| 3011. |
- Soldatov, Alexander, et al.
(författare)
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Thermal expansion of solid H2 , HD, D2 at helium temperatures
- 1993
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Ingår i: Proceedings of the 13th General Conference of the Condensed Matter Division of the European Physical Society. - : Physica scripta. - 9187308096 ; , s. 1053-
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Konferensbidrag (refereegranskat)
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| 3012. |
- Soldatov, Alexander, et al.
(författare)
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Thermal expansion of solid hydrogens
- 1992
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Ingår i: Soviet Journal of Low Temperature Physics. - 0360-0335. ; 18:2, s. 116-122
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Tidskriftsartikel (refereegranskat)abstract
- The linear thermal expansion coefficient α of solid deuterium with paramodification content of 2.25% was determined in the temperature interval 1.5-5.6 K. The contributions of the translational vibrations of the lattice αlat and the rotational motion of the molecules αrot to α are separated. The temperature dependence of αlat was determined by the expression αlat =1.475 · 10 - 7 T3+(4.5-7) · 10 - 10 T5. The possibilities of a universal description of the thermal expansion of cryocrystals with a central interaction, including quantum crystals of hydrogen isotopes, are discussed. A theoretical description is proposed and the temperature dependence of αrot is analyzed.
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| 3013. |
- Solomon, Christopher T., et al.
(författare)
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Sediment size and nutrients regulate denitrification in a tropical stream
- 2009
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Ingår i: Journal of The North American Benthological Society. - : University of Chicago Press. - 0887-3593 .- 1937-237X. ; 28:2, s. 480-490
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Tidskriftsartikel (refereegranskat)abstract
- Landuse changes might alter N cycling in tropical aquatic ecosystems, but understanding of N cycling in tropical streams is limited. We measured actual and potential denitrification rates during the dry season in Rio Las Marias, a 4(th)-order Andean piedmont stream in Venezuela. Our objectives were to describe spatial and temporal variation in denitrification, quantify the effects of nutrient availability and substratum particle size on denitrification, and explore potential effects of anthropogenic sedimentation on denitrification. In 4 experiments, actual and potential denitrification rates ranged from 0 to 160 and from 0 to 740 mu g N(2)O-N m(-2) h(-1), respectively. Rates were distributed approximately log-normally because of spatial variation. During a 1-mo period, actual denitrification rates decreased exponentially from 37 +/- 39 to 5 +/- 7 mu g N(2)O-N m(-2) h(-1) (mean +/- SD), probably because of a decline in water-column NO(3)-N concentration from 41 +/- 14 to 12 +/- 3 mu g NO(3)-N/L. The texture (particle size) of stream substrata markedly affected denitrification rates. Actual rates were low in cobble, gravel, and fine sediments (< 5 mm), but in fine sediments, rates increased in response to addition of excess NO(3)-N and organic C. In a 3-km stream reach, actual (but not potential) denitrification rates increased with the proportion of fine sediments (< 2 mm) in mixed substrata. This increase was nonlinear, and the threshold value occurred at 37% fine particles, above which actual denitrification rates were almost always high. An experiment simulating the effects of anthropogenic sedimentation showed that topsoil inputs resulted in denitrification rates similar to 8x higher than rates in trials where excess NO(3)-N and organic C were supplied. Denitrification is a small but potentially significant sink for available N in this N-limited system. Anthropogenic sedimentation associated with landuse change might significantly increase denitrification rates in streams.
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| 3014. |
- Soncin, Silvia, et al.
(författare)
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High-resolution dietary reconstruction of victims of the 79 CE Vesuvius eruption at Herculaneum by compound-specific isotope analysis
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:35
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Tidskriftsartikel (refereegranskat)abstract
- The remains of those who perished at Herculaneum in 79 CE offer a unique opportunity to examine lifeways across an ancient community who lived and died together. Historical sources often allude to differential access to foodstuffs across Roman society but provide no direct or quantitative information. By determining the stable isotope values of amino acids from bone collagen and deploying Bayesian models that incorporate knowledge of protein synthesis, we were able to reconstruct the diets of 17 adults from Herculaneum with unprecedented resolution. Significant differences in the proportions of marine and terrestrial foods consumed were observed between males and females, implying that access to food was differentiated according to gender. The approach also provided dietary data of sufficient precision for comparison with assessments of food supply to modern populations, opening up the possibility of benchmarking ancient diets against contemporary settings where the consequences for health are better understood.
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| 3015. |
- Song, Wenzhi, et al.
(författare)
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Development of Tbet- and CD11c-expressing B cells in a viral infection requires T follicular helper cells outside of germinal centers.
- 2022
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Ingår i: Immunity. - : Elsevier BV. - 1097-4180 .- 1074-7613. ; 55:2
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Tidskriftsartikel (refereegranskat)abstract
- Tbet+CD11c+ B cells arise during type 1 pathogen challenge, aging, and autoimmunity in mice and humans. Here, we examined the developmental requirements of this B cell subset. In acute infection, T follicular helper (Tfh) cells, but not Th1 cells, drove Tbet+CD11c+ B cell generation through proximal delivery of help. Tbet+CD11c+ B cells developed prior to germinal center (GC) formation, exhibiting phenotypic and transcriptional profiles distinct from GC B cells. Fate tracking revealed that most Tbet+CD11c+ B cells developed independently of GC entry and cell-intrinsic Bcl6 expression. Tbet+CD11c+ and GC B cells exhibited minimal repertoire overlap, indicating distinct developmental pathways. As the infection resolved, Tbet+CD11c+ B cells localized to the marginal zone where splenic retention depended on integrins LFA-1 and VLA-4, forming a competitive memory subset that contributed to antibody production and secondary GC seeding upon rechallenge. Therefore, Tbet+CD11c+ B cells comprise a GC-independent memory subset capable of rapid and robust recall responses.
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| 3016. |
- Sorgenfrei, Nomi L. A. N., et al.
(författare)
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Photodriven Transient Picosecond Top-Layer Semiconductor to Metal Phase-Transition in p-Doped Molybdenum Disulfide
- 2021
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Ingår i: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095. ; 33:14
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Tidskriftsartikel (refereegranskat)abstract
- Visible light is shown to create a transient metallic S-Mo-S surface layer on bulk semiconducting p-doped indirect-bandgap 2H-MoS2. Optically created electron-hole pairs separate in the surface band bending region of the p-doped semiconducting crystal causing a transient accumulation of electrons in the surface region. This triggers a reversible 2H-semiconductor to 1T-metal phase-transition of the surface layer. Electron-phonon coupling of the indirect-bandgap p-doped 2H-MoS2 enables this efficient pathway even at a low density of excited electrons with a distinct optical excitation threshold and saturation behavior. This mechanism needs to be taken into consideration when describing the surface properties of illuminated p-doped 2H-MoS2. In particular, light-induced increased charge mobility and surface activation can cause and enhance the photocatalytic and photoassisted electrochemical hydrogen evolution reaction of water on 2H-MoS2. Generally, it opens up for a way to control not only the surface of p-doped 2H-MoS2 but also related dichalcogenides and layered systems. The findings are based on the sensitivity of time-resolved electron spectroscopy for chemical analysis with photon-energy-tuneable synchrotron radiation.
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| 3017. |
- Sousa, João M., et al.
(författare)
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Accuracy and precision of zero-echo-time, single- and multi-atlas attenuation correction for dynamic [11C]PE2I PET-MR brain imaging
- 2020
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Ingår i: EJNMMI Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A valid photon attenuation correction (AC) method is instrumental for obtaining quantitatively correct PET images. Integrated PET/MR systems provide no direct information on attenuation, and novel methods for MR-based AC (MRAC) are still under investigation. Evaluations of various AC methods have mainly focused on static brain PET acquisitions. In this study, we determined the validity of three MRAC methods in a dynamic PET/MR study of the brain.METHODS: Nine participants underwent dynamic brain PET/MR scanning using the dopamine transporter radioligand [11C]PE2I. Three MRAC methods were evaluated: single-atlas (Atlas), multi-atlas (MaxProb) and zero-echo-time (ZTE). The 68Ge-transmission data from a previous stand-alone PET scan was used as reference method. Parametric relative delivery (R1) images and binding potential (BPND) maps were generated using cerebellar grey matter as reference region. Evaluation was based on bias in MRAC maps, accuracy and precision of [11C]PE2I BPND and R1 estimates, and [11C]PE2I time-activity curves. BPND was examined for striatal regions and R1 in clusters of regions across the brain.RESULTS: For BPND, ZTE-MRAC showed the highest accuracy (bias < 2%) in striatal regions. Atlas-MRAC exhibited a significant bias in caudate nucleus (- 12%) while MaxProb-MRAC revealed a substantial, non-significant bias in the putamen (9%). R1 estimates had a marginal bias for all MRAC methods (- 1.0-3.2%). MaxProb-MRAC showed the largest intersubject variability for both R1 and BPND. Standardized uptake values (SUV) of striatal regions displayed the strongest average bias for ZTE-MRAC (~ 10%), although constant over time and with the smallest intersubject variability. Atlas-MRAC had highest variation in bias over time (+10 to - 10%), followed by MaxProb-MRAC (+5 to - 5%), but MaxProb showed the lowest mean bias. For the cerebellum, MaxProb-MRAC showed the highest variability while bias was constant over time for Atlas- and ZTE-MRAC.CONCLUSIONS: Both Maxprob- and ZTE-MRAC performed better than Atlas-MRAC when using a 68Ge transmission scan as reference method. Overall, ZTE-MRAC showed the highest precision and accuracy in outcome parameters of dynamic [11C]PE2I PET analysis with use of kinetic modelling.
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| 3018. |
- Sowerby, Leigh J., et al.
(författare)
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International registry of otolaryngologist–head and neck surgeons with COVID-19
- 2020
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Ingår i: International Forum of Allergy and Rhinology. - : Wiley. - 2042-6976 .- 2042-6984. ; 10:11, s. 1201-1208
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Tidskriftsartikel (refereegranskat)abstract
- Background: It has become clear that healthcare workers are at high risk, and otolaryngology has been theorized to be among the highest risk specialties for coronavirus disease 2019 (COVID-19). The purpose of this study was to detail the international impact of COVID-19 among otolaryngologists, and to identify instructional cases. Methods: Country representatives of the Young Otolaryngologists–International Federation of Otolaryngologic Societies (YO-IFOS) surveyed otolaryngologists through various channels. Nationwide surveys were distributed in 19 countries. The gray literature and social media channels were searched to identify reported deaths of otolaryngologists from COVID-19. Results: A total of 361 otolaryngologists were identified to have had COVID-19, and data for 325 surgeons was available for analysis. The age range was 25 to 84 years, with one-half under the age of 44 years. There were 24 deaths in the study period, with 83% over age 55 years. Source of infection was likely clinical activity in 175 (54%) cases. Prolonged exposure to a colleague was the source for 37 (11%) surgeons. Six instructional cases were identified where infections occurred during the performance of aerosol-generating operations (tracheostomy, mastoidectomy, epistaxis control, dacryocystorhinostomy, and translabyrinthine resection). In 3 of these cases, multiple operating room attendees were infected, and in 2, the surgeon succumbed to complications of COVID-19. Conclusion: The etiology of reported cases within the otolaryngology community appear to stem equally from clinical activity and community spread. Multiple procedures performed by otolaryngologists are aerosol-generating procedures (AGPs) and great care should be taken to protect the surgical team before, during, and after these operations.
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| 3019. |
- Soyama, Hitoshi, et al.
(författare)
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Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging
- 2023
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Ingår i: Ultrasonics Sonochemistry. - 1350-4177. ; 101
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model.
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| 3020. |
- Spanou, Chara E.S., et al.
(författare)
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Targeting of bone morphogenetic protein complexes to heparin/heparan sulfate glycosaminoglycans in bioactive conformation
- 2023
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Ingår i: FASEB Journal. - 0892-6638. ; 37:1
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Tidskriftsartikel (refereegranskat)abstract
- Bone morphogenetic proteins (BMP) are powerful regulators of cellular processes such as proliferation, differentiation, and apoptosis. However, the specific molecular requirements controlling the bioavailability of BMPs in the extracellular matrix (ECM) are not yet fully understood. Our previous work showed that BMPs are targeted to the ECM as growth factor-prodomain (GF-PD) complexes (CPLXs) via specific interactions of their PDs. We showed that BMP-7 PD binding to the extracellular microfibril component fibrillin-1 renders the CPLXs from an open, bioactive V-shape into a closed, latent ring shape. Here, we show that specific PD interactions with heparin/heparan sulfate glycosaminoglycans (GAGs) allow to target and spatially concentrate BMP-7 and BMP-9 CPLXs in bioactive V-shape conformation. However, targeting to GAGs may be BMP specific, since BMP-10 GF and CPLX do not interact with heparin. Bioactivity assays on solid phase in combination with interaction studies showed that the BMP-7 PD protects the BMP-7 GF from inactivation by heparin. By using transmission electron microscopy, molecular docking, and site-directed mutagenesis, we determined the BMP-7 PD-binding site for heparin. Further, fine-mapping of the fibrillin-1-binding site within the BMP-7 PD and molecular modeling showed that both binding sites are mutually exclusive in the open V- versus closed ring-shape conformation. Together, our data suggest that targeting exquisite BMP PD-binding sites by extracellular protein and GAG scaffolds integrates BMP GF bioavailability in a contextual manner in development, postnatal life, and connective tissue disease.
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