| 61. |
- Nawaz, S., et al.
(författare)
-
Explainable machine learning for diffraction patterns
- 2023
-
Ingår i: Journal of applied crystallography. - : International Union of Crystallography (IUCr). - 0021-8898 .- 1600-5767. ; 56:5, s. 1494-1504
-
Tidskriftsartikel (refereegranskat)abstract
- Serial crystallography experiments at X-ray free-electron laser facilities produce massive amounts of data but only a fraction of these data are useful for downstream analysis. Thus, it is essential to differentiate between acceptable and unacceptable data, generally known as 'hit' and 'miss', respectively. Image classification methods from artificial intelligence, or more specifically convolutional neural networks (CNNs), classify the data into hit and miss categories in order to achieve data reduction. The quantitative performance established in previous work indicates that CNNs successfully classify serial crystallography data into desired categories [Ke, Brewster, Yu, Ushizima, Yang & Sauter (2018). J. Synchrotron Rad. 25, 655-670], but no qualitative evidence on the internal workings of these networks has been provided. For example, there are no visualization methods that highlight the features contributing to a specific prediction while classifying data in serial crystallography experiments. Therefore, existing deep learning methods, including CNNs classifying serial crystallography data, are like a 'black box'. To this end, presented here is a qualitative study to unpack the internal workings of CNNs with the aim of visualizing information in the fundamental blocks of a standard network with serial crystallography data. The region(s) or part(s) of an image that mostly contribute to a hit or miss prediction are visualized.
|
|
| 62. |
- Nawaz, Shahid, 1978, et al.
(författare)
-
Microwave Response of Superconducting YBa2Cu3O7-delta Nanowire Bridges Sustaining the Critical Depairing Current: Evidence of Josephson-like Behavior
- 2013
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:16, s. 167004-
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the zero-field critical supercurrent of YBa2Cu3O7-delta bridges patterned from 50 nm thick films as a function of bridge width, ranging from 2 mu m to 50 nm. The critical current density monotonically increases for decreasing bridge width even for widths smaller than the Pearl length. This behavior is accounted for by considering current crowding effects at the junction between the bridge and the wider electrodes. Comparison to numerical calculations of the current distributions in our bridge geometries of various widths yields a (local) critical current density at 4.2 K of 1.3 x 10(8) Lambda/cm(2), the Ginzburg Landau depairing current density. The observation of up to 160 Shapiro-like steps in the current voltage characteristics under microwave irradiation substantiates the pristine character of our nanobridges with cross sections as small as 50 x 50 nm(2).
|
|
| 63. |
- Nawaz, Sohail, et al.
(författare)
-
Migration and chemical consumption of deltamethrin and piperonyl butoxide from polyethylene in aqueous media
- 2013
-
Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 4:1, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- Deltamethrin (DM), an important insecticide (synthetic pyrethroid) together with synergist piperonyl butoxide (PBO), is used for food storage and insect control purposes. It is often impregnated in polymers for controlled and effective release of insecticide. The migration and chemical consumption of DM and PBO from moulded polyethylene sheets was studied. The thermal behaviour of pristine DM and the prepared polyethylene compound was studied by differential scanning calorimetry. DM did not crystallize and remained in a liquid state after cooling to room temperature. Evaporation rates and activation energies of evaporation were determined by thermogravimetry for pristine DM, PBO, a solution of DM and PBO and for the PE compound. Evaporation from the DM/PBO solution was greater than that predicted from the evaporation rates of the individual compounds, which suggested that the DM/PBO solution obeyed non-ideal solution properties. The migration of DM and PBO from the polyethylene was studied in liquid water at 80 and 95 °C and in air of different relative humidities (60 and 80%) at 80 °C. Exposure to liquid water caused degradation and hydrolysis of the ester bond in DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas the loss of DM and PBO in air at 80°C (60 and 80 %RH) was negligible over 30 days.
|
|
| 64. |
- Papasikas, N, et al.
(författare)
-
Interpretation of reflections from the central part of the Siljan Ring impact structure based on results from the Stenberg-1 borehole
- 1997
-
Ingår i: Tectonophysics. - : Elsevier. - 0040-1951 .- 1879-3266. ; 269:3-4, s. 237-245
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In 1984, 1985 and 1990, several multichannel seismic reflection profiles were shot over the Siljan Ring, a meteorite impact structure believed to have been formed approximately 360 Ma ago. The bedrock of the area consists mainly of gneisses and granites and the ring itself of Palaeozoic sedimentary rocks lying on top granites. Dolerite dikes of different age and orientation have been mapped in the area. The existence of dolerite intrusions at depth has been verified through the drilling of two deep boreholes, Gravberg-1 and Stenberg-1. Interpretation of seismic data and borehole data from the Gravberg-1 borehole showed a strong correlation between high-amplitude subhorizontal reflections and dolerite sills.Geophysical and geological well-logging in the Stenberg-1 borehole showed the occurrence of dolerites in the borehole. Profile 4, running E-W across the borehole, has been reprocessed in order to improve the seismic image. Several thick dolerites below 5.7 km in the borehole correlate with high-amplitude reflectors on the seismic section. Both the logging data and the seismic interpretation suggest that these intrusions are subhorizontal and laterally continuous. Above 5.7 km in the borehole, the dolerites are thinner and are in some cases associated with fracture zones. On the seismic section at these depths there is a complex system of weaker dipping reflectors. Some of these dipping reflectors correlate with either fracture zones, thin dolerites or a combination of both.
|
|
| 65. |
- Papasodoro, Charles, et al.
(författare)
-
Area, elevation and mass changes of the two southernmost ice caps of the Canadian Arctic Archipelago between 1952 and 2014
- 2015
-
Ingår i: The Cryosphere. - : European Geosciences Union (EGU). - 1994-0416 .- 1994-0424. ; 9, s. 1535-1550
-
Tidskriftsartikel (refereegranskat)abstract
- Grinnell and Terra Nivea Ice Caps are located onthe southern Baffin Island, Nunavut, in the Canadian Arctic Archipelago. These relatively small ice caps have received little attention compared to the much larger ice masses further north. Their evolution can, however, give valuable information about the impact of the recent Arctic warming at lower latitudes (i.e. ∼62.5◦ N). In this paper, we measure or estimate historical and recent changes of area, elevation and mass of both ice caps using in situ, airborne and spaceborne data sets, including imagery from the Pléiades satellites. The area of Terra Nivea Ice Cap has decreased by 34 % since the late 1950s, while that of Grinnell Ice Cap has decreased by 20 % since 1952. For both ice caps, the areal reduction accelerated at the beginning of the 21st century. The estimated glacier-wide mass balance was−0.37 ± 0.21 m a^−1 water equivalent (w.e.) over Grinnell Ice Cap for the 1952–2014 period, and −0.47 ± 0.16 m a^−1 w.e. over Terra Nivea Ice Cap for the 1958/59–2014 period. Terra Nivea Ice Cap has experienced an accelerated rate of mass loss of −1.77 ± 0.36 m a^−1 w.e. between 2007 and 2014.This rate is 5.9 times as negative when compared to the 1958/59–2007 period (−0.30 ± 0.19 m a^−1 w.e.) and 2 times as negative when compared to the mass balance of other glaciers in the southern parts of Baffin Island over the 2003– 2009 period. A similar acceleration in mass loss is sus-pected for the Grinnell Ice Cap, given the calculated elevation changes and the proximity to Terra Nivea Ice Cap. The recent increase in mass loss rates for these two ice caps is linked to a strong near-surface regional warming and a lengthening of the melt season into the autumn that may beindirectly strengthened by a later freezing of sea ice in the Hudson Strait sector. On a methodological level, our study illustrates the strong potential of Pléiades satellite data to unlock the underexploited archive of old aerial photographs.
|
|
| 66. |
- Papaspiropoulos, G., et al.
(författare)
-
High sensitivity elemental analysis methodology for upper tropospheric aerosol
- 1999
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 150:1-4, s. 356-362
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a sampling and analysis tool for aerosol particles has been developed. Its purpose is to characterize upper tropospheric aerosols, where concentrations are low. Since measurements will be made from an airplane, a time resolution of one hour is desirable. These conditions require efficient sampling and analysis with low detection limits. To accomplish this, our sampler uses impaction, concentrating the aerosol deposit on a small area. The impactor has 14 parallel sampling lines which are used sequentially to achieve the time resolution. The elemental analysis is done with Particle-Induced X-ray Emission (PIXE), profiting from its high absolute sensitivity. The aerosol is expected to contains primarily sulphur (S) and emphasis is placed on this element, however the multi-elemental nature of PIXE is of course used. Several substrates have been investigated regarding minimum detection limits. Scanning Transmission Ion Macroscopy (STIM) analysis has been conducted on two outdoor aerosol samples, rendering three-dimensional images and mass distribution profiles. The setup was tested at ground level with high time resolution (5 min). Results show that the detection capabilities are excellent.
|
|
| 67. |
|
|
| 68. |
- Radnell, David, et al.
(författare)
-
Dirichlet's problem and Sokhotski-Plemelj's jump formula on Weil-Petersson-Class quasidisks
- 2016
-
Ingår i: Annales Academiae Scientiarum Fennicae Mathematica. - : Finnish Academy of Science and Letters. - 1239-629X .- 1798-2383. ; 41:1, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- We show the solvability of the Dirichlet problem on Weil–Petersson class quasidisks and establish a Sokhotski–Plemelj jump formula for Weil–Petersson class quasicircles. Furthermore we show that the resulting Cauchy projections are bounded. In both cases the boundary data belongs to a certain conformally invariant Besov space. Moreover we show that the WP-class quasicircles are chord-arc curves.
|
|
| 69. |
- Radnell, David, et al.
(författare)
-
Quasiconformal maps of bordered Riemann surfaces with L2 Beltrami differentials
- 2017
-
Ingår i: Journal d'Analyse Mathematique. - : Springer Science and Business Media LLC. - 0021-7670 .- 1565-8538. ; 132:1, s. 229-245
-
Tidskriftsartikel (refereegranskat)abstract
- Let Σ be a Riemann surface of genus g bordered by n curves homeomorphic to the circle S1 . Consider quasiconformal maps f : Σ → Σ1 such that the restriction to each boundary curve is a Weil-Petersson class quasisymmetry. We show that any such f is homotopic to a quasiconformal map whose Beltrami differential is L2 with respect to the hyperbolic metric on Σ. The homotopy H(t,·) : Σ → Σ1 is independent of t on the boundary curves; that is H(t,p) = f(p) for all p ∈ ∂Σ.
|
|
| 70. |
- Radnell, David, et al.
(författare)
-
Quasiconformal Teichmüller theory as an analytical foundation for two dimensional conformal field theory
-
Ingår i: Contemporary Mathematics. - 0271-4132 .- 1098-3627.
-
Tidskriftsartikel (refereegranskat)abstract
- The functorial mathematical definition of conformal field theory was first formulated approximately 30 years ago. The underlying geometric category is based on the moduli space of Riemann surfaces with parametrized boundary components and the sewing operation. We survey the recent and careful study of these objects, which has led to significant connections with quasiconformal Teichmüller theory and geometric function theory. In particular we propose that the natural analytic setting for conformal field theory is the moduli space of Riemann surfaces with so-called Weil-Petersson class parametrizations. A collection of rigorous analytic results is advanced here as evidence. This class of parametrizations has the required regularity for CFT on one hand, and on the other hand are natural and of interest in their own right in geometric function theory.
|
|
