Search results for "Ih"
showing 10 items of 9382 documents
Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons
2017
High energy cosmic ray electrons plus positrons (CREs), which lose energy quickly during their propagation, provide an ideal probe of Galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been directly measured up to $\sim 2$ TeV in previous balloon- or space-borne experiments, and indirectly up to $\sim 5$ TeV by ground-based Cherenkov $\gamma$-ray telescope arrays. Evidence for a spectral break in the TeV energy range has been provided by indirect measurements of H.E.S.S., although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the …
Stereoselective synthesis of the published structure of synargentolide A and of one of its stereoisomers
2005
A stereoselective synthesis is described of the structure published for the naturally occurring synargentolide A, an α,β-unsaturated lactone. The key steps of the synthesis were a Brown´s asymmetric allylation and a ring closing metathesis. The spectroscopic data of the synthetic product were very close to those of the natural product but did not exactly match them. An epimer of the published structure was then synthesized according to a similar strategy. Again, the data of the synthetic product did not match those reported for the natural product. It is thus likely that the actual structure of synargentolide A differs from the published one in more than mere stereochemical aspects. Marco V…
Nitric Acid Trihydrate (NAT) formation at low NAT supersaturation in Polar Stratospheric Clouds (PSCs)
2005
International audience; A PSC was detected on 6 February 2003 in the Arctic stratosphere by in-situ measurements onboard the high-altitude research aircraft Geophysica. Low number densities (~10-4cm-3) of small nitric acid (HNO3) containing particles (dTNAT, these NAT particles have the potential to grow further and to remove HNO3 from the stratosphere, thereby enhancing polar ozone loss. Interestingly, the NAT particles formed in less than a day at temperatures just slightly below TNAT (T>TNAT-3.1K). This unique measurement of PSC formation at extremely low NAT saturation ratios (SNAT?10) constrains current NAT nucleation theories. We suggest, that the NAT particles have formed heterogeneo…
Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere
2014
Abstract. Nitric acid trihydrate (NAT) particles in the polar stratosphere have been shown to be responsible for vertical redistribution of reactive nitrogen (NOy). Recent observations by Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO satellite have been explained in terms of heterogeneous nucleation of NAT on foreign nuclei, revealing this to be an important formation pathway for the NAT particles. In state of the art global- or regional-scale models, heterogeneous NAT nucleation is currently simulated in a very coarse manner using a constant, saturation-independent nucleation rate. Here we present first simulations for the Arctic winter 2009/2010 applying a n…
Hyperspectral response of agronomic variables to background optical variability: Results of a numerical experiment
2022
Understanding how biophysical and biochemical variables contribute to the spectral characteristics of vegetation canopies is critical for their monitoring. Quantifying these contributions, however, remains difficult due to extraneous factors such as the spectral variability of canopy background materials, including soil/crop-residue moisture, soil-type, and non-photosynthetic vegetation (NPV). This study focused on exploring the spectral response of two important agronomic variables (1) leaf chlorophyll content (Cab ) and (2) leaf area index (LAI) under various canopy backgrounds through a global sensitivity analysis of wheat-like canopy spectra simulated using the physically-based PROSAIL …
A study on the fragmentation of sulfuric acid and dimethylamine clusters inside an atmospheric pressure interface time-of-flight mass spectrometer
2022
Abstract. Sulfuric acid and dimethylamine vapours in the atmosphere can form molecular clusters, which participate in new particle formation events. In this work, we have produced, measured, and identified clusters of sulfuric acid and dimethylamine using an electrospray ionizer coupled with a planar-differential mobility analyser, connected to an atmospheric pressure interface time-of-flight mass spectrometer (ESI–DMA–APi-TOF MS). This set-up is suitable for evaluating the extent of fragmentation of the charged clusters inside the instrument. We evaluated the fragmentation of 11 negatively charged clusters both experimentally and using a statistical model based on quantum chemical data. Th…
Mode and mechanism of neurotensin action in rat proximal colon
1997
Abstract This study examined the mechanism of action of neurotensin on intraluminal pressure in rat proximal colon. The direct and indirect contractile response to neurotensin (100 nM) was abolished in Ca 2+ -free solution, and was antagonized by nifedipine (1–5–10 nM) and potentiated by Bay K 8644 (methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate) (10–100–1000 nM). Neurotensin, in the presence of nifedipine (10 nM) and atropine (1 μM), induced a tetrodotoxin-insensitive inhibitory effect, which was antagonized by SR 48692 (2[(1-(7-chloro-4-quinolinyl)-5-(2,6-dimethoxy-phenyl)pyrazol-3-yl) carbonyl amino]tricyclo (3.3.1.1. 3.7 ) decan-2-carboxylic a…
Reliģiozitātes un kauna saistība ar attieksmi pret seksualitāti
2019
Pētījuma mērķis bija noskaidrot, vai pastāv saistība starp reliģiozitāti, kaunu un attieksmēm pret seksualitāti. Pētījumā piedalījās 150 respondenti, vecumā no 18 līdz 55 gadiem, 45 vīrieši un 105 sievietes. Respondenti ir gan dažādu kristīgo konfesiju pārstāvji, gan arī cilvēki, kuri sevi uztver kā agnostiķus vai ateistus. Pētījuma datu ieguvei tika izmantota Kauna kompasa aptauja (Compass of Shame Scale, 2006), Seksuālā kauna aptauja (Kyle Inventory of Sexual Shame, 2013), Reliģisko saistību aptauja-10 (Religious Commitment Inventory-10, 2003) un Īsa seksuālo attieksmju aptauja (Brief Sexual Attitudes Scale, 2006). Pētījuma rezultāti uzrādīja statistiski nozīmīgu saistību starp reliģiozit…
Personības vērtību saistība ar attieksmi pret homoseksualitāti pieaugušajiem.
2019
Pētījuma tēma: Personības vērtību saistība ar attieksmi pret homoseksualitāti pieaugušajiem. Pētījuma hipotēze: Pastāv sakarība starp vecuma perioda vērtībām un attieksmi pret homoseksualitāti pieaugušajiem. Pētījuma jautājumi: 1.Vai pastāv sakarība starp personības vērtībām un attieksmi pret homoseksuālismu? 2.Vai sakarība starp personas vērtībām un attieksmi pret homoseksualitāti atšķiras un pieaugušajiem dažādos vecuma posmos? Pētījuma metode: Pētījumā kopumā piedalījās 337 respondenti, no tiem 253 sievietes un 84 vīrieši (75.07 % sievietes un 24.93 % vīriešu). Respondenti tika iedalīti 3 vecuma grupās: 1.66 respondenti vecuma grupā 20-25 gadi; 2.177 respondenti vecuma grupā 26-40 gadi; …
Promocijas darbs
2011
Elektroniskā versija nesatur pielikumus