2,478 research outputs found
Dibenzo[a,g]quinolizin-8-ones: synthesis, estrogen receptor affinities, and cytostatic activity
A number of acetoxy-substituted dibenzo[a,g]quinolizin-8-ones were
synthesized by the reaction of 1-oxoisoquinolines with substituted homophthalic acid
anhydride. All of the derivatives with acetoxy groups in positions 3 and 10 bind to the
estrogen receptor. Relative binding affinities (RBA) ranged from 1.8 to 5.6 (estradiol:
RBA = 100) when the substituent at C-6 was a short alkyl group. Introduction of
additional oxygen functions in the 2- and/or 11-position decreased binding affinities.
Analyses of the enantiomers of 6-methyl (6b) and 6-ethyl (6c) derivatives revealed that
the receptor binding is mainly due to one optical isomer (e.g. (-)-6b, 9.9; (+)-6b, 0.6).
In hormone-sensitive human MCF-7 breast cancer cells, compounds with one acetoxy
group in each aromatic ring strongly inhibited cellular growth. Despite marked differences
in receptor affinity, the enantiomers displayed similar activities in this cell
culture. In hormone-independent MDA-MB 231 mammary tumor cells, only a weak
cytostatic effect was recorded at 10-5 M. In the immature mouse uterine weight test,
minimal estrogenic activity was observed. At higher doses, a significant anti-estrogenic
effect became evident. It is assumed that the estrogen antagonism is responsible for
the specific cytostatic effect in MCF-7 breast cancer cells
No temperature fluctuations in the giant HII region H 1013
While collisionally excited lines in HII regions allow one to easily probe
the chemical composition of the interstellar medium in galaxies, the possible
presence of important temperature fluctuations casts some doubt on the derived
abundances. To provide new insights into this question, we have carried out a
detailed study of a giant HII region, H 1013, located in the galaxy M101, for
which many observational data exist and which has been claimed to harbour
temperature fluctuations at a level of t^2 = 0.03-0.06. We have first
complemented the already available optical observational datasets with a
mid-infrared spectrum obtained with the Spitzer Space Telescope. Combined with
optical data, this spectrum provides unprecedented information on the
temperature structure of this giant HII region. A preliminary analysis based on
empirical temperature diagnostics suggests that temperature fluctuations should
be quite weak. We have then performed a detailed modelling using the pyCloudy
package based on the photoionization code Cloudy. We have been able to produce
photoionization models constrained by the observed Hb surface brightness
distribution and by the known properties of the ionizing stellar population
than can account for most of the line ratios within their uncertainties. Since
the observational constraints are both strong and numerous, this argues against
the presence of significant temperature fluctuations in H 1013. The oxygen
abundance of our best model is 12 + log O/H = 8.57, as opposed to the values of
8.73 and 8.93 advocated by Esteban et al. (2009) and Bresolin (2007),
respectively, based on the significant temperature fluctuations they derived.
However, our model is not able to reproduce the intensities of the oxygen
recombination lines . This cannot be attributed to observational uncertainties
and requires an explanation other than temperature fluctuations.Comment: accepted in Astronomy & Astrophysic
Green's Relations in Finite Transformation Semigroups
We consider the complexity of Green's relations when the semigroup is given
by transformations on a finite set. Green's relations can be defined by
reachability in the (right/left/two-sided) Cayley graph. The equivalence
classes then correspond to the strongly connected components. It is not
difficult to show that, in the worst case, the number of equivalence classes is
in the same order of magnitude as the number of elements. Another important
parameter is the maximal length of a chain of components. Our main contribution
is an exponential lower bound for this parameter. There is a simple
construction for an arbitrary set of generators. However, the proof for
constant alphabet is rather involved. Our results also apply to automata and
their syntactic semigroups.Comment: Full version of a paper submitted to CSR 2017 on 2016-12-1
Uniaxial pressure dependence of magnetic order in MnSi
We report comprehensive small angle neutron scattering (SANS) measurements
complemented by ac susceptibility data of the helical order, conical phase and
skyrmion lattice phase (SLP) in MnSi under uniaxial pressures. For all
crystallographic orientations uniaxial pressure favours the phase for which a
spatial modulation of the magnetization is closest to the pressure axis.
Uniaxial pressures as low as 1kbar applied perpendicular to the magnetic field
axis enhance the skyrmion lattice phase substantially, whereas the skyrmion
lattice phase is suppressed for pressure parallel to the field. Taken together
we present quantitative microscopic information how strain couples to magnetic
order in the chiral magnet MnSi.Comment: 23 pages, includes supplemen
Technological Challenges of Ambient Serious Games in Higher Education
Naturally, university courses should be designed to attract students,
engaging them to achieve learning goals. Toward this end, the use of Serious
Games has been proposed in the literature. To address positive effects, such as
content memorability and attendance rates, we propose Ambient Serious Games as
games embedded in a computer-enriched environment, which is only partially
perceived mentally by players. In this paper, we describe five technological
key challenges that must be overcome to seamlessly and beneficially integrate
an Ambient Serious Game into teaching. These challenges, derived from a
scenario, focus on the technological provision and conduct of such games based
on a software platform. They include (1) the integration of physical smart
learning objects in heterogeneous environments under dynamic constraints, (2)
the representation of abstract subject matter using smart learning objects, (3)
the guided or automatic connection of all involved components, (4) the
explanation of the components, their interaction, as well as the serious game
itself, and (5) feedback on the game state.Comment: 6 page
Wild zebra finches do not use social information from conspecific reproductive success for nest site choice and clutch size decisions
Information about the quality of local habitat can greatly help to improve an individual’s decision-making and, ultimately, its fitness. Nevertheless, little is known about the mechanisms and significance of information use in reproductive decisions, especially in unpredictable environments. We tested the hypothesis that perceived breeding success of conspecifics serves as a cue for habitat quality and hence influences breeding decisions (nest site choice and clutch size), using the zebra finch (Taeniopygia guttata) as a model species. Zebra finches breed opportunistically in the unpredictable, arid zone of Australia. They often inspect the nests of conspecifics, potentially to prospect on conspecific reproductive success, i.e., to collect social information. We conducted a clutch and brood size manipulation to experimentally create the perception of high and low quality areas. In six areas, clutch sizes of almost 300 zebra finch nests were either all increased (N = 3 areas) or reduced (N = 3 areas) throughout one breeding season. The number of breeding pairs and sizes of newly laid clutches were not significantly affected by the manipulated reproductive success of the areas. Thus, zebra finches did not use social cues for their reproductive decisions, which contrasts with findings of species in temperate zones, and could be an adaptation to the high unpredictability of their habitat. Even the personal experience of rebreeding birds did not directly affect their clutch size. Our study suggests that zebra finches employ a high level of opportunism as a key strategy for reproduction. Further, this is the first study to our knowledge using an experimental approach in the wild to demonstrate that decision-making in unpredictable natural environments might differ from decision-making in temperate environments with seasonal breeding
Indomethacin decreases viscosity of gallbladder bile in patients with cholesterol gallstone disease
There is experimental evidence that inhibition of cyclooxygenase with nonsteroidal anti-inflammatory drugs may decrease cholesterol gall-stone formation and mitigate biliary pain in gall-stone patients. The mechanisms by which NSAIDs exert these effect are unclear. In a prospective, controlled clinical trial we examined the effects of oral indomethacin on the composition of human gall-bladder bile. The study included 28 patients with symptomatic cholesterol or mixed gallstones. Of these, 8 were treated with 3 × 25 mg indomethacin daily for 7 days prior to elective cholecystectomy while 20 received no treatment and served as controls. Bile and tissue samples from the gallbladder were obtained during cholecystectomy. Indomethacin tissue levels in the gallbladder mucosa, as assessed by HPLC, were 1.05±0.4 ng/mg wet weight, a concentration known to inhibit effectively cyclooxygenase activity. Nevertheless, no differences between the treated and untreated groups were found in the concentrations of biliary mucus glycoprotein (0.94±0.27 versus 0.93±0.32 mg/ml) or total protein (5.8±0.9 versus 6.4±1.3 mg/ml), cholesterol saturation (1.3±0.2 versus 1.5±0.2), or nucleation time (2.0±3.0 versus 1.5±2.0 days). However, biliary viscosity, measured using a low-shear rotation viscosimeter, was significantly lower in patients receiving indomethacin treatment (2.9±0.6 versus 5.6±1.2 mPa.s; P < 0.02). In conclusion, in man oral indomethacin decreases bile viscosity without alteration of bile lithogenicity or biliary mucus glycoprotein content. Since mucus glycoproteins are major determinants of bile viscosity, an alteration in mucin macromolecular composition may conceivably cause the indomethacin-induced decrease in biliary viscosity and explain the beneficial effects of nonsteroidal anti-inflammatory drugs in gallstone disease
Band structure of helimagnons in MnSi resolved by inelastic neutron scattering
A magnetic helix realizes a one-dimensional magnetic crystal with a period
given by the pitch length . Its spin-wave excitations -- the
helimagnons -- experience Bragg scattering off this periodicity leading to gaps
in the spectrum that inhibit their propagation along the pitch direction. Using
high-resolution inelastic neutron scattering the resulting band structure of
helimagnons was resolved by preparing a single crystal of MnSi in a single
magnetic-helix domain. At least five helimagnon bands could be identified that
cover the crossover from flat bands at low energies with helimagnons basically
localized along the pitch direction to dispersing bands at higher energies. In
the low-energy limit, we find the helimagnon spectrum to be determined by a
universal, parameter-free theory. Taking into account corrections to this
low-energy theory, quantitative agreement is obtained in the entire energy
range studied with the help of a single fitting parameter.Comment: 5 pages, 3 figures; (v2) slight modifications, published versio
A First Estimate Of The X-Ray Binary Frequency As A Function Of Star Cluster Mass In A Single Galactic System
We use the previously-identified 15 infrared star-cluster counterparts to
X-ray point sources in the interacting galaxies NGC 4038/4039 (the Antennae) to
study the relationship between total cluster mass and X-ray binary number. This
significant population of X-Ray/IR associations allows us to perform, for the
first time, a statistical study of X-ray point sources and their environments.
We define a quantity, \eta, relating the fraction of X-ray sources per unit
mass as a function of cluster mass in the Antennae. We compute cluster mass by
fitting spectral evolutionary models to K_s luminosity. Considering that this
method depends on cluster age, we use four different age distributions to
explore the effects of cluster age on the value of \eta and find it varies by
less than a factor of four. We find a mean value of \eta for these different
distributions of \eta = 1.7 x 10^-8 M_\sun^-1 with \sigma_\eta = 1.2 x 10^-8
M_\sun^-1. Performing a \chi^2 test, we demonstrate \eta could exhibit a
positive slope, but that it depends on the assumed distribution in cluster
ages. While the estimated uncertainties in \eta are factors of a few, we
believe this is the first estimate made of this quantity to ``order of
magnitude'' accuracy. We also compare our findings to theoretical models of
open and globular cluster evolution, incorporating the X-ray binary fraction
per cluster.Comment: 20 pages, 6 figures, accepted by Ap
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