Inverse Compton cooling in Klein-Nishina regime and GRB prompt spectrum

Synchrotron radiation mechanism, when electrons are accelerated in a relativistic shock, is known to have serious problems to explain the observed gamma-ray spectrum below the peak for most Gamma-Ray Bursts (GRBs); the synchrotron spectrum below the peak is much softer than observed spectra. Recently, the possibility that electrons responsible for the radiation cool via Inverse Compton, but in the Klein-Nishina regime, has been proposed as a solution to this problem. We provide an analytical study of this effect and show that it leads to a hardening of the low energy spectrum but not by enough to make it consistent with the observed spectra for most GRBs (this is assuming that electrons are injected continuously over a time scale comparable to the dynamical time scale, as is expected for internal shocks of GRBs). In particular, we find that it is not possible to obtain a spectrum with \alpha>-0.1 (f_{\nu} \propto \nu^{\alpha}) whereas the typical observed value is \alpha\sim0. Moreover, extreme values for a number of parameters are required in order that \alpha\sim-0.1: the energy fraction in magnetic field needs to be less than about 10^{-4}, the thermal Lorentz factor of electrons should be larger than 10^6, and the radius where gamma-rays are produced should be not too far away from the deceleration radius. These difficulties suggest that the synchrotron radiation mechanism in internal shocks does not provide a self-consistent solution when \alpha>-0.2.Comment: 10 pages (single column), 2 figures, MNRAS in pres

Periodontal and Prosthetic Aspect of Biological Width Part I: Violation of Biologic Width

Ovaj pregledni rad daje širok prikaz kompleksnoga pitanja biološke širine i pokušava odgovoriti na neka pitanja koja se u svezi s tom problematikom postavljaju. To se u prvome redu odnosi na probleme koji nastaju nakon uspostave nepovoljnih odnosa u parodontu prigodom nepravilna smještaja ruba preparacije. Na početku se daje prikaz dimenzija biološke širine, a zatim razmatra pitanje smještaja ruba protetskoga rada, uspjeh restorativnih zahvata i razlozi neuspjeha.This review gives the wide aspect of the complex question of biologic width and represents an attempt to answer some of the demands in relation to it. First of all, it debates the problems that occur after improper margin placement in the periodontium. Initially, the dimensions of biologic width are contemplated and then margin placement, is discussed and the success of restorative procedures and reasons for failure

Periodontal and Prosthetic Aspect of Biological Width Part I: Violation of Biologic Width

Ovaj pregledni rad daje širok prikaz kompleksnoga pitanja biološke širine i pokušava odgovoriti na neka pitanja koja se u svezi s tom problematikom postavljaju. To se u prvome redu odnosi na probleme koji nastaju nakon uspostave nepovoljnih odnosa u parodontu prigodom nepravilna smještaja ruba preparacije. Na početku se daje prikaz dimenzija biološke širine, a zatim razmatra pitanje smještaja ruba protetskoga rada, uspjeh restorativnih zahvata i razlozi neuspjeha.This review gives the wide aspect of the complex question of biologic width and represents an attempt to answer some of the demands in relation to it. First of all, it debates the problems that occur after improper margin placement in the periodontium. Initially, the dimensions of biologic width are contemplated and then margin placement, is discussed and the success of restorative procedures and reasons for failure

Periodontal and Prosthetic Aspect of the Biological Width Part II: Reconstruction of Anatomy and Function

U drugome dijelu članka opisane su tehnike kojima se uspostavlja biološka širina, s posebnim osvrtom na ortodontske tehnike forsirane erupcije i kirurške tehnike, od gingivektomije do apikalno pomaknutoga režnja. Ispravna indikacija za pojedini zahvat, ali i pažljiva izvedba samoga zahvata, te odmjerena protetska rekonstrukcija spriječit će ponovno remećenje biološke širine.In the second part of the article the authors describe techniques for dealing with reconstruction of the biologic width. The stress is on surgical techniques, from gingivectomy to apical repositioning with osseous surgery, and orthodontic forced eruption. Correct indication for each technique, and correct procedure, as well as equilibrated prosthetic reconstruction, may preserve the biologic width and prevent its new violation

A detailed spectral study of GRB 041219A and its host galaxy

GRB 041219A is one of the longest and brightest gamma-ray bursts (GRBs) ever observed. It was discovered by the INTEGRAL satellite, and thanks to a precursor happening about 300 s before the bulk of the burst, ground based telescopes were able to catch the rarely-observed prompt emission in the optical and in the near infrared bands. Here we present the detailed analysis of its prompt gamma-ray emission, as observed with IBIS on board INTEGRAL, and of the available X-ray afterglow data collected by XRT on board Swift. We then present the late-time multi-band near infrared imaging data, collected at the TNG, and the CFHT, that allowed us to identify the host galaxy of the GRB as an under-luminous, irregular galaxy of about 5x10^9 M_Sun at best fit redshift of z=0.31 -0.26 +0.54. We model the broad-band prompt optical to gamma-ray emission of GRB 041219A within the internal shock model. We were able to reproduce the spectra and light curve invoking the synchrotron emission of relativistic electrons accelerated by a series of propagating shock waves inside a relativistic outflow. On the other hand, it is less easy to simultaneously reproduce the temporal and spectral properties of the infrared data.Comment: 12 pages, 9 figures, accepted for publication in MNRAS, Figure 5 in reduced qualit