We have created an analog of a black hole in a Bose-Einstein condensate. In this sonic black hole, sound waves, rather than light waves, cannot escape the event horizon. A steplike potential accelerates the flow of the condensate to velocities which cross and exceed the speed of sound by an order of magnitude. The Landau critical velocity is therefore surpassed. The point where the flow velocity equals the speed of sound is the sonic event horizon. The effective gravity is determined from the profiles of the velocity and speed of sound. A simulation finds negative energy excitations, by means of Bragg spectroscopy.

We report single-site resolution in a lattice with tunneling between sites, allowing for an in situ study of stochastic losses. The ratio of the loss rate to the tunneling rate is seen to determine the number fluctuations, and the overall profile of the lattice. Sub-Poissonian number fluctuations are observed. Deriving the lattice beams from a microlens array results in perfect relative stability between beams.

Purpose Coronavirus disease 2019 (COVID-19) caused a global pandemic with millions infected worldwide. Little is known on the ocular involvement associated with the disease. The aim of this study was to assess the clinical and molecular ocular involvement among patients with confirmed COVID-19 admitted to a tertiary care facility. Methods Consecutive patients admitted to the COVID-19 Ward of the Shamir Medical Center in Israel during March and April, 2020 were included. The control group included patients negative for COVID-19 admitted during a similar period to a different ward. Patients were examined by trained Ophthalmologists. SARS-CoV-2 conjunctival swab samples were obtained. Results Included were 48 patients, 16 with confirmed COVID-19 and 32 controls. Median patient age was 68.5 (interquartile range: 31.5, mean: 63 ± 21) years and 48% were male. Active conjunctival injection was present in three patients (19%) with COVID-19, compared to none in the controls (p = 0.034). Patients with COVID-19 were more likely to complain of foreign body sensation (31.3% vs 3.1%, p = 0.005) and redness of the eye (25% vs 0%, p = 0.003). Conjunctival injection was associated with loss of smell and taste (75% vs 7.7%, p = 0.018). Viral conjunctival swab tests all showed negative results for all three viral genes tested (E, N, and RdRp). Conclusions Among patients admitted to a tertiary referral center with confirmed COVID-19, active conjunctival injection was noted in one out of five cases, and was associated with loss of smell and taste. Conjunctival swabs for viral RNA were negative in patients with and without ocular involvement.