Stellar Dynamics at the Galactic Center with an Extremely Large Telescope

We discuss experiments achievable via monitoring of stellar dynamics near the massive black hole at the Galactic center with a next generation, extremely large telescope (ELT). Given the likely observational capabilities of an ELT and current knowledge of the stellar environment at the Galactic center, we synthesize plausible samples of stellar orbits around the black hole. We use the Markov Chain Monte Carlo method to evaluate the constraints that orbital monitoring places on the matter content near the black hole. Results are expressed as functions of the number N of stars with detectable orbital motions and the astrometric precision dtheta and spectroscopic precision dv at which stellar proper motions and radial velocities are monitored. For N = 100, dtheta = 0.5 mas, and dv = 10 km/s -- a conservative estimate of the capabilities of a 30 meter telescope -- the extended matter distribution enclosed by the orbits will produce measurable deviations from Keplerian motion if >1000 Msun is enclosed within 0.01 pc. The black hole mass and distance to the Galactic center will be measured to better than ~0.1%. Lowest-order relativistic effects, such as the prograde precession, will be detectable if dtheta < 0.5 mas. Higher-order effects, including frame dragging due to black hole spin, requires dtheta < 0.05 mas, or the favorable discovery of a compact, highly eccentric orbit. Finally, we calculate the rate at which monitored stars undergo detectable nearby encounters with background stars. Such encounters probe the mass function of stellar remnants that accumulate near the black hole. We find that ~30 encounters will be detected over a 10 yr baseline for dtheta = 0.5 mas.Comment: 14 pages, 5 figures; discussion no longer aperture-specific (TMT -> ELT), matches ApJ versio

Artemisinin Story from the Balkans

The isolation is reported of artemisinin (qinghaosu), a drug remarkably effective against malaria, from the aerial parts of Artemisia annua L. (sweet wormwood) at the Department of Chemistry, University of Belgrade (now Faculty of Chemistry), Serbia by the end of 1970, almost two years before the isolation of the same compound in China

Long Term Evolution of Massive Black Hole Binaries

The long-term evolution of massive black hole binaries at the centers of galaxies is studied in a variety of physical regimes, with the aim of resolving the ``final parsec problem,'' i.e., how black hole binaries manage to shrink to separations at which emission of gravity waves becomes efficient. A binary ejects stars by the gravitational slingshot and carves out a loss cone in the host galaxy. Continued decay of the binary requires a refilling of the loss cone. We show that the standard treatment of loss cone refilling, derived for collisionally relaxed systems like globular clusters, can substantially underestimate the refilling rates in galactic nuclei. We derive expressions for non-equilibrium loss-cone dynamics and calculate time scales for the decay of massive black hole binaries following galaxy mergers, obtaining significantly higher decay rates than heretofore. Even in the absence of two-body relaxation, decay of binaries can persist due to repeated ejection of stars returning to the nucleus on eccentric orbits. We show that this recycling of stars leads to a gradual, approximately logarithmic dependence of the binary binding energy on time. We derive an expression for the loss cone refilling induced by the Brownian motion of a black hole binary. We also show that numerical N-body experiments are not well suited to probe these mechanisms over long times due to spurious relaxation.Comment: Replaced to match the accepted version, ApJ, 596 (2003

Einfluß der Unterlage auf die Intensität der Photosynthese und den Transport der Assimilate bei jungen Pfropfreben

Experimente mit jungen Pfropfreben der Sorte Welschriesling auf den Unterlagen Kober 5 BE und Rupestris du Lot führten zu folgenden Ergebnissen: Die Photosynthese-Aktivität der Blätter bei jungen 'Pfropfre'ben hängt von der Unterlage ab. Von den untersuchten Unterlagen ruft Rupestris du Lot eine intensivere14C02-Aufnahme und ein besseres Sproßwachstum des Reises hervor.   Die Akkumulation der Assimilate in der Pfropfzone ist jedoch bei Pfropfung auf Kober 5 BB größer, was auf eine Hemmung des absteigenden Transportes organischer Verbindungen hinweist.Verschiedene Unterlagen beeiruflussen in verschiedenem Umfange die Biosynthese organischer Verbindungen durch die Pfropfrebe, aber auch die Veratmung der Assimilate. Darüber hinaus bedingen sie weitere physiologische Änderungen, so daß auf sehr komplizierte, noch weitgehend ungeklärte Einflüsse der Unterlage auf die junge Pfropfrebe geschlossen werden muß

Reducing the weak lensing noise for the gravitational wave Hubble diagram using the non-Gaussianity of the magnification distribution

Gravitational wave sources are a promising cosmological standard candle because their intrinsic luminosities are determined by fundamental physics (and are insensitive to dust extinction). They are, however, affected by weak lensing magnification due to the gravitational lensing from structures along the line of sight. This lensing is a source of uncertainty in the distance determination, even in the limit of perfect standard candle measurements. It is commonly believed that the uncertainty in the distance to an ensemble of gravitational wave sources is limited by the standard deviation of the lensing magnification distribution divided by the square root of the number of sources. Here we show that by exploiting the non-Gaussian nature of the lensing magnification distribution, we can improve this distance determination, typically by a factor of 2--3; we provide a fitting formula for the effective distance accuracy as a function of redshift for sources where the lensing noise dominates.Comment: matches PRD accepted version (expanded description of the cosmological parameter space + minor changes

A current driven instability in parallel, relativistic shocks

Recently, Bell has reanalysed the problem of wave excitation by cosmic rays propagating in the pre-cursor region of a supernova remnant shock front. He pointed out a strong, non-resonant, current-driven instability that had been overlooked in the kinetic treatments, and suggested that it is responsible for substantial amplification of the ambient magnetic field. Magnetic field amplification is also an important issue in the problem of the formation and structure of relativistic shock fronts, particularly in relation to models of gamma-ray bursts. We have therefore generalised the linear analysis to apply to this case, assuming a relativistic background plasma and a monoenergetic, unidirectional incoming proton beam. We find essentially the same non-resonant instability noticed by Bell, and show that also under GRB conditions, it grows much faster than the resonant waves. We quantify the extent to which thermal effects in the background plasma limit the maximum growth rate.Comment: 8 pages, 1 figur

Analysis of the impact of sociodemographic characteristics and attitudes on practice of gynaecologists and pharmacists regarding family planning methods in Serbia

Uvod i ciljevi. Stopa abortusa u Srbiji je duplo veća od stope fertiliteta i među najvišim je u Evropi. Glavni faktor koji tome doprinosi je mala upotreba moderne kontracepcije. Ciljevi disertacije su bili da se istraže stavovi i praksa ginekologa u vezi sa metodama planiranja porodice, kao i da se ispita uticaj socio-demografskih karakteristika i stavova na primenu ovih metoda. Takođe, da se istraže znanje, stavovi i praksa farmaceuta u vezi sa hitnom kontracepcijom i da se ispita veza između socio-demografskih karakteristika, znanja i stavova sa praksom. Metode istraživanja. Sprovedene su dve studije preseka sa ginekolozima i farmaceutima javnih apoteka. Podaci su analizirani chi-kvadrat testom, univarijantnom i multiplom logističkom regresijom. Rezultati i diskusija. Polovina ispitanih ginekologa je izjavila da ima moralne/etičke zamerke na metode kontracepcije, kao i da ih ne bi ponudili pacijentkinji. Ginekolozi sa zamerkama na kontracepciju imali su manje šanse da imaju zamerke na abortus (OR: 0,422). Ovakav stav je najizraženiji u Južnoj i Istočnoj Srbiji. Značajno veći broj farmaceuta nego ginekologa (12% vs. 2%, p<0,001) ne bi izdao hitnu kontracepciju ni pod kakvim uslovima. Takođe, veliki broj farmaceuta je izjavio da bi odbili izdavanje ovih proizvoda generalno (15%), kao i u specifičnim situacijama: za buduću upotrebu (72%), kada je prošlo >72 sata od odnosa (78%), kada nije došla krajnja korisnica (70%), kao i zbog godina korisnice (75%). Polovina ispitanika imala je nedovoljno znanje o hitnoj kontracepciji i upravo ta grupa je imala veće šanse da odbije njeno izdavanje generalno (OR: 1,862) i u određenim situacijama (nije krajnja korisnica (OR: 1,412) ili >72 sata od odnosa (OR: 1,445)). Farmaceuti sa više godina radnog iskustva imali veće šanse da odbiju izdavanje korisnici mlađoj od 16 godina (OR: 1,023). Zaključak. Naše istraživanje proizvelo je značajne rezultate koji se mogu primeniti za buduća istraživanja i unapređenje zdravstvene politike i prakse.Introduction and aims. Abortion rate in Serbia is duble fertility rate and amog the highest in Europe. A major factor contributing to this is the low prevalence of use of modern contraception. The aims of dissertation were to investigate attitudes and practice of gynaecologists related to family planning methods, and to examine the influence of sociodemogrphic characteristics and attitudes on use of these methods. Also, to investigate knowledge, attitudes and practice of pharmacists regarding emergency contraception and to examine the influence of socio-demogrphic characteristics, knowledge and attitudes on their practice. Methods. Two cross-sectional studies, with ginaecologists and community pharmacists, were conducted. Data were analysed by chi-square test, univariate and multiple logistic regression. Results and discussion. Half of the surveyed gynaecologists had moral/ethical objections to certain contraceptive methods, and would not offer them to patients. Those who objected to contraceptives were less likely to object to abortions (OR: 0,422). This attitude was more prevalent in Southern and Eastern Serbia. Significantly more pharmacists than gynaecologists (12% vs. 2%, p<0.001) would not provide emergency contraception to anybody under any circumstance. Also, pharmacists in large number denied these products provision overall (15%) and in particular circumstances; when it was for future use (72%), >72 h after intercourse (78%), for non-intended user (70%) and because of patient age (75%). Half of the surveyed pharmacists had poor knowledge of emergency contraception and that group was more likely to decline the provision overall (OR: 1.862) and in particular circumstances (non-intended user (OR: 1.412) or >72 h after intercourse (OR: 1.445)). Pharmacists with more work experience were more likely to deny emergency contraception requests to user younger than 16 (OR: 1.023).Conclusion. Our study produced important results that can be used to inform future research and to improve health policy and practice

Tissue specificity of 17ß-estradiol effects on insuli signaling pathway.

Insulin i estradiol imaju va.nu ulogu u regulaciji metabolizma ugljenih hidrata i lipida. Razli.ita klini.ka istra.ivanja i eksperimentalni podaci ukazuju da varijacije u koncentraciji estrogena uti.u na insulinsko delovanje. Cilj ove studije je bilo pore.enje uticaja estradiola na po.etne molekule insulinskog signalnog puta u glavnim ciljnim tkivima za insulin (jetra) i estradiol (uterus), kao i u srcu, u kome oba hormona ostvaruju zna.ajne efekte. Ovarijektomisane .enke pacova su tretirane estradiolom 6 h pre analize sadr.aja proteina i iRNK molekula signalnog puta insulina. Da bi se istakli efekti estradiola na fosforilacije i asocijacije molekula relevantne za insulinski signalni put, .ivotinje su dodatno injecirane insulinom 30 min pre eksperimenta. Tretman estradiolom nije promenio nivo insulina i glukoze u plazmi, ali je doveo do zna.ajnog smanjenja nivoa slobodnih masnih kiselina i pove.anja te.ine uterusa. U jetri, tretman estradiolom je doveo do smanjenja fosforilacije IR, kao i smanjenja proteinskog sadr.aja IRS-1, .to navodi na zaklju.ak da je estradiol suprimirao efekte insulina preko IR/IRS-1 puta i verovatno ih usmerio na alternativni put, .to je potkrepljeno i pove.anjem proteinskog sadr.aja IRS-2. U uterusu je tretman estradiolom nakon 6 h doveo do statisti.ki zna.ajnog pove.anja proteinskog sadr.aja skoro svih ispitivanih molekula signalnog puta insulina. U srcu je estradiol uzrokovao pove.anje asocijacije IRS-1/p85, pove.anja sadr.aja proteina i iRNK p85, kao i pove.anje fosforilacije Akt na Ser473. S druge strane, tretman estradiolom je u srcu izazvao i smanjenje fosforilacije tirozina IR, smanjenje proteinskog sadr.aja IRS-2 i iRNK oba IRS proteina. Rezultati ove studije ukazuju na to da tretman estradiolom indukuje tkivno specifi.ne promene u insulinskom signalnom putu. Posledice tretmana estradiolom na molekule insulinskog signalnog puta su o.iglednije u uterusu, ali je njihov fiziolo.ki zna.aj za insulinsko delovanje verovatno ve.i u jetri. S druge strane, rezultati dobijeni u srcu sugeri.u veoma kompleksnu ulogu estradiola u fiziologiji srca, koja se manifestuje i kombinacijom pozitivnog i negativnog, genomskog i negenomskog delovanja ovog hormona na molekule signalnog puta insulina.Insulin and estradiol play important role in regulation of carbohydrate and lipid metabolism. Various clinical observations and experimental data suggest that variations in the concentration of estrogens affect insulin action. The aim of the present study was to compare the impact of estradiol on early steps of insulin signaling in main target tissues of insulin (the liver) and estradiol (the uterus), and in the heart, where both hormones realize important effects. Ovariectomized female rats were treated with estradiol 6 h prior to analysis of protein and mRNA content of insulin signaling molecules. To delineate estradiol effects on phosphorylations and molecular associations relevant for insulin signaling, animals were treated additionally with insulin 30 min before the experiment. Treatment with estradiol did not change the levels of plasma insulin and glucose, but it significantly decreased the free fatty acid level and increased uterine weight. In liver, estradiol treatment decreased IR phosphorylation and IRS-1 protein content, suggesting that estradiol suppressed insulin action through IR/IRS-1 and probably redirected it to alternative pathway. This conclusion is supported with increase of IRS-2 protein content. In uterus, estradiol treatment resulted in significant increase of protein content of almost all analyzed molecules. In heart, estradiol increased IRS-1/p85 association, p85 protein and mRNA level, and Ser473Akt phosphorylation. On the other hand, estradiol treatment decreased tyrosine phosphorylation of cardiac IR, protein content of IRS-2, and mRNA of both IRS proteins. These results suggest that estradiol treatment induces tissue-specific changes in insulin signaling. Consequences of estradiol treatment on insulin signaling molecules are more apparent in uterus, but their physiological relevance for insulin action is probably more important in liver. On the other hand, results obtained in heart suggest very complex role of estradiol in heart physiology, represented by, amongst other effects, combination of positive and negative, genomic and nongenomic actions of this hormone on insulin signaling molecules

Sekundarni metaboliti biljne vrste Hypericum monogynum iz Pakistana

4-Chlorobenzoic acid (1), quercitrin (2), astilbin (3), along with beta-sitosterol, gamma-sitosterol, friedelin and beta-amyrin were isolated from the aerial parts of Hypericum monogynum. Whereas compound 1 was isolated for the first time from natural sources, flavanonol 3 was not found before in these species.4-Hlorobenzoeva kiselina (1), kvercitrin (2), astilbin (3), kao i β-sitosterol, γ- sitosterol, fridelin i β-amirin izolovani su iz nadzemnih delova biljne vrste Hypericum monogynum. Po prvi put jedinjenje 1 je izolovano iz prirodnih izvora, dok flavanonol 3 do sada nije izolovan iz ove biljne vrste