Sound Signalling in Orthoptera

The sounds produced by orthopteran insects are very diverse. They are widely studied for the insight they give into acoustic behaviour and the biophysical aspects of sound production and hearing, as well as the transduction of sound to neural signals in the ear and the subsequent processing of information in the central nervous system. The study of sound signalling is a multidisciplinary area of research, with a strong physiological contribution. This review considers recent research in physiology and the links with related areas of acoustic work on the Orthoptera

Inaugural Charles River World Congress on Animal Models in Drug Discovery and Development

https://deepblue.lib.umich.edu/bitstream/2027.42/138112/1/12967_2017_Article_1274.pd

Cascaded Orientation-Patterned Gallium Arsenide Optical Parametric Oscillator for Improved Longwave Infrared Conversion Efficiency

Optical parametric oscillators (OPOs) utilizing quasi-phase matched materials offer an appealing alternative to direct laser sources. Quasi-phase matched materials provide a useful alternative to traditional birefringent nonlinear optical materials and through material engineering, higher nonlinear coefficients can now be accessed. Orientation patterned gallium arsenide (OPGaAs) is an ideal material because of its broad IR transmission and large nonlinear coefficient. In contrast to ferroelectric materials, such as lithium niobate, where the pattern is fabricated through electric poling, zincblende materials, like OPGaAs, are grown epitaxially with the designed pattern. Generating longwave output from a much shorter pump wavelength, however, is relatively inefficiency due to the large quantum defect when compared to similar devices operating in the 3-5 æm regime. One method to increase pump to idler conversion efficiency is to recycle the undesired and higher energy signal photons into additional idler photons via a second nonlinear stage. An external amplifier stage can be utilized, where the signal and idler from the OPO are sent to a second nonlinear crystal in which the idler is amplified at the expense of the signal. Alternatively, the second crystal can be placed within the original OPO cavity where the signal from the first-stage acts as the pump for the second crystal and the resonant intensity of the signal is higher. Pumping the second crystal within the OPO should lead to higher conversion efficiency into the longwave idler. The grating period needed for the second crystal to use the signal from the first crystal to produce additional idler has the fortuitous advantage that it will not phase match to the original pump wavelength, avoiding unwanted nonlinear interactions. Therefore, a simple linear cavity can be utilized where the pump from the first-stage will simply propagate through the second crystal without undesired results. Without this feature, the pump would need to be coupled out of the cavity before it enters the second crystal. Initial numerical simulations using a custom model, implemented in MATLAB® for the proposed linear, two-stage, cascaded, OPGaAs nanosecond OPO suggest a significant improvement in conversion efficiency over a single-stage device can be obtained. The numerical model includes diffraction, crystal loss, phase mismatch, pump depletion, and back conversion, it assumes monochromatic waves and neglects group velocity dispersion. For a singly resonant oscillator (SRO) pumped by a 2.052 æm Tm:Ho,YLF laser with 45 ns pulse width, the addition of the second crystal in the cavity increases idler generation by a factor of two and exceeds the quantum defect limit. Experimentally, the cascaded OPGaAs OPO demonstrated a ̃3% slope efficiency. Limited output may be the result of improper phase matching, given that two distinct idlers wavelengths were observed. Tuning the OPGaAs crystals to generate identical idlers should improve efficiency. The linewidth of the signal serving to pump the second-stage likely reduced efficiency as well. To our knowledge, this is the first cascaded OPO using OPGaAs, and the first cascaded OPO operating in the longwave infrared where the same longwave idler was generated in the both crystals

Longwave-infrared optical parametric oscillator in orientation-patterned gallium arsenide

Coherent tunable laser sources in the longwave infrared (LWIR) spectral region are in high demand for military applications. Most lasers cannot produce outputs far into the infrared region, and therefore a conversion process is needed to achieve desired wavelengths. Quasi-phase matching is a technique that spatially modulates the nonlinear properties of a given material, periodically reversing the induced nonlinear polarization to ensure positive energy flow from the pump source to the converted fields, subject to conservation of energy and momentum. Through the use of optical parametric oscillation (OPO), and nonlinear quasi-phase matched orientation-patterned gallium arsenide (OPGaAs), producing LWIR wavelengths is possible. The OPGaAs OPO was pumped with a Q-switched 2.054μm Tm,Ho:YLF laser. As a precursor to the LWIR OPGaAs OPO, different resonator geometries were explored with a midwave (MWIR) OPGaAs OPO utilizing both SRO and DRO mirror sets. While thresholds increased with cavity length, the slope efficiencies remained relatively similar with the respective mirror set. The LWIR OPGaAs OPO explored the performance using two separate cavity configurations, an SRO and an asymmetric cavity; and five different OPGaAs samples representing three different grating periods. The highest slope efficiency in the SRO LWIR cavity was found to be ̃29%, with threshold values of ranging from ̃45-90μJ. The slope efficiencies for the asymmetric cavity range from ̃4-16% while experiencing higher thresholds of ̃150-220μJ, lower overall output power, and increased cavity instability. At higher pump energies, rollover was observed in both cavity configurations. SNLO was used to model the OPO output in the hopes that it might provide some insight into this behavior. The theoretical performance plot fit the acquired data decently but failed to predict the behavior at the higher energies. Spectroscopic data were collected for both OPO signal and idler output, presenting good agreement with theoretical tuning curves

Longwave-infrared optical parametric oscillator in orientation-patterned gallium arsenide

Coherent tunable laser sources in the longwave infrared (LWIR) spectral region are in high demand for military applications. Most lasers cannot produce outputs far into the infrared region, and therefore a conversion process is needed to achieve desired wavelengths. Quasi-phase matching is a technique that spatially modulates the nonlinear properties of a given material, periodically reversing the induced nonlinear polarization to ensure positive energy flow from the pump source to the converted fields, subject to conservation of energy and momentum. Through the use of optical parametric oscillation (OPO), and nonlinear quasi-phase matched orientation-patterned gallium arsenide (OPGaAs), producing LWIR wavelengths is possible. The OPGaAs OPO was pumped with a Q-switched 2.054μm Tm,Ho:YLF laser. As a precursor to the LWIR OPGaAs OPO, different resonator geometries were explored with a midwave (MWIR) OPGaAs OPO utilizing both SRO and DRO mirror sets. While thresholds increased with cavity length, the slope efficiencies remained relatively similar with the respective mirror set. The LWIR OPGaAs OPO explored the performance using two separate cavity configurations, an SRO and an asymmetric cavity; and five different OPGaAs samples representing three different grating periods. The highest slope efficiency in the SRO LWIR cavity was found to be ̃29%, with threshold values of ranging from ̃45-90μJ. The slope efficiencies for the asymmetric cavity range from ̃4-16% while experiencing higher thresholds of ̃150-220μJ, lower overall output power, and increased cavity instability. At higher pump energies, rollover was observed in both cavity configurations. SNLO was used to model the OPO output in the hopes that it might provide some insight into this behavior. The theoretical performance plot fit the acquired data decently but failed to predict the behavior at the higher energies. Spectroscopic data were collected for both OPO signal and idler output, presenting good agreement with theoretical tuning curves

Human cardiovascular disease model predicts xanthine oxidase inhibitor cardiovascular risk.

Some health concerns are often not identified until late into clinical development of drugs, which can place participants and patients at significant risk. For example, the United States Food and Drug Administration (FDA) labeled the xanthine oxidase inhibitor febuxostat with a"boxed" warning regarding an increased risk of cardiovascular death, and this safety risk was only identified during Phase 3b clinical trials after its approval. Thus, better preclinical assessment of drug efficacy and safety are needed to accurately evaluate candidate drug risk earlier in discovery and development. This study explored whether an in vitro vascular model incorporating human vascular cells and hemodynamics could be used to differentiate the potential cardiovascular risk associated with molecules that have similar on-target mechanisms of action. We compared the transcriptomic responses induced by febuxostat and other xanthine oxidase inhibitors to a database of 111 different compounds profiled in the human vascular model. Of the 111 compounds in the database, 107 are clinical-stage and 33 are FDA-labelled for increased cardiovascular risk. Febuxostat induces pathway-level regulation that has high similarity to the set of drugs FDA-labelled for increased cardiovascular risk. These results were replicated with a febuxostat analog, but not another structurally distinct xanthine oxidase inhibitor that does not confer cardiovascular risk. Together, these data suggest that the FDA warning for febuxostat stems from the chemical structure of the medication itself, rather than the target, xanthine oxidase. Importantly, these data indicate that cardiovascular risk can be evaluated in this in vitro human vascular model, which may facilitate understanding the drug candidate safety profile earlier in discovery and development