California Institute Of Technology Research Articles

Personal View: The barn owl — a specialist for studying sensory systems

Abstract In this personal view article, the impact of an auditory specialist, the barn owl, to our understanding of sensory processing, especially auditory processing, is discussed from the perspective of a long-lasting career. In times when research on model systems such as the mouse or the fruit fly, both generalists for most of the behaviors examined, celebrates big successes, one may ask what the work on animals occupying specialized niches, “specialists”, can contribute to advance our knowledge about sensory systems. A specialist in this context is an animal that occupies a certain ecological niche and shows corresponding adaptations in anatomy and physiology. This article presents a personal view on the impact of the work on such a specialist. In my article I shall focus on audition in the barn owl, a specialist for hunting by listening. I started my scientific career in 1979, working with houseflies, and have worked with barn owls since my time as a postdoc at the California Institute of Technology (“Caltech”, Pasadena, CA, USA) in 1985. My interest in specialists derived from my work as an ornithologist when I realized that adaptations like the long and curved bill of the curlew help animals to occupy certain ecological niches. I wanted to understand in a formal sense, and in comparison to engineering, how evolution shapes such specializations.

Carbon pillars are stronger than diamond yet elastic

Researchers have constructed microscopic carbon structures that boast the best combination of strength and elasticity of any material studied to date (Nat. Nanotechnol. 2019, DOI: 10.1038/s41565-019-0486-y). The tiny carbon pillars are stronger by weight than most existing materials and can bounce back after being pressed to half their size. The columns are also lightweight and heat resistant, making them ideal for use in aerospace components, engines, and nuclear reactor parts. Engineers could use these microscopic structures as building blocks for macroscopic materials, says Julia R. Greer, a materials scientist at the California Institute of Technology. With the pillars’ unique combination of properties, “you could build robust parts for any extreme thermal mechanical environment,” she says. The words strong and rubbery do not typically go together for materials. Strong materials are usually hard, while elastic materials that can recover their original shape after being deformed are pliable. Combining ...

INTRODUCTION TO THE SYMPOSIUM ON RESEARCH ON SOCIAL DILEMMAS

In 2002 Elinor Ostrom and some of her colleagues organized a working group on Testing Theoretical Models of Individual Behavior in Dynamic Social Dilemmas and held the first meeting of this group at Indiana University Bloomington in 2003. There have now been five subsequent meetings of different incarnations of this group (2006, Max Planck Institute, Jena; 2008, Florida State University; 2010, Rice University; 2013, California Institute of Technology; 2015, Brown University) prior to the most recent one, the seventh in total, held in 2017 at the University of Massachusetts Amherst. With each of these meetings, the size of the group and scope of the work presented has changed and shifted as new people become part of the group and as the research questions relevant to social dilemma researchers change over time. As a way of commemorating these events, the organizers have felt that it would be useful to create special issues or symposia in journals related to the meetings as a way of capturing a snapshot of the issues at the frontier of social dilemma research at each point in time. The 2013 meeting at Cal Tech was the first to take place after Ostrom's death in 2012, and it produced two such special issues, in part to memorialize her: one at the Journal of Theoretical Politics edited by Eric Coleman and Rick Wilson published in 2016, and one at Experiment Economics edited by Jimmy Walker and Mark Isaac published in 2015. In conjunction with the 2017 meetings at UMass Amherst, a call for papers went out for submissions to this current Symposium issue inviting submissions from people who have been affiliated with this group and to others working in the area so that we could present a compelling set of papers that encompass a broad range of the work aimed at helping us to better understand issues related to social dilemmas. The journal received a large number of submissions of very high‐quality work that was sent through the standard review process for the journal. In the end we are publishing eight of those submissions and are pleased with the quality and breadth of coverage these papers represent. We are also happy that while we received and will be publishing papers by authors with a direct association with these meetings, we also received many submissions by authors with no connection to the meetings and will be publishing several of these as well.

ENGAGEMENT MARKERS IN THE FEYNMAN LECTURES ON PHYSICS: APPLYING HYLAND’S INTERACTION FRAMEWORK TO SPOKEN ACADEMIC DISCOURSE

The paper presents an analysis of engagement markers in the Lectures on Physics by eminent scientist and Nobel prizewinner R. P. Feynman, based on K. Hyland’s model of interaction in academic discourse as stance and engagement. The Lectures were taught at the California Institute of Technology during 1961-63 and, having been turned into a textbook, are widely used by Physics students even today. It is argued that the Lectures owe their lasting popularity not only to the simplicity of explication, but also to Feynman’s masterful use of interaction devices, particularly reader pronouns, directives, questions, references to sharedness and personal asides. Reader pronouns are analysed in comparison with the MICASE-based reference corpus, with the most common you- and we-clusters being identified. It is established that reader pronouns, directives and questions in the Feynman’s Lectures on Physics mostly perform the functions of anticipating possible objections, eliciting prior knowledge, focusing students’ attention, stimulating their thought and creativity, while references to sharedness and personal asides serve to strengthen the lecturer’s communality with the audience, particularly through the use of humour. We draw the conclusion that Hyland’s taxonomy of engagement markers can be applied to spoken academic discourse in its entirety and can be particularly useful for the description of interactive styles of acknowledged scientists, supplementing depersonaliased corpus research in search for best practices in pedagogy.

Xile Hu

ChemCatChemVolume 11, Issue 14 p. 3127-3127 InterviewFree Access Xile Hu First published: 30 May 2019 https://doi.org/10.1002/cctc.201900931AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Xile Hu was interviewed in celebration of his Royal Society of Chemistry Homogeneous Catalysis Award. Xile Hu Professor Hu was interviewed in celebration of his Royal Society of Chemistry Homogeneous Catalysis Award. Date of birth: August 7, 1978 Position: Professor of Chemistry, Ecole Polytechnique Fédérale de Lausanne (Switzerland) E-mail: [email protected] Homepage: http://lsci.epfl.ch ORCID: 0000-0001-8335-1196 Education: 2000 B.Sc. Peking University (P. R. China). 2004 PhD under the supervision of Prof. Karsten Meyer, University of California at San Diego (USA). 2005–2007 Postdoctoral scholar under the supervision of Prof. Jonas C. Peters, California Institute of Technology (USA). Awards: 2019 Royal Society of Chemistry Homogeneous Catalysis Award 2018 Resonate Award, Caltech 2017 National Latsis Prize of Switzerland Hobbies: Napping; travel (for pleasure); complaining Figure 1Open in figure viewerPowerPoint Xile Hu I admire people who engage themselves to make the world a better place. The thing I like most about my work is the substantial freedom in research. I would have liked to have discovered a reaction that matters. Guaranteed to make me laugh is seeing memes of reviewer 3 (hint: there is a site called shitmyreviewersays). What prompted you to investigate the topics you are interested in? Often I am problem-inspired. But sometimes I enter a new field impulsively, after wandering around intellectually or reading a paper in that field. What aspects of your research do you find most exciting? Our research is broad and encompasses homogeneous, heterogeneous, and biocatalysis. We can both make and measure. Now we try to connect these three traditionally distinct domains in catalysis. Do you have any tips you would like to share with early-career scientists? Originality is probably the best ticket to peer recognition. My 3 top papers: 1“Nickamine and Analogous Nickel Pincer Catalysts for Cross-Coupling of Alkyl Halides and Hydrosilylation of Alkenes”: R. Shi, Z. Zhang, X. Hu, Acc. Chem. Res. 2019, DOI 10.1021/acs.accounts.9b00118. (This account summarizes our work on Nickamine and related nickel pincer compounds, which had lifted my independent career.) 2“An Unconventional Iron Nickel Catalyst for the Oxygen Evolution Reaction”: F. Song, M. M. Busch, B. Lassalle-Kaiser, C.-S. Hsu, E. Petkucheva, M. Bensimon, H. M. Chen, C. Corminboeuf, X. Hu, ACS Cent. Sci. 2019, 5, 558. (Along the development of an OER catalyst with off-scale activity, we proposed a bifunctional mechanism which might overcome the limitation of scaling relationship in OER.) 3“Amorphous Molybdenum Sulfide Films as Catalysts for Electrochemical Hydrogen Production in Water”: D. Merki, S. Fierro, H. Vrubela, X. Hu, Chem. Sci. 2011, 2, 1262. (The discovery of a novel class of HER catalyst. It took almost 2 years to settle the referees, but time has proven the value of the paper, which is cited 100 times a year for the last 8 years.) Volume11, Issue14July 18, 2019Pages 3127-3127 This article also appears in:Catalysis Awards FiguresReferencesRelatedInformation

Camera-based, mobile disease surveillance using Convolutional Neural Networks

Camera-based, mobile disease surveillance using Convolutional Neural Networks

Author Correction: A corridor of exposed ice-rich bedrock across Titan’s tropical region

In the version of this Article originally published, the author Rosaly Lopes was mistakenly affiliated with Northern Arizona University. Her affiliation has now been corrected to: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.

The Impact of Radiation Exposure upon Lithium-Ion Batteries for Future Planned NASA Missions to Europa

NASA is planning to launch a mission entitled the Europa Clipper which is intended to provide a detailed reconnaissance of the Jovian icy moon Europa. With one major objective being to determine the habitability of life on the moon, the mission will involve multiple flybys and will utilize a number of instruments, including an ice-penetrating radar that is intended to measure the thickness of the icy shell and possibly detect a subsurface ocean. As one would expect due to distances involved, the destination of Europa presents a number of technical challenges for the spacecraft, including being exposed to high levels of radiation and extreme temperature environments. Furthermore, NASA has stringent planetary protection protocols that must be followed that involves sterilizing the spacecraft to to avoid any potential contamination. As described previously1,2, the current power subsystem architecture for the Europa Clipper mission involves the use of solar arrays, power management electronics, and a rechargeable lithium-ion battery.3 With respect to the Li-ion battery, we are planning to utilize a “small cell” approach, which will consist of multiple high specific energy small 18650-size Li-ion cells that are assembled into large capacity multi-string batteries. Due to the excellent cell-to-cell reproducibility and proper cell matching, individual cell monitoring and balancing circuitry is not required with this approach. NASA has previously utilized this approach on a number of past missions, including Kepler, Aquarius, and SMAP. To meet the challenging mission requirements, we identified leading candidate cell chemistries that are projected to meet the mission requirements. However, in contrast to these previous missions which have utilized heritage Sony HCM 18650 cells, we are planning on using much higher specific energy cells to reduce the overall spacecraft mass. Given that we would like to use a new cell chemistry, it necessitates performing a cell qualification activity. Furthermore, the candidate cell chemistry must be demonstrated to have good cycle and storage life characteristics, especially since the cruise period to Europa is extremely long and could potentially be over 6.5 years in duration, depending upon the launch vehicle selected. To reduce the bio-burden of spacecraft components, dry heat microbial reduction (DHMR) is typically employed, which involves subjecting the samples to exposure at high temperatures (in excess of 150oC). However, since Li-ion cell technology will rapidly degrade at high temperatures, this methodology is not acceptable and alternative methods of achieving sterility must be adopted. The preferred method with respect to the Li-ion batteries is to subject them to high levels of gamma-irradiation, which has previously been demonstrated to have a minimal to low impact upon the performance characteristics.4,5 To assess the impact that would be sustained by exposure to γ-rays prior to launch to comply with planetary protection protocols, as well as to address the radiation exposure during the course of the mission, we have exposed a number of Li-ion cells and a large capacity battery module to gamma-irradiation (60Co source) at very high levels (up to 20 Mrad) to evaluate the potential impact. In order to demonstrate the impact of irradiation, a number of performance characterization tests were implemented on samples subjected to varying levels of γ-rays (either 12 Mrad or 20 Mrad), including: (i) 100% DOD cycling under various conditions, (ii) charge and discharge rate characterization over a range of temperatures, (iii) module level testing and, (vi) verification of proper functionality of internal safety protection devices. As will be discussed, good performance has been obtained with candidate high specific energy Li-ion cells, and minimal capacity loss was observed after being subjected to high levels of radiation. ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the Europa Clipper Mission. A. Ulloa-Severino, G. A. Carr, D. J. Clark, S. M. Orellana, R. Arellano, M.C. Smart, B.V. Ratnakumar, A. Boca, and S. F. Dawson. October 5, 2016. F. C. Krause, A. Lawrence, M. C. Smart, S. F. Dawson, A. Ulloa-Severino, and B. V. Ratnakumar, 227th ECS Meeting, May 28, 2015. M. C. Smart, F. C. Krause, A. Lawrence, B. V. Ratnakumar, A. Ulloa-Severino, and R. C. Ewell, 232th ECS Meeting, October 5, 2017. B. V. Ratnakumar, M. C. Smart, L. D. Whitcanack, E. D. Davies, and K. B. Chin, J. Electrochem. Soc., 151 (4), A652- A659 (2004). B. V. Ratnakumar, M. C. Smart, L. D. Whitcanack, E. D. Davies, K. B. Chin, F. Deligiannis, and S. Surampudi, J. Electrochem. Soc., 152 (2), A357- A363 (2005).

Gift of Sight: Stem-Cell Patches for Wet and Dry Macular Degeneration.

Regenerative Patch Technologies LLC was founded by Mark Humayun, MD, PhD, and David R. Hinton, MD, from the University of Southern California; and Dennis O. Clegg, PhD, from the University of California, Santa Barbara. The technology to produce the stem cell-based retinal implant is exclusively licensed to Regenerative Patch Technologies LLC from the University of Southern California, the California Institute of Technology, and the University of California, Santa Barbara. Humayun and Hinton have an equity interest in and are consultants for Regenerative Patch Technologies LLC.

How Much Will Gallium Oxide Power Electronics Cost?

Samantha Bench Reese is a senior engineer at the Strategic Energy Analysis Center at National Renewable Energy Laboratory (NREL). As an analyst, Samantha helps put early-stage research problems in context of technoeconomic tradeoffs and analytically shows technology potential through supply-chain analysis, trade-flow mapping, market research, and building bottom-up cost models. Prior to joining NREL, she helped transition products from R&D to volume manufacturing. Samantha's background is in mechanical and electrical engineering. She received an M.S. in Engineering and Applied Science from Yale University and a B.S. in Engineering and Applied Science from California Institute of Technology (Caltech). Timothy Remo is a manufacturing analyst in the Techno-Economic Analysis Group in the Strategic Energy Analysis Center at NREL. Tim’s areas of expertise include cost analysis of semiconductor manufacturing, process development and process optimization, and design of experiments. His research interests include cost-competitive renewable energy alternatives, economics of changing energy costs and demand, and challenges associated with smarter grid technology. Prior to joining NREL, Tim was a process and product engineer in the semiconductor and photovoltaics industry. Tim received his B.S. in Mechanical Engineering from University of South Florida and B.A. in Physics from University of Florida. Johney Green Jr. is an Associate Laboratory Director for Mechanical and Thermal Engineering Sciences (MTES) at NREL. He oversees NREL's transportation, buildings, wind, water, geothermal, advanced manufacturing, and concentrating solar power research programs. Prior to joining NREL, Johney held a number of leadership roles at Oak Ridge National Laboratory (ORNL), served as technical coordinator at the U.S. Department of Energy, and worked with Ford Motor Company. Green has received several awards during his career and served on numerous advisory boards. Dr. Green received his Mechanical Engineering degrees from Georgia Institute of Technology (Ph.D., M.S.) and The University of Memphis (B.S.). Andriy Zakutayev is a scientist at Materials Science Center at NREL, leading a team working on new materials for advanced energy technologies. His research interests include discovery and development of materials for solar cells, Li-ion batteries, fuel cells, power electronics, and other renewable energy technologies. Andriy is an author of more than 100 peer-reviewed publications and a reviewer for more than 50 scientific journals. He has received an EMRS Young Scientist Award along with many other professional recognitions. Dr. Zakutayev received his Ph.D. in Physics from Oregon State University and B.S. in Electronics from Lviv Polytechnic National University (Ukraine).

Navigation: from animal behaviour to guiding principles

![Figure][1] Tritonia diomedea navigating through a sea pen bed in search of prey or mates. Photo credit: Russell Wyeth and James A. Murray. Whether an animal's world is restricted to a few twigs or the avian highways that traverse the planet, creatures must navigate their surroundings

Lithium Plating–a Life-Limiting and Safety Issue in a Li-Ion Cell

Despite their advances and widespread use in various applications for the last two decades, Li-ion batteries continue to exhibit occasional failures from Li plating on the anode. Li plating can have immediate effects on performance and more devastating effects upon the safety, if the Li plating occurs in a dendritic form that could pierce through the separator causing an internal short. Even in a benign form, plated Li—lacking the protective SEI that protects the carbon anode —tends to react with electrolyte which results in a rapid growth in interfacial impedance and capacity loss during cycling. Li plating will manifest whenever intercalation kinetics (into carbon) are slower compared to lithium plating over carbon, despite the lower reversible potential of the latter. Poor cell design factors, i.e., improper matching of anode and cathode in terms of electrochemical capacities and geometric aspects with localized hotspots in current distribution, and inappropriate electrolyte, can cause Li plating on the anode. The nature of the anode, electrolyte and SEI are among the most important factors that can influence Li plating.1 Apart from the design/chemical abnormalities, lithium plating is also triggered by the operational conditions, such as fast charge rates and low operating temperatures relevant to planetary space missions. In our earlier study, we have demonstrated that the choice of the electrolyte is critical in determining the propensity towards lithium plating.2 Specifically, these studies indicate that the Li intercalation kinetics are mainly dictated by the anode surface films (SEI), which in turn could be controlled by a judicious selection of electrolyte solution, i.e., both solvent and salt. We have established a correlation between the poor lithium intercalation kinetics and the propensity towards lithium plating using different electrolytes with different solvent blends and different electrolyte additives. Recently, Li plating was observed in cells upon extended cycling at ambient temperature in a Low Earth Orbit (LEO) satellite simulation condition, involving 30 minutes of discharge and 60 minutes of charge continuously, possibly due to impeded intercalation kinetics at the anode. Likewise, exposure to high intensity radiation environments may have led to Li plating in prototype 18650 cells upon subsequent cycling. In this paper, we will discuss the Li plating phenomenon in these specific examples, and with reference to anode/cathode interfacial kinetics at low temperatures in different electrolytes. ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). REFERENCES B. V. Ratnakumar and M. C. Smart, ECS Trans. 25 (36), 241 (2010).M. C. Smart and B. V. Ratnakumar, J. Electrochem. Soc. 2011, 158 (4), A379.

ACM SIGMETRICS International Workshop on Critical Infrastructure Network Security

The second ACM SIGMETRICS International Workshop on Critical Infrastructure Network Security took place in Irvine, California, USA on June 18th 2018 in conjunction with ACM SIGMETRICS 2018. As in the previous year, the workshop received widespread community support and as a consequence we were able to conduct a successful workshop. The workshop provided a forum for scientists and engineers from research institutions and universities to present their findings on critical infrastructure security. It also provided a forum for an exchange of ideas and in-depth discussions on the future research directions in this area. The workshop featured several invited and contributed talks from researchers from institutions such as the University of Illinois at Urbana-Champaign, Princeton University, Sandia National Laboratories, Delft University (The Netherlands), ENEA (Italy), Northeastern University, Hamburg University (Germany), National University of Singapore, California Institute of Technology, New York University and University of Kentucky. To disseminate the outcome of this workshop, we are pleased to include extended abstracts of selected workshop presentations in Performance Evaluation Review (PER), the quarterly publication of ACM SIGMETRICS. A brief overview of the included papers is outlined below.

A Bibliometric Profile of the Remote Sensing Open Access Journal Published by MDPI between 2009 and 2018

Remote Sensing Open Access Journal (RS OAJ) is an international leading journal in the field of remote sensing science and technology. It was first published in the year 2009 and is currently celebrating tenth year of publications. In this research, a bibliometric analysis of RS OAJ was conducted based on 5588 articles published during the 10-year (2009–2018) time-period. The bibliometric analysis includes a comprehensive set of indicators such as dynamics and trends of publications, journal impact factor, total cites, eigenfactor score, normalized eigenfactor, CiteScore, h-index, h-classic publications, most productive countries (or territories) and institutions, co-authorship collaboration about countries (territories), research themes, citation impact of co-occurrences keywords, intellectual structure, and knowledge commutation. We found that publications of RS OAJ presented an exponential growth in the past ten years. From 2010 to 2017 (for which complete years data were available), the h-index of RS OAJ is 67. From 2009–2018, RS OAJ includes publications from 129 countries (or territories) and 3826 institutions. The leading nations contributing articles, based on 2009–2018 data, and listed based on ranking were: China, United States, Germany, Italy, France, Spain, Canada, England, Australia, Netherlands, Japan, Switzerland and Austria. The leading institutions, also for the same period and listed based on ranking were: Chinese Academy of Sciences, Wuhan University, University of Chinese Academy of Sciences, Beijing Normal University, The university of Maryland, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, China University of Geosciences, United States Geological Survey, German Aerospace Centre, University of Twente, and California Institute of Technology. For the year 2017, RS OAJ had an impressive journal impact factor of 3.4060, a CiteScore of 4.03, eigenfactor score of 0.0342, and normalized eigenfactor score of 3.99. In addition, based on 2009–2018, data co-word analysis determined that “remote sensing”, “MODIS”, “Landsat”, “LiDAR” and “NDVI” are the high-frequency of author keywords co-occurrence in RS OAJ. The main themes of RS OAJ are multi-spectral and hyperspectral remote sensing, LiDAR scanning and forestry remote sensing monitoring, MODIS and LAI data applications, Remote sensing applications and Synthetic Aperture Radar (SAR). Through author keywords citation impact analysis, we find the most influential keyword is Unmanned Aerial Vehicle (UAV), followed, forestry, Normalized Difference Vegetation Index (NDVI), terrestrial laser scanning, airborne laser scanning, forestry inventory, urban heat island, monitoring, agriculture, and laser scanning. By analyzing the intellectual structure of RS OAJ, we identify the main reference publications and find that the themes are about Random Forests, MODIS vegetation indices and image analysis, etc. RS OAJ ranks first in cited journals and third in citing, this indicates that RS OAJ has the internal knowledge flow. Our results will bring more benefits to scholars, researchers and graduate students, who hopes to get a quick overview of the RS OAJ. And this article will also be the starting point for communication between scholars and practitioners. Finally, this paper proposed a nuanced h-index (nh-index) to measure productivity and intellectual contribution of authors by considering h-index based on whether the one is first, second, third, or nth author. This nuanced approach to determining h-index of authors is powerful indicator of an academician’s productivity and intellectual contribution.

What we can learn from safety experts in other fields

Nearly every chemist has some connection to a major safety incident. For me, I started graduate school at the California Institute of Technology a year after graduate student Ramsay Bittar was severely injured when a flask overpressurized and exploded during a synthesis procedure and a shard of glass severed an artery in his neck. Years later, a colleague in the field of bioinorganic chemistry, Dartmouth College professor Karen Wetterhahn, died of mercury poisoning after exposure to dimethylmercury in her lab. Her group was working on science close to mine, and I talked with her students about how to finish their research after her death. My connection to Sheri Sangji came when the National Academies of Sciences, Engineering, and Medicine asked me to chair a committee that would prepare a new report on chemical safety. The study was commissioned partly in response to Sangji’s death, and the academies had a novel

I thought it would never happen to me

“Don’t worry, that would never happen to me” was a common refrain I used with friends and family in the wake of Sheri Sangji’s death. Although the Sangji case rightfully sparked much-needed discussion and action on academic laboratory safety at the national level, in many cases we were (are) much slower to embrace change as individuals. This was certainly the case for me. When she died, I was a third-year graduate student. I’d been working with pyrophorics for several years. I was young and felt invincible. It was difficult to comprehend the potential severe consequences of a lab accident. As a result, Sangji’s death was for me not an instant paradigm shift but rather the start of a gradual awakening to the importance of laboratory safety. In my graduate lab at the California Institute of Technology, one of the most noticeable and important changes after Sangji’s death was that we,

La- and La-/Ce-Doped BaF2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part I

In addition to La-doped barium fluoride (BaF2) crystals, La/Ce co-doped BaF2 crystals were also investigated at the California Institute of Technology, Pasadena, CA, USA. Strong cerium-induced emissions peaked at 305 and 320 nm with a decay time of 25 ns were observed, in addition to the fast and slow scintillation at 220 and 300 nm, respectively. The La/Ce co-doping was also found effective in suppressing the slow component in BaF2. Compared to La-doped crystals, the La/Ce co-doped crystals have a better light output in both 50- and 2500-ns gate. The fast/slow ratio of La/Ce co-doped crystal was found to be about 1/1, similar to La-doping, which is also considered not sufficient for pile-up suppression. A 20-cm-long La/Ce co-doped BaF2 crystal shows also excellent optical quality and light response uniformity.

Challenges in the development and verification of first-principles models in Hall-effect thruster simulations that are based on anomalous resistivity and generalized Ohm’s law**© 2018. California Institute of Technology. Government sponsorship acknowledged.

Since the inception of the Hall-effect thruster more than five decades ago, many theories have been proposed about the source(s) of the anomalous cross-field transport that is known to occur in these devices. Yet, none of these theories has been implemented in two-dimensional (2D) (r–z) simulations and successfully predicted the behavior of the discharge and the erosion of a thruster over different operating conditions and geometries. We present results from numerical experiments with a 2D (r–z) axisymmetric hydrodynamics code that show the plasma solution is relatively insensitive to very large variations in the anomalous transport in some regions of the discharge channel and near-plume. Because the changes of the plasma properties in these regions can be too small or impossible to detect in the laboratory by conventional diagnostics, the verification of a transport model becomes very challenging. Hence, without more advanced diagnostics and improved numerical models, comparisons between plasma measurements and simulation results can lead to wide-ranging theories and scalings of the anomalous resistivity.

La- and La-/Ce-Doped BaF2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part II

In addition to La-doped barium fluoride (BaF2) crystals, La/Ce co-doped BaF2 crystals were also investigated at the California Institute of Technology, Pasadena, CA, USA. Strong cerium-induced emissions peaked at 305 and 320 nm with a decay time of 25 ns were observed, in addition to the fast and slow scintillation at 220 and 300 nm, respectively. The La/Ce co-doping was also found effective in suppressing the slow component in BaF2. Compared to La-doped crystals, the La/Ce co-doped crystals have a better light output in both 50- and 2500-ns gate. The fast/slow ratio of La/Ce co-doped crystal was found to be about 1/1, similar to La-doping, which is also considered not sufficient for pile-up suppression. A 20-cm-long La/Ce co-doped BaF2 crystal shows also excellent optical quality and light response uniformity.

Nobel Prize in Chemistry – 2018

The 2018 Nobel Prize for Chemistry rewards research on the use of bacteria and viruses to generate and screen highly diverse protein sequences for improved catalytic and ligandbinding function. One half of the Prize was awarded to Professor Frances Arnold of the California Institute of Technology (California, USA). The other half was awarded jointly to Professor George P Smith of the University of Missouri (Columbia, USA) and Professor Sir Gregory P Winter of the Medical Research Council’s Laboratory of Molecular Biology (Cambridge, UK). The three winners have been amongst the tallest of stalwarts in combinatorial approaches to protein engineering.