The time lag-luminosity relation: A consequence of the Amati relation?

We use a simple pulse model to investigate the origin of the time lagluminosity relation (LLR) discovered by Norris et al.(ApJ, 534 (2000) 248). We show that, at least for single pulse bursts which satisfy both the hardness-intensity and the hardness-fluence correlations, the LLR can be simply obtained as a consequence of the Amati relation

The lag and duration-luminosity relations of gamma-ray burst pulses

Relations linking the temporal or/and spectral properties of the prompt emission of gamma-ray bursts (hereafter GRBs) to the absolute luminosity are of great importance as they both constrain the radiation mechanisms and represent potential distance indicators. Here we discuss two such relations: the lag-luminosity relation and the newly discovered duration-luminosity relation of GRB pulses. We aim to extend our previous work on the origin of spectral lags, using the duration-luminosity relation recently discovered by Hakkila et al. to connect lags and luminosity. We also present a way to test this relation which has originally been established with a limited sample of only 12 pulses. We relate lags to the spectral evolution and shape of the pulses with a linear expansion of the pulse properties around maximum. We then couple this first result to the duration-luminosity relation to obtain the lag-luminosity and lag-duration relations. We finally use a Monte-Carlo method to generate a population of synthetic GRB pulses which is then used to check the validity of the duration-luminosity relation. Our theoretical results for the lag and duration-luminosity relations are in good agreement with the data. They are rather insensitive to the assumptions regarding the burst spectral parameters. Our Monte Carlo analysis of a population of synthetic pulses confirms that the duration-luminosity relation must be satisfied to reproduce the observational duration-peak flux diagram of BATSE GRB pulses. The newly discovered duration-luminosity relation offers the possibility to link all three quantities: lag, duration and luminosity of GRB pulses in a consistent way. Some evidence for its validity have been presented but its origin is not easy to explain in the context of the internal shock model.Comment: 8 pages, 5 figures, 1 tabl

Axl-EGFR receptor tyrosine kinase hetero-interaction provides EGFR with access to pro-invasive signalling in cancer cells

© The Author(s) 2016. Acquired resistance to conventional and targeted therapies is becoming a major hindrance in cancer management. It is increasingly clear that cancer cells are able to evolve and rewire canonical signalling pathways to their advantage, thus evading cell death and promoting cell invasion. The Axl receptor tyrosine kinase (RTK) has been shown to modulate acquired resistance to EGFR-targeted therapies in both breast and lung cancers. Glioblastoma multiforme (GBM) is a highly infiltrative and invasive form of brain tumour with little response to therapy. Both Axl and EGFR have been identified as major players in gliomagenesis and invasiveness. However, the mechanisms underlying a potential signalling crosstalk between EGFR and Axl RTKs are unknown. The purpose of this study was to investigate this novel and unconventional interaction among RTKs of different families in human GBM cells. With the use of western blotting, in vitro kinase activity, co-immunoprecipitation and bimolecular fluorescence complementation assays, we show that EGF stimulates activation of Axl kinase and that there is a hetero-interaction between the two RTKs. Through small interfering RNA knockdown and quantitative PCR screening, we identified distinct gene expression patterns in GBM cells that were specifically regulated by signalling from EGFR-EGFR, Axl-Axl and EGFR-Axl RTK parings. These included genes that promote invasion, which were activated only via the EGFR-Axl axis (MMP9), while EGFR-EGFR distinctly regulated the cell cycle and Axl-Axl regulated invasion. Our findings provide critical insights into the role of EGFR-Axl hetero-dimerisation in cancer cells and reveal regulation of cell invasion via Axl as a novel function of EGFR signalling

Forward modeling using finite difference method for fractured hard rocks tracing via three-electrode array

У статті наведено результати польових електророзвідувальних робіт на півночі Ірану, отримані трьохелектродною установкою. Виконано 2D інверсію значень уявного опору, що дозволила локалізувати області з низьким питомим опором в товщі високоомних порід, пов’язані в основному із зонами тріщинуватості. Результати інверсії підтверджені буріннямВ статье представлены результаты полевых электроразведочных работ на севере Ирана, полученные трехэлектродной установкой. Выполнена 2D инверсия значений кажущегося сопротивления, позволившая локализовать области с низким удельным сопротивлением в толще высокоомных пород, связанные в основном с зонами трещиноватости. Результаты инверсии подтверждены бурением

Is the time lag-luminosity relation of GRBs a consequence of the Amati relation?

The lag-luminosity relation (LLR) provides a way of estimating GRB luminosity by measuring the spectral lags between different energy bands. We want to understand the origin of the LLR and test its validity. This appears especially important if the LLR is to be used as a distance indicator. We perform a linear analysis of the lag between two spectral bands. The lag is obtained as the time interval between the maxima of a given pulse in the two bands. We get a simple expression for the lag, which shows in a very simple way how it is related to the spectral evolution of the burst via the variation of the peak energy and spectral indices. When this expression is coupled to the Amati relation, it leads to a LLR that agrees with the observational results only if the burst's spectral evolution is limited to a decrease in peak energy during pulse decay. However, when the variation of the spectral indices is also taken into account, the predicted LLR differs from the observed one. We briefly discuss some ways to solve this problem, such as a possible correlation between pulse spikiness and burst luminosity.Comment: Accepted for publication in Astronomy & Astrophysics, 5 pages, 3 figure