UPORABA RAČUNALA U POUČAVANJU MATEMATIKE – PREGLED STANJA U SRBIJI

In this study we analyse the quantity and the quality of the use of computers in mathematics teaching in schools (both primary and secondary) in Serbia, observing two samples. The data for the first research was obtained through a sample consisting of 142 experienced teachers. By conducting a survey we determined the current situation regarding personal and school use of computers, and also examined whether or not computer usage was affected by some non-attitudinal (e.g., demographic) and attitudinal variables. The second research included 123 beginner teachers, applicants for the professional state teacher license. The collected data was based on our estimates of the applicants’ preparation for the practical part of the licensing examination. We examined the impact of some demographic and academic factors on the quality of computer usage. In both researches, the data collected was coded and analysed using the SPSS 13.0 statistical program (cross tabulation and appropriate tests for comparing groups). The aims of our researches were to determine the current situation and give some possible suggestions for improving computer useU ovom radu analiziramo kvantitetu i kvalitetu uporabe računala u poučavanju matematike u Srbiji (u osnovnim i srednjim školama) promatrajući dva uzorka. Podaci za prvo istraživanje prikupljeni su na uzorku od 142 iskusna nastavnika (sa profesionalnom licencom). Provedbom istraživanja ustanovili smo trenutnu situaciju s obzirom na privatnu uporabu računala i uporabu računala u školi, kao i utječu li na uporabu računala i neke objektivne (npr. demografija) i subjektivne varijable. Drugo istraživanje je provedeno na uzorku od 123 nastavnička pripravnika (bez profesionalne licence). Prikupljeni podaci su temeljeni na našim procjenama o pripravi praktičnog dijela stručnog ispita pripravnika. Istražili smo utjecaj nekih demografskih i akademskih čimbenika na kakvoću uporabe računala. U oba istraživanja, podaci su obrađeni uporabom statističkog programa SPSS 13.0 (unakrsno tabeliranje i odgovarajući testovi za uspoređivanje skupina). Cilj istraživanja je bio utvrditi trenutnu situaciju i predložiti moguća poboljšanja uporabe računala

Accretion Rate and the Physical Nature of Unobscured Active Galaxies

We show how accretion rate governs the physical properties of a sample of unobscured broad-line, narrow-line, and lineless active galactic nuclei (AGNs). We avoid the systematic errors plaguing previous studies of AGN accretion rate by using accurate accretion luminosities (L_int) from well-sampled multiwavelength SEDs from the Cosmic Evolution Survey (COSMOS), and accurate black hole masses derived from virial scaling relations (for broad-line AGNs) or host-AGN relations (for narrow-line and lineless AGNs). In general, broad emission lines are present only at the highest accretion rates (L_int/L_Edd > 0.01), and these rapidly accreting AGNs are observed as broad-line AGNs or possibly as obscured narrow-line AGNs. Narrow-line and lineless AGNs at lower specific accretion rates (L_int/L_Edd < 0.01) are unobscured and yet lack a broad line region. The disappearance of the broad emission lines is caused by an expanding radiatively inefficient accretion flow (RIAF) at the inner radius of the accretion disk. The presence of the RIAF also drives L_int/L_Edd < 10^-2 narrow-line and lineless AGNs to 10 times higher ratios of radio to optical/UV emission than L_int/L_Edd > 0.01 broad-line AGNs, since the unbound nature of the RIAF means it is easier to form a radio outflow. The IR torus signature also tends to become weaker or disappear from L_int/L_Edd < 0.01 AGNs, although there may be additional mid-IR synchrotron emission associated with the RIAF. Together these results suggest that specific accretion rate is an important physical "axis" of AGN unification, described by a simple model.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 9 figure

Early-Time Photometry and Spectroscopy of the Fast Evolving SN 2006AJ Associated with GRB 060218

We present early photometric and spectroscopic data on the afterglow of GRB 060218 and report the evolution of the underlying supernova 2006aj. Our data span a time-range of 4 days to 22 days after the GRB and clearly establish that SN 2006aj is a fast-evolving broad-lined Type Ic SN with an extremely short rise-time (~ 10 days) and a large optical luminosity (M_V = -18.7 mag). The SN properties are deduced well since the GRB afterglow does not contribute a significant amount to the total light output. The spectra show broad lines indicative of large expansion velocities, but are better matched by those of SN 2002ap and SN 1997ef (that are not associated with a GRB) than those of the proto-typical GRB-related SN 1998bw. We refine the redshift estimate to z = 0.0335 +/- 0.00007. The host-galaxy is a low-metallicity dwarf galaxy (with M_V \~ -16.0 mag), similar to host-galaxies of other GRB-associated SNe.Comment: 7 pages using emulateapj, 3 figures, accepted by ApJL, minor changes compared to v

Measurements of time-dependent CP asymmetries in B→D∗∓π±B \to D^{*\mp} \pi^{\pm} decays using a partial reconstruction technique

We report results on time-dependent CP asymmetries in $B \to D^{*\mp}\pi^{\pm}$ decays based on a data sample containing 657 {\times} $10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $\Upsilon(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}\pi^{\pm}$ events are identified using information only from the fast pion from the B decay and the slow pion from the subsequent decay of the $D^{*\mp}$, where the former (latter) corresponds to $D^{*+} (D^{*-})$ final states. We obtain CP violation parameters $S^+ = +0.061 \pm 0.018(\mathrm{stat}) \pm 0.012(\mathrm{syst})$ and $S^- = +0.031 \pm 0.019(\mathrm{stat}) \pm 0.015(\mathrm{syst})$.Comment: 8 pages, 5 figures, 2 tables, submitted to Physical Review D (RC

Observation of D0−Dˉ0D^0-\bar{D}^0 Mixing in e+e−e^+e^- Collisions

We observe $D^0-\bar{D}^0$ mixing in the decay $D^0\rightarrow K^+\pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x'}^2 = (0.09\pm0.22)\times 10^{-3}$ and $y' = (4.6\pm3.4)\times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53\pm0.13)\times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.Comment: 6 pages, 4 figure

First Observation of Radiative B^0 -> \phi K^0 \gamma Decays and Measurements of Their Time-Dependent CP Violation

We report the first observation of the radiative decay B^0 -> \phi K^0 \gamma using a data sample of 772 x 10^6 B B-bar pairs collected at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We observe a signal of 37+/-8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is ${\cal B}(B^0 -> \phi K^0 \gamma) = (2.74\pm 0.60 \pm 0.32) \times 10^{-6}$, where the uncertainties are statistical and systematic, respectively. We also report the first measurements of time-dependent CP violation parameters: ${\mathcal S}_{\phi K_S^0 \gamma} = +0.74^{+0.72}_{-1.05} (stat)^{+0.10}_{-0.24} (syst)$ and ${\mathcal A}_{\phi K_S^0 \gamma} = +0.35 +/- 0.58 (stat)^{+0.23}_{-0.10} (syst)$. Furthermore, we measure ${\mathcal B}(B^+ -> \phi K^+ \gamma) = (2.48 +/- 0.30 +/- 0.24) x 10^{-6}$, ${\mathcal A}_{CP} = -0.03 +/- 0.11 +/- 0.08$ and find that the signal is concentrated in the M_{\phi K} mass region near threshold.Comment: 6 pages, 3 figures, Modified version is to be published in PRD(RC

Search for charmonium and charmonium-like states in \Upsilon(2S) radiative decays

Using a sample of 158 million \Upsilon(2S) events collected with the Belle detector, charmonium and charmonium-like states with even charge parity are searched for in \Upsilon(2S) radiative decays. No significant \chi_{cJ} or \eta_c signal is observed and the following upper limits at 90% confidence level (C.L.) are obtained: BR(\Upsilon(2S)\to \gamma \chi_{c0})< 1.0 \times 10^{-4}, BR(\Upsilon(2S) \to \gamma \chi_{c1})<3.6 \times 10^{-6}, BR(\Upsilon(2S) \to \gamma \chi_{c2})<1.5 \times 10^{-5}, and BR(\Upsilon(2S) \to \gamma \eta_c)< 2.7 \times 10^{-5}. No significant signal of any charmonium-like state is observed, and we obtain the limits \BR(\Upsilon(2S)\to \gamma X(3872))\times\BR(X(3872)\to\pi^+\pi^-J/\psi)< 0.8 \times 10^{-6}, BR(\Upsilon(2S) \to \gamma X(3872))\times BR(X(3872)\to\pi^+\pi^-\pi^0 J/\psi)< 2.4\times 10^{-6}, BR(\Upsilon(2S) \to \gamma X(3915))\times BR(X(3915)\to\omega J/\psi)< 2.8\times 10^{-6}, BR(\Upsilon(2S) \to \gamma Y(4140))\times BR(Y(4140)\to\phi J/\psi)) < 1.2\times 10^{-6}, and BR(\Upsilon(2S) \to \gamma X(4350))\times BR(X(4350)\to\phi J/\psi))< 1.3\times 10^{-6} at 90% C.L.Comment: 7 pages, 6 figures, 1 tabl

Study of Excited Ξc\Xi_c States Decaying into Ξc0\Xi_c^0 and Ξc+\Xi_c^+ Baryons

Using a data sample of 980 ${\rm fb}^{-1}$ of $e^+e^-$ annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we report the results of a study of excited $\Xi_c$ states that decay, via the emission of photons and/or charged pions, into $\Xi_c^0$ or $\Xi_c^+$ ground state charmed-strange baryons. We present new measurements of the masses of all members of the $\Xi_c^{\prime}$, $\Xi_c(2645)$, $\Xi_c(2790)$, $\Xi_c(2815)$, and $\Xi_c(2980)$ isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.Comment: Submitted to PR