Surface modification of silicate, borosilicate and phosphate bioactive glasses to improve/control protein adsorption: PART I

Bioactive glasses (BGs) are promising for bone tissue regeneration. BG composition can be tailored, according to the application of interest, and/or functionalized with organic molecules/biomolecules to improve their performances. However, despite the wide knowledge concerning BGs, their interaction with proteins, fundamental for controlling the fate of the implant, has not been deeply investigated yet. Controlling or predicting protein adsorption requires a full understanding of the materials surface physico-chemical properties. In this work, four different BGs (S53P4, B25, SCNB, PhGlass) were surface-modified by four different treatments: 72 h-soaking in TRIS, 72 h soaking in simulated body fluid, APTES grafting and quaternized APTES grafting. The surfaces were then characterized both untreated and after each treatment by contact angle, zeta potential analysis, X-ray photoelectron spectroscopy, Fourier Transform InfraRed–Attenuated Total Reflectance spectroscopy and Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Inductively Coupled Plasma – Optical Emission Spectrometry was then performed to investigate the ion leaching. The aim of this study (Part I) is the physico-chemical characterization of BGs as a function of the implemented treatments, aiming to better understand how the superficial properties are successively affecting protein adsorption. Protein adsorption on untreated and treated BGs will be discussed in a following manuscript (Part II)

Thermal Time Scales in a Color Glass Condensate

In a model of relativistic heavy ion collisions wherein the unconfined quark-gluon plasma is condensed into glass, we derive the Vogel-Fulcher-Tammann cooling law. This law is well known to hold true in condensed matter glasses. The high energy plasma is initially created in a very hot negative temperature state and cools down to the Hagedorn glass temperature at an ever decreasing rate. The cooling rate is largely determined by the QCD string tension derived from hadronic Regge trajectories. The ultimately slow relaxation time is a defining characteristic of a color glass condensate.Comment: 5 pages, ReVTeX format, nofigure

Optical observations of the bright long duration peculiar GRB 021004 afterglow

The CCD magnitudes in Johnson $B,V$ and Cousins $R$ and $I$ photometric passbands are determined for the bright long duration GRB 021004 afterglow from 2002 October 4 to 16 starting $\sim$ 3 hours after the $\gamma-$ray burst. Light curves of the afterglow emission in $B$,$V$,$R$ and $I$ passbands are obtained by combining these measurements with other published data. The earliest optical emission appears to originate in a revese shock. Flux decay of the afterglow shows a very uncommon variation relative to other well-observed GRBs. Rapid light variations, especially during early times ($\Delta t < 2$ days) is superposed on an underlying broken power law decay typical of a jetted afterglow. The flux decay constants at early and late times derived from least square fits to the light curve are $0.99\pm0.05$ and $2.0\pm0.2$ respectively, with a jet break at around 7 day. Comparison with a standard fireball model indicates a total extinction of $E(B-V)=0.20$ mag in the direction of the burst. Our low-resolution spectra corrected for this extinction provide a spectral slope $\beta = 0.6\pm0.02$. This value and the flux decay constants agree well with the electron energy index $p\sim 2.27$ used in the model. The derived jet opening angle of about $7^{\circ}$ implies a total emitted gamma-ray energy $E_{\gamma} = 3.5\times10^{50}$ erg at a cosmological distance of about 20 Gpc. Multiwavelength observations indicate association of this GRB with a star forming region, supporting the case for collapsar origin of long duration GRBs.Comment: 19 pages, 3 figures, BASI, 31, 1

RACE-OC Project: Rotation and variability in the open cluster M11 (NGC6705)

Rotation and magnetic activity are intimately linked in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on stellar rotation, and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the rotation/activity/age connection. The open cluster M11 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters with different ages. Photometric observations of the open cluster M11 were carried out in June 2004 using LOAO 1m telescope. The rotation periods of the cluster members are determined by Fourier analysis of photometric data time series. We further investigated the relations between the surface activity, characterized by the light curve amplitude, and rotation. We have discovered a total of 75 periodic variables in the M11 FoV, of which 38 are candidate cluster members. Specifically, among cluster members we discovered 6 early-type, 2 eclipsing binaries and 30 bona-fide single periodic late-type variables. Considering the rotation periods of 16 G-type members of the almost coeval 200-Myr M34 cluster, we could determine the rotation period distribution from a more numerous sample of 46 single G stars at an age of about 200-230 Myr and determine a median rotation period P=4.8d. A comparison with the younger M35 cluster (~150 Myr) and with the older M37 cluster (~550 Myr) shows that G stars rotate slower than younger M35 stars and faster than older M37 stars. The measured variation of the median rotation period is consistent with the scenario of rotational braking of main-sequence spotted stars as they age.Comment: Accepted by Astronomy and Astrophysics on Dec 15, 200

Optical afterglow of the not so dark GRB 021211

We determine Johnson $B,V$ and Cousins $R,I$ photometric CCD magnitudes for the afterglow of GRB 021211 during the first night after the GRB trigger. The afterglow was very faint and would have been probably missed if no prompt observation had been conducted. A fraction of the so-called ``dark'' GRBs may thus be just ``optically dim'' and require very deep imaging to be detected. The early-time optical light curve reported by other observers shows prompt emission with properties similar to that of GRB 990123. Following this, the afterglow emission from $\sim 11$ min to $\sim 33$ days after the burst is characterized by an overall power-law decay with a slope $1.1\pm0.02$ in the $R$ passband. We derive the value of spectral index in the optical to near-IR region to be 0.6$\pm$0.2 during 0.13 to 0.8 day after the burst. The flux decay constant and the spectral slope indicate that optical observations within a day after the burst lies between cooling frequency and synchrotron maximum frequency.Comment: 4 pages, 2 figures, A&A Letters, 408, L2

Chemical Stabilisation of Sand : Part* II Construction and Studies of 50m X 4m Road

An experimental track (50m X 4m) was constructed on a loose sand bed by using two chemical-sand composition containing either 9 per cent urea formaldehyde (UF) resin or 11 per cent sodium silicate binder (on solid content basis). The trafficability studies on 5-6 cm thick stabilised track was found to vary from 1625 to 1700 psi in UF stabilised track and from 1340 to 1460 psi in silicate stabilised track. The effect of resin, desert environmental conditions and trafficability studies showed cumulative loss of load bearing capacity from 1625-1700 to 645-1125 psi

Journal Staff

We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar &lt; 1.0 and transverse momenta 30 &lt; p(T)(gamma) &lt; 200 GeV. The b-quark jets are required to have p(T)(jet) &gt; 15 GeVand vertical bar y(jet)vertical bar &lt; 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators

Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production

We present measurements of lepton (l) angular distributions in ttbar -> W+ b W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4fb^-1, collected with the D0 detector at the Fermilab Collider, we find that the angular distributions of l- relative to anti-protons and l+ relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat) +- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted) = (4.7 +- 0.1)%. This result is further combined with the measurement based on the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%. Furthermore, we present a first study of the top-quark polarization.Comment: submitted versio