Evidence for Strong Electron Correlations in a Nonsymmorphic Dirac Semimetal

Metallic iridium oxides (iridates) provide a fertile playground to explore new phenomena resulting from the interplay between topological protection, spin-orbit and electron-electron interactions. To date, however, few studies of the low energy electronic excitations exist due to the difficulty in synthesising crystals with sufficiently large carrier mean-free-paths. Here, we report the observation of Shubnikov-de Haas quantum oscillations in high-quality single crystals of monoclinic SrIrO3 in magnetic fields up to 35 T. Analysis of the oscillations reveals a Fermi surface comprising multiple small pockets with effective masses up to 4.5 times larger than the calculated band mass. Ab-initio calculations reveal robust linear band-crossings at the Brillouin zone boundary, due to its non-symmorphic symmetry, and overall we find good agreement between the angular dependence of the oscillations and the theoretical expectations. Further evidence of strong electron correlations is realized through the observation of signatures of non-Fermi liquid transport as well as a large Kadowaki-Woods ratio. These collective findings, coupled with knowledge of the evolution of the electronic state across the Ruddlesden-Popper iridate series, establishes monoclinic SrIrO3 as a topological semimetal on the boundary of the Mott metal-insulator transition. © 2021, The Author(s).We gratefully acknowledge useful discussions with A. Rost and D. F. McMorrow. We would also like to thank G. Stenning and D. Nye for help with the instruments in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source, Kuang-Yu Samuel Chang and Roos Leenen for technical assistance with the DFT calculations, and Sebastian Bette for XRD characterizations. We acknowledge the support of the HFML-Radboud University (RU)/Netherlands Organisation for Scientific Research (NWO), a member of the European Magnetic Field Laboratory. This work is part of the research program Strange Metals (Grant 16METL01) of the former Foundation for Fundamental Research on Matter, which is financially supported by the NWO and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 835279-Catch-22). We gratefully acknowledge support from the UK Engineering and Physical Sciences research council, grant EP/N034694/1. We acknowledge collaborative support from A.S. Gibbs, D. Fortes and the ISIS Crystallography Group for making available the 193Ir for the isotope work. Experiments at the ISIS Neutron and Muon Source were supported by a beamtime allocation RB1990395, DOI:10.5286/ISIS.E.RB1990395, from the Science and Technology Facilities Council. The work of D. P. and V. M. was supported by Act 211 Government of the Russian Federation, contract 02.A03.21.0006

Magnetic anisotropy of individually addressed spin states

Controlling magnetic anisotropy is a key requirement for the fundamental understanding of molecular magnetism and is a prerequisite for numerous applications in magnetic storage, spintronics, and all-spin logic devices. In order to address the question of molecular magnetic anisotropy experimentally, we have synthesized single crystals of a molecular spin system containing four antiferromagnetically coupled s=5/2 manganese(II) ions. Using low-temperature cantilever magnetometry, we demonstrate the selective population of the S=0,1,...,10 spin states upon application of magnetic fields up to 33 T and map the magnetic anisotropy of each of these states. We observe a strong dependence of the shape and size of the magnetic anisotropy on the populated spin states, and, in particular, reveal an anisotropy reversal upon going from the lowest to the highest spin state

A prospective study on the risk of exposure to HIV during surgery in Zambia

OBJECTIVE: To investigate the relative risk of occupational HIV transmission for surgeons practising in tropical Africa compared with their western colleagues. DESIGN AND SETTING: From June to November 1993, a prospective study was performed at St Francis' Hospital, Katete, Zambia (350-bed hospital which serves a community of 300,000 people). METHODS: The HIV seroprevalence among consecutive surgical patients and the incidence of occupational parenteral exposures to blood during surgery were prospectively studied in a Zambian district hospital. HIV seroprevalence was determined by taking blood from the surgical patients on admission into the operating theatre. Serum was stored at -20 degrees C and transported to the Academic Medical Centre of the University of Amsterdam, where the presence of HIV antibodies was tested by enzyme immunoassay and seropositive samples confirmed by Western blot. Number of parenteral exposures during the study period was scored by interviewing the seven surgeons and their personnel after each surgical procedure about accidental parenteral exposures to blood. The total number of parenteral exposures per surgeon per year was obtained by extrapolation. The cumulated risk of seroconversion due to parenteral blood exposure can be calculated as: 1-(1-fp)ny, where f is the population seroprevalence, p the chance of transmission per incident (estimated to be 0.46%), n the number of parenteral exposures per year and y the years of practice. RESULTS: HIV seroprevalence in the surgical patient group was 22.3%. Twelve parenteral exposures to blood (surgeons, n = 8; other personnel, n = 4) took place in 1161 operations. Number of parenteral exposures per surgeon was extrapolated to three per year. The non-dominant index finger was exposed in 10 out of the 12 parenteral exposures. Based on these data, the risk of contracting HIV infection for a surgeon practising in Zambia for 5 years is 1.5%. The risk for a surgeon working in a western hospital when f = 0.23%, n = 20 per year (5.6% of 350 operations) and y = 5 is estimated at 0.1%. CONCLUSIONS: Although occupational exposure rate was relatively low, the HIV seroprevalence was so high that the relative cumulated seroconversion risk for surgeons in tropical Africa is estimated to be 15 times higher than in western countries. This implies that health-care organizations should bear in mind that each year one out of 300 employees working in tropical Africa may become occupationally infected with HIV. A prospective study conducted in 1993 at St Francis' Hospital in Katete, Zambia, indicated that the human immunodeficiency virus (HIV) seroconversion risk among surgeons in tropical Africa may be 15 times higher that in developed countries. During the six-month study period, surgeons recorded any parenteral blood exposure and serum samples from 296 patients randomly selected from the 1078 patients undergoing surgery in this period were analyzed; of these, 66 (22.3%) were HIV-positive. During the 1161 surgical procedures, there were 12 (1%) superficial parenteral exposures, four of which were found to involve HIV-infected blood. These exposures included 10 needle-sticks with a non-hollow suture needle, one hand laceration, and one splash to the eye. Half involved obstetricians/gynecologists. For a surgeon working in Zambia for five years, the risk of contracting HIV through parenteral exposure can--on the basis of this study--be calculated at 1.5% given a 22.3% patient seroprevalence rate and an average of three exposures per year (0.7% of 400 operations per year per surgeon). For a western surgeon, this risk is 0.1% (0.23% seroprevalence rate and 20 accidental injuries per year--5.6% of 350 operations). The lower number of parenteral exposures among Zambian surgeons reflects the lack of power tools in the tropics and the relative simplicity of surgical procedures. On the basis of these findings, it can be estimated that one in every 300 surgical employees in tropical Africa will become occupationally infected with HIV, and the risk of exposure can be expected to increase along with increases in HIV seroprevalenc

Photoracemization-Based Viedma Ripening of a BINOL Derivative

Viedma ripening is a deracemization process that has been used to deracemize a range of chiral molecules. The method has two major requirements: the compound needs to crystallize as a conglomerate and it needs to be racemizable under the crystallization conditions. Although conglomerate formation can be induced in different ways, the number of racemization methods is still rather limited. To extend the scope of Viedma ripening, in the present research we applied UV-light-induced racemization in a Viedma ripening process, and report the successful deracemization of a BINOL derivative crystallizing as a conglomerate. Irradiation by UV light activates the target compound in combination with an organic base, required to promote the excited-state proton transfer (ESPT), leading thereafter to racemization. This offers a new tool towards the development of Viedma ripening processes, by using a cheap and “green” catalytic source like UV light to racemize suitable chiral compounds

The Crystalline Sponge Method in Water

The crystalline sponge method entails the elucidation of the (absolute) structure of molecules from a solution phase using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals. The host crystal that is most often used decomposes in protic or nucleophilic solvents or when guest molecules with Lewis basic substituents are introduced. Here we disclose a new class of (water) stable host crystals based on f-block metals. We show that these hosts not only increase the scope of the crystalline sponge method to a wider array of solvents and guests, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry

Photoracemization‐Based Viedma Ripening of a BINOL Derivative

BINOL=1,1’‐Bi‐2‐naphthol. Abstract Viedma ripening is a deracemization process that has been used to deracemize a range of chiral molecules. The method has two major requirements: the compound needs to crystallize as a conglomerate and it needs to be racemizable under the crystallization conditions. Although conglomerate formation can be induced in different ways, the number of racemization methods is still rather limited. To extend the scope of Viedma ripening, in the present research we applied UV‐light‐induced racemization in a Viedma ripening process, and report the successful deracemization of a BINOL derivative crystallizing as a conglomerate. Irradiation by UV light activates the target compound in combination with an organic base, required to promote the excited‐state proton transfer (ESPT), leading thereafter to racemization. This offers a new tool towards the development of Viedma ripening processes, by using a cheap and “green” catalytic source like UV light to racemize suitable chiral compounds

Ultrasonic specimen radiography for non-palpable breast lesions

A retrospective review of ultrasound guided breast excisional biopsies performed in a Surgical Unit of Princess Alexandra Hospital in 1998-99 was undertaken to assess the use of ultrasound specimen radiography. In this series a total of 55 localization biopsies were performed for impalpable lesions in 53 women. In 21 patients (38%), specimen ultrasound was used to confirm that the lesion in question had been excised, whereas for 34 lesions (62%), specimen X-ray was undertaken. In a total of six cases (10.9% overall) the radiographic abnormality was seen on ultrasound only. Real-time specimen sonography is a technique which is very appropriately utilized in conjunction with ultrasound guided excisions and can be easily performed either in the radiology department or the operative suite With minimal time delay. It could have particular application for lesions that are detected in younger women with dense breast parenchyma. The results of this review confirm specimen sonography to be a reliable technique. (C) 2002 Elsevier Science Ltd. All rights reserved