YSM Issue 93.2

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NANOMOLDEDINTO PERFECTIONSCIENTISTS DISCOVER NOVEL WAYTO PRODUCE NANOMATERIALSBY ATHENA STENORILLUSTRATION COURTESY OF ELLI E GABRIELIncreasingly today, nanotechnology is coming into our lives,allowing us to design more efficient batteries, build lightweightvehicles, and even administer needleless vaccines. However, amajor barrier to accessing the full potential of nanoscale materialsis their fabrication. A team of researchers from Yale University andWuhan University recently discovered that thermomechanicalnanomolding is a reliable method for the nanofabrication ofordered phases (OPs).OPs, a class of materials consisting of sublattices occupied byatoms, are fundamental to various functional applications. Mostfunctional materials, including superconductors, magnetic materialsand plasmonic materials, belong to this class. Creating nanoscaleOPs is challenging because traditional techniques, such as chemicalvapor deposition growth, are not practical. For example, chemicalvapor deposition growth, a technique in which a film of vaporized,decomposing chemical is deposited onto a substrate’s surface, onlyworks for easily vaporized OPs and cannot produce certain shapes.But thermomechanical nanomolding can be scaled up for massproduction, fine-tuned to obtain specific characteristics, and usedwith a variety of starting materials. In this technique, raw material waspushed into a nanomold at steady pressure and a temperature belowits melting point, to produce single-crystalline nanowires of consistentcomposition and structure. The process could be tuned so that thenanowires’ aspect ratios were high, enabling easier access to differentmorphologies. The researchers attribute their results to OPs’ tendencyto self-organize via a thermodynamic (stability-driven) rather thankinetic (speed-driven) mechanism. This new process will make OPs amore accessible class of nanomaterials, and enable the development ofexciting new applications for nanotechnology. ■Liu, N., Xie., Y., Liu, G., Sohn, S., Raj, A., Han, G., Wu, B., Cha,J.J., Liu, Z., & Schroers, J. (2020). General Nanomolding ofOrdered Phases. Physical Review Letters, 124(3). https://doi.org/10.1103/physrevlett.124.036102IMPLICATIONSOF IMPELLARETHINKING TREATMENTS FORCARDIOGENIC SCHOCKBY MIA JACKSONILLUSTRATION COURTESY OF NOORA SAIDMore than one million Americans have a heart attack eachyear. Four to twelve percent of these patients developcardiogenic shock, a condition that prevents one’s heartfrom pumping the blood necessary to meet the body’s needs.Two common treatments for cardiogenic shock include theleft ventricular assist device (LVAD) and the intra-aortic balloonpump (IABP). While LVADs are more commonly used, YaleUniversity researchers recently reported the results of a studyexamining the discrepancies in in-hospital clinical outcomesbetween the two devices.The study found that LVADs were associated with higher inhospitalmortality and in-hospital major bleeding. “Because thereis relatively little evidence in this area, we think that the analysisthat we did, and the conclusion that we made … would haveboth policy implications and regulatory implications,” explainedNihar Desai, an assistant professor at the Yale School of Medicinewho worked on this study.Given the two-and-a-half-fold increase in the utilization ofLVADs between 2015 and 2017, Desai’s research suggests thathospitals might need to rethink treatment plans for cardiogenicshock. “We hope everyone is trying to integrate these data intotheir practice, as it is on everyone to be a little more judicious of[LVADs], given little evidence that would support their use,” Desaisaid. Hopefully, this research will influence the way many doctorstreat cardiogenic shock patients. After all, for every patient thatenters the emergency room, the most common treatment optionavailable should be the best one for them. ■Desai, N.R. (2020). Association of Use of an IntravascularMicroaxial Left Ventricular Assist Device vs Intra-aorticBalloon Pump With In-Hospital Mortality and MajorBleeding Among Patients With Acute Myocardial InfarctionComplicated by Cardiogenic Shock. JAMA, 323(8), 734–45.https://doi.org/10.1001/jama.2020.02546 Yale Scientific Magazine September 2020 www.yalescientific.org
WHAT’S IN THEEARTH’S MANTLE?HOW WEAKER MATERIAL IN OLDER PLATESMAY INCREASE DEFORMATIONBY DRUHV PATELILLUSTRATION COURTESY OF ANMEI LITTLETectonic plates and subducting slabs, portions oftectonic plates that have slid under other plates, holdthe secrets to the movement of land masses. Previousevidence showed that older slabs, which are colder andsupposedly stronger, deform in the mantle more than warm,and presumably weaker, plates. This phenomenon puzzledresearchers and scientists. Professor Jennifer Girard of YaleUniversity’s Department of Earth and Planetary Sciences,along with a team of researchers including Anwar Mohiuddinand Shun-ichiro Karato, aimed to uncover the basis for thisunexpected deformation. They used a high-pressure andhigh-temperature press to simulate the conditions in theEarth’s mantle, allowing them to study the deformation andsubduction of slabs on a smaller scale.The team found that when a subducting slab mademostly of large olivine mineral plunges into the mantle, theincreased pressure causes olivine to transform into finegrainedringwoodite. “The study clearly shows that newlyformed fine-grained ringwoodite is significantly weakerthan the coarse-grained olivine,” Girard said. While newlyformed ringwoodite in cold slabs grows slowly, highertemperatures in warmer slabs cause grains of ringwooditeto grow much faster; this causes the young slabs to becomemuch stronger as the grain grows. In fact, the team believesthat this inhibited growth rate may be the reason that coldslabs deform while warmer slabs do not. These findingswill help researchers further explore and understand theunexpected behavior of tectonic plates. ■Mohiuddin, A., Karato, S. & Girard, J. (2020). Slabweakening during the olivine to ringwoodite transitionin the mantle. Nature Geoscience, 13, 170–4. https://doi.org/10.1038/s41561-019-0523-3www.yalescientific.orgANALYZINGAUTOINDUCER-3UNDERSTANDINGCRITICAL BACTERIABY JERRY RUVALCABAILLUSTRATION COURTESY OF SOPHIA ZHAOEscherichia coli is a dominant bacterial member of the humanintestinal tract and a major model organism in biology. Somemembers of E. coli contribute to a healthy gut ecosystem, whereasothers are pathogens causing over a million infections worldwidethat often develop antibiotic resistance. Despite this, mechanisms forregulation of its population-level phenotypes, which are associatedwith pathogenesis, have remained elusive. Researchers in ProfessorJason Crawford’s group in the Departments of Chemistry andMicrobial Pathogenesis at Yale University, however, have illuminated akey pathway underlying this phenomenon at the molecular level. Theyhave discovered the structure and pathway of autoinducer-3 (AI-3), anuncharacterized signal responsible for regulating virulence.This signal is secreted from the bacteria during growth, accumulatingas cells divide and allowing the bacteria to assess their numbers.Researchers isolated the metabolite by applying cellular stress. Then,the structure was determined using one- and two-dimensionalNuclear Magnetic Resonance spectroscopy. Additionally, the effects ofAI-3 were tested on both bacteria and human tissue. Upon introducingthe metabolite to a strain of E. coli that causes intestinal lesions andkidney failure, the bacteria became more virulent. When introducedto human tissue, an inflammatory effect was observed, indicatinghuman cells can detect and combat these signals.The elucidation of the AI-3 structure and pathway is a crucial stepforward in microbial pathogenesis. “It can be used to determinethe collection of genes regulated by the AI-3 molecule in otherpathogenic bacteria,” Crawford said. These findings pave the way tocombatting virulence in a variety of pathogens. ■Kim, C.S., Gatsios, A., Cuesta, S., Chong Lam, Y., Wei, Z.,Chen, H., Russell, R.M., Shine, E.E., Wang, R., Wyche, T.P.,Piizzi, G., Flavell, R.A., Palm, N.W., Sperandio, V., & Crawford,J.M. (2020). Characterization of Autoinducer-3 Structure andBiosynthesis in E. coli. ACS Central Science, 6(2), 2020, 197–206.https://doi.org/10.1021/acscentsci.9b01076September 2020 Yale Scientific Magazine 7
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