MOS CCDs for the Wide Field Imager on the XEUS Spacecraft
- A. D. Holl; C. Castelli A; I Hutchinson A; D. R. Smith A; J. Calafell A; P. Pool B; D. Burt B; R. Ambrosi C; M. French D
In recent years the XEUS mission concept has evolved and has been the subject of several industrial studies. The mission concept has now matured to the point that it could be proposed for a Phase A study and subsequent flight programme. The key feature of XEUS will be its X-ray optic with collecting area ~30-100x that of XMM. The mission is envisaged at an orbit around the L2 point in space, and is formed from two spacecraft; one for the mirrors, and the other for the focal plane detectors. With a focal length of 50m, the plate scale of the...
Development/Plasticity/Repair Neuronal Pentraxins Mediate Synaptic Refinement in the Developing Visual System
- Lisa Bjartmar; Andrew D. Huberman; Erik M. Ullian; René C. Rentería; Xiaoqin Liu; Weifeng Xu; Jennifer Prezioso; Michael W. Susman; David Stellwagen; Caleb C. Stokes; Richard Cho; Paul Worley; Robert C. Malenka; Sherry Ball; Neal S. Peachey; David Copenhagen; Barbara Chapman; Masaru Nakamoto; Ben A. Barres; Mark S. Perin
Neuronal pentraxins (NPs) define a family of proteins that are homologous to C-reactive and acute-phase proteins in the immune system and have been hypothesized to be involved in activity-dependent synaptic plasticity. To investigate the role of NPs in vivo, we generated mice that lack one, two, or all three NPs. NP1/2 knock-out mice exhibited defects in the segregation of eye-specific retinal ganglion cell (RGC) projections to the dorsal lateral geniculate nucleus, a process that involves activity-dependent synapse formation and elimination. Retinas from mice lacking NP1 and NP2 had cholinergically driven waves of activity that occurred at a frequency similar to...
Strain and Temperature Sensors Using Multimode Optical Fiber Bragg Gratings and Correlation Signal Processing
- Jirapong Lim; Qingping Yang; Barry E. Jones; Phillip R. Jackson
Abstract—Multimode fiber optic Bragg grating sensors for strain and temperature measurements using correlation signal processing methods have been developed. Two multimode Bragg grating sensors were fabricated in 62/125 m graded-index silica multimode fiber; the first sensor was produced by the holographic method and the second sensor by the phase mask technique. The sensors have signal reflectivity of approximately 35 % at peak wavelengths of 835 nm and 859 nm, respectively. Strain testing of both sensors has been done from 0 to 1000 and the temperature testing from 40 to 80 C. Strain and temperature sensitivity values are 0.55 pm and...
SINGLE SHOT LONGITUDINAL BUNCH PROFILE MEASUREMENTS BY TEMPORALLY RESOLVED ELECTRO-OPTICAL DETECTION
For the high gain operation of a SASE FEL, extremely short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of FLASH at DESY, we have installed an electrooptic measurement system to probe the time structure of the electric field of single ~100 fs electron bunches. In this technique, the field induced birefringence in an electro-optic crystal is encoded on a chirped picosecond laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single shot cross correlation with a 35 fs laser pulse using...
Acousto-optic modulation in a microstructured plastic optical fibre Bragg
- L. Bilro A; C. A. F. Marques A; L. Khan B; R. A. Oliveira C; D. J. Webb B; R. N. Nogueira A
The present work addresses the control of the mPOF Bragg grating spectrum properties through acousto-optic modulation. For the first time, the interaction of a flexural acoustic wave, generated by longitudinal excitation of different frequencies, with the Bragg grating will be presented. Also it will be demonstrated the quasi linear relationship between PZT load and maximum reflected power / 3dB bandwidth of the reflected spectrum.
Structural Health Monitoring: Practical
- Bragg Gratings; T. H. T. Chan
This paper describes the development of FBG Optical sensors for their practical application on structural health monitoring. The sensors were installed on the Tsing Ma Bridge for a trial run. The results using FBG sensors were in excellent agreement with those acquired by the bridge WASHMS. Introduction. Previous research works have shown that FBG sensors have several inherent advantages over conventional electrical sensors such as small size, light weight, non-conductivity, fast response, resistance to corrosion, higher temperature capability, and immunity to electromagnetic noise and ratio frequency interferences. The distinct advantages of FBG sensors over other types of fiber optic sensors...
Preserved in a Mouse Model of Autosomal Dominant Optic Atrophy
- Georgia Perganta; Alun R. Barnard; Christiana Katti; Athanasios Vachtsevanos; Ron H. Douglas; Robert E. Maclaren; Marcela Votruba; Sumathi Sekaran
Copyright & reuse City University London has developed City Research Online so that its users may access the research outputs of City University London's staff. Copyright © and Moral Rights for this paper are retained by the individual author(s) and / or other copyright holders. All material in City Research Online is checked for eligibility for copyright before being made available in the live archive. URLs from City Research Online may be freely distributed and linked to from other web pages. Versions of research The version in City Research Online may differ from the final published version. Users are advised...
- Jianfeng Li; Tomonori Hu; Stuart D. Jackson
A diode-cladding-pumped dual wavelength Q-switched Ho3-doped fluoride cascade fiber laser operating in the mid-infrared is demonstrated. Stable pulse trains from the 5I6 → 5I7 and 5I7 → 5I8 laser transitions were produced, and the μs-level time delay between the pulses from each transition was dependent on the pump power. At maximum pump power and at an acousto-optic modulator repetition rate of 25 kHz, the 5I6 → 5I7 transition pulse operated at 3.005 μm, a pulse energy of 29 μJ, and a pulse width of 380 ns; the 5I7 → 5I8 transition pulse correspondingly produced 7 μJ pulse energy and 260...
Measurements of stress-optic coefficient in polymer optical
- Marcin K. Szczurowski; Tadeusz Martynkien; Gabriela Statkiewicz-barabach; Waclaw Urbanczyk; Lutful Khan; David J. Webb
Analysis of Powder Samples using Combined X-ray Diffraction/X-ray Fluorescence
- X-ray Diffraction/x-ray Fluorescence; Amir Intisar; Amir Intisar; Amir Intisar
This work describes the design, development and testing of a portable charge-coupled device detector system to be used for the simultaneous collection of X-ray diffraction and X-ray fluorescence data from powdered samples. The detector was designed for both terrestrial and extra-terrestrial applications that require in-situ analysis of samples, where access to a laboratory instrument is restricted. The detector system incorporates 4 e2v technologies CCD30-11 devices, employing multi-phase pinned technology for low noise operation. Geometrical calculations and thermal studies concerning the design of the detector are presented, with particular emphasis on motivations for the chosen geometry. Initial characterisation and calibration of...
Investigation of shock waves in explosive blasts using fibre optic
- S Watson; W N Macpherson; J S Barton; J D C Jones; A Tyas; A V Pichugin; A Hindle; C Dunare; T Stevenson
> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Acousto-optic Effect in microstructured Polymer Fiber Bragg Gratings: Simulation and Experimental Overview
- Carlos A. F. Marques; Lúcia Bilro; Lutful Kahn; Roberson A. Oliveira; David J. Webb; Rogério N. Nogueira
Abstract — A fine control of the microstructured polymer fiber Bragg grating spectrum properties, such as maximum reflected power and 3-dB bandwidth, through acousto-optic modulation is presented. For simulation purposes, the device is modelled as a single structure, comprising a silica horn and a fiber Bragg grating. For similar sized structures a good correlation between the numerical results and the experimental data is obtained, allowing the strain field to be completely characterized along the whole structure. It is also shown that the microstructured polymer fiber Bragg grating requires less effort from the piezoelectric actuator to produce modification in the grating...
Distributed temperature-change sensor based on Rayleigh backscattering in an optical fiber
- R. Rathod; R. D. Pechstedt; D. A. Jackson; D. J. Webb
A frequency-modulated continuous-wave technique is used to detect the presence of frequency shifts in the Rayleigh-backscattered light in a single-mode optical fiber as a result of a changing temperature. The system is able to detect a rate of temperature change of 0.014 K/s, when a 20-cm length of fiber is heated. The system is also able to demonstrate a spatial resolution of better than 15 cm. There is currently much interest in the development of fiber-optic-based distributed temperature sensors. The fiber itself is an excellent choice for the sensing element of a distributed temperature sensor because it is readily available...
The Indigo Algorithm
- Helen L. Anderson; Helen L. Anderson; Helen L. Anderson
When image processing techniques are applied to real images, differences in information content between the horizontal and vertical directions should be considered. The minimum spatial scale at which an algorithm can be applied isotropically is limited by the characteristics of the imaging system. Below that scale, threshold values used within algorithms are dependent on the orientation of a objects in a scene. The response of an electro-optic system has been described based on the ability of a human observer to detect changes in intensity. However, when the observer is a machine rather than a human, the size of the response...
- P. J. Rudd; B. Se; Andrew James
The transient electric birefringence method, i. e. the transient Kerr effect, has been employed to study the optical, electrical and geometrical properties of three macromolecular systems. An apparatus is described in which the birefringence could be measured when d. c. electric field pulses (of duration 1pA, s to 5s and strength up to 50 KV/cm) and a. c. electric field pulses (of duration greater than 5 ms, of frequency up to 20 kHz, and strength up to 3 KV/Cm) were applied to solutions of macromolecules. Both the linear and cluadratic optical systems have been employed to measure the induced birefringence....
149 Chapter 6 Well-Defined Liquid Crystal Gels from Telechelic Polymers
- Ring-opening Metathesis Polymerization; Click Chemistry
Well-defined liquid crystal networks with controlled molecular weight between crosslinks and crosslink functionality were prepared by “click ” crosslinking of telechelic polymers produced by ring-opening metathesis polymerization (ROMP). The networks readily swell in a small molecule liquid crystal, 5CB, to form LC gels with high swelling ratios. These gels exhibit fast, reversible, and low-threshold optic switching under applied electric fields when they are unconstrained between electrodes. For a given electric field, the LC gels prepared from shorter telechelic polymers showed a reduced degree of switching than their counterparts made from longer polymer strands. The reported approach provides control over important...
> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Two-section Fiber Optic Raman Polarizer
- Sergey Sergeyev; Sergei Popov
Abstract — We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Using the Stochastic Generator approach we have derived averaged equations to calculate polarization dependent gain and meansquare gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short standard fiber with properly chosen parameters and...
Antenna-Coupled mm- Wave Electro-Opt ic Modulators and Linearized Electro-Optic Modulators
- Finbar T. Sheehy; Finbar T. Sheehy; John Alphonsus Sheehy
my father, who believed in me though I did not, supported me when I did, and laughed with me at our "failures." Ave, atque Vale. I thank Professor William B. Bridges, my thesis advisor. During my time at Caltech he has provided me with much useful advice and many fascinating insights, in areas by no means limited to the work presented here. I have come to realize how fortunate I am to have had an advisor with a genuine interest in my personal as well as professional development, a man available to me as teacher, mentor and friend. I very...
Measurement of Thermo-Optic Properties of Thin Film Dielectric Coatings
- Gregory H. Ogin; Gregory H. Ogin
First and foremost, I would like to thank my parents for spending the last 30 years reinforcing the idea that my education is a top priority for them (and in turn instilling it as a top priority for me). Thanks to all the great teachers I’ve had, from elementary school through graduate school, for pushing me forward and putting up with my antics. Thanks to my great advisers at the University of St. Thomas, Los Alamos National Laboratory, and Caltech, who kept me going through the tough parts of research and truly set me up to succeed in the world...
19 Chapter 2 Liquid Crystalline Gels by
- Self-assembly Of Triblock
Liquid crystal (LC) gels are of interest for display applications and artificial muscles, but the methods for preparing LC networks are limited. Exploring novel approaches for synthesizing LC gels and elastomers can result in improved material properties and a better-defined network structure. Here, we explore the self-assembly of triblock copolymer to produce LC gels. The LC gels are produced by mixing a small molecule LC with an end-associating side-group liquid crystalline triblock copolymer. The resulting gels are thermoreversible, and they can be easily aligned to form uniform monodomains under shear or under external magnetic or electric fields. Electro-optic measurements demonstrate...