Experimental Design and Construction for Critical Velocity Measurement in Spin-Orbit Coupled Bose-Einstein Condensates

Quantum simulation using ultra-cold atoms, such as Bose-Einstein Condensates (BECs), offers a very flexible and well controlled environment to simulate physics in different systems. For example, to simulate the effects of spin orbit coupling (SOC) on electrons in solid state systems, we can make a SOC BEC which mimics the behavior of SOC electrons. The goal of this project is to see how the superfluid property of BECs change in the presence of SOC. In particular, we plan to measure the critical velocity of an 87Rb BEC with and without SOC by stirring it with a laser. This laser needs to be blue-detuned for generating a repulsive potential as an obstacle. For this purpose, we build an external cavity diode laser (ECDL) at 776.47nm, which is blue-detuned to the D1 and D2 transition of 87Rb. To drive the ECDL, temperature and current controllers are designed and built. Since we need to focus the laser beam to the center of a BEC (about 20 by 55 micron), we set up a telescope to shrink the beam size to less than 10 micron. The optical design is accomplished by OSLO (optical system simulation software) with simulation results consistent with the Ray Transfer Matrix. To examine the superfluidity under different relative velocities, an acoustic-optic modulator will be used to move the beam against the BEC. At this point, the optical system is mostly finished. Our next step is to perform the critical velocity measurement of a BEC with and without SOC

AMPK- mediated formation of stress granules is required for dietary restriction- induced longevity in Caenorhabditis elegans

Stress granules (SGs) are nonmembranous organelles that are dynamically assembled and disassembled in response to various stressors. Under stressed conditions, polyadenylated mRNAs and translation factors are sequestrated in SGs to promote global repression of protein synthesis. It has been previously demonstrated that SG formation enhances cell survival and stress resistance. However, the physiological role of SGs in organismal aging and longevity regulation remains unclear. In this study, we used TIAR- 1::GFP and GTBP- 1::GFP as markers to monitor the formation of SGs in Caenorhabditis elegans. We found that, in addition to acute heat stress, SG formation could also be triggered by dietary changes, such as starvation and dietary restriction (DR). We found that HSF- 1 is required for the SG formation in response to acute heat shock and starvation but not DR, whereas the AMPK- eEF2K signaling is required for starvation and DR- induced SG formation but not heat shock. Moreover, our data suggest that this AMPK- eEF2K pathway- mediated SG formation is required for lifespan extension by DR, but dispensable for the longevity by reduced insulin/IGF- 1 signaling. Collectively, our findings unveil a novel role of SG formation in DR- induced longevity.In addition to heat stress, starvation and dietary restriction (DR) can activate stress granule (SG) formation in Caenorhabditis elegans. HSF- 1 and AMPK are two key regulators for the SG formations. HSF- 1 is required for the SG formation in response to acute heat shock and starvation but not DR, whereas the AMPK- eEF2K pathway is required for starvation and DR- induced SG formation but not heat shock. Furthermore, AMPK- mediated SG formation contributes to DR- induced longevity.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/1/acel13157-sup-0008-Figurelegends.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/2/acel13157-sup-0001-FigS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/3/acel13157-sup-0006-TableS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/4/acel13157-sup-0007-TableS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/5/acel13157-sup-0005-FigS5.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/6/acel13157-sup-0003-FigS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/7/acel13157.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/8/acel13157-sup-0002-FigS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/9/acel13157-sup-0004-FigS4.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155936/10/acel13157_am.pd

Use electrochemistry to charge the next dynamic thermal metamaterials

Electrochemistry has enabled a wide range of important energy technologies such as fuel cells and batteries, emerging as a powerful tool to achieve active materials and devices with novel applications. In this Perspective, we highlight the great potential of electrochemistry in propelling the next generation of dynamic thermal metamaterials with a focus on thermal radiation applications. After a brief introduction of the mechanisms of electrochemistry to change material properties, we discuss the possibilities of achieving highly tunable thermal radiation features by electrochemically manipulating the carrier densities of plasmonic materials. Recent studies in the intersections between electrochemistry, metamaterials, and thermal radiation applications are reviewed, indicating an emerging research direction incorporating these three fields — electrochemically dynamic thermal metamaterials. Towards this direction, we anticipate a promising pathway of employing conducting polymers and point out its remarkable opportunities and potential challenges. We hope this perspective could encourage more researchers to contribute to the development of this interdisciplinary field targeting the next energy technologies and applications

EWOM EFFECTS ON FACEBOOK

The rapid growth of Facebook has become an important channel of eWOM. Facebook users can openly illustrate their attitudes toward products to their friends, either by casually clicking a like or deliberately writing a comment on advertisements. This study explored how friends’ involvement in advertisements and tie strength affected Facebook users’ product attitudes, intentions to purchase, and intentions to click. Moreover, we investigated how product type moderates fWOM (eWOM on Facebook) effects. This study recruited 384 respondents to participate in a 2 (friends’ involvement in advertisements: high/low, between-subject) × 2 (tie strength: strong/weak, between-subject) × 2 (product type: search/experience, within-subject) experimental design. The results showed that friends’ involvement in advertisements positively influenced users’ intentions to click. Tie strength of Facebook friends also positively affected users’ product attitudes, intentions to purchase, and intentions to click. Lastly, product type moderated the effects of tie strength of Facebook friends on users’ product attitudes and intentions to click; however, it did not moderate the effects of friends’ involvement in advertisements on their attitudes and intentions