Optical Heterodyne-Detected Raman-Induced Kerr Effect (OHD-RIKE) Microscopy

Label-free microscopy based on Raman scattering has been increasingly used in biomedical research to image samples that cannot be labeled or stained. Stimulated Raman scattering (SRS) microscopy allows signal amplification of the weak Raman signal for fast imaging speeds without introducing the nonresonant background and coherent image artifacts that are present in coherent anti-Stokes Raman scattering (CARS) microscopy. Here we present the Raman-induced Kerr effect (RIKE) as a contrast for label-free microscopy. RIKE allows us to measure different elements of the nonlinear susceptibility tensor, both the real and imaginary parts, by optical heterodyne detection (OHD-RIKE). OHD-RIKE microscopy provides information similar to polarization CARS (P-CARS) and interferometric CARS (I-CARS) microscopy, with a simple modification of the two-beam SRS microscopy setup. We show that, while OHD-RIKE microspectroscopy can be in principle more sensitive than SRS, it does not supersede SRS microscopy of heterogeneous biological samples, such as mouse skin tissue, because it is complicated by variations of linear birefringence across the sample.Chemistry and Chemical Biolog

Maternal exposure to ambient black carbon particles and their presence in maternal and fetal circulation and organs : an analysis of two independent population-based observational studies

Funding European Research Council, Flemish Scientific Research Foundation, Kom op Tegen Kanker, UK Medical Research Council, and EU Horizon 2020. Acknowledgments The ENVIRONAGE birth cohort was initiated by the European Research Council (ERC-2012-StG 310898) and received additional funding from the Flemish Scientific Research Foundation and Kom op Tegen Kanker (KoTK). The detection equipment was funded by the METHUSALEM Program and the INCALO project (ERC-PoC). We acknowledge the Flemish Scientific Research Foundation (FWO; 1150920N to EB and G082317N). The SAFeR study was funded by the UK Medical Research Council (MR/L010011/1 and MR/P011535/1) and the EU's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie project PROTECTED (grant agreement number 722634) and FREIA project (grant agreement number 825100) as well as by NHS Grampian Endowments grants (16/11/056, 17/034, 18/14, 19/029, and 20/031) to PAF. We thank the midwives from the maternity ward of the East-Limburg Hospital in Genk, Belgium, for coordinating and supporting the study at the ward. We thank the Advanced Optical Microscopy Centre for the maintenance of the microscopic instruments. Moreover, we thank our colleagues from the Centre for Environmental Sciences for their hard work in collecting and processing the samples for the ENVIRONAGE birth cohort. Additionally, we thank the NHS Grampian Research Nurses and NHS Grampian R&D for their tireless recruitment work for the SAFeR study. We thank the past and present SAFeR team for their hard work with the fetuses and placentae. Finally, we thank the NHS Grampian Biorepository for their oversight role in SAFeR and assistance in processing and preparation of tissue sections.Peer reviewedPublisher PD

Label-Free Live-Cell Imaging of Nucleic Acids Using Stimulated Raman Scattering Microscopy

Imaging of nucleic acids is important for studying cellular processes such as cell division and apoptosis. A noninvasive label-free technique is attractive. Raman spectroscopy provides rich chemical information based on specific vibrational peaks. However, the signal from spontaneous Raman scattering is weak and long integration times are required, which drastically limits the imaging speed when used for microscopy. Coherent Raman scattering techniques, comprising coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy, overcome this problem by enhancing the signal level by up to five orders of magnitude. CARS microscopy suffers from a nonresonant background signal, which distorts Raman spectra and limits sensitivity. This makes CARS imaging of weak transitions in spectrally congested regions challenging. This is especially the case in the fingerprint region, where nucleic acids show characteristic peaks. The recently developed SRS microscopy is free from these limitations; excitation spectra are identical to those of spontaneous Raman and sensitivity is close to shot-noise limited. Herein we demonstrate the use of SRS imaging in the fingerprint region to map the distribution of nucleic acids in addition to proteins and lipids in single salivary gland cells of Drosophila larvae, and in single mammalian cells. This allows the imaging of DNA condensation associated with cell division and opens up possibilities of imaging such processes in vivo.Chemistry and Chemical Biolog

Degradation of methylammonium lead iodide perovskite structures through light and electron beam driven ion migration

[Image: see text] Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques

Разработка системы измерения производительности реализаций blockchain

Долголев Филипп Петрович Разработка системы измерения производительности реализаций blockchain Старший преподаватель кафедры системного программирования Кириленко Яков Александрович При разработке приложений на основе технологии blockchain, из-за наличия множества различных реализаций, разработчики сталкиваются с проблемой выбора. Один из важных критериев при выборе - производительность. В процессе поиска системы, позволяющей измерить производительность различных реализаций blockchain, не обнаружены ни проприетарные системы, ни с открытым исходным кодом. В рамках этой работы рассматривается разработка модульной системы, решающей эту проблему. Использованных источников: 18 Долголев, Ф. П. Разработка системы измерения производительности реализаций blockchain: выпускная квалификационная работа: защищена 01.06.2017 / Долголев Филипп Петрович. – СПб., 2017. – 21 с. – Библиография: с. 20–21.Filipp Dolgolev Blockchain Implementations Benchmarking Tool senior lecturer, dept. of software engineering Iakov Kirilenko Mathematics & mechanics, software engineering department Since there are many different types of blockchain technologies, developers are faced with a dilemma of which technology to choose when developing applications for a particular use case. One of the most important criteria effecting the selection is performance. During our research, we were unable to source either proprietary, or open source solutions allowing to benchmark various blockchain technologies performances. In this context, we are considering the development of such a solution. Sources cited: 18 Dolgolev, F. Blockchain Implementations Benchmarking Tool: Graduation thesis: Defended 01.06.2017 / Filipp Dolgolev. – St. Petersburg., 2017. – 21 pp. – Bibliography: pp. 20–21

Placental-fetal distribution of carbon particles in a pregnant rabbit model after repeated exposure to diluted diesel engine exhaust

BACKGROUND: Airborne pollution particles have been shown to translocate from the mother's lung to the fetal circulation, but their distribution and internal placental-fetal tissue load remain poorly explored. Here, we investigated the placental-fetal load and distribution of diesel engine exhaust particles during gestation under controlled exposure conditions using a pregnant rabbit model. Pregnant dams were exposed by nose-only inhalation to either clean air (controls) or diluted and filtered diesel engine exhaust (1 mg/m 3) for 2 h/day, 5 days/week, from gestational day (GD) 3 to GD27. At GD28, placental and fetal tissues (i.e., heart, kidney, liver, lung and gonads) were collected for biometry and to study the presence of carbon particles (CPs) using white light generation by carbonaceous particles under femtosecond pulsed laser illumination. RESULTS: CPs were detected in the placenta, fetal heart, kidney, liver, lung and gonads in significantly higher amounts in exposed rabbits compared with controls. Through multiple factor analysis, we were able to discriminate the diesel engine exposed pregnant rabbits from the control group taking all variables related to fetoplacental biometry and CP load into consideration. Our findings did not reveal a sex effect, yet a potential interaction effect might be present between exposure and fetal sex. CONCLUSIONS: The results confirmed the translocation of maternally inhaled CPs from diesel engine exhaust to the placenta which could be detected in fetal organs during late-stage pregnancy. The exposed can be clearly discriminated from the control group with respect to fetoplacental biometry and CP load. The differential particle load in the fetal organs may contribute to the effects on fetoplacental biometry and to the malprogramming of the fetal phenotype with long-term effects later in life

A unique recipe for glass beads at Iron Age Sardis

In large parts of the Mediterranean recipes for the earliest man-made glass changed from melting mixtures of crushed quartz pebbles and halophytic plant ashes in the Late Bronze Age to the use of quartz sands and mineral soda during the Early Iron Age. Not much is known about this transition and the experimental materials which would inevitably have been connected to such technological change. In this paper we present a unique snapshot of developments in glass technology in Anatolia during the Middle Iron Age, when glass is still a relatively rare commodity. The present work focusses on black glass beads decorated with yellow trails from eighth to seventh century BCE Sardis, glass beads that are very rare for this period, and on this site. A full elemental analysis of the beads was made, and Sr, Pb and B isotope ratios were determined. This study reveals the use of a combination of a previously unknown source of silica and of mineral soda, giving rise to elevated (granite-like) Sr isotope signatures, as well as high alumina and B concentrations. The yellow trails of glass on the beads consist of lead-tin yellow type II, lead stannate, showing the earliest occurrence of this type of opacifier/colourant so far, predating any other findings by at least four centuries. The production of these glass beads may be local to Sardis and experimental in nature. It is therefore suggested that Sardis may have played its role in the technological development of the glass craft during the Iron Age

Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites

The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster's optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics and bioimaging