1,835 research outputs found
Mach's Principle and Model for a Broken Symmetric Theory of Gravity
We investigate spontaneous symmetry breaking in a conformally invariant
gravitational model. In particular, we use a conformally invariant scalar
tensor theory as the vacuum sector of a gravitational model to examine the idea
that gravitational coupling may be the result of a spontaneous symmetry
breaking. In this model matter is taken to be coupled with a metric which is
different but conformally related to the metric appearing explicitly in the
vacuum sector. We show that after the spontaneous symmetry breaking the
resulting theory is consistent with Mach's principle in the sense that inertial
masses of particles have variable configurations in a cosmological context.
Moreover, our analysis allows to construct a mechanism in which the resulting
large vacuum energy density relaxes during evolution of the universe.Comment: 9 pages, no figure
De mogelijkheden van UV-C straling voor de bestrijding van ziekten en plagen in de akkerbouw : een literatuurstudie
In deze studie is op een rij gezet wat er voor de akkerbouw in de literatuur bekend is over de mogelijkheden van UV-C licht voor de bestrijding van ziekten en plagen. Het bleek dat er over de toepassing in de akkerbouw met lage doseringen UV-C licht en met korte blootstellingstijden, weinig relevante literatuur beschikbaar is. Daarom is ook naar andere literatuur gezocht om eventuele perspectieven voor de akkerbouw op te kunnen sporen. Het blijkt dat bacteriën relatief makkelijk gedood worden door UV-C straling. Het DNA van deze micro-organismen wordt snel beschadigd met minder reproductie of afsterving tot gevolg. De schimmels blijken sterk te verschillen in gevoeligheid voor UV-C. Door UV-C belichting van geoogste producten kunnen aanwezige pathogenen op de producten worden gedood (direct effect) of het product kan fysiologisch veranderen waardoor de pathogenen minder kans maken (geïnduceerde resistentie). De perspectieven voor de akkerbouw zijn beperkt
Signature of wide-spread clumping in B supergiant winds
We seek to establish additional observational signatures of the effects of
clumping in OB star winds. The action of clumping on strategic wind-formed
spectral lines is tested to steer the development of models for clumped winds
and thus improve the reliability of mass-loss determinations for massive
stars.The SiIV 1400 resonance line doublets of B0 to B5 supergiants are
analysed using empirical line-synthesis models. The focus is on decoding
information on wind clumping from measurements of ratios of the radial optical
depths (tau_(rad)(w)) of the red and blue components of the SiIV doublet. We
exploit in particular the fact that the two doublet components are decoupled
and formed independently for targets with relatively low wind terminal
velocities. Line-synthesis analyses reveal that the mean ratio of tau_(rad)(w)
of the blue to red SiIV components are rarely close to the canonical value of ~
2 (expected from atomic constants), and spread instead over a range of values
between ~1 and 2. These results are interpreted in terms of a photosphere that
is partially obscured by optically thick structures in the outflowing gas.The
spectroscopic signatures established in this study demonstrate the wide-spread
existence of wind clumping in B supergiants. The additional information in
unsaturated doublet profiles provides a means to quantify the porosity of the
winds.Comment: Accepted for publication in A&A Letter
Gene-modified T cells for adoptive immunotherapy of renal cell cancer maintain transgene-specific immune functions in vivo
Abstract
BACKGROUND: We have treated three patients with carboxy-anhydrase-IX (CAIX) positive metastatic renal cell cancer (RCC) by adoptive transfer of autologous T-cells that had been gene-transduced to express a single-chain antibody-G250 chimeric receptor [scFv(G250)], and encountered liver toxicity necessitating adaptation of the treatment protocol. Here, we investigate whether or not the in vivo activity of the infused scFv(G250)(+) T cells is reflected by changes of selected immune parameters measured in peripheral blood. METHODS: ScFv(G250)-chimeric receptor-mediated functions of peripheral blood mononuclear cells (PBMC) obtained from three patients during and after treatment were compared to the same functions of scFv(G250)(+) T lymphocytes prior to infusion, and were correlated with plasma cytokine levels. RESULTS: Prior to infusion, scFv(G250)(+) T lymphocytes showed in vitro high levels of scFv(G250)-chimeric receptor-mediated functions such as killing of CAIX(+) RCC cell lines and cytokine production upon exposure to these cells. High levels of IFN-gamma were produced, whilst production of TNF-alpha, interleukin-4 (IL-4), IL-5 and IL-10 was variable and to lower levels, and that of IL-2 virtually absent. PBMC taken from patients during therapy showed lower levels of in vitro scFv(G250)-receptor-mediated functions as compared to pre-infusion, whilst IFN-gamma was the only detectable cytokine upon in vitro PBMC exposure to CAIX. During treatment, plasma levels of IFN-gamma increased only in the patient with the most prominent liver toxicity. IL-5 plasma levels increased transiently during treatment in all patients, which may have been triggered by the co-administration of IL-2. CONCLUSION: ScFv(G250)-receptor-mediated functions of the scFv(G250)(+) T lymphocytes are, by and large, preserved in vivo upon administration, and may be reflected by fluctuations in plasma IFN-gamma levels
Spectral analysis of the sdO K 648, the exciting star of the planetary nebula Ps 1 in the globular cluster M 15 (NGC 7078)
We present a spectral analysis of the sdO central star K 648 based on
medium-resolution optical and high-resolution UV spectra. The photospheric
parameters are determined by means of state-of-the-art NLTE model atmosphere
techniques.
We found Teff = 39 +/- 2 kK and log g = 3.9 +/- 0.2. The helium (He/H=0.08)
and oxygen (O/H=0.001) abundances are about solar while carbon is enriched by a
factor of 2.5 (C/H=0.001). Nitrogen (N/H = 10**(-6), [N/H] = -2.0) appears at a
sub-solar value. However, these metal abundances are much higher than the
cluster's metallicity M 15: [Fe/H] = -2.25).
The surface composition appears to be a mixture of the original hydrogen-rich
material and products of helium burning (3 alpha process) which have been mixed
up to the surface. The abundances of He, C, and N are consistent with the
nebular abundance, while O is considerably more abundant in the photosphere
than in the nebula.
From a comparison of its position in the log Teff - log g plane with
evolutionary calculations a mass of 0.57 (+0.02, -0.01) Msun and a luminosity
of 3810 +/- 1200 Lsun are deduced.
Our spectroscopic distance d = 11.1 (+2.4, -2.9) kpc is in agreement with the
distance of M 15 as determined by Alves et al. (2000).
From the GHRS spectra we measure a radial velocity of vrad = -130 km/sec.Comment: 8 pages, 13 figure
Phosphorylation by protein kinase C and the responsiveness of Mg2+-ATPase to Ca2+ of myofibrils isolated from stunned and non-stunned porcine myocardinm
Previously we showed in an in situ porcine model that the thiadiazinone derivative [+]EMD 60263, a Ca2+ sensitizer without phosphodiesterase III inhibitory properties, increased contractility more profoundly in stunned than in non-stunned myocardium. This finding was consistent with the observed leftward shifts of the pCa2+/Mg2+-ATPase curves of isolated myofibrils induced by [+]EMD 60263. The aim of the present investigation was to study the possible involvement of protein kinase C in the mechanism of reduced Ca2+ responsiveness of myofilaments during stunning. No differences were observed in the maximal activity of the Ca2+-stimulated Mg2+-ATPase and in the pCa50 of myofibrils isolated from non-stunned and stunned myocardium. After phosphorylation with [gamma-32P]-ATP and excess of purified rat brain protein kinase C, the myofibrils were separated on sodiumdodecylsulphate-polyacrylamide gelectrophoresis and the 32P incorporation counted by the Molecular Imager. Ca2+/ phosphatidylserine/sn-1,2 diolein-dependent 32P incorporation catalyzed by excess of purified rat brain protein kinase C in C-protein, TnT and TnI subunits did not show any differences between myofibrils from non-stunned and stunned myocardium. However, protein kinase C-induced phosphorylation of myofibrils isolated from ventricular myocardium of sham-operated pigs resulted in a marked leftward shift of the PCa50 from 6.03 ± 0.04 to 6.44 ± 0.06 (p < 0.05), while porcine heart cyclic AMP-dependent protein kinase-induced phosphorylation resulted in an expected small rightward shift to 5.97, although statistical significance was not reached. Protein kinase C-induced phosphorylation also stimulated (80%) the maximal myofibrillar Mg2+-ATPase activity. [+]EMD 60263 (3 μM) produced a leftward shift of the myofibrillar pCa2+/Mg2+-ATPase curve which was unaffected by prior protein kinase C-induced phosphorylation. In conclusion, the findings with isolated myofibrils from myocardium of anaesthetized open-chest pigs indicate that protein kinase C might be involved in the mechanism of reduced Ca2+ responsiveness of myofilaments in stunned myocardium. However, at this stage no differences could be found between the maximal activity of the Ca2+-stimulated Mg2+ -ATPase, the pCa50 and the degree of phosphorylation of myofibrils isolated from stunned and non-stunned myocardium
The star cluster formation history of the LMC
The Large Magellanic Cloud is one of the nearest galaxies to us and is one of
only few galaxies where the star formation history can be determined from
studying resolved stellar populations. We have compiled a new catalogue of
ages, luminosities and masses of LMC star clusters and used it to determine the
age distribution and dissolution rate of LMC star clusters. We find that the
frequency of massive clusters with masses M>5000 Msun is almost constant
between 10 and 200 Myr, showing that the influence of residual gas expulsion is
limited to the first 10 Myr of cluster evolution or clusters less massive than
5000 Msun. Comparing the cluster frequency in that interval with the absolute
star formation rate, we find that about 15% of all stars in the LMC were formed
in long-lived star clusters that survive for more than 10 Myr. We also find
that the mass function of LMC clusters younger than 1 Gyr can be fitted by a
power-law mass function with slope \alpha=-2.3, while older clusters follow a
significantly shallower slope and interpret this is a sign of the ongoing
dissolution of low-mass clusters. Our data shows that for ages older than 200
Myr, about 90% of all clusters are lost per dex of lifetime. The implied
cluster dissolution rate is significantly faster than that based on analytic
estimates and N-body simulations. Our cluster age data finally shows evidence
for a burst in cluster formation about 1 Gyr ago, but little evidence for
bursts at other ages.Comment: 18 pages, 6 figures, MNRAS in pres
In vitro analysis of SERCA2 gene regulation in hypertrophic cardiomyocytes and increasing transfection efficiency by gene-gun biolistics
The transcriptional downregulation of the SERCA2 gene is studied using neonatal rat cardiomyocytes stimulated with endothelin-1 to induce hypertrophy. Liposome-based transfection of cells with a 1.9 kb SERCA2 promoter fragment directed expression of a reporter gene identical to the downregulation of genomic SERCA2 expression by endothelin-1. Results of a new gene gun technology for transient transfection of cardiomyocytes with a RSVβ-galactosidase construct are reported. This new method for propelling DNA-coated gold beads into cardiomyocytes is extremely suitable for directly testing promoter/reporter gene DNA constructs since the transfection efficiency (approximately 10%) appears to be higher than traditional transfection methods
Properties of galactic B[e] supergiants. IV. Hen3-298 and Hen3-303
We present the results of optical and near-IR spectroscopic and near-IR
photometric observations of the emission-line stars Hen3-298 and Hen3-303.
Strong emission in the H-alpha line is found in both objects. The presence of
Fe II and [O I] emission lines in the spectrum of Hen3-298 indicates that it is
a B[e] star. The double-peaked CO line profiles, found in the infrared spectrum
of Hen3-298, along with the optical line profiles suggest that the star is
surrounded by a rotating circumstellar disk. Both objects also show infrared
excesses, similar to those of B[e] stars. The radial velocities of the
absorption and emission lines as well as a high reddening level suggest that
the objects are located in the Norma spiral arm at a distance of 3-4.5 kpc. We
estimated a luminosity of log (L/L_sun) ~ 5.1 and a spectral type of no earlier
than B3 for Hen3-298. Hen3-303 seems to be a less luminous B-type object (log
(L/L_sun) ~ 4.3), located in the same spiral arm.Comment: 8 pages, 5 figures, accepted by Astronomy and Astrophysic
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