3,014 research outputs found
Ethylenedioxy homologs of N-methyl-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA) and its corresponding cathinone analog methylenedioxymethcathinone: Interactions with transporters for serotonin, dopamine, and norepinephrine
N-Methyl-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA; 'Ecstasy'; 1) and its β-keto analog methylone (MDMC; 2) are popular drugs of abuse. Little is known about their ring-expanded ethylenedioxy homologs. Here, we prepared N-methyl-(3,4-ethylenedioxyphenyl)-2-aminopropane (EDMA; 3), both of its optical isomers, and β-keto EDMA (i.e., EDMC; 4) to examine their effects at transporters for serotonin (SERT), dopamine (DAT), and norepinephrine (NET). In general, ring-expansion of the methylenedioxy group led to a several-fold reduction in potency at all three transporters. With respect to EDMA (3), S(+)3 was 6-fold, 50-fold, and 8-fold more potent than its R(-) enantiomer at SERT, DAT, and NET, respectively. Overall, in the absence of a β-carbonyl group, the ethylenedioxy (i.e., 1,4-dioxane) substituent seems better accommodated at SERT than at DAT and NET
High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts
Explosive volcanic eruptions are defined as the violent ejection of gas and hot fragments from a vent in the Earth's crust. Knowledge of ejection velocity is crucial for understanding and modeling relevant physical processes of an eruption, and yet direct measurements are still a difficult task with largely variable results. Here we apply pioneering high-speed imaging to measure the ejection velocity of pyroclasts from Strombolian explosive eruptions with an unparalleled temporal resolution. Measured supersonic velocities, up to 405 m/s, are twice higher than previously reported for such eruptions. Individual Strombolian explosions include multiple, sub-second-lasting ejection pulses characterized by an exponential decay of velocity. When fitted with an empirical model from shock-tube experiments literature, this decay allows constraining the length of the pressurized gas pockets responsible for the ejection pulses. These results directly impact eruption modeling and related hazard assessment, as well as the interpretation of geophysical signals from monitoring networks
Surface waves in solar granulation observed with {\sc Sunrise}
Solar oscillations are expected to be excited by turbulent flows in the
intergranular lanes near the solar surface. Time series recorded by the IMaX
instrument aboard the {\sc Sunrise} observatory reveal solar oscillations at
high resolution, which allow studying the properties of oscillations with short
wavelengths. We analyze two times series with synchronous recordings of Doppler
velocity and continuum intensity images with durations of 32\thinspace min and
23\thinspace min, resp., recorded close to the disk center of the Sun to study
the propagation and excitation of solar acoustic oscillations. In the Doppler
velocity data, both the standing acoustic waves and the short-lived,
high-degree running waves are visible. The standing waves are visible as
temporary enhancements of the amplitudes of the large-scale velocity field due
to the stochastic superposition of the acoustic waves. We focus on the
high-degree small-scale waves by suitable filtering in the Fourier domain.
Investigating the propagation and excitation of - and -modes with wave
numbers \thinspace 1/Mm we find that also exploding granules
contribute to the excitation of solar -modes in addition to the contribution
of intergranular lanes.Comment: 12 pages, 4 figures, to appear in a special volume on Sunrise in
Astrophysical Journal Letter
Detection of vortex tubes in solar granulation from observations with Sunrise
We have investigated a time series of continuum intensity maps and
corresponding Dopplergrams of granulation in a very quiet solar region at the
disk center, recorded with the Imaging Magnetograph eXperiment (IMaX) on board
the balloon-borne solar observatory Sunrise. We find that granules frequently
show substructure in the form of lanes composed of a leading bright rim and a
trailing dark edge, which move together from the boundary of a granule into the
granule itself. We find strikingly similar events in synthesized intensity maps
from an ab initio numerical simulation of solar surface convection. From cross
sections through the computational domain of the simulation, we conclude that
these `granular lanes' are the visible signature of (horizontally oriented)
vortex tubes. The characteristic optical appearance of vortex tubes at the
solar surface is explained. We propose that the observed vortex tubes may
represent only the large-scale end of a hierarchy of vortex tubes existing near
the solar surface.Comment: Astrophysical Journal Letters: Sunrise Special Issue, reveived 2010
June 16; accepted 2010 August
Bright points in the quiet Sun as observed in the visible and near-UV by the balloon-borne observatory Sunrise
Bright points (BPs) are manifestations of small magnetic elements in the
solar photosphere. Their brightness contrast not only gives insight into the
thermal state of the photosphere (and chromosphere) in magnetic elements, but
also plays an important role in modulating the solar total and spectral
irradiance. Here we report on simultaneous high-resolution imaging and
spectropolarimetric observations of BPs using Sunrise balloon-borne observatory
data of the quiet Sun at disk center. BP contrasts have been measured between
214 nm and 525 nm, including the first measurements at wavelengths below 388
nm. The histograms of the BP peak brightness show a clear trend toward broader
contrast distributions and higher mean contrasts at shorter wavelengths. At 214
nm we observe a peak brightness of up to five times the mean quiet-Sun value,
the highest BP contrast so far observed. All BPs are associated with a magnetic
signal, although in a number of cases it is surprisingly weak. Most of the BPs
show only weak downflows, the mean value being 240 m/s, but some display strong
down- or upflows reaching a few km/s.Comment: Accepted for publication in The Astrophysical Journal Letters on
September 08 201
Sunrise: instrument, mission, data and first results
The Sunrise balloon-borne solar observatory consists of a 1m aperture Gregory
telescope, a UV filter imager, an imaging vector polarimeter, an image
stabilization system and further infrastructure. The first science flight of
Sunrise yielded high-quality data that reveal the structure, dynamics and
evolution of solar convection, oscillations and magnetic fields at a resolution
of around 100 km in the quiet Sun. After a brief description of instruments and
data, first qualitative results are presented. In contrast to earlier
observations, we clearly see granulation at 214 nm. Images in Ca II H display
narrow, short-lived dark intergranular lanes between the bright edges of
granules. The very small-scale, mixed-polarity internetwork fields are found to
be highly dynamic. A significant increase in detectable magnetic flux is found
after phase-diversity-related reconstruction of polarization maps, indicating
that the polarities are mixed right down to the spatial resolution limit, and
probably beyond.Comment: accepted by ApJ
Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole
7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity
Novel Potent Muscarinic Receptor Antagonists: Investigation on the Nature of Lipophilic Substituents in the 5- and/or 6-Positions of the 1,4-Dioxane Nucleus
A series of novel 1,4-dioxane analogues of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M1-M5 mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between the CH2N+(CH3)3 chain in the 2-position and the cyclohexyl moiety in the 6-position, showed pKi values for mAChRs higher than those of 2 and a selectivity profile analogous to that of the clinically approved drug oxybutynin. The study of the enantiomers of 3b and the corresponding tertiary amine 33b revealed that the eutomers are (2S,6S)-(-)-3b and (2S,6S)-(-)-33b, respectively. Docking simulations on the M3 mAChR-resolved structure rationalized the experimental observations. The quaternary ammonium function, which should prevent the crossing of the blood-brain barrier, and the high M3/M2 selectivity, which might limit cardiovascular side effects, make 3b a valuable starting point for the design of novel antagonists potentially useful in peripheral diseases in which M3 receptors are involved
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