The SMAT fiber laser for industrial applications

NASA Astrophysics Data System (ADS)

Ding, Jianwu; Liu, Jinghui; Wei, Xi; Xu, Jun

2017-02-01

With the increased adoption of high power fiber laser for various industrial applications, the downtime and the reliability of fiber lasers become more and more important. Here we present our approach toward a more reliable and more intelligent laser source for industrial applications: the SMAT fiber laser with the extensive sensor network and multi-level protection mechanism, the mobile connection and the mobile App, and the Smart Cloud. The proposed framework is the first IoT (Internet of Things) approach integrated in an industrial laser not only prolongs the reliability of an industrial laser but open up enormous potential for value-adding services by gathering and analyzing the Big data from the connected SMAT lasers.

Introducing the yellow laser

NASA Astrophysics Data System (ADS)

Lincoln, James

2018-02-01

The author has acquired a yellow laser with the specific wavelength of 589 nm. Because this is the first time such a laser has been discussed in this journal, I feel it is appropriate to provide a discussion of its function and capabilities. Normal laser safety should be employed, such as not pointing it into eyes or at people, and using eye protection for the young and inexperienced. It is important to note that 589 nm is the same wavelength as the Sodium-D line (doublet). This allows for the laser to serve as a replacement for sodium lamps, and, considering its rather high price, this added value should be balanced against its cost. What follows is a list of activities that showcase the yellow laser's unique promise as an engaging piece of technology that can be used in the teaching of physics.

Fundamental Study of Nuclear Pumped Laser Plasmas.

DTIC Science & Technology

1980-12-23

PUMPED DYE LASER PMT PUMPING/ GAS HAND- LING SYSTEM ANODE SIGNAL TO SCREEN ROOM FIGURE 13 EXPERIMENTAL APPARATUS FROM ANODE OF PMT SCREEN ROOM...and G.A. Zdasiuk, " Laser Induced Collisional and Radiative Energy Transfer’, Proceedings of Laser Spectroscopy IV, June 1979. W. R. Green, M.D. Wright...AD-A130 988 FUNDAMENTAL STUDY 0F NUCLEAR PUMPED LASER PLASMAS(U) 1/ MIAMI UNIV OXFORD UHDi EPT OF PHYSIS Cs W DOWNES ET AL 23 DEC AS OASGAS 7A C OSAN

Rf Feedback free electron laser

DOEpatents

Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

1981-01-01

A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

Femtosecond Lasers and Corneal Surgical Procedures.

PubMed

Marino, Gustavo K; Santhiago, Marcony R; Wilson, Steven E

2017-01-01

Our purpose is to present a broad review about the principles, early history, evolution, applications, and complications of femtosecond lasers used in refractive and nonrefractive corneal surgical procedures. Femtosecond laser technology added not only safety, precision, and reproducibility to established corneal surgical procedures such as laser in situ keratomileusis (LASIK) and astigmatic keratotomy, but it also introduced new promising concepts such as the intrastromal lenticule procedures with refractive lenticule extraction (ReLEx). Over time, the refinements in laser optics and the overall design of femtosecond laser platforms led to it becoming an essential tool for corneal surgeons. In conclusion, femtosecond laser is a heavily utilized tool in refractive and nonrefractive corneal surgical procedures, and further technological advances are likely to expand its applications. Copyright 2017 Asia-Pacific Academy of Ophthalmology.

HO:LULF and HO:LULF Laser Materials

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Morrison, Clyde A. (Inventor); Filer, Elizabeth D. (Inventor); Jani, Mahendra G. (Inventor); Murray, Keith E. (Inventor); Lockard, George E. (Inventor)

1998-01-01

A laser host material LULF (LuLiF4) is doped with holmium (Ho) and thulium (Tm) to produce a new laser material that is capable of laser light production in the vicinity of 2 microns. The material provides an advantage in efficiency over conventional Ho lasers because the LULF host material allows for decreased threshold and upconversion over such hosts as YAG and YLF. The addition of Tm allows for pumping by commonly available GaAlAs laser diodes. For use with flashlamp pumping, erbium (Er) may be added as an additional dopant. For further upconversion reduction, the Tm can be eliminated and the Ho can be directly pumped.

Effect of Adding Oral Calcium Dobesilate to Laser Photocoagulation on the Macular Thickness in Patients with Diabetic Macular Edema: A Randomized Clinical Trial

PubMed Central

Feghhi, Mostafa; Farrahi, Fereydoun; Abbaspour, Mohammadreza; Takhtaeian, Akbar

2014-01-01

Purpose: To evaluate the effect of oral calcium dobesilate (Doxium) on macular thickness in clinically significant macular edema (CSME). Methods: Overall, 71 eyes of 40 patients with non-proliferative diabetic retinopathy and clinically significant macular edema were included. All patients were received laser treatment for macular edema. Coherence optical tomography was used to determine the retinal thickness. Patients were randomized into two groups: group A received three Doxium capsule daily and group B received three placebo capsule daily for six months. Results: The mean macular thickness before and after treatment in the group A was 340 and 257 micrometers respectively (24.5% reduced), and in the group B was 336 micrometers and 263 micrometers respectively (21.5% reduced). Macular thickness significantly decreased after treatment in both groups and the reduction in group A is higher but the difference of reduction between the two groups was not statistically significant (P>0.05). Conclusion: In respect to the effect of adding oral Doxium to Laser Photocoagulation on the macular thickness in patients with diabetic macular edema, this study showed no statistically significant difference between Doxium and placebo. PMID:25436194

Rf feedback free electron laser

DOEpatents

Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

1979-11-02

A free electron laser system and electron beam system for a free electron laser are provided which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

Constructing the AdS dual of a Fermi liquid: AdS black holes with Dirac hair

NASA Astrophysics Data System (ADS)

Čubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad

2011-10-01

We provide evidence that the holographic dual to a strongly coupled charged Fermi liquid has a non-zero fermion density in the bulk. We show that the pole-strength of the stable quasiparticle characterizing the Fermi surface is encoded in the AdS probability density of a single normalizable fermion wavefunction in AdS. Recalling Migdal's theorem which relates the pole strength to the Fermi-Dirac characteristic discontinuity in the number density at ω F , we conclude that the AdS dual of a Fermi liquid is described by occupied on-shell fermionic modes in AdS. Encoding the occupied levels in the total spatially averaged probability density of the fermion field directly, we show that an AdS Reissner-Nordström black holein a theory with charged fermions has a critical temperature, at which the system undergoes a first-order transition to a black hole with a non-vanishing profile for the bulk fermion field. Thermodynamics and spectral analysis support that the solution with non-zero AdS fermion-profile is the preferred ground state at low temperatures.

Mie resonances to tailor random lasers

NASA Astrophysics Data System (ADS)

García, P. D.; Ibisate, M.; Sapienza, R.; Wiersma, D. S.; López, C.

2009-07-01

In this paper, we present an optical characterization of photonic glass-based random lasers. We show how the resonant behavior of diffuse light transport through such systems can tailor the lasing emission when a gain medium is added to the glass. A DNA-based organic dye is used as gain medium. The resonances in the transport mean-free path influence the lasing wavelength of the random laser. The laser wavelength is therefore controlled by the sphere diameter. Furthermore, the existence of Mie resonances reduces the necessary pump energy to reach the lasing threshold.

Segmented strings in AdS 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas

We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We studymore » several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. Here, we also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.« less

Segmented strings in AdS 3

DOE PAGES

Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas; ...

2015-11-17

We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We studymore » several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. Here, we also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.« less

Effects of filling material and laser power on the formation of intermetallic compounds during laser-assisted friction stir butt welding of steel and aluminum alloys

NASA Astrophysics Data System (ADS)

Fei, Xinjiang; Jin, Xiangzhong; Peng, Nanxiang; Ye, Ying; Wu, Sigen; Dai, Houfu

2016-11-01

In this paper, two kinds of materials, Ni and Zn, are selected as filling material during laser-assisted friction stir butt welding of Q235 steel and 6061-T6 aluminum alloy, and their influences on the formation of intermetallic compounds on the steel/aluminum interface of the joints were first studied. SEM was used to analyze the profile of the intermetallic compound layer and the fractography of tensile fracture surfaces. In addition, EDS was applied to investigate the types of the intermetallic compounds. The results indicate that a thin iron-abundant intermetallic compound layer forms and ductile fracture mode occurs when Ni is added, but a thick aluminum-abundant intermetallic compound layer generates and brittle fracture mode occurs when Zn is added. So the tensile strength of the welds with Ni as filling material is greater than that with Zn as filling material. Besides, the effect of laser power on the formation of intermetallic compound layer when Ni is added was investigated. The preheated temperature field produced by laser beam in the cross section of workpiece was calculated, and the tensile strength of the joints at different laser powers was tested. Results show that only when suitable laser power is adopted, can suitable preheating temperature of the steel reach, then can thin intermetallic compound layer form and high tensile strength of the joints reach. Either excessive or insufficient laser power will reduce the tensile strength of the joints.

Diagnosis of Plasma States in X-Ray Laser Experiments

DTIC Science & Technology

1992-10-01

J e AD-A256 909 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC 4 OCT 2 6 1992’ DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS by Yang ...0619-92 HUMAN TRANSLATION FASTC-ID(RS)T-0619-92 8 October 1992 DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS By: Yang Shangjin, Cai Yuqin, Chunyu... Yang Shangjin, Cai Yuqin, and Chunyu Shutai China Academy of Engineering Physics Abstract At an LF-12 laser installation, an Nd glass laser of

A Wide Range of 3243A>G/tRNALeu(UUR) (MELAS) Mutation Loads May Segregate in Offspring through the Female Germline Bottleneck

PubMed Central

Pallotti, Francesco; Binelli, Giorgio; Fabbri, Raffaella; Valentino, Maria L.; Vicenti, Rossella; Macciocca, Maria; Cevoli, Sabina; Baruzzi, Agostino; DiMauro, Salvatore; Carelli, Valerio

2014-01-01

Segregation of mutant mtDNA in human tissues and through the germline is debated, with no consensus about the nature and size of the bottleneck hypothesized to explain rapid generational shifts in mutant loads. We investigated two maternal lineages with an apparently different inheritance pattern of the same pathogenic mtDNA 3243A>G/tRNALeu(UUR) (MELAS) mutation. We collected blood cells, muscle biopsies, urinary epithelium and hair follicles from 20 individuals, as well as oocytes and an ovarian biopsy from one female mutation carrier, all belonging to the two maternal lineages to assess mutant mtDNA load, and calculated the theoretical germline bottleneck size (number of segregating units). We also evaluated “mother-to-offspring” segregations from the literature, for which heteroplasmy assessment was available in at least three siblings besides the proband. Our results showed that mutation load was prevalent in skeletal muscle and urinary epithelium, whereas in blood cells there was an inverse correlation with age, as previously reported. The histoenzymatic staining of the ovarian biopsy failed to show any cytochrome-c-oxidase defective oocyte. Analysis of four oocytes and one offspring from the same unaffected mother of the first family showed intermediate heteroplasmic mutant loads (10% to 75%), whereas very skewed loads of mutant mtDNA (0% or 81%) were detected in five offspring of another unaffected mother from the second family. Bottleneck size was 89 segregating units for the first mother and 84 for the second. This was remarkably close to 88, the number of “segregating units” in the “mother-to-offspring” segregations retrieved from literature. In conclusion, a wide range of mutant loads may be found in offspring tissues and oocytes, resulting from a similar theoretical bottleneck size. PMID:24805791

Warped AdS3 black holes

NASA Astrophysics Data System (ADS)

Song, Wei; Anninos, Dionysios; Li, Wei; Padi, Megha; Strominger, Andrew

2009-03-01

Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -ell-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μell = 1. However we show herein that for every value of μell ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μell = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μell > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μell > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.

Warped AdS3 black holes

NASA Astrophysics Data System (ADS)

Anninos, Dionysios; Li, Wei; Padi, Megha; Song, Wei; Strominger, Andrew

2009-03-01

Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -l-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μl = 1. However we show herein that for every value of μl ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μl = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μl > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μl > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.

Fractional ablative erbium YAG laser: histological characterization of relationships between laser settings and micropore dimensions.

PubMed

Taudorf, Elisabeth H; Haak, Christina S; Erlendsson, Andrés M; Philipsen, Peter A; Anderson, R Rox; Paasch, Uwe; Haedersdal, Merete

2014-04-01

Treatment of a variety of skin disorders with ablative fractional lasers (AFXL) is driving the development of portable AFXLs. This study measures micropore dimensions produced by a small 2,940 nm AFXL using a variety of stacked pulses, and determines a model correlating laser parameters with tissue effects. Ex vivo pig skin was exposed to a miniaturized 2,940 nm AFXL, spot size 225 µm, density 5%, power levels 1.15-2.22 W, pulse durations 50-225 microseconds, pulse repetition rates 100-500 Hz, and 2, 20, or 50 stacked pulses, resulting in pulse energies of 2.3-12.8 mJ/microbeam and total energy levels of 4.6-640 mJ/microchannel. Histological endpoints were ablation depth (AD), coagulation zone (CZ) and ablation width (AW). Data were logarithmically transformed if required prior to linear regression analyses. Results for histological endpoints were combined in a mathematical model. In 138 sections from 91 biopsies, AD ranged from 16 to a maximum of 1,348 µm and increased linearly with the logarithm of total energy delivered by stacked pulses, but also depended on variations in power, pulse duration, pulse repetition rate, and pulse energy (r(2)  = 0.54-0.85, P < 0.0001). Microchannels deeper than 500 µm were created only by the highest pulse energy of 12.8 mJ/microbeam. Pulse stacking increased AD, and enlarged CZ and AW. CZ varied from 0 to 205 µm and increased linearly with total energy (r(2)  = 0.56-0.75, P < 0.0001). AW ranged from 106 to 422 µm and increased linearly with the logarithm of number of stacked pulses (r(2)  = 0.53-0.61, P < 0.001). The mathematical model estimated micropores of specific ADs with an associated range of CZs and AWs, for example, 300 µm ADs were associated with CZs from 27 to 73 µm and AWs from 190 to 347 µm. Pulse stacking with a small, low power 2,940 nm AFXL created reproducible shallow to deep micropores, and influenced micropore configuration. Mathematical modeling

Treatment of Laser Induced Retinal Injuries

DTIC Science & Technology

1989-06-21

AD Treatment of Laser Induced Retinal Injuries0 0 " Midterm Report (September 30, 1987 through March 31, 1989) .rj1- .I N. Naveh, M.D. Michael Belkin...208 11. TITLE (Incude Secunty Olasufiation) Treatment of Laser Induced Retinal Injuries 12. PERSONAL. AUTHOR(S) M. Belkin, NJ. Naveh 13a. TYPE OF REPORT...enhancement in arachidonic acid metabolism and that steroid treatment curtailed this response. In the prsent study we investigated the involvement of

Treatment of Laser Induced Retinal Injuries

DTIC Science & Technology

1985-01-01

AD TREATMENT OF LASER INDUCED RETINAL INJURIES cANNUAL/FINAL REPORT MICHAEL BELKIN INAVA NAVEH JANUARY 1985 Supported by U.S. ARMY MEDICAL RESEARCH...CF ,I446 11. TITLE (Include Security Classification) (U) Treatment of Laser Induced Retinal Injuries 12. PERSONAL AUTHOR(S) Michael Belkin 13a. TYPE...ciliary body as seen in uveitis , is associated by elevation of aqueous humor protein levels. Therefore, protein was used by some investigators as an

Amplification in Double Heterostructure GaAs Lasers.

DTIC Science & Technology

1981-03-15

done, for example, in the book by Siegman . When the laser signal which is to be amplified is a single mode, it is important to include the possibility...k A’AD-A097 862 AEROSPACE CORP EL SEGUNDO CA ELECTRONICS RESEARCH LAP) P 5 20/5 I AMPLIFICATION IN DOUBLE HETEROSTRUCTURE GAAS LASERS .(U IMAR al E...GARMIRE, M CHANG F04701-80-C-0081I UNCLASSIFIED TR GO81(6930 03)-2 SD-TA8-30 NL Amplification in Double Heterostructure GaAs Lasers E. GARMIRE nd M

Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

NASA Technical Reports Server (NTRS)

Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.; Jenkins, Luther N.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

Theoretical Aspects of Laser-Induced Periodic Surface Structure Formation,

DTIC Science & Technology

1983-11-01

r AD-A134 875 UNCLASSIFIED THEORETICAL ASPECTS OF LASER -INUUCtl) PtKlUUlt bUKhALt STRUCTURE FORMATION(U) ROCHESTER UNIV NY DEPT OF CHEMISTRY M...UR0CHESTER/DC/83/TR-43 2. COVT ACCESSION NO A. TITLE (and Subllllm) Theoretical Aspects of Laser -Induced Periodic Surface Structure Formation 7...publication in Laser -Controlled Chemical Processing of Surfaces, ed. by A. W. Johnson and D. J. Ehrlich (Elsevier, New York) 19 KEY WORDS (Continue

Fast and broadband detector for laser radiation

NASA Astrophysics Data System (ADS)

Scorticati, Davide; Crapella, Giacomo; Pellegrino, Sergio

2018-02-01

We developed a fast detector (patent pending) based on the Laser Induced Transverse Voltage (LITV) effect. The advantage of detectors using the LITV effect over pyroelectric sensors and photodiodes for laser radiation measurements is the combination of an overall fast response time, broadband spectral acceptance, high saturation threshold to direct laser irradiation and the possibility to measure pulsed as well as cw-laser sources. The detector is capable of measuring the energy of single laser pulses with repetition frequencies up to the MHz range, adding the possibility to also measure the output power of cw-lasers. Moreover, the thermal nature of the sensor enables the capability to work in a broadband spectrum, from UV to THz as well as the possibility of operating in a broad-range (10-3-102 W/cm2 ) of incident average optical power densities of the laser radiation, without the need of adopting optical filters nor other precautions.

High-efficiency microchip laser with self-injection seeding.

PubMed

Wang, Sha; Wang, Yan-biao; Yang, Xian-heng; Feng, Guo-ying; Zhou, Shou-huan

2015-12-10

In this paper, we use a small bandwidth 808 nm cw Ti:sapphire laser as a pump source to pump a picosecond microchip laser. Different focal length pump focus lenses have been tested to improve laser efficiency. A maximum slope efficiency of around 20% is obtained by a 30 mm focal length lens. The pump threshold is only 13 mW. In order to reduce the timing jitter, we explored the self-injection seeding method by adding a seeding cavity to the microchip laser. A reduction factor in the timing jitter of up to a factor of 23 relative to the unseeded laser is obtained. From the experiments, we also found that higher seeding pulse energy will help to reduce the jitter more.

Auto-simultaneous laser treatment and Ohshiro's classification of laser treatment

NASA Astrophysics Data System (ADS)

Ohshiro, Toshio

2005-07-01

When the laser was first applied in medicine and surgery in the late 1960"s and early 1970"s, early adopters reported better wound healing and less postoperative pain with laser procedures compared with the same procedure performed with the cold scalpel or with electrothermy, and multiple surgical effects such as incision, vaporization and hemocoagulation could be achieved with the same laser beam. There was thus an added beneficial component which was associated only with laser surgery. This was first recognized as the `?-effect", was then classified by the author as simultaneous laser therapy, but is now more accurately classified by the author as part of the auto-simultaneous aspect of laser treatment. Indeed, with the dramatic increase of the applications of the laser in surgery and medicine over the last 2 decades there has been a parallel increase in the need for a standardized classification of laser treatment. Some classifications have been machine-based, and thus inaccurate because at appropriate parameters, a `low-power laser" can produce a surgical effect and a `high power laser", a therapeutic one . A more accurate classification based on the tissue reaction is presented, developed by the author. In addition to this, the author has devised a graphical representation of laser surgical and therapeutic beams whereby the laser type, parameters, penetration depth, and tissue reaction can all be shown in a single illustration, which the author has termed the `Laser Apple", due to the typical pattern generated when a laser beam is incident on tissue. Laser/tissue reactions fall into three broad groups. If the photoreaction in the tissue is irreversible, then it is classified as high-reactive level laser treatment (HLLT). If some irreversible damage occurs together with reversible photodamage, as in tissue welding, the author refers to this as mid-reactive level laser treatment (MLLT). If the level of reaction in the target tissue is lower than the cells

Characteristics of Single-Event Upsets in a Fabric Switch (ADS151)

NASA Technical Reports Server (NTRS)

Buchner, Stephen; Carts, Martin A.; McMorrow, Dale; Kim, Hak; Marshall, Paul W.; LaBel, Kenneth A.

2003-01-01

Abstract-Two types of single event effects - bit errors and single event functional interrupts - were observed during heavy-ion testing of the AD8151 crosspoint switch. Bit errors occurred in bursts with the average number of bits in a burst being dependent on both the ion LET and on the data rate. A pulsed laser was used to identify the locations on the chip where the bit errors and single event functional interrupts occurred. Bit errors originated in the switches, drivers, and output buffers. Single event functional interrupts occurred when the laser was focused on the second rank latch containing the data specifying the state of each switch in the 33x17 matrix.

Laser-induced propagation and destruction of amyloid beta fibrils.

PubMed

Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

2010-06-18

The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

A Survey of Laser Lightning Rod Techniques

DTIC Science & Technology

1991-08-21

impossibility of the LLR concept. 4 REFERENCES 1. Hagen, 1969: "Diffraction-limited high irradiance Nd- glass laser system, J. Appl. Phys., 40, 511-516. 2. Greig...study", Air Force Flight Dynamics Laboratory,, Technical Report AFFDL-TR-78-60. AD A063 847. 8. Schubert, C.N., Jr. and J.R. Lippert , 1979...pp. 132-135. 9. Lippert , J.R.,1978: "Laser-Induced Lightning Concept Exper- iment", Air Force Flight Dynamics Laboratory, Technical Report AFFDL-TR

Cell-based optical assay for amyloid β-induced neuronal cell dysfunction using femtosecond-pulsed laser

NASA Astrophysics Data System (ADS)

Lee, Seunghee; Yoon, Jonghee; Choi, Chulhee

2015-03-01

Amyloid β-protein (Aβ) is known as a key molecule related to the pathogenesis of Alzheimer's disease (AD). Over time, the amyloid cascade disrupts essential function of mitochondria including Ca2+ homeostasis and reactive oxygen species (ROS) regulation, and eventually leads to neuronal cell death. However, there have been no methods that analyze and measure neuronal dysfuction in pathologic conditions quantitatively. Here, we suggest a cell-based optical assay to investigate neuronal function in AD using femtosecond-pulsed laser stimulation. We observed that laser stimulation on primary rat hippocampal neurons for a few microseconds induced intracellular Ca2+ level increases or produced intracellular ROS which was a primary cause of neuronal cell death depending on delivered energy. Although Aβ treatment alone had little effect on the neuronal morphologies and networks in a few hours, Aβ-treated neurons showed delayed Ca2+ increasing pattern and were more vulnerable to laser-induced cell death compared to normal neurons. Our results collectively indicate that femtosecond laser stimulation can be a useful tool to study neuronal dysfuction related to AD pathologies. We anticipate this optical method to enable studies in the early progression of neuronal impairments and the quantitative evaluation of drug effects on neurons in neurodegenerative diseases, including AD and Parkinson's disease in a preclinical study.

The Construction of a Nd:YAG Laser and Observation of the Output.

DTIC Science & Technology

1983-12-01

State Laser En ineering, p. 55, Springer-Verlag New York, Inc., 97.- 4. Koechner, W., p. 56. 5. Siegman , A. E., An Introduction to Lasers and Masers...AD-A138 855 THE CONSTRUCTION OF A ND YAG LASER AND OBSERVATION OF i/i THE OUTPUT(U) NAVAL POSTGRADUATE SCHOOL MONTEREY CAK H CHUNG DEC 83...CONSTRUCTION OF A Nd:YAG LASER AND OBSERVATION OF THE OUTPUT by Im. Ki Hyun Chung December 1983 Thesis Advisor: A. W. Cooper Approved for public release

Cold Cathode Electron Beam Controlled CO2 Laser Performance.

DTIC Science & Technology

1974-10-01

Siegman (ref. 7), the cavity parameters are g, - 3/2, g2 3/4 so that 0he cavity will be confocal when the mirror separation is 2.5 m. The laser output was...E. Siegman , Laser Focus 7, 42, 1971. 8. W. F. Krupke and W. R. Sooy, IEEE Journal Quant. Elec. QE-5, 575, 1969. 9. 0. R. Wood, et al., Appl. Phys...U t AD/A-000 413 COLD CATHODE ELECTRON BEAM CONTROLLED C02 LASER PERFORMANCE Leslie L. McKee, 1II, et al Air Force Weapons Laboratory Kirtland Air

Analysis of Modes in an Unstable Strip Laser Resonator.

DTIC Science & Technology

1980-12-01

1977. 9. Siegman , A.E. "Unstable Optical Resonators for Laser Applications",Proceedings of the IEEE,53(3),277-287, March 1965. 10.------- "Unstable...7 AD-AO94 722 AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOO--ETC F/6 20/5 ANALYSIS OF MODES IN AN UNSTABLE STRIP LASER RESONATORJ(U...Patterson Air Force Base, Ohio 81 2 09 018 AFIT/GEP/PH/801D-7 ANALYSIS OF ,ODES -’ IN AN JJNSTABLE STRIP LASER 3ESONATOR. THESIS AFIT/GEP/PH/800-7 James

Solid-State Laser Source of Tunable Narrow-Bandwidth Ultraviolet Radiation

NASA Technical Reports Server (NTRS)

Goldberg, Lew; Kliner, Dahv A.; Koplow, Jeffrey P.

1998-01-01

A solid-state laser source of tunable and narrow-bandwidth UV light is disclosed. The system relies on light from a diode laser that preferably generates light at infrared frequencies. The light from the seed diode laser is pulse amplified in a light amplifier, and converted into the ultraviolet by frequency tripling, quadrupling, or quintupling the infrared light. The narrow bandwidth, or relatively pure light, of the seed laser is preserved, and the pulse amplifier generates high peak light powers to increase the efficiency of the nonlinear crystals in the frequency conversion stage. Higher output powers may be obtained by adding a fiber amplifier to power amplify the pulsed laser light prior to conversion.

SAO/NASA ADS at SAO: ADS Browse Service

Science.gov Websites

Sign on [SAO/NASA ADS] ADS Browse Service ADS Home | HELP | Sitemap ADS Services Search Browse myADS Mirrors Feedback FAQ What's new Site Map Help Other NASA Centers CXC HEASARC IRSA MAST NED NSSDC -Smithsonian Center for Astrophysics [ Smithsonian logo ] The NASA Astrophysics Data System provides different

Performance Modeling of Experimental Laser Lightcrafts

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Chen, Yen-Sen; Liu, Jiwen; Myrabo, Leik N.; Mead, Franklin B., Jr.; Turner, Jim (Technical Monitor)

2001-01-01

A computational plasma aerodynamics model is developed to study the performance of a laser propelled Lightcraft. The computational methodology is based on a time-accurate, three-dimensional, finite-difference, chemically reacting, unstructured grid, pressure-based formulation. The underlying physics are added and tested systematically using a building-block approach. The physics modeled include non-equilibrium thermodynamics, non-equilibrium air-plasma finite-rate kinetics, specular ray tracing, laser beam energy absorption and refraction by plasma, non-equilibrium plasma radiation, and plasma resonance. A series of transient computations are performed at several laser pulse energy levels and the simulated physics are discussed and compared with those of tests and literatures. The predicted coupling coefficients for the Lightcraft compared reasonably well with those of tests conducted on a pendulum apparatus.

Tensionless string spectra on AdS3

NASA Astrophysics Data System (ADS)

Gaberdiel, Matthias R.; Gopakumar, Rajesh

2018-05-01

The spectrum of superstrings on AdS3 × S3 × M 4 with pure NS-NS flux is analysed for the background where the radius of the AdS space takes the minimal value ( k = 1). Both for M 4 = S3 × S1 and M 4 = T 4 we show that there is a special set of physical states, coming from the bottom of the spectrally flowed continuous representations, which agree in precise detail with the single particle spectrum of a free symmetric product orbifold. For the case of AdS3 × S3 × T 4 this relies on making sense of the world-sheet theory at k = 1, for which we make a concrete proposal. We also comment on the implications of this striking result.

Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

2011-10-01

The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987); Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (δν / ν ~ 0.03-0.19%) pulses irradiated targets at moderate to high intensities (1014-1015W/cm2) . Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (δν ~ 1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets. Work supported by DoE/NNSA.

Influence of Laser Power on the Shape of Single Tracks in Scanner Based Laser Wire Cladding

NASA Astrophysics Data System (ADS)

Barroi, A.; Gonçalves, D. Albertazzi; Hermsdorf, J.; Kaierle, S.; Overmeyer, L.

The shape of the cladding tracks is extremely important for producing layers or structures by adding them sequently. This paper shows the influence of the laser power of a diode laser in the range of 500 to 1000 W on the shapes of single tracks in scanner based laser wire cladding. The scanner was used to oscillate the beam perpendiculary to the welding direction. Stainless steel (ER 318 Si) wire with a 0.6 mm diameter was used as deposition material. Height, width, penetration, molten area and weld seam angles of single tracks were obtained from cross-sections at three different positions of each track. The influence of these different positions on the results depends on the traverse speed. The paper discusses this influence in respect to the heat dissipation in the substrate material.

Single electron beam rf feedback free electron laser

DOEpatents

Brau, C.A.; Stein, W.E.; Rockwood, S.D.

1981-02-11

A free electron laser system and electron beam system for a free electron laser which uses rf feedback to enhance efficiency are described. Rf energy is extracted from a single electron beam by decelerating cavities and energy is returned to accelerating cavities using rf returns, such as rf waveguides, rf feedthroughs, resonant feedthroughs, etc. This rf energy is added to rf klystron energy to reduce the required input energy and thereby enhance energy efficiency of the system.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Modification of biological objects in water media by CO2-laser radiation

NASA Astrophysics Data System (ADS)

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

2005-09-01

The modification of biological objects (polysaccharides and cells) by CO2-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.

Using Laser Ultrasound to Detect Subsurface Defects in Metal Laser Powder Bed Fusion Components

NASA Astrophysics Data System (ADS)

Everton, Sarah; Dickens, Phill; Tuck, Chris; Dutton, Ben

2018-03-01

Laser powder bed fusion offers many advantages over conventional manufacturing methods, such as the integration of multiple parts that can result in significant weight-savings. The increased design freedom that layer-wise manufacture allows has also been seen to enhance component performance at little or no added cost. For such benefits to be realized, however, the material quality must first be assured. Laser ultrasonic testing is a noncontact inspection technique that has been proposed as suitable for in situ monitoring of metal additive manufacturing processes. This article explores the current capability of this technique to detect manufactured, subsurface defects in Ti-6Al-4V samples, ex situ. The results are compared with x-ray computed tomography reconstructions and focus variation microscopy. Although laser ultrasound has been used to identify material discontinuities, further work is required before this technique could be implemented in situ.

An Open-path Laser Transmissometer for Atmospheric Extinction Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandran, P. M. Satheesh; Krishnakumar, C. P.; Varma, Ravi

2011-10-20

A transmissometer is an optical instrument which measures transmitted intensity of monochromatic light over a fixed pathlength. Prototype of a simple laser transmissometer has been developed for transmission (or extinction) measurements through suspended absorbers and scatterers in the atmosphere over tens of meters. Instrument consists of a continuous green diode pumped solid state laser, transmission optics, photodiode detectors and A/D data acquisition components. A modulated laser beam is transmitted and subsequently reflected and returned to the unit by a retroreflecting mirror assembly placed several tens of meters away. Results from an open-path field measurement of the instrument are described.

Demonstration of coherent addition of multiple gratings for high-energy chirped-pulse-amplified lasers.

PubMed

Kessler, Terrance J; Bunkenburg, Joachim; Huang, Hu; Kozlov, Alexei; Meyerhofer, David D

2004-03-15

Petawatt solid-state lasers require meter-sized gratings to reach multiple-kilojoule energy levels without laser-induced damage. As an alternative to large single gratings, we demonstrate that smaller, coherently added (tiled) gratings can be used for subpicosecond-pulse compression. A Fourier-transform-limited, 650-fs chirped-pulse-amplified laser pulse is maintained by replacing a single compression grating with a tiled-grating assembly. Grating tiling provides a means to scale the energy and irradiance of short-pulse lasers.

Advancing three-dimensional MEMS by complimentary laser micro manufacturing

NASA Astrophysics Data System (ADS)

Palmer, Jeremy A.; Williams, John D.; Lemp, Tom; Lehecka, Tom M.; Medina, Francisco; Wicker, Ryan B.

2006-01-01

This paper describes improvements that enable engineers to create three-dimensional MEMS in a variety of materials. It also provides a means for selectively adding three-dimensional, high aspect ratio features to pre-existing PMMA micro molds for subsequent LIGA processing. This complimentary method involves in situ construction of three-dimensional micro molds in a stand-alone configuration or directly adjacent to features formed by x-ray lithography. Three-dimensional micro molds are created by micro stereolithography (MSL), an additive rapid prototyping technology. Alternatively, three-dimensional features may be added by direct femtosecond laser micro machining. Parameters for optimal femtosecond laser micro machining of PMMA at 800 nanometers are presented. The technical discussion also includes strategies for enhancements in the context of material selection and post-process surface finish. This approach may lead to practical, cost-effective 3-D MEMS with the surface finish and throughput advantages of x-ray lithography. Accurate three-dimensional metal microstructures are demonstrated. Challenges remain in process planning for micro stereolithography and development of buried features following femtosecond laser micro machining.

Role of low-level laser therapy added to facial expression exercises in patients with idiopathic facial (Bell's) palsy.

PubMed

Ordahan, Banu; Karahan, Ali Yavuz

2017-05-01

The aim of the present study was to investigate the efficacy of low-level laser therapy in conjunction with conventional facial exercise treatment on functional outcomes during the early recovery period in patients with facial paralysis. Forty-six patients (mean age 41 ± 9.7 years; 40 women and 6 men) were randomized into two groups. Patients in the first group received low-level laser treatment as well as facial exercise treatment, while patients in the second group participated in facial exercise intervention alone. Laser treatment was administered at a wavelength of 830 nm, output power of 100 Mw, and frequency of 1 KHz using a gallium-aluminum-arsenide (GaAIAs, infrared laser) diode laser. A mean energy density of 10 J/cm 2 was administered to eight points of the affected side of the face three times per week, for a total of 6 weeks. The rate of facial improvement was evaluated using the facial disability index (FDI) before, 3 weeks after, and 6 weeks after treatment. Friedman analysis of variance was performed to compare the data from the parameters repeatedly measured in the inner-group analysis. Bonferroni correction was performed to compare between groups as a post hoc test if the variance analysis test result was significant. To detect the group differences, the Bonferroni Student t test was used. The Mann-Whitney U test was used to compare numeric data between the groups. In the exercise group, although no significant difference in FDI scores was noted between the start of treatment and week 3 (p < 0.05), significant improvement was observed at week 6 (p < 0.001). In the laser group, significant improvement in FDI scores relative to baseline was observed at 3 and 6 weeks (p < 0.001). Improvements in FDI scores were significantly greater at weeks 3 and 6 in the laser group than those in the exercise group (p < 0.05). Our findings indicate that combined treatment with low-level laser therapy (LLLT) and exercise therapy is associated with

AdS7/CFT6 with orientifolds

NASA Astrophysics Data System (ADS)

Apruzzi, Fabio; Fazzi, Marco

2018-01-01

AdS7 solutions of massive type IIA have been classified, and are dual to a large class of six-dimensional (1, 0) SCFT's whose tensor branch deformations are described by linear quivers of SU groups. Quivers and AdS vacua depend solely on the group theory data of the NS5-D6-D8 brane configurations engineering the field theories. This has allowed for a direct holographic match of their a conformal anomaly. In this paper we extend the match to cases where O6 and O8-planes are present, thereby introducing SO and USp groups in the quivers. In all of them we show that the a anomaly computed in supergravity agrees with the holographic limit of the exact field theory result, which we extract from the anomaly polynomial. As a byproduct we construct special AdS7 vacua dual to nonperturbative F-theory configurations. Finally, we propose a holographic a-theorem for six-dimensional Higgs branch RG flows.

Two Virasoro symmetries in stringy warped AdS 3

DOE PAGES

Compere, Geoffrey; Guica, Monica; Rodriguez, Maria J.

2014-12-02

We study three-dimensional consistent truncations of type IIB supergravity which admit warped AdS 3 solutions. These theories contain subsectors that have no bulk dynamics. We show that the symplectic form for these theories, when restricted to the non-dynamical subsectors, equals the symplectic form for pure Einstein gravity in AdS 3. Consequently, for each consistent choice of boundary conditions in AdS 3, we can define a consistent phase space in warped AdS 3 with identical conserved charges. This way, we easily obtain a Virasoro × Virasoro asymptotic symmetry algebra in warped AdS 3; two different types of Virasoro × Kač-Moody symmetriesmore » are also consistent alternatives. Next, we study the phase space of these theories when propagating modes are included. We show that, as long as one can define a conserved symplectic form without introducing instabilities, the Virasoro × Virasoro asymptotic symmetries can be extended to the entire (linearised) phase space. In conclusion, this implies that, at least at semi-classical level, consistent theories of gravity in warped AdS 3 are described by a two-dimensional conformal field theory, as long as stability is not an issue.« less

Two Virasoro symmetries in stringy warped AdS 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Compere, Geoffrey; Guica, Monica; Rodriguez, Maria J.

We study three-dimensional consistent truncations of type IIB supergravity which admit warped AdS 3 solutions. These theories contain subsectors that have no bulk dynamics. We show that the symplectic form for these theories, when restricted to the non-dynamical subsectors, equals the symplectic form for pure Einstein gravity in AdS 3. Consequently, for each consistent choice of boundary conditions in AdS 3, we can define a consistent phase space in warped AdS 3 with identical conserved charges. This way, we easily obtain a Virasoro × Virasoro asymptotic symmetry algebra in warped AdS 3; two different types of Virasoro × Kač-Moody symmetriesmore » are also consistent alternatives. Next, we study the phase space of these theories when propagating modes are included. We show that, as long as one can define a conserved symplectic form without introducing instabilities, the Virasoro × Virasoro asymptotic symmetries can be extended to the entire (linearised) phase space. In conclusion, this implies that, at least at semi-classical level, consistent theories of gravity in warped AdS 3 are described by a two-dimensional conformal field theory, as long as stability is not an issue.« less

Low-power laser irradiation inhibits amyloid beta-induced cell apoptosis

NASA Astrophysics Data System (ADS)

Zhang, Heng; Wu, Shengnan

2011-03-01

The deposition and accumulation of amyloid-β-peptide (Aβ) in the brain are considered a pathological hallmark of Alzheimer's disease(AD). Apoptosis is a contributing pathophysiological mechanism of AD. Low-power laser irradiation (LPLI), a non-damage physical therapy, which has been used clinically for decades of years, is shown to promote cell proliferation and prevent apoptosis. Recently, low-power laser irradiation (LPLI) has been applied to moderate AD. In this study, Rat pheochromocytoma (PC12) cells were treated with amyloid beta 25-35 (Aβ25-35) for induction of apoptosis before LPLI treatment. We measured cell viability with CCK-8 according to the manufacture's protocol, the cell viability assays show that low fluence of LPLI (2 J/cm2 ) could inhibit the cells apoptosis. Then using statistical analysis of proportion of apoptotic cells by flow cytometry based on Annexin V-FITC/PI, the assays also reveal that low fluence of LPLI (2 J/cm2 ) could inhibit the Aβ-induced cell apoptosis. Taken together, we demonstrated that low fluence of LPLI (2 J/cm2 ) could inhibit the Aβ-induced cell apoptosis, these results directly point to a therapeutic strategy for the treatment of AD through LPLI.

Phases of global AdS black holes

NASA Astrophysics Data System (ADS)

Basu, Pallab; Krishnan, Chethan; Subramanian, P. N. Bala

2016-06-01

We study the phases of gravity coupled to a charged scalar and gauge field in an asymptotically Anti-de Sitter spacetime ( AdS 4) in the grand canonical ensemble. For the conformally coupled scalar, an intricate phase diagram is charted out between the four relevant solutions: global AdS, boson star, Reissner-Nordstrom black hole and the hairy black hole. The nature of the phase diagram undergoes qualitative changes as the charge of the scalar is changed, which we discuss. We also discuss the new features that arise in the extremal limit.

Comparative genome analysis of 19 Ureaplasma urealyticum and Ureaplasma parvum strains

PubMed Central

2012-01-01

Background Ureaplasma urealyticum (UUR) and Ureaplasma parvum (UPA) are sexually transmitted bacteria among humans implicated in a variety of disease states including but not limited to: nongonococcal urethritis, infertility, adverse pregnancy outcomes, chorioamnionitis, and bronchopulmonary dysplasia in neonates. There are 10 distinct serotypes of UUR and 4 of UPA. Efforts to determine whether difference in pathogenic potential exists at the ureaplasma serovar level have been hampered by limitations of antibody-based typing methods, multiple cross-reactions and poor discriminating capacity in clinical samples containing two or more serovars. Results We determined the genome sequences of the American Type Culture Collection (ATCC) type strains of all UUR and UPA serovars as well as four clinical isolates of UUR for which we were not able to determine serovar designation. UPA serovars had 0.75−0.78 Mbp genomes and UUR serovars were 0.84−0.95 Mbp. The original classification of ureaplasma isolates into distinct serovars was largely based on differences in the major ureaplasma surface antigen called the multiple banded antigen (MBA) and reactions of human and animal sera to the organisms. Whole genome analysis of the 14 serovars and the 4 clinical isolates showed the mba gene was part of a large superfamily, which is a phase variable gene system, and that some serovars have identical sets of mba genes. Most of the differences among serovars are hypothetical genes, and in general the two species and 14 serovars are extremely similar at the genome level. Conclusions Comparative genome analysis suggests UUR is more capable of acquiring genes horizontally, which may contribute to its greater virulence for some conditions. The overwhelming evidence of extensive horizontal gene transfer among these organisms from our previous studies combined with our comparative analysis indicates that ureaplasmas exist as quasi-species rather than as stable serovars in their native

Comparative genome analysis of 19 Ureaplasma urealyticum and Ureaplasma parvum strains.

PubMed

Paralanov, Vanya; Lu, Jin; Duffy, Lynn B; Crabb, Donna M; Shrivastava, Susmita; Methé, Barbara A; Inman, Jason; Yooseph, Shibu; Xiao, Li; Cassell, Gail H; Waites, Ken B; Glass, John I

2012-05-30

Ureaplasma urealyticum (UUR) and Ureaplasma parvum (UPA) are sexually transmitted bacteria among humans implicated in a variety of disease states including but not limited to: nongonococcal urethritis, infertility, adverse pregnancy outcomes, chorioamnionitis, and bronchopulmonary dysplasia in neonates. There are 10 distinct serotypes of UUR and 4 of UPA. Efforts to determine whether difference in pathogenic potential exists at the ureaplasma serovar level have been hampered by limitations of antibody-based typing methods, multiple cross-reactions and poor discriminating capacity in clinical samples containing two or more serovars. We determined the genome sequences of the American Type Culture Collection (ATCC) type strains of all UUR and UPA serovars as well as four clinical isolates of UUR for which we were not able to determine serovar designation. UPA serovars had 0.75-0.78 Mbp genomes and UUR serovars were 0.84-0.95 Mbp. The original classification of ureaplasma isolates into distinct serovars was largely based on differences in the major ureaplasma surface antigen called the multiple banded antigen (MBA) and reactions of human and animal sera to the organisms. Whole genome analysis of the 14 serovars and the 4 clinical isolates showed the mba gene was part of a large superfamily, which is a phase variable gene system, and that some serovars have identical sets of mba genes. Most of the differences among serovars are hypothetical genes, and in general the two species and 14 serovars are extremely similar at the genome level. Comparative genome analysis suggests UUR is more capable of acquiring genes horizontally, which may contribute to its greater virulence for some conditions. The overwhelming evidence of extensive horizontal gene transfer among these organisms from our previous studies combined with our comparative analysis indicates that ureaplasmas exist as quasi-species rather than as stable serovars in their native environment. Therefore, differential

Contamination and UV lasers: lessons learned

NASA Astrophysics Data System (ADS)

Daly, John G.

2015-09-01

Laser induced damage to optical elements has been a subject of significant research, development, and improvement, since the first lasers were built over the last 50 years. Better materials, with less absorption, impurities, and defects are available, as well as surface coatings with higher laser damage resistance. However, the presence of contamination (particles, surface deposition films, or airborne) can reduce the threshold for damage by several orders of magnitude. A brief review of the anticipated laser energy levels for damage free operation is presented as a lead into the problems associated with contamination for ultraviolet (UV) laser systems. As UV lasers become more common in applications especially in areas such as lithography, these problems have limited reliability and added to costs. This has been characterized as Airborne Molecular Contamination (AMC) in many published reports. Normal engineering guidelines such as screening materials within the optical compartment for low outgassing levels is the first step. The use of the NASA outgassing database (or similar test methods) with low Total Mass Loss (TML) and Condensed Collected Volatiles Collected Mass (CVCM) is a good baseline. Energetic UV photons are capable of chemical bond scission and interaction with surface contaminant or airborne materials results in deposition of obscuring film laser footprints that continue to degrade laser system performance. Laser systems with average powers less than 5 mW have been shown to exhibit aggressive degradation. Lessons learned over the past 15 years with UV laser contamination and steps to reduce risk will be presented.

Thermal tuning On narrow linewidth fiber laser

NASA Astrophysics Data System (ADS)

Han, Peiqi; Liu, Tianshan; Gao, Xincun; Ren, Shiwei

2010-10-01

At present, people have been dedicated to high-speed and large-capacity optical fiber communication system. Studies have been shown that optical wavelength division multiplexing (WDM) technology is an effective means of communication to increase the channel capacity. Tunable lasers have very important applications in high-speed, largecapacity optical communications, and distributed sensing, it can provide narrow linewidth and tunable laser for highspeed optical communication. As the erbium-doped fiber amplifier has a large gain bandwidth, the erbium-doped fiber laser can be achieved lasing wavelength tunable by adding a tunable filter components, so tunable filter device is the key components in tunable fiber laser.At present, fiber laser wavelength is tuned by PZT, if thermal wavelength tuning is combined with PZT, a broader range of wavelength tuning is appearance . Erbium-doped fiber laser is used in the experiments,the main research is the physical characteristics of fiber grating temperature-dependent relationship and the fiber grating laser wavelength effects. It is found that the fiber laser wavelength changes continuously with temperature, tracking several temperature points observed the self-heterodyne spectrum and found that the changes in spectra of the 3dB bandwidth of less than 1kHz, and therefore the fiber laser with election-mode fiber Bragg grating shows excellent spectral properties and wavelength stability.

New massive gravity and AdS(4) counterterms.

PubMed

Jatkar, Dileep P; Sinha, Aninda

2011-04-29

We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS(4)). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS(4) Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS(3) gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory.

Floquet scalar dynamics in global AdS

NASA Astrophysics Data System (ADS)

Biasi, Anxo; Carracedo, Pablo; Mas, Javier; Musso, Daniele; Serantes, Alexandre

2018-04-01

We study periodically driven scalar fields and the resulting geometries with global AdS asymptotics. These solutions describe the strongly coupled dynamics of dual finite-size quantum systems under a periodic driving which we interpret as Floquet condensates. They span a continuous two-parameter space that extends the linearized solutions on AdS. We map the regions of stability in the solution space. In a significant portion of the unstable subspace, two very different endpoints are reached depending upon the sign of the perturbation. Collapse into a black hole occurs for one sign. For the opposite sign instead one attains a regular solution with periodic modulation. We also construct quenches where the driving frequency and amplitude are continuously varied. Quasistatic quenches can interpolate between pure AdS and sourced solutions with time periodic vev. By suitably choosing the quasistatic path one can obtain boson stars dual to Floquet condensates at zero driving field. We characterize the adiabaticity of the quenching processes. Besides, we speculate on the possible connections of this framework with time crystals.

Period adding cascades: experiment and modeling in air bubbling.

PubMed

Pereira, Felipe Augusto Cardoso; Colli, Eduardo; Sartorelli, José Carlos

2012-03-01

Period adding cascades have been observed experimentally/numerically in the dynamics of neurons and pancreatic cells, lasers, electric circuits, chemical reactions, oceanic internal waves, and also in air bubbling. We show that the period adding cascades appearing in bubbling from a nozzle submerged in a viscous liquid can be reproduced by a simple model, based on some hydrodynamical principles, dealing with the time evolution of two variables, bubble position and pressure of the air chamber, through a system of differential equations with a rule of detachment based on force balance. The model further reduces to an iterating one-dimensional map giving the pressures at the detachments, where time between bubbles come out as an observable of the dynamics. The model has not only good agreement with experimental data, but is also able to predict the influence of the main parameters involved, like the length of the hose connecting the air supplier with the needle, the needle radius and the needle length.

Antismoking Ads at the Point of Sale: The Influence of Ad Type and Context on Ad Reactions.

PubMed

Kim, Annice; Nonnemaker, James; Guillory, Jamie; Shafer, Paul; Parvanta, Sarah; Holloway, John; Farrelly, Matthew

2017-06-01

Efforts are underway to educate consumers about the dangers of smoking at the point of sale (POS). Research is limited about the efficacy of POS antismoking ads to guide campaign development. This study experimentally tests whether the type of antismoking ad and the context in which ads are viewed influence people's reactions to the ads. A national convenience sample of 7,812 adult current smokers and recent quitters was randomized to 1 of 39 conditions. Participants viewed one of the four types of antismoking ads (negative health consequences-graphic, negative social consequences-intended emotive, benefits of quitting-informational, benefits of quitting-graphic) in one of the three contexts (alone, next to a cigarette ad, POS tobacco display). We assessed participants' reactions to the ads, including perceived effectiveness, negative emotion, affective dissonance, and motivational reaction. Graphic ads elicited more negative emotion and affective dissonance than benefits of quitting ads. Graphic ads elicited higher perceived effectiveness and more affective dissonance than intended emotive ads. Antismoking ads fared best when viewed alone, and graphic ads were least influenced by the context in which they were viewed. These results suggest that in developing POS campaigns, it is important to consider the competitive pro-tobacco context in which antismoking ads will be viewed.

Genetic Variation of the Endangered Neotropical Catfish Steindachneridion scriptum (Siluriformes: Pimelodidae)

PubMed Central

Paixão, Rômulo V.; Ribolli, Josiane; Zaniboni-Filho, Evoy

2018-01-01

Steindachneridion scriptum is an important species as a resource for fisheries and aquaculture; it is currently threatened and has a reduced occurrence in South America. The damming of rivers, overfishing, and contamination of freshwater environments are the main impacts on the maintenance of this species. We accessed the genetic diversity and structure of S. scriptum using the DNA barcode and control region (D-loop) sequences of 43 individuals from the Upper Uruguay River Basin (UUR) and 10 sequences from the Upper Paraná River Basin (UPR), which were obtained from GenBank. S. scriptum from the UUR and the UPR were assigned in two distinct molecular operational taxonomic units (MOTUs) with higher inter-specific K2P distance than the optimum threshold (OT = 0.0079). The COI Intra-MOTU distances of S. scriptum specimens from the UUR ranged from 0.0000 to 0.0100. The control region indicated a high number of haplotypes and low nucleotide diversity, compatible with a new population in recent expansion process. Genetic structure was observed, with high differentiation between UUR and UPR basins, identified by BAPS, haplotype network, AMOVA (FST = 0.78, p < 0.05) and Mantel test. S. scriptum from the UUR showed a slight differentiation (FST = 0.068, p < 0.05), but not isolation-by-distance. Negative values of Tajima’s D and Fu’s Fs suggest recent demographic oscillations. The Bayesian skyline plot analysis indicated possible population expansion from beginning 2,500 years ago and a recent reduction in the population size. Low nucleotide diversity, spatial population structure, and the reduction of effective population size should be considered for the planning of strategies aimed at the conservation and rehabilitation of this important fisheries resource. PMID:29520295

Urinary excretion of uric acid is negatively associated with albuminuria in patients with chronic kidney disease: a cross-sectional study.

PubMed

Li, Fengqin; Guo, Hui; Zou, Jianan; Chen, Weijun; Lu, Yijun; Zhang, Xiaoli; Fu, Chensheng; Xiao, Jing; Ye, Zhibin

2018-04-24

Increasing evidence has shown that albuminuria is related to serum uric acid. Little is known about whether this association may be interrelated via renal handling of uric acid. Therefore, we aim to study urinary uric acid excretion and its association with albuminuria in patients with chronic kidney disease (CKD). A cross-sectional study of 200 Chinese CKD patients recruited from department of nephrology of Huadong hospital was conducted. Levels of 24 h urinary excretion of uric acid (24-h Uur), fractional excretion of uric acid (FEur) and uric acid clearance rate (Cur) according to gender, CKD stages, hypertension and albuminuria status were compared by a multivariate analysis. Pearson and Spearman correlation and multiple regression analyses were used to study the correlation of 24-h Uur, FEur and Cur with urinary albumin to creatinine ratio (UACR). The multivariate analysis showed that 24-h Uur and Cur were lower and FEur was higher in the hypertension group, stage 3-5 CKD and macro-albuminuria group (UACR> 30 mg/mmol) than those in the normotensive group, stage 1 CKD group and the normo-albuminuria group (UACR< 3 mg/mmol) (all P < 0.05). Moreover, males had higher 24-h Uur and lower FEur than females (both P < 0.05). Multiple linear regression analysis showed that UACR was negatively associated with 24-h Uur and Cur (P = 0.021, P = 0.007, respectively), but not with FEur (P = 0.759), after adjusting for multiple confounding factors. Our findings suggested that urinary excretion of uric acid is negatively associated with albuminuria in patients with CKD. This phenomenon may help to explain the association between albuminuria and serum uric acid.

Vitamin C for stabilising biological lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kar, Ajoy K.; Mackenzie, Mark D.; Cialowicz, Katarzyna I.; Saleeb, Rebecca S.; Duncan, Rory R.

2016-04-01

We report on efforts to improve the lifetime of biological lasers through the use of ascorbic acid (also commonly known as vitamin C). Fluorescent proteins and dyes, used in biological lasers, suffer from photobleaching due to the build-up of reactive oxygen species (ROS) which causes damage leading to a decrease in emission over time. This is an issue both for laser lifetime and cell health. It has previously been shown that ascorbic acid can be effective in reducing ROS levels in a variety of applications. For our experiments human embryonic kidney cells (HEK293), containing the fluorescent dye Calcein AM, were placed between two dielectric plane mirrors to form a laser cavity. The cells were pumped using the output of a Ti:Sapphire femtosecond OPO system, frequency doubled twice in BBO crystals, giving an output of 474 nm. Initial results have shown an increase in laser lifetime when ascorbic acid is added to cells indicating a reduction in the build-up of ROS.

Numerical modeling of keyhole dynamics in laser welding

NASA Astrophysics Data System (ADS)

Zhang, Wen-Hai; Zhou, Jun; Tsai, Hai-Lung

2003-03-01

Mathematical models and the associated numerical techniques have been developed to study the following cases: (1) the formation and collapse of a keyhole, (2) the formation of porosity and its control strategies, (3) laser welding with filler metals, and (4) the escape of zinc vapor in laser welding of galvanized steel. The simulation results show that the formation of porosity in the weld is caused by two competing mechanisms: one is the solidification rate of the molten metal and the other is the speed that molten metal backfills the keyhole after laser energy is terminated. The models have demonstrated that porosity can be reduced or eliminated by adding filler metals, controlling laser tailing power, or applying an electromagnetic force during keyhole collapse process. It is found that a uniform composition of weld pool is difficult to achieve by filler metals due to very rapid solidification of the weld pool in laser welding, as compared to that in gas metal arc welding.

Loops in AdS from conformal field theory

DOE PAGES

Aharony, Ofer; Alday, Luis F.; Bissi, Agnese; ...

2017-07-10

We propose and demonstrate a new use for conformal field theory (CFT) crossing equations in the context of AdS/CFT: the computation of loop amplitudes in AdS, dual to non-planar correlators in holographic CFTs. Loops in AdS are largely unexplored, mostly due to technical difficulties in direct calculations. We revisit this problem, and the dual 1=N expansion of CFTs, in two independent ways. The first is to show how to explicitly solve the crossing equations to the first subleading order in 1=N 2, given a leading order solution. This is done as a systematic expansion in inverse powers of the spin, to all orders. These expansions can be resummed, leading to the CFT data for nite values of the spin. Our second approach involves Mellin space. We show how the polar part of the four-point, loop-level Mellin amplitudes can be fully reconstructed from the leading-order data. The anomalous dimensions computed with both methods agree. In the case ofmore » $$\\phi$$ 4 theory in AdS, our crossing solution reproduces a previous computation of the one-loop bubble diagram. We can go further, deriving the four-point scalar triangle diagram in AdS, which had never been computed. In the process, we show how to analytically derive anomalous dimensions from Mellin amplitudes with an in nite series of poles, and discuss applications to more complicated cases such as the N = 4 super-Yang-Mills theory.« less

Loops in AdS from conformal field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aharony, Ofer; Alday, Luis F.; Bissi, Agnese

We propose and demonstrate a new use for conformal field theory (CFT) crossing equations in the context of AdS/CFT: the computation of loop amplitudes in AdS, dual to non-planar correlators in holographic CFTs. Loops in AdS are largely unexplored, mostly due to technical difficulties in direct calculations. We revisit this problem, and the dual 1=N expansion of CFTs, in two independent ways. The first is to show how to explicitly solve the crossing equations to the first subleading order in 1=N 2, given a leading order solution. This is done as a systematic expansion in inverse powers of the spin, to all orders. These expansions can be resummed, leading to the CFT data for nite values of the spin. Our second approach involves Mellin space. We show how the polar part of the four-point, loop-level Mellin amplitudes can be fully reconstructed from the leading-order data. The anomalous dimensions computed with both methods agree. In the case ofmore » $$\\phi$$ 4 theory in AdS, our crossing solution reproduces a previous computation of the one-loop bubble diagram. We can go further, deriving the four-point scalar triangle diagram in AdS, which had never been computed. In the process, we show how to analytically derive anomalous dimensions from Mellin amplitudes with an in nite series of poles, and discuss applications to more complicated cases such as the N = 4 super-Yang-Mills theory.« less

Loops in AdS from conformal field theory

NASA Astrophysics Data System (ADS)

Aharony, Ofer; Alday, Luis F.; Bissi, Agnese; Perlmutter, Eric

2017-07-01

We propose and demonstrate a new use for conformal field theory (CFT) crossing equations in the context of AdS/CFT: the computation of loop amplitudes in AdS, dual to non-planar correlators in holographic CFTs. Loops in AdS are largely unexplored, mostly due to technical difficulties in direct calculations. We revisit this problem, and the dual 1 /N expansion of CFTs, in two independent ways. The first is to show how to explicitly solve the crossing equations to the first subleading order in 1 /N 2, given a leading order solution. This is done as a systematic expansion in inverse powers of the spin, to all orders. These expansions can be resummed, leading to the CFT data for finite values of the spin. Our second approach involves Mellin space. We show how the polar part of the four-point, loop-level Mellin amplitudes can be fully reconstructed from the leading-order data. The anomalous dimensions computed with both methods agree. In the case of ϕ 4 theory in AdS, our crossing solution reproduces a previous computation of the one-loop bubble diagram. We can go further, deriving the four-point scalar triangle diagram in AdS, which had never been computed. In the process, we show how to analytically derive anomalous dimensions from Mellin amplitudes with an infinite series of poles, and discuss applications to more complicated cases such as the N = 4 super-Yang-Mills theory.

Direct laser sintered WC-10Co/Cu nanocomposites

NASA Astrophysics Data System (ADS)

Gu, Dongdong; Shen, Yifu

2008-04-01

In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa.

Femtosecond lasers in ophthalmology: clinical applications in anterior segment surgery

NASA Astrophysics Data System (ADS)

Juhasz, Tibor; Nagy, Zoltan; Sarayba, Melvin; Kurtz, Ronald M.

2010-02-01

The human eye is a favored target for laser surgery due to its accessibility via the optically transparent ocular tissue. Femtosecond lasers with confined tissue effects and minimized collateral tissue damage are primary candidates for high precision intraocular surgery. The advent of compact diode-pumped femtosecond lasers, coupled with computer controlled beam delivery devices, enabled the development of high precision femtosecond laser for ophthalmic surgery. In this article, anterior segment femtosecond laser applications currently in clinical practice and investigation are reviewed. Corneal procedures evolved first and remain dominant due to easy targeting referenced from a contact surface, such as applanation lenses placed on the eye. Adding a high precision imaging technique, such as optical coherence tomography (OCT), can enable accurate targeting of tissue beyond the cornea, such as the crystalline lens. Initial clinical results of femtosecond laser cataract surgery are discussed in detail in the latter portion part of the article.

Worldsheet scattering in AdS3/CFT2

NASA Astrophysics Data System (ADS)

Sundin, Per; Wulff, Linus

2013-07-01

We confront the recently proposed exact S-matrices for AdS 3/ CFT 2 with direct worldsheet calculations. Utilizing the BMN and Near Flat Space (NFS) expansions for strings on AdS 3 × S 3 × S 3 × S 1 and AdS 3 × S 3 × T 4 we compute both tree-level and one-loop scattering amplitudes. Up to some minor issues we find nice agreement in the tree-level sector. At the one-loop level however we find that certain non-zero tree-level processes, which are not visible in the exact solution, contribute, via the optical theorem, and give an apparent mismatch for certain amplitudes. Furthermore we find that a proposed one-loop modification of the dressing phase correctly reproduces the worldsheet calculation while the standard Hernandez-Lopez phase does not. We also compute several massless to massless processes.

History, instrumentation, and techniques of flexible endoscopic laser surgery in horses.

PubMed

Blikslager, A T; Tate, L P

2000-08-01

There are clearly a number of applications for which flexible endoscopic laser surgery has become the state of the art in equine surgery, and the Nd:YAG laser seems to be the most versatile instrument for this type of surgery. Nevertheless, it is critical to understand the advantages and disadvantages of each laser technique. For example, the Nd:YAG laser used in a noncontact fashion seems to be superior when ablation of tissue is required such as treatment of upper airway masses. Conversely, contact Nd:YAG laser techniques have proven themselves to be superior when more precise cutting is advantageous such as treatment of epiglottic entrapment. Ultimately, it seems that a range of lasers is necessary to ensure selection of the most appropriate technique, adding significantly to the expense of equipment but improving the outcome for a range of equine diseases.

Hybrid semiconductor fiber lasers for telecommunications

NASA Astrophysics Data System (ADS)

Khalili, Alireza

2006-12-01

Highly stable edge emitting semiconductor lasers are of utmost importance in most telecommunications applications where high-speed data transmission sets strict limits on the purity of the laser signal. Unfortunately, most edge emitting semiconductor lasers, unlike gaseous or solid-state laser sources, operate with many closely spaced axial modes, which accounts for the observed instability and large spikes in the output spectrum of such lasers. Consequently, in most telecom applications distributed feedback (DFB) or distributed Bragg reflector (DBR) techniques are used to ensure stability and single-frequency operation, further adding to the cost and complexity of such lasers. Additionally, coupling of the highly elliptical output beam of these lasers to singlemode fibers complicates the packaging procedure and sub-micron alignment of various optical components is often necessary. Utilizing the evanescent coupling between a semiconductor antiresonant reflecting optical waveguide (ARROW) and a side polished fiber, this thesis presents an alternative side-coupled laser module that eliminates the need for the cumbersome multi-component alignment processes of conventional laser packages, and creates an inherent mode selection mechanism that guarantees singlemode radiation into the fiber without any gratings. We have been able to demonstrate the first side-coupled fiber semiconductor laser in this technology, coupling more than 3mW of power at 850nm directly into a 5/125mum singlemode fiber. This mixed-cavity architecture yields a high thermal stability (˜0.06nm/°C), and negligible spectral spikes are observed. Theoretical background and simulation results, as well as several supplementary materials are also presented to further rationalize the experimental data. A side-coupled light-emitter and pre-amplifier are also proposed and discussed. We also study different architectures for attaining higher efficiency, higher output power, and wavelength tunability in such

Spinning AdS loop diagrams: two point functions

NASA Astrophysics Data System (ADS)

Giombi, Simone; Sleight, Charlotte; Taronna, Massimo

2018-06-01

We develop a systematic approach to evaluating AdS loop amplitudes with spinning legs based on the spectral (or "split") representation of bulk-to-bulk propagators, which re-expresses loop diagrams in terms of spectral integrals and higher-point tree diagrams. In this work we focus on 2pt one-loop Witten diagrams involving totally symmetric fields of arbitrary mass and integer spin. As an application of this framework, we study the contribution to the anomalous dimension of higher-spin currents generated by bubble diagrams in higher-spin gauge theories on AdS.

Holography in Lovelock Chern-Simons AdS gravity

NASA Astrophysics Data System (ADS)

Cvetković, Branislav; Miskovic, Olivera; Simić, Dejan

2017-08-01

We analyze holographic field theory dual to Lovelock Chern-Simons anti-de Sitter (AdS) gravity in higher dimensions using first order formalism. We first find asymptotic symmetries in the AdS sector showing that they consist of local translations, local Lorentz rotations, dilatations and non-Abelian gauge transformations. Then, we compute 1-point functions of energy-momentum and spin currents in a dual conformal field theory and write Ward identities. We find that the holographic theory possesses Weyl anomaly and also breaks non-Abelian gauge symmetry at the quantum level.

Gauge boson exchange in AdS d+1

NASA Astrophysics Data System (ADS)

D'Hoker, Eric; Freedman, Daniel Z.

1999-04-01

We study the amplitude for exchange of massless gauge bosons between pairs of massive scalar fields in anti-de Sitter space. In the AdS/CFT correspondence this amplitude describes the contribution of conserved flavor symmetry currents to 4-point functions of scalar operators in the boundary conformal theory. A concise, covariant, Y2K compatible derivation of the gauge boson propagator in AdS d + 1 is given. Techniques are developed to calculate the two bulk integrals over AdS space leading to explicit expressions or convenient, simple integral representations for the amplitude. The amplitude contains leading power and sub-leading logarithmic singularities in the gauge boson channel and leading logarithms in the crossed channel. The new methods of this paper are expected to have other applications in the study of the Maldacena conjecture.

Laser Assisted Microsurgical Anastomosis.

DTIC Science & Technology

1983-09-22

motion exercises of the patient post surgery and for the development of appropriate regimes for nursing and general rehabilitation of the patient...8217AD-Ai4S 48? LASER ASSISTED MICROSUROICAL ANASTOMOSIS(U) MIAMI UNIV i/i FL DEPT OF ORTHOPAEDICS AND REHABILITATION N E BURKHALTER 22 SEP 83 NBBI4-i-K...William E. Burkhalter, M.D. NOO014-81-K-0446 Professor of Orthopaedics and Rehabilitation 0. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM

Laser Cladding of Composite Bioceramic Coatings on Titanium Alloy

NASA Astrophysics Data System (ADS)

Xu, Xiang; Han, Jiege; Wang, Chunming; Huang, Anguo

2016-02-01

In this study, silicon nitride (Si3N4) and calcium phosphate tribasic (TCP) composite bioceramic coatings were fabricated on a Ti6Al4V (TC4) alloy using Nd:YAG pulsed laser, CO2 CW laser, and Semiconductor CW laser. The surface morphology, cross-sectional microstructure, mechanical properties, and biological behavior were carefully investigated. These investigations were conducted employing scanning electron microscope, energy-dispersive x-ray spectroscopy, and other methodologies. The results showed that both Si3N4 and Si3N4/TCP composite coatings were able to form a compact bonding interface between the coating and the substrate by using appropriate laser parameters. The coating layers were dense, demonstrating a good surface appearance. The bioceramic coatings produced by laser cladding have good mechanical properties. Compared with that of the bulk material, microhardness of composite ceramic coatings on the surface significantly increased. In addition, good biological activity could be obtained by adding TCP into the composite coating.

Laser Diagnostics for Reacting Flows

DTIC Science & Technology

2007-01-30

image the exit region of an underexpanded jet. Background IRPLIF involves the excitation of molecular vibrational modes via infrared laser radiation (an...excitation wavelength of 2.0 pm is used for this work), followed by imaging of the subsequent vibrational fluorescence (fluorescence is collected...with an IR-active vibrational mode, such as CO2, are naturally present in sufficient abundance. Even in situations where they need to be added, small

Next-Generation A/D Sampler ADS3000+ for VLBI2010

NASA Technical Reports Server (NTRS)

Takefuji, Kazuhiro; Takeuchi, Hiroshi; Tsutsumi, Masanori; Koyama, Yasuhiro

2010-01-01

A high-speed A/D sampler, called ADS3000+, has been developed in 2008, which can sample one analog signal up to 4 Gbps to versatile Linux PC. After A/D conversion, the ADS3000+ can perform digital signal processing such as real-time DBBC (Digital Base Band Conversion) and FIR filtering such as simple CW RFI filtering using the installed FPGAs. A 4 Gsps fringe test with the ADS3000+ has been successfully performed. The ADS3000+ will not exclusively be used for VLBI but will also be employed in other applications.

High Average Power Diode Pumped Solid State Lasers: Power Scaling With High Spectral and Spatial Coherence

DTIC Science & Technology

2009-03-30

seeded with 15 W of single-frequency laser light at 1064 nm and cladding -pumped of 700 W in the forward direction and 300 W in the opposite direction...57-W single-mode phosphate fiber laser Our early studies of phosphate fiber lasers taught us that adding an air-hole to the inner cladding and... cladding -pumped with a fiber-coupled laser diode at 977 nm through a dichroic beam splitter placed on the OC side. The fiber ends were cooled using the

Laser parametric instability experiments of a 3ω, 15 kJ, 6-ns laser pulse in gas-filled hohlraums at the Ligne d'Intégration Laser facility

NASA Astrophysics Data System (ADS)

Rousseaux, C.; Huser, G.; Loiseau, P.; Casanova, M.; Alozy, E.; Villette, B.; Wrobel, R.; Henry, O.; Raffestin, D.

2015-02-01

Experimental investigation of stimulated Raman (SRS) and Brillouin (SBS) scattering have been obtained at the Ligne-d'Intégration-Laser facility (LIL, CEA-Cesta, France). The parametric instabilities (LPI) are driven by firing four laser beamlets (one quad) into millimeter size, gas-filled hohlraum targets. A quad delivers energy on target of 15 kJ at 3ω in a 6-ns shaped laser pulse. The quad is focused by means of 3ω gratings and is optically smoothed with a kinoform phase plate and with smoothing by spectral dispersion-like 2 GHz and/or 14 GHz laser bandwidth. Open- and closed-geometry hohlraums have been used, all being filled with 1-atm, neo-pentane (C5H12) gas. For SRS and SBS studies, the light backscattered into the focusing optics is analyzed with spectral and time resolutions. Near-backscattered light at 3ω and transmitted light at 3ω are also monitored in the open geometry case. Depending on the target geometry (plasma length and hydrodynamic evolution of the plasma), it is shown that, at maximum laser intensity about 9 × 1014 W/cm2, Raman reflectivity noticeably increases up to 30% in 4-mm long plasmas while SBS stays below 10%. Consequently, laser transmission through long plasmas drops to about 10% of incident energy. Adding 14 GHz bandwidth to the laser always reduces LPI reflectivities, although this reduction is not dramatic.

Semiconductor Lasers Containing Quantum Wells in Junctions

NASA Technical Reports Server (NTRS)

Yang, Rui Q.; Qiu, Yueming

2004-01-01

In a recent improvement upon In(x)Ga(1-x)As/InP semiconductor lasers of the bipolar cascade type, quantum wells are added to Esaki tunnel junctions, which are standard parts of such lasers. The energy depths and the geometric locations and thicknesses of the wells are tailored to exploit quantum tunneling such that, as described below, electrical resistances of junctions and concentrations of dopants can be reduced while laser performances can be improved. In(x)Ga(1-x)As/InP bipolar cascade lasers have been investigated as sources of near-infrared radiation (specifically, at wavelengths of about 980 and 1,550 nm) for photonic communication systems. The Esaki tunnel junctions in these lasers have been used to connect adjacent cascade stages and to enable transport of charge carriers between them. Typically, large concentrations of both n (electron-donor) and p (electron-acceptor) dopants have been necessary to impart low electrical resistances to Esaki tunnel junctions. Unfortunately, high doping contributes free-carrier absorption, thereby contributing to optical loss and thereby, further, degrading laser performance. In accordance with the present innovation, quantum wells are incorporated into the Esaki tunnel junctions so that the effective heights of barriers to quantum tunneling are reduced (see figure).

Proof of the Feasibility of Coherent and Incoherent Schemes for Pumping a Gamma-Ray Laser

DTIC Science & Technology

1988-07-01

DIP!; ilLE-CWPj AD-A 799 638 The University of Texas at DallasCenter for Quantlin, Electronics The Gamma-Ray Laser Project Quarterly Report April...AND INCOHERENT SCHEMES FOR PUMPING A GAMMA-RAY LASER Principal Investigator: Carl B. Collins The University of Texas at Dallas Center for Quantum...FEASIBILITY OF Quarterly Technical Progress COHERENT AND INCOHERENT SCHEMES /I/RR - 61WARA FOR PUMPING A GAMMA-RAY LASER 6.PERFORMINO ORG. REPORT NUMBER

Laser frequency stabilization and shifting by using modulation transfer spectroscopy

NASA Astrophysics Data System (ADS)

Cheng, Bing; Wang, Zhao-Ying; Wu, Bin; Xu, Ao-Peng; Wang, Qi-Yu; Xu, Yun-Fei; Lin, Qiang

2014-10-01

The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 → F' = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro—optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.

Geoscience laser altimeter system-stellar reference system

NASA Astrophysics Data System (ADS)

Millar, Pamela S.; Sirota, J. Marcos

1998-01-01

GLAS is an EOS space-based laser altimeter being developed to profile the height of the Earth's ice sheets with ~15 cm single shot accuracy from space under NASA's Mission to Planet Earth (MTPE). The primary science goal of GLAS is to determine if the ice sheets are increasing or diminishing for climate change modeling. This is achieved by measuring the ice sheet heights over Greenland and Antarctica to 1.5 cm/yr over 100 km×100 km areas by crossover analysis (Zwally 1994). This measurement performance requires the instrument to determine the pointing of the laser beam to ~5 urad (1 arcsecond), 1-sigma, with respect to the inertial reference frame. The GLAS design incorporates a stellar reference system (SRS) to relate the laser beam pointing angle to the star field with this accuracy. This is the first time a spaceborne laser altimeter is measuring pointing to such high accuracy. The design for the stellar reference system combines an attitude determination system (ADS) with a laser reference system (LRS) to meet this requirement. The SRS approach and expected performance are described in this paper.

Vacuum degeneracy and Conformal Mass in Lovelock AdS gravity

NASA Astrophysics Data System (ADS)

Arenas-Henriquez, Gabriel; Miskovic, Olivera; Olea, Rodrigo

2017-11-01

It is shown that the notion of Conformal Mass can be defined within a given anti-de Sitter (AdS) branch of a Lovelock gravity theory as long as the corresponding vacuum is not degenerate. Indeed, conserved charges obtained by the addition of Kounterterms to the bulk action turn out to be proportional to the electric part of the Weyl tensor, when the fall-off of a generic solution in that AdS branch is considered. The factor of proportionality is the degeneracy condition for the vacua in the particular Lovelock AdS theory under study. This last feature explains the obstruction to define Conformal Mass in the degenerate case.

Heat effect of pulsed Er:YAG laser radiation

NASA Astrophysics Data System (ADS)

Hibst, Raimund; Keller, Ulrich

1990-06-01

Pulsed Er:YAG laser radiation has been found to be effective for dental enamel and dentin removal. Damage to the surrounding hard tissue is little, but before testing the Er:YAG laser clinically for the preparation of cavities, possible effects on the soft tissue of the pulp must be known. In order to estimate pulp damage , temperature rise in dentin caused by the laser radiation was measured by a thermocouple. Additionally, temperature distributions were observed by means of a thermal imaging system. The heat effect of a single Er:YAG laser pulse is little and limited to the vicinity of the impact side. Because heat energy is added with each additional pulse , the temperature distribution depends not only on the radiant energy, but also on the number of pulses and the repetition rate. Both irradiation conditions can be found , making irreversible pulp damage either likely or unlikely. The experimental observations can be explained qualitatively by a simple model of the ablation process.

Picosecond absorption relaxation measured with nanosecond laser photoacoustics

PubMed Central

Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

2010-01-01

Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural—including strongly scattering and nonfluorescent—materials. PMID:21079726

Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

PubMed

Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

2010-10-18

Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

Performance Modeling of an Experimental Laser Propelled Lightcraft

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Chen, Yen-Sen; Liu, Jiwen; Myrabo, Leik N.; Mead, Franklin B., Jr.

2000-01-01

A computational plasma aerodynamics model is developed to study the performance of an experimental laser propelled lightcraft. The computational methodology is based on a time-accurate, three-dimensional, finite-difference, chemically reacting, unstructured grid, pressure- based formulation. The underlying physics are added and tested systematically using a building-block approach. The physics modeled include non-equilibn'um thermodynamics, non-equilibrium air-plasma finite-rate kinetics, specular ray tracing, laser beam energy absorption and equi refraction by plasma, non-equilibrium plasma radiation, and plasma resonance. A series of transient computations are performed at several laser pulse energy levels and the simulated physics are discussed and compared with those of tests and literature. The predicted coupling coefficients for the lightcraft compared reasonably well with those of tests conducted on a pendulum apparatus.

Featured Invention: Laser Scaling Device

NASA Technical Reports Server (NTRS)

Dunn, Carol Anne

2008-01-01

In September 2003, NASA signed a nonexclusive license agreement with Armor Forensics, a subsidiary of Armor Holdings, Inc., for the laser scaling device under the Innovative Partnerships Program. Coupled with a measuring program, also developed by NASA, the unit provides crime scene investigators with the ability to shoot photographs at scale without having to physically enter the scene, analyzing details such as bloodspatter patterns and graffiti. This ability keeps the scene's components intact and pristine for the collection of information and evidence. The laser scaling device elegantly solved a pressing problem for NASA's shuttle operations team and also provided industry with a useful tool. For NASA, the laser scaling device is still used to measure divots or damage to the shuttle's external tank and other structures around the launchpad. When the invention also met similar needs within industry, the Innovative Partnerships Program provided information to Armor Forensics for licensing and marketing the laser scaling device. Jeff Kohler, technology transfer agent at Kennedy, added, "We also invited a representative from the FBI's special photography unit to Kennedy to meet with Armor Forensics and the innovator. Eventually the FBI ended up purchasing some units. Armor Forensics is also beginning to receive interest from DoD [Department of Defense] for use in military crime scene investigations overseas."

Diffusion and chaos from near AdS 2 horizons

DOE PAGES

Blake, Mike; Donos, Aristomenis

2017-02-03

We calculate the thermal diffusivity D =more » $$\\kappa/c_\\rho$$ and butterfy velocity $$\\upsilon_\\beta$$ in holographic models that flow to $$AdS_2$$ x $R^d$ fixed points in the infra-red. We show that both these quantities are governed by the same irrelevant deformation of $$AdS_2$$ and hence establish a simple relationship between them. When this deformation corresponds to a universal dilaton mode of dimension $$\\Delta$$ = 2 then this relationship is always given by D = $$\\upsilon_B^2$$/(2$$\\pi$$T).« less

AdS6 solutions of type II supergravity

NASA Astrophysics Data System (ADS)

Apruzzi, Fabio; Fazzi, Marco; Passias, Achilleas; Rosa, Dario; Tomasiello, Alessandro

2014-11-01

Very few AdS6 × M 4 supersymmetric solutions are known: one in massive IIA, and two IIB solutions dual to it. The IIA solution is known to be unique; in this paper, we use the pure spinor approach to give a classification for IIB supergravity. We reduce the problem to two PDEs on a two-dimensional space Σ. M 4 is then a fibration of S 2 over Σ; the metric and fluxes are completely determined in terms of the solution to the PDEs. The results seem likely to accommodate near-horizon limits of ( p, q)-fivebrane webs studied in the literature as a source of CFT5's. We also show that there are no AdS6 solutions in eleven-dimensional supergravity.

Geometry and supersymmetry of heterotic warped flux AdS backgrounds

NASA Astrophysics Data System (ADS)

Beck, S.; Gutowski, J.; Papadopoulos, G.

2015-07-01

We classify the geometries of the most general warped, flux AdS backgrounds of heterotic supergravity up to two loop order in sigma model perturbation theory. We show under some mild assumptions that there are no AdS n backgrounds with n ≠ 3. Moreover the warp factor of AdS3 backgrounds is constant, the geometry is a product AdS 3 × M 7 and such solutions preserve, 2, 4, 6 and 8 supersymmetries. The geometry of M 7 has been specified in all cases. For 2 supersymmetries, it has been found that M 7 admits a suitably restricted G 2 structure. For 4 supersymmetries, M 7 has an SU(3) structure and can be described locally as a circle fibration over a 6-dimensional KT manifold. For 6 and 8 supersymmetries, M 7 has an SU(2) structure and can be described locally as a S 3 fibration over a 4-dimensional manifold which either has an anti-self dual Weyl tensor or a hyper-Kähler structure, respectively. We also demonstrate a new Lichnerowicz type theorem in the presence of α' corrections.

[Value-Added--Adding Economic Value in the Food Industry].

ERIC Educational Resources Information Center

Welch, Mary A., Ed.

1989-01-01

This booklet focuses on the economic concept of "value added" to goods and services. A student activity worksheet illustrates how the steps involved in processing food are examples of the concept of value added. The booklet further links food processing to the idea of value added to the Gross National Product (GNP). Discussion questions,…

IR-laser assisted additive freeform optics manufacturing.

PubMed

Hong, Zhihan; Liang, Rongguang

2017-08-02

Computer-controlled additive manufacturing (AM) processes, also known as three-dimensional (3D) printing, create 3D objects by the successive adding of a material or materials. While there have been tremendous developments in AM, the 3D printing of optics is lagging due to the limits in materials and tight requirements for optical applicaitons. We propose a new precision additive freeform optics manufacturing (AFOM) method using an pulsed infrared (IR) laser. Compared to ultraviolet (UV) curable materials, thermally curable optical silicones have a number of advantages, such as strong UV stability, non-yellowing, and high transmission, making it particularly suitable for optical applications. Pulsed IR laser radiation offers a distinct advantage in processing optical silicones, as the high peak intensity achieved in the focal region allows for curing the material quickly, while the brief duration of the laser-material interaction creates a negligible heat-affected zone.

Generation of cavitation luminescence by laser-induced exothermic chemical reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung Park, Han; Diebold, Gerald J.

2013-08-14

Absorption of high power laser radiation by aqueous carbon suspensions is known to result in the formation of highly compressed bubbles of hydrogen and carbon monoxide through the endothermic carbon-steam reaction. The bubbles expand rapidly, overreaching their equilibrium diameter, and then collapse tens to hundreds of microseconds after formation to give a flash of radiation. Here we report on the effects of laser-initiated exothermic chemical reaction on cavitation luminescence. Experiments with hydrogen peroxide added to colloidal carbon suspensions show that both the time of the light flash following the laser pulse and the intensity of luminescence increase with hydrogen peroxidemore » concentration, indicating that large, highly energetic gas bubbles are produced. Additional experiments with colloidal carbon suspensions show the effects of high pressure on the luminescent intensity and its time of appearance following firing of the laser.« less

Thermodynamic and classical instability of AdS black holes in fourth-order gravity

NASA Astrophysics Data System (ADS)

Myung, Yun Soo; Moon, Taeyoon

2014-04-01

We study thermodynamic and classical instability of AdS black holes in fourth-order gravity. These include the BTZ black hole in new massive gravity, Schwarzschild-AdS black hole, and higher-dimensional AdS black holes in fourth-order gravity. All thermo-dynamic quantities which are computed using the Abbot-Deser-Tekin method are used to study thermodynamic instability of AdS black holes. On the other hand, we investigate the s-mode Gregory-Laflamme instability of the massive graviton propagating around the AdS black holes. We establish the connection between the thermodynamic instability and the GL instability of AdS black holes in fourth-order gravity. This shows that the Gubser-Mitra conjecture holds for AdS black holes found from fourth-order gravity.

Laser-Induced Modification Of Energy Bands Of Transparent Solids

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly

2010-10-01

Laser-induced variations of electron energy bands of transparent solids significantly affect the initial stages of laser-induced ablation (LIA) influencing rates of ionization and light absorption by conduction-band electrons. We analyze fast variations with characteristic duration in femto-second time domain that include: 1) switching electron functions from bonding to anti-bonding configuration due to laser-induced ionization; 2) laser-driven oscillations of electrons in quasi-momentum space; and 3) direct distortion of the inter-atomic potential by electric field of laser radiation. Among those effects, the latter two have zero delay and reversibly modify band structure taking place from the beginning of laser action. They are of special interest due to their strong influence on the initial stage and threshold of laser ablation. The oscillations modify the electron-energy bands by adding pondermotive potential. The direct action of radiation's electric field leads to high-frequency Franz-Keldysh effect (FKE) spreading the allowed electron states into the forbidden-energy bands. FKE provides decrease of the effective band gap while the electron oscillations lead either to monotonous increase or oscillatory variations of the gap. We analyze the competition between those two opposite trends and their role in initiating LIA.

Collapse and Nonlinear Instability of AdS Space with Angular Momentum

NASA Astrophysics Data System (ADS)

Choptuik, Matthew W.; Dias, Óscar J. C.; Santos, Jorge E.; Way, Benson

2017-11-01

We present a numerical study of rotational dynamics in AdS5 with equal angular momenta in the presence of a complex doublet scalar field. We determine that the endpoint of gravitational collapse is a Myers-Perry black hole for high energies and a hairy black hole for low energies. We investigate the time scale for collapse at low energies E , keeping the angular momenta J ∝E in anti-de Sitter (AdS) length units. We find that the inclusion of angular momenta delays the collapse time, but retains a t ˜1 /E scaling. We perturb and evolve rotating boson stars, and find that boson stars near AdS space appear stable, but those sufficiently far from AdS space are unstable. We find that the dynamics of the boson star instability depend on the perturbation, resulting either in collapse to a Myers-Perry black hole, or development towards a stable oscillating solution.

On information loss in AdS 3/CFT 2

DOE PAGES

Fitzpatrick, A. Liam; Kaplan, Jared; Li, Daliang; ...

2016-05-18

We discuss information loss from black hole physics in AdS 3, focusing on two sharp signatures infecting CFT 2 correlators at large central charge c: ‘forbidden singularities’ arising from Euclidean-time periodicity due to the effective Hawking temperature, and late-time exponential decay in the Lorentzian region. We study an infinite class of examples where forbidden singularities can be resolved by non-perturbative effects at finite c, and we show that the resolution has certain universal features that also apply in the general case. Analytically continuing to the Lorentzian regime, we find that the non-perturbative effects that resolve forbidden singularities qualitatively change themore » behavior of correlators at times t ~S BH, the black hole entropy. This may resolve the exponential decay of correlators at late times in black hole backgrounds. By Borel resumming the 1/c expansion of exact examples, we explicitly identify ‘information-restoring’ effects from heavy states that should correspond to classical solutions in AdS 3. Lastly, our results suggest a line of inquiry towards a more precise formulation of the gravitational path integral in AdS 3.« less

Semiclassical Virasoro blocks from AdS 3 gravity

DOE PAGES

Hijano, Eliot; Kraus, Per; Perlmutter, Eric; ...

2015-12-14

We present a unified framework for the holographic computation of Virasoro conformal blocks at large central charge. In particular, we provide bulk constructions that correctly reproduce all semiclassical Virasoro blocks that are known explicitly from conformal field theory computations. The results revolve around the use of geodesic Witten diagrams, recently introduced in [1], evaluated in locally AdS 3 geometries generated by backreaction of heavy operators. We also provide an alternative computation of the heavy-light semiclassical block — in which two external operators become parametrically heavy — as a certain scattering process involving higher spin gauge fields in AdS 3; thismore » approach highlights the chiral nature of Virasoro blocks. Finally, these techniques may be systematically extended to compute corrections to these blocks and to interpolate amongst the different semiclassical regimes.« less

EXACT S-MATRICES FOR AdS3/CFT2

NASA Astrophysics Data System (ADS)

Ahn, Changrim; Bombardelli, Diego

2013-12-01

We propose exact S-matrices for the AdS3/CFT2 duality between type IIB strings on AdS3×S3×M4 with M4 = S3×S1 or T4 and the corresponding two-dimensional conformal field theories. We fix the two-particle S-matrices on the basis of the symmetries su(1|1) and su(1|1)×su(1|1). A crucial justification comes from the derivation of the all-loop Bethe ansatz matching exactly the recent conjecture proposed by Babichenko et al. [J. High Energy Phys.1003, 058 (2010), arXiv:0912.1723 [hep-th

Minimal surfaces in AdS space and integrable systems

NASA Astrophysics Data System (ADS)

Burrington, Benjamin A.; Gao, Peng

2010-04-01

We consider the Pohlmeyer reduction for spacelike minimal area worldsheets in AdS5. The Lax pair for the reduced theory is found, and written entirely in terms of the A3 = D3 root system, generalizing the B2 affine Toda system which appears for the AdS4 string. For the B2 affine Toda system, we show that the area of the worlsheet is obtainable from the moduli space Kähler potential of a related Hitchin system. We also explore the Saveliev-Leznov construction for solutions of the B2 affine Toda system, and recover the rotationally symmetric solution associated to Painleve transcendent.

Financial and health literacy predict incident AD dementia and AD pathology

PubMed Central

Yu, Lei; Wilson, Robert S.; Schneider, Julie A.; Bennett, David A.; Boyle, Patricia A.

2017-01-01

Background Domain specific literacy is a multidimensional construct that requires multiple resources including cognitive and non-cognitive factors. Objective We test the hypothesis that domain specific literacy is associated with AD dementia and AD pathology after controlling for cognition. Methods Participants were community based older persons who completed a baseline literacy assessment, underwent annual clinical evaluations for up to 8 years and agreed to organ donation after death. Financial and health literacy was measured using 32 questions and cognition was measured using 19 tests. Annual diagnosis of AD dementia followed standard criteria. AD pathology was examined post-mortem by quantifying plaques and tangles. Cox models examined the association of literacy with incident AD dementia. Performance of model prediction for incident AD dementia was assessed using indices for integrated discrimination improvement and continuous net reclassification improvement. Linear regression models examined the independent association of literacy with AD pathology in autopsied participants. Results All 805 participants were free of dementia at baseline and 102 (12.7%) developed AD dementia during the follow-up. Lower literacy was associated with higher risk for incident AD dementia (p<0.001), and the association persisted after controlling for cognition (Hazard Ratio=1.50, p=0.004). The model including the literacy measure had better predictive performance than the one with demographics and cognition only. Lower literacy also was associated with higher burden of AD pathology after controlling for cognition (β=0.07, p=0.035). Conclusion Literacy predicts incident AD dementia and AD pathology in community-dwelling older persons, and the association is independent of traditional measures of cognition. PMID:28157101

3D printing of graphene-doped target for "matrix-free" laser desorption/ionization mass spectrometry.

PubMed

Wang, Dingyi; Huang, Xiu; Li, Jie; He, Bin; Liu, Qian; Hu, Ligang; Jiang, Guibin

2018-03-13

We report a graphene-doped resin target fabricated via a 3D printing technique for laser desorption/ionization mass spectrometry analysis. The graphene doped in the target acts as an inherent laser absorber and ionization promoter, thus permitting the direct analysis of samples without adding matrix. This work reveals a new strategy for easy designing and fabrication of functional mass spectrometry devices.

What's the point? Hole-ography in Poincaré AdS

NASA Astrophysics Data System (ADS)

Espíndola, Ricardo; Güijosa, Alberto; Landetta, Alberto; Pedraza, Juan F.

2018-01-01

In the context of the AdS/CFT correspondence, we study bulk reconstruction of the Poincaré wedge of AdS_3 via hole-ography, i.e., in terms of differential entropy of the dual CFT_2. Previous work had considered the reconstruction of closed or open spacelike curves in global AdS, and of infinitely extended spacelike curves in Poincaré AdS that are subject to a periodicity condition at infinity. Working first at constant time, we find that a closed curve in Poincaré is described in the CFT by a family of intervals that covers the spatial axis at least twice. We also show how to reconstruct open curves, points and distances, and obtain a CFT action whose extremization leads to bulk points. We then generalize all of these results to the case of curves that vary in time, and discover that generic curves have segments that cannot be reconstructed using the standard hole-ographic construction. This happens because, for the nonreconstructible segments, the tangent geodesics fail to be fully contained within the Poincaré wedge. We show that a previously discovered variant of the hole-ographic method allows us to overcome this challenge, by reorienting the geodesics touching the bulk curve to ensure that they all remain within the wedge. Our conclusion is that all spacelike curves in Poincaré AdS can be completely reconstructed with CFT data, and each curve has in fact an infinite number of representations within the CFT.

Measurement of Fluorine Atom Concentrations and Reaction Rates in Chemical Laser Systems.

DTIC Science & Technology

1981-09-01

AD-A1RA 070 AERODYNEERESEARCHUINC BEDFORDM MA F/6_20/5 MEASURE MENT OF FLUORINE ATOM CONCENTRATIONS AND REACTION RATFS -ETC(U) SEP_ A A C STANT ON...0772 LEVELIg 00 ~ARI-RR-272 cO0 MEASUREMENT OF FLUORINE ATOM CONCENTRATIONS AND REACTION RATES IN CHEMICAL LASER SYSTEMS ANNUAL TECHNICAL REPORT by...MEASUREMENT OF FLUORINE ATOM CONCENTRATIONS AND Annual Report REACTION RATES IN CHEMICAL LASER SYSTEMS 23 July 1980 - 23 July 1981 S. PERFORMING ORG. REPORT

Bubble formation during pulsed laser ablation: mechanism and implications

NASA Astrophysics Data System (ADS)

van Leeuwen, Ton G. J. M.; Jansen, E. Duco; Motamedi, Massoud; Welch, Ashley J.; Borst, Cornelius

1993-07-01

Holmium ((lambda) equals 2.09 micrometers ) and excimer ((lambda) equals 308 nm) lasers are used for ablation of tissue. In a previous study it was demonstrated that both excimer and holmium laser pulses produce fast expanding and collapsing vapor bubbles. To investigate whether the excimer induced bubble is caused by vaporization of water, the threshold fluence for bubble formation at a bare fiber tip in water was compared between the excimer laser (pulse length 115 ns) and the Q-switched and free-running holmium lasers (pulse length 1 microsecond(s) to 250 microsecond(s) , respectively). To induce bubble formation by excimer laser light in water, the absorber oxybuprocaine-hydrochloride (OBP-HCl) was added to the water. Fast flash photography was used to measure the threshold fluence as a function of the water temperature (6 - 90 degree(s)C) at environmental pressure. The ultraviolet excimer laser light is strongly absorbed by blood. Therefore, to document the implications of bubble formation at fluences above the tissue ablation threshold, excimer laser pulses were delivered in vitro in hemoglobin solution and in vivo in the femoral artery of the rabbit. We conclude that the principal content of the fast bubble induced by a 308 nm excimer laser pulse is water vapor. Therefore, delivery of excimer laser pulses in a water or blood environment will cause fast expanding water vapor bubbles, which may induce mechanical damage to adjacent tissue.

String in AdS black hole: A thermo field dynamic approach

NASA Astrophysics Data System (ADS)

Cantcheff, M. Botta; Gadelha, Alexandre L.; Marchioro, Dáfni F. Z.; Nedel, Daniel Luiz

2012-10-01

Based on Maldacena’s description of an eternal anti-de Sitter (AdS) black hole, we reassess the thermo field dynamics (TFD) formalism in the context of the AdS/CFT correspondence. The model studied here involves the maximally extended AdS-Schwarschild solution and two (noninteracting) copies of the conformal field theory (CFT) associated to the global AdS spacetime, along with an extension of the string by imposing natural gluing conditions in the horizon. We show that the gluing conditions in the horizon define a string boundary state which is identified with the TFD thermal vacuum, globally defined in the Kruskal extension of the AdS black hole. We emphasize the connection of this picture with unitary SU(1,1) TFD formulation, and we show that information about the bulk and the conformal boundary is present in the SU(1,1) parameters. Using the unitary SU(1,1) TFD formulation, a canonical prescription for calculating the world sheet real time thermal Green’s function is made, and the entropy associated with the entanglement of the two CFT’s is calculated.

Tweaking one-loop determinants in AdS3

NASA Astrophysics Data System (ADS)

Castro, Alejandra; Keeler, Cynthia; Szepietowski, Phillip

2017-10-01

We revisit the subject of one-loop determinants in AdS3 gravity via the quasi-normal mode method. Our goal is to evaluate a one-loop determinant with chiral boundary conditions for the metric field; chirality is achieved by imposing Dirichlet boundary conditions on certain components while others satisfy Neumann. Along the way, we give a generalization of the quasinormal mode method for stationary (non-static) thermal backgrounds, and propose a treatment for Neumann boundary conditions in this framework. We evaluate the graviton one-loop determinant on the Euclidean BTZ background with parity-violating boundary conditions (CSS), and find excellent agreement with the dual warped CFT. We also discuss a more general falloff in AdS3 that is related to two dimensional quantum gravity in lightcone gauge. The behavior of the ghost fields under both sets of boundary conditions is novel and we discuss potential interpretations.

Continuous-spin mixed-symmetry fields in AdS(5)

NASA Astrophysics Data System (ADS)

Metsaev, R. R.

2018-05-01

Free mixed-symmetry continuous-spin fields propagating in AdS(5) space and flat R(4,1) space are studied. In the framework of a light-cone gauge formulation of relativistic dynamics, we build simple actions for such fields. The realization of relativistic symmetries on the space of light-cone gauge mixed-symmetry continuous-spin fields is also found. Interrelations between constant parameters entering the light-cone gauge actions and eigenvalues of the Casimir operators of space-time symmetry algebras are obtained. Using these interrelations and requiring that the field dynamics in AdS(5) be irreducible and classically unitary, we derive restrictions on the constant parameters and eigenvalues of the second-order Casimir operator of the algebra.

Photovoltaic cells for laser power beaming

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Jain, Raj K.

1992-01-01

To better understand cell response to pulsed illumination at high intensity, the PC-1DC finite-element computer model was used to analyze the response of solar cells to pulsed laser illumination. Over 50% efficiency was calculated for both InP and GaAs cells under steady-state illumination near the optimum wavelength. The time-dependent response of a high-efficiency GaAs concentrator cell to a laser pulse was modelled, and the effect of laser intensity, wavelength, and bias point was studied. Designing a cell to accommodate pulsed input can be done either by accepting the pulsed output and designing a cell to minimize adverse effects due to series resistance and inductance, or to design a cell with a long enough minority carrier lifetime, so that the output of the cell will not follow the pulse shape. Two such design possibilities are a monolithic, low-inductance voltage-adding GaAs cell, or a high-efficiency, light-trapping silicon cell. The advantages of each design will be discussed.

Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflector.

PubMed

Moody, J D; Clancy, T J; Frieders, G; Celliers, P M; Ralph, J; Turnbull, D P

2014-11-01

Laser pre-pulse and early-time laser reflection from the hohlraum wall onto the capsule (termed "glint") can cause capsule imprint and unwanted early-time shocks on indirect drive implosion experiments. In a minor modification to the existing velocity interferometer system for any reflector diagnostic on NIF a fast-response vacuum photodiode was added to detect this light. The measurements show evidence of laser pre-pulse and possible light reflection off the hohlraum wall and onto the capsule.

F-theory and AdS3/CFT2 (2, 0)

NASA Astrophysics Data System (ADS)

Couzens, Christopher; Martelli, Dario; Schäfer-Nameki, Sakura

2018-06-01

We continue to develop the program initiated in [1] of studying supersymmetric AdS3 backgrounds of F-theory and their holographic dual 2d superconformal field theories, which are dimensional reductions of theories with varying coupling. Imposing 2d N=(0,2) supersymmetry,wederivethegeneralconditionsonthegeometryforTypeIIB AdS3 solutions with varying axio-dilaton and five-form flux. Locally the compact part of spacetime takes the form of a circle fibration over an eight-fold Y_8^{τ } , which is elliptically fibered over a base \\tilde{M}_6 . We construct two classes of solutions given in terms of a product ansatz \\tilde{M}_6}=Σ × {M}_4 , where Σ is a complex curve and \\tilde{M}_4 is locally a Kähler surface. In the first class \\tilde{M}_4 is globally a Kähler surface and we take the elliptic fibration to vary non-trivially over either of these two factors, where in both cases the metrics on the total space of the elliptic fibrations are not Ricci-flat. In the second class the metric on the total space of the elliptic fibration over either curve or surface are Ricci-flat. This results in solutions of the type AdS3 × K3 × ℳ 5 τ , dual to 2d (0, 2) SCFTs, and AdS3 × S 3/Γ × CY 3, dual to 2d (0, 4) SCFTs, respectively. In all cases we compute the charges for the dual field theories with varying coupling and find agreement with the holographic results. We also show that solutions with enhanced 2d N=(2,2) supersymmetry must have constant axio-dilaton. Allowing the internal geometry to be non-compact leads to the most general class of Type IIB AdS5 solutions with varying axio-dilaton, i.e. F-theoretic solutions, that are dual to 4d N=1 SCFTs.

High power multiple wavelength diode laser stack for DPSSL application without temperature control

NASA Astrophysics Data System (ADS)

Hou, Dong; Yin, Xia; Wang, Jingwei; Chen, Shi; Zhan, Yun; Li, Xiaoning; Fan, Yingmin; Liu, Xingsheng

2018-02-01

High power diode laser stack is widely used in pumping solid-state laser for years. Normally an integrated temperature control module is required for stabilizing the output power of solid-state laser, as the output power of the solid-state laser highly depends on the emission wavelength and the wavelength shift of diode lasers according to the temperature changes. However the temperature control module is inconvenient for this application, due to its large dimension, high electric power consumption and extra adding a complicated controlling system. Furthermore, it takes dozens of seconds to stabilize the output power when the laser system is turned on. In this work, a compact hard soldered high power conduction cooled diode laser stack with multiple wavelengths is developed for stabilizing the output power of solid-state laser in a certain temperature range. The stack consists of 5 laser bars with the pitch of 0.43mm. The peak output power of each bar in the diode laser stack reaches as much as 557W and the combined lasing wavelength spectrum profile spans 15nm. The solidstate laser, structured with multiple wavelength diode laser stacks, allows the ambient temperature change of 65°C without suddenly degrading the optical performance.

Stability of warped AdS3 vacua of topologically massive gravity

NASA Astrophysics Data System (ADS)

Anninos, Dionysios; Esole, Mboyo; Guica, Monica

2009-10-01

AdS3 vacua of topologically massive gravity (TMG) have been shown to be perturbatively unstable for all values of the coupling constant except the chiral point μl = 1. We study the possibility that the warped vacua of TMG, which exist for all values of μ, are stable under linearized perturbations. In this paper, we show that spacelike warped AdS3 vacua with Compère-Detournay boundary conditions are indeed stable in the range μl>3. This is precisely the range in which black hole solutions arise as discrete identifications of the warped AdS3 vacuum. The situation somewhat resembles chiral gravity: although negative energy modes do exist, they are all excluded by the boundary conditions, and the perturbative spectrum solely consists of boundary (pure large gauge) gravitons.

Comparison on different repetition rate locking methods in Er-doped fiber laser

NASA Astrophysics Data System (ADS)

Yang, Kangwen; Zhao, Peng; Luo, Jiang; Huang, Kun; Hao, Qiang; Zeng, Heping

2018-05-01

We demonstrate a systematic comparative research on the all-optical, mechanical and opto-mechanical repetition rate control methods in an Er-doped fiber laser. A piece of Yb-doped fiber, a piezoelectric transducer and an electronic polarization controller are simultaneously added in the laser cavity as different cavity length modulators. By measuring the cavity length tuning ranges, the output power fluctuations, the temporal and frequency repetition rate stability, we show that all-optical method introduces the minimal disturbances under current experimental condition.

Mitochondrial tRNALeu(UUR) C3275T, tRNAGln T4363C and tRNALys A8343G mutations may be associated with PCOS and metabolic syndrome.

PubMed

Ding, Yu; Xia, Bo-Hou; Zhang, Cai-Juan; Zhuo, Guang-Chao

2018-02-05

Polycystic ovary syndrome (PCOS) is a very prevalent endocrine disease affecting reproductive women. Clinically, patients with this disorder are more vulnerable to develop type 2 diabetes mellitus (T2DM), cardiovascular events, as well as metabolic syndrome (MetS). To date, the molecular mechanism underlying PCOS remains largely unknown. Previously, we showed that mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) mutation was an important cause for PCOS. In the current study, we described the clinical and biochemical features of a three-generation pedigree with maternally transmitted MetS, combined with PCOS. A total of three matrilineal relatives exhibited MetS including obesity, high triglyceride (TG) and Hemoglobin A1c (HbA1c) levels, and hypertension. Whereas one patient from the third generation manifestated PCOS. Mutational analysis of the whole mitochondrial genes from the affected individuals identified a set of genetic variations belonging to East Asia haplogroup B4b1c. Among these variants, the homoplasmic C3275T mutation disrupted a highly evolutionary conserved base-pairing (28A-46C) on the variable region of tRNA Leu(UUR) , whereas the T4363C mutation created a new base-pairing (31T-37A) in the anticodon stem of tRNA Gln , furthermore, the A8343G mutation occurred at the very conserved position of tRNA Lys and may result the failure in mitochondrial tRNAs (mt-tRNAs) metabolism. Biochemical analysis revealed the deficiency in mitochondrial functions including lower levels of mitochondrial membrane potential (MMP), ATP production and mtDNA copy number, while a significantly increased reactive oxygen species (ROS) generation was observed in polymononuclear leukocytes (PMNs) from the individuals carrying these mt-tRNA mutations, suggesting that these mutations may cause mitochondrial dysfunction that was responsible for the clinical phenotypes. Taken together, our data indicated that mt-tRNA mutations were associated with MetS and PCOS in this

The clinical characteristics of patients with mitochondrial tRNA Leu(UUR)m.3243A > G mutation: Compared with type 1 diabetes and early onset type 2 diabetes.

PubMed

Zhu, Jie; Yang, Peng; Liu, Xiang; Yan, Li; Rampersad, Sharvan; Li, Feng; Li, Hong; Sheng, Chunjun; Cheng, Xiaoyun; Zhang, Manna; Qu, Shen

2017-08-01

This study presents nine patients with mitochondrial tRNA Leu (UUR) m.3243A>G mutation and compares the clinical characteristics and diabetes complications with type 1 diabetes (T1DM) or early onset type 2 diabetes (T2DM). The study covers 9 patients with MIDD, 33 patients with T1DM and 86 patients (age of onset ≤35years) with early onset T2DM, matched for sex, age at onset of diabetes, duration of diabetes. All patients with MIDD were confirmed as carrying the m.3243A>G mitochondrial DNA mutation. Serum HbA1c, beta-cell function, retinal and renal complications of diabetes, bone metabolic markers, lumbar spine and femoral neck BMD bone mineral density were compared to characterize the clinical features of all patients. Nine patients were from five unrelated families, and the mean (SD) onset age of those patients was 31.2±7.2year. Two patients required insulin at presentation, and six patients progressed to insulin requirement after a mean of 7.2years. β-Cell function in the MIDD group was intermediate between T1DM and early-onset T2DM. In MIDD, four patients were diagnosed as diabetic retinopathy (4/9) and five patients (5/9) had macroalbuminuria. The number of patients with diabetic retinopathy and macroalbuminuria in the MIDD group was comparable to T1DM or early-onset T2DM. The rate of osteoporosis (BMD T-score<-2.5 SD) in the patient with MIDD was higher than the T1DM or early-onset T2DM group. Our study indicates that of the nine subjects with MIDD, three patients (1-II-1, 1-II-3, 1-II-4) who came from the same family had a history of acute pancreatitis. Compared with T1DM or early-onset T2DM matched for sex, age, duration of diabetes, MIDD patients had the highest rate of osteoporosis. Copyright © 2017 Elsevier Inc. All rights reserved.

17 CFR 240.17Ad-4 - Applicability of §§ 240.17Ad-2, 240.17Ad-3 and 240.17Ad-6(a) (1) through (7) and (11).

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Applicability of §§ 240.17Ad-2, 240.17Ad-3 and 240.17Ad-6(a) (1) through (7) and (11). 240.17Ad-4 Section 240.17Ad-4 Commodity... Commission or the Office of the Comptroller of the Currency, prepare and maintain in its possession a...

17 CFR 240.17Ad-4 - Applicability of §§ 240.17Ad-2, 240.17Ad-3 and 240.17Ad-6(a) (1) through (7) and (11).

Code of Federal Regulations, 2011 CFR

2011-04-01

... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Applicability of §§ 240.17Ad-2, 240.17Ad-3 and 240.17Ad-6(a) (1) through (7) and (11). 240.17Ad-4 Section 240.17Ad-4 Commodity... Commission or the Office of the Comptroller of the Currency, prepare and maintain in its possession a...

Nanosecond-laser induced crosstalk of CMOS image sensor

NASA Astrophysics Data System (ADS)

Zhu, Rongzhen; Wang, Yanbin; Chen, Qianrong; Zhou, Xuanfeng; Ren, Guangsen; Cui, Longfei; Li, Hua; Hao, Daoliang

2018-02-01

The CMOS Image Sensor (CIS) is photoelectricity image device which focused the photosensitive array, amplifier, A/D transfer, storage, DSP, computer interface circuit on the same silicon substrate[1]. It has low power consumption, high integration,low cost etc. With large scale integrated circuit technology progress, the noise suppression level of CIS is enhanced unceasingly, and its image quality is getting better and better. It has been in the security monitoring, biometrice, detection and imaging and even military reconnaissance and other field is widely used. CIS is easily disturbed and damaged while it is irradiated by laser. It is of great significance to study the effect of laser irradiation on optoelectronic countermeasure and device for the laser strengthening resistance is of great significance. There are some researchers have studied the laser induced disturbed and damaged of CIS. They focused on the saturation, supersaturated effects, and they observed different effects as for unsaturation, saturation, supersaturated, allsaturated and pixel flip etc. This paper research 1064nm laser interference effect in a typical before type CMOS, and observring the saturated crosstalk and half the crosstalk line. This paper extracted from cmos devices working principle and signal detection methods such as the Angle of the formation mechanism of the crosstalk line phenomenon are analyzed.

Interaction of gold nanoparticles with nanosecond laser pulses: Nanoparticle heating

NASA Astrophysics Data System (ADS)

Nedyalkov, N. N.; Imamova, S. E.; Atanasov, P. A.; Toshkova, R. A.; Gardeva, E. G.; Yossifova, L. S.; Alexandrov, M. T.; Obara, M.

2011-04-01

Theoretical and experimental results on the heating process of gold nanoparticles irradiated by nanosecond laser pulses are presented. The efficiency of particle heating is demonstrated by in-vitro photothermal therapy of human tumor cells. Gold nanoparticles with diameters of 40 and 100 nm are added as colloid in the cell culture and the samples are irradiated by nanosecond pulses at wavelength of 532 nm delivered by Nd:YAG laser system. The results indicate clear cytotoxic effect of application of nanoparticle as more efficient is the case of using particles with diameter of 100 nm. The theoretical analysis of the heating process of nanoparticle interacting with laser radiation is based on the Mie scattering theory, which is used for calculation of the particle absorption coefficient, and two-dimensional heat diffusion model, which describes the particle and the surrounding medium temperature evolution. Using this model the dependence of the achieved maximal temperature in the particles on the applied laser fluence and time evolution of the particle temperature is obtained.

Electronic gating circuit and ultraviolet laser excitation permit improved dosimeter sensitivity

NASA Technical Reports Server (NTRS)

Eggenberger, D.; King, D.; Longnecker, A.; Schutt, D.

1968-01-01

Standard dosimeter reader, modified by adding an electronic gating circuit to trigger the intensity level photomultiplier, increases readout sensitivity of photoluminescent dosimeter systems. The gating circuit is controlled by a second photomultiplier which senses a short ultraviolet pulse from a laser used to excite the dosimeter.

Infrared realization of dS2 in AdS2

NASA Astrophysics Data System (ADS)

Anninos, Dionysios; Hofman, Diego M.

2018-04-01

We describe a two-dimensional geometry that smoothly interpolates between an asymptotically AdS2 geometry and the static patch of dS2. We find this ‘centaur’ geometry to be a solution of dilaton gravity with a specific class of potentials for the dilaton. We interpret the centaur geometry as a thermal state in the putative quantum mechanics dual to the AdS2 evolved with the global Hamiltonian. We compute the thermodynamic properties and observe that the centaur state has finite entropy and positive specific heat. The static patch is the infrared part of the centaur geometry. We discuss boundary observables sensitive to the static patch region.

QCD Condensates and Holographic Wilson Loops for Asymptotically AdS Spaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quevedo, R. Carcasses; Goity, Jose L.; Trinchero, Roberto C.

2014-02-01

The minimization of the Nambu-Goto (NG) action for a surface whose contour defines a circular Wilson loop of radius a placed at a finite value of the coordinate orthogonal to the border is considered. This is done for asymptotically AdS spaces. The condensates of dimension n = 2, 4, 6, 8, and 10 are calculated in terms of the coefficients in the expansion in powers of the radius a of the on-shell subtracted NG action for small a->0. The subtraction employed is such that it presents no conflict with conformal invariance in the AdS case and need not introduce anmore » additional infrared scale for the case of confining geometries. It is shown that the UV value of the gluon condensates is universal in the sense that it only depends on the first coefficients of the difference with the AdS case.« less

An improved algorithm of laser spot center detection in strong noise background

NASA Astrophysics Data System (ADS)

Zhang, Le; Wang, Qianqian; Cui, Xutai; Zhao, Yu; Peng, Zhong

2018-01-01

Laser spot center detection is demanded in many applications. The common algorithms for laser spot center detection such as centroid and Hough transform method have poor anti-interference ability and low detection accuracy in the condition of strong background noise. In this paper, firstly, the median filtering was used to remove the noise while preserving the edge details of the image. Secondly, the binarization of the laser facula image was carried out to extract target image from background. Then the morphological filtering was performed to eliminate the noise points inside and outside the spot. At last, the edge of pretreated facula image was extracted and the laser spot center was obtained by using the circle fitting method. In the foundation of the circle fitting algorithm, the improved algorithm added median filtering, morphological filtering and other processing methods. This method could effectively filter background noise through theoretical analysis and experimental verification, which enhanced the anti-interference ability of laser spot center detection and also improved the detection accuracy.

Static Einstein-Maxwell Black Holes with No Spatial Isometries in AdS Space.

PubMed

Herdeiro, Carlos A R; Radu, Eugen

2016-11-25

We explicitly construct static black hole solutions to the fully nonlinear, D=4, Einstein-Maxwell-anti-de Sitter (AdS) equations that have no continuous spatial symmetries. These black holes have a smooth, topologically spherical horizon (section), but without isometries, and approach, asymptotically, global AdS spacetime. They are interpreted as bound states of a horizon with the Einstein-Maxwell-AdS solitons recently discovered, for appropriate boundary data. In sharp contrast to the uniqueness results for a Minkowski electrovacuum, the existence of these black holes shows that single, equilibrium, black hole solutions in an AdS electrovacuum admit an arbitrary multipole structure.

AdS 2 holographic dictionary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cvetic, Mirjam; Papadimitriou, Ioannis

Here, we construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well defined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetriesmore » and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Compère, Song and Strominger, in agreement with the results of Castro and Song. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS 2 × S 2 or conformally AdS 2 × S 2 solutions of the STU model in four dimensions, including non extremal black holes. As a result, the four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called ‘subtracted geometries�

AdS 2 holographic dictionary

DOE PAGES

Cvetic, Mirjam; Papadimitriou, Ioannis

2016-12-02

Here, we construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well defined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetriesmore » and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Compère, Song and Strominger, in agreement with the results of Castro and Song. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS 2 × S 2 or conformally AdS 2 × S 2 solutions of the STU model in four dimensions, including non extremal black holes. As a result, the four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called ‘subtracted geometries�

Witten diagrams revisited: the AdS geometry of conformal blocks

DOE PAGES

Hijano, Eliot; Kraus, Per; Perlmutter, Eric; ...

2016-01-25

Here, we develop a new method for decomposing blocks. The steps involved are elementary, requiring no explicit integration, and operate directly in position space. Central to this construction is an appealingly simple answer to the question: what object in AdS computes a conformal block? The answer is a "geodesic Witten diagram", which is essentially an ordinary exchange Witten diagram, except that the cubic vertices are not integrated over all of AdS, but only over bulk geodesics connecting the boundary operators. In particular, we also consider the case of four-point functions of scalar operators, and show how to easily reproduce existingmore » results for the relevant conformal blocks in arbitrary dimension.« less

Numerical study on the selective excitation of Helmholtz-Gauss beams in end-pumped solid-state digital lasers with the control of the laser gain transverse position provided by off-axis end pumping

NASA Astrophysics Data System (ADS)

Tsai, Ko-Fan; Chu, Shu-Chun

2018-03-01

This study proposes a complete and unified method for selective excitation of any specified nearly nondiffracting Helmholtz-Gauss (HzG) beam in end-pumped solid-state digital lasers. Four types of the HzG beams: cosine-Gauss beams, Bessel-Gauss beams, Mathieu-Gauss beams, and, in particular, parabolic-Gauss beams are successfully demonstrated to be generated with the proposed methods. To the best of the authors’ knowledge, parabolic-Gauss beams have not yet been directly generated from any kind of laser system. The numerical results of this study show that one can successfully achieve any lasing HzG beams directly from the solid-state digital lasers with only added control of the laser gain transverse position provided by off-axis end pumping. This study also presents a practical digital laser set-up for easily manipulating off-axis pumping in order to achieve the control of the laser gain transverse gain position in digital lasers. The reported results in this study provide advancement of digital lasers in dynamically generating nondiffracting beams. The control of the digital laser cavity gain position creates the possibility of achieving real-time selection of more laser modes in digital lasers, and it is worth further investigation in the future.

Generation of a cylindrically symmetric, polarized laser beam with narrow linewidth and fine tunability

NASA Astrophysics Data System (ADS)

Hirayama, Toru; Kozawa, Yuichi; Nakamura, Takahiro; Sato, Shunichi

2006-12-01

We demonstrated a generation of cylindrically symmetric, polarized laser beams with narrow linewidth and fine tunability. Since an LP11 mode beam in an optical fiber is a superposition of an HE21 (hybrid) mode beam and a TE01 or TM01 mode beam, firstly, a higher order transverse (TEM01 or TEM10) mode laser beam with narrow linewidth and fine tunability was generated from an external cavity diode laser (ECDL) in conjunction with a phase adjustment plate. Then the beam generated was passed in a two mode optical fiber. A doughnut shaped laser beam with the cylindrically symmetric polarization (a radially or azimuthally polarized beam) was obtained by properly adding stress-induced birefringence in the optical fiber.

Half-BPS Wilson loop and AdS 2/CFT 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giombi, Simone; Roiban, Radu; Tseytlin, Arkady A.

Here, we study correlation functions of local operator insertions on the 1/2-BPS Wilson line in N=4 super Yang–Mills theory. These correlation functions are constrained by the 1d superconformal symmetry pre-served by the 1/2-BPS Wilson line and define a defect CFT 1 living on the line. At strong coupling, a set of elementary operator insertions with protected scaling dimensions correspond to fluctuations of the dual fundamental string in AdS 5×S 5 ending on the line at the boundary and can be thought of as light fields propagating on the AdS 2 worldsheet. We use AdS/CFT techniques to compute the tree-level AdSmore » 2 Witten diagrams describing the strong coupling limit of the four-point functions of the dual operator insertions. Using the OPE, we also extract the leading strong coupling corrections to the anomalous dimensions of the “two-particle” operators built out of elementary excitations. In the case of the circular Wilson loop, we match our results for the 4-point functions of a special type of scalar insertions to the prediction of localization to 2d Yang–Mills theory.« less

Half-BPS Wilson loop and AdS 2/CFT 1

DOE PAGES

Giombi, Simone; Roiban, Radu; Tseytlin, Arkady A.

2017-09-01

Here, we study correlation functions of local operator insertions on the 1/2-BPS Wilson line in N=4 super Yang–Mills theory. These correlation functions are constrained by the 1d superconformal symmetry pre-served by the 1/2-BPS Wilson line and define a defect CFT 1 living on the line. At strong coupling, a set of elementary operator insertions with protected scaling dimensions correspond to fluctuations of the dual fundamental string in AdS 5×S 5 ending on the line at the boundary and can be thought of as light fields propagating on the AdS 2 worldsheet. We use AdS/CFT techniques to compute the tree-level AdSmore » 2 Witten diagrams describing the strong coupling limit of the four-point functions of the dual operator insertions. Using the OPE, we also extract the leading strong coupling corrections to the anomalous dimensions of the “two-particle” operators built out of elementary excitations. In the case of the circular Wilson loop, we match our results for the 4-point functions of a special type of scalar insertions to the prediction of localization to 2d Yang–Mills theory.« less

Value Added?

ERIC Educational Resources Information Center

UCLA IDEA, 2012

2012-01-01

Value added measures (VAM) uses changes in student test scores to determine how much "value" an individual teacher has "added" to student growth during the school year. Some policymakers, school districts, and educational advocates have applauded VAM as a straightforward measure of teacher effectiveness: the better a teacher,…

Evaporation of large black holes in AdS: coupling to the evaporon

NASA Astrophysics Data System (ADS)

Rocha, Jorge V.

2008-08-01

Large black holes in an asymptotically AdS spacetime have a dual description in terms of approximately thermal states in the boundary CFT. The reflecting boundary conditions of AdS prevent such black holes from evaporating completely. On the other hand, the formulation of the information paradox becomes more stringent when a black hole is allowed to evaporate. In order to address the information loss problem from the AdS/CFT perspective we then need the boundary to become partially absorptive. We present a simple model that produces the necessary changes on the boundary by coupling a bulk scalar field to the evaporon, an external field propagating in one extra spatial dimension. The interaction is localized at the boundary of AdS and leads to partial transmission into the additional space. The transmission coefficient is computed in the planar limit and perturbatively in the coupling constant. Evaporation of the large black hole corresponds to cooling down the CFT by transferring energy to an external sector.

Hairy black holes and the endpoint of AdS4 charged superradiance

NASA Astrophysics Data System (ADS)

Dias, Óscar J. C.; Masachs, Ramon

2017-02-01

We construct hairy black hole solutions that merge with the anti-de Sitter (AdS4) Reissner-Nordström black hole at the onset of superradiance. These hairy black holes have, for a given mass and charge, higher entropy than the corresponding AdS4-Reissner-Nordström black hole. Therefore, they are natural candidates for the endpoint of the charged superradiant instability. On the other hand, hairy black holes never dominate the canonical and grand-canonical ensembles. The zero-horizon radius of the hairy black holes is a soliton (i.e. a boson star under a gauge transformation). We construct our solutions perturbatively, for small mass and charge, so that the properties of hairy black holes can be used to testify and compare with the endpoint of initial value simulations. We further discuss the near-horizon scalar condensation instability which is also present in global AdS4-Reissner-Nordström black holes. We highlight the different nature of the near-horizon and superradiant instabilities and that hairy black holes ultimately exist because of the non-linear instability of AdS.

Smooth causal patches for AdS black holes

NASA Astrophysics Data System (ADS)

Raju, Suvrat

2017-06-01

We review the paradox of low energy excitations of a black hole in anti-de Sitter space (AdS). An appropriately chosen unitary operator in the boundary theory can create a locally strong excitation near the black hole horizon, whose global energy is small as a result of the gravitational redshift. The paradox is that this seems to violate a general rule of statistical mechanics, which states that an operator with energy parametrically smaller than k T cannot create a significant excitation in a thermal system. When we carefully examine the position dependence of the boundary unitary operator that produces the excitation and the bulk observable necessary to detect the anomalously large effect, we find that they do not both fit in a single causal patch. This follows from a remarkable property of position-space AdS correlators that we establish explicitly and resolves the paradox in a generic state of the system, since no combination of observers can both create the excitation and observe its effect. As a special case of our analysis, we show how this resolves the "Born rule" paradox of Marolf and Polchinski [J. High Energy Phys. 01 (2016) 008, 10.1007/JHEP01(2016)008] and we verify our solution using an independent calculation. We then consider boundary states that are finely tuned to display a spontaneous excitation outside the causal patch of the infalling observer, and we propose a version of causal patch complementarity in AdS/CFT that resolves the paradox for such states as well.

Iron-Nickel Meteorite Zapped by Mars Rover Laser

NASA Image and Video Library

2016-11-02

The dark, golf-ball-size object in this composite, colorized view from the Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover shows a grid of shiny dots where ChemCam had fired laser pulses used for determining the chemical elements in the target's composition. The analysis confirmed that this object, informally named "Egg Rock," is an iron-nickel meteorite. Iron-nickel meteorites are a common class of space rocks found on Earth, and previous examples have been found on Mars, but Egg Rock is the first on Mars to be examined with a laser-firing spectrometer. The laser pulses on Oct. 30, 2016, induced bursts of glowing gas at the target, and ChemCam's spectrometer read the wavelengths of light from those bursts to gain information about the target's composition. The laser pulses also burned through the dark outer surface, exposing bright interior material. This view combines two images taken later the same day by ChemCam's remote micro-imager (RMI) camera, with color added from an image taken by Curiosity's Mast Camera (Mastcam). A Mastcam image of Egg Rock is at PIA21134. http://photojournal.jpl.nasa.gov/catalog/PIA21133

Effect of ZrO2 Powders on the Pyrolysis of Polycarbosilanes Coating Under Laser Ablation

NASA Astrophysics Data System (ADS)

Cheng, Han; Chen, Zhaofeng; Tao, Jie; Yan, Bo; Li, Cong; Wang, Liangbing; Zhang, Ying; Fang, Dan; Wan, Shuicheng; Wu, Wangping

Aircrafts hold the outstanding mastery of the sky in modern wars, however the laser beam weapons can carry out laser attacking to aircrafts. The purpose of the present paper is to research on a new type laser protective material. Polycarbosilanes (PCS)/divinylbenzene mixtures containing ZrO2 powders were brushed to the surface of the aluminum alloy plates and then cured at 150°C for 6 h. The PCS-coated plates were ablated by laser for 3 s. The phase identification of as-ablated powders was examined by X-ray diffraction. The results indicated that the as-ablated powders of cured PCS were composed of major phase β-SiC and smaller amounts of free carbon. The PCS composite coating played a certain role of laser ablation resistance. The effect of added ZrO2 powders on the pyrolysis of PCS-coating under laser ablation is conspicuous.

Position space analysis of the AdS (in)stability problem

NASA Astrophysics Data System (ADS)

Dimitrakopoulos, Fotios V.; Freivogel, Ben; Lippert, Matthew; Yang, I.-Sheng

2015-08-01

We investigate whether arbitrarily small perturbations in global AdS space are generically unstable and collapse into black holes on the time scale set by gravitational interactions. We argue that current evidence, combined with our analysis, strongly suggests that a set of nonzero measure in the space of initial conditions does not collapse on this time scale. We perform an analysis in position space to study this puzzle, and our formalism allows us to directly study the vanishing-amplitude limit. We show that gravitational self-interaction leads to tidal deformations which are equally likely to focus or defocus energy, and we sketch the phase diagram accordingly. We also clarify the connection between gravitational evolution in global AdS and holographic thermalization.

Beyond AdS Space-times, New Holographic Correspondences and Applications

NASA Astrophysics Data System (ADS)

Ghodrati, Mahdis

The AdS/CFT correspondence conjectures a mathematical equivalence between string theories and gauge theories. In a particular limit it allows a description of strongly coupled conformal field theory via weakly coupled gravity. This feature has been used to gain insight into many condensed matter (CM) systems. However, to apply the duality in more physical scenarios, one needs to go beyond the usual AdS/CFT framework and extend the duality to non-AdS situations. To describe Lifshitz and hyperscaling violating (HSV) phenomena in CM one uses gauge fields on the gravity side which naturally realize the breaking of Lorentz invariance. These gravity constructions often contain naked singularities. In this thesis, we construct a resolution of the infra-red (IR) singularity of the HSV background. The idea is to add squared curvature terms to the Einstein-Maxwell dilaton action to build a flow from AdS4 in the ultra violate (UV) to an intermediating HSV region and then to an AdS2 x R 2 region in the IR. This general solution is free from the naked singularities and would be more appropriate for applications of HSV in physical systems. We also study the Schwinger effect by using the AdS/CFT duality. We present the phase diagrams of the Schwinger effect and also the "butterfly shaped-phase diagrams" of the entanglement entropy for four different confining supergravity backgrounds. Comparing different features of all of these diagrams could point out to a potential relation between the Schwinger effect and the entanglement entropy which could lead to a method of measuring entanglement entropy in the laboratory. Finally, we study the "new massive gravity" theory and the different black hole solutions it admits. We first present three different methods of calculating the conserved charges. Then, by calculating the on-shell Gibbs free energy we construct the Hawking-Page phase diagrams for different solutions in two thermodynamical ensembles. As the massive gravity models are

3D Laser Imprint Using a Smoother Ray-Traced Power Deposition Method

NASA Astrophysics Data System (ADS)

Schmitt, Andrew J.

2017-10-01

Imprinting of laser nonuniformities in directly-driven icf targets is a challenging problem to accurately simulate with large radiation-hydro codes. One of the most challenging aspects is the proper construction of the complex and rapidly changing laser interference structure driving the imprint using the reduced laser propagation models (usually ray-tracing) found in these codes. We have upgraded the modelling capability in our massively-parallel fastrad3d code by adding a more realistic EM-wave interference structure. This interference model adds an axial laser speckle to the previous transverse-only laser structure, and can be impressed on our improved smoothed 3D raytrace package. This latter package, which connects rays to form bundles and performs power deposition calculations on the bundles, is intended to decrease ray-trace noise (which can mask or add to imprint) while using fewer rays. We apply this improved model to 3D simulations of recent imprint experiments performed on the Omega-EP laser and the Nike laser that examined the reduction of imprinting due to very thin high-Z target coatings. We report on the conditions in which this new model makes a significant impact on the development of laser imprint. Supported by US DoE/NNSA.

Laser-induced scleral shrinkage for refractive surgery

NASA Astrophysics Data System (ADS)

Ren, Qiushi; Simon, Gabriel; Parel, Jean-Marie A.; Shen, Jin-Hui

1994-06-01

We investigate the laser refractive scleroplasty (LRS) as a potential minimal-invasive method for correcting post-operative astigmatism. The scleral shrinkage near limbus was induced on 6 cadaver eyes using a 200 micrometers fiber optic probe coupled to a pulsed Ho:YAG laser. The diameter of the treatment spot was 0.8 mm. The output energy measured at tip was 60.2+/- 0.6 mJ. The treatments consisted of multiple sector patterns placed along the major axis of astigmatism parallel to the limbus, and round patterns placed along the limbus. Three treatment spots were applied on each side of the sector. The separation among sectors and limbus is 1 mm. Keratometry and topography of the cornea were measured after each sector or round pattern treatment. Effect of 5 and 10 pulses at each treatment spot were compared. Histology was performed to evaluate laser tissue damage. The major axis of astigmatism was shifted 90 degrees after the sector pattern treatment and amount of dioptric change increased when adding a new treatment or using more treatment pulses. However, the spherical equivalent of the eyes was essentially unchanged. The keratometry of the corneas remained the same after the round pattern treatment. Laser refractive scleroplasty may be applied for the correction of post-operative astigmatism.

Quantum spectral curve for the η-deformed AdS5 × S5 superstring

NASA Astrophysics Data System (ADS)

Klabbers, Rob; van Tongeren, Stijn J.

2017-12-01

The spectral problem for the AdS5 ×S5 superstring and its dual planar maximally supersymmetric Yang-Mills theory can be efficiently solved through a set of functional equations known as the quantum spectral curve. We discuss how the same concepts apply to the η-deformed AdS5 ×S5 superstring, an integrable deformation of the AdS5 ×S5 superstring with quantum group symmetry. This model can be viewed as a trigonometric version of the AdS5 ×S5 superstring, like the relation between the XXZ and XXX spin chains, or the sausage and the S2 sigma models for instance. We derive the quantum spectral curve for the η-deformed string by reformulating the corresponding ground-state thermodynamic Bethe ansatz equations as an analytic Y system, and map this to an analytic T system which upon suitable gauge fixing leads to a Pμ system - the quantum spectral curve. We then discuss constraints on the asymptotics of this system to single out particular excited states. At the spectral level the η-deformed string and its quantum spectral curve interpolate between the AdS5 ×S5 superstring and a superstring on "mirror" AdS5 ×S5, reflecting a more general relationship between the spectral and thermodynamic data of the η-deformed string. In particular, the spectral problem of the mirror AdS5 ×S5 string, and the thermodynamics of the undeformed AdS5 ×S5 string, are described by a second rational limit of our trigonometric quantum spectral curve, distinct from the regular undeformed limit.

Diode Laser Velocity Measurements by Modulated Filtered Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Mach, J. J.; Varghese, P. L.; Jagodzinski, J. J.

1999-01-01

The ability of solid-state lasers to be tuned in operating frequency at MHz rates by input current modulation, while maintaining a relatively narrow line-width, has made them useful for spectroscopic measurements. Their other advantages include low cost, reliability, durability, compact size, and modest power requirements, making them a good choice for a laser source in micro-gravity experiments in drop-towers and in flight. For their size, they are also very bright. In a filtered Rayleigh scattering (FRS) experiment, a diode laser can be used to scan across an atomic or molecular absorption line, generating large changes in transmission at the resonances for very small changes in frequency. The hyperfine structure components of atomic lines of alkali metal vapors are closely spaced and very strong, which makes such atomic filters excellent candidates for sensitive Doppler shift detection and therefore for high-resolution velocimetry. In the work we describe here we use a Rubidium vapor filter, and work with the strong D(sub 2) transitions at 780 nm that are conveniently accessed by near infrared diode lasers. The low power output of infrared laser diodes is their primary drawback relative to other laser systems commonly used for velocimetry. However, the capability to modulate the laser frequency rapidly and continuously helps mitigate this. Using modulation spectroscopy and a heterodyne detection scheme with a lock-in amplifier, one can extract sub-microvolt signals occurring at a specific frequency from a background that is orders of magnitude stronger. The diode laser modulation is simply achieved by adding a small current modulation to the laser bias current. It may also be swept repetitively in wavelength using an additional lower frequency current ramp.

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.

Microstructural Development in a Laser-Remelted Al-Zn-Si-Mg Coating.

PubMed

Godec, M; Podgornik, B; Nolan, D

2017-11-23

In the last five decades, there has been intense development in the field of Zn-Al galvanic coating modification. Recently, Mg was added to improve corrosion properties. Further improvements to the coating are possible with additional laser surface treatment. In this article, we focus on remelting the Al-Zn-Mg-Si layer, using a diode laser with a wide-beam format, concentrating on the microstructure development during extreme cooling rates. Laser remelting of the Al-Zn-Mg-Si coating and rapid self-quenching produces a finer grain size, and a microstructure that is substantially refined and homogenized with respect to the phase distribution. Using EBSD results, we are able to understand microstructure modification. The laser modified coating has some porosity and intergranular cracking which are difficult to avoid, however this does not seem to be detrimental to mechanical properties, such as ductility on bending. The newly developed technology has a high potential for improved corrosion performance due to highly refined microstructure.

Compact RGBY light sources with high luminance for laser display applications

NASA Astrophysics Data System (ADS)

Paschke, Katrin; Blume, Gunnar; Werner, Nils; Müller, André; Sumpf, Bernd; Pohl, Johannes; Feise, David; Ressel, Peter; Sahm, Alexander; Bege, Roland; Hofmann, Julian; Jedrzejczyk, Daniel; Tränkle, Günther

2018-02-01

Watt-class visible laser light with a high luminance can be created with high-power GaAs-based lasers either directly in the red spectral region or using single-pass second harmonic generation (SHG) for the colors in the blue-yellow spectral region. The concepts and results of red- and near infrared-emitting distributed Bragg reflector tapered lasers and master oscillator power amplifier systems as well as their application for SHG bench-top experiments and miniaturized modules are presented. Examples of these high-luminance light sources aiming at different applications such as flying spot display or holographic 3D cinema are discussed in more detail. The semiconductor material allows an easy adaptation of the wavelength allowing techniques such as six-primary color 3D projection or color space enhancement by adding a fourth yellow color.

Nanosecond time transfer via shuttle laser ranging experiment

NASA Technical Reports Server (NTRS)

Reinhardt, V. S.; Premo, D. A.; Fitzmaurice, M. W.; Wardrip, S. C.; Cervenka, P. O.

1978-01-01

A method is described to use a proposed shuttle laser ranging experiment to transfer time with nanosecond precision. All that need be added to the original experiment are low cost ground stations and an atomic clock on the shuttle. It is shown that global time transfer can be accomplished with 1 ns precision and transfer up to distances of 2000 km can be accomplished with better than 100 ps precision.

Vacuum currents in braneworlds on AdS bulk with compact dimensions

NASA Astrophysics Data System (ADS)

Bellucci, S.; Saharian, A. A.; Vardanyan, V.

2015-11-01

The two-point function and the vacuum expectation value (VEV) of the current density are investigated for a massive charged scalar field with arbitrary curvature coupling in the geometry of a brane on the background of AdS spacetime with partial toroidal compactification. The presence of a gauge field flux, enclosed by compact dimensions, is assumed. On the brane the field obeys Robin boundary condition and along compact dimensions periodicity conditions with general phases are imposed. There is a range in the space of the values for the coefficient in the boundary condition where the Poincaré vacuum is unstable. This range depends on the location of the brane and is different for the regions between the brane and AdS boundary and between the brane and the horizon. In models with compact dimensions the stability condition is less restrictive than that for the AdS bulk with trivial topology. The vacuum charge density and the components of the current along non-compact dimensions vanish. The VEV of the current density along compact dimensions is a periodic function of the gauge field flux with the period equal to the flux quantum. It is decomposed into the boundary-free and brane-induced contributions. The asymptotic behavior of the latter is investigated near the brane, near the AdS boundary and near the horizon. It is shown that, in contrast to the VEVs of the field squared an denergy-momentum tensor, the current density is finite on the brane and vanishes for the special case of Dirichlet boundary condition. Both the boundary-free and brane-induced contributions vanish on the AdS boundary. The brane-induced contribution vanishes on the horizon and for points near the horizon the current is dominated by the boundary-free part. In the near-horizon limit, the latter is connected to the corresponding quantity for a massless field in the Minkowski bulk by a simple conformal relation. Depending on the value of the Robin coefficient, the presence of the brane can either

Transformations of asymptotically AdS hyperbolic initial data and associated geometric inequalities

NASA Astrophysics Data System (ADS)

Cha, Ye Sle; Khuri, Marcus

2018-01-01

We construct transformations which take asymptotically AdS hyperbolic initial data into asymptotically flat initial data, and which preserve relevant physical quantities. This is used to derive geometric inequalities in the asymptotically AdS hyperbolic setting from counterparts in the asymptotically flat realm, whenever a geometrically motivated system of elliptic equations admits a solution. The inequalities treated here relate mass, angular momentum, charge, and horizon area. Furthermore, new mass-angular momentum inequalities in this setting are conjectured and discussed.

Open string fluctuations in AdS space with and without torsion

NASA Astrophysics Data System (ADS)

Larsen, A. L.; Lomholt, M. A.

2003-09-01

The equations of motion and boundary conditions for the fluctuations around a classical open string, in a curved space-time with torsion, are considered in compact and world-sheet covariant form. The rigidly rotating open strings in anti de Sitter space with and without torsion are investigated in detail. By carefully analyzing the tangential fluctuations at the boundary, we show explicitly that the physical fluctuations (which at the boundary are combinations of normal and tangential fluctuations) are finite, even though the world-sheet is singular there. The divergent 2-curvature thus seems less dangerous than expected in these cases. The general formalism can be straightforwardly used also to study the (bosonic part of the) fluctuations around the closed strings, recently considered in connection with the AdS/conformal field theory duality, on AdS5×S5 and AdS3×S3×T4.

AdS5×S(5) mirror model as a string sigma model.

PubMed

Arutyunov, Gleb; van Tongeren, Stijn J

2014-12-31

Doing a double Wick rotation in the world sheet theory of the light cone AdS5×S(5) superstring results in an inequivalent, so-called mirror theory that plays a central role in the field of integrability in the AdS-CFT correspondence. We show that this mirror theory can be interpreted as the light cone theory of a free string on a different background. This background is related to dS5×H(5) by a double T-duality, and has hidden supersymmetry. The geometry can also be extracted from an integrable deformation of the AdS5×S(5) sigma model, and we prove the observed mirror duality of these deformed models at the bosonic level as a byproduct. While we focus on AdS5×S(5), our results apply more generally.

Fermionic currents in AdS spacetime with compact dimensions

NASA Astrophysics Data System (ADS)

Bellucci, S.; Saharian, A. A.; Vardanyan, V.

2017-09-01

We derive a closed expression for the vacuum expectation value (VEV) of the fermionic current density in a (D +1 )-dimensional locally AdS spacetime with an arbitrary number of toroidally compactified Poincaré spatial dimensions and in the presence of a constant gauge field. The latter can be formally interpreted in terms of a magnetic flux treading the compact dimensions. In the compact subspace, the field operator obeys quasiperiodicity conditions with arbitrary phases. The VEV of the charge density is zero and the current density has nonzero components along the compact dimensions only. They are periodic functions of the magnetic flux with the period equal to the flux quantum and tend to zero on the AdS boundary. Near the horizon, the effect of the background gravitational field is small and the leading term in the corresponding asymptotic expansion coincides with the VEV for a massless field in the locally Minkowski bulk. Unlike the Minkowskian case, in the system consisting of an equal number of fermionic and scalar degrees of freedom, with same masses, charges and phases in the periodicity conditions, the total current density does not vanish. In these systems, the leading divergences in the scalar and fermionic contributions on the horizon are canceled and, as a consequence of that, the charge flux, integrated over the coordinate perpendicular to the AdS boundary, becomes finite. We show that in odd spacetime dimensions the fermionic fields realizing two inequivalent representations of the Clifford algebra and having equal phases in the periodicity conditions give the same contribution to the VEV of the current density. Combining the contributions from these fields, the current density in odd-dimensional C -,P - and T -symmetric models are obtained. As an application, we consider the ground state current density in curved carbon nanotubes described in terms of a (2 +1 )-dimensional effective Dirac model.

Symmetry operators of Killing spinors and superalgebras in AdS5

NASA Astrophysics Data System (ADS)

Ertem, Ümit

2016-04-01

We construct the first-order symmetry operators of Killing spinor equation in terms of odd Killing-Yano forms. By modifying the Schouten-Nijenhuis bracket of Killing-Yano forms, we show that the symmetry operators of Killing spinors close into an algebra in AdS5 spacetime. Since the symmetry operator algebra of Killing spinors corresponds to a Jacobi identity in extended Killing superalgebras, we investigate the possible extensions of Killing superalgebras to include higher-degree Killing-Yano forms. We found that there is a superalgebra extension but no Lie superalgebra extension of the Killing superalgebra constructed out of Killing spinors and odd Killing-Yano forms in AdS5 background.

Functional determinants of radial operators in AdS2

DOE PAGES

Aguilera-Damia, Jeremías; Faraggi, Alberto; Zayas, Leopoldo Pando; ...

2018-06-01

We study the zeta-function regularization of functional determinants of Laplace and Dirac-type operators in two-dimensional Euclidean AdS2 space. More specifically, we consider the ratio of determinants between an operator in the presence of background fields with circular symmetry and the free operator in which the background fields are absent. By Fourier-transforming the angular dependence, one obtains an infinite number of one-dimensional radial operators, the determinants of which are easy to compute. The summation over modes is then treated with care so as to guarantee that the result coincides with the two-dimensional zeta-function formalism. The method relies on some well-known techniquesmore » to compute functional determinants using contour integrals and the construction of the Jost function from scattering theory. Our work generalizes some known results in flat space. The extension to conformal AdS2 geometries is also considered. We provide two examples, one bosonic and one fermionic, borrowed from the spectrum of fluctuations of the holographic 1/4-BPS latitude Wilson loop.« less

Functional determinants of radial operators in AdS 2

NASA Astrophysics Data System (ADS)

Aguilera-Damia, Jeremías; Faraggi, Alberto; Zayas, Leopoldo Pando; Rathee, Vimal; Silva, Guillermo A.

2018-06-01

We study the zeta-function regularization of functional determinants of Laplace and Dirac-type operators in two-dimensional Euclidean AdS 2 space. More specifically, we consider the ratio of determinants between an operator in the presence of background fields with circular symmetry and the free operator in which the background fields are absent. By Fourier-transforming the angular dependence, one obtains an infinite number of one-dimensional radial operators, the determinants of which are easy to compute. The summation over modes is then treated with care so as to guarantee that the result coincides with the two-dimensional zeta-function formalism. The method relies on some well-known techniques to compute functional determinants using contour integrals and the construction of the Jost function from scattering theory. Our work generalizes some known results in flat space. The extension to conformal AdS 2 geometries is also considered. We provide two examples, one bosonic and one fermionic, borrowed from the spectrum of fluctuations of the holographic 1/4 -BPS latitude Wilson loop.

The AdS3 propagator and the fate of locality

NASA Astrophysics Data System (ADS)

Chen, Hongbin; Fitzpatrick, A. Liam; Kaplan, Jared; Li, Daliang

2018-04-01

We recently used Virasoro symmetry considerations to propose an exact formula for a bulk proto-field ϕ in AdS3. In this paper we study the propagator < ϕϕ>. We show that many techniques from the study of conformal blocks can be generalized to compute it, including the semiclassical monodromy method and both forms of the Zamolodchikov recursion relations. When the results from recursion are expanded at large central charge, they match gravitational perturbation theory for a free scalar field coupled to gravity in our chosen gauge. We find that although the propagator is finite and well-defined at long distances, its perturbative expansion in {G}_N=3/2c exhibits UV/IR mixing effects. If we nevertheless interpret < ϕϕ> as a probe of bulk locality, then when {G}_{N{m}_{φ }}≪ 1 locality breaks down at the new short-distance scale {σ}_{\\ast}˜ √[4]{G_N{R}_{AdS}^3} . For ϕ with very large bulk mass, or at small central charge, bulk locality fails at the AdS length scale. In all cases, locality `breakdown' manifests as singularities or branch cuts at spacelike separation arising from non-perturbative quantum gravitational effects.

For the safe use of lasers in educational institutions: elementary through university

NASA Astrophysics Data System (ADS)

Seeber, Fredrick P.

1995-10-01

The use of lasers by the academic community continues to dramatically escalate. Academia is inundated with a profusion of lasers, each with a diverse function. Traditional departments such as biology, chemistry, and physics have introduced the use of lasers as an essential element of tutelage. Even the more distinctive departments such as Cancer Research, Civil Engineering, Earth and Planetary Science, Plasma Fusion, Spectroscopy, and so forth, have incorporated the laser in the composition of their educational mechanism. The literature indicates most ocular accidents happen during alignment procedures, which is an everyday activity for educational laboratories. Also, the improper use of laser safety eye wear is a major area of concern for laser safety in education institutions. More Class II, III, and IV lasers are used in universities, colleges, laser electro-optic technical colleges and high schools than probably any other area: for teaching, research, laboratory experiments, and demonstrations. Relatively large numbers of students work in laboratory groups in confined area, with various lasers of different wavelengths in the same laboratory. Open cavity and beam paths of Class IV lasers are common in these environments. Most educational institutions do not have laser safety officers or standard operation procedures. This paper will discuss the development of a new laser safety standard by an ANSI ad-hoc committee and by the executive committee of the ANSI Z-136 intended to provide adequate, reasonable, and practical guidance for educators, students, and spectators found in classrooms, lecture halls, and laboratories associated with universities, colleges, high, and elementary schools.

Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik, E-mail: dskim87@postech.ac.kr

2015-09-21

In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of themore » clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.« less

Euclidean Wilson loops and minimal area surfaces in lorentzian AdS 3

DOE PAGES

Irrgang, Andrew; Kruczenski, Martin

2015-12-14

The AdS/CFT correspondence relates Wilson loops in N=4 SYM theory to minimal area surfaces in AdS 5 × S 5 space. If the Wilson loop is Euclidean and confined to a plane (t, x) then the dual surface is Euclidean and lives in Lorentzian AdS 3 c AdS 5. In this paper we study such minimal area surfaces generalizing previous results obtained in the Euclidean case. Since the surfaces we consider have the topology of a disk, the holonomy of the flat current vanishes which is equivalent to the condition that a certain boundary Schrödinger equation has all its solutionsmore » anti-periodic. If the potential for that Schrödinger equation is found then reconstructing the surface and finding the area become simpler. In particular we write a formula for the Area in terms of the Schwarzian derivative of the contour. Finally an infinite parameter family of analytical solutions using Riemann Theta functions is described. In this case, both the area and the shape of the surface are given analytically and used to check the previous results.« less

Holographic Rényi entropy in AdS3/LCFT2 correspondence

NASA Astrophysics Data System (ADS)

Chen, Bin; Song, Feng-yan; Zhang, Jia-ju

2014-03-01

The recent study in AdS3/CFT2 correspondence shows that the tree level contribution and 1-loop correction of holographic Rényi entanglement entropy (HRE) exactly match the direct CFT computation in the large central charge limit. This allows the Rényi entanglement entropy to be a new window to study the AdS/CFT correspondence. In this paper we generalize the study of Rényi entanglement entropy in pure AdS3 gravity to the massive gravity theories at the critical points. For the cosmological topological massive gravity (CTMG), the dual conformal field theory (CFT) could be a chiral conformal field theory or a logarithmic conformal field theory (LCFT), depending on the asymptotic boundary conditions imposed. In both cases, by studying the short interval expansion of the Rényi entanglement entropy of two disjoint intervals with small cross ratio x, we find that the classical and 1-loop HRE are in exact match with the CFT results, up to order x 6. To this order, the difference between the massless graviton and logarithmic mode can be seen clearly. Moreover, for the cosmological new massive gravity (CNMG) at critical point, which could be dual to a logarithmic CFT as well, we find the similar agreement in the CNMG/LCFT correspondence. Furthermore we read the 2-loop correction of graviton and logarithmic mode to HRE from CFT computation. It has distinct feature from the one in pure AdS3 gravity.

Characterization of a novel miniaturized burst-mode infrared laser system for IR-MALDESI mass spectrometry imaging.

PubMed

Ekelöf, Måns; Manni, Jeffrey; Nazari, Milad; Bokhart, Mark; Muddiman, David C

2018-03-01

Laser systems are widely used in mass spectrometry as sample probes and ionization sources. Mid-infrared lasers are particularly suitable for analysis of high water content samples such as animal and plant tissues, using water as a resonantly excited sacrificial matrix. Commercially available mid-IR lasers have historically been bulky and expensive due to cooling requirements. This work presents a novel air-cooled miniature mid-IR laser with adjustable burst-mode output and details an evaluation of its performance for mass spectrometry imaging. The miniature laser was found capable of generating sufficient energy for complete ablation of animal tissue in the context of an IR-MALDESI experiment with exogenously added ice matrix, yielding several hundred confident metabolite identifications. Graphical abstract The use of a novel miniature 2.94 μm burst-mode laser in IR-MALDESI allows for rapid and sensitive mass spectrometry imaging of a whole mouse.

Multi-operational tuneable Q-switched mode-locking Er fibre laser

NASA Astrophysics Data System (ADS)

Qamar, F. Z.

2018-01-01

A wavelength-spacing tuneable, Q-switched mode-locking (QML) erbium-doped fibre laser based on non-linear polarization rotation controlled by four waveplates and a cube polarizer is proposed. A mode-locked pulse train using two quarter-wave plates and a half-wave plate (HWP) is obtained first, and then an extra HWP is inserted into the cavity to produce different operation regimes. The evolutions of temporal and spectral dynamics with different orientation angles of the extra HWP are investigated. A fully modulated stable QML pulse train is observed experimentally. This is, to the author’s best knowledge, the first experimental work reporting QML operation without adding an extra saturable absorber inside the laser cavity. Multi-wavelength pulse laser operation, multi-pulse train continuous-wave mode-locking operation and pulse-splitting operations are also reported at certain HWP angles. The observed operational dynamics are interpreted as a mutual interaction of dispersion, non-linear effect and insertion loss. This work provides a new mechanism for fabricating cheap tuneable multi-wavelength lasers with QML pulses.

Boundary stress tensor and asymptotically AdS3 non-Einstein spaces at the chiral point

NASA Astrophysics Data System (ADS)

Giribet, Gaston; Goya, Andrés; Leston, Mauricio

2011-09-01

Chiral gravity admits asymptotically AdS3 solutions that are not locally equivalent to AdS3; meaning that solutions do exist which, while obeying the strong boundary conditions usually imposed in general relativity, happen not to be Einstein spaces. In topologically massive gravity (TMG), the existence of non-Einstein solutions is particularly connected to the question about the role played by complex saddle points in the Euclidean path integral. Consequently, studying (the existence of) nonlocally AdS3 solutions to chiral gravity is relevant to understanding the quantum theory. Here, we discuss a special family of nonlocally AdS3 solutions to chiral gravity. In particular, we show that such solutions persist when one deforms the theory by adding the higher-curvature terms of the so-called new massive gravity. Moreover, the addition of higher-curvature terms to the gravity action introduces new nonlocally AdS3 solutions that have no analogues in TMG. Both stationary and time-dependent, axially symmetric solutions that asymptote AdS3 space without being locally equivalent to it appear. Defining the boundary stress tensor for the full theory, we show that these non-Einstein geometries have associated vanishing conserved charges.

External cavity diode laser setup with two interference filters

NASA Astrophysics Data System (ADS)

Martin, Alexander; Baus, Patrick; Birkl, Gerhard

2016-12-01

We present an external cavity diode laser setup using two identical, commercially available interference filters operated in the blue wavelength range around 450 nm. The combination of the two filters decreases the transmission width, while increasing the edge steepness without a significant reduction in peak transmittance. Due to the broad spectral transmission of these interference filters compared to the internal mode spacing of blue laser diodes, an additional locking scheme, based on Hänsch-Couillaud locking to a cavity, has been added to improve the stability. The laser is stabilized to a line in the tellurium spectrum via saturation spectroscopy, and single-frequency operation for a duration of two days is demonstrated by monitoring the error signal of the lock and the piezo drive compensating the length change of the external resonator due to air pressure variations. Additionally, transmission curves of the filters and the spectra of a sample of diodes are given.

A universal counting of black hole microstates in AdS4

NASA Astrophysics Data System (ADS)

Azzurli, Francesco; Bobev, Nikolay; Crichigno, P. Marcos; Min, Vincent S.; Zaffaroni, Alberto

2018-02-01

Many three-dimensional N=2 SCFTs admit a universal partial topological twist when placed on hyperbolic Riemann surfaces. We exploit this fact to derive a universal formula which relates the planar limit of the topologically twisted index of these SCFTs and their three-sphere partition function. We then utilize this to account for the entropy of a large class of supersymmetric asymptotically AdS4 magnetically charged black holes in M-theory and massive type IIA string theory. In this context we also discuss novel AdS2 solutions of eleven-dimensional supergravity which describe the near horizon region of large new families of supersymmetric black holes arising from M2-branes wrapping Riemann surfaces.

Image Ads and Issue Ads in U.S. Presidential Advertising: Using Videostyle To Explore Stylistic Differences in Televised Political Ads From 1952 to 2000.

ERIC Educational Resources Information Center

Johnston, Anne; Kaid, Lynda Lee

2002-01-01

Explores the differences in techniques, strategies, narratives, and symbols used in 1,213 television issue ads and image ads from 13 U.S. presidential campaigns. Concludes that although the majority of both types of ads were positive, negative appeals dominated a higher percentage of issue ads as compared with image ads. (SG)

Laser Processing of Carbon Nanotube Transparent Conducting Films

NASA Astrophysics Data System (ADS)

Mann, Andrew

Transparent conducting films, or TCFs, are 2D electrical conductors with the ability to transmit light. Because of this, they are used in many popular electronics including smart phones, tablets, solar panels, and televisions. The most common material used as a TCF is indium tin oxide, or ITO. Although ITO has great electrical and optical characteristics, it is expensive, brittle, and difficult to pattern. These limitations have led researchers toward other materials for the next generation of displays and touch panels. The most promising material for next generation TCFs is carbon nanotubes, or CNTs. CNTs are cylindrical tubes of carbon no more than a few atoms thick. They have different electrical and optical properties depending on their atomic structure, and are extremely strong. As an electrode, they conduct electricity through an array of randomly dispersed tubes. The array is highly transparent because of gaps between the tubes, and size and optical properties of the CNTs. Many research groups have tried making CNT TCFs with opto-electric properties similar to ITO but have difficultly achieving high conductivity. This is partly attributed to impurities from fabrication and a mix of different tube types, but is mainly caused by low junction conductivity. In functionalized nanotubes, junction conductivity is impaired by covalently bonded molecules added to the sidewalls of the tubes. The addition of this molecule, known as functionalization, is designed to facilitate CNT dispersion in a solvent by adding properties of the molecule to the CNTs. While necessary for a good solution, functionalization decreases the conductivity in the CNT array by creating defects in the tube's structures and preventing direct inter-carbon bonding. This research investigates removing the functional coating (after tube deposition) by laser processing. Laser light is able to preferentially heat the CNTs because of their optical and electrical properties. Through local conduction

λ/26 silver nanodots fabricated by direct laser writing through highly sensitive two-photon photoreduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Yaoyu; Gu, Min, E-mail: mgu@swin.edu.au

We demonstrated an approach to break the diffraction limit and realise deep-subwavelength two-photon direct laser writing by employing a highly sensitive photoreduction process. The photoreduction photosensitivity increased by at least 4 times while the wavelength of the fabrication laser beam was tuned from 800 nm to 580 nm. The increase of the photosensitivity resulted in improved resolution for the silver dot fabrication. By developing the photoreduction material with adding electron donors, the photosensitivity further increased and enabled the realisation of a single silver dot at 22 nm which is λ/26 for the wavelength of the fabrication laser beam.

Taurine supplementation for prevention of stroke-like episodes in MELAS: a multicentre, open-label, 52-week phase III trial.

PubMed

Ohsawa, Yutaka; Hagiwara, Hiroki; Nishimatsu, Shin-Ichiro; Hirakawa, Akihiro; Kamimura, Naomi; Ohtsubo, Hideaki; Fukai, Yuta; Murakami, Tatsufumi; Koga, Yasutoshi; Goto, Yu-Ichi; Ohta, Shigeo; Sunada, Yoshihide

2018-04-17

The aim of this study was to evaluate the efficacy and safety of high-dose taurine supplementation for prevention of stroke-like episodes of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes), a rare genetic disorder caused by point mutations in the mitochondrial DNA that lead to a taurine modification defect at the first anticodon nucleotide of mitochondrial tRNA Leu(UUR) , resulting in failure to decode codons accurately. After the nationwide survey of MELAS, we conducted a multicentre, open-label, phase III trial in which 10 patients with recurrent stroke-like episodes received high-dose taurine (9 g or 12 g per day) for 52 weeks. The primary endpoint was the complete prevention of stroke-like episodes during the evaluation period. The taurine modification rate of mitochondrial tRNA Leu(UUR) was measured before and after the trial. The proportion of patients who reached the primary endpoint (100% responder rate) was 60% (95% CI 26.2% to 87.8%). The 50% responder rate, that is, the number of patients achieving a 50% or greater reduction in frequency of stroke-like episodes, was 80% (95% CI 44.4% to 97.5%). Taurine reduced the annual relapse rate of stroke-like episodes from 2.22 to 0.72 (P=0.001). Five patients showed a significant increase in the taurine modification of mitochondrial tRNA Leu(UUR) from peripheral blood leukocytes (P<0.05). No severe adverse events were associated with taurine. The current study demonstrates that oral taurine supplementation can effectively reduce the recurrence of stroke-like episodes and increase taurine modification in mitochondrial tRNA Leu(UUR) in MELAS. UMIN000011908. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Massive quiver matrix models for massive charged particles in AdS

DOE PAGES

Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric

2016-01-11

Here, we present a new class of N = 4 supersymmetric quiver matrix models and argue that it describes the stringy low-energy dynamics of internally wrapped D-branes in four-dimensional anti-de Sitter (AdS) flux compactifications. The Lagrangians of these models differ from previously studied quiver matrix models by the presence of mass terms, associated with the AdS gravitational potential, as well as additional terms dictated by supersymmetry. These give rise to dynamical phenomena typically associated with the presence of fluxes, such as fuzzy membranes, internal cyclotron motion and the appearance of confining strings. We also show how these models can bemore » obtained by dimensional reduction of four-dimensional supersymmetric quiver gauge theories on a three-sphere.« less

The eleven observations of comets between 687 AD and 1114 AD recorded in the Anglo Saxon Chronicle

NASA Technical Reports Server (NTRS)

Mardon, E. G.; Williams, J.; Mardon, A. A.

1992-01-01

This research paper is an examination of the eleven cometary references (679AD, 729AD, 892AD, 950AD, 975AD, 995AD, 1066AD, 1097AD, 1106AD, 1110AD and 1114AD) found in the various manuscripts of The Anglo Saxon Chronicle between 678 AD and 1114 AD. The manuscripts contain more than 35 celestial observations. This is an examination of astronomical phenomena and other climatic or natural events, that are described in The Anglo Saxon Chronicle, which is also referred to as The Old English Annals.

The eleven observations of comets between 687 AD and 1114 AD recorded in the Anglo Saxon Chronicle

NASA Astrophysics Data System (ADS)

Mardon, E. G.; Mardon, A. A.; Williams, J.

1992-12-01

This research paper is an examination of the eleven cometary references (679AD, 729AD, 892AD, 950AD, 975AD, 995AD, 1066AD, 1097AD, 1106AD, 1110AD and 1114AD) found in the various manuscripts of The Anglo Saxon Chronicle between 678 AD and 1114 AD. The manuscripts contain more than 35 celestial observations. This is an examination of astronomical phenomena and other climatic or natural events, that are described in The Anglo Saxon Chronicle, which is also referred to as The Old English Annals.

A Route to Chaos after Bifurcation in a Two-section Semiconductor Laser Using Opto-electronic Delayed Feedback at Each In-current

NASA Astrophysics Data System (ADS)

Yan, Sen-lin

2014-12-01

We study dynamics in an opto-electronic delayed feedback two-section semiconductor laser. We predict theoretically that the system can result in bistability and bifurcation. We analyze numerically the route to chaos from stability to bifurcation by varying the delayed time, feedback strength and two in-currents. The system displays the four distinct types or modes of stable, periodic pulsed or self-pulsing, undamped oscillating or beating, and chaos. The frequency and intensity varying with the delayed time in the self-pulsation regions are discussed detailedly to find that the pulsing frequency is reduced with the long delayed time while the pulsing intensity is added. And the chaotic pulsing frequency is increased with the large in-current Ja. The laser relaxation oscillation frequency is decreased with the large in-current Jb. One in-current characterize dynamics in the laser to conduce to stable, periodic pulsed, beating and chaotic states by altering its values. The other in-current characterize dynamics in the chaotic laser to be controlled to a stable state after a road to quasi-period by adding the values.

Proper temperature of the Schwarzschild AdS black hole revisited

NASA Astrophysics Data System (ADS)

Eune, Myungseok; Kim, Wontae

2017-10-01

The Unruh temperature calculated by using the global embedding of the Schwarzschild AdS spacetime into the Minkowski spacetime was identified with the local proper temperature; however, it became imaginary in a certain region outside the event horizon. So, the temperature was assumed to be zero of non-thermal radiation for that region. In this work, we revisit this issue in an exactly soluble two-dimensional Schwarzschild AdS black hole and present an alternative resolution to this problem in terms of the Tolman's procedure. However, the process appears to be non-trivial in the sense that the original procedure assuming the traceless energy-momentum tensor should be extended in such a way that it should cover the non-vanishing case of the energy-momentum tensor in the presence of the trace anomaly. Consequently, we show that the proper temperature turns out to be real everywhere outside the event horizon without any imaginary value, in particular, it vanishes at both the horizon and the asymptotic infinity.

LIGHT - from laser ion acceleration to future applications

NASA Astrophysics Data System (ADS)

Roth, Markus; Light Collaboration

2013-10-01

Creation of high intensity multi-MeV ion bunches by high power lasers became a reliable tool during the last 15 years. The laser plasma source provides for TV/m accelerating field gradients and initially sub-ps bunch lengths. However, the large envelope divergence and the continuous exponential energy spectrum are substential drawbacks for many possible applications. To face this problem, the LIGHT collaboration was founded (Laser Ion Generation, Handling and Transport). The collaboration consists of several university groups and research centers, namely TU Darmstadt, JWGU Frankfurt, HI Jena, HZDR Dresden and GSI Darmstadt. The central goal is building a test beamline for merging laser ion acceleration with conventional accelerator infrastructure at the GSI facility. In the latest experiments, low divergent proton bunches with a central energy of up to 10 MeV and containing >109 particles could be provided at up to 2.2 m behind the plasma source, using a pulsed solenoid. In a next step, a radiofrequency cavity will be added to the beamline for phase rotation of these bunches, giving access to sub-ns bunch lengths and reaching highest intensities. An overview of the LIGHT objectives and the recent experimental results will be given. This work was supported by HIC4FAIR.

Laser Assisted Micro Wire GMAW and Droplet Welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

FUERSCHBACH, PHILLIP W.; LUCK, D. L.; BERTRAM, LEE A.

2002-03-01

Laser beam welding is the principal welding process for the joining of Sandia weapon components because it can provide a small fusion zone with low overall heating. Improved process robustness is desired since laser energy absorption is extremely sensitive to joint variation and filler metal is seldom added. This project investigated the experimental and theoretical advantages of combining a fiber optic delivered Nd:YAG laser with a miniaturized GMAW system. Consistent gas metal arc droplet transfer employing a 0.25 mm diameter wire was only obtained at high currents in the spray transfer mode. Excessive heating of the workpiece in this modemore » was considered an impractical result for most Sandia micro-welding applications. Several additional droplet detachment approaches were investigated and analyzed including pulsed tungsten arc transfer(droplet welding), servo accelerated transfer, servo dip transfer, and electromechanically braked transfer. Experimental observations and rigorous analysis of these approaches indicate that decoupling droplet detachment from the arc melting process is warranted and may someday be practical.« less

Integrability of the Ad{{S}_{5}}\\times {{S}^{5}} superstring and its deformations

NASA Astrophysics Data System (ADS)

van Tongeren, Stijn J.

2014-10-01

This article reviews the application of integrability to the spectral problem of strings on Ad{{S}5}× {{S}5} and its deformations. We begin with a pedagogical introduction to integrable field theories culminating in the description of their finite-volume spectra through the thermodynamic Bethe ansatz (TBA). Next, we apply these ideas to the Ad{{S}5}× {{S}5} string and in later sections discuss how to account for particular integrable deformations. Through the AdS/CFT correspondence this gives an exact description of anomalous scaling dimensions of single trace operators in planar N=4 supersymmetry Yang-Mills theory, its ‘orbifolds’, and β and γ-deformed supersymmetric Yang-Mills theory. We also touch upon some subtleties arising in these deformed theories. Furthermore, we consider complex excited states (bound states) in the su(2) sector and give their TBA description. Finally we discuss the TBA for a quantum deformation of the Ad{{S}5}× {{S}5} superstring S-matrix, with close relations to among others Pohlmeyer reduced string theory, and briefly indicate more recent developments in this area.

A Modular Control Platform for a Diode Pumped Alkali Laser

NASA Astrophysics Data System (ADS)

Shapiro, J.; Teare, S.

Many of the difficulties of creating compact, high power laser systems can be overcome if the heat dissipating properties of chemical lasers can be combined with the efficiency of diode lasers. Recently, the novel idea of using solid state diode lasers to pump gaseous gain media, such as is done in diode pumped alkali lasers (DPALs), has been proposed and early experiments have shown promising results. However, a number of technical issues need to be overcome to realize high output power from these lasers. In order to achieve higher power, the efficiency of coupling between pump laser energy and the chemical cell must be increased, and eventually multiple high power diode pumps must be combined and synchronized so that their energy can pump the chemical cell. Additionally, an inter-cavity adaptive optics system may be a requirement to be able to propagate these lasers with high efficiency. DPAL systems are complex and require a significant amount of data fusion and active feedback to control and optimize their performance. There are a wide range of components including pump lasers, gain cells and monitoring points needed to study and refine the overall laser system. In support of this dynamic development environment, we have developed a hardware framework using commercial off the shelf (COTS) components which supports the rapid assembly of functional system blocks into a cohesive integrated system. Critical to this system are a simple communication protocol, industry standard communication pipes (USB, Bluetooth, etc), and flexible high level scripting. Simplifying the integration process has the benefit of allowing flexible "on the fly" modifications to adapt the system as needed and enhance available functionality. The modular nature of the architecture allows scalability and adaptability as more pieces are added to the system. Key components of this system are demonstrated for selected portions of a DPAL system using a USB backbone.

Spectrophone stabilized laser with line center offset frequency control

NASA Technical Reports Server (NTRS)

Kavaya, M. J.; Menzies, R. T. (Inventor)

1984-01-01

Continuous offset tuning of a frequency stabilized CW gas laser is achieved by using a spectrophone filled with the same gas as the laser for sensing a dither modulation, detecting a first or second derivative of the spectrophone output with a lock-in amplifier, the detected output of which is integrated, and applying the integrator output as a correction signal through a circuit which adds to the dither signal from an oscillator a dc offset that is adjusted with a potentiometer to a frequency offset from the absorption line center of the gas, but within the spectral linewidth of the gas. Tuning about that offset frequency is achieved by adding a dc value to the detected output of the dither modulation before integration using a potentiometer.

Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakry, A.; Abdulrhmann, S.; Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg

2016-06-15

We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding themore » second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.« less

IDA Gamma-Ray Laser Annual Summary Report (1990): Investigation of the Feasibility of Developing A Laser Using Nuclear Transitions

DTIC Science & Technology

1992-04-01

Broadening in the Theory of Superradiant Emission," Acta Physica Polonica , Vol. A39, 1971, pp. 633-638. 8. B. Balko, I.W. Kay, and J. Neuberger, IDA...Cuopy 1 3 of 60 copies AD-A259 475 IDA PAPER P-2533 IDA GAMMA-RAY LASER ANNUAL SUMMARY REPORT (1990) Investigation of the Feasibility of Developing a ...embody results of major projects which ( a ) have a direct bearing on decisions affecting major programs, (b) address issues of significant concern to

On supersymmetric AdS6 solutions in 10 and 11 dimensions

NASA Astrophysics Data System (ADS)

Gutowski, J.; Papadopoulos, G.

2017-12-01

We prove a non-existence theorem for smooth, supersymmetric, warped AdS 6 solutions with connected, compact without boundary internal space in D = 11 and (massive) IIA supergravities. In IIB supergravity we show that if such AdS 6 solutions exist, then the NSNS and RR 3-form fluxes must be linearly independent and certain spinor bilinears must be appropriately restricted. Moreover we demonstrate that the internal space admits an so(3) action which leaves all the fields invariant and for smooth solutions the principal orbits must have co-dimension two. We also describe the topology and geometry of internal spaces that admit such a so(3) action and show that there are no solutions for which the internal space has topology F × S 2, where F is an oriented surface.

Digital Quantum Simulation of Minimal AdS /CFT

NASA Astrophysics Data System (ADS)

García-Álvarez, L.; Egusquiza, I. L.; Lamata, L.; del Campo, A.; Sonner, J.; Solano, E.

2017-07-01

We propose the digital quantum simulation of a minimal AdS /CFT model in controllable quantum platforms. We consider the Sachdev-Ye-Kitaev model describing interacting Majorana fermions with randomly distributed all-to-all couplings, encoding nonlocal fermionic operators onto qubits to efficiently implement their dynamics via digital techniques. Moreover, we also give a method for probing nonequilibrium dynamics and the scrambling of information. Finally, our approach serves as a protocol for reproducing a simplified low-dimensional model of quantum gravity in advanced quantum platforms as trapped ions and superconducting circuits.

Handling And Safety Aspects Of Fiber Optic Laser Beam Delivery Systems

NASA Astrophysics Data System (ADS)

Schonborn, K.-H.; Wodrich, W.

1988-06-01

Using lasers for therapeutic applications is getting more and more accepted. In ophthalmology Ar-lasers for intraocular applications are quite common. The Nd:YAG-laser is used as a high power tool in connection with silica fibers for different extracorporal and intracorporal applications. The CO2-laser is the cutting laser, one problem being the beam transmission: The state of the art in fibers is not sufficient up to now. Because of the high power used safety against laser radiation hazard is of great importance. The safety in laser use is primarily dependent on the surgeons cautiousness, e.g. using laser protection goggels, observing that the spot of the aiming beam is present etc. On the other hand the laser and fiber system has to be inherently safe by appropriate technical means as far as possible. An additional aspect adding to safety is the handling: With easier system handling less attention of the surgeon is necessary for driving the apparatus. Thus he can concentrate on the patient and on the procedure. In considering the fiber system one important point in handling and safety is the coupling of the fiber to the laser head. The development philosophy in this coupling may be divided into two groups: - one is trying to use standard connectors which were initially developed for data transmission; - the other is using special connectors. One example of the first group is the guiding of the laser beam from the Ar-laser to the slit-lamp in ophtalmology. Here the well-known F-SMA connectors together with a special fiber with adapted numerical aperture are used. The advantage of such a system is the low price of the connector. For high power lasers such as the clinical Nd:YAG lasers with 40 to 150 W those connectors are not suitable. Up to now every laser manufacturer developed his own connector system in this field.

Multi-Skyrmions on AdS2 × S2, rational maps and popcorn transitions

NASA Astrophysics Data System (ADS)

Canfora, Fabrizio; Tallarita, Gianni

2017-08-01

By combining two different techniques to construct multi-soliton solutions of the (3 + 1)-dimensional Skyrme model, the generalized hedgehog and the rational map ansatz, we find multi-Skyrmion configurations in AdS2 ×S2. We construct Skyrmionic multi-layered configurations such that the total Baryon charge is the product of the number of kinks along the radial AdS2 direction and the degree of the rational map. We show that, for fixed total Baryon charge, as one increases the charge density on ∂ (AdS2 ×S2) , it becomes increasingly convenient energetically to have configurations with more peaks in the radial AdS2 direction but a lower degree of the rational map. This has a direct relation with the so-called holographic popcorn transitions in which, when the charge density is high, multi-layered configurations with low charge on each layer are favored over configurations with few layers but with higher charge on each layer. The case in which the geometry is M2 ×S2 can also be analyzed.

Topological terms, AdS2 n gravity, and renormalized entanglement entropy of holographic CFTs

NASA Astrophysics Data System (ADS)

Anastasiou, Giorgos; Araya, Ignacio J.; Olea, Rodrigo

2018-05-01

We extend our topological renormalization scheme for entanglement entropy to holographic CFTs of arbitrary odd dimensions in the context of the AdS /CFT correspondence. The procedure consists in adding the Chern form as a boundary term to the area functional of the Ryu-Takayanagi minimal surface. The renormalized entanglement entropy thus obtained can be rewritten in terms of the Euler characteristic and the AdS curvature of the minimal surface. This prescription considers the use of the replica trick to express the renormalized entanglement entropy in terms of the renormalized gravitational action evaluated on the conically singular replica manifold extended to the bulk. This renormalized action is obtained in turn by adding the Chern form as the counterterm at the boundary of the 2 n -dimensional asymptotically AdS bulk manifold. We explicitly show that, up to next-to-leading order in the holographic radial coordinate, the addition of this boundary term cancels the divergent part of the entanglement entropy. We discuss possible applications of the method for studying CFT parameters like central charges.

A statistical study of the relationship between surface quality and laser induced damage

NASA Astrophysics Data System (ADS)

Turner, Trey; Turchette, Quentin; Martin, Alex R.

2012-11-01

Laser induced damage of optical components is a concern in many applications in the commercial, scientific and military market sectors. Numerous component manufacturers supply "high laser damage threshold" (HLDT) optics to meet the needs of this market, and consumers pay a premium price for these products. While there's no question that HLDT optics are manufactured to more rigorous standards (and are therefore inherently more expensive) than conventional products, it is not clear how this added expense translates directly into better performance. This is because the standard methods for evaluating laser damage, and the underlying assumptions about the validity of traditional laser damage testing, are flawed. In particular, the surface and coating defects that generally lead to laser damage (in many laserparameter regimes of interest) are widely distributed over the component surface with large spaces in between them. As a result, laser damage testing typically doesn't include enough of these defects to achieve the sample sizes necessary to make its results statistically meaningful. The result is a poor correlation between defect characteristics and damage events. This paper establishes specifically why this is the case, and provides some indication of what might be done to remedy the problem.

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)

Electrically controllable liquid crystal random lasers below the Fréedericksz transition threshold.

PubMed

Lee, Chia-Rong; Lin, Jia-De; Huang, Bo-Yuang; Lin, Shih-Hung; Mo, Ting-Shan; Huang, Shuan-Yu; Kuo, Chie-Tong; Yeh, Hui-Chen

2011-01-31

This investigation elucidates for the first time electrically controllable random lasers below the threshold voltage in dye-doped liquid crystal (DDLC) cells with and without adding an azo-dye. Experimental results show that the lasing intensities and the energy thresholds of the random lasers can be decreased and increased, respectively, by increasing the applied voltage below the Fréedericksz transition threshold. The below-threshold-electric-controllability of the random lasers is attributable to the effective decrease of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by increasing the electric-field-aligned order of LCs below the threshold, thereby increasing the diffusion constant and decreasing the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the decrease in the lasing intensity of the random lasers and the increase in their energy thresholds. Furthermore, the addition of an azo-dye in DDLC cell can induce the range of the working voltage below the threshold for the control of the random laser to reduce.

Closed Timelike Curves in (2+1)-AdS Gravity

NASA Astrophysics Data System (ADS)

Valtancoli, P.

We build the (2+1)-AdS gravity generalization of the Gott time machine using a first-order formalism for solving the scattering of point sources. The two-body dynamics is solved by two invariant masses, whose difference is simply related to the total angular momentum of the system. We show how to build a time machine when at least one of the two invariant masses is no more real but acquires an imaginary part.

Stochastic quantization of conformally coupled scalar in AdS

NASA Astrophysics Data System (ADS)

Jatkar, Dileep P.; Oh, Jae-Hyuk

2013-10-01

We explore the relation between stochastic quantization and holographic Wilsonian renormalization group flow further by studying conformally coupled scalar in AdS d+1. We establish one to one mapping between the radial flow of its double trace deformation and stochastic 2-point correlation function. This map is shown to be identical, up to a suitable field re-definition of the bulk scalar, to the original proposal in arXiv:1209.2242.

Exploring the bulk in AdS /CFT : A covariant approach

NASA Astrophysics Data System (ADS)

Engelhardt, Netta

2017-03-01

I propose a general, covariant way of defining when one region is "deeper in the bulk" than another. This definition is formulated outside of an event horizon (or in the absence thereof) in generic geometries; it may be applied to both points and surfaces, and it may be used to compare the depth of bulk points or surfaces relative to a particular boundary subregion or relative to the entire boundary. Using the recently proposed "light-cone cut" formalism, the comparative depth between two bulk points can be determined from the singularity structure of Lorentzian correlators in the dual field theory. I prove that, by this definition, causal wedges of progressively larger regions probe monotonically deeper in the bulk. The definition furthermore matches expectations in pure AdS and in static AdS black holes with isotropic spatial slices, where a well-defined holographic coordinate exists. In terms of holographic renormalization group flow, this new definition of bulk depth makes contact with coarse graining over both large distances and long time scales.

Ablation depth and its effects on corneal biomechanical changes in laser in situ keratomileusis and epipolis laser in situ keratomileusis.

PubMed

Zhang, Lin; Wang, Yan; Yang, Xiaoyan

2014-04-01

To assess the corneal biomechanical parameters prior to and following laser in situ keratomileusis (LASIK) and epipolis laser in situ keratomileusis (epi-LASIK) and evaluate the probable correlative factors. Corneal hysteresis (CH), corneal resistance factor (CRF) and other biomechanical metrics were measured and evaluated with an ocular response analyzer preoperatively and 1 month postoperatively. Compared with preoperative values, CH and CRF decreased significantly after surgery in both groups (P = 0.000). The LASIK group exhibited a positive correlation between ablation depth (AD) and ∆CH/∆CRF with a strong r value (r = 0.543, P = 0.000; r = 0.574, P = 0.000). In the epi-LASIK group, however, the correlation was much weaker (r = -0.090, P = 0.682; r = 0.093, P = 0.673), although there were no significant differences between LASIK and epi-LASIK groups in postoperative CH (P = 0.730) and CRF (P = 0.736), and in the changes between CH (P = 0.539) and CRF (P = 0.881). Corneal biomechanical changes correlated with AD in LASIK but not in epi-LASIK, and it appeared that patients with identical demographics and similar attempted corrections are more likely to face a greater danger when undergoing LASIK than epi-LASIK. Therefore, the surface ablation procedure was recommended instead of lamellar ablation especially for correcting high myopia from a biomechanical viewpoint.

Small black holes in global AdS spacetime

NASA Astrophysics Data System (ADS)

Jokela, Niko; Pönni, Arttu; Vuorinen, Aleksi

2016-04-01

We study the properties of two-point functions and quasinormal modes in a strongly coupled field theory holographically dual to a small black hole in global anti-de Sitter spacetime. Our results are seen to smoothly interpolate between known limits corresponding to large black holes and thermal AdS space, demonstrating that the Son-Starinets prescription works even when there is no black hole in the spacetime. Omitting issues related to the internal space, the results can be given a field theory interpretation in terms of the microcanonical ensemble, which provides access to energy densities forbidden in the canonical description.

High efficiency laser-pumped emerald lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, S.T.

1987-09-25

Highly efficient laser operation has been achieved in emerald. In a quasi-cw laser-pumped emerald laser, 64% output slope efficiency has been measured at 768 nm, corresponding to a laser quantum yield of 76%. An output power of 1.6 W was reached at 3.6 W of pump power at 647.1 nm from a krypton laser, and was pump power limited. The emerald laser has a tuning range of 720 to 842 nm. The round trip loss excluding the excited state absorption (ESA) is 0.4%/cm. These results indicate the high laser efficiency and the high optical quality of the emerald attainable inmore » the present laser.« less

Constant curvature black holes in Einstein AdS gravity: Euclidean action and thermodynamics

NASA Astrophysics Data System (ADS)

Guilleminot, Pablo; Olea, Rodrigo; Petrov, Alexander N.

2018-03-01

We compute the Euclidean action for constant curvature black holes (CCBHs), as an attempt to associate thermodynamic quantities to these solutions of Einstein anti-de Sitter (AdS) gravity. CCBHs are gravitational configurations obtained by identifications along isometries of a D -dimensional globally AdS space, such that the Riemann tensor remains constant. Here, these solutions are interpreted as extended objects, which contain a (D -2 )-dimensional de-Sitter brane as a subspace. Nevertheless, the computation of the free energy for these solutions shows that they do not obey standard thermodynamic relations.

Lasers '81

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, C.B.

1982-01-01

Progress in lasers is discussed. The subjects addressed include: excimer lasers, surface spectroscopy, modern laser spectroscopy, free electron lasers, cavities and propagation, lasers in medicine, X-ray and gamma ray lasers, laser spectroscopy of small molecules and clusters, optical bistability, excitons, nonlinear optics in the X-ray and gamma ray regions, collective atomic phenomena, tunable IR lasers, far IR/submillimeter lasers, and laser-assisted collisions. Also treated are: special applications, multiphoton processes in atoms and small molecules, nuclear pumped lasers, material processing and applications, polarization, high energy lasers, laser chemistry, IR molecular lasers, laser applications of collision and dissociation phenomena, solid state laser materials,more » phase conjugation, advances in laser technology for fusion, metal vapor lasers, picosecond phenomena, laser ranging and geodesy, and laser photochemistry of complex molecules.« less

AdVEGF-All6A+ Preconditioning of Murine Ischemic Skin Flaps Is Comparable to Surgical Delay.

PubMed

Gersch, Robert P; Fourman, Mitchell S; Phillips, Brett T; Nasser, Ahmed; McClain, Steve A; Khan, Sami U; Dagum, Alexander B; Bui, Duc T

2015-08-01

Surgical flap delay is commonly used in preconditioning reconstructive flaps to prevent necrosis. However, staged procedures are not ideal. Pharmacologic up-regulation of angiogenic and arteriogenic factors before flap elevation poses a nonsurgical approach to improve flap survival. Male Sprague Dawley rats were divided into control (n = 16), surgical delay (Delay), AdNull, AdEgr-1, and AdVEGF (n ≥ 9/group) groups. Delay rats had a 9 cm × 3 cm cranial based pedicle skin flap incised 10 days prior to elevation. Adenoviral groups received 28 intradermal injections (10(9) pu/animal total) throughout the distal two thirds of the flap 1 week prior to elevation. At postoperative day (POD) 0 flaps were elevated and silicone sheeting was placed between flap and wound bed. Perfusion analysis in arbitrary perfusion units of the ischemic middle third of the flap using laser Doppler imaging was conducted preoperatively and on POD 0, 3, and 7. Clinical and histopathologic assessments of the skin flaps were performed on POD 7. AdVEGF (50.8 ± 10.9 APU) and AdEgr-1 (39.3 ± 10.6 APU) perfusion levels were significantly higher than controls (16.5 ± 4.2 APU) on POD 7. Delay models were equivalent to controls (25.9 ± 6.8 APU). AdVEGF and Delay animals showed significantly more viable surface area on POD 7 (14.4 ± 1.3 cm(2), P < 0.01 and 12.4 ± 1.2 cm(2), P < 0.05, respectively) compared with Controls (8.7 ± 0.7 cm(2)). AdVEGF preconditioning resulted in flap survival comparable to surgical delay. Adenoviral preconditioning maintained perfusion levels postoperatively while surgical delay did not.

AdVEGF-All6A+ Preconditioning of Murine Ischemic Skin Flaps Is Comparable to Surgical Delay

PubMed Central

Gersch, Robert P.; Fourman, Mitchell S.; Phillips, Brett T.; Nasser, Ahmed; McClain, Steve A.; Khan, Sami U.; Dagum, Alexander B.

2015-01-01

Background: Surgical flap delay is commonly used in preconditioning reconstructive flaps to prevent necrosis. However, staged procedures are not ideal. Pharmacologic up-regulation of angiogenic and arteriogenic factors before flap elevation poses a nonsurgical approach to improve flap survival. Methods: Male Sprague Dawley rats were divided into control (n = 16), surgical delay (Delay), AdNull, AdEgr-1, and AdVEGF (n ≥ 9/group) groups. Delay rats had a 9 cm × 3 cm cranial based pedicle skin flap incised 10 days prior to elevation. Adenoviral groups received 28 intradermal injections (109 pu/animal total) throughout the distal two thirds of the flap 1 week prior to elevation. At postoperative day (POD) 0 flaps were elevated and silicone sheeting was placed between flap and wound bed. Perfusion analysis in arbitrary perfusion units of the ischemic middle third of the flap using laser Doppler imaging was conducted preoperatively and on POD 0, 3, and 7. Clinical and histopathologic assessments of the skin flaps were performed on POD 7. Results: AdVEGF (50.8 ± 10.9 APU) and AdEgr-1 (39.3 ± 10.6 APU) perfusion levels were significantly higher than controls (16.5 ± 4.2 APU) on POD 7. Delay models were equivalent to controls (25.9 ± 6.8 APU). AdVEGF and Delay animals showed significantly more viable surface area on POD 7 (14.4 ± 1.3 cm2, P < 0.01 and 12.4 ± 1.2 cm2, P < 0.05, respectively) compared with Controls (8.7 ± 0.7 cm2). Conclusions: AdVEGF preconditioning resulted in flap survival comparable to surgical delay. Adenoviral preconditioning maintained perfusion levels postoperatively while surgical delay did not. PMID:26495207

Target tracking and pointing for arrays of phase-locked lasers

NASA Astrophysics Data System (ADS)

Macasaet, Van P.; Hughes, Gary B.; Lubin, Philip; Madajian, Jonathan; Zhang, Qicheng; Griswold, Janelle; Kulkarni, Neeraj; Cohen, Alexander; Brashears, Travis

2016-09-01

Arrays of phase-locked lasers are envisioned for planetary defense and exploration systems. High-energy beams focused on a threatening asteroid evaporate surface material, creating a reactionary thrust that alters the asteroid's orbit. The same system could be used to probe an asteroid's composition, to search for unknown asteroids, and to propel interplanetary and interstellar spacecraft. Phased-array designs are capable of producing high beam intensity, and allow beam steering and beam profile manipulation. Modular designs allow ongoing addition of emitter elements to a growing array. This paper discusses pointing control for extensible laser arrays. Rough pointing is determined by spacecraft attitude control. Lateral movement of the laser emitter tips behind the optical elements provides intermediate pointing adjustment for individual array elements and beam steering. Precision beam steering and beam formation is accomplished by coordinated phase modulation across the array. Added cells are incorporated into the phase control scheme by precise alignment to local mechanical datums using fast, optical relative position sensors. Infrared target sensors are also positioned within the datum scheme, and provide information about the target vector relative to datum coordinates at each emitter. Multiple target sensors allow refined determination of the target normal plane, providing information to the phase controller for each emitter. As emitters and sensors are added, local position data allows accurate prediction of the relative global position of emitters across the array, providing additional constraints to the phase controllers. Mechanical design and associated phase control that is scalable for target distance and number of emitters is presented.

Sex steroid levels and AD-like pathology in 3xTgAD mice

PubMed Central

Ma, Chunqi; Taves, Matthew D.; Soma, Kiran K.; Mufson, Elliott J.

2014-01-01

Decreases in testosterone (T) and 17β-oestradiol (E2) are associated with an increased risk for Alzheimer's disease (AD), which has been attributed to an increase in beta amyloid (Aβ) and tau pathologic lesions. While recent studies have used transgenic animal models to test the effects of sex steroid manipulations on AD-like pathology, virtually none have systematically characterised the associations between AD lesions and sex steroid levels in the blood or brain in any mutant model. The present study evaluated age-related changes in T and E2 concentrations, as well as androgen receptor (AR) and oestrogen receptor (ER) α and β expression, in brain regions displaying AD pathology in intact male and female 3xTgAD and non-transgenic (ntg) mice. We report for the first time that circulating and brain T levels significantly increase in male 3xTgAD mice with age, but without changes in AR-immunoreactive (ir) cell number in either the hippocampal CA1 or medial amygdala. The age-related increase in hippocampal T levels correlated positively with increases in the conformational tau isoform, Alz50. These data suggest that the over-expression of human tau may up regulate the hypothalamic-pituitary-gonadal axis in these mice. Although circulating and brain E2 levels remained stable with age in both male and female 3xTgAD and ntg mice, ER-ir cell number in the hippocampus and medial amygdala decreased with age in female transgenic mice. Further, E2 levels were significantly higher in the hippocampus than in serum, suggesting local production of E2. Although triple transgenic mice mimic AD-like pathology, they do not fully replicate changes in human sex steroid levels, and may not be the best model for studying the effects of sex steroids on AD lesions. PMID:22889357

Entanglement entropy of AdS5 × S5 with massive flavors

NASA Astrophysics Data System (ADS)

Hu, Sen; Wu, Guozhen

2018-01-01

We consider backreacted AdS5 × S5 coupled with Nf massive flavors introduced by D7 branes. The backreacted geometry is in the Veneziano limit with fixed Nf/Nc. By dividing one of the directions into a line segment with length l, we get two subspaces. Then we calculate the entanglement entropy between them. With the method of [I. R. Klebanov, D. Kutasov and A. Murugan, Nucl. Phys. B 796, 274 (2008)], we are able to find the cut-off independent part of the entanglement entropy and finally find that this geometry shows no confinement/deconfinement phase transition at zero temperature from the holographic entanglement entropy point of view similar to the case in pure AdS5 × S5.

AdS black disk model for small-x DIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cornalba, Lorenzo; Costa, Miguel S.; Penedones, Joao

2011-05-23

Using the approximate conformal invariance of QCD at high energies we consider a simple AdS black disk model to describe saturation in DIS. Deep inside saturation the structure functions have the same power law scaling, F{sub T}{approx}F{sub L}{approx}{sup -}{omega}, where {omega} is related to the expansion rate of the black disk with energy. Furthermore, the ratio F{sub L}/F{sub T} is given by the universal value (1+{omega}/3+{omega}), independently of the target.

The Tetrahedral Zamolodchikov Algebra and the {AdS_5× S^5} S-matrix

NASA Astrophysics Data System (ADS)

Mitev, Vladimir; Staudacher, Matthias; Tsuboi, Zengo

2017-08-01

The S-matrix of the {AdS_5× S^5} string theory is a tensor product of two centrally extended su{(2|2)\\ltimes R^2 S-matrices, each of which is related to the R-matrix of the Hubbard model. The R-matrix of the Hubbard model was first found by Shastry, who ingeniously exploited the fact that, for zero coupling, the Hubbard model can be decomposed into two XX models. In this article, we review and clarify this construction from the AdS/CFT perspective and investigate the implications this has for the {AdS_5× S^5} S-matrix.

Laser ablated micropillar energy directors for ultrasonic welding of microfluidic systems

NASA Astrophysics Data System (ADS)

Esben Poulsen, Carl; Kistrup, Kasper; Korsgaard Andersen, Nis; Taboryski, Rafael; Fougt Hansen, Mikkel; Wolff, Anders

2016-06-01

We present a new type of energy director (ED) for ultrasonic welding of microfluidic systems. These micropillar EDs are based on the replication of cone like protrusion structures introduced using a pico-second laser and may therefore be added to any mould surface accessible to a pico-second laser beam. The technology is demonstrated on an injection moulded microfluidic device featuring high-aspect ratio (h  ×  w  =  2000 μm  ×  550 μm) and free-standing channel walls, where bonding is achieved with no detectable channel deformation. The bonding strength is similar to conventional EDs and the fabricated system can withstand pressures of over 9.5 bar.

Enhancement of light absorption by blood to Nd:YAG laser using PEG-modified gold nanorods.

PubMed

Xing, Linzhuang; Li, Dong; Chen, Bin; Dai, Yuze; Wu, Wenjuan; Wang, Guoxiang

2016-10-01

On the basis of the principle of selective photothermolysis, laser therapy has been the most effective treatment strategy for Port-wine stains (PWSs) caused by the expansion of dermal capillaries. Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser at 1064 nm wavelength has great potential for deeply buried PWS, although its application is limited because of its weak absorption by blood. The purpose of this study is to investigate the effect of PEG-modified gold nanorods (NRs) on the blood absorption enhancement for Nd:YAG laser. PEG-modified gold nanorods (NRs) were synthesized via the seeded growth method. Then, the effect of PEG-modified gold NRs on blood light absorbance was investigated through adding different concentration of PEG-modified gold NRs to 1 ml of blood at room temperature. Finally, the optical properties of whole mice blood with or without PEG-modified gold NRs under slow heating were investigated. The average length and width of PEG-modified gold NRs are 79.5 ± 10.5 and 13.5 ± 0.9 nm, respectively, with the aspect ratio of 5.89, and a strong absorption peak exists at ∼1050 nm in the near-infrared range. A linear correlation between the blood absorbance at 1064 nm and the amount of PEG-modified gold NRs was obtained. The absorbance at 1064 nm increased 17.6, 33.0, 48.3, and 65.4 times when 0.4, 0.8, 1.2, and 1.6 mg of PEG-modified gold NRs was added to 1 ml of blood at room temperature, respectively. After adding 0.8 mg of PEG-modified gold NRs to 1 ml of blood, blood absorbance at 1064 nm at different temperatures increased by an average of 24.0 times. After intravenously injecting PEG-modified gold NRs (0.87 mg/ml) into Sprague-Dawley mice, the blood absorbance at 1064 nm increased from 0.014 to 0.5. Our findings suggest that PEG-modified gold NRs injection is an efficient way to enhance light absorption by blood to Nd:YAG laser. Lasers Surg. Med. 48:790-803, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley

Partition functions with spin in AdS2 via quasinormal mode methods

DOE PAGES

Keeler, Cynthia; Lisbão, Pedro; Ng, Gim Seng

2016-10-12

We extend the results of [1], computing one loop partition functions for massive fields with spin half in AdS 2 using the quasinormal mode method proposed by Denef, Hartnoll, and Sachdev [2]. We find the finite representations of SO(2,1) for spin zero and spin half, consisting of a highest weight state |hi and descendants with non-unitary values of h. These finite representations capture the poles and zeroes of the one loop determinants. Together with the asymptotic behavior of the partition functions (which can be easily computed using a large mass heat kernel expansion), these are sufficient to determine the fullmore » answer for the one loop determinants. We also discuss extensions to higher dimensional AdS 2n and higher spins.« less

Thermodynamics and phase transition of charged AdS black holes with a global monopole

NASA Astrophysics Data System (ADS)

Deng, Gao-Ming; Fan, Jinbo; Li, Xinfei; Huang, Yong-Chang

2018-01-01

Thermodynamical properties of charged AdS black holes with a global monopole still remain obscure. In this paper, we investigate the thermodynamics and phase transition of the black holes in the extended phase space. It is shown that thermodynamical quantities of the black holes exhibit an interesting dependence on the internal global monopole, and they perfectly satisfy both the first law of thermodynamics and Smarr relation. Furthermore, analysis of the local and the global thermodynamical stability manifests that the charged AdS black hole undergoes an elegant phase transition at critical point. Of special interest, critical behaviors of the black holes resemble a Van der Waals liquid-gas system. Our results not only reveal the effect of a global monopole on thermodynamics of AdS black holes, but also further support that Van der Waals-like behavior of the black holes is a universal phenomenon.

Supergravity backgrounds for deformations of AdS n × S n supercoset string models

DOE PAGES

Lunin, O.; Roiban, R.; Tseytlin, A. A.

2014-12-11

We considermore » type IIB supergravity backgrounds corresponding to the deformed AdS n × S n × T 10 - 2 n supercoset string models of the type constructed in arXiv:1309.5850[2] which depend on one deformation parameter κ. In AdS 2 × S 2 case we find that the deformed metric can be extended to a full supergravity solution with non-trivial dilaton, RR scalar and RR 5-form strength. The solution depends on a free parameter a that should be chosen as a particular function of κ to correspond to the deformed supercoset model. In AdS 3 × S 3 case the full solution supported by the dilaton, RR scalar and RR 3-form strength exists only in the two special cases, a = 0 and a = 1 . We conjecture that there may be a more general one-parameter solution supported by several RR fields that for particular a = a ( κ ) corresponds to the supercoset model. In the most complicated deformed AdS 5 × S 5 case we were able to find only the expressions for the dilaton and the RR scalar. The full solution is likely to be supported by a combination of the 5-form and 3-form field strengths. We comment on the singularity structure of the resulting metric and exact dilaton field.« less

Supergravity backgrounds for deformations of AdS n × S n supercoset string models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lunin, O.; Roiban, R.; Tseytlin, A. A.

We considermore » type IIB supergravity backgrounds corresponding to the deformed AdS n × S n × T 10 - 2 n supercoset string models of the type constructed in arXiv:1309.5850[2] which depend on one deformation parameter κ. In AdS 2 × S 2 case we find that the deformed metric can be extended to a full supergravity solution with non-trivial dilaton, RR scalar and RR 5-form strength. The solution depends on a free parameter a that should be chosen as a particular function of κ to correspond to the deformed supercoset model. In AdS 3 × S 3 case the full solution supported by the dilaton, RR scalar and RR 3-form strength exists only in the two special cases, a = 0 and a = 1 . We conjecture that there may be a more general one-parameter solution supported by several RR fields that for particular a = a ( κ ) corresponds to the supercoset model. In the most complicated deformed AdS 5 × S 5 case we were able to find only the expressions for the dilaton and the RR scalar. The full solution is likely to be supported by a combination of the 5-form and 3-form field strengths. We comment on the singularity structure of the resulting metric and exact dilaton field.« less

The generalization of charged AdS black hole specific volume and number density

NASA Astrophysics Data System (ADS)

Wang, Zi-Liang; He, Miao; Fang, Chao; Sun, Dao-Quan; Deng, Jian-Bo

2017-04-01

In this paper, by proposing a generalized specific volume, we restudy the P- V criticality of charged AdS black holes in the extended phase space. The results show that most of the previous conclusions can be generalized without change, but the ratio {\\tilde{ρ }}_c should be 3 {\\tilde{α }}/16 in general case. Further research on the thermodynamical phase transition of black hole leads us to a natural interpretation of our assumption, and more black hole properties can be generalized. Finally, we study the number density for charged AdS black hole in higher dimensions, the results show the necessity of our assumption.

The Effects of Atmospheric Water Vapor Absorption on Infrared Laser Propagation in the 5 Micrometer Band.

DTIC Science & Technology

1983-05-01

which allows for thermal linedr expansion of the structure. 32 1 I 2. Second Harmonic Generation The second harmonic generation was achieved by mounting a...filter unit and then to the reference channel lock-in amplifier. C. TESTS 1 . DC Amplifier and A/D Calibration The Ectron DC amplifiers and the Altair A/D...AD-A130 788 THE EFFECTS OF ATMOSPHERIC WATER VAPOR ABSORPTION ON 1 / INFRARED LASER PRUPA..(U) OHIO STATE UNIV COLUMBUS ELECTROSCIENCE LAB L G WALTER

Design and implementation of a system for laser assisted milling of advanced materials

NASA Astrophysics Data System (ADS)

Wu, Xuefeng; Feng, Gaocheng; Liu, Xianli

2016-09-01

Laser assisted machining is an effective method to machine advanced materials with the added benefits of longer tool life and increased material removal rates. While extensive studies have investigated the machining properties for laser assisted milling(LAML), few attempts have been made to extend LAML to machining parts with complex geometric features. A methodology for continuous path machining for LAML is developed by integration of a rotary and movable table into an ordinary milling machine with a laser beam system. The machining strategy and processing path are investigated to determine alignment of the machining path with the laser spot. In order to keep the material removal temperatures above the softening temperature of silicon nitride, the transformation is coordinated and the temperature interpolated, establishing a transient thermal model. The temperatures of the laser center and cutting zone are also carefully controlled to achieve optimal machining results and avoid thermal damage. These experiments indicate that the system results in no surface damage as well as good surface roughness, validating the application of this machining strategy and thermal model in the development of a new LAML system for continuous path processing of silicon nitride. The proposed approach can be easily applied in LAML system to achieve continuous processing and improve efficiency in laser assisted machining.

Operation and tests of a DDC101 A/D

NASA Astrophysics Data System (ADS)

Nguyen, H.

1994-11-01

For the KTeV PMT laser monitoring system, one needs a high resolution device with a large dynamic range to be used for digitizing PIN photodiodes. The dynamic range should be wider than or comparable to the KTeV digitizer (17-bits). The Burr-Brown DDC101 is a precision, wide dynamic range, charge digitizing A/D converter with 20-bit resolution, packaged in a 28-pin plastic, double-wide DP. Low level current output devices such as photosensors can be directly connected to its input. The digital output can be clocked-out serially from the pins. For typical operations, a relatively wide gate of 1 msec should be used. The full scale charge is 500 pC for unipolar mode. The bipolar mode scale is +/- 250 pC. The advertised integral nonlinearity is 0.003% of FSR. This document describes only the basic DDC101 operations since full detail can be found in the DDC101 manual. Tests results are given in section 3.

Characterization of skin tissue soldering using diode laser and indocyanine green: in vitro studies.

PubMed

Khosroshahi, M E; Nourbakhsh, M S; Saremi, S; Tabatabaee, F

2010-03-01

Laser tissue soldering based on protein as biological glues and other compounds can provide greater bond strength and less collateral damage. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. The purpose of this in vitro study was to examine the impact of different parameters of laser soldering on the thermo-physical properties of the skin. A mixture of albumin solder and ICG was prepared, and then the coated samples were irradiated by an 810 nm diode laser under different conditions. The temperature rise, number of scans (N(s)), and scan velocity (V(s)) were investigated in this study. The results showed that, at each laser irradiance (I), the tensile strength (sigma) of incisions repaired in static mode was higher than in dynamic mode and that the sigma increased with both increasing N(s) and increasing I. It is therefore important to consider the trade off between scan velocity and surface temperature for achieving an optimum operating condition.

Phased laser array for generating a powerful laser beam

DOEpatents

Holzrichter, John F.; Ruggiero, Anthony J.

2004-02-17

A first injection laser signal and a first part of a reference laser beam are injected into a first laser element. At least one additional injection laser signal and at least one additional part of a reference laser beam are injected into at least one additional laser element. The first part of a reference laser beam and the at least one additional part of a reference laser beam are amplified and phase conjugated producing a first amplified output laser beam emanating from the first laser element and an additional amplified output laser beam emanating from the at least one additional laser element. The first amplified output laser beam and the additional amplified output laser beam are combined into a powerful laser beam.

Laser network survey and orbit recovery. [altimeter evaluation in GEOS-C project

NASA Technical Reports Server (NTRS)

Berbert, J. H.

1974-01-01

Simulations were performed for the anticipated GEOS-C laser network stations at Goddard, Bermuda, and Florida to predict how well survey and orbit will be recovered. Lasers were added one at a time at Grand Turk, Antigua, and Panama to estimate the contribution from these additional sites. Time tag biases of 50 microseconds, survey uncertainties of 10 meters in each coordinate, laser range biases and noise estimates of 20 cm each, and conventional gravity uncertainties were included in the simulations. The results indicate that survey can be recovered to about 1 meter and Grand Turk can be recovered better than Antigua or Panama. Reducing the probably pessimistic assumed time tag biases and gravity field uncertainties improves the results. Using these survey recovery estimates, the short arc GEOS-C satellite heights for altimeter intercomparison orbits can be recovered within the calibration area to better than the required two meters.

Design and verification of a novel hollow vibrating module for laser machining.

PubMed

Wang, Zhaozhao; Jang, Seungbong; Kim, EunHee; Jeon, Yongho; Lee, Soo-Hun; Lee, Moon G

2015-04-01

If a vibration module is added on laser machining system, the quality of surface finish and aspect ratio on metals can be significantly enhanced. In this study, a single mobility model of vibrating laser along the path of laser beam was put forward. In order to realize the desired unidirectional motion, a resonance type vibration module with optical lens was designed and manufactured. This cylindrical module was composed of curved-beam flexure elements. The cylindrical coordinate system was established to describe the relationship of a curved-beam flexure element's motion and deformation. In addition, the stiffness matrix of the curved-beam element was obtained. Finite element method and dynamical modeling were provided to analyze the resonance frequency and the displacement of the motion. The feasibility of the design was demonstrated with the help of experiments on frequency response. Experimental results show good agreement with theoretical analysis and simulation predictions.

What makes an ad a cigarette ad? Commercial tobacco imagery in the lesbian, gay, and bisexual press

PubMed Central

Smith, E.; Offen, N.; Malone, R.

2005-01-01

Objectives: To determine the extent of commercial tobacco imagery in the lesbian, gay, and bisexual (LGB) press. Methods: Content analysis of all advertising containing tobacco related text or imagery in 20 LGB community periodicals, published between January 1990 and December 2000. Results: 3428 ads were found: 689 tobacco product ads, 1607 ads for cessation products or services, 99 ads with a political message about tobacco, and 1033 non-tobacco ads that showed tobacco (NAST). Although cessation ads were numerically dominant, tobacco product ads and NAST occupied more space and were more likely to use images. NAST almost never had an anti-tobacco message. Formal sponsorship between tobacco and other companies was very rare. Lesbian periodicals had proportionally more NAST and fewer cessation ads. Conclusions: Cigarette ads were outnumbered by NAST. Although these ads do not usually show brands, and are unlikely to be the result of formal sponsorship agreements, they may be "selling" smoking. Tobacco control advocates should persuade editors to refuse tobacco product ads and those with gratuitous tobacco imagery. PMID:16286500

Gain measurements and spatial coherence in neon-like x-ray lasers

NASA Astrophysics Data System (ADS)

Krishnan, J.; Cairns, C.; Dwivedi, L.; Holden, M.; Key, M. H.; Lewis, C. L. S.; MacPhee, A.; Neely, D.; Norreys, P. A.; Pert, G. J.; Ramsden, S. A.; Smith, C. G.; Tallents, G. J.; Zhang, J.

1995-05-01

Many of the applications with x-ray lasers require high quality output radiation with properties such as short wavelength and a high degree of coherence (longitudinal and spatial). Ne-like Yttrium (Z=39) is potentially a bright and monochromatic XUV lasing medium. The output at 15.5 nm is monochromatic due to the overlap of the J=2-1 and J=0-1 lines. A gain coefficient of 3±1 was obtained at 15.5 nm by irradiating 100 μm wide yttrium stripes at 6×1013 W/cm2 with 1.06 μm, 650 ps pulses from the Rutherford Appleton Laboratory VULCAN laser. We have investigated improving x-ray laser spatial coherence utilizing a series of amplifiers instead of the standard double target configuration. An ``injector-amplifier'' scheme was successfully demonstrated with the Ne-like Ge x-ray laser. A spatially small and coherent part of the 23 nm beam from the standard double target geometry has been relayed using a W/Si multilayer mirror onto a single or double target configuration situated at a distance of ˜1.5 m from the mirror and pumped by two 150 mm diameter beams of VULCAN laser. A beam ``foot-print monitor'' was employed with a flat mirror to relay 23 nm output onto a film pack to record the spatial variation of the x-ray laser beam. Analyzing the fringes obtained through a cross-wire placed in front of the beam shows that an increase in spatial coherence was achieved by adding amplifiers to the x-ray laser beam line.

Complexity of the AdS soliton

NASA Astrophysics Data System (ADS)

Reynolds, Alan P.; Ross, Simon F.

2018-05-01

We consider the holographic complexity conjectures in the context of the AdS soliton, which is the holographic dual of the ground state of a field theory on a torus with antiperiodic boundary conditions for fermions on one cycle. The complexity is a non-trivial function of the size of the circle with antiperiodic boundary conditions, which sets an IR scale in the dual geometry. We find qualitative differences between the calculations of complexity from spatial volume and action (CV and CA). In the CV calculation, the complexity for antiperiodic boundary conditions is smaller than for periodic, and decreases monotonically with increasing IR scale. In the CA calculation, the complexity for antiperiodic boundary conditions is larger than for periodic, and initially increases with increasing IR scale, eventually decreasing to zero as the IR scale becomes of order the UV cutoff. We compare these results to a simple calculation for free fermions on a lattice, where we find the complexity for antiperiodic boundary conditions is larger than for periodic.

CW laser pumped emerald laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shand, M.L.; Lai, S.T.

1984-02-01

A CW laser-pumped emerald laser is reported. A 34 percent output power slope efficiency is observed with longitudinal pumping by a krypton laser in a nearly concentric cavity. The laser has been tuned from 728.8 to 809.0 nm. Losses in emerald are larger than those of alexandrite determined in a similar cavity. The present data also indicate that the excited state absorption minimum is shifted from that of alexandrite. 13 references.

New laser materials for laser diode pumping

NASA Technical Reports Server (NTRS)

Jenssen, H. P.

1990-01-01

The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.

Subpicosecond pulses from a neodymium-glass laser with a solid-liquid phototropic shutter

NASA Astrophysics Data System (ADS)

Altshuler, G. B.; Dulneva, E. G.; Karasev, V. B.; Okishev, A. V.; Telegin, L. S.

1985-02-01

Subpicosecond, spectrally limited pulses were generated in a mode-locked silicate-Nd-glass laser by means of a phototropic shutter. The shutter featured molecules of an organic dye added to a matrix composed of an isobutyl alcohol-filled quartz micropore glass plate. A coating on the inner surface of one of the cell windows was 0.99 reflective at the lasing wavelength. Single pulses with 0.5-1 psec length were generated, validating the use of a solid-liquid shutter for producing subpicosecond pulses with a Nd-glass laser. Furthermore, the liquid component permitted output powers of up to 5 W/sq cm without eliciting thermooptical effects.

Adiabatic pumping solutions in global AdS

NASA Astrophysics Data System (ADS)

Carracedo, Pablo; Mas, Javier; Musso, Daniele; Serantes, Alexandre

2017-05-01

We construct a family of very simple stationary solutions to gravity coupled to a massless scalar field in global AdS. They involve a constantly rising source for the scalar field at the boundary and thereby we name them pumping solutions. We construct them numerically in D = 4. They are regular and, generically, have negative mass. We perform a study of linear and nonlinear stability and find both stable and unstable branches. In the latter case, solutions belonging to different sub-branches can either decay to black holes or to limiting cycles. This observation motivates the search for non-stationary exactly timeperiodic solutions which we actually construct. We clarify the role of pumping solutions in the context of quasistatic adiabatic quenches. In D = 3 the pumping solutions can be related to other previously known solutions, like magnetic or translationally-breaking backgrounds. From this we derive an analytic expression.

Hippocampal lipid differences in Alzheimer's disease: a human brain study using matrix-assisted laser desorption/ionization-imaging mass spectrometry.

PubMed

Mendis, Lakshini H S; Grey, Angus C; Faull, Richard L M; Curtis, Maurice A

2016-10-01

Alzheimer's disease (AD), the leading cause of dementia, is pathologically characterized by β-amyloid plaques and tau tangles. However, there is also evidence of lipid dyshomeostasis-mediated AD pathology. Given the structural diversity of lipids, mass spectrometry is a useful tool for studying lipid changes in AD. Although there have been a few studies investigating lipid changes in the human hippocampus in particular, there are few reports on how lipids change in each hippocampal subfield (e.g., Cornu Ammonis [CA] 1-4, dentate gyrus [DG] etc.). Since each subfield has its own function, we postulated that there could be lipid changes that are unique to each. We used matrix-assisted laser desorption/ionization-imaging mass spectrometry to investigate specific lipid changes in each subfield in AD. Data from the hippocampus region of six age- and gender-matched normal and AD pairs were analyzed with SCiLS lab 2015b software (SCiLS GmbH, Germany; RRID:SCR_014426), using an analysis workflow developed in-house. Hematoxylin, eosin, and luxol fast blue staining were used to precisely delineate each anatomical hippocampal subfield. Putative lipid identities, which were consistent with published data, were assigned using MS/MS. Both positively and negatively charged lipid ion species were abundantly detected in normal and AD tissue. While the distribution pattern of lipids did not change in AD, the abundance of some lipids changed, consistent with trends that have been previously reported. However, our results indicated that the majority of these lipid changes specifically occur in the CA1 region. Additionally, there were many lipid changes that were specific to the DG. Matrix-assisted laser desorption/ionization-imaging mass spectrometry and our analysis workflow provide a novel method to investigate specific lipid changes in hippocampal subfields. Future work will focus on elucidating the role that specific lipid differences in each subfield play in AD pathogenesis.

Genetics Home Reference: maternally inherited diabetes and deafness

MedlinePlus

... Maassen JA. Mutation in mitochondrial tRNA(Leu)(UUR) gene in a large pedigree with maternally transmitted type II diabetes mellitus ... are genome editing and CRISPR-Cas9? What is precision medicine? What ...

Loop corrections for Kaluza-Klein AdS amplitudes

NASA Astrophysics Data System (ADS)

Aprile, F.; Drummond, J. M.; Heslop, P.; Paul, H.

2018-05-01

Recently we conjectured the four-point amplitude of graviton multiplets in AdS5 × S5 at one loop by exploiting the operator product expansion of N = 4 super Yang-Mills theory. Here we give the first extension of those results to include Kaluza-Klein modes, obtaining the amplitude for two graviton multiplets and two states of the first KK mode. Our method again relies on resolving the large N degeneracy among a family of long double-trace operators, for which we obtain explicit formulas for the leading anomalous dimensions. Having constructed the one-loop amplitude we are able to obtain a formula for the one-loop corrections to the anomalous dimensions of all twist five double-trace operators.

Feasible Application Area Study for Linear Laser Cutting in Paper Making Processes

NASA Astrophysics Data System (ADS)

Happonen, A.; Stepanov, A.; Piili, H.

Traditional industry sectors, like paper making industry, tend to stay within well-known technology rather than going forward towards promising, but still quite new technical solutions and applications. This study analyses the feasibility of the laser cutting in large-scale industrial paper making processes. Aim was to reveal development and process related challenges and improvement potential in paper making processes by utilizing laser technology. This study has been carried out, because there still seems to be only few large-scale industrial laser processing applications in paper converting processes worldwide, even in the beginning of 2010's. Because of this, the small-scale use of lasers in paper material manufacturing industry is related to a shortage of well-known and widely available published research articles and published measurement data (e.g. actual achieved cut speeds with high quality cut edges, set-up times and so on). It was concluded that laser cutting has strong potential in industrial applications for paper making industries. This potential includes quality improvements and a competitive advantage for paper machine manufacturers and industry. The innovations have also added potential, when developing new paper products. An example of these kinds of products are ones with printed intelligence, which could be a new business opportunity for the paper industries all around the world.

Functional Safety of Hybrid Laser Safety Systems - How can a Combination between Passive and Active Components Prevent Accidents?

NASA Astrophysics Data System (ADS)

Lugauer, F. P.; Stiehl, T. H.; Zaeh, M. F.

Modern laser systems are widely used in industry due to their excellent flexibility and high beam intensities. This leads to an increased hazard potential, because conventional laser safety barriers only offer a short protection time when illuminated with high laser powers. For that reason active systems are used more and more to prevent accidents with laser machines. These systems must fulfil the requirements of functional safety, e.g. according to IEC 61508, which causes high costs. The safety provided by common passive barriers is usually unconsidered in this context. In the presented approach, active and passive systems are evaluated from a holistic perspective. To assess the functional safety of hybrid safety systems, the failure probability of passive barriers is analysed and added to the failure probability of the active system.

On the on-shell: the action of AdS4 black holes

NASA Astrophysics Data System (ADS)

Halmagyi, Nick; Lal, Shailesh

2018-03-01

We compute the on-shell action of static, BPS black holes in AdS4 from N=2 gauged supergravity coupled to vector multiplets and show that for a certain class it is equal to minus the entropy of the black hole. Holographic renormalization is used to demonstrate that with Neumann boundary conditions on the scalar fields, the divergent and finite contributions from the asymptotic boundary vanish. The entropy arises from the extrinsic curvature on Σ g × S 1 evaluated at the horizon, where Σ g may have any genus g ≥ 0. This provides a clarification of the equivalence between the partition function of the twisted ABJM theory on Σ g × S 1 and the entropy of the dual black hole solutions. It also demonstrates that the complete entropy resides on the AdS2 × Σ g horizon geometry, implying the absence of hair for these gravity solutions.

Laser system using ultra-short laser pulses

DOEpatents

Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

2009-10-27

A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

Matera Laser Ranging Observatory (MLRO): An overview

NASA Technical Reports Server (NTRS)

Varghese, Thomas K.; Decker, Winfield M.; Crooks, Henry A.; Bianco, Giuseppe

1993-01-01

The Agenzia Spaziale Italiana (ASI) is currently under negotiation with the Bendix Field Engineering Corporation (BFEC) of the Allied Signal Aerospace Company (ASAC) to build a state-of-the-art laser ranging observatory for the Centro di Geodesia Spaziale, in Matera, Italy. The contract calls for the delivery of a system based on a 1.5 meter afocal Cassegrain astronomical quality telescope with multiple ports to support a variety of experiments for the future, with primary emphasis on laser ranging. Three focal planes, viz. Cassegrain, Coude, and Nasmyth will be available for these experiments. The open telescope system will be protected from dust and turbulence using a specialized dome which will be part of the building facilities to be provided by ASI. The fixed observatory facility will be partitioned into four areas for locating the following: laser, transmit/receive optics, telescope/dome enclosure, and the operations console. The optical tables and mount rest on a common concrete pad for added mechanical stability. Provisions will be in place for minimizing the effects of EMI, for obtaining maximum cleanliness for high power laser and transmit optics, and for providing an ergonomic environment fitting to a state-of-the-art multipurpose laboratory. The system is currently designed to be highly modular and adaptable for scaling or changes in technology. It is conceived to be a highly automated system with superior performance specifications to any currently operational system. Provisions are also made to adapt and accommodate changes that are of significance during the course of design and integration.

Laser Induced Fluorescence Detection of Gums in Jet Fuels

DTIC Science & Technology

1992-05-01

Classification) Laser Induced Fluorescence Detection of GLus in Jet Fuels 12 PERSONAL AUTHOR(S) David W. Naegeli and Ralph H. Hill 13a. TYPE OF REPORT 13b...degraded jet fuel.( ) 47 REFERENCES 1. Fodor, G.E.; Naegeli , D.W.; Kohl, K.B.; Cuellar, J.P., Jr., Interim Report BFLRF No. 199, AD A163590, Belvoir Fuels...and Lubricants Research Facility, Southwest Research Institute, San Antonio, TX, June 1985. 2. Fodor, G.E.; Naegeli , D.W., Proceedings of the 2nd

Microstructure and Properties of Zircon-Added Carbon Refractories for Blast Furnace

NASA Astrophysics Data System (ADS)

Zhu, Tianbin; Li, Yawei; Sang, Shaobai; Chen, Xilai; Zhao, Lei; Li, Yuanbing; Li, Shujing

2012-11-01

Microstructure and properties of zircon-added carbon refractory specimens for blast furnace (BF) were investigated with the aid of X-ray diffraction (XRD), a scanning electron microscope (SEM), energy-dispersive X-ray, mercury porosimetry, and a laser thermal conductivity (TC) meter. Additives could influence the matrix structures and improve the properties of specimens. With the increase of zircon powder content, the amount of SiC whiskers formed increased and their aspect ratio became larger, and the SiC whiskers tended to be distributed homogeneously. Zircon powder additions decreased the mean pore diameter and increased <1- μm pore volume by filling in pores via SiC, improved the TC and the cold crushing strength (CCS) due to the in-situ formation of the more well-developed SiC whiskers with high TC, and significantly reduced the molten iron attack to carbon specimens.

Application of CO laser for laser balloon angioplasty

NASA Astrophysics Data System (ADS)

Miyamoto, Akira; Sakurada, Masami; Mizuno, Kyoichi; Kurita, Akira; Nakamura, Haruo; Suda, Akira; Arai, Tsunenori; Kikuchi, Makoto

1990-07-01

CO laser may be efficient for thermal fusion of intima of arterial wall without adventitial tissue damage because of high tissue absorption. To investigate the efficacy of CO laser as a laser bam for laser balloon angioplasty (LBA). CO laser was irradiated to aortic tissue through 3Oim polyethylene membrane and tissue temperature was measured by a thermistor. At 2Owatt/cm2 200joules/cm2 continuous laser exposure (CE), tissue temperature was above 100°C within a depth of 1mm and rapidly decreased to 60 °C or below between 2 and 3mm in depth. Moreover, adventitial temperature could be decreased by changing duty ratio (exposure duration/interval) of intermittent laser exposure (IE) despite of the same laser energy. Light microscopy showed high degree of medial coagulation necrosis in CE, however thermal coagulation was observed only at the surface of intima of aortic tissue in IE at duty ratio 1 / 2. These findings suggested CO laser could coagulate intimal layer with less deep thermal damage compared to Nd- YAG laser and that IE was better for superficial welding than CE at the same energy. We concluded that CO laser might be more efficient as a laser beam for LBA than Nd-YAG laser.

A note on the entropy of rotating BPS AdS7 × S4 black holes

NASA Astrophysics Data System (ADS)

Hosseini, Seyed Morteza; Hristov, Kiril; Zaffaroni, Alberto

2018-05-01

In this note we show that the entropy of BPS, rotating, electrically charged AdS7 × S 4 black holes can be obtained by an extremization principle involving a particular combination of anomaly coefficients of the six-dimensional N=(2,0) theory. This result extends our previous finding for BPS, rotating AdS5 × S 5 black holes.

Laser Wakefield Acceleration Experiments Using HERCULES Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuoka, T.; McGuffey, C.; Dollar, F.

2009-07-25

Laser wakefield acceleration (LWFA) in a supersonic gas-jet using a self-guided laser pulse was studied by changing laser power and plasma electron density. The recently upgraded HERCULES laser facility equipped with wavefront correction enables a peak intensity of 6.1x10{sup 19} W/cm{sup 2} at laser power of 80 TW to be delivered to the gas-jet using F/10 focusing optics. We found that electron beam charge was increased significantly with an increase of laser power from 30 TW to 80 TW and showed density threshold behavior at a fixed laser power. We also studied the influence of laser focusing conditions by changingmore » the f-number of the optics to F/15 and found an increase in density threshold for electron production compared to the F/10 configuration. The analysis of different phenomena such as betatron motion of electrons, side scattering of the laser pulse for different focusing conditions, the influence of plasma density down ramp on LWFA are shown.« less

Surface-active element effects on the shape of GTA, laser, and electron-beam welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiple, C.R.; Roper, J.R.; Stagner, R.T.

1983-03-01

Laser and electron-beam welds were passed across selenium-doped zones in 21-6-9 stainless steel. The depth/width (d/w) ratio of a defocused laser weld with a weld pool shape similar to a GTA weld increased by over 200% in a zone where 66 ppm selenium had been added. Smaller increases were observed in selenium-doped zones for a moderately defocused electron beam weld with a higher d/w ratio in undoped base metal. When laser or electron beam weld penetration was by a keyhole mechanism, no change in d/w ratio occurred in selenium-doped zones. The results confirm the surface-tension-driven fluid-flow model for the effectmore » of minor elements on GTA weld pool shape. Other experimental evidence bearing on the effect of minor elements on GTA weld penetration is summarized.« less

Antibacterial effects of laser ablated Ni nanoparticles

NASA Astrophysics Data System (ADS)

Shamaila, S.; Wali, H.; Sharif, R.; Nazir, J.; Zafar, N.; Rafique, M. S.

2013-10-01

The interaction of nickel nanoparticles with Escherichia coli (E. coli) bacteria has been studied. The nickel nanoparticles have been fabricated by continuous wave laser ablation of nickel target and their properties are studied using different characterization techniques. The antibacterial activity of nickel nanoparticles was checked against E. coli bacteria. Escherichia coli were cultured in nutrients broth and different concentrations of nickel nanoparticles were added to bacterial culture solution to investigate the interaction of nickel nanoparticles with bacteria and to check toxicity of the nickel nanoparticles against E. coli. The fabricated Ni nanoparticles have exhibited considerable antimicrobial activity against E. coli.

Value Added in English Schools

ERIC Educational Resources Information Center

Ray, Andrew; McCormack, Tanya; Evans, Helen

2009-01-01

Value-added indicators are now a central part of school accountability in England, and value-added information is routinely used in school improvement at both the national and the local levels. This article describes the value-added models that are being used in the academic year 2007-8 by schools, parents, school inspectors, and other…

Hagedorn Temperature of AdS5/CFT4 via Integrability

NASA Astrophysics Data System (ADS)

Harmark, Troels; Wilhelm, Matthias

2018-02-01

We establish a framework for calculating the Hagedorn temperature of AdS5/CFT4 via integrability. Concretely, we derive the thermodynamic Bethe ansatz equations that yield the Hagedorn temperature of planar N =4 super Yang-Mills theory at any value of the 't Hooft coupling. We solve these equations perturbatively at weak coupling via the associated Y system, confirming the known results at tree level and one-loop order as well as deriving the previously unknown two-loop Hagedorn temperature. Finally, we comment on solving the equations at finite coupling.

IR and He-Ne laser in the treatment of wounds and painful disorders in horses and in dogs

NASA Astrophysics Data System (ADS)

Canavesio, Ermes; Casiraghi, Emanuela; Codazza, Danilo

1996-05-01

To evaluate the therapeutic applications of laser, 3 dogs and 26 horses were selected for the treatment of skin lesions, and 1 dog and 16 horses for analgesic treatment. The equipment used consisted of either red or infrared light laser apparatuses modified in order to increase the manageability and the power of the instrument. It was observed that He-Ne laser allowed a more rapid restitutio ad integrum with a lesser amount of J/cm2 and so apparatuses were advantageous for the treatment of fistolous tracts complicated by abscess formation. In fact, by using sterilizable optical fibers, it was possible to reach the deeper parts of the tract. When considering the rapidity of the healing process of different body areas, the withers seems to necessitate the longest period of time to recover. Infrared laser is best used for pain relief and satisfactory results were observed without resting the animals. Significant and beneficial effects from laser therapy are obtained after 7 - 10 days of therapy.

Propagation of High Power Pulses of 10.6 micrometers Radiation from A CO2 TEA Laser of Novel Design through Clouds Produced by Adiabatic Expansion in the Laboratory

DTIC Science & Technology

1976-07-01

A AD PROPAGATION OF HIGH POWER PULSES OF 10.6 pm RADIATION FROM A C02 TEA LASER OF NOVEL DESIGN THROUGH CLOUDS PRODUCED BY ADIABATIC E•XPANS:’)N IN...PART A: CO2 LASER uEVELOPMENT Al High Power CO2 TEA Laser 2 A2 CW CO2 Laser 6 References 8 Diagrams 9 PART 8: CLOUD PROLDUCTION 61 Cloud Chamber...offer versatility, efficienr-y and high power . This report is concerned with the attenuation of 10.eum radiatiins, both high power pulsL.o and 04, by

Frequency stabilization of diode-laser-pumped solid state lasers

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1988-01-01

The goal of the NASA Sunlite program is to fly two diode-laser-pumped solid-state lasers on the space shuttle and while doing so to perform a measurement of their frequency stability and temporal coherence. These measurements will be made by combining the outputs of the two lasers on an optical radiation detector and spectrally analyzing the beat note. Diode-laser-pumped solid-state lasers have several characteristics that will make them useful in space borne experiments. First, this laser has high electrical efficiency. Second, it is of a technology that enables scaling to higher powers in the future. Third, the laser can be made extremely reliable, which is crucial for many space based applications. Fourth, they are frequency and amplitude stable and have high temporal coherence. Diode-laser-pumped solid-state lasers are inherently efficient. Recent results have shown 59 percent slope efficiency for a diode-laser-pumped solid-state laser. As for reliability, the laser proposed should be capable of continuous operation. This is possible because the diode lasers can be remote from the solid state gain medium by coupling through optical fibers. Diode lasers are constructed with optical detectors for monitoring their output power built into their mounting case. A computer can actively monitor the output of each diode laser. If it sees any variation in the output power that might indicate a problem, the computer can turn off that diode laser and turn on a backup diode laser. As for stability requirements, it is now generally believed that any laser can be stabilized if the laser has a frequency actuator capable of tuning the laser frequency as far as it is likely to drift in a measurement time.

Effective Ad-Hoc Committees.

ERIC Educational Resources Information Center

Young, David G.

1983-01-01

Ad-hoc committees may be symbolic, informational, or action committees. A literature survey indicates such committees' structural components include a suprasystem and three subsystems involving linkages, production, and implementation. Other variables include size, personal factors, and timing. All the factors carry implications about ad-hoc…

Caregivers' male gender is associated with poor nutrient intake in AD families (NuAD-trial).

PubMed

Puranen, T M; Pietila, S E; Pitkala, K H; Kautiainen, H; Raivio, M; Eloniemi-Sulkava, U; Jyvakorpi, S K; Suominen, M

2014-07-01

Alzheimer patients (AD) are known to be at risk for malnutrition and their older spouses may also have nutritional problems. The aim of our study was to clarify the association of caregivers' sex on the nutrient intake of AD couples. Our study uses the baseline data of a randomized nutritional trial exploring the effectiveness of nutrition intervention among home-dwelling AD patients. The central AD register in Finland was used to recruit AD patients living with a spousal caregiver, 99 couples participated in our study. Nutritional status was assessed using the Mini-Nutritional Assessment (MNA). Nutrient intakes for both AD patients and their spouses were calculated from 3-day food diaries. The mean age of caregivers and AD spouses was 75.2 (SD 7.0) and 77.4 years (SD 5.6), respectively. According to the MNA, 40% of male and 52% of female AD spouses were at risk for malnutrition. Among male caregivers, the mean energy and protein intakes were 1605 kcal (SD 458) and 0.93 g/body kg (SD 0.30), whereas the respective figures for their female AD spouses were 1313 kcal (SD 340) and 0.86 g/body kg (SD 0.32), respectively. Among female caregivers, the mean energy and protein intakes were 1536 kcal (SD 402) and 1.00 g/body kg (SD 0.30), whereas the respective figures for their male AD spouses were 1897 kcal (SD 416) and 1.04 g/body kg (SD 0.30). The interaction between male caregiver sex and lower energy (p<0.001) and lower protein intake (p=0.0048) (adjusted for age and MMSE) was significant. Similar differences between caregiver sexes were observed with the intake of various nutrients. A gender difference exists in the ability to cope with caregiver responsibilities related to nutrition. A need exists for tailored nutritional guidance among older individuals and especially among male caregivers.

Introducing ADS Labs

NASA Astrophysics Data System (ADS)

Accomazzi, Alberto; Henneken, E.; Grant, C. S.; Kurtz, M. J.; Di Milia, G.; Luker, J.; Thompson, D. M.; Bohlen, E.; Murray, S. S.

2011-05-01

ADS Labs is a platform that ADS is introducing in order to test and receive feedback from the community on new technologies and prototype services. Currently, ADS Labs features a new interface for abstract searches, faceted filtering of results, visualization of co-authorship networks, article-level recommendations, and a full-text search service. The streamlined abstract search interface provides a simple, one-box search with options for ranking results based on a paper relevancy, freshness, number of citations, and downloads. In addition, it provides advanced rankings based on collaborative filtering techniques. The faceted filtering interface allows users to narrow search results based on a particular property or set of properties ("facets"), allowing users to manage large lists and explore the relationship between them. For any set or sub-set of records, the co-authorship network can be visualized in an interactive way, offering a view of the distribution of contributors and their inter-relationships. This provides an immediate way to detect groups and collaborations involved in a particular research field. For a majority of papers in Astronomy, our new interface will provide a list of related articles of potential interest. The recommendations are based on a number of factors, including text similarity, citations, and co-readership information. The new full-text search interface allows users to find all instances of particular words or phrases in the body of the articles in our full-text archive. This includes all of the scanned literature in ADS as well as a select portion of the current astronomical literature, including ApJ, ApJS, AJ, MNRAS, PASP, A&A, and soon additional content from Springer journals. Fulltext search results include a list of the matching papers as well as a list of "snippets" of text highlighting the context in which the search terms were found. ADS Labs is available at http://adslabs.org

Exact microstate counting for dyonic black holes in AdS4

NASA Astrophysics Data System (ADS)

Benini, Francesco; Hristov, Kiril; Zaffaroni, Alberto

2017-08-01

We present a counting of microstates of a class of dyonic BPS black holes in AdS4 which precisely reproduces their Bekenstein-Hawking entropy. The counting is performed in the dual boundary description, that provides a non-perturbative definition of quantum gravity, in terms of a twisted and mass-deformed ABJM theory. We evaluate its twisted index and propose an extremization principle to extract the entropy, which reproduces the attractor mechanism in gauged supergravity.

Canine transurethral laser prostatectomy using a rotational technique

NASA Astrophysics Data System (ADS)

Cromeens, Douglas M.; Johnson, Douglas E.

1995-05-01

Conventional radical prostatectomy in the dog has historically been attended by unacceptably high incidence of urinary incontinence (80 - 100%). Ablation of the prostate can be accomplished in the dog by transurethral irradiation of the prostate with the Nd:YAG laser and a laterally deflecting fiber. Exposure has ranged between 40 and 60 watts for 60 seconds at 4 fixed locations. Although prostatectomies performed with the above described technique offers significant advantage over conventional prostatectomies, the high power density at each location can result in small submucosal explosions (`popcorn effect') that increase the potential for bleeding and rupture of the prostatic capsule. We describe a new technique in which the energy is applied continuously by a laser fiber rotating around a central point. Delivering 40 watts of Nd:YAG energy for 4 minutes using a new angle-delivery device (UrotekTM), we produced results comparable to those of other previously reported techniques in the canine model with two added advantages: (1) a more even application of heat resulting in no `popcorn' effect and (2) a more reliably predictable area of coagulative necrosis within a given axial plane. This technique should provide additional safety for the veterinary surgeon performing visual laser ablation of the prostate in the dog.

Gas Lasers

NASA Astrophysics Data System (ADS)

Dixit, S. K.

The field of gas lasers, started with the invention of He-Ne laser in 1961, has witnessed tremendous growth in terms of technology development, research into gaseous gain medium, resonator physics and application in widely diverse arenas. This was possible due to high versatility of gas lasers in terms of operating wavelengths, power, beam quality and mode of operation. In recent years, there is a definite trend to replace the gas lasers, wherever possible, by more efficient and compact solid-state lasers. However, for many industrial, medical and military applications, the gas lasers still rule the roost due to their high-power capabilities with good beam quality at specific wavelengths. This chapter presents a short review covering the operating principle, important technical details and application potential of all the important gas lasers such as He-Ne, CO2, argon ion, copper vapour, excimer and chemical lasers. These neutral atoms, ions and molecule gas lasers are discussed as per applicable electrical, chemical and optical excitation schemes. The optically pumped gas lasers, recently experiencing resurgence, are discussed in the context of far infrared THz molecular lasers, diode-pumped alkali lasers and optically pumped gas-filled hollow-core fibre lasers.

The complexity of identifying Ryu-Takayanagi surfaces in AdS 3/CFT 2

DOE PAGES

Bao, Ning; Chatwin-Davies, A.

2016-11-07

Here, we present a constructive algorithm for the determination of Ryu-Takayanagi surfaces in AdS 3/CFT 2 which exploits previously noted connections between holographic entanglement entropy and max-flow/min-cut. We then characterize its complexity as a polynomial time algorithm.

Zooming in on AdS3/CFT2 near a BPS bound

NASA Astrophysics Data System (ADS)

Hartong, Jelle; Lei, Yang; Obers, Niels; Oling, Gerben

2018-05-01

Any ( d + 1)-dimensional CFT with a U(1) flavor symmetry, a BPS bound and an exactly marginal coupling admits a decoupling limit in which one zooms in on the spectrum close to the bound. This limit is an Inönü-Wigner contraction of so(2 , d+1)⊕ u(1) that leads to a relativistic algebra with a scaling generator but no conformal generators. In 2D CFTs, Lorentz boosts are abelian and by adding a second u(1) we find a contraction of two copies of sl(2, ℝ) ⊕ u(1) to two copies of P 2 c , the 2-dimensional centrally extended Poincaré algebra. We show that the bulk is described by a novel non-Lorentzian geometry that we refer to as pseudo-Newton-Cartan geometry. Both the Chern-Simons action on sl(2, ℝ) ⊕ u(1) and the entire phase space of asymptotically AdS3 spacetimes are well-behaved in the corresponding limit if we fix the radial component for the u(1) connection. With this choice, the resulting Newton-Cartan foliation structure is now associated not with time, but with the emerging holographic direction. Since the leaves of this foliation do not mix, the emergence of the holographic direction is much simpler than in AdS3 holography. Furthermore, we show that the asymptotic symmetry algebra of the limit theory consists of a left- and a right-moving warped Virasoro algebra.

Thermodynamics of charged Lovelock: AdS black holes

NASA Astrophysics Data System (ADS)

Prasobh, C. B.; Suresh, Jishnu; Kuriakose, V. C.

2016-04-01

We investigate the thermodynamic behavior of maximally symmetric charged, asymptotically AdS black hole solutions of Lovelock gravity. We explore the thermodynamic stability of such solutions by the ordinary method of calculating the specific heat of the black holes and investigating its divergences which signal second-order phase transitions between black hole states. We then utilize the methods of thermodynamic geometry of black hole spacetimes in order to explain the origin of these points of divergence. We calculate the curvature scalar corresponding to a Legendre-invariant thermodynamic metric of these spacetimes and find that the divergences in the black hole specific heat correspond to singularities in the thermodynamic phase space. We also calculate the area spectrum for large black holes in the model by applying the Bohr-Sommerfeld quantization to the adiabatic invariant calculated for the spacetime.

Fine Grained Chaos in AdS2 Gravity

NASA Astrophysics Data System (ADS)

Haehl, Felix M.; Rozali, Moshe

2018-03-01

Quantum chaos can be characterized by an exponential growth of the thermal out-of-time-order four-point function up to a scrambling time u^*. We discuss generalizations of this statement for certain higher-point correlation functions. For concreteness, we study the Schwarzian theory of a one-dimensional time reparametrization mode, which describes two-dimensional anti-de Sitter space (AdS2 ) gravity and the low-energy dynamics of the Sachdev-Ye-Kitaev model. We identify a particular set of 2 k -point functions, characterized as being both "maximally braided" and "k -out of time order," which exhibit exponential growth until progressively longer time scales u^*(k)˜(k -1 )u^*. We suggest an interpretation as scrambling of increasingly fine grained measures of quantum information, which correspondingly take progressively longer time to reach their thermal values.

Fine Grained Chaos in AdS_{2} Gravity.

PubMed

Haehl, Felix M; Rozali, Moshe

2018-03-23

Quantum chaos can be characterized by an exponential growth of the thermal out-of-time-order four-point function up to a scrambling time u[over ^]_{*}. We discuss generalizations of this statement for certain higher-point correlation functions. For concreteness, we study the Schwarzian theory of a one-dimensional time reparametrization mode, which describes two-dimensional anti-de Sitter space (AdS_{2}) gravity and the low-energy dynamics of the Sachdev-Ye-Kitaev model. We identify a particular set of 2k-point functions, characterized as being both "maximally braided" and "k-out of time order," which exhibit exponential growth until progressively longer time scales u[over ^]_{*}^{(k)}∼(k-1)u[over ^]_{*}. We suggest an interpretation as scrambling of increasingly fine grained measures of quantum information, which correspondingly take progressively longer time to reach their thermal values.

Prototype laser-diode-pumped solid state laser transmitters

NASA Technical Reports Server (NTRS)

Kane, Thomas J.; Cheng, Emily A. P.; Wallace, Richard W.

1989-01-01

Monolithic, diode-pumped Nd:YAG ring lasers can provide diffraction-limited, single-frequency, narrow-linewidth, tunable output which is adequate for use as a local oscillator in a coherent communication system. A laser was built which had a linewidth of about 2 kHz, a power of 5 milliwatts, and which was tunable over a range of 30 MHz in a few microseconds. This laser was phase-locked to a second, similar laser. This demonstrates that the powerful technique of heterodyne detection is possible with a diode-pumped laser used as the local oscillator. Laser diode pumping of monolithic Nd:YAG rings can lead to output powers of hundreds of milliwatts from a single laser. A laser was built with a single-mode output of 310 mW. Several lasers can be chained together to sum their power, while maintaining diffraction-limited, single frequency operation. This technique was demonstrated with two lasers, with a total output of 340 mW, and is expected to be practical for up to about ten lasers. Thus with lasers of 310 mW, output of up to 3 W is possible. The chaining technique, if properly engineered, results in redundancy. The technique of resonant external modulation and doubling is designed to efficiently convert the continuous wave, infrared output of our lasers into low duty-cycle pulsed green output. This technique was verified through both computer modeling and experimentation. Further work would be necessary to develop a deliverable system using this technique.

Thermodynamic Volume in AdS/CFT

NASA Astrophysics Data System (ADS)

Kim, Kyung Kiu; Ahn, Byoungjoon

2018-01-01

In this note, we study on extended thermodynamics of AdS black holes by varying cosmological constant. We found and discussed pressure and volume of both bulk and boundary physics through AdS/CFT correspondence. In particular, we derive the relation between thermodynamic volume and a chemical potential for M2 brane dual to four dimensional AdS space. In addition, we show that thermodynamic volume of hyperbolic black hole is related to `entanglement pressure' coming from a generalized first law of entanglement entropy.

Laser principles.

PubMed

Bogdan Allemann, Inja; Kaufman, Joely

2011-01-01

Since the construction of the first laser in the 1960s, the role that lasers play in various medical specialities, including dermatology, has steadily increased. However, within the last 2 decades, the technological advances and the use of lasers in the field of dermatology have virtually exploded. Many treatments have only become possible with the use of lasers. Especially in aesthetic medicine, lasers are an essential tool in the treatment armamentarium. Due to better research and understanding of the physics of light and skin, there is now a wide and increasing array of different lasers and devices to choose from. The proper laser selection for each indication and treatment requires a profound understanding of laser physics and the basic laser principles. Understanding these principles will allow the laser operator to obtain better results and help avoid complications. This chapter will give an in-depth overview of the physical principles relevant in cutaneous laser surgery. Copyright © 2011 S. Karger AG, Basel.

Some semiclassical structure constants for AdS 4 × CP 3

NASA Astrophysics Data System (ADS)

Ahn, Changrim; Bozhilov, Plamen

2018-02-01

We compute structure constants in three-point functions of three string states in AdS 4× CP 3 in the framework of the semiclassical approach. We consider HHL correlation functions where two of the states are "heavy" string states of finite-size giant magnons carrying one or two angular momenta and the other one corresponds to such "light" states as dilaton operators with non-zero momentum, primary scalar operators, and singlet scalar operators with higher string levels.

Laser-induced oxidation of cholesterol observed during MALDI-TOF mass spectrometry.

PubMed

McAvey, Kevin M; Guan, Bing; Fortier, Chanel A; Tarr, Matthew A; Cole, Richard B

2011-04-01

Conditions for the detection of three odd-electron cholesterol oxidation peaks were determined and these peaks were shown to be artifacts of the matrix-assisted laser desorption time of flight (MALDI-TOF) process. Matrix choice, solvent, laser intensity and cholesterol concentration were systematically varied to characterize the conditions leading to the highest signals of the radical cation peaks, and it was found that initial cholesterol solution concentration and resultant density of solid cholesterol on the MALDI target were important parameters in determining signal intensities. It is proposed that hydroxyl radicals, generated as a result of laser irradiation of the employed 2,5-dihydroxybenzoic acid (DHB) matrix, initiate cholesterol oxidation on the MALDI target. An attempt to induce the odd-electron oxidation peaks by means of adding an oxidizing agent succeeded using an acetonitrile solution of DHB, cholesterol, and cumene hydroperoxide. Moreover, addition of free radical scavengers reduced the abundances of some oxidation products under certain conditions. These results are consistent with the mechanism of oxidation proposed herein involving laser-induced hydroxyl radical production followed by attack on neutral cholesterol. Hydroxyl radical production upon irradiation of dithranol matrix may also be responsible for generation of the same radical peaks observed from cholesterol in dithranol by an analogous mechanism. © American Society for Mass Spectrometry, 2011

Myths & Facts about Value-Added Analysis

ERIC Educational Resources Information Center

TNTP, 2011

2011-01-01

This paper presents myths as well as facts about value-added analysis. These myths include: (1) "Value-added isn't fair to teachers who work in high-need schools, where students tend to lag far behind academically"; (2) "Value-added scores are too volatile from year-to-year to be trusted"; (3) "There's no research behind value-added"; (4) "Using…

Particle collisions near a three-dimensional warped AdS black hole

NASA Astrophysics Data System (ADS)

Bécar, Ramón; González, P. A.; Vásquez, Yerko

2018-04-01

In this paper we consider the warped AdS3 black hole solution of topologically massive gravity with a negative cosmological constant, and we study the possibility that it acts as a particle accelerator by analyzing the energy in the center of mass (CM) frame of two colliding particles in the vicinity of its horizon, which is known as the Bañnados, Silk and West (BSW) process. Mainly, we show that the critical angular momentum (L_c) of the particle decreases when the warping parameter(ν ) increases. Also, we show that despite the particle with L_c being able to exist for certain values of the conserved energy outside the horizon, it will never reach the event horizon; therefore, the black hole cannot act as a particle accelerator with arbitrarily high CM energy on the event horizon. However, such a particle could also exist inside the outer horizon, with the BSW process being possible on the inner horizon. On the other hand, for the extremal warped AdS3 black hole, the particle with L_c and energy E could exist outside the event horizon and, the CM energy blows up on the event horizon if its conserved energy fulfills the condition E2>(ν 2+3)l2/3(ν ^{2-1)}, with the BSW process being possible.

Introducing ADS 2.0

NASA Astrophysics Data System (ADS)

Accomazzi, Alberto; Kurtz, M. J.; Henneken, E. A.; Grant, C. S.; Thompson, D.; Luker, J.; Chyla, R.; Murray, S. S.

2014-01-01

In the spring of 1993, the Smithsonian/NASA Astrophysics Data System (ADS) first launched its bibliographic search system. It was known then as the ADS Abstract Service, a component of the larger Astrophysics Data System effort which had developed an interoperable data system now seen as a precursor of the Virtual Observatory. As a result of the massive technological and sociological changes in the field of scholarly communication, the ADS is now completing the most ambitious technological upgrade in its twenty-year history. Code-named ADS 2.0, the new system features: an IT platform built on web and digital library standards; a new, extensible, industrial strength search engine; a public API with various access control capabilities; a set of applications supporting search, export, visualization, analysis; a collaborative, open source development model; and enhanced indexing of content which includes the full-text of astronomy and physics publications. The changes in the ADS platform affect all aspects of the system and its operations, including: the process through which data and metadata are harvested, curated and indexed; the interface and paradigm used for searching the database; and the follow-up analysis capabilities available to the users. This poster describes the choices behind the technical overhaul of the system, the technology stack used, and the opportunities which the upgrade is providing us with, namely gains in productivity and enhancements in our system capabilities.

ADS Bumblebee comes of age

NASA Astrophysics Data System (ADS)

Accomazzi, Alberto; Kurtz, Michael J.; Henneken, Edwin; Grant, Carolyn S.; Thompson, Donna M.; Chyla, Roman; McDonald, Steven; Shaulis, Taylor J.; Blanco-Cuaresma, Sergi; Shapurian, Golnaz; Hostetler, Timothy W.; Templeton, Matthew R.; Lockhart, Kelly E.

2018-01-01

The ADS Team has been working on a new system architecture and user interface named “ADS Bumblebee” since 2015. The new system presents many advantages over the traditional ADS interface and search engine (“ADS Classic”). A new, state of the art search engine features a number of new capabilities such as full-text search, advanced citation queries, filtering of results and scalable analytics for any search results. Its services are built on a cloud computing platform which can be easily scaled to match user demand. The Bumblebee user interface is a rich javascript application which leverages the features of the search engine and integrates a number of additional visualizations such as co-author and co-citation networks which provide a hierarchical view of research groups and research topics, respectively. Displays of paper analytics provide views of the basic article metrics (citations, reads, and age). All visualizations are interactive and provide ways to further refine search results. This new search system, which has been in beta for the past three years, has now matured to the point that it provides feature and content parity with ADS Classic, and has become the recommended way to access ADS content and services. Following a successful transition to Bumblebee, the use of ADS Classic will be discouraged starting in 2018 and phased out in 2019. You can access our new interface at https://ui.adsabs.harvard.edu

Toward the development of a low-cost laser Doppler module for ophthalmic microscopes

NASA Astrophysics Data System (ADS)

Cattini, Stefano; Rovati, Luigi

2012-03-01

A laser Doppler module easily integrated into a commercial ophthalmic microscope is proposed. Such setup adds flow measurement capability to standard visual inspection of the fundus. The proposed instrument may provide important clinical information such as the detection of vessel occlusion provided by surgical treatments (i.e. photocoagulation). The measuring system is based on a self-mixing laser diode Doppler flowmeter (SM-DF). Reduced costs, easy implementation and small size represent the main features of SM-DF. Moreover, this technique offers the advantage to have the excitation and measurement beams spatially overlapped, thus both overcoming the alignment difficulty of traditional laser Doppler flowmeter and, well fitting with to limited optical aperture of the pupil. Thanks to an on-board DSP-microcontroller, the optoelectronic module directly estimates the blood flow; USB connection and an ad-hoc developed user-friendly software interface allow displaying the result on a personal computer. Preliminary test demonstrates the applicability of the proposed measuring system.

SAO/NASA ADS at SAO: User Feedback

Science.gov Websites

Sign on [SAO/NASA ADS] User Feedback ADS Home | HELP | Sitemap ADS Services Search Browse myADS Mirrors Feedback FAQ What's new Site Map Help Other NASA Centers CXC HEASARC IRSA MAST NED NSSDC PDS [NASA] NASA ads at cfa.harvard.edu

Investigation of Laser Parameters in Silicon Pulsed Laser Conduction Welding

NASA Astrophysics Data System (ADS)

Shayganmanesh, Mahdi; Khoshnoud, Afsaneh

2016-03-01

In this paper, laser welding of silicon in conduction mode is investigated numerically. In this study, the effects of laser beam characteristics on the welding have been studied. In order to model the welding process, heat conduction equation is solved numerically and laser beam energy is considered as a boundary condition. Time depended heat conduction equation is used in our calculations to model pulsed laser welding. Thermo-physical and optical properties of the material are considered to be temperature dependent in our calculations. Effects of spatial and temporal laser beam parameters such as laser beam spot size, laser beam quality, laser beam polarization, laser incident angle, laser pulse energy, laser pulse width, pulse repetition frequency and welding speed on the welding characteristics are assessed. The results show that how the temperature dependent thermo-physical and optical parameters of the material are important in laser welding modeling. Also the results show how the parameters of the laser beam influence the welding characteristics.

Ad hoc vs. Non-ad hoc Percutaneous Coronary Intervention Strategies in Patients With Stable Coronary Artery Disease.

PubMed

Toyota, Toshiaki; Morimoto, Takeshi; Shiomi, Hiroki; Ando, Kenji; Ono, Koh; Shizuta, Satoshi; Kato, Takao; Saito, Naritatsu; Furukawa, Yutaka; Nakagawa, Yoshihisa; Horie, Minoru; Kimura, Takeshi

2017-03-24

Few studies have evaluated the prevalence and clinical outcomes of ad hoc percutaneous coronary intervention (PCI), performing diagnostic coronary angiography and PCI in the same session, in stable coronary artery disease (CAD) patients.Methods and Results:From the CREDO-Kyoto PCI/CABG registry cohort-2, 6,943 patients were analyzed as having stable CAD and undergoing first PCI. Ad hoc PCI and non-ad hoc PCI were performed in 1,722 (24.8%) and 5,221 (75.1%) patients, respectively. The cumulative 5-year incidence and adjusted risk for all-cause death were not significantly different between the 2 groups (15% vs. 15%, P=0.53; hazard ratio: 1.15, 95% confidence interval: 0.98-1.35, P=0.08). Ad hoc PCI relative to non-ad hoc PCI was associated with neutral risk for myocardial infarction, any coronary revascularization, and bleeding, but was associated with a trend towards lower risk for stroke (hazard ratio: 0.78, 95% confidence interval: 0.60-1.02, P=0.06). Ad hoc PCI in stable CAD patients was associated with at least comparable 5-year clinical outcomes as with non-ad hoc PCI. Considering patients' preference and the cost-saving, the ad hoc PCI strategy might be a safe and attractive option for patients with stable CAD, although the prevalence of ad hoc PCI was low in the current study population.

Parameters in fractional laser assisted delivery of topical anesthetics: Role of laser type and laser settings.

PubMed

Meesters, Arne A; Nieboer, Marilin J; Kezic, Sanja; de Rie, Menno A; Wolkerstorfer, Albert

2018-05-07

Efficacy of topical anesthetics can be enhanced by pretreatment of the skin with ablative fractional lasers. However, little is known about the role of parameters such as laser modality and laser density settings in this technique. Aims of this study were to compare the efficacy of pretreatment with two different ablative fractional laser modalities, a CO 2 laser and an Er:YAG laser, and to assess the role of laser density in ablative fractional laser assisted topical anesthesia. In each of 15 healthy subjects, four 10 × 10 mm test regions on the back were randomized to pretreatment (70-75 μm ablation depth) with CO 2 laser at 5% density, CO 2 laser at 15% density, Er:YAG laser at 5% density or Er:YAG laser at 15% density. Articaine hydrochloride 40 mg/ml + epinephrine 10 μg/ml solution was applied under occlusion to all four test regions. After 15 minutes, a pass with the CO 2 laser (1,500 μm ablation depth) was administered as pain stimulus to each test region. A reference pain stimulus was given on unanesthetized skin. The main outcome parameter, pain, was scored on a 0-10 visual analogue scale (VAS) after each pain stimulus. Median VAS scores were 1.50 [CO 2 5%], 0.50 [CO 2 15%], 1.50 [Er:YAG 5%], 0.43 [Er:YAG 15%], and 4.50 [unanesthetized reference]. VAS scores for all pretreated test regions were significantly lower compared to the untreated reference region (P < 0.01). We found no significant difference in VAS scores between the CO 2 and the Er:YAG laser pretreated regions. However, VAS scores were significantly lower at 15% density compared to 5% density for both for the CO 2 laser (P < 0.05) and the Er:YAG laser (P < 0.01). Pretreatment with the CO 2 laser was considered slightly more painful than pretreatment with Er:YAG laser by the subjects. Fractional laser assisted topical anesthesia is effective even with very low energy settings and an occlusion time of only 15 minutes. Both the CO 2 laser and the Er:YAG laser can

A novel synonymous variant in the AVP gene associated with adFNDI causes partial RNA missplicing.

PubMed

Kvistgaard, Helene; Christensen, Jane H; Johansson, Jan-Ove; Gregersen, Niels; Rittig, Charlotte; Rittig, Soeren; Corydon, Thomas Juhl

2018-06-27

Objective: Autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) is characterized by severe polyuria and polydipsia and is caused by variations in the gene encoding the AVP prohormone. The study aimed to ascertain a correct diagnosis, to identify the underlying genetic cause of adFNDI in a Swedish kindred, and to test the hypothesis that the identified synonymous exonic variant in the AVP gene (c.324G>A), causes missplicing, and endoplasmic reticulum (ER) retention of the prohormone. Three affected family members were admitted for fluid deprivation test and dDAVP challenge test. Direct sequencing of the AVP gene was performed in affected subjects, and genotyping of the identified variant was performed in family members. The variant was examined by expression of AVP minigenes containing the entire coding regions as well as intron 2 of AVP. Clinical tests revealed significant phenotypical variation with both complete and partial adFNDI phenotype. DNA analysis revealed a synonymous c.324G>A substitution in one allele of the AVP gene in affected family members only. Cellular studies revealed both normally spliced and misspliced pre-mRNA in cells transfected with the AVP c.324G>A minigene. Confocal laser scanning microscopy showed collective localization of the variant prohormone to ER and vesicular structures at the tip of cellular processes. We have identified a synonymous variant affecting the second nucleotide of exon 3 in the AVP gene (c.324G>A) in a kindred in which adFNDI segregates. Notably, we showed that this variant causes partial missplicing of pre-mRNA resulting in accumulation of variant prohormone in ER. Our study suggests that even a small amount of aberrant mRNA might be sufficient to disturb cellular function resulting in adFNDI.
. ©2018S. Karger AG, Basel.

Laser device

DOEpatents

Scott, Jill R [Idaho Falls, ID; Tremblay, Paul L [Idaho Falls, ID

2007-07-10

A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

Laser device

DOEpatents

Scott, Jill R.; Tremblay, Paul L.

2004-11-23

A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

Laser microphone

DOEpatents

Veligdan, James T.

2000-11-14

A microphone for detecting sound pressure waves includes a laser resonator having a laser gain material aligned coaxially between a pair of first and second mirrors for producing a laser beam. A reference cell is disposed between the laser material and one of the mirrors for transmitting a reference portion of the laser beam between the mirrors. A sensing cell is disposed between the laser material and one of the mirrors, and is laterally displaced from the reference cell for transmitting a signal portion of the laser beam, with the sensing cell being open for receiving the sound waves. A photodetector is disposed in optical communication with the first mirror for receiving the laser beam, and produces an acoustic signal therefrom for the sound waves.

Isometry group orbit quantization of spinning strings in AdS3 × S3

NASA Astrophysics Data System (ADS)

Heinze, Martin; Jorjadze, George; Megrelidze, Luka

2015-03-01

Describing the bosonic AdS3 × S3 particle and string in SU(1,1) × SU(2) group variables, we provide a Hamiltonian treatment of the isometry group orbits of solutions via analysis of the pre-symplectic form. For the particle we obtain a one-parameter family of orbits parameterized by creation-annihilation variables, which leads to the Holstein-Primakoff realization of the isometry group generators. The scheme is then applied to spinning string solutions characterized by one winding number in AdS3 and two winding numbers in S3. We find a two-parameter family of orbits, where quantization again provides the Holstein-Primakoff realization of the symmetry generators with an oscillator-type energy spectrum. Analyzing the minimal energy at strong coupling, we verify the spectrum of short strings at special values of winding numbers.

Use of flexible hollow-core CO2 laser in microsurgical resection of CNS lesions: early surgical experience.

PubMed

Killory, Brendan D; Chang, Steve W; Wait, Scott D; Spetzler, Robert F

2010-06-01

The CO2 laser has a long history in both experimental and clinical neurosurgery. However, its use over the past decade has been limited by its cumbersome design and bulky set-up of the micromanipulator. These limitations are amplified when it is used with the operating microscope. These restrictions are addressed by the Omniguide fiber, which delivers the beam through flexible hollow-core photonic bandgap mirror fibers and allows the laser to be wielded like any other surgical instrument. The attending neurosurgeon prospectively assessed the usefulness of the laser in its first 45 consecutive uses at our institution based on a scale of 1 to 5. The series included 11 cavernous malformations, 14 meningiomas, 7 ependymomas, 3 metastases, 3 astrocytomas, and 7 miscellaneous lesions. The laser was set up 91 times and used in 45 cases. The Omniguide fiber failed 5 times. No adverse events involving patients or staff were associated with laser use. The mean utility score was 3.7 +/- 0.8 (range, 2-5). The laser was most helpful in debulking fibrous lesions too tough for ultrasonic aspiration and lesions adherent to delicate neurovascular structures. The laser was not helpful with highly vascular tumors. In our early experience, the Omniguide laser was very helpful in selected cases in resecting specific types of lesions without complications; we have added the device to our neurosurgical armamentarium.

AdS5 solutions from M5-branes on Riemann surface and D6-branes sources

DOE PAGES

Bah, Ibrahima

2015-09-24

Here, we describe the gravity duals of four-dimensional N = 1 superconformal field theories obtained by wrapping M5-branes on a punctured Riemann surface. The internal geometry, normal to the AdS 5 factor, generically preserves two U(1)s, with generators (J +, J –), that are fibered over the Riemann surface. The metric is governed by a single potential that satisfies a version of the Monge-Ampère equation. The spectrum of N = 1 punctures is given by the set of supersymmetric sources of the potential that are localized on the Riemann surface and lead to regular metrics near a puncture. We usemore » this system to study a class of punctures where the geometry near the sources corresponds to M-theory description of D6-branes. These carry a natural (p, q) label associated to the circle dual to the killing vector pJ + + qJ – which shrinks near the source. In the generic case the world volume of the D6-branes is AdS 5 × S 2 and they locally preserve N = 2 supersymmetry. When p = –q, the shrinking circle is dual to a flavor U(1). The metric in this case is non-degenerate only when there are co-dimension one sources obtained by smearing M5-branes that wrap the AdS 5 factor and the circle dual the superconformal R-symmetry. The D6-branes are extended along the AdS 5 and on cups that end on the co-dimension one branes. In the special case when the shrinking circle is dual to the R-symmetry, the D6-branes are extended along the AdS 5 and wrap an auxiliary Riemann surface with an arbitrary genus. When the Riemann surface is compact with constant curvature, the system is governed by a Monge-Ampère equation.« less

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2004-01-13

Sequenced pulses of light from an excitation laser with at least two resonator cavities with separate output couplers are directed through a light modulator and a first polarzing analyzer. A portion of the light not rejected by the first polarizing analyzer is transported through a first optical fiber into a first ignitor laser rod in an ignitor laser. Another portion of the light is rejected by the first polarizing analyzer and directed through a halfwave plate into a second polarization analyzer. A first portion of the output of the second polarization analyzer passes through the second polarization analyzer to a second, oscillator, laser rod in the ignitor laser. A second portion of the output of the second polarization analyzer is redirected by the second polarization analyzer to a second optical fiber which delays the beam before the beam is combined with output of the first ignitor laser rod. Output of the second laser rod in the ignitor laser is directed into the first ignitor laser rod which was energized by light passing through the first polarizing analyzer. Combined output of the first ignitor laser rod and output of the second optical fiber is focused into a combustible fuel where the first short duration, high peak power pulse from the ignitor laser ignites the fuel and the second long duration, low peak power pulse directly from the excitation laser sustains the combustion.

Localized AdS_{5}×S^{5} Black Holes.

PubMed

Dias, Óscar J C; Santos, Jorge E; Way, Benson

2016-10-07

According to heuristic arguments, global AdS_{5}×S^{5} black holes are expected to undergo a phase transition in the microcanonical ensemble. At high energies, one expects black holes that respect the symmetries of the S^{5}; at low energies, one expects "localized" black holes that appear pointlike on the S^{5}. According to anti-de Sitter/conformal field theory correspondence, N=4 supersymmetric Yang-Mills (SYM) theory on a 3-sphere should therefore exhibit spontaneous R-symmetry breaking at strong coupling. In this Letter, we numerically construct these localized black holes. We extrapolate the location of this phase transition, and compute the expectation value of the broken scalar operator with lowest conformal dimension. Via the correspondence, these results offer quantitative predictions for N=4 SYM theory.

Hollow fiber optics with improved durability for high-peak-power pulses of Q-switched Nd:YAG lasers.

PubMed

Matsuura, Yuji; Tsuchiuchi, Akio; Noguchi, Hiroshi; Miyagi, Mitsunobu

2007-03-10

To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light.

Laser shocking of materials: Toward the national ignition facility

DOE PAGES

Meyers, M. A.; Remington, B. A.; Maddox, B.; ...

2010-01-16

In recent years a powerful experimental tool has been added to the arsenal at the disposal of the materials scientist investigating materials response at extreme regimes of strain rates, temperatures, and pressures: laser compression. In this paper, this technique has been applied successfully to mono-, poly-, and nanocrystalline metals and the results have been compared with predictions from analytical models and molecular dynamics simulations. Special flash x-ray radiography and flash x-ray diffraction, combined with laser shock propagation, are yielding the strength of metals at strain rates on the order of 10 7–10 8 s -1 and resolving details of themore » kinetics of phase transitions. A puzzling result is that experiments, analysis, and simulations predict dislocation densities that are off by orders of magnitude. Finally, other surprises undoubtedly await us as we explore even higher pressure/strain rate/temperature regimes enabled by the National Ignition Facility.« less

Duality invariance of s ≥ 3/2 fermions in AdS

DOE PAGES

Deser, S.; Seminara, D.

2014-09-30

The research show that in D = 4 AdS, s ≥ 3/2 partially massless (PM) fermions retain the duality invariances of their flat space massless counterparts. They have tuned ratios m 2/M 2 ≠ 0 that turn them into sums of effectively massless unconstrained helicity ±(s, ···, 3/2) excitations, shorn of the lowest (non-dual) helicity ±1/2-rung and — more generally — of succeeding higher rung as well. Each helicity mode is separately duality invariant, like its flat space counterpart.

New Kaluza-Klein instantons and the decay of AdS vacua

DOE PAGES

Ooguri, Hirosi; Spodyneiko, Lev

2017-07-19

We construct a generalization of Witten’s Kaluza-Klein instanton, where a higher-dimensional sphere (rather than a circle as in Witten’s instanton) collapses to zero size and the geometry terminates at a bubble of nothing, in a low energy effective theory of M theory. We then use the solution to exhibit the instability of nonsupersymmetric AdS 5 vacua in M theory compactified on positive Kähler-Einstein spaces, providing further evidence for the recent conjecture that any nonsupersymmetric anti–de Sitter vacuum supported by fluxes must be unstable.

Thermodynamic Geometry of Charged AdS Black Hole Surrounded by Quintessence

NASA Astrophysics Data System (ADS)

Wei, Shao-Wen; Man, Qing-Tao; Yu, Hao

2018-02-01

In this paper, we study the thermodynamic geometry for the charged AdS black hole surrounded by quintessence. Three different kinds of the geometries are constructed, and the corresponding curvatures are obtained. It is found that there are different divergence behaviors of these curvatures, which is general thought to closely link to the phase transition of the black hole. Supported by the National Natural Science Foundation of China under Grant Nos. 11675064, 11205074, and the Fundamental Research Funds for the Central Universities under Grant No. lzujbky-2016-121

Combined treatment for Coats’ disease: retinal laser photocoagulation combined with intravitreal bevacizumab injection was effective in two cases

PubMed Central

2014-01-01

Background The exact pathogenetic mechanisms of Coats’ disease remain unknown. In this report, we show two cases of Coats’ disease that achieved a favorable prognosis with the combined treatment of intravitreal bevacizumab (IVB) injection prior to photocoagulation, although both initially resisted photocoagulation therapy. Case presentations Case 1 was a 15-year-old boy with initial visual acuity of 0.4 OD. At the temporal retina, aneurysms and abnormal telangiectatic vessels were observed. Hard exudates and an exudative retinal detachment extended to the fovea. He was diagnosed as having Coats’ disease at stage 3A and we performed laser photocoagulation as an initial approach to treat peripheral aneurysms and telangiectatic vessels. After the treatment, the exudative retinal detachment was eased and visual acuity improved to 1.0; however, recurrence occurred after 5 months. The exudative change was resistant against laser photocoagulation therapy and we therefore added IVB as an adjuvant before photocoagulation. Fourteen days after IVB injection phased laser photocoagulation was given to cover the abnormal capillaries, aneurysms and the leakage area spotted in FA. A good prognosis was obtained with decreased exudation and improved visual acuity. Case 2 was an 11-year-old boy with decreased visual acuity of 0.15 OS at the initial visit. Hard exudates, retinal edema and serous retinal detachment were seen at the macula and peripheral retina. Fluorescein angiography revealed telangiectatic capillaries at the temporal retina. Our diagnosis was Coats’ disease at stage 3A. Extensive photocoagulation was performed as an initial treatment to the lesion. However, the exudative change was severe and resistant against the photocoagulation treatment. Therefore, we added IVB as an adjuvant before photocoagulation. Exudative change in the retina seemed to be eased 7 days after IVB injection, therefore, phased laser phototherapy was added to cover the abnormal

Laser Therapy in the Treatment of Achilles Tendinopathy: A Randomised Controlled Trial

NASA Astrophysics Data System (ADS)

Tumilty, Steve; Munn, Joanne; Haxby Abbott, J.; Mcdonough, Suzanne; Hurley, Deirdre A.; Basford, Jeffrey R.; David Baxter, G.

2010-05-01

Background: Low Level Laser Therapy (LLLT) has emerged as a possible treatment modality for tendinopathies. Human studies have investigated LLLT for Achilles Tendinopathy and the effectiveness remains contentious. Purpose: To assess the clinical effectiveness of Low-Level Laser Therapy (LLLT) in the management of Achilles Tendinopathy. Method: Forty patients were randomised into an active laser or placebo group; all patients, therapists and investigator were blinded to allocation. All patients were given an eccentric exercise program and irradiated 3 times per week for 4 weeks with either an active or placebo laser at 6 standardized points over the affected tendons. Irradiation parameters in the active laser group were: 810 nm, 100 mW, applied to 6 points on the tendon for 30 seconds giving a dose of 3 J per point and 18 J per session; power density 100 mW/cm2. Outcome measures were the VISA-A questionnaire and a visual analogue scale of pain. Patients were measured before treatment, at 4 and 12 weeks. ANCOVA was used to analyze data, using the effects of baseline measurements as a covariate. Results: Within groups, there were significant improvements (p<0.05) at 4 and 12 weeks for all outcome measures, except pain for the laser group at 4 weeks (p = 0.13). Between groups differences at both 4 and 12 weeks showed no significant difference between groups (p>0.05). Conclusion: This use of the above parameters demonstrated no added benefit of LLLT over that of eccentric exercise in the treatment of Achilles Tendinopathy.

Safe laser application requires more than laser safety

NASA Astrophysics Data System (ADS)

Frevel, A.; Steffensen, B.; Vassie, L.

1995-02-01

An overview is presented concerning aspects of laser safety in European industrial laser use. Surveys indicate that there is a large variation in the safety strategies amongst industrial laser users. Some key problem areas are highlighted. Emission of hazardous substances is a major problem for users of laser material processing systems where the majority of the particulate is of a sub-micrometre size, presenting a respiratory hazard. Studies show that in many cases emissions are not frequently monitored in factories and uncertainty exists over the hazards. Operators of laser machines do not receive adequate job training or safety training. The problem is compounded by a plethora of regulations and standards which are difficult to interpret and implement, and inspectors who are not conversant with the technology or the issues. A case is demonstrated for a more integrated approach to laser safety, taking into account the development of laser applications, organizational and personnel development, in addition to environmental and occupational health and safety aspects. It is necessary to achieve a harmonization between these elements in any organization involved in laser technology. This might be achieved through establishing technology transfer centres in laser technology.

Laser Safety: A Laser Alignment Practical Training Course

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woods, Michael; Edstrom, Steve; /SLAC

2011-01-26

SLAC National Accelerator Laboratory has developed a Laser Alignment Practical Training Course as one of its core laser safety classes. The course is taught to small groups of up to three students and takes 1-3 hours to complete. This practical course is not a substitute for site-specific On-the-Job Training; it does, however, provide a good introduction in core laser safety practices that can be broadly applied. Alignment and diagnostic tasks are performed with low power lasers. Students learn safe alignment and diagnostic techniques and how to avoid common mistakes that might lead to an accident. The class is taught bymore » laser supervisors, enabling them to assess the skill level of new laser personnel and determine the subsequent level of supervision needed. The course has six alignment tasks. For each task, discussion points are given for the instructor to review with the students. The optics setup includes different wavelength lasers, a beam expander, mirrors, irises, a periscope, a beam-splitting polarizer and a diffraction grating. Diagnostic tools include viewing cards, an IR viewer and a ccd camera. Laser eyewear is available to block some laser wavelengths in the setup.« less

A 10Gbps optical burst switching network incorporating ultra-fast (5ns) wavelength switched tunable laser sources

NASA Astrophysics Data System (ADS)

Ryan, Neil; Todd, Michael; Farrell, Tom; Lavin, Adrian; Rigole, Pierre-Jean; Corbett, Brian; Roycroft, Brendan; Engelstaedter, Jan-Peter

2017-11-01

This paper outlines the development of a prototype optical burst mode switching network based upon a star topology, the ultimate application of which could be as a transparent payload processor onboard satellite repeaters. The network architecture incorporates multiple tunable laser sources, burst mode receivers and a passive optical router (Arrayed Waveguide Grating). Each tunable optical signal should carry >=10Gbps and be capable of wavelength switching in c. 5ns timescales. Two monolithic tunable laser types, based upon different technologies, will be utilised: a Slotted Fabry Perot laser (a Fabry Perot laser with slots added in order to introduce controlled cavity perturbations); and a Modulated Grating Y-Branch Laser (MGY: a widely tunable, multi-section device similar to the DBR laser). While the Slotted Fabry Perot laser is expected to achieve the required switching times, it is an immature technology not yet capable of achieving tunability over 80 ITU channels from a single chip. The MGY device is a more mature technology and has full C-band ITU channel coverage, but is not capable of the required short switching times. Hence, in order to facilitate the integration of this more mature technology into the prototype breadboard with the requisite switching time capabilities, a system of `dual laser' transmitters is being developed to enable data transmission from one MGY laser while the other switches and vice-versa. This work is being performed under ESA contract AO 1-5025/06/NL/PM, Optical Technologies for Ultra - fast Processing.

Lasers and laser-like devices: part one.

PubMed

Stewart, Nicholas; Lim, Adrian C; Lowe, Patricia M; Goodman, Greg

2013-08-01

Lasers have been used in dermatology for nearly 50 years. Through their selective targeting of skin chromophores they have become the preferred treatment for many skin conditions, including vascular malformations, photorejuvenation and acne scars. The technology and design of lasers continue to evolve, allowing greater control of laser parameters and resulting in increased safety and efficacy for patients. Innovations have allowed the range of conditions and the skin types amenable to treatment, in both general and cosmetic dermatology, to expand over the last decade. Integrated skin cooling and laser beam fractionation, for example, have improved safety, patient tolerance and decreased downtime. Furthermore, the availability and affordability of quality devices continues to increase, allowing clinicians not only to access laser therapies more readily but also to develop their personal experience in this field. As a result, most Australian dermatologists now have access to laser therapies, either in their own practice or within referable proximity, and practical knowledge of these technologies is increasingly required and expected by patients. Non-laser energy devices utilising intense pulsed light, plasma, radiofrequency, ultrasound and cryolipolysis contribute to the modern laser practitioners' armamentarium and will also be discussed. © 2013 The Authors. Australasian Journal of Dermatology © 2013 The Australasian College of Dermatologists.

Logarithmic corrections to entropy of magnetically charged AdS4 black holes

NASA Astrophysics Data System (ADS)

Jeon, Imtak; Lal, Shailesh

2017-11-01

Logarithmic terms are quantum corrections to black hole entropy determined completely from classical data, thus providing a strong check for candidate theories of quantum gravity purely from physics in the infrared. We compute these terms in the entropy associated to the horizon of a magnetically charged extremal black hole in AdS4×S7 using the quantum entropy function and discuss the possibility of matching against recently derived microscopic expressions.

Laser surgery: using the carbon dioxide laser.

PubMed Central

Wright, V. C.

1982-01-01

In 1917 Einstein theorized tha through an atomic process a unique kind of electromagnetic radiation could be produced by stimulated emission. When such radiation is in the optical or infrared spectrum it is termed laser (light amplification by stimulated emission of radiation) light. A laser, a high-intensity light source, emits a nearly parallel electromagnetic beam of energy at a given wavelength that can be captured by a lens and concentrated in the focal spot. The wavelength determines how the laser will be used. The carbon dioxide laser is now successfully employed for some surgical procedures in gynecology, otorhinolaryngology, neurosurgery, and plastic and general surgery. The CO2 laser beam is directed through the viewing system of an operating microscope or through a hand-held laser component. Its basic action in tissue is thermal vaporization; it causes minimal damage to adjacent tissues. Surgeons require special training in the basic methods and techniques of laser surgery, as well as in the safety standards that must be observed. Images FIG. 5 PMID:7074503

Mystery cloud of AD 536

NASA Technical Reports Server (NTRS)

Stothers, R. B.

1984-01-01

The possible cause of the densest and most persistent dry fog on record, which was observed in Europe and the Middle East during AD 536 and 537, is discussed. The fog's long duration toward the south and the high sulfuric acid signal detected in Greenland in ice cores dated around AD 540 support the theory that the fog was due to the explosion of the Rabaul volcano, the occurrence of which has been dated at about AD 540 by the radiocarbon method.

Transurethral vaporesection of prostate: diode laser or thulium laser?

PubMed

Tan, Xinji; Zhang, Xiaobo; Li, Dongjie; Chen, Xiong; Dai, Yuanqing; Gu, Jie; Chen, Mingquan; Hu, Sheng; Bai, Yao; Ning, Yu

2018-05-01

This study compared the safety and effectiveness of the diode laser and thulium laser during prostate transurethral vaporesection for treating benign prostate hyperplasia (BPH). We retrospectively analyzed 205 patients with BPH who underwent a diode laser or thulium laser technique for prostate transurethral vaporesection from June 2016 to June 2017 and who were followed up for 3 months. Baseline characteristics of the patients, perioperative data, postoperative outcomes, and complications were compared. We also assessed the International Prostate Symptom Score (IPSS), quality of life (QoL), maximum flow rate (Q max ), average flow rate (AFR), and postvoid residual volume (PVR) at 1 and 3 months postoperatively to evaluate the functional improvement of each group. There were no significant differences between the diode laser and thulium laser groups related to age, prostate volume, operative time, postoperative hospital stays, hospitalization costs, or perioperative data. The catheterization time was 3.5 ± 0.8 days for the diode laser group and 4.7 ± 1.8 days for the thulium laser group (p < 0.05). Each group had dramatic improvements in IPSS, QoL, Q max , AFR, and PVR compared with the preoperative values (p < 0.05), although there were no significant differences between the two groups. Use of both diode laser and thulium laser contributes to safe, effective transurethral vaporesection in patients with symptomatic BPH. Diode laser, however, is better than thulium laser for prostate transurethral vaporesection because of its shorter catheterization time. The choice of surgical approach is more important than the choice of laser types during clinical decision making for transurethral laser prostatectomy.

InGaAs concentrator cells for laser power converters and tandem cells

NASA Technical Reports Server (NTRS)

Wojtczuk, S.; Vernon, S.; Gagnon, E.

1993-01-01

In(0.53)Ga(0.47)As N-on-P concentrator cells were made as part of an effort to develop 1.315 micron laser power converters. The 1.315 micron laser power conversion efficiency was estimated as 29.4 percent (at 5.57 W/cm(sup 2)) based on an 86 percent measured external quantum efficiency at 1.315 microns, and a measured open circuit voltage (484 mV), and fill-factor (67 percent) at the equivalent AM0 short-circuit photocurrent (5.07 A/cm(sup 2)). A 13.5 percent percent AMO efficiency was achieved at 89 suns and 25 C. Measured one-sun and 100-sun AMO efficiency, log I-V analysis, and quantum efficiency are presented for InGaAs cells with and without InP windows to passivate the front surface. Windowed cells performed better at concentration than windowless cells. Lattice mismatch between InGaAs epilayers and InP substrate was less than 800 ppm. Theoretical efficiency is estimated for 1.315 microns laser power converters versus the bandgap energy. Adding aluminum to InGaAs to form In(x)Al(y)Ga(1-x-y)As is presented as a way to achieve an optimal bandgap for 1.315 microns laser power conversion.

Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

NASA Astrophysics Data System (ADS)

Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

2015-12-01

The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

Laser safety considerations for a mobile laser program

NASA Astrophysics Data System (ADS)

Flor, Mary

1997-05-01

An increased demand for advanced laser technology, especially in the area of cutaneous and cosmetic procedures has prompted physicians to use mobile laser services. Utilization of a mobile laser service allows physicians to provide the latest treatments for their patients while minimizing overhead costs. The high capital expense of laser systems is often beyond the financial means of individual clinicians, group practices, free-standing clinics and smaller community hospitals. Historically rapid technology turnover with laser technology places additional risk which is unacceptable to many institutions. In addition, health care reform is mandating consolidation of equipment within health care groups to keep costs at a minimum. In 1994, Abbott Northwestern Hospital organized an in-house mobile laser technology service which employs a group of experienced laser specialists to deliver and support laser treatments for hospital outreach and other regional physicians and health care facilities. Many of the hospital's internal safety standards and policies are applicable to the mobile environment. A significant challenge is client compliance because of the delicate balance of managing risk while avoiding being viewed as a regulator. The clinics and hospitals are assessed prior to service to assure minimum laser safety standards for both the patient and the staff. A major component in assessing new sites is to inform them of applicable regulatory standards and their obligations to assure optimum laser safety. In service training is provided and hospital and procedures are freely shared to assist the client in establishing a safe laser environment. Physician and nursing preceptor programs are also made available.

X-ray laser system, x-ray laser and method

DOEpatents

London, Richard A.; Rosen, Mordecai D.; Strauss, Moshe

1992-01-01

Disclosed is an x-ray laser system comprising a laser containing generating means for emitting short wave length radiation, and means external to said laser for energizing said generating means, wherein when the laser is in an operative mode emitting radiation, the radiation has a transverse coherence length to width ratio of from about 0.05 to 1. Also disclosed is a method of adjusting the parameters of the laser to achieve the desired coherence length to laser width ratio.

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.

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2003-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In a third embodiment, alternating short and long pulses of light from the excitation light source are directed into the ignitor laser. Each of the embodiments of the invention can be multiplexed so as to provide laser light energy sequentially to more than one ignitor laser.

COGNITIVELY NORMAL INDIVIDUALS WITH AD PARENTS MAY BE AT RISK FOR DEVELOPING AGING-RELATED CORTICAL THINNING PATTERNS CHARACTERISTIC OF AD

PubMed Central

Reiter, Katherine; Alpert, Kathryn I.; Cobia, Derin J.; Kwasny, Mary J.; Morris, John C.; Csernansky, John C.; Wang, Lei

2012-01-01

Children of Alzheimer's Disease (AD) patients are at heightened risk of developing AD due to genetic influences, including the apolipoprotein E4 (ApoE4) allele. In this study, we assessed the earliest cortical changes associated with AD in 71 cognitively healthy, adult children of AD patients (AD offspring) as compared with 69 with no family history of AD (non-AD offspring). Cortical thickness measures were obtained using FreeSurfer from 1.5T magnetic resonance (MR) scans. ApoE genotyping was obtained. Primary analyses examined family history and ApoeE4 effects on cortical thickness. Secondary analyses examined age effects within groups. All comparisons were adjusted using False Discovery Rate at a significance threshold of p < 0.05. There were no statistically significant differences between family history and ApoE4 groups. Within AD offspring, increasing age was related to reduced cortical thickness (atrophy) over large areas of the precuneus, superior frontal and superior temporal gyri, starting at around age 60. Further, these patterns existed within female and maternal AD offspring, but were absent in male and paternal AD offspring. Within non-AD offspring, negative correlations existed over small regions of the superior temporal, insula and lingual cortices. These results suggest that as AD offspring age, cortical atrophy is more prominent, particularly if the parent with AD is mother or if the AD offspring is female. PMID:22503937

Supersymmetric Renyi entropy in CFT 2 and AdS 3

DOE PAGES

Giveon, Amit; Kutasov, David

2016-01-01

We show that in any two dimensional conformal field theory with (2, 2) super-symmetry one can define a supersymmetric analog of the usual Renyi entropy of a spatial region A. It differs from the Renyi entropy by a universal function (which we compute) of the central charge, Renyi parameter n and the geometric parameters of A. In the limit n → 1 it coincides with the entanglement entropy. Thus, it contains the same information as the Renyi entropy but its computation only involves correlation functions of chiral and anti-chiral operators. We also show that this quantity appears naturally in stringmore » theory on AdS3.« less

Closed strings and moduli in AdS3/CFT2

NASA Astrophysics Data System (ADS)

Sax, Olof Ohlsson; Stefański, Bogdan

2018-05-01

String theory on AdS3 × S3 × T4 has 20 moduli. We investigate how the perturbative closed string spectrum changes as we move around this moduli space in both the RR and NSNS flux backgrounds. We find that, at weak string coupling, only four of the moduli affect the energies. In the RR background the only effect of these moduli is to change the radius of curvature of the background. On the other hand, in the NSNS background, the moduli introduce worldsheet interactions which enable the use of integrability methods to solve the spectral problem. Our results show that the worldsheet theory is integrable across the 20 dimensional moduli space.

Mass-deformed ABJM and black holes in AdS4

NASA Astrophysics Data System (ADS)

Bobev, Nikolay; Min, Vincent S.; Pilch, Krzysztof

2018-03-01

We find a class of new supersymmetric dyonic black holes in four-dimensional maximal gauged supergravity which are asymptotic to the SU(3) × U(1) invariant AdS4 Warner vacuum. These black holes can be embedded in eleven-dimensional supergravity where they describe the backreaction of M2-branes wrapped on a Riemann surface. The holographic dual description of these supergravity backgrounds is given by a partial topological twist on a Riemann surface of a three-dimensional N=2 SCFT that is obtained by a mass-deformation of the ABJM theory. We compute explicitly the topologically twisted index of this SCFT and show that it accounts for the entropy of the black holes.

The Geoscience Laser Altimeter System Laser Transmitter

NASA Technical Reports Server (NTRS)

Afzal, R. S.; Dallas, J. L.; Yu, A. W.; Mamakos, W. A.; Lukemire, A.; Schroeder, B.; Malak, A.

2000-01-01

The Geoscience Laser Altimeter System (GLAS), scheduled to launch in 2001, is a laser altimeter and lidar for tile Earth Observing System's (EOS) ICESat mission. The laser transmitter requirements, design and qualification test results for this space- based remote sensing instrument are presented.

Studies on lasers and laser devices

NASA Technical Reports Server (NTRS)

Harris, S. E.; Siegman, A. E.; Young, J. F.

1983-01-01

The goal of this grant was to study lasers, laser devices, and uses of lasers for investigating physical phenomena are studied. The active projects included the development of a tunable, narrowband XUV light source and its application to the spectroscopy of core excited atomic states, and the development of a technique for picosecond time resolution spectroscopy of fast photophysical processes.

Introduction to the AdS/CFT Correspondence

NASA Astrophysics Data System (ADS)

Nąstase, Horaǧiu

2015-09-01

Preface; Introduction; Part I. Background: 1. Elements of quantum field theory and gauge theory; 2. Basics of general relativity. Anti-de Sitter space; 3. Basics of supersymmetry; 4. Basics of supergravity; 5. Kaluza-Klein dimensional reduction; 6. Black holes and p-branes; 7. String theory actions and spectra; 8. Elements of conformal field theory; 9. D-branes; Part II. Basics of AdS/CFT for N = 4 SYM vs AdS5 × S5: 10. The AdS/CFT correspondence: motivation, definition and spectra; 11. Witten prescription and 3-point correlator calculations; 12. Holography in Lorentzian signature: Poincaré and global; 13. Solitonic objects in AdS/CFT; 14. Quarks and the Wilson loop; 15. Finite temperature and N = 4 SYM plasmas; 16. Scattering processes and gravitational shockwave limit; 17. The pp-wave correspondence; 18. Spin chains; Part III. AdS/CFT Developments and Gauge-Gravity Dualities: 19. Other conformal cases; 20. The 3 dimensional ABJM model vs. AdS4 × CP3; 21. Gravity duals; 22. Holographic renormalization; 23. RG flow between fixed points; 24. Phenomenological gauge-gravity duality I: AdS/QCD; 25. Phenomenological gauge-gravity duality II: AdS/CMT; 26. Gluon scattering: the Alday-Maldacena prescription; 27. Holographic entanglement entropy: the Ryu-Takayanagi prescription.

The Geoscience Laser Altimeter System (GLAS) Laser Transmitter

NASA Technical Reports Server (NTRS)

Afzal, Robert S.; Yu, Anthony W.; Dallas, Joseph L.; Melak, Anthony; Lukemir, Alan; Ramos-Izqueirdo, L.; Mamakos, William

2007-01-01

The Geoscience Laser Altimeter System (GLAS), launched in January 2003, is a laser altimeter and lidar for the Earth Observing System's (EOS) ICESat mission. GLAS accommodates three, sequentially operated, diode-pumped, solid-state, Nd:YAG laser transmitters. The laser transmitter requirements, design and qualification test results for this space-based remote sensing instrument is summarized and presented

Asymptotically locally AdS and flat black holes in Horndeski theory

NASA Astrophysics Data System (ADS)

Anabalon, Andres; Cisterna, Adolfo; Oliva, Julio

2014-04-01

In this paper we construct asymptotically locally AdS and flat black holes in the presence of a scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exists a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. For a certain region in the space of parameters, the thermodynamic analysis reveals a critical temperature at which a Hawking-Page phase transition between the black hole and the soliton occurs. We extend the solution to arbitrary dimensions greater than 4 and show that the presence of a cosmological term in the action allows one to consider the case in which the standard kinetic term for the scalar it is not present. In such a scenario, the solution reduces to an asymptotically flat black hole.

Critical behavior and microscopic structure of charged AdS black holes via an alternative phase space

NASA Astrophysics Data System (ADS)

Dehyadegari, Amin; Sheykhi, Ahmad; Montakhab, Afshin

2017-05-01

It has been argued that charged Anti-de Sitter (AdS) black holes have similar thermodynamic behavior as the Van der Waals fluid system, provided one treats the cosmological constant as a thermodynamic variable (pressure) in an extended phase space. In this paper, we disclose the deep connection between charged AdS black holes and Van der Waals fluid system from an alternative point of view. We consider the mass of an AdS black hole as a function of square of the charge Q2 instead of the standard Q, i.e. M = M (S ,Q2 , P). We first justify such a change of view mathematically and then ask if a phase transition can occur as a function of Q2 for fixed P. Therefore, we write the equation of state as Q2 =Q2 (T , Ψ) where Ψ (conjugate of Q2) is the inverse of the specific volume, Ψ = 1 / v. This allows us to complete the analogy of charged AdS black holes with Van der Waals fluid system and derive the phase transition as well as critical exponents of the system. We identify a thermodynamic instability in this new picture with real analogy to Van der Waals fluid with physically relevant Maxwell construction. We therefore study the critical behavior of isotherms in Q2- Ψ diagram and deduce all the critical exponents of the system and determine that the system exhibits a small-large black hole phase transition at the critical point (Tc , Qc2 ,Ψc). This alternative view is important as one can imagine such a change for a given single black hole i.e. acquiring charge which induces the phase transition. Finally, we disclose the microscopic properties of charged AdS black holes by using thermodynamic geometry. Interestingly, we find that scalar curvature has a gap between small and large black holes, and this gap becomes exceedingly large as one moves away from the critical point along the transition line. Therefore, we are able to attribute the sudden enlargement of the black hole to the strong repulsive nature of the internal constituents at the phase transition.

A consistent and unified picture for critical phenomena of f(R) AdS black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Jie-Xiong; Li, Gu-Qiang; Wu, Yu-Cheng, E-mail: mojiexiong@gmail.com, E-mail: zsgqli@hotmail.com, E-mail: wuyucheng0827@163.com

A consistent and unified picture for critical phenomena of charged AdS black holes in f ( R ) gravity is drawn in this paper. Firstly, we investigate the phase transition in canonical ensemble. We derive the explicit solutions corresponding to the divergence of C {sub Q} . The two solutions merge into one when the condition Q {sub c} =√(−1/3 R {sub 0}) is satisfied. The curve of specific heat for Q < Q {sub c} has two divergent points and can be divided into three regions. Both the large radius region and the small radius region are thermodynamically stablemore » with positive specific heat while the medium radius region is unstable with negative specific heat. However, when Q > Q {sub c} , the specific heat is always positive, implying the black holes are locally stable and no phase transition will take place. Secondly, both the T − r {sub +} curve and T − S curve f ( R ) AdS black holes are investigated and they exhibit Van der Vaals like behavior as the P − v curve in the former research. Critical physical quantities are obtained and they are consistent with those derived from the specific heat analysis. We carry out numerical check of Maxwell equal area law for the cases Q =0.2 Q {sub c} , 0.4 Q {sub c} , 0.6 Q {sub c} , 0.8 Q {sub c} . The relative errors are amazingly small and can be negligible. So the Maxwell equal area law holds for T − S curve of f ( R ) black holes. Thirdly, we establish geometrothermodynamics for f ( R ) AdS black hole to examine the phase structure. It is shown that the Legendre invariant scalar curvature R would diverge exactly where the specific heat diverges. To summarize, the above three perspectives are consistent with each other, thus providing a unified picture which deepens the understanding of critical phenomena of f ( R ) AdS black holes.« less

Cognitively normal individuals with AD parents may be at risk for developing aging-related cortical thinning patterns characteristic of AD.

PubMed

Reiter, Katherine; Alpert, Kathryn I; Cobia, Derin J; Kwasny, Mary J; Morris, John C; Csernansky, John C; Wang, Lei

2012-07-02

Children of Alzheimer's disease (AD) patients are at heightened risk of developing AD due to genetic influences, including the apolipoprotein E4 (ApoE4) allele. In this study, we assessed the earliest cortical changes associated with AD in 71 cognitively healthy, adult children of AD patients (AD offspring) as compared with 69 with no family history of AD (non-AD offspring). Cortical thickness measures were obtained using FreeSurfer from 1.5T magnetic resonance (MR) scans. ApoE genotyping was obtained. Primary analyses examined family history and ApoeE4 effects on cortical thickness. Secondary analyses examined age effects within groups. All comparisons were adjusted using False Discovery Rate at a significance threshold of p<0.05. There were no statistically significant differences between family history and ApoE4 groups. Within AD offspring, increasing age was related to reduced cortical thickness (atrophy) over large areas of the precuneus, superior frontal and superior temporal gyri, starting at around age 60. Further, these patterns existed within female and maternal AD offspring, but were absent in male and paternal AD offspring. Within non-AD offspring, negative correlations existed over small regions of the superior temporal, insula and lingual cortices. These results suggest that as AD offspring age, cortical atrophy is more prominent, particularly if the parent with AD is mother or if the AD offspring is female. Copyright © 2012 Elsevier Inc. All rights reserved.

Q ‑ Φ criticality and microstructure of charged AdS black holes in f(R) gravity

NASA Astrophysics Data System (ADS)

Deng, Gao-Ming; Huang, Yong-Chang

2017-12-01

The phase transition and critical behaviors of charged AdS black holes in f(R) gravity with a conformally invariant Maxwell (CIM) source and constant curvature are further investigated. As a highlight, this research is carried out by employing new state parameters (T,Q, Φ) and contributes to deeper understanding of the thermodynamics and phase structure of black holes. Our analyses manifest that the charged f(R)-CIM AdS black hole undergoes a first-order small-large black hole phase transition, and the critical behaviors qualitatively behave like a Van der Waals liquid-vapor system. However, differing from the case in Einstein’s gravity, phase structures of the black holes in f(R) theory exhibit an interesting dependence on gravity modification parameters. Moreover, we adopt the thermodynamic geometry to probe the black hole microscopic properties. The results show that, on the one hand, both the Ruppeiner curvature and heat capacity diverge exactly at the critical point, on the other hand, the f(R)-CIM AdS black hole possesses the property as ideal Fermi gases. Of special interest, we discover a microscopic similarity between the black holes and a Van der Waals liquid-vapor system.

Secure ADS-B authentication system and method

NASA Technical Reports Server (NTRS)

Viggiano, Marc J (Inventor); Valovage, Edward M (Inventor); Samuelson, Kenneth B (Inventor); Hall, Dana L (Inventor)

2010-01-01

A secure system for authenticating the identity of ADS-B systems, including: an authenticator, including a unique id generator and a transmitter transmitting the unique id to one or more ADS-B transmitters; one or more ADS-B transmitters, including a receiver receiving the unique id, one or more secure processing stages merging the unique id with the ADS-B transmitter's identification, data and secret key and generating a secure code identification and a transmitter transmitting a response containing the secure code and ADSB transmitter's data to the authenticator; the authenticator including means for independently determining each ADS-B transmitter's secret key, a receiver receiving each ADS-B transmitter's response, one or more secure processing stages merging the unique id, ADS-B transmitter's identification and data and generating a secure code, and comparison processing comparing the authenticator-generated secure code and the ADS-B transmitter-generated secure code and providing an authentication signal based on the comparison result.

Laser ranging with the MéO telescope to improve orbital accuracy of space debris

NASA Astrophysics Data System (ADS)

Hennegrave, L.; Pyanet, M.; Haag, H.; Blanchet, G.; Esmiller, B.; Vial, S.; Samain, E.; Paris, J.; Albanese, D.

2013-05-01

Improving orbital accuracy of space debris is one of the major prerequisite to performing reliable collision prediction in low earth orbit. The objective is to avoid false alarms and useless maneuvers for operational satellites. This paper shows how laser ranging on debris can improve the accuracy of orbit determination. In March 2012 a joint OCA-Astrium team had the first laser echoes from space debris using the MéO (Métrologie Optique) telescope of the Observatoire de la Côte d'Azur (OCA), upgraded with a nanosecond pulsed laser. The experiment was conducted in full compliance with the procedures dictated by the French Civil Aviation Authorities. To perform laser ranging measurement on space debris, the laser link budget needed to be improved. Related technical developments were supported by implementation of a 2J pulsed laser purchased by ASTRIUM and an adapted photo detection. To achieve acquisition of the target from low accuracy orbital data such as Two Lines Elements, a 2.3-degree field of view telescope was coupled to the original MéO telescope 3-arcmin narrow field of view. The wide field of view telescope aimed at pointing, adjusting and acquiring images of the space debris for astrometry measurement. The achieved set-up allowed performing laser ranging and angular measurements in parallel, on several rocket stages from past launches. After a brief description of the set-up, development issues and campaigns, the paper discusses added-value of laser ranging measurement when combined to angular measurement for accurate orbit determination. Comparison between different sets of experimental results as well as simulation results is given.

New Features in ADS Labs

NASA Astrophysics Data System (ADS)

Accomazzi, Alberto; Kurtz, M. J.; Henneken, E. A.; Grant, C. S.; Thompson, D.; Di Milia, G.; Luker, J.; Murray, S. S.

2013-01-01

The NASA Astrophysics Data System (ADS) has been working hard on updating its services and interfaces to better support our community's research needs. ADS Labs is a new interface built on the old tried-and-true ADS Abstract Databases, so all of ADS's content is available through it. In this presentation we highlight the new features that have been developed in ADS Labs over the last year: new recommendations, metrics, a citation tool and enhanced fulltext search. ADS Labs has long been providing article-level recommendations based on keyword similarity, co-readership and co-citation analysis of its corpus. We have now introduced personal recommendations, which provide a list of articles to be considered based on a individual user's readership history. A new metrics interface provides a summary of the basic impact indicators for a list of records. These include the total and normalized number of papers, citations, reads, and downloads. Also included are some of the popular indices such as the h, g and i10 index. The citation helper tool allows one to submit a set of records and obtain a list of top 10 papers which cite and/or are cited by papers in the original list (but which are not in it). The process closely resembles the network approach of establishing "friends of friends" via an analysis of the citation network. The full-text search service now covers more than 2.5 million documents, including all the major astronomy journals, as well as physics journals published by Springer, Elsevier, the American Physical Society, the American Geophysical Union, and all of the arXiv eprints. The full-text search interface interface allows users and librarians to dig deep and find words or phrases in the body of the indexed articles. ADS Labs is available at http://adslabs.org

Laser plasma interaction at an early stage of laser ablation

NASA Astrophysics Data System (ADS)

Lu, Y. F.; Hong, M. H.; Low, T. S.

1999-03-01

Laser scattering and its interaction with plasma during KrF excimer laser ablation of silicon are investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. For laser fluence above 5.8 J/cm2, the second peak rises earlier to overlap with the first one. The optical signal is fitted by a pulse distribution for the scattered laser light and a drifted Maxwell-Boltzmann distribution with a center-of-mass velocity for the plasma. Peak amplitude and its arrival time, full width at half maximum (FWHM), starting time, and termination time of the profiles are studied for different laser fluences and detection angles. Laser pulse is scattered from both the substrate and the plasma with the latter part as a dominant factor during the laser ablation. Peak amplitude of the scattered laser signal increases but its FWHM decreases with the laser fluence. Angular distribution of the peak amplitude can be fitted with cosn θ(n=4) while the detection angle has no obvious influence on the FWHM. In addition, FWHM and peak amplitude of plasma signal increase with the laser fluence. However, starting time and peak arrival time of plasma signal reduce with the laser fluence. The time interval between plasma starting and scattered laser pulse termination is proposed as a quantitative parameter to characterize laser plasma interaction. Threshold fluence for the interaction is estimated to be 3.5 J/cm2. For laser fluence above 12.6 J/cm2, the plasma and scattered laser pulse distributions tend to saturate.

Femtosecond laser in laser in situ keratomileusis

PubMed Central

Salomão, Marcella Q.; Wilson, Steven E.

2014-01-01

Flap creation is a critical step in laser in situ keratomileusis (LASIK). Efforts to improve the safety and predictability of the lamellar incision have fostered the development of femtosecond lasers. Several advantages of the femtosecond laser over mechanical microkeratomes have been reported in LASIK surgery. In this article, we review common considerations in management and complications of this step in femtosecond laser–LASIK and concentrate primarily on the IntraLase laser because most published studies relate to this instrument. PMID:20494777

What's the Value in Value-Added?

ERIC Educational Resources Information Center

Duffrin, Elizabeth

2011-01-01

A growing number of school districts are adopting "value-added" measures of teaching quality to award bonuses or even tenure. And two competitive federal grants are spurring them on. Districts using value-added data are encouraged by the results. But researchers who support value-added measures advise caution. The ratings, which use a…

Task five report: Laser communications for data acquisition networks. [characteristics of lasers and laser systems for optical communication applications

NASA Technical Reports Server (NTRS)

1973-01-01

Laser communication technology and laser communication performance are reviewed. The subjects discussed are: (1) characteristics of laser communication systems, (2) laser technology problems, (3) means of overcoming laser technology problems, and (4) potential schedule for including laser communications into data acquisition networks. Various types of laser communication systems are described and their capabilities are defined.

Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays

NASA Technical Reports Server (NTRS)

Hemmati, H.; Lesh, J. R.

1989-01-01

Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.

ADS pilot program Plan

NASA Technical Reports Server (NTRS)

Clauson, J.; Heuser, J.

1981-01-01

The Applications Data Service (ADS) is a system based on an electronic data communications network which will permit scientists to share the data stored in data bases at universities and at government and private installations. It is designed to allow users to readily locate and access high quality, timely data from multiple sources. The ADS Pilot program objectives and the current plans for accomplishing those objectives are described.

From free fields to AdS space. II

NASA Astrophysics Data System (ADS)

Gopakumar, Rajesh

2004-07-01

We continue with the program of paper I [Phys. Rev. D 70, 025009 (2004)] to implement open-closed string duality on free gauge field theory (in the large-N limit). In this paper we consider correlators such as <∏ni=1TrΦJi(xi)>. The Schwinger parametrization of this n-point function exhibits a partial gluing up into a set of basic skeleton graphs. We argue that the moduli space of the planar skeleton graphs is exactly the same as the moduli space of genus zero Riemann surfaces with n holes. In other words, we can explicitly rewrite the n-point (planar) free-field correlator as an integral over the moduli space of a sphere with n holes. A preliminary study of the integrand also indicates compatibility with a string theory on AdS space. The details of our argument are quite insensitive to the specific form of the operators and generalize to diagrams of a higher genus as well. We take this as evidence of the field theory’s ability to reorganize itself into a string theory.

Consistency analysis on laser signal in laser guided weapon simulation

NASA Astrophysics Data System (ADS)

Yin, Ruiguang; Zhang, Wenpan; Guo, Hao; Gan, Lin

2015-10-01

The hardware-in-the-loop simulation is widely used in laser semi-active guidance weapon experiments, the authenticity of the laser guidance signal is the key problem of reliability. In order to evaluate the consistency of the laser guidance signal, this paper analyzes the angle of sight, laser energy density, laser spot size, atmospheric back scattering, sun radiation and SNR by comparing the different working state between actual condition and hardware-in-the-loop simulation. Based on measured data, mathematical simulation and optical simulation result, laser guidance signal effects on laser seeker are determined. By using Monte Carlo method, the laser guided weapon trajectory and impact point distribution are obtained, the influence of the systematic error are analyzed. In conclusion it is pointed out that the difference between simulation system and actual system has little influence in normal guidance, has great effect on laser jamming. The research is helpful to design and evaluation of laser guided weapon simulation.

Design and comparison of laser windows for high-power lasers

NASA Astrophysics Data System (ADS)

Niu, Yanxiong; Liu, Wenwen; Liu, Haixia; Wang, Caili; Niu, Haisha; Man, Da

2014-11-01

High-power laser systems are getting more and more widely used in industry and military affairs. It is necessary to develop a high-power laser system which can operate over long periods of time without appreciable degradation in performance. When a high-energy laser beam transmits through a laser window, it is possible that the permanent damage is caused to the window because of the energy absorption by window materials. So, when we design a high-power laser system, a suitable laser window material must be selected and the laser damage threshold of the window must be known. In this paper, a thermal analysis model of high-power laser window is established, and the relationship between the laser intensity and the thermal-stress field distribution is studied by deducing the formulas through utilizing the integral-transform method. The influence of window radius, thickness and laser intensity on the temperature and stress field distributions is analyzed. Then, the performance of K9 glass and the fused silica glass is compared, and the laser-induced damage mechanism is analyzed. Finally, the damage thresholds of laser windows are calculated. The results show that compared with K9 glass, the fused silica glass has a higher damage threshold due to its good thermodynamic properties. The presented theoretical analysis and simulation results are helpful for the design and selection of high-power laser windows.

Laser and Light-based Treatment of Keloids – A Review

PubMed Central

Mamalis, A.D.; Lev-Tov, H.; Nguyen, D.H.; Jagdeo, J.R.

2015-01-01

Keloids are an overgrowth of fibrotic tissue outside the original boundaries of an injury and occur secondary to defective wound healing. Keloids often have a functional, aesthetic, or psychosocial impact on patients as highlighted by quality-of-life studies. Our goal is to provide clinicians and scientists an overview of the data available on laser and light-based therapies for treatment of keloids, and highlight emerging light-based therapeutic technologies and the evidence available to support their use. We employed the following search strategy to identify the clinical evidence reported in the biomedical literature: in November 2012, we searched PubMed.gov, Ovid MEDLINE, Embase, and Cochrane Reviews (1980-present) for published randomized clinical trials, clinical studies, case series, and case reports related to the treatment of keloids. The search terms we utilized were ‘keloid(s)’ AND ‘laser’ OR ‘light-emitting diode’ OR ‘photodynamic therapy’ OR ‘intense pulsed light’ OR ‘low level light’ OR ‘phototherapy.’ Our search yielded 347 unique articles. Of these, 33 articles met our inclusion and exclusion criteria. We qualitatively conclude that laser and light-based treatment modalities may achieve favorable patient outcomes. Clinical studies using CO2 laser are more prevalent in current literature and a combination regimen may be an adequate ablative approach. Adding light-based treatments, such as LED phototherapy or photodynamic therapy, to laser treatment regimens may enhance patient outcomes. Lasers and other light-based technology have introduced new ways to manage keloids that may result in improved aesthetic and symptomatic outcomes and decreased keloid recurrence. PMID:24033440

A scintillator-based online detector for the angularly resolved measurement of laser-accelerated proton spectra.

PubMed

Metzkes, J; Karsch, L; Kraft, S D; Pawelke, J; Richter, C; Schürer, M; Sobiella, M; Stiller, N; Zeil, K; Schramm, U

2012-12-01

In recent years, a new generation of high repetition rate (~10 Hz), high power (~100 TW) laser systems has stimulated intense research on laser-driven sources for fast protons. Considering experimental instrumentation, this development requires online diagnostics for protons to be added to the established offline detection tools such as solid state track detectors or radiochromic films. In this article, we present the design and characterization of a scintillator-based online detector that gives access to the angularly resolved proton distribution along one spatial dimension and resolves 10 different proton energy ranges. Conceived as an online detector for key parameters in laser-proton acceleration, such as the maximum proton energy and the angular distribution, the detector features a spatial resolution of ~1.3 mm and a spectral resolution better than 1.5 MeV for a maximum proton energy above 12 MeV in the current design. Regarding its areas of application, we consider the detector a useful complement to radiochromic films and Thomson parabola spectrometers, capable to give immediate feedback on the experimental performance. The detector was characterized at an electrostatic Van de Graaff tandetron accelerator and tested in a laser-proton acceleration experiment, proving its suitability as a diagnostic device for laser-accelerated protons.

Effective Management of a pregnancy tumour using a soft tissue diode laser: a case Report.

PubMed

Sharma, Ambika; Mathur, Vijay Prakash; Sardana, Divesh

2014-12-27

Pregnancy tumours (PTs) are a non-neoplastic, reactive, inflammatory conditional gingival enlargement which occurs in the oral cavity during pregnancy. The lesion most frequently occurs on the gingiva but may also develop on the lip, tongue, oral mucosa and palate. When a large PT develops, it can interfere with mastication, speech, maintenance of oral hygiene and can be aesthetically disfiguring. The treatment of PTs depends upon the size of the lesion; smaller lesions can regress after parturition however large lesions need to be surgically removed. Conventional surgical techniques have the disadvantage of more bleeding from the surgical site and delay in healing of the scar tissue. The diode laser is a relatively new alternative to conventional surgical technique in intra-oral areas with the added advantage of bloodless procedures and rapid healing. The purpose of the present study is to highlight the management of a PT in a 25-year-old female using a diode laser delivering a painless, bloodless procedure with rapid postoperative healing. Diode laser excision of a persistent pregnancy tumour in a postpartum patient was safe and effective with minimal bleeding, good coagulation, and good wound healing. Among other lasers, the diode laser can therefore be considered for excisional treatment of persistent PTs.

An alternative path to the boundary: The CFT as the Fourier space of AdS

NASA Astrophysics Data System (ADS)

Tolfree, Ian M.

2009-12-01

In this thesis we shed new light on the conjectured duality between an n + 1 dimensional theory of gravity in anti de Sitter space (AdS) and an n dimensional conformal field theory (CFT) by showing that the CFT can be interpreted as the Fourier space of AdS. We then make use of this to gain insight into the nature of black hole entropy. In the first part of this thesis, we give an introduction to the ideas of and review the basics of the AdS/CFT. In the next section we make use of well known integral geometry techniques to derive the Fourier transformation of a function on AdS and see it is a function with compact support on the boundary. Comparing this to the literature, we find that the Green's functions from the literature are actually the Fourier weights of the transformation and that the boundary values of fields appearing in the correspondence are the Fourier coefficients of the transformation. One is thus left to interpret the CFT as the quantized version of a classical theory in AdS and the dual operator as the Fourier coefficients. Group theoretic considerations are discussed in relation to the transformation and its potential use in constructing QCD like theories. In the last section, we then build upon this to study the BTZ black hole. Named after its authors, Banados, Teitelboim and Zanelli, the BTZ black hole is a three dimensional (two space plus one time dimension) black hole in anti de Sitter space. Following standard procedures for modifying Fourier Transformations to accommodate quotient spaces we arrive at a mapping in a black hole background consistent with known results that yields the exact micro-states of a scalar field in a black hole background. We find that the micro-states are the Fourier coefficients on the boundary, which transform under the principal series representation of SL(2, R). Using the knowledge of how to represent a bulk scalar field in the CFT, and knowing how a black hole interacts with a scalar field, we deduce the

Laser apparatus

DOEpatents

Lewis, Owen; Stogran, Edmund M.

1980-01-01

Laser apparatus is described wherein an active laser element, such as the disc of a face-pumped laser, is mounted in a housing such that the weight of the element is supported by glass spheres which fill a chamber defined in the housing between the walls of the housing and the edges of the laser element. The uniform support provided by the spheres enable the chamber and the pump side of the laser element to be sealed without affecting the alignment or other optical properties of the laser element. Cooling fluid may be circulated through the sealed region by way of the interstices between the spheres. The spheres, and if desired also the cooling fluid may contain material which absorbs radiation at the wavelength of parasitic emissions from the laser element. These parasitic emissions enter the spheres through the interface along the edge surface of the laser element and it is desirable that the index of refraction of the spheres and cooling fluid be near the index of refraction of the laser element. Thus support, cooling, and parasitic suppression functions are all accomplished through the use of the arrangement.

Operation of Ho:YAG ultrafast laser inscribed waveguide lasers.

PubMed

McDaniel, Sean; Thorburn, Fiona; Lancaster, Adam; Stites, Ronald; Cook, Gary; Kar, Ajoy

2017-04-20

We report fabrication and operation of multi-watt level waveguide lasers utilizing holmium-doped yttrium aluminum garnet (Ho:YAG). The waveguides were fabricated using ultrafast laser inscription, which relies on a chirped pulse ytterbium fiber laser to create depressed cladding structures inside the material. A variety of waveguides were created inside the Ho:YAG samples. We demonstrate output powers of ∼2  W from both a single-mode 50 μm waveguide laser and a multimode 80 μm waveguide laser. In addition, laser action from a co-doped Yb:Ho:YAG sample under in-band pumping conditions was demonstrated.

Synchrotron emission from nanowire array targets irradiated by ultraintense laser pulses

NASA Astrophysics Data System (ADS)

Martinez, B.; d’Humières, E.; Gremillet, L.

2018-07-01

We present a numerical study, based on two-dimensional particle-in-cell simulations, of the synchrotron emission induced during the interaction of femtosecond laser pulses of intensities I = 1021–1023 W cm‑2 with nanowire arrays. Through an extensive parametric scan on the target parameters, we identify and characterize several dominant radiation mechanisms, mainly depending on the transparency or opacity of the plasma produced by the wire expansion. At I = 1022 W m‑2, the emission of high-energy (>10 keV) photons attains a maximum conversion efficiency of ∼10% for 36–50 nm wire widths and 1 μm interspacing. This maximum radiation yield is found to be similar to that achieved in a uniform plasma of same average (sub-solid) density, but nanowire arrays provide efficient radiation sources over a broader parameter range. Moreover, we examine the variations of the photon spectra with the laser intensity and the wire material, and we demonstrate that the radiation efficiency can be further enhanced by adding a plasma mirror at the backside of the nanowire array. Finally, we briefly consider the influence of a finite laser focal spot and oblique incidence angle.

Comparative study of two intraoral laser techniques for soft tissue surgery

NASA Astrophysics Data System (ADS)

Swick, Michael D.; Richter, Alexander

2003-06-01

Historically, 810nm has been the predominant wavelength used for intraoral surgery, when diode lasers have been discussed, due to their large numbers in the market place. The techniques used intraorally with the 810nm diode have been relatively similar in most cases. Low powers, 1 or 2 watts, using continuous wave, are employed. The purpose of this study is to compare the thermal damage of the technique of using continuous wave at low powers, to using higher powers with a pulse mode and water for coolant, with the 980nm diode wavelength. During the study the laser fiber was held immobile eliminating surgical manipulation as an error. The resultant histology proves, while the volume of vaporization dramatically increases, thus giving the clinician the ability to reduce the time for destructive conduction of excess heat for a given procedure, the amount of coagulation actually decreases in width and depth. As an added benefit charring, which has been implicated in delayed healing is virtually eliminated. This evidence, coupled with excellent clinical results, lends validity to the use of pulsed higher powers and water coolant for the 980nm diode laser.

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2002-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. The beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being recombined with the first portion after a delay before injection into the ignitor laser. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones.

Quantum statistical relation for black holes in nonlinear electrodynamics coupled to Einstein-Gauss-Bonnet AdS gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miskovic, Olivera; Olea, Rodrigo

2011-03-15

We consider curvature-squared corrections to Einstein-Hilbert gravity action in the form of a Gauss-Bonnet term in D>4 dimensions. In this theory, we study the thermodynamics of charged static black holes with anti-de Sitter (AdS) asymptotics, and whose electric field is described by nonlinear electrodynamics. These objects have received considerable attention in recent literature on gravity/gauge dualities. It is well-known that, within the framework of anti-de Sitter/conformal field theory (AdS/CFT) correspondence, there exists a nonvanishing Casimir contribution to the internal energy of the system, manifested as the vacuum energy for global AdS spacetime in odd dimensions. Because of this reason, wemore » derive a quantum statistical relation directly from the Euclidean action and not from the integration of the first law of thermodynamics. To this end, we employ a background-independent regularization scheme which consists, in addition to the bulk action, of counterterms that depend on both extrinsic and intrinsic curvatures of the boundary (Kounterterm series). This procedure results in a consistent inclusion of the vacuum energy and chemical potential in the thermodynamic description for Einstein-Gauss-Bonnet AdS gravity regardless of the explicit form of the nonlinear electrodynamics Lagrangian.« less

Laser propulsion for orbit transfer - Laser technology issues

NASA Technical Reports Server (NTRS)

Horvath, J. C.; Frisbee, R. H.

1985-01-01

Using reasonable near-term mission traffic models (1991-2000 being the assumed operational time of the system) and the most current unclassified laser and laser thruster information available, it was found that space-based laser propulsion orbit transfer vehicles (OTVs) can outperform the aerobraked chemical OTV over a 10-year life-cycle. The conservative traffic models used resulted in an optimum laser power of about 1 MW per laser. This is significantly lower than the power levels considered in other studies. Trip time was taken into account only to the extent that the system was sized to accomplish the mission schedule.

Laser frequency modulator for modulating a laser cavity

DOEpatents

Erbert, Gaylen V.

1992-01-01

The present invention relates to a laser frequency modulator for modulating a laser cavity. It is known in the prior art to utilize a PZT (piezoelectric transducer) element in combination with a mirror to change the cavity length of a laser cavity (which changes the laser frequency). Using a PZT element to drive the mirror directly is adequate at frequencies below 10 kHz. However, in high frequency applications (100 kHz and higher) PZT elements alone do not provide a sufficient change in the cavity length. The present invention utilizes an ultrasonic concentrator with a PZT element and mirror to provide modulation of the laser cavity. With an ultrasonic concentrator, the mirror element at the end of a laser cavity can move at larger amplitudes and higher frequencies.

Holographic reconstruction of AdS exchanges from crossing symmetry

DOE PAGES

Alday, Luis F.; Bissi, Agnese; Perlmutter, Eric

2017-08-31

Motivated by AdS/CFT, we address the following outstanding question in large N conformal field theory: given the appearance of a single-trace operator in the O x O OPE of a scalar primary O, what is its total contribution to the vacuum four-point function (OOOO) as dictated by crossing symmetry? We solve this problem in 4d conformal field theories at leading order in 1/N. Viewed holographically, this provides a field theory reconstruction of crossing-symmetric, four-point exchange amplitudes in AdS 5. Our solution takes the form of a resummation of the large spin solution to the crossing equations, supplemented by corrections atmore » finite spin, required by crossing. The method can be applied to the exchange of operators of arbitrary twist τ and spin s, although it vastly simplifies for even-integer twist, where we give explicit results. The output is the set of OPE data for the exchange of all double-trace operators [OO] n,ℓ. We find that the double-trace anomalous dimensions γ n,ℓ are negative, monotonic and convex functions of ℓ, for all n and all ℓ > s. This constitutes a holographic signature of bulk causality and classical dynamics of even-spin fields. We also find that the “derivative relation” between double-trace anomalous dimensions and OPE coefficients does not hold in general, and derive the explicit form of the deviation in several cases. Finally, we study large n limits of γ n,ℓ, relevant for the Regge and bulk-point regimes.« less

Investigations of Photochemistry Using Holography and Photoacoustic Spectroscopy.

DTIC Science & Technology

1984-09-28

Donald M. Burland PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK CD International Business Machines, Inc. AE OKUI UUR San...Hans Coufal Institution: International Business Machines Corporation San Jose Research Laboratory 5600 Cottle Road, San Jose, CA 95193 " Funding

High throughput laser processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harley, Gabriel; Pass, Thomas; Cousins, Peter John

A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

16 CFR 460.18 - Insulation ads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Insulation ads. 460.18 Section 460.18... INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation and... the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.” (b) If...

16 CFR 460.18 - Insulation ads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Insulation ads. 460.18 Section 460.18... INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation and... the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.” (b) If...

16 CFR 460.18 - Insulation ads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Insulation ads. 460.18 Section 460.18... INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation and... the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.” (b) If...

16 CFR 460.18 - Insulation ads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Insulation ads. 460.18 Section 460.18... INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation and... the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.” (b) If...

16 CFR 460.18 - Insulation ads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Insulation ads. 460.18 Section 460.18... INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation and... the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.” (b) If...

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)

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2002-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In the embodiment of the invention claimed herein, the beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being combined with either the first portion after a delay before injection into the ignitor laser.

Phasing surface emitting diode laser outputs into a coherent laser beam

DOEpatents

Holzrichter, John F [Berkeley, CA

2006-10-10

A system for generating a powerful laser beam includes a first laser element and at least one additional laser element having a rear laser mirror, an output mirror that is 100% reflective at normal incidence and <5% reflective at an input beam angle, and laser material between the rear laser mirror and the output mirror. The system includes an injector, a reference laser beam source, an amplifier and phase conjugater, and a combiner.

Ytterbium-doped borate fluoride laser crystals and lasers

DOEpatents

Schaffers, Kathleen I.; DeLoach, Laura D.; Payne, Stephen A.; Keszler, Douglas A.

1997-01-01

A new class of solid state laser crystals and lasers are formed from Yb-doped borate fluoride host crystals. The general formula for the host crystals is MM'(BO.sub.3)F, where M, M' are monovalent, divalent aria trivalent metal cations. A particular embodiment of the invention is Yb-doped BaCaBO.sub.3 F (Yb:BCBF). BCBF and some of the related derivative crystals are capable of nonlinear frequency conversion, whereby the fundamental of the laser is converted to a longer or shorter wavelength. In this way, these new crystals can simultaneously serve as self-frequency doubling crystals and laser materials within the laser resonator.

Histologic evaluation of laser lipolysis: pulsed 1064-nm Nd:YAG laser versus cw 980-nm diode laser.

PubMed

Mordon, Serge; Eymard-Maurin, Anne Françoise; Wassmer, Benjamin; Ringot, Jean

2007-01-01

The use of the laser as an auxiliary tool has refined the traditional technique for lipoplasty. During laser lipolysis, the interaction between the laser and the fat produced direct cellular destruction before the suction, reduced bleeding, and promoted skin tightening. This study sought to perform a comparative histologic evaluation of laser lipolysis with the pulsed 1064-nm Nd:YAG laser versus a continuous 980-nm diode laser. A pulsed 1064-nm Nd:YAG (Smart-Lipo; Deka, Italy) and a CW 980-nm diode laser (Pharaon, Osyris, France) were evaluated at different energy settings for lipolysis on the thighs of a fresh cadaver. The lasers were coupled to a 600-microm optical fiber inserted in a 1-mm diameter cannula. Biopsy specimens were taken on irradiated and non-irradiated areas. Hematoxylin-erythrosin-safran staining and immunostaining (anti-PS100 polyclonal antibody) were performed to identify fat tissue damage. In the absence of laser exposures (control specimens), cavities created by cannulation were seen; adipocytes were round in appearance and not deflated. At low energy settings, tumescent adipocytes were observed. At higher energy settings, cytoplasmic retraction, disruption of membranes, and heat-coagulated collagen fibers were noted; coagulated blood cells were also present. For the highest energy settings, carbonization of fat tissue involving fibers and membranes was clearly seen. For equivalent energy settings, 1064-nm and 980-nm wavelengths gave similar histologic results. Laser lipolysis is a relatively new technique that is still under development. Our histologic findings suggest several positive benefits of the laser, including skin retraction and a reduction in intraoperative bleeding. The interaction of the laser with the tissue is similar at 980 nm and 1064 nm with the same energy settings. Because higher volumes of fat are removed with higher total energy, a high-power 980-nm diode laser could offer an interesting alternative to the 1064-nm Nd

Interferometer design and controls for pulse stacking in high power fiber lasers

NASA Astrophysics Data System (ADS)

Wilcox, Russell; Yang, Yawei; Dahlen, Dar; Xu, Yilun; Huang, Gang; Qiang, Du; Doolittle, Lawrence; Byrd, John; Leemans, Wim; Ruppe, John; Zhou, Tong; Sheikhsofla, Morteza; Nees, John; Galvanauskas, Almantas; Dawson, Jay; Chen, Diana; Pax, Paul

2017-03-01

In order to develop a design for a laser-plasma accelerator (LPA) driver, we demonstrate key technologies that enable fiber lasers to produce high energy, ultrafast pulses. These technologies must be scalable, and operate in the presence of thermal drift, acoustic noise, and other perturbations typical of an operating system. We show that coherent pulse stacking (CPS), which requires optical interferometers, can be made robust by image-relaying, multipass optical cavities, and by optical phase control schemes that sense pulse train amplitudes from each cavity. A four-stage pulse stacking system using image-relaying cavities is controlled for 14 hours using a pulse-pattern sensing algorithm. For coherent addition of simultaneous ultrafast pulses, we introduce a new scheme using diffractive optics, and show experimentally that four pulses can be added while a preserving pulse width of 128 fs.

ALMDS laser system

NASA Astrophysics Data System (ADS)

Kushina, Mark E.; Heberle, Geoff; Hope, Michael; Hall, David; Bethel, Michael; Calmes, Lonnie K.

2003-06-01

The ALMDS (Airborne Laser Mine Detection System) has been developed utilizing a solid-state laser operating at 532nm for naval mine detection. The laser system is integrated into a pod that mounts externally on a helicopter. This laser, along with other receiver systems, enables detailed underwater bathymetry. CEO designs and manufactures the laser portion of this system. Arete Associates integrates the laser system into the complete LIDAR package that utilizes sophisticated streak tube detection technology. Northrop Grumman is responsible for final pod integration. The laser sub-system is comprised of two separate parts: the LTU (Laser Transmitter Unit) and the LEU (Laser Electronics Unit). The LTU and LEU are undergoing MIL-STD-810 testing for vibration, shock, temperature storage and operation extremes, as well as MIL-STD-704E electrical power testing and MIL-STD-461E EMI testing. The Nd:YAG MOPA laser operates at 350 Hz pulse repetition frequency at 45 Watts average 532nm power and is controlled at the system level from within the helicopter. Power monitor circuits allow real time laser health monitoring, which enables input parameter adjustments for consistent laser behavior.

Aspects of warped AdS3/CFT2 correspondence

NASA Astrophysics Data System (ADS)

Chen, Bin; Zhang, Jia-Ju; Zhang, Jian-Dong; Zhong, De-Liang

2013-04-01

In this paper we apply the thermodynamics method to investigate the holographic pictures for the BTZ black hole, the spacelike and the null warped black holes in three-dimensional topologically massive gravity (TMG) and new massive gravity (NMG). Even though there are higher derivative terms in these theories, the thermodynamics method is still effective. It gives consistent results with the ones obtained by using asymptotical symmetry group (ASG) analysis. In doing the ASG analysis we develop a brute-force realization of the Barnich-Brandt-Compere formalism with Mathematica code, which also allows us to calculate the masses and the angular momenta of the black holes. In particular, we propose the warped AdS3/CFT2 correspondence in the new massive gravity, which states that quantum gravity in the warped spacetime could holographically dual to a two-dimensional CFT with {c_R}={c_L}=24 /{Gm{β^2√{{2( {21-4{β^2}} )}}}}.

Miniaturized X-ray Generation by Pyroelectric Effect using Short Pulse Laser

DTIC Science & Technology

2011-11-30

turned out that only 0.2 ℃ temperature change during 10 ns caused a giant current such as 20 mA. This value was 104 ~ 105 times larger than the...where εosc = qeEl2 /(meω2) is the electron quiver energy, EI ≈ 19√ = 4.65x 104 V/cm is the electric field of laser radiation for I = 6x106 W...duration the integration of Eq. (5) gives: (9) where )(/ adR NNha   , Rhb

DAWN: Dynamic Ad-hoc Wireless Network

DTIC Science & Technology

2016-06-19

DAWN: Dynamic Ad-hoc Wireless Network The DAWN (Dynamic Ad-hoc Wireless Networks) project is developing a general theory of complex and dynamic... wireless communication networks. To accomplish this, DAWN adopts a very different approach than those followed in the past and summarized above. DAWN... wireless communication networks. The members of DAWN investigated difference aspects of wireless mobile ad hoc networks (MANET). The views, opinions and/or

Laser photocoagulation - eye

MedlinePlus

Laser coagulation; Laser eye surgery; Photocoagulation; Laser photocoagulation - diabetic eye disease; Laser photocoagulation - diabetic retinopathy; Focal photocoagulation; Scatter (or pan retinal) photocoagulation; Proliferative ...

Brick walls and AdS/CFT

NASA Astrophysics Data System (ADS)

Kay, Bernard S.; Ortíz, L.

2014-05-01

We discuss the relationship between the bulk-boundary correspondence in Rehren's algebraic holography (and in other `fixed-background', QFT-based, approaches to holography) and in mainstream string-theoretic `Maldacena AdS/CFT'. Especially, we contrast the understanding of black-hole entropy from the point of view of QFT in curved spacetime—in the framework of 't Hooft's `brick wall' model—with the understanding based on Maldacena AdS/CFT. We show that the brick-wall modification of a Klein-Gordon field in the Hartle-Hawking-Israel state on dimensional Schwarzschild AdS has a well-defined boundary limit with the same temperature and entropy as the brick-wall-modified bulk theory. One of our main purposes is to point out a close connection, for general AdS/CFT situations, between the puzzle raised by Arnsdorf and Smolin regarding the relationship between Rehren's algebraic holography and mainstream AdS/CFT and the puzzle embodied in the `complementarity principle' proposed by Mukohyama and Israel in their work on the brick-wall approach to black hole entropy. Working on the assumption that similar results will hold for bulk QFT other than the Klein-Gordon field and for Schwarzschild AdS in other dimensions, and recalling the first author's proposed resolution to the Mukohyama-Israel puzzle based on his `matter-gravity entanglement hypothesis', we argue that, in Maldacena AdS/CFT, the algebra of the boundary CFT is isomorphic only to a proper subalgebra of the bulk algebra, albeit (at non-zero temperature) the (GNS) Hilbert spaces of bulk and boundary theories are still the `same'—the total bulk state being pure, while the boundary state is mixed (thermal). We also argue from the finiteness of its boundary (and hence, on our assumptions, also bulk) entropy at finite temperature, that the Rehren dual of the Maldacena boundary CFT cannot itself be a QFT and must, instead, presumably be something like a string theory.

Laser-diode pumped 40-W Yb:YAG ceramic laser.

PubMed

Hao, Qiang; Li, Wenxue; Pan, Haifeng; Zhang, Xiaoyi; Jiang, Benxue; Pan, Yubai; Zeng, Heping

2009-09-28

We demonstrated a high-power continuous-wave (CW) polycrystalline Yb:YAG ceramic laser pumped by fiber-pigtailed laser diode at 968 nm with 400 mum fiber core. The Yb:YAG ceramic laser performance was compared for different Yb(3+) ion concentrations in the ceramics by using a conventional end-pump laser cavity consisting of two flat mirrors with output couplers of different transmissions. A CW laser output of 40 W average power with M(2) factor of 5.8 was obtained with 5 mol% Yb concentration under 120 W incident pump power. This is to the best of our knowledge the highest output power in end-pumped bulk Yb:YAG ceramic laser.

Infrared laser system

DOEpatents

Cantrell, Cyrus D.; Carbone, Robert J.; Cooper, Ralph S.

1977-01-01

An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture.

Infrared laser system

DOEpatents

Cantrell, Cyrus D.; Carbone, Robert J.; Cooper, Ralph

1982-01-01

An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture.

Ceramic Laser Materials

PubMed Central

Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

2012-01-01

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

Laser cutting: industrial relevance, process optimization, and laser safety

NASA Astrophysics Data System (ADS)

Haferkamp, Heinz; Goede, Martin; von Busse, Alexander; Thuerk, Oliver

1998-09-01

Compared to other technological relevant laser machining processes, up to now laser cutting is the application most frequently used. With respect to the large amount of possible fields of application and the variety of different materials that can be machined, this technology has reached a stable position within the world market of material processing. Reachable machining quality for laser beam cutting is influenced by various laser and process parameters. Process integrated quality techniques have to be applied to ensure high-quality products and a cost effective use of the laser manufacturing plant. Therefore, rugged and versatile online process monitoring techniques at an affordable price would be desirable. Methods for the characterization of single plant components (e.g. laser source and optical path) have to be substituted by an omnivalent control system, capable of process data acquisition and analysis as well as the automatic adaptation of machining and laser parameters to changes in process and ambient conditions. At the Laser Zentrum Hannover eV, locally highly resolved thermographic measurements of the temperature distribution within the processing zone using cost effective measuring devices are performed. Characteristic values for cutting quality and plunge control as well as for the optimization of the surface roughness at the cutting edges can be deducted from the spatial distribution of the temperature field and the measured temperature gradients. Main influencing parameters on the temperature characteristic within the cutting zone are the laser beam intensity and pulse duration in pulse operation mode. For continuous operation mode, the temperature distribution is mainly determined by the laser output power related to the cutting velocity. With higher cutting velocities temperatures at the cutting front increase, reaching their maximum at the optimum cutting velocity. Here absorption of the incident laser radiation is drastically increased due to

Lasers.

PubMed

Passeron, T

2012-12-01

Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

[Lasers].

PubMed

Passeron, T

2012-11-01

Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Ultrafast pulsed laser utilizing broad bandwidth laser glass

DOEpatents

Payne, Stephen A.; Hayden, Joseph S.

1997-01-01

An ultrafast laser uses a Nd-doped phosphate laser glass characterized by a particularly broad emission bandwidth to generate the shortest possible output pulses. The laser glass is composed primarily of P.sub.2 O.sub.5, Al.sub.2 O.sub.3 and MgO, and possesses physical and thermal properties that are compatible with standard melting and manufacturing methods. The broad bandwidth laser glass can be used in modelocked oscillators as well as in amplifier modules.

Effects of diode laser welding with dye-enhanced glue on tensile strength of sutures commonly used in urology.

PubMed

Kirsch, A J; Chang, D T; Kayton, M L; Libutti, S K; Connor, J P; Hensle, T W

1996-01-01

Tissue welding using laser-activated protein solders may soon become an alternative to sutured tissue approximation. In most cases, approximating sutures are used both to align tissue edges and provide added tensile strength. Collateral thermal injury, however, may cause disruption of tissue alignment and weaken the tensile strength of sutures. The objective of this study was to evaluate the effect of laser welding on the tensile strength of suture materials used in urologic surgery. Eleven types of sutures were exposed to diode laser energy (power density = 15.9 W/cm2) for 10, 30, and 60 seconds. Each suture was compared with and without the addition of dye-enhanced albumin-based solder. After exposure, each suture material was strained (2"/min) until ultimate breakage on a tensometer and compared to untreated sutures using ANOVA. The strength of undyed sutures were not significantly affected; however, violet and green-dyed sutures were in general weakened by laser exposure in the presence of dye-enhanced glue. Laser activation of the smallest caliber, dyed sutures (7-0) in the presence of glue caused the most significant loss of tensile strength of all sutures tested. These results indicate that the thermal effects of laser welding using our technique decrease the tensile strength of dyed sutures. A thermally resistant suture material (undyed or clear) may prevent disruption of wounds closed by laser welding techniques.

Laser Ablation of Biological Tissue Using Pulsed CO{sub 2} Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

2010-10-13

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. Wemore » simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO{sub 2} laser (wavelength: 10.6 {mu}m; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.« less

Type IIB supergravity solution for the T-dual of the η-deformed AdS 5 × S 5 superstring

NASA Astrophysics Data System (ADS)

Hoare, B.; Tseytlin, A. A.

2015-10-01

We find an exact type IIB supergravity solution that represents a one-parameter deformation of the T-dual of the AdS 5 × S 5 background (with T-duality applied in all 6 abelian bosonic isometric directions). The non-trivial fields are the metric, dilaton and RR 5-form only. The latter has remarkably simple "undeformed" form when written in terms of a "deformation-rotated" vielbein basis. An unusual feature of this solution is that the dilaton contains a linear dependence on the isometric coordinates of the metric precluding a straightforward reversal of T-duality. If we still formally dualize back, we find exactly the metric, B-field and product of dilaton with RR field strengths as recently extracted from the η-deformed AdS 5 × S 5 superstring action in arXiv:1507.04239. We also discuss similar solutions for deformed AdS n × S n backgrounds with n = 2 , 3. In the η → i limit we demonstrate that all these backgrounds can be interpreted as special limits of gauged WZW models and are also related to (a limit of) the Pohlmeyer-reduced models of the AdS n × S n superstrings.

Ytterbium-doped borate fluoride laser crystals and lasers

DOEpatents

Schaffers, K.I.; DeLoach, L.D.; Payne, S.A.; Keszler, D.A.

1997-10-14

A new class of solid state laser crystals and lasers are formed from Yb-doped borate fluoride host crystals. The general formula for the host crystals is MM{prime}(BO{sub 3})F, where M, M{prime} are monovalent, divalent aria trivalent metal cations. A particular embodiment of the invention is Yb-doped BaCaBO{sub 3}F (Yb:BCBF). BCBF and some of the related derivative crystals are capable of nonlinear frequency conversion, whereby the fundamental of the laser is converted to a longer or shorter wavelength. In this way, these new crystals can simultaneously serve as self-frequency doubling crystals and laser materials within the laser resonator. 6 figs.

Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes

NASA Astrophysics Data System (ADS)

Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.

2015-03-01

Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.

Investigations on laser transmission welding of absorber-free thermoplastics

NASA Astrophysics Data System (ADS)

Mamuschkin, Viktor; Olowinsky, Alexander; Britten, Simon W.; Engelmann, Christoph

2014-03-01

Within the plastic industry laser transmission welding ranks among the most important joining techniques and opens up new application areas continuously. So far, a big disadvantage of the process was the fact that the joining partners need different optical properties. Since thermoplastics are transparent for the radiation of conventional beam sources (800- 1100 nm) the absorbance of one of the joining partners has to be enhanced by adding an infrared absorber (IR-absorber). Until recently, welding of absorber-free parts has not been possible. New diode lasers provide a broad variety of wavelengths which allows exploiting intrinsic absorption bands of thermoplastics. The use of a proper wavelength in combination with special optics enables laser welding of two optically identical polymer parts without absorbers which can be utilized in a large number of applications primarily in the medical and food industry, where the use of absorbers usually entails costly and time-consuming authorization processes. In this paper some aspects of the process are considered as the influence of the focal position, which is crucial when both joining partners have equal optical properties. After a theoretical consideration, an evaluation is carried out based on welding trials with polycarbonate (PC). Further aspects such as gap bridging capability and the influence of thickness of the upper joining partner are investigated as well.

Multipurpose end-station for coherent diffraction imaging and scattering at FERMI@Elettra free-electron laser facility.

PubMed

Capotondi, Flavio; Pedersoli, Emanuele; Bencivenga, Filippo; Manfredda, Michele; Mahne, Nicola; Raimondi, Lorenzo; Svetina, Cristian; Zangrando, Marco; Demidovich, Alexander; Nikolov, Ivaylo; Danailov, Miltcho; Masciovecchio, Claudio; Kiskinova, Maya

2015-05-01

The Diffraction and Projection Imaging (DiProI) beamline at FERMI, the Elettra free-electron laser (FEL), hosts a multi-purpose station that has been opened to users since the end of 2012. This paper describes the core capabilities of the station, designed to make use of the unique features of the FERMI-FEL for performing a wide range of static and dynamic scattering experiments. The various schemes for time-resolved experiments, employing both soft X-ray FEL and seed laser IR radiation are presented by using selected recent results. The ongoing upgrade is adding a reflection geometry setup for scattering experiments, expanding the application fields by providing both high lateral and depth resolution.

LaserFest Celebration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dr. Alan Chodos; Elizabeth A. Rogan

LaserFest was the yearlong celebration, during 2010, of the 50th anniversary of the demonstration of the first working laser. The goals of LaserFest were: to highlight the impact of the laser in its manifold commercial, industrial and medical applications, and as a tool for ongoing scientific research; to use the laser as one example that illustrates, more generally, the route from scientific innovation to technological application; to use the laser as a vehicle for outreach, to stimulate interest among students and the public in aspects of physical science; to recognize and honor the pioneers who developed the laser and itsmore » many applications; to increase awareness among policymakers of the importance of R&D funding as evidenced by such technology as lasers. One way in which LaserFest sought to meet its goals was to encourage relevant activities at a local level all across the country -- and also abroad -- that would be identified with the larger purposes of the celebration and would carry the LaserFest name. Organizers were encouraged to record and advertise these events through a continually updated web-based calendar. Four projects were explicitly detailed in the proposals: 1) LaserFest on the Road; 2) Videos; 3) Educational material; and 4) Laser Days.« less

Dissociation of β-Sheet Stacking of Amyloid β Fibrils by Irradiation of Intense, Short-Pulsed Mid-infrared Laser.

PubMed

Kawasaki, Takayasu; Yaji, Toyonari; Ohta, Toshiaki; Tsukiyama, Koichi; Nakamura, Kazuhiro

2018-02-05

Structure of amyloid β (Aβ) fibrils is rigidly stacked by β-sheet conformation, and the fibril state of Aβ is profoundly related to pathogenesis of Alzheimer's disease (AD). Although mid-infrared light has been used for various biological researches, it has not yet been known whether the infrared light changes the fibril structure of Aβ. In this study, we tested the effect of irradiation of intense mid-infrared light from a free-electron laser (FEL) targeting the amide bond on the reduction of β-sheet content in Aβ fibrils. The FEL reduced entire contents of proteins exhibiting β-sheet structure in brain sections from AD model mice, as shown by synchrotron-radiation infrared microscopy analysis. Since Aβ 1-42 fibril absorbed a considerable FEL energy at amide I band (6.17 μm), we irradiated the FEL at 6.17 μm and found that β-sheet content of naked Aβ 1-42 fibril was decreased using infrared microscopic analysis. Consistent with the decrease in the β-sheet content, Congo-red signal is decreased after the irradiation to Aβ 1-42 fibril. Furthermore, electron microscopy analysis revealed that morphologies of the fibril and proto-fibril were largely changed after the irradiation. Thus, mid-infrared light dissociates β-sheet structure of Aβ fibrils, which justifies exploration of possible laser-based therapy for AD.

The Effect of Comparatively-Framed versus Similarity-Framed E-Cigarette and Snus Print Ads on Young Adults' Ad and Product Perceptions.

PubMed

Banerjee, Smita C; Greene, Kathryn; Li, Yuelin; Ostroff, Jamie S

2016-07-01

This study examined the effects of comparative-framing [C-F; ads highlighting differences between the advertised product and conventional cigarettes and/or smokeless tobacco products] versus similarity-framing (S-F; ads highlighting congruence with conventional cigarettes and/or smokeless tobacco products) in e-cigarette and snus ads on young adult smokers' and non-smokers' ad- and product-related perceptions. One thousand fifty one (1,051) young adults (18-24 years; 76% women; 50% smokers) from existing consumer panels were recruited in a within-subjects quasi-experiment. Each participant viewed 4 online advertisements, varied by tobacco product type (e-cigarette or snus) and ad framing (C-F or S-F). The dependent measures for this study were ad-related (ad perceptions, ad credibility) and product-related perceptions (absolute and comparative risk perceptions, product appeal, and product use intentions). Former and current smokers rated C-F ads as more persuasive than S-F ads, as evidenced by favorable ad perceptions and high product use intentions. Former and current smokers also rated e-cigarette ads with more favorable ad perceptions, low absolute and comparative risk perceptions, high product appeal, and high product use intentions as compared to snus ads. However, the effect sizes of the significant differences are less than.2, indicating small magnitude of difference between the study variables. Unless FDA regulates e-cig and snus advertising, there is a potential of decreasing risk perceptions and increasing use of e-cigs among young adults. Further research on implicit/explicit comparative claims in e-cigarettes and snus advertisements that encourage risk misperceptions is recommended.

Hardware Verification of Laser Noise Cancellation and Gravitational Wave Extraction using Time-Delay Interferometry

NASA Astrophysics Data System (ADS)

Mitryk, Shawn; Mueller, Guido

The Laser Interferometer Space Antenna (LISA) is a space-based modified Michelson interfer-ometer designed to measure gravitational radiation in the frequency range from 30 uHz to 1 Hz. The interferometer measurement system (IMS) utilizes one-way laser phase measurements to cancel the laser phase noise, reconstruct the proof-mass motion, and extract the gravitational wave (GW) induced laser phase modulations in post-processing using a technique called time-delay interferometry (TDI). Unfortunately, there exist few hard-ware verification experiments of the IMS. The University of Florida LISA Interferometry Simulator (UFLIS) is designed to perform hardware-in-the-loop simulations of the LISA interferometry system, modeling the characteris-tics of the LISA mission as accurately as possible. This depends, first, on replicating the laser pre-stabilization by locking the laser phase to an ultra-stable Zerodur cavity length reference using the PDH locking method. Phase measurements of LISA-like photodetector beat-notes are taken using the UF-phasemeter (PM) which can measure the laser BN frequency to within an accuracy of 0.22 uHz. The inter-space craft (SC) laser links including the time-delay due to the 5 Gm light travel time along the LISA arms, the laser Doppler shifts due to differential SC motion, and the GW induced laser phase modulations are simulated electronically using the electronic phase delay (EPD) unit. The EPD unit replicates the laser field propagation between SC by measuring a photodetector beat-note frequency with the UF-phasemeter and storing the information in memory. After the requested delay time, the frequency information is added to a Doppler offset and a GW-like frequency modulation. The signal is then regenerated with the inter-SC laser phase affects applied. Utilizing these components, I will present the first complete TDI simulations performed using the UFLIS. The LISA model is presented along-side the simulation, comparing the generation and

Observation of laser beam profile progression inside an extended laser cavity

NASA Astrophysics Data System (ADS)

Wu, Frank F.; Farrell, Thomas C.

2013-03-01

This report presents the result of the laser beam profile progression in target-in-the-loop (TIL) system. This simulation experiment is to verify whether it is possible to form a tight hot spot similar to a single transversal mode in an extended laser cavity. Therefore, it is very important to observe the progression of the laser profile at a laser cavity mirror when a seeded high energy laser pulse is injected into the TIL system. The extended laser cavity is formed with a high reflectivity mirror on one end and an optical phase conjugated mirror as the second mirror, with potential disturbance media inside. The laser oscillation occurs only when it is triggered with a single frequency high energy laser pulse to overcome the threshold condition. With a laser cavity length of around 11 meters and a seeded laser pulse of 10 ns, we have been able to acquire and distinguish the laser beam profiles of each round-trip. Inserting a scattering media and other distortion elements can simulate atmospheric effects.

Development of high-power CO2 lasers and laser material processing

NASA Astrophysics Data System (ADS)

Nath, Ashish K.; Choudhary, Praveen; Kumar, Manoj; Kaul, R.

2000-02-01

Scaling laws to determine the physical dimensions of the active medium and optical resonator parameters for designing convective cooled CO2 lasers have been established. High power CW CO2 lasers upto 5 kW output power and a high repetition rate TEA CO2 laser of 500 Hz and 500 W average power incorporated with a novel scheme for uniform UV pre- ionization have been developed for material processing applications. Technical viability of laser processing of several engineering components, for example laser surface hardening of fine teeth of files, laser welding of martensitic steel shroud and titanium alloy under-strap of turbine, laser cladding of Ni super-alloy with stellite for refurbishing turbine blades were established using these lasers. Laser alloying of pre-placed SiC coating on different types of aluminum alloy, commercially pure titanium and Ti-6Al-4V alloy, and laser curing of thermosetting powder coating have been also studied. Development of these lasers and results of some of the processing studies are briefly presented here.

Measurement of solubility and water sorption of dental nanocomposites light cured by argon laser.

PubMed

Mirsasaani, Seyed Shahabeddin; Ghomi, Farhad; Hemati, Mehran; Tavasoli, Tina

2013-03-01

Different parameters used for photoactivation process and also composition provide changes in the properties of dental composites. In the present work the effect of different power density of argon laser and filler loading on solubility (SL) and water sorption (WS) of light-cure dental nanocomposites was studied. The resin of nanocomposites was prepared by mixing bisphenol A glycol dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) with a mass ratio of 65/35. 20 wt.% and 25 wt.% of nanosilica fillers with a primary particle size of 10 nm were added to the resin. Camphorquinone (CQ) and DMAEMA were added as photoinitiator system. The nanocomposites were cured by applying the laser beam at the wavelength of 472 nm and power densities of 260 and 340 mW/cm(2) for 40 sec. Solubility and water sorption were then measured according to ISO 4049, which in our case, the maximums were 2.2% and 4.3% at 260 mW/cm(2) and 20% filler, respectively. The minimum solubility (1.2%) and water sorption (3.8%) were achieved for the composite containing 25% filler cured at 340 mW/cm(2). The results confirmed that higher power density and filler loading decreased solubility of unreacted monomers and water sorption and improved physico-mechanical properties of nanocomposites.

Ultrafast pulsed laser utilizing broad bandwidth laser glass

DOEpatents

Payne, S.A.; Hayden, J.S.

1997-09-02

An ultrafast laser uses a Nd-doped phosphate laser glass characterized by a particularly broad emission bandwidth to generate the shortest possible output pulses. The laser glass is composed primarily of P{sub 2}O{sub 5}, Al{sub 2}O{sub 3} and MgO, and possesses physical and thermal properties that are compatible with standard melting and manufacturing methods. The broad bandwidth laser glass can be used in modelocked oscillators as well as in amplifier modules. 7 figs.

Characterization of atopic skin and the effect of a hyperforin-rich cream by laser scanning microscopy.

PubMed

Meinke, Martina C; Richter, Heike; Kleemann, Anke; Lademann, Juergen; Tscherch, Kathrin; Rohn, Sascha; Schempp, Christoph M

2015-05-01

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease that affects both children and adults in an increasing manner. The treatment of AD often reduces subjective skin parameters, such as itching, dryness, and tension, but the inflammation cannot be cured. Laser scanning microscopy was used to investigate the skin surface, epidermal, and dermal characteristics of dry and atopic skin before and after treatment with an ointment rich in hyperforin, which is known for its anti-inflammatory effects. The results were compared to subjective parameters and transepidermal water loss, stratum corneum moisture, and stratum corneum lipids. Using biophysical methods, in particular laser scanning microscopy, it was found that atopic skin has distinct features compared to healthy skin. Treatment with a hyperforin-rich ointment resulted in an improvement of the stratum corneum moisture, skin surface dryness, skin lipids, and the subjective skin parameters, indicating that the barrier is stabilized and improved by the ointment. But in contrast to the improved skin surface, the inflammation in the deeper epidermis/dermis often continues to exist. This could be clearly shown by the reflectance confocal microscopy (RCM) measurements. Therefore, RCM measurements could be used to investigate the progress in treatment of atopic dermatitis.

Characterization of atopic skin and the effect of a hyperforin-rich cream by laser scanning microscopy

NASA Astrophysics Data System (ADS)

Meinke, Martina C.; Richter, Heike; Kleemann, Anke; Lademann, Juergen; Tscherch, Kathrin; Rohn, Sascha; Schempp, Christoph M.

2015-05-01

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease that affects both children and adults in an increasing manner. The treatment of AD often reduces subjective skin parameters, such as itching, dryness, and tension, but the inflammation cannot be cured. Laser scanning microscopy was used to investigate the skin surface, epidermal, and dermal characteristics of dry and atopic skin before and after treatment with an ointment rich in hyperforin, which is known for its anti-inflammatory effects. The results were compared to subjective parameters and transepidermal water loss, stratum corneum moisture, and stratum corneum lipids. Using biophysical methods, in particular laser scanning microscopy, it was found that atopic skin has distinct features compared to healthy skin. Treatment with a hyperforin-rich ointment resulted in an improvement of the stratum corneum moisture, skin surface dryness, skin lipids, and the subjective skin parameters, indicating that the barrier is stabilized and improved by the ointment. But in contrast to the improved skin surface, the inflammation in the deeper epidermis/dermis often continues to exist. This could be clearly shown by the reflectance confocal microscopy (RCM) measurements. Therefore, RCM measurements could be used to investigate the progress in treatment of atopic dermatitis.

Alteration of mTOR signaling occurs early in the progression of Alzheimer disease (AD): analysis of brain from subjects with pre-clinical AD, amnestic mild cognitive impairment and late-stage AD.

PubMed

Tramutola, Antonella; Triplett, Judy C; Di Domenico, Fabio; Niedowicz, Dana M; Murphy, Michael P; Coccia, Raffaella; Perluigi, Marzia; Butterfield, D Allan

2015-06-01

The clinical symptoms of Alzheimer disease (AD) include a gradual memory loss and subsequent dementia, and neuropathological deposition of senile plaques and neurofibrillary tangles. At the molecular level, AD subjects present overt amyloid β (Aβ) production and tau hyperphosphorylation. Aβ species have been proposed to overactivate the phosphoinositide3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) axis, which plays a central role in proteostasis. The current study investigated the status of the PI3K/Akt/mTOR pathway in post-mortem tissue from the inferior parietal lobule (IPL) at three different stages of AD: late AD, amnestic mild cognitive impairment (MCI) and pre-clinical AD (PCAD). Our findings suggest that the alteration of mTOR signaling and autophagy occurs at early stages of AD. We found a significant increase in Aβ (1-42) levels, associated with reduction in autophagy (Beclin-1 and LC-3) observed in PCAD, MCI, and AD subjects. Related to the autophagy impairment, we found a hyperactivation of PI3K/Akt/mTOR pathway in IPL of MCI and AD subjects, but not in PCAD, along with a significant decrease in phosphatase and tensin homolog. An increase in two mTOR downstream targets, p70S6K and 4EBP1, occurred in AD and MCI subjects. Both AD and MCI subjects showed increased, insulin receptor substrate 1, a candidate biomarker of brain insulin resistance, and GSK-3β, a kinase targeting tau phosphorylation. Nevertheless, tau phosphorylation was increased in the clinical groups. The results hint at a link between Aβ and the PI3K/Akt/mTOR axis and provide further insights into the relationship between AD pathology and insulin resistance. In addition, we speculate that the alteration of mTOR signaling in the IPL of AD and MCI subjects, but not in PCAD, is due to the lack of substantial increase in oxidative stress. The figure represents the three different stages of Alzheimer Disease: Preclinical Alzheimer Disease (PCAD), Mild cognitive impairment (MCI

Transition from AdS universe to DS universe in the BPP model

NASA Astrophysics Data System (ADS)

Kim, Wontae; Yoon, Myungseok

2007-04-01

It can be shown that in the BPP model the smooth phase transition from the asymptotically decelerated AdS universe to the asymptotically accelerated DS universe is possible by solving the modified semiclassical equations of motion. This transition comes from noncommutative Poisson algebra, which gives the constant curvature scalars asymptotically. The decelerated expansion of the early universe is due to the negative energy density with the negative pressure induced by quantum back reaction, and the accelerated late-time universe comes from the positive energy and the negative pressure which behave like dark energy source in recent cosmological models.

Asymptotical AdS space from nonlinear gravitational models with stabilized extra dimensions

NASA Astrophysics Data System (ADS)

Günther, U.; Moniz, P.; Zhuk, A.

2002-08-01

We consider nonlinear gravitational models with a multidimensional warped product geometry. Particular attention is payed to models with quadratic scalar curvature terms. It is shown that for certain parameter ranges, the extra dimensions are stabilized if the internal spaces have a negative constant curvature. In this case, the four-dimensional effective cosmological constant as well as the bulk cosmological constant become negative. As a consequence, the homogeneous and isotropic external space is asymptotically AdS4. The connection between the D-dimensional and the four-dimensional fundamental mass scales sets a restriction on the parameters of the considered nonlinear models.

Pediatric endocanalicular diode laser dacryocystorhinostomy: results of a minimally invasive surgical technique.

PubMed

Uysal, Ismail Onder; Ozçimen, Muammer; Yener, Halil Ibrahim; Kal, Ali

2011-09-01

The purpose of this study was to evaluate the effectiveness of endocanalicular diode laser dacryocystorhinostomy (DCR), which is a minimally invasive surgical technique, in pediatric patients with congenital nasolacrimal duct obstruction (NLDO). A retrospective study was carried out on patients treated between October 2008 and August 2009 for nasolacrimal duct obstruction with an endocanalicular diode laser procedure. Patients diagnosed as having nasolacrimal duct obstruction were included in this study and an endocanalicular diode laser procedure was performed. The main outcome measures were patients' previous treatments, clinical presentation, operative and postoperative complications, postoperative follow-up and resolution of epiphora. Eighteen children (10 girls, 8 boys) with a mean age of 6.11 ± 2.08 years (range, 4-10) underwent 20 endocanalicular laser DCR operations for congenital NLDO. In all eyes (100%), there was a history of epiphora and chronic dacryocystitis; two (10%) presented with acute dacryocystitis. Previous procedures included probing and irrigation of all eyes (100%) and silicone tube intubation in nine eyes (45%). None of the patients underwent any previous DCR operations. During a mean postoperative follow-up period of 20.50 ± 3.24 months (range, 14-24 months), the anatomical success rate (patency of ostium on nasal endoscopy) was 100%, and the clinical success rate (resolution of epiphora) was 85%. Endocanalicular diode laser DCR is an effective treatment modality for pediatric patients with congenital NLDO that compares favorably with the reported success rates of external and endoscopic endonasal DCR. Moreover, it has an added advantage of shorter operative time, less morbidity and avoidance of overnight admission.

The Effect of Comparatively-Framed versus Similarity-Framed E-Cigarette and Snus Print Ads on Young Adults’ Ad and Product Perceptions

PubMed Central

Banerjee, Smita C.; Greene, Kathryn; Li, Yuelin; Ostroff, Jamie S.

2016-01-01

Objectives This study examined the effects of comparative-framing [C-F; ads highlighting differences between the advertised product and conventional cigarettes and/or smokeless tobacco products] versus similarity-framing (S-F; ads highlighting congruence with conventional cigarettes and/or smokeless tobacco products) in e-cigarette and snus ads on young adult smokers’ and non-smokers’ ad- and product-related perceptions. Methods One thousand fifty one (1,051) young adults (18–24 years; 76% women; 50% smokers) from existing consumer panels were recruited in a within-subjects quasi-experiment. Each participant viewed 4 online advertisements, varied by tobacco product type (e-cigarette or snus) and ad framing (C-F or S-F). The dependent measures for this study were ad-related (ad perceptions, ad credibility) and product-related perceptions (absolute and comparative risk perceptions, product appeal, and product use intentions). Results Former and current smokers rated C-F ads as more persuasive than S-F ads, as evidenced by favorable ad perceptions and high product use intentions. Former and current smokers also rated e-cigarette ads with more favorable ad perceptions, low absolute and comparative risk perceptions, high product appeal, and high product use intentions as compared to snus ads. However, the effect sizes of the significant differences are less than.2, indicating small magnitude of difference between the study variables. Conclusions Unless FDA regulates e-cig and snus advertising, there is a potential of decreasing risk perceptions and increasing use of e-cigs among young adults. Further research on implicit/explicit comparative claims in e-cigarettes and snus advertisements that encourage risk misperceptions is recommended. PMID:28042597

Development of Laser Propulsion and Tracking System for Laser-Driven Micro-Airplane

NASA Astrophysics Data System (ADS)

Ishikawa, Hiroyasu; Kajiwara, Itsuro; Hoshino, Kentaro; Yabe, Takashi; Uchida, Shigeaki; Shimane, Yoshichika

2004-03-01

The purposes of this paper are to improve the control performance of the developed laser tracking system and to develop an integrated laser propulsion/tracking system for realizing a continuous flight and control of the micro-airplane. The laser propulsion is significantly effective to achieve the miniaturization and lightening of the micro-airplane. The laser-driven micro-airplane has been studied with a paper-craft airplane and YAG laser, resulting in a successful glide of the airplane. In the next stage of the laser-driven micro-airplane development, the laser tracking is expected as key technologies to achieve continuous propulsion. Furthermore, the laser propulsion system should be combined with the laser tracking system to supply continuous propulsion. Experiments are carried out to evaluate the performance of the developed laser tracking system and integrated laser propulsion/tracking system.

Tunable fiber Bragg grating ring lasers using macro fiber composite actuators

NASA Astrophysics Data System (ADS)

Geddis, Demetris L.; Allison, Sidney G.; Shams, Qamar A.

2006-10-01

The research reported herein includes the fabrication of a tunable optical fiber Bragg grating (FBG) fiber ring laser (FRL)1 from commercially available components as a high-speed alternative tunable laser source for NASA Langley's optical frequency domain reflectometer (OFDR) interrogator, which reads low reflectivity FBG sensors. A Macro-Fiber Composite (MFC) actuator invented at NASA Langley Research Center (LaRC) was selected to tune the laser. MFC actuators use a piezoelectric sheet cut into uniaxially aligned rectangular piezo-fibers surrounded by a polymer matrix and incorporate interdigitated electrodes to deliver electric fields along the length of the piezo-fibers. This configuration enables MFC actuators to produce displacements larger than the original uncut piezoelectric sheet. The FBG filter was sandwiched between two MFC actuators, and when strained, produced approximately 3.62 nm of wavelength shift in the FRL when biasing the MFC actuators from -500 V to 2000 V. This tunability range is comparable to that of other tunable lasers and is adequate for interrogating FBG sensors using OFDR technology. Three different FRL configurations were studied. Configuration A examined the importance of erbium-doped fiber length and output coupling. Configuration B demonstrated the importance of the FBG filter. Configuration C added an output coupler to increase the output power and to isolate the filter. Only configuration C was tuned because it offered the best optical power output of the three configurations. Use of Plastic Optical Fiber (POF) FBG's holds promise for enhanced tunability in future research.

Laser application in neurosurgery

PubMed Central

Belykh, Evgenii; Yagmurlu, Kaan; Martirosyan, Nikolay L.; Lei, Ting; Izadyyazdanabadi, Mohammadhassan; Malik, Kashif M.; Byvaltsev, Vadim A.; Nakaji, Peter; Preul, Mark C.

2017-01-01

Background: Technological innovations based on light amplification created by stimulated emission of radiation (LASER) have been used extensively in the field of neurosurgery. Methods: We reviewed the medical literature to identify current laser-based technological applications for surgical, diagnostic, and therapeutic uses in neurosurgery. Results: Surgical applications of laser technology reported in the literature include percutaneous laser ablation of brain tissue, the use of surgical lasers in open and endoscopic cranial surgeries, laser-assisted microanastomosis, and photodynamic therapy for brain tumors. Laser systems are also used for intervertebral disk degeneration treatment, therapeutic applications of laser energy for transcranial laser therapy and nerve regeneration, and novel diagnostic laser-based technologies (e.g., laser scanning endomicroscopy and Raman spectroscopy) that are used for interrogation of pathological tissue. Conclusion: Despite controversy over the use of lasers for treatment, the surgical application of lasers for minimally invasive procedures shows promising results and merits further investigation. Laser-based microscopy imaging devices have been developed and miniaturized to be used intraoperatively for rapid pathological diagnosis. The multitude of ways that lasers are used in neurosurgery and in related neuroclinical situations is a testament to the technological advancements and practicality of laser science. PMID:29204309

Analysis of incidence of bulla formation after tattoo treatment using the combination of the picosecond Alexandrite laser and fractionated CO2 ablation.

PubMed

Au, Sonoa; Liolios, Ana M; Goldman, Mitchel P

2015-02-01

The picosecond Alexandrite laser has shown increased efficacy in tattoo removal in comparison to Q-switched lasers. However, bulla formation is a well-known and expected side effect of this novel treatment and causes patient discomfort. To analyze the incidence of bulla formation after tattoo treatment using the combination of the picosecond Alexandrite laser and fractionated CO2 ablation. This is a retrospective chart review to determine the incidence of bulla formation after laser tattoo removal in 95 patients who were treated with either with the picosecond Alexandrite laser alone or in combination with fractional CO2 ablation. Twenty-six patients (32%) treated with the picosecond laser alone experienced blistering, whereas none of the patients treated with the combination of the picosecond laser and fractionated CO2 ablation experienced blistering. The difference in incidence of bulla formation between the 2 groups was found to be statistically significant (p < .05). This study shows a significant decrease in bulla formation associated with tattoo treatment when fractionated CO2 ablation is added to the picosecond Alexandrite laser, which is consistent with observations from a previous case series. This is important because decreasing extensive blistering likely results in increased patient satisfaction and willingness to return for future treatments.

Fiber Optic Laser Accelerometer

DTIC Science & Technology

2007-11-06

embodiment of a fiber laser accelerometer 10. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type...cavity fiber laser or a distributed feedback fiber laser. In a 4 Attorney Docket No. 97966 Fabry - Perot type fiber laser, the laser cavity is a length...type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting the signal from the fiber laser by

High Energy Scattering in the AdS/CFT Correspondence

NASA Astrophysics Data System (ADS)

Penedones, Joao

2007-12-01

This work explores the celebrated AdS/CFT correspondence in the regime of high energy scattering in Anti--de Sitter (AdS) spacetime. In particular, we develop the eikonal approximation to high energy scattering in AdS and explore its consequences for the dual Conformal Field Theory (CFT). Using position space Feynman rules, we rederive the eikonal approximation for high energy scattering in flat space. Following this intuitive position space perspective, we then generalize the eikonal approximation for high energy scattering in AdS and other spacetimes. Remarkably, we are able to resum, in terms of a generalized phase shift, ladder and cross ladder Witten diagrams associated to the exchange of an AdS spin j field, to all orders in the coupling constant. By the AdS/CFT correspondence, the eikonal amplitude in AdS is related to the four point function of CFT primary operators in the regime of large 't Hooft coupling, including all terms of the 1/N expansion. We then show that the eikonal amplitude determines the behavior of the CFT four point function for small values of the cross ratios in a Lorentzian regime and that this controls its high spin and dimension conformal partial wave decomposition. These results allow us to determine the anomalous dimension of high spin and dimension double trace primary operators, by relating it to the AdS eikonal phase shift. Finally we find that, at large energies and large impact parameters in AdS, the gravitational interaction dominates all other interactions, as in flat space. Therefore, the anomalous dimension of double trace operators, associated to graviton exchange in AdS, yields a universal prediction for CFT's with AdS gravitational duals.

Intraoral laser welding: ultrastructural and mechanical analysis to compare laboratory laser and dental laser.

PubMed

Fornaini, Carlo; Passaretti, Francesca; Villa, Elena; Rocca, Jean-Paul; Merigo, Elisabetta; Vescovi, Paolo; Meleti, Marco; Manfredi, Maddalena; Nammour, Samir

2011-07-01

The Nd:YAG laser has been used since 1970 in dental laboratories to weld metals on dental prostheses. Recently in several clinical cases, we have suggested that the Nd:YAG laser device commonly utilized in the dental office could be used to repair broken fixed, removable and orthodontic prostheses and to weld metals directly in the mouth. The aim of this work was to evaluate, using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and dynamic mechanical analysis (DMA), the quality of the weld and its mechanical strength, comparing a device normally used in dental laboratory and a device normally used in the dental office for oral surgery, the same as that described for intraoral welding. Metal plates of a Co-Cr-Mo dental alloy and steel orthodontic wires were subjected to four welding procedures: welding without filler metal using the laboratory laser, welding with filler metal using the laboratory laser, welding without filler metal using the office laser, and welding with filler metal using the office laser. The welded materials were then analysed by SEM, EDS and DMA. SEM analysis did not show significant differences between the samples although the plates welded using the office laser without filler metal showed a greater number of fissures than the other samples. EDS microanalysis of the welding zone showed a homogeneous composition of the metals. Mechanical tests showed similar elastic behaviours of the samples, with minimal differences between the samples welded with the two devices. No wire broke even under the maximum force applied by the analyser. This study seems to demonstrate that the welds produced using the office Nd:YAG laser device and the laboratory Nd:YAG laser device, as analysed by SEM, EDS and DMA, showed minimal and nonsignificant differences, although these findings need to be confirmed using a greater number of samples.

Micro-laser

DOEpatents

Hutchinson, Donald P.; Richards, Roger K.

2003-07-22

A micro-laser is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide and at least one amplifying medium in the waveguide. PBG features are positioned between the first and second subwavelength resonant gratings and allow introduction of amplifying mediums into the highly resonant guided micro-laser microcavity. The micro-laser may be positioned on a die of a bulk substrate material with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a micro-laser is disclosed. A method for tuning the micro-laser is also disclosed. The micro-laser may be used as an optical regenerator, or a light source for data transfer or for optical computing.

Laser scanning confocal microscopy and laser tweezers based experiments to understand dentine-bacteria interactions

NASA Astrophysics Data System (ADS)

Peng, Sum Chee; Mohanty, Samarendra; Gupta, P. K.; Kishen, Anil

2007-02-01

Failure of endodontic treatment is commonly due to Enterococcal infection. In this study influence of chemical treatments of type-I collagen membrane by chemical agents commonly used in endodontic treatment on Enterococcus faecalis cell adherence was evaluated. In order to determine the change in number of adhering bacteria after chemical treatment, confocal laser scanning microscopy was used. For this, overnight culture of E faecalis in All Culture broth was applied to chemically treated type-I collagen membrane. It was found that Ca(OH) II treated groups had statistically significant (p value=0.05) increase in population of bacteria adherence. The change in adhesion force between bacteria and collagen was determined by using optical tweezers (1064 nm). For this experiment, Type-I collagen membrane was soaked for 5 mins in a media that contained 50% all culture media and 50% saturated Ca(OH) II . The membrane was spread on the coverslip, on which diluted bacterial suspension was added. The force of laser tweezers on the bacteria was estimated at different trap power levels using viscous drag method and trapping stiffness was calculated using Equipartition theorem method. Presence of Ca(OH) II was found to increase the cell-substrate adherence force from 0.38pN to >2.1pN. Together, these experiments show that it was highly probable that the increase in adherence to collagen was due to a stronger adhesion in the presence of Ca (OH) II.

Enabling vendor independent photoacoustic imaging systems with asynchronous laser source

NASA Astrophysics Data System (ADS)

Wu, Yixuan; Zhang, Haichong K.; Boctor, Emad M.

2018-02-01

Channel data acquisition, and synchronization between laser excitation and PA signal acquisition, are two fundamental hardware requirements for photoacoustic (PA) imaging. Unfortunately, however, neither is equipped by most clinical ultrasound scanners. Therefore, less economical specialized research platforms are used in general, which hinders a smooth clinical transition of PA imaging. In previous studies, we have proposed an algorithm to achieve PA imaging using ultrasound post-beamformed (USPB) RF data instead of channel data. This work focuses on enabling clinical ultrasound scanners to implement PA imaging, without requiring synchronization between the laser excitation and PA signal acquisition. Laser synchronization is inherently consisted of two aspects: frequency and phase information. We synchronize without communicating the laser and the ultrasound scanner by investigating USPB images of a point-target phantom in two steps. First, frequency information is estimated by solving a nonlinear optimization problem, under the assumption that the segmented wave-front can only be beamformed into a single spot when synchronization is achieved. Second, after making frequencies of two systems identical, phase delay is estimated by optimizing the image quality while varying phase value. The proposed method is validated through simulation, by manually adding both frequency and phase errors, then applying the proposed algorithm to correct errors and reconstruct PA images. Compared with the ground truth, simulation results indicate that the remaining errors in frequency correction and phase correction are 0.28% and 2.34%, respectively, which affirm the potential of overcoming hardware barriers on PA imaging through software solution.

Navigated Pattern Laser System versus Single-Spot Laser System for Postoperative 360-Degree Laser Retinopexy.

PubMed

Kulikov, Alexei N; Maltsev, Dmitrii S; Boiko, Ernest V

2016-01-01

Purpose . To compare three 360°-laser retinopexy (LRP) approaches (using navigated pattern laser system, single-spot slit-lamp (SL) laser delivery, and single-spot indirect ophthalmoscope (IO) laser delivery) in regard to procedure duration, procedural pain score, technical difficulties, and the ability to achieve surgical goals. Material and Methods . Eighty-six rhegmatogenous retinal detachment patients (86 eyes) were included in this prospective randomized study. The mean procedural time, procedural pain score (using 4-point Verbal Rating Scale), number of laser burns, and achievement of the surgical goals were compared between three groups (pattern LRP (Navilas® laser system), 36 patients; SL-LRP, 28 patients; and IO-LRP, 22 patients). Results . In the pattern LRP group, the amount of time needed for LRP and pain level were statistically significantly lower, whereas the number of applied laser burns was higher compared to those in the SL-LRP group and in the IO-LRP group. In the pattern LRP, SL-LRP, and IO-LRP groups, surgical goals were fully achieved in 28 (77.8%), 17 (60.7%), and 13 patients (59.1%), respectively ( p > 0.05). Conclusion . The navigated pattern approach allows improving the treatment time and pain in postoperative 360° LRP. Moreover, 360° pattern LRP is at least as effective in achieving the surgical goal as the conventional (slit-lamp or indirect ophthalmoscope) approaches with a single-spot laser.

Lasers in otorhinolaryngology

NASA Astrophysics Data System (ADS)

Pais Clemente, Manuel P.

1992-03-01

Lasers are now commonly accepted and widely used surgical instruments in otorhinolaryngology. There have been a great number of technological advances with lasers that have contributed to the expansion of this new surgical modality with an increased number of medical applications. Surgical strategies have also changed and are more favorable toward conservative surgery in which less tissues is removed than with more radical resections. This combination of improving technology and medical attitudes has changed the field of otorhinolaryngology, and resulted in an expanding use of laser surgery. Since 1973 we have been using the carbon dioxide laser in the treatment of diseases of the upper aero digestive systems, learning this new surgical technique from the pioneer work of Strong, Jako, and Vaughan. It is our conviction that a laser surgeon must have a thorough knowledge of laser biophysics, instrumentation, safety protocols, and surgical indications, and have the technical skills to perform laser surgery. Laser technology continues to improve at an increased speed, and it is imperative to update knowledge of current and potential applications of lasers in our specialty. It is the purpose of this article to present our clinical experience of 18 years with the use of lasers in surgery of ORL, emphasizing the carbon dioxide laser.

Compact Hybrid Laser Rod and Laser System

NASA Technical Reports Server (NTRS)

Pierrottet, Diego F. (Inventor); Busch, George E. (Inventor); Amzajerdian, Farzin (Inventor)

2017-01-01

A hybrid fiber rod includes a fiber core and inner and outer cladding layers. The core is doped with an active element. The inner cladding layer surrounds the core, and has a refractive index substantially equal to that of the core. The outer cladding layer surrounds the inner cladding layer, and has a refractive index less than that of the core and inner cladding layer. The core length is about 30 to 2000 times the core diameter. A hybrid fiber rod laser system includes an oscillator laser, modulating device, the rod, and pump laser diode(s) energizing the rod from opposite ends. The rod acts as a waveguide for pump radiation but allows for free-space propagation of laser radiation. The rod may be used in a laser resonator. The core length is less than about twice the Rayleigh range. Degradation from single-mode to multi-mode beam propagation is thus avoided.

Diode-pumped Cr-doped ZnMnSe and ZnMgSe lasers

NASA Astrophysics Data System (ADS)

Říha, A.; Němec, M.; Jelínková, H.; Čech, M.; Vyhlídal, D.; Doroshenko, M. E.; Komar, V. K.; Gerasimenko, A. S.

2017-12-01

Chromium ions Cr2+ are known to have good fluorescence properties in the mid-infrared spectral region around the wavelength of 2.5 μm. The aim of this study was the investigation of new laser crystal materials - Zn0.95Mn0.05Se, Zn0.70Mn 0.30Se, and Zn0.75Mg0.25Se doped by Cr2+ ions and comparison of their spectral and laser characteristics. The spectroscopic parameters as absorption and fluorescence spectra as well as lifetimes were measured. As optical pumping the laser diode generating radiation at the wavelength of 1.69 μm (pulse repetition rate 10 Hz, pulse width 2 ms) was used. The longitudinal-pumped resonator was hemispherical with an output coupler radius of curvature 150 mm. The laser emission spectra were investigated and the highest intensity of emitted radiation was achieved at wavelengths 2451 nm, 2469 nm, and 2470 nm from the Cr:Zn0.95Mn0.05Se, Cr:Zn0.70Mn0.30Se, and Cr:Zn0.75Mg0.25Se laser systems, respectively. The input-output characteristics of laser systems were measured; the maximum output peak power 177 mW was obtained for Cr:Zn0.95Mn0.05Se laser system with slope efficiency of 6.3 % with respect to absorbed peak power. The output peak power as well as output beam spatial structure were stable during measurements. For the selection of the lasing wavelength, the single 1.5 mm thick quartz plate was placed at the Brewster angle inside the optical resonator between the output coupler and laser active medium. This element provided the tuning in the wavelength range 2290-2578 nm, 2353-2543 nm, and 2420-2551 nm for Cr:Zn0.95Mn0.05Se, Cr:Zn0.70Mn0.30Se, and Cr:Zn0.75Mg0.25Se, respectively. The obtained spectral FWHM linewidth of the individual output radiation was 10 nm. A comparison with previously measured Cr:ZnSe laser system was added in the end

High-Power DFB Diode Laser-Based CO-QEPAS Sensor: Optimization and Performance.

PubMed

Ma, Yufei; Tong, Yao; He, Ying; Yu, Xin; Tittel, Frank K

2018-01-04

A highly sensitive carbon monoxide (CO) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was demonstrated. A high-power distributed feedback (DFB), continuous wave (CW) 2.33 μm diode laser with an 8.8 mW output power was used as the QEPAS excitation source. By optimizing the modulation depth and adding an optimum micro-resonator, compared to a bare quartz tuning fork (QTF), a 10-fold enhancement of the CO-QEPAS signal amplitude was achieved. When water vapor acting as a vibrational transfer catalyst was added to the target gas, the signal was further increased by a factor of ~7. A minimum detection limit (MDL) of 11.2 ppm and a calculated normalized noise equivalent absorption (NNEA) coefficient of 1.8 × 10 -5 cm -1 W/√Hz were obtained for the reported CO-QEPAS sensor.

Feedback Form for the ADS Abstract Service

Science.gov Websites

ADS Feedback Form for the ADS Abstract Service Please use this form to report bugs or send comments to the ADS Abstract Project. Thank you for your feedback. ❉ Required field Your Name: ❉ Your E

Active and separate secretion of fiber and penton base during the early phase of Ad2 or Ad5 infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yuhua; Zhang, Bo; Hou, Weihong

Fiber and penton base overproduced in adenovirus (Ad) infected cells can be secreted prior to progeny release and thereby regulate progeny spread. We aimed to investigate the mechanisms of fiber and penton base secretion in Ad2- or Ad5-infected A549 cells. Our flow cytometry analyses detected abundant surface fiber molecules, but little penton base molecules at 12 h post infection. Immunogold staining combined with transmission electron microscopic analyses revealed separate, non-co-localized release of fiber and penton base in the proximity of the plasma membrane. Depolymerization of microtubule and actin cytoskeletons, and inhibition of Rock kinase and myosin II activity together demonstratedmore » cytoskeletal network-dependent fiber secretion. Inhibition of intracellular calcium [Ca{sup 2+}]{sub i} signaling caused diminished fiber secretion, which was associated with diminished progeny production. Thus, fiber and penton base are actively and separately secreted during the early stages of Ad2 or Ad5 infection, their secretion may play important role in Ad life cycle. - Highlights: •Excessive production of structural proteins is common to viral infection, which may regulate the host-virus equilibrium and the spreading of viruses. •The adenovirus (Ad) structural proteins, fiber and penton base, are respectively important for Ad binding to its receptor and subsequent internalization in host cells. In Ad infected cells, these two structural proteins are excessively produced. •The mechanisms underlying the release of fiber and penton base molecules at the early phase of Ad infection is yet poorly understood. •Our studies show that in Ad5 or Ad2 infected A549 cells, fiber and penton base molecules are actively and separately secreted. •Fiber secretion is dependent on cytoskeleton-mediated protein traffic. •Inhibition of myosin II motor and Ca{sup 2+} signaling activity significantly diminishes fiber secretion. •These findings could contribute to our

Controlling the excitation process of free electrons by a femtosecond elliptically polarized laser

NASA Astrophysics Data System (ADS)

Gao, Lili; Wang, Feng; Jiang, Lan; Qu, Liangti; Lu, Yongfeng

2015-11-01

This paper is focused on the excitation rates of free electrons of an aluminum (Al) bulk irradiated by an elliptically polarized laser in simulation, using time-dependent density functional theory (TDDFT). The polarized 400 nm, 10 fs laser pulse consisted of two elementary sinusoidal beams, and is adjusted by changing the phase difference φ and the intersection angle θ of the polarization directions between the two beams. The simulation includes cases of φ = π/2 with θ = 30°, θ = 45°, θ = 60°, θ = 90°, θ = 120°, θ = 135°, θ = 150°, and cases of θ = 90° with φ = π/4, φ = π/3, φ = π/2, φ = 2π/3, φ = 3π/4. The absorbed energy, the excitation rates and the density distributions of free electrons after laser termination are investigated. At the given power intensity (1×1014Wcm-2), pulse width (10 fs) and wavelength (400 nm) of each elementary laser beam, computational results indicate that the excitation rate of free electrons is impacted by three major factors: the long axis direction of the laser projected profile, the amplitude difference of the first main oscillation (1st AD), and the total amplitude difference of main oscillations (TAD) of the external electric field. Among the aforementioned three factors for the excitation rate of free electrons, the direction of long axis plays the most significant role. The screen effect is crucial to compare the importance of the remaining two factors. The analysis approach to investigate the electron dynamics under an elliptically polarized laser is both pioneering and effective.

Research on the laser angle deception jamming technology of laser countermeasure

NASA Astrophysics Data System (ADS)

Ma, Shi-wei; Chen, Wen-jian; Gao, Wei; Duan, Yuan-yuan

2015-10-01

In recent years , laser guided weapons behave very well at destroying the military goals in the local wars, the single-shot probability, effective range and hitting precision getting better. And the semi-active laser guided weapons are the most widely used laser guided weapons. In order to improve the viability and protect important military goals, it's necessary to study the technology to against the semi-active guided weapons. This paper studies the working principle, the advantages and disadvantages of the semi-active guided weapons at first, and analyze the possibility of laser angle deception jamming system working. Then it analyzes the working principle and process of laser angle deception jamming technology. Finally it designs a half-real simulation system of laser angle deception jamming, which consists of semi-active laser guided weapons simulation system and laser angle deception jamming system. The simulation system demonstrates the working process of the laser angle deception jamming system. This paper provides fundamental base for the research on the countermeasure technology of semi-active laser guided weapons.

Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes.

PubMed

Clare, Richard M; Le Louarn, Miska; Béchet, Clementine

2011-02-01

We propose ground-layer adaptive optics (GLAO) to improve the seeing on the 42 m European Extremely Large Telescope. Shack-Hartmann wavefront sensors (WFSs) with laser guide stars (LGSs) will experience significant spot elongation due to off-axis observation. This spot elongation influences the design of the laser launch location, laser power, WFS detector, and centroiding algorithm for LGS GLAO on an extremely large telescope. We show, using end-to-end numerical simulations, that with a noise-weighted matrix-vector-multiply reconstructor, the performance in terms of 50% ensquared energy (EE) of the side and central launch of the lasers is equivalent, the matched filter and weighted center of gravity centroiding algorithms are the most promising, and approximately 10×10 undersampled pixels are optimal. Significant improvement in the 50% EE can be observed with a few tens of photons/subaperture/frame, and no significant gain is seen by adding more than 200 photons/subaperture/frame. The LGS GLAO is not particularly sensitive to the sodium profile present in the mesosphere nor to a short-timescale (less than 100 s) evolution of the sodium profile. The performance of LGS GLAO is, however, sensitive to the atmospheric turbulence profile.

Ad Hoc Access Gateway Selection Algorithm

NASA Astrophysics Data System (ADS)

Jie, Liu

With the continuous development of mobile communication technology, Ad Hoc access network has become a hot research, Ad Hoc access network nodes can be used to expand capacity of multi-hop communication range of mobile communication system, even business adjacent to the community, improve edge data rates. For mobile nodes in Ad Hoc network to internet, internet communications in the peer nodes must be achieved through the gateway. Therefore, the key Ad Hoc Access Networks will focus on the discovery gateway, as well as gateway selection in the case of multi-gateway and handover problems between different gateways. This paper considers the mobile node and the gateway, based on the average number of hops from an average access time and the stability of routes, improved gateway selection algorithm were proposed. An improved gateway selection algorithm, which mainly considers the algorithm can improve the access time of Ad Hoc nodes and the continuity of communication between the gateways, were proposed. This can improve the quality of communication across the network.

Laser beam-plasma plume interaction during laser welding

NASA Astrophysics Data System (ADS)

Hoffman, Jacek; Moscicki, Tomasz; Szymanski, Zygmunt

2003-10-01

Laser welding process is unstable because the keyhole wall performs oscillations which results in the oscillations of plasma plume over the keyhole mouth. The characteristic frequencies are equal to 0.5-4 kHz. Since plasma plume absorbs and refracts laser radiation, plasma oscillations modulate the laser beam before it reaches the workpiece. In this work temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, being not diluted by the shielding gas. As expected the values of electron density are about two times higher in peaks than their time-averaged values. Since the plasma absorption coefficient scales as ~N2e/T3/2 (for CO2 laser radiation) the results show that the power of the laser beam reaching the metal surface is modulated by the plasma plume oscillations. The attenuation factor equals 4-6% of the laser power but it is expected that it is doubled by the refraction effect. The results, together with the analysis of the colour pictures from streak camera, allow also interpretation of the dynamics of the plasma plume.

Self-consistent geodesic equation and quantum tunneling from charged AdS black holes

NASA Astrophysics Data System (ADS)

Deng, Gao-Ming

2017-12-01

Some urgent shortcomings in previous derivations of geodesic equations are remedied in this paper. In contrast to the unnatural and awkward treatment in previous works, here we derive the geodesic equations of massive and massless particles in a unified and self- consistent manner. Furthermore, we extend to investigate the Hawking radiation via tunneling from charged black holes in the context of AdS spacetime. Of special interest, the application of the first law of black hole thermodynamics in tunneling integration manifestly simplifies the calculation.

Nd:GdVO4 ring laser pumped by laser diodes

NASA Astrophysics Data System (ADS)

Hao, E. J.; Li, T.; Wang, Z. D.; Zhang, Y.

2013-02-01

The design and operation of a laser diode-pumped Nd:GdVO4 ring laser is described. A composite crystal (Nd:GdVO4/YVO4) with undoped ends is single-end pumped by a fiber-coupled laser diode (LD) at 808 nm. A four-mirror ring cavity is designed to keep the laser operating unidirectionally, which eliminates spatial hole burning in the standing-wave cavity. This laser can operate either as continuous wave (CW) or Q-switched. The single-frequency power obtained was 9.1 W at 1063 nm. Q-switched operation produced 0.23 mJ/pulse at 20 kHz in the fundamental laser.

In-Flight Performance of the Mercury Laser Altimeter Laser Transmitter

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Sun, Xiaoli; Li, Steven X.; Cavanaugh, John F.; Neumann, Gregory A.

2014-01-01

The Mercury Laser Altimeter (MLA) is one of the payload instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which was launched on August 3, 2004. MLA maps Mercury's shape and topographic landforms and other surface characteristics using a diode-pumped solid-state laser transmitter and a silicon avalanche photodiode receiver that measures the round-trip time of individual laser pulses. The laser transmitter has been operating nominally during planetary flyby measurements and in orbit about Mercury since March 2011. In this paper, we review the MLA laser transmitter telemetry data and evaluate the performance of solid-state lasers under extended operation in a space environment.

Fiber Based Seed Laser for CO 2 Ultrafast Laser Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yuchuan

A compact and effective 10-micron femtosecond laser with pulse duration <500fs and repetition rate of >100Hz or smaller is desirable by DOE for seeding CO 2 ultrafast laser systems to improve the stability, reliability and efficiency in generating 10-micron laser from GW up to 100TW peak power, which is irreplaceable in driving an accelerator for particle beam generation due to the efficiency proportional to the square of the laser wavelength. Agiltron proposes a fiber based ultrafast 10-micron seed laser that can provide the required specifications and high performance. Its success will directly benefit DOE’s compact proton and ion sources. Themore » innovative technology can be used for ultrafast laser generation over the whole mid-IR range, and speed up the development of mid-IR laser applications. Agiltron, Inc. has successfully completed all tasks and demonstrated the feasibility of a fiber based 10-micron ultrafast laser in Phase I of the Program. We built a mode-locked fiber laser that generated < 400fs ultrafast laser pulses and successfully controlled the repetition rate to be the required 100Hz. Using this mode-locked laser, we demonstrated the feasibility of parametric femtosecond laser generation based on frequency down conversion. The experimental results agree with our simulation results. The investigation results of Phase I will be used to optimize the design of the laser system and build a fully functional prototype for delivery to the DOE in the Phase II program. The prototype development in Phase II program will be in the collaboration with Professor Chandrashekhar Joshi, the leader of UCLA Laser-Plasma group. Prof. Joshi discovered a new mechanism for generation of monoenergetic proton/ion beams: Shock Wave Acceleration in a near critical density plasma and demonstrated that high-energy proton beams using CO 2 laser driven collisionless shocks in a gas jet plasma, which opened an opportunity to develop a rather compact high-repetition rate

Information computer program for laser therapy and laser puncture

NASA Astrophysics Data System (ADS)

Badovets, Nadegda N.; Medvedev, Andrei V.

1995-03-01

An informative computer program containing laser therapy and puncture methods has been developed. It was used successfully in connection with the compact Russian medical laser apparatus HELIOS-O1M in laser treatment and the education process.

Lasers in space

NASA Astrophysics Data System (ADS)

Michaelis, M. M.; Forbes, A.; Bingham, R.; Kellett, B. J.; Mathye, A.

2008-05-01

A variety of laser applications in space, past, present, future and far future are reviewed together with the contributions of some of the scientists and engineers involved, especially those that happen to have South African connections. Historically, two of the earliest laser applications in space, were atmospheric LIDAR and lunar ranging. These applications involved atmospheric physicists, several astronauts and many of the staff recruited into the Soviet and North American lunar exploration programmes. There is a strong interest in South Africa in both LIDAR and lunar ranging. Shortly after the birth of the laser (and even just prior) theoretical work on photonic propulsion and space propulsion by laser ablation was initiated by Georgii Marx, Arthur Kantrowitz and Eugen Saenger. Present or near future experimental programs are developing in the following fields: laser ablation propulsion, possibly coupled with rail gun or gas gun propulsion; interplanetary laser transmission; laser altimetry; gravity wave detection by space based Michelson interferometry; the de-orbiting of space debris by high power lasers; atom laser interferometry in space. Far future applications of laser-photonic space-propulsion were also pioneered by Carl Sagan and Robert Forward. They envisaged means of putting Saenger's ideas into practice. Forward also invented a laser based method for manufacturing solid antimatter or SANTIM, well before the ongoing experiments at CERN with anti-hydrogen production and laser-trapping. SANTIM would be an ideal propellant for interstellar missions if it could be manufactured in sufficient quantities. It would be equally useful as a power source for the transmission of information over light year distances. We briefly mention military lasers. Last but not least, we address naturally occurring lasers in space and pose the question: "did the Big Bang lase?"

The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy.

PubMed

Thomas, S; Pensel, J; Engelhardt, R; Meyer, W; Hofstetter, A G

1988-01-01

To date, there are two fairly well-established alternatives for laser-induced shock-wave lithotripsy in clinical practice. The Q-switched Nd:YAG laser is distinguished by the high-stone selectivity of its coupler systems. The necessity of a coupler system and its fairly small conversion rate of light energy into mechanical energy present serious drawbacks. Furthermore, the minimal outer diameter of the transmission system is 1.8 mm. The pulsed-dye laser can be used with a highly flexible and uncomplicated 200-micron fiber. However, the laser system itself is more complicated than the Q-switched Nd:YAG laser and requires a great deal of maintenance. Biological evaluation of damage caused by direct irradiation shows that both laser systems produce minor damage of different degrees. YAG laser lithotripsy with the optomechanical coupler was assessed in 31 patients with ureteral calculi. The instability and limited effectiveness of the fiber application system necessitated auxiliary lithotripsy methods in 14 cases. Dye-laser lithotripsy is currently being tested in clinical application. Further development, such as systems for blind application or electronic feedback mechanisms to limit adverse tissue effects, have yet to be optimized. Nevertheless, laser-induced shock-wave lithotripsy has the potential to become a standard procedure in the endourologic management of stone disease.

Exploring Ultrahigh-Intensity Laser-Plasma Interaction Physics with QED Particle-in-Cell Simulations

NASA Astrophysics Data System (ADS)

Luedtke, S. V.; Yin, L.; Labun, L. A.; Albright, B. J.; Stark, D. J.; Bird, R. F.; Nystrom, W. D.; Hegelich, B. M.

2017-10-01

Next generation high-intensity lasers are reaching intensity regimes where new physics-quantum electrodynamics (QED) corrections to otherwise classical plasma dynamics-becomes important. Modeling laser-plasma interactions in these extreme settings presents a challenge to traditional particle-in-cell (PIC) codes, which either do not have radiation reaction or include only classical radiation reaction. We discuss a semi-classical approach to adding quantum radiation reaction and photon production to the PIC code VPIC. We explore these intensity regimes with VPIC, compare with results from the PIC code PSC, and report on ongoing work to expand the capability of VPIC in these regimes. This work was supported by the U.S. DOE, Los Alamos National Laboratory Science program, LDRD program, NNSA (DE-NA0002008), and AFOSR (FA9550-14-1-0045). HPC resources provided by TACC, XSEDE, and LANL Institutional Computing.

Pulsed-laser capabilities at the Laser-Hardened Materials Evaluation Laboratory (LHMEL)

NASA Astrophysics Data System (ADS)

Royse, Robert W.; Seibert, Daniel B., II; Lander, Michael L.; Eric, John J.

2000-08-01

Pulsed laser capabilities at the Laser Hardened Material Evaluation Laboratory are described relevant to optical coupling, impulse generation and laser propulsion. Capabilities of the Nd:Glass laser are presented as well as supporting test systems.

Effects of laser fluence on silicon modification by four-beam laser interference

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Le; Li, Dayou; JR3CN and IRAC, University of Bedfordshire, Luton LU1 3JU

2015-12-21

This paper discusses the effects of laser fluence on silicon modification by four-beam laser interference. In this work, four-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of surface structures, and the number of laser pulses was applied to the process in air. By controlling the parameters of laser irradiation, different shapes of silicon structures were fabricated. The results were obtained with the single laser fluence of 354 mJ/cm{sup 2}, 495 mJ/cm{sup 2}, and 637 mJ/cm{sup 2}, the pulse repetition rate of 10 Hz, the laser exposure pulses of 30, 100, and 300, the laser wavelength of 1064 nm, andmore » the pulse duration of 7–9 ns. The effects of the heat transfer and the radiation of laser interference plasma on silicon wafer surfaces were investigated. The equations of heat flow and radiation effects of laser plasma of interfering patterns in a four-beam laser interference distribution were proposed to describe their impacts on silicon wafer surfaces. The experimental results have shown that the laser fluence has to be properly selected for the fabrication of well-defined surface structures in a four-beam laser interference process. Laser interference patterns can directly fabricate different shape structures for their corresponding applications.« less

Beam conditioner for free electron lasers and synchrotrons

DOEpatents

Liu, H.; Neil, G.R.

1998-09-08

A focused optical has been used to introduce an optical pulse, or electromagnetic wave, collinear with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM{sub 10} mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron. 4 figs.

Beam conditioner for free electron lasers and synchrotrons

DOEpatents

Liu, Hongxiu; Neil, George R.

1998-01-01

A focused optical is been used to introduce an optical pulse, or electromagnetic wave, colinearly with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM.sub.10 mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron.

Optical radiation hazards of laser welding processes. Part II: CO2 laser.

PubMed

Rockwell, R J; Moss, C E

1989-08-01

There has been an extensive growth within the last five years in the use of high-powered lasers in various metalworking processes. The two types of lasers used most frequently for laser welding/cutting processes are the Neodymium-yttrium-aluminum-garnet (Nd:YAG) and the carbon dioxide (CO2) systems. When such lasers are operated in an open beam configuration, they are designated as a Class IV laser system. Class IV lasers are high-powered lasers that may present an eye and skin hazard under most common exposure conditions, either directly or when the beam has been diffusely scattered. Significant control measures are required for unenclosed (open beam), Class IV laser systems since workers may be exposed to scattered or reflected beams during the operation, maintenance, and service of these lasers. In addition to ocular and/or skin exposure hazards, such lasers also may present a multitude of nonlaser beam occupational concerns. Radiant energy measurements are reported for both the scattered laser radiation and the plasma-related plume radiations released during typical high-powered CO2 laser-target interactions. In addition, the application of the nominal hazard zone (NHZ) and other control measures also are discussed with special emphasis on Class IV industrial CO2 laser systems.

Laser microprocessing technologies for automotive, flexible electronics, and solar energy sectors

NASA Astrophysics Data System (ADS)

Nikumb, Suwas; Bathe, Ravi; Knopf, George K.

2014-10-01

Laser microprocessing technologies offer an important tool to fulfill the needs of many industrial sectors. In particular, there is growing interest in applications of these processes in the manufacturing areas such as automotive parts fabrication, printable electronics and solar energy panels. The technology is primarily driven by our understanding of the fundamental laser-material interaction, process control strategies and the advancement of significant fabrication experience over the past few years. The wide-ranging operating parameters available with respect to power, pulse width variation, beam quality, higher repetition rates as well as precise control of the energy deposition through programmable pulse shaping technologies, enables pre-defined material removal, selective scribing of individual layer within a stacked multi-layer thin film structure, texturing of material surfaces as well as precise introduction of heat into the material to monitor its characteristic properties are a few examples. In this research, results in the area of laser surface texturing of metals for added hydrodynamic lubricity to reduce friction, processing of ink-jet printed graphene oxide for flexible printed electronic circuit fabrication and scribing of multi-layer thin films for the development of photovoltaic CuInGaSe2 (CIGS) interconnects for solar panel devices will be discussed.

Laser safety research and modeling for high-energy laser systems

NASA Astrophysics Data System (ADS)

Smith, Peter A.; Montes de Oca, Cecilia I.; Kennedy, Paul K.; Keppler, Kenneth S.

2002-06-01

The Department of Defense has an increasing number of high-energy laser weapons programs with the potential to mature in the not too distant future. However, as laser systems with increasingly higher energies are developed, the difficulty of the laser safety problem increases proportionally, and presents unique safety challenges. The hazard distance for the direct beam can be in the order of thousands of miles, and radiation reflected from the target may also be hazardous over long distances. This paper details the Air Force Research Laboratory/Optical Radiation Branch (AFRL/HEDO) High-Energy Laser (HEL) safety program, which has been developed to support DOD HEL programs by providing critical capability and knowledge with respect to laser safety. The overall aim of the program is to develop and demonstrate technologies that permit safe testing, deployment and use of high-energy laser weapons. The program spans the range of applicable technologies, including evaluation of the biological effects of high-energy laser systems, development and validation of laser hazard assessment tools, and development of appropriate eye protection for those at risk.

SAO/NASA ADS at SAO: Mirror Sites

Science.gov Websites

, Garching, Germany Astronomisches Rechen-Institut, Heidelberg, Germany Institute of Astronomy of the Russian Observatory, Chinese Academy of Science, Beijing, China Inter-University Centre for Astronomy and Astrophysics Intensive Astronomy, South Africa [ADS] ADS [CfA] CfA [NASA] NASA ads at cfa.harvard.edu