Development of respirable virtual-cyclone samplers.

Health-based aerosol sampling should reflect how particles penetrate and deposit in various regions of the human respiratory system. Therefore, size-selective sampling should be adopted when monitoring aerosol concentration in the atmosphere. However, cyclone samplers, the most commonly used respirable sampler type in the workplace, show specific particle size-dependent bias toward the international respirable convention. Additionally, cyclone samplers are vulnerable to the dust loading effect resulting in an underestimation of respirable particulate matter. In the previous study, a virtual cyclone has been employed to overcome the dust loading effect, but still had the disadvantage of high aerosol penetration of large particle sizes. Therefore, in this work, the effects of key dimensions of virtual cyclones including chamber width (or inlet width), chamber size and inlet height on the separation performance were further studied and the configurations of virtual cyclones were modified to best fit the ISO/CEN/ACGIH respirable convention. Experimental results demonstrated that a better match with the ISO/CEN/ACGIH respirable convention curve can be achieved by increasing the chamber width to over 20 mm. Moreover, the new virtual cyclones can operate at a flow rate up to 21.5 L/min to collect more respirable particulate matter for the increasingly stringent respirable dust standards. The new virtual cyclones demonstrate accurate and constant measurement of the respirable dust for exposure assessment.

Absolute frequency of cesium 6S1/2-6D3/2 hyperfine transition with a precision to nuclear magnetic octupole interaction.

We have determined the fundamental frequency of the cesium atom 6S1/2-6D3/2 two-photon transition, for the first time, to our knowledge. Moreover, our high-resolution scheme made it possible to address the influence of the nuclear magnetic octupole on the hyperfine structure. We found that the octupole-interaction hyperfine constant deduced from the cesium 6D-level has a value nearly eight times larger than what has been deduced from the 6P-level.

Robust sub-millihertz-level offset locking for transferring optical frequency accuracy and for atomic two-photon spectroscopy.

Robust sub-millihertz-level offset locking was achieved with a simple scheme, by which we were able to transfer the laser frequency stability and accuracy from either cesium-stabilized diode laser or comb laser to the other diode lasers who had serious frequency jitter previously. The offset lock developed in this paper played an important role in atomic two-photon spectroscopy with which record resolution and new determination on the hyperfine constants of cesium atom were achieved. A quantum-interference experiment was performed to show the improvement of light coherence as an extended design was implemented.

Isomalyngamide A, A-1 and their analogs suppress cancer cell migration in vitro.

Isomalyngamide A (1) and A-1 (2) were isolated from the Taiwanese Lyngbya majuscule and the latter structure was elucidated by a combination of NMR spectroscopic analysis and HRESIMS measurement. We report the isolation of isomalyngamide A (1), discovery of isomalyngamide A-1 (2) and their synthetic analogs (3-9), which are further demonstrated to have therapeutic potential against tumor cell migration at the level of nanomolar to micromolar ranges, perhaps, by inactivating the expression of p-FAK, FAK, p-Akt and Akt through ß1 integrin-mediated antimetastatic pathway.