An investigation for the development of an integrated optical data preprocessor

A laboratory model of a 16 channel integrated optical data preprocessor was fabricated and tested in response to a need for a device to evaluate the outputs of a set of remote sensors. It does this by accepting the outputs of these sensors, in parallel, as the components of a multidimensional vector descriptive of the data and comparing this vector to one or more reference vectors which are used to classify the data set. The comparison is performed by taking the difference between the signal and reference vectors. The preprocessor is wholly integrated upon the surface of a LiNbO3 single crystal with the exceptions of the source and the detector. He-Ne laser light is coupled in and out of the waveguide by prism couplers. The integrated optical circuit consists of a titanium infused waveguide pattern, electrode structures and grating beam splitters. The waveguide and electrode patterns, by virtue of their complexity, make the vector subtraction device the most complex integrated optical structure fabricated to date

Pairwise comparison device

Apparatus for comparing first and second sets of voltages having one-to-one correspondence, and providing an indication responsive to the magnitudes of the pairwise differences of the voltages; typically comprising a plurality of channel waveguides (11), each having a first electrode (12) on one side of the channel (11) and a second electrode (13) on the opposite side of the channel (11); contacts (14) and conductors (16) for connecting each voltage of the first set to the first electrode (12) of one waveguide (11); contacts (b 15) and conductors (17) for connecting each voltage of the second set to the second electrode (13) of the waveguide (11) to the first electrode (12) of which the corresponding voltage of the first set is connected; a coupling prism (18), a beam splitter (19), and a waveguide portion (20) for directing to the input end (21,22) of each waveguide (11) a substantially plane wave of coherent light (as indicated at 23,24,25) having predetermined relative intensity and phase; and a detector (51) and associated circuitry (52,58) responsive to the light emerging (as indicated at 26) from the output end (28,29) of the waveguides (11) (via a beam splitter 44 and a coupling prism 45) for providing an indication that is a function of the pairwise relative magnitudes of the first set of voltages and the second set of voltages

Spin-spin correlators in Majorana representation

In the Majorana representation of a spin 1/2 we find an identity which relates spin-spin correlators to one-particle fermionic correlators. This should be contrasted with the straightforward approach in which two-particle (four-fermion) correlators need to be calculated. We discuss applications to the analysis of the dynamics of a spin coupled to a dissipative environment and of a quantum detector performing a continuous measurement of a qubit's state

Feasibility investigation of integrated optics Fourier transform devices

The possibility of producing an integrated optics data processing device based upon Fourier transformations or other parallel processing techniques, and the ways in which such techniques may be used to upgrade the performance of present and projected NASA systems were investigated. Activities toward this goal include; (1) production of near-diffraction-limited geodesic lenses in glass waveguides; (2) development of grinding and polishing techniques for the production of geodesic lenses in LiNbO3 waveguides; (3) development of a characterization technique for waveguide lenses; and (4) development of a theory for corrected aspheric geodesic lenses. A holographic subtraction system was devised which should be capable of rapid on-board preprocessing of a large number of parallel data channels. The principle involved is validated in three demonstrations

An investigation for the development of an integrated optical data preprocessor

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

Mapping a Suppressor of dmc1-2 in Arabidopsis thaliana

Meiosis is a cellular process in which a diploid cell produces four haploid gamete cells. During Meiosis I, crossovers (COs) between homologous chromosomes result in the reciprocal exchange of genetic material; these COs ensure proper segregation of chromosomes. Without COs, abnormal segregation of unpaired chromosomes in meiosis leaves Arabidopsis thaliana sterile. During crossing-over, DMC1 mediates the strand invasion process. Previous studies have shown that dmc1 null mutants lack COs and are sterile. The Copenhaver laboratory isolated a hypomorphic allele of DMC1 (dmc1-2) and used it to identify suppressor mutants that restore fertility. These were called suppressors of dmc1-2 mutants (sdm lines). Here, we crossed a sdm candidate line (sdm17) to a polymorphic parent (Landsberg erecta), and screened the resulting F1s to identify heterozygotes. Seeds from a single F1 plant were used to generate a F2 mapping population. From this population, dmc1-2-/-; sdm17-/- plants were identified by genotyping and phenotypic (fertility) analysis. Fertile F2s will be pooled for Illumina sequencing. This will allow us to genetically map the SDM17 locus. The results obtained from this study will provide novel insight into genes that interact with DMC1 in Arabidopsis, which are not well-characterized.Bachelor of Scienc

Evaporated As2S3 Luneburg lenses for LiNbO3:Ti optical waveguides

Luneburg lenses of good quality were formed on high index optical waveguides by evaporation of arsenic trisulfide glass through simple masks. Using only two thin circular aperture masks, lenses with focal spots of a few times the diffraction limited width at f/4 were obtained. These lenses were designed for and tested at both visible (633 nm) and infrared wavelengths. Procedures for the design, fabrication, and testing of lenses of this type are described

Preeclampsia and Cardiovascular Disease in a Large UK Pregnancy Cohort of Linked Electronic Health Records: A CALIBER Study.

BACKGROUND: The associations between pregnancy hypertensive disorders and common cardiovascular disorders have not been investigated at scale in a contemporaneous population. We aimed to investigate the association between preeclampsia, hypertensive disorders of pregnancy, and subsequent diagnosis of 12 different cardiovascular disorders. METHODS: We used linked electronic health records from 1997 to 2016 to recreate a UK population-based cohort of 1.3 million women, mean age at delivery 28 years, with nearly 1.9 million completed pregnancies. We used multivariable Cox models to determine the associations between hypertensive disorders of pregnancy, and preeclampsia alone (term and preterm), with 12 cardiovascular disorders in addition to chronic hypertension. We estimated the cumulative incidence of a composite end point of any cardiovascular disorder according to preeclampsia exposure. RESULTS: During the 20-year study period, 18 624 incident cardiovascular disorders were observed, 65% of which had occurred in women under 40 years. Compared to women without hypertension in pregnancy, women who had 1 or more pregnancies affected by preeclampsia had a hazard ratio of 1.9 (95% confidence interval 1.53-2.35) for any stroke, 1.67 (1.54-1.81) for cardiac atherosclerotic events, 1.82 (1.34-2.46) for peripheral events, 2.13 (1.64-2.76) for heart failure, 1.73 (1.38-2.16) for atrial fibrillation, 2.12 (1.49-2.99) for cardiovascular deaths, and 4.47 (4.32-4.62) for chronic hypertension. Differences in cumulative incidence curves, according to preeclampsia status, were apparent within 1 year of the first index pregnancy. Similar patterns of association were observed for hypertensive disorders of pregnancy, while preterm preeclampsia conferred slightly further elevated risks. CONCLUSIONS: Hypertensive disorders of pregnancy, including preeclampsia, have a similar pattern of increased risk across all 12 cardiovascular disorders and chronic hypertension, and the impact was evident soon after pregnancy. Hypertensive disorders of pregnancy should be considered as a natural screening tool for cardiovascular events, enabling cardiovascular risk prevention through national initiatives

A Majorana Fermion t-J Model in One Dimension

We study a rotation invariant Majorana fermion model in one dimension using diagrammatic perturbation theory and numerical diagonalization of small systems. The model is inspired by a Majorana representation of the antiferromagnetic spin-1/2 chain, and it is similar in form to the t-J model of electrons, except that the Majorana fermions carry spin-1 and Z_2 charge. We discuss the implications of our results for the low-energy excitations of the spin-1/2 chain. We also discuss a generalization of our model from 3 species of Majorana fermions to N species; the SO(4) symmetric model is particularly interesting.Comment: 29 LaTeX pages, 11 postscript figure