1. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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2. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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3. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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4. |
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5. |
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6. |
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7. |
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8. |
- Cirasuolo, M., et al.
(författare)
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MOONS: the Multi-Object Optical and Near-infrared Spectrograph for the VLT
- 2014
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Ingår i: Ground-based and Airborne Instrumentation for Astronomy V. - : SPIE. - 1996-756X .- 0277-786X. ; 9147, s. 91470-91470
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Konferensbidrag (refereegranskat)abstract
- MOONS (the Multi-Object Optical and Near-infrared Spectrograph) has been selected by ESO as a third-generation instrument for the Very Large Telescope (VLT). The light grasp of the large collecting area offered by the VLT (8.2m diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8 -1.8 mu m) of MOONS will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of Galactic, extragalactic and cosmological studies, and it will provide crucial follow-up for major facilities such as Gaia, VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very first galaxies and reionization of the Universe at redshifts of z > 8-9, just a few million years after the Big Bang. From five years of observations MOONS will provide high-quality spectra for > 3M stars in our Galaxy and the Local Group, and for 1-2M galaxies at z > 1 (for an SDSS-like survey), promising to revolutionize our understanding of the Universe. The baseline design consists of similar to 1000 fibres, deployable over a field-of-view of similar to 500 arcmin(2), the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8 -1.8 mu m with two spectral resolving powers: in the medium-resolution mode (R similar to 4,000-6,000) the entire wavelength range is observed simultaneously, while the high-resolution mode will cover three selected sub-regions simultaneously: one region with R similar to 8,000 near the Ca II triplet to measure stellar radial velocities, and two regions at R similar to 20,000 (one in each of the J- and H-bands), for precision measurements of chemical abundances.
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9. |
- Arndt, D. S., et al.
(författare)
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STATE OF THE CLIMATE IN 2017
- 2018
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 99:8, s. S1-S310
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Forskningsöversikt (refereegranskat)
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10. |
- Arndt, D. S., et al.
(författare)
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State of the Climate in 2016
- 2017
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 98:8, s. S1-S280
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Tidskriftsartikel (refereegranskat)abstract
- In 2016, the dominant greenhouse gases released into Earth's atmosphere-carbon dioxide, methane, and nitrous oxide-continued to increase and reach new record highs. The 3.5 +/- 0.1 ppm rise in global annual mean carbon dioxide from 2015 to 2016 was the largest annual increase observed in the 58-year measurement record. The annual global average carbon dioxide concentration at Earth's surface surpassed 400 ppm (402.9 +/- 0.1 ppm) for the first time in the modern atmospheric measurement record and in ice core records dating back as far as 800000 years. One of the strongest El Nino events since at least 1950 dissipated in spring, and a weak La Nina evolved later in the year. Owing at least in part to the combination of El Nino conditions early in the year and a long-term upward trend, Earth's surface observed record warmth for a third consecutive year, albeit by a much slimmer margin than by which that record was set in 2015. Above Earth's surface, the annual lower troposphere temperature was record high according to all datasets analyzed, while the lower stratospheric temperature was record low according to most of the in situ and satellite datasets. Several countries, including Mexico and India, reported record high annual temperatures while many others observed near-record highs. A week-long heat wave at the end of April over the northern and eastern Indian peninsula, with temperatures surpassing 44 degrees C, contributed to a water crisis for 330 million people and to 300 fatalities. In the Arctic the 2016 land surface temperature was 2.0 degrees C above the 1981-2010 average, breaking the previous record of 2007, 2011, and 2015 by 0.8 degrees C, representing a 3.5 degrees C increase since the record began in 1900. The increasing temperatures have led to decreasing Arctic sea ice extent and thickness. On 24 March, the sea ice extent at the end of the growth season saw its lowest maximum in the 37-year satellite record, tying with 2015 at 7.2% below the 1981-2010 average. The September 2016 Arctic sea ice minimum extent tied with 2007 for the second lowest value on record, 33% lower than the 1981-2010 average. Arctic sea ice cover remains relatively young and thin, making it vulnerable to continued extensive melt. The mass of the Greenland Ice Sheet, which has the capacity to contribute similar to 7 m to sea level rise, reached a record low value. The onset of its surface melt was the second earliest, after 2012, in the 37-year satellite record. Sea surface temperature was record high at the global scale, surpassing the previous record of 2015 by about 0.01 degrees C. The global sea surface temperature trend for the 21st century-to-date of +0.162 degrees C decade(-1) is much higher than the longer term 1950-2016 trend of +0.100 degrees C decade(-1). Global annual mean sea level also reached a new record high, marking the sixth consecutive year of increase. Global annual ocean heat content saw a slight drop compared to the record high in 2015. Alpine glacier retreat continued around the globe, and preliminary data indicate that 2016 is the 37th consecutive year of negative annual mass balance. Across the Northern Hemisphere, snow cover for each month from February to June was among its four least extensive in the 47-year satellite record. Continuing a pattern below the surface, record high temperatures at 20-m depth were measured at all permafrost observatories on the North Slope of Alaska and at the Canadian observatory on northernmost Ellesmere Island. In the Antarctic, record low monthly surface pressures were broken at many stations, with the southern annular mode setting record high index values in March and June. Monthly high surface pressure records for August and November were set at several stations. During this period, record low daily and monthly sea ice extents were observed, with the November mean sea ice extent more than 5 standard deviations below the 1981-2010 average. These record low sea ice values contrast sharply with the record high values observed during 2012-14. Over the region, springtime Antarctic stratospheric ozone depletion was less severe relative to the 1991-2006 average, but ozone levels were still low compared to pre-1990 levels. Closer to the equator, 93 named tropical storms were observed during 2016, above the 1981-2010 average of 82, but fewer than the 101 storms recorded in 2015. Three basins-the North Atlantic, and eastern and western North Pacific-experienced above-normal activity in 2016. The Australian basin recorded its least active season since the beginning of the satellite era in 1970. Overall, four tropical cyclones reached the Saffir-Simpson category 5 intensity level. The strong El Nino at the beginning of the year that transitioned to a weak La Nina contributed to enhanced precipitation variability around the world. Wet conditions were observed throughout the year across southern South America, causing repeated heavy flooding in Argentina, Paraguay, and Uruguay. Wetter-than-usual conditions were also observed for eastern Europe and central Asia, alleviating the drought conditions of 2014 and 2015 in southern Russia. In the United States, California had its first wetter-than-average year since 2012, after being plagued by drought for several years. Even so, the area covered by drought in 2016 at the global scale was among the largest in the post-1950 record. For each month, at least 12% of land surfaces experienced severe drought conditions or worse, the longest such stretch in the record. In northeastern Brazil, drought conditions were observed for the fifth consecutive year, making this the longest drought on record in the region. Dry conditions were also observed in western Bolivia and Peru; it was Bolivia's worst drought in the past 25 years. In May, with abnormally warm and dry conditions already prevailing over western Canada for about a year, the human-induced Fort McMurray wildfire burned nearly 590000 hectares and became the costliest disaster in Canadian history, with $3 billion (U.S. dollars) in insured losses.
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11. |
- Ades, M., et al.
(författare)
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Global Climate : in State of the climate in 2019
- 2020
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 101:8, s. S17-S127
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Tidskriftsartikel (refereegranskat)
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12. |
- Ades, M., et al.
(författare)
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GLOBAL CLIMATE
- 2020
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Ingår i: BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY. - 0003-0007 .- 1520-0477. ; 101:8
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Tidskriftsartikel (refereegranskat)
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13. |
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14. |
- Al-Khalili, A, et al.
(författare)
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Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:12, s. 5700-5708
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Tidskriftsartikel (refereegranskat)abstract
- Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD.
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15. |
- Bykov, Maxim, et al.
(författare)
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High-Pressure Synthesis of Dirac Materials: Layered van der Waals Bonded BeN4 Polymorph
- 2021
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 126:17
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here, we employ the laser-heated diamond anvil cell technique for synthesis of a Dirac material BeN4. A triclinic phase of beryllium tetranitride tr-BeN4 was synthesized from elements at similar to 85 GPa. Upon decompression to ambient conditions, it transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds and consisting of polyacetylene-like nitrogen chains with conjugated pi systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The BeN4 layer, i.e., beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions.
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16. |
- Bykov, Maxim, et al.
(författare)
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Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN2: High-Pressure Route to Pentagonal 2D Materials
- 2021
-
Ingår i: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 15:8, s. 13539-13546
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Tidskriftsartikel (refereegranskat)abstract
- Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nano-electronics. In this work we report the synthesis of nickel diazenide NiN2 which possesses atomic-thick layers comprised of Ni2N3 pentagons forming Cairo-type tessellation. The layers of NiN2 are weakly bonded with the calculated exfoliation energy of 0.72 J/m(2), which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (P4/mbm) and possesses significant anisotropy of elastic properties. The single-layer NiN2 is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN2 to be a precursor of a pentagonal 2D material with a tunable direct band gap.
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17. |
- Bykov, Maxim, et al.
(författare)
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Stabilization of Polynitrogen Anions in Tantalum-Nitrogen Compounds at High Pressure
- 2021
-
Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 60:16, s. 9003-9008
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of polynitrogen compounds is of great importance due to their potential as high-energy-density materials (HEDM), but because of the intrinsic instability of these compounds, their synthesis and stabilization is a fundamental challenge. Polymeric nitrogen units which may be stabilized in compounds with metals at high pressure are now restricted to non-branched chains with an average N-N bond order of 1.25, limiting their HEDM performances. Herein, we demonstrate the synthesis of a novel polynitrogen compound TaN5 via a direct reaction between tantalum and nitrogen in a diamond anvil cell at circa 100 GPa. TaN5 is the first example of a material containing branched all-single-bonded nitrogen chains [N-5(5-)](infinity). Apart from that we discover two novel Ta-N compounds: TaN4 with finite N-4(4-) chains and the incommensurately modulated compound TaN2-x, which is recoverable at ambient conditions.
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18. |
- Martin, Nicolas F., et al.
(författare)
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The Pristine survey - XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3
- 2022
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 516:4, s. 5331-5354
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Tidskriftsartikel (refereegranskat)abstract
- We use the photometric metallicities provided by the panoramic Pristine survey to study the veracity and derive the metallicities of the numerous stellar streams found by the application of the STREAMFINDER algorithm to the Gaia Early Data Release 3 data. All 26 streams present in Pristine show a clear metallicity distribution function, which provides an independent check of the reality of these structures, supporting the reliability of STREAMFINDER in finding streams and the power of Pristine to measure precise metallicities. We further present six candidate structures with coherent phase-space and metallicity signals that are very likely streams. The majority of studied streams are very metal-poor (14 structures with [Fe/H] < −2.0) and include three systems with [Fe/H] < −2.9 (C-11, C-19, and C-20). These streams could be the closest debris of low-luminosity dwarf galaxies or may have originated from globular clusters of significantly lower metallicity than any known current Milky Way globular cluster. Our study shows that the promise of the Gaia data for Galactic Archeology studies can be substantially strengthened by quality photometric metallicities, allowing us to peer back into the earliest epochs of the formation of our Galaxy and its stellar halo constituents.
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19. |
- Menkveld, Albert J., et al.
(författare)
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Nonstandard Errors
- 2024
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Ingår i: JOURNAL OF FINANCE. - : Wiley-Blackwell. - 0022-1082 .- 1540-6261. ; 79:3, s. 2339-2390
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Tidskriftsartikel (refereegranskat)abstract
- In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty-nonstandard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for more reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants.
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20. |
- Schio, L., et al.
(författare)
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Double Photoionization of Nitrosyl Chloride by Synchrotron Radiation in the 24-70 eV Photon Energy Range
- 2023
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Ingår i: Molecules. - 1420-3049. ; 28:13
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of nitrosyl chloride (ClNO) exposed to ionizing radiation was studied by direct probing valence-shell electrons in temporal coincidence with ions originating from the fragmentation process of the transient ClNO2+. Such a molecular dication was produced by double photoionization with synchrotron radiation in the 24-70 eV photon energy range. The experiment has been conducted at the Elettra Synchrotron Facility of Basovizza (Trieste, Italy) using a light beam linearly polarized with the direction of the polarization vector parallel to the ClNO molecular beam axis. ClNO molecules crossing the photon beam at right angles in the scattering region are generated by effusive expansion and randomly oriented. The threshold energy for the double ionization of ClNO (30.1 & PLUSMN; 0.1 eV) and six dissociation channels producing NO+/Cl+, N+/Cl+, N+/O+, O+/Cl+, ClN+/O+, NO+/Cl2+ ion pairs, with their relative abundance and threshold energies, have been measured.
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21. |
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22. |
- Achen, M G, et al.
(författare)
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Vascular endothelial growth factor D (VEGF-D) is a ligand for the tyrosine kinases VEGF receptor 2 (Flk1) and VEGF receptor 3 (Flt4).
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 95:2
-
Tidskriftsartikel (refereegranskat)abstract
- We have identified a member of the VEGF family by computer-based homology searching and have designated it VEGF-D. VEGF-D is most closely related to VEGF-C by virtue of the presence of N- and C-terminal extensions that are not found in other VEGF family members. In adult human tissues, VEGF-D mRNA is most abundant in heart, lung, skeletal muscle, colon, and small intestine. Analyses of VEGF-D receptor specificity revealed that VEGF-D is a ligand for both VEGF receptors (VEGFRs) VEGFR-2 (Flk1) and VEGFR-3 (Flt4) and can activate these receptors. However. VEGF-D does not bind to VEGFR-1. Expression of a truncated derivative of VEGF-D demonstrated that the receptor-binding capacities reside in the portion of the molecule that is most closely related in primary structure to other VEGF family members and that corresponds to the mature form of VEGF-C. In addition, VEGF-D is a mitogen for endothelial cells. The structural and functional similarities between VEGF-D and VEGF-C define a subfamily of the VEGFs.
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23. |
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24. |
- Allum, F., et al.
(författare)
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A localized view on molecular dissociation via electron-ion partial covariance
- 2022
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Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy. Methodologically, we employ electron-ion partial covariance imaging as a technique to isolate otherwise elusive features in a two-dimensional photoelectron spectrum arising from different photofragmentation pathways. The experimental and theoretical results for the time-resolved electron spectra of the 4d(3/2) and 4d(5/2) atomic and molecular levels that are disentangled by this method provide a key step towards studying structural and chemical changes from a specific spectator site. Coincidence experiments at free-electron lasers enable time resolved site-specific investigations of molecular photochemistry at high signal rates, but isolating individual dissociation processes still poses a considerable technical challenge. Here, the authors use electron-ion partial covariance imaging to isolate otherwise elusive chemical shifts in UV-induced photofragmentation pathways of the prototypical chiral molecule 1-iodo-2-methylbutane.
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25. |
- Andersson, Patrik U, 1970, et al.
(författare)
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Formation of Highly Rovibrationally Excited Ammonia from Dissociative Recombination of NH4
- 2010
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 1:17, s. 2519-2523
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Tidskriftsartikel (refereegranskat)abstract
- The internal energy distribution of ammonia formed in the dissociative recombination (DR) of NH4+ with electrons has been studied by an imaging technique at the ion storage ring CRYRING. The DR process resulted in the formation of NH3 + H (0.90 ± 0.01), with minor contributions from channels producing NH2 + H2 (0.05 ± 0.01) and NH2 + 2H (0.04 ± 0.02). The formed NH3 molecules were highly internally excited, with a mean rovibrational energy of 3.3 ± 0.4 eV, which corresponds to 70% of the energy released in the neutralization process. The internal energy distribution was semiquantitatively reproduced by ab initio direct dynamics simulations, and the calculations suggested that the NH3 molecules are highly vibrationally excited while rotational excitation is limited. The high internal excitation and the translational energy of NH3 and H will influence their subsequent reactivity, an aspect that should be taken into account when developing detailed models of the interstellar medium and ammonia-containing plasmas.
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26. |
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27. |
- Blunden, Jessica, et al.
(författare)
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State of the Climate in 2012
- 2013
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 94:8, s. S1-S258
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Tidskriftsartikel (refereegranskat)abstract
- For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Ni a-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in to the effects of La Ni a, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near-or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7 N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global 2 emissions from fossil fuel combustion and cement production reached a record 9.5 +/- 0.5 Pg C in 2011 and a new record of 9.7 +/- 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, 2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.
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28. |
- Blunden, Jessica, et al.
(författare)
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State of the climate in 2013
- 2014
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Ingår i: Bulletin of the American Meteorological Society. - 0003-0007. ; 95
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Tidskriftsartikel (refereegranskat)abstract
- © 2014, American Meteorological Society. All rights reserved. In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earth’s surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series.
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29. |
- Bykov, Maxim, et al.
(författare)
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High-Pressure Synthesis of Metal-Inorganic Frameworks Hf4N20 center dot N-2, WN8 center dot N-2, and Os5N28 center dot 3 N-2 with Polymeric Nitrogen Linkers
- 2020
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 59:26, s. 10321-10326
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Tidskriftsartikel (refereegranskat)abstract
- Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one-step synthesis of metal-inorganic frameworks Hf4N20 center dot N2, WN 8 center dot N2, and Os5N28 center dot 3N2 via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf4N20, WN 8, and Os5N28) are built from transition-metal atoms linked either by polymeric polydiazenediyl (polyacetylene-like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high-pressure reaction between Hf and N2 also leads to a non-centrosymmetric polynitride Hf2N11 that features double-helix catenapoly[tetraz-1-ene-1,4-diyl] nitrogen chains [-N-N-N=N-](infinity.)
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30. |
- Bykova, Elena, et al.
(författare)
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Novel Class of Rhenium Borides Based on Hexagonal Boron Networks Interconnected by Short B-2 Dumbbells
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:18, s. 8138-8152
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal borides are known due to their attractive mechanical, electronic, refractive, and other properties. A new class of rhenium borides was identified by synchrotron single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells between 26 and 75 GPa. Recoverable to ambient conditions, compounds rhenium triboride (ReB3) and rhenium tetraboride (ReB4) consist of close-packed single layers of rhenium atoms alternating with boron networks built from puckered hexagonal layers, which link short bonded (similar to 1.7 angstrom) axially oriented B-2 dumbbells. The short and incompressible Re-B and B-B bonds oriented along the hexagonal c-axis contribute to low axial compressibility comparable with the linear compressibility of diamond. Sub-millimeter samples of ReB3 and ReB4 were synthesized in a large-volume press at pressures as low as 33 GPa and used for material characterization. Crystals of both compounds are metallic and hard (Vickers hardness, H-V = 34(3) GPa). Geometrical, crystal-chemical, and theoretical analysis considerations suggest that potential ReBx compounds with x > 4 can be based on the same principle of structural organization as in ReB3 and ReB4 and possess similar mechanical and electronic properties.
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31. |
- Bykova, Elena, et al.
(författare)
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Synthesis, crystal structure, and properties of stoichiometric hard tungsten tetraboride, WB4
- 2022
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 10:37, s. 20111-20120
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten tetraboride has been known so far as a non-stoichiometric compound with a variable composition (e.g. WB4-x, WB4+x). Its mechanical properties could exceed those of hard tungsten carbide, which is widely used nowadays in science and technology. The existence of stoichiometric WB4 has not been proven yet, and its structure and crystal chemistry remain debatable to date. Here we report the synthesis of single crystals of the stoichiometric WB4 phase under high-pressure high-temperature conditions. The crystal structure of WB4 was determined using synchrotron single-crystal X-ray diffraction. In situ high-pressure compressibility measurements show that the bulk modulus of WB4 is 238.6(2) GPa for B = 5.6(0). Measurements of mechanical properties of bulk polycrystalline sub-millimeter size samples under ambient conditions reveal a hardness of similar to 36 GPa, confirming that the material falls in the category of superhard materials.
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32. |
- Cabras, T., et al.
(författare)
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Top-down HPLC-ESI-MS characterization of rat gliadoralin A, a new member of the family of rat submandibular gland glutamine-rich proteins and potential substrate of transglutaminase
- 2013
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306. ; 36:17, s. 2848-2861
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Tidskriftsartikel (refereegranskat)abstract
- During HPLC-ESI-MS/MS analysis of rat submandibular saliva secreted under isoprenaline stimulation, a protein with an experimental [M+H](1+) = 10544.24 m/z was detected (17.5 +/- 0.7 min). The MS/MS fragmentation pattern, manually investigated, allowed establishing an internal sequence in agreement with a DNA-derived sequence of an unknown rat protein coded D3Z9M3 (Swiss-Prot). To match the experimental MS/MS fragmentation pattern and protein mass with theoretical data, the removal from the N terminus of the signal peptide and from the C terminus of three amino acid (a.a.) residues (Arg-Ala-Val) and the cyclization of the N-terminal glutamine in pyroglutamic had to be supposed, resulting in a mature protein of 90 a.a. HPLC-ESI-MS/MS of the trypsin digest ensured 100% sequence coverage. For the high glutamine content (34/90 = 37.8%) we propose to name this protein rat gliadoralin A 1-90. Low amounts of five different isoforms were sporadically detected, which did not significantly change their relative amounts after stimulation. Gliadoralin A is substrate for transglutaminase-2, having Lys 60 and different Gln residues as major determinants for enzyme recognition. In silico investigation of superior structures evidenced that a small part of the protein adopts an -helical fold, whereas large segments are unfolded, suggesting an unordered conformation.
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33. |
- Chen, S. C., et al.
(författare)
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Development of A Minimum Dataset for the Monitoring of Recombinant Human Growth Hormone (rhGH) Therapy Use in Children with Growth Hormone Deficiency (GHD) - A GloBE-Reg Initiative
- 2023
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Ingår i: Hormone Research in Paediatrics. - 1663-2818 .- 1663-2826.
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Tidskriftsartikel (refereegranskat)abstract
- Introduction Although there are some recommendations in the literature on the assessments that should be performed in children on recombinant human growth hormone (rhGH) therapy, the level of consensus on these measurements is not clear. The objective of the current study was to identify the minimum dataset (MDS) that could be measured in a routine clinical setting across the world, aiming to minimise burden on clinicians and improve quality of data collection. Methods This study was undertaken by the GH Scientific Study Group (SSG) in GloBE-Reg, a new project that has developed a common registry platform that can support long-term safety and effectiveness studies of drugs. Twelve clinical experts from 7 international endocrine organisations identified by the GloBE-Reg Steering Committee, 2 patient representatives and representatives from 2 pharmaceutical companies with previous GH registry expertise collaborated to develop this recommendation. A comprehensive list of data fields routinely collected by each of the clinical and industry experts for children with GHD was compiled. Each member was asked to determine the: (1) Importance of the data field and (2) Ease of data collection. Data fields that achieved 70% consensus in terms of importance qualified for the MDS, provided <50% deemed the item difficult to collect.Results A total of 246 items were compiled and 27 removed due to redundancies, with 219 items subjected to the grading system. Of the 219 items, 111 achieved at least 70% consensus as important data to collect when monitoring children with GH deficiency (GHD) on rhGH treatment. Sixty-nine of the 219 items were deemed easy to collect. Combining the criteria of importance and ease of data collection, 63 met the criteria for the MDS. Several anomalies to the MDS rule were identified and highlighted for discussion, including whether the patients were involved in current or previous clinical trials, need for HbA1c monitoring, other past medical history, and adherence, enabling formulation of the final MDS recommendation of 43 items; 20 to be completed once, 14 every 6 months and 9 every 12 months.Conclusion In summary, this exercise performed through the GloBE-Reg initiative provides a recommendation of the minimum dataset requirement, collected through real-world data, for the monitoring of safety and effectiveness of rhGH in children with GHD, both for the current daily preparations and the newer long-acting growth hormone.
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34. |
- Colombo, GI, et al.
(författare)
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The Association between HDL-C and Subclinical Atherosclerosis Depends on CETP Plasma Concentration: Insights from the IMPROVE Study
- 2021
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Ingår i: Biomedicines. - : MDPI AG. - 2227-9059. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- The impact of cholesteryl ester transfer protein (CETP) on atherosclerosis is highly debated. This study aimed to investigate the associations between plasma CETP or CETP genotypes and carotid intima-media thickness (cIMT) and the influence of high-density lipoprotein cholesterol (HDL-C) on these associations. Plasma CETP and HDL-C concentrations were measured in 552 subjects free of any pharmacological treatment from the IMPROVE cohort, which includes 3711 European subjects at high cardiovascular risk. CETP single-nucleotide polymorphisms (SNPs) and cIMT measures (cIMTmax; cIMTmean–max of bifurcations, common and internal carotids; plaque-free common carotid [PF CC]-IMTmean) were available for the full cohort. In drug-free subjects, plasma CETP correlated with HDL-C levels (r = 0.19, p < 0.0001), but not with cIMT variables. When stratified according to HDL-C quartiles, CETP positively correlated with cIMTmax and cIMTmean–max, but not with PF CC-IMTmean, in the top HDL-C quartile only. Positive associations between the CETP concentration and cIMTmax or cIMTmean–max were found in the top HDL-C quartile, whereas HDL-C levels were negatively correlated with cIMTmax and cIMTmean–max when the CETP concentration was below the median (HDL-C × CETP interaction, p = 0.001 and p = 0.003 for cIMTmax and cIMTmean–max, respectively). In the full cohort, three CETP SNPs (rs34760410, rs12920974, rs12708968) were positively associated with cIMTmax. rs12444708 exhibited a significant interaction with HDL-C levels in the prediction of cIMTmax. In conclusion, a significant interplay was found between plasma CETP and/or CETP genotype and HDL-C in the prediction of carotid plaque thickness, as indexed by cIMTmax. This suggests that the association of HDL-C with carotid atherosclerosis is CETP-dependent.
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35. |
- Frasinski, L. J., et al.
(författare)
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Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:7, s. 073002-
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Tidskriftsartikel (refereegranskat)abstract
- When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called partial covariance mapping'' to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.
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36. |
- Grüttner, K., et al.
(författare)
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CONTREX : Design of embedded mixed-criticality CONTRol systems under consideration of EXtra-functional properties
- 2017
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Ingår i: Microprocessors and microsystems. - : Elsevier B.V.. - 0141-9331 .- 1872-9436. ; 51, s. 39-55
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Tidskriftsartikel (refereegranskat)abstract
- The increasing processing power of today's HW/SW platforms leads to the integration of more and more functions in a single device. Additional design challenges arise when these functions share computing resources and belong to different criticality levels. CONTREX complements current activities in the area of predictable computing platforms and segregation mechanisms with techniques to consider the extra-functional properties, i.e., timing constraints, power, and temperature. CONTREX enables energy efficient and cost aware design through analysis and optimization of these properties with regard to application demands at different criticality levels. This article presents an overview of the CONTREX European project, its main innovative technology (extension of a model based design approach, functional and extra-functional analysis with executable models and run-time management) and the final results of three industrial use-cases from different domain (avionics, automotive and telecommunication).
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37. |
- Ji, Cheng, et al.
(författare)
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Stability of Ar(H2)2 to 358 GPa
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:14, s. 3596-3600
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Tidskriftsartikel (refereegranskat)abstract
- "Chemical precompression" through introducing impurity atoms into hydrogen has been proposed as a method to facilitate metallization of hydrogen under external pressure. Here we selected Ar(H-2)(2), a hydrogen-rich compound with molecular hydrogen, to explore the effect of "doping" on the intermolecular interaction of H-2 molecules and metallization at ultrahigh pressure. Ar(H-2)(2) was studied experimentally by synchrotron X-ray diffraction to 265 GPa, by Raman and optical absorption spectroscopy to 358 GPa, and theoretically using the density-functional theory. Our measurements of the optical bandgap and the vibron frequency show that Ar(H-2)(2) retains 2-eV bandgap and H-2 molecular units up to 358 GPa. This is attributed to reduced intermolecular interactions between H-2 molecules in Ar(H-2)(2) compared with that in solid H-2. A splitting of the molecular vibron mode above 216 GPa suggests an orientational ordering transition, which is not accompanied by a change in lattice symmetry. The experimental and theoretical equations of state of Ar(H-2)(2) provide direct insight into the structure and bonding of this hydrogen-rich system, suggesting a negative chemical pressure on H-2 molecules brought about by doping of Ar.
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38. |
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39. |
- Mac Giolla Phadraig, Caoimhin, et al.
(författare)
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Behaviour support in dentistry: A Delphi study to agree terminology in behaviour management
- 2024
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Ingår i: Community Dentistry and Oral Epidemiology. - : John Wiley & Sons. - 0301-5661 .- 1600-0528. ; 52:4, s. 550-571
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Dental behaviour support (DBS) describes all specific techniques practiced to support patients in their experience of professional oral healthcare. DBS is roughly synonymous with behaviour management, which is an outdated concept. There is no agreed terminology to specify the techniques used to support patients who receive dental care. This lack of specificity may lead to imprecision in describing, understanding, teaching, evaluating and implementing behaviour support techniques in dentistry. Therefore, this e-Delphi study aimed to develop a list of agreed labels and descriptions of DBS techniques used in dentistry and sort them according to underlying principles of behaviour.Methods: Following a registered protocol, a modified e-Delphi study was applied over two rounds with a final consensus meeting. The threshold of consensus was set a priori at 75%. Agreed techniques were then categorized by four coders, according to behavioural learning theory, to sort techniques according to their mechanism of action.Results: The panel (n = 35) agreed on 42 DBS techniques from a total of 63 candidate labels and descriptions. Complete agreement was achieved regarding all labels and descriptions, while agreement was not achieved regarding distinctiveness for 17 techniques. In exploring underlying principles of learning, it became clear that multiple and differing principles may apply depending on the specific context and procedure in which the technique may be applied.Discussion: Experts agreed on what each DBS technique is, what label to use, and their description, but were less likely to agree on what distinguishes one technique from another. All techniques were describable but not comprehensively categorizable according to principles of learning. While objective consistency was not attained, greater clarity and consistency now exists. The resulting list of agreed terminology marks a significant foundation for future efforts towards understanding DBS techniques in research, education and clinical care.
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40. |
- Mucke, Melanie, et al.
(författare)
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Covariance mapping of two-photon double core hole states in C2H2 and C2H6 produced by an x-ray free electron laser
- 2015
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Few-photon ionization and relaxation processes in acetylene (C2H2) and ethane (C2H6) were investigated at the linac coherent light source x-ray free electron laser (FEL) at SLAC, Stanford using a highly efficient multi-particle correlation spectroscopy technique based on a magnetic bottle. The analysis method of covariance mapping has been applied and enhanced, allowing us to identify electron pairs associated with double core hole (DCH) production and competing multiple ionization processes including Auger decay sequences. The experimental technique and the analysis procedure are discussed in the light of earlier investigations of DCH studies carried out at the same FEL and at third generation synchrotron radiation sources. In particular, we demonstrate the capability of the covariance mapping technique to disentangle the formation of molecular DCH states which is barely feasible with conventional electron spectroscopy methods.
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41. |
- Murphy, B. F., et al.
(författare)
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Femtosecond X-ray-induced explosion of C-60 at extreme intensity
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding molecular femtosecond dynamics under intense X-ray exposure is critical to progress in biomolecular imaging and matter under extreme conditions. Imaging viruses and proteins at an atomic spatial scale and on the time scale of atomic motion requires rigorous, quantitative understanding of dynamical effects of intense X-ray exposure. Here we present an experimental and theoretical study of C-60 molecules interacting with intense X-ray pulses from a free-electron laser, revealing the influence of processes not previously reported. Our work illustrates the successful use of classical mechanics to describe all moving particles in C-60, an approach that scales well to larger systems, for example, biomolecules. Comparisons of the model with experimental data on C-60 ion fragmentation show excellent agreement under a variety of laser conditions. The results indicate that this modelling is applicable for X-ray interactions with any extended system, even at higher X-ray dose rates expected with future light sources.
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42. |
- Schio, L., et al.
(författare)
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A Study of H2O2 with Threshold Photoelectron Spectroscopy (TPES) and Electronic Structure Calculations: Redetermination of the First Adiabatic Ionization Energy (AIE)
- 2016
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 120:27, s. 5220-5229
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Tidskriftsartikel (refereegranskat)abstract
- In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy and photoelectron (PE) spectroscopy. The TPE spectrum has been recorded in the 10.0-21.0 eV ionization energy region, and the PE spectrum has been recorded at 21.22 eV photon energy. Five bands have been observed which have been assigned on the basis of UCCSD(T)-F12/VQZ-F12 and IP-EOM CCSD calculations. Vibrational structure has only been resolved in the TPE spectrum of the first band, associated with the (X) over tilde (2)Bg H2O2+ <- (X) over tilde (1)A H2O2 ionization, on its low energy side. This structure is assigned with the help of harmonic Franck-Condon factor calculations that use the UCCSD(T)-F12a/VQZ-F12 computed adiabatic ionization energy (AIE), and UCCSD(T)-F12a/VQZ-F12 computed equilibrium geometric parameters and harmonic vibrational frequencies for the H2O2 (X) over tilde (1)A state and the H2O2 (X) over tilde (2)Bg state. These calculations show that the main vibrational structure on the leading edge of the first TPE band is in the O-O stretching mode (omega(3)) and the HOOH deformation mode (omega(4)), and comparison of the simulated spectrum to the experimental spectrum gives the first AIE of H2O2 as (10.685 +/- 0.005) eV and omega(4) = (850 +/- 30) and omega(3) = (1340 +/- 30) cm(-1) in the (X) over tilde (2)Bg state of H2O2+. Contributions from ionization of vibrationally excited levels in the torsion mode have been identified in the TPE spectrum of the first band and the need for a vibrationally resolved TPE spectrum from vibrationally cooled molecules, as well as higher level Franck-Condon factors than performed in this work, is emphasized.
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43. |
- Stock, Kristin, et al.
(författare)
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Neural precursor cells induce cell death of high-grade astrocytomas through stimulation of TRPV1
- 2012
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1546-170X .- 1078-8956. ; 18:8, s. 1232-1232
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Tidskriftsartikel (refereegranskat)abstract
- Primary astrocytomas of grade 3 or 4 according to the classification system of the World Health Organization (high-grade astrocytomas or HGAs) are preponderant among adults and are almost invariably fatal despite the use of multimodal therapy. Here we show that the juvenile brain has an endogenous defense mechanism against HGAs. Neural precursor cells (NPCs) migrate to HGAs, reduce glioma expansion and prolong survival time by releasing endovanilloids that activate the vanilloid receptor (transient receptor potential vanilloid subfamily member-1 or TRPV1) on HGA cells. TRPV1 is highly expressed in tumor and weakly expressed in tumor-free brain. TRPV1 stimulation triggers tumor cell death through the branch of the endoplasmic reticulum stress pathway that is controlled by activating transcription factor-3 (ATF3). The antitumorigenic response of NPCs is lost with aging. NPC-mediated tumor suppression can be mimicked in the adult brain by systemic administration of the synthetic vanilloid arvanil, suggesting that TRPV1 agonists have potential as new HGA therapeutics.
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44. |
- Therriault, J., et al.
(författare)
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Biomarker modeling of Alzheimer’s disease using PET-based Braak staging
- 2022
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Ingår i: Nature Aging. - : Springer Science and Business Media LLC. - 2662-8465. ; 2:6, s. 526-535
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Tidskriftsartikel (refereegranskat)abstract
- Gold-standard diagnosis of Alzheimer’s disease (AD) relies on histopathological staging systems. Using the topographical information from [18F]MK6240 tau positron-emission tomography (PET), we applied the Braak tau staging system to 324 living individuals. We used PET-based Braak stage to model the trajectories of amyloid-β, phosphorylated tau (pTau) in cerebrospinal fluid (pTau181, pTau217, pTau231 and pTau235) and plasma (pTau181 and pTau231), neurodegeneration and cognitive symptoms. We identified nonlinear AD biomarker trajectories corresponding to the spatial extent of tau-PET, with modest biomarker changes detectable by Braak stage II and significant changes occurring at stages III–IV, followed by plateaus. Early Braak stages were associated with isolated memory impairment, whereas Braak stages V–VI were incompatible with normal cognition. In 159 individuals with follow-up tau-PET, progression beyond stage III took place uniquely in the presence of amyloid-β positivity. Our findings support PET-based Braak staging as a framework to model the natural history of AD and monitor AD severity in living humans.
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45. |
- Therriault, J., et al.
(författare)
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Determining Amyloid-β Positivity Using 18F-AZD4694 PET Imaging
- 2021
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - : Society of Nuclear Medicine. - 1535-5667. ; 62:2, s. 247-252
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid-β deposition into plaques is a pathologic hallmark of Alzheimer disease appearing years before the onset of symptoms. Although cerebral amyloid-β deposition occurs on a continuum, dichotomization into positive and negative groups has advantages for diagnosis, clinical management, and population enrichment for clinical trials. 18F-AZD4694 (also known as 18F-NAV4694) is an amyloid-β imaging ligand with high affinity for amyloid-β plaques. Despite being used in multiple academic centers, no studies have assessed a quantitative cutoff for amyloid-β positivity using 18F-AZD4694 PET. Methods: We assessed 176 individuals [young adults (n = 22), cognitively unimpaired elderly (n = 89), and cognitively impaired (n = 65)] who underwent amyloid-β PET with 18F-AZD4694, lumbar puncture, structural MRI, and genotyping for APOEε418F-AZD4694 values were normalized using the cerebellar gray matter as a reference region. We compared 5 methods for deriving a quantitative threshold for 18F-AZD4694 PET positivity: comparison with young-control SUV ratios (SUVRs), receiver-operating-characteristic (ROC) curves based on clinical classification of cognitively unimpaired elderly versus Alzheimer disease dementia, ROC curves based on visual Aβ-positive/Aβ-negative classification, gaussian mixture modeling, and comparison with cerebrospinal fluid measures of amyloid-β, specifically the Aβ42/Aβ40 ratio. Results: We observed good convergence among the 4 methods: ROC curves based on visual classification (optimal cut point, 1.55 SUVR), ROC curves based on clinical classification (optimal cut point, 1.56 SUVR) gaussian mixture modeling (optimal cut point, 1.55 SUVR), and comparison with cerebrospinal fluid measures of amyloid-β (optimal cut point, 1.51 SUVR). Means and 2 SDs from young controls resulted in a lower threshold (1.33 SUVR) that did not agree with the other methods and labeled most elderly individuals as Aβ-positive. Conclusion: Good convergence was obtained among several methods for determining an optimal cutoff for 18F-AZD4694 PET positivity. Despite conceptual and analytic idiosyncrasies linked with dichotomization of continuous variables, an 18F-AZD4694 threshold of 1.55 SUVR had reliable discriminative accuracy. Although clinical use of amyloid PET is currently by visual inspection of scans, quantitative thresholds may be helpful to arbitrate disagreement among raters or in borderline cases. © 2021 by the Society of Nuclear Medicine and Molecular Imaging.
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46. |
- Therriault, J., et al.
(författare)
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Equivalence of plasma p-tau217 with cerebrospinal fluid in the diagnosis of Alzheimer's disease
- 2023
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Ingår i: Alzheimers & Dementia. - 1552-5260. ; 19:11, s. 4967-4977
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Plasma biomarkers are promising tools for Alzheimer's disease (AD) diagnosis, but comparisons with more established biomarkers are needed.METHODS: We assessed the diagnostic performance of p-tau(181), p-tau(217), and p-tau(231) in plasma and CSF in 174 individuals evaluated by dementia specialists and assessed with amyloid-PET and tau-PET. Receiver operating characteristic (ROC) analyses assessed the performance of plasma and CSF biomarkers to identify amyloid-PET and tau-PET positivity.RESULTS: Plasma p-tau biomarkers had lower dynamic ranges and effect sizes compared to CSF p-tau. Plasma p-tau(181) (AUC = 76%) and p-tau(231) (AUC = 82%) assessments performed inferior to CSF p-tau(181) (AUC = 87%) and p-tau(231) (AUC = 95%) for amyloid-PET positivity. However, plasma p-tau(217) (AUC = 91%) had diagnostic performance indistinguishable from CSF (AUC = 94%) for amyloid-PET positivity.DISCUSSION: Plasma and CSF p-tau(217) had equivalent diagnostic performance for biomarker-defined AD. Our results suggest that plasma p-tau(217) may help reduce the need for invasive lumbar punctures without compromising accuracy in the identification of AD.
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47. |
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48. |
- Zhaunerchyk, Vitali, et al.
(författare)
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Disentangling formation of multiple-core holes in aminophenol molecules exposed to bright X-FEL radiation
- 2015
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 48:24
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Tidskriftsartikel (refereegranskat)abstract
- Competing multi-photon ionization processes, some leading to the formation of double core hole states, have been examined in 4-aminophenol. The experiments used the linac coherent light source (LCLS) x-ray free electron laser, in combination with a time-of-flight magnetic bottle electron spectrometer and the correlation analysis method of covariance mapping. The results imply that 4-aminophenol molecules exposed to the focused x-ray pulses of the LCLS sequentially absorb more than two x-ray photons, resulting in the formation of multiple core holes as well as in the sequential removal of photoelectrons and Auger electrons (so-called PAPA sequences).
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49. |
- Zhaunerchyk, Vitali, et al.
(författare)
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Using covariance mapping to investigate the dynamics of multi-photon ionization processes of Ne atoms exposed to X-FEL pulses
- 2013
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16, s. 164034-
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation into the electron emission processes of Ne atoms exposed to intense femtosecond x-ray pulses, provided by the Linac Coherent Light Source Free Electron Laser (FEL) at Stanford. The covariance mapping technique is applied to analyse the data, and the capability of this approach to disentangle both linear and nonlinear correlation features which may be hidden on coincidence maps of the same data set is demonstrated. Different correction techniques which enable improvements on the quality of the spectral features extracted from the covariance maps are explored. Finally, a method for deriving characteristics of the x-ray FEL pulses based on covariance mapping in combination with model simulations is presented.
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