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1

Nano-optical microlens with ultrashort focal length using negative refraction  

E-print Network

Nano-optical microlens with ultrashort focal length using negative refraction B. D. F. Casse,a W. TD finite-difference time-domain simulations. Such ultrarefractive negative-index nano for miniaturization in the microelec- tronics industry and the advent of fiber optics for communi- cations purposes

Sridhar, Srinivas

2

Precise Measurement of Effective Focal Length  

NASA Technical Reports Server (NTRS)

Computerized instrument measures effective focal lengths to 0.01 percent accuracy. Laser interferometers measure mirror angle and stage coordinate y in instrument for accurate measurment of focal properties of optical systems. Operates under computer control to measure effective focal length, focal surface shape, modulation transfer function, and astigmatism.

Wise, T. D.; Young, J. B.

1983-01-01

3

Optical system design of solar-blind UV target simulator with long focal length  

NASA Astrophysics Data System (ADS)

Ultraviolet (UV) radiation of 200nm-300nm waveband from the sun is absorbed by atmosphere, which is often referred to the solar-blind region of the solar spectrum. Solar-blind characteristics of this waveband have important application value, especially in military fields. The application of solar-blind waveband has developed very rapidly, which is receiving more and more attention. Sometimes, to test the performance of a UV optical system, a standard solar-blind UV target simulator is needed as the UV light source. In this paper, an optical system of a solar-blind UV target simulator is designed with waveband 240nm-280nm. To simulate a far UV target, the focal length of this UV optical system needs to be long. Besides, different field of view (FOV) of the system should meet aplanatic condition. The optional materials are very few for UV optical systems, in which only CaF2 and JGS1 are commonly used. Various aberrations are difficult to be corrected. To save production cost and enhance the precision of fabrication and test, aspheric surfaces and binary elements are not adopted in the system. Moreover, doublet or triplet cannot be used in UV optical system considering possible cracking for different thermal expansion coefficients of different materials. After optimization, the system is composed of 4 lenses with focal length 500mm. MTF curves of different FOV coincide together. The maximum RMS radius of the optimized system has almost the same size as Airy disk, which proves the good image quality after system optimization. The aplanatic condition is met very well in this system. In the spot diagram, root mean square (RMS) radius changes from 3 microns to 3.6 microns, which has similar size with Airy disk and meets aplanatic condition very well. This optical system of solar-blind UV target simulator also has relatively loose tolerance data, which can prove the system is designed in an optimal state.

Chen, Yu; Huo, Furong; Zheng, Liqin

2014-11-01

4

Variable focal length deformable mirror  

DOEpatents

A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

Headley, Daniel (Albuquerque, NM); Ramsey, Marc (Albuquerque, NM); Schwarz, Jens (Albuquerque, NM)

2007-06-12

5

Focal length and focal depth of metallic superlens  

NASA Astrophysics Data System (ADS)

We consider the problems of focal length and focal depth of subwavelength imaging via a silver slab of metallic superlens. The performance limit of the metallic superlens was associated with the losses in the metallic film. The transmittance through a metal film is quite low and decreases exponentially with the thickness of the metal film. In the visible wavelength region, the permittivity of Ag can be approximated by the Drude model, so it can be described as the plural permittivity. The real part ( ?' ) of permittivity of the metal slab has been preferably index matched to the host material, and the imaginary part ( ?'' ) is considered to prevent ideal reconstruction of the image. Because superlens are usually made of metals with significant intrinsic loss ( ?''>0 ), the image is blurred and it is regarded as an ultimate limitation to a near field perfect lens. The real part ( ?' )and the imaginary part ( ?'' ) of permittivity of the metal slab is the function of the incident wavelength, so we discuss the relationship of the focal length, focal depth and the incident wavelength. We also derive the expression for the resolution limit of metallic lens and demonstrate that the area of its subwavelength performance is usually limited to the near-field zone.

Cao, Pengfei; Cheng, Lin; Li, Ying; Zhang, Xiaoping; Kong, Weijie; Gong, Li; Zhao, Xining

2012-10-01

6

Crystal diffraction lens with variable focal length  

DOEpatents

A method and apparatus for altering the focal length of a focusing element of one of a plurality of pre-determined focal lengths by changing heat transfer within selected portions of the element by controlled quantities is disclosed. Control over heat transfer is accomplished by manipulating one or more of a number of variables, including: the amount of heat or cold applied to surfaces; type of fluids pumped through channels for heating and cooling; temperatures, directions of flow and rates of flow of fluids; and placement of channels. 19 figures.

Smither, R.K.

1991-04-02

7

Variable-focal length lens using IPMC  

Microsoft Academic Search

We fabricated a liquid lens type variable-focal length lens(VFLL), which is composed of a container with a movable silicon plate having a pupil (diameter: 4 mm) covered by a thin polydimethylsiloxane (PDMS) film, a liquid enclosed in the container and a plural IPMCs fixed above the container for pushing the silicon plate downward. By applying a force to the silicon

Ippei SHIMIZU; Kunitomo KIKUCHI; Shigeki TSUCHITANI

2009-01-01

8

A potential individual cell malignancy indicator: focal length  

NASA Astrophysics Data System (ADS)

The label-free technique of optofluidic intracavity spectroscopy (OFIS) utilizes the optical transmission spectrum of a cell in a microfluidic Fabry-Pérot (F-P) cavity to distinguish cells from cancerous cell lines and baseline normal blood cells. The classification between canine hemangiosarcoma (HSA) cancer cells and monocytes in canine normal peripheral blood mononuclear cells (PBMCs) had been demonstrated with 95% sensitivity and 98% specificity. Now with a new optical model that treats the cell settled at the bottom of the cavity as a thin lens, the focal length of cells was extracted and used as an individual cell malignancy indicator.

Wang, Weina; Lear, Kevin L.

2011-03-01

9

Acoustic lens with variable focal length for photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

A liquid acoustic lens with variable focal length is described for photoacoustic microscopy. This liquid lens takes advantage of the elastic and deformable lens interface to tune its focal length in a pneumatical manner. The curvature of the lens interface as well as the dependant focal length was characterized as a function of the infusion volume of the liquid. Experiments were carried out to demonstrate the zooming ability of this liquid acoustic lens. Targets embedded at different depths were photoacoustically imaged without performing mechanically axial scanning.

Song, Chaolong; Xi, Lei; Jiang, Huabei

2013-11-01

10

Long Focal Length Large Mirror Fabrication System  

NASA Technical Reports Server (NTRS)

The goals of this ambitious program are (1) to develop systems to make large superpolished optical mirrors, (2) to develop low scatter polishing techniques using centrifugal elutriation, (3) to develop a means of measuring scatter at any point on the mirror, (4) to polish a Hindle sphere to measure the optical figure of a one meter diameter convex mandrel, and (5) to fabricate low scatter, large adaptive optic graphite filled, cyanate ester replica transfer mirrors using these mandrels. Deliverables are a 30 cm diameter superpolished composite AO mirror. We fabricated a 1/3rd meter superpolished zerodur flat mandrel and with the support of our major subcontractor, Composite Mirror Applications Inc (CMA) we have demonstrated a 30 cm lightweight cyanate ester mirror with an rms microroughness between 0.6 and 0.8 nm and 8 faceplate influence function of 5 cm. The influence function was chosen to be comparable to the atmospheric correlation coefficient r(sub 0) which is about 5 cm at sea level. There was no print-thru of the graphite fibers in the cyanate ester surface (the bane of many previous efforts to use cyanate ester mirrors). Our subcontractor has devised a means for developing a 30-50 nm thick layer of graphite free pure ester resin on the surface of the mirrors. This graphite fiber filled material has a thermal expansion coefficient in the 10(exp -8) centimeter per Kelvin range (the same range of expansion coefficient as Zerodur and ULE glasses) and does not take up water and swell, so it is a nearly ideal mirror material in these areas. Unfortunately for these 0.8mm thick faceplates, the number of plies is not enough to result in isometric coverage. Isolated figure irregularities can appear, making it necessary to go to thicker faceplates. The influence function will then only approximate the length of r(sub 0), at higher altitudes or longer wavelengths. The influence function goes as the cube of the thickness, so we are now making a faceplate optimized for an infrared wavelength, possibly that used for the AO system of the Keck telescope, instead of 0.63 microns. We have polished a 55 cm diameter mandrel to better than 1/20th wave optical figure in the visible using centrifugal elutriation. CMA has just told us that it needs to retool to get optimum mirror faceplate quality in this size, so implementing the 55 cm AO mirror may be delayed somewhat. We expect to complete our 1/3 rd meter AO mirror on time using novel piezoelectric actuators with a throw of one micrometer per volt, as compared to 0.005 micrometers per volt for conventional piezoelectric actuators. We will then demonstrate its AO performance interferometrically.

Bennett, H. E.

2003-01-01

11

Determination of long focal length of lenses with Talbot interferometer  

NASA Astrophysics Data System (ADS)

In this paper, a method for high-accuracy determination of long focal length based on Talbot interferometer is presented. Through changing the angle between two gratings, systematic errors are reduced effectively by calibration. The collimation of the light is determined by a standard concave mirror. The experimental results reveal that the relative error is 0.1%, and the repeatability is better than 0.1%. As the method is simple and somewhat insensitive to environmental effects, it is especially useful for measuring long focal-length lenses.

Jin, Xiaorong; Yu, Honglei; Bai, Jian; Hou, Xiyun

2012-10-01

12

Adaptive liquid crystal lens with large focal length tunability  

E-print Network

Crystal Displays (Wiley, New York, 2001). 13. S. Gauza, H. Wang, C. H. Wen, S. T. Wu, A. J. Seed and RAdaptive liquid crystal lens with large focal length tunability Hongwen Ren and Shin-Tson Wu crystal (LC) cell. The inner surface of the glass shell and the bottom surface of the LC cell are coated

Wu, Shin-Tson

13

Biomimetic small scale variable focal length lens unit using synthetic elastomer actuators  

NASA Astrophysics Data System (ADS)

Having a combination of a gel-like soft lens, ligaments, and the Ciliary muscles, the human eyes are effectively working for various focal lengths without a complicated group of lens. The simple and compact but effective optical system should deserve numerous attentions from various technical field especially portable information technology device industry. Noting the limited physical space of those deivces, demanding shock durability, and massive volume productivity, the present paper proposes a biomimetic optical lens unit that is organized with a circular silicone lens and an annular dielectric polymer actuator. Unlike the traditional optical lens mechanism that normally acquires a focus by changing its focal distance with moving lens or focal plane. the proposed optical system changes its lens thickness using a annulary connected polymer actuator in order to get image focuses. The proposed biomimetic lens system ensures high shock durability, compact physical dimensions, fast actuations, simple manufacturing process, and low production cost.

Kim, Baek-chul; Chung, Jinah; Lee, Y.; Nam, Jae-Do; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, J. C.

2011-04-01

14

Effects of environment factors on imaging performance of long focal length space camera  

NASA Astrophysics Data System (ADS)

In course of developing, testing, launching and working in orbit, Space camera has to undergo the shock of external loads and changing environment. The optical performance of a long focal length space camera is largely determined by external mechanical loads and ambient temperature. The performance of the camera is a result of the interaction between environment factors. The performance of the optical system should be making an accurate forecast when a modern optical instrument is designed. In this paper, the research methods are reviewed firstly. Then the related technologies are described. The analysis methods of environment temperature and structural characteristics effecting space camera imaging performance are also discussed.

Guo, Quanfeng; Jin, Guang; Dong, Jihong; Li, Wei; Li, Yanchun; Wang, Haiping; Wang, Kejun; Zhao, Weiguo

2012-10-01

15

The Modernization of a Long-Focal Length Fringe-Type Laser Velocimeter  

NASA Technical Reports Server (NTRS)

A long-focal length laser velocimeter constructed in the early 1980's was upgraded using current technology to improve usability, reliability and future serviceability. The original, free-space optics were replaced with a state-of-the-art fiber-optic subsystem which allowed most of the optics, including the laser, to be remote from the harsh tunnel environment. General purpose high-speed digitizers were incorporated in a standard modular data acquisition system, along with custom signal processing software executed on a desktop computer, served as the replacement for the signal processors. The resulting system increased optical sensitivity with real-time signal/data processing that produced measurement precisions exceeding those of the original system. Monte Carlo simulations, along with laboratory and wind tunnel investigations were used to determine system characteristics and measurement precision.

Meyers, James F.; Lee, Joseph W.; Cavone, Angelo A.; Fletcher, Mark T.

2012-01-01

16

Focal length measurement based on the wavefront difference method by a Fizeau interferometer.  

PubMed

A method for measuring the focal length of the lens by a Fizeau interferometer is proposed. Based on the Gaussian imaging equation and the longitudinal displacements of the object point and image point, a precise formula for focal length calculation is deduced. The longitudinal displacement of the object points is determined by the wavefront difference method with a subnanometer resolution. An experimental system for focal length measurements is set up to verify the principle. The sources of uncertainty in measurement are discussed. Both the positive and negative lens experimental results indicate that the measurement accuracy is less than 0.16% under normal experimental environment. PMID:25321352

Yang, Zhongming; Gao, Zhishan; Dou, Jiantai; Wang, Xinxing

2014-09-01

17

Controllable focal spot for direct-drive laser fusion based on electro-optic effect  

NASA Astrophysics Data System (ADS)

In direct-drive laser fusion, the sufficient uniformity of focal spot for realizing high efficient compression and central ignition is required. However, the laser beams are difficult to achieve sufficient uniform for compressing the shell symmetrically inward. We proposed a novel scheme to achieve controllable focal length based on electro-optic effect. The electro-optic crystal was placed in the front of the laser fusion system and applied the electro field with approximate spherical distribution. Since the wavefront of laser beam is transformed through the electro-optic crystal, the focal spot of the transformed laser beam would be changed on the target. Theoretical analysis and numerical simulation have been made, and the results show that the proposed scheme could achieve enough controllable focal spot on the target.

Zhong, Zheqiang; Hu, Xiaochun; Li, Zelong; Ye, Rong; Zhang, Bin

2014-09-01

18

Embedding perspective cue in holographic projection display by virtual variable-focal-length lenses  

NASA Astrophysics Data System (ADS)

To make a view perspective cue emerging in reconstructed images, a new approach is proposed by incorporating virtual variable-focal-length lenses into computer generated Fourier hologram (CGFH). This approach is based on a combination of monocular vision principle and digital hologram display, thus it owns properties coming from the two display models simultaneously. Therefore, it can overcome the drawback of the unsatisfied visual depth perception of the reconstructed three-dimensional (3D) images in holographic projection display (HPD). Firstly, an analysis on characteristics of conventional CGFH reconstruction is made, which indicates that a finite depthof- focus and a non-adjustable lateral magnification are reasons of the depth information lack on a fixed image plane. Secondly, the principle of controlling lateral magnification in wave-front reconstructions by virtual lenses is demonstrated. And the relation model is deduced, involving the depth of object, the parameters of virtual lenses, and the lateral magnification. Next, the focal-lengths of virtual lenses are determined by considering perspective distortion of human vision. After employing virtual lenses in the CGFH, the reconstructed image on focal-plane can deliver the same depth cues as that of the monocular stereoscopic image. Finally, the depthof- focus enhancement produced by a virtual lens and the effect on the reconstruction quality from the virtual lens are described. Numerical simulation and electro-optical reconstruction experimental results prove that the proposed algorithm can improve the depth perception of the reconstructed 3D image in HPD. The proposed method provides a possibility of uniting multiple display models to enhance 3D display performance and viewer experience.

Li, Zhaohui; Zhang, Jianqi; Wang, Xiaorui; Zhao, Fuliang

2014-10-01

19

Determination of the focal length of microlens array by spherical wavefronts  

NASA Astrophysics Data System (ADS)

We propose an experimental method consisting of a standard Fizeau interferometer with transmission sphere (TS) for the determination of the focal length of microlens array (MLA) by spherical wavefronts. The TS is axially translated to produce a spherical wavefront of different curvatures with respect to the MLA. The align mode provision of the interferometer helps to monitor the tilt of the MLA with respect to the spherical wavefront. The focal length is determined from the measured distance of adjacent image spots for various spherical wavefronts at the focal plane of the MLA. Error analysis and experimental demonstration with an off-the-shelf MLA are addressed here.

Kumar, Marimuthu Senthil; Sharma, Rahul; Narayanamurthy, Chittur Subramanian; Kumar, Alur Seelin Kiran

2014-06-01

20

Simplified model of an O-ring-driven liquid-filled lens for calculating focal length  

NASA Astrophysics Data System (ADS)

The purpose of this study was to develop a mathematical model that could be used to obtain the approximate focal length of O-ring-driven liquid-filled lenses. An O-ring-driven liquid-filled lens is composed of a base plate, a glass-covered liquid reservoir, a pliable membrane, an O-ring, a spring, and three actuators. The movement of the ring changes the focal length or the focus position. In previous studies, the commercial software ANSYS was used to find the membrane deformation and ZEMAX was used to find the focal length. The procedures used in those previous studies are complicated and generally require considerable design work. The proposed mathematical method employs the principle of liquid volume conservation to simplify the calculations that approximate the focal length of the lens. The result is confirmed on ZEMAX to ensure that the method is practicable. Consequently, focal lengths of lenses with different ring thicknesses, radii, and squeezing depths to contact the membrane can be calculated immediately.

Lin, Chih-Wei; Shaw, Dein

2009-07-01

21

Microlenses with tuned focal characteristics for optical wireless imaging  

NASA Astrophysics Data System (ADS)

Microlenses are fabricated and investigated for integrated imaging applications. The microlenses are fabricated by an in situ polymer electro-dispensing technique that enables user-controlled microlens sizes and shapes, by direct-dispensing and voltage-tuning with a metal micro-needle tip in a filler solution. Theoretical and experimental analyses are carried out for three limiting-cases of electro-dispensed microlenses: an acute-angle microlens with a 30° contact angle, a right-angle microlens with a 90° contact angle, and an obtuse-angle microlens with a 120° contact angle. It is found that the right-angle microlens, with a 500 ?m diameter, yields an especially short focal length (700 ?m) and exceedingly large numerical aperture (0.533). These characteristics can meet the needs of emerging applications, such as optical wireless devices, which demand compact device integration and broad field-of-view imaging. The microlenses are tested in optical wireless imaging receivers, for signal-to-noise ratio performance, and it is found that the right-angle microlens can offer significant (10 dB) performance enhancements.

Jin, Xian; Guerrero, Daniel; Klukas, Richard; Holzman, Jonathan F.

2014-07-01

22

Technique for the focal-length measurement of positive lenses using Fizeau interferometry  

SciTech Connect

We present what we believe is a new technique for the focal-length measurement of positive lenses using Fizeau interferometery. The technique utilizes the Gaussian lens equation. The image distance is measured interferometrically in terms of the radius of curvature of the image-forming wavefront emerging from the lens. The radii of curvature of the image-forming wavefronts corresponding to two different axial object positions of known separation are measured. The focal length of the lens is determined by solving the equations obtained using the Gaussian lens equation for the two object positions. Results obtained for a corrected doublet lens of a nominal focal length of 200.0 mm with a measurement uncertainty of {+-}2.5% is presented.

Pavan Kumar, Yeddanapudi; Chatterjee, Sanjib

2009-02-01

23

Technique for the focal-length measurement of positive lenses using Fizeau interferometry.  

PubMed

We present what we believe is a new technique for the focal-length measurement of positive lenses using Fizeau interferometery. The technique utilizes the Gaussian lens equation. The image distance is measured interferometrically in terms of the radius of curvature of the image-forming wavefront emerging from the lens. The radii of curvature of the image-forming wavefronts corresponding to two different axial object positions of known separation are measured. The focal length of the lens is determined by solving the equations obtained using the Gaussian lens equation for the two object positions. Results obtained for a corrected doublet lens of a nominal focal length of 200.0 mm with a measurement uncertainty of +/-2.5% is presented. PMID:19183601

Kumar, Yeddanapudi Pavan; Chatterjee, Sanjib

2009-02-01

24

Bioluminescence microscopy using a short focal-length imaging lens.  

PubMed

Bioluminescence from cells is so dim that bioluminescence microscopy is performed using an ultra low-light imaging camera. Although the image sensor of such cameras has been greatly improved over time, such improvements have not been made commercially available for microscopes until now. Here, we customized the optical system of a microscope for bioluminescence imaging. As a result, bioluminescence images of cells could be captured with a conventional objective lens and colour imaging camera. As bioluminescence microscopy requires no excitation light, it lacks the photo-toxicity associated with fluorescence imaging and permits the long-term, nonlethal observation of living cells. Thus, bioluminescence microscopy would be a powerful tool in cellular biology that complements fluorescence microscopy. PMID:24386879

Ogoh, K; Akiyoshi, R; May-Maw-Thet; Sugiyama, T; Dosaka, S; Hatta-Ohashi, Y; Suzuki, H

2014-03-01

25

Focal Plane Alignment Utilizing Optical CMM  

NASA Technical Reports Server (NTRS)

In many applications, an optical detector has to be located relative to mechanical reference points. One solution is to specify stringent requirements on (1) mounting the optical detector relative to the chip carrier, (2) soldering the chip carrier onto the printed circuit board (PCB), and (3) installing the PCB to the mechanical structure of the subsystem. Figure 1 shows a sketch of an optical detector mounted relative to mechanical reference with high positional accuracy. The optical detector is typically a fragile wafer that cannot be physically touched by any measurement tool. An optical coordinate measuring machine (CMM) can be used to position optical detectors relative to mechanical reference points. This approach will eliminate all requirements on positional tolerances. The only requirement is that the PCB is manufactured with oversized holes. An exaggerated sketch of this situation is shown in Figure 2. The sketch shows very loose tolerances on mounting the optical detector in the chip carrier, loose tolerance on soldering the chip carrier to the PCB, and finally large tolerance on where the mounting screws are located. The PCB is held with large screws and oversized holes. The PCB is mounted loosely so it can move freely around. The optical CMM measures the mechanical reference points. Based on these measurements, the required positions of the optical detector corners can be calculated. The optical CMM is commanded to go to the position where one detector corner is supposed to be. This is indicated with the cross-hairs in Figure 2(a). This figure is representative of the image of the optical CMM monitor. Using a suitable tapping tool, the PCB is manually tapped around until the corner of the optical detector is at the crosshairs of the optical CMM. The CMM is commanded to another corner, and the process is repeated a number of times until all corners of the optical detector are within a distance of 10 to 30 microns of the required position. The situation is sketched in Figure 2(b) (the figure also shows the tapping tool and where to tap). At this point the fasteners for the PCB are torqued slightly so the PCB can still move. The PCB location is adjusted again with the tapping tool. This process is repeated 3 to 4 times until the final torque is achieved. The oversized mounting holes are then filled with a liquid bonding agent to secure the board in position (not shown in the sketch). A 10- to 30-micron mounting accuracy has been achieved utilizing this method..

Liebe, Carl Christian; Meras, Patrick L.; Clark, Gerald J.; Sedaka, Jack J.; Kaluzny, Joel V.; Hirsch, Brian; Decker, Todd A.; Scholtz, Christopher R.

2012-01-01

26

Focal length measurement of a microlens-array by grating shearing interferometry.  

PubMed

Based on grating shearing interferometry, a simple technique is introduced for focal length measurements of a microlens-array (MLA). The measurement system is composed of a He-Ne laser, condenser, collimator, the MLA under testing, a Ronchi grating, and CCD sensor. The plane wavefront from the collimator is transformed to a spherical wavefront by the MLA, while the curvature center is at the focus. Interference stripes appear at the overlap between the zero-order and first-order diffractive patterns of the grating and are detected by the CCD sensor. By analyzing the period change of stripes, the focal length is determined after the defocus of the grating is calculated. To validate the feasibility, an experiment is performed. The measurement uncertainty is discussed and measurement accuracy was determined to be 2%. PMID:25322367

Zhu, Xianchang; Hu, Song; Zhao, Lixin

2014-10-10

27

The influence of beam energy, mode and focal length on the control of laser ignition in an internal combustion engine  

Microsoft Academic Search

This work involves a study on laser ignition (LI) in an internal combustion (IC) engine and investigates the effects on control of engine combustion performance and stability of varying specific laser parameters (beam energy, beam quality, minimum beam waist size, focal point volume and focal length). A Q-switched Nd : YAG laser operating at the fundamental wavelength 1064 nm was

J. D. Mullett; R. Dodd; C. J. Williams; G. Triantos; G. Dearden; A. T. Shenton; K. G. Watkins; S. D. Carroll; A. D. Scarisbrick; S. Keen

2007-01-01

28

Long focal-length measurement using divergent beam and two gratings of different periods.  

PubMed

A new accurate method for long focal-length measurement based on Talbot interferometry is proposed. A divergent beam and two Ronchi gratings of different periods are employed, as the alternative of the collimated beam and two identical gratings, to achieve higher measurement accuracy. Moreover, with divergent beam, lenses of large aperture can be easily measured without scanning, which is required when it comes to traditional collimated beam. Numerical analysis and experiments were carried out. The results demonstrate the proposed method features remarkably high accuracy and repeatability. PMID:25402033

Luo, Jia; Bai, Jian; Zhang, Jinchun; Hou, Changlun; Wang, Kaiwei; Hou, Xiyun

2014-11-17

29

Hard X-ray microbeam lithography using a Fresnel zone plate with a long focal length.  

PubMed

Focused hard X-ray microbeams for use in X-ray nanolithography have been investigated. A 7.5?keV X-ray beam generated at an undulator was focused to about 3?µm using a Fresnel zone plate fabricated on silicon. The focused X-ray beam retains a high degree of collimation owing to the long focal length of the zone plate, which greatly facilitates hard X-ray nanoscale lithography. The focused X-ray microbeam was successfully utilized to fabricate patterns with features as small as 100?nm on a photoresist. PMID:21335899

Lee, S Y; Cho, I H; Kim, J M; Kang, H C; Noh, D Y

2011-03-01

30

Measurement of the effective focal shift in an optical trap  

E-print Network

, and Steven M. Block Departments of Biological Sciences and Applied Physics, Stanford University, Stanford focal shift. Measurements of this quantity deviate from electromagnetic calculations of the focal shift

Block, Steven

31

Scaling of the generation of high-order harmonics in large gas media with focal length  

SciTech Connect

We present theoretical and experimental results on high-order harmonic generation in a low-density few-centimeter-long gas medium (L{sub med}{<=} 10 cm). We study the dependence with focal length of harmonic efficiency. Theoretically, we consider in detail the generation of the 25th harmonic of a short pulse Ti:sapphire laser in argon. Within the strong-field approximation for the atomic dipole, and a complete account of the macroscopic propagation, we compute the number of photons produced as a function of the medium parameters and the focusing conditions. The simulations show that, at constant intensity, the emission of the 25th harmonic scales with the focal length as {approx}f{sup 4} at low pressure (P=2 Torr) and as {approx}f{sup 6} at higher pressure (P=5 Torr). At constant laser energy, we find that the harmonic signal scales approximately as f{sup 2} at low pressure and as f{sup 4} at higher pressure. Those numerical results are compared with experimental data.

Boutu, W.; Auguste, T.; Caumes, J. P.; Carre, B. [Service des Photons, Atomes et Molecules, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France); Merdji, H. [Service des Photons, Atomes et Molecules, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France); PULSE Institute for Ultrafast Energy Science, Stanford Linear Accelerator Center, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

2011-11-15

32

Materials for intraocular lenses enabling photo-controlled tuning of focal length in vivo  

NASA Astrophysics Data System (ADS)

Typical postoperative complications in cataract surgery are that refractive power and curvature of the implanted intraocular lens (IOL) do not have optimum values, requiring the patient to wear viewing aids. This is mainly because biometric data relevant for calculation of the IOL's shape cannot be determined with the required precision. Hence, there is a need for methods to tune the focal length postoperatively in a non-invasive manner. We have developed polymers where we can induce a change in refractive index by linking or cleaving bonds between a su.ciently large number of side groups of the polymer main chain in a photoinduced cycloaddition or cycloreversion reaction, respectively. These photoreactions lead to a change in refractive index great enough to be interesting for the concept of in vivo tunable IOL's. The photochemical reaction can be triggered by a two-photon process (TPA) using a pulsed laser system, i.e. the energy required for bond breaking is provided by two photons in the visible range. This is important because light in the UV cannot induce undesired changes of the refractive index owing to the strong UV-absorption of the cornea. Undesired changes due to light in the visible range of the spectrum are unlikely to happen because photon density of sun light is much too low for TPA. Due to the excellent spatial resolution that can be achieved with two-photon processes one cannot only modify the refractive index of the entire lens but also selectively in well defined areas enabling to correct for aberrations such as astigmatism. Here, we present new polymers that do not only exhibit a photo induced change of refractive index great enough to induce a change of focal length of more than two diopters in a standard IOL. These new polymers have also significantly improved material properties with respect to the fabrication of the IOL and the TPA-sensitivities and the light energy required to induce the refractive index change.

Träger, Jens; Heinzer, Jasmin; Kim, Hee-Cheol; Hampp, Norbert

2007-07-01

33

Tunable liquid crystal lens array by encapsulation with a photo-reactive polymer for short focal length  

NASA Astrophysics Data System (ADS)

We demonstrated an electrically tunable liquid crystal (LC) lens array with a short focal length by self-encapsulation with a polymer layer of photo-reactive mesogens (RMs). The underlying concept relies primarily on the encapsulation of the LC with a thin curvilinear polymer layer in contact with air for the reduction of the focal length. The polymer-encapsulated (PE)-LC lens array was produced on a patterned substrate by selective wetting inscription through the phase separation of the LC and the RMs. In the field-off state, the focal length of the PE-LC lens was measured to be about 3 mm which is shorter than a conventional case by a factor of three (about 9 mm). The wettability inscription by ultraviolet light enables to build up any size of the LC lens in array over large-area without using a wet-chemical etching process for flexible optoelectronic and photonic applications.

Kim, Se-Um; Lee, Sanghun; Na, Jun-Hee; Lee, Sin-Doo

2014-02-01

34

Modeling of a Variable Focal Length Flat Lens Using Left Handed Metamaterials  

NASA Technical Reports Server (NTRS)

Left Handed Metamaterials (LHM) were originally purposed by Victor Veselago in1968. These substances would allow a flat structure to focus electromagnetic (EM) waves because they have a negative index of refraction. A similar structure made from conventional materials, those with a positive index of refraction, would disperse the waves. But until recently, these structures have been purely theoretical because substances with both a negative permittivity and negative permeability, material properties necessary for a negative index of refraction, do not naturally exist, Recent developments have produced a structure composed of an array of thin wires and split ring resonators that shows a negative index of refraction. area smaller than a square wavelength. How small the area is can be determined by how perfectly the lens is polished and how pure the substance is that composes the lens. These lenses must also be curved for focusing to occur. The focal length is determined by the curvature of the lens and the material. On the other hand, a flat structure made from LHM would focus light because of the effect of a negative index of refraction in Snell s law. The focal length could also be varied by simply adjusting the distance of the lens from the source of radiation. This could create many devices that are adjustable to different situations in fields such as biomedical imaging and communication. the software package XFDTD which solves Maxwell s equations in the frequency domain as well as the time domain. The program used Drude models of materials to simulate the effect of negative permittivity and negative permeability. Because of this, a LHM can be simulated as a solid block of material instead of an array of wires and split ring resonators. After a flat lens is formed, I am to examine the focusing effect of the lens and determine if a higher resolution flat lens can be developed. Traditional lenses made from conventional materials cannot focus an EM wave onto an My goal was to model LHMs and create a flat lens from them. This was to be done using

Reinert, Jason

2004-01-01

35

Optical Arc-Length Sensor For TIG Welding  

NASA Technical Reports Server (NTRS)

Proposed subsystem of tungsten/inert-gas (TIG) welding system measures length of welding arc optically. Viewed by video camera, in one of three alternative optical configurations. Length of arc measured instead of inferred from voltage.

Smith, Matthew A.

1990-01-01

36

FOCAL PLANE WAVEFRONT SENSING USING RESIDUAL ADAPTIVE OPTICS SPECKLES  

SciTech Connect

Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance the Strehl ratio or suppress the residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphs and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly changing residual atmospheric speckles at the 6.5 m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor measurements are used to estimate the residual wavefront, allowing us to approximately compute the rapidly evolving phase and amplitude of speckle halo. When combined with relatively short, synchronized science camera images, the complex speckle estimates can be used to interferometrically analyze the images, leading to an estimate of the static diffraction halo with NCP effects included. In an operational system, this information could be collected continuously and used to iteratively correct quasi-static NCP errors or suppress imperfect coronagraphic halos.

Codona, Johanan L.; Kenworthy, Matthew, E-mail: jlcodona@gmail.com [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2013-04-20

37

Focal-Plane Image and Beam Quality Sensors for Adaptive Optics  

E-print Network

Laboratory, Adelphi, MD 20783 Abstract Control of adaptive optical elements for real-time wavefront phase to the requirements of high resolution, real-time adaptive optical systems. In this paper we introduce two VLSI focal of a large class of optical systems and adaptive real-time correction of an optical field's wavefront spatial

Cauwenberghs, Gert

38

An Optical See-Through Head Mounted Display with Addressable Focal Planes  

E-print Network

An Optical See-Through Head Mounted Display with Addressable Focal Planes Sheng Liu*, Dewen Cheng, respectively. ABSTRACT Most existing stereoscopic head mounted displays (HMDs), presenting a pair of the viewer to the focal distances presented by the prototype. KEYWORDS: Display hardware, head mounted

Hua, Hong

39

Three mirror optical path length corrector  

NASA Astrophysics Data System (ADS)

A system of three high-speed tilt mirrors with a coupled control system used for correcting absolute optical path length (OPL) variations in a beam train has been analyzed. The system uses the principle that three one-degree-of-freedom tilt mirrors can be used to simultaneously control three fundamental beam parameters: tilt (beam jitter), translation (beam walk), and OPL (piston error). Closed-form solutions to the three coupled equations have been found and will be presented. Two special cases have been studied in detail. The first case used the three mirror system to maintain the current state of tilt and translation while independently controlling the absolute OPL for phasing. The second case uses the three mirror system to correct or negate any tilt or translation while imparting an absolute OPL on the beam as well. The limitations of the small angle approximation have been examined as well as a practical concept for the control system. Applications to laser beam trains, phased arrays, or astronomical systems employing interferometric imaging techniques are discussed.

Tyson, Robert K.

40

Spot size and effective focal length measurements for a fast axial flow CO{sub 2} laser  

SciTech Connect

An evaluation of the variation in focal plane position and spot size for a 1,650 W fast axial flow CO{sub 2} laser was performed. Multiple measurements of the focused beam were taken at stepped intervals along the beam axis to create a composite representation of the focus region. Measurements were made at several power levels from low to full power for each of five nominally identical lenses. It was found that as laser output power increases, the minimum focused spot radius increases, and the position of minimum focus shifts toward the laser resonator. These effects were attributed to observed variations in the diameter of the beam entering the focusing lens. For the ZnSe (f = 127 mm) lenses examined, variations in spot radius and focal plane position were seen. Lenses with high rated absorption had a larger variation in spot size and effective focal length than those with low absorption. Lenses that had previously been degraded by welding had the greatest variation.

Steele, R.J. [Naval Air Warfare Center, China Lake, CA (United States); Fuerschbach, P.W.; MacCallum, D.O. [Sandia National Labs., Albuquerque, NM (United States)

1997-12-31

41

Polarization-dependent optical tuning of focal intensity of liquid crystal polymer microlens array  

NASA Astrophysics Data System (ADS)

This work demonstrates the feasibility of a microlens array (MLA) with a focal intensity that can be optically tuned by controlling the polarization of incident light. The proposed MLA has a focusing unit based on birefringent liquid crystalline polymer (LCP) and a tuning unit with a photo-alignment layer for controlling the polarization state of incident laser light. The optically variable refractive indices of LCP allow a positive or negative MLA to be realized by controlling the polarization of the incident light.

Huang, S.-Y.; Tung, T.-C.; Ting, C.-L.; Jau, H.-C.; Li, M.-S.; Hsu, H.-K.; Fuh, A. Y.-G.

2011-07-01

42

Improved optical performance near the butt regions of multichip focal planes  

NASA Technical Reports Server (NTRS)

A technique for improving the optical characteristics at the butted edges of linear-multichip focal-plane imaging arrays is presented. It is shown that the air gap between butted imaging chips causes significant crosstalk. By filling the gap with a material that has an index of refraction more closely matched to that of the substrate, it is possible to reduce the optical crosstalk significantly.

Strong, R. T.; Kinnard, K. F.

1988-01-01

43

Focal plane optics in far-infrared and submillimeter astronomy  

NASA Technical Reports Server (NTRS)

The construction of airborne observatories, high mountain-top observatories, and space observatories designed especially for infrared and submillimeter astronomy has opened fields of research requiring new optical techniques. A typical far-IR photometric study involves measurement of a continuum spectrum in several passbands between approx 30 microns and 1000 microns and diffraction-limited mapping of the source. At these wavelengths, diffraction effects strongly influence the design of the field optics systems which couple the incoming flux to the radiation sensors (cold bolometers). The Airy diffraction disk for a typical telescope at submillimeter wavelengths approx 100 microns-1000 microns is many millimeters in diameter; the size of the field stop must be comparable. The dilute radiation at the stop is fed through a Winston nonimaging concentrator to a small cavity containing the bolometer. The purpose of this paper is to review the principles and techniques of infrared field optics systems, including spectral filters, concentrators, cavities, and bolometers (as optical elements), with emphasis on photometric systems for wavelengths longer than 60 microns.

Hildebrand, R. H.

1985-01-01

44

High-speed focal modulation microscopy using acousto-optical modulators  

PubMed Central

Focal Modulation Microscopy (FMM) is a single-photon excitation fluorescence microscopy technique which effectively rejects the out-of-focus fluorescence background that arises when imaging deep inside biological tissues. Here, we report on the implementation of FMM in which laser intensity modulation at the focal plane is achieved using acousto-optic modulators (AOM). The modulation speed is greatly enhanced to the MHz range and thus enables real-time image acquisition. The capability of FMM is demonstrated by imaging fluorescence labeled vasculatures in mouse brain as well as self-made tissue phantom. PMID:21258527

Chong, Shau Poh; Wong, Chee Howe; Wong, Kit Fei; Sheppard, Colin J.R.; Chen, Nanguang

2010-01-01

45

Light ray field capture using focal plane sweeping and its optical reconstruction using 3D displays.  

PubMed

We propose a method to capture light ray field of three-dimensional scene using focal plane sweeping. Multiple images are captured using a usual camera at different focal distances, spanning the three-dimensional scene. The captured images are then back-projected to four-dimensional spatio-angular space to obtain the light ray field. The obtained light ray field can be visualized either using digital processing or optical reconstruction using various three-dimensional display techniques including integral imaging, layered display, and holography. PMID:25401577

Park, Jae-Hyeung; Lee, Sung-Keun; Jo, Na-Young; Kim, Hee-Jae; Kim, Yong-Soo; Lim, Hong-Gi

2014-10-20

46

Adaptive optics operation with focal wavefront sensor in a coronagraph for direct observation of exoplanets  

NASA Astrophysics Data System (ADS)

A stellar coronagraph system for direct observations of extra solar planets is under development by combining unbalanced nulling interferometer (UNI), adaptive optics, and a focal plane mask coronagraph1,2,3,4,5,6. It can reach a high contrast as using ?/10000 precision optics by ?/1000 quality ones. However, a sufficient high contrast is not obtained yet in the experiment before. It is thought that the remained speckle noise at the final coronagraph focal plane detector are produced by a "non-common path error" of ?/100 level, which is a wavefront error of the coronagraph different from that of a wavefront sensor (WFS) of adaptive optics, even when the WFS indicates ?/1000 conversion. The non-common path error can be removed by the dark zone method that is the way of wavefront correction by wavefront sensing at the final focal plane detector, although it has an issue of operation for very faint targets because of a slow feedback loop. In the present paper, we describe that our coronagraph system becomes practically higher contrast by upgrading the control method of deformable mirror (DM) with the WFS assisted by final focal plane wavefront sensing method. We accomplished contrast of 8×10-7 relative to the star in experiment.

Oya, Masahito; Nishikawa, Jun; Horie, Masaaki; Sato, Kazuma; Fukase, Masao; Murakami, Naoshi; Kotani, Takayuki; Kumagai, Shiomi; Tamura, Motohide; Tanaka, Yosuke; Kurokawa, Takashi

2014-08-01

47

Measurement of Trap Length for an Optical Trap  

NASA Technical Reports Server (NTRS)

The trap length along the beam axis for an optical trap formed with an upright, oil-immersion microscope was measured. The goals for this effort were twofold. It was deemed useful to understand the depth to which an optical trap can reach for purposes of developing a tool to assist in the fabrication of miniature devices. Additionally, it was desired to know whether the measured trap length favored one or the other of two competing theories to model an optical trap. The approach was to trap a microsphere of known size and mass and raise it from its initial trap position. The microsphere was then dropped by blocking the laser beam for a pre-determined amount of time. Dropping the microsphere in a free-fall mode from various heights relative to the coverslip provides an estimate of how the trapping length changes with depth in water in a sample chamber on a microscope slide. While it was not possible to measure the trap length with sufficient precision to support any particular theory of optical trap formation, it was possible to find regions where the presence of physical boundaries influenced optical traps, and determine that the trap length, for the apparatus studied, is between 6 and 7 m. These results allow more precise control using optical micromanipulation to assemble miniature devices by providing information about the distance over which an optical trap is effective.

Wrbanek, Susan Y.

2009-01-01

48

Dynamic optical properties in graphene: Length versus velocity gauge  

SciTech Connect

The dynamic optical properties of graphene are theoretically investigated in both length gauge and velocity gauge in the presence of ultrafast optical radiation field. The two gauges present different results of dynamic photo-induced carriers and optical conductance due to distinct dependencies on electric field and non-resonant optical absorption, while the two gauges give identical results in the steady state time. It shows that the choice of gauge affects evidently the dynamic optical properties of graphene. The velocity gauge represents an outcome of a real physical experiment.

Dong, H. M.; Han, K., E-mail: han6409@263.net [Department of Physics, China University of Mining and Technology, Xuzhou 221116 (China); Xu, W. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Department of Physics, Yunnan University, Kunming 650091 (China)

2014-02-14

49

Tuning the Scattering Length with an Optically Induced Feshbach Resonance  

NASA Astrophysics Data System (ADS)

We demonstrate optical tuning of the scattering length in a Bose-Einstein condensate as predicted by Fedichev et al. [Phys. Rev. Lett. 77, 2913 (1996)]. In our experiment, atoms in a 87Rb condensate are exposed to laser light which is tuned close to the transition frequency to an excited molecular state. By controlling the power and detuning of the laser beam we can change the atomic scattering length over a wide range. In view of laser-driven atomic losses, we use Bragg spectroscopy as a fast method to measure the scattering length of the atoms.

Theis, M.; Thalhammer, G.; Winkler, K.; Hellwig, M.; Ruff, G.; Grimm, R.; Denschlag, J. Hecker

2004-09-01

50

Tuning the scattering length with an optically induced Feshbach resonance.  

PubMed

We demonstrate optical tuning of the scattering length in a Bose-Einstein condensate as predicted by Fedichev et al. [Phys. Rev. Lett. 77, 2913 (1996)]. In our experiment, atoms in a 87Rb condensate are exposed to laser light which is tuned close to the transition frequency to an excited molecular state. By controlling the power and detuning of the laser beam we can change the atomic scattering length over a wide range. In view of laser-driven atomic losses, we use Bragg spectroscopy as a fast method to measure the scattering length of the atoms. PMID:15447258

Theis, M; Thalhammer, G; Winkler, K; Hellwig, M; Ruff, G; Grimm, R; Hecker Denschlag, J

2004-09-17

51

Measurement of the Length of an Optical Trap  

NASA Technical Reports Server (NTRS)

NASA Glenn has been involved in developing optical trapping and optical micromanipulation techniques in order to develop a tool that can be used to probe, characterize, and assemble nano and microscale materials to create microscale sensors for harsh flight environments. In order to be able to assemble a sensor or probe candidate sensor material, it is useful to know how far an optical trap can reach; that is, the distance beyond/below the stable trapping point through which an object will be drawn into the optical trap. Typically, to measure the distance over which an optical trap would influence matter in a horizontal (perpendicular to beam propagation) direction, it was common to hold an object in one optical trap, place a second optical trap a known distance away, turn off the first optical trap, and note if the object was moved into the second trap when it was turned on. The disadvantage of this technique is that it only gives information of trap influence distance in horizontal (x y) directions. No information about the distance of the influence of the trap is gained in the direction of propagation of the beam (the z direction). A method was developed to use a time-of-flight technique to determine the length along the propagation direction of an optical trap beam over which an object may be drawn into the optical trap. Test objects (polystyrene microspheres) were held in an optical trap in a water-filled sample chamber and raised to a pre-determined position near the top of the sample chamber. Next, the test objects were released by blocking the optical trap beam. The test objects were allowed to fall through the water for predetermined periods of time, at the end of which the trapping beam was unblocked. It was noted whether or not the test object returned to the optical trap or continued to fall. This determination of the length of an optical trap's influence by this manner assumes that the test object falls through the water in the sample chamber at terminal velocity for the duration of its fall, so that the distance of trap influence can be computed simply by: d = VTt, where d is the trap length (or distance of trap reach), VT is the terminal velocity of the test object, and t is the time interval over which the object is allowed to fall.

Wrbanek, Susan Y.

2010-01-01

52

Measurement and compensation of laser-induced wavefront deformations and focal shifts in near IR optics.  

PubMed

We demonstrate the feasibility of passive compensation of the thermal lens effect in fused silica optics, placing suitable optical materials with negative dn/dT in the beam path of a high power near IR fiber laser. Following a brief overview of the involved mechanisms, photo-thermal absorption measurements with a Hartmann-Shack sensor are described, from which coefficients for surface/coating and bulk absorption in various materials are determined. Based on comprehensive knowledge of the 2D wavefront deformations resulting from absorption, passive compensation of thermally induced aberrations in complex optical systems is possible, as illustrated for an F-Theta objective. By means of caustic measurements during high-power operation we are able to demonstrate a 60% reduction of the focal shift in F-Theta lenses through passive compensation. PMID:25401572

Stubenvoll, Martin; Schäfer, Bernd; Mann, Klaus

2014-10-20

53

Remote focal scanning optical projection tomography with an electrically tunable lens.  

PubMed

We describe a remote focal scanning technique for optical projection tomography (OPT) implemented with an electrically tunable lens (ETL) that removes the need to scan the specimen or objective lens. Using a 4× objective lens the average spatial resolution is improved by ?46% and the light collection efficiency by a factor of ?6.76, thereby enabling increased acquisition speed and reduced light dose. This convenient implementation is particularly appropriate for lower magnifications and larger sample diameters where axial objective scanning would encounter problems with speed and stability. PMID:25360356

Chen, Lingling; Kumar, Sunil; Kelly, Douglas; Andrews, Natalie; Dallman, Margaret J; French, Paul M W; McGinty, James

2014-10-01

54

Clinical and optic coherence tomography findings of focal choroidal excavation in Chinese patients  

PubMed Central

Background To describe the clinical and optical coherence tomography (OCT) features of focal choroidal excavation in Chinese patients. Methods Retrospectively, thirty-seven eyes (in 31 patients) that demonstrated focal choroidal excavation on spectral-domain OCT were collected. Their clinical characteristics and other features were also collected and analyzed. Results In total, 42 focal choroidal excavations were identified in 31 patients, including 25 unilateral and 6 bilateral (37 eyes). The abnormal changes in these eyes with choroidal excavation were more prominent at the outer part of the neuro-retina, the retinal pigment epithelium (RPE) and the choroid. The average transverse diameter and depth of the excavations were 670.8 ?m and 106.9 ?m, respectively. In addition to the conforming and nonconforming types, the excavations could also be classified into 2 types according to their shape: type 1 – small with a sharp, cut-down contour; and type 2 – slightly larger with a gradual edge. The transverse diameter/depth ratio of the two types were significantly different (type1: 4.57?±?1.65, type 2: 10.0?±?5.2; p?=?0.000). Four central serous chorioretinopathy (CSCR) cases were confirmed by fluorescein angiography; in these cases, the retinal detachment was larger than the area of excavation, and the inner segment/outer segment (IS/OS) and external limiting membrane (ELM) were above those of the normal part. Concomitant CNV was also found in another 2 cases. Conclusions Focal choroidal excavation was not uncommon in Chinese patients. The choroid and the RPE at the excavation were impaired or vulnerable to other damage. Additionally, OCT might be useful in the differentiation between nonconforming excavations and ones with CSCR. PMID:24886645

2014-01-01

55

Holographic optical tweezers combined with back-focal-plane displacement detection.  

PubMed

A major problem with holographic optical tweezers (HOTs) is their incompatibility with laser-based position detection methods, such as back-focal-plane interferometry (BFPI). The alternatives generally used with HOTs, like high-speed video tracking, do not offer the same spatial and temporal bandwidths. This has limited the use of this technique in precise quantitative experiments. In this paper, we present an optical trap design that combines digital holography and back-focal-plane displacement detection. We show that, with a particularly simple setup, it is possible to generate a set of multiple holographic traps and an additional static non-holographic trap with orthogonal polarizations and that they can be, therefore, easily separated for measuring positions and forces with the high positional and temporal resolutions of laser-based detection. We prove that measurements from both polarizations contain less than 1% crosstalk and that traps in our setup are harmonic within the typical range. We further tested the instrument in a DNA stretching experiment and we discuss an interesting property of this configuration: the small drift of the differential signal between traps. PMID:24514607

Marsà, Ferran; Farré, Arnau; Martín-Badosa, Estela; Montes-Usategui, Mario

2013-12-16

56

Extended-length fiber optic carbon dioxide monitoring  

NASA Astrophysics Data System (ADS)

This paper discusses the design and performance of fiber optic distributed intrinsic sensors for dissolved carbon dioxide, based on the use optical fibers fabricated so that their entire lengths are chemically sensitive. These fibers use a polymer-clad, silica-core structure where the cladding undergoes a large, reversible, change in optical absorbance in the presence of CO2. The local "cladding loss" induced by this change is thus a direct indication of the carbon dioxide concentration in any section of the fiber. To create these fibers, have developed a carbon dioxide-permeable polymer material that adheres well to glass, is physically robust, has a refractive index lower than fused silica, and acts as excellent hosts for a unique colorimetric indicator system that respond to CO2. We have used this proprietary material to produce carbon-dioxide sensitive fibers up to 50 meters long, using commercial optical fiber fabrication techniques. The sensors have shown a measurement range of dissolved CO2 of 0 to 1,450 mg/l (0 to 100% CO2 saturation), limit of detection of 0.3 mg/l and precision of 1.0 mg/l in the 0 to 50 mg/l dissolved CO2 range, when a 5 meter-long sensor fiber segment is used. Maximum fiber length, minimum detectable concentration, and spatial resolution can be adjusted by adjusting indicator concentration and fiber design.

Delgado-Alonso, Jesus; Lieberman, Robert A.

2013-05-01

57

A substrate-free optical readout focal plane array with a heat sink structure  

NASA Astrophysics Data System (ADS)

A substrate-free optical readout focal plane array (FPA) operating in 8-12 ?m with a heat sink structure (HSS) was fabricated and its performance was tested. The temperature distribution of the FPA with an HSS investigated by using a commercial FLIR IR camera shows excellent uniformity. The thermal cross-talk effect existing in traditional substrate-free FPAs was eliminated effectively. The heat sink is fabricated successfully by electroplating copper, which provides high thermal capacity and high thermal conductivity, on the frame of substrate-free FPA. The FPA was tested in the optical-readout system, the results show that the response and NETD are 13.6 grey/K (F / # = 0.8) and 588 mK, respectively.

Rmwen, Liu; Yanmei, Kong; Binbin, Jiao; Zhigang, Li; Haiping, Shang; Dike, Lu; Chaoqun, Gao; Dapeng, Chen; Qingchuan, Zhang

2013-02-01

58

3D modeling of architectural objects from video data obtained with the fixed focal length lens geometry  

NASA Astrophysics Data System (ADS)

The article describes the process of creating 3D models of architectural objects on the basis of video images, which had been acquired by a Sony NEX-VG10E fixed focal length video camera. It was assumed, that based on video and Terrestrial Laser Scanning data it is possible to develop 3D models of architectural objects. The acquisition of video data was preceded by the calibration of video camera. The process of creating 3D models from video data involves the following steps: video frames selection for the orientation process, orientation of video frames using points with known coordinates from Terrestrial Laser Scanning (TLS), generating a TIN model using automatic matching methods. The above objects have been measured with an impulse laser scanner, Leica ScanStation 2. Created 3D models of architectural objects were compared with 3D models of the same objects for which the self-calibration bundle adjustment process was performed. In this order a PhotoModeler Software was used. In order to assess the accuracy of the developed 3D models of architectural objects, points with known coordinates from Terrestrial Laser Scanning were used. To assess the accuracy a shortest distance method was used. Analysis of the accuracy showed that 3D models generated from video images differ by about 0.06 ÷ 0.13 m compared to TLS data. Artyku? zawiera opis procesu opracowania modeli 3D obiektów architektonicznych na podstawie obrazów wideo pozyskanych kamer? wideo Sony NEX-VG10E ze sta?oogniskowym obiektywem. Przyj?to za?o?enie, ?e na podstawie danych wideo i danych z naziemnego skaningu laserowego (NSL) mo?liwe jest opracowanie modeli 3D obiektów architektonicznych. Pozyskanie danych wideo zosta?o poprzedzone kalibracj? kamery wideo. Model matematyczny kamery by? oparty na rzucie perspektywicznym. Proces opracowania modeli 3D na podstawie danych wideo sk?ada? si? z nast?puj?cych etapów: wybór klatek wideo do procesu orientacji, orientacja klatek wideo na podstawie wspó?rz?dnych odczytanych z chmury punktów NSL, wygenerowanie modelu 3D w strukturze TIN z wykorzystaniem metod automatycznej korelacji obrazów. Opracowane modele 3D zosta?y porównane z modelami 3D tych samych obiektów, dla których zosta?a przeprowadzona samokalibracja metod? wi?zek. W celu oceny dok?adno?ci opracowanych modeli 3D obiektów architektonicznych wykorzystano punkty naziemnego skaningu laserowego. Do oceny dok?adno?ci wykorzystano metod? najkrótszej odleg?o?ci. Analiza dok?adno?ci wykaza?a, ?e dok?adno?? modeli 3D generowanych na podstawie danych wideo wynosi oko?o 0.06 ÷ 0.13m wzgl?dem danych NSL.

Deli?, Paulina; K?dzierski, Micha?; Fry?kowska, Anna; Wili?ska, Michalina

2013-12-01

59

Exploiting Satellite Focal Plane Geometry for Automatic Extraction of Traffic Flow from Single Optical Satellite Imagery  

NASA Astrophysics Data System (ADS)

The focal plane assembly of most pushbroom scanner satellites is built up in a way that different multispectral or multispectral and panchromatic bands are not all acquired exactly at the same time. This effect is due to offsets of some millimeters of the CCD-lines in the focal plane. Exploiting this special configuration allows the detection of objects moving during this small time span. In this paper we present a method for automatic detection and extraction of moving objects - mainly traffic - from single very high resolution optical satellite imagery of different sensors. The sensors investigated are WorldView-2, RapidEye, Pléiades and also the new SkyBox satellites. Different sensors require different approaches for detecting moving objects. Since the objects are mapped on different positions only in different spectral bands also the change of spectral properties have to be taken into account. In case the main distance in the focal plane is between the multispectral and the panchromatic CCD-line like for Pléiades an approach for weighted integration to receive mostly identical images is investigated. Other approaches for RapidEye and WorldView-2 are also shown. From these intermediate bands difference images are calculated and a method for detecting the moving objects from these difference images is proposed. Based on these presented methods images from different sensors are processed and the results are assessed for detection quality - how many moving objects can be detected, how many are missed - and accuracy - how accurate is the derived speed and size of the objects. Finally the results are discussed and an outlook for possible improvements towards operational processing is presented.

Krauß, T.

2014-11-01

60

Fiber-optic liquid level sensor based on coupling optical path length variation  

NASA Astrophysics Data System (ADS)

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm.

Nath, Pabitra; Kumarjit Singh, Hidam; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

61

Fiber-optic liquid level sensor based on coupling optical path length variation.  

PubMed

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm. PMID:22667647

Nath, Pabitra; Singh, Hidam Kumarjit; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

62

Localization method of fiber optics defects on short length of optical cable  

NASA Astrophysics Data System (ADS)

Physical simulation of optical fiber cladding defects and experimental investigation results are described in present paper. By these results it is confirmed that assumption about fiber light-guide cladding defects localization on short length of optical fiber by comparison polarization backscattering characteristic with sliding correlation test is correct. Samples of defects localization on less then 2 km optical fiber with less then 100 m error are represented.

Dmitriev, Eugeniy V.

2010-12-01

63

Optical Scattering Lengths in Large Liquid-Scintillator Neutrino Detectors  

E-print Network

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents PXE, LAB, and Dodecane which are under discussion for next-generation experiments like SNO+, Hanohano, or LENA. Results comprise the wavelength range from 415 to 440nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Wurm, Michael; Goeger-Neff, Marianne; Hofmann, Martin; Lachenmaier, Tobias; Lewke, Timo; Undagoitita, Teresa Marrodan; Meindl, Quirin; Moellenberg, Randoplh; Oberauer, Lothar; Potzel, Walter; Tippmann, Marc; Todor, Sebastian; Traunsteiner, Christoph; Winter, Juergen

2010-01-01

64

Difference length scheduling for asynchronous optical packet switching  

NASA Astrophysics Data System (ADS)

The average queue delay of optical packet increases when the packets block in the virtual output queue header in the asynchronous optical packet switching. We analyze the character of variable length Internet packet and propose the preemptive short packets priority (PSPP) algorithm for reducing the total packet waiting time in the queue. In the PSPP algorithm, the short packet can preempt the transmission time of the long packet and can be served first. The analysis and the simulation shows the PSPP algorithm can make the average waiting time of the short packet decrease to zero almost and can decrease the total packet average waiting time largely when the traffic load is middle and low. The PSPP can guarantee the low average waiting delay for the real time TCP traffic implementation.

Liu, Huanlin; Chen, Qianbin; Pan, Yingjun

2006-09-01

65

Integration of advanced optical functions near the focal plane array: first steps toward the on-chip infrared camera  

NASA Astrophysics Data System (ADS)

Today, both military and civilian applications require miniaturized and cheap optical systems. The miniaturization of imaging systems leads to breakthroughs in optical design. Multichannel systems, inspired by the compound eyes of insects, offer great opportunities as the principle is to divide the information contained in the whole scene into the different optical channels. An interesting approach is to take advantage of the infrared focal plane array technology and environment to integrate these systems near the detector, leading to very compact architectures. This paper presents a compact optical architecture based on a multichannel imaging system entirely integrated in the dewar used to cool the detector. This work gives encouraging results to prepare the next step in the miniaturization of optical systems, which is the integration of the imaging function directly on the focal plane array (wafer-level integration), leading to the design of an on-chip infrared camera.

de la Barrière, Florence; Druart, Guillaume; Guérineau, Nicolas; Taboury, Jean; Fendler, Manuel

2010-08-01

66

The focal plane adaptive optics test box of the Observatoire du Mont-Mégantic  

NASA Astrophysics Data System (ADS)

With the upcoming construction of Extremely Large Telescopes, several existing technologies are being pushed beyond their performance limit and it becomes essential to develop and evaluate new alternatives. The "Observatoire du Mont Mégantic" (OMM) hosts a telescope having a 1.6-meter diameter primary. The OMM telescope is known to be an excellent location to develop and test precursor instruments which are then upscaled to larger telescopes (ex. SPIOMM which led to SITELLE at the CFHT). We present a specifically designed focal plane box for the OMM which will allow to evaluate, directly on-sky, the performance of a number of next generation adaptive optics related technologies The system will able us to compare the performance of several new wavefront sensors in contrast with the current standard, the Shack-Hartman wavefront sensor.

Deschênes, William; Brousseau, Denis; Lavigne, Jean-Francois; Thibault, Simon; Véran, Jean-Pierre

2014-08-01

67

Focal-plane wavefront sensing with high-order adaptive optics systems  

NASA Astrophysics Data System (ADS)

We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working with an extremely high resolution (larger than 150x150 correcting elements). We use focal-plane images collected successively, the corresponding phase-diversity information and numerically efficient algorithms to calculate the required wavefront updates. Different approaches are considered in numerical simulations, and laboratory experiments are shown to confirm the results. We compare the performances of the standard Gerchberg-Saxton algorithm, Fast and Furious (use of small-phase assumption to take advantage of linearisation) and recently proposed phase-retrieval methods based on convex optimisation. The results indicate that the calibration task is easiest with algorithms similar to Fast and Furious, at least in the framework we considered.

Korkiakoski, Visa; Keller, Christoph U.; Doelman, Niek; Kenworthy, Matthew; Otten, Gilles; Verhaegen, Michel

2014-08-01

68

To construct a stable and tunable optical trap in the focal region of a high numerical aperture lens  

NASA Astrophysics Data System (ADS)

Based on the diffraction theory, the focusing properties of a radially polarized quadratic Bessel-Gaussian beam (QBG) with on-axis radial phase variance wavefront are investigated theoretically in the focal region of a high numerical aperture (NA) objective lens. The phase wavefront C and pupil beam parameter ? of QBG are the functions of the radial coordinate. The detailed numerical calculation of the focusing property of a QBG beam is presented. The numerical calculation shows that the beam parameter ? and phase parameter C have greater effect on the total electric field intensity distribution. It is observed that under the condition of different ?, evolution principle of focal pattern differs very remarkably on increasing C. Also, some different focal shapes may appear, including rhombic shape, quadrangular shape, two-spherical crust focus shape, two-peak shape, one dark hollow focus, two dark hollow focuses pattern, and triangle dark hollow focus, which find wide optical applications such as optical trapping and nanopatterning.

Kandasamy, Gokulakrishnan; Ponnan, Suresh; Sivasubramonia Pillai, T. V.; Balasundaram, Rajesh K.

2014-05-01

69

Laser Metrology for an Optical-Path-Length Modulator  

NASA Technical Reports Server (NTRS)

Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical-path-length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner-cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase. Each gauge is required to measure the amplitude of the motion of the pick-off mirror, assuming that the motions of the pick-off mirror and the corner-cube retroreflector are identical, so as to measure the amplitude of motion of the corner- cube retroreflector to within an error of the order of picometers at each excitation frequency. Each gauge is a polarization-insensitive heterodyne interferometer that includes matched collimators, beam separators, and photodiodes (see figure). The light needed for operation of the gauge comprises two pairs of laser beams, the beams in each pair being separated by a beat frequency of 80 kHz. The laser beams are generated by an apparatus, denoted the heterodyne plate, that includes stabilized helium-neon lasers, acousto-optical modulators, and associated optical and electronic subsystems. The laser beams are coupled from the heterodyne plate to the collimators via optical fibers.

Gursel, Yekta

2005-01-01

70

Calibration of optical tweezers with positional detection in the back focal plane  

SciTech Connect

We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.

Tolic-Noerrelykke, Simon F.; Schaeffer, Erik; Howard, Jonathon; Pavone, Francesco S.; Juelicher, Frank; Flyvbjerg, Henrik [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany) and European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy) and Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden (Germany); European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany); Isaac Newton Institute for Mathematical Sciences, Cambridge CB3 0EH (United Kingdom); Biosystems Department, Risoe National Laboratory, DK-4000 Roskilde (Denmark) and Danish Polymer Centre, Risoe National Laboratory, DK-4000 Roskilde (Denmark)

2006-10-15

71

The Focal Plane Package of the Solar Optical telescope on Solar B  

NASA Astrophysics Data System (ADS)

The Solar-B satellite will be launched into a full-sun low-earth orbit in the fall of 2006 from Japan's Uchinoura Space center. It includes the 50-cm diameter Solar Optical Telescope with its Focal Plane Package (FPP), for near-UV and visible observations of the photosphere and chromosphere at very high (diffraction limited) angular resolution. The FPP has a Spectro-Polarimeter (SP) for precision measurements of photospheric vector magnetic fields over a 160 x 320 arcsecond field of view; a Narrowband Filter Imager (NFI) with a tunable birefringent filter for magnetic, Doppler, and intensity maps over the same field of view; and a Broadband Filter Imager (BFI) for highest resolution images in six wavelengths (G band, Ca II H, continua, etc.) over two-thirds of that field of view. A polarization modulator in the telescope allows measurement of Stokes parameters at all wavelengths in the SP and NFI. The NFI wavelengths include both photospheric and chromospheric lines (Fe I, Mg b, Na D, H-alpha). All images are stabilized by a tip-tilt mirror and correlation tracker. This presentation will include pictures and description of the instrument, results from calibration and sun testing, portions of the draft science plan, and some preliminary JOP's. Solar-B is an international cooperative mission between JAXA/ISAS of Japan, NASA of the United States, and PPARC of the United Kingdom. The Solar Optical Telescope has been developed by the National Astronomical Observatory of Japan, Mitsubishi Electric Company, and JAXA/ISAS. The FPP has been developed by the Lockheed Martin Advanced Technology Center, High Altitude Observatory, and NASA.

Tarbell, Theodore D.

2006-06-01

72

On the resolution enhancement of optical beams with extreme focal depth  

NASA Astrophysics Data System (ADS)

A recurring problem in optical design concerns the optimization of the resolution of a beam whose focal depth is several orders of magnitude larger than its wavelength. The cornerstone of such an optimization is the specification of a figure of merit by which the resolution of a typical beam is to be evaluated. In this thesis, the figure of merit takes the form of the mean encircled energy. Aside from providing simple equations for numerical optimization, this merit function allows for a tractible analysis of the behavior of the optimal solution to these equations through asymptotic methods. Such analysis is illustrated here first for the simplest case of symmetric Gaussian beams for both the 2D and 3D cases, where asymptotic analysis is used to find an accurate global approximation for the beam that maximizes mean encircled energy fraction over a given region of interest. For an apertured beam, the equation for the optimal mean encircled energy fraction takes the form of an integral eigenvalue equation, and asymptotic methods are possible for small aperture diameters. On the other hand, when the aperture width is large, it is better to decompose the beam into Hermite- or Laguerre-Gaussian modes. Here, a novel method is derived for computing the matrix whose eigenvector-corresponding to the largest eigenvalue-contains the coefficients of the individual modes in the optimal beam. Much of the analysis presented here is derived for symmetric beams; on the other hand, it is shown that the results for the optimal unapertured beam can be extended to elliptical beams with few modifications. The results in this thesis take on many forms, ranging from approximate expressions for parameters describing the optimal beams to comparisons between the globally optimal beams and corresponding simpler beams. One valuable lesson learned, however, is that although the globally optimal mean encircled energy fraction is rarely more than 10% greater than that for the optimal Gaussian beam, it turns out that in most cases, the beam obtained by an optimization technique specified here has far superior focal depth and resolution properties than those of the optimal Gaussians.

Gordon, Ronald Lawrence

1998-07-01

73

Determination of charge-carrier diffusion length in the photosensing layer of HgCdTe n-on-p photovoltaic infrared focal plane array detectors  

SciTech Connect

In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents j{sub ph} being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at j{sub ph}???0) charge-carrier diffusion length l{sub d} {sub eff} as a function of j{sub ph} for j{sub ph} ? 0 inferred from our experimental data proved to be consistent with the behavior of l{sub d} {sub eff} vs j{sub ph} as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe.

Vishnyakov, A. V.; Stuchinsky, V. A., E-mail: stuchin@isp.nsc.ru; Brunev, D. V.; Zverev, A. V.; Dvoretsky, S. A. [Institute of Semiconductor Physics, Russian Academy of Science, Siberian Division, 13, Acad. Lavrent'ev Avenue, Novosibirsk 630090 (Russian Federation)

2014-03-03

74

Correlation of Choroidal Thickness and Volume Measurements with Axial Length and Age Using Swept Source Optical Coherence Tomography and Optical Low-Coherence Reflectometry  

PubMed Central

Purpose. To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). Methods. A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12?mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). Results. The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F = 23.146, P < 0.001) followed by axial length (F = 4.902, P = 0.03). Refractive error was not statistically significant (F = 1.16, P = 0.28). Conclusions. SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time. PMID:25013793

Michalewski, Janusz; Nawrocka, Zofia; Bednarski, Maciej; Nawrocki, Jerzy

2014-01-01

75

OPTICAL FIELD PARAMETERS: Estimate of the minimal coherence length of probe optical radiation in interferometry  

NASA Astrophysics Data System (ADS)

The minimal coherence length of probe optical radiation sufficient for formation of a homogeneous interference structure is estimated. The estimate is based on the analysis of the interference structure in the intensity distribution of the field scattered by rough surfaces and point objects and also formed in interferometers. Analysis was performed for the field intensity detected for the time T > 10?c (under the condition that the coherence time of the probe radiation is ?c > 3/?0, where ?0 is the central frequency of the emission spectrum). It is shown that the minimal coherence length Lc of the probe radiation, at which the homogeneous stratified interference structure of the scattered field can be still formed, is 8? (? is the central wavelength). The possibility of using this result for determining the maximal information content of the method of low-coherence optical tomography is analysed.

Bakut, P. A.; Mandrosov, V. I.

2007-01-01

76

Automated optical testing of LWIR objective lenses using focal plane array sensors  

NASA Astrophysics Data System (ADS)

The image quality of today's state-of-the-art IR objective lenses is constantly improving while at the same time the market for thermography and vision grows strongly. Because of increasing demands on the quality of IR optics and increasing production volumes, the standards for image quality testing increase and tests need to be performed in shorter time. Most high-precision MTF testing equipment for the IR spectral bands in use today relies on the scanning slit method that scans a 1D detector over a pattern in the image generated by the lens under test, followed by image analysis to extract performance parameters. The disadvantages of this approach are that it is relatively slow, it requires highly trained operators for aligning the sample and the number of parameters that can be extracted is limited. In this paper we present lessons learned from the R and D process on using focal plane array (FPA) sensors for testing of long-wave IR (LWIR, 8-12 m) optics. Factors that need to be taken into account when switching from scanning slit to FPAs are e.g.: the thermal background from the environment, the low scene contrast in the LWIR, the need for advanced image processing algorithms to pre-process camera images for analysis and camera artifacts. Finally, we discuss 2 measurement systems for LWIR lens characterization that we recently developed with different target applications: 1) A fully automated system suitable for production testing and metrology that uses uncooled microbolometer cameras to automatically measure MTF (on-axis and at several o-axis positions) and parameters like EFL, FFL, autofocus curves, image plane tilt, etc. for LWIR objectives with an EFL between 1 and 12mm. The measurement cycle time for one sample is typically between 6 and 8s. 2) A high-precision research-grade system using again an uncooled LWIR camera as detector, that is very simple to align and operate. A wide range of lens parameters (MTF, EFL, astigmatism, distortion, etc.) can be easily and accurately measured with this system.

Winters, Daniel; Erichsen, Patrik; Domagalski, Christian; Peter, Frank; Heinisch, Josef; Dumitrescu, Eugen

2012-10-01

77

An optical see-through head mounted display with addressable focal planes  

Microsoft Academic Search

Most existing stereoscopic head mounted displays (HMDs), presenting a pair of stereoscopic images at a fixed focal distance, lack the ability to correctly render the naturally coupled accommodation and convergence cues. Psychophysical studies have shown that such displays may cause many adverse consequences such as visual fatigue, diplopic vision, degraded oculomotor response, and depth perception errors. In this paper, we

Sheng Liu; Dewen Cheng; Hong Hua

2008-01-01

78

Integrated measurements of acoustical and optical thin layers II: Horizontal length scales  

E-print Network

Polytechnic State University, San Luis Obispo, CA 93407, USA b College of Oceanic and Atmospheric Sciences-optics Bioacoustics Bioluminescence Length scales Autocorrelation a b s t r a c t The degree of layered organization

Benoit-Bird, Kelly J.

79

Fabrication of long-focal-length plano-convex microlens array by combining the micro-milling and injection molding processes.  

PubMed

A uniform plano-convex spherical microlens array with a long focal length was fabricated by combining the micromilling and injection molding processes in this work. This paper presents a quantitative study of the injection molding process parameters on the uniformity of the height of the microlenses. The variation of the injection process parameters, i.e., barrel temperature, mold temperature, injection speed, and packing pressure, was found to have a significant effect on the uniformity of the height of the microlenses, especially the barrel temperature. The filling-to-packing switchover point is also critical to the uniformity of the height of the microlenses. The optimal uniformity was achieved when the polymer melts completely filled the mold cavity, or even a little excessively filled the cavity, during the filling stage. In addition, due to the filling resistance, the practical filling-to-packing switchover point can vary with the change of the filling processing conditions and lead to a non-negligible effect on the uniformity of the height of the microlenses. Furthermore, the effect of injection speed on the uniformity of the height of the microlenses was analyzed in detail. The results indicated that the effect of injection speed on the uniformity of the height of the microlenses is mainly attributed to the two functions of injection speed: transferring the filling-to-packing switchover point and affecting the distribution of residual flow stress in the polymer melt. PMID:25402902

Chen, Lei; Kirchberg, Stefan; Jiang, Bing-Yan; Xie, Lei; Jia, Yun-Long; Sun, Lei-Lei

2014-11-01

80

Study of the length dependence of frequency-doubled light in optical fibers  

Microsoft Academic Search

It is found that the length dependence for frequency-doubled light in optical fibers is directly related to the amount of green seed used during the preparation stage. These measurements also show that self-phase modulation is not responsible for the saturation of the SHG signal with length. From these measurements it is also seen that the SH light is subject to

B. Batdorf; C. Krautschik; U. Österberg; G. Stegeman; J. W. Leitch; J. R. Rotgé; T. F. Morse

1989-01-01

81

Characterization of a Test Site for the Measuring of the Focal Point of Reflective Optical Elements for Concentrator Photovoltaic  

E-print Network

In order to achieve a large deployment of renewable energies, the electricity production costs have to be as low as possible. Many different technologies have been proposed to achieve the best efficiency to cost ratio. One of those is concentrating photovoltaics (CPV) which takes advantage of the high efficiency of multi-junction cells while limiting the costs by reducing the size of the cell and concentrating the direct irradiance with a cheaper optical element. Next to the widely used Fresnel lenses concave mirrors could be of interest as concentrator optic. As for the whole module those optics have to minimize losses and production costs at once. Measuring scattering and slope errors of the mirrors is of great importance to achieve an optimal design and production process. Therefore an optical test site doing so by observing the 2D irradiance distribution in the focal point has been built at the Fraunhofer ISE. The aim of this thesis is to characterize this test site. Therefore the behavior of the differen...

Frick, Manuel

2014-01-01

82

arXiv:physics/0511072v2[physics.optics]14Apr2006 Optical fibers with interferometric path length stability by controlled heating for  

E-print Network

(at a velocity of 1 cm per year) will have to be controlled. Moreover, fiber length fluctuations havearXiv:physics/0511072v2[physics.optics]14Apr2006 Optical fibers with interferometric path length path length of an optical fiber to an accuracy of about 1/100 of the laser wavelength. We study

Peters, Achim

83

Overall spatial characterization of nonparaxial radially polarized beams propagating from the focal plane of a high-focusing optical system  

NASA Astrophysics Data System (ADS)

The spatial structure of nonparaxial radially polarized fields, propagating from the focal plane of a high-focusing optical system, is analytically characterized by means of certain overall parameters. The procedure is based in a formal analogy with the irradiance-moments framework used for describing paraxial beams. The dependence on the propagation distance from the focal plane is derived for the effective beam width recently defined for this type of vectorial highly focused field. Due to the different behavior of the transverse and longitudinal components of the field, they are investigated in separate ways. We also introduce for this kind of nonparaxial field the concepts of beam waist (plane where the transverse beam size reaches the minimum value) and collimation coefficient (connected with the beam spreading). The suitability of the proposed global description is examined by considering, at each transverse plane, the power-content ratio within a circle whose radius is the beam width. The above results are applied to an illustrative example.

Martínez-Herrero, R.; Mejías, P. M.; Manjavacas, A.

2011-08-01

84

Optically controlled thermal management on the nanometer length scale  

NASA Astrophysics Data System (ADS)

The manipulation of polymers and biological molecules or the control of chemical reactions on a nanometer scale by means of laser pulses shows great promise for applications in modern nanotechnology, biotechnology, molecular medicine or chemistry. A controllable, parallel, highly efficient and very local heat conversion of the incident laser light into metal nanoparticles without ablation or fragmentation provides the means for a tool like a 'nanoreactor', a 'nanowelder', a 'nanocrystallizer' or a 'nanodesorber'. In this paper we explain theoretically and show experimentally the interaction of laser radiation with gold nanoparticles on a polymethylmethacrylate (PMMA) layer (one-photon excitation) by means of different laser pulse lengths, wavelengths and pulse repetition rates. To the best of our knowledge this is the first report showing the possibility of highly local (in a 40 nm range) regulated heat insertion into the nanoparticle and its surroundings without ablation of the gold nanoparticles. In an earlier paper we showed that near-infrared femtosecond irradiation can cut labeled DNA sequences in metaphase chromosomes below the diffraction-limited spot size. Now, we use gold as well as silver-enhanced gold nanoparticles on DNA (also within chromosomes) as energy coupling objects for femtosecond laser irradiation with single-and two-photon excitation. We show the results of highly localized destruction effects on DNA that occur only nearby the nanoparticles.

Garwe, F.; Bauerschäfer, U.; Csaki, A.; Steinbrück, A.; Ritter, K.; Bochmann, A.; Bergmann, J.; Weise, A.; Akimov, D.; Maubach, G.; König, K.; Hüttmann, G.; Paa, W.; Popp, J.; Fritzsche, W.

2008-02-01

85

In vivo optical reflectance imaging of spreading depression waves in rat brain with and without focal cerebral ischemia.  

PubMed

Spreading depression (SD) waves occur in focal cerebral ischemia of the brain. Optical reflectance imaging at 550 +/- 10-nm wavelength using a charge-coupled device (CCD) camera, called optical intrinsic signal imaging (OISI) in the neuroscience community, provides high resolution imaging of SD waves based on changes in blood perfusion. We present optical images of SD waves in normal rat brain induced by a pinprick, and the spontaneous SD waves that follow middle cerebral artery occlusion (MCAO). The images of change in reflectance are calculated as A = (I-I(o))I(o), where I is pixel intensity as some timepoint and I(o) is the initial intensity just prior to an SD wave. Difference images B = [I(i)-I(i-1)]I(o), where I(i) is the image at time i and I(i-1) is the previous image at time i-1 (a 6.4-s interval), significantly sharpen the boundaries between leading and trailing edges of the SD wave. Maximum rate-of-change images C = max(B) display the maximum pixel value of B within the duration of a single SD wave, and provide an image that visualizes the entire penumbra. The penumbra appear bright due to a rapid drop in perfusion, while the normal brain and infarct area appear dark. PMID:16822052

Chen, Shangbin; Feng, Zhe; Li, Pengcheng; Jacques, Steven L; Zeng, Shaoqun; Luo, Qingming

2006-01-01

86

Uncertainty evaluation for calibration of optical fiber length standard using time-of-flight method  

NASA Astrophysics Data System (ADS)

The time-of-flight method was used to calibrate an optical fiber length standard and its uncertainty of measurement was evaluated theoretically and experimentally according to the Evaluation of measurement data - Guide to the expression of uncertainty in measurement (GUM), JCGM 100:2008. The major uncertainty components in the measurement of transit time difference were identified and analyzed. The uncertainty due to temperature instability was investigated experimentally in the temperature range from 20 °C to 25 °C using a temperature chamber with precise temperature control. The temperature coefficient of the fiber length standard was derived by linear regression of the measurement data. The experimental results showed that the temperature control is critical for the calibration of optical fiber length standard. When the temperature instability was improved from +/- 2 °C to +/- 0.1 °C, the expanded measurement uncertainties for the optical fiber length standard (optical length : ~11780 m) were significantly reduced from 0.16 m to 0.014 m at wavelength of 1310 nm and from 0.19 m to 0.015 m at wavelength of 1550 nm.

Huang, Xuebo; Xu, Gan; Wang, Dong Liang

2010-08-01

87

Focal-Plane Image and Beam Quality Sensors for Adaptive Optics  

Microsoft Academic Search

Control of adaptive optical elements for real-time wavefront phase distortion compen- sation is a rapidly growing field of research and technology development. Wavefront cor- rection is essential for reliable long distance, near-ground laser communication as well as for imaging extended objects over large distances. Crucial to adaptively correcting the wavefront is a performance metric that can be directly evaluated from

Marc Cohent; Gert Cauwenberghst; Mikhail Vorontsovt; Gary Carhart

2001-01-01

88

Temporal characterization of FEL micropulses as function of cavity length detuning using frequency-resolved optical gating  

SciTech Connect

Results of frequency resolved optical gating (FROG) measurements on the Stanford mid-IR FEL system show the effect of FEL cavity length detuning on the micropulse temporal structure. The FROG technique enables the acquisition of complete and uniquely invertible amplitude and phase temporal dependence of optical pulses. Unambiguous phase and amplitude profiles are recovered from the data. The optical pulses are nearly transform limited, and the pulse length increases with cavity length detuning.

Richman, B.A. [Stanford Univ., CA (United States); DeLong, K.W.; Trebino, R. [Sandia National Lab., Livermore, CA (United States)

1995-12-31

89

Drawing of High-Strength Long-Length Optical Fibers for Submarine Cables  

Microsoft Academic Search

A drawing process for high-strength long-length optical fibers intended for submarine cables was developed using a carbon resistance furnace. Surface treatment conditions for preforms as well as drawing furnace cleanliness for minimizing flaw formations on the fibers during the drawing process are described. Furthermore, an evaluation of the mechanical performance of long fibers is discussed on the basis of the

SHIGEKI SAKAGUCHI

1984-01-01

90

High-temperature laser interferometer for thermal expansion and optical-length measurements  

Microsoft Academic Search

A simple laser interferometer has been utilized to measure the thermal expansion and optical-length variation with temperature of highly reactive fluorides at high temperatures. The interferometer is a modification of the Jamin interferometer in which a laser beam is split into two parallel beams which traverse nearly identical paths and are reflected from the sample and a reference mirror. The

T. S. AuroraS; S. M. Day; V. King; D. O. Pederson

1984-01-01

91

Extremely fast focal-plane wavefront sensing for extreme adaptive optics  

E-print Network

We present a promising approach to the extremely fast sensing and correction of small wavefront errors in adaptive optics systems. As our algorithm's computational complexity is roughly proportional to the number of actuators, it is particularly suitable to systems with 10,000 to 100,000 actuators. Our approach is based on sequential phase diversity and simple relations between the point-spread function and the wavefront error in the case of small aberrations. The particular choice of phase diversity, introduced by the deformable mirror itself, minimizes the wavefront error as well as the computational complexity. The method is well suited for high-contrast astronomical imaging of point sources such as the direct detection and characterization of exoplanets around stars, and it works even in the presence of a coronagraph that suppresses the di?raction pattern. The accompanying paper in these proceedings by Korkiakoski et al. describes the performance of the algorithm using numerical simulations and laboratory...

Keller, Christoph U; Doelman, Niek; Fraanje, Rufus; Andrei, Raluca; Verhaegen, Michel

2012-01-01

92

Optimal design of optical length in low turbidity measurement system with wavelength 1310 nm and 1550 nm  

NASA Astrophysics Data System (ADS)

To meet the need of long distance transmission in low turbidity measurement system for low-loss, a new optical structure with wavelength 1310nm and 1550nm as the incident light is employed. In this research, experiments have been done for different optical length of the two wavelength light sources. The results show that: first, the transmitted light intensity has big difference under the circumstance of same concentration and optical length, though the loss has no remarkable difference transmitted in optical fiber between 1310nm and 1550nm. Second, the optimized optical length for better absorbance has been determined for 1310nm and 1550nm and it is irrelevant to the incident intensity. Third, the intensity of the two transmitted light decreases exponentially with the increase of optical length. For example, when the range of the optical length of 1310nm is 0.5mm-2mm, the transmitted intensity is about 60%-79% and the absorbance is 0.12-0.42. The transmitted intensity is about 5%-44%. When the range of the optical length of 1550nm is 0.5mm-2mm and the absorbance is still 0.12-0.42. Our experimental data provides the basis both for the optical length selection of these two light sources in water and the near-infrared spectral wavelength selection.

Cao, Hui-bin; Liu, Jian-guo; Gui, Hua-qiao; Wang, Jie; Wang, Huan-qin

2014-11-01

93

Path-length-multiplexed scattering-angle-diverse optical coherence tomography for retinal imaging  

PubMed Central

A low-resolution path-length-multiplexed scattering angle diverse optical coherence tomography (PM-SAD-OCT) is constructed to investigate the scattering properties of the retinal nerve fiber layer (RNFL). Low-resolution PM-SADOCT retinal images acquired from a healthy human subject show the variation of RNFL scattering properties at retinal locations around the optic nerve head. The results are consistent with known retinal ganglion cell neural anatomy and principles of light scattering. Application of PM-SAD-OCT may provide potentially valuable diagnostic information for clinical retinal imaging. PMID:24177097

Wang, Bingqing; Yin, Biwei; Dwelle, Jordan; Rylander, H. Grady; Markey, Mia K.; Milner, Thomas E.

2014-01-01

94

Axial and peripheral eye length measured with optical low coherence reflectometry.  

PubMed

An optical low-coherence reflectometer (OLCR device) is described that allows the precise and noncontact measurement of eye length. The device measures eye length both on-axis and off-axis, thus enabling the determination of eye shape, an ocular parameter thought to be important in the development of refractive error. It is essential for several applications in ophthalmology and vision science. This improved OLCR device operates using a single-beam interferometer with a beam deflection mechanism that allows the precise measurement of eye length along the visual axis and within 15 deg horizontally and vertically from the fovea. The validity of this instrument and its revised software is evaluated by measuring the reproducibility of axial length results in an adult eye and an artificial eye, and by correlating axial eye length measured in a group of ten adult eyes with axial eye length obtained with A-scan ultrasound in the same eyes. The precision obtained with adult subjects is compared with that obtained with children. PMID:14563204

Schmid, Gregor F

2003-10-01

95

Vitelliform focal choroidal excavation.  

PubMed

Focal choroidal excavations (FCE) are characterized by foveal or perifoveal choroid excavations seen on optical coherence tomography (OCT). The authors report a case of FCE associated with a vitelliform lesion within the excavation. A case of FCE associated with a small vitelliform lesion has been described previously, but the larger extent of the vitelliform lesion observed in the current case has not been previously reported. This may represent a novel category of FCE, vitelliform focal choroidal excavation, in which deposition of vitelliform material is associated with its development. PMID:24877636

Or, Chris; Forooghian, Farzin

2014-01-01

96

Optical tuning of the scattering length of cold alkaline-earth-metal atoms  

SciTech Connect

It is possible to tune the scattering length for the collision of ultracold {sup 1}S{sub 0} ground-state alkaline-earth-metal atoms using an optical Feshbach resonance. This is achieved with a laser far detuned from an excited molecular level near the frequency of the atomic intercombination {sup 1}S{sub 0}-{sup 3}P{sub 1} transition. Simple resonant-scattering theory, illustrated by the example of {sup 40}Ca, allows an estimate of the magnitude of the effect. Unlike alkali metal species, large changes of the scattering length are possible while atom loss remains small, because of the very narrow linewidth of the molecular photoassociation transition. This raises prospects for control of atomic interactions for a system without magnetically tunable Feshbach resonance levels.

Ciurylo, R. [Atomic Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8423, Gaithersburg, Maryland 20899-8423 (United States); Instytut Fizyki, Uniwersytet Mikolaja Kopernika, ul. Grudziadzka 5/7, 87-100 Torun (Poland); Tiesinga, E.; Julienne, P.S. [Atomic Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8423, Gaithersburg, Maryland 20899-8423 (United States)

2005-03-01

97

Long gage-length fiber optic sensors for monitoring pipeline integrity  

NASA Astrophysics Data System (ADS)

This paper describes the use of FOX-TEK's long gage-length FT fiber optic sensors (FOS) for monitoring the integrity of pipelines and refinery components. Site assessment protocols and installation methods are described, in addition to the different FOS configurations required to monitor component integrity. It is shown how sensor information can also be used for process control, involving the monitoring of line temperature, pressure, and pipe wall thinning. Models are described that allow the operator to interpret field data to detect corrosion rates, pipe bending, movement and buckling.

Tennyson, R. C.; Morison, W. D.

2006-03-01

98

Variable-length cell for studies of gas spectra with extremely short optical paths.  

PubMed

We present a cell for studies of light transmission through very strongly absorbing gases. It uses a fixed window and a mirror, parallel to the latter and attached to a micrometric linear motion feedthrough monitoring mirror-window distances from 0 to a couple of centimeters. This device is tested by recording CO2 gas spectra near 4.3 ?m using a Fourier transform spectrometer. Their analysis shows that optical-path lengths between 20 and 2000 ?m have been obtained. This now enables spectroscopic measurements of self-broadening coefficients of O16C12O16 lines in the ?3 band, for instance, and opens perspectives for optical soundings of thin films of porous materials. PMID:25089968

Morales, Sébastien B; Pangui, Edouard; Landsheere, Xavier; Tran, Ha; Hartmann, Jean-Michel

2014-07-01

99

Effects of varying surfactant chain lengths on the magnetic, optical and hyperthermia properties of ferrofluids  

NASA Astrophysics Data System (ADS)

We report studies of the structural, magnetic, magneto-thermal and magneto-optic properties of dextran, oleic acid, lauric acid and myristic acid surfacted Fe3O4 nanoparticles of hydrodynamic sizes ranging from 32 nm to 92 nm. All the samples showed saturation magnetization of ˜50 emu/g, significantly smaller than the bulk value for Fe3O4, together with superparamagnetic behavior. The ac magnetization measurements on the dextran coated nanoparticles showed frequency dependent blocking temperature, consistent with superparamgnetic blocking. The ferrofluid heating rates in a 250 Gauss, 100 kHz ac magnetic field varied with the chain lengths of the surfactants, with higher heating rates for longer chains. DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid sample revealed different optical signatures for different surfactants.

Rablau, Corneliu; Vaishnava, Prem; Regmi, Rajesh; Sudakar, Chandran; Black, Correy; Lawes, Gavin; Naik, Ratna; Lavoie, Melissa; Kahn, David

2009-03-01

100

Correlation effects in the optical spectra of porphyrin oligomer chains: Exciton confinement and length dependence  

NASA Astrophysics Data System (ADS)

Excited states of ethylene-linked free-base porphyrin oligomers and polymer are studied using many-body perturbation theory (MBPT) within the GW approximation and the Bethe-Salpeter equation. Trends in the electronic levels with oligomer length are analysed and the correct long-range behaviour in the band gap is obtained. High polarizabilities and strong redshifts in the optical absorption peaks are predicted in agreement with observations on other strongly conjugated oligoporphyrins. We explain these trends by means of spatial and spectral analyses of the exciton character. Although Wannier-Mott and charge-transfer excitons are identified in the optical spectra, the strongest polarizabilities are actually associated with small, tightly bound excitons (Frenkel-like), in contrast to expectations. Furthermore, the common procedure of extrapolating polymer properties from oligomer calculations is examined from a MBPT perspective.

Hogan, Conor; Palummo, Maurizia; Gierschner, Johannes; Rubio, Angel

2013-01-01

101

Effect of focal size on the laser ignition of compressed natural gas-air mixture  

NASA Astrophysics Data System (ADS)

Laser ignition of compressed natural gas-air mixtures was investigated in a constant volume combustion chamber (CVCC) as well as in a single cylinder engine. Laser ignition has several potential advantages over conventional spark ignition system. Laser ignition relies on the fact that optical breakdown (plasma generation) in gases occurs at high intensities of ?1011 W/cm2. Such high intensities can be achieved by focusing a pulsed laser beam to small focal sizes. The focal spot size depends on several parameters such as laser wavelength, beam diameter at the converging lens, beam quality and focal length. In this investigation, the focal length of the converging lens and the beam quality were varied and the corresponding effects on minimum ignition energy as well as pressure rise were recorded. The flame kernel was visualized and correlated with the rate of pressure rise inside the combustion chamber. This investigation will be helpful in the optimization of laser and optics parameters in laser ignition. It was found that beam quality factor and focal length of focusing lens have a strong impact on the minimum ignition energy required for combustion. Combustion duration depends on the energy density at the focal spot and size of the flame kernel.

Srivastava, Dhananjay Kumar; Wintner, Ernst; Agarwal, Avinash Kumar

2014-07-01

102

Influence of core diameter and length of polymer optical fiber on Brillouin scattering properties  

NASA Astrophysics Data System (ADS)

Brillouin scattering in perfluorinated graded-index polymer optical fibers (PFGI-POFs) is potentially useful in developing high-accuracy distributed temperature sensors with reduced strain sensitivity. In this study, we investigate, both experimentally and theoretically, the influence of the fiber core diameter and length on the Brillouin gain spectra (BGS) in PFGI-POFs. First, we show that smaller core diameter drastically enhances the Stokes power using PFGI-POFs with 62.5-?m and 120-?m core diameters, and discuss the Brillouin threshold power. Then, we demonstrate that the PFGI-POF length has little influence on the BGS when the length is longer than 50 m. We also predict that, at 1.55-?m wavelength, it is difficult to reduce the Brillouin threshold power of PFGI-POFs below that of long silica single-mode fibers even if their core diameter is sufficiently reduced to satisfy the single-mode condition. Finally, making use of the enhanced Stokes signal, we confirm the Brillouin linewidth narrowing effect.

Mizuno, Yosuke; Ishigure, Takaaki; Nakamura, Kentaro

2012-02-01

103

Influence of the word length and input power on nonlinear crosstalk induced by hybrid optical amplifiers  

NASA Astrophysics Data System (ADS)

In this paper, the influence of the word length (WL) of a pseudo-random bit sequence (PRBS) and the input laser power on nonlinear crosstalk induced by the different hybrid optical amplifiers (HOAs) has been examined. It is found that the crosstalk is strongly dependent on the WL and very sensitive to the relative powers of the input signals at 0.2 nm and 0.4 nm of the channel spacing. It is shown that the proposed hybrid Raman-EDFA induces lesser crosstalk as compared to other HOAs. The performance of Raman-EDFA HOA is also investigated for 16 × 10 Gbps dense wavelength division multiplexed (DWDM) system at 0.2 nm of channel spacing.

Singh, Simranjit; Kaler, R. S.

2013-10-01

104

Effective optical path length for tandem diffuse cubic cavities as gas absorption cell  

NASA Astrophysics Data System (ADS)

Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap < 0.01, which coincided well with theoretical analysis. The simulating EOPL was smaller than experimental results at fap > 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

2014-12-01

105

Coupling-length phase matching for nonlinear optical frequency conversion in parallel waveguides  

NASA Astrophysics Data System (ADS)

We describe and analyze a quasi-phase-matching scheme for nonlinear optical frequency conversion where the spatial modulation of mode intensity in coupled parallel waveguides provides the required modulation in the generation of the frequency conversion signal, instead of a variation of any material parameter or propagation constant. We analyze this coupling-length phase-matching (CLPM) scheme both for second-order frequency conversion, such as second harmonic generation or difference-frequency generation, as well as for third-order four-wave mixing processes, for which we consider the example of generating a longer wavelength by third-order nonlinear mixing of two shorter wavelength waves. Numerous phase-matching conditions are identified in each case. We show that the maximum photon conversion efficiencies reached after an optimum propagation length are always higher than half those obtained for perfect phase matching in a single waveguide, with nearly 100% photon conversion possible for several of the CLPM conditions we studied.

Biaggio, Ivan; Coda, Virginie; Montemezzani, Germano

2014-10-01

106

A Method for Determining the Nominal Occular Hazard Zone for Gaussian Beam Laser Rangers with a Firmware Controlled Variable Focal Length  

NASA Technical Reports Server (NTRS)

LIDAR systems that maintain a constant beam spot size on a retroreflector in order to increase the accuracy of bearing and ranging data must use a software controlled variable position lens. These systems periodically update the estimated range and set the position of the focusing lens accordingly. In order to precisely calculate the r NOHD for such a system, the software method for setting the variable position lens and gaussian laser propagation can be used to calculate the irradiance at any point given the range estimation. NASA s Space Shuttle LIDAR, called the Trajectory Control Sensor (TCS), uses this configuration. Analytical tools were developed using Excel and VBA to determine the radiant energy to the International Space Station (ISS) crewmembers eyes while viewing the shuttle on approach and departure. Various viewing scenarios are considered including the use of through-the-lens imaging optics and the window transmissivity at the TCS wavelength. The methodology incorporates the TCS system control logic, gaussian laser propagation, potential failure mode end states, and guidance from American National Standard for the Safe Use of Lasers (ANSI Z136.1-2007). This approach can be adapted for laser safety analyses of similar LIDAR systems.

Picco, C. E.; Shavers, M. R.; Victor, J. M.; Duron, J. L.; Bowers, W. h.; Gillis, D. B.; VanBaalen, M.

2009-01-01

107

Electro-optic KTN Devices  

NASA Astrophysics Data System (ADS)

We have grown KTN crystals with optical quality, and developed high-speed beam deflectors and variable focal length lenses based on KTN's large electro-optic effect. Furthermore, by using the KTN beam deflectors, we have developed a swept light source for OCT operable at 200 kHz.

Yagi, Shogo; Fujiura, Kazuo

108

Optical biometry intraocular lens power calculation using different formulas in patients with different axial lengths  

PubMed Central

AIM : To investigate the predictability of intraocular lens (IOL) power calculation using the IOLMaster and different IOL power calculation formulas in eyes with various axial length (AL). METHODS : Patients were included who underwent uneventful phacoemulsification with IOL implantation in the Department of Ophthalmology, Far Eastern Memorial Hospital, Taipei, Taiwan, China from February 2007 to January 2009. Preoperative AL and keratometric values (Ks) were measured by IOLMaster optical biometry. Patients were divided into 3 groups based on AL less than 22mm (Group 1), 22–26mm (Group 2), and more than 26mm (Group 3). The power of the implanted IOL was used to calculate the predicted postoperative spherical equivalence (SE) by various formulas: the Haigis, Hoffer Q, Holladay 1, and SRK/T. The predictive accuracy of each formula was analyzed by comparing the difference between the actual and predicted postoperative SE (MedAE, median absolute error). All the patients had follow-up periods exceeding 3 months. RESULTS : Totally, there were 200 eyes (33 eyes in Group 1, 92 eyes in Group 2, 75 eyes in Group 3). In all patients, the Haigis had the significantly lower MedAE generated by the other formulas (P<0.05). In Group 1 to 3, the MedAE calculated by the Haigis was either significantly lower or comparable to those calculated by the other formulas. CONCLUSION : Compared with other formulas using IOLMaster biometric data, the Haigis formula yields superior refractive results in eyes with various AL. PMID:23638414

Wang, Jia-Kang; Chang, Shu-Wen

2013-01-01

109

Axial length measurement acquisition rates of two optical biometers in cataractous eyes  

PubMed Central

Purpose To compare the ability of two optical biometers to acquire the axial length (AL) measurement in cataractous eyes. Methods This prospective, comparative, single-center study comprised 105 eyes (63 patients). AL was acquired by the composite mean value of 20 measurements (composite-20 IM) and five measurements (composite-5 IM) (IOLMaster® 500 version 7.1 software), and the standard mean value of the first five measurements (standard-5 LS, Lenstar LS 900®). Anterior chamber depth (ACD) and average keratometry (K) readings were acquired. Results AL was acquired in 83.8%, 92.4%, and 84.8% of eyes for the composite-5 IM, composite-20 IM, and standard-5 LS, respectively. Standard-5 LS AL measurements were significantly shorter (P<0.001). IOLMaster® 500-acquired ACD (corneal epithelium to lens) measurements were significantly shorter (P<0.001). IOLMaster® 500 average K measurements were significantly steeper (P<0.001). Conclusion The composite-20 IM had the highest AL acquisition success rate of the three versions evaluated. AL, ACD, and average Ks were statistically different between the two biometers, although the differences were clinically insignificant. PMID:25092960

Epitropoulos, Alice

2014-01-01

110

CO[sub 2] laser beam propagation with ZnSe optics  

SciTech Connect

Beam propagation characteristics of ZnSe optics used in kiloWatt power CO[sub 2] laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO[sub 2] laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM[sub 00], TEM[sub 01], TEM[sub 10] and TEM[sub 20]. Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive and cylindrical lenses of 5in focal length and a 10in focal length integrading lens. Reflective optics included an integrator and a 5in focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

Leong, K.H.; Liu, Yi; Holdridge, D.J.

1992-01-01

111

CO{sub 2} laser beam propagation with ZnSe optics  

SciTech Connect

Beam propagation characteristics of ZnSe optics used in kiloWatt power CO{sub 2} laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO{sub 2} laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM{sub 00}, TEM{sub 01}, TEM{sub 10} and TEM{sub 20}. Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive and cylindrical lenses of 5in focal length and a 10in focal length integrading lens. Reflective optics included an integrator and a 5in focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

Leong, K.H.; Liu, Yi; Holdridge, D.J.

1992-11-01

112

Production and installation of long length optical fiber cable for shallow water use  

Microsoft Academic Search

Accompanying the expansion of optical fiber communication systems, needs for optical submarine cables have been increased particularly in off-shore areas, shallow channels and bays. Optical fiber cables to be layed on the sea bottom must be protected from damages during installation and extended use. The problems presented by these optical fiber cables are similar to those of conventional metal cables.

T. Ohshima; H. Horima; Y. Tokumaru; K. Aoto; T. Higashimoto

1986-01-01

113

The effect of collimator lenses on the performance of an optical coherence tomography system  

NASA Astrophysics Data System (ADS)

The effect of using collimator lenses with different focal lengths on the performance of a spectral-domain adaptive optics optical coherence tomography (AO-OCT) system has been studied. In vivo OCT scans of a healthy human retina were taken separately with different collimator lenses. Although shorter focal length lenses provide a smaller beam diameter at the pupil of the eye, and therefore a larger diffraction-limited spot size, on the return path the shorter focal length collimators demonstrate a better performance focusing the sinc-function-like intensity distribution returning from the eye on the fiber tip. The results might have applications in the OCT imaging of challenging cases.

Fält, Pauli; Zawadzki, Robert J.; Cense, Barry

2011-03-01

114

Focal Reducer for CQUEAN (Camera for QUasars in EArly uNiverse)  

NASA Astrophysics Data System (ADS)

A focal reducer is developed for CQUEAN (Camera for QUasars in EArly uNiverse), which is a CCD imaging system on the 2.1 m Otto Struve telescope at the McDonald observatory. It allows CQUEAN to secure a wider field of view by reducing the effective focal length by a factor of three. The optical point spread function without seeing effects is designed to be within one pixel (0.283 arcsec) over the field of view of 4.82 arcmin × 4.82 arcmin in optimum wavelength ranges of 0.8-1.1 ?m. In this paper, we describe and discuss the characteristics of optical design, the lens and barrel fabrications and the alignment processes.The observation results show that the image quality of the focal reducer confirms the expectations from the design.

Lim, Juhee; Chang, Seunghyuk; Pak, Soojong; Kim, Youngju; Park, Won-Kee; Im, Myungshin

2013-08-01

115

Unilateral isolated proximal femoral focal deficiency.  

PubMed

Objective. To discuss a patient with a prenatal diagnosis of unilateral isolated femoral focal deficiency. Case. Antenatal diagnosis of unilateral isolated femoral focal deficiency was made at 20 weeks of gestation. The length of left femur was shorter than the right, and fetal femur length was below the fifth percentile. Proximal femoral focal deficiency was diagnosed. After delivery, the diagnosis was confirmed with skeletal radiographs and magnetic resonance imaging. In prenatal ultrasonographic examination, the early recognition and exclusion of skeletal dysplasias is important; moreover, treatment plans should be initiated, and valuable information should be provided to the family. PMID:23984135

Do?er, Emek; Köpük, Sule Y; Cak?ro?lu, Yi?it; Cak?r, Ozgür; Yücesoy, Gülseren

2013-01-01

116

Unilateral Isolated Proximal Femoral Focal Deficiency  

PubMed Central

Objective. To discuss a patient with a prenatal diagnosis of unilateral isolated femoral focal deficiency. Case. Antenatal diagnosis of unilateral isolated femoral focal deficiency was made at 20 weeks of gestation. The length of left femur was shorter than the right, and fetal femur length was below the fifth percentile. Proximal femoral focal deficiency was diagnosed. After delivery, the diagnosis was confirmed with skeletal radiographs and magnetic resonance imaging. In prenatal ultrasonographic examination, the early recognition and exclusion of skeletal dysplasias is important; moreover, treatment plans should be initiated, and valuable information should be provided to the family. PMID:23984135

Do?er, Emek; Köpük, ?ule Y.; Çak?ro?lu, Yi?it; Çak?r, Özgür; Yücesoy, Gülseren

2013-01-01

117

Active optics Shack-Hartmann sensor: using spot sizes to measure the seeing at the focal plane of a telescope  

E-print Network

Real-time seeing estimation at the focus of a telescope is nowadays strongly emphasized as this knowledge virtually drives the dimensioning of adaptive optics systems and instrument operational aspects. In this context we study the interest of using active optics Shack-Hartmann (AOSH) sensor images to provide accurate estimate of the seeing. The AOSH practically delivers long exposure spot PSFs -- at the critical location of the telescope focus -- being directly related to the atmospheric seeing in the line of sight. Although AOSH sensors are not specified to measure spot sizes but slopes, we show that accurate seeing estimation from AOSH images can be obtained with a dedicated algorithm. The sensitivity and comparison of two algorithms to various parameters is analyzed in a systematic way, demonstrating that efficient estimation of the seeing can be obtained by adequate means.

Martinez, P; Sarazin, M; Navarrete, J

2012-01-01

118

Measurement of cranial optical path length as a function of age using phase resolved near infrared spectroscopy.  

PubMed

Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying the source/ detector separation by a laboratory measured differential path length factor (DPF) which accounts for the increased distance traveled by light due to scattering. DPF has been measured by time of flight techniques on small populations of adults and postmortem infants. The values for adults are greater than those for newborns, and it is not clear how to interpolate the present data for studies on children. Recent developments in instrumentation using phase resolved spectroscopy techniques have produced a bedside unit which can measure optical path length on any subject. We have developed an intensity modulated optical spectrometer which measures path length at four wavelengths. Two hundred and eighty three subjects from 1 d of age to 50 y were studied. Measurements were made at a fixed frequency of 200 MHz and a source detector separation of 4.5 cm. Results suggest a slowly varying age dependence of DPF, following the relation DPF690 = 5.38 + 0.049A0.877, DPF744 = 5.11 + 0.106A0.723, DPF807 = 4.99 + 0.067A0.814, and DPF832 = 4.67 + 0.062A0.819, where DPF690 is the DPF measured at 690 nm and A is age is expressed in years from full term. There was a wide scatter of values, however, implying that ideally DPF should be measured at the time of each study. PMID:8726247

Duncan, A; Meek, J H; Clemence, M; Elwell, C E; Fallon, P; Tyszczuk, L; Cope, M; Delpy, D T

1996-05-01

119

Full length article Optical pulse dynamics in fiber links with dispersion compensation  

Microsoft Academic Search

We examine optical pulse propagation in a transmission system with periodical pulse amplification and dispersion compensation both numerically and by a variational method. We confirm by direct numerical simulations the validity of the concept of a \\

Ildar Gabitov; Elena G. Shapiro; Sergei K. Turitsyn; L. D. Landau; Theoretische Physik

1997-01-01

120

Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants  

Microsoft Academic Search

The time taken for an extremely short pulse of near-infrared laser light to traverse the heads of 6 preterm infants was measured after death. The values obtained were used to calculate a differential path length factor (DPF), defined as the mean distance travelled by the photons divided by the distance between the points where light entered and left the head.

J. S. Wyatt; M. Cope; D. T. Delpy; P. van der Zee; S. R. Arridge; A. D. Edwards; E. O. R. Reynolds

1990-01-01

121

Vergence, Vision, and Geometric Optics  

ERIC Educational Resources Information Center

Provides a definition of vergence in terms of the curvature of the wave fronts, and gives examples to illustrate the advantages of this approach. The vergence treatment of geometrical optics provides both conceptual and algebraic advantages, particularly for the life science student, over the traditional object distance-image distance-focal length

Keating, Michael P.

1975-01-01

122

Imaging and full-length biometry of the eye during accommodation using spectral domain OCT with an optical switch  

PubMed Central

Abstract: An optical switch was implemented in the reference arm of an extended depth SD-OCT system to sequentially acquire OCT images at different depths into the eye ranging from the cornea to the retina. A custom-made accommodation module was coupled with the delivery of the OCT system to provide controlled step stimuli of accommodation and disaccommodation that preserve ocular alignment. The changes in the lens shape were imaged and ocular distances were dynamically measured during accommodation and disaccommodation. The system is capable of dynamic in vivo imaging of the entire anterior segment and eye-length measurement during accommodation in real-time. PMID:22808424

Ruggeri, Marco; Uhlhorn, Stephen R.; De Freitas, Carolina; Ho, Arthur; Manns, Fabrice; Parel, Jean-Marie

2012-01-01

123

Space telescope optical telescope assembly/scientific instruments. Phase B: Preliminary design and program definition study. Volume 2A. focal plane camera  

NASA Technical Reports Server (NTRS)

Trade studies were conducted to ensure the overall feasibility of the focal plane camera in a radial module. The primary variable in the trade studies was the location of the pickoff mirror, on axis versus off-axis. Two alternatives were: (1) the standard (electromagnetic focus) SECO submodule, and (2) the MOD 15 permanent magnet focus SECO submodule. The technical areas of concern were the packaging affected parameters of thermal dissipation, focal plane obscuration, and image quality.

1976-01-01

124

Optical evaluation of carrier lifetime and diffusion length in synthetic diamonds  

Microsoft Academic Search

The key electronic parameters of high-pressure-high-temperature and chemical-vapor-deposition grown diamonds have been determined at interband (h?=5.82 eV) or below bandgap (h?=4.68 eV) photoexcitation, using a picosecond transient grating (TG) technique. TG kinetics directly provided the values of ambipolar diffusion coefficient (6–10 cm2\\/s) and carrier lifetime (in a range from 0.17 to 2.8 ns) for crystals grown under different conditions. The carrier diffusion length was

T. Malinauskas; K. Jarasiunas; E. Ivakin; V. Ralchenko; A. Gontar; S. Ivakhnenko

2008-01-01

125

Field test and evaluation of IR focal plane arrays at the U.S. Air Force, Malabar Facility  

NASA Astrophysics Data System (ADS)

An IR camera employing reimaging optics with a cold Lyot stop, provisions for spectral filtering, and a detector/mux chip mounting assembly has been developed for a ground-based telescope, in order to serve as a breadboard facility for advanced focal-plane array (FPA) detector technologies in a field-test environment. Attention is presently given to an impurity-band conduction extrinsic silicon FPA coupled to an f/4.2, 100-inch focal length Newtonian telescope; operation is in the 9.5-11.5 micron wavelength band. Digitized FPA output is recorded for image reconstruction and analysis. The camera's first application will be in missile plume observations.

Fraser, James C.; Newby, Harold D.

1989-10-01

126

Adaptive beam shaping by controlled thermal lensing in optical elements  

Microsoft Academic Search

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained

Muzammil A. Arain; Volker Quetschke; Joseph Gleason; Luke F. Williams; Malik Rakhmanov; Jinho Lee; Rachel J. Cruz; Guido Mueller; D. B. Tanner; David. H. Reitze

2007-01-01

127

X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect  

SciTech Connect

It will be challenging to measure the temporal profile of the hard X-ray SASE beam independently from the electron beam in the LCLS and other 4th generation light sources. A fast interaction mechanism is needed that can be probed by an ultrafast laser pulse in a pump-probe experiment. It is proposed to exploit the rotation in polarization of light reflected from a thin magnetized film, known as the surface magneto optic Kerr effect (SMOKE), to witness the absorption of the x-ray pulse in the thin film. The change in spin orbit coupling induced by the x-ray pulse occurs on the subfemtosecond time scale and changes the polarization of the probe beam. The limitation to the technique lies with the bandwidth of the probe laser pulse and how short the optical pulse can be made. The SMOKE mechanism will be described and the choices of materials for use with 1.5 {angstrom} x-rays. A schematic description of the pump-probe geometry for x-ray diagnosis is also described.

Krejcik, P.; /SLAC

2006-10-04

128

Bunch Length Monitoring at the A0 Photoinjector Using a Quasi-Optical Schottky Detector  

SciTech Connect

Noninvasive bunch duration monitoring has a crucial importance for modern accelerators intended for short wavelength FEL's, colliders and in some beam dynamics experiments. Monitoring of the bunch compression in the Emittance Exchange Experiment at the A0 Photoinjector was done using a parametric presentation of the bunch duration via Coherent Synchrotron Radiation (CSR) emitted in a dipole magnet and measured with a wideband quasi-optical Schottky Barrier Detector (SBD). The monitoring resulted in a mapping of the quadrupole parameters allowing a determination of the region of highest compression of the bunch in the sub-picosecond range. The obtained data were compared with those measured using the streak camera. A description of the technique and the results of simulations and measurements are presented and discussed in this report.

Kazakevich, G.; Davidsaver, M.; Edwards, H.; Fliller, R.; Koeth, T.; Lumpkin, A.; Nagaitsev, S.; Ruan, J.; Thurman-Keup, R.; /Fermilab; Jeong, Y.U.; /KAERI, Taejon; Kubarev, V.; /Novosibirsk, IYF

2009-05-01

129

Optical Design of a Broadband Infrared Spectrometer for Bunch Length Measurement at the Linac Coherent Light Source  

SciTech Connect

The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off-axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.

Williams, Kiel; /SLAC

2012-09-07

130

Fabrication of ZnO nanorods and assessment of changes in optical and gas sensing properties by increasing their lengths  

NASA Astrophysics Data System (ADS)

We report a low-temperature process to synthesize highly oriented arrays of ZnO nanorods, based on the epitaxial growth of the ZnO seed layer at a low temperature of 70 °C. The ZnO seed layer was deposited by sol-gel process under mild conditions on the glass substrates. The morphologies and crystal structures of the film and nanorods were characterized by x-ray diffraction and scanning electron microscopy, respectively. ZnO nanorods were grown on ZnO seed layers by hydrothermal method. The effect of growth period on the morphology and optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and gas sensing properties of the grown ZnO seed layer (film) and nanorods were investigated. The long nanorods on the seed layer were observed. The increase in the length of the nanorods resulted in a significant reduction in the optical band-gap energy of the nanorods, which was attributed to the formation of further defects in the nanorods during their fast growth. The surface of the ZnO nanorods grown for 6 h was relatively hydrophilic (with a water contact angle of 18°). The fabricated sensors were used to gauge different concentrations of ethanol vapor in the air at different temperatures and evaluated the surface resistance of the sensors as a function of operating temperature and ethanol concentrations. The results showed that the sensitivity of the nanorods changed from 1.3 to 6 (at 300 °C) by increasing the growth period.

Mehrabian, Masood; Mirabbaszadeh, Kavoos; Afarideh, Hossein

2013-12-01

131

A Flat Focal Plane for LSST  

NASA Astrophysics Data System (ADS)

LSST is a wide field (10 sq. deg) survey instrument with active optics control and will provide better than 0.2 arcsecond instrumental contribution to imaging across the field. A principle requirement for achieving this is a very flat focal plane ( 10 microns PV) comprised of nearly 200 individual sensors, together with active feedback derived from 4 curvature wavefront sensors at the corners of the focal plane. We present our plans for building up a modular, flat focal plane for LSST and how flatness under operational conditions will be assured. The importance for delivering a flat focal plane will be underscored by discussing the specific structure of the LSST beam in the presence of residual wavefront error, and what sorts of systematics to the point spread function can be tolerated, given LSST's weak lensing mission.

Rasmussen, Andrew; Chang, C.; Kahn, S. M.; O'Connor, P.; Takacs, P.; Schindler, R.; Nordby, M.; LSST Camera Team

2009-01-01

132

Active optical zoom system.  

PubMed

In this work, we propose an active optical zoom system. The zoom module of the system is formed by a liquid lens and a spatial light modulator (SLM). By controlling the focal lengths of the liquid lens and the encoded digital lens on the SLM panel, we can change the magnification of an image without mechanical moving parts and keep the output plane stationary. The magnification can change from 1/3 to 3/2 as the focal length of the encoded lens on the SLM changes from infinity to 24 cm. The proposed active zoom system is simple and flexible, and has widespread application in optical communications, imaging systems, and displays. PMID:25402905

Wang, Di; Wang, Qiong-Hua; Shen, Chuan; Zhou, Xin; Liu, Chun-Mei

2014-11-01

133

Diamond turned optics  

NASA Astrophysics Data System (ADS)

Diamond turning techniques for high power laser optics were developed during the 70s and 80s as the alternative to conventional polishing of optical surfaces. In principle there are two main areas of applications for diamond tooled high power CO2 laser optics: (1) Aspheric transmissive ZnSe-/Ge-lenses for focussing at very short focal lengths or parabolic Cu- surfaces for laser welding heads. (2) Cu-surfaces for use as extracavity and intracavity beam bending mirrors. In this presentation we concentrate on item two.

Chmelir, Martina; Berger, Manfred R.

1994-08-01

134

Exact optics - II. Exploration of designs on- and off-axis  

NASA Astrophysics Data System (ADS)

The two-mirror telescopes/cameras that have no coma, no spherical aberration and arbitrarily fast focal ratios form a two-parameter (s, K) family of exact optical designs analytically derived earlier. We explore the full range of these designs in the s-K plane. Here s is the mirror separation/focal length and K is the distance from secondary to focus/focal length. Besides perfect-focus analogues of most well-known telescope designs, there are families of spectrograph cameras, X-ray telescopes and solar furnaces. Systems with s= 2 have minimum astigmatism and have exceptionally good images.

Willstrop, R. V.; Lynden-Bell, D.

2003-06-01

135

Making the ATHENA optics using silicon pore optics  

NASA Astrophysics Data System (ADS)

Silicon Pore Optics, after 10 years of development, forms now the basis for future large (L) class astrophysics Xray observatories, such as the ATHENA mission to study the hot and energetic universe, matching the L2 science theme recently selected by ESA for launch in 2028. The scientific requirements result in an optical design that demands high angular resolution (5") and large effective area (2 m2 at a few keV) of an X-ray lens with a focal length of 12 to14 m. Silicon Pore Optics was initially based on long (25 to 50 m) focal length telescope designs, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation). With the advent of shorter focal length missions we started to develop mirrors having a secondary curvature, allowing the production of Wolter-I type optics, which are on axis aberration-free. In this paper we will present the new manufacturing process, discuss the impact of the ATHENA optics design on the technology development and present the results of the latest X-ray test campaigns.

Collon, Maximilien J.; Ackermann, Marcelo; Günther, Ramses; Chatbi, Abdelhakim; Vacanti, Giuseppe; Vervest, Mark; Yanson, Alex; Beijersbergen, Marco W.; Bavdaz, Marcos; Wille, Eric; Haneveld, Jeroen; Olde Riekerink, Mark; Koelewijn, Arenda; van Baren, Coen; Müller, Peter; Krumrey, Michael; Burwitz, Vadim; Sironi, Giorgia; Ghigo, Mauro

2014-07-01

136

Focal shift in tightly focused Laguerre-Gaussian beams  

NASA Astrophysics Data System (ADS)

We study the nonparaxial propagation behavior of Laguerre-Gaussian (LG) beams under the tight focusing condition by using the Rayleigh-Sommerfeld integrals. We obtain an analytical formula and show the focal shift with respect to the geometric focus of a high numerical-aperture objective. An analytical expression for the focal shift of a tightly focused LG beam increases with the focal length while decreases with the beam waist. This approach can be extended to deal with the tight focusing field and the focal shift of LG vector fields with space-variant polarization distributions or other focusing behaviors such as the 4? focusing and the Fresnel zone plates.

Ren, Zhi-Cheng; Qian, Sheng-Xia; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

2015-01-01

137

Atom optical shop testing of electrostatic lenses using an atom interferometer Ivan Hromada1  

E-print Network

Atom optical shop testing of electrostatic lenses using an atom interferometer Ivan Hromada1 of Arizona, Tucson, Arizona 85721, USA (Dated: December 5, 2013) We used an atom interferometer for atom optical shop testing of lenses for atomic de Broglie waves. We measured focal lengths and spherical

Cronin, Alex D.

138

The Noninvasive Measurement of Absolute Cerebral Deoxyhemoglobin Concentration and Mean Optical Path Length in the Neonatal Brain by Second Derivative Near Infrared Spectroscopy (Regular Articles)  

Microsoft Academic Search

We have used second differential near infrared spectroscopy of water to determine the mean optical path length of the neonatal brain. By obtaining the ratio of the second differential features of deoxyhemoglobin to those of water, the absolute cerebral concentration of deoxyhemoglobin can be monitored continuously and noninvasively. Nineteen neonates were studied; the gestational age at birth varied from 23

S. J. MATCHER; Chris Cooper; Hamamatsu Photonics

139

A unique, accurate LWIR optics measurement system  

NASA Astrophysics Data System (ADS)

A compact low-cost LWIR test station has been developed that provides real time MTF testing of IR optical systems and EO imaging systems. The test station is intended to be operated by a technician and can be used to measure the focal length, blur spot size, distortion, and other metrics of system performance. The challenges and tradeoffs incorporated into this instrumentation will be presented. The test station performs the measurement of an IR lens or optical system's first order quantities (focal length, back focal length) including on and off-axis imaging performance (e.g., MTF, resolution, spot size) under actual test conditions to enable the simulation of their actual use. Also described is the method of attaining the needed accuracies so that derived calculations like focal length (EFL = image shift/tan(theta)) can be performed to the requisite accuracy. The station incorporates a patented video capture technology and measures MTF and blur characteristics using newly available lowcost LWIR cameras. This allows real time determination of the optical system performance enabling faster measurements, higher throughput and lower cost results than scanning systems. Multiple spectral filters are also accommodated within the test stations which facilitate performance evaluation under various spectral conditions.

Fantone, Stephen D.; Orband, Daniel G.

2011-05-01

140

Effect of conjugation length on nonlinear optical parameters of anthraquinone dyes investigated using He-Ne laser operating in CW mode  

NASA Astrophysics Data System (ADS)

We report the studies on third-order optical nonlinearity and optical limiting of anthraquinone dyes. Z-scan technique was employed to evaluate the nonlinear parameters such as nonlinear absorption coefficient ?eff and nonlinear index of refraction n2. Continuous wave He-Ne laser was used as the source of excitation. The estimated values of ?eff, n2 and ?(3) are of the order of 10-3 cm/W, 10-5 esu and 10-7 esu respectively. The presence of donor and acceptor groups in the structure results in increase in conjugation length. This resulted in the enhancement of nonlinear optical parameters values of the dye. Multiple diffraction rings were observed when the samples were exposed to laser beam due to thermal lensing. Dyes exhibited good optical limiting behavior under the experimental conditions. The results indicate that the dyes investigated here are materialise as candidates for photonics device applications such as optical power limiters.

Pramodini, S.; Poornesh, P.

2014-10-01

141

Biomimetic optical system using polymer lenses with tunable focus  

NASA Astrophysics Data System (ADS)

A biomimetic system using polymer lenses for the optical design and application is developed. The system mainly consisted of a bionic cornea lens, voice coil motor, compression ring, bionic crystalline lens, substrate, and CCD sensor. By controlling the current of the voice coil motor, we could change the motion of the compression ring to alter the curvature radius of the bionic crystalline lens, thus adjusting the focal length of the whole system. The integrated constructure of the optical system was presented, as well as the detailed description of the lens composition, material, and fabrication process. Images under different displacement loads were captured, the relationship among the curvature radius, observed back focal length, and predicted effective focal length was analyzed, and the spot diagram of the optical system was simulated using ZEMAX software. The focal length of the optical system ranged from 17.3 to 24.5 mm under a tiny displacement load from 0 to 0.14 mm. Besides, the images captured at different rotating angles presented almost identical patterns and the same image quality, which showed good robustness to the gravity. The biomimetic optical system is of interest to develop an integrated, low-cost, and stable imaging system.

Liang, Dan; Xiang, Ke; Du, Jia-Wei; Yang, Jun-Nan; Wang, Xuan-Yin

2014-10-01

142

The design and application of large area intensive lens array focal spots measurement system  

NASA Astrophysics Data System (ADS)

Concentrating Photovoltaic (CPV) modules are getting thinner and using smaller cells now days. Correspondingly, large area intensive lens arrays with smaller unit dimension and shorter focal length are wanted. However, the size and power center of lens array focal spots usually differ from the design value and are hard to measure, especially under large area situation. It is because the machining error and deformation of material of the lens array are hard to simulate in the optical design process. Thus the alignment error between solar cells and focal spots in the module assembly process will be hard to control. Under this kind of situation, the efficiency of CPV module with thinner body and smaller cells is much lower than expected. In this paper, a design of large area lens array focal spots automatic measurement system is presented, as well as its prototype application results. In this system, a four-channel parallel light path and its corresponding image capture and process modules are designed. These modules can simulate focal spots under sunlight and have the spots image captured and processed using charge coupled devices and certain gray level algorithm. Thus the important information of focal spots such as spot size and location will be exported. Motion control module based on grating scale signal and interval measurement method are also employed in this system in order to get test results with high speed and high precision on large area lens array no less than 1m×0.8m. The repeatability of the system prototype measurement is +/-10?m with a velocity of 90 spot/min. Compared to the original module assembled using coordinates from optical design, modules assembled using data exported from the prototype is 18% higher in output power, reaching a conversion efficiency of over 31%. This system and its design can be used in the focal spot measurement of planoconvex lens array and Fresnel lens array, as well as other kinds of large area lens array application with small focal spots.

Chen, Bingzhen; Yao, Shun; Yang, Guanghui; Dai, Mingchong; Wang, Zhiyong

2014-12-01

143

Electrostatic-Force-Modulated Microaspherical Lens for Optical Pickup Head  

Microsoft Academic Search

This paper proposes a novel method for the modulation and fabrication of an aspherical microlens from a photocurable polymer for use in optical pickup heads. This novel modulation method can be employed not only to dynamically control the focal length and morphology of the microlens but also to fabricate aspherical lenses after UV curing of the photosensitive polymer. Forces in

Kuo-Yung Hung; Fan-Gang Tseng; Tsung-Hsin Liao

2008-01-01

144

Optical and electro-optical devices in tactical reconnaissance-some human factors issues  

NASA Astrophysics Data System (ADS)

Long focal length devices, both optical and electro-optical, will have an important position in the sensor suite of future tactical reconnaissance aircraft. Careful attention must be paid to aircrew capabilities and needs during system design and integration if these devices are to be fully exploited. Man/machine function allocation and aircrew needs with respect to information and control requirements are particularly critical. The sensitivity of system performance to design decisions related to these issues is discussed.

Fitzgerald, Joe A.

1980-12-01

145

Combining Single-Molecule Optical Trapping and Small-Angle X-Ray Scattering Measurements to Compute the Persistence Length of a Protein ER/K ?-Helix  

PubMed Central

Abstract A relatively unknown protein structure motif forms stable isolated single ?-helices, termed ER/K ?-helices, in a wide variety of proteins and has been shown to be essential for the function of some molecular motors. The flexibility of the ER/K ?-helix determines whether it behaves as a force transducer, rigid spacer, or flexible linker in proteins. In this study, we quantify this flexibility in terms of persistence length, namely the length scale over which it is rigid. We use single-molecule optical trapping and small-angle x-ray scattering, combined with Monte Carlo simulations to demonstrate that the Kelch ER/K ?-helix behaves as a wormlike chain with a persistence length of ?15 nm or ?28 turns of ?-helix. The ER/K ?-helix length in proteins varies from 3 to 60 nm, with a median length of ?5 nm. Knowledge of its persistence length enables us to define its function as a rigid spacer in a translation initiation factor, as a force transducer in the mechanoenzyme myosin VI, and as a flexible spacer in the Kelch-motif-containing protein. PMID:19948129

Sivaramakrishnan, S.; Sung, J.; Ali, M.; Doniach, S.; Flyvbjerg, H.; Spudich, J.A.

2009-01-01

146

Postsurgical focal testicular infarct.  

PubMed

A 74-year-old man was surgically treated owing to incarcerated right inguinal hernia. Following surgery, he developed a focal hemorrhagic testicular infarct localized in the anterior pole of the right testis. The cause of the infarct seemed to bei either thrombosis or compression by edema of the veins draining the testis. PMID:3727192

Nistal, M; Palacios, J; Regadera, J; Paniagua, R

1986-01-01

147

The noninvasive measurement of absolute cerebral deoxyhemoglobin concentration and mean optical path length in the neonatal brain by second derivative near infrared spectroscopy.  

PubMed

We have used second differential near infrared spectroscopy of water to determine the mean optical path length of the neonatal brain. By obtaining the ratio of the second differential features of deoxyhemoglobin to those of water, the absolute cerebral concentration of deoxyhemoglobin can be monitored continuously and noninvasively. Nineteen neonates were studied; the gestational age at birth varied from 23 to 38 wk, and the postconceptual age, when the spectra were recorded, ranged from 35 to 48 wk. The calculated mean deoxyhemoglobin concentration was 14.6 +/- 4.0 microM; the differential path length factor (mean optical path length/optode separation) calculated from the water peak at 730 nm was 4.66 +/- 1.01, and that calculated at the 830-nm peak was 3.91 +/- 0.75. These values are consistent with path length measurements using laser time-of-flight spectroscopy on postmortem neonates and phase-resolved spectroscopy on live neonates. Induced arterial oxygen saturation decreases from 98 to 93% showed no significant change in the mean optical path length, despite significant cerebral desaturation. Changes in the deoxyhemoglobin concentration after this procedure were identical, whether measured by second differential analysis at 760 nm or by multilinear regression over the wavelength range 740-900 nm. When combined with existing methods of measuring total cerebral hemoglobin concentration, second differential near infrared spectroscopy can be used to derive the mean cerebral oxygen saturation. A preliminary experiment outlined the feasibility of this approach and yielded a saturation value of 63%, consistent with near infrared sampling of a predominantly venous pool in the brain. PMID:8825383

Cooper, C E; Elwell, C E; Meek, J H; Matcher, S J; Wyatt, J S; Cope, M; Delpy, D T

1996-01-01

148

Improvements of the Focal Plane of SASSYER  

NASA Astrophysics Data System (ADS)

The Small Angle Separator System at Yale for Evaporation Residues (SASSYER) at Yale University is a gas-filled recoil separator, specializing in the investigation of the production and the structure of nuclei heavier than ^208Pb. New instrumentation for the focal plane of SASSYER under development at WNSL at Yale will replace the previous equipment with a compact chamber for double-sided silicon detectors (DSSD). Here we are reporting on improvements of the focal plane of SASSYER, including DSSD electronics, a detector cooling system, and ion optics tests. MUX-16 boards from MESYTEC, 16 channel multiplexed amplifiers, were tested and quantified. An alcohol cooling system, related to the DSSD, was characterized. The ion optics tests extracted effective magnetic rigidities of the separator. Results of the tests will be presented. This work was supported by the NSF grant PHY 0555665, Jeffress Fund J-809, and USDOE grant DE-FG02-91ER-40609.

Crump, Danielle; Heinz, Andreas; Winkler, Ryan; Frank, Daniel; Qian, Jing; Fetea, Mirela

2007-10-01

149

Focal cortical dysplasia – review  

PubMed Central

Summary Focal cortical dysplasia is a malformation of cortical development, which is the most common cause of medically refractory epilepsy in the pediatric population and the second/third most common etiology of medically intractable seizures in adults. Both genetic and acquired factors are involved in the pathogenesis of cortical dysplasia. Numerous classifications of the complex structural abnormalities of focal cortical dysplasia have been proposed – from Taylor et al. in 1971 to the last modification of Palmini classification made by Blumcke in 2011. In general, three types of cortical dysplasia are recognized. Type I focal cortical dysplasia with mild symptomatic expression and late onset, is more often seen in adults, with changes present in the temporal lobe. Clinical symptoms are more severe in type II of cortical dysplasia usually seen in children. In this type, more extensive changes occur outside the temporal lobe with predilection for the frontal lobes. New type III is one of the above dysplasias with associated another principal lesion as hippocampal sclerosis, tumor, vascular malformation or acquired pathology during early life. Brain MRI imaging shows abnormalities in the majority of type II dysplasias and in only some of type I cortical dysplasias. The most common findings on MRI imaging include: focal cortical thickening or thinning, areas of focal brain atrophy, blurring of the gray-white junction, increased signal on T2- and FLAIR-weighted images in the gray and subcortical white matter often tapering toward the ventricle. On the basis of the MRI findings, it is possible to differentiate between type I and type II cortical dysplasia. A complete resection of the epileptogenic zone is required for seizure-free life. MRI imaging is very helpful to identify those patients who are likely to benefit from surgical treatment in a group of patients with drug-resistant epilepsy. However, in type I cortical dysplasia, MR imaging is often normal, and also in both types the lesion seen on MRI may be smaller than the seizure-generating region seen in the EEG. The abnormalities may also involve vital for life brain parts, where curative surgery will not be an option. Therefore, other diagnostic imaging techniques such as FDG PET, MEG, DTI and intra-cranial EEG are widely used to establish the diagnosis and to decide on management. With advances in both genetics and neuroimaging, we may develop a better understanding of patients with drug-resistant epilepsy, which will help us to provide more successful pharmacological and/or surgical treatment in the future. PMID:22844307

Kabat, Joanna; Król, Przemys?aw

2012-01-01

150

Measuring Length  

NSDL National Science Digital Library

This article focuses on young students encountering the measurement of length. The article cites examples of key concepts in recognizing length as an attribute and in proper and improper ways to measure length. Conservation and additivity of length, standard and non-standard units, iteration, and the zero point are among the topics presented.

2009-08-01

151

Arbitrary micropatterning method in femtosecond laser microprocessing using diffractive optical elements  

Microsoft Academic Search

We successfully developed an arbitrary micro-patterning method with femtosecond pulses using a multi-level phase type diffractive optical element (DOE) and a focusing objective lens. The large chromatic dispersion effects of DOE resulting from the spectral bandwidth of femtosecond pulses can be reduced with the appropriate DOE focal length and the proper distance between the DOE and the focusing lens. The

Yutaka Kuroiwa; Nobuhito Takeshima; Yoshihiro Narita; Shuhei Tanaka; Kazuyuki Hirao

2004-01-01

152

A combined electron beam/optical lithography process step for the fabrication of sub-half-micron-gate-length MMIC chips  

NASA Technical Reports Server (NTRS)

Advanced radar and communication systems rely heavily on state-of-the-art microelectronics. Systems such as the phased-array radar require many transmit/receive (T/R) modules which are made up of many millimeter wave - microwave integrated circuits (MMIC's). The heart of a MMIC chip is the Gallium Arsenide (GaAs) field-effect transistor (FET). The transistor gate length is the critical feature that determines the operating frequency of the radar system. A smaller gate length will typically result in a higher frequency. In order to make a phased array radar system economically feasible, manufacturers must be capable of producing very large quantities of small-gate-length MMIC chips at a relatively low cost per chip. This requires the processing of a large number of wafers with a large number of chips per wafer, minimum processing time, and a very high chip yield. One of the bottlenecks in the fabrication of MIMIC chips is the transistor gate definition. The definition of sub-half-micron gates for GaAs-based field-effect transistors is generally performed by direct-write electron beam lithography (EBL). Because of the throughput limitations of EBL, the gate-layer fabrication is conventionally divided into two lithographic processes where EBL is used to generate the gate fingers and optical lithography is used to generate the large-area gate pads and interconnects. As a result, two complete sequences of resist application, exposure, development, metallization and lift-off are required for the entire gate structure. We have baselined a hybrid process, referred to as EBOL (electron beam/optical lithography), in which a single application of a multi-level resist is used for both exposures. The entire gate structure, (gate fingers, interconnects and pads), is then formed with a single metallization and lift-off process. The EBOL process thus retains the advantages of the high-resolution E-beam lithography and the high throughput of optical lithography while essentially eliminating an entire lithography/metallization/lift-off process sequence. This technique has been proven to be reliable for both trapezoidal and mushroom gates and has been successfully applied to metal-semiconductor and high-electron-mobility field-effect transistor (MESFET and HEMT) wafers containing devices with gate lengths down to 0.10 micron and 75 x 75 micron gate pads. The yields and throughput of these wafers have been very high with no loss in device performance. We will discuss the entire EBOL process technology including the multilayer resist structure, exposure conditions, process sensitivities, metal edge definition, device results, comparison to the standard gate-layer process, and its suitability for manufacturing.

Sewell, James S.; Bozada, Christopher A.

1994-01-01

153

Derivation of regional aerodynamic roughness length by combining optical remote sensing and ground measurements over agricultural land in Heihe River Basin  

NASA Astrophysics Data System (ADS)

Information of temporal and spatial variation of aerodynamic roughness length is required in most land surface models. The current research presents a practical approach for determining spatially distributed vegetation aerodynamic roughness length with fine temporal and spatial resolution by combining remote sensing and ground measurements. The basic framework of Raupach (1992), with the bulk surface parameters revised by Jasinski et al. (2005) has been applied to optical remote sensing data of HJ-1A/1B missions. In addition, a method for estimating regional scale vegetation height was introduced, so the aerodynamic roughness length, which is more preferred by users than the height normalized form has been developed. Direct validation on different vegetation classes have finally been performed taking advantage of the data-dense field experiments of Heihe Watershed Allied Telemetry Experimental Research (HiWATER). The roughness model had an overall good performance on most of Eddy Covariance sites of HiWATER. However, deviations still existed on different sites, and these have been further analyzed.

Chen, Qiting; Jia, Li; Hutjes, Ronald

2014-11-01

154

Demonstration of a Horseshoe-Shaped Longitudinal Focal Profile  

SciTech Connect

The three-dimensional laser focal region has been spatially shaped so that in the focal plane the transverse intensity distribution is centrally peaked, whereas at multiple defocused planes along the laser propagation direction, the distribution is annular. The longitudinal profile of such a shaped laser focal volume is approximately in the form of a “horseshoe.” The horseshoe-shaped longitudinal profile was realized experimentally from a single laser beam by the incoherent coaxial combination of Laguerre–Gaussian and Gaussian modes generated from segmented optical elements. The ponderomotive forces associated with this three-dimensional focal intensity distribution can potentially generate a quasi-collimated, forward-directed bunch of electrons from a low-density gas target at high laser intensities.

Brijesh, P.; Kessler, T.J.; Zuegel, J.D.; Meyerhofer, D.D.

2007-03-26

155

High performance optical materials cyclo olefin polymer ZEONEX  

NASA Astrophysics Data System (ADS)

ZEON CORPORATION developed innovative optical plastic Cyclo Olefin Polymer (COP), ZEONEX (R) with own technology in 1990 then started commercial production of ZEONEX (R) for optical applications with its very unique properties such as high light transmission, low birefringence, low water absorption, and high glass-transition temperature etc. ZEONEX (R) exhibits outstanding optical performance even under high humidity and temperature conditions. In order to meet increasing requirements of optical market, ZEON CORPORATION newly developed ZEONEX (R)F52R which has high glass-transition temperature 156 deg. C and shows the feature of very low focal length change after high-temperature and high-humidity test.

Obuchi, Kazuyuki; Komatsu, Masaaki; Minami, Koji

2007-09-01

156

Optical fiber imaging laser radar  

Microsoft Academic Search

We develop an optical fiber imaging laser radar based on the focal plane array detection method using a small number of detectors less than the number of the focal plane array resolution. For the development of this kind of the focal array detection method, we produce the optical fiber dissector, the movable aperture, and the small-number parallel multichannel pulse counter

Akira Akiyama; Yukiteru Kakimoto; Kazuhisa Kanda; Masahiro Kuwabara; Hiroyuki Yasuo; Eiichiro Mutoh; Hideo Kumagai; Takahiro Watanabe; Minoru Doshida; Hiromitsu Ishii

2005-01-01

157

Robust focusing optics for high-power laser welding  

NASA Astrophysics Data System (ADS)

As available power levels from both fiber and disc lasers rapidly increase, so does the need for more robust beam delivery solutions. Traditional transmissive optics for 1 micron lasers have proven to be problematic in the presence of higher power densities and are more susceptible to focal shift. A new, fully-reflective, optical solution has been developed using mirrors rather than lenses and windows to achieve the required stable focal spot, while still protecting the delicate fiber end. This patent-approved beam focusing solution, referred to as high power reflective focusing optic (HPRFO), involves specialty mirrors and a flowing gas orifice that prevents ingress of contaminants into the optically sensitive region of the assembly. These mirrors also provide a unique solution for increasing the distance between the sensitive optics and the contamination-filled region at the work, without sacrificing spot size. Longer focal lengths and lower power densities on large mass, water-cooled, copper mirrors deliver the robustness needed at increasingly high power levels. The HPRFO exhibits excellent beam quality and minimal focal shift at a fraction of commercially available optics, and has demonstrated consistent reliability on applications requiring 15 kW with prolonged beam-on times.

McAllister, Blake

2014-02-01

158

Standard Length versus Total Length  

Microsoft Academic Search

In an effort to determine the length measurement most representative of the bulk of the fish, the standard length and the total length were each compared with the weight of the fish. This comparison was made for four species of game fish, yellow perch (Perca flavescens), wall-eyed pike (Stizostedion v. vitreum), rock bass (Ambloplites rupestris), and lake trout (Cristivomer n.

William F. Royce

1942-01-01

159

Length scales and structural dynamics in nematogen pseudonematic domains measured with 2D IR vibrational echoes and optical Kerr effect experiments.  

PubMed

Nematogen liquids in the isotropic phase are macroscopically homogeneous but on multinanometer length scales have pseudonematic domains with correlation lengths that grow as the isotropic to nematic phase transition temperature (TNI) is approached from above. Orientational relaxation of nematogens in the isotropic phase manifests as two fast power laws and a slow exponential decay when measured by optical heterodyne detected optical Kerr effect (OHD-OKE) experiments. The long time exponential relaxation is associated with complete randomization of pseudonematic domains. We examine the effect of local orientational correlation on spectral diffusion (structural evolution) experienced by a vibrational probe molecule within the pseudonematic domains of 4-cyano-4'-pentylbiphenyl (5CB) using two-dimensional infrared (2D IR) vibrational echo spectroscopy. The addition of low concentration 4-pentyl-4'-thiocyanobiphenyl (5SCB) as a long-lived vibrational probe to 5CB is shown to lower TNI of the sample slightly, but the fast power law dynamics and exponential decays observed by OHD-OKE spectroscopy are unchanged. We compare the complete orientational relaxation and spectral diffusion for samples of 5SCB in 5CB to 5SCB in 4-pentylbiphenyl (5B) at four temperatures above TNI. 5B has a molecular structure similar to 5CB but is not a nematogen. At all but the lowest temperature, the spectral diffusion in 5CB and 5B is described well as a triexponential decay with very similar time constants. The results demonstrate that the presence of local orientational order at temperatures well above TNI does not affect the spectral diffusion (structural evolution) within pseudonematic domains when the correlation lengths are short. However, when the temperature of the sample is held very close to TNI, the spectral diffusion in 5CB slows dramatically while that in 5B does not. It is only as the correlation length becomes very long that its presence impacts the spectral diffusion (structural fluctuations) sensed by the vibrational probes located in pseudonematic domains. The orientational relaxation is modeled with schematic mode coupling theory (MCT). Fitting with MCT provides density and orientational correlation functions. The density correlation decays are similar for 5B and 5CB, but the orientational correlation decays are much slower for 5CB. Additionally, the time dependence of the spectral diffusion in 5CB is strikingly similar to that of the density correlation function decay, while the orientational correlation function decay is far too slow to contribute to the spectral diffusion. Therefore, density fluctuations are likely the source of spectral diffusion at temperatures at least 5 K above TNI. PMID:24521155

Sokolowsky, Kathleen P; Bailey, Heather E; Fayer, Michael D

2014-07-17

160

Focal plane scanner with reciprocating spatial window  

NASA Technical Reports Server (NTRS)

A focal plane scanner having a front objective lens, a spatial window for selectively passing a portion of the image therethrough, and a CCD array for receiving the passed portion of the image. All embodiments have a common feature whereby the spatial window and CCD array are mounted for simultaneous relative reciprocating movement with respect to the front objective lens, and the spatial window is mounted within the focal plane of the front objective. In a first embodiment, the spatial window is a slit and the CCD array is one-dimensional, and successive rows of the image in the focal plane of the front objective lens are passed to the CCD array by an image relay lens interposed between the slit and the CCD array. In a second embodiment, the spatial window is a slit, the CCD array is two-dimensional, and a prism-grating-prism optical spectrometer is interposed between the slit and the CCD array so as to cause the scanned row to be split into a plurality of spectral separations onto the CCD array. In a third embodiment, the CCD array is two-dimensional and the spatial window is a rectangular linear variable filter (LVF) window, so as to cause the scanned rows impinging on the LVF to be bandpass filtered into spectral components onto the CCD array through an image relay lens interposed between the LVF and the CCD array.

Mao, Chengye (Inventor)

2000-01-01

161

Jell-O Optics: Edibly Exploring Snell's Law and Optical Power  

NASA Astrophysics Data System (ADS)

This presentation details a laboratory exercise and/or demonstration of refraction with an inexpensive, simple set-up: a pan of Jell-O, protractors, and laser pointers. This activity is presented from the perspective of an optical sciences graduate student who has spent the school year team-teaching high school math and physics (through Academic Decathlon). The goal is to present some of the fundamentals of optics with an enjoyable and affordable approach. The concepts include Snell's law, index of refraction, and optical power/focal length as they relate to the curvature of a lens.

Hendryx, Jennifer; Reynolds, Mathias

2012-03-01

162

Focal nodular hyperplasia (FNH).  

PubMed

Focal nodular hyperplasia (FNH) is a benign tumour of the liver (hepatic tumour), which is the second most prevalent tumour of the liver (the first is hepatic hemangioma). It has a higher incidence in females, 20-40 years old, but also occurs in men and even in children. It is usually asymptomatic, rarely grows or bleeds, and has no malignant potential. This tumour was once often resected because it was difficult to distinguish from hepatic adenoma, but with modem multiphase imaging it is now diagnosed strictly by imaging criteria, and not resected. We present the case of a 78 years old man who presented to emergency room (ER) with a history of dry cough, chest pain and mild dyspnea. Chest X-ray showed ascension of the right hemidiaphragm, and a homogeneous round opacity of 6/6.2 cm in the right cardiophrenic angle. The first suspicion was of pulmonary tumor, but the final diagnosis was FNH, confirmed by CT scan. We discuss the differential diagnosis and prognosis of this entity. The particularities of the case are the presentation with respiratory symptoms and pulmonary mass, and the age of the patient. PMID:25000678

Nat, Laura; Poant?, Laura Irina

2014-01-01

163

Diffraction optics for terahertz waves  

NASA Astrophysics Data System (ADS)

Conventional lenses are important components for many terahertz applications, but ordinary lenses are very difficult to fabricate for short-focal lengths. Multi-level phase-corrected zoned lens antennas have been investigated with particular application at terahertz wavelengths. These zoned lenses (or diffractive optics) give better performance than ordinary lenses, and because of their planar construction are easier and cheaper to fabricate. The depths of cut needed for a grooved zone plate are quite small, even when materials with low dielectric constants are used. Zoned lenses have been built and tested at various frequencies from 100 GHz to 1.5 THz, with phase correction levels of half-wave, quarter-wave, or eighth-wavelength. The inherent losses in transparent materials increase monotonically over this frequency range. Typical low-loss materials include polystyrene, polyethylene, Teflon, polycarbonate, polystyrene foam, foamed polyethylene, low density polytetrafluoroethylene (PTFE), TPX, quartz, sapphire, and silicon. Low dielectric-constant materials are normally preferred to reduce reflection and attenuation losses. Techniques for cutting or milling the materials to small dimensions are important, because at 1.0 THz an eighth-wavelength correction for silicon is only 15 ?m. Another characteristic of zoned diffraction optics is their frequency behavior. Previous investigations have considered their bandwidth dependence and quasi-periodic extended frequency response for a specified focal length. As frequency changes, the focal point moves along the axis of the zoned lens. An analysis is given to explain this effect.

Wiltse, James C.

2004-09-01

164

Impact Of Focal Plane Technologies On IR System Design  

NASA Astrophysics Data System (ADS)

"Since the mid 1970's focal plane array technologies have been investigated to develop prototypes for a new generation of high sensitivity infra red equipements such as thermal imaging and surveillance systems and missile seekers. These technologies involve to use new design rules in the system conceptiontrade off between state of the art in detector and processing electronic technology, optics, cryogenic and mecanical constraints should be made. In this paper we develop our ideas on system design using focal plane arrays both in 3-5 microns and in 8-10 microns wavelength ranges : focal plane architectural design (scanning versus starring), new optical concept to reduce the backround photon flux, frame averager, digital or analog signal processing in image restoration. Some examples based on our experiences in this field are given".

Chatard, J. P.; Sirieix, M.

1983-11-01

165

Ladybug Lengths  

NSDL National Science Digital Library

This lesson introduces students to the measurable attribute of length and provides practice in measuring length using non-standard units. The lesson is launched using the story Ladybug on the Move by Richard Fowler. Lesson objectives, teaching ideas, and handouts are included.

2012-01-01

166

First results from the ground calibration of the NuSTAR flight optics  

Microsoft Academic Search

NuSTAR is a hard X-ray satellite experiment to be launched in 2012. Two optics with 10.15 m focal length focus Xrays with energies between 5 and 80 keV onto CdZnTe detectors located at the end of a deployable mast. The FM1 and FM2 flight optics were built at the same time based on the same design and with very similar

Jason E. Koglin; Hongjun An; Nicolas Barrière; Nicolai F. Brejnholt; Finn E. Christensen; William W. Craig; Charles J. Hailey; Anders Clemen Jakobsen; Kristin K. Madsen; Kaya Mori; Melania Nynka; Monica Fernandez-Perea; Michael J. Pivovaroff; Andrew Ptak; Clio Sleator; Doug Thornhill; Julia K. Vogel; Daniel R. Wik; William W. Zhang

2011-01-01

167

Focal Myositis of Unilateral Leg  

PubMed Central

Focal myositis is a rare, benign inflammatory pseudotumor of the skeletal muscle of unknown etiology. In Korea, there is no case report of focal myositis, which is not combined with connective tissue disease. We present an unusual case of focal myositis with ankle contracture, involving more than two muscles. A 26-year-old man visited our clinic complaining of right ankle contracture and leg muscle pain. Physical examination revealed no muscle weakness or any other neurological abnormality. T2-weighted magnetic resonance imaging of the right leg demonstrated diffuse high signal intensity of the right gastrocnemius, flexor digitorum longus, and tibialis anterior muscles. Needle electromyography showed profuse denervation potentials with motor unit action potentials of short duration and small amplitude from the involved muscles. All these findings suggested a diagnosis of focal inflammatory myositis and the patient was put under oral prednisolone and physical therapy. PMID:22506226

Jun, Jin; Im, Sun; Park, Joo Hyun; Yoo, Soon Hei

2011-01-01

168

Statistical Earthquake Focal Mechanism Forecasts  

NASA Astrophysics Data System (ADS)

The new whole Earth focal mechanism forecast, based on the GCMT catalog, has been created. In the present forecast, the sum of normalized seismic moment tensors within 1000 km radius is calculated and the P- and T-axes for the focal mechanism are evaluated on the basis of the sum. Simultaneously we calculate an average rotation angle between the forecasted mechanism and all the surrounding mechanisms. This average angle shows tectonic complexity of a region and indicates the accuracy of the prediction. The method was originally proposed by Kagan and Jackson (1994, JGR). Recent interest by CSEP and GEM has motivated some improvements, particularly to extend the previous forecast to polar and near-polar regions. The major problem in extending the forecast is the focal mechanism calculation on a spherical surface. In the previous forecast as our average focal mechanism was computed, it was assumed that longitude lines are approximately parallel within 1000 km radius. This is largely accurate in the equatorial and near-equatorial areas. However, when one approaches the 75 degree latitude, the longitude lines are no longer parallel: the bearing (azimuthal) difference at points separated by 1000 km reach about 35 degrees. In most situations a forecast point where we calculate an average focal mechanism is surrounded by earthquakes, so a bias should not be strong due to the difference effect cancellation. But if we move into polar regions, the bearing difference could approach 180 degrees. In a modified program focal mechanisms have been projected on a plane tangent to a sphere at a forecast point. New longitude axes which are parallel in the tangent plane are corrected for the bearing difference. A comparison with the old 75S-75N forecast shows that in equatorial regions the forecasted focal mechanisms are almost the same, and the difference in the forecasted focal mechanisms rotation angle is close to zero. However, though the forecasted focal mechanisms are similar, closer to the 75 latitude degree, the difference in the rotation angle is large (around a factor 1.5 in some places). The Gamma-index was calculated for the average focal mechanism moment. A non-zero Index indicates that earthquake focal mechanisms around the forecast point have different orientations. Thus deformation complexity displays itself in the average rotation angle and in the Index. However, sometimes the rotation angle is close to zero, whereas the Index is large, testifying to a large CLVD presence. Both new 0.5x0.5 and 0.1x0.1 degree forecasts are posted at http://eq.ess.ucla.edu/~kagan/glob_gcmt_index.html.

Kagan, Y. Y.; Jackson, D. D.

2013-12-01

169

NbN hot-electron bolometer receivers and focal plane arrays for the terahertz range  

Microsoft Academic Search

The next generation of hot electron bolometric (HEB) mixer receivers for terahertz frequencies is under development. In order to improve sensitivity and integration time, terahertz focal plane arrays with HEB elements are required. We have designed, fabricated, and tested a three-element focal plane array with HEB devices. We implemented a quasi-optical power coupling scheme using three elliptical silicon lenses. Recently

Sigfrid Yngvesson; Eyal Gerecht; Fernando Rodriguez-Morales; John Nicholson; Dazhen Gu; Richard Zannoni; Xin Zhao; Thomas Goyette; William Gorveatt; Jason Dickinson; Jerry Waldman

2004-01-01

170

Variable focal lens controlled by an external voltage: An application of electrowetting  

NASA Astrophysics Data System (ADS)

We use electrocapillarity in order to change the contact angle of a transparent drop, thus realizing a lens of variable focal length (B. Berge, J. Peseux, Patent deposited in Grenoble France, October 8th 1997, numéro d'enregistrement national 97 12781). The key point is the application of gradients of wettability, which control the shape of the drop edge, in our case a centered circle of variable radius. The quality and reversibility of the lens are surprisingly good. The optical power variation can be 5 to 10 times the one of the human eye, for a comparable diameter, with a typical response time of 0.03 s and a dissipated power of a few mW.

Berge, B.; Peseux, J.

2000-10-01

171

Measuring Length  

NSDL National Science Digital Library

Practice measuring length. Play this fun game to work on length. Measure the teddy Next, practice measuring to the nearest 1/2 inch. Measure to 1/2 inches If your ready for a challenge, practice this next game: Measure to 1/4 inches Play the Fish Tales game! *Once you have played all the games, have an adult sign your planner that you practiced these games! You'll ...

Miss Lerdahl

2010-01-26

172

Optical modeling for a two-stage parabolic trough concentrating photovoltaic\\/thermal system using spectral beam splitting technology  

Microsoft Academic Search

A two-stage parabolic trough concentrating photovoltaic\\/thermal (PV\\/T) system is described, which contains a concentrator, a spectral beam splitting filter, an evacuated collector tube and the solar cell components. The nondimensional optical model with the focal length of the concentrator as the characteristic length has been developed to analyze the properties of the concentrating system using the beam splitting filter. The

Shouli Jiang; Peng Hu; Songping Mo; Zeshao Chen

2010-01-01

173

An Optical Wavefront Sensor Based on a Double Layer Microlens Array  

PubMed Central

In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA) to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS) above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin), the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution. PMID:22346643

Lin, Vinna; Wei, Hsiang-Chun; Hsieh, Hsin-Ta; Su, Guo-Dung John

2011-01-01

174

Determination of carrier lifetime and diffusion length in Al-doped 4H–SiC epilayers by time-resolved optical techniques  

NASA Astrophysics Data System (ADS)

A series of p-type 4H–SiC epilayers with aluminium concentration ranging from 2? × ?1016 to 8? × ?1019?cm?3 were investigated by time-resolved optical techniques in order to determine the effect of aluminium doping on high-injection carrier lifetime at room temperature and the diffusion coefficient at different injections (from ?3? × ?1018 to ?5? × ?1019?cm?3) and temperatures (from 78 to 730?K). We find that the defect limited carrier lifetime ?SRH decreases from 20?ns in the low-doped samples down to ?0.6?ns in the heavily doped epilayers. Accordingly, the ambipolar diffusion coefficient decreases from Da = 3.5?cm2?s?1 down to ?0.6?cm2?s?1, corresponding to the hole mobility of µh = 70?cm2?Vs?1 and 12?cm2?Vs?1, respectively. In the highly doped epilayers, the injection-induced decrease of the diffusion coefficient, due to the transition from the minority carrier diffusion to the ambipolar diffusion, provided the electron diffusion coefficient of De ? 3?cm2?s?1. The Al-doping resulted in the gradual decrease of the ambipolar diffusion length, from LD = 2.7?µm down to LD = 0.25?µm in the epilayers with the lowest and highest aluminium concentrations.

Liaugaudas, Gediminas; Dargis, Donatas; Kwasnicki, Pawel; Arvinte, Roxana; Zielinski, Marcin; Jaraši?nas, K?stutis

2015-01-01

175

Math Focal Points: Grade 7  

NSDL National Science Digital Library

In this wiki page, Math Focal Points: Grade 7, the third of the Middle School Portal series, it offers resources that support the teaching of the three areas of emphasis highlighted for seventh-grade learners. The three focal points and the related sections of resources are apply proportionality, including scale factor, percentage, and unit rate problems. Wiki pages in the section titled ratio and proportion deal with real-world situations, such as finding percentages and building scale models, as well as online scenarios that help students visualize the mathematical concepts involved.

2008-05-01

176

ORFEUS focal plane instrumentation: The Berkeley spectrometer  

NASA Technical Reports Server (NTRS)

A spectrograph for the ORFEUS mission that incorporates four varied line-space, spherically figured diffraction gratings was designed. The ORFEUS, a 1-m normal incidence telescope is equipped with 2 focal plane spectrographs. The Berkeley spectrograph was developed with an optimizing raytracing computer code. Each grating accepts the light from 20 percent of the aperture of the telescope primary mirror and has a unique set of characteristics to cover a sub-bandpass within the 390 to 1200 A spectral range. Two photon-counting detectors incorporating a time delay readout system are used to record the spectra from all four gratings simultaneously. The nominal design achieves a spectral resolution (FWHM) in excess of 5500 at all wavelengths within the bandpass. The resolution is limited primarily by the detector spatial resolution. The 1 sigma astigmatism of this design varies between 13 and 150 micrometer on the same focal surface. An independent, direct imaging system tracks the drift of the target within the spectrometer aperture and allows measurement of the misalignment between the telescope optical axis and that of the external star tracker. The resolution and astigmatism achievable with this design are superior to those of a standard Rowland spectrograph designed with the same constraints.

Hurwitz, Mark; Bowyer, Stuart

1988-01-01

177

Focal process of the great Chilean earthquake May 22, 1960  

Microsoft Academic Search

Long-period strain seismogram recorded at Pasadena is used to determine the focal process of the 1960 Chilean earthquake. Synthetic seismograms computed for various fault models are matched with the observed strain seismogram to determine the fault parameters. A low-angle (~ 10°) thrust model with rupture length of 800 km and rupture velocity of 3.5 km\\/sec is consistent with the observed

Hiroo Kanamori; John J. Cipar

1974-01-01

178

Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host.  

PubMed

In the second of a three-part series, spectral absorption behavior of nonlinear optical (NLO) dyes incorporated into amorphous polycarbonate, comprised of a homologous series of dialkyl spacer groups extending from the midsection of the dye molecule, is characterized by UV-Vis and photothermal deflection spectroscopy. The dyes are structural analogs of the NLO dye FTC [2-(3-cyano-4-{2-[5-(2-{4-[ethyl-(2-methoxyethyl)amino]phenyl}vinyl)-3,4-diethylthiophen-2-yl]vinyl}-5,5-dimethyl-5H-furan-2-ylidene)malononitrile]. Previous Monte Carlo calculations [B. H. Robinson and L. R. Dalton, J. Phys. Chem. A 104, 4785 (2000)] predict a strong dependence of the macroscopic nonlinear optical susceptibility on the chromophore waist: length aspect ratio in electric-field-poled films arising from interactions between chromophores. It is expected that these interactions will play a role in the absorption characteristics of unpoled films, as well. The spacer groups range in length from diethyl to dihexyl, and each dye is studied over a wide range of concentrations. Among the four dyes studied, a universal dependence of near-IR loss on inhomogeneous broadening of the dye main absorption peak is found. The inhomogeneous width and its concentration dependence are seen to vary with spacer length in a manner characteristic of the near-IR loss-concentration slope at transmission wavelengths of 1.06 and 1.3 mum, but not at 1.55 mum. The lower wavelength loss behavior is assigned to purely Gaussian broadening, and is described by classical mixing thermodynamic quantities based on the Marcus theory of inhomogeneous broadening [R. A. Marcus, J. Chem. Phys. 43, 1261 (1965)], modeled as a convolution of dye-dye dipole broadening and dye-polymer van der Waals broadening. The Gaussian dipole interactions follow a Loring dipole-broadening description [R. F. Loring, J. Phys. Chem. 94, 513 (1990)] dominated by the excited-state dipole moment, and have a correlated homogeneous broadening contribution. The long-wavelength loss behavior has a non-Gaussian dye-dye dipole contribution which follows Kador's broadening analysis [L. Kador, J. Chem. Phys. 95, 5574 (1991)], with a net broadening described by a convolution of this term with a Gaussian van der Waals interaction given by Obata et al. [M. Obata, S. Machida, and K. Horie, J. Polym. Sci. B 37, 2173 (1999)], with each term governed by the dye spacer length. A minimum in broadening and loss-concentration slope at a spacer length of four carbons per alkyl at all wavelengths has important consequences for practical waveguide devices, and is of higher aspect ratio than the spherical limit shown by Robinson and Dalton to minimize dipole interactions under a poling field. PMID:16008487

Barto, Richard R; Frank, Curtis W; Bedworth, Peter V; Ermer, Susan; Taylor, Rebecca E

2005-06-15

179

Demonstration Telescopes Using "Dollar Optics"  

NASA Astrophysics Data System (ADS)

I propose a poster that illustrates the use of "dollar optics” for experimentation and for the creation of demonstration telescopes. Handling a variety of lenses and mirrors provides an opportunity for discovering practical optics. Some part of this path of exploration must have been traveled by Galileo as he experimented with spectacle lenses. "Dollar optics” include reading glasses (positive meniscus lenses), convex and concave mirrors, Fresnel sheets, magnifying lenses, and eye loupes. Unwanted distance spectacles (negative meniscus lenses) are available at second-hand stores. Galileo telescopes, "long” 17th century telescopes, and useful demonstration models of Newtonian reflectors can be made with "dollar” optics. The poster will illustrate practical information about "dollar optics” and telescopes: magnification, focal length, and "diopters” disassembling spectacles; creating cheap mounts for spectacle lenses; the importance of optical axes and alignment; eyepieces; and focusing. (A table would be useful with the poster to set out a hands-on display of "dollar optic” telescopes.) Educators, experimenters, and those concerned with astronomy outreach might be interested in this poster. Working with "dollar optics” requires facility with simple tools, interest in planning projects, patience, imagination, and the willingness to invest some time and effort. "Dollar optics” may help to foster creativity and hands-on enthusiasm - as did Galileo's work with simple lenses 400 years ago. "Oh! When will there be an end put to the new observations and discoveries of this admirable instrument?” - Galileo Galilei as quoted by Henry C. King, The History of the Telescope.

Ross, Paul

2008-05-01

180

Development of a Long-Focal-Range Annular Array Ultrasonic Transducer  

NASA Astrophysics Data System (ADS)

Conventional annular array transducers designed with Fresnel divided elements have a limited maximum size of the aperture of the transducer. In this study, we designed and fabricated a prototype of a large-aperture annular array transducer to inspect next-generation semiconductors. A new annular array pattern was designed with a wide focal range and a large focal length using equal areas for the inner elements and equal stroke widths for the outer elements. The prototype was fabricated by epoxy bonding with a patterned metal electrode on a flexible printed circuit and a piezoelectric copolymer. As a result of evaluation, we obtained a fine spatial resolution below 100 µm and a narrow relative sensitivity variation of 6.5 dB for a large focal length and a wide focal range from 10 to 30 mm.

Korai, Yusuke; Baba, Atsushi

2012-07-01

181

[Focal liver lesion, incidental finding].  

PubMed

The differential diagnosis of incidentally found Focal Liver Lesions (FLL) is complex. Screening procedures so far are only defined for patients with liver cirrhosis. Characterization of a FLL begins as soon as it is detected. Taking patients history and thorough clinical examination are essential. An imaging procedure that is used to detect liver masses should also allow the examiner to determine whether the lesion is benign or malignant. Conventional B-mode US and colour Doppler imaging are effective at detecting and characterizing typical liver cysts and calcifications. Laboratory data, computed tomography, magnetic resonance imaging and imaging guided liver biopsy are complementary methods.Contrast Enhanced Ultrasound (CEUS) is a well established diagnostic imaging technique for a variety of indications and applications. One of the most important applications is in the liver where it is frequently a first-line technique for the detection and diagnosis (characterization) of focal liver lesions (FLL). In this setting the accurate differentiation of benign from malignant lesions is critical to ensure the patient undergoes the appropriate therapeutic option. This has been documented in recently published guidelines, in particular in terms of the enhancement patterns of the most common FLL hemangioma, focal nodular hyperplasia hepatocellular adenoma and their differentiation from malignant lesions. In this article the role of CEUS in the characterization of incidentally found FLL is described. PMID:23033169

Dietrich, C F; Jenssen, C

2012-10-01

182

Accurate cell counts in live mouse embryos using optical quadrature and differential interference contrast microscopy  

NASA Astrophysics Data System (ADS)

Present imaging techniques used in in vitro fertilization (IVF) clinics are unable to produce accurate cell counts in developing embryos past the eight-cell stage. We have developed a method that has produced accurate cell counts in live mouse embryos ranging from 13-25 cells by combining Differential Interference Contrast (DIC) and Optical Quadrature Microscopy. Optical Quadrature Microscopy is an interferometric imaging modality that measures the amplitude and phase of the signal beam that travels through the embryo. The phase is transformed into an image of optical path length difference, which is used to determine the maximum optical path length deviation of a single cell. DIC microscopy gives distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a single cell in the DIC image and combining it with the maximum optical path length deviation of a single cell creates an ellipsoidal model cell of optical path length deviation. Subtracting the model cell from the Optical Quadrature image will either show the optical path length deviation of the culture medium or reveal another cell underneath. Once all the boundaries are used in the DIC image, the subtracted Optical Quadrature image is analyzed to determine the cell boundaries of the remaining cells. The final cell count is produced when no more cells can be subtracted. We have produced exact cell counts on 5 samples, which have been validated by Epi-Fluorescence images of Hoechst stained nuclei.

Warger, William C., II; Newmark, Judith A.; Zhao, Bing; Warner, Carol M.; DiMarzio, Charles A.

2006-02-01

183

Mechanical properties of individual focal adhesions probed with a magnetic microneedle.  

PubMed

A permanent magnetic microneedle was developed to apply tensional forces to integrin receptors via ligand-coated magnetic microbeads while optically analyzing the mechanical properties of individual focal adhesions. Force application (130 pN for 3 s) through activated beta1 integrins produced less bead displacement than when unligated integrins were stressed. This strengthening response differed markedly on a bead-by-bead basis, correlated directly with local focal adhesion assembly, and was similar when analyzed at 4 degrees C, indicating that it was due to passive material properties of the cell. Viscoelastic analysis clarified that recruitment of focal adhesion proteins increased the local elastic stiffness of the adhesion complex without changing its viscous behavior. These data indicate that individual focal adhesions exhibit distinct mechanical properties that depend upon local focal adhesion assembly, and that these local variations in micromechanics can be detected and analyzed within living cells using the permanent magnetic microneedle technique. PMID:14697256

Matthews, Benjamin D; Overby, Darryl R; Alenghat, Francis J; Karavitis, John; Numaguchi, Yasuchi; Allen, Philip G; Ingber, Donald E

2004-01-16

184

Focal shift in spatial-variant polarized vector Bessel-Gauss beams  

NASA Astrophysics Data System (ADS)

The three dimensional intensity distribution of focused spatial-variant polarized vector Bessel-Gauss beams is investigated in the vicinity of the focal plane by using the Richards-Wolf vectorial diffraction method. The local polarized states of the incident beams vary between linearity and ellipse, and can be easily controlled in real time by a new parameter, namely the phase delay angle, which is introduced by a liquid crystal variable retarder. Our analysis proves the existence of a focal shift toward the focusing objective for this type of beam. The dependence of the focal shift on the different parameters of the beams is discussed in detail. Numerical results indicate that the magnitude of the focal shift is associated with the mode number, the local polarization, the beam width and the wavelength of the incident beams. The controllability of the focal shift indirectly caused by the phase delay angle will have great potential applications in optical micro-manipulation.

Yang, Yanfang; Leng, Mei; He, Ying; Liu, Haigang; Chang, Qiang; Li, Chunfang

2013-01-01

185

Focal fibrous hyperplasia: A review of 193 cases  

PubMed Central

Context: Focal fibrous hyperplasia, also known as irritation or traumatic fibroma, is a reactive, inflammatory hyperplastic lesion of the connective tissue. Aim: The aim of this study is to perform a retrospective study of a focal fibrous hyperplasia of 18 years. Materials and Methods: We retrospectively reviewed 193 cases of focal fibrous hyperplasia of the oral cavity from the medical and histological reports of the Department of Oral Pathology, Pernambuco University, Brazil, during the period between January 1992 and December 2009. Settings and Design: Data with regard to age, gender, location, size of the lesion (equal to or less than 1 cm, between 1 and 2 cm and greater than 2 cm), pain, history of trauma, treatment, length of follow-up (from diagnosis to release or last review) and recurrence, were collected. Results: The most commonly affected site was the buccal mucosa (n = 119, 61.7%). Almost two-thirds of the cases were concentrated from the second to the fifth decade of life. Females were more affected than men and a history of trauma was related by 90.7% of the patients. Two recurrences were notified (1.0%). Conclusion: Further studies are needed on the distribution of the lesion in different ethnic and geographical populations. The influence of sex hormones on the development of focal fibrous hyperplasia must be clarified. PMID:25364187

de Santana Santos, Thiago; Martins-Filho, Paulo Ricardo Saquete; Piva, Marta Rabello; de Souza Andrade, Emanuel Sávio

2014-01-01

186

The Camera for LSST and its Focal Plane Array  

NASA Astrophysics Data System (ADS)

Optically fed by LSST's fast and wide-field optics, the camera has a 9.6 square degree FOV in a 3.2 Gigapixel focal plane array. The focal plane is tiled by 189 4Kx4K CCD science sensors with 10?m (0.2 arcsec) pixels and also houses four diagnostic ("corner raft") packages that provide guide- and wavefront-sensors at opposing sides of the field. The focal plane array is highly modular and features a parallelized readout scheme, allowing the entire array to be read in 2 seconds. Dedicated front- and back-end electronics boards housed within the cryostat vacuum vessel operate sensors in raft groups (3x3 sensors; 144 data channels) while mechanically identical "rafts” are precision-mounted on a rigid silicon carbide grid structure. Three large, refractive lens elements act as the optical system's corrector (the third, L3, provides the vacuum barrier for the cryostat), and one of six possible band-pass filters is positioned in the beam at any given time. Mechanisms within the camera include a mechanical shutter and a carousel filter changer assembly. The camera control system manages all aspects of camera operation including image capture, thermal monitoring and control, vacuum control, filter changes, and communication with the observatory control system. The data acquisition system records and pre-processes raw images, provides up to 3 days of storage capacity, and provides very high throughput data transfer to downstream data management.

Rasmussen, Andrew; Gilmore, K.; Kahn, S. M.; Geary, J.; Marshall, S.; Nordby, M.; O'Connor, P.; Olivier, S.; Oliver, J.; Radeka, V.; Schalk, T.; Schindler, R.; Tyson, J.; Van Berg, R.; LSST Camera Team

2010-01-01

187

Holographic Optical Elements as Scanning Lidar Telescopes  

NASA Technical Reports Server (NTRS)

We have developed and investigated the use of holographic optical elements (HOEs) and holographic transmission gratings for scanning lidar telescopes. For example, rotating a flat HOE in its own plane with the focal spot on the rotation axis makes a very simple and compact conical scanning telescope. We developed and tested transmission and reflection HOEs for use at the first three harmonic wavelengths of Nd:YAG lasers. The diffraction efficiency, diffraction angle, focal length, focal spot size and optical losses were measured for several HOEs and holographic gratings, and found to be suitable for use as lidar receiver telescopes, and in many cases could also serve as the final collimating and beam steering optic for the laser transmitter. Two lidar systems based on this technology have been designed, built, and successfully tested in atmospheric science applications. This technology will enable future spaceborne lidar missions by significantly lowering the size, weight, power requirement and cost of a large aperture, narrow field of view scanning telescope.

Schwemmer, Geary K.; Rallison, Richard D.; Wilkerson, Thomas D.; Guerra, David V.

2005-01-01

188

Geometrical parameter analysis of the high sensitivity fiber optic angular displacement sensor  

E-print Network

In this work, we present an analysis of the influence of the geometrical parameters on the sensitivity and linear range of the fiber optic angular displacement sensor, through computational simulations and experiments. The geometrical parameters analyzed were the lens focal length, the gap between fibers, the fibers cladding radii, the emitting fiber critical angle (or, equivalently, the emitting fiber numerical aperture), and the standoff distance (distance between the lens and the reflective surface). Besides, we analyzed the sensor sensitivity regarding any spurious linear displacement. The simulation and experimental results showed that the parameters which play the most important roles are the emitting fiber core radius, the lens focal length, and the light coupling efficiency, while the remaining parameters have little influence on sensor characteristics. This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the fo...

Sakamoto, João M S; Kitano, Cláudio; Tittmann, Bernhard R

2015-01-01

189

Fish Tank Optics.  

ERIC Educational Resources Information Center

Describes procedures for a demonstration of the focal length of spherical lenses and mirrors using an aquarium, a flashlight, and nondairy creamer. Enables nonquantitative three-dimensional observation of these phenomena. (DDR)

McCausland, Stuart; Allard, Brian

1997-01-01

190

Focusing and imaging of a virtual all-optical tunable terahertz Fresnel zone plate.  

PubMed

A virtual all-optical tunable terahertz Fresnel zone plate is achieved utilizing the localized distribution of the transient electron plasma on a silicon wafer. Its focusing and imaging performance are experimentally demonstrated. Experimental results show that the effect of the virtual zone plate is the same as an actual one. Adjusting the spatial pattern of the electron plasma, the central wavelength and the focal length of the virtual zone plate can be all-optically dynamically steered. The research is a significant step to the development of tunable optical imaging elements. PMID:24322118

Wang, Xinke; Xie, Zhenwei; Sun, Wenfeng; Feng, Shengfei; Cui, Ye; Ye, Jiasheng; Zhang, Yan

2013-11-15

191

Acousto-optic infrared spectral imager for Pluto fast flyby  

NASA Technical Reports Server (NTRS)

Acousto-optic tunable filters (AOTF's) enable the design of compact, two-dimensional imaging spectrometers with high spectral and spatial resolution and with no moving parts. Tellurium dioxide AOTF's operate from about 400 nm to nearly 5 microns, and a single device will tune continuously over one octave by changing the RF acoustic frequency applied to the device. An infrared (1.2-2.5 micron) Acousto-Optic Imaging Spectrometer (AImS) was designed that closely conforms to the surface composition mapping objectives of the Pluto Fast Flyby. It features a 75-cm focal length telescope, infrared AOTF, and 256 x 256 NICMOS-3 focal plane array for acquiring narrowband images with a spectral resolving power (lambda/delta(lambda)) exceeding 250. We summarize the instrument design features and its expected performance at the Pluto-Charon encounter.

Glenar, D. A.; Hillman, J. J.

1993-01-01

192

SNAP Satellite Focal Plane Development  

SciTech Connect

The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.

Bebek, C.; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, S.; Bercovitz, J.; Bergstrom, L.; Berstein, G.P.; Bester, M.; Bohlin, R.; Bonissent, A.; Bower, C.; Campbell, M.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Ellis, R.; Emmett, W.; Eriksson, M.; Fouchez,D.; Fruchter, A.; Genat, J-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Heetderks, H.; Holland, S.; Huterer, D.; Johnson, W.; Kadel, R.; Karcher,A.; Kim, A.; Kolbe, W.; Lafever, R.; Lamoureaux, J.; Lampton, M.; Lefevre, O.; Levi, M.; Levin, D.; Linder, E.; Loken, S.; Malina, R.; Mazure, A.; McKay, T.; McKee, S.; Miquel, R.; Morgan, N.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Roe, N.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Prieto, E.; Rabinowitz,D.; Refregier, A.; Rhodes, J.; Schubnell, M.; Sholl, M.; Smadja, G.; Smith, R.; Smoot, G.; Snyder, J.; Spadafora, A.; Szymkowiak, A.; Tarle,G.; Taylor, K.; Tilquin, A.; Tomasch, A.; Vincent, D.; von der Lippe, H.; Walder, J-P.; Wang, G.

2003-07-07

193

Coherence Length for a Trapped Bose Gas  

Microsoft Academic Search

Matter waves can be assigned a coherence length analogous to the corresponding quantity in optics. We show that there is a dramatic increase in coherence length associated with the appearance of Bose-Einstein condensation in a trapped ideal Bose gas. The large increase in coherence length occurs even for temperatures just below the critical temperature at which only a small proportion

Stephen M. Barnett; Sonja Franke-Arnold; Aidan S. Arnold; Colin Baxter

194

Focal angioplasty: theory and clinical application.  

PubMed

Percutaneous transluminal coronary angioplasty (PTCA) has been performed with 20 mm long uni-diameter balloons for over 17 years with excellent results. It has now become possible to combine both compliant and non-compliant balloon material on a single device, allowing the interventionalist to direct the force of dilation to the lesion focally. This concept has been termed "focal angioplasty." This article reviews the concept of focal angioplasty, including the physics of balloon dilation, and describes current clinical applications for focal angioplasty. We discuss use of the focal angioplasty technique for PTCA and stenting and review the results of several ongoing clinical trials. While the acute results using focal angioplasty have been promising, long-term benefits have not been fully studied and will require completion of ongoing trials. PMID:9408636

Hodgson, J M

1997-12-01

195

Rapid, Accurate, and Non-Invasive Measurement of Zebrafish Axial Length and Other Eye Dimensions Using SD-OCT Allows Longitudinal Analysis of Myopia and Emmetropization  

PubMed Central

Refractive errors in vision can be caused by aberrant axial length of the eye, irregular corneal shape, or lens abnormalities. Causes of eye length overgrowth include multiple genetic loci, and visual parameters. We evaluate zebrafish as a potential animal model for studies of the genetic, cellular, and signaling basis of emmetropization and myopia. Axial length and other eye dimensions of zebrafish were measured using spectral domain-optical coherence tomography (SD-OCT). We used ocular lens and body metrics to normalize and compare eye size and relative refractive error (difference between observed retinal radial length and controls) in wild-type and lrp2 zebrafish. Zebrafish were dark-reared to assess effects of visual deprivation on eye size. Two relative measurements, ocular axial length to body length and axial length to lens diameter, were found to accurately normalize comparisons of eye sizes between different sized fish (R2?=?0.9548, R2?=?0.9921). Ray-traced focal lengths of wild-type zebrafish lenses were equal to their retinal radii, while lrp2 eyes had longer retinal radii than focal lengths. Both genetic mutation (lrp2) and environmental manipulation (dark-rearing) caused elongated eye axes. lrp2 mutants had relative refractive errors of ?0.327 compared to wild-types, and dark-reared wild-type fish had relative refractive errors of ?0.132 compared to light-reared siblings. Therefore, zebrafish eye anatomy (axial length, lens radius, retinal radius) can be rapidly and accurately measured by SD-OCT, facilitating longitudinal studies of regulated eye growth and emmetropization. Specifically, genes homologous to human myopia candidates may be modified, inactivated or overexpressed in zebrafish, and myopia-sensitizing conditions used to probe gene-environment interactions. Our studies provide foundation for such investigations into genetic contributions that control eye size and impact refractive errors. PMID:25334040

Collery, Ross F.; Veth, Kerry N.; Dubis, Adam M.; Carroll, Joseph; Link, Brian A.

2014-01-01

196

Athermal design for infrared refractive, diffractive, reflective hybrid optical system  

NASA Astrophysics Data System (ADS)

Thermal properties and dispersive capacity of diffractive optical elements were expounded in this paper, and the conclusion that optothermal expansion coefficient of diffractive optical element is independent of refractive index of the material was derived. The design method to athermalize the hybrid infrared optical system was studied, a new hybrid system with diffractive surface was structured on the foundation of refractive/reflective optical system using optical design software ZEMAX, and the surface was simulated by MATLAB. The image quality was improved obviously compared with the one without diffractive surface. The system worked at 3.7~4.8?m band with its' effective focal length of 70mm, field of view of 2° and possessed better athermal performance in the temperature range -40°~+60°. The image quality achieved diffractive limit, besides, a compact structure, small volume and light weight were other advantages of the hybrid system.

Cheng, Ximin; Xie, Weimin; Bai, Yu; Jia, Xin; Xing, Tingwen

2014-09-01

197

Adaptive beam shaping by controlled thermal lensing in optical elements  

NASA Astrophysics Data System (ADS)

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained through dynamic heating of an optical element by an external pump beam. The system is especially suitable for use in interferometric gravitational wave interferometers employing high laser power, allowing for in situ control of the laser modal properties and compensation for thermal lensing of the primary laser. Using CO2 laser heating of fused-silica substrates, we demonstrate a focal length variable from infinity to 4.0 m, with a slope of 0.082 diopter/W of absorbed heat. For on-axis operation, no higher-order modes are introduced by the adaptive optical element. Theoretical modeling of the induced optical path change and predicted thermal lens agrees well with measurement.

Arain, Muzammil A.; Quetschke, Volker; Gleason, Joseph; Williams, Luke F.; Rakhmanov, Malik; Lee, Jinho; Cruz, Rachel J.; Mueller, Guido; Tanner, D. B.; Reitze, David. H.

2007-04-01

198

Signal processing on the focal plane array: an overview  

NASA Astrophysics Data System (ADS)

Raytheon's Infrared Operations (RIO) has invented and developed a new class of focal plane arrays; the Adaptive IR Sensor (AIRS) and Thinfilm Analog Image Processor (TAIP). The AIRS FPA is based upon biologically inspired on-focal- plane circuitry, which adaptively removes detector and optic temperature drift and l/f induced fixed pattern noise. This third-generation multimode IRFPA, also called a Smart FPA, is a 256x256-array format capable of operation in four modes: 1) Direct Injection (DI), 2) Adaptive Non-uniformity Correction (NUC), 3) Motion/Edge Detection, and 4) Subframe Averaging. Also the 320x240 TAIP results have shown excellent image processing in the form of Spatial and Temporal processing.

Graham, Roger W.; Trautfield, Walter C.; Taylor, Scott M.; Murray, Mark P.; Mesh, Frank J.; Horn, Stuart B.; Finch, James A.; Dang, Khoa V.; Caulfield, John T.

2000-12-01

199

Focal choroidal excavation associated with polypoidal choroidal vasculopathy.  

PubMed

A 48-year-old woman presented with blurred vision in her right eye for 6 weeks. Visual acuity was 20/300 and 20/25 in the right and left eyes, respectively. Fundus examination showed subretinal hemorrhage in the superonasal macula in the right eye, whereas the left eye was normal. Fluorescein angiography showed blocked fluorescence from hemorrhage and a round distinct hypofluorescent spot along the inferotemporal arcade. Indocyanine green angiography revealed hyperfluorescent tubular and aneurysmal dilatations consistent with polypoidal choroidal vasculopathy in the superior macula. Spectral-domain optical coherence tomography showed retinal pigment epithelial irregularities and detachment. Scans through the round area of hypofluorescence revealed a conforming focal choroidal excavation and thinning of the underlying choriocapillaries. Because the pathogenesis of focal choroidal excavation is currently unclear, the authors propose the possibility of an acquired etiology related to loss of choriocapillaries from perfusion abnormalities as evidenced here. PMID:23883536

Say, Emil Anthony T; Jani, Pooja D; Appenzeller, Matthew F; Houghton, Odette M

2013-01-01

200

Focal Molography: Coherent Microscopic Detection of Biomolecular Interaction  

NASA Astrophysics Data System (ADS)

We introduce and theoretically investigate here a novel analytical method that we have called focal molography, in which molecular interactions are made visible through scattering of coherent light by a coherent pattern of molecules. The scattered light quantifies the presence of molecules at molecular interaction sites. It is separated from noncoherent background scatter by a combination of local dark-field illumination, interference enhancement, and spatial filtering. The latter is achieved by holographic focusing of the wave field generated by the coherently assembled molecules onto an Airy disk and by subtraction of the noncoherent irradiance in the focal plane outside the disk from the irradiance in the disk. This new microscopic method allows distinct detection of low-refractive-index contrast in the nanoenvironment of biomolecules from which information on the interaction of the coherently assembled molecules with molecules in a liquid or gaseous sample may be deduced. The noncoherent surroundings of the coherently assembled molecules consist of freely diffusing solvent and solute molecules. The surroundings, as well as changes in temperature, do not contribute to the coherent signal in the diffraction focus. Interference lithography or high-resolution-imaging lithography can be used to synthesize the coherent pattern of molecules on a monolithic substrate. The coherent pattern of molecules constitutes a synthetic phase hologram that creates a diffraction-limited light wave. We suggest the term "mologram" for the coherent assembly of functional nanostructures and the term "focal molography" for label-free or labeled analysis of molecular interactions through the measurement of the properties of light in the focus of the mologram. We derive analytical formulas that express the detection signal and the sensitivity of focal molography on the surface of a high-refractive-index thin-film optical waveguide in terms of known parameters. We discuss the implementation of a readout system for molograms on a thin-film optical waveguide by adapting a confocal laser-scanning microscope to a bifocal laser-scanning microscope.

Fattinger, Christof

2014-07-01

201

Optimal focal-plane restoration  

NASA Technical Reports Server (NTRS)

Image restoration can be implemented efficiently by calculating the convolution of the digital image and a small kernel during image acquisition. Processing the image in the focal-plane in this way requires less computation than traditional Fourier-transform-based techniques such as the Wiener filter and constrained least-squares filter. Here, the values of the convolution kernel that yield the restoration with minimum expected mean-square error are determined using a frequency analysis of the end-to-end imaging system. This development accounts for constraints on the size and shape of the spatial kernel and all the components of the imaging system. Simulation results indicate the technique is effective and efficient.

Reichenbach, Stephen E.; Park, Stephen K.

1989-01-01

202

Optical Design and Receiving Characteristics of Two Lens Type Visible Light Communication System  

NASA Astrophysics Data System (ADS)

This paper describes the optical design for two lens type visible light communication system to reduce back ground noise. The system is composed of image sensor, receiving element and control software. The selected area for the receiving element was calculated by considering the chip size, focal length of lens and the pitch between image sensor and receiving element on the PCB board. The communication length is expected in proportional to the focal length of lens. LED sources were modulated with sub-carrier 4bit pulse position modulation of visible light ID at the carrier frequency of 28.8kHz. The communicational length of the system by using commercialized high sensitive photo transistor was measured up to 16.5m for the focal length of 12mm. In the photo-transistor array system, the brightness and illuminant size from the image sensor is used to identify the signal source. The system separates the data from multi signal sources by selecting the arbitrary receiving element.

Matsumoto, Yoshinori; Nakada, Hiromichi

203

Focal glomerulosclerosis in patients with unilateral nephrectomy  

Microsoft Academic Search

Focal glomerulosclerosis in patients with unilateral nephrectomy. To investigate whether proteinuria and focal glomerulosclerosis (FSG) might develop in humans as well as in experimental models following a reduction in renal mass, we performed a retrospective study of 24 patients previously nephrectomized for unilateral renal disease. None of the patients presented signs of systemic diseases, Alport syndrome, essential hypertension, reflux nephropathy,

Pietro Zucchelli; Leonardo Cagnoli; Silvia Casanova; Ugo Donini; Sonia Pasquali

1983-01-01

204

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Influence of the coherence length of a laser on the noise characteristics of frequency-modulated fiber-optic communication lines  

NASA Astrophysics Data System (ADS)

The time dependences of the mode noise where determined for a fiber-optic communication line of length 20 km subjected to modulation at a subcarrier frequency of 70 MHz. The communication line consisted of multimode graded-index fiber waveguides. The spectral width of the emission line of the radiation source (? = 1.3 ?m) employed in this study was determined. It was found that a change in the frequency modulation depth of a signal by 2 dB could reduce the mode noise level by 10 dB.

Bessonov, Yu L.; Dianov, Evgenii M.; Duraev, V. P.; Kirik, Yu M.; Kuznetsov, A. V.; Prokhorov, A. M.; Shcherbakov, E. A.

1988-10-01

205

Experimental Optics  

NASA Astrophysics Data System (ADS)

1. Elementary laws of optics; 2. Some applications of the laws of reflection and refraction; 3. Experiments with plane surfaces; 4. The spectrometer; 5. Experiments with prisms; 6. Spherical mirrors; 7. Thin lenses; 8. Experiments with thin lenses; 9. Coaxial optical systems - thick lenses; 10. Experiments with coaxial systems; 11. Astigmatism and focal lines; 12. Interference and polarisation by reflexion; 13. Diffraction grating and zone plate.

Searle, G. F. C.

2014-05-01

206

Micro-camera and micro-spectrometer designs adapted to large infrared focal plane arrays  

NASA Astrophysics Data System (ADS)

Today's infrared focal plane arrays concentrate in a small volume of typically 1 cm3 the results of three decades of research in microelectronics and packaging. Several technological breakthroughs have already been achieved leading to the development of infrared focal plane arrays (IRFPA's) for high-performances applications requiring spatial and thermal resolution, also for low-cost and high-manufacturing volumes (technology of uncooled micro-bolometers). The next step is to reduce the optics and make it compatible with the successful IRFPA's fabrication technology. This paper presents some methods and technologies we are exploring for high-performance and small infrared systems. These developments have led to a tool box of micro-concepts described by an optical function (imagery or spectrometry) integrated in the vicinity of the IRFPA. For this, old optical concepts have been revisited (pinhole optics, Talbot effect) and first demonstrations of original IRFPA-based micro-optical assemblies will be given.

Guérineau, Nicolas; Druart, Guillaume; de la Barrière, Florence; Gillard, Frédéric; Rommeluère, Sylvain; Primot, Jérôme; Deschamps, Jo"l.; Taboury, Jean; Fendler, Manuel

2010-05-01

207

Multiplicative and subtractive focal volume engineering in coherent Raman microscopy  

PubMed Central

Rigorous calculations are performed to study the effective reduction of the nonlinear excitation volumes when using phase-only masks to condition the pump and Stokes driving fields. Focal volume reduction was achieved using both a multiplicative operation of the excitation fields as well as a subtractive operation. Using a tunable optical bottle beam for the Stokes field, an effective reduction of the width of the excitation volume by a factor of 1.5 can be achieved in the focal plane. Further reduction of the focal volume introduces a rapid growth of sidelobes, which renders such volumes unsuitable for imaging applications. In addition, phase sensitive detection was found to provide information from selective sub-divisions of the engineered coherent anti-Stokes Raman scattering excitation volume. In the case of isolated nanoparticles, an apparent resolution improvement by a factor of 3 is demonstrated, and it is shown that the size of sub-diffraction-limited particles can be accurately determined using phase sensitive detection. PMID:21045900

Raghunathan, Varun; Potma, Eric Olaf

2012-01-01

208

Four-mirror optical system with ultra-low distortion  

NASA Astrophysics Data System (ADS)

Optical systems with long effective focal length and large-aperture will play more important roles in space remote sensor in the future. Coaxis optical systems have been widely adopted due to its advantages including good symmetrical characteristics, compact structure, satisfying volume and rotary inertia. But the distortion of the coaxis three-mirror-anastigmat system is often larger than one percent of the image height and past correction is hard, which is unfavourable especially for surveying and mapping camera. Based on the design ideas and aberration theoretical analysis of Coaxis reflective optics, four-mirror systems with long focal length is presented in this paper, which can achieve high image quality and ultra-low distortion .The forth reflective mirror is set near the exit pupil to correct the aberration related to the pupil, and the processing difficulty of the primary mirror is also lowered. Example of the optical design and image quality forecasting is also given at the end of the paper.

Tang, Tian-jin

2014-07-01

209

The AIRES Optical Design  

NASA Technical Reports Server (NTRS)

AIRES (Airborne InfraRed Echelle Spectrometer) is the facility spectrometer for SOFIA (Stratospheric Observatory For Infrared Astronomy). AIRES is a long-slit (approximately 160 in) spectrometer designed to cover the 17 to 210-micron range with good sensitivity using three spectroscopic arrays. Initially, only the 30-130 micron, mid-wavelength array will be available. The instrument has a cryogenic K-mirror to perform field rotation and a slit-viewing camera (lambda < 28 microns, FOV = 160 in diameter) to image source morphology and verify telescope pointing. AIRES employs a large echelle grating to achieve a spectral resolving power (lambda/delta lambda) of approximately 1.0 x 10(exp 6)/lambda (sub mu), where lambda (sub mu) is the wavelength in microns. Hyperfine, Inc. has ruled and tested the AIRES' echelle; its wave-front error is 0.028 waves RMS (root mean square) at 10.6 microns. The instrument is housed in a liquid-helium cryostat which is constrained in diameter (approximately 1 m) and length (approximately 2 m) by the observatory. Hence, the length of the echelle (approximately 1.1 m) and the focal length of its collimator (approximately 5.2 m) severely drive the optical design and packaging. The final design uses diamond-turned aluminum optics and has up to 19 reflections inside the cryostat, depending on the optical path. This design was generated, optimized, and toleranced using Code V. The predicted performance is nearly diffraction-limited at 17 microns; the error budget is dominated by design residuals. Light loss due to slit rotation and slit curvature has been minimized. A thorough diffraction analysis with GLAD (G-Level Analysis Drawer) was used to size the mirrors and baffles; the internal light loss is shown to be a strong function of slit width.

Haas, Michael R.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

210

Varying focal fields with asymmetric-sector-shaped vector beams  

NASA Astrophysics Data System (ADS)

We theoretically and experimentally investigate the focusing properties of asymmetric-sector-shaped vector beams with localized linear polarization. Simulation results show that the shape-only modulation of the vector beam allows one to simultaneously change the intensity, phase, polarization, as well as spin angular momentum distributions of the focused field. Experimentally, we generate asymmetric-sector-shaped vector beams and study its intensity distributions and the polarization characteristics at the focal plane, which are in good agreements with the numerical simulations. The presented approach enriches the methods for focus engineering and inspires the manipulation of the angular momentum of light, which would be useful for optical manipulation.

Pan, Yang; Gu, Bing; Xu, Danfeng; Zhan, Qiwen; Cui, Yiping

2015-01-01

211

Focal brain inflammation and autism.  

PubMed

Increasing evidence indicates that brain inflammation is involved in the pathogenesis of neuropsychiatric diseases. Autism spectrum disorders (ASD) are characterized by social and learning disabilities that affect as many as 1/80 children in the USA. There is still no definitive pathogenesis or reliable biomarkers for ASD, thus significantly curtailing the development of effective therapies. Many children with ASD regress at about age 3 years, often after a specific event such as reaction to vaccination, infection, stress or trauma implying some epigenetic triggers, and may constitute a distinct phenotype. ASD children respond disproportionally to stress and are also affected by food and skin allergies. Corticotropin-releasing hormone (CRH) is secreted under stress and together with neurotensin (NT) stimulates mast cells and microglia resulting in focal brain inflammation and neurotoxicity. NT is significantly increased in serum of ASD children along with mitochondrial DNA (mtDNA). NT stimulates mast cell secretion of mtDNA that is misconstrued as an innate pathogen triggering an auto-inflammatory response. The phosphatase and tensin homolog (PTEN) gene mutation, associated with the higher risk of ASD, which leads to hyper-active mammalian target of rapamycin (mTOR) signalling that is crucial for cellular homeostasis. CRH, NT and environmental triggers could hyperstimulate the already activated mTOR, as well as stimulate mast cell and microglia activation and proliferation. The natural flavonoid luteolin inhibits mTOR, mast cells and microglia and could have a significant benefit in ASD. PMID:23570274

Theoharides, Theoharis C; Asadi, Shahrzad; Patel, Arti B

2013-01-01

212

Scale Length of Disk Galaxies  

NASA Astrophysics Data System (ADS)

As a part of a Euro-VO research initiative, we have undertaken a programme aimed at studying the scale length of 54909 Sa-Sd spiral galaxies from the SDSS DR6 catalogue. We have retrieved u, g, r, i, z-band images for all galaxies in order to derive the light profiles. We also calculate asymmetry parameters to select non-disturbed disks for which we will derive exponential disk scale lengths. As images in different bands probe different optical depths and stellar populations, it is likely that a derived scale length value should depend on waveband, and our goal is to use the scale length variations with band pass, inclination, galaxy type, redshift, and surface brightness, in order to better understand the nature of spiral galaxies.

Fathi, K.; Allen, M.; Gonzalez-Solares, E.; Hatziminaoglou, E.; Peletier, R.

2009-07-01

213

Development of a cable reel development system using a rotary joint for kilometer lengths of two-fiber multi-mode fiber optic cable  

SciTech Connect

Brookhaven National Laboratory (BNL) recently developed a two-component system for use during remote inspections. The system consists of a mobile unit with television cameras and other equipment and a stationary base station. A variety of signals must be continually transmitted between the two system components as the mobile unit is moved from the location to another. Two channels of broadband (10MHz) NTSC video are transmitted from the mobile unit to the base station, and a bi-directional ``talk set`` provides audio communication between personnel at each location. In addition, several channels of RS-232 are required to support present and future instruments used at the mobile unit and controlled by personnel at the base station. Brookhaven developed a mobile unit which communicated with a base station over a 2-fiber multimode fiber optic cable. One of the design requirements was maintaining constant communication with the base station during the time the mobile unit was moved about. To provide uninterrupted communications, deployment of the 1-km long fiber optic cable was initially performed with a ``spinning reel`` mechanism. The spinning reel mechanism proved to be mechanically unsuitable, and so the cable deployment mechanism was redesigned to spool the cable off the reel. The requirement for uninterrupted communications required a two-channel fiber optic rotary joint in the design. Incorporation of the rotary joint into the design is described, and appropriate reference material is included.

Curtiss, J.A.; Jahelka, J.R.

1995-08-11

214

Dynamic Mechanisms of Neocortical Focal Seizure Onset  

PubMed Central

Recent experimental and clinical studies have provided diverse insight into the mechanisms of human focal seizure initiation and propagation. Often these findings exist at different scales of observation, and are not reconciled into a common understanding. Here we develop a new, multiscale mathematical model of cortical electric activity with realistic mesoscopic connectivity. Relating the model dynamics to experimental and clinical findings leads us to propose three classes of dynamical mechanisms for the onset of focal seizures in a unified framework. These three classes are: (i) globally induced focal seizures; (ii) globally supported focal seizures; (iii) locally induced focal seizures. Using model simulations we illustrate these onset mechanisms and show how the three classes can be distinguished. Specifically, we find that although all focal seizures typically appear to arise from localised tissue, the mechanisms of onset could be due to either localised processes or processes on a larger spatial scale. We conclude that although focal seizures might have different patient-specific aetiologies and electrographic signatures, our model suggests that dynamically they can still be classified in a clinically useful way. Additionally, this novel classification according to the dynamical mechanisms is able to resolve some of the previously conflicting experimental and clinical findings. PMID:25122455

Wang, Yujiang; Goodfellow, Marc; Taylor, Peter Neal; Baier, Gerold

2014-01-01

215

Optical zoom camera module using two poly-dimethylsiloxane deformable mirrors.  

PubMed

Miniaturization is an essential trend in the design of portable devices. Motor-driven lens technology is a traditional way to achieve autofocus and optical zoom functions. This approach usually requires considerable space and consumes significant power. Reflective optics is a methodology that not only can fold the optical path, but it has the advantage of low chromatic aberration. In this paper, we use a deformable mirror as a reflecting element in an optical zoom system. For its low Young's modulus and residual stress, we choose polydimethylsiloxane as a deformable membrane that can provide a large stroke. The optical zoom module consists of a pair of micromachined deformable mirrors. The thickness of this module is 10 mm, which enables 2× optical zoom. The smallest effective focal length is 4.7 mm at a full field angle of 52°, and the f-number is 4.4. The largest effective focal length of the module is 9.4 mm, and the f-number is 6.4. PMID:25322427

Huang, Yu-Hung; Wei, Hsiang-Chun; Hsu, Wei-Yao; Cheng, Yuan-Chieh; Su, Guo-Dung John

2014-10-10

216

Compressive optical MONTAGE photography  

NASA Astrophysics Data System (ADS)

The Compressive Optical MONTAGE Photography Initiative (COMP-I) is an initiative under DARPA's MONTAGE program. The goals of COMP-I are to produce 1 mm thick visible imaging systems and 5 mm thick IR systems without compromising pixel-limited resolution. Innovations of COMP-I include focal-plane coding, block-wise focal plane codes, birefringent, holographic and 3D optical elements for focal plane remapping and embedded algorithms for image formation. In addition to meeting MONTAGE specifications for sensor thickness, focal plane coding enables a reduction in the transverse aperture size, physical layer compression of multispectral and hyperspectral data cubes, joint optical and electronic optimization for 3D sensing, tracking, feature-specific imaging and conformal array deployment.

Brady, David J.; Feldman, Michael; Pitsianis, Nikos; Guo, J. P.; Portnoy, Andrew; Fiddy, Michael

2005-08-01

217

Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices  

NASA Technical Reports Server (NTRS)

Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties.

Wood, V. E.; Busch, J. R.; Verber, C. M.

1982-01-01

218

Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty  

SciTech Connect

Purpose: To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Methods: Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Results: Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table is provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. Conclusions: The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.

Cepek, Jeremy, E-mail: jcepek@robarts.ca; Fenster, Aaron [Robarts Research Institute, London, Ontario N6A 5K8, Canada and Biomedical Engineering, The University of Western Ontario, London, Ontario N6A 5B9 (Canada)] [Robarts Research Institute, London, Ontario N6A 5K8, Canada and Biomedical Engineering, The University of Western Ontario, London, Ontario N6A 5B9 (Canada); Lindner, Uri; Trachtenberg, John [Department of Surgical Oncology, Division of Urology, University Health Network, Toronto, Ontario M5G 2C4 (Canada)] [Department of Surgical Oncology, Division of Urology, University Health Network, Toronto, Ontario M5G 2C4 (Canada); Davidson, Sean R. H. [Ontario Cancer Institute, University Health Network, Toronto, Ontario M5G 2M9 (Canada)] [Ontario Cancer Institute, University Health Network, Toronto, Ontario M5G 2M9 (Canada); Haider, Masoom A. [Department of Medical Imaging, Sunnybrook Health Sciences Center, Toronto, Ontario M4N 3M5, Canada and Department of Medical Imaging, University of Toronto, Toronto, Ontario M5S 2J7 (Canada)] [Department of Medical Imaging, Sunnybrook Health Sciences Center, Toronto, Ontario M4N 3M5, Canada and Department of Medical Imaging, University of Toronto, Toronto, Ontario M5S 2J7 (Canada); Ghai, Sangeet [Department of Medical Imaging, University Health Network, Toronto, Ontario M5G 2M9 (Canada)] [Department of Medical Imaging, University Health Network, Toronto, Ontario M5G 2M9 (Canada)

2014-01-15

219

Spatial calibration of an optical see-through head-mounted display.  

PubMed

We present here a method for calibrating an optical see-through head-mounted display (HMD) using techniques usually applied to camera calibration (photogrammetry). Using a camera placed inside the HMD to take pictures simultaneously of a tracked object and features in the HMD display, we could exploit established camera calibration techniques to recover both the intrinsic and extrinsic properties of the HMD (width, height, focal length, optic centre and principal ray of the display). Our method gives low re-projection errors and, unlike existing methods, involves no time-consuming and error-prone human measurements, nor any prior estimates about the HMD geometry. PMID:18599125

Gilson, Stuart J; Fitzgibbon, Andrew W; Glennerster, Andrew

2008-08-15

220

Single-mode laser studies: Design and performance of a fixed-wave length source and coupling of lasers to thin-film optical waveguides  

NASA Technical Reports Server (NTRS)

A module developed for the generation of a stable single wavelength to be used for a fiber optic multiplexing scheme is described. The laser is driven with RZ pulses, and the temperature is stabilized thermoelectrically. The unit is capable of maintaining a fixed wavelength within about 6 A as the pulse duty cycle is changed between 0 and 100 percent. This is considered the most severe case, and much tighter tolerances are obtainable for constant input power coding schemes. Using a constricted double heterostructure laser, a wavelength shift of 0.083 A mA is obtained due to laser self-heating by a dc driving current. The thermoelectric unit is capable of maintaining a constant laser heat-sink temperature within 0.02 C. In addition, miniature lenses and couplers are described which allow efficient coupling of single wavelength modes of junction lasers to thin film optical waveguides. The design of the miniature cylinder lenses and the prism coupling techniques allow 2 mW of single wavelength mode junction laser light to b coupled into thin film waveguides using compact assemblies. Selective grating couplers are also studied.

Ladany, I.; Hammer, J. M.

1980-01-01

221

Genetics Home Reference: Focal dermal hypoplasia  

MedlinePLUS

... Patients and Families Resources for Health Professionals What glossary definitions help with understanding focal dermal hypoplasia? anophthalmia ; ... many other terms in the Genetics Home Reference Glossary . See also Understanding Medical Terminology . References (10 links) ...

222

An MLPO Algorithm for Fast Evaluation of the Focal Plane Fields of Reflector Antennas  

E-print Network

An MLPO Algorithm for Fast Evaluation of the Focal Plane Fields of Reflector Antennas Christine antennas for a range of incidence angles and frequencies is proposed. The algorithm is based and phase correction. Keywords- reflector antennas; physical optics; fast multilevel algorithms. I

Paris-Sud XI, Université de

223

Image interpolation and denoising for division of focal plane sensors using  

E-print Network

polarization imaging employ four different pixelated polarization filters, commonly referred to as division, 1710­721 (2014). #12;5. V. Gruev, R. Perkins, and T. Yor, "Ccd polarization imaging sensor division-of-focal-plane polarization imaging sensor," Journal of Biomedical Optics 17, 116001

Columbia University

224

Laser-beam attenuation for spatial profiling of small focal spots  

SciTech Connect

We describe an attenuation scheme for high-power laser beams which uses only two optical surfaces and is continuously variable over several orders of magnitude. We demonstrate its application to the spatial profiling of a pulsed DF laser focal spot with 10/sup -2/ cm diameter and >10/sup 10/ W/cm/sup 2/ peak irradiance.

Nichols, D.B.; Hall, R.B.

1980-08-01

225

Diffractive microlens array monolithic integration with PtSi focal plane array  

Microsoft Academic Search

A diffractive microlens arrays can completely collect the light at the focal plane and concentrate it into a smaller spot size on the detector plane; the photodetector area can be substantially reduced. Increased gamma radiation hardening and noise reduction result from the decrease in photodectector sensitive area. The diffractive microlens arrays have been designed by considering the independent optical and

Yi Li; Xinjian Yi; Liping Cai; Sihai Chen; Sixian Chen

2000-01-01

226

Finding the Focal Axes of Offset Antennas  

NASA Technical Reports Server (NTRS)

Focal axis of offset paraboloidal reflector antennas determined by direct measurement instead of trial and error. Two feed horns transmit sum or difference pattern to antenna under test, which reflects energy to far-field detector. When axis of feed horns coincides with focal axis of antenna reflector, far-field detector records minimum in amplitude difference and maximum in absolute-magnitude phase difference between sum and difference signals.

Schmidt, R. F.

1982-01-01

227

Focal liver lesions: sinusoidal phase of CEUS  

Microsoft Academic Search

Ultrasound examination is the first imaging modality for hepatic study in neoplastic and chronic liver diseases. Focal liver\\u000a lesions frequently cause diagnostic problems in terms of characterization, especially when small and hypoechoic to the rest\\u000a of the parenchyma. Contrast- enhanced ultrasonography (CEUS) has shown its value in the characterization of focal liver lesions.\\u000a This study assessed the value of the

M. D’Onofrio; E. Martone; N. Faccioli; G. Zamboni; R. Pozzi Mucelli

2006-01-01

228

The design and evaluation of grazing incidence relay optics  

NASA Technical Reports Server (NTRS)

X-ray astronomy, both solar and celestial, has many needs for high spatial resolution observations which have to be performed with electronic detectors. If the resolution is not to be detector limited, plate scales in excess of 25 microns arc/sec, corresponding to focal lengths greater than 5 m, are required. In situations where the physical size is restricted, the problem can be solved by the use of grazing incidence relay optics. A system was developed which employs externally polished hyperboloid-hyperboloid surfaces to be used in conjunction with a Wolter-Schwarzschild primary. The secondary is located in front of the primary focus and provides a magnification of 4, while the system has a plate scale of 28 microns arc/sec and a length of 1.9 m. The design, tolerance specification, fabrication and performance at visible and X-ray wavelengths of this optical system are described.

Davis, John M.; Chase, R. C.; Silk, J. K.; Krieger, A. S.

1989-01-01

229

Influence of the length and grafting density of PNIPAM chains on the colloidal and optical properties of quantum dot/PNIPAM assemblies.  

PubMed

Structural and optical characterization of water soluble, thermo-responsive quantum dot/poly(N-isopropyl acrylamide) (QD/PNIPAM) hybrid particles using fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements performed at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM is reported. By increasing the temperature above the LCST, the signature of the PNIPAM chain collapse covering the QDs is revealed by FCS measurements. Despite the significant structural change, the TCSPC measurements show that the fluorescence lifetimes remain of the same order of magnitude at T > LCST. Such QD/PNIPAM hybrid particles with water solubility and robust thermo-responsive behavior at physiologically relevant temperatures are potentially useful for (bio)molecular sensing and separation applications. PMID:21576806

Tagit, Oya; Tomczak, Nikodem; Jafarpour, Aliakbar; Ja?czewski, Dominik; Han, Ming Yong; Vancso, G Julius; Herek, Jennifer L

2011-07-01

230

Hand-held optical fuel pin scanner  

DOEpatents

An optical scanner for indicia arranged in a focal plane perpendicular to an optical system including a rotatable dove prism. The dove prism transmits a rotating image to a stationary photodiode array.

Kirchner, Tommy L. (Richland, WA); Powers, Hurshal G. (Richland, WA)

1987-01-01

231

DIVA optical telescope  

NASA Astrophysics Data System (ADS)

The German Instrument for Multi-channel Photometry and Astrometry (DIVA), dedicated to the German (DLR) small extraterrestrial satellite program, is intended as a kind of technology precursor mission to GAIA. DIVA is scheduled for launch in 2004 and shall perform a sky survey to measure within 2 years life time the positions, parallaxes, magnitudes, etc. of about 35 million stars. The main instrument, covering the spectral range of 400-1000nm, observes 2 fields of view (0.6° x 0.77°) by a single Focal Plane Assembly (FPA). The focal length is 11200mm. The DIVA Optomechanics is based on a high precision Three Mirror Anastigmat (TMA) concept with 8 mirrors, 5 of them flat. An extremely high short term stability (torsion tolerance) of 0.3 mas over 10h only has to be realized only by passive means to achieve the astrometrical performance requirements. The paper describes the phase B2 design activities wrt. the optomechanical and thermal design of the main instrument. Special emphasis is given to an exhausting, but very pragmatic thermomechanical and optical performance trade off between a cost effective athermal design concept, applying mirrors and an optical bench made from a specially treated isotropic aluminum alloy, and a thermally stable hybrid material concept based on a Carbon Fiber Reinforced Plastics (CFRP) sandwich structure and Zerodur mirrors. The selection of the final baseline design solution shall be reported. According to the very high long and short scale surface properties of the candidate aluminum mirrors a sophisticated manufacturing procedure was established based on conventional and ion beam polishing techniques. The representative breadboard mirror test results will be given.

Graue, Roland; Kampf, Dirk; Röser, Siegfried; Bastian, Ulrich; Seifert, Walter

2003-02-01

232

Measuring Crack Length in Coarse Grain Ceramics  

NASA Technical Reports Server (NTRS)

Due to a coarse grain structure, crack lengths in precracked spinel specimens could not be measured optically, so the crack lengths and fracture toughness were estimated by strain gage measurements. An expression was developed via finite element analysis to correlate the measured strain with crack length in four-point flexure. The fracture toughness estimated by the strain gaged samples and another standardized method were in agreement.

Salem, Jonathan A.; Ghosn, Louis J.

2010-01-01

233

The study of characteristics of the beam scanning for millimeter-wave focal plane array imaging systems  

Microsoft Academic Search

Recent progress in millimeter-wavelength optics, antennas, receivers and other components permits greatly enhanced system performance in a wide range of applications. Arrays of detectors in the focal plane offer a major avenue for increasing the data rate of millimeter-wave imaging systems. All-reflective systems with focal-plane arrays of monolithic elements promise major improvements in millimeter-wave imaging applications. In this review we

Zhang Yong; Li Xingguo

1998-01-01

234

The Imaging Properties of the Gas Pixel Detector as a Focal Plane Polarimeter  

NASA Astrophysics Data System (ADS)

X-rays are particularly suited to probing the physics of extreme objects. However, despite the enormous improvements of X-ray astronomy in imaging, spectroscopy, and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as a candidate instrument to fill the gap created by more than 30 yr without measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time, and the polarization angle of every single photon, it allows us to perform polarimetry of subsets of data singled out from the spectrum, the light curve, or an image of the source. The GPD has an intrinsic, very fine imaging capability, and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray testing facility of the Max-Planck-Institut für extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it with a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like pulsar wind nebulae and supernova remnants as case studies for the XIPE configuration and also discuss possible improvements by coupling the detector with advanced optics that have a finer angular resolution and larger effective areas to study extended objects with more detail.

Fabiani, S.; Costa, E.; Del Monte, E.; Muleri, F.; Soffitta, P.; Rubini, A.; Bellazzini, R.; Brez, A.; de Ruvo, L.; Minuti, M.; Pinchera, M.; Sgró, C.; Spandre, G.; Spiga, D.; Tagliaferri, G.; Pareschi, G.; Basso, S.; Citterio, O.; Burwitz, V.; Burkert, W.; Menz, B.; Hartner, G.

2014-06-01

235

Assessing the effect of laser beam width on quantitative evaluation of optical properties of intraocular lens implants.  

PubMed

The design and manufacture of intraocular lenses (IOLs) depend upon the identification and quantitative preclinical evaluation of key optical properties and environmental parameters. The confocal laser method (CLM) is a new technique for measuring IOL optical properties, such as dioptric power, optical quality, refractive index, and geometrical parameters. In comparison to competing systems, the CLM utilizes a fiber-optic confocal laser design that significantly improves the resolution, accuracy, and repeatability of optical measurements. Here, we investigate the impact of changing the beam diameter on the CLM platform for the evaluation of IOL dioptric powers. Due to the Gaussian intensity profile of the CLM laser beam, the changes in focal length and dioptric power associated with changes in beam diameter are well within the tolerances specified in the ISO IOL standard. These results demonstrate some of the advanced potentials of the CLM toward more effectively and quantitatively evaluating IOL optical properties. PMID:24817618

Walker, Bennett N; James, Robert H; Chakravarty, Aurin; Calogero, Don; Ilev, Ilko K

2014-05-01

236

Assessing the effect of laser beam width on quantitative evaluation of optical properties of intraocular lens implants  

NASA Astrophysics Data System (ADS)

The design and manufacture of intraocular lenses (IOLs) depend upon the identification and quantitative preclinical evaluation of key optical properties and environmental parameters. The confocal laser method (CLM) is a new technique for measuring IOL optical properties, such as dioptric power, optical quality, refractive index, and geometrical parameters. In comparison to competing systems, the CLM utilizes a fiber-optic confocal laser design that significantly improves the resolution, accuracy, and repeatability of optical measurements. Here, we investigate the impact of changing the beam diameter on the CLM platform for the evaluation of IOL dioptric powers. Due to the Gaussian intensity profile of the CLM laser beam, the changes in focal length and dioptric power associated with changes in beam diameter are well within the tolerances specified in the ISO IOL standard. These results demonstrate some of the advanced potentials of the CLM toward more effectively and quantitatively evaluating IOL optical properties.

Walker, Bennett N.; James, Robert H.; Chakravarty, Aurin; Calogero, Don; Ilev, Ilko K.

2014-05-01

237

Pivoted document length normalization  

Microsoft Academic Search

Automatic information retrieval systems have to deal with documents of varying lengths in a text collection. Document length normalization is used to fairly retrieve documents of all lengths. In this study, we ohserve that a normalization scheme that retrieves documents of all lengths with similar chances as their likelihood of relevance will outperform another scheme which retrieves documents with chances

Amit Singhal; Chris Buckley; Manclar Mitra

1996-01-01

238

Submillisecond Optical Knife-Edge Testing  

NASA Technical Reports Server (NTRS)

Fast computer-controlled sampling of optical knife-edge response (KER) signal increases accuracy of optical system aberration measurement. Submicrosecond-response detectors in optical focal plane convert optical signals to electrical signals converted to digital data, sampled and feed into computer for storage and subsequent analysis. Optical data are virtually free of effects of index-of-refraction gradients.

Thurlow, P.

1983-01-01

239

Large-format InGaAs focal plane arrays for SWIR imaging  

NASA Astrophysics Data System (ADS)

FLIR Electro Optical Components will present our latest developments in large InGaAs focal plane arrays, which are used for low light level imaging in the short wavelength infrared (SWIR) regime. FLIR will present imaging from their latest small pitch (15 ?m) focal plane arrays in VGA and High Definition (HD) formats. FLIR will present characterization of the FPA including dark current measurements as well as the use of correlated double sampling to reduce read noise. FLIR will show imagery as well as FPA-level characterization data.

Hood, Andrew D.; MacDougal, Michael H.; Manzo, Juan; Follman, David; Geske, Jonathan C.

2012-06-01

240

The Statistics of Calcium-Mediated Focal Excitations on a One-Dimensional Cable  

PubMed Central

It is well known that various cardiac arrhythmias are initiated by an ill-timed excitation that originates from a focal region of the heart. However, up to now, it is not known what governs the timing, location, and morphology of these focal excitations. Recent studies have shown that these excitations can be caused by abnormalities in the calcium (Ca) cycling system. However, the cause-and-effect relationships linking subcellular Ca dynamics and focal activity in cardiac tissue is not completely understood. In this article, we present a minimal model of Ca-mediated focal excitations in cardiac tissue. This model accounts for the stochastic nature of spontaneous Ca release on a one-dimensional cable of cardiac cells. Using this model, we show that the timing of focal excitations is equivalent to a first passage time problem in a spatially extended system. In particular, we find that for a short cable the mean first passage time increases exponentially with the number of cells in tissue, and is critically dependent on the ratio of inward to outward currents near the threshold for an action potential. For long cables excitations occurs due to ectopic foci that occur on a length scale determined by the minimum length of tissue that can induce an action potential. Furthermore, we find that for long cables the mean first passage time decreases as a power law in the number cells. These results provide precise criteria for the occurrence of focal excitations in cardiac tissue, and will serve as a guide to determine the propensity of Ca-mediated triggered arrhythmias in the heart. PMID:22325268

Chen, Wei; Asfaw, Mesfin; Shiferaw, Yohannes

2012-01-01

241

FocalCall: An R Package for the Annotation of Focal Copy Number Aberrations  

PubMed Central

In order to identify somatic focal copy number aberrations (CNAs) in cancer specimens and to distinguish them from germ-line copy number variations (CNVs), we developed the software package FocalCall. FocalCall enables user-defined size cutoffs to recognize focal aberrations and builds on established array comparative genomic hybridization segmentation and calling algorithms. To distinguish CNAs from CNVs, the algorithm uses matched patient normal signals as references or, if this is not available, a list with known CNVs in a population. Furthermore, FocalCall differentiates between homozygous and heterozygous deletions as well as between gains and amplifications and is applicable to high-resolution array and sequencing data. PMID:25506197

Krijgsman, Oscar; Benner, Christian; Meijer, Gerrit A; van de Wiel, Mark A; Ylstra, Bauke

2014-01-01

242

Polished Panel Optical Receiver for Simultaneous RF/Optical Telemetry with Large DSN Antennas  

NASA Technical Reports Server (NTRS)

The polished panel optical receiver concept described here makes use of aluminum panels on the main reflector of the Deep Space Network's (DSN's) 34-meter antennas at optical wavelengths by polishing and coating their surface to efficiently reflect near-infrared wavelengths in the 1,064 1,550-nanometer range. Achievable surface smoothness is not a limiting factor for aluminum panels, and initial field experiments indicate that the surface quality of microwave aluminum panels is sufficient to concentrate the light into small, but not diffraction-limited, spots at their primary focus. Preliminary analysis of data from high-quality microwave panels has shown that the light can be concentrated into 200 400 microradian cones, resulting in spot diameters of 2-4 mm at the 10-meter primary focus F(0) shown in the figure, or 2-4 cm spots at F(1) after magnification by the subreflector, which results in an effective focal length of about 100 meters. Three distinct implementation options are possible, with theoretically identical tracking and communications performance: Option 1: The communications assembly could be placed directly behind the subreflector at F(0), but this placement would require replacing the existing all-aluminum subreflector with a new design that transmits optical wavelengths but reflects RF, thus transmitting the optical signal to the primary focus of the parabolic polished aluminum panels at F(0), as shown in the figure. Option 2: Alternately, the optical communications assembly could be located near the first available focal-spot F(1) following reflection by the subreflector (which would have to be polished), next to the input to the beam waveguide on the main reflector as shown in the figure. Option 3: Finally, the optical communications assembly could be placed inside the pedestal room, and separated from the RF signal after the ellipsoid and before the signal reached the microwave receiver via an RF/optical dichroic near F(3).

Vilnrotter, Victor A.; Hoppe, Daniel J.

2011-01-01

243

Brain Network Organization in Focal Epilepsy: A Systematic Review and Meta-Analysis  

PubMed Central

Normal brain functioning is presumed to depend upon interacting regions within large-scale neuronal networks. Increasing evidence exists that interictal network alterations in focal epilepsy are associated with cognitive and behavioral deficits. Nevertheless, the reported network alterations are inconclusive and prone to low statistical power due to small sample sizes as well as modest effect sizes. We therefore systematically reviewed the existing literature and conducted a meta-analysis to characterize the changes in whole-brain interictal focal epilepsy networks at sufficient power levels. We focused on the two most commonly used metrics in whole-brain networks: average path length and average clustering coefficient. Twelve studies were included that reported whole-brain network average path length and average clustering coefficient characteristics in patients and controls. The overall group difference, quantified as the standardized mean average path length difference between epilepsy and control groups, corresponded to a significantly increased average path length of 0.29 (95% confidence interval (CI): 0.12 to 0.45, p?=?0.0007) in the epilepsy group. This suggests a less integrated interictal whole-brain network. Similarly, a significantly increased standardized mean average clustering coefficient of 0.35 (CI: 0.05 to 0.65, p?=?0.02) was found in the epilepsy group in comparison with controls, pointing towards a more segregated interictal network. Sub-analyses revealed similar results for functional and structural networks in terms of effect size and directionality for both metrics. In addition, we found individual network studies to be prone to low power due to the relatively small group differences in average path length and average clustering coefficient in combination with small sample sizes. The pooled network characteristics support the hypothesis that focal epilepsy has widespread detrimental effects, that is, reduced integration and increased segregation, on whole brain interictal network organization, which may relate to the co-morbid cognitive and behavioral impairments often reported in patients with focal epilepsy. PMID:25493432

Jansen, Floor E.; Stam, Cornelis J.; Braun, Kees P. J.; Otte, Willem M.

2014-01-01

244

Optical fuel pin scanner  

DOEpatents

An optical scanner for indicia arranged in a focal plane at a cylindrical outside surface by use of an optical system including a rotatable dove prism. The dove prism transmits a rotating image of an encircled cylindrical surface area to a stationary photodiode array.

Kirchner, Tommy L. (Richland, WA); Powers, Hurshal G. (Richland, WA)

1983-01-01

245

Smart optical writing head design for laser-based manufacturing  

NASA Astrophysics Data System (ADS)

Proposed is a smart optical writing head design suitable for high precision industrial laser based machining and manufacturing applications. The design uses an Electronically Controlled Variable Focus Lens (ECVFL) which enables the highest achievable spatial resolution of writing head spot sizes for axial target distances reaching 8 meters. A proof-of-concept experiment is conducted using a visible wavelength laser with a collimated beam that is coupled to beam conditioning optics which includes an electromagnetically actuated deformable membrane liquid ECVFL cascaded with a bias convex lens of fixed focal length. Electronic tuning and control of the ECVFL keeps the laser writing head far-field spot beam radii under 1 mm that is demonstrated over a target range of 20 cm to 800 cm. Applications for the proposed writing head design, which can accommodate both continuous wave and pulsed wave sources, include laser machining, high precision industrial molding of components, as well as materials processing requiring material sensitive optical power density control.

Amin, M. Junaid; Riza, Nabeel A.

2014-03-01

246

Kalman Filter for Calibrating a Telescope Focal Plane  

NASA Technical Reports Server (NTRS)

The instrument-pointing frame (IPF) Kalman filter, and an algorithm that implements this filter, have been devised for calibrating the focal plane of a telescope. As used here, calibration signifies, more specifically, a combination of measurements and calculations directed toward ensuring accuracy in aiming the telescope and determining the locations of objects imaged in various arrays of photodetectors in instruments located on the focal plane. The IPF Kalman filter was originally intended for application to a spaceborne infrared astronomical telescope, but can also be applied to other spaceborne and ground-based telescopes. In the traditional approach to calibration of a telescope, (1) one team of experts concentrates on estimating parameters (e.g., pointing alignments and gyroscope drifts) that are classified as being of primarily an engineering nature, (2) another team of experts concentrates on estimating calibration parameters (e.g., plate scales and optical distortions) that are classified as being primarily of a scientific nature, and (3) the two teams repeatedly exchange data in an iterative process in which each team refines its estimates with the help of the data provided by the other team. This iterative process is inefficient and uneconomical because it is time-consuming and entails the maintenance of two survey teams and the development of computer programs specific to the requirements of each team. Moreover, theoretical analysis reveals that the engineering/ science iterative approach is not optimal in that it does not yield the best estimates of focal-plane parameters and, depending on the application, may not even enable convergence toward a set of estimates.

Kang, Bryan; Bayard, David

2006-01-01

247

Megapixel QWIP Focal Plane Array And 320x256 Pixel Co-Located Mid-Wave And Long-Wave Dual-Band QWIP Focal Plane Array  

Microsoft Academic Search

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE ? T) of 17 mK at a 95K operating temperature with f\\/2.5 optics at 300K background and the LWIR detector array has demonstrated a

S. D. Gunapala; S. V. Bandara; J. K. Liu; C. J. Hill; S. B. Rafol; J. M. Mumolo; J. T. Trinh; M. Z. Tidrow; P. D. LeVan

248

Length Conversions and Length-Weight Relations for Pallid Sturgeon  

Microsoft Academic Search

We developed conversion formulas for standard length to fork length, fork length to total length, and standard length to total length for 30 pallid sturgeons Scaphirhynchus albus from the upper Missouri River. Formulas for converting length to weight were also developed for each of the length measurements. We add our length and weight data on 30 specimens of this rare

K. D. Keenlyne; S. J. Maxwell

1993-01-01

249

Ambroxol-induced focal epileptic seizure.  

PubMed

It is well known that in epileptic patients some compounds and different drugs used for the treatment of comorbidities can facilitate or provoke seizures, this evidence regarding a wide spectrum of pharmacological categories. The potential facilitating factors usually include direct toxic effects or pharmacological interactions of either active ingredients or excipients. We report the case of a patient with drug-resistant epilepsy who experienced focal epileptic seizures, easily and constantly reproducible, after each administration of a cough syrup. This is, to our knowledge, the first electroencephalogram-documented case of focal epileptic seizures induced by cough syrup containing ambroxol as active ingredient. PMID:24824664

Lapenta, Leonardo; Morano, Alessandra; Fattouch, Jinane; Casciato, Sara; Fanella, Martina; Giallonardo, Anna Teresa; Di Bonaventura, Carlo

2014-01-01

250

Rasmussen's encephalitis presenting as focal cortical dysplasia  

PubMed Central

Rasmussen's encephalitis is a rare syndrome characterized by intractable seizures, often associated with epilepsia partialis continua and symptoms of progressive hemispheric dysfunction. Seizures are usually the hallmark of presentation, but antiepileptic drug treatment fails in most patients and is ineffective against epilepsia partialis continua, which often requires surgical intervention. Co-occurrence of focal cortical dysplasia has only rarely been described and may have implications regarding pathophysiology and management. We describe a rare case of dual pathology of Rasmussen's encephalitis presenting as a focal cortical dysplasia (FCD) and discuss the literature on this topic.

O'Rourke, D.J.; Bergin, A.; Rotenberg, A.; Peters, J.; Gorman, M.; Poduri, A.; Cryan, J.; Lidov, H.; Madsen, J.; Harini, C.

2014-01-01

251

New multiband IR imaging optics  

NASA Astrophysics Data System (ADS)

We report new multispectral materials that transmit from 0.9 to < 12 µm in wavelength. These materials fill up the glass map for multispectral optics and vary in refractive index from 2.38 to 3.17. They show a large spread in dispersion (Abbe number) and offer some unique solutions for multispectral optics designs. One of the glasses developed is a very good candidate to replace Ge, as it has a combination of excellent properties, including high Abbe number in the LWIR, high index of 3.2, 60% lower dn/dT, and better thermal stability at working temperatures. Our results also provide a wider selection of optical materials to enable simpler achromat designs. For example, we have developed other glasses that have relatively high Abbe number in both the MWIR and LWIR regions, while our MILTRAN ceramic has low Abbe number in both regions. This makes for a very good combination of glasses and MILTRAN ceramic (analogous to crown and flint glasses in the visible) for MWIR + LWIR dual band imaging. We have designed preliminary optics for one such imager with f/2.5, 51 mm focal length and 22 degrees FOV using a spaced doublet of NRL's glass and MILTRAN ceramic. NRL's approach reduces the number of elements, weight, complexity and cost compared with the approach using traditional optics. Another important advantage of using NRL glasses in optics design is their negative or very low positive dn/dT, that makes it easier to athermalize the optical system.

Bayya, Shyam; Sanghera, Jasbinder; Kim, Woohong; Gibson, Daniel; Fleet, Erin; Shaw, Brandon; Hunt, Michael; Aggarwal, Ishwar

2013-06-01

252

The focal plane instrumentation for the DUNE mission  

E-print Network

DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed. The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9x4 array together with the associated mechanical support structure and electronics processing chains. Four additional CCDs dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced e2v CCD203-82 devices with square 12 $\\mu$m pixels, operating from 550-920nm. Combining four rows of CCDs provides a total exposure time of 1500s. The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength ...

Booth, Jeff; Eisenhauer, Frank; Refregier, Alexandre

2008-01-01

253

Performance characterization of a PIAA complex focal plane mask  

NASA Astrophysics Data System (ADS)

The Phase Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is an architecture for directly observing extrasolar planets, and can achieve performance near the theoretical limits for any direct-detection instrument. PIAACMC can be designed for centrally-obscured and segmented apertures, which is particularly useful for next-generation telescopes. The PIAACMC architecture includes aspheric PIAA optics, and a complex phase-shifting focal plane mask that provides a pi phase shift to a portion of the on-axis starlight. The phase-shifted starlight is forced to interfere destructively with the un-shifted starlight, causing the starlight to be eliminated, and allowing a region for high-contrast imaging near the star.The main challenge in designing the complex focal plane mask is to achieve deep contrast over a wide spectral band. Another challenge for the mask design is to avoid sharp features, which can be difficult to manufacture. We present a solution to the design challenge by dividing the mask into sections and optimizing the phase shift produced by each section. We also demonstrate a method to design the mask with a smooth profile. One remaining challenge is to measure the performance of the mask. We present a method to compute the phase profile of the mask based on measurements of the diffraction pattern. The computed phase profile is used to simulate the expected coronagraph performance.

Newman, Kevin; Belikov, Ruslan; Guyon, Olivier; Pluzhnik, Eugene

2015-01-01

254

Infrared MUSIC from Z technology focal planes  

Microsoft Academic Search

Presented is the Multiple Signal Classification (MUSIC) algorithm which uses the high frequency differences in sensed time signals to discriminate, count, and accurately locate closely spaced targets. Z technology focal planes allow the implementation of this algorithm and the trade-off between finer spatial resolution systems and systems with coarser resolution but higher sampling rates.

C. Ralph Waters; Anthony Sommese; Douglas Johnston; Herb Landau

1989-01-01

255

Focal Dermal Hypoplasia: A Rare Case Report  

PubMed Central

Focal dermal hypoplasia (Goltz syndrome) is a rare genetic multisystem disorder primarily involving the skin, skeletal system, eyes, and face. We report the case of an eight-month-old female child who presented with multiple hypopigmented atrophic macules along the lines of blaschko, skeletal anomalies, umbilical hernia, developmental delay, hypoplastic nails, syndactyly, and lobster claw deformity characteristic of Goltz syndrome. PMID:25657436

Srinivas, Sahana M; Hiremagalore, Ravi

2015-01-01

256

Considerations for patient selection for focal therapy  

PubMed Central

Focal therapy for prostate cancer is a nascent and emerging field. As such, the patient selection criteria for this new treatment paradigm are evolving in parallel to both the technology on which this approach depends and to our unfolding understanding of the natural history of prostate cancer. Until, and while, prospective trials of focal therapy are being reported, patient selection criteria will be flexible and very dependent on the therapeutic goals. We must carefully define the therapeutic intentions of focal therapy before engaging in the actual process of determining optimal patient selection. The therapeutic intent will define the most appropriate candidate for such therapy. Patient selection encompasses multiple complex issues including the type of prostate biopsy (12 core transrectal versus mapping transperineal) to the type of imaging (multiparametric magnetic resonance imaging or enhanced ultrasound) to the specific anatomical location of the disease within the prostate (apex, mid-prostate, base) and a comprehensive assessment of the patient’s overall health and life expectancy. It is not as simple as saying a patient with a certain grade or a certain number of cores is or is not appropriate for focal therapy. There are many more considerations for a reasonable and thoughtful approach to this new treatment. PMID:24294291

Pisters, Louis L.

2013-01-01

257

Complex source description of focal regions  

NASA Astrophysics Data System (ADS)

Closed-form solutions of the two-dimensional homogeneous wave equation are presented that provide focal-region descriptions corresponding to a converging bundle of rays. The solutions do have evanescent wave content and can be described as a source-sink pair or particle-antiparticle pair, collocated in complex space, with the complex location being critical in the determination of beam shape and focal region size. The wave solutions are not plagued by singularities, have a finite energy, and have a limitation on how small the focal size can get, with a penalty for limiting small spot sizes in the form of impractically high associated reactive energy. The electric-field-defined spot-size limiting value is 0.35?×0.35?, which is about 38% of the Poynting-vector-defined minimum spot size (0.8?×0.4?) and corresponds to a condition related to the maximum possible beam angle. A multiple set of solutions is introduced, and the elementary solutions are used to produce new solutions via superposition, resulting in fields with chiral character or with increased depth of focus. We do not claim generality, as the size of focal regions exhibited by the closed-form solutions has a lower bound and hence is not able to account for Pendry's "ideal lens" scenario.

Monzon, Cesar; Forester, Donald W.; Moore, Peter

2006-04-01

258

4 Assessment 4.1 Focal Species  

E-print Network

, Beaver Aquatic/Fish: Fish focal species were defined that a) have special cultural significance, b significant or rare as determined by applicable state or federal resource management agencies and-generated acreage figures may differ from IBIS acreage figures as an artifact of using tw

259

Universities: A Focal Point for Economic Development.  

ERIC Educational Resources Information Center

Higher education can act as a focal point of economic development. The most widely recognized type of economic development entails an association between a university, its research facilities, and private industry. An example of this partnership is the one between Stanford University and the industries in the "Silicon Valley." (MLW)

Maidique, Modesto A.

1988-01-01

260

Large format multicolor QWIP focal plane arrays  

NASA Astrophysics Data System (ADS)

Mid-wave infrared (MWIR) and long-wave infrared (LWIR) multicolor focal plane array (FPA) cameras are essential for many DoD and NASA applications including Earth and planetary remote sensing. In this paper we summarize our recent development of large format multicolor QWIP FPA that cover MWIR and LWIR bands.

Soibel, A.; Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Ting, D. Z.; Hill, C. J.; Nguyen, J.

2009-05-01

261

Large format multicolor QWIP focal plane arrays  

Microsoft Academic Search

Mid-wave infrared (MWIR) and long-wave infrared (LWIR) multicolor focal plane array (FPA) cameras are essential for many DoD and NASA applications including Earth and planetary remote sensing. In this paper we summarize our recent development of large format multicolor QWIP FPA that cover MWIR and LWIR bands.

A. Soibel; S. D. Gunapala; S. V. Bandara; J. K. Liu; J. M. Mumolo; D. Z. Ting; C. J. Hill; J. Nguyen

2009-01-01

262

Eigenfunction expansion of the electric fields in the focal region of a high numerical aperture focusing system.  

PubMed

The Debye-Wolf electromagnetic diffraction integral is now routinely used to describe focusing by high numerical (NA) lenses. We obtain an eigenfunction expansion of the electric vector field in the focal region in terms of Bessel and generalized prolate spheroidal functions. Our representation has many optimal and desirable properties which offer considerable simplification to the evaluation and analysis of the Debye- Wolf integral. It is potentially also useful in implementing two-dimensional apodization techniques to synthesize electromagnetic field distributions in the focal region of a high NA lenses. Our work is applicable to many areas, such as optical microscopy, optical data storage and lithography. PMID:18542431

Sherif, Sherif S; Foreman, Matthew R; Török, Peter

2008-03-01

263

Development and testing of an innovative two-arm focal-plane thermal strap (TAFTS)  

NASA Astrophysics Data System (ADS)

Temperature control of optical focal planes comes with the intrinsic challenge of creating a pathway that is both extremely flexible mechanically and highly conductive thermally. The task is further complicated because science-caliber optical focal planes are extremely delicate, yet time, cost, and their unique nature means that their mechanical resiliency is rarely tested and documented. The mechanical engineer tasked with the thermo-mechanical design must then create a highly conductive thermal link that minimizes the tensile and shear stresses transmitted to the focal plane without design parameters on an acceptable stiffness and without data on the stiffness of previously implemented thermal links. This paper describes the development and testing of the thermal link developed for the Portable Remote Imaging Spectrometer (PRISM) instrument. It will provide experimentally determined mechanical stiffness plots in the three axes of interest. Analytical and experimental thermal conductance results for the two-arm focal-plane thermal strap (TAFTS), from cryogenic to room temperatures, are also presented. The paper also briefly describes some elements of the fabrication process followed in developing a novel design solution, which provides high conductance and symmetrical mechanical loading, while providing enhanced flexibility in all three dimensions.

Urquiza, E.; Vasquez, C.; Rodriguez, J.; Van Gorp, B.

2012-04-01

264

Measuring Thermodynamic Length  

SciTech Connect

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

265

Application study of the optical biopsy system for small experimental animals  

NASA Astrophysics Data System (ADS)

An optical biopsy system for small experimental animals has been developed. The system includes endoscope probe, portable probe and two kinds of miniaturized Raman probes. The micro Raman probe (MRP) is made of optical fibers and the ball lens hollow optical fiber Raman probe (BHRP) is made of hollow fiber. The former has large focal depth and suitable to measure average spectra of subsurface tissue. The latter has rather small focal depth and it is possible to control focal length by selecting ball lens attached at the probe head. It is suitable to survey materials at the fixed depth in the tissue. The system is applied to study various small animal cancer models, such as esophagus and stomach rat models and subcutaneous mouse models of pancreatic cancers. In the studies of subcutaneous tumor model mouse, it is suggested that protein conformational changes occur in the tumor tissue within few minutes after euthanasia of the mouse. No more change is observed for the following ten minutes. Any alterations in the molecular level are not observed in normal skin, muscle tissues. Since the change completes in such a short time, it is suggested that this phenomenon caused by termination of blood circulation.

Sato, Hidetoshi; Suzuki, Toshiaki; Morita, Shin-ichi; Maruyama, Atsushi; Shimosegawa, Toru; Matsuura, Yuji; Kanai, Gen'ichi; Ura, Nobuo; Masutani, Koji; Ozaki, Yukihiro

2008-02-01

266

Development of microchannel plate x-ray optics  

NASA Technical Reports Server (NTRS)

The goal of this research program was to develop a novel technique for focusing x-rays based on the optical system of a lobster's eye. A lobster eye employs many closely packed reflecting surfaces arranged within a spherical or cylindrical shell. These optics have two unique properties: they have unlimited fields of view and can be manufactured via replication of identical structures. Because the angular resolution is given by the ratio of the size of the individual optical elements to the focal length, optical elements with size on the order of one hundred microns are required to achieve good angular resolution with a compact telescope. We employed anisotropic etching of single crystal silicon wafers for the fabrication of micron-scale optical elements. This technique, commonly referred to as silicon micromachining, is based on silicon fabrication techniques developed by the microelectronics industry. We have succeeded in producing silicon lenses with a geometry suitable for a 1-d focusing x-ray optics. These lenses have an aspect ratio (40:1) suitable for x-ray reflection and have very good optical surface alignment. We have developed a number of process refinements which improved the quality of the lens geometry and the repeatability of the etch process. In addition to the silicon fabrication, an x-ray beam line was constructed at Columbia for testing the optics. Most recently, we have done several experiments to find the fundamental limits that the anisotropic etch process placed on the etched surface roughness.

Kaaret, Philip

1995-01-01

267

Extended depth of focus adaptive optics spectral domain optical coherence tomography  

PubMed Central

We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

2012-01-01

268

Visual Scanning Hartmann Optical Tester (VSHOT) Uncertainty Analysis (Milestone Report)  

SciTech Connect

In 1997, an uncertainty analysis was conducted of the Video Scanning Hartmann Optical Tester (VSHOT). In 2010, we have completed a new analysis, based primarily on the geometric optics of the system, and it shows sensitivities to various design and operational parameters. We discuss sources of error with measuring devices, instrument calibrations, and operator measurements for a parabolic trough mirror panel test. These help to guide the operator in proper setup, and help end-users to understand the data they are provided. We include both the systematic (bias) and random (precision) errors for VSHOT testing and their contributions to the uncertainty. The contributing factors we considered in this study are: target tilt; target face to laser output distance; instrument vertical offset; laser output angle; distance between the tool and the test piece; camera calibration; and laser scanner. These contributing factors were applied to the calculated slope error, focal length, and test article tilt that are generated by the VSHOT data processing. Results show the estimated 2-sigma uncertainty in slope error for a parabolic trough line scan test to be +/-0.2 milliradians; uncertainty in the focal length is +/- 0.1 mm, and the uncertainty in test article tilt is +/- 0.04 milliradians.

Gray, A.; Lewandowski, A.; Wendelin, T.

2010-10-01

269

Pupil imaging with a high sensitivity, LWIR focal plane array  

NASA Astrophysics Data System (ADS)

We describe an integrated sensor assembly serving as both a component technology demonstration and a potential means of detecting distant point sources of infrared radiation. The objective of the demonstration was to show that usefully long integration times could be achieved with a low-background and well capacity, LWIR focal plane array optimized for use with cooled optics in space. The system controls extraneous background radiation with a small (150 ?m) cooled pinhole that nevertheless transmits all the radiation of a point source collected by the fore-optic. Broad waveband response (~3 to 12 ?m) results from optimization of the fore-optic for both MW and LWIR, as well as from a broadband anti-reflection coating on the field lens that is used at the pinhole to reimage the entrance aperture and its surrounding cold stop. Integration times in excess of 10 msec have been achieved for room temperature backgrounds with the FPA cold stage operated at 50 Kelvin, and noise performance has been bracketed with single frames of data collected over several integration times and over several minutes duration. However, anomalous signal behavior has been observed as the temperature of a remote blackbody increases. Although operation to date has been with a lower operability, engineering grade FPA, plans are to eventually upgrade to a higher quality device.

LeVan, Paul D.; Hubbs, John E.; Pratt, Quinn T.

2014-10-01

270

Physical Activity Performance of Focal Middle School Students  

ERIC Educational Resources Information Center

Histograms of push-ups and curl-ups from a sample of more than 9,000 students show periodic spikes at five and 10 unit intervals. This article argues that these spikes are related to focal points, a game theoretic concept popularized by Nobel Laureate Thomas Schelling. Being focal on one test makes one more likely to be focal on the other. Focal

Erfle, Stephen E.; Gelbaugh, Corey M.

2013-01-01

271

Microtubule-Actin Cross-talk at Focal Adhesions  

NSDL National Science Digital Library

Focal adhesions are dynamic structures in which traction forces are exerted against the substratum during cell migration and are sites for the organization of signaling complexes. Palazzo and Gundersen discuss how focal adhesions may also be the site of cross-talk between the actin-based and microtubule-based cytoskeletons. Microtubules appear to deliver factors that can regulate the formation and dissolution of focal adhesions, whereas focal adhesions contribute to microtubule localization and stability.

Alexander F. Palazzo (Columbia University; Department of Anatomy and Cell Biology REV)

2002-07-02

272

How Focal Adhesion Size Depends on Integrin Affinity Tong Zhao,,  

E-print Network

How Focal Adhesion Size Depends on Integrin Affinity Tong Zhao,, Ying Li,, and Aaron R. Dinner the thermodynamics and kinetics of integrin receptor binding and clustering impact the formation of focal adhesions in their environment. Cells on chemically well-defined surfaces were observed to have distributions of focal adhesions

Dinner, Aaron

273

Focal decompositions for linear differential equations of the second order  

Microsoft Academic Search

Focal decomposition associated to an ordinary differential equation of the sec- ond order is a partition of the set of all two-points boundary value problems ac- cording to the number of their solutions. Two equations are called focally equiv- alent if there exists a homomorphism of the set of two-points problems to itself such that the image of the focal

L. Birbrair; M. Sobolevsky; P. Sobolevskii

2003-01-01

274

Circumference and Arc Length  

NSDL National Science Digital Library

This unit will introduce you to circumference of a circle, and how to find the measurement of the edge of a piece of pizza! (Arc length!) Ok. Let's make sure you remember circumference of a circle, you know, the distance around a circle? Click on the following link and take notes! Circle Circumference Now we can use that to find the arc length, or the length of the crust part of the edge of a pizza! Take notes: Arcs in Circles Now, let's ...

Neubert, Mrs.

2011-03-24

275

Source-Coupling For Hybrid Focal Planes  

NASA Astrophysics Data System (ADS)

32 x 32 and 64 x 64 staring infrared focal plane arrays with epitaxial HgCdTe and InAsSb photovoltaic detectors coupled to surface channel CCD multiplexers have been fabri-cated and characterized. The backside-illuminated detector arrays have bandgaps suitable for operation in either the 3-5 or 8-12 ?m region. A source-coupled input circuit with background suppression is utilized. Performance characterization of the multiplexer will be given at cryogenic temperatures. CCD charge transfer efficiency and MOSFET threshold voltages have been measured as functions of temperature. The input circuit 1/f noise will be characterized. The detectivity and noise equivalent temperature of the hybrid focal planes will also be discussed.

Chow, K.; Blackwell, J. D.; Rode, J. P.; Sieb, D. H.; Lin, W. N.

1981-12-01

276

Chest pain in focal musculoskeletal disorders.  

PubMed

The musculoskeletal system is a recognized source of chest pain. However, despite the apparently benign origin, patients with musculoskeletal chest pain remain under-diagnosed, untreated, and potentially continuously disabled in terms of anxiety, depression, and activities of daily living. Several overlapping conditions and syndromes of focal disorders, including Tietze syndrome, costochondritis, chest wall syndrome, muscle tenderness, slipping rib, cervical angina, and segmental dysfunction of the cervical and thoracic spine, have been reported to cause pain. For most of these syndromes, evidence arises mainly from case stories and empiric knowledge. For segmental dysfunction, clinical features of musculoskeletal chest pain have been characterized in a few clinical trials. This article summarizes the most commonly encountered syndromes of focal musculoskeletal disorders in clinical practice. PMID:20380955

Stochkendahl, Mette Jensen; Christensen, Henrik Wulff

2010-03-01

277

Dynamic reactive astrocytes after focal ischemia  

PubMed Central

Astrocytes are specialized and most numerous glial cell type in the central nervous system and play important roles in physiology. Astrocytes are also critically involved in many neural disorders including focal ischemic stroke, a leading cause of brain injury and human death. One of the prominent pathological features of focal ischemic stroke is reactive astrogliosis and glial scar formation associated with morphological changes and proliferation. This review paper discusses the recent advances in spatial and temporal dynamics of morphology and proliferation of reactive astrocytes after ischemic stroke based on results from experimental animal studies. As reactive astrocytes exhibit stem cell-like properties, knowledge of dynamics of reactive astrocytes and glial scar formation will provide important insights for astrocyte-based cell therapy in stroke.

Ding, Shinghua

2014-01-01

278

Single-view Perspective Shape-from-Texture with Focal Length Estimation: A Piecewise Affine Approach  

E-print Network

the 3D shape of a surface using the Shape-From-Texture (SFT) cue. In the classical SFT setting is available at www.irit.fr/Pierre.Gurdjos/ECCV2002/ #12;ing to this intuition, it seems that uncalibrated SFT is well- posed. However, this is not true when the textons are small, which is precisely a SFT assumption

Bartoli, Adrien

279

In size preserving video tracking, the camera's focal length (zoom) is adjusted automatically to compensate for  

E-print Network

. The existing method of choice for real-time target scale estimation applies structure from motion (SFM) based/background separation algorithm, the affine shape method. The resulting segmentation automatically adapts to the target preserving their sizes. 1. Introduction Video tracking systems with automatic zoom control have attracted

Abidi, Mongi A.

280

Liquid Lens module with wide field-of-view and variable focal length  

Microsoft Academic Search

A novel wide angle and variable-focus imaging module based on a miniaturized liquid lens is presented for capsule endoscopy\\u000a applications. For these applications, it is desirable to have features such as a wide field of view (FOV), variable focus,\\u000a small size, and low power consumption, thereby taking full advantage of the miniaturized liquid lens. The proposed imaging\\u000a module has three

Sang Won Seo; Seungoh Han; Jun Ho Seo; Woo Bum Choi; Man Young Sung

2010-01-01

281

Prolonged deficits after focal inhibitory seizures  

Microsoft Academic Search

Introduction: Seizures are most commonly associated with positive phenomena such as tonic, clonic or myoclonic movements, automatisms,\\u000a paresthesias and hallucinations. Negative phenomena, however, are not an uncommon manifestation of seizure activity. Examples\\u000a of negative seizure phenomena include speech arrest, aphasia, amaurosis, amnesia, numbness, deafness, neglect and atonic seizures.\\u000a Less commonly described in the literature are focal inhibitory motor seizures.\\u000a \\u000a \\u000a Methods

Miguel Bussière; David Pelz; Robert H Reid; G. Bryan Young

2005-01-01

282

A Reflective Gaussian Coronagraph for Extreme Adaptive Optics: Laboratory Performance  

Microsoft Academic Search

We report laboratory results of a coronagraphic test bench to assess the intensity reduction differences between a ``Gaussian'' tapered focal plane coronagraphic mask and a classical hard-edged ``top hat'' function mask at extreme adaptive optics (ExAO) Strehl ratios of ~94%. However, unlike a traditional coronagraph design, we insert a reflective focal plane mask at 45° to the optical axis. We

Laird M. Close; Nick Siegler; Eric L. Nielsen; Thomas Stalcup

2006-01-01

283

Adaptation in the optical properties of the crystalline lens in the eyes of the Lessepsian migrant Siganus rivulatus.  

PubMed

Vision is an important source of information for many animals. The crystalline lens plays a central role in the visual pathway and hence the ecology of fishes. In this study, we tested whether the different light regimes in the Mediterranean and Red Seas have an effect on the optical properties of the lenses in the rivulated rabbitfish, Siganus rivulatus. This species has migrated through the Suez Canal from the Red Sea and established a vital population in the Mediterranean Sea. Longitudinal spherical aberration curves and focal lengths of the fish lenses were measured by laser scans and compared between the two populations. In addition, rivulated rabbitfish from the Mediterranean Sea were exposed to colored light (yellow, green and blue) and unfiltered light for periods of 1 or 13 days to test for short-term adjustments. Lens focal length was significantly longer (3%) in the Rea Sea population. The shorter focal length of the Mediterranean population can be explained as an adaptation to the dimmer light environment, as this difference makes the Mediterranean eyes 5% more sensitive than the eyes of the Red Sea population. The difference may be due to genetic differences or, more likely, adaptive developmental plasticity. Short-term regulatory mechanisms do not seem to be involved. PMID:21795569

Gagnon, Yakir L; Shashar, Nadav; Kröger, Ronald H H

2011-08-15

284

Multitiered wavefront sensor using binary optics  

Microsoft Academic Search

Wavefront sensors have been used to make measurements in fluid-dynamics and for closed loop control of adaptive optics. In most common Shack-Hartmann wavefront sensors, the light is broken up into series of rectangular or hexagonal apertures that divide the light into a series of focal spots. The position of these focal spots is used to determine the wavefront slopes over

Daniel R. Neal; Mial E. Warren; James K. Gruetzner; Tony G. Smith; R. R. Rosenthal; Thomas S. McKechnie

1994-01-01

285

Focal plane actuation to achieve ultra-high resolution on suborbital balloon payloads  

NASA Astrophysics Data System (ADS)

Over the past few years there has been remarkable success flying imaging telescope systems suspended from suborbital balloon payload systems. These imaging systems have covered optical, ultraviolet, sub-­-millimeter and infrared passbands (i.e. BLAST, STO, SBI, Fireball and others). In recognition of these advances NASA is now considering ambitious programs to promote planetary imaging from high altitude at a fraction of the cost of similar fully orbital systems. The challenge with imaging from a balloon payload is delivering the full diffraction-­-limited resolution of the system from a moving payload. Good progress has been made with damping mechanisms and oscillation control to remove most macroscopic movement in the departures of the imaging focal plane from a static configuration, however a jitter component remains that is difficult to remove using external corrections. This paper reports on work to demonstrate in the laboratory the utility and performance of actuating a detector focal plane (of whatever type) to remove the final jitter terms using an agile hexapod design. The input to this demonstration is the jitter signal generated by the pointing system of a previously flown balloon mission (the Stratospheric Terahertz Observatory, STO). Our group has a mature jitter compensation system that thermally isolates the control head from the focal plane itself. This allows the hexapod to remain at ambient temperature in a vacuum environment with the focal plane cooled to cryogenic temperatures. Our lab design mounts the focal plane on the hexapod in a custom cryostat and delivers an active optical stimulus together with the corresponding jitter signal, using the actuation of the hexapod to correct for the departures from a static, stable configuration. We believe this demonstration will make the case for inclusion of this technological solution in future balloon-­-borne imaging systems requiring ultra-­-high resolution.

Scowen, Paul A.; Miller, Alex; Challa, Priya; Veach, Todd; Groppi, Chris; Mauskopf, Phil

2014-07-01

286

Neandertal clavicle length.  

PubMed

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W; Auerbach, Benjamin M

2014-03-25

287

Optical system design for infrared imaging system of Korea Superconducting Tokamak Advanced Research (KSTAR) device  

NASA Astrophysics Data System (ADS)

The first infrared imaging system, for monitoring the temperature of the inner wall and localized hot spot such as the ICRH antenna was installed on the midplane of the D-port in the Korea Superconducting Tokamak Advanced Research (KSTAR). The cassette system of KSTAR makes a periscope inevitable for infrared imaging system. The periscope is composed of a 3 functional optical lens set (input beam shaper, beam deliverer, output beam shaper). CaF2 was chosen for the material of the lens elements. As an infrared image camera, FLIR/ThermoVision SC6000HS is used. The infrared camera has 640 × 512 pixel resolution and a camera lens set with 25.4 mm of focus length and 50 mm of input pupil. The periscope was designed to have 2.7 m of overall length, 19.07 mm of focal length and 3.81 of f-number.

Oh, S.; Seo, D.; KSTAR Team

2012-02-01

288

The pressure-dependent performance of a substrate-free focal plane array in an uncooled infrared imaging system  

Microsoft Academic Search

Uncooled focal plane arrays (FPAs) are being developed for a wide range of infrared imaging applications. A substrate-free FPA for optical readout infrared imaging is fabricated with a pixel pitch of 120 mum. The pressure dependences of thermal conductance of a FPA with\\/without substrate are studied by modeling analysis. Infrared imaging experiments are performed to validate the modeling analysis. At

Zhiming Xiong; Qingchuan Zhang; Jie Gao; Xiaoping Wu; Dapeng Chen; Binbin Jiao

2007-01-01

289

Focal adhesions as mechanosensors: the two-spring model  

E-print Network

Adhesion-dependent cells actively sense the mechanical properties of their environment through mechanotransductory processes at focal adhesions, which are integrin-based contacts connecting the extracellular matrix to the cytoskeleton. Here we present first steps towards a quantitative understanding of focal adhesions as mechanosensors. It has been shown experimentally that high levels of force are related to growth of and signaling at focal adhesions. In particular, activation of the small GTPase Rho through focal adhesions leads to the formation of stress fibers. Here we discuss one way in which force might regulate the internal state of focal adhesions, namely by modulating the internal rupture dynamics of focal adhesions. A simple two-spring model shows that the stiffer the environment, the more efficient cellular force is built up at focal adhesions by molecular motors interacting with the actin filaments.

Ulrich S. Schwarz; Thorsten Erdmann; Ilka B. Bischofs

2006-08-03

290

Limits of spectral resolution in optical measurements  

NASA Astrophysics Data System (ADS)

Nowadays a growing number of scientists relies on optical spectral measurements for their research. The market is full of new plug-and-play equipment for spectral analysis that take the fuss out of the measurements. As with other instruments (computers, lasers, etc.) the researcher does?t need any longer to work with someone with a post-graduate formation on the technology to be able to do excellent research. But, as in every instrument, there are limitations on the instrument use that affect its precision and resolution. Currently there is in the market a large variety of equipment for spectral measurements. They range from the huge long focal length double pass monochromators to the small pocket size USB connected array spectrometers. The different configurations have different sensitivities on the light input system, light intensity, coherence, polarization, etc. In this talk we will discuss a few of the limitations in spectral measurements that can be found in experimental setups.

Marques, Manuel B.

2014-08-01

291

Achromatic negative index lens with diffractive optics  

NASA Astrophysics Data System (ADS)

In this paper, achromatization of a negative index lens is achieved by introducing the diffractive optical elements (DOEs) into the negative index lens. The diffraction efficiency of the negative index material (NIM) DOEs is deduced based on the special propagating laws and imaging properties of negative index lenses, and the expression for microstructure height is given. As an example, an achromatic refractive–diffractive negative index lens with 150 mm focal length and 15 mm entrance pupil diameter is discussed from wavelength 0.848 ?m through wavelength 0.912 ?m to wavelength 1.114 ?m. According to the deduced expression for the NIM DOEs, the diffraction efficiency is calculated, and the diffraction efficiency curve is fitted by interpolation.

Piao, Mingxu; Cui, Qingfeng; Zhang, Bo

2015-02-01

292

Focal damage to macaque photoreceptors produces persistent visual loss  

PubMed Central

Insertion of light-gated channels into inner retina neurons restores neural light responses, light evoked potentials, visual optomotor responses and visually-guided maze behavior in mice blinded by retinal degeneration. This method of vision restoration bypasses damaged outer retina, providing stimulation directly to retinal ganglion cells in inner retina. The approach is similar to that of electronic visual protheses, but may offer some advantages, such as avoidance of complex surgery and direct targeting of many thousands of neurons. However, the promise of this technique for restoring human vision remains uncertain because rodent animal models, in which it has been largely developed, are not ideal for evaluating visual perception. On the other hand, psychophysical vision studies in macaque can be used to evaluate different approaches to vision restoration in humans. Furthermore, it has not been possible to test vision restoration in macaques, the optimal model for human-like vision, because there has been no macaque model of outer retina degeneration. In this study, we describe development of a macaque model of photoreceptor degeneration that can in future studies be used to test restoration of perception by visual prostheses. Our results show that perceptual deficits caused by focal light damage are restricted to locations at which photoreceptors are damaged, that optical coherence tomography (OCT) can be used to track such lesions, and that adaptive optics retinal imaging, which we recently used for in vivo recording of ganglion cell function, can be used in future studies to examine these lesions. PMID:24316158

Strazzeri, Jennifer M.; Hunter, Jennifer J.; Masella, Benjamin D.; Yin, Lu; Fischer, William S.; DiLoreto, David A.; Libby, Richard T.; Williams, David R.; Merigan, William H.

2014-01-01

293

A kinetic model for RNA-interference of focal adhesions  

PubMed Central

Background Focal adhesions are integrin-based cell-matrix contacts that transduce and integrate mechanical and biochemical cues from the environment. They develop from smaller and more numerous focal complexes under the influence of mechanical force and are key elements for many physiological and disease-related processes, including wound healing and metastasis. More than 150 different proteins localize to focal adhesions and have been systematically classified in the adhesome project (http://www.adhesome.org). First RNAi-screens have been performed for focal adhesions and the effect of knockdown of many of these components on the number, size, shape and location of focal adhesions has been reported. Results We have developed a kinetic model for RNA interference of focal adhesions which represents some of its main elements: a spatially layered structure, signaling through the small GTPases Rac and Rho, and maturation from focal complexes to focal adhesions under force. The response to force is described by two complementary scenarios corresponding to slip and catch bond behavior, respectively. Using estimated and literature values for the model parameters, three time scales of the dynamics of RNAi-influenced focal adhesions are identified: a sub-minute time scale for the assembly of focal complexes, a sub-hour time scale for the maturation to focal adhesions, and a time scale of days that controls the siRNA-mediated knockdown. Our model shows bistability between states dominated by focal complexes and focal adhesions, respectively. Catch bonding strongly extends the range of stability of the state dominated by focal adhesions. A sensitivity analysis predicts that knockdown of focal adhesion components is more efficient for focal adhesions with slip bonds or if the system is in a state dominated by focal complexes. Knockdown of Rho leads to an increase of focal complexes. Conclusions The suggested model provides a kinetic description of the effect of RNA-interference of focal adhesions. Its predictions are in good agreement with known experimental results and can now guide the design of RNAi-experiments. In the future, it can be extended to include more components of the adhesome. It also could be extended by spatial aspects, for example by the differential activation of the Rac- and Rho-pathways in different parts of the cell. PMID:23311633

2013-01-01

294

The focal plane instrumentation for the DUNE mission  

E-print Network

DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed. The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9x4 array together with the associated mechanical support structure and electronics processing chains. Four additional CCDs dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced e2v CCD203-82 devices with square 12 $\\mu$m pixels, operating from 550-920nm. Combining four rows of CCDs provides a total exposure time of 1500s. The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength bands Y, J, and H, the mechanical support structure, and the detector readout and signal processing electronics. The FPA is operated at a maximum temperature of 140 K for low dark current of 0.02e$-$/s. Each sensor chip assembly has 2048 x 2048 square pixels of 18 $\\mu$m size (0.15 arcsec), sensitive in the 0.8 to 1.7 $\\mu$m wavelength range. As the spacecraft is scanning the sky, the image motion on the NIR FPA is stabilized by a de-scanning mirror during the integration time of 300 s per detector. The total integration time of 1500 seconds is split among the three NIR wavelengths bands. DUNE has been proposed to ESA's Cosmic Vision program and has been jointly selected with SPACE for an ESA Assessment Phase which has led to the joint Euclid mission concept.

Jeff Booth; Mark Cropper; Frank Eisenhauer; Alexandre Refregier; the DUNE collaboration

2008-07-25

295

Time-reversed ultrasonically encoded optical focusing into tissue-mimicking media with thickness up to 70 mean free paths  

PubMed Central

In turbid media such as biological tissue, multiple scattering hinders direct light focusing at depths beyond one transport mean free path. As a solution to this problem, time-reversed ultrasonically encoded (TRUE) optical focusing is proposed based on ultrasonic encoding of diffused laser light and optical time reversal. In TRUE focusing, a laser beam of long coherence length illuminates a turbid medium, where the incident light undergoes multiple scattering and part of it gets ultrasonically encoded within the ultrasonic focal zone. A conjugated wavefront of the ultrasonically encoded light is then generated by a phase conjugate mirror outside the medium, which traces back the trajectories of the ultrasonically encoded diffused light and converges light to the ultrasonic focal zone. Here, we report the latest experimental improvement in TRUE optical focusing that increases its penetration in tissue-mimicking media from a thickness of 3.75 to 7.00 mm. We also demonstrate that the TRUE focus depends on the focal diameter of the ultrasonic transducer. PMID:21895321

Liu, Honglin; Xu, Xiao; Lai, Puxiang; Wang, Lihong V.

2011-01-01

296

9-fold Fresnel-Köhler concentrator with Fresnel lens of variable focal point.  

PubMed

Non-uniform irradiance patterns over Multi-Junction Cells gives rise to power losses, especially when considering spectral irradiance distributions over different junctions. Thermal effects on Silicone-on-Glass lenses affect spectral irradiance distributions. A new Photovoltaic Concentrator (CPV), formed by nine optical channels, each one with a Köhler configuration, has been designed to overcome these effects at high concentrations for a large acceptance angle. A Fresnel Lens with a Variable Focal Point is proposed to prevent optical crosstalk in multichannel systems. When integrated into the concentrator, improves the acceptance angle. These designs are designed to fulfill the expected requirements of four junction CPV systems. PMID:24978078

Mendes-Lopes, João; Benítez, Pablo; Zamora, Pablo; Miñano, Juan C

2014-06-30

297

Quantifying tissue hemodynamics by NIRS versus DOT: global versus focal changes in cerebral hemodynamics  

NASA Astrophysics Data System (ADS)

Near infrared spectroscopy (NIRS) is used to quantify changes in oxy-hemoglobin (HbO) and deoxy-hemoglobin (Hb) concentrations in tissue. The analysis uses the modified Beer-Lambert law, which is generally valid for quantifying global concentration changes. We examine the errors that result from analyzing focal changes in HbO and Hb concentrations. We find that the measured focal change in HbO and Hb are linearly proportional to the actual focal changes but that the proportionally constants are different. Thus relative changes in HbO and Hb cannot, in general, be quantified. However, we show that under certain circumstances it is possible to quantify these relative changes. This builds the case for diffuse optical tomography (DOT) which in general should be able to quantify focal changes in HbO and Hb through the use of image reconstruction algorithms that deconvolve the photon diffusion point-spread-function. We demonstrate the differences between NIRS and DOT using a rat model of somatosensory stimulation.

Boas, David A.; Cheng, Xuefeng; Marota, John A.; Mandeville, Joseph B.

1999-09-01

298

Design of the segmented primary optical telescope  

NASA Astrophysics Data System (ADS)

Following with the "high-resolution upsurge" appeared in many counties in recent few years, it is an inevitable trend to increase the size of the Optical Telescope. However, because of the volume constrains of space-borne astronomical instruments, segmented reflector is thought as the main measure of future astro-physical missions by many scientists. In this paper, a coaxial three-mirror anastigmatic system (TMA) with a segmented primary mirror is modeled in optical software. The optical system, which has 2.4m aperture, 48m focal length and the field-view angle of 0.3°×0.06°, works in the 450nm~900nm wave band. The `1+6' aperture-stiching model is applied. Firstly, the initial structure of the system is inputted to the CODEV, and a certain constraint functions are set, and then the system automatically optimizes. Finally, designing results show that the Modulation Transfer Function (MTF) is really very near to the limit of diffraction. We get a good image quality of the optical system design results.

Zhang, Kaisheng; Yan, Aqi; Cao, Jianzhong; Fan, Zheyuan; Wu, Li; Zhang, Zhi; Zhu, Qing

2013-09-01

299

Laser skin perforator with focal point detection  

NASA Astrophysics Data System (ADS)

The development of laser skin perforator device for obtaining blood samples is presented. The use of photoelectric proximity photoelectric sensor permits to determine the focal point eliminating any contact and them avoiding the risk of contamination. Perforation of about 0.2 mm - 0.5 mm in diameter can be obtained in order to take the sample of blood. The method permits to make the blood analysis not only avoiding the contamination risk but also diminishing the pain sensation in comparison with metal lancet.

Ponce, L.; Arronte, M.; Cabrera, J. L.; Flores, T.

2006-02-01

300

Simulating focal demyelinating neuropathies: membrane property abnormalities.  

PubMed

Membrane properties such as potentials (intracellular, extracellular, electrotonic) and axonal excitability indices (strength-duration and charge-duration curves, strength-duration time constants, rheobasic currents, recovery cycles) can now be measured in healthy subjects and patients with demyelinating neuropathies. They are regarded here in two cases of simultaneously reduced paranodal seal resistance and myelin lamellae in one to three consecutive internodes of human motor nerve fiber. The investigations are performed for 70 and 96% myelin reduction values. The first value is not sufficient to develop a conduction block, but the second leads to a block and the corresponding demyelinations are regarded as mild and severe. For both the mild and severe demyelinations, the paranodally internodally focally demyelinated cases (termed as PIFD1, PIFD2, and PIFD3, respectively, with one, two, and three demyelinated internodes) are simulated using our previous double-cable model of the fiber. The axon model consists of 30 nodes and 29 internodes. The membrane property abnormalities obtained can be observed in vivo in patients with demyelinating forms of Guillain-Barré syndrome (GBS) and multifocal motor neuropathy (MMN). The study confirms that focal demyelinations are specific indicators for acquired demyelinating neuropathies. Moreover, the following changes have been calculated in our previous papers: (1) uniform reduction of myelin thickness in all internodes (Stephanova et al. in Clin Neurophysiol 116: 1153-1158, 2005); (2) demyelination of all paranodal regions (Stephanova and Daskalova in Clin Neurophysiol 116: 1159-1166, 2005a); (3) simultaneous reduction of myelin thickness and paranodal demyelination in all internodes (Stephanova and Daskalova in Clin Neurophysiol 116: 2334-2341, 2005b); and (4) reduction of myelin thickness of up to three internodes (Stephanova et al., in J Biol Phys, 2006a,b, DOI: 10.1007/s10867-005-9001-9; DOI: 10.1007/s10867-006-9008-x). The membrane property abnormalities obtained in the homogeneously demyelinated cases are quite different and abnormally greater than those in the case investigated here of simultaneous reduction in myelin thickness and paranodal demyelination of up to three internodes. Our previous and present results show that unless focal demyelination is severe enough to cause outright conduction block, changes are so slight as to be essentially indistinguishable from normal values. Consequently, the excitability-based approaches that have shown strong potential as diagnostic tools in systematically demyelinated conditions may not be useful in detecting mild focal demyelinations, independently of whether they are internodal, paranodal, or paranodal internodal. PMID:17072638

Stephanova, D I; Alexandrov, A S; Kossev, A; Christova, L

2007-02-01

301

Psychiatric symptoms associated with focal hand dystonia.  

PubMed

Myoclonus dystonia and idiopathic dystonia are associated with a greater frequency of obsessive compulsive disorder (OCD) and major depression. We investigated the frequency of OCD in 39 patients with primary focal hand dystonia (FHD) using a semistructured interview. OCD and subsyndromal OCD was diagnosed in 5 of 39 (12.82%) patients with FHD, whereas OCD occurs in 2.3% of the general population. Recurrent depression occurred in (7 of 39) 17.95% of patients with FHD along with a family history of depression in (16 of 39) 41.02%. Overlapping mechanisms manifesting as FHD may also predispose to OC symptoms and likely implicates a common striatal dysfunction. PMID:20737548

Voon, Valerie; Butler, Tracy R; Ekanayake, Vindhya; Gallea, Cecile; Ameli, Rezvan; Murphy, Dennis L; Hallett, Mark

2010-10-15

302

Myofilament length dependent activation  

SciTech Connect

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

2010-05-25

303

A Characteristic Particle Length  

E-print Network

It is argued that there are characteristic intervals associated with any particle that can be derived without reference to the speed of light $c$. Such intervals are inferred from zeros of wavefunctions which are solutions to the Schr\\"odinger equation. The characteristic length is $\\ell=\\beta^2\\hbar^2/(8Gm^3)$, where $\\beta=3.8\\dots$; this length might lead to observational effects on objects the size of a virus.

Mark D. Roberts

2014-06-14

304

Activation of pyk2\\/Related Focal Adhesion Tyrosine Kinase and Focal Adhesion Kinase in Cardiac Remodeling  

Microsoft Academic Search

Cellular remodeling during progression of dilation in- volves focal adhesion contact reorganization. However, the signaling mechanisms and structural consequences leading to impaired cardiomyocyte adhesion are poorly defined. These events were studied in tropomodulin- overexpressing transgenic mice that develop dilated cardiomyopathy associated with chronic elevation of in- tracellular calcium. Analysis of tropomodulin-overex- pressing transgenic hearts by immunoblot and confocal microscopy revealed

Jaime Melendez; Sara Welch; Erik Schaefer; Christine S. Moravec; Shalom Avraham; Hava Avraham; Mark A. Sussman

2002-01-01

305

Can biologic treatment induce cutaneous focal mucinosis?  

PubMed Central

Skin mucinosis is a rare skin disease which clinically manifests as firm papules and waxy nodules. We report a case of a 66-year-old female psoriatic patient who developed skin mucinosis during biological therapy. Because of a previous lack of response to the local and conventional systemic treatment of psoriasis, the patient received biological therapy (infliximab from June 2008 to May 2009 – initial clinical improvement and loss of treatment effectiveness in the 36th week of the therapy; adalimumab from June 2009 to January 2010 – lack effectiveness; ustekinumab from March 2012 to the present). Throughout 2 months we observed a manifestation of the skin mucinosis as well-demarcated, yellow and brown, papulo-nodular lesions of 5–10 mm in diameter, localized on the back. Histopathological examination with alcian blue staining demonstrated mucin deposits in the dermis. On the basis of clinical and histopathological findings, the diagnosis of cutaneous focal mucinosis was established. We present the case because of the extremely rare occurrence of the disease. Scarce literature and data suggest that there is an association between focal mucinosis and thyroid dysfunction, as well as possible adverse effects of biological therapy with TNF-? antagonists. PMID:25610359

W?odarczyk, Marcin; Sobolewska, Aleksandra; Sieniawska, Joanna; Rogowski-Tylman, Micha?; Sysa-Jedrzejowska, Anna; Olejniczak-Staruch, Irmina; Narbutt, Joanna

2014-01-01

306

The Piriform Cortex and Human Focal Epilepsy  

PubMed Central

It is surprising that the piriform cortex, when compared to the hippocampus, has been given relatively little significance in human epilepsy. Like the hippocampus, it has a phylogenetically preserved three-layered cortex that is vulnerable to excitotoxic injury, has broad connections to both limbic and cortical areas, and is highly epileptogenic – being critical to the kindling process. The well-known phenomenon of early olfactory auras in temporal lobe epilepsy highlights its clinical relevance in human beings. Perhaps because it is anatomically indistinct and difficult to approach surgically, as it clasps the middle cerebral artery, it has, until now, been understandably neglected. In this review, we emphasize how its unique anatomical and functional properties, as primary olfactory cortex, predispose it to involvement in focal epilepsy. From recent convergent findings in human neuroimaging, clinical epileptology, and experimental animal models, we make the case that the piriform cortex is likely to play a facilitating and amplifying role in human focal epileptogenesis, and may influence progression to epileptic intractability. PMID:25538678

Vaughan, David N.; Jackson, Graeme D.

2014-01-01

307

Focal Conic Flower Textures at Curved Interfaces  

NASA Astrophysics Data System (ADS)

Focal conic domains (FCDs) in smectic-A liquid crystals have drawn much attention both for their exquisitely structured internal form and for their ability to direct the assembly of micro- and nanomaterials in a variety of patterns. A key to directing FCD assembly is control over the eccentricity of the domain. Here, we demonstrate a new paradigm for creating spatially varying FCD eccentricity by confining a hybrid-aligned smectic with curved interfaces. In particular, we manipulate interface behavior with colloidal particles in order to experimentally produce two examples of what has recently been dubbed the flower texture, where the focal hyperbolae diverge radially outward from the center of the texture, rather than inward as in the canonical eventail or fan texture. We explain how this unconventional assembly can arise from appropriately curved interfaces. Finally, we present a model for this system that applies the law of corresponding cones, showing how FCDs may be embedded smoothly within a "background texture" of large FCDs and concentric spherical layers, in a manner consistent with the qualitative features of the smectic flower. Such understanding could potentially lead to disruptive liquid crystal technologies beyond displays, including patterning, smart surfaces, microlens arrays, sensors and nanomanufacturing.

Beller, Daniel A.; Gharbi, Mohamed A.; Honglawan, Apiradee; Stebe, Kathleen J.; Yang, Shu; Kamien, Randall D.

2013-12-01

308

Fast nonparaxial scalar focal field calculations.  

PubMed

An efficient algorithm for calculating nonparaxial scalar field distributions in the focal region of a lens is discussed. The algorithm is based on fast Fourier transform implementations of the first Rayleigh-Sommerfeld diffraction integral and assumes that the input field at the pupil plane has a larger extent than the field in the focal region. A sampling grid is defined over a finite region in the output plane and referred to as a tile. The input field is divided into multiple separate spatial regions of the size of the output tile. Finally, the input tiles are added coherently to form a summed tile, which is propagated to the output plane. Since only a single tile is propagated, there are significant reductions of computational load and memory requirements. This method is combined either with a subpixel sampling technique or with a chirp z-transform to realize smaller sampling intervals in the output plane than in the input plane. For a given example the resulting methods enable a speedup of approximately 800× in comparison to the normal angular spectrum method, while the memory requirements are reduced by more than 99%. PMID:24977358

Hillenbrand, Matthias; Hoffmann, Armin; Kelly, Damien P; Sinzinger, Stefan

2014-06-01

309

Focal Conic Flower Textures at Curved Interfaces  

E-print Network

Focal conic domains (FCDs) in smectic-A liquid crystals have drawn much attention both for their exquisitely structured internal form and for their ability to direct the assembly of micro- and nanomaterials in a variety of patterns. A key to directing FCD assembly is control over the eccentricity of the domain. Here, we demonstrate a new paradigm for creating spatially varying FCD eccentricity by confining a hybrid-aligned smectic with curved interfaces. In particular, we manipulate interface behavior with colloidal particles in order to experimentally produce two examples of what has recently been dubbed the flower texture, where the focal hyperbolae diverge radially outward from the center of the texture, rather than inward as in the canonical eventail or fan texture. We explain how this unconventional assembly can arise from appropriately curved interfaces. Finally, we present a model for this system that applies the law of corresponding cones, showing how FCDs may be embedded smoothly within a "background texture" of large FCDs and concentric spherical layers, in a manner consistent with the qualitative features of the smectic flower. Such understanding could potentially lead to disruptive liquid crystal technologies beyond displays, including patterning, smart surfaces, microlens arrays, sensors and nanomanufacturing.

Daniel A. Beller; Mohamed A. Gharbi; Apiradee Honglawan; Kathleen J. Stebe; Shu Yang; Randall D. Kamien

2013-10-25

310

PIPKI? Regulates Focal Adhesion Dynamics and Colon Cancer Cell Invasion  

PubMed Central

Focal adhesion assembly and disassembly are essential for cell migration and cancer invasion, but the detailed molecular mechanisms regulating these processes remain to be elucidated. Phosphatidylinositol phosphate kinase type I? (PIPKI?) binds talin and is required for focal adhesion formation in EGF-stimulated cells, but its role in regulating focal adhesion dynamics and cancer invasion is poorly understood. We show here that overexpression of PIPKI? promoted focal adhesion formation, whereas cells expressing either PIPKI?K188,200R or PIPKI?D316K, two kinase-dead mutants, had much fewer focal adhesions than those expressing WT PIPKI? in CHO-K1 cells and HCT116 colon cancer cells. Furthermore, overexpression of PIPKI?, but not PIPKI?K188,200R, resulted in an increase in both focal adhesion assembly and disassembly rates. Depletion of PIPKI? by using shRNA strongly inhibited formation of focal adhesions in HCT116 cells. Overexpression of PIPKI?K188,200R or depletion of PIPKI? reduced the strength of HCT116 cell adhesion to fibronection and inhibited the invasive capacities of HCT116 cells. PIPKI? depletion reduced PIP2 levels to ?40% of control and PIP3 to undetectable levels, and inhibited vinculin localizing to focal adhesions. Taken together, PIPKI? positively regulates focal adhesion dynamics and cancer invasion, most probably through PIP2-mediated vinculin activation. PMID:21931851

Sunkara, Manjula; Spearman, Heather; Morris, Andrew J.; Huang, Cai

2011-01-01

311

Focal therapy for prostate cancer: rationale and treatment opportunities.  

PubMed

Focal therapy is an emerging treatment modality for localised prostate cancer that aims to reduce the morbidity seen with radical therapy, while maintaining cancer control. Focal therapy treatment strategies minimise damage to non-cancerous tissue, with priority given to the sparing of key structures such as the neurovascular bundles, external sphincter, bladder neck and rectum. There are a number of ablative technologies that can deliver energy to destroy cancer cells as part of a focal therapy strategy. The most widely investigated are cryotherapy and high-intensity focussed ultrasound. Existing radical therapies, such as brachytherapy and external beam radiotherapy, also have the potential to be applied in a focal manner. The functional outcomes of focal therapy from several phase I and II trials have been encouraging, with low rates of urinary incontinence and erectile dysfunction. Robust medium- and long-term cancer control outcomes are currently lacking. Controversies in focal therapy remain, notably treatment paradigms based on the index lesion hypothesis, appropriate patient selection for focal therapy and how the efficacy of focal therapy should be assessed. This review articles discusses the current status of focal therapy, highlighting controversies and emerging strategies that can influence treatment outcomes for the future. PMID:23759249

Kasivisvanathan, V; Emberton, M; Ahmed, H U

2013-08-01

312

Focal Therapy for Prostate Cancer: Rationale and Treatment Opportunities  

PubMed Central

Focal therapy is an emerging treatment modality for localised prostate cancer that aims to reduce the morbidity seen with radical therapy, while maintaining cancer control. Focal therapy treatment strategies minimise damage to non-cancerous tissue, with priority given to the sparing of key structures such as the neurovascular bundles, external sphincter, bladder neck and rectum. There are a number of ablative technologies that can deliver energy to destroy cancer cells as part of a focal therapy strategy. The most widely investigated are cryotherapy and high-intensity focussed ultrasound. Existing radical therapies, such as brachytherapy and external beam radiotherapy, also have the potential to be applied in a focal manner. The functional outcomes of focal therapy from several phase I and II trials have been encouraging, with low rates of urinary incontinence and erectile dysfunction. Robust medium- and long-term cancer control outcomes are currently lacking. Controversies in focal therapy remain, notably treatment paradigms based on the index lesion hypothesis, appropriate patient selection for focal therapy and how the efficacy of focal therapy should be assessed. This review articles discusses the current status of focal therapy, highlighting controversies and emerging strategies that can influence treatment outcomes for the future. PMID:23759249

Kasivisvanathan, V.; Emberton, M.; Ahmed, H.U.

2013-01-01

313

Botulinum Toxin Physiology in Focal Hand and Cranial Dystonia  

PubMed Central

The safety and efficacy of botulinum toxin for the treatment of focal hand and cranial dystonias are well-established. Studies of these adult-onset focal dystonias reveal both shared features, such as the dystonic phenotype of muscle hyperactivity and overflow muscle contraction and divergent features, such as task specificity in focal hand dystonia which is not a common feature of cranial dystonia. The physiologic effects of botulinum toxin in these 2 disorders also show both similarities and differences. This paper compares and contrasts the physiology of focal hand and cranial dystonias and of botulinum toxin in the management of these disorders. PMID:23202323

Karp, Barbara Illowsky

2012-01-01

314

Multi-chroic Dual-Polarization Bolometric Focal Plane for Studies of the Cosmic Microwave Background  

NASA Astrophysics Data System (ADS)

We are developing multi-chroic antenna-coupled Transition Edge Sensor (TES) focal planes for Cosmic Microwave Background (CMB) polarimetry. In each pixel, a dual polarized sinuous antenna collects light over a two-octave frequency band. Each antenna couples to the telescope with a contacting silicon lens. The antenna couples the broadband RF signal to microstrip transmission lines, and then filter banks split the broadband signal into several frequency bands. A TES bolometer detects the power in each band and polarization. We will describe the design of this device and demonstrate its performance with optical data measured using prototype pixels. Our measurements show low ellipticity beams, low cross-polarization, and properly partitioned bands in banks of 2, 3, and 7 filters. Finally, we will describe how we will upgrade the Polarbear CMB experiment using the focal planes of these detectors to increase the experiment's mapping speed and its ability to discriminate between the CMB and polarized foregrounds.

Suzuki, A.; Arnold, K.; Edwards, J.; Engargiola, G.; Ghribi, A.; Holzapfel, W.; Lee, A.; Meng, X.; Myers, M.; O'Brient, R.; Quealy, E.; Rebeiz, G.; Richards, P.

2012-06-01

315

Quantitative Characterization of Super-Resolution Infrared Imaging Based on Time-Varying Focal Plane Coding  

NASA Astrophysics Data System (ADS)

High resolution infrared image has been the goal of an infrared imaging system. In this paper, a super-resolution infrared imaging method using time-varying coded mask is proposed based on focal plane coding and compressed sensing theory. The basic idea of this method is to set a coded mask on the focal plane of the optical system, and the same scene could be sampled many times repeatedly by using time-varying control coding strategy, the super-resolution image is further reconstructed by sparse optimization algorithm. The results of simulation are quantitatively evaluated by introducing the Peak Signal-to-Noise Ratio (PSNR) and Modulation Transfer Function (MTF), which illustrate that the effect of compressed measurement coefficient r and coded mask resolution m on the reconstructed image quality. Research results show that the proposed method will promote infrared imaging quality effectively, which will be helpful for the practical design of new type of high resolution ! infrared imaging systems.

Wang, X.; Yuan, Y.; Zhang, J.; Chen, Y.; Cheng, Y.

2014-10-01

316

Relativistic Length Agony Continued  

NASA Astrophysics Data System (ADS)

We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

Redzic, D. V.

2014-06-01

317

Deep Moonquake Focal Mechanisms: Recovery and Implications  

NASA Technical Reports Server (NTRS)

A defining characteristic of deep moonquakes is their tendency to occur with tidal periodicity, prompting previous studies to infer that they are related to the buildup and release of tidal stress within the Moon. In studies of tidal forcing, a key constraint is the focal mechanism: the fault parameters describing the type of failure moonquakes represent. The quality of the lunar seismic data and the limited source/receiver geometries of the Apollo seismic network prohibit the determination of deep moonquake fault parameters using first-motion polarities, as is typically done in terrestrial seismology. Without being able to resolve tidal stress onto a known failure plane, we can examine only gross qualities of the tidal stress tensor with respect to moonquake occurrence, so we cannot fully address the role of tidal stress in moonquake generation. We will examine the extent to which shear (S) and compression (P) wave amplitude ratios can constrain moonquake fault geometry by determining whether, for a given cluster, there exists a focal mechanism that can produce a radiation pattern consistent with the amplitudes measured by the Apollo instruments. Amplitudes are read in the ray coordinate frame, directly from seismograms for which the P and S arrivals are clearly identifiable on all long-period channels of the four Apollo stations. We apply an empirical station correction to account for site effects and the differences between P- and S-wave attenuation. Instead of focusing on the best fitting solution only, we formulate the inverse problem using a falsification criterion: all source orientations that do not reproduce the observed SV/P ratios within an error margin derived from the uncertainty of amplitude readings are rejected. All others are accepted as possible solutions. The inversion is carried out using an exhaustive grid search on a regular grid with predefined step size, encompassing all possible combinations of strike, dip and slip. To assess the sensitivity of the inversion for the uncertainty of the lunar interior structure, we carry out repeated inversions with different velocity structures. Our data set consist of a total of 106 events from 25 deep moonquake clusters. The largest contribution of 37 events originates from the most active cluster, A001, while other clusters are represented by 1 to 9 events. Since the definition of a cluster implies that all events share the same source orientation, a comparison of the inversion results of all events from one cluster will reduce ambiguities of the inversion. Once we obtain a suite of fault parameters for a given source, we can attempt to further constrain the focal mechanism with refined analyses of tidal stresses and predictions based on synthetic seismograms.

Knapmeyer, Martin; Weber, Renee C.

2011-01-01

318

Quasi-optical mirrors made by a conventional milling machine  

Microsoft Academic Search

Conclusion A modified method for machining off-axis mirrors has been described. By a careful choice of machine parameters, revolution surface can be generated with a sufficient accuracy for ?>15 µm. A large set of spherical, paraboloidal and ellipsoidal mirrors, whose focal lengths are comprised between 50 mm and 900 mm, have been machined using the method. Focal ratio improving the

Daniel Boucher; Jean Burie; Robin Bocquet; Weidong Chen

1992-01-01

319

Comparison of performances between GASIR molded optics and existing IR optics  

NASA Astrophysics Data System (ADS)

Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses with well controlled properties. These materials called GASIR 1 and GASIR 2 are transparent in the 3-5 and 8-12 ?m atmospheric windows allowing a great range of applications in thermal imaging. A high precision industrial moulding process has been developed and set up allowing to mould GASIR material directly into high quality finished spherical, aspherical and diffractive lenses. This process is especially attractive for medium and high volume applications. Specific antireflection coatings have also been developed offering a maximum transmission of 98% when coated with high efficiency coating. Several optics from 17.5 mm F/1 to 100 mm F/1.25 focal length based on existing germanium optics have been redesigned especially for GASIR 1 and GASIR 2 glasses. The lenses have been manufactured using Umicore"s moulding technology. These chalcogenide moulded optics are used in various applications like imaging, process control, military applications and their performances (modulation transfer function has been measured) are reviewed and compared to the existing solutions made of traditional IR optics.

Guimond, Yann M.; Franks, John; Bellec, Yann

2004-08-01

320

Deep Moonquake Focal Mechanisms: Recovery and Implications  

NASA Technical Reports Server (NTRS)

A defining characteristic of deep moonquakes is their tendency to occur with tidal periodicity, prompting previous studies to infer that they are related to the buildup and release of tidal stress within the Moon [refs]. In studies of tidal forcing, a key constraint is the focal mechanism: the fault parameters describing the type of failure moonquakes represent. The quality of the lunar seismic data and the limited source/receiver geometries of the Apollo seismic network prohibit the determination of deep moonquake fault parameters using first-motion polarities, as is typically done in terrestrial seismology [ref]. Without being able to resolve tidal stress onto a known failure plane, we can examine only gross qualities of the tidal stress tensor with respect to moonquake occurrence, so we cannot fully address the role of tidal stress in moonquake generation.

Weber, Renee C.; Knapmeyer, Martin

2012-01-01

321

[Benign focal epilepsy of childhood (BFEC)].  

PubMed

Thirty cases of benign focal epilepsy of childhood were reported. The seizures were partial or generalized motor ones in all cases. One patient had episodes of visual hallucination with motor seizures. No objective examination has demonstrated cerebral lesions in all cases. The most characteristic in the present study was that the attacks were in relation to the sleep in 90% of cases, 56.7% of all patients had nocturnal seizure only. The characteristic EEG patterns were the spike or sharp discharges in Rolandic area in 29 cases, and occipital sharps or sharp wave complexes in one patient on normal background activities. The discharge rate of Rolandic spikes or sharps were significantly higher during sleep than during the awake stage, and 12 cases had Rolandic discharges only during sleep. Sleep EEG recordings is suggested when children were suspected of having such kind of seizure type but having a normal EEG pattern when awake. Brief induced sleep is usually adequate. PMID:1395939

Liu, X

1992-06-01

322

Focal Epilepsy Associated with Glioneuronal Tumors  

PubMed Central

Glioneuronal tumors are an increasingly recognized cause of partial seizures that occur primarily in children and young adults. Focal epilepsy associated with glioneuronal tumors is often resistant to pharmacological treatment. The cellular mechanisms underlying the epileptogenicity of glioneuronal tumors remain largely unknown. The involved mechanisms are certain to be multifactorial and depend on specific tumor histology, integrity of the blood-brain barrier, characteristics of the peritumoral environment, circuit abnormalities, or cellular and molecular defects. Glioneuronal tumors presenting with epilepsy were observed to have relatively benign biological behavior. The completeness of the tumor resection is of paramount importance in avoiding tumor progression and malignant transformation, which are rare in cases of epileptogenic glioneuronal tumors. An evolving understanding of the various mechanisms of tumor-related epileptogenicity may also lead to a more defined surgical objective and effective therapeutic strategies, including antiepileptogenic treatments, to prevent epilepsy in at-risk patients. PMID:22389832

Loiacono, Giulia; Cirillo, Chiara; Chiarelli, Francesco; Verrotti, Alberto

2011-01-01

323

Proliferating trichilemmal cyst with focal calcification.  

PubMed

A 64-year-old man presented with a superficial, well-demarcated, skin-colored tumor on the left posterior scalp that measured 4 x 5 x 6 cm. The tumor was nearly hairless, rubbery, non-tender, and mobile over the underlying subcutaneous tissues. The lesion had grown slowly since arising approximately 30 years ago. Treatment options were declined in the past. However, with relatively more rapid growth over the past five years, the nodule began to cause intermittent pain and interfere with the patient's ability to lie on his back. The patient denied a history of similar lesions in himself or his family. A biopsy specimen showed a ruptured proliferating trichilemmal cyst with focal calcification. Complete excision is recommended for all benign proliferating variants owing to their potential for locally aggressive behavior and malignant transformation. PMID:19061624

Anolik, Robert; Firoz, Bahar; Walters, Ruth F; Meehan, Shane A; Tsou, Hui C; Whitlow, Michael; Wainwright, Brent

2008-01-01

324

Smart trigger logic for focal plane arrays  

DOEpatents

An electronic device includes a memory configured to receive data representing light intensity values from pixels in a focal plane array and a processor that analyzes the received data to determine which light values correspond to triggered pixels, where the triggered pixels are those pixels that meet a predefined set of criteria, and determines, for each triggered pixel, a set of neighbor pixels for which light intensity values are to be stored. The electronic device also includes a buffer that temporarily stores light intensity values for at least one previously processed row of pixels, so that when a triggered pixel is identified in a current row, light intensity values for the neighbor pixels in the previously processed row and for the triggered pixel are persistently stored, as well as a data transmitter that transmits the persistently stored light intensity values for the triggered and neighbor pixels to a data receiver.

Levy, James E; Campbell, David V; Holmes, Michael L; Lovejoy, Robert; Wojciechowski, Kenneth; Kay, Randolph R; Cavanaugh, William S; Gurrieri, Thomas M

2014-03-25

325

Focal cerebral lesions and painting abilities.  

PubMed

Focal lesions such as strokes significantly affect painting production in the vast majority of artists. In particular, painters, when they resume painting, show changes in their painting style. In exceptional cases, there may be an apparent improvement in style, but in most cases, the changes represent nothing short of deterioration. This, however, varies according to the hemisphere affected. Painters with left-hemisphere lesions tend to show an inability to deal adequately with perspective and also tend to use simplified colors with fewer nuances. One often witnesses an evolution toward simpler, often "naïve" techniques, and at times rigid geometric repetitive features. Painters with right-hemisphere lesions also become unable to represent tridimensionality. In addition, their figures are often drawn in very summary fashion, with lack of coordination between volumes and space and a chromatic impoverishment; their main problem, however, is visuospatial, leading to neglect of the left side of the canvas. PMID:24041319

Mazzucchi, Anna; Sinforiani, Elena; Boller, François

2013-01-01

326

Effect of dense planer focal plane array on device performances  

NASA Astrophysics Data System (ADS)

As the technologies in focal plane array (FPA) progresses, the industry is pushing for smaller pixel size and spacing between the pixels. The reduction in pixel size and spacing will increase both the resolution and fill factor which reduces the cost and increases the performance. However, as the density of the array elements increases, the crosstalk between the nearest neighboring pixels become a significant issue. Here we examine the case for a planer FPA with epitaxially grown NIN+ structure and the planer junctions are formed by diffusing P-type dopant into the N doped layer. We first examine the possible spacing by considering the lateral depletion region width to set the upper boundary for the spacing. The depletion region width is calculated by solving Poisson's equation for Gaussian doping profile and the isolation of adjacent pixel is dependent on the formation of the back to back diodes to block the current flowing towards the device. Therefore overlap of the depletion regions indicates shorting and sets the minimum possible spacing for this structure. The electrical and optical crosstalks are modeled by using a DC resistive model to gauge the effect of current flow as the spacing reduces. Series of device arrays with various device pitches and device sizes ranging from 5 ?m to 10 ?m with device pitch from 5.5 ?m to 15 ?m are fabricated and tested under both dark and illumination conditions for their electrical performances including the crosstalk. The simulated and measured results will be presented.

Lin, Tony; Olah, Robert; Dutta, Achyut K.

2014-05-01

327

Focal cortical dysplasias in autism spectrum disorders  

PubMed Central

Background Previous reports indicate the presence of histological abnormalities in the brains of individuals with autism spectrum disorders (ASD) suggestive of a dysplastic process. In this study we identified areas of abnormal cortical thinning within the cerebral cortex of ASD individuals and examined the same for neuronal morphometric abnormalities by using computerized image analysis. Results The study analyzed celloidin-embedded and Nissl-stained serial full coronal brain sections of 7 autistic (ADI-R diagnosed) and 7 age/sex-matched neurotypicals. Sections were scanned and manually segmented before implementing an algorithm using Laplace’s equation to measure cortical width. Identified areas were then subjected to analysis for neuronal morphometry. Results of our study indicate the presence within our ASD population of circumscribed foci of diminished cortical width that varied among affected individuals both in terms of location and overall size with the frontal lobes being particularly involved. Spatial statistic indicated a reduction in size of neurons within affected areas. Granulometry confirmed the presence of smaller pyramidal cells and suggested a concomitant reduction in the total number of interneurons. Conclusions The neuropathology is consistent with a diagnosis of focal cortical dysplasia (FCD). Results from the medical literature (e.g., heterotopias) and our own study suggest that the genesis of this cortical malformation seemingly resides in the heterochronic divisions of periventricular germinal cells. The end result is that during corticogenesis radially migrating neuroblasts (future pyramidal cells) are desynchronized in their development from those that follow a tangential route (interneurons). The possible presence of a pathological mechanism in common among different conditions expressing an autism-like phenotype argue in favor of considering ASD a “sequence” rather than a syndrome. Focal cortical dysplasias in ASD may serve to explain the high prevalence of seizures and sensory abnormalities in this patient population. PMID:24252498

2013-01-01

328

Focal ratio degradation in lightly fused hexabundles  

NASA Astrophysics Data System (ADS)

We are now moving into an era where multi-object wide-field surveys, which traditionally use single fibres to observe many targets simultaneously, can exploit compact integral field units (IFUs) in place of single fibres. Current multi-object integral field instruments such as Sydney-AAO Multi-object Integral field spectrograph have driven the development of new imaging fibre bundles (hexabundles) for multi-object spectrographs. We have characterized the performance of hexabundles with different cladding thicknesses and compared them to that of the same type of bare fibre, across the range of fill fractions and input f-ratios likely in an IFU instrument. Hexabundles with 7-cores and 61-cores were tested for focal ratio degradation (FRD), throughput and cross-talk when fed with inputs from F/3.4 to >F/8. The five 7-core bundles have cladding thickness ranging from 1 to 8 ?m, and the 61-core bundles have 5 ?m cladding. As expected, the FRD improves as the input focal ratio decreases. We find that the FRD and throughput of the cores in the hexabundles match the performance of single fibres of the same material at low input f-ratios. The performance results presented can be used to set a limit on the f-ratio of a system based on the maximum loss allowable for a planned instrument. Our results confirm that hexabundles are a successful alternative for fibre imaging devices for multi-object spectroscopy on wide-field telescopes and have prompted further development of hexabundle designs with hexagonal packing and square cores.

Bryant, J. J.; Bland-Hawthorn, J.; Fogarty, L. M. R.; Lawrence, J. S.; Croom, S. M.

2014-02-01

329

Length, Perimeter, and Area  

NSDL National Science Digital Library

This lesson is designed to introduce students to the concepts of length, perimeter, and area. This lesson provides links to discussions and activities related to perimeter and area as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with learning about perimeter and area.

2010-01-01

330

Lengths of Ladybugs  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "Ladybug on the Move" by Richard Fowler and measure the distance the ladybug travels on each page using yarn. Next, learners make their own "Go Ladybug Go!" books and use lima beans and a ladybug ruler to make and record measurements.

Lessonplans, Utah

2012-09-18

331

Mappability and read length  

PubMed Central

Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 ? 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability. PMID:25426137

Li, Wentian; Freudenberg, Jan

2014-01-01

332

Controllable parabolic lensed liquid-core optical fiber by using electrostatic force.  

PubMed

For typical optical fiber system, an external lens accessory set is required to adjust the optical path of output light, which however is limited by the fixed parameter of the lens accessory setup. Considering spherical aberration in the imaging process and its small focusable spot size, a complicated lens combination is required to compensate the aberration. This paper has demonstrated a unique method to fabricate liquid-core lensed fibers by filling water and NOA61 respectively into hollow Teflon AF fibers and silicate fiber, the radius of curvature of the liquid lens can be controlled by adjusting the applied voltage on the core liquid and even parabolic shape lens can be produced with enough applied voltage. The experiment has successfully demonstrated a variation of focal length from 0.628 mm to 0.111 mm responding to the change of applied voltage from 0V to 3.2KV (L = 2mm) for the Teflon AF fiber, as well as a variation of focal length from 0.274 mm to 0.08 mm responding to the change of applied voltage from 0V to 3KV (L = 2mm) for the silicate fiber. Further simulation shows that the focused spot size can be reduced to 2 µm by adjusting the refractive index and fiber geometry. Solid state parabolic lensed fiber can be produced after NOA61 is solidified by the UV curing. PMID:25321295

Tang, Chun Yin; Zhang, Xuming; Chai, Yang; Hui, Long; Tao, Lili; Tsang, Yuen H

2014-08-25

333

Osteogenic lineage restriction by osteoprogenitors cultured on nanometric grooved surfaces: The role of focal adhesion maturation?  

PubMed Central

The differentiation of progenitor cells is dependent on more than biochemical signalling. Topographical cues in natural bone extracellular matrix guide cellular differentiation through the formation of focal adhesions, contact guidance, cytoskeletal rearrangement and ultimately gene expression. Osteoarthritis and a number of bone disorders present as growing challenges for our society. Hence, there is a need for next generation implantable devices to substitute for, or guide, bone repair in vivo. Cellular responses to nanometric topographical cues need to be better understood in vitro in order to ensure the effective and efficient integration and performance of these orthopedic devices. In this study, the FDA-approved plastic polycaprolactone was embossed with nanometric grooves and the response of primary and immortalized osteoprogenitor cells observed. Nanometric groove dimensions were 240 nm or 540 nm deep and 12.5 ?m wide. Cells cultured on test surfaces followed contact guidance along the length of groove edges, elongated along their major axis and showed nuclear distortion; they formed more focal complexes and lower proportions of mature adhesions relative to planar controls. Down-regulation of the osteoblast marker genes RUNX2 and BMPR2 in primary and immortalized cells was observed on grooved substrates. Down-regulation appeared to directly correlate with focal adhesion maturation, indicating the involvement of ERK 1/2 negative feedback pathways following integrin-mediated FAK activation. PMID:24252447

Cassidy, John W.; Roberts, Jemma N.; Smith, Carol-Anne; Robertson, Mary; White, Kate; Biggs, Manus J.; Oreffo, Richard O.C.; Dalby, Matthew J.

2014-01-01

334

Focal electrical status (FES): a new finding associated with polymicrogyria.  

PubMed

Polymicrogyria (PMG), a malformation of cortical organization, may, occasionally, be associated with electrical status epilepticus of sleep and focal electrical status. The aim of this study was to better characterize the latter association. This was an historic cohort study. Inclusion criteria were diagnosis of PMG on neuroimaging and presence of focal electrical status on EEG. Focal electrical status was considered when patients presented with continuous epileptiform abnormalities over a focal area on awakeness, which became bilateral and synchronous during sleep. Interictal EEGs lasted for at least 20 minutes and up to 4 hours and were performed during awakeness and sleep. Neuroimaging findings were classified as holosylvian PMG and hemispheric PMG. All patients, except one, had asymmetric neuroimaging findings, mostly on the right side. All patients had partial motor seizures, which were easily controlled with antiepileptic drugs in two of them. Despite seizure control, their EEGs still registered focal electrical status. The other four patients presented with atonic seizures and/or atypical absences. All patients showed awakeness focal electrical status that was activated by sleep. Focal electrical status is a different EEG pattern from other continuous electrographical patterns previously described, such as electrical status epilepticus of sleep, continuous epileptiform discharges, and rhythmic epileptiform discharges. Each one has its own peculiarity. Focal electrical status seems to be associated with asymmetric and extensive PMG. PMID:19424084

Teixeira, Karine C S; Cendes, Fernando; Guerreiro, Carlos A M; Guerreiro, Marilisa M

2009-06-01

335

In vitro Phosphorylation of the Focal Adhesion Targeting Domain of Focal Adhesion Kinase by Src Kinase  

PubMed Central

Focal adhesion kinase (FAK), a key regulator of cell adhesion and migration, is overexpressed in many types of cancer. The C-terminal focal adhesion targeting (FAT) domain of FAK is necessary for proper localization of FAK to focal adhesions and subsequent activation. Phosphorylation of Y926 in the FAT domain by the tyrosine kinase Src has been shown to promote metastasis and invasion in vivo by linking the FAT domain to the MAPK pathway via its interaction with Grb2. Several groups have reported that inherent conformational dynamics in the FAT domain likely regulate phosphorylation of Y926; however, what regulates these dynamics is unknown. In this paper, we demonstrate that there are two sites of in vitro Src-mediated phosphorylation in the FAT domain: Y926, which has been shown to affect FAK function in vivo, and Y1008, which has no known biological role. The phosphorylation of these two tyrosine residues is pH dependent, but this does not reflect the pH dependence of Src kinase activity. CD and NMR data indicate that the stability and conformational dynamics of the FAT domain are sensitive to changes in pH over a physiological pH range. In particular, regions of the FAT domain previously shown to regulate phosphorylation of Y926 as well as regions near Y1008 show pH-dependent dynamics on the ?s-ms time scale. PMID:22372511

Cable, Jennifer; Prutzman, Kirk; Gunawardena, Harsha P.; Schaller, Michael D.; Chen, Xian; Campbell, Sharon L.

2012-01-01

336

Combined Scanning Transmission Electron Microscopy Tilt- and Focal Series  

SciTech Connect

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller missing wedge artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.

Dahmen, Tim [German Research Center for Artificial Intelligence (DFKI), Germany] [German Research Center for Artificial Intelligence (DFKI), Germany; Baudoin, Jean-Pierre G [ORNL] [ORNL; Lupini, Andrew R [ORNL] [ORNL; Kubel, Christian [Karlsruhe Institute of Technology, Leopoldshafen, Germany] [Karlsruhe Institute of Technology, Leopoldshafen, Germany; Slusallek, Phillip [German Research Center for Artificial Intelligence (DFKI), Germany] [German Research Center for Artificial Intelligence (DFKI), Germany; De Jonge, Niels [ORNL] [ORNL

2014-01-01

337

Method for computer-aided alignment of complex optical system  

NASA Astrophysics Data System (ADS)

For making complex optical system meet the design requirement, such as the space camera used in remote sensing and UVX lithophotography, especially for off-axis all-reflecting optical system, alignment technology is so necessary. In this paper, a method is presented. Based on the ideas of linearity instead of non-linearity and difference quotient instead of differential quotient, a mathematical model for computer-aided alignment is proposed. This model included the characteristics of the optical system, wavefront difference of its exit pupil and its misalignment of the misaligned optical system. Then comparing self-compiled software with alignment package of CODE V, as a result, this self-compiled software is much more valid than alignment package of CODE V. For a large aperture, long focal length and off-axis three-mirror optical system, computer-aided alignment is successful. Finally, the wavefront error of the middle field is 0.094 waves RMS and the wavefront error of +0.7 field is 0.106 waves RMS and the wavefront error of -0.7 field is 0.125 waves RMS at ?=632.8nm are obtained.

Yang, Xiaofei; Han, ChangYuan; Yu, Jingchi

2006-02-01

338

Adaptive Optics Communications Performance Analysis  

NASA Technical Reports Server (NTRS)

The performance improvement obtained through the use of adaptive optics for deep-space communications in the presence of atmospheric turbulence is analyzed. Using simulated focal-plane signal-intensity distributions, uncoded pulse-position modulation (PPM) bit-error probabilities are calculated assuming the use of an adaptive focal-plane detector array as well as an adaptively sized single detector. It is demonstrated that current practical adaptive optics systems can yield performance gains over an uncompensated system ranging from approximately 1 dB to 6 dB depending upon the PPM order and background radiation level.

Srinivasan, M.; Vilnrotter, V.; Troy, M.; Wilson, K.

2004-01-01

339

An empirical assessment of the focal species hypothesis.  

PubMed

Biodiversity surrogates and indicators are commonly used in conservation management. The focal species approach (FSA) is one method for identifying biodiversity surrogates, and it is underpinned by the hypothesis that management aimed at a particular focal species will confer protection on co-occurring species. This concept has been the subject of much debate, in part because the validity of the FSA has not been subject to detailed empirical assessment of the extent to which a given focal species actually co-occurs with other species in an assemblage. To address this knowledge gap, we used large-scale, long-term data sets of temperate woodland birds to select focal species associated with threatening processes such as habitat isolation and loss of key vegetation attributes. We quantified co-occurrence patterns among focal species, species in the wider bird assemblage, and species of conservation concern. Some, but not all, focal species were associated with high levels of species richness. One of our selected focal species was negatively associated with the occurrence of other species (i.e., it was an antisurrogate)-a previously undescribed property of nominated focal species. Furthermore, combinations of focal species were not associated with substantially elevated levels of bird species richness, relative to levels associated with individual species. Our results suggest that although there is some merit to the underpinning concept of the FSA, there is also a need to ensure that actions are sufficiently flexible because management tightly focused on a given focal species may not benefit some other species, including species of conservation concern, such of which might not occur in species-rich assemblages. PMID:25048948

Lindenmayer, D B; Lane, P W; Westgate, M J; Crane, M; Michael, D; Okada, S; Barton, P S

2014-12-01

340

Telomere length in reproduction.  

PubMed

Telomeres, noncoding hexameric tandem repeats located at the ends of chromosomes, maintain chromosome stability and genome integrity. These guanine-rich repeats are highly conserved during evolution, and their role is dependent on their length and structure. They have multiple functions, including regulating the reproductive lifespan by mediating synapsis and homologous recombination of the chromosomes. Short telomeres result in meiotic arrest, segregation abnormalities and dysjunction, which lead to an increased incidence of aneuploid germ cells. In addition, shortened telomeres in men result in apoptosis of germ cells, whereas, in women, they result in meiotic arrest. In somatic cells, telomere shortening occurs at each consecutive round of replication, which induces senescence in vitro and in vivo. However there is a 2-fold elongation of telomeres during spermatogenesis. Spermatozoa, are terminally differentiated cells, have longer telomeres than spermatogonia and pachytene spermatocytes. In addition to genetic factors, lifestyle factors and psychological stress also play crucial role in modulating telomere length. Because not much is known about its role in reproduction, we focused this review on the function, structure and length dynamics of the telomere in the reproductive process. PMID:22928904

Thilagavathi, J; Venkatesh, S; Dada, R

2013-10-01

341

Planck-Length Phenomenology  

E-print Network

This author's recent proposal of interferometric tests of Planck-scale-related properties of space-time is here revisited from a strictly phenomenological viewpoint. The results announced previously are rederived using elementary dimensional considerations. The dimensional analysis is then extended to the other two classes of experiments (observations of neutral kaons at particle accelerators and observations of the gamma rays we detect from distant astrophysical sources) which have been recently considered as opportunities to explore "foamy" properties of space-time. The emerging picture suggests that there is an objective and intuitive way to connect the sensitivities of these three experiments with the Planck length. While in previous studies the emphasis was always on some quantum-gravity scenario and the analysis was always primarily aimed at showing that the chosen scenario would leave a trace in a certain class of doable experiments, the analysis here reported takes as starting point the experiments and, by relating in a direct quantitative way the sensitivities to the Planck length, provides a model-independent description of the status of Planck-length phenomenology.

Giovanni Amelino-Camelia

2000-08-04

342

Lengthy Relationships: Foot Length, Stride, Leg Length, Height  

NSDL National Science Digital Library

Paleontologists occasionally find ancient tracks and footprints preserved in the rocks. This lesson opens the door to analysing those footprints, and gleaning information about body size and activities of the extinct animals that made the tracks. Students will learn that patterns can reveal much about the past, in light of the present; and that bipedalism has appeared several times. Relationships will be found between foot length and leg length; foot length and height; leg length and height; stride length and leg length; and stride length and speed.

Johnson, Jennifer

343

Src SH2 Arginine 175 Is Required for Cell Motility: Specific Focal Adhesion Kinase Targeting and Focal Adhesion Assembly Function  

Microsoft Academic Search

Src kinase is a crucial mediator of adhesion-related signaling and motility. Src binds to focal adhesion kinase (FAK) through its SH2 domain and subsequently activates it for phosphorylation of downstream substrates. In addition to this binding function, data suggested that the SH2 domain might also perform an important role in targeting Src to focal adhesions (FAs) to enable further substrate

Myeong Gu Yeo; Michael A. Partridge; Ellen J. Ezratty; Qiong Shen; Gregg G. Gundersen; Eugene E. Marcantonio

2006-01-01

344

Evaluation of Hemodynamics in Focal Steatosis and Focal Spared Lesion of the Liver Using Contrast-Enhanced Ultrasonography with Sonazoid  

PubMed Central

We aim to investigate the hemodynamics in focal steatosis and focal spared lesion of the liver using contrast-enhanced ultrasonography (CEUS) with Sonazoid. The subjects were 47 patients with focal steatosis and focal spared lesion. We evaluated enhancement patterns (hyperenhancement, isoenhancement, and hypoenhancement) in the vascular phase and the presence or absence of a hypoechoic area in the postvascular phase for these lesions using CEUS. Of the 24 patients with focal steatosis, the enhancement pattern was isoenhancement in 19 and hypoenhancement in 5. Hypoechoic areas were noted in the postvascular phase in 3 patients. Of the 23 patients with focal spared lesions, the enhancement pattern was isoenhancement in 18 and hyperenhancement in 5. No hypoechoic areas were noted in the postvascular phase in any patient. The hemodynamics in focal steatosis and focal spared lesions in nondiffuse fatty liver can be observed using low-invasive procedures in real-time by CEUS. It was suggested that differences in the dynamics of enhancement in the vascular phase of CEUS were influenced by the fat deposits in the target lesion, the surrounding liver parenchyma, and the third inflow. PMID:25165582

Shiozawa, Kazue; Ikehara, Takashi; Kogame, Michio; Shinohara, Mie; Shinohara, Masao; Ishii, Koji; Igarashi, Yoshinori; Makino, Hiroyuki

2014-01-01

345

Focal shift and focal switch of flat-topped Mathieu-Gaussian beams passing through an apertured lens system  

NASA Astrophysics Data System (ADS)

By introducing a hard aperture function into a finite sum of complex Gaussian functions, an approximate analytical expression predominating the distribution of axial intensity for the flat-topped Mathieu-Gauss (FTMG) beams passing through a system with the aperture and lens separated has been derived. The focal shift and the focal switch effect of FTMG beams passing through the system is studied in detail. Numerical calculations have shown that the position of real focal plane is not coincident with the geometrical focus but is somewhat shifted toward the lens. The focal shift and focal switch of FTMG beams take place when the relative separation s/f = 1 by a suitable choice of beam parameter and truncation parameter, for example, the beam parameter is smaller than its corresponding critical value or the truncation parameter is between its two corresponding critical values.

Tang, Bin; Wen, Wei

2009-06-01

346

Focusing Effects in Interferometric Analysis of Graded-index Optical Fibers.  

PubMed

The effects of ray bending due to graded refractive-index profiles have been studied in relation to the measurement of optical-fiber refractive-index profiles by microscopic interferometric techniques. In particular, the wavefront curvature produced by a simple parabolic profile has been calculated analytically. It is concluded that profile measurements by currently used methods require samples for which the fiber thickness (length) is much less than the effective focal length of the fiber. For parabolic profile fibers with diameter d greater, similar 100 microm, this poses no problem; however, for small-core versions of this fiber, sample thicknesses of 10-15 microm may be required and an alternate measurement technique is described. Interferograms made on a Leitz transmitted-light interference microscope are included in illustrations. PMID:20134845

Stone, J; Burrus, C A

1975-01-01

347

Pars Plana Vitrectomy Combined with Focal Endolaser Photocoagulation for Idiopathic Macular Telangiectasia  

PubMed Central

Background. To report the outcome of pars plana vitrectomy (PPV) combined with intraoperative endolaser focal photocoagulation (PC) on eyes with idiopathic macular telangiectasis (MacTel) type 1. Methods. This was a retrospective study of two female patients with MacTel type 1 who were resistant to focal photocoagulation, sub-Tenon triamcinolone injection, and/or antiangiogenic drugs. The best-corrected visual acuity (BCVA) was determined, and fluorescein angiography (FA) and spectral domain optical coherence tomography (SD-OCT) were performed before and after surgery for up to 19 months. Results. After surgery, the BCVA gradually improved from 20/100 to 20/20 at 19 months in Case 1 and from 20/50 to 20/13 at 13 months in Case 2. Fluorescein angiography (FA) showed leakage at the late phase, and OCT showed that the cystoid macular edema was resolved and the fovea was considerably thinner postoperatively. Conclusion. Patients with MacTel type 1 who are refractory to the other types of treatments can benefit from PPV combined with intraoperative endolaser focal PC with functional and morphological improvements. PMID:24876845

Terauchi, Gaku; Matsumoto, Celso Soiti; Shinoda, Kei; Matsumoto, Harue; Imamura, Yutaka; Watanabe, Emiko; Kondo, Takaaki; Mizota, Atsushi

2014-01-01

348

Pars plana vitrectomy combined with focal endolaser photocoagulation for idiopathic macular telangiectasia.  

PubMed

Background. To report the outcome of pars plana vitrectomy (PPV) combined with intraoperative endolaser focal photocoagulation (PC) on eyes with idiopathic macular telangiectasis (MacTel) type 1. Methods. This was a retrospective study of two female patients with MacTel type 1 who were resistant to focal photocoagulation, sub-Tenon triamcinolone injection, and/or antiangiogenic drugs. The best-corrected visual acuity (BCVA) was determined, and fluorescein angiography (FA) and spectral domain optical coherence tomography (SD-OCT) were performed before and after surgery for up to 19 months. Results. After surgery, the BCVA gradually improved from 20/100 to 20/20 at 19 months in Case 1 and from 20/50 to 20/13 at 13 months in Case 2. Fluorescein angiography (FA) showed leakage at the late phase, and OCT showed that the cystoid macular edema was resolved and the fovea was considerably thinner postoperatively. Conclusion. Patients with MacTel type 1 who are refractory to the other types of treatments can benefit from PPV combined with intraoperative endolaser focal PC with functional and morphological improvements. PMID:24876845

Terauchi, Gaku; Matsumoto, Celso Soiti; Shinoda, Kei; Matsumoto, Harue; Imamura, Yutaka; Watanabe, Emiko; Kondo, Takaaki; Mizota, Atsushi

2014-01-01

349

The QWIP focal plane assembly for NASA's Landsat Data Continuity Mission  

NASA Astrophysics Data System (ADS)

The Thermal Infrared Sensor (TIRS) is a QWIP based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM) [1]. The TIRS instrument is a dual channel far infrared imager with the two bands centered at 10.8?m and 12.0?m. The focal plane assembly (FPA) consists of three 640x512 GaAs Quantum Well Infrared Photodetector (QWIP) arrays precisely mounted to a silicon carrier substrate that is mounted on an invar baseplate. The two spectral bands are defined by bandpass filters mounted in close proximity to the detector surfaces. The focal plane operating temperature is 43K. The QWIP arrays are hybridized to Indigo ISC9803 readout integrated circuits (ROICs). Two varieties of QWIP detector arrays are being developed for this project, a corrugated surface structure QWIP and a grating surface structure QWIP. This paper will describe the TIRS system noise equivalent temperature difference sensitivity as it affects the QWIP focal plane performance requirements: spectral response, dark current, conversion efficiency, read noise, temperature stability, pixel uniformity, optical crosstalk and pixel yield. Additional mechanical constraints as well as qualification through Technology Readiness Level 6 (TRL 6) will also be discussed.

Jhabvala, M.; Reuter, D.; Choi, K.; Sundaram, M.; Jhabvala, C.; La, A.; Waczynski, A.; Bundas, J.

2010-04-01

350

Clinical course of focal choroidal excavation in Vogt–Koyanagi–Harada disease  

PubMed Central

We describe focal choroidal excavation (FCE) in a case of Vogt–Koyanagi–Harada (VKH) disease and compare the findings with different chorioretinal conditions. A 55-year-old man was diagnosed with VKH based on panuveitis and exudative retinal detachments. Spectral-domain optical coherence tomography demonstrated a dome-shaped protrusion with a nonconforming pattern at the fovea, which had been detected as a conforming pattern 1 year before the onset. The FCE pattern returned into a conforming pattern following corticosteroid therapy. These findings suggest that the natively existent FCE could be affected by pathophysiological changes of VKH as well as other chorioretinal conditions. PMID:25506207

Nishikawa, Yuko; Fujinami, Kaoru; Watanabe, Ken; Noda, Toru; Tsunoda, Kazushige; Akiyama, Kunihiko

2014-01-01

351

Towards a comprehensive eye model for zebrafish retinal imaging using full range spectral domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

In regenerative medicine, the zebrafish is a prominent animal model for studying degeneration and regeneration processes, e.g. of photoreceptor cells in the retina. By means of optical coherence tomography (OCT), these studies can be conducted over weeks using the same individual and hence reducing the variability of the results. To allow an improvement of zebrafish retinal OCT imaging by suitable optics, we developed a zebrafish eye model using geometrical data obtained by in vivo dispersion encoded full range OCT as well as a dispersion comprising gradient index (GRIN) lens model based on refractive index data found in the literature. Using non-sequential ray tracing, the focal length of the spherical GRIN lens (diameter of 0.96 mm) was determined to be 1.22 mm at 800 nm wavelength giving a Matheissen's ratio (ratio of focal length to radius of the lens) of 2.54, which fits well into the range between 2.19 and 2.82, found for various fish lenses. Additionally, a mean refractive index of 1.64 at 800 nm could be retrieved for the lens to yield the same focal position as found for the GRIN condition. With the aid of the zebrafish eye model, the optics of the OCT scanner head were adjusted to provide high-resolution retinal images with a field of view of 30° x 30°. The introduced model therefore provides the basis for improved retinal imaging with OCT and can be further used to study the image formation within the zebrafish eye.

Gaertner, Maria; Weber, Anke; Cimalla, Peter; Köttig, Felix; Brand, Michael; Koch, Edmund

2014-03-01

352

A multi-tiered wavefront sensor using binary optics  

Microsoft Academic Search

Wavefront sensors have been used to make measurements in fluid- dynamics and for closed loop control of adaptive optics. In most common Shack-Hartmann wavefront wavefront sensors, the light is broken up into series of rectangular or hexagonal apertures that divide the light into a series of focal spots. The position of these focal spots is used to determine the wavefront

D. R. Neal; M. E. Warren; J. K. Gruetzner; T. G. Smith; R. R. Rosenthal; T. S. McKechnie

1994-01-01

353

Radiant energy absorption enhancement in optical imaging systems  

NASA Technical Reports Server (NTRS)

Reimaging system efficiently uses incident light and overcomes previous imaging detector problems. Optical system collects reflected and focal plane transmitted light and redirects it so it again impinges on focal plane in register with original image. Reimaging unabsorbed light increases light absorption and detector use probability.

Brown, R. M.; Gunter, W. D., Jr.

1971-01-01

354

Vasoconstrictive neurovascular coupling during focal ischemic depolarizations.  

PubMed

Ischemic depolarizing events, such as repetitive spontaneous periinfarct spreading depolarizations (PIDs), expand the infarct size after experimental middle cerebral artery (MCA) occlusion. This worsening may result from increased metabolic demand, exacerbating the mismatch between cerebral blood flow (CBF) and metabolism. Here, we present data showing that anoxic depolarization (AD) and PIDs caused vasoconstriction and abruptly reduced CBF in the ischemic cortex in a distal MCA occlusion model in mice. This reduction in CBF during AD increased the area of cortex with 20% or less residual CBF by 140%. With each subsequent PID, this area expanded by an additional 19%. Drugs that are known to inhibit cortical spreading depression (CSD), such as N-methyl-D-aspartate receptor antagonists MK-801 and 7-chlorokynurenic acid, and sigma-1 receptor agonists dextromethorphan and carbetapentane, did not reduce the frequency of PIDs, but did diminish the severity of episodic hypoperfusions, and prevented the expansion of severely hypoperfused cortex, thus improving CBF during 90 mins of acute focal ischemia. In contrast, AMPA receptor antagonist NBQX, which does not inhibit CSD, did not impact the deterioration in CBF. When measured 24 h after distal MCA occlusion, infarct size was reduced by MK-801, but not by NBQX. Our results suggest that AD and PIDs expand the CBF deficit, and by so doing negatively impact lesion development in ischemic mouse brain. Mitigating the vasoconstrictive neurovascular coupling during intense ischemic depolarizations may provide a novel hemodynamic mechanism of neuroprotection by inhibitors of CSD. PMID:16340958

Shin, Hwa Kyoung; Dunn, Andrew K; Jones, Phillip B; Boas, David A; Moskowitz, Michael A; Ayata, Cenk

2006-08-01

355

Multiwavelength infrared focal plane array detector  

NASA Technical Reports Server (NTRS)

A multiwavelength focal plane array infrared detector is included on a common substrate having formed on its top face a plurality of In.sub.x Ga.sub.1-x As (x.ltoreq.0.53) absorption layers, between each pair of which a plurality of InAs.sub.y P.sub.1-y (y<1) buffer layers are formed having substantially increasing lattice parameters, respectively, relative to said substrate, for preventing lattice mismatch dislocations from propagating through successive ones of the absorption layers of decreasing bandgap relative to said substrate, whereby a plurality of detectors for detecting different wavelengths of light for a given pixel are provided by removing material above given areas of successive ones of the absorption layers, which areas are doped to form a pn junction with the surrounding unexposed portions of associated absorption layers, respectively, with metal contacts being formed on a portion of each of the exposed areas, and on the bottom of the substrate for facilitating electrical connections thereto.

Forrest, Stephen R. (Inventor); Olsen, Gregory H. (Inventor); Kim, Dong-Su (Inventor); Lange, Michael J. (Inventor)

1995-01-01

356

Digital-pixel focal plane array development  

NASA Astrophysics Data System (ADS)

Since 2006, MIT Lincoln Laboratory has been developing Digital-pixel Focal Plane Array (DFPA) readout integrated circuits (ROICs). To date, four 256 × 256 30 ?m pitch DFPA designs with in-pixel analog to digital conversion have been fabricated using IBM 90 nm CMOS processes. The DFPA ROICs are compatible with a wide range of detector materials and cutoff wavelengths; HgCdTe, QWIP, and InGaAs photo-detectors with cutoff wavelengths ranging from 1.6 to 14.5 ?m have been hybridized to the same digital-pixel readout. The digital-pixel readout architecture offers high dynamic range, A/C or D/C coupled integration, and on-chip image processing with low power orthogonal transfer operations. The newest ROIC designs support two-color operation with a single Indium bump connection. Development and characterization of the two-color DFPA designs is presented along with applications for this new digital readout technology.

Brown, Matthew G.; Baker, Justin; Colonero, Curtis; Costa, Joe; Gardner, Tom; Kelly, Mike; Schultz, Ken; Tyrrell, Brian; Wey, Jim

2010-01-01

357

Dynamic MEG imaging of focal neuronal sources  

SciTech Connect

We describe inverse methods for using the magnetoencephalogram (MEG) to image neural current sources associated with functional activation in the cerebral cortex. A Bayesian formulation is presented that is based on a Gibbs prior which reflects the sparse, focal nature of neural activation. The model includes a dynamic component so that we can utilize the full spatio-temporal data record to reconstruct a sequence of images reflecting changes in the current source amplitudes during activation. The model consists of the product of a binary field, representing the areas of activation in the cerebral cortex, and a time series at each site which represents the dynamic changes in the source amplitudes at the active sites. Our estimation methods are based on the optimization of three different functions of the posterior density. Each of these methods requires the estimation of a binary field which we compute using a mean field annealing method. We demonstrate and compare our methods in application to computer generated and experimental phantom data.

Phillips, J.W.; Leahy R.M. [Univ. of Southern California, Los Angeles, CA (United States); Mosher, J.C. [Los Alamos National Lab., NM (United States)

1996-12-31

358

LWIR/MWIR adaptive focal plane array  

NASA Astrophysics Data System (ADS)

An Adaptive Focal Plane Array (AFPA) device that enables a "chip scale" imaging spectrometer is being developed. The AFPA device consists of an array of MEMS tunable filters that is intimately coupled to a dual band IR FPA. The MEMS filters provide narrowband tuning in the LWIR and simultaneous broadband imaging in the MWIR. Each filter element can be independently tuned. In the current design, each filter tunes the wavelength of pixel subarrays. Ultimately, filter size will be reduced to achieve independent wavelength tunability for each pixel element. This unique architecture of an AFPA device enables adaptive spectral analysis of the scene. Rather than collecting the complete hyperspectral cube, methods being developed will enable selection of spatially optimized spectral band sets for a variety of targets and materials that are selected "on-the-fly" to maximize the contrast between the local background and the target or material to be identified. The analyzed LWIR spectral information may then be overlaid with a pixel registered high resolution MWIR image.

Gunning, William J.; Johnson, Jeffrey L.; DeNatale, Jeffrey F.

2004-12-01

359

The dispersion-focalization theory of sound systems  

NASA Astrophysics Data System (ADS)

The Dispersion-Focalization Theory states that sound systems in human languages are shaped by two major perceptual constraints: dispersion driving auditory contrast towards maximal or sufficient values [B. Lindblom, J. Phonetics 18, 135-152 (1990)] and focalization driving auditory spectra towards patterns with close neighboring formants. Dispersion is computed from the sum of the inverse squared inter-spectra distances in the (F1, F2, F3, F4) space, using a non-linear process based on the 3.5 Bark critical distance to estimate F2'. Focalization is based on the idea that close neighboring formants produce vowel spectra with marked peaks, easier to process and memorize in the auditory system. Evidence for increased stability of focal vowels in short-term memory was provided in a discrimination experiment on adult French subjects [J. L. Schwartz and P. Escudier, Speech Comm. 8, 235-259 (1989)]. A reanalysis of infant discrimination data shows that focalization could well be the responsible for recurrent discrimination asymmetries [J. L. Schwartz et al., Speech Comm. (in press)]. Recent data about children vowel production indicate that focalization seems to be part of the perceptual templates driving speech development. The Dispersion-Focalization Theory produces valid predictions for both vowel and consonant systems, in relation with available databases of human languages inventories.

Schwartz, Jean-Luc; Abry, Christian; Boë, Louis-Jean; Vallée, Nathalie; Ménard, Lucie

2005-04-01

360

Optimization of the acousto-optic signal detection in cylindrical geometry  

NASA Astrophysics Data System (ADS)

The use of ultrasonic tagging of multiple scattered photons within turbid media for tomographic imaging is typically performed using optical detection in transmission mode. This study aimed to optimize the detection of the acousto-optic (AO) signal in cylindrical geometry, with a view to using the technique to measure blood oxygenation in the internal jugular vein of infants in the future. In our experiments, homogeneous phantoms of multiple transport scattering coefficients were constructed for the described geometry mimicking the infant neck. The optical source was systematically repositioned at different angles relative to the optical detector and the resulting AO signal was measured. The experimental results were also compared to focused ultrasound AO Monte Carlo (MC) simulation results. It was found that the optimal modulation depth and noise variance were highly dependent on the overlap region between the optical path length of the optical source-detector pair and the ultrasound focal zone. Therefore the optimal positions for both the optical and ultrasound probes could be estimated from both experimental and simulation results for a given geometry.

Gunadi, Sonny; Powell, Samuel; Elwell, Clare E.; Leung, Terence S.

2010-02-01

361

Effects of thermal deformations on the sensitivity of optical systems for space application  

NASA Astrophysics Data System (ADS)

In this paper the results of the thermo-elastic analysis performed on the Stereo Imaging Channel of the imaging system SIMBIO-SYS for the BepiColombo ESA mission to Mercury is presented. The aim of the work is to determine the expected stereo reconstruction accuracy of the surface of the planet Mercury, i.e. the target of BepiColombo mission, due to the effects of the optics misalignments and deformations induced by temperature changes during the mission lifetime. The camera optics and their mountings are modeled and processed by a thermo-mechanical Finite Element Model (FEM) program, which reproduces the expected optics and structure thermo-elastic variations in the instrument foreseen operative temperature range, i.e. between -20 °C and 30 °C. The FEM outputs are elaborated using a MATLAB optimization routine: a non-linear least square algorithm is adopted to determine the surface equation (plane, spherical, nth polynomial) which best fits the deformed optical surfaces. The obtained surfaces are then directly imported into ZEMAX raytracing code for sequential raytrace analysis. Variations of the optical center position, boresight direction, focal length and distortion are then computed together with the corresponding image shift on the detector. The overall analysis shows the preferable use of kinematic constraints, instead of glue classical solution, for optical element mountings, this minimize the uncertainty on the Mercury Digital Terrain Model (DTM) reconstructed via a stereo-vision algorithm based on the triangulation from two optical channels.

Segato, Elisa; Da Deppo, Vania; Debei, Stefano; Cremonese, Gabriele; Cherubini, Giovanni

2010-07-01

362

Lengths on rotating platforms  

NASA Astrophysics Data System (ADS)

The paper treats the issue of the length of a rotating circumference as seen from on board the moving disk and from an inertial reference frame. It is shown that, properly defining a measuring process, the result is in both cases 2?R thus dissolving the Ehrenfest paradox. The same holds good when considering that, for the rotating observer, the perceived radius coincides with the curvature radius of a space-time helix and a complete round trip corresponds to an angle which differs from the one seen by the inertial observer. The apparent contradiction with the Lorentz contraction is discussed.

Tartaglia, A.

1999-02-01

363

Length of the Day  

NSDL National Science Digital Library

In this activity, students measure the length of the day using the rotation of the Earth, and discover that the Sun is not exactly in the same place at the same clock time every day, understand that the changes are due to motions of the Earth, and lead to differences in solar, star, and sidereal time. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

364

Focal laser photocoagulation in non-center involved diabetic macular edema.  

PubMed

This study was performed to evaluate the functional and anatomic outcomes of focal macular laser photocoagulation in eyes with non-center involved macular edema (non-CI ME). Forty-nine eyes of 43 patients with non-CI ME were included. Focal macular laser photocoagulation was conducted on twenty-nine eyes of 25 patients, while 20 eyes of 18 patients with non-CI ME were followed without treatment and served as the control group. Data relating to best corrected visual acuity (BCVA; Early Treatment Diabetic Retinopathy Study) and central subfield thickness (CST), inner zone thickness (IZT), outer zone thickness (OZT), and total macular volume (TMV) as determined by optical coherence tomography (OCT) were collected and compared between the groups. At 12 months, VA decreased by a mean of 0.4 letters in the treatment group and 3.3 letters in the control group (p=0.03). Gain in VA ?5 letters was noted in 6 (21%) of the eyes in the treatment group versus 1 (5%) eye in the control group (p=0.12). At 12 months, average IZT decreased by 22.6 microns in the treatment group and increased by 10.9 microns in the control group (p<0.001). The treatment group revealed significant reduction in CST, average OZT, and TMV as compared to the control group at 12 months (all p<0.05).Generally, focal laser photocoagulation may have more favourable visual outcomes in this specific group of diabetic patients than does observation. In addition, focal laser treatment provided better outcomes with improvement in OCT parameters as compared to the control group. PMID:24804275

Perente, Irfan; Alkin, Zeynep; Ozkaya, Abdullah; Dardabounis, Doukas; Ogreden, Tulin Aras; Konstantinidis, Aristeidis; Kyratzoglou, Konstantinos; Yazici, Ahmet Taylan

2014-01-01

365

Focal spot measurements using a digital flat panel detector  

NASA Astrophysics Data System (ADS)

Focal spot size is one of the crucial factors that affect the image quality of any x-ray imaging system. It is, therefore, important to measure the focal spot size accurately. In the past, pinhole and slit measurements of x-ray focal spots were obtained using direct exposure film. At present, digital detectors are replacing film in medical imaging so that, although focal spot measurements can be made quickly with such detectors, one must be careful to account for the generally poorer spatial resolution of the detector and the limited usable magnification. For this study, the focal spots of a diagnostic x-ray tube were measured with a 10-?m pinhole using a 194-?m pixel flat panel detector (FPD). The twodimensional MTF, measured with the Noise Response (NR) Method was used for the correction for the detector blurring. The resulting focal spot sizes based on the FWTM (Full Width at Tenth Maxima) were compared with those obtained with a very high resolution detector with 8-?m pixels. This study demonstrates the possible effect of detector blurring on the focal spot size measurements with digital detectors with poor resolution and the improvement obtained by deconvolution. Additionally, using the NR method for measuring the two-dimensional MTF, any non-isotropies in detector resolution can be accurately corrected for, enabling routine measurement of non-isotropic x-ray focal spots. This work presents a simple, accurate and quick quality assurance procedure for measurements of both digital detector properties and x-ray focal spot size and distribution in modern x-ray imaging systems.

Jain, Amit; Panse, A.; Bednarek, Daniel R.; Rudin, Stephen

2014-03-01

366

Focal spot measurements using a digital flat panel detector.  

PubMed

Focal spot size is one of the crucial factors that affect the image quality of any x-ray imaging system. It is, therefore, important to measure the focal spot size accurately. In the past, pinhole and slit measurements of x-ray focal spots were obtained using direct exposure film. At present, digital detectors are replacing film in medical imaging so that, although focal spot measurements can be made quickly with such detectors, one must be careful to account for the generally poorer spatial resolution of the detector and the limited usable magnification. For this study, the focal spots of a diagnostic x-ray tube were measured with a 10-?m pinhole using a 194-?m pixel flat panel detector (FPD). The two-dimensional MTF, measured with the Noise Response (NR) Method was used for the correction for the detector blurring. The resulting focal spot sizes based on the FWTM (Full Width at Tenth Maxima) were compared with those obtained with a very high resolution detector with 8-?m pixels. This study demonstrates the possible effect of detector blurring on the focal spot size measurements with digital detectors with poor resolution and the improvement obtained by deconvolution. Additionally, using the NR method for measuring the two-dimensional MTF, any non-isotropies in detector resolution can be accurately corrected for, enabling routine measurement of non-isotropic x-ray focal spots. This work presents a simple, accurate and quick quality assurance procedure for measurements of both digital detector properties and x-ray focal spot size and distribution in modern x-ray imaging systems. PMID:25302004

Jain, Amit; Panse, A; Bednarek, Daniel R; Rudin, Stephen

2014-03-19

367

Focal spot measurements using a digital flat panel detector  

PubMed Central

Focal spot size is one of the crucial factors that affect the image quality of any x-ray imaging system. It is, therefore, important to measure the focal spot size accurately. In the past, pinhole and slit measurements of x-ray focal spots were obtained using direct exposure film. At present, digital detectors are replacing film in medical imaging so that, although focal spot measurements can be made quickly with such detectors, one must be careful to account for the generally poorer spatial resolution of the detector and the limited usable magnification. For this study, the focal spots of a diagnostic x-ray tube were measured with a 10-?m pinhole using a 194-?m pixel flat panel detector (FPD). The two-dimensional MTF, measured with the Noise Response (NR) Method was used for the correction for the detector blurring. The resulting focal spot sizes based on the FWTM (Full Width at Tenth Maxima) were compared with those obtained with a very high resolution detector with 8-?m pixels. This study demonstrates the possible effect of detector blurring on the focal spot size measurements with digital detectors with poor resolution and the improvement obtained by deconvolution. Additionally, using the NR method for measuring the two-dimensional MTF, any non-isotropies in detector resolution can be accurately corrected for, enabling routine measurement of non-isotropic x-ray focal spots. This work presents a simple, accurate and quick quality assurance procedure for measurements of both digital detector properties and x-ray focal spot size and distribution in modern x-ray imaging systems. PMID:25302004

Jain, Amit; Panse, A.; Bednarek, Daniel R.; Rudin, Stephen

2014-01-01

368

HAb18G/CD147 Regulates Vinculin-Mediated Focal Adhesion and Cytoskeleton Organization in Cultured Human Hepatocellular Carcinoma Cells  

PubMed Central

Focal adhesions (FAs), integrin-mediated macromolecular complexes located at the cell membrane extracellular interface, have been shown to regulate cell adhesion and migration. Our previous studies have indicated that HAb18G/CD147 (CD147) is involved in cytoskeleton reorganization and FA formation in human hepatocellular carcinoma (HCC) cells. However, the precise mechanisms underlying these processes remain unclear. In the current study, we determined that CD147 was involved in vinculin-mediated FA focal adhesion formation in HCC cells. We also found that deletion of CD147 led to reduced vinculin-mediated FA areas (P<0.0001), length/width ratios (P<0.0001), and mean intensities (P<0.0001). CD147 promoted lamellipodia formation by localizing Arp2/3 to the leading edge of the cell. Deletion of CD147 significantly reduced the fluorescence (t1/2) recovery times (22.7±3.3 s) of vinculin-mediated focal adhesions (P<0.0001). In cell-spreading assays, CD147 was found to be essential for dynamic focal adhesion enlargement and disassembly. Furthermore, the current data showed that CD147 reduced tyrosine phosphorylation in vinculin-mediated focal adhesions, and enhanced the accumulation of the acidic phospholipid phosphatidylinositol-4, 5-bisphosphate (PIP2). Together, these results revealed that CD147 is involved in vinculin-mediated focal adhesion formation, which subsequently promotes cytoskeleton reorganization to facilitate invasion and migration of human HCC cells. PMID:25033086

Nan, Gang; Xu, Bao-Qing; Jiang, Jian-Li; Chen, Zhi-Nan

2014-01-01

369

High-energy x-ray optics with silicon saw-tooth refractive lenses.  

SciTech Connect

Silicon saw-tooth refractive lenses have been in successful use for vertical focusing and collimation of high-energy X-rays (50-100 keV) at the 1-ID undulator beamline of the Advanced Photon Source. In addition to presenting an effectively parabolic thickness profile, as required for aberration-free refractive optics, these devices allow high transmission and continuous tunability in photon energy and focal length. Furthermore, the use of a single-crystal material (i.e. Si) minimizes small-angle scattering background. The focusing performance of such saw-tooth lenses, used in conjunction with the 1-ID beamline's bent double-Laue monochromator, is presented for both short ({approx}1:0.02) and long ({approx}1:0.6) focal-length geometries, giving line-foci in the 2 {micro}m-25 {micro}m width range with 81 keV X-rays. In addition, a compound focusing scheme was tested whereby the radiation intercepted by a distant short-focal-length lens is increased by having it receive a collimated beam from a nearer (upstream) lens. The collimation capabilities of Si saw-tooth lenses are also exploited to deliver enhanced throughput of a subsequently placed small-angular-acceptance high-energy-resolution post-monochromator in the 50-80 keV range. The successful use of such lenses in all these configurations establishes an important detail, that the pre-monochromator, despite being comprised of vertically reflecting bent Laue geometry crystals, can be brilliance-preserving to a very high degree.

Shastri, S. D.; Almer, J. A.; Ribbing, C. R.; Cederstrom, B. C.; X-Ray Science Division; Uppsala Univ.; Royal Inst. of Tech.

2007-01-01

370

Fabrication of polymer microlens at the apex of optical fiber  

NASA Astrophysics Data System (ADS)

We report a simple, inexpensive fabrication method to fabricate polymer microlens at the apex of optical fiber. When compared to other established protocols for fabricating microlensed fiber, this procedure allows simple and inexpensive microlensed fiber fabrication with high reproducibility. Also it is possible to tune the focal length and working distance of the fabricated lens in a wider range by controlling the curing parameters such as curing power, beam shape of the curing beam and curing time. The novel curing procedure, where a specially structured curing laser beam of wavelength 405nm was used for curing, is the key factor for this extended flexibility. Once cured, the UV curable adhesive used for fabricating these lenses had a very good transmission in visible and near-IR region, making it ideal for communication and biophotonics applications. This fabrication technique can be used in a variety of applications owing to its ability to achieve customized microlenses for specific applications.

Ma, Nan; Ashok, Praveen C.; Gunn-Moore, Frank J.; Dholakia, Kishan

2011-08-01

371

Hollow fiber optic probe for in vivo Raman measurement  

NASA Astrophysics Data System (ADS)

A hollow optical fiber Raman probe equipped with a ball lens is developed to study the stomach cancer. The probe generates little Raman scattering or fluorescence noise because the HOF confine light into the air core. In order to maximize the collection efficiency and the spatial resolution, material and size of the ball lens is optimized. The total diameter of the probe head is 0.64 mm. The probe is useful for measurement of layered sample by the contact mode because it has very short focal length and high depth resolution. In vivo experiments in a stomach of a living rat demonstrate the high viability of the probe for noninvasive diagnosis of the stomach cancer.

Katagiri, Takashi; Hattori, Yusuke; Komachi, Yuichi; Matsuura, Yuji; Tashiro, Hideo; Sato, Hidetoshi

2006-10-01

372

Progress toward light weight high angular resolution multilayer coated optics  

SciTech Connect

We have been working on 3 separate projects that together will give us the ability to make 1 arc second, light weight Wolter I optics that work above 40 keV. The three separate tasks are: (a) plasma spraying of metal-coated micro-balloons; (b) coating of the inside of Wolter I mirrors, (c) actuator designs for improving figure quality. We give a progress report on our work on all three areas. In summary, for future space missions it will be desirable for them to be affordable by reducing mass, keeping the focal length manageable, and yet having high figure quality. The avenues we have described above are straight forward paths to achieving this goal, but a great deal of work needs to be done to take us from the concept stage to a functional system.

Ulmer, M.P.; Graham, M.E.; Vaynman, S.; Echt, J.; Farber, M.; Ehlert, S.; Varlese, S. (NWU); (Ball Aero. & Tech.)

2008-11-18

373

Dynamics of similariton pulses in length-inhomogeneous active fibres  

SciTech Connect

The possibility of producing self-similar frequency-modulated (FM) optical wave packets in length-inhomogeneous active fibres is studied for optical pulses with the initial Gaussian, hyperbolic-secant or parabolic shape. The conditions for converting these pulses into stable parabolic-type pulses with a constant frequency-modulation rate are considered. It is shown that the use of FM pulses of parabolic shape in active and length-inhomogeneous fibres can ensure the creation of an all-fibre generator-amplifier-compressor system with peak powers up to 1 MW and higher in the generated pulses. (nonlinear optical phenomena)

Zolotovskii, Igor' O; Sementsov, Dmitrii I; Yavtushenko, M S [Ulyanovsk State University, Ulyanovsk (Russian Federation); Senatorov, A K; Sysolyatin, A A [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation)

2010-05-26

374

First-order design of a reflective viewfinder for adaptive optics ophthalmoscopy  

PubMed Central

Adaptive optics (AO) ophthalmoscopes with small fields of view have limited clinical utility. We propose to address this problem in reflective instruments by incorporating a viewfinder pupil relay designed by considering pupil and image centering and conjugation. Diverting light from an existing pupil optical relay to the viewfinder relay allows switching field of view size. Design methods that meet all four centering and conjugation conditions using either a single concave mirror or with two concave mirrors forming an off-axis afocal telescope are presented. Two different methods for calculating the focal length and orientation of the concave mirrors in the afocal viewfinder relay are introduced. Finally, a 2.2 × viewfinder mode is demonstrated in an AO scanning light ophthalmoscope. PMID:23187514

Dubra, Alfredo; Sulai, Yusufu N.

2012-01-01

375

First-order design of a reflective viewfinder for adaptive optics ophthalmoscopy.  

PubMed

Adaptive optics (AO) ophthalmoscopes with small fields of view have limited clinical utility. We propose to address this problem in reflective instruments by incorporating a viewfinder pupil relay designed by considering pupil and image centering and conjugation. Diverting light from an existing pupil optical relay to the viewfinder relay allows switching field of view size. Design methods that meet all four centering and conjugation conditions using either a single concave mirror or with two concave mirrors forming an off-axis afocal telescope are presented. Two different methods for calculating the focal length and orientation of the concave mirrors in the afocal viewfinder relay are introduced. Finally, a 2.2 × viewfinder mode is demonstrated in an AO scanning light ophthalmoscope. PMID:23187514

Dubra, Alfredo; Sulai, Yusufu N

2012-11-19

376

Fast optical spectrometer for the charge exchange diagnostic on RFX-mod  

SciTech Connect

A new fast visible spectrometer built for the charge exchange diagnostic system of the RFX-mod Reversed Field pinch experiment is described. The optical mounting is of the Littrow type. The spectral resolution is defined by a 3000 grooves/mm, 180x143 mm{sup 2} wide reflection grating, and a focal length of 400 mm. The collimating optics is based on a commercial high quality f/2.8 telephoto lens, so that the input fibers can be vertically stacked without space in between. The detector is a two-dimensional charge coupled device back-illuminated sensor to ensure high quantum efficiency. Thus the spectrometer combines high speed, high spectral resolution, and excellent imaging quality.

Gazza, E.; Valisa, M. [Consorzio RFX, Associazione Euratom-ENEA sulla fusione, 35127 Padova (Italy)

2009-03-15

377

Length of stain dosimeter  

NASA Technical Reports Server (NTRS)

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Lueck, Dale E. (inventor)

1994-01-01

378

Integrated 585GHz Hot-Electron Mixer Focal-Plane Arrays Based on Annular Slot Antennas for Imaging Applications  

Microsoft Academic Search

We have developed 585-GHz quasi-optical mixers and focal-plane arrays (FPAs) comprised of planar annular slot antennas (ASAs) with integrated niobium hot-electron bolometers for imaging applications. In order to optimize the single-element mixer design, the embedding impedance of the single ASA presented to the bolometer is analyzed using the induced electromotive force (EMF) method by including the antenna feed contribution. This

Lei Liu; Haiyong Xu; Arthur W. Lichtenberger; Robert M. Weikle II

2010-01-01

379

Design of apochromatic telescopic optical system based on PWC method  

NASA Astrophysics Data System (ADS)

According to technical requirements,an apochromatic telescopic optical system which is characterized by the focal length 1.5m~2m,with the visible region spectrum band is needed.The successful design consists in using normal glasses based on PWC method to get a completely secondary-spectrum-removed and cramped construction telescopic optical system in this paper.Firstly, by the aberration theory and ZEMAX optical design software,a catadioptric achromatic optical system composed of a reflecting mirror and a couple of air-spaced negative doublets are designed.The initial configuration of optical system is calculated by PWC method and the proper couple of air-spaced negative doublets are chosen by the theory of achromatic.By comparing with various optical systems with different couple of air-spaced negative doublets, it is found that the combination of the heavy crown glass ZK7 and heavy flint glass ZF3 is effective to correct chromatic aberration and its secondary spectrum value is minimality.It can conclude that fact with the abbe number of ZK7 is twice than ZF3 make the good result and give guiding to the design of the same type of optical system. Secondary,according to the theory of secondary spectrum,the secondary spectrum value to be corrected is analyzed and the compensation can be changed by adjust the magnification power.The comparison is presented and the final telescopic optical system with cramped construction is achieved, and the goal of apochromatism and other aberration is reached.

Wei, Xiao-Xiao; Xu, Feng; Yu, Jian-jun

2011-11-01

380

Adaptive focal plane array (AFPA) technologies for integrated infrared microsystems  

NASA Astrophysics Data System (ADS)

Hyperspectral imaging in the infrared bands is traditionally performed using a broad spectral response focal plane array, integrated in a grating or a Fourier transform spectrometer. This paper describes an approach for miniaturizing a hyperspectral detection system on a chip by integrating a Micro-Electro-Mechanical-System (MEMS) based tunable Fabry Perot (FP) filter directly on a photodetector. A readout integrated circuit (ROIC) serves to both integrate the detector signal as well as to electrically tune the filter across the wavelength band. We report the first such demonstration of a tunable MEMS filter monolithically integrated on a HgCdTe detector. The filter structures, designed for operation in the 1.6-2.5 ?m wavelength band, were fabricated directly on HgCdTe detectors, both in photoconducting and high density vertically integrated photodiode (HDVIP) detectors. The HDVIP detectors have an architecture that permits operation in the standard photodiode mode at low bias voltages (<=0.5V) or in the electron avalanche photodiode (EAPD) mode with gain at bias voltages of ~20V. In the APD mode gain values of 100 may be achieved at 20 V at 200 K. The FP filter consists of distributed Bragg mirrors formed of Ge-SiO-Ge, a sacrificial spacer layer within the cavity and a silicon nitride spacer membrane for support. Mirror stacks fabricated on silicon, identical to the structures that will form the optical cavity, have been characterized to determine the optimum filter characteristics. The measured full width at half maximum (FWHM) was 34 nm at the center wavelength of 1780 nm with an extinction ratio of 36.6. Fully integrated filters on HgCdTe photoconductors with a center wavelength of approximately 1950 nm give a FWHM of approximately 100 nm, and a peak responsivity of approximately 8×10 4 V/W. Initial results for the filters on HDVIP detectors exhibit FWHM of 140 nm.

Mitra, P.; Beck, J. D.; Skokan, M. R.; Robinson, J. E.; Antoszewski, J.; Winchester, K. J.; Keating, A. J.; Nguyen, T.; Silva, K. K. M. B. D.; Musca, C. A.; Dell, J. M.; Faraone, L.

2006-05-01

381

Recovery of Deep Moonquake Focal Mechanisms  

NASA Technical Reports Server (NTRS)

Deep moonquakes are clustered not only in space but also in time: their recurrence times correspond to the durations of the anomalistic and draconic months, with some clusters preferring one of the two periods, while others are active with both periods. A key constraint for the understanding of the connection between the orbital motion of the Moon and its seismic activity is the focal mechanism: the orientation of the fault surface on which failure occurs during the quake. Due to the small aperture of the Apollo seismic network and the strong scattering of seismic waves within the lunar crust, the evaluation of P wave first motions to constrain the strike and dip of the fault planes is not feasible. Instead we evaluate the amplitude ratios of P and S waves. Seismograms are rotated into the P-SV-SH coordinate frame and amplitudes are determined as averages over short time windows after the arrival to reduce the impact of the scattering coda, which is independent of the source orientation. We allow for reversals of the fault motion, as observed for some clusters in previous studies, by taking into account the absolute amplitude only, without sign. An empirical site correction factor is applied to correct for amplitude distortions in the crust. We construct ensembles of fault plane solutions using an exhaustive grid search by accepting all orientations that reproduce the measured amplitude ratios within the observed standard deviations. Since all events of a given cluster are supposed to share the same fault plane, the combination of the individual inversion results further constrains the orientation. We evaluate 106 events from 25 different moonquake clusters. The most active cluster A001 contributes 37 events, while others contribute 1 to 9 events per cluster. Comparison of fault orientations with the variation of the tidal stress results in preferred orientations.

Weber, Renee C.; Knapmeyer, Martin

2012-01-01

382

Energy-Length Rule  

E-print Network

Lorentz ordering (causality) implies the following rule: for any given energy p0 of a system there is a certain interval c0 on x0 so that their product is the Lorentz ordering constant L It means p0c0 = L. The constant L=hc. Hence Planck constant h in a similar way as c are both consequences of Lorentz metric. The basic ideas are: 1. Lorentz metric implies that x0 must represent a length like the other components of x in X 2. The dual metric space X* is well defined since the Lorentz metric tensor is not singular. The components of the vectors p in X*are interpreted as representing energy. The properties of the physical systems that are direct consequences of the detailed structure of X and X*, and so expressed through the Lorentz Limit L are presented.

Alexandru C Mihul; Eleonora A Mihul

2006-08-25

383

Metagenomics: read length matters.  

PubMed

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (approximately 100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (approximately 750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72% of the COG hits found using long reads. Noting the current limitation in computational approaches for the analysis of short sequences, the use of short-read-length libraries does not appear to be an appropriate tool for the metagenomic characterization of microbial communities. PMID:18192407

Wommack, K Eric; Bhavsar, Jaysheel; Ravel, Jacques

2008-03-01

384

Metagenomics: Read Length Matters? †  

PubMed Central

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (?100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (?750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72% of the COG hits found using long reads. Noting the current limitation in computational approaches for the analysis of short sequences, the use of short-read-length libraries does not appear to be an appropriate tool for the metagenomic characterization of microbial communities. PMID:18192407

Wommack, K. Eric; Bhavsar, Jaysheel; Ravel, Jacques

2008-01-01

385

Perverted head shaking nystagmus in focal pontine infarction.  

PubMed

Although several papers have been published on perverted head shaking nystagmus (PHSN) associated with focal brainstem or cerebellar lesion, there are no reports of a focal pontine infarct that causes PHSN. We report a patient with focal pontine infarction who presented with sustained dizziness, limb dysmetria on the left extremity, decreased sensations to position and vibration of the left extremity, and gait imbalance. Only vestibular abnormality was downbeat nystagmus after vigorous head shakings. The maximum slow phase velocity of PHSN was 26°/s, and its duration was about 20s. This is the first report of PHSN associated with focal pontine infarction. Crossed ventral tegmental tract and velocity storage mechanism of vestibulocerebellum might be related on PHSN in this case. PMID:21146834

Kim, Hyun-Ah; Lee, Hyung; Sohn, Sung-Il; Kim, Ji Soo; Baloh, Robert W

2011-02-15

386

Quantitative multi-modal analysis of pediatric focal epilepsy  

E-print Network

For patients with medically refractive focal epilepsy, surgical intervention to remove the epileptic foci is often the last alternative for permanent cure. The success of such surgery is highly dependent on the doctor's ...

Eow, Andy Khai Siang

2005-01-01

387

Mechanical design and analysis of focal plate for gravity deformation  

NASA Astrophysics Data System (ADS)

The surface accuracy of astronomical telescope focal plate is a key indicator to precision stellar observation. To conduct accurate deformation measurement for focal plate in different status, a 6-DOF hexapod platform was used for attitude adjustment. For the small adjustment range of a classic 6-DOF hexapod platform, an improved structural arrangement method was proposed in the paper to achieve ultimate adjustment of the focal plate in horizontal and vertical direction. To validate the feasibility of this method, an angle change model which used ball hinge was set up for the movement and base plate. Simulation results in MATLAB suggested that the ball hinge angle change of movement and base plate is within the range of the limiting angle in the process of the platform plate adjusting to ultimate attitude. The proposed method has some guiding significance for accurate surface measurement of focal plate.

Wang, Jianping; Chu, Jiaru; Hu, Hongzhuan; Li, Kexuan; Zhou, Zengxiang

2014-07-01

388

Real-time focal stack compositing for handheld mobile cameras  

NASA Astrophysics Data System (ADS)

Extending the depth of field using a single lens camera on a mobile device can be achieved by capturing a set of images each focused at a different depth or focal stack then combine these samples of the focal stack to form a single all-in-focus image or an image refocused at a desired depth of field. Focal stack compositing in real time for a handheld mobile camera has many challenges including capturing, processing power, handshaking, rolling shutter artifacts, occlusion, and lens zoom effect. In this paper, we describe a system for a real time focal stack compositing system for handheld mobile device with an alignment and compositing algorithms. We will also show all-in-focus images captured and processed by a cell phone camera running on Android OS.

Solh, Mashhour

2013-03-01

389

Levetiracetam in focal epilepsy and hepatic porphyria: a case report.  

PubMed

We report a patient with focal epilepsy and latent hereditary coproporphyria who had exacerbation of clinical symptoms of porphyria under treatment with valproate and primidone and was then treated with levetiracetam without exacerbation of clinically latent porphyria. PMID:15101839

Paul, Friedemann; Meencke, Heinz-Joachim

2004-05-01

390

Two-dimensional tracking of ncd motility by back focal plane interferometry.  

PubMed

A technique for detecting the displacement of micron-sized optically trapped probes using far-field interference is introduced, theoretically explained, and used to study the motility of the ncd motor protein. Bead motions in the focal plane relative to the optical trap were detected by measuring laser intensity shifts in the back-focal plane of the microscope condenser by projection on a quadrant diode. This detection method is two-dimensional, largely independent of the position of the trap in the field of view and has approximately 10-micros time resolution. The high resolution makes it possible to apply spectral analysis to measure dynamic parameters such as local viscosity and attachment compliance. A simple quantitative theory for back-focal-plane detection was derived that shows that the laser intensity shifts are caused primarily by a far-field interference effect. The theory predicts the detector response to bead displacement, without adjustable parameters, with good accuracy. To demonstrate the potential of the method, the ATP-dependent motility of ncd, a kinesin-related motor protein, was observed with an in vitro bead assay. A fusion protein consisting of truncated ncd (amino acids 195-685) fused with glutathione-S-transferase was adsorbed to silica beads, and the axial and lateral motions of the beads along the microtubule surface were observed with high spatial and temporal resolution. The average axial velocity of the ncd-coated beads was 230 +/- 30 nm/s (average +/- SD). Spectral analysis of bead motion showed the increase in viscous drag near the surface; we also found that any elastic constraints of the moving motors are much smaller than the constraints due to binding in the presence of the nonhydrolyzable nucleotide adenylylimidodiphosphate. PMID:9533719

Allersma, M W; Gittes, F; deCastro, M J; Stewart, R J; Schmidt, C F

1998-02-01

391

Two-dimensional tracking of ncd motility by back focal plane interferometry.  

PubMed Central

A technique for detecting the displacement of micron-sized optically trapped probes using far-field interference is introduced, theoretically explained, and used to study the motility of the ncd motor protein. Bead motions in the focal plane relative to the optical trap were detected by measuring laser intensity shifts in the back-focal plane of the microscope condenser by projection on a quadrant diode. This detection method is two-dimensional, largely independent of the position of the trap in the field of view and has approximately 10-micros time resolution. The high resolution makes it possible to apply spectral analysis to measure dynamic parameters such as local viscosity and attachment compliance. A simple quantitative theory for back-focal-plane detection was derived that shows that the laser intensity shifts are caused primarily by a far-field interference effect. The theory predicts the detector response to bead displacement, without adjustable parameters, with good accuracy. To demonstrate the potential of the method, the ATP-dependent motility of ncd, a kinesin-related motor protein, was observed with an in vitro bead assay. A fusion protein consisting of truncated ncd (amino acids 195-685) fused with glutathione-S-transferase was adsorbed to silica beads, and the axial and lateral motions of the beads along the microtubule surface were observed with high spatial and temporal resolution. The average axial velocity of the ncd-coated beads was 230 +/- 30 nm/s (average +/- SD). Spectral analysis of bead motion showed the increase in viscous drag near the surface; we also found that any elastic constraints of the moving motors are much smaller than the constraints due to binding in the presence of the nonhydrolyzable nucleotide adenylylimidodiphosphate. PMID:9533719

Allersma, M W; Gittes, F; deCastro, M J; Stewart, R J; Schmidt, C F

1998-01-01

392

Symmetry distribution between hook length and part length for partitions  

E-print Network

2009/04/09 Symmetry distribution between hook length and part length for partitions Christine Bessenrodt and Guo-Niu Han ABSTRACT. -- It is known that the two statistics on integer partitions "hook and to the left of v, in the same column as v and under v). See Fig.1. We define the hook length (resp. part

Bessenrodt, Christine

393

A Lightweight, Precision-Deployable, Optical Bench for High Energy Astrophysics Missions  

NASA Astrophysics Data System (ADS)

The small angle of total reflection for X-rays, forcing grazing incidence optics with large collecting areas to long focal lengths, has been a fundamental barrier to the advancement of high-energy astrophysics. Design teams around the world have long recognized that a significant increase in effective area beyond Chandra and XMM-Newton requires either a deployable optical bench or separate X-ray optics and instrument module on formation flying spacecraft. Here, we show that we have in hand the components for a lightweight, precision-deployable optical bench that, through its inherent design features, is the affordable path to the next generation of imaging high-energy astrophysics missions. We present our plans for a full-scale engineering model of a deployable optical bench for Explorer-class missions. We intend to use this test article to raise the technology readiness level (TRL) of the tensegrity truss for a lightweight, precision-deployable optical bench for high-energy astrophysics missions from TRL 3 to TRL 5 through a set of four well-defined technology milestones. The milestones cover the architecture's ability to deploy and control the focal point, characterize the deployed dynamics, determine long-term stability, and verify the stowed load capability. Our plan is based on detailed design and analysis work and the construction of a first prototype by our team. Building on our prior analysis and the high TRL of the architecture components we are ready to move on to the next step. The key elements to do this affordably are two existing, fully characterized, flight-quality, deployable booms. After integrating them into the test article, we will demonstrate that our architecture meets the deployment accuracy, adjustability, and stability requirements. The same test article can be used to further raise the TRL in the future.

Danner, Rolf; Dailey, D.; Lillie, C.

2011-09-01

394

Thermally induced changes in the focal distance of composite mirrors - Composites with a zero coefficient of thermal expansion of the radius of curvature  

NASA Technical Reports Server (NTRS)

Calculations are presented of the coefficient of thermal expansion (CTE) of the radius of curvature of the reflector face sheets made of a quasi-isotropic composite. It is shown that, upon cooling, the change of the CTE of the focal distance of the mirror is equal to that of the radius of the curvature of the reflector face sheet. The CTE of the radius of the curvature of a quasi-isotropic composite face sheet depends on both the in-plane and the out-of-plane CTEs. The zero in-plane CTE of a face sheet does not guarantee mirrors with no focal length changes.

Dolgin, Benjamin P.

1992-01-01

395

The dispersion-focalization theory of sound systems  

Microsoft Academic Search

The Dispersion-Focalization Theory states that sound systems in human languages are shaped by two major perceptual constraints: dispersion driving auditory contrast towards maximal or sufficient values [B. Lindblom, J. Phonetics 18, 135-152 (1990)] and focalization driving auditory spectra towards patterns with close neighboring formants. Dispersion is computed from the sum of the inverse squared inter-spectra distances in the (F1, F2,

Jean-Luc Schwartz; Christian Abry; Louis-Jean Boë; Nathalie Vallée; Lucie Ménard

2005-01-01

396

Focal retrograde amnesia documented with matching anterograde and retrograde procedures  

Microsoft Academic Search

Focal retrograde amnesia is an unusual and theoretically challenging form of memory disorder. The case of a 65-year-old woman presenting with focal retrograde amnesia is reported. Following a cardiac arrest and subsequent hypoxia she remained in a coma for 24 h with evidence of epileptiform activity during the early recovery period. MR scans, 4 and 7 months post-onset, showed mild

Lilianne Manning

2002-01-01

397

Inflammatory pancreatic masses: problems in differentiating focal pancreatitis from carcinoma  

SciTech Connect

The authors studied 19 patients with focal inflammatory masses of the pancreas over an 18-month period. In 13 cases, transhepatic cholangiography and/or endoscopic retrograde cholangiopancreatography were unsuccessful in differentiating pancreatitis from carcinoma. Eighteen patients had a history of alcohol abuse, and 12 had had pancreatitis previously. Pre-existing glandular injury appears to be a prerequisite to formation of focal inflammatory pancreatic masses.

Neff, C.C.; Simeone, J.F.; Wittenberg, J.; Mueller, P.R.; Ferrucci, J.T. Jr.

1984-01-01

398

Three-dimensional shape-controllable focal spot array created by focusing vortex beams modulated by multi-value pure-phase grating.  

PubMed

We propose a method for creating a three-dimensional (3D) shape-controllable focal spot array by combination of a two-dimensional (2D) pure-phase modulation grating and an additional axial shifting pure-phase modulation composed of four-quadrant phase distribution unit at the back aperture of a high numerical aperture (NA) objective. It is demonstrated that the one-dimensional (1D) grating designed by optimized algorithm of selected number of equally spaced arbitrary phase value in a single period could produce desired number of equally spaced diffraction spot with identical intensity. It is also shown that the 2D pure-phase grating designed with this method could generate 2D diffraction spot array. The number of the spots in the array along each of two dimensions depends solely on the number of divided area with different phase values of the dimension. We also show that, by combining the axial translation phase modulation at the back aperture, we can create 3D focal spot array at the focal volume of the high NA objective. Furthermore, the shape or intensity distribution of each focal spot in the 3D focal array can be manipulated by introducing spatially shifted multi vortex beams as the incident beam. These kinds of 3D shape-controllable focal spot array could be utilized in the fabrication of artificial metamaterials, in parallel optical micromanipulation and multifocal multiphoton microscopic imaging. PMID:25321514

Zhu, Linwei; Sun, Meiyu; Zhu, Mengjun; Chen, Jiannong; Gao, Xiumin; Ma, Wangzi; Zhang, Dawei

2014-09-01

399

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor); Mattes, Brenton L. (Inventor); Charnetski, Clark J. (Inventor)

1999-01-01

400

Fiber optic temperature sensor  

NASA Technical Reports Server (NTRS)

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

2000-01-01

401

Focal-plane wave front sensing strategies for high contrast imaging: experimental validations on SPHERE  

NASA Astrophysics Data System (ADS)

Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also challenging areas in modern astronomy. The challenge is due to the very large contrast between the host star and the planet at very small angular separations. SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe [1]) is a secondgeneration instrument for the ESO VLT dedicated to this scientific objective. It combines an extreme adaptive optics system [2], various coronagraphic devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetric capabilities in the visible and near-infrared spectral ranges. The limitation of such a high contrast imaging system is mainly driven by the presence of intensity residual in the scientific focal plane, caused by uncorrected quasi-static optical aberrations upstream of the coronagraphic mask. The measurement and compensation of these aberrations is mandatory in order to reach the level of contrast requested by exoplanet imaging. We present in this paper the final experimental validation of the baseline method developed in the framework of SPHERE instrument for the conpensation of NCPA. The method is based on a differential measurement with phase diversity, and a compensation with an optimised modification of reference slopes.

Sauvage, Jean-François; Fusco, Thierry; Petit, Cyril; Mugnier, Laurent; Paul, Baptiste; Costille, Anne

2012-07-01

402

Back-focal-plane position detection with extended linear range for photonic force microscopy.  

PubMed

In photonic force microscopes, the position detection with high temporal and spatial resolution is usually implemented by a quadrant position detector placed in the back focal plane of a condenser. An objective with high numerical aperture (NA) for the optical trap has also been used to focus a detection beam. In that case the displacement of the probe at a fixed position of the detector produces a unique and linear response only in a restricted region of the probe displacement, usually several hundred nanometers. There are specific experiments where the absolute position of the probe is a relevant measure together with the probe position relative the optical trap focus. In our scheme we introduce the detection beam into the condenser with low NA through a pinhole with tunable size. This combination permits us to create a wide detection spot and to achieve the linear range of several micrometers by the probe position detection without reducing the trapping force. PMID:22945141

Martínez, Ignacio A; Petrov, Dmitri

2012-09-01

403

Alignment Tolerances for ALMA Optics  

Microsoft Academic Search

A tolerance analysis of the alignment of the ALMA FE optics is presented. The following performance criteria are taken into account: a) loss of on- axis efficiency from aperture plane misalignment; b) focal plane co- alignment of the two beams of each band; c) aberrations when off-axis mirrors operate between wavefronts not centered on the foci of the ellipsoid; d)

B. Lazareff

404

Compact Focal Plane Assembly for Planetary Science  

NASA Technical Reports Server (NTRS)

A compact radiometric focal plane assembly (FPA) has been designed in which the filters are individually co-registered over compact thermopile pixels. This allows for construction of an ultralightweight and compact radiometric instrument. The FPA also incorporates micromachined baffles in order to mitigate crosstalk and low-pass filter windows in order to eliminate high-frequency radiation. Compact metal mesh bandpass filters were fabricated for the far infrared (FIR) spectral range (17 to 100 microns), a game-changing technology for future planetary FIR instruments. This fabrication approach allows the dimensions of individual metal mesh filters to be tailored with better than 10- micron precision. In contrast, conventional compact filters employed in recent missions and in near-term instruments consist of large filter sheets manually cut into much smaller pieces, which is a much less precise and much more labor-intensive, expensive, and difficult process. Filter performance was validated by integrating them with thermopile arrays. Demonstration of the FPA will require the integration of two technologies. The first technology is compact, lightweight, robust against cryogenic thermal cycling, and radiation-hard micromachined bandpass filters. They consist of a copper mesh supported on a deep reactive ion-etched silicon frame. This design architecture is advantageous when constructing a lightweight and compact instrument because (1) the frame acts like a jig and facilitates filter integration with the FPA, (2) the frame can be designed so as to maximize the FPA field of view, (3) the frame can be simultaneously used as a baffle for mitigating crosstalk, and (4) micron-scale alignment features can be patterned so as to permit high-precision filter stacking and, consequently, increase the filter bandwidth and sharpen the out-of-band rolloff. The second technology consists of leveraging, from another project, compact and lightweight Bi0.87Sb0.13/Sb arrayed thermopiles. These detectors consist of 30-layer thermopiles deposited in series upon a silicon nitride membrane. At 300 K, the thermopile arrays are highly linear over many orders of magnitude of incident IR power, and have a reported specific detectivity that exceeds the requirements imposed on future mission concepts. The bandpass filter array board is integrated with a thermopile array board by mounting both boards on a machined aluminum jig.

Brown, Ari; Aslam, Shahid; Huang, Wei-Chung; Steptoe-Jackson, Rosalind

2013-01-01

405

MicroSight Optics  

SciTech Connect

MicroSight is an innovative gunsight technology that allows a marksman's eye to focus on both the front gunsight and the intended target. The MicroSight improves both firearm safety and performance by imaging two objects at different focal distances. The MicroSight was developed at Idaho National Laboratory, and has been licensed by Apollo Optical Systems. You can learn more about INL's research programs at http://www.facebook.com/idahonationallaboratory.

None

2010-01-01

406

A cryogenic optical telescope for inertial pointing in the milli-arc-sec range  

Microsoft Academic Search

We report the test results of the prototype telescope which is part of a system that provides the inertial reference frame\\u000a for Gravity Probe B. The fused silica star-tracking telescope, which has an effective focal length of 3.8 m at room temperature,\\u000a experienced a 5 cm focal position shift upon cooling to 4.2 K. A method to compensate this focal

Suwen Wang; D.-H. Gwo; R. K. Kirschman; J. A. Lipa

1996-01-01

407

Metagenomics: Read length matters  

E-print Network

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (?100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (?750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72 % of the COG hits found using long reads.

K. Eric Wommack; Jaysheel Bhavsar; Jacques Ravel

2008-01-01

408

Nd3+ doped CAS glasses: A thermo-optical and spectroscopic investigation  

NASA Astrophysics Data System (ADS)

Previous works have showed that calcium aluminosilicate (CAS) glasses, when prepared under vacuum conditions, are good candidates for solid state laser medium hosts and optical devices due to their appropriated thermal, optical and mechanical properties. These promising results led us to investigate the thermo-optical properties and emission spectra as a function of temperature in Nd3+ doped CAS glasses. Temperature changes in optical systems can cause structural modifications to the host, as well as other effects, such as emission quenching, or self-focalization. In this work, two series of CAS glasses, doped up to 5 wt.% Nd2O3, were prepared and characterized. Measurements of thermal coefficient of optical path length (dS/dT) and emission were performed on both series of Nd3+ doped CAS. In addition, measurements of optical absorption coefficient and emission lifetime were carried out. The results are discussed in terms of temperature dependence of these properties and Nd2O3 content. Comparisons with other glasses, such as LSCAS (low-silica calcium aluminosilicate) are also presented.

Steimacher, A.; Barboza, M. J.; Pedrochi, F.; Astrath, N. G. C.; Rohling, J. H.; Baesso, M. L.; Medina, A. N.

2014-11-01

409

Multiple pass reimaging optical system  

NASA Technical Reports Server (NTRS)

An optical imaging system for enabling nonabsorbed light imaged onto a photodetective surface to be collected and reimaged one or more times onto that surface in register with the original image. The system includes an objective lens, one or more imaging lenses, one or more retroreflectors and perhaps a prism for providing optical matching of the imaging lens focal planes to the photo detective surface.

Gunter, W. D., Jr.; Brown, R. M. (inventors)

1973-01-01

410

Coaxial atomizer liquid intact lengths  

NASA Technical Reports Server (NTRS)

Average intact lengths of round liquid jets generated by airblast coaxial atomizer were measured from over 1500 photographs. The intact lengths were studied over a jet Reynolds number range of 18,000 and Weber number range of 260. Results are presented for two different nozzle geometries. The intact lengths were found to be strongly dependent on Re and We numbers. An empirical equation was derived as a function of these parameters. A comparison of the intact lengths for round jets and flat sheets shows that round jets generate shorter intact lengths.

Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

1991-01-01

411

CD38 Exacerbates Focal Cytokine Production, Postischemic Inflammation and Brain Injury after Focal Cerebral Ischemia  

PubMed Central

Background Converging evidence suggests that inflammatory processes significantly influence brain injury and clinical impairment in ischemic stroke. Although early studies suggested a key role of lymphocytes, recent data has emphasized the orchestrating function of innate immunity, i.e., macrophages and microglia. The bifunctional receptor and ectoenzyme CD38 synthesizes calcium-mobilizing second messengers (e.g., cyclic ADP-ribose), which have been shown to be necessary for activation and migration of myeloid immune cells. Therefore, we investigated the dynamics of CD38 in stroke and the impact of CD38-deficiency on cytokine production, inflammation and cerebral damage in a mouse model of cerebral ischemia-reperfusion. Methodology/Principal Findings We show that the local expression of the chemokine MCP-1 was attenuated in CD38-deficient mice compared with wildtype mice after focal cerebral ischemia and reperfusion. In contrast, no significant induction of MCP-1 expression was observed in peripheral blood after 6 hours. Flow cytometry analysis revealed less infiltrating macrophages and lymphocytes in the ischemic hemisphere of CD38-deficient mice, whereas the amount of resident microglia was unaltered. An up-regulation of CD38 expression was observed in macrophages and CD8+ cells after focal cerebral ischemia in wildtype mice, whereas CD38 expression was unchanged in microglia. Finally, we demonstrate that CD38-deficiency decreases the cerebral ischemic injury and the persistent neurological deficit after three days of reperfusion in this murine temporary middle cerebral artery occlusion (tMCAO) model. Conclusion/Significance CD38 is differentially regulated following stroke and its deficiency attenuates the postischemic chemokine production, the immune cell infiltration and the cerebral injury after temporary ischemia and reperfusion. Therefore CD38 might prove a therapeutic target in ischemic stroke. PMID:21625615

Gelderblom, Mathias; Ludewig, Peter; Leypoldt, Frank; Koch-Nolte, Friedrich; Gerloff, Christian; Magnus, Tim

2011-01-01

412

Tests of optical fibres for astronomical instrumentation at ESO  

Microsoft Academic Search

This paper presents results on transmission and focal ratio degradation (FRD) measurements on 18 types of optical fibers considered for astronomical instrumentation at La Silla, together with results on the optical coupling of fibers with microlenses. Results show that spectral transmission of optical fibers doped with high content of OH(-) radicals is close to the theoretical limit in the near-UV

Gerardo Avila

1988-01-01

413

Transmissive Diffractive Optical Element Solar Concentrators  

NASA Technical Reports Server (NTRS)

Solar-thermal-radiation concentrators in the form of transmissive diffractive optical elements (DOEs) have been proposed as alternatives to mirror-type solar concentrators now in use. In comparison with functionally equivalent mirror-type solar concentrators, the transmissive, diffractive solar concentrators would weigh and cost less, and would be subject to relaxed mechanical tolerances. A DOE concentrator would be made from a thin, flat disk or membrane of a transmissive material having a suitable index of refraction. By virtue of its thinness, the DOE concentrator would have an areal mass density significantly less than that of a functionally equivalent conventional mirror. The DOE concentrator would have a relatively wide aperture--characterized by a focal-length/aperture-diameter ratio ('f number') on the order of 1. A kinoform (a surface-relief phase hologram) of high diffractive order would be microfabricated onto one face of the disk. The kinoform (see figure) would be designed to both diffract and refract incident solar radiation onto a desired focal region, without concern for forming an image of the Sun. The high diffractive order of this kinoform (in contradistinction to the low diffractive orders of some other kinoforms) would be necessary to obtain the desired f number of 1, which, in turn, would be necessary for obtaining a desired concentration ratio of 2,500 or greater. The design process of optimizing the concentration ratio of a proposed DOE solar concentrator includes computing convolutions of the optical bandwidth of the Sun with the optical transmission of the diffractive medium. Because, as in the cases of other non-imaging, light-concentrating optics, image quality is not a design requirement, the process also includes trading image quality against concentration ratio. A baseline design for one example calls for an aperture diameter of 1 m. This baseline design would be scalable to a diameter as large as 10 m, or to a smaller diameter for a laboratory test article. Initial calculations have indicated that the characteristics of the test article would be readily scalable to a full-size unit.

Baron, Richard; Moynihan, Philip; Price, Douglas

2008-01-01

414

The optical design of a visible adaptive optics system for the Magellan Telescope  

NASA Astrophysics Data System (ADS)

The Magellan Adaptive Optics system will achieve first light in November of 2012. This AO system contains several subsystems including the 585-actuator concave adaptive secondary mirror, the Calibration Return Optic (CRO) alignment and calibration system, the CLIO 1-5 microm IR science camera, the movable guider camera and active optics assembly, and the W-Unit, which contains both the Pyramid Wavefront Sensor (PWFS) and the VisAO visible science camera. In this dissertation, we present details of the design, fabrication, assembly, alignment, and laboratory performance of the VisAO camera and its optical components. Many of these components required a custom design, such as the Spectral Differential Imaging Wollaston prisms and filters and the coronagraphic spots. One component, the Atmospheric Dispersion Corrector (ADC), required a unique triplet design that had until now never been fabricated and tested on sky. We present the design, laboratory, and on-sky results for our triplet ADC. We also present details of the CRO test setup and alignment. Because Magellan is a Gregorian telescope, the ASM is a concave ellipsoidal mirror. By simulating a star with a white light point source at the far conjugate, we can create a double-pass test of the whole system without the need for a real on-sky star. This allows us to test the AO system closed loop in the Arcetri test tower at its nominal design focal length and optical conjugates. The CRO test will also allow us to calibrate and verify the system off-sky at the Magellan telescope during commissioning and periodically thereafter. We present a design for a possible future upgrade path for a new visible Integral Field Spectrograph. By integrating a fiber array bundle at the VisAO focal plane, we can send light to a pre-existing facility spectrograph, such as LDSS3, which will allow 20 mas spatial sampling and R˜1,800 spectra over the band 0.6-1.05 microm. This would be the highest spatial resolution IFU to date, either from the ground or in space.

Kopon, Derek

415

Optical tweezers for confocal microscopy  

NASA Astrophysics Data System (ADS)

In confocal laser scanning microscopes (CLSMs), lasers can be used for image formation as well as tools for the manipulation of microscopic objects. In the latter case, in addition to the imaging lasers, the light of an extra laser has to be focused into the object plane of the CLSM, for example as optical tweezers. Imaging as well as trapping by optical tweezers can be done using the same objective lens. In this case, z-sectioning for 3D imaging shifts the optical tweezers with the focal plane of the objective along the optical axis, so that a trapped object remains positioned in the focal plane. Consequently, 3D imaging of trapped objects is impossible without further measures. We present an experimental set-up keeping the axial trapping position of the optical tweezers at its intended position whilst the focal plane can be axially shifted over a distance of about 15 ?m. It is based on fast-moving correctional optics synchronized with the objective movement. First examples of application are the 3D imaging of chloroplasts of Elodea densa (Canadian waterweed) in a vigorous cytoplasmic streaming and the displacement of zymogen granules in pancreatic cancer cells (AR42 J).

Hoffmann, A.; Meyer zu Hörste, G.; Pilarczyk, G.; Monajembashi, S.; Uhl, V.; Greulich, K. O.

2000-11-01

416

Advanced simulation methods to detect resonant frequency stack up in focal plane design  

NASA Astrophysics Data System (ADS)

Wire used to connect focal plane electrical connections to external electrical circuitry can be modeled using the length, diameter and loop height to determine the resonant frequency. The design of the adjacent electric board and mounting platform can also be analyzed. The combined resonant frequency analysis can then be used to decouple the different component resonant frequencies to eliminate the potential for metal fatigue in the wires. It is important to note that the nominal maximum stress values that cause metal fatigue can be much less than the ultimate tensile stress limit or the yield stress limit and are degraded further at resonant frequencies. It is critical that tests be done to qualify designs that are not easily simulated due to material property variation and complex structures. Sine wave vibration testing is a critical component of qualification vibration and provides the highest accuracy in determining the resonant frequencies which can be reduced or uncorrelated improving the structural performance of the focal plane assembly by small changes in design damping or modern space material selection. Vibration flow down from higher levels of assembly needs consideration for intermediary hardware, which may amplify or attenuate the full up system vibration profile. A simple pass through of vibration requirements may result in over test or missing amplified resonant frequencies that can cause system failure. Examples are shown of metal wire fatigue such as discoloration and microscopic cracks which are visible at the submicron level by the use of a scanning electron microscope. While it is important to model and test resonant frequencies the Focal plane must also be constrained such that Coefficient of Thermal expansion mismatches are allowed to move and not overstress the FPA.

Adams, Craig; Malone, Neil R.; Torres, Raymond; Fajardo, Armando; Vampola, John; Drechsler, William; Parlato, Russell; Cobb, Christopher; Randolph, Max; Chiourn, Surath; Swinehart, Robert

2014-09-01

417

Utilization of a Curved Focal Surface Array in a 3.5m Wide Field of View Telescope  

NASA Astrophysics Data System (ADS)

Wide field of view optical telescopes have a range for uses in both the astronomical and space surveillance purposes. In designing these systems, a number of factors must be taken into account and design trades accomplished to best balance the performance and cost of the system to meet various program constraints. One design trade that has been discussed of the past decade is the curving of the digital focal surface array to meet the field curvature versus the utilization of optical elements to flatten the field curvature for a more traditional focal plane array. For the Defense Advanced Research Projects Agency (DARPA) 3.5m Space Surveillance Telescope (SST) the choice was made to curve the array to best satisfy the stressing telescope performance parameters, along with programmatic challenges. The results of this design choice led to a system that meets all of the initial program goals and stands ready to dramatically improve the nation's space surveillance capabilities. This paper will discuss the implementation of the curved focal surface array, the performance achieved by the array and the delta cost difference in the curved array versus a typical flat array.

Blake, T.; Faccenda, W.; Lambour, R.; Shah, R.; Smith, A.; Gregory, J. G.; Pearce, E. C.; Woods, D.; Sundbeck, S.; Bolden, M.

2013-09-01

418

Combined scanning transmission electron microscopy tilt- and focal series.  

PubMed

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt-focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller "missing wedge" artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography. PMID:24548618

Dahmen, Tim; Baudoin, Jean-Pierre; Lupini, Andrew R; Kübel, Christian; Slusallek, Philipp; de Jonge, Niels

2014-04-01

419

[Focal surgery in testis cancer: current state of the art].  

PubMed

Radical orchiectomy is the standard treatment of testicular neoplasia causing androgen insufficiency, infertility and psychological stress. Focal surgery allows the preservation of fertility, endocrine function and integrity of the genital anatomy, with preservation of the image of the male body. The EAU guidelines suggest focal surgery in case of synchronous bilateral tumors, metachronous contralateral tumours, tumour in solitary testis with normal pre-operative testosterone levels, when the tumor volume less than 30% of the testicular volume. There are two focal surgical techniques: tumorectomy and polar resection, followed by biopsies and frozen section of the resection bed. In case of benign tumours, the treatment is often curative. In case of malignancy, carcinoma in situ is frequently found in the surrounding tissues. Adjuvant treatment with chemotherapy or radiotherapy is performed with a fair success rate. These adjuvant treatments reduce or delete the functional benefits achieved by conservative surgery. The evidence of the literature suggests that focal surgery is a valid option for all patients with testicular tumours that are not palpable and small sized, with the advantage of avoiding unnecessary radical orchiectomy in most cases. Therefore, the selection criteria for focal surgery are the mass size (less than 25 mm) and a safety distance of the tumor from the rete testis, in order to preserve testicular vascularization. A close follow-up with ultrasound, testicular markers and radiological examinations is mandatory in case of germ cell neoplasia treated conservatively in patients with indications for conservative surgery. PMID:24419923

Palermo, Giuseppe; Antonucci, Michele; Recupero, Salvatore Marco; Fiorillo, Alessandro; Vittori, Matteo; Bassi, Pier Francesco; Gulino, Gaetano

2013-01-01

420

The Focal Surface of the JEM-EUSO Instrument  

SciTech Connect

The Extreme Universe Space Observatory on JEM/EF (JEM-EUSO) is a space mission to study extremely high-energy cosmic rays. The JEM-EUSO instrument is a wide-angle refractive telescope in the near-ultraviolet wavelength region which will be mounted to the International Space Station. Its goal is to measure time-resolved fluorescence images of extensive air showers in the atmosphere. In this paper we describe in detail the main features and technological aspects of the focal surface of the instrument. The JEM-EUSO focal surface is a spherically curved surface, with an area of about 4.5m{sup 2}. The focal surface detector is made of more than 5,000 multi-anode photomultipliers (MAPMTs). Current baseline is Hamamatsu R11265-03-M64. The approach to the focal surface detector is highly modular. Photo-Detector-Modules (PDM) are the basic units that drive the mechanical structure and data acquisition. Each PDM consists of 9 Elementary Cells (ECs). The EC, which is the basic unit of the MAPMT support structure and of the front-end electronics, contains 4 units of MAPMTs. In total, about 1,200 ECs or about 150 PDMs are arranged on the whole of the focal surface of JEM-EUSO.

Kawasaki, Y. [Computational Astrophysics Lab., ASI, RIKEN (Japan); EUSO Team, ASI, RIKEN (Japan); Casolino, M. [INFN and Physics Department of Univresity of Rome 'Tor Vergata' (Italy); EUSO Team, ASI, RIKEN (Japan); Gorodetzky, P. [APC-AstroParticule et Cosmologie (France); Santangelo, A. [Universitity of Tuebingen (Germany); Ricci, M. [INFN, Laboratori Nazionali di Frascati (Italy); Kajino, F. [Department of Physics, Konan University (Japan); Ebisuzaki, T. [Computational Astrophysics Lab., ASI, RIKEN (Japan)

2011-09-22

421

When Is Input Salient? An Exploratory Study of Sentence Location and Word Length Effects on Input Processing  

ERIC Educational Resources Information Center

Sentence position and word length have been claimed to contribute to the perceptual salience of words. The perceptual salience of words in turn is said to predict L2 developmental sequences. Data for such claims come from sentence repetition tasks that required perceptual re-encoding of input and that did not control for focal accent. We used a…

Carroll, Susanne E.

2012-01-01

422

Nonlinear focal shift beyond the geometrical focus in moderately focused acoustic beams.  

PubMed

The phenomenon of the displacement of the position along the axis of the pressure, intensity, and radiation force maxima of focused acoustic beams under increasing driving voltages (nonlinear focal shift) is studied for the case of a moderately focused beam. The theoretical and experimental results show the existence of this shift along the axis when the initial pressure in the transducer increases until the acoustic field reaches the fully developed nonlinear regime of propagation. Experimental data show that at high amplitudes and for moderate focusing, the position of the on-axis pressure maximum and radiation force maximum can surpass the geometrical focal length. On the contrary, the on-axis pressure minimum approaches the transducer under increasing driving voltages, increasing the distance between the positive and negative peak pressure in the beam. These results are in agreement with numerical KZK model predictions and the existed data of other authors and can be explained according to the effect of self-refraction characteristic of the nonlinear regime of propagation. PMID:23927186

Camarena, Francisco; Adrián-Martínez, Silvia; Jiménez, Noé; Sánchez-Morcillo, Víctor

2013-08-01

423

Resonant optical antennas.  

PubMed

We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations that take into account the finite metallic conductivity at optical frequencies. Because optical antennas link propagating radiation and confined/enhanced optical fields, they should find applications in optical characterization, manipulation of nanostructures, and optical information processing. PMID:15947182

Mühlschlegel, P; Eisler, H-J; Martin, O J F; Hecht, B; Pohl, D W

2005-06-10

424

Advances in Focal Plane Wavefront Estimation for Directly Imaging Exoplanets  

NASA Astrophysics Data System (ADS)

To image cold exoplanets directly in visible light, an instrument on a telescope needs to suppress starlight by about 9 orders of magnitude at small separations from the star. A coronagraph changes the point spread function to create regions of high contrast where exoplanets or disks can be seen. Aberrations on the optics degrade the contrast by several orders of magnitude, so all high-contrast imaging systems incorporate one or more deformable mirrors (DMs) to recover regions of high contrast. With a coronagraphic instrument planned for the WFIRST-AFTA space telescope, there is a pressing need for faster, more robust estimation and control schemes for the DMs. Non-common path aberrations limit conventional phase conjugation schemes to medium star-to-planet contrast ratios of about 1e-6. High-contrast imaging requires estimation and control of both phase and amplitude in the same beam path as the science camera. Field estimation is a challenge since only intensity is measured; the most common approach, including that planned for WFIRST-AFTA, is to use DMs to create diversity, via pairs of small probe shapes, thereby allowing disambiguation of the electric field. Most implementations of DM Diversity require at least five images per electric field estimate and require narrowband measurements. This paper describes our new estimation algorithms that improve the speed (by using fewer images) and bandwidth of focal plane wavefront estimation. For narrowband estimation, we are testing nonlinear, recursive algorithms such as an iterative extended Kalman filter (IEKF) to use three images each iteration and build better, more robust estimates. We are also exploring the use of broadband estimation without the need for narrowband sub-filters and measurements. Here we present simulations of these algorithms with realistic noise and small signals to show how they might perform for WFIRST-AFTA. Once validated in simulations, we will test these algorithms experimentally in Princeton's HCIL and in the Jet Propulsion Laboratory's (JPL's) High Contrast Imaging Testbed (HCIT). Developing these faster, more robust wavefront estimators is a crucial for increasing the science yield of the WFIRST-AFTA coronagraphic instrument.

Eldorado Riggs, A. J.; Kasdin, N. Jeremy; Groff, Tyler Dean

2015-01-01

425

Focal depth measurement of scanning helium ion microscope  

NASA Astrophysics Data System (ADS)

When facing the challenges of critical dimension measurement of complicated nanostructures, such as of the three dimension integrated circuit, characterization of the focal depth of microscopes is important. In this Letter, we developed a method for characterizing the focal depth of a scanning helium ion microscope (HIM) by using an atomic force microscope tip characterizer (ATC). The ATC was tilted in a sample chamber at an angle to the scanning plan. Secondary electron images (SEIs) were obtained at different positions of the ATC. The edge resolution of the SEIs shows the nominal diameters of the helium ion beam at different focal levels. With this method, the nominal shapes of the helium ion beams were obtained with different apertures. Our results show that a small aperture is necessary to get a high spatial resolution and high depth of field images with HIM. This work provides a method for characterizing and improving the performance of HIM.

Guo, Hongxuan; Itoh, Hiroshi; Wang, Chunmei; Zhang, Han; Fujita, Daisuke

2014-07-01

426

Visible and shortwave infrared focal planes for remote sensing instruments  

NASA Astrophysics Data System (ADS)

The development of solid-state sensor technology for multispectral linear array (MLA) instruments is described. A buttable four-spectral-band linear-format CCD and a buttable two-spectral band linear-format short-wave IR CCD have been designed, and first samples have been demonstrated. In addition, first-sample four-band interference filters have been fabricated, and hybrid packaging technology is being developed. Based on this development work, the design and construction of focal planes for a Shuttle sortie MLA instrument have begun. This work involves a visible and near-IR focal plane with 2048 pixels x 4 spectral bands and a short-wave IR focal plane with 1024 pixels x 2 spectral bands.

Tower, J. R.; McCarthy, B. M.; Pellon, L. E.; Strong, R. T.; Elabd, H.

1984-01-01

427

Structures linking microfilament bundles to the membrane at focal contacts  

PubMed Central

We used quick-freeze, deep-etch, rotary replication and immunogold cytochemistry to identify a new structure at focal contacts. In Xenopus fibroblasts, elongated aggregates of particles project from the membrane to contact bundles of actin microfilaments. Before terminating, a single bundle of microfilaments interacts with several aggregates that appear intermittently over a distance of several microns. Aggregates are enriched in proteins believed to mediate actin- membrane interactions at focal contacts, including beta 1-integrin, vinculin, and talin, but they appear to contain less alpha-actinin and filamin. We also identified a second, smaller class of aggregates of membrane particles that contained beta 1-integrin but not vinculin or talin and that were not associated with actin microfilaments. Our results indicate that vinculin, talin, and beta 1-integrin are assembled into distinctive structures that mediate multiple lateral interactions between microfilaments and the membrane at focal contacts. PMID:7686554

1993-01-01

428

PRISM project optical instrument  

NASA Technical Reports Server (NTRS)

The scientific goal of the Passively-cooled Reconnaissance of the InterStellar Medium (PRISM) project is to map the emission of molecular hydrogen at 17.035 micrometers and 28.221 micrometers. Since the atmosphere is opaque at these infrared wavelengths, an orbiting telescope is being studied. The availability of infrared focal plane arrays enables infrared imaging spectroscopy at the molecular hydrogen wavelengths. The array proposed for PRISM is 128 pixels square, with a pixel size of 75 micrometers. In order to map the sky in a period of six months, and to resolve the nearer molecular clouds, each pixel must cover 0.5 arcminutes. This sets the focal length at 51.6 cm. In order for the pixel size to be half the diameter of the central diffraction peak at 28 micrometers would require a telescope aperture of 24 cm; an aperture of 60 cm has been selected for the PRISM study for greater light gathering power.

Taylor, Charles R.

1994-01-01

429

Contractility Modulates Cell Adhesion Strengthening Through Focal Adhesion Kinase and Assembly of Vinculin-Containing Focal Adhesions  

PubMed Central

Actin-myosin contractility modulates focal adhesion assembly, stress fiber formation, and cell migration. We analyzed the contributions of contractility to fibroblast adhesion strengthening using a hydrodynamic adhesion assay and micropatterned substrates to control cell shape and adhesive area. Serum addition resulted in adhesion strengthening to levels 30–40% higher than serum-free cultures. Inhibition of myosin light chain kinase or Rho-kinase blocked phosphorylation of myosin light chain to similar extents and eliminated the serum-induced enhancements in strengthening. Blebbistatin-induced inhibition of myosin II reduced serum-induced adhesion strength to similar levels as those obtained by blocking myosin light chain phosphorylation. Reductions in adhesion strengthening by inhibitors of contractility correlated with loss of vinculin and talin from focal adhesions without changes in integrin binding. In vinculin-null cells, inhibition of contractility did not alter adhesive force, whereas controls displayed a 20% reduction in adhesion strength, indicating that the effects of contractility on adhesive force are vinculin-dependent. Furthermore, in cells expressing FAK, inhibitors of contractility reduced serum-induced adhesion strengthening as well as eliminated focal adhesion assembly. In contrast, in the absence of FAK, these inhibitors did not alter adhesion strength or focal adhesion assembly. These results indicate that contractility modulates adhesion strengthening via FAK-dependent, vinculin-containing focal adhesion assembly. PMID:20205236

Dumbauld, David W.; Shin, Heungsoo; Gallant, Nathan D.; Michael, Kristin E.; Radhakrishna, Harish; García, Andrés J.

2010-01-01

430

IMPEDANCE OF FINITE LENGTH RESISTOR  

SciTech Connect

We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

2005-05-15

431

Development of spider micro-structured optical arrays for x-ray optics  

NASA Astrophysics Data System (ADS)

The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. Test spider structures, have been bent to a radius of curvature smaller than 5 cm, indicating that in complete devices a suitable focal length using a tandem pair configuration could be achieved. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the spider MOA device design. Prototype devices have been manufactured using a Viscous Plastic Processing technique for the PZT piezoelectric actuators, and a single wet etch step using {111} planes in a (110) silicon wafer for both the silicon channels and the spider structure. A surface roughness of 1.2 nm was achieved on the silicon channel walls. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the development of spider MOA's comparing FEA modelling with the results obtained for prototype structures.

Rodriguez Sanmartin, Daniel; Zhang, Dou; Button, Tim; Meggs, Carl; Atkins, Carolyn; Doel, Peter; Brooks, David; Feldman, Charlotte; Willingale, Richard; Michette, Alan; Pfauntsch, Slawka; Sahraei, Shahin; Shand, Matthew; James, Ady; Willis, Graham; Dunare, Camelia; Stevenson, Tom; Parkes, William; Smith, Andy

2010-09-01

432

Development status of the AIRS IR focal plane assembly  

NASA Astrophysics Data System (ADS)

The atmospheric infrared sounder (AIRS) is a high resolution IR spectrometer (lambda/(Delta) (lambda) congruent 1200) which will map global temperatures and identify atmospheric aerosols from orbit by monitoring key atmospheric absorption lines. The focal plane consists of ten bilinear photovoltaic (PV) and two photoconductive (PC) HgCdTe detector arrays (modules) sampling a 3.7 to 15.4 micrometer spectral window in 15 bands. To attain the desired temperature accuracy, tight constraints on focal plane performance parameters such as linearity better than 0.1%, quantum efficiency (QE) on the order of 70%, low noise or noise equivalent quantum flux density (NEQFD), and no outages at key spectral lines have been imposed. Assessment of focal plane performance begins at the detector and readout levels where flight candidate detector arrays and CMOS readouts are selected. PV detector arrays and their readouts are hybridized (PC modules are wire-bonded directly) into modules which are then individually tested under simulated flight conditions. Five of the twelve module types are incorporated into an engineering-level (EM) focal plane upon which the module level tests are repeated as a prelude to the fabrication and testing of a separate, fully populated, flight-level (PFM) focal plane. Module testing has demonstrated that many difficult system requirements have been met, and work continues to optimize module performance. Lockheed Martin IR Imaging Systems' (LMIRIS) overall design of the infrared (IR) detector/Dewar assembly and focal plane development program is given, followed by a summary of PV and PC module data.

Libonate, G. Scott; Denley, Brian; Krueger, Eric E.; Rutter, James H., Jr.; Stobie, James A.; Terzis, C. L.