Scaling pair count to next galaxy surveys Plaszczynski, S; Campagne, J E; Peloton, J ...
Monthly notices of the Royal Astronomical Society,
02/2022, Letnik:
510, Številka:
2
Journal Article
Recenzirano
ABSTRACT
Counting pairs of galaxies or stars according to their distance is at the core of real-space correlation analyses performed in astrophysics and cosmology. Upcoming galaxy surveys (LSST, ...Euclid) will measure properties of billions of galaxies challenging our ability to perform such counting in a minute-scale time relevant for the usage of simulations. The problem is only limited by efficient access to the data, hence belongs to the big data category. We use the popular Apache Spark framework to address it and design an efficient high-throughput algorithm to deal with hundreds of millions to billions of input data. To optimize it, we revisit the question of non-hierarchical sphere pixelization based on cube symmetries and develop a new one dubbed the ‘Similar Radius Sphere Pixelization’ (SARSPix) with very close to square pixels. It provides the most adapted indexing over the sphere for all distance-related computations. Using LSST-like fast simulations, we compute autocorrelation functions on tomographic bins containing between a hundred million to one billion data points. In each case, we achieve the construction of a standard pair-distance histogram in about 2 min, using a simple algorithm that is shown to scale, over a moderate number of nodes (16–64). This illustrates the potential of this new techniques in the field of astronomy where data access is becoming the main bottleneck. They can be easily adapted to other use-cases as nearest-neighbours search, catalogue cross-match or cluster finding. The software is publicly available from https://github.com/astrolabsoftware/SparkCorr.
Odorant binding proteins (OBPs) are small soluble proteins found in olfactory systems that are capable of binding several types of odorant molecules. Cantilevers based on polycrystalline diamond ...surfaces are very promising as chemical transducers. Here two methods were investigated for chemically grafting porcine OBPs on polycrystalline diamond surfaces for biosensor development. The first approach resulted in random orientation of the immobilized proteins over the surface. The second approach based on complexing a histidine-tag located on the protein with nickel allowed control of the proteins׳ orientation. Evidence confirming protein grafting was obtained using electrochemical impedance spectroscopy, fluorescence imaging and X-ray photoelectron spectroscopy. The chemical sensing performances of these OBP modified transducers were assessed. The second grafting method led to typically 20% more sensitive sensors, as a result of better access of ligands to the proteins active sites and also perhaps a better yield of protein immobilization. This new grafting method appears to be highly promising for further investigation of the ligand binding properties of OBPs in general and for the development of arrays of non-specific biosensors for artificial olfaction applications.
•We grafted porcine odorant binding protein (OBP) onto diamond surfaces.•Orientation of immobilized OBP could be controlled.•The process has been applied successfully to bio-MEMS sensors.•OBP grafted diamond cantilevers detect odorant molecules such as 2,4-dinitrotoluene.
Hydrogen terminations (C-H) confer to diamond layers specific surface properties such as a negative electron affinity and a superficial conductive layer, opening the way to specific functionalization ...routes. For example, efficient covalent bonding of diazonium salts or of alkene moieties can be performed on hydrogenated diamond thin films, owing to electronic exchanges at the interface. Here, we report on the chemical reactivity of fully hydrogenated High Pressure High Temperature (HPHT) nanodiamonds (H-NDs) towards such grafting, with respect to the reactivity of as-received NDs. Chemical characterizations such as FTIR, XPS analysis and Zeta potential measurements reveal a clear selectivity of such couplings on H-NDs, suggesting that C-H related surface properties remain dominant even on particles at the nanoscale. These results on hydrogenated NDs open up the route to a broad range of new functionalizations for innovative NDs applications development.
Abstract
Although nanodiamonds (NDs) appear as one of the most promising nanocarbon materials available so far for biomedical applications, their risk for human health remains unknown. Our work was ...aimed at defining the cytotoxicity and genotoxicity of two sets of commercial carboxylated NDs with diameters below 20 and 100 nm, on six human cell lines chosen as representative of potential target organs: HepG2 and Hep3B (liver), Caki-1 and Hek-293 (kidney), HT29 (intestine) and A549 (lung). Cytotoxicity of NDs was assessed by measuring cell impedance (xCELLigence® system) and cell survival/death by flow cytometry while genotoxicity was assessed by γ-H2Ax foci detection, which is considered the most sensitive technique for studying DNA double-strand breaks. To validate and check the sensitivity of the techniques, aminated polystyrene nanobeads were used as positive control in all assays. Cell incorporation of NDs was also studied by flow cytometry and luminescent N-V center photoluminescence (confirmed by Raman microscopy), to ensure that nanoparticles entered the cells. Overall, we show that NDs effectively entered the cells but NDs do not induce any significant cytotoxic or genotoxic effects on the six cell lines up to an exposure dose of 250 µg/mL. Taken together these results strongly support the huge potential of NDs for human nanomedicine but also their potential as negative control in nanotoxicology studies.
► A novel tool for attenuated total reflectance (ATR) FTIR employing diamond-coated prism. ► Enhanced sensitivity, resolution and repeatability. ► IR absorption spectra characterizing surface ...moieties, in particular on plasma-oxidized and hydrogenated diamond nanoparticles.
Linear antenna microwave chemical vapor deposition process was used to homogeneously coat a 7cm long silicon prism by 85nm thin nanocrystalline diamond (NCD) layer. To show the advantages of the NCD-coated prism for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of nanoparticles, we apply diamond nanoparticles (DNPs) of 5nm nominal size with various surface modifications by a drop-casting of their methanol dispersions. ATR-FTIR spectra of as-received, air-annealed, plasma-oxidized, and plasma-hydrogenated DNPs were measured in the 4000–1500cm−1 spectral range. The spectra show high spectral resolution, high sensitivity to specific DNP surface moieties, and repeatability. The NCD coating provides mechanical protection against scratching and chemical stability of the surface. Moreover, unlike on bare Si surface, NCD hydrophilic properties enable optically homogeneous coverage by DNPs with some aggregation on submicron scale as evidenced by scanning electron microscopy and atomic force microscopy. Compared to transmission FTIR regime with KBr pellets, direct and uniform deposition of DNPs on NCD-ATR prism significantly simplifies and speeds up the analysis (from days to minutes). We discuss prospects for in situ monitoring of surface modifications and molecular grafting.
•Front and back side SIMS analysis of delta-layer boron-doped is a first for diamond.•Combination of front and back side depth profiling improves delta-layer analyses.•Sharp interfaces are evidenced ...on both sides of the delta-layer boron-doped diamond.•The growth of delta-layer boron doped diamond is now well controlled.
Nowadays the availability of very thin diamond layers in the range of nanometers as well as the possibility to characterize such delta-layer structures are required for the field of photonics and spintronics, but also for the development of next generation high power devices involving boron doping. The fabrication of diamond structures with abrupt interfaces such as superlattices and quantum wells has been recently improved. A very accurate characterization is then essential even though the analysis of such structures is arduous and challenging. SIMS analyses are commonly used to obtain depth profiles of dopants. However, below 10nm in thickness, SIMS induced ion mixing effects which are no longer negligible. Then the raw SIMS profile might differ from the real dopant profile. In this study, we have analyzed a diamond structure containing a thin boron epilayer, especially synthesized to achieve SIMS analysis on both sides and to overcome the effects of ion mixing. We evidence the ion mixing induced by primary ions. Such a structure is a delta diamond layer, comparable to classical boron-doped delta-layer in silicon. Our results show that the growth of boron-doped delta-layer in diamond is now well controlled in terms of thickness and interfaces.
The chemical evolution of the iridium surface along the successive steps of BEN was investigated using electron spectroscopy techniques (XPS, AES). To this end, a sequential study was carried out in ...an UHV analysis chamber connected to a MPCVD reactor. First, experimental results were obtained on iridium surfaces exposed to a methane plasma without bias. They show a sp
2 carbon layer formation on iridium, probably due to the segregation during cooling of carbon solubilized at high temperature in iridium. In this scenario, the iridium surface would be uncovered by carbon as BEN starts. Then, the consequences of BEN were observed: (i) formation of a thicker carbon layer at the iridium surface due to carbon segregation and sub-implantation (ii) chemical modification of iridium neighboring within the first nanometers; (iii) diamond nucleation.
► In this study, we examine iridium surface evolution by spectroscopic analysis. ► Hydrogen methane plasma exposure leads to carbon dissolution into iridium matrix. ► Bias enhanced nucleation enhanced the quantity of carbon. ► Surface analysis reveals several mechanisms competing during BEN on iridium.
Topography and chemical evolutions of the iridium surface in the successive steps of bias-enhanced nucleation and growth were investigated using scanning electron microscopy (SEM), atomic force ...microscopy (AFM), and nano-Auger analyses. This sequential approach, which was performed in localized areas at the nanoscale, provides three new experimental and complementary concepts that can enhance the knowledge of nucleation pathways on iridium. First, SEM imaging at low-acceleration voltage enables the detection of diamond nuclei or stable precursors after the BEN step. Second, domains consist of iridium furrows that are covered by an amorphous carbon overlayer, with a thickness of 6.8nm, according to AFM and X-ray photoemission spectroscopy data. Third, SEM observations also suggest a close relationship between furrows created under ion bombardment and domains in our study conditions. These results prompted us to propose a scheme that describes the topography and surface chemistry of domains.
•Detection of diamond nuclei after the BEN step by SEM.•Domains = iridium furrows covered by an amorphous carbon overlayer.•Close relation between furrows and domains.
The surface chemistry governs most of the physical and chemical properties of nanodiamonds (NDs). X-ray Photoemission Spectroscopy is a method of choice to characterize the surface of NDs. The ...present paper reviews on XPS studies focusing on modifications of surface terminations or grafting of biomolecules and polymers on NDs. The second part illustrates studies in which XPS can even be used as a specific tool to investigate in situ the reactivity and the stability of NDs toward various atmospheres like plasma or UHV annealing.
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•Review on XPS focusing on surface modifications or grafting of nanodiamonds.•XPS allows to investigate the in situ reactivity of nanodiamonds in various environment.•Comparison of XPS analysis with other characterization techniques.
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