Establishing Age-Adjusted Reference Ranges for Iris-Related Parameters in Open Angle Eyes with Anterior Segment Optical Coherence Tomography.

PubMed

Peterson, Jeffrey R; Blieden, Lauren S; Chuang, Alice Z; Baker, Laura A; Rigi, Mohammed; Feldman, Robert M; Bell, Nicholas P

2016-01-01

Define criteria for iris-related parameters in an adult open angle population as measured with swept source Fourier domain anterior segment optical coherence tomography (ASOCT). Ninety-eight eyes of 98 participants with open angles were included and stratified into 5 age groups (18-35, 36-45, 46-55, 56-65, and 66-79 years). ASOCT scans with 3D mode angle analysis were taken with the CASIA SS-1000 (Tomey Corporation, Nagoya, Japan) and analyzed using the Anterior Chamber Analysis and Interpretation software. Anterior iris surface length (AISL), length of scleral spur landmark (SSL) to pupillary margin (SSL-to-PM), iris contour ratio (ICR = AISL/SSL-to-PM), pupil radius, radius of iris centroid (RICe), and iris volume were measured. Outcome variables were summarized for all eyes and age groups, and mean values among age groups were compared using one-way analysis of variance. Stepwise regression analysis was used to investigate demographic and ocular characteristic factors that affected each iris-related parameter. Mean (±SD) values were 2.24 mm (±0.46), 4.06 mm (±0.27), 3.65 mm (±0.48), 4.16 mm (±0.47), 1.14 (±0.04), 1.51 mm2 (±0.23), and 38.42 μL (±4.91) for pupillary radius, RICe, SSL-to-PM, AISL, ICR, iris cross-sectional area, and iris volume, respectively. Both pupillary radius (P = 0.002) and RICe (P = 0.027) decreased with age, while SSL-to-PM (P = 0.002) and AISL increased with age (P = 0.001). ICR (P = 0.54) and iris volume (P = 0.49) were not affected by age. This study establishes reference values for iris-related parameters in an adult open angle population, which will be useful for future studies examining the role of iris changes in pathologic states.

Theory of a Traveling Wave Feed for a Planar Slot Array Antenna

NASA Technical Reports Server (NTRS)

Rengarajan, Sembiam

2012-01-01

Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside. The traveling wave planar slot array consists of a long feed waveguide containing resonant-centered inclined coupling slots in the broad wall, coupling power into an array of stacked radiating waveguides orthogonal to it. The radiating waveguides consist of longitudinal offset radiating slots in a standing wave configuration. For the traveling wave feed of a planar slot array, one has to design the tilt angle and length of each coupling slot such that the amplitude and phase of excitation of each radiating waveguide are close to the desired values. The coupling slot spacing is chosen for an appropriate beam squint. Scattering matrix parameters of resonant coupling slots are used in the design process to produce appropriate excitations of radiating waveguides with constraints placed only on amplitudes. Since the radiating slots in each radiating waveguide are designed to produce a certain total admittance, the scattering (S) matrix of each coupling slot is reduced to a 2x2 matrix. Elements of each 2x2 S-matrix and the amount of coupling into the corresponding radiating waveguide are expressed in terms of the element S11. S matrices are converted into transmission (T) matrices, and the T matrices are multiplied to cascade the coupling slots and waveguide sections, starting from the load end and proceeding towards the source. While the use of non-resonant coupling slots may provide an additional degree of freedom in the design, resonant coupling slots simplify the design process. The amplitude of the wave going to the load is set at unity. The S11 parameter, r of the coupling slot closest to the load, is assigned an arbitrary value. A larger value of r will reduce the power dissipated in the load while increasing the reflection coefficient at the input port. It is now possible to obtain the excitation of the radiating waveguide closest to the load and the coefficients of the wave incident and reflected at the input port of this coupling slot. The next coupling slot parameter, r , is chosen to realize the excitation of that radiating waveguide. One continues this process moving towards the source, until all the coupling slot parameters r and hence the S11 parameter of the 4-port coupler, r, are known for each coupling slot. The goal is to produce the desired array aperture distribution in the feed direction. From an interpolation of the computed moment method data for the slot parameters, all the coupling slot tilt angles and lengths are obtained. From the excitations of the radiating waveguides computed from the coupling values, radiating slot parameters may be obtained so as to attain the desired total normalized slot admittances. This process yields the radiating slot parameters, offsets, and lengths. The design is repeated by choosing different values of r for the last coupling slot until the percentage of power dissipated in the load and the input reflection coefficient values are satisfactory. Numerical results computed for the radiation pattern, the tilt angles and lengths of coupling slots, and excitation phases of the radiating waveguides, are presented for an array with uniform amplitude excitation. The design process has been validated using computer simulations. This design procedure is valid for non-uniform amplitude excitations as well.

LOADED WAVEGUIDES

DOEpatents

Mullett, L.B.; Loach, B.G.; Adams, G.L.

1958-06-24

>Loaded waveguides are described for the propagation of electromagnetic waves with reduced phase velocities. A rectangular waveguide is dimensioned so as to cut-off the simple H/sub 01/ mode at the operating frequency. The waveguide is capacitance loaded, so as to reduce the phase velocity of the transmitted wave, by connecting an electrical conductor between directly opposite points in the major median plane on the narrower pair of waveguide walls. This conductor may take a corrugated shape or be an aperature member, the important factor being that the electrical length of the conductor is greater than one-half wavelength at the operating frequency. Prepared for the Second U.N. International ConferThe importance of nuclear standards is duscussed. A brief review of the international callaboration in this field is given. The proposal is made to let the International Organization for Standardization (ISO) coordinate the efforts from other groups. (W.D.M.)

Dielectric loaded surface plasmon waveguides for datacom applications

NASA Astrophysics Data System (ADS)

Weeber, J.-C.; Hassan, K.; Nielsen, M. G.; Pitilakis, A.; Tsilipakos, O.; Kriezis, E. E.; Fatome, J.; Finot, C.; Markey, L.; Albrektsen, O.; Bozhevolnyi, S. I.; Dereux, A.

2012-04-01

We rst report on design, fabrication and characterizations of thermally-controlled plasmonic routers relying on the interference of a plasmonic and a photonic mode supported by wide enough dielectric loaded waveguides. We show that, by owing a current through the gold lm on which the dielectric waveguides are deposited, the length of the beating created by the interference of the two modes can be controlled accurately. By operating such a plasmonic dual-mode interferometer switch, symmetric extinction ratio of 7dB are obtained at the output ports of a 2x2 router. Next, we demonstrate ber-to-ber characterizations of stand-alone dielectric loaded surface plasmon waveguide (DLSPPW) devices by using grating couplers. The couplers are comprised of dielectric loaded gratings with carefully chosen periods and duty-cycles close to 0.5. We show that insertion loss below 10dB per coupler can be achieved with optimized gratings. This coupling scheme is used to operate Bit-Error-Rate (BER) measurements for the transmission of a 10Gbits/s signal along a stand-alone straight DLSPPW. We show in particular that these waveguides introduce a rather small BER power penalty (below 1dB) demonstrating the suitability of this plasmonic waveguiding platform for high-bit rate transmission.

Photonic Waveguide Choke Joint with Absorptive Loading

NASA Technical Reports Server (NTRS)

Wollack, Edward J. (Inventor); U-Yen, Kongpop (Inventor); Chuss, David T. (Inventor)

2016-01-01

A photonic waveguide choke includes a first waveguide flange member having periodic metal tiling pillars, a dissipative dielectric material positioned within an area between the periodic metal tiling pillars and a second waveguide flange member disposed to be coupled with the first waveguide flange member and in spaced-apart relationship separated by a gap. The first waveguide flange member has a substantially smooth surface, and the second waveguide flange member has an array of two-dimensional pillar structures formed therein.

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

DOE PAGES

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; ...

2017-09-06

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). One part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on themore » beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. Thus, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. Additonally, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.« less

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

NASA Astrophysics Data System (ADS)

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; Longtin, Jon

2017-09-01

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). A part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on the beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. As a result, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. In addition, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.

Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

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

Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan

Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). One part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on themore » beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. Thus, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. Additonally, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.« less

IRIS Toxicological Review of 2-Hexanone (Interagency Science Discussion Draft)

EPA Science Inventory

On September 25, 2009, the IRIS Summary and Toxicological Review of 2-hexanone was finalized and loaded onto the IRIS database. The Toxicological Review of 2-hexanone was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external peer revie...

Differences in iris thickness among African Americans, Caucasian Americans, Hispanic Americans, Chinese Americans, and Filipino-Americans.

PubMed

Lee, Roland Y; Huang, Guofu; Porco, Travis C; Chen, Yi-Chun; He, Mingguang; Lin, Shan C

2013-12-01

To evaluate the capability of iris thickness parameters to explain the difference in primary angle-closure glaucoma prevalence among the different racial groups. In this prospective study, 436 patients with open and narrow angles that met inclusion criteria were consecutively recruited from the UCSF general ophthalmology and glaucoma clinics to receive anterior segment optical coherence tomography imaging under standardized dark conditions. Images from 11 patients were removed due to poor visibility of the scleral spurs and the remaining images were analyzed using the Zhongshan Angle Assessment Program to assess the following measurements for the nasal and temporal angle of the anterior chamber: iris thickness at 750 and 2000 μm from the scleral spurs and the maximum iris thickness at middle one third of the iris. Iris thickness parameters were compared among and within the following 5 different racial groups: African Americans, Caucasian Americans, Hispanic Americans, Chinese Americans, and Filipino-Americans. In comparing iris parameters among the open-angle racial groups, significant differences were found for nasal iris thickness at 750 and 2000 μm from the scleral spurs in which Chinese Americans displayed the highest mean value (P=0.01, P<0.0001). Among the narrow-angle racial groups, significant difference was found for nasal iris thickness at 2000 μm from the scleral in which Chinese Americans showed the highest mean value (P<0.0001). Significant difference was also found for temporal maximum iris thickness at middle one third of the iris in which African Americans exhibited the highest mean value (P=0.021). Iris thickness was modeled as a function of angle status using linear mixed-effects regression, adjusting for age, sex, pupil diameter, spherical equivalent, ethnicity, and the use of both eyes in patients. The iris thickness difference between the narrow-angle and open-angle groups was significant (P=0.0007). Racial groups that historically showed higher prevalence of primary angle-closure glaucoma possess thicker irides.

IRIS Toxicological Review of 1,2,3-trichloropropane (Interagency Science Discussion Draft)

EPA Science Inventory

On September 30, 2009, the IRIS Summary and Toxicological Review of 1,2,3-trichloropropane (TCP) was finalized and loaded onto the IRIS database. The Toxicological Review of TCP was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external...

Wavelength selection by dielectric-loaded plasmonic components

NASA Astrophysics Data System (ADS)

Holmgaard, Tobias; Chen, Zhuo; Bozhevolnyi, Sergey I.; Markey, Laurent; Dereux, Alain; Krasavin, Alexey V.; Zayats, Anatoly V.

2009-02-01

Fabrication, characterization, and modeling of waveguide-ring resonators and in-line Bragg gratings for wavelength selection in the telecommunication range are reported utilizing dielectric-loaded surface plasmon-polariton waveguides. The devices were fabricated by depositing subwavelength-sized polymer ridges on a smooth gold film using industrially compatible large-scale UV photolithography. We demonstrate efficient and compact wavelength-selective filters, including waveguide-ring resonators with an insertion loss of ˜2 dB and a footprint of only 150 μm2 featuring narrow bandwidth (˜20 nm) and high contrast (˜13 dB) features in the transmission spectrum. The performance of the components is found in good agreement with the results obtained by full vectorial three-dimensional finite element simulations.

Mycobacterial Antigen Driven Activation of CD14++CD16− Monocytes Is a Predictor of Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome

PubMed Central

Andrade, Bruno B.; Singh, Amrit; Narendran, Gopalan; Schechter, Melissa E.; Nayak, Kaustuv; Subramanian, Sudha; Anbalagan, Selvaraj; Jensen, Stig M. R.; Porter, Brian O.; Antonelli, Lis R.; Wilkinson, Katalin A.; Wilkinson, Robert J.; Meintjes, Graeme; van der Plas, Helen; Follmann, Dean; Barber, Daniel L.; Swaminathan, Soumya; Sher, Alan; Sereti, Irini

2014-01-01

Paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is an aberrant inflammatory response occurring in a subset of TB-HIV co-infected patients initiating anti-retroviral therapy (ART). Here, we examined monocyte activation by prospectively quantitating pro-inflammatory plasma markers and monocyte subsets in TB-HIV co-infected patients from a South Indian cohort at baseline and following ART initiation at the time of IRIS, or at equivalent time points in non-IRIS controls. Pro-inflammatory biomarkers of innate and myeloid cell activation were increased in plasma of IRIS patients pre-ART and at the time of IRIS; this association was confirmed in a second cohort in South Africa. Increased expression of these markers correlated with elevated antigen load as measured by higher sputum culture grade and shorter duration of anti-TB therapy. Phenotypic analysis revealed the frequency of CD14++CD16− monocytes was an independent predictor of TB-IRIS, and was closely associated with plasma levels of CRP, TNF, IL-6 and tissue factor during IRIS. In addition, production of inflammatory cytokines by monocytes was higher in IRIS patients compared to controls pre-ART. These data point to a major role of mycobacterial antigen load and myeloid cell hyperactivation in the pathogenesis of TB-IRIS, and implicate monocytes and monocyte-derived cytokines as potential targets for TB-IRIS prevention or treatment. PMID:25275318

Fiber-coupled dielectric-loaded plasmonic waveguides.

PubMed

Gosciniak, Jacek; Volkov, Valentyn S; Bozhevolnyi, Sergey I; Markey, Laurent; Massenot, Sébastien; Dereux, Alain

2010-03-01

Fiber in- and out-coupling of radiation guided by dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) is realized using intermediate tapered dielectric waveguides. The waveguide structures fabricated by large-scale UV-lithography consist of 1-microm-thick polymer ridges tapered from 10-microm-wide ridges deposited directly on a magnesium fluoride substrate to 1-microm-wide ridges placed on a 50-nm-thick and 100-microm-wide gold stripe. Using fiber-to-fiber transmission measurements at telecom wavelengths, the performance of straight and bent DLSPPWs is characterized demonstrating the overall insertion loss below 24 dB, half of which is attributed to the DLSPPW loss of propagation over the 100-microm-long distance.

Radio frequency (RF) microwave components and subsystems using loaded ridge waveguide

DOEpatents

Kang, Yoon W.

2013-08-20

A waveguide having a non-conductive material with a high permeability (.mu., .mu..sub.r for relative permeability) and/or a high permittivity (.di-elect cons., .di-elect cons..sub.r for relative permittivity) positioned within a housing. When compared to a hollow waveguide, the waveguide of this invention, reduces waveguide dimensions by .varies..mu. ##EQU00001## The waveguide of this invention further includes ridges which further reduce the size and increases the usable frequency bandwidth.

Low-loss bloch wave guiding in open structures and highly compact efficient waveguide-crossing arrays

DOEpatents

Popovic, Milos

2011-03-08

Low-loss waveguide structures may comprise a multimode waveguide supporting a periodic light intensity pattern, and attachments disposed at the waveguide adjacent low-intensity regions of the light intensity pattern.

Efficient extraction of high power THz radiation generated by an ultra-relativistic electron beam in a dielectric loaded waveguide

DOE PAGES

Antipov, S.; Baryshev, S. V.; Kostin, R.; ...

2016-10-03

Here, we have measured an intense THz radiation produced by a sub-picosecond, relativistic electron bunch in a dielectric loaded waveguide. For efficient THz pulse extraction, the dielectric loaded waveguide end was cut at an angle. For an appropriate choice of angle cut, such antenna converts the TM 01 mode excited in the waveguide into a free-space fundamental Gauss-Hermite mode propagating at an angle with respect to the electron beam trajectory. Simulations show that more than 95% of energy can be extracted using such a simple approach. More than 40 oscillations of about 170 ps long 0.48 THz signal were explicitlymore » measured with an interferometer and 10 μJ of energy per pulse, as determined with a calorimetric energy meter, were delivered outside the electron beamline to an area suitable for THz experiments.« less

A high frequency analysis of electromagnetic plane wave scattering by perfectly-conducting semi-infinite parallel plate and rectangular waveguides with absorber coated inner walls

NASA Technical Reports Server (NTRS)

Noh, H. M.; Pathak, P. H.

1986-01-01

An approximate but sufficiently accurate high frequency solution which combines the uniform geometrical theory of diffraction (UTD) and the aperture integration (AI) method is developed for analyzing the problem of electromagnetic (EM) plane wave scattering by an open-ended, perfectly-conducting, semi-infinite hollow rectangular waveguide (or duct) with a thin, uniform layer of lossy or absorbing material on its inner wall, and with a planar termination inside. In addition, a high frequency solution for the EM scattering by a two dimensional (2-D), semi-infinite parallel plate waveguide with a absorber coating on the inner walls is also developed as a first step before analyzing the open-ended semi-infinite three dimensional (3-D) rectangular waveguide geometry. The total field scattered by the semi-infinite waveguide consists firstly of the fields scattered from the edges of the aperture at the open-end, and secondly of the fields which are coupled into the waveguide from the open-end and then reflected back from the interior termination to radiate out of the open-end. The first contribution to the scattered field can be found directly via the UTD ray method. The second contribution is found via the AI method which employs rays to describe the fields in the aperture that arrive there after reflecting from the interior termination. It is assumed that the direction of the incident plane wave and the direction of observation lie well inside the forward half space tht exists outside the half space containing the semi-infinite waveguide geometry. Also, the medium exterior to the waveguide is assumed to be free space.

IRIS: Supporting & Managing the Research Life-Cycle

ERIC Educational Resources Information Center

Bollini, Andrea; Mennielli, Michele; Mornati, Susanna; Palmer, David T.

2016-01-01

IRIS is a new Current Research Information System (CRIS) developed by Cineca to upgrade and replace two previous solutions that have been used by Italian universities in the last 10 years. At the end of 2015, sixty-three Italian institutions are using IRIS. One of the main components of IRIS is DSpace-CRIS, an open source solution that can also be…

Waveguide module comprising a first plate with a waveguide channel and a second plate with a raised portion in which a sealing layer is forced into the waveguide channel by the raised portion

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

Strassner, II, Bernd H.; Liedtke, Richard; McDonald, Jacob Jeremiah

The various technologies presented herein relate to utilizing a sealing layer of malleable material to seal gaps, etc., at a joint between edges of a waveguide channel formed in a first plate and a surface of a clamping plate. A compression pad is included in the surface of the clamping plate and is dimensioned such that the upper surface of the pad is less than the area of the waveguide channel opening on the first plate. The sealing layer is placed between the waveguide plate and the clamping plate, and during assembly of the waveguide module, the compression pad deformsmore » a portion of the sealing layer such that it ingresses into the waveguide channel opening. Deformation of the sealing layer results in the gaps, etc., to be filled, improving the operational integrity of the joint.« less

HMSIW-based switchable units using super compact loaded shunt stubs and its applications on SIW/HMSIW switches

NASA Astrophysics Data System (ADS)

Chen, Haidong; Che, Wenquan; Zhang, Tianyu; Cao, Yue; Feng, Wenjie

2018-06-01

Half-mode substrate integrated waveguide (HMSIW) switchable unit, built by HMSIW section with loaded single or multi-microstrip shunt stub(s), was proposed in this work. Both shorted and opened stubs were studied, investigated and compared, bandwidth enhancement method for proposed switchable units was proposed and demonstrated. Based on these switchable units, narrowband and broadband HMSIW single-pole-single-through (SPST) switches, SIW SPST switch and SIW/HMSIW-based single-pole-double-through (SPDT) switch were designed, fabricated and measured. Good performances were observed experimentally for these proposed circuits, showing the advantages of proposed concept and an excellent candidate for switchable or reconfigurable SIW/HMSIW circuits or systems.

HyspIRI Low Latency Concept and Benchmarks

NASA Technical Reports Server (NTRS)

Mandl, Dan

2010-01-01

Topics include HyspIRI low latency data ops concept, HyspIRI data flow, ongoing efforts, experiment with Web Coverage Processing Service (WCPS) approach to injecting new algorithms into SensorWeb, low fidelity HyspIRI IPM testbed, compute cloud testbed, open cloud testbed environment, Global Lambda Integrated Facility (GLIF) and OCC collaboration with Starlight, delay tolerant network (DTN) protocol benchmarking, and EO-1 configuration for preliminary DTN prototype.

The numerical-analytical implementation of the cross-sections method to the open waveguide transition of the "horn" type

NASA Astrophysics Data System (ADS)

Divakov, Dmitriy; Malykh, Mikhail; Sevastianov, Leonid; Sevastianov, Anton; Tiutiunnik, Anastasiia

2017-04-01

In the paper we construct a method for approximate solution of the waveguide problem for guided modes of an open irregular waveguide transition. The method is based on straightening of the curved waveguide boundaries by introducing new variables and applying the Kantorovich method to the problem formulated in the new variables to get a system of ordinary second-order differential equations. In the method, the boundary conditions are formulated by analogy with the partial radiation conditions in the similar problem for closed waveguide transitions. The method is implemented in the symbolic-numeric form using the Maple computer algebra system. The coefficient matrices of the system of differential equations and boundary conditions are calculated symbolically, and then the obtained boundary-value problem is solved numerically using the finite difference method. The chosen coordinate functions of Kantorovich expansions provide good conditionality of the coefficient matrices. The numerical experiment simulating the propagation of guided modes in the open waveguide transition confirms the validity of the method proposed to solve the problem.

Open-ended half-mode substrate integrated waveguide sensor with ground flange for complex permittivity measurement

USDA-ARS?s Scientific Manuscript database

A novel open-ended half-mode substrate integrated waveguide (HMSIW) sensor with ground flange for measuring complex permittivity of liquids, semisolids, and granular and particulate materials is presented. The open-ended HMSIW is designed and fabricated on FR4 substrate. The ground flange was custo...

IRIS Toxicological Review of 2-Hexanone (Interagency ...

EPA Pesticide Factsheets

On September 25, 2009, the IRIS Summary and Toxicological Review of 2-hexanone was finalized and loaded onto the IRIS database. The Toxicological Review of 2-hexanone was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external peer reviewers, and by the public. In the new IRIS process, introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices will be made publicly available. Accordingly, interagency comments and the interagency draft of the 2-hexanone IRIS assessment are posted on this site. The draft Toxicological Review of 2-hexanone provides scientific support and rationale for the hazard identification and dose-response assessment pertaining to chronic exposure to 2-hexanone.

IRIS Toxicological Review of 1,2,3-trichloropropane ...

EPA Pesticide Factsheets

On September 30, 2009, the IRIS Summary and Toxicological Review of 1,2,3-trichloropropane (TCP) was finalized and loaded onto the IRIS database. The Toxicological Review of TCP was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external peer reviewers, and by the public. In the new IRIS process, introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices will be made publicly available. Accordingly, interagency comments and the interagency draft of the TCP IRIS assessment are posted on this site. This Tox Review provides scientific support and rationale for the hazard and dose-response assessment pertaining to chronic exposure to 1,2,3-trichloropropane.

DIELECTRIC-LOADED WAVE-GUIDES

DOEpatents

Robertson-Shersby-Harvie, R.B.; Mullett, L.B.

1957-04-23

This patent presents a particular arrangement for delectric loading of a wave-guide carrying an electromagnetic wave in the E or TM mode of at least the second order, to reduce the power dissipated as the result of conduction loss in the wave-guide walls. To achieve this desirabie result, the effective dielectric constants in the radial direction of adjacent coaxial tubular regions bounded approximateiy by successive nodai surfaces within the electromagnetic field are of two different values alternating in the radial direction, the intermost and outermost regions being of the lower value, and the dielectric constants between nodes are uniform.

Dielectric-loaded plasmonic waveguide in the visible spectral range

NASA Astrophysics Data System (ADS)

Melentiev, P. N.; Kuzin, A. A.; Balykin, V. I.; Ignatov, A. I.; Merzlikin, A. M.

2017-12-01

Dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) are a practically valuable type of plasmonic waveguide. The properties of DLSPPWs at telecommunication wavelengths have been studied in detail. However, the efficient optical excitation of DLSPPWs in the visible spectral range has still not been realized. In this work, we present the results of our experimental investigations of DLSPPWs in the visible spectral range. In addition, a new configuration for the excitation and detection of the DLSPPW mode has been proposed and realized. The propagation of plasmon wave up to a distance of 45 µm in the DLSPPW has been demonstrated.

Open transverse-slot substrate-integrated waveguide sensor for biomass permittivity determination

USDA-ARS?s Scientific Manuscript database

A novel open transverse-slot substrate-integrated waveguide sensor is presented. The sensor is designed and fabricated for dielectric poperties measurements on sawdust at 8 GHz. Different configurations of the sensor were investigated by using simulation software and relationships between the simula...

A coupled modal-finite element method for the wave propagation modeling in irregular open waveguides.

PubMed

Pelat, Adrien; Felix, Simon; Pagneux, Vincent

2011-03-01

In modeling the wave propagation within a street canyon, particular attention must be paid to the description of both the multiple reflections of the wave on the building facades and the radiation in the free space above the street. The street canyon being considered as an open waveguide with a discontinuously varying cross-section, a coupled modal-finite element formulation is proposed to solve the three-dimensional wave equation within. The originally open configuration-the street canyon open in the sky above-is artificially turned into a close waveguiding structure by using perfectly matched layers that truncate the infinite sky without introducing numerical reflection. Then the eigenmodes of the resulting waveguide are determined by a finite element method computation in the cross-section. The eigensolutions can finally be used in a multimodal formulation of the wave propagation along the canyon, given its geometry and the end conditions at its extremities: initial field condition at the entrance and radiation condition at the output. © 2011 Acoustical Society of America

PLATEAU IRIS--DIAGNOSIS AND TREATMENT.

PubMed

Stefan, Cornel; Iliescu, Daniela Adriana; Batras, Mehdi; Timaru, Cristina Mihaela; De Simone, Algerino

2015-01-01

The objective of our study was to review the current knowledge on the diagnosis and treatment options of plateau iris configuration and syndrome. Relevant publications on plateau iris that were published until 2014. Plateau iris syndrome is a form of primary angle closure glaucoma caused by a large or anteriorly positioned ciliary body that leads to mechanical obstruction of trabecular meshwork. This condition is most often found in younger patients. Plateau iris has been considered an abnormal anatomic variant of the iris that can be diagnosed on ultrasound biomicroscopy or optical coherence tomography of anterior segment. Patients with plateau iris syndrome can be recognized by the lack of response in angle opening after iridotomy. The treatment of choice in these cases is argon laser peripheral iridoplasty.

Compact waveguide power divider with multiple isolated outputs

DOEpatents

Moeller, Charles P.

1987-01-01

A waveguide power divider (10) for splitting electromagnetic microwave power and directionally coupling the divided power includes an input waveguide (21) and reduced height output waveguides (23) interconnected by axial slots (22) and matched loads (25) and (26) positioned at the unused ends of input and output guides (21) and (23) respectively. The axial slots are of a length such that the wave in the input waveguide (21) is directionally coupled to the output waveguides (23). The widths of input guide (21) and output guides (23) are equal and the width of axial slots (22) is one half of the width of the input guide (21).

A New User Interface for On-Demand Customizable Data Products for Sensors in a SensorWeb

NASA Technical Reports Server (NTRS)

Mandl, Daniel; Cappelaere, Pat; Frye, Stuart; Sohlberg, Rob; Ly, Vuong; Chien, Steve; Sullivan, Don

2011-01-01

A SensorWeb is a set of sensors, which can consist of ground, airborne and space-based sensors interoperating in an automated or autonomous collaborative manner. The NASA SensorWeb toolbox, developed at NASA/GSFC in collaboration with NASA/JPL, NASA/Ames and other partners, is a set of software and standards that (1) enables users to create virtual private networks of sensors over open networks; (2) provides the capability to orchestrate their actions; (3) provides the capability to customize the output data products and (4) enables automated delivery of the data products to the users desktop. A recent addition to the SensorWeb Toolbox is a new user interface, together with web services co-resident with the sensors, to enable rapid creation, loading and execution of new algorithms for processing sensor data. The web service along with the user interface follows the Open Geospatial Consortium (OGC) standard called Web Coverage Processing Service (WCPS). This presentation will detail the prototype that was built and how the WCPS was tested against a HyspIRI flight testbed and an elastic computation cloud on the ground with EO-1 data. HyspIRI is a future NASA decadal mission. The elastic computation cloud stores EO-1 data and runs software similar to Amazon online shopping.

Pigment dispersion syndrome and pigmentary glaucoma--a major review.

PubMed

Niyadurupola, Nuwan; Broadway, David C

2008-12-01

Pigment dispersion syndrome (PDS) is an interesting condition that can lead to secondary open angle glaucoma. Pigmentary glaucoma is primarily a disease of young people, myopes and men. PDS is characterized by the presence of Krukenberg spindles, iris trans-illumination defects, trabecular meshwork pigmentation and backward bowing of the iris. Posterior bowing of the iris causes rubbing of the pigmented iris epithelium against lens structures, liberation of pigment and trabecular meshwork changes that result in reduced aqueous outflow with the risk of glaucoma. Peripheral laser iridotomy can reverse backward bowing of the iris and may prevent progression of pigmentary glaucoma.

IRIS Bimonthly Public Meeting (Apr 2014)

EPA Pesticide Factsheets

EPA hosted a public meeting/webinar to provide an opportunity for the public to give input and participate in an open discussion regarding several IRIS chemical assessments for Diethyl Phthalate (DEP) and Hexabromocyclododecane (HBCD).

PLATEAU IRIS – DIAGNOSIS AND TREATMENT

PubMed Central

Stefan, Cornel; Iliescu, Daniela Adriana; Batras, Mehdi; Timaru, Cristina Mihaela; De Simone, Algerino

2015-01-01

Objectives: The objective of our study was to review the current knowledge on the diagnosis and treatment options of plateau iris configuration and syndrome. Systematic review methodology: Relevant publications on plateau iris that were published until 2014. Conclusions: Plateau iris syndrome is a form of primary angle closure glaucoma caused by a large or anteriorly positioned ciliary body that leads to mechanical obstruction of trabecular meshwork. This condition is most often found in younger patients. Plateau iris has been considered an abnormal anatomic variant of the iris that can be diagnosed on ultrasound biomicroscopy or optical coherence tomography of anterior segment. Patients with plateau iris syndrome can be recognized by the lack of response in angle opening after iridotomy. The treatment of choice in these cases is argon laser peripheral iridoplasty PMID:27373109

IRIS Toxicological Review of Cerium Oxide and Cerium ...

EPA Pesticide Factsheets

On September 29, 2009, the IRIS Summary and Toxicological Review of Cerium Oxide and Cerium Compounds was finalized and loaded onto the IRIS database. The Toxicological Review of Cerium Oxide and Cerium Compounds was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external peer reviewers, and by the public. In the new IRIS process, introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices will be made publicly available. Accordingly, interagency comments and the interagency draft of the Cerium Oxide and Cerium Compounds IRIS assessment are posted on this site. The draft Toxicological Review of Cerium Oxide and Cerium Compounds provides scientific support and rationale for the hazard identification and dose-response assessment pertaining to chronic exposure to cerium oxide and cerium compounds.

Microfabricated Waveguide Atom Traps.

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

Jau, Yuan-Yu

A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading coldmore » atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.« less

Endogenous ethylene does not regulate opening of unstressed Iris flowers but strongly inhibits it in water-stressed flowers.

PubMed

Çelikel, Fisun G; van Doorn, Wouter G

2012-09-15

The floral buds of Iris flowers (Iris x hollandica) are enclosed by two sheath leaves. Flower opening depends on lifting the flower up to a position whereby the tepals can move laterally. This upward movement is carried out by elongation of the subtending pedicel and ovary. In the pedicels and ovaries of unstressed control flowers, the concentration of ACC (1-aminocyclopropane-1-carboxylic acid) and the rate of ethylene production increased during d 0-1 of flower opening, and then decreased. Exposure to ≥200 nL L(-1) ethylene for 24 h at 20°C inhibited elongation of the pedicel+ovary, and inhibited flower opening. However, pulsing of unstressed flowers with solutions containing inhibitors of ethylene synthesis (AOA, AVG), or an inhibitor of ethylene action (STS), did not affect pedicel+ovary elongation or flower opening. When the flowers were dehydrated for 2 d at 20°C and 60% RH, they did not open when subsequently placed in water, and showed inhibited elongation in the pedicel+ovary. This dehydration treatment resulted in elevated pedicel+ovary ACC levels and in increased ethylene production. Treatment with STS prevented the increase in ACC levels and ethylene production, overcame the effect of dehydration on elongation of the pedicel+ovary, and resulted in full flower opening. It is concluded that flower opening in unstressed Iris flowers is not regulated by endogenous ethylene. An increase in endogenous ethylene above normal levels during stress, by contrast, strongly inhibited flower opening, due to its inhibitory effect on elongation of the pedicel+ovary. Copyright © 2012 Elsevier GmbH. All rights reserved.

Electromagnetic scattering from a class of open-ended waveguide discontinuities

NASA Technical Reports Server (NTRS)

Altintas, A.; Pathak, P. H.; Burnside, Walter D.

1986-01-01

A relatively simple high frequency analysis of electromagnetic scattering from a class of open-ended waveguide discontinuites was developed. The waveguides are composed of perfectly-conducting sections in which the electromagnetic field can be written as the sum of waveguide modes. Junctions are formed at the open end and also within interior regions where different sections are joined. The reflection and transmission properties of each junction are described in terms of a scattering matrix which is determined by combining the modal ray picture with high frequency techniques such as the Geometrical Theory of Diffraction (GTD), the Equivalent Current Method (ECM), and modifications of the Physical Theory of Diffraction (PTD). A new set of equivalent circuits are employed in this ECM analysis which leads to a simple treatment of many types of junction discontinuities. Also, a new procedure is presented to improve the efficiency of the aperture integration at the open end which is required in the PTD procedure for finding the fields radiated from (or coupled to) the open end. Once the scattering matrices are determined, they are then combined using a self-consistent multiple scattering method to obtain the total scattered fields.

Biolayer modeling and optimization for the SPARROW biosensor

NASA Astrophysics Data System (ADS)

Feng, Ke

2007-12-01

Biosensor direct detection of molecular binding events is of significant interest in applications from molecular screening for cancer drug design to bioagent detection for homeland security and defense. The Stacked Planar Affinity Regulated Resonant Optical Waveguide (SPARROW) structure based on coupled waveguides was recently developed to achieve increased sensitivity within a fieldable biosensor device configuration. Under ideal operating conditions, modification of the effective propagation constant of the structure's sensing waveguide through selective attachment of specific targets to probes on the waveguide surface results in a change in the coupling characteristics of the guide over a specifically designed interaction length with the analyte. Monitoring the relative power in each waveguide after interaction enables 'recognition' of those targets which have selectively bound to the surface. However, fabrication tolerances, waveguide interface roughness, biolayer surface roughness and biolayer partial coverage have an effect on biosensor behavior and achievable limit of detection (LOD). In addition to these influences which play a role in device optimization, the influence of the spatially random surface loading of molecular binding events has to be considered, especially for low surface coverage. In this dissertation an analytic model is established for the SPARROW biosensor which accounts for these nonidealities with which the design of the biosensor can be guided and optimized. For the idealized case of uniform waveguide transducer layers and biolayer, both theoretical simulation (analytical expression) and computer simulation (numerical calculation) are completed. For the nonideal case of an inhomogeneous transducer with nonideal waveguide and biolayer surfaces, device output power is affected by such physical influences as surface scattering, coupling length, absorption, and percent coverage of binding events. Using grating and perturbation techniques we explore the influence of imperfect surfaces and random surface loading on scattering loss and coupling length. Results provide a range of achievable limits of detection in the SPARROW device for a given target size, surface loading, and detectable optical power.

A new phase-correlation-based iris matching for degraded images.

PubMed

Krichen, Emine; Garcia-Salicetti, Sonia; Dorizzi, Bernadette

2009-08-01

In this paper, we present a new phase-correlation-based iris matching approach in order to deal with degradations in iris images due to unconstrained acquisition procedures. Our matching system is a fusion of global and local Gabor phase-correlation schemes. The main originality of our local approach is that we do not only consider the correlation peak amplitudes but also their locations in different regions of the images. Results on several degraded databases, namely, the CASIA-BIOSECURE and Iris Challenge Evaluation 2005 databases, show the improvement of our method compared to two available reference systems, Masek and Open Source for Iris (OSRIS), in verification mode.

Detection of Ionospheric Alfven Resonator Signatures Onboard C/NOFS: Implications for IRI Modeling

NASA Technical Reports Server (NTRS)

Simoes, F.; Klenzing, J.; Ivanov, S.; Pfaff, R.; Rowland, D.; Bilitza, D.

2011-01-01

The 2008-2009 long-lasting solar minimum activity has been the one of its kind since the dawn of space age, offering exceptional conditions for investigating space weather in the near-Earth environment. First ever detection of Ionospheric Alfven Resonator (IAR) signatures in orbit offers new means for investigating ionospheric electrodynamics, namely MHD (MagnetoHydroDynamics) wave propagation, aeronomy processes, ionospheric dynamics, and Sun-Earth connection mechanisms at a local scale. Local and global plasma density heterogeneities in the ionosphere and magnetosphere allow for formation of waveguides and resonators where magnetosonic and shear Alfven waves propagate. The ionospheric magnetosonic waveguide results from complete magnetosonic wave reflection about the ionospheric F-region peak, where the Alfven index of refraction presents a maximum. MHD waves can also be partially trapped in the vertical direction between the lower boundary of the ionosphere and the magnetosphere, a resonance mechanism known as IAR. In this work we present C/NOFS (Communications/Navigation Outage Forecasting System) Extremely Low Frequency (ELF) electric field measurements related to IAR signatures, discuss the resonance and wave propagation mechanisms in the ionosphere, and address the electromagnetic inverse problem from which electron/ion distributions can be derived. These peculiar IAR electric field measurements provide new, complementary methodologies for inferring ionospheric electron and ion density profiles, and also contribute for the investigation of ionosphere dynamics and space weather monitoring. Specifically, IAR spectral signatures measured by C/NOFS contribute for improving the International Reference Ionosphere (IRI) model, namely electron density and ion composition.

Integrated plasmonic semi-circular launcher for dielectric-loaded surface plasmon-polariton waveguide.

PubMed

Li, Xiaowei; Huang, Lingling; Tan, Qiaofeng; Bai, Benfeng; Jin, Guofan

2011-03-28

A semi-circular plasmonic launcher integrated with dielectric-loaded surface plasmon-polaritons waveguide (DLSPPW) is proposed and analyzed theoretically, which can focus and efficiently couple the excited surface plasmon polaritons (SPPs) into the DLSPPW via the highly matched spatial field distribution with the waveguide mode in the focal plane. By tuning the incident angle or polarization of the illuminating beam, it is shown that the launcher may be conveniently used as a switch or a multiplexer that have potential applications in plasmonic circuitry. Furthermore, from an applicational point of view, it is analyzed how the coupling performance of the launcher can be further improved by employing multiple semi-circular slits.

A folded waveguide ICRF antenna for PBX-M and TFTR

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Carter, M. D.; Fogelman, C. H.; Yugo, J. J.; Baity, F. W.; Bell, G. L.; Gardner, W. L.; Goulding, R. H.; Hoffman, D. J.; Ryan, P. M.; Swain, D. W.; Taylor, D. J.; Wilson, R.; Bernabei, S.; Kugel, H.; Ono, M.

1996-02-01

The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current-strap type antennas. These features are particularly beneficial for reactor-relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX-M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross-section that can be installed as either a fast wave (FW) or ion-Bernstein wave (IBW) launcher by 90° rotation. Two new features of the design are: a shorter quarter-wavelength resonator configuration and a rear-feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.

Carbon loaded Teflon (CLT): a power density meter for biological experiments using millimeter waves.

PubMed

Allen, Stewart J; Ross, James A

2007-01-01

The standard technique for measurement of millimeter wave fields utilizes an open-ended waveguide attached to a HP power meter. The alignment of the waveguide with the propagation (K) vector is critical to making accurate measurements. Using this technique, it is difficult and time consuming to make a detailed map of average incident power density over areas of biological interest and the spatial resolution of this instrument does not allow accurate measurements in non-uniform fields. For biological experiments, it is important to know the center field average incident power density and the distribution over the exposed area. Two 4 ft x 4 ft x 1/32 inch sheets of carbon loaded Teflon (CLT) (one 15% carbon and one 25% carbon) were procured and a series of tests to determine the usefulness of CLT in defining fields in the millimeter wavelength range was initiated. Since the CLT was to be used both in the laboratory, where the environment was well controlled, and in the field, where the environment could not be controlled, tests were made to determine effects of change in environmental conditions on ability to use CLT as a millimeter wave dosimeter. The empirical results of this study indicate CLT to be an effective dosimeter for biological experiments both in the laboratory and in the field.

Waveguide-mode polarization gaps in square spiral photonic crystals

NASA Astrophysics Data System (ADS)

Liu, Rong-Juan; John, Sajeev; Li, Zhi-Yuan

2015-09-01

We designed waveguide channels in two types of square spiral photonic crystals. Wide polarization gaps, in which only one circular polarization wave is allowed while the other counter-direction circular polarization wave is forbidden, can be opened up on the waveguide modes within the fundamental photonic band gap according to the calculation of band structures and transmission spectra. This phenomenon is ascribed to the chirality of the waveguide and is independent of the chirality of the background photonic crystal. Moreover, the transmission spectra show a good one-way property of the waveguide channels. The chiral quality factor demonstrates the handedness of the allowed and impeded chiral waveguide modes, and further proved the property of the waveguide-mode polarization gap. Such waveguides with waveguide-mode polarization gap are a good candidate for one-way waveguides with robust backscattering-immune transport.

Characterization of CMOS metal based dielectric loaded surface plasmon waveguides at telecom wavelengths.

PubMed

Weeber, J-C; Arocas, J; Heintz, O; Markey, L; Viarbitskaya, S; Colas-des-Francs, G; Hammani, K; Dereux, A; Hoessbacher, C; Koch, U; Leuthold, J; Rohracher, K; Giesecke, A L; Porschatis, C; Wahlbrink, T; Chmielak, B; Pleros, N; Tsiokos, D

2017-01-09

Dielectric loaded surface plasmon waveguides (DLSPPWs) comprised of polymer ridges deposited on top of CMOS compatible metal thin films are investigated at telecom wavelengths. We perform a direct comparison of the properties of copper (Cu), aluminum (Al), titanium nitride (TiN) and gold (Au) based waveguides by implementing the same plasmonic waveguiding configuration for each metal. The DLSPPWs are characterized by leakage radiation microscopy and a fiber-to-fiber configuration mimicking the cut-back method. We introduce the ohmic loss rate (OLR) to analyze quantitatively the properties of the CMOS metal based DLSPPWs relative to the corresponding Au based waveguides. We show that the Cu, Al and TiN based waveguides feature extra ohmic loss compared to Au of 0.027 dB/μm, 0.18 dB/μm and 0.52 dB/μm at 1550nm respectively. The dielectric function of each metal extracted from ellipsometric spectroscopic measurements is used to model the properties of the DLSP-PWs. We find a fairly good agreement between experimental and modeled DLSPPWs properties except for Al featuring a large surface roughness. Finally, we conclude that TiN based waveguides sustaining intermediate effective index (in the range 1.05-1.25) plasmon modes propagate over very short distances restricting the the use of those modes in practical situations.

Ordinal measures for iris recognition.

PubMed

Sun, Zhenan; Tan, Tieniu

2009-12-01

Images of a human iris contain rich texture information useful for identity authentication. A key and still open issue in iris recognition is how best to represent such textural information using a compact set of features (iris features). In this paper, we propose using ordinal measures for iris feature representation with the objective of characterizing qualitative relationships between iris regions rather than precise measurements of iris image structures. Such a representation may lose some image-specific information, but it achieves a good trade-off between distinctiveness and robustness. We show that ordinal measures are intrinsic features of iris patterns and largely invariant to illumination changes. Moreover, compactness and low computational complexity of ordinal measures enable highly efficient iris recognition. Ordinal measures are a general concept useful for image analysis and many variants can be derived for ordinal feature extraction. In this paper, we develop multilobe differential filters to compute ordinal measures with flexible intralobe and interlobe parameters such as location, scale, orientation, and distance. Experimental results on three public iris image databases demonstrate the effectiveness of the proposed ordinal feature models.

Iris: Constructing and Analyzing Spectral Energy Distributions with the Virtual Observatory

NASA Astrophysics Data System (ADS)

Laurino, O.; Budynkiewicz, J.; Busko, I.; Cresitello-Dittmar, M.; D'Abrusco, R.; Doe, S.; Evans, J.; Pevunova, O.

2014-05-01

We present Iris 2.0, the latest release of the Virtual Astronomical Observatory application for building and analyzing Spectral Energy Distributions (SEDs). With Iris, users may read in and display SEDs inspect and edit any selection of SED data, fit models to SEDs in arbitrary spectral ranges, and calculate confidence limits on best-fit parameters. SED data may be loaded into the application from VOTable and FITS files compliant with the International Virtual Observatoy Alliance interoperable data models, or retrieved directly from NED or the Italian Space Agency Science Data Center; data in non-standard formats may also be converted within the application. Users may seamlessy exchange data between Iris and other Virtual Observatoy tools using the Simple Application Messaging Protocol. Iris 2.0 also provides a tool for redshifting, interpolating, and measuring integratd fluxes, and allows simple aperture corrections for individual points and SED segments. Custom Python functions, template models and template libraries may be imported into Iris for fitting SEDs. Iris may be extended through Java plugins; users can install third-party packages, or develop their own plugin using Iris' Software Development Kit. Iris 2.0 is available for Linux and Mac OS X systems.

Planar waveguide nanolaser configured by dye-doped hybrid nanofilm on substrate

NASA Astrophysics Data System (ADS)

Tikhonov, E. A.; Yashchuk, V. P.; Telbiz, G. M.

2018-04-01

Dye-doped hybrid silicate/titanium nanofilms on the glass substrate structures of asymmetrical waveguides were studied by way of laser systems. The threshold, spatial and spectral features of the laser oscillation of genuine and hollow waveguides were determined. The pattern of stimulated radiation included two concurrent processes: single-mode waveguide lasing and lateral small divergence emission. Comparison of the open angle of the lateral beams and grazing angles of the waveguide lasing mode provides an insight into the effect of leaky mode emission followed by Lummer-Gehrcke interference.

IRIS Bimonthly Public Meeting (Jun 2014)

EPA Pesticide Factsheets

On June 25-27, 2014, EPA hosted a public meeting/webinar, to provide an opportunity for the public to give input and participate in an open discussion regarding several IRIS chemical assessments of Hexavalent Chromium (Cr(VI)) and Inorganic Arsenic (iAs).

Modal, ray, and beam techniques for analyzing the EM scattering by open-ended waveguide cavities

NASA Technical Reports Server (NTRS)

Pathak, Prabhakar H.; Burkholder, Robert J.

1989-01-01

The problem of high-frequency electromagnetic (EM) scattering by open-ended waveguide cavities with an interior termination is analyzed via three different approaches. When cavities can be adequately modeled by joining together piecewise separable waveguide sections, a hybrid combination of asymptotic high-frequency and modal techniques is employed. In the case of more arbitrarily shaped waveguide cavities for which modes cannot even be defined in the conventional sense, the geometrical optics ray approach proves to be highly useful. However, at sufficiently high frequencies, both of these approaches tend to become inefficient. Hence, a paraxial Gaussian batch technique, which retains much of the simplicity of the ray approximation but is potentially more efficient, is investigated. Typical numerical results based on the different approaches are discussed.

Dielectric Covered Planar Antennas at Submillimeter Wavelengths for Terahertz Imaging

NASA Technical Reports Server (NTRS)

Chattopadhyay, Goutam; Gill, John J.; Skalare, Anders; Lee, Choonsup; Llombart, Nuria; Siegel, Peter H.

2011-01-01

Most optical systems require antennas with directive patterns. This means that the physical area of the antenna will be large in terms of the wavelength. When non-cooled systems are used, the losses of microstrip or coplanar waveguide lines impede the use of standard patch or slot antennas for a large number of elements in a phased array format. Traditionally, this problem has been solved by using silicon lenses. However, if an array of such highly directive antennas is to be used for imaging applications, the fabrication of many closely spaced lenses becomes a problem. Moreover, planar antennas are usually fed by microstrip or coplanar waveguides while the mixer or the detector elements (usually Schottky diodes) are coupled in a waveguide environment. The coupling between the antenna and the detector/ mixer can be a fabrication challenge in an imaging array at submillimeter wavelengths. Antennas excited by a waveguide (TE10) mode makes use of dielectric superlayers to increase the directivity. These antennas create a kind of Fabry- Perot cavity between the ground plane and the first layer of dielectric. In reality, the antenna operates as a leaky wave mode where a leaky wave pole propagates along the cavity while it radiates. Thanks to this pole, the directivity of a small antenna is considerably enhanced. The antenna consists of a waveguide feed, which can be coupled to a mixer or detector such as a Schottky diode via a standard probe design. The waveguide is loaded with a double-slot iris to perform an impedance match and to suppress undesired modes that can propagate on the cavity. On top of the slot there is an air cavity and on top, a small portion of a hemispherical lens. The fractional bandwidth of such antennas is around 10 percent, which is good enough for heterodyne imaging applications.The new geometry makes use of a silicon lens instead of dielectric quarter wavelength substrates. This design presents several advantages when used in the submillimeter-wave and terahertz bands: a) Antenna fabrication compatible with lithographic techniques. b) Much simpler fabrication of the lens. c) A simple quarter-wavelength matching layer of the lens will be more efficient if a smaller portion of the lens is used. d) The directivity is given by the lens diameter instead of the leaky pole (the bandwidth will not depend anymore on the directivity but just on the initial cavity). The feed is a standard waveguide, which is compatible with proven Schottky diode mixer/detector technologies. The development of such technology will benefit applications where submillimeter- wave heterodyne array designs are required. The main fields are national security, planetary exploration, and biomedicine. For national security, wideband submillimeter radars could be an effective tool for the standoff detection of hidden weapons or bombs concealed by clothing or packaging. In the field of planetary exploration, wideband submillimeter radars can be used as a spectrometer to detect trace concentrations of chemicals in atmospheres that are too cold to rely on thermal imaging techniques. In biomedicine, an imaging heterodyne system could be helpful in detecting skin diseases.

Thermo-optic microring resonator switching elements made of dielectric-loaded plasmonic waveguides

NASA Astrophysics Data System (ADS)

Tsilipakos, Odysseas; Kriezis, Emmanouil E.; Bozhevolnyi, Sergey I.

2011-04-01

Thermo-optic switching elements made of dielectric-loaded plasmonic (DLSPP) waveguides are theoretically investigated by utilizing the three-dimensional vector finite element method. The configurations considered employ microring resonators, whose resonant frequency is varied by means of thermal tuning. First, a classic add-drop filter with parallel access waveguides is examined. Such a component features very poor drop port extinction ratio (ER). We therefore extend the analysis to add-drop filters with perpendicular access waveguides, which are found to exhibit superior drop port ERs, due to interference effects associated with the drop port transmission. In the process, the performance of a DLSPP waveguide crossing is also assessed, since it is a building block of those filters whose bus waveguides intersect. An elliptic tapering scheme is proposed for minimizing cross talk and its effect on the filter performance is explored. The dual-resonator add-drop filter with perpendicular bus waveguides and an untreated waveguide crossing of Sec. V can act as an efficient 2×2 switching element (the single-resonator variant can only act as a 1×2 switch due to structure asymmetry), possessing two equivalent input ports and featuring high ERs for both output ports over a broad wavelength range. Specifically, an extinction ratio of at least 8 dB can be attained for both output ports over a wavelength range of 3.2 nm, accommodating four 100-GHz-spaced channels. Switching times are in the order of a few microseconds, rendering the aforementioned structure capable of handling real-world routing scenarios.

Realizable feed-element patterns for multibeam reflector antenna analysis

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.; Cramer, P., Jr.; Woo, K.; Lee, S. W.

1981-01-01

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Ultra-large nonlinear parameter in graphene-silicon waveguide structures.

PubMed

Donnelly, Christine; Tan, Dawn T H

2014-09-22

Mono-layer graphene integrated with optical waveguides is studied for the purpose of maximizing E-field interaction with the graphene layer, for the generation of ultra-large nonlinear parameters. It is shown that the common approach used to minimize the waveguide effective modal area does not accurately predict the configuration with the maximum nonlinear parameter. Both photonic and plasmonic waveguide configurations and graphene integration techniques realizable with today's fabrication tools are studied. Importantly, nonlinear parameters exceeding 10(4) W(-1)/m, two orders of magnitude larger than that in silicon on insulator waveguides without graphene, are obtained for the quasi-TE mode in silicon waveguides incorporating mono-layer graphene in the evanescent part of the optical field. Dielectric loaded surface plasmon polariton waveguides incorporating mono-layer graphene are observed to generate nonlinear parameters as large as 10(5) W(-1)/m, three orders of magnitude larger than that in silicon on insulator waveguides without graphene. The ultra-large nonlinear parameters make such waveguides promising platforms for nonlinear integrated optics at ultra-low powers, and for previously unobserved nonlinear optical effects to be studied in a waveguide platform.

IRIS Public Science Meeting (June 2016)

EPA Pesticide Factsheets

This June 2016 public meeting is made available to solicit comments on the public comment draft of the IRIS Assessment of tert-Butanol. The draft document was re-opened in the docket for a 60-day public comment period closing on July 16, 2016.

Bunch radiation from a semi-infinite waveguide with dielectric filling inside a waveguide with larger radius

NASA Astrophysics Data System (ADS)

Galyamin, S. N.; Tyukhtin, A. V.; Vorobev, V. V.; Aryshev, A.

2018-02-01

We consider a point charge and Gaussian bunch of charged particles moving along the axis of a circular perfectly conducting pipe with uniform dielectric filling and open end. It is supposed that this semi-infinite waveguide is located in collinear infinite vacuum pipe with perfectly conducting walls and larger diameter. We deal with two cases corresponding to the open end of the inner waveguide with and without flange. Radiation produced by a charge or bunch flying from dielectric part to wide vacuum part is analyzed. We use modified residue-calculus technique and construct rigorous analytical theory describing scattered field in each sub-area of the structure. Cherenkov radiation generated in the dielectric waveguide and penetrating into the vacuum regions of the structure is of main interest throughout the present paper. We show that this part of radiation can be easily analyzed using the presented formalism. We also perform numerical simulation in CST PS code and verify the analytical results.

Immune reconstitution inflammatory syndrome associated with toxoplasmic encephalitis in HIV-infected patients.

PubMed

van Bilsen, Ward P H; van den Berg, Charlotte H S B; Rijnders, Bart J A; Brinkman, Kees; Mulder, Jan W; Gelinck, Luc B S; Hoepelman, Andy I M; Wit, Ferdinand W N M; van de Beek, Diederik; Prins, Jan M

2017-06-19

To investigate the incidence and risk factors of immune reconstitution inflammatory syndrome (IRIS) associated with toxoplasmic encephalitis (TE) in patients starting combination antiretroviral therapy (cART). A historical multicenter cohort study. We included all HIV-infected patients diagnosed with toxoplasmic encephalitis in six Dutch hospitals between 1996 and 2016. Diagnosis of TE-IRIS was made using predefined IRIS criteria. We distinguished paradoxical TE-IRIS (worsening of underlying treated infection) from unmasking TE-IRIS (unmasking of subclinical infection after start of cART). We compared CD4 cell count, plasma viral load and timing of cART initiation between patients with and without paradoxical TE-IRIS. A total of 211 toxoplasmic encephalitis cases were included. Among 143 cases at risk for paradoxical TE-IRIS, we identified five cases of paradoxical TE-IRIS (3.5%). In six other cases, we could not differentiate paradoxical TE-IRIS from recurrence of disease due to inadequate secondary Toxoplasma prophylaxis. There was no difference in time between start of toxoplasmic encephalitis treatment and cART initiation for patients who did or did not develop paradoxical TE-IRIS (P = 0.50). Within the group of 2228 patients who started cART while having a CD4 cell count below 200 × 10 cells/l and receiving adequate primary prophylaxis, we identified eight cases of unmasking TE-IRIS (0.36%). Unmasking TE-IRIS could not be differentiated from a newly occurring toxoplasmic encephalitis in six other patients, as they were not receiving adequate primary prophylaxis against Toxoplasma. Unmasking TE-IRIS was rare in this cohort, whereas paradoxical TE-IRIS did occur more often. We found no relationship between the timing of cART initiation and the occurrence of paradoxical TE-IRIS.

A hybrid waveguide cell for the dielectric properties of reservoir rocks

NASA Astrophysics Data System (ADS)

Siggins, A. F.; Gunning, J.; Josh, M.

2011-02-01

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1-2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods.

Aperture excited dielectric antennas

NASA Technical Reports Server (NTRS)

Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

1974-01-01

The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

NASA HyspIRI Workshop Report

USDA-ARS?s Scientific Manuscript database

On October 21-23rd 2008 NASA held a three-day workshop to consider the Hyperspectral and Infrared Imager (HyspIRI) mission recommended for implementation by the 2007 National Research Council Earth Science Decadal Survey. The open workshop provided a forum to present the initial observational requir...

Characterizing the Attenuation of Coaxial and Rectangular Microwave-Frequency Waveguides at Cryogenic Temperatures (Open Access, Publisher’s Version)

DTIC Science & Technology

2017-05-04

Wallraff *Correspondence: philipp.kurpiers@phys.ethz.ch Department of Physics, ETH Zürich, Zürich, CH-8093, Switzerland Abstract Low- loss waveguides...and single photon levels. More specifically, we characterize the frequency-dependent loss of a range of coaxial and rectangular microwave waveguides...down to 0.005 dB/m using a resonant-cavity technique. We study the loss tangent and relative permittivity of commonly used dielectric waveguide materials

Fabrication of thermal microphotonic sensors and sensor arrays

DOEpatents

Shaw, Michael J.; Watts, Michael R.; Nielson, Gregory N.

2010-10-26

A thermal microphotonic sensor is fabricated on a silicon substrate by etching an opening and a trench into the substrate, and then filling in the opening and trench with silicon oxide which can be deposited or formed by thermally oxidizing a portion of the silicon substrate surrounding the opening and trench. The silicon oxide forms a support post for an optical resonator which is subsequently formed from a layer of silicon nitride, and also forms a base for an optical waveguide formed from the silicon nitride layer. Part of the silicon substrate can be selectively etched away to elevate the waveguide and resonator. The thermal microphotonic sensor, which is useful to detect infrared radiation via a change in the evanescent coupling of light between the waveguide and resonator, can be formed as a single device or as an array.

Glaucoma: Symptoms and Causes

MedlinePlus

... damage. The types of glaucoma include the following: Open-angle glaucoma Open-angle glaucoma is the most common form of ... angle formed by the cornea and iris remains open, but the trabecular meshwork is partially blocked. This ...

Universal nondestructive mm-wave integrated circuit test fixture

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R. (Inventor); Shalkhauser, Kurt A. (Inventor)

1990-01-01

Monolithic microwave integrated circuit (MMIC) test includes a bias module having spring-loaded contacts which electrically engage pads on a chip carrier disposed in a recess of a base member. RF energy is applied to and passed from the chip carrier by chamfered edges of ridges in the waveguide passages of housings which are removably attached to the base member. Thru, Delay, and Short calibration standards having dimensions identical to those of the chip carrier assure accuracy and reliability of the test. The MMIC chip fits in an opening in the chip carrier with the boundaries of the MMIC lying on movable reference planes thereby establishing accuracy and flexibility.

Space domain analysis of micro-IDG structure

NASA Astrophysics Data System (ADS)

Izzat, Narian; Pennock, Steve R.; Rozzi, Tullio

1994-06-01

The Microstrip Loaded Inset Dielectric Waveguide has been proposed as a transmission medium alternative to microstrip, and as a useful antenna medium at X-band and millimetric frequencies. In the present analysis we consider the case where a multi-layer, multi-conductor microstrip circuit may be housed within Inset Dielectric Waveguide.

Thirty Years of Innovation in Seismology with the IRIS Consortium

NASA Astrophysics Data System (ADS)

Sumy, D. F.; Woodward, R.; Aderhold, K.; Ahern, T. K.; Anderson, K. R.; Busby, R.; Detrick, R. S.; Evers, B.; Frassetto, A.; Hafner, K.; Simpson, D. W.; Sweet, J. R.; Taber, J.

2015-12-01

The United States academic seismology community, through the National Science Foundation (NSF)-funded Incorporated Research Institutions for Seismology (IRIS) Consortium, has promoted and encouraged a rich environment of innovation and experimentation in areas such as seismic instrumentation, data processing and analysis, teaching and curriculum development, and academic science. As the science continually evolves, IRIS helps drive the market for new research tools that enable science by establishing a variety of standards and goals. This has often involved working directly with manufacturers to better define the technology required, co-funding key development work or early production prototypes, and purchasing initial production runs. IRIS activities have helped establish de-facto international standards and impacted the commercial sector in areas such as seismic instrumentation, open-access data management, and professional development. Key institutional practices, conducted and refined over IRIS' thirty-year history of operations, have focused on open-access data availability, full retention of maximum-bandwidth, continuous data, and direct community access to state-of-the-art seismological instrumentation and software. These practices have helped to cultivate and support a thriving commercial ecosystem, and have been a key element in the professional development of multiple generations of seismologists who now work in both industry and academia. Looking toward the future, IRIS is increasing its engagement with industry to better enable bi-directional exchange of techniques and technology, and enhancing the development of tomorrow's workforce. In this presentation, we will illustrate how IRIS has promoted innovations grown out of the academic community and spurred technological advances in both academia and industry.

Linkage analysis excludes the glaucoma locus on 1q from involvement in autosomal dominant glaucoma with iris hypoplasia

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

Heon, E.; Sheth, B.P.; Kalenak, J.W.

1994-09-01

Genetic factors have been implicated in a variety of types of glaucoma including primary open-angle glaucoma, infantile glaucoma, pigmentary glaucoma, and juvenile open-angle glaucoma. We previously mapped the disease-causing gene for one type of juvenile open angle glaucoma to chromosome 1q21-31. Weatherill and Hart (1969) and Pearce (1983) each noted the association of iris hypoplasia and early-onset autosomal dominant glaucoma. We recently had the opportunity to study a large family (12 affected members) with this phenotype. Affected individuals developed glaucoma at an average age of 30 years. These patients also have a strikingly underdeveloped iris stroma which causes a peculiarmore » eye color. Linkage analysis was able to completely exclude the 1q glaucoma locus from involvement in the disorder that affects this family. A complete clinical description of the family and linkage results at additional candidate loci will be presented.« less

Radio Frequency Power Load and Associated Method

NASA Technical Reports Server (NTRS)

Srinivasan, V. Karthik (Inventor); Freestone, Todd M. (Inventor); Sims, William Herbert, III (Inventor)

2014-01-01

A radio frequency power load and associated method. A radio frequency power load apparatus may include a container with an ionized fluid therein. The apparatus may include one conductor immersed in a fluid and another conductor electrically connected to the container. A radio frequency transmission system may include a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus may include a fluid having an ion source therein, one conductor immersed in a fluid, and another conductor electrically connected to the container. A method of dissipating power generated by a radio frequency transmission system may include constructing a waveguide with ionized fluid in a container and connecting the waveguide to an amplifier of the transmission system.

Millimeter-Wave Generation Via Plasma Three-Wave Mixing

DTIC Science & Technology

1988-06-01

are coupled to a third space -charge wave with dispersion 2w W k -k k . (16) A plasma-loaded-waveguide mode is excited at the intersection of this...DISPERSION "FAST" W PLASMA WAVE Wc PLASMA WAVE A-lA oppositely directed EPWs with different phase velocities (wp/k., and wO/k. 2) are coupled to a third ... space -charge wave with dispersion 2w I- k k .(16) e 2 A plaama-loaded-waveguide mode is excited at the intersection of this coupled space-charge wave

Multi-frequency klystron designed for high efficiency

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

Jensen, Aaron

A multi-frequency klystron has an electron gun which generates a beam, a circuit of bunch-align-collect (BAC) tuned cavities that bunch the beam and amplify an RF signal, a collector where the beam is collected and dumped, and a standard output cavity and waveguide coupled to a window to output RF power at a fundamental mode to an external load. In addition, the klystron has additional bunch-align-collect (BAC) cavities tuned to a higher harmonic frequency, and a harmonic output cavity and waveguide coupled via a window to an additional external load.

Directional emissivity from two-dimensional infrared waveguide arrays

NASA Astrophysics Data System (ADS)

Burckel, D. Bruce; Davids, Paul S.; Finnegan, Patrick S.; Figueiredo, Pedro N.; Ginn, James C.

2015-09-01

Fabrication and optical characterization of surfaces covered with open-ended metallic waveguides are presented along with numerical modeling of these structures. Both modeling and measurement of the structures indicate that the 2-D array of 3D metallic waveguides modify both the direction and spectral content of the emissivity, resulting in directionality normal to the surface due to the optical axis of the waveguides and spectrally narrow emissivity due to the lateral dimensions of the waveguides. Furthermore, the optical behavior of these structures is placed in the broader context of other structured emission/absorption surfaces such as organ pipe modes, surface plasmon modes, and coherent thermal emission from gratings.

Magnetically tunable unidirectional waveguide based on magnetic photonic crystals

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

Tong, Weiwei; Wang, Jiafu, E-mail: wangjiafu1981@126.com, E-mail: qushaobo@mail.xjtu.edu.cn; Wang, Jun

2016-08-01

In this letter, we presented a magnetically tunable ferrite-loaded unidirectional waveguide based on magnetic photonic crystals. Two rows of ferrite rods are symmetrically arranged near the two lateral sides of the rectangular waveguide, where they are biased with static magnetic fields with the same amplitude and opposite directions along the rod axis. Since the magnetic one-way transmission is induced by the magnetic surface plasmon resonance, the operating band of the unidirectional waveguide can be tuned by changing the biased magnetic field intensity. To validate the design, a prototype was fabricated and measured. Both the simulation and experiment results verify themore » unidirectional transmission property.« less

Risk factors and frequency of tuberculosis-associated immune reconstitution inflammatory syndrome among HIV/Tuberculosis co-infected patients in Southern India.

PubMed

Vignesh, Ramachandran; Swathirajan, Chinnambedu R; Solomon, Sunil S; Shankar, Esaki Muthu; Murugavel, Kailapuri G

2017-01-01

Immune reconstitution inflammatory syndrome (IRIS) continues to be a complication in HIV/tuberculosis (TB) co-infected patients initiating highly active antiretroviral therapy (HAART). The aim of this study was to evaluate the risk factors associated with developing IRIS to identify a possible biomarker to predict or diagnose IRIS in patients initiating HAART. A total of 175 HIV/TB co-infected patients initiating HAART were followed up longitudinally during September 2010 to May 2013 attending a HIV care clinic in Chennai. Patients were followed up longitudinally after HAART initiation and baseline demographic, laboratory parameters and treatment characteristics between patients with IRIS events and those without IRIS events were compared. Chi-square or Fisher's exact test for categorical variables and a Wilcoxon rank-sum test for continuous variables were performed using SPSS, version 12.0 software. Patients with IRIS had a significantly lower median baseline CD4+ T-cell count (P = 0.0039). There were no differences in terms of sex, CD4 T-cell %, plasma viral load, time interval between initiating ATT and HAART between the IRIS and non-IRIS patients. Low CD4+ T-cell count (<100 cells/μL) could be used as a marker to screen and monitor patients initiating HAART.

Novel On-wafer Radiation Pattern Measurement Technique for MEMS Actuator Based Reconfigurable Patch Antennas

NASA Technical Reports Server (NTRS)

Simons, Rainee N.

2002-01-01

The paper presents a novel on-wafer, antenna far field pattern measurement technique for microelectromechanical systems (MEMS) based reconfigurable patch antennas. The measurement technique significantly reduces the time and the cost associated with the characterization of printed antennas, fabricated on a semiconductor wafer or dielectric substrate. To measure the radiation patterns, the RF probe station is modified to accommodate an open-ended rectangular waveguide as the rotating linearly polarized sampling antenna. The open-ended waveguide is attached through a coaxial rotary joint to a Plexiglas(Trademark) arm and is driven along an arc by a stepper motor. Thus, the spinning open-ended waveguide can sample the relative field intensity of the patch as a function of the angle from bore sight. The experimental results include the measured linearly polarized and circularly polarized radiation patterns for MEMS-based frequency reconfigurable rectangular and polarization reconfigurable nearly square patch antennas, respectively.

Opening and closing of band gaps in magnonic waveguide by rotating the triangular antidots - A micromagnetic study

NASA Astrophysics Data System (ADS)

Vivek, T.; Bhoomeeswaran, H.; Sabareesan, P.

2018-05-01

Spin waves in ID periodic triangular array of antidots are encarved in a permalloy magnonic waveguide is investigated through micromagnetic simulation. The effect of the rotating array of antidots and in-plane rotation of the scattering centers on the band structure are investigated, to indicate new possibilities of fine tuning of spin-wave filter pass and stop bands. The results show that, the opening and closing of band gaps paves a way for band pass and stop filters on waveguide. From the results, the scattering center and strong spatial distribution field plays crucible role for controlling opening and closing bandgap width of ˜12 GHz for 0° rotation. We have obtained a single narrow bandgap of width 1GHz is obtained for 90° rotation of the antidot. Similarly, the tunability is achieved for desired microwave applications done by rotating triangular antidots with different orientation.

Energy-efficient lighting system for television

DOEpatents

Cawthorne, Duane C.

1987-07-21

A light control system for a television camera comprises an artificial light control system which is cooperative with an iris control system. This artificial light control system adjusts the power to lamps illuminating the camera viewing area to provide only sufficient artificial illumination necessary to provide a sufficient video signal when the camera iris is substantially open.

KSC-2013-2730

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2731

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2726

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2733

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2734

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2732

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2669

NASA Image and Video Library

2013-06-11

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June is seen in a hangar at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2668

NASA Image and Video Library

2013-06-11

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June is seen in a hangar at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2666

NASA Image and Video Library

2013-06-11

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June is seen in a hangar at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2665

NASA Image and Video Library

2013-06-11

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June is seen in a hangar at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2667

NASA Image and Video Library

2013-06-11

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June is seen in a hangar at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2727

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit is moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

IrisDenseNet: Robust Iris Segmentation Using Densely Connected Fully Convolutional Networks in the Images by Visible Light and Near-Infrared Light Camera Sensors

PubMed Central

Arsalan, Muhammad; Naqvi, Rizwan Ali; Kim, Dong Seop; Nguyen, Phong Ha; Owais, Muhammad; Park, Kang Ryoung

2018-01-01

The recent advancements in computer vision have opened new horizons for deploying biometric recognition algorithms in mobile and handheld devices. Similarly, iris recognition is now much needed in unconstraint scenarios with accuracy. These environments make the acquired iris image exhibit occlusion, low resolution, blur, unusual glint, ghost effect, and off-angles. The prevailing segmentation algorithms cannot cope with these constraints. In addition, owing to the unavailability of near-infrared (NIR) light, iris recognition in visible light environment makes the iris segmentation challenging with the noise of visible light. Deep learning with convolutional neural networks (CNN) has brought a considerable breakthrough in various applications. To address the iris segmentation issues in challenging situations by visible light and near-infrared light camera sensors, this paper proposes a densely connected fully convolutional network (IrisDenseNet), which can determine the true iris boundary even with inferior-quality images by using better information gradient flow between the dense blocks. In the experiments conducted, five datasets of visible light and NIR environments were used. For visible light environment, noisy iris challenge evaluation part-II (NICE-II selected from UBIRIS.v2 database) and mobile iris challenge evaluation (MICHE-I) datasets were used. For NIR environment, the institute of automation, Chinese academy of sciences (CASIA) v4.0 interval, CASIA v4.0 distance, and IIT Delhi v1.0 iris datasets were used. Experimental results showed the optimal segmentation of the proposed IrisDenseNet and its excellent performance over existing algorithms for all five datasets. PMID:29748495

IrisDenseNet: Robust Iris Segmentation Using Densely Connected Fully Convolutional Networks in the Images by Visible Light and Near-Infrared Light Camera Sensors.

PubMed

Arsalan, Muhammad; Naqvi, Rizwan Ali; Kim, Dong Seop; Nguyen, Phong Ha; Owais, Muhammad; Park, Kang Ryoung

2018-05-10

The recent advancements in computer vision have opened new horizons for deploying biometric recognition algorithms in mobile and handheld devices. Similarly, iris recognition is now much needed in unconstraint scenarios with accuracy. These environments make the acquired iris image exhibit occlusion, low resolution, blur, unusual glint, ghost effect, and off-angles. The prevailing segmentation algorithms cannot cope with these constraints. In addition, owing to the unavailability of near-infrared (NIR) light, iris recognition in visible light environment makes the iris segmentation challenging with the noise of visible light. Deep learning with convolutional neural networks (CNN) has brought a considerable breakthrough in various applications. To address the iris segmentation issues in challenging situations by visible light and near-infrared light camera sensors, this paper proposes a densely connected fully convolutional network (IrisDenseNet), which can determine the true iris boundary even with inferior-quality images by using better information gradient flow between the dense blocks. In the experiments conducted, five datasets of visible light and NIR environments were used. For visible light environment, noisy iris challenge evaluation part-II (NICE-II selected from UBIRIS.v2 database) and mobile iris challenge evaluation (MICHE-I) datasets were used. For NIR environment, the institute of automation, Chinese academy of sciences (CASIA) v4.0 interval, CASIA v4.0 distance, and IIT Delhi v1.0 iris datasets were used. Experimental results showed the optimal segmentation of the proposed IrisDenseNet and its excellent performance over existing algorithms for all five datasets.

Low reflectance high power RF load

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M.

2016-02-02

A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

Low reflectance radio frequency load

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M

2014-04-01

A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

A reciprocity formulation for the EM scattering by an obstacle within a large open cavity

NASA Technical Reports Server (NTRS)

Pathak, Prabhakar H.; Burkholder, Robert J.

1993-01-01

A formulation based on a generalized reciprocity theorem is developed for analyzing the external high frequency EM scattering by a complex obstacle inside a relatively arbitrary open-ended waveguide cavity when it is illuminated by an external source. This formulation is also extended to include EM fields whose time dependence may be nonperiodic. A significant advantage of this formulation is that it allows one to break up the analysis into two independent parts; one deals with the waveguide cavity shape alone and the other with the obstacle alone. The external scattered field produced by the obstacle (in the presence of the waveguide cavity structure) is given in terms of a generalized reciprocity integral over a surface S(T) corresponding to the interior waveguide cavity cross section located conveniently but sufficiently close to the obstacle. Furthermore, the fields coupled into the cavity from the source in the exterior region generally need to propagate only one-way via the open front end (which is directly illuminated) to the interior surface S(T) in this approach, and not back, in order to find the external field scattered by the obstacle.

Enhanced iris recognition method based on multi-unit iris images

NASA Astrophysics Data System (ADS)

Shin, Kwang Yong; Kim, Yeong Gon; Park, Kang Ryoung

2013-04-01

For the purpose of biometric person identification, iris recognition uses the unique characteristics of the patterns of the iris; that is, the eye region between the pupil and the sclera. When obtaining an iris image, the iris's image is frequently rotated because of the user's head roll toward the left or right shoulder. As the rotation of the iris image leads to circular shifting of the iris features, the accuracy of iris recognition is degraded. To solve this problem, conventional iris recognition methods use shifting of the iris feature codes to perform the matching. However, this increases the computational complexity and level of false acceptance error. To solve these problems, we propose a novel iris recognition method based on multi-unit iris images. Our method is novel in the following five ways compared with previous methods. First, to detect both eyes, we use Adaboost and a rapid eye detector (RED) based on the iris shape feature and integral imaging. Both eyes are detected using RED in the approximate candidate region that consists of the binocular region, which is determined by the Adaboost detector. Second, we classify the detected eyes into the left and right eyes, because the iris patterns in the left and right eyes in the same person are different, and they are therefore considered as different classes. We can improve the accuracy of iris recognition using this pre-classification of the left and right eyes. Third, by measuring the angle of head roll using the two center positions of the left and right pupils, detected by two circular edge detectors, we obtain the information of the iris rotation angle. Fourth, in order to reduce the error and processing time of iris recognition, adaptive bit-shifting based on the measured iris rotation angle is used in feature matching. Fifth, the recognition accuracy is enhanced by the score fusion of the left and right irises. Experimental results on the iris open database of low-resolution images showed that the averaged equal error rate of iris recognition using the proposed method was 4.3006%, which is lower than that of other methods.

Rugged Iris Mechanism

NASA Technical Reports Server (NTRS)

Ferragut, Nelson J.

2005-01-01

A rugged iris mechanism has been designed to satisfy several special requirements, including a wide aperture in the "open" position, full obscuration in the "closed" position, ability to function in a cryogenic or other harsh environment, and minimization of friction through minimization of the number of components. An important element of the low-friction aspect of the design is maximization of the flatness of, and provision of small gaps between, adjacent iris blades. The tolerances of the design can be very loose, accommodating thermal expansions and contractions associated with large temperature excursions. The design is generic in that it is adaptable to a wide range of aperture sizes and can be implemented in a variety of materials to suit the thermal, optical, and mechanical requirements of various applications. The mechanism (see figure) includes an inner flat ring, an outer flat ring, and an even number of iris blades. The iris blades shown in front in the figure are denoted as "upper," and the iris blades shown partly hidden behind the front ones are denoted as "lower." Each iris blade is attached to the inner ring by a pivot assembly and to the outer ring by a roller/slider assembly. The upper and lower rings are co-centered and are kept in sliding contact. The iris is opened or closed by turning the outer ring around the center while holding the inner ring stationary. The mechanism is enclosed in a housing (not shown in the figure) that comprises an upper and a lower housing shell. The housing provides part of the sliding support for the outer ring and keeps the two rings aligned as described above. The aforementioned pivot assemblies at the inner ring also serve as spacers for the housing. The lower housing shell contains part of the lower sliding surface and features for mounting the overall mechanism and housing assembly. The upper housing shell contains part of the upper sliding surface.

Non-Markovian dynamics of a qubit due to single-photon scattering in a waveguide

NASA Astrophysics Data System (ADS)

Fang, Yao-Lung L.; Ciccarello, Francesco; Baranger, Harold U.

2018-04-01

We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubit's dynamical map. Tools of open quantum systems theory allow us then to show the general features of this map, find the corresponding non-Linbladian master equation, and assess in a rigorous way its non-Markovian nature. The qubit dynamics has distinctive features that, in particular, do not occur in emission processes. Two fundamental sources of non-Markovianity are present: the finite width of the photon wavepacket and the time delay for propagation between the qubit and the end of the semi-infinite waveguide.

High-Power Rf Load

DOEpatents

Tantawi, Sami G.; Vlieks, Arnold E.

1998-09-01

A compact high-power RF load comprises a series of very low Q resonators, or chokes [16], in a circular waveguide [10]. The sequence of chokes absorb the RF power gradually in a short distance while keeping the bandwidth relatively wide. A polarizer [12] at the input end of the load is provided to convert incoming TE.sub.10 mode signals to circularly polarized TE.sub.11 mode signals. Because the load operates in the circularly polarized mode, the energy is uniformly and efficiently absorbed and the load is more compact than a rectangular load. Using these techniques, a load having a bandwidth of 500 MHz can be produced with an average power dissipation level of 1.5 kW at X-band, and a peak power dissipation of 100 MW. The load can be made from common lossy materials, such as stainless steel, and is less than 15 cm in length. These techniques can also produce loads for use as an alternative to ordinary waveguide loads in small and medium RF accelerators, in radar systems, and in other microwave applications. The design is easily scalable to other RF frequencies and adaptable to the use of other lossy materials.

Modal analysis and cut-off conditions of multichannel surface-acoustic-waveguide structures.

PubMed

Griffel, G; Golan, G; Ruschin, S; Seidman, A; Croitoru, N

1988-01-01

Multichannel guides for surface acoustic waves can improve the efficiency of SAW (surface acoustic-wave) devices significantly. Focusing, steering, and modulating the propagating acoustical modes can be achieved similarly to optical waveguided devices. A general formulation is presented for the analysis of the lateral waveguiding properties of Rayleigh modes in surfaces loaded with deposited strips of different materials. General expressions are obtained for the number of modes and cutoff conditions in these structures. As examples of applications, a simple directional coupler and an electrically controlled coupler are proposed.

Nonlinear ball chain waveguides for acoustic emission and ultrasound sensing of ablation

NASA Astrophysics Data System (ADS)

Pearson, Stephen H.

Harsh environment acoustic emission and ultrasonic wave sensing applications often benefit from placing the sensor in a remote and more benign physical location by using waveguides to transmit elastic waves between the structural location under test and the transducer. Waveguides are normally designed to have high fidelity over broad frequency ranges to minimize distortion -- often difficult to achieve in practice. This thesis reports on an examination of using nonlinear ball chain waveguides for the transmission of acoustic emission and ultrasonic waves for the monitoring of thermal protection systems undergoing severe heat loading, leading to ablation and similar processes. Experiments test the nonlinear propagation of solitary, harmonic and mixed harmonic elastic waves through a copper tube filled with steel and elastomer balls and various other waveguides. Triangulation of pencil lead breaks occurs on a steel plate. Data are collected concerning the usage of linear waveguides and a water-cooled linear waveguide. Data are collected from a second water-cooled waveguide monitoring Atmospheric Reentry Materials in UVM's Inductively-Coupled Plasma Torch Facility. The motion of the particles in the dimer waveguides is linearly modeled with a three ball and spring chain model and the results are compared per particle. A theoretical nonlinear model is presented which is capable of exactly modeling the motion of the dimer chains. The shape of the waveform propagating through the dimer chain is modeled in a sonic vacuum. Mechanical pulses of varying time widths and amplitudes are launched into one end of the ball chain waveguide and observed at the other end in both time and frequency domains. Similarly, harmonic and mixed harmonic mechanical loads are applied to one end of the waveguide. Balls of different materials are analyzed and discriminated into categories. A copper tube packed with six steel particles, nine steel or marble particles and a longer copper tube packed with 17 steel particles are studied with a frequency sweep. The deformation experienced by a single steel particle in the dimer chain is approximated. Steel ball waveguides and steel rods are fitted with piezoelectric sensors to monitor the force at different points inside the waveguide during testing. The corresponding frequency responses, including intermodulation products, are compared based on amplitude and preloads. A nonlinear mechanical model describes the motion of the dimer chains in a vacuum. Based on the results of these studies it is anticipated that a nonlinear waveguide will be designed, built, and tested as a possible replacement for the high-fidelity waveguides presently being used in an Inductively Coupled Plasma Torch facility for high heat flux thermal protection system testing. The design is intended to accentuate acoustic emission signals of interest, while suppressing other forms of elastic wave noise.

Immune reconstitution inflammatory syndrome in HIV and sporotrichosis coinfection: report of two cases and review of the literature.

PubMed

Lyra, Marcelo Rosandiski; Nascimento, Maria Letícia Fernandes Oliveira; Varon, Andréa Gina; Pimentel, Maria Inês Fernandes; Antonio, Liliane de Fátima; Saheki, Maurício Naoto; Bedoya-Pacheco, Sandro Javier; Valle, Antonio Carlos Francesconi do

2014-01-01

We report 2 cases of patients with immune reconstitution inflammatory syndrome (IRIS) associated with cutaneous disseminated sporotrichosis and human immunodeficiency virus (HIV) coinfection. The patients received specific treatment for sporotrichosis. However, after 4 and 5 weeks from the beginning of antiretroviral therapy, both patients experienced clinical exacerbation of skin lesions despite increased T CD4+ cells (T cells cluster of differentiation 4 positive) count and decreased viral load. Despite this exacerbation, subsequent mycological examination after systemic corticosteroid administration did not reveal fungal growth. Accordingly, they were diagnosed with IRIS. However, the sudden withdrawal of the corticosteroids resulted in the recurrence of IRIS symptoms. No serious adverse effects could be attributed to prednisone. We recommend corticosteroid treatment for mild-to-moderate cases of IRIS in sporotrichosis and HIV coinfection with close follow-up.

Analysis of the EM scattering from arbitrary open-ended waveguide cavities using axial Gaussian Beam tracking

NASA Technical Reports Server (NTRS)

Burkholder, R. J.; Pathak, P. H.

1988-01-01

The electromagnetic (EM) scattering from a planar termination located inside relatively arbitrarily shaped open-ended waveguide cavities with smoothly curved interior walls is analyzed using a Gaussian Beam (GB) expansion of the incident plane wave fields in the open end. The cavities under consideration may contain perfectly-conducting interior walls with or without a thin layer of material coating, or the walls may be characterized by an impedance boundary condition. In the present approach, the GB's are tracked only to the termination of the waveguide cavity via beam reflections from interior waveguide cavity walls. The Gaussian beams are tracked approximately only along their beam axes; this approximation which remains valid for relatively well focussed beams assumes that an incident GB gives rise to a reflected GB with parameters related to the incident beam and the radius of curvature of the wall. It is found that this approximation breaks down for GB's which come close to grazing a convex surface and when the width of the incident beam is comparable to the radius of curvature of the surface. The expansion of the fields at the open end depend on the incidence angle only through the expansion coefficients, so the GB's need to be tracked through the waveguide cavity only once for a wide range of incidence angles. At the termination, the sum of all the GB's are integrated using a result developed from a generalized reciprocity principle, to give the fields scattered from the interior of the cavity. The rim edge at the open end of the cavity is assumed to be sharp and the external scattering from the rim is added separately using Geometrical Theory of Diffraction. The results based on the present approach are compared with solutions based on the hybrid asymptotic modal method. The agreement is found to be very good for cavities made up of planar surfaces, and also for cavities with curved surfaces which are not too long with respect to their width.

A hybrid asymptotic-modal analysis of the EM scattering by an open-ended S-shaped rectangular waveguide cavity

NASA Technical Reports Server (NTRS)

Law, P. H.; Burkholder, R. J.; Pathak, P. H.

1988-01-01

The electromagnetic fields (EM) backscatter from a 3-dimensional perfectly conducting S-shaped open-ended cavity with a planar interior termination is analyzed when it is illuminated by an external plane wave. The analysis is based on a self-consistent multiple scattering method which accounts for the multiple wave interactions between the open end and the interior termination. The scattering matrices which described the reflection and transmission coefficients of the waveguide modes reflected and transmitted at each junction between the different waveguide sections, as well at the scattering from the edges at the open end are found via asymptotic high frequency methods such as the geometrical and physical theories of diffraction used in conjunction with the equivalent current method. The numerical results for an S-shaped inlet cavity are compared with the backscatter from a straight inlet cavity; the backscattered patterns are different because the curvature of an S-shaped inlet cavity redistributes the energy reflected from the interior termination in a way that is different from a straight inlet cavity.

Reducing Line Edge Roughness in Si and SiN through plasma etch chemistry optimization for photonic waveguide applications

NASA Astrophysics Data System (ADS)

Marchack, Nathan; Khater, Marwan; Orcutt, Jason; Chang, Josephine; Holmes, Steven; Barwicz, Tymon; Kamlapurkar, Swetha; Green, William; Engelmann, Sebastian

2017-03-01

The LER and LWR of subtractively patterned Si and SiN waveguides was calculated after each step in the process. It was found for Si waveguides that adjusting the ratio of CF4:CHF3 during the hard mask open step produced reductions in LER of 26 and 43% from the initial lithography for isolated waveguides patterned with partial and full etches, respectively. However for final LER values of 3.0 and 2.5 nm on fully etched Si waveguides, the corresponding optical loss measurements were indistinguishable. For SiN waveguides, introduction of C4H9F to the conventional CF4/CHF3 measurement was able to reduce the mask height budget by a factor of 5, while reducing LER from the initial lithography by 26%.

Clinical characteristics of tuberculosis-associated immune reconstitution inflammatory syndrome in North Indian population of HIV/AIDS patients receiving HAART.

PubMed

Karmakar, Suman; Sharma, Surendra K; Vashishtha, Richa; Sharma, Abhishek; Ranjan, Sanjay; Gupta, Deepak; Sreenivas, Vishnubhatla; Sinha, Sanjeev; Biswas, Ashutosh; Gulati, Vinay

2011-01-01

IRIS is an important complication that occurs during management of HIV-TB coinfection and it poses difficulty in diagnosis. Previous studies have reported variable incidence of IRIS. The present study was undertaken to describe the pattern of TB-associated IRIS using recently proposed consensus case-definitions for TB-IRIS for its use in resource-limited settings. A prospective analysis of ART-naïve adults started on HAART from November, 2008 to May, 2010 was done in a tertiary care hospital in north India. A total 224 patients divided into two groups, one with HIV-TB and the other with HIV alone, were followedup for a minimum period of 3 months. The diagnosis of TB was categorised as ''definitive" and ''probable". Out of a total of 224 patients, 203 completed followup. Paradoxical TB-IRIS occurred in 5 of 123 (4%) HIV-TB patients while 6 of 80 (7.5%) HIV patients developed ART-associated TB. A reduction in plasma viral load was significantly (P = .016) associated with paradoxical TB-IRIS. No identifiable risk factors were associated with the development of ART-associated TB. The consensus case-definitions are useful tools in the diagnosis of TB-associated IRIS. High index of clinical suspicion is required for an early diagnosis.

Method of adiabatic modes in studying problems of smoothly irregular open waveguide structures

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

Sevastianov, L. A., E-mail: sevast@sci.pfu.edu.ru; Egorov, A. A.; Sevastyanov, A. L.

2013-02-15

Basic steps in developing an original method of adiabatic modes that makes it possible to solve the direct and inverse problems of simulating and designing three-dimensional multilayered smoothly irregular open waveguide structures are described. A new element in the method is that an approximate solution of Maxwell's equations is made to obey 'inclined' boundary conditions at the interfaces between themedia being considered. These boundary conditions take into account the obliqueness of planes tangent to nonplanar boundaries between the media and lead to new equations for coupled vector quasiwaveguide hybrid adiabatic modes. Solutions of these equations describe the phenomenon of 'entanglement'more » of two linear polarizations of an irregular multilayered waveguide, the appearance of a new mode in an entangled state, and the effect of rotation of the polarization plane of quasiwaveguide modes. The efficiency of the method is demonstrated by considering the example of numerically simulating a thin-film generalized waveguide Lueneburg lens.« less

KSC-2013-2627

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Detail of the Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2620

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Detail of the Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2625

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Detail of the Orbital Sciences Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

A quasioptically stabilized resonant-tunneling-diode oscillator for the millimeter- and submillimeter-wave regions

NASA Technical Reports Server (NTRS)

Brown, Elliott R.; Parker, Christopher D.; Molvar, Karen M.; Stephan, Karl D.

1992-01-01

A semiconfocal open-cavity resonator has been used to stabilize a resonant-tunneling-diode waveguide oscillator at frequencies near 100 GHz. The high quality factor of the open cavity resulted in a linewidth of approximately 10 kHz at 10 dB below the peak, which is about 100 times narrower than the linewidth of an unstabilized waveguide oscillator. This technique is well suited for resonant-tunneling-diode oscillators in the submillimeter-wave region.

Wilber 3: A Python-Django Web Application For Acquiring Large-scale Event-oriented Seismic Data

NASA Astrophysics Data System (ADS)

Newman, R. L.; Clark, A.; Trabant, C. M.; Karstens, R.; Hutko, A. R.; Casey, R. E.; Ahern, T. K.

2013-12-01

Since 2001, the IRIS Data Management Center (DMC) WILBER II system has provided a convenient web-based interface for locating seismic data related to a particular event, and requesting a subset of that data for download. Since its launch, both the scale of available data and the technology of web-based applications have developed significantly. Wilber 3 is a ground-up redesign that leverages a number of public and open-source projects to provide an event-oriented data request interface with a high level of interactivity and scalability for multiple data types. Wilber 3 uses the IRIS/Federation of Digital Seismic Networks (FDSN) web services for event data, metadata, and time-series data. Combining a carefully optimized Google Map with the highly scalable SlickGrid data API, the Wilber 3 client-side interface can load tens of thousands of events or networks/stations in a single request, and provide instantly responsive browsing, sorting, and filtering of event and meta data in the web browser, without further reliance on the data service. The server-side of Wilber 3 is a Python-Django application, one of over a dozen developed in the last year at IRIS, whose common framework, components, and administrative overhead represent a massive savings in developer resources. Requests for assembled datasets, which may include thousands of data channels and gigabytes of data, are queued and executed using the Celery distributed Python task scheduler, giving Wilber 3 the ability to operate in parallel across a large number of nodes.

Nanoscale devices based on plasmonic coaxial waveguide resonators

NASA Astrophysics Data System (ADS)

Mahigir, A.; Dastmalchi, P.; Shin, W.; Fan, S.; Veronis, G.

2015-02-01

Waveguide-resonator systems are particularly useful for the development of several integrated photonic devices, such as tunable filters, optical switches, channel drop filters, reflectors, and impedance matching elements. In this paper, we introduce nanoscale devices based on plasmonic coaxial waveguide resonators. In particular, we investigate threedimensional nanostructures consisting of plasmonic coaxial stub resonators side-coupled to a plasmonic coaxial waveguide. We use coaxial waveguides with square cross sections, which can be fabricated using lithography-based techniques. The waveguides are placed on top of a silicon substrate, and the space between inner and outer coaxial metals is filled with silica. We use silver as the metal. We investigate structures consisting of a single plasmonic coaxial resonator, which is terminated either in a short or an open circuit, side-coupled to a coaxial waveguide. We show that the incident waveguide mode is almost completely reflected on resonance, while far from the resonance the waveguide mode is almost completely transmitted. We also show that the properties of the waveguide systems can be accurately described using a single-mode scattering matrix theory. The transmission and reflection coefficients at waveguide junctions are either calculated using the concept of the characteristic impedance or are directly numerically extracted using full-wave three-dimensional finite-difference frequency-domain simulations.

HIV Immune Recovery Inflammatory Syndrome and Central Nervous System Paracoccidioidomycosis.

PubMed

de Almeida, Sérgio Monteiro; Roza, Thiago Henrique

2017-04-01

The immune reconstitution inflammatory syndrome (IRIS) is a deregulated inflammatory response to invading microorganisms. It is manifested when there is an abrupt change in host immunity from an anti-inflammatory and immunosuppressive state to a pro-inflammatory state as a result of rapid depletion or removal of factors that promote immune suppression or inhibition of inflammation. The aim of this paper is to discuss and re-interpret the possibility of association of paracoccidioidomycosis (PCM) with IRIS in the central nervous system (CNS) in a case from Brazil published by Silva-Vergara ML. et al. (Mycopathologia 177:137-141, 6). An AIDS patient who was not receiving medical care developed pulmonary PCM successfully treated with itraconazole. The patient developed central nervous system PCM (NPCM) after starting the ARV therapy with recovery of immunity and control of HIV viral load, although it was not interpreted as IRIS by the authors, it fulfills the criteria for CNS IRIS. This could be the first case of NPCM associated with IRIS described. Although not frequent, IRIS must be considered in PCM patients and HIV, from endemic areas or patients that traveled to endemic areas, receiving ARV treatment and with worsening symptoms.

The Epidemiology of IRIS in Southern India: An Observational Cohort Study

PubMed Central

Thambuchetty, Nisha; Mehta, Kayur; Arumugam, Karthika; Shekarappa, Umadevi G.; Idiculla, Jyothi; Shet, Anita

2018-01-01

Immune reconstitution inflammatory syndrome (IRIS) is an uncommon but dynamic phenomenon seen among patients initiating antiretroviral therapy (ART). We aimed to describe incidence, risk factors, clinical spectrum, and outcomes among ART-naive patients experiencing IRIS in southern India. Among 599 eligible patients monitored prospectively between 2012 and 2014, there were 59.3% males, with mean age 36.6 ± 7.8 years. Immune reconstitution inflammatory syndrome incidence rate was 51.3 per 100 person-years (95% confidence interval: 44.5-59.2). One-third (31.4%) experienced at least 1 IRIS event, at a median of 27 days since ART initiation. Mucocutaneous infections and candidiasis were common IRIS events, followed by tuberculosis. Significant risk factors included age >40 years, body mass index <18.5 kg/m2, CD4 count <100 cells/mm3, viral load >10 000 copies/mL, hemoglobin <1 g/dL, and erythrocyte sedimentation rate >50 mm/h. Immune reconstitution inflammatory syndrome–related morality was 1.3% (8 of 599); 3 patients died of complicated diarrhea. These findings highlight the current spectrum of IRIS in South India and underscore the importance of heightened vigilance for anemia and treatment of diarrhea and candidiasis during ART initiation. PMID:28399724

Method for energy recovery of spent ERL beams

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

Marhauser, Frank; Hannon, Fay; Rimmer, Robert

A method for recovering energy from spent energy recovered linac (ERL) beams. The method includes adding a plurality of passive decelerating cavities at the beam dump of the ERL, adding one or more coupling waveguides between the passive decelerating cavities, setting an adequate external Q (Qext) to adjust to the beam loading situation, and extracting the RF energy through the coupling waveguides.

Long-range dielectric-loaded surface plasmon polariton waveguides operating at telecommunication wavelengths.

PubMed

Volkov, Valentyn S; Han, Zhanghua; Nielsen, Michael G; Leosson, Kristjan; Keshmiri, Hamid; Gosciniak, Jacek; Albrektsen, Ole; Bozhevolnyi, Sergey I

2011-11-01

We report on the realization of long-range dielectric-loaded surface plasmon polariton waveguides (LR-DLSPPWs) consisting of straight and bent subwavelength dielectric ridges deposited on thin and narrow metal stripes supported by a dielectric buffer layer covering a low-index substrate. Using imaging with a near-field optical microscope and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1425-1545 nm), we demonstrate low-loss (propagation length ∼500 μm) and well-confined (mode width ∼1 μm) LR-DLSPPW mode guiding and determine the propagation and bend loss.

KSC-2013-2910

NASA Image and Video Library

2013-06-25

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, NASA hosted a prelaunch mission briefing on the Interface Region Imaging Spectrograph, or IRIS, solar observatory scheduled to launch on a Pegasus XL rocket. Participating in the news conference are George Diller, NASA Public Affairs, Dr. S. Pete Worden, director of NASA's Ames Research Center in Calif., Jeffrey Newmark, IRIS Program scientist at NASA Headquarters in Washington D.C., and Alan Title, IRIS principal investigator with Lockheed Martin. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/ Daniel Casper

Immune reconstitution inflammatory syndrome in HIV-infected patients with Pneumocystis jirovecii pneumonia.

PubMed

Roade Tato, Luisa; Burgos Cibrian, Joaquín; Curran Fábregas, Adrià; Navarro Mercadé, Jordi; Willekens, Rein; Martín Gómez, María Teresa; Ribera Pascuet, Esteban; Falcó Ferrer, Vicenç

2017-11-26

The incidence of immune reconstitution inflammatory syndrome (IRIS) in HIV-infected patients after an episode of Pneumocystis jirovecii pneumonia (PJP) seems to be lower than with other opportunistic infections. We conducted an observational study in order to determine the incidence, clinical characteristics and outcome of patients diagnosed with PJP-related IRIS. We conducted an observational study of HIV patients diagnosed with PJP-related IRIS from January 2000 to November 2015. We analyzed epidemiological and clinical characteristics as well as laboratory findings. We also carried out a systematic review of published cases. Six cases of IRIS out of 123 (4.9%) HIV-infected patients with PJP who started ART were diagnosed. All six cases were men with a median age of 34 (IQR: 8) years. The six patients developed paradoxical IRIS. Subjects younger than 40 years old (p=0.084) and with an HIV-RNA viral load >100000 copies/ml (p=0.081) at diagnosis showed a tendency to develop IRIS. Thirty-seven published cases of PJP-related IRIS were identified. Although 51% of cases involved respiratory failure, no deaths were reported. PJP-related IRIS is rare condition compared to other opportunistic infections. It can lead to a severe respiratory failure in a significant proportion of cases, although no deaths have been reported. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

KSC-2012-5883

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-1784

NASA Image and Video Library

2013-03-05

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the three stages of the Orbital Sciences Corp. Pegasus XL rocket have been mated in preparation for the launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than April 29, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-2728

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences launch team monitors the Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit as the rocket and payload are moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2012-5878

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians prepare to install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-1785

NASA Image and Video Library

2013-03-05

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the three stages of the Orbital Sciences Corp. Pegasus XL rocket have been mated in preparation for the launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than April 29, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5881

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5884

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5887

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the aft skirt on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-2725

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences launch team monitors the Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit as the rocket and payload are moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2483

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. - A mission logo decal for the launch of NASA's IRIS solar observatory aboard an Orbital Sciences Pegasus XL rocket. The decal is on the side of the Pegasus. Engineers are working inside a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2012-5885

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, a technician helps install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5886

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-1786

NASA Image and Video Library

2013-03-06

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the three stages of the Orbital Sciences Corp. Pegasus XL rocket have been mated in preparation for the launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than April 29, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5889

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the aft skirt on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-2484

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. - A mission logo decal for the launch of NASA's IRIS solar observatory aboard an Orbital Sciences Pegasus XL rocket. The decal is on the side of the Pegasus. Engineers are working inside a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2729

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences launch team monitors the Pegasus XL rocket that will lift NASA's IRIS solar observatory into orbit as the rocket and payload are moved from a hangar onto a transporter at Vandenberg Air Force Base. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2012-5890

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians install the aft skirt on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2012-5879

NASA Image and Video Library

2012-10-09

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, technicians prepare to install the wing on the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-2203

NASA Image and Video Library

2013-04-25

VANDENBERG AIR FORCE BASE, Calif. -- The Interface Region Imaging Spectrograph, or IRIS, is being readied for mating to the Orbital Sciences Corp. Pegasus XL rocket that will launch the spacecraft. IRIS will be covered in a fairing after it's connected to the nose of the Pegasus to protect the spacecraft from atmospheric heating and stress during launch. Upcoming work includes electrical verification testing. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

Opto-mechanical subsystem of a 10 micrometer wavelength receiver terminal. Waveguide laser local oscillator. Servo system

NASA Technical Reports Server (NTRS)

1975-01-01

An engineering model opto-mechanical subsystem for a 10.6-micrometer laser heterodyne receiver is developed, and a CO2 waveguide local oscillator and servo electronics are provided for the receiver. Design goals are presented for the subsystems and overall package design is described. Thermal and mechanical distortion loading tests were performed and the results are included.

Clinical Characteristics of Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome in North Indian Population of HIV/AIDS Patients Receiving HAART

PubMed Central

Karmakar, Suman; Sharma, Surendra K.; Vashishtha, Richa; Sharma, Abhishek; Ranjan, Sanjay; Gupta, Deepak; Sreenivas, Vishnubhatla; Sinha, Sanjeev; Biswas, Ashutosh; Gulati, Vinay

2011-01-01

Background & Objective. IRIS is an important complication that occurs during management of HIV-TB coinfection and it poses difficulty in diagnosis. Previous studies have reported variable incidence of IRIS. The present study was undertaken to describe the pattern of TB-associated IRIS using recently proposed consensus case-definitions for TB-IRIS for its use in resource-limited settings. Methods. A prospective analysis of ART-naïve adults started on HAART from November, 2008 to May, 2010 was done in a tertiary care hospital in north India. A total 224 patients divided into two groups, one with HIV-TB and the other with HIV alone, were followedup for a minimum period of 3 months. The diagnosis of TB was categorised as ‘‘definitive” and ‘‘probable”. Results. Out of a total of 224 patients, 203 completed followup. Paradoxical TB-IRIS occurred in 5 of 123 (4%) HIV-TB patients while 6 of 80 (7.5%) HIV patients developed ART-associated TB. A reduction in plasma viral load was significantly (P = .016) associated with paradoxical TB-IRIS. No identifiable risk factors were associated with the development of ART-associated TB. Conclusion. The consensus case-definitions are useful tools in the diagnosis of TB-associated IRIS. High index of clinical suspicion is required for an early diagnosis. PMID:21197457

Wavelength-tunable optical ring resonators

DOEpatents

Watts, Michael R [Albuquerque, NM; Trotter, Douglas C [Albuquerque, NM; Young, Ralph W [Albuquerque, NM; Nielson, Gregory N [Albuquerque, NM

2009-11-10

Optical ring resonator devices are disclosed that can be used for optical filtering, modulation or switching, or for use as photodetectors or sensors. These devices can be formed as microdisk ring resonators, or as open-ring resonators with an optical waveguide having a width that varies adiabatically. Electrical and mechanical connections to the open-ring resonators are made near a maximum width of the optical waveguide to minimize losses and thereby provide a high resonator Q. The ring resonators can be tuned using an integral electrical heater, or an integral semiconductor junction.

Wavelength-tunable optical ring resonators

DOEpatents

Watts, Michael R [Albuquerque, NM; Trotter, Douglas C [Albuquerque, NM; Young, Ralph W [Albuquerque, NM; Nielson, Gregory N [Albuquerque, NM

2011-07-19

Optical ring resonator devices are disclosed that can be used for optical filtering, modulation or switching, or for use as photodetectors or sensors. These devices can be formed as microdisk ring resonators, or as open-ring resonators with an optical waveguide having a width that varies adiabatically. Electrical and mechanical connections to the open-ring resonators are made near a maximum width of the optical waveguide to minimize losses and thereby provide a high resonator Q. The ring resonators can be tuned using an integral electrical heater, or an integral semiconductor junction.

The all-optical modulator in dielectric-loaded waveguide with graphene-silicon heterojunction structure

NASA Astrophysics Data System (ADS)

Sun, Feiying; Xia, Liangping; Nie, Changbin; Shen, Jun; Zou, Yixuan; Cheng, Guiyu; Wu, Hao; Zhang, Yong; Wei, Dongshan; Yin, Shaoyun; Du, Chunlei

2018-04-01

All-optical modulators based on graphene show great promise for on-chip optical interconnects. However, the modulation performance of all-optical modulators is usually based on the interaction between graphene and the fiber, limiting their potential in high integration. Based on this point, an all-optical modulator in a dielectric-loaded waveguide (DLW) with a graphene-silicon heterojunction structure (GSH) is proposed. The DLW raises the waveguide mode, which provides a strong light-graphene interaction. Sufficient tuning of the graphene Fermi energy beyond the Pauli blocking effect is obtained with the presented GSH structure. Under the modulation light with a wavelength of 532 nm and a power of 60 mW, a modulation efficiency of 0.0275 dB µm-1 is achieved for light with a communication wavelength of 1.55 µm in the experiment. This modulator has the advantage of having a compact footprint, which may make it a candidate for achieving a highly integrated all-optical modulator.

TB-IRIS and remodelling of the T cell compartment in highly immunosuppressed HIV+ patients with TB: the CAPRI T (ANRS-12614) study

PubMed Central

Haridas, V.; Pean, P.; Jasenosky, L.D.; Madec, Y.; Laureillard, D.; Sok, T.; Sath, S.; Borand, L.; Marcy, O.; Chan, S.; Tsitsikov, E.; Delfraissy, J.-F.; Blanc, F.-X.; Goldfeld, A.E.

2015-01-01

Objective To investigate the impact of tuberculosis (TB)-associated immune reconstitution syndrome (IRIS) upon immunological recovery and the T cell compartment after initiation of TB and antiretroviral therapy (ART). Design and methods We prospectively evaluated T cell immunophenotypes by flow cytometry and cytokines by Luminex assays in a subset (n=154) of highly immunosuppressed HIV+ patients with TB from the CAMELIA randomized clinical trial. We compared findings from patients who developed TB-IRIS to findings from patients who did not develop TB-IRIS. Data were evaluated with mixed effect linear regression, Kaplan-Meier estimates, and Wilcoxon rank sum tests, and q-values were calculated to control for multiple comparisons. Results Development of TB-IRIS was associated with significantly greater pre-ART frequencies of HLA-DR+CD45RO+CD4+, CCR5+CD4+, OX40+CD4+, and Fas+ effector memory (EM) CD8+ T cells, and significantly elevated levels of plasma IL-6, IL-1β, IL-8, and IL-10 and viral load. Post-ART initiation, EM CD4+ and Fas+ EM CD4+ T cell frequencies significantly expanded, and central memory (CM) CD4+ T cell frequencies significantly contracted in patients who experienced TB-IRIS. By week 34 post-TB treatment initiation, EM/CM CD4+ T cell ratios were markedly higher in TB-IRIS versus non-TB-IRIS patients. Conclusions A distinct pattern of pre-ART T cell and cytokine markers appear to poise the immune response to develop TB-IRIS. Experience of TB-IRIS is then associated with long-term remodeling of the CD4+ T cell memory compartment towards an EM-dominated phenotype. We speculate that these pre- and post-ART TB-IRIS-associated immune parameters may contribute to superior immune control of TB/HIV co-infection and better clinical outcome. PMID:25486415

KSC-2013-2739

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The launch crew of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2745

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences L-1011 aircraft called "Stargazer" arrives at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2740

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The launch crew of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2738

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The launch crew of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2743

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences L-1011 aircraft called "Stargazer" arrives at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2736

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The cockpit of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2744

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. – One of the portable control trailers is set up at Vandenberg Air Force Base for the upcoming launch of an Orbital Sciences Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2735

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The Orbital Sciences L-1011 aircraft called "Stargazer" arrives at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2737

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. - The launch crew of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

A comparative study between shielded and open coplanar waveguide discontinuities

NASA Technical Reports Server (NTRS)

Dib, Nihad I.; Harokopus, W. P., Jr.; Ponchak, G. E.; Katehi, L. P. B.

1993-01-01

A comparative study between open and shielded coplanar waveguide (CPW) discontinuities is presented. The space domain integral equation method is used to characterize several discontinuities such as the open-end CPW and CPW series stubs. Two different geometries of CPW series stubs (straight and bent stubs) are compared with respect to resonant frequency and radiation loss. In addition, the encountered radiation loss due to different CPW shunt stubs is evaluated experimentally. The notion of forced radiation simulation is presented, and the results of such a simulation are compared to the actual radiation loss obtained rigorously. It is shown that such a simulation cannot give reliable results concerning radiation loss from printed circuits.

Integrated Optical Dipole Trap for Cold Neutral Atoms with an Optical Waveguide Coupler

NASA Astrophysics Data System (ADS)

Lee, J.; Park, D. H.; Mittal, S.; Meng, Y.; Dagenais, M.; Rolston, S. L.

2013-05-01

Using an optical waveguide, an integrated optical dipole trap uses two-color (red and blue-detuned) traveling evanescent wave fields for trapping cold neutral atoms. To achieve longitudinal confinement, we propose using an integrated optical waveguide coupler, which provides a potential gradient along the beam propagation direction sufficient to confine atoms. This integrated optical dipole trap can support an atomic ensemble with a large optical depth due to its small mode area. Its quasi-TE0 waveguide mode has an advantage over the HE11 mode of a nanofiber, with little inhomogeneous Zeeman broadening at the trapping region. The longitudinal confinement eliminates the need for a 1D optical lattice, reducing collisional blockaded atomic loading, potentially producing larger ensembles. The waveguide trap allows for scalability and integrability with nano-fabrication technology. We analyze the potential performance of such integrated atom traps and present current research progress towards a fiber-coupled silicon nitride optical waveguide integrable with atom chips. Work is supported by the ARO Atomtronics MURI. Work is supported by the ARO Atomtronics MURI.

Micropore and nanopore fabrication in hollow antiresonant reflecting optical waveguides

PubMed Central

Holmes, Matthew R.; Shang, Tao; Hawkins, Aaron R.; Rudenko, Mikhail; Measor, Philip; Schmidt, Holger

2011-01-01

We demonstrate the fabrication of micropore and nanopore features in hollow antiresonant reflecting optical waveguides to create an electrical and optical analysis platform that can size select and detect a single nanoparticle. Micropores (4 μm diameter) are reactive-ion etched through the top SiO2 and SiN layers of the waveguides, leaving a thin SiN membrane above the hollow core. Nanopores are formed in the SiN membranes using a focused ion-beam etch process that provides control over the pore size. Openings as small as 20 nm in diameter are created. Optical loss measurements indicate that micropores did not significantly alter the loss along the waveguide. PMID:21922035

Micropore and nanopore fabrication in hollow antiresonant reflecting optical waveguides.

PubMed

Holmes, Matthew R; Shang, Tao; Hawkins, Aaron R; Rudenko, Mikhail; Measor, Philip; Schmidt, Holger

2010-01-01

We demonstrate the fabrication of micropore and nanopore features in hollow antiresonant reflecting optical waveguides to create an electrical and optical analysis platform that can size select and detect a single nanoparticle. Micropores (4 μm diameter) are reactive-ion etched through the top SiO(2) and SiN layers of the waveguides, leaving a thin SiN membrane above the hollow core. Nanopores are formed in the SiN membranes using a focused ion-beam etch process that provides control over the pore size. Openings as small as 20 nm in diameter are created. Optical loss measurements indicate that micropores did not significantly alter the loss along the waveguide.

KSC-2013-2485

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. - An Orbital Sciences Pegasus XL rocket undergoes launch preparations inside a hangar at Vandenberg Air Force Base for NASA's IRIS mission, short for Interface Region Imaging Spectrograph. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2486

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. - An Orbital Sciences Pegasus XL rocket undergoes launch preparations inside a hangar at Vandenberg Air Force Base for NASA's IRIS mission, short for Interface Region Imaging Spectrograph. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

Analysis of hybrid dielectric-plasmonic slot waveguide structures with 3D Fourier Modal Methods

NASA Astrophysics Data System (ADS)

Ctyroky, J.; Kwiecien, P.; Richter, I.

2013-03-01

Recently, plasmonic waveguides have been intensively studied as promising basic building blocks for the construction of extremely compact photonic devices with subwavelength characteristic dimensions. A number of different types of plasmonic waveguide structures have been recently proposed, theoretically analyzed, and their properties experimentally verified. The fundamental trade-off in the design of plasmonic waveguides for potential application in information technologies lies in the contradiction between their mode field confinement and propagation loss: the higher confinement, the higher loss, and vice versa. Various definitions of figures of merit of plasmonic waveguides have been also introduced for the characterization of their properties with a single quantity. In this contribution, we theoretically analyze one specific type of a plasmonic waveguide - the hybrid dielectric-loaded plasmonic waveguide, or - as we call it in this paper - the hybrid dielectric-plasmonic slot waveguide, which exhibits very strong field confinement combined with acceptable losses allowing their application in some integrated plasmonic devices. In contrast to the structures analyzed previously, our structure makes use of a single low-index dielectric only. We first define the effective area of this waveguide type, and using waveguide parameters close to the optimum we analyze several waveguide devices as directional couplers, multimode interference couplers (MMI), and the Mach-Zehnder interferometer based on the MMI couplers. For the full-vector 3D analysis of these structures, we use modelling tools developed in-house on the basis of the Fourier Modal Method (FMM). Our results thus serve to a dual purpose: they confirm that (i) these structures represent promising building blocks of plasmonic devices, and (ii) our FMM codes are capable of efficient 3D vector modelling of plasmonic waveguide devices.

Improved Modeling of Open Waveguide Aperture Radiators for use in Conformal Antenna Arrays

NASA Astrophysics Data System (ADS)

Nelson, Gregory James

Open waveguide apertures have been used as radiating elements in conformal arrays. Individual radiating element model patterns are used in constructing overall array models. The existing models for these aperture radiating elements may not accurately predict the array pattern for TEM waves which are not on boresight for each radiating element. In particular, surrounding structures can affect the far field patterns of these apertures, which ultimately affects the overall array pattern. New models of open waveguide apertures are developed here with the goal of accounting for the surrounding structure effects on the aperture far field patterns such that the new models make accurate pattern predictions. These aperture patterns (both E plane and H plane) are measured in an anechoic chamber and the manner in which they deviate from existing model patterns are studied. Using these measurements as a basis, existing models for both E and H planes are updated with new factors and terms which allow the prediction of far field open waveguide aperture patterns with improved accuracy. These new and improved individual radiator models are then used to predict overall conformal array patterns. Arrays of open waveguide apertures are constructed and measured in a similar fashion to the individual aperture measurements. These measured array patterns are compared with the newly modeled array patterns to verify the improved accuracy of the new models as compared with the performance of existing models in making array far field pattern predictions. The array pattern lobe characteristics are then studied for predicting fully circularly conformal arrays of varying radii. The lobe metrics that are tracked are angular location and magnitude as the radii of the conformal arrays are varied. A constructed, measured array that is close to conforming to a circular surface is compared with a fully circularly conformal modeled array pattern prediction, with the predicted lobe angular locations and magnitudes tracked, plotted and tabulated. The close match between the patterns of the measured array and the modeled circularly conformal array verifies the validity of the modeled circularly conformal array pattern predictions.

KSC-2013-2643

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – The Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June is seen after the payload fairing was connected over NASA's IRIS spacecraft. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2494

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers unwrap NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2012-5601

NASA Image and Video Library

2012-09-25

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians install the avionics shelf on the third stage of the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

KSC-2013-2493

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers unwrap NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2012-5602

NASA Image and Video Library

2012-09-25

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians install the avionics shelf on the third stage of the Orbital Sciences Corp. Pegasus XL rocket which will launch the Interface Region Imaging Spectrograph, or IRIS, spacecraft. Scheduled for launch from Vandenberg Air Force Base no earlier than Feb. 27, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. For more information, visit http://iris.gsfc.nasa.gov Photo credit: NASA/Randy Beaudoin

Waveguide-loaded silica fibers for coupling to high-index micro-resonators

NASA Astrophysics Data System (ADS)

Latawiec, P.; Burek, M. J.; Venkataraman, V.; Lončar, M.

2016-01-01

Tapered silica fibers are often used to rapidly probe the optical properties of micro-resonators. However, their low refractive index precludes phase-matching when coupling to high-index micro-resonators, reducing efficiency. Here, we demonstrate efficient optical coupling from tapered fibers to high-index micro-resonators by loading the fibers with an ancillary adiabatic waveguide-coupler fabricated via angled-etching. We demonstrate greatly enhanced coupling to a silicon multimode micro-resonator when compared to coupling via the bare fiber only. Signatures of resonator optical bistability are observed at high powers. This scheme can be applied to resonators of any size and material, increasing the functional scope of fiber coupling.

Analysis and synthesis of (SAR) waveguide phased array antennas

NASA Astrophysics Data System (ADS)

Visser, H. J.

1994-02-01

This report describes work performed due to ESA contract No. 101 34/93/NL/PB. Started is with a literature study on dual polarized waveguide radiators, resulting in the choice for the open ended square waveguide. After a thorough description of the mode matching infinite waveguide array analysis method - including finiteness effects - that forms the basis for all further described analysis and synthesis methods, the accuracy of the analysis software is validated by comparison with measurements on two realized antennas. These antennas have centered irises in the waveguide apertures and a dielectric wide angle impedance matching sheet in front of the antenna. A synthesis method, using simulated annealing and downhill simplex, is described next and different antenna designs, based on the analysis of a single element in an infinite array environment, are presented. Next, designs of subarrays are presented. Shown is the paramount importance of including the array environment in the design of a subarray. A microstrip patch waveguide exciter and subarray feeding network are discussed and the depth of the waveguide radiator is estimated. Chosen is a rectangular grid array with waveguides of 2.5 cm depth without irises and without dielectric sheet, grouped in linear 8 elements subarrays.

Strongly Confined Spoof Surface Plasmon Polaritons Waveguiding Enabled by Planar Staggered Plasmonic Waveguides

NASA Astrophysics Data System (ADS)

Ye, Longfang; Xiao, Yifan; Liu, Yanhui; Zhang, Liang; Cai, Guoxiong; Liu, Qing Huo

2016-12-01

We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW’s propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes.

Strongly Confined Spoof Surface Plasmon Polaritons Waveguiding Enabled by Planar Staggered Plasmonic Waveguides.

PubMed

Ye, Longfang; Xiao, Yifan; Liu, Yanhui; Zhang, Liang; Cai, Guoxiong; Liu, Qing Huo

2016-12-05

We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW's propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes.

Near-Field Microwave Detection of Corrosion Precursor Pitting under Thin Dielectric Coatings in Metallic Substrate

NASA Astrophysics Data System (ADS)

Hughes, D.; Zoughi, R.; Austin, R.; Wood, N.; Engelbart, R.

2003-03-01

Detection of corrosion precursor pitting on metallic surfaces under various coatings and on bare metal is of keen interest in evaluation of aircraft fuselage. Near-field microwave nondestructive testing methods, utilizing open-ended rectangular waveguides and coaxial probes, have been used extensively for detection of surface flaws in metals, both on bare metal and under a dielectric coating. This paper presents the preliminary results of using microwave techniques to detect corrosion precursor pitting under paint and primer, applique and on bare metal. Machined pits of 500 μm diameter were detected using open-ended rectangular waveguides at V-Band under paint and primer and applique, and on bare metal. Using coaxial probes, machined pits with diameters down to 150 μm on bare metal were also detected. Relative pit size and density were shown on a corrosion-pitted sample using open-ended rectangular waveguides at frequencies of 35 GHz to 70 GHz. The use of Boeing's MAUS™ scanning systems provided improved results by alleviating standoff variation and scanning artifact. Typical results of this investigation are also presented.

Low loss hollow-core waveguide on a silicon substrate

NASA Astrophysics Data System (ADS)

Yang, Weijian; Ferrara, James; Grutter, Karen; Yeh, Anthony; Chase, Chris; Yue, Yang; Willner, Alan E.; Wu, Ming C.; Chang-Hasnain, Connie J.

2012-07-01

Optical-fiber-based, hollow-core waveguides (HCWs) have opened up many new applications in laser surgery, gas sensors, and non-linear optics. Chip-scale HCWs are desirable because they are compact, light-weight and can be integrated with other devices into systems-on-a-chip. However, their progress has been hindered by the lack of a low loss waveguide architecture. Here, a completely new waveguiding concept is demonstrated using two planar, parallel, silicon-on-insulator wafers with high-contrast subwavelength gratings to reflect light in-between. We report a record low optical loss of 0.37 dB/cm for a 9-μm waveguide, mode-matched to a single mode fiber. Two-dimensional light confinement is experimentally realized without sidewalls in the HCWs, which is promising for ultrafast sensing response with nearly instantaneous flow of gases or fluids. This unique waveguide geometry establishes an entirely new scheme for low-cost chip-scale sensor arrays and lab-on-a-chip applications.

Contribution of Different Anatomical and Physiologic Factors to Iris Contour and Anterior Chamber Angle Changes During Pupil Dilation: Theoretical Analysis

PubMed Central

Jouzdani, Sara; Amini, Rouzbeh; Barocas, Victor H.

2013-01-01

Purpose. To investigate the contribution of three anatomical and physiologic factors (dilator thickness, dynamic pupillary block, and iris compressibility) to changes in iris configuration and anterior chamber angle during pupil dilation. Methods. A mathematical model of the anterior segment based on the average values of ocular dimensions was developed to simulate pupil dilation. To change the pupil diameter from 3.0 to 5.4 mm in 10 seconds, active dilator contraction was applied by imposing stress in the dilator region. Three sets of parameters were varied in the simulations: (1) a thin (4 μm, 1% of full thickness) versus a thick dilator (covering the full thickness iris) to quantify the effects of dilator anatomy, (2) in the presence (+PB) versus absence of pupillary block (−PB) to quantify the effect of dynamic motion of aqueous humor from the posterior to the anterior chamber, and (3) a compressible versus an incompressible iris to quantify the effects of iris volume change. Changes in the apparent iris–lens contact and angle open distance (AOD500) were calculated for each case. Results. The thin case predicted a significant increase (average 700%) in iris curvature compared with the thick case (average 70%), showing that the anatomy of dilator plays an important role in iris deformation during dilation. In the presence of pupillary block (+PB), AOD500 decreased 25% and 36% for the compressible and incompressible iris, respectively. Conclusions. Iris bowing during dilation was driven primarily by posterior location of the dilator muscle and by dynamic pupillary block, but the effect of pupillary block was not as large as that of the dilator anatomy according to the quantified values of AOD500. Incompressibility of the iris, in contrast, had a relatively small effect on iris curvature but a large effect on AOD500; thus, we conclude that all three effects are important. PMID:23482467

Relationship between iris surface features and angle width in Asian eyes.

PubMed

Sidhartha, Elizabeth; Nongpiur, Monisha Esther; Cheung, Carol Y; He, Mingguang; Wong, Tien Yin; Aung, Tin; Cheng, Ching-Yu

2014-10-23

To examine the associations between iris surface features with anterior chamber angle width in Asian eyes. In this prospective cross-sectional study, we recruited 600 subjects from a large population-based study, the Singapore Epidemiology of Eye Diseases (SEED) study. We obtained standardized digital slit-lamp iris photographs and graded the iris crypts (by number and size), furrows (by number and circumferential extent), and color (higher grade denoting darker iris). Vertical and horizontal cross-sections of anterior chamber were imaged using anterior segment optical coherence tomography. Angle opening distance (AOD), angle recess area (ARA), and trabecular-iris space area (TISA) were measured using customized software. Associations of the angle width with the iris surface features in the subject's right eyes were assessed using linear regression analysis. A total of 464 eyes of the 464 subjects (mean age: 57.5 ± 8.6 years) had complete and gradable data for crypts and color, and 423 eyes had gradable data for furrows. After adjustment for age, sex, ethnicity, pupil size, and corneal arcus, higher crypt grade was independently associated with wider AOD750 (β [change in angle width per grade higher] = 0.018, P = 0.023), ARA750 (β = 0.022, P = 0.049), and TISA750 (β = 0.011, P = 0.019), and darker iris was associated narrower ARA750 (β = -0.025, P = 0.044) and TISA750 (β = -0.013, P = 0.011). Iris surface features, assessed and measured from slit-lamp photographs, correlated well with anterior chamber angle width; irises with more crypts and lighter color were associated with wider angle. These findings may provide another imaging modality to assess angle closure risk based on iris surface features. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

A two-stage heating scheme for heat assisted magnetic recording

NASA Astrophysics Data System (ADS)

Xiong, Shaomin; Kim, Jeongmin; Wang, Yuan; Zhang, Xiang; Bogy, David

2014-05-01

Heat Assisted Magnetic Recording (HAMR) has been proposed to extend the storage areal density beyond 1 Tb/in.2 for the next generation magnetic storage. A near field transducer (NFT) is widely used in HAMR systems to locally heat the magnetic disk during the writing process. However, much of the laser power is absorbed around the NFT, which causes overheating of the NFT and reduces its reliability. In this work, a two-stage heating scheme is proposed to reduce the thermal load by separating the NFT heating process into two individual heating stages from an optical waveguide and a NFT, respectively. As the first stage, the optical waveguide is placed in front of the NFT and delivers part of laser energy directly onto the disk surface to heat it up to a peak temperature somewhat lower than the Curie temperature of the magnetic material. Then, the NFT works as the second heating stage to heat a smaller area inside the waveguide heated area further to reach the Curie point. The energy applied to the NFT in the second heating stage is reduced compared with a typical single stage NFT heating system. With this reduced thermal load to the NFT by the two-stage heating scheme, the lifetime of the NFT can be extended orders longer under the cyclic load condition.

Integrated optical dipole trap for cold neutral atoms with an optical waveguide coupler

NASA Astrophysics Data System (ADS)

Lee, J.; Park, D. H.; Mittal, S.; Dagenais, M.; Rolston, S. L.

2013-04-01

An integrated optical dipole trap uses two-color (red and blue-detuned) traveling evanescent wave fields for trapping cold neutral atoms. To achieve longitudinal confinement, we propose using an integrated optical waveguide coupler, which provides a potential gradient along the beam propagation direction sufficient to confine atoms. This integrated optical dipole trap can support an atomic ensemble with a large optical depth due to its small mode area. Its quasi-TE0 waveguide mode has an advantage over the HE11 mode of a nanofiber, with little inhomogeneous Zeeman broadening at the trapping region. The longitudinal confinement eliminates the need for a one dimensional optical lattice, reducing collisional blockaded atomic loading, potentially producing larger ensembles. The waveguide trap allows for scalability and integrability with nano-fabrication technology. We analyze the potential performance of such integrated atom traps.

KSC-2013-2628

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2490

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers unwrap NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2503

NASA Image and Video Library

2013-05-30

VANDENBERG AFB, Calif. – Engineers prepare to install a radial retraction system on NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2601

NASA Image and Video Library

2013-06-10

VANDENBERG AFB, Calif. – Engineers conduct inspections on NASA's IRIS spacecraft with blacklights before the payload fairing before it is connected. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2642

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team engineers monitor the connection of the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2640

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – The payload fairing locked in place over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2618

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team members watch as engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2613

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Engineers attach the starboard side of the payload fairing into place for NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2581

NASA Image and Video Library

2013-06-05

VANDENBERG AFB – Engineers move the port side of the payload fairing before it is connected into place for NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2477

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers prepare to connect NASA's IRIS spacecraft to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2617

NASA Image and Video Library

2013-06-10

VANDENBERG AFB - Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2636

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2641

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers monitor the connection of the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2619

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – NASA's IRIS spacecraft before the second half of the payload fairing is installed over it. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2480

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers prepare to connect NASA's IRIS spacecraft to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2635

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2481

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers prepare to connect NASA's IRIS spacecraft to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2633

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team members move the second half of the payload fairing before it is placed over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2489

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers unwrap NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2639

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2504

NASA Image and Video Library

2013-05-30

VANDENBERG AFB, Calif. – Engineers install a radial retraction system on NASA's IRIS spacecraft after its connection to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2637

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2630

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team members move the second half of the payload fairing before it is placed over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2602

NASA Image and Video Library

2013-06-10

VANDENBERG AFB, Calif. – Engineers conduct inspections on NASA's IRIS spacecraft with blacklights before the payload fairing before it is connected. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2580

NASA Image and Video Library

2013-06-05

- VANDENBERG AFB – An engineer makes preparations on the starboard side of the payload fairing before it is connected into place for NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2626

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team members move the second half of the payload fairing before it is placed over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2616

NASA Image and Video Library

2013-06-11

Orbital Sciences engineers connect the payload fairing over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2482

NASA Image and Video Library

2013-05-29

VANDENBERG AFB, Calif. – Engineers prepare to connect NASA's IRIS spacecraft to the nose of an Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg no earlier than June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Randy Beaudoin

KSC-2013-2629

NASA Image and Video Library

2013-06-10

VANDENBERG AFB – Orbital Sciences team members move the second half of the payload fairing before it is placed over NASA's IRIS spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit in June. The work is taking place in a hangar at Vandenberg Air Force Base where IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg June 26, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: NASA/Tony Vauclin

KSC-2013-2828

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2825

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2831

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2885

NASA Image and Video Library

2013-06-24

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, mission managers participate in a pre-launch dress rehearsal in the Launch Vehicle Data Center for NASA’s Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26 aboard an Orbital Sciences Pegasus XL rocket, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region in to the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun’s visible surface and upper atmosphere, is where most of the sun’s ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth’s climate. For more information, visit http://www.nasa.gov/iris. Photo credit: NASA/Daniel Casper

KSC-2013-2830

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2832

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2912

NASA Image and Video Library

2013-06-25

VANDENBERG AIR FORCE BASE, Calif. – Final checkouts are being completed at Vandenberg Air Force Base in California as preparations continue for the launch from the L-1011 carrier aircraft of the Orbital Sciences Corp. Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/ Daniel Casper

KSC-2013-2833

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2824

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2888

NASA Image and Video Library

2013-06-24

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, mission managers participate in a pre-launch dress rehearsal in the Launch Vehicle Data Center for NASA’s Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26 aboard an Orbital Sciences Pegasus XL rocket, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region in to the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun’s visible surface and upper atmosphere, is where most of the sun’s ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth’s climate. For more information, visit http://www.nasa.gov/iris. Photo credit: NASA/Daniel Casper

KSC-2013-2827

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2826

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2887

NASA Image and Video Library

2013-06-24

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, mission managers participate in a pre-launch dress rehearsal in the Launch Vehicle Data Center for NASA’s Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26 aboard an Orbital Sciences Pegasus XL rocket, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region in to the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun’s visible surface and upper atmosphere, is where most of the sun’s ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth’s climate. For more information, visit http://www.nasa.gov/iris. Photo credit: NASA/Daniel Casper

KSC-2013-2911

NASA Image and Video Library

2013-06-25

VANDENBERG AIR FORCE BASE, Calif. – Final checkouts are being completed at Vandenberg Air Force Base in California as preparations continue for the launch from the L-1011 carrier aircraft of the Orbital Sciences Corp. Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/ Daniel Casper

KSC-2013-2829

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2886

NASA Image and Video Library

2013-06-24

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, mission managers participate in a pre-launch dress rehearsal in the Launch Vehicle Data Center for NASA’s Interface Region Imaging Spectrograph, or IRIS, solar observatory. Scheduled for launch from Vandenberg on June 26 aboard an Orbital Sciences Pegasus XL rocket, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region in to the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun’s visible surface and upper atmosphere, is where most of the sun’s ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth’s climate. For more information, visit http://www.nasa.gov/iris. Photo credit: NASA/Daniel Casper

KSC-2013-2834

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – Technicians and engineers at Vandenberg Air Force Base in California mate the Pegasus XL rocket with the Interface Region Imaging Spectrograph, or IRIS, solar observatory to the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2012-2821

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – A truck carrying the third stage of the Orbital Sciences Pegasus XL rocket arrives at Vandenberg Air Force Base in California. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2820

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – A truck carrying all three stages of the Orbital Sciences Pegasus XL rocket arrives at Vandenberg Air Force Base in California. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2826

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – A truck carrying all three stages of the Orbital Sciences Pegasus XL rocket arrives at Vandenberg Air Force Base in California. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

Vesicles between plasma membrane and cell wall prior to visible senescence of Iris and Dendrobium flowers.

PubMed

Kamdee, Channatika; Kirasak, Kanjana; Ketsa, Saichol; van Doorn, Wouter G

2015-09-01

Cut Iris flowers (Iris x hollandica, cv. Blue Magic) show visible senescence about two days after full opening. Epidermal cells of the outer tepals collapse due to programmed cell death (PCD). Transmission electron microscopy (TEM) showed irregular swelling of the cell walls, starting prior to cell collapse. Compared to cells in flowers that had just opened, wall thickness increased up to tenfold prior to cell death. Fibrils were visible in the swollen walls. After cell death very little of the cell wall remained. Prior to and during visible wall swelling, vesicles (paramural bodies) were observed between the plasma membrane and the cell walls. The vesicles were also found in groups and were accompanied by amorphous substance. They usually showed a single membrane, and had a variety of diameters and electron densities. Cut Dendrobium hybrid cv. Lucky Duan flowers exhibited visible senescence about 14 days after full flower opening. Paramural bodies were also found in Dendrobium tepal epidermis and mesophyll cells, related to wall swelling and degradation. Although alternative explanations are well possible, it is hypothesized that paramural bodies carry enzymes involved in cell wall breakdown. The literature has not yet reported such bodies in association with senescence/PCD. Copyright © 2015 Elsevier GmbH. All rights reserved.

Fin-line horn antenna

DOEpatents

Reindel, John

1990-01-01

A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.

Microwave applicator for in-drum processing of radioactive waste slurry

DOEpatents

White, Terry L.

1994-01-01

A microwave applicator for processing of radioactive waste slurry uses a waveguide network which splits an input microwave of TE.sub.10 rectangular mode to TE.sub.01 circular mode. A cylindrical body has four openings, each receiving 1/4 of the power input. The waveguide network includes a plurality of splitters to effect the 1/4 divisions of power.

A Waveguide-coupled Thermally-isolated Radiometric Source

NASA Technical Reports Server (NTRS)

Rostem, Karwan; Chuss, David T.; Lourie, Nathan P.; Voellmer, George M.; Wollack, Edward

2013-01-01

The design and validation of a dual polarization source for waveguide-coupled millimeter and sub-millimeter wave cryogenic sensors is presented. The thermal source is a waveguide mounted absorbing conical dielectric taper. The absorber is thermally isolated with a kinematic suspension that allows the guide to be heat sunk to the lowest bath temperature of the cryogenic system. This approach enables the thermal emission from the metallic waveguide walls to be subdominant to that from the source. The use of low thermal conductivity Kevlar threads for the kinematic mount effectively decouples the absorber from the sensor cold stage. Hence, the absorber can be heated to significantly higher temperatures than the sensor with negligible conductive loading. The kinematic suspension provides high mechanical repeatability and reliability with thermal cycling. A 33-50 GHz blackbody source demonstrates an emissivity of 0.999 over the full waveguide band where the dominant deviation from unity arises from the waveguide ohmic loss. The observed thermal time constant of the source is 40 s when the absorber temperature is 15 K. The specific heat of the lossy dielectric MF-117 is well approximated by Cv(T) = 0.12 T(exp 2.06) mJ/g/K between 3.5 K and 15 K.

KSC-2013-2742

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. – A look through the inside of the fuselage of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2741

NASA Image and Video Library

2013-06-13

VANDENBERG ABF, Calif. – A look through the inside of the fuselage of the Orbital Sciences L-1011 aircraft called "Stargazer" after arrival at Vandenberg Air Force Base for the upcoming launch of the company's Pegasus XL rocket lifting NASA's IRIS solar observatory into orbit. The aircraft will carry the winged rocket to an altitude of 39,000 feet before releasing the Pegasus so its own motors can ignite to send the IRIS into space. The L-1011 is a modified airliner equipped to hold the Pegasus under its body safely. IRIS, short for Interface Region Imaging Spectrograph, is being prepared for launch from Vandenberg June 26. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

Ponderomotive electron acceleration in a silicon-based nanoplasmonic waveguide.

PubMed

Sederberg, S; Elezzabi, A Y

2014-10-17

Ponderomotive electron acceleration is demonstrated in a semiconductor-loaded nanoplasmonic waveguide. Photogenerated free carriers are accelerated by the tightly confined nanoplasmonic fields and reach energies exceeding the threshold for impact ionization. Broadband (375 nm ≤ λ ≤ 650  nm) white light emission is observed from the nanoplasmonic waveguides. Exponential growth of visible light emission confirms the exponential growth of the electron population, demonstrating the presence of an optical-field-driven electron avalanche. Electron sweeping dynamics are visualized using pump-probe measurements, and a sweeping time of 1.98 ± 0.40 ps is measured. These findings offer a means to harness the potential of the emerging field of ultrafast nonlinear nanoplasmonics.

Using Floquet periodicity to easily calculate dispersion curves and wave structures of homogeneous waveguides

NASA Astrophysics Data System (ADS)

Hakoda, Christopher; Rose, Joseph; Shokouhi, Parisa; Lissenden, Clifford

2018-04-01

Dispersion curves are essential to any guided-wave-related project. The Semi-Analytical Finite Element (SAFE) method has become the conventional way to compute dispersion curves for homogeneous waveguides. However, only recently has a general SAFE formulation for commercial and open-source software become available, meaning that until now SAFE analyses have been variable and more time consuming than desirable. Likewise, the Floquet boundary conditions enable analysis of waveguides with periodicity and have been an integral part of the development of metamaterials. In fact, we have found the use of Floquet boundary conditions to be an extremely powerful tool for homogeneous waveguides, too. The nuances of using periodic boundary conditions for homogeneous waveguides that do not exhibit periodicity are discussed. Comparisons between this method and SAFE are made for selected homogeneous waveguide applications. The COMSOL Multiphysics software is used for the results shown, but any standard finite element software that can implement Floquet periodicity (user-defined or built-in) should suffice. Finally, we identify a number of complex waveguides for which dispersion curves can be found with relative ease by using the periodicity inherent to the Floquet boundary conditions.

Clinical and Anterior Segment Anatomical Features in Primary Angle Closure Subgroups Based on Configurations of Iris Root Insertion.

PubMed

Hong, Ji Wook; Yun, Sung-Cheol; Sung, Kyung Rim; Lee, Jong Eun

2016-06-01

To compare the clinical and anterior segment anatomical features in primary angle closure sub-groups based on configurations of iris root insertion. Primary angle closure patients were imaged using anterior segment optical coherence tomography. Anterior chamber depth, iris curvature, iris thickness (IT) at the scleral spur and 500, 750, and 1,500 µm from the scleral spur (IT0, IT500, IT750, and IT1500), lens vault, iris area, angle opening distance (AOD500), angle recess area (ARA750), and trabecular iris space area (TISA750) were measured. Iris root insertion was categorized into a non-basal insertion group (NBG) and basal insertion group (BG). In total, 43 eyes of 39 participants belonged to the NBG and 89 eyes of 53 participants to the BG. The mean age of participants was greater in the NBG than the BG (62.7 ± 5.7 vs. 59.8 ± 7.3 years, p = 0.043), and the baseline intraocular pressure was higher in the BG than the NBG (16.4 ± 4.4 vs. 14.9 ± 3.3 mmHg, p = 0.037). The BG showed a greater IT0 (0.265 ± 0.04 vs. 0.214 ± 0.03 mm, p < 0.001) and iris area (1.59 ± 0.24 vs. 1.52 ± 0.27 mm(2), p = 0.045), lower ARA750 (0.112 ± 0.08 vs. 0.154 ± 0.08 mm(2), p = 0.017) and AOD500 (0.165 ± 0.07 vs. 0.202 ± 0.08 mm, p = 0.014) compared to the NBG. The BG had a narrower anterior chamber angle, thicker peripheral iris, and higher pretreatment intraocular pressure.

Control of acoustic absorption in one-dimensional scattering by resonant scatterers

NASA Astrophysics Data System (ADS)

Merkel, A.; Theocharis, G.; Richoux, O.; Romero-García, V.; Pagneux, V.

2015-12-01

We experimentally report perfect acoustic absorption through the interplay of the inherent losses and transparent modes with high Q factor. These modes are generated in a two-port, one-dimensional waveguide, which is side-loaded by isolated resonators of moderate Q factor. In symmetric structures, we show that in the presence of small inherent losses, these modes lead to coherent perfect absorption associated with one-sided absorption slightly larger than 0.5. In asymmetric structures, near perfect one-sided absorption is possible (96%) with a deep sub-wavelength sample ( λ / 28 , where λ is the wavelength of the sound wave in the air). The control of strong absorption by the proper tuning of the radiation leakage of few resonators with weak losses will open possibilities in various wave-control devices.

HRMS sky survey wideband feed system design for DSS 24 beam waveguide antenna

NASA Technical Reports Server (NTRS)

Stanton, P. H.; Lee, P. R.; Reilly, H. F.

1993-01-01

The High-Resolution Microwave Survey (HRMS) Sky Survey project will be implemented on the DSS 24 beam waveguide (BWG) antenna over the frequency range of 2.86 to 10 GHz. Two wideband, ring-loaded, corrugated feed horns were designed to cover this range. The horns match the frequency-dependent gain requirements for the DSS 24 BWG system. The performance of the feed horns and the calculated system performance of DSS 24 are presented.

THz-wave generation via difference frequency mixing in strained silicon based waveguide utilizing its second order susceptibility χ((2)).

PubMed

Saito, Kyosuke; Tanabe, Tadao; Oyama, Yutaka

2014-07-14

Terahertz (THz) wave generation via difference frequency mixing (DFM) process in strain silicon membrane waveguides by introducing the straining layer is theoretically investigated. The Si(3)N(4) straining layer induces anisotropic compressive strain in the silicon core and results in the appearance of the bulk second order nonlinear susceptibility χ((2)) by breaking the crystal symmetry. We have proposed waveguide structures for THz wave generation under the DFM process by .using the modal birefringence in the waveguide core. Our simulations show that an output power of up to 0.95 mW can be achieved at 9.09 THz. The strained silicon optical device may open a widow in the field of the silicon-based active THz photonic device applications.

Analysis of three-dimensional-cavity-backed aperture antennas using a Combined Finite Element Method/Method of Moments/Geometrical Theory of Diffraction technique

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.; Cockrell, C. R.; Beck, F. B.

1995-01-01

A combined finite element method (FEM) and method of moments (MoM) technique is presented to analyze the radiation characteristics of a cavity-fed aperture in three dimensions. Generalized feed modeling has been done using the modal expansion of fields in the feed structure. Numerical results for some feeding structures such as a rectangular waveguide, circular waveguide, and coaxial line are presented. The method also uses the geometrical theory of diffraction (GTD) to predict the effect of a finite ground plane on radiation characteristics. Input admittance calculations for open radiating structures such as a rectangular waveguide, a circular waveguide, and a coaxial line are shown. Numerical data for a coaxial-fed cavity with finite ground plane are verified with experimental data.

Evaluation of Cellular Phenotypes Implicated in Immunopathogenesis and Monitoring Immune Reconstitution Inflammatory Syndrome in HIV/Leprosy Cases

PubMed Central

Giacoia-Gripp, Carmem Beatriz Wagner; Sales, Anna Maria; Nery, José Augusto da Costa; Santos-Oliveira, Joanna Reis; de Oliveira, Ariane Leite; Sarno, Euzenir Nunes; Morgado, Mariza Gonçalves

2011-01-01

Background It is now evident that HAART-associated immunological improvement often leads to a variety of new clinical manifestations, collectively termed immune reconstitution inflammatory syndrome, or IRIS. This phenomenon has already been described in cases of HIV coinfection with Mycobacterium leprae, most of them belonging to the tuberculoid spectrum of leprosy disease, as observed in leprosy reversal reaction (RR). However, the events related to the pathogenesis of this association need to be clarified. This study investigated the immunological profile of HIV/leprosy patients, with special attention to the cellular activation status, to better understand the mechanisms related to IRIS/RR immunopathogenesis, identifying any potential biomarkers for IRIS/RR intercurrence. Methods/Principal Findings Eighty-five individuals were assessed in this study: HIV/leprosy and HIV-monoinfected patients, grouped according to HIV-viral load levels, leprosy patients without HIV coinfection, and healthy controls. Phenotypes were evaluated by flow cytometry for T cell subsets and immune differentiation/activation markers. As expected, absolute counts of the CD4+ and CD8+ T cells from the HIV-infected individuals changed in relation to those of the leprosy patients and controls. However, there were no significant differences among the groups, whether in the expression of cellular differentiation phenotypes or cellular activation, as reflected by the expression of CD38 and HLA-DR. Six HIV/leprosy patients identified as IRIS/RR were analyzed during IRIS/RR episodes and after prednisone treatment. These patients presented high cellular activation levels regarding the expression of CD38 in CD8+ cells T during IRIS/RR (median: 77,15%), dropping significantly (p<0,05) during post-IRIS/RR moments (median: 29,7%). Furthermore, an increase of cellular activation seems to occur prior to IRIS/RR. Conclusion/Significance These data suggest CD38 expression in CD8+ T cells interesting tool identifying HIV/leprosy individuals at risk for IRIS/RR. So, a comparative investigation to leprosy patients at RR should be conducted. PMID:22205964

Evaluation of cellular phenotypes implicated in immunopathogenesis and monitoring immune reconstitution inflammatory syndrome in HIV/leprosy cases.

PubMed

Giacoia-Gripp, Carmem Beatriz Wagner; Sales, Anna Maria; Nery, José Augusto da Costa; Santos-Oliveira, Joanna Reis; de Oliveira, Ariane Leite; Sarno, Euzenir Nunes; Morgado, Mariza Gonçalves

2011-01-01

It is now evident that HAART-associated immunological improvement often leads to a variety of new clinical manifestations, collectively termed immune reconstitution inflammatory syndrome, or IRIS. This phenomenon has already been described in cases of HIV coinfection with Mycobacterium leprae, most of them belonging to the tuberculoid spectrum of leprosy disease, as observed in leprosy reversal reaction (RR). However, the events related to the pathogenesis of this association need to be clarified. This study investigated the immunological profile of HIV/leprosy patients, with special attention to the cellular activation status, to better understand the mechanisms related to IRIS/RR immunopathogenesis, identifying any potential biomarkers for IRIS/RR intercurrence. Eighty-five individuals were assessed in this study: HIV/leprosy and HIV-monoinfected patients, grouped according to HIV-viral load levels, leprosy patients without HIV coinfection, and healthy controls. Phenotypes were evaluated by flow cytometry for T cell subsets and immune differentiation/activation markers. As expected, absolute counts of the CD4+ and CD8+ T cells from the HIV-infected individuals changed in relation to those of the leprosy patients and controls. However, there were no significant differences among the groups, whether in the expression of cellular differentiation phenotypes or cellular activation, as reflected by the expression of CD38 and HLA-DR. Six HIV/leprosy patients identified as IRIS/RR were analyzed during IRIS/RR episodes and after prednisone treatment. These patients presented high cellular activation levels regarding the expression of CD38 in CD8+ cells T during IRIS/RR (median: 77,15%), dropping significantly (p<0,05) during post-IRIS/RR moments (median: 29,7%). Furthermore, an increase of cellular activation seems to occur prior to IRIS/RR. These data suggest CD38 expression in CD8+ T cells interesting tool identifying HIV/leprosy individuals at risk for IRIS/RR. So, a comparative investigation to leprosy patients at RR should be conducted.

Microwave applicator for in-drum processing of radioactive waste slurry

DOEpatents

White, T.L.

1994-06-28

A microwave applicator for processing of radioactive waste slurry uses a waveguide network which splits an input microwave of TE[sub 10] rectangular mode to TE[sub 01] circular mode. A cylindrical body has four openings, each receiving 1/4 of the power input. The waveguide network includes a plurality of splitters to effect the 1/4 divisions of power. 4 figures.

A Short Open Calibration (SOC) Technique to Calculate the Propagation Characteristics of Substrate Integrated Waveguide

DTIC Science & Technology

2015-07-01

integrated with the commercial electromagnetic software for accurate extraction of propagation constant of substrate integrated waveguide ( SIW ) with...respectively. After three distinctive equivalent circuit networks are described for SOC de-embedding procedure. The propagation constants of SIW with...final, the phase and attenuation constants of SIW are derived to demonstrate the propagation and leakage characteristics of SIW . Index Terms

Integrated electrochromic aperture diaphragm

NASA Astrophysics Data System (ADS)

Deutschmann, T.; Oesterschulze, E.

2014-05-01

In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50μm. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

Distinct iris gene expression profiles of primary angle closure glaucoma and primary open angle glaucoma and their interaction with ocular biometric parameters.

PubMed

Seet, Li-Fong; Narayanaswamy, Arun; Finger, Sharon N; Htoon, Hla M; Nongpiur, Monisha E; Toh, Li Zhen; Ho, Henrietta; Perera, Shamira A; Wong, Tina T

2016-11-01

This study aimed to evaluate differences in iris gene expression profiles between primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) and their interaction with biometric characteristics. Prospective study. Thirty-five subjects with PACG and thirty-three subjects with POAG who required trabeculectomy were enrolled at the Singapore National Eye Centre, Singapore. Iris specimens, obtained by iridectomy, were analysed by real-time polymerase chain reaction for expression of type I collagen, vascular endothelial growth factor (VEGF)-A, -B and -C, as well as VEGF receptors (VEGFRs) 1 and 2. Anterior segment optical coherence tomography (ASOCT) imaging for biometric parameters, including anterior chamber depth (ACD), anterior chamber volume (ACV) and lens vault (LV), was also performed pre-operatively. Relative mRNA levels between PACG and POAG irises, biometric measurements, discriminant analyses using genes and biometric parameters. COL1A1, VEGFB, VEGFC and VEGFR2 mRNA expression was higher in PACG compared to POAG irises. LV, ACD and ACV were significantly different between the two subgroups. Discriminant analyses based on gene expression, biometric parameters or a combination of both gene expression and biometrics (LV and ACV), correctly classified 94.1%, 85.3% and 94.1% of the original PACG and POAG cases, respectively. The discriminant function combining genes and biometrics demonstrated the highest accuracy in cross-validated classification of the two glaucoma subtypes. Distinct iris gene expression supports the pathophysiological differences that exist between PACG and POAG. Biometric parameters can combine with iris gene expression to more accurately define PACG from POAG. © 2016 The Authors. Clinical & Experimental Ophthalmology published by John Wiley & Sons Australia, Ltd on behalf of Royal Australian and New Zealand College of Ophthalmologists.

Initial results for a 170 GHz high power ITER waveguide component test stand

NASA Astrophysics Data System (ADS)

Bigelow, Timothy; Barker, Alan; Dukes, Carl; Killough, Stephen; Kaufman, Michael; White, John; Bell, Gary; Hanson, Greg; Rasmussen, Dave

2014-10-01

A high power microwave test stand is being setup at ORNL to enable prototype testing of 170 GHz cw waveguide components being developed for the ITER ECH system. The ITER ECH system will utilize 63.5 mm diameter evacuated corrugated waveguide and will have 24 >150 m long runs. A 170 GHz 1 MW class gyrotron is being developed by Communications and Power Industries and is nearing completion. A HVDC power supply, water-cooling and control system has been partially tested in preparation for arrival of the gyrotron. The power supply and water-cooling system are being designed to operate for >3600 second pulses to simulate the operating conditions planned for the ITER ECH system. The gyrotron Gaussian beam output has a single mirror for focusing into a 63.5 mm corrugated waveguide in the vertical plane. The output beam and mirror are enclosed in an evacuated duct with absorber for stray radiation. Beam alignment with the waveguide is a critical task so a combination of mirror tilt adjustments and a bellows for offsets will be provided. Analysis of thermal patterns on thin witness plates will provide gyrotron mode purity and waveguide coupling efficiency data. Pre-prototype waveguide components and two dummy loads are available for initial operational testing of the gyrotron. ORNL is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under Contract DE-AC-05-00OR22725.

KSC-2012-2824

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – Inside a hangar at Vandenberg Air Force Base in California, technicians offload the second stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2828

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians prepare to offload the first stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2827

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians prepare to offload the first stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2825

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – Inside a hangar at Vandenberg Air Force Base in California, technicians offload the second stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2822

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – Inside a hangar at Vandenberg Air Force Base in California, technicians prepare to offload the third stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2831

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians offload the first stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2829

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians prepare to offload the first stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2830

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – At Vandenberg Air Force Base in California, technicians offload the first stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-2823

NASA Image and Video Library

2012-05-11

Vandenberg Air Force Base, Calif. – Inside a hangar at Vandenberg Air Force Base in California, technicians prepare to offload the third stage of the Orbital Sciences Pegasus XL rocket from the truck in which it was transported. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2013-2204

NASA Image and Video Library

2013-04-25

VANDENBERG AIR FORCE BASE, Calif. -- Half of the fairing that will be fitted to the nose of the Orbital Sciences Corp. Pegasus XL rocket is ready for its installation around the Interface Region Imaging Spectrograph, or IRIS, spacecraft. The fairing will protect the spacecraft from atmospheric heating and stress during launch. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2012-4672

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane moves the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4677

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane lowers the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4674

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane moves the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4673

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane moves the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4671

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians prepare the wing for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4675

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane lowers the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4676

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians assist as a crane lowers the wing closer for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

KSC-2012-4670

NASA Image and Video Library

2012-08-21

Vandenberg Air Force Base, Calif. – Inside a processing facility at Vandenberg Air Force Base in California, technicians prepare the wing for a fit check with the Orbital Sciences Pegasus XL launch vehicle. NASA’s Interface Region Imaging Spectrograph, or IRIS, spacecraft will launch aboard the Pegasus XL in late 2012. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and heliosphere, or region around the sun. Photo credit: NASA/Randy Beaudoin

Demonstration of a high repetition rate capillary discharge waveguide

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

Gonsalves, A. J., E-mail: ajgonsalves@lbl.gov; Pieronek, C.; Daniels, J.

2016-01-21

A hydrogen-filled capillary discharge waveguide operating at kHz repetition rates is presented for parameters relevant to laser plasma acceleration (LPA). The discharge current pulse was optimized for erosion mitigation with laser guiding experiments and MHD simulation. Heat flow simulations and measurements showed modest temperature rise at the capillary wall due to the average heat load at kHz repetition rates with water-cooled capillaries, which is promising for applications of LPAs such as high average power radiation sources.

VASIR: An Open-Source Research Platform for Advanced Iris Recognition Technologies.

PubMed

Lee, Yooyoung; Micheals, Ross J; Filliben, James J; Phillips, P Jonathon

2013-01-01

The performance of iris recognition systems is frequently affected by input image quality, which in turn is vulnerable to less-than-optimal conditions due to illuminations, environments, and subject characteristics (e.g., distance, movement, face/body visibility, blinking, etc.). VASIR (Video-based Automatic System for Iris Recognition) is a state-of-the-art NIST-developed iris recognition software platform designed to systematically address these vulnerabilities. We developed VASIR as a research tool that will not only provide a reference (to assess the relative performance of alternative algorithms) for the biometrics community, but will also advance (via this new emerging iris recognition paradigm) NIST's measurement mission. VASIR is designed to accommodate both ideal (e.g., classical still images) and less-than-ideal images (e.g., face-visible videos). VASIR has three primary modules: 1) Image Acquisition 2) Video Processing, and 3) Iris Recognition. Each module consists of several sub-components that have been optimized by use of rigorous orthogonal experiment design and analysis techniques. We evaluated VASIR performance using the MBGC (Multiple Biometric Grand Challenge) NIR (Near-Infrared) face-visible video dataset and the ICE (Iris Challenge Evaluation) 2005 still-based dataset. The results showed that even though VASIR was primarily developed and optimized for the less-constrained video case, it still achieved high verification rates for the traditional still-image case. For this reason, VASIR may be used as an effective baseline for the biometrics community to evaluate their algorithm performance, and thus serves as a valuable research platform.

VASIR: An Open-Source Research Platform for Advanced Iris Recognition Technologies

PubMed Central

Lee, Yooyoung; Micheals, Ross J; Filliben, James J; Phillips, P Jonathon

2013-01-01

The performance of iris recognition systems is frequently affected by input image quality, which in turn is vulnerable to less-than-optimal conditions due to illuminations, environments, and subject characteristics (e.g., distance, movement, face/body visibility, blinking, etc.). VASIR (Video-based Automatic System for Iris Recognition) is a state-of-the-art NIST-developed iris recognition software platform designed to systematically address these vulnerabilities. We developed VASIR as a research tool that will not only provide a reference (to assess the relative performance of alternative algorithms) for the biometrics community, but will also advance (via this new emerging iris recognition paradigm) NIST’s measurement mission. VASIR is designed to accommodate both ideal (e.g., classical still images) and less-than-ideal images (e.g., face-visible videos). VASIR has three primary modules: 1) Image Acquisition 2) Video Processing, and 3) Iris Recognition. Each module consists of several sub-components that have been optimized by use of rigorous orthogonal experiment design and analysis techniques. We evaluated VASIR performance using the MBGC (Multiple Biometric Grand Challenge) NIR (Near-Infrared) face-visible video dataset and the ICE (Iris Challenge Evaluation) 2005 still-based dataset. The results showed that even though VASIR was primarily developed and optimized for the less-constrained video case, it still achieved high verification rates for the traditional still-image case. For this reason, VASIR may be used as an effective baseline for the biometrics community to evaluate their algorithm performance, and thus serves as a valuable research platform. PMID:26401431

[Changes in the secretion of somatotropin and insulin in hyperthyroidism].

PubMed

Cavagnini, F; Peracchi, M; Panerai, A E; Pinto, M

1975-06-01

Twenty hyperthyroid patients were investigated for growth hormone (GH) and immunoreactive insulin (IRI) secretion in response to insulin hypoglycaemia, arginine infusion and glucose-induced hyperglycaemia. GH response to either insulin hypoglycaemia or arginine infusion was significantly reduced in these patients compared with 20 normal subjects. Thyrotoxic patients also displayed an abnormal GH pattern after a 100 g oral glucose load: in fact, serum GH underwent a paradoxical increase in spite of abnormally high levels attained by blood glucose. IRI secretion was also clearly reduced in response to arginine infusion and moderately blunted after oral glucose. In a group of patients re-evaluated under euthyroid conditions, a fair increase of GH response to the provocative stimuli jointly with the restoration of a normal suppressibility of serum GH by glucose were noted; by contrast, no significant change of IRI response to arginine or glucose took place. Likewise, the impairment of glucose tolerance was not improved. These findings indicate that an impairment of GH and IRI secretion is present in hyperthyroidism. The possibility that a potentiation of the catecholamine effects caused by the thyroid hormones is involved in this alteration deserves consideration.

Fusion of Renewable Ring Resonator Lasers and Ultrafast Laser Inscribed Photonic Waveguides

PubMed Central

Chandrahalim, Hengky; Rand, Stephen C.; Fan, Xudong

2016-01-01

We demonstrated the monolithic integration of reusable and wavelength reconfigurable ring resonator lasers and waveguides of arbitrary shapes to out-couple and guide laser emission on the same fused-silica chip. The ring resonator hosts were patterned by a single-mask standard lithography, whereas the waveguides were inscribed in the proximity of the ring resonator by using 3-dimensional femtosecond laser inscription technology. Reusability of the integrated ring resonator – waveguide system was examined by depositing, removing, and re-depositing dye-doped SU-8 solid polymer, SU-8 liquid polymer, and liquid solvent (toluene). The wavelength reconfigurability was validated by employing Rhodamine 6G (R6G) and 3,3′-Diethyloxacarbocyanine iodide (CY3) as exemplary gain media. In all above cases, the waveguide was able to couple out and guide the laser emission. This work opens a door to reconfigurable active and passive photonic devices for on-chip coherent light sources, optical signal processing, and the investigation of new optical phenomena. PMID:27600872

Fusion of Renewable Ring Resonator Lasers and Ultrafast Laser Inscribed Photonic Waveguides.

PubMed

Chandrahalim, Hengky; Rand, Stephen C; Fan, Xudong

2016-09-07

We demonstrated the monolithic integration of reusable and wavelength reconfigurable ring resonator lasers and waveguides of arbitrary shapes to out-couple and guide laser emission on the same fused-silica chip. The ring resonator hosts were patterned by a single-mask standard lithography, whereas the waveguides were inscribed in the proximity of the ring resonator by using 3-dimensional femtosecond laser inscription technology. Reusability of the integrated ring resonator - waveguide system was examined by depositing, removing, and re-depositing dye-doped SU-8 solid polymer, SU-8 liquid polymer, and liquid solvent (toluene). The wavelength reconfigurability was validated by employing Rhodamine 6G (R6G) and 3,3'-Diethyloxacarbocyanine iodide (CY3) as exemplary gain media. In all above cases, the waveguide was able to couple out and guide the laser emission. This work opens a door to reconfigurable active and passive photonic devices for on-chip coherent light sources, optical signal processing, and the investigation of new optical phenomena.

30GHz Ge electro-absorption modulator integrated with 3 μm silicon-on-insulator waveguide.

PubMed

Feng, Ning-Ning; Feng, Dazeng; Liao, Shirong; Wang, Xin; Dong, Po; Liang, Hong; Kung, Cheng-Chih; Qian, Wei; Fong, Joan; Shafiiha, Roshanak; Luo, Ying; Cunningham, Jack; Krishnamoorthy, Ashok V; Asghari, Mehdi

2011-04-11

We demonstrate a compact waveguide-based high-speed Ge electro-absorption (EA) modulator integrated with a single mode 3 µm silicon-on-isolator (SOI) waveguide. The Ge EA modulator is based on a horizontally-oriented p-i-n structure butt-coupled with a deep-etched silicon waveguide, which transitions adiabatically to a shallow-etched single mode large core SOI waveguide. The demonstrated device has a compact active region of 1.0 × 45 µm(2), a total insertion loss of 2.5-5 dB and an extinction ratio of 4-7.5 dB over a wavelength range of 1610-1640 nm with -4V(pp) bias. The estimated Δα/α value is in the range of 2-3.3. The 3 dB bandwidth measurements show that the device is capable of operating at more than 30 GHz. Clear eye-diagram openings at 12.5 Gbps demonstrates large signal modulation at high transmission rate. © 2011 Optical Society of America

Radio-frequency and microwave load comprising a carbon-bonded carbon fiber composite

DOEpatents

Lauf, R.J.; McMillan, A.D.; Johnson, A.C.; Everleigh, C.A.; Moorhead, A.J.

1998-04-21

A billet of low-density carbon-bonded carbon fiber (CBCF) composite is machined into a desired attenuator or load element shape (usually tapering). The CBCF composite is used as a free-standing load element or, preferably, brazed to the copper, brass or aluminum components of coaxial transmission lines or microwave waveguides. A novel braze method was developed for the brazing step. The resulting attenuator and/or load devices are robust, relatively inexpensive, more easily fabricated, and have improved performance over conventional graded-coating loads. 9 figs.

Radio-frequency and microwave load comprising a carbon-bonded carbon fiber composite

DOEpatents

Lauf, Robert J.; McMillan, April D.; Johnson, Arvid C.; Everleigh, Carl A.; Moorhead, Arthur J.

1998-01-01

A billet of low-density carbon-bonded carbon fiber (CBCF) composite is machined into a desired attenuator or load element shape (usually tapering). The CBCF composite is used as a free-standing load element or, preferably, brazed to the copper, brass or aluminum components of coaxial transmission lines or microwave waveguides. A novel braze method was developed for the brazing step. The resulting attenuator and/or load devices are robust, relatively inexpensive, more easily fabricated, and have improved performance over conventional graded-coating loads.

Waveguide studies for FOM FEM

NASA Astrophysics Data System (ADS)

Best, Robert W.; Urbanus, Wim H.; Verhoeven, Toon (A.)G. A.; Jerby, Eli; Ganzel, Ronit

1993-07-01

A 1 MW cw 200 GHz tunable efficient free electron maser is being designed at the FOM Institute for application in magnetic fusion research. In this paper several waveguide types are considered, including open waveguides. Computer simulations of the amplification and guiding of the mm wave in the undulator are reported. The simulation code is G3DH, written by E. Jerby, which solves a matrix dispersion relation. Gain vs frequency curves are shown. Efficiency calculations indicate that some tapering is needed to reach the desired 1 MW mm wavepower. Simulations of a tapered undulator are presented by Caplan, and overview of the FOM FEM is given by Urbanus et al. at this conference.

Low- and high-index sol-gel films for planar and channel-doped waveguides

NASA Astrophysics Data System (ADS)

Canva, Michael; Chaput, Frederic; Lahlil, Khalid; Rachet, Vincent; Goudket, Helene; Boilot, Jean-Pierre; Levy, Yves

2001-11-01

In view of realizing integrated optic components based on effects such as electro-optic, chi(2):chi(2) cascading, stimulated emission,... one has to first synthesize materials with the proper functionality; this may be achieved by doping solid state matrices by the appropriate organic chromophores. Second, and as important, these materials have to be properly structured into the final optical guiding structures. We shall report on issues related to the realization of chromophore-doped planar waveguides as well as channel waveguides. These structures were realized by either photo-transformation such as photo- chromism and photo-bleaching or reactive ion etching technique, starting with chromophore doped sol-gel materials at high loading contents for which optical index may be controlled via the local dopant concentration. With these materials and techniques, waveguides and components characterized by propagation losses of the order of a cm-1, measured off the edge of the absorption band of the doping species, were fabricated. In order to be also able to study and use waveguide functionalized with low concentration of chromophore species, we developed new sol-gel materials of high optical index, yet low temperature processed. These new films are under study to evaluate their potential as host for organic doped waveguides devices.

Low Loss Nanostructured Polymers for Chip-scale Waveguide Amplifiers.

PubMed

Chen, George F R; Zhao, Xinyu; Sun, Yang; He, Chaobin; Tan, Mei Chee; Tan, Dawn T H

2017-06-13

On-chip waveguide amplifiers offer higher gain in small device sizes and better integration with photonic devices than the commonly available fiber amplifiers. However, on-chip amplifiers have yet to make its way into the mainstream due to the limited availability of materials with ideal light guiding and amplification properties. A low-loss nanostructured on-chip channel polymeric waveguide amplifier was designed, characterized, fabricated and its gain experimentally measured at telecommunication wavelength. The active polymeric waveguide core comprises of NaYF 4 :Yb,Er,Ce core-shell nanocrystals dispersed within a SU8 polymer, where the nanoparticle interfacial characteristics were tailored using hydrolyzed polyhedral oligomeric silsesquioxane-graft-poly(methyl methacrylate) to improve particle dispersion. Both the enhanced IR emission intensity from our nanocrystals using a tri-dopant scheme and the reduced scattering losses from our excellent particle dispersion at a high solid loading of 6.0 vol% contributed to the outstanding optical performance of our polymeric waveguide. We achieved one of the highest reported gain of 6.6 dB/cm using a relatively low coupled pump power of 80 mW. These polymeric waveguide amplifiers offer greater promise for integrated optical circuits due to their processability and integration advantages which will play a key role in the emerging areas of flexible communication and optoelectronic devices.

A waveguide-coupled thermally isolated radiometric source.

PubMed

Rostem, K; Chuss, D T; Lourie, N P; Voellmer, G M; Wollack, E J

2013-04-01

The design and validation of a dual polarization source for waveguide-coupled millimeter and sub-millimeter wave cryogenic sensors is presented. The thermal source is a waveguide mounted absorbing conical dielectric taper. The absorber is thermally isolated with a kinematic suspension that allows the guide to be heat sunk to the lowest bath temperature of the cryogenic system. This approach enables the thermal emission from the metallic waveguide walls to be subdominant to that from the source. The use of low thermal conductivity Kevlar threads for the kinematic mount effectively decouples the absorber from the sensor cold stage. Hence, the absorber can be heated to significantly higher temperatures than the sensor with negligible conductive loading. The kinematic suspension provides high mechanical repeatability and reliability with thermal cycling. A 33-50 GHz blackbody source demonstrates an emissivity of 0.999 over the full waveguide band where the dominant deviation from unity arises from the waveguide ohmic loss. The observed thermal time constant of the source is 40 s when the absorber temperature is 15 K. The specific heat of the lossy dielectric, MF-117, is well approximated by C(v)(T) = 0.12 T (2.06) mJ g(-1) K(-1) between 3.5 K and 15 K.

NASA 2008 HyspIRI whitepaper and workshop report

USGS Publications Warehouse

,; Mars, John

2009-01-01

From October 21-23, 2008, NASA held a three-day workshop to consider the Hyperspectral Infrared Imager (HyspIRI) mission recommended for implementation by the 2007 report from the U.S. National Research Council Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, also known as the Earth Science Decadal Survey. The open workshop provided a forum to present the initial observational requirements for the mission and assess its anticipated impact on scientific and operational applications as well as obtain feedback from the broader scientific community on the mission concept. The workshop participants concluded the HyspIRI mission would provide a significant new capability to study ecosystems and natural hazards at spatial scales relevant to human resource use. In addition, participants confirmed that the proposed instrument designs could meet the measurement requirements and be implemented through the use of current technology. The workshop participants, like the Decadal Survey itself, strongly endorsed the need for the HyspIRI mission and felt the mission, as defined, would accomplish the intended science.

KSC-2013-2835

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the Pegasus XL rocket with the attached Interface Region Imaging Spectrograph IRIS solar observatory rolled out of the hangar on its transporter to the runway at Vandenberg. There, the rocket and spacecraft were mated with the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2839

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the Pegasus XL rocket with the attached Interface Region Imaging Spectrograph IRIS solar observatory rolled out of the hangar on its transporter to the runway at Vandenberg. There, the rocket and spacecraft were mated with the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2837

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the Pegasus XL rocket with the attached Interface Region Imaging Spectrograph IRIS solar observatory rolled out of the hangar on its transporter to the runway at Vandenberg. There, the rocket and spacecraft were mated with the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2840

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the Pegasus XL rocket with the attached Interface Region Imaging Spectrograph IRIS solar observatory rolled out of the hangar on its transporter to the runway at Vandenberg. There, the rocket and spacecraft were mated with the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

KSC-2013-2843

NASA Image and Video Library

2013-06-19

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, the Pegasus XL rocket with the attached Interface Region Imaging Spectrograph IRIS solar observatory rolled out of the hangar on its transporter to the runway at Vandenberg. There, the rocket and spacecraft were mated with the Orbital Sciences L-1011 carrier aircraft. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/Randy Beaudoin

Index matching of TE and TM modes in organic multilayer waveguides

NASA Astrophysics Data System (ADS)

Thompson, Jonathan; Schmitzer, Heidrun; Wagner, Hans Peter

We investigate transverse electric (TE) and magnetic (TM) mode propagation in organic multilayers consisting of aluminum quinoline (Alq3) and perylenetetracarboxylic dianhydride (PTCDA). In particular, we analyze two multilayer waveguides, Alq3-PTCDA-Alq3 and PTCDA-Alq3-PTCDA, engineered to give index matching according to modeling. The waveguides were grown on a glass substrate via organic molecular beam deposition. Fabry-Perot oscillations observed from reflection measurements were used to confirm the individual layer thicknesses. We were able to observe refractive index matching between TE0 and TE1, as well as TE2 and TE3 modes for the PTCDA-Alq3-PTCDA waveguide due to the light propagation through the top and bottom PTCDA layers, respectively. In addition, we were able to match TE1 and TM1, as well as TE3 and TM3 modes in the Alq3-PTCDA-Alq3 multilayer due to the birefringence of the PTCDA layer. Furthermore, we are able to create mode matching for a range of wavelengths due to the similar effective refractive index dispersion of different waveguide modes. The ability to phase match different waveguide modes opens a wide range of potential applications including polarization-insensitive propagation and mode switching by adding a thin magnetic metal film within the waveguide and applying an external magnetic field.

Tests of Low-Noise MMIC Amplifier Module at 290 to 340 GHz

NASA Technical Reports Server (NTRS)

Gaier, Todd; Samoska, Lorene; Fung, King Man; Deal, William; Mei, Xiaobing; Lai, Richard

2009-01-01

A document presents data from tests of a low-noise amplifier module operating in the frequency range from 290 to 340 GHz said to be the highest-frequency low-noise, solid-state amplifier ever developed. The module comprised a three-stage monolithic microwave integrated circuit (MMIC) amplifier integrated with radial probe MMIC/waveguide transitions and contained in a compact waveguide package, all according to the concepts described in the immediately preceding article and in the referenced prior article, "Integrated Radial Probe Transition From MMIC to Waveguide" (NPO-43957), NASA Tech Briefs Vol. 31, No. 5 (May 2007), page 38. The tests included measurements by the Y-factor method, in which noise figures are measured repeatedly with an input noise source alternating between an "on" (hot-load) condition and an "off" (cold-load) condition. (The Y factor is defined as the ratio between the "on" and "off" noise power levels.) The test results showed that, among other things, the module exhibited a minimum noise figure of about 8.7 dB at 325 GHz and that the gain at that frequency under the bias conditions that produced the minimum noise figure was between about 9 and 10 dB.

KSC-2013-2205

NASA Image and Video Library

2013-04-25

VANDENBERG AIR FORCE BASE, Calif. -- The Interface Region Imaging Spectrograph, or IRIS, is being readied for mating to the Orbital Sciences Corp. Pegasus XL rocket that will launch the spacecraft. A fairing will be fitted to the nose of the Pegasus to protect the spacecraft from atmospheric heating and stress during launch. Upcoming work includes electrical verification testing. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2206

NASA Image and Video Library

2013-04-25

VANDENBERG AIR FORCE BASE, Calif. -- The Interface Region Imaging Spectrograph, or IRIS, is being readied for mating to the Orbital Sciences Corp. Pegasus XL rocket that will launch the spacecraft. A fairing will be fitted to the nose of the Pegasus to protect the spacecraft from atmospheric heating and stress during launch. Upcoming work includes electrical verification testing. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

KSC-2013-2207

NASA Image and Video Library

2013-04-25

VANDENBERG AIR FORCE BASE, Calif. -- The Interface Region Imaging Spectrograph, or IRIS, is being readied for mating to the Orbital Sciences Corp. Pegasus XL rocket that will launch the spacecraft. A fairing will be fitted to the nose of the Pegasus to protect the spacecraft from atmospheric heating and stress during launch. Upcoming work includes electrical verification testing. IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. Photo credit: VAFB/Randy Beaudoin

Real Time Data for Seismology at the IRIS Data Management Center, AN Nsf-Sponsored Facility

NASA Astrophysics Data System (ADS)

Benson, R. B.; Ahern, T. K.; Trabant, C.; Weertman, B. R.; Casey, R.; Stromme, S.; Karstens, R.

2012-12-01

When IRIS was incorporated in 1984, it committed to provide long-term support for the science of seismology. It first upgraded analog networks by installing observatory grade digital seismic recording equipment (by constructing the Global Seismic Network to upgrade the World Wide Standardized Seismographic Network) that became the backbone of the International Federation of Digital Seismic Networks (FDSN), and in 1990 constructed a state-of-the-art data center that would allow free and open access to data to everyone. For the first decade, IRIS leveraged a complicated system of telemetry which laid the foundation for delivering (relatively) high rate and continuous seismic time series data to the IRIS Data Management Center, which was designed to accept data that arrived with highly variable latencies and on many media formats. This meant that science had to often wait until data became complete, which at the time was primarily related to studying earthquakes or similar events. During the 1990's, numerous incremental but small improvements were made to get data into the hands of users with less latency, leveraging dialup, satellite telemetry, and a variety of Internet protocols. But beginning in 2000, the IRIS Data Management Center began the process of accumulating data comprehensively in real time. It was first justified because it eliminated the time-consuming transcription and manual data handling on various media formats, like magnetic tapes, CD's and DVD's. However, the switch to real-time telemetry proved to be a major improvement technologically because it not only simplified data transfer, it opened access to a large volume of previously inaccessible data (local resource limitations), and many networks began willingly providing their geophysical data to the broad research community. It also enabled researchers the ability to process data in different and streamlined ways, by incorporating data directly into workflows and processing packages. Any network on the Internet, small or large, can now share data, and today, the IRIS DMC receives nearly all of its seismic data from regional and international networks in real time. We will show that this evolution to managing real time data has provided the framework for accomplishing many important benefits that illustrate that open, real time data should be the goal of every observatory operation and can provide: - Faster (therefore cost and data saving) quality control, - Data products that highlight source properties and provide teachable moments - Data delivery to regional or national networks around the globe for immediate access for monitoring. -Use in teaching the public, providing streaming data to museums, schools, etc.

Microfluidic resonant waveguide grating biosensor system for whole cell sensing

NASA Astrophysics Data System (ADS)

Zaytseva, Natalya; Miller, William; Goral, Vasily; Hepburn, Jerry; Fang, Ye

2011-04-01

We report on a fluidic resonant waveguide grating (RWG) biosensor system that enables medium throughput measurements of cellular responses under microfluidics in a 32-well format. Dynamic mass redistribution assays under microfluidics differentiate the cross-desensitization process between the β2-adrenoceptor agonist epinephrine and the adenylate cyclase activator forskolin mediated signaling. This system opens new possibility to study cellular processes that are otherwise difficult to achieve using conventional RWG configurations.

Plateau Iris - Therapeutic options and functional results after treatment.

PubMed

Feraru, Crenguța; Bâlha, Andrei; Aursulesei, Victor; Filip, Andrei; Pantalon, Anca

2017-01-01

We present the therapeutic options and functional results in patients with plateau iris (syndrome or configuration) in consecutive case series. Material and method: Our study included newly diagnosed patients with acute angle closure by "plateau iris" (configuration or syndrome), between June 2016 and April 2017. Series of 8 consecutive patients met the inclusion criteria, all being females. All the patients underwent an individualized treatment according to the underlying mechanism and evolution. Functional results (visual acuity, IOP, topical medication) were reported in the current paper. Results: For 10 months, we diagnosed 14 eyes, from 9 patients with acute angle closure by Plateau Iris, distributed as it follows: 6 eyes with closed angle glaucoma (optic disk and visual field changes), 8 eyes with plateau iris syndrome and 2 eyes with plateau iris configuration. 7/ 8 patients were misdiagnosed with primary open angle glaucoma, whereas only one patient had the correct diagnosis of closed angle glaucoma and underwent peripheral laser iridotomy. As treatment options in our study, we recommended and performed argon laser peripheral iridoplasty + iridotomy in 10/ 14 eyes, cataract lens was extracted in 4 eyes and then replaced with PC-IOL, whereas 2 eyes required a filtering anti-glaucoma surgery (trabeculectomy + PI). 2 eyes from the same patient could not be treated as intended as the patient refused the treatment. In this unique case, Pilocarpine (4%) was temporarily indicated. Conclusion: Plateau iris represents a diagnostic trap, but based on a thorough gonioscopic examination and a good patient history, the right diagnosis can be made, all along with a correct therapeutic approach.

Numerical stress analysis of the iris tissue induced by pupil expansion: Comparison of commercial devices

PubMed Central

Wang, Xiaofei; Perera, Shamira A.; Girard, Michaël J. A.

2018-01-01

Purpose (1) To use finite element (FE) modelling to estimate local iris stresses (i.e. internal forces) as a result of mechanical pupil expansion; and to (2) compare such stresses as generated from several commercially available expanders (Iris hooks, APX dilator and Malyugin ring) to determine which design and deployment method are most likely to cause iris damage. Methods We used a biofidelic 3-part iris FE model that consisted of the stroma, sphincter and dilator muscles. Our FE model simulated expansion of the pupil from 3 mm to a maximum of 6 mm using the aforementioned pupil expanders, with uniform circular expansion used for baseline comparison. FE-derived stresses, resultant forces and area of final pupil opening were compared across devices for analysis. Results Our FE models demonstrated that the APX dilator generated the highest stresses on the sphincter muscles, (max: 6.446 MPa; average: 5.112 MPa), followed by the iris hooks (max: 5.680 MPa; average: 5.219 MPa), and the Malyugin ring (max: 2.144 MPa; average: 1.575 MPa). Uniform expansion generated the lowest stresses (max: 0.435MPa; average: 0.377 MPa). For pupil expansion, the APX dilator required the highest force (41.22 mN), followed by iris hooks (40.82 mN) and the Malyugin ring (18.56 mN). Conclusion Our study predicted that current pupil expanders exert significantly higher amount of stresses and forces than required during pupil expansion. Our work may serve as a guide for the development and design of next-generation pupil expanders. PMID:29538452

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions.

PubMed

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-08-22

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar.

High-Performance Flexible Waveguiding Photovoltaics

PubMed Central

Chou, Chun-Hsien; Chuang, Jui-Kang; Chen, Fang-Chung

2013-01-01

The use of flat-plane solar concentrators is an effective approach toward collecting sunlight economically and without sun trackers. The optical concentrators are, however, usually made of rigid glass or plastics having limited flexibility, potentially restricting their applicability. In this communication, we describe flexible waveguiding photovoltaics (FWPVs) that exhibit high optical efficiencies and great mechanical flexibility. We constructed these FWPVs by integrating poly-Si solar cells, a soft polydimethylsiloxane (PDMS) waveguide, and a TiO2-doped backside reflector. Optical microstructures that increase the light harvesting ability of the FWPVs can be fabricated readily, through soft lithography, on the top surface of the PDMS waveguide. Our optimized structure displayed an optical efficiency of greater than 42% and a certified power conversion efficiency (PCE) of 5.57%, with a projected PCE as high as approximately 18%. This approach might open new avenues for the harvesting of solar energy at low cost with efficient, mechanically flexible photovoltaics. PMID:23873225

Reconfigurable origami-inspired acoustic waveguides

PubMed Central

Babaee, Sahab; Overvelde, Johannes T. B.; Chen, Elizabeth R.; Tournat, Vincent; Bertoldi, Katia

2016-01-01

We combine numerical simulations and experiments to design a new class of reconfigurable waveguides based on three-dimensional origami-inspired metamaterials. Our strategy builds on the fact that the rigid plates and hinges forming these structures define networks of tubes that can be easily reconfigured. As such, they provide an ideal platform to actively control and redirect the propagation of sound. We design reconfigurable systems that, depending on the externally applied deformation, can act as networks of waveguides oriented along one, two, or three preferential directions. Moreover, we demonstrate that the capability of the structure to guide and radiate acoustic energy along predefined directions can be easily switched on and off, as the networks of tubes are reversibly formed and disrupted. The proposed designs expand the ability of existing acoustic metamaterials and exploit complex waveguiding to enhance control over propagation and radiation of acoustic energy, opening avenues for the design of a new class of tunable acoustic functional systems. PMID:28138527

Highly localized distributed Brillouin scattering response in a photonic integrated circuit

NASA Astrophysics Data System (ADS)

Zarifi, Atiyeh; Stiller, Birgit; Merklein, Moritz; Li, Neuton; Vu, Khu; Choi, Duk-Yong; Ma, Pan; Madden, Stephen J.; Eggleton, Benjamin J.

2018-03-01

The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit. This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift and linewidth, essential information for the further development of high quality photonic-phononic waveguides for SBS applications.

Chemical-assisted femtosecond laser writing of lab-in-fibers.

PubMed

Haque, Moez; Lee, Kenneth K C; Ho, Stephen; Fernandes, Luís A; Herman, Peter R

2014-10-07

The lab-on-chip (LOC) platform has presented a powerful opportunity to improve functionalization, parallelization, and miniaturization on planar or multilevel geometries that has not been possible with fiber optic technology. A migration of such LOC devices into the optical fiber platform would therefore open the revolutionary prospect of creating novel lab-in-fiber (LIF) systems on the basis of an efficient optical transport highway for multifunctional sensing. For the LIF, the core optical waveguide inherently offers a facile means to interconnect numerous types of sensing elements along the optical fiber, presenting a radical opportunity for optimizing the packaging and densification of diverse components in convenient geometries beyond that available with conventional LOCs. In this paper, three-dimensional patterning inside the optical fiber by femtosecond laser writing, together with selective chemical etching, is presented as a powerful tool to form refractive index structures such as optical waveguides and gratings as well as to open buried microfluidic channels and optical resonators inside the flexible and robust glass fiber. In this approach, optically smooth surfaces (~12 nm rms) are introduced for the first time inside the fiber cladding that precisely conform to planar nanograting structures when formed by aberration-free focusing with an oil-immersion lens across the cylindrical fiber wall. This process has enabled optofluidic components to be precisely embedded within the fiber to be probed by either the single-mode fiber core waveguide or the laser-formed optical circuits. We establish cladding waveguides, X-couplers, fiber Bragg gratings, microholes, mirrors, optofluidic resonators, and microfluidic reservoirs that define the building blocks for facile interconnection of inline core-waveguide devices with cladding optofluidics. With these components, more advanced, integrated, and multiplexed fiber microsystems are presented demonstrating fluorescence detection, Fabry-Perot interferometric refractometry, and simultaneous sensing of refractive index, temperature, and bending strain. The flexible writing technique and multiplexed sensors described here open powerful prospects to migrate the benefits of LOCs into a more flexible and miniature LIF platform for highly functional and distributed sensing capabilities. The waveguide backbone of the LIF inherently provides an efficient exchange of information, combining sensing data that are attractive in telecom networks, smart catheters for medical procedures, compact sensors for security and defense, shape sensors, and low-cost health care products.

Transverse-electric plasmonic modes of cylindrical graphene-based waveguide at near-infrared and visible frequencies

PubMed Central

Kuzmin, Dmitry A.; Bychkov, Igor V.; Shavrov, Vladimir G.; Kotov, Leonid N.

2016-01-01

Transverse-electric (TE) surface plasmons (SPs) are very unusual for plasmonics phenomenon. Graphene proposes a unique possibility to observe these plasmons. Due to transverse motion of carriers, TE SPs speed is usually close to bulk light one. In this work we discuss conditions of TE SPs propagation in cylindrical graphene-based waveguides. We found that the negativity of graphene conductivity’s imaginary part is not a sufficient condition. The structure supports TE SPs when the core radius of waveguide is larger than the critical value Rcr. Critical radius depends on the light frequency and the difference of permittivities inside and outside the waveguide. Minimum value of Rcr is comparable with the wavelength of volume wave and corresponds to interband carriers transition in graphene. We predict that use of multilayer graphene will lead to decrease of critical radius. TE SPs speed may differ more significantly from bulk light one in case of epsilon-near-zero core and shell of the waveguide. Results may open the door for practical applications of TE SPs in optics, including telecommunications. PMID:27225745

High frequency resonant waveguide grating imager for assessing drug-induced cardiotoxicity

NASA Astrophysics Data System (ADS)

Ferrie, Ann M.; Wu, Qi; Deichmann, Oberon D.; Fang, Ye

2014-05-01

We report a high-frequency resonant waveguide grating imager for assessing compound-induced cardiotoxicity. The imager sweeps the wavelength range from 823 nm to 838 nm every 3 s to identify and monitor compound-induced shifts in resonance wavelength and then switch to the intensity-imaging mode to detect the beating rhythm and proarrhythmic effects of compounds on induced pluripotent stem cell-derived cardiomyocytes. This opens possibility to study cardiovascular biology and compound-induced cardiotoxicity.

54. View from ground level in building no. 105 showing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

54. View from ground level in building no. 105 showing lower radar scanner switch at open port door. Note incoming waveguide and control switch at lower left of photograph and note several waveguides leaving top of scanner switch around the circumference of switch. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

Zero-bias 40Gbit/s germanium waveguide photodetector on silicon.

PubMed

Vivien, Laurent; Polzer, Andreas; Marris-Morini, Delphine; Osmond, Johann; Hartmann, Jean Michel; Crozat, Paul; Cassan, Eric; Kopp, Christophe; Zimmermann, Horst; Fédéli, Jean Marc

2012-01-16

We report on lateral pin germanium photodetectors selectively grown at the end of silicon waveguides. A very high optical bandwidth, estimated up to 120GHz, was evidenced in 10 µm long Ge photodetectors using three kinds of experimental set-ups. In addition, a responsivity of 0.8 A/W at 1550 nm was measured. An open eye diagrams at 40Gb/s were demonstrated under zero-bias at a wavelength of 1.55 µm.

Progress Toward an IRIS++ Database Open to the Helioseismological Community

NASA Astrophysics Data System (ADS)

Gelly, B.; Khalikov, S.; Pallé, P. L.; IRIS Team

The IRIS network is now fourteen years old, and has continuously been taking data since 1989. The data analysis, which produced some noticeable scientifical results, like the measurement of the ell = 1 rotationnal splitting or the measurement of the solar acoustic cut-off frequency, was mainly performed with the summer campaigns data of 1989 to 1992. P-mode frequency and width tables were recently published using the same subset of the IRIS data . We are now finishing the calibration and the timing of the whole set of IRIS data from 89 to 97, which will increase by a factor of 4 the amount of available data. The duty cycle of the IRIS network ranges from about 65% over 3 months of the summer campaigns to some 23% over one year in the worst case. To improve our duty cycle we developed several collaborations with other teams running similar instruments: (1) the Mark I instrument, ran at the IAC for many years, a potassium resonance single pixel device, also part of the BiSON network (Elsworth et al., 1988). (2) Alexandro Cacciani's MOF, ran at the JPL in Pasadena. Although this is a sodium resonance imaging instrument, it has been used in ``one pixel'' format for several summer seasons since 1989 (Cacciani et al., 1984). (3) the LOWL instrument is a Doppler imager also based on a Magneto-Optical Filter (MOF), operated at the Mauna Loa solar observatory since 1994 (Tomczyk et al., 1995). The merging of those 'alien' data has been carefully adressed at the calibration ands timing stages, and we can now present the advantages of such a-posteriori collaborations. We endeavour to set-up the corresponding database of 'one-pixel seismological data from ground-based intruments' in Nice and to open it to the scientific community of this meeting by the end of 1998. This database will soon have the potential to trace the spectral features of the solar signal over one 11-years cycle.

Two-dimensional analysis of palpebral opening in blepharoptosis: visual iris-pupil complex percentage by digital photography.

PubMed

Choi, Yeop; Eo, SuRak

2014-04-01

The vertical dimension of the palpebral fissure and the marginal reflex distance are conventionally used to assess the amount or degree of blepharoptosis, and levator function is assessed by measuring total upper lid excursion between the extremes of down-gaze and up-gaze. However, these are 1-dimensional measures obtained with a ruler, and the results obtained are dependent on examiner skill. Digital photographs were obtained of 692 patients before and after upper blepharoplasty. Visual iris-pupil complex percentage (VIP) was measured in the 1,305 eyes by digital calculation using Adobe Photoshop CS3 (Adobe Systems, Inc). Perioperative eye images in primary gaze were evaluated independently by 2 surgeons, 2 nurses, and a graphic designer, and after excluding 50 eyes which were nonconcordant and 29 eyes which revealed retracted upper lids, the remaining 1,305 eyes were classified into 4 major groups, that is, into excellent (n = 415), good (n = 435), subclinical (n = 270), and prominent ptosis (n = 185) groups. In addition, eyes were subdivided into 5 types according to the iris-pupil complex position within the palpebral fissure. Visual iris-pupil complex percentages were from 85% to 94% in the excellent, from 78% to 84% in the good, from 70% to 77% in the subclinical ptosis, and below 70% in the prominent ptosis group. Patients in the subclinical or prominent ptosis eye group required surgery for blepharoptosis. Iris-pupil complex relation to the palpebral opening was classified into 5 eye types, namely, standard (n = 961), scleral (n = 266), sinking (n = 151), retracted (n = 3), and fish (n = 3). The authors devised a new prospective measurement method for assessing blepharoptosis in a clinical setting. Graphical comparisons between the devised method of measuring VIP and mathematical estimations showed that the devised method is easier, more practical, and more precise for measuring degree of blepharoptosis from general population trends, and that VIP also provides a useful objective index for evaluating the postoperative results of blepharoptosis.

Phakic iris-fixated intraocular lens placement in the anterior chamber: effects on aqueous flow.

PubMed

Repetto, Rodolfo; Pralits, Jan O; Siggers, Jennifer H; Soleri, Paolo

2015-05-01

Phakic intraocular lenses (pIOLs) are used for correcting vision; in this paper we investigate the fluid dynamical effects of an iris-fixated lens in the anterior chamber. In particular, we focus on changes in the wall shear stress (WSS) on the cornea and iris, which could be responsible for endothelial and pigment cell loss, respectively, and also on the possible increase of the intraocular pressure, which is known to correlate with the incidence of secondary glaucoma. We use a mathematical model to study fluid flow in the anterior chamber in the presence of a pIOL. The governing equations are solved numerically using the open source software OpenFOAM. We use an idealized standard geometry for the anterior chamber and a realistic geometric description of the pIOL. We consider separately the main mechanisms that produce fluid flow in the anterior chamber. The numerical simulations allow us to obtain a detailed description of the velocity and pressure distribution in the anterior chamber, and indicated that implantation of the pIOL significantly modifies the fluid dynamics in the anterior chamber. However, lens implantation has negligible influence on the intraocular pressure and does not produce a significant increase of the shear stress on the cornea, while the shear stress on the iris, although increased, is not enough to cause detachment of cells. We conclude that alterations in the fluid dynamics in the anterior chamber as a result of lens implantation are unlikely to be the cause of medical complications associated with its use.

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions

PubMed Central

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-01-01

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar. PMID:27556469

Traveling wave linear accelerator with RF power flow outside of accelerating cavities

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

Dolgashev, Valery A.

A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities hasmore » a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.« less

Comparison of factors associated with occludable angle between american Caucasians and ethnic Chinese.

PubMed

Wang, Ye Elaine; Li, Yingjie; Wang, Dandan; He, Mingguang; Lin, Shan

2013-11-21

To determine if factors associated with gonioscopy-determined occludable angle among American Caucasians are similar to those found in ethnic Chinese. This is a prospective cross-sectional study with 120 American Caucasian, 116 American Chinese, and 116 mainland Chinese subjects. All three groups were matched for sex and age (40-80 years). Gonioscopy was performed for each subject (occludable angles = posterior trabecular meshwork not visible for ≥2 quadrants). Anterior segment optical coherence tomography and customized software was used to measure anterior segment biometry and iris parameters, including anterior chamber depth/width (ACD, ACW), lens vault (LV), and iris thickness/area/curvature. In both Chinese and Caucasians, eyes with occludable angles had smaller ACD and ACW, and larger LV and iris curvature than eyes with open angles (all P < 0.005). Chinese eyes had smaller ACD and ACW than Caucasian eyes (both P < 0.01) in the occludable angle cohort. Iris characteristics did not differ significantly between Chinese and Caucasians in the occludable angle cohort. Based on multivariate logistic regression, gonioscopy-determined occludable angle was significantly associated with LV, iris area, and sex (all P < 0.03) in Chinese; and with LV, ACD, iris thickness, age, and sex (all P < 0.04) in Caucasians. Several factors associated with occludable angle differed between Caucasians and Chinese, suggesting potentially different mechanisms in occludable angle development in the two racial groups. This is the first study to demonstrate that lens vault is an important anterior segment optical coherence tomography parameter in the screening for angle closure in Caucasians. In addition, iris thickness was a significant predictor for occludable angles in Caucasians but was not in ethnic Chinese.

Comparison of Factors Associated With Occludable Angle Between American Caucasians and Ethnic Chinese

PubMed Central

Wang, Ye Elaine; Li, Yingjie; Wang, Dandan; He, Mingguang; Lin, Shan

2013-01-01

Purpose. To determine if factors associated with gonioscopy-determined occludable angle among American Caucasians are similar to those found in ethnic Chinese. Methods. This is a prospective cross-sectional study with 120 American Caucasian, 116 American Chinese, and 116 mainland Chinese subjects. All three groups were matched for sex and age (40–80 years). Gonioscopy was performed for each subject (occludable angles = posterior trabecular meshwork not visible for ≥2 quadrants). Anterior segment optical coherence tomography and customized software was used to measure anterior segment biometry and iris parameters, including anterior chamber depth/width (ACD, ACW), lens vault (LV), and iris thickness/area/curvature. Results. In both Chinese and Caucasians, eyes with occludable angles had smaller ACD and ACW, and larger LV and iris curvature than eyes with open angles (all P < 0.005). Chinese eyes had smaller ACD and ACW than Caucasian eyes (both P < 0.01) in the occludable angle cohort. Iris characteristics did not differ significantly between Chinese and Caucasians in the occludable angle cohort. Based on multivariate logistic regression, gonioscopy-determined occludable angle was significantly associated with LV, iris area, and sex (all P < 0.03) in Chinese; and with LV, ACD, iris thickness, age, and sex (all P < 0.04) in Caucasians. Conclusions. Several factors associated with occludable angle differed between Caucasians and Chinese, suggesting potentially different mechanisms in occludable angle development in the two racial groups. This is the first study to demonstrate that lens vault is an important anterior segment optical coherence tomography parameter in the screening for angle closure in Caucasians. In addition, iris thickness was a significant predictor for occludable angles in Caucasians but was not in ethnic Chinese. PMID:24168992

Intelligent detection of cracks in metallic surfaces using a waveguide sensor loaded with metamaterial elements.

PubMed

Ali, Abdulbaset; Hu, Bing; Ramahi, Omar

2015-05-15

This work presents a real life experiment of implementing an artificial intelligence model for detecting sub-millimeter cracks in metallic surfaces on a dataset obtained from a waveguide sensor loaded with metamaterial elements. Crack detection using microwave sensors is typically based on human observation of change in the sensor's signal (pattern) depicted on a high-resolution screen of the test equipment. However, as demonstrated in this work, implementing artificial intelligence to classify cracked from non-cracked surfaces has appreciable impact in terms of sensing sensitivity, cost, and automation. Furthermore, applying artificial intelligence for post-processing data collected from microwave sensors is a cornerstone for handheld test equipment that can outperform rack equipment with large screens and sophisticated plotting features. The proposed method was tested on a metallic plate with different cracks and the obtained experimental results showed good crack classification accuracy rates.

Radiation of a charge flying in a partially loaded dielectric section of a waveguide

NASA Astrophysics Data System (ADS)

Grigoreva, Aleksandra A.; Tyukhtin, Andrey V.; Vorobev, Viktor V.; Galyamin, Sergey N.; Antipov, Sergey

2018-03-01

We consider the electromagnetic field of a point charged particle moving along the axis of a cylindrical waveguide from a homogeneously filled area to a dielectric loading area having an axially symmetrical channel. We are interested in studying the Cherenkov radiation excited in the bilayer area. The solution is performed by expanding the field in each area in a series of orthogonal eigenmodes. The main attention is focused on investigation of the wave field in the bilayer section. We show that, at a given observation point, the "reduced wakefield" is simplified with time (the number of modes decreases). The obtained results are generalized for the case of a bunch with Gaussian longitudinal profile. The typical numerical results for wakefield formation process are presented. These results agree with simulations done by the industry standard electromagnetic code CST Particle Studio.

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

NASA Astrophysics Data System (ADS)

Vinatier, T.; Assmann, R. W.; Dorda, U.; Lemery, F.; Marchetti, B.

2017-07-01

In this paper, we investigate with ASTRA simulations the beam dynamics in dielectric-loaded waveguides driven by THz pulses, used as linac structure for the AXSIS project. We show that the bunch properties at the linac exit are very sensitive to the phase velocity of the THz pulse and are limited by the strong phase slippage of the bunch respective to it. We also show that the bunch properties are optimized when low frequencies (< 300 GHz) are used inside the linac, and that the longitudinal focal point can be put several tens of cm away from the linac exit thanks to ballistic bunching. However, a strong asymmetry in the bunch transverse sizes remains for which a solution is still to be found. Work supported by the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement n. 609920.

Intelligent Detection of Cracks in Metallic Surfaces Using a Waveguide Sensor Loaded with Metamaterial Elements

PubMed Central

Ali, Abdulbaset; Hu, Bing; Ramahi, Omar M.

2015-01-01

This work presents a real-life experiment implementing an artificial intelligence model for detecting sub-millimeter cracks in metallic surfaces on a dataset obtained from a waveguide sensor loaded with metamaterial elements. Crack detection using microwave sensors is typically based on human observation of change in the sensor's signal (pattern) depicted on a high-resolution screen of the test equipment. However, as demonstrated in this work, implementing artificial intelligence to classify cracked from non-cracked surfaces has appreciable impacts in terms of sensing sensitivity, cost, and automation. Furthermore, applying artificial intelligence for post-processing the data collected from microwave sensors is a cornerstone for handheld test equipment that can outperform rack equipment with large screens and sophisticated plotting features. The proposed method was tested on a metallic plate with different cracks, and the experimental results showed good crack classification accuracy rates. PMID:25988871

Reverse surface-polariton cherenkov radiation

PubMed Central

Tao, Jin; Wang, Qi Jie; Zhang, Jingjing; Luo, Yu

2016-01-01

The existence of reverse Cherenkov radiation for surface plasmons is demonstrated analytically. It is shown that in a metal-insulator-metal (MIM) waveguide, surface plasmon polaritons (SPPs) excited by an electron moving at a speed higher than the phase velocity of SPPs can generate Cherenkov radiation, which can be switched from forward to reverse direction by tuning the core thickness of the waveguide. Calculations are performed in both frequency and time domains, demonstrating that a radiation pattern with a backward-pointing radiation cone can be achieved at small waveguide core widths, with energy flow opposite to the wave vector of SPPs. Our study suggests the feasibility of generating and steering electron radiation in simple plasmonic systems, opening the gate for various applications such as velocity-selective particle detections. PMID:27477061

Anterior Segment Morphology in Primary Angle Closure Glaucoma using Ultrasound Biomicroscopy

PubMed Central

Balakrishna, Nagalla

2017-01-01

Aim To evaluate the configuration of the anterior chamber angle quantitatively and study the morphological changes in the eye with ultrasound biomicroscopy (UBM) in primary angle closure glaucoma (PACG) patients after laser peripheral iridotomy (LPI). Materials and methods A total of 185 eyes of 185 PACG patients post-LPI and 126 eyes of 126 normal subjects were included in this prospective study. All subjects underwent complete ophthalmic evaluation, A-scan biometry, and UBM. The anterior segment and angle parameters were measured quantitatively and compared in both groups using Student’s t-test. Results The PACG patients had shorter axial length, shallower central anterior chamber depth anterior chamber depth (ACD), and anteriorly located lens when compared with normal subjects. Trabecular iris angle (TIA) was significantly narrow (5.73 ± 7.76°) in patients with PACG when compared with normal subjects (23.75 ± 9.38°). The angle opening distance at 500 pm from scleral spur (AOD 500), trabecular-ciliary process distance (TCPD), iris-ciliary process distance (ICPD), and iris-zonule distance (IZD) were significantly shorter in patients with PACG than in normal subjects (p < 0.0001). The iris lens angle (ILA), scleral-iris angle (SIA), and scleral-ciliary process angle (SCPA) were significantly narrower in patients with PACG than in normal subjects (p < 0.0001). The iris-lens contact distance (ILCD) was greater in PACG group than in normal (p = 0.001). Plateau iris was seen in 57/185 (30.8%) of the eyes. Anterior positioned ciliary processes were seen in 130/185 eyes (70.3%) of eyes. Conclusion In PACG patients, persistent apposition angle closure is common even after LPI, which could be due to anterior rotation of ciliary body and plateau iris and overcrowding of anterior segment due to shorter axial length and relative anterior lens position. How to cite this article: Mansoori T, Balakrishna N. Anterior Segment Morphology in Primary Angle Closure Glaucoma using Ultrasound Biomicroscopy. J Curr Glaucoma Pract 2017;11(3):86-91. PMID:29151682

An investigation for the development of an integrated optical data preprocessor

NASA Technical Reports Server (NTRS)

Verber, C. M.; Vahey, D. W.; Kenan, R. P.; Wood, V. E.; Hartman, N. F.; Chapman, C. M.

1978-01-01

The successful fabrication and demonstration of an integrated optical circuit designed to perform a parallel processing operation by utilizing holographic subtraction to simultaneously compare N analog signal voltages with N predetermined reference voltages is summarized. The device alleviates transmission, storage and processing loads of satellite data systems by performing, at the sensor site, some preprocessing of data taken by remote sensors. Major accomplishments in the fabrication of integrated optics components include: (1) fabrication of the first LiNbO3 waveguide geodesic lens; (2) development of techniques for polishing TIR mirrors on LiNbO3 waveguides; (3) fabrication of high efficiency metal-over-photoresist gratings for waveguide beam splitters; (4) demonstration of high S/N holographic subtraction using waveguide holograms; and (5) development of alignment techniques for fabrication of integrated optics circuits. Important developments made in integrated optics are the discovery and suggested use of holographic self-subtraction in LiNbO3, development of a mathematical description of the operating modes of the preprocessor, and the development of theories for diffraction efficiency and beam quality of two dimensional beam defined gratings.

Model based Computerized Ionospheric Tomography in space and time

NASA Astrophysics Data System (ADS)

Tuna, Hakan; Arikan, Orhan; Arikan, Feza

2018-04-01

Reconstruction of the ionospheric electron density distribution in space and time not only provide basis for better understanding the physical nature of the ionosphere, but also provide improvements in various applications including HF communication. Recently developed IONOLAB-CIT technique provides physically admissible 3D model of the ionosphere by using both Slant Total Electron Content (STEC) measurements obtained from a GPS satellite - receiver network and IRI-Plas model. IONOLAB-CIT technique optimizes IRI-Plas model parameters in the region of interest such that the synthetic STEC computations obtained from the IRI-Plas model are in accordance with the actual STEC measurements. In this work, the IONOLAB-CIT technique is extended to provide reconstructions both in space and time. This extension exploits the temporal continuity of the ionosphere to provide more reliable reconstructions with a reduced computational load. The proposed 4D-IONOLAB-CIT technique is validated on real measurement data obtained from TNPGN-Active GPS receiver network in Turkey.

Analysis of the effect of a rectangular cavity resonator on acoustic wave transmission in a waveguide

NASA Astrophysics Data System (ADS)

Porter, R.; Evans, D. V.

2017-11-01

The transmission of acoustic waves along a two-dimensional waveguide which is coupled through an opening in its wall to a rectangular cavity resonator is considered. The resonator acts as a classical band-stop filter, significantly reducing acoustic transmission across a range of frequencies. Assuming wave frequencies below the first waveguide cut-off, the solution for the reflected and transmitted wave amplitudes is formulated exactly within the framework of inviscid linear acoustics. The main aim of the paper is to develop an approximation in closed form for reflected and transmitted amplitudes when the gap in the thin wall separating the waveguide and the cavity resonator is assumed to be small. This approximation is shown to accurately capture the effect of all cavities resonances, not just the fundamental Helmholtz resonance. It is envisaged this formula (and more generally the mathematical approach adopted) could be used in the development of acoustic metamaterial devices containing resonator arrays.

Cooling atomic ions with visible and infra-red light

NASA Astrophysics Data System (ADS)

Lindenfelser, F.; Marinelli, M.; Negnevitsky, V.; Ragg, S.; Home, J. P.

2017-06-01

We demonstrate the ability to load, cool and detect singly charged calcium ions in a surface electrode trap using only visible and infrared lasers for the trapped-ion control. As opposed to the standard methods of cooling using dipole-allowed transitions, we combine power broadening of a quadrupole transition at 729 nm with quenching of the upper level using a dipole allowed transition at 854 nm. By observing the resulting 393 nm fluorescence we are able to perform background-free detection of the ion. We show that this system can be used to smoothly transition between the Doppler cooling and sideband cooling regimes, and verify theoretical predictions throughout this range. We achieve scattering rates which reliably allow recooling after collision events and allow ions to be loaded from a thermal atomic beam. This work is compatible with recent advances in optical waveguides, and thus opens a path in current technologies for large-scale quantum information processing. In situations where dielectric materials are placed close to trapped ions, it carries the additional advantage of using wavelengths which do not lead to significant charging, which should facilitate high rate optical interfaces between remotely held ions.

High strength fused silica flexures manufactured by femtosecond laser

NASA Astrophysics Data System (ADS)

Bellouard, Yves; Said, Ali A.; Dugan, Mark; Bado, Philippe

2009-02-01

Flexures are mechanical elements used in micro- and precision-engineering to precisely guide the motion of micro-parts. They consist of slender bodies that deform elastically upon the application of a force. Although counter-intuitive at first, fused silica is an attractive material for flexure. Pending that the machining process does not introduce surface flaws that would lead to catastrophic failure, the material has a theoretically high ultimate tensile strength of several GPa. We report on high-aspect ratio fused silica flexures manufactured by femtosecond laser combined with chemical etching. Notch-hinges with thickness as small as twenty microns and aspect ratios comparable to aspect ratios obtained by Deep- Reactive-Ion-Etching (DRIE) were fabricated and tested under different loading conditions. Multiple fracture tests were performed for various loading conditions and the cracks morphologies were analyzed using Scanning Electron Microscopy. The manufactured elements show outstanding mechanical properties with flexural strengths largely exceeding those obtained with other technologies and materials. Fused silica flexures offer a mean to combine integrated optics with micro-mechanics in a single monolithic substrate. Waveguides and mechanical elements can be combined in a monolithic devices opening new opportunities for integrated opto-mechatronics devices.

Multi-image encryption based on synchronization of chaotic lasers and iris authentication

NASA Astrophysics Data System (ADS)

Banerjee, Santo; Mukhopadhyay, Sumona; Rondoni, Lamberto

2012-07-01

A new technique of transmitting encrypted combinations of gray scaled and chromatic images using chaotic lasers derived from Maxwell-Bloch's equations has been proposed. This novel scheme utilizes the general method of solution of a set of linear equations to transmit similar sized heterogeneous images which are a combination of monochrome and chromatic images. The chaos encrypted gray scaled images are concatenated along the three color planes resulting in color images. These are then transmitted over a secure channel along with a cover image which is an iris scan. The entire cryptology is augmented with an iris-based authentication scheme. The secret messages are retrieved once the authentication is successful. The objective of our work is briefly outlined as (a) the biometric information is the iris which is encrypted before transmission, (b) the iris is used for personal identification and verifying for message integrity, (c) the information is transmitted securely which are colored images resulting from a combination of gray images, (d) each of the images transmitted are encrypted through chaos based cryptography, (e) these encrypted multiple images are then coupled with the iris through linear combination of images before being communicated over the network. The several layers of encryption together with the ergodicity and randomness of chaos render enough confusion and diffusion properties which guarantee a fool-proof approach in achieving secure communication as demonstrated by exhaustive statistical methods. The result is vital from the perspective of opening a fundamental new dimension in multiplexing and simultaneous transmission of several monochromatic and chromatic images along with biometry based authentication and cryptography.

Compact Feeding Network for Array Radiations of Spoof Surface Plasmon Polaritons

NASA Astrophysics Data System (ADS)

Xu, Jun Jun; Yin, Jia Yuan; Zhang, Hao Chi; Cui, Tie Jun

2016-03-01

We propose a splitter feeding network for array radiations of spoof surface plasmon polaritons (SPPs), which are guided by ultrathin corrugated metallic strips. Based on the coupled mode theory, SPP fields along a single waveguide in a certain frequency range can be readily coupled into two adjacent branch waveguides with the same propagation constants. We propose to load U-shaped particles anti-symmetrically at the ends of such two branch waveguides, showing a high integration degree of the feeding network. By controlling linear phase modulations produced by the U-shaped particle chain, we demonstrate theoretically and experimentally that the SPP fields based on bound modes can be efficiently radiated to far fields in broadside direction. The proposed method shows that the symmetry of electromagnetic field modes can be exploited to the SPP transmission network, providing potential solutions to compact power dividers and combiners for microwave and optical devices and systems.

Analyzing the power coupled between partially coherent waveguide fields in different states of coherence.

PubMed

Withington, Stafford; Yassin, Ghassan

2002-07-01

A procedure is described for calculating the power coupled between partially coherent waveguide fields that are in different states of coherence. The method becomes important when it is necessary to calculate the power transferred from a distributed source S to a distributed load L through a length of multimode metallic, or dielectric, waveguide. It is shown that if the correlations between the transverse components of the electric and magnetic fields of S and L are described by coherence matrices M and M', respectively, then the normalized average power coupled between them is (eta) = Tr[MM']/Tr[M]Tr[M'], where Tr denotes the trace. When the modal impedances are equal, this expression for the coupled power reduces to an equation derived in a previous paper [J. Opt. Soc. Am. A 18, 3061 (2001)], by use of thermodynamic arguments, for the power coupled between partially coherent free-space beams.

Dispersion Characteristics of a Helix Loaded Waveguide.

DTIC Science & Technology

1985-09-01

be employed to increase the bandwidth of gyroton amplifiers. The structure consists of helical wires contained concentrially 6. in a cylindrical...bandwidth of gyroton amplifiers. The structure consists of helical wires contained concentrially in a cylindrical conductor. The helical wires are close

Weak form implementation of the semi-analytical finite element (SAFE) method for a variety of elastodynamic waveguides

NASA Astrophysics Data System (ADS)

Hakoda, Christopher; Lissenden, Clifford; Rose, Joseph L.

2018-04-01

Dispersion curves are essential to any guided wave NDE project. The Semi-Analytical Finite Element (SAFE) method has significantly increased the ease by which these curves can be calculated. However, due to misconceptions regarding theory and fragmentation based on different finite-element software, the theory has stagnated, and adoption by researchers who are new to the field has been slow. This paper focuses on the relationship between the SAFE formulation and finite element theory, and the implementation of the SAFE method in a weak form for plates, pipes, layered waveguides/composites, curved waveguides, and arbitrary cross-sections is shown. The benefits of the weak form are briefly described, as is implementation in open-source and commercial finite element software.

Inertial Manifolds for Navier-Stokes Equations and Related Dynamical Systems

DTIC Science & Technology

1991-05-31

Graphics IRIS (SGI). The RLE files for the animation are loaded to an Abekas and recorded to tape by Betacam . This computational work was done by using the...scripts and comments, are loaded to the Abekas-A60 digital image storage device, and then recorded to the Betacam BVW-75 analog tape recorder. Static...interfacing, huge data files are output to the Data Vault parallelly with little cost. In addition to the SGIs, Abekas, Betacam and Solitaire, the

LOADED WAVE GUIDES FOR LINEAR ACCELERATORS

DOEpatents

Walkinshaw, W.; Mullett, L.B.

1959-12-01

A periodically loaded waveguide having substantially coaxially arranged elements which provide an axial field for the acceleration of electrons is described. Radiofrequency energy will flow in the space between the inner wall of an outer guide and the peripheries of equally spaced irises or washes arranged coaxially with each other and with the outer guide, where the loading due to the geometry of the irises is such as to reduce the phase velocity of the r-f energy flowing in the guide from a value greater than that of light to the velocity of light or less.

Er:YAG delamination of immersed biological membranes using sealed flexible hollow waveguides

NASA Astrophysics Data System (ADS)

Sagi-Dolev, A. M.; Dror, Jacob; Inberg, Alexandra; Ferencz, J. R.; Croitoru, Nathan I.

1996-04-01

The radiation of Er-YAG laser ((lambda) equals 2.94 micrometer) gives selective interaction with tissues. The extinction in soft tissues is only a few micrometers and in hard tissues is of the order of hundreds of micrometers. This makes this type of laser very suitable for treatments in dentistry, orthopedy, or ophthalmology. Because the usual silica fibers are not transmitting the radiation at lambda equals 2.94 micrometer of this laser, many applications cannot be presently performed. Fused silica hollow fibers for Er-YAG radiation were developed in our laboratory and several possible applications in dentistry, orthopedy and ophthalmology were indicated. Hole opening and implantation preparation of teeth were experimented, using Er-YAG laser and hollow plastic waveguide delivery systems. Hole drilling in cow bones was demonstrated for applications in orthopedy. A new procedure of delivering Er-YAG radiation on fibrotic membranes of inner eggshell as a model of the membranes in eyes was developed employing silica hollow waveguides of 0.5 and 0.7 mm ID or a plastic waveguide of 1.0 mm ID. For this purpose waveguides with sealed distal tip were employed to enable us to approach the delivery system through liquid media near to the membrane. This experiment demonstrates the possibility of surgical applications in vitectomy in ophthalmology using Er-YAG laser and silica hollow waveguides.

Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis.

PubMed

Zhou, Hao; Zhang, Ying; Hu, Shunying; Shi, Chen; Zhu, Pingjun; Ma, Qiang; Jin, Qinhua; Cao, Feng; Tian, Feng; Chen, Yundai

2017-08-01

The cardiac microvascular system, which is primarily composed of monolayer endothelial cells, is the site of blood supply and nutrient exchange to cardiomyocytes. However, microvascular ischemia/reperfusion injury (IRI) following percutaneous coronary intervention is a woefully neglected topic, and few strategies are available to reverse such pathologies. Here, we studied the effects of melatonin on microcirculation IRI and elucidated the underlying mechanism. Melatonin markedly reduced infarcted area, improved cardiac function, restored blood flow, and lower microcirculation perfusion defects. Histological analysis showed that cardiac microcirculation endothelial cells (CMEC) in melatonin-treated mice had an unbroken endothelial barrier, increased endothelial nitric oxide synthase expression, unobstructed lumen, reduced inflammatory cell infiltration, and less endothelial damage. In contrast, AMP-activated protein kinase α (AMPKα) deficiency abolished the beneficial effects of melatonin on microvasculature. In vitro, IRI activated dynamin-related protein 1 (Drp1)-dependent mitochondrial fission, which subsequently induced voltage-dependent anion channel 1 (VDAC1) oligomerization, hexokinase 2 (HK2) liberation, mitochondrial permeability transition pore (mPTP) opening, PINK1/Parkin upregulation, and ultimately mitophagy-mediated CMEC death. However, melatonin strengthened CMEC survival via activation of AMPKα, followed by p-Drp1 S616 downregulation and p-Drp1 S37 upregulation, which blunted Drp1-dependent mitochondrial fission. Suppression of mitochondrial fission by melatonin recovered VDAC1-HK2 interaction that prevented mPTP opening and PINK1/Parkin activation, eventually blocking mitophagy-mediated cellular death. In summary, this study confirmed that melatonin protects cardiac microvasculature against IRI. The underlying mechanism may be attributed to the inhibitory effects of melatonin on mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis via activation of AMPKα. © 2017 The Authors. Journal of Pineal Research Published by John Wiley & Sons Ltd.

The IRIS Data Management Center: Enabling Access to Observational Time Series Spanning Decades

NASA Astrophysics Data System (ADS)

Ahern, T.; Benson, R.; Trabant, C.

2009-04-01

The Incorporated Research Institutions for Seismology (IRIS) is funded by the National Science Foundation (NSF) to operate the facilities to generate, archive, and distribute seismological data to research communities in the United States and internationally. The IRIS Data Management System (DMS) is responsible for the ingestion, archiving, curation and distribution of these data. The IRIS Data Management Center (DMC) manages data from more than 100 permanent seismic networks, hundreds of temporary seismic deployments as well as data from other geophysical observing networks such as magnetotelluric sensors, ocean bottom sensors, superconducting gravimeters, strainmeters, surface meteorological measurements, and in-situ atmospheric pressure measurements. The IRIS DMC has data from more than 20 different types of sensors. The IRIS DMC manages approximately 100 terabytes of primary observational data. These data are archived in multiple distributed storage systems that insure data availability independent of any single catastrophic failure. Storage systems include both RAID systems of greater than 100 terabytes as well as robotic tape robots of petabyte capacity. IRIS performs routine transcription of the data to new media and storage systems to insure the long-term viability of the scientific data. IRIS adheres to the OAIS Data Preservation Model in most cases. The IRIS data model requires the availability of metadata describing the characteristics and geographic location of sensors before data can be fully archived. IRIS works with the International Federation of Digital Seismographic Networks (FDSN) in the definition and evolution of the metadata. The metadata insures that the data remain useful to both current and future generations of earth scientists. Curation of the metadata and time series is one of the most important activities at the IRIS DMC. Data analysts and an automated quality assurance system monitor the quality of the incoming data. This insures data are of acceptably high quality. The formats and data structures used by the seismological community are esoteric. IRIS and its FDSN partners are developing web services that can transform the data holdings to structures that are more easily used by broader scientific communities. For instance, atmospheric scientists are interested in using global observations of microbarograph data but that community does not understand the methods of applying instrument corrections to the observations. Web processing services under development at IRIS will transform these data in a manner that allows direct use within such analysis tools as MATLAB® already in use by that community. By continuing to develop web-service based methods of data discovery and access, IRIS is enabling broader access to its data holdings. We currently support data discovery using many of the Open Geospatial Consortium (OGC) web mapping services. We are involved in portal technologies to support data discovery and distribution for all data from the EarthScope project. We are working with computer scientists at several universities including the University of Washington as part of a DataNet proposal and we intend to enhance metadata, further develop ontologies, develop a Registry Service to aid in the discovery of data sets and services, and in general improve the semantic interoperability of the data managed at the IRIS DMC. Finally IRIS has been identified as one of four scientific organizations that the External Research Division of Microsoft wants to work with in the development of web services and specifically with the development of a scientific workflow engine. More specific details of current and future developments at the IRIS DMC will be included in this presentation.

COMGEN - A PROGRAM FOR GENERATING FINITE ELEMENT MODELS OF COMPOSITE MATERIALS AT THE MICRO LEVEL (SGI IRIS VERSION)

NASA Technical Reports Server (NTRS)

Melis, M. E.

1994-01-01

A significant percentage of time spent in a typical finite element analysis is taken up in the modeling and assignment of loads and constraints. This process not only requires the analyst to be well-versed in the art of finite element modeling, but also demands familiarity with some sort of preprocessing software in order to complete the task expediently. COMGEN (COmposite Model GENerator) is an interactive FORTRAN program which can be used to create a wide variety of finite element models of continuous fiber composite materials at the micro level. It quickly generates batch or "session files" to be submitted to the finite element pre- and post-processor program, PATRAN. (PDA Engineering, Costa Mesa, CA.) In modeling a composite material, COMGEN assumes that its constituents can be represented by a "unit cell" of a fiber surrounded by matrix material. Two basic cell types are available. The first is a square packing arrangement where the fiber is positioned in the center of a square matrix cell. The second type, hexagonal packing, has the fiber centered in a hexagonal matrix cell. Different models can be created using combinations of square and hexagonal packing schemes. Variations include two- and three- dimensional cases, models with a fiber-matrix interface, and different constructions of unit cells. User inputs include fiber diameter and percent fiber-volume of the composite to be analyzed. In addition, various mesh densities, boundary conditions, and loads can be assigned to the models within COMGEN. The PATRAN program then uses a COMGEN session file to generate finite element models and their associated loads which can then be translated to virtually any finite element analysis code such as NASTRAN or MARC. COMGEN is written in FORTRAN 77 and has been implemented on DEC VAX series computers under VMS and SGI IRIS series workstations under IRIX. If the user has the PATRAN package available, the output can be graphically displayed. Without PATRAN, the output is tabular. The VAX VMS version is available on a 5.25 inch 360K MS-DOS format diskette (standard distribution media) or a 9-track 1600 BPI DEC VAX FILES-11 format magnetic tape, and it requires about 124K of main memory. The standard distribution media for the IRIS version is a .25 inch streaming magnetic tape cartridge in UNIX tar format. The memory requirement for the IRIS version is 627K. COMGEN was developed in 1990. DEC, VAX and VMS are trademarks of Digital Equipment Corporation. PATRAN is a registered trademark of PDA Engineering. SGI IRIS and IRIX are trademarks of Silicon Graphics, Inc. MS-DOS is a registered trademark of Microsoft Corporation. UNIX is a registered trademark of AT&T.

Nanoklystron: A Monolithic Tube Approach to THz Power Generation

NASA Technical Reports Server (NTRS)

Siegel, Peter H.; Fung, Andy; Manohara, Harish; Xu, Jimmy; Chang, Baohe

2001-01-01

The authors propose a new approach to THz power generation: the nanoklystron. Utilizing silicon micromachining techniques, the design and fabrication concept of a monolithic THz vacuum-tube reflex-klystron source is described. The nanoklystron employs a separately fabricated cathode structure composed of densely packed carbon nanotube field emitters and an add-in repeller. The nanotube cathode is expected to increase the current density, extend the cathode life and decrease the required oscillation voltage to values below 100 V. The excitation cavity is based on ridged-waveguide and differs from the conventional cylindrical re-entrant structures found in lower frequency klystrons. A quasi-static field analysis of the cavity and output coupling structure show excellent control of the quality factor and desired field distribution. Output power is expected to occur through an iris coupled matched rectangular waveguide and integrated pyramidal feed horn. The entire circuit is designed so as to be formed monolithically from two thermocompression bonded silicon wafers processed using deep reactive ion etching (DRIE) techniques. To expedite prototyping, a 600 GHz mechanically machined structure has been designed and is in fabrication. A complete numeric analysis of the nanoklystron circuit, including the electron beam dynamics has just gotten underway. Separate evaluation of the nanotube cathodes is also ongoing. The authors will describe the progress to date as well as plans for the immediate implementation and testing of nanoklystron prototypes at 640 and 1250 GHz.

Solid State Research, 1980:4

DTIC Science & Technology

1980-10-31

and is initiated at the periphery of the de- vice at opening in the SijNj layer. Rate measurement* of thi* prove** made on the GKOUSS imager using...dimensions, single-mode opera- tion can be obtained. There is a stripe opening in the oxide film running parallel to the etched rib, which can be...seen in cross section in Fig. I-l(a). This stripe opening is the nucleation region for the epitaxial growth. Other oxide-confined waveguide

Microwave corrosion detection using open ended rectangular waveguide sensors

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

Qaddoumi, N.; Handjojo, L.; Bigelow, T.

The use of microwave and millimeter wave nondestructive testing methods utilizing open ended rectangular waveguide sensors has shown great potential for detecting minute thickness variations in laminate structures, in particular those backed by a conducting plate. Slight variations in the dielectric properties of materials may also be detected using a set of optimal parameters which include the standoff distance and the frequency of operation. In a recent investigation, on detecting rust under paint, the dielectric properties of rust were assumed to be similar to those of Fe{sub 2}O{sub 3} powder. These values were used in an electromagnetic model that simulatesmore » the interaction of fields radiated by a rectangular waveguide aperture with layered structures to obtain optimal parameters. The dielectric properties of Fe{sub 2}O{sub 3} were measured to be very similar to the properties of paint. Nevertheless, the presence of a simulated Fe{sub 2}O{sub 3} layer under a paint layer was detected. In this paper the dielectric properties of several different rust samples from different environments are measured. The measurements indicate that the nature of real rust is quite diverse and is different from Fe{sub 2}O{sub 3} and paint, indicating that the presence of rust under paint can be easily detected. The same electromagnetic model is also used (with the newly measured dielectric properties of real rust) to obtain an optimal standoff distance at a frequency of 24 GHz. The results indicate that variations in the magnitude as well as the phase of the reflection coefficient can be used to obtain information about the presence of rust. An experimental investigation on detecting the presence of very thin rust layers (2.5--5 x 10{sup {minus}2} mm [09--2.0 x 10{sup {minus}3} in.]) using an open ended rectangular waveguide probe is also conducted. Microwave images of rusted specimens, obtained at 24 GHz, are also presented.« less

Design of a Wideband 900 GHz Balanced Frequency Tripler for Radioastronomy

NASA Technical Reports Server (NTRS)

Tripon-Canseliet, Charlotte; Maestrini, Alain; Mehdi, Imran

2004-01-01

We report on the design of a fix-tuned split-block waveguide balanced frequency tripler working nominally at 900GHz. It uses a GaAs Schottky planar diode pair in a balanced configuration. The circuit will be fabricated with JPL membrane technology in order to minimize dielectric loading. The multiplier is bias-less to dramatically ease the mounting and the operating procedure. At room temperature, the expected output power is 50- 130 (micro)W in the band 800-970 GHz when the tripler is pumped with 4mW. By modifying the waveguide input and output matching circuit, the multiplier can be tuned to operate at lower frequencies.

Waferscale nanophotonic circuits made from diamond-on-insulator substrates.

PubMed

Rath, P; Gruhler, N; Khasminskaya, S; Nebel, C; Wild, C; Pernice, W H P

2013-05-06

Wide bandgap dielectrics are attractive materials for the fabrication of photonic devices because they allow broadband optical operation and do not suffer from free-carrier absorption. Here we show that polycrystalline diamond thin films deposited by chemical vapor deposition provide a promising platform for the realization of large scale integrated photonic circuits. We present a full suite of photonic components required for the investigation of on-chip devices, including input grating couplers, millimeter long nanophotonic waveguides and microcavities. In microring resonators we measure loaded optical quality factors up to 11,000. Corresponding propagation loss of 5 dB/mm is also confirmed by measuring transmission through long waveguides.

Open Resonator for Summation of Powers in Sub-Terahertz and Terahertz Frequencies

NASA Astrophysics Data System (ADS)

Kuz'michev, I. K.; Yeryomka, V. D.; May, A. V.; Troshchilo, A. S.

2017-03-01

Purpose: Study of excitation features for the first higher axialasymmetric type oscillations in an open resonator connected into the waveguide transmission line. Design/methodology/approach: To determine the efficiency of higher oscillation excitation in the resonator by using the highest wave of a rectangular waveguide, the coefficient of the antenna surface utilization is used. The coefficient of reflection from the open resonator is determined by the known method of summation of the partial coefficients of reflection from the resonant system. Findings: The excitation efficiency of the first higher axial asymmetric type TEM10q oscillations in an open resonator connected into the waveguide transmission line, using the TE20 type wave, is considered. The research efforts were made with accounting for the electromagnetic field vector nature. It is shown that for certain sizes of exciting coupler the excitation efficiency of the working excitation is equal to 0.867. Besides, this resonant system has a single frequency response within a wide band of frequencies. Due to this, it can be applied for summation of powers for individual sources of oscillations. Since this resonant system allows separating the matching functions as to the field and coupling, it is possible to provide any prescribed coupling of sources with a resonant volume. For this purpose, one- dimensional diffraction gratings (E-polarization) are used. Conclusions: With the matched excitation of axially asymmetric modes of oscillations the resonant system has an angular and frequency spectrum selection that is of great practical importance for powers summation. By application of one- dimensional diffraction gratings (E-polarization), located in apertures of coupling elements, the active elements can be matched with the resonant volume.

Experimental Testing of a Metamaterial Slow Wave Structure for High-Power Microwave Generation

NASA Astrophysics Data System (ADS)

Shipman, K.; Prasad, S.; Andreev, D.; Fisher, D. M.; Reass, D. B.; Schamiloglu, E.; Gilmore, M.

2017-10-01

A high-power L band source has been developed using a metamaterial (MTM) to produce a double negative slow wave structure (SWS) for interaction with an electron beam. The beam is generated by a 700 kV, 6 kA short pulse (10 ns) accelerator. The design of the SWS consists of a cylindrical waveguide, loaded with alternating split-rings that are arrayed axially down the waveguide. The beam is guided down the center of the rings, where electrons interact with the MTM-SWS producing radiation. Power is extracted axially via a circular waveguide, and radiated by a horn antenna. Microwaves are characterized by an external detector placed in a waveguide. Mode characterization is performed using a neon bulb array. The bulbs are lit by the electric field, resulting in an excitation pattern that resembles the field pattern. This is imaged using an SLR camera. The MTM structure has electrically small features so breakdown is a concern. In addition to high speed cameras, a fiber-optic-fed, sub-ns photomultiplier tube array diagnostic has been developed and used to characterize breakdown light. Work supported by the Air Force Office of Scientific Research, MURI Grant FA9550-12-1-0489.

Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

PubMed

Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

2016-06-01

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

MUSTANG: A Community-Facing Web Service to Improve Seismic Data Quality Awareness Through Metrics

NASA Astrophysics Data System (ADS)

Templeton, M. E.; Ahern, T. K.; Casey, R. E.; Sharer, G.; Weertman, B.; Ashmore, S.

2014-12-01

IRIS DMC is engaged in a new effort to provide broad and deep visibility into the quality of data and metadata found in its terabyte-scale geophysical data archive. Taking advantage of large and fast disk capacity, modern advances in open database technologies, and nimble provisioning of virtual machine resources, we are creating an openly accessible treasure trove of data measurements for scientists and the general public to utilize in providing new insights into the quality of this data. We have branded this statistical gathering system MUSTANG, and have constructed it as a component of the web services suite that IRIS DMC offers. MUSTANG measures over forty data metrics addressing issues with archive status, data statistics and continuity, signal anomalies, noise analysis, metadata checks, and station state of health. These metrics could potentially be used both by network operators to diagnose station problems and by data users to sort suitable data from unreliable or unusable data. Our poster details what MUSTANG is, how users can access it, what measurements they can find, and how MUSTANG fits into the IRIS DMC's data access ecosystem. Progress in data processing, approaches to data visualization, and case studies of MUSTANG's use for quality assurance will be presented. We want to illustrate what is possible with data quality assurance, the need for data quality assurance, and how the seismic community will benefit from this freely available analytics service.

Dynamics of quantum correlation between separated nitrogen-vacancy centers embedded in plasmonic waveguide

PubMed Central

Yang, Wan-li; An, Jun-Hong; Zhang, Cheng-jie; Chen, Chang-yong; Oh, C. H.

2015-01-01

We investigate the dynamics of quantum correlation between two separated nitrogen vacancy centers (NVCs) placed near a one-dimensional plasmonic waveguide. As a common medium of the radiation field of NVCs propagating, the plasmonic waveguide can dynamically induce quantum correlation between the two NVCs. It is interesting to find that such dynamically induced quantum correlation can be preserved in the long-time steady state by locally applying individual driving on the two NVCs. In particular, we also show that a large degree of quantum correlation can be established by this scheme even when the distance between the NVCs is much larger than their operating wavelength. This feature may open new perspectives for devising active decoherence-immune solid-state optical devices and long-distance NVC-based quantum networks in the context of plasmonic quantum electrodynamics. PMID:26493045

Association between light-to-dark changes in angle width and iris parameters in light, dark and changes from light-to-dark conditions.

PubMed

Lee, Roland Y; Lin, Shuai-Chun; Chen, Rebecca I; Barbosa, Diego T; Lin, Shan C

2016-09-01

To evaluate the association between light-to-dark changes in angle width parameters and iris parameters in light, dark and changes from light-to-dark conditions. In this prospective, cross-sectional study, anterior segment optical coherence tomography images, obtained under light and dark conditions, were analysed to determine angle opening distance measured at 500 μm from the scleral spur (AOD500), trabecular-iris space area at 500 μm from the scleral spur (TISA500), iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), iris area (IArea) and pupil diameter (PD). Multivariable linear mixed-effect regression models were used to evaluate the association between light-to-dark changes in angle width parameters (AOD500, TISA500) and iris parameters (IT750, IT2000, IArea, PD) in light, dark and changes from light-to-dark conditions. 534 eyes from 314 non-glaucomatous subjects were analysed. IT750, IT2000, IArea and PD in light conditions were significantly associated with light-to-dark changes in AOD500 (p<0.05). IT750, IT2000 and IArea in light conditions were significantly associated with light-to-dark changes in TISA500 (p<0.05). IT750 in dark conditions was significantly associated with light-to-dark changes in AOD500 and TISA500 (p<0.05). Light-to-dark changes in IT2000, IArea and PD were significantly associated with light-to-dark changes in AOD500 (p<0.05). Light-to-dark changes in IArea were significantly associated with light-to-dark changes in TISA500 (p<0.05). Evaluation of iris parameters in light, dark and changes from light-to-dark conditions demonstrated that IT750, IT2000, IArea and PD in light conditions are significant predictors of light-to-dark changes in angle width. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

KSC-2013-2909

NASA Image and Video Library

2013-06-25

VANDENBERG AIR FORCE BASE, Calif. – At Vandenberg Air Force Base in California, NASA hosted a prelaunch news conference on the Interface Region Imaging Spectrograph, or IRIS, solar observatory scheduled to launch on a Pegasus XL rocket. Participating in the news conference are George Diller, NASA Public Affairs, Geoffrey Yoder, deputy associate administrator for the Programs, Science Mission Directorate at NASA Headquarters in Washington, D.C., Tim Dunn, NASA launch director/NASA Launch Manager at the Kennedy Space Center in Florida, Bryan Baldwin, Pegasus launch vehicle program director for Orbital Sciences Corp. of Dulles, Va., Gary Kushner, IRIS project manager for Lockheed Martin's Solar and Astrophysics Laboratory in Palo Alto, Calif., and First Lt. Jennifer Kelley, launch weather officer for the U.S. Air Force 30th Operations Support Squadron at Vandenberg. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun’s corona using spectrometry and imaging. The IRIS mission will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. The interface region, located between the sun's visible surface and upper atmosphere, is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. For more information, visit http://www.nasa.gov/iris Photo credit: NASA/ Daniel Casper

A modal approach based on perfectly matched layers for the forced response of elastic open waveguides

NASA Astrophysics Data System (ADS)

Gallezot, M.; Treyssède, F.; Laguerre, L.

2018-03-01

This paper investigates the computation of the forced response of elastic open waveguides with a numerical modal approach based on perfectly matched layers (PML). With a PML of infinite thickness, the solution can theoretically be expanded as a discrete sum of trapped modes, a discrete sum of leaky modes and a continuous sum of radiation modes related to the PML branch cuts. Yet with numerical methods (e.g. finite elements), the waveguide cross-section is discretized and the PML must be truncated to a finite thickness. This truncation transforms the continuous sum into a discrete set of PML modes. To guarantee the uniqueness of the numerical solution of the forced response problem, an orthogonality relationship is proposed. This relationship is applicable to any type of modes (trapped, leaky and PML modes) and hence allows the numerical solution to be expanded on a discrete sum in a convenient manner. This also leads to an expression for the modal excitability valid for leaky modes. The physical relevance of each type of mode for the solution is clarified through two numerical test cases, a homogeneous medium and a circular bar waveguide example, excited by a point source. The former is favourably compared to a transient analytical solution, showing that PML modes reassemble the bulk wave contribution in a homogeneous medium. The latter shows that the PML mode contribution yields the long-term diffraction phenomenon whereas the leaky mode contribution prevails closer to the source. The leaky mode contribution is shown to remain accurate even with a relatively small PML thickness, hence reducing the computational cost. This is of particular interest for solving three-dimensional waveguide problems, involving two-dimensional cross-sections of arbitrary shapes. Such a problem is handled in a third numerical example by considering a buried square bar.

Predictors of Intraocular Pressure After Phacoemulsification in Primary Open-Angle Glaucoma Eyes with Wide Versus Narrower Angles (An American Ophthalmological Society Thesis)

PubMed Central

Lin, Shan C.; Masis, Marisse; Porco, Travis C.; Pasquale, Louis R.

2017-01-01

Purpose To assess if narrower-angle status and anterior segment optical coherence tomography (AS-OCT) parameters can predict intraocular pressure (IOP) drop in primary open-angle glaucoma (POAG) patients after cataract surgery. Methods This was a prospective case series of consecutive cataract surgery patients with POAG and no peripheral anterior synechiae (PAS) using a standardized postoperative management protocol. Preoperatively, patients underwent gonioscopy and AS-OCT. The same glaucoma medication regimen was resumed by 1 month. Potential predictors of IOP reduction included narrower-angle status by gonioscopy and angle-opening distance (AOD500) as well as other AS-OCT parameters. Mixed-effects regression adjusted for use of both eyes and other potential confounders. Results We enrolled 66 eyes of 40 glaucoma patients. The IOP reduction at 1 year was 4.2±3 mm Hg (26%, P<.001) in the narrower-angle group vs 2.2±3 mm Hg (14%, P<.001) in the wide-angle group (P=.027 for difference), as classified by gonioscopy. By AOD500 classification, the narrower-angle group had 3.4±3 mm Hg (21%, P<.001) reduction vs 2.5±3 mm Hg (16%, P<.001) in the wide-angle group (P=.031 for difference). When the entire cohort was assessed, iris thickness, iris area, and lens vault were correlated with increasing IOP reduction at 1 year (P<.05 for all). Conclusions In POAG eyes, cataract surgery lowered IOP to a greater degree in the narrower-angle group than in the wide-angle group, and parameters relating to iris thickness and area, as well as lens vault, were correlated with IOP reduction. These findings can guide ophthalmologists in their selection of cataract surgery as a potential management option. PMID:29147104

Predictors of Intraocular Pressure After Phacoemulsification in Primary Open-Angle Glaucoma Eyes with Wide Versus Narrower Angles (An American Ophthalmological Society Thesis).

PubMed

Lin, Shan C; Masis, Marisse; Porco, Travis C; Pasquale, Louis R

2017-08-01

To assess if narrower-angle status and anterior segment optical coherence tomography (AS-OCT) parameters can predict intraocular pressure (IOP) drop in primary open-angle glaucoma (POAG) patients after cataract surgery. This was a prospective case series of consecutive cataract surgery patients with POAG and no peripheral anterior synechiae (PAS) using a standardized postoperative management protocol. Preoperatively, patients underwent gonioscopy and AS-OCT. The same glaucoma medication regimen was resumed by 1 month. Potential predictors of IOP reduction included narrower-angle status by gonioscopy and angle-opening distance (AOD500) as well as other AS-OCT parameters. Mixed-effects regression adjusted for use of both eyes and other potential confounders. We enrolled 66 eyes of 40 glaucoma patients. The IOP reduction at 1 year was 4.2±3 mm Hg (26%, P <.001) in the narrower-angle group vs 2.2±3 mm Hg (14%, P <.001) in the wide-angle group ( P =.027 for difference), as classified by gonioscopy. By AOD500 classification, the narrower-angle group had 3.4±3 mm Hg (21%, P <.001) reduction vs 2.5±3 mm Hg (16%, P <.001) in the wide-angle group ( P =.031 for difference). When the entire cohort was assessed, iris thickness, iris area, and lens vault were correlated with increasing IOP reduction at 1 year ( P <.05 for all). In POAG eyes, cataract surgery lowered IOP to a greater degree in the narrower-angle group than in the wide-angle group, and parameters relating to iris thickness and area, as well as lens vault, were correlated with IOP reduction. These findings can guide ophthalmologists in their selection of cataract surgery as a potential management option.

Infrared photothermal imaging of trace explosives on relevant substrates

NASA Astrophysics Data System (ADS)

Kendziora, Christopher A.; Furstenberg, Robert; Papantonakis, Michael; Nguyen, Viet; Borchert, James; Byers, Jeff; McGill, R. Andrew

2013-06-01

We are developing a technique for the stand-off detection of trace explosives on relevant substrate surfaces using photo-thermal infrared (IR) imaging spectroscopy (PT-IRIS). This approach leverages one or more compact IR quantum cascade lasers, tuned to strong absorption bands in the analytes and directed to illuminate an area on a surface of interest. An IR focal plane array is used to image the surface and detect small increases in thermal emission upon laser illumination. The PT-IRIS signal is processed as a hyperspectral image cube comprised of spatial, spectral and temporal dimensions as vectors within a detection algorithm. The ability to detect trace analytes on relevant substrates is critical for stand-off applications, but is complicated by the optical and thermal analyte/substrate interactions. This manuscript describes recent PT-IRIS experimental results and analysis for traces of RDX, TNT, ammonium nitrate (AN) and sucrose on relevant substrates (steel, polyethylene, glass and painted steel panels). We demonstrate that these analytes can be detected on these substrates at relevant surface mass loadings (10 μg/cm2 to 100 μg/cm2) even at the single pixel level.

Incidence and risk factors for immune reconstitution inflammatory syndrome in an ethnically diverse HIV type 1-infected cohort.

PubMed

Ratnam, I; Chiu, C; Kandala, N-B; Easterbrook, P J

2006-02-01

It is estimated that 10%-25% of patients who start highly active antiretroviral therapy (HAART) experience immune reconstitution inflammatory syndrome (IRIS). Our objective was to determine the incidence, clinical spectrum, and predictors of IRIS in an ethnically diverse cohort of patients initiating HAART. A retrospective study of all patients starting HAART between 1 January 2000 and 31 August 2002 at a human immunodeficiency virus (HIV) clinic in London was performed. All laboratory measurements and data on antiretroviral therapies were obtained from the clinic database. Medical records were reviewed to identify clinical events consistent with IRIS during the 6 months after HAART was initiated. A total of 199 patients were included, of whom 50.8% were male, 59.3% were black African, 29.1% were white, and 10.5% were black Caribbean. The median baseline CD4 cell count and HIV RNA load were 174x10(6) cells/L (interquartile range [IQR], 82-285x10(6) cells/L) and 37,830 copies/mL (IQR, 4809-149,653 copies/mL), respectively. Forty-four patients (22.7%) experienced an IRIS event at a median of 12 weeks after HAART initiation (IQR, 4-24 weeks after initiation); 22 events (50%) involved genital herpes, 10 (23%) involved genital warts, 4 (9.0%) involved molluscum contagiosum, and 4 (9.0%) involved varicella zoster virus infection. Five patients had mycobacterial infections, 4 had hepatitis B, 1 had Pneumocystis jirovecci infection, and 1 had Kaposi sarcoma. The strongest independent predictors of IRIS were younger age at initiation of HAART (P=.003), baseline CD4 cell percentage of <10% (odds ratio [OR], 2.97; IQR, 1.17-7.55) compared with >15%, and ratio of CD4 cell percentage to CD8 cell percentage of <0.15 (OR, 3.45; 95% confidence interval, 1.27-9.1) compared with >0.3. Approximately one-quarter of patients who start HAART experience an IRIS event. The majority are dermatological, in particular genital herpes and warts. Patients with advanced immunodeficiency at HAART initiation are at greatest risk of developing IRIS and should be appropriately screened and monitored.

Characterization and on-sky demonstration of an integrated photonic spectrograph for astronomy.

PubMed

Cvetojevic, N; Lawrence, J S; Ellis, S C; Bland-Hawthorn, J; Haynes, R; Horton, A

2009-10-12

We present results from the first on-sky demonstration of a prototype astronomical integrated photonic spectrograph (IPS) using the Anglo-Australian Telescope near-infrared imaging spectrometer (IRIS2) at Siding Spring Observatory to observe atmospheric molecular OH emission lines. We have succeeded in detecting upwards of 27 lines, and demonstrated the practicality of the IPS device for astronomy. Furthermore, we present a laboratory characterization of the device, which is a modified version of a commercial arrayed-waveguide grating multiplexer. We measure the spectral resolution full-width-half-maximum to be 0.75 +/- 0.05 nm (giving R = lambda/deltalambda = 2100 +/- 150 at 1500 nm). We find the free spectral range to be 57.4 +/- 0.6 nm and the peak total efficiency to be approximately 65%. Finally, we briefly discuss the future steps required to realize an astronomical instrument based on this technology concept.

Effects of a westernized lifestyle on the association between fasting serum nonesterified fatty acids and insulin secretion in Japanese men.

PubMed

Kamei, Nozomu; Yamane, Kiminori; Nakanishi, Shuhei; Ishida, Kazufumi; Ohtaki, Megu; Okubo, Masamichi; Kohno, Nobuoki

2005-06-01

The effects of the prolonged elevation of nonesterified fatty acid (NEFA) levels on insulin secretion have been controversial and thought to be sex-specific. To investigate the association between a westernized lifestyle and the effects of NEFA on insulin secretion in Japanese men, we examined 67 nondiabetic Japanese-American men and 220 nondiabetic native Japanese men who underwent a 75-g oral glucose tolerance test (OGTT). Most Japanese Americans we surveyed are genetically identical to Japanese living in Japan, but their lifestyle is more westernized. Sets of multiple regression analyses were performed to evaluate the relationship between the sum of the immunoreactive insulin (IRI) levels during the OGTT ((Sigma)IRI) and clinical parameters. Japanese Americans had higher levels of fasting IRI, (Sigma)IRI, and a higher insulin resistance index (homeostasis model assessment for insulin resistance [HOMA-IR]) than native Japanese, whereas there were no significant differences in fasting NEFA and triglyceride levels. A multiple regression analysis adjusted for age, fasting triglycerides, and body mass index (BMI) demonstrated that the fasting NEFA level was an independent determinant of the (Sigma)IRI only in Japanese-American men ( P = .001), but not in native Japanese men ( P = .054). Even when HOMA-IR was included in models instead of BMI, the NEFA level was a significant variable of (Sigma)IRI only in Japanese Americans ( P < .001), and not in native Japanese ( P = .098). In addition, a multiple regression analysis adjusted for age, fasting triglycerides, and BMI demonstrated that the fasting NEFA level was the only independent determinant of (Sigma)C-peptide in Japanese-American men ( P = .041). In conclusion, NEFA seems to be associated with insulin secretion independent of obesity or HOMA-IR. A westernized lifestyle may increase the effects of serum fasting NEFA levels on total insulin secretion after a glucose load in Japanese men.

A high power microwave triggered RF opening switch.

PubMed

Beeson, S; Dickens, J; Neuber, A

2015-03-01

A 4-port S-band waveguide structure was designed and fabricated such that a signal of any amplitude (less than 1 MW) can be switched from a normally closed state, <0.5 dB insertion loss (IL), to an open state >30 dB IL by initiating plasma in a gas cell situated at the junction of this waveguide and one propagating a megawatt level magnetron pulse. The 90/10 switching time is as low as 20 ns with a delay of ∼30 ns between the onset of the high power microwave pulse and the initial drop of the signal. Two ports of this device are for the high power triggering pulse while the other two ports are for the triggered signal in a Moreno-like coupler configuration. In order to maintain high isolation, these two sets of waveguides are rotated 90° from each other with a TE111 resonator/plasma cell located at the intersection. This manuscript describes the design and optimization of this structure using COMSOL 4.4 at the design frequency of 2.85 GHz, comparison of simulated scattering parameters with measured "cold tests" (testing without plasma), and finally the temporal waveforms of this device being used to successfully switch a low power CW signal from 2 W to <5 mW on a sub-microsecond timescale.

Telecom meets terahertz

NASA Astrophysics Data System (ADS)

Nikitin, Alexey Y.

2018-01-01

Excitation and gate tuning of terahertz plasmons in dual-layer graphene integrated into on-chip telecom photonic waveguides using infrared lasers has now been demonstrated. This may open the door to atomically thick optoelectronic devices for security, tomography or data processing.

From SHG to mid-infrared SPDC generation in strained silicon waveguides

NASA Astrophysics Data System (ADS)

Castellan, Claudio; Trenti, Alessandro; Mancinelli, Mattia; Marchesini, Alessandro; Ghulinyan, Mher; Pucker, Georg; Pavesi, Lorenzo

2017-08-01

The centrosymmetric crystalline structure of Silicon inhibits second order nonlinear optical processes in this material. We report here that, by breaking the silicon symmetry with a stressing silicon nitride over-layer, Second Harmonic Generation (SHG) is obtained in suitably designed waveguides where multi-modal phase-matching is achieved. The modeling of the generated signal provides an effective strain-induced second order nonlinear coefficient of χ(2) = (0.30 +/- 0.02) pm/V. Our work opens also interesting perspectives on the reverse process, the Spontaneous Parametric Down Conversion (SPDC), through which it is possible to generate mid-infrared entangled photon pairs.

100 GHz pulse waveform measurement based on electro-optic sampling

NASA Astrophysics Data System (ADS)

Feng, Zhigang; Zhao, Kejia; Yang, Zhijun; Miao, Jingyuan; Chen, He

2018-05-01

We present an ultrafast pulse waveform measurement system based on an electro-optic sampling technique at 1560 nm and prepare LiTaO3-based electro-optic modulators with a coplanar waveguide structure. The transmission and reflection characteristics of electrical pulses on a coplanar waveguide terminated with an open circuit and a resistor are investigated by analyzing the corresponding time-domain pulse waveforms. We measure the output electrical pulse waveform of a 100 GHz photodiode and the obtained rise times of the impulse and step responses are 2.5 and 3.4 ps, respectively.

Electrically Small Folded Slot Antenna Utilizing Capacitive Loaded Slot Lines

NASA Technical Reports Server (NTRS)

Scardelletti, Maximilian C.; Ponchak, George E.; Merritt, Shane; Minor, John S.; Zorman, Christian A.

2007-01-01

This paper presents an electrically small, coplanar waveguide fed, folded slot antenna that uses capacitive loading. Several antennas are fabricated with and without capacitive loading to demonstrate the ability of this design approach to reduce the resonant frequency of the antenna, which is analogous to reducing the antenna size. The antennas are fabricated on Cu-clad Rogers Duriod(TM) 6006 with multilayer chip capacitors to load the antennas. Simulated and measured results show close agreement, thus, validating the approach. The electrically small antennas have a measured return loss greater than 15 dB and a gain of 5.4, 5.6, and 2.7 dBi at 4.3, 3.95, and 3.65 GHz, respectively.

Simulation of Blast Loading on an Ultrastructurally-based Computational Model of the Ocular Lens

DTIC Science & Technology

2012-10-01

mechanisms of traumatic cataract forma - tion that may require cataract surgery (implantation of an intraocular lens (IOL)) are not well understood in...cornea and cutting through the iris and zonules. This was done by making a small incision with a diamond-head blade at the edge of the cornea and using

Eccentric superconducting RF cavity separator structure

DOEpatents

Aggus, John R.; Giordano, Salvatore T.; Halama, Henry J.

1976-01-01

Accelerator apparatus having an eccentric-shaped, iris-loaded deflecting cavity for an rf separator for a high energy high momentum, charged particle accelerator beam. In one embodiment, the deflector is superconducting, and the apparatus of this invention provides simplified machining and electron beam welding techniques. Model tests have shown that the electrical characteristics provide the desired mode splitting without adverse effects.

Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

NASA Astrophysics Data System (ADS)

Yang, Xin Mi; Wen, Juan; Liu, Chang Rong; Liu, Xue Guan; Cui, Tie Jun

2015-12-01

Design of bandwidth-enhanced circularly polarized (CP) patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM). In particular, the embedded meander line (EML) structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM) exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna) has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

Preparing NASA's Next Solar Satellite for Launch

NASA Image and Video Library

2017-12-08

Orbital Sciences team members move the second half of the payload fairing before it is placed over NASA's IRIS (Interface Region Imaging Spectrograph) spacecraft. The fairing connects to the nose of the Orbital Sciences Pegasus XL rocket that will lift the solar observatory into orbit. The work is taking place in a hangar at Vandenberg Air Force Base, where IRIS is being prepared for launch on a Pegasus XL rocket. Scheduled for launch from Vandenberg on June 26, 2013, IRIS will open a new window of discovery by tracing the flow of energy and plasma through the chromospheres and transition region into the sun's corona using spectrometry and imaging. IRIS fills a crucial gap in our ability to advance studies of the sun-to-Earth connection by tracing the flow of energy and plasma through the foundation of the corona and the region around the sun known as the heliosphere. High res file available here: 1.usa.gov/11yal3w Photo Credit: NASA/Tony Vauclin NASA image use policy. 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

The IRIS Data Management Center: An international "network of networks", providing open, automated access to geographically distributed sensors of geophysical and environmental data.

NASA Astrophysics Data System (ADS)

Benson, R. B.; Ahern, T. K.; Trabant, C.

2006-12-01

The IRIS Data Management System has long supported international collaboration for seismology by both deploying a global network of seismometers and creating and maintaining an open and accessible archive in Seattle, WA, known as the Data Management Center (DMC). With sensors distributed on a global scale spanning more than 30 years of digital data, the DMC provides a rich repository of observations across broad time and space domains. Primary seismological data types include strong motion and broadband seismometers, conventional and superconducting gravimeters, tilt and creep meters, GPS measurements, along with other similar sensors that record accurate and calibrated ground motion. What may not be as well understood is the volume of environmental data that accompanies typical seismological data these days. This poster will review the types of time-series data that are currently being collected, how they are collected, and made freely available for download at the IRIS DMC. Environmental sensor data that is often co-located with geophysical data sensors include temperature, barometric pressure, wind direction and speed, humidity, insolation, rain gauge, and sometimes hydrological data like water current, level, temperature and depth. As the primary archival institution of the International Federation of Digital Seismograph Networks (FDSN), the IRIS DMC collects approximately 13,600 channels of real-time data from 69 different networks, from close to 1600 individual stations, currently averaging 10Tb per year in total. A major contribution to the IRIS archive currently is the EarthScope project data, a ten-year science undertaking that is collecting data from a high-resolution, multi-variate sensor network. Data types include magnetotelluric, high-sample rate seismics from a borehole drilled into the San Andreas fault (SAFOD) and various types of strain data from the Plate Boundary Observatory (PBO). In addition to the DMC, data centers located in other countries are networked seamlessly, and are providing access for researchers to these data from national networks around the world utilizing the IRIS developed Data Handling Interface (DHI) system. This poster will highlight some of the DHI enabled clients that allow geophysical information to be directly transferred to the clients. This ability allows one to construct a virtual network of data centers providing the illusion of a single virtual observatory. Furthermore, some of the features that will be shown include direct connections to MATLAB and the ability to access globally distributed sensor data in real time. We encourage discussion and participation from network operators who would like to leverage existing technology, as well as enabling collaboration.

COMPARATIVE THERMOREGULATORY RESPONSE TO PASSIVE HEAT LOADING BY EXPOSURE TO RADIOFREQUENCY RADIATION

EPA Science Inventory

Colonic and tail skin temperature of the unrestrained Fischer rat were measured immediately after a 90 min exposure to 600 MHz radiofrequency radiation in a waveguide-type system. Ambient temperature (Ta) was maintained at either 20, 28, or 35 C. The specific absorption rate (SAR...

Beamed microwave power transmitting and receiving subsystems radiation characteristics

NASA Technical Reports Server (NTRS)

Dickinson, R. M.

1980-01-01

Measured characteristics of the spectrum of typical converters and the distribution of radiated Radio Frequency (RF) energy from the terminals (transmitting antenna and rectenna) of a beamed microwave power subsystem are presented for small transmitting and receiving S-band (2.45 GHz) subarrays. Noise and harmonic levels of tube and solid-state RF power amplifiers are shown. The RF patterns and envelope of a 64 element slotted waveguide antenna are given for the fundamental frequency and harmonics through the fifth. Reflected fundamental and harmonic patterns through the fourth for a 42 element rectenna subarray are presented for various dc load and illumination conditions. Bandwidth measurements for the waveguide antenna and rectenna are shown.

Adiabatic wavelength redshift by dynamic carrier depletion using p -i -n -diode-loaded photonic crystal waveguides

NASA Astrophysics Data System (ADS)

Kondo, K.; Baba, T.

2018-03-01

We demonstrate an adiabatic wavelength redshift using dynamic carrier depletion. Free carriers are first induced through two-photon absorption of a control pulse and then extracted by a reverse-biased p-i-n diode formed on a Si photonic crystal waveguide, resulting in rapid carrier depletion. A copropagating signal pulse is redshifted by the consequent increase in refractive index. We experimentally evaluated the dynamics of the carrier depletion by the pump-probe method and explored suitable conditions for adiabatic redshift. The signal's redshift was observed, and was confirmed to originate in the dynamic carrier depletion. The redshift was experimentally determined as 0.21 nm.

Ultra-wideband tunable resonator based on varactor-loaded complementary split-ring resonators on a substrate-integrated waveguide for microwave sensor applications.

PubMed

Sam, Somarith; Lim, Sungjoon

2013-04-01

This paper presents the modeling, design, fabrication, and measurement of an ultra-wideband tunable twoport resonator in which the substrate-integrated waveguide, complementary split-ring resonators (CSRRs), and varactors are embedded on the same planar platform. The tuning of the passband frequency is generated by a simple single dc voltage of 0 to 36 V, which is applied to each varactor on the CSRRs. Different capacitance values and resonant frequencies are produced while a nearly constant absolute bandwidth is maintained. The resonant frequency is varied between 0.83 and 1.58 GHz and has a wide tuning ratio of 90%.

Theoretical investigation of intensity-dependent optical nonlinearity in graphene-aided D-microfiber

NASA Astrophysics Data System (ADS)

Shah, Manoj Kumar; Lu, Rongguo; Zhang, Yali; Ye, Shengwei; Zhang, Shangjian; Liu, Yong

2018-01-01

We theoretically investigate the intensity-dependent optical nonlinearity in graphene-aided D-microfiber, by tuning the chemical potential of graphene and varying radial distance and radii of the D-microfiber. Utilizing an interplay between graphene and the enhanced evanescent field of a guided mode in the waveguide of interest, the net utility of nonlinear coefficient is harnessed up to a very high value of 106 W-1m-1. Importantly, which is ∼ two orders of magnitude larger than in PMMA-graphene-PMMA waveguide. The highly dispersive nature of the waveguide, D ∼ 103 ps/nm-km, and large nonlinear figure-of-merit, FOMNL ∼ 1.29, have raised the possibilities of utilizing slow light structures to operate devices at few watts power level with microscale length. These studies have opened one window towards the next-generation all fiber-optic graphene nonlinear optical devices.

High-frequency asymptotic methods for analyzing the EM scattering by open-ended waveguide cavities

NASA Technical Reports Server (NTRS)

Burkholder, R. J.; Pathak, P. H.

1989-01-01

Four high-frequency methods are described for analyzing the electromagnetic (EM) scattering by electrically large open-ended cavities. They are: (1) a hybrid combination of waveguide modal analysis and high-frequency asymptotics, (2) geometrical optics (GO) ray shooting, (3) Gaussian beam (GB) shooting, and (4) the generalized ray expansion (GRE) method. The hybrid modal method gives very accurate results but is limited to cavities which are made up of sections of uniform waveguides for which the modal fields are known. The GO ray shooting method can be applied to much more arbitrary cavity geometries and can handle absorber treated interior walls, but it generally only predicts the major trends of the RCS pattern and not the details. Also, a very large number of rays need to be tracked for each new incidence angle. Like the GO ray shooting method, the GB shooting method can handle more arbitrary cavities, but it is much more efficient and generally more accurate than the GO method because it includes the fields diffracted by the rim at the open end which enter the cavity. However, due to beam divergence effects the GB method is limited to cavities which are not very long compared to their width. The GRE method overcomes the length-to-width limitation of the GB method by replacing the GB's with GO ray tubes which are launched in the same manner as the GB's to include the interior rim diffracted field. This method gives good accuracy and is generally more efficient than the GO method, but a large number of ray tubes needs to be tracked.

Facilitate, Collaborate, Educate: the Role of the IRIS Consortium in Supporting National and International Research in Seismology (Invited)

NASA Astrophysics Data System (ADS)

Simpson, D. W.; Beck, S. L.

2009-12-01

Over the twenty-five years since its founding in 1984, the IRIS Consortium has contributed in fundamental ways to change the practice and culture of research in seismology in the US and worldwide. From an original founding group of twenty-two U.S. academic institutions, IRIS membership has now grown to 114 U.S. Member Institutions, 20 Educational Affiliates and 103 Foreign Affiliates. With strong support from the National Science Foundation, additional resources provided by other federal agencies, close collaboration with the U.S. Geological Survey and many international partners, the technical resources of the core IRIS programs - the Global Seismographic Network (GSN), the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL), the Data Management System (DMS) and Education and Outreach - have grown to become a major national and international source of experimental data for research on earthquakes and Earth structure, and a resource to support education and outreach to the public. While the primary operational focus of the Consortium is to develop and maintain facilities for the collection of seismological data for basic research, IRIS has become much more than an instrument facility. It has become a stimulus for collaboration between academic seismological programs and a focus for their interactions with national and international partners. It has helped establish the academic community as a significant contributor to the collection of data and an active participant in global research and monitoring. As a consortium of virtually all of the Earth science research institutions in the US, IRIS has helped coordinate the academic community in the development of new initiatives, such as EarthScope, to strengthen the support for science and argue for the relevance of seismology and its use in hazard mitigation. The early IRIS pioneers had the foresight to carefully define program goals and technical standards for the IRIS facilities that have stood the test of time. Many of these technical standards for equipment and data exchange have extended to become de-facto global standards and influenced instrument development and network practices throughout the world. A governance structure for the Consortium was created that continues to encourage strong community guidance in the operation and evolution of IRIS programs. From the outset, there was a commitment to maintaining a complete archive of all IRIS data, with significant emphasis on metadata and quality control. Building on long-standing traditions of collaboration in seismological research, an explicit IRIS policy of free and open data exchange has expanded the culture of data sharing among it members, which, through example, encouragement and support, has extended to influence the data policies of numerous other organizations in seismology and the Earth sciences. The technical revolution in sensors, communications and data collection that accompanied the early development of IRIS is now available to the entire world. The challenge for IRIS and the seismology community in the decades ahead will be to encourage the implementation of these technologies, along with appropriate training and resources, to further the research community’s endeavors to understand the structure and evolution of our planet and apply that knowledge to the mitigation of earthquake hazards.

Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications.

PubMed

Smirnov, Serguei; Anoshkin, Ilya V; Demchenko, Petr; Gomon, Daniel; Lioubtchenko, Dmitri V; Khodzitsky, Mikhail; Oberhammer, Joachim

2018-06-21

Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.

Simultaneous Detection of Two Chemicals Using a TE20-Mode Substrate-Integrated Waveguide Resonator

PubMed Central

Salim, Ahmed

2018-01-01

Microwave resonators working as sensors can detect only a single analyte at a time. To address this issue, a TE20-mode substrate-integrated waveguide (SIW) resonator is exploited, owing to its two distinct regions of high-intensity electric fields, which can be manipulated by loading two chemicals. Two microfluidic channels with unequal fluid-carrying capacities, engraved in a polydimethylsiloxane (PDMS) sheet, can perturb the symmetric electric fields even if loaded with the two extreme cases of dielectric [ethanol (E), deionized water (DI)] and [deionized water, ethanol]. The four layers of the sandwiched structure considered in this study consisted of a top conductive pattern and a bottom ground, both realized on a Rogers RT/Duroid 5880. PDMS-based channels attached with an adhesive serve as the middle layers. The TE20-mode SIW with empty channels resonates at 8.26 GHz and exhibits a −25 dB return loss with an unloaded quality factor of Q ≈ 28. We simultaneously load E and DI and demonstrate the detection of the four possible combinations: [E, DI], [DI, E], [E, E], and [DI, DI]. The performance of our proposed method showed increases in sensitivity (MHz/εr) of 7.5%, 216%, and 1170% compared with three previously existing multichannel microwave chemical sensors. PMID:29518981

Designing a new post-hole seismological station on Antarctica inlandsis (Concordia station)

NASA Astrophysics Data System (ADS)

Bès de Berc, M.; Maggi, A.; Leveque, J. J.; Thore, J. Y.

2015-12-01

Concordia (75°S 123°E) is a scientific base operated by French and Italian polar institutes IPEV (Institut Paul-Emile Victor) and PNRA (Programma Nazionale di Ricerche in Antartide, and is located on the inlandsis of the East Antarctica plateau. It hosts a seismological station CCD which has provided observatory quality data since the year 2000, has been integrated into the Geoscope network since 2008 and whose data are now available in real-time from IRIS. The current seismic vault is located 800m from Concordia base, as far away as is deemed logistically possible by IPEV, at a depth of 12m. The vault is thermally very stable, but given the close distance to the base, suffers from increased diurnal noise (up to 40 dB) at frequencies above 1Hz, especially in the summer season. Anthropic noise is trapped in the firn (snow) layer, which forms an 100-110m thick waveguide, and is picked up very easily in the seismic vault. The vault is made from steel containers buried vertically in the snow. The hydrostatic pressure of the snow is deforming them: we see container cracking events on the seismograms, and also visual evidence of container deformation inside the vault. In the near future, this deformation will create a security problem.We have decided to progressively abandon our current vault, and construct a new post-hole seismological installation nearby. We plan to drill to 130m depth, which would place us below the firn layer waveguide and also below the ice pinch-out depth. To be able to run the station for several years and change or service the instrumentation if required, we need to keep the hole open, to avoid any hydrostatic movement, and to maintain good coupling between the sensor and the surrounding hard ice. To achieve these goals, we shall install a casing in the fin layer and then drill a few meters more without casing in hard ice. After installing the instrument, we shall then fill the whole hole with a drilling fluid whose density is similar to that of ice.The drilling will be carried out by the French drilling facility C2FN (Centre de Carottage et de Forage National) of the CNRS (Centre National de la Recherche Scientifique), and the is planned for the 2018-2019 summer season.

Low-to-high refractive index contrast transition (RICT) device for low loss polymer-based optical coupling

NASA Astrophysics Data System (ADS)

Calabretta, N.; Cooman, I. A.; Stabile, R.

2018-04-01

We propose for the first time a coupling device concept for passive low-loss optical coupling, which is compatible with the ‘generic’ indium phosphide (InP) multi-project-wafer manufacturing. A low-to-high vertical refractive index contrast transition InP waveguide is designed and tapered down to adiabatically couple light into a top polymer waveguide. The on-chip embedded polymer waveguide is engineered at the chip facets for offering refractive-index and spot-size-matching to silica fiber-arrays. Numerical analysis shows that coupling losses lower than 1.5 dB can be achieved for a TE-polarized light between the InP waveguide and the on-chip embedded polymer waveguide at 1550 nm wavelength. The performance is mainly limited by the difficulty to control single-mode operation. However, coupling losses lower than 1.9 dB can be achieved for a bandwidth as large as 200 nm. Moreover, the foreseen fabrication process steps are indicated, which are compatible with the ‘generic’ InP multi-project-wafer manufacturing. A fabrication error tolerance study is performed, indicating that fabrication errors occur only in 0.25 dB worst case excess losses, as long as high precision lithography is used. The obtained results are promising and may open the route to large port counts and cheap packaging of InP-based photonic integrated chips.

A Contemporary Concept of the Blood-Aqueous Barrier

PubMed Central

Freddo, Thomas F.

2012-01-01

This review traces the evolution of the concept of the blood-aqueous barrier (BAB) during the past 20 years. The classical model simply stipulated that the tight junctions of the iris vasculature and ciliary epithelium excluded plasma proteins from the aqueous humor (AH). It failed to reconcile the presence of AH protein levels equal to 1% of that found in plasma. Moreover, models of barrier kinetics assumed that the processes of AH secretion and plasma protein entry were directly linked. Thus, elevations of AH protein levels could only be explained by a pathological breakdown of the BAB. Over the last 20 years it has been shown that the plasma proteins in normal AH by-pass the posterior chamber entirely. Instead, these proteins diffuse from the capillaries of ciliary body stroma, into the iris stroma and then into the anterior chamber. This creates a reservoir of plasma-proteins in the iris stroma that is not derived from the iris vessels. This reservoir is prevented from diffusing posteriorly by tight junctions in the posterior iris epithelium. The one-way valve created by the pupil resting on the anterior lens capsule, combined with the continuous, forward flow of AH through the pupil, prevents protein reflux into the posterior chamber. Importantly, in the new paradigm, secretion of AH and the entry of plasma proteins into AH, are semi-independent events. This opens the possibility that AH protein levels could increase in the absence of breakdown of the BAB. Clinical consequences of this new paradigm of the BAB are discussed. PMID:23128417

Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models

NASA Astrophysics Data System (ADS)

Mauritsen, T.; Stevens, B. B.

2015-12-01

Current climate models exhibit equilibrium climate sensitivities to a doubling of CO2 of 2.0-4.6 K and a weak increase of global mean precipitation. But inferences from the observational record place climate sensitivity near the lower end of the range, and indicate that models underestimate changes in certain aspects of the hydrological cycle under warming. Here we show that both these discrepancies can be explained by a controversial hypothesis of missing negative tropical feedbacks in climate models, known as the iris-effect: Expanding dry and clear regions in a warming climate yield a negative feedback as more infrared radiation can escape to space through this metaphorical opening iris. At the same time the additional infrared cooling of the atmosphere must be balanced by latent heat release thereby accelerating the hydrological cycle. Alternative suggestions of too little aerosol cooling, missing volcanic eruptions, or insufficient ocean heat uptake in models may explain a slow observed transient warming, but are not able to explain the observed enhanced hydrological cycle. We propose that a temperature-dependency of the extent to which precipitating convective clouds cluster or aggregate into larger clouds constitutes a plausible physical mechanism for the iris-effect. On a large scale, organized convective states are dryer than disorganized convection and therefore radiate more in the longwave to space. Thus, if a warmer atmosphere can host more organized convection, then this represents one possible mechanism for an iris-effect. The challenges in modeling, understanding and possibly quantifying a temperature-dependency of convection are, however, substantial.

A contemporary concept of the blood-aqueous barrier.

PubMed

Freddo, Thomas F

2013-01-01

This review traces the evolution of the concept of the blood-aqueous barrier (BAB) during the past 20 years. The Classical model simply stipulated that the tight junctions of the iris vasculature and ciliary epithelium excluded plasma proteins from the aqueous humor (AH). It failed to reconcile the presence of AH protein levels equal to 1% of that found in plasma. Moreover, models of barrier kinetics assumed that the processes of AH secretion and plasma protein entry were directly linked. Thus, elevations of AH protein levels could only be explained by a pathological breakdown of the BAB. Over the last 20 years it has been shown that the plasma proteins in normal AH by-pass the posterior chamber entirely. Instead, these proteins diffuse from the capillaries of ciliary body stroma, into the iris stroma and then into the anterior chamber. This creates a reservoir of plasma-proteins in the iris stroma that is not derived from the iris vessels. This reservoir is prevented from diffusing posteriorly by tight junctions in the posterior iris epithelium. The one-way valve created by the pupil resting on the anterior lens capsule, combined with the continuous, forward flow of AH through the pupil, prevents protein reflux into the posterior chamber. Importantly, in the new paradigm, secretion of AH and the entry of plasma proteins into AH, are semi-independent events. This opens the possibility that AH protein levels could increase in the absence of breakdown of the BAB. Clinical consequences of this new paradigm of the BAB are discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biometric Factors Associated With Acute Primary Angle Closure: Comparison of the Affected and Fellow Eye.

PubMed

Atalay, Eray; Nongpiur, Monisha E; Baskaran, Mani; Sharma, Sourabh; Perera, Shamira A; Aung, Tin

2016-10-01

To compare ocular biometric and anterior segment parameters between the affected and fellow eye in subjects with acute primary angle closure (APAC). We evaluated 76 subjects with unilateral APAC who had undergone bilateral laser peripheral iridotomy before enrollment. Imaging was done using anterior segment optical coherence tomography and a customized software was used to measure the following: angle opening distance (AOD750); trabecular-iris space area (TISA750); iris thickness (IT750); iris curvature (ICURV); iris area (IAREA); anterior chamber depth; area and volume (ACD; ACA and ACV); anterior chamber width (ACW); anterior vault (ACD+LV); lens vault (LV); and pupil diameter (PD). We used A-scan ultrasonography to measure axial length (AL) and lens thickness (LT). Mean differences in ocular biometric and anterior segment parameters were assessed using linear mixed model adjusting for PD. A total of 53 subjects (36 females, 67.9%) with a mean age of 62.7 ± 8.1 years were analyzed after excluding 17 unanalyzable images in at least one eye. Affected eyes had shallower ACD, smaller ACA, ACV, anterior vault, TISA750, AOD750, and ICURV (all P < 0.05). Axial length, ACW, LV, LT, IAREA, and IT750 did not differ between the eyes. In the affected eyes, IT750 was significantly associated AOD750 (P < 0.05); whereas in the fellow eyes, IT750 and AL was predictive of AOD750 (all P < 0.05). Eyes with previous APAC had smaller anterior segment dimensions when compared with their fellow eyes. Iris thickness was the strongest predictor of angle width in both affected and fellow eyes.

A single-stage optical load-balanced switch for data centers.

PubMed

Huang, Qirui; Yeo, Yong-Kee; Zhou, Luying

2012-10-22

Load balancing is an attractive technique to achieve maximum throughput and optimal resource utilization in large-scale switching systems. However current electronic load-balanced switches suffer from severe problems in implementation cost, power consumption and scaling. To overcome these problems, in this paper we propose a single-stage optical load-balanced switch architecture based on an arrayed waveguide grating router (AWGR) in conjunction with fast tunable lasers. By reuse of the fast tunable lasers, the switch achieves both functions of load balancing and switching through the AWGR. With this architecture, proof-of-concept experiments have been conducted to investigate the feasibility of the optical load-balanced switch and to examine its physical performance. Compared to three-stage load-balanced switches, the reported switch needs only half of optical devices such as tunable lasers and AWGRs, which can provide a cost-effective solution for future data centers.

Analysis of limited-diffractive and limited-dispersive X-waves generated by finite radial waveguides

NASA Astrophysics Data System (ADS)

Fuscaldo, Walter; Pavone, Santi C.; Valerio, Guido; Galli, Alessandro; Albani, Matteo; Ettorre, Mauro

2016-05-01

In this work, we analyze the spatial and temporal features of electromagnetic X-waves propagating in free space and generated by planar radiating apertures. The performance of ideal X-waves is discussed and compared to practical cases where the important effects related to the finiteness of the radiating aperture and the wavenumber dispersion are taken into account. In particular, a practical device consisting of a radial waveguide loaded with radiating slots aligned along a spiral path is considered for the practical case in the millimeter-wave range. A common mathematical framework is defined for a precise comparison of the spatiotemporal properties and focusing capabilities of the generated X-wave. It is clearly shown that the fractional bandwidth of the radiating aperture has a key role in the longitudinal confinement of an X-wave in both ideal and practical cases. In addition, the finiteness of the radiating aperture as well as the wavenumber dispersion clearly affect both the transverse and the longitudinal profiles of the generated radiation as it travels beyond the depth-of-field of the generated X-wave. Nevertheless, the spatiotemporal properties of the X-wave are preserved even in this "dispersive-finite" case within a defined region and duration related to the nondiffractive range and fractional bandwidth of the spectral components of the generated X-wave. The proposed analysis may open new perspectives for the efficient generation of X-waves over finite radiating apertures at millimeter waves where the dispersive behavior of realistic devices is no longer negligible.

A COAXIAL MAGIC-T

DTIC Science & Technology

Three different designs of coaxial hybrid junctions having perf ormance analogous to a wave-guide magic -T are discussed. The experimental results...loads, decoupling greater than 70 db can be obtained. An application of the magic -T in phase measurement is described which is independent of the signal amplitude and is similar to the homodyne system of phase measurement.

Study on a discal TEM-TE{sub 11} mode converter loaded high-efficiency magnetically insulated transmission line oscillator

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

Zhang, Xiaoping, E-mail: zhangxiaoping@nudt.edu.cn; Yuan, Chengwei; Li, Yangmei

2015-12-15

An integrative high power microwave device is proposed, which consists of a high-efficiency L-band Magnetically Insulated Transmission Line Oscillator (MILO) and a discal TEM–TE{sub 11} mode converter. The MILO with a shrunken load composed of a step-like cathode and a ladder-like beam collector can generate a 1.58 GHz, 5.7 GW microwave with the efficiency of 20.8% at the diode voltage of 560 kV in simulation. The discal converter utilizes a pair of sectorial two-double radial waveguides and a pair of sectorial cross section waveguides to adjust the phase-difference and realizes the mode conversion in a length of less than halfmore » wavelength at 1.58 GHz. In the preliminary experiment, the proposed device generates over 2 GW, 1.575 GHz microwave with the pulse duration of over 50 ns in a 420 kV diode voltage; the corresponding efficiency is 14.9%; the radiation pattern is the ideal TE{sub 11} mode.« less

The aerosol rabbit model of TB latency, reactivation and immune reconstitution inflammatory syndrome

PubMed Central

Manabe, Yukari C.; Kesavan, Anup K.; Lopez-Molina, Javier; Hatem, Christine L.; Brooks, Megan; Fujiwara, Ricardo; Hochstein, Karl; Pitt, M. Louise M.; Tufariello, JoAnn; Chan, John; McMurray, David N.; Bishai, William R.; Dannenberg, Arthur M.; Mendez, Susana

2015-01-01

The large reservoir of human latent tuberculosis (TB) contributes to the global success of the pathogen, Mycobacterium tuberculosis (Mtb). We sought to test whether aerosol infection of rabbits with Mtb H37Rv could model paucibacillary human latent TB. The lung burden of infection peaked at 5 weeks after aerosol infection followed by host containment of infection that was achieved in all rabbits. One-third of rabbits had at least one caseous granuloma with culturable bacilli at 36 weeks after infection suggesting persistent paucibacillary infection. Corticosteroid-induced immunosuppression initiated after disease containment resulted in reactivation of disease. Seventy-two percent of rabbits had culturable bacilli in the right upper lung lobe homogenates compared to none of the untreated controls. Discontinuation of dexamethasone led to predictable lymphoid recovery, with a proportion of rabbits developing multicentric large caseous granuloma. The development and severity of the immune reconstitution inflammatory syndrome (IRIS) was dependent on the antigen load at the time of immunosuppression and subsequent bacillary replication during corticosteroid-induced immunosuppression. Clinically, many aspects were similar to IRIS in severely immunosuppressed HIV-infected patients who have functional restoration of T cells in response to effective (highly active) antiretroviral therapy. This corticosteroid model is the only animal model of the IRIS. Further study of the rabbit model of TB latency, reactivation and IRIS may be important in understanding the immunopathogenesis of these poorly modeled states as well as for improved diagnostics for specific stages of disease. PMID:18068491

Practical microstructured and plasmonic terahertz waveguides

NASA Astrophysics Data System (ADS)

Markov, Andrey

The terahertz frequency range, with frequencies lying between 100 GHz and 10 THz, has strong potential for various technological and scientific applications such as sensing, imaging, communications, and spectroscopy. Most terahertz (THz) sources are immobile and THz systems use free-space propagation in dry air where losses are minimal. Designing efficient THz waveguides for flexible delivery of broadband THz radiation is an important step towards practical applications of terahertz techniques. THz waveguides can be very useful on the system integration level when used for connection of the diverse THz point devices, such as sources, filters, sensor cells, detectors, etc. The most straightforward application of waveguides is to deliver electromagnetic waves from the source to the point of detection. Cumbersome free-space optics can be replaced by waveguides operating in the THz range, which could lead to the development of compact THz time domain spectroscopy systems. Other promising applications of THz waveguides are in sensing and imaging. THz waveguides have also been shown to operate in subwavelength regimes, offering mode confinement in waveguide structures with a size smaller than the diffraction limit, and thus, surpassing the resolution of free-space THz imaging systems. In order to design efficient terahertz waveguides, the frequency dependent loss and dispersion of the waveguide must be minimized. A possible solution would be to increase the fraction of mode power propagating through air. In this thesis, the usage of planar porous air/dielectric waveguides and metal wire/dielectric hybrid terahertz fibers will be discussed. First, I present a novel design of a planar porous low-loss waveguide, describe its fabrication, and characterize it in view of its potential applications as a low-loss waveguide and sensor in the THz spectral range. The waveguide structure features a periodic sequence of layers of thin (25-50 mum) polyethylene film that are separated by low-loss air layers of comparable thickness. A large fraction of the modal fields in these waveguides is guided in the low-loss air region, thus effectively reducing the waveguide transmission losses. I consider that such waveguides can be useful not only for low-loss THz wave delivery, but also for sensing of biological and chemical specimens in the terahertz region, by placing the recognition elements directly into the waveguide microstructure. The main advantage of the proposed planar porous waveguide is the convenient access to its optical mode, since the major portion of THz power launched into such a waveguide is confined within the air layers. Moreover, small spacing between the layers promotes rapid loading of the analyte into the waveguide due to strong capillary effect (< 1 s filling of a 10 cm long waveguide with an analyte). The transmission and absorption properties of such waveguides have been investigated both experimentally using THz-TDS spectroscopy and theoretically using finite element software. The modal refractive index of porous waveguides is smaller compared to pure polymer and it is easy to adjust by changing the air spacing between the layers, as well as the number of layers in the core. The porous waveguide exhibits considerably smaller transmission losses than bulk material. In the following chapters I review another promising approach towards designing of low-loss, low-dispersion THz waveguides. The hybrid metal/dielectric waveguides use a plasmonic mode guided in the gap between two parallel wires that are, in turn, encapsulated inside a low-loss, low-refractive index, micro-structured cladding that provides mechanical stability and isolation from the environment. I describe several promising techniques that can be used to encapsulate the two-wire waveguides, while minimizing the negative impact of dielectric cladding on the waveguide optical properties. In particular, I detail the use of low-density foams and microstructured plastic claddings as two enabling materials for the two-wire waveguide encapsulation. The hybrid fiber design is more convenient for practical applications than a classic two metal wire THz waveguide as it allows direct manipulations of the fiber without the risk of perturbing its core-guided mode. I present a detailed analysis of the modal properties of the hybrid metal/dielectric waveguides, compare them with the properties of a classic two-wire waveguide, and then present strategies for the improvement of hybrid waveguide performance by using higher cladding porosity or utilizing inherently porous cladding material. I study coupling efficiency into hybrid waveguides and conclude that it can be relatively high (>50%) in the broad frequency range ˜0.5 THz. Not surprisingly, optical properties of such fibers are inferior to those of a classic two-wire waveguide due to the presence of lossy dielectric near an inter-wire gap. At the same time, composite fibers outperform porous fibers of the same geometry both in bandwidth of operation and in lower dispersion. I demonstrate that hybrid metal/dielectric porous waveguides can have a very large operational bandwidth, while supporting tightly confined, air-bound modes both at high and low frequencies. This is possible as, at higher frequencies, hybrid fibers can support ARROW-like low-loss air-bound modes, while changing their guidance mechanism to plasmonic confinement in the inter-wire air gap at lower frequencies. Finally, I describe an intriguing resonant property of some hybrid plasmonic modes of metal / dielectric waveguides that manifests itself in the strong frequency dependent change in the modal confinement from dielectric-bound to air-bound. I discuss how this property can be used to construct THz refractometers. Introduction of even lossless analytes into the fiber core leads to significant changes in the modal losses, which is used as a transduction mechanism. The resolution of the refractometer has been investigated numerically as a function of the operation frequency and the geometric parameters of the fiber. With a refractive index resolution on the order of ˜10-3 RIU, the composite fiber-based sensor is capable of identifying various gaseous analytes and aerosols or measuring the concentration of dust particles in the air.

Multifrequency synthetic aperture radar antenna comparison study. [for remote sensing

NASA Technical Reports Server (NTRS)

Blevins, B. A.

1983-01-01

Three multifrequency, dual polarization SAR antenna designs are reviewed. The SAR antenna design specifications were for a "straw man' SAR which would approximate the requirements for projected shuttle-based SAR's. Therefore, the physical dimensions were constrained to be compatible with the space shuttle. The electrical specifications were similar to those of SIR-A and SIR-B with the addition of dual polarization and the addition of C and X band operation. Early in the antenna design considerations, three candidate technologies emerged as having promise. They were: (1) microstrip patch planar array antennas, (2) slotted waveguide planar array antennas, and (3) open-ended waveguide planar array antennas.

Integrable models of quantum optics

NASA Astrophysics Data System (ADS)

Yudson, Vladimir; Makarov, Aleksander

2017-10-01

We give an overview of exactly solvable many-body models of quantum optics. Among them is a system of two-level atoms which interact with photons propagating in a one-dimensional (1D) chiral waveguide; exact eigenstates of this system can be explicitly constructed. This approach is used also for a system of closely located atoms in the usual (non-chiral) waveguide or in 3D space. Moreover, it is shown that for an arbitrary atomic system with a cascade spontaneous radiative decay, the fluorescence spectrum can be described by an exact analytic expression which accounts for interference of emitted photons. Open questions related with broken integrability are discussed.

Infrared photothermal imaging spectroscopy for detection of trace explosives on surfaces.

PubMed

Kendziora, Christopher A; Furstenberg, Robert; Papantonakis, Michael; Nguyen, Viet; Byers, Jeff; Andrew McGill, R

2015-11-01

We are developing a technique for the standoff detection of trace explosives on relevant substrate surfaces using photothermal infrared (IR) imaging spectroscopy (PT-IRIS). This approach leverages one or more compact IR quantum cascade lasers, which are tuned to strong absorption bands in the analytes and directed to illuminate an area on a surface of interest. An IR focal plane array is used to image the surface and detect increases in thermal emission upon laser illumination. The PT-IRIS signal is processed as a hyperspectral image cube comprised of spatial, spectral, and temporal dimensions as vectors within a detection algorithm. The ability to detect trace analytes at standoff on relevant substrates is critical for security applications but is complicated by the optical and thermal analyte/substrate interactions. This manuscript describes a series of PT-IRIS experimental results and analysis for traces of RDX, TNT, ammonium nitrate, and sucrose on steel, polyethylene, glass, and painted steel panels. We demonstrate detection at surface mass loadings comparable with fingerprint depositions ( 10μg/cm2 to 100μg/cm2) from an area corresponding to a single pixel within the thermal image.

Mitochondria-targeted antioxidant MitoQ reduced renal damage caused by ischemia-reperfusion injury in rodent kidneys: Longitudinal observations of T2 -weighted imaging and dynamic contrast-enhanced MRI.

PubMed

Liu, Xiaoge; Murphy, Michael P; Xing, Wei; Wu, Huanhuan; Zhang, Rui; Sun, Haoran

2018-03-01

To investigate the effect of mitochondria-targeted antioxidant MitoQ in reducing the severity of renal ischemia-reperfusion injury (IRI) in rats using T 2 -weighted imaging and dynamic contrast-enhanced MRI (DCE-MRI). Ischemia-reperfusion injury was induced by temporarily clamping the left renal artery. Rats were pretreated with MitoQ or saline. The MRI examination was performed before and after IRI (days 2, 5, 7, and 14). The T 2 -weighted standardized signal intensity of the outer stripe of the outer medulla (OSOM) was measured. The unilateral renal clearance rate k cl was derived from DCE-MRI. Histopathology was evaluated after the final MRI examination. The standardized signal intensity of the OSOM on IRI kidneys with MitoQ were lower than those with saline on days 5 and 7 (P = 0.004, P < 0.001, respectively). K cl values of IRI kidneys with MitoQ were higher than those with saline at all time points (P = 0.002, P < 0.001, P = 0.001, P < 0.001). Histopathology showed that renal damage was the most predominant on the OSOM of IRI kidneys with saline, which was less obvious with MitoQ (P < 0.001). These findings demonstrate that MitoQ can reduce the severity of renal damage in rodent IRI models using T 2 -weighted imaging and DCE-MRI. Magn Reson Med 79:1559-1667, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Mitochondria‐targeted antioxidant MitoQ reduced renal damage caused by ischemia‐reperfusion injury in rodent kidneys: Longitudinal observations of T 2‐weighted imaging and dynamic contrast‐enhanced MRI

PubMed Central

Liu, Xiaoge; Murphy, Michael P.; Xing, Wei; Wu, Huanhuan; Zhang, Rui

2017-01-01

Purpose To investigate the effect of mitochondria‐targeted antioxidant MitoQ in reducing the severity of renal ischemia‐reperfusion injury (IRI) in rats using T2‐weighted imaging and dynamic contrast‐enhanced MRI (DCE‐MRI). Methods Ischemia‐reperfusion injury was induced by temporarily clamping the left renal artery. Rats were pretreated with MitoQ or saline. The MRI examination was performed before and after IRI (days 2, 5, 7, and 14). The T2‐weighted standardized signal intensity of the outer stripe of the outer medulla (OSOM) was measured. The unilateral renal clearance rate kcl was derived from DCE‐MRI. Histopathology was evaluated after the final MRI examination. Results The standardized signal intensity of the OSOM on IRI kidneys with MitoQ were lower than those with saline on days 5 and 7 (P = 0.004, P < 0.001, respectively). Kcl values of IRI kidneys with MitoQ were higher than those with saline at all time points (P = 0.002, P < 0.001, P = 0.001, P < 0.001). Histopathology showed that renal damage was the most predominant on the OSOM of IRI kidneys with saline, which was less obvious with MitoQ (P < 0.001). Conclusions These findings demonstrate that MitoQ can reduce the severity of renal damage in rodent IRI models using T2‐weighted imaging and DCE‐MRI. Magn Reson Med 79:1559–1667, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:28608403

Facially Amphipathic Glycopolymers Inhibit Ice Recrystallization.

PubMed

Graham, Ben; Fayter, Alice E R; Houston, Judith E; Evans, Rachel C; Gibson, Matthew I

2018-05-02

Antifreeze glycoproteins (AFGPs) from polar fish are the most potent ice recrystallization (growth) inhibitors known, and synthetic mimics are required for low-temperature applications such as cell cryopreservation. Here we introduce facially amphipathic glycopolymers that mimic the three-dimensional structure of AFGPs. Glycopolymers featuring segregated hydrophilic and hydrophobic faces were prepared by ring-opening metathesis polymerization, and their rigid conformation was confirmed by small-angle neutron scattering. Ice recrystallization inhibition (IRI) activity was reduced when a hydrophilic oxo-ether was installed on the glycan-opposing face, but significant activity was restored by incorporating a hydrophobic dimethylfulvene residue. This biomimetic strategy demonstrates that segregated domains of distinct hydrophilicity/hydrophobicity are a crucial motif to introduce IRI activity, which increases our understanding of the complex ice crystal inhibition processes.

Acoustic solitons in waveguides with Helmholtz resonators: transmission line approach.

PubMed

Achilleos, V; Richoux, O; Theocharis, G; Frantzeskakis, D J

2015-02-01

We report experimental results and study theoretically soliton formation and propagation in an air-filled acoustic waveguide side loaded with Helmholtz resonators. We propose a theoretical modeling of the system, which relies on a transmission-line approach, leading to a nonlinear dynamical lattice model. The latter allows for an analytical description of the various soliton solutions for the pressure, which are found by means of dynamical systems and multiscale expansion techniques. These solutions include Boussinesq-like and Korteweg-de Vries pulse-shaped solitons that are observed in the experiment, as well as nonlinear Schrödinger envelope solitons, that are predicted theoretically. The analytical predictions are in excellent agreement with direct numerical simulations and in qualitative agreement with the experimental observations.

Anisotropic metamaterial waveguide driven by a cold and relativistic electron beam

NASA Astrophysics Data System (ADS)

Torabi, Mahmoud; Shokri, Babak

2018-03-01

We study the interaction of a cold and relativistic electron beam with a cylindrical waveguide loaded by an anisotropic and dispersive metamaterial layer. The general dispersion relation for the transverse magnetic (TM) mode, through the linear fluid model and Maxwell equations decomposition method, is derived. The effects of some metamaterial parameters on dispersion relation are presented. A qualitative discussion shows the possibility of monomodal propagation band widening and obtaining more control on dispersion relation behavior. Especially for epsilon negative near zero metamaterials, these effects are considerable. Finally, the anisotropy and metamaterial layer thickness impacts on wave growth rate for different metamaterials are considered. The results demonstrate that we can control both wave growth rate and voltage of saturation peak by metamaterial parameters.

Metal-capped silicon organic micro-ring electro-optical modulator (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zaki, Aya O.; Kirah, Khaled A.; Swillam, Mohamed A.

2017-02-01

An ultra-compact hybrid plasmonic waveguide ring electro-optical modulator is designed to be easily fabricated on silicon on insulator (SOI) substrates using standard silicon photonics technology. The proposed waveguide is based on a buried standard silicon waveguide of height 220 nm topped with polymer and metal. The key advantage of this novel design is that only the silicon layer of the waveguide is structured as a coupled ring resonator. Then, the device is covered with electro-optical polymer and metal in post processes with no need for lithography or accurate mask alignment techniques. The simple fabrication method imposes many design challenges to obtain a resonator of reasonable loaded quality factor and high extinction ratio. Here, the performance of the resonator is optimized in the telecom wavelength range around 1550 nm using 3D FDTD simulations. The design of the coupling junction between the access waveguide and the tightly bent ring is thoroughly studied. The extension of the metal over the coupling region is exploited to make the critical dimension of the design geometry at least 2.5 times larger than conventional plasmonic resonators and the design is thus more robust. In this paper, we demonstrate an electro-optical modulator that offers an insertion loss < 1 dB, a modulation depth of 12 dB for an applied peak to peak voltage of only 2 V and energy consumption of 1.74 fJ/bit. The performance is superior to previously reported hybrid plasmonic ring resonator based modulators while the design shows robustness and low fabrication cost.

KSC-2013-2939

NASA Image and Video Library

2013-06-27

VANDENBERG AIR FORCE BASE, Calif. – The Orbital Sciences L-1011 aircraft takes off from Vandenberg Air Force Base in California at 9:30 p.m. EDT, headed over the Pacific Ocean to release the Pegasus XL rocket carrying NASA's Interface Region Imaging Spectrograph, or IRIS, solar observatory. Release of the rocket from under the wing of the aircraft is scheduled for 10:27 p.m. EDT. IRIS will open a new window of discovery using spectrometry and imaging to trace the flow of energy and plasma through the chromospheres and transition region into the sun’s corona. The spacecraft will observe how solar material moves, gathers energy and heats up as it travels through a largely unexplored region of the solar atmosphere. This interface region, located between the sun's visible surface and its upper atmosphere, is where most of its ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate. NASA's Launch Services Program at the agency's Kennedy Space Center in Florida is managing the countdown and launch. For more information, visit http://www.nasa.gov/iris. Photo credit: NASA/Daniel Casper

Symposium: Special Education Services and Interagency Systems of Care in California.

ERIC Educational Resources Information Center

Willis, J., Ed.; Liberton, C., Ed.; Kutash, K., Ed.; Friedman, R., Ed.

Two papers summarize a symposium on special education services and interagency systems of care for children and adolescents with severe emotional disturbance (SED) in California. The first paper, "Opening the Floodgates? The Influence of a System of Care on Referrals to Special Education" (Iris Zanglis, Michael J. Furlong, Michelle Wood,…

Low-cost fabrication of optical waveguides, interconnects and sensing structures on all-polymer-based thin foils

NASA Astrophysics Data System (ADS)

Rezem, Maher; Kelb, Christian; Günther, Axel; Rahlves, Maik; Reithmeier, Eduard; Roth, Bernhard

2016-03-01

Micro-optical sensors based on optical waveguides are widely used to measure temperature, force and strain but also to detect biological and chemical substances such as explosives or toxins. While optical micro-sensors based on silicon technology require complex and expensive process technologies, a new generation of sensors based completely on polymers offer advantages especially in terms of low-cost and fast production techniques. We have developed a process to integrate micro-optical components such as embedded waveguides and optical interconnects into polymer foils with a thickness well below one millimeter. To enable high throughput production, we employ hot embossing technology, which is capable of reel-to-reel fabrication with a surface roughness in the optical range. For the waveguide fabrication, we used the thermoplastic polymethylmethacrylate (PMMA) as cladding and several optical adhesives as core materials. The waveguides are characterized with respect to refractive indices and propagation losses. We achieved propagation losses are as low as 0.3 dB/cm. Furthermore, we demonstrate coupling structures and their fabrication especially suited to integrate various light sources such as vertical-cavity surface-emitting lasers (VCSEL) and organic light emitting diodes (OLED) into thin polymer foils. Also, we present a concept of an all-polymer and waveguide based deformation sensor based on intensity modulation, which can be fabricated by utilizing our process. For future application, we aim at a low-cost and high-throughput reel-to-reel production process enabling the fabrication of large sensor arrays or disposable single-use sensing structures, which will open optical sensing to a large variety of application fields ranging from medical diagnosis to automotive sensing.

Full wave characterization of microstrip open end discontinuities patterned on anisotropic substrates using potential theory

NASA Technical Reports Server (NTRS)

Toncich, S. S.; Collin, R. E.; Bhasin, K. B.

1993-01-01

A technique for a full wave characterization of microstrip open end discontinuities fabricated on uniaxial anisotropic substrates using potential theory is presented. The substrate to be analyzed is enclosed in a cutoff waveguide, with the anisotropic axis aligned perpendicular to the air-dielectric interface. A full description of the sources on the microstrip line is included with edge conditions built in. Extention to other discontinuities is discussed.

IRIS Burst Spectra Co-spatial to a Quiet-Sun Ellerman-like Brightening

NASA Astrophysics Data System (ADS)

Nelson, C. J.; Freij, N.; Reid, A.; Oliver, R.; Mathioudakis, M.; Erdélyi, R.

2017-08-01

Ellerman bombs (EBs) have been widely studied over the past two decades; however, only recently have the counterparts of these events been observed in the quiet-Sun. The aim of this article is to further understand small-scale quiet-Sun Ellerman-like brightenings (QSEBs) through research into their spectral signatures, including investigating whether the hot signatures associated with some EBs are also visible co-spatial to any QSEBs. We combine Hα and Ca II 8542 Å line scans at the solar limb with spectral and imaging data sampled by the Interface Region Imaging Spectrograph (IRIS). Twenty-one QSEBs were identified with average lifetimes, lengths, and widths measured to be around 120 s, 0.″63, and 0.″35, respectively. Three of these QSEBs displayed clear repetitive flaring through their lifetimes, comparable to the behavior of EBs in active regions. Two QSEBs in this sample occurred co-spatial to increased emission in SDO/AIA 1600 Å and IRIS slit-jaw imager 1400 Å data; however, these intensity increases were smaller than those reported co-spatially with EBs. One QSEB was also sampled by the IRIS slit during its lifetime, displaying increases in intensity in the Si IV 1393 Å and Si IV 1403 Å cores, as well as the C II and Mg II line wings, analogous to IRIS bursts (IBs). Using RADYN simulations, we are unable to reproduce the observed QSEB Hα and Ca II 8542 Å line profiles, leaving the question of the temperature stratification of QSEBs open. Our results imply that some QSEBs could be heated to transition region temperatures, suggesting that IB profiles should be observed throughout the quiet-Sun.

IRIS Burst Spectra Co-spatial to a Quiet-Sun Ellerman-like Brightening

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

Nelson, C. J.; Erdélyi, R.; Freij, N.

Ellerman bombs (EBs) have been widely studied over the past two decades; however, only recently have the counterparts of these events been observed in the quiet-Sun. The aim of this article is to further understand small-scale quiet-Sun Ellerman-like brightenings (QSEBs) through research into their spectral signatures, including investigating whether the hot signatures associated with some EBs are also visible co-spatial to any QSEBs. We combine H α and Ca ii 8542 Å line scans at the solar limb with spectral and imaging data sampled by the Interface Region Imaging Spectrograph ( IRIS ). Twenty-one QSEBs were identified with average lifetimes,more » lengths, and widths measured to be around 120 s, 0.″63, and 0.″35, respectively. Three of these QSEBs displayed clear repetitive flaring through their lifetimes, comparable to the behavior of EBs in active regions. Two QSEBs in this sample occurred co-spatial to increased emission in SDO /AIA 1600 Å and IRIS slit-jaw imager 1400 Å data; however, these intensity increases were smaller than those reported co-spatially with EBs. One QSEB was also sampled by the IRIS slit during its lifetime, displaying increases in intensity in the Si iv 1393 Å and Si iv 1403 Å cores, as well as the C ii and Mg ii line wings, analogous to IRIS bursts (IBs). Using RADYN simulations, we are unable to reproduce the observed QSEB H α and Ca ii 8542 Å line profiles, leaving the question of the temperature stratification of QSEBs open. Our results imply that some QSEBs could be heated to transition region temperatures, suggesting that IB profiles should be observed throughout the quiet-Sun.« less

A PML-FDTD ALGORITHM FOR SIMULATING PLASMA-COVERED CAVITY-BACKED SLOT ANTENNAS. (R825225)

EPA Science Inventory

A three-dimensional frequency-dependent finite-difference time-domain (FDTD) algorithm with perfectly matched layer (PML) absorbing boundary condition (ABC) and recursive convolution approaches is developed to model plasma-covered open-ended waveguide or cavity-backed slot antenn...

Direct acceleration of electrons by a CO2 laser in a curved plasma waveguide

PubMed Central

Yi, Longqing; Pukhov, Alexander; Shen, Baifei

2016-01-01

Laser plasma interaction with micro-engineered targets at relativistic intensities has been greatly promoted by recent progress in the high contrast lasers and the manufacture of advanced micro- and nano-structures. This opens new possibilities for the physics of laser-matter interaction. Here we propose a novel approach that leverages the advantages of high-pressure CO2 laser, laser-waveguide interaction, as well as micro-engineered plasma structure to accelerate electrons to peak energy greater than 1 GeV with narrow slice energy spread (~1%) and high overall efficiency. The acceleration gradient is 26 GV/m for a 1.3 TW CO2 laser system. The micro-bunching of a long electron beam leads to the generation of a chain of ultrashort electron bunches with the duration roughly equal to half-laser-cycle. These results open a way for developing a compact and economic electron source for diverse applications. PMID:27320197

Deterministic quantum state transfer between remote qubits in cavities

NASA Astrophysics Data System (ADS)

Vogell, B.; Vermersch, B.; Northup, T. E.; Lanyon, B. P.; Muschik, C. A.

2017-12-01

Performing a faithful transfer of an unknown quantum state is a key challenge for enabling quantum networks. The realization of networks with a small number of quantum links is now actively pursued, which calls for an assessment of different state transfer methods to guide future design decisions. Here, we theoretically investigate quantum state transfer between two distant qubits, each in a cavity, connected by a waveguide, e.g., an optical fiber. We evaluate the achievable success probabilities of state transfer for two different protocols: standard wave packet shaping and adiabatic passage. The main loss sources are transmission losses in the waveguide and absorption losses in the cavities. While special cases studied in the literature indicate that adiabatic passages may be beneficial in this context, it remained an open question under which conditions this is the case and whether their use will be advantageous in practice. We answer these questions by providing a full analysis, showing that state transfer by adiabatic passage—in contrast to wave packet shaping—can mitigate the effects of undesired cavity losses, far beyond the regime of coupling to a single waveguide mode and the regime of lossless waveguides, as was proposed so far. Furthermore, we show that the photon arrival probability is in fact bounded in a trade-off between losses due to non-adiabaticity and due to coupling to off-resonant waveguide modes. We clarify that neither protocol can avoid transmission losses and discuss how the cavity parameters should be chosen to achieve an optimal state transfer.

Analysis of the electromagnetic scattering from an inlet geometry with lossy walls

NASA Technical Reports Server (NTRS)

Myung, N. H.; Pathak, P. H.; Chunang, C. D.

1985-01-01

One of the primary goals is to develop an approximate but sufficiently accurate analysis for the problem of electromagnetic (EM) plane wave scattering by an open ended, perfectly-conducting, semi-infinite hollow circular waveguide (or duct) with a thin, uniform layer of lossy or absorbing material on its inner wall, and with a simple termination inside. The less difficult but useful problem of the EM scattering by a two-dimensional (2-D), semi-infinite parallel plate waveguide with an impedance boundary condition on the inner walls was chosen initially for analysis. The impedance boundary condition in this problem serves to model a thin layer of lossy dielectric/ferrite coating on the otherwise perfectly-conducting interior waveguide walls. An approximate but efficient and accurate ray solution was obtained recently. That solution is presently being extended to the case of a moderately thick dielectric/ferrite coating on the walls so as to be valid for situations where the impedance boundary condition may not remain sufficiently accurate.

Microwave transmission measurements through a magnetic photonic crystal

NASA Astrophysics Data System (ADS)

Radwan, Mohamed Zein; Dewar, Graeme

We have measured the 12 - 18 GHz microwave transmission through, and the reflection from, a nickel zinc ferrite penetrated by a wire lattice. The metamaterial efficiently transmitted microwaves under conditions for which the index of refraction was negative. The wires, 0.29 mm in diameter, were threaded through Teflon tubes and centered in holes 1.7 mm in diameter drilled through the ferrite. The holes formed a square array with a lattice constant of 3.0 mm. A ferrite sample containing the wire array filled a length of 3.0 cm inside standard WR-62 waveguide and a static magnetic field between 0.042 and 13.0 kOe was applied parallel to the wires. We measured the transmission relative to an open waveguide and the reflection relative to a reflective metal plate across the waveguide face. We observed transmission modes at combinations of magnetic field and microwave frequency for which both the permeability of the ferrite and permittivity of the wire array were negative.

Nanophotonic Optical Isolator Controlled by the Internal State of Cold Atoms

NASA Astrophysics Data System (ADS)

Sayrin, Clément; Junge, Christian; Mitsch, Rudolf; Albrecht, Bernhard; O'Shea, Danny; Schneeweiss, Philipp; Volz, Jürgen; Rauschenbeutel, Arno

2015-10-01

The realization of nanophotonic optical isolators with high optical isolation even at ultralow light levels and low optical losses is an open problem. Here, we employ the link between the local polarization of strongly confined light and its direction of propagation to realize low-loss nonreciprocal transmission through a silica nanofiber at the single-photon level. The direction of the resulting optical isolator is controlled by the spin state of cold atoms. We perform our experiment in two qualitatively different regimes, i.e., with an ensemble of cold atoms where each atom is weakly coupled to the waveguide and with a single atom strongly coupled to the waveguide mode. In both cases, we observe simultaneously high isolation and high forward transmission. The isolator concept constitutes a nanoscale quantum optical analog of microwave ferrite resonance isolators, can be implemented with all kinds of optical waveguides and emitters, and might enable novel integrated optical devices for fiber-based classical and quantum networks.

Resent Status of ITER Equatorial Launcher Development

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

Takahashi, K.; Kajiwara, K.; Kasugai, A.

2009-11-26

The ITER equatorial launcher is divided into a front shield and a port plug. The front shield is composed of fourteen blanket shield modules so as to form three openings for the injection of mm-wave beams into plasma. Twenty-four waveguide transmission lines, internal shields, cooling pipes and so on are installed in the port plug. The transmission lines consist of the corrugated waveguides, miter bends and the free space propagation region utilizing two mirrors in front of the waveguide outlet. The analysis of mm-wave beam propagation in the region shows that the transmission efficiency more than 99.5% is attained. Themore » high power experiments of the launcher mock-up have been carried out and the measured field patterns at each mirror and the outlet of the launcher are agreed with the calculations. It is concluded that the transmission line components in the launcher mock-up are fabricated as designed and the present mm-wave design in the launcher is feasible.« less

Femtosecond laser inscription of asymmetric directional couplers for in-fiber optical taps and fiber cladding photonics.

PubMed

Grenier, Jason R; Fernandes, Luís A; Herman, Peter R

2015-06-29

Precise alignment of femtosecond laser tracks in standard single mode optical fiber is shown to enable controllable optical tapping of the fiber core waveguide light with fiber cladding photonic circuits. Asymmetric directional couplers are presented with tunable coupling ratios up to 62% and bandwidths up to 300 nm at telecommunication wavelengths. Real-time fiber monitoring during laser writing permitted a means of controlling the coupler length to compensate for micron-scale alignment errors and to facilitate tailored design of coupling ratio, spectral bandwidth and polarization properties. Laser induced waveguide birefringence was harnessed for polarization dependent coupling that led to the formation of in-fiber polarization-selective taps with 32 dB extinction ratio. This technology enables the interconnection of light propagating in pre-existing waveguides with laser-formed devices, thereby opening a new practical direction for the three-dimensional integration of optical devices in the cladding of optical fibers and planar lightwave circuits.

Improved Biomolecular Thin-Film Sensor based on Plasmon Waveguide Resonance

NASA Astrophysics Data System (ADS)

Byard, Courtney; Aslan, Mustafa; Mendes, Sergio

2009-05-01

The design, fabrication, and characterization of a plasmon waveguide resonance (PWR) sensor are presented. Glass substrates are coated with a 35 nm gold film using electron beam evaporation, and then covered with a 143 nm aluminum oxide waveguide using an atomic layer deposition process, creating a smooth, highly transparent dielectric film. When probed in the Kretschmann configuration, the structure allows for an efficient conversion of an incident optical beam into a surface wave, which is mainly confined in the dielectric layer and exhibits a deep and narrow angular resonance. The performance (reflectance vs. incidence angle in TE polarization) is modeled using a transfer-matrix approach implemented into a Mathematica code. Our simulations and experimental data are compared with that of surface plasmon resonance (SPR) sensor using the same criteria. We show that the resolution of PWR is approximately ten times better than SPR, opening opportunities for more sensitive studies in various applications including research in protein interactions, pharmaceutical drug development, and food analysis.

Spectral and mode properties of surface plasmon polariton waveguides studied by near-field excitation and leakage-mode radiation measurement

PubMed Central

2014-01-01

We present a method to couple surface plasmon polariton (SPP) guiding mode into dielectric-loaded SPP waveguide (DLSPPW) devices with spectral and mode selectivity. The method combined a transmission-mode near-field spectroscopy to excite the SPP mode and a leakage radiation optical microscope for direct visualization. By using a near-field fiber tip, incident photons with different wavelengths were converted into SPPs at the metal/dielectric interface. Real-time SPP radiation images were taken through leakage radiation images. The wavelength-dependent propagation lengths for silver- and gold-based DLSPPWs were measured and compared. It confirms that silver-based SPP has a propagation length longer than a gold-based one by 1.25, 1.38, and 1.52 times for red, green, and blue photons. The resonant coupling as a function of wavelength in dual DLSPPWs was measured. The coupling lengths measured from leakage radiation images were in good agreement with finite-difference time domain simulations. In addition, the propagation profile due to multi-SPP modes interference was studied by changing position of the fiber tip. In a multimode DLSPPW, SPP was split into two branches with a gap of 2.237 μm when the tip was at the center of the waveguide. It became a zigzag profile when the SPP was excited at the corner of the waveguide. PMID:25177228

A case report of progressive obstruction of Ex-PRESS miniature glaucoma shunt after transient flat anterior chamber and treatment using Nd:YAG laser.

PubMed

Tanito, Masaki; Sano, Ichiya; Ohira, Akihiro

2015-01-08

We report a case of Ex-PRESS miniature glaucoma shunt obstruction resulting from progressive iris synechial formation after transient anterior chamber shallowing. A 68-year-old woman with pseudoexfoliation glaucoma in her right eye underwent filtration surgery with implantation of the Ex-PPESS shunt (model P-50, Alcon Japan, Tokyo, Japan) in combination with intra-surgical 0.04% mitomycin C use. After the anterior chamber injection of viscoelastic material and 100% sulfur hexafluoride gas for treatment of early postoperative over filtration, the intraocular pressure (IOP) was controlled between 9 and 12 mmHg. On postoperative day 121, gonioscopy showed that synechial formation around the shunt obstructed the axial port leaving the relief port opened. On postoperative day 274, the intraocular pressure increased to 40 mmHg and synechiae obstructed both the axial and relief ports. Dispersion of iris tissue by neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (2 mJ, one shot to each port) opened both ports and immediately lowered the IOP, leaving peripheral anterior synechiae around the shunt. Up to postoperative day 400, the IOP was controlled between 13 and 15 mmHg, and the cystic bleb was maintained. The synechiae formed gradually extends around the shunt's shaft and can result in later external obstruction of the relief port. The current case requires further follow-up since synechiae remaining around the shaft can cause future obstruction. We emphasize the fact that, if the iris synechiae to the shunt once formed, it can progress and obstruct the shunt ports later.

An Open Rectangular Waveguide Grating for Millimeter-Wave Traveling-Wave Tubes

NASA Astrophysics Data System (ADS)

Liao, Ming-Liang; Wei, Yan-Yu; Wang, Hai-Long; Huang, Yu; Xu, Jin; Liu, Yang; Guo, Guo; Niu, Xin-Jian; Gong, Yu-Bin; Park, Gun-Sik

2016-09-01

Not Available Supported by the National Natural Science Foundation of China under Grant No 61271029, the National Science Fund for Distinguished Young Scholars of China under Grant No 61125103, and the National Research Foundation of Korea under Grant No MSIP: NRF-2009-0083512.

Conformal mapping and bound states in bent waveguides

NASA Astrophysics Data System (ADS)

Sadurní, E.; Schleich, W. P.

2010-12-01

Is it possible to trap a quantum particle in an open geometry? In this work we deal with the boundary value problem of the stationary Schroedinger (or Helmholtz) equation within a waveguide with straight segments and a rectangular bending. The problem can be reduced to a one-dimensional matrix Schroedinger equation using two descriptions: oblique modes and conformal coordinates. We use a corner-corrected WKB formalism to find the energies of the one-dimensional problem. It is shown that the presence of bound states is an effect due to the boundary alone, with no classical counterpart for this geometry. The conformal description proves to be simpler, as the coupling of transversal modes is not essential in this case.

Surface modification of tooth root canal after application of an X-ray opaque waveguide

NASA Astrophysics Data System (ADS)

Dostálová, T.; Jelínková, H.; Šulc, J.; Němec, M.; Koranda, P.; Bartoňová, M.; Radina, P.; Miyagi, M.; Shi, Y.-W.; Matsuura, Y.

The interest in endodontic use of dental laser systems has been increasing. With the development of thin and flexible delivery systems for various wavelengths, laser applications in endodontics may become even more desirable. The aim of this study is to check the X-ray opacity of a hollow waveguide and to observe the results after laser root canal treatment. The root canal systems of 10 molars were treated endodontically by laser. For the laser radiation source, an Er:YAG laser system generating a wavelength of 2940 nm and an Alexandrite laser system generating a wavelength of 375 nm were used. The hollow waveguide used was checked under X-ray . A root canal surface treated by laser radiation was analyzed by a scanning electron microscope (SEM). The special hollow glass waveguide used was visible in the root canal system under X-ray imaging. Surface modification of the root canal after laser treatment was not found. After conventional treatment the root canal was enlarged. The surface was covered with a smear layer. After application of both laser systems, the smear layer was removed. The resulting canal surface was found to be clean and smooth. Under SEM observation open dentinal tubules were visible. No cracks were present, nor were surface modifications observed.

Diffractometer data collecting method and apparatus

DOEpatents

Steinmeyer, P.A.

1991-04-16

Diffractometer data is collected without the use of a movable receiver. A scanning device, positioned in the diffractometer between a sample and detector, varies the amount of the beam diffracted from the sample that is received by the detector in such a manner that the beam is detected in an integrated form. In one embodiment, a variable diameter beam stop is used which comprises a drop of mercury captured between a pair of spaced sheets and disposed in the path of the diffracted beam. By varying the spacing between the sheets, the diameter of the mercury drop is varied. In another embodiment, an adjustable iris diaphragm is positioned in the path of the diffracted beam and the iris opening is adjusted to control the amount of the beam reaching the detector. 5 figures.

Diffractometer data collecting method and apparatus

DOEpatents

Steinmeyer, Peter A.

1991-04-16

Diffractometer data is collected without the use of a movable receiving s. A scanning device, positioned in the diffractometer between a sample and detector, varies the amount of the beam diffracted from the sample that is received by the detector in such a manner that the beam is detected in an integrated form. In one embodiment, a variable diameter beam stop is used which comprises a drop of mercury captured between a pair of spaced sheets and disposed in the path of the diffracted beam. By varying the spacing between the sheets, the diameter of the mercury drop is varied. In another embodiment, an adjustable iris diaphragm is positioned in the path of the diffracted beam and the iris opening is adjusted to control the amount of the beam reaching the detector.

Efficient 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation

NASA Technical Reports Server (NTRS)

Hochuli, U. E.; Haldemann, P. R.

1988-01-01

Details of a 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation are presented. The amplifier delivers 30 W into a 50-Ohm load while requiring only 40 W of dc power from a 28-V supply and 100 mW of rf drive power for an overall efficiency of 75 percent. A coupling-starting network design theory is given that provides the initiation over voltage for the discharge plasma from an rf power source of limited output voltage capability. The network then matches the drive circuit to the new input impedance of the operating discharge without any adjustments. This design theory applies to the whole class of networks whose losses can be approximated by a loss conductance in parallel with the gas discharge.

A new RF window designed for high-power operation in an S-band LINAC RF system

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Kim, Seung-Hwan; Hwang, Woonha; Ryu, Jiwan; Roh, Sungjoo

2016-09-01

A new RF window is designed for high-power operation at the Pohang Light Source-II (PLSII) S-band linear accelerator (LINAC) RF system. In order to reduce the strength of the electric field component perpendicular to the ceramic disk, which is commonly known as the main cause of most discharge breakdowns in ceramic disk, we replace the pill-box type cavity in the conventional RF window with an overmoded cavity. The overmoded cavity is coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the iris and the number of possible mode competitions. The finite-difference time-domain (FDTD) simulation, CST MWS, was used in the design process. The simulated maximum electric field component perpendicular to the ceramic for the new RF window is reduced by an order of magnitude compared with taht for the conventional RF window, which holds promise for stable high-power operation.

Self-consistent simulation of an electron beam for a new autoresonant x-ray generator based on TE 102 rectangular mode

NASA Astrophysics Data System (ADS)

Dugar-Zhabon, V. D.; Orozco, E. A.; Herrera, A. M.

2016-02-01

The space cyclotron autoresonance interaction of an electron beam with microwaves of TE 102 rectangular mode is simulated. It is shown that in these conditions the beam electrons can achieve energies which are sufficient to generate hard x-rays. The physical model consists of a rectangular cavity fed by a magnetron oscillator through a waveguide with a ferrite isolator, an iris window and a system of dc current coils which generates an axially symmetric magnetic field. The 3D magnetic field profile is that which maintains the electron beam in the space autoresonance regime. To simulate the beam dynamics, a full self-consistent electromagnetic particle-in-cell code is developed. It is shown that the injected 12keV electron beam of 0.5A current is accelerated to energy of 225keV at a distance of an order of 17cm by 2.45GHz standing microwave field with amplitude of 14kV/cm.

Hybrid organic-inorganic sol-gel materials and components for integrated optoelectronics

NASA Astrophysics Data System (ADS)

Lu, Dong

On the technical platform of hybrid organic-inorganic sol-gel, the integrated optoelectronics in the forms of heterogeneous integration between the hybrid sol-gel waveguide and the high refractive index semiconductors and the nonlinear functional doping of disperse red chromophore into hybrid sol-gel is developed. The structure of hybrid sol-gel waveguide on high index semiconductor substrate is designed with BPM-CAD software. A hybrid sol-gel based on MAPTMS and TEOS suitable for lower cladding for the waveguide is developed. The multi-layer hybrid sol-gel waveguide with good mode confinement and low polarization dependence is fabricated on Si and InP. As proof of concept, a 1 x 12 beam splitter based on multimode interference is fabricated on silicon substrate. The device shows excess loss below 0.65 dB and imbalance below 0.28 dB for both TE and TM polarization. A nonlinear active hybrid sol-gel doped with disperse red 13 has been developed by simple co-solvent method. It permits high loading concentration and has low optical loss at 1550 nm. The second-order nonlinear property of the active sol-gel is induced with corona poling and studied with second harmonic generation. A 3-fold of enhancement in the poling efficiency is achieved by blue light assisted corona poling. The chromophore alignment stability is improved by reducing the free volume of the formed inorganic network from the sol-gel condensation reaction. An active sol-gel channel waveguide has been fabricated using active and passive hybrid sol-gel materials by only photopatterning and spin-coating. An amplitude modulator based on the active sol-gel containing 30 wt.% of DR13 shows an electro-optic coefficient of 14 pm/V at 1550 nm and stable operation within the observation time of 24 days.

Nanoassembled dynamic optical waveguides and sensors based on zeolite L nanocontainers

NASA Astrophysics Data System (ADS)

Barroso, Álvaro; Dieckmann, Katrin; Alpmann, Christina; Buscher, Tim; Studer, Armido; Denz, Cornelia

2015-03-01

Although optical functional devices as waveguides and sensors are of utmost importance for metrology on the nano scale, the micro-and nano-assembly by optical means of functional materials to create such optical elements has yet not been considered. In the last years, an elegant strategy based on holographic optical tweezers (HOT) has been developed to design and fabricate permanent and dynamic three-dimensional micro- and nanostructures based on functional nanocontainers as building blocks. Nanocontainers that exhibit stable and ordered voids to hierarchically organize guest materials are especially attractive. Zeolite L are a type of porous micro-sized crystals which features a high number of strictly one-dimensional, parallel aligned nanochannels. They are highly interesting as building blocks of functional nano-and microsystems due to their potential as nanocontainers to accommodate various different guest molecules and to assemble them in specific configurations. For instance, based on zeolite L crystals, microscopic polarization sensors and chains of several microcrystals for hierarchical supramolecular organization have been realized. Here, we demonstrate the ability of nanocontainers in general, and zeolite L crystals in particular to represent the basic constituent of optical functional microsystems. We show that the capability of HOT to manipulate multitude of non-spherical microparticles in three dimensions can be exploited for the investigation of zeolite L nanocontainers as dynamic optical waveguides. Moreover, we implement as additional elements dye-loaded zeolite L to sense the guiding features of these novel waveguides with high spatial precision and microspheres to enhance the light coupling into the zeolite L waveguides. With this elaborated approach of using nanocontainers as tailored building blocks for functional optical systems a new era of bricking optical components in a lego-like style becomes feasible.

Using a conformal water bolus to adjust heating patterns of microwave waveguide applicators

NASA Astrophysics Data System (ADS)

Stauffer, Paul R.; Rodrigues, Dario B.; Sinahon, Randolf; Sbarro, Lyndsey; Beckhoff, Valeria; Hurwitz, Mark D.

2017-02-01

Background: Hyperthermia, i.e., raising tissue temperature to 40-45°C for 60 min, has been demonstrated to increase the effectiveness of radiation and chemotherapy for cancer. Although multi-element conformal heat applicators are under development to provide more adjustable heating of contoured anatomy, to date the most often used applicator to heat superficial disease is the simple microwave waveguide. With only a single power input, the operator must be resourceful to adjust heat treatment to accommodate variable size and shape tumors spreading across contoured anatomy. Methods: We used multiphysics simulation software that couples electromagnetic, thermal and fluid dynamics physics to simulate heating patterns in superficial tumors from commercially available microwave waveguide applicators. Temperature distributions were calculated inside homogenous muscle and layered skin-fat-muscle-tumor-bone tissue loads for a typical range of applicator coupling configurations and size of waterbolus. Variable thickness waterbolus was simulated as necessary to accommodate contoured anatomy. Physical models of several treatment configurations were constructed for comparison of simulation results with experimental specific absorption rate (SAR) measurements in homogenous muscle phantom. Results: Accuracy of the simulation model was confirmed with experimental SAR measurements of three unique applicator setups. Simulations demonstrated the ability to generate a wide range of power deposition patterns with commercially available waveguide antennas by controllably varying size and thickness of the waterbolus layer. Conclusion: Heating characteristics of 915 MHz waveguide antennas can be varied over a wide range by controlled adjustment of microwave power, coupling configuration, and waterbolus lateral size and thickness. The uniformity of thermal dose delivered to superficial tumors can be improved by cyclic switching of waterbolus thickness during treatment to proactively shift heat peaks and nulls around under the aperture, thereby reducing patient pain while increasing minimum thermal dose by end of treatment.

Midlatitude D region variations measured from broadband radio atmospherics

NASA Astrophysics Data System (ADS)

Han, Feng

The high power, broadband very low frequency (VLF, 3--30 kHz) and extremely low frequency (ELF, 3--3000 Hz) electromagnetic waves generated by lightning discharges and propagating in the Earth-ionosphere waveguide can be used to measure the average electron density profile of the lower ionosphere (D region) across the wave propagation path due to several reflections by the upper boundary (lower ionosphere) of the waveguide. This capability makes it possible to frequently and even continuously monitor the D region electron density profile variations over geographically large regions, which are measurements that are essentially impossible by other means. These guided waves, usually called atmospherics (or sferics for short), are recorded by our sensors located near Duke University. The purpose of this work is to develop and implement algorithms to derive the variations of D region electron density profile which is modeled by two parameters (one is height and another is sharpness), by comparing the recorded sferic spectra to a series of model simulated sferic spectra from using a finite difference time domain (FDTD) code. In order to understand the time scales, magnitudes and sources for the midlatitude nighttime D region variations, we analyzed the sferic data of July and August 2005, and extracted both the height and sharpness of the D region electron density profile. The heights show large temporal variations of several kilometers on some nights and the relatively stable behavior on others. Statistical calculations indicate that the hourly average heights during the two months range between 82.0 km and 87.2 km with a mean value of 84.9 km and a standard deviation of 1.1 km. We also observed spatial variations of height as large as 2.0 km over 5 degrees latitudes on some nights, and no spatial variation on others. In addition, the measured height variations exhibited close correlations with local lightning occurrence rate on some nights but no correlation with local lightning or displaced lightning on others. The nighttime profile sharpness during 2.5 hours in two different nights was calculated, and the results were compared to the equivalent sharpness derived from International Reference Ionosphere (IRI) models. Both the absolute values and variation trends in IRI models are different from those in broadband measurements. Based on sferic data similar to those for nighttime, we also measured the day-time D region electron density profile variations in July and August 2005 near Duke University. As expected, the solar radiation is the dominant but not the only determinant source for the daytime D region profile height temporal variations. The observed quiet time heights showed close correlations with solar zenith angle changes but unexpected spatial variations not linked to the solar zenith angle were also observed on some days, with 15% of days exhibiting regional differences larger than 0.5 km. During the solar flare, the induced height change was approximately proportional to the logarithm of the X-ray fluxes. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short (wavelength 0.5--4 A), rather than the long (wavelength 1--8 A) X-ray flux changes. The daytime profile sharpness during morning, noontime and afternoon periods in three different days and for the solar zenith angle range 20 to 75 degrees was calculated. These broadband measured results were compared to narrowband VLF measurements, IRI models and Faraday rotation base IRI models (called FIRI). The estimated sharpness from all these sources was more consistent when the solar zenith angle was small than when it was large. By applying the nighttime and daytime measurement techniques, we also derived the D region variations during sunrise and sunset periods. The measurements showed that both the electron density profile height and sharpness decrease during the sunrise period while increase during the sunset period.

Damage Processes in a Quasi-Isotropic Composite Short Beam Under Three- Point Loading

DTIC Science & Technology

1992-01-01

American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103 12a. DISTRIBUTION /AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE...three- point bend test Is investigated for a composite with a quasi-isotropic layup. Failue is found to Initiate iri a region near the point of...Composites Technology & Research, Winter 1991 Copyright American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103 REFERENCE

Portable six-port reflectometer for determining moisture content of biomass material

USDA-ARS?s Scientific Manuscript database

A portable six-port reflectometer (SPR) for determining moisture content of biomass material is proposed for the first time in this paper. The proposed system consists of a 5.13 GHz reflectometer used with an open-ended half-mode substrateintegrated waveguide (HMSIW) sensor. The complex permittivity...

Safety and efficacy of phacoemulsification and intraocular lens implantation through a small pupil using minimal iris manipulation.

PubMed

Papaconstantinou, Dimitris; Kalantzis, George; Brouzas, Dimitris; Kontaxakis, Anastasios; Koutsandrea, Chryssanthi; Diagourtas, Andreas; Georgalas, Ilias

2016-01-01

The aim of this study was to compare the results of phacoemulsification through a small pupil using minimal iris manipulation versus phacoemulsification through a well-dilated pupil. This prospective randomized control (comparative) study comprised 78 patients (group I) with a maximally dilated pupil size of ≤4.00 mm and 45 patients (group II) with dilated pupil size of ≥7.00 mm. In group I patients, only viscodilation and minimal push-and-pull iris stretching with two collar-button iris-retractor hooks were utilized without iris manipulation. Phacoemulsification was performed by two senior surgeons and the technique used consisted of either stop and chop or quick chop, infusion/aspiration of lens cortex, capsular bag refill with ocular viscoelastic devices, and implantation of an acrylic foldable intraocular lens. Patients were examined on the first day and 1 month postoperatively. Forty-six eyes of group I patients had pseudoexfoliation syndrome, eleven eyes had previous glaucoma surgery, 14 eyes had angle-closure or open-angle glaucoma, and seven eyes had posterior synechiae with iritis. In group I patients, the mean pupil size measured under an operating microscope was 3.2 mm preoperatively, 4.3 mm after viscoelastic and mechanical pupil dilation, and 4.1 mm at the end of a surgical procedure. Rupture of the zonular fibers occurred in six patients of group I and the intraocular lens was implanted in the sulcus. Small iris-sphincter rupture and small hemorrhages occurred in four eyes during pupillary manipulation, but they were not evident at the end of the surgery. In group II patients, no intraoperative complications occurred. Signs of significant corneal edema and iritis were observed more frequently in group I eyes (26 eyes and 20 eyes, respectively) on the first postoperative day in comparison with group II eyes (ten eyes and six eyes, respectively). Intraocular pressure was <20 mmHg in all eyes of both groups. One month postoperatively, the pupil was round and reactive to light, the anterior chamber was quiet, and the cornea was clear in all eyes. The best-corrected visual acuity on Snellen chart was 20/40 (Monoyer's scale) or better in both groups. Phacoemulsification through a small pupil using minimal iris manipulation can be safe and exhibits the same results as those obtained with phacoemulsification through normal pupils.

ENHANCED GENE DELIVERY IN PORCINE VASCULATURE TISSUE FOLLOWING INCORPORATION OF ADENO-ASSOCIATED VIRUS NANOPARTICLES INTO POROUS SILICON MICROPARTICLES

PubMed Central

McConnell, Kellie I.; Rhudy, Jessica; Yokoi, Kenji; Gu, Jianhua; Mack, Aaron; Suh, Junghae; La Francesca, Saverio; Sakamoto, Jason; Serda, Rita E.

2014-01-01

There is an unmet clinical need to increase lung transplant successes, patient satisfaction and to improve mortality rates. We offer the development of a nanovector-based solution that will reduce the incidence of lung ischemic reperfusion injury (IRI) leading to graft organ failure through the successful ex vivo treatment of the lung prior to transplantation. The innovation is in the integrated application of our novel porous silicon (pSi) microparticles carrying adeno-associated virus (AAV) nanoparticles, and the use of our ex vivo lung perfusion/ventilation system for the modulation of pro-inflammatory cytokines initiated by ischemic pulmonary conditions prior to organ transplant that often lead to complications. Gene delivery of anti-inflammatory agents to combat the inflammatory cascade may be a promising approach to prevent IRI following lung transplantation. The rationale for the device is that the microparticle will deliver a large payload of virus to cells and serve to protect the AAV from immune recognition. The microparticle-nanoparticle hybrid device was tested both in vitro on cell monolayers and ex vivo using either porcine venous tissue or a pig lung transplantation model, which recapitulates pulmonary IRI that occurs clinically post-transplantation. Remarkably, loading AAV vectors into pSi microparticles increases gene delivery to otherwise non-permissive endothelial cells. PMID:25180449

FAQs about IRIs.

ERIC Educational Resources Information Center

Paris, Scott G.; Carpenter, Robert D.

2003-01-01

Provides information about informal reading inventories (IRI), an early reading assessment. Explains what IRIs are; who should administer an IRI; when and how to administer an IRI; the reliability of data from IRIs; and the limitations of IRIs. (PM)

Novel Metamaterial Blueprints and Elements for Electromagnetic Applications

NASA Astrophysics Data System (ADS)

Odabasi, Hayrettin

In the first part of this dissertation, we explore the metric invariance of Maxwell's equations to design metamaterial blueprints for three novel electromagnetic devices. The metric invariance of Maxwell's equations here means that the effects of an (hypothetical) distortion of the background spatial domain on the electromagnetic fields can be mimicked by properly chosen material constitutive tensors. The exploitation of such feature of Maxwell's equations to derive metamaterial devices has been denoted as `transformation optics' (TO). The first device proposed here consists of metamaterial blueprints of waveguide claddings for (waveguide) miniaturization. These claddings provide a precise control of mode distribution and frequency cut-off. The proposed claddings are distinct from conventional dielectric loadings as the former do not support hybrid modes and are impedance-matched to free-space. We next derive a class of metamaterial blueprints designed for low-profile antenna applications, whereby a simple spatial transformation is used to yield uniaxial metamaterial substrate with electrical height higher than its physical height and surface waves are not supported, which is an advantage for patch antenna applications. We consider the radiation from horizontal wire and patch antennas in the presence of such substrates. Fundamental characteristics such as return loss and radiation pattern of the antennas are investigated in detail. Finally, transformation optics is also applied to design cylindrical impedance-matched absorbers. In this case, we employ a complex-valued transformation optics approach (in the Fourier domain) as opposed to the conventional real-valued approach. A connection of such structures with perfectly matched layers and recently proposed optical pseudo black-hole devices is made. In the second part of this dissertation, we move from the derivation of metamaterial blueprints to the application of pre-defined unit-cell metamaterial structures for miniaturization purposes. We first employ electric-field-coupled (ELC) resonators and complementary electric-field-coupled (CELC) resonators to design a new class of electrically small antennas. Since electric-field coupled resonators were recently proposed in the literature to obtain negative permittivity response, we next propose ELC resonators as a new type of waveguide loadings to provide mode control and waveguide miniaturization.

Iris Image Classification Based on Hierarchical Visual Codebook.

PubMed

Zhenan Sun; Hui Zhang; Tieniu Tan; Jianyu Wang

2014-06-01

Iris recognition as a reliable method for personal identification has been well-studied with the objective to assign the class label of each iris image to a unique subject. In contrast, iris image classification aims to classify an iris image to an application specific category, e.g., iris liveness detection (classification of genuine and fake iris images), race classification (e.g., classification of iris images of Asian and non-Asian subjects), coarse-to-fine iris identification (classification of all iris images in the central database into multiple categories). This paper proposes a general framework for iris image classification based on texture analysis. A novel texture pattern representation method called Hierarchical Visual Codebook (HVC) is proposed to encode the texture primitives of iris images. The proposed HVC method is an integration of two existing Bag-of-Words models, namely Vocabulary Tree (VT), and Locality-constrained Linear Coding (LLC). The HVC adopts a coarse-to-fine visual coding strategy and takes advantages of both VT and LLC for accurate and sparse representation of iris texture. Extensive experimental results demonstrate that the proposed iris image classification method achieves state-of-the-art performance for iris liveness detection, race classification, and coarse-to-fine iris identification. A comprehensive fake iris image database simulating four types of iris spoof attacks is developed as the benchmark for research of iris liveness detection.

Knowing what the brain is seeing in three dimensions: A novel, noninvasive, sensitive, accurate, and low-noise technique for measuring ocular torsion.

PubMed

Otero-Millan, Jorge; Roberts, Dale C; Lasker, Adrian; Zee, David S; Kheradmand, Amir

2015-01-01

Torsional eye movements are rotations of the eye around the line of sight. Measuring torsion is essential to understanding how the brain controls eye position and how it creates a veridical perception of object orientation in three dimensions. Torsion is also important for diagnosis of many vestibular, neurological, and ophthalmological disorders. Currently, there are multiple devices and methods that produce reliable measurements of horizontal and vertical eye movements. Measuring torsion, however, noninvasively and reliably has been a longstanding challenge, with previous methods lacking real-time capabilities or suffering from intrusive artifacts. We propose a novel method for measuring eye movements in three dimensions using modern computer vision software (OpenCV) and concepts of iris recognition. To measure torsion, we use template matching of the entire iris and automatically account for occlusion of the iris and pupil by the eyelids. The current setup operates binocularly at 100 Hz with noise <0.1° and is accurate within 20° of gaze to the left, to the right, and up and 10° of gaze down. This new method can be widely applicable and fill a gap in many scientific and clinical disciplines.

Knowing what the brain is seeing in three dimensions: A novel, noninvasive, sensitive, accurate, and low-noise technique for measuring ocular torsion

PubMed Central

Otero-Millan, Jorge; Roberts, Dale C.; Lasker, Adrian; Zee, David S.; Kheradmand, Amir

2015-01-01

Torsional eye movements are rotations of the eye around the line of sight. Measuring torsion is essential to understanding how the brain controls eye position and how it creates a veridical perception of object orientation in three dimensions. Torsion is also important for diagnosis of many vestibular, neurological, and ophthalmological disorders. Currently, there are multiple devices and methods that produce reliable measurements of horizontal and vertical eye movements. Measuring torsion, however, noninvasively and reliably has been a longstanding challenge, with previous methods lacking real-time capabilities or suffering from intrusive artifacts. We propose a novel method for measuring eye movements in three dimensions using modern computer vision software (OpenCV) and concepts of iris recognition. To measure torsion, we use template matching of the entire iris and automatically account for occlusion of the iris and pupil by the eyelids. The current setup operates binocularly at 100 Hz with noise <0.1° and is accurate within 20° of gaze to the left, to the right, and up and 10° of gaze down. This new method can be widely applicable and fill a gap in many scientific and clinical disciplines. PMID:26587699

Arterial waveguide model for shear wave elastography: implementation and in vitro validation

NASA Astrophysics Data System (ADS)

Vaziri Astaneh, Ali; Urban, Matthew W.; Aquino, Wilkins; Greenleaf, James F.; Guddati, Murthy N.

2017-07-01

Arterial stiffness is found to be an early indicator of many cardiovascular diseases. Among various techniques, shear wave elastography has emerged as a promising tool for estimating local arterial stiffness through the observed dispersion of guided waves. In this paper, we develop efficient models for the computational simulation of guided wave dispersion in arterial walls. The models are capable of considering fluid-loaded tubes, immersed in fluid or embedded in a solid, which are encountered in in vitro/ex vivo, and in vivo experiments. The proposed methods are based on judiciously combining Fourier transformation and finite element discretization, leading to a significant reduction in computational cost while fully capturing complex 3D wave propagation. The developed methods are implemented in open-source code, and verified by comparing them with significantly more expensive, fully 3D finite element models. We also validate the models using the shear wave elastography of tissue-mimicking phantoms. The computational efficiency of the developed methods indicates the possibility of being able to estimate arterial stiffness in real time, which would be beneficial in clinical settings.

Hydrogen and oxygen stable isotope signatures of goethite hydration waters by thermogravimetry-enabled laser spectroscopy

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

Oerter, Erik; Singleton, Michael; Davisson, Lee

The hydrogen and oxygen stable isotope composition (δ 2H and δ 18O values) of mineral hydration waters can give information on the environment of mineral formation. Here we present and validate an approach for the stable isotope analysis of mineral hydration waters based on coupling a thermogravimetric analyzer with a laser-based isotope ratio infrared spectroscopy instrument (Picarro L-2130i), which we abbreviate as TGA-IRIS. TGA-IRIS generates δ 2H and δ 18O values of liquid water samples with precision for δ 2H of ± 1.2‰, and for δ 18O of ± 0.17‰. For hydration waters in goethite, precision for δ 2H rangesmore » from ± 0.3‰ to 1.6‰, and for δ 18O ranges from ± 0.17‰ to 0.27‰. The ability of TGA-IRIS to generate detailed water yield data and δ 2H and δ 18O values of water at varying temperatures allows for the differentiation of water in varying states of binding on mineral surfaces and within the mineral matrix. TGA-IRIS analyses of hydrogen isotopes in goethite yields δ 2H values that reflect the hydrogen of the OH – phase in the mineral and are comparable to that made by IRMS and found in the literature. In contrast, δ 18O values on goethite reflect the oxygen in OH – groups bound to Fe (Fe-OH group), and not the oxygen bound only to Fe (Fe-O group) in the mineral crystal lattice, and may not be comparable to literature δ 18O values made by IRMS that reflect the total O in the mineral. TGA-IRIS presents the possibility to isotopically differentiate the various oxygen reservoirs in goethite, which may allow the mineral to be used as a single mineral geothermometer. As a result, TGA-IRIS measurements of hydration waters are likely to open new avenues and possibilities for research on hydrated minerals.« less

Hydrogen and oxygen stable isotope signatures of goethite hydration waters by thermogravimetry-enabled laser spectroscopy

DOE PAGES

Oerter, Erik; Singleton, Michael; Davisson, Lee

2017-10-22

The hydrogen and oxygen stable isotope composition (δ 2H and δ 18O values) of mineral hydration waters can give information on the environment of mineral formation. Here we present and validate an approach for the stable isotope analysis of mineral hydration waters based on coupling a thermogravimetric analyzer with a laser-based isotope ratio infrared spectroscopy instrument (Picarro L-2130i), which we abbreviate as TGA-IRIS. TGA-IRIS generates δ 2H and δ 18O values of liquid water samples with precision for δ 2H of ± 1.2‰, and for δ 18O of ± 0.17‰. For hydration waters in goethite, precision for δ 2H rangesmore » from ± 0.3‰ to 1.6‰, and for δ 18O ranges from ± 0.17‰ to 0.27‰. The ability of TGA-IRIS to generate detailed water yield data and δ 2H and δ 18O values of water at varying temperatures allows for the differentiation of water in varying states of binding on mineral surfaces and within the mineral matrix. TGA-IRIS analyses of hydrogen isotopes in goethite yields δ 2H values that reflect the hydrogen of the OH – phase in the mineral and are comparable to that made by IRMS and found in the literature. In contrast, δ 18O values on goethite reflect the oxygen in OH – groups bound to Fe (Fe-OH group), and not the oxygen bound only to Fe (Fe-O group) in the mineral crystal lattice, and may not be comparable to literature δ 18O values made by IRMS that reflect the total O in the mineral. TGA-IRIS presents the possibility to isotopically differentiate the various oxygen reservoirs in goethite, which may allow the mineral to be used as a single mineral geothermometer. As a result, TGA-IRIS measurements of hydration waters are likely to open new avenues and possibilities for research on hydrated minerals.« less

Predictors of intraocular pressure change after phacoemulsification in patients with pseudoexfoliation syndrome.

PubMed

Moghimi, Sasan; Johari, Mohammadkarim; Mahmoudi, Alireza; Chen, Rebecca; Mazloumi, Mehdi; He, Mingguang; Lin, Shan C

2017-03-01

To evaluate anterior chamber biometric factors and intraoperative metrics associated with the intraocular pressure (IOP) reduction after phacoemulsification in non-glaucomatous pseudoexfoliative syndrome (PXS) eyes. Thirty-three patients were enrolled in this prospective interventional study. Images were excluded if they had poor quality, poor perpendicularity or inability to locate sclera spurs. Anterior chamber depth (ACD), anterior chamber area (ACA), iris thickness, iris area, iris curvature, lens vault, angle opening distance (AOD500, AOD750) and trabecular iris space area (TISA500, TISA750) were measured in qualified images using the Zhongshan Angle Assessment Program and compared preoperatively and 3 months postoperatively. Cumulative dissipated energy (CDE), aspiration time and infusion fluid usage during cataract surgery were obtained from the phacoemulsification machine's metrics record. Postoperative IOP change was compared with these anatomical and intraoperative metric parameters. Mean IOP was 18.1±3.4 mm Hg preoperatively and decreased by 3.3 mm Hg (18%) to 14.8±3.6 mm Hg at 3 months postoperatively (p<0.001). All angle parameters, ACD and ACA increased significantly postoperatively (p<0.001 for all) and iris curvature decreased (p<0.001). In univariate analysis, preoperative IOP (B=-0.668, p=0.002), infusion fluid usage (B=-0.040, p=0.04) and aspiration time (B=-0.045, p=0.003) were negatively associated with IOP decrease after phacoemulsification. Changes in IOP did not demonstrate significant associations with CDE measurements or anterior segment optical coherence tomography measurements, including preoperative angle, iris or anterior segment parameters. In the final multivariate regression model, preoperative IOP (B=-0.668, p=0.002) and infusion fluid usage (B=-0.041, p=0.04) were significantly associated with IOP drop and together can predict 45.1% (p=0.002) of the variability in IOP change. Non-glaucomatous patients with PXS experience moderate IOP reduction following phacoemulsification, and this effect is correlated with preoperative IOP, aspiration time and infusion fluid used intraoperatively. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Iris Matching Based on Personalized Weight Map.

PubMed

Dong, Wenbo; Sun, Zhenan; Tan, Tieniu

2011-09-01

Iris recognition typically involves three steps, namely, iris image preprocessing, feature extraction, and feature matching. The first two steps of iris recognition have been well studied, but the last step is less addressed. Each human iris has its unique visual pattern and local image features also vary from region to region, which leads to significant differences in robustness and distinctiveness among the feature codes derived from different iris regions. However, most state-of-the-art iris recognition methods use a uniform matching strategy, where features extracted from different regions of the same person or the same region for different individuals are considered to be equally important. This paper proposes a personalized iris matching strategy using a class-specific weight map learned from the training images of the same iris class. The weight map can be updated online during the iris recognition procedure when the successfully recognized iris images are regarded as the new training data. The weight map reflects the robustness of an encoding algorithm on different iris regions by assigning an appropriate weight to each feature code for iris matching. Such a weight map trained by sufficient iris templates is convergent and robust against various noise. Extensive and comprehensive experiments demonstrate that the proposed personalized iris matching strategy achieves much better iris recognition performance than uniform strategies, especially for poor quality iris images.

A traveling-wave forward coupler design for a new accelerating mode in a silicon woodpile accelerator

DOE PAGES

Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.; ...

2016-03-01

Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less

A traveling-wave forward coupler design for a new accelerating mode in a silicon woodpile accelerator

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

Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.

Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less

Modeling of induction-linac based free-electron laser amplifiers

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

Jong, R.A.; Fawley, W.M.; Scharlemann, E.T.

We describe the modeling of an induction-linac based free-electron laser (IFEL) amplifier for producing multimegawatt levels of microwave power. We have used the Lawrence Livermore National Laboratory (LLNL) free-electron laser simulation code, FRED, and the simulation code for sideband calculations, GINGER for this study. For IFEL amplifiers in the frequency range of interest (200 to 600 GHz), we have devised a wiggler design strategy which incorporates a tapering algorithm that is suitable for free-electron laser (FEL) systems with moderate space-charge effects and that minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal atmore » the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. As an example, we shall describe an FEL amplifier designed to produce an average power of about 10 MW at a frequency of 280 GHz to be used for electron cyclotron resonance heating of tokamak fusion devices. 17 refs., 4 figs.« less

Microwave ice accretion meter

NASA Technical Reports Server (NTRS)

Magenheim, Bertram (Inventor); Rocks, James K. (Inventor)

1984-01-01

A system for indicating ice thickness and rate of ice thickness growth on surfaces is disclosed. The region to be monitored for ice accretion is provided with a resonant surface waveguide which is mounted flush, below the surface being monitored. A controlled oscillator provides microwave energy via a feed point at a controllable frequency. A detector is coupled to the surface waveguide and is responsive to electrical energy. A measuring device indicates the frequency deviation of the controlled oscillator from a quiescent frequency. A control means is provided to control the frequency of oscillation of the controlled oscillator. In a first, open-loop embodiment, the control means is a shaft operated by an operator. In a second, closed-loop embodiment, the control means is a processor which effects automatic control.

Microwave Spectroscopy of a Single Permalloy Chiral Metamolecule on a Coplanar Waveguide

NASA Astrophysics Data System (ADS)

Kodama, Toshiyuki; Kusanagi, Yusaku; Okamoto, Satoshi; Kikuchi, Nobuaki; Kitakami, Osamu; Tomita, Satoshi; Hosoito, Nobuyoshi; Yanagi, Hisao

2018-05-01

We investigate the microwave spectroscopies of a micrometer-sized single permalloy (Py) chiral structure on coplanar waveguides (CPWs). Under an external dc magnetic field applied in a direction perpendicular to the microwave propagation, the Py chiral structure loaded on the center of the CPW signal line shows Kittel-mode ferromagnetic resonance. Contrastingly, the structure on the signal-line edge highlights two additional resonances: spin-wave resonance at a higher frequency, and unique resonance at a lower frequency of approximately 7.8 GHz. The resonance signal at 7.8 GHz originates from magnetically induced, geometry-driven resonance, although the resonance frequency does not depend on the external magnetic field. Moreover, the displacement of the Py structures on the signal line results in nonreciprocal microwave transmission, which is traced back to the edge-guide mode.

Side-polished fiber based gain-flattening filter for erbium doped fiber amplifiers

NASA Astrophysics Data System (ADS)

Varshney, R. K.; Singh, A.; Pande, K.; Pal, B. P.

2007-03-01

A simple and accurate novel normal mode analysis has been developed to take into account the effect of the non-uniform depth of polishing in the study of the transmission characteristics of optical waveguide devices based on loading of a side-polished fiber half-coupler with a multimode planar waveguide. We apply the same to design and fabricate a gain-flattening filter suitable for fiber amplifiers. The wavelength dependent filtering action of the overall device could demonstrate flattening of an EDFA gain spectrum within ±0.7 dB over a bandwidth of 30 nm in the C-band. Results obtained by the present analysis agree very well with our experimental results. This present analysis should be very useful in the accurate design and analysis of any SPF-MMOW device/component including side-polished fiber based sensors.

Photonic Waveguide Choke Joint with Non-Absorptive Loading

NASA Technical Reports Server (NTRS)

Wollack, Edward J. (Inventor); U-Yen, Kongpop (Inventor); Chuss, David T. (Inventor)

2016-01-01

A waveguide choke joint includes a first array of pillars positioned on a substrate, each pillar in the first array of pillars having a first size and configured to receive an input plane wave at a first end of the choke joint. The choke joint has a second end configured to transmit the input plane wave away from the choke joint. The choke joint further includes a second array of pillars positioned on the substrate between the first array of pillars and the second end of the choke joint. Each pillar in the second array of pillars has a second size. The choke joint also has a third array of pillars positioned on the substrate between the second array and the second end of the choke joint. Each pillar in the third array of pillars has a third size.

Antigen-Specific Interferon-Gamma Responses and Innate Cytokine Balance in TB-IRIS

PubMed Central

Goovaerts, Odin; Jennes, Wim; Massinga-Loembé, Marguerite; Ceulemans, Ann; Worodria, William; Mayanja-Kizza, Harriet; Colebunders, Robert; Kestens, Luc

2014-01-01

Background Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) remains a poorly understood complication in HIV-TB patients receiving antiretroviral therapy (ART). TB-IRIS could be associated with an exaggerated immune response to TB-antigens. We compared the recovery of IFNγ responses to recall and TB-antigens and explored in vitro innate cytokine production in TB-IRIS patients. Methods In a prospective cohort study of HIV-TB co-infected patients treated for TB before ART initiation, we compared 18 patients who developed TB-IRIS with 18 non-IRIS controls matched for age, sex and CD4 count. We analyzed IFNγ ELISpot responses to CMV, influenza, TB and LPS before ART and during TB-IRIS. CMV and LPS stimulated ELISpot supernatants were subsequently evaluated for production of IL-12p70, IL-6, TNFα and IL-10 by Luminex. Results Before ART, all responses were similar between TB-IRIS patients and non-IRIS controls. During TB-IRIS, IFNγ responses to TB and influenza antigens were comparable between TB-IRIS patients and non-IRIS controls, but responses to CMV and LPS remained significantly lower in TB-IRIS patients. Production of innate cytokines was similar between TB-IRIS patients and non-IRIS controls. However, upon LPS stimulation, IL-6/IL-10 and TNFα/IL-10 ratios were increased in TB-IRIS patients compared to non-IRIS controls. Conclusion TB-IRIS patients did not display excessive IFNγ responses to TB-antigens. In contrast, the reconstitution of CMV and LPS responses was delayed in the TB-IRIS group. For LPS, this was linked with a pro-inflammatory shift in the innate cytokine balance. These data are in support of a prominent role of the innate immune system in TB-IRIS. PMID:25415590

Slow light effect analysis excited by plasmon-induced transparency in metal-dielectric-metal waveguide

NASA Astrophysics Data System (ADS)

Jin, Gui; Huang, Xiaoyi

2018-02-01

We propose and demonstrate a metal-dielectric-metal(MDM) waveguide side coupled with two stubs to realize plasmon induced transparency (PIT) effect. The dispersion relation of the structure has been plotted by solving the dispersion equation of MDM three layer structure, the transmission spectrum is investigated by coupled mode theory (CMT) and Finite Element Method (FEM) simulation, the CMT results can. The surface plasmon device can also be used as a EIT-like filter with a variable full width of half-maximum (FWHM) and highest transmission over 88%. The maximum group index ng is 42 with a group velocity of 0.023ܿ and transmission of 48%, The normalized delay-bandwidth product (NDBP) can be modulated through changing the gap width of resonators and waveguide bus, the highest is 0.641 at gap width 10 nm, and lowest is 0.246 at 30 nm. The dispersion of group velocity (GVD) changes drastically at narrow gap width and becomes more and more flat at broader gap width, this opens up an avenue for designing optical buffers, switches and modulators.

Projecting light beams with 3D waveguide arrays

NASA Astrophysics Data System (ADS)

Crespi, Andrea; Bragheri, Francesca

2017-01-01

Free-space light beams with complex intensity patterns, or non-trivial phase structure, are demanded in diverse fields, ranging from classical and quantum optical communications, to manipulation and imaging of microparticles and cells. Static or dynamic spatial light modulators, acting on the phase or intensity of an incoming light wave, are the conventional choices to produce beams with such non-trivial characteristics. However, interfacing these devices with optical fibers or integrated optical circuits often requires difficult alignment or cumbersome optical setups. Here we explore theoretically and with numerical simulations the potentialities of directly using the output of engineered three-dimensional waveguide arrays, illuminated with linearly polarized light, to project light beams with peculiar structures. We investigate through a collection of illustrative configurations the far field distribution, showing the possibility to achieve orbital angular momentum, or to produce elaborate intensity or phase patterns with several singularity points. We also simulate the propagation of the projected beam, showing the possibility to concentrate light. We note that these devices should be at reach of current technology, thus perspectives are open for the generation of complex free-space optical beams from integrated waveguide circuits.

L-shaped fiber-chip grating couplers with high directionality and low reflectivity fabricated with deep-UV lithography.

PubMed

Benedikovic, Daniel; Alonso-Ramos, Carlos; Pérez-Galacho, Diego; Guerber, Sylvain; Vakarin, Vladyslav; Marcaud, Guillaume; Le Roux, Xavier; Cassan, Eric; Marris-Morini, Delphine; Cheben, Pavel; Boeuf, Frédéric; Baudot, Charles; Vivien, Laurent

2017-09-01

Grating couplers enable position-friendly interfacing of silicon chips by optical fibers. The conventional coupler designs call upon comparatively complex architectures to afford efficient light coupling to sub-micron silicon-on-insulator (SOI) waveguides. Conversely, the blazing effect in double-etched gratings provides high coupling efficiency with reduced fabrication intricacy. In this Letter, we demonstrate for the first time, to the best of our knowledge, the realization of an ultra-directional L-shaped grating coupler, seamlessly fabricated by using 193 nm deep-ultraviolet (deep-UV) lithography. We also include a subwavelength index engineered waveguide-to-grating transition that provides an eight-fold reduction of the grating reflectivity, down to 1% (-20  dB). A measured coupling efficiency of -2.7  dB (54%) is achieved, with a bandwidth of 62 nm. These results open promising prospects for the implementation of efficient, robust, and cost-effective coupling interfaces for sub-micrometric SOI waveguides, as desired for large-volume applications in silicon photonics.

Iris reconstruction combined with iris-claw intraocular lens implantation for the management of iris-lens injured patients.

PubMed

Hu, Shufang; Wang, Mingling; Xiao, Tianlin; Zhao, Zhenquan

2016-03-01

To study the efficiency and safety of iris reconstruction combined with iris-claw intraocular lens (IOL) implantation in the patients with iris-lens injuries. Retrospective, noncomparable consecutive case series study. Eleven patients (11 eyes) following iris-lens injuries underwent iris reconstructions combined with iris-claw IOL implantations. Clinical data, such as cause and time of injury, visual acuity (VA), iris and lens injuries, surgical intervention, follow-up period, corneal endothelial cell count, and optical coherence tomography, were collected. Uncorrected VA (UCVA) in all injured eyes before combined surgery was equal to or <20/1000. Within a 1.1-4.2-year follow-up period, a significant increase, equal to or better than 20/66, in UCVA was observed in six (55%) cases, and in best-corrected VA (BCVA) was observed in nine (82%) cases. Postoperative BCVA was 20/40 or better in seven cases (64%). After combined surgery, the iris returned to its natural round shape or smaller pupil, and the iris-claw IOLs in the 11 eyes were well-positioned on the anterior surface of reconstructed iris. No complications occurred in those patients. Iris reconstruction combined with iris-claw IOL implantation is a safe and efficient procedure for an eye with iris-lens injury in the absence of capsular support.

Evaluating empathy in Colombian ex-combatants: Examination of the internal structure of the Interpersonal Reactivity Index (IRI) in Spanish.

PubMed

Garcia-Barrera, Mauricio A; Karr, Justin E; Trujillo-Orrego, Natalia; Trujillo-Orrego, Sandra; Pineda, David A

2017-01-01

The Republic of Colombia has a long-standing history of internal armed conflict, further complicated by the ideological assumptions underlying their war. In recent years, its government designed the Program for Reincorporation to Civilian Life (Programa para la Reincorporación a la Vida Civil, PRVC), aiming demobilization of thousands of insurgents who were involved in guerilla and paramilitary forces. One PRVC goal involves the psychological characterization of its reincorporated members, aiming the informed design of effective and efficacious interventions to improve their adjustment. We are interested in the examination of empathy in this population. Empathy refers to the ability to predict, understand, and experience other's feelings. Empathy appears to have an effect on level of aggressive behavior. The Interpersonal Reactivity Index (IRI; Davis, 1980, 1983) is a well-established 28-item self-report tool for the assessment of empathy, including 4 scales: Perspective Taking, Fantasy, Empathic Concern, and Personal Distress. Versions in Spanish were validated in Spain and Chile, but no norms for Colombians exist. We examined the factorial structure of the IRI in a sample of 548 (83.4% males) members of the PRVC. Ten items with low factor loadings were eliminated following a series of confirmatory factor analyses (CFA). The final 4-factor model (Model 2) reached an acceptable fit (e.g., CFI = .898). A second-order CFA demonstrated that empathic concern correlated too high with a common "empathy" latent factor. With these results at hand, our 18-item IRI version in Spanish achieved a factorial structure comparable to that previously validated for Spanish speakers from other countries. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency in two stub resonators side-coupled with a plasmonic waveguide system

NASA Astrophysics Data System (ADS)

Wang, Boyun; Zeng, Qingdong; Xiao, Shuyuan; Xu, Chen; Xiong, Liangbin; Lv, Hao; Du, Jun; Yu, Huaqing

2017-11-01

We theoretically and numerically investigate a low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency (PIT) in two stub resonators side-coupled with a metal-dielectric-metal (MDM) plasmonic waveguide system. The optical Kerr effect is enhanced by the local electromagnetic field of surface plasmon polaritons (SPPs) and the plasmonic waveguide based on graphene-Ag composite material structures with large effective Kerr nonlinear coefficient. An ultrafast response time of the order of 1 ps is reached because of ultrafast carrier relaxation dynamics of graphene. With dynamically tuning the propagation phase of the plasmonic waveguide, π-phase shift of the transmission spectrum in the PIT system is achieved under excitation of a pump light with an intensity as low as 5.8 MW cm-2. The group delay is controlled between 0.14 and 0.67 ps. Moreover, the tunable bandwidth of about 42 nm is obtained. For the indirect coupling between two stub cavities or the phase coupling scheme, the phase shift multiplication effect of the PIT effect is found. All observed schemes are analyzed rigorously through finite-difference time-domain simulations and coupled-mode formalism. This work not only paves the way towards the realization of on-chip integrated nanophotonic devices but also opens the possibility of the construction of ultrahigh-speed information processing chips based on plasmonic circuits.

Advanced designs for non-imaging submillimeter-wave Winston cone concentrators

NASA Astrophysics Data System (ADS)

Nelson, A. O.; Grossman, E. N.

2014-05-01

We describe the design and simulation of several non-imaging concentrators designed to couple submillimeter wavelength radiation from free space into highly overmoded, rectangular, WR-10 waveguide. Previous designs are altered to improve the uniformity of efficiency rather than the efficiency itself. The concentrators are intended for use as adapters between instruments using overmoded WR-10 waveguide as input or output and sources propagating through free space. Previous simulation and measurement have shown that the angular response is primarily determined by the Winston cone and is well predicted by geometric optics theory while the efficiencies are primarily determined by the transition section. Additionally, previous work has shown insensitivity to polarization, orientation and beam size. Several separate concentrator designs are studied, all of which use a Winston cone (also known as a compound parabolic concentrator) with an input diameter ranging from 4 mm to 16 mm, and "throat" diameters of less than 0.5 mm to 4 mm as the initial interface. The use of various length adiabatic circular-to-rectangular transition sections is investigated, along with the effect of an additional, 25 mm waveguide section designed to model the internal waveguide of the power meter. Adapters without a transition section and a rectangular Winston cone throat aperture and double cone configurations are also studied. Adapters are analyzed in simulation for consistent efficiency across the opening aperture.

Evolution of the Concordia seismological observatory station CCD (GEOSCOPE network): a new post-hole installation on Antarctica inlandsis

NASA Astrophysics Data System (ADS)

Zigone, D.; Danecek, P.; Bès de Berc, M.; Maggi, A.; Thore, J. Y.; Leveque, J. J.; Vallee, M.; Bernard, A.; Sayadi, J.; Morelli, A.; Delladio, A.; Chappellaz, J. A.; Alemany, O.; Possenti, P.; Stutzmann, E.; Bonaime, S.; Pesqueira, F.; Pardo, C.; Vincent, D.

2017-12-01

Concordia (75°S 123°E) is a scientific base operated by French polar institute IPEV (Institut Paul-Emile Victor) and Italian Antarctic Program PNRA (Programma Nazionale di Ricerche in Antartide), and is located at Dome C, on the ice sheet of the East Antarctica plateau. It hosts a seismological observatory (CCD), which is jointly operated by EOST (Strasbourg) and INGV (Roma). The highly strategic location and remoteness is the key strength of our program, which has provided observatory quality data since 2000. The station has been integrated into the GEOSCOPE network in 2008 and the data are now available in real time through GEOSCOPE and IRIS. The observatory is located at distance of 1km from the base. The current installation is placed at a depth of 12m in an artificial vault constructed from two shipping containers and buried in the snow. The vault is thermally very stable, but the relatively close proximity to the base causes increased diurnal noise ( 40 dB) at frequencies above 1Hz, especially during the summer season. The uppermost 100 m thick firn (snow) layer forms a waveguide, where anthropic noise from the base is trapped and easily picked up by the seismometers (T240 and STS2). Another limitation comes from the hydrostatic pressure of the snow which is continuously deforming the metallic structures: we record container cracking events on the seismograms, and we see visual evidence of structural deformations inside the tunnel and the vault. We propose an evolution of the CCD station towards a post-hole installation. Placing a sensor at a depth of approximately 130 meters, will reduce noise from thermal effects, from tilting and from anthropogenic activity, because it would be located below the firn layer waveguide and the ice pinch-out depth. In order to operate the borehole station for several years, we intend to keep the hole open and the sensor accessible, while ensuring good coupling between the sensor and the surrounding hard ice. To achieve these goals and to avoid any hydrostatic movement, we shall install a PEHD casing in the upper section of the borehole located in the firn layer. After installing the instrument in the hard ice, we shall then fill the hole with silicone oil whose density is similar to that of ice. The drilling is scheduled to start in January 2018. Updates on the project will be presented at the meeting.

Three-Dimensional Morphometric Analysis of the Iris by Swept-Source Anterior Segment Optical Coherence Tomography in a Caucasian Population.

PubMed

Invernizzi, Alessandro; Giardini, Piero; Cigada, Mario; Viola, Francesco; Staurenghi, Giovanni

2015-07-01

We analyzed by swept-source anterior segment optical coherence tomography (SS-ASOCT) the three-dimensional iris morphology in a Caucasian population, and correlated the findings with iris color, iris sectors, subject age, and sex. One eye each from consecutive healthy emmetropic (refractive spherical equivalent ± 3 diopters) volunteers were selected for the study. The enrolled eye underwent standardized anterior segment photography to assess iris color. Iris images were assessed by SS-ASOCT for volume, thickness, width, and pupil size. Sectoral variations of morphometric data among the superior, nasal, inferior, and temporal sectors were recorded. A total of 135 eyes from 57 males and 78 females, age 49 ± 17 years, fulfilled the inclusion criteria. All iris morphometric parameters varied significantly among the different sectors (all P < 0.0001). Iris total volume and thickness were significantly correlated with increasingly darker pigmentation (P < 0.0001, P = 0.0384, respectively). Neither width nor pupil diameter was influenced by iris color. Age did not affect iris volume or thickness; iris width increased and pupil diameter decreased with age (rs = 0.52, rs = -0.58, respectively). There was no effect of sex on iris volume, thickness, or pupil diameter; iris width was significantly greater in males (P = 0.007). Morphology of the iris varied by iris sector, and iris color was associated with differences in iris volume and thickness. Morphological parameter variations associated with iris color, sector, age, and sex can be used to identify pathological changes in suspect eyes. To be effective in clinical settings, construction of iris morphological databases for different ethnic and racial populations is essential.

Satellite and Ground Signatures of Kinetic and Inertial Scale ULF Alfven Waves Propagating in Warm Plasma in Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Rankin, R.; Sydorenko, D.

2015-12-01

Results from a 3D global numerical model of Alfven wave propagation in a warm multi-species plasma in Earth's magnetosphere are presented. The model uses spherical coordinates, accounts for a non-dipole magnetic field, vertical structure of the ionosphere, and an air gap below the ionosphere. A realistic density model is used. Below the exobase altitude (2000 km) the densities and the temperatures of electrons, ions, and neutrals are obtained from the IRI and MSIS models. Above the exobase, ballistic (originating from the ionosphere and returning to ionosphere) and trapped (bouncing between two reflection points above the ionosphere) electron populations are considered similar to [Pierrard and Stegen (2008), JGR, v.113, A10209]. Plasma parameters at the exobase provided by the IRI are the boundary conditions for the ballistic electrons while the [Carpenter and Anderson (1992), JGR, v.97, p.1097] model of equatorial electron density defines parameters of the trapped electron population. In the simulations that are presented, Alfven waves with frequencies from 1 Hz to 0.01 Hz and finite azimuthal wavenumbers are excited in the magnetosphere and compared with Van Allen Probes data and ground-based observations from the CARISMA array of ground magnetometers. When short perpendicular scale waves reflect form the ionosphere, compressional Alfven waves are observed to propagate across the geomagnetic field in the ionospheric waveguide [e.g., Lysak (1999), JGR, v.104, p.10017]. Signals produced by the waves on the ground are discussed. The wave model is also applied to interpret recent Van Allen Probes observations of kinetic scale ULF waves that are associated with radiation belt electron dynamics and energetic particle injections.

Iris reconstruction combined with iris-claw intraocular lens implantation for the management of iris-lens injured patients

PubMed Central

Hu, Shufang; Wang, Mingling; Xiao, Tianlin; Zhao, Zhenquan

2016-01-01

Aim: To study the efficiency and safety of iris reconstruction combined with iris-claw intraocular lens (IOL) implantation in the patients with iris-lens injuries. Settings and Design: Retrospective, noncomparable consecutive case series study. Materials and Methods: Eleven patients (11 eyes) following iris-lens injuries underwent iris reconstructions combined with iris-claw IOL implantations. Clinical data, such as cause and time of injury, visual acuity (VA), iris and lens injuries, surgical intervention, follow-up period, corneal endothelial cell count, and optical coherence tomography, were collected. Results: Uncorrected VA (UCVA) in all injured eyes before combined surgery was equal to or <20/1000. Within a 1.1–4.2-year follow-up period, a significant increase, equal to or better than 20/66, in UCVA was observed in six (55%) cases, and in best-corrected VA (BCVA) was observed in nine (82%) cases. Postoperative BCVA was 20/40 or better in seven cases (64%). After combined surgery, the iris returned to its natural round shape or smaller pupil, and the iris-claw IOLs in the 11 eyes were well-positioned on the anterior surface of reconstructed iris. No complications occurred in those patients. Conclusions: Iris reconstruction combined with iris-claw IOL implantation is a safe and efficient procedure for an eye with iris-lens injury in the absence of capsular support. PMID:27146932

Effect of laser beam conditioning on fabrication of clean micro-channel on stainless steel 316L using second harmonic of Q-switched Nd:YAG laser

NASA Astrophysics Data System (ADS)

Singh, Sanasam Sunderlal; Baruah, Prahlad Kr; Khare, Alika; Joshi, Shrikrishna N.

2018-02-01

Laser micromachining of metals for fabrication of micro-channels generate ridge formation along the edges accompanied by ripples along the channel bed. The ridge formation is due to the formation of interference pattern formed by back reflections from the beam splitter and other optical components involved before focusing on the work piece. This problem can be curtailed by using a suitable aperture or Iris diaphragm so as to cut the unwanted portion of the laser beam before illuminating the sample. This paper reports an experimental investigation on minimizing this problem by conditioning the laser beam using an Iris diaphragm and using optimum process parameters. In this work, systematic experiments have been carried out using the second harmonic of a Q-switched Nd:YAG laser to fabricate micro-channels. Initial experiments revealed that formation of ridges along the sides of micro-channel can easily be minimized with the help of Iris diaphragm. Further it is noted that a clean micro-channel of depth 43.39 μm, width up to 64.49 μm and of good surface quality with average surface roughness (Ra) value of 370 nm can be machined on stainless steel (SS) 316L by employing optimum process condition: laser beam energy of 30 mJ/pulse, 11 number of laser scans and scan speed of 169.54 μm/s with an opening of 4 mm diameter of Iris diaphragm in the path of the laser beam.

Optical Coherence Tomography Angiography Features of Iris Racemose Hemangioma in 4 Cases.

PubMed

Chien, Jason L; Sioufi, Kareem; Ferenczy, Sandor; Say, Emil Anthony T; Shields, Carol L

2017-10-01

Optical coherence tomography angiography (OCTA) allows visualization of iris racemose hemangioma course and its relation to the normal iris microvasculature. To describe OCTA features of iris racemose hemangioma. Descriptive, noncomparative case series at a tertiary referral center (Ocular Oncology Service of Wills Eye Hospital). Patients diagnosed with unilateral iris racemose hemangioma were included in the study. Features of iris racemose hemangioma on OCTA. Four eyes of 4 patients with unilateral iris racemose hemangioma were included in the study. Mean patient age was 50 years, all patients were white, and Snellen visual acuity was 20/20 in each case. All eyes had sectoral iris racemose hemangioma without associated iris or ciliary body solid tumor on clinical examination and ultrasound biomicroscopy. By anterior segment OCT, the racemose hemangioma was partially visualized in all cases. By OCTA, the hemangioma was clearly visualized as a uniform large-caliber vascular tortuous loop with intense flow characteristics superimposed over small-caliber radial iris vessels against a background of low-signal iris stroma. The vascular course on OCTA resembled a light bulb filament (filament sign), arising from the peripheral iris (base of light bulb) and forming a tortuous loop on reaching its peak (midfilament) near the pupil (n = 3) or midzonal iris (n = 1), before returning to the peripheral iris (base of light bulb). Intravenous fluorescein angiography performed in 1 eye depicted the iris hemangioma; however, small-caliber radial iris vessels were more distinct on OCTA than intravenous fluorescein angiography. Optical coherence tomography angiography is a noninvasive vascular imaging modality that clearly depicts the looping course of iris racemose hemangioma. Optical coherence tomography angiography depicted fine details of radial iris vessels, not distinct on intravenous fluorescein angiography.

Iris Crypts Influence Dynamic Changes of Iris Volume.

PubMed

Chua, Jacqueline; Thakku, Sri Gowtham; Tun, Tin A; Nongpiur, Monisha E; Tan, Marcus Chiang Lee; Girard, Michael J A; Wong, Tien Yin; Quah, Joanne Hui Min; Aung, Tin; Cheng, Ching-Yu

2016-10-01

To determine the association of iris surface features with iris volume change after physiologic pupil dilation in adults. Cross-sectional observational study. Chinese adults aged ≥ 50 years without ocular diseases. Digital iris photographs were taken from eyes of each participant and graded for crypts (by number and size) and furrows (by number and circumferential extent) following a standardized grading scheme. Iris color was measured objectively, using the Commission Internationale de l'Eclairage (CIE) L* color parameter (higher value denoting lighter iris). The anterior segment was imaged by swept-source optical coherence tomography (SS-OCT) (Casia; Tomey, Nagoya, Japan) under bright light and dark room conditions. Iris volumes in light and dark conditions were measured with custom semiautomated software, and the change in iris volume was quantified. Associations of the change in iris volume after pupil dilation with underlying iris surface features in right eyes were assessed using linear regression analysis. Iris volume change after physiologic pupil dilation from light to dark condition. A total of 65 Chinese participants (mean age, 59.8±5.7 years) had gradable data for iris surface features. In light condition, higher iris crypt grade was associated independently with smaller iris volume (β [change in iris volume in millimeters per crypt grade increment] = -1.43, 95% confidence interval [CI], -2.26 to -0.59; P = 0.001) and greater reduction of iris volume on pupil dilation (β [change in iris volume in millimeters per crypt grade increment] = 0.23, 95% CI, 0.06-0.40; P = 0.010), adjusting for age, gender, presence of corneal arcus, and change in pupil size. Iris furrows and iris color were not associated with iris volume in light condition or change in iris volume (all P > 0.05). Although few Chinese persons have multiple crypts on their irides, irides with more crypts were significantly thinner and lost more volume on pupil dilation. In view that the latter feature is known to be protective for acute angle-closure attack, it is likely that the macroscopic and microscopic composition of the iris is a contributing feature to angle-closure disease. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

An alternative way to increase the power gain of resonant rings

NASA Astrophysics Data System (ADS)

Zhuang, Dehao; Liu, Yunqi; Wang, Fang; Lin, Lin; Feng, Liwen; Quan, Shengwen; Liu, Kexin

2018-03-01

Resonant rings which can amplify RF power through the coupling of waves are used for high power breakdown tests, unidirectional filters, or pulse-shaping techniques. Usually, the RF output terminal of a resonant ring is connected to a matched load. For the resonant ring at Peking University, the matched load has been replaced by a waveguide shorting plate to obtain higher conditioning power for the 1.3 GHz capacitive type power couplers. The power gain is increased significantly with this short termination with the same input RF power. Working mechanism analysis, experiments, and results of this modified resonant ring will be presented.

Fuzzy difference-of-Gaussian-based iris recognition method for noisy iris images

NASA Astrophysics Data System (ADS)

Kang, Byung Jun; Park, Kang Ryoung; Yoo, Jang-Hee; Moon, Kiyoung

2010-06-01

Iris recognition is used for information security with a high confidence level because it shows outstanding recognition accuracy by using human iris patterns with high degrees of freedom. However, iris recognition accuracy can be reduced by noisy iris images with optical and motion blurring. We propose a new iris recognition method based on the fuzzy difference-of-Gaussian (DOG) for noisy iris images. This study is novel in three ways compared to previous works: (1) The proposed method extracts iris feature values using the DOG method, which is robust to local variations of illumination and shows fine texture information, including various frequency components. (2) When determining iris binary codes, image noises that cause the quantization error of the feature values are reduced with the fuzzy membership function. (3) The optimal parameters of the DOG filter and the fuzzy membership function are determined in terms of iris recognition accuracy. Experimental results showed that the performance of the proposed method was better than that of previous methods for noisy iris images.

Results in Combined Cataract Surgery With Prosthetic Iris Implantation in Patients With Previous Iridocyclectomy for Iris Melanoma.

PubMed

Snyder, Michael E; Osher, Robert H; Wladecki, Trisha M; Perez, Mauricio A; Augsburger, James J; Corrêa, Zélia

2017-03-01

To present visual and functional results following implantation of iris prosthesis combined with cataract surgery in eyes with previous iridocyclectomy for iris melanoma or presumed iris melanoma. Retrospective noncomparative case series. Sixteen patients (16 eyes) with iris defects after iridocyclectomy for iris melanoma in 15 cases and iris adenoma in 1 case underwent prosthetic iris device implantation surgery. Prosthetic iris implantation was combined with phacoemulsification and intraocular lens (IOL) implantation. The visual acuity, subjective glare and photophobia reduction, anatomic outcome, and complications were reviewed. Best-corrected visual acuity was improved in 13 eyes (81.25%), remained stable in 2 eyes (12.25%), and decreased in 1 eye (6.25%). Photophobia and glare improved in every case except for 1 (93.75%). Notably, after surgery 12 patients (75.00%) reported no photophobia and 10 patients (62.50%) reported no glare. The median postoperative follow-up was 29.5 months, with a minimum of 5 months and a maximum of 189 months. All iris devices were in the correct position, and all eyes achieved the desired anatomic result. The IOL optic edges were covered in all areas by either residual iris or opaque portions of a prosthetic iris device. In patients who have undergone previous iridocyclectomy for presumed iris melanoma, combined cataract surgery and iris prosthesis placement, with or without iris reconstruction, can lead to visual improvement as well as reduction of both glare and photophobia. Copyright © 2016 Elsevier Inc. All rights reserved.

High-power broadband plasma maser with magnetic self-insulation

NASA Astrophysics Data System (ADS)

Litvin, Vitaliy O.; Loza, Oleg T.

2018-01-01

Presented in this paper are the results of a particle-in-cell modelling of a novel high-power microwave (HPM) source which combines the properties of two devices. The first prototype is a magnetically insulated transmission line oscillator (MILO), an HPM self-oscillator which does not need an external magnetic field and irradiates a narrow spectrum depending on its iris-loaded slow-wave structure. The second prototype is a plasma maser, a Cherenkov HPM amplifier driven by a high-current relativistic electron beam propagating in a strong external magnetic field in plasma which acts as a slow-wave structure. The radiation frequency of plasma masers mainly depends on an easily variable plasma concentration; hence, their spectrum may overlap a few octaves. The plasma-based HPM device described in this paper operates without an external magnetic field: it looks like an MILO in which the iris-loaded slow-wave structure is substituted by a hollow plasma tube. The small pulse duration of ˜1.5 ns prevents a feedback rise in the 20-cm long generation section so that the device operates as a noise amplifier. Unlike conventional ultra wideband generators, the spectrum depends not only on the pulse duration but mainly on plasma, so the operation frequency of the device ranges within 12 GHz. For irradiated frequencies above 2 GHz, the total pulse energy efficiency of 7% is demonstrated at the HPM power level ˜1 GW.

Trade off between variable and fixed size normalization in orthogonal polynomials based iris recognition system.

PubMed

Krishnamoorthi, R; Anna Poorani, G

2016-01-01

Iris normalization is an important stage in any iris biometric, as it has a propensity to trim down the consequences of iris distortion. To indemnify the variation in size of the iris owing to the action of stretching or enlarging the pupil in iris acquisition process and camera to eyeball distance, two normalization schemes has been proposed in this work. In the first method, the iris region of interest is normalized by converting the iris into the variable size rectangular model in order to avoid the under samples near the limbus border. In the second method, the iris region of interest is normalized by converting the iris region into a fixed size rectangular model in order to avoid the dimensional discrepancies between the eye images. The performance of the proposed normalization methods is evaluated with orthogonal polynomials based iris recognition in terms of FAR, FRR, GAR, CRR and EER.

Toward More Accurate Iris Recognition Using Cross-Spectral Matching.

PubMed

Nalla, Pattabhi Ramaiah; Kumar, Ajay

2017-01-01

Iris recognition systems are increasingly deployed for large-scale applications such as national ID programs, which continue to acquire millions of iris images to establish identity among billions. However, with the availability of variety of iris sensors that are deployed for the iris imaging under different illumination/environment, significant performance degradation is expected while matching such iris images acquired under two different domains (either sensor-specific or wavelength-specific). This paper develops a domain adaptation framework to address this problem and introduces a new algorithm using Markov random fields model to significantly improve cross-domain iris recognition. The proposed domain adaptation framework based on the naive Bayes nearest neighbor classification uses a real-valued feature representation, which is capable of learning domain knowledge. Our approach to estimate corresponding visible iris patterns from the synthesis of iris patches in the near infrared iris images achieves outperforming results for the cross-spectral iris recognition. In this paper, a new class of bi-spectral iris recognition system that can simultaneously acquire visible and near infra-red images with pixel-to-pixel correspondences is proposed and evaluated. This paper presents experimental results from three publicly available databases; PolyU cross-spectral iris image database, IIITD CLI and UND database, and achieve outperforming results for the cross-sensor and cross-spectral iris matching.

A high resolution cavity BPM for the CLIC Test Facility

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

Chritin, N.; Schmickler, H.; Soby, L.

2010-08-01

In frame of the development of a high resolution BPM system for the CLIC Main Linac we present the design of a cavity BPM prototype. It consists of a waveguide loaded dipole mode resonator and a monopole mode reference cavity, both operating at 15 GHz, to be compatible with the bunch frequencies at the CLIC Test Facility. Requirements, design concept, numerical analysis, and practical considerations are discussed.

Behavioral and autonomic thermoregulation in hamsters during microwave-induced heat exposure

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

Gordon, C.J.; Long, M.D.; Fehlner, K.S.

1984-01-01

Preferred ambient temperature (Ta) and ventilatory frequency were measured in free-moving hamsters exposed to 2450-MHz microwaves. A waveguide exposure system that permits continuous monitoring of the absorbed heat load accrued from microwave exposure was imposed with a longitudinal temperature gradient which allowed hamsters to select their preferred Ta. Ventilatory frequency was monitored remotely by analysing the rhythmic shifts in unabsorbed microwave energy passing down the waveguide. Without microwave exposure hamsters selected an average T2 of 30.2 C. This preferred Ta did not change until the rate of heat absorption (SAR) from microwave exposure exceeded approx. 2 W kg-1. In amore » separate experiment, a SAR of 2.0 W kg-1 at a Ta of 30C was shown to promote an average 0.5 C increase in colonic temperature. Hamsters maintained their ventilatory frequency at baseline levels by selecting a cooler Ta during microwave exposure. These data support previous studies suggesting that during thermal stress behavioral thermo-regulation (i.e. preferred Ta) takes prescedence over autonomic thermoregulation (i.e. ventilatory frequency). It is apparent that selecting a cooler Ta is a more efficient and/or effective than autonomic thermoregulation for dissipating a heat load accrued from microwave exposure.« less

NONLINEAR AND FIBER OPTICS: Analysis of the mode noise in interference fiber channels used for the distribution of microwave signals

NASA Astrophysics Data System (ADS)

Bratchikov, A. N.; Glukhov, I. P.

1991-03-01

The results are given of a statistical theory of the speckle generalized to interference channels used for the distribution of microwave signals using multimode fiber waveguides with step and graded refractive-index profiles. A method is described for estimating the mode noise level in the open and closed regimes with one longitudinal speckle. The influence of the degree of mode filtering, losses at microbends, and spectral properties of a laser source on the statistical properties and the mode noise level is demonstrated. Numerical estimates are obtained of the ratio of the powers of the signal and mode noise for interference channels with typical parameters of fiber waveguides and a qualitative description is given of the effect of the mode noise.

Multiple detuned-resonator induced transparencies in MIM plasmonic waveguide

NASA Astrophysics Data System (ADS)

Liu, Li; Xia, Sheng-Xuan; Luo, Xin; Zhai, Xiang; Yu, Ya-Bin; Wang, Ling-Ling

2018-07-01

We propose a simple plasmonic waveguide system based on two-detuned resonators, which demonstrates multiple detuned-resonator induced transparencies at visible and near-infrared region. The performance of electromagnetic responses can be agile manipulated by tuning the asymmetry degree of the structure and the width of the split gap. Three transmission dips exist with the symmetrical design while three peaks emerge between the dip-position of the transmission spectra with two detuned resonators. The physical mechanism behind the plasmon-induced transparency (PIT) resonance is revealed as being attributed to the constructive interference between the confined modes in the detuned resonators. The former tend to the role of two coupled radiative oscillators. The work may open up avenues for the control of light in highly integrated optical circuits.

20 Gbps operation of membrane-based GaInAs/InP waveguide-type p-i-n photodiode bonded on Si substrate

NASA Astrophysics Data System (ADS)

Gu, Zhichen; Inoue, Daisuke; Amemiya, Tomohiro; Nishiyama, Nobuhiko; Arai, Shigehisa

2018-02-01

A GaInAs/InP waveguide-type p-i-n membrane photodetector is shown to be a strong candidate for on-chip optical interconnection. A responsivity of 0.95 A/W is estimated for a device length of 30 µm. The 3 dB cutoff frequency is measured to be 13.3 GHz at a reverse bias of 3 V, which is in good agreement with the observed clear eye opening pattern up to 20 Gbps for a non-return-to-zero signal. Moreover, a bit error rate of less than 1 × 10-9 is obtained at data rates of 20 and 10 Gbps with input powers of -10 and -13 dBm, respectively.

Giant nonlinear response at a plasmonic nanofocus drives efficient four-wave mixing

NASA Astrophysics Data System (ADS)

Nielsen, Michael P.; Shi, Xingyuan; Dichtl, Paul; Maier, Stefan A.; Oulton, Rupert F.

2017-12-01

Efficient optical frequency mixing typically must accumulate over large interaction lengths because nonlinear responses in natural materials are inherently weak. This limits the efficiency of mixing processes owing to the requirement of phase matching. Here, we report efficient four-wave mixing (FWM) over micrometer-scale interaction lengths at telecommunications wavelengths on silicon. We used an integrated plasmonic gap waveguide that strongly confines light within a nonlinear organic polymer. The gap waveguide intensifies light by nanofocusing it to a mode cross-section of a few tens of nanometers, thus generating a nonlinear response so strong that efficient FWM accumulates over wavelength-scale distances. This technique opens up nonlinear optics to a regime of relaxed phase matching, with the possibility of compact, broadband, and efficient frequency mixing integrated with silicon photonics.

Rainbow Trapping in Hyperbolic Metamaterial Waveguide

PubMed Central

Hu, Haifeng; Ji, Dengxin; Zeng, Xie; Liu, Kai; Gan, Qiaoqiang

2013-01-01

The recent reported trapped “rainbow” storage of light using metamaterials and plasmonic graded surface gratings has generated considerable interest for on-chip slow light. The potential for controlling the velocity of broadband light in guided photonic structures opens up tremendous opportunities to manipulate light for optical modulation, switching, communication and light-matter interactions. However, previously reported designs for rainbow trapping are generally constrained by inherent difficulties resulting in the limited experimental realization of this intriguing effect. Here we propose a hyperbolic metamaterial structure to realize a highly efficient rainbow trapping effect, which, importantly, is not limited by those severe theoretical constraints required in previously reported insulator-negative-index-insulator, insulator-metal-insulator and metal-insulator-metal waveguide tapers, and therefore representing a significant promise to realize the rainbow trapping structure practically. PMID:23409240

A large iris-like expansion of a mechanosensitive channel protein induced by membrane tension

NASA Technical Reports Server (NTRS)

Betanzos, Monica; Chiang, Chien-Sung; Guy, H. Robert; Sukharev, Sergei

2002-01-01

MscL, a bacterial mechanosensitive channel of large conductance, is the first structurally characterized mechanosensor protein. Molecular models of its gating mechanisms are tested here. Disulfide crosslinking shows that M1 transmembrane alpha-helices in MscL of resting Escherichia coli are arranged similarly to those in the crystal structure of MscL from Mycobacterium tuberculosis. An expanded conformation was trapped in osmotically shocked cells by the specific bridging between Cys 20 and Cys 36 of adjacent M1 helices. These bridges stabilized the open channel. Disulfide bonds engineered between the M1 and M2 helices of adjacent subunits (Cys 32-Cys 81) do not prevent channel gating. These findings support gating models in which interactions between M1 and M2 of adjacent subunits remain unaltered while their tilts simultaneously increase. The MscL barrel, therefore, undergoes a large concerted iris-like expansion and flattening when perturbed by membrane tension.

Phytofilter - environmental friendly solution for purification of surface plate from urbanized territories

NASA Astrophysics Data System (ADS)

Ruchkinova, O.; Shchuckin, I.

2017-06-01

Its proved, that phytofilters are environmental friendly solution of problem of purification of surface plate from urbanized territories. Phytofilters answer the nowadays purposes to systems of purification of land drainage. The main problem of it is restrictions, connecter with its use in the conditions of cold temperature. Manufactured a technology and mechanism, which provide a whole-year purification of surface plate and its storage. Experimentally stated optimal makeup of filtering load: peat, zeolite and sand in per cent of volume, which provides defined hydraulic characteristics. Stated sorbate and ion-selective volume of complex filtering load of ordered composition in dynamic conditions. Estimated dependences of exit concentrations of oil products and heavy metals on temperature by filtering through complex filtering load of ordered composition. Defined effectiveness of purification at phytofiltering installation. Fixed an influence of embryophytes on process of phytogeneration and capacity of filtering load. Recommended swamp iris, mace reed and reed grass. Manufactured phytofilter calculation methodology. Calculated economic effect from use of phytofiltration technology in comparison with traditional block-modular installations.

Results of the Round Robin on opening-load measurement conducted by ASTM Task Group E24.04.04 on Crack Closure Measurement and Analysis

NASA Technical Reports Server (NTRS)

Phillips, Edward P.

1989-01-01

An experimental Round Robin on the measurement of the opening load in fatigue crack growth tests was conducted on Crack Closure Measurement and Analysis. The Round Robin evaluated the current level of consistency of opening load measurements among laboratories and to identify causes for observed inconsistency. Eleven laboratories participated in the testing of compact and middle-crack specimens. Opening-load measurements were made for crack growth at two stress-intensity factor levels, three crack lengths, and following an overload. All opening-load measurements were based on the analysis of specimen compliance data. When all of the results reported (from all participants, all measurement methods, and all data analysis methods) for a given test condition were pooled, the range of opening loads was very large--typically spanning the lower half of the fatigue loading cycle. Part of the large scatter in the reported opening-load results was ascribed to consistent differences in results produced by the various methods used to measure specimen compliance and to evaluate the opening load from the compliance data. Another significant portion of the scatter was ascribed to lab-to-lab differences in producing the compliance data when using nominally the same method of measurement.

Waveguide arrangements based on adiabatic elimination

DOEpatents

Suchowski, Haim; Mrejen, Michael; Wu, Chihhui; Zhang, Xiang

2016-09-13

This disclosure provides systems, methods, and apparatus related to nanophotonics. In one aspect, an arrangement of waveguides includes a substrate and three waveguides. Each of the three waveguides may be a linear waveguide. A second waveguide is positioned between a first waveguide and a third waveguide. The dimensions and positions of the first, the second, and the third waveguides are specified to substantially eliminate coupling between the first waveguide and the third waveguide over a distance of about 1 millimeter to 2 millimeters along lengths of the first waveguide, the second waveguide, and the third waveguide.

Results of the second Round Robin on opening-load measurement conducted by ASTM Task Group E24.04.04 on crack closure measurement and analysis

NASA Technical Reports Server (NTRS)

Phillips, E. P.

1993-01-01

A second experimental Round Robin on the measurement of the crack opening load in fatigue crack growth tests has been completed by the ASTM Task Group E24.04.04 on Crack Closure Measurement and Analysis. Fourteen laboratories participated in the testing of aluminum alloy compact tension specimens. Opening-load measurements were made at three crack lengths during constant Delta K, constant stress ratio tests by most of the participants. Four participants made opening-load measurements during threshold tests. All opening-load measurements were based on the analysis of specimens compliance behavior, where the displacement/strain was measured either at the crack mouth or the mid-height back face location. The Round Robin data were analyzed for opening load using two non-subjective analysis methods: the compliance offset and the correlation coefficient methods. The scatter in the opening load results was significantly reduced when some of the results were excluded from the analysis population based on an accept/reject criterion for raw data quality. The compliance offset and correlation coefficient opening load analysis methods produced similar results for data populations that had been screened to eliminate poor quality data.

[Clinical aspects and therapy of the posner-schlossmann-syndrom (author's transl)].

PubMed

Hollwich, F

1978-05-01

Difficulties in the early diagnosis of the Posner-Schlossmann syndrome can be avoided by looking for the following typical clinical signs: Very fine, unpigmented precipitates, which are often only signly present, and which are scattered over the entire cornea: bright white in incident light, translucent in reflected light, and in transmitted light dark in spots. Posterior synechiae are not present. Obvious differences in color or heterochromia are present in only 30-40% of the cases. In the remaining cases, there ist only a slight color difference or unilateral, diffusely trophic hypochromia of the iris, often only after several attacks. The chamber angle is and remains open during the attacks. There are similarities between glaucomatocyclitic crisis and heterochromic cyclitis: Unilaterality, the same specific precipitates, no synechiae, and practically the same percentage of color differences of the iris. Hypochromic dystrophy of the iris dependent on the magnitude and duration of the cyclitic process. In both cases, there is the same rate of physical changes, pointing to a congenital damage of the sympathetic nervous system (status dysraphicus Passow). Hence, the Posner-Schlossmann syndrome can be regarded as a special case of heterochromic cyclitis. Neither miotics nor mydriatics, nor operation during the crisis. Acetazolamide (Diamox) combined with local cortisone will stop the crisis.

Heterogeneous microring and Mach-Zehnder modulators based on lithium niobate and chalcogenide glasses on silicon

DOE PAGES

Rao, Ashutosh; Patil, Aniket; Chiles, Jeff; ...

2015-08-20

In this study, thin films of lithium niobate are wafer bonded onto silicon substrates and rib-loaded with a chalcogenide glass, Ge 23Sb 7S 70, to demonstrate strongly confined single-mode submicron waveguides, microring modulators, and Mach-Zehnder modulators in the telecom C band. The 200 μm radii microring modulators present 1.2 dB/cm waveguide propagation loss, 1.2 × 10 5 quality factor, 0.4 GHz/V tuning rate, and 13 dB extinction ratio. The 6 mm long Mach-Zehnder modulators have a half-wave voltage-length product of 3.8 V.cm and an extinction ratio of 15 dB. The demonstrated work is a key step towards enabling wafer scalemore » dense on-chip integration of high performance lithium niobate electro-optical devices on silicon for short reach optical interconnects and higher order advanced modulation schemes.« less

Heterogeneous microring and Mach-Zehnder modulators based on lithium niobate and chalcogenide glasses on silicon

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

Rao, Ashutosh; Patil, Aniket; Chiles, Jeff

In this study, thin films of lithium niobate are wafer bonded onto silicon substrates and rib-loaded with a chalcogenide glass, Ge 23Sb 7S 70, to demonstrate strongly confined single-mode submicron waveguides, microring modulators, and Mach-Zehnder modulators in the telecom C band. The 200 μm radii microring modulators present 1.2 dB/cm waveguide propagation loss, 1.2 × 10 5 quality factor, 0.4 GHz/V tuning rate, and 13 dB extinction ratio. The 6 mm long Mach-Zehnder modulators have a half-wave voltage-length product of 3.8 V.cm and an extinction ratio of 15 dB. The demonstrated work is a key step towards enabling wafer scalemore » dense on-chip integration of high performance lithium niobate electro-optical devices on silicon for short reach optical interconnects and higher order advanced modulation schemes.« less

Compact photonic crystal circulator with flat-top transmission band created by cascading magneto-optical resonance cavities.

PubMed

Wang, Qiong; Ouyang, Zhengbiao; Lin, Mi; Liu, Qiang

2015-11-20

A new type of compact three-port circulator with flat-top transmission band (FTTB) in a two-dimensional photonic crystal has been proposed, through coupling the cascaded magneto-optical resonance cavities to waveguides. The coupled-mode theory is applied to investigate the coupled structure and analyze the condition to achieve FTTB. According to the theoretical analysis, the structure is further optimized to ensure that the condition for achieving FTTB can be satisfied for both cavity-cavity coupling and cavity-waveguide coupling. Through the finite-element method, it is demonstrated that the design can realize a high quality, nonreciprocal circulating propagation of waves with an insertion loss of 0.023 dB and an isolation of 23.3 dB, covering a wide range of operation frequency. Such a wideband circulator has potential applications in large-scale integrated photonic circuits for guiding or isolating harmful optical reflections from load elements.

Effective mie-scattering and CO2 absorption in the dust-laden Martian atmosphere and its impact on radiative-convective temperature changes in the lower scale heights

NASA Technical Reports Server (NTRS)

Pallmann, A. J.

1976-01-01

A time dependent computer model of radiative-convective-conductive heat transfer in the Martian ground-atmosphere system was refined by incorporating an intermediate line strength CO2 band absorption which together with the strong-and weak-line approximation closely simulated the radiative transmission through a vertically inhomogeneous stratification. About 33,000 CO2 lines were processed to cover the spectral range of solar and planetary radiation. Absorption by silicate dust particulates, was taken into consideration to study its impact on the ground-atmosphere temperature field as a function of time. This model was subsequently attuned to IRIS, IR-radiometric and S-band occultation data. Satisfactory simulations of the measured IRIS spectra were accomplished for the dust-free condition. In the case of variable dust loads, the simulations were sufficiently fair so that some inferences into the effect of dust on temperature were justified.

IRIS - A Community-Based Facility to Support Research in Seismology

NASA Astrophysics Data System (ADS)

Ingate, S.; Ahern, T.; Butler, R.; Fowler, J.; Simpson, D.; Taber, J.; van der Vink, G.

2002-12-01

The IRIS Consortium was established in 1984 in response to growing pressure from the research community for enhanced facilities in global and lithospheric seismology. At the same time, the National Science Foundation was encouraging improvements in technology and infrastructure that were sorely needed to ensure the future health of the nation's research endeavors. The governance of IRIS and growth of the facility programs have been guided by strong involvement of the research community. The IRIS management governance and structure serves as an interface between the scientific community, funding agencies, and the programs of IRIS. The structure is designed to focus scientific talent on common objectives, to encourage broad participation, and to efficiently manage its programs. IRIS is governed by a Board of Directors consisting of representatives from each of IRIS' 99 member institutions. Operational policies are set by an Executive Committee elected by the Board of Directors. The Executive Committee, in turn, appoints members to the Planning Committee, the Program Coordination Committee, and the four Standing Committees that provide oversight of the Global Seismographic Network (GSN), the Program of Array Seismic Studies of the Continental Lithosphere (PASSCAL), the Data Management System (DMS), and the Education and Outreach Program (E&O). In addition, special advisory committees and ad hoc working groups are convened for special tasks. Development of the IRIS programs has rested on strong core support from the Instrumentation and Facilities Program of the National Science Foundation's Earth Science Division, augmented with funding from the Department of Defense, Department of Energy, member universities, and private organizations. Close collaboration with the US Geological Survey and other national and foreign institutions has greatly extended the geographical coverage and strengthened the intellectual input that is essential to guiding the evolution of the IRIS programs. In the 18 years since the founding of IRIS, the core programs have grown to meet most of the original design goals and the Consortium continues to evolve in response to the community's changing needs. The GSN has now 126 permanent seismic stations distributed throughout the world with real-time connectivity to nearly 90 sites and dial-up links to most others. In addition to seismometers, microbarographs are installed at 19 sites and GPS instrumentation is located at 16 sites. The PASSCAL program supports between 50 and 60 experiments per year, from a lending pool of 250 broadband seismic sensor systems, and over 800 higher frequency systems for active source experiments. All seismic data acquired under the GSN and PASSCAL programs are made openly and freely available to anyone on the Internet, through the DMS. The DMS currently receives over 6Tb per year, and is able to service most requests for data within hours. Shipments in 2002 serviced nearly 60,000 requests, comprising nearly 1Tb of data, made to 563 different seismologists from 145 institutions in 33 countries around the world. The E&O program is relatively young, yet is making considerable inroads through its museum partnership (reaching 8,000,000 people per year); distribution of inexpensive seismographs; development of teaching modules and other educational materials for schools; technical support to internet-enabled school-based networks; workshops for geoscience educators; and undergraduate summer internships.

Dispersion analysis of leaky guided waves in fluid-loaded waveguides of generic shape.

PubMed

Mazzotti, M; Marzani, A; Bartoli, I

2014-01-01

A fully coupled 2.5D formulation is proposed to compute the dispersive parameters of waveguides with arbitrary cross-section immersed in infinite inviscid fluids. The discretization of the waveguide is performed by means of a Semi-Analytical Finite Element (SAFE) approach, whereas a 2.5D BEM formulation is used to model the impedance of the surrounding infinite fluid. The kernels of the boundary integrals contain the fundamental solutions of the space Fourier-transformed Helmholtz equation, which governs the wave propagation process in the fluid domain. Numerical difficulties related to the evaluation of singular integrals are avoided by using a regularization procedure. To improve the numerical stability of the discretized boundary integral equations for the external Helmholtz problem, the so called CHIEF method is used. The discrete wave equation results in a nonlinear eigenvalue problem in the complex axial wavenumbers that is solved at the frequencies of interest by means of a contour integral algorithm. In order to separate physical from non-physical solutions and to fulfill the requirement of holomorphicity of the dynamic stiffness matrix inside the complex wavenumber contour, the phase of the radial bulk wavenumber is uniquely defined by enforcing the Snell-Descartes law at the fluid-waveguide interface. Three numerical applications are presented. The computed dispersion curves for a circular bar immersed in oil are in agreement with those extracted using the Global Matrix Method. Novel results are presented for viscoelastic steel bars of square and L-shaped cross-section immersed in water. Copyright © 2013 Elsevier B.V. All rights reserved.

An effective approach for iris recognition using phase-based image matching.

PubMed

Miyazawa, Kazuyuki; Ito, Koichi; Aoki, Takafumi; Kobayashi, Koji; Nakajima, Hiroshi

2008-10-01

This paper presents an efficient algorithm for iris recognition using phase-based image matching--an image matching technique using phase components in 2D Discrete Fourier Transforms (DFTs) of given images. Experimental evaluation using CASIA iris image databases (versions 1.0 and 2.0) and Iris Challenge Evaluation (ICE) 2005 database clearly demonstrates that the use of phase components of iris images makes possible to achieve highly accurate iris recognition with a simple matching algorithm. This paper also discusses major implementation issues of our algorithm. In order to reduce the size of iris data and to prevent the visibility of iris images, we introduce the idea of 2D Fourier Phase Code (FPC) for representing iris information. The 2D FPC is particularly useful for implementing compact iris recognition devices using state-of-the-art Digital Signal Processing (DSP) technology.