The Dizzying Depths of the Cylindrical Mirror

NASA Astrophysics Data System (ADS)

DeWeerd, Alan J.; Hill, S. Eric

2005-02-01

A typical introduction to geometrical optics treats plane and spherical mirrors. At first glance, it may be surprising that texts seldom mention the cylindrical mirror, except for the occasional reference to use in fun houses and to viewing anamorphic art.1,2 However, even a cursory treatment reveals its complexity. Holzberlein used an extended object to qualitatively illustrate that images are produced both before and behind a concave cylindrical mirror.3 He also speculated on how this extreme astigmatism results in an observer's dizziness. By considering a simple point object, we make a more detailed analysis of the cylindrical mirror and the dizziness it induces. First, we illustrate how rays from a point object reflect to form not one point image but two line images. Next, we describe how an observer perceives a likeness of the object. Finally, we suggest how confusing depth cues induce dizziness. Although we focus on the concave cylindrical mirror, the discussion is easy to generalize to the convex cylindrical mirror.

Multispectral scanner optical system

NASA Technical Reports Server (NTRS)

Stokes, R. C.; Koch, N. G. (Inventor)

1980-01-01

An optical system for use in a multispectral scanner of the type used in video imaging devices is disclosed. Electromagnetic radiation reflected by a rotating scan mirror is focused by a concave primary telescope mirror and collimated by a second concave mirror. The collimated beam is split by a dichroic filter which transmits radiant energy in the infrared spectrum and reflects visible and near infrared energy. The long wavelength beam is filtered and focused on an infrared detector positioned in a cryogenic environment. The short wavelength beam is dispersed by a pair of prisms, then projected on an array of detectors also mounted in a cryogenic environment and oriented at an angle relative to the optical path of the dispersed short wavelength beam.

Wavefront error measurement of the concave ellipsoidal mirrors of the METIS coronagraph on ESA Solar Orbiter mission

NASA Astrophysics Data System (ADS)

Sandri, P.

2017-12-01

The paper describes the alignment technique developed for the wavefront error measurement of ellipsoidal mirrors presenting a central hole. The achievement of a good alignment with a classic setup at the finite conjugates when mirrors are uncoated cannot be based on the identification and materialization at naked eye of the retro-reflected spot by the mirror under test as the intensity of the retro-reflected spot results to be ≈1E-3 of the intensity of the injected laser beam of the interferometer. We present the technique developed for the achievement of an accurate alignment in the setup at the finite conjugate even in condition of low intensity based on the use of an autocollimator adjustable in focus position and a small polished flat surface on the rear side of the mirror. The technique for the alignment has successfully been used for the optical test of the concave ellipsoidal mirrors of the METIS coronagraph of the ESA Solar Orbiter mission. The presented method results to be advantageous in terms of precision and of time saving also when the mirrors are reflective coated and integrated into their mechanical hardware.

Acoustic Models of Optical Mirrors

ERIC Educational Resources Information Center

Mayer, V. V.; Varaksina, E. I.

2014-01-01

Students form a more exact idea of the action of optical mirrors if they can observe the wave field being formed during reflection. For this purpose it is possible to organize model experiments with flexural waves propagating in thin elastic plates. The direct and round edges of the plates are used as models of plane, convex and concave mirrors.…

Measurement of the configuration of a concave surface by the interference of reflected light

NASA Technical Reports Server (NTRS)

Kumazawa, T.; Sakamoto, T.; Shida, S.

1985-01-01

A method whereby a concave surface is irradiated with coherent light and the resulting interference fringes yield information on the concave surface is described. This method can be applied to a surface which satisfies the following conditions: (1) the concave face has a mirror surface; (2) the profile of the face is expressed by a mathematical function with a point of inflection. In this interferometry, multilight waves reflected from the concave surface interfere and make fringes wherever the reflected light propagates. Interference fringe orders. Photographs of the fringe patterns for a uniformly loaded thin silicon plate clamped at the edge are shown experimentally. The experimental and the theoretical values of the maximum optical path difference show good agreement. This simple method can be applied to obtain accurate information on concave surfaces.

Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials

NASA Technical Reports Server (NTRS)

Shukla, R. P.; Dokhanian, Mostafa; Venkateswarlu, Putcha; George, M. C.

1990-01-01

The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.

Optical measurements of the mirrors and of the interferential filter of the Metis coronagraph on Solar Orbiter

NASA Astrophysics Data System (ADS)

Sandri, P.; Sarra, P.; Radaelli, P.; Morea, D.; Melich, R.; Berlicki, A.; Antonucci, E.; Castronuovo, M. M.; Fineschi, S.; Naletto, G.; Nicolini, G.; Romoli, M.

2017-08-01

The paper describes the wavefront error measurements of the concave ellipsoidal mirrors M1 and M2, of the concave spherical mirror M0 and of the flat interferential filter IF of the Metis coronagraph. Metis is an inverted occultation coronagraph on board of the ESA Solar Orbiter mission providing a broad-band imaging of the full corona in linearly polarized visible-light (580 - 640 nm) and a narrow-band imaging of the full corona in the ultraviolet Lyman α (121.6 nm). Metis will observe the solar outer atmosphere from a close distance to the Sun as 0.28 A.U. and from up to 35deg out-of-ecliptic. The measurements of wavefront error of the mirrors and of the interferential filter of Metis have been performed in a ISO5 clean room both at component level and at assembly level minimizing, during the integration, the stress introduced by the mechanical hardware. The wavefront error measurements have been performed with a digital interferometer for mirrors M0, M1 and M2 and with a Shack-Hartmann wavefront sensor for the interferential filter.

Transparent 3D display for augmented reality

NASA Astrophysics Data System (ADS)

Lee, Byoungho; Hong, Jisoo

2012-11-01

Two types of transparent three-dimensional display systems applicable for the augmented reality are demonstrated. One of them is a head-mounted-display-type implementation which utilizes the principle of the system adopting the concave floating lens to the virtual mode integral imaging. Such configuration has an advantage in that the threedimensional image can be displayed at sufficiently far distance resolving the accommodation conflict with the real world scene. Incorporating the convex half mirror, which shows a partial transparency, instead of the concave floating lens, makes it possible to implement the transparent three-dimensional display system. The other type is the projection-type implementation, which is more appropriate for the general use than the head-mounted-display-type implementation. Its imaging principle is based on the well-known reflection-type integral imaging. We realize the feature of transparent display by imposing the partial transparency to the array of concave mirror which is used for the screen of reflection-type integral imaging. Two types of configurations, relying on incoherent and coherent light sources, are both possible. For the incoherent configuration, we introduce the concave half mirror array, whereas the coherent one adopts the holographic optical element which replicates the functionality of the lenslet array. Though the projection-type implementation is beneficial than the head-mounted-display in principle, the present status of the technical advance of the spatial light modulator still does not provide the satisfactory visual quality of the displayed three-dimensional image. Hence we expect that the head-mounted-display-type and projection-type implementations will come up in the market in sequence.

Fabrication of large diffractive optical elements in thick film on a concave lens surface.

PubMed

Xie, Yongjun; Lu, Zhenwu; Li, Fengyou

2003-05-05

We demonstrate experimentally the technique of fabricating large diffractive optical elements (DOEs) in thick film on a concave lens surface (mirrors) with precise alignment by using the strategy of double exposure. We adopt the method of double exposure to overcome the difficulty of processing thick photoresist on a large curved substrate. A uniform thick film with arbitrary thickness on a concave lens can be obtained with this technique. We fabricate a large concentric circular grating with a 10-ìm period on a concave lens surface in film with a thickness of 2.0 ìm after development. It is believed that this technique can also be used to fabricate larger DOEs in thicker film on the concave or convex lens surface with precise alignment. There are other potential applications of this technique, such as fabrication of micro-optoelectromechanical systems (MOEMS) or microelectromechanical systems (MEMS) and fabrication of microlens arrays on a large concave lens surface or convex lens surface with precise alignment.

Reflective optical imaging system

DOEpatents

Shafer, David R.

2000-01-01

An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements are characterized in order from object to image as convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention increases the slit dimensions associated with ringfield scanning optics, improves wafer throughput and allows higher semiconductor device density.

Reflective optical imaging method and circuit

DOEpatents

Shafer, David R.

2001-01-01

An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements are characterized in order from object to image as convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention increases the slit dimensions associated with ringfield scanning optics, improves wafer throughput and allows higher semiconductor device density.

Adaptive Optics at the World’s Biggest Optical Telescope

DTIC Science & Technology

2010-09-01

bottom up. The reflective, and deformable, component of each of the LBT’s mirrors is a concave Zerodur shell, 1.6 mm in average thickness and 911 mm in...Physik, 85748 Garching, Germany ABSTRACT The Large Binocular Telescope (LBT) on Mt. Graham, Arizona, comprises two 8.4 m primary mirrors on a...adaptive optics (AO) was incorporated into the design through two adaptive secondary mirrors (ASM), each 91 cm in diameter with 672 actuators, which feed

Gregorian optical system with non-linear optical technology for protection against intense optical transients

DOEpatents

Ackermann, Mark R [Albuquerque, NM; Diels, Jean-Claude M [Albuquerque, NM

2007-06-26

An optical system comprising a concave primary mirror reflects light through an intermediate focus to a secondary mirror. The secondary mirror re-focuses the image to a final image plane. Optical limiter material is placed near the intermediate focus to optically limit the intensity of light so that downstream components of the optical system are protected from intense optical transients. Additional lenses before and/or after the intermediate focus correct optical aberrations.

A full-parallax 3D display with restricted viewing zone tracking viewer's eye

NASA Astrophysics Data System (ADS)

Beppu, Naoto; Yendo, Tomohiro

2015-03-01

The Three-Dimensional (3D) vision became widely known as familiar imaging technique now. The 3D display has been put into practical use in various fields, such as entertainment and medical fields. Development of 3D display technology will play an important role in a wide range of fields. There are various ways to the method of displaying 3D image. There is one of the methods that showing 3D image method to use the ray reproduction and we focused on it. This method needs many viewpoint images when achieve a full-parallax because this method display different viewpoint image depending on the viewpoint. We proposed to reduce wasteful rays by limiting projector's ray emitted to around only viewer using a spinning mirror, and to increase effectiveness of display device to achieve a full-parallax 3D display. We propose a method by using a tracking viewer's eye, a high-speed projector, a rotating mirror that tracking viewer (a spinning mirror), a concave mirror array having the different vertical slope arranged circumferentially (a concave mirror array), a cylindrical mirror. About proposed method in simulation, we confirmed the scanning range and the locus of the movement in the horizontal direction of the ray. In addition, we confirmed the switching of the viewpoints and convergence performance in the vertical direction of rays. Therefore, we confirmed that it is possible to realize a full-parallax.

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

Mandula, Gábor, E-mail: mandula.gabor@wigner.mta.hu; Kis, Zsolt; Lengyel, Krisztián

We report on a method for real-time dynamic calibration of a tunable external cavity diode laser by using a partially mode-matched plano-concave Fabry-Pérot interferometer in reflection geometry. Wide range laser frequency scanning is carried out by piezo-driven tilting of a diffractive grating playing the role of a frequency selective mirror in the laser cavity. The grating tilting system has a considerable mechanical inertness, so static laser frequency calibration leads to false results. The proposed real-time dynamic calibration based on the identification of primary- and Gouy-effect type secondary interference peaks with known frequency and temporal history can be used for amore » wide scanning range (from 0.2 GHz to more than 1 GHz). A concave spherical mirror with a radius of R = 100 cm and a plain 1% transmitting mirror was used as a Fabry-Pérot interferometer with various resonator lengths to investigate and demonstrate real-time calibration procedures for two kinds of laser frequency scanning functions.« less

The image-forming mirror in the eye of the scallop

NASA Astrophysics Data System (ADS)

Palmer, Benjamin A.; Taylor, Gavin J.; Brumfeld, Vlad; Gur, Dvir; Shemesh, Michal; Elad, Nadav; Osherov, Aya; Oron, Dan; Weiner, Steve; Addadi, Lia

2017-12-01

Scallops possess a visual system comprising up to 200 eyes, each containing a concave mirror rather than a lens to focus light. The hierarchical organization of the multilayered mirror is controlled for image formation, from the component guanine crystals at the nanoscale to the complex three-dimensional morphology at the millimeter level. The layered structure of the mirror is tuned to reflect the wavelengths of light penetrating the scallop’s habitat and is tiled with a mosaic of square guanine crystals, which reduces optical aberrations. The mirror forms images on a double-layered retina used for separately imaging the peripheral and central fields of view. The tiled, off-axis mirror of the scallop eye bears a striking resemblance to the segmented mirrors of reflecting telescopes.

Space Shuttle Projects

NASA Image and Video Library

1996-02-01

The STS-77 crew patch displays the Shuttle Endeavour in the lower left and its reflection within the tripod and concave parabolic mirror of the SPARTAN Inflatable Antenna Experiment (IAE). The center leg of the tripod also delineates the top of the Spacehab's shape, the rest of which is outlined in gold just inside the red perimeter. The Spacehab was carried in the payload bay and housed the Commercial Float Zone Furnace (CFZF). Also depicted within the confines of the IAE mirror are the mission's rendezvous operations with the Passive Aerodynamically-Stabilized Magnetically-Damped satellite (PAM/STU) appears as a bright six-pointed star-like reflection of the sun on the edge of the mirror with Endeavour in position to track it. The sunlight on the mirror's edge, which also appears as an orbital sunset, is located over Goddard Space Flight Center, the development facility for the SPARTAN/IAE and Technology Experiments Advancing Missions in Space (TEAMS) experiments. The reflection of the Earth is oriented to show the individual countries of the crew as well as the ocean which Captain Cook explored in the original Endeavour. The mission number 77 is featured as twin stylized chevrons and an orbiting satellite as adapted from NASA's logo. The stars at the top are arranged as seen in the northern sky in the vicinity of the constellation Ursa Minor. The field of 11 stars represents both the TEAMS cluster of experiments (the four antennae of GPS Attitude and Navigation Experiment (GANE), the single canister of Liquid Metal Thermal Experiment (LMTE), the three canisters of Vented Tank Resupply Experiment (VTRE), and the three canisters of PAM/STU) and the 11th flight of Endeavour. The constellation at the right shows the fourth flight of Spacehab Experiments.

New high-precision deep concave optical surface manufacturing capability

NASA Astrophysics Data System (ADS)

Piché, François; Maloney, Chris; VanKerkhove, Steve; Supranowicz, Chris; Dumas, Paul; Donohue, Keith

2017-10-01

This paper describes the manufacturing steps necessary to manufacture hemispherical concave aspheric mirrors for high- NA systems. The process chain is considered from generation to final figuring and includes metrology testing during the various manufacturing steps. Corning Incorporated has developed this process by taking advantage of recent advances in commercially available Satisloh and QED Technologies equipment. Results are presented on a 100 mm concave radius nearly hemispherical (NA = 0.94) fused silica sphere with a better than 5 nm RMS figure. Part interferometric metrology was obtained on a QED stitching interferometer. Final figure was made possible by the implementation of a high-NA rotational MRF mode recently developed by QED Technologies which is used at Corning Incorporated for production. We also present results from a 75 mm concave radius (NA = 0.88) Corning ULE sphere that was produced using sub-aperture tools from generation to final figuring. This part demonstrates the production chain from blank to finished optics for high-NA concave asphere.

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor); Olson, Todd E. (Inventor)

1996-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. A second embodiment uses two curvilinear mirrors and one planar mirror, with a gain medium positioned in the optical path between each curvilinear mirror and the planar mirror. A third embodiment uses two curvilinear mirrors and two planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses a curvilinear mirror and three planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses four planar mirrors and a focusing lens system, with a gain medium positioned between the four mirrors. A fifth embodiment uses first and second planar mirrors, a focusing lens system and a third mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the third mirror. A sixth embodiment uses two planar mirrors and a curvilinear mirror and a fourth mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the fourth mirror. In a seventh embodiment, first and second mirrors face a third mirror, all curvilinear, in a White Cell configuration, and a gain medium is positioned adjacent to one of the mirrors.

Ray Tracing with Virtual Objects.

ERIC Educational Resources Information Center

Leinoff, Stuart

1991-01-01

Introduces the method of ray tracing to analyze the refraction or reflection of real or virtual images from multiple optical devices. Discusses ray-tracing techniques for locating images using convex and concave lenses or mirrors. (MDH)

Compact sensitive instrument for direct ultrasonic visualization of defects.

PubMed

Bar-Cohen, Y; Ben-Joseph, B; Harnik, E

1978-12-01

A simple ultrasonic imaging cell based on the confocal combination of a plano-concave lens and a concave spherical mirror is described. When used in conjunction with a stroboscopic schlieren visualization system, it has the main attributes of a practical nondestructive testing instrument: it is compact, relatively inexpensive, and simple to operate; its sensitivity is fair, resolution and fidelity are good; it has a fairly large field of view and a test piece can be readily scanned. The scope of its applicability is described and discussed.

[From otoscope to ophthalmoscope and back. The interwoven history of their invention and introduction into medical practice. Pictures from the history of otorhinolaryngology, illustrated by instruments from the collection of the Ingolstadt German Medical History Museum].

PubMed

Feldmann, H

1995-11-01

Friedrich Hofmann, medical officer in Burgsteinfurt, Westphalia, Germany, in 1841 described a concave mirror with a central aperture in it as the ideal instrument that allowed reflecting and focussing light into the external auditory canal and simultaneously inspecting the tympanic membrane without obstructing either the light or the view. He recommended his device also for the inspection of other concealed regions of the body. His invention was referred to by Martell Frank in his textbook of otology in 1845, but otherwise attracted no attention. Hermann Helmholtz, physiologist in Königsberg, East Prussia, devised his ophthalmoscope in 1850-51 in order to study the phenomenon of glowing eyes. With this instrument he was the first to see the retina of a living human. As means of illumination he used small panes of glass similar to cover-glasses which were introduced into the common visual axis of the observer and the subject at such an angle that light from a lamp was reflected into the subject's eye while the observer inspected the subject's retina through the glass and an appropriate lens. He recommended this type of illumination also for otoscopy. His invention was at once acclaimed throughout the world and opened completely new opportunities in ophthalmology. The slanting panes of glass, however, were not the ideal solution for illumination. It was only one year later that Ruete in Göttingen replaced them with a concave mirror with a central aperture, and there is every indication that Frank's report on Hofmann's mirror had suggested this technique to him. During the following two years quite a number of other modifications of the ophthalmoscope were constructed, all of them using the concave mirror with a central aperture, which soon became synonymous with the ophthalmoscope as such. Von Tröltsch, otologist and ophthalmologist in Würzburg, presented a concave mirror with a central aperture for otoscopy in Paris in 1855-56. His instrument was obviously derived from the already well known ophthalmoscope by adapting the diameter and focal distance to this special application. His primary concern was to use daylight instead of artificial light for otoscopy. Von Tröltsch did not know Hofmann's publication, but later did not hesitate to acknowledge Hofmann's priority. It was von Tröltsch who popularized the concave reflector with a central aperture as the instrument of choice in otoscopy, and subsequently also for rhinoscopy and laryngoscopy. Further modifications were devised to have the hands free for operations. Thus the reflector was fixed to the forehead by strap and buckle or a vulcanite band, or it was provided with a handle that was to be held between the teeth, or it was attached to a spectacle frame. The details of this interwoven history are related and highlighted by numerous quotations and historical illustrations.

Influence of Layup Sequence on the Surface Accuracy of Carbon Fiber Composite Space Mirrors

NASA Astrophysics Data System (ADS)

Yang, Zhiyong; Liu, Qingnian; Zhang, Boming; Xu, Liang; Tang, Zhanwen; Xie, Yongjie

2018-04-01

Layup sequence is directly related to stiffness and deformation resistance of the composite space mirror, and error caused by layup sequence can affect the surface precision of composite mirrors evidently. Variation of layup sequence with the same total thickness of composite space mirror changes surface form of the composite mirror, which is the focus of our study. In our research, the influence of varied quasi-isotropic stacking sequences and random angular deviation on the surface accuracy of composite space mirrors was investigated through finite element analyses (FEA). We established a simulation model for the studied concave mirror with 500 mm diameter, essential factors of layup sequences and random angular deviations on different plies were discussed. Five guiding findings were described in this study. Increasing total plies, optimizing stacking sequence and keeping consistency of ply alignment in ply placement are effective to improve surface accuracy of composite mirror.

Gaussian-reflectivity mirror resonator for a high-power transverse-flow CO2 laser.

PubMed

Ling, Dongxiong; Chen, Junruo; Li, Junchang

2006-05-01

A Gaussian-reflectivity mirror resonator is proposed to achieve high-quality laser beams. To analyze the laser fields in a Gaussian-reflectivity mirror resonator, the diffraction integral equations of a Gaussian-reflectivity mirror resonator are converted to the finite-sum matrix equations. Consequently, according to the Fox-Li laser self-reproducing principle, we describe the mode fields and their losses in the proposed resonator as eigenvectors and eigenvalues of a transfer matrix. The conclusion can be drawn from the numerical results that, if a Gaussian-reflectivity mirror is adopted for a plano-concave resonator, a fundamental mode can easily be obtained from a transverse-flow CO2 laser and high-quality laser beams can be expected.

Design, Fabrication, Optical Testing, and Performance of Diamond Machined Aspheric Mirrors for Ground-Based Near-IR Astronomy

NASA Technical Reports Server (NTRS)

Ohl, Raymond G.; Mink, Ronald; Chambers, V. John; Connelly, Joseph A.; Mentzell, J. Eric; Tveekrem, June L.; Howard, Joseph M.; Preuss, Werner; Schroeder, Mechthild; Sohn, Alex;

Reflective optical imaging systems with balanced distortion

DOEpatents

Hudyma, Russell M.

2001-01-01

Optical systems compatible with extreme ultraviolet radiation comprising four reflective elements for projecting a mask image onto a substrate are described. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical systems are particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput, and allows higher semiconductor device density. The inventive optical systems are characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

Laser-based study of geometrical optics at school level

NASA Astrophysics Data System (ADS)

Garg, Amit; Dhingra, Vishal; Sharma, Reena; Mittal, Ankit; Tiwadi, Raman; Chakravarty, Pratik

2011-10-01

Students at the school level from grade 7 to 12 are taught various concepts of geometrical optics but with little hands-on activities. Light propagation through different media, image formation using lenses and mirrors under different conditions and application of basic principles to characterization of lenses, mirrors and other instruments has been a subject which although fascinates students but due to lack of suitable demonstrating setups, students find difficulty in understanding these concepts and hence unable to appreciate the importance of such concepts in various useful scientific apparatus, day to day life, instruments and devices. Therefore, students tend to cram various concepts related to geometrical optics instead of understanding them. As part of the extension activity in the University Grants Commission major research project "Investigating science hands-on to promote innovation and research at undergraduate level" and University of Delhi at Acharya Narendra Dev College SPIE student chapter, students working under this optics outreach programme have demonstrated various experiments on geometrical optics using a five beam laser ray box and various optical components like different types of mirrors, lenses, prisms, optical fibers etc. The various hands-on activities includes demonstrations on laws of reflection, image formation using plane, concave and convex mirrors, mirror formula, total internal reflection, light propagation in an optical fiber, laws of refraction, image formation using concave and convex lenses and combination of these lenses, lens formula, light propagation through prisms, dispersion in prism, defects in eye- Myopia and hypermetropia. Subjects have been evaluated through pre and post tests in order to measure the improvement in their level of understanding.

A comparison of performance of lightweight mirrors

NASA Technical Reports Server (NTRS)

Cho, Myung K.; Richard, Ralph M.; Hileman, Edward A.

1990-01-01

Four lightweight solid contoured back mirror shapes (a double arch, a single arch, a modified single arch, and a double concave mirror) and a cellular sandwich lightweight meniscus mirror, have been considered for the primary mirror of the Space Infrared Telescope Facility (SIRTF). A parametric design study using these shapes for the SIRTF 40 inch primary mirror with a focal ratio f/2 is presented. Evaluations of the optical performance and fundamental frequency analyses are performed to compare relative merits of each mirror configuration. Included in these are structural, optical, and frequency analyses for (1) different back contour shapes, (2) different number and location of the support points, and (3) two gravity orientations (ZENITH and HORIZON positions). The finite element program NASTRAN is used to obtain the structural deflections of the optical surface. For wavefront error analysis, FRINGE and PCFRINGE programs are used to evaluate the optical performance. A scaling law relating the optical and structural performance for various mirror contoured back shapes is developed.

Reflective optical imaging system with balanced distortion

DOEpatents

Chapman, Henry N.; Hudyma, Russell M.; Shafer, David R.; Sweeney, Donald W.

1999-01-01

An optical system compatible with short wavelength (extreme ultraviolet) An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput and allows higher semiconductor device density. The inventive optical system is characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

Coherent beam combination using self-phase locked stimulated Brillouin scattering phase conjugate mirrors with a rotating wedge for high power laser generation.

PubMed

Park, Sangwoo; Cha, Seongwoo; Oh, Jungsuk; Lee, Hwihyeong; Ahn, Heekyung; Churn, Kil Sung; Kong, Hong Jin

2016-04-18

The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers. We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM. Its phase locking ability and the usefulness on the beam-combination laser are demonstrated experimentally. A four-beam combination is demonstrated using this SBS-PCM scheme. The relative phases between the beams were measured to be less than λ/24.7.

Condenser for ring-field deep-ultraviolet and extreme-ultraviolet lithography

DOEpatents

Chapman, Henry N.; Nugent, Keith A.

2001-01-01

A condenser for use with a ring-field deep ultraviolet or extreme ultraviolet lithography system. A condenser includes a ripple-plate mirror which is illuminated by a collimated beam at grazing incidence. The ripple plate comprises a plate mirror into which is formed a series of channels along an axis of the mirror to produce a series of concave surfaces in an undulating pattern. Light incident along the channels of the mirror is reflected onto a series of cones. The distribution of slopes on the ripple plate leads to a distribution of angles of reflection of the incident beam. This distribution has the form of an arc, with the extremes of the arc given by the greatest slope in the ripple plate. An imaging mirror focuses this distribution to a ring-field arc at the mask plane.

Extreme-UV lithography condenser

DOEpatents

Sweatt, William C.; Sweeney, Donald W.; Shafer, David; McGuire, James

2001-01-01

Condenser system for use with a ringfield camera in projection lithography where the condenser includes a series of segments of a parent aspheric mirror having one foci at a quasi-point source of radiation and the other foci at the radius of a ringfield have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ringfield camera about one of the beams and fall onto the ringfield radius as a coincident image as an arc of the ringfield. The condenser has a set of correcting mirrors with one of the correcting mirrors of each set, or a mirror that is common to said sets of mirrors, from which the radiation emanates, is a concave mirror that is positioned to shape a beam segment having a chord angle of about 25 to 85 degrees into a second beam segment having a chord angle of about 0 to 60 degrees.

Apparatus for Teaching Physics

ERIC Educational Resources Information Center

Gottlieb, Herbert H.

1977-01-01

Describes: how to measure index of refraction by the thickness method; how to teach the concept of torque using a torque wrench; how to produce a real image with a concave mirror; how to eliminate the interface effects of a Pyrex containers; and an apparatus to illustrate Bernoulli's Principle. (MLH)

Surface Figure Measurement of Silicon Carbide Mirrors at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Blake, Peter; Mink, Ronald G.; Chambers, John; Robinson, F. David; Content, David; Davila, Pamela

2005-01-01

The surface figure of a developmental silicon carbide mirror, cooled to 87 K and then 20 K within a cryostat, was measured with unusually high precision at the Goddard Space Flight Center (GSFC). The concave spherical mirror, with a radius of 600 mm and a clear aperture of 150 mm, was fabricated of sintered silicon carbide. The mirror was mounted to an interface plate representative of an optical bench, made of the material Cesic@, a composite of silicon, carbon, and silicon carbide. The change in optical surface figure as the mirror and interface plate cooled from room temperature to 20 K was 3.7 nm rms, with a standard uncertainty of 0.23 nm in the rms statistic. Both the cryo-change figure and the uncertainty are among the lowest such figures yet published. This report describes the facilities, experimental methods, and uncertainty analysis of the measurements.

Condenser for ring-field deep ultraviolet and extreme ultraviolet lithography

DOEpatents

Chapman, Henry N.; Nugent, Keith A.

2002-01-01

A condenser for use with a ring-field deep ultraviolet or extreme ultraviolet lithography system. A condenser includes a ripple-plate mirror which is illuminated by a collimated or converging beam at grazing incidence. The ripple plate comprises a flat or curved plate mirror into which is formed a series of channels along an axis of the mirror to produce a series of concave surfaces in an undulating pattern. Light incident along the channels of the mirror is reflected onto a series of cones. The distribution of slopes on the ripple plate leads to a distribution of angles of reflection of the incident beam. This distribution has the form of an arc, with the extremes of the arc given by the greatest slope in the ripple plate. An imaging mirror focuses this distribution to a ring-field arc at the mask plane.

Inverting Image Data For Optical Testing And Alignment

NASA Technical Reports Server (NTRS)

Shao, Michael; Redding, David; Yu, Jeffrey W.; Dumont, Philip J.

1993-01-01

Data from images produced by slightly incorrectly figured concave primary mirror in telescope processed into estimate of spherical aberration of mirror, by use of algorithm finding nonlinear least-squares best fit between actual images and synthetic images produced by multiparameter mathematical model of telescope optical system. Estimated spherical aberration, in turn, converted into estimate of deviation of reflector surface from nominal precise shape. Algorithm devised as part of effort to determine error in surface figure of primary mirror of Hubble space telescope, so corrective lens designed. Modified versions of algorithm also used to find optical errors in other components of telescope or of other optical systems, for purposes of testing, alignment, and/or correction.

Condenser for illuminating a ringfield camera with synchrotron emission light

DOEpatents

Sweatt, W.C.

1996-04-30

The present invention relates generally to the field of condensers for collecting light from a synchrotron radiation source and directing the light into a ringfield of a lithography camera. The present invention discloses a condenser comprising collecting, processing, and imaging optics. The collecting optics are comprised of concave and convex spherical mirrors that collect the light beams. The processing optics, which receive the light beams, are comprised of flat mirrors that converge and direct the light beams into a real entrance pupil of the camera in a symmetrical pattern. In the real entrance pupil are located flat mirrors, common to the beams emitted from the preceding mirrors, for generating substantially parallel light beams and for directing the beams toward the ringfield of a camera. Finally, the imaging optics are comprised of a spherical mirror, also common to the beams emitted from the preceding mirrors, images the real entrance pupil through the resistive mask and into the virtual entrance pupil of the camera. Thus, the condenser is comprised of a plurality of beams with four mirrors corresponding to a single beam plus two common mirrors. 9 figs.

Condenser for illuminating a ringfield camera with synchrotron emission light

DOEpatents

Sweatt, William C.

1996-01-01

The present invention relates generally to the field of condensers for collecting light from a synchrotron radiation source and directing the light into a ringfield of a lithography camera. The present invention discloses a condenser comprising collecting, processing, and imaging optics. The collecting optics are comprised of concave and convex spherical mirrors that collect the light beams. The processing optics, which receive the light beams, are comprised of flat mirrors that converge and direct the light beams into a real entrance pupil of the camera in a symmetrical pattern. In the real entrance pupil are located flat mirrors, common to the beams emitted from the preceding mirrors, for generating substantially parallel light beams and for directing the beams toward the ringfield of a camera. Finally, the imaging optics are comprised of a spherical mirror, also common to the beams emitted from the preceding mirrors, images the real entrance pupil through the resistive mask and into the virtual entrance pupil of the camera. Thus, the condenser is comprised of a plurality of beams with four mirrors corresponding to a single beam plus two common mirrors.

Lens testing using total internal reflection holography

DOEpatents

Hildebrand, Bernard P.

1976-12-14

Accurate, rapid and inexpensive testing and inspecting of lens surfaces tugh holographic means requiring no beamsplitters, mirrors or overpower optics, and wherein a hologram formed in accordance with one aspect of the invention contains the entire interferometer and serves as both a master and illuminating source for both concave and convex surfaces to be so tested.

Fast, purely growing collisionless reconnection as an eigenfunction problem related to but not involving linear whistler waves

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

Bellan, Paul M.

If either finite electron inertia or finite resistivity is included in 2D magnetic reconnection, the two-fluid equations become a pair of second-order differential equations coupling the out-of-plane magnetic field and vector potential to each other to form a fourth-order system. The coupling at an X-point is such that out-of-plane even-parity electric and odd-parity magnetic fields feed off each other to produce instability if the scale length on which the equilibrium magnetic field changes is less than the ion skin depth. The instability growth rate is given by an eigenvalue of the fourth-order system determined by boundary and symmetry conditions. Themore » instability is a purely growing mode, not a wave, and has growth rate of the order of the whistler frequency. The spatial profile of both the out-of-plane electric and magnetic eigenfunctions consists of an inner concave region having extent of the order of the electron skin depth, an intermediate convex region having extent of the order of the equilibrium magnetic field scale length, and a concave outer exponentially decaying region. If finite electron inertia and resistivity are not included, the inner concave region does not exist and the coupled pair of equations reduces to a second-order differential equation having non-physical solutions at an X-point.« less

A complete ray-trace analysis of the Mirage toy

NASA Astrophysics Data System (ADS)

Adhya, Sriya; Noé, John W.

2007-06-01

The `Mirage' (Opti-Gone International) is a well-known optics demonstration (PIRA index number 6A20.35) that uses two opposed concave mirrors to project a real image of a small object into space. We studied image formation in the Mirage by standard 2x2 matrix methods and by exact ray tracing, with particular attention to additional real images that can be observed when the mirror separation is increased beyond one focal length. We find that the three readily observed secondary images correspond to 4, 6, or 8 reflections, respectively, contrary to previous reports.

Fabrication of a high-precision spherical micromirror by bending a silicon plate with a metal pad.

PubMed

Wu, Tong; Hane, Kazuhiro

2011-09-20

We demonstrate here the fabrication of a smooth mirror surface by bending a thin silicon plate. A spherical surface is achieved by the bending moment generated in the circumference of the micromirror. Both convex and concave spherical micromirrors are realized through the anodic bonding of silicon and Pyrex glass. Since the mirror surface is originated from the polished silicon surface and no additional etching is introduced for manufacturing, the surface roughness is thus limited to the polishing error. This novel approach opens possibilities for fabricating a smooth surface for micromirror and microlens applications.

Multispectral variable magnification glancing incidence x ray telescope

NASA Technical Reports Server (NTRS)

Hoover, Richard B. (Inventor)

1992-01-01

A multispectral, variable magnification, glancing incidence, x-ray telescope capable of broadband, high resolution imaging of solar and stellar x-ray and extreme ultraviolet radiation sources is discussed. The telescope includes a primary optical system which focuses the incoming radiation to a primary focus. Two or more rotatable mirror carriers, each providing a different magnification, are positioned behind the primary focus at an inclination to the optical axis. Each carrier has a series of ellipsoidal mirrors, and each mirror has a concave surface covered with a multilayer (layered synthetic microstructure) coating to reflect a different desired wavelength. The mirrors of both carriers are segments of ellipsoids having a common first focus coincident with the primary focus. A detector such as an x-ray sensitive photographic film is positioned at the second respective focus of each mirror so that each mirror may reflect the image at the first focus to the detector at the second focus. The carriers are selectively rotated to position a selected mirror for receiving radiation from the primary optical system, and at least the first carrier may be withdrawn from the path of the radiation to permit a selected mirror on the second carrier to receive the radiation.

Water window imaging x ray microscope

NASA Technical Reports Server (NTRS)

Hoover, Richard B. (Inventor)

1992-01-01

A high resolution x ray microscope for imaging microscopic structures within biological specimens has an optical system including a highly polished primary and secondary mirror coated with identical multilayer coatings, the mirrors acting at normal incidence. The coatings have a high reflectivity in the narrow wave bandpass between 23.3 and 43.7 angstroms and have low reflectivity outside of this range. The primary mirror has a spherical concave surface and the secondary mirror has a spherical convex surface. The radii of the mirrors are concentric about a common center of curvature on the optical axis of the microscope extending from the object focal plane to the image focal plane. The primary mirror has an annular configuration with a central aperture and the secondary mirror is positioned between the primary mirror and the center of curvature for reflecting radiation through the aperture to a detector. An x ray filter is mounted at the stage end of the microscope, and film sensitive to x rays in the desired band width is mounted in a camera at the image plane of the optical system. The microscope is mounted within a vacuum chamber for minimizing the absorption of x rays in air from a source through the microscope.

Mirrors for High Resolution X-Ray Optics---Figure Preserving IR/PT Coating

NASA Technical Reports Server (NTRS)

Chan, Kai-Wing; Olsen, Lawrence; Sharpe, Marton; Numata, Ai; McClelland, Ryan; Saha, Timo; Zhang, Will

2016-01-01

Coating stress of 10 - 20 nm of Ir is sufficiently high to distort the figure of arc-second thin lightweight mirrors. For iridium: --Stress sigma 4 GPa for 15 nm film implies 60 Nm integrated stress-- Need less than 3 N/m (or stress less than 200 MPa) for sub-arcsecond optics. Basic Approaches for Mitigation. A. Annealing the film-- Glass can be heat up to 400 C without distortion. Silicon is even more resistant.-- It was found that recovery is limited by residual thermal stress from taking the mirror down from high T. B. Coating bi-layer films with compressive stress with tensile stress. C. Front-and-back coating with magnetron sputtering or atomic layer deposition-- Sputtering involve spanning of substrates. Geometric difference in setup (convexness/concaveness of curved mirrors) does not permit precise front-and-back matching-- Atomic layer deposition can provide a uniform deposition front and back simultaneously.

Refractive Index of a Transparent Liquid Measured with a Concave Mirror

ERIC Educational Resources Information Center

Joshi, Amitabh; Serna, Juan D.

2012-01-01

Measuring the refractive index "n" of a substance or medium is part of every introductory physics course. Various approaches to determine this index have been developed over the years based on the different ways light reflects and transmits in the medium. In this paper, the authors would like to present a simple geometrical derivation of the…

High-Accuracy Surface Figure Measurement of Silicon Mirrors at 80 K

NASA Technical Reports Server (NTRS)

Blake, Peter; Mink, Ronald G.; Chambers, John; Davila, Pamela; Robinson, F. David

2004-01-01

This report describes the equipment, experimental methods, and first results at a new facility for interferometric measurement of cryogenically-cooled spherical mirrors at the Goddard Space Flight Center Optics Branch. The procedure, using standard phase-shifting interferometry, has an standard combined uncertainty of 3.6 nm rms in its representation of the two-dimensional surface figure error at 80, and an uncertainty of plus or minus 1 nm in the rms statistic itself. The first mirror tested was a concave spherical silicon foam-core mirror, with a clear aperture of 120 mm. The optic surface was measured at room temperature using standard absolute techniques; and then the change in surface figure error from room temperature to 80 K was measured. The mirror was cooled within a cryostat. and its surface figure error measured through a fused-silica window. The facility and techniques will be used to measure the surface figure error at 20K of prototype lightweight silicon carbide and Cesic mirrors developed by Galileo Avionica (Italy) for the European Space Agency (ESA).

Testing and inspecting lens by holographic means

DOEpatents

Hildebrand, Bernard P.

1976-01-01

Processes for the accurate, rapid and inexpensive testing and inspecting of oncave and convex lens surfaces through holographic means requiring no beamsplitters, mirrors or overpower optics, and wherein a hologram formed in accordance with one aspect of the invention contains the entire interferometer and serves as both a master and illuminating source for both concave and said convex surfaces to be so tested.

Schmidt Telescope

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

A type of telescope, invented by the Estonian optician Bernhard Schmidt (1879-1935), that is used to photograph large areas of the sky. Because, in its original design, it was useable only for photography, the instrument is also known as the Schmidt camera. The Schmidt uses a concave spherical mirror as its light collector and corrects for the optical defect, known as spherical aberration, that i...

Reactive solid surface morphology variation via ionic diffusion.

PubMed

Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

2012-08-14

In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

Wide acceptance angle, high concentration ratio, optical collector

NASA Technical Reports Server (NTRS)

Kruer, Mark Arthur (Inventor)

1990-01-01

The invention is directed to an optical collector requiring a wide acceptance angle, and a high concentration ratio. The invention is particularly adapted for use in solar collectors of cassegrain design. The optical collector system includes a parabolic circular concave primary mirror and a hyperbolic circular convex secondary mirror. The primary mirror includes a circular hole located at its center wherein a solar collector is located. The mirrored surface of the secondary mirror has three distinct zones: a center circle, an on-axis annulus, and an off-axis section. The parabolic shape of the primary mirror is chosen so that the primary mirror reflects light entering the system on-axis onto the on-axis annulus. A substantial amount of light entering the system off-axis is reflected by the primary mirror onto either the off-axis section or onto the center circle. Subsequently, the off-axis sections reflect the off-axis light toward the solar collector. Thus, off-axis light is captured which would otherwise be lost to the system. The novelty of the system appears to lie in the configuration of the primary mirror which focuses off-axis light onto an annular portion of the secondary mirror to enable capture thereof. This feature results in wide acceptance angle and a high concentration ratio, and also compensates for the effects of non-specular reflection, and enables a cassegrain configuration to be used where such characteristics are required.

Optical Testing of Diamond Machined, Aspheric Mirrors for Groundbased, Near-IR Astronomy

NASA Technical Reports Server (NTRS)

Chambers, V. John; Mink, Ronald G.; Ohl, Raymond G.; Connelly, Joseph A.; Mentzell, J. Eric; Arnold, Steven M.; Greenhouse, Matthew A.; Winsor, Robert S.; MacKenty, John W.

2002-01-01

The Infrared Multi-Object Spectrometer (IRMOS) is a facility-class instrument for the Kitt Peak National Observatory 4 and 2.1 meter telescopes. IRMOS is a near-IR (0.8-2.5 micron) spectrometer and operates at approximately 80 K. The 6061-T651 aluminum bench and mirrors constitute an athermal design. The instrument produces simultaneous spectra at low- to mid-resolving power (R=lambda/delta lambda= 300-3000) of approximately 100 objects in its 2.8 x 2.0 arcmin field. We describe ambient and cryogenic optical testing of the IRMOS mirrors across a broad range in spatial frequency (figure error, mid-frequency error, and microroughness). The mirrors include three rotationally symmetric, off-axis conic sections, one off-axis biconic, and several flat fold mirrors. The symmetric mirrors include convex and concave prolate and oblate ellipsoids. They range in aperture from 94x86 mm to 286x269 mm and in f-number from 0.9 to 2.4. The biconic mirror is concave and has a 94x76 mm aperture, R(sub x)=377 mm, k(sub x)=0.0778, R(sub y)=407 mm, and k(sub y)=0.1265 and is decentered by -2 mm in X and 227 mm in Y. All of the mirrors have an aspect ratio of approximately 6:1. The surface error fabrication tolerances are less than 10 nm RMS microroughness, 'best effort' for mid-frequency error, and less than 63.3 nm RMS figure error. Ambient temperature (approximately 293 K) testing is performed for each of the three surface error regimes, and figure testing is also performed at approximately 80 K. Operation of the ADE Phaseshift MicroXAM white light interferometer (micro-roughness) and the Bauer Model 200 profilometer (mid-frequency error) is described. Both the sag and conic values of the aspheric mirrors make these tests challenging. Figure testing is performed using a Zygo GPI interferometer, custom computer generated holograms (CGH), and optomechanical alignment fiducials. Cryogenic CGH null testing is discussed in detail. We discuss complications such as the change in prescription with temperature and thermal gradients. Correction for the effect of the dewar window is also covered. We discuss the error budget for the optical test and alignment procedure. Data reduction is accomplished using commercial optical design and data analysis software packages. Results from CGH testing at cryogenic temperatures are encouraging thus far.

Variable magnification glancing incidence x ray telescope

NASA Technical Reports Server (NTRS)

Hoover, Richard (Inventor)

1990-01-01

A multispectral glancing incidence x ray telescope is disclosed, which capable of broadband, high resolution imaging of solar and stellar x ray and extreme ultraviolet radiation sources includes a primary optical system which focuses the incoming radiation to a primary focus. Two or more ellipsoidal mirrors are positioned behind the primary focus at an inclination to the optical axis, each mirror having a concave surface coated with a multilayer synthetic microstructure coating to reflect a desired wavelength. The ellipsoidal mirrors are segments of respective ellipsoids having a common first focus coincident with the primary focus. A detector such as an x ray sensitive photographic film is positioned at the second focus of each of the ellipsoids so that each of the ellipsoidal mirrors may reflect the image at the first focus to the detector. In one embodiment the mirrors are inclined at different angles and has its respective second focus at a different location, separate detectors being located at the respective second focus. The mirrors are arranged so that the magnification and field of view differ, and a solenoid activated arm may withdraw at least one mirror from the beam to select the mirror upon which the beam is to impinge so that selected magnifications and fields of view may be detected.

REOSC Delivers the Best Astronomical Mirror in the World to ESO

NASA Astrophysics Data System (ADS)

1999-12-01

On December 14, 1999, REOSC , the Optical Department of the SAGEM Group , finished the polishing of the fourth 8.2-m main mirror for the Very Large Telescope (VLT) of the European Southern Observatory. The mirror was today delivered to ESO at a ceremony at the REOSC factory in Saint Pierre du Perray, just south of Paris. The precision of the form of the mirror that was achieved during the polishing process is 8.5 nanometer (1 nanometer = 1 millionth of a millimetre) over the optical surface. This exceptional value corresponds to an optical resolution (theoretical image sharpness) of 0.03 arcseconds in the visible spectrum. This corresponds to distinguishing two objects separated by only 15 cm at a distance of 1000 km and will allow to detect astronomical objects that are 10,000 million times fainter than what can be perceived with the unaided eye. This impressive measure of quality, achieved by the REOSC teams during much painstaking work, implies that this VLT mirror is the most accurate in the world. In fact, all four 8.2-m VLT main mirrors polished by REOSC are well within the very strict specifications set by ESO, but this is the best of them all. The celebration today is the successful highlight of a contract initiated more than ten years ago, during which REOSC has perfected new polishing and control techniques - innovations improved and developed in a unique workshop dedicated to these giant mirrors. These methods and means are directly applicable to the new generations of segmented mirrors that are now being developed for astronomy and space observations. They are, in this sense, at the foremost front of optical technology. REOSC, the Optical Department of the SAGEM Group , is specialised in the study and realisation of high-precision optics for astronomy, space, defence, science and industry. For earlier information about the work on the VLT mirrors, cf. ESO Press Release 15/95 (13 November 1995). The SAGEM Group is a French high-technology group. It employs about 15,500 people - more information is available at URL: www.sagem.com. Information about the ESO and the VLT project is available via the ESO website: www.eso.org. Some Key Dates The polishing at REOSC of the main mirrors for the four VLT Unit Telescopes has been a major industrial feat. Here are some of the main dates: July 1989 ESO and REOSC sign contract for the polishing of the four 8.2-m and various associated activities July 1989 - April 1992 Design activities, construction of REOSC production plant April 1992 Mirror Container and concrete dummy mirror blank completed - test transport May 1992 Inauguration of REOSC production plant July 1993 Delivery of first 8.2-m mirror blank to ESO at Schott Glaswerke AG (Mainz, Germany) October 1994 Delivery of second 8.2-m mirror blank to ESO at Schott Glaswerke AG September 1995 Delivery of third 8.2-m mirror blank to ESO at Schott Glaswerke AG May 1996 Acceptance by ESO of first polished mirror at REOSC September 1996 Delivery of fourth 8.2-m mirror blank to ESO at Schott Glaswerke AG October 1996 Acceptance by ESO of second polished mirror at REOSC June 1997 Acceptance by ESO of third polished mirror at REOSC October - December 1997 Transport and delivery of first mirror to Paranal by Gondrand (France) August - September 1998 Transport and delivery of second mirror to Paranal by Gondrand December 1998 - January 1999 Transport and delivery of third mirror to Paranal by Gondrand December 1999 Acceptance by ESO of fourth polished mirror at REOSC February 1999 - April 2000 Transport and delivery of fourth mirror to Paranal by Gondrand Note [1] A Press Release on the REOSC event and the delivery of the fourth VLT main mirror to ESO is also published by SAGEM (in French and English). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO PR Photo 44/99 may be reproduced, if credit is given to SAGEM and the European Southern Observatory.

High power continuous-wave titanium:sapphire laser

DOEpatents

Erbert, G.V.; Bass, I.L.; Hackel, R.P.; Jenkins, S.L.; Kanz, V.K.; Paisner, J.A.

1993-09-21

A high-power continuous-wave laser resonator is provided, wherein first, second, third, fourth, fifth and sixth mirrors form a double-Z optical cavity. A first Ti:sapphire rod is disposed between the second and third mirrors and at the mid-point of the length of the optical cavity, and a second Ti:sapphire rod is disposed between the fourth and fifth mirrors at a quarter-length point in the optical cavity. Each Ti:sapphire rod is pumped by two counter-propagating pump beams from a pair of argon-ion lasers. For narrow band operation, a 3-plate birefringent filter and an etalon are disposed in the optical cavity so that the spectral output of the laser consists of 5 adjacent cavity modes. For increased power, seventy and eighth mirrors are disposed between the first and second mirrors to form a triple-Z optical cavity. A third Ti:sapphire rod is disposed between the seventh and eighth mirrors at the other quarter-length point in the optical cavity, and is pumped by two counter-propagating pump beams from a third pair of argon-ion lasers. 5 figures.

Testing of the Gemini secondary mirrors

NASA Astrophysics Data System (ADS)

Otto, Wolfgang

1999-09-01

The first 1-m secondary mirror for the Gemini 8-m telescopes project was delivered by Zeiss in 1998, and 2nd mirror will be delivered in the summer of 1999. For first use during commissioning we produced an extreme lightweight Zerodur solution prefabricated at Schott. To reach the 85 percent weight reduction a novel etching technique was used. INterferometric testing was done performing full aperture measurements using a concave matrix. In progress with the fabrication process of the matrix we applied 3D-mechanical measurements, IR-interferometry, and VIS-interferometry using null lenses to reach the final intrinsic quality of 6 nm rms. For interferometric testing of the secondaries phase shifting interferometry with a tunable laser diode was applied. The optical test results of the secondaries show, that the mirrors are well within specification. The finally achieved intrinsic surface quality is 17 nm rms for Unit 1 and 13 nm rms for Unit 2, dominated by cutting effects which were introduced by removing the oversize at the inner and outer edge of the mirror after the final polishing step.

Leonardo da Vinci (1452-1519)

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Painter, inventor and polymath, born in Vinci (near Empolia), Italy. Although astronomy does not figure large in Leonardo's works, he realized the possibility of constructing a telescope (`making glasses to see the Moon enlarged'). He suggested that `… in order to observe the nature of the planets, open the roof and bring the image of a single planet onto the base of a concave mirror. The image o...

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles.

PubMed

Bucaro, Michael A; Kolodner, Paul R; Taylor, J Ashley; Sidorenko, Alex; Aizenberg, Joanna; Krupenkin, Tom N

2009-04-09

In this paper, we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality-for example, a dynamic 3D projector, i.e., a light source which can scan an image onto a moving, nonplanar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles

NASA Astrophysics Data System (ADS)

Krupenkin, Tom; Bucaro, Mike; Kolodner, Paul; Taylor, Ashley; Sidorenko, Alex; Aizenberg, Joanna

2009-03-01

In this work we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically-functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality - for example, a dynamic 3D projector; i.e., a light source which can scan an image onto a moving, non-planar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Spherical mirror grazing incidence x-ray optics

NASA Technical Reports Server (NTRS)

Cash, Jr., Webster C. (Inventor)

1997-01-01

An optical system for x-rays combines at least two spherical or near spherical mirrors for each dimension in grazing incidence orientation to provide the functions of a lens in the x-ray region. To focus x-ray radiation in both the X and the Y dimensions, one of the mirrors focusses the X dimension, a second mirror focusses the Y direction, a third mirror corrects the X dimension by removing comatic aberration and a fourth mirror corrects the Y dimension. Spherical aberration may also be removed for an even better focus. The order of the mirrors is unimportant.

Worthwhile optical method for free-form mirrors qualification

NASA Astrophysics Data System (ADS)

Sironi, G.; Canestrari, R.; Toso, G.; Pareschi, G.

2013-09-01

We present an optical method for free-form mirrors qualification developed by the Italian National Institute for Astrophysics (INAF) in the context of the ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Project which includes, among its items, the design, development and installation of a dual-mirror telescope prototype for the Cherenkov Telescope Array (CTA) observatory. The primary mirror panels of the telescope prototype are free-form concave mirrors with few microns accuracy required on the shape error. The developed technique is based on the synergy between a Ronchi-like optical test performed on the reflecting surface and the image, obtained by means of the TraceIT ray-tracing proprietary code, a perfect optics should generate in the same configuration. This deflectometry test allows the reconstruction of the slope error map that the TraceIT code can process to evaluate the measured mirror optical performance at the telescope focus. The advantages of the proposed method is that it substitutes the use of 3D coordinates measuring machine reducing production time and costs and offering the possibility to evaluate on-site the mirror image quality at the focus. In this paper we report the measuring concept and compare the obtained results to the similar ones obtained processing the shape error acquired by means of a 3D coordinates measuring machine.

Seeing the Universe: On the Cusp of Technology

NASA Astrophysics Data System (ADS)

Impey, C.

2009-08-01

Since Galileo Galilei turned his modest spyglass to the night sky 400 years ago, his heirs have enhanced his legacy by the method of using successively larger lenses, and then concave mirrors. Astronomers have even succeeded in stilling the night air with flexible optics, letting their telescopes register the sharpest images that optics will allow. New technologies allow the creation of telescopes that would be unrecognizable to Galileo. They don't use glass mirrors or lenses and they often gather radiation that's invisible to the eye. Astronomers have even managed to use the Earth as a telescope. These innovations have given us a sharper vision of the universe, and a better sense of our place in space and time.

Multispectral glancing incidence X-ray telescope

NASA Technical Reports Server (NTRS)

Hoover, Richard B. (Inventor)

1990-01-01

A multispectral glancing incidence X-ray telescope is illustrated capable of broadband, high-resolution imaging of solar and stellar X-ray and extreme ultraviolet radiation sources which includes a primary optical system preferably of the Wolter I type having a primary mirror system (20, 22). The primary optical system further includes an optical axis (24) having a primary focus (F1) at which the incoming radiation is focused by the primary mirrors. A plurality of ellipsoidal mirrors (30a, 30b, 30cand 30d) are carried at an inclination to the optical axis behind the primary focus (F1). A rotating carrier (32) is provided on which the ellipsoidal mirrors are carried so that a desired one of the ellipsoidal mirrors may be selectively positioned in front of the incoming radiation beam (26). In the preferred embodiment, each of the ellipsoidal mirrors has an identical concave surface carrying a layered synthetic microstructure coating tailored to reflect a desired wavelength of 1.5 .ANG. or longer. Each of the identical ellipsoidal mirrors has a second focus (F2) at which a detector (16) is carried. Thus the different wavelength image is focused upon the detector irregardless of which mirror is positioned in front of the radiation beam. In this manner, a plurality of low wavelengths in a wavelength band generally less than 30 angstroms can be imaged with a high resolution.

Zucchi, Niccolo (1586-1670)

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Born in Parma, Italy, became a Jesuit, and in 1608, or perhaps 1616, used a lens to observe the image produced by a concave mirror, the first reflecting telescope. He described it in a book Optica Philosophica, in 1652. He was the first to observe the spots on Jupiter, in 1630. In about 1640, he is reported to have examined spots on Mars, as discovered by Fontana, but this must be regarded skepti...

Successful Graded Mirror Therapy in a Patient with Chronic Deafferentation Pain in Whom Traditional Mirror Therapy was Ineffective: A Case Report.

PubMed

Mibu, Akira; Nishigami, Tomohiko; Tanaka, Katsuyoshi; Osumi, Michihiro; Tanabe, Akihito

2016-04-01

A 43-year-old man had deafferentation pain in his right upper extremity secondary to brachial plexus avulsion from a traffic accident 23 years previously. On our initial examination, he had severe tingling pain with numbness in the right fingers rated 10 on the numerical rating scale. The body perception of the affected third and fourth fingers was distorted in the flexed position. Although he performed traditional mirror therapy (TMT) for 4 weeks in the same methods as seen in previous studies, he could not obtain willed motor imagery and pain-alleviation effect. Therefore, we modified the task of TMT: Graded mirror therapy (GMT). GMT consisted of five stages: (1) observation of the mirror reflection of the unaffected side without imagining any movements of the affected side; (2) observation of the mirror reflection of the third and fourth fingers changing shape gradually adjusted from a flexed position to a extended position; (3) observation of the mirror reflection of passive movement; (4) motor imagery of affected fingers with observation of the mirror reflection (similar to TMT); (5) motor imagery of affected fingers without mirror. Each task was performed for 3 to 4 weeks. As a result, pain intensity during mirror therapy gradually decreased and finally disappeared. The body perception of the affected fingers also improved, and he could imagine the movement of the fingers with or without mirror. We suggested that GMT starting from the observation task without motor imagery may effectively decrease deafferentation pain compared to TMT. © 2016 World Institute of Pain.

STS-77 crew insignia

NASA Image and Video Library

1996-05-09

STS077-S-001 (February 1996) --- The STS-77 crew patch, designed by the crew members, displays the space shuttle Endeavour the lower left and its reflection within the tripod and concave parabolic mirror of the Shuttle Pointed Autonomous Research Tool for Astronomy (SPARTAN) Inflatable Antenna Experiment (IAE). The center leg of the tripod also delineates the top of the Spacehab?s shape, the rest of which is outlined in gold just inside the red perimeter. The Spacehab is carried in the payload bay and houses the Commercial Float Zone Furnace (CFZF) and Space Experiment Facility (SEF) experiments. Also depicted within the confines the IAE mirror are the mission?s rendezvous operations with the Passive Aerodynamically Stabilized Magnetically Damped Satellite/Satellite Test Unit (PAM/STU) satellite and a reflection of Earth. The PAM/STU satellite appears as a bright six-pointed star-like reflection of the sun on the edge of the mirror with the space shuttle Endeavour in position to track it. The sunglint on the mirror?s edge, which also appears as an orbital sunset, is located over Goddard Space Flight Center (GSFC), the development facility for the SPARTAN/IAE and Technology Experiments Advancing Missions in Space (TEAMS) experiments. The reflection of Earth is oriented to show the individual countries of the crew as well as the ocean which Captain Cook explored in the original Endeavour. The mission number ?77? is featured as twin stylized chevrons and an orbiting satellite as adapted from NASA?s logo. The stars at the top are arranged as seen in the northern sky in the vicinity of the constellation Ursa Minor. The field of 11 stars represents both the TEAMS cluster of experiments (the four antennae of Global Positioning System Attitude and Navigation Experiment (GANE), the single canister of Liquid Metal Thermal Experiment (LMTE), the three canisters of Vented Tank Resupply Experiment (VTRE), and the canisters of PAM/STU, and the 11th flight of the Endeavour. The constellation at the right shows the four stars of the Southern Cross for the fourth flight of Spacehab. The NASA insignia design for space shuttle flights is reserved for use by the astronauts and for other official use as the NASA Administrator may authorize. Public availability has been approved only in the forms of illustrations by the various news media. When and if there is any change in this policy, which is not anticipated, the change will be publicly announced. Photo credit: NASA

Deterministic magnetorheological finishing of optical aspheric mirrors

NASA Astrophysics Data System (ADS)

Song, Ci; Dai, Yifan; Peng, Xiaoqiang; Li, Shengyi; Shi, Feng

2009-05-01

A new method magnetorheological finishing (MRF) used for deterministical finishing of optical aspheric mirrors is applied to overcome some disadvantages including low finishing efficiency, long iterative time and unstable convergence in the process of conventional polishing. Based on the introduction of the basic principle of MRF, the key techniques to implement deterministical MRF are also discussed. To demonstrate it, a 200 mm diameter K9 class concave asphere with a vertex radius of 640mm was figured on MRF polish tool developed by ourselves. Through one process about two hours, the surface accuracy peak-to-valley (PV) is improved from initial 0.216λ to final 0.179λ and root-mean-square (RMS) is improved from 0.027λ to 0.017λ (λ = 0.6328um ). High-precision and high-efficiency convergence of optical aspheric surface error shows that MRF is an advanced optical manufacturing method that owns high convergence ratio of surface figure, high precision of optical surfacing, stabile and controllable finishing process. Therefore, utilizing MRF to finish optical aspheric mirrors determinately is credible and stabile; its advantages can be also used for finishing optical elements on varieties of types such as plane mirrors and spherical mirrors.

Polishing aspheric mirrors of zero-thermal expansion cordierite ceramics (NEXCERA) for space telescope

NASA Astrophysics Data System (ADS)

Sugawara, Jun; Kamiya, Tomohiro; Mikashima, Bumpei

2017-09-01

Ultra-low thermal expansion ceramics NEXCERATM is regarded as one of potential candidate materials crucial for ultralightweight and thermally-stable optical mirrors for space telescopes which are used in future optical missions satisfying extremely high observation specifications. To realize the high precision NEXCERA mirrors for space telescopes, it is important to develop a deterministic aspheric shape polishing and a precise figure correction polishing method for the NEXCERA. Magnetorheological finishing (MRF) was tested to the NEXCERA aspheric mirror from best fit sphere shape, because the MRF technology is regarded as the best suited process for a precise figure correction of the ultralightweight mirror with thin sheet due to its advantage of low normal force polishing. As using the best combination of material and MR fluid, the MRF was performed high precision figure correction and to induce a hyperbolic shape from a conventionally polished 100mm diameter sphere, and achieved the sufficient high figure accuracy and the high quality surface roughness. In order to apply the NEXCERA to a large scale space mirror, for the next step, a middle size solid mirror, 250 mm diameter concave parabola, was machined. It was roughly ground in the parabolic shape, and was lapped and polished by a computer-controlled polishing machine using sub-aperture polishing tools. It resulted in the smooth surface of 0.6 nm RMS and the figure accuracy of λ/4, being enough as pre-MRF surface. A further study of the NEXCERA space mirrors should be proceeded as a figure correction using the MRF to lightweight mirror with thin mirror sheet.

Lacan’s Construction and Deconstruction of the Double-Mirror Device

PubMed Central

Vanheule, Stijn

2011-01-01

In the 1950s Jacques Lacan developed a set-up with a concave mirror and a plane mirror, based on which he described the nature of human identification. He also formulated ideas on how psychoanalysis, qua clinical practice, responds to identification. In this paper Lacan’s schema of the two mirrors is described in detail and the theoretical line of reasoning he aimed to articulate with aid of this spatial model is discussed. It is argued that Lacan developed his double-mirror device to clarify the relationship between the drive, the ego, the ideal ego, the ego-ideal, the other, and the Other. This model helped Lacan describe the dynamics of identification and explain how psychoanalytic treatment works. He argued that by working with free association, psychoanalysis aims to articulate unconscious desire, and bypass the tendency of the ego for misrecognition. The reasons why Lacan stressed the limits of his double-mirror model and no longer considered it useful from the early 1960s onward are examined. It is argued that his concept of the gaze, which he qualifies as a so-called “object a,” prompted Lacan move away from his double-mirror set-up. In those years Lacan gradually began to study the tension between drive and signifier. The schema of the two mirrors, by contrast, focused on the tension between image and signifier, and missed the point Lacan aimed to address in this new era of his work. PMID:21949511

High power continuous-wave titanium:sapphire laser

DOEpatents

Erbert, Gaylen V.; Bass, Isaac L.; Hackel, Richard P.; Jenkins, Sherman L.; Kanz, Vernon K.; Paisner, Jeffrey A.

1993-01-01

A high-power continuous-wave laser resonator (10) is provided, wherein first, second, third, fourth, fifth and sixth mirrors (11-16) form a double-Z optical cavity. A first Ti:Sapphire rod (17) is disposed between the second and third mirrors (12,13) and at the mid-point of the length of the optical cavity, and a second Ti:Sapphire rod (18) is disposed between the fourth and fifth mirrors (14,15) at a quarter-length point in the optical cavity. Each Ti:Sapphire rod (17,18) is pumped by two counter-propagating pump beams from a pair of argon-ion lasers (21-22, 23-24). For narrow band operation, a 3-plate birefringent filter (36) and an etalon (37) are disposed in the optical cavity so that the spectral output of the laser consists of 5 adjacent cavity modes. For increased power, seventy and eighth mirrors (101, 192) are disposed between the first and second mirrors (11, 12) to form a triple-Z optical cavity. A third Ti:Sapphire rod (103) is disposed between the seventh and eighth mirrors (101, 102) at the other quarter-length point in the optical cavity, and is pumped by two counter-propagating pump beams from a third pair of argon-ion lasers (104, 105).

Laser Resonator

NASA Technical Reports Server (NTRS)

Harper, L. L. (Inventor)

1983-01-01

An optical resonator cavity configuration has a unitary mirror with oppositely directed convex and concave reflective surfaces disposed into one fold and concertedly reversing both ends of a beam propagating from a laser rod disposed between two total internal reflection prisms. The optical components are rigidly positioned with perpendicularly crossed virtual rooflines by a compact optical bed. The rooflines of the internal reflection prisms, are arranged perpendicularly to the axis of the laser beam and to the optical axes of the optical resonator components.

Measurement of aspheric mirror segments using Fizeau interferometry with CGH correction

NASA Astrophysics Data System (ADS)

Burge, James H.; Zhao, Chunyu; Dubin, Matt

2010-07-01

Large aspheric primary mirrors are proposed that use hundreds segments that all must be aligned and phased to approximate the desired continuous mirror. We present a method of measuring these concave segments with a Fizeau interferometer where a spherical convex reference surface is held a few millimeters from the aspheric segment. The aspheric shape is accommodated by a small computer generated hologram (CGH). Different segments are measured by replacing the CGH. As a Fizeau test, nearly all of the optical elements and air spaces are common to both the measurement and reference wavefront, so the sensitivities are not tight. Also, since the reference surface of the test plate is common to all tests, this system achieves excellent control for the radius of curvature variation from one part to another. This paper describes the test system design and analysis for such a test, and presents data from a similar 1.4-m test performed at the University of Arizona.

Flight solar calibrations using the Mirror Attenuator Mosaic (MAM): Low scattering mirror

NASA Technical Reports Server (NTRS)

Lee, Robert B., III

1992-01-01

Measurements of solar radiances reflected from the mirror attenuator mosaic (MAM) were used to calibrate the shortwave portions of the Earth Radiation Budget Experiment (ERBE) thermistor bolometer scanning radiometers. The MAM is basically a low scattering mirror which has been used to attenuate and reflect solar radiation into the fields of view for the broadband shortwave (0.2 to 5 micrometers) and total (0.2 to 50.0+ micrometers) ERBE scanning radiometers. The MAM assembly consists of a tightly packed array of aluminum, 0.3175-cm diameter concave spherical mirrors and field of view limiting baffles. The spherical mirrors are masked by a copper plate, electro-plated with black chrome. Perforations (0.14 centimeter in diameter) in the copper plate serve as apertures for the mirrors. Black anodized aluminum baffles limit the MAM clear field of view to 7.1 degrees. The MAM assemblies are located on the Earth Radiation Budget Satellite (ERBS) and on the National Oceanic and Atmospheric Administration NOAA-9 and NOAA-10 spacecraft. The 1984-1985 ERBS and 1985-1986 NOAA-9 solar calibration datasets are presented. Analyses of the calibrations indicate that the MAM exhibited no detectable degradation in its reflectance properties and that the gains of the shortwave scanners did not change. The stability of the shortwave radiometers indicates that the transmission of the Suprasil W1 filters did not degrade detectably when exposed to Earth/atmosphere-reflected solar radiation.

Preliminary studies of radiation coupling between remote soft X-ray laser amplifiers

NASA Astrophysics Data System (ADS)

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

1994-01-01

Coupling of a soft X-ray laser beam with a relaying concave mirror in a sequentially pumped amplifier geometry using the Ne-like Ge system has been studied experimentally. Preliminary observations indicate an increase in the spatial coherence of the amplified relayed beam. In addition, near-field imaging of one of the amplifier plasmas shows a double-lobed intensity pattern of the emergent beam indicating refractive guiding of the amplified beam with components both normal and tangential to the target surface.

Axicon based conical resonators with high power copper vapor laser.

PubMed

Singh, Bijendra; Subramaniam, V V; Daultabad, S R; Chakraborty, Ashim

2010-07-01

We report for the first time the performance of axicon based conical resonators (ABCRs) in a copper vapor laser, with novel results. The unstable conical resonator comprising of conical mirror (reflecting axicon) with axicon angle approximately pi/18, cone angle approximately 160 degrees, and a convex mirror of 60 cm radius of curvature was effective in reducing the average beam divergence to approximately 0.15 mrad (approximately 25 fold reduction compared to standard multimode plane-plane cavity) with output power of approximately 31 W. Extraction efficiency of approximately 50%-60% and beam divergence of <1 mrad was achieved in other stable ABCR configurations using flat and concave mirrors with the axicon. This is a significant improvement compared to 4-5 mrad normally observed in conventional stable resonators in copper vapor lasers. The conical resonators with copper vapor laser provide high misalignment tolerance beta approximately 4-5 mrad where beta is the tilt angle of the conical mirror from optimum position responsible for approximately 20% decline in laser power. The depth of focus d was approximately three times larger in case of conical resonator as compared to that of standard spherical unstable resonator under similar beam divergence and focusing conditions.

Photovoltaic generator with a spherical imaging lens for use with a paraboloidal solar reflector

DOEpatents

Angel, Roger P

2013-01-08

The invention is a generator for photovoltaic conversion of concentrated sunlight into electricity. A generator according to the invention incorporates a plurality of photovoltaic cells and is intended for operation near the focus of a large paraboloidal reflector pointed at the sun. Within the generator, the entering concentrated light is relayed by secondary optics to the cells arranged in a compact, concave array. The light is delivered to the cells at high concentration, consistent with high photovoltaic conversion efficiency and low cell cost per unit power output. Light enters the generator, preferably first through a sealing window, and passes through a field lens, preferably in the form of a full sphere or ball lens centered on the paraboloid focus. This lens forms a concentric, concave and wide-angle image of the primary reflector, where the intensity of the concentrated light is stabilized against changes in the position of concentrated light entering the generator. Receiving the stabilized light are flat photovoltaic cells made in different shapes and sizes and configured in a concave array corresponding to the concave image of a given primary reflector. Photovoltaic cells in a generator are also sized and interconnected so as to provide a single electrical output that remains high and stable, despite aberrations in the light delivered to the generator caused by, for example, mispointing or bending of the primary reflector. In some embodiments, the cells are set back from the image formed by the ball lens, and part of the light is reflected onto each cell small secondary reflectors in the form of mirrors set around its perimeter.

SOFIA secondary mirror Hindle test analysis

NASA Astrophysics Data System (ADS)

Davis, Paul K.

2003-02-01

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a NASA facility, nearing completion, consisting of an infrared telescope of 2.5 meter system aperture flying in a modified Boeing 747. Its Cassegrain secondary mirror has recently completed polishing. The SOFIA Project Office at Ames Research Center considered it important to perform an independent analysis of secondary mirror figure. The polishing was controlled by the standard test for a convex hyperboloid, the Hindle test, in a modified form with a meniscus lens partially reflecting on the concave face, rather than a fully reflecting mirror with a central hole. The spacing between this meniscus lens and the secondary mirror was controlled by three peripherally located spacing spheres. This necessitated special analysis to determine what the resulting curvature and conic constant of the mirror would be, if manufacturing imprecisions of the test set-up components were to be taken into account. This set-up was specially programmed, and the resulting hyperboloid calculated for the nominal case, and all extreme cases from the reported error limits on the manufacturing of the components. The results were then verified using the standard program CODE-V of Optical Research Associates. The conclusion is that the secondary mirror has a vertex radius of curvature of 954.05 mm +/- .1 mm (design value: 954.13), and a conic constant of -1.2965 +/- .001 (dimensionless, design value: -1.298). Such small divergences from design are to be expected, and these are within the refocusing ability of SOFIA, and would result in an acceptably small amount of spherical aberration in the image.

Method of and apparatus for collecting solar radiation utilizing variable curvature cylindrical reflectors

DOEpatents

Treytl, William J.; Slemmons, Arthur J.; Andeen, Gerry B.

1979-01-01

A heliostat apparatus includes a frame which is rotatable about an axis which is parallel to the aperture plane of an elongate receiver. A plurality of flat flexible mirror elements are mounted to the frame between several parallel, uniformly spaced resilient beams which are pivotally connected at their ends to the frame. Channels are mounted to the sides of the beams for supporting the edges of the mirror elements. Each of the beams has a longitudinally varying configuration designed to bow into predetermined, generally circular curvatures of varying radii when the center of the beam is deflected relative to the pivotally connected ends of the beams. All of the parallel resilient beams are simultaneously deflected by a cam shaft assembly extending through openings in the centers of the beams, whereby the mirror elements together form an upwardly concave, cylindrical reflecting surface. The heliostat is rotated about its axis to track the apparent diurnal movement of the sun, while the reflecting surface is substantially simultaneously bowed into a cylindrical trough having a radius adapted to focus incident light at the plane of the receiver aperture.

Cholesteric microlenses and micromirrors in the beetle cuticle and in synthetic oligomer films: a comparative study

NASA Astrophysics Data System (ADS)

Agez, Gonzague; Bayon, Chloé; Mitov, Michel

2017-02-01

The polygonal texture in cholesteric liquid crystals consist in an array of contiguous polygonal cells. The optical response and the structure of polygonal texture are investigated in the cuticle of beetle Chrysina gloriosa and in synthetic oligomer films. In the insect carapace, the polygons are concave and behave as spherical micro-mirrors whereas they are convex and behave as diverging microlenses in synthetic films. The characteristics of light focusing (spot, donut or continuum background) are highly tunable with the wavelength and the polarization of the incident light.

Polarization nondegenerate fiber Fabry-Perot cavities with large tunable splittings

NASA Astrophysics Data System (ADS)

Cui, Jin-Ming; Zhou, Kun; Zhao, Ming-Shu; Ai, Ming-Zhong; Hu, Chang-Kang; Li, Qiang; Liu, Bi-Heng; Peng, Jin-Lan; Huang, Yun-Feng; Li, Chuan-Feng; Guo, Guang-Can

2018-04-01

We demonstrate a type of microcavity with large tunable splitting of polarization modes. This polarization nondegenerate cavity consists of two ellipsoidal concave mirrors with controllable eccentricity by CO2 laser machining on fiber end facets. The experiment shows that the cavities can combine the advantages of high finesse above 104 and large tunable polarization mode splitting to the GHz range. As the splitting of the cavity can be finely controlled to match atom hyperfine levels or optomechanics phonons, it will blaze a way in experiments on cavity quantum electrodynamics and cavity optomechanics.

NASA superconducting magnetic mirror facility. [for thermonuclear research

NASA Technical Reports Server (NTRS)

Reinmann, J. J.; Swanson, M. C.; Nichols, C. R.; Bloy, S. J.; Nagy, L. A.; Brady, F. J.

1973-01-01

The design details and initial test results of a superconducting magnetic mirror facility that has been constructed at NASA Lewis Research Center for use in thermonuclear research are summarized. The magnet system consists of four solenoidal coils which are individually rated at 5.0 T. Each coll is composed of an inner, middle, and outer winding. The inner winding is wound of stabilized Nb3Sn superconducting ribbon, and the middle and outer windings are wound of stabilized Nb-Ti superconducting wire. When arranged in the mirror geometry, the four coils will produce 8.7 T at the mirrors and a 1.8 mirror ratio. The magnet has a 41-cm diameter clear bore which is open to atmosphere. Distance between the mirrors is 111 cm. Presently there are only three magnets in the facility; the fourth magnet is being rebuilt.

NASA superconducting magnetic mirror facility

NASA Technical Reports Server (NTRS)

Reinmann, J. J.; Swanson, M. C.; Nichols, C. R.; Obloy, S. J.; Nagy, L. A.; Brady, F. J.

1973-01-01

This report summarizes the design details and initial test results of a superconducting magnetic mirror facility that has been constructed at NASA Lewis Research Center for use in thermonuclear research. The magnet system consists of four solenoidal coils which are individually rated at 5.0 T. Each coil is composed of an inner, middle, and outer winding. The inner winding is wound of stabilized Nb3SN superconducting ribbon, and the middle and outer windings are wound of stabilized Nb-Ti superconducting wire. When arranged in the mirror geometry, the four coils will produce 8.7 T at the mirrors and a 1.8 mirror ratio. The magnet has a 41-cm diameter clear bore which is open to atmosphere. Distance between the mirrors is 111 cm. Presently there are only three magnets in the facility; the fourth magnet is being rebuilt.

Full-field 3D shape measurement of specular object having discontinuous surfaces

NASA Astrophysics Data System (ADS)

Zhang, Zonghua; Huang, Shujun; Gao, Nan; Gao, Feng; Jiang, Xiangqian

2017-06-01

This paper presents a novel Phase Measuring Deflectometry (PMD) method to measure specular objects having discontinuous surfaces. A mathematical model is established to directly relate the absolute phase and depth, instead of the phase and gradient. Based on the model, a hardware measuring system has been set up, which consists of a precise translating stage, a projector, a diffuser and a camera. The stage locates the projector and the diffuser together to a known position during measurement. By using the model-based and machine vision methods, system calibration is accomplished to provide the required parameters and conditions. The verification tests are given to evaluate the effectiveness of the developed system. 3D (Three-Dimensional) shapes of a concave mirror and a monolithic multi-mirror array having multiple specular surfaces have been measured. Experimental results show that the proposed method can obtain 3D shape of specular objects having discontinuous surfaces effectively

Nonparabolic solar concentrators matching the parabola.

PubMed

Cooper, Thomas; Schmitz, Max; Good, Philipp; Ambrosetti, Gianluca; Pedretti, Andrea; Steinfeld, Aldo

2014-08-01

We consider the limit of geometric concentration for a focusing concave mirror, e.g., a parabolic trough or dish, designed to collect all radiation within a finite acceptance angle and direct it to a receiver with a flat or circular cross-section. While a concentrator with a parabolic cross-section indeed achieves this limit, it is not the only geometry capable of doing so. We demonstrate that there are infinitely many solutions. The significance of this finding is that geometries which can be more easily constructed than the parabola can be utilized without loss of concentration, thus presenting new avenues for reducing the cost of solar collectors. In particular, we investigate a low-cost trough mirror profile which can be constructed by inflating a stack of thin polymer membranes and show how it can always be designed to match the geometric concentration of a parabola of similar form.

Control of a 45-cm long x-ray deformable mirror with either external or internal metrology

NASA Astrophysics Data System (ADS)

Poyneer, Lisa A.; Pardini, Tommaso; McCarville, Thomas; Palmer, David; Brooks, Audrey

2014-09-01

Our 45-cm long x-ray deformable mirror has 45 actuators along the tangential axis, along with one strain gauge per actuator and eight temperature sensors. We discuss the detailed calibration of the mirror's figure response to voltage (fourth-order) and the strain gauges' response to figure changes (linear). The mirror's cylinder shape changes with temperature, which can be tracked with the temperature sensors. We present initial results of measuring figure change with the strain gauges, which works very well for large changes (> 10 nm peak-to- valley), but is noisy with a single strain reading for small changes (5 nm peak-to-valley).

Improved Mirror Source Method in Roomacoustics

NASA Astrophysics Data System (ADS)

Mechel, F. P.

2002-10-01

Most authors in room acoustics qualify the mirror source method (MS-method) as the only exact method to evaluate sound fields in auditoria. But evidently nobody applies it. The reason for this discrepancy is the abundantly high numbers of needed mirror sources which are reported in the literature, although such estimations of needed numbers of mirror sources mostly are used for the justification of more or less heuristic modifications of the MS-method. The present, intentionally tutorial article accentuates the analytical foundations of the MS-method whereby the number of needed mirror sources is reduced already. Further, the task of field evaluation in three-dimensional spaces is reduced to a sequence of tasks in two-dimensional room edges. This not only allows the use of easier geometrical computations in two dimensions, but also the sound field in corner areas can be represented by a single (directional) source sitting on the corner line, so that only this "corner source" must be mirror-reflected in the further process. This procedure gives a drastic reduction of the number of needed equivalent sources. Finally, the traditional MS-method is not applicable in rooms with convex corners (the angle between the corner flanks, measured on the room side, exceeds 180°). In such cases, the MS-method is combined below with the second principle of superposition(PSP). It reduces the scattering task at convex corners to two sub-tasks between one flank and the median plane of the room wedge, i.e., always in concave corner areas where the MS-method can be applied.

Production of the 4.1-m Zerodur mirror blank for the VISTA Telescope

NASA Astrophysics Data System (ADS)

Doehring, Thorsten; Jedamzik, Ralf; Wittmer, Volker; Thomas, Armin

2004-09-01

VISTA (Visible and Infrared Survey Telescope for Astronomy) is designed to be the world's largest wide field telescope. After finishing of the construction the telescope will be part of ESO and located in Chile close to the VLT observatory at Cerro Paranal. In November 2001 SCHOTT was selected by the VISTA project office at the Royal Observatory of Edinburgh to deliver the 4.1 m diameter primary mirror blank. The manufacturing of the mirror blank made from the zero expansion material Zerodur was challenging especially due to the f/1 design. Several tons of the glass ceramic material were removed during the grinding operation. A meniscus blank with a diameter of 4100 mm and a thickness of 171.5 mm was generated, having a large central hole of 1200 mm and an aspherical shape of the concave surface. Also the handling and turning operations needed special effort and were performed by a skilled team. This paper presents details and pictures of the corresponding production and inspection sequence at SCHOTT. The geometrical parameters were measured during manufacturing by help of a laser tracker system and the achieved parameters were compared with the initial technical specification. The final quality inspection verified the excellent quality of the mirror blank. The close co-operation between the astronomers and industry resulted in a project management without problems. In April 2003 the VISTA blank was delivered successfully within a ceremony dedicated to the anniversary of "100 years of astronomical mirror blanks from SCHOTT."

Controlling Laser Spot Size in Outer Space

NASA Technical Reports Server (NTRS)

Bennett, Harold E.

2005-01-01

Three documents discuss a method of controlling the diameter of a laser beam projected from Earth to any altitude ranging from low orbit around the Earth to geosynchronous orbit. Such laser beams are under consideration as means of supplying power to orbiting spacecraft at levels of the order of tens of kilowatts apiece. Each such beam would be projected by use of a special purpose telescope having an aperture diameter of 15 m or more. Expanding the laser beam to such a large diameter at low altitude would prevent air breakdown and render the laser beam eyesafe. Typically, the telescope would include an adaptive-optics concave primary mirror and a convex secondary mirror. The laser beam transmitted out to the satellite would remain in the near field on the telescope side of the beam waist, so that the telescope focal point would remain effective in controlling the beam width. By use of positioning stages having submicron resolution and repeatability, the relative positions of the primary and secondary mirrors would be adjusted to change the nominal telescope object and image distances to obtain the desired beam diameter (typically about 6 m) at the altitude of the satellite. The limiting distance D(sub L) at which a constant beam diameter can be maintained is determined by the focal range of the telescope 4 lambda f(sup 2) where lambda is the wavelength and f the f/number of the primary mirror. The shorter the wavelength and the faster the mirror, the longer D(sub L) becomes.

Normal incidence X-ray mirror for chemical microanalysis

DOEpatents

Carr, Martin J.; Romig, Jr., Alton D.

1990-01-01

A non-planar, focusing mirror, to be utilized in both electron column instruments and micro-x-ray fluorescence instruments for performing chemical microanalysis on a sample, comprises a concave, generally spherical base substrate and a predetermined number of alternating layers of high atomic number material and low atomic number material contiguously formed on the base substrate. The thickness of each layer is an integral multiple of the wavelength being reflected and may vary non-uniformly according to a predetermined design. The chemical analytical instruments in which the mirror is used also include a predetermined energy source for directing energy onto the sample and a detector for receiving and detecting the x-rays emitted from the sample; the non-planar mirror is located between the sample and detector and collects the x-rays emitted from the sample at a large solid angle and focuses the collected x-rays to the sample. For electron column instruments, the wavelengths of interest lie above 1.5 nm, while for x-ray fluorescence instruments, the range of interest is below 0.2 nm. Also, x-ray fluorescence instruments include an additional non-planar focusing mirror, formed in the same manner as the previously described m The invention described herein was made in the performance of work under contract with the Department of Energy, Contract No. DE-AC04-76DP00789, and the United States Government has rights in the invention pursuant to this contract.

Structural design of a large deformable primary mirror for a space telescope

NASA Astrophysics Data System (ADS)

Hansen, J. G. R.

A 4 meter aperture deformable primary mirror is designed with the mirror and its supports integrated into a single structure. The integrated active mirror's minimal weight makes it desirable for a space telescope as well as a terrestrial application. Utilizing displacement actuators, the active controls at the mirror's surface include position control and slope control in both the radial and tangential directions at each of the 40 control points. Influence functions for each of the controls are nearly independent, reducing the complexity of the control system. Experiments with breadboard models verify the structural concept and the techniques used in the finite element method of computer structural analysis. The majority of this paper is a description of finite element analysis results. Localization of influence functions is exhaustively treated. For gravity loads, a thermal gradient through the mirror thickness, and a uniform thermal soak, diffraction limited performance of the 4m design is evaluated. Loads are applied to defocus the mirror and to cause fourth-order astigmatism. Mirror scallop, instigated by a focus shift, has been virtually eliminated with the 40-actuator design. The structural concept is so effective that it should be considered for uncontrolled primary mirrors as well as active mirrors.

The introduction of spurious models in a hole-coupled Fabry-Perot open resonator

NASA Technical Reports Server (NTRS)

Cook, Jerry D.; Long, Kenwyn J.; Heinen, Vernon O.; Stankiewicz, Norbert

1992-01-01

A hemispherical open resonator has previously been used to make relative comparisons of the surface resistivity of metallic thin-film samples in the submillimeter wavelength region. This resonator is fed from a far-infrared laser via a small coupling hole in the center of the concave spherical mirror. The experimental arrangement, while desirable as a coupling geometry for monitoring weak emissions from the cavity, can lead to the introduction of spurious modes into the cavity. Sources of these modes are identified, and a simple alteration of the experimental apparatus to eliminate such modes is suggested.

Aberration analysis of the putative projector for Lorenzo Lotto's Husband and wife: image analysis through computer ray-tracing

NASA Astrophysics Data System (ADS)

Robinson, Dirk; Stork, David G.

2008-02-01

A recent theory claims that the late-Italian Renaissance painter Lorenzo Lotto secretly built a concave-mirror projector to project an image of a carpet onto his canvas and trace it during the execution of Husband and wife (c. 1543). Key evidence adduced to support this claim includes "perspective anomalies" and changes in "magnification" that the theory's proponents ascribe to Lotto refocusing his projector to overcome its limitations in depth of field. We find, though, that there are important geometrical constraints upon such a putative optical projector not incorporated into the proponents' analyses, and that when properly included, the argument for the use of optics loses its force. We used Zemax optical design software to create a simple model of Lotto's studio and putative projector, and incorporated the optical properties proponents inferred from geometrical properties of the depicted carpet. Our central contribution derives from including the 116-cm-wide canvas screen; we found that this screen forces the incident light to strike the concave mirror at large angles (>= 15°) and that this, in turn, means that the projected image would reveal severe off-axis aberrations, particularly astigmatism. Such aberrations are roughly as severe as the defocus blur claimed to have led Lotto to refocus the projector. In short, we find that the projected images would not have gone in and out of focus in the way claimed by proponents, a result that undercuts their claim that Lotto used a projector for this painting. We speculate on the value of further uses of sophisticated ray-tracing analyses in the study of fine arts.

Aberration-free, all-reflective laser pulse stretcher

DOEpatents

Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.; Fochs, Scott N.

1999-09-28

An all-reflective pulse stretcher for laser systems employing chirped-pulse amplification enables on-axis use of the focusing mirror which results in ease of use, significantly decreased sensitivity to alignment and near aberration-free performance. By using a new type of diffraction grating which contains a mirror incorporated into the grating, the stretcher contains only three elements: 1) the grating, 2) a spherical or parabolic focusing mirror, and 3) a flat mirror. Addition of a fourth component, a retro-reflector, enables multiple passes of the same stretcher resulting in stretching ratios beyond the current state of the art in a simple and compact design. The pulse stretcher has been used to stretch pulses from 20 fsec to over 600 psec (a stretching ratio in excess of 30,000).

X-ray beam-shaping via deformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics.

PubMed

Spiga, D

2018-01-01

X-ray mirrors with high focusing performances are commonly used in different sectors of science, such as X-ray astronomy, medical imaging and synchrotron/free-electron laser beamlines. While deformations of the mirror profile may cause degradation of the focus sharpness, a deliberate deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators. The resulting profile can be characterized with suitable metrology tools and correlated with the expected optical quality via a wavefront propagation code or, sometimes, predicted using geometric optics. In the latter case and for the special class of profile deformations with monotonically increasing derivative, i.e. concave upwards, the point spread function (PSF) can even be predicted analytically. Moreover, under these assumptions, the relation can also be reversed: from the desired PSF the required profile deformation can be computed analytically, avoiding the use of trial-and-error search codes. However, the computation has been so far limited to geometric optics, which entailed some limitations: for example, mirror diffraction effects and the size of the coherent X-ray source were not considered. In this paper, the beam-shaping formalism in the framework of physical optics is reviewed, in the limit of small light wavelengths and in the case of Gaussian intensity wavefronts. Some examples of shaped profiles are also shown, aiming at turning a Gaussian intensity distribution into a top-hat one, and checks of the shaping performances computing the at-wavelength PSF by means of the WISE code are made.

Integrated Cavity QED in a linear Ion Trap Chip for Enhanced Light Collection

NASA Astrophysics Data System (ADS)

Benito, Francisco; Jonathan, Sterk; Boyan, Tabakov; Haltli, Raymond; Tigges, Chris; Stick, Daniel; Balin, Matthew; Moehring, David

2012-06-01

Realizing a scalable trapped-ion quantum information processor may require integration of tools to manipulate qubits into trapping devices. We present efforts towards integrating a 1 mm optical cavity into a microfabricated surface ion trap to efficiently connect nodes in a quantum network. The cavity is formed by a concave mirror and a flat coated silicon mirror around a linear trap where ytterbium ions can be shuttled in and out of the cavity mode. By utilizing the Purcell effect to increase the rate of spontaneous emission into the cavity mode, we expect to collect up to 13% of the emitted photons. This work was supported by Sandia's Laboratory Directed Research and Development (LDRD) and the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Development of a high-speed nanoprofiler using normal vector tracing

NASA Astrophysics Data System (ADS)

Kitayama, T.; Matsumura, H.; Usuki, K.; Kojima, T.; Uchikoshi, J.; Higashi, Y.; Endo, K.

2012-09-01

A new high-speed nanoprofiler was developed in this study. This profiler measures normal vectors and their coordinates on the surface of a specimen. Each normal vector and coordinate is determined by making the incident light path and the reflected light path coincident using 5-axis controlled stages. This is ensured by output signal of quadrant photo diode (QPD). From the acquired normal vectors and their coordinates, the three-dimensional shape is calculated by a reconstruction algorithm based on least-squares. In this study, a concave spherical mirror with a 400 mm radius of curvature was measured. As a result, a peak of 30 nm PV was observed at the center of the mirror. Measurement repeatability was 1 nm. In addition, cross-comparison with a Fizeau interferometer was implemented and the results were consistent within 10 nm. In particular, the high spatial frequency profile was highly consistent, and any differences were considered to be caused by systematic errors.

Restraint deformation and corrosion protection of gold deposited aluminum mirrors for cold optics of mid-infrared instruments

NASA Astrophysics Data System (ADS)

Uchiyama, Mizuho; Miyata, Takashi; Sako, Shigeyuki; Kamizuka, Takafumi; Nakamura, Tomohiko; Asano, Kentaro; Okada, Kazushi; Onaka, Takashi; Sakon, Itsuki; Kataza, Hirokazu; Sarugaku, Yuki; Kirino, Okiharu; Nakagawa, Hiroyuki; Okada, Norio; Mitsui, Kenji

2014-07-01

We report the restraint deformation and the corrosion protection of gold deposited aluminum mirrors for mid-infrared instruments. To evaluate the deformation of the aluminum mirrors by thermal shrinkage, monitoring measurement of the surface of a mirror has been carried out in the cooling cycles from the room temperature to 100 K. The result showed that the effect of the deformation was reduced to one fourth if the mirror was screwed with spring washers. We have explored an effective way to prevent the mirror from being galvanically corroded. A number of samples have been prepared by changing the coating conditions, such as inserting an insulation layer, making a multi-layer and overcoating water blocking layer, or carrying out precision cleaning before coating. Precision cleaning before the deposition and protecting coat with SiO over the gold layer seemed to be effective in blocking corrosion of the aluminum. The SiO over-coated mirror has survived the cooling test for the mid-infrared use and approximately 1 percent decrease in the reflectance has been detected at 6-25 microns compared to gold deposited mirror without coating.

Optical configuration with fixed transverse magnification for self-interference incoherent digital holography.

PubMed

Imbe, Masatoshi

2018-03-20

The optical configuration proposed in this paper consists of a 4-f optical setup with the wavefront modulation device on the Fourier plane, such as a concave mirror and a spatial light modulator. The transverse magnification of reconstructed images with the proposed configuration is independent of locations of an object and an image sensor; therefore, reconstructed images of object(s) at different distances can be scaled with a fixed transverse magnification. It is yielded based on Fourier optics and mathematically verified with the optical matrix method. Numerical simulation results and experimental results are also given to confirm the fixity of the reconstructed images.

Fabrication of mirror templates in silica with micron-sized radii of curvature

NASA Astrophysics Data System (ADS)

Najer, Daniel; Renggli, Martina; Riedel, Daniel; Starosielec, Sebastian; Warburton, Richard J.

2017-01-01

We present the fabrication of exceptionally small-radius concave microoptics on fused silica substrates using CO2 laser ablation and subsequent reactive ion etching. The protocol yields on-axis near-Gaussian depressions with a radius of curvature ≲5 μm at shallow depth and low surface roughness of 2 Å. This geometry is appealing for cavity quantum electrodynamics where small mode volumes and low scattering losses are desired. We study the optical performance of the structures within a tunable Fabry-Pérot type microcavity and demonstrate near-coating-limited loss rates ( F = 25 000 ) and small focal lengths consistent with their geometrical dimensions.

Improved methods for dewarping images in convex mirrors in fine art: applications to van Eyck and Parmigianino

NASA Astrophysics Data System (ADS)

Usami, Yumi; Stork, David G.; Fujiki, Jun; Hino, Hideitsu; Akaho, Shotaro; Murata, Noboru

2011-03-01

We derive and demonstrate new methods for dewarping images depicted in convex mirrors in artwork and for estimating the three-dimensional shapes of the mirrors themselves. Previous methods were based on the assumption that mirrors were spherical or paraboloidal, an assumption unlikely to hold for hand-blown glass spheres used in early Renaissance art, such as Johannes van Eyck's Portrait of Giovanni (?) Arnolfini and his wife (1434) and Robert Campin's Portrait of St. John the Baptist and Heinrich von Werl (1438). Our methods are more general than such previous methods in that we assume merely that the mirror is radially symmetric and that there are straight lines (or colinear points) in the actual source scene. We express the mirror's shape as a mathematical series and pose the image dewarping task as that of estimating the coefficients in the series expansion. Central to our method is the plumbline principle: that the optimal coefficients are those that dewarp the mirror image so as to straighten lines that correspond to straight lines in the source scene. We solve for these coefficients algebraically through principal component analysis, PCA. Our method relies on a global figure of merit to balance warping errors throughout the image and it thereby reduces a reliance on the somewhat subjective criterion used in earlier methods. Our estimation can be applied to separate image annuli, which is appropriate if the mirror shape is irregular. Once we have found the optimal image dewarping, we compute the mirror shape by solving a differential equation based on the estimated dewarping function. We demonstrate our methods on the Arnolfini mirror and reveal a dewarped image superior to those found in prior work|an image noticeably more rectilinear throughout and having a more coherent geometrical perspective and vanishing points. Moreover, we find the mirror deviated from spherical and paraboloidal shape; this implies that it would have been useless as a concave projection mirror, as has been claimed. Our dewarped image can be compared to the geometry in the full Arnolfini painting; the geometrical agreement strongly suggests that van Eyck worked from an actual room, not, as has been suggested by some art historians, a "fictive" room of his imagination. We apply our method to other mirrors depicted in art, such as Parmigianino's Self-portrait in a convex mirror and compare our results to those from earlier computer graphics simulations.

Variable magnification variable dispersion glancing incidence imaging x-ray spectroscopic telescope

NASA Technical Reports Server (NTRS)

Hoover, Richard B. (Inventor)

1991-01-01

A variable magnification variable dispersion glancing incidence x-ray spectroscopic telescope capable of multiple high spatial revolution imaging at precise spectral lines of solar and stellar x-ray and extreme ultraviolet radiation sources includes a pirmary optical system which focuses the incoming radiation to a primary focus. Two or more rotatable carries each providing a different magnification are positioned behind the primary focus at an inclination to the optical axis, each carrier carrying a series of ellipsoidal diffraction grating mirrors each having a concave surface on which the gratings are ruled and coated with a mutlilayer coating to reflect by diffraction a different desired wavelength. The diffraction grating mirrors of both carriers are segments of ellipsoids having a common first focus coincident with the primary focus. A contoured detector such as an x-ray sensitive photogrpahic film is positioned at the second respective focus of each diffraction grating so that each grating may reflect the image at the first focus to the detector at the second focus. The carriers are selectively rotated to position a selected mirror for receiving radiation from the primary optical system, and at least the first carrier may be withdrawn from the path of the radiation to permit a selected grating on the second carrier to receive radiation.

Variable magnification variable dispersion glancing incidence imaging x ray spectroscopic telescope

NASA Technical Reports Server (NTRS)

Hoover, Richard (Inventor)

1990-01-01

A variable magnification variable dispersion glancing incidence x ray spectroscopic telescope capable of multiple high spatial revolution imaging at precise spectral lines of solar and stellar x ray and extreme ultraviolet radiation sources includes a primary optical system which focuses the incoming radiation to a primary focus. Two or more rotatable carriers each providing a different magnification are positioned behind the primary focus at an inclination to the optical axis, each carrier carrying a series of ellipsoidal diffraction grating mirrors each having a concave surface on which the gratings are ruled and coated with a multilayer coating to reflect by diffraction a different desired wavelength. The diffraction grating mirrors of both carriers are segments of ellipsoids having a common first focus coincident with the primary focus. A contoured detector such as an x ray sensitive photographic film is positioned at the second respective focus of each diffraction grating so that each grating may reflect the image at the first focus to the detector at the second focus. The carriers are selectively rotated to position a selected mirror for receiving radiation from the primary optical system, and at least the first carrier may be withdrawn from the path of the radiation to permit a selected grating on the second carrier to receive radiation.

"First Light" Approaches for Fourth VLT Unit Telescope

NASA Astrophysics Data System (ADS)

2000-08-01

These days, the ESO staff at Paranal is having a strong feeling of "déja-vu". Only seven months after the third 8.2-m VLT Unit Telescope, MELIPAL , achieved "First Light", this crucial moment is now rapidly approaching for YEPUN , the fourth and last of the giants at the ESO observatory. Following successful coating with a thin layer of aluminium in early June 2000, the 8.2-m primary Zerodur mirror (M1) was placed in its supporting cell and safely attached to the mechanical structure of YEPUN on July 31. On August 26, the 1.1-m M2 Beryllium Mirror for YEPUN was coated. Again, this delicate operation went very well and the measured reflectivity was excellent, about 91%. The M2 mirror and its support were then assembled and successfully installed at the telescope on Sunday, August 27. Before the optical mirrors were installed, and with dummies in their place, careful tests were made of most telescope functions. In particular, this included accurate balancing of the 450-tonnes telescope frame on its hydrostatic oil bearings, as well as precise adjustment of all motions. It now remains for the ESO engineers to do the final performance optimization of the entire telescope. The work on the fourth telescope has been particularly noticeable because a large proportion of the assembly, integration, tuning and testing was organised and executed by ESOs young group of capable engineers and technicians. As the engineering staff at Paranal has grown and during the earlier work on the first three telescopes, they have been acquiring the necessary expertise to autonomously integrate and maintain the 8.2-m telescopes. During the coming "First Light" observations, light from the selected celestial objects will be registered by the VLT Test Camera at the Cassegrain Focus. This comparatively simple instrument was also used for the consecutive "First Light" events for ANTU ( May 1998 ), KUEYEN ( March 1999 ) and MELIPAL ( January 2000 ). It is mounted on the telescope's optical axis within the M1 Mirror Cell, just behind the main mirror. It is planned to make one or more of these first images available on the web soon thereafter. This is the caption to ESO PR Photos 21a-b/00 . They may be reproduced, if credit is given to the European Southern Observatory. Note, however, that since these photos were electronically recorded and were primarily obtained to document the ongoing activities at Paranal, they are not of full professional quality for photographic reproduction.

Relationship of central incisor implant placement to the ridge configuration anterior to the nasopalatine canal in dentate and partially edentulous individuals: a comparative study

PubMed Central

2015-01-01

Background. The aims of this study were to investigate the ridge contour anterior to the nasopalatine canal, and the difference between the incidences of the nasopalatine canal perforation in dentate and partially edentulous patients by cone-beam computed tomography. Methods. Cone-beam computed tomography scan images from 72 patients were selected from database and divided into dentate and partially edentulous groups. The configuration of the ridge anterior to the canal including palatal concavity depth, palatal concavity height, palatal concavity angle, bone height coronal to the incisive foramen, and bone width anterior to the canal was measured. A virtual implant placement procedure was used, and the incidences of perforation were evaluated after implant placement in the cingulum position with the long axis along with the designed crown. Results. Comparing with variable values from dentate patients, the palatal concavity depth and angle were greater by 0.9 mm and 4°, and bone height was shorter by 1.1 mm in partially edentulous patients, respectively. Bone width in edentulous patients was narrower than in dentate patients by 1.2 mm at incisive foramen level and 0.9 mm at 8 mm subcrestal level, respectively. After 72 virtual cylindrical implants (4.1 × 12 mm) were placed, a total of 12 sites (16.7%) showed a perforation and three-fourths occurred in partially edentulous patients. After replacing with 72 tapered implants (4.3 × 13 mm), only 6 implants (8.3%) broke into the canal in the partially edentulous patient group. Conclusions. The nasopalatine canal may get close to the implant site and the bone width anterior to the canal decreases after the central incisor extraction. The incidence of nasopalatine canal perforation may occur more commonly during delayed implant placement in central incisor missing patients. PMID:26557434

Optical testing of the LSST combined primary/tertiary mirror

NASA Astrophysics Data System (ADS)

Tuell, Michael T.; Martin, Hubert M.; Burge, James H.; Gressler, William J.; Zhao, Chunyu

2010-07-01

The Large Synoptic Survey Telescope (LSST) utilizes a three-mirror design in which the primary (M1) and tertiary (M3) mirrors are two concentric aspheric surfaces on one monolithic substrate. The substrate material is Ohara E6 borosilicate glass, in a honeycomb sandwich configuration, currently in production at The University of Arizona's Steward Observatory Mirror Lab. In addition to the normal requirements for smooth surfaces of the appropriate prescriptions, the alignment of the two surfaces must be accurately measured and controlled in the production lab. Both the pointing and centration of the two optical axes are important parameters, in addition to the axial spacing of the two vertices. This paper describes the basic metrology systems for each surface, with particular attention to the alignment of the two surfaces. These surfaces are aspheric enough to require null correctors for each wavefront. Both M1 and M3 are concave surfaces with both non-zero conic constants and higher-order terms (6th order for M1 and both 6th and 8th orders for M3). M1 is hyperboloidal and can utilize a standard Offner null corrector. M3 is an oblate ellipsoid, so has positive spherical aberration. We have chosen to place a phase-etched computer-generated hologram (CGH) between the mirror surface and the center-of-curvature (CoC), whereas the M1 null lens is beyond the CoC. One relatively new metrology tool is the laser tracker, which is relied upon to measure the alignment and spacings. A separate laser tracker system will be used to measure both surfaces during loose abrasive grinding and initial polishing.

A KPC-Scale X-Ray Jet in the BL Lac Source S5 2007+777

NASA Technical Reports Server (NTRS)

Sambruna, Rita M.; Donato, Davide; Cheung, C.C.; Tavecchio, F.; Maraschi, L.

2008-01-01

X-ray jets in AGN are commonly observed in FRII and FRI radiogalaxies, but rarely in BL Lacs, most probably due to their orientation close to the line of sight and the ensuing foreshortening effects. Only three BL Lacs are known so far to contain a kpc-scale X-ray jet. In this paper, we present the evidence for the existence of a fourth extended X-ray jet in the classical radio-selected source S5 2007+777, which for its hybrid FRI/II radio morphology has been classified as a HYMOR (HYbrid MOrphology Radio source). Our Chandra ACISS observations of this source revealed an X-ray counterpart to the 19"-long radio jet. Interestingly, the X-ray properties of the kpc-scale jet in S5 2007+777 are very similar to those observed in FRII jets. First, the X-ray morphology closely mirrors the radio one, with the X-rays being concentrated in the discrete radio knots. Second, the X-ray continuum of the jet/brightest knot is described by a very hard power law, with photon index gamma(sub x) approximately 1. Third, the optical upper limit from archival HST data implies a concave radio-to-X-ray SED. If the X-ray emission is attributed to IC/CMB with equipartition, strong beaming (delta= 13) is required, implying a very large scale (Mpc) jet. The beaming requirement can be somewhat relaxed assuming a magnetic field lower than equipartition. Alternatively, synchrotron emission from a second population of very high-energy electrons is viable. Comparison to other HYMOR jets detected with Chandra is discussed, as well as general implications for the origin of the FRI/II division.

Self-aligning concave relativistic plasma mirror with adjustable focus

DOE PAGES

Tsai, Hai-En; Arefiev, Alexey V.; Shaw, Joseph M.; ...

2017-01-04

We report an experimental-computational study of the optical properties of plasma mirrors (PMs) at the incident laser frequency when irradiated directly at relativistic intensity (10 180<10 19W/cm 2) by near-normally incident (4°), high-contrast, 30 fs, 800 nm laser pulses. We find that such relativistic PMs are highly reflective (0.6–0.8) and focus a significant fraction of reflected light to intensity as large as ~10I0 at distance f as small as ~25 μm from the PM, provided that pre-pulses do not exceed 10 14 W/cm 2 prior to ~20 ps before arrival of the main pulse peak. Particle-in-cell simulations show that focusingmore » results from denting of the reflecting surface by light pressure combined with relativistic transparency and that reflectivity and f can be adjusted by controlling pre-plasma length L over the range 0.5 ≲L ≲ 3 μm. Pump-probe reflectivity measurements show that the PM's focusing properties evolve on a ps time scale.« less

Self-aligning concave relativistic plasma mirror with adjustable focus

NASA Astrophysics Data System (ADS)

Tsai, Hai-En; Arefiev, Alexey V.; Shaw, Joseph M.; Stark, David J.; Wang, Xiaoming; Zgadzaj, Rafal; Downer, M. C.

2017-01-01

We report an experimental-computational study of the optical properties of plasma mirrors (PMs) at the incident laser frequency when irradiated directly at relativistic intensity ( 10 18 < I 0 < 10 19 W / cm 2 ) by near-normally incident ( 4 ° ), high-contrast, 30 fs, 800 nm laser pulses. We find that such relativistic PMs are highly reflective ( 0.6 - 0.8 ) and focus a significant fraction of reflected light to intensity as large as ˜ 10 I 0 at distance f as small as ˜ 25 μ m from the PM, provided that pre-pulses do not exceed 1014 W/cm2 prior to ˜ 20 ps before arrival of the main pulse peak. Particle-in-cell simulations show that focusing results from denting of the reflecting surface by light pressure combined with relativistic transparency and that reflectivity and f can be adjusted by controlling pre-plasma length L over the range 0.5 ≲ L ≲ 3 μ m. Pump-probe reflectivity measurements show that the PM's focusing properties evolve on a ps time scale.

Device for collecting and analyzing matrix-isolated samples

DOEpatents

Reedy, Gerald T.

1979-01-01

A gas-sample collection device is disclosed for matrix isolation of individual gas bands from a gas chromatographic separation and for presenting these distinct samples for spectrometric examination. The device includes a vacuum chamber containing a rotatably supported, specular carrousel having a number of external, reflecting surfaces around its axis of rotation for holding samples. A gas inlet is provided for depositing sample and matrix material on the individual reflecting surfaces maintained at a sufficiently low temperature to cause solidification. Two optical windows or lenses are installed in the vacuum chamber walls for transmitting a beam of electromagnetic radiation, for instance infrared light, through a selected sample. Positioned within the chamber are two concave mirrors, the first aligned to receive the light beam from one of the lenses and focus it to the sample on one of the reflecting surfaces of the carrousel. The second mirror is aligned to receive reflected light from that carrousel surface and to focus it outwardly through the second lens. The light beam transmitted from the sample is received by a spectrometer for determining absorption spectra.

Motor control may support mirror neuron research with new hypotheses and methods. Reply to comments on "Grasping synergies: A motor-control approach to the mirror neuron mechanism"

NASA Astrophysics Data System (ADS)

D'Ausilio, Alessandro; Bartoli, Eleonora; Maffongelli, Laura

2015-03-01

We are grateful to all commentators for their insightful commentaries and observations that enrich our proposal. One of our aims was indeed to bridge the gap between fields of research that, progressing independently, are facing similar issues regarding the neural representation of motor knowledge. In this respect, we were pleased to receive feedback from eminent researchers on both the mirror neuron as well as the motor control fields. Their expertise covers animal and human neurophysiology, as well as the computational modeling of neural and behavioral processes. Given their heterogeneous cultural perspectives and research approaches, a number of important open questions were raised. For simplicity we separated these issues into four sections. In the first section we present methodological aspects regarding how synergies can be measured in paradigms investigating the human mirror system. The second section regards the fundamental definition of what exactly synergies might be. The third concerns how synergies can generate testable predictions in mirror neuron research. Finally, the fourth section deals with the ultimate question regarding the function of the mirror neuron system.

Multiwavelength micromirrors in the cuticle of scarab beetle Chrysina gloriosa.

PubMed

Agez, Gonzague; Bayon, Chloé; Mitov, Michel

2017-01-15

Beetles from the genus Chrysina show vivid reflections from bright green to metallic silver-gold as a consequence of the cholesteric liquid crystal organization of chitin molecules. Particularly, the cuticle of Chrysina gloriosa exhibits green and silver stripes. By combining confocal microscopy and spectrophotometry, scanning electron microscopy and numerical simulations, the relationship between the reflectance and the structural parameters for both stripes at the micro- and nanoscales are established. Over the visible and near IR spectra, polygonal cells in tessellated green stripes behave as multiwavelength selective micro-mirrors and the silver stripes as specular broadband mirrors. Thermoregulation, conspecifics or intra-species communication, or camouflage against predators are discussed as possible functions. As a prerequisite to bio-inspired artificial replicas, the physical characteristics of the polygonal texture in Chrysina gloriosa cuticle are compared to their equivalents in synthetic cholesteric oligomers and their fundamental differences are ascertained. It is shown that the cuticle has concave cells whereas the artificial films have convex cells, contrary to expectation and assumption in the literature. The present results may provide inspiration for fabricating multiwavelength selective micromirrors or spatial wavelength-specific light modulators. Many insects own a tessellated carapace with bumps, pits or indentations. Little is known on the physical properties of these geometric variations and biological functions are unknown or still debated. We show that the polygonal cells in scarab beetle Chrysina gloriosa behave as multiwavelength selective micromirrors over the visible and infrared spectra, with a variety of spatial patterns. In the context of biomimetic materials, we demonstrate that the carapace has concave cells whereas the artificial films have convex cells, contrary to expectation in the literature. Thermoregulation, communication or camouflage are discussed as advanced functions. Results may provide inspiration for fabricating spatial wavelength-specific light modulators and optical packet switching in routing technologies. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Reflective correctors for the Hubble Space Telescope axial instruments

NASA Technical Reports Server (NTRS)

Bottema, Murk

1993-01-01

Reflective correctors to compensate the spherical aberration in the Hubble Space Telescope are placed in front of three of the axial scientific instruments (a camera and two spectrographs) during the first scheduled refurbishment mission. The five correctors required are deployed from a new module that replaces the fourth axial instrument. Each corrector consists of a field mirror and an aspherical, aberration-correcting reimaging mirror. In the camera the angular resolution capability is restored, be it in reduced fields, and in the spectrographs the potential for observations in crowded areas is regained along with effective light collection at the slits.

Intuitive optics: what great apes infer from mirrors and shadows.

PubMed

Völter, Christoph J; Call, Josep

2018-05-02

There is ongoing debate about the extent to which nonhuman animals, like humans, can go beyond first-order perceptual information to abstract structural information from their environment. To provide more empirical evidence regarding this question, we examined what type of information great apes (chimpanzees, bonobos, and orangutans) gain from optical effects such as shadows and mirror images. In an initial experiment, we investigated whether apes would use mirror images and shadows to locate hidden food. We found that all examined ape species used these cues to find the food. Follow-up experiments showed that apes neither confused these optical effects with the food rewards nor did they merely associate cues with food. First, naïve chimpanzees used the shadow of the hidden food to locate it but they did not learn within the same number of trials to use a perceptually similar rubber patch as indicator of the hidden food reward. Second, apes made use of the mirror images to estimate the distance of the hidden food from their own body. Depending on the distance, apes either pointed into the direction of the food or tried to access the hidden food directly. Third, apes showed some sensitivity to the geometrical relation between mirror orientation and mirrored objects when searching hidden food. Fourth, apes tended to interpret mirror images and pictures of these mirror images differently depending on their prior knowledge. Together, these findings suggest that apes are sensitive to the optical relation between mirror images and shadows and their physical referents.

Advanced astigmatism-corrected tandem Wadsworth mounting for small-scale spectral broadband imaging spectrometer.

PubMed

Lei, Yu; Lin, Guan-yu

2013-01-01

Tandem gratings of double-dispersion mount make it possible to design an imaging spectrometer for the weak light observation with high spatial resolution, high spectral resolution, and high optical transmission efficiency. The traditional tandem Wadsworth mounting is originally designed to match the coaxial telescope and large-scale imaging spectrometer. When it is used to connect the off-axis telescope such as off-axis parabolic mirror, it presents lower imaging quality than to connect the coaxial telescope. It may also introduce interference among the detector and the optical elements as it is applied to the short focal length and small-scale spectrometer in a close volume by satellite. An advanced tandem Wadsworth mounting has been investigated to deal with the situation. The Wadsworth astigmatism-corrected mounting condition for which is expressed as the distance between the second concave grating and the imaging plane is calculated. Then the optimum arrangement for the first plane grating and the second concave grating, which make the anterior Wadsworth condition fulfilling each wavelength, is analyzed by the geometric and first order differential calculation. These two arrangements comprise the advanced Wadsworth mounting condition. The spectral resolution has also been calculated by these conditions. An example designed by the optimum theory proves that the advanced tandem Wadsworth mounting performs excellently in spectral broadband.

Method of manufacturing large dish reflectors for a solar concentrator apparatus

DOEpatents

Angel, Roger P [Tucson, AZ; Olbert, Blain H [Tucson, AZ

2011-12-27

A method of manufacturing monolithic glass reflectors for concentrating sunlight in a solar energy system is disclosed. The method of manufacturing allows large monolithic glass reflectors to be made from float glass in order to realize significant cost savings on the total system cost for a solar energy system. The method of manufacture includes steps of heating a sheet of float glass positioned over a concave mold until the sheet of glass sags and stretches to conform to the shape of the mold. The edges of the dish-shaped glass are rolled for structural stiffening around the periphery. The dish-shaped glass is then silvered to create a dish-shaped mirror that reflects solar radiation to a focus. The surface of the mold that contacts the float glass preferably has a grooved surface profile comprising a plurality of cusps and concave valleys. This grooved profile minimizes the contact area and marring of the specular glass surface, reduces parasitic heat transfer into the mold and increases mold lifetime. The disclosed method of manufacture is capable of high production rates sufficiently fast to accommodate the output of a conventional float glass production line so that monolithic glass reflectors can be produced as quickly as a float glass production can make sheets of float glass to be used in the process.

Long-term facial improvement after repeated BoNT-A injections and mirror biofeedback exercises for chronic facial synkinesis: a case-series study.

PubMed

Mandrini, Silvia; Comelli, Mario; Dall'angelo, Anna; Togni, Rossella; Cecini, Miriam; Pavese, Chiara; Dalla Toffola, Elena

2016-12-01

Only few studies have considered the effects of the combined treatment with onabotulinumtoxinA (BoNT-A) injections and biofeedback (BFB) rehabilitation in the recovery of postparetic facial synkinesis (PPFS). To explore the presence of a persistent improvement in facial function out of the pharmacological effect of BoNT-A in subjects with established PPFS, after repeated sessions of BoNT-A injections combined with an educational facial training program using mirror biofeedback (BFB) exercises. Secondary objective was to investigate the trend of the presumed persistent improvement. Case-series study. Outpatient Clinic of Physical Medicine and Rehabilitation Unit. Twenty-seven patients (22 females; mean age 45±16 years) affected by an established peripheral facial palsy, treated with a minimum of three BoNT-A injections in association with mirror BFB rehabilitation. The interval between consecutive BoNT-A injections was at least five months. At baseline and before every BoNT-A injection+mirror BFB session (when the effect of the previous BoNT-A injection had vanished), patients were assessed with the Italian version of Sunnybrook Facial Grading System (SB). The statistical analysis considered SB composite and partial scores before each treatment session compared to the baseline scores. A significant improvement of the SB composite and partial scores was observed until the fourth session. Considering the "Symmetry of Voluntary Movement" partial score, the main improvement was observed in the muscles of the lower part of the face. In a chronic stage of postparetic facial synkinesis, patients may benefit from a combined therapy with repeated BoNT-A injections and an educational facial training program with mirror BFB exercises, gaining an improvement of the facial function up to the fourth session. This improvement reflects the acquired ability to use facial muscle correctly. It doesn't involve the injected muscles but those trained with mirror biofeedback exercises and it persists also when BoNT-A action has vanished. The combined therapy with repeated BoNT-A injections and an educational facial training program using mirror BFB exercises may be useful in the motor recovery of the muscles of the lower part of the face not injected but trained.

Correlation between cervical vertebral maturation and chronological age in a group of Iranian females.

PubMed

Safavi, Seyed Mohammadreza; Beikaii, Hanie; Hassanizadeh, Raheleh; Younessian, Farnaz; Baghban, Alireza Akbarzadeh

2015-01-01

Correlation between chronological age at different stages of cervical vertebral maturation (CVM) is important in clinical orthodontic practice. The objective of this study was to evaluate the correlation between CVM stage and chronological age in a group of Iranian female patients. This study was conducted on 196 digital lateral cephalometry of female patients with the age ranged 9-14 years. The CVM stage was determined with two calibrated examiners, using the method developed by Baccetti and its correlation with mean chronological age was assessed by the Spearman rank-order. The intra and inter-agreements were evaluated by weighted Kappa statistics in overall diagnosis of stages, in addition to determination of presence or absent of concavities at the lower border of second, third and fourth cervical vertebrae and the shapes of the third and fourth vertebrae. P < 0.05 was considered as significant. The correlation coefficient between CVM stages and chronological age was relatively low (r = 0.62). The least amount of inter-observer agreement was determined to be at the clinical decision of the shape of the fourth vertebra. Regarding the low reported correlation, the concomitant usage of other skeletal indicators seems necessary for precise determination of physiological age of the patients.

Diamond Machining of an Off-Axis Biconic Aspherical Mirror

NASA Technical Reports Server (NTRS)

Ohl, Raymond G.; Preuss, Werner; Sohn, Alex; MacKenty, John

2009-01-01

Two diamond-machining methods have been developed as part of an effort to design and fabricate an off-axis, biconic ellipsoidal, concave aluminum mirror for an infrared spectrometer at the Kitt Peak National Observatory. Beyond this initial application, the methods can be expected to enable satisfaction of requirements for future instrument mirrors having increasingly complex (including asymmetrical), precise shapes that, heretofore, could not readily be fabricated by diamond machining or, in some cases, could not be fabricated at all. In the initial application, the mirror is prescribed, in terms of Cartesian coordinates x and y, by aperture dimensions of 94 by 76 mm, placements of -2 mm off axis in x and 227 mm off axis in y, an x radius of curvature of 377 mm, a y radius of curvature of 407 mm, an x conic constant of 0.078, and a y conic constant of 0.127. The aspect ratio of the mirror blank is about 6. One common, "diamond machining" process uses single-point diamond turning (SPDT). However, it is impossible to generate the required off-axis, biconic ellipsoidal shape by conventional SPDT because (1) rotational symmetry is an essential element of conventional SPDT and (2) the present off-axis biconic mirror shape lacks rotational symmetry. Following conventional practice, it would be necessary to make this mirror from a glass blank by computer-controlled polishing, which costs more than diamond machining and yields a mirror that is more difficult to mount to a metal bench. One of the two present diamond machining methods involves the use of an SPDT machine equipped with a fast tool servo (FTS). The SPDT machine is programmed to follow the rotationally symmetric asphere that best fits the desired off-axis, biconic ellipsoidal surface. The FTS is actuated in synchronism with the rotation of the SPDT machine to generate the difference between the desired surface and the best-fit rotationally symmetric asphere. In order to minimize the required stroke of the FTS, the blanks were positioned at a large off-axis distance and angle, and the axis of the FTS was not parallel to the axis of the spindle of the SPDT machine. The spindle was rotated at a speed of 120 rpm, and the maximum FTS speed was 8.2 mm/s.

Status of Reconstruction of Fragmented Diamond-on-Silicon Collector From Genesis Spacecraft Solar Wind Concentrator

NASA Technical Reports Server (NTRS)

Rodriquez, Melissa C.; Calaway, M. C.; McNamara, K. M.; Hittle, J. D.

2009-01-01

In addition to passive solar wind collector surfaces, the Genesis Discovery Mission science canister had on board an electrostatic concave mirror for concentrating the solar wind ions, known as the concentrator . The 30-mm-radius collector focal point (the target) was comprised of 4 quadrants: two of single crystal SiC, one of polycrystalline 13C diamond and one of diamond-like-carbon (DLC) on a silicon substrate. [DLC-on-silicon is also sometimes referenced as Diamond-on-silicon, DOS.] Three of target quadrants survived the hard landing intact, but the DLC-on-silicon quadrant fractured into numerous pieces (Fig. 1). This abstract reports the status of identifying the DLC target fragments and reconstructing their original orientation.

Single frequency free-running low noise compact extended-cavity semiconductor laser at high power level

NASA Astrophysics Data System (ADS)

Garnache, Arnaud; Myara, Mikhaël.; Laurain, A.; Bouchier, Aude; Perez, J. P.; Signoret, P.; Sagnes, I.; Romanini, D.

2017-11-01

We present a highly coherent semiconductor laser device formed by a ½-VCSEL structure and an external concave mirror in a millimetre high finesse stable cavity. The quantum well structure is diode-pumped by a commercial single mode GaAs laser diode system. This free running low noise tunable single-frequency laser exhibits >50mW output power in a low divergent circular TEM00 beam with a spectral linewidth below 1kHz and a relative intensity noise close to the quantum limit. This approach ensures, with a compact design, homogeneous gain behaviour and a sufficiently long photon lifetime to reach the oscillation-relaxation-free class-A regime, with a cut off frequency around 10MHz.

FIND TIME FOR POETRY, GRADES THREE AND FOUR.

ERIC Educational Resources Information Center

Alameda County School Dept., Hayward, CA.

ENRICHMENT SUGGESTIONS FOR USE IN THE THIRD AND FOURTH GRADES ARE PRESENTED. VARIOUS LEVELS OF POETRY APPRECIATION ARE--(1) ENJOYMENT OF RHYTHM, MELODY, AND STORY, (2) APPRECIATION OF SEEING ONE'S OWN EXPERIENCES MIRRORED IN POETRY, (3) PROJECTION INTO A WORLD OTHER THAN THAT IN WHICH ONE LIVES, (4) UNDERSTANDING OF SYMBOLISM AND HIDDEN MEANINGS,…

City Schools as Mirrors of Modern Urban Life.

ERIC Educational Resources Information Center

Jacobs, Gregory S.; Markowitz, Ruth Jacknow; Taylor, Clarence; Rousmaniere, Kate

2001-01-01

Reviews four books that examine educational topics that are closely linked to the history of cities. Three are rooted in the contentious, complex story of education in New York City, focusing on: Jewish women as the dominant group of public school teachers, progressive reform agendas, and school desegregation movements. The fourth examines school…

Three-Dimensional Electromagnetic High Frequency Axisymmetric Cavity Scars.

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

Warne, Larry Kevin; Jorgenson, Roy Eberhardt

This report examines the localization of high frequency electromagnetic fi elds in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This report treats both the case where the opposing sides, or mirrors, are convex, where there are no interior foci, and the case where they are concave, leading to interior foci. The scalar problem is treated fi rst but the approximations required to treat the vector fi eld components are also examined. Particular att ention is focused on the normalization through themore » electromagnetic energy theorem. Both projections of the fi eld along the scarred orbit as well as point statistics are examined. Statistical comparisons are m ade with a numerical calculation of the scars run with an axisymmetric simulation. This axisymmetric cas eformstheoppositeextreme(wherethetwomirror radii at each end of the ray orbit are equal) from the two -dimensional solution examined previously (where one mirror radius is vastly di ff erent from the other). The enhancement of the fi eldontheorbitaxiscanbe larger here than in the two-dimensional case. Intentionally Left Blank« less

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

DOEpatents

Doughty, Frank C.; Spencer, John E.

2000-12-19

In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

A new optical head tracing reflected light for nanoprofiler

NASA Astrophysics Data System (ADS)

Okuda, K.; Okita, K.; Tokuta, Y.; Kitayama, T.; Nakano, M.; Kudo, R.; Yamamura, K.; Endo, K.

2014-09-01

High accuracy optical elements are applied in various fields. For example, ultraprecise aspherical mirrors are necessary for developing third-generation synchrotron radiation and XFEL (X-ray Free Electron LASER) sources. In order to make such high accuracy optical elements, it is necessary to realize the measurement of aspherical mirrors with high accuracy. But there has been no measurement method which simultaneously achieves these demands yet. So, we develop the nanoprofiler that can directly measure the any surfaces figures with high accuracy. The nanoprofiler gets the normal vector and the coordinate of a measurement point with using LASER and the QPD (Quadrant Photo Diode) as a detector. And, from the normal vectors and their coordinates, the three-dimensional figure is calculated. In order to measure the figure, the nanoprofiler controls its five motion axis numerically to make the reflected light enter to the QPD's center. The control is based on the sample's design formula. We measured a concave spherical mirror with a radius of curvature of 400 mm by the deflection method which calculates the figure error from QPD's output, and compared the results with those using a Fizeau interferometer. The profile was consistent within the range of system error. The deflection method can't neglect the error caused from the QPD's spatial irregularity of sensitivity. In order to improve it, we have contrived the zero method which moves the QPD by the piezoelectric motion stage and calculates the figure error from the displacement.

Bessel-Gauss resonator with spherical output mirror: geometrical- and wave-optics analysis.

PubMed

Gutiérrez-Vega, Julio C; Rodríguez-Masegosa, Rodolfo; Chávez-Cerda, Sabino

2003-11-01

A detailed study of the axicon-based Bessel-Gauss resonator with concave output coupler is presented. We employ a technique to convert the Huygens-Fresnel integral self-consistency equation into a matrix equation and then find the eigenvalues and the eigenfields of the resonator at one time. A paraxial ray analysis is performed to find the self-consistency condition to have stable periodic ray trajectories after one or two round trips. The fast-Fourier-transform-based Fox and Li algorithm is applied to describe the three-dimensional intracavity field distribution. Special attention was directed to the dependence of the output transverse profiles, the losses, and the modal-frequency changes on the curvature of the output coupler and the cavity length. The propagation of the output beam is discussed.

Log-Concavity and Strong Log-Concavity: a review

PubMed Central

Saumard, Adrien; Wellner, Jon A.

2016-01-01

We review and formulate results concerning log-concavity and strong-log-concavity in both discrete and continuous settings. We show how preservation of log-concavity and strongly log-concavity on ℝ under convolution follows from a fundamental monotonicity result of Efron (1969). We provide a new proof of Efron's theorem using the recent asymmetric Brascamp-Lieb inequality due to Otto and Menz (2013). Along the way we review connections between log-concavity and other areas of mathematics and statistics, including concentration of measure, log-Sobolev inequalities, convex geometry, MCMC algorithms, Laplace approximations, and machine learning. PMID:27134693

Impact of Electro-Magneto Concave Collector on the Characterizations of Electrospun Nanofibers

NASA Astrophysics Data System (ADS)

Shehata, Nader; Abdelkader, Mohamed

2018-05-01

We introduce a modified approach to produce aligned nanofibers through electro-magneto concave collectors. Both electric and magnetic fields distributions are simulated with COMSOL Multiphysics for different collectors including conventional, concave and modified concave collectors by adding magnetic discs in the back. Orientation matrices are evaluated for each collector in the study, and the highest degree of alignment is found to be with the modified concave collector with a percentage of 68%, followed by the concave collector with a percentage of 57%, which shows an improvement of the proposed method by adding a magnetic field. The generated nanofiber mats from the electro-magneto concave collector show improvements in both mechanical (Young's modulus = 117.66 MPa) and thermal properties compared to both concave and conventional collectors.

Charter Schools and Urban Education Improvement: A Comparison of Newark's District and Charter Schools

ERIC Educational Resources Information Center

Barr, Jason M.; Sadovnik, Alan R.; Visconti, Louisa

2006-01-01

This article compares student achievement of fourth graders in charter schools and district public schools in Newark, New Jersey. We find that Newark and New Jersey's charter schools mirror the educational inequalities of the state as a whole, as well as its Abbott Districts. The data indicate that charter schools are similar to district urban…

GLOBAL RATES OF CONVERGENCE OF THE MLES OF LOG-CONCAVE AND s-CONCAVE DENSITIES

PubMed Central

Doss, Charles R.; Wellner, Jon A.

2017-01-01

We establish global rates of convergence for the Maximum Likelihood Estimators (MLEs) of log-concave and s-concave densities on ℝ. The main finding is that the rate of convergence of the MLE in the Hellinger metric is no worse than n−2/5 when −1 < s < ∞ where s = 0 corresponds to the log-concave case. We also show that the MLE does not exist for the classes of s-concave densities with s < −1. PMID:28966409

The optical design of a visible adaptive optics system for the Magellan Telescope

NASA Astrophysics Data System (ADS)

Kopon, Derek

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.

Propagation of waves from an arbitrary shaped surface-A generalization of the Fresnel diffraction integral

NASA Astrophysics Data System (ADS)

Feshchenko, R. M.; Vinogradov, A. V.; Artyukov, I. A.

2018-04-01

Using the method of Laplace transform the field amplitude in the paraxial approximation is found in the two-dimensional free space using initial values of the amplitude specified on an arbitrary shaped monotonic curve. The obtained amplitude depends on one a priori unknown function, which can be found from a Volterra first kind integral equation. In a special case of field amplitude specified on a concave parabolic curve the exact solution is derived. Both solutions can be used to study the light propagation from arbitrary surfaces including grazing incidence X-ray mirrors. They can find applications in the analysis of coherent imaging problems of X-ray optics, in phase retrieval algorithms as well as in inverse problems in the cases when the initial field amplitude is sought on a curved surface.

In-Fiber Optic Salinity Sensing: A Potential Application for Offshore Concrete Structure Protection.

PubMed

Luo, Dong; Li, Peng; Yue, Yanchao; Ma, Jianxun; Yang, Hangzhou

2017-05-04

The protection of concrete structures against corrosion in marine environments has always been a challenge due to the presence of a saline solution-A natural corrosive agent to the concrete paste and steel reinforcements. The concentration of salt is a key parameter influencing the rate of corrosion. In this paper, we propose an optical fiber-based salinity sensor based on bundled multimode plastic optical fiber (POF) as a sensor probe and a concave mirror as a reflector in conjunction with an intensity modulation technique. A refractive index (RI) sensing approach is analytically investigated and the findings are in agreement with the experimental results. A maximum sensitivity of 14,847.486/RIU can be achieved at RI = 1.3525. The proposed technique is suitable for in situ measurement and monitoring of salinity in liquid.

High-brightness-solar-pumped Nd:YAG laser design

NASA Astrophysics Data System (ADS)

Lando, Mordechai; Jenkins, David G.; Bernstein, Hana; O'Gallagher, Joseph J.; Winston, Roland; Lewandowski, Allan

1995-06-01

We have designed a Nd:YAG laser to be pumped by the High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory. Based on the unique features of the HFSF, the design objectives are high brightness and superior efficiency in primary mirror area utilization. The HFSF has a primary mirror of 11.5 m2 and a 1.85 f-number. With such a high f-number, the target is set off-axis and does not block incoming solar flux. Moreover, large f-number enables concentration which approaches the theoretical limit, and a two- dimensional non-imaging concentrator deposits the solar flux onto the internal part of a 10 mm diameter laser rod. For high brightness, we plan a wide low-loss fundamental mode and a laser rod aperture that suppresses high order modes. To get a fundamental mode, of up to a 2.5 mm waist, we have designed a convex-concave resonator, following well-known g1g2 equals 0.5 design for resonators with internal beam focusing. We have used the edge ray principle to design the concentrator, and ray traced the deposited power inside the laser rod. A 1.3% Nd doping level supports a maximal power deposition inside a 5 mm diameter.

Effects of various cavity designs on the performance of a CO2 TEA laser with an unstable resonator

NASA Technical Reports Server (NTRS)

Zhao, Yanzeng; Post, Madison J.; Lawrence, T. R.

1992-01-01

Unstable resonator modeling has been carried out for an injection-seeded CO2 transversely excited atmosphere (TEA) laser in the NOAA/ERL/Wave Propagation Laboratory (WPL) Doppler lidar to examine the effects of various cavity designs on the quality of the output beam. The results show the effects of an injection pinhole, electrode spacing, mirror tilt, and radial reflectivity function of the output coupler. The electrode spacing in this laser has negligible effect. The injection pinhole, however, produces complicated structures in the output patterns. If the pinhole is removed, the output pattern is much smoother, and the frequency jitter is smaller. Misalignment sensitivity is very closely related to the radial reflectivity function. The superparabolic function provides the highest coupling efficiency, largest beam size, and good collimation, but produces a slightly higher misalignment sensitivity compared with a parabolic function. The Gaussian function provides the lowest misalignment sensitivity, but it produces the smallest beam size and the largest beam divergence. Also, the coupling coefficient is 50 percent lower than the optimum value. Methods for using a flat diffraction grating in unstable resonators are also investigated. The best way is to use a flat grating/positive lens combination to replace the back concave mirror.

Mirror buckling of freestanding graphene membranes induced by local heating due to a scanning tunneling microscope tip

NASA Astrophysics Data System (ADS)

Schoelz, J. K.; Neek Amal, M.; Xu, P.; Barber, S. D.; Ackerman, M. L.; Thibado, P. M.; Sadeghi, A.; Peeters, F. M.

2014-03-01

Scanning tunneling microscopy has been an invaluable tool in the study of graphene at the atomic scale. Several STM groups have managed to obtain atomic scale images of freestanding graphene membranes providing insight into the behavior of the stabilized ripple geometry. However, we found that the interaction between the STM tip and the freestanding graphene sample may induce additional effects. By varying the tunneling parameters, we can tune the position of the sample, in either a smooth or step like fashion. These phenomena were investigated by STM experiments, continuum elasticity theory and large scale molecular dynamics simulations. These results confirm that by increasing the tip bias, the electrostatic attraction between the tip and sample increases. When applied on a concave surface, this can result in mirror buckling which leads to a large scale movement of the sample. Interestingly, due in part to the negative coefficient of thermal expansion of graphene, buckling transitions can also be induced through local heating of the surface using the STM tip. Financial support by O.N.R. grant N00014-10-1-0181, N.S.F grant DMR-0855358, EU-Marie Curie IIF postdoc Fellowship/299855 (for M. N. A.), ESF-EuroGRAPHENE project CONGRAN, F.S.F (FWO-Vl), and Methusalem Foundation of the Flemish Government.

Generalized Convexity and Concavity Properties of the Optimal Value Function in Parametric Nonlinear Programming.

DTIC Science & Technology

1983-04-11

existing ones. * -37- !I T-472 REFERENCES [1] Avriel, M., W. E. Diewert, S. Schaible and W. T. Ziemba (1981). Introduction to concave and generalized concave...functions. In Generalized Concavity in Optimization and Economics (S. Schaible and W. T. Ziemba , eds.), Academic Press, New York, pp. 21-50. (21 Bank...Optimality conditions involving generalized convex mappings. In Generalized Concavity in Optimization and Economics (S. Schaible and W. T. Ziemba

Flat-field VLS spectrometers for laboratory applications

NASA Astrophysics Data System (ADS)

Ragozin, Evgeny N.; Belokopytov, Aleksei A.; Kolesnikov, Aleksei O.; Muslimov, Eduard R.; Shatokhin, Aleksei N.; Vishnyakov, Eugene A.

2017-05-01

Our intention is to develop high-resolution stigmatic spectral imaging in the XUV (2 - 40 nm). We have designed, aligned and tested a broadband stigmatic spectrometer for a range of 12-30 nm, which makes combined use of a normalincidence multilayer mirror (MM) (in particular, a broadband aperiodic MM) and a grazing-incidence plane varied linespace (VLS) reflection grating. The concave MM produces a slightly astigmatic image of the radiation source (for instance, the entrance slit), and the VLS grating produces a set of its dispersed stigmatic spectral images. The multilayer structure determines the spectral width of the operating range, which may amount to more than an octave in wavelength (e.g. 12.5-30 nm for an aperiodic Mo/Si MM), while the VLS grating controls the spectral focal curve. The stigmatism condition is satisfied simultaneously for two wavelengths, 14 and 27 nm. In this case, the condition of non-rigorous stigmatism is fulfilled for the entire wavelength range. A LiF laser plasma spectrum was recorded in one 0.5 J laser shot. A spatial resolution of 26 μm and a spectral resolution of 900 were demonstrated in the 12.5 - 25 nm range. We also report the design of a set of flat-field spectrometers of Harada type with VLS gratings. VLS gratings were made by ebeam and interference lithography. A technique (analytical + numerical) was developed for calculating optical schemes for writing plane and concave VLS gratings with predefined line density variation.

NASA/USRA advanced space design program: The laser powered interorbital vehicle

NASA Technical Reports Server (NTRS)

1989-01-01

A preliminary design is presented for a low-thrust Laser Powered Interorbital Vehicle (LPIV) intended for cargo transportation between an earth space station and a lunar base. The LPIV receives its power from two iodide laser stations, one orbiting the earth and the other located on the surface of the moon. The selected mission utilizes a spiral trajectory, characteristic of a low-thrust spacecraft, requiring 8 days for a lunar rendezvous and an additional 9 days for return. The ship's configuration consists primarily of an optical train, two hydrogen plasma engines, a 37.1 m box beam truss, a payload module, and fuel tanks. The total mass of the vehicle fully loaded is 63300 kg. A single plasma, regeneratively cooled engine design is incorporated into the two 500 N engines. These are connected to the spacecraft by turntables which allow the vehicle to thrust tangentially to the flight path. Proper collection and transmission of the laser beam to the thrust chambers is provided through the optical train. This system consists of the 23 m diameter primary mirror, a convex parabolic secondary mirror, a beam splitter and two concave parabolic tertiary mirrors. The payload bay is capable of carrying 18000 kg of cargo. The module is located opposite the primary mirror on the main truss. Fuel tanks carrying a maximum of 35000 kg of liquid hydrogen are fastened to tracks which allow the tanks to be moved perpendicular to the main truss. This capability is required to prevent the center of mass from moving out of the thrust vector line. The laser beam is located and tracked by means of an acquisition, pointing and tracking system which can be locked onto the space-based laser station. Correct orientation of the spacecraft with the laser beam is maintained by control moment gyros and reaction control rockets. Additionally an aerobrake configuration was designed to provide the option of using the atmospheric drag in place of propulsion for a return trajectory.

Detection of Convexity and Concavity in Context

ERIC Educational Resources Information Center

Bertamini, Marco

2008-01-01

Sensitivity to shape changes was measured, in particular detection of convexity and concavity changes. The available data are contradictory. The author used a change detection task and simple polygons to systematically manipulate convexity/concavity. Performance was high for detecting a change of sign (a new concave vertex along a convex contour…

Convexity and Concavity Properties of the Optimal Value Function in Parametric Nonlinear Programming.

DTIC Science & Technology

1982-12-21

and W. T. ZIEMBA (1981). Intro- duction to concave and generalized concave functions. In Gener- alized Concavity in Optimization and Economics (S...Schaible and W. T. Ziemba , eds.), pp. 21-50. Academic Press, New York. BANK, B., J. GUDDAT, D. KLATTE, B. KUMMER, and K. TAMMER (1982). Non- Linear

APPROXIMATION AND ESTIMATION OF s-CONCAVE DENSITIES VIA RÉNYI DIVERGENCES.

PubMed

Han, Qiyang; Wellner, Jon A

2016-01-01

In this paper, we study the approximation and estimation of s -concave densities via Rényi divergence. We first show that the approximation of a probability measure Q by an s -concave density exists and is unique via the procedure of minimizing a divergence functional proposed by [ Ann. Statist. 38 (2010) 2998-3027] if and only if Q admits full-dimensional support and a first moment. We also show continuity of the divergence functional in Q : if Q n → Q in the Wasserstein metric, then the projected densities converge in weighted L 1 metrics and uniformly on closed subsets of the continuity set of the limit. Moreover, directional derivatives of the projected densities also enjoy local uniform convergence. This contains both on-the-model and off-the-model situations, and entails strong consistency of the divergence estimator of an s -concave density under mild conditions. One interesting and important feature for the Rényi divergence estimator of an s -concave density is that the estimator is intrinsically related with the estimation of log-concave densities via maximum likelihood methods. In fact, we show that for d = 1 at least, the Rényi divergence estimators for s -concave densities converge to the maximum likelihood estimator of a log-concave density as s ↗ 0. The Rényi divergence estimator shares similar characterizations as the MLE for log-concave distributions, which allows us to develop pointwise asymptotic distribution theory assuming that the underlying density is s -concave.

APPROXIMATION AND ESTIMATION OF s-CONCAVE DENSITIES VIA RÉNYI DIVERGENCES

PubMed Central

Han, Qiyang; Wellner, Jon A.

2017-01-01

In this paper, we study the approximation and estimation of s-concave densities via Rényi divergence. We first show that the approximation of a probability measure Q by an s-concave density exists and is unique via the procedure of minimizing a divergence functional proposed by [Ann. Statist. 38 (2010) 2998–3027] if and only if Q admits full-dimensional support and a first moment. We also show continuity of the divergence functional in Q: if Qn → Q in the Wasserstein metric, then the projected densities converge in weighted L1 metrics and uniformly on closed subsets of the continuity set of the limit. Moreover, directional derivatives of the projected densities also enjoy local uniform convergence. This contains both on-the-model and off-the-model situations, and entails strong consistency of the divergence estimator of an s-concave density under mild conditions. One interesting and important feature for the Rényi divergence estimator of an s-concave density is that the estimator is intrinsically related with the estimation of log-concave densities via maximum likelihood methods. In fact, we show that for d = 1 at least, the Rényi divergence estimators for s-concave densities converge to the maximum likelihood estimator of a log-concave density as s ↗ 0. The Rényi divergence estimator shares similar characterizations as the MLE for log-concave distributions, which allows us to develop pointwise asymptotic distribution theory assuming that the underlying density is s-concave. PMID:28966410

A study of the depth and size of concave cube Au nanoparticles as highly sensitive SERS probes

NASA Astrophysics Data System (ADS)

Romo-Herrera, J. M.; González, A. L.; Guerrini, L.; Castiello, F. R.; Alonso-Nuñez, G.; Contreras, O. E.; Alvarez-Puebla, R. A.

2016-03-01

High and uniform near fields are localized at the eight similar sharp corners of cubic gold nanoparticles. Moreover, by introducing concavity in the particle lateral planes, such field intensities can be further increased and tuned in the near infrared region without altering the overall size of the nanoparticles. Herein, we perform a thorough investigation of the morphological, crystallographic and plasmonic properties of concave gold nanocubes (GNCs) in the sub-70 nm size range, for their potential application as highly efficient SERS substrates in size-limiting cases. Theoretical calculations indicate that the highest increment of the near-field is located at the eight sharp tips and, interestingly, a medium near-field increment is also activated over the volume next to the concave surface. Remarkably, the plasmonic response of the concave cubic morphology showed great sensitivity to the concavity degree. Experimental SERS analysis nicely matches the outcome of the theoretical model, confirming that medium-sized concave GNCs (35 nm side length) possess the highest SERS activity upon excitation with a 633 nm laser, whereas larger 61 nm side concave GNCs dominate the optical response at 785 nm. Due to their size-intensity trade off, we envision that such small concave gold nanocubes can provide a highly active and efficient SERS platform for size-limiting applications, especially when near infrared excitations are required.High and uniform near fields are localized at the eight similar sharp corners of cubic gold nanoparticles. Moreover, by introducing concavity in the particle lateral planes, such field intensities can be further increased and tuned in the near infrared region without altering the overall size of the nanoparticles. Herein, we perform a thorough investigation of the morphological, crystallographic and plasmonic properties of concave gold nanocubes (GNCs) in the sub-70 nm size range, for their potential application as highly efficient SERS substrates in size-limiting cases. Theoretical calculations indicate that the highest increment of the near-field is located at the eight sharp tips and, interestingly, a medium near-field increment is also activated over the volume next to the concave surface. Remarkably, the plasmonic response of the concave cubic morphology showed great sensitivity to the concavity degree. Experimental SERS analysis nicely matches the outcome of the theoretical model, confirming that medium-sized concave GNCs (35 nm side length) possess the highest SERS activity upon excitation with a 633 nm laser, whereas larger 61 nm side concave GNCs dominate the optical response at 785 nm. Due to their size-intensity trade off, we envision that such small concave gold nanocubes can provide a highly active and efficient SERS platform for size-limiting applications, especially when near infrared excitations are required. Electronic supplementary information (ESI) available: Nanoparticle size distribution analysis (Fig. SI-1); extended TEM analysis on nanocubes morphology (Fig. SI-2, SI-3 and SI-4); comparison of GNCs size and concavity degree (Fig. SI-4); optical response calculations using the curved edges model (Fig. SI-5); simulated optical absorption spectra as a function of the concavity depth (Fig. SI-6); background SERS spectrum (Fig. SI-8) and details on the calculation of the SERS enhancement factors. See DOI: 10.1039/c6nr01155a

Variable pathlength cavity spectroscopy development of an automated prototype

NASA Astrophysics Data System (ADS)

Schmeling, Ryan Andrew

Spectroscopy is the study of the interaction of electromagnetic radiation (EMR) with matter to probe the chemical and physical properties of atoms and molecules. The primary types of analytical spectroscopy are absorption, emission, and scattering methods. Absorption spectroscopy can quantitatively determine the chemical concentration of a given species in a sample by the relationship described by Beer's Law. Upon inspection of Beer's Law, it becomes apparent that for a given analyte concentration, the only experimental variable is the pathlength. Over the past ˜75 years, several approaches to physically increasing the pathlength have been reported in the literature. These have included not only larger cuvettes and novel techniques such as Differential Optical Absorption Spectroscopy, but also numerous designs that are based upon the creation of an optical cavity in which multiple reflections through the sample are made possible. The cavity-based designs range from the White Cell (1942) to Cavity Ring-Down Spectroscopy (O'Keefe and Deacon, 1998). In the White Cell approach, the incident beam is directed off-axis to repeatedly reflect concave mirror surfaces. Numerous variations of the White Cell design have been reported, and it has found wide application in infrared absorption spectroscopy in what have become to be known as "light pipes". In the CRDS design, on the other hand, highly reflective dielectric mirrors situated for on-axis reflections result in the measurement of the exponential decay of trapped light that passes through the exit mirror. CRDS has proven over the past two decades to be a powerful technique for ultra-trace analysis (< 10-15 g), with practical applications ranging from atmospheric monitoring of greenhouse gases to biomedical "breath screening" as a means to identify disease states. In this thesis, a novel approach to ultra-trace analysis by absorption spectroscopy is described. In this approach known as Variable Pathlength Cavity Spectroscopy (VPCS), a high finesse optical cavity is created by two flat, parallel, dielectric mirrors -- one of which is rotating. Source light from a pulsed dye laser (488 nm) enters the optical cavity in the same manner as in Cavity Ring-Down Spectroscopy (CRDS), i.e., by passing through the cavity entrance mirror. However, unlike CRDS in which the mirrors are fixed, concave, and mechanically unaltered, the cavity exit mirror contains a slit (1.0 mm diameter) that is rotated at high speed on an axle, thereby transmitting a small fraction of the trapped light to a photomultiplier tube detector. In this approach, unlike CRDS, absorbance is measured directly. In previous prototype designs of the VPCS instrument, instrument control (alignment) and data acquisition and reduction were performed manually; these functions were both inefficient and tedious. Despite this, the VPCS was validated in "proof of concept" testing, as described with a previous prototype (Frost, 2011). Frost demonstrated that the pathlength enhancement increased 53-fold compared to single-pass absorption measurements in monitoring NO2 (g) at part-per-billion levels. The goal of the present work is to improve upon the previous prototype ("P4") that required manual alignment, data collection, and data reduction by creating a completely automated version of VPCS -- i.e., the "P5" prototype. By developing source code in LabVIEW(TM), demonstration that the VPCS can be completely controlled in an automated fashion is described. Computationally, a Field-Programmable Gate Array is used to automate the process of data collection and reduction in real-time. It is shown that the inputs and outputs of the P5 instrument can be continuously monitored, allowing for real-time triggering of the source laser, collection of all data, and reduction of the data to report absorbance. Furthermore, it is shown that the VPCS can be automatically aligned -- also in real-time on the order of microseconds -- to a high degree of precision by using servo-actuators that adjust the beam position based upon the input from a sensitive CCD camera. With the implementation of this hardware and LabVIEW code, more precise data collection and reduction is done. With this new fully automated design, the instrument characteristics (e.g., to include factors such as rotation speed, off-set angle, and pathlength variation) can improve the enhancement by ˜130-fold vs. single-pass absorption measurements.

Design of ITER divertor VUV spectrometer and prototype test at KSTAR tokamak

NASA Astrophysics Data System (ADS)

Seon, Changrae; Hong, Joohwan; Song, Inwoo; Jang, Juhyeok; Lee, Hyeonyong; An, Younghwa; Kim, Bosung; Jeon, Taemin; Park, Jaesun; Choe, Wonho; Lee, Hyeongon; Pak, Sunil; Cheon, MunSeong; Choi, Jihyeon; Kim, Hyeonseok; Biel, Wolfgang; Bernascolle, Philippe; Barnsley, Robin; O'Mullane, Martin

2017-12-01

Design and development of the ITER divertor VUV spectrometer have been performed from the year 1998, and it is planned to be installed in the year 2027. Currently, the design of the ITER divertor VUV spectrometer is in the phase of detail design. It is optimized for monitoring of chord-integrated VUV signals from divertor plasmas, chosen to contain representative lines emission from the tungsten as the divertor material, and other impurities. Impurity emission from overall divertor plasmas is collimated through the relay optics onto the entrance slit of a VUV spectrometer with working wavelength range of 14.6-32 nm. To validate the design of the ITER divertor VUV spectrometer, two sets of VUV spectrometers have been developed and tested at KSTAR tokamak. One set of spectrometer without the field mirror employs a survey spectrometer with the wavelength ranging from 14.6 nm to 32 nm, and it provides the same optical specification as the spectrometer part of the ITER divertor VUV spectrometer system. The other spectrometer with the wavelength range of 5-25 nm consists of a commercial spectrometer with a concave grating, and the relay mirrors with the same geometry as the relay mirrors of the ITER divertor VUV spectrometer. From test of these prototypes, alignment method using backward laser illumination could be verified. To validate the feasibility of tungsten emission measurement, furthermore, the tungsten powder was injected in KSTAR plasmas, and the preliminary result could be obtained successfully with regard to the evaluation of photon throughput. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

Spectroscopic characterization of novel multilayer mirrors intended for astronomical and laboratory applications

NASA Astrophysics Data System (ADS)

Ragozin, Eugene N.; Mednikov, Konstantin N.; Pertsov, Andrei A.; Pirozhkov, Alexander S.; Reva, Anton A.; Shestov, Sergei V.; Ul'yanov, Artem S.; Vishnyakov, Eugene A.

2009-05-01

We report measurements of the reflection spectra of (i) concave (spherical and parabolic) Mo/Si, Mg/Si, and Al/Zr multilayer mirrors (MMs) intended for imaging solar spectroscopy in the framework of the TESIS/CORONAS-FOTON Satellite Project and of (ii) an aperiodic Mo/Si MM optimized for maximum uniform reflectivity in the 125-250 Å range intended for laboratory applications. The reflection spectra were measured in the configuration of a transmission grating spectrometer employing the radiation of a tungsten laser-driven plasma as the source. The function of detectors was fulfilled by backside-illuminated CCDs coated with Al or Zr/Si multilayer absorption filters. High-intensity second-order interference reflection peaks at wavelengths of about 160 Å were revealed in the reflection spectra of the 304-Å Mo/Si MMs. By contrast, the second-order reflection peak in the spectra of the new-generation narrow-band (~12 Å FWHM) 304-Å Mg/Si MMs is substantially depressed. Manifestations of the NEXAFS structure of the L2, 3 absorption edges of Al and Al2O3 were observed in the spectra recorded. The broadband Mo/Si MM was employed as the focusing element of spectrometers in experiments involving (i) the charge exchange of multiply charged ions with the donor atoms of a rare-gas jet; (ii) the spectroscopic characterization of a debris-free soft X-ray radiation source excited by Nd laser pulses in a Xe jet (iii) near-IR-to-soft-X-ray frequency conversion (double Doppler effect) occurring in the retroreflection from the relativistic electron plasma wake wave (flying mirror) driven by a multiterawatt laser in a pulsed helium jet.

A small mode volume tunable microcavity: Development and characterization

NASA Astrophysics Data System (ADS)

Greuter, Lukas; Starosielec, Sebastian; Najer, Daniel; Ludwig, Arne; Duempelmann, Luc; Rohner, Dominik; Warburton, Richard J.

2014-09-01

We report the realization of a spatially and spectrally tunable air-gap Fabry-Pérot type microcavity of high finesse and cubic-wavelength-scale mode volume. These properties are attractive in the fields of opto-mechanics, quantum sensing, and foremost cavity quantum electrodynamics. The major design feature is a miniaturized concave mirror with atomically smooth surface and radius of curvature as low as 10 μm produced by CO2 laser ablation of fused silica. We demonstrate excellent mode-matching of a focussed laser beam to the microcavity mode and confirm from the frequencies of the resonator modes that the effective optical radius matches the physical radius. With these small radii, we demonstrate wavelength-size beam waists. We also show that the microcavity is sufficiently rigid for practical applications: in a cryostat at 4 K, the root-mean-square microcavity length fluctuations are below 5 pm.

[Restore of the ancient "moxibustion the pulse" method].

PubMed

Wu, Qi-Fei; Bai, Xing-Hua

2013-03-01

The manipulation of ancient "moxibustion the pulse" method are replicated and discussed through literature review. It turned out that the old year moxa was the best material for moxibustion in ancient times because of its mild heat power and uninjurious to the skin or blood and vessels; it was believed by the ancient people that the ideal fire to light moxa which could play the curative effect best was "sunfire" (lighted through the bronze concave mirror focussing) while the prohibited were "eight kinds of wood fire"; the moxibustion area were the convergence of the pulse on limb ends. The way to determine the time and amount of moxibustion were various, but in general the moxa amount was larger; still after moxibustion, proper exercise and diet were recommended, the nursing methods of the moxibustion sore were recorded. In ancient times, moxibustion was not only a treatment method but also an unique culture carrier to reflect the faith and worship.

Imaging spectrometer/camera having convex grating

NASA Technical Reports Server (NTRS)

Reininger, Francis M. (Inventor)

2000-01-01

An imaging spectrometer has fore-optics coupled to a spectral resolving system with an entrance slit extending in a first direction at an imaging location of the fore-optics for receiving the image, a convex diffraction grating for separating the image into a plurality of spectra of predetermined wavelength ranges; a spectrometer array for detecting the spectra; and at least one concave sperical mirror concentric with the diffraction grating for relaying the image from the entrance slit to the diffraction grating and from the diffraction grating to the spectrometer array. In one embodiment, the spectrometer is configured in a lateral mode in which the entrance slit and the spectrometer array are displaced laterally on opposite sides of the diffraction grating in a second direction substantially perpendicular to the first direction. In another embodiment, the spectrometer is combined with a polychromatic imaging camera array disposed adjacent said entrance slit for recording said image.

Infrared radiation from explosions in a spark-ignition engine

NASA Technical Reports Server (NTRS)

Marvin, Charles F , Jr; Caldwell, Frank R; Steele, Sydney

1935-01-01

This report presents the results of an investigation to determine the variations in intensity and spectral distribution of the radiant energy emitted by the flames during normal and knocking explosions in an engine. Radiation extending into the infrared was transmitted by a window of fluorite, placed either near the spark plug or over the detonation zone at opposite ends of the combustion chamber. Concave, surface-silvered mirrors focused the beam, first at the slit of a stroboscope which opened for about 2 degrees of crank angle at any desired point in the engine cycle, and then upon the target of a sensitive thermocouple for measuring radiation intensity. Spectral distribution of the radiant energy was determined by placing over the window, one at a time, a series of five filters selected with a view to identifying, as far as possible without the use of a spectrograph, the characteristic emissions of water vapor, carbon dioxide, and incandescent carbon.

Inquiry learning: Students' perception of light wave phenomena in an informal environment

NASA Astrophysics Data System (ADS)

Ford, Ken

This study involved identifying students' perception of light phenomena and determined if they learned the scientific concepts of light that were presented to them by an interactive science exhibit. The participants in this study made scientific inquiry about light by using a powerful white light source, a prism, converging lenses, diverging lenses, concave and convex mirrors in an informal science setting. The sample used in the study consisted of 40 subjects (15 males and 25 females) in a college program at a University located in the Southern region of the United States. The participants were selected using a convenient sampling process from a population enrolled in a pre-calculus class and a physics class. The participants were engaged in pretest on light wave phenomena using the Inquiry Laboratory Light Island exhibit. After the pretest, the participants were engaged in activities, where they reflected white light off the surface of concave and convex mirrors, refracted white light through converging and diverging lens, and passed white light through a prism. They also made observations of the behavior and characteristics of light from the patterns that it created. After three weeks, the participants were given the Inquiry Laboratory Light Island exhibit posttest. The findings of the study indicated that the means yielded a higher average for the participants' posttest scores. The t-Test results were statistically significant, which confirmed that the concepts of light wave phenomena were perceived and learned by the participants. The Inquiry Laboratory survey questions analyzed using the chi-square test suggested that participants were in agreement with the concepts about light. In addition, Cramer's phi and Cramer's V suggested a moderate relationship and association between the genders of the participants on the concepts of light wave phenomena. Furthermore, the interview and observation protocol processes confirmed that students perceived and learned the science concepts of light wave phenomena by the way they responded to the researcher's interview questions. Implications from the study suggested that further study be carried out on the learning process in an informal science setting and should be supported by corporations, businesses, educational institutions, and organizations. Although the findings from this study aided in the development of a structured approach that enhanced student motivation, interest, and learning about light waves in physics/physical science there is still a need to do more research in this area.

High-accuracy process based on the corrective calibration of removal function in the magnetorheological finishing

NASA Astrophysics Data System (ADS)

Zhong, Xianyun; Fan, Bin; Wu, Fan

2017-08-01

The corrective calibration of the removal function plays an important role in the magnetorheological finishing (MRF) high-accuracy process. This paper mainly investigates the asymmetrical characteristic of the MRF removal function shape and further analyzes its influence on the surface residual error by means of an iteration algorithm and simulations. By comparing the ripple errors and convergence ratios based on the ideal MRF tool function and the deflected tool function, the mathematical models for calibrating the deviation of horizontal and flowing directions are presented. Meanwhile, revised mathematical models for the coordinate transformation of an MRF machine is also established. Furthermore, a Ø140-mm fused silica plane and a Ø196 mm, f/1∶1, fused silica concave sphere samples are taken as the experiments. After two runs, the plane mirror final surface error reaches PV 17.7 nm, RMS 1.75 nm, and the polishing time is 16 min in total; after three runs, the sphere mirror final surfer error reaches RMS 2.7 nm and the polishing time is 70 min in total. The convergence ratios are 96.2% and 93.5%, respectively. The spherical simulation error and the polishing result are almost consistent, which fully validate the efficiency and feasibility of the calibration method of MRF removal function error using for the high-accuracy subaperture optical manufacturing.

Measurement of aspheric mirror by nanoprofiler using normal vector tracing

NASA Astrophysics Data System (ADS)

Kitayama, Takao; Shiraji, Hiroki; Yamamura, Kazuya; Endo, Katsuyoshi

2016-09-01

Aspheric or free-form optics with high accuracy are necessary in many fields such as third-generation synchrotron radiation and extreme-ultraviolet lithography. Therefore the demand of measurement method for aspherical or free-form surface with nanometer accuracy increases. Purpose of our study is to develop a non-contact measurement technology for aspheric or free-form surfaces directly with high repeatability. To achieve this purpose we have developed threedimensional Nanoprofiler which detects normal vectors of sample surface. The measurement principle is based on the straightness of laser light and the accurate motion of rotational goniometers. This machine consists of four rotational stages, one translational stage and optical head which has the quadrant photodiode (QPD) and laser source. In this measurement method, we conform the incident light beam to reflect the beam by controlling five stages and determine the normal vectors and the coordinates of the surface from signal of goniometers, translational stage and QPD. We can obtain three-dimensional figure from the normal vectors and their coordinates by surface reconstruction algorithm. To evaluate performance of this machine we measure a concave aspheric mirror with diameter of 150 mm. As a result we achieve to measure large area of 150mm diameter. And we observe influence of systematic errors which the machine has. Then we simulated the influence and subtracted it from measurement result.

A path following algorithm for the graph matching problem.

PubMed

Zaslavskiy, Mikhail; Bach, Francis; Vert, Jean-Philippe

2009-12-01

We propose a convex-concave programming approach for the labeled weighted graph matching problem. The convex-concave programming formulation is obtained by rewriting the weighted graph matching problem as a least-square problem on the set of permutation matrices and relaxing it to two different optimization problems: a quadratic convex and a quadratic concave optimization problem on the set of doubly stochastic matrices. The concave relaxation has the same global minimum as the initial graph matching problem, but the search for its global minimum is also a hard combinatorial problem. We, therefore, construct an approximation of the concave problem solution by following a solution path of a convex-concave problem obtained by linear interpolation of the convex and concave formulations, starting from the convex relaxation. This method allows to easily integrate the information on graph label similarities into the optimization problem, and therefore, perform labeled weighted graph matching. The algorithm is compared with some of the best performing graph matching methods on four data sets: simulated graphs, QAPLib, retina vessel images, and handwritten Chinese characters. In all cases, the results are competitive with the state of the art.

Mirror, Mirror by the Stairs: The Impact of Mirror Exposure on Stair versus Elevator Use in College Students.

PubMed

Hodgin, Katie L; Graham, Dan J

2016-01-01

Previous research has indicated that self-awareness-inducing mirrors can successfully incite behaviors that align with one's personal values, such as helping others. Other research has found a large discrepancy between the high percentage of young adults who report valuing the healthfulness of physical activity (PA) and the low percentage who actually meet PA participation standards. However, few studies have examined how mirror exposure and both perceived and actual body size influence highly valued PA participation among college students. The present study assessed stair versus elevator use on a western college campus and hypothesized that mirror exposure would increase the more personally healthy transportation method of stair use. In accordance with previous research, it was also hypothesized that males and those with a lower body mass index (BMI) would be more likely to take the stairs, and that body size distorting mirrors would impact the stair-elevator decision. One hundred sixty-seven students (51% male) enrolled in an introductory psychology course were recruited to take a survey about their "transportation choices" at an indoor campus parking garage. Participants were individually exposed to either no mirror, a standard full-length mirror, or a full-length mirror manipulated to make the reflected body size appear either slightly thinner or slightly wider than normal before being asked to go to the fourth floor of the garage for a survey. Participants' choice of floor-climbing method (stairs or elevator) was recorded, and they were administered an Internet-based survey assessing demographic information, BMI, self-awareness, perceived body size, and other variables likely to be associated with stair use. Results from logistic regression analyses revealed that participants who were not exposed to a mirror [odds ratios (OR) = 0.37, 95% CI: 0.14-0.96], males (OR = 0.33, 95% CI: 0.13-0.85), those with lower BMI (OR = 0.84, 95% CI: 0.71-0.99), those with higher exercise participation (OR = 1.09, 95% CI: 1.02-1.18), and those engaging in more unhealthy weight-control behaviors (OR = 1.55, 95% CI: 1.14-2.11) showed increased odds of taking the stairs. Implications and future directions are discussed.

Mirror, Mirror by the Stairs: The Impact of Mirror Exposure on Stair versus Elevator Use in College Students

PubMed Central

Hodgin, Katie L.; Graham, Dan J.

2016-01-01

Previous research has indicated that self-awareness-inducing mirrors can successfully incite behaviors that align with one’s personal values, such as helping others. Other research has found a large discrepancy between the high percentage of young adults who report valuing the healthfulness of physical activity (PA) and the low percentage who actually meet PA participation standards. However, few studies have examined how mirror exposure and both perceived and actual body size influence highly valued PA participation among college students. The present study assessed stair versus elevator use on a western college campus and hypothesized that mirror exposure would increase the more personally healthy transportation method of stair use. In accordance with previous research, it was also hypothesized that males and those with a lower body mass index (BMI) would be more likely to take the stairs, and that body size distorting mirrors would impact the stair–elevator decision. One hundred sixty-seven students (51% male) enrolled in an introductory psychology course were recruited to take a survey about their “transportation choices” at an indoor campus parking garage. Participants were individually exposed to either no mirror, a standard full-length mirror, or a full-length mirror manipulated to make the reflected body size appear either slightly thinner or slightly wider than normal before being asked to go to the fourth floor of the garage for a survey. Participants’ choice of floor-climbing method (stairs or elevator) was recorded, and they were administered an Internet-based survey assessing demographic information, BMI, self-awareness, perceived body size, and other variables likely to be associated with stair use. Results from logistic regression analyses revealed that participants who were not exposed to a mirror [odds ratios (OR) = 0.37, 95% CI: 0.14–0.96], males (OR = 0.33, 95% CI: 0.13–0.85), those with lower BMI (OR = 0.84, 95% CI: 0.71–0.99), those with higher exercise participation (OR = 1.09, 95% CI: 1.02–1.18), and those engaging in more unhealthy weight-control behaviors (OR = 1.55, 95% CI: 1.14–2.11) showed increased odds of taking the stairs. Implications and future directions are discussed. PMID:27200333

Initiation Capacity of a Specially Shaped Booster Pellet and Numerical Simulation of Its Initiation Process

NASA Astrophysics Data System (ADS)

Hu, Li-Shuang; Hu, Shuang-Qi; Cao, Xiong; Zhang, Jian-Ren

2014-01-01

The insensitive main charge explosive is creating new requirements for the booster pellet of detonation trains. The traditional cylindrical booster pellet has insufficient energy output to reliably initiate the insensitive main charge explosive. In this research, a concave spherical booster pellet was designed. The initiation capacity of the concave spherical booster pellet was studied using varied composition and axial steel dent methods. The initiation process of the concave spherical booster pellet was also simulated by ANSYS/LS-DYNA. The results showed that using a concave spherical booster allows a 42% reduction in the amount of explosive needed to match the initiation capacity of a conventional cylindrical booster of the same dimensions. With the other parameters kept constant, the initiation capacity of the concave spherical booster pellet increases with decreased cone angle and concave radius. The numerical simulation results are in good agreement with the experimental data.

Like No. 1 Mike Leavitt, most atop the 100 Most Powerful wield their influence from D.C., and help determine how money is spent.

PubMed

Romano, Michael

2005-08-22

Modem Healthcare's fourth annual ranking of the 100 Most Powerful People in Healthcare boasts an eclectic group. Those who practice medicine and teach it to others share the list with presidents of companies and the president of the country. Lawmakers and information technology risk-takers round out a roster that mirrors the industry's diversity and highlights the many ways people contribute to healthcare.

High voltage photo-switch package module having encapsulation with profiled metallized concavities

DOEpatents

Sullivan, James S; Sanders, David M; Hawkins, Steven A; Sampayan, Stephen A

2015-05-05

A photo-conductive switch package module having a photo-conductive substrate or wafer with opposing electrode-interface surfaces metalized with first metallic layers formed thereon, and encapsulated with a dielectric encapsulation material such as for example epoxy. The first metallic layers are exposed through the encapsulation via encapsulation concavities which have a known contour profile, such as a Rogowski edge profile. Second metallic layers are then formed to line the concavities and come in contact with the first metal layer, to form profiled and metalized encapsulation concavities which mitigate enhancement points at the edges of electrodes matingly seated in the concavities. One or more optical waveguides may also be bonded to the substrate for coupling light into the photo-conductive wafer, with the encapsulation also encapsulating the waveguides.

Profile convexities in bedrock and alluvial streams

NASA Astrophysics Data System (ADS)

Phillips, Jonathan D.; Lutz, J. David

2008-12-01

Longitudinal profiles of bedrock streams in central Kentucky, and of coastal plain streams in southeast Texas, were analyzed to determine the extent to which they exhibit smoothly concave profiles and to relate profile convexities to environmental controls. None of the Kentucky streams have smoothly concave profiles. Because all observed knickpoints are associated with vertical joints, if they are migrating it either occurs rapidly between vertical joints, or migrating knickpoints become stalled at structural features. These streams have been adjusting to downcutting of the Kentucky River for at least 1.3 Ma, suggesting that the time required to produce a concave profile is long compared to the typical timescale of environmental change. A graded concave longitudinal profile is not a reasonable prediction or benchmark condition for these streams. The characteristic profile forms of the Kentucky River gorge area are contingent on a particular combination of lithology, structure, hydrologic regime, and geomorphic history, and therefore do not represent any general type of equilibrium state. Few stream profiles in SE Texas conform to the ideal of the smoothly, strongly concave profile. Major convexities are caused by inherited topography, geologic controls, recent and contemporary geomorphic processes, and anthropic effects. Both the legacy of Quaternary environmental change and ongoing changes make it unlikely that consistent boundary conditions will exist for long. Further, the few exceptions within the study area-i.e., strongly and smoothly concave longitudinal profiles-suggest that ample time has occurred for strongly concave profiles to develop and that such profiles do not necessarily represent any mutual adjustments between slope, transport capacity, and sediment supply. The simplest explanation of any tendency toward concavity is related to basic constraints on channel steepness associated with geomechanical stability and minimum slopes necessary to convey flow. This constrained gradient concept (CGC) can explain the general tendency toward concavity in channels of sufficient size, with minimal lithological constraints and with sufficient time for adjustment. Unlike grade- or equilibrium-based theories, the CGC results in interpretations of convex or low-concavity profiles or reaches in terms of local environmental constraints and geomorphic histories rather than as "disequilibrium" features.

Slope gradient and shape effects on soil profiles in the northern mountainous forests of Iran

NASA Astrophysics Data System (ADS)

Fazlollahi Mohammadi, M.; Jalali, S. G. H.; Kooch, Y.; Said-Pullicino, D.

2016-12-01

In order to evaluate the variability of the soil profiles at two shapes (concave and convex) and five positions (summit, shoulder, back slope, footslope and toeslope) of a slope, a study of a virgin area was made in a Beech stand of mountain forests, northern Iran. Across the slope positions, the soil profiles demonstrated significant changes due to topography for two shape slopes. The solum depth of the convex slope was higher than the concave one in all five positions, and it decreased from the summit to shoulder and increased from the mid to lower slope positions for both convex and concave slopes. The thin solum at the upper positions and concave slope demonstrated that pedogenetic development is least at upper slope positions and concave slope where leaching and biomass productivity are less than at lower slopes and concave slope. A large decrease in the thickness of O and A horizons from the summit to back slope was noted for both concave and convex slopes, but it increased from back slope toward down slope for both of them. The average thickness of B horizons increased from summit to down slopes in the case of the concave slope, but in the case of convex slope it decreased from summit to shoulder and afterwards it increased to the down slope. The thicknesses of the different horizons varied in part in the different positions and shape slopes because they had different plant species cover and soil features, which were related to topography.

Methods and apparatus for laser beam scanners with different actuating mechanisms

NASA Astrophysics Data System (ADS)

Chen, Si-hai; Xiang, Si-hua; Wu, Xin; Dong, Shan; Xiao, Ding; Zheng, Xia-wei

2009-07-01

In this paper, 3 types of laser beam scanner are introduced. One is transmissive beam scanner, which is composed of convex and concave microlens arrays (MLAs). By moving the concave lens in the plane vertical to the optical axis, the incident beam can be deflected in two dimensions. Those two kinds of MLAs are fabricated by thermal reflow and replication process. A set of mechanical scanner frame is fabricated with the two MLAs assembling in it. The testing result shown that the beam deflection angles are 9.5° and 9.6°, in the 2 dimension(2D) with the scanning frequency of 2 HZ and 8 HZ, respectively. The second type of laser beam scanner is actuated by voice coil actuators (VCAs). Based on ANSOFT MAXWELL software, we have designed VCAs with small size and large force which have optimized properties. The model of VCAs is built using AutoCAD and is analyzed by Ansoft maxwell. According to the simulation results, high performance VCAs are fabricated and tested. The result is that the force of the VCAs is 6.39N/A, and the displacement is +/-2.5mm. A set up of beam scanner is fabricated and actuated by the designed VCAs. The testing result shown that the two dimensional scanning angle is 15° and 10° respectively at the frequency of 60HZ. The two dimensional scanning angle is 8.3° and 6° respectively at the frequency of 100HZ. The third type of scanner is actuated by amplified piezoelectric actuators (APAs). The scanning mirror is actuated by the piezoelectric (PZ) actuators with the scanning frequency of 700HZ, 250HZ and 87HZ respectively. The optical scanning angle is +/-0.5° at the three frequencies.

On the impact of a concave nosed axisymmetric body on a free surface

NASA Astrophysics Data System (ADS)

Mathai, Varghese; Govardhan, Raghuraman N.; Arakeri, Vijay H.

2015-02-01

We report on an experimental study of the vertical impact of a concave nosed axisymmetric body on a free surface. Previous studies have shown that bodies with a convex nose, like a sphere, produce a well defined splash with a relatively large cavity behind the model. In contrast, we find that with a concave nose, there is hardly a splash and the cavity extent is greatly reduced. This may be explained by the fact that in the concave nosed case, the initial impact is between a confined air pocket and the free surface unlike in the convex nosed case. From measurements of the unsteady pressure in the concave nose portion, we show that in this case, the maximum pressures are significantly lower than the classically expected "water hammer" pressures and also lower than those generally measured on other geometries. Thus, the presence of an air pocket in the case of a concave nosed body adds an interesting dimension to the classical problem of impact of solid bodies on to a free surface.

Optical design for ATHENA X-ray telescope based on slumped mirror segments

NASA Astrophysics Data System (ADS)

Proserpio, Laura; Breunig, Elias; Friedrich, Peter; Winter, Anita

2014-07-01

The Hot and Energetic Universe will be the focus of future ESA missions: in late 2013 the theme was selected for the second large-class mission in the Cosmic Vision science program. Fundamental questions on how and why ordinary matter assemble into galaxies and clusters, and how black holes grow and influence their surroundings can be addressed with an advanced X-ray observatory. The currently proposed ATHENA mission presents all the potentiality to answer the outstanding questions. It is based on the heritage of XMM-Newton and on the previous studies for IXO mission. The scientific payload will require state of the art instrumentations. In particular, the baseline for the X-ray optical system, delivering a combination of large area, high angular resolution, and large field of view, is the Silicon Pore Optics technology (SPO) developed by ESA in conjunction with the Cosine Measurement Systems. The slumping technology is also under development for the manufacturing of future X-ray telescopes: for several years the Max Planck Institute for Extraterrestrial physics (MPE) has been involved in the analysis of the indirect slumping approach, which foresees the manufacturing of segmented X-ray shells by shaping thin glass foils at high temperatures over concave moulds so to avoid any contact of the optical surface with other materials during the process, preserving in this way the original X-ray quality of the glass surface. The paper presents an alternative optical design for ATHENA based on the use of thin glass mirror segments obtained through slumping.

Measurement of super large radius optics in the detection of gravitational waves

NASA Astrophysics Data System (ADS)

Yang, Cheng; Han, Sen; Wu, Quanying; Liang, Binming; Hou, Changlun

2015-10-01

The existence of Gravitational Wave (GW) is one of the greatest predictions of Einstein's relative theory. It has played an important part in the radiation theory, black hole theory, space explore and so on. The GW detection has been an important aspect of modern physics. With the research proceeding further, there are still a lot of challenges existing in the interferometer which is the key instrument in GW detection especially the measurement of the super large radius optics. To solve this problem, one solution , Fizeau interference, for measuring the super large radius has been presented. We change the tradition that curved surface must be measured with a standard curved surface. We use a flat mirror as a reference flat and it can lower both the cost and the test requirement a lot. We select a concave mirror with the radius of 1600mm as a sample. After the precision measurement and analysis, the experimental results show that the relative error of radius is better than 3%, and it can fully meet the requirements of the measurement of super large radius optics. When calculating each pixel with standard cylinder, the edges are not sharp because of diffraction or some other reasons, we detect the edge and calculate the diameter of the cylinder automatically, and it can improve the precision a lot. In general, this method is simple, fast, non-traumatic, and highly precision, it can also provide us a new though in the measurement of super large radius optics.

The measurement of an aspherical mirror by three-dimensional nanoprofiler

NASA Astrophysics Data System (ADS)

Tokuta, Yusuke; Okita, Kenya; Okuda, Kohei; Kitayama, Takao; Nakano, Motohiro; Nakatani, Shun; Kudo, Ryota; Yamamura, Kazuya; Endo, Katsuyoshi

2015-09-01

Aspherical optical elements with high accuracy are important in several fields such as third-generation synchrotron radiation and extreme-ultraviolet lithography. Then the demand of measurement method for aspherical or free-form surface with nanometer resolution is rising. Our purpose is to develop a non-contact profiler to measure free-form surfaces directly with repeatability of figure error of less than 1 nm PV. To achieve this purpose we have developed three-dimensional Nanoprofiler which traces normal vectors of sample surface. The measurement principle is based on the straightness of LASER light and the accuracy of a rotational goniometer. This machine consists of four rotational stages, one translational stage and optical head which has the quadrant photodiode (QPD) and LASER head at optically equal position. In this measurement method, we conform the incident light beam to reflect the beam by controlling five stages and determine the normal vectors and the coordinates of the surface from signal of goniometers, translational stage and QPD. We can obtain three-dimensional figure from the normal vectors and the coordinates by a reconstruction algorithm. To evaluate performance of this machine we measure a concave aspherical mirror ten times. From ten results we calculate measurement repeatability, and we evaluate measurement uncertainty to compare the result with that measured by an interferometer. In consequence, the repeatability of measurement was 2.90 nm (σ) and the difference between the two profiles was +/-20 nm. We conclude that the two profiles was correspondent considering systematic errors of each machine.

"First Light" Approaches for VLT MELIPAL

NASA Astrophysics Data System (ADS)

2000-01-01

The year 1999 was a very busy one at ESO's Paranal Observatory , the site of the Very Large Telescope (VLT). Soon after the official Inauguration on March 5, 1999, regular observations started with the first 8.2-m VLT Unit Telescope ANTU . During the first nine months of operation (April - December 1999), about 79,000 exposures were made with the FORS1 and ISAAC astronomical instruments at this telescope. Altogether, more than 68 Gigabytes of unique data were gathered during this period for about 200 individual research programmes and stored in the VLT Data Archive. "First Light" was successfully achieved early in the year for the second 8.2-m VLT Unit telescope, KUEYEN . It has since been equipped with two powerful instruments, UVES and FORS2. Science observations with this telescope will start on April 1, 2000. Already in early December 1999, ahead of the schedule, the third 8.2-m Zerodur mirror in its cell was attached to the third 8.2-m VLT Unit Telescope, MELIPAL , cf. ESO PR Photos 42a-ad/99. The moment of "First Light" is approaching for this telescope. Originally planned for mid-February 2000, this significant event is now expected to take place about two weeks ahead of schedule, in late January 2000. From then on, the VLT will possess nearly 160 square metres of extremely accurate, highly reflecting mirror surface. While the observations for "First Light" and the subsequent commissioning period will be carried out with the VLT Test Camera, MELIPAL will receive its first special astronomical instrument, the VIsible MultiObject Spectrograph (VIMOS) towards the middle of the year. It is optimized for large field imaging and spectroscopic surveys and will become a real workhorse of the VLT for this type of research projects, together with the Near InfraRed MultiObject Spectrograph (NIRMOS) , to be installed later at the fourth 8.2-m Unit Telescope, YEPUN . YEPUN will have "First Light" later this year and the work on this telescope also progresses well. The "M1 Dummy" that was mounted on the telescope frame for balance during the mechanical assembly was removed on January 4. The next day, it was transported down to the Base Camp storage area where it was lifted off the Carriage using a combination of two cranes. The empty M1 Carriage was then moved to the Mirror Maintenance Building (MMB) where the fourth M1 Cell with a dummy concrete mirror was loaded. Later that day it was transported up to YEPUN and the next morning (January 6), the Mirror Cell was moved inside the enclosure. Over the next weeks, it will be fitted to the back of the telescope structure. In parallel, the "M2 Unit" on which the 1.1-m secondary mirror of beryllium will later be mounted, is now being assembled in the Integration Laboratory in the MMB. The following digital photos were obtained during the past days and illustrate the recent work.

[Design method of convex master gratings for replicating flat-field concave gratings].

PubMed

Zhou, Qian; Li, Li-Feng

2009-08-01

Flat-field concave diffraction grating is the key device of a portable grating spectrometer with the advantage of integrating dispersion, focusing and flat-field in a single device. It directly determines the quality of a spectrometer. The most important two performances determining the quality of the spectrometer are spectral image quality and diffraction efficiency. The diffraction efficiency of a grating depends mainly on its groove shape. But it has long been a problem to get a uniform predetermined groove shape across the whole concave grating area, because the incident angle of the ion beam is restricted by the curvature of the concave substrate, and this severely limits the diffraction efficiency and restricts the application of concave gratings. The authors present a two-step method for designing convex gratings, which are made holographically with two exposure point sources placed behind a plano-convex transparent glass substrate, to solve this problem. The convex gratings are intended to be used as the master gratings for making aberration-corrected flat-field concave gratings. To achieve high spectral image quality for the replicated concave gratings, the refraction effect at the planar back surface and the extra optical path lengths through the substrate thickness experienced by the two divergent recording beams are considered during optimization. This two-step method combines the optical-path-length function method and the ZEMAX software to complete the optimization with a high success rate and high efficiency. In the first step, the optical-path-length function method is used without considering the refraction effect to get an approximate optimization result. In the second step, the approximate result of the first step is used as the initial value for ZEMAX to complete the optimization including the refraction effect. An example of design problem was considered. The simulation results of ZEMAX proved that the spectral image quality of a replicated concave grating is comparable with that of a directly recorded concave grating.

Optical design of a stigmatic spectroheliometer for photometric studies of dynamic phenomena at extreme-ultraviolet wavelengths

NASA Technical Reports Server (NTRS)

Huber, M. C. E.; Timothy, J. G.

1977-01-01

The design of a stigmatic spectroheliometer for photometric studies of dynamic phenomena in the solar atmosphere at extreme ultraviolet (EUV) wavelengths is described. The normal-incidence spectrometer requires only one reflective surface, and is equipped with a series of exit slits and associated one-dimensional detector arrays that are mounted at the secondary (vertical) foci of the concave diffraction grating. It is shown that such a spectrometer mounted at the focus of an off-axis paraboloid telescope mirror of the size employed in the EUV spectroheliometer flown on Skylab could record monochromatic images of a 2 x 2 (arcmin) sq field-of-view with a spatial resolution element of 1 x 1 (arcsec) sq in a time of 4 s, 24 s, or 4 min, depending on whether the region studied is flaring, active, or quiet. The resulting spectroheliograms would have an average photometric precision of 10% and a spectral purity of 0.1 A.

Injection molding lens metrology using software configurable optical test system

NASA Astrophysics Data System (ADS)

Zhan, Cheng; Cheng, Dewen; Wang, Shanshan; Wang, Yongtian

2016-10-01

Optical plastic lens produced by injection molding machine possesses numerous advantages of light quality, impact resistance, low cost, etc. The measuring methods in the optical shop are mainly interferometry, profile meter. However, these instruments are not only expensive, but also difficult to alignment. The software configurable optical test system (SCOTS) is based on the geometry of the fringe refection and phase measuring deflectometry method (PMD), which can be used to measure large diameter mirror, aspheric and freeform surface rapidly, robustly, and accurately. In addition to the conventional phase shifting method, we propose another data collection method called as dots matrix projection. We also use the Zernike polynomials to correct the camera distortion. This polynomials fitting mapping distortion method has not only simple operation, but also high conversion precision. We simulate this test system to measure the concave surface using CODE V and MATLAB. The simulation results show that the dots matrix projection method has high accuracy and SCOTS has important significance for on-line detection in optical shop.

A 5mm catheter for constant resolution probing in Fourier domain optical coherence endoscopy

NASA Astrophysics Data System (ADS)

Lee, Kye-Sung; Wu, Lei; Xie, Huikai; Ilegbusi, Olusegun; Costa, Marco; Rolland, Jannick P.

2007-02-01

A 5mm biophotonic catheter was conceived for optical coherence tomography (OCT) with collimation optics, an axicon lens, and custom design imaging optics, yielding a 360 degree scan aimed at imaging within concave structures such as lung lobes. In OCT a large depth of focus is necessary to image a thick sample with a constant high transverse resolution. There are two approaches to achieving constant lateral resolution in OCT: Dynamic focusing or Bessel beam forming. This paper focuses on imaging with Bessel beams. A Bessel beam can be generated in the sample arm of the OCT interferometer when axicon optics is employed instead of a conventional focusing lens. We present a design for a 5mm catheter that combines an axicon lens with imaging optics and the coupling of a MEMS mirror attached to a micromotor that allow 360 degree scanning with a resolution of about 5 microns across a depth of focus of about 1.2mm.

Optical system design, analysis, and production for advanced technology systems; Proceedings of the Meeting, Innsbruck, Austria, Apr. 15-17, 1986

NASA Technical Reports Server (NTRS)

Fischer, Robert E. (Editor); Rogers, Philip J. (Editor)

1986-01-01

The present conference considers topics in the fields of optical systems design software, the design and analysis of optical systems, illustrative cases of advanced optical system design, the integration of optical designs into greater systems, and optical fabrication and testing techniques. Attention is given to an extended range diffraction-based merit function for lens design optimization, an assessment of technologies for stray light control and evaluation, the automated characterization of IR systems' spatial resolution, a spectrum of design techniques based on aberration theory, a three-field IR telescope, a large aperture zoom lens for 16-mm motion picture cameras, and the use of concave holographic gratings as monochomators. Also discussed are the use of aspherics in optical systems, glass choice procedures for periscope design, the fabrication and testing of unconventional optics, low mass mirrors for large optics, and the diamond grinding of optical surfaces on aspheric lens molds.

Spectral sideband produced by a hemispherical concave multilayer on the African shield-bug Calidea panaethiopica (Scutelleridae)

NASA Astrophysics Data System (ADS)

Vigneron, Jean Pol; Ouedraogo, Moussa; Colomer, Jean-François; Rassart, Marie

2009-02-01

The African shield-backed bug Calidea panaethiopica is a very colorful insect which produces a range of iridescent yellow, green, and blue reflections. The cuticle of the dorsal side of the insect, on the shield, the prothorax and part of the head, is pricked of uniformly distributed hemispherical hollow cavities a few tens micrometers deep. Under normal illumination and viewing the insect’s muffin-tin shaped surface gives rise to two distinct colors: a yellow spot arising from the bottom of the well and a blue annular cloud that appears to float around the yellow spot. This effect is explained by multiple reflections on a hemispherical Bragg mirror with a mesoscopic curvature. A multiscale computing methodology was found to be needed to evaluate the reflection spectrum for such a curved multilayer. This multiscale approach is very general and should be useful for dealing with visual effects in many natural and artificial systems.

Anatomical study of the pelvis in patients with adolescent idiopathic scoliosis

PubMed Central

Qiu, Xu-Sheng; Zhang, Jun-Jie; Yang, Shang-Wen; Lv, Feng; Wang, Zhi-Wei; Chiew, Jonathan; Ma, Wei-Wei; Qiu, Yong

2012-01-01

Standing posterior–anterior (PA) radiographs from our clinical practice show that the concave and convex ilia are not always symmetrical in patients with adolescent idiopathic scoliosis (AIS). Transverse pelvic rotation may explain this observation, or pelvic asymmetry may be responsible. The present study investigated pelvic symmetry by examining the volume and linear measurements of the two hipbones in patients with AIS. Forty-two female patients with AIS were recruited for the study. Standing PA radiographs (covering the thoracic and lumbar spinal regions and the entire pelvis), CT scans and 3D reconstructions of the pelvis were obtained for all subjects. The concave/convex ratio of the inferior ilium at the sacroiliac joint medially (SI) and the anterior superior iliac spine laterally (ASIS) were measured on PA radiographs. Hipbone volumes and several distortion and abduction parameters were measured by post-processing software. The concave/convex ratio of SI–ASIS on PA radiographs was 0.97, which was significantly < 1 (P < 0.001). The concave and convex hipbone volumes were comparable in patients with AIS. The hipbone volumes were 257.3 ± 43.5 cm3 and 256.9 ± 42.6 cm3 at the concave and convex sides, respectively (P > 0.05). Furthermore, all distortion and abduction parameters were comparable between the convex and concave sides. Therefore, the present study showed that there was no pelvic asymmetry in patients with AIS, although the concave/convex ratio of SI–ASIS on PA radiographs was significantly < 1. The clinical phenomenon of asymmetrical concave and convex ilia in patients with AIS in preoperative standing PA radiographs may be caused by transverse pelvic rotation, but it is not due to developmental asymmetry or distortion of the pelvis. PMID:22133294

Anatomical study of the pelvis in patients with adolescent idiopathic scoliosis.

PubMed

Qiu, Xu-Sheng; Zhang, Jun-Jie; Yang, Shang-Wen; Lv, Feng; Wang, Zhi-Wei; Chiew, Jonathan; Ma, Wei-Wei; Qiu, Yong

2012-02-01

Standing posterior-anterior (PA) radiographs from our clinical practice show that the concave and convex ilia are not always symmetrical in patients with adolescent idiopathic scoliosis (AIS). Transverse pelvic rotation may explain this observation, or pelvic asymmetry may be responsible. The present study investigated pelvic symmetry by examining the volume and linear measurements of the two hipbones in patients with AIS. Forty-two female patients with AIS were recruited for the study. Standing PA radiographs (covering the thoracic and lumbar spinal regions and the entire pelvis), CT scans and 3D reconstructions of the pelvis were obtained for all subjects. The concave/convex ratio of the inferior ilium at the sacroiliac joint medially (SI) and the anterior superior iliac spine laterally (ASIS) were measured on PA radiographs. Hipbone volumes and several distortion and abduction parameters were measured by post-processing software. The concave/convex ratio of SI-ASIS on PA radiographs was 0.97, which was significantly < 1 (P < 0.001). The concave and convex hipbone volumes were comparable in patients with AIS. The hipbone volumes were 257.3 ± 43.5 cm(3) and 256.9 ± 42.6 cm(3) at the concave and convex sides, respectively (P > 0.05). Furthermore, all distortion and abduction parameters were comparable between the convex and concave sides. Therefore, the present study showed that there was no pelvic asymmetry in patients with AIS, although the concave/convex ratio of SI-ASIS on PA radiographs was significantly < 1. The clinical phenomenon of asymmetrical concave and convex ilia in patients with AIS in preoperative standing PA radiographs may be caused by transverse pelvic rotation, but it is not due to developmental asymmetry or distortion of the pelvis. © 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society.

A 15-MHz 1-3 Piezocomposite Concave Array Transducer for Ophthalmic Imaging.

PubMed

Cha, Jung Hyui; Kang, Byungwoo; Jang, Jihun; Chang, Jin Ho

2015-11-01

Because of the spherical shape of the human eye, the anterior segments of the eye, particularly the cornea and the lens, create high levels of refraction and reflection of ultrasound which negatively affect the performance of linear and convex arrays. To minimize the ultrasound energy loss, a 15-MHz concave array transducer was designed, fabricated, and characterized; its footprint is able to mesh well with the shape of the cornea. The concave array has a curvature with a radius of 15 mm and 128 elements with a 1.44- pitch. Its elevational focus and view angle are 30 mm and 72.3°, respectively, thus allowing the imaging area to cover the retinal region of interest in the posterior segment. As an active layer, a 1-3 piezocomposite was designed and fabricated in response to the bidirectional (i.e., azimuthal and elevational) curvature of the concave array and the high coupling coefficient. From the performance evaluation, it was found that the completed concave array is able to provide a center frequency of 15.95 MHz and a -6-dB fractional bandwidth of 67.8% after electrical tuning has been conducted. The crosstalk level was measured to be less than -25 dB. It was verified that the concave array is robust to the refraction and reflection from the cornea through pulse-echo testing using a custom-made eye-mimicking phantom. Furthermore, images of both the wire-target phantom and the ex vivo porcine eye were acquired by the finished concave array, which was connected to a commercial ultrasound scanner equipped with a research package. The evaluation results demonstrated that the developed concave array transducer is a possible alternative to conventional arrays for effectively imaging the posterior segment of the eye.

Semiconductor light-emitting devices having concave microstructures providing improved light extraction efficiency and method for producing same

DOEpatents

Tansu, Nelson; Gilchrist, James F; Ee, Yik-Khoon; Kumnorkaew, Pisist

2013-11-19

A conventional semiconductor LED is modified to include a microlens layer over its light-emitting surface. The LED may have an active layer including at least one quantum well layer of InGaN and GaN. The microlens layer includes a plurality of concave microstructures that cause light rays emanating from the LED to diffuse outwardly, leading to an increase in the light extraction efficiency of the LED. The concave microstructures may be arranged in a substantially uniform array, such as a close-packed hexagonal array. The microlens layer is preferably constructed of curable material, such as polydimethylsiloxane (PDMS), and is formed by soft-lithography imprinting by contacting fluid material of the microlens layer with a template bearing a monolayer of homogeneous microsphere crystals, to cause concave impressions, and then curing the material to fix the concave microstructures in the microlens layer and provide relatively uniform surface roughness.

Efficient proton acceleration and focusing by an ultraintense laser interacting with a parabolic double concave target with an extended rear

NASA Astrophysics Data System (ADS)

Bake, Muhammad Ali; Xie, Bai-Song; Aimidula, Aimierding; Wang, Hong-Yu

2013-07-01

A new scheme for acceleration and focusing of protons via an improved parabolic double concave target irradiated by an ultraintense laser pulse is proposed. When an intense laser pulse illuminates a concave target, the hot electrons are concentrated on the focal region of the rear cavity and they form a strong space-charge-separation field, which accelerates the protons. For a simple concave target, the proton energy spectrum becomes very broad outside the rear cavity because of transverse divergence of the electromagnetic fields. However, particle-in-cell simulations show that, when the concave target has an extended rear, the hot electrons along the wall surface induce a transverse focusing sheath field, resulting in a clear enhancement of proton focusing, which makes the lower proton energy spread, while, leads to a little reduction of the proton bunch peak energy.

Improving Beamline X-ray Optics by Analyzing the Damage to Crystallographic Structure

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

Zientek, John; Maj, Jozef; Navrotski, Gary

2015-01-02

The mission of the X-ray Characterization Laboratory in the X-ray Science Division (XSD) at the Advanced Photon Source (APS) is to support both the users and the Optics Fabrication Facility that produces high performance optics for synchrotron X-ray beamlines. The Topography Test Unit (TTU) in the X-ray Lab has been successfully used to characterize diffracting crystals and test monochromators by quantifying residual surface stresses. This topographic method has also been adapted for testing standard X-ray mirrors, characterizing concave crystal optics and in principle, can be used to visualize residual stresses on any optic made from single crystalline material. The TTUmore » has been instrumental in quantitatively determining crystal mounting stresses which are mechanically induced by positioning, holding, and cooling fixtures. It is this quantitative aspect that makes topography so useful since the requirements and responses for crystal optics and X-ray mirrors are quite different. In the case of monochromator crystals, even small residual or induced stresses, on the order of tens of kPa, can cause detrimental distortions to the perfect crystal rocking curves. Mirrors, on the other hand, are much less sensitive to induced stresses where stresses that are an order of magnitude greater can be tolerated. This is due to the fact that the surface rather than the lattice-spacing determines a mirror’s performance. For the highly sensitive crystal optics, it is essential to measure the in-situ rocking curves using topographs as mounting fixtures are adjusted. In this way, high heat-load monochromator crystals can be successfully mounted with minimum stress. Topographical analysis has been shown to be a highly effective method to visualize and quantify the distribution of stresses, to help identify methods that mitigate stresses, and most notably to improve diffractive crystal optic rocking curves.« less

Programmable Illumination and High-Speed, Multi-Wavelength, Confocal Microscopy Using a Digital Micromirror

PubMed Central

Martial, Franck P.; Hartell, Nicholas A.

2012-01-01

Confocal microscopy is routinely used for high-resolution fluorescence imaging of biological specimens. Most standard confocal systems scan a laser across a specimen and collect emitted light passing through a single pinhole to produce an optical section of the sample. Sequential scanning on a point-by-point basis limits the speed of image acquisition and even the fastest commercial instruments struggle to resolve the temporal dynamics of rapid cellular events such as calcium signals. Various approaches have been introduced that increase the speed of confocal imaging. Nipkov disk microscopes, for example, use arrays of pinholes or slits on a spinning disk to achieve parallel scanning which significantly increases the speed of acquisition. Here we report the development of a microscope module that utilises a digital micromirror device as a spatial light modulator to provide programmable confocal optical sectioning with a single camera, at high spatial and axial resolution at speeds limited by the frame rate of the camera. The digital micromirror acts as a solid state Nipkov disk but with the added ability to change the pinholes size and separation and to control the light intensity on a mirror-by-mirror basis. The use of an arrangement of concave and convex mirrors in the emission pathway instead of lenses overcomes the astigmatism inherent with DMD devices, increases light collection efficiency and ensures image collection is achromatic so that images are perfectly aligned at different wavelengths. Combined with non-laser light sources, this allows low cost, high-speed, multi-wavelength image acquisition without the need for complex wavelength-dependent image alignment. The micromirror can also be used for programmable illumination allowing spatially defined photoactivation of fluorescent proteins. We demonstrate the use of this system for high-speed calcium imaging using both a single wavelength calcium indicator and a genetically encoded, ratiometric, calcium sensor. PMID:22937130

Programmable illumination and high-speed, multi-wavelength, confocal microscopy using a digital micromirror.

PubMed

Martial, Franck P; Hartell, Nicholas A

2012-01-01

Confocal microscopy is routinely used for high-resolution fluorescence imaging of biological specimens. Most standard confocal systems scan a laser across a specimen and collect emitted light passing through a single pinhole to produce an optical section of the sample. Sequential scanning on a point-by-point basis limits the speed of image acquisition and even the fastest commercial instruments struggle to resolve the temporal dynamics of rapid cellular events such as calcium signals. Various approaches have been introduced that increase the speed of confocal imaging. Nipkov disk microscopes, for example, use arrays of pinholes or slits on a spinning disk to achieve parallel scanning which significantly increases the speed of acquisition. Here we report the development of a microscope module that utilises a digital micromirror device as a spatial light modulator to provide programmable confocal optical sectioning with a single camera, at high spatial and axial resolution at speeds limited by the frame rate of the camera. The digital micromirror acts as a solid state Nipkov disk but with the added ability to change the pinholes size and separation and to control the light intensity on a mirror-by-mirror basis. The use of an arrangement of concave and convex mirrors in the emission pathway instead of lenses overcomes the astigmatism inherent with DMD devices, increases light collection efficiency and ensures image collection is achromatic so that images are perfectly aligned at different wavelengths. Combined with non-laser light sources, this allows low cost, high-speed, multi-wavelength image acquisition without the need for complex wavelength-dependent image alignment. The micromirror can also be used for programmable illumination allowing spatially defined photoactivation of fluorescent proteins. We demonstrate the use of this system for high-speed calcium imaging using both a single wavelength calcium indicator and a genetically encoded, ratiometric, calcium sensor.

Sagittal endplate morphology of the lower lumbar spine.

PubMed

Lakshmanan, Palaniappan; Purushothaman, Balaji; Dvorak, Vlasta; Schratt, Walter; Thambiraj, Sathya; Boszczyk, Maximilian

2012-05-01

The sagittal profile of lumbar endplates is discrepant from current simplified disc replacement and fusion device design. Endplate concavity is symmetrical in the coronal plane but shows considerable variability in the sagittal plane, which may lead to implant-endplate mismatch. The aim of this investigation is to provide further analysis of the sagittal endplate morphology of the mid to lower lumbar spine study (L3–S1), thereby identifying the presence of common endplate shape patterns across these levels and providing morphological reference values complementing the findings of previous studies. Observational study. A total of 174 magnetic resonance imaging (MRI) scans of the adult lumbar spine from the digital archive of our centre, which met the inclusion criteria, were studied. Superior (SEP) and inferior (IEP) endplate shape was divided into flat (no concavity), oblong (homogeneous concavity) and ex-centric (inhomogeneous concavity). The concavity depth (ECD) and location of concavity apex (ECA) relative to endplate diameter of the vertebrae L3–S1 were determined. Flat endplates were only predominant at the sacrum SEP (84.5%). The L5 SEP was flat in 24.7% and all other endplates in less than 10%. The majority of endplates were concave with a clear trend of endplate shape becoming more ex-centric from L3 IEP (56.9% oblong vs. 37.4% ex-centric) to L5 IEP (4% oblong vs. 94.3% ex-centric). Ex-centric ECA were always found in the posterior half of the lumbar endplates. Both the oblong and ex-centric ECD was 2-3 mm on average with the IEP of a motion segment regularly possessing the greater depth. A sex- or age-related difference could not be found. The majority of lumbar endplates are concave, while the majority of sacral endplates are flat. An oblong and an ex-centric endplate shape can be distinguished, whereby the latter is more common at the lower lumbar levels. The apex of the concavity of ex-centric discs is located in the posterior half of the endplate and the concavity of the inferior endplate is deeper than that of the superior endplate. Based on the above, the current TDR and ALIF implant design does not sufficiently match the morphology of lumbar endplates in the sagittal plane.

Convexity and concavity constants in Lorentz and Marcinkiewicz spaces

NASA Astrophysics Data System (ADS)

Kaminska, Anna; Parrish, Anca M.

2008-07-01

We provide here the formulas for the q-convexity and q-concavity constants for function and sequence Lorentz spaces associated to either decreasing or increasing weights. It yields also the formula for the q-convexity constants in function and sequence Marcinkiewicz spaces. In this paper we extent and enhance the results from [G.J.O. Jameson, The q-concavity constants of Lorentz sequence spaces and related inequalities, Math. Z. 227 (1998) 129-142] and [A. Kaminska, A.M. Parrish, The q-concavity and q-convexity constants in Lorentz spaces, in: Banach Spaces and Their Applications in Analysis, Conference in Honor of Nigel Kalton, May 2006, Walter de Gruyter, Berlin, 2007, pp. 357-373].

Rotating concave eddy current probe

DOEpatents

Roach, Dennis P [Albuquerque, NM; Walkington, Phil [Albuquerque, NM; Rackow, Kirk A [Albuquerque, NM; Hohman, Ed [Albuquerque, NM

2008-04-01

A rotating concave eddy current probe for detecting fatigue cracks hidden from view underneath the head of a raised head fastener, such as a buttonhead-type rivet, used to join together structural skins, such as aluminum aircraft skins. The probe has a recessed concave dimple in its bottom surface that closely conforms to the shape of the raised head. The concave dimple holds the probe in good alignment on top of the rivet while the probe is rotated around the rivet's centerline. One or more magnetic coils are rigidly embedded within the probe's cylindrical body, which is made of a non-conducting material. This design overcomes the inspection impediment associated with widely varying conductivity in fastened joints.

Nanoantennas for enhancing and confining the magnetic optical field

NASA Astrophysics Data System (ADS)

Grosjean, Thierry; Mivelle, Mathieu; Baida, Fadi I.; Burr, Geoffrey W.; Fischer, Ulrich C.

2011-05-01

We propose different optical antenna structures for enhancing and confining the magnetic optical field. A common feature of these structures are concave corners in thin metal films as locations of the enhanced magnetic field. This proposal is inspired by Babinet's principle as the concave edges are the complementary structures to convex metal corners, which are known to be locations of a strongly enhanced electric field. Bowtie antennas and the bowtie apertures of appropriate size were shown to exhibit resonances in the infrared frequency range with an especially strong enhancement of the electrical field in the gap between 2 convex metal corners. We show by numerical calculations, that the complementary structures, the complementary bowtie aperture - the diabolo antenna - and the complementary bow tie antenna - two closely spaced triangular apertures in a metal film with a narrow gap between two opposing concave corners - exhibit resonances with a strongly enhanced magnetic field at the narrow metal constriction between the concave corners. We suggest sub-wavelength circuits of concave and convex corners as building blocks of planar metamaterials.

Light-trapping surface coating with concave arrays for efficiency enhancement in amorphous silicon thin-film solar cells

NASA Astrophysics Data System (ADS)

Liu, Daiming; Wang, Qingkang

2018-08-01

Light trapping is particularly important because of the desire to produce low-cost solar cells with the thinnest possible photoactive layers. Herein, along the research line of "optimization →fabrication →characterization →application", concave arrays were incorporated into amorphous silicon thin-film solar cell for lifting its photoelectric conversion efficiency. In advance, based on rigorous coupled wave analysis method, optics simulations were performed to obtain the optimal period of 10 μm for concave arrays. Microfabrication processes were used to etch concave arrays on glass, and nanoimprint was devoted to transfer the pattern onto polymer coatings with a high fidelity. Spectral characterizations prove that the concave-arrays coating enjoys excellent the light-trapping behaviors, by reducing the reflectance to 7.4% from 8.6% of bare glass and simultaneously allowing a high haze ratio of ∼ 70% in 350-800 nm. Compared with bare cell, the concave-arrays coating based amorphous silicon thin-film solar cell possesses the improving photovoltaic performances. Relative enhancements are 3.46% and 3.57% in short circuit current and photoelectric conversion efficiency, respectively. By the way, this light-trapping coating is facile, low-cost and large-scale, and can be straightforward introduced in other ready-made solar devices.

Trunk rotational strength asymmetry in adolescents with idiopathic scoliosis: an observational study

PubMed Central

McIntire, Kevin L; Asher, Marc A; Burton, Douglas C; Liu, Wen

2007-01-01

Background Recent reports have suggested a rotational strength weakness in rotations to the concave side in patients with idiopathic scoliosis. There have been no studies presenting normative values of female adolescent trunk rotational strength to which a comparison of female adolescents with idiopathic scoliosis could be made. The purpose of this study was to determine trunk rotational strength asymmetry in a group of female adolescents with AIS and a comparison group of healthy female adolescents without scoliosis. Methods Twenty-six healthy adolescent females served as the healthy group (HG) (average age 14 years) and fourteen otherwise healthy adolescent females with idiopathic scoliosis served as the idiopathic scoliosis group (ISG) (average age 13.5 years, average Cobb 28°). Participant's isometric trunk rotational strength was measured in five randomly ordered trunk positions: neutral, 18° and 36° of right and left pre-rotation. Rotational strength asymmetry was compared within each group and between the two groups using several different measures. Results The HG showed strength asymmetry in the 36° pre-rotated trunk positions when rotating towards the midline (p < 0.05). The ISG showed strength asymmetry when rotating towards the concavity of their primary curve from the neutral position (p < 0.05) and when rotating towards the concavity from the 18° (p < 0.05) and 36° (p < 0.05) concave pre-rotated positions. The ISG is significantly weaker than the HG when rotating away from the midline toward the concave (ISG)-left (HG) side from the concave/left pre-rotated 18° (p < 0.05) and 36° (p < 0.05) positions. Conclusion The AIS females were found to be significantly weaker when contracting toward their main curve concavity in the neutral and concave pre-rotated positions compared to contractions toward the convexity. These weaknesses were also demonstrated when compared to the group of healthy female adolescent controls. Possible mechanisms for the strength asymmetry in ISG are discussed. PMID:17620141

Analysis of a 10 megawatt space-based solar-pumped neodymium laser system

NASA Technical Reports Server (NTRS)

Kurweg, U. H.

1984-01-01

A ten megawatt solar-pumped continuous liquid laser system for space applications is examined. It is found that a single inflatable mirror of 434 m diameter used in conjunction with a conical secondary concentrator is sufficient to side pump a liquid neodymium lasant in an annular tube of 6 m length and 1 m outer and 0.8 m inner diameter. About one fourth of intercepted radiation converging on the laser tube is absorbed and one fifth of this radiation is effective in populating the upper levels. The liquid lasant is flowed through the annular laser cavity at 1.9 m/s and is cooled via a heat exchanger and a large radiator surface comparable in size to the concentrating mirror. The power density of incident light within the lasant of approximately 68 watt/cu cm required for cw operation is exceeded in the present annular configuration. Total system weight corresponds to 20,500 kg and is thus capable of being transported to near Earth orbit by a single shuttle flight.

Examining the Effects of Chromatic Aberration, Object Distance, and Eye Shape on Image-Formation in the Mirror-Based Eyes of the Bay Scallop Argopecten irradians.

PubMed

Speiser, Daniel I; Gagnon, Yakir Luc; Chhetri, Raghav K; Oldenburg, Amy L; Johnsen, Sönke

2016-11-01

The eyes of scallops form images using a concave spherical mirror and contain two separate retinas, one layered on top of the other. Behavioral and electrophysiological studies indicate that the images formed by these eyes have angular resolutions of about 2°. Based on previous ray-tracing models, it has been thought that the more distal of the two retinas lies near the focal point of the mirror and that the proximal retina, positioned closer to the mirror at the back of the eye, receives light that is out-of-focus. Here, we propose three mechanisms through which both retinas may receive focused light: (1) chromatic aberration produced by the lens may cause the focal points for longer and shorter wavelengths to fall near the distal and proximal retinas, respectively; (2) focused light from near and far objects may fall on the distal and proximal retinas, respectively; and (3) the eyes of scallops may be dynamic structures that change shape to determine which retina receives focused light. To test our hypotheses, we used optical coherence tomography (OCT), a method of near-infrared optical depth-ranging, to acquire virtual cross-sections of live, intact eyes from the bay scallop Argopecten irradians Next, we used a custom-built ray-tracing model to estimate the qualities of the images that fall on an eye's distal and proximal retinas as functions of the wavelengths of light entering the eye (400-700 nm), object distances (0.01-1 m), and the overall shape of the eye. When we assume 550 nm wavelength light and object distances greater than 0.01 m, our model predicts that the angular resolutions of the distal and proximal retinas are 2° and 7°, respectively. Our model also predicts that neither chromatic aberration nor differences in object distance lead to focused light falling on the distal and proximal retinas simultaneously. However, if scallops can manipulate the shapes of their eyes, perhaps through muscle contractions, we speculate that they may be able to influence the qualities of the images that fall on their proximal retinas and-to a lesser extent-those that fall on their distal retinas as well. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.

Examining the Effects of Chromatic Aberration, Object Distance, and Eye Shape on Image-Formation in the Mirror-Based Eyes of the Bay Scallop Argopecten irradians

PubMed Central

Speiser, Daniel I.; Gagnon, Yakir Luc; Chhetri, Raghav K.; Oldenburg, Amy L.; Johnsen, Sönke

2016-01-01

The eyes of scallops form images using a concave spherical mirror and contain two separate retinas, one layered on top of the other. Behavioral and electrophysiological studies indicate that the images formed by these eyes have angular resolutions of about 2°. Based on previous ray-tracing models, it has been thought that the more distal of the two retinas lies near the focal point of the mirror and that the proximal retina, positioned closer to the mirror at the back of the eye, receives light that is out-of-focus. Here, we propose three mechanisms through which both retinas may receive focused light: (1) chromatic aberration produced by the lens may cause the focal points for longer and shorter wavelengths to fall near the distal and proximal retinas, respectively; (2) focused light from near and far objects may fall on the distal and proximal retinas, respectively; and (3) the eyes of scallops may be dynamic structures that change shape to determine which retina receives focused light. To test our hypotheses, we used optical coherence tomography (OCT), a method of near-infrared optical depth-ranging, to acquire virtual cross-sections of live, intact eyes from the bay scallop Argopecten irradians. Next, we used a custom-built ray-tracing model to estimate the qualities of the images that fall on an eye’s distal and proximal retinas as functions of the wavelengths of light entering the eye (400–700 nm), object distances (0.01–1 m), and the overall shape of the eye. When we assume 550 nm wavelength light and object distances greater than 0.01 m, our model predicts that the angular resolutions of the distal and proximal retinas are 2° and 7°, respectively. Our model also predicts that neither chromatic aberration nor differences in object distance lead to focused light falling on the distal and proximal retinas simultaneously. However, if scallops can manipulate the shapes of their eyes, perhaps through muscle contractions, we speculate that they may be able to influence the qualities of the images that fall on their proximal retinas and—to a lesser extent—those that fall on their distal retinas as well. PMID:27549200

Heat exchanger for power generation equipment

DOEpatents

Nirmalan, Nirm Velumylm; Bowman, Michael John

2005-06-14

A heat exchanger for a turbine is provided wherein the heat exchanger comprises a heat transfer cell comprising a sheet of material having two opposed ends and two opposed sides. In addition, a plurality of concavities are disposed on a surface portion of the sheet of material so as to cause hydrodynamic interactions and affect a heat transfer rate of the turbine between a fluid and the concavities when the fluid is disposed over the concavities.

Cryogenic optical testing results of JWST aspheric test plate lens

NASA Astrophysics Data System (ADS)

Smith, Koby Z.; Towell, Timothy C.

2011-09-01

The James Webb Space Telescope (JWST) Secondary Mirror Assembly (SMA) is a circular 740mm diameter beryllium convex hyperboloid that has a 23.5nm-RMS (λ/27 RMS) on-orbit surface figure error requirement. The radius of curvature of the SMA is 1778.913mm+/-0.45mm and has a conic constant of -1.6598+/-0.0005. The on-orbit operating temperature of the JWST SMA is 22.5K. Ball Aerospace & Technologies Corp. (BATC) is under contract to Northrop Grumman Aerospace Systems (NGAS) to fabricate, assemble, and test the JWST SMA to its on-orbit requirements including the optical testing of the SMA at its cryogenic operating temperature. BATC has fabricated and tested an Aspheric Test Plate Lens (ATPL) that is an 870mm diameter fused silica lens used as the Fizeau optical reference in the ambient and cryogenic optical testing of the JWST Secondary Mirror Assembly (SMA). As the optical reference for the SMA optical test, the concave optical surface of the ATPL is required to be verified at the same 20K temperature range required for the SMA. In order to meet this objective, a state-of-the-art helium cryogenic testing facility was developed to support the optical testing requirements of a number of the JWST optical testing needs, including the ATPL and SMA. With the implementation of this cryogenic testing facility, the ATPL was successfully cryogenically tested and performed to less than 10nm-RMS (λ/63 RMS) surface figure uncertainty levels for proper reference backout during the SMA optical testing program.

Design of compressors for FEL pulses using deformable gratings

NASA Astrophysics Data System (ADS)

Bonora, Stefano; Fabris, Nicola; Frassetto, Fabio; Giovine, Ennio; Miotti, Paolo; Quintavalla, Martino; Poletto, Luca

2017-06-01

We present the optical layout of soft X-rays compressors using reflective grating specifically designed to give both positive or negative group-delay dispersion (GDD). They are tailored for chirped-pulse-amplification experiments with FEL sources. The optical design originates from an existing compressor with plane gratings already realized and tested at FERMI, that has been demonstrated capable to introduce tunable negative GDD. Here, we discuss two novel designs for compressors using deformable gratings capable to give both negative and positive GDD. Two novel designs are discussed: 1) a design with two deformable gratings and an intermediate focus between the twos, that is demonstrated capable to introduce positive GDD; 2) a design with one deformable grating giving an intermediate focus, followed by a concave mirror and a plane grating, that is capable to give both positive and negative GDD depending on the distance between the second mirror and the second grating. Both the designs are tunable in wavelength and GDD, by acting on the deformable gratings, that are rotated to tune the wavelength and the GDD and deformed to introduce the radius required to keep the spectral focus. The deformable gratings have a laminar profile and are ruled on a thin silicon plane substrate. A piezoelectric actuator is glued on the back of the substrate and is actuated to give a radius of curvature that is varying from infinite (plane) to few meters. The ruling procedure, the piezoelectric actuator and the efficiency measurements in the soft X-rays will be presented. Some test cases are discussed for wavelengths shorter than 12 nm.

An evaluation of multilayer mirrors for the soft x ray and extreme ultraviolet wavelength range that were irradiated with neutrons

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

Regan, S.P.; May, M.J.; Soukhanovskii, V.

1997-01-01

The Plasma Spectroscopy Group at the Johns Hopkins University develops high photon throughput multilayer mirror (MLM) based soft x ray and extreme ultraviolet (XUV 10 {Angstrom}{lt}{lambda}{lt}304 {Angstrom}) spectroscopic diagnostics for magnetically confined fusion plasmas. The D-T reactions in large fusion reactor type devices such as the International Thermonuclear Experimental Reactor will produce neutrons at a rate as high as 5{times}10{sup 19} ns{sup -1}. The MLMs, which are used as dispersive and focusing optics, will not be shielded from these neutrons. In an effort to assess the potential radiation damage, four MLMs (No. 1: Mo/Si, d=87.8 {Angstrom}, Zerodur substrate with 50more » cm concave spherical curvature; No. 2: W/B{sub 4}C, d=22.75 {Angstrom}, Si wafer substrate; No. 3: W/C, d=25.3 {Angstrom}, Si wafer substrate; and No. 4: Mo/Si, d=186.6 {Angstrom}, Si wafer substrate) were irradiated with fast neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF). The neutron beam at LASREF has an energy distribution that peaks at 1{endash}2 MeV with a tail that extends out to 100 MeV. The MLMs were irradiated to a fast neutron fluence of 1.1{times}10{sup 19} ncm{sup {minus}2} at 270{endash}300{degree}C. A comparison between the dispersive and reflective characteristics of the irradiated MLMs and the corresponding qualities of control samples will be given. {copyright} {ital 1997 American Institute of Physics.}« less

Turbulent boundary layers subjected to multiple curvatures and pressure gradients

NASA Technical Reports Server (NTRS)

Bandyopadhyay, Promode R.; Ahmed, Anwar

1993-01-01

The effects of abruptly applied cycles of curvatures and pressure gradients on turbulent boundary layers are examined experimentally. Two two-dimensional curved test surfaces are considered: one has a sequence of concave and convex longitudinal surface curvatures and the other has a sequence of convex and concave curvatures. The choice of the curvature sequences were motivated by a desire to study the asymmetric response of turbulent boundary layers to convex and concave curvatures. The relaxation of a boundary layer from the effects of these two opposite sequences has been compared. The effect of the accompaying sequences of pressure gradient has also been examined but the effect of curvature dominates. The growth of internal layers at the curvature junctions have been studied. Measurements of the Gortler and corner vortex systems have been made. The boundary layer recovering from the sequence of concave to convex curvature has a sustained lower skin friction level than in that recovering from the sequence of convex to concave curvature. The amplification and suppression of turbulence due to the curvature sequences have also been studied.

Resolution of x-ray parabolic compound refractive diamond lens defined at the home laboratory

NASA Astrophysics Data System (ADS)

Polyakov, S. N.; Zholudev, S. I.; Gasilov, S. V.; Martyushov, S. Yu.; Denisov, V. N.; Terentiev, S. A.; Blank, V. D.

2017-05-01

Here we demonstrate performance of an original lab system designed for testing of X-ray parabolic compound refractive lenses (CRL) manufactured from a high-quality single-crystalline synthetic diamond grown by the high-pressure hightemperature technique. The basic parameters of a diamond CRL comprised from 28 plano-concave lenses such as the focal length of 634 mm, transmissivity of 0.36, field of view of 1 mm and resolution of 6 µm have been determined. Usually such measurements are performed on synchrotron radiation facilities. In this work characterization of CRL was performed by means of instruments and components that are available for laboratories such as the Rigaku 9kW rotating anode X-ray generator, the PANalytical parallel beam X-ray mirror, a 6 m long optical bench, high precision multi-axis goniometers, high resolution X-ray emulsion films, and ultra-fast high-sensitive X-ray area detector PIXel3D. Developed setup was used to find differences between experimental and design parameters, which is very important for the improvement of CRLs manufacturing technology.

Rocket propulsion by thermonuclear micro-bombs ignited with intense relativistic electron beams.

NASA Technical Reports Server (NTRS)

Winterberg, F.

1971-01-01

Discussion of a method for the ignition of a thermonuclear microbomb by means of an intense relativistic electron beam with regard to its potential application to rocket propulsion. With such a system, exhaust velocities up to 1000 km/sec, corresponding to a specific impulse of 100,000 sec, seem to be within the realm of possibility. The rocket is propelled by a chain of thermonuclear microbombs exploded in a concave magnetic mirror produced by superconducting field coils. The magnetic pressure of the field reflects the fireball generated by the explosion. For the large capacitor bank required to generate the intense relativistic electron beam, a desirable lightweight design may be possible through use of ferroelectric materials. Because of the high cost of the T-D and He 3-D thermonuclear material, the system has to be optimized by minimizing the T-D and He 3-D consumption by a proper TD and He 3-D fuel to hydrogen propellant mass ratio, leading to a larger total system mass than would be absolutely necessary.

Second-surface silvered glass solar mirrors of very high reflectance

NASA Astrophysics Data System (ADS)

Butel, Guillaume P.; Coughenour, Blake M.; Macleod, H. Angus; Kennedy, Cheryl E.; Olbert, Blain H.; Angel, J. Roger P.

2011-10-01

This paper reports methods developed to maximize the overall reflectance second-surface silvered glass. The reflectance at shorter wavelengths is increased with the aid of a dielectric enhancing layer between the silver and the glass, while at longer wavelengths it is enhanced by use of glass with negligible iron content. The calculated enhancement of reflectance, compared to unenhanced silver on standard low-iron float glass, corresponds to a 4.4% increase in reflectance averaged across the full solar spectrum, appropriate for CSP, and 2.7% for CPV systems using triple junction cells. An experimental reflector incorporating these improvements, of drawn crown glass and a silvered second-surface with dielectric boost, was measured at NREL to have 95.4% solar weighted reflectance. For comparison, non-enhanced, wetsilvered reflectors of the same 4 mm thickness show reflectance ranging from 91.6 - 94.6%, depending on iron content. A potential drawback of using iron-free drawn glass is reduced concentration in high concentration systems because of the inherent surface errors. This effect is largely mitigated for glass shaped by slumping into a concave mold, rather than by bending.

Asymmetric Bulkheads for Cylindrical Pressure Vessels

NASA Technical Reports Server (NTRS)

Ford, Donald B.

2007-01-01

Asymmetric bulkheads are proposed for the ends of vertically oriented cylindrical pressure vessels. These bulkheads, which would feature both convex and concave contours, would offer advantages over purely convex, purely concave, and flat bulkheads (see figure). Intended originally to be applied to large tanks that hold propellant liquids for launching spacecraft, the asymmetric-bulkhead concept may also be attractive for terrestrial pressure vessels for which there are requirements to maximize volumetric and mass efficiencies. A description of the relative advantages and disadvantages of prior symmetric bulkhead configurations is prerequisite to understanding the advantages of the proposed asymmetric configuration: In order to obtain adequate strength, flat bulkheads must be made thicker, relative to concave and convex bulkheads; the difference in thickness is such that, other things being equal, pressure vessels with flat bulkheads must be made heavier than ones with concave or convex bulkheads. Convex bulkhead designs increase overall tank lengths, thereby necessitating additional supporting structure for keeping tanks vertical. Concave bulkhead configurations increase tank lengths and detract from volumetric efficiency, even though they do not necessitate additional supporting structure. The shape of a bulkhead affects the proportion of residual fluid in a tank that is, the portion of fluid that unavoidably remains in the tank during outflow and hence cannot be used. In this regard, a flat bulkhead is disadvantageous in two respects: (1) It lacks a single low point for optimum placement of an outlet and (2) a vortex that forms at the outlet during outflow prevents a relatively large amount of fluid from leaving the tank. A concave bulkhead also lacks a single low point for optimum placement of an outlet. Like purely concave and purely convex bulkhead configurations, the proposed asymmetric bulkhead configurations would be more mass-efficient than is the flat bulkhead configuration. In comparison with both purely convex and purely concave configurations, the proposed asymmetric configurations would offer greater volumetric efficiency. Relative to a purely convex bulkhead configuration, the corresponding asymmetric configuration would result in a shorter tank, thus demanding less supporting structure. An asymmetric configuration provides a low point for optimum location of a drain, and the convex shape at the drain location minimizes the amount of residual fluid.

Availability of cosmetic treatment using novel cosmetics-based material on patients with craniofacial concavity.

PubMed

Koyama, Shigeto; Kanetaka, Hiroyasu; Sagehashi, Yoshinori; Sasaki, Keiichi; Sato, Naoko

2018-03-09

Patients treated with maxillofacial prosthetics often experience emotional problems because of the remaining facial skin concavity such as a surgical scar. In such cases, cosmetic treatment can potentially correct their skin tone imperfections and deformities. This study aimed to evaluate the clinical availability of novel cosmetics-based material for craniofacial small concavity by initiating a cosmetic treatment in a preliminary case. Eighteen patients with aesthetic problems such as craniofacial deformities, small defects, and concavities on their faces underwent cosmetic treatment that was performed by makeup practitioners. Data were collected from the patient's charts and a survey questionnaire. A visual analog scale was used to conduct a survey regarding the satisfaction levels of the patients following cosmetic treatment with a novel cosmetics-based material. The cosmetic treatment was performed for a concavity on the left midface of a 67-year-old woman with partial maxillectomy. The novel cosmetics-based material was manufactured from a semi-translucent oil base. The satisfaction level of the patient increased after undergoing the cosmetic treatment. Regarding clinical applications, the novel cosmetics-based material can help reduce their cosmetic disturbance and restore the small deformity. These results suggest that the cosmetic treatment with the novel cosmetics-based material can be used as a subsidiary method for facial prostheses or an independent new method for correcting patients' small craniofacial concavity and for reducing visible deformity. Copyright © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Processing convexity and concavity along a 2-D contour: figure-ground, structural shape, and attention.

PubMed

Bertamini, Marco; Wagemans, Johan

2013-04-01

Interest in convexity has a long history in vision science. For smooth contours in an image, it is possible to code regions of positive (convex) and negative (concave) curvature, and this provides useful information about solid shape. We review a large body of evidence on the role of this information in perception of shape and in attention. This includes evidence from behavioral, neurophysiological, imaging, and developmental studies. A review is necessary to analyze the evidence on how convexity affects (1) separation between figure and ground, (2) part structure, and (3) attention allocation. Despite some broad agreement on the importance of convexity in these areas, there is a lack of consensus on the interpretation of specific claims--for example, on the contribution of convexity to metric depth and on the automatic directing of attention to convexities or to concavities. The focus is on convexity and concavity along a 2-D contour, not convexity and concavity in 3-D, but the important link between the two is discussed. We conclude that there is good evidence for the role of convexity information in figure-ground organization and in parsing, but other, more specific claims are not (yet) well supported.

Majorization Minimization by Coordinate Descent for Concave Penalized Generalized Linear Models

PubMed Central

Jiang, Dingfeng; Huang, Jian

2013-01-01

Recent studies have demonstrated theoretical attractiveness of a class of concave penalties in variable selection, including the smoothly clipped absolute deviation and minimax concave penalties. The computation of the concave penalized solutions in high-dimensional models, however, is a difficult task. We propose a majorization minimization by coordinate descent (MMCD) algorithm for computing the concave penalized solutions in generalized linear models. In contrast to the existing algorithms that use local quadratic or local linear approximation to the penalty function, the MMCD seeks to majorize the negative log-likelihood by a quadratic loss, but does not use any approximation to the penalty. This strategy makes it possible to avoid the computation of a scaling factor in each update of the solutions, which improves the efficiency of coordinate descent. Under certain regularity conditions, we establish theoretical convergence property of the MMCD. We implement this algorithm for a penalized logistic regression model using the SCAD and MCP penalties. Simulation studies and a data example demonstrate that the MMCD works sufficiently fast for the penalized logistic regression in high-dimensional settings where the number of covariates is much larger than the sample size. PMID:25309048

Endophthalmitis after descemet stripping endothelial keratoplasty with concave-oriented dislocation on slit-lamp optical coherence topography.

PubMed

Kaiura, Terry L; Ritterband, David C; Koplin, Richard S; Shih, Carolyn; Palmierto, Pat M; Seedor, John A

2010-02-01

To present the first reported case of Descemet membrane stripping endothelial keratoplasty (DSEK)-associated endophthalmitis with concave dislocation on slit-lamp optical coherence topography (SL-OCT). An 86-year-old man underwent DSEK for corneal decompensation secondary to prior surgery. On all postoperative visits, a slit-lamp examination and SL-OCT were performed. On the first postoperative day, the lenticle was dislocated in a concave configuration as imaged with the SL-OCT. On the second postoperative day, the patient had eye pain, nausea, and increased intraocular pressure. On SL-OCT imaging, the concave configuration and fibrin stranding were imaged. With intraocular pressure lowering, the patient's pain subsided, and he was scheduled for a lenticle refloat the following day. The next day, endophthalmitis was diagnosed secondary to exuberant purulent inflammation. At surgery, the lenticle was removed, cultures were obtained, and pars plana vitrectomy and intravitreal injections were administered. Intraoperative cultures were positive for heavy growth of Streptococcus pneumoniae. Endophthalmitis is a potential complication for any intraocular procedure including DSEK. SL-OCT imaging postoperatively may reveal concave lenticle configuration and subtle anterior chamber fibrin stranding may be early sign of endophthalmitis.

Present-day stress field in subduction zones: Insights from 3D viscoelastic models and data

NASA Astrophysics Data System (ADS)

Petricca, Patrizio; Carminati, Eugenio

2016-01-01

3D viscoelastic FE models were performed to investigate the impact of geometry and kinematics on the lithospheric stress in convergent margins. Generic geometries were designed in order to resemble natural subduction. Our model predictions mirror the results of previous 2D models concerning the effects of lithosphere-mantle relative flow on stress regimes, and allow a better understanding of the lateral variability of the stress field. In particular, in both upper and lower plates, stress axes orientations depend on the adopted geometry and axes rotations occur following the trench shape. Generally stress axes are oriented perpendicular or parallel to the trench, with the exception of the slab lateral tips where rotations occur. Overall compression results in the upper plate when convergence rate is faster than mantle flow rate, suggesting a major role for convergence. In the slab, along-strike tension occurs at intermediate and deeper depths (> 100 km) in case of mantle flow sustaining the sinking lithosphere and slab convex geometry facing mantle flow or in case of opposing mantle flow and slab concave geometry facing mantle flow. Along-strike compression is predicted in case of sustaining mantle flow and concave slabs or in case of opposing mantle flow and convex slabs. The slab stress field is thus controlled by the direction of impact of mantle flow onto the slab and by slab longitudinal curvature. Slab pull produces not only tension in the bending region of subducted plate but also compression where upper and lower plates are coupled. A qualitative comparison between results and data in selected subductions indicates good match for South America, Mariana and Tonga-Kermadec subductions. Discrepancies, as for Sumatra-Java, emerge due to missing geometric (e.g., occurrence of fault systems and local changes in the orientation of plate boundaries) and rheological (e.g., plasticity associated with slab bending, anisotropy) complexities in the models.

Classroom Note: Concavity and the Second Law of Thermodynamics

ERIC Educational Resources Information Center

Dunning-Davies, J.

2003-01-01

The importance of the mathematical notion of concavity in relation to thermodynamics is stressed and it is shown how it can be useful in increasing the enthusiasm of physics' students for their mathematics' courses.

First Giant Mirror for the ESO VLT Ready at REOSC

NASA Astrophysics Data System (ADS)

1995-11-01

The REOSC Contract In 1989, the European Southern Observatory (ESO), the European Organisation for Astronomy, awarded to REOSC, a subsidiary of the SFIM Group and located in Saint Pierre du Perray (France), a comprehensive contract for the polishing of four 8.2-metre diameter mirrors for the unit telescopes of the ESO Very Large Telescope (VLT) project. These mirrors are the largest ever manufactured and polished. This contract comprises not only the polishing and high-precision optical testing of each giant mirror, but also the safe condition of transportation of the blanks which were manufactured by Schott Glaswerke in Mainz (Germany). In order to fulfill the contract, REOSC conceived, built and equipped a novel, high-tech workshop which would allow to polish and test the mirrors, each of which has a surface area of more than 50 square metres. First 8.2-Metre Mirror is Ready and within Specifications The REOSC polishing facility for giant mirrors was built in Saint Pierre du Perray, just south of Paris. It is equipped with two machines: one for grinding and the other for polishing the mirrors, and both with 150-actuator systems that support the thin and flexible mirrors. All equipment is computer controlled. State-of-the-art interferometers probe the accuracy of the mirror surface as the polishing proceeds; they are installed at the top level of the facility in a 30-metre high tower, at the centre of the mirror's radius of curvature. The success of the work at REOSC is now evident by the fact that careful measurements of the first mirror earlier this month have shown that the final optical surface is correct to within 0.00005 millimetres. For illustration, this corresponds to an accuracy of only 1 millimetre deviation over a surface with a diameter of 165 kilometres (equivalent to the entire Paris area)! ESO Receives the First VLT Mirror After having been carefully placed in a special transport box designed by REOSC, the first mirror blank, weighing 23.5 tons and with a replacement value of about 20 million DEM, was transported from Mainz to Saint Pierre du Perray in July 1993. The shaping and polishing phases lasted two years and were completed in October 1995. After one month's hard work, dedicated to optical and mechanical verifications by ESO and REOSC, the mirror's various characteristics have now been found to be in accordance with the contract specifications. Following the technical acceptance, the first mirror was re-installed in its transport container on November 13, 1995. It will thereafter be formally handed over to ESO during a ceremony at REOSC on Tuesday, November 21, 1995. The mirror will be stored at the REOSC facility until its future departure to ESO's VLT Observatory on Cerro Paranal, a 2650 m high summit in the Andean Cordillera in northern Chile. Here it will be installed in the first VLT unit telescope, soon after the assembly of the mechanical parts has been completed. Future Plans at REOSC The polishing of the second VLT mirror, as well as the grinding of the third mirror which was transported from Mainz to Saint Pierre du Perray at the beginning of October 1995, have already started. The transport of the fourth blank will take place in March 1996. With the construction, in a subsequent phase, of a workshop of more than 6000 square metres and mostly dedicated to space and astronomy, the SFIM group will have invested more than 50 million French Francs at the Saint Pierre du Perray site alone. The group is also involved in the contract related to the actuator support system; this is a clear indication of its determination to maintain its position within this scientific-technological market. In addition to the ESO VLT mirrors, REOSC will also polish the two 8.2-metre diameter mirrors of the Gemini programme of the Association of Universities for Research in Astronomy (AURA) in the United States. This important work was entrusted REOSC, following an international call for tenders, in which also US firms participated. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Pipe gripper

DOEpatents

Moyers, S.M.

1975-12-16

A device for gripping the exterior surface of a pipe or rod is described which has a plurality of wedges, each having a concave face which engages the outer surface of the pipe and each having a smooth face opposing the concave face. The wedges are seated on and their grooved concave faces are maintained in circular alignment by tapered axial segments of an opening extending through a wedge-seating member. The wedges are allowed to slide across the tapered axial segments so that such a sliding movement acts to vary the diameter of the circular alignment.

A search asymmetry reversed by figure-ground assignment.

PubMed

Humphreys, G W; Müller, H

2000-05-01

We report evidence demonstrating that a search asymmetry favoring concave over convex targets can be reversed by altering the figure-ground assignment of edges in shapes. Visual search for a concave target among convex distractors is faster than search for a convex target among concave distractors (a search asymmetry). By using shapes with ambiguous local figure-ground relations, we demonstrated that search can be efficient (with search slopes around 10 ms/item) or inefficient (with search slopes around 30-40 ms/item) with the same stimuli, depending on whether edges are assigned to concave or convex "figures." This assignment process can operate in a top-down manner, according to the task set. The results suggest that attention is allocated to spatial regions following the computation of figure-ground relations in parallel across the elements present. This computation can also be modulated by top-down processes.

Left-Right Asymmetric Morphogenesis in the Xenopus Digestive System

USGS Publications Warehouse

Muller, Jennifer K.; Prather, D.R.; Nascone-Yoder, N. M.

2003-01-01

The morphogenetic mechanisms by which developing organs become left-right asymmetric entities are unknown. To investigate this issue, we compared the roles of the left and right sides of the Xenopus embryo during the development of anatomic asymmetries in the digestive system. Although both sides contribute equivalently to each of the individual digestive organs, during the initial looping of the primitive gut tube, the left side assumes concave topologies where the right side becomes convex. Of interest, the concave surfaces of the gut tube correlate with expression of the LR gene, Pitx2, and ectopic Pitx2 mRNA induces ectopic concavities in a localized manner. A morphometric comparison of the prospective concave and convex surfaces of the gut tube reveals striking disparities in their rate of elongation but no significant differences in cell proliferation. These results provide insight into the nature of symmetry-breaking morphogenetic events during left-right asymmetric organ development. ?? 2003 Wiley-Liss, Inc.

Pt3Co concave nanocubes: synthesis, formation understanding, and enhanced catalytic activity toward hydrogenation of styrene.

PubMed

Wang, Chenyu; Lin, Cuikun; Zhang, Lihua; Quan, Zewei; Sun, Kai; Zhao, Bo; Wang, Feng; Porter, Nathan; Wang, Yuxuan; Fang, Jiye

2014-02-03

We report a facile synthesis route to prepare high-quality Pt3Co nanocubes with a concave structure, and further demonstrate that these concave Pt3Co nanocubes are terminated with high-index crystal facets. The success of this preparation is highly dependent on an appropriate nucleation process with a successively anisotropic overgrowth and a preservation of the resultant high-index planes by control binding of oleyl-amine/oleic acid with a fine-tuned composition. Using a hydrogenation of styrene as a model reaction, these Pt3Co concave nanocubes as a new class of nanocatalysts with more open structure and active atomic sites located on their high-index crystallographic planes exhibit an enhanced catalytic activity in comparison with low-indexed surface terminated Pt3Co nanocubes in similar size. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of convexity in perception of symmetry and in visual short-term memory.

PubMed

Bertamini, Marco; Helmy, Mai Salah; Hulleman, Johan

2013-01-01

Visual perception of shape is affected by coding of local convexities and concavities. For instance, a recent study reported that deviations from symmetry carried by convexities were easier to detect than deviations carried by concavities. We removed some confounds and extended this work from a detection of reflection of a contour (i.e., bilateral symmetry), to a detection of repetition of a contour (i.e., translational symmetry). We tested whether any convexity advantage is specific to bilateral symmetry in a two-interval (Experiment 1) and a single-interval (Experiment 2) detection task. In both, we found a convexity advantage only for repetition. When we removed the need to choose which region of the contour to monitor (Experiment 3) the effect disappeared. In a second series of studies, we again used shapes with multiple convex or concave features. Participants performed a change detection task in which only one of the features could change. We did not find any evidence that convexities are special in visual short-term memory, when the to-be-remembered features only changed shape (Experiment 4), when they changed shape and changed from concave to convex and vice versa (Experiment 5), or when these conditions were mixed (Experiment 6). We did find a small advantage for coding convexity as well as concavity over an isolated (and thus ambiguous) contour. The latter is consistent with the known effect of closure on processing of shape. We conclude that convexity plays a role in many perceptual tasks but that it does not have a basic encoding advantage over concavity.

Low Density Lipoprotein and Non-Newtonian Oscillating Flow Biomechanical Parameters for Normal Human Aorta.

PubMed

Soulis, Johannes V; Fytanidis, Dimitrios K; Lampri, Olga P; Giannoglou, George D

2016-04-01

The temporal variation of the hemodynamic mechanical parameters during cardiac pulse wave is considered as an important atherogenic factor. Applying non-Newtonian blood molecular viscosity simulation is crucial for hemodynamic analysis. Understanding low density lipoprotein (LDL) distribution in relation to flow parameters will possibly spot the prone to atherosclerosis aorta regions. The biomechanical parameters tested were averaged wall shear stress (AWSS), oscillatory shear index (OSI) and relative residence time (RRT) in relation to the LDL concentration. Four non-Newtonian molecular viscosity models and the Newtonian one were tested for the normal human aorta under oscillating flow. The analysis was performed via computational fluid dynamic. Tested viscosity blood flow models for the biomechanical parameters yield a consistent aorta pattern. High OSI and low AWSS develop at the concave aorta regions. This is most noticeable in downstream flow region of the left subclavian artery and at concave ascending aorta. Concave aorta regions exhibit high RRT and elevated LDL. For the concave aorta site, the peak LDL value is 35.0% higher than its entrance value. For the convex site, it is 18.0%. High LDL endothelium regions located at the aorta concave site are well predicted with high RRT. We are in favor of using the non-Newtonian power law model for analysis. It satisfactorily approximates the molecular viscosity, WSS, OSI, RRT and LDL distribution. Concave regions are mostly prone to atherosclerosis. The flow biomechanical factor RRT is a relatively useful tool for identifying the localization of the atheromatic plaques of the normal human aorta.

Relationship between spontaneous expiratory flow-volume curve pattern and air-flow obstruction in elderly COPD patients.

PubMed

Nozoe, Masafumi; Mase, Kyoshi; Murakami, Shigefumi; Okada, Makoto; Ogino, Tomoyuki; Matsushita, Kazuhiro; Takashima, Sachie; Yamamoto, Noriyasu; Fukuda, Yoshihiro; Domen, Kazuhisa

2013-10-01

Assessment of the degree of air-flow obstruction is important for determining the treatment strategy in COPD patients. However, in some elderly COPD patients, measuring FVC is impossible because of cognitive dysfunction or severe dyspnea. In such patients a simple test of airways obstruction requiring only a short run of tidal breathing would be useful. We studied whether the spontaneous expiratory flow-volume (SEFV) curve pattern reflects the degree of air-flow obstruction in elderly COPD patients. In 34 elderly subjects (mean ± SD age 80 ± 7 y) with stable COPD (percent-of-predicted FEV(1) 39.0 ± 18.5%), and 12 age-matched healthy subjects, we measured FVC and recorded flow-volume curves during quiet breathing. We studied the SEFV curve patterns (concavity/convexity), spirometry results, breathing patterns, and demographics. The SEFV curve concavity/convexity prediction accuracy was examined by calculating the receiver operating characteristic curves, cutoff values, area under the curve, sensitivity, and specificity. Fourteen subjects with COPD had a concave SEFV curve. All the healthy subjects had convex SEFV curves. The COPD subjects who had concave SEFV curves often had very severe airway obstruction. The percent-of-predicted FEV(1)% (32.4%) was the most powerful SEFV curve concavity predictor (area under the curve 0.92, 95% CI 0.83-1.00), and had the highest sensitivity (0.93) and specificity (0.88). Concavity of the SEFV curve obtained during tidal breathing may be a useful test for determining the presence of very severe obstruction in elderly patients unable to perform a satisfactory FVC maneuver.

Prospect for a 60 GHz multicharged ECR ion source

NASA Astrophysics Data System (ADS)

Thuillier, T.; Bondoux, D.; Angot, J.; Baylac, M.; Froidefond, E.; Jacob, J.; Lamy, T.; Leduc, A.; Sole, P.; Debray, F.; Trophime, C.; Skalyga, V.; Izotov, I.

2018-05-01

The conceptual design of a fourth generation hybrid electron cyclotron resonance (ECR) ion source operated at 60 GHz is proposed. The axial magnetic mirror is generated with a set of three Nb3Sn coils, while the hexapole is made with room temperature (RT) copper coils. The motivations for such a hybrid development are to study further the ECR plasma physics and the intense multicharged ion beams' production and transport at a time when a superconducting (SC) hexapole appears unrealistic at 60 GHz. The RT hexapole coil designed is an evolution of the polyhelix technology developed at the French High Magnetic Field Facility. The axial magnetic field is generated by means of 3 Nb3Sn SC coils operated with a maximum current density of 350 A/mm2 and a maximum coil load line factor of 81%. The ECR plasma chamber resulting from the design features an inner radius of 94 mm and a length of 500 mm. The radial magnetic intensity is 4.1 T at the wall. Characteristic axial mirror peaks are 8 and 4.5 T, with 1.45 T minimum in between.

A four kHz repetition rate compact TEA CO2 laser

NASA Astrophysics Data System (ADS)

Zheng, Yijun; Tan, Rongqing

2013-09-01

A compact transversely excited atmospheric (TEA) CO2 laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×103 mm3. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable，the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns．To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO2 laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×103 mm3 with the cavity length of 520mm.

Hot slumping glass technology for the grazing incidence optics of future missions with particular reference to IXO

NASA Astrophysics Data System (ADS)

Ghigo, M.; Basso, S.; Bavdaz, M.; Conconi, P.; Citterio, O.; Civitani, M.; Friedrich, P.; Gallieni, D.; Guldimann, B.; Martelli, F.; Negri, R.; Pagano, G.; Pareschi, G.; Parodi, G.; Proserpio, L.; Salmaso, B.; Scaglione, F.; Spiga, D.; Tagliaferri, G.; Terzi, L.; Tintori, M.; Vongehr, M.; Wille, E.; Winter, A.; Zambra, A.

2010-07-01

The mirrors of the International X-ray Observatory (IXO) consist of a large number of high quality segments delivering a spatial resolution better than 5 arcsec. A study concerning the slumping of thin glass foils for the IXO mirrors is under development in Europe, funded by ESA and led by the Brera Observatory. We are investigating two approaches, the "Direct" and "Indirect" slumping technologies, being respectively based on the use of convex and concave moulds. In the first case during the thermal cycle the optical surface of the glass is in direct contact with the mould surface, while in the second case it is the rear side of the foil which touches the master. Both approaches present pros and cons and aim of this study is also to make an assessment of both processes and to perform a trade-off between the two. The thin plates are made of D263glass produced by Schott. Each plate is 0.4 mm thick, with a reflecting area of 200 mm x 200 mm; the mould are made of Fused Silica. After the thermal cycle the slumped MPs are characterized to define their optical quality and microroughness. The adopted integration process foresees the bonding of the slumped foils to a rigid backplane by means of reinforcing ribs. During the bonding process the plates are constrained to stay in close contact to the surface of the master (i.e. the same mould used for the hot slumping process) by the application of a vacuum pump suction. In this way spring-back deformations and low frequency errors still present on the foil profile after slumping can be corrected. In this paper we present the preliminary results concerning achieved during the first part of the project.

All-reflective optical target illumination system with high numerical aperture

DOEpatents

Thomas, Carlton E.; Sigler, Robert D.; Hoeger, John G.

1979-01-01

An all-reflective optical system for providing illumination of a target focal region at high numerical aperture from a pair of confluent collimated light beams. The collimated beams are each incident upon an associated concave eccentric pupil paraboloidal reflective surface, and thereby each focused through an opening in an associated outer ellipsoidal reflective surface onto a plane reflector. Each beam is reflected by its associated plane reflector onto the opposing concave surface of the outer ellipsoids to be focused through an opening in the plane surface onto an opposing inner concave ellipsoidal reflective surface, and thence onto the target region.

An adhered-particle analysis system based on concave points

NASA Astrophysics Data System (ADS)

Wang, Wencheng; Guan, Fengnian; Feng, Lin

2018-04-01

Particles adhered together will influence the image analysis in computer vision system. In this paper, a method based on concave point is designed. First, corner detection algorithm is adopted to obtain a rough estimation of potential concave points after image segmentation. Then, it computes the area ratio of the candidates to accurately localize the final separation points. Finally, it uses the separation points of each particle and the neighboring pixels to estimate the original particles before adhesion and provides estimated profile images. The experimental results have shown that this approach can provide good results that match the human visual cognitive mechanism.

MOF-templated synthesis of porous Co(3)O(4) concave nanocubes with high specific surface area and their gas sensing properties.

PubMed

Lü, Yinyun; Zhan, Wenwen; He, Yue; Wang, Yiting; Kong, Xiangjian; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

2014-03-26

Porous metal oxides nanomaterials with controlled morphology have received great attention because of their promising applications in catalysis, energy storage and conversion, gas sensing, etc. In this paper, porous Co3O4 concave nanocubes with extremely high specific surface area (120.9 m(2)·g(-1)) were synthesized simply by calcining Co-based metal-organic framework (Co-MOF, ZIF-67) templates at the optimized temperature (300 °C), and the formation mechanism of such highly porous structures as well as the influence of the calcination temperature are well explained by taking into account thermal behavior and intrinsic structural features of the Co-MOF precursors. The gas-sensing properties of the as-synthesized porous Co3O4 concave nanocubes were systematically tested towards volatile organic compounds including ethanol, acetone, toluene, and benzene. Experimental results reveal that the porous Co3O4 concave nanocubes present the highest sensitivity to ethanol with fast response/recovery time (< 10 s) and a low detection limit (at least 10 ppm). Such outstanding gas sensing performance of the porous Co3O4 concave nanocubes benefits from their high porosity, large specific surface area, and remarkable capabilities of surface-adsorbed oxygen.

A comparison of hand-wrist bone and cervical vertebral analyses in measuring skeletal maturation.

PubMed

Gandini, Paola; Mancini, Marta; Andreani, Federico

2006-11-01

To compare skeletal maturation as measured by hand-wrist bone analysis and by cervical vertebral analysis. A radiographic hand-wrist bone analysis and cephalometric cervical vertebral analysis of 30 patients (14 males and 16 females; 7-18 years of age) were examined. The hand-wrist bone analysis was evaluated by the Bjork index, whereas the cervical vertebral analysis was assessed by the cervical vertebral maturation stage (CVMS) method. To define vertebral stages, the analysis consisted of both cephalometric (13 points) and morphologic evaluation of three cervical vertebrae (concavity of second, third, and fourth vertebrae and shape of third and fourth vertebrae). These measurements were then compared with the hand-wrist bone analysis, and the results were statistically analyzed by the Cohen kappa concordance index. The same procedure was repeated after 6 months and showed identical results. The Cohen kappa index obtained (mean +/- SD) was 0.783 +/- 0.098, which is in the significant range. The results show a concordance of 83.3%, considering that the estimated percentage for each case is 23.3%. The results also show a correlation of CVMS I with Bjork stages 1-3 (interval A), CVMS II with Bjork stage 4 (interval B), CVMS III with Bjork stage 5 (interval C), CVMS IV with Bjork stages 6 and 7 (interval D), and CVMS V with Bjork stages 8 and 9 (interval E). Vertebral analysis on a lateral cephalogram is as valid as the hand-wrist bone analysis with the advantage of reducing the radiation exposure of growing subjects.

Smith-Purcell radiation from concave dotted gratings

NASA Astrophysics Data System (ADS)

Sergeeva, D. Yu.; Tishchenko, A. A.; Aryshev, A. S.; Strikhanov, M. N.

2018-02-01

We present the first-principles theory of Smith-Purcell effect from the concave dotted grating consisting of bent chains of separated micro- or nanoparticles. The numerical analysis demonstrates that the obtained spectral-angular distributions change significantly depending on the structure of the grating.

Theoretical fringe profiles with crossed Babinet compensators in testing concave aspheric surfaces.

PubMed

Saxena, A K; Lancelot, J P

1982-11-15

This paper presents the theory for the use of crossed Babinet compensators in testing concave aspheric surfaces. Theoretical fringe profiles for a sphere and for an aspheric surface with primary aberration are shown. Advantages of this method are discussed.

Pd@Pt core-shell concave decahedra: A class of catalysts for the oxygen reduction reaction with enhanced activity and durability

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

Wang, Xue; Vera, Madeline; Chi, Miaofang

Here, we report a facile synthesis of multiply twinned Pd@Pt core shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 degrees C, naturally generating a core shell structure covered by concave facets. The nonuniformity inmore » the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm 2 pt) and mass (1.60 A/mg/ 2 pt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm 2 pt and 0.32 A/mg pt, respectively). After 10 000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mg pt, more than twice that of the pristine Pt/C catalyst.« less

Pd@Pt core-shell concave decahedra: A class of catalysts for the oxygen reduction reaction with enhanced activity and durability

DOE PAGES

Wang, Xue; Vera, Madeline; Chi, Miaofang; ...

2015-11-13

Here, we report a facile synthesis of multiply twinned Pd@Pt core shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 degrees C, naturally generating a core shell structure covered by concave facets. The nonuniformity inmore » the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm 2 pt) and mass (1.60 A/mg/ 2 pt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm 2 pt and 0.32 A/mg pt, respectively). After 10 000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mg pt, more than twice that of the pristine Pt/C catalyst.« less

Maximally dense packings of two-dimensional convex and concave noncircular particles.

PubMed

Atkinson, Steven; Jiao, Yang; Torquato, Salvatore

2012-09-01

Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London) 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space R(d). While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and "moonlike" shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures.

Maximally dense packings of two-dimensional convex and concave noncircular particles

NASA Astrophysics Data System (ADS)

Atkinson, Steven; Jiao, Yang; Torquato, Salvatore

2012-09-01

Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London)NATUAS0028-083610.1038/nature08239 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space Rd. While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and “moonlike” shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures.

Iris concavity, corneal biomechanics, and their correlations with ocular biometry in a cohort of 10- to 12-year-old UK school boys: baseline data.

PubMed

Shah, Ameet; Low, Sancy; Garway-Heath, David F; Foster, Paul J; Barton, Keith

2014-04-17

Pigment dispersion syndrome is associated with iris concavity. This study investigated the prevalence of iris concavity, defined as a measurement of ≤-0.1 mm, in a cohort of 10- to 12-year-old boys, and explored the relationship between iris curvature and anterior segment biometry. Associations with corneal biomechanical parameters also were explored. A cohort of school boys (n = 96) was recruited from a local school. Anterior segment optical coherence tomography (AS-OCT) was performed under accommodative and nonaccommodative conditions, and iris curvature quantified. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with the ocular response analyzer (ORA). Noncontact axial biometry was performed using laser interferometry. The prevalence of iris concavity was 24% on distance fixation, increasing to 65% on accommodation. Variables significantly associated with nonaccommodating iris curvature were lens vault (P = 0.02) and mean keratometry (P = 0.02). For both variables acting jointly, R(2) = 0.30. Variables associated significantly with accommodating iris curvature were anterior chamber depth (P = 0.009), lens vault (P = 0.049), and mean scleral spur angle (P < 0.0001). For these three variables acting jointly, R(2) = 0.33. Significant association was found between CH and spur-to-spur distance (R(2) = 0.07, P = 0.025). Iris concavity was a common finding in this cohort and related to anterior segment biometric parameters. Further work is required to clarify whether anatomical differences exist between iris concavity seen in the adolescent eye and that found in adults with pigment dispersion syndrome. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

An interesting sexually dimorphic species, Neoribates isabelaensis sp. nov. (Acari, Oribatida, Parakalummidae) with remarks on sexual dimorphism in Oripodoidea.

PubMed

Bayartogtokh, Badamdorj; Ermilov, Sergey G; Corpuz-Raros, Leonila

2017-11-10

A new species Neoribates isabelaensis sp. nov. showing an interesting sexual dimorphism is described from bamboo litter on Luzon Island in the Philippines. This species is unique among other species of Neoribates in the structure of the posterior part of notogaster in males, which has a large round concavity bearing a pair of large sacculi S3. The specific function of this structure is not yet known, but the found sexual dimorphism is presumably involved in pheromonal communication allowing rapid sperm transfer. This is the fourth Neoribates species displaying sexually dimorphic characters. Additionally, Neoribates isabelaensis sp. nov. differs from the morphologically most similar species, Neoribates barbatus Hammer, 1968, by its smaller body size, pointed rostrum, long and setiform bothridial setae and the localization of notogastral setae h1 and h2, which insert close to each other. Further, we discussed all cases of sexual dimorphism in the family Parakalummidae as well as other related groups of Oripodoidea, and the possible function of these modifications.

Theory of the mode stabilization mechanism in concave-micromirror-capped vertical-cavity surface-emitting lasers

NASA Astrophysics Data System (ADS)

Park, Si-Hyun; Park, Yeonsang; Jeon, Heonsu

2003-08-01

We have investigated theoretically the transverse mode stabilization mechanism in oxide-confined concave-micromirror-capped vertical-cavity surface-emitting lasers (CMC-VCSELs) as reported by Park et al. [Appl. Phys. Lett. 80, 183 (2002)]. From detailed numerical calculations on a model CMC-VCSEL structure, we found that mode discrimination factors appear to be periodic in the micromirror layer thickness with a periodicity of λ/2. We also found that there are two possible concave micromirror structures for the fundamental transverse mode laser operation. These structures can be grouped according to the thickness of the concave micromirror layer: whether it is an integer or a half-integer multiple of λ/2. The optimal micromirror curvature radius differs accordingly for each case. In an optimally designed CMC-VCSEL model structure, the fundamental transverse mode can be favored as much as 4, 8, and 13 times more strongly than the first, second, and third excited modes, respectively.

Impact of trailing edge shape on the wake and propulsive performance of pitching panels

NASA Astrophysics Data System (ADS)

Van Buren, T.; Floryan, D.; Brunner, D.; Senturk, U.; Smits, A. J.

2017-01-01

The effects of changing the trailing edge shape on the wake and propulsive performance of a pitching rigid panel are examined experimentally. The panel aspect ratio is AR=1 , and the trailing edges are symmetric chevron shapes with convex and concave orientations of varying degree. Concave trailing edges delay the natural vortex bending and compression of the wake, and the mean streamwise velocity field contains a single jet. Conversely, convex trailing edges promote wake compression and produce a quadfurcated wake with four jets. As the trailing edge shape changes from the most concave to the most convex, the thrust and efficiency increase significantly.

Disturbance functions of the Goertler instability on an airfoil

NASA Technical Reports Server (NTRS)

Dagenhart, J. R.; Mangalam, S. M.

1986-01-01

Goertler vortices arise in boundary layers along concave surfaces due to centrifugal effects. This paper presents some results of an experiment conducted to study the development of these vortices on an airfoil with a pressure gradient in the concave region where an attached laminar boundary layer was insured with suction through a perforated panel. A sublimating chemical technique was used to visualize Goertler vortices and the velocity field was measured by laser velocimetry. Experimental disturbance functions are compared with those predicted by the linear stability theory. The trend of vortex amplification in the concave zone and damping in the following convex region is shown to essentially follow the theoretical predictions.

Single-pulse femtosecond laser fabrication of concave microlens- and micromirror arrays in chalcohalide glass

NASA Astrophysics Data System (ADS)

Kadan, Viktor; Blonskyi, Ivan; Shynkarenko, Yevhen; Rybak, Andriy; Calvez, Laurent; Mytsyk, Bohdan; Spotyuk, Oleh

2017-11-01

The diffraction-limited plano-concave microlens- and micromirror arrays were produced in chalcohalide glass of 65GeS2-25Ga2S3-10CsCl composition transparent from ∼0.5 to 11 μm. Only a single 200 fs laser pulse with 800 nm central wavelength is required to form microlens, which after metal coating becomes a concave micromirror. This process can serve as a basis for flexible technology to fabricate regular microlens and micromirror arrays for optotelecom applications, its performance being limited only by repetition rate of the laser pulses (typically 1000 microlenses per second).

A proof of the log-concavity conjecture related to the computation of the ergodic capacity of MIMO channels

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

Gurvitis, Leonid

2009-01-01

An upper bound on the ergodic capacity of MIMO channels was introduced recently in [1]. This upper bound amounts to the maximization on the simplex of some multilinear polynomial p({lambda}{sub 1}, ..., {lambda}{sub n}) with non-negative coefficients. In general, such maximizations problems are NP-HARD. But if say, the functional log(p) is concave on the simplex and can be efficiently evaluated, then the maximization can also be done efficiently. Such log-concavity was conjectured in [1]. We give in this paper self-contained proof of the conjecture, based on the theory of H-Stable polynomials.

Cone Quasi-Concave Multi-Objective Programming Theory and Dominance Cone Constructions.

DTIC Science & Technology

1988-08-01

generalized cone concavity and nondominated solutions for later use in our development. We also derive some properties of generalized cone concavity. A set S...A-quasiconcave on S" if g(.x 1+(1-X)x 2)-Min{g(x0), g(x 2)) e IntA forallxl*x 2 E SandX e (0,1), where (in ( gi (x’), gi (x2)) Min [g (0i), g (x2 ) - 1...will lead to elimination of the points of J3 by using the dominance cone W3 . Associated with W3 , only the points of J1 and J2 are nondominated, and

Near-Wall Measurements of a Three-Dimensional Turbulent Boundary Layer.

DTIC Science & Technology

1995-08-01

Baskaran, Pontikis , and Bradshaw (1989) extended the infinite swept wing study of Bradshaw and Pontikos, by adding surface curvature, both concave...on a concave surface," Thermosciences Div., Stanford University, Stanford, CA, Report MD-47. Baskaran, V., Pontikis , Y.G., k Bradshaw, P. (1989

Improved acoustic levitation apparatus

NASA Technical Reports Server (NTRS)

Berge, L. H.; Johnson, J. L.; Oran, W. A.; Reiss, D. A.

1980-01-01

Concave driver and reflector enhance and shape levitation forces in acoustic resonance system. Single-mode standing-wave pattern is focused by ring element situated between driver and reflector. Concave surfaces increase levitating forces up to factor of 6 as opposed to conventional flat surfaces, making it possible to suspend heavier objects.

Slow approach to steady motion of a concave body in a free-molecular gas

NASA Astrophysics Data System (ADS)

Tsuji, Tetsuro; Arai, Junichi; Kawano, Satoyuki

2015-07-01

A body in a free-molecular gas accelerated by a constant external force is considered on the basis of kinetic theory. The body is an infinitely long rectangular hollow column with one face removed, and thus it has a squarish U -shaped cross section. The concave part of the body points toward the direction of motion, and thus the gas molecules may be trapped in the concavity. Gas molecules undergo diffuse reflection on a base part, whereas specular reflection on two lateral parts. It is numerically shown that the velocity of the body approaches a terminal velocity, for which a drag force exerted by the gas counterbalances the external force, in such a way that their difference decreases in proportion to the inverse square of time for a large time. This rate of approach is slower than the known rate proportional to the inverse cube of time in the case of a body without concavity [Aoki et al., Phys. Rev. E 80, 016309 (2009), 10.1103/PhysRevE.80.016309]. Based on the detailed investigation on the velocity distribution function of gas molecules impinging on the body, it is clarified that the concavity prevents some molecules from escaping to infinity. This trapping enhances the effect of recollision between the body and the gas molecules, which is the cause of the inverse power laws, and thus leads to the slower approach.

Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

NASA Astrophysics Data System (ADS)

Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

2015-12-01

Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

Novel high-NA MRF toolpath supports production of concave hemispheres

NASA Astrophysics Data System (ADS)

Maloney, Chris; Supranowitz, Chris; Dumas, Paul

2017-10-01

Many optical system designs rely on high numerical aperture (NA) optics, including lithography and defense systems. Lithography systems require high-NA optics to image the fine patterns from a photomask, and many defense systems require the use of domes. The methods for manufacturing such optics with large half angles have often been treated as proprietary by most manufacturers due to the challenges involved. In the past, many high-NA concave surfaces could not be polished by magnetorheological finishing (MRF) due to collisions with the hardware underneath the polishing head. By leveraging concepts that were developed to enable freeform raster MRF capabilities, QED Technologies has implemented a novel toolpath to facilitate a new high-NA rotational MRF mode. This concept involves the use of the B-axis (rotational axis) in combination with a "virtual-axis" that utilizes the geometry of the polishing head. Hardware collisions that previously restricted the concave half angle limit can now be avoided and the new functionality has been seamlessly integrated into the software. This new MRF mode overcomes past limitations for polishing concave surfaces to now accommodate full concave hemispheres as well as extend the capabilities for full convex hemispheres. We discuss some of the previous limitations, and demonstrate the extended capabilities using this novel toolpath. Polishing results are used to qualify the new toolpath to ensure similar results to the "standard" rotational MRF mode.

Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction.

PubMed

Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

2015-12-18

Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

[Design of flat field holographic concave grating for near-infrared spectrophotometer].

PubMed

Xiang, Xian-Yi; Wen, Zhi-Yu

2008-07-01

Near-infrared spectrum analysis can be used to determine the nature or test quantitatively some chemical compositions by detecting molecular double frequency and multiple frequency absorption. It has been used in agriculture, biology, petrifaction, foodstuff, medicament, spinning and other fields. Near-infrared spectrophotometer is the main apparatus for near-infrared spectrum analysis, and the grating is the most important part of the apparatus. Based on holographic concave grating theory and optic design software CODE V, a flat field holographic concave grating for near-infrared spectrophotometer was designed from primary structure, which relied on global optimization of the software. The contradiction between wide spectrum bound and limited spectrum extension was resolved, aberrations were reduced successfully, spectrum information was utilized fully, and the optic structure of spectrometer was highly efficient. Using CODE V software, complex high-order aberration equations need not be solved, the result can be evaluated quickly, flat field and resolving power can be kept in balance, and the work efficiency is also enhanced. A paradigm of flat field holographic concave grating is given, it works between 900 nm to 1 700 nm, the diameter of the concave grating is 25 mm, and F/ # is 1. 5. The design result was analyzed and evaluated. It was showed that if the slit source, whose width is 50 microm, is used to reconstruction, the theoretic resolution capacity is better than 6.3 nm.

Assessment of the performance of a compact concentric spectrometer system for Atmospheric Differential Optical Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Whyte, C.; Leigh, R. J.; Lobb, D.; Williams, T.; Remedios, J. J.; Cutter, M.; Monks, P. S.

2009-12-01

A breadboard demonstrator of a novel UV/VIS grating spectrometer has been developed based upon a concentric arrangement of a spherical meniscus lens, concave spherical mirror and curved diffraction grating suitable for a range of atmospheric remote sensing applications from the ground or space. The spectrometer is compact and provides high optical efficiency and performance benefits over traditional instruments. The concentric design is capable of handling high relative apertures, owing to spherical aberration and comma being near zero at all surfaces. The design also provides correction for transverse chromatic aberration and distortion, in addition to correcting for the distortion called "smile", the curvature of the slit image formed at each wavelength. These properties render this design capable of superior spectral and spatial performance with size and weight budgets significantly lower than standard configurations. This form of spectrometer design offers the potential for exceptionally compact instrument for differential optical absorption spectroscopy (DOAS) applications from LEO, GEO, HAP or ground-based platforms. The breadboard demonstrator has been shown to offer high throughput and a stable Gaussian line shape with a spectral range from 300 to 450 nm at 0.5 nm resolution, suitable for a number of typical DOAS applications.

The Science of Optics; The History of Art

NASA Astrophysics Data System (ADS)

Falco, Charles

Recently, renowned artist David Hockney observed that certain drawings and paintings from as early as the Renaissance seemed almost ''photographic'' in detail. Following an extensive visual investigation of western art of the past 1000 years, he made the revolutionary claim that artists even of the prominence of van Eyck and Bellini must have used optical aids. However, many art historians insisted there was no supporting evidence for such a remarkable assertion. In this talk I will show a wealth of optical evidence for his claim that Hockney and I subsequently discovered during an unusual, and remarkably productive, collaboration between an artist and a scientist. I also discuss the imaging properties of the concave mirror and some of the implications this work has for the history of science as well as the history of art (and the modern fields of machine vision and computerized image analysis). These discoveries convincingly demonstrate optical instruments were in use - by artists, not scientists - nearly 200 years earlier than commonly thought possible, and account for the remarkable transformation in the reality of portraits that occurred early in the 15th century. Acknowledgment: This work was done in collaboration with David Hockney.

Modeling of Focused Acoustic Field of a Concave Multi-annular Phased Array Using Spheroidal Beam Equation

NASA Astrophysics Data System (ADS)

Yu, Li-Li; Shou, Wen-De; Hui, Chun

2012-02-01

A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation (SBE) for multi-annular phased elements are studied. Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O'Neil and Khokhlov—Zabolotskaya—Kuznetsov (KZK) model, respectively. Axial dynamic focusing and the harmonic effects are presented. The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.

The investigation of flow instabilities on a rotating disk with curvature in the radial direction

NASA Technical Reports Server (NTRS)

Intemann, P. A.; Clarkson, M. H.

1982-01-01

The major objective is to explore any visible differences of the flow field with wall curvature of the test body, including possible interaction between Taylor-Gortler instabilities present along concave walls and the inflexional instabilities investigated here. An experimental study was conducted with emphasis placed on making visual observations and recording photographically the flow instabilities present under three different rotating bodies: a flat disk, a concave paraboloid, and a convex paraboloid. The data collected for the three test bodies lead to the conclusion that the wall curvature of the concave and convex paraboloids did not alter the observed flow field significantly from that observed on the flat disk.

Au@Pd core-shell nanobricks with concave structures and their catalysis of ethanol oxidation.

PubMed

Wang, Wenjin; Zhang, Jie; Yang, Shengchun; Ding, Bingjun; Song, Xiaoping

2013-10-01

Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2 PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the existence of solutions of an equation arising in the theory of laminar flow in a uniformly porous channel with injection

NASA Technical Reports Server (NTRS)

Shih, K. G.

1986-01-01

The existence of concave solutions of Berman's equation which describes the laminar flow in channels with injection through porous walls is established. It was found that the (unique) concave solutions exist for all injection Reynolds number R < 0.

Quantitative test for concave aspheric surfaces using a Babinet compensator.

PubMed

Saxena, A K

1979-08-15

A quantitative test for the evaluation of surface figures of concave aspheric surfaces using a Babinet compensator is reported. A theoretical estimate of the sensitivity is 0.002lambda for a minimum detectable phase change of 2 pi x 10(-3) rad over a segment length of 1.0 cm.

REGULARIZATION FOR COX’S PROPORTIONAL HAZARDS MODEL WITH NP-DIMENSIONALITY*

PubMed Central

Fan, Jianqing; Jiang, Jiancheng

2011-01-01

High throughput genetic sequencing arrays with thousands of measurements per sample and a great amount of related censored clinical data have increased demanding need for better measurement specific model selection. In this paper we establish strong oracle properties of non-concave penalized methods for non-polynomial (NP) dimensional data with censoring in the framework of Cox’s proportional hazards model. A class of folded-concave penalties are employed and both LASSO and SCAD are discussed specifically. We unveil the question under which dimensionality and correlation restrictions can an oracle estimator be constructed and grasped. It is demonstrated that non-concave penalties lead to significant reduction of the “irrepresentable condition” needed for LASSO model selection consistency. The large deviation result for martingales, bearing interests of its own, is developed for characterizing the strong oracle property. Moreover, the non-concave regularized estimator, is shown to achieve asymptotically the information bound of the oracle estimator. A coordinate-wise algorithm is developed for finding the grid of solution paths for penalized hazard regression problems, and its performance is evaluated on simulated and gene association study examples. PMID:23066171

REGULARIZATION FOR COX'S PROPORTIONAL HAZARDS MODEL WITH NP-DIMENSIONALITY.

PubMed

Bradic, Jelena; Fan, Jianqing; Jiang, Jiancheng

2011-01-01

High throughput genetic sequencing arrays with thousands of measurements per sample and a great amount of related censored clinical data have increased demanding need for better measurement specific model selection. In this paper we establish strong oracle properties of non-concave penalized methods for non-polynomial (NP) dimensional data with censoring in the framework of Cox's proportional hazards model. A class of folded-concave penalties are employed and both LASSO and SCAD are discussed specifically. We unveil the question under which dimensionality and correlation restrictions can an oracle estimator be constructed and grasped. It is demonstrated that non-concave penalties lead to significant reduction of the "irrepresentable condition" needed for LASSO model selection consistency. The large deviation result for martingales, bearing interests of its own, is developed for characterizing the strong oracle property. Moreover, the non-concave regularized estimator, is shown to achieve asymptotically the information bound of the oracle estimator. A coordinate-wise algorithm is developed for finding the grid of solution paths for penalized hazard regression problems, and its performance is evaluated on simulated and gene association study examples.

STRONG ORACLE OPTIMALITY OF FOLDED CONCAVE PENALIZED ESTIMATION.

PubMed

Fan, Jianqing; Xue, Lingzhou; Zou, Hui

2014-06-01

Folded concave penalization methods have been shown to enjoy the strong oracle property for high-dimensional sparse estimation. However, a folded concave penalization problem usually has multiple local solutions and the oracle property is established only for one of the unknown local solutions. A challenging fundamental issue still remains that it is not clear whether the local optimum computed by a given optimization algorithm possesses those nice theoretical properties. To close this important theoretical gap in over a decade, we provide a unified theory to show explicitly how to obtain the oracle solution via the local linear approximation algorithm. For a folded concave penalized estimation problem, we show that as long as the problem is localizable and the oracle estimator is well behaved, we can obtain the oracle estimator by using the one-step local linear approximation. In addition, once the oracle estimator is obtained, the local linear approximation algorithm converges, namely it produces the same estimator in the next iteration. The general theory is demonstrated by using four classical sparse estimation problems, i.e., sparse linear regression, sparse logistic regression, sparse precision matrix estimation and sparse quantile regression.

Investigation of Artificial Forced Cooling in the Bridgman Crystal Growth of Cadmium Zinc Telluride

NASA Astrophysics Data System (ADS)

Liu, Juncheng; Li, Jiao; Zhang, Guodong; Li, Changxing; Lennon, Craig; Sivananthan, Siva

2007-08-01

The effects of artificial forced cooling on the solid liquid interface and on solute segregation were investigated by modeling the vertical Bridgman method for the single-crystal growth of CdZnTe, taking into consideration effects such as increasing the axial outward heat flux from the crucible bottom, the radial outward heat flux from the crucible wall, and the carbon film thickness on the crucible inner wall. Axial artificially forced cooling noticeably increases convection and the temperature gradient in the melt next to the solid liquid interface, and substantially reduces interface concavity at the initial solidification stage. Interface concavity increases a little when the solidification proceeds further, however. Axial artificially forced cooling reduces radial solute segregation of the initial segment of the grown crystal and slightly increases the solute iso-concentration segment. Radial artificially forced cooling enhances melt convection substantially, affects solid liquid interface concavity only slightly, and hardly affects solute segregation in the grown crystal. Doubling the carbon film thickness weakens convection of the melt in front of the interface, substantially increases interface concavity, and hardly affects solute segregation in the grown crystal.

An experimental investigation of turbulent boundary layers along curved surfaces

NASA Technical Reports Server (NTRS)

So, R. M. C.; Mellor, G. L.

1972-01-01

A curved wall tunnel was designed, and an equilibrium turbulent boundary layer was set up on the straight section preceding the curved test section. Turbulent boundary layer flows with uniform and adverse pressure distributions along convex and concave walls were investigated. Hot-wire measurements along the convex surface indicated that turbulent mixing between fluid layers was very much reduced. However, the law of the wall held and the skin friction, thus determined, correlated well with other measurements. Hot-wire measurements along the concave test wall revealed a system of longitudinal vortices inside the boundary layer and confirmed that concave curvature enhances mixing. A self-consistent set of turbulent boundary layer equations for flows along curved surfaces was derived together with a modified eddy viscosity. Solution of these equations together with the modified eddy viscosity gave results that correlated well with the present data on flows along the convex surface with arbitrary pressure distribution. However, it could only be used to predict the mean characteristics of the flow along concave walls because of the existence of the system of longitudinal vortices inside the boundary layer.

STRONG ORACLE OPTIMALITY OF FOLDED CONCAVE PENALIZED ESTIMATION

PubMed Central

Fan, Jianqing; Xue, Lingzhou; Zou, Hui

2014-01-01

Folded concave penalization methods have been shown to enjoy the strong oracle property for high-dimensional sparse estimation. However, a folded concave penalization problem usually has multiple local solutions and the oracle property is established only for one of the unknown local solutions. A challenging fundamental issue still remains that it is not clear whether the local optimum computed by a given optimization algorithm possesses those nice theoretical properties. To close this important theoretical gap in over a decade, we provide a unified theory to show explicitly how to obtain the oracle solution via the local linear approximation algorithm. For a folded concave penalized estimation problem, we show that as long as the problem is localizable and the oracle estimator is well behaved, we can obtain the oracle estimator by using the one-step local linear approximation. In addition, once the oracle estimator is obtained, the local linear approximation algorithm converges, namely it produces the same estimator in the next iteration. The general theory is demonstrated by using four classical sparse estimation problems, i.e., sparse linear regression, sparse logistic regression, sparse precision matrix estimation and sparse quantile regression. PMID:25598560

Atmospheric lidar multi-user instrument system definition study

NASA Technical Reports Server (NTRS)

Greco, R. V. (Editor)

1980-01-01

A spaceborne lidar system for atmospheric studies was defined. The primary input was the Science Objectives Experiment Description and Evolutionary Flow Document. The first task of the study was to perform an experiment evolutionary analysis of the SEED. The second task was the system definition effort of the instrument system. The third task was the generation of a program plan for the hardware phase. The fourth task was the supporting studies which included a Shuttle deficiency analysis, a preliminary safety hazard analysis, the identification of long lead items, and development studies required. As a result of the study an evolutionary Lidar Multi-User Instrument System (MUIS) was defined. The MUIS occupies a full Spacelab pallet and has a weight of 1300 kg. The Lidar MUIS laser provides a 2 joule frequency doubled Nd:YAG laser that can also pump a tuneable dye laser wide frequency range and bandwidth. The MUIS includes a 1.25 meter diameter aperture Cassegrain receiver, with a moveable secondary mirror to provide precise alignment with the laser. The receiver can transmit the return signal to three single and multiple photomultiple tube detectors by use of a rotating fold mirror. It is concluded that the Lidar MUIS proceed to program implementation.

The development and characterization of advanced broadband mirror coatings for the far-UV

NASA Astrophysics Data System (ADS)

Egan, Arika; Fleming, Brian T.; Wiley, James; Quijada, Manuel; Del Hoyo, Javier; Hennessy, John; Hicks, Brian; France, Kevin; Kruczek, Nicholas; Erickson, Nicholas

2017-08-01

We present a progress report on the development of new broadband mirror coatings that demonstrate > 80% reflectivities from 1020-5000Å. Four different coating recipes are presented as candidates for future far-ultraviolet (FUV) sensitive broadband observatories. Three samples were first coated with aluminum (Al) and lithium fluoride (LiF) at the NASA Goddard Space Flight Center (GSFC) using a new high-temperature physical vapor deposition (PVD) process. Two of these samples then had an ultrathin (10-20 Å) protective coat of either magnesium fluoride (MgF2) or aluminum fluoride (AlF3) applied using atomic later deposition (ALD) at the NASA Jet Propulsion Laboratory (JPL). A fourth sample was coated with Al and a similar high temperature PVD coating of AlF3. Polarized reflectivities into the FUV for each sample were obtained through collaboration with the Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. We present a procedure for using these reflectivities as a baseline for calculating the optical constants of each coating recipe. Given these results, we describe plans for improving our measurement methodology and techniques to develop and characterize these coating recipes for future FUV missions.

Detection of longitudinal ulcer using roughness value for computer aided diagnosis of Crohn's disease

NASA Astrophysics Data System (ADS)

Oda, Masahiro; Kitasaka, Takayuki; Furukawa, Kazuhiro; Watanabe, Osamu; Ando, Takafumi; Goto, Hidemi; Mori, Kensaku

2011-03-01

The purpose of this paper is to present a new method to detect ulcers, which is one of the symptoms of Crohn's disease, from CT images. Crohn's disease is an inflammatory disease of the digestive tract. Crohn's disease commonly affects the small intestine. An optical or a capsule endoscope is used for small intestine examinations. However, these endoscopes cannot pass through intestinal stenosis parts in some cases. A CT image based diagnosis allows a physician to observe whole intestine even if intestinal stenosis exists. However, because of the complicated shape of the small and large intestines, understanding of shapes of the intestines and lesion positions are difficult in the CT image based diagnosis. Computer-aided diagnosis system for Crohn's disease having automated lesion detection is required for efficient diagnosis. We propose an automated method to detect ulcers from CT images. Longitudinal ulcers make rough surface of the small and large intestinal wall. The rough surface consists of combination of convex and concave parts on the intestinal wall. We detect convex and concave parts on the intestinal wall by a blob and an inverse-blob structure enhancement filters. A lot of convex and concave parts concentrate on roughed parts. We introduce a roughness value to differentiate convex and concave parts concentrated on the roughed parts from the other on the intestinal wall. The roughness value effectively reduces false positives of ulcer detection. Experimental results showed that the proposed method can detect convex and concave parts on the ulcers.

High-resolution compact spectrometer based on a custom-printed varied-line-spacing concave blazed grating.

PubMed

Chen, Jianwei; Chen, Wang; Zhang, Guodong; Lin, Hui; Chen, Shih-Chi

2017-05-29

We present the modeling, design and characterization of a compact spectrometer, achieving a resolution better than 1.5 nm throughout the visible spectrum (360-825 nm). The key component in the spectrometer is a custom-printed varied-line-space (VLS) concave blazed grating, where the groove density linearly decreases from the center of the grating (530 g/mm) at a rate of 0.58 nm/mm to the edge (528 g/mm). Parametric models have been established to deterministically link the system performance with the VLS grating design parameters, e.g., groove density, line-space varying rate, and to minimize the system footprint. Simulations have been performed in ZEMAX to confirm the results, indicating a 15% enhancement in system resolution versus common constant line-space (CLS) gratings. Next, the VLS concave blazed grating is fabricated via our vacuum nanoimprinting system, where a polydimethylsiloxane (PDMS) stamp is non-uniformly expanded to form the varied-line-spacing pattern from a planar commercial grating master (600 g/mm) for precision imprinting. The concave blazed grating is measured to have an absolute diffraction efficiency of 43%, higher than typical holographic gratings (~30%) used in the commercial compact spectrometers. The completed compact spectrometer contains only one optical component, i.e., the VLS concave grating, as well as an entrance slit and linear photodetector array, achieving a footprint of 11 × 11 × 3 cm 3 , which makes it the most compact and resolving (1.46 nm) spectrometer of its kind.

The two-state dimer receptor model: a general model for receptor dimers.

PubMed

Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferrada, Carla; Ferré, Sergi; Fuxe, Kjell; Cortés, Antoni; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

2006-06-01

Nonlinear Scatchard plots are often found for agonist binding to G-protein-coupled receptors. Because there is clear evidence of receptor dimerization, these nonlinear Scatchard plots can reflect cooperativity on agonist binding to the two binding sites in the dimer. According to this, the "two-state dimer receptor model" has been recently derived. In this article, the performance of the model has been analyzed in fitting data of agonist binding to A(1) adenosine receptors, which are an example of receptor displaying concave downward Scatchard plots. Analysis of agonist/antagonist competition data for dopamine D(1) receptors using the two-state dimer receptor model has also been performed. Although fitting to the two-state dimer receptor model was similar to the fitting to the "two-independent-site receptor model", the former is simpler, and a discrimination test selects the two-state dimer receptor model as the best. This model was also very robust in fitting data of estrogen binding to the estrogen receptor, for which Scatchard plots are concave upward. On the one hand, the model would predict the already demonstrated existence of estrogen receptor dimers. On the other hand, the model would predict that concave upward Scatchard plots reflect positive cooperativity, which can be neither predicted nor explained by assuming the existence of two different affinity states. In summary, the two-state dimer receptor model is good for fitting data of binding to dimeric receptors displaying either linear, concave upward, or concave downward Scatchard plots.

Navier-Stokes Computations With One-Equation Turbulence Model for Flows Along Concave Wall Surfaces

NASA Technical Reports Server (NTRS)

Wang, Chi R.

2005-01-01

This report presents the use of a time-marching three-dimensional compressible Navier-Stokes equation numerical solver with a one-equation turbulence model to simulate the flow fields developed along concave wall surfaces without and with a downstream extension flat wall surface. The 3-D Navier- Stokes numerical solver came from the NASA Glenn-HT code. The one-equation turbulence model was derived from the Spalart and Allmaras model. The computational approach was first calibrated with the computations of the velocity and Reynolds shear stress profiles of a steady flat plate boundary layer flow. The computational approach was then used to simulate developing boundary layer flows along concave wall surfaces without and with a downstream extension wall. The author investigated the computational results of surface friction factors, near surface velocity components, near wall temperatures, and a turbulent shear stress component in terms of turbulence modeling, computational mesh configurations, inlet turbulence level, and time iteration step. The computational results were compared with existing measurements of skin friction factors, velocity components, and shear stresses of the developing boundary layer flows. With a fine computational mesh and a one-equation model, the computational approach could predict accurately the skin friction factors, near surface velocity and temperature, and shear stress within the flows. The computed velocity components and shear stresses also showed the vortices effect on the velocity variations over a concave wall. The computed eddy viscosities at the near wall locations were also compared with the results from a two equation turbulence modeling technique. The inlet turbulence length scale was found to have little effect on the eddy viscosities at locations near the concave wall surface. The eddy viscosities, from the one-equation and two-equation modeling, were comparable at most stream-wise stations. The present one-equation turbulence model is an effective approach for turbulence modeling in the near solid wall surface region of flow over a concave wall.

Passive Fetal Heart Monitoring System

NASA Technical Reports Server (NTRS)

Bryant, Timothy D. (Inventor); Wynkoop, Mark W. (Inventor); Holloway, Nancy M. H. (Inventor); Zuckerwar, Allan J. (Inventor)

2004-01-01

A fetal heart monitoring system preferably comprising a backing plate having a generally concave front surface and a generally convex back surface, and at least one sensor element attached to the concave front surface for acquiring acoustic fetal heart signals produced by a fetus within a body. The sensor element has a shape that conforms to the generally concave back surface of the backing plate. In one embodiment, the at least one sensor element comprises an inner sensor, and a plurality of outer sensors surrounding the inner sensor. The fetal heart monitoring system can further comprise a web belt, and a web belt guide movably attached to the web belt. The web belt guide being is to the convex back surface of the backing plate.

Concave Pd-Ru nanocubes bounded with high active area for boosting ethylene glycol electrooxidation

NASA Astrophysics Data System (ADS)

Xiong, Zhiping; Xu, Hui; Li, Shumin; Gu, Zhulan; Yan, Bo; Guo, Jun; Du, Yukou

2018-01-01

This paper reported our extensive efforts in the design of concave PdRu nanocubes via a facile wet-chemical strategy. Different from the previously reported PdRu nanostructures, the as-prepared concave PdRu nanocubes combined the advantages of fascinating nanocube structure, synergistic and electronic effect as well as high surface area. All of these beneficial terms endow them to exhibit superior electrocatalytic activity and long-term stability towards ethylene glycol oxidation as compared with commercial Pd/C. Our work highlights the significance of shape-controlled of PdRu nanostructures over the electrocatalytic performances towards the electrooxidation of ethylene glycol (EG), which will pave up a new strategy for boosting the development of renewable and clean energy technology.

Concave utility, transaction costs, and risk in measuring discounting of delayed rewards.

PubMed

Kirby, Kris N; Santiesteban, Mariana

2003-01-01

Research has consistently found that the decline in the present values of delayed rewards as delay increases is better fit by hyperbolic than by exponential delay-discounting functions. However, concave utility, transaction costs, and risk each could produce hyperbolic-looking data, even when the underlying discounting function is exponential. In Experiments 1 (N = 45) and 2 (N = 103), participants placed bids indicating their present values of real future monetary rewards in computer-based 2nd-price auctions. Both experiments suggest that utility is not sufficiently concave to account for the superior fit of hyperbolic functions. Experiment 2 provided no evidence that the effects of transaction costs and risk are large enough to account for the superior fit of hyperbolic functions.

The concave cusp as a determiner of figure-ground.

PubMed

Stevens, K A; Brookes, A

1988-01-01

The tendency to interpret as figure, relative to background, those regions that are lighter, smaller, and, especially, more convex is well known. Wherever convex opaque objects abut or partially occlude one another in an image, the points of contact between the silhouettes form concave cusps, each indicating the local assignment of figure versus ground across the contour segments. It is proposed that this local geometric feature is a preattentive determiner of figure-ground perception and that it contributes to the previously observed tendency for convexity preference. Evidence is presented that figure-ground assignment can be determined solely on the basis of the concave cusp feature, and that the salience of the cusp derives from local geometry and not from adjacent contour convexity.

Heating-induced phase transformation in zeolite brewsterite: new 4- and 5-coordinated (Si,Al) sites

NASA Astrophysics Data System (ADS)

Alberti, A.; Sacerdoti, M.; Quartieri, S.; Vezzalini, G.

The dehydration-rehydration processes and phase transformations of brewsterite (space group P21/m, ideal formula (Sr,Ba)Al2Si6O16.5H2O) were studied by single crystal X-ray diffraction on two samples heated in an evacuated capillary for 24 h at 280°C and 330°C, respectively, and then cooled to room temperature. After the data collection, the capillary of the crystal heated at 280°C was broken, the sample was kept at room conditions for one month, and diffraction data were recollected. Brewsterite heated in vacuum at 280°C shows a strong decrease of the unit cell volume (about 10%) and the statistical breaking of the T1-O7-T2 bridge of the 4-ring of the 4254 PBU. T1 cation, in 31% of cases, migrates to a new tetrahedral site, which shares three vertices with the previously occupied one; the fourth vertex is on the mirror plane, and joins two adjacent layers. T2 cation, in 20% of cases, migrates to a new site, which is characterized by a 5-fold coordination. This coordination polyhedron shares three vertices with the previously occupied tetrahedron; the fourth vertex is on the mirror plane, and joins two adjacent layers; the fifth one is unshared. The formation of these new T-O-T bridges prevents the re-expansion and rehydration of the heated brewsterite; as a consequence, the crystal brought back to room conditions does not show any noticeable structural difference with respect to that heated at 280°C. The exchangeable cations, which occupy only one extraframework site in the untreated brewsterite, spread over several sites. The sample heated at 330°C shows a further decrease in the unit cell volume of about 2% with respect to the sample heated at 280°C, and an increase in the migration percentage of T1 and T2 cations to the new sites.

Fabrication of concave micromirrors for single cell imaging via controlled over-exposure of organically modified ceramics in single step lithography

PubMed Central

Bonabi, A.; Cito, S.; Tammela, P.; Jokinen, V.

2017-01-01

This work describes the fabrication of concave micromirrors to improve the sensitivity of fluorescence imaging, for instance, in single cell analysis. A new approach to fabrication of tunable round (concave) cross-sectional shaped microchannels out of the inorganic-organic hybrid polymer, Ormocomp®, via single step optical lithography was developed and validated. The concave micromirrors were implemented by depositing and patterning thin films of aluminum on top of the concave microchannels. The round cross-sectional shape was due to residual layer formation, which is inherent to Ormocomp® upon UV exposure in the proximity mode. We show that it is possible to control the residual layer thickness and thus the curved shape of the microchannel cross-sectional profile and eventually the focal length of the micromirror, by simply adjusting the UV exposure dose and the distance of the proximity gap (to the photomask). In general, an increase in the exposure dose or in the distance of the proximity gap results in a thicker residual layer and thus an increase in the radius of the microchannel curvature. Under constant exposure conditions, the radius of curvature is almost linearly dependent on the microchannel aspect ratio, i.e., the width (here, 20–200 μm) and the depth (here, 15–45 μm). Depending on the focal length, up to 8-fold signal enhancement over uncoated, round Ormocomp® microchannels was achieved in single cell imaging with the help of the converging micromirrors in an epifluorescence microscopy configuration. PMID:28652888

Fabrication of concave micromirrors for single cell imaging via controlled over-exposure of organically modified ceramics in single step lithography.

PubMed

Bonabi, A; Cito, S; Tammela, P; Jokinen, V; Sikanen, T

2017-05-01

This work describes the fabrication of concave micromirrors to improve the sensitivity of fluorescence imaging, for instance, in single cell analysis. A new approach to fabrication of tunable round (concave) cross-sectional shaped microchannels out of the inorganic-organic hybrid polymer, Ormocomp ® , via single step optical lithography was developed and validated. The concave micromirrors were implemented by depositing and patterning thin films of aluminum on top of the concave microchannels. The round cross-sectional shape was due to residual layer formation, which is inherent to Ormocomp ® upon UV exposure in the proximity mode. We show that it is possible to control the residual layer thickness and thus the curved shape of the microchannel cross-sectional profile and eventually the focal length of the micromirror, by simply adjusting the UV exposure dose and the distance of the proximity gap (to the photomask). In general, an increase in the exposure dose or in the distance of the proximity gap results in a thicker residual layer and thus an increase in the radius of the microchannel curvature. Under constant exposure conditions, the radius of curvature is almost linearly dependent on the microchannel aspect ratio, i.e., the width (here, 20-200  μ m) and the depth (here, 15-45  μ m). Depending on the focal length, up to 8-fold signal enhancement over uncoated, round Ormocomp ® microchannels was achieved in single cell imaging with the help of the converging micromirrors in an epifluorescence microscopy configuration.

Monotonicity and Logarithmic Concavity of Two Functions Involving Exponential Function

ERIC Educational Resources Information Center

Liu, Ai-Qi; Li, Guo-Fu; Guo, Bai-Ni; Qi, Feng

2008-01-01

The function 1 divided by "x"[superscript 2] minus "e"[superscript"-x"] divided by (1 minus "e"[superscript"-x"])[superscript 2] for "x" greater than 0 is proved to be strictly decreasing. As an application of this monotonicity, the logarithmic concavity of the function "t" divided by "e"[superscript "at"] minus "e"[superscript"(a-1)""t"] for "a"…

Thermal Stability of Metal Nanocrystals: An Investigation of the Surface and Bulk Reconstructions of Pd Concave Icosahedra [On the Thermal Stability of Metal Nanocrystals: An Investigation of the Surface and Bulk Reconstructions of Pd Concave Icosahedra

DOE PAGES

Gilroy, Kyle D.; Elnabawy, Ahmed O.; Yang, Tung -Han; ...

2017-04-27

Despite the remarkable success in controlling the synthesis of metal nanocrystals, it still remains a grand challenge to stabilize and preserve the shapes or internal structures of metastable kinetic products. In this work, we address this issue by systematically investigating the surface and bulk reconstructions experienced by a Pd concave icosahedron when subjected to heating up to 600 °C in vacuum. We used in situ high-resolution transmission electron microscopy to identify the equilibration pathways of this far-from-equilibrium structure. We were able to capture key structural transformations occurring during the thermal annealing process, which were mechanistically rationalized by implementing self-consistent plane-wavemore » density functional theory (DFT) calculations. Specifically, the concave icosahedron was found to evolve into a regular icosahedron via surface reconstruction in the range of 200–400 °C, and then transform into a pseudospherical crystalline structure through bulk reconstruction when further heated to 600 °C. As a result, the mechanistic understanding may lead to the development of strategies for enhancing the thermal stability of metal nanocrystals.« less

Effect of punch tip geometry and embossment on the punch tip adherence of a model ibuprofen formulation.

PubMed

Roberts, Matthew; Ford, James L; MacLeod, Graeme S; Fell, John T; Smith, George W; Rowe, Philip H; Dyas, A Mark

2004-07-01

The sticking of a model ibuprofen-lactose formulation with respect to compaction force, punch tip geometry and punch tip embossment was assessed. Compaction was performed at 10, 25 or 40 kN using an instrumented single-punch tablet press. Three sets of 'normal' concave punches were used to evaluate the influence of punch curvature and diameter. The punches were 10, 11 and 12 mm in diameter, respectively. The 10-mm punch was embossed with a letter 'A' logo to assess the influence of an embossment on sticking. Flat-faced punches (12.5 mm) were used for comparison with the concave tooling. Surface profiles (Taylor Hobson Talysurf 120) of the upper punch faces were obtained to evaluate the surface quality of the tooling used. Following compaction, ibuprofen attached to the upper punch face was quantified by spectroscopy. Increasing punch curvature from flat-faced punches to concave decreased sticking. Altering punch diameter of the concave punches had no effect on sticking when expressed as microg mm(-2). The embossed letter 'A' logo increased sticking considerably owing to the probable concentration of shear stresses at the lateral faces of the embossed logo.

A new signal restoration method based on deconvolution of the Point Spread Function (PSF) for the Flat-Field Holographic Concave Grating UV spectrometer system

NASA Astrophysics Data System (ADS)

Dai, Honglin; Luo, Yongdao

2013-12-01

In recent years, with the development of the Flat-Field Holographic Concave Grating, they are adopted by all kinds of UV spectrometers. By means of single optical surface, the Flat-Field Holographic Concave Grating can implement dispersion and imaging that make the UV spectrometer system design quite compact. However, the calibration of the Flat-Field Holographic Concave Grating is very difficult. Various factors make its imaging quality difficult to be guaranteed. So we have to process the spectrum signal with signal restoration before using it. Guiding by the theory of signals and systems, and after a series of experiments, we found that our UV spectrometer system is a Linear Space- Variant System. It means that we have to measure PSF of every pixel of the system which contains thousands of pixels. Obviously, that's a large amount of calculation .For dealing with this problem, we proposes a novel signal restoration method. This method divides the system into several Linear Space-Invariant subsystems and then makes signal restoration with PSFs. Our experiments turn out that this method is effective and inexpensive.

Buckling and bone modeling as factors in the development of idiopathic scoliosis.

PubMed

Goto, Manabu; Kawakami, Noriaki; Azegami, Hideyuki; Matsuyama, Yukihiro; Takeuchi, Kenzen; Sasaoka, Ryu

2003-02-15

Computational analysis using the finite-element method was used to examine a possible etiology of idiopathic scoliosis. To compare changes in the coronal and the transverse planes of idiopathic thoracic scoliosis with changes produced in a finite-element buckling model, and to investigate the influence of bone modeling on the buckling spine. Although it is now widely accepted that growth is related strongly to the onset and progression of scoliosis, the pathomechanism or etiology of idiopathic scoliosis still is not clear. A previous study showed that a buckling phenomenon caused by anterior spinal overgrowth can produce scoliosis, and that the fourth buckling mode matched the clinical characteristics associated with the thoracic type of idiopathic scoliosis. The fourth buckling mode occurs when the first, second, and third buckling modes are prevented. The spinal finite-element model used in this study consisted of 68,582 elements and 84,603 nodes. The transverse changes seen in the computed tomography images of 41 patients with idiopathic thoracic scoliosis (apex, T8; average Cobb angle, 52.5 degrees) were compared with those produced in the fourth buckling mode. Bone modeling (bone formation and resorption) was simulated as heat deformation caused by changes in temperature. The bone formation and resorption were simulated, respectively, by positive and negative volume changes in proportion to the stress that occurred in the buckling spine. Computed tomography images of scoliosis show that as the scoliosis becomes more severe, the thoracic cage decreases on the convex side of the curve and increases on the concave side. The opposite thoracic cage deformation was obtained in the fourth buckling mode. In patients with scoliosis, the sternum essentially remains in its original position with respect to the vertebrae, but in the linear buckling model, it shifted in the direction of vertebral body rotation. In contrast to clinical data, the incremental deformation resulting from bone formation corrected the original curve, and the thoracic cage distorted. On the other hand, incremental deformation resulting from bone resorption worsened the original curve, and the thoracic cage distorted in a manner similar to that described by the clinical data. This computational investigation suggests that scoliotic changes in the spinal column triggered by the buckling phenomenon are counteracted by bone formation, but worsened by bone resorption. The authors hypothesized that scoliosis progressed with resorption of loaded bone. However, it is unclear whether this hypothesis applies to a living body in practice because of the effects from additional factors.

Method for simultaneously making a plurality of acoustic signal sensor elements

NASA Technical Reports Server (NTRS)

Bryant, Timothy D. (Inventor); Wynkoop, Mark W. (Inventor); Holloway, Nancy M. H. (Inventor); Zuckerwar, Allan J. (Inventor)

2005-01-01

A fetal heart monitoring system preferably comprising a backing plate having a generally concave front surface and a generally convex back surface, and at least one sensor element attached to the concave front surface for acquiring acoustic fetal heart signals produced by a fetus within a body. The sensor element has a shape that conforms to the generally concave back surface of the backing plate. In one embodiment, the at least one sensor element comprises an inner sensor, and a plurality of outer sensors surrounding the inner sensor. The fetal heart monitoring system can further comprise a web belt, and a web belt guide movably attached to the web belt. The web belt guide being is to the convex back surface of the backing plate.

Study on High Speed Lithium Jet For Neutron Source of Boron Neutron Capture Therapy (BNCT)

NASA Astrophysics Data System (ADS)

Takahashi, Minoru; Kobayashi, Tooru; Zhang, Mingguang; Mák, Michael; Štefanica, Jirí; Dostál, Václav; Zhao, Wei

The feasibility study of a liquid lithium type proton beam target was performed for the neutron source of the boron neutron capture therapy (BNCT). As the candidates of the liquid lithium target, a thin sheet jet and a thin film flow on a concave wall were chosen, and a lithium flow experiment was conducted to investigate the hydrodynamic stability of the targets. The surfaces of the jets and film flows with a thickness of 0.5 mm and a width of 50 mm were observed by means of photography. It has been found that a stable sheet jet and a stable film flow on a concave wall can be formed up to certain velocities by using a straight nozzle and a curved nozzle with the concave wall, respectively.

Method for Simultaneously Making a Plurality of Acoustic Signal Sensor Elements

NASA Technical Reports Server (NTRS)

Bryant, Timothy D.; Wynkoop, Mark W.; Holloway, Nancy M. H.; Zuckerwar, Allan J.

2005-01-01

A fetal heart monitoring system preferably comprising a backing plate having a generally concave front surface and a generally convex back surface, and at least one sensor element attached to the concave front surface for acquiring acoustic fetal heart signals produced by a fetus within a body. The sensor element has a shape that conforms to the generally concave back surface of the backing plate. In one embodiment, the at least one sensor element comprises an inner sensor, and a plurality of outer sensors surrounding the inner sensor. The fetal heart monitoring system can further comprise a web belt, and a web belt guide movably attached to the web belt. The web belt guide being is to the convex back surface of the backing plate.

Reproducible and recyclable SERS substrates: Flower-like Ag structures with concave surfaces formed by electrodeposition

NASA Astrophysics Data System (ADS)

Bian, Juncao; Shu, Shiwei; Li, Jianfu; Huang, Chao; Li, Yang Yang; Zhang, Rui-Qin

2015-04-01

Direct synthesis of three-dimensional Ag structures on solid substrates for the purposes of producing reproducible and recyclable surface-enhanced Raman scattering (SERS) applications remains challenging. In this work, flower-like Ag structures with concave surfaces (FACS) were successfully electrodeposited onto ITO glass using the double-potentiostatic method. The FACS, with an enhancement factor of the order of 108, exhibited a SERS signal intensity 3.3 times stronger than that measured from Ag nanostructures without concave surfaces. A cleaning procedure involving lengthy immersion of the sample in ethanol and KNO3 was proposed to recycle the substrate and confirmed by using rhodamine 6G, adenine, and 4-aminothiophenol as target molecules. The findings can help to advance the practical applications of Ag nanostructure-based SERS substrates.

Anion Binding to Hydrophobic Concavity is Central to the Salting-in Effects of Hofmeister Chaotropes

PubMed Central

Gibb, Corinne L. D.; Gibb, Bruce C.

2011-01-01

For over 120 years it has been appreciated that certain salts (kosmotropes) cause the precipitation of proteins, whilst others (chaotropes) increase their solubility. The cause of this, “Hofmeister effect” is still unclear; especially with the original concept that kosmotropic anions “make” water structure and chaotropes “break” it being countered by recent studies suggesting otherwise. Here, we present the first direct evidence that chaotropic anions have an affinity for hydrophobic concavity, and that it is competition between a convex hydrophobe and the anion for a binding site that leads to the apparent weakening of the hydrophobic effect by chaotropes. In combination, these results suggest that chaotropes primarily induce protein solubilization by direct binding to concavity in the molten globule state of a protein. PMID:21524086

Fully EMU suited MS Peterson and MS Musgrave in airlock

NASA Technical Reports Server (NTRS)

1983-01-01

Fully extravehicular mobility unit (EMU) suited Mission Specialist (MS) Peterson (wearing glasses) and MS Musgrave with service and cooling umbilical (SCU) connected to their displays and control modules (DCMs) participate in airlock prebreathe procedures. Three-fourths of the STS-6 astronaut crew appear in this unusual 35mm frame exposed in the airlock of the Earth-orbiting Challenger, Orbiter Vehicle (OV) 099. Musgrave's helmet visor encompasses all the action in the frame. Peterson is reflected on the right side of Musgrave's visor with Pilot Bobko, wearing conventional onboard clothing and photographing, the activity appearing at the center of the frame. The reversed numbers (1 and 2) in the mirrored image represents the extravehicular activity (EVA) designations for the two mission specialists.

Outlet strut fracture and leaflet escape of Bjork-Shiley convexo-concave valve.

PubMed

Uchino, Gaku; Yoshida, Hideo; Sakoda, Naoya; Hattori, Shigeru; Kawabata, Takuya; Saiki, Munehiro; Fujita, Yasufumi; Yunoki, Keiji; Hisamochi, Kunikazu; Mine, Yoshinari

2017-06-01

Prosthetic valve fracture is a serious complication and may arise in patient post-valve replacement. We experienced an outlet strut fracture and leaflet escape of a Bjork-Shiley convexo-concave valve. We performed an emergency redo mitral valve replacement and successfully retrieved the fractured strut and escaped leaflet from superficial femoral artery and the abdominal aorta. The patient showed an uneventful postoperative recovery.

Active optics: off axis aspherics generation for high contrast imaging

NASA Astrophysics Data System (ADS)

Hugot, E.; Laslandes, M.; Ferrari, M.; Vives, S.; Moindrot, S.; El Hadi, K.; Dohlen, K.

2017-11-01

Active Optics methods, based on elasticity theory, allow the aspherisation of optical surfaces by stress polishing but also active aspherisation in situ. Researches in this field will impact the final performance and the final cost of any telescope or instrument. The stress polishing method is well suited for the superpolishing of aspheric components for astronomy. Its principle relies on spherical polishing with a full-sized tool of a warped substrate, which becomes aspherical once unwarped. The main advantage of this technique is the very high optical quality obtained either on form or on high spatial frequency errors. Furthermore, the roughness can be decreased down to a few angstroms, thanks the classical polishing with a large pitch tool, providing a substantial gain on the final scientific performance, for instance on the contrast on coronagraphic images, but also on the polishing time and cost. Stress polishing is based on elasticity theory, and requires an optimised deformation system able to provide the right aspherical form on the optical surface during polishing. The optical quality of the deformation is validated using extensive Finite Element Analysis, allowing an estimation of residuals and an optimisation of the warping harness. We describe here the work realised on stress polishing of toric mirrors for VLT-SPHERE and then our actual work on off axis aspherics (OAA) for the ASPIICS-Proba3 mission for solar coronagraphy. The ASPIICS optical design made by Vives et al is a three mirrors anastigmat including a concave off axis hyperboloid and a convex off axis parabola (OAP). We are developing a prototype in order to demonstrate the feasibility of this type of surface, using a multi-mode warping harness (Lemaitre et al). Furthermore, we present our work on variable OAP, meaning the possibility to adjust the shape of a simple OAP in situ with a minimal number of actuators, typically one actuator per optical mode (Focus, Coma and Astigmatism). Applications for future space telescopes and instrumentation are discussed.

Structures of pseudechetoxin and pseudecin, two snake-venom cysteine-rich secretory proteins that target cyclic nucleotide-gated ion channels: implications for movement of the C-terminal cysteine-rich domain

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

Suzuki, Nobuhiro; Department of Biochemistry, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602; Yamazaki, Yasuo

2008-10-01

The structures of pseudechetoxin and pseudecin suggest that both proteins bind to cyclic nucleotide-gated ion channels in a manner in which the concave surface occludes the pore entrance. Cyclic nucleotide-gated (CNG) ion channels play pivotal roles in sensory transduction by retinal photoreceptors and olfactory neurons. The elapid snake toxins pseudechetoxin (PsTx) and pseudecin (Pdc) are the only known protein blockers of CNG channels. These toxins belong to a cysteine-rich secretory protein (CRISP) family containing an N-terminal pathogenesis-related proteins of group 1 (PR-1) domain and a C-terminal cysteine-rich domain (CRD). PsTx and Pdc are highly homologous proteins, but their blocking affinitiesmore » on CNG channels are different: PsTx blocks both the olfactory and retinal channels with ∼15–30-fold higher affinity than Pdc. To gain further insights into their structure and function, the crystal structures of PsTx, Pdc and Zn{sup 2+}-bound Pdc were determined. The structures revealed that most of the amino-acid-residue differences between PsTx and Pdc are located around the concave surface formed between the PR-1 domain and the CRD, suggesting that the concave surface is functionally important for CNG-channel binding and inhibition. A structural comparison in the presence and absence of Zn{sup 2+} ion demonstrated that the concave surface can open and close owing to movement of the CRD upon Zn{sup 2+} binding. The data suggest that PsTx and Pdc occlude the pore entrance and that the dynamic motion of the concave surface facilitates interaction with the CNG channels.« less

Longitudinal study of iris concavity, corneal biomechanics, and correlations to ocular biometry in a cohort of 10- to 12-year-old UK schoolboys: 2-year follow-up data.

PubMed

Shah, Ameet; Lascaratos, Gerassimos; Garway-Heath, David F; Foster, Paul J; Barton, Keith

2014-06-10

To explore changes in iris curvature over a 2-year period. To investigate associations between iris curvature and ocular biometric parameters. To explore relationships between a number of nonocular measurements and ocular biometric parameters. Schoolboys enrolled 2 years previously were invited to return for anterior segment optical coherence tomography, corneal hysteresis (CH), corneal resistance factor (CRF), and axial biometric measurements. Refractive error was assessed and measures of height, weight, waist circumference, digit ratio, and percentage body fat taken. Mean spherical equivalent refraction reduced by 0.76 diopters and mean iris concavity, defined as a measurement of less than or equal to -0.1 mm, increased by 0.018 mm at distance fixation and 0.04 mm on accommodation. Compared with 2 years previously, the prevalence of iris concavity increased from 24% to 32% on distance fixation and from 65% to 84% on accommodation. Variables significantly associated with nonaccommodating iris curvature were anterior chamber depth (ACD, P = 0.029) and mean scleral spur angle (P = 0.0001). Variables significantly associated with accommodating iris curvature were ACD (P = 0.02), lens vault (P = 0.047), and scleral spur angle (P < 0.0001). Significant association was again found between CH and accommodating spur-to-spur distance (R(2) = 0.13, P = 0.007). Iris concavity was more prevalent in this cohort of schoolboys than 2 years earlier. The degree of concavity remains related to ACD and lens vault. The association between spur-to-spur distance and CH was similar at baseline and after 2 years. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Pricing of Water Resources With Depletable Externality: The Effects of Pollution Charges

NASA Astrophysics Data System (ADS)

Kitabatake, Yoshifusa

1990-04-01

With an abstraction of a real-world situation, the paper views water resources as a depletable capital asset which yields a stream of services such as water supply and the assimilation of pollution discharge. The concept of the concave or convex water resource depletion function is then introduced and applied to a general two-sector, three-factor model. The main theoretical contribution is to prove that when the water resource depletion function is a concave rather than a convex function of pollution, it is more likely that gross regional income will increase with a higher pollution charge policy. The concavity of the function is meant to imply that with an increase in pollution released, the ability of supplying water at a certain minimum quality level diminishes faster and faster. A numerical example is also provided.

Flat field concave holographic grating with broad spectral region and moderately high resolution.

PubMed

Wu, Jian Fen; Chen, Yong Yan; Wang, Tai Sheng

2012-02-01

In order to deal with the conflicts between broad spectral region and high resolution in compact spectrometers based on a flat field concave holographic grating and line array CCD, we present a simple and practical method to design a flat field concave holographic grating that is capable of imaging a broad spectral region at a moderately high resolution. First, we discuss the principle of realizing a broad spectral region and moderately high resolution. Second, we provide the practical method to realize our ideas, in which Namioka grating theory, a genetic algorithm, and ZEMAX are used to reach this purpose. Finally, a near-normal-incidence example modeled in ZEMAX is shown to verify our ideas. The results show that our work probably has a general applicability in compact spectrometers with a broad spectral region and moderately high resolution.

Experimental study of the laminar-turbulent transition of a concave wall in a parallel flow

NASA Technical Reports Server (NTRS)

Bippes, H.

1978-01-01

The instability of the laminar boundary layer flow along a concave wall was studied. Observations of these three-dimensional boundary layer phenomena were made using the hydrogen-bubble visualization technique. With the application of stereo-photogrammetric methods in the air-water system it was possible to investigate the flow processes qualitatively and quantitatively. In the case of a concave wall of sufficient curvature, a primary instability occurs first in the form of Goertler vortices with wave lengths depending upon the boundary layer thickness and the wall curvature. At the onset the amplification rate is in agreement with the linear theory. Later, during the non-linear amplification stage, periodic spanwise vorticity concentrations develop in the low velocity region between the longitudinal vortices. Then a meandering motion of the longitudinal vortex streets subsequently ensues, leading to turbulence.

Fluid blade disablement tool

DOEpatents

Jakaboski, Juan-Carlos [Albuquerque, NM; Hughs, Chance G [Albuquerque, NM; Todd, Steven N [Rio Rancho, NM

2012-01-10

A fluid blade disablement (FBD) tool that forms both a focused fluid projectile that resembles a blade, which can provide precision penetration of a barrier wall, and a broad fluid projectile that functions substantially like a hammer, which can produce general disruption of structures behind the barrier wall. Embodiments of the FBD tool comprise a container capable of holding fluid, an explosive assembly which is positioned within the container and which comprises an explosive holder and explosive, and a means for detonating. The container has a concavity on the side adjacent to the exposed surface of the explosive. The position of the concavity relative to the explosive and its construction of materials with thicknesses that facilitate inversion and/or rupture of the concavity wall enable the formation of a sharp and coherent blade of fluid advancing ahead of the detonation gases.

A high speed compact microwave interferometer for density fluctuation measurements in Sino-UNIted Spherical Tokamak

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

Zhong, H., E-mail: zhongh14@126.com; Tan, Y.; Liu, Y. Q.

2016-11-15

A single-channel 3 mm interferometer has been developed for plasma density diagnostics in the Sino-UNIted Spherical Tokamak (SUNIST). The extremely compact microwave interferometer utilizes one corrugated feed horn antenna for both emitting and receiving the microwave. The beam path lies on the equatorial plane so the system would not suffer from beam path deflection problems due to the symmetry of the cross section. A focusing lens group and an oblique vacuum window are carefully designed to boost the signal to noise ratio, which allows this system to show good performance even with the small-diameter central column itself as a reflector,more » without a concave mirror. The whole system discards the reference leg for maximum compactness, which is particularly suitable for the small-sized tokamak. An auto-correcting algorithm is developed to calculate the phase evolution, and the result displays good phase stability of the whole system. The intermediate frequency is adjustable and can reach its full potential of 2 MHz for best temporal resolution. Multiple measurements during ohmic discharges proved the interferometer’s capability to track typical density fluctuations in SUNIST, which enables this system to be utilized in the study of MHD activities.« less

Assessment of the performance of a compact concentric spectrometer system for Atmospheric Differential Optical Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Whyte, C.; Leigh, R. J.; Lobb, D.; Williams, T.; Remedios, J. J.; Cutter, M.; Monks, P. S.

2009-08-01

A breadboard demonstrator of a novel UV/VIS grating spectrometer for atmospheric research has been developed based upon a concentric arrangement of a spherical meniscus lens, concave spherical mirror and curved diffraction grating suitable for a range of remote sensing applications from the ground or space. The spectrometer is compact and provides high optical efficiency and performance benefits over traditional instruments. The concentric design is capable of handling high relative apertures, owing to spherical aberration and coma being near zero at all surfaces. The design also provides correction for transverse chromatic aberration and distortion, in addition to correcting for the distortion called "smile", the curvature of the slit image formed at each wavelength. These properties render this design capable of superior spectral and spatial performance with size and weight budgets significantly lower than standard configurations. This form of spectrometer design offers the potential for an exceptionally compact instrument for differential optical absorption spectroscopy (DOAS) applications particularly from space (LEO, GEO orbits) and from HAPs or ground-based platforms. The breadboard demonstrator has been shown to offer high throughput and a stable Gaussian line shape with a spectral range from 300 to 450 nm at better than 0.5 nm resolution, suitable for a number of typical DOAS applications.

On the improvement of signal repeatability in laser-induced air plasmas

NASA Astrophysics Data System (ADS)

Zhang, Shuai; Sheta, Sahar; Hou, Zong-Yu; Wang, Zhe

2018-04-01

The relatively low repeatability of laser-induced breakdown spectroscopy (LIBS) severely hinders its wide commercialization. In the present work, we investigate the optimization of LIBS system for repeatability improvement for both signal generation (plasma evolution) and signal collection. Timeintegrated spectra and images were obtained under different laser energies and focal lengths to investigate the optimum configuration for stable plasmas and repeatable signals. Using our experimental setup, the optimum conditions were found to be a laser energy of 250 mJ and a focus length of 100 mm. A stable and homogeneous plasma with the largest hot core area in the optimum condition yielded the most stable LIBS signal. Time-resolved images showed that the rebounding processes through the air plasma evolution caused the relative standard deviation (RSD) to increase with laser energies of > 250 mJ. In addition, the emission collection was improved by using a concave spherical mirror. The line intensities doubled as their RSDs decreased by approximately 25%. When the signal generation and collection were optimized simultaneously, the pulse-to-pulse RSDs were reduced to approximately 3% for O(I), N(I), and H(I) lines, which are better than the RSDs reported for solid samples and showed great potential for LIBS quantitative analysis by gasifying the solid or liquid samples.

Degenerate band edge laser

NASA Astrophysics Data System (ADS)

Veysi, Mehdi; Othman, Mohamed A. K.; Figotin, Alexander; Capolino, Filippo

2018-05-01

We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality (Q ) factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

Optical and mechanical design and characterization of the new baffle for the 2.4-m Thai National Telescope

NASA Astrophysics Data System (ADS)

Buisset, Christophe; Prasit, Apirat; Lépine, Thierry; Poshyajinda, Saran

2015-09-01

The first astronomical images obtained at the 2.4 m Thai National Telescope (TNT) during observations in bright moon conditions were contaminated by high levels of light scattered by the telescope structure. We identified that the origins of this scattered light were the M3 folding mirror baffle and the tube placed inside the fork between the M3 and the M4 mirrors. We thus decided to design and install a new baffle. In a first step, we calculated the optical and mechanical inputs needed to define the baffle optical design. These inputs were: the maximum length of the baffle, the maximum dimensions of the vanes and the incident beam diameter between M3 and M4 mirrors. In a second step, we defined the number, the position and the diameter of the vanes to remove the critical objects from the detector's FOV by using a targeted method. Then, we verified that the critical objects were moved away from the detector's view. In a third step, we designed and manufactured the baffle. The mechanical design is made of 21 sections (1 section for each vane) and comprises an innovative mechanism for the adjustment of the baffle position. The baffle installation and adjustment is performed in less than 20 minutes by 2 operators. In a fourth step, we installed and characterized the baffle by using a pinhole camera. We quantified the performance improvement and we identified the baffle areas at the origin of the residual stray light signal. Finally, we performed targeted on-sky observations to test the baffle in real conditions.

Characterization of Piezoelectric Energy Harvesting MEMS

DTIC Science & Technology

2015-12-01

dimensional image of the piezoelectric energy harvester under test. The image shows the intrinsic stress within the material resulting in the curved ...amount of deformation. This indicates that the center pad is curved concave up in the z-direction at rest, which may affect the stiffness of the...greatest amount of deformation; blue indicates the least amount of deformation. This indicates that the center pad is curved concave up in the z

A Bayesian observer replicates convexity context effects in figure-ground perception.

PubMed

Goldreich, Daniel; Peterson, Mary A

2012-01-01

Peterson and Salvagio (2008) demonstrated convexity context effects in figure-ground perception. Subjects shown displays consisting of unfamiliar alternating convex and concave regions identified the convex regions as foreground objects progressively more frequently as the number of regions increased; this occurred only when the concave regions were homogeneously colored. The origins of these effects have been unclear. Here, we present a two-free-parameter Bayesian observer that replicates convexity context effects. The Bayesian observer incorporates two plausible expectations regarding three-dimensional scenes: (1) objects tend to be convex rather than concave, and (2) backgrounds tend (more than foreground objects) to be homogeneously colored. The Bayesian observer estimates the probability that a depicted scene is three-dimensional, and that the convex regions are figures. It responds stochastically by sampling from its posterior distributions. Like human observers, the Bayesian observer shows convexity context effects only for images with homogeneously colored concave regions. With optimal parameter settings, it performs similarly to the average human subject on the four display types tested. We propose that object convexity and background color homogeneity are environmental regularities exploited by human visual perception; vision achieves figure-ground perception by interpreting ambiguous images in light of these and other expected regularities in natural scenes.

The effects of streamwise concave curvature on turbulent boundary layer structure

NASA Astrophysics Data System (ADS)

Jeans, A. H.; Johnston, J. P.

1982-06-01

Concave curvature has a relatively large, unpredictable effect on turbulent boundary layers. Some, but not all previous studies suggest that a large-scale, stationary array of counter-rotating vortices exists within the turbulent boundary layer on a concave wall. The objective of the present study was to obtain a qualitative model of the flow field in order to increase our understanding of the underlying physics. A large free-surface water channel was constructed in order to perform a visual study of the flow. Streamwise components of mean velocity and turbulence intensity were measured using a hot film anemometer. The upstream boundary was spanwise uniform with a momentum thickness to radius of curvature of 0.05. Compared to flat wall flow, large-scale, randomly distributed sweeps and ejections were seen in the boundary layer on the concave wall. The sweeps appear to suppress the normal mechanism for turbulence production near the wall by inhibiting the bursting process. The ejections appear to enhance turbulence production in the outer layers as the low speed fluid convected from regions near the wall interacts with the higher speed fluid farther out. The large-scale structures did not occur at fixed spanwise locations, and could not be called roll cells or vortices.

Performance of thin CaSO4:Dy pellets for calibration of a Sr90+Y90 source

NASA Astrophysics Data System (ADS)

Oliveira, M. L.; Caldas, L. V. E.

2007-09-01

Because of the radionuclide long half-life, Sr90+Y90, plane or concave sources, utilized in brachytherapy, have to be calibrated initially by the manufacturer and then routinely while they are utilized. Plane applicators can be calibrated against a conventional extrapolation chamber, but concave sources, because of their geometry, should be calibrated using relative dosimeters, as thermoluminescent (TL) materials. Thin CaSO4:Dy pellets are produced at IPEN specially for beta radiation detection. Previous works showed the feasibility of this material in the dosimetry of Sr90+Y90 sources in a wide range of absorbed dose in air. The aim of this work was to study the usefulness of these pellets for the calibration of a Sr90+Y90 concave applicator. To reach this objective, a special phantom was designed and manufactured in PTFE with semi spherical geometry. Because of the dependence of the TL response on the mass of the pellet, the response of each pellet was normalized by its mass in order to reduce the dispersion on TL response. Important characteristics of this material were obtained in reference of a standard Sr90+Y90 source, and the pellets were calibrated against a plane applicator; then they were utilized to calibrate the concave applicator.

Predictions of the quantum landscape multiverse

NASA Astrophysics Data System (ADS)

Mersini-Houghton, Laura

2017-02-01

The 2015 Planck data release has placed tight constraints on the class of inflationary models allowed. The current best fit region favors concave downwards inflationary potentials, since they produce a suppressed tensor to scalar index ratio r. Concave downward potentials have a negative curvature {{V}\\prime \\prime} , therefore a tachyonic mass square that drives fluctuations. Furthermore, their use can become problematic if the field rolls in a part of the potential away from the extrema, since the semiclassical approximation of quantum cosmology, used for deriving the most probable wavefunction of the universe from the landscape and for addressing the quantum to classical transition, breaks down away from the steepest descent region. We here propose a way of dealing with such potentials by inverting the metric signature and solving for the wavefunction of the universe in the Euclidean sector. This method allows us to extend our theory of the origin of the universe from a quantum multiverse, to a more general class of concave inflationary potentials where a straightforward application of the semiclassical approximation fails. The work here completes the derivation of modifications to the Newtonian potential and to the inflationary potential, which originate from the quantum entanglement of our universe with all others in the quantum landscape multiverse, leading to predictions of observational signatures for both types of inflationary models, concave and convex potentials.

High-Speed Unsteady Flows around Concave Axisymmetric Bodies: Flow Instabilities and their Suppression

NASA Astrophysics Data System (ADS)

Panaras, A.; Drikakis, D.

2009-01-01

The axisymmetric concave body, i.e. a body in which the normals to its surface intersect, is a typical configuration about which shock/shock interactions appear. Various shapes of axisymmetric concave bodies are used in a variety of applications in aeronautics. For exampe: axisymmetric jet inlets with conical centerbody, ballistic missiles drag reduction by spike, plasma or hot gas injection, parachutes for pilot-ejection capsules. However, it is well known that two distinct modes of instability appear around a concave body in the high-speed flow regime, for a certain range of geometric parameters. These instabilities can cause undesirable effects such as severe vibration of the structure, heating and pressure loads. According to the experimental evidence, the unsteady flow is characterized by periodic radial inflation and collapse of the conical separation bubble formed around the forebody (pulsation). Various explanations have been given for the driving mechanism of the instabilities. They are based on interpretation of experimental results or on numerical simulation of the related flows. A merging of the leading explanations is done, and basic rules for the passive suppression of the instabilities are applied, in order to enforce the proposed driving mechanism of the instabilities. Most of the analysis is based on numerical simulations.

Physical and numerical aspects of the high-speed unsteady flow around concave axisymmetric bodies

NASA Astrophysics Data System (ADS)

Panaras, Argyris; Drikakis, Dimitris

2011-09-01

The axisymmetric concave body is a typical configuration about which shock/shock interactions appear. Various shapes of axisymmetric concave bodies are used in a variety of applications in aeronautics, for example, axisymmetric jet inlets with conical centerbody, ballistic missiles drag reduction by spike, plasma or hot gas injection, parachutes for pilot-ejection capsules. However, it is well known that two distinct modes of instability appear around a concave body in the high-speed flow regime for a certain range of geometric parameters. These instabilities can cause undesirable effects such as severe vibration of the structure, heating and pressure loads. According to the experimental evidence, the unsteady flow is characterised by periodic radial inflation and collapse of the conical separation bubble formed around the forebody (pulsation). Various explanations have been given for the driving mechanism of the instabilities. In the present, merging of the leading explanations is done, and basic rules for the passive suppression of the instabilities are applied, in order to enforce their proposed driving. In addition, the effect of the flow initialisation method on the flow structure predicted by numerical simulations is examined. For certain configurations, bifurcation of the time-dependent flow has been found. This behaviour is explained with recourse to the phenomenon of hysteresis, which is an inherent feature of the examined flows.

Organizing principles for dense packings of nonspherical hard particles: Not all shapes are created equal

NASA Astrophysics Data System (ADS)

Torquato, Salvatore; Jiao, Yang

2012-07-01

We have recently devised organizing principles to obtain maximally dense packings of the Platonic and Archimedean solids and certain smoothly shaped convex nonspherical particles [Torquato and Jiao, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.81.041310 81, 041310 (2010)]. Here we generalize them in order to guide one to ascertain the densest packings of other convex nonspherical particles as well as concave shapes. Our generalized organizing principles are explicitly stated as four distinct propositions. All of our organizing principles are applied to and tested against the most comprehensive set of both convex and concave particle shapes examined to date, including Catalan solids, prisms, antiprisms, cylinders, dimers of spheres, and various concave polyhedra. We demonstrate that all of the densest known packings associated with this wide spectrum of nonspherical particles are consistent with our propositions. Among other applications, our general organizing principles enable us to construct analytically the densest known packings of certain convex nonspherical particles, including spherocylinders, “lens-shaped” particles, square pyramids, and rhombic pyramids. Moreover, we show how to apply these principles to infer the high-density equilibrium crystalline phases of hard convex and concave particles. We also discuss the unique packing attributes of maximally random jammed packings of nonspherical particles.

Transverse plane of apical vertebra of structural thoracic curve: vertebra displacement versus vertebral deformation.

PubMed

Kotwicki, Tomasz; Napiontek, Marek; Nowakowski, Andrzej

2006-01-01

CT transversal scans of the trunk provided at the level of Th8 or Th9 (apical vertebra) of 23 patients with structural thoracic scoliosis were reviewed. The following parameters were studied: 1) alpha angle formed by the axis of vertebra and the axis of spinous process, 2) beta concave and beta convex angle between the spinous process and the left and right transverse process respectively, 3) gamma concave and gamma convex angle between the axis of vertebra and the left and right transverse process respectively, 4) rotation angle to the sagittal plane according to Aaro and Dahlborn, 5) Cobb angle. Values of measured parameters demonstrated a common pattern of intravertebral deformity: counter clockwise deviation of the spinous process (alpha angle 15,0 +/-8,5 degrees), beta concave (69,8 +/-8,5 degrees) significantly greater than beta convex (38,8 +/-8,5 degrees), gamma concave (54,3 +/-7,8 degrees) not different from gamma convex (56,0 +/-8,0 degrees). Strong linear positive correlation between alpha angle and Aaro-Dahlborn angle was observed (r=0,78, p<0,05). Changes in morphology of apical vertebra due to intravertebral bone remodelling followed the vertebral spatial displacement and there existed a linear correlation in between. The two processes develop in opposite directions.

Seamless lamination of a concave-convex architecture with single-layer graphene.

PubMed

Park, Ji-Hoon; Lim, Taekyung; Baik, Jaeyoon; Seo, Keumyoung; Moon, Youngkwon; Park, Noejung; Shin, Hyun-Joon; Kwak, Sang Kyu; Ju, Sanghyun; Ahn, Joung Real

2015-11-21

Graphene has been used as an electrode and channel material in electronic devices because of its superior physical properties. Recently, electronic devices have changed from a planar to a complicated three-dimensional (3D) geometry to overcome the limitations of planar devices. The evolution of electronic devices requires that graphene be adaptable to a 3D substrate. Here, we demonstrate that chemical-vapor-deposited single-layer graphene can be transferred onto a silicon dioxide substrate with a 3D geometry, such as a concave-convex architecture. A variety of silicon dioxide concave-convex architectures were uniformly and seamlessly laminated with graphene using a thermal treatment. The planar graphene was stretched to cover the concave-convex architecture, and the resulting strain on the curved graphene was spatially resolved by confocal Raman spectroscopy; molecular dynamic simulations were also conducted and supported the observations. Changes in electrical resistivity caused by the spatially varying strain induced as the graphene-silicon dioxide laminate varies dimensionally from 2D to 3D were measured by using a four-point probe. The resistivity measurements suggest that the electrical resistivity can be systematically controlled by the 3D geometry of the graphene-silicon dioxide laminate. This 3D graphene-insulator laminate will broaden the range of graphene applications beyond planar structures to 3D materials.

Alternative hypotheses to explain why biodiversity-ecosystem functioning relationships are concave-up in some natural ecosystems but concave-down in manipulative experiments.

PubMed

Mora, Camilo; Danovaro, Roberto; Loreau, Michel

2014-06-25

Recent studies of the relationship between biodiversity and functioning in marine ecosystems have yielded non-saturating patterns that contrast sharply with the results of experimental studies, where ecosystem functioning rapidly saturates with increases in biodiversity. Here we provide a simple theoretical framework of three alternative hypotheses that, individually or combined, are likely to explain this contrast: i) the use of functional richness instead of species richness, ii) an increased production efficiency of species in producing biomass when more ecological interactions are present, and iii) the fact that communities are likely assembled in an ordered succession of species from low to high ecological efficiency. Our results provide theoretical support for concave-up biodiversity-ecosystem functioning relationships in natural ecosystems and confirm that the loss of species can have substantially larger effects on the functioning of natural ecosystems than anticipated from controlled manipulative experiments.

GLOBAL SOLUTIONS TO FOLDED CONCAVE PENALIZED NONCONVEX LEARNING

PubMed Central

Liu, Hongcheng; Yao, Tao; Li, Runze

2015-01-01

This paper is concerned with solving nonconvex learning problems with folded concave penalty. Despite that their global solutions entail desirable statistical properties, there lack optimization techniques that guarantee global optimality in a general setting. In this paper, we show that a class of nonconvex learning problems are equivalent to general quadratic programs. This equivalence facilitates us in developing mixed integer linear programming reformulations, which admit finite algorithms that find a provably global optimal solution. We refer to this reformulation-based technique as the mixed integer programming-based global optimization (MIPGO). To our knowledge, this is the first global optimization scheme with a theoretical guarantee for folded concave penalized nonconvex learning with the SCAD penalty (Fan and Li, 2001) and the MCP penalty (Zhang, 2010). Numerical results indicate a significant outperformance of MIPGO over the state-of-the-art solution scheme, local linear approximation, and other alternative solution techniques in literature in terms of solution quality. PMID:27141126

Antireflective surface with a step in the taper: Numerical optimization and large-area fabrication

NASA Astrophysics Data System (ADS)

Shinotsuka, Kei; Hongo, Koki; Dai, Kotaro; Hirama, Satoru; Hatta, Yoshihisa

2017-02-01

In this study, we developed a practical method to improve the optical performance of subwavelength antireflective two-dimensional (2D) gratings. A numerical simulation of both convex and concave paraboloids suggested that surface reflectivity drastically decreases when a step is introduced in the taper. The optimum height and depth of a step provided average reflectances of 0.098% for convex protrusions and 0.040% for concave protrusions in the visible range. Furthermore, a stepped paraboloid was experimentally fabricated by dry etching of a Si substrate with SiO2 particle monolayer mask. A cyclo-olefin polymer (COP) reverse replica (concave) imprinted by the Si mold exhibited a measured reflectance of 0.077% on average in the visible range. It was also demonstrated that the antireflective structure was fabricated on the whole surface of a 6 in. Si wafer, which is a sufficient size for industrial utilization.

Experiments in Transitional Boundary Layers With Emphasis on High Free-Stream Disturbance Level, Surface Concave Curvature and Strong Favorable Streamwise Pressure Gradient Effects

NASA Technical Reports Server (NTRS)

Simon, T. W.; Volino, R. J.

2007-01-01

Experiments on boundary layer transition with flat, concave and convex walls and various levels of free-stream disturbance and with zero and strong streamwise acceleration have been conducted. Measurements of both fluid mechanics and heat transfer processes were taken. Examples are profiles of mean velocity and temperature; Reynolds normal and shear stresses; turbulent streamwise and cross-stream heat fluxed; turbulent Prandtl number; and streamwise variations of wall skin friction and heat transfer coefficient values. Free-stream turbulence levels were varied over the range from about 0.3 percent to about 8 percent. The effects of curvature on the onset of transition under low disturbance conditions are clear; concave curvature leads to an earlier and more rapid transition and the opposite is true for convex curvature This was previously known but little documentation of the transport processes in the flow was available

Alternative hypotheses to explain why biodiversity-ecosystem functioning relationships are concave-up in some natural ecosystems but concave-down in manipulative experiments

PubMed Central

Mora, Camilo; Danovaro, Roberto; Loreau, Michel

2014-01-01

Recent studies of the relationship between biodiversity and functioning in marine ecosystems have yielded non-saturating patterns that contrast sharply with the results of experimental studies, where ecosystem functioning rapidly saturates with increases in biodiversity. Here we provide a simple theoretical framework of three alternative hypotheses that, individually or combined, are likely to explain this contrast: i) the use of functional richness instead of species richness, ii) an increased production efficiency of species in producing biomass when more ecological interactions are present, and iii) the fact that communities are likely assembled in an ordered succession of species from low to high ecological efficiency. Our results provide theoretical support for concave-up biodiversity-ecosystem functioning relationships in natural ecosystems and confirm that the loss of species can have substantially larger effects on the functioning of natural ecosystems than anticipated from controlled manipulative experiments. PMID:24962477

Optimal Portfolio Selection Under Concave Price Impact

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

Ma Jin, E-mail: jinma@usc.edu; Song Qingshuo, E-mail: songe.qingshuo@cityu.edu.hk; Xu Jing, E-mail: xujing8023@yahoo.com.cn

2013-06-15

In this paper we study an optimal portfolio selection problem under instantaneous price impact. Based on some empirical analysis in the literature, we model such impact as a concave function of the trading size when the trading size is small. The price impact can be thought of as either a liquidity cost or a transaction cost, but the concavity nature of the cost leads to some fundamental difference from those in the existing literature. We show that the problem can be reduced to an impulse control problem, but without fixed cost, and that the value function is a viscosity solutionmore » to a special type of Quasi-Variational Inequality (QVI). We also prove directly (without using the solution to the QVI) that the optimal strategy exists and more importantly, despite the absence of a fixed cost, it is still in a 'piecewise constant' form, reflecting a more practical perspective.« less

Critical Concavity of a Drainage Basin for Steady-State

NASA Astrophysics Data System (ADS)

Byun, Jongmin; Paik, Kyungrock

2015-04-01

Longitudinal profiles of natural streams are known to show concave forms. Saying A as drainage area, channel gradient S can be expressed as the power-law, S≈A-θ (Flint, 1974), which is one of the scale-invariant features of drainage basin. According to literature, θ of most natural streams falls into a narrow range (0.4 < θ < 0.7) (Tucker and Whipple, 2002). It leads to fundamental questions: 'Why does θ falls into such narrow range?' and 'How is this related with other power-law scaling relationships reported in natural drainage basins?' To answer above questions, we analytically derive θ for a steady-state drainage basin following Lane's equilibrium (Lane, 1955) throughout the corridor and named this specific case as the 'critical concavity'. In the derivation, sediment transport capacity is estimated by unit stream power model (Yang, 1976), yielding a power function of upstream area. Stability of channel at a local point occurs when incoming flux equals outgoing flux at the point. Therefore, given the drainage at steady-state where all channel beds are stable, the exponent of the power function should be zero. From this, we can determine the critical concavity. Considering ranges of variables associated in this derivation, critical concavity cannot be resolved as a single definite value, rather a range of critical concavity is suggested. This range well agrees with the widely reported range of θ (0.4 < θ < 0.7) in natural streams. In this theoretical study, inter-relationships between power-laws such as hydraulic geometry (Leopold and Maddock, 1953), dominant discharge-drainage area (Knighton et al., 1999), and concavity, are coupled into the power-law framework of stream power sediment transport model. This allows us to explore close relationships between their power-law exponents: their relative roles and sensitivity. Detailed analysis and implications will be presented. References Flint, J. J., 1974, Stream gradient as a function of order, magnitude, and discharge, Water Resources Research, 10, 969-973. Knighton, A. D., 1999, Downstream variation in stream power, Geomorphology, 29, 293-306. Lane, E. W., 1955, The importance of fluvial morphology in hydraulic engineering, American Society of Civil Engineers, Proceedings, 81, 1-17 Leopold, L. B., Maddock, T., 1953, The hydraulic geometry of stream channels and some physiographic implications, United States Government Printing Office, 1953. Tucker, G. E., Whipple, K. X., 2002, Topographic outcomes predicted by stream erosion models: Sensitivity analysis and intermodel comparison, Journal of Geophysical Research, 107(B9), 2179, doi:10.1029/2001JB000162, 2002. Yang, C. T., 1976, Minimum unit stream power and fluvial hydraulics, Journal of Hydraulics Division, ASCE 102, 919-934.

In-cylinder flows of a motored four-stroke engine with flat-crown and slightly concave-crown pistons

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

Huang, R.F.; Yang, H.S.; Yeh, C.-N.

2008-04-15

The temporal and spatial evolution processes of the in-cylinder flow structures and turbulence intensities in the symmetry and offset planes of a motored four-valve, four-stroke engine during the intake and compression strokes are diagnosed by using a particle image velocimeter. Two pistons of different crown shapes (flat-crown and slightly concave-crown pistons) are studied. The inception, establishment, and evolution of the tumbling vortical flow structures during the intake and compression strokes are clearly depicted. Quantitative strengths of the rotating vortical flow motions are presented by a dimensionless parameter, the tumble ratio, which can represent the mean angular velocity of the vorticesmore » in the target plane. The turbulence intensity of the in-cylinder flow is also calculated by using the measured time-varying velocity data. The results show that the flat-crown piston induces higher bulk-averaged tumble ratio and turbulence intensity than the slightly concave-crown piston does because the tumble ratio and turbulence generated by the flat-crown piston in the offset planes during the compression stroke are particularly large. The engine with the flat-crown piston also presents larger torque and power outputs and lower hydrocarbon emission than that with the slightly concave-crown piston. This might be caused by the enhanced combustion in the engine cylinder due to the stronger tumble ratio and turbulence intensity. (author)« less

TCP Throughput Profiles Using Measurements over Dedicated Connections

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

Rao, Nageswara S.; Liu, Qiang; Sen, Satyabrata

Wide-area data transfers in high-performance computing infrastructures are increasingly being carried over dynamically provisioned dedicated network connections that provide high capacities with no competing traffic. We present extensive TCP throughput measurements and time traces over a suite of physical and emulated 10 Gbps connections with 0-366 ms round-trip times (RTTs). Contrary to the general expectation, they show significant statistical and temporal variations, in addition to the overall dependencies on the congestion control mechanism, buffer size, and the number of parallel streams. We analyze several throughput profiles that have highly desirable concave regions wherein the throughput decreases slowly with RTTs, inmore » stark contrast to the convex profiles predicted by various TCP analytical models. We present a generic throughput model that abstracts the ramp-up and sustainment phases of TCP flows, which provides insights into qualitative trends observed in measurements across TCP variants: (i) slow-start followed by well-sustained throughput leads to concave regions; (ii) large buffers and multiple parallel streams expand the concave regions in addition to improving the throughput; and (iii) stable throughput dynamics, indicated by a smoother Poincare map and smaller Lyapunov exponents, lead to wider concave regions. These measurements and analytical results together enable us to select a TCP variant and its parameters for a given connection to achieve high throughput with statistical guarantees.« less

Ag@Au concave cuboctahedra: A unique probe for monitoring Au-catalyzed reduction and oxidation reactions by surface-enhanced Raman spectroscopy

DOE PAGES

Zhang, Jiawei; Winget, Sarah A.; Wu, Yiren; ...

2016-01-26

In this paper, we report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au 3+ by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets. The concavemore » cuboctahedra embrace excellent SERS activity that is more than 70-fold stronger than that of the original Ag cuboctahedra at an excitation wavelength of 785 nm. The concave cuboctahedra also exhibit remarkable stability in the presence of an oxidant such as H 2O 2 because of the protection by a complete Au shell. These two unique attributes enable in-situ SERS monitoring of the reduction of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) by NaBH4 through a 4,4'-dimercaptoazobenzene ( trans-DMAB) intermediate and the subsequent oxidation of 4-ATP back to trans-DMAB upon the introduction of H 2O 2.« less

Ag@Au concave cuboctahedra: A unique probe for monitoring Au-catalyzed reduction and oxidation reactions by surface-enhanced Raman spectroscopy

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

Zhang, Jiawei; Winget, Sarah A.; Wu, Yiren

In this paper, we report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au 3+ by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets. The concavemore » cuboctahedra embrace excellent SERS activity that is more than 70-fold stronger than that of the original Ag cuboctahedra at an excitation wavelength of 785 nm. The concave cuboctahedra also exhibit remarkable stability in the presence of an oxidant such as H 2O 2 because of the protection by a complete Au shell. These two unique attributes enable in-situ SERS monitoring of the reduction of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) by NaBH4 through a 4,4'-dimercaptoazobenzene ( trans-DMAB) intermediate and the subsequent oxidation of 4-ATP back to trans-DMAB upon the introduction of H 2O 2.« less

Magnetic field controlled floating-zone single crystal growth of intermetallic compounds

NASA Astrophysics Data System (ADS)

Hermann, R.; Gerbeth, G.; Priede, J.

2013-03-01

Radio-frequency (RF) floating zone single crystal growth is an important technique for the preparation of single bulk crystals. The advantage of the floating-zone method is the crucible-free growth of single crystals of reactive materials with high melting points. The strong heat diffusion on the surface, as well as the melt convection in the molten zone due to induction heating, often leads to an undesired solid-liquid interface geometry with a concave (towards the solid phase) outer rim. These concave parts aggravate the single crystal growth over the full cross-section. A two-phase stirrer was developed at IFW Dresden in order to avoid the problems connected with these concave parts. It acts as a magnetic field pump and changes the typical double vortex structure to a single roll structure, thus pushing hot melt into the regions where the concave parts may arise. The current in the secondary coil is induced by the primary coil, and the capacitor and the resistance of the secondary circuit are adjusted to get a stable 90 degree phase-shift between the coil currents. Single crystal growth of industrial relevant RuAl and TiAl intermetallic compounds was performed based on the material parameters and using the adjusted two-phase stirrer. Very recently, the magnetic system was applied to the crystal growth of biocompatible TiNb alloys and antiferromagnetic Heusler MnSi compounds.

TAF(II)170 interacts with the concave surface of TATA-binding protein to inhibit its DNA binding activity.

PubMed

Pereira, L A; van der Knaap, J A; van den Boom, V; van den Heuvel, F A; Timmers, H T

2001-11-01

The human RNA polymerase II transcription factor B-TFIID consists of TATA-binding protein (TBP) and the TBP-associated factor (TAF) TAF(II)170 and can rapidly redistribute over promoter DNA. Here we report the identification of human TBP-binding regions in human TAF(II)170. We have defined the TBP interaction domain of TAF(II)170 within three amino-terminal regions: residues 2 to 137, 290 to 381, and 380 to 460. Each region contains a pair of Huntington-elongation-A subunit-Tor repeats and exhibits species-specific interactions with TBP family members. Remarkably, the altered-specificity TBP mutant (TBP(AS)) containing a triple mutation in the concave surface is defective for binding the TAF(II)170 amino-terminal region of residues 1 to 504. Furthermore, within this region the TAF(II)170 residues 290 to 381 can inhibit the interaction between Drosophila TAF(II)230 (residues 2 to 81) and TBP through competition for the concave surface of TBP. Biochemical analyses of TBP binding to the TATA box indicated that TAF(II)170 region 290-381 inhibits TBP-DNA complex formation. Importantly, the TBP(AS) mutant is less sensitive to TAF(II)170 inhibition. Collectively, our results support a mechanism in which TAF(II)170 induces high-mobility DNA binding by TBP through reversible interactions with its concave DNA binding surface.

Longitudinal Stream Profile Morphology and Patterns of Knickpoint Propagation in the Bighorn Range

NASA Astrophysics Data System (ADS)

Safran, E. B.; Anderson, R. S.; Riihimaki, C. A.; Armstrong, J.

2005-12-01

The northern U. S. Rocky Mountains and the adjacent sedimentary basins are in a transient state of response to regional, Late Cenozoic exhumation. Assembling the history of landscape change there requires interpreting the morphology and genesis of transient landforms such as knickpoints in longitudinal stream profiles. We used concavity and normalized channel steepness indices to quantify the longitudinal profile morphology of >75 streams draining the east side of the Bighorn Range and the adjacent Powder River Basin. Our analyses show that individual units in the range-margin sedimentary cover rock exert a strong influence on longitudinal profile morphology. In the Tongue River and Crazy Woman Creek drainages, more than 50% of the streams examined had knickpoints localized within a resistant, siliceous dolomite. Knickpoints on most streams with drainage areas greater than ~100 km2 at the range front have migrated headward into the gneissic and plutonic core of the range. In the Clear Creek drainage, where the lateral extent of sedimentary cover rock is more restricted than in the adjacent drainages, knickpoints do not align with any particular unit. River profiles in the Powder River Basin beyond 10-20 km from the range front exhibit concavities of ~0.3-0.6 and normalized channel steepness indices of 40-60 (using 0.45 as a reference concavity). All profiles analyzed that extend into the mountain range exhibit at least one reach with exceptionally high (>2) concavity and relatively high (100-600) normalized channel steepness index, highlighting zones of transient adjustment to local base-level drop in the basin. Headwater reaches of range-draining streams exhibit variable but moderate values of concavity (0.15-0.9) and normalized channel steepness index (20-100). The varied morphology of these reaches reflects their passage across a relict surface of low relief but also the effects of glaciation and/or the signature of the narrow summit spine that caps the range.

Supramolecular clusters between carbohydrates and concave pyridines. Detection in the gas phase by resonance-enhanced multi-photon ionization reflectron time-of-flight mass spectrometer.

PubMed

Liebig, Timo; Lüning, Ulrich; Grotemeyer, Jürgen

2006-01-01

For the first time the formation of supramolecular clusters between concave pyridines and different carbohydrates could be observed in the gas phase. The different clusters have been investigated by means of laser desorption into a supersonic beam followed by resonant multi photon excitation yielding mass spectra with high intensity of the different cluster. These preliminary results open a way for the investigations of the hydrogen bonds in these compounds.

Rare earth elements in sinters from the geothermal waters (hot springs) on the Tibetan Plateau, China

NASA Astrophysics Data System (ADS)

Feng, Jin-Liang; Zhao, Zhen-Hong; Chen, Feng; Hu, Hai-Ping

2014-10-01

The mineralogical and geochemical composition of sinters from the geothermal areas on the Tibetan Plateau was determined. They occur as siliceous, salty and calcareous sinters but biogenic siliceous sinters were also found. The analyses indicate that there are no distinct inter -element relationships between individual rare earth elements (REEs) and other elements. Formed from the same geothermal water, the mineralogical and chemical composition of the sinters is influenced by their genesis and formation conditions. The REE distributions depend on the origin of the sinters. Fe-Mn phases in sinters tend to scavenge more REEs from geothermal water. Neither the REE fractionation nor the Ce anomaly seems to be associated with Fe-Mn phases in the sinters. The fourth tetrads of some sinters display weak W-type (concave) effects. In contrast, the third tetrads present large effects in some sinters due to positive Gd anomalies. The origin of the positive Eu anomalies in some sinters seems to be caused by preferential dissolution of feldspars during water-rock interaction. The complexing ligands in geothermal water may contribute significantly to the fractionation of REEs in sinters. The dominant CO32- and HCO3- complexing in geothermal water favors enrichment of heavy REEs in calcareous sinters.

Hierarchical concave layered triangular PtCu alloy nanostructures: rational integration of dendritic nanostructures for efficient formic acid electrooxidation.

PubMed

Wu, Fengxia; Lai, Jianping; Zhang, Ling; Niu, Wenxin; Lou, Baohua; Luque, Rafael; Xu, Guobao

2018-05-08

The rational construction of multi-dimensional layered noble metal nanostructures is a great challenge since noble metals are not layer-structured materials. Herein, we report a one-pot hydrothermal synthetic method for PtCu hierarchical concave layered triangular (HCLT) nanostructures using dl-carnitine, KI, poly(vinylpyrrolidone), CuCl2, and H2PtCl6. The PtCu HCLT nanostructure is comprised of multilayered triangular dendrites. Its layer number is tunable by changing dl-carnitine concentrations, and the concavity/convexity of the PtCu triangle nanostructures is tunable by changing the H2PtCl6/CuCl2 ratio or KI concentrations. Hierarchical trigonal bipyramid nanoframes are also obtained under certain conditions. Because of its advantageous nanostructure and bimetallic synergetic effect, the obtained PtCu HCLT nanostructure exhibits enhanced electrocatalytic activity and prolonged stability to formic acid oxidation compared to commercial Pt black, Pd/C and some other nanostructures.

POOL server: machine learning application for functional site prediction in proteins.

PubMed

Somarowthu, Srinivas; Ondrechen, Mary Jo

2012-08-01

We present an automated web server for partial order optimum likelihood (POOL), a machine learning application that combines computed electrostatic and geometric information for high-performance prediction of catalytic residues from 3D structures. Input features consist of THEMATICS electrostatics data and pocket information from ConCavity. THEMATICS measures deviation from typical, sigmoidal titration behavior to identify functionally important residues and ConCavity identifies binding pockets by analyzing the surface geometry of protein structures. Both THEMATICS and ConCavity (structure only) do not require the query protein to have any sequence or structure similarity to other proteins. Hence, POOL is applicable to proteins with novel folds and engineered proteins. As an additional option for cases where sequence homologues are available, users can include evolutionary information from INTREPID for enhanced accuracy in site prediction. The web site is free and open to all users with no login requirements at http://www.pool.neu.edu. m.ondrechen@neu.edu Supplementary data are available at Bioinformatics online.

Torsional deformity of apical vertebra in adolescent idiopathic scoliosis.

PubMed

Kotwicki, Tomasz; Napiontek, Marek

2002-01-01

CT scans of structural thoracic idiopathic scoliosis were reviewed in nine patients admitted to our department for scoliosis surgery. The apical vertebra scans were chosen and the following parameters were evaluated: 1) alpha angle formed by the axis of vertebra and the axis of spinous process 2) beta concave and beta convex angle between the spinous process and the left and right transverse process, respectively, 3) gamma concave and gamma convex angle between the axis of vertebra and the left and right transverse process, respectively, 4) the rotation angle to the sagittal plane. The constant deviation of the spinous process towards the convex side of the curve was observed. The vertebral body itself was distorted towards the concavity of the curve. The angle between the spinous process and the transverse process was smaller on the convex side of the curve. The torsional, intravertebral deformity of the apical vertebra was a factor acting in the direction opposite to the rotation, in the sense to reduce the deformity of the spine in idiopathic scoliosis.

Assessing the influence of lower facial profile convexity on perceived attractiveness in the orthognathic patient, clinician, and layperson.

PubMed

Naini, Farhad B; Donaldson, Ana Nora A; McDonald, Fraser; Cobourne, Martyn T

2012-09-01

The aim was a quantitative evaluation of how the severity of lower facial profile convexity influences perceived attractiveness. The lower facial profile of an idealized image was altered incrementally between 14° to -16°. Images were rated on a Likert scale by orthognathic patients, laypeople, and clinicians. Attractiveness ratings were greater for straight profiles in relation to convex/concave, with no significant difference between convex and concave profiles. Ratings decreased by 0.23 of a level for every degree increase in the convexity angle. Class II/III patients gave significantly reduced ratings of attractiveness and had greater desire for surgery than class I. A straight profile is perceived as most attractive and greater degrees of convexity or concavity deemed progressively less attractive, but a range of 10° to -12° may be deemed acceptable; beyond these values surgical correction is desired. Patients are most critical, and clinicians are more critical than laypeople. Copyright © 2012 Elsevier Inc. All rights reserved.

Automatic choroid cells segmentation and counting based on approximate convexity and concavity of chain code in fluorescence microscopic image

NASA Astrophysics Data System (ADS)

Lu, Weihua; Chen, Xinjian; Zhu, Weifang; Yang, Lei; Cao, Zhaoyuan; Chen, Haoyu

2015-03-01

In this paper, we proposed a method based on the Freeman chain code to segment and count rhesus choroid-retinal vascular endothelial cells (RF/6A) automatically for fluorescence microscopy images. The proposed method consists of four main steps. First, a threshold filter and morphological transform were applied to reduce the noise. Second, the boundary information was used to generate the Freeman chain codes. Third, the concave points were found based on the relationship between the difference of the chain code and the curvature. Finally, cells segmentation and counting were completed based on the characteristics of the number of the concave points, the area and shape of the cells. The proposed method was tested on 100 fluorescence microscopic cell images, and the average true positive rate (TPR) is 98.13% and the average false positive rate (FPR) is 4.47%, respectively. The preliminary results showed the feasibility and efficiency of the proposed method.

Responses to novel odors mediate maternal behavior and concaveation in gerbils.

PubMed

Clark, M M; Spencer, C A; Galef, B G

1986-01-01

In a series of three experiments we examined: (Experiment 1) responses to novel odors by early- and late-maturing not-pregnant, pregnant, nursing and postweaning female Mongolian gerbils, (Experiment 2) the response of the same eight groups of female gerbils to unfamiliar pups, and (Experiment 3) the rate of induction of maternal behavior by concaveation in early- and late-maturing nulliparous gerbils. We found: (1) that those females that responded relatively positively to novel odors in Experiment 1 were more likely to retrieve and less likely to attack unfamiliar pups in Experiment 2 than those females responding relatively negatively to novel odors in Experiment 1, and (2) that early-maturing nulliparous gerbils both responded more positively to novel odors and exhibited more rapid induction of maternal behavior by concaveation than late-maturing nulliparous gerbils. The results both confirm and extend Fleming and Rosenblatt's (1974) hypothesis that differences in response to novel odors mediate individual differences in maternal responsiveness.

Flow and performance of an air-curtain biological safety cabinet.

PubMed

Huang, Rong Fung; Chou, Chun I

2009-06-01

Using laser-assisted smoke flow visualization and tracer gas concentration detection techniques, this study examines aerodynamic flow properties and the characteristics of escape from containment, inward dispersion, and cross-cabinet contamination of a biological safety cabinet installed with an air curtain across the front aperture. The experimental method partially simulates the NSF/ANSI 49 standards with the difference that the biological tracer recommended by these standards is replaced by a mixture of 10% SF(6) in N(2). The air curtain is set up across the cabinet aperture plane by means of a narrow planar jet issued from the lower edge of the sash and a suction flow going through a suction slot installed at the front edge of the work surface. Varying the combination of jet velocity, suction flow velocity, and descending flow velocity reveals three types of characteristic flow modes: 'straight curtain', 'slightly concave curtain', and 'severely concave curtain'. Operating the cabinet in the straight curtain mode causes the air curtain to impinge on the doorsill and therefore induces serious escape from containment. In the severely concave curtain mode, drastically large inward dispersion and cross-cabinet contamination were observed because environmental air entered into the cabinet and a three-dimensional vortical flow structure formed in the cabinet. The slightly concave curtain mode presents a smooth and two-dimensional flow pattern with an air curtain separating the outside atmosphere from the inside space of the cabinet, and therefore exhibited negligibly small escape from containment, inward dispersion, and cross-cabinet contamination.

“Soft that molds the hard:” Geometric morphometry of lateral atlantoaxial joints focusing on the role of cartilage in changing the contour of bony articular surfaces

PubMed Central

Prasad, Prashant Kumar; Salunke, Pravin; Sahni, Daisy; Kalra, Parveen

2017-01-01

Purpose: The existing literature on lateral atlantoaxial joints is predominantly on bony facets and is unable to explain various C1-2 motions observed. Geometric morphometry of facets would help us in understanding the role of cartilages in C1-2 biomechanics/kinematics. Objective: Anthropometric measurements (bone and cartilage) of the atlantoaxial joint and to assess the role of cartilages in joint biomechanics. Materials and Methods: The authors studied 10 cadaveric atlantoaxial lateral joints with the articular cartilage in situ and after removing it, using three-dimensional laser scanner. The data were compared using geometric morphometry with emphasis on surface contours of articulating surfaces. Results: The bony inferior articular facet of atlas is concave in both sagittal and coronal plane. The bony superior articular facet of axis is convex in sagittal plane and is concave (laterally) and convex medially in the coronal plane. The bony articulating surfaces were nonconcordant. The articular cartilages of both C1 and C2 are biconvex in both planes and are thicker than the concavities of bony articulating surfaces. Conclusion: The biconvex structure of cartilage converts the surface morphology of C1-C2 bony facets from concave on concavo-convex to convex on convex. This reduces the contact point making the six degrees of freedom of motion possible and also makes the joint gyroscopic. PMID:29403249

Study of Unsteady Flows with Concave Wall Effect

NASA Technical Reports Server (NTRS)

Wang, Chi R.

2003-01-01

This paper presents computational fluid dynamic studies of the inlet turbulence and wall curvature effects on the flow steadiness at near wall surface locations in boundary layer flows. The time-stepping RANS numerical solver of the NASA Glenn-HT RANS code and a one-equation turbulence model, with a uniform inlet turbulence modeling level of the order of 10 percent of molecular viscosity, were used to perform the numerical computations. The approach was first calibrated for its predictabilities of friction factor, velocity, and temperature at near surface locations within a transitional boundary layer over concave wall. The approach was then used to predict the velocity and friction factor variations in a boundary layer recovering from concave curvature. As time iteration proceeded in the computations, the computed friction factors converged to their values from existing experiments. The computed friction factors, velocity, and static temperatures at near wall surface locations oscillated periodically in terms of time iteration steps and physical locations along the span-wise direction. At the upstream stations, the relationship among the normal and tangential velocities showed vortices effects on the velocity variations. Coherent vortices effect on the velocity components broke down at downstream stations. The computations also predicted the vortices effects on the velocity variations within a boundary layer flow developed along a concave wall surface with a downstream recovery flat wall surface. It was concluded that the computational approach might have the potential to analyze the flow steadiness in a turbine blade flow.

The human female heart incorporates glucose more efficiently than the male heart.

PubMed

Kakinuma, Yoshihiko; Okada, Shoshiro; Nogami, Munenobu; Kumon, Yoshitaka

2013-10-03

Oestrogen is known to play a cardioprotective role in cardiovascular diseases, as demonstrated in a number of animal studies. However, few human studies have investigated sex-based differences with regard to cardiac glucose uptake using (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT). Therefore, we evaluated healthy male and female subjects who underwent FDG-PET/CT examination to determine whether there was a sex-related difference in cardiac glucose uptake with age. In females, the prevalence of maximal FDG uptake (PET score 2) demonstrated a convex pattern with ageing, and it peaked at age 51-60 years in the females, gradually decreasing to a minimum at age >70 years. In contrast, the prevalence of maximal FDG uptake by age in males was a mirror image of that in females, i.e. it formed a concave pattern with a nadir at 61-70 years, followed by an increase in the prevalence. These findings suggest that female hearts depend more on glucose as an energy substrate as they age, however, efficient glucose uptake is attenuated with increasing age. In contrast, the male heart sustains its glucose uptake capacity at age >70 years. This characteristic sex-based difference in cardiac glucose uptake might be related to the female predominance of Takotsubo cardiomyopathy. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

NASA Astrophysics Data System (ADS)

Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

2016-08-01

The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

Design of interferometer system on Versatile Experiment Spherical Torus (VEST) at Seoul National University

NASA Astrophysics Data System (ADS)

Choi, D. H.; An, Y. H.; Chung, K. J.; Hwang, Y. S.

2012-01-01

A 94 GHz heterodyne interferometer system was designed to measure the plasma density of VEST (Versatile Experiment Spherical Torus), which was recently built at Seoul National University. Two 94 GHz Gunn oscillators with a frequency difference of 40 MHz were used in the microwave electronics part of a heterodyne interferometer system. A compact beam focusing system utilizing a pair of plano-convex lenses and a concave mirror was designed to maximize the effective beam reception and spatial resolution. Beam path analysis based on Gaussian optics was used in the design of the beam focusing system. The design of the beam focusing system and the beam path analysis were verified with a couple of experiments that were done within an experimental framework that considered the real dimensions of a vacuum vessel. Optimum distances between the optical components and the beam radii along the beam path obtained from the experiments were in good agreement with the beam path analysis using the Gaussian optics. Both experimentation and numerical calculations confirmed that the designed beam focusing system maximized the spatial resolution of the measurement; moreover, the beam waist was located at the center of the plasma to generate a phase shift more effectively in plasmas. The interferometer system presented in this paper is expected to be used in the measurements of line integrated plasma densities during the start-up phase of VEST.

Free-stream turbulence and concave curvature effects on heated, transitional boundary layers, volume 1

NASA Technical Reports Server (NTRS)

Kim, J.; Simon, T. W.

1991-01-01

An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-streem turbulence levels was performed. Where possible, sampling according to the intermittency function was made. Such sampling allowed segregation of the signal into two types of behavior: laminar-like and turbulent-like. The results from the investigation are discussed. Documentation is presented in two volumes. Volume one contains the text of the report including figures and supporting appendices. Volume two contains data reduction program listings and tabulated data.

Jet printing of convex and concave polymer micro-lenses.

PubMed

Blattmann, M; Ocker, M; Zappe, H; Seifert, A

2015-09-21

We describe a novel approach for fabricating customized convex as well as concave micro-lenses using substrates with sophisticated pinning architecture and utilizing a drop-on-demand jet printer. The polymeric lens material deposited on the wafer is cured by UV light irradiation yielding lenses with high quality surfaces. Surface shape and roughness of the cured polymer lenses are characterized by white light interferometry. Their optical quality is demonstrated by imaging an USAF1951 test chart. The evaluated modulation transfer function is compared to Zemax simulations as a benchmark for the fabricated lenses.

On the three-dimensional instability of laminar boundary layers on concave walls

NASA Technical Reports Server (NTRS)

Gortler, Henry

1954-01-01

A study is made of the stability of laminar boundary-layer profiles on slightly curved walls relative to small disturbances that result from vortices whose axes are parallel to the principal direction of flow. The result is an eigenvalue problem by which, for a given undisturbed flow at a prescribed wall, the amplification or decay is computed for each Reynolds number and each vortex thickness. For neutral disturbances (zero amplification) a critical Reynolds number is determined for each vortex distribution. The numerical calculation produces amplified disturbances on concave walls only.

The nonconvex multi-dimensional Riemann problem for Hamilton-Jacobi equations

NASA Technical Reports Server (NTRS)

Bardi, Martino; Osher, Stanley

1991-01-01

Simple inequalities are presented for the viscosity solution of a Hamilton-Jacobi equation in N space dimensions when neither the initial data nor the Hamiltonian need be convex (or concave). The initial data are uniformly Lipschitz and can be written as the sum of a convex function in a group of variables and a concave function in the remaining variables, therefore including the nonconvex Riemann problem. The inequalities become equalities wherever a 'maxmin' equals a 'minmax', and thus a representation formula for this problem is obtained, generalizing the classical Hopi formulas.

[Strut fracture of a convex-concave 60 degree Björk-Shiley mitral valve prosthesis 5 years after implantation--metallurgic analysis of the prosthesis strut].

PubMed

Lemke, B; Rathmann, J; Wiebe, V; Witzel, U

1991-08-01

Acute mechanical failure of prosthetic heart valves is rare, but associated with high mortality when occurring. For convexo-concave Björk-Shiley prostheses only fractures of the outlet strut are reported. We present a case of lethal mechanical complication 5 years after implantation. By additional metallurgic analysis we were able to identify a sequential course of the outlet strut fracture. This could lead to new approaches for early detection of this complication.

Simple proof of the concavity of the entropy power with respect to Gaussian noise

NASA Technical Reports Server (NTRS)

Dembo, Amir

1989-01-01

A very simple proof of M. H. Costa's result that the entropy power of Xt = X + N (O, tI) is concave in t, is derived as an immediate consequence of an inequality concerning Fisher information. This relationship between Fisher information and entropy is found to be useful for proving the central limit theorem. Thus, one who seeks new entropy inequalities should try first to find new inequalities about Fisher information, or at least to exploit the existing ones in new ways.

Q-switched Nd:YAG/V:YAG microchip 1338 nm laser for laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

2017-12-01

Q-switched microchip laser emitting radiation at wavelength 1338nm was tested as a radiation source for laser induced breakdown spectroscopy (LIBS). This laser used sandwich crystal which combined in one piece the cooling part (undoped YAG crystal 4mm long), the active laser part (Nd:YAG crystal 12mm long), and the saturable absorber (V:YAG crystal 0.7mm long). The diameter of this crystal was 5 mm. The microchip resonator consisted of dielectric mirrors directly deposited on the monolith crystal surfaces. The pump mirror (HT @ 808 nm, HR @ 1.3 ¹m) was placed on the undoped YAG part. The output coupler (R = 90% @ 1338 nm) was placed on the V:YAG part. The fibre-coupled 808nm pumping laser diode was operating in pulsed regime (rep. rate 250 Hz, pulse width 300 ¹s, pulse energy 6 mJ). Using this pumping, stable and high reproducible Q-switched pulses were generated at wavelength 1338 nm. Pulse length was 6.2 ns (FWHM) and the mean output power was 33mW. The single pulse energy and peak power was 0.13mJ and 21kW, respectively. Laser was operating in fundamental TEM00 mode. The laser radiation was focused on a tested sample using single plano-convex lens (focal length 75 mm). The focal spot radius was 40 ¹m. The corresponding peak-power density was 0.83GW/cm2. The laser induced break-down was successfully reached and corresponding laser-induced plasma spectra were recorded for set of metallic elements (Cu, Ag, Au, In, Zn, Al, Fe, Ni, Cr) and alloys (Sn-Pb solder, duralumin, stainless-steel, brass). To record the spectra, StellarNet BLACK-Comet concave grating CCD-based spectrometer was used without any special collimation optics. Thanks to used laser wavelength far from the detector sensitivity, no special filtering was needed to overcome the CCD dazzling. The constructed laser could significantly improve repletion-rate of up-to-date LIBS devices.

Comparison of thawing and freezing dark energy parametrizations

NASA Astrophysics Data System (ADS)

Pantazis, G.; Nesseris, S.; Perivolaropoulos, L.

2016-05-01

Dark energy equation of state w (z ) parametrizations with two parameters and given monotonicity are generically either convex or concave functions. This makes them suitable for fitting either freezing or thawing quintessence models but not both simultaneously. Fitting a data set based on a freezing model with an unsuitable (concave when increasing) w (z ) parametrization [like Chevallier-Polarski-Linder (CPL)] can lead to significant misleading features like crossing of the phantom divide line, incorrect w (z =0 ), incorrect slope, etc., that are not present in the underlying cosmological model. To demonstrate this fact we generate scattered cosmological data at both the level of w (z ) and the luminosity distance DL(z ) based on either thawing or freezing quintessence models and fit them using parametrizations of convex and of concave type. We then compare statistically significant features of the best fit w (z ) with actual features of the underlying model. We thus verify that the use of unsuitable parametrizations can lead to misleading conclusions. In order to avoid these problems it is important to either use both convex and concave parametrizations and select the one with the best χ2 or use principal component analysis thus splitting the redshift range into independent bins. In the latter case, however, significant information about the slope of w (z ) at high redshifts is lost. Finally, we propose a new family of parametrizations w (z )=w0+wa(z/1 +z )n which generalizes the CPL and interpolates between thawing and freezing parametrizations as the parameter n increases to values larger than 1.

Mysterious coloring: structural origin of color mixing for two breeds of Papilio butterflies.

PubMed

Diao, Ying-Ying; Liu, Xiang-Yang

2011-05-09

The structural origin of the coloration mechanisms and related extraordinary optical properties of the wing scales of two breeds of Papilio butterflies, namely, Papilio ulysses and Papilio blumei, are explored. The precise ordered biophotonic nanostructures of the wing scales are characterized by scanning electron microscopy (SEM). Despite their structural similarities, the two breeds of Papilio butterflies do not exhibit any analogy in their optical performances. When illuminated with UV-Vis light, P. ulysses gives rise to two reflection peaks: one is from concavities, and the other is from ridges. These two spectral peaks shift their positions under different illumination angles (normal and 45° incident light). In contrast, the spectra for the green scales of P. blumei give one broad reflection peak, and the peak remains the same under normal and 45° incident light. The optical microscopy images indicate that the cap-shaped concavities on P. blumei's wing scales generate an abnormal bicolor reflection with a strong polarization effect. Both of these two breeds of butterflies take advantage of color mixing strategy: the blue color of P. ulysses is mixed by the colors reflected from concavities and ridges; the green color of P. blumei is produced by the biocolor reflection from concavities. The differences of their coloration mixing mechanisms and optical performances are due to the variations of their nanostructures. The investigation of the color mixing mechanisms of these biologically photonic nanostructures may offer a convenient way for fabricating optical devices based on biomimicry. © 2011 Optical Society of America

The concave iris in pigment dispersion syndrome.

PubMed

Liu, Lance; Ong, Ee Lin; Crowston, Jonathan

2011-01-01

To visualize the changes of the iris contour in patients with pigment dispersion syndrome after blinking, accommodation, and pharmacologic miosis using anterior segment optical coherence tomography. Observational case series. A total of 33 eyes of 20 patients with pigment dispersion syndrome. Each eye was imaged along the horizontal 0- to 180-degree meridian using the Visante Anterior Segment Imaging System (Carl Zeiss Meditec, Dublin, CA). Scans were performed at baseline and after focusing on an internal fixation target for 5 minutes, forced blinking, accommodation, and pharmacologic miosis with pilocarpine 2%. Quantitative analysis of the changes in the iris configuration. After 5 minutes of continual fixation, the iris became planar with the mean ± standard deviation curvature decreasing from 214 ± 74 μm to 67 ± 76 μm (P < 0.05). The iris remained planar in all patients with pigment dispersion syndrome after forced blinking, but the iris concavity recovered to 227 ± 113 μm (P = 0.34) and 238 ± 119 μm (P = 0.19) with the -3.0 and -6.0 diopter lenses, respectively. Pilocarpine-induced miosis caused the iris to assume a planar configuration in all subjects. This study shows that the iris in pigment dispersion syndrome assumes a planar configuration when fixating and that the concavity of the iris surface is not restored by blinking. Accommodation restored the iris concavity, suggesting that the posterior curvature of the iris in pigment dispersion syndrome is induced and probably maintained, at least in part, by accommodation. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Folded concave penalized learning in identifying multimodal MRI marker for Parkinson’s disease

PubMed Central

Liu, Hongcheng; Du, Guangwei; Zhang, Lijun; Lewis, Mechelle M.; Wang, Xue; Yao, Tao; Li, Runze; Huang, Xuemei

2016-01-01

Background Brain MRI holds promise to gauge different aspects of Parkinson’s disease (PD)-related pathological changes. Its analysis, however, is hindered by the high-dimensional nature of the data. New method This study introduces folded concave penalized (FCP) sparse logistic regression to identify biomarkers for PD from a large number of potential factors. The proposed statistical procedures target the challenges of high-dimensionality with limited data samples acquired. The maximization problem associated with the sparse logistic regression model is solved by local linear approximation. The proposed procedures then are applied to the empirical analysis of multimodal MRI data. Results From 45 features, the proposed approach identified 15 MRI markers and the UPSIT, which are known to be clinically relevant to PD. By combining the MRI and clinical markers, we can enhance substantially the specificity and sensitivity of the model, as indicated by the ROC curves. Comparison to existing methods We compare the folded concave penalized learning scheme with both the Lasso penalized scheme and the principle component analysis-based feature selection (PCA) in the Parkinson’s biomarker identification problem that takes into account both the clinical features and MRI markers. The folded concave penalty method demonstrates a substantially better clinical potential than both the Lasso and PCA in terms of specificity and sensitivity. Conclusions For the first time, we applied the FCP learning method to MRI biomarker discovery in PD. The proposed approach successfully identified MRI markers that are clinically relevant. Combining these biomarkers with clinical features can substantially enhance performance. PMID:27102045

Detection and Purging of Specular Reflective and Transparent Object Influences in 3d Range Measurements

NASA Astrophysics Data System (ADS)

Koch, R.; May, S.; Nüchter, A.

2017-02-01

3D laser scanners are favoured sensors for mapping in mobile service robotics at indoor and outdoor applications, since they deliver precise measurements at a wide scanning range. The resulting maps are detailed since they have a high resolution. Based on these maps robots navigate through rough terrain, fulfil advanced manipulation, and inspection tasks. In case of specular reflective and transparent objects, e.g., mirrors, windows, shiny metals, the laser measurements get corrupted. Based on the type of object and the incident angle of the incoming laser beam there are three results possible: a measurement point on the object plane, a measurement behind the object plane, and a measurement of a reflected object. It is important to detect such situations to be able to handle these corrupted points. This paper describes why it is difficult to distinguish between specular reflective and transparent surfaces. It presents a 3DReflection- Pre-Filter Approach to identify specular reflective and transparent objects in point clouds of a multi-echo laser scanner. Furthermore, it filters point clouds from influences of such objects and extract the object properties for further investigations. Based on an Iterative-Closest-Point-algorithm reflective objects are identified. Object surfaces and points behind surfaces are masked according to their location. Finally, the processed point cloud is forwarded to a mapping module. Furthermore, the object surface corners and the type of the surface is broadcasted. Four experiments demonstrate the usability of the 3D-Reflection-Pre-Filter. The first experiment was made in a empty room containing a mirror, the second experiment was made in a stairway containing a glass door, the third experiment was made in a empty room containing two mirrors, the fourth experiment was made in an office room containing a mirror. This paper demonstrate that for single scans the detection of specular reflective and transparent objects in 3D is possible. It is more reliable in 3D as in 2D. Nevertheless, collect the data of multiple scans and post-filter them as soon as the object was bypassed should pursued. This is why future work concentrates on implementing a post-filter module. Besides, it is the aim to improve the discrimination between specular reflective and transparent objects.

Restricted mobility of side chains on concave surfaces of solenoid proteins may impart heightened potential for intermolecular interactions.

PubMed

Ramya, L; Gautham, N; Chaloin, Laurent; Kajava, Andrey V

2015-09-01

Significant progress has been made in the determination of the protein structures with their number today passing over a hundred thousand structures. The next challenge is the understanding and prediction of protein-protein and protein-ligand interactions. In this work we address this problem by analyzing curved solenoid proteins. Many of these proteins are considered as "hub molecules" for their high potential to interact with many different molecules and to be a scaffold for multisubunit protein machineries. Our analysis of these structures through molecular dynamics simulations reveals that the mobility of the side-chains on the concave surfaces of the solenoids is lower than on the convex ones. This result provides an explanation to the observed preferential binding of the ligands, including small and flexible ligands, to the concave surface of the curved solenoid proteins. The relationship between the landscapes and dynamic properties of the protein surfaces can be further generalized to the other types of protein structures and eventually used in the computer algorithms, allowing prediction of protein-ligand interactions by analysis of protein surfaces. © 2015 Wiley Periodicals, Inc.

Device for absorbing mechanical shock

DOEpatents

Newlon, Charles E.

1980-01-01

This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

Device for absorbing mechanical shock

DOEpatents

Newlon, C.E.

1979-08-29

This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

Directable weathering of concave rock using curvature estimation.

PubMed

Jones, Michael D; Farley, McKay; Butler, Joseph; Beardall, Matthew

2010-01-01

We address the problem of directable weathering of exposed concave rock for use in computer-generated animation or games. Previous weathering models that admit concave surfaces are computationally inefficient and difficult to control. In nature, the spheroidal and cavernous weathering rates depend on the surface curvature. Spheroidal weathering is fastest in areas with large positive mean curvature and cavernous weathering is fastest in areas with large negative mean curvature. We simulate both processes using an approximation of mean curvature on a voxel grid. Both weathering rates are also influenced by rock durability. The user controls rock durability by editing a durability graph before and during weathering simulation. Simulations of rockfall and colluvium deposition further improve realism. The profile of the final weathered rock matches the shape of the durability graph up to the effects of weathering and colluvium deposition. We demonstrate the top-down directability and visual plausibility of the resulting model through a series of screenshots and rendered images. The results include the weathering of a cube into a sphere and of a sheltered inside corner into a cavern as predicted by the underlying geomorphological models.

Supersonic cavity flows over concave and convex walls

NASA Astrophysics Data System (ADS)

Ye, A. Ran; Das, Rajarshi; Setoguchi, Toshiaki; Kim, Heuy Dong

2016-04-01

Supersonic cavity flows are characterized by compression and expansion waves, shear layer, and oscillations inside the cavity. For decades, investigations into cavity flows have been conducted, mostly with flows at zero pressure gradient entering the cavity in straight walls. Since cavity flows on curved walls exert centrifugal force, the features of these flows are likely to differ from those of straight wall flows. The aim of the present work is to study the flow physics of a cavity that is cut out on a curved wall. Steady and unsteady numerical simulations were carried out for supersonic flow through curved channels over the cavity with L/H = 1. A straight channel flow was also analyzed which serves as the base model. The velocity gradient along the width of the channel was observed to increase with increasing the channel curvature for both concave and convex channels. The pressure on the cavity floor increases with the increase in channel curvature for concave channels and decreases for convex channels. Moreover, unsteady flow characteristics are more dependent on channel curvature under supersonic free stream conditions.

Head rice rate measurement based on concave point matching

PubMed Central

Yao, Yuan; Wu, Wei; Yang, Tianle; Liu, Tao; Chen, Wen; Chen, Chen; Li, Rui; Zhou, Tong; Sun, Chengming; Zhou, Yue; Li, Xinlu

2017-01-01

Head rice rate is an important factor affecting rice quality. In this study, an inflection point detection-based technology was applied to measure the head rice rate by combining a vibrator and a conveyor belt for bulk grain image acquisition. The edge center mode proportion method (ECMP) was applied for concave points matching in which concave matching and separation was performed with collaborative constraint conditions followed by rice length calculation with a minimum enclosing rectangle (MER) to identify the head rice. Finally, the head rice rate was calculated using the sum area of head rice to the overall coverage of rice. Results showed that bulk grain image acquisition can be realized with test equipment, and the accuracy rate of separation of both indica rice and japonica rice exceeded 95%. An increase in the number of rice did not significantly affect ECMP and MER. High accuracy can be ensured with MER to calculate head rice rate by narrowing down its relative error between real values less than 3%. The test results show that the method is reliable as a reference for head rice rate calculation studies. PMID:28128315

The improvement of GaN-based LED grown on concave nano-pattern sapphire substrate with SiO2 blocking layer

NASA Astrophysics Data System (ADS)

Lin, Jyun-Hao; Huang, Shyh-Jer; Su, Yan-Kuin; Huang, Kai-Wen

2015-11-01

In contrast to convex nano-pattern sapphire substrates (NPSS), which are frequently used to fabricate high-quality nitride-based light-emitting diodes (LEDs), concave NPSS have been paid relatively less attention. In this study, a concave NPSS was fabricated, and its nitride epitaxial growth process was evaluated in a step by step manner. A SiO2 layer was used to avoid nucleation over the sidewall and bottom of the nano-patterns to reduce dislocation reformation. Traditional LED structures were grown on the NPSS layer to determine its influence on device performance. X-ray diffraction, etched pit density, inverse leakage current, and internal quantum efficiency (IQE) results showed that dislocations and non-radiative recombination centers are reduced by the NPSS constructed with a SiO2 blocking layer. An IQE twice that on a planar substrate was also achieved; such a high IQE significantly enhanced the external quantum efficiency of the resultant device. Taken together, the results demonstrate that the SiO2 blocking layer proposed in this work can enhance the performance of LEDs.

Diffusive-to-ballistic transition of the modulated heat transport in a rarefied air chamber

NASA Astrophysics Data System (ADS)

Gomez-Heredia, C. L.; Macias, J.; Ordonez-Miranda, J.; Ares, O.; Alvarado-Gil, J. J.

2017-01-01

Modulated heat transfer in air subject to pressures from 760 Torr to 10-4 Torr is experimentally studied by means of a thermal-wave resonant cavity placed in a vacuum chamber. This is done through the analysis of the amplitude and phase delay of the photothermal signal as a function of the cavity length and pressure through of the Knudsen's number. The viscous, transitional, and free molecular regimes of heat transport are observed for pressures P>1.5 Torr, 25 mTorr

Effects of radiator shapes on the bubble diving and dispersion of ultrasonic argon process.

PubMed

Liu, Xuan; Xue, Jilai; Zhao, Qiang; Le, Qichi; Zhang, Zhiqiang

2018-03-01

In this work, three ultrasonic radiators in different shapes have been designed in order to investigate the effects of radiator shapes on the argon bubble dispersion and diving as well as the degassing efficiency on magnesium melt. The radiator shape has a strong influence on the bubble diving and dispersion by ultrasound. A massive argon bubble slowly flows out from the radiator with the hemispherical cap, due to the covering hemispherical cap. Using a concave radiator can intensively crush the argon bubbles and drive them much deep into the water/melt, depending on the competition between the argon flow and opposite joint shear force from the concave surface. The evolution of wall bubbles involves the ultrasonic cavities carrying dissolved gas, migrating to the vessel wall, and escaping from the liquid. Hydrogen removal can be efficiently achieved using a concave radiator. The hydrogen content can be reduced from 22.3 μg/g down to 8.7 μg/g. Mechanical properties are significantly promoted, due to the structure refinement and efficient hydrogen removal. Copyright © 2017 Elsevier B.V. All rights reserved.

Debris thickness patterns on debris-covered glaciers

NASA Astrophysics Data System (ADS)

Anderson, Leif S.; Anderson, Robert S.

2018-06-01

Many debris-covered glaciers have broadly similar debris thickness patterns: surface debris thickens and tends to transition from convex- to concave-up-down glacier. We explain this pattern using theory (analytical and numerical models) paired with empirical observations. Down glacier debris thickening results from the conveyor-belt-like nature of the glacier surface in the ablation zone (debris can typically only be added but not removed) and from the inevitable decline in ice surface velocity toward the terminus. Down-glacier thickening of debris leads to the reduction of sub-debris melt and debris emergence toward the terminus. Convex-up debris thickness patterns occur near the up-glacier end of debris covers where debris emergence dominates (ablation controlled). Concave-up debris thickness patterns occur toward glacier termini where declining surface velocities dominate (velocity controlled). A convex-concave debris thickness profile inevitably results from the transition between ablation-control and velocity-control down-glacier. Debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time. By establishing this expected debris thickness pattern, the effects of climate change on debris cover can be better identified.

An examination of the factor structure of the Sociocultural Attitudes Towards Appearance Questionnaire-3 in Malaysia.

PubMed

Swami, Viren

2009-03-01

The present study examined the factor structure of a Malay translation of the Sociocultural Attitudes Towards Appearance Questionnaire-3 among a community sample of 554 Malaysian women. Results of an exploratory factor analysis revealed the existence of four factors, two of which (Information and Internalization-Athlete) mirrored those found among Western samples. An additional factor was an amalgamation of two factors reported in the West, namely Pressure and Internalization-General. A fourth factor consisted of six items, four of which cross-loaded onto previous factors, and was consequently dropped from analyses. Cronbach's alpha coefficients for the three retained factors were all above .82, and the three factors were significantly correlated with each other and with participants' body mass index. The results of this study stress the need for locally developed scales in the study of body image and a shift away from reliance on scales developed in the West.

Inhibiting the TE1-mode diffraction losses in terahertz parallel-plate waveguides using concave plates.

PubMed

Mbonye, Marx; Mendis, Rajind; Mittleman, Daniel M

2012-12-03

We present numerical and experimental results on inhibiting diffraction losses associated with the lowest order transverse electric (TE1) mode of a terahertz (THz) parallel-plate waveguide (PPWG) via the use of slightly concave plates. We find that there is an optimal radius of curvature that inhibits the diffraction for a given waveguide operating at a given frequency. We also find that introducing this curvature does not introduce any additional group-velocity dispersion. These results support the possibility of realizing long range transport of THz radiation using the TE1 mode of the PPWG.

Note: Attenuation motion of acoustically levitated spherical rotor

NASA Astrophysics Data System (ADS)

Lü, P.; Hong, Z. Y.; Yin, J. F.; Yan, N.; Zhai, W.; Wang, H. P.

2016-11-01

Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

Note: Attenuation motion of acoustically levitated spherical rotor.

PubMed

Lü, P; Hong, Z Y; Yin, J F; Yan, N; Zhai, W; Wang, H P

2016-11-01

Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

Sclerochronology of Holocene oyster shells (Crassostrea gigas) from the West Coast of Bohai Sea, China

NASA Astrophysics Data System (ADS)

Fan, C.; Koeniger, P.; Wang, H.; Frechen, M.

2009-04-01

Sclerochronology, the study of periodic increments in skeletal organisms, can decipher the life history and environmental records preserved in fossil shells. Although there have been a number of studies that apply isotopic analyses to shells in open ocean and fresh water, investigations for brackish environments are rare. One of the common inhabitants in estuaries is the Crassostrea oyster. Kirby et al. (1998) demonstrated a close correspondence between the ligamental increments of convex and concave bands and yearly ^18O cycles; Andrus and Crowe (2000) found a close correspondence between translucent growth bands on the cross-section of the hinge and yearly ^18O cycles. They conclude that the morphological features on hinge and growth bands on the cross-section are formed annually and can be used to determine accurately age and growth rate in this species. However, Surge et al. (2001) could not find that these morphologic features have seasonal significance in the C. virginica shells. Therefore, these concave ridges are not reliable independent proxies of seasonality. These studies were carried out with C. virginica shells; none was studied with nature C. gigas, which was widely distributed along the Pacific coastal area. C. gigas has been introduced from its native home to all over the world, ranging from North America to Australia and Europe; it has become an important commercial harvest in many of these places. Buried Holocene oyster shells of C. gigas were sampled from a huge buried oyster reef on the West of Bohai Sea, China. One of these shells was selected for high resolution micro-sampling and stable isotope analyses testing the assumption that C. gigas ligamental increments are annual in nature. We analyzed 236 consecutive samples from the shell to show that morphologic features both on hinge and cross-section are annual by comparing them to the ^18O profiles. We tested the assumption that the morphologic features of C.gigas are delineated by convex tops and concave bottoms on hinge and corresponding translucent growth bands on cross-section. The shell has 13.5 ligamental increments, based on 13.5 convex bands and 13 concave bottoms on hinge. Convex tops correspond to ^18O minima (summers), whereas concave bottoms correspond to ^18O maxima, which were formed during the low temperature of winter in the study area. We demonstrate that the ligamental increments of convex tops, concave bottoms and translucent growth bands in the studied C. gigas shell are suitable indicators of annual growth increments. The life spans, growth rates, and the timing of death can be determined from the ligament increments and isotope profiles of buried oyster shells.

Acquisition of Motor and Cognitive Skills through Repetition in Typically Developing Children

PubMed Central

Magallón, Sara; Narbona, Juan; Crespo-Eguílaz, Nerea

2016-01-01

Background Procedural memory allows acquisition, consolidation and use of motor skills and cognitive routines. Automation of procedures is achieved through repeated practice. In children, improvement in procedural skills is a consequence of natural neurobiological development and experience. Methods The aim of the present research was to make a preliminary evaluation and description of repetition-based improvement of procedures in typically developing children (TDC). Ninety TDC children aged 6–12 years were asked to perform two procedural learning tasks. In an assembly learning task, which requires predominantly motor skills, we measured the number of assembled pieces in 60 seconds. In a mirror drawing learning task, which requires more cognitive functions, we measured time spent and efficiency. Participants were tested four times for each task: three trials were consecutive and the fourth trial was performed after a 10-minute nonverbal interference task. The influence of repeated practice on performance was evaluated by means of the analysis of variance with repeated measures and the paired-sample test. Correlation coefficients and simple linear regression test were used to examine the relationship between age and performance. Results TDC achieved higher scores in both tasks through repetition. Older children fitted more pieces than younger ones in assembling learning and they were faster and more efficient at the mirror drawing learning task. Conclusions These findings indicate that three consecutive trials at a procedural task increased speed and efficiency, and that age affected basal performance in motor-cognitive procedures. PMID:27384671

Current status of Japanese detectors

NASA Astrophysics Data System (ADS)

Tatsumi, Daisuke; Takahashi, Ryutaro; Arai, Koji; Nakagawa, Noriyasu; Agatsuma, Kazuhiro; Yamazaki, Toshitaka; Fukushima, Mitsuhiro; Fujimoto, Masa-Katsu; Takamori, Akiteru; Bertolini, Alessandro; Sannibale, Virginio; DeSalvo, Riccardo; Márka, Szabolcs; Ando, Masaki; Tsubono, Kimio; Akutsu, Tomomi; Yamamoto, Kazuhiro; Ishitsuka, Hideki; Uchiyama, Takashi; Miyoki, Shinji; Ohashi, Masatake; Kuroda, Kazuaki; Awaya, Norichika; Kanda, Nobuyuki; Araya, Akito; Telada, Souichi; Tomaru, Takayuki; Haruyama, Tomiyoshi; Yamamoto, Akira; Sato, Nobuaki; Suzuki, Toshitaka; Shintomi, Takakazu

2007-10-01

The current status of the TAMA and CLIO detectors in Japan is reported in this paper. These two interferometric gravitational wave detectors are being developed for the large cryogenic gravitational wave telescope (LCGT) which is a future plan for detecting gravitational wave signals at least once per year. TAMA300 is being upgraded to improve the sensitivity in a low-frequency region after the last observational experiment in 2004. To reduce the seismic noises, we are installing a new seismic isolation system, called the TAMA seismic attenuation system, for the four test masses. We confirmed stable mass locks of a cavity and improvements of length and angular fluctuations by using two SASs. We are currently optimizing the performance of the third and fourth SASs. We continue TAMA300 operation and R&D studies for the LCGT. The next data taking is planned for the summer of 2007. CLIO is a 100 m baseline length prototype detector for LCGT to investigate interferometer performance in cryogenic condition. The key features of CLIO are that it locates the Kamioka underground site for a low-seismic noise level, and adopts cryogenic Sapphire mirrors for low-thermal noise level. The first operation of the cryogenic interferometer was successfully demonstrated in February 2006. Current sensitivity at room temperature is close to the target sensitivity within a factor of 4. Several observational experiments at room temperature have been done. Once the displacement noise reaches the thermal noise level of room temperature, its improvement by cooling test mass mirrors should be demonstrated.

Acquisition of Motor and Cognitive Skills through Repetition in Typically Developing Children.

PubMed

Magallón, Sara; Narbona, Juan; Crespo-Eguílaz, Nerea

2016-01-01

Procedural memory allows acquisition, consolidation and use of motor skills and cognitive routines. Automation of procedures is achieved through repeated practice. In children, improvement in procedural skills is a consequence of natural neurobiological development and experience. The aim of the present research was to make a preliminary evaluation and description of repetition-based improvement of procedures in typically developing children (TDC). Ninety TDC children aged 6-12 years were asked to perform two procedural learning tasks. In an assembly learning task, which requires predominantly motor skills, we measured the number of assembled pieces in 60 seconds. In a mirror drawing learning task, which requires more cognitive functions, we measured time spent and efficiency. Participants were tested four times for each task: three trials were consecutive and the fourth trial was performed after a 10-minute nonverbal interference task. The influence of repeated practice on performance was evaluated by means of the analysis of variance with repeated measures and the paired-sample test. Correlation coefficients and simple linear regression test were used to examine the relationship between age and performance. TDC achieved higher scores in both tasks through repetition. Older children fitted more pieces than younger ones in assembling learning and they were faster and more efficient at the mirror drawing learning task. These findings indicate that three consecutive trials at a procedural task increased speed and efficiency, and that age affected basal performance in motor-cognitive procedures.

Interactions between Hofmeister anions and the binding pocket of a protein.

PubMed

Fox, Jerome M; Kang, Kyungtae; Sherman, Woody; Héroux, Annie; Sastry, G Madhavi; Baghbanzadeh, Mostafa; Lockett, Matthew R; Whitesides, George M

2015-03-25

This paper uses the binding pocket of human carbonic anhydrase II (HCAII, EC 4.2.1.1) as a tool to examine the properties of Hofmeister anions that determine (i) where, and how strongly, they associate with concavities on the surfaces of proteins and (ii) how, upon binding, they alter the structure of water within those concavities. Results from X-ray crystallography and isothermal titration calorimetry show that most anions associate with the binding pocket of HCAII by forming inner-sphere ion pairs with the Zn(2+) cofactor. In these ion pairs, the free energy of anion-Zn(2+) association is inversely proportional to the free energetic cost of anion dehydration; this relationship is consistent with the mechanism of ion pair formation suggested by the "law of matching water affinities". Iodide and bromide anions also associate with a hydrophobic declivity in the wall of the binding pocket. Molecular dynamics simulations suggest that anions, upon associating with Zn(2+), trigger rearrangements of water that extend up to 8 Å away from their surfaces. These findings expand the range of interactions previously thought to occur between ions and proteins by suggesting that (i) weakly hydrated anions can bind complementarily shaped hydrophobic declivities, and that (ii) ion-induced rearrangements of water within protein concavities can (in contrast with similar rearrangements in bulk water) extend well beyond the first hydration shells of the ions that trigger them. This study paints a picture of Hofmeister anions as a set of structurally varied ligands that differ in size, shape, and affinity for water and, thus, in their ability to bind to—and to alter the charge and hydration structure of—polar, nonpolar, and topographically complex concavities on the surfaces of proteins.

Effects of local and global mechanical distortions to hypervelocity boundary layers

NASA Astrophysics Data System (ADS)

Flaherty, William P.

The response of hypervelocity boundary layers to global mechanical distortions due to concave surface curvature is examined. Surface heat transfer, visual boundary layer thickness, and pressure sensitive paint (PSP) data are obtained for a suite of models with different concave surface geometries. Results are compared to predictions using existing approximate methods. Near the leading edge, good agreement is observed, but at larger pressure gradients, predictions diverge significantly from the experimental data. Up to a factor of five underprediction is reported in regions with greatest distortion. Curve fits to the experimental data are compared with surface equations. It is demonstrated that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle for all model geometries, even at the conditions of greatest distortion. As a means of introducing additional local distortions, vortex generators are used to impose streamwise structures into the boundary layer. The response of the large scale vortical structures to an adverse pressure gradient is investigated. For a flat plate baseline case, heat transfer augmentation at similar levels to turbulent flow is measured. For the concave geometries, increases in heat transfer by factors up to 2.6 are measured over the laminar values, though for higher turning angle cases, a relaxation to below undisturbed values is reported at turning angles between 10 and 15 degrees. The scaling of heat transfer with turning angle that is identified for the laminar boundary layer response is found to be robust even in the presence of the imposed vortex structures. PSP measurements indicated that natural streaks form over concave models even when imposed vorticity is present. Correlations found between the heat transfer and natural streak formation are discussed and indicate possible vortex interactions.

Large eddy simulation of a boundary layer with concave streamwise curvature

NASA Technical Reports Server (NTRS)

Lund, Thomas S.

1993-01-01

One of the most exciting recent developments in the field of large eddy simulation (LES) is the dynamic subgrid-scale model. The dynamic model concept is a general procedure for evaluating model constants by sampling a band of the smallest scales actually resolved in the simulation. To date, the procedure has been used primarily in conjunction with the Smagorinsky model. The dynamic procedure has the advantage that the value of the model constant need not be specified a priori, but rather is calculated as a function of space and time as the simulation progresses. This feature makes the dynamic model especially attractive for flows in complex geometries where it is difficult or impossible to calibrate model constants. The dynamic model was highly successful in benchmark tests involving homogeneous and channel flows. Having demonstrated the potential of the dynamic model in these simple flows, the overall direction of the LES effort at CTR shifted toward an evaluation of the model in more complex situations. The current test cases are basic engineering-type flows for which Reynolds averaged approaches were unable to model the turbulence to within engineering accuracy. Flows currently under investigation include a backward-facing step, wake behind a circular cylinder, airfoil at high angles of attack, separated flow in a diffuser, and boundary layer over a concave surface. Preliminary results from the backward-facing step and cylinder wake simulations are encouraging. Progress on the LES of a boundary layer on a concave surface is discussed. Although the geometry of a concave wall is not very complex, the boundary layer that develops on its surface is difficult to model due to the presence of streamwise Taylor-Gortler vortices. These vortices arise as a result of a centrifugal instability associated with the convex curvature.

The Björk-Shiley 70 degree convexo-concave prosthesis strut fracture problem (present state of information).

PubMed

Ostermeyer, J; Horstkotte, D; Bennett, J; Huysmans, H; Lindblom, D; Olin, C; Orinius, E; Semb, G

1987-04-01

Between June 1980 and June 1983 4028 Björk-Shiley 70 degree convexo-concave prosthetic heart valves were distributed and implanted in Australia, Canada, Europe and South Africa. As of March 1986, a total of 52 outlet strut fractures (1.29%; 70% CL: 1.1%-1.5%) have been reported from 29 implant institutions in 12 countries. The majority (82.7%) occurred in Europe. Intervals between implantation and fracture were 13 days to 45.3 months (mean: 18.4 months; 70% CL: 16.6 months-20.1 months). The mortality rate after strut fracture was 78.7% (70% CL: 72.5%-84.9%). Upon stratification of the fracture by valve sizes and types it becomes evident that 75% (70% CL: 68.8%-81.2%) of all fractures are related to the sizes 29 mm to 33 mm (which virtually represent the same valve size) and predominantly to mitral valves (p less than 0.01). The large valves again have been stratified into two subsets, namely those fabricated from flanges originally machined as Björk-Shiley 60 degree convexo-concave valves (group I) and later produced valves machined initially to 70 degree specifications (group II). In group I the fracture rate was 5.2% (70% CL: 4.2%-6.2%) versus 1.6% (70% CL: 1.1%-2.1%) in group II (p less than 0.01), which identifies the group I 29 mm-33 mm Björk-Shiley 70 degree convexo-concave valves as the highest risk group for strut fracture. The rates are based upon all available information as of March 16, 1986.(ABSTRACT TRUNCATED AT 250 WORDS)

Numerical Optimization of converging diverging miniature cavitating nozzles

NASA Astrophysics Data System (ADS)

Chavan, Kanchan; Bhingole, B.; Raut, J.; Pandit, A. B.

2015-12-01

The work focuses on the numerical optimization of converging diverging cavitating nozzles through nozzle dimensions and wall shape. The objective is to develop design rules for the geometry of cavitating nozzles for desired end-use. Two main aspects of nozzle design which affects the cavitation have been studied i.e. end dimensions of the geometry (i.e. angle and/or curvature of the inlet, outlet and the throat and the lengths of the converging and diverging sections) and wall curvatures(concave or convex). Angle of convergence at the inlet was found to control the cavity growth whereas angle of divergence of the exit controls the collapse of cavity. CFD simulations were carried out for the straight line converging and diverging sections by varying converging and diverging angles to study its effect on the collapse pressure generated by the cavity. Optimized geometry configurations were obtained on the basis of maximum Cavitational Efficacy Ratio (CER)i.e. cavity collapse pressure generated for a given permanent pressure drop across the system. With increasing capabilities in machining and fabrication, it is possible to exploit the effect of wall curvature to create nozzles with further increase in the CER. Effect of wall curvature has been studied for the straight, concave and convex shapes. Curvature has been varied and effect of concave and convex wall curvatures vis-à-vis straight walls studied for fixed converging and diverging angles.It is concluded that concave converging-diverging nozzles with converging angle of 20° and diverging angle of 5° with the radius of curvature 0.03 m and 0.1530 m respectively gives maximum CER. Preliminary experiments using optimized geometry are indicating similar trends and are currently being carried out. Refinements of the CFD technique using two phase flow simulations are planned.

Studies on H-Translocating ATPases in Plants of Varying Resistance to Salinity : I. Salinity during Growth Modulates the Proton Pump in the Halophyte Atriplex nummularia.

PubMed

Braun, Y; Hassidim, M; Lerner, H R; Reinhold, L

1986-08-01

Membrane vesicles were isolated from the roots of the halophyte Atriplex nummularia Lindl. H(+)-translocating Mg(2+)-ATPase activity was manifested by the establishment of a positive membrane potential (measured as SCN(-) accumulation); and also by the establishment of a transmembrane pH gradient (measured by quinacrine fluorescence quenching). H(+)-translocation was highly specific to ATP and was stable to oligomycin. Growing the plants in the presence of 400 millimolar NaCl doubled the proton-translocating activity per milligram of membrane protein and otherwise modulated it in the following ways. First, the flat pH profile observed in non-salt-grown plants was transformed to one showing a peak at about pH 6.2. Second, the lag effect observed at low ATP concentration in curves relating SCN(-) accumulation to ATP concentration was abolished; the concave curvature shown in the double reciprocal plot was diminished. Third, sensitivity to K-2 (N-morpholino)ethanesulfonic acid stimulation was shown in salt-grown plants (about 40% stimulation) but was absent in non-salt-grown plants. Fourth, the KCl concentration bringing about 50% dissipation of ATP-dependent SCN(-) accumulation was 20 millimolar for salt-grown plants and 50 millimolar for non-salt-grown plants. Vanadate sensitivity was shown in both cases. No clear NO(3) (-) inhibition was observed.

Studies on H+-Translocating ATPases in Plants of Varying Resistance to Salinity 1

PubMed Central

Braun, Yael; Hassidim, Miriam; Lerner, Henri R.; Reinhold, Leonora

1986-01-01

Membrane vesicles were isolated from the roots of the halophyte Atriplex nummularia Lindl. H+-translocating Mg2+-ATPase activity was manifested by the establishment of a positive membrane potential (measured as SCN− accumulation); and also by the establishment of a transmembrane pH gradient (measured by quinacrine fluorescence quenching). H+-translocation was highly specific to ATP and was stable to oligomycin. Growing the plants in the presence of 400 millimolar NaCl doubled the proton-translocating activity per milligram of membrane protein and otherwise modulated it in the following ways. First, the flat pH profile observed in non-salt-grown plants was transformed to one showing a peak at about pH 6.2. Second, the lag effect observed at low ATP concentration in curves relating SCN− accumulation to ATP concentration was abolished; the concave curvature shown in the double reciprocal plot was diminished. Third, sensitivity to K-2 (N-morpholino)ethanesulfonic acid stimulation was shown in salt-grown plants (about 40% stimulation) but was absent in non-salt-grown plants. Fourth, the KCl concentration bringing about 50% dissipation of ATP-dependent SCN− accumulation was 20 millimolar for salt-grown plants and 50 millimolar for non-salt-grown plants. Vanadate sensitivity was shown in both cases. No clear NO3− inhibition was observed. Images Fig. 3 PMID:16664942

The cervical vertebral maturation method: A user's guide.

PubMed

McNamara, James A; Franchi, Lorenzo

2018-03-01

The cervical vertebral maturation (CVM) method is used to determine the craniofacial skeletal maturational stage of an individual at a specific time point during the growth process. This diagnostic approach uses data derived from the second (C2), third (C3), and fourth (C4) cervical vertebrae, as visualized in a two-dimensional lateral cephalogram. Six maturational stages of those three cervical vertebrae can be determined, based on the morphology of their bodies. The first step is to evaluate the inferior border of these vertebral bodies, determining whether they are flat or concave (ie, presence of a visible notch). The second step in the analysis is to evaluate the shape of C3 and C4. These vertebral bodies change in shape in a typical sequence, progressing from trapezoidal to rectangular horizontal, to square, and to rectangular vertical. Typically, cervical stages (CSs) 1 and CS 2 are considered prepubertal, CS 3 and CS 4 circumpubertal, and CS 5 and CS 6 postpubertal. Criticism has been rendered as to the reproducibility of the CVM method. Diminished reliability may be observed at least in part due to the lack of a definitive description of the staging procedure in the literature. Based on the now nearly 20 years of experience in staging cervical vertebrae, this article was prepared as a "user's guide" that describes the CVM stages in detail in attempt to help the reader use this approach in everyday clinical practice.

Fourth Generation Light Sources

NASA Astrophysics Data System (ADS)

Winick, Herman

1997-05-01

Concepts and designs are now being developed at laboratories around the world for light sources with performance levels that exceed present sources, including the very powerful and successful third generation synchrotron radiation sources that have come on line in the past few years. Workshops (M. Cornacchia and H. Winick (eds), Workshop on Fourth Generation Light Sources, Feb. 24-27, 1992, SSRL Report 92/02) (J.-L. Laclare (ed), ICFA Workshop on Fourth Generation Light Sources, Jan. 22-25, 1996, ESRF Report) have been held to review directions for future sources. A main thrust is to increase the brightness and coherence of the radiation using storage rings with lower electron-beam emittance or free-electron lasers (FELs). In the infra-red part of the spectrum very high brightness and coherence is already provided by FEL user facilities driven by linacs and storage rings. It now appears possible to extend FEL operation to the VUV, soft X-ray and even hard X-ray spectral range, to wavelengths down to the angstrom range, using high energy linacs equipped with high-brightness rf photoinjectors and bunch-length compressors. R&D to develop such sources is in progress at BNL, DESY, KEK, SLAC and other laboratories. In the absence of mirrors to form optical cavities, short wavelengths are reached in FEL systems in which a high peak current, low-emittance electron beam becomes bunch-density modulated at the optical wavelength in a single pass through a long undulator by self-amplified spontaneous emission (SASE); i.e.; startup from noise. A proposal to use the last kilometer of the three kilometer SLAC linac (the first two kilometers will be used for injection to the PEP II B-Factory) to provide 15 GeV electron beams to reach 1.5 Angstroms by SASE in a 100 m long undulator is in preparation.

Development of 40-in hybrid hologram screen for auto-stereoscopic video display

NASA Astrophysics Data System (ADS)

Song, Hyun Ho; Nakashima, Y.; Momonoi, Y.; Honda, Toshio

2004-06-01

Usually in auto stereoscopic display, there are two problems. The first problem is that large image display is difficult, and the second problem is that the view zone (which means the zone in which both eyes are put for stereoscopic or 3-D image observation) is very narrow. We have been developing an auto stereoscopic large video display system (over 100 inches diagonal) which a few people can view simultaneously1,2. Usually in displays that are over 100 inches diagonal, an optical video projection system is used. As one of auto stereoscopic display systems the hologram screen has been proposed3,4,5,6. However, if the hologram screen becomes too large, the view zone (corresponding to the reconstructed diffused object) causes color dispersion and color aberration7. We also proposed the additional Fresnel lens attached to the hologram screen. We call the screen a "hybrid hologram screen", (HHS in short). We made the HHS 866mm(H)×433mm(V) (about 40 inch diagonal)8,9,10,11. By using the lens in the reconstruction step, the angle between object light and reference light can be small, compared to without the lens. So, the spread of the view zone by the color dispersion and color aberration becomes small. And also, the virtual image which is reconstructed from the hologram screen can be transformed to a real image (view zone). So, it is not necessary to use a large lens or concave mirror while making a large hologram screen.

432- μm laser's beam-waist measurement for the polarimeter/interferometer on the EAST tokamak

NASA Astrophysics Data System (ADS)

Wang, Z. X.; Liu, H. Q.; Jie, Y. X.; Wu, M. Q.; Lan, T.; Zhu, X.; Zou, Z. Y.; Yang, Y.; Wei, X. C.; Zeng, L.; Li, G. S.; Gao, X.

2014-10-01

A far-infrared (FIR) polarimeter/interferometer (PI) system is under development for measurements of the current-density and the electron-density profiles in the EAST tokamak. The system will utilize three identical 432- μm CHCOOH lasers pumped by a CO2 laser. Measurements of the laser beam's waist size and position are basic works. This paper will introduce three methods with a beam profiler and several focusing optical elements. The beam profiler can be used to show the spatial energy distribution of the laser beam. The active area of the profiler is 12.4 × 12.4 mm2. Some focusing optical elements are needed to focus the beam in order for the beam profiler to receive the entire laser beam. Two principles and three methods are used in the measurement. The first and the third methods are based on the same principle, and the second method adopts an other principle. Due to the fast and convenient measurement, although the first method is a special form of the third and it can only give the size of beam waist, it is essential to the development of the experiment and it can provide guidance for the choices of the sizes of the optical elements in the next step. A concave mirror, a high-density polyethylene (HDPE) lens and a polymethylpentene (TPX) lens are each used in the measurement process. The results of these methods are close enough for the design of PI system's optical path.

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit.

PubMed

Eckelmann, Jens; Saggiomo, Vittorio; Fischmann, Svenja; Lüning, Ulrich

2012-01-01

A bi-macrocycle with an incorporated isophthalamide substructure was synthesized by double amide formation between an isophthaloyl dichloride and two equivalents of a bis(alkenyloxy)aniline, followed by ring-closing metathesis and hydrogenation. In contrast to many related isophthalamides, the concave host exhibits a better binding for oxides, such as DMSO or pyridine-N-oxide, than for halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated K(ass) of pyridine-N-oxide of ca. 40 M(-1), NMR titration confirms 25 M(-1).

Compound cooling flow turbulator for turbine component

DOEpatents

Lee, Ching-Pang; Jiang, Nan; Marra, John J; Rudolph, Ronald J

2014-11-25

Multi-scale turbulation features, including first turbulators (46, 48) on a cooling surface (44), and smaller turbulators (52, 54, 58, 62) on the first turbulators. The first turbulators may be formed between larger turbulators (50). The first turbulators may be alternating ridges (46) and valleys (48). The smaller turbulators may be concave surface features such as dimples (62) and grooves (54), and/or convex surface features such as bumps (58) and smaller ridges (52). An embodiment with convex turbulators (52, 58) in the valleys (48) and concave turbulators (54, 62) on the ridges (46) increases the cooling surface area, reduces boundary layer separation, avoids coolant shadowing and stagnation, and reduces component mass.

Static properties of hydrostatic thrust gas bearings with curved surfaces.

NASA Technical Reports Server (NTRS)

Rehsteiner, F. H.; Cannon, R. H., Jr.

1971-01-01

The classical treatment of circular, hydrostatic, orifice-regulated thrust gas bearings, in which perfectly plane bearing plates are assumed, is extended to include axisymmetric, but otherwise arbitrary, plate profiles. Plate curvature has a strong influence on bearing load capability, static stiffness, tilting stiffness, and side force per unit misalignment angle. By a suitable combination of gas inlet impedance and concave plate profile, the static stiffness can be made almost constant over a wide load range, and to remain positive at the closure load. Extensive measurements performed with convex and concave plates agree with theory to within the experimental error throughout and demonstrate the practical feasibility of using curved plates.

On q-non-extensive statistics with non-Tsallisian entropy

NASA Astrophysics Data System (ADS)

Jizba, Petr; Korbel, Jan

2016-02-01

We combine an axiomatics of Rényi with the q-deformed version of Khinchin axioms to obtain a measure of information (i.e., entropy) which accounts both for systems with embedded self-similarity and non-extensivity. We show that the entropy thus obtained is uniquely solved in terms of a one-parameter family of information measures. The ensuing maximal-entropy distribution is phrased in terms of a special function known as the Lambert W-function. We analyze the corresponding "high" and "low-temperature" asymptotics and reveal a non-trivial structure of the parameter space. Salient issues such as concavity and Schur concavity of the new entropy are also discussed.

A Selective Review of Group Selection in High-Dimensional Models

PubMed Central

Huang, Jian; Breheny, Patrick; Ma, Shuangge

2013-01-01

Grouping structures arise naturally in many statistical modeling problems. Several methods have been proposed for variable selection that respect grouping structure in variables. Examples include the group LASSO and several concave group selection methods. In this article, we give a selective review of group selection concerning methodological developments, theoretical properties and computational algorithms. We pay particular attention to group selection methods involving concave penalties. We address both group selection and bi-level selection methods. We describe several applications of these methods in nonparametric additive models, semiparametric regression, seemingly unrelated regressions, genomic data analysis and genome wide association studies. We also highlight some issues that require further study. PMID:24174707

Calibration of strontium-90 eye applicator using a strontium external beam standard.

PubMed

Siddle, D; Langmack, K

1999-07-01

Four techniques for measuring the dose rate from Sr-90 concave eye plaques are presented. The techniques involve calibrating a concave eye plaque against a Sr-90 teletherapy unit using X-Omat film, radiochromic film, black LiF TLD discs and LiF chips. The mean dose rate predicted by these dosimeters is 7.5 cGy s(-1). The dose rate quoted by the manufacturer is 33% lower than this value, which is consistent with discrepancies reported by other authors. Calibration against a 6 MV linear accelerator was also carried out using each of the above dosimetric devices, and appropriate sensitivity correction factors have been presented.

Calibration of strontium-90 eye applicator using a strontium external beam standard

NASA Astrophysics Data System (ADS)

Siddle, D.; Langmack, K.

1999-07-01

Four techniques for measuring the dose rate from Sr-90 concave eye plaques are presented. The techniques involve calibrating a concave eye plaque against a Sr-90 teletherapy unit using X-Omat film, radiochromic film, black LiF TLD discs and LiF chips. The mean dose rate predicted by these dosimeters is 7.5 cGy s-1. The dose rate quoted by the manufacturer is 33% lower than this value, which is consistent with discrepancies reported by other authors. Calibration against a 6 MV linear accelerator was also carried out using each of the above dosimetric devices, and appropriate sensitivity correction factors have been presented.

Measurement and Numerical Calculation of Force on a Particle in a Strong Acoustic Field Required for Levitation

NASA Astrophysics Data System (ADS)

Kozuka, Teruyuki; Yasui, Kyuichi; Tuziuti, Toru; Towata, Atsuya; Lee, Judy; Iida, Yasuo

2009-07-01

Using a standing-wave field generated between a sound source and a reflector, it is possible to trap small objects at nodes of the sound pressure distribution in air. In this study, a sound field generated under a flat or concave reflector was studied by both experimental measurement and numerical calculation. The calculated result agrees well with the experimental data. The maximum force generated between a sound source of 25.0 mm diameter and a concave reflector is 0.8 mN in the experiment. A steel ball of 2.0 mm in diameter was levitated in the sound field in air.

Development of a single-axis ultrasonic levitator and the study of the radial particle oscillations

NASA Astrophysics Data System (ADS)

Baer, Sebastian; Andrade, Marco A. B.; Esen, Cemal; Adamowski, Julio Cezar; Ostendorf, Andreas

2012-05-01

This work describes the development and analysis of a new single-axis acoustic levitator, which consists of a 38 kHz Langevin-type piezoelectric transducer with a concave radiating surface and a concave reflector. The new levitator design allows to significantly reducing the electric power necessary to levitate particles and to stabilize the levitated sample in both radial and axial directions. In this investigation the lateral oscillations of a levitated particle were measured with a single point Laser Doppler Vibrometer (LDV) and an image evaluation technique. The lateral oscillations were measured for different values of particle diameter, particle density and applied electrical power.

Energy-Efficient Cognitive Radio Sensor Networks: Parametric and Convex Transformations

PubMed Central

Naeem, Muhammad; Illanko, Kandasamy; Karmokar, Ashok; Anpalagan, Alagan; Jaseemuddin, Muhammad

2013-01-01

Designing energy-efficient cognitive radio sensor networks is important to intelligently use battery energy and to maximize the sensor network life. In this paper, the problem of determining the power allocation that maximizes the energy-efficiency of cognitive radio-based wireless sensor networks is formed as a constrained optimization problem, where the objective function is the ratio of network throughput and the network power. The proposed constrained optimization problem belongs to a class of nonlinear fractional programming problems. Charnes-Cooper Transformation is used to transform the nonlinear fractional problem into an equivalent concave optimization problem. The structure of the power allocation policy for the transformed concave problem is found to be of a water-filling type. The problem is also transformed into a parametric form for which a ε-optimal iterative solution exists. The convergence of the iterative algorithms is proven, and numerical solutions are presented. The iterative solutions are compared with the optimal solution obtained from the transformed concave problem, and the effects of different system parameters (interference threshold level, the number of primary users and secondary sensor nodes) on the performance of the proposed algorithms are investigated. PMID:23966194

Scaling relationships and concavity of small valley networks on Mars

NASA Astrophysics Data System (ADS)

Penido, Julita C.; Fassett, Caleb I.; Som, Sanjoy M.

2013-01-01

Valley networks are widely interpreted as the preserved erosional record of water flowing across the martian surface. The manner in which valley morphometric properties scale with drainage area has been widely examined on Earth. Earlier studies assessing these properties on Mars have suggested that martian valleys are morphometrically distinct from those on Earth. However, these earlier measurements were generally made on large valley systems because of the limited topographic data available. In this study, we determine the scaling properties of valley networks at smaller scales than have been previously assessed, using digital elevation models from the High Resolution Stereo Camera (HRSC). We find a Hack's law exponent of 0.74, larger than on Earth, and our measurements also reveal that individual small valleys have concave up, concave down, and quasi-linear longitudinal profiles, consistent with earlier studies of dissected terrain on Mars. However, for many valleys, widths are observed to increase downstream similarly to how they scale in terrestrial channels. The similarities and differences between valley networks on Mars and Earth are consistent with the idea that valleys on Mars are comparatively immature, and precipitation was a likely mechanism for delivering water to these networks.

3D morphometry of red blood cells by digital holography.

PubMed

Memmolo, Pasquale; Miccio, Lisa; Merola, Francesco; Gennari, Oriella; Netti, Paolo Antonio; Ferraro, Pietro

2014-12-01

Three dimensional (3D) morphometric analysis of flowing and not-adherent cells is an important aspect for diagnostic purposes. However, diagnostics tools need to be quantitative, label-free and, as much as possible, accurate. Recently, a simple holographic approach, based on shape from silhouette algorithm, has been demonstrated for accurate calculation of cells biovolume and displaying their 3D shapes. Such approach has been adopted in combination with holographic optical tweezers and successfully applied to cells with convex shape. Nevertheless, unfortunately, the method fails in case of specimen with concave surfaces. Here, we propose an effective approach to achieve correct 3D shape measurement that can be extended in case of cells having concave surfaces, thus overcoming the limit of the previous technique. We prove the new procedure for healthy red blood cells (RBCs) (i.e., discocytes) having a concave surface in their central region. Comparative analysis of experimental results with a theoretical 3D geometrical model of RBC is discussed in order to evaluate accuracy of the proposed approach. Finally, we show that the method can be also useful to classify, in terms of morphology, different varieties of RBCs. © 2014 International Society for Advancement of Cytometry.

Flexible top-emitting OLEDs for lighting: bending limits

NASA Astrophysics Data System (ADS)

Schwamb, Philipp; Reusch, Thilo C.; Brabec, Christoph J.

2013-09-01

Flexible OLED light sources have great appeal due to new design options, being unbreakable and their low weight. Top-emitting OLED device architectures offer the broadest choice of substrate materials including metals which are robust, impermeable to humidity, and good thermal conductors making them promising candidates for flexible OLED device substrates. In this study, we investigate the bending limits of flexible top-emitting OLED lighting devices with transparent metal electrode and thin film encapsulation on a variety of both metal and plastic foils. The samples were subjected to concave and convex bending and inspected by different testing methods for the onset of breakdown for example visible defects and encapsulation failures. The critical failure modes were identified as rupture of the transparent thin metal top electrode and encapsulation for convex bending and buckling of the transparent metal top electrode for concave bending. We investigated influences from substrate material and thickness and top coating thickness. The substrate thickness is found to dominate bending limits as expected by neutral layer modeling. Coating shows strong improvements for all substrates. Bending radii <15mm are achieved for both convex and concave testing without damage to devices including their encapsulation.

Suppressing Ghost Diffraction in E-Beam-Written Gratings

NASA Technical Reports Server (NTRS)

Wilson, Daniel; Backlund, Johan

2009-01-01

A modified scheme for electron-beam (E-beam) writing used in the fabrication of convex or concave diffraction gratings makes it possible to suppress the ghost diffraction heretofore exhibited by such gratings. Ghost diffraction is a spurious component of diffraction caused by a spurious component of grating periodicity as described below. The ghost diffraction orders appear between the main diffraction orders and are typically more intense than is the diffuse scattering from the grating. At such high intensity, ghost diffraction is the dominant source of degradation of grating performance. The pattern of a convex or concave grating is established by electron-beam writing in a resist material coating a substrate that has the desired convex or concave shape. Unfortunately, as a result of the characteristics of electrostatic deflectors used to control the electron beam, it is possible to expose only a small field - typically between 0.5 and 1.0 mm wide - at a given fixed position of the electron gun relative to the substrate. To make a grating larger than the field size, it is necessary to move the substrate to make it possible to write fields centered at different positions, so that the larger area is synthesized by "stitching" the exposed fields.

Evolution of optimal Hill coefficients in nonlinear public goods games.

PubMed

Archetti, Marco; Scheuring, István

2016-10-07

In evolutionary game theory, the effect of public goods like diffusible molecules has been modelled using linear, concave, sigmoid and step functions. The observation that biological systems are often sigmoid input-output functions, as described by the Hill equation, suggests that a sigmoid function is more realistic. The Michaelis-Menten model of enzyme kinetics, however, predicts a concave function, and while mechanistic explanations of sigmoid kinetics exist, we lack an adaptive explanation: what is the evolutionary advantage of a sigmoid benefit function? We analyse public goods games in which the shape of the benefit function can evolve, in order to determine the optimal and evolutionarily stable Hill coefficients. We find that, while the dynamics depends on whether output is controlled at the level of the individual or the population, intermediate or high Hill coefficients often evolve, leading to sigmoid input-output functions that for some parameters are so steep to resemble a step function (an on-off switch). Our results suggest that, even when the shape of the benefit function is unknown, biological public goods should be modelled using a sigmoid or step function rather than a linear or concave function. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of cooling performance of impinging jet array over various dimpled surfaces

NASA Astrophysics Data System (ADS)

Kim, Sun-Min; Kim, Kwang-Yong

2016-04-01

Various configurations of an impinging jet-dimple array cooling system were evaluated in terms of their heat transfer and pressure drop performances. The steady incompressible laminar flow and heat transfer in the cooling system were analyzed using three-dimensional Navier-Stokes equations. The obtained numerical results were validated by a comparison with experimental data for the local Nusselt number distribution. The area-averaged Nusselt number on the projected area and the pressure drop through the system were selected as the performance parameters. Among the four tested configurations—inline concave, staggered concave, inline convex, and staggered convex—the staggered convex impinging jet-dimple array showed the best heat transfer performance whereas the staggered-concave configuration showed the lowest pressure drop. A parametric study with two geometric variables, i.e., the height of dimple and the diameter of dimple, was also conducted for the staggered-convex impinging jet-dimple array. As a result, the best heat transfer and pressure drop performances were achieved when the ratio of the height of dimple to the diameter of jet was 0.8. And, the increase in the ratio of the diameter of dimple to the diameter of jet yielded monotonous increase in the heat transfer performance.

Minimal norm constrained interpolation. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Irvine, L. D.

1985-01-01

In computational fluid dynamics and in CAD/CAM, a physical boundary is usually known only discreetly and most often must be approximated. An acceptable approximation preserves the salient features of the data such as convexity and concavity. In this dissertation, a smooth interpolant which is locally concave where the data are concave and is locally convex where the data are convex is described. The interpolant is found by posing and solving a minimization problem whose solution is a piecewise cubic polynomial. The problem is solved indirectly by using the Peano Kernal theorem to recast it into an equivalent minimization problem having the second derivative of the interpolant as the solution. This approach leads to the solution of a nonlinear system of equations. It is shown that Newton's method is an exceptionally attractive and efficient method for solving the nonlinear system of equations. Examples of shape-preserving interpolants, as well as convergence results obtained by using Newton's method are also shown. A FORTRAN program to compute these interpolants is listed. The problem of computing the interpolant of minimal norm from a convex cone in a normal dual space is also discussed. An extension of de Boor's work on minimal norm unconstrained interpolation is presented.

Thermal Inactivation Characteristics of Bacillus subtilis Spores at Ultrahigh Temperatures1

PubMed Central

Edwards, J. L.; Busta, F. F.; Speck, M. L.

1965-01-01

The thermal inactivation characteristics of Bacillus subtilis A spores suspended in skim milk with the use of large-scale ultrahigh temperature (UHT) processing equipment were investigated in terms of survival as measured with two plating media. Data on survival immediately after UHT treatments were recorded in temperature-survivor curves, time-survivor curves, and decimal reduction time (DRT) curves. The temperature-survivor curves emphasized that inactivation is accelerated more by increases in the treatment temperature than by increases in the exposure time. Time-survivor curves and DRT curves were not linear. Generally, exceedingly concave time-survivor curves were observed with the standard plating medium; however, only slightly concave curves were observed when CaCl2 and sodium dipicolinate were added to the medium. For a given UHT sample, larger D values were obtained by use of the medium with the added CaCl2 and sodium dipicolinate. The DRT curves of all data were concave and appeared to have two discrete slopes (zD values). The zD values observed in the upper UHT range (above 260 F; 127 C) were twice those observed at lower test temperatures. PMID:4956036

Temperature actuated shutdown assembly for a nuclear reactor

DOEpatents

Sowa, Edmund S.

1976-01-01

Three identical bimetallic disks, each shaped as a spherical cap with its convex side composed of a layer of metal such as molybdenum and its concave side composed of a metal of a relatively higher coefficient of thermal expansion such as stainless steel, are retained within flanges attached to three sides of an inner hexagonal tube containing a neutron absorber to be inserted into a nuclear reactor core. Each disk holds a metal ball against its normally convex side so that the ball projects partially through a hole in the tube located concentrically with the center of each disk; at a predetermined temperature an imbalance of thermally induced stresses in at least one of the disks will cause its convex side to become concave and its concave side to become convex, thus pulling the ball from the hole in which it is located. The absorber has a conical bottom supported by the three balls and is small enough in relation to the internal dimensions of the tube to allow it to slip toward the removed ball or balls, thus clearing the unremoved balls or ball so that it will fall into the reactor core.

Novel fabrication method of microlens arrays with High OLED outcoupling efficiency

NASA Astrophysics Data System (ADS)

Kim, Hyun Soo; Moon, Seong Il; Hwang, Dong Eui; Jeong, Ki Won; Kim, Chang Kyo; Moon, Dae-Gyu; Hong, Chinsoo

2016-03-01

We presented a novel fabrication method of pyramidal and hemispherical polymethylmethacrylate (PMMA) microlens arrays to improve the outcoupling efficiency. Pyramidal microlens arrays were fabricated by replica molding processes using concave-pyramidal silicon molds prepared by the wet etching method. Concave-hemispherical PMMA thin film was used as a template for fabrication of the hemispherical microlens array. The concave-hemispherical PMMA template was prepared by blowing a N2 gas stream onto the thin PMMA film suspended on a silicon pedestal. A PMMA microlens arrays with hemispherical structure were fabricated by a replica molding process. The outcoupling efficiency of the hemispherical microlens array was greater than that of the pyramidal microlens array. The outcoupling efficiency of hemispherical microlens arrays with a higher contact angle was larger than that of those with lower contact angle. This indicates that, for the hemispherical microlens with larger contact angle, more light can be extracted from the OLEDs due to the decrease in the incident angle of the light at the interface between an air and a hemispherical microlens arrays. After attaching a hemispherical microlens array with contact angle of 50.4° onto the OLEDs, the luminance was enhanced by approximately 117%.

Scoliosis corrective force estimation from the implanted rod deformation using 3D-FEM analysis.

PubMed

Abe, Yuichiro; Ito, Manabu; Abumi, Kuniyoshi; Sudo, Hideki; Salmingo, Remel; Tadano, Shigeru

2015-01-01

Improvement of material property in spinal instrumentation has brought better deformity correction in scoliosis surgery in recent years. The increase of mechanical strength in instruments directly means the increase of force, which acts on bone-implant interface during scoliosis surgery. However, the actual correction force during the correction maneuver and safety margin of pull out force on each screw were not well known. In the present study, estimated corrective forces and pull out forces were analyzed using a novel method based on Finite Element Analysis (FEA). Twenty adolescent idiopathic scoliosis patients (1 boy and 19 girls) who underwent reconstructive scoliosis surgery between June 2009 and Jun 2011 were included in this study. Scoliosis correction was performed with 6mm diameter titanium rod (Ti6Al7Nb) using the simultaneous double rod rotation technique (SDRRT) in all cases. The pre-maneuver and post-maneuver rod geometry was collected from intraoperative tracing and postoperative 3D-CT images, and 3D-FEA was performed with ANSYS. Cobb angle of major curve, correction rate and thoracic kyphosis were measured on X-ray images. Average age at surgery was 14.8, and average fusion length was 8.9 segments. Major curve was corrected from 63.1 to 18.1 degrees in average and correction rate was 71.4%. Rod geometry showed significant change on the concave side. Curvature of the rod on concave and convex sides decreased from 33.6 to 17.8 degrees, and from 25.9 to 23.8 degrees, respectively. Estimated pull out forces at apical vertebrae were 160.0N in the concave side screw and 35.6N in the convex side screw. Estimated push in force at LIV and UIV were 305.1N in the concave side screw and 86.4N in the convex side screw. Corrective force during scoliosis surgery was demonstrated to be about four times greater in the concave side than in convex side. Averaged pull out and push in force fell below previously reported safety margin. Therefore, the SDRRT maneuver was safe for correcting moderate magnitude curves. To prevent implant breakage or pedicle fracture during the maneuver in a severe curve correction, mobilization of spinal segment by releasing soft tissue or facet joint could be more important than using a stronger correction maneuver with a rigid implant.

Vitamin D Receptor gene (VDR) transcripts in bone, cartilage, muscles and blood and microarray analysis of vitamin D responsive genes expression in paravertebral muscles of Juvenile and Adolescent Idiopathic Scoliosis patients

PubMed Central

2012-01-01

Background VDR may be considered as a candidate gene potentially related to Idiopathic Scoliosis susceptibility and natural history. Transcriptional profile of VDR mRNA isoforms might be changed in the structural tissues of the scoliotic spine and potentially influence the expression of VDR responsive genes. The purpose of the study was to determine differences in mRNA abundance of VDR isoforms in bone, cartilage and paravertebral muscles between tissues from curve concavity and convexity, between JIS and AIS and to identify VDR responsive genes differentiating Juvenile and Adolescent Idiopathic Scoliosis in paravertebral muscles. Methods In a group of 29 patients with JIS and AIS, specimens of bone, cartilage, paravertebral muscles were harvested at the both sides of the curve apex together with peripheral blood samples. Extracted total RNA served as a matrix for VDRs and VDRl mRNA quantification by QRT PCR. Subsequent microarray analysis of paravertebral muscular tissue samples was performed with HG U133A chips (Affymetrix). Quantitative data were compared by a nonparametric Mann Whitney U test. Microarray results were analyzed with GeneSpring 11GX application. Matrix plot of normalized log-intensities visualized the degree of differentiation between muscular tissue transcriptomes of JIS and AIS group. Fold Change Analysis with cutoff of Fold Change ≥2 identified differentially expressed VDR responsive genes in paravertebral muscles of JIS and AIS. Results No significant differences in transcript abundance of VDR isoforms between tissues of the curve concavity and convexity were found. Statistically significant difference between JIS and AIS group in mRNA abundance of VDRl isoform was found in paravertebral muscles of curve concavity. Higher degree of muscular transcriptome differentiation between curve concavity and convexity was visualized in JIS group. In paravertebral muscles Tob2 and MED13 were selected as genes differentially expressed in JIS and AIS group. Conclusions In Idiopathic Scolioses transcriptional activity and alternative splicing of VDR mRNA in osseous, cartilaginous, and paravertebral muscular tissues are tissue specific and equal on both sides of the curve. The number of mRNA copies of VDRl izoform in concave paravertebral muscles might be one of the factors differentiating JIS and AIS. In paravertebral muscles Tob2 and Med13 genes differentiate Adolescent and Juvenile type of Idiopathic Scoliosis. PMID:23259508

The role of hillslope topography on shallow landslides activation and basin saturation propensity

NASA Astrophysics Data System (ADS)

Lanni, C.; Pretto, I.; Rigon, R.

2009-12-01

Shallow Landslides are one of the most important causes of loss of human life and socio-economic damage related to the hydro-geological risk issues. In the past years a big number of researches have developed tools to assess for the stability condition of hillslopes at the basin-scale. Montgomery and Dietrich (1994), for instance, with their own SHALSTAB model, give a simple way to evaluate the safety factor of mountain hillslopes, coupling the infinite slope stability model with a very simple steady-state hydrological model based on the work by O'Loughlin (1986) and which has similarities to TOPOG (Beven and Kirkby, 1979). The state of art gives the possibility to evaluate the transient nature of the generated pore-pressure fields within soil-thickness during and after the rainfalls. A valuable tool to fulfill this purpose may be the GEOtop model (Rigon et al., 2006) born to solve the 3-dimensional form of Richards’ equation. The present work, which was held using GEOtop model, investigates the stability conditions and the water table level of nine characteristic hillslope types when steady-state conditions are reached. The artificial simple basins are created combining three different curvature's profile (straight, concave and convex) and three different plan shapes (parallel, convergent and divergent) (fig.1). In the analysis the hillslope soil thickness is imposed constant, while the bedrock is considered impermeable. Different intensity rainfalls are simulated. The results show that in the case of the lowest intensity rainfall, basins with convex shape present higher percentage of saturated area than concave and straight ones. Also, convergent hillslopes generally produce a higher percentage of saturated area than the other plan shapes. Moreover, in the case of higher intensity rainfalls, the concave profile curvature seems to be the first order controller on the saturation process. Regarding the stability conditions, convergent hillslopes generally presents a lower mean safety factor than parallel and divergent ones. Furthermore, concave hillslopes presents higher instability propensity, so that, as it is in the real word, concave hillslope tends to become convex because of the natural erosive process. Lastly, the obtained results are compared with the output given by the application of the SHALSTAB model considering the same setup used in the GEOtop numerical simulations.

Finite Element Analysis of High Heat Load Deformation and Mechanical Bending Correction of a Beamline Mirror for the APS Upgrade

NASA Astrophysics Data System (ADS)

Goldring, Nicholas

The impending Advanced Photon Source Upgrade (APS-U) will introduce a hard x-ray source that is set to surpass the current APS in brightness and coherence by two to three orders of magnitude. To achieve this, the storage ring light source will be equipped with a multi-bend achromat (MBA) lattice. In order to fully exploit and preserve the integrity of new beams actualized by upgraded storage ring components, improved beamline optics must also be introduced. The design process of new optics for the APS-U and other fourth generation synchrotrons involves the challenge of accommodating unprecedented heat loads. This dissertation presents an ex-situ analysis of heat load deformation and the subsequent mechanical bending correction of a 400 mm long, grazing-incidence, H2O side-cooled, reflecting mirror subjected to x-ray beams produced by the APS-U undulator source. Bending correction is measured as the smallest rms slope error, sigmarms, that can be resolved over a given length of the heat deformed geometry due to mechanical bending. Values of sigmarms in the <0.1 microrad regime represent a given mirror length over which incident x-ray beams from modern sources can be reflected without significant loss of quality. This study assumes a perfectly flat mirror surface and does not account for finish errors or other contributions to sigmarms beyond the scope of thermal deformation and elastic bending. The methodology of this research includes finite element analysis (FEA) employed conjointly with an analytical solution for mechanical bending deflection by means of an end couple. Additionally, the study will focus on two beam power density profiles predicted by the APS-U which were created using the software SRCalc. The profiles account for a 6 GeV electron beam with second moment widths of 0.058 and 0.011 mm in the x- and y- directions respectively; the electron beam is passed through a 4.8 m long, 28 mm period APS-U undulator which produces the x-ray beam incident at a 3 mrad grazing angle on the flat mirror surface for both cases. The first power density profile is the most extreme case created by the undulator at it's closest gap with a critical energy of 3 keV (k y=2.459); the second profile is generated for the case in which the undulator is tuned to emit at 8 keV (ky=1.026). The 3 keV case is of particular interest as it represents one of the most intense peak heat loads predicted to be incident on first optics at the APS-U. The FEA results revealed that the deflection due to the 3 keV heat load yields a 10.9 microrad rms slope error over the full mirror length. The projected correction via the elastic bending of the substrate yields a 0.10 microrad sigma rms within the center longitudinal 300 mm. The FEA also predicts that the 8 keV heat load deflection can be corrected to a sigma rms of 0.11 microrad within the center 300 mm from 1.50 microrad over the entire length. Attempts to optimize the end couple to correct over the entire 400 mm mirror length were unable to resolve the heat load deflection rms slope error to within a <0.1 microrad value for either case. However, if a larger corrected surface is required, a longer mirror can be implemented so as to absorb the heat load of a larger beam than necessary which can then be cut by an aperture to the desired size and energy range.

Timecourse of mirror and counter-mirror effects measured with transcranial magnetic stimulation

PubMed Central

Cavallo, Andrea; Heyes, Cecilia; Becchio, Cristina; Bird, Geoffrey

2014-01-01

The human mirror system has been the subject of much research over the past two decades, but little is known about the timecourse of mirror responses. In addition, it is unclear whether mirror and counter-mirror effects follow the same timecourse. We used single-pulse transcranial magnetic stimulation to investigate the timecourse of mirror and counter-mirror responses in the human brain. Experiment 1 demonstrated that mirror responses can be measured from around 200 ms after observed action onset. Experiment 2 demonstrated significant effects of counter-mirror sensorimotor training at all timepoints at which a mirror response was found in Experiment 1 (i.e. from 200 ms onward), indicating that mirror and counter-mirror responses follow the same timecourse. By suggesting similarly direct routes for mirror and counter-mirror responses, these results support the associative account of mirror neuron origins whereby mirror responses arise as a result of correlated sensorimotor experience during development. More generally, they contribute to theorizing regarding mirror neuron function by providing some constraints on how quickly mirror responses can influence social cognition. PMID:23709352

Timecourse of mirror and counter-mirror effects measured with transcranial magnetic stimulation.

PubMed

Cavallo, Andrea; Heyes, Cecilia; Becchio, Cristina; Bird, Geoffrey; Catmur, Caroline

2014-08-01

The human mirror system has been the subject of much research over the past two decades, but little is known about the timecourse of mirror responses. In addition, it is unclear whether mirror and counter-mirror effects follow the same timecourse. We used single-pulse transcranial magnetic stimulation to investigate the timecourse of mirror and counter-mirror responses in the human brain. Experiment 1 demonstrated that mirror responses can be measured from around 200 ms after observed action onset. Experiment 2 demonstrated significant effects of counter-mirror sensorimotor training at all timepoints at which a mirror response was found in Experiment 1 (i.e. from 200 ms onward), indicating that mirror and counter-mirror responses follow the same timecourse. By suggesting similarly direct routes for mirror and counter-mirror responses, these results support the associative account of mirror neuron origins whereby mirror responses arise as a result of correlated sensorimotor experience during development. More generally, they contribute to theorizing regarding mirror neuron function by providing some constraints on how quickly mirror responses can influence social cognition. © The Author (2013). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

PubMed Central

Eckelmann, Jens; Saggiomo, Vittorio; Fischmann, Svenja

2012-01-01

Summary A bi-macrocycle with an incorporated isophthalamide substructure was synthesized by double amide formation between an isophthaloyl dichloride and two equivalents of a bis(alkenyloxy)aniline, followed by ring-closing metathesis and hydrogenation. In contrast to many related isophthalamides, the concave host exhibits a better binding for oxides, such as DMSO or pyridine-N-oxide, than for halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated K ass of pyridine-N-oxide of ca. 40 M−1, NMR titration confirms 25 M−1. PMID:22423268

Effect of trailing edge shape on the wake and propulsive performance of pitching panels

NASA Astrophysics Data System (ADS)

van Buren, Tyler; Floryan, Daniel; Brunner, Daniel; Senturk, Utku; Smits, Alexander

2016-11-01

We present the effects of the trailing edge shape on the wake and propulsive performance of a pitching panel with an aspect ratio of 1. The trailing edges are symmetric chevron shapes with convex and concave orientations of varying degree. Concave trailing edges delay the natural vortex bending and compression of the wake, and the streamwise velocity field contains a single jet-like structure. Conversely, convex trailing edges promote wake compression and produce a wake split into four jets. Deviation from the square trailing edge mostly reduces the thrust and efficiency. Supported by the Office of Naval Research under MURI Grant Number N00014-14-1-0533.

Spatial imaging in the soft x-ray region (20--304 A) utilizing the astigmatism of a grazing incidence concave grating

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

Nudelfuden, A.; Solanki, R.; Moos, H.W.

1985-03-15

Soft x-ray (20--304--A) astigmatic line shapes were measured in order to evaluate the spatial imaging properties of a Rowland mounted concave grating in grazing incidence. The practicability of coarse 1-D spatial imaging in the soft x-ray region is demonstrated. Spatial resolution equivalent to approx.4 cm at a source distance of 2 m can be achieved with practical parameters (e.g., sensitivity and time resolution) for a fusion diagnostic spectrograph. The results are compared to computer-generated ray tracings and found to be in good agreement. The ray tracing program which models the grazing incidence optics is discussed.

A Case of Successful Surgical Repair for Pectus Arcuatum Using Chondrosternoplasty

PubMed Central

Kim, Sang Yoon; Park, Samina; Kim, Eung Rae; Park, In Kyu; Kim, Young Tae; Kang, Chang Hyun

2016-01-01

Pectus arcuatum is a rare complex chest wall deformity. A 31-year-old female presented with a severely protruding upper sternum combined with a concave lower sternum. We planned a modified Ravitch-type operation. Through vertical mid-sternal incision, chondrectomies were performed from the second to fifth costal cartilages, saving the perichondrium. Horizontal osteotomy was performed in a wedge shape on the most protruding point, and followed by an additional partial osteotomy at the most concaved point. The harvested wedge-shape bone fragments were minced and re-implanted to the latter osteotomy site. The osteotomized sternum was fixed with multiple wirings. With chondrosternoplasty, a complex chest wall deformity can be corrected successfully. PMID:27298803

A Case of Successful Surgical Repair for Pectus Arcuatum Using Chondrosternoplasty.

PubMed

Kim, Sang Yoon; Park, Samina; Kim, Eung Rae; Park, In Kyu; Kim, Young Tae; Kang, Chang Hyun

2016-06-01

Pectus arcuatum is a rare complex chest wall deformity. A 31-year-old female presented with a severely protruding upper sternum combined with a concave lower sternum. We planned a modified Ravitch-type operation. Through vertical mid-sternal incision, chondrectomies were performed from the second to fifth costal cartilages, saving the perichondrium. Horizontal osteotomy was performed in a wedge shape on the most protruding point, and followed by an additional partial osteotomy at the most concaved point. The harvested wedge-shape bone fragments were minced and re-implanted to the latter osteotomy site. The osteotomized sternum was fixed with multiple wirings. With chondrosternoplasty, a complex chest wall deformity can be corrected successfully.

On the origin of enhanced sensitivity in nanoscale FET-based biosensors

PubMed Central

Shoorideh, Kaveh; Chui, Chi On

2014-01-01

Electrostatic counter ion screening is a phenomenon that is detrimental to the sensitivity of charge detection in electrolytic environments, such as in field-effect transistor-based biosensors. Using simple analytical arguments, we show that electrostatic screening is weaker in the vicinity of concave curved surfaces, and stronger in the vicinity of convex surfaces. We use this insight to show, using numerical simulations, that the enhanced sensitivity observed in nanoscale biosensors is due to binding of biomolecules in concave corners where screening is reduced. We show that the traditional argument, that increased surface area-to-volume ratio for nanoscale sensors is responsible for their increased sensitivity, is incorrect. PMID:24706861

Fabricating small-scale, curved, polymeric structures with convex and concave menisci through interfacial free energy equilibrium.

PubMed

Cheng, Chao-Min; Matsuura, Koji; Wang, I-Jan; Kuroda, Yuka; LeDuc, Philip R; Naruse, Keiji

2009-11-21

Polymeric curved structures are widely used in imaging systems including optical fibers and microfluidic channels. Here, we demonstrate that small-scale, poly(dimethylsiloxane) (PDMS)-based, curved structures can be fabricated through controlling interfacial free energy equilibrium. Resultant structures have a smooth, symmetric, curved surface, and may be convex or concave in form based on surface tension balance. Their curvatures are controlled by surface characteristics (i.e., hydrophobicity and hydrophilicity) of the molds and semi-liquid PDMS. In addition, these structures are shown to be biocompatible for cell culture. Our system provides a simple, efficient and economical method for generating integrateable optical components without costly fabrication facilities.

A Generic Self-Assembly Process in Microcompartments and Synthetic Protein Nanotubes.

PubMed

Uddin, Ismail; Frank, Stefanie; Warren, Martin J; Pickersgill, Richard W

2018-05-01

Bacterial microcompartments enclose a biochemical pathway and reactive intermediate within a protein envelope formed by the shell proteins. Herein, the orientation of the propanediol-utilization (Pdu) microcompartment shell protein PduA in bacterial microcompartments and in synthetic nanotubes, and the orientation of PduB in synthetic nanotubes are revealed. When produced individually, PduA hexamers and PduB trimers, tessellate to form flat sheets in the crystal, or they can self-assemble to form synthetic protein nanotubes in solution. Modelling the orientation of PduA in the 20 nm nanotube so as to preserve the shape complementarity and key interactions seen in the crystal structure suggests that the concave surface of the PduA hexamer faces out. This orientation is confirmed experimentally in synthetic nanotubes and in the bacterial microcompartment produced in vivo. The PduB nanotubes described here have a larger diameter, 63 nm, with the concave surface of the trimer again facing out. The conserved concave surface out characteristic of these nano-structures reveals a generic assembly process that causes the interface between adjacent subunits to bend in a common direction that optimizes shape complementarity and minimizes steric clashes. This understanding underpins engineering strategies for the biotechnological application of protein nanotubes. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of complex free-standing nanostructures with concave and convex curvature via the layer-by-layer approach.

PubMed

Raoufi, Mohammad; Schönherr, Holger

2014-02-18

We report on the fabrication of unprecedented free-standing complex polymeric nanoobjects, which possess both concave and convex curvatures, by exploiting the layer-by-layer (LBL) deposition of polyelectrolytes. In a combined top-down/bottom-up replication approach pore diameter-modulated anodic aluminum oxide (AAO) templates, fabricated by temperature modulation hard anodization (TMHA), were replicated with multilayers of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) to yield open nanotubes with diameters in the wide and narrow segments of 210 and 150 nm, respectively. To obtain stable pore diameter-modulated nanopores, which possess segment lengths between 1 and 5 μm and 5 and 10 μm in the narrow and wide pore portion, respectively, conventional hard anodization of aluminum was followed by a subsequent temperature-modulated anodization. After removing the backside aluminum electrode, silanizing the aluminum oxide, and passivating the exposed membrane surface with a thin layer of gold, PSS and PAH were deposited alternatingly to yield LBL multilayers. For optimized LBL multilayer thicknesses and compactness, established in separate experiments on silicon substrates and nanoporous AAO with straight pores, free-standing polymeric nanoobjects with concave and convex curvatures, were obtained. These were stable for wall thickness to pore diameter ratios of ≥0.08.

Effects of Periodic Unsteady Wake Flow and Pressure Gradient on Boundary Layer Transition Along the Concave Surface of a Curved Plate. Part 3

NASA Technical Reports Server (NTRS)

Schobeiri, M. T.; Radke, R. E.

1996-01-01

Boundary layer transition and development on a turbomachinery blade is subjected to highly periodic unsteady turbulent flow, pressure gradient in longitudinal as well as lateral direction, and surface curvature. To study the effects of periodic unsteady wakes on the concave surface of a turbine blade, a curved plate was utilized. On the concave surface of this plate, detailed experimental investigations were carried out under zero and negative pressure gradient. The measurements were performed in an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate. Boundary layer measurements using a hot-wire probe were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. As the results show, the turbulent patches generated by the wakes have different leading and trailing edge velocities and merge with the boundary layer resulting in a strong deformation and generation of a high turbulence intensity core. After the turbulent patch has totally penetrated into the boundary layer, pronounced becalmed regions were formed behind the turbulent patch and were extended far beyond the point they would occur in the corresponding undisturbed steady boundary layer.

Adaptive evolution of defense ability leads to diversification of prey species.

PubMed

Zu, Jian; Wang, Jinliang; Du, Jianqiang

2014-06-01

In this paper, by using the adaptive dynamics approach, we investigate how the adaptive evolution of defense ability promotes the diversity of prey species in an initial one-prey-two-predator community. We assume that the prey species can evolve to a safer strategy such that it can reduce the predation risk, but a prey with a high defense ability for one predator may have a low defense ability for the other and vice versa. First, by using the method of critical function analysis, we find that if the trade-off is convex in the vicinity of the evolutionarily singular strategy, then this singular strategy is a continuously stable strategy. However, if the trade-off is weakly concave near the singular strategy and the competition between the two predators is relatively weak, then the singular strategy may be an evolutionary branching point. Second, we find that after the branching has occurred in the prey strategy, if the trade-off curve is globally concave, then the prey species might eventually evolve into two specialists, each caught by only one predator species. However, if the trade-off curve is convex-concave-convex, the prey species might eventually branch into two partial specialists, each being caught by both of the two predators and they can stably coexist on the much longer evolutionary timescale.

Experimental and Computational Investigation of a Translating-Throat Single-Expansion-Ramp Nozzle

NASA Technical Reports Server (NTRS)

Deere, Karen A.; Asbury, Scott C.

1999-01-01

An experimental and computational study was conducted on a high-speed, single-expansion-ramp nozzle (SERN) concept designed for efficient off-design performance. The translating-throat SERN concept adjusts the axial location of the throat to provide a variable expansion ratio and allow a more optimum jet exhaust expansion at various flight conditions in an effort to maximize nozzle performance. Three design points (throat locations) were investigated to simulate the operation of this concept at subsonic-transonic, low supersonic, and high supersonic flight conditions. The experimental study was conducted in the jet exit test facility at the Langley Research Center. Internal nozzle performance was obtained at nozzle pressure ratios (NPR's) up to 13 for six nozzles with design nozzle pressure ratios near 9, 42, and 102. Two expansion-ramp surfaces, one concave and one convex, were tested for each design point. Paint-oil flow and focusing schlieren flow visualization techniques were utilized to acquire additional flow data at selected NPR'S. The Navier-Stokes code, PAB3D, was used with a two-equation k-e turbulence model for the computational study. Nozzle performance characteristics were predicted at nozzle pressure ratios of 5, 9, and 13 for the concave ramp, low Mach number nozzle and at 10, 13, and 102 for the concave ramp, high Mach number nozzle.

Functional morphology and evolution of specialized mouthparts of Cephenniini (Insecta, Coleoptera, Staphylinidae, Scydmaeninae).

PubMed

Jałoszyński, Paweł; Beutel, Rolf G

2012-11-01

We present the results of a morphological study of the labium and labial (premental) discs in Cephenniini, ant-like stone beetles feeding on oribatid mites. The discs are composed of a cuticular plate connected by a circumferential ring with the hypopharyngeal suspensorium. The discs have likely developed from the premental cuticle and from internal sclerotizations of the labium. The shape of the external plate can be changed from flat to concave and vice versa by contractions and relaxations of the labial muscles. Contractions result in a flat or only slightly concave shape whereas during relaxation the discs become strongly concave and adhere tightly to the captured mite. Once this is achieved, detaining of the prey is energy-free. Based on known hypotheses concerning the evolution of Oribatida and Staphylinidae, we exclude the possibility of a co-evolution of "proto-Cephenniini" with yet unarmored "proto-Oribatida", and suggest three alternative scenarios: i) the predators co-evolved with a particular early lineage of Oribatida that has acquired the hard armor relatively recently; ii) ancestors of Cephenniini gradually shifted from feeding on other types of prey towards fully armored Oribatida; or iii) the labial discs have originally developed for functions not related to feeding. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels.

PubMed

Mohammadi, Mahshid; Sharp, Kendra V

2015-03-01

This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these "dry" bubbles, contact line forces and a possible capillary pressure gradient induced by pinning act on the bubbles and resist motion. Without sufficient driving force (e.g., external pressure), a dry bubble is brought to stagnation. For the first time, a bipartite theoretical model that estimates the required pressure difference across the length of stagnant bubbles with concave and convex back interfaces to overcome the contact line forces and stimulate motion is proposed. To validate our theory, the pressure required to move a single dry bubble in square microchannels exhibiting contact angle hysteresis has been measured. The working fluid was deionized water. The experiments have been conducted on coated glass channels with different surface hydrophilicities that resulted in concave and convex back interfaces for the bubbles. The experimental results were in agreement with the model's predictions for square channels. The predictions of the concave and convex back models were within 19% and 27% of the experimental measurements, respectively.

Do Mirror Glasses Have the Same Effect on Brain Activity as a Mirror Box? Evidence from a Functional Magnetic Resonance Imaging Study with Healthy Subjects

PubMed Central

Milde, Christopher; Rance, Mariela; Kirsch, Pinar; Trojan, Jörg; Fuchs, Xaver; Foell, Jens; Bekrater-Bodmann, Robin

2015-01-01

Since its original proposal, mirror therapy has been established as a successful neurorehabilitative intervention in several neurological disorders to recover motor function or to relieve pain. Mirror therapy seems to operate by reactivating the contralesional representation of the non-mirrored limb in primary motor- and somatosensory cortex. However, mirror boxes have some limitations which prompted the use of additional mirror visual feedback devices. The present study evaluated the utility of mirror glasses compared to a mirror box. We also tested the hypothesis that increased interhemispheric communication between the motor hand areas is the mechanism by which mirror visual feedback recruits the representation of the non-mirrored limb. Therefore, mirror illusion capacity and brain activations were measured in a within-subject design during both mirror visual feedback conditions in counterbalanced order with 20 healthy subjects inside a magnetic resonance imaging scanner. Furthermore, we analyzed task-dependent functional connectivity between motor hand representations using psychophysiological interaction analysis during both mirror tasks. Neither the subjective quality of mirror illusions nor the patterns of functional brain activation differed between the mirror tasks. The sensorimotor representation of the non-mirrored hand was recruited in both mirror tasks. However, a significant increase in interhemispheric connectivity between the hand areas was only observed in the mirror glasses condition, suggesting different mechanisms for the recruitment of the representation of the non-mirrored hand in the two mirror tasks. We conclude that the mirror glasses might be a promising alternative to the mirror box, as they induce similar patterns of brain activation. Moreover, the mirror glasses can be easy applied in therapy and research. We want to emphasize that the neuronal mechanisms for the recruitment of the affected limb representation might differ depending on conceptual differences between MVF devices. However, our findings need to be validated within specific patient groups. PMID:26018572

Astounding Jumping Disk.

ERIC Educational Resources Information Center

Guzdziol, Edward S.

1991-01-01

Activities involving concave rubber disks are utilized to illustrate the scientific principles of kinetic and potential energy. Provides teacher instructions and questions related to the activity. (MDH)

Phenotypic characteristics of adolescents with concave and convex facial profiles - The National Health Examination Survey.

PubMed

Hujoel, P P; Bollen, A-M; Yuen, K C J; Hujoel, I A

2016-10-01

It has been suggested that facial traits are informative on the inherited susceptibility to tuberculosis and obesity, two current global health issues. Our aim was to compare the phenotypic characteristics of adolescents with dental markers for a concave (n=420), a convex (n=978), and a straight (n=3542) facial profile in a nationally representative sample of United States adolescents. The results show that adolescents with a concave facial profile, when compared to a straight facial profile, had an increased waist-to-height ratio (Δ, 1.1 [95% CI 0.5-1.7], p<0.003) and an increased acne prevalence (OR, 1.5 [95% CI 1.2-1.9], p<0.001). Adolescents with a convex facial profile, when compared to a straight facial profile, had an increased prevalence of tuberculosis (OR, 4.3 [95% CI 1.4-13.1], p<0.02), increased ectomorphy (Δ, 0.3 [95% CI 0.2-0.4], p<0.0001), increased left-handedness (OR, 1.4 [95% CI 1.1-1.7], p<0.007), increased color-blindness (OR, 1.7 [95% CI 1.3-2.3], p<0.004), and rhesus ee phenotype (OR, 1.3 [95% CI 1.1-1.5], p<0.008). Adolescents with a concave facial profile, when compared to a convex profile, had increased mesomorphy (Δ, 1.3 [95% CI 1.1-1.5], p<0.0001), increased endomorphy (Δ, 0.5 [95% CI 0.4-0.6], p<0.0001), lower ectomorphy (Δ, 0.5 [95% CI 0.4-0.6], p<0.0001), and lower vocabulary test scores (Δ, 2.3 [95% CI 0.8-3.8], p<0.008). It is concluded that population-based survey data confirm that distinct facial features are associated with distinct somatotypes and distinct disease susceptibilities. Copyright © 2016 Elsevier GmbH. All rights reserved.

Association between scapula bony morphology and snapping scapula syndrome.

PubMed

Spiegl, Ulrich J; Petri, Maximilian; Smith, Sean W; Ho, Charles P; Millett, Peter J

2015-08-01

Scapular incongruity has been described as a contributing factor to the development of snapping scapula syndrome (SSS). The purpose of this retrospective case-control study was to determine the association between scapula bony morphology on magnetic resonance imaging (MRI) and the diagnosis of SSS. Bony morphologies of the scapula were evaluated on MRI scans of 26 patients with SSS and 19 patients with non-SSS pathologies. The medial scapula corpus angle (MSCA) was measured on axial MRI sequences. Scapulae were categorized as straight, S shaped, or concave. Two independent observers performed the measurements. Interobserver and intraobserver agreements of MSCA measurements were determined with intraclass correlation coefficients. Axial scapula bony morphology identified 28 scapulae of the straight type, 14 S-shaped scapulae, and 5 concave scapulae. All 5 concave scapulae had confirmed SSS. Measurement of the MSCA showed excellent interobserver agreement of 0.80 (95% confidence interval [CI], 0.67 to 0.89) and intraobserver agreement of 0.70 (95% CI, 0.52 to 0.82). There were significant differences in the mean MSCAs between shoulders with SSS (14.4° ± 19.3°) and non-SSS shoulders (-3.3° ± 15.3°, P = .001). The odds ratio was 8.4 (95% CI, 2.2 to 31.8) for positive MSCA and SSS. The scapulothoracic distance was significantly decreased in the SSS group (14.9 ± 5.8 mm) compared with the non-SSS patients (24.0 ± 6.7 mm, P < .001). Anterior angulation of the medial scapula in the axial plane was associated with SSS. Patients with a concave-shaped scapula and a positive MSCA have a 12-fold increased risk of SSS. The MSCA may prove helpful in determining the location and amount of scapular resection needed for patients with SSS. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Biomechanical analysis of the effect of congruence, depth and radius on the stability ratio of a simplistic 'ball-and-socket' joint model.

PubMed

Ernstbrunner, L; Werthel, J-D; Hatta, T; Thoreson, A R; Resch, H; An, K-N; Moroder, P

2016-10-01

The bony shoulder stability ratio (BSSR) allows for quantification of the bony stabilisers in vivo. We aimed to biomechanically validate the BSSR, determine whether joint incongruence affects the stability ratio (SR) of a shoulder model, and determine the correct parameters (glenoid concavity versus humeral head radius) for calculation of the BSSR in vivo. Four polyethylene balls (radii: 19.1 mm to 38.1 mm) were used to mould four fitting sockets in four different depths (3.2 mm to 19.1mm). The SR was measured in biomechanical congruent and incongruent experimental series. The experimental SR of a congruent system was compared with the calculated SR based on the BSSR approach. Differences in SR between congruent and incongruent experimental conditions were quantified. Finally, the experimental SR was compared with either calculated SR based on the socket concavity or plastic ball radius. The experimental SR is comparable with the calculated SR (mean difference 10%, sd 8%; relative values). The experimental incongruence study observed almost no differences (2%, sd 2%). The calculated SR on the basis of the socket concavity radius is superior in predicting the experimental SR (mean difference 10%, sd 9%) compared with the calculated SR based on the plastic ball radius (mean difference 42%, sd 55%). The present biomechanical investigation confirmed the validity of the BSSR. Incongruence has no significant effect on the SR of a shoulder model. In the event of an incongruent system, the calculation of the BSSR on the basis of the glenoid concavity radius is recommended.Cite this article: L. Ernstbrunner, J-D. Werthel, T. Hatta, A. R. Thoreson, H. Resch, K-N. An, P. Moroder. Biomechanical analysis of the effect of congruence, depth and radius on the stability ratio of a simplistic 'ball-and-socket' joint model. Bone Joint Res 2016;5:453-460. DOI: 10.1302/2046-3758.510.BJR-2016-0078.R1. © 2016 Ernstbrunner et al.

Enhanced oxygen permeability in membrane-bottomed concave microwells for the formation of pancreatic islet spheroids.

PubMed

Lee, GeonHui; Jun, Yesl; Jang, HeeYeong; Yoon, Junghyo; Lee, JaeSeo; Hong, MinHyung; Chung, Seok; Kim, Dong-Hwee; Lee, SangHoon

2018-01-01

Oxygen availability is a critical factor in regulating cell viability that ultimately contributes to the normal morphogenesis and functionality of human tissues. Among various cell culture platforms, construction of 3D multicellular spheroids based on microwell arrays has been extensively applied to reconstitute in vitro human tissue models due to its precise control of tissue culture conditions as well as simple fabrication processes. However, an adequate supply of oxygen into the spheroidal cellular aggregation still remains one of the main challenges to producing healthy in vitro spheroidal tissue models. Here, we present a novel design for controlling the oxygen distribution in concave microwell arrays. We show that oxygen permeability into the microwell is tightly regulated by varying the poly-dimethylsiloxane (PDMS) bottom thickness of the concave microwells. Moreover, we validate the enhanced performance of the engineered microwell arrays by culturing non-proliferated primary rat pancreatic islet spheroids on varying bottom thickness from 10 μm to 1050 μm. Morphological and functional analyses performed on the pancreatic islet spheroids grown for 14 days prove the long-term stability, enhanced viability, and increased hormone secretion under the sufficient oxygen delivery conditions. We expect our results could provide knowledge on oxygen distribution in 3-dimensional spheroidal cell structures and critical design concept for tissue engineering applications. In this study, we present a noble design to control the oxygen distribution in concave microwell arrays for the formation of highly functional pancreatic islet spheroids by engineering the bottom of the microwells. Our new platform significantly enhanced oxygen permeability that turned out to improve cell viability and spheroidal functionality compared to the conventional thick-bottomed 3-D culture system. Therefore, we believe that this could be a promising medical biotechnology platform to further develop high-throughput tissue screening system as well as in vivo-mimicking customised 3-D tissue culture systems. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Transient bedrock channel evolution across a precipitation gradient: A case study from Kohala, Hawaii.

NASA Astrophysics Data System (ADS)

Gasparini, N. M.; Han, J.; Johnson, J. P.; Menking, J. A.

2011-12-01

This study uses observations from the Kohala Peninsula, on the Big Island of Hawaii, and numerical modeling, to explore how precipitation gradients may affect fluvial bedrock incision and channel morphology. Orographic precipitation patterns result in over 4 m/yr of rainfall on the wet side of the peninsula and less than 0.5 m/yr on the dry side. These precipitation patterns likely strongly contribute to the observed channel morphology. Further, the region is subsiding, leading to prolonged transient channel evolution. We explore changes in a number of channel morphologic parameters with watershed averaged precipitation rate. We use PRISM precipitation data and data from isohyets developed from historic rain gauge data. Not surprisingly, valley depth, measured from a 10 meter DEM, increases with spatially averaged precipitation rate. We also find that channel profile form varies with precipitation rate, with drier channels exhibiting a straight to slightly concave channel form and wetter channels exhibiting a convex to concave channel form. The precipitation value at which this transition in channel profile form occurs depends on the precipitation data-set used, highlighting the need for more accurate measurements of precipitation in settings with extreme precipitation patterns similar to our study area. The downstream pattern in precipitation is likely significant in the development of the convex-concave profile form. Numerical modeling results support that precipitation patterns such as those observed on the wet-side of the Kohala Peninsula may contribute to the convex-concave profile form. However, we emphasize that while precipitation patterns may contribute to the channel form, these channel features are transient and not expected to be sustained in steady-state landscapes. We also emphasize that it is fluvial discharge, as driven by precipitation, rather than precipitation alone, that drives the processes shaping the channel form. Because fluvial discharge is integrative, relatively extreme precipitation gradients are required to produce anomalous channel profile forms.

Folded concave penalized sparse linear regression: sparsity, statistical performance, and algorithmic theory for local solutions.

PubMed

Liu, Hongcheng; Yao, Tao; Li, Runze; Ye, Yinyu

2017-11-01

This paper concerns the folded concave penalized sparse linear regression (FCPSLR), a class of popular sparse recovery methods. Although FCPSLR yields desirable recovery performance when solved globally, computing a global solution is NP-complete. Despite some existing statistical performance analyses on local minimizers or on specific FCPSLR-based learning algorithms, it still remains open questions whether local solutions that are known to admit fully polynomial-time approximation schemes (FPTAS) may already be sufficient to ensure the statistical performance, and whether that statistical performance can be non-contingent on the specific designs of computing procedures. To address the questions, this paper presents the following threefold results: (i) Any local solution (stationary point) is a sparse estimator, under some conditions on the parameters of the folded concave penalties. (ii) Perhaps more importantly, any local solution satisfying a significant subspace second-order necessary condition (S 3 ONC), which is weaker than the second-order KKT condition, yields a bounded error in approximating the true parameter with high probability. In addition, if the minimal signal strength is sufficient, the S 3 ONC solution likely recovers the oracle solution. This result also explicates that the goal of improving the statistical performance is consistent with the optimization criteria of minimizing the suboptimality gap in solving the non-convex programming formulation of FCPSLR. (iii) We apply (ii) to the special case of FCPSLR with minimax concave penalty (MCP) and show that under the restricted eigenvalue condition, any S 3 ONC solution with a better objective value than the Lasso solution entails the strong oracle property. In addition, such a solution generates a model error (ME) comparable to the optimal but exponential-time sparse estimator given a sufficient sample size, while the worst-case ME is comparable to the Lasso in general. Furthermore, to guarantee the S 3 ONC admits FPTAS.

Effect of Asymmetric Tension on Biomechanics and Metabolism of Vertebral Epiphyseal Plate in a Rodent Model of Scoliosis.

PubMed

Li, Qian-Yi; Zhong, Gui-Bin; Liu, Zu-de; Lao, Li-Feng

2017-08-01

To investigate the effect of asymmetric tension on idiopathic scoliosis (IS) and to understand its pathogenic mechanism. The rodent model of scoliosis was established using Sprague-Dawley rats with left rib-tethering from T 6 to T 12 , tail and shoulder amputation, and high-cage feeding. Vertebrae epiphyseal cartilage plates were harvested from the convex and concave sides. To analyze differences on the convex and concave sides, finite element analysis was carried out to determine the mechanical stress. Protein expression on epiphyseal cartilage was evaluated by western blot. Micro-CT was taken to evaluate the bone quality of vertebral on both sides. Scoliosis curves presented in X-ray radiographs of the rats. Finite element analysis was carried out on the axial and transverse tension of the spine. Stresses of the convex side were -170.14, -373.18, and -3832.32 MPa (X, Y, and Z axis, respectively), while the concave side showed stresses of 361.99, 605.55, and 3661.95 MPa. Collagen type II, collagen type X, Sox 9, RunX2, VEGF, and aggrecan were expressed significantly more on the convex side (P < 0.05). There was asymmetric expression of protein on the epiphyseal cartilage plate at molecular level. Compared with the convex side, the concave side had significantly lower value in the BV/TV and Tb.N, but higher value in the Tb.Sp (P < 0.05). There was asymmetry of bone quality in micro-architecture. In this study, asymmetric tension contributed to asymmetry in protein expression and bone quality on vertebral epiphyseal plates, ultimately resulting in asymmetry of anatomy. In addition, asymmetry of anatomy aggravated asymmetric tension. It is the first study to show that there is an asymmetrical vicious circle in IS. © 2017 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Influence of implant rod curvature on sagittal correction of scoliosis deformity.

PubMed

Salmingo, Remel Alingalan; Tadano, Shigeru; Abe, Yuichiro; Ito, Manabu

2014-08-01

Deformation of in vivo-implanted rods could alter the scoliosis sagittal correction. To our knowledge, no previous authors have investigated the influence of implanted-rod deformation on the sagittal deformity correction during scoliosis surgery. To analyze the changes of the implant rod's angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted. Twenty adolescent idiopathic scoliosis patients underwent surgery. Average age at the time of operation was 14 years. The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. Two implant rods were attached to the concave and convex side of the spinal deformity. The preoperative implant rod geometry was measured before surgical implantation. The postoperative implant rod geometry after surgery was measured by computed tomography. The implant rod angle of curvature at the sagittal plane was obtained from the implant rod geometry. The angle of curvature between the implant rod extreme ends was measured before implantation and after surgery. The sagittal curvature between the corresponding spinal levels of healthy adolescents obtained by previous studies was compared with the implant rod angle of curvature to evaluate the sagittal curve correction. The difference between the postoperative implant rod angle of curvature and normal spine sagittal curvature of the corresponding instrumented level was used to evaluate over or under correction of the sagittal deformity. The implant rods at the concave side of deformity of all patients were significantly deformed after surgery. The average degree of rod deformation Δθ at the concave and convex sides was 15.8° and 1.6°, respectively. The average preoperative and postoperative implant rod angle of curvature at the concave side was 33.6° and 17.8°, respectively. The average preoperative and postoperative implant rod angle of curvature at the convex side was 25.5° and 23.9°, respectively. A significant relationship was found between the degree of rod deformation and preoperative implant rod angle of curvature (r=0.60, p<.005). The implant rods at the convex side of all patients did not have significant deformation. The results indicate that the postoperative sagittal outcome could be predicted from the initial rod shape. Changes in implant rod angle of curvature may lead to over- or undercorrection of the sagittal curve. Rod deformation at the concave side suggests that corrective forces acting on that side are greater than the convex side. Copyright © 2014 Elsevier Inc. All rights reserved.

Piazzi On Ceres and Pacific On Earth Are Tectonically Comparable Features

NASA Astrophysics Data System (ADS)

Kochemasov, G.

Earth is more than 10 times larger than Ceres but the wave planetary tectonics [1] is not perplexed with this. Theorem 1 states that "Celestial bodies are dichotomic". This theorem is valid for bodies of various sizes, compositions and physical states. What is common for all of them that they are moving, moving in non-circular orbits, and rotate. These properties are sufficient for invoking inertia forces making celestial bodies oscillate and acquire a convexo-concave shape. of the recent planetological achievements three should be mentioned particularly as they concern small celestial bodies where general rules of body shaping are expressed very sharply. A small aster- oid 433 Eros, the largest asteroid 1 Ceres and Borrelli comet were studied in different scales but all of them have essential features predicted by the wave planetology. The convexo-concave shape of asteroid Eros (stony, 33 km long) is repeated in comet Bor- relli (icy, 8 km long). Borrelli's convex hemisphere is sharply jagged because of exten- sion. The same is observed on Eros ("saddle") but in a lesser degree. Borrelli's concave strongly contracted hemisphere is a source of a large complexly built tail of expulsion. This extruded material samples interior of the comet and leaves whitish spots in the centre of the concave side. Eros also have many signes of past degassing in a form of regular net of pits (craters); in the centre of the concave side is a large complexly built crater Psych. Both oblong bodies -Eros and Borrelli - have different opposite ends: blunt and sharp, predicted by the wave planetology (the Arctic-Antarctic symp- tom). The oblong body of Ceres (major/minor axes of 898/788 km [2] and 970/ 930 km,[Parker &Stern]) according to HST (J.Parker &Stern) has a prominent dusky dark spot (Piazzi) from one side. It occupies a significant part of the asteroid (about 250 km, more than a quarter the size of Ceres) and probably might be assigned to a depression. Tectonically one may compare this depression with the Pacific basin hollow on Earth. One may state that the wave planetology is a science which can predict. References: [1] Kochemasov G.G. (1999) Theorems of wave planetary tectonics // Geophys. Res. Abstr., v.1, #3, 700; [2] McCarthy D.W.,Jr., Freeman J.D., Drummond J.D. (1994) High resolution images of Vesta at 1.65 micron // Icarus,v.108, #2, pt.1, 285-297.

XIPE: the x-ray imaging polarimetry explorer

NASA Astrophysics Data System (ADS)

Soffitta, P.; Bellazzini, R.; Bozzo, E.; Burwitz, V.; Castro-Tirado, A.; Costa, E.; Courvoisier, T.; Feng, H.; Gburek, S.; Goosmann, R.; Karas, V.; Matt, G.; Muleri, F.; Nandra, K.; Pearce, M.; Poutanen, J.; Reglero, V.; Sabau Maria, D.; Santangelo, A.; Tagliaferri, G.; Tenzer, C.; Vink, J.; Weisskopf, M. C.; Zane, S.; Agudo, I.; Antonelli, A.; Attina, P.; Baldini, L.; Bykov, A.; Carpentiero, R.; Cavazzuti, E.; Churazov, E.; Del Monte, E.; De Martino, D.; Donnarumma, I.; Doroshenko, V.; Evangelista, Y.; Ferreira, I.; Gallo, E.; Grosso, N.; Kaaret, P.; Kuulkers, E.; Laranaga, J.; Latronico, L.; Lumb, D. H.; Macian, J.; Malzac, J.; Marin, F.; Massaro, E.; Minuti, M.; Mundell, C.; Ness, J. U.; Oosterbroek, T.; Paltani, S.; Pareschi, G.; Perna, R.; Petrucci, P.-O.; Pinazo, H. B.; Pinchera, M.; Rodriguez, J. P.; Roncadelli, M.; Santovincenzo, A.; Sazonov, S.; Sgro, C.; Spiga, D.; Svoboda, J.; Theobald, C.; Theodorou, T.; Turolla, R.; Wilhelmi de Ona, E.; Winter, B.; Akbar, A. M.; Allan, H.; Aloisio, R.; Altamirano, D.; Amati, L.; Amato, E.; Angelakis, E.; Arezu, J.; Atteia, J.-L.; Axelsson, M.; Bachetti, M.; Ballo, L.; Balman, S.; Bandiera, R.; Barcons, X.; Basso, S.; Baykal, A.; Becker, W.; Behar, E.; Beheshtipour, B.; Belmont, R.; Berger, E.; Bernardini, F.; Bianchi, S.; Bisnovatyi-Kogan, G.; Blasi, P.; Blay, P.; Bodaghee, A.; Boer, M.; Boettcher, M.; Bogdanov, S.; Bombaci, I.; Bonino, R.; Braga, J.; Brandt, W.; Brez, A.; Bucciantini, N.; Burderi, L.; Caiazzo, I.; Campana, R.; Campana, S.; Capitanio, F.; Cappi, M.; Cardillo, M.; Casella, P.; Catmabacak, O.; Cenko, B.; Cerda-Duran, P.; Cerruti, C.; Chaty, S.; Chauvin, M.; Chen, Y.; Chenevez, J.; Chernyakova, M.; Cheung, C. C. Teddy; Christodoulou, D.; Connell, P.; Corbet, R.; Coti Zelati, F.; Covino, S.; Cui, W.; Cusumano, G.; D'Ai, A.; D'Ammando, F.; Dadina, M.; Dai, Z.; De Rosa, A.; de Ruvo, L.; Degenaar, N.; Del Santo, M.; Del Zanna, L.; Dewangan, G.; Di Cosimo, S.; Di Lalla, N.; Di Persio, G.; Di Salvo, T.; Dias, T.; Done, C.; Dovciak, M.; Doyle, G.; Ducci, L.; Elsner, R.; Enoto, T.; Escada, J.; Esposito, P.; Eyles, C.; Fabiani, S.; Falanga, M.; Falocco, S.; Fan, Y.; Fender, R.; Feroci, M.; Ferrigno, C.; Forman, W.; Foschini, L.; Fragile, C.; Fuerst, F.; Fujita, Y.; Gasent-Blesa, J. L.; Gelfand, J.; Gendre, B.; Ghirlanda, G.; Ghisellini, G.; Giroletti, M.; Goetz, D.; Gogus, E.; Gomez, J.-L.; Gonzalez, D.; Gonzalez-Riestra, R.; Gotthelf, E.; Gou, L.; Grandi, P.; Grinberg, V.; Grise, F.; Guidorzi, C.; Gurlebeck, N.; Guver, T.; Haggard, D.; Hardcastle, M.; Hartmann, D.; Haswell, C.; Heger, A.; Hernanz, M.; Heyl, J.; Ho, L.; Hoormann, J.; Horak, J.; Huovelin, J.; Huppenkothen, D.; Iaria, R.; Inam Sitki, C.; Ingram, A.; Israel, G.; Izzo, L.; Burgess, M.; Jackson, M.; Ji, L.; Jiang, J.; Johannsen, T.; Jones, C.; Jorstad, S.; Kajava, J. J. E.; Kalamkar, M.; Kalemci, E.; Kallman, T.; Kamble, A.; Kislat, F.; Kiss, M.; Klochkov, D.; Koerding, E.; Kolehmainen, M.; Koljonen, K.; Komossa, S.; Kong, A.; Korpela, S.; Kowalinski, M.; Krawczynski, H.; Kreykenbohm, I.; Kuss, M.; Lai, D.; Lan, M.; Larsson, J.; Laycock, S.; Lazzati, D.; Leahy, D.; Li, H.; Li, J.; Li, L.-X.; Li, T.; Li, Z.; Linares, M.; Lister, M.; Liu, H.; Lodato, G.; Lohfink, A.; Longo, F.; Luna, G.; Lutovinov, A.; Mahmoodifar, S.; Maia, J.; Mainieri, V.; Maitra, C.; Maitra, D.; Majczyna, A.; Maldera, S.; Malyshev, D.; Manfreda, A.; Manousakis, A.; Manuel, R.; Margutti, R.; Marinucci, A.; Markoff, S.; Marscher, A.; Marshall, H.; Massaro, F.; McLaughlin, M.; Medina-Tanco, G.; Mehdipour, M.; Middleton, M.; Mignani, R.; Mimica, P.; Mineo, T.; Mingo, B.; Miniutti, G.; Mirac, S. M.; Morlino, G.; Motlagh, A. V.; Motta, S.; Mushtukov, A.; Nagataki, S.; Nardini, F.; Nattila, J.; Navarro, G. J.; Negri, B.; Negro, Matteo; Nenonen, S.; Neustroev, V.; Nicastro, F.; Norton, A.; Nucita, A.; O'Brien, P.; O'Dell, S.

2016-07-01

XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden.

VizieR Online Data Catalog: Gravitational waves from known pulsars (Aasi+, 2014)

NASA Astrophysics Data System (ADS)

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Ceron, E. A.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bersanetti, D.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bo, Nd C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Bruckner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderon Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglia, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M. Jr; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deleglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; Derosa, R.; Desalvo, R.; Dhurandhar, S.; di Fiore, L.; di Lieto, A.; di Palma, I.; di, Virgilio A.; Diaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endroczi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; Gonzalez, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Gossler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Iafrate, J.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jaranowski, P.; Jimenez-Forteza, F.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, H.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kefelian, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimen, Ko S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kremin, A.; Kringel, V.; Krishnan, B.; Krolak, A.; Kucharczyk, C.; Kudla, S.; Kuehn, G.; Kumar, A.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lebigot, E. O.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levine, B.; Lewis, J. B.; Lhuillier, V.; Li, T. G. F.; Lin, A. C.; Littenberg, T. B.; Litvine, V.; Liu, F.; Liu, H.; Liu, Y.; Liu, Z.; Lloyd, D.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Luan, J.; Lubinski, M. J.; Luck, H.; Lundgren, A. P.; MacArthur, J.; MacDonald, E.; Machenschalk, B.; Macinnis, M.; MacLeod, D. M.; Magana-Sandoval, F.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marka, S.; Marka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Mokler, F.; Moraru, D.; Moreno, G.; Morgado, N.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nanda, Kumar D.; Nardecchia, I.; Nash, T.; Naticchioni, L.; Nayak, R.; Necula, V.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; O'Reilly, B.; Ortega Larcher, W.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Peiris, P.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pindor, B.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Poole, V.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Racz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Roever, C.; Rolland, L.; Rollins, J. G.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosinska, D.; Rowan, S.; Rudiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Soden, K.; Son, E. J.; Sorazu, B.; Souradeep, T.; Sperandio, L.; Staley, A.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Straniero, N.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; Ter Braack, A. P. M.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Verma, S.; Vetrano, F.; Vicere, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vlcek, B.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vrinceanu, D.; Vyachanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Walker, M.; Wallace, L.; Wan, Y.; Wang, J.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wibowo, S.; Wiesner, K.; Wilkinson, C.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Yvert, M.; Zadrozny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.; Buchner, S.; Cognard, I.; Corongiu, A.; D'Amico, N.; Espinoza, C. M.; Freire, P. C. C.; Gotthelf, E. V.; Guillemot, L.; Hessels, J. W. T.; Hobbs, G. B.; Kramer, M.; Lyne, A. G.; Marshall, F. E.; Possenti, A.; Ransom, S. M.; Ray, P. S.; Roy, J.; Stappers, B. W.; VIRGO Collaboration

2017-06-01

In this paper we have used calibrated data from the Virgo second (Aasi et al. 2012CQGra..29o5002A) and fourth science runs (VSR2 and VSR4) and the LIGO sixth science run (S6). Virgo's third science run (VSR3) was relatively insensitive in comparison with VSR4 and has not been included in this analysis. This was partially because Virgo introduced monolithic mirror suspensions prior to VSR4 which improved sensitivity in the low-frequency range. During S6, the two LIGO 4 km detectors at Hanford, Washington (LHO/H1), and Livingston, Louisiana (LLO/L1), were running in an enhanced configuration (Adhikari et al. 2006, Enhanced LIGO, Tech. Rep. LIGO-T060156-v01, California Institute of Technology, Massachusetts Institute of Technology, https://dcc.ligo.org/LIGO-T060156-v1/public) over that from the previous S5 run (Abbott et al. 2009RPPh...72g6901A). (1 data file).

The social summit: a gender perspective.

PubMed

1995-01-01

This editorial introduction to an issue of INSTRAW News notes that the UN has undertaken a year long series of important international conferences, starting with the September 1994 Conference on Population and Development. The second major conference is the World Summit for Social Development, and the third is the Fourth World Conference on Women. At these conferences, the international community is coming together to rescue the people whose lives have been threatened by the legacy of the Cold War: ethnic, religious, and cultural violence and exacerbation of the gap between rich and poor. Women are an integral part of the developing social agenda because women are a magnifying glass, rather than simply a mirror, of the problems of society. This issue of INSTRAW News provides a broad overview of how gender issues have evolved and the changes which occurred as a result. Specific gender issues are analyzed as they impact the three core items of the Social Summit agenda: attacking poverty, creating jobs, and building social solidarity.

The New Hard X-ray Mission

NASA Astrophysics Data System (ADS)

Pareschi, Giovanni; Tagliaferri, Gianpiero; Argan, Andrea; Bellazzini, Ronaldo; Catalano, Osvaldo; Costa, Enrico; Cusumano, Giancarlo; Fiore, Fabrizio; Fiorini, Carlo; Malaguti, Giuseppe; Matt, Giorgio; Mereghetti, Sandro; Micela, Giuseppina; Perola, Giuseppe Cesare; Villa, Gabriele

2010-07-01

The Italian New Hard X-ray Mission (NHXM) is an evolution of the HEXIT-Sat concept, extending up to 80 keV the fine imaging capability today available only at E<10 keV, with the further addition of photoelectric imaging polarimetry. NHXM consists of four identical mirrors, with a 10 m focal length, achieved after launch by means of a deployable structure. Three of the four telescopes will have at their focus three identical spectro-imaging cameras, while a X-ray imaging polarimeter will be placed at the focus of the fourth. In order to ensure a low and stable background, NHXM will be place on a low Earth equatorial orbit. NHXM will provide a real breakthrough on a number of hot astrophysical issues, broadly falling under two main topics: i) censing the black holes in the Universe and probing the physics of accretion in the most diverse conditions; ii) investigating the particle acceleration mechanisms at work in different contexts, and the effects of radiative transfer in highly magnetized plasmas and strong gravitational fields.

Optical Modeling Activities for NASA's James Webb Space Telescope (JWST): V. Operational Alignment Updates

NASA Technical Reports Server (NTRS)

Howard, Joseph M.; Ha, Kong Q.; Shiri, Ron; Smith, J. Scott; Mosier, Gary; Muheim, Danniella

2008-01-01

This paper is part five of a series on the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two papers discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third paper investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory, and the fourth introduced the software toolkits used to perform much of the optical analysis for JWST. The work here models observatory operations by simulating line-of-sight image motion and alignment drifts over a two-week period. Alignment updates are then simulated using wavefront sensing and control processes to calculate and perform the corrections. A single model environment in Matlab is used for evaluating the predicted performance of the observatory during these operations.

Procedural Learning in Children With Developmental Coordination, Reading, and Attention Disorders.

PubMed

Magallón, Sara; Crespo-Eguílaz, Nerea; Narbona, Juan

2015-10-01

The aim is to assess repetition-based learning of procedures in children with developmental coordination disorder (DCD), reading disorder (RD) and attention-deficit hyperactivity disorder (ADHD). Participants included 187 children, studied in 4 groups: (a) DCD comorbid with RD and ADHD (DCD+RD+ADHD) (n = 30); (b) RD comorbid with ADHD (RD+ADHD) (n = 48); (c) ADHD (n = 19); and typically developing children (control group) (n = 90). Two procedural learning tasks were used: Assembly learning and Mirror drawing. Children were tested on 4 occasions for each task: 3 trials were consecutive and the fourth trial was performed after an interference task. Task performance by DCD+RD+ADHD children improved with training (P < .05); however, the improvement was significantly lower than that achieved by the other groups (RD+ADHD, ADHD and controls) (P < .05). In conclusion, children with DCD+RD+ADHD improve in their use of cognitive-motor procedures over a short training period. Aims of intervention in DCD+RD+ADHD should be based on individual learning abilities. © The Author(s) 2015.

The neuronal correlates of mirror therapy: an fMRI study on mirror induced visual illusions in patients with stroke.

PubMed

Michielsen, Marian E; Smits, Marion; Ribbers, Gerard M; Stam, Henk J; van der Geest, Jos N; Bussmann, Johannes B J; Selles, Ruud W

2011-04-01

To investigate the neuronal basis for the effects of mirror therapy in patients with stroke. 22 patients with stroke participated in this study. The authors used functional MRI to investigate neuronal activation patterns in two experiments. In the unimanual experiment, patients moved their unaffected hand, either while observing it directly (no-mirror condition) or while observing its mirror reflection (mirror condition). In the bimanual experiment, patients moved both hands, either while observing the affected hand directly (no-mirror condition) or while observing the mirror reflection of the unaffected hand in place of the affected hand (mirror condition). A two-factorial analysis with movement (activity vs rest) and mirror (mirror vs no mirror) as main factors was performed to assess neuronal activity resultant of the mirror illusion. Data on 18 participants were suitable for analysis. Results showed a significant interaction effect of movement×mirror during the bimanual experiment. Activated regions were the precuneus and the posterior cingulate cortex (p<0.05 false discovery rate). In this first study on the neuronal correlates of the mirror illusion in patients with stroke, the authors showed that during bimanual movement, the mirror illusion increases activity in the precuneus and the posterior cingulate cortex, areas associated with awareness of the self and spatial attention. By increasing awareness of the affected limb, the mirror illusion might reduce learnt non-use. The fact that the authors did not observe mirror-related activity in areas of the motor or mirror neuron system questions popular theories that attribute the clinical effects of mirror therapy to these systems.

Mirror agnosia and the mirrored-self misidentification delusion: a hypnotic analogue.

PubMed

Connors, Michael H; Cox, Rochelle E; Barnier, Amanda J; Langdon, Robyn; Coltheart, Max

2012-05-01

Mirrored-self misidentification is the delusional belief that one's reflection in the mirror is a stranger. Current theories suggest that one pathway to the delusion is mirror agnosia (a deficit in which patients are unable to use mirror knowledge when interacting with mirrors). This study examined whether a hypnotic suggestion for mirror agnosia can recreate features of the delusion. Ten high hypnotisable participants were given either a suggestion to not understand mirrors or to see the mirror as a window. Participants were asked to look into a mirror and describe what they saw. Participants were tested on their understanding of mirrors and received a series of challenges. Participants then received a detailed postexperimental inquiry. Three of five participants given the suggestion to not understand mirrors reported seeing a stranger and maintained this belief when challenged. These participants also showed signs of mirror agnosia. No participants given the suggestion to see a window reported seeing a stranger. Results indicate that a hypnotic suggestion for mirror agnosia can be used to recreate the mirrored-self misidentification delusion. Factors influencing the effectiveness of hypnotic analogues of psychopathology, such as participants' expectations and interpretations, are discussed.

Collisional and dynamical history of Gaspra

NASA Technical Reports Server (NTRS)

Greenberg, R.; Nolan, M. C.; Bottke, W. F., Jr.; Kolvoord, R. A.

1993-01-01

Interpretation of the impact record on Gaspra requires understanding of the effects of collisions on a target body of Gaspra's size and shape, recognition of impact features that may have different morphologies from craters on larger planets, and models of the geological processes that erase and modify impact features. Crater counts on the 140 sq km of Gaspra imaged at highest resolution by the Galileo spacecraft show a steep size-frequency distribution (cumulative power-law index near -3.5) from the smallest resolvable size (150 m diameter) up through the large feature (1.5 km diameter crater) of familiar crater-like morphology. In addition, there appear to be as many as eight roughly circular concavities with diameters greater than 3 km visible on the asteroid. If we restrict our crater counts to features with traditionally recognized crater morphologies, these concavities would not be included. However, if we define craters to include any concave structures that may represent local or regional damage at an impact size, then the larger features on Gaspra are candidates for consideration. Acceptance of the multi-km features as craters has been cautious for several reasons. First, scaling laws (the physically plausible algorithms for extrapolating from experimental data) indicate that Gaspra could not have sustained such large-crater-forming impacts without being disrupted; second, aside from concavity, the larger structures have no other features (e.g. rims) that can be identified with known impact craters; and third, extrapolation of the power-law size distribution for smaller craters predicts no craters larger than 3 km over the entire surface. On the other hand, recent hydrocode modeling of impacts shows that for given impact (albeit into a sphere), the crater size is much larger than given by scaling laws. Gaspra-size bodies can sustain formation of up to 8-km craters without disruption. Besides allowing larger impact craters, this result doubles the lifetime since the last catastrophic fragmentation event up to one billion years. Events that create multi-km craters also globally damage the material structure, such that regolith is produced, whether or not Gaspra 'initially' had a regolith, contrary to other models in which initial regolith is required in order to allow current regolith. Because the globally destructive shock wave precedes basin formation, crater size is closer to the large size extrapolated from gravity-scaling rather than the strength-scaling that had earlier been assumed for such small bodies. This mechanism may also help explain the existence of Stickney on Phobos. Moreover, rejection of the large concavities as craters based on unfamiliar morphology would be premature, because (aside from Stickney) we have no other data on such large impact structures on such a small, irregular body. The eight candidate concavities cover an area greater than that counted for smaller craters, because they are most apparent where small craters cannot be seen: on low resolution images and at the limb on high resolution images. We estimate that there are at least two with diameter greater than 4 km per 140 sq km, which would have to be accounted for in any model that claims these are impact craters.

Effects of a mirror-induced visual illusion on a reaching task in stroke patients: implications for mirror therapy training.

PubMed

Selles, Ruud W; Michielsen, Marian E; Bussmann, Johannes B J; Stam, Henk J; Hurkmans, Henri L; Heijnen, Iris; de Groot, Danielle; Ribbers, Gerard M

2014-09-01

Although most mirror therapy studies have shown improved motor performance in stroke patients, the optimal mirror training protocol still remains unclear. To study the relative contribution of a mirror in training a reaching task and of unilateral and bimanual training with a mirror. A total of 93 stroke patients at least 6 months poststroke were instructed to perform a reaching task as fast and as fluently as possible. They performed 70 practice trials after being randomly allocated to 1 of 5 experimental groups: training with (1) the paretic arm with direct view (Paretic-No Mirror), (2) the nonparetic arm with direct view (Nonparetic-No Mirror), (3) the nonparetic arm with mirror reflection (Nonparetic Mirror), (4) both sides and with a nontransparent screen preventing visual control of paretic side (Bilateral-Screen), and (5) both sides with mirror reflection of the nonparetic arm (Bilateral-Mirror). As baseline and follow-up, patients performed 6 trials using only their paretic side. Primary outcome measure was the movement time. We found the largest intervention effect in the Paretic-No Mirror condition. However, the Nonparetic-Mirror condition was not significantly different from the Paretic-No Mirror condition, while the Unaffected-No Mirror condition had significantly less improvement than the Paretic-No Mirror condition. In addition, movement time improved significantly less in the bimanual conditions and there was no difference between both bimanual conditions or between both mirror conditions. The present study confirms that using a mirror reflection can facilitate motor learning. In this task, bimanual movement using mirror training was less effective than unilateral training. © The Author(s) 2014.

New method for evaluation of cervical vertebral maturation based on angular measurements.

PubMed

Alhadlaq, Adel M; Al-Shayea, Eman I

2013-04-01

To investigate the validity of a new approach to assess the cervical vertebral maturation based on angular measurements of the lower border concavity of cervical vertebral bodies. Hand-wrist and lateral cephalometric radiographs of 197 male subjects with age range of 10-15 years attending the orthodontic clinic at King Saud University, Riyadh, Kingdom of Saudi Arabia were utilized. The study was carried out between September 2009 and May 2011. The study sample was divided into 6 groups (group 1: 10 years to group 6: 15 years) based on the chronological age of the subject. The skeletal age of the subjects was determined using Greulich and Pyle's standard radiographic atlas, and skeletal maturation was assessed by Fishman's skeletal maturity indicators. The cervical vertebral maturation (CVM) of subjects was determined using angular measurements of the second, third, and fourth cervical vertebral bodies. The validity of the newly developed method was assessed by examining the correlation between CVM stages determined by the angular measurements and the skeletal maturation level as determined by the standard hand-wrist methods. A significant correlation (r=0.94) was found between the angular CVM stages and the skeletal age determined by Greulich and Pyle's atlas from hand-wrist radiographs. Also, a high correlation (r=0.94) was found between the angular CVM stages and the Fishman's hand-wrist skeletal maturity indicators. The new angular measurement approach to determine CVM is valid and has the potential to be applied in assessing skeletal maturity level in growing male children.

Device for installing rocket engines

NASA Technical Reports Server (NTRS)

George, T. R., Jr. (Inventor)

1976-01-01

A device for installing rocket engines is reported that is supported at a cant relative to vertical by an axially extensible, tiltable pedestal. A lifting platform supports the rocket engine at its thrust chamber exit, including a mount having a concentric base characterized by a concave bearing surface, a plurality of uniformly spaced legs extended radially from the base, and an annular receiver coaxially aligned with the base and affixed to the distal ends of said legs for receiving the thrust chamber exit. The lifting platform rests on a seat concentrically related to the pedestal and affixed to an extended end portion thereof having a convex bearing surface mated in sliding engagement with the concave bearing surface of the annular base for accommodating a rocking motion of the platform.

Simple fabrication of closed-packed IR microlens arrays on silicon by femtosecond laser wet etching

NASA Astrophysics Data System (ADS)

Meng, Xiangwei; Chen, Feng; Yang, Qing; Bian, Hao; Du, Guangqing; Hou, Xun

2015-10-01

We demonstrate a simple route to fabricate closed-packed infrared (IR) silicon microlens arrays (MLAs) based on femtosecond laser irradiation assisted by wet etching method. The fabricated MLAs show high fill factor, smooth surface and good uniformity. They can be used as optical devices for IR applications. The exposure and etching parameters are optimized to obtain reproducible microlens with hexagonal and rectangular arrangements. The surface roughness of the concave MLAs is only 56 nm. This presented method is a maskless process and can flexibly change the size, shape and the fill factor of the MLAs by controlling the experimental parameters. The concave MLAs on silicon can work in IR region and can be used for IR sensors and imaging applications.

Acoustic suspension system

NASA Technical Reports Server (NTRS)

Lee, M. C.; Wang, T. G. (Inventor)

1983-01-01

An acoustic levitation system is described, with single acoustic source and a small reflector to stably levitate a small object while the object is processed as by coating or heating it. The system includes a concave acoustic source which has locations on opposite sides of its axis that vibrate towards and away from a focal point to generate a converging acoustic field. A small reflector is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector is located about one-half wavelength from the focal point and is concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

Nonlinear characterization of a single-axis acoustic levitator.

PubMed

Andrade, Marco A B; Ramos, Tiago S; Okina, Fábio T A; Adamowski, Julio C

2014-04-01

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jump phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.

An elicitation of utility for quality of life under prospect theory.

PubMed

Attema, Arthur E; Brouwer, Werner B F; l'Haridon, Olivier; Pinto, Jose Luis

2016-07-01

This paper performs several tests of decision analysis applied to the health domain. First, we conduct a test of the normative expected utility theory. Second, we investigate the possibility to elicit the more general prospect theory. We observe risk aversion for gains and losses and violations of expected utility. These results imply that mechanisms governing decisions in the health domain are similar to those in the monetary domain. However, we also report one important deviation: utility is universally concave for the health outcomes used in this study, in contrast to the commonly found S-shaped utility for monetary outcomes, with concave utility for gains and convex utility for losses. Copyright © 2016 Elsevier B.V. All rights reserved.

Elective removal of convexo-concave Björk-Shiley valves.

PubMed

Rajesh, P B; Smith, G H; Lawford, P V; Black, M M

1994-08-01

Replacement has been an accepted method for treating advanced cardiac valvular disease for more than 25 years. However, the perfect prosthesis has yet to be developed, judging by the number of devices available. A prosthesis that initially appears promising may cause problems in due course, and indeed some devices have been modified or withdrawn from clinical use. A notable example of a prosthetic valve that has give problems is the Björk-Shiley convexo-concave prosthesis, some models of which have undergone mechanical failure due to strut fracture. We report the elective removal of such a valve and the subsequent examination of the prosthesis. The results of this examination suggest that a policy of elective removal is justified.

Instability and sound emission from a flow over a curved surface

NASA Technical Reports Server (NTRS)

Maestrello, L.; Parikh, P.; Bayliss, A.

1988-01-01

The growth and decay of a wavepacket convecting in a boundary layer over a concave-convex surface is studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiation is computed using the linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. It is shown that on the concave portion the amplitude of the wavepacket increases and its bandwidth broadens while on the convex portion some of the components in the packet are stabilized. The pressure field decays exponentially away from the surface and then algebraically exhibits a decay characteristic of acoustic waves in two dimensions. The far-field acoustic pressure exhibits a peak at a frequency corresponding to the inflow instability frequency.

Discontinuous gradient differential equations and trajectories in the calculus of variations

NASA Astrophysics Data System (ADS)

Bogaevskii, I. A.

2006-12-01

The concept of gradient of smooth functions is generalized for their sums with concave functions. An existence, uniqueness, and continuous dependence theorem for increasing time is formulated and proved for solutions of an ordinary differential equation the right-hand side of which is the gradient of the sum of a concave and a smooth function. With the use of this result a physically natural motion of particles, well defined even at discontinuities of the velocity field, is constructed in the variational problem of the minimal mechanical action in a space of arbitrary dimension. For such a motion of particles in the plane all typical cases of the birth and the interaction of point clusters of positive mass are described.

Nonlinear characterization of a single-axis acoustic levitator

NASA Astrophysics Data System (ADS)

Andrade, Marco A. B.; Ramos, Tiago S.; Okina, Fábio T. A.; Adamowski, Julio C.

2014-04-01

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jump phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.

MSFC Test Results for Selected Mirrors: Brush-Wellman/Goodrich 0.5 meter Joined-Beryllium Mirror; IABG 0.5 meter C/SiC Mirror; Xinetics 0.5 meter SiC Mirror; and Kodak 0.23 meter SiO2 Mirror

NASA Technical Reports Server (NTRS)

Hadaway, James; Blackwell, Lisa; Matthews, Gary; Eng, Ron; Stahl, Phil; Hraba, John; Thornton, Gary

2002-01-01

The results of cryo tests performed at the XRCF on the above mirrors will be presented. Each mirror was tested from room-temperature to around 30 K. The first three were tested together on a 3-mirror stand in the large chamber using the PhaseCam interferometer, while the Kodak mirror was tested in the small chamber using the EPI interferometer.

Extraction of space-charge-dominated ion beams from an ECR ion source: Theory and simulation

NASA Astrophysics Data System (ADS)

Alton, G. D.; Bilheux, H.

2004-05-01

Extraction of high quality space-charge-dominated ion beams from plasma ion sources constitutes an optimization problem centered about finding an optimal concave plasma emission boundary that minimizes half-angular divergence for a given charge state, independent of the presence or lack thereof of a magnetic field in the extraction region. The curvature of the emission boundary acts to converge/diverge the low velocity beam during extraction. Beams of highest quality are extracted whenever the half-angular divergence, ω, is minimized. Under minimum half-angular divergence conditions, the plasma emission boundary has an optimum curvature and the perveance, P, current density, j+ext, and extraction gap, d, have optimum values for a given charge state, q. Optimum values for each of the independent variables (P, j+ext and d) are found to be in close agreement with those derived from elementary analytical theory for extraction with a simple two-electrode extraction system, independent of the presence of a magnetic field. The magnetic field only increases the emittances of beams through additional aberrational effects caused by increased angular divergences through coupling of the longitudinal to the transverse velocity components of particles as they pass though the mirror region of the electron cyclotron resonance (ECR) ion source. This article reviews the underlying theory of elementary extraction optics and presents results derived from simulation studies of extraction of space-charge dominated heavy-ion beams of varying mass, charge state, and intensity from an ECR ion source with emphasis on magnetic field induced effects.

A very wide band telescope for Planck using optical and radio frequency techniques

NASA Astrophysics Data System (ADS)

Fargant, Guy; Dubruel, Denis; Cornut, Myriam; Riti, Jean-Bernard; Passvogel, Thomas; de Maagt, Peter; Anderegg, Michel; Tauber, Jan

2017-11-01

Planck associated to FIRST is one of the ESA scientific missions belonging to the Horizon 2000 programme. It will be launched by an Ariane 5 in 2007. Planck aims at obtaining very accurate images of the Cosmic Microwave Background fluctuations, thanks to a spaceborne telescope featuring a wide wavelength range and an excellent control of straylight and thermal variations. The telescope is based on an off-axis gregorian design consisting of two concave ellipsoidal mirrors with a 1.5-meter pupil, derived from radio frequency antenna, but with a very wide spectral domain which ranges from far infrared (350 μm) up to millimetric wavelengths (10 mm). Its field of view is large (10 degrees) owing to a high number of detectors in the focal plane. The short wavelength detectors (bolometers operating at 0.1 K) are located at the centre of the focal plane unit while the long wavelength ones (based on HEMT amplifier technology operating at 20 K) are located at the periphery. The Planck telescope operates at a temperature below 60 K. This level is achieved in a passive way, i.e. using a cryogenic radiator. Furthermore, this radiator must accommodate a set of coolers dedicated to the focal plane unit, cooling one of the experiments down to 0.1 K. The Planck mission leads to very stringent requirements (straylight, thermal stability) that can only be achieved by designing the spacecraft at system level, combining optical, radio frequency and thermal techniques in order to achieve the required performance.

Compact neutron imaging system using axisymmetric mirrors

DOEpatents

Khaykovich, Boris; Moncton, David E; Gubarev, Mikhail V; Ramsey, Brian D; Engelhaupt, Darell E

2014-05-27

A dispersed release of neutrons is generated from a source. A portion of this dispersed neutron release is reflected by surfaces of a plurality of nested, axisymmetric mirrors in at least an inner mirror layer and an outer mirror layer, wherein the neutrons reflected by the inner mirror layer are incident on at least one mirror surface of the inner mirror layer N times, wherein N is an integer, and wherein neutrons reflected by the outer mirror are incident on a plurality of mirror surfaces of the outer layer N+i times, where i is a positive integer, to redirect the neutrons toward a target. The mirrors can be formed by a periodically reversed pulsed-plating process.

Double arch mirror study

NASA Technical Reports Server (NTRS)

Vukobratovich, D.; Hillman, D.

1983-01-01

The development of a method of mounting light weight glass mirrors for astronomical telescopes compatible with the goals of the Shuttle Infrared Telescope Facility (SIRTF) was investigated. A 20 in. diameter double arch lightweight mirror previously fabricated was modified to use a new mount configuration. This mount concept was developed and fabricated. The mounting concept of the double mounting mirror is outlined. The modifications made to the mirror, fabrication of the mirror mount, and room temperature testing of the mirror and mount and the extension of the mirror and mount concept to a full size (40 in. diameter) primary mirror for SIRTF are discussed.

High stroke pixel for a deformable mirror

DOEpatents

Miles, Robin R.; Papavasiliou, Alexandros P.

2005-09-20

A mirror pixel that can be fabricated using standard MEMS methods for a deformable mirror. The pixel is electrostatically actuated and is capable of the high deflections needed for spaced-based mirror applications. In one embodiment, the mirror comprises three layers, a top or mirror layer, a middle layer which consists of flexures, and a comb drive layer, with the flexures of the middle layer attached to the mirror layer and to the comb drive layer. The comb drives are attached to a frame via spring flexures. A number of these mirror pixels can be used to construct a large mirror assembly. The actuator for the mirror pixel may be configured as a crenellated beam with one end fixedly secured, or configured as a scissor jack. The mirror pixels may be used in various applications requiring high stroke adaptive optics.

[Motion control of moving mirror based on fixed-mirror adjustment in FTIR spectrometer].

PubMed

Li, Zhong-bing; Xu, Xian-ze; Le, Yi; Xu, Feng-qiu; Li, Jun-wei

2012-08-01

The performance of the uniform motion of the moving mirror, which is the only constant motion part in FTIR spectrometer, and the performance of the alignment of the fixed mirror play a key role in FTIR spectrometer, and affect the interference effect and the quality of the spectrogram and may restrict the precision and resolution of the instrument directly. The present article focuses on the research on the uniform motion of the moving mirror and the alignment of the fixed mirror. In order to improve the FTIR spectrometer, the maglev support system was designed for the moving mirror and the phase detection technology was adopted to adjust the tilt angle between the moving mirror and the fixed mirror. This paper also introduces an improved fuzzy PID control algorithm to get the accurate speed of the moving mirror and realize the control strategy from both hardware design and algorithm. The results show that the development of the moving mirror motion control system gets sufficient accuracy and real-time, which can ensure the uniform motion of the moving mirror and the alignment of the fixed mirror.

Scaling laws for light weight optics, studies of light weight mirrors mounting and dynamic mirror stress, and light weight mirror and mount designs

NASA Technical Reports Server (NTRS)

Vukobratovich, Daniel; Richard, Ralph M.; Valente, Tina M.; Cho, Myung K.

1990-01-01

Scaling laws for light-weight optical systems are examined. A cubic relationship between mirror diameter and weight has been suggested and used by many designers of optical systems as the best description for all light-weight mirrors. A survey of existing light-weight systems in the open literature was made to clarify this issue. Fifty existing optical systems were surveyed with all varieties of light-weight mirrors including glass and beryllium structured mirrors, contoured mirrors, and very thin solid mirrors. These mirrors were then categorized and weight to diameter ratio was plotted to find a best curve for each case. A best fitting curve program tests nineteen different equations and ranks a goodness-to-fit for each of these equations. The resulting relationship found for each light-weight mirror category helps to quantify light-weight optical systems and methods of fabrication and provides comparisons between mirror types.

Wear Behavior of Medium Carbon Steel with Biomimetic Surface Under Starved Lubricated Conditions

NASA Astrophysics Data System (ADS)

Zhang, Zhihui; Shao, Feixian; Liang, Yunhong; Lin, Pengyu; Tong, Xin; Ren, Luquan

2017-07-01

Friction and wear under starved lubrication condition are both key life-related factors for mechanical performance of many structural parts. In this paper, different surface morphologies on medium carbon steel were fabricated using laser, inspired by the surface coupling effect of biological system. The friction and sliding wear behaviors of biomimetic specimens (characterized by convex and concave units on the specimen surface) were studied under starved lubrication condition. The stress distribution on different sliding surfaces under sliding friction was studied using finite element method. The results showed that the tribological performance of studied surfaces under starved lubrication condition depended not only on the surface morphology but also on the structure of biomimetic units below surface (subsurface structure). The friction coefficient of biomimetic surface was effectively reduced by the concave unit depth, while the refined microstructure with higher hardness led to the much better wear resistance. In addition to lubricant reserving and wear debris trapping effect derived from the surface concave morphology, it was believed that the well-formed subsurface structure of biomimetic units could carry much heavy loads against tribopair, which enhanced the function of surface topography and resulted in complementary lubrication in the wear contact area. The uniform stress distribution on the entire biomimetic surface also played an important role in stabilizing the friction coefficient and reducing the wear cracks.

Geomorphological control on variably saturated hillslope hydrology and slope instability

USGS Publications Warehouse

Giuseppe, Formetta; Simoni, Silvia; Godt, Jonathan W.; Lu, Ning; Rigon, Riccardo

2016-01-01

In steep topography, the processes governing variably saturated subsurface hydrologic response and the interparticle stresses leading to shallow landslide initiation are physically linked. However, these processes are usually analyzed separately. Here, we take a combined approach, simultaneously analyzing the influence of topography on both hillslope hydrology and the effective stress fields within the hillslope itself. Clearly, runoff and saturated groundwater flow are dominated by gravity and, ultimately, by topography. Less clear is how landscape morphology influences flows in the vadose zone, where transient fluxes are usually taken to be vertical. We aim to assess and quantify the impact of topography on both saturated and unsaturated hillslope hydrology and its effects on shallow slope stability. Three real hillslope morphologies (concave, convex, and planar) are analyzed using a 3-D, physically based, distributed model coupled with a module for computation of the probability of failure, based on the infinite slope assumption. The results of the analyses, which included parameter uncertainty analysis of the results themselves, show that convex and planar slopes are more stable than concave slopes. Specifically, under the same initial, boundary, and infiltration conditions, the percentage of unstable areas ranges from 1.3% for the planar hillslope, 21% for convex, to a maximum value of 33% for the concave morphology. The results are supported by a sensitivity analysis carried out to examine the effect of initial conditions and rainfall intensity.

Development of the tongue coating analyzer based on concave grating monochrometer and virtual instrument

NASA Astrophysics Data System (ADS)

Ren, Zhong; Liu, Guodong; Zeng, Lvming; Huang, Zhen; Zeng, Wenping

2010-10-01

The tongue coating diagnosis is an important part in tongue diagnosis of traditional Chinese medicine (TCM).The change of the thickness and color of the tongue coating can reflect the pathological state for the patient. By observing the tongue coating, a Chinese doctor can determine the nature or severity of disease. Because some limitations existed in the tongue diagnosis method of TCM and the method based on the digital image processing, a novel tongue coating analyzer(TCA) based on the concave grating monochrometer and virtual instrument is developed in this paper. This analyzer consists of the light source system, check cavity, optical fiber probe, concave grating monochrometer, spectrum detector system based on CCD and data acquisition (DAQ) card, signal processing circuit system, computer and data analysis software based on LabVIEW, etc. Experimental results show that the novel TCA's spectral range can reach 300-1000 nm, its wavelength resolution can reach 1nm, and this TCA uses the back-split-light technology and multi-channel parallel analysis. Compared with the TCA based on the image processing technology, this TCA has many advantages, such as, compact volume, simpler algorithm, faster processing speed, higher accuracy, cheaper cost and real-time handle data and display the result, etc. Therefore, it has the greatly potential values in the fields of the tongue coating diagnosis for TCM.

Concave 1-norm group selection

PubMed Central

Jiang, Dingfeng; Huang, Jian

2015-01-01

Grouping structures arise naturally in many high-dimensional problems. Incorporation of such information can improve model fitting and variable selection. Existing group selection methods, such as the group Lasso, require correct membership. However, in practice it can be difficult to correctly specify group membership of all variables. Thus, it is important to develop group selection methods that are robust against group mis-specification. Also, it is desirable to select groups as well as individual variables in many applications. We propose a class of concave \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$1$\\end{document}-norm group penalties that is robust to grouping structure and can perform bi-level selection. A coordinate descent algorithm is developed to calculate solutions of the proposed group selection method. Theoretical convergence of the algorithm is proved under certain regularity conditions. Comparison with other methods suggests the proposed method is the most robust approach under membership mis-specification. Simulation studies and real data application indicate that the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$1$\\end{document}-norm concave group selection approach achieves better control of false discovery rates. An R package grppenalty implementing the proposed method is available at CRAN. PMID:25417206

Study on Dynamic Development of Three-dimensional Weld Pool Surface in Stationary GTAW

NASA Astrophysics Data System (ADS)

Huang, Jiankang; He, Jing; He, Xiaoying; Shi, Yu; Fan, Ding

2018-04-01

The weld pool contains abundant information about the welding process. In particular, the type of the weld pool surface shape, i. e., convex or concave, is determined by the weld penetration. To detect it, an innovative laser-vision-based sensing method is employed to observe the weld pool surface of the gas tungsten arc welding (GTAW). A low-power laser dots pattern is projected onto the entire weld pool surface. Its reflection is intercepted by a screen and captured by a camera. Then the dynamic development process of the weld pool surface can be detected. By observing and analyzing, the change of the reflected laser dots reflection pattern, for shape of the weld pool surface shape, was found to closely correlate to the penetration of weld pool in the welding process. A mathematical model was proposed to correlate the incident ray, reflected ray, screen and surface of weld pool based on structured laser specular reflection. The dynamic variation of the weld pool surface and its corresponding dots laser pattern were simulated and analyzed. By combining the experimental data and the mathematical analysis, the results show that the pattern of the reflected laser dots pattern is closely correlated to the development of weld pool, such as the weld penetration. The concavity of the pool surface was found to increase rapidly after the surface shape was changed from convex to concave during the stationary GTAW process.

Initial stage oxidation on nano-trenched Si(1 0 0) surface

NASA Astrophysics Data System (ADS)

Sun, Yu; Liu, Yi-Lun; Izumi, Satoshi; Chen, Xue-Feng; Zhai, Zhi; Tian, Shao-Hua

2018-01-01

As the size of an electronic element shrinks to nanoscale, trench design of Si strongly influences the performance of related semiconductor devices. By reactive force field molecular dynamics (ReaxFF MD) simulation, the initial stage oxidation on nano-trenched Si(1 0 0) angled 60°, 90°, 120°, 150° under temperatures from 300 K to 1200 K has been studied. Inhomogeneous oxidation at the convex-concave corners of the Si surface was observed. In general, the initial oxidation process on the Si surface was that, firstly, the O atoms ballistically transported into surface, then a high O concentration induced compressive stress at the surface layers, which prevented further oxidation. Compared to the concave corner, the convex one contacted a larger volume of oxygen at the very beginning stage, leading an anisotropic absorption of O atoms. Afterwards, a critical compression was produced at both the convex and concave corners to limit the oxidation. As a result, an inhomogeneous oxide film grew on nano-trenched Si. Meanwhile, due to enhanced O transport and compression relaxation by increasing temperature, the inhomogeneous oxidation was more obvious under 1200 K. These present results explained the observed experimental phenomena on the oxidation of non-planar Si and provided an aspect on the design of nano-trenched electronic components in the semiconductor field.

Concave Urinary Crystallines: Direct Evidence of Calcium Oxalate Crystals Dissolution by Citrate In Vivo

PubMed Central

Shang, Yun-Feng; Xu, Meng; Zhang, Guang-Na; Ouyang, Jian-Ming

2013-01-01

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K3cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118 mg/L after K3cit intake from 289 ± 83 mg/L before K3cit intake. After the amount of urinary citrate was increased, it complexed with Ca2+ ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K3cit intake. The mechanism of inhibition of formation of CaOx stones by K3cit was possibly due to the complexation of Ca2+ with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K3cit intake. PMID:24363634

Fabrication of agarose concave petridish for 3D-culture microarray method for spheroids formation of hepatic cells.

PubMed

Zhang, Binbin; Li, Yang; Wang, Gaoshang; Jia, Zhidong; Li, Haiyan; Peng, Qing; Gao, Yi

2018-04-19

Liver is one of the most important organ in the body. But there are many limitations about liver transplantation for liver failure. It is quite important to develop the xenogeneic biological liver for providing an alternation to transplantation or liver regeneration. In this paper, we proposed a method to construct a novel kind of agarose 3D-culture concave microwell array for spheroids formation of hepatic cells. Using the 3D printing method, the microwell array was fabricated with an overall size of 6.4 mm × 6.4 mm, containing 121 microwells with 400 μm width/400 μm thickness. By exploiting the Polydimethylsiloxane (PDMS) membranes as a bridge, we finally fabricated the agarose one. We co-cultured three types of liver cells with bionics design in the microwell arrays. Using the methods described above, the resulting co-formed hepatocyte spheroids maintained the high viability and stable liver-specific functions. This engineered agarose concave microwell array could be a potentially useful tool for forming the elements for biological liver support. After developing the complete system, we also would consider to scale up the application of this system. It will be not only applied to the therapy of human organ damage, but also to the development of disease models and drug screening models.

Carbon monoxide mass transfer for syngas fermentation in a stirred tank reactor with dual impeller configurations.

PubMed

Ungerman, Andrew J; Heindel, Theodore J

2007-01-01

This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding.

Fast response Fabry-Perot interferometer microfluidic refractive index fiber sensor based on concave-core photonic crystal fiber.

PubMed

Tian, Jiajun; Lu, Zejin; Quan, Mingran; Jiao, Yuzhu; Yao, Yong

2016-09-05

We report a fast response microfluidic Fabry-Perot (FP) interferometer refractive index (RI) fiber sensor based on a concave-core photonic crystal fiber (CPCF), which is formed by directly splicing a section CPCF with a section of single mode fiber. The CPCF is made by cleaving a section of multimode photonic crystal fiber with an axial tension. The shallow concave-core of CPCF naturally forms the FP cavity with a very short cavity length. The inherent large air holes in the cladding of CPCF are used as the open channels to let liquid sample come in and out of FP cavity. In order to shorten the liquid channel length and eliminate the harmful reflection from the outside end face of the CPCF, the CPCF is cleaved with a tilted tensile force. Due to the very small cavity capacity, the short length and the large sectional area of the microfluidic channels, the proposed sensor provides an easy-in and easy-out structure for liquids, leading to great decrement of the measuring time. The proposed sensor exhibits fast measuring speed, the measuring time is less than 359 and 23 ms for distilled water and pure ethanol, respectively. We also experimentally study and demonstrate the superior performances of the sensor in terms of high RI sensitivity, good linear response, low temperature cross-sensitivity and easy fabrication.

Chinese "Magic" Mirrors.

ERIC Educational Resources Information Center

Swinson, Derek B.

1992-01-01

Chinese "magic" mirrors are made from bronze with the front side a mirror and the reverse side a molded image. When light is reflected from the mirror,the image on the reverse side appears. Discusses reflections of conventional mirrors, possible explanations for the magic mirror phenomenon, and applications of the phenomenon to…

Plasma confinement apparatus using solenoidal and mirror coils

DOEpatents

Fowler, T. Kenneth; Condit, William C.

1979-01-01

A plasma confinement apparatus, wherein multiple magnetic mirror cells are linked by magnetic field lines inside of a solenoid with the mirroring regions for adjacent magnetic mirror cells each formed by a separate mirror coil inside of the solenoid. The magnetic mirror cells may be field reversed.

Mirror Metrology Using Nano-Probe Supports

NASA Technical Reports Server (NTRS)

Robinson, David; Hong, Maoling; Byron, Glenn; McClelland, Ryan; Chan, Kai-Wing

2012-01-01

Thin, lightweight mirrors are needed for future x-ray space telescopes in order to increase x-ray collecting area while maintaining a reduced mass and volume capable of being launched on existing rockets. However, it is very difficult to determine the undistorted shape of such thin mirrors because the mounting of the mirror during measurement causes distortion. Traditional kinematic mounts have insufficient supports to control the distortion to measurable levels and prevent the mirror from vibrating during measurement. Over-constrained mounts (non-kinematic) result in an unknown force state causing mirror distortion that cannot be determined or analytically removed. In order to measure flexible mirrors, it is necessary to over-constrain the mirror. Over-constraint causes unknown distortions to be applied to the mirror. Even if a kinematic constraint system can be used, necessary imperfections in the kinematic assumption can lead to an unknown force state capable of distorting the mirror. Previously, thicker, stiffer, and heavier mirrors were used to achieve low optical figure distortion. These mirrors could be measured to an acceptable level of precision using traditional kinematic mounts. As lighter weight precision optics have developed, systems such as the whiffle tree or hydraulic supports have been used to provide additional mounting supports while maintaining the kinematic assumption. The purpose of this invention is to over-constrain a mirror for optical measurement without causing unacceptable or unknown distortions. The invention uses force gauges capable of measuring 1/10,000 of a Newton attached to nano-actuators to support a thin x-ray optic with known and controlled forces to allow for figure measurement and knowledge of the undeformed mirror figure. The mirror is hung from strings such that it is minimally distorted and in a known force state. However, the hanging mirror cannot be measured because it is both swinging and vibrating. In order to stabilize the mirror for measurement, nano-probes support the mirror, causing the mirror to be over-constrained.

Compact Reflective Imaging Spectrometer Design Utilizing An Immersed Grating And Anamorphic Mirror

DOEpatents

Lerner, Scott A.

2006-01-10

A compact imaging spectrometer comprising an entrance slit, an anamorphic mirror, a grating, and a detector array. The entrance slit directs light to the anamorphic mirror. The anamorphic mirror receives the light and directs the light to the grating. The grating receives the light from the anamorphic mirror and defracts the light back onto the anamorphic mirror. The anamorphic mirror focuses the light onto a detector array.

Analysis on influence of installation error of off-axis three-mirror optical system on imaging line-of-sight

NASA Astrophysics Data System (ADS)

Gao, Lingyu; Li, Xinghua; Guo, Qianrui; Quan, Jing; Hu, Zhengyue; Su, Zhikun; Zhang, Dong; Liu, Peilu; Li, Haopeng

2018-01-01

The internal structure of off-axis three-mirror system is commonly complex. The mirror installation error in assembly always affects the imaging line-of-sight and further degrades the image quality. Due to the complexity of the optical path in off-axis three-mirror optical system, the straightforward theoretical analysis on the variations of imaging line-of-sight is extremely difficult. In order to simplify the theoretical analysis, an equivalent single-mirror system is proposed and presented in this paper. In addition, the mathematical model of single-mirror system is established and the accurate expressions of imaging coordinate are derived. Utilizing the simulation software ZEMAX, off-axis three-mirror model and single-mirror model are both established. By adjusting the position of mirror and simulating the line-of-sight rotation of optical system, the variations of imaging coordinates are clearly observed. The final simulation results include: in off-axis three-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is approximately 30 um/″; in single-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is 31.5 um/″. Compared to the simulation results of the off-axis three-mirror model, the 5% relative error of single-mirror model analysis highly satisfies the requirement of equivalent analysis and also verifies its validity. This paper presents a new method to analyze the installation error of the mirror in the off-axis three-mirror system influencing on the imaging line-of-sight. Moreover, the off-axis three-mirror model is totally equivalent to the single-mirror model in theoretical analysis.

On-orbit solar calibrations using the Aqua Clouds and Earth's Radiant Energy System (CERES) in-flight calibration system

NASA Astrophysics Data System (ADS)

Wilson, Robert S.; Priestley, Kory J.; Thomas, Susan; Hess, Phillip

2009-08-01

The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometers were used to measure earth-reflected solar and earth-emitted longwave radiances, at satellite altitude. The bolometers measured the earth radiances in the broadband shortwave solar (0.3 - 5.0 micrometers) and total (0.3->100 micrometers) spectral bands as well as in the (8 - 12 micrometers) water vapor window spectral band over geographical footprints as small as 10 kilometers at nadir. In May 2002, the fourth and fifth sets of CERES bolometers were launched aboard the Aqua spacecraft. Ground vacuum calibrations defined the initial count conversion coefficients that were used to convert the bolometer output voltages into filtered earth radiances. The mirror attenuator mosaic (MAM), a solar diffuser plate, was built into the CERES instrument package calibration system in order to define in-orbit shifts or drifts in the sensor responses. The shortwave and total sensors are calibrated using the solar radiances reflected from the MAM's. Each MAM consists of baffle-solar diffuser plate systems, which guide incoming solar radiances into the instrument fields-of-view of the shortwave and total wave sensor units. The MAM diffuser reflecting type surface consists of an array of spherical aluminum mirror segments, which are separated by a Merck Black A absorbing surface, overcoated with silicon dioxide. Temperature sensors are located in each MAM plate and baffle. The CERES MAM wass designed to yield calibration precisions approaching .5 percent for the total and shortwave detectors. In this paper, the MAM solar calibration procedures are presented along with on-orbit results. Comparisons are also made between the Aqua,Terra and the Tropical Rainfall Measurement Mission (TRMM) CERES MAM solar calibrations.

Self-focusing of a high current density ion beam extracted with concave electrodes in a low energy region around 150 eV.

PubMed

Hirano, Y; Kiyama, S; Koguchi, H; Sakakita, H

2014-02-01

Spontaneous self-focusing of ion beam with high current density (Jc ∼ 2 mA/cm(2), Ib ∼ 65 mA) in low energy region (∼150 eV) is observed in a hydrogen ion beam extracted from an ordinary bucket type ion source with three electrodes having concave shape (acceleration, deceleration, and grounded electrodes). The focusing appears abruptly in the beam energy region over ∼135-150 eV, and the Jc jumps up from 0.7 to 2 mA/cm(2). Simultaneously a strong electron flow also appears in the beam region. The electron flow has almost the same current density. Probably these electrons compensate the ion space charge and suppress the beam divergence.

Towards a portable Raman spectrometer using a concave grating and a time-gated CMOS SPAD.

PubMed

Li, Zhiyun; Deen, M Jamal

2014-07-28

A low-cost, compact Raman spectrometer suitable for the on-line water monitoring applications is explored. A custom-designed concave grating for wavelength selection was fabricated and tested. The detection of the Raman signal is accomplished with a time-gated single photon avalanche diode (TG-SPAD). A fixed gate window of 3.5ns is designed and applied to the TG-SPAD. The temporal resolution of the SPAD was ~60ps when tested with a 7ps, 532nm solid-state laser. To test the efficiency of the gating in fluorescence signal suppression, different detection windows (3ns-0.25ns) within the 3.5ns gate window are used to measure the Raman spectra of Rhodamine B. Strong Raman peaks are resolved with this low-cost system.

Nonlinear characterization of a single-axis acoustic levitator

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

Andrade, Marco A. B.; Ramos, Tiago S.; Okina, Fábio T. A.

2014-04-15

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jumpmore » phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.« less

Method and apparatuses for ion cyclotron spectrometry

DOEpatents

Dahl, David A [Idaho Falls, ID; Scott, Jill R [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

2012-03-06

An ion cyclotron spectrometer may include a vacuum chamber that extends at least along a z-axis and means for producing a magnetic field within the vacuum chamber so that a magnetic field vector is generally parallel to the z-axis. The ion cyclotron spectrometer may also include means for producing a trapping electric field within the vacuum chamber. The trapping electric field may comprise a field potential that, when taken in cross-section along the z-axis, includes at least one section that is concave down and at least one section that is concave up so that ions traversing the field potential experience a net magnetron effect on a cyclotron frequency of the ions that is substantially equal to zero. Other apparatuses and a method for performing ion cyclotron spectrometry are also disclosed herein.

Diffusion accessibility as a method for visualizing macromolecular surface geometry.

PubMed

Tsai, Yingssu; Holton, Thomas; Yeates, Todd O

2015-10-01

Important three-dimensional spatial features such as depth and surface concavity can be difficult to convey clearly in the context of two-dimensional images. In the area of macromolecular visualization, the computer graphics technique of ray-tracing can be helpful, but further techniques for emphasizing surface concavity can give clearer perceptions of depth. The notion of diffusion accessibility is well-suited for emphasizing such features of macromolecular surfaces, but a method for calculating diffusion accessibility has not been made widely available. Here we make available a web-based platform that performs the necessary calculation by solving the Laplace equation for steady state diffusion, and produces scripts for visualization that emphasize surface depth by coloring according to diffusion accessibility. The URL is http://services.mbi.ucla.edu/DiffAcc/. © 2015 The Protein Society.

Piling-to-buckling transition in the drying process of polymer solution drop on substrate having a large contact angle.

PubMed

Kajiya, Tadashi; Nishitani, Eisuke; Yamaue, Tatsuya; Doi, Masao

2006-01-01

We studied the drying process of polymer solution drops placed on a substrate having a large contact angle with the drop. The drying process takes place in three stages. First, the droplet evaporates keeping the contact line fixed. Second, the droplet shrinks uniformly with receding contact line. Finally the contact line is pinned again, and the droplet starts to be deformed. The shape of the final polymer deposit changes from concave dot, to flat dot, and then to concave dot again with the increase of the initial polymer concentration. This shape change is caused by the gradual transition from the solute piling mechanism proposed by Deegan to the crust buckling mechanism proposed by de Gennes and Pauchard.

Five-year results after valve replacement with the Björk-Shiley 70 degrees convexo-concave prosthesis.

PubMed

Koldsland, S; Svennevig, J L; Abdelnoor, M; Aas, H; Semb, G

1992-01-01

In the 18 months up to July 1983, 120 Björk-Shiley convexo-concave prostheses with 70 degrees opening angle were implanted in 47 women and 61 men aged 19-78 (mean 58.6) years. The prosthetic valves were aortic in 65 cases, mitral in 23 and both aortic and mitral in 20 cases. Emergency operation was required in ten cases, and concomitant surgery was performed in 43 (39.8%). The early mortality was 5.5%. A follow-up study, comprising 498 patient years, revealed 73.1% 5-year survival. There were three mechanical failures of prosthesis, in one of which re-replacement was successful. Elective prosthesis replacement was performed in four other cases judged to be at high risk of strut fracture.

Combustor for a low-emissions gas turbine engine

DOEpatents

Glezer, Boris; Greenwood, Stuart A.; Dutta, Partha; Moon, Hee-Koo

2000-01-01

Many government entities regulated emission from gas turbine engines including CO. CO production is generally reduced when CO reacts with excess oxygen at elevated temperatures to form CO2. Many manufactures use film cooling of a combustor liner adjacent to a combustion zone to increase durability of the combustion liner. Film cooling quenches reactions of CO with excess oxygen to form CO2. Cooling the combustor liner on a cold side (backside) away from the combustion zone reduces quenching. Furthermore, placing a plurality of concavities on the cold side enhances the cooling of the combustor liner. Concavities result in very little pressure reduction such that air used to cool the combustor liner may also be used in the combustion zone. An expandable combustor housing maintains a predetermined distance between the combustor housing and combustor liner.

Hartley and Itokawa: small comet and asteroid with similar morphologies and structures

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2011-10-01

" Orbits ma ke s tructures " [1-3]. This three-word sentence means that as all cosmic bodies moves in non-circular keplerian orbits they all are subjected to an action of inertia -gravity warping waves. These waves arise in bodies as a result of periodically changing accelerations causing inertia-gravity forces. These forces are absorbed by bodies masses and make them to warp. This warping is smoothed by gravity making globular shapes of the larger bodies. But smaller bodies with rather weak gravity keep their warped shapes. The wave nature warping happens in four interfering direct ions (ortho - and diagonal) and in various wavelengths. The fundamental wave 1 long 2π R makes ubiquitous tectonic dichotomy: an oppos ition of the uplifted segment-hemisphere and the subsided one. For small bodies a result of this is in their convexo-concave shape [3] (Fig. 1-7). The uplifted bulging segment expands and is breaking by cracks, faults, rifts. The opposed subsided concave segment contracts. As a result in the middle of an oblong body is formed a narrow thoroughly squeezed and degassed portion - a neck or waist (wringed out wet linen). Subsequently here at a weakened place could happen a break - formation of binaries, polycomponental bodies, satellites. Figures 1 to 4 show development stages of small bodies leading to a full separation of two parts. Traces of warping waves of four directions are often seen on surfaces of many celestial bodies as cross -cutting lineations. A recent example of the small core of the Hartley 2 comet (2 km long) is very impressive. At received points of view are clearly seen at least three ortho- and diagonal lineations often marked by small outgassing craters (Fig. 1). Crossing lineations produce square forms (craters ) earlier s een on the Eros ' s urface. Wave comp res s ion lineations make the Hart ley 2 t o appear as a wafer ca ke. A " wa is t" (neck) is formed as a res ult of nearing a concave depression, from one side, and deep cracks at the convex bulge, from the antipodean side (Fig. 5). The smaller rocky asteroid Itokawa (0.5 km long, Fig. 2) is surprisingly similar in shape and structure to the icy core of Hart ley. It is also bent and rich in cross-cutting lineations o 4 direct ions marked by small holes-craters. But here they are ext inct and lack of gas -dust jets. One sees a transition from a volat ile rich comet core to an ext inct mostly rocky mass - asteroid. In both cases (comet core and as teroid) in the middle develops a smooth "wais t". The bulged convex and antipodal concave segments -hemispheres in rotating bodies require somewhat different densities of composing them masses to equilibrate angular momentum of two halves (compare with the Ea rth's hemis pheres : the eas tern continental "granitic" and wes tern Pacific "bas altic"). The near-IR images of two asteroids (Fig.6-7) confirm this. The concave and convex s ides are co mpos itionally d ifferent. In the Eros ' cas e the concave s ide is rich er in pyroxene, thus denser.

Impedance Matched to Vacuum, Invisible Edge, Diffraction Suppressed Mirror

NASA Technical Reports Server (NTRS)

Hagopian, John G. (Inventor); Roman, Patrick A. (Inventor); Shiri, Sharham (Inventor); Wollack, Edward J. (Inventor)

2015-01-01

Diffraction suppressed mirrors having an invisible edge are disclosed for incident light at both targeted wavelengths and broadband incident light. The mirrors have a first having at least one discontiguous portion having a plurality of nanostructured apertures. The discontiguous mirror portion impedance matches a relatively high impedance portion of the mirror to a relatively low impedance portion of the mirror, thereby reducing the diffraction edge effect otherwise present in a conventional mirror.

Study Of Pre-Shaped Membrane Mirrors And Electrostatic Mirrors With Nonlinear-Optical Correction

DTIC Science & Technology

2002-01-01

mirrors have been manufactured of glass-like material Zerodur with very low coefficient of linear expansion. They have a more light cellular construction...primary and flat secondary mirrors are both segmented ones. In the case of the primary mirror made of traditional materials such as Zerodur or fused...FINAL REPORT ISTC Project #2103p “Study of Pre-Shaped Membrane Mirrors and Electrostatic Mirrors with Nonlinear-Optical Correction” Manager

Mirror-Image Equivalence and Interhemispheric Mirror-Image Reversal

PubMed Central

Corballis, Michael C.

2018-01-01

Mirror-image confusions are common, especially in children and in some cases of neurological impairment. They can be a special impediment in activities such as reading and writing directional scripts, where mirror-image patterns (such as b and d) must be distinguished. Treating mirror images as equivalent, though, can also be adaptive in the natural world, which carries no systematic left-right bias and where the same object or event can appear in opposite viewpoints. Mirror-image equivalence and confusion are natural consequences of a bilaterally symmetrical brain. In the course of learning, mirror-image equivalence may be established through a process of symmetrization, achieved through homotopic interhemispheric exchange in the formation of memory circuits. Such circuits would not distinguish between mirror images. Learning to discriminate mirror-image discriminations may depend either on existing brain asymmetries, or on extensive learning overriding the symmetrization process. The balance between mirror-image equivalence and mirror-image discrimination may nevertheless be precarious, with spontaneous confusions or reversals, such as mirror writing, sometimes appearing naturally or as a manifestation of conditions like dyslexia. PMID:29706878

Mirror-Image Equivalence and Interhemispheric Mirror-Image Reversal.

PubMed

Corballis, Michael C

2018-01-01

Mirror-image confusions are common, especially in children and in some cases of neurological impairment. They can be a special impediment in activities such as reading and writing directional scripts, where mirror-image patterns (such as b and d ) must be distinguished. Treating mirror images as equivalent, though, can also be adaptive in the natural world, which carries no systematic left-right bias and where the same object or event can appear in opposite viewpoints. Mirror-image equivalence and confusion are natural consequences of a bilaterally symmetrical brain. In the course of learning, mirror-image equivalence may be established through a process of symmetrization, achieved through homotopic interhemispheric exchange in the formation of memory circuits. Such circuits would not distinguish between mirror images. Learning to discriminate mirror-image discriminations may depend either on existing brain asymmetries, or on extensive learning overriding the symmetrization process. The balance between mirror-image equivalence and mirror-image discrimination may nevertheless be precarious, with spontaneous confusions or reversals, such as mirror writing, sometimes appearing naturally or as a manifestation of conditions like dyslexia.

Being "Secondary" is Important for a Webb Telescope Mirror

NASA Image and Video Library

2017-12-08

NASA release July 19, 2011 Click here to learn about the James Webb Space Telescope The secondary mirror (shown here) was polished at the L3 Integrated Optical Systems - Tinsley in Richmond, Calif. to accuracies of less than one millionth of an inch. That accuracy is important for forming the sharpest images when the mirrors cool to -400°F (-240°C) in the cold of space. The Webb's secondary mirror was recently completed, following polishing and gold-coating. "Secondary" may not sound as important as "primary" but when it comes to the next-generation James Webb Space Telescope a secondary mirror plays a critical role in ensuring the telescope gathers information from the cosmos. The Webb's secondary mirror was recently completed, following polishing and gold-coating. There are four different types of mirrors that will fly on the James Webb Space Telescope, and all are made of a light metal called beryllium. It is very strong for its weight and holds its shape across a range of temperatures. There are primary mirror segments (18 total that combined make the large primary mirror providing a collecting area of 25 meters squared/269.1 square feet), the secondary mirror, tertiary mirror and the fine steering mirror. Unlike the primary mirror, which is molded into the shape of a hexagon, the secondary mirror is perfectly rounded. The mirror is also convex, so the reflective surface bulges toward a light source. It looks much like a curved mirror that you'll see on the wall near the exit of a parking garage that lets motorists see around a corner. This mirror is coated with a microscopic layer of gold to enable it to efficiently reflect infrared light (which is what the Webb telescope's cameras see). The quality of the secondary mirror surface is so good that the final convex surface at cold temperatures does not deviate from the design by more than a few millionths of a millimeter - or about one ten thousandth the diameter of a human hair. "As the only convex mirror on the Webb telescope, the secondary mirror has always been recognized to be the hardest of all of the mirrors to polish and test, so we are delighted that its performance meets all specifications," said Lee Feinberg, Webb Optical Telescope manager at NASA's Goddard Space Flight Center in Greenbelt, Md. Convex mirrors are particularly hard to test because light that strikes them diverges away from the mirror. Feinberg noted, "The Webb telescope convex secondary mirror is approximately the size of the Spitzer Space Telescope's primary mirror and is by far the largest convex cryogenic mirror ever built for a NASA program." It was data from the Spitzer's mirrors that helped make the decision to use beryllium for the Webb telescope mirrors. Spitzer's mirrors were also made of beryllium. So why is this mirror so critical? Because the secondary mirror captures light from the 18 primary mirror segments and relays those distant images of the cosmos to the telescope's science cameras. The secondary mirror is mounted on folding "arms" that position it in front of the 18 primary mirror segments. The secondary mirror will soon come to NASA's Goddard Space Flight Center in Greenbelt, Md. where it will be installed on the telescope structure. Then, as a complete unit, the telescope structure and mirrors will undergo acoustic and vibration testing. The secondary mirror was developed at Ball Aerospace & Technology Corp. of Boulder, Colo. and the mirror recently completed polishing at the L3–IOS-Tinsley facility in Richmond, Calif. Northrop Grumman space Systems is the prime contractor on the Webb telescope program. The James Webb Space Telescope is the world’s next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, Webb will observe the most distant objects in the universe, provide images of the very first galaxies ever formed and see unexplored planets around distant stars. The Webb Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency. Credit:NASA/Ball Aerospace/Tinsley NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram