond laser radiation and ice hexagonal plate crystal depending upon location of this crystal and filamentation conditions are represented.

  18. Deep trap, laser activated image converting system

    NASA Technical Reports Server (NTRS)

    Maserjian, J. (Inventor)

    1975-01-01

    Receiving an optical image on the surface of a photoconducting semiconductor is presented, storing the image in deep traps of the semiconductor, and later scanning the semiconductor with a laser beam to empty the deep traps, thereby producing a video signal. The semiconductor is illuminated with photons of energy greater than the band gap producing electron-hole pairs in the semiconductor which subsequently fill traps in energy from the band edges. When the laser beam of low energy photons excites the trapped electrons and holes out of the traps into the conduction and valence bands, a photoconductivity can be observed.

  19. Active diaphragm rupture with laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Torikai, H.; Yang, Q. S.; Watanabe, K.; Sasoh, A.

    We performed shock tube operations with a layer of diaphragm being ruptured by laser beam irradiation. Mylar or Cellophane was examined as the diaphragm material. It has been demonstrated that shock tube can be operated with this new technique. The absorbed energy depends on the material and thickness of the diaphragm and is an important control parameter.

  20. Practical and ethical considerations for using social media in community consultation and public disclosure activities.

    PubMed

    Galbraith, Kyle L

    2014-10-01

    Social media are becoming increasingly integrated into both the clinical and the research dimensions of emergency medicine. They can provide methods for sharing crucial information to targeted individuals or groups in a rapid fashion. As a result, investigators conducting emergency research under the exception from prospective informed consent requirements are beginning to turn to social media platforms as they engage in required community consultation and public disclosure activities before their research begins. At present, there are limited data regarding how effectively social media have been used for performing those consultation and disclosure activities. This article offers investigators four specific areas to consider before using social media in consultation and outreach efforts. First, understand the forms of outreach social media platforms can provide. Second, recognize how those outreach methods relate to the specific goals of community consultation and public disclosure. Third, consider whether or not the intended audiences of community consultation and public disclosure will be available via social media. Finally, think about how social media outreach efforts will be measured and assessed before consultation and disclosure activities are under way. PMID:25308139

  1. Substrate-emitting semiconductor laser with a trapezoidal active region

    SciTech Connect

    Dikareva, N V; Nekorkin, S M; Karzanova, M V; Zvonkov, B N; Aleshkin, V Ya; Dubinov, A A; Afonenko, A A

    2014-04-28

    Semiconductor lasers with a narrow (∼2°) directional pattern in the planes both parallel and perpendicular to the p–n junction are fabricated. To achieve a low radiation divergence in the p–n junction plane, the active region in this plane was designed in the form of a trapezium. The narrow directional pattern in the plane perpendicular to the p–n junction was ensured by the use of a leaky mode, through which more than 90% of laser power was coupled out. (lasers)

  2. Comparison of laser-activated tissue solders and thrombin-activated cryoprecipitate for wound closure

    NASA Astrophysics Data System (ADS)

    Kayton, Mark L.; Libutti, Steven K.; Bessler, Marc; Allendorf, John D. F.; Eiref, Simon D.; Marx, Gerard; Mou, Xiaode; Morales, Alfredo M.; Treat, Michael R.; Nowygrod, Roman

    1994-09-01

    To determine the relative strengths of various biologic adhesives at several timepoints, we compared thrombin-activated SD (solvent-detergent treated) cryoprecipitate with laser- activated SD cryoprecipitate and a laser-activated, albumin-based glue. Male Sprague-Dawley rats (n equals 79) received four, 3-cm, dorsal skin incisions which were closed with either laser- activated cryoprecipitate, laser-activated albumin solder, thrombin-activated cryoprecipitate, or standard skin staples. The cryoprecipitate was derived from pooled human plasma and was treated with a solvent-detergent process, rendering it free of envelope-coated viruses (i.e., HBV, HIV). An 808-nm diode laser was used to activate each solder with an average duration of exposure of 75 seconds per incision. Animals were sacrificed for evaluation of wound tensile strength and histology at 0 hours, 2 hours, 4 hours, and 4 days. At all timepoints tested, laser-activated solders were significantly stronger than thrombin-activated cryoprecipitate (p < 0.03) and control wounds (p < 0.003). There was no significant difference in tensile strength between the two types of laser-activated solder at any timepoint.

  3. Early and current physical activity: relationship with intima-media thickness and metabolic variables in adulthood.

    PubMed

    Lima, Manoel C S; Barbosa, Maurício F; Diniz, Tiego A; Codogno, Jamile S; Freitas Júnior, Ismael F; Fernandes, Rômulo A

    2014-08-29

    Background: It is unclear whether early physical activity has a greater influence on intima-media thickness and metabolic variables than current physical activity. Objective: To analyze the relationship between current and early physical activity, metabolic variables, and intima-media thickness measures in adults. Method: The sample was composed of 55 healthy subjects of both sexes (33 men and 22 women). Total body fat and trunk fat were estimated by dual-energy X-ray absorptiometry. Carotid and femoral intima-media thickness were measured using a Doppler ultrasound device. A 12-hour fasting blood sample collection was taken (fasting glucose and lipid profile). Early physical activity was assessed through face-to-face interview, and the current physical activity was assessed by pedometer (Digi-Walker Yamax, SW200), which was used for a period of seven days. Results: Current physical activity was negatively related to total cholesterol (rho=-0.31), while early physical activity was negatively related to triglycerides (rho=-0.42), total cholesterol (rho=-0.28), very low density lipoprotein (rho=-0.44), and carotid intima-media thickness (rho=-0.50). In the multivariate model, subjects engaged in sports activities during early life had lower values of very low density lipoprotein (b=-8.74 [b=-16.1; -1.47]) and carotid intima-media thickness (b=-0.17 [95%CI: -0.28; -0.05]). Conclusion: Early 95%CI physical activity has a significant influence on carotid intima-media thickness, regardless of the current physical activity. PMID:25185030

  4. Early and current physical activity: relationship with intima-media thickness and metabolic variables in adulthood

    PubMed Central

    Lima, Manoel C. S.; Barbosa, Maurício F.; Diniz, Tiego A.; Codogno, Jamile S.; Freitas, Ismael F.; Fernandes, Rômulo A.

    2014-01-01

    Background: It is unclear whether early physical activity has a greater influence on intima-media thickness and metabolic variables than current physical activity. Objective: To analyze the relationship between current and early physical activity, metabolic variables, and intima-media thickness measures in adults. Method: The sample was composed of 55 healthy subjects of both sexes (33 men and 22 women). Total body fat and trunk fat were estimated by dual-energy X-ray absorptiometry. Carotid and femoral intima-media thickness were measured using a Doppler ultrasound device. A 12-hour fasting blood sample collection was taken (fasting glucose and lipid profile). Early physical activity was assessed through face-to-face interview, and the current physical activity was assessed by pedometer (Digi-Walker Yamax, SW200), which was used for a period of seven days. Results: Current physical activity was negatively related to total cholesterol (rho=-0.31), while early physical activity was negatively related to triglycerides (rho=-0.42), total cholesterol (rho=-0.28), very low density lipoprotein (rho=-0.44), and carotid intima-media thickness (rho=-0.50). In the multivariate model, subjects engaged in sports activities during early life had lower values of very low density lipoprotein (b=-8.74 [b=-16.1; -1.47]) and carotid intima-media thickness (b=-0.17 [95%CI: -0.28; -0.05]). Conclusion: Early 95%CI physical activity has a significant influence on carotid intima-media thickness, regardless of the current physical activity. PMID:25372009

  5. Activation of cells using femtosecond laser beam (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Batabyal, Subrata; Satpathy, Sarmishtha; Kim, Young-tae; Mohanty, Samarendra K.

    2016-03-01

    Study of communication in cellular systems requires precise activation of targeted cell(s) in the network. In contrast to chemical, electrical, thermal, mechanical stimulation, optical stimulation is non-invasive and is better suited for stimulation of targeted cells. As compared to visible lasers, the near infrared (NIR) microsecond/nanosecond pulsed laser beams are being used as preferred stimulation tool as they provide higher penetration depth in tissues. Femotosecond (FS) laser beams in NIR are also being used for direct and indirect (i.e. via two-photon optogenetics) stimulation of cells. Here, we present a comparative evaluation of efficacy of NIR FS laser beam for direct (no optogenetic sensitization) and 2ph optogenetic stimulation of cells. Further, for the first time, we demonstrate the use of blue (~450 nm, obtained by second harmonic generation) FS laser beam for stimulation of cells with and without Channelrhodopisn-2 (ChR2) expression. Comparative analysis of photocurrent generated by blue FS laser beam and continuous wave blue light for optogenetics stimulation of ChR2 transfected HEK cells will be presented. The use of ultrafast laser micro-beam for focal, non-contact, and repeated stimulation of single cells in a cellular circuitry allowed us to study the communication between different cell types.

  6. Fission-activated laser as primary power for CW laser propulsion

    SciTech Connect

    Monroe, D.K.

    1993-12-31

    Recent advances in the development of reactor-pumped lasers (RPL`s) have stimulated renewed interest in the concept of laser-powered propulsion. This paper surveys a number of laser propulsion concepts and identifies the one that is most promising from the standpoint of practicality. It is proposed that a ground-based FALCON (Fission-Activated Laser CONcept) RPL can provide primary for this launch vehicle design. The laser-vehicle system could launch small payloads into low-earth orbit (LEO) with high repetition rates and at low costs per kilogram. For the favored design, thruster efficiencies are currently estimated to be about 50%, with 80% being seen as a potentially realizable goal after further design refinements. Laser launch system simulations indicate that with a buy-in laser power of 10 MW, it will be possible to obtain specific impulses in the range of 600 to 800 seconds and payload-to-power ratios of 1 to 3 kg/MW.

  7. Fission-activated laser as primary power for CW laser propulsion

    SciTech Connect

    Monroe, D.K.

    1994-12-31

    Recent advances in the development of reactor-pumped lasers (RPL`s) have stimulated renewed interest in the concept of laser-powered propulsion. This paper surveys a number of laser propulsion concepts and identifies the one that is most promising from the standpoint of practicality. It is proposed that a ground-based FALCON (Fission-Activated Laser CONcept) RPL can provide primary power for this launch vehicle design. The laser-vehicle system could launch small payloads into low-earth orbit (LEO) with high repetition rates and at low costs per kilogram. For the favored design, thruster efficiencies are currently estimated to be about 500%, with 800% being seen as a potentially realizable goal after further design refinements. Laser launch system simulations indicate that, with a buy-in laser power of 10 MW, it will be possible to obtain specific impulses in the range of 600 to 800 seconds and payload-to-power ratios of 1 to 3 kg/MW.

  8. Use of Bioluminescence to Study Reactive Solute Transport and Biofilm Growth and Activity in Porous Media

    NASA Astrophysics Data System (ADS)

    Sharp, R. R.; Gerlach, R.; Al, C. B.

    2004-12-01

    Using a meso-scale porous media flat plate reactor we utilized a naturally bioluminescent biofilm (V. fischeri) and tracer studies to obtain information on the interactions between biofilms and reactive flow in porous media. The growth and development of the V. fischeri biofilm in a porous media geometry was studied using digital time lapse images of the bioluminescent signal given off by the developing biofilm. The effect of biofilm development on porous media hydrodynamics was examined using dye tracer studies and image analysis. The natural bioluminescence of the V. fischeri allowed real-time, in-situ study of biofilm development in porous media, without destruction of the biofilm. Dye studies and image analysis enabled the study of effects of biofilm accumulation on porous media hydraulics, with comparisons to plug flow and completely mixed systems with varying degrees of biofilm accumulation. The hydraulic conductivity of the porous media/biofilm system was continuously monitored showing a 1 to 4 order of magnitude decrease in hydraulic conductivity as a function of biofilm thickness and accumulation. The real-time nature of the study permitted us to visualize dynamic flow channel formation within the biofilm/porous media system. In addition, the sensitivity of the V. fischeri biofilm to dissolved oxygen allowed us to capture real-time images of reactive transport within the system. Using bioluminescent imaging, the location of active biomass, as well as the relative degree of biological activity, could be visualized and monitored over time. This work is the first meso-scale visualization of the interactions between biofilm and flow in porous media.

  9. Effect of media milling on lipid-lowering and antioxidant activities of chitosan.

    PubMed

    Zhang, Wei; Xia, Wenshui

    2015-01-01

    The effect of media milling on lipid-lowering and antioxidant activities of chitosan was studied in rats fed high-fat diets. Results showed that media-milled chitosan was more effective than chitosan in reducing body weight gain and liver fat accumulation of rats. Compared with chitosan, the reducing effects of media-milled chitosan on serum triacylglycerol (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were increased by 10.1, 7.5 and 10.2%, and liver TG and TC-reducing effects were increased by 16.2 and 14.6%, respectively. Rats fed media-milled chitosan showed decreased levels of free fatty acid (FFA) and thiobarbituric acid-reactive substances (TBARS) and increased superoxide dismutase (SOD) activity. The cholesterol and fat in feces of rats fed media-milled chitosan were higher than those of rats fed chitosan. These results suggested media milling enhanced the lipid-lowering and antioxidant activities of chitosan, and the reason might be partly due to its effect on strengthening the ability of chitosan in promoting fecal lipid excretions. PMID:25450554

  10. Activity of respiratory system during laser irradiation of brain structures

    NASA Astrophysics Data System (ADS)

    Merkulova, N. A.; Sergeyeva, L. I.

    1984-06-01

    The performance of one of the principal links of the respiratory system, the respiratory center, was studied as a function of the exposure of the medulla oblongata and the sensomotor zone of the cerebral hemisphere cortex to low level laser irradiation in the red wavelength of the spectrum. Experiments were done on white rats under barbital anesthesia. Under such conditions a substantial effect was observed on the activity of the respiratory center. Laser light may display activating or inhibitory influences, in some cases the bilateral symmetry of the activity of the respiratory center is affected indicating deep changes in the integrative mechanism of the functioning of the right and left sides of the hemispheres. The laser beam effect depends on many factors: specific light properties, duration of the exposure, repetition of exposures, initial functional state of the CNS, etc.

  11. Laser Initiated Ordnance (LIO) activities in NASA

    NASA Technical Reports Server (NTRS)

    Schulze, Norman R.

    1994-01-01

    Laser initiated ordnance appears to offer the advantages of greater reliability, enhanced safety, lighter, less costly products, and improvements in spacecraft system designs which can lead to higher operational efficiency. But the lack of flight demonstrations has prevented the application of this new technology into new programs. Hence, a three-phase technology program was initiated by NASA to provide flight proof of their technical and programmatic feasibility: flight demonstration aboard an unmanned commercial vehicle (Pegasus), use as a Space Shuttle payload, and the most demanding of applications, namely, solid rocket motor vehicle ignition and flight termination. The programs investigate, via flight demonstrations the use of fully solid state laser diode systems to reduce potential hazards imposed by stray electrical signals. Inadvertent ignition has proven to cause serious problems. While the current electromechanical have been made safe, the result has been complex systems. Now is the time to take advantage of this new technology to further enhance safety and reliability of spacecraft systems. Two of the three phases are underway; an announcement of opportunity for the third, a sounding rocket flight demonstration, was made at the workshop.

  12. Diode-end-pumped solid-state lasers with dual gain media for multi-wavelength emission

    NASA Astrophysics Data System (ADS)

    Cho, C. Y.; Chang, C. C.; Chen, Y. F.

    2015-01-01

    We develop a theoretical model for designing a compact efficient multi-wavelength laser with dual gain media in a shared resonator. The developed model can be used to analyze the optimal output reflectivity for each wavelength to achieve maximum output power for multi-wavelength emission. We further demonstrate a dual-wavelength laser at 946 nm and 1064 nm with Nd:YAG and Nd:YVO4 crystals to confirm the numerical analysis. Under optimum conditions and at incident pump power of 17 W, output power at 946 nm and 1064 nm was up to 2.51 W and 2.81 W, respectively.

  13. Protest, Performance and Politics: The Use of "Nano-Media" in Social Movement Activism in South Africa

    ERIC Educational Resources Information Center

    Dawson, Marcelle C.

    2012-01-01

    Considering the lack of coverage in the mass media of certain kinds of social movement activity, many movements make use of smaller scale, independent media to publicise their struggles. From the vantage point of social movements in South Africa, this paper addresses what Mojca Pajnik and John Downing call "nano-media". Based on interviews with…

  14. Individual Differences in Coping with Stressful Mass Media: An Activation-Arousal View.

    ERIC Educational Resources Information Center

    Sparks, Glenn G.; Spirek, Melissa M.

    1988-01-01

    Reports on two studies summarizing recent advances in the study of behavioral dispositions by detailing the activation-arousal framework. Uses the Miller Behavioral Style Scale to measure individual differences in activation/arousal while viewing a negative emotional film segment and media coverage of the explosion of the space shuttle…

  15. The Effectiveness of Social Media Activities on Taiwanese Undergraduates' EFL Grammar Achievement

    ERIC Educational Resources Information Center

    Singman, Cooper

    2012-01-01

    The purpose of this study was to compare the effects of social media language learning activities with traditional language learning activities on the development of L2 grammatical competence in two English as a Foreign Language (EFL) classes at a Taiwanese university. The study was grounded in four bodies of knowledge: (a) the…

  16. Effects of Near-Infrared Laser on Neural Cell Activity

    NASA Astrophysics Data System (ADS)

    Mochizuki-Oda, Noriko; Kataoka, Yosky; Yamada, Hisao; Awazu, Kunio

    2004-08-01

    Near-infrared laser has been used to relieve patients from various kinds of pain caused by postherpetic neuralgesia, myofascial dysfunction, surgical and traumatic wound, cancer, and rheumatoid arthritis. Clinically, He-Ne (λ=632.8 nm, 780 nm) and Ga-Al-As (805 ± 25 nm) lasers are used to irradiate trigger points or nerve ganglion. However the precise mechanisms of such biological actions of the laser have not yet been resolved. Since laser therapy is often effective to suppress the pain caused by hyperactive excitation of sensory neurons, interactions with laser light and neural cells are suggested. As neural excitation requires large amount of energy liberated from adenosine triphosphate (ATP), we examined the effect of 830-nm laser irradiation on the energy metabolism of the rat central nervous system and isolated mitochondria from brain. The diode laser was applied for 15 min with irradiance of 4.8 W/cm2 on a 2 mm-diameter spot at the brain surface. Tissue ATP content of the irradiated area in the cerebral cortex was 19 % higher than that of the non-treated area (opposite side of the cortex), whereas the ADP content showed no significant difference. Irradiation at another wavelength (652 nm) had no effect on either ATP or ADP contents. The temperature of the brain tissue was increased 4.5 - 5.0 °C during the irradiation of both 830-nm and 652-nm laser light. Direct irradiation of the mitochondrial suspension did not show any wavelength-dependent acceleration of respiration rate nor ATP synthesis. These results suggest that the increase in tissue ATP content did not result from the thermal effect, but from specific effect of the laser operated at 830 nm. Electrophysiological studies showed the hyperpolarization of membrane potential of isolated neurons and decrease in membrane resistance with irradiation of the laser, suggesting an activation of potassium channels. Intracellular ATP is reported to regulate some kinds of potassium channels. Possible mechanisms

  17. Overview of the laser activities at Rheinmetall Waffe Munition

    NASA Astrophysics Data System (ADS)

    Ludewigt, Klaus; Riesbeck, Thomas; Schünemann, B.; Graf, A.; Jung, Markus; Schreiber, Th.; Eberhardt, Ramona; Tünnermann, A.

    2012-11-01

    The paper will give an overview over the laser weapon activities at RWM (Rheinmetall Waffe Munition) over the last years. Starting from the actual scenarios for laser weapon applications as: CRAM (Counter Rocket Artillery Mortar), Air Defence and UXO (unexploded ordnance) clearing. The basic requirements of a future laser weapon as beam diameter, beam quality, tracking capability, adaptive optics were deduced. For the UXO scenario a mobile directed energy laser demonstrator for humanitarian mine and UXO clearing based on fiber lasers is presented. Based on the parameters the system concept including the cooling system, power supply and the integration into the armoured vehicle TM 170 are explained. The contribution show first experiments of UXO and IED clearing. Different technical approaches to achieve laser power in the 100 kW regime combined with very good beam quality are discussed to fulfil the requirements of the CRAM and Air Defence scenario. Spectral coupling and the beam superimposing both are performed by Rheinmetall Waffe Munition. At the spectral coupling the basic technology parameters for the fiber laser and the dielectric grating as the latest results were put into context with the power levels reached at other groups. For the beam super imposing technology the basic experiments regarding the tracking capability and compensation of the atmosphere on the test range at Unterlüß will be explained. A generic 10 kW Laser Weapon Demonstrator based on 2 Laser Weapon Modules (LWM) from RWM each 5 kW fiber Laser with beam forming and tracking integrate by the team of RWM and RAD (Rheinmetall Air Defense) into a Ground based Air Defend system consisting of Skyguard and Millenium turret are presented. The flight path of the UAV within the valley of the life firing range at Ochsenboden Switzerland is shown. Selected results of the successful tests against UAV's are presented. It shows the capability of the generic 10 kW Laser Weapon Demonstrator to track and

  18. Method for optical pumping of thin laser media at high average power

    DOEpatents

    Zapata, Luis E.; Beach, Raymond J.; Honea, Eric C.; Payne, Stephen A.

    2004-07-13

    A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

  19. Laser-heating-based active optics for synchrotron radiation applications.

    PubMed

    Yang, Fugui; Li, Ming; Gao, Lidan; Sheng, Weifan; Liu, Peng; Zhang, Xiaowei

    2016-06-15

    Active optics has attracted considerable interest from researchers in synchrotron radiation facilities because of its capacity for x-ray wavefront correction. Here, we report a novel and efficient technique for correcting or modulating a mirror surface profile based on laser-heating-induced thermal expansion. An experimental study of the characteristics of the surface thermal deformation response indicates that the power of a milliwatt laser yields a bump height as low as the subnanometer scale and that the variation of the spot size modulates the response function width effectively. In addition, the capacity of the laser-heating technique for free-form surface modulation is demonstrated via a one-dimensional surface correction experiment. The developed method is a promising new approach toward effective x-ray active optics coupled with at-wavelength metrology techniques. PMID:27304296

  20. The changing face(book) of psychiatry: can we justify 'following' patients' social media activity?

    PubMed

    Cox-George, Chantal

    2015-12-01

    Individuals with mental health issues may post information on social networking sites that can provide an insight into their mental health status. It could be argued that doctors (and specifically psychiatrists) should understand the way in which social media is used by their patients to gain a better insight into their illnesses. However, choosing to actively monitor a patient's social media activity raises important questions about the way in which medical students, qualified clinicians and other healthcare professionals obtain information about patients. While this may be framed as a mere form of 'collateral history-taking', there are obvious practical and ethical problems with doing so. Here, a case is made against monitoring the social media activity of patients involved with psychiatric services. PMID:26755986

  1. "Bridging Activities," New Media Literacies, and Advanced Foreign Language Proficiency

    ERIC Educational Resources Information Center

    Thorne, Steven L.; Reinhardt, Jonathon

    2008-01-01

    In this article we propose the pedagogical model "bridging activities" to address advanced foreign language proficiency in the context of existing and emerging internet communication and information tools and communities. The article begins by establishing the need for language and genre-focused activities at the advanced level that attend to the…

  2. Study of the fragmentation phenomena of TiO2 nanoparticles produced by femtosecond laser ablation in aqueous media

    NASA Astrophysics Data System (ADS)

    Alnassar, S. I.; Akman, E.; Oztoprak, B. G.; Kacar, E.; Gundogdu, O.; Khaleel, A.; Demir, A.

    2013-10-01

    Since last decade, Pulsed Laser Ablation in Liquid (PLAL) has become an increasingly important technique for the production of the nanoparticles (NPs) since it usually provides high purity nanoparticle systems. This paper reports on the production and fragmentation of titanium oxide TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in Sodium Dodecyl Sulfate (SDS) solution using an ultrafast Ti:Sapphire laser. After the production of TiO2 nanoparticles for 30 min of laser irradiation, second harmonics of the laser wavelength are re-applied for different energies (180,120, 60 µJ) to SDS solution containing TiO2 colloids in order to fragment relatively large pieces to obtain smaller ones. It was found that size of nanoparticles after the treatment is independent of the initial characteristics of colloids, but depends strongly on laser parameters especially pulse energy and on the presence of chemically active species in the solution. It was reported that particle size and size distribution range can be decreased using second harmonics of Ti:Sapphire laser wavelengths by using different values of energy. Re-irradiation process at average energy value of 180 μJ decreased average particle size from 185 nm to 110 nm. Characterization of the NPs was studied by applying various techniques such as UV-visible (UV-vis.), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS) and Fourier Transform Infra-Red (FTIR).

  3. Scaling of strontium-vapor laser active volume

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Polunin, Yu. P.

    2008-01-01

    Variations in the energy performance of a self-terminating Sr-vapor laser (SrVL) are examined. The active laser volume is varied between 20 and 650 cm 3. A linear relation is revealed between the average power delivered by the SrVL and its active volume. The SrVL efficiency is found to increase with active volume and to be comparable with that of a copper-vapor laser for an active volume V = 650 cm 3 (0.45 %). As the volume is increased, the total lasing pulse duration increases from 30 to 120 ns. The beam divergence problems associated with the use of a Fabry-Perot cavity or an unstable resonator of the telescopic type are discussed. A total average power of 13.5 W is obtained from V = 650 cm 3 at a lasing PRR F = 19 kHz. The output power generated at different laser wavelengths is as follows: 10.4 W at λ = 6.456 μm, 2.6 W at λ = 3 μm, and 0.5 W at λ = 1 μm. The wavelength dependence of the lasing pulse duration is considered.

  4. Influence of Culture Media on Detection of Carbapenem Hydrolysis by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

    PubMed

    Ramos, Ana Carolina; Carvalhaes, Cecília Godoy; Cordeiro-Moura, Jhonatha Rodrigo; Rockstroh, Anna Carolina; Machado, Antonia Maria Oliveira; Gales, Ana Cristina

    2016-07-01

    In this study, we evaluated the influence of distinct bacterial growth media on detection of carbapenemase hydrolysis by matrix-assisted laser desorption ionization-time of flight mass spectrometry. False-negative results were observed for OXA-25-, OXA-26-, and OXA-72-producing Acinetobacter baumannii isolates grown on MacConkey agar medium. The other culture media showed 100% sensitivity and 100% specificity for detecting carbapenemase. PMID:27076665

  5. Self-reflection and self-transmission of pulsed radiation by laser-evaporated media

    NASA Astrophysics Data System (ADS)

    Furzikov, Nickolay P.

    1991-05-01

    Analysis of the known laser-induced evaporation (thermodestruction) model predicts the quasiperiodic oscillation of the effective absorption depth between its normal value and some minute quantity consisting of a part of the incident wavelength. This prediction explains the experimental data on the polymer laser ablation depth as well as the reflection transient drop of the laserdestructed aluminum.

  6. Media multitasking is associated with distractibility and increased prefrontal activity in adolescents and young adults.

    PubMed

    Moisala, M; Salmela, V; Hietajärvi, L; Salo, E; Carlson, S; Salonen, O; Lonka, K; Hakkarainen, K; Salmela-Aro, K; Alho, K

    2016-07-01

    The current generation of young people indulges in more media multitasking behavior (e.g., instant messaging while watching videos) in their everyday lives than older generations. Concerns have been raised about how this might affect their attentional functioning, as previous studies have indicated that extensive media multitasking in everyday life may be associated with decreased attentional control. In the current study, 149 adolescents and young adults (aged 13-24years) performed speech-listening and reading tasks that required maintaining attention in the presence of distractor stimuli in the other modality or dividing attention between two concurrent tasks. Brain activity during task performance was measured using functional magnetic resonance imaging (fMRI). We studied the relationship between self-reported daily media multitasking (MMT), task performance and brain activity during task performance. The results showed that in the presence of distractor stimuli, a higher MMT score was associated with worse performance and increased brain activity in right prefrontal regions. The level of performance during divided attention did not depend on MMT. This suggests that daily media multitasking is associated with behavioral distractibility and increased recruitment of brain areas involved in attentional and inhibitory control, and that media multitasking in everyday life does not translate to performance benefits in multitasking in laboratory settings. PMID:27063068

  7. Do mass media campaigns improve physical activity? a systematic review and meta-analysis

    PubMed Central

    2013-01-01

    Background Mass media campaigns are frequently used to influence the health behaviors of various populations. There are currently no quantitative meta-analyses of the effect of mass media campaigns on physical activity in adults. Methods We searched six electronic databases from their inception to August 2012 and selected prospective studies that evaluated the effect of mass media campaigns on physical activity in adults. We excluded studies that did not have a proper control group or did not report the uncertainties of the effect estimates. Two reviewers independently screened the title/abstracts and full articles. We used random-effects models to pool effect estimates across studies for 3 selected outcomes. Results Nine prospective cohorts and before-after studies that followed-up 27,601 people over 8 weeks to 3 years met the inclusion criteria. Based on the pooled results from these studies, mass media campaigns had a significant effect on promoting moderate intensity walking (pooled relative risk (RR) from 3 studies=1.53, 95% Confidence Interval: 1.25 to 1.87), but did not help participants achieve sufficient levels of physical activity [4 studies pooled RR=1.02, 95% CI: 0.91 to 1.14)]. The apparent effect of media campaigns on reducing sedentary behavior (pooled RR=1.15, 95% CI: 1.03 to 1.30) was lost when a relatively low-quality study with large effects was excluded in a sensitivity analysis. In subgroup analyses, campaigns that promoted physical activity as a ‘social norm’ seemed to be more effective in reducing sedentary behavior. Conclusion Mass media campaigns may promote walking but may not reduce sedentary behavior or lead to achieving recommended levels of overall physical activity. Further research is warranted on different campaign types and in low- and middle- income countries. PMID:23915170

  8. Self-Organized Transition to Coherent Activity in Disordered Media

    NASA Astrophysics Data System (ADS)

    Singh, Rajeev; Xu, Jinshan; Garnier, Nicolas G.; Pumir, Alain; Sinha, Sitabhra

    2012-02-01

    Synchronized oscillations are of critical functional importance in many biological systems. We show that such oscillations can arise without centralized coordination in a disordered system of electrically coupled excitable and passive cells. Increasing the coupling strength results in waves that lead to coherent periodic activity, exhibiting cluster, local and global synchronization under different conditions. Our results may explain the self-organized transition in a pregnant uterus from transient, localized activity initially to system-wide coherent excitations just before delivery.

  9. Room temperature synthesized rutile TiO2 nanoparticles induced by laser ablation in liquid and their photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Peisheng; Cai, Weiping; Fang, Ming; Li, Zhigang; Zeng, Haibo; Hu, Jinlian; Luo, Xiangdong; Jing, Weiping

    2009-07-01

    TiO2 nanoparticles were prepared by one-step pulsed laser ablation of a titanium target immersed in a poly-(vinylpyrrolidone) solution at room temperature. The products were systematically characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). The results indicated that the rutile TiO2 nanocrystalline particles were one-step synthesized at room temperature and the mean size in diameter is about 50 nm with a narrow size distribution. A probable formation process was proposed on the basis of the microstructure and the instantaneous plasma plume induced by the laser. Photocatalytic activity was monitored by degradation of a methylene blue solution. The as-prepared rutile TiO2 nanoparticles demonstrate a good photocatalytic performance. This work shows that pulsed laser ablation in liquid media is a good method to synthesize some nanosized materials which are difficult to produce by other conventional methods.

  10. Subpicosecond solitons in an actively mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Jones, D. J.; Haus, H. A.; Ippen, E. P.

    1996-11-01

    Experimental results are presented for a study of the stability regime of an actively mode-locked polarization-maintaining fiber ring laser used as a memory. Observations indicate that the pulse widths in the memory can be reduced (by soliton effects) by a factor of approximately 4.4 below the pulse widths predicted by standard active mode-locking theory. Stability regions for the solitons are mapped and compared with theoretical predictions.

  11. Active Wavelength Control of an External Cavity Quantum Cascade Laser

    PubMed Central

    Tsai, Tracy; Wysocki, Gerard

    2012-01-01

    We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3σ precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm−1. Since this control method can be applied to any external cavity laser with little to no modification, such a precision provides an excellent opportunity for spectroscopic applications that target molecular absorption lines at standard atmospheric conditions. PMID:23483850

  12. Media activism and Internet use by people with HIV/AIDS.

    PubMed

    Gillett, James

    2003-09-01

    This paper seeks to understand better the media practices of people who are directly affected by an illness or health problem. Internet sites that have been created by people with HIV/AIDS are examined as a strategy for self-representation. This analysis identifies four prominent 'organising themes' in Internet sites: autobiography; expertise; self promotion; and dissent. It is argued that there is a connection between media activism within the contemporary AIDS movement and Internet use among people with HIV/AIDS. This paper discusses the potential of the Internet, as a form of media activism, to raise the private troubles of people with health problems as public issues through a revitalisation of the public sphere in contemporary post-industrial societies. PMID:12919448

  13. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

  14. Development history of the laser

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Ivan A.

    2011-01-01

    An attempt is made at objectively assessing the contribution made by Soviet scientists to the origination of laser physics, which the author believes tends to be underestimated abroad. Together with the concept of induced radiation, the three-level method and the open resonator were to become cornerstone proposals for laser physics, as were semiconductor active media, carrier injection through the p-n junction, double heterostructure lasers, and laser fusion.

  15. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy.

    PubMed

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications. PMID:27036765

  16. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.

  17. An actively mode-locked Ho: YAG solid laser pumped by a Tm: YLF laser

    NASA Astrophysics Data System (ADS)

    Yao, B. Q.; Cui, Z.; Wang, J.; Duan, X. M.; Dai, T. Y.; Du, Y. Q.; Yuan, J. H.; Liu, W.

    2015-02-01

    A continuous wave mode-locked (CWML) Ho: YAG laser based on an acousto-optic modulator (AOM) pumped by a 1.9 μm Tm: YLF laser is demonstrated. This is the first time a report on an active CWML Ho: YAG laser has been published. A maximum output power of 1.04 W at 2097.25 nm in the CWML regime is obtained at a pump power of 13.2 W, corresponding to a slope efficiency of 13.3%. The mode-locked pulse repetition frequency is 82.76 MHz and the single pulse energy is 12.57 nJ. The mode-locked pulse width is 102 ps measured through a no-background second harmonic autocorrelation with KTP as the nonlinear crystal. Furthermore, the M2 factor is calculated to be 1.146.

  18. Pop Culture Media Icons: Stimuli for Language Activities.

    ERIC Educational Resources Information Center

    Mason, Keith

    1997-01-01

    Describes activities in Spanish language classes inspired by popular movies and television programs such as "Evita,""The Sound of Music,""The Wizard of Oz,""Carousel,""I Dream of Jeannie,""I Love Lucy," and "Charlie's Angels." Notes that these programs' familiarity establishes a familiar context in which to practice grammar, vocabulary, and other…

  19. YouTube, Critical Pedagogy, and Media Activism

    ERIC Educational Resources Information Center

    Kellner, Douglas; Kim, Gooyong

    2010-01-01

    Critical pedagogy believes education to be a form of cultural politics that is fundamental to social transformation aiming to cultivate human agency and transformative activity. The explosion of information and communication technologies (ICTs) has provided ordinary people with unprecedented opportunities to take on the ruling educational power…

  20. Laser activated nanothermolysis of leukemia cells monitored by photothermal microscopy

    NASA Astrophysics Data System (ADS)

    Lapotko, Dmitri; Lukianova, Ekaterina; Shnip, Alexander; Zheltov, George; Potapnev, Michail; Savitsky, Valeriy; Klimovich, Olga; Oraevsky, Alexander

    2005-04-01

    We are developing new diagnostic and therapeutic technologies for leukemia based on selective targeting of leukemia cells with gold nanoparticles and thermomechanical destruction of the tumor cells with laser-induced microbubbles. Clusters of spherical gold nanoparticles that have strong optical absorption of laser pulses at 532 nm served as nucleation sites of vapor microbubbles. The nanoparticles were targeted selectively to leukemia cells using leukemia-specific surface receptors and a set of two monoclonal antibodies. Application of a primary myeloid-specific antibody to tumor cells followed by targeting the cells with 30-nm nanoparticles conjugated with a secondary antibody (IgG) resulted in formation of nanoparticulate clusters due to aggregation of IgGs. Formation of clusters resulted in substantial decrease of the damage threshold for target cells. The results encourage development of Laser Activated Nanothermolysis as a Cell Elimination Therapy (LANCET) for leukemia. The proposed technology can be applied separately or in combination with chemotherapy for killing leukemia cells without damage to other blood cells. Potential applications include initial reduction of concentration of leukemia cells in blood prior to chemotherapy and treatment of residual tumor cells after the chemotherapy. Laser-induced bubbles in individual cells and cell damage were monitored by analyzing profile of photothermal response signals over the entire cell after irradiation with a single 10-ns long laser pulse. Photothermal microscopy was utilized for imaging formation of microbubbles around nanoparticulate clusters.

  1. Laser and spectroscopic properties of chromium-activated forsterite

    SciTech Connect

    Petricevic, V.; Gayen, S.K.; Alfano, R.R. )

    1989-10-20

    Room-temperature pulsed laser action has been obtained in chromium-activated forsterite (Cr:Mg{sub 2}SiO{sub 4}) for both 532-nm and 1064-nm pumping. Free running laser emission in both cases is centered at 1235 nm and has bandwidth of {similar to}20 nm. Slope efficiency as high as 22% has been measured. Using different sets of output mirrors and a single birefringent plate as the intracavity wavelength-selecting element tunability over the 1167--1268 nm spectral range has been demonstrated. Continuous-wave laser operation at room temperature has been obtained for 1064-nm pumping from a cw Nd:YAG laser. The output power slope efficiency is 6.8%. The gain cross section is estimated to be 1.1{times}10{sup {minus}19} cm{sup 2}. Spectroscopic studies suggest that the laser action is due to a center' other than the trivalent chromium (Cr{sup 3+}), presumably the tetravalent chromium (Cr{sup 4+}) in a tetrahedrally coordinated site.

  2. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  3. High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

    NASA Astrophysics Data System (ADS)

    Todt, Michael A.; Albert, Daniel R.; Davis, H. Floyd

    2016-06-01

    A method is described for generating intense pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) laser radiation by resonance enhanced four-wave mixing of commercial pulsed nanosecond lasers in laser vaporized mercury under windowless conditions. By employing noncollinear mixing of the input beams, the need of dispersive elements such as gratings for separating the VUV/XUV from the residual UV and visible beams is eliminated. A number of schemes are described, facilitating access to the 9.9-14.6 eV range. A simple and convenient scheme for generating wavelengths of 125 nm, 112 nm, and 104 nm (10 eV, 11 eV, and 12 eV) using two dye lasers without the need for dye changes is described.

  4. Performing Stenographic Activities. Transcribe from Recorded Media. Student's Manual and Instructor's Manual.

    ERIC Educational Resources Information Center

    Harrison, Pam

    Supporting performance objective 74 of the V-TECS (Vocational-Technical Education Consortium of States) Secretarial Catalog, both a set of student materials and an instructor's manual on transcribing from recorded media are included in this packet. (The packet is the first in a set of four on performing stenographic activities--CE 016 974-976.)…

  5. Thai Youths and Global Warming: Media Information, Awareness, and Lifestyle Activities

    ERIC Educational Resources Information Center

    Chokriensukchai, Kanchana; Tamang, Ritendra

    2010-01-01

    This study examines the exposure of Thai youths to media information on global warming, the relationship between exposure to global warming information and awareness of global warming, and the relationship between that awareness and lifestyle activities that contribute to global warming. A focus group of eight Thai youths provided information that…

  6. Integrated Health and Physical Education Program to Reduce Media Use and Increase Physical Activity in Youth

    ERIC Educational Resources Information Center

    Clocksin, Brian D.; Wattson, Doris L.; Williams, Daniel P.; Randsell, Lynda

    2009-01-01

    The purpose of this project was to compare an integrated health and physical education curriculum, focused on reducing media use and on increasing physical activity in middle school adolescents, to traditional and nonintegrated health and physical education curricula. Two middle schools' health and physical education classes were assigned to an…

  7. Factors Affecting Instructional Development Activities of Selected K-12 Media Professionals.

    ERIC Educational Resources Information Center

    Turner, Philip M.; Martin, Nina N.

    The goal of this study was to establish relationships and/or determine differences between various factors and the extent of instructional development activity. Subjects were 43 graduates of a masters program in library education, currently employed as school media professionals at the K-12 level, who responded to a mailed questionnaire. Forty…

  8. LASERS: Efficient chemical oxygen — iodine laser with a high total pressure of the active medium

    NASA Astrophysics Data System (ADS)

    Zagidullin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.; Heiger, G. D.; Madden, T. J.

    2001-01-01

    A new concept of obtaining a high total pressure of the active medium of a chemical oxygen — iodine laser (OIL) is proposed and verified. The nozzle unit of the laser consists of the alternating vertical arrays of cylindrical nozzles to produce high-pressure nitrogen jets, plane slotted nozzles for the flow of O2(1Δ) oxygen, and vertical arrays of cylindrical nozzles to inject the N2 — I2 mixture between the first two streams. For a molar chlorine flow rate of 39.2 mmol s-1, the output power was 700 W and the chemical efficiency was 19.7 %. The combined use of the ejector nozzle unit proposed to obtain the active medium and a super-sonic diffuser allows a significant simplification of the ejection system for the exhaust active medium of the OIL.

  9. Depolarization effects in the active remote sensing of random media

    NASA Technical Reports Server (NTRS)

    Zuniga, M.; Kong, J. A.; Tsang, L.

    1980-01-01

    Backscattering cross sections for depolarization are derived for the active remote sensing of a two-layer random medium. It is shown that the depolarization effects arise as a second-order term in albedo under the Born approximation. The results of the backscattering cross sections are illustrated as functions of frequency and incident angles and used to match experimental data collected from a vegetation field.

  10. Perfluoro-n-hexyl iodide as gain media for high power, continuous solar-pumped lasers

    NASA Technical Reports Server (NTRS)

    Lee, Ja H.; Tabibi, Bagher M.; Humes, Donald H.; Weaver, Willard R.

    1990-01-01

    A comparative study of CW laser performance with n-C6F13I and n-C3F7I was performed using a 10-W solar-simulator-pumped laser system. The measured output power for n-C6F13I is near 10 W and is comparable to that of n-C3F7I. However, n-C6F13I has the advantages of easy purification and repeated use.

  11. Growth and quasistabilization of large-scale spikes on laser beams in self-focusing media

    NASA Astrophysics Data System (ADS)

    Abbi, S. C.; Kothari, N. C.; Subrahmanyam, V. R.

    1985-07-01

    We present numerical calculations concerning the growth of a large-scale Gaussian spike riding axially over a Gaussian profile intense laser beam. Incorporation of both self-focusing and depletion of the laser beam leads to a criticality with regard to the spike's initial relative intensity due to the counteracting behavior of these two effects, thereby determining the net power transfer to the spike and its quasistabilization.

  12. Direct time-domain observation of laser pulse filaments in transparent media

    SciTech Connect

    Dachraoui, H.; Oberer, C.; Michelswirth,; Heinzmann, U.

    2010-10-15

    The interplay among self-focusing, energy depletion, and plasma formation is fundamental to the understanding of laser-matter interaction. In this article, we present the first direct time-resolved observations of the propagation of intense femtosecond laser pulses experiencing conical emission, self-focusing, self-guiding, beam filamentation, plasma defocusing, and continuum generation in wide-band-gap dielectrics. We demonstrate that continuum generation involves different mechanisms as a function of deposited energy.

  13. Spectroscopic properties and amplified spontaneous emission of fluorescein laser dye in ionic liquids as green media

    NASA Astrophysics Data System (ADS)

    AL-Aqmar, Dalal M.; Abdelkader, H. I.; Abou Kana, Maram T. H.

    2015-09-01

    The use of ionic liquids (ILs) as milieu materials for laser dyes is a promising field and quite competitive with volatile organic solvents and solid state-dye laser systems. This paper investigates some photo-physical parameters of fluorescein dye incorporated into ionic liquids; 1-Butyl-3-methylimidazolium chloride (BMIM Cl), 1-Butyl-3-methylimidazolium tetrachloroaluminate (BMIM AlCl4) and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4) as promising host matrix in addition to ethanol as reference. These parameters are: absorption and emission cross-sections, fluorescence lifetime and quantum yield, in addition to the transition dipole moment, the attenuation length and oscillator strength were also investigated. Lasing characteristics such as amplified spontaneous emission (ASE), the gain, and the photostability of fluorescein laser dye dissolved in different host materials were assessed. The composition and properties of the matrix of ILs were found that it has great interest in optimizing the laser performance and photostability of the investigated laser dye. Under transverse pumping of fluorescein dye by blue laser diode (450 nm) of (400 mW), the initial ASE for dye dissolved in BMIM AlCl4 and ethanol were decreased to 39% and 36% respectively as time progressed 132 min. Relatively high efficiency and high fluorescence quantum yield (11.8% and 0.82% respectively) were obtained with good photostability in case of fluorescein in BMIM BF4 that was decreased to ∼56% of the initial ASE after continuously pumping with 400 mW for 132 min.

  14. Laser light triggered-activated carbon nanosystem for cancer therapy.

    PubMed

    Chu, Maoquan; Peng, Jinliang; Zhao, Jiajia; Liang, Shanlu; Shao, Yuxiang; Wu, Qiang

    2013-02-01

    Among carbon-based nanomaterials, activated carbon (AC) may be an ideal candidate as a carrier for tumor therapeutic agents. Here we found a new property of nanoscale activated carbon (NAC) with narrow size distribution, namely the rapid conversion of light to thermal energy both in vitro and in vivo. An aqueous suspension of 200 μL of NAC (1 mg/mL) exhibited a rapid temperature increase of more than 35 °C after irradiation for 20 min with a 655-nm laser; this was within the temperature range for effective tumor treatment. We demonstrated that lung cancer cells (H-1299) incubated with bamboo nano-AC (BNAC) were killed with high efficiency after laser irradiation. In addition, mouse tumors with sizes smaller than the laser spot that had been injected with BNAC disappeared after irradiation. For tumors larger than the laser spot area, the incorporation of the photosensitizer ZnPc obviously increased the tumor growth inhibition efficiency of BNAC. BNAC-ZnPc was found to exhibit a synergistic effect when photothermal and photodynamic therapies were administered in combination. These results indicated that NAC can be used for high efficiency cancer phototherapy. PMID:23228422

  15. Feedback-induced phase transitions in active porous media

    NASA Astrophysics Data System (ADS)

    Ocko, Samuel; Mahadevan, L.

    2014-11-01

    We consider a reduced-complexity model for an active porous medium where flow and resistance are coupled to each other i.e. the porous medium is modified by the flow and in turn modifies the flow. Using numerical simulations, we show that this results in both channelization and wall-building transitions depending on the form of the feedback. A continuum model allows us to understand the qualitative features of the resulting phase diagram, and suggests ways to realize complex architectures using simple rules in engineered systems. Human Frontiers Science Program Grant RGP0066/2012- TURNER.

  16. Antioxidant activity of betanidin: electrochemical study in aqueous media.

    PubMed

    Wybraniec, Sławomir; Stalica, Paweł; Spórna, Aneta; Nemzer, Boris; Pietrzkowski, Zbigniew; Michałowski, Tadeusz

    2011-11-23

    The antioxidative mechanism of action of betalains is of significant interest because these pigments are recently emerging as highly bio-active natural compounds with potential benefits to human health. Betanidin, the basic betacyanin, comprises the 5,6-dihydroxyl moiety, which results in its high antioxidant activity. Oxidation of betanidin by voltammetric techniques and chro matographic identification of the oxidation products with spectrophotometric and mass spectrometric detection (LC-DAD-MS/MS) were performed. Two main oxidation peaks for betanidin are observable at pH 3-5. These peaks become merged at higher pH, suggesting a different mechanism of oxidation at higher and lower pH values. The low oxidation potential of betanidin confirms its very strong reduction properties. The presence of two prominent oxidized products, 2-decarboxy-2,3-dehydrobetanidin and 2,17-bidecarboxy-2,3-dehydrobetanidin, indicates their generation through two reaction routes with two different quinonoid intermediates: dopachrome derivative and quinone methide. Both lead to the decarboxylative dehydrogenation of betanidin. Subsequent oxidation and rearrangement of the conjugated chromophoric system results in formation of 14,15-dehydrogenated derivatives. PMID:21913685

  17. Simplified Solutions for Activity Deposited on Moving Filter Media.

    PubMed

    Smith, David L; Chabot, George E

    2016-10-01

    Simplified numerical solutions for particulate activity viewed on moving filter continuous air monitors are developed. The monitor configurations include both rectangular window (RW) and circular window (CW) types. The solutions are demonstrated first for a set of basic airborne radioactivity cases, for a series of concentration pulses, and for indicating the effects of step changes in reactor coolant system (RCS) leakage for a pressurized water reactor. The method is also compared to cases from the prior art. These simplified solutions have additional benefits: They are easily adaptable to multiple radionuclides, they will accommodate collection and detection efficiencies that vary in known ways across the collection area, and they also ease the solution programming. PMID:27575345

  18. Active imaging with the aids of polarization retrieve in turbid media system

    NASA Astrophysics Data System (ADS)

    Tao, Qiangqiang; Sun, Yongxuan; Shen, Fei; Xu, Qiang; Gao, Jun; Guo, Zhongyi

    2016-01-01

    We propose a novel active imaging based on the polarization retrieve (PR) method in turbid media system. In our simulations, the Monte Carlo (MC) algorithm has been used to investigate the scattering process between the incident photons and the scattering particles, and the visually concordant object but with different polarization characteristics in different regions, has been selected as the original target that is placed in the turbid media. Under linearly and circularly polarized illuminations, the simulation results demonstrate that the corresponding polarization properties can provide additional information for the imaging, and the contrast of the polarization image can also be enhanced greatly compared to the simplex intensity image in the turbid media. Besides, the polarization image adjusted by the PR method can further enhance the visibility and contrast. In addition, by PR imaging method, with the increasing particles' size in Mie's scale, the visibility can be enhanced, because of the increased forward scattering effect. In general, in the same circumstance, the circular polarization images can offer a better contrast and visibility than that of linear ones. The results indicate that the PR imaging method is more applicable to the scattering media system with relatively larger particles such as aerosols, heavy fog, cumulus, and seawater, as well as to biological tissues and blood media.

  19. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    Major accomplishments under NASA grant NAG-1-1346 are summarized. (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed and several design parameters to be used for the construction of a femtosecond forsterite laser were revealed by simulation. (2) femtosecond pulses from a continuous wave mode-locked chromium doped forsterite laser were generated. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured. (3) Self-mode-locked operation of the Cr:forsterite laser was achieved. Synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking. The pulses generated had an FWHM of 105 fs and were tunable between 1230-1270 nm. (4) Numerical calculations indicated that the pair of SF 14 prisms used in the cavity compensated for quadratic phase but introduced a large cubic phase term. Further calculations of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same amount of quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was observed in the stability of the self mode-locked forsterite laser and in the ease of achieving mode locking. Using the same experimental arrangement and a new forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

  20. Estimation of thermoelastic deformations in the near-surface layers of condensed media upon absorption of time-modulated laser radiation

    NASA Astrophysics Data System (ADS)

    Muratikov, K. L.

    2015-10-01

    Nonstationary thermoelastic deformation in the near-surface layers of condensed media are determined in the quasi-static approximation. The deformations are induced by the absorbed laser radiation. A 3D model is used to derive analytical expressions for normal and radial components of the deformation vector of the surface.

  1. In-situ bioconjugation in stationary media and in liquid flow by femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Sajti, Csaba László; Petersen, Svea; Menéndez-Manjón, Ana; Barcikowski, Stephan

    2010-11-01

    In-situ functionalization of gold nanoparticles with fluorophore-tagged oligonucleotides is studied by comparing femtosecond laser ablation in stationary liquid and in biomolecule flow. Femtosecond laser pulses induce significant degradation to sensitive biomolecules when ablating gold in a stationary solution of oligonucleotides. Contrary, in-situ conjugation of nanoparticles in biomolecule flow considerably reduces the degree of degradation studied by gel electrophoresis and UV-Vis spectrometry. Ablating gold with 100 μJ femtosecond laser pulses DNA sequence does not degrade, while the degree of fluorophore tag degradation was 84% in stationary solution compared to 5% for 1 mL/min liquid flow. It is concluded that femtosecond laser-induced degradation of biomolecules is triggered by absorption of nanoparticle conjugates suspended in the colloid and not by ablation of the target. Quenching of nanoparticle size appears from 0.5 μM biomolecule concentration for 0.3 μg/s nanoparticle productivity indicating the successful surface functionalization. Finally, increasing the liquid flow rate from stationary to 450 mL/min enhances nanoparticle productivity from 0.2 μg/s to 1.5 μg/s, as increasing liquid flow allows removal of light absorbing nanoparticles from the ablation zone, avoiding attenuation of subsequent laser photons.

  2. Acoustic experimental investigation of interaction femtosecond laser pulses with gas-aerosol media and biological tissues

    NASA Astrophysics Data System (ADS)

    Bochkarev, N. N.; Kabanov, A. M.; Stepanov, A. N.

    2008-02-01

    Using two optical acoustic approaches we experimentally investigated spatial location of filament zone of propagation channel of focused laser radiation. For femtosecond pulses passing in air it was shown that nonlinear focus length had spatial scale of 1/P at initial power P moderate for self-focusing and at optical system focus distance significantly lower than Rayleigh beam length. The results of experimental optical acoustic investigation of femto- and nanosecond pulses attenuation by some biological tissues (muscular tissue, adipose tissue, cutaneous covering, milk) and optical breakdown thresholds on these one are presented. It was shown that penetration depth of short laser pulse radiation into biological tissues is the same as for longer one. However, amplitude of acoustic response to a process of interaction of femtosecond laser pulse with biological tissue is larger in several times than that to interaction with nanosecond pulses of the same power and spectral distribution. The obtained of threshold values can be interesting for tabulation of limit allowable levels of irradiation at work with laser radiation. Such values are unknown for femtosecond laser pulses today.

  3. Insight in the Chemistry of Laser-Activated Dental Bleaching

    PubMed Central

    De Moor, Roeland Jozef Gentil; Meire, Maarten August; De Coster, Peter Jozef; Walsh, Laurence James

    2015-01-01

    The use of optical radiation for the activation of bleaching products has not yet been completely elucidated. Laser light is suggested to enhance the oxidizing effect of hydrogen peroxide. Different methods of enhancing hydrogen peroxide based bleaching are possible. They can be classified into six groups: alkaline pH environment, thermal enhancement and photothermal effect, photooxidation effect and direct photobleaching, photolysis effect and photodissociation, Fenton reaction and photocatalysis, and photodynamic effect. PMID:25874251

  4. Research on range-gated laser active imaging seeker

    NASA Astrophysics Data System (ADS)

    You, Mu; Wang, PengHui; Tan, DongJie

    2013-09-01

    Compared with other imaging methods such as millimeter wave imaging, infrared imaging and visible light imaging, laser imaging provides both a 2-D array of reflected intensity data as well as 2-D array of range data, which is the most important data for use in autonomous target acquisition .In terms of application, it can be widely used in military fields such as radar, guidance and fuse. In this paper, we present a laser active imaging seeker system based on range-gated laser transmitter and sensor technology .The seeker system presented here consist of two important part, one is laser image system, which uses a negative lens to diverge the light from a pulse laser to flood illuminate a target, return light is collected by a camera lens, each laser pulse triggers the camera delay and shutter. The other is stabilization gimbals, which is designed to be a rotatable structure both in azimuth and elevation angles. The laser image system consists of transmitter and receiver. The transmitter is based on diode pumped solid-state lasers that are passively Q-switched at 532nm wavelength. A visible wavelength was chosen because the receiver uses a Gen III image intensifier tube with a spectral sensitivity limited to wavelengths less than 900nm.The receiver is image intensifier tube's micro channel plate coupled into high sensitivity charge coupled device camera. The image has been taken at range over one kilometer and can be taken at much longer range in better weather. Image frame frequency can be changed according to requirement of guidance with modifiable range gate, The instantaneous field of views of the system was found to be 2×2 deg. Since completion of system integration, the seeker system has gone through a series of tests both in the lab and in the outdoor field. Two different kinds of buildings have been chosen as target, which is located at range from 200m up to 1000m.To simulate dynamic process of range change between missile and target, the seeker system has

  5. Elasticity-induced force reversal between active spinning particles in dense passive media

    PubMed Central

    Aragones, J. L.; Steimel, J. P.; Alexander-Katz, A.

    2016-01-01

    The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium. PMID:27112961

  6. Elasticity-induced force reversal between active spinning particles in dense passive media

    DOE PAGESBeta

    Aragones, J. L.; Steimel, J. P.; Alexander-Katz, A.

    2016-04-26

    The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between themore » active stresses and elasticity of the system. Finally, this discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium.« less

  7. Elasticity-induced force reversal between active spinning particles in dense passive media

    NASA Astrophysics Data System (ADS)

    Aragones, J. L.; Steimel, J. P.; Alexander-Katz, A.

    2016-04-01

    The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium.

  8. Elasticity-induced force reversal between active spinning particles in dense passive media.

    PubMed

    Aragones, J L; Steimel, J P; Alexander-Katz, A

    2016-01-01

    The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium. PMID:27112961

  9. Sutureless cataract incision closure using laser-activated tissue glues

    NASA Astrophysics Data System (ADS)

    Eaton, Alexander M.; Bass, Lawrence S.; Libutti, Steven K.; Schubert, Herman D.; Treat, Michael R.

    1991-06-01

    With the advent of phacoemulsification and foldable intraocular lenses, there is renewed interest in sutureless cataract wound. We report the use of laser activated tissue glues for the closure of scleral tunnel cataract incisions. Two glue mixtures were tested in enucleated porcine eyes. Glue A was composed of hyaluronic acid, human albumin, and indocyanine green dye. Glue B contained hyaluronic acid, chondroitin sulfate, human albumin, and indocyanine green dye. A Spectra Physics diode laser (808 nm) with a power density of 7-1 1 watts/cm2 was used for glue activation. Wound bursting pressures, as determined by the presence of fluid at the wound margin, was significantly higher with both glue combinations than without the glue (Plaser activated tissue glues may be an alternative to suture closure of scleral tunnel cataract incisions.

  10. Influence of Saline on Temperature Profile of Laser Lithotripsy Activation

    PubMed Central

    Silva, Igor N.; Donalisio da Silva, Rodrigo; Gustafson, Diedra; Sehrt, David; Kim, Fernando J.

    2015-01-01

    Abstract Purpose: We established an ex vivo model to evaluate the temperature profile of the ureter during laser lithotripsy, the influence of irrigation on temperature, and thermal spread during lithotripsy with the holmium:yttrium-aluminum-garnet (Ho:YAG) laser. Materials and Methods: Two ex vivo models of Ovis aries urinary tract and human calcium oxalate calculi were used. The Open Ureteral Model was opened longitudinally to measure the thermal profile of the urothelium. On the Clinical Model, anterograde ureteroscopy was performed in an intact urinary system. Temperatures were measured on the external portion of the ureter and the urothelium during lithotripsy and intentional perforation. The lithotripsy group (n=20) was divided into irrigated (n=10) and nonirrigated (n=10), which were compared for thermal spread length and values during laser activation. The intentional perforation group (n=10) was evaluated under saline flow. The Ho:YAG laser with a 365 μm laser fiber and power at 10W was used (1J/Pulse at 10 Hz). Infrared Fluke Ti55 Thermal Imager was used for evaluation. Maximum temperature values were recorded and compared. Results: On the Clinical Model, the external ureteral wall obtained a temperature of 37.4°C±2.5° and 49.5°C±2.3° (P=0.003) and in the Open Ureteral Model, 49.7°C and 112.4°C with and without irrigation, respectively (P<0.05). The thermal spread along the external ureter wall was not statically significant with or without irrigation (P=0.065). During intentional perforation, differences in temperatures were found between groups (opened with and without irrigation): 81.8°±8.8° and 145.0°±15.0°, respectively (P<0.005). Conclusion: There is an increase in the external ureteral temperature during laser activation, but ureteral thermal values decreased when saline flow was applied. Ureter thermal spread showed no difference between irrigated and nonirrigated subgroups. This is the first laser lithotripsy thermography study

  11. Enzymatic activity in the presence of surfactants commonly used in dissolution media, Part 1: Pepsin.

    PubMed

    Guzman, Maria L; Marques, Margareth R; Olivera Me, Maria E; Stippler, Erika S

    2016-01-01

    The United States Pharmacopeia (USP) General Chapters Dissolution 〈711〉 and Disintegration and Dissolution of Dietary Supplements 〈2040〉 allows the use of enzymes in dissolution media when gelatin capsules do not conform to dissolution specifications due to cross linking. Possible interactions between enzymes and surfactants when used together in dissolution media could result in loss of the enzymatic activity. Pepsin is an enzyme commonly used in dissolution media, and in this work, the activity of pepsin was determined in the presence of different surfactants as usually found in case of dissolution tests of certain gelatin capsule formulations. Pepsin enzymatic activity was determined according to the Ninth Edition of the Food Chemicals Codex (FCC) 9 method, in dissolution conditions: simulated gastric fluid, 37 °C and 50 rpm. Sodium dodecyl sulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), polysorbate 80 (Tween 80) and octoxynol 9 (Triton X100) in concentrations above and below their critical micellar concentrations were selected. Results showed a significant reduction in the activity of pepsin at all the concentrations of SDS assayed. On the contrary, CTAB, Tween 80, and Triton X100 did not alter the enzymatic activity at of pepsin any of the concentration assayed. This data demonstrates a rational selection of the surfactant to be used when pepsin is required in dissolution test. PMID:27047734

  12. Enzymatic activity in the presence of surfactants commonly used in dissolution media, Part 1: Pepsin

    PubMed Central

    Guzman, Maria L; Marques, Margareth R; Olivera ME, Maria E; Stippler, Erika S

    2016-01-01

    The United States Pharmacopeia (USP) General Chapters Dissolution 〈711〉 and Disintegration and Dissolution of Dietary Supplements 〈2040〉 allows the use of enzymes in dissolution media when gelatin capsules do not conform to dissolution specifications due to cross linking. Possible interactions between enzymes and surfactants when used together in dissolution media could result in loss of the enzymatic activity. Pepsin is an enzyme commonly used in dissolution media, and in this work, the activity of pepsin was determined in the presence of different surfactants as usually found in case of dissolution tests of certain gelatin capsule formulations. Pepsin enzymatic activity was determined according to the Ninth Edition of the Food Chemicals Codex (FCC) 9 method, in dissolution conditions: simulated gastric fluid, 37 °C and 50 rpm. Sodium dodecyl sulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), polysorbate 80 (Tween 80) and octoxynol 9 (Triton X100) in concentrations above and below their critical micellar concentrations were selected. Results showed a significant reduction in the activity of pepsin at all the concentrations of SDS assayed. On the contrary, CTAB, Tween 80, and Triton X100 did not alter the enzymatic activity at of pepsin any of the concentration assayed. This data demonstrates a rational selection of the surfactant to be used when pepsin is required in dissolution test. PMID:27047734

  13. Mechanism of dark decomposition of iodine donor in the active medium of a pulsed chemical oxygen - iodine laser

    SciTech Connect

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, A I; Sorokin, Vadim N

    2002-06-30

    A scheme is proposed that describes the dark decomposition of iodide - the donor of iodine - and the relaxation of singlet oxygen in the chlorine-containing active medium of a pulsed chemical oxygen - iodine laser (COIL). For typical compositions of the active media of pulsed COILs utilising CH{sub 3}I molecules as iodine donors, a branching chain reaction of the CH{sub 3}I decomposition accompanied by the efficient dissipation of singlet oxygen is shown to develop even at the stage of filling the active volume. In the active media with CF{sub 3}I as the donor, a similar chain reaction is retarded due to the decay of CF{sub 3} radicals upon recombination with oxygen. The validity of this mechanism is confirmed by a rather good agreement between the results of calculations and the available experimental data. The chain decomposition of alkyliodides accompanied by an avalanche production of iodine atoms represents a new way of efficient chemical production of iodine for a COIL. (active media)

  14. Photophysical and photochemical properties of coumarin laser dyes in amphiphilic media

    NASA Astrophysics Data System (ADS)

    Jones, G., II; Jackson, W. R.; Kanoktanaporn, S.; Bergmark, W. R.

    1983-10-01

    Photophysical properties of coumarin laser dyes solubilized in aqueous detergent or cyclodextrin solutions have been investigated. Dyes appear to be incorporated in hydrated (hydrogen bonded) sites within detergent micelles. Photodegradation is inhibited for detergent solubilized dye. Electron transfer photochemistry is examined by flash photolysis.

  15. Artificial eye for in vitro experiments of laser light interaction with aqueous media

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; Noojin, Gary D.; Hammer, Daniel X.; Thomas, Robert J.; Rockwell, Benjamin A.

    1997-01-01

    An artificial eye has been designed and assembled that mimics the focusing geometry of the living eye. The artificial eye's focusing characteristics are measured and compared with those of the in vivo system. The artificial eye is used to measure several nonlinear optical phenomena that may have an impact on the laser damage thresholds of the retina produced by ultrashort laser pulses. We chose a focal length of 17 mm to simulate the rhesus monkey eye, with a visual cone angle of 8.4 deg for a 2.5-mm diameter laser beam input. The measured focal point image diameter was 5.6 plus or minus 1 micrometer, which was 1.5 times the calculated diffraction-limited image diameter. This focusing system had the best M2 of all the systems evaluated. We used the artificial eye to measure the threshold for laser- induced breakdown, stimulated Brillouin scattering, super- continuum generation, and pulse temporal broadening due to group velocity dispersion.

  16. Value added cleaning and disinfection of the root canal: laser-activated irrigation and laser-induced photoporation

    NASA Astrophysics Data System (ADS)

    De Moor, Roeland J. G.; Meire, Maarten A.

    2016-03-01

    Among present-day marketed systems ultrasonic activation appears to be the best way to activate and potentiate endodontic irrigants. An alternative for ultrasonic activation of irrigants is laser activated irrigation (LAI) or photoninitiated acoustic streaming. Based on present-day research it appears that LAI (especially with Erbium lasers) can be more efficient for debris removal out of root canals and interaction with the endodontic biofilms thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for LAI. Another way to interact with biofilms is to rely on laser-induced photoporation in combination with gold nanoparticles ( AuNPs). The latter is an alternative physical method for delivering macromolecules in cells. Nanosized membrane pores can be created upon pulsed laser illumination. Depending on the laser energy, pores are created through either direct heating of the AuNPs or by vapour nanobubbles that can emerge around the AuNPs.

  17. Surface temperature measurements in a porous media burner using a new laser-induced phosphorescence intensity ratio technique

    NASA Astrophysics Data System (ADS)

    Jaber, A.; Zigan, L.; Sakhrieh, A.; Leipertz, A.

    2013-07-01

    Applying the laser-induced phosphorescence technique, the phosphorescence from a phosphor-coated surface can be used for the determination of the surface temperature during hydrocarbon fuel combustion in a porous media burner. A mixture of dysprosium-cerbium double-doped: yttrium aluminium garnet (Dy:Er:YAG) thermographic phosphor powder and an adhesive agent was used for coating the front surface of the burner which was operated with a thermal load of 1000 W and 2000 W and equivalence ratios of 0.7 and 0.8. A pulsed laser of 355 nm wavelength was used for phosphorescence excitation and a spectrometer for luminescence detections. An adapted intensity ratio (IR) method was applied for temperature determination and compared with two other IR methods. Temperature calibrations were executed in an oven which can be operated up to 2073 K. Imprecision and inaccuracy of the temperature measurements in the phosphor and the mixture calibrations and in the burner-coated front surface have been investigated. The adapted IR method allowed temperature measurements which were more accurate than the other two IR methods, applied for comparison. Compared to additionally performed thermocouple measurements and to published results in the literature using an infrared camera, the adapted IR method turned out to be the more accurate one. The temperature results were also in good agreement with numerical simulations given in the literature.

  18. Chromium doped ZnSe and ZnS gain media for optically and electrically pumped mid-IR lasers

    NASA Astrophysics Data System (ADS)

    Kim, C.; Peppers, J. M.; Martyshkin, D. V.; Fedorov, V. V.; Mirov, S. B.

    2009-02-01

    We report methods of fabrication and laser-spectroscopic characterization of mid-IR gain media based on micron size Cr2+:ZnSe/ZnS powders, as well as Cr2+:ZnSe/ZnS doped fluorocarbon polymer films, and perfluorocarbon liquids. All samples demonstrated strong mid-IR luminescence over 2000-3000nm spectral range under optical 1700nm excitation. The random lasing of the doped liquids and polymer films was realized with pump energy density of 100 and 15mJ/cm2, respectively. Previously we have demonstrated mid-IR electroluminescence of Cr:ZnSe with n-conductivity provided by thermal diffusion of Al and Zn. However, the formation of conductivity was accompanied by compensation of the Cr2+ optical centers and relatively weak chromium electroluminescence. In this paper we report study of the Cr2+ compensation in the crystals co-doped with donor and acceptor impurities. Optical and electrical characterization of Cr:ZnSe crystals with Ag, Cu, Al, In, and Zn co-dopants were studied to optimize mid-IR electroluminescens of the Cr2+ ions. The best results were obtained with p-conductive Ag:Cr:ZnSe samples featuring a low 600 Ωcm resistivity. First mid-IR electroluminescence in presumable p-type Ag:Cr:ZnSe was demonstrated, which could prove valuable for developing laser diodes that function in this spectral region.

  19. Optical nonuniformities in nuclear-pumped cylindrical lasers

    SciTech Connect

    Mat'ev, V Yu; Borovkov, V V; Mel'nikov, S P

    2000-03-31

    The optical nonuniformities, formed as a result of the effect of the inhomogeneous energy deposition by the fission fragments irradiating the laser-active gas from thin uranium-containing layers, were calculated for cylindrical nuclear-pumped gas lasers. The results of the calculations agree with the experiment. (active media. lasers)

  20. Graphene active plasmonic metamaterials for new types of terahertz lasers

    NASA Astrophysics Data System (ADS)

    Otsuji, Taiichi; Watanabe, Takayuki; Satou, Akira; Popov, Vyacheslav; Ryzhii, Victor

    2013-05-01

    This paper reviews recent advances in graphene active plasmonic metamaterials for new types of terahertz lasers. We theoretically discovered that when the population of Dirac Fermionic carriers in graphene are inverted by optical or electrical pumping the excitation of graphene plasmons by the THz photons results in propagating surface plasmon polaritons with giant gain in a wide THz range. Furthermore, when graphene is patterned in a micro- or nano-ribbon array by grating gate metallization, the structure acts as an active plasmonic metamaterial, providing a super-radiant plasmonic lasing with giant gain at the plasmon modes in a wide THz frequency range.

  1. Three-dimensional imaging simulation of active laser detection based on DLOS method

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanxin; Zhou, Honghe; Chen, Xiang; Yuan, Yuan; Shuai, Yong; Tan, Heping

    2016-07-01

    The technology of active laser detection is widely used in many different fields nowadays. With the development of computer technology, programmable software simulation can provide reference for the design of active laser detection. The characteristics of the active laser detecting systems also can be judged more visual. Based on the features of the active laser detection, an improved method of radiative transfer calculation (Double Line Of Sight) was developed, and the simulation models of complete active laser detecting imaging were founded. Compared with the results calculated by the Monte Carlo method, the correctness of the improved method was verified. The results of active laser detecting imaging of complex three-dimensional targets in different atmospheric scenes were compared. The influence of different atmospheric dielectric property were analyzed, which provides effective reference for the design of active laser detection.

  2. Media Education Initiatives by Media Organizations: The Uses of Media Literacy in Hong Kong Media

    ERIC Educational Resources Information Center

    Chu, Donna; Lee, Alice Y. L.

    2014-01-01

    As more media organizations have engaged in media education, this paper investigates the goals and practices of these activities. This article coins media education initiatives by media organizations with the term "media-organization media literac"y (MOML). Four MOML projects in Hong Kong were selected for examination. Built on critical…

  3. Improved catalytic activity of laser generated bimetallic and trimetallic nanoparticles.

    PubMed

    Singh, Rina; Soni, R K

    2014-09-01

    We report synthesis of silver nanoparticles, bimetallic (Al2O3@Ag) nanoparticles and trimetallic (Al2O3@AgAu) nanoparticles by nanosecond pulse laser ablation (PLA) in deionized water. Two-step laser ablation methodologies were adopted for the synthesis of bi- and tri-metallic nanoparticles. In this method a silver or gold target was ablated in colloidal solution of γ-alumina nanoparticles prepared by PLA. The TEM image analysis of bimetallic and trimetallic particles reveals deposition of fine silver particles and Ag-Au alloy particles, respectively, on large alumina particles. The laser generated nanoparticles were tested for catalytic reduction of 4-nitrophenol to 4-aminophenol and showed excellent catalytic behaviour. The catalytic rate was greatly improved by incorporation of additional metal in silver nanoparticles. The catalytic efficiency of trimetallic Al2O3@AgAu for reduction of 4-nitrophenol to 4-aminophenol was remarkably enhanced and the catalytic reaction was completed in just 5 sec. Even at very low concentration, both Al2O3@Ag nanoparticles and Al2O3@AgAu nanoparticles showed improved rate of catalytic reduction than monometallic silver nanoparticles. Our results demonstrate that alumina particles in the solution not only provide the active sites for particle dispersion but also improve the catalytic activity. PMID:25924343

  4. High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

    DOEpatents

    Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.

    2005-07-05

    A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

  5. Filamentation and supercontinuum generation in solid-state dielectric media with picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Galinis, J.; Tamošauskas, G.; GražulevičiÅ«tÄ--, I.; KeblytÄ--, E.; Jukna, V.; Dubietis, A.

    2015-09-01

    Filamentation and supercontinuum generation with 1.3-ps, 1055-nm laser pulses in YAG crystal is investigated numerically and experimentally. Numerical simulations based on solving the unidirectional nonparaxial propagation equation uncover that the self-focusing dynamics of a picosecond laser pulse markedly differs from that observed in a femtosecond filamentation regime. We show that spatiotemporal transformation of the picosecond pulse is governed by the free electron plasma, which defocuses and absorbs its rear part, resulting in the formation of several subpulses of femtosecond duration, which thereafter undergo peculiar spatiotemporal dynamics and have different contributions to spectral superbroadening. The numerical findings are confirmed experimentally by measuring the spatiotemporal intensity profiles of the wave packet at various stages of propagation where relevant events of the spectral broadening occur.

  6. Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

    NASA Astrophysics Data System (ADS)

    Baladi, Arash; Sarraf Mamoory, Rasoul

    2010-10-01

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

  7. Analysis of the restricting factors of laser countermeasure active detection technology

    NASA Astrophysics Data System (ADS)

    Zhang, Yufa; Sun, Xiaoquan

    2016-07-01

    The detection effect of laser active detection system is affected by various kinds of factors. In view of the application requirement of laser active detection, the influence factors for laser active detection are analyzed. The mathematical model of cat eye target detection distance has been built, influence of the parameters of laser detection system and the environment on detection range and the detection efficiency are analyzed. Various parameters constraint detection performance is simulated. The results show that the discovery distance of laser active detection is affected by the laser divergence angle, the incident angle and the visibility of the atmosphere. For a given detection range, the laser divergence angle and the detection efficiency are mutually restricted. Therefore, in view of specific application environment, it is necessary to select appropriate laser detection parameters to achieve optimal detection effect.

  8. Direct protein detection from biological media through electrospray-assisted laser desorption ionization/mass spectrometry.

    PubMed

    Huang, Min-Zong; Hsu, Hsiu-Jung; Lee, Jen-Yih; Jeng, Jingyueh; Shiea, Jentaie

    2006-05-01

    We report here using a novel technology-electrospray-assisted laser desorption ionization (ELDI)/mass spectrometry-for the rapid and sensitive detection of the major proteins that exist in dried biological fluids (e.g., blood, tears, saliva, serum), bacterial cultures, and tissues (e.g., porcine liver and heart) under ambient conditions. This technique required essentially no sample pretreatment. The proteins in the samples were desorbed using a pulsed nitrogen laser without the assistance of an organic matrix. The desorbed protein molecules were then post-ionized through their fusion into the charged solvent droplets produced from the electrospray of an acidic methanol solution; electrospray ionization (ESI) proceeded from the newly formed droplets to generate the ESI-like protein ions. This new ionization approach combines some of the features of electrospray ionization with those of matrix-assisted laser desorption ionization (MALDI), that is, sampling of a solid surface with spatial resolution, generating ESI-like mass spectra of the desorbed proteins, and operating under ambient conditions. PMID:16674100

  9. Growth fusion of submicron spherical boron carbide particles by repetitive pulsed laser irradiation in liquid media

    NASA Astrophysics Data System (ADS)

    Ishikawa, Yoshie; Feng, Qi; Koshizaki, Naoto

    2010-06-01

    We studied the fabrication of B4C submicron particles by laser irradiation of boron nanoparticles dispersed in an organic solvent. The spherical shape of the formed particles suggests that instantaneous melt formation and solidification by quenching are involved in the particle-forming process. B4C particles gradually became larger with irradiation time at relatively low laser fluence (1.5 J cm-2 pulse-1) by repetitive melting and fusion of the particles, and the B4C yield increased with irradiation time to 90% for 600 min of irradiation. At higher laser fluences, the B4C yield decreased due to the explosive ablation of boron or B4C to form H3BO3, and thus only the larger B4C particles were observed. The dielectric constant of the organic solvent also affected the generated B4C particle size, probably due to the degree of particle aggregation. Thus, this technique can provide a new approach for fabricating spherical submicron particles of ceramic materials, such as carbides, with simple and safe processes.

  10. Solitary Waves in the Model of Active Media, Taking into Account Effects of Relaxation

    NASA Astrophysics Data System (ADS)

    Likus, W.; Vladimirov, V. A.

    2015-04-01

    We study a system of differential equations simulating transport phenomena in active structured media. The model is a generalization of McKean's modification of the celebrated FitzHugh-Nagumo system, describing the nerve impulse propagation in axon. It takes into account the effects of memory, connected with the presence of internal structure. We construct explicitly the localized traveling wave solutions and analyze their stability.

  11. [Messages about physical activity and nutrition offered by Quebec mass media?].

    PubMed

    Renaud, Lise; Lagaé, Marie Claude; Caron-Bouchard, Monique

    2009-01-01

    As social elements of our environment, mass media are regarded as determinants of individual and population beliefs, social norms and habits. Since it is recognized that they influence population health, this study aims to obtain a better portrait of Quebec media content regarding physical activity and nutrition messages on a public health level. First, we analyzed the content of fictional television shows (n = 1 3) and advertisements broadcast during those shows (n = 68). Second, we reviewed the content of La Presse newspaper and of French television Société Radio-Canada from 1986 to 2005 with regard to physical activity and nutrition messages. Our results indicate a difference between how men and women are portrayed on French television, with women more often being shown as underweight and men as at or above healthy body weight. The results also show that during the 20-year period of the reviewed content, there were fewer messages about physical activity than about nutrition. To be successful in their goal of improving population health, mass media should address both subjects together in their messages. PMID:19507724

  12. Quantum dots as active material for quantum cascade lasers: comparison to quantum wells

    NASA Astrophysics Data System (ADS)

    Michael, Stephan; Chow, Weng W.; Schneider, Hans Christian

    2016-03-01

    We review a microscopic laser theory for quantum dots as active material for quantum cascade lasers, in which carrier collisions are treated at the level of quantum kinetic equations. The computed characteristics of such a quantum-dot active material are compared to a state-of-the-art quantum-well quantum cascade laser. We find that the current requirement to achieve a comparable gain-length product is reduced compared to that of the quantum-well quantum cascade laser.

  13. A bistatic laser monitor

    NASA Astrophysics Data System (ADS)

    Trigub, M. V.; Torgaev, S. N.; Evtushenko, G. S.; Troitskii, V. O.; Shiyanov, D. V.

    2016-06-01

    A prototype of a bistatic laser projection system employing copper bromide vapor based active media is presented that allows remote objects and high-speed processes to be monitored online. The proposed scheme employs two active elements: one in the source for lighting the object and another in the image brightness amplifier.

  14. Application of a high-power KrF laser for the study of supersonic gas flows and the development of hydrodynamic instabilities in layered media

    SciTech Connect

    Zvorykin, V D; Lebo, I G

    2000-06-30

    The design of a miniature laser shock tube for the study of a wide range of hydrodynamic phenomena in liquids at pressures greater than 10 kbar and in supersonic flows with large Mach numbers (greater than 10) is discussed. A substance filling a chamber of quadratic cross section, with a characteristic size of several centimetres, is compressed and accelerated due to local absorption of 100 ns, 100 J KrF laser pulses near the entrance window. It is proposed to focus a laser beam by a prism raster, which provides a uniform intensity distribution over the tube cross section. The system can be used to study the hypersonic flow past objects of complex shape and the development of hydrodynamic instabilities in the case of a passage of a shock wave or a compression wave through the interfaces between different media. (laser applications and other topics in quantum electronics)

  15. Simulations of the kinetics of the active medium of an X-ray laser heated by high-power picosecond pulses

    SciTech Connect

    Politov, V Yu; Lykov, V A; Shinkarev, M K

    2000-12-31

    The gain on the 3S - 3P transitions of Ne-like ions produced upon material heating by high-power picosecond laser pulses was numerically simulated. The dependence of the gain on the average value of the nuclear charge Z and the irradiation intensity was investigated. The shortest wavelength of X-rays that can be produced from the plasma of Ne-like ions was predicted. (active media)

  16. Photonic crystal lasers using wavelength-scale embedded active region

    NASA Astrophysics Data System (ADS)

    Matsuo, Shinji; Sato, Tomonari; Takeda, Koji; Shinya, Akihiko; Nozaki, Kengo; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya; Fujii, Takuro; Hasebe, Koichi; Kakitsuka, Takaaki

    2014-01-01

    Lasers with ultra-low operating energy are desired for use in chip-to-chip and on-chip optical interconnects. If we are to reduce the operating energy, we must reduce the active volume. Therefore, a photonic crystal (PhC) laser with a wavelength-scale cavity has attracted a lot of attention because a PhC provides a large Q-factor with a small volume. To improve this device's performance, we employ an embedded active region structure in which the wavelength-scale active region is buried with an InP PhC slab. This structure enables us to achieve effective confinement of both carriers and photons, and to improve the thermal resistance of the device. Thus, we have obtained a large external differential quantum efficiency of 55% and an output power of -10 dBm by optical pumping. For electrical pumping, we use a lateral p-i-n structure that employs Zn diffusion and Si ion implantation for p-type and n-type doping, respectively. We have achieved room-temperature continuous-wave operation with a threshold current of 7.8 µA and a maximum 3 dB bandwidth of 16.2 GHz. The results of an experimental bit error rate measurement with a 10 Gbit s-1 NRZ signal reveal the minimum operating energy for transferring a single bit of 5.5 fJ. These results show the potential of this laser to be used for very short reach interconnects. We also describe the optimal design of cavity quality (Q) factor in terms of achieving a large output power with a low operating energy using a calculation based on rate equations. When we assume an internal absorption loss of 20 cm-1, the optimized coupling Q-factor is 2000.

  17. Structural properties of silicon nanoparticles formed by pulsed laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Eroshova, O. I.; Perminov, P. A.; Zabotnov, S. V.; Gongal'skii, M. B.; Ezhov, A. A.; Golovan', L. A.; Kashkarov, P. K.

    2012-11-01

    Silicon nanoparticles have been formed as a result of the irradiation of single-crystal silicon targets in distilled water and liquid nitrogen, by, respectively, picosecond and femtosecond laser pulses. The main structural properties of these nanoparticles have been investigated by atomic force microscopy, transmission electron microscopy, electron diffraction, Raman scattering, and photoluminescence spectroscopy. These particles are found to be mainly spherical. The presence of crystalline and amorphous silicon phases under picosecond ablation in water is established experimentally. Irradiation by femtosecond pulses in liquid nitrogen can yield nanoparticles smaller than 5 nm in size, which are quantum dots with a characteristic photoluminescence peak near 750 nm.

  18. Effects of surface active agents on DNAPL migration and distribution in saturated porous media.

    PubMed

    Cheng, Zhou; Gao, Bin; Xu, Hongxia; Sun, Yuanyuan; Shi, Xiaoqing; Wu, Jichun

    2016-11-15

    Dissolved surface active agents such as surfactant and natural organic matter can affect the distribution and fate of dense nonaqueous liquids (DNAPLs) in soil and groundwater systems. This work investigated how two common groundwater surface active agents, humic acid (HA) and Tween 80, affected tetrachloroethylene (PCE) migration and source zone architecture in saturated porous media under environmentally relevant conditions. Batch experiments were first conducted to measure the contact angles and interfacial tensions (IFT) between PCE and quartz surface in water containing different amount of surface active agents. Results showed that the contact angle increased and IFT decreased with concentration of surface active agent increasing, and Tween 80 was much more effective than HA. Five 2-D flow cell experiments were then conducted. Correspondingly, Tween 80 showed strong effects on the migration and distribution of PCE in the porous media due to its ability to change the medium wettability from water-wet into intermediate/NAPL-wet. The downward migration velocities of the PCE in three Tween 80 cells were slower than those in the other two cells. In addition, the final saturation of the PCE in the cells containing surface active agents was higher than that in the water-only cell. Results from this work indicate that the presence of surface active agents in groundwater may strongly affect the fate and distribution of DNAPL through altering porous medium wettability. PMID:27450259

  19. Generation and Amplification of Tunable Multicolored Femtosecond Laser Pulses by Using Cascaded Four-Wave Mixing in Transparent Bulk Media

    PubMed Central

    Liu, Jun; Kobayashi, Takayoshi

    2010-01-01

    We have reviewed the generation and amplification of wavelength-tunable multicolored femtosecond laser pulses using cascaded four-wave mixing (CFWM) in transparent bulk media, mainly concentrating on our recent work. Theoretical analysis and calculations based on the phase-matching condition could explain well the process semi-quantitatively. The experimental studies showed: (1) as many as fifteen spectral up-shifted and two spectral down-shifted sidebands were obtained simultaneously with spectral bandwidth broader than 1.8 octaves from near ultraviolet (360 nm) to near infrared (1.2 μm); (2) the obtained sidebands were spatially separated well and had extremely high beam quality with M2 factor better than 1.1; (3) the wavelengths of the generated multicolor sidebands could be conveniently tuned by changing the crossing angle or simply replacing with different media; (4) as short as 15-fs negatively chirped or nearly transform limited 20-fs multicolored femtosecond pulses were obtained when one of the two input beams was negatively chirped and the other was positively chirped; (5) the pulse energy of the sideband can reach a μJ level with power stability better than 1% RMS; (6) broadband two-dimensional (2-D) multicolored arrays with more than ten periodic columns and more than ten rows were generated in a sapphire plate; (7) the obtained sidebands could be simultaneously spectra broadened and power amplified in another bulk medium by using cross-phase modulation (XPM) in conjunction with four-wave optical parametric amplification (FOPA). The characterization showed that this is interesting and the CFWM sidebands generated by this novel method have good enough qualities in terms of power stability, beam quality, and temporal features suited to various experiments such as ultrafast multicolor time-resolved spectroscopy and multicolor-excitation nonlinear microscopy. PMID:22399882

  20. Chemistry Is in the News: Taxonomy of authentic news media-based learning activities1

    NASA Astrophysics Data System (ADS)

    Glaser, Rainer E.; Carson, Kathleen M.

    2005-09-01

    A brief history is given of approaches that aim at achieving a connectedness of the content of organic chemistry courses to real world issues. Recently, such approaches have relied more and more on online media resources, the tools of the Internet and the World Wide Web. We propose a six-level taxonomy of ‘authentic news media-based learning activities’ to provide a conceptual framework for the description and discussion of such approaches. The Chemistry Is in the News project was designed to allow students to draw explicit connections between the course content and real world issues in ways that engage the students in a full range of cognitive skills. The activities consisted in the study, creation, and peer review of news portfolios by student collaborative groups. A news portfolio consists of an authentic news article taken from the popular press with interpretive comments and questions.

  1. On-line molecular iodine isotopologue detection in gaseous media during spent nuclear fuel reprocessing using a laser-induced fluorescence method

    NASA Astrophysics Data System (ADS)

    Kireev, S. V.; Shnyrev, S. L.

    2015-06-01

    The paper reports on on-line measurement of the {}129{{\\text{I}}2}, 127I129I, and {}127{{\\text{I}}2} concentrations during spent nuclear fuel (SNF) reprocessing using a laser-induced fluorescence method. A He-Ne laser (632.8 nm) was used as a fluorescence excitation source. The detection limits obtained for molecular iodine isotopologue concentrations demonstrate the possibility of using this method for iodine control both in gaseous technological media generated during SNF reprocessing and after passing through the gas purification system (in atmosphere emission).

  2. Laser beam propagation through bulk nonlinear media: Numerical simulation and experiment

    NASA Astrophysics Data System (ADS)

    Kovsh, Dmitriy I.

    This dissertation describes our efforts in modeling the propagation of high intensity laser pulses through optical systems consisting of one or multiple nonlinear elements. These nonlinear elements can be up to 103 times thicker than the depth of focus of the laser beam, so that the beam size changes drastically within the medium. The set of computer codes developed are organized in a software package (NLO_BPM). The ultrafast nonlinearities of the bound-electronic n2 and two-photon absorption as well as time dependent excited-state, free-carrier and thermal nonlinearities are included in the codes for modeling propagation of picosecond to nanosecond pulses and pulse trains. Various cylindrically symmetric spatial distributions of the input beam are modeled. We use the cylindrical symmetry typical of laser outputs to reduce the CPU and memory requirements making modeling a real- time task on PC's. The hydrodynamic equations describing the rarefaction of the medium due to heating and electrostriction are solved in the transient regime to determine refractive index changes on a nanosecond time scale. This effect can be simplified in some cases by an approximation that assumes an instantaneous expansion. We also find that the index change obtained from the photo-acoustic equation overshoots its steady-state value once the ratio between the pulse width and the acoustic transit time is greater than unity. We numerically study the sensitivity of the closed- aperture Z-scan experiment to nonlinear refraction for various input beam profiles. If the beam has a ring structure with a minimum (or zero) on axis in the far field, the sensitivity of Z-scan measurements can be increased by up to one order of magnitude. The linear propagation module integrated with the nonlinear beam propagation codes allows the simulation of typical experiments such as Z-scan and optical limiting experiments. We have used these codes to model the performance of optical limiters. We study two of the

  3. Higher Media Multi-Tasking Activity Is Associated with Smaller Gray-Matter Density in the Anterior Cingulate Cortex

    PubMed Central

    Loh, Kep Kee; Kanai, Ryota

    2014-01-01

    Media multitasking, or the concurrent consumption of multiple media forms, is increasingly prevalent in today’s society and has been associated with negative psychosocial and cognitive impacts. Individuals who engage in heavier media-multitasking are found to perform worse on cognitive control tasks and exhibit more socio-emotional difficulties. However, the neural processes associated with media multi-tasking remain unexplored. The present study investigated relationships between media multitasking activity and brain structure. Research has demonstrated that brain structure can be altered upon prolonged exposure to novel environments and experience. Thus, we expected differential engagements in media multitasking to correlate with brain structure variability. This was confirmed via Voxel-Based Morphometry (VBM) analyses: Individuals with higher Media Multitasking Index (MMI) scores had smaller gray matter density in the anterior cingulate cortex (ACC). Functional connectivity between this ACC region and the precuneus was negatively associated with MMI. Our findings suggest a possible structural correlate for the observed decreased cognitive control performance and socio-emotional regulation in heavy media-multitaskers. While the cross-sectional nature of our study does not allow us to specify the direction of causality, our results brought to light novel associations between individual media multitasking behaviors and ACC structure differences. PMID:25250778

  4. Low level laser therapy reduces inflammation in activated Achilles tendinitis

    NASA Astrophysics Data System (ADS)

    Bjordal, Jan M.; Iversen, Vegard; Lopes-Martins, Rodrigo Alvaro B.

    2006-02-01

    Objective: Low level laser therapy (LLLT) has been forwarded as therapy for osteoarthritis and tendinopathy. Results in animal and cell studies suggest that LLLT may act through a biological mechanism of inflammatory modulation. The current study was designed to investigate if LLLT has an anti-inflammatory effect on activated tendinitis of the Achilles tendon. Methods: Seven patients with bilateral Achilles tendonitis (14 tendons) who had aggravated symptoms by pain-inducing activity immediately prior to the study. LLLT (1.8 Joules for each of three points along the Achilles tendon with 904nm infrared laser) and placebo LLLT were administered to either Achilles tendons in a random order to which patients and therapist were blinded. Inflammation was examined by 1) mini-invasive microdialysis for measuring the concentration of inflammatory marker PGE II in the peritendinous tissue, 2) ultrasound with Doppler measurement of peri- and intratendinous blood flow, 3) pressure pain algometry and 4) single hop test. Results: PGE 2- levels were significantly reduced at 75, 90 and 105 minutes after active LLLT compared both to pre-treatment levels (p=0.026) and to placebo LLLT (p=0.009). Changes in pressure pain threshold (PPT) were significantly different (P=0.012) between groups. PPT increased by a mean value of 0.19 kg/cm2 [95%CI:0.04 to 0.34] after treatment in the active LLLT group, while pressure pain threshold was reduced by -0.20 kg/cm2 [95%CI:-0.45 to 0.05] after placebo LLLT. Conclusion: LLLT can be used to reduce inflammatory musculskeletal pain as it reduces inflammation and increases pressure pain threshold levels in activity-induced pain episodes of Achilles tendinopathy.

  5. Small-angle approximation to the transfer of narrow laser beams in anisotropic scattering media

    NASA Technical Reports Server (NTRS)

    Box, M. A.; Deepak, A.

    1981-01-01

    The broadening and the signal power detected of a laser beam traversing an anisotropic scattering medium were examined using the small-angle approximation to the radiative transfer equation in which photons suffering large-angle deflections are neglected. To obtain tractable answers, simple Gaussian and non-Gaussian functions for the scattering phase functions are assumed. Two other approximate approaches employed in the field to further simplify the small-angle approximation solutions are described, and the results obtained by one of them are compared with those obtained using small-angle approximation. An exact method for obtaining the contribution of each higher order scattering to the radiance field is examined but no results are presented.

  6. LASER-driven fast electron dynamics in gaseous media under the influence of large electric fields

    NASA Astrophysics Data System (ADS)

    Batani, D.; Baton, S. D.; Manclossi, M.; Piazza, D.; Koenig, M.; Benuzzi-Mounaix, A.; Popescu, H.; Rousseaux, C.; Borghesi, M.; Cecchetti, C.; Schiavi, A.

    2009-03-01

    We present the results of experiments performed at the LULI laboratory, using the 100 TW laser facility, on the study of the propagation of fast electrons in gas targets. The implemented diagnostics included chirped shadowgraphy and proton imaging. Proton images showed the presence of very large fields in the gas (produced by charge separation). In turn, these imply a strong inhibition of propagation, and a slowing down of the fast electron cloud as it penetrates in the gas. Indeed chirped shadowgraphy images show a reduction in time of the velocity of the electron cloud from the initial value, of the order of a fraction of c, over a time scale of a few picoseconds.

  7. An active alignment method for post launch co-alignment of laser beam combiner systems

    NASA Technical Reports Server (NTRS)

    Yu, A. W.; Green, J. W.; Maynard, W. L.; Minott, P. O.; Krainak, M. A.

    1992-01-01

    A laser transmitter for high bandwidth geosynchronous satellite communications is described. High optical power is achieved by combining semiconductor laser diodes. An active alignment scheme is proposed for achieving the +/- 20 microrad post launch multiple laser angular co-alignment requirement.

  8. Cost-effectiveness analysis of a statewide media campaign to promote adolescent physical activity.

    PubMed

    Peterson, Michael; Chandlee, Margaret; Abraham, Avron

    2008-10-01

    A cost-effectiveness analysis of a statewide social marketing campaign was performed using a statewide surveillance survey distributed to 6th through 12th graders, media production and placement costs, and 2000 census data. Exposure to all three advertisements had the highest impact on both intent and behavior with 65.6% of the respondents considering becoming more active and 58.3% reporting becoming more active. Average cost of the entire campaign was $4.01 per person to see an ad, $7.35 per person to consider being more active, and $8.87 per person to actually become more active, with billboards yielding the most positive cost-effectiveness. Findings highlight market research as an essential part of social marketing campaigns and the importance of using multiple marketing modalities to enhance cost-effectiveness and impact. PMID:18367641

  9. Growth, Sporulation, and Germination of Clostridium perfringens in Media of Controlled Water Activity1

    PubMed Central

    Kang, Chunghee K.; Woodburn, Margy; Pagenkopf, Andrea; Cheney, Roberta

    1969-01-01

    Requirements in terms of water activity (aw) for the growth, sporulation, and germination of Clostridium perfringens were determined. Strain A48 was used in all phases, and in addition either NCTC 8239 or NCTC 8797 was used for growth, sporulation, and germination studies. The desired aw of the test media was obtained by the addition of one of three solutes: glycerol, sucrose, or sodium chloride. The freezing point depression method was used to determine the aw. The basal medium for growth and germination was Fluid Thioglycollate Medium. It had an aw of 0.995 and produced maximum growth and fastest growth rate among the six levels of aw tested. The lowest aw supporting growth and germination of C. perfringens was between 0.97 and 0.95 in the test media made with sucrose or sodium chloride and 0.93 or below in the test media adjusted with glycerol. Spore production by C. perfringens in Ellner's or modified medium required a higher aw than growth. PMID:4313168

  10. Micro-poromechanics model of fluid-saturated chemically active fibrous media

    PubMed Central

    Misra, Anil; Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette

    2014-01-01

    We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill’s volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete. PMID:25755301

  11. Pricing a Protest: Forecasting the Dynamics of Civil Unrest Activity in Social Media

    PubMed Central

    Roan, Michael; Ramakrishnan, Naren

    2015-01-01

    Online social media activity can often be a precursor to disruptive events such as protests, strikes, and “occupy” movements. We have observed that such civil unrest can galvanize supporters through social networks and help recruit activists to their cause. Understanding the dynamics of social network cascades and extrapolating their future growth will enable an analyst to detect or forecast major societal events. Existing work has primarily used structural and temporal properties of cascades to predict their future behavior. But factors like societal pressure, alignment of individual interests with broader causes, and perception of expected benefits also affect protest participation in social media. Here we develop an analysis framework using a differential game theoretic approach to characterize the cost of participating in a cascade, and demonstrate how we can combine such cost features with classical properties to forecast the future behavior of cascades. Using data from Twitter, we illustrate the effectiveness of our models on the “Brazilian Spring” and Venezuelan protests that occurred in June 2013 and November 2013, respectively. We demonstrate how our framework captures both qualitative and quantitative aspects of how these uprisings manifest through the lens of tweet volume on Twitter social media. PMID:26441072

  12. Poromechanics Parameters of Fluid-Saturated Chemically Active Fibrous Media Derived from a Micromechanical Approach.

    PubMed

    Misra, Anil; Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette

    2013-01-01

    The authors have derived macroscale poromechanics parameters for chemically active saturated fibrous media by combining microstructure-based homogenization with Hill's volume averaging. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's Lemmas. The advantage of this approach is that the resultant continuum model assumes a form suited to study porous materials, while retaining the effect of discrete fiber deformation. As a result, the model is able to predict the influence of microscale phenomena such as fiber buckling on the overall behavior, and in particular, on the poromechanics constants. The significance of the approach is demonstrated using the effect of drainage and fiber nonlinearity on monotonic compressive stress-strain behavior. The model predictions conform to the experimental observations for articular cartilage. The method can potentially be extended to other porous materials such as bone, clays, foams, and concrete. PMID:25419475

  13. Pricing a Protest: Forecasting the Dynamics of Civil Unrest Activity in Social Media.

    PubMed

    Goode, Brian J; Krishnan, Siddharth; Roan, Michael; Ramakrishnan, Naren

    2015-01-01

    Online social media activity can often be a precursor to disruptive events such as protests, strikes, and "occupy" movements. We have observed that such civil unrest can galvanize supporters through social networks and help recruit activists to their cause. Understanding the dynamics of social network cascades and extrapolating their future growth will enable an analyst to detect or forecast major societal events. Existing work has primarily used structural and temporal properties of cascades to predict their future behavior. But factors like societal pressure, alignment of individual interests with broader causes, and perception of expected benefits also affect protest participation in social media. Here we develop an analysis framework using a differential game theoretic approach to characterize the cost of participating in a cascade, and demonstrate how we can combine such cost features with classical properties to forecast the future behavior of cascades. Using data from Twitter, we illustrate the effectiveness of our models on the "Brazilian Spring" and Venezuelan protests that occurred in June 2013 and November 2013, respectively. We demonstrate how our framework captures both qualitative and quantitative aspects of how these uprisings manifest through the lens of tweet volume on Twitter social media. PMID:26441072

  14. Poromechanics Parameters of Fluid-Saturated Chemically Active Fibrous Media Derived from a Micromechanical Approach

    PubMed Central

    Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette

    2014-01-01

    The authors have derived macroscale poromechanics parameters for chemically active saturated fibrous media by combining microstructure-based homogenization with Hill's volume averaging. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's Lemmas. The advantage of this approach is that the resultant continuum model assumes a form suited to study porous materials, while retaining the effect of discrete fiber deformation. As a result, the model is able to predict the influence of microscale phenomena such as fiber buckling on the overall behavior, and in particular, on the poromechanics constants. The significance of the approach is demonstrated using the effect of drainage and fiber nonlinearity on monotonic compressive stress-strain behavior. The model predictions conform to the experimental observations for articular cartilage. The method can potentially be extended to other porous materials such as bone, clays, foams, and concrete. PMID:25419475

  15. Monte Carlo simulations of converging laser beam propagating in turbid media with parallel computing

    NASA Astrophysics Data System (ADS)

    Wu, Di; Lu, Jun Q.; Hu, Xin H.; Zhao, S. S.

    1999-11-01

    Due to its flexibility and simplicity, Monte Carlo method is often used to study light propagation in turbid medium where the photons are treated like classic particles being scattered and absorbed randomly based on a radiative transfer theory. However, due to the need of large number of photons to produce statistically significance results, this type of calculations requires large computing resources. To overcome such difficulty, we implemented parallel computing technique into our Monte Carlo simulations. The algorithm is based on the fact that the classic particles are uncorrelated, and the trajectories of multiple photons can be tracked simultaneously. When a beam of focused light incident to the medium, the incident photons are divided into groups according to the available processes on a parallel machine and the calculations are carried out in parallel. Utilizing PVM (Parallel Virtual Machine, a parallel computing software), the parallel programs in both C and FORTRAN are developed on the massive parallel computer Cray T3E at the North Carolina Supercomputer Center and a local PC-cluster network running UNIX/Sun Solaris. The parallel performances of our codes have been excellent on both Cray T3E and the PC clusters. In this paper, we present results on a focusing laser beam propagating through a highly scattering and diluted solution of intralipid. The dependence of the spatial distribution of light near the focal point on the concentration of intralipid solution is studied and its significance is discussed.

  16. Numerical calculation of nonlinear ultrashort laser pulse propagation in transparent Kerr media

    NASA Astrophysics Data System (ADS)

    Arnold, Cord L.; Heisterkamp, Alexander; Ertmer, Wolfgang; Lubatschowski, Holger

    2005-03-01

    In the focal region of tightly focused ultrashort laser pulses, sufficient high intensities to initialize nonlinear ionization processes are easily achieved. Due to these nonlinear ionization processes, mainly multiphoton ionization and cascade ionization, free electrons are generated in the focus resulting in optical breakdown. A model including both nonlinear pulse propagation and plasma generation is used to calculate numerically the interaction of ultrashort pulses with their self-induced plasma in the vicinity of the focus. The model is based on a (3+1)-dimensional nonlinear Schroedinger equation describing the pulse propagation coupled to a system of rate equations covering the generation of free electrons. It is applicable to any transparent Kerr medium, whose linear and nonlinear optical parameters are known. Numerical calculations based on this model are used to understand nonlinear side effects, such as streak formation, occurring in addition to optical breakdown during short pulse refractive eye surgeries like fs-LASIK. Since the optical parameters of water are a good first-order approximation to those of corneal tissue, water is used as model substance. The free electron density distribution induced by focused ultrashort pulses as well as the pulses spatio-temporal behavior are studied in the low-power regime around the critical power for self-focusing.

  17. Azimuthally unstable resonators for high-power CO[sub 2] lasers with annular gain media

    SciTech Connect

    Ehrlichmann, D.; Habich, U.; Plum, H.D.; Loosen, P.; Herziger, G. )

    1994-06-01

    Stable-unstable resonators have proved suitable for the extraction of a high-quality beam from a gain area that consists of a rectangular slab. Such gain areas have two substantially different transverse dimensions, and the resonators are stable in the small dimension while unstable in the larger one. Using off-axis unstable resonators avoids a central beam obscuration and improves beam quality. The adaptation of stable-unstable resonators to annular gain areas is described in this paper. The resulting resonators are stable in the radial direction and unstable in the azimuthal direction. Different unstable resonators, wound to match the annular geometry, are presented. The resonator modes are calculated numerically using a 3D-diffraction code that considers gain and misalignment. Resonator design parameters are obtained from a geometrical description of the resonator. Experimental results from a diffusion-cooled CO[sub 2] laser confirm theoretical predictions and show that the resonators are capable of extracting beams that are nearly diffraction-limited with high efficiency from an annular gain medium. Output powers of 2 kW have been obtained from a gain length of 1.8 m.

  18. Measurement of glucose concentration in turbid media by the polarization state of backscattered laser light

    NASA Astrophysics Data System (ADS)

    Kafidova, Galina A.; Aksenov, Evgenii T.; Petrov, Victor M.

    2013-06-01

    Biological tissues, including human skin, are complex objects for optical measurements. Because of its multi-component structure, they are characterized by a combined response to various dynamic changes, both inside and outside of the biological object. Change of glucose concentration in the blood leads to a number of processes, which affect the light scattering properties of the skin and subcutaneous layers, herewith scattering coefficient and the polarization of the scattered light vary. The possibility of non-invasive blood glucose detection by parameters of backscattered laser light was experimentally demonstrated. Degree of polarization of light scattered by human skin and model objects was registered and dependence of the polarization state of backscattered radiation on the glucose concentration in the human blood was shown. A laboratory model of a differential polarimeter, which allows registering the parameters of the polarized radiation scattered by human skin and glucose containing models was developed. Using the developed model, model and full-scale experiments were conducted. In the model experiments, the light scattered in the forward and backwards direction by the following model objects: a 20% solution of milk and a 50% solution of whole human blood was investigated. The ability of the developed sensor to noninvasively detect the concentration of glucose in the blood was demonstrated.

  19. [Media use and physical activity patterns of adolescent participants in obesity therapy: Analysis of the impact of selected sociodemographic factors].

    PubMed

    Wulff, Hagen; Wagner, Petra

    2016-02-01

    To meet the challenge of obesity, effective therapeutic concepts for adolescents focusing on lifestyle changes are necessary. Particularly relevant are nutrition and physical activity patterns associated with media use, which can be influenced by sociodemographic factors. For the optimization of obesity therapy approaches, it is essential to analyze these sociodemographic factors to adjust the aims, content, and methods of interventions, and to use the potential of media in treatment concepts. Thus, the research question is: what are the media and physical activity patterns of 11- to 17-year-old participants in obesity therapy, depending on sociodemographic factors? The national multicenter study was conducted from 2012 to 2013. A questionnaire was administered to 564 participants aged 13.4 ± 1.6 (mean ± standard deviation) years. Standardized instruments were used to assess the variables physical activity, media use, and sociodemographic factors. Participants were physically active for 1 h on 3.3 ± 1.8 days per week, 8.5 % daily. Televisions, mobile phones, and computers were available in all sociodemographic groups and were used for 2 h per day. Sociodemographic differences can be seen in the extent of media usage (h/day). These differences can be found between girls and boys concerning their usage of mobile phones (2.49 vs. 1.90; p  < 0.001), between 11- to 13- and 14- to 17-year-old children concerning their usage of game consoles (0.55 vs. 1.65; p  = 0.007), and in the correlation analysis of media usage and physical activity. Compared with existing literature, the survey results reveal reduced activity and increased media use, which vary among the groups. Thus, differentiated therapy approaches appear to be reasonable. Future research needs to evaluate to what extent media, despite the risks, can contribute to the methodological support of therapy, training, and aftercare concepts. PMID:26689417

  20. Serial mass-media campaigns to promote physical activity: reinforcing or redundant?

    PubMed Central

    Owen, N; Bauman, A; Booth, M; Oldenburg, B; Magnus, P

    1995-01-01

    Changes associated with two serial, nationwide, mass-media-based campaigns to promote physical activity conducted by the National Heart Foundation of Australia in 1990 and 1991 were examined. Surveys conducted before and after each campaign found statistically significant differences in message awareness (46% vs 71% in 1990; 63% vs 74% in 1991). In 1990, there were significant increases in walking, particularly among older people, and in intentions to exercise. No such changes were apparent in 1991. In the case of these two campaigns, conducted 1 year apart, the second may have been redundant. PMID:7856786

  1. Identification of chondrocyte proliferation with the fluorescent-activated cell sorter following laser irradiation and thermal and mechanical treatments

    NASA Astrophysics Data System (ADS)

    Pandoh, Nidhi S.; Truong, Mai T.; Diaz, Sergio H.; Chao, Kenneth; Hou, Stephen; Gardiner, David M.; Wong, Brian J. F.

    2003-06-01

    Laser irradiation may cause a proliferative response in cartilage leading to new, less invasive treatment modalities for diseases such as osteoarthritis. Our previous studies have shown that laser irradiation causes chondrocytes to proliferate on the periphery of the laser-irradiated region and this effect is dose dependent. In this study, flow cytometry was used for cell counting because the colorimetric assay used previously was relatively insensitive to small proliferative responses. Ex-vivo rabbit nasal septal cartilages were harvested and subjected to one of three treatments: laser irradiation, heating, or mechanical modification. Specimens were irradiated with an Nd:YAG laser (λ=1.32μm, 4-16 sec, 6 W/cm2), heated by immersion in saline or contact heating, and mechanically modified by scoring with a scalpel or crushing with a metal stamp. Specimens were incubated for 7-21 days in growth media containing 10μM Bromodeoxyuridine (BrdU) then chondrocytes were isolated with enzymatic digestion. Cells were incubated with fluorescein conjugated anti-BrdU monoclonal antibody (Roche Diagnostic, Basel, Switzerland; counterstained with propidium iodide (PI). Fluorescent-activated cell counting was performed by flow cytometry (λ=488 nm, Model BD LSR Flow Cytometer, Becton Dickson) identifying cells with emissions measured at 515 nm (anti-BrdU) and 620 nm (PI). Analysis showed a population of cells in S-phase of the cell cycle indicating these cells had undergone cell division. This provides further evidence that laser irradiation causes a proliferative response in chondrocytes and may lead to new treatments for degenerative articular diseases and disorders.

  2. The effect of SiO2 content on activation volumes in exchange coupled composite media

    NASA Astrophysics Data System (ADS)

    Chureemart, J.; Lari, L.; Nolan, T. P.; O'Grady, K.

    2013-08-01

    The activation volume, Vact, and the physical grain volume, VTEM, have been investigated on identical structures of exchange coupled composite media with three different contents of silicon dioxide (SiO2) utilised for intergranular exchange decoupling. Time dependence measurements known as the waiting time method have been used to determine Vact. Transmission Electron Microscopy analysis has been carried out to investigate the grain size distribution and the composition distribution at the grain boundaries using bright field high resolution-scanning transmission electron microscopy (BF HR-STEM) and high angle annular dark-field (HAADF) modes. We found that Vact and VTEM decrease as the oxide content is increased. The activation volume and the single grain volume are in excellent agreement for the samples with the highest oxide content indicating complete exchange decoupling. The BF HR-STEM and HAADF STEM images indicate excellent SiO2 segregation at the grain boundaries. This result implies that the activation volume in advanced recording media can be estimated via the correlation to the grain size.

  3. Laser Technology.

    ERIC Educational Resources Information Center

    Gauger, Robert

    1993-01-01

    Describes lasers and indicates that learning about laser technology and creating laser technology activities are among the teacher enhancement processes needed to strengthen technology education. (JOW)

  4. Platelet-activating factor and laser trauma of the iris

    SciTech Connect

    Verbey, N.L.; Van Delft, J.L.; Van Haeringen, N.J.; Braquet, P.

    1989-06-01

    Local application of platelet-activating factor (PAF) on the rabbit eye caused a dose-dependent significant increase in intraocular pressure (IOP). After laser irradiation of the iris the IOP showed a hypertensive phase of about 3 hr. Prophylactic treatment with the PAF antagonist BN 52021 but not with indomethacin abolished the hypertensive phase. Elevated levels of protein (10.6 +/- 0.9 g/l) and prostaglandin E2 (PGE2, 1.7 +/- 0.2 ng/ml) were measured in the aqueous humor 2 hr after laser irradiation of the iris. Prophylactic treatment with BN 52021 showed lower levels of protein (6.1 +/- 0.7) and PGE2 (1.1 +/- 0.02); with indomethacin pretreatment the level of protein was 3.4 +/- 0.7 g/l and of PGE2 0.10 +/- 0.02 ng/ml. A role of PAF as a mediator in ocular inflammatory response is suggested.

  5. Optical Storage System for 0.4 mm Substrate Media Using 405 nm Laser Diode and Numerical Aperture 0.60/0.65 Objective Lens

    NASA Astrophysics Data System (ADS)

    Ko, Jungwan; Park, In Sik; Yoon, Du-Seop; Chung, Chong-Sam; Kim, Yoon-Gi; Ro, Myong-Do; Doh, Tae-Yong; Shin, Dong-Ho

    2001-03-01

    The most important application of the blue-laser optical storage system is the recording high-definition digital broadcasting. For this application, the next-generation blue laser optical storage system requires a data capacity of at least 2 h of a digital broadcasting data stream with a data transfer rate of 23.5 megabits per second (Mbps). In addition to the capacity goal, system compatibility with the conventional digital versatile disc (DVD) system as well as the compact disc (CD) system is important. In order to satisfy the requirements of blue-laser optical storage, a system for media with a substrates thickness of 0.4 mm was proposed, and improved molding technology, crosstalk cancellation technology, dynamic tilt compensation technology and quadrature phase shift keying (QPSK) modulated wobble addressing method were developed for the system. We confirm the feasibility of the proposed system for media with a 0.4 mm substrate using a 405 nm blue laser diode and objective lens with a numerical aperture (NA) of 0.6 (0.65 for rewritable system).

  6. Laser acupuncture induced specific cerebral cortical and subcortical activations in humans.

    PubMed

    Siedentopf, Christian M; Koppelstaetter, Florian; Haala, Ilka Anna; Haid, Veronika; Rhomberg, Paul; Ischebeck, Anja; Buchberger, Waltraud; Felber, Stephan; Schlager, Andreas; Golaszewski, Stefan M

    2005-09-01

    As recent studies demonstrated, acupuncture can elicit activity in specific brain areas. This study aims to explore further the central effect using laser acupuncture. We investigated the cerebral effects of laser acupuncture at both acupoints GB43 with functional magnetic resonance imaging (fMRI). As a control condition the laser was mounted at the same acupoints but without application of laser stimulation. The group results showed significant brain activations within the thalamus, nucleus subthalamicus, nucleus ruber, the brainstem, and the Brodmann areas 40 and 22 for the acupuncture condition. No significant brain activations were observed within the placebo condition. The activations we observed were laser acupuncture-specific and predominantly ipsilateral. This supports the assumption that acupuncture is mediated by meridians, since meridians do not cross to the other side. Furthermore, we could show that laser acupuncture allows one to design a pure placebo condition. PMID:15990948

  7. Active beam shaping in multiple laser guide stars

    NASA Astrophysics Data System (ADS)

    Jones, Katharine J.

    2012-10-01

    Adaptive beam shaping is a critical part of multiple Laser Guide Stars (LGS) for Multiple Conjugate Adaptive Optics (MCAO) for ground-based astronomical telescopes. There are two kinds of Laser Guide Stars: Na Laser Guide Stars (at 589 nm and 92 km altitude) and Rayleigh Laser Guide Stars (at 532 nm and 20 km altitude). Multiple Conjugate Adaptive Optics (MCAO) corrects for each "layer" of atmosphere independently. Multiple Laser Guide Stars are being developed to achieve a measure of tilt and increase the isoplanatic patch. Multiple Laser Guide Stars are being combined with Multiple Conjugate Optics in the Large Binocular Telescope (LBT): more than one Laser Guide Star (4-5) and two different wavelengths: 589 nm and 532 nm. Other observatories have multiple Laser Guide Stars but only one wavelength: 589 nm or 532 nm. Because Laser Guide Stars are launched into the atmosphere, adaptive beam shaping will be carried out before the laser is launched and will be different depending on which laser is being used, presumably to effect the tightest beam which can be achieved at the power level which is required to provide the requisite return to gound-based wavefront sensors. A complete range of devices are used. Beam attenuation and divergnece will take place. Multiple Laser Guide Stars of major observatories (SOR, LBT, MMT, ESO VLT and Gemini South) will be evaluated for effective adaptive beam shaping and impact on performance

  8. Active/passive mode-locked laser oscillator

    DOEpatents

    Fountain, William D.; Johnson, Bertram C.

    1977-01-01

    A Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity is described. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode-locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are idealy suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train.

  9. On the modified active region design of interband cascade lasers

    SciTech Connect

    Motyka, M.; Ryczko, K.; Dyksik, M.; Sęk, G.; Misiewicz, J.; Weih, R.; Dallner, M.; Kamp, M.; Höfling, S.

    2015-02-28

    Type II InAs/GaInSb quantum wells (QWs) grown on GaSb or InAs substrates and designed to be integrated in the active region of interband cascade lasers (ICLs) emitting in the mid infrared have been investigated. Optical spectroscopy, combined with band structure calculations, has been used to probe their electronic properties. A design with multiple InAs QWs has been compared with the more common double W-shaped QW and it has been demonstrated that it allows red shifting the emission wavelength and enhancing the transition oscillator strength. This can be beneficial for the improvements of the ICLs performances, especially when considering their long-wavelength operation.

  10. Active laser ranging with frequency transfer using frequency comb

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyuan; Wei, Haoyun; Yang, Honglei; Li, Yan

    2016-05-01

    A comb-based active laser ranging scheme is proposed for enhanced distance resolution and a common time standard for the entire system. Three frequency combs with different repetition rates are used as light sources at the two ends where the distance is measured. Pulse positions are determined through asynchronous optical sampling and type II second harmonic generation. Results show that the system achieves a maximum residual of 379.6 nm and a standard deviation of 92.9 nm with 2000 averages over 23.6 m. Moreover, as for the frequency transfer, an atom clock and an adjustable signal generator, synchronized to the atom clock, are used as time standards for the two ends to appraise the frequency deviation introduced by the proposed system. The system achieves a residual fractional deviation of 1.3 × 10-16 for 1 s, allowing precise frequency transfer between the two clocks at the two ends.

  11. The action of microsecond-pulsed plasma-activated media on the inactivation of human lung cancer cells

    NASA Astrophysics Data System (ADS)

    Kumar, Naresh; Park, Ji Hoon; Jeon, Su Nam; Park, Bong Sang; Choi, Eun Ha; Attri, Pankaj

    2016-03-01

    In the present work, we have generated reactive species (RS) through microsecond-pulsed plasma (MPP) in the cell culture media using a Marx generator with point-point electrodes of approximately 0.06 J discharge energy/pulse. RS generated in culture media through MPP have a selective action between growth of the H460 lung cancer cells and L132 normal lung cells. We observed that MPP-activated media (MPP-AM) induced apoptosis on H460 lung cancer cells through an oxidative DNA damage cascade. Additionally, we studied the apoptosis-related mRNA expression, DNA oxidation and polymerase-1 (PARP-1) cleaved analysis from treated cancer cells. The result proves that radicals generated through MPP play a pivotal role in the activation of media that induces the selective killing effect.

  12. Active compensation of large dispersion of femtosecond pulses for precision laser ranging.

    PubMed

    Lee, Sang-Hyun; Lee, Joohyung; Kim, Young-Jin; Lee, Keunwoo; Kim, Seung-Woo

    2011-02-28

    We describe an active way of compensation for large dispersion induced in the femtosecond light pulses travelling in air for laser ranging. The pulse duration is consistently regulated at 250 fs by dispersion control, allowing sub-micrometer resolution in measuring long distances by means of time-of-flight measurement. This method could facilitate more reliable applications of femtosecond pulses for satellite laser ranging, laser altimetry and active LIDAR applications. PMID:21369227

  13. Characterization of the superoxide anion radical scavenging activity by tetracycline antibiotics in aprotic media.

    PubMed

    Kładna, Aleksandra; Kruk, Irena; Michalska, Teresa; Berczyński, Paweł; Aboul-Enein, Hassan Y

    2011-01-01

    The tetracycline family antibiotics are widely used as human and veterinary treatments. The drugs are effective as antibiotics and also show antimicrobial and non-microbial action. However, the antioxidant properties of tetracyclines have not been characterized in aprotic media. To better understand their biological functions, the in vitro superoxide anion radical (O2•¯) scavenging activities of tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline were characterized, along with a very efficient O2•¯ scavenger, tiron, in dimethyl sulphoxide (DMSO), using ultra-weak chemiluminescence (CL). We found that tetracycline, chlortetracycline and doxycycline efficiently inhibited CL from the O2•¯-generating system at concentration levels of 0.02-1.0 mmol/L. Methacycline and oxytetracycline were the O2•¯ scavengers at concentration levels of 0.01-0.1 mmol/L, whereas when their concentration was lowered the drugs were capable of generating O2•¯, leading to CL enhancement. For all the data obtained in this study, the scavenging activity for the compounds tested decreased in the following order: tetracycline > doxycycline > chlortetracycline > tiron methacycline > oxytetracycline. These results indicate that the tetracycline drugs directly alter O2•¯ redox chemistry in aprotic media. PMID:21413138

  14. Modeling and optimization of actively Q-switched Nd-doped quasi-three-level laser

    NASA Astrophysics Data System (ADS)

    Yan, Renpeng; Yu, Xin; Li, Xudong; Chen, Deying; Gao, Jing

    2013-09-01

    The energy transfer upconversion and the ground state absorption are considered in solving the rate equations for an active Q-switched quasi-three-level laser. The dependence of output pulse characters on the laser parameters is investigated by solving the rate equations. The influence of the energy transfer upconversion on the pulsed laser performance is illustrated and discussed. By this model, the optimal parameters could be achieved for arbitrary quasi-three-level Q-switched lasers. An acousto-optical Q-switched Nd:YAG 946 nm laser is constructed and the reliability of the theoretical model is demonstrated.

  15. Short-pulse actively Q-switched Er:YAG lasers.

    PubMed

    Ottaway, David J; Harris, Lachlan; Veitch, Peter J

    2016-07-11

    We report the shortest duration pulses obtained to date from an actively Q-switched Er:YAG laser pumped by a low spectral and spatial brightness laser diode. The 14.5 ns, 6 mJ pulses were obtained using a 1470 nm laser diode end-pumped co-planar folded zigzag slab architecture. We also present an analytical model that accurately predicts the pulse energy-duration product achievable from virtually all Q-switched Er:YAG lasers and high repetition rate quasi-three-level Q-switched lasers in general. PMID:27410810

  16. Actively mode-locked GaInAsP laser with subpicosecond output

    SciTech Connect

    Corzine, S.W.; Bowers, J.E.; Przybylek, G.; Koren, U.; Miller, B.I.; Soccolich, C.E.

    1988-02-01

    We actively mode lock a high-frequency GaInAsP laser at a rate of 16 GHz to obtain nearly transform-limited hyperbolic secant pulses with a pulse width of 0.58 ps. This is the shortest pulse width yet demonstrated for either passively or actively mode-locked semiconductor lasers.

  17. Diode laser threshold current density and lasing wavelength as functions of active region thickness

    SciTech Connect

    Streifer, W.; Scifres, D.R.; Burnham, R.D.

    1983-03-01

    Based on a simple model of the band-to-band absorption of a diode laser active region, we formulatean expression for modal gain as a function of pumping current. Using this result yields expressions for threshold current density and lasing photon energy which depend on device parameters including active region thickness, laser length, internal losses, facet reflectivity, etc.

  18. Using Laser Scanning Cytometry to investigate the transport of nano-scale latex particles in porous media

    NASA Astrophysics Data System (ADS)

    Li, Y.; May, R.

    2011-12-01

    The increased production and widespread application of nanomaterials in recent years has been unprecedented. Once entering water environment, many engineered nanomaterials may form stable aggregates sized from several nanometers to several microns. While classic filtration theory predicts enhanced deposition for small-sized particles, different observations have been reported on the influences of particle size on the deposition. Therefore, further investigation on the effects of nano-scale particle size on their transport is necessary. While typical column experiments can provide valuable insights, such methods do not clearly distinguish how spatial and temporal changes in hydrodynamic conditions affect particle transport. Pore scale experiments can be setup to directly visualize particle transport and retention in pore spaces. Such techniques require high resolution to observe nano-scale particles, which is thus typically limited to observe only several pore spaces. In this work, we explored the possibility of using Laser Scanning Cytometery (LSC) to investigate the transport of nano-scale particles in porous media. Retention of 510nm, 210nm and 57 nm florescent latex particles in a flow cell (50mm x 5mm x 0.8mm) packed with 20-30 mesh glass beads were scanned by LSC. We were able to obtain the spatial distribution of retained nanoparticles in the flow cell (Figure 1). Particle spatial distributions corresponding to different environmental factors (e.g. ionic strength, flow velocity, injection duration) were statistically compared for different sized particles. Insights gained from this work could be beneficial for both nanomaterial-based remediation technology design and evaluation of the potential risks of engineered nanomaterials.

  19. Effect of laser irradiation of nanoparticles in aqueous uranium salt solutions on nuclide activity

    SciTech Connect

    Simakin, Aleksandr V; Shafeev, Georgii A

    2011-07-31

    This paper presents an experimental study of the effect of laser irradiation of aqueous uranyl chloride solutions containing gold nanoparticles on the activity of the uranium series radionuclides {sup 234}Th, {sup 234m}Pa, and {sup 235}U. The solutions were exposed to femtosecond Ti:sapphire laser pulses and to the second or third harmonic of a Nd:YAG laser (150-ps pulses) at a peak intensity in the medium of {approx}10{sup 12} W cm{sup -2}. The activities of the radionuclides in the irradiated solutions were shown to differ markedly from their equilibrium values. The sign of the deviation depends on the laser wavelength. The measured activity deviations can be interpreted as evidence that laser exposure of nanoparticles accelerates the alpha and beta decays of the radionuclides. The observed effects are accounted for in terms of a mechanism that involves resonant enhancement of optical waves by metallic nanoparticles. (interaction of laser radiation with matter)

  20. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  1. Intra-Urban Human Mobility and Activity Transition: Evidence from Social Media Check-In Data

    PubMed Central

    Wu, Lun; Zhi, Ye; Sui, Zhengwei; Liu, Yu

    2014-01-01

    Most existing human mobility literature focuses on exterior characteristics of movements but neglects activities, the driving force that underlies human movements. In this research, we combine activity-based analysis with a movement-based approach to model the intra-urban human mobility observed from about 15 million check-in records during a yearlong period in Shanghai, China. The proposed model is activity-based and includes two parts: the transition of travel demands during a specific time period and the movement between locations. For the first part, we find the transition probability between activities varies over time, and then we construct a temporal transition probability matrix to represent the transition probability of travel demands during a time interval. For the second part, we suggest that the travel demands can be divided into two classes, locationally mandatory activity (LMA) and locationally stochastic activity (LSA), according to whether the demand is associated with fixed location or not. By judging the combination of predecessor activity type and successor activity type we determine three trip patterns, each associated with a different decay parameter. To validate the model, we adopt the mechanism of an agent-based model and compare the simulated results with the observed pattern from the displacement distance distribution, the spatio-temporal distribution of activities, and the temporal distribution of travel demand transitions. The results show that the simulated patterns fit the observed data well, indicating that these findings open new directions for combining activity-based analysis with a movement-based approach using social media check-in data. PMID:24824892

  2. Research on laser protection: an overview of 20 years of activities at Fraunhofer IOSB

    NASA Astrophysics Data System (ADS)

    Ritt, G.; Walter, D.; Eberle, B.

    2013-10-01

    Since the advent of the laser in 1960, the protection of human eyes and sensors against intended or unintended damage by laser radiation is a hot research topic. As long as the parameters of a laser source such as the wavelength and the output power are known, adequate laser safety can be ensured simply by utilizing conventional laser protection filters which are based on absorption or interference effects. This is typically the case in cooperative environments like a laboratory or industrial facilities. A very different situation prevails in military defense or civil security. There, the parameters of encountering laser threats are usually unknown. Protection measures, helping against all types of laser threats, are the long desired objective of countless research activities. The biggest challenge in finding an effective measure arises from single laser pulses of unknown wavelength. The problem demands for a passive protection concept and may be based for example on intensity dependent effects. Moreover, the requested solutions shall comprise add-on possibilities like thin films to be put on existing optics, windshields or glasses. Unfortunately, such an all-embracing solution is still far out of reach. The Fraunhofer IOSB has been working on the evaluation and development of non-conventional laser protection methods for more than 20 years. An overview of the past and present research activities shall be presented, comprising protection measures against laser damaging and laser dazzling.

  3. Comparative bactericidal activities of lasers operating at seven different wavelengths

    NASA Astrophysics Data System (ADS)

    Watson, Ian A.; Ward, Glenn D.; Wang, RuiKang K.; Sharp, James H.; Budgett, David M.; Stewart-Tull, Duncan E.; Wardlaw, Alastair C.; Chatwin, Christopher R.

    1996-10-01

    Seven laser instruments, delivering radiation at a selection of wavelengths in the range of 0.355 to 118 micrometers , we investigated for their ability to kill Escherichia coli as a lawn of the bacteria on nutrient agar culture plates. Easily the most effective was a 600-W CO2 laser operating at 10.6 micrometers , which produced 1.2-cm2 circular zones of sterilization at energy densities of around 8 J cm-2 in a 30-msec exposure. Circular zones with an area of 0.7 cm2 were achieved with 200 W from a Nd:YAG laser delivering 8-ms, 10-J pulses of 1.06 micrometers radiation at 20 Hz. The exposure time, however, was 16 s and the energy density was more than 240 times higher than with the CO2 laser. This difference is believed to be partly due to the much higher absorption of radiation at 10.6 micrometers , by water in the bacterial cells and the surrounding medium. Sterilization was observed after exposure to frequency- tripled Nd:YAG laser radiation at 355 nm. Lasers that were totally ineffective in killing Escherichia coli were the far infrared laser, the laser diode array, and the argon ion laser. The speed at which laser sterilization can be achieved is particularly attractive to the medical and food industries.

  4. Application of copper vapour lasers for controlling activity of uranium isotopes

    SciTech Connect

    Barmina, E V; Sukhov, I A; Lepekhin, N M; Priseko, Yu S; Filippov, V G; Simakin, Aleksandr V; Shafeev, Georgii A

    2013-06-30

    Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed. (laser applications and other topics in quantum electronics)

  5. Frames and knowledge in mixed media: how activation changes information intake.

    PubMed

    Veenstra, Aaron S; Sayre, Ben; Shah, Dhavan V; McLeod, Douglas M

    2008-08-01

    Many people consider strategic framing, the journalistic tendency to reduce politics to a game or competition focused on the tactical maneuvers of political actors, to be harmful to democracy because it erodes citizen interest in the democratic process. Our results demonstrate that this is not always the case. Testing the effects of textual strategic frames and video processing in a digital environment, we show that strategic frames may also provide a context that is more conducive to learning in mixed media news environments than that provided by value frames, those focused on the value conflict between principled policy opponents. Further analysis reveals that this effect is most clearly seen among people who read political blogs (i.e., those who are already active and interested in politics). Our data suggest that for individuals with cognitive networks built around ideological concerns, such as blog readers, value-framed messages provide cues to stop encoding new information, while strategically framed messages lead people to continue absorbing and learning in mixed media environments. PMID:18721093

  6. Surface characterization and in vivo evaluation of laser sintered and machined implants followed by resorbable-blasting media process: A study in sheep

    PubMed Central

    Bowers, Michelle; Yoo, Daniel; Marin, Charles; Gil, Luiz; Shabaka, Nour; Goldstein, Matt; Janal, Malvin; Tovar, Nick; Bonfante, Estevam; Coelho, Paulo

    2016-01-01

    Background This study aimed to compare the histomorphometric and histological bone response to laser-sintered implants followed by resorbable-blasting media (RBM) process relative to standard machined/RBM surface treated implants. Material and Methods Six male sheep (n=6) received 2 Ti-6Al-4V implants (1 per surface) in each side of the mandible for 6 weeks in vivo. The histomorphometric parameters bone-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated. Results Optical interferometry revealed higher Sa and Sq values for the laser-sintered/RBM surface in relation to standard/RBM implants. No significant differences in BIC were observed between the two groups (p>0.2), but significantly higher BAFO was observed for standard/RBM implants (p<0.01). Conclusions The present study demonstrated that both surfaces were biocompatible and osseoconductive, and the combination of laser sintering and RBM has no advantage over the standard machined implants with subsequent RBM. Key words:Dental implants, osseointegration, resorbable- blasting media, sheep, in vivo. PMID:26827064

  7. Media Richness and Social Information Processing: Rationale for Multifocal Continuing Medical Education Activities.

    ERIC Educational Resources Information Center

    Gilman, Stuart C.; Turner, Jeanine Warisse

    2001-01-01

    Media richness theory suggests that media choice results from matching characteristics with content requirements. Social information processing theory adds the influence of social norms and familiarity with media types. In applying both to continuing medical information, consideration of content and participant environment guides selection of…

  8. Dissociation and regeneration kinetics of carbon dioxide in the active medium of sealed-off transverse RF-excited CO{sub 2} lasers

    SciTech Connect

    Vesnov, I G

    2010-06-23

    An improved mathematical model describing the dissociation and regenerations kinetics of carbon dioxide in the active medium of sealed-off transverse RF-excited CO{sub 2} lasers is presented. It is shown that the calculation of the active medium composition of such lasers requires the equations of the gas-mixture kinetics to take into account the diffuse flow of oxygen atoms on metal electrodes and on the surface of heterogeneous catalysts used to reduce the degree of the carbon dioxide dissociation. The rate constants of the heterogeneous recombination reaction CO + O {yields} CO{sub 2} on the surface of alumina ceramics and Al{sub 2}O{sub 3} are determined. (active media)

  9. The changing face(book) of psychiatry: can we justify ‘following’ patients' social media activity?

    PubMed Central

    Cox-George, Chantal

    2015-01-01

    Individuals with mental health issues may post information on social networking sites that can provide an insight into their mental health status. It could be argued that doctors (and specifically psychiatrists) should understand the way in which social media is used by their patients to gain a better insight into their illnesses. However, choosing to actively monitor a patient's social media activity raises important questions about the way in which medical students, qualified clinicians and other healthcare professionals obtain information about patients. While this may be framed as a mere form of ‘collateral history-taking’, there are obvious practical and ethical problems with doing so. Here, a case is made against monitoring the social media activity of patients involved with psychiatric services. PMID:26755986

  10. Generation of parthenogenetic goat blastocysts: effects of different activation methods and culture media.

    PubMed

    Malik, Hruda Nanda; Singhal, Dinesh Kumar; Saugandhika, Shrabani; Dubey, Amit; Mukherjee, Ayan; Singhal, Raxita; Kumar, Sudarshan; Kaushik, Jai Kumar; Mohanty, Ashok Kumar; Das, Bikash Chandra; Bag, Sadhan; Bhanja, Subrata Kumar; Malakar, Dhruba

    2015-06-01

    The present study was carried out to investigate the effects of different activation methods and culture media on the in vitro development of parthenogenetic goat blastocysts. Calcium (Ca2+) ionophore, ethanol or a combination of the two, used as activating reagents, and embryo development medium (EDM), modified Charles Rosenkrans (mCR2a) medium and research vitro cleave (RVCL) medium were used to evaluate the developmental competence of goat blastocysts. Quantitative expression of apoptosis, stress and developmental competence-related genes were analysed in different stages of embryos. In RVCL medium, the cleavage rate of Ca2+ ionophore-treated oocytes (79.61 ± 0.86) was significantly (P < 0.05) higher than in ethanol (74.90 ± 1.51) or in the combination of both Ca2+ ionophore and ethanol. In mCR2a or EDM, hatched blastocyst production rate of Ca2+ ionophore-treated oocytes (8.33 ± 1.44) was significantly higher than in ethanol (6.46 ± 0.11) or in the combined treatment (6.70 ± 0.24). In ethanol, the cleavage, blastocyst and hatched blastocyst production rates in RVCL medium (74.90 ± 1.51, 18.30 ± 1.52 and 8.24 ± 0.15, respectively) were significantly higher than in EDM (67.81 ± 3.21, 14.59 ± 0.27 and 5.59 ± 0.42) or mCR2a medium (65.09 ± 1.57, 15.36 ± 0.52 and 6.46 ± 0.11). The expression of BAX, Oct-4 and GlUT1 transcripts increased gradually from 2-cell stage to blastocyst-stage embryos, whereas the transcript levels of Bcl-2 and MnSOD were significantly lower in blastocysts. In addition, different activation methods and culture media had little effect on the pattern of variation and relative abundance of the above genes in different stages of parthenogenetic activated goat embryos. In conclusion, Ca2+ ionophore as the activating agent, and RVCL as the culture medium are better than other tested options for development of parthenogenetic activated goat blastocysts. PMID:24405529

  11. Inhibitory activity of postbiotic produced by strains of Lactobacillus plantarum using reconstituted media supplemented with inulin

    PubMed Central

    2014-01-01

    Background The present study aimed to determine the inhibitory activity of postbiotic produced by L. plantarum using reconstituted media supplemented with different levels of inulin and to select the best combination based on the modified inhibitory activity (MAU/mL) against pathogens. Methods Postbiotics were produced by 6 strains of L. plantarum (RG11, RG14, RI11, UL4, TL1 and RS5) using reconstituted media supplemented with different levels of Inulin (0, 0.2, 0.4, 0.6, 0.8, and 1.0) yielding 36 combinations. Results The combination of postbiotic and inulin had higher inhibitory activity than postbiotic alone against all indicator organisms except Pediococcus acidilactici, and E. coli. The RI11 + 0.8% Inulin, RG14 + 0.8% Inulin and RG14 + 0% Inulin had significantly (p < 0.05) higher MAU/mL against P. acidilactici than other treatments. The RI11 + 0.8% Inulin and RG14 + 0.4% Inulin had a significantly (p < 0.05) higher MAU/mL against VRE. The MAU/mL against L. monocytogenes was greater in RI11 + 1.0% Inulin, RI11 + 0.6% Inulin and RI11 + 0.8% Inulin. The combinations of RS5 + 1.0% Inulin, RS5 + 0.8% Inulin and RS5 + 0.6% Inulin had greater MAU/mL against S. enterica; whereas in E. coli, the inhibitory activity had higher activity that can only be found in RS5 + 0.8% Inulin. Conclusion Combination of postbiotics and inulin which had higher optical density tends to have lower pH which corresponds to increased inhibitory activity against indicator organisms. The results of this study show that postbiotics and inulin supplementation enable to inhibit proliferation of pathogenic bacteria. PMID:24991236

  12. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, F.H.; Moore, J.C.

    1999-05-25

    A method is disclosed for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase. 43 figs.

  13. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, Frances H.; Moore, Jeffrey C.

    1999-01-01

    A method for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase.

  14. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, Frances H.; Moore, Jeffrey C.

    1998-01-01

    A method for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase.

  15. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, F.H.; Moore, J.C.

    1998-04-21

    A method is disclosed for isolating and identifying modified para-nitrobenzyl esterases. These enzymes exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase. 43 figs.

  16. Synchronization of active/passive mode-locked erbium fiber lasers

    NASA Astrophysics Data System (ADS)

    Kaechele, Walter; Haus, Joseph W.; Hayduk, Michael J.; Erdmann, Reinhard K.; Teegarden, Kenneth J.

    1997-07-01

    Injection seeding of a passively mode-locked fiber laser by an actively mode-locked fiber laser source is described. The passively mode-locked laser employs a multiple quantum well saturable absorber to establish pulsed operation. Mode-locked synchronized operation was maintained with average injection powers as low as 1.3 mW. Stable synchronized pulses were observed with pulse widths as narrow as 10 ps.

  17. Laser-activated protein solder for peripheral nerve repair

    NASA Astrophysics Data System (ADS)

    Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.

    1995-05-01

    A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

  18. Active stabilization of a diode laser injection lock.

    PubMed

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed. PMID:27370428

  19. Active stabilization of a diode laser injection lock

    NASA Astrophysics Data System (ADS)

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  20. Optical Properties of Active Regions in Terahertz Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Dyksik, M.; Motyka, M.; Rudno-Rudziński, W.; Sęk, G.; Misiewicz, J.; Pucicki, D.; Kosiel, K.; Sankowska, I.; Kubacka-Traczyk, J.; Bugajski, M.

    2016-07-01

    In this work, AlGaAs/GaAs superlattice, with layers' sequence and compositions imitating the active and injector regions of a quantum cascade laser designed for emission in the terahertz spectral range, was investigated. Three independent absorption-like optical spectroscopy techniques were employed in order to study the band structure of the minibands formed within the conduction band. Photoreflectance measurements provided information about interband transitions in the investigated system. Common transmission spectra revealed, in the target range of intraband transitions, mainly a number of lines associated with the phonon-related processes, including two-phonon absorption. In contrast, differential transmittance realized by means of Fourier-transform spectroscopy was utilized to probe the confined states of the conduction band. The obtained energy separation between the second and third confined electron levels, expected to be predominantly contributing to the lasing, was found to be ~9 meV. The optical spectroscopy measurements were supported by numerical calculations performed in the effective mass approximation and XRD measurements for layers' width verification. The calculated energy spacings are in a good agreement with the experimental values.

  1. Phase stabilization of an actively mode-locked ring laser

    NASA Astrophysics Data System (ADS)

    Takada, Akira; Saika, Makoto; Nagano, Shigenori

    2015-03-01

    A phase-resolved system based on swept source optical coherence tomography (SS-OCT) has to incorporate a phase-stabilized wavelength-swept light source. The phase variation is induced by fluctuation of a beginning swept frequency. The conventional phase-sensitive SS-OCTs use a fiber Bragg grating (FBG) in order to avoid A-scan trigger fluctuations. However this method does not always solve the trigger fluctuation problem. In actively mode-locked ring lasers (AMLLs), the beginning swept frequency fluctuates by abrupt frequency change between the end of a sweep and the beginning of the subsequent one. To overcome this issue, we proposes a new phase stabilization method. By employing the method with an auxiliary reference configuration, the sweeping phase has successfully stabilized because the timing jitter is calculated by interference signals from the auxiliary reference path. In this research, we have proposed the phase stabilization method that has nanometer sensitivity with millisecond response. In addition, the method has successfully suppressed the depth dependence of phase instability.

  2. Laser-activated remote phosphor conversion with ceramic phosphors

    NASA Astrophysics Data System (ADS)

    Lenef, Alan; Kelso, John; Tchoul, Maxim; Mehl, Oliver; Sorg, Jörg; Zheng, Y.

    2014-09-01

    Direct laser activation of a remote phosphor, or LARP, is a highly effective approach for producing very high luminance solid-state light sources. Such sources have much smaller étendue than LEDs of similar power, thereby greatly increasing system luminous fluxes in projection and display applications. While several commercial products now employ LARP technology, most current configurations employ phosphor powders in a silicone matrix deposited on rotating wheels. These provide a low excitation duty cycle that helps limit quenching and thermal overload. These systems already operate close to maximum achievable pump powers and intensities. To further increase power scaling and eliminate mechanical parts to achieve smaller footprints, OSRAM has been developing static LARP systems based on high-thermal conductivity monolithic ceramic phosphors. OSRAM has recently introduced a static LARP product using ceramic phosphor for endoscopy and also demonstrated a LARP concept for automotive forward lighting1. We first discuss the basic LARP concept with ceramic phosphors, showing how their improved thermal conductivity can achieve both high luminous fluxes and luminance in a static configuration. Secondly, we show the importance of scattering and low optical losses to achieving high overall efficiency and light extraction. This is shown through experimental results and radiation transport calculations. Finally, we discuss some of the fundamental factors which limit the ultimate luminance achievable with ceramic converted LARP, including optical pumping effects and thermal quenching.

  3. Conditioned Media from Microvascular Endothelial Cells Cultured in Simulated Microgravity Inhibit Osteoblast Activity

    PubMed Central

    Cazzaniga, Alessandra; Castiglioni, Sara; Maier, Jeanette A. M.

    2014-01-01

    Background and Aims. Gravity contributes to the maintenance of bone integrity. Accordingly, weightlessness conditions during space flight accelerate bone loss and experimental models in real and simulated microgravity show decreased osteoblastic and increased osteoclastic activities. It is well known that the endothelium and bone cells cross-talk and this intercellular communication is vital to regulate bone homeostasis. Because microgravity promotes microvascular endothelial dysfunction, we anticipated that the molecular cross-talk between endothelial cells exposed to simulated microgravity and osteoblasts might be altered. Results. We cultured human microvascular endothelial cells in simulated microgravity using the rotating wall vessel device developed by NASA. Endothelial cells in microgravity show growth inhibition and release higher amounts of matrix metalloproteases type 2 and interleukin-6 than controls. Conditioned media collected from microvascular endothelial cells in simulated microgravity were used to culture human osteoblasts and were shown to retard osteoblast proliferation and inhibit their activity. Discussion. Microvascular endothelial cells in microgravity are growth retarded and release high amounts of matrix metalloproteases type 2 and interleukin-6, which might play a role in retarding the growth of osteoblasts and impairing their osteogenic activity. Conclusions. We demonstrate that since simulated microgravity modulates microvascular endothelial cell function, it indirectly impairs osteoblastic function. PMID:25210716

  4. Active Interrogation of Sensitive Nuclear Material Using Laser Driven Neutron Beams

    SciTech Connect

    Favalli, Andrea; Roth, Markus

    2015-05-01

    An investigation of the viability of a laser-driven neutron source for active interrogation is reported. The need is for a fast, movable, operationally safe neutron source which is energy tunable and has high-intensity, directional neutron production. Reasons for the choice of neutrons and lasers are set forth. Results from the interrogation of an enriched U sample are shown.

  5. Activation analysis of indium, KCl, and melamine by using a laser-induced neutron source

    NASA Astrophysics Data System (ADS)

    Lee, Sungman; Lee, Kitae; Cha, Hyungki

    2014-04-01

    A laser-induced repetitively operated fast neutron source with a neutron yield of 4 × 105 n/pulse and a pulse repetition rate of 5 Hz, which was developed using a deuterated polystyrene film target and a 24-TW femtosecond laser, was applied for laser activation analyses of indium, KCl, and melamine samples. The nuclear reactions of the measured gamma spectra for the activated samples were identified as (n, γ), (n, n'), and (n, 2n) reactions. These indicate possible usage of the neutron source for practical activation analyses of various materials.

  6. Optical anomalies in Biological media; Using naturally occurring birefringence and radiance dependent nonlinear optics to our advantage in the laser treatment of arrhythmias.

    NASA Astrophysics Data System (ADS)

    Splinter, Robert; Svenson, Robert H.; Sosa, Eduardo; Buchele d'Avila, Andre Luiz; Scanavacca, Mauricio; Pruitt, Ernest; Kasell, Jackie H.

    2003-02-01

    When irradiating particular biological media in general there will be a range of optical properties to deal with, with respect to the irradiating wavelength, and the respective tissues that make up the organ under treatment or being imaged. In addition to this we saw changing optical properties under influence of denaturization, dehydration and carbonization. We also observed optical nonlinearities that are irradiance dependent, in addition to the birefringence which affects the light distribution throughout the tissue differently than the polarization birefringence used in optical polarization microscopy. In the treatment of ventricular tachycardia with laser photocoagulation the success of the procedure depends on whether sufficient energy has been directed to the relevant region of the myocardium to ablate the entire arrhythmogenic focus. A new high power diode laser operating in the near infrared was used in an animal infarct model and in human arrhythmia ablation. The light distribution measured for Chagasic heart tissues at the diode laser wavelength demonstrated the key potential to create controlled deep photocoagulation lesions. From our observations we may conclude that the diode laser - catheter combination offers significant potential for the elimination of arrhythmia's resulting from Chagas disease.

  7. Laser-activated protein bands for peripheral nerve repair

    NASA Astrophysics Data System (ADS)

    Lauto, Antonio; Trickett, Rodney I.; Malik, Richard; Dawes, Judith M.; Owen, Earl R.

    1996-01-01

    A 100 micrometer core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the protein based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 plus or minus 5 min. (n equals 24) compared to 23 plus or minus 9 min (n equals 13) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 plus or minus 5 g, while microsutured nerves had a tensile strength of 40 plus or minus 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study, with a total of fifty-seven adult male wistar rats, compared laser solder repaired tibial nerves to conventional microsuture repair. Twenty-four laser soldered nerves and thirteen sutured nerves were characterized at three months and showed successful regeneration with average compound muscle action potentials (CMAP) of 2.4 plus or minus 0.7 mV and 2.7 plus or minus 0.8 mV respectively. Histopathology of the in vivo study, confirmed the comparable regeneration of axons in laser and suture operated nerves. A faster, less damaging and long lasting laser based anastomotic technique is presented.

  8. Collisional thulium vapour gas-discharge laser

    SciTech Connect

    Gerasimov, V A; Pavlinskii, A V

    2004-01-31

    A collisional laser on a system of atomic levels based on the principle proposed by Gould is built for the first time. The population of the upper laser level and relaxation of the lower level occur upon inelastic collisions of excited thulium atoms with helium atoms. The lower-level relaxation occurs in a reaction with an energy defect of > 13000 cm{sup -1}. (active media. lasers)

  9. Photothermal effects of laser-activated surface plasmonic gold nanoparticles on the apoptosis and osteogenesis of osteoblast-like cells.

    PubMed

    Rau, Lih-Rou; Huang, Wan-Yu; Liaw, Jiunn-Woei; Tsai, Shiao-Wen

    2016-01-01

    The specific properties of gold nanoparticles (AuNPs) make them a novel class of photothermal agents that can induce cancer cell damage and even death through the conversion of optical energy to thermal energy. Most relevant studies have focused on increasing the precision of cell targeting, improving the efficacy of energy transfer, and exploring additional functions. Nevertheless, most cells can uptake nanosized particles through nonspecific endocytosis; therefore, before hyperthermia via AuNPs can be applied for clinical use, it is important to understand the adverse optical-thermal effects of AuNPs on nontargeted cells. However, few studies have investigated the thermal effects induced by pulsed laser-activated AuNPs on nearby healthy cells due to nonspecific treatment. The aim of this study is to evaluate the photothermal effects induced by AuNPs plus a pulsed laser on MG63, an osteoblast-like cell line, specifically examining the effects on cell morphology, viability, death program, and differentiation. The cells were treated with media containing 50 nm AuNPs at a concentration of 5 ppm for 1 hour. Cultured cells were then exposed to irradiation at 60 mW/cm(2) and 80 mW/cm(2) by a Nd:YAG laser (532 nm wavelength). We observed that the cytoskeletons of MG63 cells treated with bare AuNPs followed by pulsed laser irradiation were damaged, and these cells had few bubbles on the cell membrane compared with those that were not treated (control) or were treated with AuNPs or the laser alone. There were no significant differences between the AuNPs plus laser treatment group and the other groups in terms of cell viability, death program analysis results, or alkaline phosphatase and calcium accumulation during culture for up to 21 days. However, the calcium deposit areas in the cells treated with AuNPs plus laser were larger than those in other groups during the early culture period. PMID:27555768

  10. Photothermal effects of laser-activated surface plasmonic gold nanoparticles on the apoptosis and osteogenesis of osteoblast-like cells

    PubMed Central

    Rau, Lih-Rou; Huang, Wan-Yu; Liaw, Jiunn-Woei; Tsai, Shiao-Wen

    2016-01-01

    The specific properties of gold nanoparticles (AuNPs) make them a novel class of photothermal agents that can induce cancer cell damage and even death through the conversion of optical energy to thermal energy. Most relevant studies have focused on increasing the precision of cell targeting, improving the efficacy of energy transfer, and exploring additional functions. Nevertheless, most cells can uptake nanosized particles through nonspecific endocytosis; therefore, before hyperthermia via AuNPs can be applied for clinical use, it is important to understand the adverse optical–thermal effects of AuNPs on nontargeted cells. However, few studies have investigated the thermal effects induced by pulsed laser-activated AuNPs on nearby healthy cells due to nonspecific treatment. The aim of this study is to evaluate the photothermal effects induced by AuNPs plus a pulsed laser on MG63, an osteoblast-like cell line, specifically examining the effects on cell morphology, viability, death program, and differentiation. The cells were treated with media containing 50 nm AuNPs at a concentration of 5 ppm for 1 hour. Cultured cells were then exposed to irradiation at 60 mW/cm2 and 80 mW/cm2 by a Nd:YAG laser (532 nm wavelength). We observed that the cytoskeletons of MG63 cells treated with bare AuNPs followed by pulsed laser irradiation were damaged, and these cells had few bubbles on the cell membrane compared with those that were not treated (control) or were treated with AuNPs or the laser alone. There were no significant differences between the AuNPs plus laser treatment group and the other groups in terms of cell viability, death program analysis results, or alkaline phosphatase and calcium accumulation during culture for up to 21 days. However, the calcium deposit areas in the cells treated with AuNPs plus laser were larger than those in other groups during the early culture period. PMID:27555768

  11. Fiber-laser pumped actively Q-switched Er:LuYAG laser at 1648 nm

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Wang, Y.; Zhao, T.; Zhu, H. Y.; Shen, D. Y.

    2016-02-01

    We demonstrated an acousto-optic Q-switched 1648 nm Er:LuYAG laser resonantly pumped by a cladding-pumped Er,Yb fiber laser at 1532 nm. Stable Q-switching operation was obtained with the pulse repetition rate (PRR) varying from 200 Hz to 10 kHz. At PRR of 200 Hz, the laser yielded Q-switched pulses with 3.3 mJ pulse energy and 65 ns pulse duration, corresponding to a peak power of 50.7 kW for 10.4 W of incident pump power.

  12. The effect of various media and hormones via suspension culture on secondary metabolic activities of (Cape Jasmine) Gardenia jasminoides Ellis.

    PubMed

    Farzinebrahimi, Reza; Mat Taha, Rosna; Rashid, Kamaludin; Syafawati Yaacob, Jamilah

    2014-01-01

    The leaf of Gardenia jasminoides Ellis was used as explants and was cultured on MS and WPM media supplemented with various concentrations of NAA, IAA, 2,4-D, IBA, TDZ, and Kn (0 to 5 mg L(-1) with 0.5 increment). After six months, the higher percentage of callus (100%) and the best dry and fresh weight of callus were formed on WPM medium supplemented with 2,4-D and NAA (2.0-3.0 mg L(-1)) and this amount was decreased from (84%) to (69%) when this media supplemented with Kinetin and TDZ (1 mg L(-1)) respectively were used. Leaf segments cultured on WPM media added with Kn (1 mg L(-1)) and TDZ (2 mg L(-1)) yielded the least amount of callus. It was found that WPM media added with IAA (4.5-5.0 mg L(-1)) were optimum for root induction from G. jasminoides plantlets. Antibacterial screening of leaf extracts (in vivo) showed no inhibitory effect against E. coli, P. aeruginosa, S. aureus, and B. cereus, in contrast to callus extracts from leaf cultures supplemented with NAA, which showed inhibition activity against E. coli and B. cereus. The callus extracts from leaf cultures grown on both MS and WPM media showed higher antioxidant and superoxide dismutase activities than leaf extracts. PMID:24967432

  13. The Effect of Various Media and Hormones via Suspension Culture on Secondary Metabolic Activities of (Cape Jasmine) Gardenia jasminoides Ellis

    PubMed Central

    Mat Taha, Rosna; Rashid, Kamaludin; Syafawati Yaacob, Jamilah

    2014-01-01

    The leaf of Gardenia jasminoides Ellis was used as explants and was cultured on MS and WPM media supplemented with various concentrations of NAA, IAA, 2,4-D, IBA, TDZ, and Kn (0 to 5 mg L−1 with 0.5 increment). After six months, the higher percentage of callus (100%) and the best dry and fresh weight of callus were formed on WPM medium supplemented with 2,4-D and NAA (2.0-3.0 mg L−1) and this amount was decreased from (84%) to (69%) when this media supplemented with Kinetin and TDZ (1 mg L−1) respectively were used. Leaf segments cultured on WPM media added with Kn (1 mg L−1) and TDZ (2 mg L−1) yielded the least amount of callus. It was found that WPM media added with IAA (4.5–5.0 mg L−1) were optimum for root induction from G. jasminoides plantlets. Antibacterial screening of leaf extracts (in vivo) showed no inhibitory effect against E. coli, P. aeruginosa, S. aureus, and B. cereus, in contrast to callus extracts from leaf cultures supplemented with NAA, which showed inhibition activity against E. coli and B. cereus. The callus extracts from leaf cultures grown on both MS and WPM media showed higher antioxidant and superoxide dismutase activities than leaf extracts. PMID:24967432

  14. Active mode locking of quantum cascade lasers in an external ring cavity.

    PubMed

    Revin, D G; Hemingway, M; Wang, Y; Cockburn, J W; Belyanin, A

    2016-01-01

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents. PMID:27147409

  15. Active mode locking of quantum cascade lasers in an external ring cavity

    NASA Astrophysics Data System (ADS)

    Revin, D. G.; Hemingway, M.; Wang, Y.; Cockburn, J. W.; Belyanin, A.

    2016-05-01

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents.

  16. Active mode locking of quantum cascade lasers in an external ring cavity

    PubMed Central

    Revin, D. G.; Hemingway, M.; Wang, Y.; Cockburn, J. W.; Belyanin, A.

    2016-01-01

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents. PMID:27147409

  17. Laser ion source activities at Brookhaven National Laboratory

    DOE PAGESBeta

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010more » of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.« less

  18. Laser ion source activities at Brookhaven National Laboratory

    SciTech Connect

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010 of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.

  19. Passive and Active Protective Clothing against High-Power Laser Radiation

    NASA Astrophysics Data System (ADS)

    Hennigs, C.; Hustedt, M.; Kaierle, S.; Wenzel, D.; Markstein, S.; Hutter, A.

    The main objective of the work described in this paper was the development of passive and active protective clothing for the protection of the human skin against accidental laser irradiation and of active protective curtains. Here, the passive systems consist of functional multi-layer textiles, providing a high level of passive laser resistance. In addition, the active functional multi-layer textiles incorporate sensors that detect laser exposure and are, by means of a safety control, able to deactivate the laser beam automatically.Due to the lack of regulations for testing and qualifying textiles to be used as laser PPE, test methods were defined and validated. Additionally, corresponding testing set-ups were developed.Finally, the gap with respect to standardization was bridged by the definition of a test procedure and the requirements with respect to laser PPE.The developments were demonstrated by a set of tailored functional passive and active laser-protective clothing prototypes (gloves, jackets, aprons, trousers) and active curtains as well as by a prototype testing rig, providing the possibility to perform the specified low-power and high-power textile test procedure.

  20. ERRORS IN APPLYING LOW ION-STRENGTH ACTIVITY COEFFICIENT ALGORITHMS TO HIGHER IONIC-STRENGTH AQUATIC MEDIA

    EPA Science Inventory

    The toxicological and regulatory communities are currently exploring the use of free-ion-activity- models as a means of reducing uncertainties in current methods for assessing metals bioavailabi- lity from contaminated aquatic media. While most practitioners would support the des...

  1. 76 FR 6839 - ActiveCore Technologies, Inc., Battery Technologies, Inc., China Media1 Corp., Dura Products...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-08

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION ActiveCore Technologies, Inc., Battery Technologies, Inc., China Media1 Corp., Dura Products... concerning the securities of Battery Technologies, Inc. because it has not filed any periodic reports...

  2. Tetravalent Chromium (Cr(4+)) as Laser-Active Ion for Tunable Solid-State Lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    During 10/31/92 - 3/31/93, the following summarizes our major accomplishments: (1) the self-mode-locked operation of the Cr:forsterite laser was achieved; (2) synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking; and (3) the pulses generated had a FWHW of 105 fs and were tunable between 1230 - 1270 nm.

  3. Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

    SciTech Connect

    Adraider, Y.; Pang, Y.X.; Nabhani, F.; Hodgson, S.N.; Sharp, M.C.; Al-Waidh, A.

    2014-06-01

    Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surface morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.

  4. Impact of water activity of diverse media on spore germination of Aspergillus and Penicillium species.

    PubMed

    Nanguy, Sidjè Paule-Marina; Perrier-Cornet, Jean-Marie; Bensoussan, Maurice; Dantigny, Philippe

    2010-08-15

    The effects of water activity (a(w)) of diverse media i/ culture medium for sporogenesis, a(w sp) ii/ liquid spore suspension medium, a(w su) and iii/ medium for germination, a(w ge), on the germination time t(G) of Aspergillus carbonarius, Aspergillus flavus, Penicillium chrysogenum and Penicillium expansum were assessed according to a screening matrix at 0.95 and 0.99 a(w). It was shown that i/ reduced t(G)s were obtained at 0.95 a(w sp) except for P. expansum ii/ a significant effect of a(w su) on t(G) was demonstrated for A. carbonarius, P. chrysogenum and P. expansum iii/ the most important factor for controlling the germination time was the medium for germination except for A. carbonarius (a(w su)). In accordance with the fact that fungal spores can swell as soon as they are suspended in an aqueous solution it is recommended to re-suspend fungal spores in a solution at the same water activity as that of subsequent germination studies. PMID:20673593

  5. Actively mode-locked all fiber laser with cylindrical vector beam output.

    PubMed

    Zhou, Yong; Wang, Anting; Gu, Chun; Sun, Biao; Xu, Lixin; Li, Feng; Chung, Dick; Zhan, Qiwen

    2016-02-01

    We demonstrated an all fiber actively mode-locked laser that emits a cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in a short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode-locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity. PMID:26907420

  6. Continuous-wave and actively Q-switched Nd:LSO crystal lasers

    NASA Astrophysics Data System (ADS)

    Zhuang, S.; Li, D.; Xu, X.; Wang, Z.; Yu, H.; Xu, J.; Chen, L.; Zhao, Y.; Guo, L.; Xu, X.

    2012-04-01

    With a fiber coupled laser diode array as the pump source, Nd-doped Lu2SiO5 (Nd:LSO) crystal lasers at 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions were demonstrated. The active Q-switched dual-wavelength lasers at about 1.08 μm, as well as continuous-wave (CW) and active Q-switched lasers at 1357 nm are reported for the first time, to the best of our knowledge. Considering the small emission cross-sections and long fluorescence lifetime, this material possesses large energy storage ability and excellent Q-switched properties. The special emission wavelength at 1357 nm will have promising applications to be used in many fields, such as THz generation, pumping of Cr3+:LiSAF, repumping of strontium optical clock, laser Doppler velocimeter and distributed fiber sensor.

  7. Kinetic Monte Carlo simulations of thermally activated magnetization reversal in dual-layer Exchange Coupled Composite recording media

    NASA Astrophysics Data System (ADS)

    Plumer, M. L.; Almudallal, A. M.; Mercer, J. I.; Whitehead, J. P.; Fal, T. J.

    The kinetic Monte Carlo (KMC) method developed for thermally activated magnetic reversal processes in single-layer recording media has been extended to study dual-layer Exchange Coupled Composition (ECC) media used in current and next generations of disc drives. The attempt frequency is derived from the Langer formalism with the saddle point determined using a variant of Bellman Ford algorithm. Complication (such as stagnation) arising from coupled grains having metastable states are addressed. MH-hysteresis loops are calculated over a wide range of anisotropy ratios, sweep rates and inter-layer coupling parameter. Results are compared with standard micromagnetics at fast sweep rates and experimental results at slow sweep rates.

  8. Comparison of Tunable Diode Laser Absorption Spectroscopy and Isothermal Micro-calorimetry for Non-invasive Detection of Microbial Growth in Media Fills

    PubMed Central

    Brueckner, David; Roesti, David; Zuber, Ulrich Georg; Schmidt, Rainer; Kraehenbuehl, Stefan; Bonkat, Gernot; Braissant, Olivier

    2016-01-01

    Two methods were investigated for non-invasive microbial growth-detection in intact glass vials as possible techniques for automated inspection of media-filled units. Tunable diode laser absorption spectroscopy (TDLAS) was used to determine microbially induced changes in O2 and CO2 concentrations within the vial headspaces. Isothermal microcalorimetry (IMC) allowed the detection of metabolic heat production. Bacillus subtilis and Streptococcus salivarius were chosen as test organisms. Parameters as robustness, sensitivity, comparability and time to detection (TtD) were evaluated to assess method adequacy. Both methods robustly detected growth of the tested microorganisms within less than 76 hours using an initial inoculum of <10CFU. TDLA turned out to be less sensitive than TDLA and IMC, as some false negative results were observed. Compared to the visual media-fill examination of spiked samples, the investigated techniques were slightly slower regarding TtD. Although IMC showed shorter TtD than TDLAS the latter is proposed for automating the media-fill inspection, as larger throughput can be achieved. For routine use either TDLA or a combination of TDLA and TDLA should be considered. IMC may be helpful for replacing the sterility assessment of commercial drug products before release. PMID:27282661

  9. Comparison of Tunable Diode Laser Absorption Spectroscopy and Isothermal Micro-calorimetry for Non-invasive Detection of Microbial Growth in Media Fills.

    PubMed

    Brueckner, David; Roesti, David; Zuber, Ulrich Georg; Schmidt, Rainer; Kraehenbuehl, Stefan; Bonkat, Gernot; Braissant, Olivier

    2016-01-01

    Two methods were investigated for non-invasive microbial growth-detection in intact glass vials as possible techniques for automated inspection of media-filled units. Tunable diode laser absorption spectroscopy (TDLAS) was used to determine microbially induced changes in O2 and CO2 concentrations within the vial headspaces. Isothermal microcalorimetry (IMC) allowed the detection of metabolic heat production. Bacillus subtilis and Streptococcus salivarius were chosen as test organisms. Parameters as robustness, sensitivity, comparability and time to detection (TtD) were evaluated to assess method adequacy. Both methods robustly detected growth of the tested microorganisms within less than 76 hours using an initial inoculum of <10CFU. TDLA turned out to be less sensitive than TDLA and IMC, as some false negative results were observed. Compared to the visual media-fill examination of spiked samples, the investigated techniques were slightly slower regarding TtD. Although IMC showed shorter TtD than TDLAS the latter is proposed for automating the media-fill inspection, as larger throughput can be achieved. For routine use either TDLA or a combination of TDLA and TDLA should be considered. IMC may be helpful for replacing the sterility assessment of commercial drug products before release. PMID:27282661

  10. Decreasing Excessive Media Usage while Increasing Physical Activity: A Single-Subject Research Study

    ERIC Educational Resources Information Center

    Larwin, Karen H.; Larwin, David A.

    2008-01-01

    The Kaiser Family Foundation released a report entitled "Kids and Media Use" in the United States that concluded that children's use of media--including television, computers, Internet, video games, and phones--may be one of the primary contributor's to the poor fitness and obesity of many of today's adolescents. The present study examines the…

  11. Online Activities, Digital Media Literacy, and Networked Individualism of Korean Youth

    ERIC Educational Resources Information Center

    Park, Sora; Kim, Eun-mee; Na, Eun-Yeong

    2015-01-01

    Networked individualism enables Internet users to connect and socialize via their loose and transient multiple networks, whereas digital media literacy is a precondition of effective Internet use. In this study, an attempt has been made to find the link between networked individualism, digital media literacy, and young people's perception of their…

  12. "Chemistry Is in the News": Taxonomy of Authentic News Media-Based Learning Activities. Research Report

    ERIC Educational Resources Information Center

    Glaser, Rainer E.; Carson, Kathleen M.

    2005-01-01

    A brief history is given of approaches that aim at achieving a connectedness of the content of organic chemistry courses to real world issues. Recently, such approaches have relied more and more on online media resources, the tools of the Internet and the World Wide Web. We propose a six-level taxonomy of 'authentic news media-based learning…

  13. Biological activity of photoproducts of merocyanine 540 generated by laser-light activation

    NASA Astrophysics Data System (ADS)

    Gulliya, Kirpal S.; Chanh, Tran C.; Pervaiz, Shazib; Harriman, Anthony; Matthews, James Lester

    1992-08-01

    Controlled exposure of photoactive compounds to light prior to their use in biological targets results in the formation of heretofore unknown photoproducts. This process of photoproduct generation, termed "preactivation," renders the photactive compound capable of systemic use without further dependence on light. Preactivation of mercyanin 540 (MC540) and several other photoactive compounds is achievable by exposure to CW and pulse laser radiation. The singlet oxygen generated at excited states attacks the dye molucule itself, resulting in the formation of biologically active photoproducts. For preactivated MC540 (photoproducts of MC540) generated by exposure to argon laser light (514 nm) and light from free-electron laser, we have demonstrated its effectiveness in selective killing of certain types of cultured tumor cells as well as human immunodeficiency virus type 1 (HIV-1) with very low, if any, damage to normal cells and tisues. For example, approximately 90% of the Burkitt's lymphoma Daudi cells and HL-60 leukemic cells are killed by preactivated MC540 at a concentration of 120 μg/ml. A two-hour treatment of cultured cells with buthionine sulfoxamine followed by the treatement with preactivated MC540 reults in 99.99% inhibition of clonogenic tumor stem cell growth. We also have demonstrated that preactivated MC540 is very effective in killing cell-free and cell-associated HIV-1. It also is very effective in killing HIV-1 and simian immunodeficiency virus (SIV) in virus-infected blood in vitro as determined by reverse transcriptase, P24, P17, core antigen expression and synctium formation. Treatment of HIV-1 with preactivated MC540 renders the treated HIV-1 incapable of binding to CD4 target molecules on T cells as determined by immunofluorescence and radioimmunoprecipitation assays. In vivo toxicology studies show that preactivated MC540 is very well tolerated and does not produce any signs of adverse reaction at the therapeutic doses, as determined by

  14. Application of copper vapour lasers for controlling activity of uranium isotopes

    NASA Astrophysics Data System (ADS)

    Barmina, E. V.; Sukhov, I. A.; Lepekhin, N. M.; Priseko, Yu S.; Filippov, V. G.; Simakin, Aleksandr V.; Shafeev, Georgii A.

    2013-06-01

    Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed.

  15. Monolithically integrated active waveguides and lasers using rare-earth doped spin-on glass

    SciTech Connect

    Ashby, C.I.H.; Sullivan, C.T.; Vawter, G.A.

    1996-09-01

    This LDRD program No. 3505.230 explored a new approach to monolithic integration of active waveguides and rare-earth solid state lasers directly onto III-V substrates. It involved selectively incorporating rare-earth ions into spin-on glasses (SOGs) that could be solvent cast and then patterned with conventional microelectronic processing. The patterned, rare-earth spin-on glasses (RESOGs) were to be photopumped by laser diodes prefabricated on the wafer and would serve as directly integrated active waveguides and/or rare-earth solid state lasers.

  16. Effect of the active-ion concentration on the lasing dynamics of holmium fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-12-09

    The lasing dynamics of fibre lasers with a core based on quartz glass doped with holmium ions to concentrations in the range of 10{sup 19}-10{sup 20} cm{sup -3} is investigated. It is shown that fibre lasers with a high concentration of active holmium ions generate pulses, but a decrease in the holmium concentration changes the lasing from pulsed to cw regime. At the same time, a decrease in the active-ion concentration and the corresponding increase in the fibre length in the cavity reduce the lasing efficiency. (lasers)

  17. Materials and Activities for Teachers and Children: A Project to Develop and Evaluate Multi-Media Kits for Elementary Schools, Volume I. Final Report.

    ERIC Educational Resources Information Center

    Kresse, Frederick H.

    The Children's Museum in Boston developed MATCH Boxes (Materials and Activities for Teachers and Children) to provide self-contained, multi-media kits for elementary school use. The project sought to determine an optimum balance of activities and various media which would involve the student directly in the learning process and would make use of…

  18. Media-Smart Youth: Eat, Think, and Be Active! A Workshop Curriculum for Youth Ages 11 to 13. Guide for Training Program Facilitators

    ERIC Educational Resources Information Center

    Shriver, Eunice Kennedy

    2008-01-01

    The Media-Smart Youth: Eat, Think, and Be Active! program is an engaging curriculum that helps young people understand the complex media world around them so they can make thoughtful decisions about issues important to their health, specifically nutrition and physical activity. This training guide was developed in response to the requests of…

  19. Active space debris removal by using laser propulsion

    NASA Astrophysics Data System (ADS)

    Rezunkov, Yu. A.

    2013-03-01

    At present, a few projects on the space debris removal by using highpower lasers are developed. One of the established projects is the ORION proposed by Claude Phipps from Photonics Associates Company and supported by NASA (USA) [1]. But the technical feasibility of the concept is limited by sizes of the debris objects (from 1 to 10 cm) because of a small thrust impulse generated at the laser ablation of the debris materials. At the same time, the removal of rocket upper stages and satellites, which have reached the end of their lives, has been carried out only in a very small number of cases and most of them remain on the Low Earth Orbits (LEO). To reduce the amount of these large-size objects, designing of space systems allowing deorbiting upper rocket stages and removing large-size satellite remnants from economically and scientifically useful orbits to disposal ones is considered. The suggested system is based on high-power laser propulsion. Laser-Orbital Transfer Vehicle (LOTV) with the developed aerospace laser propulsion engine is considered as applied to the problem of mitigation of man-made large-size space debris in LEO.

  20. Clinical and Spectrophotometric Evaluation of LED and Laser Activated Teeth Bleaching

    PubMed Central

    Lo Giudice, R.; Pantaleo, G.; Lizio, A.; Romeo, U.; Castiello, G.; Spagnuolo, G.; Giudice, G. Lo

    2016-01-01

    Background: Auxiliary power sources (LED and laser) are used in in-office teeth bleaching techniques to accelerate the redox reaction of the whitening gel to increase ease of use, to improve comfort and safety, and to decrease the procedure time. Objective: The aim this study is to evaluate the efficiency of the teeth whitening procedures performed with hydrogen peroxide and carbamide peroxide, LED or Laser activated. Method: 18 patients, affected by exogenous dyschromia, were treated with a bleaching agent composed by 35% hydrogen peroxide and 10% carbamide peroxide. They were divided into two groups: in the first group the bleaching agent was activated by a LED lamp; in the second group it was activated by a Laser diode lamp. Both groups were subjected to 3 bleaching cycle of 15’ each. The chromatic evaluations were performed before and after one week from the treatment, using a chromatic scale and a spectrophotometer. The mean value of pre, post bleaching and follow-up were analyzed using a T-test, with results statistically significant for P<0,05. Results: Results showed that the variations in brightness, chroma and hue are significantly influenced by the interaction between the whitening agent and the original colour of the teeth. Laser-activation has marginally improved the bleaching effectiveness. All patients treated with laser activation complained an increase in dental sensitivity. Conclusion: The use of laser-activating systems did not improve the efficacy of bleaching. PMID:27386010

  1. Quality assessment and anti-obesity activity of Stellaria media (Linn.) Vill

    PubMed Central

    2012-01-01

    Background Obesity is recognized as a social problem, associated with serious health risks and increased mortality. Numerous trials have been conducted to find and develop new anti-obesity drugs through herbal sources to minimize side effects associated with the present anti-obesity drugs. The present study was designed to evaluate the quality control parameters, quantitative phytochemical analysis (total phenolic, total flavonoids and total saponin content), and the anti-obesity effect of lyophilized juice (LJ) of Stellaria media (Linn.) Vill. by employing in vitro and in vivo models. Methods In vitro studies were performed to evaluate the inhibitory activity of LJ on pancreatic amylase and lipase. The in vivo pancreatic lipase activity was evaluated by measurement of plasma triacylglycerol levels after oral administration of lipid emulsion to swiss albino mice. Furthermore, the anti-obesity effect of LJ was assessed at two doses, 400 mg/kg and 900 mg/kg body weight in mice fed a high-fat-diet with or without LJ for 6 weeks. Results The LJ inhibited pancreatic amylase and lipase activity in vitro and elevated plasma triacylglycerol level in mice. LJ suppressed the increase in body weight, retroperitoneal adipose tissue, liver weights and serum parameters viz., total cholesterol, total triglyceride, LDL-cholesterol level at the dose of 900 mg/kg body weight of the mice fed with high fat diet. The total phenolic, flavonoid and saponin contents were found to be 0.26 mg/g, 1.4 mg/g and 1.19 μg/g respectively of LJ. Conclusion The anti-obesity effects of LJ in high-fat-diet fed mice may be partly mediated through delaying the intestinal absorption of dietary fat and carbohydrate by inhibiting digestive enzymes. PMID:22943464

  2. Active and passive coherent beam combining of thulium-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Zhou, Pu; Wang, Xiaolin; Ma, Yanxing; Ma, Haotong; Han, Kai; Xu, Xiaojun; Liu, Zejin

    2010-11-01

    Thulium-doped fiber laser (TFL), which emitted near 2 μm laser beam, has become the latest revolution in highpower fiber laser technology. Further increasing the output power will face great challenges induced by nonlinear effects; coherent beam combining of TFL can increase laser output power while simultaneously maintaining beam quality. In this manuscript, we will present our detailed investigation on coherent beam combining of TFLs. Three different approaches, i.e., interferometric array, mutual injection locking and active phasing based on multi-dithering technique, are employed. In the interferometric array scheme, coherent combining is realized by using an intracavity fiber coupler in an all-fiber laser array configuration. Efficient coherent combining can be achieved by providing sufficient loss discrimination. High combining efficiency of 85% for two fiber laser has been obtained. In mutual injection locking scheme, mutual coherence between the two fiber lasers is established by means of mutual coupling through two 3dB couplers. High combining efficiency of 99% for two fiber laser has been obtained, and the fringe contrast of the intensity pattern at the receiving plane is as high as 93%. In active phasing scheme, when the phase control system is in the closed loop, the fringe contrast of far-field intensity pattern is improved by more than 75 % from 10 % in open loop, and the residual phase error is less than λ/20.

  3. Particle size distributions, size concentration relationships, and adherence to hands of selected geologic media derived from mining, smelting, and quarrying activities.

    PubMed

    Bergstrom, Carolyn; Shirai, Jeffry; Kissel, John

    2011-09-15

    Hand-to-mouth activity, especially in children, is a potentially significant pathway of exposure to soil contaminants. Hand-mouthing behavior is of particular concern in areas impacted by mining, smelting, and quarrying activities as these activities may lead to elevated levels of heavy metals in soil. In order to estimate potential exposures to contaminated geologic media attributable to hand-to-mouth contact, it is useful to characterize adherence of those media to skin, as contaminant concentrations in adhered media may differ greatly from unfractionated, whole media concentrations. Such an investigation has been undertaken to aid estimation of exposures to arsenic, cadmium, lead, and zinc in nine different geologic media collected in the Pacific Northwest region of the United States. After establishing the particle size distribution of each medium (fractions <63 μm, 63-150 μm, 150-250 μm, and 250 μm-2mm were determined) and target elemental concentrations within each particle size fraction, an active handling protocol involving six volunteers was conducted. Wet media always adhered to a greater extent than dry media and adhered media generally had higher elemental concentrations than bulk media. Regression analyses suggest smaller particle fractions may have higher elemental concentrations. Results of application of a maximum likelihood estimation technique generally indicate that handling of dry media leads to preferential adherence of smaller particle sizes, while handling of wet media does not. Because adhered material can differ greatly in particle size distribution from that found in bulk material, use of bulk concentrations in exposure calculations may lead to poor estimation of actual exposures. Since lead has historically been a metal of particular concern, EPA's Integrated Exposure Uptake Biokinetic (IEUBK) Model was used to examine the potential consequences of evaluating ingestion of the selected media assuming concentrations in adhering versus

  4. Mid-infrared tunable laser based on the Cr:ZnSe active crystal

    NASA Astrophysics Data System (ADS)

    Koranda, Petr; Jelínková, Helena; Nemec, Michal; Šulc, Jan; Doroshenko, Maxim E.; Basiev, Tasoltan T.; Komar, Vitaly K.; Gerasimenko, Andriy S.; Puzikov, Vyacheslav M.; Badikov, V. V.; Badikov, D. V.

    2008-02-01

    Broadly tunable mid-infrared laser sources operated at room-temperature are desired in many technological and medical applications. The aim of the project was to design and construct broadly tunable powerful Cr:ZnSe laser. The investigated Cr:ZnSe various shaped bulk crystals were grown by the Bridgman method or by the floating zone method. The absorption spectrum was measured to be from 1500 to 2000 nm and the emission spectrum was from 2100 to 2800 nm. Three different lasers were utilized for coherent longitudinal pumping of Cr:ZnSe laser, namely flashlamp-pumped Er:YAP laser (generated wavelength 1660 nm), diode-pumped Tm:YLF laser (generated wavelength 1912 nm) and diode-pumped Tm:YAP laser (generated wavelength 1980 nm). The constructed Cr:ZnSe laser operated in pulsed as well as in continuous-wave regime. In the first case the Cr:ZnSe crystal grown by the floating zone method was studied. The maximal output power in continuous-wave regime was 310 mW with the slope-efficiency 73% for the Tm:YAP laser pumping. In the second case the Cr:ZnSe prism grown by the Bridgman method which served simultaneously as laser active medium and intracavity dispersive element was investigated. For the Er:YAP laser pumping the maximal output energy was 20 mJ with the slope-efficiency 36%. The output radiation was tunable in the range from 2050 nm up to 2750 nm. For the Tm:YAP laser pumping the maximal output power in continuous-wave regime was 175 mW with the slope-efficiency 24%. The output radiation was tunable in the interval from 2220 nm up to 2680 nm. The generated radiation beam spatial structure was close to TEM00.

  5. Deformation of partially pumped active mirrors for high average-power diode-pumped solid-state lasers.

    PubMed

    Albach, Daniel; LeTouzé, Geoffroy; Chanteloup, Jean-Christophe

    2011-04-25

    We discuss the deformation of a partially pumped active mirror amplifier as a free standing disk, as implemented in several laser systems. We rely on the Lucia laser project to experimentally evaluate the analytical and numerical deformation models. PMID:21643092

  6. Efficacy and causal mechanism of an online social media intervention to increase physical activity: Results of a randomized controlled trial

    PubMed Central

    Zhang, Jingwen; Brackbill, Devon; Yang, Sijia; Centola, Damon

    2015-01-01

    Objective: To identify what features of social media – promotional messaging or peer networks – can increase physical activity. Method: A 13-week social media-based exercise program was conducted at a large Northeastern university in Philadelphia, PA. In a randomized controlled trial, 217 graduate students from the University were randomized to three conditions: a control condition with a basic online program for enrolling in weekly exercise classes led by instructors of the University for 13 weeks, a media condition that supplemented the basic program with weekly online promotional media messages that encourage physical activity, and a social condition that replaced the media content with an online network of four to six anonymous peers composed of other participants of the program, in which each participant was able to see their peers' progress in enrolling in classes. The primary outcome was the number of enrollments in exercise classes, and the secondary outcomes were self-reported physical activities. Data were collected in 2014. Results: Participants enrolled in 5.5 classes on average. Compared with enrollment in the control condition (mean = 4.5), promotional messages moderately increased enrollment (mean = 5.7, p = 0.08), while anonymous social networks significantly increased enrollment (mean = 6.3, p = 0.02). By the end of the program, participants in the social condition reported exercising moderately for an additional 1.6 days each week compared with the baseline, which was significantly more than an additional 0.8 days in the control condition. Conclusion: Social influence from anonymous online peers was more successful than promotional messages for improving physical activity. Clinical Trial Registration: ClinicalTrials.gov: NCT02267369. PMID:26844132

  7. Low threshold, actively Q-switched Nd 3+:YVO 4 self-Raman laser and frequency doubled 588 nm yellow laser

    NASA Astrophysics Data System (ADS)

    Wang, Baoshan; Tan, Huiming; Peng, Jiying; Miao, Jieguang; Gao, Lanlan

    2007-03-01

    We reported an actively Q-switched, intracavity Nd3+:YVO4 self-Raman laser at 1176 nm with low threshold and high efficiency. From the extracavity frequency doubling by use of LBO nonlinear crystal, over 3.5 mW, 588 nm yellow laser is achieved. The maximum Raman laser output at is 182 mW with 1.8 W incident pump power. The threshold is only 370 mW at a pulse repetition frequency of 5 kHz. The optical conversion efficiency from incident to the Raman laser is 10%, and 1.9% from Raman laser to the yellow.

  8. Laser micromachining of through via interconnects in active die for 3-D multichip module

    SciTech Connect

    Chu, D.; Miller, W.D.

    1995-09-01

    One method to increase density in integrated circuits (IC) is to stack die to create a 3-D multichip module (MCM). In the past, special post wafer processing was done to bring interconnects out to the edge of the die. The die were sawed, glued, and stacked. Special processing was done to create interconnects on the edge to provide for interconnects to each of the die. These processes require an IC type fabrication facility (fab) and special processing equipment. In contrast, we have developed packaging assembly methods to created vertical through vias in bond pads of active silicon die, isolate these vias, and metal fill these vias without the use of a special IC fab. These die with through vias can then be joined and stacked to create a 3-D MCM. Vertical through vias in active die are created by laser micromachining using a Nd:YAG laser. Besides the fundamental 1064 nm (infra-red) laser wavelength of a Nd:YAG laser, modifications to our Nd:YAG laser allowed us to generate the second harmonic 532 nm (green) laser wavelength and fourth harmonic 266nm (ultra violet) laser wavelength in laser micromachining for these vias. Experiments were conducted to determine the best laser wavelengths to use for laser micromachining of vertical through vias in order to minimize damage to the active die. Via isolation experiments were done in order to determine the best method in isolating the bond pads of the die. Die thinning techniques were developed to allow for die thickness as thin as 50 {mu}m. This would allow for high 3-D density when the die are stacked. A method was developed to metal fill the vias with solder using a wire bonder with solder wire.

  9. Femtosecond-laser-produced low-density plasmas in transparent biological media: a tool for the creation of chemical, thermal, and thermomechanical effects below the optical breakdown threshold

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Noack, Joachim; Huettmann, Gereon; Paltauf, Guenther

    2002-04-01

    The irradiance threshold for femtosecond optical breakdown in aqueous media is approximately equals 1.0x1013W cm-2. At the breakdown threshold, a plasma with a free electron density of about 1021cm-3 is generated, and the energy density in the breakdown region is sufficiently high to cause the formation of a bubble which can be experimentally observed. We found previously that plasmas with a free electron density <1021cm-3 are formed also in a fairly large irradiance range below the breakdown threshold. The present study investigates the chemical, thermal, and thermomechanical effects produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and avalanche ionization to numerically simulate the temporal evolution of the free electron density during the laser pulse for a given irradiance, and to calculate the irradiance dependence of the free-electron density and volumetric energy density reached at the end of the laser pulse. The value of the energy density created by each laser pulse is then used to calculate the temperature distribution in the focal region after application of a single laser pulse and of series of pulses. The results of the temperature calculations yield, finally, the starting point for calculations of the thermoelastic stresses that are generated during the formation of the low-density plasmas. We found that, particularly for short wavelengths, a large 'tuning range' exists for the creation of spatially extremely confined chemical, thermal and mechanical effects via free electron generation through nonlinear absorption. Photochemical effects dominate at the lower end of this irradiance range, whereas at the upper end they are mixed with thermal effects and modified by thermoelastic stresses. Above the breakdown threshold, the spatial confinement is partly destroyed by cavitation bubble formation

  10. Interaction of the excited ions-activators in laser crystals

    NASA Astrophysics Data System (ADS)

    Zubenko, D. A.; Noginov, M. A.; Ostroumov, Vasiliy G.; Semenkov, S. G.; Smirnov, V. A.; Shcherbakov, Ivan A.

    1992-11-01

    Processes of interaction of excited ions are investigated in several laser crystals: Er-Er -- in YSGG:Cr, Er and GSAG:Cr,Er crystals; Ho-Ho -- in YSGG:Cr, Ho crystals; Tm-Tm -- in YSGG:Cr,Tm and YAG:Cr,Tm crystals; Tm-Ho -- in YSGG:Cr, Tm, Ho and YSAG:Cr, Tm, Ho crystals; Cr-Cr -- in 11 of different laser crystals (ruby, YAG, GSGG, YSGG, LICAF, et al.); Cr-TR (Er, Ho, Tb, Tm, Nd, -- TR) in YAG, YSGG, GSGG, GSAG crystals.

  11. Electrocatalytic activities of alkyne-functionalized copper nanoparticles in oxygen reduction in alkaline media

    NASA Astrophysics Data System (ADS)

    Liu, Ke; Song, Yang; Chen, Shaowei

    2014-12-01

    Stable alkyne-capped copper nanoparticles were prepared by chemical reduction of copper acetate with sodium borohydride in the presence of alkyne ligands. Transmission electron microscopic measurements showed that nanoparticles were well dispersed with a diameter in the range of 4-6 nm. FTIR and photoluminescence spectroscopic measurements confirmed the successful attachment of the alkyne ligands onto the nanoparticle surface most likely forming Cu-Ctbnd interfacial bonds. XPS measurements indicated the formation of a small amount of CuO in the nanoparticles with a satellite peak where the binding energy red-shifted with increasing Cu(II) concentration. Cu2O was also detected in the nanoparticles. Similar results were observed with commercial CuO nanoparticles. Electrochemical studies showed that the as-prepared alkyne-capped copper nanoparticles exhibited apparent electrocatalytic activity in oxygen reduction in alkaline media, a performance that was markedly better than those reported earlier with poly- or single-crystalline copper electrodes; and the fraction of peroxides in the final products decreased with decreasing concentration of oxide components in the nanoparticles.

  12. Antimicrobial activity of hop extracts against Listeria monocytogenes in media and in food.

    PubMed

    Larson, A E; Yu, R R; Lee, O A; Price, S; Haas, G J; Johnson, E A

    1996-12-01

    Growth of Listeria monocytogenes was inhibited in culture media and in certain foods by four hop extracts (I-IV) containing varying concentrations of alpha-and beta-acids. Extracts (II and III) containing the highest concentrations of beta-acids were inhibitory at 0.01 mg/l in trypticase soy broth. In food, these hop extracts showed varying magnitudes of inhibition. In coleslaw, hop extract III at 1 mg/g enhanced the rate of inactivation of L. monocytogenes Scott A. Hop extract II was inhibitory at 0.1 and 1 mg/ml in skim and 2% milk, and was inhibitory at 1 mg/ml in whole milk. Hop extract II was listericidal in cottage cheese at 0.1 to 3 g/kg. No inhibition of L. monocytogenes by hop extract III was observed in Camembert cheese. Overall, the antimicrobial activity of hop extracts in food appeared to increase with acidity and lower fat content. Our results indicate that hop extracts could be used to control L. monocytogenes in minimally processed food with low fat content. PMID:8930705

  13. STS-101 crew talks with the media after TCDT activities at the pad

    NASA Technical Reports Server (NTRS)

    2000-01-01

    After Terminal Countdown Demonstration Test (TCDT) activities at Launch Pad 39A, the STS-101 crew talk to the media. At the far left is George Diller, with NASA Public Affairs, who is moderating the event. At the microphone Commander James D. Halsell Jr. answers a question. Next to him, standing left to right, are Pilot Scott J. 'Doc' Horowitz and Mission Specialists Mary Ellen Weber, Jeffrey N. Williams, James Voss, Susan J. Helms and Yuri Usachev of Russia. The TCDT includes emergency egress training and a simulated launch countdown. During their mission to the International Space Station, the STS-101 crew will be delivering logistics and supplies, plus preparing the Station for the arrival of the Zvezda Service Module, expected to be launched by Russia in July 2000. Also, the crew will conduct one space walk to perform maintenance on the Space Station. This will be the third assembly flight for the Space Station. STS-101 is scheduled to launch April 24 at 4:15 p.m. from Launch Pad 39A.

  14. Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery

    NASA Astrophysics Data System (ADS)

    Brujan, E.-A.

    2005-01-01

    The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

  15. Blocking macrophage migration inhibitory factor activity alleviates mouse acute otitis media in vivo.

    PubMed

    Zhang, Jin; Xu, Min; Zheng, Qingyin; Zhang, Yan; Ma, Weijun; Zhang, Zhaoqiang

    2014-11-01

    This study was to investigate the role of macrophage migration inhibitory factor (MIF) in mouse acute otitis media (AOM), we hypothesize that blocking MIF activity will relieve mouse AOM. A mouse AOM model was constructed by injecting lipopolysaccharide (LPS) into the middle ear of C57BL/6 mice through the tympanic membrane (TM). MIF levels were measured by real-time PCR (RT-PCR) and ELISA after LPS application. Normal or AOM mice were given PBS or ISO-1 (MIF antagonist) every day for 10 days and the hearing levels were determined by measuring auditory brainstem response (ABR) threshold. After the ABR test finished, H&E staining was conducted and the inflammation was also measured by detecting interleukin (IL)-1β, tumor necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF) levels with RT-PCR and ELISA. TLR-4 expression was determined by western blotting and NF-κB activation was determined by electrophoretic mobility shift assays. Compared with the normal control, MIF levels in the middle ear of LPS-induced AOM mice were significant increased. The ABR results showed that mean ABR thresholds in ISO-1 treated AOM mice were significantly reduced compared with PBS treated AOM mice since day 7, indicating that ISO-1 treatment potentially improved the hearing levels of AOM mice. H&E staining showed that ISO-1 treatment could reduce the mucosal thickness of AOM mice. In ISO-1 treated mice, TLR-4 expression and levels of IL-1β, TNF-α and VEGF were significantly lower compared with PBS treated AOM mice. ISO-1 treatment also significantly inhibited NF-κB activation in AOM mice compared with PBS treated AOM mice. These results suggested that blocking the activity of MIF by ISO-1 could reduce the inflammation in AOM mice in which process TLR-4 and NF-κB were involved. The reduction in MIF activity is conducive to alleviate mouse AOM, which may serve as a potential therapeutic target for the treatment of AOM. PMID:25108100

  16. Role of ROS-mediated TGF beta activation in laser photobiomodulation

    NASA Astrophysics Data System (ADS)

    Arany, Praveen R.; Chen, Aaron Chih-Hao; Hunt, Tristan; Mooney, David J.; Hamblin, Michael

    2009-02-01

    The ability of laser light to modulate specific biological processes has been well documented but the precise mechanism mediating these photobiological interactions remains an area of intense investigation. We recently published the results of our clinical trial with 30 patients in an oral tooth-extraction wound healing model using a 904nm GaAs laser (Oralaser 1010, Oralia, Konstnaz, Germany), assessing healing parameters using routine histopathology and immunostaining (Arany et al Wound Rep Regen 2007, 15, 866). We observed a better organized healing response in laser irradiated oral tissues that correlated with an increased expression of TGF-beta1 immediately post laser irradiation. Our data suggested the source of latent TGF-beta1 might be from the degranulating platelets in the serum, an abundant source of in vivo latent TGF-beta, in the freshly wounded tissues. Further, we also demonstrated the ability of the low power near-infrared laser irradiation to activate the latent TGF-beta complexes in vitro at varying fluences from 10sec (0.1 J/cm2) to 600secs (6 J/cm2). Using serum we observed two isoforms, namely TGF-beta1 and TGF-beta3, were capable of being activated by laser irradiation using an isoform-specific ELISA and a reporter based (p3TP) assay system. We are presently pursuing the precise photomolecular mechanisms focusing on potential chromophores, wavelength and fluence parameters affecting the Latent TGF-beta activation process in serum. As ROS mediated TGF-beta activation has been previously demonstrated and we are also exploring the role of Laser generated-ROS in this activation process. In summary, we present evidence of a potential molecular mechanism for laser photobiomodulation in its ability to activate latent TGF-beta complexes.

  17. Microbial Activity and Precipitation at Solution-Solution Mixing Zones in Porous Media -- Subsurface Biogeochemical Research

    SciTech Connect

    Colwell, Frederick; Wildenschild, Dorthe; Wood, Brian; Gerlach, Robin; Mitchell, Andrew; Redden, George

    2014-08-29

    The goal for this research was to understand how best to add compounds to receptive microbial communities in porous media in order to achieve optimal calcite precipitation in a volumetrically significant space and to understand the physiological health of the cells that are responsible for the calcite precipitation. The specific objectives were to: (1) develop better tools for visually examining biofilms in porous media and calcium carbonate precipitation being mediated by microbes in porous media, and (2) demonstrate the effectiveness of using that tool within a flow cell model system.

  18. Activation of Carbonyl-Containing Molecules with Solid Lewis Acids in Aqueous Media

    SciTech Connect

    Román-Leshkov, Yuriy; Davis, Mark E.

    2011-09-28

    Current interest in reacting carbonyl-containing molecules in aqueous media is primarily due to the growing emphasis on conversion of biomass to fuels and chemicals. Recently, solid Lewis acids have been shown to perform catalytic reactions with carbonyl-containing molecules such as sugars in aqueous media. Here, catalysis mediated by Lewis acids is briefly discussed, Lewis acid solids that perform catalysis in aqueous media are then described, and the review is concluded with a few comments on the outlook for the future.

  19. Bifunctional enhancement of oxygen reduction reaction activity on Ag catalysts due to water activation on LaMnO3 supports in alkaline media

    NASA Astrophysics Data System (ADS)

    Park, Shin-Ae; Lee, Eun-Kyung; Song, Hannah; Kim, Yong-Tae

    2015-08-01

    Ag is considered to be one of the best candidates for oxygen reduction reaction electrocatalysts in alkaline media for application in various electrochemical energy devices. In this study, we demonstrate that water activation is a key factor in enhancing the ORR activity in alkaline media, unlike in acid environments. Ag supported on LaMnO3 having a high oxophilicity showed a markedly higher ORR activity than that on carbon with inert surfaces. Through various electrochemical tests, it was revealed that the origin of the enhanced ORR activity of Ag/LaMnO3 is the bifunctional effect mainly due to the water activation at the interface between Ag and LaMnO3. Furthermore, the ligand effect due to the charge transfer from Mn to Ag leads to the enhancement of both oxygen activation on Ag and water activation on Mn sites, and hence, an improvement in the ORR activity of Ag/LaMnO3. On the other hand, the strain effect based on the fine structure variation in the lattice was negligible. We therefore suggest that the employment of a co-catalyst or support with highly oxophilic nature and the maximization of the interface between catalyst and support should be considered in the design of electrocatalysts for the ORR in alkaline media.

  20. Bifunctional enhancement of oxygen reduction reaction activity on Ag catalysts due to water activation on LaMnO3 supports in alkaline media.

    PubMed

    Park, Shin-Ae; Lee, Eun-Kyung; Song, Hannah; Kim, Yong-Tae

    2015-01-01

    Ag is considered to be one of the best candidates for oxygen reduction reaction electrocatalysts in alkaline media for application in various electrochemical energy devices. In this study, we demonstrate that water activation is a key factor in enhancing the ORR activity in alkaline media, unlike in acid environments. Ag supported on LaMnO3 having a high oxophilicity showed a markedly higher ORR activity than that on carbon with inert surfaces. Through various electrochemical tests, it was revealed that the origin of the enhanced ORR activity of Ag/LaMnO3 is the bifunctional effect mainly due to the water activation at the interface between Ag and LaMnO3. Furthermore, the ligand effect due to the charge transfer from Mn to Ag leads to the enhancement of both oxygen activation on Ag and water activation on Mn sites, and hence, an improvement in the ORR activity of Ag/LaMnO3. On the other hand, the strain effect based on the fine structure variation in the lattice was negligible. We therefore suggest that the employment of a co-catalyst or support with highly oxophilic nature and the maximization of the interface between catalyst and support should be considered in the design of electrocatalysts for the ORR in alkaline media. PMID:26310526

  1. Bifunctional enhancement of oxygen reduction reaction activity on Ag catalysts due to water activation on LaMnO3 supports in alkaline media

    PubMed Central

    Park, Shin-Ae; Lee, Eun-Kyung; Song, Hannah; Kim, Yong-Tae

    2015-01-01

    Ag is considered to be one of the best candidates for oxygen reduction reaction electrocatalysts in alkaline media for application in various electrochemical energy devices. In this study, we demonstrate that water activation is a key factor in enhancing the ORR activity in alkaline media, unlike in acid environments. Ag supported on LaMnO3 having a high oxophilicity showed a markedly higher ORR activity than that on carbon with inert surfaces. Through various electrochemical tests, it was revealed that the origin of the enhanced ORR activity of Ag/LaMnO3 is the bifunctional effect mainly due to the water activation at the interface between Ag and LaMnO3. Furthermore, the ligand effect due to the charge transfer from Mn to Ag leads to the enhancement of both oxygen activation on Ag and water activation on Mn sites, and hence, an improvement in the ORR activity of Ag/LaMnO3. On the other hand, the strain effect based on the fine structure variation in the lattice was negligible. We therefore suggest that the employment of a co-catalyst or support with highly oxophilic nature and the maximization of the interface between catalyst and support should be considered in the design of electrocatalysts for the ORR in alkaline media. PMID:26310526

  2. Laser Holography. High Tech with High Potential for Learning Activities.

    ERIC Educational Resources Information Center

    Schlegel, Ronald D.

    1986-01-01

    This article discusses the procedure, historical development, and applications of holography, and discusses the feasibility and value of implementing a unit or course of study of laser holography into an existing photography laboratory and curriculum. An equipment and supplies list, giving supplies and cost, is included. (CT)

  3. Tetravalent Chromium (Cr(4+)) as Laser-Active Ion for Tunable Solid-State Lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    During 10/31/91 - 3/31/92, the following summarizes are major accomplishments: (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed; and (2) the simulation revealed several design parameters to be used for the construction of a femtosecond forsterite laser.

  4. Lewis Acid Pairs for the Activation of Biomass-derived Oxygenates in Aqueous Media

    SciTech Connect

    Roman, Yuriy

    2015-09-14

    The objective of this project is to understand the mechanistic aspects behind the cooperative activation of oxygenates by catalytic pairs in aqueous media. Specifically, we will investigate how the reactivity of a solid Lewis acid can be modulated by pairing the active site with other catalytic sites at the molecular level, with the ultimate goal of enhancing activation of targeted functional groups. Although unusual catalytic properties have been attributed to the cooperative effects promoted by such catalytic pairs, virtually no studies exist detailing the use heterogeneous water-tolerant Lewis pairs. A main goal of this work is to devise rational pathways for the synthesis of porous heterogeneous catalysts featuring isolated Lewis pairs that are active in the transformation of biomass-derived oxygenates in the presence of bulk water. Achieving this technical goal will require closely linking advanced synthesis techniques; detailed kinetic and mechanistic investigations; strict thermodynamic arguments; and comprehensive characterization studies of both materials and reaction intermediates. For the last performance period (2014-2015), two technical aims were pursued: 1) C-C coupling using Lewis acid and base pairs in Lewis acidic zeolites. Tin-, zirconium-, and hafnium containing zeolites (e.g., Sn-, Zr-, and Hf-Beta) are versatile solid Lewis acids that selectively activate carbonyl functional groups. In this aim, we demonstrate that these zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions. 2) One-pot synthesis of MWW zeolite nanosheets for activation of bulky substrates. Through

  5. Laser active imaging-guided anti-tank missile system small-scale integration design

    NASA Astrophysics Data System (ADS)

    Yan, Mingliang; Shan, Xiangqian; Qu, Zhou

    2010-10-01

    At present, the domestic and international third-generation anti-tank missiles, laser-guided missiles are mostly divided into active laser-guided and laser semi-active guidance, this guidance system, there are vulnerable to electronic interference, can not be fully realized after launching deficiencies. Article based on this, an in-depth understanding of imaging-guided laser-active working principle, based on the pairs of third-generation anti-tank missile guidance system, boldly proposed to improve the anti-tank missiles, laser-active small-scale integration of imaging guidance system design, the main purpose is to improve a certain type of The optical target missile, TV angle measurement, laser-guided instruction transmission means, so that anti-tank missiles to achieve forward-looking, the next obstacle avoidance TV and multi-functional integration of the entire after launching smart missiles, and in theory be able to study the new antitank missiles play a certain reference.

  6. Possibilities of increasing the pumping efficiency of solid active medium laser generators by optimizing the pumping cavity profile

    NASA Astrophysics Data System (ADS)

    Dontu, O.; Ganatsios, S.; Alexandrescu, N.

    2008-03-01

    The paper presents some design elements concerning the optical pumping cavities of the laser generators with active solid medium, as well as the way of increasing their performance. We start from the fact that the laser cavity is a closed optical system, where the active laser medium and the pumping source are conjugated, in order to achieve a maximum concentration of the light flux of the pumping source towards the active medium. We discuss the simple elliptical section laser pumping cavities (with one pumping lamp) and triple elliptical (with three lamps), also presenting a series on calculus nomograms, very useful to those who design the laser generation optical pumping cavities.

  7. Effects of sitting time associated with media consumption on physical activity patterns and daily energy expenditure of Saudi school students.

    PubMed

    Alghadir, Ahmad H; Gabr, Sami A; Iqbal, Zaheen A

    2015-09-01

    [Purpose] This study was performed to assess the effect of daily sitting time during media consumption on physical fitness, total energy expenditure (TEE), and body composition indices of Saudi school children. [Subjects and Methods] A total of 180 healthy Saudi school students (8-18 years) were included in this study. Sitting time, total energy expenditure, and levels of physical activity were evaluated with pre-validated internet based questionnaires. Body composition indices were evaluated using anthropometric analysis. [Results] Out of the studied participants, only 22.2% of students were physically inactive. Children with moderate and active physical scores demonstrated less sedentary behavior (TV viewing and computer usage), lower body composition values (BMI, WC, WHtR), and higher TEE than sedentary or mild activity level participants. Boys showed higher fitness scores and less sedentary behavior than girls. Media sitting time among the studied subjects correlated negatively with physical scores and positively with body composition. [Conclusion] The data presented here suggests that poor physical fitness, lower TEE, and longer sitting times differentially influence normal body composition indices among school children which may lead to overweight or obese individuals. Thus, decreasing sitting time during media consumption and enhancing physical activity may play a pivotal role in preventing obesity in young children. PMID:26504298

  8. Effects of sitting time associated with media consumption on physical activity patterns and daily energy expenditure of Saudi school students

    PubMed Central

    Alghadir, Ahmad H.; Gabr, Sami A.; Iqbal, Zaheen A.

    2015-01-01

    [Purpose] This study was performed to assess the effect of daily sitting time during media consumption on physical fitness, total energy expenditure (TEE), and body composition indices of Saudi school children. [Subjects and Methods] A total of 180 healthy Saudi school students (8–18 years) were included in this study. Sitting time, total energy expenditure, and levels of physical activity were evaluated with pre-validated internet based questionnaires. Body composition indices were evaluated using anthropometric analysis. [Results] Out of the studied participants, only 22.2% of students were physically inactive. Children with moderate and active physical scores demonstrated less sedentary behavior (TV viewing and computer usage), lower body composition values (BMI, WC, WHtR), and higher TEE than sedentary or mild activity level participants. Boys showed higher fitness scores and less sedentary behavior than girls. Media sitting time among the studied subjects correlated negatively with physical scores and positively with body composition. [Conclusion] The data presented here suggests that poor physical fitness, lower TEE, and longer sitting times differentially influence normal body composition indices among school children which may lead to overweight or obese individuals. Thus, decreasing sitting time during media consumption and enhancing physical activity may play a pivotal role in preventing obesity in young children. PMID:26504298

  9. Laser-ablated active doping technique for visible spectroscopy measurements on Z.

    SciTech Connect

    Gomez, Matthew Robert

    2013-09-01

    Visible spectroscopy is a powerful diagnostic, allowing plasma parameters ranging from temperature and density to electric and magnetic fields to be measured. Spectroscopic dopants are commonly introduced to make these measurements. On Z, dopants are introduced passively (i.e. a salt deposited on a current-carrying surface); however, in some cases, passive doping can limit the times and locations at which measurements can be made. Active doping utilizes an auxiliary energy source to disperse the dopant independently from the rest of the experiment. The objective of this LDRD project was to explore laser ablation as a method of actively introducing spectroscopic dopants. Ideally, the laser energy would be delivered to the dopant via fiber optic, which would eliminate the need for time-intensive laser alignments in the Z chamber. Experiments conducted in a light lab to assess the feasibility of fibercoupled and open-beam laser-ablated doping are discussed.

  10. The power of the bubble: comparing ultrasonic and laser activated irrigation

    NASA Astrophysics Data System (ADS)

    De Moor, Roeland J. G.; Meire, Maarten A.; Verdaasdonk, Rudolf M.

    2014-01-01

    The major problem of irrigation is the fluid motion within the confined geometry of the root canal : efficient dispersion of the liquid is difficult, conventional irrigation is limited due to the absence of turbulence over much of the canal volume, vapour lock may limit apical cleaning and disinfection, there is also a stagnation plane beyond the needle tip. The best way to improve irrigant penetration and biofilm removal is achieved by means of the agitation of the fluid. Today ultrasonic activation appears to be the best way to activate and potentiate irrigants among the present-day used means and marketed systems. Another way to activate irrigation solutions is the use of lasers: laser activated irrigation or photon-initiated acoustic streaming have been investigated. Based on present-day research it appears that the efficacy of laser activation (especially with Erbium lasers) can be more efficient thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for laser activated irrigation.

  11. Zig-zag active-mirror laser with cryogenic Yb3+:YAG/YAG composite ceramics.

    PubMed

    Furuse, Hiroaki; Kawanaka, Junji; Miyanaga, Noriaki; Saiki, Taku; Imasaki, Kazuo; Fujita, Masayuki; Takeshita, Kenji; Ishii, Shinya; Izawa, Yasukazu

    2011-01-31

    We report on a novel amplifier configuration concept for a 10 kW laser system using a zig-zag optical path based on a cryogenic Yb:YAG Total-Reflection Active-Mirror (TRAM) laser. The laser material is a compact composite ceramic, in which three Yb:YAG TRAMs are combined in series to increase the output power. Output powers of up to 214 W with a slope efficiency of 63% have been demonstrated for CW operation, even at a quite low pump intensity of less than 170 W/cm2. Further scaling could achieve output powers of more than 10 kW. PMID:21369064

  12. Thermal analysis on grad-doped active-mirror Yb:YAG ceramic lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojin; Wang, Jianlei; Jiang, Benxue

    2015-11-01

    Heat conduction, temperature distribution, thermal stress, and thermally induced refractive index of a diode-pumped active-mirror grad-doped Yb:YAG ceramic laser are analyzed and compared to a uniform-doped Yb:YAG ceramic laser. It is found that a rationally designed grad-doped Yb:YAG ceramic has a smaller temperature gradient than a uniform-doped Yb:YAG ceramic with the same absorption pump power, which results in higher output energy in the grad-doped Yb:YAG ceramic laser.

  13. Effect of active-ion concentration on holmium fibre laser efficiency

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-08-03

    We have measured the fraction of holmium ions that relax nonradiatively to the ground level as a result of interaction at a metastable level in optical fibres with a silica-based core doped with holmium ions to 2 x 10{sup 19} - 2 x 10{sup 20} cm{sup -3}. The percentage of such ions has been shown to depend on the absolute active-ion concentration. The fibres have been used to make a number of 2.05-{mu}m lasers, and their slope efficiency has been measured. The laser efficiency decreases with increasing holmium concentration in the fibres (lasers)

  14. Nutrient removal using biosorption activated media: preliminary biogeochemical assessment of an innovative stormwater infiltration basin.

    PubMed

    O'Reilly, Andrew M; Wanielista, Martin P; Chang, Ni-Bin; Xuan, Zhemin; Harris, Willie G

    2012-08-15

    Soil beneath a stormwater infiltration basin receiving runoff from a 23 ha predominantly residential watershed in north-central Florida, USA, was amended using biosorption activated media (BAM) to study the effectiveness of this technology in reducing inputs of nitrogen and phosphorus to groundwater. The functionalized soil amendment BAM consists of a 1.0:1.9:4.1 mixture (by volume) of tire crumb (to increase sorption capacity), silt and clay (to increase soil moisture retention), and sand (to promote sufficient infiltration), which was applied to develop an innovative stormwater infiltration basin utilizing nutrient reduction and flood control sub-basins. Comparison of nitrate/chloride (NO(3)(-)/Cl(-)) ratios for the shallow groundwater indicates that prior to using BAM, NO(3)(-) concentrations were substantially influenced by nitrification or variations in NO(3)(-) input. In contrast, for the new basin utilizing BAM, NO(3)(-)/Cl(-) ratios indicate minor nitrification and NO(3)(-) losses with the exception of one summer sample that indicated a 45% loss. Biogeochemical indicators (denitrifier activity derived from real-time polymerase chain reaction and variations in major ions, nutrients, dissolved and soil gases, and stable isotopes) suggest that NO(3)(-) losses are primarily attributable to denitrification, whereas dissimilatory nitrate reduction to ammonium is a minor process. Denitrification was likely occurring intermittently in anoxic microsites in the unsaturated zone, which was enhanced by the increased soil moisture within the BAM layer and resultant reductions in surface/subsurface oxygen exchange that produced conditions conducive to increased denitrifier activity. Concentrations of total dissolved phosphorus and orthophosphate (PO(4)(3-)) were reduced by more than 70% in unsaturated zone soil water, with the largest decreases in the BAM layer where sorption was the most likely mechanism for removal. Post-BAM PO(4)(3-)/Cl(-) ratios for shallow

  15. Nutrient removal using biosorption activated media: preliminary biogeochemical assessment of an innovative stormwater infiltration basin

    USGS Publications Warehouse

    O'Reilly, Andrew M.; Wanielista, Martin P.; Chang, Ni-Bin; Xuan, Zhemin; Harris, Willie G.

    2012-01-01

    Soil beneath a stormwater infiltration basin receiving runoff from a 22.7 ha predominantly residential watershed in central Florida, USA, was amended using biosorption activated media (BAM) to study the effectiveness of this technology in reducing inputs of nitrogen and phosphorus to groundwater. The functionalized soil amendment BAM consists of a 1.0:1.9:4.1 mixture (by volume) of tire crumb (to increase sorption capacity), silt and clay (to increase soil moisture retention), and sand (to promote sufficient infiltration), which was applied to develop a prototype stormwater infiltration basin utilizing nutrient reduction and flood control sub-basins. Comparison of nitrate/chloride (NO3-/Cl-) ratios for the shallow groundwater indicate that prior to using BAM, NO3- concentrations were substantially influenced by nitrification or variations in NO3- input. In contrast, for the prototype basin utilizing BAM, NO3-/Cl- ratios indicate minor nitrification and NO3- losses with the exception of one summer sample that indicated a 45% loss. Biogeochemical indicators (denitrifier activity derived from real-time polymerase chain reaction and variations in major ions, nutrients, dissolved and soil gases, and stable isotopes) suggest NO3- losses are primarily attributable to denitrification, whereas dissimilatory nitrate reduction to ammonium is a minor process. Denitrification was likely occurring intermittently in anoxic microsites in the unsaturated zone, which was enhanced by increased soil moisture within the BAM layer and resultant reductions in surface/subsurface oxygen exchange that produced conditions conducive to increased denitrifier activity. Concentrations of total dissolved phosphorus and orthophosphate (PO43-) were reduced by more than 70% in unsaturated zone soil water, with the largest decreases in the BAM layer where sorption was the most likely mechanism for removal. Post-BAM PO43-/Cl- ratios for shallow groundwater indicate predominantly minor increases and

  16. Waterproof active paper via laser surface micropatterning of magnetic nanoparticles.

    PubMed

    Chitnis, G; Ziaie, B

    2012-09-26

    Paper is one of the oldest and most abundant materials known to man. Recently, there has been a considerable interest in creating paper devices by combining paper with other functional materials. In this letter, we demonstrate a simple fabrication technique to create water-resistant ferro-patterns on wax paper using CO(2) laser ablation. A resolution of about 100 μm is achieved which is mostly limited by the cellulose fiber size (~50 μm) in the wax paper and can be improved by using a smaller cellulose matrix. Laser ablation results in modification of surface morphology and chemistry, leading to a change in surface energy. We also present a 2D model for ferrofluid deposition relating the size of the pattern to the amount of ferroparticles deposited on the surface. Finally, a paper gripper is presented to demonstrate advantages of our technique, which allows microscale patterning and machining in a single step. PMID:22939525

  17. Laser Activated Flow Regulator for Glaucoma Drainage Devices

    PubMed Central

    Olson, Jeffrey L.; Velez-Montoya, Raul; Bhandari, Ramanath

    2014-01-01

    Purpose To assess the capabilities of a new glaucoma drainage device regulator in controlling fluid flow as well as to demonstrate that this effect may be titratable by noninvasive means. Methods A rigid eye model with two main ports was used. On the first port, we placed a saline solution column. On the second, we placed a glaucoma shunt. We then measured the flow and flow rate through the system. After placing the regulator device on the tip of the tube, we measured again with the intact membrane and with the membrane open 50% and 100%. For the ex vivo testing we used a similar setting, using a cadaveric porcine eye, we measured again the flow and flow rate. However, this time we opened the membrane gradually using laser shots. A one-way analysis of variance and a Fisher's Least Significant Difference test were used for statistical significance. We also calculated the correlation between the numbers of laser shots applied and the main outcomes. Results The flow through the system with the glaucoma drainage device regulator (membrane intact and 50% open) was statistically lower than with the membrane open 100% and without device (P < 0.05). The flow was successfully controlled by the number of laser shots applied, and showed a positive correlation (+ 0.9). The flow rate was almost doubled every 10 shots and statistically lower than without device at all time (P < 0.05). Conclusions The glaucoma drainage device regulator can be controlled noninvasively with laser, and allows titratable control of aqueous flow. Translational Relevance Initial results and evidence from this experiment will justify the initiation of in vivo animal trials with the glaucoma drainage device regulator; which brings us closer to possible human trials and the chance to significantly improve the existing technology to treat glaucoma surgically. PMID:25374772

  18. UV laser activated digital etching of GaAs

    SciTech Connect

    Meguro, T.; Aoyagi, Y.

    1996-12-31

    The self-limited etching characteristics of digital etching employing an UV laser/Cl{sub 2}/GaAs system are presented. The self-limiting nature is the key mechanism and plays an important role in digital etching for obtaining etch rates independent of etching parameters. Surface processes based on photodissociation of physisorbed chlorine on GaAs with diffusion of negatively charged Cl into GaAs are also discussed.

  19. Optimized geometric configuration of active ring laser gyroscopes

    NASA Astrophysics Data System (ADS)

    Gormley, John; Salloum, Tony

    2016-05-01

    We present a thorough derivation of the Sagnac effect for a ring laser gyroscope of any arbitrary polygonal configuration. We determine optimized alternative geometric configurations for the mirrors. The simulations incur the implementation of a lasing medium with the standard square system, triangular, pentagonal, and oblongated square configuration (diamond). Simulations of possible new geometric configurations are considered, as well as the possibility of adjusting the concavity of the mirrors.

  20. Laser-activated remote phosphor light engine for projection applications

    NASA Astrophysics Data System (ADS)

    Daniels, Martin; Mehl, Oliver; Hartwig, Ulrich

    2015-09-01

    Recent developments in blue emitting laser diodes enable attractive solutions in projection applications using phosphors for efficient light conversion with very high luminance levels. Various commercially available projectors incorporating this technology have entered the market in the past years. While luminous flux levels are still comparable to lamp-based systems, lifetime expectations of classical lamp systems are exceeded by far. OSRAM GmbH has been exploring this technology for several years and has introduced the PHASER® brand name (Phosphor + laser). State-of-the-art is a rotating phosphor wheel excited by blue laser diodes to deliver the necessary primary colors, either sequentially for single-imager projection engines, or simultaneously for 3-panel systems. The PHASER® technology enables flux and luminance scaling, which allows for smaller imagers and therefore cost-efficient projection solutions. The resulting overall efficiency and ANSI lumen specification at the projection screen of these systems is significantly determined by the target color gamut and the light transmission efficiency of the projection system. With increasing power and flux level demand, thermal issues, especially phosphor conversion related, dominate the opto-mechanical system design requirements. These flux levels are a great challenge for all components of an SSL-projection system (SSL:solid-state lighting). OSRAḾs PHASER® light engine platform is constantly expanded towards higher luminous flux levels as well as higher luminance levels for various applications. Recent experiments employ blue laser pump powers of multiple 100 Watts to excite various phosphors resulting in luminous flux levels of more than 40 klm.

  1. Thin-disk laser based on an Yb:YAG / YAG composite active element

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I. I.; Mukhin, I. B.; Vadimova, O. L.; Palashov, O. V.

    2015-03-01

    A thin-disk laser module based on an Yb:YAG / YAG composite active element is developed with a small-signal gain of 1.25 and a stored energy of 400 mJ under cw pumping. The gain and thermally induced phase distortions in the module are studied experimentally. Based on this module, a thin-disk laser with an average power of 300 W and a slope efficiency of 42% is designed.

  2. Widely tunable active Bragg reflector integrated lasers in InGaAsP-InP

    SciTech Connect

    Broberg, B.; Nilsson, S.

    1988-04-18

    Monolithic InGaAsP-InP lasers comprising an active Bragg reflector integrated with a separately pumped wide-band gain region have been developed. The lasers operate in a dynamic single mode in the 1.55 ..mu..m wavelength region. By adjusting the current through the Bragg reflector, the wavelength can be tuned. The maximum tuning range is 11.6 nm.

  3. Laser-activated nano-biomaterials for tissue repair and controlled drug release

    SciTech Connect

    Matteini, P; Ratto, F; Rossi, F; Pini, R

    2014-07-31

    We present recent achievements of minimally invasive welding of biological tissue and controlled drug release based on laser-activated nano-biomaterials. In particular, we consider new advancements in the biomedical application of near-IR absorbing gold nano-chromophores as an original solution for the photothermal repair of surgical incisions and as nanotriggers of controlled drug release from hybrid biopolymer scaffolds. (laser biophotonics)

  4. Hollow raspberry-like PdAg alloy nanospheres: High electrocatalytic activity for ethanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Hu, Yongli; Liu, Mingrui; Zheng, Yixiong

    2015-03-01

    Palladium-silver (PdAg) alloy nanospheres with unique structure were prepared using a one-pot procedure based on the galvanic replacement reaction. Their electrocatalytic activity for ethanol oxidation in alkaline media was evaluated. The morphology and crystal structure of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical characterization techniques, including cyclic voltammetry (CV) and chronoamperometry (CA) measurements were used to analyze the electrochemical performance of the PdAg alloy nanospheres. The SEM and TEM images showed that the PdAg alloy nanospheres exhibit a hierarchical nanostructure with hollow interiors and porous walls. Compared to the commercial Pd/C catalyst, the as-prepared PdAg alloy nanospheres exhibit superior electrocatalytic activity and stability towards ethanol electro-oxidation in alkaline media, showing its potential as a new non-Pt electro-catalyst for direct alcohol fuel cells (DAFCs).

  5. Numerical Simulation of Damage during Forging with Superimposed Hydrostatic Pressure by Active Media

    SciTech Connect

    Behrens, B.-A.; Hagen, T.; Roehr, S.; Sidhu, K. B.

    2007-05-17

    The effective reduction of energy consumption and a reasonable treatment of resources can be achieved by minimizing a component's weight using lightweight metals. In this context, aluminum alloys play a major role. Due to their material-sided restricted formability, the mentioned aluminum materials are difficult to form. The plasticity of a material is ascertained by its maximum forming limit. It is attained, when the deformation causes mechanical damage within the material. Damage of that sort is reached more rapidly, the greater the tensile strength rate in relation to total tension rate. A promising approach of handling these low ductile, high-strength aluminum alloys within a forming process, is forming with a synchronized superposition of comprehensive stress by active media such as by controlling oil pressure. The influence of superimposed hydrostatic pressure on the flow stress was analyzed as well as the formability for different procedures at different hydrostatic pressures and temperature levels. It was observed that flow stress is independent of superimposed hydrostatic pressure. Neither the superimposed pressure has an influence on the plastic deformation, nor does a pressure dependent material hardening due to increasing hydrostatic pressure take place. The formability increases with rising hydrostatic pressure. The relative gain at room temperature and increase of the superimposed pressure from 0 to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore in this paper, based on these experimental observations, it is the intended to develop a numerical simulation in order to predict ductile damage that occurs in the bulk forging process with superimposed hydrostatic pressure based Lemaitre's damage model.

  6. EFFECT OF LASER LIGHT ON LASER PLASMAS: Explosive breeding of point defects as a mechanism for multipulse damage to absorbing media

    NASA Astrophysics Data System (ADS)

    Volodin, B. L.; Emel'yanov, Vladimir I.; Shlykov, Yu G.

    1993-01-01

    A mechanism based on the concept of an explosive breeding of point defects is outlined for the multipulse damage to semiconductors by short laser pulses. Analytic expressions are derived for the critical temperature, the critical intensity, and the intensity dependence of the critical number of pulses. The theoretical results agree well with experimental data.

  7. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media. [CO/sub 2/ laser oscillator and pulse smoother

    DOEpatents

    McLellan, E.J.

    1980-10-17

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode and cathode to below breakdown voltage using a dc voltage source. An array of resistors or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO/sub 2/ laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  8. Survivals of mouse oocytes approach 100% after vitrification in 3-fold diluted media and ultra-rapid warming by an IR laser pulse✰

    PubMed Central

    Jin, Bo; Kleinhans, F.W.; Mazur, Peter

    2014-01-01

    Vitrification is the most sought after route to the cryopreservation of animal embryos and oocytes and other cells of medical, genetic, and agricultural importance. Current thinking is that successful vitrification requires that cells be suspended in and permeated by high concentrations of protective solutes and that they be cooled at very high rates to below − 100°C. We report here that neither of these beliefs holds for mouse oocytes. Rather, we find that if mouse oocytes are suspended in media that produce considerable osmotic dehydration before vitrification and are subsequently warmed at ultra high rates (10,000,000°C/min) achieved by a laser pulse, nearly 100% will survive even when cooled rather slowly and when the concentration of solutes in the medium is only 1/3rd of standard. PMID:24662030

  9. Survivals of mouse oocytes approach 100% after vitrification in 3-fold diluted media and ultra-rapid warming by an IR laser pulse.

    PubMed

    Jin, Bo; Kleinhans, F W; Mazur, Peter

    2014-06-01

    Vitrification is the most sought after route to the cryopreservation of animal embryos and oocytes and other cells of medical, genetic, and agricultural importance. Current thinking is that successful vitrification requires that cells be suspended in and permeated by high concentrations of protective solutes and that they be cooled at very high rates to below -100°C. We report here that neither of these beliefs holds for mouse oocytes. Rather, we find that if mouse oocytes are suspended in media that produce considerable osmotic dehydration before vitrification and are subsequently warmed at ultra high rates (10,000,000°C/min) achieved by a laser pulse, nearly 100% will survive even when cooled rather slowly and when the concentration of solutes in the medium is only 1/3rd of standard. PMID:24662030

  10. Assessing media access and use among Latina adolescents to inform development of a physical activity promotion intervention incorporating text messaging.

    PubMed

    Mojica, Cynthia M; Parra-Medina, Deborah; Yin, Zenong; Akopian, David; Esparza, Laura A

    2014-07-01

    Increasing physical activity (PA) during preadolescence and adolescence is critical to reversing the obesity epidemic. A recent report described the promising role of eHealth--the use of new media for purposes of health promotion--in reducing and preventing childhood obesity. This study assessed access/use of various media (cell phones, computers, gaming systems, Internet) among adolescent Latino girls and examined the relationship between PA and media access/use. A convenience sample of 110 Latino girls ages 11 to 14 was recruited from Girl Scouts of Southwest Texas and other groups. The media survey was self-administered (April-July 2010) on personal digital assistants. Of the girls, 55% reported owning a cell phone and spending 40 (SD = 4.2) hours per week talking, texting, listening to music, and browsing the Internet. Cell phone access increased significantly with age (p = .029). Compared to those with no cell phone, girls with a cell phone have greater odds of reporting more than 5 days of PA in the past week (odds ratio = 5.5, 95% confidence interval [CI] = 2.1, 14) and engaging in daily physical education classes (odds ratio = 2.6, 95% CI = 1.1, 5.9). Since girls with cell phones report greater PA, cell phones may be an effective strategy for communicating with girls about engaging in PA. PMID:24357863

  11. Ultra-long and high-stability random laser based on EDF gain-media and Rayleigh scattering distributed mirror

    NASA Astrophysics Data System (ADS)

    Aporta, I.; Quintela, M. A.; Rodríguez-Cobo, L.; López-Higuera, J. M.

    2015-09-01

    An ultra-long, low-threshold and high-stability Random distributed feedback fiber laser (RDF-FL) based on Erbium-doped fiber (EDF) to provide the gain medium, and single mode fiber (SMF) as a distributed mirror in combination with fiber-brag grating (FBG) to form the cavity is proposed in this paper. Typical random laser radiation for a SMF length of 50 km with a low-threshold of 10 dBm and high-stability (~0.1 dB) is achieved, thanks to the design of the cavity and the high-gain from the pumped erbium-doped fiber. Besides, 200 km quasi-losses random laser due to the distributed mirror and the FBG reflector is demonstrated.

  12. Photothermal and photoacoustic processes of laser activated nano-thermolysis of cells

    NASA Astrophysics Data System (ADS)

    Lapotko, Dmitri; Lukianova, Ekaterina; Mitskevich, Pavel; Smolnikova, Victoria; Potapnev, Michail; Konopleva, Marina; Andreeff, Michael; Oraevsky, Alexander

    2007-02-01

    Laser Activated Nano-Thermolysis was recently proposed for selective damage of individual target (cancer) cells by pulsed laser induced microbubbles around superheated clusters of optically absorbing nanoparticles (NP). One of the clinical applications of this technology is the elimination of residual tumor cells from human blood and bone marrow. Clinical standards for the safety and efficacy of such procedure require the development and verification of highly selective and controllable mechanisms of cell killing. Our previous experiments showed that laser-induced microbubble is the main damaging factor in the case cell irradiation by short laser pulses above the threshold. Our current aim was to study the cell damage mechanisms and analyze selectivity and efficacy of cell damage as a function of NP parameters, NP-cell interaction conditions, and conditions of bubble generation around NP and NP clusters in cells. Generation of laser-induced bubbles around gold NP with diameters 10-250 nm was studied in Acute Myeloblast Leukemia (AML) cultures, normal stem and model K562 human cells. Short laser pulses (10 ns, 532 nm) were applied to those cells in vitro and the processes in cells were investigated with photothermal, fluorescent and atomic force microscopies and also with fluorescence flow cytometry. We have found that the best selectivity of cell damage is achieved by (1) forming large clusters of optically absorbing NP in target cells and (2) irradiating the cells with single laser pulses with the lowest fluence that can generate microbubble only around large clusters but not around single NP. Laser microbubbles with the lifetime from 20 ns to 2000 ns generated in individual cells caused damage and lysis of the cellular membrane and consequently cell death. Laser microbubbles did not damage normal cells around the damaged target (tumor) cell. Laser irradiation with equal fluence did not cause any damage of cells without accumulated NP clusters.

  13. Status of MBI activities: Will a transient collisional x-ray laser with high repetition rate come soon?

    NASA Astrophysics Data System (ADS)

    Nickles, Peter V.; Janulewicz, Karol A.; Priebe, Gerd; Lucianetti, Antonio; Kroemer, Robert K.; Gerlitzke, Anne-Kathrin; Sandner, Wolfgang

    2003-12-01

    Some prospects for development of collisional X-ray lasers with a high repetition rate based on the output characteristics of a transient Ni-like Ag soft X-ray laser pumped by a single picosecond laser pulse are analysed. Such problems as target technology, new driver development and the active medium parameters are discussed.

  14. The production of VEGF involving MAP kinase activation by low level laser therapy in human granulosa cells

    PubMed Central

    Utsunomiya-Kai, Yufuko; Kai, Kentaro; Miyakawa, Isao; Ohshiro, Toshio; Narahara, Hisashi

    2012-01-01

    Objective: The function of granulosa cells is regulated by various hormones and growth factors. Our aim is to clarify the regulation of vascular endothelial growth factor (VEGF) production via mitogen-activated protein kinase (MAPK) induced by low level laser therapy (LLLT) in human granulosa cells. Methods: A human granulosa cell line, KGN cells, were cultured and incubated after LLLT (60mW, GaAlAs 830nm). The levels of VEGF in the culture media were determined by an enzyme-linked immunosorbent assay. The activation of MAP kinase in KGN cells was detected by western blot analysis. Results: VEGF production was significantly increased by LLLT in a time-dependent manner. MAP kinase activity was increased by LLLT. In addition it was enhanced by LLLT and follicle-stimulating hormone (FSH) stimulation. Conclusions: The results suggested that VEGF is induced by LLLT through mechanisms involving MAPK. The increase in VEGF may contribute to neovascularization, which in turn would promote various ovulation phenomena as well as follicular growth. PMID:24511196

  15. Influence of lasing parameters on the cleaning efficacy of laser-activated irrigation with pulsed erbium lasers.

    PubMed

    Meire, Maarten A; Havelaerts, Sophie; De Moor, Roeland J

    2016-05-01

    Laser-activated irrigation (LAI) using erbium lasers is an irrigant agitation technique with great potential for improved cleaning of the root canal system, as shown in many in vitro studies. However, lasing parameters for LAI vary considerably and their influence remains unclear. Therefore, this study sought to investigate the influence of pulse energy, pulse frequency, pulse length, irradiation time and fibre tip shape, position and diameter on the cleaning efficacy of LAI. Transparent resin blocks containing standardized root canals (apical diameter of 0.4 mm, 6 % taper, 15 mm long, with a coronal reservoir) were used as the test model. A standardized groove in the apical part of each canal wall was packed with stained dentin debris. The canals were filled with irrigant, which was activated by an erbium: yttrium aluminium garnet (Er:YAG) laser (2940 nm, AT Fidelis, Fotona, Ljubljana, Slovenia). In each experiment, one laser parameter was varied, while the others remained constant. In this way, the influence of pulse energy (10-40 mJ), pulse length (50-1000 μs), frequency (5-30 Hz), irradiation time (5-40 s) and fibre tip shape (flat or conical), position (pulp chamber, canal entrance, next to groove) and diameter (300-600 μm) was determined by treating 20 canals per parameter. The amount of debris remaining in the groove after each LAI procedure was scored and compared among the different treatments. The parameters significantly (P < 0.05, Kruskal-Wallis) affecting debris removal from the groove were fibre tip position, pulse length, pulse energy, irradiation time and frequency. Fibre tip shape and diameter had no significant influence on the cleaning efficacy. PMID:26861988

  16. Features of infrared ultrabroadband supercontinuum generation under filamentation of femtosecond laser pulses in solid media with various bandgaps

    NASA Astrophysics Data System (ADS)

    Frolov, S. A.; Trunov, V. I.

    2015-12-01

    Recent theoretical and experimental studies show that filamentation of femtosecond pulses in middle infrared range in solids can generate intense supercontinuum (SC) with width of a several octaves. The structure and dynamics of the spectrum formation is different from those observed during filamentation of femtosecond pulses in the near infrared range of the spectrum. With numerical modeling we investigate features of infrared (IR) SC generation in a number of solid-state media transparent in a broad infrared range with various bandgaps, including KBr (7.6 eV), ZnS (3.68 eV) and ZnSe (2.71 eV) for different pump wavelengths. SC formation dynamics is analyzed. With comparison of different media, including one with artificial bandgap, we find that lower bandgap decreases SC bandwidth and filamentation length.

  17. Report of the Working Group on Media Accelerators

    SciTech Connect

    Sessler, A.M.

    1982-04-12

    A summary is given of the activities of those in the Media Accelerator Group. Attention was focused on the Inverse Cherenkov Accelerator, the Laser Focus Accelerator, and the Beat Wave Accelerator. For each of these the ultimate capability of the concept was examined as well as the next series of experiments which needs to be performed in order to advance the concept.

  18. In vivo carotid artery closure by laser activation of hyaluronan-embedded gold nanorods

    NASA Astrophysics Data System (ADS)

    Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Rossi, Giacomo; Esposito, Giuseppe; Puca, Alfredo; Albanese, Alessio; Maira, Giulio; Pini, Roberto

    2010-07-01

    We prove the first application of near-infrared-absorbing gold nanorods (GNRs) for in vivo laser closure of a rabbit carotid artery. GNRs are first functionalized with a biopolymeric shell and then embedded in hyaluronan, which gives a stabilized and handy laser-activable formulation. Four rabbits undergo closure of a 3-mm longitudinal incision performed on the carotid artery by means of a 810-nm diode laser in conjunction with the topical application of the GNRs composite. An effective surgery is obtained by using a 40-W/cm2 laser power density. The histological and electron microscopy evaluation after a 30-day follow-up demonstrates complete healing of the treated arteries with full re-endothelization at the site of GNRs application. The absence of microgranuloma formation and/or dystrophic calcification is evidence that no host reaction to nanoparticles interspersed through the vascular tissue occurred. The observation of a reshaping and associated blue shift of the NIR absorption band of GNRs after laser treatment supports the occurrence of a self-terminating process, and thus of additional safety of the minimally invasive laser procedure. This study underlines the feasibility of using GNRs for in vivo laser soldering applications, which represents a step forward toward the introduction of nanotechnology-based therapies in minimally invasive clinical practices.

  19. Effect of sample preparation on the discrimination of bacterial isolates cultured in liquid nutrient media using laser induced breakdown spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laser induced breakdown spectroscopy (LIBS) is used as the basis for discrimination between 2 genera of gram-negative bacteria and 2 genera of gram-positive bacteria representing pathogenic threats commonly found in poultry processing rinse waters. Because LIBS-based discrimination relies primarily ...

  20. Photophysical and photochemical properties of coumarin laser dyes in amphiphilic media. Technical report, 1 Jan-31 Oct 83

    SciTech Connect

    Jones, G. II; Jackson, W.R.; Kanoktanaporn, S.; Bergmark, W.R.

    1983-10-31

    Photophysical properties of coumarin laser dyes solubilized in aqueous detergent or cyclodextrin solutions have been investigated. Dyes appear to be incorporated in hydrated (hydrogen bonded) sites within detergent micelles. Photodegradation is inhibited for detergent solubilized dye. Electron transfer photochemistry is examined by flash photolysis.

  1. Second space Christmas for ESA: Huygens to begin its final journey to Titan/ Media activities.

    NASA Astrophysics Data System (ADS)

    2004-12-01

    , designed, developed and assembled the Cassini orbiter. NASA's Deep Space Network, also managed by JPL, will be providing communications support via the Cassini orbiter and relaying it to ESA’s control centre in Darmstadt for processing. The Italian Space Agency provided the high-gain antenna on the Cassini orbiter, much of the radio system and elements of several of Cassini's science instruments. The Huygens payload has been provided by teams including from CNES, DLR, ASI and PPARC, and outside Europe, from NASA. Practical arrangements for the Media wishing to cover the event These dramatic events marking the first attempt ever to unveil the mysteries of Titan in-situ, a distant world bigger than Mercury and Pluto which may hold clues to the early days of our own planet, will be marked by several media activities not to be missed. Pencil them into your diary. Saturday 25 December Spacecraft operations will be run at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. The ESA Media Relations Office in Paris will be operational from 04:00 hrs to 12:00 CET. ESA specialists can be reached for interviews and comments via the ESA News Desk on +33(0)1.53.69.71.55. Contacts: Franco Bonacina, Anne-Marie Rémondin, Roberto Lo Verde. Interviews from JPL can also be arranged by calling the JPL media relations office at + 1. 818-354-5011. ESA specialists at JPL: Jean-Pierre Lebreton, Claudio Sollazzo. 05:08 CET - Expected separation of the Huygens probe from the Cassini orbiter ~07:00 CET - Status report upon successful separation from NASA/JPL 10:00 CET at the latest : ESA press release assessing the separation of the Huygens probe ~10:00 CET - ESA TV Video News Release produced at JPL during separation (contact for TVs: Claus Habfast: + 31(0)6.51.18.14.96, claus.habfast@esa.int) Transmission details will be on http://television.esa.int 12:00 CET - Replay of ESA TV Video News Release on separation Thursday 13 January ESA’s ESOC establishment in Darmstadt, Germany

  2. Non-conventional methods and media for the activation and manipulation of carbon nanoforms.

    PubMed

    Vázquez, Ester; Giacalone, Francesco; Prato, Maurizio

    2014-01-01

    Very often, chemical transformations require tedious and long procedures, which, sometimes, can be avoided using alternative methods and media. New protocols, enabling us to save time and solvents, allow us also to explore new reaction profiles. This Tutorial Review focuses on the physical and chemical behavior of carbon nanoforms, CNFs (fullerenes, nanotubes, nanohorns, graphene, etc.) when non-conventional methods and techniques, such as microwave irradiation, mechano-chemistry or highly ionizing radiations are employed. In addition, the reactivity of CNFs in non-conventional media such as water, fluorinated solvents, supercritical fluids, or ionic liquids is also discussed. PMID:23945754

  3. Some New Lidar Equations for Laser Pulses Scattered Back from Optically Thick Media Such as Clouds, Dense Aerosol Plumes, Sea Ice, Snow, and Turbid Coastal Waters

    NASA Technical Reports Server (NTRS)

    Davis, Anthony B.

    2013-01-01

    I survey the theoretical foundations of the slowly-but-surely emerging field of multiple scattering lidar, which has already found applications in atmospheric and cryospheric optics that I also discuss. In multiple scattering lidar, returned pulses are stretched far beyond recognition, and there is no longer a one-to-one connection between range and return-trip timing. Moreover, one can exploit the radial profile of the diffuse radiance field excited by the laser source that, by its very nature, is highly concentrated in space and collimated in direction. One needs, however, a new class of lidar equations to explore this new phenomenology. A very useful set is derived from radiative diffusion theory, which is found at the opposite asymptotic limit of radiative transfer theory than the conventional (single-scattering) limit used to derive the standard lidar equation. In particular, one can use it to show that, even if the simple time-of-flight-to-range connection is irretrievably lost, multiply-scattered lidar light can be used to restore a unique profiling capability with coarser resolution but much deeper penetration into a wide variety of optical thick media in nature. Several new applications are proposed, including a laser bathymetry technique that should work for highly turbid coastal waters.

  4. The Role of Water Activity and Capillarity in Partially Saturated Porous Media at Geologic CO2 Storage Sites

    NASA Astrophysics Data System (ADS)

    Heath, J. E.; Bryan, C. R.; Matteo, E. N.; Dewers, T. A.; Wang, Y.

    2012-12-01

    The activity of water in supercritical CO2 may affect performance of geologic CO2 storage, including CO2 injectivity, and shrink-swell properties and sealing efficiency of clayey caprocks. We present a pore-scale unit cell model of water film adsorption and capillary condensation as an explicit function of water activity in supercritical CO2. This model estimates water film configuration in slit to other pore shapes with edges and corners. With the model, we investigate water saturation in porous media in mineral-CO2-water systems under different water activities. Maximum water activities in equilibrium with an aqueous phase are significantly less than unity due to dissolution of CO2 in water (i.e., the mole fraction of water in the aqueous phase is much less than one) and variable dissolved salt concentration. The unit cell approach is used to upscale from the single pore to the core-sample-scale, giving saturation curves as a function of water activity in the supercritical phase and the texture of the porous media. We evaluate the model and the importance of water activity through ongoing small angle neutron scattering experiments and other column experiments, which investigate shrink-swell properties and capillarity under realistic in situ stresses. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Delivery of molecules into cells using carbon nanoparticles activated by femtosecond laser pulses.

    PubMed

    Chakravarty, Prerona; Qian, Wei; El-Sayed, Mostafa A; Prausnitz, Mark R

    2010-08-01

    A major barrier to drug and gene delivery is crossing the cell's plasma membrane. Physical forces applied to cells via electroporation, ultrasound and laser irradiation generate nanoscale holes in the plasma membrane for direct delivery of drugs into the cytoplasm. Inspired by previous work showing that laser excitation of carbon nanoparticles can drive the carbon-steam reaction to generate highly controlled shock waves, we show that carbon black nanoparticles activated by femtosecond laser pulses can facilitate the delivery of small molecules, proteins and DNA into two types of cells. Our initial results suggest that interaction between the laser energy and carbon black nanoparticles may generate photoacoustic forces by chemical reaction to create transient holes in the membrane for intracellular delivery. PMID:20639882

  6. Fully automated hybrid diode laser assembly using high precision active alignment

    NASA Astrophysics Data System (ADS)

    Böttger, Gunnar; Weber, Daniel; Scholz, Friedemann; Schröder, Henning; Schneider-Ramelow, Martin; Lang, Klaus-Dieter

    2016-03-01

    Fraunhofer IZM, Technische Universität Berlin and eagleyard Photonics present various implementations of current micro-optical assemblies for high quality free space laser beam forming and efficient fiber coupling. The laser modules shown are optimized for fast and automated assembly in small form factor packages via state-of-the-art active alignment machinery, using alignment and joining processes that have been developed and established in various industrial research projects. Operational wavelengths and optical powers ranging from 600 to 1600 nm and from 1 mW to several W respectively are addressed, for application in high-resolution laser spectroscopy, telecom and optical sensors, up to the optical powers needed in industrial and medical laser treatment.

  7. High-power diode lasers with an aluminium-free active region at 915 nm

    NASA Astrophysics Data System (ADS)

    Michel, N.; Hassiaoui, I.; Calligaro, M.; Lecomte, M.; Parillaud, O.; Krakowski, M.; Borruel, L.; García-Tijero, J.-M.; Esquivias, I.; Sukecki, S.; Larkins, E. C.

    2005-11-01

    We have developed high-power lasers, which are based on an Al-free active region at 915 nm. The laser structure has very low internal losses of 0.5 cm-1, a very low transparency current density of 86 A/cm2, and a high internal quantum efficiency of 86%. Based on these good results, we have realised narrow-aperture, index-guided tapered lasers which deliver 1 W CW with and M2 beam quality factor of 3.0 using both the 1/e2 and standard-deviation methods. We have also fabricated index-guided tapered lasers with a Clarinet shape, which deliver 0.65 W CW with an M2 beam quality factor of less than 1.5 at 1/e2, and less than 2.5 using the standard deviation method.

  8. Antimicrobial activity of plant essential oils using food model media: efficacy, synergistic potential and interactions with food components.

    PubMed

    Gutierrez, J; Barry-Ryan, C; Bourke, P

    2009-04-01

    The aim of this study was to optimise the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria spp. and spoilage bacteria using food model media based on lettuce, meat and milk. The EOs evaluated were lemon balm, marjoram, oregano and thyme and their minimum inhibitory concentrations (MIC) were determined against Enterobacter spp., Listeria spp., Lactobacillus spp., and Pseudomonas spp. using the agar dilution method and/or the absorbance based microplate assay. MICs were significantly lower in lettuce and beef media than in TSB. Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs. EO combinations were investigated using the checkerboard method and Oregano combined with thyme had additive effects against spoilage organisms. Combining lemon balm with thyme yielded additive activity against Listeria strains. The effect of simple sugars and pH on antimicrobial efficacy of oregano and thyme was assessed in a beef extract and tomato serum model media. EOs retained greater efficacy at pH 5 and 2.32% sugar, but sugar concentrations above 5% did not negatively impact EO efficacy. In addition to proven antimicrobial efficacy, careful selection and investigation of EOs appropriate to the sensory profile of foods and composition of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars. PMID:19171255

  9. Effect of active species on animal cells in culture media induced by DBD Plasma irradiation using air

    NASA Astrophysics Data System (ADS)

    Ohtsubo, Tetsuya; Ono, Reoto; Hayashi, Nobuya

    2015-09-01

    Little has been reported on action mechanism of active species produced by plasmas affecting living cells. In this study, active species in culture medium generated by torch type DBD and variations of animal cells are attempted to be clarified. Animal cells are irradiated by DBD plasma through various media such as DMEM, PBS and distilled water. Irradiation period is 1 to 15 min. The distance between the lower tip of plasma touch and the surface of the medium is 10 mm. Concentrations of NO2 -, O2 in liquid are measured. After the irradiation, the cells were cultivated in culture medium and their modifications are observed by microscope and some chemical reagents. Concentration of NO2 - and H2 O2 in all media increased with discharge period. Increase rate of NO2 -concentration is much higher than that of hydrogen peroxide. After plasma irradiation for 15 min, concentrations of NO2 were 80 mg/L in DMEM, 30 mg/L in PBS and 15 mg/L in distilled water. Also, the concentration of H2 O2 became 3mg/L in DMEM, 6.5 mg/L in PBS and 6.5mg/L in distilled water. The significant inactivation of cells was observed in the PBS. Above results indicate that, in this experiment, H2 O2 or OH radicals would affect animal cells in culture media.

  10. Active laser radar (lidar) for measurement of corresponding height and reflectance images

    NASA Astrophysics Data System (ADS)

    Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

    1997-08-01

    For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

  11. Metal vapor lasers with increased reliability

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Sabotinov, N. V.; Polunin, Yu. P.; Shumeiko, A. S.; Kostadinov, I. K.; Vasilieva, A. V.; Reimer, I. V.

    2015-12-01

    Results of investigation and development of an excitation pulse generator with magnetic pulse compression by saturation chokes for pumping of active media of CuBr, Sr, and Ca vapor lasers are presented. A high-power IGBT transistor is used as a commutator. The generator can operate at excitation pulse repetition frequencies up to 20 kHz. The total average power for all laser lines of the CuBr laser pumped by this generator is ~6.0 W; it is ~1.3-1.7 W for the Sr and Ca lasers.

  12. Laser Doppler And Range Systems For Spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, P. W.; Gagliardi, R. M.

    1990-01-01

    Report discusses two types of proposed laser systems containing active transponders measuring distance (range) and line-of-sight velocity (via Doppler effect) between deep space vehicle and earth-orbiting satellite. Laser system offers diffraction advantage over microwave system. Delivers comparable power to distant receiver while using smaller transmitting and receiving antennas and less-powerful transmitter. Less subject to phase scintillations caused by passage through such inhomogeneous media as solar corona. One type of system called "incoherent" because range and Doppler measurements do not require coherence with laser carrier signals. Other type of system called "coherent" because successful operation requires coherent tracking of laser signals.

  13. Increasing Activeness and Learning Outcomes by Developing Borland Delphi 7.0 Application as Instructional Media

    ERIC Educational Resources Information Center

    Setyorini, Dyna; Churiyah, Madziatul

    2016-01-01

    This study aims to produce instructional media of petty cash fund with Borland Delphi 7.0 application in the Finance Administration subject, Managing Petty Cash Fund material in class XII APK in Vocational High School (SMK) Negeri 1 Pasuruan, East Java, Indonesia. This study used "Research and Development" (R&D) design procedures…

  14. Stacks of Ideas. Activities for the Library Media Center and Classroom, K-8.

    ERIC Educational Resources Information Center

    Estes, Bettie, Ed.

    Designed to encourage cooperative program planning between the library media specialist and the classroom teacher, this guide consists of 26 teaching units in all elementary (K-8) curriculum areas. At least one teaching unit with learner outcomes and related information skills is included in each content area with an indication of the particular…

  15. Developing an Active Media Center in a Jewish Day School K-8 through Creative Management.

    ERIC Educational Resources Information Center

    Singer, Rhona

    The practicum described in this report was designed to create a dynamic, functional media center with an interdisciplinary library skills program for students in kindergarten to grade 8 in a private Jewish day school in a residential neighborhood in a southeast coastal city enrolling 300 students. An additional goal was to use volunteers to…

  16. Contested Science in the Media: Linguistic Traces of News Writers' Framing Activity

    ERIC Educational Resources Information Center

    Dahl, Trine

    2015-01-01

    Science reporting in the media often involves contested issues, such as, for example, biotechnology, climate change, and, more recently, geoengineering. The reporter's framing of the issue is likely to influence readers' perception of it. The notion of framing is related to how individuals and groups perceive and communicate about the…

  17. Passively cooled 405 W ytterbium fibre laser utilising a novel metal coated active fibre

    NASA Astrophysics Data System (ADS)

    Daniel, Jae M. O.; Simakov, Nikita; Hemming, Alexander; Clarkson, W. Andrew; Haub, John

    2016-03-01

    We present a novel metal coated triple clad active fibre design, utilising an all glass inner cladding structure and aluminium outer coating. This metal coated active fibre enables a number of benefits to high power laser design, such as increase robustness and extended operating temperature range. As a demonstration of the advantages of this design a passively cooled ytterbium fibre laser is presented. A 20 m length of active fibre was coiled into a planar arrangement and mounted onto a high emissivity heatsink. Up to 405 W of output power was achieved without the need for active water or forced air cooling. The slope efficiency of this source was 74 % and maximum outer heat sink temperature was ~140°C. This arrangement allowed for significant weight and size savings to be achieved with the active fibre laser head weighing less than 100 g. We will discuss the design choices and trade-offs of metal coated active fibre on high power fibre laser systems as well as the prospects for further power scaling to the kW level.

  18. Final Report - Montana State University - Microbial Activity and Precipitation at Solution-Solution Mixing Zones in Porous Media

    SciTech Connect

    Gerlach, Robin

    2014-10-31

    Background. The use of biological and chemical processes that degrade or immobilize contaminants in subsurface environments is a cornerstone of remediation technology. The enhancement of biological and chemical processes in situ, involves the transport, displacement, distribution and mixing of one or more reactive agents. Biological and chemical reactions all require diffusive transport of solutes to reaction sites at the molecular scale and accordingly, the success of processes at the meter-scale and larger is dictated by the success of phenomena that occur at the micron-scale. However, current understanding of scaling effects on the mixing and delivery of nutrients in biogeochemically dynamic porous media systems is limited, despite the limitations this imposes on the efficiency and effectiveness of the remediation challenges at hand. Objectives. We therefore proposed to experimentally characterize and computationally describe the growth, evolution, and distribution of microbial activity and mineral formation as well as changes in transport processes in porous media that receive two or more reactive amendments. The model system chosen for this project was based on a method for immobilizing 90Sr, which involves stimulating microbial urea hydrolysis with ensuing mineral precipitation (CaCO3), and co-precipitation of Sr. Studies at different laboratory scales were used to visualize and quantitatively describe the spatial relationships between amendment transport and consumption that stimulate the production of biomass and mineral phases that subsequently modify the permeability and heterogeneity of porous media. Biomass growth, activity, and mass deposition in mixing zones was investigated using two-dimensional micro-model flow cells as well as flow cells that could be analyzed using synchrotron-based x-ray tomography. Larger-scale flow-cell experiments were conducted where the spatial distribution of media properties, flow, segregation of biological activity and

  19. Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 2. Limiting parameters of the branching chain dark decomposition reaction of iodides

    SciTech Connect

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N

    2009-08-31

    The final stages in the development of a branching chain decomposition reaction of iodide in the active medium of a pulsed chemical oxygen-iodine laser (COIL) are analysed. Approximate expressions are derived to calculate the limiting parameters of the chain reaction: the final degree of iodide decomposition, the maximum concentration of excited iodine atoms, the time of its achievement, and concentrations of singlet oxygen and iodide at that moment. The limiting parameters, calculated by using these expressions for a typical composition of the active medium of a pulsed COIL, well coincide with the results of numerical calculations. (active media)

  20. Single Circularly Polarized Attosecond Pulse Generation by Intense Few Cycle Elliptically Polarized Laser Pulses and Terahertz Fields from Molecular Media

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-01-01

    We present a method for producing a single circularly polarized attosecond pulse by an intense few cycle elliptically polarized laser pulse combined with a terahertz field from numerical solutions of the time-dependent Schrödinger equation for the molecular ion H2+. It is found that in the presence of a 62.5 THz (λ=4800nm) field at an intensity of ˜1014W/cm2, a single circularly polarized 114 as pulse can be generated by an elliptical polarized laser pulse at a wavelength of 400 nm with an ellipticity of ɛ=0.59. The efficiency of circular polarization attosecond pulse generation is interpreted based on a classical model of single electron recollision with the parent ion.

  1. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Conditions during passage of short optical pulses across a strongly scattering media

    NASA Astrophysics Data System (ADS)

    Tereshchenko, Sergei A.; Podgaetskii, Vitalii M.; Vorob'ev, Nikolai S.; Smirnov, A. V.

    1996-03-01

    A transient two-flux model of the interaction of light with a strongly scattering medium is developed on the basis of the concept of the paraxial photon propagating along the direction of thin pulsed laser beam incident on such a medium. An analitic expression for the radiation flux transmitted by a scattering medium is derived. Calculations are made of the dependences of the parameters of the temporal distributions of the transmitted radiation on the characteristics of the scattering medium. It is swown that the absorption and scattering coefficients of such a medium con be determined from the profile of the temporal distributions of the transmitted radiation. An experimental determination of the temporal distributions is reported for the radiation from a picosecond neodymium laser transmitted by a model scattering medium (a solution of dried milk in water). The experimental results are described well by the theoretical model.

  2. Bubble-cell interactions with laser-activated polymeric microcapsules

    NASA Astrophysics Data System (ADS)

    Versluis, Michel; Lajoinie, Guillaume; van Rooij, Tom; Skachkov, Ilya; Kooiman, Klazina; de Jong, Nico; Physics of Fluids Group, University of Twente Team; Biomedical Engineering, Erasmus MC Team

    2015-11-01

    Polymeric microcapsules that are made light-absorbing by the addition of a dye in their shell can generate cavitation microbubbles with spatiotemporal control when irradiated by a pulsed laser. These particles less than 3 μm in size can circulate through the body, bind to tissues and are expected to be readily detected, even if a single cavitation bubble is produced. In this paper, we study the impact of such cavitation bubbles on a cell monolayer and quantify it in terms of cell poration and cell viability. Two capsules formulations were used; the first one encapsulates a low boiling point oil and induced less cell damage than the second that was loaded with a high boiling point oil. We also report the generation of stable bubbles by the first capsule formulation that completely absorb the cells in their close vicinity. Physics of Fluid group MIRA Institute for Biomedical Technology and Technical Medicine MESA+ Institute for Nanotechnology.

  3. Efficacy of laser-based irrigant activation methods in removing debris from simulated root canal irregularities.

    PubMed

    Deleu, Ellen; Meire, Maarten A; De Moor, Roeland J G

    2015-02-01

    In root canal therapy, irrigating solutions are essential to assist in debridement and disinfection, but their spread and action is often restricted by canal anatomy. Hence, activation of irrigants is suggested to improve their distribution in the canal system, increasing irrigation effectiveness. Activation can be done with lasers, termed laser-activated irrigation (LAI). The purpose of this in vitro study was to compare the efficacy of different irrigant activation methods in removing debris from simulated root canal irregularities. Twenty-five straight human canine roots were embedded in resin, split, and their canals prepared to a standardized shape. A groove was cut in the wall of each canal and filled with dentin debris. Canals were filled with sodium hypochlorite and six irrigant activation procedures were tested: conventional needle irrigation (CI), manual-dynamic irrigation with a tapered gutta percha cone (manual-dynamic irrigation (MDI)), passive ultrasonic irrigation, LAI with 2,940-nm erbium-doped yttrium aluminum garnet (Er:YAG) laser with a plain fiber tip inside the canal (Er-flat), LAI with Er:YAG laser with a conical tip held at the canal entrance (Er-PIPS), and LAI with a 980-nm diode laser moving the fiber inside the canal (diode). The amount of remaining debris in the groove was scored and compared among the groups using non-parametric tests. Conventional irrigation removed significantly less debris than all other groups. The Er:YAG with plain fiber tip was more efficient than MDI, CI, diode, and Er:YAG laser with PIPS tip in removing debris from simulated root canal irregularities. PMID:24091791

  4. Infrared Laser Activation of Soluble and Membrane Protein Assemblies in the Gas Phase.

    PubMed

    Mikhailov, Victor A; Liko, Idlir; Mize, Todd H; Bush, Matthew F; Benesch, Justin L P; Robinson, Carol V

    2016-07-19

    Collision-induced dissociation (CID) is the dominant method for probing intact macromolecular complexes in the gas phase by means of mass spectrometry (MS). The energy obtained from collisional activation is dependent on the charge state of the ion and the pressures and potentials within the instrument: these factors limit CID capability. Activation by infrared (IR) laser radiation offers an attractive alternative as the radiation energy absorbed by the ions is charge-state-independent and the intensity and time scale of activation is controlled by a laser source external to the mass spectrometer. Here we implement and apply IR activation, in different irradiation regimes, to study both soluble and membrane protein assemblies. We show that IR activation using high-intensity pulsed lasers is faster than collisional and radiative cooling and requires much lower energy than continuous IR irradiation. We demonstrate that IR activation is an effective means for studying membrane protein assemblies, and liberate an intact V-type ATPase complex from detergent micelles, a result that cannot be achieved by means of CID using standard collision energies. Notably, we find that IR activation can be sufficiently soft to retain specific lipids bound to the complex. We further demonstrate that, by applying a combination of collisional activation, mass selection, and IR activation of the liberated complex, we can elucidate subunit stoichiometry and the masses of specifically bound lipids in a single MS experiment. PMID:27328020

  5. Mirror with a variable amplitude - phase reflectance. 2. Modelling of a laser resonator with an active output mirror

    SciTech Connect

    Kiiko, V V; Kislov, V I; Ofitserov, Evgenii N

    2011-03-31

    We present the operator model of the laser resonator with an active output mirror based on the Fabry - Perot interferometer with nonflat (spherical and aspherical) mirrors and an adjustable gap. The results of numerical simulation of a microchip laser with a thermal lens and an active output interferometer-based mirror are given. It is shown that the use of an active interferometer as the output cavity mirror allows one to control the number of transverse modes of laser radiation and its power; in this case, the beam divergence can be reduced by a factor of 1.5 - 2.5. (laser resonators)

  6. Selective photo-activation analysis with laser-driven x-rays

    NASA Astrophysics Data System (ADS)

    Banerjee, Sudeep; Golovin, Grigory; Powers, Nathan; Liu, Cheng; Chen, Shouyuan; Petersen, Chad; Zhang, Jun; Ghebregziabher, Isaac; Zhao, Baozhen; Brown, Kevin; Mills, Jared; Umstadter, Donald; Haden, Dan; Silano, Jack; Karwowski, Hugon

    2013-04-01

    We discuss a technique for the identification of nuclear isotopes by selective photo-activation analysis. A narrow divergence beam of high-energy photons is produced when a laser driven electron beam Compton backscatters off a counter-propagating high-intensity laser pulse. The x-rays from this compact laser-driven synchrotron light source are MeV energy, narrow-bandwidth, tunable, polarized, and bright (10^8 photons s-1). Such characteristics make these x-rays well-suited for nuclear interrogation by means of triggering (γ,f) and (γ,xn) reactions. The narrow bandwidth of the x-ray light can be exploited to selectively activate nuclei with isotopic sensitivity, without causing unwanted background from collateral activation. Additionally, the polarized nature of the x-rays can be used to study anisotropy of neutron emission, for precise identification of isotopes. Activation by laser-driven synchrotron x-rays will be compared with activation by bremsstrahlung.

  7. Characteristics of 308 nm excimer laser activated arterial tissue photoemission under ablative and non-ablative conditions.

    PubMed

    Laufer, G; Wollenek, G; Rüeckle, B; Buchelt, M; Kuckla, C; Ruatti, H; Buxbaum, P; Fasol, R; Zilla, P

    1989-01-01

    The present study was designed to assess the characteristics of tissue photoemission obtained from normal and atherosclerotic segments of human postmortem femoral arteries by 308 nm excimer laser irradiation of 60 ns pulsewidth. Three ablative (20, 30, and 40 mJ/pulse) and three non-ablative (2.5, 5, and 10 mJ/pulse) energy fluences were employed. Both the activating laser pulses and the induced photoemission were guided simultaneously over one and the same 1,000 micron core optical fiber that was positioned in direct tissue contact perpendicular to the vascular surface. The spectral lineshape of normal arterial and noncalcified atherosclerotic structures was characterized by a broad-continuum, double-peak emission of relevant intensity between wavelengths of 360 and 500 nm, with the most prominent emission in the range of 400-415 (407 nm peak) and 430-445 nm (437 nm peak). Fibrous and lipid atherosclerotic lesions, however, exhibited a significantly reduced intensity at 437 nm compared to normal artery layers (P less than 0.001), expressed as a 407/437 nm ratio of 1.321 +/- 0.075 for fibrous and 1.392 +/- 0.104 for lipid lesions. Normal artery components presented with approximately equal intensity at both emission peaks (407/437 nm ratio: intima, 1.054 +/- 0.033; media, 1.024 +/- 0.019; adventitia, 0.976 +/- 0.021). Comparison of spectral lineshape obtained under various energy fluences within a group of noncalcified tissues disclosed no substantial difference using the 407/437 nm ratio (P greater than 0.05). In contrast, calcified lesions revealed high-intensity multiple-line (397, 442, 461, and 528 nm) emission spectra under ablative energy fluences, whereas a low-intensity broad-continuum, single-peak spectrum resulted from irradiation beyond the ablation threshold. Thus, these findings suggest fluorescence phenomena for broad-continuum spectra, and plasma emission for multiple-line spectra as an underlying photodynamic process. Regardless of the activating

  8. Noninvasive diode laser activation of transient receptor potential proteins and nociceptors

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Cooper, Brian Y.; Nemenov, Michael I.

    2007-02-01

    We investigated diode laser (980 nm) evoked activation of transient receptor potential proteins (TRPV1 and TRPV2). C and A-delta (Aδ) nociceptor families are primarily responsible for pain mediation in the peripheral nervous system. TRPV1 proteins have been associated with heat evoked pain in C fibers while Aδ fibers have been associated with TRPV2. Diode laser stimulation allows a margin of safety between non-invasive activation and damage 19, 22, 34. Laser pulses (20-50 ms, 0.1-10 W, 980 nm) were used to stimulate: A) in vitro: excised patches from HEK293 cells expressing TRPV1; B) in vitro: rat DRG nociceptors expressing either TRPV1 or TRPV2; and C) in vivo: C-fibers of the rat saphenous nerve (SN) trunk. Cell currents were recorded using standard patch clamp methods. The SN was also stimulated electrically with bipolar electrodes. Stimulation (20-50 ms) of HEK and DRG cells expressing TRPV1 was highly reproducible. Activation and peak currents were achieved at estimated peak temperatures of 55°C and 70°C. Threshold activation was also observed in DRG neurons expressing TRPV2. The conduction velocity for laser-activated saphenous nerve afferents was in the C fiber range (0.5-1 m/s). Electrically stimulated nerve contained stimulation artifacts and complex neural components with conduction velocities ranging from 0.3-30 m/s. Diode laser activation of TRPV1 protein is a reproducible and effective means to probe TRP activity in both in vivo and in vitro preparations

  9. Optical power of semiconductor lasers with a low-dimensional active region

    SciTech Connect

    Asryan, Levon V.; Sokolova, Zinaida N.

    2014-01-14

    A comprehensive analytical model for the operating characteristics of semiconductor lasers with a low-dimensional active region is developed. Particular emphasis is given to the effect of capture delay of both electrons and holes from a bulk optical confinement region into a quantum-confined active region and an extended set of rate equations is used. We derive a closed-form expression for the internal quantum efficiency as an explicit function of the injection current and parameters of a laser structure. Due to either electron or hole capture delay, the internal efficiency decreases with increasing injection current above the lasing threshold thus causing sublinearity of the light-current characteristic of a laser.

  10. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    SciTech Connect

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  11. Axicon-based annular laser trap for studies on sperm activity

    NASA Astrophysics Data System (ADS)

    Shao, Bing; Vinson, Jaclyn M.; Botvinick, Elliot L.; Esener, Sadik C.; Berns, Michael W.

    2005-08-01

    As a powerful and noninvasive tool, laser trapping has been widely applied for the confinement and physiological study of biological cells and organelles. Researchers have used the single spot laser trap to hold individual sperm and quantitatively evaluated the motile force generated by a sperm. Early studies revealed the relationship between sperm motility and swimming behavior and helped the investigations in medical aspects of sperm activity. As sperm chemotaxis draws more and more interest in fertilization research, the studies on sperm-egg communication may help to explain male or female infertility and provide exciting new approaches to contraception. However, single spot laser trapping can only be used to investigate an individual target, which has limits in efficiency and throughput. To study the chemotactic response of sperm to eggs and to characterize sperm motility, an annular laser trap with a diameter of several hundred microns is designed, simulated with ray tracing tool, and implemented. An axicon transforms the wavefront such that the laser beam is incident on the microscope objective from all directions while filling the back aperture completely for high efficiency trapping. A trapping experiment with microspheres is carried out to evaluate the system performance. The power requirement for annular sperm trapping is determined experimentally and compared with theoretical calculations. With a chemo-attractant located in the center and sperm approaching from all directions, the annular laser trapping could serve as a speed bump for sperm so that motility characterization and fertility sorting can be performed efficiently.

  12. Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent

    PubMed Central

    Baer, Géraldine M; Small, Ward; Wilson, Thomas S; Benett, William J; Matthews, Dennis L; Hartman, Jonathan; Maitland, Duncan J

    2007-01-01

    Background Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. Methods A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. Results At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W. Conclusion We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated. PMID:18042294

  13. Laser-activated solder weld repair of the inferior alveolar nerve in rats

    NASA Astrophysics Data System (ADS)

    Curtis, Nigel J.; Lauto, Antonio; Trickett, Rodney I.; Owen, Earl R.; Walker, D. M.

    1997-05-01

    A new laser activated solder weld technique is described for the microsurgical repair of the inferior alveolar nerve in rats. The laser weld technique used an albumin based solder, containing indocyanine cardiogreen, plus an infrared diode laser. Seven animals had inferior alveolar nerve repairs performed using the laser weld technique and these were compared against corresponding unoperated controls plus three cases of nerve section without repair. Histochemical analysis was performed utilizing neuron counts and horseradish peroxidase tracer (HRP) uptake in the trigeminal ganglion following sacrifice and staining of frozen sections with cresyl violet and diaminobenzidene. The results of this analysis showed comparable mean neuron counts and mean HRP uptake by neurons for the unoperated control and laser weld groups with considerable reduction of mean values in cases of nerve section with no repair. Sections of the repaired inferior alveolar nerves, stained with Masson's trichrome, showed no adverse reactions by axons or epineurium to the coagulative repair with the solder and demonstrated regeneration of myelinated axons at the time of sacrifice. In summary a new technique of laser weld repair of the inferior alveolar nerve is described which, on initial analysis, appears to be a reliable alternative to traditional techniques.

  14. Low-level Ga-Al-As laser irradiation enhances osteoblast proliferation through activation of Hedgehog signaling pathway

    NASA Astrophysics Data System (ADS)

    Li, Qiushi; Qu, Zhou; Chen, Yingxin; Liu, Shujie; Zhou, Yanmin

    2014-12-01

    Low-level laser irradiation has been reported to promote bone formation, but the molecular mechanism is still unclear. Hedgehog signaling pathway has been reported to play an important role in promoting bone formation. The aim of the present study was to examine whether low-level Ga-Al-As laser (808 nm) irradiation could have an effect on Hedgehog signaling pathway during osteoblast proliferation in vitro. Mouse osteoblastic cell line MC3T3-E1 was cultured in vitro. The cultures after laser irradiation (3.75J/cm2) were treated with recombinant N-terminals Sonic Hedgehog (N-Shh)or Hedgehog inhibitor cyclopamine (cy). The experiment was divided into 4 group, group 1:laser irradiation, group 2: laser irradiation and N-Shh, group 3: laser irradiation and cy, group 4:control with no laser irradiation. On day 1,2 and 3,cell proliferation was determined by cell counting, Cell Counting Kit-8.On 12 h and 24 h, cell cycle was detected by flow cytometry. Proliferation activity of laser irradiation and N-Shh group was remarkably increased compared with those of laser irradiation group. Proliferation activity of laser irradiation and cy group was remarkably decreased compared with those of laser irradiation group, however proliferation activity of laser irradiation and cy group was remarkably increased compared with those of control group. These results suggest that low-level Ga-Al-As laser irradiation activate Hedgehog signaling pathway during osteoblast proliferation in vitro. Hedgehog signaling pathway is one of the signaling pathways by which low-level Ga-Al-As laser irradiation regulates osteoblast proliferation.

  15. Broadband phase-coherent optical frequency synthesis with actively linked Ti:sapphire and Cr:forsterite femtosecond lasers.

    PubMed

    Bartels, Albrecht; Newbury, Nathan R; Thomann, Isabell; Hollberg, Leo; Diddams, Scott A

    2004-02-15

    We link the output spectra of a Ti:sapphire and a Cr:forsterite femtosecond laser phase coherently to form a continuous frequency comb with a wavelength coverage of 0.57-1.45 microm at power levels of 1 nW to 40 microW per frequency mode. To achieve this, the laser repetition rates and the carrier-envelope offset frequencies are phase locked to each other. The coherence time between the individual components of the two combs is 40 micros. The timing jitter between the lasers is 20 fs. The combined frequency comb is self-referenced for access to its overall offset frequency. We report the first demonstration to our knowledge of an extremely broadband and continuous, high-powered and phase-coherent frequency comb from two femtosecond lasers with different gain media. PMID:14971767

  16. Investigations of Air Perfusion through Porous Media and Super-Hydrophobic Surface Active Gas Replenishment

    NASA Astrophysics Data System (ADS)

    Perlin, Marc; Gose, James W.; Golovin, Kevin; Ceccio, Steven L.; Tuteja, Anish

    2015-11-01

    Super-hydrophobic (SH) materials have been used successfully to generate reduced skin-friction in laminar flows. Success in the laminar regime has led researchers to try SH materials in turbulent flows. More often than not, this has been unsuccessful at providing meaningful skin-friction drag reduction, and has even generated increased drag. This failure is frequently attributed to the wetting of an SH surface or equivalently the transition from the Cassie-Baxter to the Wenzel state. The result is fluid flow over an essentially roughened surface. In this investigation the researchers aim to perfuse small amounts of gas through porous media, including sintered and foam metals, to attain skin-friction drag reduction in a fully-developed turbulent channel flow. As air is perfused through porous media, the solid - liquid interaction at the interface transitions to a solid - liquid - gas interaction. This can result in an interface that functions similarly to SH materials. Controlled air perfusion that provides the necessary replenishment of lost gas at the interface might prevent wetting, and thus eliminate or reduce the effect of the roughness on the flow. This latter possibility is investigated by perfusing small amounts of gas through porous media with and without SH coatings. To quantify the effectiveness of this method, pressure drop is used to infer friction drag along the surface in a fully-developed turbulent channel flow. The authors recognize the support of ONR.

  17. Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity.

    PubMed

    Buccheri, Maria A; D'Angelo, Daniele; Scalese, Silvia; Spanò, Simon F; Filice, Simona; Fazio, Enza; Compagnini, Giuseppe; Zimbone, Massimo; Brundo, Maria V; Pecoraro, Roberta; Alba, Anna; Sinatra, Fulvia; Rappazzo, Giancarlo; Privitera, Vittorio

    2016-06-17

    The antibacterial activity and possible toxicity of graphene oxide and laser-irradiated graphene oxide (iGO) were investigated. Antibacterial activity was tested on Escherichia coli and shown to be higher for GO irradiated for at least three hours, which seems to be correlated to the resulting morphology of laser-treated GO and independent of the kind and amount of oxygen functionalities. X-ray photoelectron spectroscopy, Raman spectroscopy, dynamic light scattering and scanning electron microscopy (SEM) show a reduction of the GO flakes size after visible laser irradiation, preserving considerable oxygen content and degree of hydrophilicity. SEM images of the bacteria after the exposure to the iGO flakes confirm membrane damage after interaction with the laser-modified morphology of GO. In addition, a fish embryo toxicity test on zebrafish displayed that neither mortality nor sublethal effects were caused by the different iGO solutions, even when the concentration was increased up to four times higher than the one effective in reducing the bacteria survival. The antibacterial properties and the absence of toxicity make the visible laser irradiation of GO a promising option for water purification applications. PMID:27158973

  18. Efficacy of LED versus KTP laser activation of photodynamic bleaching of tetracycline-stained dentine.

    PubMed

    Bennett, Zackary Y; Walsh, Laurence J

    2015-09-01

    In some well-established laser applications where large spot sizes are used, an array of high-intensity light emitting diodes (LED) emitting at similar wavelength could potentially replace the laser. This situation applies for the photodynamic bleaching of stains in teeth. This study compared the relative efficacy of an array of visible green LED (535 nm ± 15 nm) with a KTP laser in photodynamic bleaching of tetracycline-stained dentine in human tooth roots. After establishing consistent staining in 96 roots using a validated method, the roots were sectioned into 2-3-mm thick horizontal slices that were treated with gels containing rhodamine B (Smartbleach® or Smartbleach® 3LT). Colour changes were tracked up to 1 month after treatment. While both systems were effective in bleaching the tetracycline-stained dentine, KTP laser activation gave greater bleaching efficacy than LED activation, enhancing the action of the gel. Use of the KTP laser would be preferable over an LED system when confronted with tetracycline staining. Use of this photodynamic bleaching method offers valuable means to reduce the severity of tetracycline staining. PMID:25288264

  19. Activation of C-fiber nociceptors by low-power diode laser.

    PubMed

    Azevedo, Eduardo; Silva, Andressa; Martins, Raquel; Andersen, Monica L; Tufik, Sergio; Manzano, Gilberto M

    2016-03-01

    Objective The evaluation of selective activation of C-fibers to record evoked potentials using the association of low-power diode laser (810 nm), tiny-area stimulation and skin-blackening. Method Laser-evoked potentials (LEPs) were obtained from 20 healthy young subjects. An aluminum plate with one thin hole was attached to the laser probe to provide tiny-area stimulation of the hand dorsum and the stimulated area was covered with black ink. Results The mean intensity used for eliciting the ultra-late laser-evoked potential (ULEP) was 70 ± 32 mW. All subjects showed a clear biphasic potential that comprised a negative peak (806 ± 61 ms) and a positive deflection (1033 ± 60 ms), corresponding to the ULEP related to C-fiber activation. Conclusion C-fiber-evoked responses can be obtained using a very low-power diode laser when stimulation is applied to tiny areas of darkened skin. This strategy offers a non-invasive and easy methodology that minimizes damage to the tissue. PMID:27050852

  20. Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity

    NASA Astrophysics Data System (ADS)

    Buccheri, Maria A.; D’Angelo, Daniele; Scalese, Silvia; Spanò, Simon F.; Filice, Simona; Fazio, Enza; Compagnini, Giuseppe; Zimbone, Massimo; Brundo, Maria V.; Pecoraro, Roberta; Alba, Anna; Sinatra, Fulvia; Rappazzo, Giancarlo; Privitera, Vittorio

    2016-06-01

    The antibacterial activity and possible toxicity of graphene oxide and laser-irradiated graphene oxide (iGO) were investigated. Antibacterial activity was tested on Escherichia coli and shown to be higher for GO irradiated for at least three hours, which seems to be correlated to the resulting morphology of laser-treated GO and independent of the kind and amount of oxygen functionalities. X-ray photoelectron spectroscopy, Raman spectroscopy, dynamic light scattering and scanning electron microscopy (SEM) show a reduction of the GO flakes size after visible laser irradiation, preserving considerable oxygen content and degree of hydrophilicity. SEM images of the bacteria after the exposure to the iGO flakes confirm membrane damage after interaction with the laser-modified morphology of GO. In addition, a fish embryo toxicity test on zebrafish displayed that neither mortality nor sublethal effects were caused by the different iGO solutions, even when the concentration was increased up to four times higher than the one effective in reducing the bacteria survival. The antibacterial properties and the absence of toxicity make the visible laser irradiation of GO a promising option for water purification applications.

  1. Self-organized bursts of coherent stimulated Raman scattering and hot electron transport in speckled laser plasma media.

    PubMed

    Yin, L; Albright, B J; Rose, H A; Bowers, K J; Bergen, B; Kirkwood, R K

    2012-06-15

    Nonlinear electron trapping physics governs the onset and saturation of stimulated Raman scattering (SRS) in laser beams with many speckles. Hot electrons from intense speckles, produced during SRS daughter electron-plasma-wave bowing and filamentation, seed and enhance the growth of SRS in neighboring speckles by reducing Landau damping. Trapping-induced nonlinearity and speckle interaction through transport of hot electrons and back- and sidescattered SRS waves enable the system of speckles to self-organize and exhibit coherent, sub-ps SRS bursts with more than 100% instantaneous reflectivity, consistent with a SRS transverse coherence width much larger than a speckle width. PMID:23004283

  2. Self-Organized Bursts of Coherent Stimulated Raman Scattering and Hot Electron Transport in Speckled Laser Plasma Media

    NASA Astrophysics Data System (ADS)

    Yin, L.; Albright, B. J.; Rose, H. A.; Bowers, K. J.; Bergen, B.; Kirkwood, R. K.

    2012-06-01

    Nonlinear electron trapping physics governs the onset and saturation of stimulated Raman scattering (SRS) in laser beams with many speckles. Hot electrons from intense speckles, produced during SRS daughter electron-plasma-wave bowing and filamentation, seed and enhance the growth of SRS in neighboring speckles by reducing Landau damping. Trapping-induced nonlinearity and speckle interaction through transport of hot electrons and back- and sidescattered SRS waves enable the system of speckles to self-organize and exhibit coherent, sub-ps SRS bursts with more than 100% instantaneous reflectivity, consistent with a SRS transverse coherence width much larger than a speckle width.

  3. Measurement of pressure changes during laser-activated irrigant by an erbium, chromium: yttrium, scandium, gallium, garnet laser.

    PubMed

    Peeters, Harry Huiz; De Moor, Roeland J G

    2015-07-01

    The use of Er,Cr:YSGG laser to activate irrigants results in the creation of vapour bubbles and shockwaves. The present study evaluated the magnitude of pressure changes in the root canal during laser-activated irrigation. The root canal of a single extracted maxillary canine was enlarged to a size 40/0.06 file. A pressure sensor was inserted apically into the root canal. The tooth was processed as follows. In the EDTA condition, the tooth was irrigated with 17 % EDTA; in the NaOCl condition, the tooth was irrigated with 3 % NaOCl. In all conditions, the irrigants were activated at 0.75 and 1.75 W for 60 s using RFT2 and MZ2 tips; to analyse the effect of tip placement, the tip was activated at the orifice and after inserting the tip 5 mm deeper than the orifice. Data showed no significant difference between irrigation regimens (p > 0.05). There were no significant differences of the pressure between RFT2 and MZ2 tips (p > 0.05). The placement of tips closer to the apex resulted in significantly higher pressure than at the orifice (p < 0.001). The use of 1.75 W power resulted in a significantly higher increase of pressure compared to 0.75 W (p < 0.001), regardless either the type of solutions or tips used. The magnitude of the pressure changes in the root canal at 0.75 W was significantly lower than 1.75 W regardless of either type of tips or solutions used. The closer the insertion of the tip to the apex, the higher the pressure. PMID:24906483

  4. Scattering of light passing through a statistically rough interface between media with different refractive indices after laser correction of vision

    SciTech Connect

    Semchishen, A V; Seminogov, V N; Semchishen, V A

    2012-04-30

    Forward scattering of light passing through large-scale irregularities of the interface between two media having different refractive indices is considered. An analytical expression for the ratio of intensities of directional and diffusion components of scattered light in the far-field zone is derived. It is theoretically shown that the critical depth of possible interface relief irregularities, starting from which the intensity of the diffuse component in the passing light flow becomes comparable with the directional light component, responsible for the image formation on the eye retina, is 3 - 4 {mu}m, with the increase in the refractive index in the postoperational zone taken into account. These profile depth values agree with the experimentally measured ones and may affect the contrast sensitivity of vision.

  5. Scattering of light passing through a statistically rough interface between media with different refractive indices after laser correction of vision

    NASA Astrophysics Data System (ADS)

    Semchishen, A. V.; Seminogov, V. N.; Semchishen, V. A.

    2012-04-01

    Forward scattering of light passing through large-scale irregularities of the interface between two media having different refractive indices is considered. An analytical expression for the ratio of intensities of directional and diffusion components of scattered light in the far-field zone is derived. It is theoretically shown that the critical depth of possible interface relief irregularities, starting from which the intensity of the diffuse component in the passing light flow becomes comparable with the directional light component, responsible for the image formation on the eye retina, is 3 — 4 μm, with the increase in the refractive index in the postoperational zone taken into account. These profile depth values agree with the experimentally measured ones and may affect the contrast sensitivity of vision.

  6. Study of new FNAL-NICADD extruded scintillator as active media of large EMCal of ALICE at LHC

    SciTech Connect

    Oleg A. Grachov et al.

    2004-05-04

    The current conceptual design of proposed Large EMCal of ALICE at LHC is based largely on the scintillating mega-tile/fiber technology implemented in CDF Endplug upgrade project and in both barrel and endcap electromagnetic calorimeters of the STAR. The cost of scintillating material leads us to the choice of extruded polystyrene based scintillator, which is available in new FNAL-NICADD facility. Result of optical measurements, such as light yield and light yield variation, show that it is possible to use this material as active media of Large EMCal of ALICE at LHC.

  7. Compact, efficient, scalable neodymium laser co-doped with activator ions and pumped by visible laser diodes

    NASA Astrophysics Data System (ADS)

    Scheps, Richard

    1994-02-01

    Efficient, low threshold laser emission from a laser crystal doped with chromium and neodymium ions is obtained when pumped by visible laser diodes in the range of 610 nm to 680 nm. A typical laser Cr,Nd:GSGG crystal having an extraordinarily broad absorption bandwidth allows high pump efficiencies when using visible laser diodes, particularly in comparison to the Nd:YAG laser. The broad absorption bandwidth tolerance of the Cr,Nd:GSGG crystal to the pumping wavelengths allows visible diode pumping of the neodymium transition without regard to the wavelength of the visible diodes. Longitudinal or end-pumping to take advantage of the emission properties of the visible laser diodes, a nearly hemispherical laser resonator configuration and other co-doped Cr,Nd laser host materials are disclosed.

  8. APPLICATION OF LASERS AND LASER-OPTICAL METHODS IN LIFE SCIENCES Two-photon fluorescence microscopy signal formation in highly scattering media: theoretical and numerical simulation

    NASA Astrophysics Data System (ADS)

    Sergeeva, Ekaterina A.; Katichev, A. R.; Kirillin, M. Yu

    2011-01-01

    Using the radiative transfer theory and Monte Carlo simulations, we analyse the effect of scattering in a medium and of the size of the detector pinhole on the formation of the fluorescent signal in standard two-photon fluorescence microscopy (TPFM) systems. The theoretical analysis is based on a small-angle diffusion approximation of the radiative transfer equation, adapted to calculate the propagation of focused infrared radiation in media similar to the biological tissues in their optical properties. The accuracy of the model is evaluated by comparing the calculated excitation intensity in a highly scattering medium with the results of Monte Carlo simulations. To simulate a tightly focused Gaussian beam by the Monte Carlo method, the so called 'ray-optics' approach that correctly takes into account the finite size and shape of the beam waist is applied. It is shown that in the combined confocal and two-photon scanning microscopy systems not equipped with an external 'nondescanned' detector, the scattering significantly affects both the nonlinear excitation efficiency in the medium and the fluorescence collection efficiency of the system. In such systems, the rate of the useful TPFM signal in-depth decay is 1.5 — 2 times higher than in systems equipped with a 'nondescanned' detector.

  9. Short cavity active mode locking fiber laser for optical sensing and imaging

    NASA Astrophysics Data System (ADS)

    Lee, Hwi Don; Han, Ga Hee; Jeong, Syung Won; Jeong, Myung Yung; Kim, Chang-Seok; Shin, Jun Geun; Lee, Byeong Ha; Eom, Tae Joong

    2014-05-01

    We demonstrate a highly linear wavenumber- swept active mode locking (AML) fiber laser for optical sensing and imaging without any wavenumber-space resampling process. In this all-electric AML wavenumber-swept mechanism, a conventional wavelength selection filter is eliminated and, instead, the suitable programmed electric modulation signal is directly applied to the gain medium. Various types of wavenumber (or wavelength) tunings can be implemented because of the filter-less cavity configuration. Therefore, we successfully demonstrate a linearly wavenumber-swept AML fiber laser with 26.5 mW of output power to obtain an in-vivo OCT image at the 100 kHz swept rate.

  10. Laser method of biological activity stimulation of cryoconserved hemopoietic tissue transplant

    NASA Astrophysics Data System (ADS)

    Khyznyak, Anatoly I.; Lesnik, Svetlana A.; Kogut, Georgy I.; Glukhenkaya, Galina T.

    1994-02-01

    The biological activity of cryoconserved fetal liver cells of mice (FLM) having undergone the He-Ne laser action has been estimated by the efficiency of their transplantation to mice- recipients exposed to lethal x-ray dose. The survival rate 30 days after x-ray exposure for those mice was 75% in comparison with 70% for mice with cryoconserved nonirradiated graft. The trial animals' peripheral blood investigations have been made. The obtained results indicate that the laser method of cryoconserved cells stimulation can help to increase the therapeutic efficiency of mielotransplantation.

  11. Pulsed laser triggered high speed microfluidic fluorescence activated cell sorter†‡

    PubMed Central

    Wu, Ting-Hsiang; Chen, Yue; Park, Sung-Yong; Hong, Jason; Teslaa, Tara; Zhong, Jiang F.; Di Carlo, Dino; Teitell, Michael A.

    2014-01-01

    We report a high speed and high purity pulsed laser triggered fluorescence activated cell sorter (PLACS) with a sorting throughput up to 20 000 mammalian cells s−1 with 37% sorting purity, 90% cell viability in enrichment mode, and >90% purity in high purity mode at 1500 cells s−1 or 3000 beads s−1. Fast switching (30 μs) and a small perturbation volume (~90 pL) is achieved by a unique sorting mechanism in which explosive vapor bubbles are generated using focused laser pulses in a single layer microfluidic PDMS channel. PMID:22361780

  12. Inflicting controlled nonthermal damage to subcellular structures by laser-activated gold nanoparticles.

    PubMed

    Krpetić, Zeljka; Nativo, Paola; Sée, Violaine; Prior, Ian A; Brust, Mathias; Volk, Martin

    2010-11-10

    We show that low-intensity laser irradiation of cancer cells containing endosomal gold nanoparticles leads to endosome rupture and escape of the nanoparticles into the cytosol without affecting the cells' viability. The low light intensity of our experiments allows us to rule out photothermal effects as the underlying mechanism, and we present results that suggest photoinduced radicals as the photogenerated active species. This nonthermal mechanism may also be important in the context of cell death at higher laser intensities, which had been reported previously. PMID:20923168

  13. Measuring of object vibration using sinusoidal-modulation laser-diode active interferometer

    NASA Astrophysics Data System (ADS)

    Ai, Yong; Cao, Qinfeng; Lu, Su

    1996-09-01

    Using the character that the emitting optical frequency of the laser diode is controlled by the injected current, the ability of eliminating environmental disturbance of the sinusoidal modulation laser diode active interferometer will be raised by more than one hundred times through putting the disturbed interference signal produced by the environment into the interferometer. When vibrating frequency of objects is different from that of the sinusoidol modulation, 'beat- frequency' will be produced in the interfere signal, which can be analyzed to get the vibrating frequency of objects. This paper described the operation principle and theoretical delusion of the 'beat-frequency' method.

  14. A history of semi-active laser dome and window materials

    NASA Astrophysics Data System (ADS)

    Sullivan, Roger M.

    2014-05-01

    Semi-Active Laser (SAL) guidance systems were developed starting in the mid-1960's and today form an important class of precision guided weapons. The laser wavelengths generally fall in the short wave infrared region of the spectrum. Relative to passive, image based, infrared seekers the optical demands placed on the domes or windows of SAL seekers is very modest, allowing the use of low cost, easily manufactured materials, such as polycarbonate. This paper will examine the transition of SAL window and dome science and technology from the laboratory to battlefield, with special emphasis on the story of polycarbonate domes.

  15. Network interdependency between social media and stock trading activities: Evidence from China

    NASA Astrophysics Data System (ADS)

    Lin, Shen; Ren, Da; Zhang, Wei; Zhang, Yongjie; Shen, Dehua

    2016-06-01

    The emergence of social media accelerates the research on information dissemination and its corresponding influence on trading tendency. Based on empirical study of the dynamic relationship between the ratio of re-post microblog and original microblog (RRO) and average volume per transaction (VPT), we find the following results: (1) In microblog network, stocks with high RRO are often accompanied with low statistical VPT; (2) When the discussion about one stock is quite lively in microblog network (such as the blog postings reach a summit), it does not statistically cause the fluctuations of VPT of the stock; (3) Overall speaking, RRO plays a significant role in inverting u-shaped relationship with VPT.

  16. Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy

    USGS Publications Warehouse

    Pedone, V.A.; Cercone, K.R.; Burruss, R.C.

    1990-01-01

    Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

  17. High-power ultralow-noise semiconductor external cavity lasers based on low-confinement optical waveguide gain media

    NASA Astrophysics Data System (ADS)

    Juodawlkis, Paul W.; Loh, William; O'Donnell, Frederick J.; Brattain, Michael A.; Plant, Jason J.

    2010-02-01

    For the past several years, we have been developing a new class of high-power, low-noise semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. The key characteristics of the SCOW design are (i) large (> 5 x 5 μm), symmetric, fundamental-transverse-mode operation attained through a combination of coupledmode filtering and low index-contrast, (ii) very low optical confinement factor (Γ ~ 0.3-0.5%), and (iii) low excessoptical loss (αi ~ 0.5 cm-1). The large transverse mode and low confinement factor enables SCOW lasers (SCOWLs) and amplifiers (SCOWAs) having Watt-class output power. The low confinement factor also dictates that the waveguide length be very large (0.5-1 cm) to achieve useful gain, which provides the benefits of small ohmic and thermal resistance. In this paper, we review the operating principles and performance of the SCOW gain medium, and detail its use in 1550-nm single-frequency SCOW external cavity lasers (SCOWECLs). The SCOWECL consists of a doublepass, curved-channel InGaAlAs quantum-well SCOWA and a narrowband (2.5 GHz) fiber Bragg grating (FBG) external cavity. We investigate the impact of the cavity Q on SCOWECL performance by varying the FBG reflectivity. We show that a bench-top SCOWECL having a FBG reflectivity of R = 10% (R = 20%) has a maximum output power of 450 mW (400 mW), linewidth of 52 kHz (28 kHz), and RIN at 2-MHz offset frequency of -155 dB/Hz (-165 dB/Hz).

  18. Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

    PubMed

    Macleod, Neil A; Molero, Francisco; Weidmann, Damien

    2015-01-26

    A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers. PMID:25835851

  19. Delivery of siRNA to ovarian cancer cells using laser-activated carbon nanoparticles

    PubMed Central

    Sengupta, Aritra; Mezencev, Roman; McDonald, John F; Prausnitz, Mark R

    2015-01-01

    Aim The RNAi-mediated knockdown of gene expression is an attractive tool for research and therapeutic purposes but its implementation is challenging. Here we report on a new method based on photoacoustic delivery of siRNA developed to address some of these challenges. Materials & methods Physical properties and photoacoustic emission of carbon black (CB) particles upon near-infrared laser irradiation were characterized. Next, ovarian cancer cells Hey A8-F8 were exposed to near-infrared nanosecond laser pulses in the presence of siRNA targeting EGFR gene and CB particles. The intracellular delivery of siRNA and silencing of the target gene were determined by specific qPCR assays. Results & conclusion Laser-activated CB nanoparticles generated photoacoustic emission and enabled intracellular delivery of siRNA and significant knockdown of its target EGFR mRNA. This physical method represents a new promising approach to targeted therapeutic delivery of siRNA. PMID:26080699

  20. Photothermal effects in connective tissues mediated by laser-activated gold nanorods.

    PubMed

    Ratto, Fulvio; Matteini, Paolo; Rossi, Francesca; Menabuoni, Luca; Tiwari, Neha; Kulkarni, Sulabha K; Pini, Roberto

    2009-06-01

    We report a study on the application of laser-activated nanoparticles in the direct welding of connective tissues, which may become a valuable technology in biomedicine. We use colloidal gold nanorods as new near-infrared chromophores to mediate functional photothermal effects in the eye lens capsules. Samples obtained ex vivo from porcine eyes are treated to simulate heterotransplants with 810-nm diode laser radiation in association with a stain of gold nanorods of aspect ratio approximately 4. This stain is applied at the interface between a patch of capsule from a donor eye and the capsule of a recipient eye. Then, by administration of laser pulses of 40 msec and approximately 100-140 J/cm(2), we achieved the local denaturation of the endogenous collagen filaments, which reveals that the treated area reached temperatures above 50 degrees C. The thermal damage is confined within 50-70 mum in a radial distance from the irradiated area. PMID:19223241

  1. Generation of dissipative solitons in an actively mode-locked ultralong fibre laser

    SciTech Connect

    Koliada, N A; Nyushkov, B N; Ivanenko, A V; Kobtsev, Sergey M; Harper, Paul; Turitsyn, Sergei K; Denisov, Vladimir I; Pivtsov, V S

    2013-02-28

    A single-pulse actively mode-locked fibre laser with a cavity length exceeding 1 km has been developed and investigated for the first time. This all-fibre erbium-doped laser has a normal intracavity dispersion and generates dissipative 8-ns solitons with a fundamental repetition rate of 163.8 kHz; the energy per pulse reaches 34 nJ. The implemented mode locking, based on the use of intracavity intensity modulator, provides self-triggering and high stability of pulsed lasing. A possibility of continuous tuning of the centre lasing wavelength in the range of 1558 - 1560 nm without any tunable spectral selective elements in the cavity is demonstrated. The tuning occurs when controlling the modulation signal frequency due to the forced change in the pulse repetition time (group delay) under the conditions of intracavity chromatic dispersion. (laser optics 2012)

  2. Activity of retinal ganglion cells following intense, nanosecond laser flashes. Final report, 1983-1986

    SciTech Connect

    Glickman, R.D.

    1989-01-01

    The effects of intense, but nonlesion-producing, laser exposures of 20-ns duration were determined on the light responses and spontaneous activity of retinal ganglion cells recorded in situ from the rhesus monkey. (Following a single, 20-ns exposure centered on its receptive field, a ganglion cell produced an 'afterdischarge' of maintained action potentials). The duration of the afterdischarge depended on the diameter of the laser beam on the retina and on the beam's intensity. Laser exposures subtending 0.5 to 2.0 deg, and delivering 45 to 60% of the maximum permissible exposure, elicited afterdischarges that lasted up to 80 s. When the beam diameter was decreased to 0.25 deg, the afterdischarge was reduced to 30 s, and to less than 5 s with the 0.12-deg beam. Light sensitivity after the laser exposure recovered rapidly during the first 10 s and then more slowly, but exponentially, until it reached the preflash level. Color-opponent ganglion cells exhibited a phenomenon called 'response-reversal' after the laser exposure, presumably due to selective adaptation of a mid-wavelength cone-input. Because a 20-ns exposure, regardless of intensity, is likely to photoregenerate more than half of the available visual pigment, the effects of ganglion cell response described here are not likely to be due solely to pigment bleaching.

  3. Rapid prototyping of reflectors for vehicle lighting using laser activated remote phosphor

    NASA Astrophysics Data System (ADS)

    Lachmayer, Roland; Kloppenburg, Gerolf; Wolf, Alexander

    2015-03-01

    Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class vehicles mainly use HID or LED as light source. As a further step in this development laser diode based systems offer high luminance, efficiency and allow the realization of new styling concepts and new dynamic lighting functions. These white laser diode systems can either be realized by mixing different spectral sources or by combining diodes with specific phosphors. Based on the approach of generating light using a laser and remote phosphor, lighting modules are manufactured. Four blue laser diodes (450 nm) are used to activate a phosphor coating and thus to achieve white light. A segmented paraboloid reflector generates the desired light distribution for an additional car headlamp. We use high speed milling and selective laser melting to build the reflector system for this lighting module. We compare the spectral reflection grade of these materials. Furthermore the generated modules are analyzed regarding their efficiency and light distribution. The use of Rapid Prototyping technologies allows an early validation of the chosen concept and is supposed to reduce cost and time in the product development process significantly. Therefor we discuss costs and times of the applied manufacturing technologies.

  4. Using Social Media to Teach Social Media

    ERIC Educational Resources Information Center

    Rheingold, Howard

    2008-01-01

    By showing students how to use Web-based channels to inform publics, advocate positions, contest claims, and organize action around issues they care about, participatory media education can influence civic behavior positively throughout their lives. Participatory media literacy is necessarily a hands-on enterprise, requiring active use of digital…

  5. Induced polarization and self-potential geophysical signature of bacterial activity in porous media (Invited)

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2013-12-01

    The first part of the presentation will be dedicated to the spectral induced polarization signature of bacteria in porous media. We developed a quantitative model to investigate frequency-domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (alpha-polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and alpha-polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to the cation exchange capacity of the bacteria. The mobility of the counterions in this Stern layer is found to be very small (4.7×10-10 m2s-1 V-1 at 25°C). This implies a very low relaxation frequency for the alpha-polarization of the bacteria cells (typically around 0.1 to 5 Hertz) in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred non-intrusively from time lapse frequency-domain induced polarization data. The second part of the presentation will concern the biogeobattery mechanism showing new data, the concept of transient biogeobattery and the influence of the concentration of the electron acceptors in the process.

  6. Control of spiral-wave dynamics in active media by periodic modulation of excitability

    NASA Astrophysics Data System (ADS)

    Steinbock, Oliver; Zykov, Vladimir; Müller, Stefan C.

    1993-12-01

    EXCITABLE media exhibit a wide variety of geometrically complex spatio-temporal patterns, perhaps the most striking of which are rotating spiral waves. Spiral waves have now been observed in many excitable systems, including heart muscle1, aggregating slime-mould cells2, retinae3, CO oxidation on platinum4 and oscillatory chemical systems such as the Belousov-Zhabotinsky (BZ) reaction5,6. In the last case, the spiral cores trace out circular or hypocycloidal trajectories, depending on the specific reaction conditions7-9. In addition, if the excitability of the BZ reaction is light-sensitive10-13, constant illumination has been shown to influence the dynamics of spiral waves14,15. Here we investigate the effect of illumination that is periodically modulated in time. We find that, for a single set of reaction conditions, the motion of the spiral cores can be forced to describe a wide range of open and closed hypocycloidal trajectories, in phase with the applied modulation frequency. Numerical simulations using a modified version of the Oregonator model16,17 of the BZ reaction reproduce this behaviour. We suggest that the modulation of excitability with weak external forces might be used as a means for controlling the dynamics of other excitable media.

  7. A laser-induced repetitive fast neutron source applied for gold activation analysis

    NASA Astrophysics Data System (ADS)

    Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

    2012-12-01

    A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 × 105 n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He4 nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T3.

  8. A laser-induced repetitive fast neutron source applied for gold activation analysis

    SciTech Connect

    Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

    2012-12-15

    A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 Multiplication-Sign 10{sup 5} n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He{sup 4} nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T{sup 3}.

  9. Doubly active Q switching and mode locking of an all-fiber laser.

    PubMed

    Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, Jose L; Andrés, Miguel V

    2009-09-15

    Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train. PMID:19756079

  10. A laser-induced repetitive fast neutron source applied for gold activation analysis.

    PubMed

    Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

    2012-12-01

    A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 × 10(5) n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He(4) nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T(3). PMID:23277984

  11. Active eye-tracking for an adaptive optics scanning laser ophthalmoscope

    PubMed Central

    Sheehy, Christy K.; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

    2015-01-01

    We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone. PMID:26203370

  12. Wavelength-tunable actively mode-locked erbium-doped fiber ring laser using a distributed feedback semiconductor laser as mode locker and tunable filter

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

    A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a distributed feedback semiconductor laser as an intensity mode locker and a tunable optical filter. Very stable optical pulse trains at gigabit repetition rates were generated using harmonica mode locking. The supermode noise was suppressed to 60 dB below the signal level and the root-mean-square timing jitter (0.45 kHz-1 MHz) was found to be about 1% of the pulse duration. A continuous wavelength tuning range of 1.8 nm was achieved by changing the semiconductor laser temperature from 11.4 to 30 °C.

  13. Prosocial effects of media.

    PubMed

    Hogan, Marjorie J

    2012-06-01

    Parents, teachers, health care providers, and other caring adults worry about the harmful influence of media messages and images on children and teens and wonder how to recognize and encourage positive and healthy use of media. For decades, experts have commented on the power of media. Media depictions can lead to negative attitudes and behavior in some young viewers. This article discusses whether prosocial, tolerant, and cooperative attitudes and behavior can be learned and imitated by children and adolescents and whether media can nurture or stimulate creativity or actively promote health and well-being in young consumers. PMID:22643170

  14. Theoretical, experimental, and computational aspects of optical property determination of turbid media by using frequency-domain laser infrared photothermal radiometry.

    PubMed

    Nicolaides, L; Chen, Y; Mandelis, A; Vitkin, I A

    2001-10-01

    In this work, the optical and thermal properties of tissuelike materials are measured by using frequency-domain infrared photothermal radiometry. This technique is better suited for quantitative multiparameter optical measurements than the widely used pulsed-laser photothermal radiometry (PPTR) because of the availability of two independent signal channels, amplitude and phase, and the superior signal-to-noise ratio provided by synchronous lock-in detection. A rigorous three-dimensional (3-D) thermal-wave formulation with a 3-D diffuse and coherent photon-density-wave source is applied to data from model phantoms. The combined theoretical, experimental, and computational methodology shows good promise with regard to its analytical ability to measure optical properties of turbid media uniquely, as compared with PPTR, which exhibits uniqueness problems. From data sets obtained by using calibrated test phantoms, the reduced optical scattering and absorption coefficients were found to be within 20% and 10%, respectively, of the values independently derived by using Mie theory and spectrophotometric measurements. PMID:11583272

  15. SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

    2014-10-01

    Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

  16. Sutureless microvascular anastomoses by a biodegradable laser-activated solid protein solder.

    PubMed

    Maitz, P K; Trickett, R I; Dekker, P; Tos, P; Dawes, J M; Piper, J A; Lanzetta, M; Owen, E R

    1999-11-01

    A new sutureless technique to successfully anastomose the abdominal aorta of rats (1.3 mm in diameter) by using a fully biodegradable, laser-activated protein solder is presented. A total of 90 rats were divided into two groups randomly. In group one, the anastomoses were performed by using conventional microsuturing technique, whereas in group two, the anastomoses were performed by using a new laser welding technique. In addition, each of the two groups were divided into five subgroups and evaluated at different follow-up periods (10 minutes, 1 hour, 1 day, 1 week, and 6 weeks). At these intervals, the anastomoses were evaluated for patency and tensile strength. Three anastomoses in each subgroup were processed for light and electron microscopy. All anastomoses were found to be patent. The mean clamp time of the anastomoses performed with conventional suturing was 20.6 minutes compared with 7.2 minutes for the laser-activated welded anastomoses (p < 0.001). The strain measurements showed a stronger mechanical bond of the sutured anastomoses in the initial phase. However, at 6 weeks the tensile strength of the laser-welded anastomoses was higher compared with the conventional suture technique. Histologic evaluations revealed a near complete resorption of the solder after 6 weeks. The junction site of the vessel ends cannot be determined on the luminal side of the artery. In conclusion, a resorbable protein used as a solder, activated by a diode laser, can provide a reliable, safe, and rapid arterial anastomosis, which could be performed by any microsurgeon faster than conventional suturing after a short learning curve. PMID:10541175

  17. Investigation of optical limiting properties of Aluminium nanoparticles prepared by pulsed laser ablation in different carrier media

    SciTech Connect

    Kuladeep, Rajamudili; Jyothi, L.; Narayana Rao, D.; Prakash, P.; Mayank Shekhar, S.; Durga Prasad, M.

    2013-12-28

    In this communication, we carried out the systematic investigation of nonlinear absorption and scattering properties of Aluminium nanoparticles (Al NPs) in various polar and non-polar solvents. Al NPs were synthesized with pulsed Nd:YAG laser operated at 1064 nm by ablating Al target in polar and non-polar liquid environment like chloroform, chlorobenzene, toluene, benzene, and carbon tetrachloride. Synthesized Al NPs colloids of various solvents differ in appearance and UV-Vis extinction spectra exhibit absorption in the UV region. The characterization of Al NPs performed by Transmission electron microscopy (TEM) studies reveal that NPs are made up of a well crystallized Al inner part (bright zone) embedded with an amorphous metal Al shell (dark region). Growth, aggregation, and precipitation mechanisms which influence the optical properties and stability of NPs are found to be related to the dipole moment of the surrounding liquid environment. The nonlinear absorption and scattering studies are performed by open aperture Z-scan technique with 532 nm under nanosecond pulse excitation. The Z-scan measurements are fitted theoretically to estimate both two-photon absorption (TPA) and nonlinear scattering (NLS) coefficients. In polar solvents like chlorobenzene, chloroform synthesized Al NPs exhibited higher TPA, NLS coefficient values, and lower optical limiting threshold values in comparison with partially polar solvent like toluene and non-polar solvents like benzene and carbontetrachloride. These results indicate the potential use of Al NPs as a versatile optical limiting material.

  18. Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

    NASA Astrophysics Data System (ADS)

    Guillon, S.; Pili, E.; Agrinier, P.

    2012-05-01

    CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO2 carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of δ 13C in CO2. Using a set of reference gases of known CO2 concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO2 concentration, and 0.05 ‰ for δ 13C at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of δ 13C on CO2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO2 concentration and 1.3 ‰ for δ 13C, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source.

  19. Investigation of optical limiting properties of Aluminium nanoparticles prepared by pulsed laser ablation in different carrier media

    NASA Astrophysics Data System (ADS)

    Kuladeep, Rajamudili; Jyothi, L.; Prakash, P.; Mayank Shekhar, S.; Durga Prasad, M.; Narayana Rao, D.

    2013-12-01

    In this communication, we carried out the systematic investigation of nonlinear absorption and scattering properties of Aluminium nanoparticles (Al NPs) in various polar and non-polar solvents. Al NPs were synthesized with pulsed Nd:YAG laser operated at 1064 nm by ablating Al target in polar and non-polar liquid environment like chloroform, chlorobenzene, toluene, benzene, and carbon tetrachloride. Synthesized Al NPs colloids of various solvents differ in appearance and UV-Vis extinction spectra exhibit absorption in the UV region. The characterization of Al NPs performed by Transmission electron microscopy (TEM) studies reveal that NPs are made up of a well crystallized Al inner part (bright zone) embedded with an amorphous metal Al shell (dark region). Growth, aggregation, and precipitation mechanisms which influence the optical properties and stability of NPs are found to be related to the dipole moment of the surrounding liquid environment. The nonlinear absorption and scattering studies are performed by open aperture Z-scan technique with 532 nm under nanosecond pulse excitation. The Z-scan measurements are fitted theoretically to estimate both two-photon absorption (TPA) and nonlinear scattering (NLS) coefficients. In polar solvents like chlorobenzene, chloroform synthesized Al NPs exhibited higher TPA, NLS coefficient values, and lower optical limiting threshold values in comparison with partially polar solvent like toluene and non-polar solvents like benzene and carbontetrachloride. These results indicate the potential use of Al NPs as a versatile optical limiting material.

  20. 3D Imaging of Porous Media Using Laser Scanning Confocal Microscopy with Application to Microscale Transport Processes

    SciTech Connect

    Fredrich, J.T.

    1999-02-10

    We present advances in the application of laser scanning confocal microscopy (LSCM) to image, reconstruct, and characterize statistically the microgeometry of porous geologic and engineering materials. We discuss technical and practical aspects of this imaging technique, including both its advantages and limitations. Confocal imaging can be used to optically section a material, with sub-micron resolution possible in the lateral and axial planes. The resultant volumetric image data, consisting of fluorescence intensities for typically {approximately}50 million voxels in XYZ space, can be used to reconstruct the three-dimensional structure of the two-phase medium. We present several examples of this application, including studying pore geometry in sandstone, characterizing brittle failure processes in low-porosity rock deformed under triaxial loading conditions in the laboratory, and analyzing the microstructure of porous ceramic insulations. We then describe approaches to extract statistical microgeometric descriptions from volumetric image data, and present results derived from confocal volumetric data sets. Finally, we develop the use of confocal image data to automatically generate a three-dimensional mesh for numerical pore-scale flow simulations.