Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario

ABSTRACT It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the Fermi Gamma-ray Space Telescope and consider a specific photospheric model, in which the kinetic energy of a low-magnetization outflow is dissipated locally by internal shocks below the photosphere. We construct a table model with a physically motivated parameter space and fit it to time-resolved spectra of the 36 brightest Fermi GRBs with a known redshift. We find that about two-thirds of the examined spectra cannot be described by the model, as it typically underpredicts the observed flux. However, since the sample is strongly biased towards bright GRBs, we argue that this fraction will be significantly lowered when considering the full population. From the successful fits we find that the model can reproduce the full range of spectral slopes present in the sample. For these cases we also find that the dissipation consistently occurs at a radius of ∼1012 cm and that only a few per cent efficiency is required. Furthermore, we find a positive correlation between the fireball luminosity and the Lorentz factor. Such a correlation has been previously reported by independent methods. We conclude that if GRB spectra are due to photospheric emission, the dissipation cannot only be the specific scenario we consider here.

A Krylov enhanced proper orthogonal decomposition method for frequency domain model reduction

Purpose This paper aims to describe a method for efficient frequency domain model order reduction. The method attempts to combine the desirable attributes of Krylov reduction and proper orthogonal decomposition (POD) and is entitled Krylov enhanced POD (KPOD). Design/methodology/approach The KPOD method couples Krylov’s moment-matching property with POD’s data generalization ability to construct reduced models capable of maintaining accuracy over wide frequency ranges. The method is based on generating a sequence of state- and frequency-dependent Krylov subspaces and then applying POD to extract a single basis that generalizes the sequence of Krylov bases. Findings The frequency response of a pre-stressed microelectromechanical system resonator is used as an example to demonstrate KPOD’s ability in frequency domain model reduction, with KPOD exhibiting a 44 per cent efficiency improvement over POD. Originality/value The results indicate that KPOD greatly outperforms POD in accuracy and efficiency, making the proposed method a potential asset in the design of frequency-selective applications.

Impact of improved farm technology on pulses production in Karnataka

The current study aimed at evaluating technical efficiency and change in output of pulse crops in Karnataka. Totally 180 farmers were selected for eliciting required information on adoption of A3P technology. The results of the study revealed that majority of the farmers were operating above 80 per cent efficiency levels in both pulses across the farmers of A3P and Non-A3P. Further, more than 53 per cent of farmers' under redgram and 56 per cent under bengalgram have achieved 100 per cent efficiency level in A3P farmers category. Decomposition of the difference in total output between A3P and Non-A3P farmers was 13.23 and 14.86 per cent in redgram and bengalgram crops respectively. The A3P technology has alone contributed to the extent of 29 and 22 per cent to the total change in redgram and bengalgram output indicating output can be increased by about 29 and 22 per cent if the farmers could switch over from traditional practices (Non-A3P) to A3P technology. There is need to educate farmers on optimum use of inputs through conducting intensive trainings on A3P technology by KVK’s and other extension agencies to increase the supply of pulses in the country.

Real-time implementation of an algorithm for self-repairing control systems based on LQG optimization

In this paper a self-repairing real-time control (SRC) system based on LQG (Linear Quadratic Gaussian) optimization is proposed. Its transputer implementation and a real-time aircraft application are presented. The SRC system is composed of the monitoring of the control system, the detection and diagnosis of the failure and the reconfiguration of the control laws. The proposed SRC system is suitable for real-time operation because of the parallel nature of its architecture. The INMOS multitransputer implementation of the SRC applied to an aircraft model provides 56 per cent efficiency compared to a single-transputer implementation.

MOLECULAR GROWTH REQUIREMENTS OF SINGLE MAMMALIAN CELLS

Two purified serum protein fractions, fetuin and serum albumin, will replace whole or dialyzed serum in supporting the growth of single S3 HeLa cells in an otherwise chemically defined nutrient solution. In the serum-free medium, single S3 cells will form macroscopic colonies with essentially 100 per cent efficiency. The generation time of S3 cells in the serum-free medium is approximately 50 per cent greater than that observed in an optimal, serum-containing medium. All components of the serum-free medium are available commercially, except fetuin, which can easily be prepared in substantial quantities. The problem of the purity of the protein preparations and of their possible roles in promoting cell growth is discussed.

THE TOTAL LUMINOUS EFFICIENCY OF LUMINOUS BACTERIA

Methods are described for measuring the light emitted by an emulsion of luminous bacteria of given thickness, and calculating the light emitted by a single bacterium, measuring 1.1 x 2.2 micra, provided there is no absorption of light in the emulsion. At the same time, the oxygen consumed by a single bacterium was measured by recording the time for the bacteria to use up .9 of the oxygen dissolved in sea water from air (20 per cent oxygen). The luminescence intensity does not diminish until the oxygen concentration falls below 2 per cent, when the luminescence diminishes rapidly. Above 2 per cent oxygen (when the oxygen dissolving in sea water from pure oxygen at 760 mm. Hg pressure = 100 per cent) the bacteria use equal amounts of oxygen in equal times, while below 2 per cent oxygen it seems very likely that rate of oxygen absorption is proportional to oxygen concentration. By measuring the time for a tube of luminous bacteria of known concentration saturated with air (20 per cent oxygen) to begin to darken (2 per cent oxygen) we can calculate the oxygen absorbed by one bacterium per second. The bacteria per cc. are counted on a blood counting slide or by a centrifugal method, after measuring the volume of a single bacterium (1.695 x 10–12 cc.). Both methods gave results in good agreement with each other. The maximum value for the light from a single bacterium was 24 x 10–14 lumens or 1.9 x 10–14 candles. The maximum value for lumen-seconds per mg. of oxygen absorbed was 14. The average value for lumen-seconds per mg. O2 was 9.25. The maximum values were selected in calculating the efficiency of light production, since some of the bacteria counted may not be producing light, although they may still be using oxygen. The "diet" of the bacteria was 60 per cent glycerol and 40 per cent peptone. To oxidize this mixture each mg. of oxygen would yield 3.38 gm. calories or 14.1 watts per second. 1 lumen per watt is therefore produced by a normal bacterium which emits 14 lumen-seconds per mg. O2 absorbed. Since the maximum lumens per watt are 640, representing 100 per cent efficiency, the total luminous efficiency if .00156. As some of the oxygen is used in respiratory oxidation which may have nothing to do with luminescence, the luminescence efficiency must be higher than 1 lumen per watt. Experiments with KCN show that this substance may reduce the oxygen consumption to 1/20 of its former value while reducing the luminescence intensity only ¼. A partial separation of respiratory from luminescence oxidations is therefore effected by KCN, and our efficiency becomes 5 lumens per watt, or .0078. This is an over-all efficiency, based on the energy value of the "fuel" of the bacteria, regarded as a power plant for producing light. It compares very favorably with the 1.6 lumens per watt of a tungsten vacuum lamp or the 3.9 lumens per watt of a tungsten nitrogen lamp, if we correct the usual values for these illuminants, based on watts at the lamp terminals, for a 20 per cent efficiency of the power plant converting the energy of coal fuel into electric current. The specific luminous emission of the bacteria is 3.14 x 10–6 lumens per cm2. One bacterium absorbs 215,000 molecules of oxygen per second and emits 1,280 quanta of light at λmax = 510µµ. If we suppose that a molecule of oxygen uniting with luminous material gives rise to the emission of 1 quantum of light energy, only 1/168 of the oxygen absorbed is used in luminescence. On this basis the efficiency becomes 168 lumens per watt or 26.2 per cent.