Singly ionized ytterbium, with ultranarrow optical clock transitions at 467 and 436 nm, is a convenient system for the realization of optical atomic clocks and tests of present-day variation of fundamental constants. We present the first direct measurement of the frequency ratio of these two clock transitions, without reference to a cesium primary standard, and using the same single ion of 171Yb+. The absolute frequencies of both transitions are also presented, each with a relative standard uncertainty of 6×10(-16). Combining our results with those from other experiments, we report a threefold improvement in the constraint on the time variation of the proton-to-electron mass ratio, μ/μ=0.2(1.1)×10(-16)  yr(-1), along with an improved constraint on time variation of the fine structure constant, α/α=-0.7(2.1)×10(-17)  yr(-1).

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Electrophilic borylation using BCl3 and benzothiadiazole to direct the C–H functionalisation of an adjacent aromatic unit produces fused boracyclic materials with minimally changed HOMO energies but significantly reduced LUMO energies.

A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light‐emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface‐energy‐patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near‐infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.

We report modulation transfer spectroscopy on the D2 transitions in 85 Rb and 87 Rb using a simple home-built electro-optic modulator (EOM). We show that both the gradient and amplitude of modulation transfer spectroscopy signals, for the 87 Rb F = 2 → F = 3 and the 85 Rb F = 3 → F = 4 transitions, can be significantly enhanced by expanding the beams, improving the signals for laser frequency stabilization. The signal gradient for these transitions is increased by a factor of 3 and the peak to peak amplitude was increased by a factor of 2. The modulation transfer signal for the 85 Rb F = 2 → F transitions is also presented to highlight how this technique can generate a single, clear line for laser frequency stabilization even in cases where there are a number of closely spaced hyperfine transitions.