Precision spectroscopy and density-dependent frequency shifts in ultracold Sr

By varying the density of an ultracold $^{88}$Sr sample from $10^9$ cm$^{-3}$ to $> 10^{12}$ cm$^{-3}$, we make the first definitive measurement of the density-related frequency shift and linewidth broadening of the $^1S_0$ - $^3P_1$ optical clock transition in an alkaline earth system. In addition, we report the most accurate measurement to date of the $^{88}$Sr $^1S_0 - ^3P_1$ optical clock transition frequency. Including a detailed analysis of systematic errors, the frequency is ($434 829 121 312 334 \pm 20_{stat} \pm 33_{sys}$) Hz.Comment: 4 pages, 4 figures, 1 table. submitte

Environmental effect on vision-based structural dynamic displacement monitoring

Structural dynamic displacement is an important indicator of the health condition of long-span bridges. Monitoring of bridge dynamic displacement has been a critical task within the context of structural health monitoring (SHM). Traditionally, the structural displacement measurement methods are contact, wired and time-consuming. With the great progress of image processing technique and vision robot science, the visionbased monitoring systems have been developed rapidly and received a huge amount of attentions in the field of SHM. However, in the practical applications, the environmental factors will affect the operational performance of the vision-based system. In this study, a series of comparative experiments are conducted to explore the robustness of vision-based structural dynamic displacement monitoring under varying illumination conditions by use of various types of vision targets (quick response (QR) code and LED lamp). The experimental results indicate that the robustness of the vision-based system is weakened under poor illumination conditions when the QR code is used to be the vision target in comparison with the vision target of LED lamp

Non-contact structural vibration monitoring under varying environmental conditions

The vision-based structural displacement measurement technology is an advanced non-contact means for structural vibration monitoring. In the practical applications, different kinds of sources will affect the measurement accuracy of the vision-based displacement measurement system. In this study, the effect of the environmental factor on the operational performance of the vision-based displacement measurement system is investigated. Comparative analyses of the results obtained from the experiments with various types of vapor levels and vision targets (quick response (QR) codes and infrared emitters) indicate that the environmental factor has a significant effect on the system performance and measurement accuracy of the vision-based displacement measurement system

Bottom-Up versus Top-Down Induction of Sleep by Zolpidem Acting on Histaminergic and Neocortex Neurons

Zolpidem, a GABAA receptor-positive modulator, is the gold-standard drug for treating insomnia. Zolpidem prolongs IPSCs to decrease sleep latency and increase sleep time, effects that depend on α2 and/or α3 subunit-containing receptors. Compared with natural NREM sleep, zolpidem also decreases the EEG power, an effect that depends on α1 subunit-containing receptors, and which may make zolpidem-induced sleep less optimal. In this paper, we investigate whether zolpidem needs to potentiate only particular GABAergic pathways to induce sleep without reducing EEG power. Mice with a knock-in F77I mutation in the GABAA receptor γ2 subunit gene are zolpidem-insensitive. Using these mice, GABAA receptors in the frontal motor neocortex and hypothalamic (tuberomammillary nucleus) histaminergic-neurons of γ2I77 mice were made selectively sensitive to zolpidem by genetically swapping the γ2I77 subunits with γ2F77 subunits. When histamine neurons were made selectively zolpidem-sensitive, systemic administration of zolpidem shortened sleep latency and increased sleep time. But in contrast to the effect of zolpidem on wild-type mice, the power in the EEG spectra of NREM sleep was not decreased, suggesting that these EEG power-reducing effects of zolpidem do not depend on reduced histamine release. Selective potentiation of GABAA receptors in the frontal cortex by systemic zolpidem administration also reduced sleep latency, but less so than for histamine neurons. These results could help with the design of new sedatives that induce a more natural sleep

Fatigue Crack Growth And Piezoelectric Property Decay Induced By Cyclic Electric Fields For An Actuation Piezoceramic

Degradation of piezoelectric properties of piezomaterials has long been a concern in the applications of actuators and sensors. In this work, alternating electric field induced fatigue crack growth and effect of cyclic electric field on piezoelectric property decay were characterized for a polarized PZT-PIC151. The results show that a relatively high alternating electric field drives the pre-existing microcracks to grow very fast initially due to the superposition of electrostriction induced stress and residual stress at the crack tip, then slow down gradually to becoming dormant. The butterfly loop evolution shows that cyclic electric field strongly degrades the piezoelectric properties due to the frequent domain switching. The output strain decays more than 50% after 106 electric cycles at 0.9 Ec for PIC 151 pellet bonded on an aluminum beam