Search for: All records

Nickel stable isotopes (δ⁶⁰Ni) provide insight to Ni biogeochemistry in the modern and past oceans. Here, we present the first Pacific Ocean high‐resolution dissolved Ni concentration and δ⁶⁰Ni data, from the US GEOTRACES GP15 cruise. As in other ocean basins, increases in δ⁶⁰Ni toward the surface ocean are observed across the entire transect, reflecting preferential biological uptake of light Ni isotopes, however the observed magnitude of fractionation is larger in the tropical Pacific than the North Pacific Subtropical Gyre. Such surface ocean fractionation by phytoplankton should accumulate isotopically lighter Ni in the deep Pacific, yet we find that North Pacific deep ocean δ⁶⁰Ni is similar to previously reported values from the deep Atlantic. Finally, we find that seawater dissolved δ⁶⁰Ni in regions with hydrothermal input can be either higher or lower than background deep ocean δ⁶⁰Ni, depending on vent geochemistry and proximity.

 

This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (WDS) for Paleoclimatology. The associated NCEI study type is Paleoceanography. The data include parameters of paleocean (oxygen isotopes) with a geographic location of North Atlantic Ocean. The time period coverage is from 22423 to 563 in calendar years before present (BP). See metadata information for parameter and study location details. Please cite this study when using the data. 

Variations in the Atlantic Meridional Overturning Circulation (AMOC) redistribute heat and nutrients, causing pronounced anomalies of temperature and nutrient concentrations in the subsurface ocean. However, exactly how millennial‐scale deglacial AMOC variability influenced the subsurface is debated, and the role of other deglacial forcings of subsurface temperature change is unclear. Here, we present a new deglacial temperature reconstruction, which, with published records, helps assess competing hypotheses for deglacial warming in the upper tropical North Atlantic. Our record provides new evidence of regional subsurface warming in the western tropical North Atlantic within the core of modern Antarctic Intermediate Water (AAIW) during Heinrich Stadial 1 (HS1), an early deglacial interval of iceberg discharge into the North Atlantic. Our results are consistent with model simulations that suggest subsurface heat accumulates in the northern high‐latitude convection regions and along the upper AMOC return path when the AMOC weakens, and with warming due to rising greenhouse gases. Warming of AAIW may have also contributed to warming in the tropics at modern AAIW depths during late HS1. Nutrient andreconstructions from the same site suggest a link between AMOC intensity and the northward extent of AAIW in the northern tropics across the deglaciation and on millennial time scales. However, the timing of the initial deglacial increase in AAIW to the northern tropics is ambiguous. Deglacial trends and variability ofin the upper North Atlantic have likely biased temperature reconstructions based on the elemental composition of calcitic benthic foraminifera.

 

Abstract In two-dimensional (2D) NbSe 2 crystal, which lacks inversion symmetry, strong spin-orbit coupling aligns the spins of Cooper pairs to the orbital valleys, forming Ising Cooper pairs (ICPs). The unusual spin texture of ICPs can be further modulated by introducing magnetic exchange. Here, we report unconventional supercurrent phase in van der Waals heterostructure Josephson junctions (JJs) that couples NbSe 2 ICPs across an atomically thin magnetic insulator (MI) Cr 2 Ge 2 Te 6 . By constructing a superconducting quantum interference device (SQUID), we measure the phase of the transferred Cooper pairs in the MI JJ. We demonstrate a doubly degenerate nontrivial JJ phase ( ϕ ), formed by momentum-conserving tunneling of ICPs across magnetic domains in the barrier. The doubly degenerate ground states in MI JJs provide a two-level quantum system that can be utilized as a new dissipationless component for superconducting quantum devices. Our work boosts the study of various superconducting states with spin-orbit coupling, opening up an avenue to designing new superconducting phase-controlled quantum electronic devices. 

The field of Mechatronics and Robotics Engineering (MRE) is emerging as a distinct academic discipline. Previously, courses in this field have been housed in departments of Mechanical Engineering, Electrical Engineering, or Computer Science, instead of a standalone department or curriculum. More recently, single, freestanding courses have increasingly grown into course sequences and concentrations, with entire baccalaureate and graduate degree programs now being offered. The field has been legitimized in recent years with the National Center for Education Statistics creating the Classification of Instructional Programs (CIP) code 14.201 Mechatronics, Robotics, and Automation Engineering. As of October 2019, ABET accredits a total of 9 B.S. programs in the field: 5 Mechatronics Engineering, 3 Robotics Engineering, 1 Mechatronics and Robotics Engineering, and none in Automation Engineering. Despite recent tremendous and dynamic growth, MRE lacks a dedicated professional organization and has no discipline-specific ABET criteria. As the field grows more important and widespread, it becomes increasingly relevant to formalize and standardize the curricula of these programs. This paper begins a conversation about the contents of a cohesive concept inventory for MRE. The impetus for this effort grew from a set of four industry and government sponsored workshops held around the country named the Future of Mechatronics and Robotics Engineering (FoMRE). These workshops brought together multidisciplinary academic professionals and industry leaders in the field, and ran from September 2018 to September 2019. The study presented here focuses primarily on programs at the baccalaureate level, but informs discussion at the graduate level as well. A survey is prepared with lists of potential concept inventory items, and asks university faculty, students and practicing engineers to identify which concepts lie at the core of MRE. Because of the interdisciplinary nature of the field, a wide range of basic concepts including physical quantities and units, circuit analysis, digital logic, electronics, programming, computer-aided design, solid and fluid mechanics, chemistry, dynamic systems and controls, and mathematics are considered. Questions ask participants to rank the priority or importance of potential core concepts from these categories and also provide opportunities for open-ended response. The results of this survey identify gaps between existing undergraduate curricula, student experience, and employer expectations, and continuing work will provide insight into the direction of a unifying curricular design for MRE education.