Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational-Wave Event S190521g.

We report the first plausible optical electromagnetic counterpart to a (candidate) binary black hole merger. Detected by the Zwicky Transient Facility, the electromagnetic flare is consistent with expectations for a kicked binary black hole merger in the accretion disk of an active galactic nucleus [B. McKernan, K. E. S. Ford, I. Bartos et al., Astrophys. J. Lett. 884, L50 (2019)AJLEEY2041-821310.3847/2041-8213/ab4886] and is unlikely [

Medication abortion failure in women with and without previous cesarean delivery.

OBJECTIVE: To investigate the association between previous cesarean delivery and medication abortion failure and the association between parity and failure. METHODS: Data were abstracted from 2035 consecutive charts of women who underwent medication abortion in 2011. All women were at 63 days gestation or less and received mifepristone 200mg orally and misoprostol 800 mcg buccally. We used multivariate logistic regression to assess the relationship between failure, defined as requiring either curettage or additional medication, and prior cesarean delivery. We also examined the relationship between failure and parity. RESULTS: Follow-up was available on 1609 (79%) patients. Overall, 4.5% of patients experienced failure. Neither cesarean delivery nor parity was associated with failure; 6.5% of women with prior cesarean delivery experienced failure, compared to 3.7% of nulliparous women [adjusted odds ratio (aOR), 1.79, 95% confidence interval (CI), 0.83-3.87]. With regard to parity, 4.7% of women with two or more previous births experienced failure, compared to 3.7% of nulliparous women (aOR, 1.07, 95% CI, 0.54-2.14). CONCLUSION: We did not find significant associations between prior cesarean delivery and failure or parity and failure. A previous study of patients who had received a less effective regimen reported significant associations between cesarean delivery and failure and parity and failure. While our results do not rule out the possibility of modest associations due to our limited statistical power, they are reassuring relative to previous findings. IMPLICATIONS: Our results suggest that if there are differences in women's odds of medication abortion failure by obstetric history, such differences are unlikely to be large. Providers and patients may factor this information into decision making about methods of pregnancy termination.

Optical design of a free-space photonic switching system.

The optical design of a photonic switching system is described in detail. The system is a 4-f imaging system with one lens design based on a Petzval lens and the second lens design based on a double Gauss lens. The assembled system is 60 mm x 70 mm x 370 mm and features a single imaging stage, pupil division for beam combination, and a single fiber bundle for both input and output. A brief description of the system requirements is provided, and the implication of some of these requirements for the paraxial design is explained. The choice of design forms for the lenses is explained, the design process is outlined, and the final lens designs are provided. Lens tolerancing is outlined and the final lens tolerances are provided. Finally, the assembly and the alignment processes are described.

Asynchronous transfer mode distribution network by use of an optoelectronic VLSI switching chip.

We describe a new optoelectronic switching system demonstration that implements part of the distribution fabric for a large asynchronous transfer mode (ATM) switch. The system uses a single optoelectronic VLSI modulator-based switching chip with more than 4000 optical input-outputs. The optical system images the input fibers from a two-dimensional fiber bundle onto this chip. A new optomechanical design allows the system to be mounted in a standard electronic equipment frame. A large section of the switch was operated as a 208-Mbits/s time-multiplexed space switch, which can serve as part of an ATM switch by use of an appropriate out-of-band controller. A larger section with 896 input light beams and 256 output beams was operated at 160 Mbits/s as a slowly reconfigurable space switch.

Coating-induced wave-front aberrations: on-axis astigmatism and chromatic aberration in all-reflecting systems.

The coatings used on telescope mirrors and other optical interfaces can have a marked effect on an optical system's image quality. We describe the wave-front aberrations, particularly the defocus and on-axis astigmatism, that are induced by the s- and p-phase shifts of coatings. These coating-induced wave-front aberrations are very small, particularly near the design wavelengths of the coatings, but they can under certain circumstances overshadow the geometric wave-front aberrations of the system. The wave-front aberrations that are induced by reflection-enhanced coatings on an À/1.5 Cassegrain telescope are numerically evaluated as an example. A theory of coating-induced on-axis astigmatism and chromatic aberration is presented, and a simple algorithm that uses polarization ray tracing to calculate coating-induced defocus and astigmatism coefficients in radially symmetric systems is provided.

Distortion-adjusting optical elements.

Distortion can be corrected in an image by placing a fourth-order aspheric optical element near the image plane. Moving the aspheric surface longitudinally changes the amount of distortion that is added by the aspheric surface without changing the paraxial image. Third-order astigmatism limits the performance of distortion correctors and may be eliminated by adding another fourth-order aspheric surface. Example elements were fabricated by diamond turning and were shown to introduce distortion without significantly degrading image quality. Three arrangements of distortion correctors are discussed: a single-element planoaspheric arrangement, an antisymmetric two-element arrangement, and a biaspheric arrangement in which distortion is not adjustable.