Pilot Mixer Cooling Hole Arrangement for Fuel Nozzle of a Gas Turbine Engine

A mixer assembly for a gas turbine engine is provided, including a main mixer, and a pilot mixer having an annular housing. The pilot mixer can further include features to cool portions of the annular housing, such as a radial edge of the annular housing

Angled Radial Fuel/Air Delivery System for Combustor

A combustor is provided. The combustor may comprise an axial fuel delivery system, and a radial fuel delivery system aft of the axial fuel delivery system. The radial fuel delivery system may be configured to direct fuel at least partially towards the axial fuel delivery system. A radial fuel delivery system is also provided. The system may comprise a combustor including a combustor liner, a mixer coupled to the combustor liner, and a nozzle disposed within the mixer, wherein the mixer and the nozzle are configured to direct fuel in a direction at least partially forward

Shallow decay phase of GRB X-ray afterglows from relativistic wind bubbles

The postburst object of a GRB is likely to be a highly magnetized, rapidly rotating compact object (e.g., a millisecond magnetar), which could produce an ultrarelativistic electron-positron-pair wind. The interaction of such a wind with an outwardly expanding fireball ejected during the burst leads to a relativistic wind bubble (RWB). We numerically calculate the dynamics and radiative properties of RWBs and use this model to explain the shallow decay phase of the early X-ray afterglows observed by Swift. We find that RWBs can fall into two types: forward-shock-dominated and reverse-shock-dominated bubbles. Their radiation during a period of $\sim 10^{2}-10^{5}$ seconds is dominated by the shocked medium and the shocked wind, respectively, based on different magnetic energy fractions of the shocked materials. For both types, the resulting light curves always have a shallow decay phase. In addition, we provide an example fit to the X-ray afterglows of GRB 060813 and GRB 060814 and show that they could be produced by forward-shock-dominated and reverse-shock-dominated bubbles, respectively. This implies that, for some early afterglows (e.g., GRB 060814), the long-lasting reverse shock emission is strong enough to explain their shallow decay phase.Comment: 5 pages, 4 figures, Accepted for Publication in A&

Combustor Assembly for a Turbine Engine

A combustor assembly includes a first wall, a second wall, a bulkhead and a plurality of fuel injectors. The bulkhead forms a combustion chamber with the first and the second walls. The fuel injectors are configured with the first wall in a unique and/or a fluctuating pattern

Tail emission from a ring-like jet: its application to shallow decays of early afterglows and to GRB 050709

Similar to the pulsar, the magnetic axis and the spin axis of the gamma-ray burst source may not lie on the same line. This may cause a ring-like jet due to collimation of the precessing magnetic axis. We analyze the tail emission from such a jet, and find that it has a shallow decay phase with temporal index equal to -1/2 if the Lorentz factor of the ejecta is not very high. This phase is consistent with the shallow decay phase of some early X-ray afterglow detected by {\it{swift}}. The ring-like jet has a tail cusp with sharp rising and very sharp decay. This effect can provide an explanation for the re-brightening and sharp decay of the X-ray afterglow of GRB 050709.Comment: 6 pages, 2 figures. Accepted by ChJA

All-optical retrieval of the global phase for two-dimensional Fourier-transform spectroscopy

A combination of spatial interference patterns and spectral interferometry are used to find the global phase for non-collinear two-dimensional Fourier-transform (2DFT) spectra. Results are compared with those using the spectrally resolved transient absorption (STRA) method to find the global phase when excitation is with co-linear polarization. Additionally cross-linear polarized 2DFT spectra are correctly phased using the all-optical technique, where the SRTA is not applicable.Comment: 6 pages, 7 figures, journal publicatio

Efficiency Crisis of Swift Gamma-Ray Bursts with Shallow X-ray Afterglows: Prior Activity or Time-Dependent Microphysics?

Most X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase t^{-1/2} in the first few hours. This is not predicted by the standard afterglow model and needs an explanation. We discuss that the shallow decay requires an unreasonably high gamma-ray efficiency, >75-90%, within current models, which is difficult to produce by internal shocks. Such a crisis may be avoided if a weak relativistic explosion occurs ~10^3-10^6 s prior to the main burst or if the microphysical parameter of the electron energy increases during the shallow decay, \epsilon_e ~ t^{1/2}. The former explanation predicts a very long precursor, while both prefer dim optical flashes from the reverse shock, as was recently reported. We also calculate the multi-wavelength afterglows and compare them with observations. No optical break at the end of the shallow X-ray decay indicates a preference for the time-dependent microphysics model with additionally decaying magnetic fields, \epsilon_B ~ t^{-0.6}.Comment: 7 pages, 1 figure, accepted for publication in A&

Listen to Nice

In describing Humphrey Jennings’ wartime documentary propaganda film, 'Listen to Britain' (1942), a film with an overtly poetic sensibility and dominantly musical soundtrack, John Corner asserts that ‘through listening to Britain, we are enabled to properly look at it'. This idea of sound leading our attention to the images has underpinned much of the collaborative work between composer and sound designer, Geoffrey Cox, and documentary filmmaker, Keith Marley. It is in this context that the article will analyse an extract of A Film About Nice (Marley and Cox 2010), a contemporary re-imagining of Jean Vigo’s silent documentary, 'A propos de Nice' (1930). Reference will be made throughout to the historical context, and the filmic and theoretical influences that have informed the way music and creative sound design have been used to place emphasis on hearing a place, as much as seeing it

The diverse broad-band light-curves of Swift GRBs reproduced with the cannonball model

Two radiation mechanisms, inverse Compton scattering (ICS) and synchrotron radiation (SR), suffice within the cannonball (CB) model of long gamma ray bursts (LGRBs) and X-ray flashes (XRFs) to provide a very simple and accurate description of their observed prompt emission and afterglows. Simple as they are, the two mechanisms and the burst environment generate the rich structure of the light curves at all frequencies and times. This is demonstrated for 33 selected Swift LGRBs and XRFs, which are well sampled from early until late time and faithfully represent the entire diversity of the broad-band light curves of Swift LGRBs and XRFs. Their prompt gamma-ray and X-ray emission is dominated by ICS of `glory' light. During their fast decline phase, ICS is taken over by SR, which dominates their broad-band afterglow. The pulse shape and spectral evolution of the gamma-ray peaks and the early-time X-ray flares, and even the delayed optical `humps' in XRFs, are correctly predicted. The `canonical' and non-canonical X-ray light curves and the chromatic behaviour of the broad-band afterglows are well reproduced. In particular, in canonical X-ray light curves, the initial fast decline and rapid softening of the prompt emission, the transition to the plateau phase, the subsequent gradual steepening of the plateau to an asymptotic power-law decay, and the transition from chromatic to achromatic behaviour of the light curves agrees well with those predicted by the CB model. The Swift early-time data on XRF 060218 are inconsistent with a black-body emission from a shock break-out through a stellar envelope. Instead, they are well described by ICS of glory light by a jet breaking out from SN2006aj.Comment: Accepted for publication in The Astrophysical Journal. 63 pages, 10 (multiple) figure

Estimating Z-ring radius and contraction in dividing Escherichia coli

We present a fluorescence recovery after photobleaching-based method for monitoring the progression of septal Z-ring contraction in dividing Escherichia coli cells. In a large number of cells undergoing division, we irreversibly bleached cytosolically expressed Enhanced Green Fluorescent Protein on one side of the septal invagination and followed the fluorescence relaxation on both sides of the septum. Since the relaxation time depends on the cross-sectional area of the septum, it can be used to determine the septal radius r. Assuming that the fraction of the observed cells with r-values in a given interval reflects the duration of that interval in the division process we could derive an approximate time-course for the contraction event, as a population average. By applying the method repeatedly on individual cells, the contraction process was also followed in real time. On a population average level, our data are best described by a linear contraction process in time. However, on the single cell level the contraction processes display a complex behaviour, with varying levels of activity. The proposed approach provides a simple yet versatile method for studying Z-ring contraction in vivo, and will help to elucidate its underlying mechanisms